8: Nou cung dung, phon loai, ctao, nguyon ly làm viec, xoc dinh coc thung so chonh cua coc loai moy tron hon hop bo tong (moy tron tu do và tron cuong buc.
I. may tron be tong
1. Phan loai
* Theo phuong phap nhao tron: may nhao tron cuong buc (may tron cuong buc) va loai may tron nhao tron tu do (may tron tu do).
* Theo nguyen li lam viec: may tron lam viec lien tuc va may tron chu ky.
* Theo kha nang di dong: may tron co dinh va di dong.
2. May tron be tong tu do
Viec nhao tron cac phoi lieu trong may tron tu do duoc tien hanh trong cac thung tron, o thanh trong cua thung tron co lap co dinh cac canh tron. Khi thung tron quay, hon hop duoc nang len nho cac canh tron va nho luc ma sat toi do cao can thiet roi do hon hop xuong. Do dong nhat cua hon hop duoc dam bao sau 3040 chu trinh nang va do.
De hon hop duoc nhao tron tu do trong thung tron, dung tich hinh hoc cua thung tron phai lon hon khoang 2,53 lan dung luong tron Vo. Thong thuong trong xay dung, cac loai thung tron co Vo= 100; 250; 500; 1000; 1200; 2400 va 4500lit. Thuc te, cac may tron be tong thuong duoc goi ten theo dung luong tron Vo. Toc do quay cua thung tron khong lon, boi vi neu qua lon thi luc quan tinh li tam cua hon hop se can tro qua trinh nhao tron tu do.
a. May tron be tong kieu roi tu do loai di dong
May tron be tong (hinh 9-1) gom co: gia may 1, tren do co lap dat thung tron dang qua tao 6 voi co cau dan dong 8, he thong cung cap nuoc 3, bang dien 2, gau nap phoi lieu 4, co the truot tren gia truot 10 va co cau nang gau 5.
He thong cung cap nuoc gom co: dong ho do nuoc, van dieu khien bang tay va thiet bi phu khac. Thung tron duoc lap dat bang then voi dau ra cua truc co cau dan dong quay 8, co cau nay duoc co dinh o tren gia treo lat thung, gia treo duoc treo o gia may thong qua cac o do. Khi gia treo quay thi truc quay cua thung tron se bi nghieng di so voi phuong nam ngang o vi tri nap la 350, o vi tri tron la 70, o vi tri xa 450. Co cau dan dong bang tay de lam nghieng thung tron bao gom: Vo lang quay, hop giam toc 7 va co cau dinh vi ma sat. Dia dinh vi duoc phanh dung nho thanh keo lo xo 11, thanh keo nay co ban dap dieu khien 9. Thung tron duoc truyen chuyen dong quay nho duoc noi truc truc tiep voi dong co-hop giam toc.
Hinh 9-1. May tron be tong kieu roi tu do loai di dong
1- Gia may; 2- Bang dien; 3- He thong cung cap nuoc; 4- Gau nap phoi lieu; 5- Co cau nang gau; 6- Thung tron; 7- Hop giam toc; 8- Co cau dan dong; 9- Ban dap dieu khien; 10- Gia truot; 11- Thanh keo lo xo.
b. May tron be tong kieu roi tu do loai co dinh
May tron be tong tu do co dinh (hinh 9-2) gom co gia may 9 tren gia co lap co dinh cac tru do 7, gia treo 8 co mang theo co cau dan dong va thung tron 4 duoc lap vao cac o do cua cac tru do. Thung tron duoc tua tu do tren cac con lan do 5, 10 va duoc ngan chan tranh chuyen dich doc truc thung nho con lan chan 6. Thung tron duoc truyen chuyen dong quay tu dong co dien qua hop giam toc toi vanh banh rang 3 co dinh tren thung tron.
May tron be tong tu do co dinh co thung tron nghieng do:1- Xy lanh khi nen quay thung; 2- Pheu nap; 3- Vanh rang; 4-Thung tron; 5, 10- Con lan do; 6- Con lan chan; 7- Tru do; 8- Gia treo; 9-Gia may.
Cac phoi lieu duoc nap vao thung tron thong qua pheu nap 2. Thanh pham duoc xa ra khi thung tron nghieng di mot goc 550 so voi phuong nam ngang. De nghieng thung tron thi gia treo phai quay nho xilanh khi nen 1.
3. May tron be tong cuong buc
a. May tron be tong cuong buc lam viec chu ki
Loai may nay dung de san xuat hon hop be tong co do lon cua cot lieu khong qua 70mm va cung duoc dung de san xuat vua xay dung, san xuat hon hop trong linh vuc san xuat vat lieu thuy tinh va gom xay dung.
Pho bien nhat la loai may tron ro to, boi vi cac bo phan cong tac cua no co the lam viec voi van toc cao. Trong cac loai may tron nay hon hop duoc nhao tron trong khoang khong gian vanh dai tron cua vo thung co dinh boi he thong cac canh tron, duoc lap dat voi cac ban kinh khac nhau va duoi cac goc khac nhau. Ket cau loai may tron nhu vay hop li hon nhieu so voi loai may tron tao cac dong nguoc nhau co thung tron quay
b. May tron be tong cuong buc lam viec lien tuc
Loai may tron nay duoc su dung rat rong rai de san xuat vua be tong va vua xay dung, trang bi cho cac tram tron lam viec lien tuc voi nang suat 5, 10 va 30m3/h. Hien nay duoc dung pho bien la loai may tron canh hai truc nam ngang (hinh 9-5).
Thong qua cac thiet bi dinh luong tuong ung cac phoi lieu duoc nap theo dong lien tuc vao thung tron dang mang 8, ben trong thung tron co bo tri 2 truc tron 6 co gan cac canh tron 7 quay nguoc chieu nhau. Cac canh tron duoc lap dat nghieng so voi truc tron, sao cho hon hop duoc tuan hoan manh me theo phuong huong tam va tu tu di chuyen ve phia cua xa 5. Cac truc tron duoc truyen chuyen dong quay tu dong co 1 qua bo truyen dai 2, hop giam toc 3 va cap banh rang truyen dong 4.
Chat luong nhao tron cua hon hop o che do lam viec lien tuc cua may tron chi dam bao duoc neu nhu hon hop duoc luu giu o trong thung tron mot khoang thoi gian can thiet.
Dieu nay chi dat duoc khi dam bao su tuong quan hop li giua chieu dai cua may tron, van toc goc cua cac truc tron va so do lap dat cac canh tron. Tren moi truc tron co lap dat 3060 canh tron duoc bo tri nghieng mot goc 40450 so voi truc tron. Mot so canh tron duoc bo tri duoi cac goc nghieng sao cho hinh thanh cac dong hon hop chuyen dong dan cheo nhau, do vay lam giam toc do di chuyen doc truc cua hon hop va tao ra cac vung nhao tron manh me.
May tron lam viec lien tuc co hai truc tron nam ngang: a- Hinh chung; b- So do truyen dong cho cac truc tron; 1- Dong co; 2- Truyen dong dai; 3- Hop giam toc; 4- Cap banh rang chu dong; 5- Cua xa; 6- Truc tron; 7- Canh tron; 8- Thung tron hinh mang.
4. Xac dinh nang suat cua may tron be tong
- Nang suat cua may tron chu ky duoc tinh theo cong thuc:
= Vo . f. m. ktg , m3/h
trong do Vo - dung luong tron, m3;
f - he so xuat lieu, bang ti so giua dung tich be tong da tron xong va dung luong tron:
Doi voi vua be tong f = 0,650,70; doi voi vua xay dung f = 0,750,85;
m - so me vua tron duoc trong 1 gio:
voi t1 - thoi gian nap cac phoi lieu vao thung tron, t1= (1020)s;
t2 - thoi gian tron hon hop, t2= (60150)s (neu keo dai qua be tong se bi vua, do vay neu phai cho khi do be tong thi chi duoc tron kho sau do khi nao dung moi duoc tron uot);
t3 - thoi gian xa be tong, t3= (1030)s;
ktg - he so su dung thoi gian.
- Nang suat cua may tron cuong buc lam viec lien tuc:
Q= 60 Av, m3/h
trong do: - dien tich trung binh mat cat ngang cua dong vat lieu co trong thung tron, m2;
d- duong kinh canh tron, m;
kn- he so nap lieu, kn¬=0.280.34;
v = S.n- toc do di chuyen cua hon hop theo huong doc truc thung tron, m/ph;
S- buoc canh tron, m;
n- so vong quay cua truc trong 1 giay, vg/ph.
