GB575874A - Improvements in or relating to the liquid pressure operation of machine tools - Google Patents

Abstract

575,874. Hydraulic machines. AUTOMOTIVE PRODUCTS CO., Ltd., and CARLTON, Q. H. April 19, 1944, No. 7284. [Class 69 (ii)] A liquid-pressure machine tool feeding system comprises a pump &c. 12 supplying liquid under pressure to the motors 11a &c. which advance the tools and are controlled by valves 80a &c., Fig. 2, the valves being operated by liquid - pressure columns through ports 17a from master cylinders 19a &c. The return valve strokes may be effected by springs 84a. The annular space around the " rod '' 73a of the motor piston is open to pressure liquid from the pump permanently by way of the ports 15a, 83a and a grooved part of the valve ; pressure supplied through the port 17a moves the valve to allow the pump liquid access to the piston head, moving the piston to the left and with it a plunger 77a which thus enlarges the liquid space in front of the valve and allows the spring to return it to off position, the stroke being thus determined by that of the master cylinder. Similarly retraction of the master piston(s) causes the valve to move to the left and so connect the head of the piston with the space behind the valve which is connected through port 16a with an atmospheric reservoir 13, the valve being returned by the movement of the plunger 77a as before and the stroke thus controlled. Relief valves 86a, 89a are provided. Fig. 3 shows a motor for the end tool slides D, E in which the piston has an extension 95d which is opened to the supply of pump liquid through a passage 87d controlled by the valve, the space 75d being connected to the reservoir through a passage controlled by a check valve 104d. When a port 107d in the piston extension reaches the main working space 75d a valve 96d uncovers radial ports 98d and when these reach this space the pump liquid acts in the main space and the piston moves more slowly with greater force. When the piston is retracted, the valve 80d is in position to open the port 87d to the reservoir connection, and liquid ejected from the main space acts on a piston 102d to open the valve 104d and allow the liquid to pass to the reservoir. The apparatus operates by momentary closure of a switch 49 completing a circuit through solenoids 38a, 38d from positive connection through lines 51, 56 controlled by switch 52 to negative connection 47. This shifts valves 34a, 34d to connect the discharge of pump 12 with the working'spaces of cylinders 29a, 29d, thus actuating their pistons which mechanically actuate the upper plungers of the master cylinders 20a, 20d &c. to bring the tools to cutting position. At the lowest points of these plungers, switches 57a, 57d are closed, making a circuit through solenoid 38f to shift its valve to actuate plunger 28f, engaging a clutch F, and so causing the constantly rotating shaft 24 to drive shaft 23 and actuate the lower plungers 21a &c. of the master cylinders for the cutting feed through cams 22a &c. Rotation of the shaft also causes a projection 53 on a cam 26 thereon to close a switch 54 and afterwards open a switch 52 breaking the circuits for solenoids 38a, 38d, and retracting the motor pistons. Further rotation brings the lower plungers to retracted positions, and again opens switch 54, de-energizing solenoid 38f and unclutching shaft 23. Separate switches 52 may be provided for the cross and end slides ; the plungers 20a &c. may be operated mechanically ; a single plunger may be provided in place of the slow and quick plungers. A variable-delivery pump, with a relief valve, may be employed, controlled from the cam shaft.