Patent GB-333202-A (GB)
Title: Improvements in or relating to pneumatic drop stamps
IPC: B21J7/36
Filed: 1929-04-30
Abstract: 333,202. Jackson, L. Mellersh-, (Pneumatic Drop Hammer Co.). April 30, 1929. Steam and other fluidpressure hammers.-A pneumatic drop stamp, wherein the hammer is raised by a piston connected thereto and working in a cylinder comprises an operating valve and means for positioning it to direct fluid pressure to the cylinder to raise the hammer or to release fluid pressure therefrom to allow the hammer to drop, means operated by the fall of the hammer to reset the operating valve admitting fluid pressure to the cylinder for raising the hammer, a control valve controlling the admission of th6 fluid pressure to the operating valve and cylinder to diminish the speed of the hammer as it approaches the limit of its upward movement and means operated by the hammer for operating the control valve. The hammer 19 slides on columns 16 connected by a crosshead 17 supporting the pneumatic, cylinder 22 containing the piston 25 with piston rod 20 connected to the hammer 19. Air is admitted to the cylinder via passage 29 and rotary operating valve 30 and control valve 33 from a passage 34 at the end of a supply pipe. The valve 30 has two ports 301, 302, Fig. 10, adapted in the position shown to exhaust the air from the cylinder to the exhaust passage 31, or, when turned through a right angle, to admit air to the cylinder from the passage 331. An opening 309 in the valve allows air to escape into the space between the valve and its bushing 304 to equalize the pressure round the valve. The control valve 33 has opposite ports adapted to connect passage 331 to supply passage 34 and openings 332 for air escape into the space between the valve and bushing 334. Valve 33 is operated by a square vertical rod 63 rotated automatically during the rise and fall of the hammer by a projection 66 engaging a cam 60 on the rod. Valve 30 is operated by a square rod 35 rotated automatically by a projection 61 on the hammer engaging a cam 65 on the rod and is also under hand control of a lever 48 and arm 47. Each square rod has a locking block 43 with flats co-operating with a flat plate 44 on a spring pin 45 to hold the rod against movement and complete its movement when partly turned. Lever 48 engages arm 47, as shown in Fig. 8, by means of a spring-pressed pin 49, the head 52 of which engages a cam lever 53 so that by the time the movement of the arm 47 is completed the pin 49 moves out of contact with the arm. Lever 48 has a recess 483 engaged by a locking detent 55 on a lever 54 linked by a rod 58 to a lever 57, whereby both hands are required to operate the hammer, thus ensuring safety of the operator's hands. The blow may be cushioned more or less by restricting the exhaust through the exhaust valve 32 by means of rod 74 and lever 76. The connection of the piston rnd 20 with the hammer 19, shown in Fig. 11, comprises a rubber block 90 between the head 88 and the end of the cavity 80 and leather discs 89 between head 88 and block 84 which latter is positioned in recess 83 by a quarter turn and locked by a pin 85. In the normal position with the hammer raised, the valve 30 establishes communication between the passages 29 and 331, the valve 33 is slightly turned to cut off passage 331 from supply passage 34 and the hammer is sustained by air passing through by-pass 70. Operation of lever 48 turns valve 30 and opens the cylinder via passage 29 to exhaust valve 32, allowing hammer to fall. During the descent projection 66 and cam 60 open control valve 33 and near the end of the descent projection 61 and cam 65 rotate valve 30 so that after the blow air enters the cylinder and raises hammer again. As the hammer approaches the limit of its upstroke projection 66 and cam 60 close valve 33, the upstroke being completed by air expansion and air entering through the bypass 70. Specification 342,024, [Group XXVI], is referred to.