Patent GB-702039-A (GB)
Title: Improvements in hydraulic power transmission apparatus
IPC: F16H49/00
Filed: 1950-01-26
Abstract: 702,039. Metal-working presses. WALES, G. F. Jan. 26, 1950 [Jan. 28, 1949], No. 2095/50. Class 83 (4). [Also in Group XXIX) Power transmission apparatus which may be used in presses comprises co-operating driving and driven elements which together wholly enclose a space for a liquid by which movement of one element may be transmitted to the other and a chamber for a body of the liquid one of the elements being movable to establish and cut off communication between the space and the chamber so that the elements may continuously move relatively to one another or be caused to move in unison by liquid trapped between them. Fig. 13 shows part of a punch press comprising eccentric 24 on the end of a shaft 44 which through a connecting rod 25 reciprocates a piston 26. The reciprocation of the piston is only transmitted to a cylinder 36 if a pin 45 is withdrawn to release it. The operation can be seen from Fig. 3. When the pin 45 is in the position shown the cylinder 36 is positively held and the piston reciprocates in the cylinder and forces liquid to and from between the cylinder and a reservoir 27 through ports 37. If, however, the pin is withdrawn the cylinder is tree to move downwardly and cuts off communication with the reservoir (Fig. 12C) thus trapping liquid in the cylinder and the piston then forces the cylinder down through the medium of the liquid. On the return stroke a shoulder 29 on the piston engages a ring 30 carried by the cylinder and raises it again. The pin if released by the operator enters the bore 41. A ring 38 carried by an outer member 31 is adjustable to vary the opening of the ports 37 to provide for liquids of different viscosity. A valve 50 is provided to allow air to enter the reservoir 27. Vapour pressure in the reservoir due to heating up in operation helps the downward movement of the cylinder 36. The valve 50 could be omitted by providing a vent opening in the housing but the noise and vapour emitting therefrom might be objectionable. Valve 50 could be replaced by a source of liquid pressure in the case of inverted or horizontal installations. Fig. 10 shows a modification in which a piston 56 biased by resilient means 57 is carried in the lower end of the cylinder 36. As shown a stop 67 for the cylinder 36 may be provided. Alternatively a plate may be placed across the faces of the relatively reciprocable member 36 and the piston 56 and the stop removed. In a drawing process a single or double draw can be provided by removing stop 67 so as to permit movement of either the piston 56 or the ram 36. If a solid die were used the bed of the press could be utilized to provide a solid stop base the latter being engaged by the ram 36. By a suitable die and resilient pressure pad design a double drawing operation can be provided as the resilient resisting force of the pressure pad under either ram 36 or 56 could be varied to cause either ram to operate first. Various means for relieving the pressure in the cylinder in the event of the apparatus jamming are referred to. The whole of the apparatus 20 is a self contained unit which with the connecting rod 25 can be removed. Any means may be employed to operate the piston 26. Instead of operating a punch the cylinder 36 could operate a cutting or other tool or machine element. Fig. 13 illustrates the apparatus 20 as it would appear when mounted to a machine of the same general character as is illustrated in Fig. 13 of U.S.A. Specification 2,364,011 referred to.