Patent GB-847810-A (GB)
Title: Improvements in mechanism for feeding blanks or components to power presses and likemachines
Inventor: EVANS FREDERICK ARTHUR
IPC: B21D43/02
Filed: 1955-12-02
Abstract: 847,810. Feeding sheets. PRESS EQUIPMENT Ltd. March 4, 1957 [Dec. 2, 1955; March 7, 1956], Nos. 34516/55 and 7154/56. Class 100(1) Single sheet feeds; control &c. devices :- Mechanism for feeding blanks or components to power presses &c, comprises mechanism driven as a unit and serving to pick up components and to feed them into and remove them from intermittently operating tools, in combination with automatically operating safety means whereby the feeding mechanism is stopped or the setting in motion of the means for actuating the tools is prevented if the various steps in the feeding of a component do not take place normally in relation to the operation of the tools. The feeding mechanism may be applied to a single press, or for feeding components through a number of sets of tools in separate presses assembled in line. In the form shown in Figs. 1 and 3, the press is one of a number of power presses operating sequentially on blanks or components which are fed from one press to other by suction grippers 34. Each frame 10 is open in end view, the frames are all in one straight line, and the tools and blank feeding means of each press are driven from a crankshaft 11. The feeding means comprises a stationary longitudinally extending bar 12, and a carriage 13 mounted for vertical movements thereon by means of bell-crank levers 14 pivoted at 15. The vertical arms of these levers are connected together by rods 17, and one of the vertical arms is connected to the piston rod of a fluid-pressure cylinder 18, which causes raising and lowering of the carriage 13. Sliding movement is imparted to the carriage 13 by a rod 21, a lever 22 secured on a shaft 23 mounted in a frame bracket, an arm 25 secured on the shaft 23, a rod 26 of adjustable length, and a bell-crank lever 27 which urges the rod 26 through the medium of two compression springs 30. The other end of the lever 27 carries a roller engaging a cam groove 29 in a face cam fixed on the crankshaft 11. The stroke of this drive assembly is limited by micrometer stops 33 on the lever 22 co-operating with fixed abutments. Two suction pick-up heads 34, spaced at intervals on the carriage 13 equal to half the spacing between the tools of adjacent presses, are connected through a valve 36 and a flexible pipe to a source of vacuum. The shape of the cam groove 29 is such that the feed assembly 12, 13 is stationary ion a neutral position in which the pick-up heads 34 are midway between the tools of adjacent presses, the assembly then moves in one direction to bring the first head 34 over a loading table and the second head 34 over the bottom tool &c. of the press. The carriage 13 is now lowered, blanks &c. are picked up from the loading table and tools, respectively, by the two heads 34, the carriage is raised, the assembly is moved in the opposite direction to carry the blank from the loading table above the tools of the press, and blank from the press over the next loading table. The carriage is now lowered and the blanks released. The loading tables may be omitted, and the pick-up heads may transfer the blariks from the tools of one press to the next. The safety control mechanism, shown in Fig. 3, includes a connecting pipe 42 between one suction pick-up head 34 to a vacuum switch 43 in series with a switch 44 controlled by a cam 45 on the press crankshaft 11. These switches are in the circuit of a solenoid 46 of a valve 47 which controls a compressed air cylinder 48 for operating the extractor 49 of the key clutch of the press. If a blank or component is not picked up by either of the suction heads 34, the switch 43 remains closed and, when the switch 44 is closed, the solenoid 46 is energised and opens the valve 47 which energises the cylinder 48 and the extractor 49 is retracted, whereupon the clutch is not engaged and the press does not make its next stroke. The cylinder 18 for raising and lowering the carriage 13 is supplied with compressed air through a valve controlled by, a solenoid in a circuit containing a switch which is closed twice by cams during each rotation of the crankshaft 11. The air cylinder 18 may be single acting, in which case the carriage 13 is lowered by a spring or under gravity. In the modification shown diagrammatically in Fig. 8, the blank &c. feeding means is driven independently of the press, and is controlled by a motor-driven cam shaft 80 (not shown) which also controls the starting operations of the press. As before, a stationary bar has a gripper carriage 61 mounted for vertical movements thereon by bell-crank levers, and the carriage is reciprocated over the bar by a double-ended compressed air cylinder 63 divided by a central partition into two aligned cylinders, the piston of one being connected to a fixed member, and the piston of the other being connected bv a linkage to the feed carriage. The carriage 61, which is raised and lowered by a compressed air cylinder 70, carries a number of spaced grippers each having pairs of jaws operated by an air cylinder 74 associated with a detector switch 76 which is actuated if the jaws fail to grip a blank or component. The press is set in motion when a pedal 78 is depressed by an air cylinder 77. The cam shaft 80 (not shown) is driven from an electric motor, and cams 79 thereon control air valves 93, 96 and 97 in a compressed air system, and electric switches 108 and 111. Compressed air from a main pipe 92 passes through the valve 93 to the cylinder 70, through a valve 94 to the cylinders 74 of the grippers, through a solenoidoperated valve 95 and the valves 96, 97 to the double-ended cylinder 63, and through a pipe 105 and a solenoid-operated valve 106 to the cylinder 77. A switch 98 in the circuit of the valve 95 is actuated by a cam 99 on the crankshaft 100 of the press. When the press is started, the switch 98 is closed, the solenoid valve 95 is closed to cut off air to the valves 96, 97, but air is allowed to pass by way of pilot line 101 and shuttle valves 102, 103 to return the feeding mechanism to a neutral position, if it is not already there. In the circuit of the valve 106, a switch 107 is closed by the carriage 61 when the latter returns to neutral position, and the switch 108 is operated by a cam 79. If the carriage has not returned to the neutral position, the solenoid is not energised and the press is not set in motion. A branch air pipe 109 between the valve 106 and air cylinder 77 leads to a pressure operated switch 110 which is normally open but is closed when the cylinder 77 is energised. This switch is in parallel with the cam-operated switch 111 in the circuit of the motor driving the cam shaft 80 (not shown), and the switch 111 is in series with the detector switches 76 on the grippers for the blanks &c. If either of the grippers fails to pick up a blank the corresponding switch 76 opens and the motor is stopped. If the carriage 61 has not returned to neutral position, the cylinder 77 is not energised to trip the press clutch, the switch 110 will not be closed, and the cam shaft motor is stopped. The motor is controlled by a starter unit 112 and control unit 113. The valve 94 is opened by the downward movement of the carriage 61 so that the gripper cylinders 74 are energised to close the grippers on to the blanks &c. The spacing of the grippers and the cycle of operations of the feeding assembly is substantially as described in respect of Figs. 1 and 3. Grippers:-The grippers used in the second construction each comprise an angularly adjustable arm, two gripper jaws pivotally mounted at the outer end of the arm so that the two inner limbs of the jaws engage a wedge which is moved along the arm to open and close the jaws, an air cylinder 74, Fig. 8, mounted on the arm and connected with the wedge, and a detector switch 76, Fig. 8, also on the arm and which is actuated if the travel of the wedge exceeds a predetermined amount owing to the failure of the jaws to grasp a blank or component. When the switch 76 is actuated, the motor driving the main cam shaft is stopped.