Patent GB-464306-A (GB)
Title: Improvements in or relating to pressure fluid operated pattern controlled reproducing devices for metal, wood, or like cutting or grinding machines
IPC: B23Q35/18
Filed: 1936-03-04
Abstract: 464,306. Fluid-pressure servomotorcontrol systems. SCHMIDTMANN, F. W. March 4, 1936, Nos. 6590 and 6591. Convention dates, March 4, 1935 and Dec. 12, 1935. [Class 135] [Also in Groups XXII and XXIII] In fluid - pressure - controlled copying - mechanism for metal, wood, and like cutting machines the tool or work holder is attached to a screwed spindle adjustable by a hand or motor-operated nut on a fluid-pressure plunger whose supply is controlled by a tracer-operated valve. As applied to a knee-type milling-machine, the knee B, Fig. 1, is vertically adjustable on the machine frame A and an outer pillar S, by means of a screwed spindle a rotatable in a nut b on the plunger c by means of bevel gearing v and a hand wheel H or a motor (not shown). The plunger c slides in a guide d and its reduced lower end d<1> operates in a fluidpressure cylinder d<2>. Fluid is supplied to the cylinder d<1> by a pipe e and pump F from a reservoir E. A valve f, Fig. 2, slides in a chamber h communicating with the cylinder d<2> through a slot in its side and has a passage k therein which leads fluid from the cylinder to the space i below the valve. A rack on the valve engages a pinion q, Fig. 1, connected by bevel gearing k2, telescopic shaft w<2> and bevel gearing k<1> to a pinion p meshing with a rack on a tracer m carrying a roller n engaging a pattern o attached to the work table D. The tracer slides vertically in a housing l which is laterally adjustable on a frame R vertically adjustable on the knee B. The arrangement is such that the tracer m and valve f move in opposite directions. In operation, with the knee B and plunger c at the lowermost position, the pump F is started to supply pressure below the annular face c<1>, of the plunger and by the passage k to the space i, thereby raising valve seat t on the valve into contact with the face c<1> of the plunger to cut off exhaust from the cylinder d<2> past the valve t and by the chamber h and pipe g to the sump E. The plunger c is accordingly raised and the valve t is maintained in contact therewith until the tracer m engages the pattern o. Further motion of the tracer and valve is consequently arrested and a slight upward movement of the plunger separates the face c<1> from the valve t and allows fluid to escape from the cylinder d<2> to exhaust. This reduces the pressure in the cylinder d<2> and steps the upward movement of the work, the work then moving up or down relatively to the cutter (not shown) as the valve f is displaced due to movements of the tracer during its traverse along the pattern o. Fluid in the space i leaks to the sump by a pipe s and throttle valve r which may be adjusted to vary the pressure by which the valve f is forced against the face c<1> of the plunger, and consequently the pressure by which the tracer is forced against the pattern. When the plunger c is vertical as shown in Fig. 1, the weight of the knee B and work table &c. counteracts the fluid pressure below the plunger, but when the latter is arranged horizontally, e.g. for operating a lathe toolslide, the counteracting force is produced by springs &c. or by a weight and cable. In an alternative arrangement the plunger c may control the vertical position of the cutter spindle and-outboard bearing whilst the work remains at constant height. In a modified construction, the valve f<2>, Fig. 4, is arranged below the plunger c and has rack teeth connected by a pinion q to an auxiliary valve f<1>, operating in a chamber h connected by a pipe s to the cylinder d. The pinion q is operated by the tracer m as shown in Fig. 1. When pressure is admitted to the cylinder d by the supply pipe e, it also passes to the chamber h by the pipe s and depresses the valve f<1>, thereby raising the valve f<2> against the plunger and preventing pressure from escaping from the cylinder through the hollow interior of the valve f<2>. On rotation of the pinion by pressure of the pattern on the tracer, however, the valve f<2> is lowered and fluid may escape from the cylinder to exhaust through the valve, thereby stopping further upward movement of the plunger. Exhaust fluid may proceed to the lower end of the chamber h by a passage h<1>. In a further modification the valve f of Fig. 1 is arranged below the plunger c and coacts with the lower end of a vertical passage in the plunger leading to exhaust by means of a flexible pipe. In another modification the valve f, Fig. 6, is slidable in the chamber h at the side of the plunger c and carries an auxiliaryvalve v, t coacting with a seat v, s in the bottom of the plunger, a spring r<1> tending to open this valve to allow fluid to flow from the supply e through a passage k in the valve f to exhaust at g. A projection d<2> on the bottom of the cylinder d provides clearance for the valve v, t at the bottom of the stroke and the pinion q engages the valve f through a slot in the side of the plunger. In this modification fluid flows by pipe e into the cylinder d and lifts the plunger c until equilibrium is established through the valve v, t being opened by the spring r<1>. Movement of the valve f by means of the tracer and pattern then causes the valve v, t to be further opened or closed and so lowers or raises the plunger accordingly. When the plunger is arranged horizontally it may consist of a piston 2, Fig. 7, slidable in the cylinder 1 and carried by a rod 3. A valve 5, operated by the tracer, passes through the piston and has a reduced portion 6 slightly longer than the passage in the piston so as to provide ports 7, 7<1> at each side thereof. In the position of rest shown in Fig. 7, fluid is supplied at equal pressures to both sides of the piston by pumps s, s<1> and then passes to exhaust through the ports 7, 71 and the hollow interior 9 of the piston rod, but if the valve 5 is displaced to one side or the other, one of the ports 7, 7<1> will be reduced and the other enlarged, thus lowering the pressure on one side of the piston and increasing it on the other. This causes movement of the piston until equilibrium has again been restored. The tracer is biassed towards the pattern by springs &c. In a modification of the horizontal plunger, exhaust takes place through the hollcw interior of the valve 5 instead of the piston rod 3. For horizontal copying the tracer m may be arranged to be horizontally movable under control of the pattern.