392307_0346
DESCRIPTION
BáoTRANSCRIPT
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Chng 1.GII THIU V THIT B NNG
CHUYN1.- Cc nh ngha:
- My nng chuyn l khoa hc nghin cu vic c gii ha qu trnh nng chuyn cc vt nng nhm nng cao nng sut lao ng, gim nh sc lao ng cho con ngi.- Da vo c im ca qu trnh vn chuyn vt liu,ngi ta phn bit 2 chng loi chnh:
+ My nng (cn gi l my trc): y l loi thit b m qu trnh lm vic lp li c chu k. Mt chu k cng tc bao gm thi gian c ti v thi gian chy khng.
+ My vn chuyn lin tc: loi thit b ny, vt liu c vn chuyn theo tng dng lin tc.- Vi my nng ngi ta cn phn bit:
+ My nng n gin: Ch c mt chuyn ng cng tc l nng v h vt. V d Cc loi kch, Ti, palng xch, vn thng xy dng...
+ My trc dng cu: Cu trc, cng trc. cc loi thit b ny, ngoi chuyn ng nng h vt, cn c cc chuyn ng tnh tin ngang v dc di chuyn vt nng n v tr yu cu.
+ Cn trc cc loi: Qu trnh di chuyn vt nng c thc hin nh c cu quay cn hoc thay i khu ca cn.
2.- Cc thng s c bn ca my trc:2.1.- Trng ti (Sc nng) : L trng lng ln nht m my
c th nng c theo tnh ton thit k. Trng ti c th phi k n trng lng ca b phn mang vt.
Trng ti c k hiu l [Q], c n v o l Tn hoc KG hoc N. i lng ny thng c tiu chun ha.
2.2.- Cc thng s ng hc ca cc b phn cng tc: Tc nng vt (Vn), tc di chuyn (Vdc), tc quay ca cn trc (n)...
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2.3.- Cc thng s hnh hc: Ty thuc vo loi thit b, ta c: cao nng, Khu i vi my trc dng cu; cao nng, tm vi i vi cc loi cn trc.
3.- Ch lm vic ca my trc:C th xem ch lm vic ca my trc nh l mt thng
s tng hp cn c trn c s phi hp cc tiu ch v mc s dng my theo ti v theo thi gian.
Trn c s tiu chun ISO, Vit nam c tiu chun TCVN 5862 -1995 quy nh 8 nhm ch lm vic cho my trc c k hiu t A1 n A8. i vi cc c cu trong my nng tiu chun quy nh 8 nhm ch lm vic c k hiu t M1 n M8.
Cc nhm CLV i vi my trc c xc nh trn c s phi hp 10 cp s dng my theo thi gian, k hiu U0 n U9 v 4 cp s dng my theo ti c k hiu t Q1 n Q4.
Tng t CLV i vi cc c cu trong my nng cng c xc nh trn c s phi hp 10 cp s dng my theo thi gian, k hiu T0 n T9 v 4 cp s dng my theo ti c k hiu t L1 n L4.
c trung cho mc s dng my theo ti trng l h s ph ti c xc nh theo cng thc:
n
i
i
T
ip P
P
C
Ck
1
3
max
Trong : Ci : s chu k vn hnh ng vi cc mc ti khc nhau.CT =Ci : tng chu k vn hnh vi cc mc ti khc nhauPi : mc ti ng vi chu k CiPmax : Mc ti ln nht c php vn hnh.
Tng t, i vi cc c cu trong my nng, h s ph ti c tnh theo cng thc:
n
i
i
T
im P
P
t
tk
1
3
max
Trong :
-
ti : thi gian trung bnh (h) s dng c cu ng vi cc mc ti khc nhau.
tT =ti : tng thi gian vn hnh vi cc mc ti khc nhauPi : mc ti ng vi thi gian s dng t iPmax : Mc ti ln nht c php vn hnh. xc nh cc h s ph ti, cn thit phi xy dng cc s
gia ti. Cc s gia ti c xy dng trn c s thc t hoc kinh nghim tham kho.
1 1
0,4 0,4
0.2
0,1 0,5 1 0,5 1
S gia ti CLV [Nh] S gia ti CLV [N]
(kP = 0.1 25) ( kP = 0.5)
c trng cho mc s dng my theo thi gian l l tng chu k vn hnh ca my. Mt chu k vn hnh c xc nh t lc bt u nng ti v kt thc khi my sn sng nhn ti tip theo.
Tng t thi gian s dng c cu (c tnh bng gi) c xc nh khi c cu ang trong trng thi chuyn ng.
Cc bng 1,2,3,4,5,6 cho ta cc s liu c th.
Pi/Pmax
Ci/CT
Pi/Pmax
Ci/CT
-
Ngoi tiu chun phn CLV ca my trc nh trnh by trn, hin nay vn cn tn ti cch phn loi theo TCVN 4244-86 quy nh 4 nhm CLV (Nh [Nh], Trung bnh [TB], Nng [N] v Rt nng [RN]) da trn cc tiu ch sau y:
1.- H s s dng c cu theo ti trng:kQ = Qtb/Q
Trong : Qtb: trng lng trung bnh ca vt nng,Q: Trng ti.
2.- Cng lm vic ca ng c:C% = To/T
Trong : To = tm + tlvVi: To: thi gian lm vic ca ng c trong
mt chu k hot ng ca c cu.tm : thi gian mt ln m mytlv: thi gian chuyn ng vi tc n nh.
T thi gian mt chu k lm vic ca c cu.T = To + tph + td tph: Tng thi gian phanh. td: tng thi gian dng my.3.- H s s dng c cu trong ngy:
kng = 24
ngaytrongvieclamgioSo
4.- H s s dng c cu trong nm:kn =
365
namtrongvieclamngaySo
5.- S chu k lm vic trong mt gi.6.- S ln m my trong 1 chu k7.- Nhit mi trng chung quanh.
Bng 9 cho mi tng quan gia cch phan loi theo c v mi.
4.- Ti trng v cc trng hp ti trng tnh ton:4.1.- Cc loi ti tc dng ln my.
-
Trong qu trnh lm vic, my trc c th chu cc ti trng sau y:
- Trng ti- Ti trng do trng lng bn thn my- Ti trng do gi.- Ti trng ng
Trong bi ton ng lc hc c th xem c cu quy dn thnh mt hay nhiu khi lng. Trng hp n gin nht l quy dn c cu v s mt khi lng v lin kt gia cc khi lng l tuyt i cng.
4.2.- Cc trng hp ti trng tnh ton:Trng hp 1.- Ti trng bnh thng trong iu kin lm
vic bnh thng.Trong trng hp ny cc ti trng phi k n l trng ti,
trng lng bn thn my, ti trng gi trong iu kin thi tit bnh thng, ti trng ng bnh thng. Cc chi tit my trong trng hp ny c thit k hoc tnh kim nghim theo sc bn mi. ng c c chn theo cng sut tnh v c kim nghim theo iu kin pht nhit.
Trng hp 2.- Ti trng ln nht trong iu kin lm vic.Trong trng hp ny cc ti trng phi k n l trng ti,
trng lng bn thn my, ti trng gi trong iu kin thi tit bnh thng, ti trng ng ln nht xut hin do phanh t ngt. Cc chi tit my trong trng hp ny c thit k hoc tnh kim nghim theo sc bn tnh.
Trng hp 3.- Ti trng ln nht trong iu kin khng lm vic.
Trong trng hp ny cc ti trng phi k n l trng lng bn thn my, ti trng gi trong iu kin bt bnh thng. Cc chi tit my trong trng hp ny c thit k hoc tnh kim nghim theo n nh.
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Chng 2
CC C PHN CA THIT B MANG TI
1. - Cp thp v cc thit b c nh u cp.1.1- Cp thpCu to: c ch to t cc si thp bng phng
php bn. Cc si thp c ch to bng phng php ko ngui, c bn cao (1400-2000 N/mm2). Cc si thp bn thnh tao cp hoc cp bn n. Tao cp c th c nhiu lp si vi ng knh si thp c th khc nhau.
Phn loi:- Theo cu to: + Cp bn n, nu c bn trc tip
t cc si thp. + Cp bn kp: c hnh thnh t nhng tao cp (cp bn n) bng phng php bn + Cp bn ba: c hnh thnh bng phng php bn t nhng tao cp (cp bn kp)
- Theo c im v tip xc: Nu cc si thp trong cp tip xc nhau theo im, ta c cp tip xc im. Tng t, ta c cp tip xc ng.
- Ngi ta cn phn bit cp bn xui khi chiu bn ca cc lp si v tao cp l nh nhau, cp bn cho khi chiu bn ca cc thnh phn ny l ngc nhau.
So vi cp bn cho cp bn xui mm v do vy c tui th cao hn. Tuy nhin cp d b bung ra khi mt u cp t do.
Trong mt s trng hp ngi ta dng cp chng xoay c kt cu bn hn hp.
-
Cp bn xui
Cp bn n
Cp bn cho Cp bn kp
Tnh, chn cp:Trong qu trnh lm vic, cc si thp trong cp chu lc
phc tp, gm ko, un xon, dp.... trong ko l ch yu. tnh chon cp ngi ta s dng cng thc kinh nghim sau:
Smax n STrong : Smax: lc cng ln nht
n: h s an ton, c chn theo CLV,S: lc ko t cho php, thng c xc nh
bng thc nghimCn c vo lc ko t cho php, tin hnh chon cp cho
thit b.Thc t, qu trnh ph hng cp khng xy ra t ngt. Cc
si thp trong qu trnh chu lc s b t dn v mi, cho n khi s si thp b t tnh trn mt bc bn cp qu nhiu s dn n t cp.
Tui th ca dy cp c quy nh trn c s s si thp b t tnh trn mt bc bn cp.
1.- H s an ton bn ca cp thp:Cng dng thit b nCp ti trong cc thit b dn ng bng tay 4
Ch nh 5Cp nng vt trong cc thit b dn ng Ch trung bnh 5,5
-
bng ng c Ch nng v rt nng 6Cp neo cn v ct 3,5Cp dung trong ti xy dng c ch ngi 9
Vn < 1m/s 9Vn = (1 2) m/s 12Vn = (2 3) m/s 13Vn = (3 4) m/s 14
Thang my
Vn = (4 5) m/s 15
hn ch s ph hng cc si thp do mi, ngi ta quy nh t s ng knh cp v ng knh rng rc (tang):
ed
D
c
o
H s e:Dng cho cc loi c cu nng vt, nng cn v Palng in.
Ch lm vic e Loa myNh 18 Cn trcTrung bnh 20 NtNng 25 NtRt nng 30 NtDn ng bng tay 16 Nt
20 Palng in
Quy nh s si thp b t tnh trn mt bc bn cp:
H s an ton n
Kt cu cp
6 x 19 6 x 37Bn xui Bn cho Bn xui Bn cho
6 6 12 11 126 - 7 7 14 13 267 8 16 15 30
-
1.2.- Thit b c nh u cp: Dy cp phi c c nh mt u trn thn my (vo cht,
trc), u kia c nh trn tang. c nh u cp trn thn my c th dng cc phng
php sau:- Phng php tt cp.- Phng php dng bulng kp.- Phng php dng ng cn.- Phng php dng kha chm.
trnh s tip xc trc tip gia dy cp v cht ngi ta thng dng vng lt cp
-
- Trng hp dng bulng, tnh lc sit theo cng thc:P =
c
Sn
.2
. vi: c: h s cn chuyn ng (c = 0,35 0,4)
n: h s an ton kp cp ( n = 1,25 1,5)
S: lc cng dyKim tra bn cho bulng:
][
4
..
.3,12
1
dZ
P
- Trng hp dng kho chm: Gc chm < vI l gc ma st; l gc chm
-
c nh cp trn tang, c th dng cc phng php:- Tm m t trong lng tang kt hp vi bulng.- Chm t trong lng tang- Tm kp kt hp vi bulng gi cp trn b mt tang .
Tnh ton cho trng hp dng tm kp gi cp trn b mt tang bng bulng:
gim ti cho bulng kp cp trn tang thng xuyn phi tn ti t nht 1,5 vng cp. Do lc cng cp ti v tr A c gi tr:
fA e
SSS max1
Trong f : h s ma st gia cp vi mt tang; gc m = (4-6).
Lc S1 c cn bng bi cc lc: - Ma st gia cp- mt tang v cp - tm kp trong
on AB,CD.- Ma st gia cp-mt tang trong on BC.
Lc sit bulng P c xc nh theo cng thc sau:
c
SnP 1
..65,0
-
Trong : n: h s an ton kp cp (n = 1,25 - 1,5).c: H s cn chuyn ng ca cp trong tm kp
(c = 0,35 - 0,4)0,65 l gi tr k n nh hng ca ma st gia
cp vi b mt tang trong on BC.Ngoi ra cn phi k n lc gy un bulng vi Mu = P.f.l.
T tnh kim tra bn bulng theo cng thc:
2.- Rng rc:Thng c ch to t vt liu thp hoc gang xm bng
phng php c hoc gia cng c. Thng c ch to lin khi nu ng knh khng ln (
-
m bo cc tiu ch ny, cc kch thc c quy nh nh sau:
r = (0.53 - 0.6)d 2 = (400 - 600)h = (2 - 2.5)d
Cp khi vng qua puly cn m bo iu kin: Thng = 60Hiu sut ca rng rc:Khi cp vng qua rng rc th s c cc tn tht do:- Ma st trong trc- Khc phc cng ca dyTheo nh ngha, hiu sut ca rng rc c xc nh:
Trong Sv l lc cng cp trn nhnh cun vo rng rcSr l lc cng trn nhnh ra khi rng rc.
Tu thuc vo trc l ln hoc trt m ta c hiu sut:Loi iu kin lm vic Hiu sut
Bi trn km, lm vic nhit cao 0.94It khi c bi trn 0.95Bi trn nh k 0.96
trt
Bi trn t ng 0.97Bi trn km, lm vic nhit cao 0.97 lnBi trn nh k 0.98
h
D
1
tantan
r
v
S
S
Sv Sr
-
Chng 3: Palng cp.n: L h thng gm cc rng rc c nh v rng rc di
ng lin kt vi nhau qua dy cp nhm lm li lc hoc li tc. Trn hnh v cho ta mt s s palng cp thng gp.
Thng s c bn c trng cho palng cp l bi sut, k hiu a, c nh ngha nh sau:
Bi sut ca palng cp l s ln lc cng trong cc nhnh dy gim i so vi trng hp treo vt trc tip.
Tu thuc vo s nhnh dy cun ln tang , ta phn bit palng n v palng kp: Trong trng hp ch c mt nhnh dy chy ln tang, ta c palng n, trng hp th hai l palng kp.
i vi palng n th bi sut ca palng ng bng s nhnh dy treo vt.
-
Palng kp c th c xem nh 2 palng n ghp li, mi palng n chu 1/2 ti.
Hiu sut ca Palng, Lc cng cp ln nht: (Xt cho trng hp palng n)
Trong trng hp vt nng c treo tnh, lc cng trong cc nhnh dy l nh nhau v bng Q/a. Khi vt nng dch chuyn (chng hn theo hng i ln) th lc cng trong cc nhnh dy c s sai khc. Nh phn hiu sut ca rng rc, lc cng hai nhnh ca rng rc c quan h:
r
v
S
S
Gi s c s ca palng cp nh hnh v,Ta c:S1 =S1S2 = S1.S3 =S2. = S1.2..Sa = = S1.a-1_____________________S1 + S2 + S3 + Sa= S1(1 + +2 + 3+ + a-1) = Q
1
1.1.1
a
S = Q
Do vy, lc cng dy trong nhnh S1 s l:
Puly cn bng
QTang
S1S2S3S4Sa
-
aQS
1
1.1
Nu trc khi cun ln tang dy cp cn phi vng qua m rng rc th ti nhnh cp cun ln tang lc cng dy s l:
mam QS
S
.11
.1max
Hiu sut ca palng:Gi p l hiu sut ca palng, theo nh ngha ta c:
1.
.1
.
.
max aahS
hQ map
Nhn xt:1.- Khi tng a th p s gim, do khi chn a phi cn nhc
m bo lc cng dy nh m khng lm hiu sut qu thp.Mt khc khi tng a th lng cp cun ln tang s tng (gp
a ln) dn n kch thc tang ln, ng thi tc nng vt chm li (gim a ln).
2.- Vi palng kp th vic tnh ton c p dng cng thc ca palng n vi ti trng bng Q/2 v bi sut a/2.
4.- Tang cun cp:Cng dng: Cun cp di chuyn vt nng.Hnh dng: Thng c dng hnh tr. Trong mt s trng
hp c th c dng nn hoc ng knh thay i. B mt tang c th ct rnh hoc trn. Vi tang tr c th cun nhiu lp cp; Vi tang ct rnh ch cun mt lp cp.
Vt liu v phng php ch to: C th ch to bng phng php c bng vt liu gang xm hoc thp hoc bng phng php hn vi may t thp tm cun.
Tang c lp trn trc bng ln. C th truyn chuyn ng quay cho tang t trc tang hoc trc tip ln tang (qua bnh rng c nh vi thnh tang, hoc khp rng c bit)
Cc thng s c bn: Gm ng knh, chiu di, b dy thnh tang.
ng knh danh ngha:i vi tang ct rnh, ng knh danh ngha (D0) c quy
c tnh n tm cp.
-
i vi tang trn, ng knh danh ngha (D0) c quy c tnh n tm lp cp th nht.
ng knh tang c chn theo iu kin cp khng b un qu nhiu e
d
D
c
o
Chiu di phn lm vic:Khi nng vt vi cao nng H, bi sut palng a th di
cp cun ln tang l L = H.a.i vi tang ct rnh: Mt cch gn ng chiu di mt
vng cp cun l .D0, nh vy s vng cp cun ht chiu di L l: Z0 = H.a/D0.
Theo quy nh v an ton, trn tang nht thit phi tn ti t (1,5 - 2) vng cp d tr, mt khc s vng cp nm trong tm kp ( c nh cp trn tang) phi l(1-1,5) vng. Do chiu di phn tang c ct rnh l:
L0 = (Z0 + Z dt + Z k).t t: bc rnh cp, thng ly gi tr t = dc + (1-
2)mmi vi tang trn: S lp cp thng khng ln hn 6. Gi
ng knh tnh n tm lp cp u tin l D1. Gi s c n lp cp; mi lp c Z vng cp, vy chiu di lng cp c th cun c l:
L = .Z(D1 + D2 ++Dn) = .Z(n.D +n2dc)vi Dn = D + (2n-1)dc (D: ng knh ngoi ca tang)
Mt khc dung lng cp cn cun vi cao nng H v bi sut ca palng a l :
2 dc
DD'
-
Lc = H.a +(2 - 3 )Do.Vy s vng cp c rt ra t iu kin L = Lc
).(
.).32(.2
cdnnD
DaHZ
Chiu di phn lm vic ca tang s l: Lo = Z.t vi t = dc. (vi l h s do cc vng cp khng st nhau, thng chn = 1,1)
B dy thnh tang: Tnh chn trn c s m bo sc bn.Trong qu trnh lm vic, tang chu ng sut nn, un, xon
trong ng sut nn l ln nht, do dy cp cun quanh tang gy ra.
Xt trng hp mt vnh tang ct rnh c dy mt bc cun cp t chu lc nh hnh v:
Xt phn t vnh tang c tit din dF = Rd.t, chu lc tc dung dN = p.dF.
Chiu tt c cc lc tc dng trn vnh tang ln phng y, ta c:
tpRdRtpdNS ...2cos...2cos.2.22/2/
max
Suy ra: tR
Sp
.max
t
D'D
Smax
dR
Smax
y
x
pdF
dN
-
p dng cng thc Lame khi xem thnh tang nh ng dy (c p sut mt ngoi l p, p sut mt trong = 0), ta c:
tSR
pRR
Rp
RR
Rp
.).'(
.2
'
2. max
2
22
2
max
C th chn s b b dy thnh tang theo cng thc kimh mghim:
Vi tang lm bng gang: = 0,02 D + (6-10)mmVi tang lm bng thp: = 0,01 D + 3 mm
-
1chng 4:
Cc phng php ni trc tang vi trc hp gim tc
Thng thng, tang c truyn mmen xon t trc qua mi ghp then. Trong mt s trng hp, mmen xon c truyn trc tip cho vnh rng ghp trn thnh tang. Trc tang c ni vi trc ra ca hp gim tc qua cc phng thc sau:
- Bng khp ni.- Bng khp rng c bit.
5.- Thit b mang tiYu cu chung i vi thit b mang ti l:- m bo an ton- Thi gian xp d ngn, nhm nng cao nng sut.- Trng lng nh- Kt cu n gin, gi thnh r5.1.- Mc treo: L thit b vn nng, thch ng vi mi vt
liu vn chuyn.Tu thuc hnh dng, ngi ta phn bit mc n v mc kp. Theo phng thc ch to, c mc lin khi v mc ghp.
Yu cu cao v an ton. trnh cp tut khi mc cn thit phi trang b kho ming mc.
5.1.1.- Mc n:Vt liu ch to: Thp t Carbon (C20, C25..)Phng php ch to: Rn t do hoc rn khun.Hnh dng: Nh hnh v.
-
2Cc dng hng ca mc n:- t cung mc,- Gy thn mc ( ti tit din A-A)- Dt thn mc (ti tit din B-B)- Mn , bin dng.. thn mc.Tnh ton mc:- Kim nghim bn ko ti tit din cung mc:
21.4
d
Q
- Kim tra bn ko + un ti tit din A-A (theo l thuyt thanh cong).
yR
y
kRF
M
RF
M
F
Q
oo
u
o
u ....
Trong :- F: din tch tit din mt ct,- Mu: momen un tit din; Mu = - Q. Ro- Ro bn knh cong tnh n lp trung ho ca tit din,- y: tung tnh t lp trung ho n im xt.- k: h s hnh dng hnh hc ca mt ct.
2
1
1y
y o
dFyR
y
Fk
p dng cng thc trn , ta c:
hD
c
kF
QD
c
kF
Q
2
..
.2.
.
22
11
Thng chn tit din hnh thang m bo iu kin sc bn u cho tit din. Trong mi trng hp ta cn kim tra iu kin 1 []
Tng t, chng ta c cng thc xc nh ng sut php ti mt ct B-B, vi iu kin lc gy ko lch tm l Q2 = Q/2. Ngoi ra cn phi k thm ng ct
= Q/2.F,ng sut tng ng theo thuyt bn th nng bin i hnh
dng: 22 .3
5.1.2.- Mc kp:
-
3 Thng c s dng mc cc vt th c dng hnh tr, chiu di ln, chu lc i xng.
Hnh dng v s tnh ton ton mc kp c trnh by trn hnh v.5.2.- Cm treo mc:
Trong thit b nng thng dng ch yu l cm treo mc vi nhiu nhnh cp vng qua mt s cc rng rc. Cc rng rc c lp trn cc thanh ngang trn bng bi. Mc treo c lp trn thanh ngang di bng c vng ta di c dng cu c th t la c.
Thanh ngang trn v di c lin kt vi nhau bng cc tm chu lc. Ngi ta phn bit cm treo mc thng v cm treo mc ngn.
Trong trng hp cm treo mc ngn, trc rng rc cng ng
thi l thanh ngang. Do s puly dn cp phi l s chn.Trong qu trnh lm vic, thanh ngang chu un vi Mu ln
nht ti mt ct chnh gia thanh. uWu
u
M
Trong : Wu l momen chng un c tnh n phn l x u mc.
-
4Ngoi ra cn phi kim tra ng sut dp ti tit din ni vi tm treo.
p Q/(2.d1.2) < [p]
Cm treo mc thng Cm mc treo ngn
5.3.- Cc thit b cp vt nng:Trong trng hp vt mang c hnh dng kch thc nht
nh, tng nng sut xp d, ngi ta thng dng cc thit b cp chuyn dng.
5.3.1.- Thit b cp i xng:
Thng dng cp cc vt nng hnh khi nhma st gia 2 m kp vi b mt vt nng. c th nng c th lc ma st phi ln:
b b
c
QT.cos
T.sin
C
-
5F = k.Q/2 trong k l h s an ton; k = 1.5Hoc: N = k.Q/(2.f) ; f l h s ma st.B qua khi lng cc thanh kp, vit phng
trnh cn bng momen i vi im C, ta c:0...sin..cos. dNaFcTbT
Mt khc:
cos.2Q
T
Do :
c
baf
dk
f
dkakcb
df
Qka
Qkc
Qb
Q
tan
0...tan
0..2
..2
..tan.2
.2
Phng trnh trn cho ta quan h gia cc gi tr a,b,c,d,. c th cp c nhiu vt c kch thc khc nhau,
m cp lin kt vi tay n bng khp quay:
Ngoi ra c th dng thit b kp i xng vn nng:
2.2.- Thit b cp khng i xng; nng cc vt th mng nh dm thp, tm thp ngi
ta thng dng thit b cp lch tm, c s nh hnh v.
Q
N1
F1F2N1
-
6 thit b lm vic c th lc tng hp N & F phi i qua tm khp quay. Mun vy:
Tan f1
Trong f1 l h s ma st gia bnh lch tm v vt kp_________________________________________________________________________
Thng s v ray thng dng
Ray b b1 h B G [KG/m]
30 55 60 120 105 3024 50 54 110 95 24
-
Chng 5:
THIT B DNG & PHANH HM1.- GIi THIU CHUNG
Thit b dng l c cu dng gi vt nng trng thi treo nh vo kt cu ca n. Thit b ny ch cho php my trc hot ng theo chiu nng vt. Thng dng thit b dng bnh cc,thit b dng dng con ln.
Thit b phanh hm dng dng hn chuyn ng sau mt thi gian ngn hoc hm iu ho tc . thc hin qu trnh phanh, hm, thit b phi c tiu tn mt nng lng.
Ngi ta phn bit cc thit b phanh hm trn c s:- Theo kt cu: Phanh m, phanh ai, phanh a, phanh nn,
phanh ly tm,- Theo trng thi hot ng: Phanh thng ng, phanh
thng m,- Theo nguyn tc iu khin c phanh t ng, phanh iu
khin bng tay, chn.
Yu cu:Cc thit b phanh hm phi m bo an ton, c tin cy
cao. Quy phm v an ton lao ng quy nh cht ch cc tiu ch v vic s dng v loi b phanh.
- Phanh phi c momen phanh ln.- ng m phanh nhanh, nhy, tin cy cao- Kt cu n gin, d ch to- D kim tra, iu chnh, thay th- Nh gn, gi thnh r.
Thng s c bn tnh ton thit k phanh l momen phanh (Mph). Momen phanh phi chn ln m bo phanh c. Tuy vy nu gi tr Mph qu ln s dn n ti trng ng ln nh hng n tnh bn ca cc chi tit my.
-
Ga tr momen phanh c chon theo cng thc:Mph = nph.Mx
Trong : Mx l momen xon do trng lng vt nng gy ra trn trc t phanh.
Theo nguyn tc c th t phanh bt c trc no ca c cu. Tuy nhin nu b tr phanh trn trc ng c th kch thc phanh s nh gn.
Vi trng hp b tr phanh trc ng c th Mx c xc nh theo cng thc:
.i.a.2
.QDM
o
ox
nph l h s an ton phanh, c xc nh theo CLV. Gi tr nph:
CLV nphNh (M3, M4 ) 1,5TB (M5, M6) 1,75N (M7) 2RN (M8) 2,5
Ngoi ra momen phanh c th c kim tra theo iu kin:Mph = Mt + M1 + M2
Trong : M1 l mmen cn thit khc phc lc qun tnh ca cc b phn my c chuyn ng tnh tin.
M2 l mmen cn thit khc phc lc qun tnh ca cc b phn my c chuyn ng quay.
2.- Thit b dng bnh cc:a.- S - nguyn l lm vic:Gm bnh cc n khp vi con cc. L xo cc m bo s n
khp gia 2 khu ny. Bnh cc ch c quay mt chiu do dng rng khng i xng ca n.
V tr trc lp con cc nn b tr sao cho phng lc vng ln nht t bnh cc tc dng ln con cc i qua tm ca trc.
Bnh cc c th lp trn bt c trc no ca c cu nng. Tuy vy kch thc c cu cc khng ln th nn lp trn trc nhanh.
-
Trong trng hp lp bnh cc trn trc tang th an ton cao, nhng kch thc ca c cu cc ln.
m bo cho con cc vo n khp vi rng bnh cc d dng th gc trc ca rng phi m bo iu kin
Psin.tan> Pcoshoc
Trong l gc ma st. Vi vt liu thp 200
Tnh ton c cu cc:V tr chu lc ln nht l khi con cc chm vo n khp vi
rng bnh cc. Di tc dng ca lc vng P, rng bnh cc c nguy c:
- B dp b mt do p sut - B gy chn rng do un.
a.- Theo iu kin bn dp: p
b
Pp vi
Z.m
M.2
D
M.2P xx
Trong : b l chiu rng ca rng bnh cc; b = B.mThay vo ta c:
e
h
B
a
P
Q
D
-
Bx
B2 .Z.p
M.2mp
.Z.m
.Mx.2p
b.- Theo iu kin bn un ta c:
u
u
W
M
trong : Mu = P.h = Z.m
M.2
D
M.2 xx
Wu = b.a2/6
Vi b = b.m v a = 1,5 m h = m , ta c:
3b m.Z..25,2
Mx.12
Thit b dng kiu con ln: C s hot ng nh hnh v, gm v 1 gn vo thn
my, li 2 lp c nh vi trc, c cc rnh cn t con ln 3. Khi quay theo chiu nng ( ngc kim ng h) li 2 quay
cng c cu. Theo qun tnh, con ln nm phn khe h rng ca rnh cn. Khi quay theo chiu h, cc con ln b y dn vo phn hp ca rnh cn gy t hm v vt c gi trng thi treo.
F
F
-
Quan h kch thc c xc nh trn c s m bo iu kin t hm ca con ln trong mt chm.
m bo iu kin t hm ca con ln:tg /2 < tg hoc :
Lc nn ln mi con ln c xc nh t iu kin cn bng lc ca bc2:
Z.2
D.N.fMx hoc: Z.D.f
M.2N x
vi = 1,2 - 1,4 h s an ton dng.
Trn c s N, xc nh bn tip xc ca con ln.
3.- Phanh m:Qu trnh phanh c thc hin nh s ma st gia cc m
phanh v bnh phanh. C th c phanh 1 m, phanh 2 m. Lc ng phanh c th l i trng, hoc l xo. Lc m phanh l lc nam chm in hoc bm thu lc. Phanh m c s dng rng ri trong cc loi ti v c cu ny trc c truyn ng in c lp. y chng ti gii thiu phanh 2 m l xo in t.
S , nguyn l lm vic:
Nguyn l lm vic:Phanh ng do lc l xo phanh 5. Phanh m nh nam chm in 8, kt hp vi l xo ph 9. ai c phanh 6 c th iu chnh c lc phanh. ai c 7 m phanh, phc v sa cha. C hnh trnh 10 hn ch m ca cc m phanh.
Tnh ton lc l xo: phanh c: MF = Mph
12
3
64 5 7
89
10
a
L D
N
K
-
F.D = Mph N.f.D = Mph N = Mph / f.D
Lc cn thit phanh K = N.a/L=
L
a
Df
M ph..
Lc trn l xo phanh cn thit to ra phI khc phc thm lc trn l xo ph v lc do cn nam chm tc dng: Plx = K + P ph + P nc
Lc ln nht tc dng ln l xo c xc nh khi m phanh. Lc ny, l xo b nn mt on 2..L/a. C:
Plxmax = Plx + c.2..L/a trong : c l cng ca l xo. Dng Plxmax kim
tra bn cho l xo.Kim tra p lc trn b mt ma st theo cng thc:
pS.b
1.
D.f
M
F
Np ph
N
Trong : b l b rng m phanhS = D/2.sin ; = 60 - 900: gc m ca m phanh
trn bnh phanh.
4.- Phanh ai:Thc hin qu trnh phanh nh vo ma st gia dy ai v
bnh phanh. Dy ai thng bng thp (c th lt g, da, hoc aming tang ma st).Lc ma st gia dy ai v bnh phanh bng hiu lc cng gia hai nhnh ai. Quan h lc cng trn hai nhnh ai c xc nh theo cng thc Euler:
S2 = S1.e f Trong b l gc m gia dy ai v bnh
phanh. phanh c th: MF = Mph
F.D/2 = Mph D: ng knh bnh bnh phanh
phf MDeSDSS 212. 112
-
)1(
..2
)1(
.2
1
1
f
fph
f
ph
eD
eMS
eD
MS
p lc trn b mt phanh:dA
dNp Trong :dN vi phn p
lc; dN = S.ddA: Vi phn din tch;dA = D.B.d/2
T ta c BD
Sp
BD
Sp
.
.2
.
.2 1min
2max
a.- Phanh ai n gin: S nguyn l lm vic nh hnh v. C:
L
aSK
.2
Khi bnh phanh i chiu quay, S1 v S2 i v tr cho nhau. Do vy lc K s thay I gi tr. Ch thch hp cho c cu nng khi mmen phanh khi h ln hn mmen phanh khi nng. f
nangph
haph e
M
M
H Nng
K
D
aL
-
1Chng 6: Phanh ai hai chiu
Trong trng hp momen phanh khng thay I th phI s dng phanh ai hai chiu theo s sau:
Trong trng hp ny, lc phanh K c xc nh theo cng thc:
L
aSSK
.12 ,
Do lc phanh khng ph thuc vo chiu Mmen phanh.
p lc cho php I vI mt s vt liu dng lm bnh phanh.Vt liu p lc [p] N/mm2
Tm lt ai Bnh phanh Phanh dng Phanh hn ch tc
Thp Gang hoc thp 15 10Aming Gang hoc thp 6 3
G Gang 6 4
5.- Phanh p trc:L cc loi phanh c lc phanh ng phng vi trc t
phanh. Thuc loi phanh ny c th k cc loi phanh a, phanh nn.
S nguyn l lm vic ca phanh nn c th hin nh trn hnh v. y lc phanh do l xo tc dng thng qua tay n ln trc t phanh. p lc trn mt ma st nn to nn
K
D
La
aK
-
2mmen ma st thng c momen phanh. trnh kt mt nn, nn ly gc nn /2 ln hn gc ma st ca b mt tip xc. Thng ly = 16 25o.
phanh c: MF Mph f.N.Dm/2 Mph f.P.Dm/(2.sin) Mph
m
ph
Df
MP
.
sin..2
Kim tra bn b mt tip xc theo sc bn dp. p
DD
P
DD
Np
)'(
.4
)'(
sin..42222
Phanh a c xem l phanh nn vI gc = 90o. gim lc phanh ngi ta thng dng nhiu i mt a. Trong trng hp ny, lc phanh P c xc nh:
m
ph
DfZ
MP
..
.2 vi Z l s i mt a ma st.
6.- Phanh t ng:
L nhng loi phanh m lc phanh c to ra bi chnh trng lng ca vt nng. Do vy phanh ny cn c tn l phanh trng vt.Tu theo trng thi tip xc ca cc b mt ma st trng qu trnh h vt m ngi ta phn bit phanh t ng c mt ma st tch ri hay khng tch ri.
Tnh cht t ng ca loi phanh ny th hin cc im sau:
-
3- T ng thc hin qu trnh phanh,- T ng iu chnh lc phanh.
a.- Phanh t ng c mt ma st khng tch ri:
Nguyn l lm vic:DI tc dng ca trng lng vt nng, trn trc ca bnh vt
(1) c Mbv, v do trn trc vt (2)c lc chiu trc P. Lc chiu trc P ng vai tr ca lc phanh v lun lun tn ti khi c trng lng vt nng. C cu cc (4) ch cho php bnh cc quay theo chiu nng vt.
Khi nng vt c khI cng chuyn ng nh ma st trn cc mt tip xc (3). Khi ngng nng, bnh cc b gi li, ng thi do ma st trn cc mt (3) nn trc vt 2 khng quay v dn n vt c gi trng thi treo.
Mun h vt phI tc dng mt mmen h thng c ma st trn cc mt (3).
Tnh ton cc thng s hnh hc ca phanh: phanh c th MF MphMomen ma st do lc phanh P gy ra: tp
bv
moF fDa
DQDM ....sin...2
Momen phanh:
otpo
otvph ia
DQnMnM ...
..2
...
So snh ta c:f
Dn
iD
obv
om ..sin..
.
1Nu iu kin trn khng tho mn th phI iu chnh cc
thng s phanh, c th l Dm, f.Mun h vt phI tc dng mt Mmen h:
Mh = Mph -Mtv = (n - 1)Mtv
1
23
4
Smax
-
4Nh vy qu trnh h vt c tiu hao nng lng, ng thi cc mt st c trt nn chng mn. y l nhc im c bn ca loi phanh ny.
a.- Phanh t ng c mt ma st khng tch ri:
Cc mt ma st (2-3 ; 3-4) c th tch ri nhau trong qu trnh h vt do kt cu mI ghp ren gia bnh rng (5) v trc (1). a ma st (3) ng thi cng l bnh cc, c lp lng khng vi trc 1. C cu cc (3) ch cho php bnh cc quay theo chiu nng vt.
Di tc dng ca trng lng vt nng, trn bnh rng (5) s c mmen bnh rng (MBR). Do kt cu ca mi ghp ren vt nn MBR ny ng vai tr mmen vn ai c, lm cho cc b mt ma st hot ng.
Khi nng vt, c c cu cng chuyn ng.Khi ngng nng, c cu cc hot ng v nh ma st trn cc
mt ma st nn vt c gi trng thi treo.Khi trc (1) quay theo chiu h vt, cc mt ma st tch rI,
vt nng t i xung. Mt khc MBR lun c xu th lm cho cc mt ma st hot ng. Do , qu trnh h vt c thc hin mt cch iu ho.
Tnh ton cc thng s hnh hc ca phanh: phanh c th MF MphMomen ma st do lc phanh P gy ra: fPDfPDM mmF ..2
.2
Trong P l lc dc trc trn bnh rng (5) (lc sit ai c) do trng lng vt nng gy ra. xc nh P ta xt s cn bng lc ca bnh rng (5).
)(.2
.2
.. tgdPDfPM mmBR
3
3
421
5
-
5Suy ra : otpmm
o
o
mm
BR
tgdD
fia
DQ
tgdD
f
MP
..
)(.22
....2
..
)(.22
.
Thay vo cng thc tnh MF ta c:f
tgdD
fia
DDQM otp
mmo
mo ...
)(.22
....2
..F
Momen phanh:
otpo
oBRph ia
DQnMnM ...
..2
...
So snh ta c: MF Mph n
tgdmDm
f
fDm )(.
22.
.
Trong : Dm l ng knh trung bnh ca cc mt a ma st,dm l ng knh trung bnh ca ren mi ghp.
Nu iu kin trn khng tho mn th phi iu chnh cc thng s phanh, c th l Dm, f.
7.- Tay quay an ton:Theo quy phm an ton, tt c cc thit b nng dn ng bng
tay u phi c trang b tay quay an ton. Tay quay an ton l tay quay c trang b phanh cng vi c cu cc gi vt trng thi treo khi ngng nng. Cc loi phanh trng vt phn trn cng nh tay quay hnh v bn l cc v
L xo phanh Roto Stato Stato Stato Stato Bnh phanh B phanh phanh
Hnh thnh khi lin kt cng
-
6d v tay quay an ton.
-
Chng 7:
CC C CU CNG TC CHNH TRONG MY TRC
I.- C CU NNG VT:L c cu c mt trong tt c cc thit b my trc. TCVN
5862-95 quy nh 8 nhm ch lm vic cho c cu nng, k hiu M1...M8. Tu theo ngun dn ng, c cu nng c chia thnh c cu nng dn ng bng tay v c cu nng dn ng bng my.
1.- c im:
Dn ng bng tay- Trng ti khng ln,
thng Q 5T- C th c yu cu khng
cao v vt liu, cng ngh ch to v lp rp mt s b phn my.
- B phn truyn ng thng h, bi trn nh k.
- B tr phanh t ng kiu bnh rng hoc trc vt.
Dn ng bng my- Ti trng ln, c th t
n 500T- Yu cu cao v vt liu,
cng ngh ch to v lp rp cc b phn my.
- B phn truyn ng thng c b ch to di dng hp gim tc, che kn v bi trn thng xuyn bng du.
- B tr phanh m hoc phanh a l xo in t.
-
2.- Trnh t tnh ton c cu nng dn ng bng tay:
a.- S liu cn cho trc: - Trng ti Q- cao nng H
b.- Yu cu tnh ton: - m bo an ton, bn cc chi tit, b phn my,- Khng yu cu m bo nng sut ,- T s truyn b truyn c xc nh trn c s m bo
nng c vt nng theo yu cu- Cc b truyn bnh rng c tnh kim nghim theo sc bn
un.
c.- Trnh t:1.- Chn loi dy v s treo vt. Thng dng cp thp
hoc xch hn.2.- Tnh lc cng dy ln nht S max, trn c s tnh chn
dy. 3.- Tnh cc kch thc c bn ca tang (a xch) v rng
rc.4.- Tnh ton, thit k b truyn:
a.- Xc nh t s truyn chung:tq
tgo M
Mi
b.- Phn phi t s truyn v thit k cc b truyn.5.- Quyt nh v tr t phanh v tnh ton thit k phanh.6.- Thit k cc b phn cn li (cm mc treo, cm tang,
khp ni)
3.- Trnh t tnh ton c cu nng dn ng bng ng c:
-
a.- S liu cn cho trc: - Trng ti Q- cao nng H- Vn tc nng vt Vn- Ch lm vic
b.- Yu cu tnh ton: - m bo an ton, bn cc chi tit, b phn my,- T s truyn b truyn c xc nh trn c s m bo vn
tc nng theo yu cu- Cc b truyn bnh rng c tnh kim nghim theo sc bn
tip xc.
c.- Trnh t:1.- Chn loi dy v s treo vt. Thng dng cp thp
hoc xch hn.2.- Tnh lc cng dy ln nht S max, trn c s tnh chn
dy. 3.- Tnh cc kch thc c bn ca tang (a xch) v rng
rc.4.- Tnh ton, thit k b truyn:
a.- Xc nh t s truyn chung:dc
tgo n
ni
b.- Phn phi t s truyn v thit k cc b truyn.5.- Quyt nh v tr t phanh v tnh ton thit k phanh.6.- Thit k cc b phn cn li (cm mc treo, cm tang,
khp ni)
4.- Qu trnh m my c cu nng:Qua trnh m my c cu nng l qu trnh chuyn c cu t
trng thi tnh sang trng thi ng. Do ngoi mmen cn tnh do trng lng vt nng gy ra, ng c cn phi khc phc mmen cn ng do qun tnh ca cc b phn my chuyn ng
-
c gia tc gy nn. Phng trnh mmen trc ng c trong giai on m my:
Mm = Mt + M1 + M2Trong :
- Mt l momen cn tnh do trong lng vt nng gy ra trn trc ng c; du + ng vi trng hp nng vt, du - ng vi trng hp h vt.
- M1 l momen cn ng do cc b phn my chuyn ng tnh tin c gia tc gy ra trn trc ng c.
- M2 l momen cn ng do cc b phn my chuyn ng quay c gia tc gy ra trn trc ng c.
C: ...2.
o
ot ia
DQM
Xc nh biu thc ca M1
...2.
1o
oqd ia
DPM
vI Pq l lc qun tnh do vt nng gy ra,
mo
dco
m
tgo
m
nmq tia
nD
g
Q
ta
nD
g
Q
t
V
g
Qj
g
QP
...60
...
..60
...
.60..
Thay biu thc Pq ta c:
1
....
..
375
1
...2.
...60
...
...2
.22
2
1m
dc
o
o
o
o
mo
dco
o
oqd t
n
ia
DQ
ia
D
tia
nD
g
Q
ia
DPM
Xc nh biu thc ca M2Gi :
- Gk l trng lng ca tit my quay th k lp trn trc th l.- l l gia tc gc ca trc th l.- Ik l momen qun tnh khi lng ca tit my quay th k.
4.
2kk
k
D
g
GI vI Dk l ng knh qun tnh ca tit my
quay kMmen lc qun tnh ca tit my quay k (tnh trn trc l):
mo
dckk
mo
dckk
m
lkk
m
lkklklq ti
nDG
ti
n
g
DG
t
n
g
DG
tg
DGIM
..
375
.
..60
..2.
.4
.
.60
..2.
.4
..
.4
..
2222
/
-
Quy dn v trc ng c, ta c:
lmo
dckkq
k
ti
nDGM
12
2
1/..
.375
.
Vy
n
k m
dcIkkm
l
n
k mlo
dckkd t
nDG
ti
nDGM
1
2
1 1 12
2
2 .375
..
1.
..
375
.
Do : Mm = ...2.
o
o
ia
DQ + 1
....
..
375
122
2
m
dc
o
o
t
n
ia
DQ +
n
k m
dcIkk
t
nDG
1
2
.375
..
(*)Phng trnh (*) c s dng kim tra iu kin m my
ca ng c in nu bit thI gian m my tm. Ngc li, nu bit mmen m my ca ng c th tnh thi gian m my theo cng thc:
tmm
dc
om
n
kIkk
o
odcm
MMGD
n
ia
QM
DGia
DQnt
1.).(
.375
...2
1...
1.
.
.
375
2
1
222
2
Trong : (GD)m l momen quy dn v trc ng c.
n
kIkk
o
om DG
ia
DQGD
1
222
22 ..
1.
.
.)(
-
Chng 8:
Chn ng c in cho thit b nngng c c chn phi m bo cc tiu ch sau:
- Momen quay ln m bo khi ng c vi gia tc cho trc.
- ng c khng b nng qu gii hn cho php iu kin lm vic.
- Cng sut ng c khng qu ln v s gy gia tc m my ln, ng thi khng kinh t.
c im ca thit b nng l lm vic theo ch ngn hn lp li. Trong mt chu k lm vic, my thc hin nhiu mc tI khc nhau trong nhng nhng khong thi gian tng ng khc nhau. Do ngi ta thng s dng Momen trung bnh Mtb thay cho momen tnh tin hnh xc nh cng sut ca ng c.V mt tiu hao nng lng v pht nhit ca ng c th Mtb c xem l tng ng vi ch gia ti thc t
Mt trong cc thng s c trng cho ch lm vic ny ca ng c in l cung lm vic thc t ca ng c k hiu C%. Cc gi tr ny thng khng trng vi cng chun (C%ch) l 15,25,40,60 %. Do sau khi tin hnh tnh ton cng sut trung bnh ca ng c, phi chuyn sang cng sut tng ng vi cng chun:
chtbtd CD
CDNN
Trnh t tnh chn ng c c thc hin nh sau:1.- Xy dng biu gia ti thc t ca c cu trong cc chu
k lm vic, trn s s xc nh cng chy thc t ca ng c:
dphodm
odm
ck
lv
tttt
tt
t
tCD%
-
2.- Xc nh cng sut tnh yu cu khi c cu lm vic n nh vi ti trong danh ngha. S b tnh chn ng c theo cng sut tnh Nt. i vi c cu nng, do thng t khi lm vic vi mc ti ton phn nn c th chn ng c c cng sut nh hn gi tr tnh mt t.
Trn c s xc nh Mmen m my trung bnh ca ng c. ( Mm = m. Mdn, trong m l h s qu ti trung bnh khi m my, Mdn l momen danh ngha).
3.- Theo s gia ti xc nh cc mc ti Mi v cc khong thi gian tng ng ti, trong c c thi gian m my. T xc nh mmen trung bnh bnh phng v cng sut trung bnh:
ck
n
iimm
td t
tMtMM
1
.22 .
KwnMN tbtb 9550.
Chuyn sang cng sut tng ng vi cng chun trn c s chn ng c.
ng c c chn vi Nc Nt s m bo cc iu kin v khi ng v pht nhit
II.- C CU DI CHUYN:
Thc hin cc chuyn ng tnh tin ngang hoc nghing cho ton my hoc mt b phn my. S khc bit ca cc c cu di chuyn c cn c vo:
- ng ray di chuyn: Kiu treo hoc kiu t.- Cch truyn lc: bnh xe dn hoc cp ko- Cch truyn momen xon cho bnh xe: trc tip hoc qua
trc bnh xe- Phng thc dn ng: chung hoc ring
-
1.- Bnh xe v ray:a.- GiI thiu:S lng bnh xe b tr trn mi gi ta c th l 1,2,3 hoc
4 bnh. Trong trng hp s lng bnh xe trn mi gi ta ln hn 1 ngi ta phi dng cc cu cn bng m bo phn b u ti cho cc bnh xe.
Vt liu ch to bnh xe l thp c, hoc thp rn, thp cn. Trong trng hp khng yu cu cao c th dng gang xm. Yu cu cng b mt ca bnh xe phi cao chng mi mn : HB = 300-400 (Lu rng cng b mt bnh xe phi nh hn b mt ray).
Theo iu kin truyn chuyn ng phn bit bnh xe ch ng v bnh b dn ng. S bnh xe ch ng c th l 25%, 50% hoc 100% tng s bnh xe. Bnh xe c lp trn trc theo cc phng thc nh hnh v.
-
- Trng hp t bnh xe trn trc tm: trc c b tr ngay trong lng bnh xe nn kt cu cm bnh xe gn nhng lp rp iu chnh phc tp.
- Trng hp t trn trc truyn , kt cu tuy c cng knh hn, song d dng trong lp t, kim tra, sa cha nn c s dng ph bin trong my trc.
ln dng cho bnh xe l lng cu hai dy m bo tnh t la ca trc.
Tu theo loi my, cng dng v c im lm vic m bnh xe c th dng tr, cn, trng. Cc bnh xe c th c g c hai bn, mt bn hoc khng.
Chiu rng ca mt ln bnh xe c hai thnh bn phi ln mt ray t 15 20 mm I vi trng hp Palng; 30-40 mm I vi bnh xe cn trc.
Ray dng trong my trc c th l ray ng st hoc ray chuyn dng cho my trc. C th dng thp cn vung hoc ch nht c nhit luyn. Trong trng hp thit b my trc treo th dng ngay cnh dI ca dm I l ng chy ca bnh xe.
Vic c nh ray trn dm c thc hin theo cc phng thc nh hnh v:
b.- Tnh ton bnh xe & ray:Trong qu trnh lm vic tI trng tc dng ln bnh xe thay
I, do tI trng tnh ton l gi tr tng ng c tnh n cc yu t v s thay I tI, v ch lm vic:
Pt = .kc.Pmax
-
Trong : - l h s ph
thuc vo s thay I tI trng
- kc l h s ph thuc vo ch lm vic ca thit b
- Pmax: tI trng ln nht tc dng ln bnh xe.
Q/Go 0.05 0.980.3 0.90.4 0.880.50 0.861 0.8
CLV Nh TB N RNkc 1.1 1.2 1.4 1.6
Tu theo hnh dng bnh xe v ray, ta c trng hp tip xc ng v trng hp tip xc im.
p dng l thuyt HEZT,Trng hp tip xc ng :
-
Rb
EPttx .
..418,0 Trong E: mun n hi tng
ng:
21
1 2..2
EE
EEE
Trong E1, E2 l mun n hi ca vt liu bnh xe v ray. Trng hp bnh xe lm bng thp, c E1= E2= 2.1*105 N/mm2.
Lc ny :Rb
Pttx .
.190 []Trng hp tip xc im :
3max
2
2..
r
EPm ttx trong : rmax = max (r,R), m l h
s ph thuc vo t s: rmin/rmaxTrng hp bnh xe lm bng thp:
3
max2
..3600r
Pm ttx
-
Chng 9:
Cc phng n dn ng trong c cu di chuyn vi bnh xe dn- VI xe ln hoc cu ln c khu khng ln c th dng
mt ng c dn ng chung cho cc bnh xe ch ng. - Trong trng hp khu ca cu ln hoc i vi cng
trc, thng dng phng n dn ng ring.VI phng n dn ng chung c th dng phng n trc
truyn quay nhanh (p.n a) hoc chm (p.n b). Trng hp trc truyn quay chm, kch thc trc truyn ln, ko theo cc nI trc cng c kch thc ln. Tuy nhin do trc truyn quay chm nn khng yu cu cao v chnh xc ch to v lp rp.
Ngc li, vi phng n trc truyn quay nhanh, d phi dng 2 hp gim tc nhng tnh kinh t cao hn. Tuy nhin i hi s chnh xc trong ch to v lp rp.
Trong trng hp dn ng ring, hai cm dn cu phi tuyt i ng b. Mt khc yu cu kt cu kim loi ca cu trc phi m bo cng vng cao trnh xin lch. Tuy nhin, vI trng hp ny, vic lp rp n gin., gi thnh khng cao.3.- Tnh ton c cu di chuyn bng bnh xe dn:
3.1.- Lc cn chuyn ng:Lc cn tnh Wt tc ng trong cc giai on chuyn ng n
nh cng nh khng n nh, gm cc lc cn do ma st, do nghing ca ray v do gi.
-
Wt = WF + W + Wg - Lc cn chuyn ng do ma st:
Gm cc momen ma st trong trc bnh xe v momen cn ln do ma st gia bnh xe vI ng ray: Lc cn chuyn ng do ma st c xc nh theo cng thc:
bxt D
2f.dP.W
vi : P: tng ti trng tc dng ln cc bnh xe: P = Q + Go
Go l trng lng ca xe ln hoc cu ln tu trng hp tnh ton.
f: H s ma st trng trc : H s cn lnNgoi ra cn phI k n nh hng do ma st thnh bn ca
bnh xe vi ng ray.C
bxF D
2f.dk.P.W
H s cn ln [mm] vi ng knh bnh xe [mm]Kiu ray
200 - 300 400-500 600-700 800 900 -1000
Ray u bng
0,3 0,5 0,6 0,7 0,7
Ray u vng
0,4 0,6 0,8 1 1,2
H s ma st trong trc H s k n nh hng ca ma st thnh bnh xe vi ray
Loi f Kiu c cu k trt: Cu trc ln
P
d Dbx
-
- Loi h- Loi kn, c m c
0,10,08
- Bnh xe hnh cn- Bnh xe hnh tr c g
1,21,5
ln- Bi, a- Cn
0,0150,02
Xe ln- Bnh xe hnh cn- Bnh xe hnh tr c g
2,52
3.2.- Chn ng c dn ng c cu di chuyn:Trong qu trnh khi ng c cu di chuyn, ngoi cc lc
cn tnh nh trnh by trn, cn c cc lc cn ng.
m
dcom
o
t
V
g
GQj
g
GQ
.60..Wd
Do vy cng sut ca ng c dn ng c th c xc nh theo cng thc:
max
dcd
)7,06,0.(.1000.60
VW)3,11,1(W
dc
tN
ng c cn c th tin hnh tnh chn theo cng sut tnh:
dc
dct.
60.1000.
VW
tN vi Nc >= NtSau tin hnh kim tra iu kin m my v iu kin
bm. Nu khng c yu cu v tm th ch cn kim tra theo iu kin bm l .
Trong trng hp dn ng ring, tnh n s san ti khng u gia cc ng c, cn chn cng sut ca mi ng c bng 60% cng sut tng. 3.3.- Qu trnh m my c cu di chuyn:
Tng t nh c cu nng, Qu trnh m my c cu di chuyn l qu trnh chuyn c cu t trng thi tnh sang trng thi ng. Do ngoi mmen cn tnh , ng c cn phi khc phc mmen cn ng do qun tnh ca cc b phn my chuyn ng c gia tc gy nn. Phng trnh mmen trc ng c trong giai on m my:
Mm = Mt + M1 + M2Trong :
-
- Mt l momen cn tnh do lc cn tnh gy ra trn trc ng c;
- M1 l momen cn ng do cc b phn my chuyn ng tnh tin c gia tc gy ra trn trc ng c.
- M2 l momen cn ng do cc b phn my chuyn ng quay c gia tc gy ra trn trc ng c.
C:dcdc
bxt i
DM ...2
Wt
Xc nh biu thc ca M1
dcdc
bxdd i
DM ..2
.W1
vI Pq l lc qun tnh do vt nng gy ra,
mdc
dcbxo
m
bxbxo
m
dcom
od ti
nD
g
GQ
t
nD
g
GQ
t
V
g
GQj
g
GQ
..60
...
.60
...
.60..W
Thay biu thc Pq ta c:
dcm
dc
dc
bxod t
n
i
DGQM
1..
.
..
375
12
2
1
Xc nh biu thc ca M2Tng t nh trng hp c cu nng, ta c:
n
k m
dcIkkm
l
n
k mlo
dckkd t
nDG
ti
nDGM
1
2
1 1 12
2
2 .375
..
1.
..
375
.
Do : Mm = dcdc
bx
i
D
..2.Wt +
1..
.
..
375
12
2
m
dc
dc
bxo
t
n
i
DGQ +
n
k m
dcIkk
t
nDG
1
2
.375
..
(*)Phng trnh (*) c s dng kim tra iu kin m my
ca ng c in nu bit thi gian m my tm. Ngc li, nu bit mmen m my ca ng c th tnh thI gian m my theo cng thc:
tm
dc
dcdc
bxm
n
kIkk
dc
bxodcm
MMGD
n
i
DM
DGi
DGQnt
1)..(
.375
..2
.W1
...1
..
375
2
t1
22
2
-
Trong : (GD2) l momen quy dn v trc ng c.
-
Chng 10: Qu trnh phanh c cu di chuyn
Khng ph thuc chiu chuyn ng, Phng trnh mmen trc ng c trong giai on phanh:
Mm = - M*t + M*1 + M*2Trong :
- M*t l momen cn tnh do lc cn tnh gy ra trn trc ng c;
- M*1 l momen cn ng do cc b phn my chuyn ng tnh tin c gia tc gy ra trn trc ng c.
- M*2 l momen cn ng do cc b phn my chuyn ng quay c gia tc gy ra trn trc ng c.
C:dc
dcbxt i
DM
..2
.*W* t
trong W*t l lc cn tnh khi phanh, v lu trong cng thc tnh lc cn tnh ly k = 1; cc thnh phn lc cn do nghing ca ng ray v do gi nu tnh phi ly du (-)
dc
ph
dc
dc
bxod t
n
i
DGQM ..
.
..
375
1*
2
2
1
Do : Mph = dcdc
bx
i
D ..2
.Wt + dcph
dc
dc
bxo
t
n
i
DGQ ...
..
375
12
2 +
n
k ph
dcIkk
t
nDG
1
2
.375
.. (*)
Phng trnh (*) c s dng kim tra iu kin phanh nu bit thi gian phanh tph. Ngc li, nu bit mmen phanh th tnh thi gian phanh theo cng thc:
tph
dc
tph
n
kIkkdc
dc
bxodcph
MMGD
n
MMDG
i
DGQnt
*
1)..(
.375
*
1....
.
375
2
1
22
2
3.-5.- Kim tra iu kin bm c cu di chuyn:
-
Trong qu trnh khi ng v qu trnh phanh, c bit trng thi khng ti, xe ln (cu ln) c th b trt trn do khng m bo iu kin bm dnh.
kim tra iu kin bm ta dng tiu ch h s an ton bm v c nh ngha bng biu thc:
truotgayLuc
bamLuckb 1,2
a.- Khi m my xe (cu) trng thi khng ti, h s an ton bm c kim tra theo cng thc:
2,1
.D
d.f.G-W
.
0dt
o
g
jG
Gk
m
o
db
Trong : - Gd: Tng p lc ln cc bnh dn khi khng c vt nng- : h s bm ca bnh xe trn ray. Trng hp my lm vic
ngoi trI, = 0,12; lm vic trong nh = 0,2 ; trng hp c ri ct trn ng ray, = 0,5.
- Wot: Tng lc cn tnh khi khng c vt nng.
- Jom: Gia tc trung trung bnh ca xe khi m my khng c vt
nng.
mo
mo
t
vj
.60 vI tom: thi gian m my khng c vt
nng.
dcdc
bxm
n
kIkk
dc
bxodcm
i
DM
DGi
DGnt
..2
.W
1...
1.
375 t01
22
20
b.- Khi phanh xe (cu) trng thi khng ti, h s an ton bm c kim tra theo cng thc:
2,1*W-.
.
o0
t
ph
o
db
g
jG
Gk
-
pho
pho
t
vj
.60 vi toph: thi gian m my khng c vt
nng.
dc
dcbxph
n
kIkkdc
dc
bxodcph
i
DM
DGi
DGnt
.2
..W
1....
375 t01
22
20
Khi thit k, thng xut pht t gia tc cho php khng xy ra trt trn m chn ng c c mmen m my ph hp.
m bo iu kin bm, gia tc m my khng ti khng c vt qu gi tr: jom jomax vi:
tomax W..2,1
.
bx
d
o
o
D
dfGd
G
G
gj
3.6.- Trnh t tnh ton c cu di chuyn:1.- Chn s dn ng cho cc bnh xe dn,2.- Tnh ton thit k bnh xe v ray,3.- Tnh ton lc cn chuyn ng, s b chn ng c theo
cng sut tnh.4.- Tnh ton thit k cc b truyn:
- idc = nc/nbx- Phn phI t s truyn, tnh cc b truyn.
5.- Kim tra ng c in v iu kin m my v iu kin bm.
- T yu cu h s an ton bm, xc nh gia tc m my ln nht trng thi khng tI:
tomax W..2,1
.
bx
d
o
o
D
dfGd
G
G
gj
- Tnh thI gian m my theo gia tc max.60 o
mo
j
vt
- Tnh mmen m my ln nht Mom m bo an ton bm, so snh vi Mm(c) (Mm(c)
-
Thng c p dng i vi cc loi cn trc xy dng, cng trc. Vi phng thc ny, cc c cu nng v c cu di chuyn c th b tr ngoi xe ln nn lm gim lc tc dng tp trung ln kt cu kim loi.
Lc cn chuyn ng trong trng hp ny, ngoi cc thnh phn k trong c cu di chuyn bng bnh xe dn, cn c cc thnh phn do hiu lc cng dy 2 nhnh cp ca c cu nng v lc cn do trong lng ca dy ko.
W = WF + W + Wg + Wh + H Trong :
Wh l hiu lc cng trn 2 nhnh dy ca palng nng vt:
aa
Q
1.
1.1W
1
h
Gc l lc cn do trng lng phn dy cp t do b vng:
h
lq
.8
.H
2
vi q: trng lng 1 mt dy ; h: vng cho php ca dy ko ; (h = 1/30 - 1/50) l; l: chiu di phn dy ko b vng
Mmen cn thit trn trc tang:
41
41
..2
..H.-W
tg
tg
DM
III.- C CU THAY I TM VI:1.- i cng:Tm vi c nh ngha l khong cch gia trc quay ca
cn trc v vt nng. Thay i tm vi ca cn trc, kt hp vi c cu nng vt v c cu quay cn nhm m bo vn chuyn vt nng n ng v tr yu cu.
-
C th thc hin vic thay i tm vi cho cc loi cn trc theo 2 phng n:
- Dng ti ko xe ln di chuyn trn cn : Phng n ny thng gp trong cn trc thp xy dng hoc mt s cc loi cn trc chuyn dng. V thc cht y ch l c cu di chuyn xe ln bng dy ko.
Uu im ca phng n ny l cng sut tiu hao cho vic thay i tm vi nh, d dng t c tm vi b nht, vt nng t chao lc. Tuy nhin tnh c ng khng cao v kch thc ca cn ln.
- Thay i gc nghing ca cn:Vic thay i gc nghing ca cn c th s dng cc
phng n lin kt cng vi cn nh trn hnh v: Trong cc phng n phng n (c) dng xy lanh thu lc c s dng ph bin hn c
Vi cc phng n nng cn lin kt cng, i hi tiu tn
nng lng ln khi nng cn. S d nh vy v nng cn cng ng thi l nng vt.
Ngoi cc phng n trn cn c phng n nng cn thng qua palng nng cn nh hnh v.
Trong trng hp ny, c th xem c cu thay i tm vi nh l c cu nng cn.
Phng n ny c cc c im:+ Trng lng ca cn nh,+ Tnh c ng cao+ Cng sut tiu hao cho nng cn khng ln,+ Kh t c tm vi nh
-
V mt s cu to, c cu nng cn hon ton ging nh c cu nng vt. Tuy nhin trong qu trnh nng cn, lc cng cp s c gi tr thay i do lc nng cn Fc thay i. Do nu s dng tang tr th s dn n cng sut trn trc tang khng n nh. khc phc dng tang cn hoc tang c ng knh thay i.
Wc
Gc
Wv
Lc L
H
Fc
Q
e
Sv
h
-
1Chng 11:
Tnh ton palng nng cnS liu cn bit trc gm: S ng hc ca c cu nng
cn, kch thc, hnh dng trng lng cn v cc thit b ph; Trng ti; Tc quay ca cn; Thi gian thay i tm viCh lm vic ca cn trc
Cc ti trng chnh tc dng ln h thng gm:- Q: trng lng vt nng - Gc: trng lng cn- Wv, Wc: ti trng gi tc dng ln vt nng v ln cn- Sv: Lc cng ca dy nng vt- Fc: lc nng cn- Lc qun tnh xut hin trong qu trnh khi ng
nng cn Pq- Lc qun tnh ly tm nu qu trnh m my nng cn
c kt hp vi quay cn.Cn xc nh lc nng cn v xem i lng ny nh l
trng lng vt nng tin hnh tnh ton thit k c cu nng cn nh c cu nng vt.
B qua cc lc cn do gi Wv, Wc, cc ti trng ng qun tnh, vit phng trnh mmen cc lc i vi khp quay cn:
Q.L + Gc.Lc - Fc . H - Sv . e = 0T ta c lc nng cn:
H
... eSLGLQF vccc
Qua cng thc ny ta nhn thy rng ti trng nng cn s c gi tr thay i theo v tr ca cn.
Lc cng dy ln nht c xc nh tng t nh palng nng vt.
-
2p
cc a
FS .max
Trong trng hp dng tang hnh tr, cn tnh lc cng cp theo cng thc lc cng trung bnh bnh phng:
i
icmmc t
tSS i
.2
T cng sut ng c c xc nh theo cng thc:
.1000.60. c
mc VSN
Trong Vc l vn tc trung bnh ca cp cun ln tang, c xc nh theo cng thc:
t
*
ahVc
Vi h l lng thay i khong cch gia tm cm rng rc c nh v rng rc di ng tng ng vi khong thi gian nng cn t.
Vi phng n lin kt mm, c th c s lin kt gia palng nng cn v palng nng vt. iu c th thc hin nng cn m khng cn nng vt, iu ny lm gim thiu cng sut ca ng c nng cn.
Lin kt Palng nng cn v nng vt Lin kttang nng cn v nng vt khi nng cn
Ti nngTi nng vt
Ti nng cn
Tang nng vt
Tang nng cnLy hp
-
3Trng hp lin kt tang nng cn v tang nng vt, hai tang c lin kt vi nhau bng ly hp; Ly hp ny ng khi nng cn. Chiu cun dy ln 2 tang ngc nhau nn khi nng cn s ng thi h vt v ngc li.
Trong palng nng cn ch dng dy l cp thp. Trong trng hp c s lin kt gia 2 palng, bi sut ca palng nng cn c xc nh sao cho lc cng dy l gn nh nhau c th dng cng mt kch thc dy cho palng nng cn v nng vt.
IV.- C CU QUAY: C cu quay dng thc hin chuyn ng quay cho phn
quay ca cn trc.1.- c im chung:
- C cu quay c th b tr trn phn quay hoc khng quay ca cn trc, nhng thng b tr trn phn quay.
- Vn tc quay ca cn trc thng rt b; nq = (1 - 3) vng /pht. Do t s truyn ca c cu thng rt ln (750 - 1000). Cm truyn chuyn ng thng gm hai phn: Hp gim tc (Trc vt - bnh vt; hoc bnh rng hnh tinh) , v cp bnh rng h: iq = i0 . i br.
- Qun tnh khi khi ng thng rt ln. Thi gian chuyn ng n nh ngn. Do cng sut ng c thng chn ln gp 3-4 ln cng sut tnh.
2.- Tnh mmen cn quay:Mmen cn quay trong cn trc gm mmen cn quay do ma
st, mmen cn quay do nghing ca cn trc, mmen cn quay do gi.
a.- Mmen cn quay do ma st:Tu thuc vo h thng ta quay, xc nh cc lc cn, t
tnh cc mmen cn quay.
-
4 Trng hp h thng ta quay kiu ct nh cc hnh v trn, ta c:
Cc phn lc tI A,B: XA = XB =
H
LGLQ ii .. v YA = Q + GiTrong Li l khong cch t lc tc dng n trc quay.Mmen cn quay do ma st:
2
'..
2..
2.. ABA
ABAf
dfY
dfX
dfXM cho trng hp cc trc tI
A v B l cc ln thng thng.VI trng hp cn trc ct c nh, vng ta quay B c th
c b tr 2, 4 hoc nhiu con ln, vI trng hp 2 con ln, ta c:
QQ
Gt
Go
A
BH
A
B
H Go
-
5 Kt cu cm + chn
Lc tc dng ln mi con ln:
cos.2BXN ,
Mmen ma st tI vng ta B:
cl
clcBf D
DDdfNM
).2.( trong :d: ng knh trc con ln,Dc ng knh ct Dcl ng knh con ln
Trng hp dng vng ta quay vi nhiu con lnt gi thit ti trng tc dng ln mi con ln phn b theo quy lut :
xx NN cos.1 , chiu tt c cc lc trn phng ca XB, c:
XB
-
6XB = N1 + 2. Nx. cosx = N1 + 2.N1. cos2xT : x
BXN 21 cos.21
Ngoi ra, do k n kh nng x lch gia cc con ln, ti trng tc dng ln con ln s khng tun th ng nh gi thit, ti trng tnh ton cho con ln:
Nx = 1,25 NXCng thc xc nh mmen ma st trong trng hp ny:
cl
clc
x
xB
Bf D
DDXM
.2.
cos.21
cos.21..25,1
2
Trng hp h thng ta quay l vng ta quay nm ngang, hoc thit b ta quay kiu bi cu, hoc a, ta c cc s nh trn hnh v.
b.- Mmen cn quay do nghing ca mt nn:Trong qu trnh lm vic, mmen un do cc ti trng tc
dng ln ct:Mu = Q.L + Gi.Li.
gim mmen un ct, i vi cn trc ct c nh thng dng i trng (Gt) c xc nh theo iu kin Mu khi y ti v khi khng ti l bng nhau.
dt
oodt L
LGLQG
.2
..2.
-
7Khi mt nn b nghing gc a th mmen cn quay s c gi tr ln nht khi mt phng ti trng vung gc vi phng nghing.
M = Mu. Sin
c.- Mmen cn quay do gi:
Trong trng hp thit b t ngoi tri,cn thit phi tnh Mg.
Mg = p. Ag.L*Ngoi mmen cn tnh, khi khI ng,
cn c mmen cn ng c gi tr rt lnv qun tnh ca phn quay.
M = Jq.q = m
qi
i
t
nL
g
G
.60
..2.. 2
= 2..4..375 iim
q LGt
n
= qm
q GDt
n).(
.3752
(GD2)q: tng mmen ca phn quay
3.- Qu trnh m my c cu quay:Tng t nh c cu di chuyn, mmen cn tnh Mt khng
ph thuc vo chiu quay ca cn trc, lun cn chuyn ng, phng trnh mmen trc ng c trong giai on m my:
Mm = Mt + M1 + M2Trong :
- Mt l momen cn tnh do lc cn tnh gy ra trn trc ng c;
- M1 l momen cn ng do qun tnh cc b phn my lp trn phn quay.
- M2 l momen cn ng do cc b phn my thuc c cu quay c gia tc gy ra trn trc ng c.
Mm = qqi .
Mq +
qm
dc
q
q
t
n
i
DG
1
...
..
375
12
2
+
n
k m
dcIkk
t
nDG
1
2
.375
..
Mu sin
Mu sin
-
8T phng trnh trn, c th tnh kim tra Mm hoc tm.
5.- Tnh chn ng c in cho c cu quay:ng c in c cu quay c tnh chn theo cng sut
tnh: W
.9550
.K
nMN
q
qqt trong : Mq [N.m] n [vg/ph]
Do mmen ng c gi tr rt ln trong thI k m my nn ng c thng c chn c: Nc = (3-4) Nt
Sau tin hnh kim tra iu kin m my theo thI gian m my chn theo kinh nghim.________________________________________________________________
-
Chng 12:
MT S THIT B NNG THNG DNG
I.- Cc thit b nng n gin:L cc thit b nng ch thc hin chuyn ng nng, h.Gm cc thit b: Kch, Ti, Palng.1.- Kch: Thc hin nng h vt vi cao nng khng ln;
h< 0.7 mt. Tu thuc nguyn l dn ng b phn cng tc, phn bit: Kch thanh rng, kch vt, kch thu lc.a.- Kch thanh rng:
S nguyn l c th hin nh hnh v.u kch c dn ng bng b truyn bnh rng thanh
rng. Theo quy phm an ton, kch c trang b tay quay an ton. Quan h gia Q v P c th hin qua cng thc:
P = Q.r/(R.io.). r: bn knh vng ln bnh rng n khp vI thanh rng
b.- Kch vt: Thc hin cao nng H = 0,2 0,4 mt.
-
Ren dng cho vt l ren hnh thang c gc nng = 4 5o. u kch lp trn trc vt nh l chn.
Quan h gia lc P v tI trng Q:]
2.
2).([. m
Dfm
dtgQLP trong :
dm: ng knh trung bnh ca ren vtDm: ng knh trung bnh ca u ta f: h s ma st mt ta: gc ma st mt ren.Hiu sut ca kch vt:
mm
m
mm
m
Dfdtg
tgd
Df
dtgQ
tgdQ
PL
sQ
.).(
.
2.2
.2
).(
)(...
2.
.
-
c.- Kch thu lc
u kch chuyn ng i ln nh bm thu lc bm du vo y u nng. Vic h u nng c thc hin khi m van x du. Kch vt c th t n trng ti 750 tn v cao nng n 0,7 mt.Theo nguyn tc p sut khng i trong thnh bnh kn, ta c:
2
D
'
'
dQ
A
AQP
A
P
A
Qp
Lc tc dng ln tay bm:
1
...1
..
2
L
r
D
dQ
L
rPPo
Do t s d/D nn kch vt c th t c trng ti ln.
2.- Ti:Ti l thit b nng ch c trang b c cu nng. Dng thc
hin vic nng h vt nng theo phng thng ng hoc phng nghing. TiI c th l thit b c lp hoc l b phn my ca mt thit b my trc khc. TI c lp t c nh trn nn, tng hoc trn kt cu kim loi ca my trc.
-
Cc b phn chnh ca ti gm: B phn dn ng, b phn truyn ng, tang cun cp v thit b phanh hm. Tu thuc ngun dn ng, phn bit ti tay v ti my. Ti c th dn ng mt tang hoc nhiu tang. C th c ti 1 hoc hai cp tc .
-
Ti ma st vi tang c ng knh thay i, c th ko vt vi chiu di cp ln. Dng lm ca tang m bo cp khng chy dc theo ng sinh.
Quan h lc ko : FZ = FH . ef3.- Palng:Tng t nh ti, palng l thit b nng thc hin nng h
vt nhng l thit b c ng v thng c b tr trn dm ca cc my trc khc nh cu trc, cng trc.Trong nhiu trng hp, palng c trang b thm c cu di chuyn v c gi tn l xe ln.
Tu thuc ngun dn ng c palng tay v palng in.
-
II- Cu trc ln:c s dng trong nh xng phc v cho vic ch to, sa
cha, lp rp. c b tr trn cao nn khng chim din tch mt bng phn xng. Cu trc c trang b cc c cu nng, c cu
-
di chuyn xe v c cu di chuyn cu nn c th vn chuyn vt nng n bt c mt to no trong khng gian phn xng.
Tu thuc vo khu v ti trng, c cu trc 1 dm hoc 2 dm.
1.- S cu trc ln:
Trn s cu trc ln 1 dm, c dm chnh chu lc (1),
dm cuI (5), cc dn ph (4), Palng in (3)v cabin (2). Trn cc dm cui c lp cc bnh xe v c dn ng bng c cu di chuyn cu.
2.- Kt cu cc dm:Trong kt cu kim loi ca cu trc, dm chnh l b phn
chu lc ch yu. Yu cu ca dm chnh l phi m bo bn v cng.
I vI trng hp cu trc 1 dm, tit din dm phi c dng ch I treo palng. Trng hp n gin nht l dng dm n khng c gia cng. Nu iu kin cng vng cng nh bn khng c m bo th phi gia cng.
-
i vi trng hp cu trc 2 dm, tit din dm thng c dng hnh hp ch nht. Theo quy phm an ton, cn phI b tr sn thao tc tin cho vic bo dng, sa cha Palng
Ngoi vic gia cng cho tit din dm, trong nhiu trng hp phI dng thm dng khung, dn tng cng vng. Lin kt gia dm chnh v dm cui c th bng mi ghp bulng hoc mi ghp hn.
Dm cui thng c kt cu tit din hnh hp hoc 2 thp U ghp li.
Vic b tr hp trc cc bnh xe c th tin hnh theo phng thc hp trc ring hoc b tr bi ngay trong lng bnh xe.
3.- c im tnh ton cu trc:
-
Chng 13: c im tnh ton cu trc
Cc bc tnh ton:- Xc nh thng s c bn ca cu trc, Q,H, L, Vn, Vxe,
Vcu, CLV.- S b xc nh trng lng ca kt cu kim loI dm
chnh, cc b phn lp t trn cu nh cabin, xe ln.- Thit k cc c cu cng tc (c cu nng vt, c cu di
chuyn xe con, c cu di chuyn cu trc..). Cc tnh ton ny c trnh by cc phn trc.
- Tnh kt cu kim loi dm chnh.Mt cch n gin, xt trng hp dm chu lc khi xe ln
c v tr gia dm, s lc tc dng nh hnh v:
Mmen lc ln nht do tI trng gy ra tI v tr gia dm :Mumax =1,25*[ (Q + Gxe)*L/8 + q*L
2/8]Kim tra bn:ng sut ln nht tI v tr gia dm:
u
max
WuM
Xc inh vng tI v tr gia dm:
xx
xe
JE
Lq
JE
LGQf
*384
*5
**48
*)( 43
So snh vI vng cho php [f] = L/700
q
L
L/2
-
Khong cch gia 2 dm chnh trong trng hp cu trc 2 dm c xc nh trn c s m bo lc nn ngang ca bnh xe ln thnh ray khng qu ln do s xin lch ca cu trc.
S tnh cho nh hnh v:C lc nn ph gia thnh bnh xe v ray:
2.E
W.LE
MN
trong W l lc cn ph do thnh bnh xe tip xc vI ng ray.
m bo lc dn ng mI bn (W/2) thng c ma st khi c N, cn thit:
fL
EffN .
2.E
W.L.
2
W
Trong tnh ton ly f = 1/5 - 1/7
III.- Cng trc:Khc vI cu trc, cng trc di chuyn c trn ray b tr
mt t nh c cu di chuyn cng. Theo kt cu thp, cng trc c loi cng xn hoc khng. Tu thuc khu v ti trng c th c cng trc mt dm hoc hai dm. Kt cu kim loi ca chn cng cng nh cc dm rt a dng. Trong trng hp khu nh hn 25 mt, c th c 2 chn cng u lin kt cng vi dm. Trong nhiu trng hp, to s tu ng ca cc chn cng, trnh x lch v kt bnh xe trn ray, mt trong hai chn cng c lp khp quay vi dm.
Xe con ca cng trc c th l palng in treo hoc chy trn ray b tr trn hai dm chnh. C cu nng ca cng trc c th b tr ngoi xe con gim ti. Vic dn ng xe con c th c thc hin bng c cu dn ng bnh xe dn hoc tI ko. C cu di chuyn cng thng dng phng n dn ng ring. Nu dn ng chung th phi b tr trn cao khi vng thit b mt t.
-
1Chng 14: Thang my
I.- I cng:Dng vn chuyn ngi v hng ho trong cc nh cao
tng. 1.- Theo cng dng, phn bit:- Thang ch ngi cng dng chung, c tc n 1.4 m/s,
trng tI n 1000KG, thang my ch ngI tc cao V= 2m/s tI trng nng trn 1000KG.
- Thang my vn chuyn bnh nhn (c bng ca, xe y) c ngI i km
- Thang my ch ngi v hng,- Thang my ch hng c ngI i km- Thang my ch hng khng c ngI i km.
2.- Theo phng thc dn ng cabin, phn bit:- Thang my dn ng bng ti vi tang cun cp- Thang my dn ng bng ti vi puly ma st.
Thng thang my vi phng thc dn ng bng ti vi tang cun cp ch cn s dng cho thang nng hng. So vi phng thc dn ng bng ti vi tang cun cp, phng n dn ng bng puly ma st c cc u im sau:
- Lc ko trn puly nh (do tc dng ca i trng), dn n kch thc nh gn, khng ph thuc vo chiu cao nng.
- An ton trong lm vic v cabi c treo bng nhiu si cp (3-5 sI).
3.- Cc b phn chnh ca thang my:- B phn dn ng, truyn ng, cp nng.- Cabin cng h thng treo, c cu ng m ca cabin- I trng- Ging thang, h thng dn hng cabin, I trng
-
2- Cc b phn an ton: Phanh, c cu hm tc , h thn gim chn
- H thng iu khin cng cc trang b in.4.- Cc phng n dn ng cabin:
Phng n a.- Ti puly ma stPhng n b.- Ti tang cun cpPhng n c.- Ti puly ma st c puly phPhng n d.- Ti puly ma st c puly ph tng gc mPhng n e.- Ti puly ma st c puly ph v c dng palng cp li lcPhng n f, g.- Ti puly ma st c puly ph, trm dn ng t di
5.- Cabin thang my:L b phn mang ti ca thang my. Gm kt cu khung chu
lc v cc vch che to bung cabin.
-
3
Khung ng gm dm trn v dm di, mi dm c ch to t hai thanh thp hnh U ghp li. Cc dm ny lin kt vi cc thanh thp hnh L to thnh khung ng. Dm trn ca khung ng lin kt vi h thng treo cabin. Dm di ca khung ng khung nm ca cabin. Khung nm thng c ch to bng phng php ghp hn cc thp hnh V hoc L.Cc khung c lin kt vi nhau bng bulng. Ti u trn ca dm trn v dm di ca
-
4khung ng c lp cc ngm dn hng.
Theo nguyn l lm vic c ngm dn hng vi ma st trt v ma st ln. Loi ngm dn hng vi ma st ln thng p dng cho thang my c tc cao, ti trng ln.
Ray dn hng trong trng hp thang ch hng c th l cc loi thp hnh U,V Trong trng hp thang my c ngi nn dng cc loi ray chuyn dng nh trn hnh v.
II.- Tnh ton b phn dn ng:
1.- Cc thng s c bn: - Trng tI (khng k trng lng cabin): Q [KG]- Tc cabin [m/s]- Chiu cao nng, cc im dng.- Kch thc cabin.- Tnh cht iu khin
2.- Xc nh trng lng cc b phn ca h thng cn bng
Trong trng hp cao nng khng ln (
-
5a.- nh ngha h s ko:Theo quy nh, s rnh ca puly ma st trong thang my ch
ngI l t 3- 5. y rnh thng c dng hnh thang, trn, hoc trn c ct rnh. Trong trng hp y rnh c dng trn c x rnh:
sinsin2
sin2
sin4
tf
Trng hp rnh cp b mn, gc = , lc ny:
sin2
sin14
tf v vi rnh trn khng c x rnh:
4tf
Trng hp rnh hnh thang, c
2sin
f
f t
Trong cc cng thc trn ft l h s ma st thay thQuan h lc cng trn 2 nhnh cp:
tfeSS .minmax trong l gc m ca cp trn Puly
ng knh danh ngha ca Puly ma st xc nh theo cng thc:
D dc.e vi e = 30 (thang ch hng) e = 40 cho thang ch ngi, e= 45 cho thang ch ngI c tc cao.
Tu theo v tr v tnh trng lm vic m c th c gi tr ca S1 hoc S2 l ln hn. Trong mI trng hp, ta k hiu S2 l lc cng c gi tr ln v S1 l lc cng c gi tr nh; Lc ny lc vng trn puly ma st bng hiu ca 2 gi tr lc cng.
P = S2 - S1Kh nng truyn c lc bng ma st c gi tr
ln nht ( khc phc lc vng Pmax) m khng xy ra S1
S2
-
6s trt trnca dy cp trn puly c gi l kh nng ko ca puly ma st.
Theo cng thc Euler, c:tfeSS .12 hoc: tfeS
S 1
2
Trong ft: h s ma st thay th gia cp v puly.: gc m ca cp trn puly.
Nhn xt rng t s (1
2
S
S ) t gi tr cng ln th kh nng chng trt cng ln. Do vy ef c trng cho kh nng ko v c gi l h s ko ca puly ma st. tng kh nng ko th dng cc bin php hoc tng f hoc tng .
b.- Xc nh h s ko: xc nh h s ko, ta xc nh gi tr ca t s
1
2
S
S ng vi cc trng hp sau:
- Trng thi th tI tnh: D
GQK
S
S n .21
2 (tI cht khi th tnh l 2Q)
- Trng thi lm vic, khi cabin v tr thp nht v cao nht, c k n ti trng ng pht sinh trong qu trnh chuyn ng khng n nh (m my, phanh)
-
7
Xc nh t s 1
2
S
S theo cng thc:
Khi cabin y tI, v tr dI cng: .1
2
D
GQK
S
S n
Khi cabin khng tI, v tr trn cng: .1
2
d
n
GK
GD
S
S
ag
ag
h s tI trng ng (a: gia tc m my hoc
phanh)4.- Tnh chn cp:Lc cng cp ln nht c xc nh theo ti tnh khi Cabin
y ti v nm v tr trn hoc di cng. Trong trng hp khng dng xch cn bng:
Za
GQKS d
.max hoc
Za
GQKS n
.max
Chn cp theo lc ko t S n.Smaxn l h. s an ton (n = 9 -15).
5.- Tnh chn ng c:ng c phi khc phc cc lc cn:- Lc vng trn puly Pmax = (S2 S1) max
-
8- Lc ma st b phn dn hng.So vI lc vng, lc cn do ma st chim mt t trng khng ng k. Thng ly tng lc cn cn khc phc P = k.(S2 S1) max vI k = 1,1 - 1,2. Lc ny cng sut ng c c tnh chn theo cng thc:
N .1000.vP [Kw]
III.- Thit b an ton C kh: trnh cho cabin ri trong ging thang khi b t cp hoc
h vi tc vt qu gi tr cho php, cn thit phi trang b phanh an ton.
Theo nguyn l lm vic, phn bit phanh dng t ngt v phanh dng c trt; theo kt cu c phanh kiu nm v phanh kiu bnh cam. Theo s dn ng c phanh an ton mc vi cp nng v phanh an ton mc vi b hn ch tc .
Trong trng hp dng ti vi tang cun cp (thang my ch hng) thng dng phanh an ton kiu nm, mc vi cp nng. Trng hp dng ti vi puly ma st (thang my ch ngi) dng phanh an ton ni vi cp ca b hn ch tc .
Phanh an ton kiu nm, mc vi cp nng
S xc nh gc t nm
-
9S nguyn l phanh an ton kiu
nm, mc vi b hn ch tc
Nguyn tc hot ng:i vi trng hp phanh an ton mc vi cp nng, khi treo
cabin, cp nng c cng ko cc tay n lm cho nm i xung, to khe h trong chm. Khi t hoc chng cp nng, lao xo (5) s ko n (4) lm cho chm hot ng, gi cabin trng thi treo.
Tng t trong trng hp phanh an ton ni vi cp ca b hn ch tc , nu cabin vt tc cho php, b hn ch tc s dng li, ko theo b phanh kiu nm hot ng.
___________________________________________________________
H thng dn ng phanh an ton nI vI b hm tc
-
Chng 15:
MY VN CHUYN LIN TCI.-i cng:
1.- Cc thng s c bn:My chuyn lin tc thc hin vn chuyn vt liu
nhiu dng khc nhau (thng dng vn, ri) theo tng tuyn xc nh.
Cc thng s c trng cho my chuyn lin tc:- Nng sut- Tc vn chuyn v[m/s]- Chiu di L[m], cao vn chuyn H[m], gc
nghing t my [o].a.- Nng sut: L lng vt liu vn chuyn c trong n v thi
gian. Nng sut c th tnh theo th tch [m3/h], khi lng[Tn/h] hoc n chic [chic/h].
Cng thc chung tnh nng sut:Q = 0,36 qvl.v [T/h]
Trng hp vt liu c vn chuyn trong ng hoc mng : vAQ o ....3600 [T/h] = 3600.Ao..v [m3/h]
Trng hp vt liu ri c vt chuyn theo dng lin tc:
vAQ ...3600 [T/h] = 3600.A.v [m3/h]Trong : qvl : trng lng vt liu vn chuyn trn 1 mt chiu di
[N/m].v: Tc dng vt liu [m/s]
-
A0: Din tch tit din ng, mng [m2]A: Din tch mt ct dng vt liu [m2]: Khi lng ca mt n v th tch vt liu
[T/m3]: H s in y mng, ng.
Khi vt liu c vn chuyn trong cc gu ti, c dung tch L [m3], bc t gu l t th: v
t
LQ ....36,0
[T/h]Tng t trng hp vn chuyn tng kin hng vi
trng lng G [N]:v
t
GQ ..36,0 [T/h]
Trng hp i tng vn chuyn l mt sn phm th nng sut c tnh:
t
vZ 3600 [ chic/h]
b.- Cng sut dn ng:Khi vn chuyn theo phng ng, cng sut cn thit
khi vn chuyn vt liu ln mt cao l H vi nng sut l Q:
N 360
.HQ
Khi vn chuyn theo phng ngang th lc cn chung l:
W = qvl . L . c T cng sut cn thit khi vn chuyn vt liu trn
on nm ngang L:
360
..
1000..36.0
..
1000
..
1000
W.v cLQ
v
cLQcLqN vlng
Trng hp tng qut, my vn chuyn vt liu trn chiu di L [m] v cao H [m] vi nng sut Q [T/h], th cng sut tiu hao l:
1
..360
LcHQ
N [Kw]
-
Trong c: l h s cn chuyn ng, l hiu sut chung ca my.
Tu theo nguyn l dn ng b phn cng tc, phn bit:
My chuyn lin tc c b phn ko: Bng ti, xch ti..
My chuyn lin tc khng c b phn ko: Bng chuyn con ln, mng lc..
II.- BNG TI AI:
Bng ti ai l dng MCLT c b phn ko. Nguyn tc truyn ng thc hin nh ma st. B phn ko y l btruyn ma st gia cc tang v bng ai. Tm bng cng ng thi ng vai tr ca b phn mang vt liu.
1.- Nguyn l truyn lc ko bng ma st:Truyn lc ko t tang dn ng sang tm bng hoc
puly sang dy cp c thc hin theo nguyn tc truyn ng ma st.
Quan h gia lc cng trn hai nhnh ai:feSS 12
Trong f: h s ma st gia vt liu tm bng v tang.: gc m ca tm bng trn tang. S2: Lc cng trn nhnh bng i vo tang dn.S1: Lc cng trn nhnh bng i ra khi tang dn.
thc hin truyn ng:- To lc cng ban u.- Tc dng momen xon Mx trn tang dn.Trn nhnh i vo tang dn lc cng tng ln, trn nhnh i ra khi tang dn, lc cng gim i:
S2 S1
-
Trn mt phn cung m pha nhnh i ra khi tang dn c s trt n hi, c gi l cung trt. Mt phn cung pha nhnh i vo tang dn khng c trt gi l cung tnh.
Thc ra:trf
.12 eSS Do :
dt
f
k
eSS
.1
2 (kdt: h s d tr ma st kdt= 1,15 - 1,2)
Kh nng truyn lc ko ln nht c thc hin khi iu kin f.12 eSS c m bo.
Hiu lc cng bng trn hai nhnh bng chnh l lc ma st. Trng hp ti ln hn lc ma st th xy ra s trt trn ca bng trn tang.
tng kh nng ti:- Tng gc m - Tng h s ma st (c th tng f n 0,3 - 0,6)
2.- Cc b phn chnh ca bng ti:
a.- Tm bng: L b phn mang ti ch yu ca bng ti, t tin nhng c nguy c chng hng nht. Yu cu tm bng phi m bo bn ko v un, n hi v dn di nh, c kh nng chng chy, kh nng chng mn tt.
-
Cu to tm bng gm phn li chu lc v lp bc bo v. Phn li thng l vi hoc cp an thnh tm, phn bc thng l cao su.
Cc tm li vi thng lm t si t nhn to c bn cao, chiu dy mi lp t 0,2 0,5 mm. Gii hn bn ca mt mm chiu rng mt lp vi cn t n 600 800 N/mm. Lp cao su mt mt dnh kt cc li vi nhau, mt khc c tc dng bo v phn li, chng li cc ph hng do tc dng c hc v mi trng bn ngoi. Sc bn ko t ca lp cao su cn t gi tr 20N/mm2.
S lng cc lp li ph thuc vo chiu rng ca tm bng.B 300 400 500 650 800 1000 1200 1400 1600Z 3-4 3-5 3-6 3-7 4-8 5-10 5-12 7-12 8-12
Chiu dy cc lp cao su bo v 2 mt bng ph thuc vo chng loi v c tnh ca vt liu vn chuyn.
Bng vi li cp, c bn cao hn v dn di cng nh hn so vi bng vi cao su. Tuy nhin gi thnh cao nn hin nay ph bin vn dng bng vi cao su.
Trong trng hp vt liu vn chuyn c cnh sc v nhit cao, ngi ta c th dng bng thp tm.
Kch thc c bn ca bng l chiu rng B. Vi bng vi - cao su chiu rng B ly cc gi tr sau:
B= 300, 400, 500, 650, 800, 1000, 1200, 1400, 1600Thng s ny c xc nh trn c s m bo nng
sut v vn tc yu cu. Hin nay chiu rng ca tm bng c ch to theo tiu chun.
S lp vi trong tm bng c xc nh trn c s sc bn ko t.
dpB
nSZ
.
.max trong :
Smax : lc cng bng ln nht
B
-
n: h s d tr bn cho tm bng,ph thuc vo s lpli
Z 2-4 4-5 6-8 9-11 12-14n 9 9,5 10 10,5 11
B chiu rng tm bng[p]: lc ko t cho php ca mt mm chiu rng mt
lp vI
Vt liu bng
Li cp Vi dt tsI bng
Vi dt t sI tng hp
p [N/mm] 1500 -6000
55 150
n 7 8,5 9,5 - 10 8,5 10,5
-
Chng 16: Trm dn ng
Gm ngun dn ng (thng l ng c in), hp gim tc truyn chuyn ng quay cho tang dn. tng khnng ko cho tang dn, dng bin php tng h s ma st (tang chn khng, tang nam chm in t), hoc tng gc m.Vic ph trn b mt tang dn ng mt lp vt liu tng ma st c th cho h s dnh bm n 0,35 - 0,5.
ng knh tang c xc nh theo cng thc: D k.Z vi k :h s t l
Vi tang dn : k = 125 khi Z = 2 - 6; k = 150 khi Z = 7-12
Vi tang cng bng v tang i hng k = 50 - 125.Chiu rng ca tang nn ly ln hn chiu rng bng t
100 -200 mm
c.- Trm ko cng:Nhm to lc cng ban u cho tm bng c th
truyn lc ma st. Ngoi ra, sau thi gian lm vic bng bdn nn cn thit phi cng bng.
C th dng phng php cng bng thng xuyn hoc nh k. Vi thit b cng bng nh k, lc cng bng thay i theo bc nhy dn n tui th ca bng gim.
-
Dng vt iu khin cng Dng ti ko
Gc chy ca vt liu vn chuyn
Gc chy ca vt liu [0]Vt liu vn
chuyn
Khi lng ring [T/m3
]
Khi ng ()
Khi tnh ()
Gi trTnh ton
Gc nghing cho php ca bng
[0]Angtraxit 0.95 -
122.5 45 20 17 - 18
ptit kh 1.5 -1.7
15 -20 31 -45 20 18 - 22
t st t
1.9 - 2 20 - 25 45 25 20 - 26
Si vin trn
1.6 -1.7
22.5 45 20 18
t nn m tnhin
1.6 20 45 20 18
vi cc
1.5 -2.2
20 40 20 18
cc 1.8 -2.2
20 40 20 20
Ct kh 1.4 -1.65
20 45 20 20
Ct t 1.5 -1.7
25 50 25 20 - 22
-
Than 0.83 15 - 22 30 - 45 20 18
H s ph thuc hnh dng bng (kb)
Gc chy tnh ton ca vt liuS dy con ln bng 150 200 250Bng phng 1 con ln
250 330 420
500 580 660Bng mng 2 con ln
= 200 = 450
570 615 660
Bng mng 3 con ln
= 200 170 550 640 = 30 550 625 700 590 660 730 635 690 750
Bng mng con ln trc mm
519 570 610
H s gc nghing t bng (k)
Kh nng t chy ca vt liu
Gc nghing t bng (0)
5 10 15 18 20 22 -24
Nhiu 0.95 0.90 0.85 0.82 0.80Trung bnh 1 0.98 0.95 0.93 0.90 0.85
t 1 1 0.98 0.96 0.95 0.90
-
d.- H thng con ln :Trn nhnh c ti thng dng 2 hoc nhiu dy con
ln to cho bng c hnh lng mng khi vt liu vnchuyn dng vn ri. Trn nhnh khng ti c th dng 1 dy con ln.
Bc t con ln trn nhnh khng ti thng ly gp 2 ln so vi nhnh c ti, Bc t con ln ti v tr cht tithng ly 1/2 so vi nhnh c ti.
Bc t con ln c xc nh theo chiu rng bng v chng loi vt liu (1 - 1,5 m).
ng knh con ln d = 108 mm khi B = 400 - 800 mm
d = 159 mm khi B = 800 - 1600 mmCon ln c lp trn trc theo phng thc trc quay
hoc khng quay (thng gp hn).Ngoi ra cn phi k n cc thit b np liu, d liu,
thit b lm sch bng, thit b nh tm cho bng
3.- Tnh ton bng ti:S liu tnh ton:Nng sut Q [T/h]; chiu di vn chuyn L [m]; gc
nghing t bng [o]; loi vt liu vn chuyn.a.- Tnh chiu rng tm bng: (B)Chiu rng tm bng c xc nh trn c s m bo
nng sut yu cu.C: Q = 3600.A.v. [T/h] trong :
A: din tch tit din dng vt liu [m/s]V: vn tc vn chuyn [m2]: khi lng ring ca vt liu [T/m3]
-
Theo kinh nghim, chiu rng dng vt liu trn bng (b) c ly
b = 0,8B [ m].Nu t: 2.
3600b
kA b , ta c:
Q = kb.(0,8B)2.v Xc nh kb trong mt s trng hp:
Khi dng 1 dy con ln, c:A = 2.
4
tan.
4
tan..b
bb dd
Vy, ta c: 4
tan.3600 dbk
Khi dng 3 dy con ln, c:
Gi s b1 = b2A = A1 + A2 = d
bb
bb tan.4
'sin..
2
' 22
1
VI b = b1 + 2. b2 . cos = b1 ( 1 + 2. cos) Do :
4
tan.cos.21sin.cos1.
9
4
tan.cos.21.sin.cos1
4
tan.cos.21.sin..
2
)cos.21(
22
221
21
2211
11
b
bb
bbbb
A
Vy:
4
tan.cos.21sin.cos1.400 2
bk
Ngoi ra khi bng ti t nghing mt gc so vi phng ngang, th cn a thm vo h s k. Lc ny:
Q = kb.k(0,8B)2.v Gi tr ca c chn nh hn gc ma st gia vt liu v bng t 7 - 10 o
b
d
b2b1
b
-
T , c th xc nh chiu rng bng theo cng thc: m
vkk
QB
b ...25,1 ( sau chn li theo tiu
chun)i vi vt liu dng n chic, chiu rng bng c
ly ln hn kch fhc ln nht ca vt vt chuyn t 100 -200mm
Vn tc ca bng c xc nh trn c s va m bo nng sut, li va m bo vt liu khng b vng ra ngoi (do B nh).
Gi tr ca vn tc c chn ph thuc vo tnh cht vt liu vn chuyn v chiu rng bng (1 - 4 m/s). Ngoi ra gi tr ca vn tc cn ph thuc vo phng thc d liu.
-
Chng 17:
Xc nh lc ko bng tiLc ko bng ti phi khc phc cc lc cn chuyn
ng sau:- Lc cn khi tm bng di chuyn trn nhng con ln
ta c nh: Gm lc cn do ma st trong trc con ln , ma st ln gia tm bng v con ln.
- Lc cn do trng lng ca vt liu v bng trn nhng on bng nghing.
- Lc cn do bng vng qua cc on cong.
Do , lc cn chuyn ng c tnh ton theo nhng on bng c c im khc nhau v hnh hc cng nh vtnh trng chu lc:
- Trn nhng on bng thng, c ti nm ngang:Wctng = [ qvl + qb+qcl ].li .c trong :
qvl : trng lng mt n v di ca vt liu trn bngqb : trng lng ca mt n v di tm bng qcl: trng lng phn b trn mt dn v di ca cc
con ln trn nhnh c tic: h s cn chuyn ng (xc nh bng thc nghim)li: chiu di cc on bng
- Trn nhng on bng thng, c ti nm nghing:Wctngh = [ qvl + qb+qcl ].cos. li .c [ qvl + qb
].sin. li trong :i l gc nghing ca on bng so vi phng ngang Du + khi bng theo hng chuyn ng i lnDu - khi bng theo hng chuyn ng i xung
-
Tng qut:Trn nhng on bng c ti:
Wct = [ qvl + qb+qcl ].cos.Li .c [ qvl + qb ].sin.Li VI: = 0 nu nh on bng t nm ngangTng t, trn nhng on bng khng ti:
Wkt = [ qb+qcl ].cos. Li .c qb .sin. Li k n lc cn chuyn ng khi bng vng qua cc
on cong, mt cch gn ng, ngi ta a thm vo h sk.
Vy: W = k. (Wct + Wkt)
Trong cc cng thc trn: mN
v
Qqvl /36,0
vi Q{t/h]v [m/s]q0 = oB(Z +1 + 2) Trong : ,1, 2 l chiu dy
ca lp li vi v cc lp cao su 2 mt y [m], 0 l trng lng ring ca bng (vi bng vi cao su o = 1 -1,15)
t
Gq clcl
trong Gcl: tng trng lng phn quay ca cc con ln tI mt v tr t: bc t con ln trn nhnh c tI
'
''
t
Gq clcl
trong Gcl: tng trng lng phn quay ca cc con ln ti mt v tr . Thng b tr 1 con ln.
t: bc t con ln trn nhnh c tI.
Sau khi xc nh c lc ko bng ti ta tin hnh chn ng c theo cng sut tnh:
kwNt 1000..vWo vi l hiu sut chung ca trm
dn ngc.- Tnh lc cng bng trn ta tnh lc cn chuyn
ng theo cc h s cn c v k. C th tnh lc cn chuyn
-
ng mt cch chnh xc hn khi xt n cc yu t nh hng n lc cn khi bng i qua cc tang i hng, tang cng bng, tang dn. cng nh cc v tr cht, d ti, lm sch bngLc cng bng nhng v tr khc nhau c xc nh theo nguyn tc:
Si+1 = Si + Wi- i+1
Gn ng: Wtg = (Sv +Sr).sin (/2).f .(d/D)
Tng lc cn theo ng bng khp kn c xc nhW =Wct + Wkt + Wt + Wc + Wcht+ Wdt +Wls + WctLc cng bng ti im cun vo tang dn c xc
nh:
i19 W)()( SSSS rv (1)Mt khc ta c quan h gia Sv v Sr theo cng thc
Euler:
S6
S1
S2S3
S4
S5
S7S8 S9
L1
Sr
dD
Sv R
Sv
Sr
-
dt
fv
r k
eSS
. vi kdt = 1,15 - 1,2 (2)
T 2 phng trnh trn ta c th xc nh Sv, Sr v t xc nh cc Si.
Cc cng thc gn ng xc nh cc lc cn chuynng:
- Khi bng trt trn thanh dn hng cong:Wtr = Sv ( e
f -1) vi l gc m ca bng trn thanh dn hng
- Khi bng vng qua cc tang i hng, tng cng bng:
Wtg = Sv(kt -1)kt ph thuc vo gc m ca bng trn puly:
180kt 1,02-1,03 1,03-1,04 1,05-1,06
- Khi bng vng qua tang dn ng:Wtd = (0,03 - 0,05) (Sv + Sr)
..Trong cc lc cng Si, ta tm c lc cng bng ln v
nh nht kim tra sc bn cho bng cng nh vng bng theo quy nh.
- Lc cng bng ti thiuCn kim tra lc cng nh nht trn nhnh c ti vi
iu kin:
ftq
S.8
. 2min
S lc trn mt bc bng ti c th hin nh hnh v:Ta c: Sx . sin ' = q.x. cos
q
A
B
Of x
Sx
x
y
q.sin
C
Smin
'
q.cos
-
V Sx. Cos' = ST : tg ' = q.x.cos / SVi tg ' = dy/dx, c:
dy/dx = q.x. cos/STch phn 2 v ca phng trnh, c:
CS
xqdx
S
xqy cos..2
..cos.
. 2
Theo iu kin bin: x = 0 y = 0 c: C = 0 , Khi
-
Chng 18: XCH TIKhc vi bng ti, b phn ko v b phn mang ti
trong xch ti thng l phn bit.B phn ko trong xch ti l b truyn xch (1 hoc 2
dy). B truyn xch c th l xch ng bn l, xch hn hoc xch dp nh hnh. Tu theo b phn mang vt, ngi ta phn bit:
- Xch ti tm: B phn mang ti l cc bn thp- Xch ti co: vt liu c cha trong mng v c
vn chuyn bi cc tm co.- Xch ti treo: vt liu c cha trong cc thng treo
v c xch ko vn chuyn.1.- B phn ko :B phn ko trong xch ti l cc loi xch ko. Cc
thng s ca xch ko c ly theo TCVN 1583 - 74 i vi xch hn mt trn, TCVN 1585- 74 i vi xch dp v TCVN 1588 - 74 i vi xch tm bn l.
u im ca xch ko l dn di nh, kch thc ca a xch ( i vi xch bn l, xch dp) hoc rng rc xch ( i vi xch hn) nh, d tho lp vn chuyn.
Nhc im l khi lng nng, gi thnh cao v tc vn chuyn chm hn so vi bng.
Cng ging nh cp, vic tnh ton xch c tin hnh theo lc ko t:
Smax. n
-
S l ti trng ph hng.ng knh vng ln ca a xch (tnh n tm bn l
xch) :Vi xch hn:
Z
tD
o90sin
trong : tl bc xch; Z l s
rng ca a xch. Vi xch bn l: Z
tD
o180sin
2.-Xch ti tm:a.- S cu to: C s nh trn hnh v, gm cc b
phn:B truyn xch, gm xch ko (3), c dn ng bng
cc a xch dn (7) v cc bnh cng xch (10). Cc bn thp
(4) c lin kt vi trc con ln to thnh bng ti thp. Bng ti c di chuyn trn ng ray (6) nh xch ko.
-
Cc dng xch bn
Cc bn thp c th c thnh bn hoc khng. Thnh bn c th c c nh vi bn thp hoc vi khung kt cu kim loi ca xch ti.
So vi bng ti, xch ti c u im l vn chuyn c vt liu nhit cao, c cnh sc. Lc ko xch ti n nh v c gi tr ln, do vy xch ti c th c chiu di ln vi nng sut cao. Tuy nhin bng bn c kt cu phc tp, trng lng nng hn, gi thnh cao, chi ph cho bo dng ln.
Phn bit bng bn theo:- Tit din ngang, - Theo tit din dc, - Theo cu to
xch ko, - Theo s lng xch ko
-
Cc dng bn bng
b.- Xc nh cc thng s hnh hc ca bn bng:Cc thng s hnh hc ca bn bng (chiu rng, chiu
cao) c xc nh trn c s m bo nng sut yu cu khi vn tc c chn trc.
Thng vn tc ca xch ti c chn vx < 1,2 m/sC: Q = 3600.A.v.k
T : kv
QA
...3600
Tu theo kt cu bn bng, c A = B2. tg/4 hoc: A = B.h + B2. tg/4
Kch thc h c chn theo cc gi tr100,125,160,200,250,320 mm tu theo chiu rng ca bn bng: 400,500,650,800,1000,1200,1400,1600 mm
c.- Lc cn chuyn ng v cng sut ng c dn ng:Tng t nh bng ti, lc cn chuyn ng trong bng
bn bao gm:- Lc cn do ma st,- Lc cn do trng lng ca xch ti v vt liu khi
xch ti t nghing,
hB
-
- Lc cn ti cc v tr a xch.
C: Wo = k. (Wct + W kt) vi k = 1,1.Trong :Wct = [ qvl + qx ].cos. Li .c [ qvl + qx ].sinLi Wkt = qx.cos L .c qx .sin.Li
Trng hp ch c hai nhnh xch ti song song, t nghing gc , ta c:
Wo = k[ qvl + 2.qx ].cos. L .c + qvl .sin. L]Cng sut tnh:
kwNt 1000..vWo vi l hiu sut chung ca trm
dn ngd.- Tnh lc cng xch ,tnh chnh xc lc ko xch ti :Tng t nh bng ti, tnh lc cng xch Si ta chia
xch ko thnh nhiu on c cng c tnh chu ti v tin hnh tnh ton cho tng im theo chu tuyn.
Nguyn tc: Si+1 = Si + Wi - i+1Trong Wi - i+1 l lc cn chuyn ng trn on xch
ti (i - i+1)im xut pht thng chn l im xch ra khi a
xch dn. Gi tr Si chn ban u tnh l Smin nhm m bo
xch ti khng b vng qu gi tr cho php. Thng chn Smin gi tr t (1000 - 3000)N
Trong trng hp xch ko l 2 dy th lc cng xch tnh ton l:
Stt = (0,55 - 0,6 ).Smax Lc cn khi xch vng qua cc a xch i hng hoc
a cng xch l:Wx = (0,06 - 0,08).Sv
-
Lc cn a xch dn:Wxd = (0,03 - 0,05)(Sv +Sr)
-
1Chng 19: Xch ti coa