Patent GB-803579-A (GB)
Title: A hydraulically actuated drop hammer
IPC: B21J7/24
Filed: 1956-05-10
Abstract: 803,579. Forging hammers. LANGENSTEIN & SCHEMANN A.G. May 10, 1956 [May 13, 1955], No. 14553/56. Class 83 (4). An hydraulic drop hammer has its tup 3 connected to a piston 8 which is raised by pressure liquid admitted through a port 10 below the piston and during the up stroke a gaseous medium, such as air, is compressed in the space 70 above the piston to assist the down stroke of the tup, and means are provided for increasing the supply of gaseous medium in the chamber 70. The tup 3 co-operates with an anvil 2 and slides in vertical guides 4 in the hammer frame 5 above which is mounted an oil reservoir 7. The oil therein may be at atmospheric pressure or under air pressure of from two to four atmospheres. A gear type oil pump 11 driven through a clutch 12 by an electric motor 13 delivers the oil through a pipe 17 to a chamber 17a. This chamber has a by-pass duct 19 closable by a mechanically operated piston valve 20, and a check valve 18 leading to a pipe 45 connected with the cylinder port 10 and also through a pipe 47 with a spring-loaded damping piston 48. A release valve 30 exhausts the pipe 45 for initiating the down stroke and a further valve 29 is used to effect slow downward movement of the ram. The valves 20, 29, 30 are each connected by linkage to a rotatable shaft 24 carrying an operating arm 33 connected by a vertical rod 32 and cross shaft 54 with a foot pedal 56. A dividing wall 71 in the working cylinder 6 separates the space 70 from an upper pressure chamber 75 provided with a pressure gauge 74 and a spring-loaded safety valve 78. A hand-operated valve 73 in the dividing wall 71 permits communication between the chambers 70, 75 when desired. Chamber 70 is connected through pipe 79 with a valve chamber 80 having a one-way atmosphere valve 84 and a check valve 81 providing communication with the chamber 75. Valve 81 may be held closed by a stop 83. With the valve 73 closed and the valve 81 released, reciprocation of the piston 8 causes air to be drawn through valve 84 and delivered through valve 81 to pressurize the chamber 75. In operation and with the hydraulic valves 20, 29, 30 closed, the pressure oil flowing into pipe 45 and through port 10 raises the piston 8 and during the up stroke the tup 3 engages a bell-crank lever 36a, 36b which causes the rod 32 to be slightly raised to open the by-pass duct 19. Valve 18 thus closes and holds the piston 8 in its raised position. Slight depression of the pedal 56 causes the inching valve 29 to open and exhaust the pipe 45 slowly and full depression of the pedal causes the release valve 30 to open and allow the tup to drop. If the tup rebounds on impact a non- return valve 51 may open to drawn liquid from the reservoir directly into the pipe 17. During the following up stroke of the piston the air in chamber 70 is compressed causing the upward movement to be braked and to assist gravity during the subsequent down stroke. By opening the valve 73 chamber 70 will communicate directly with pressurized chamber 75 in which the air may be pressurized to about 3.5 atmospheres, thereby causing stronger hammer blows. In an alternative construction, chamber 70 may communicate through pipes 79, 79a with a valve 85 leading to a compressed-air container 86 which is used to pressurize the space 70 directly. Specification 803,580 is referred to.