Patent GB-623734-A (GB)
Title: Automatic machine for grinding drills
IPC: B24B19/04
Filed: 1946-04-09
Abstract: 623,734. Grinding twist drills. FOUQUET, E. April 9, 1946, No. 10937. Convention date, Dec. 19, 1945. [Class 60] [Also in Group XXII] An automatic machine for the production of twist drills comprises means for imparting to the needles of hardened steel used for the production of the drills a highspeed helical movement relative to two grinding wheels rotating at high-speed, one of which is adapted to grind out the flutes and has its axis oblique with reference to the direction of displacement of the needles, the other of which is adapted to form clearance ribs adjacent said flutes by relieving the periphery of the drills and has its axis parallel to said displacement; means s are provided for  automatically transferring the drill from the zone of operation of one grinding  wheel to the zone of operation of the other grinding wheel. A machine comprises a grinding wheel M for grinding the flutes, the wheel being belt driven by an electric motor and being adjustable vertically and also about a vertical axis; a grinding wheel M<SP>1</SP> for grinding to form clearance is belt driven by an electric motor and is adjustable horizontally. A cradle comprises a hollow central part 6 mounted in bearings 4, 5 on the machine frame and having longitudinal bars 7, 8 with a fixed crosshead 9 and a movable crosshead 12. A hollow tube 13 journalled in the part 6 is formed at one end as a chuck having a portion 14 which when a rod 16 is moved axially, causes clamping segments 15 to grip the drill blank 18 being ground. Spring fingers 135 serve to maintain a light holding pressure when the chuck is opened, so that the blank remains in position until ejected by the next succeeding one. Blanks from a gravity hopper 119 are pushed into the hollow rod 16 by a piston 122 operated through a connecting rod 125 and crank by an electric motor 127 which is energized at the appropriate times. A retaining hook 133 is provided. The clamping rod 16 is moved axially by means of a nut 17 threading into the crosshead 12 and rotated, at the appropriate times, by a motor 33 through gearing including a slippng clutch 26, 27. The tube 13 has a threaded part 36 co-operating with a normally stationary unit 38 to give the helical motion to the work; the tube 13 is rotated by means of a sleeve 47 splined thereto and formed with a bevel gear 49 meshing with a bevel gear 51 on a shaft 52 carrying a sun wheel 53; planet pinions 54 are carried by a normally stationary cage 55 which can, however, be rotated by an electric motor 97 through gearing 96, 95, 93, 56. The planet pinions 54 also mesh with a second sun wheel 61 which is rotated by an electric motor 91 through the following train. The motor drives through gears 89, 88, 86, 85 a shaft 84 carrying a crank arm 83 connected by rod 82 to an arm 81 secured to a shaft 78 carrying a toothed sector 77 engaging a pinion 75 on a shaft carrying a gear 65 which, through an adjustable idler 64, drives the gear 63 on the shaft of the second sun wheel 61. Rotation of the motor 91 thus causes oscillation of the sector 77 whereby the sun wheel 61 is turned first in one direction and then in the other; with the motor 97 deenergized so that the cage 55 is stationary, the tube 13 is thus rotated first in one direction and then in the other. For indexing, the motor 97 is energized, thus rotating the cage 55 so as to impart additional rotation to the tube 13; simultaneously the motor 97 rotates the nut 38 through gears 92, 59, 57, 46 whereby the axial position of the screwed part 36 relative to the nut 38 remains unchanged. The screwed part 36 is slightly conical and co-operates with a roller 101 mounted in the machine frame so that the flutes are ground progressively shallower towards their ends. The cradle is urged by spring 107 into its upper position, in which the flutes are ground by the grinding wheel M, and is moved down into its lower position, in which the clearance is ground by the grinding wheel M<SP>1</SP>, by means of a cam 111 rotated, at the appropriate time, by a motor 117. Energization of the various motors at the appropriate points in the cycle is controlled by a controller 164 which is set into operation by the motor 91 through suitable gearing. The cycle of operations is as follows. The tube 13 being full of blanks, the motor 33 is energized to close the chuck; the motor 91 causes the tube 13 to be rotated in one direction, thus moving the work in one direction while in contact with the flute grinding wheel M; motor 117 is then energized to lower the cradle; the tube 13 is then rotated in the opposite direction, moving the work bacg again while in contact with the clearance grinding wheel M'; the motor 97 is then energized, indexing the drill, after which the operations are repeated. Finally, the motor 33 is energized to open the chuck, and the motor 127 is energized to cause a fresh blank to be pushed into the tube 13 thus ejecting the finished blank.