Patent GB-425918-A (GB)
Title: Improvements in and relating to hydraulically operated drilling machines
IPC: B23B47/22
Filed: 1933-09-27
Abstract: 425,918. Hydraulic transmission of power. LELAND-GIFFORD CO., Worcester, Massachusetts, U.S.A.-(Assignees of Hirvonen, E. J. ; Worcester, Massachusetts, U.S.A.) Sept. 27, 1933, No. 26630. Convention date, Oct. 8, 1932. [Class 69 (ii)] [See also Group XXII] In a drilling-machine for drilling deep holes, the drill is fed hydraulically in stages, being withdrawn rapidly between the stages to clear the drill from cuttings and being fed rapidly to the bottom of the hole after each withdrawal, the feed being then continued again, at cutting speed to a more advanced point. When the final depth has been reached the drill is rapidly withdrawn to a fully retracted position and is maintained stationary there. The machine comprises a drill a, Fig. 1, secured by a chuck 30 to a shaft 32 splined within a hollow shaft driven by gearing from an electric motor 42. The shaft 32 is journalled in a slide 36 adjustably secured by a screw 58 to the piston rod of a hydraulic cylinder 54, Fig. 8, which is supplied with fluid for a forward stroke by a pipe 142 leading from a speedregulating valve 136 supplied by a reversing valve 120. A pump 110, preferably of the gear type, draws from a reservoir 112 and supplies through a compressed-air accumulator 116. to the reversing valve 120. In the machine, the valves 120, 136 are located adjacently in a casing 40 beneath the cylinder 54 and the casing itself forms the reservoir 112. A cross-head 70 on the piston rod 56 carries a bar 64 having mounted thereon a cam 76 which acts on a pin 162 attached to a lever 160, the other arm 164 of which is adjustably attached by screws 166 to a slide 170 connected to the reversing valve 126. A spring pressed plunger 174 acts on a V-shaped dog 176 on the lever 160 to give a snap action. In operation, a valve 178 is operated by hand to admit fluid from a pressure pipe 180 to a pipe 184 and thence to a piston 188, moving this piston to the left against its spring 190<1> and acting on a projection 192 on the slide 170 to move the reversing valve 126 to the extreme left hand position shown in Fig. 8. This admits fluid from the pipe 118 to pipe 134 and through unrestricted passages in the speed-controlling valve 136 to the rear of the piston 52 for a rapid advance of the drill slide 36, the exhaust from the front of the piston 52 passing freely through an unrestricted port 146 in the valve 126. The cam 76 moves with the slide, and when the drill is almost in contact with the work b, a rise 78 on the cam lifts the pin 162 onto a dwell portion 80, thereby rocking the lever 160 to move the reversing valve 126 slightly to the right, closing the exhaust port 146 and restricting the flow through the pipe 134 to the rear side of the piston 52. The exhaust from the cylinder 54 now passes through an adjustable throttle valve 150 and pipe 148 to exert a back pressure on the piston 52. This back pressure is admitted by a pipe 152 to the valve 136, thereby moving the valve to the right against its spring 140 and partially throttling the supply at the rear of the piston 52. Variations in the resistance of the work to the drill alter the back pressure and so control the feeding supply to the piston 52 to give a constant rate of feed. When the drill has penetrated the work for the first stage of the feed, a dog 92, Figs. 1 and 23 adjustably attached to a bar 82 secured on the bar 64 meets a block -220, Figs. 21 and 23, loosely mounted in a slot 222 in the cam 76 and engaging a pivot pin 224 at one side of the slot. A projection 234 on the dog 92 slides and oscillates the block against a spring to cause a bevelled surface 230 thereon to engage the pin 162 and rock the lever 160 to move the valve 126 farther to the right into position for a rapid retraction of the tool slide. The cam 76 is secured to a rack 216, Fig. 23, on the bar 82 by means of a pawl 212, Fig. 21, but when the pin 162 on the lever 160 is moved by the bevel 78 on the cam 76 to start the slow cutting feed, the pin also acts on an arm 218 of the pawl 212 to disengage it from the rack and allow the pin to hold the cam 76 stationary whilst the bar 82 and rack 216 advance with the tool throughout the cutting stroke. The cam 76 is thus moved relatively to the bar 82, as shown successively in Figs. 23-25, and hence relatively to the tool slide, by an amount equal to the cutting feed so that on the next stage of the drilling the tool slide will be permitted to advance by this additional amount at the rapid rate before the bevel 78 meets the pin 162 to start the next cutting stroke. Several dogs 92, 94, 96 are mounted on the bar 82 according to the number of stages required to produce the final depth of drilling, the length of each stage being determined by the position of its dog on the bar 82. The block 220 normally lies within the slot 222 but when the pin 162 is lifted onto the dwell 80 of the cam 76, it also acts on the bevel 230 of the block to project its rear end 232 into the path of the dogs 92 &c. The oscillation of the lever 160 into reverse position frees the pin 162 from the arm 218 and allows the pawl 212 to re-engage with the rack 216 whilst a spring plunger restores the block 220 to its original position in the slot 222. When the drill has withdrawn from the work after drilling the first stage, sufficiently to clear itself of cuttings, a finger 106, normally held in the depressed position shown in Figs. 1 and 8, engages a block 258 pivoted at 260 on a stationary casing. The block is thereby oscillated to cause a pin 262 thereon to depress a valve 202 and admit pressure fluid behind the piston 188 to throw the valve 126 into the rapid forward position again, this continuing until the drill has almost reached the bottom of the hole drilled in the first stage, whereupon the cam 76 institutes the slow cutting feed and is then released from the rack 216 and held stationary to be set for the next stage. When the final drilling depth has been attained the last reversing dog 96 on the bar 82 engages a pin 246, Fig. 25, on a pawl 238 pivoted on the fixed plate 68, thereby moving the pawl into the path of a pin 236 on the cam 76 so that the cam is maintained stationary as the drill and bar 82 are retracted, the pawl 212 riding over the teeth of the rack in this direction. During the retraction, the finger 106 rides over a cam plate 264 on the cam 76 whereby it is raised over the block 258 and hence is prevented from actuating the valve 202 to start another forward feed. The retraction continues until a cam face 102 in a block 98 attached to the bar 64 moving with the drill head encounters the pin 152 on the lever 160 to move the valve 126 to its neutral position in which the drill head is locked against movement, the flow and exhaust to the cylinder 54 being completely shut off by the valve. To return the drill slide to this position at any intermediate point of the cycle, the valve 178 is operated by hand to admit pressure fluid to a pipe 182, Fig. 8, thus actuating a piston 186 to move the slide 170, lever 160 and valve 126 into rapid reverse position and simultaneously to actuate a piston 276. This piston rocks a lever 278 which oscillates a trip 266 against the action of a spring plunger to place a tail 2661 on the trip in position to lift the lever 106 and prevent it from operating the reversing block 258 during the rearward movement. In the fully retracted position the bevel 102 again sets the valve 126 to cause the feed mechanism to remain stationary. The drill head may also be retracted manually and the mechanism re-set by manipulating the lever 160 through a handle 161, Fig. 1, therein, and simultaneously moving the pin 246, Fig. 25, into position for tripping the cam 76 and restoring it to its starting position on the rack 216. At the end of the full retractive movement a finger 250 on the block 98 engages the pin 246 with its bevelled end to rotate the plate 238 back to its inoperative position, and release the cam 76. In order to reverse the feed should the drill encounter excessive resistance, such as by a chip becoming lodged under the cutting edge, a valve 286, Fig. 8, is biassed by an adjustable spring so as to cut off fluid supply from a pipe 296 to the piston 186 which controls the reversing valve 126. A pipe 300 connects the valve 286 to the pressure side of the piston 52, the arrangement being such that excessive resistance to the feed of the drill causes the pressure in the cylinder 54 to rise, thereby lifting the valve 286 and admitting pressure to the piston 186 to reverse the feed. Feed and retraction of the drill are repeated alternately unil the resistance has been overcome. The spring pressure on the valve 286 is adjusted by a screwed ring 304, Fig. 1 and a lock nut 306.