Patent GB-190515869-A (GB)
Title: Improvements in Power Hammers and Percussive Tools.
Inventor: STOCKS HARRY BENWELL
Filed: 1905-08-03
Granted: 1906-03-22
Abstract: 15,869. Stocks, H. B. Aug. 3. Fluid-pressure hammers. -A pneumatic power hammer or other percussive tool of the kind described in Specification No. 19,949, A.D. 1904, driven by an air-compressor, is provided with air-loaded valves of such proportions as to be held in equilibrium by the normal action of the air pressures, but actuated when the normal ratio is disturbed by an impulse from the air-compressor. The motion of the valve is given by the rise and fall of pressures above and below a normal value depending on the quantity of air discharged from the compressor compared with that taken by the hammer. The handle is secured to the cylinder flange 20 by a screwed ring 21, which is locked by a stud 23 passing through one of a number of holes in boss and ring and held in position by a split ring 24. The conical valve-box 12 in which the air-balanced differential valve 13 slides has a high-pressure inlet 25 connected by a port 27 with the end 14 of the valve, and a low-pressure inlet 26 connected by a port 28 with the end 15 of the valve. These inlets are attached by separate tubes to the air-compressor, and -are connected, when not in use, with the atmosphere by a port 53, which may be closed by a spring- controlled piston 51 operated by a thumb-lever. When the parts are in the position shown in Fig. 1, air passes through the high-pressure inlet 25, recess 16 in the valve, and the ports 46, and moves the annular valve 17 to the position shown, air consequently passing through the ports 43 in the shell 19 and forcing out the piston 9, exhaust taking place through the passages 31 and ports 33. When the neck 44 of the piston comes opposite the port 29<a>, low-pressure air is exhausted from the front end valve head 15 through the ports 41, 32, a slight fall below normal of the pressure in front of the valve 14, caused by the rear end of the cylinder absorbing slightly more high-pressure air than, the compressor is capable of delivering at the maximum pressure, enables low-pressure air to return to the valve, the remainder of the stroke of the piston being effected by expansion. Low-pressure air then passes in through the ports 28, 29, returns the annular valve 17, and itself passes through the ports 30,31 and returns the piston, exhaust passing through the ports 32, 41 and also the ports 33, Fig. 3. When the piston on its return stroke uncovers the ports 41, 29<a>, part of the low-pressure air passes into the -atmosphere and part into the front of the valve head 15 and the valve is reversed. A by-pass 40 is provided for the port 29 to prevent low-pressure air from exceeding the required pressure when the valve is as shown in Fig. 1. The ports 29<a> may be made in connexion with the rear of the valve head 15 and their position varied according to the degree of expansive working, and in this case the recess 44 in the piston is not required, as is also the case when the tools are low speed, which do not require ports 29<a>, but instead may have a port L, Fig. 17, and holes M. Extra ports P, Q may be used to assist in distributing high-pressure air to the annular groove G. The annular distributing-valve may be replaced by one of piston form, and the highpressure and low.pressure differential piston valves may be -separate as shown at 65, 64, Fig. 5 ; the valve 65 communicates with the inlet 67 and by means of a by-pass 79 with the low-pressure air inlet 67<a>, and the valve 64 with the inlet 67<a> and by a by-pass 80 with the inlet 67. Vents 81 are provided to allow escape of air on equilibrium being established in the valve chambers, and a bypass 90 for preventing the low air pressure from exceeding requirements.