Patent GB-546316-A (GB)
Title: A new or improved apparatus for grinding parallel circumferential grooves
IPC: B24B3/12
Filed: 1941-04-29
Abstract: 546,316. Grinding-machines. NEWMAN, W. H. April 29, 1941, No. 5554. [Class 60] Thread milling-cutters with the teeth formed from a series of annuli are finish ground in a machine in which the work is fed towards the wheel to engage the latter to depth in one groove and is then withdrawn in part and given a compound movement to form the crest and is then fed to depth in the next grove and so on the motions being derived from fluid-operated pistons in conjunction with lost motion devices and a series of control valves. The cutter 2 to be ground is mounted between centres on arms 6, 7 mounted on a rockable and slidable shaft 8. The rocking is controlled by an eccentric 42, and the compound movement by an eccentric 51, cam 38 and screw 16. A cam 15 rotating with the cutter 2 engages a roller 54 on a lever 53 and in conjunction with a spring 55 effects the backing off of the teeth. With the parts in the position shown in Fig. 10 and with the cam 38 stationary the eccentric 42 having its maximum throw towards the arm 53 holds the cam 15 and with it the cutter 2 at the greatest distance from the grinding wheel 1. Oil under pressure is applied at 63 to a valve 65 controlled by a cam 66 on the shaft 23 and thence to the cylinder 49 to advance, the rack 45 and rotate the shaft 43 and eccentric 42; a regulating valve 67 in the exhaust from the other end of the cylinder 49 controlling the ratio of motion. When the full depth of cut is obtained the end of the rod of the valve 71<SP>2</SP> enters a notch in the flange 56 of a box connected to the shaft 43 by a coiled spring. The resulting movement of the valve 71<SP>2</SP> admits oil to the valve 68 and cylinder 37. The wheel 25 commences to turn and the pawl 28, Fig. 5 engaging the tooth 29 on the shaft 24 turns the cam 38 into the dotted line position, Fig. 10, leaving the arm 40 and turning the variable throw eccentric 51 to withdraw the cutter from the wheel. When the pawl 28 engages the tooth 31 carried by the shaft 23 it has been raised by the surface 31<SP>1</SP> and trips from the tooth 29. The shaft 24 is now at rest and the shaft 23 turns the screw 16 feeding the cutter axially. As soon as the pin 32 takes up the lost motion permitted by the cut away part 30 both shafts rotate together, and the combined action of the cam 38 and screw 16 generate the crest of the thread-like form of the cutter. During the passage from the flank and cut forming position to the crest generating position the movement is rapid but when generation begins the cam 69 moves the valve 70 to close direct supply to the cylinder 37 and pass it through the regulating valve 70 so that generation takes place at a slow speed, the valve being again moved after generation is complete so that the piston finishes its stroke at high speed. A cross head 34 on the piston then engages a dog on the valve rod 73 moving the valve 72 and effecting withdrawal of the valve rod 71<SP>2</SP> from the flange 56 and the box 57 is returned by its spring to its initial position against a stop on the shaft 43. The movement of the valve 71<SP>2</SP> also causes the return of the piston 36 during which the pawl 28 rotates idly. At the end of the return stroke the cross head 34 engages another dog on the valve rod and returns the end of the valve 71<SP>2</SP> into contact with the flange 56. During this time the cam 66 has moved the valve 65 and effected the return of the piston 48 completing the cycle. The grinding wheel may be tried by the means described in Specification 494,704.