Patent GB-668939-A (GB)
Title: Improvements in power-operated mechanism for securing tools in machine-tool spindles
IPC: B23B31/26
Filed: 1950-02-07
Abstract: 668,939. Lathes. VLIEG, C. B. DE. Feb. 7, 1950, No. 3144/50. Class 83 (iii). A tool securing and locking mechanism for the spindles of boring, facing and milling - machines and like machine-tools in which a tapered toolshank is adapted to seat in a socket of the machine spindle and is secured therein by a draw-bar carried within the spindle is characterized in that electric power means is provided to engage a normally disengaged clutch and to operate the draw-bar to move the tool into seating engagement with the socket in the machine spindle. Headstock spindles.- The hollow spindle 12 is supported at its forward end in a conventional manner in the carriage 33 and at its rear end is supported by ball-bearings 31. An electric motor is mounted on the vertically-adjustable spindle-head 23 for driving the spindle by gearing (not shown). Chucks.-The forward end of the spindlebore is flared to take the steeply-tapered end of the tool shank 25, and the latter has a screwthreaded recess 14 and a collar 29 provided with recesses 28 to take driving lugs on the spindleend. A draw-bar supported within the hollow spindle is screwed to engage the internal threads 14 of the tool shank. The draw-rod 13 has a collar 57 on one side of which is a thrustrace 58 and on the other side a compressionspring 61. The inner end of the draw-rod is splined into a bush 62 which is free to rotate in the end of the spindle 12 and has on its outer face clutch teeth 81. The latter engage corresponding teeth 82 on an oppositely positioned splined bush 71. This bush is held on the end of a hollow short spline-ended shaft 72 by a rod 84 and spring 88. The shaft 72 is journalled in bearings 73, 74, in a partition-wall and end-wall respectively of the spindle-slide casting 32. Rotatable on a bearing-bush 93 surrounding the splined bush 71 is a speed-responsive device which comprises a number of balls 97 arranged in circumferentially-spaced radial slots on one half of the device 91, the other half 92 being in the form of a flared cover engaging the balls. The halves are slidably keyed to rotate together and as the device is rotated at a certain speed the balls wedge the part 92 to the left, Fig. 3, and this moves the bush 71, against the pressure of spring 88, until its clutch teeth engage those of the bush 62. An electric motor 104 carried by the spindle-carriage, drives through toothed gearing the speed-responsive device, this is driven at a high speed while the splined shaft 72 is driven at a low speed for rotating the drawrod when the clutch members 81, 82 are engaged. A safety-switch 116 is engaged by an extension on the rod 84 and ensures that the spindle drive motor is out of operation when the tool clamping - mechanism commences to function. Switches are provided on the vertically adjustable head for forward and reverse operation of motor 104, the tool shank 17 being pushed by hand into the socket of spindle 12 against the reaction of spring 61 before starting the motor for a tightening operation. When the tool shank is sufficiently tight the motor 104 stalls.