Patent GB-371008-A (GB)
Title: Improvements in or relating to automatic broaching machines
IPC: B23D37/04
Filed: 1930-12-13
Abstract: 371,008. Broaching. LAPOINTE, F. J., 410, W. Huron Street, Ann Arbor, Michigan, U.S.A. Dec. 13, 1930, No. 37660. Convention date, Aug. 8. [Class 83 (iii).] In a pull-broaching machine in which the broach is continuously reciprocated, the broach is automatically disconnected from the drawhead between successive reciprocations thereof and the work-pieces are fed laterally between the broach and drawhead in succession ready to be operated upon during the succeeding stroke. The drawhead 3, Fig. 4, is attached to a cylinder 4 which reciprocates over a vertical piston 7 attached to the bed 14 of the machine by a hollow rod 13. Fluid is admitted above the piston for the working stroke by a pipe 9 over which the cylinder 4 slides and is guided, connection being made by a further pipe 10 to a control valve 20. Fluid is admitted below the piston by a pipe 16 connecting the valve 20 to the rod 13. The drawhead 3 and the piston 7 are located above a work-plate 1 against which the work is pressed during broaching. The work-pieces, e.g. bushings, are fed to the machine from a hopper by means of a pipe 27, Fig. 7, whose lower end is closed by a plate 28. The plate 28 is reciprocated by the piston of a fixed fluid-pressure cylinder 40 so as to bring a pocket 29 therein beneath the pipe 27, and allow a bushing to fall against an adjustable or replaceable positioning stop 36 in the pocket which is open on one side to allow removal of the work by the broach whilst the plate is returning for the next blank. Spring-pressed balls 30 are provided in recesses in the pocket to retain the work prior to broaching. The drawhead 3 comprises a shell 56, Fig. 7, provided with inclined recesses 59 for co-operation with clamping dogs 60 for the broach, the dogs being separated to release the broach by means of pins 61 on a lever 55 pivoted to the head at 57 and operated by a pivoted catch 65 on the machine frame 2. The upper end of the broach and the dogs 60 are provided with interengaging teeth 62, preferably in the form of V-threads. The movements of the machine are controlled automatically by means of a bracket 84, Fig. 1, connected to the upper end of the cylinder 4 and carrying a trip collar 86 and a slidable rod 88. In operation, as the broach moves downwards after a working stroke, an arm 90 on the rod 88 meets the upper end of a rod 91 attached to a piston valve in a casing 45, the valve being normally pressed upwards by a spring 92 engaging a collar 98, and thereby depresses the valve and admits oil to the inner end of the cylinder 40 to move the plate 28 so as to carry a new blank beneath an opening 37 in the work-plate 1. Shortly before the blank reaches this position the lever 55 on the drawhead engages the trip 65 whereupon the dogs 60 ride up the inclines 59 and the broach is released and dropped into a tapered socket 70, Fig. 4, on a bracket 73 attached to a cylinder 71. The bracket 73 is adjustable according to the length of broach used and the cylinder 71 slides on a fixed piston attached to a hollow rod 75 which admits fluid to the upper portion of the cylinder. Two rods attached to the cylinder slide through a fixed bracket 81 to guide it. When the drawhead Teaches the lower limit of its stroke the collar 86 meets a stop 85, Fig. 1, attached to a rod 87 slidable through a bracket 89 and supported by a link 93 and a pivoted arm 94, thereby rocking the arm downwards and actuating the piston of the valve 20 through a rod 83. This admits oil simultaneously to the cylinders 4, 71, but due to the differences in cylinder diameters and in loads, the cylinder 71 acts first, causing the broach to be raised until its upper end 63 spreads apart the dogs 60 and then passes between them to be gripped thereby when the head 3 is raised by the cylinder 4. The broach then performs its upward working stroke, at the end of which the collar 86 engages a stop 85 on the rod 87 to raise the valve 20. Oil is thereupon admitted to the lower end of the cylinder 4 and the head 3 and broach descend, the exhaust pressure in the pipe 9, which is still in communication with the cylinder 71, being sufficient to maintain the socket 70 in the raised position until the trip 65 causes the broach to be dropped thereon. When the drawhead comes to rest the pressure falls sufficiently for the socket 70 to descend and allow a fresh workpiece to be introduced in line with the broach. A latch 95, Fig. 1, is pressed by a spring to engage over a collar 98 on the valve rod 91 to maintain pressure in the cylinder 40 until the broach has passed partly through the work and pressed it against the work-plate 1, whereupon a cam 100 on the rod 88 withdraws the latch and allows the valve 45 to lift, thus admitting oil to the opposite end of the cylinder 40 and moving the plate 28 to the left in Fig. 1 to receive a new work-piece from the tube 27. On downward movement of the valve rod 91 a conical surface beneath the collar 98 withdraws the latch 95 and then allows it to snap back to hold the valve depressed. Oil under pressure is supplied to the cylinders 4, 71 by a pump 21, Fig. 4, and to the cylinder 40 by a pump 48, both pumps being geared together. The exhaust from the cylinders returns to a sump 23 formed in the machine frame 2. The finished work-pieces drop from the broach when it has passed through them and are deflected by a plate 107 into a receptacle, a hole 108 in the plate 107 serving to maintain the broach in alignment with the head 3. Beds and framings ; cuttings, catching and removing.-A platform 106, Figs. 1 and 4, may be provided for the operator and the machine is enclosed completely by the framing 2. The socket 70 has a conical lower surface 109 and side apertures 110 to facilitate the escape of cuttings which adhere to the broach and the cylinder 71 is provided with an outlet pipe 115 for the escape of oil which leaks past the piston therein, the top end of the pipe being bent downwards to prevent ingress of cuttings to the cylinder. A plate 113 protects the hollow piston-rod 75 from cuttings.