Improvements in or relating to control apparatus for hydraulic broaching machines


509,271. Hydraulic broaching - machines LAPOINTE MACHINE TOOL CO., Ltd. (Lapointe Machine Tool Co.). Feb. 17, 1938, No. 5025. [Class 69 (ii)] [Also in Group XXII] In a hydraulic broaching-machine a manual or automatic ram controlling device actuates a pilot valve which controls a hydraulic relay mechanically connected to the main control valve. The ram cylinder 10 which moves the piston rod 12 downwards on the working stroke is connected by lines 30, 32 to the main valve M. The line 32 has an adjustable back pressure valve 33 which may be by-passed by a check valve 35 opening towards the cylinder 10. A pump P preferably of variable delivery type delivers fluid to a longitudinal channel in the main valve through a line 20 and in the neutral position shown in Fig. 1 this fluid passes to the exhaust line 28. The machine is controlled from a lever 15 which may be actuated either manually from a handle 17 or automatically. The lever operates the spindle of a pilot valve V which is supplied from an auxiliary pump P' through a line 65. The pilot valve is connected through lines 80, 81 provided with adjustable needle valves 82, 83 respectively to the relay R the piston 51 of which is connected to a lever 53 on a spindle 54 which is also connected by an arm 55 to the main valve so that the. relay and main valve pistons move in unison. The needle valves may be by-passed by check valves 86, 87 to permit free flow from the relay to the pilot valve. Surplus oil from the pump P' passes through a relief valve 66 and line 67 and circulates round the casing of pump P for lubricating and cooling. In operation, in the neutral position shown in Fig. 1, delivery from the pump P<1> passes through lines 80, 81 maintains a balanced pressure on the relay valve to keep the valve in its neutral position while the main pump delivery passes through line 28 to exhaust. When the valve V is moved to the left the relay valve is moved to the left at a controlled speed by flow through the needle valve 82 carrying with it the main valve so that the main pump delivery passes through line 30 to move the ram downwards on its working stroke. Fluid beneath the ram piston passes through the back pressure valve 33 and line 28 to exhaust. Similarly when the pilot valve V is moved to the right, flow from the auxiliary pump passes to line 81 and moves the relay valve and thus also the main valve to the right. In this position the main pump flow passes to the bottom of the main cylinder through the valve 35 and returns the ram to its upper position. The pistons of the main valve are notched at their ends so as to avoid too sudden opening or closing of the valve ports.




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