Patent GB-886461-A (GB)
Title: Level control and stop device for hydraulic press brake and the like
IPC: B30B15/24
Filed: 1960-01-01
Abstract: 886,461. Hydraulic presses. CINCINNATI SHAPER CO. Jan. 1, 1960 [Jan. 2, 1959; Jan. 21, 1959], No. 104/60. Class 69 (2). An hydraulic press having a frame 10, Fig. 1, and a bath 12 comprises a vane 13 connected to the pistons of a pair of cylinders 14 mounted on the frame, a control system which has means 21 to detect continuously which of the pistons is in advance of its proper position in either direction of movement and is in operative connection with means 46, Figs. 4 and 8, to bleed hydraulic fluid from the pressure side of the cylinder of the advanced piston, and top and bottom stops 106, 112, Fig. 12, vertically adjustable, with respect to the frame, the bottom stop being independent of movement of the frame. The detecting means consists of a steel tape 21, Fig. 1, which passes above and below pulleys 25, 26, respectively, and has one end secured by a clamp 20, Fig. 6, to a spindle 16 mounted in a bracket 15 fixed to a cross member 11 of the frame. The opposite end of the tape is secured by a clamp 52, Fig. 4, to a spindle 48 mounted in a member 44 of a carriage 37. The spindle 48 is secured to the spool of a valve 46 which is connected to lines 73, 74, Fig. 8, leading from a pump P to the cylinders 14. The spindle 48 is spring-urged upwardly and can move a small amount both upwardly and downwardly relative to the member 44. During parallel movement of the vane, the movement of the pulleys has no effect on the ends of the tape. If one end of the ram advances with respect to the other, the displacement of the pulleys moves the upper end of the tape to move the spool of the valve 46, the slightest of movements, say 0.0001 inch, bleeding fluid from the cylinder of the leading piston to a sump 120. The spindle 16, Fig. 6, is urged downwardly by a spring 17 and the clamp 20 has an extension 22 which, in the event of a gross misalignment of the ram in one direction, or breakage of the tape, operates a limit switch 24. The carriage 37 is vertically adjustable on the cross member 11 by a hand wheel 45 and spindle 42, Fig. 3, and in the event of a gross misalignment of the ram in the opposite direction, the tape pulls the carriage down, the spindle 42, which is in threaded engagement with a sleeve 29, moving the latter downwardly against a spring 32 so that an extension 33a operates a further limit switch 36. Adjustment of the carriage 37 by the hand wheel 45 causes the body of the valve 46 to move relative to its spool and fluid to be bled from one or other of the cylinders 14 until the ram has assumed a desired angle and the body of the valve moved to a position to stop further bleeding of the cylinder. The tape and valve 45 then function during operation of the press to retain the ram at the desired angular setting. A counter 40 enables the movement of the carriage, and hence the angle at which the ram is adjusted, to be determined. The movement of the ram is limited by the top and bottom stops 106, 112, Fig. 12. The stop 106 is adjustably-clampable on a rod 104 secured to the frame and is a clearance fit on a threaded rod 96 connected by bevel gearing 94 to a rod 95 mounted in bearings 97 in the bed 12. The rod is rotatable by a hand wheel 98 to vertically adjust the lower stop 112, the amount of movement being determined by an indicator mechanism; distortion of the frame during pressing operations does not affect the position of the stop 112. The stops 106, 112 actuate limit switches 85, 87 which control a solenoid-operated pilot valve 71, Fig. 8, controlling a main reversing valve 72 which directs the supply of fluid pressure from the pump P to the upper or lower ends of the cylinders 14. In the event of overshoot of the ram, a plate 118, Fig. 12, engages the stops which are swung out of position against the action of springs 115. The pump is of the type which supplies equal volumes of fluid to the lines 73, 74 leading to the cylinders 14. An adjustable cam 109 is carried by the rod 104 and during part of the movement of the ram operates a switch 90 controlling a solenoid-operated differential valve 70, Fig. 8, which, in one position, connects the lines 123, 124 leading from the lower ends of the cylinders to the sump 120, and in its alternative position, blocks the flow to the sump so that the fluid passes through one-way valves 146, 148 to be added to the fluid from the pump supplied to the upper ends of the cylinders for rapid movement of the ram. During the downward movement of the ram, fluid from below the pistons passes through pressure-relief valves 125, 126 to the differentialpressure valve 70, and during upward movement flows through the lines 121, 122 to a back-pressure valve 140. The pressure in the lines 121, 122 connected to the upper ends of the cylinders is indicated on a gauge 130 and a pressure switch 131 is provided to raise the ram if the pressure exceeds a predetermined value. The press is controlled by a foot switch and a selector switch in an electrical relay circuit containing the up and down limit switches 85, 87, the pressure switch 131 and the safety limit switches 24, 36. The selector switch can be set to a " normal " position, in which the operation of the switch is automatic when the foot switch is actuated and in which, upon release of the foot switch the ram rises, and an " inch " position in which the ram can be moved incrementally downwards by operation of the foot switch, the ram remaining stationary upon release of the foot switch. Signal lights indicate the direction of movement of the ram.