May CNLT co nhieu hop can chi quay thea mQt chieu va di,it noi tiep nhau. Ph(ii dUde can cung mot ilic qua Ian IUdt cac hop can.
May CNLT co nhh~u kieu lo;;ti voi nhi~m v~ can khae nhau
- May can phoi chuan bj : de' t~o phoi cho cac may can khac nhu : can phan
lo~i, ean dliy, can ong.. DAy la may can ph6i vuong tU 300 xuong (55 + 150)mm. No co the' gam nhieu nhom hQp can voi cac duang kinh trl,lc khac nhau. Toc d(l can (5 + 6) m/s.
- May can Him (hay can la) : dung can cae phoi det thanh bang tMp r¢ng tu (500 + 2300)mm, day (0,8 + 20)mm. Ph6i co the' ni;j.ng toi 45T" Toc dQ can 30m/s
va nang suat co the' d<:lt 6,000.000T/nam May can tam co 2 nh6m h¢p ean nhom can tho va nh6m can tinh.
,
May can Ii co thCi la lien tl,lC (neu ph6i di lfin IUQt tu hQp can nay sang h¢p can khac mQt cach lilln tl,lc) hoi;j.c nua lien tl,lc (neu phOi dUQc can di can l<:l-i a hQp can nay rai moi qua Mp can khac).
- May can phan IO<:li fiH da d~ng ve th~ IO<:l-i Thanh pham la cac chung IO<:l-i thep khac nhau vi! hinh dang, kich thl1oc,
- May cin day san ph am la day thep (5 + 10)mm.
- May can ong ; cd the la can nhiin (d~' dam bao kfch thttac ngaal cua 6ng), can dat (de khu sJ,t kh6ng d6ng deu duang kfnh, lam nhan m~t trang va m!).t ngoai cua 6ng), can tdp hay chu6t (de thu nha duang kinh 6ng).
Di'! hie'u v~ mOt day chuylln tr~n may CNLT, ta xet qua c6ng ngM may can la : Ph6i det dUQc nung trang 16 nung d€n (1150 -;.. 1280)oC va chuyen tbi b:lng Ian thu nh,(in, Wi h()p can tho cd trl,lc thAng dang. d day ph6i duqc danh vay (ri do nung nong) va duqc djnh kich thuac chuiin ve chieu r('lng. Sau dd, bAng Ian lam vi~c dua ph6i Wi h()p can thO cua may danh yay de ti€p tl,lC danh Yay va can ep giam kfch thuac chieu day dll"n 25')f, kich thubc ban diiu. Ti€p thea, ph6i dU<;lc chuyen tai h('lp dn vl.ln nang dao chieu 4 trt,lC (2 trl,lc lam vililc, 2 trl,lc tJ,ta) d~ can di, can l<:Ii til 3 -;.. !)
. Ian vA cho ra ph6i thep dAy (20 + 35) mm. Sau do, duqc b:lng Ian trung gian chuye'n 't6i may cAt bay de cat bavia. Cuoi clIng, chuyen t6i nhOm hOp can tinh cd 6 -;- 8 hOp can 4 tr\lc quay m¢t chieu de' can Mn tl,lC Tru6c khi k€t thuc can tinh, bang thcp ll,li dUQc cat bavia va ra khoi nhom hOp can tinh thi dUQc bAng IAn (da.i Wi 200m) chuye'n vao may quffn de quan va.o cac rul6. Trong khi chuyen tr~n bang Ian vao may guiln, kim lo~i duqc thOi lam l?nh xu6ng nhi~t d¢ cAn de qwln.
May CNLT co d~c diem la ;
- Toc d¢ can caa n~n n!lng suat caa.
- Qua cac Ian can, kim lo~i chua nguOi nhieu nen chat lUQng san pham t6t,
tu6i th9 trl,lc can caa han, giam dUQc su.1t tii§u haa nAng luqng. - May lam vi~c voi toc dO caa nlln hay xu.1t hi~n phl,l Uti xung.
- Kim IO!,li can tr~n nhieu h¢p can clIng m('lt luc n~n giii'a cac h('lp can ph.?ti co
m6i lien M ch~t che ve t6c dO.
a) Di~u ki(!n dij.c trung. Dieu ki~n d!).c trung cho can Mn tl,lC III kh6i lU<;lng ph6i qua cac h¢p can trong 1 dan vi thai gian la kh6ng d6i (hlnh 8 - 30) :
F,Vj = const (8-35)
trang dd :
Fj - ti€t di~n pMi trttoc hic vao hOp can thu i, Vj - tdc d¢ phoi truoc luc vila h9p can thu. i.
Neu kh6ng dAm baa dieu ki~n (8-35) thl xAy ra hi~n tuQng :
- can nen (ep) : Khi khoi Iugng ph6i ra cua 1 hOp can nha han kh6i lUQ"ng phOi taL
- can keo (cAng) : Khi kh6i lUl;mg phOi ra cua 1 hOp can Ion han kh6i luqng ph6i Wi.
Do cd 81,1" VUQt truac (xern § 8.2) nen t6c dO phOi ra kh6i trl,lc la :
w,D
2 (1 + s)
Fj'lj _ .. '
Hi"" S - 30. Can lien tvc 3 h~p cfm.
trong dd : VI' WI' D - la toc d¢ dai, t6c d¢ goc, duang kinh cua truc can ; 9 -
d<J vt1<;lt trliac (xern §8.2
Va dH~u ki~n dl)C tntng (8 - 35) co the viet:
FD wI (1 + s) = const (8-36)
( IJ ilJ
Vai 2 h¢p di.n lien ti~p (hlnh 8 - 31 )
ta co /nnh II - .11. C:on II) un oi lM v6ng FJDJwJ (1 + 91) = F1D1w1(1 + sl) Neu DJ = Dz = D thi ta co : = trong dci (8-38)
gQi it'J. h~ 96 keo ;
b) Cac chi! dt) can. Hai hOp can lien tilp thlla mdn dieu ki¢n (8-37) tid phai
kMng chiu cang hay nen. Do la. trq.ng tluii
can tlf. do. Truon.g hqp n.a.y vrl = vv1'
V-, , = b (8 - 37) = b (8 - 37) (f) IZ! + w, w2 + ,\-, ~" ''rz
Khi ph6i co tiet di~n nha, co the gilta
2 hl;lp can co d(l v6ng nao do rna neu db vang ouy trl su6t qua trlnh can thi chi' d¢ clin vlin Ja ch~ d(l t\1 do. Ta vAn cd
v rl = Vy1 (hlnh 8 - 32). ffllth II - .12 . C;in H,I Ull co U~ v6ng. Bay gia, n~u gilt wI = const rna tang w2 thl pMi se chin rn¢t I\1C co.ng. Lt,tc nay co xu hullng tang t6c d(l ra vrl 0 b(lp can (1) va giarn t6c d¢ vao Vy2 0 b(lp can (2).
Neu giii' WI = const rna giarn w
2 thi pMi se ch~u mOt i\1c nen. Lt,tc nay cd xu hUo-ng giarn t6c d(l ra vrl i'J Mp can (1) va ta.ng t6c d(l vao vv2 a h¢p can (2)
Khi DI = D1 (d1.1Ong kinh trl,lc can 2 h(lp can gi6ng nhau) thl It,tc cang hay nen
xac djnh hoi bi~'u thu-c :
T (J - 1)(1 + 51) 1 + 91 (1+J1+S2)~ trong dci : 142
I(J - h(! s6 dnh den s\f vLiQt truoc do It,tc T b - ti s6 thay d6i t6c d¢ hOp can (2)
o =
w' 2 - toe d~ h<)p can (2) sau khi thay d6i.
Tit do ta th.1y : tuy toe d(l quay gilill cae hOp crin, co the co cae ch6 dO (trang thai) can khac nhau.
- Can tv do o = 1, T = 0
w2 1 + sl - Can keo (can can g) 0 > 1, T > 0 va > ,
wI 1 + "
(0 I. ht? so keo cang)
w2 1 + 51
- Can nen (can ep) 0 < 1, T < 0 v' - = ,
wI 1 + "
(0 ill h(> s6 nen ep)
a ch€ d¢ can keo, m5men dOng cd truy~n dqng hQp can (2) se tang :
D2
Mz=Moz+TT con cua d(>ng cd truytln d(lng h(lp can (1) se gilim
DI
M! = Mol - T 2
trong do : Mol ' Mol ill mOmen cua 2 d¢ng co do a ch€ d¢ can tl,1 do.
Neu d'!,c tinh cua 2 dOng co m{!m thi do Ml ta.ng , t6c dO om s('! giarn nhanh va do M, giArn, toe d¢ DDl se tang nhanh. Tli do hl.lD ch€ dl1QC 81,1 ta.ng h1e cang T. M~t khac, trvc can co bien dl.lng dim h6i khi can n~n neu dOng co D1 co d~c
dnh mem thl !uc m6men giam, bien dl.lng dan h6i cua trvc h¢p can (1) cling giArn. Dieu do lAm ta.ng hIe ep cua tr\lc l~n phOi, giAm nha ti~t di~n phOi b) can, tang duc;1C t6c d¢ ra vrl . K~t qua cl1ng hl;ln ch€ th@m h!c ca.ng T.
V~y, d~c tinh mem clla dOng co la m¢t y~u t6 de tl,t My ll;li cAn bAng trong can kl~o, song chua dap ung duc;1C y@u criu cua may CNLT nen van cAn co cac sa d6 dieu chinh.
a ch€ d¢ can nen, phOi giUa 2 hop can co dQ vOng. D¢ vOng nAy luOn thay ddi trong qua trinh can, song khOng duc;1c qua mOt giai h~n cho phep. Vi~c dieu chinh dO vOng nay trong may CNLT co the th1!C hi~n ba.ng tay (khi t6c d¢ can nha) hay tI,t dQng (khi t6c d¢ can Ian).
Neu ph6i dai L duc;1c can vai t6c dQ v
L
t = - hay
v
thi thOi gian
~L '
t = -
~v
can 1 ph6i Ja :
6. L lit chi~u dai doan vOng them, 6.v Is dao dQng t6c dO gWa 2 h¢p can.
Suy ra ~1 = L -~v
nghia Iii, chil~u dai pM.n vong them ti l(l vdi d¢ dai ph6i va va d¢ thay dOi tuang d6i cua t6e do ean.
e) Phu tdi J:ung. Trong may CNLT, do m6i quan hQ chi),t eFte v{! toc d() giua
cae h¢p can ma khi thay d6i se hIm thay dOi chtr d¢ ean (da xet tren) n~n ph1,l tAi xung eo y nghia quan trong.
Khi h¢p can ngo~m ph6i s6 xu1t hi~n tai xung lam toc d!) d¢ng ca b~ giam
m~nh. Dae dnh qua d¢ cua tOe d¢ va dong d¢ng cd bien dQng. Bien d¢ng nay phl,l thuqc ti 56 gifta hang 56 thai gian cd
di~n Ted clla he truyen d()ng va hA.ng ~ <1
s6 thai gian di{m tu mach phan !lng
Ted ~
d(mg cd Tli la -
T,
Ve Ii thuyet, (hinh 8 - 33) ta da biel daa d()ng xay ra khi
Ted
4T, < 1
nghla 13 khi Ted < 4TlI.
t
•
o
m"h 8 - 33. ChC dO ean (,'Ii rung.
Vi ml.l-ch di~n cam nfln khi co xung ph1,l tai thi dong di~n thay dOi chl),m pha hdn (hlnh 8 - 34).
Trang khaAng thai gian (to + tl ) thi dong dOng cd nha han dong tai dnh Ie' t6c dO d¢ng ca giAm da:n.
Trang khoang thai gian (tl + t2 ) thi dong d¢ng ca Ian hdn dong tai dnh
Ie. t6c dO dOng ca ta.ng dan ....
Nhu hinh 8 - 34, ~wd la d¢ giAm t6e dQ ~we Ia dq giAm t6e tlnh, we la toc dO 6'n djnh.
Khi co tai xUng, t6c d¢ dOng Cd a
che dO qua dO dt1~c xac d~nh thea dl)c dnh dOng ca ed xet den Sl,lt ap do cam
khang tren mliich phan dng nen dT, U-I~Il-Llldt k vai k la M s6. w w, t--'l\ i Ie I, I, ffl"h 8 - 34. ~ t I, f, fJ /
SI,I eh.\l.m ph!!. eua dong di¢n Irong tnldng ho;)p phI,! tai xung.
Vi luc co tAi xung
dT,
L dt Ian nl'ln /luId cllng UIO.
Vlli may CNLT, khi ph6i va~ may, Ian IUQ't qua cae h¢p can, daa dOng do tM xung hie ngo?m ph6i cua cae hOp can cd th~ phS. va s~ cAn bAng toe dO giua eac hOp can, gAy ra san pham kern vA thl),m chi pM. hong ch~ dO ca.n cua may.
Hl1lu qua tren co thg th!iy ro khi xem xet qua tdnh ngol;lm phbi cua 2 hQp can lien tiep (hlnh 8 - 35). Tl;li thbi didm t]> phbi tai hi?p can (1). Do ngol;lm pMi, toc dQ dong Cd Dl giam va dao dOng. Tl;li thbi diem t 2, phoi toi h¢p can (2). Do ngol;lm ph6i, t6c de) d.,ng Cd D2 giam va dao 1:IOng. K€t quA, trong khoang thbi s!an (t2 + t), idc de) w2 > w"
ltic T > O. Trong khoang thbi gian (t3 + t4) t6c d~ (.:12 < wi'
IlJC T < 0 v.v ... Nhu v{l.y, che d¢ can ph6i hi thay d6i, luc thl cAn keo, Wc thl can nen ...
M¢t van d~ nua din de c~p
(2 ) , , --, -,-. ..--+;f: , , I , no: T<O ,
Ifj"h lJ-3.'i. lJieu dO quan he It'ic dO eua 2 hOp din lien liep
khi ngo:;tm pMi.
a da.y Ia voi dong Cd co dl).c dnh m~m thi bii'!n dOng t6c de) cang IOn dAn den bii'!n dc;mg IlJC T Ibn, do do, khong nl!n dung d¢ng Cd co d~c dnh Cd qua m~m.
Tom ll;li : a may CNLT can dap I1ng yl!u cliu Cd ban la duy trl mOt ti 86 t6c d6 nhat dinh giua cac hOp can va di~u chinh dligc t6c dO dOng cd thea yeu cliu cua <!hi'! d¢ can.