GB329921A - - Google Patents

Abstract

329,921. Chicago Pneumatic Tool Co., (Assignees of Nell, G. M.). Oct. 25, 1928, [Convention date]. Percussive drills.-The fluid is distributed by a hollow valve having four differential areas upon which the pressure acts to lock and reverse the valve. The blow of the piston 4 is shown imparted through an anvil block 7 slidably mounted in a guide 8. The cylinder has one or more transverse annular grooves 9 connected to atmosphere by one or more ports 10. The rear of the piston chamber is closed by a plug 11 provided with an extension which enters a recess in the piston provided to reduce its weight. The valve chamber is arranged close to the cylinder to reduce the length of the passages. The fluid to return the piston passes through the valve and chambers and passages 16, 17, 18, 18a. The left-hand end 19 of the valve is smaller than the right-hand end 20 thereof, and a shoulder 21 is provided so that sum of the areas 19, 21 exceeds the area 20. The valve also has a flange 22 with a forward shoulder 23. The areas 20, 23 together exceed the areas 19, 21. The faces of the flange 22 are vented to atmosphere by a large vent 24 and a restricted vent 25 respectively. A piston-controlled cylinder passage 26 extends to the area 23. The passages 26, 25 form an auxiliary rear exhaust to the main cylinder. A forward auxiliary exhaust to the main cylinder through passages and chambers 18<a>, 18, 17, 16, groove 27 and the chamber 9 and controlled by the valve is also provided. In the position of the valve shown in Fig. 1, the pressure fluid is acting on areas 19, 20, 21. When during its forward motion, the piston uncovers port 26, fluid pressure builds up on area 23 and the valve is shifted rearwardly and cuts off the motive fluid before chamber 9 is uncovered. The pressure on areas 21, 23 is relieved and the valve completes its movement and is held to the left since the area 20 exceeds the area 19. The piston is reversed. After the exhaust is closed, compression pressure builds up on area 21, and when the pressure on areas 19, 21 exceed the pressure on area 20 the valve is moved forwardly. The piston momentum completes the valve movement and the main exhaust is opened. A radial leakage port 30 may be provided to speed up the building up of pressure on area 21. In each direction of motion, the valve is reversed before the main exhaust is opened.