Patent GB-1230165-A (GB)
IPC: F15B11/22
Filed: 1968-04-18
Abstract: 1,230,165. Shearing. ENTWICKLUNG VON OLHYDRAULIK UND MASCHINENBAU G m b.H. 18 April, 1968 [18 April, 1967], No. 18537/68. Heading B3W.  Control means for maintaining an hydraulically actuated movable press platen 52, particularly in a trimming press parallel with a fixed platen 52<SP>1</SP> by controlling the flow of fluid to the cylinders 9 and 67 includes a shaft 53 extending along the platen 52 and carrying at each end a pinion 54, 55 and in the centre a pinion 56, the pinion 56 engaging a rack bar 57, mounted on a fixed stop 83, Fig. 8, for sliding movement in the direction of movement of the platen, and each end pinion co-operating with a respective freely-suspended rack 47, 50 and 48, 51 to rotate a spindle 43 or 44 and thus a disc 18 or 19 in a direction selectively to connect fluid passages through a valve body 3 to counteract any deviation from parallelism as the platen is lowered. Pinions 45, 46 on spindles 43, 44 engage rack bar portions 47, 48 respectively. Hollows in the disc faces such as 73a in disc 18, shown in Fig. 3, in broken-line superimposed on the adjacent end face of valve body 3, selectively and variably connect fluid passages in the body 3 as the discs are rotated. Disc 19 is formed and arranged in similar but reverse fashion. A piston (16) extending substantially the length of the body 3 is normally spring-loaded to central position (shown in Fig. 1) in which it blocks fluid flow to the cylinders 9, 67. For a press stroke fluid is supplied to the chamber (63) at the right hand end of the body to move the piston to the left. While the platen 52 moves parallel to platen 52<SP>1</SP>, pinions 54-56 run over the rack bar portions 50, 61 and 57. If the platen becomes skewed, the left-hand cylinder 67 leading the right, the rack-bar portion 50 is drawn downwards and the rack bar portion 51 is raised, causing the discs 18 and 19 to rotate anticlockwise when viewed from their respective ends of the valve body. This throttles the flow of fluid to the upper chamber and from the lower chamber of cylinder 67 and increases the flow of fluid to the upper chamber and from the lower chamber of cylinder 9. If the error is still not corrected further anticlockwise rotation of the discs establishes communication between the upper chamber of cylinder 67 and a return circuit and completely cuts off the flow of fluid from the lower chamber of cylinder 67 to the return circuit, fluid flowing to a "dead end" in the body 3, so that pressure builds up beneath the piston of cylinder 67. The platen can be accurately stopped and its working stroke varied by means of an adjustable stop 80 on the platen 52, Fig. 8. The rack bar 57 is constrained to move downwards with the platen 52, over the distance indicated by arrows, once the stop 80 has engaged the bar. The shaft 53, and racks 47, 50 and 48, 51 are thus lowered and cause the pinions 45, 46 and discs 18, 19 to rotate in opposite directions when viewed from their respective ends of the body 3 which cuts off the flow of fluid to the upper chamber of both cylinders 9 and 67 and stops the platen 52. The valve body may be formed in two sections for operating the respective cylinders.