GB781722A - Improvements relating to guards for bending machines, press brakes and like machinesused for bending sheet metal - Google Patents

Abstract

781,722. Machinery guards. INDUSTRIAL GUARDING EQUIPMENT, Ltd. March 30, 1954 [Dec. 30, 1952; July 28, 1953], Nos. 32938/52 and 20850/53. Class 80 (4). In a bending machine controlled by a pressure fluid (preferably pneumatic) system upon actuation of a pedal 8, Fig. 9, or the like, a guard 3 is caused to descend under gravity and be locked in position by mechanical means actuated by fluid pressure before the beam 1, which is reciprocated by a clutch-controlled crankshaft, commences its down stroke, the guard being withdrawn by fluid pressure means just before the completion of the down stroke to avoid interference with the bent workpiece. The pedal 8 actuates a link 11 coupled to a pair of pivoted arms 12, Fig. 14, carrying a lever 13 which has a jaw 23 whereby the lever 13, and therefore the link 11 and pedal 8, may be coupled to a clutch-actuating link 15 on operation of the piston rod of a cylinder 22. Initially the lever 13 and link 15 are uncoupled, and depression of the pedal 8 to a first position causes the nose of a spring-loaded lever 16 mounted on the lever 13 to open an exhaust valve 20 and then rest on a stop 18. Opening of the valve 20, Fig. 7, exhausts a guard-raising cylinder 49 and allows the guard, which is carried by links connected to a shaft 44, to close under gravity. The consequent rotation of the shaft 44 moves a locking quadrant 51, Fig. 10, out of abutment with a quadrant 27 on a shaft 29 and simultaneously causes a finger 50 to open a valve 41 admitting fluid from a supply 78 through a valve 63 to one end of a cylinder 31. The other end of cylinder 31 is exhausted through a valve 56 coupled to the valve 63. The piston rod of cylinder 31 then rotates the quadrant 27 into guard-locking engagement with an upper edge of the quadrant 51 to prevent its clockwise return, and as this locking movement is concluded a nose 26 on an auxiliary quadrant integral with the quadrant 27 engages a member 28 to open a valve 25. The valve 25 then admits fluid to one end of the cylinder 22 causing it to couple the links 11 and 15 as described above, the movement allowing exhaust valve 20 to close. The operator may then, by additional depression of the pedal 8 to a second position (overcoming the resistance of the spring- loaded lever 16), engage the clutch to start the rotation of the machine crankshaft. Geared to the crankshaft by a chain 37, Fig. 9, is a cam shaft 36, Fig. 13, carrying a cam 56a which, as the beam 1 nears the completion of its down stroke, changes over the twin valves 56, 63 to admit fluid to the other end of the cylinder 31. The quadrant 27 is then withdrawn clear of the quadrant 51 to unlock the guard and to cause a nose 54 on the quadrant 27 to open a valve 52 admitting fluid to the cylinder 49, whereby the guard is raised and held raised until the pedal has been released and redepressed to open valve 20 and commence a fresh operating cycle. The valves 56, 63 are carried by one arm of a bell crank pivoted on the cam shaft 36, the other arm being adjustably held by a bolt passing through an arcuate slot in a fixed member so that the moment at which the guard is unlocked and raised may be adjustably predetermined. Towards the end of the return stroke of the beam 1, a cam 35 on the shaft 36 opens a valve 32 to admit fluid to the other end of the cylinder 22, causing the latter to disengage the lever 13 from the link 15 whereupon the clutch is automatically disengaged and the working cycle thus completed. According to the first Provisional Specification the fluid control system is modified so that the machine clutch is automatically engaged when the guard is locked, no further pedal actuation being required. In this construction a push knob is provided whereby the pedal may be locked to cause continuous stroking of the machine.