546,066. Percussive tools ; valve gear. CHICAGO PNEUMATIC TOOL CO. May 5, 1941, No. 5843. Convention date, Aug. 2, 1940. [Class 124] [Also in Group XXVI] In a single-shot pneumatic riveter or like pressure-fluid operated tool having a power piston 14 reciprocated in a cylinder 11 under the control of a distributing valve 46 the movement of which from a first to a second position is actuated by a pressure-responsive valve 47 which opens to pass pressure-fluid through a passage 97 to a chamber 83 enclosing a portion of the valve 46, additional means are provided for automatically holding the valve 46 in its second position, by further pressure-fluid passing through a port 82 to the chamber 83, and for automatically disabling the actuating valve 47 by pressure-fluid from chamber 83 returning through the passage 97. The working plunger 24 is moved towards the stationary die 26 by the piston 14 through the intermediary of a pair of rollers 18, the upper roller engaging a guide block 19 and the lower roller engaging a pivoted lever 21. The plunger 24 is urged upwards by a spring 28 and a depression 29 in the lever 21 causes a quick initial downward movement of the plunger. To allow for different lengths of rivets, a cut-out portion 38 of the plunger is engaged by a setting member adjustably mounted on the front plate 32. Compressed air supplied by a hose 41 to a bore 44 passes to the piston 14 under the control of a throttle valve 45 which is engaged by a set screw 53 on an operating lever 54 and moves against a spring 58. The lower end of the valve 45 carries a disc valve 55 and when this is depressed the air flows from the bore 44 into valve bushing 49 and through ports 62, annular groove 63, passage 64 (see diagrammatic Fig. 4), chamber 65, annular groove 66 in valve bushing 51, ports 67, around reduced portion 68 of valve 46, ports 69, annular groove 71, and passage 72 to the upper end of the cylinder 11. When a predetermined peak pressure is reached in cylinder 11 at the end of the compression stroke, the valve 46 is automatically moved downwards under the control of the pressure relief valve 47. The latter is provided with a head 47B engageable with a shoulder 90 on the bushing 52, and with a reduced stem 47A having a longitudinal bore 102 and a port 103 just below the head 47B. Pressure air from the cylinder 11 acts, through passage 101 and port 99, on the lower end of the valve 47 and at the predetermined pressure raises it with a snap action and allows air to pass through bore 102, ports 103, 96, passage 97, and port 98 into the chamber 83. The peak pressure may be determined by means of a vented adjusting screw 106 which acts, through a spring 105 and a plunger 104, in the upper end of the valve 47. When the valve 46 is depressed, its head closes the ports 67 and air directed into chamber 65 is momentarily held by the resistance of a check valve 48. After a rise in pressure, this air is forced past the valve 48 and through passage 77, groove 76, ports 75, reduced portion 74 of valve 46, ports 78, groove 79, and passage 81 to the lower end of the cylinder 11. The valve 46 is held in the lower position by live air passing from passage 64, through groove 66 and the reduced-diameter port 82 to the chamber 83. Some of this air flows back along passage 97 to hold the valve 47 positively on its seat during the return stroke, and to hold the plunger 104 in its upper position. When the operating lever 54 is released, the valve 55 is closed by the spring 58 to cut off the live air from the passage 64, and the valve 46 is raised by the spring 73. The upper or lower end of the cylinder 11 is connected to a main exhaust port 85 by means of passage 72 or 81, groove 71 or 79, port 69 or 78, reduced portion 68 or 74 of valve 46, and ports 88, groove 87, and passage 86. The chamber 83 is connected to the exhaust port 85 by a port 91 and a metering valve 92 in a passage 89. When the throttle valve 45 is closed, the interior of the bushing 49, the feed passage 64, and chamber 65 are connected to the exhaust port 85 by ports 95, groove 94, and passage 93. By releasing the lever 54 the tool may be arrested at any part of its stroke. A second depression of the lever will complete the stroke, or the tool may be conditioned for a return stroke by depressing the valve 46 by means of a manually operable plunger 108, and thus depressing the lever 54.