Patent GB-482554-A (GB)
Title: Improvements in and relating to vertical broaching machine
IPC: B23D37/04
Filed: 1937-05-20
Abstract: 482,554. Hydraulic broaching-machines. TRIGGS, W. W. (Lapointe Machine Tool Co.) May 20, 1937, No. 14030. [Class 83 (iii)] In a vertical push-down broaching-machine, the broach is released from its holder and drops on to a support near the end of the working stroke and the upward movement of the broach holder is begun prior to the reengagement of the broach therewith, the broach support being moved upwardly at a higher speed than the broach holder so that the broach overtakes the holder. The main broaching cylinder 21 has a piston-rod 23 carrying the broach-holding head 26 and guided by an arm 24 moving on vertical guides 25. The head 26 has one or more (two are shown) recesses to receive the upper rods of the broaches B which operate on one or more work pieces W mounted on a table 41. The broaches are locked to the head by a spring- pressed locking-bar 30 carrying studs 32 engaging circumferential grooves in the broaches. The end of the locking-bar is bevelled at 43, Fig. 4, so that at a predetermined point in the downward movement, the locking-bar is pushed back by engagement with a post 40 to release the broaches which fall on to a support 45 below the work-holder. When the broach head rises the locking-bar is returned by its spring to normal locking position. The broach support slides on vertical guides and is connected to a piston-rod 47 extending through a cylinder 48 and carrying a piston 49. A pump P delivers fluid through a pipe 51 to a reversing-valve R and connected by pipes 61, 62 to the main cylinder. Exhaust pipes 66, 67 lead to the reservoir T through separately adjustable back-pressure valves 68, 69. These valves, Fig. 3, may each comprise a notched element 83 slidable transversely to control the flow through the valve. The central piston portion 73 of the reversing- valve is operated through lever mechanism 75-78 from a handle 80. The upper end of the support cylinder is connected by a pipe 70 to the return line 67 and the lower end to the line 62 leading to the lower end of the main cylinder. When the handle 80 is in neutral position, Fig. 1, the pump flow passes to both return pipes 66, 67. Downward movement of the handle raises the valve piston 73 and supplies line 61 with pressure fluid for the working stroke. Line 62 is at the same time connected to line 67 which exhausts through back-pressure valve 69. The lines 70 and 71 are also both under the back pressure in line 67 so that the pressures on the two sides of piston 49 balance and the broach support moves downwards to its lowest position by gravity. At a predetermined point in the working stroke the broaches are released by the post 40 and drop on to the broach holder. When the handle 80 is moved upwards the valve R is shifted to direct pressure fluid to line 62, while exhaust passes through lines 61, 66 and backpressure valve 68. The line 71 is also under pump pressure while line 70 is under the back pressure of valve 69 which offers low resistance to the small flow from cylinder 48, so that the piston 49 and the broach support are moved upwards more rapidly than the main cylinder. The broaches are thus again locked to the head as soon as the locking-bar clears the post 40 whereupon cylinder 49 reaches the end of its movement and the head completes its upward stroke. In a modification, the broach support is manually operated by means of a hand lever and cable, the handle being operated to lift the broach holder at the time when the reversing-valve is shifted to produce the upward broach movement. Specification 445,309 is referred to.