Patent GB-266331-A (GB)
Title: Device for transmitting motion from a rectilinearly reciprocating member to a rotatable member
IPC: F16D41/00
Filed: 1927-02-08
Abstract: 266,331. Wellton, O. G. Feb. 18. 1926, [Convention date]. Toothed gearing.--Reciprocating motion is converted into uni-directional rotary motion by means of a compound arrangement of worm and screw gearing comprising primary and secondary pairs with different frictional coefficients or relations producing the result that a worm, rotatably mounted on the reciprocating member and in engagement with a wheel to be driven, is non- rotatable and acts as a toothed rack during the forward stroke whilst it is rotated idly so as not to drive the wheel during the return stroke. Means are provided for reversing the direction of drive and a form is described in which a pair of worms act alternately to render the stroke effective. In the arrangement shown in Figs. 1 and 2, a pair of worms 5, 6 integral with a sleeve 2 rotatably mounted on the reciprocating member 1. mesh with worm-wheels 7, 8 on a pair of shafts 9, 13 connected by a chain 11 so as to rotate equally in the same direction. The wheel 7 is fixed to the shaft 9 but the wheel 8 is engaged by inclined keys 16 on an axially adjustable sleeve 14 to permit of rotary adjustment relatively to the wheel 7. The wheels are set so that when the wheel 8 meshes loosely with the worm 6 the teeth of the wheel 7 press in one direction or the other against the threads of the worm 5 according to the direction in which it is desired to drive the shaft 9. As shown, when the reciprocating member 1 is moved to the left, the worm 5 acts as a rack and rotates the wheel 7, the wheel 8 being simultaneously rotated through the chain 11. On the return stroke contact occurs between the threads of the worm 6 and the teeth of the wheel 8 and under the resistance of the load or other holding means,. slipping occurs causing the worm 6 to rotate and with it the worm 5, to screw back idly through the teeth of the wheel 7. To obtain this effect the coefficient of friction of the gear pair 6, 8 must be less than that of the pair 5, 7. Alternatively or additionally, the worms may be of different pitch, the gear ratios in this case being different or gearing being introduced between the worms. In the modification shown in Fig. 5, the wheel 43 on the shaft 45 is driven by the worm 42 acting as a rack when the reciprocatory carrier 35 is traversed to the left. Through means not shown the shaft 45 is geared to a shaft 46 mounted in fixed bearings 41 and formed with a screw thread 39, to cause this shaft to rotate synchronously to enable a sleeve and pinion 44, 48 threaded thereon to be traversed with the carrier 35 without rotating, the pinion 48 being in mesh with a pinion 47 on the worm 42. During return movement of the carrier 35 to the right, owing to the lost motion between the teeth of the wheel 43 and worm 42 and the resistance of the load, the pinion 48 screws back on the now stationary thread 39 and rotates the worm 42 so that the latter may work back through the teeth of the stationary wheel 43. In order to reverse the direction of drive, a device corresponding to the sleeve 14 in Fig. 2 is provided in the gearing between the shafts 45 and 46, to enable the wheel 43 to be set to press against one side or the other of the worm thread. Fig. 4 shows a modification of Fig. 5, in which the sleeve 44 and shaft thread 39 are replaced by a sleeve 26 and shaft 28 arranged concentrically within the worm 25, the gearing between the two members comprising one. or more planet pinions 30 mounted on studs 31 on the sleeve 26 and meshing with a fixed rack 32 on the reciprocatory member 20 as well as with teeth 33 on the worm, this arrangement giving a two-to-one ratio. A form is shown in Fig. 6 in which two shafts 63, 64, geared to rotate in opposite directions, are stated to be driven continuously by a pair of oppositely-handed worms 59, 60 carried by the reciprocating member 50 and, acting alternately as racks, in engagement with the worm wheels 61. 62. The worms ride on oppositelyinclined threads formed on a shaft 56 mounted to rotate in stationary bearings 57, 58 in a frame 51. Gearing (not shown) interconnects the shaft 64 with a pinion 65 on the threaded shaft 56 to produce synchronized rotations, the arrangement being that whilst one or other worm acts as a rack according to the direction of the stroke, the other worm as well as the shaft 56 is rotated to allow the requisite idle return motion of that member. To enable the direction of rotation of the driven shafts 63, 64 to be reversed, the pinion 65 engaging the threaded shaft 56 may be moved axially by means of a hand lever 66 operating a cap 67 screwed into the frame 51 and carrying the outer race of the bearing 58.