Patent GB-339356-A (GB)
Title: Improvements in hydraulic feeding systems for metal cutting and like machine tools
IPC: B23Q5/26
Filed: 1929-09-07
Abstract: 339,356. Pollak, J. E., (Lodge & Shipley Machine Tool Co.). Sept. 7, 1929. Turning; driving machines. -A hydraulic feeding system for a metalcutting or like machine tool comprises means for establishing a constant pressure difference between a source of fluid and a motor of variable resistance, consisting of a control element which is movable in a casing to provide a variable bye-pass for the fluid supply, the element being urged in one direction by the pressure of the supply and in the other direction by the pressure of the motor, the latter pressure being assisted by auxiliary means such as a weight. The piston rod 3 of the hydraulic motor 1 is secured to a lathe carriage by nuts 66 and carries adjustable lock-nuts 44, 67 which coact respectively with the stuffing-box 4 and bracket 68 to limit the carriage movements. Opposite ends of the cylinder 1 are connected by pipes 15, 16 to a distributor valve 5 of the sliding piston type, the valve having three positions determined by a spring plunger engaging notches in an extension 52. The valve body has a number of slots such as 18<1> communicating with an outer chamber 18 connected by a pipe 10 to a sump 11. The pump 12 delivers fluid to the valve through a pipe 13. A bye-pass valve 7, actuated either manually by a lever 8 or automatically by dogs 9 on a control rod 55 is adapted to bye-pass the pump discharge from the central valve chamber 14 to the exhaust. The pump delivery also passes through a highpressure valve 19 to a valve 45 (shown in two parts in Fig. 1) which may be rotated to admit fluid to either end of the valve casing. A pipe 21 connects the distributor valve to a pressure control valve 22 which is also connected to exhaust through a pipe 26. This valve, Fig. 5, comprises a lower chamber 33 which, by upward movement of the control element or plunger 29 carrying a weight 30 may be connected through a. taper bore 32 and passage 35 to a chamber 34. The lower chamber 33 is connected by a small-bore pipe 24 to a throttle valve 25 and thence through the valve 45 to the lefthand side, Fig. 1, of the cylinder 1. Between the throttle valve and the valve 45, the pipe 24 is joined by a pipe 23 leading to the upper chamber 28 of the pressure control valve. Thus when resistance to the movement of piston 2 to the right increases the pressure on top of plunger 29 also increases. This causes the plunger to move downwards and checks the flow between the chambers 33, 34 and pressure in the line 24 accordingly rises so that the movement of the piston is unimpeded. When a decrease in resistance to piston movement occurs the pressure in the line 24 correspondingly falls. The throttle valve 25 comprises a tapered plug 36, Fig. 7, engaging in a body provided with two ports 40, 41, the plug having a tapered notch cut in its periphery for varying the flow between the ports. A scale is provided on the body for indicating the setting of this valve. The control rod 55 is connected to a three-armed lever 57 whose other arms carry rollers 58 engageable by dogs 59 on a rod 60 moving with the carriage. The rod 60 may also be fitted with dogs 65 which coact with rack rods 64 to move the throttle valve 25 to change the feed speed at any desired intervals. In Fig. 1 the valve 45 is positioned for feeding to the right and the pump 12 is discharging into the right hand end of the cylinder 1 for rapid return of the carriage to the left. The movement of the rod 60 at a predetermined point causes the right hand dog 59 to engage its roller 58 and shift the rod 55 and the distributor valve to its central position. At the same time one of the dogs 9 depresses the valve 7 and fluid now passes from the pipe 13 to exhaust passage 18, the piston 2 remaining at rest. To start the forward movement, lever 56 is moved to the right thus closing the valve 7 and shifting the distributor valve to the left hand position, where fluid can flow through pipe 16 to the left hand end of the piston to give a rapid approach movement to the carriage. During this movement the weight 30 prevents flow between the pipes 21, 26. As the left hand dog 59 moves to the right it moves the rod 55 to the left to mid position, but in this case the pivoted operative part of the dog 9 allows the valve 7 to remain closed. Fluid now flows through the throttle valve 25 for the working feed of the piston 2 to the right and this continues until the nuts 44 engage the stuffing box 4 whereupon valve 19 opens temporarily and fluid passes through valve 45 and conduit 20<a> to shift the piston 6 to the left and give rapid return of the working piston 2. In a modification, Fig. 4, the rod 3 may carry a nut having rack teeth engaging a pinion arranged to give cross feed to the top slide. The nut may have limited movement between abutments on the carriage so that if the feed of the carriage is to the left, the first movement of the rod 3 moves the nut relative to the carriage to give an infeed to the top slide. Similarly the first return movement of the rod 3 causes withdrawal of the top slide.