Patent GB-918842-A (GB)
Title: Improvements in or relating to automatic feed devices for machine tools
Inventor: EIDSFORTH ROBERT
IPC: B24B47/20
Filed: 1958-05-23
Abstract: 918,842. Variable-speed ratchet gearing. BRITISH NORTHROP Ltd. May 25, 1959 [May 23, 1958], No. 16573/58. Class 80 (2). [Also in Group XXIII] An intermittent automatic feed for a machine tool includes a ratchet-and-pawl device, there being also provided a release member adjustable between limits but arranged so that it must always lie in the path of the driving movement of part of the pawl or a member connected to the pawl, and arranged so that when struck by that part or member it causes the pawl to be disengaged from the ratchet. The grinding-wheel head of a plain grinder is fed towards the work-table by screw and nut mechanism driven by a shaft 10. The latter is connected by gearing 30, 26, 24, 22 to a shaft 14 on which is keyed a graduated hand wheel 18 having a handle 20 by which fast feed is effected. A shaft 32 rotatable in the hand wheel 18 is formed at its rear end as a gear 36 meshing with an internal gear ring 38 carried by the hand wheel 18 for rotation relative thereto and carrying on its exterior a stop co-operating with a fixed stop. A lever 40 keyed to the front end of the shaft 32 has slidable therein a peg 42 having at its front end a knob 46, its rear end being adapted to engage any one of a circular series of holes 48 in a plate 50. Witn the peg 42 engaging one of the holes, the gear ring 38 is locked to the hand wheel 18 for rotation therewith, and fast infeed is limited by engagement of the stop on the gear ring 38 with the fixed stop. For fine feed the peg 42 is withdrawn from the hole and the lever 40 operated to rotate the gear ring 38 relative to the hand wheel and remove its stop from the fixed stop by a distance which will give the required infeed. A piston 54 on a rod 56 is slidable in a cylinder in a block 52 fixed to the feedbox casing 12. A rod 60 is slidable in a bore in the block 52, its movement being limited by a peg 64 engaging a recess 66 in the rod. A slot 68 in the rod 60 receives a peg 70 projecting from a rotatable control member 72. A pair of ports 74 formed through the control member are so arranged that, when the rod 60 is pulled forwardly by the operator, they register with ports 78, 80 in the block to provide two passageways, one to each side of the piston 54. Pipes 82 from an hydraulic control mechanism lead to the ports 78, the control mechanism being arranged to supply pressure oil to each of the ports 80 alternately at the end of each working stroke of the work-table. If the rod 60 is pushed rearwardly, the hydraulic mechanism is ineffective to move the piston 54. The end of the pistonrod 56 carries a cam 86 co-operating with the end 90 of a cam bar 88 so that at each stroke of the piston 54 the cam 88 is first raised and then lowered. The upper end of the cam bar 88 rotatably carries a shoe 91 engaging a slot 98 in one arm of a lever 100 pivoted on the bush 16 for the shaft 14. A pawl 102 is pivotally mounted on the other arm of the lever 100 for engagement with the teeth of an internal ratchet wheel 104 fixed to the hand wheel 18. A spring 106 acts on the lever 100 to urge the cam bar 88 downwardly. An arm 110 pivoted on the bush 16 carries a roller 112 co-operating with an inclined shoulder 114 formed on the pawl to disengage the pawl from the ratchet teeth. For adjusting the position of the roller 112, a handle 116 projects from the arm 110 through a slot in the casing 12, the ends of the slot acting as stops for the handle to limit the adjustment of the arm 110. A marker fixed to the handle may co-operate with a scale on the casing 12 adjacent the slot. A fixed pad 120 disengages the pawl from the ratchet teeth as the pawl returns to its starting position to establish the beginning of the turning movement of the ratchet wheel.