Patent GB-289519-A (GB)
Title: Improvements in automatic friction drop stamps
IPC: B21J7/36
Filed: 1927-01-26
Abstract: 289,519. Massey, Ltd., B. & S., Massey, H. F., and Wells, L. W. Jan. 26, 1927. Power hammers.-In an automatic friction drop stamp the operating part such as a foot lever first puts the stamp into operation on being moved from its position of rest and then by further movement regulates the length of the automatic strokes. The trip q is attached by a lifting belt r to an arm s loose on the shaft t, which has fast thereon a drum v surrounded by a clutch device of the band brake type in driving connection with the arm s and brought into action by a cord so as to rotate the arm and lift the trip. One end of the cord w is attached to the clutch device by an arm x, Fig. 4; the cord passes round a sleeve t<1> fixed on the shaft t, then over a pulley y and its other end is attached to a sleeve s<1> attached by a rod s<2> to the arm s. The pulley is carried on a lever z, Fig. 6, pivoted at 1 on a bracket 2a projecting from a casting 2 in which is formed a cylinder 3 having a piston 5 and rod 6 connected by pin and slot <7> with the other end of the lever z so that the cord w is tightened and slackened alternately as the piston 5 is moved up and down by compressed air. The holding up device for normally sustaining the trip in elevated position comprises a brake pulley b and a band brake a connected by a lever e to an eccentric on a plate i mounted on the spindle g and influenced by a spring k which keeps the brake in action; a cam surface n<3> on a bar n attached to the foot lever o is adapted to engage a roller L on the plate i, whereby the lever e is tilted and the band brake a released. Compressed air is admitted to either end of the cylinder 3 by means of a control valve 8, Fig. 8, working in a cylindrical chamber 10 and a relay valve 9 working in a chamber 11. The central parts of the two valve chambers are in communication with each other at 13 and with an air supply pipe 14. Ports 15, 16 in the wall of the chamber 10 are in communication with spaces 15, 16 at the ends of the relay valve chamber 11 and when uncovered by scroll faces 82, 83 on the control valve 8 admit air pressure to either of two heads 91, 92 at the ends of the relay valve 9 so that the latter is moved against either of the end stops 121, 122 and air is admitted from the opening 13 to either end of the cylinder 3 by means of passages 19 or 20 and ports 19 or 20 in the central part of the wall of the relay valve chamber, the exhaust air from the other end of the cylinder 3 escaping through the other of the passages and ports 19, 20 and through one or other of the outlet ports 21, 22 in the wall of the relay valve chamber. Outlet ports 17, 18 are also provided at the ends of the control valve chamber 10. The control valve 8 has two movements, one a longitudinal movement effected automatically by the lifting arm s and the other a rotary movement effected by the foot lever o. The first movement is effected as follows. The sleeve s<1> moving with the arm s has a spiral groove 23 engaging a pin 241 on a lever 24 which moves about a fulcrum 261 and has a slot 242 at its other end engaging a projection 252 on a rod 2) which slides in lugs on the cylinder casting 2 and has an arm 253 engaging between collars 84, 85 on the stem 86 of the control valve 8; the fulcrum 261 is eccentrically disposed on a rotary shaft 26 adjustable by an arm 262 so that the movement of the trip q can be adjusted if the belt r is changed or varies in length. The rotary movement of the valve 8 derived from the foot lever o is effected by a pinion 30 splined to the valve stem 86 and engaging rack teeth on a rod 31 connected to the foot lever o by a bell crank 32, link 34 and rod n. The movement of the foot lever is limited by a stud 36 on the rod n contacting with the arms 352, 353 of an adjustable fork 351. Depression of the foot lever from the position A to B releases the hold up device o permitting the trip to fall, and the automatic tightening and loosening of the cord w by the pneumatic cylinder keeps the stamp in action; further depression of the foot lever from the position B to C varies the stroke by causing rotation of the control valve 8 which owing to the scroll shape of the valve faces 82, 83 varies the time of opening and closing of the ports 15, 16. The upper parts of the scroll faces 82, 83, Fig. 8, serve to control the length of stroke whilst the lower parts regulate the height at which the trip is held up. Adjustment of the fork 351 to the left lessens the movement of the foot lever and reduces the height of the hold up and the length of the stroke. The shortest strokes are given with the foot lever in middle position; downward movement of the lever from this position lengthens the stroke and upward movement increases the height of the hold up. In the modification shown in Figs. 9 and 12 the hold up brake a is adapted to be released by a single acting piston 40 with piston rod 401 connected by a cord 38 to the plate i of the brake lever e. The space in the cylinder 41 round the piston rod is connected by a pipe to a port 42 in the wall of the control valve chamber 10, the valve 8 having in addition to the scroll valve faces a central pocket 46 formed by collars and ribs 45. When the valve 8 is turned by the action of the foot lever to place the port 42 and inlet 13 in communication air passes through the port 42 into the cylinder 41 and releases the hold up brake a, but if the valve is turned to place the port 42 in communication with the exhaust port 43 air escapes from the cylinder 41 and the spring k pulls the brake a into action. In the construction of board drop stamp shown in Figs. 13, 14, wherein the lifting rollers 47, 48 are brought into and out of action by eccentrics 49, 50 and the trip is held up by dogs 52, 53 engaging the board 51, the lifting rollers are brought into action by a rod 55 actuated by the piston rod 6 of the air cylinder 2 and the dogs are released by a lever 56 connected by a rod 57 to the piston rod 401 of a cylinder brought into action by the rotation of the control valve spindle 86 which is effected by the foot lever. The self acting mechanism for moving the valve longitudinally to bring the lifting rollers automatically into and out of action comprises a finger 58 on the trip q coacting with a curved bar 59 carried on a spring influenced shaft 60 having an arm 61 connected by a link 62 to a bell crank 63 engaging between collars 84, 85 on the valve spindle.