Patent GB-516887-A (GB)
Title: Improvements in or relating to grinding machines
IPC: B24B5/18
Filed: 1938-07-12
Abstract: 516,887. Grinding-machines. CINCINNATI GRINDERS, Inc. July 12, 1938, No. 20625. Convention date, July 16, 1937. [Class 60] [Also in Group XXIX] In a centreless grinder of the infeed type, movements of the regulating wheel towards the grinding-wheel are produced by a fluid piston moving in a cylinder under the control of a valve with follow-up means connected to the piston, and movements of the wheel away from the grinding-wheel are produced by a separate piston in a second cylinder, the movements of the valve being controlled by a timing cam; work loading and ejecting mechanism also is provided controlled by fluid pressure means. The machine comprises a bed 10 on which is mounted a fixed axis, a grinding-wheel 11, and in a slide 14 a regulating wheel 12. The slide 14 carries a nut 15 in which engages a screwed part 16 of a shaft 17 having mounted thereon for rotation, but not axial movement, by means of ball thrust bearings 85, a piston 18 movable in a cylinder 19 integral with a bracket 20 mounted oil the bed 10. The shaft 17 carries a hand-wheel 21 so that the slide 14 can be. adjusted manually in order that, for all work diameters, the piston 18 mav have the same initial position, movement therefrom serving to approach the regulating - wheel towards the grinding - wheel. The slide is retracted from the advanced operative position by another piston 22 moving in a cylinder 24 and having a stroke equal to the sum of the stroke of the piston 18 and movement due to the screw 16. Workpieces 25 shown as having pointed ends 26 are fed from a hopper 28 by a pusher 29 which moves each piece successively to working position on a rest 31, the pusher being connected to a piston 37 moving in a cylinder 38; when the work is ground to size the regulating-wheel is retracted and the work falls from the rest into a shoot 33. The cylinder 38 has ports 40, 41 connected to ports 44, 45 of a reversing valve 46, to a port 47 of which fluid is fed by a pump 48 from a reservoir 50, the valve also having exhaust ports 51, 52 leading to the reservoir. The valve comprises a plunger 54 with annular grooves 56, 57 and the plunger is pressed by reduced fluid pressure against an adjustable screw 96 carried by an arm 55 connected to the shaft 17. The movements of the piston 18 are controlled by a follow-up valve 58 comprising a slidable sleeve 59 in which is slidable a plunger 60, the sleeve having annular grooves 61, 64, 66 holes connecting the groove 64 to the interior of the sleeve to form a port 68 normally 'closed by a spool 69 on the plunger, so'that movement of the plunger 60 to the left allows fluid to flow from port 47 through a. passage 62, an annular groove 71 in plunger 60 and a passage 65 to the cylinder 19; reverse movement connects port 68, through an annular groove 72 in the plunger 60 to an exhaust port 73. The plunger 60 is held by reduced fluid pressure against a plunger 74 carrying a roller 75 engaging a cam-wheel 76; the sleeve 59 also is held by fluid pressure against the arm 55. The return movement piston 22 has an area less than that of the piston 18 and is constantly under full fluid pressure by a pipe 82. The reduced pressure for holding the valves in position is obtained by means of two check valves 97, 98 arranged in series, a connecting pipe 100 leading to the spaces 101, 102; a throttle' valve 106 serves to regulate the speed of the loading piston 37. The machine operates in a cycle controlled by the cam 76, which is rotated through reduction gearing by an electric motor and is shaped to give a dwell 117 for retraction of the work pusher 29, followed by a sharp rise 118 to cause rapid movement of the piston and regulating wheel to cortract the grinding throat, the plunger 54 being moved to cause the work pusher to insert a new workpiece, a dwell 120 being provided to allow of completion of this movement. The cam then has a slow rise 122 for rough grinding, followed by a dwell 123 for sparking out, this again being followed by a sudden fall 124 for retraction-of the regulating-wheel to allow the work to fall off the rest 31. The'arm 55 is supported on the shaft 17 by double thrust bearings 92.