Patent GB-515279-A (GB)
Title: Improvements in milling and like machines for copying and reproducing
IPC: B23Q35/18
Filed: 1938-05-28
Abstract: 515,279. Milling-machines. BRISTOL AEROPLANE CO., Ltd., and BOLAS, J. T. May 28, 1938, No. 15995: [Class 83 (iii)] In a milling &c. machine wherein a feeler cooperates with a pattern to control the movement of the cutter with respect to the work, the feeler and cutter are traversed with respect to the pattern and work by a reciprocating hydraulic motor which is reversed by a hydraulic valve operated by a pneumatic motor, electrical means being controlled by pressure between the feeler and pattern and being connected to a pneumatic valve for actuating the pneumatic motor. The machine comprises a cutter head 17 traversable on ways 18 on the bed by means of the piston rod 19 of a hydraulic cylinder 21 in the bed, the head carrying a tracer 23 and a cutter 15 rotated by an electric motor 16. The work 26, such as the cylinder of an air-cooled internal combustion engine which is to have the inter-fin spaces machined, is mounted on a work table 12 which also carries the pattern 25 co-operating with the tracer 23. The tracer is pivoted at 29, Fig. 4, on the cutter head 17 and carries contacts 31, 32 normally held by springs 40, 41 between spring contacts 35, 36 fixed on the head. The tracer is earthed and when displaced from its mid position completes the circuit from a battery &c. 45 to one or other of the solenoids 43, 48 whose armatures are connected to valves 60, 61 in a box 64 supplied with air pressure at 65. These valves control pneumatic pistons 67, 70 which operate the hydraulic reversing valve 81 for the cuttertraversing piston 20. In operation, oil is supplied by. a motor-driven pump 85 through a headcontrolled stop valve 90 to a pipe 75, whence it proceeds past the valve 81 to the left-hand end of cylinder 21, both of the valves 60, 61 being closed. This traverses the cutter along the work to cut an inter-fin space therein and when the tracer engages the end of the space in the pattern 25 it is deflected to close the circuit to solenoid 43 and thereby the valve 60 is raised. Air is thus admitted to piston 67 which moves the valve 81 to the left, exhaust from the piston 70.taking place through the valve 61 and under a cap 159, as shown by the arrows. In its left-hand position the valve 81 connects the right-hand end of cylinder 21 to supply and the left-hand end to the exhaust line 80, thereby reversing the traverse of the cutter. Simultaneously with movement of the reversing valve, air is admitted by pipe 110 below a piston 107 to raise a pin 106 and rock an escapement lever 97 about its pivot 98, thus removing a pin 100 thereon from the path of an index pin 101 on a disc 95 and allowing a rotary hydraulic motor 93, fed by a pipe 94 from the pump, to rotate the disc. Oscillation of the lever 97 brings a cam 99 thereon into the path of the next pin 102 which rocks the lever back to its original position so that the pin 102 engages the pin 100 to stop further rotation of the disc. The disc is connected by gearing to the feed screw of the work-table 12 so that the latter will be given a depth-of-cut feed for the next traverse of the cutter. A similar sequence of operations occurs at the opposite end of the cutter traverse. The speed of traverse is adjusted by throttling the exhaust from the cylinder 21 by means of a hand-controlled valve 115, and the speed of the feed motor 93 is controlled by a manuallyoperated valve 118. Reducing valves 116, 117 are placed in the supply pipes to the escapement pistons 105, 107 to vary the speed of operation of these pistons and hence to adjust the exact time at which the feed takes place. If a space wider than the cutter is required in the work, a lateral feed, either manual or automatic, may be imparted thereto. Vents 120, 121, 130 &c. are provided in the pneumatic cylinders to allow free motion of the pistons, and the traverse may be imparted to the work whilst the cutter remains stationary. According to the Provisional Specification a spring-loaded relief valve may be placed in the circuit of the cylinder 21 to regulate the operating pressure and may be manipulated at any time by the operator to stop the traverse instantly. The valve may also be opened by dogs on the machine to form a depth-of-cut stop, and the hydraulic motor 93 may be supplied from the exhaust of the cylinder 21.