Patent GB-976016-A (GB)
Title: Improvements relating to epicyclic gearing
IPC: B23P19/08
Filed: 1963-01-16
Abstract: 976,016. Toothed gearing; slip couplings. ILLINOIS TOOL WORKS Inc. Jan. 16, 1963 [June 1, 1962 (2)], No. 2006/63. Headings F2C and F2Q. Uniform rotation of a shaft 60, Fig. 3, driven from a motor 54 preferably through a variablespeed belt drive (not shown) and worm gearing 56, is converted into cylindrically varying or intermittent rotation of a gear 22 by a planetary pinion 24 carried in a yoke 66 on a plate 64 fixed to the shaft 60 and rolling on a stationary gear 20, at least one of the gears 20, 24, 22 having its teeth at non-uniform circumferential intervals-i.e. although the gears themselves are circular the base curves and rolling pitch curves are non-circular. It is stated that non- imiformly toothed gears may also be used in any gearing having parallel, skew or perpendicular axes (e.g. spiral bevel gearing). As shown, the gear 22 and pinion 24 have uniform involute teeth, there being 72 teeth on the gear 22, but the gear 20 has 74 involute teeth which vary in shape around the gear from teeth corresponding to a 71-tooth wheel to teeth corresponding to a 76-tooth wheel. The teeth in the sector corresponding to a 72-tooth wheel are identical with the teeth on gear 22, and so produce a dwell period in the drive. The slight backward rotation which should result from the teeth corresponding to a 71-tooth wheel may be avoided by allowing backlash between the gears 22, 24. Alternatively the " 71-tooth " teeth may be replaced by " 72-tooth " teeth. In either construction there is a substantial dwell period with a smooth acceleration and deceleration and the gear 22 is thus intermittently rotated at a reduced speed dependent on the difference between the numbers of teeth on gears 20, 22. In a modification the gear 20 has 38 teeth on half its periphery and 36 teeth on the other half, thus providing a drive having abrupt acceleration and deceleration at the end and beginning of a long dwell. Such a gear may be formed in two halves. Fig. 4 shows in its upper and lower parts the teeth 26a, 26b on gear 20 corresponding respectively to a 72-tooth and 76-tooth wheel. The two sets of teeth have the same outer diameter 30 and the same root diameter 32 (although this may be varied). Two base circles 34a, 34b are different-i.e. the base curve around the gear is not a circle and the pitch circles 46a, 46b are likewise different to give a variation in velocity ratio-i.e. the rolling pitch curve is also not a circle. It is stated that since the normal distances BCP are the same for all teeth, a smooth rolling action is obtained in any phase of mesh. Means 78, Fig. 3, are provided for adjusting the angular position of the stationary gear 20 and so adjusting the phase between fingers 77 of a mechanism 76 reciprocated by a face cam 74 on the shaft 60, and a plate 72 coupled to the gear 22 through an overload-released coupling 70. The intermittent drive is applied to a machine assembling washers or lock washers on to fastening screws. The plate 72, Fig. 6, rotates intermittently in a hopper 104 full of washers causing them to fall into peripheral recesses 73 on the plate and so allowing reciprocating fingers 77 to insert a screw blank through each washer. Each screw blank is fed to the fingers from a hopper (not shown) and after insertion through a washer is fed to mechanism which rolls a screw thread on the blank, the thread serving to retain the washer loosely on the screw. The complete machine is illustrated in Fig. 5 (not shown) but is not described in detail. The intermittent drive of Fig. 3 is shown in detail in Figs. 7 and 8. The worm wheel 58 rotates on a fixed shaft 98 secured to a casting 100, and is keyed to a sleeve 92 corresponding to shaft 60 of Fig. 3. The sleeve 92 drives the cam 74 through a key 96 and drives the planet carrier 64 through a bolt 62. The planetary pinion 24 rolls on a stationary gear 20 angularly positioned by an arm 106 bolted thereto, the arm 106 forming the phase-adjusting device 78 of Fig. 3 and being adjustable against the action of a spring 114 by screw 126 engaging a boss 110 on the arm. Resilient material 130 may be inserted between the screw and boss to damp out vibrations due to gear errors. The driven gear 22 has a hub 134 coupled to a surrounding plate 140 by an overload released coupling comprising four radial projections 136, Fig. 10, on the hub 134 engaging the ends of square pins 154 held by springs 156 in grooves 148 in the plate 140. A lug on each pin 154 engages a bore in the plate 140 to retain the pin against radial movement. On overload the pins 154 rock within the grooves 148 to allow projections 136 to pass. The plate 140, Fig. 8, seats on the plate 72 and is coupled to it by a single pin 146. The parts are pressed together by springs 164 reacting against a plate 160 loosely retained on the plate 140 by bolts 162, the plate 160 being engaged by the underside of the rotating cam 74 which is axially retained on the fixed shaft 98 by a screw 168. When it is required to change the plate 72 to suit different washers the screw 168 is removed, allowing the entire assembly 74, 160, 140, 72 to be lifted off. A new plate 72 is then engaged with the pin 146. In a modification, Fig. 9 (not shown), in which several screws must be undone to change a plate 72, the overload-released coupling comprises two facially-toothed rings spring-pressed together. Specifications 533,358 and 654,659 are referred to.