Patent GB-621043-A (GB)
Title: Automatic positioning means for machine tool support
IPC: B23Q5/28
Filed: 1946-02-12
Abstract: 621,043. Positioning mechanisms for machine tool tables. VLIEG, C. B. DE. Feb. 12, 1946, No. 4349. [Class 83 (iii)] [Also in Groups XXIV and XXXVII] Means are provided for repeatedly reversing the direction of movement of the motorcontrolled work or tool support of a machine tool during its passage to a pre-selected position, and means responsive to the movement of the support to such position are provided for controlling the motor so as to relax the driving train. Table feeds; clutch-operating mechanisms.- A boring and milling machine comprises a work table 10, Fig. 1, actuated by a lead screw 30, and a tool head 12 actuated by a lead screw 34. The lead screws are rotated by a drive shaft 20 having a gear 22 meshing with a sliding gear 24 which may be clutched by a handle 40 either to a shaft 26 geared to the tool head screw 34 or to a shaft 26e geared to the work table screw 30; the screws may also be manually rotated from shafts 39 and 29. The shaft 20 is driven for rapid traverse in either direction by a two-speed reversible electric motor 13 through a chain drive 17, 18, 19 and for slow traverse by a similar motor 14 through wormtype reduction gearing 42, 43. The rapid drive is transmitted through a clutch actuator 21, Fig. 4a, comprising a sleeve 19a having jaws 104 engaging jaws 103b on a sleeve 103a which abuts on a sleeve 97 having clutch teeth 97a. When the sprocket 19 is driven, cam surfaces 104a and 103c on the jaws move the sleeves 103a and 97 to disengage the clutch teeth 97a from teeth 102a on a sleeve 102 to which the gear 43 is keyed, until the drive is taken up by stop surfaces 104b and 103d on the jaws. When the sprocket 19 ceases to be driven, the clutch is re-engaged by a spring 43c to take up the low-speed drive. Gauging devices.-The table 10 carries a split screwed support 64, Fig. 6, which is adjustable along a T-slot and has a micrometer screw 65 for adjusting the position of gauge blocks 66 in a trough 63b. A bracket 83a, Fig. 7, on the machine base carries a pivoted pointer 93 co-operating with a scale on the table, a micrometer gauge 84, a switch 60 and a vertical shaft 86. The shaft 86 carries a lever 85 engaged by the blocks 66 and a lever 87, one arm 87b of which operates the - micrometer gauge plunger 84a and the other arm 87a operates the switch plunger 60a. The shaft is biassed in opposite directions by springs 90, 91, the force of the spring 90 being greater so that the arm 87a is held against an adjustable stop 87c, with the micrometer gauge reading zero and the arm 87a and the switch plunger 60a in bare touching engagement. The spring 90 acts on a rod 88 seated in a ball socket 89 at one end and having a slotted end 88b engaging a pin 88c between the two lever arms so that the assembly can be rotated over top deadcentre to remove the lever 85 from the path of the blocks 66 when traversing the table fully to the right. The gauge and switch 68, Fig. 1, for the tool head are similar, but are mounted on the tool head and co-operate with gauge blocks 71 on a vertical column of the machine. Operation.-The table 10, carrying the work piece 11, and the tool head 12 are first adjusted manually to the required position for drilling a hole H<SP>1</SP>. A gauge block 66 is then inserted between the micrometer screw 65 and the lever 85 and the screw adjusted to give a zero reading on the gauge. The work table is then withdrawn to the left and the clutch handle 40 moved to engage the shaft 20 with the drive for the lead screw 30 and, through a connection U, to set a selector switch 54. On operation of a push-button 59, the table is traversed rapidly to the right by the motor 13 until, at the working position, the switch 60 is operated to reverse the rotation of the motor 13 which, acting against the momentum of the moving parts, brings the table to a stop at a point to the right of the working position. An adjustable timer 160 controls the time interval of the reverse rotation of the motor 13, and then energizes the slot traverse motor 14 to move the table at medium speed back to the left. The restoration of the switch 60 to its original position by the spring 91, when the table reaches the working position, reverses the rotation of the motor 14 to brake the table to a stop at a point just to the left of the working position, and to return it again to the right at slot speed until the switch 60 is again operated. The carry-over of the table is negligible, but the operation of the switch 60 again reverses the rotation of the motor 14 to drive the table to the left, for a brief interval under the control of a timer 190, sufficiently to relax the driving connection between the motor and table so that the table is floating freely on the bed, to which it is then clamped. The tool head 12 may be similarly set for automatic positioning under the control of the push-button 59 after setting the clutch handle 40 to engage the drive to the lead screw 34 and re-set the switch 54 so that the switch 68 controls the head positioning. For automatic positioning when drilling a hole H<SP>2</SP>, an additional gauge block whose length equals the distance between the two holes is inserted. Traverse of the work table or the tool head in either direction by means of the motor 13 is obtained independently of the automatic means by operating pushbuttons 57, 58 after selection of the drive by the clutch handle 40; the limits of movement of the work table are controlled by limit switches 51, 53 and the lower limit of the tool head is controlled by a switch 52.