Patent GB-325010-A (GB)
Title: Hydraulic feed for the slides of metal cutting and like machine tools
IPC: B23Q5/26
Filed: 1928-08-09
Abstract: 325,010. Potter, W. W. Oct. 31, 1927, [Convention date]. Divided on 299,764. Lathes. - In a hydraulicallyoperated machine tool such as the vertical spindle lathe described in Specification 299,764 the moving parts are actuated by hydraulic cylinders which are supplied with high pressure fluid at low volume for the slow working feeds and low pressure fluid at greater volume for the idle movements. The vertical slides 37 are each fitted with a cross slide 44 and each carriage 37 is actuated by a cylinder 47 which is fed from a hydraulic circuit shown in Fig. 5. An electric motor 55 drives a duplex pump preferably of the intermeshing gear type, comprising a high pressure unit 53 of low capacity and a low pressure idle motion unit 54 of high capacity. The rotor shafts of the two pumps may be connected by gearing 189 and driven from the main driving motor 193. The pumps are fed from a reservoir 58 and the delivery passes an automatic shut off valve 59 which is closed by a spring and is normally held open by a solenoid 61. A switch 193<a> is connected to the valve 59 so that when this valve is closed the motor circuit is broken. Beyond the valve 59, the delivery pipes 51, 52 of the high and low pressure pumps respectively, communicate with a control valve 50. In one construction this valve includes a casing 65, Fig. 7, with a high pressure port 66, Fig. 11, low pressure port 67, ports 68, 69, connected to the carriage cylinder 47 for forward and reverse movements respectively, ports 70, 71 connected to the cross slide cylinder for forward and reverse movements respectively and an exhaust port 72 connected to the tank 58. The valve body carries a rotary valve 73 closed at the ends and having grooves 77 which, on rotation of the body change the port connections to give the required cycle of movements. The various valve positions are obtainable by hand or automatically through electrical switch devices. The spindle of the valve 73 carries a gear 98 driven from a gear 99 on the rotor of a motor 100. The gear 98 carries detents 102 moving on different orbital paths and each coacting with one of a series of switches 101 in circuits 103 including push switches 104 which are normally open but which may be closed by dogs 105 on the carriage 37. The circuit of the motor 100 includes a contactor 107 so that when a switch 104 is closed by its dog, the motor is started and continues to run to rotate the valve until a detent 102 engages the appropriate switch 101 and breaks the circuit. When this occurs, the motor is braked by a spring shoe 109 which is held up by a solenoid when the motor is running and is released as soon as the circuit is broken. In some cases a delay-action device is employed so that a tool may clean up its cut before reversal of its slide. This comprises a stationary contact 113, Fig. 21, and a movable contact 114 carried by a plunger under dash pot control so that when a contact 105 actuates a lever 119 to depress the cylinder 117 a time interval elapses before the contacts 114, 113 come into engagement to close the motor circuit. The various positions of the valve which give the connections required for rapid approach, slow feed and quick withdrawal of the slides are described in the specification. A metering valve 120 is provided in the high pressure line to regulate the feed. This valve comprises a body having a slotted liner 122, Fig. 20, communicating with the line 51. The rotary portion 125 has a helix adjacent the slot 123 to determine the flow through the valve and the rotation of the valve is effected through lever mechanism from a cam on the carriage 37. Other feed cycles may be obtained by suitable modification of the control valve. A safety device 134 is provided in the high pressure line so that if a predetermined pressure is exceeded a switch 135 in the main motor circuit is opened. A hand switch 136 is also provided in this circuit. Hand switches 137 are included in the circuits 103 and when one of these switches is operated to close the circuit of the corresponding detent operated switch it breaks the circuit of the automatic switch 104. The cross slide also carries dogs 105<a> operating switches 104<a> which are included in the above described circuits. The buttons of the switches 105, 105a on the moving members are arranged diagonally so that each coacts with its proper switch. In some cases a rack 140 on the cross-slide engages a pinion 141 geared to a rack on a dog-carrying slide 40. By this construction the slide 40 combines the movements of both the longitudinal slide and the cross slide and mav be used to control the switches of both units. The hand switches are adapted for remote control and two sets shown, Fig. 24, as unit 1 and unit 2 with a master switch M.S. are provided. Actuation of a master switch 245 first breaks the circuit of the automatic switches and then closes the circuit of the corresponding switch in both units. Other arrangements of master switching are described. Reference has been directed by the Comptroller to Specifications 21595/99, 28696/13, 172,192, 188,013, 275,676, and 297,104.