Patent GB-655512-A (GB)
Title: Power-operated tool for setting flanged screw sockets
IPC: B25B27/00
Filed: 1948-10-22
Abstract: 655,512. Blind riveting. CHICAGO PNEUMATIC TOOL CO. Oct. 22, 1948, No. 27533. Convention date, Jan. 23. [Class 43] A blind riveting gun for setting internally threaded rivets comprises a housing including a work chamber which contains an air motor for rotating the screwthreaded mandrel, and also a work piston which encloses the air motor and causes relative movement between the mandrel and nose piece of the tool to set the rivet, means, including a pneumatic arrangement, being provided in said housing for operating the air motor and work piston. Fig. 1A shows the tool diagramatically. Operation of the gun is automatic on actuating the trigger 59. On partially raising the trigger an adjustable projection 119 on a rod 102 opens a spring-loaded valve 115 to allow live air, which has pased over an oiling felt 94, to pass via a passage 141 to reversing and distributing valves 153, 154. With the valve 153 in its initial forward position the air passes via a passage 163 into a work chamber 165 to drive a sliding vane type rotary air motor 213. The motor rotates the mandrel 58, so that it engages a rivet, through reduction gearing coupled to the mandrel by a driving sleeve. The exhaust air from the motor is fed via passage 243 to the distributing valve 154 which in the position shown allows the exhaust air to escape to atmosphere; the forward end of an air cylinder 69 housing a piston 71 is in connection by passage 246 with such passage 243 and therefore open to atmosphere. Live air introduced into the passage 141 via the valve 115 also enters a branch pipe leading into a passage 256, some air passing via a passage 261 to a valve chamber 258 and some passing to a valve fitting 269 at the forward end of the cylinder 69. On fully raising the trigger 59 a second adjustable projection 136 on the rod 102 opens a spring-loaded valve 125, allowing live air to pass via a passage 284, the distributing valve chamber 142 and a passage 286 to the rear end of the cylinder 69 to drive the piston 71 forward on a power stroke, whereupon a spring- loaded exhaust valve 278 at the rear of the cylinder closes; the air in front of the piston is exhausted to atmosphere via the passage 246 as previously mentioned. On each power stroke the forward end of a piston rod 73 acts as a plunger in an oil chamber 287, forcing high pressure oil past a spring-loaded valve 288 into a passage 302 to the upper end of the work chamber 165 to force down a work piston 197 for the setting operation. The nosepiece 60 and a sleeve 181, in which it is axially adjustable to suit the length of rivet used, are depressed against the action of springs 186 by the pressure of the piston 197 on a member 189 which rests on pins 188 extending up from the sleeve 181 through a fixed cup-shaped member 174. The mandrel 58 projects rotatably through the member 174, being supported therein by an integral collar 177. The motor and associated parts are housed within, and move with, the piston 197, rotational movement of which is prevented by a pin and slot connection with a fixed sleeve 171. Several strokes of the piston 71 are required to complete the setting, each power stroke forcing more oil past the valve 288. Oil in a reservoir 319 is sealed from an air space by a deformable rubber sac 321, anchored by a member 381 and prevented from closing the oil outlet 323 by a perforated metal baffle 322. Some of the live air supplied to the valve fitting 269 via the valve 115 passes, when the valve 268 is opened by the piston 71 at the end of its power stroke, via a passage 337 to a throttling orifice 338 leading into the air space of the reservoir. This air pressure on the sac 321 feeds oil through the outlet 323 to the oil chamber 287 via a spring- controlled valve 327, opened by the oil pressure and also by the suction of the plunger 73 in the chamber 287 during each return stroke of the piston 71. By maintaining air pressure on the sac 321 during return strokes, the oil passages will be filled regardless of the angular position of the gun although the pressure is not high at any time since air can escape to atmosphere through a second throttling orifice 339. When live air enters the passage 337 at the end of a power stroke of the piston 71 some passes through a branch pipe to the centre of the reversing and distributing valve assembly, forcing the rear valve 154 back against the action of a spring 347. As a result the air supply from the valve 125 to the rear end of the cylinder 69 is shut off and said rear end is opened to exhaust. The live air passing the valve 125 is simultaneously diverted by the valve 154 into the passage 243; some of this air passes through the passage 246 to the forward end of the cylinder 69 to return the piston 71, and some passes on to the air motor 213, which is thus subjected to live air on both sides. As soon as the piston 71 allows the forward valve 268 to close, live air in the passage 337 is trapped (except for the leak to the air space of the reservoir 319), and continues to press back the distributing valve 154, this live air being supplemented via a passage 349 receiving air from the valve 115. The valve 154 returns to its original position when the piston 71 opens the rear valve 278 so that the passage 337 is vented, whereupon the live air and exhaust are again applied to opposite sides of the cylinder 69 and the next powerstroke stroke begins. The piston 71 continues to move back and forth until sufficient oil has accumulated above the hydraulic piston 197 to set the rivet, whereupon during the final power stroke of the cycle a relief valve 267 opens as hereafter described. The valve 267 is held closed by an enlargement 307 at the top of a shank 305 loaded by a spring 304. As the piston 197 is gradually forced down it carries with it a trip lever 311 until engagement of the latter with an adjustable lock nut 314 on the shank 305 forces the latter down slightly so that the air valve 267 is cracked. The live air previously supplied to the relief valve chamber 258 now acts on the enlargement 307, causing the shank 305 and a surrounding sleeve 303 to plunge to their lower positions. Descent of the sleeve 303 first cuts of the oil supply to the work chamber 165 to halt the setting operation. and then allows oil from the chamber 287 to flow back to the reservoir 319. Oil from the work chamber 165 is forced back by the hydraulic piston 197 returning under the action of its spring 203. Thus the strokeof the piston 197, which governs the amount by which the rivet is upset. is controlled by the position of the lock nut 314. When the relief valve 267 opens live air also passes into a passage 354 to move both reversing valves 153, 154 rearwardly, live air from the valve 115 then being trapped in front of the valve 153. This movement of the valves results in reversal of the live air and exhaust to opposite ends of the cylinder 69 and hence in return of the piston 71, and also allows live air to pass via the passage 243 to the air motor while opening the passage 163 to exhaust. The motor is therefore operated in the reverse direction and the mandrel 58 is disengaged from the set rivet. During the first stage of the working cycle when the mandrel is engaging the rivet, the flange of the latter is drawn up into contact with the nosepiece 60; this stalls the air motor, and during all power strokes of the air piston 71 air pressure in the passage 163 holds the flange of the rivet against the nosepiece. When, during return strokes of the piston 71, air pressure on the motor is equalized by live air in the passage 243 so that no torque is exerted on the rivet, the latter is already firmly held in the workpiece since the setting operation has begun-