Patent GB-532069-A (GB)
Title: Improvements in and relating to machines for drilling, screwing and tapping
IPC: B23G1/16
Filed: 1939-08-15
Abstract: 532,069. Boring, screwing and tapping machines. NATIONAL ACME CO. Aug. 15, 1939. No. 23561. Convention date, Sept. 3, 1938. [Class 83 (iii)] In a screw-tapping or boring machine the tool spindle is fed rapidly before and after the tapping operation and during one of its traverses actuates means for turning the work holder end for end so that the other end of the work may be operated upon. The machine comprises a tool-spindle 6, Fig. 5, carrying a tap, die or boring head by means of a self-aligning holder and rotatable in bearings in a head 5 vertically slidable on a pillar 2a. The spindle is driven by gearing 6<SP>1</SP> from a splined shaft rotated through gearing in a box 3a from a variable speed electric motor 4a. A lead screw I is journalled in the box 3a and is driven by worm and change gearing 12 from the motor. The work, such as a pipe coupling 30, is held by concentric grippers in a work-holder mounted on trunnions 29 so that when one end of the work has been operated upon it may be indexed 180 degrees for operation on the other end. A stop o is movable into position below the holder so that a work piece placed therein by hand will be located at the correct level. In operation a lever 1', Fig. 7, is actuated by hand to control a valve A and cause fluid from a pump 50 to operate a plunger Q, Figs. 6 and 7, and rotate a cam plate 26 to release the work jaws 21. A 'plunger o' is also operated through a delay action valve B to move the stop o under the holder after the previous work piece has dropped out. In this position of lever 1<SP>1</SP> a second hand lever 3<SP>1</SP>, for starting the machine cycle, is locked in inoperative position but after inserting a work piece in the holder 'the operator returns the lever 1<SP>1</SP> to its former position, thus releasing the lever 3' 'and admitting fluid to a plunger P to clamp the work :and 'return the stop o after a time lag caused by the valve l which controls .valve D to admit fluid to a cylinder L whose piston is connected to the tool head 5, thus moving the head rapidly towards the work. The hand lever 1<SP>1</SP> is locked in inoperative position when the lever 3' is actuated. When the tool approaches the work a 'trip lever R on the head 5 engages a stop to actuate a valve F and admit fluid to cylinders G whose pistons engage half-nuts with the rota'ting lead screw I for the cutting feed, and at the same time a valve E is actuated to cut off fluid supply to the cylinder L. After the required length of thread has been cut the die-hand or tap is collapsed and a trip lever RA operates the valve F to release the halfnuts from the lead 'screw an'd simultaneously a valve S is actuated to rotate the valve c operate the valve D and reverse the action of the cylinder L so that 'the head 5 will be retracted rapidly. On reaching the top of its travel the piston in cylinder L traps fluid above a hole T and forces it into a valve V 'from which it 'passes to a cylinder W and ejects a plunger W<SP>1</SP> connected by a lever 23, Figs. 5 and 7, to a bolt X which locks the work holder. This withdraws the bolt from the index plate Y and a cam on the lever simultaneously actuates a valve Z to admit fluid 'to a cylinder AB, forcing out a piston carrying a rack AC meshing with a pinion 23<SP>1</SP>, Fig. '6, on the work holder trunnion to index the work through 180 degrees. During its forward stroke, the rack AC engages means which rotate the valve C to its next position, thus cutting off fluid from 'the cylinder W to release the bolt X and allow a spring AD to engage the bolt with the next notch of the index plate. The lever 23 releases the valve Z during its retraction and causes return of the rack AC, the pinion 23' rotating idly on a roller clutch. Valve Z also admits fluid to valve D and starts the tool head 5 on a second rapid traverse towards the work for operating on the remaining end thereof, the cycle being the same as before except that when the head reaches its upper limit of travel the valve S rotates the valve into a position in which the machine is stopped instead of causing indexing of the work holder. The lever 3<SP>1</SP> is then returned to inoperative position, allowing the lever 1<SP>1</SP> to be moved and thus actuating valve A and cylinder Q to release the work. Valve A also controls a fluid-operated table M which transfers the work, after it has dropped from the holder, on to a conveyer 25, Fig. 4 (not shown) to remove it from the machine, and the cylinder o' is also actuated by valve A, through a delay action valve B, to move the positioning stop o under the work,holder after the finished work has dropped therefrom. If the work tends to stick to one of the jaws it is positively disengaged by stops in the holder so that it may drop out freely. For operating on one end only of the work the valve C may be arranged to stop the machine after a working operation of the tool head, instead of causing indexing of the work. The pump 50 supplies low pressure oil in large quantities for the machine operating cylinders and high pressure oil, regulated at 28, to the work gripping cylinder. The tap is re-set on the upward stroke of the head 5 by a slide 20, Fig. 5, operated automatically, and if resetting is not effected properly a safety device (not shown) stops the machine. A safety device for limiting the downward traverse of the head is also provided, and a limit switch stops the motor 4a if the tap does not release after a working operation. Lubricating cutting tools and work.-The cutting oil is controlled by a valve which is only turned on when the lead screw nut is engaged. Balancing parts.-The tool head 5 is balanced by a weight sliding vertically in the pillar 2a and fluid is cushioned in the bottom of the cylinder L to arrest the rapid approach of the tool head towards the work before the half nuts engage the lead screw.