Patent GB-1273961-A (GB)
Title: Intermittent rotary motion device
IPC: F16H31/00
Filed: 1971-01-04
Abstract: 1,273,961. Stopping machines at definite positions or intervals. NATIONAL CASH REGISTER CO. 4 Jan., 1971 [19 Jan., 1970], No. 223/71. Heading F2E. [Also in Divisions B6 and G2] An intermittent rotary motion device ineludes at least first and second output members 80, 82, Fig. 2, attached to a common torsion shaft 68, means, e.g. motor 120, for rotating the shaft at a constant angular velocity, and exciter units, operated, e.g. electromagnetically, arranged to produce in the rotating shaft a series of torsional impulses which superimpose on the rotation of the shaft and output members a series of oscillations of regular frequency and amplitude about the axis of rotation of the shaft so that in operation the output members undergo a series of advances and dwells in each revolution, each dwell of the first output member occurring when the second output member is rotating at substantially twice the constant angular velocity, and vice versa. As shown, the exciter units each comprise a stator 102 or 104 having axial teeth on its inner periphery, a rotor 108 or 110 fixed to or forming part of the shaft 68 and having corresponding teeth on its periphery, and a D.C.-energized coil 106 located in the respective stator, whereby rotational motion of the shaft causes magnetic interaction between the teeth to produce the torsional impulses. Preferably the teeth are symmetrically disposed, and the number on stator or rotor determines the number of dwells. To provide for the out-of-phase relationship of the dwells of the two output members 80, 82, the teeth of the rotor and stator of the exciter unit on the right are respectively aligned when the device is stationary, while the rotor teeth of the exciter unit on the left are located opposite the spaces between the stator teeth. Also as shown, the output members each comprise a print drum with rows of type characters 98 or 100, the rows on one drum being staggered in relation to the rows on the other drum, and at least one of the drums having magnetic markings associated with magnetic pick-up means (not illustrated) to provide for actuation of print hammers 122 or 126 in group 124 or 128 respectively in correlation with drum position to print particular characters in particular positions. Printing occurs during a dwell. Each drum is secured, cantilever fashion, at one end only to a thickened part, 70 or 72, of the shaft. In operation, motor 120 is energized, and as shaft 68 is being accelerated up to operating speed, both coils 106 are D.C.-energized, so that the drums begin to oscillate in opposition. The impulses build up to a resonant steady-state amplitude producing a distribution pattern of torsional flexing analogous to standing waves. The free ends 92, 94 of the drums lie on either side of a transverse nodal plane, 78, of the shaft 68. In an example, each drum has a diameter of three-and-a-quarter inches, and sixty-four rows of type characters, and each rotor and stator has sixty-four teeth. The shaft speed is 1500 r.p.m. and the dwells occur at 1600 cycles per second. By providing one centrally-mounted doublelength centre drum and two end drums, (Fig. 3, not shown) the shaft diameter may be reduced. In Fig. 4 (not shown) five drums and two end half-length drums are provided. In all cases adjacent drums oscillate in opposition. Figs. 6A and 6B show a more elaborate twodrum example where the torsion shaft 288 is hollow and welded in a nodal region 294, Fig. 6B, around a solid input shaft 292, dry endbearings 420, Fig. 6A, and 422, Fig. 6B, permitting relative torsional movements of shafts 288 and 292 at these locations. Shaft 292 has a pin-and-slot connection with a drive shaft 262 rotated by a motor 272 through belt 270. Both ends of input shaft 292 are inwardly conical, so the assembly of shafts 292, 288 and drums 274, 276 may be de-mounted (and optionally, lowered into felt-lined cradles 418) by moving a spring- loaded lever-and-link mechanism 392, 396, 400, 404, 406, 408, Fig. 6A, to the left by a handle (398, Fig. 7, not shown), whereby a ballmounted support member 344, housing a conically-ended stub shaft 304, is also moved to the left. The stator 314, 316, 318 of the righthand exciter unit 308, Fig. 6B, is secured to a cylindrical tubular member 242 which is rotatably mounted within a bracket 240 to permit rotational pre-adjustment of the stator for correct "out-of-phase" operation. Figs. 12 and 13 show part of a rotor with tapered teeth of trapezoidal cross-section, and Fig. 16 shows a two-part stator with teeth 496 matching those of the rotor, and a coil 502: these are suitable for Figs. 6A, 6B.