GB742335A - Improvements in or relating to machines for processing leather - Google Patents

Abstract

742,335. Staking-machines for leather. RHEINMETALL AKT.-GES. Aug. 31, 1953 [July 2, 1953], No. 24065/53. Class 76. [Also in Group XXIX] In a leather-staking machine having a rotating knife cylinder, a resilient pressure device for pressing the workpiece against the cylinder and a vertically reciprocatable workpiece holder, the pressure device and workpiece holder are operated hydraulically by means of cylinders, each of which is separately connected to the output side of a pump in a pressure liquid circulating system, and each cylinder is separately controlled by individual throttle valves. As shown in Fig. 1, leather is held in a holder carried by a frame 17 which in its upward travel carries the leather between a helically knifed cylinder 2 and a resilient pressure device 5 in the form of a leather belt held under tension by spring 8. The pressure device is moved towards the knifed cylinder by a rigid bar 10 connected thereto at right angles and pivoted at 9, under the action of a plunger 12 in a hydraulic cylinder 13. The workpiece holder is moved upwards by a piston acting in hydraulic cylinder 19. A pressure fluid is fed from pump 28 to hydraulic cylinder 13 via pipe 50 and returns via pipe 52, valve 48 and line 53. Similarly fluid is fed to cylinder 19 by line 34 and 36 and returns to the fluid store 31 through valve 33 and line 35. On closing valve 33 or 48 pressure is built up in cylinder 19 or 13 respectively, thereby raising the workpiece holder or applying the pressure pad 5. On opening the valves the pressure in the cylinders drops and the moving parts are restored to their starting position under their own weight. The hydraulic cylinder 19, Fig. 5, consists of a hollow piston 25 working in a surrounding cylinder 24 which through a ball-and-socket 26 is connected to the workpiece holder. Fluid under pressure is fed through port 38 to the interior of piston 25 from which it leaves through an orifice 46 in a spring- loaded inner plunger 40, thereby causing an initial slow moment between the piston 25 and the surrounding cylinder 24, the inner plunger 40 remaining in contact with the base 43 of the cylinder until its movement is arrested by a ring 45 on the piston. Ports 41 in the piston walls are thus uncovered and with increased oil flow the cylinder and piston move more quickly relative to each other, the inner plunger 40 travelling with the piston in abutment with ring 45. At the extreme end of the stroke damping is effected by a sleeve 9<SP>1</SP> which gradually masks poits 41, thereby gradually decreasing oil feed. The hydraulic cylinder 13 (Fig. 6) operating the pressure device 5 consists of a piston 12 working in cylinder 13. Pressure fluid passes from pipe 50 around the groove 51 of the piston until the operating valve 48 (Fig. 1) is closed, when the pressure build-up forces fluid through an aperture 54 in the piston into the cylinder whereupon slow relative movement occurs until the piston moves past the inlet pipe 50 whereupon the relative movement is increased. A damping device at the extreme position is not normally necessary and an abutment 56 (Fig. 1) may be provided in the frame to limit vertical movement of piston 12. The control valves 33 and 48 may be spring loaded so that if excess pressure builds up, the valve will open to allow liquid to circulate therethrough back to the pressure fluid store 31.