GB856730A - Stretching machines - Google Patents

Abstract

856,730. Stretching. HYDRAULIK G.m.b.H. Jan. 31, 1958 [March 30, 1957], No. 3312/58. Addition to 838,632 and modified by 844,897. Class 83 (4). Apparatus for stretching metal sheets includes crossheads, for gripping the ends of a sheet, one of which crossheads is pushed away from the other, to stretch the sheet, by hydraulic means between the crossheads, the movable part of the hydraulic means acting through pressure-members which extend from the means to the movable crosshead, pressure members extending also between the fixed crosshead and a stationary part of the hydraulic means to take up reaction, is characterized in that shock-absorbing means is provided for pressure-members which extend to the crosshead which remains stationary during stretching, the inner ends of which pressure-members are secured to pistons in the same cylinders as pistons which, during stretching, move the pressure members extending to the movable crosshead. A crosshead 1 gripping one end of a sheet is pushed away from a stationary crosshead 2 gripping the other end of the sheet by a pair of pressure-members 5 extending, one on each side of the sheet, between centrally-disposed hydraulic cylinders 3 and the crosshead 1, pistons 4 in the cylinders 3 being connected to the members 5 which have means 10 adjustably locked thereon to abut the crosshead 1. Stationary pressure-members 6 extend from the cylinders 3 to the stationary crosshead 2, locking- members 9 on the members 6 abutting the crosshead 2. Pistons 7 on the inner ends of the members 6 are normally held stationary in the cylinders 3 by shock-absorbing means 8 which each include a piston 26, connected by a rod 25 to a member 6, normally held pressed against the end of a cylinder 27 by pressure liquid from a reservoir 16 loaded by air pressure. If a sheet should tear while being stretched the resultant shock moves the piston 7 back, the piston 26 moving back in its cylinder 27. The pressuremembers 6 may alternatively be backed by plate-springs instead of the means 8. The positions of the crossheads 1, 2 are adjusted prior to stretching by rods 11 moved by pistons 12 in cylinders 13 normally closed at their outer ends by pistons 14 pressed against stops 17 by pressure from the reservoir 16. If a sheet breaks during stretching the resultant shock moves the piston 14 back.