Patent GB-707684-A (GB)
Title: Improvements in or relating to a control mechanism for a planing, milling or like machine tool
IPC: B23Q35/18
Filed: 1952-01-01
Abstract: 707,684. Fluid-pressure servomotor-control systems; rotary-cylindrical valves. ROCKFORD MACHINE TOOL CO. Jan. 1, 1952 [Feb. 10, 1951], No. 24/52. Class 135. [Also in Group XXII] A hydraulically-controlled copy-planing, copymilling or like machine tool has a reciprocating slide 14 carrying a tool 15 and tracer 16, a slide 11 carrying the work-piece 12 and pattern 13 and a piston 53 connected to the slide 14, the smaller piston-rod end of the piston being supplied with the constant full pressure of a main pump 23 and the larger head end of the piston being supplied from the pump through a traceroperated rotary valve 21 which controls the amount of a continuous bleed back to a sump 29. An auxiliary pump 24 supplies pressure to a piston 33 to counterbalance the weight of the tool slide 14 and a solenoid-operated valve 51 reduces the pressure on the head end of the piston 53 at the end of the working stroke so that the tool slide is raised from the work for the return stroke. Tracer and tracer valve.-The verticallymovable tracer rod 110 has a ball tip 111 and is connected by a ball-ended lever 119 to the rotor 80 of the valve 21. A sleeve 74 surrounds the rotor and three ports are provided in the valve body 70, one 104 connected to the pressure supply pipe 44 and leading through an opening 105 in the sleeve to an annular groove 86 in the rotor, another 106 connected to a drain pipe 46 and leading through a opening 107 in the sleeve to an annular groove 85 at the other end of the rotor and a third 103 connected by a pipe 45 to the cylinder 52 and leading to an annular groove 102 in the body. The groove 102 communicates through slots 75 in the sleeve with a number of slots 100, 101 opening alternately at opposite ends of the rotor to the grooves 85 and 86. The number of grooves in the rotor is greater than the number of slots in the sleeve so that at least some of the slots and grooves overlap in all positions of the rotor and the slots 75 are inclined slightly in the longitudinal direction so that the slots and grooves overlap with a shearing effect which allows accurate adjustment of the orifice size by the tracer. Oil leaking past oil-retarding grooves 83 in the rotor drains through a central bore 96 to a pipe 97. Operation.-In the neutral position of the valve rotor 80, the slots 75 overlap slightly with both the grooves 100 and the grooves 101 so that the supply pressure in the groove 86 is throttled before entering the groove 102 and some of the fluid is drained off through the groove 85 to a back-pressure valve 48 and thence to a sump 29, the resultant pressure being such as to equalize the forces on the piston 53. As the tracer rod moves up or down in response to the shape of the pattern, the relative openings between the slots 75 and each set of grooves is varied and the pressure on the head end of the piston 53 is controlled to move the tool slide 14 up or down correspondingly. At the end of a working stroke, dogs on the tool slide cause a pressure-responsive switch 65 to be cut-off from the pressure of the auxiliary pump 24 so that the solenoid 60 of the tool-lift valve 51 is de-energized and a spring moves the valve to the position in which the pressure supply to the head end of the piston 53 is led to the sump 29 through a throttling valve 63 and the tool is lifted from the work during the return stroke. The tool may be lifted from the work at any time by switching off a switch 67 and will also be lifted if the electrical circuit fails.