DRIVE TRANSMISSION

Abstract: In a drive transmission for converting oscillatory motion into uni-directional rotary motion of a drive shaft (S), the oscillatory drive is applied, through a gudgeon pin (12) to the ring gear member (10) of a planetary gear system. The sun gear (17) is fast with drive shaft (S) and the planet gears (15) are mounted in a cage (14) fast for rotation with the inner race of a one-way clutch (C) whose outer race is fixed against rotation in housing walls (W).

Description: Drive Transmission This invention relates to drive trans¬ missions. International Patent Application PCT/GB89/00473 discloses a drive transmission in which oscillatory motion is converted to uni-directional rotary motion through one-way clutches, each com¬ prising an outer race to which oscillatory motion is applied, an inner race fast with an output shaft and a plurality of drive elements, or sprags, mounted between the races, to transmit uni-directional drive from the outer race to the inner race. The present invention is mainly characterized in that the transmission further comprises a planet¬ ary gear system P having an outer, ring gear member to which oscillatory motion is applied, an inner, sun gear keyed to the output shaft and a plurality of planet gears rotatably mounted in a cage, the said clutch having its inner race fast with the said cage and its outer race secured against rotation. With this construction, the sprags (or equiv¬ alent elements) do not have to Ghase a rotating shaft in order to re-engage but merely act as backstops, giving the clutch a greater life-expectancy. Also, in a particularly advantageous applica- tion, in which the oscillatory drive is derived from the small end of a connecting-rod, the amplitude of oscillation of the connecting-rod can be substantially reduced, by virtue of the velocity ratio derived from the planetary gearing. One form of transmission in accordance with the invention is described below, with reference to the accompanying drawings, in which: Fig. 1 is an axial cross-section of the trans¬ mission; and Figs. 2 and 3 are cross-sections on the lines II-II and III, respectively in Fig. 1 The drive is shown in Fig. 1 mounted on an output shaft S supported in bearings through side walls W of a fixed housing, e.g. of a transmission casing. The drive consists basically of a planetary gear system and a one-way sprag clutch indicated generally at P and C, respectively. The gear system P comprises an outer member 10 of generally annular form with a pair of radially projecting arms 11 which support gudgeon pin 12. This pin is coupled in use to an oscillatory drive member, not shown, which may be a reciprocating piston. The outer member 10 is supported on rotary bearings at its opposite ends and is formed internally with an annular ring, gear 13. Four equispaced planet gears 15 are individually mounted for rotation about their own axes in a cage 1 formed in two parts 14A and 14B rigidly secured together by spacers 16. The planet gears mesh in conventional manner with the ring gear 13 and with a sun gear 17 which is keyed to the output shaft S. The cage part 14B is fast with the inner annular member 17 of the clutch C which is freely rotatable with the cage 14. The outer annular member 18 of the clutch is secured to the adjacent wall W. Sprags 19 are positioned in the annular space between the members 17 and 18 of the clutch in known manner to permit relative rotation between the members in one direction of rotation but to prevent relative rotation in the opposite sense. As shown in the drawings, galleys are formed in the outer member 17 (and cage 14) and through the planet gears to facilitate lubrication through an oil or grease nipple 21. In operation, oscillatory motion is continu¬ ously applied to the member 10, through gudgeon pin 12 with an amplitude of, say 30°. In a forward direction of drive, the outer gear 13 rotates the planet gears 15 while the cage 14 is locked against rotation by the action of the sprag clutch, so that the planet gears rotate about their own fixed axes to drive the sun gear and thus the output shaft S. The gearing of the planetary gear system will cause the shaft S to rotate at approximately twice the speed of the ring gear which is thus displaced through 60°. In the return stroke of the housing 10, the planet gears revolve, in the opposite direction, and because the inner member of the clutch is free to rotate about the output shaft, the cage 14 is also free to rotate relative to the ring gear and to the sun gear, the latter continuing to rotate with the output shaft. In a particularly advantageous application, three drives as described above are mounted on a common output shaft and their outer members 10 are coupled to respective connecting rods which are driven 180° out of phase with each other. Thus the drives effect their forward driving cycles in sequence to maintain a continuous drive of the output shaft. Compared with corresponding arrangements in which (without the planetary gearing) the oscillatory drive is directly applied to the outer races of sprag clutches, the above described arrangement has several advantages. For example, the amplitude of oscillation 5 of the connecting rods is halved and this in turn permits the small ends to be positioned further from the axis of the output shaft and thereby to follow a straighter path, without unduly increasing the length of arc of movement of the small ends. Also, the sprag 10: (or equivalent) elements do not have to chase a rotating shaft in order to re-engage but merely act as back-stops, and the clutches have a greater life- expeέϊ&ancy. 15

Claims: CLAIMS : 1. A drive transmission for converting oscillatory motion into uni-directional rotary motion of an output shaft (S), the transmission including a one-way clutch (C), comprising an inner race (17), an outer race (18) and a plurality of drive elements (19) between the said races, characterized in that the transmission further comprises a planetary gear system (P) having an outer ring gear member (10) to which oscillatory motion is applied, an inner, sun gear (17) keyed to the output shaft (S) and a plurality of planet gears (15) rotatably mounted in a cage (14), the said clutch (C) having its inner race (17) fast with the said cage (14) and its outer race (18) secured against rotation. 2. A drive transmission according to claim 1, characterized in that ring gear member (10) is of generally annular form, having a radially projecting arm or arms (11) to which oscillatory drive is directly applied, for example by the small end of a piston rod. 3. A drive transmission according to claim 1 or 2, characterized in that a plurality of such trans- missions are operatively coupled to a common output shaft (S) and arranged out-of-phase with each other to provide a continuous rotary drive of the output shaft.

Inventors: EGAN MICHAEL JOSEPH, EGAN, MICHAEL, JOSEPH
Applicants: BARTON GORDON P, EGAN MICHAEL J, BARTON, GORDON, PAGE, EGAN, MICHAEL, JOSEPH
Application year: 1990
Main classification: F16H31
IPC codes: F16H31