Patent GB-297104-A (GB)
Title: Improvements in hydraulically propelled metal-cutting and like machine tools
IPC: B23C9/00
Filed: 1928-07-30
Abstract: 297,104. Cincinnati Milling Machine Co., (Assignees of Ernst, H., and Nenninger, L. F.). Sept. 15, 1927, [Convention date]. Milling-machines.-In a hydraulically-operated machine-tool such as a milling-machine the table or other work support is fed by hydraulic pressure opposed by a metering escapement which controls the speed of movement, a control valve or valves being automatically operated by trip mechanism to move the table through various predetermined feed cycles. A large capacity pump is employed for effecting rapid traversing movements where no tooling resistance is offered and a low capacity high pressure pump is employed for power feeding against the resistance of the escapement pump back pressure. The table is thus held rigidly under this differential control and the feed may be in the same direction as the cutter rotation without the possibility of overrunning of the table. The machine is driven from a motor 1 which through chain gearing 3, 4, drives a clutch sleeve. 6<1>, Fig. 5, carrying a pinion 6 which is connected by further gearing to the driving pinion 13 of the hydraulic system. The latter comprises a constant pressure pump Bo, a rapid traverse pump RT, and a variable escapement pump Z. The pumps RT and B<o> are both driven from the shaft of a gear 14, Fig. 12, while the escapement pump is driven from the gear 14 through a gear 15. The cutter-spindle S<1> is driven in either direction from the clutch sleeve 6<1> through clutch element a reversing bevel gearing d, e, vertical shaft f bevel gearing g, and spur gears l, m. Axial adjustment of the spindle is effected from a turn bolt 1<a> operating a wormwheel 3a engaging a rack on the spindle sleeve 4<a>. The clutch 6<1> is actuated through levers a<1> by a member 16 operated by a rod 17. When the clutch is released the member 16 engages a fixed braking surface 16<a> to stop the spindle. The rod 17 is actuated through lever mechanism by a hand lever D. In order to prevent the stopping of the cutter rotation while the feed is still operating the lever D is interlocked with the controlling mechanism of the hydraulic gearing. The shaft 22 of the lever carries a pin 23 coacting with a lug E<1> on the shaft of a lever E controlling the hydraulic feed, the arrangement being such that the lever E can only be moved to start the feed after the lever D has been shifted to start the spindle, and return movement of the lever D automatically stops the feed. Automatic means for effecting this control are also provided. A trip plunger A is arranged to receive an angular movement which rotates the shaft 22 to start the spindle. For stopping the hydraulic feed automatically a, trip B is depressed by stops on the table thus lifting a pawl B<2> from a stop rod G which is then moved to the left by its spring to arrest the feed through a suitable stop valve. The plunger A and a control handle H are each connected to a rod K. In addition to its twoposition angular setting, the plunger A may have two different axial positions, the four positions of the plunger being communicated through the rod K and lever k<1> to give angular and longitudinal shifts to the main valve L. This valve comprises an outer casing N provided with seven peripheral grooves, the end grooves S, Y, communicating with the left hand end of the cylinder T<30> which actuates the table T<1>, and the central groove V with the right hand end of the cylinder. The pumps are arranged in the manner indicated in Fig. 28, the fluid being derived from a reservoir 105. The groove V is filled by the pump RT or rapid traversing and when this supply is not in use it is bye-passed back to the reservoir through a pipe T<9>. The channel W receives the delivery from the pressure pump B" and from the escapement pump Z, the inlet to the latter being drawn from the channel X. When the rapid traverse pump is in operation, the channels W and X are connected to bye-pass the high pressure oil. A high-pressure relief valve 107 is ..provided in the case of stoppage of the table and in order to ensure a constant supply to the escapement pump a shunt line 114 is provided with a one way check valve 110. A further check valve and a low-pressure. relief valve 109 are also provided. In order to establish the appropriate communications, the channels are provided with a number of ports which coact with longitudinal slots L<1> arranged in the valve element L, the development of the grooves, ports and slots being shown in Fig. 28. The valve Lo is designed for a feed cycle comprising a rapid approach followed by a slow feed and then followed by a rapid return traverse to a final stop. A modified valve, element may be employed in which a reciprocating feed cycle is obtained. In this case there occurs a rapid traverse to the left followed by a feed to the left and then a rapid traverse to the right followed by a feed to the. right. An auxiliary valve M operated by the stop rod G is employed in this case for stopping the movement. These valves may also be employed in machines having ordinary hydraulic feeds without escapement control. In addition to the automatic hydraulic feed, the table may also be fed by an auxiliary hand-operated pump for setting up and adjustment purposes. This manual feed comprises a pump casing R, Fig. 43, carrying a shaft 39 rotated from a handle R' and provided with an eccentric 39<a> which actuates two plunger pumps R<2>, R<3>, of unequal capacity. The inlet and exhaust of the pumps are controlled by a rotary valve R<4> carried by the shaft 39. The pumps are connected to the table and automatic system as shown in Fig. 43. The pumps R<2>, R<3> operate to withdraw fluid from one side of the main feed piston and inject it on the other side, thus providing a means of adjustment. The unequal capacities of the pumps R<2>, R<3>, are arranged to compensate for the differences in the effective area of the piston on its two sides owing to the diameter of the piston rod. Mechanical means are also provided for adjusting the table. This comprises a screw and nut connection between the piston rod and the table, the nut 54, Fig. 41, being rotated by a hand wheel 56. The escapement pump comprises a cylinder block 30, Fig. 12, having radially disposed cylinders and surrounded by a casing element 31 driven by the gear 15. The delivery of the pump is determined by the relative positions of the axes of the cylinder block 30 and casing 31 and to adjust this delivery the cylinder block is supported on a rock arm 30<a> journaled on a, pivot 30b. The action of the pump may be controlled so as to vary the rate of feed during the operation in milling a pieces of varying area. The casing P carries a shaft 32a provided with an eccentric 32 operating the rock arm 30<a>, the eccentric being rotated from a cam 60 on the work table through a plunger rod 34 and rack and pinion 33. The automatic control for this pump may be disengaged by depressing the plunger 34 by means of a, hand-operated eccentric 62. Manual adjustment of the variable escapement pump after disengaging the automatic adjustment may be effected by means of a second eccentric 67 mounted on a shaft 66 carrying a spring pin 68 moving over apertures in the casing. In order to render the feed uniform in either direction and to compensate for the diameter of the piston rod, the effective action of the escapement pump is varied on reversal of the work table. This is effected by means of a lever 35 coacting with the plunger 34 operating the controlling eccentric. According to the direction of movement of the tables a pawl 37<a> assumes either the full line or dotted position shown in Fig. 13, thus permitting slight movement of the plunger to give the required compensation. In some operations it is desirable, for the cutter to run in contact with the work for some time for clearing up the cut without feed, and in this case, the reversal of the main valve, is effected, after a suitable pause, by hydraulic means, Fig. 39. Such a modification may be used for milling half bearings 77 with a reciprocating feed cycle. The translation of the table may be arrested positively by stops such as 78, 79. The main valve is connected by a lever 85 to the piston of a cylinder 82. A spring valve 90 is connected to the hydraulic, system as shown and, when the table is arrested, the fall of pressure in front of the main piston produced by the continued operation of the escapement pump causes the spring valve to move to admit fluid through a throttle, valve 95 to a reversing- valve 98 and thence to the cylinder 82 to actuate the main valve. The lever 85 has a. lost-motion connection with the valve 98 and during the movement of the lever 85 this motion is taken up to shift the valve to a position to admit oil to the other end of the cylinder 82 after the next arrest of the table at the other end of its travel. A simplified modification of this system may be employed for a one way feed cycle, the valve M then being dispensed with and only one positive table stop being required. To indicate the extent of the table movements, a, rack 150, Fig. 46, on the table may be arranged to drive a gear train comprising a gear carrying a pointer 154 which indicates inches of travel and a second gear carrying a pointer 156 indicating thousandths of an inch.