GB703259A - Improvements in or relating to automatic feed mechanism for power presses and like machines - Google Patents

Abstract

703,259. Metal-strip feeds. BIRMINGHAM TOOL & GAUGE CO., Ltd. Aug. 17, 1951 [Aug. 29, 1950], No. 21271/50. Class 83 (4) Automatic feed mechanism for power presses in which the table carrying the feed grippers is hydraulically operated is characterized in that a piston is disposed in the hydraulic feed lines to the reciprocating table for absorbing the initial movement of the fluid until the built-up pressure overcomes a spring-loaded valve thus causing the table to pause for a predetermined period at each end of its movement. The base 11 of a press houses a valve block 1 which carries a support 2 for two parallel cylinders 3, 4 containing hydraulic pistons 5, 6 respectively arranged to operate in opposite directions on a table 7 carried by a saddle 8 which slides in guides on the cylinders 3, 4. At one end of the table 7 is a gripper 9 and a similar fixed gripper 10 extends across the table and is mounted on the base 11. Each gripper comprises a hinged pressure pad 12 and a pad 14 on which the strip 13 is placed. A rubber diaphragm 15 is located under the pad 14 and is acted upon by pressure fluid to urge the pad 14 towards the cover pad 12 which is secured by a fastening 56. The cylinders 3, 4 are connected through the valve block 1 by pipes 16, 17 to a transmitter telemotor as disclosed in Specification 703,313, [Group XXIX], for supplying and withdrawing fluid alternatively from said cylinders 3, 4. The fluid line from the pipe 17 passes directly through the block I to the forward cylinder 3 but the other fluid line leads from the pipe 16 to the return cylinder 4 through valve controlled ducts in the block 1 whereby the reciprocation of the table 7 is controlled in relation to the opening and closing of the gripperswhich are operated by a separate hydraulic system. Just prior to the commencement of the forward movement of the table the gripper 9 grips the strip whilst the gripper 10 is released thereby enabling the strip to be fed forward At its extreme forward position the table pauses whilst the gripper 9 is released and the gripper 10 is operated to grip the strip while the table is returned to its initial position. In operation pressure fluid from the telemotor passes through ducts 21, 22 in the block 1 to the forward cylinder 3. However, before operating the piston 5 in the cylinder 3, the fluid passes along a duct 23 (Fig. 6) from the duct 21 to one end of, a piston 24 which moves in its bore in the block 1 and-displaces fluid into a duct 25 and thence to a duct 26 which leads to the reduced end portion 27 of a piston 18 which operates the separate hydraulic system for the grippers. The fluid displaced into the duct 25 can only move into the duct 26 because the end of the duct 25 which communicates with a duct 36 is closed by a valve 39 provided with a reduced part 40 which allows passage of fluid into a duct 42 when the fluid pressure is sufficient to open the valve. Spring loading of the valve is adjusted by screw means 52. The duct 36 leads into an annular space 49 around a valve 45 having a flat 43 (Fig. 9) which permits passage of fluid to the rear of the valve to hold the valve on its seat. Movement of the piston 18 to the left (Figs. 2 and 5), expels oil from the bore 53 via the port 28 and a flexible pipe 35 to the gripper 9. At the same time the piston 18 draws oil into its bore from the gripper 10 via a port 32 and a pipe 31 and so releases the gripper 10. A reservoir 19 communicates with the bore 53 to replenish any fluid losses. As the table moves forward fluid is expelled from the return cylinder 4 and passes through ducts 34, 26, 25, 36 to, an annular space 38 around the valve 39 and through the reduced part 40 of the valve to the duct 42 and via the pipe. 16 to the telemotor. When the table reaches its extreme forward position the telemotor reverses the fluid movement through the pipes 16 and 17. Thus the fluid moves up the duct 32 and into contact with the other reduced end 44 of the piston 18 and also the valve 45 but owing to the high pressure setting of the valve 45 by the screw means 46 movement of the piston first takes place to operate the gripper 10 and release the gripper 9. Also the reduced end 27 of the piston forces fluid through ducts 26, 25, 48 to return the piston 24 to its initial position. After the piston 18 has operated the grippers the fluid pressure' builds up and overcomes the valve 45 and passes to the ducts 50, 36, 25 the latter communicating with the return cylinder 4 via ducts 26 and 34 to operate the piston 6 for effecting the return movement of the table 7. The fluid pressure in the duct 42 is unable to lift the valve 39 as a small bore duct leads from the duct 42 to the rear of the valve 39 thus holding the valve on its seating. As the table 7 returns the piston 5 enters the cylinder 3 expelling fluid therefrom to the telemotor. For feeding thin strip two table units may be disposed one each side of the press and for supporting very thin strip the movable gripper may have a rearward extension constantly and slidably engaging a forward extension on the fixed gripper.