Patent GB-825643-A (GB)
Title: An actuating mechanism for a screw-threading tap or a mechanical screwdriver, nut applicator or the like
IPC: B25B23/14
Filed: 1956-06-26
Abstract: 825,643. Tapping; screwing-up screws &c. BAIN, R. Aug. 21, 1957 [June 26, 1956], No. 19718/56. Class 83 (3). [Also in Groups XVII and XXIV] A mechanism for screw-tapping machines, machines for screwing caps on bottles, screwdrivers and nut &c. runners, comprises a driving spindle 21, a driven spindle 22, a planet pinion 27 for driving spindle 22 from spindle 21 and movable in a unidirectional orbital-path, stops 41, 48 for determining successive positions of the pinion 27 and movable by a force transmitted through the pinion, arid stop-locking means 40, 67 releasable by a force associated with the driven spindle. As applied to adapting a drilling-machine for tapping, the mechanism is attached to and driven by the drill-spindle, which rotates the spindle 21. The pinion 27, driven by a gear 26 on the spindle 21, is held in mesh with a pinion 29 by the stop 41, to rotate and advance the tap-spindle 22, then moved in an orbital-path until held, by the stop 48, in mesh with a gear 32 for withdrawing the tap. The stop 48 also holds the pinion in the inoperative position depicted in Fig. 3. The attachment includes a frame 20 supporting a nut 25 engaging a lead-screw 24 on the tap-spindle 22. The frame also supports the pinion 27 in a freelymounted carrier 28, the gears 29, 32 in pivoted carriers 33, 36, Fig. 2, held by springs 35, 38, respectively, against stops 34, 37 on the frame, and feed-stops 51 on a control-rod 50 connected by a lever 54 to a link 55 in the mechanism for locking the stops 41, 48. The link 55 has shoulders 56, 57 which act alternately on a T-lever 58 pivoted on an arm 59, to which is attached the link 60 of a toggle mechanism 60, 61. Link 61 is connected by a link 62 to a bell-crank 63 connected by a link 64 to another toggle-mechanism 65, 66. This mechanism is connected to the lever 40 by the bar 67. The link 65 is also connected to a bell-crank 68 connected by a link 69 to an arm 70 carrying a roller 71, which is adjustable by a screw 72 and slides in a slot 73 in an arm 74 attached by a lever 75 to a pivot. The free-end of arm 74 is attached by a link 76 to a further togglemechanism 77, 78, the junction of which is connected by a spring-loaded link 79, 80 to the T-lever 58. This junction is also connected, by a link 81, to the pivoted armature 82 of a magnet 83. The link 78 of the toggle mechanism co-operates with a stop 84, and is connected to a bell-crank 86 biased by a spring 85 under compression. Operation.-The mechanism is held in the inoperative position, Figs. 3 and 6, by a stop 89 contacting a spring-pressed catch 87 on the bar 67, the stop 48 engaging the spindle 43 of the pinion 27. Upon disengaging the catch, as by a push-button, to initiate a tapping operation, the pinion 27 proceeds, in the direction of the arrow, in an orbital path towards the gear 29, displacing the stop between its guide-pins 49, and thus moving the locking mechanism to the setting depicted in Fig. 7. In this setting, held by engagement between the armature 82 and the magnet 83, stop 41 interrupts the orbital movement of the pinion when the pinion meshes with gear 29, which drives through an intermediate gear 30 a gear 31 on the tapspindle 22. The tapping-feed continues until contact between the lower-feed-stop 51 and gear 31 displaces rod 50 and thus link 55 which, through shoulder 56, compresses spring 80 until this over-comes the force of the magnet 83 and collapses the toggle mechanism 77, 78, which returns to the setting of Fig. 6. The stop 41, released by the locking mechanism, is carried along by the pinion 27, which resumes its orbital movement until arrested in mesh with the gear 32 by stop 48, which was positioned by displacement of the stop 41. In this setting (Fig. 8, not shown), the locking- meehanism is again retained by the magnet 83, until gear 31 on the tapping spindle contacts the upper-stop 51, displacing the rod 50 and the link 55 on which shoulder 57 contacts lever 58, to release the armature 82 and collapse the toggle-mechanism. Thus the locking-mechanism is again released and the stop 48 freed for further movement by the pinion 27, into the position depicted in Fig. 3, wherein it is held by the catch 87. If the tap encounters an obstruction, the increase in torque on the pinion 27, and thus of force on the lever 40 and bar 67, forces the link 78 against the stop 84 and collapses the toggle-mechanism 77, 78 against the action of the spring 85. The pinion then moves into engagement with the reverse drive-gear 32. Screwing-up mechanism.-To adapt the mechanism described for driving screws or nuts, gears 29 or 32, depending upon the direction of drive required, is disengaged by movement of its carrier, as by displacement of the carrierstop. The lower-stop 51 and stop 89 are also moved to inoperative positions, and the lead screw 24 is removed. The maximum torque applied is adjusted by movement of the roller 71 in the slot 73. Assuming a clockwise driving direction, gear 32 being disengaged, the pinion 27 drives the gear 29 until the increase in torque forces the link 78 against the stop 84 and releases the locking mechanism, thus allowing the pinion 27 to disengage and move into the position (Fig. 5, not shown), in which it is stopped by the stop 48. From this position, the operative re-engages the armature 82 with the magnet 83, causing pinion 27 to return to the starting position shown in Fig. 4. In a modification for driving screws or nuts, and which may be attached to a portable tool, a pair of offset planet pinions 91, 92, Fig. 9, on stopspindles 124, 125 projecting through a carrier 93, are driven by a sun-gear 90 on the driveshaft 21, and drive selectively gears 95, 96 on a non-rotatable shaft 94. Gear 95 meshes with a gear 99 on a shaft 98 geared at 101, 102 to the screw-driving &c. shaft 22, and a gear 97 fixed to the gear 96 meshes with a gear 100 on the shaft 98 to give a second and lower drive-speed for shaft 22. Stops 122, 123, 119, Fig. 13, control the positions of the planet-wheels, and a mechanism 103, 106, 109, 110, 113 releases the stop 122 automatically upon a rise in torque demand, and engages, for a tightening twist, the low-speed drive. The lever 103 is pivoted at 104 and loaded by a spring 105. On one end of the. lever 103 is pivoted a bellcrank 106 loaded by a spring 107, and which co-operates with a fixed stop 108. The lever 109 forms with lever 106 a toggle-mechanism pivoted to lever 110 loaded by a spring 111. A pair of links 113, formed with the stopsurfaces 122, 123, is pinned at 112 to the lever 103, and each is guided by a slot 114 receiving a pin 115 on which are pivoted a pair of levers 116 carrying the shaft 94. Each lever 116 is pressed against a stop 117 by a spring. In the neutral setting, Fig. 13, the planet pinions are held out of engagement with the gears 95, 96 by engagement between the manually-operable stop 119 and the spindle 124, the release mechanism for stops 122, 123 being set by the springs 105, 107, 111. Upon operation of the stop 119 against the action of its spring 120, the planet-pinions are released and move in an orbital path until pinion 91 meshes with gear 95 and its spindle 124 encounters stop 122 (Fig. 10, not shown), thus connecting the high-speed drive. An increase in torque demand at the end of the screwing-up &c. operation displaces the links and collapses the toggle-mechanism 106, 109, the pinion 91 thus freed resuming its orbital movement until arrested by contact between the spindle 125 and stop 123 (Fig. 11, not shown). Straightening of the toggle-mechanism 106, 109, by the springs 105, 107, 111, frees the spindle 125, which is again arrested, by stop 122, with pinion 92 in mesh with gear 96 for transmitting the tightening twist. A further increase in torque demand again collapses the togglemechanism, allowing the pinion to return to the neutral position.