VARIABLE RATIO ROTARY TRANSMISSION

Abstract: A rotation transmission mechanism (10; 200) having coaxially rotatable input and output shafts (12, 14; 212, 214). A plurality of coupling elements (32, 34; 220, 222) are carried by the input shaft (12, 212) for rotation with the input shaft. The coupling elements (32, 34; 220, 222) are constrained for movement in and out relative to the axis of the input shaft (12; 212). Each coupling element (32, 34; 220, 222) is arranged to reciprocate back and forth relative to the axis of the input shaft (12, 212) during rotation of the input shaft (12, 212). Cam means (82, 80, 98; 274, 270, 272) is provided for selectively transferring the movements of the coupling elements to effect incremental rotations of the output shaft. The reciprocatory movements of the coupling elements are provided by virtue of driving of the coupling elements through eccentric means (52, 38, 36; 230, 232, 260, 262), the eccentric means operating pursuant to the rotation of the input shaft (12; 212) to effect the said reciprocatory movements with an amplitude which is dependent upon the degree of eccentricity. By varying the eccentricity the amplitudes are varied whereby to vary the incremental movements which are imparted to the output shaft (14; 214) during each rotation of the input shaft (12; 212) whereby to vary the drive ratio between the input shaft (12; 212) and output shaft (14; 214).

Description: TITLE '^VARIABLE RATIO ROTARY TRANSMISSION" TECHNICAL TIELD OF THE INVENTION This invention relates to rotation transmission mechanisms and particularly, but not exclusively, to rotation transmission mechanisms in which the drive ratio from an input shaft to an output shaft is variable. DISCLOSUR-E OF THE .INVENTION According to the present invention there is provided a rotation transmission mechanism comprising two separate rotatable members, a plurality of coupling elements carried y one said member for rotation with said one member about the axis of rotation of said one member, movement means in use acting on said coupling elements pursuant to rotation of said one member to cause the coupling elements to undergo oscillatory movements relative to said one member such that at least parts of said elements move towards and away from said axis, and coupling means in use selectively coupling and uncoupling said coupling elements to the other said member whereby each said coupling element is so coupled during respective selected parts of cycles of said oscillatory movements thereof, whereby to cause translation of those parts of the oscillatory movements,and of corresponding then occurring parts of the rotational movements of the coupling elements about said axis,to effect respective incremental rotational movements of said other member, said incremental rotational movements being undirectional and consecutive whereby continuous rotation of said one member causes at least substantially continuous rotation of said other member. -The invention is further described by way of example only with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cutaway perspective view of one form of mechanism constructed in accordance with the invention. Figure 2 is an axial section of the mechanism of Figure 1. Figure 3 is a section substantially on the line 3-3 in Figure 2. Figure 4 is a perspective view ' of certain of the components of the mechanism of Figure 1 and illustrating their manner of fitment together. Figure 5 is an end view of the mechanism of Figure 1. Figure 6 is an axial section of an alternative form of mechanism constructed in accordance with the invention. Figure 7 is a cross-section substantially on the line 7-7 in Figure 6. DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS The mechanism 10 illustrated in Figures 1 to 5 includes an input shaft 12 and an axially aligned output shaft 14. " Shaft 12 carries, towards one end, a disc-like part, hereinafter called a torque converter web, designated generally by reference numeral 16. Torque converter web 16 is fixed relative to shaft 12. Torque converter web 16 has, on one face thereof, two diametrically opposed bosses 18, 20 of similar form. The bosses 18, 20 support respective shafts 22, 24 for rotation relative to the torque converter web. The shafts 22, 24 extend through the bosses and through the torque converter web 16 itself, having axes which are parallel to the axis of shafts 12 and 14 and which are diametrically opposed. Shafts 22, 24 have gear wheels 26, 28 fixedly secured thereto, the gear wheels being located to the face of torque converter web 16 opposite that on which bosses 18 and 20 are formed. As best illustrated in Figure 5, output shaft 14 has fixed thereto a further gear wheel 30 which meshes with gear wheels 26, 28. In general principle, the mechanism 10 operates by driving the shaft 14 from shaft 12 via the torque converter web 16 and the gears 26 and 28 somewhat in the fashion of a conventional eip-cyclic gear train. That is to say if, for example, gear wheels 26, 28 are constrained so as not to rotate about their own axes during" rotation of shaft 12 and torque converter web 16, then the gear wheel 30 is locked in angular position relative to the axes of the shafts 22 and 24 so that " the wheel 30 and shaft 14 rotate together with shaft 12 and torque converter web 16. By means described later, however, the mechanism 10 is operable to cause selective rotations of the gear wheels 26 and 28 about their own axes and relative to the torque converter web 16, during rotation of the torque converter web 16,in a fashion such as to drive the gear wheel 30 and shaft 14 at a -speed different to the speed of rotation of the shaft 12 and torque converter web 16. Broadly speaking, the mechanism 10 includes rack and pinion movement means for effecting rotational movements of the gear.wheels 26, 28 about their own axes, and selective coupling means operable to couple the movement means for such driving only during selected times during each rotation of the shaft 12 and torque converter web 16. The movement means includes two generally radially extending elongate toothed racks 32, 34, pivotally secured, at inner ends thereof, to a ring 36 which is mounted on a bearing member 38 for rotation around the bearing member. The bearing member 38 has a cylindrical outer surface on which the inner surface of the ring 38 runs, the axis 40 of that surface being parallel to but displaced from the axis 42 of the shaft 12. Bearing member 38 is manipulatable as described later to permit variation of the relative displacement between axes 40 and 42 thus to vary the degree of eccentricity of the exterior surface of the bearing member relative ■ to the shaft 12. However, the bearing member 38 is maintained in generally fixed angular orientation relative to the axis of shaft 12. This is achieved by a coupling of the bearing member 38 to a fixed support member 44. Support member 44 has a tubular portion 44a coaxially arranged with the axis of shaft 12,and a forked radially outwardly extending yoke 46 is provided on portion 44a. Yoke 46 has two parallel arms 46a, 46b of which only arm 46a is visible in Figure 1, the two arms being visible in Figure 4. An axially extending pin 48 projects from one face of bearing member 38 and is retained between the two arms 46a, 46b of yoke 46. Thus, the pin 48 is constrained against rotation relative to member 44 but is slidable radially of the axis of shaft 12, between the two arms 46a, 46b. The degree of eccentricity of the axis 40 of the outer surface of member 38 to the axis 42 of shaft 12 is variable. More particularly, the bearing member 38 is of generally annular form having a cylindrical inner surface which is eccentric relative to the axis 40 of the outer surface of bearing member 38, having an axis 50 which is displaced from axis 40. An eccentric cylindrical lobe 52 is neatly accommodated within ΛΕl member 38 so that the inner surface of the bearing member ' is engaged with the outer surface of the lobe in a manner permitting relative rotation between the lobe and the member 38. The axis of the lobe outer surface is coincident with the axis 50 of the inner surface of the bearing member 38. Lobe 52 is carried at an inner end of a tube 54 coaxially arranged about shaft 12 and interposed between the shaft 12 and the tubular portion 44a of the support member 44. The lobe 52 is arranged with the axis . 50 displaced from the axis of the tube 54 which latter axis is coincident with the axis 42 of the shaft 12. The outer end of the tube 54 is provided with a radially extending handle 56 permitting manual rotation of the tube 54 • about the axis 42 thereby to move the axis 50 on a circular path around the axis 42. Bearing in mind that the bearing member 38 is constrained so that, at the location of the pin 48, it is constrained against movement otherwise than along the radial line defined by the yoke 46, the effect of turning the handle 56 and eccentric lobe 52 is to move the bearing member 38 ' so that the eccentricity thereof is varied. That is to say, so that the spacing of the axis 40 is varied relative to the location of axis 42. The ring 36 has two spaced sidewardly extending annular flanges 36a, 36b. The rack 32 is secured to the ring 36 by a pivot pin 58 extending on an axis parallel to and spaced from the axis 40 about which ring 36 is rσtatable. The pin passes through aligned apertures in the flanges 36a, 36b and through the rack 32. Rack 34 is pivotally connected to ring 36 by means of a further pin 60 which is arranged with its axis parallel to axis 40 and which pin extends through an opening in the rack 34 and into slots 62 in the flanges 36a and 36b. Slots 62 are of arcuate configuration having centres of curvature arranged on the axis 40. The inner end of the rack 32 is thus pivotally secured at a fixed location on ring 36 whilst the inner end of rack 34 is pivotally secured to the ring 36 at a location which may vary to a limited extent by movement of the pin 60 in the slots 62. The racks 32, 34 extend outwardly from, the pins 58 and 60 generally radially relative to both axes 40, 42 and through generally radially extending openings 18a, 20a in the bosses 18, 20. Shafts 22, 24 are coaxially received, at ends thereof remote from gears 26, 28,in respective hollow shafts 64, 66 which extend outwardly from the bosses 18, 20. Inner ends of the shafts 64, 66, within bosses 18, 20.,carry pinions 68, 70 which are in toothed engagement with teeth on the respective racks 32, 34. " . As the torque converter web 16 rotates during rotation of shaft 12, the outer ends of the racks 32, 34 are carried around with the torque converter web. The manner of mounting of the racks 32, 34 is such as to permit a limited degree of movement OM?I of the racks in the common median plane thereof transverse to the axis of shaft 12. However, such movement is essentially limited, by appropriate dimensioning of the openings 18a, 20a, to movement along generally linear paths in and out relative to the axes 40, 42. Thus, during turning of the torque converter web 16, the inner ends of the racks 32, 34 tend to be carried around with the torque conveter web, so carrying the ring 36 around with the torque converter web also, the ring 36 then running around the bearing member 38. However, because of the eccentricity of the ring 36 relative to the axis of shaft 12, the distance of the pins 58, 60 from the axis of shaft 12 cyclically varies during such rotation thus causing the racks 32, 34 to undergo corresponding in and out reciprocating movements relative to the axis of shaft 12. These movements are transferred to cause cyclic back and forth rotational movements of the respective pinions 68, 70. The aforementioned coupling means, operates to couple the respective pairs of shafts 22, 64 and 24, 66 selectively during each revolution of torque converter web 16. The coupling means includes coupling mechanisms 72, 74 respectively associated with the pairs of shafts 64, 22 and 66, 24. The two mechanisms are of like form and the following description of the mechanism 72 is equally applicable .to the mechanism 74. Mechanism MFI 72 includes a cylindrical housing 76 formed on the end of shaft 64 remote from boss 18. Housing 76 has a hollow interior and the shaft 22 extends / at the end remote from gear 26,into this hollow interior. At the end of the shaft 22 within the hollow interior, the shaft 22 is provided with a gear wheel 78 which is secured to' the shaft 22 for rotation, therewith. The outer end of the housing 76 has a circular bore therethrough, leading into the hollow interior of the housing 76,and a cam follower member 80 is slidably received in that bore for movement towards and away from boss 18 coaxially with shafts 22 and 64. The outer end of the member 80 carries a cam follower portion 80a which extends away from ' housing 76 and which is engaged with a cam surface 82 provided on a transverse face of an outstanding disc-like portion 84 formed on support member 44. The innermost end of the cam follower member 80 is in the form of a small diameter spigot 90 which is slidably accommodated in a bore 92 at the end of shaft 22 within the hollow interior of housing 76. A helical compression spring 96 is positioned in bore 92 to provide an outward bias force between the inner blind end of the bore 92 and the inner end of the spigot 92 whereby to resiliently bias the cam follower member into engagement with the cam surface 82. Housing 76 has a pivotal cam element 98 mounted thereon for pivotal movement relative to the housing. Element 98 has a free end portion 98a which is biased. by means of a spring (not shown) acting on the element into engagement with the exterior surface of the cam follower member 80. The cam follower member 72 shown in Figure 1 is illustrated in a condition at which it is depressed inwardly of housing 76 by virtue of interengagement with the cam surface 82. In this condition, the cam element 98 is in a relatively lifted position, with the end portion 98a being engaged on a relatively large diameter cylindrical surface 85 of member 80. However, when the cam follower member 80 is moved relatively outwardly from the housing 76 under influence of cooperation therewith with the cam surface 82, the end portion 98a of the cam element 98 rides down a frustoconical surface portion 100 on the cam follower -member 80 so that the cam element 98 is pivoted, in an anti-clockwise direction as viewed in Figure 1, about the location 102 at which it is pivotally secured to the housing 76. When this movement occurs, an edge portion 104 of the cam element 98 is brought into engagement with the toothed periphery of the gear wheel 78 thereby locking the gear wheel relative to the housing 76 and thus also locking the shaft 64 to the shaft 22. Figure 2 shows member 74 conditioned for this locking of shafts 24, 66. By appropriate shaping of the surface 82, the mechanism 72 is arranged to lock the shafts 22 and 64 together for rotation during one part only of the cycle comprising one turning movement of the torque converter web 16. This part of the c: :?ι cycle, which for relatively small degrees of eccentricity of the ring 36 constitutes roughly one-half of each ' cycle,is arranged to coincide with uni-directional movement of the rack 32 whereby rotation of the pinion 68 pursuant to movement of the rack is transferred to .cause corresponding rotation of gear wheel 26 only in one direction for each cycle of turning movement. The arrangement of the mechanism 74 is such that it also operates, on the remainder of each cycle of operation,to couple the shafts 24, 66 for uni-directional rotation of the gear wheel 28, with the directions of .rotation of gear wheels 26 and 28 being organized to be the same. Thus, incremental rotational movements are applied to the gear wheels 26, 28 during each rotation of the torque converter web 16, these incremental rotations being arranged to impart substantially continuous rotation to the gear wheel 30 and thus to the shaft 14. As previously mentioned, variation in the amount of rotational movement imparted to wheels 26, 28, during each cycle of rotation of the shaft 12 will vary the relative extent to which the shaft 14 is rotated during each, cycle of rotation of the shaft 12. Since the amount of turning of the gear wheels 26, 28 during each cycle of rotation of the torque converter web 16 is dependent on the corresponding amount of reciprocatory movement of each rack 32, 34 during each rotation, the amount of turning can thus -be varied by varying the eccentricity of the ring 36 relative to shaft 12. As described previously, that eccentricity can be varied by movement of handle 56 so that the handle 56 provides a means for varying the drive ratio between the shafts 12 and 14. Figures 6 and 7 show an alternative form of mechanism 200 constructed in accordance with the invention. Mechanism 200 comprises an input shaft 212 and an output shaft 214. A torque converter web 216 of disc-like configuration is affixed to shaft 212 for rotation therewith. As shown, the shafts 212 and 214 are coaxial, the shaft 212 being hollow and receiving the shaft 214. Shaft 214 has fixedly secured thereto for rotation therewith a toothed drive wheel 218 having a series of ratchet teeth 218a therearound. The torque converter web 216 carries two pawls 220, 222 which are carried around with the torque 'converter web during rotation thereof and which have hooked inner ends 220a, 222a and which can be selectively brought into engagement with the toothed drive wheel 218 for effecting turning thereof as the torque converter web turns. Pawls 220, 222 have pins 230, 232 at outer ends thereof. These pins are arranged with axes parallel to the common axis of the shafts 212, 214 and are received in respective slots 240, 242 in the periphery of the torque converter web 216. Slots 240, 242 are arranged in radial alignment, and the pins 230, 232 and thus the outer ends of the pawls 220, 222 are accordingly confined for generally radial movement relative to the axis of the torque converter web 216. The pins 230, 232 are however arranged to permit the pawls 220, 224 to be swung about the axes of the pins relative to the torque converter web 216. The pins 230, 232 extend axially to either transverse side of the torque converter web 216 and the free ends thereof are engaged on cam surfaces 260a, 262a respectively formed at the edges of respective like eccentric rings 260, 262. Rings 260, 262 are arranged with their axes coincident but displaced from the axis of the shafts 214, 212. By use of springs (not shown) the pins 230, 232 are maintained biased against the circular eccentric cam surfaces 260a, 262a.during rotation of the torque converter web 216. Thus, the pins 230, 232 and thus also the outer ends of the pawls 220, 222 are caused to execute back and forth reciprocatory motion along the lengths of the slots 240, 242 during rotation of torque converter web 216. The inner ends 220a, 222a of the pawls 220, 222 carry pins 270, 272 which extend generally parallel to the axes of shafts 214, 212 and which are resiliently biased, by springs, (not shown) into engagement with O PI y Sλ. V/IPO the exterior surface of a cam 274 positioned around the axis of the shafts 212, 214. This cam is so shaped as t.o cause the inner ends 220a, 222a to be lifted against the aforementioned resilient bias applied thereto away from the periphery of the toothed wheel 218,during respective parts of each rotation of torque converter web 216 through one revolution,but to permit the resilient bias applied to the inner ends 220a, 222a to bias the inner ends 220a, 222a into engagement with the periphery of the toothed wheel 218 during respective other parts of each - rotation of torque converter web 216 through one revolution. " The arrangement of the cam 274 is surh that the pawls 220, 222 so engage the toothed wheel 218 in alternation and during movements of the "outer ends of the pawls only either outwardly or inwardly as the case may be during the reciprocatory movement of the outer ends relative to the slots 240, 242. In this way, the pawls are arranged to provide incremental rotational movements of the toothed wheel 218, pursuant to rotation of the torque converter web 216, which incremental movements are, by appropriate fashioning of the cam 274, arranged to ' impart substantially continuous rotation to the wheel 218 when the shaft 212 is rotated. By varying the degree of eccentricity of the rings 260, 262 relative to the common axis of the shafts 212, 214, it is possible to vary the extent of the incremental rotational movements for each revolution of the shaft 212 whereby to vary the drive ratio from the input shaft 212 to the output shaft 214. The described construction has been advanced merely by way of explanation and many modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

Claims: CLAIMS 1. A rotation transmission mechanism comprising two separate rotatable members, a plurality of coupling elements carried by one said member for' rotation with said one member about the axis of rotation of said one member, movement means in use acting on said coupling elements pursuant to rotation of said one member to cause the coupling elements to undergo oscillatory movements relative to said one member such that at least parts of said elements move towards and away from said axis, and coupling means in use selectively coupling and uncoupling said coupling elements to the other said member whereby each said coupling element is so coupled during respective selected parts of cycles of said oscillatory movements thereof, whereby to cause translation of those parts of the oscillatory movements and of corresponding then occurring parts of the rotational movement of the coupling elements -about said axis to effect respective incremental rotational movements of said other member, said incremental rotational movements being unidirectional and consecutive whereby continuous rotation of said one member causes at least substantially continuous rotation of said other member. 2. A mechanism as claimed in claim 1, wherein said coupling elements are arrayed about the axis of said one member and said movement means operates in use to effect said oscillatory movements of the coupling elements as reciprocatory generally linear OI.'IPI movements; said coupling means further including rotatable driving elements mounted to said one member for rotation about respective axes which are at eccentric locations relative to the axis of said one member; said coupling means in use operating to cause said driving elements to be coupled to said coupling elements for rotation of said driving elements during said parts of said oscillatory movements, said other member being arranged for driving thereof from said driving elements. 3. A mechanism as claimed in claim 2, wherein said coupling means includes rotatable drive elements drivingly engaged with respective said coupling elements- for rotation thereof pursuant to said linear reciprocatory movement of the coupling elements; said coupling means operating to couple said drive elements to said driving elements for rotation of the driving elements pursuant to rotation of the drive elements only during said parts of the oscillatory movements of the respective said coupling elements. 4. A mechanism as claimed in claim 3 - wherein said coupling elements are toothed racks extending generally radially outwardly from said axis of said one member and being constrained at least substantially for lengthwise movement thereof relative to said one member, said drive elements comprising gears engaged with respective said racks, said coupling means including clutch means operable to clutch OMPI respective said gears to rotationally drive the driving elements about their axes during rotation of the said one member and during the respective said parts of the reciprocatory movements of the said racks. 5. A mechanism as claimed in claim 4, wherein said members are coaxial and the driving elements are planetary toothed wheels which are drivingly coupled to one or more toothed wheels on said other member. 6. A mechanism as claimed in claim 5, wherein said movement means constrains portions of said coupling elements for movement in an eccentric circulatory path relative to the axis of said one member. 7. A mechanism as claimed in claim 6, wherein said eccentric circulatory path is substantially circular. 8. A mechanism as claimed in claim 7, wherein . the eccentricity of said circulatory path, is variable whereby to vary the drive ratio of said one member relative to said other member. 9. A mechanism as claimed in any one of the. claims 4 to 8, said clutch means defining a cam track and cam followers, the last-mentioned cam followers respectively engaging the last-mentioned can track during rotation of the coupling elements about the axis of said one member and effecting said coupling and decoupling by latching and unlatching respectively of respective ones of said drive elements with respective ones of the driving elements for rotation of the so defined pairs of drive and driving elements, for, on the one hand, rotation together, and, .on the other hand, for the free rotation one relative to the other. 10. A mechanism as claimed in claim 1, wherein said coupling elements are mounted, at said parts thereof, for swinging movements thereof relative to the said one member, but are- constrained so that said parts thereof move on respective paths in and out relative to said axis during said oscillatory- movements. 11. A mechanism as claimed in claim 10, wherein said other member has a toothed wheel thereon and said coupling means operates to swing free ends of the coupling elements remote from the said parts thereof into and out of driving engagement with said toothed member for effecting said coupling and decoupling. 12. A mechanism as claimed in claim 11, wherein said parts of said coupling elements are carried in generally radial slots in said one element for said oscillatory movements thereof and said movement means comprises a cam track eccentrically arranged about the axis of said one member and engaging cam followers defined on said parts of said coupling elements. 13. A mechanism as claimed in cali 12, wherein said cam track is generally circular. 14. A mechanism as claimed in claim 13, wherein the eccentricity of said cam track relative to said axis of said one member is variable whereby to vary the amplitudes of said oscillatory movements of said coupling elements and to thereby vary the magnitudes of said incremental rotational movements and the drive ratio from said one member to said other member. 15. A rotation transmission mechanism substantially as herein described with reference to the accompanying drawings. 16. The steps or features disclosed herein or any combination thereof. OMPI

Inventors: WILLMOT ERIC P
Applicants: WILLMOT ERIC P
Application year: 1981
Main classification: F16H29
IPC codes: F16H29