Patent GB-422757-A (GB)
Title: Improvements in or relating to broaching machines
IPC: B21G3/04
Filed: 1934-04-21
Abstract: 422,757. Hydraulic transmission of power. CINCINNATI MILLING MACHINE CO., Cincinnati, Ohio, U.S.A.-(Assignees of Romaine, M., and Roehm, E. G.) April 21, 1934, No. 12083. Convention date, May 3, 1933. [Class 69 (ii)] [See also Group XXII] A hydraulically-operated broaching-machine has a tool-carrying ram coacting with a work supporting table which has two work stations and is reciprocable for alternately presenting the work stations to the tools. The bed has guideways for the work-table 32 and is secured to a hollow column which is subdivided into a number of compartments, the lowest 36, containing the hydraulic fluid, being surmounted by a chamber 37 containing an electric motor 40 which drives a pair of pumps 43, 42, the former being of high pressure and high volume and the latter of low pressure and low volume. Another chamber 46 contains the reversing valves controlling the ram and table respectively. The work-table 32 is secured to the piston-rod 52 of a piston working in a hydraulic cylinder 54 and carries a block coacting with adjustable stops to determine the two positions of the table. The pump 43, Fig. 24, is connected by a line 67 having a pressure relief valve 69 to a safety latch valve casing 70 and thence by line 71 to a reversing valve 72 having a plunger 83 with a number of piston portions 84 ... 87 and a number of radial ports communicating with circumferential grooves. When the valve plunger 83 is in its extreme left hand position the pressure line 71 is connected with a port 78 leading to the left hand side of the table piston 55. In the right hand position of the valve, pressure fluid is admitted through port 76 to the right hand side of piston 55 while in the neutral position shown in Fig. 24 the pressure fluid passes into a line 95. The valve plunger is shifted by fluid pressure admitted through lines 102, 103 from a pilot control valve 104 in circuit with the small low pressure pump 42. This valve also consists of a central plunger moving in a sleeve provided with radial ports communicating with circumferential grooves. Hydraulic resistance coils 145, 146 are located in conduits leading from this pilot valve. The valve plunger has a notched extension 149 coacting with a shifter 152 mounted on a shaft 153 which may be manually oscillated by a lever 154. The shaft 153 also has roller carrying arms 156, 157 coacting with cam surfaces on dogs 159, 160, Fig. 9, for shifting the valve automatically. A pivoted detent 165, Fig. 10, coacts with notches in the shifter 152 to hold the valve in either of its extreme positions while a latch member 170 controlled by a piston and spring coacts with a projection 169 to limit the movement of the pilot valve from either of its extreme positions to one of two intermediate neutral positions. In operation, after a work piece has been loaded, the manual lever 154 is operated to shift the pilot valve to its extreme position wherein pressure is admitted to line 102 to shift the main valve and actuate the table piston and the table movement continues until one of the table dogs actuates the shaft 153 to move the pilot valve to a neutral position where it is held by the latch 170. In this position the main table control valve is moved to the neutral position shown in Fig. 24 and thus cuts off the pressure on the table just before the table engages a positive stop. After the cutting-off of the main pressure the table is moved up to its stop without shock by the pilot valve fluid pressure passing through one of the choke coils 145, 146 and is held against its stop during operation by the pilot-pressure bleeding through the choke coils. After completing a work piece the lever 154 is again operated to shift the pilot valve to its other extreme position and reverse the table which is moved up to and held against a second adjustable stop in the above-described manner. The tool ram 35 is operated by a piston 189 in a cylinder controlled by a ram-reversing valve 194, Fig. 24, of similar construction to the table reversing valve and supplied with fluid through the conduit 95 only when the table reversing valve is in a neutral position and the table is in one of its working positions. Another valve 223 in this system is adapted to maintain a back pressure on one side of the ram piston. The ramreversing valve may be power shifted by fluid pressure through leads 232, 230 connected to a ram pilot valve 231 having right, left and intermediate positions. In the right hand position, Fig. 24, pressure fluid is admitted through lead 232, moving the main ramreversing valve to the right and causing the ram to move downwardly on the working stroke. Similarly in the left position of the pilot valve the ram is withdrawn and in the neutral position the ram remains in its raised position. The pilot valve may be manually actuated by a lever 257 or automatically through a notched actuator 254, Fig. 12, coacting with a detent 265. The actuator is moved in one direction by a cylinder 268, the piston of which carries an actuating dog 273, this cylinder being supplied by lines 147, 148 of the pilot control valve 104. In the other direction the ram pilot valve is actuated through a link 260 and rocker 284 coacting with dogs 287, 288 on the ram. The dog 287 is arranged to reverse the ram at its lower position while the dog 288 stops the ram at its upper position. The piston valve 177 forming part of the table pilot valve control mechanism is supplied from the low volume pump. In one position of this valve, pressure passes into the conduit 176 and lifts the latch so that the table pilot valve may be thrown to either extreme position. This position of valve 177 is obtained only when the ram is in its uppermost position and is controlled by a dog 305 on the ram. An interlock is thus provided between the ram and table movements. The back pressure valve 223 is formed within the casing of the ram reversing valve and includes a spring-pressed plunger portion 318. One end of this valve is connected through a choke coil 328, check valve 326, choke coil 330, and the line 193 to the upper end of the ram cylinder. Another choke coil allows the hydraulic fluid to bleed from the valve 223 which acts as a differential balancing valve. When no pressure exists on the valve plunger flow through ports 311 is shut off and back pressure is created in the line 222, the flow in which passes through choke coils 332, 334 to opposite ends of the valve. The resistances are so proportioned that the ports 311 are uncovered to allow the broaches to act at the required speed. If the ram tends to run ahead the valve moves to the right to throttle the flow through ports 311 to check the movement of the ram. If the broaches encounter heavy resistance, oil is forced through choke 330, and check valve 326 and pressure is built up on the right hand side of the valve to uncover the ports 311 and reduce the back pressure. In order to overcome the tendency of the ram to fall owing to seepage from the ram cylinder, a small amount of fluid is constantly fed to the cylinder through a line 337 connected through a choke 338 to the low volume pump and to maintain the cylinder on the other side of the piston always full a branch from the choke 338 is connected through a further choke 340 to the upper side of the piston. Any excess from this circuit passes to a drain 341. In order to prevent descent of the ram piston when the machine is shut down, a safety latch mechanism 70, Fig. 24, is provided.. In one position, this valve allows flow from the high pressure pump to the line 71 and through a bell-crank withdraws a locking pawl from a rack 368 secured to the ram. If the pressure drops in the line 133 the valve plunger is moved by a spring to lock the ram in position. The locking pawl may also be actuated manually.