Patent GB-1012712-A (GB)
Title: Improvements in or relating to variable speed transmission mechanisms
Inventor: ADAMS JOHN REGINALD
IPC: F16H3/34
Filed: 1961-05-30
Abstract: 1,012,712. Change-speed gear. RANK PRECISION INDUSTRIES Ltd., [trading as TAYLOR, TAYLOR & HOBSON]. May 30, 1962 [May 30, 1961], No. 19520/61. Heading F2D. A change-speed gear for use in apparatus measuring the roughness or undulations of a surface of circular cross-section, or in the drive of a multispeed paper and pen recorder in equipment measuring the accuracy of gear teeth, comprises a number of parallel main spindles grouped around a driven spindle, input means from which a drive is applied to one of the main spindles, gearing through which the main spindles are driven in sequence one from another with the same transmission ratio between each pair of consecutive spindles, a selector moved to interpose gearing between any one of the main spindles and a driven spindle so that the driven spindle can be rotated at any one of a series of speeds in geometric progression, and output means driven by the driven spindle. In one form, an electric motor D drives the first of a series of main spindles A<SP>1</SP> . . . A<SP>9</SP> each carrying a gear pair B<SP>1</SP>, C<SP>1</SP>, &c., the larger gear B<SP>1</SP> of each gear pair meshing the smaller gear C<SP>2</SP> &c. of the next pair and so on, the main spindles lying upon an arc having a centre comprised by a driven spindle G in the form of an output gear. A selector cage E<SP>2</SP> rotatable by a hand wheel E<SP>1</SP> on a shaft E carries a series of three coaxial idle gears F<SP>1</SP> . . . F<SP>3</SP>, the idle gear F<SP>1</SP> always meshing the driven gear G and the three'idle gears together being selectively engaged one-at-a-time with the larger gears B<SP>1</SP> &c. of each gear pair, the gear pairs being off-set in three planes to prevent fouling, as shown in Fig. 2. In the form shown, the ratio between each gear pair such as B<SP>1</SP>, C<SP>2</SP> is 2 : 1, so that by moving the selector E<SP>2</SP> round the axis of the driven gear G, successive ratio steps in the same proportion are obtained. As the alternate spindles A<SP>1</SP>, A<SP>3</SP>, A<SP>5</SP> &c. rotate in one direction, and the intermediate main spindles A<SP>2</SP>, A<SP>4</SP> &c. rotate in the opposite direction, a reverse gear is provided between the driven gear G and a final output shaft J. As shown in Fig. 3, the driven gear G meshes a long pinion H<SP>1</SP> axially slidable upon a shaft H so that either it meshes directly with a pinion J<SP>1</SP> upon the driven shaft, or alternatively meshes through lay shaft gears K<SP>1</SP>, K<SP>2</SP> with a second gear J' upon the output shaft. As a modification, a reverse gear controlled by rotation of the selector hand wheel E<SP>1</SP>, to cause unirotational drive of the output shaft J, may be provided. In this form, a cam L, Fig. 4, is mounted upon the selector shaft E, and has alternate crests and dwells engaged by a pair of follower rollers L<SP>4</SP>, L<SP>5</SP> at the ends of arms L<SP>1</SP>, L<SP>2</SP> spring-biased towards each other about a pivot L'. The arm L<SP>1</SP> carries a gear M<SP>1</SP> which always engages a gear M which may drive the output shaft J, and the gear M<SP>1</SP> is meshed with or held out of engagement with the driven gear G depending upon whether the roller L<SP>4</SP> is upon the crest of, or in a dwell point in, the cam L. Similarly, the arm L carries a meshing gear pair M<SP>2</SP>, M<SP>3</SP>, the former permanently meshing the gear M and the latter being selectively meshed with the driven gear G. The arrangement is such that only one of the gears M<SP>1</SP>, M<SP>3</SP> meshes the driven gear G at a time, and each stepped rotation of the selector shaft E changes the direction of drive through the reversing train. Accordingly, the output shaft J always rotates in the same direction. As a further modification, Fig. 5 (not shown), the gear pairs upon the main spindles are off-set axially in four separate planes and the selector cage carries four trains of gears; two of these trains are comprised by a single idle gear each, and the other two trains each comprise two meshing idle gears. The single idle gears mesh alternate gear pairs on the main spindles, and the two-gear idle trains mesh selectively with the appropriate intermediate gears on the main spindles, again producing unidirectional rotation of the output shaft. To obtain a continuously-variableratio covering the whole range of the gearing, the output shaft may be connected to a simple disc-and-roller friction gear, Fig. 6 (not shown), which is manually controlled, the maximum variation in ratio of the friction gear being greater than the ratio steps between each ratio of the change-mesh gearing. In another modification also giving unidirectional rotation to the driven shaft, Figs. 7, 8 (also not shown), a pair of non-meshing idle gears in the selector cage are meshed selectively with gears fast on alternate main spindles and with idle gears freely journalled on the same main spindles, these latter in turn meshing gears fast on the intermediate main spindles.