440,852. Broaching-machines. KING, T. ST. P. C., c/o Lapointe Machine Tool Co., Ltd., Edgware, Middlesex. Dec. 21, 1934, No. 36708. [Class 83 (iii)] In the vertical hydraulic broaching-machine, the broach is drawn downwards through the work piece by means of a pair of cylinders, the fluid being transferred during the working stroke from one cylinder to the other to balance the load produced by the work resistance and avoid side thrust on the cross-head guides. The plate 3 carries a pair of cylinders 4, 5 the respective piston rods 8, 9 of which are connected to a cross-head 10 slidable in guides. A socket 12 in the cross-head carries a pull bushing 13 coacting with the lower end of broach 14 which at its upper end is mounted in a bushing of a slide 16 movable in vertical guides and connected to the piston rod 18 of a cylinder 20. The work 22 is fitted over an apertured extension 21 of the plate 3. The cylinders 4, 5 are supplied from a plunp 24 through valve 25 and the cylinder 20 by an auxiliary pump 74, through a valve 27 both pumps being driven by a motor 75. The base of cylinder 5 is connected to the upper end of cylinder 4 by a pipe 31 and the pipe 53 leading to the base of cylinder 4 is also connected to the upper end of cylinder 5 so that oil is transferred from one cylinder to another as the cross-head moves upwards or downwards. The valve operating mechanism consists of rods 36, 37. The rod 36 is actuated by slide 16 and acts through lever 38, link 39 and bell-crank 40 on a pivoted cam 41. The link 39 of this mechanism is also connected through lever 43 and rod 44 to the valve 27. Manual operation of this mechanism is effected from a handle 45c. Relief valves are provided at 47, 48 and a connection 54 from the main valve leads to a back pressure valve 52 connected at 58 to drain pipe 49 when the valve moves against a spring 56. The control rod 37 carries a sleeve 62 secured to the cross-head and carrying a roller 67 coacting with the cam 41. The lower end of the sleeve also coacts with a collar 63 to rock a lever 64 connected to the main valve. In operation the valve 27 is handset to the position shown in Fig. 1 wherein oil is admitted to the upper end of cylinder 20 thus moving slide 16 downwards with the broach until the broach engages in the pull bushing 13. Resistance then builds up the pressure in cylinder 20 and causes relief valve 48 to open thus, through line 32 causing the main valve to be moved to the left so that oil is delivered to the bottom of cylinder 5 and to the top of cylinder 4 thus moving the cross-head downwards on the power stroke. The speed of this movement is slower than the normal movement of the piston of cylinder 20 but excess of oil delivered to this cylinder passes through relief valve 47. During the working stroke of the piston 6 the lower end of cylinder 4 is under slight pressure through the valve 52. The effective area of cylinder 4 is double that of the cylinder 5 and the axis of cylinder 5 and the broaching axis are equidistant from the axis of cylinder 4 so that the load on the tool is balanced by the pressure in the lower part of cylinder 5 and there is a slide thrust on the cross-head. During the working stroke fluid from the lower part of cylinder 4 flows to the upper part of cylinder 7 and excess fluid flows through the valve 56 which opens against its spring pressure, to the drain. At the end of the working stroke an arm 59 is rocked by engagement with a stop 60 to release the upper end of the broach and at the same time collar 61 is actuated to operate the lever mechanism to return the valve 27 to neutral. Slide 16 then remains at rest while the cross-head continues downwards until sleeve 62 engages collar 63 to return the main valve to neutral. At the end of the down stroke the roller 67 actuates the cam 41 to move the valve 27 to a position wherein oil flows through line 33 to shift the main valve and admit oil to the lower end of cylinder 4. The cross-head then moves upwards until roller 67 engages cam portion 41x to move the valve 27 to allow flow to the base of cylinder 20 to raise the slide 16. At this point the broach has been engaged with the slide 16 and disengaged from the pull bushing 13 so that the broach moves quickly up in advance of the cross-head thus giving the operator time to reload the work table while the cross-head is still moving upwards. At the end of the upward cross-head movement both valves are in a neutral position ready for a fresh cycle. By pulling the broach downwards through the work the lubrication of the broach and work is facilitated.