Patent GB-545660-A (GB)
Title: Improvements in and relating to variable ratio gear mechanism
IPC: F16H3/66
Filed: 1940-12-02
Abstract: 545,660. Variable-speed gearing. LICHTWITZ, O. Dec. 2, 1940, No. 17169. [Classes 80 (ii) and 80 (iii)] [Also in Group XXII] In variable ratio gearing wherein the movement of the initial shaft is transmitted through a number of spindles to differential gears through which the resultant movement is composed, each spindle is driven by a separate cone of gear wheels through an idler and gear slidable on the respective spindle. The ratios are graduated as the whole numbers or as their reciprocals and the varying of ratio is effected by setting levers in predetermined positions. A gear train which forms a basis of the mechanism is shown in Figs. 1, 2, 3 and consists of a driving shaft 11 to which is secured a wheel 12. meshing with a wheel 13 on an intermediate shaft 14 to which is secured an arm 15 carrying a planet gear 16 engaging an annulus 19 and a sun 17. The sun is keyed to the driven shaft 18, but the annulus is loose thereon and carries a wheel 20 adapted to be driven from the driving shaft 11 through a gear 21 and idler gears 22, 24 either of which can be thrown into engagement with the gear 20 by a fork 23 so as to drive the annulus forward or backward and give a plus or minus effect. The mechanism shown in Figs. 4, 5 will give all integer ratios between 1 : 1 and 555:1 and by using the numbers 0 to 5 only. Thus 37 is dealt with as being 4 tens mimus 3 units. On the driving shaft 25 are mounted three similar groups of stepped gears 26, 27, 28 each containing five wheels, and the groups reading from left to right correspond to hundreds, tens and units. Parallel to the driving shaft are three aligned spindles 29, 30, 31 each of which has slidably keyed thereon a gear wheel 32, 33, 34 in mesh with an idler 35, 36, 37 mounted in forks 38, 39, 40 pivoted on the respective spindles. Thus the idlers may be brought into mesh with any gear in its respective cone. Located adjacent the gear 1 of each cone is a fixed wheel or segment O with which the idler may be locked. The forks have handles 41, 42, 43 projecting through apertures 44, 45, 46 in a casing 47. A gear wheel 49 on the hundreds cone meshes with a wheel 50 on a shaft 51 corresponding to the shaft 14 in Fig. 1. The sun pinion 53 is secured to a second intermediate shaft 54 with arm 55, sun 56 on the driven shaft 57 and an annulus 63. The spindles 30, 31 carry reversing gears 58, 61 adapted to coact with the gear wheels 59, 62, as in Figs. 2, 3, and the levers 64, 65 of these gears project through slots 66, 67, Fig. 5, with ends marked + and -. Thus, for a ratio 342:1 the lever 41 is placed in recess 3 of slot 44, the lever 42 in recess 4 of slot 45 and lever 43 in recess 2 of slot 46; the levers 64, 65 both being placed 'at the + end of their respective slots. In a modification the + and - levers may be omitted and two cones, each with 9 gears, are employed to give ratios from 1:1 to 99:1. In a further modification, Figs. 8, 9 (not. shown), bevel differentials are employed. The driven shaft may be used as the driving shaft in which case the ratios will be the reciprocals of the whole numbers. In such a use it is necessary to prevent all the change-gear levers from being geared with the fixed wheel O at the same time. This is effected by providing the levers with extensions 93, 94, 95, Fig. 11, adapted to engage wedge elements 96, 97, 98 which co-operate with other wedge elements 99, 100. The wedges slide in a frame. 101 which provides room sufficient only for two of the levers being set at 0 As applied to a gear-hobbing machine the main shaft 102, Fig. 12. drives the tool spindle 105 and also the work table 111 through a variable gear box A as described above and a differental 107 . . 109. The output shaft 106 of gear box A also drives through clutch 114 a second variable gear mechanism B the output shaft 116 of which drives the feed screw 118 for the cutter slide. The output shaft 116 has a gear 119 which drives a gear 120 of gear box C through intermediate wheels 124, 125, Fig. 14, and the output shaft 122 is geared to a wheel 113 on the bevel wheel 112 to modify the revolutions of the blank when cutting helical gears. When cutting non-helical gears, the shaft 122 must be locked and the input shaft 121 must be reversible for cutting right and left-handed gears. In order that shaft 122 may be locked only when gear box C is disconnected, a lever 123, Fig. 14, pivoting about a shaft 121 carries meshing idlers 124, 125. When lever 123 is in mid-position neither idler is in mesh with wheel 119. The lever is locked in this position by a pin engaging a hole 127 therein, such pin: at the same time unlocking a lever 129 so that a detent 131 thereon may engage a gap 132 of a locking wheel 133 on shaft 122. As applied to a dividing bead, Fig. 15, the dividing crank 134 is secured to input shaft 135 of the variable ratio gear and has a spring pin or bolt 137. The output shaft 139 has secured to it a carrier 140 supporting planets 141 engaging a free side wheel 142 which has secured to it a worm wheel 143 capable of being locked by a spring bolt 146. The other side wheel 148 is geared to the dividing spindle 150. For spur gears the worm wheel 143 is locked, but when cutting spiral gears, the bolt is disengaged and the usual change gears provide between the feed screw 152 and the worm shaft 145. Thus the differential permits of the independent use of the mechanism for indexing and for turning the work-piece during milling. The hole 137 may be replaced by a plate with a row of holes.