ZA200403348B

ZA200403348B - Infinitely variable transmission machine

Info

Publication number: ZA200403348B
Application number: ZA2004/03348A
Authority: ZA
Inventors: Jacobus Naude Johannes
Original assignee: Jacobus Naude Johannes
Priority date: 2001-11-16
Filing date: 2004-05-04
Publication date: 2005-04-26
Also published as: AU2002360863A1; WO2003042575A3; WO2003042575A2

Description

INFINITELY VARIABLE TRANSMISSION MACHINE

FIELD OF THE INVENTION

This invention relates to an infinitely variable transmission (IVT) machine of the type which utilises diametrically variable members such as tapered cones, variable pulleys, sprockets and the like which are driven by belts or chains and which by variation of the diameters of the variable members are capable of changing the ratio of rotation of their output angular velocity members relatively to their input velocities.

BACKGROUND TO THE INVENTION

Currently commercial versions of IVT machines of the above type rely on direct frictional belt or chain drive of their diametrically variable members. In the case of the belt driven machines reliance is placed on a friction interface between a rubber-like or flexible steel belt operating in a traction fluid to provide a dynamic friction interface between the belt and the diametrically variable member which it drives. This is particularly so in the case of toroidal or variable pulley systems that depend on the “interlocking” nature of the traction fluid molecules under extreme pressure to provide the drive traction. Not only do these friction machines have limited kilowatt (in the region of 130kw) or torque output ranges but additionally require highly advanced computer control to achieve “interlocking” between the frictionally driven surfaces of the machine.

The variable sprocket chain drive versions of the machines suffer from problems in synchronising the sprocket teeth with the chain or rely on a fit while applying load.

Typical machines of the above type are disclosed in the following patent related publications -

WO 00/08380, US005443423A, CHB16493A5, US4878883, GB2062142A, DE3501663A1,

US3956944, US5984814.

SUMMARY OF THE INVENTION

An infinitely variable transmission machine according to the invention includes a frame which carries an endless flexible driven element, a circular track arrangement which is variable in diameter and on which the driven element bears in use, means for varying the diameter of the track arrangement, an angular velocity output shaft which passes centrally through the track arrangement, a driven angular velocity input wheel which is engaged with the driven element, means for holding the driven element in tension as the diameter of the track arrangement is varied to vary the ratio of rotation of the output shaft relatively to that of the input wheel, a plurality of extraction devices which are fixed adjacent to each other to the output shaft, an arm which is connected to and extends in a radial direction from each of the extraction devices with all of the arms being rotatable about the output shaft in a common plane with the driven element being connected to each of the arms at spaced intervals over its length in such a manner that the driven element is movable in the axial direction of the arms so that the output shaft will be engaged and partially rotated by each of the extraction devices in turn to cause a single revolution of the output shaft when the arm to which it is connected achieves a greater angular velocity than that of the output shaft as the driven element is driven over the track arrangement.

The track arrangement may comprise a radially slotted guide disc which is fixed to the machine output shaft, foot elements in each of the disc slots with each element including a body which is slidably engaged in the slot, a foot on the body which projects outwardly from one face of the disc so that the feet collectively define a circular track for the driven element, a drive formation on the body which projects from the opposite face of the disc, and means for concomitantly moving the foot element drive formations radially inwardly and outwardly in the disc slots to vary the diameter of the circular track. } : The foot element moving means may be a control disc which is rotatable about the machine output shaft and carries a continuous spiral groove in which the drive formations of the foot elements are slidably located in a circle which is concentric with the machine output shaft axis, about which the foot elements are moved inwardly and outwardly in the guide disc slots on rotation of the control disc relatively to the guide disc.

The guide disc may be fixed to the machine output shaft and the foot element moving means may be a contro! disc which is rotatable by and with the guide disc, is movable towards and away from the guide disc and has a radially grooved frusto conical face which faces the guide disc, the foot element drive formations are elongated in the axial direction of the control disc with their free ends engaged with and slidably located in the control disc slots so that relative movement of the guide and control discs toward and away from each other in the axial direction of the machine output shaft will cause the foot elements to move radially inwardly and outwardly in the slots of the guide and control discs to vary the diameter of the circular track.

The track arrangement, in another form of the invention, comprises two discs which have facing frusto conical faces with at least one of the discs being rotated by the machine output shaft, a composite driven element which consists of two driven elements which are each located over one of the conical faces of the discs and are held in a parallel spaced relationship by pins which pass through them with the extraction device arms passing, at equally spaced intervals of the composite drive element, through spaces between the pins between the two driven elements and means for holding each of the driven elements in tension as the diameter of the track arrangement is varied.

The or each driven element may be a chain and the input wheel is a sprocket which is driven by ‘ an angular velocity input shaft. . The or each chain tensioning means may be a movable idler sprocket which engaged with the chain between the track arrangement and the driven input sprocket.

.

The input and idler sprockets are conveniently carried on cranked arms which are each rotatably mounted in a frame component of the machine and are movable between a first position in which the sprockets are adjacent each other and a second position in which they are spaced from each other at a position further from the track arrangement than they are in their first position and the machine includes control means for moving the cranked arms between their two position of operation, as the diameter of the track arrangement is varied, to hold the chain in tension.

The track arrangement diameter varying means in one form of the invention may be a differential gear arrangement, in which one of the bevel wheels is gear driven from the machine output shaft and the opposite bevel wheel is driven in the opposite direction by a gear on the control disc with the control disc being rotated relatively to the guide disc by causing a differential angular velocity across the differential gear by rotating the differential gear cage by a controller. Preferably, a suitable machine controller controls both the chain tensioning and differential gear controllers to hold the driver chain in tension as the diameter of the chain track is varied.

The or each flexible drive element may be a transversely ribbed belt and the or each angular velocity input wheel is a wheel having a ribbed tread surface.

In another form of the invention the extraction device arms are telescopic in length with their free ends connected at spaced intervals to the flexible drive element.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is now described by way of example only with reference to the drawings in which :

Figure 1 is an isometric view of the IVT machine of the invention in its high ratio mode of operation as seen from the front and one side,

Figure 2 is an isometric view of the machine in its low range mode of operation as seen from the rear and one side,

Figure 3 is a sectional side elevation of the machine of Figures 1 and 2,

Figure 4 is an exploded isometric view of the chain track arrangement of the machine,

Figure 5 is an exploded isometric view of a fragment of a guide plate of the Figure 4 track arrangement and a single chain track foot element as used with the guide plate,

Figure 6 is a sectioned side elevation of the assembled track arrangement of Figure 4,

Figure 7 is a side elevation of the machine,

Figure 8 is an end elevation of the Figure 7 machine shown sectioned on the line 8-8 in Figure 7 in its high range mode of operation,

Figure 9 is a view similar to that of Figure 8 illustrating the machine in its low range mode of operation,

Figure 10 is an isometric view of the sprag clutch arrangement of the machine,

Figure 11 is an isometric view of the chain tensioning arrangement of the machine,

Figure 12 is an end elevation of the machine as shown sectioned on the line 12-12 in Figure 7,

Figure 13 is an end elevation of the machine shown sectioned on the line 13-13 in Figure 7,

Figure 14 is an end elevation shown sectioned on the line 14-14 in Figure 7,

Figure 15 is an end elevation shown sectioned on the line 15-15 in Figure 7,

Figure 16 is an end elevation shown sectioned on the line 16-16 in Figure 7, and

Figure 17 is an exploded isometric view of a second embodiment of the chain track arrangement of the machine of the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS :

The IVT machine of the invention is shown in Figures 1 to 3 and 8 and 9 to include a frame 10 which carries a diametrically variable track arrangement 12, an output shaft 14 which passes centrally through the track arrangement 12, a drive sprocket 16 which is driven by an angular velocity input shaft 18, an idler sprocket 20, a driven chain 22, five extraction devices 24 which are connected to the output shaft 14, a radial arm 26 which is fixed to the outer race of each of the extraction devices, chain holders 28 which are slidably located on the arms 26 and which are fixed at equal intervals to the chain 22 and a machine control arrangement indicated generally at 30.

The chain 22 track arrangement 12, in this embodiment of the invention, is shown in Figures 4 to 7 to consist of a rear cover plate 32, a control plate 34 the front face of which carries a continuous spiralled groove 36, a guide plate 38 which carries radial slots 40 and chain support foot elements 42. :

The foot elements 42 are each shaped, as shown in Figure 5, to include a slide body 44, a chain support foot 46, and on the opposite side of the body, three rearwardly projecting key formations 48. The slide body is oppositely grooved with the grooves being slidably engaged with complementally shaped ribs in the slots 40 in the guide plate 38, as shown in Figure 5, when the feet are slidably located in the grooves 40. When so located on the guide plate 38 the feet 46 of the elements 42 project forwardly from the front face of the plate 38.

With all of the foot elements 42 located in the guide plate slot 40, as shown in Figure 6, the control plate 34 is pressed up against the back of the guide plate 38 with the key formations 48 of the foot elements 42 located in a uniform diameter in the spiral groove in the control plate. In this position the feet 46 provide a circular track 50 which carries the upper bite of the driven chain 22.

The chain track 50 is varied in diameter on the guide plate 38 by rotating the control plate 34 relatively to the plate 38 to cause the spiral groove 36 in the plate to wind the key formations 48 of the foot elements 42 radially upwardly or downwardly in the guide plate slots 40 in much the same fashion as the jaws in the lathe or drill chuck. The plates 34 and 38 are held together by the cover plate 32 which is fixed to the guide 38 plate by screws which pass through holes in its skirt and into threaded bores on the peripheral edge of the plate 38. A secondary purpose of the cover plate and its attaching screws is to stabilise the plate 38 sectors between the slots 40 against deformation by the cantilever loads imposed on them in use.

The assembled track arrangement 12 is shown in Figure 6 in which it is seen that the control plate 34 is fixed to a stepped boss 52. The lesser diameter portion of the boss 52 carries bearings in which the machine output shaft 14 is rotatable and a control gear 54 which is fixed to the boss 52. The guide plate 38 carries a rearwardly projecting boss 55 which is fixed to the output shaft 14 of the machine and is located in and rotatable relatively to the control plate 34 boss 52. ’ The arm 26 and sprag clutch 24 arrangement is illustrated in Figure 10. In the drawing the arms 26 have been shortened for ease of illustration and only one of the chain holders 28 is shown slidably located on one of the arms.

The five extraction devices 24, in this embodiment of the invention, are sprag clutches and are shown in Figure 10 to be axially aligned on the machine input shaft 14, not shown. To ensure that the arms 26 rotate in a common plane the first clutch from the right in the drawing and the second and fifth clutches are attached to spaced bearings 56 by bridge pieces 57 on which the arms are mounted for coplanar rotation.

The chain holder 28 in Figure 10 more clearly shows the holders to consist of a rectangular body which is holed by a hole which is complementally shaped to the cross-sectional shape of the arm 26 which carries it and includes two inwardly directed holed lugs which are attached to the chain 22 by elongated chain link pins. :

The track arrangement 12 is located in the machine of the invention by being mounted on the output shaft 14 which is in turn located in the machine in bearings 58 in the front and rear plate elements of the frame 10, as shown in Figures 3 and 7, in which it is journaled for rotation. The output shaft 14 carries an output gear 60 which is fixed to it as shown in Figure 6.

Figures 8 and 9 illustrate the relative positioning of the track arrangement 12, the chain tensioning, drive and idler sprockets 16 and 20 in the low and high ratio positions respectively of the machine.

As is more clearly seen in Figure 11 the sprockets 16 and 20 are carried on cranked arms 62 and 64. The sprocket 20 merely idles with its stub axle on bearings in the inner horizontal leg of the arm 64 and the drive sprocket is driven by the machine input shaft 14 which passes through bearings in an extended inner horizontal leg of the arm 62. The outer horizontal legs of the arms 62 and 64 are rotatably located in bearings or bushes, not shown, in partition walls 66 and 68 of the frame 10, as shown in Figures 1 and 3.

Link arms 70 are fixed to extensions to the inner legs of the arms 62 and 64. The arms 70 are pivotally connected at their free ends by a guide pin 72, as also shown in Figure 13, which is guided for movement in a vertical slot 74 in the frame partition wall 66. A control arm 76 is fixed to the outer horizontal leg of the arm 64 and carries at its free end a pivotal block 78 in which a control rod 80 is threadedly engaged. The rod 80 is slidably supported adjacent its non- threaded end in a support block 82 which is pivotally mounted to the rear face of the partition wall 68 as shown in Figure 16. The unthreaded end of the rod 80 carries a control wheel 84.

The chain sprockets 16 and 20 are, as is most clearly seen in Figures 3 and 7, situated in the frame 10 forwardly of the wall partition 66 and the link arms 70 against the rear face of the partition 66. The partition wall 66 and 68 includes two divergent arcuate slots 86, shown in

Figures 8, 9, 14 and 15, in which the rearwardly extending portions of the inner horizontal portions of the arms 62 and 64 are movable.

The Figure 9 chain tensioning sprocket arrangement is shown in the drawing in the low ratio position of the machine in which the chain track arrangement 50 is at its maximum diameter. As the machine ratio is increased by a reduction in the diameter of the track arrangement 12, as will be explained below, the resultant loss of tension of the driven chain 22, due to a slackening of the chain, is taken up by the sprockets 16 and 20 by movement of the sprockets towards their more spaced position from each other and the chain track at the high ratio position of the chain track 50, as shown in Figure 8, and by the dotted line positions of the sprockets in Figure 11.

The chain tensioning movement of the sprockets 16 and 20 is achieved by rotation of the control wheel 84 in Figure 11 in a clockwise direction to move the threaded block 78 towards the right in the drawing simultaneously with a reduction in the chain track 12. This movement of block 78 will cause the control arm 76 to follow the block 78 to the right and so rotate the sprocket arm 64 in a clockwise direction with this movement causing the link arm 70 to move downwardly to move the sprocket arm 62 concomitantly in an anticlockwise and down direction until the high ratio limit position of the dotted sprockets in Figure 11 is reached, and as is shown in Figure 8, or a desired ratio position between the limits is reached. To lower the ratio of the machine the control wheel 84 is rotated in an opposite direction.

As the angular velocity input shaft 18 to the machine follows the chain tensioning movement of the drive sprocket 16 it is necessary that the sprocket 16 input drive shaft is coupled to the prime mover which is to drive the machine through a flexible or like coupling. In this embodiment of the invention an intermediate shaft 87 which carries two universal joints 88 is employed to serve this purpose, see Figures 7, 3 and 15.

In addition to the chain tensioning arrangement which is described above with reference to

Figure 11, the machine control arrangement 30 includes the output gear 60 which is fixed to the output shaft 14 as shown in Figures 2, 3 and 7 and a substantially conventional differential gear arrangement 90 which is shown in Figures 2, 15 and 18.

The differential gear arrangement 90 includes a cage 91 which carries two bevel wheels 92, two differential pinions 94 which are carried by and rotatable on a common shaft 96 and a control gear 98 which surrounds and is fixed to the cage 91. One of the bevel wheels 92 is fixed to a shaft which carries a gear 100 which is driven by the machine output gear 60 through an idler gear 102. The remaining differential bevel wheel 92 is fixed to a shaft which is rotated by a gear 104 which is in turn driven by the control gear 54 which is attached to the control plate boss 52 of the track arrangement 12, as shown in Figure 6. The ratio between the output shaft gear 60 and the differential gear 100 is 1:1 in the same direction while the ratio between the control plate gear 54 and the gear 104 is 1:1 in the opposite direction.

In use, with an input angular velocity applied to the input shaft 18 rotating the driven chain 22 . and the track arrangement 50, rotation of the differential control gear and so the cage 91, will cause, through normal differential action of the cage bevel wheels and pinions, a differential in angular velocity across the differential gear arrangement 90 which will cause relative rotation of the control plate 34 relatively to the guide plate 38. This relative plate movement will cause the ring of chain support elements 42 to be wound by the spiral control plate groove radially outwardly or inwardly as required by the direction of rotation of the control gear 98 to "5 respectively increase or decrease the diameter of the chain track 50. The relative movement of the plates 34 and 38 will cease when rotation of the differential control gear is stopped.

In practice the control wheel 84 of the chain tensioning arrangement of Figure 11 and the control gear 98 of the differential arrangement 90 are replaced by any suitable hydraulic, mechanical or electrical positioning arrangement.

The operation of the machine of the invention is now described. For the purposes of this description it is assumed that a constant input velocity of 1000rpm is applied in the direction of the arrow on the drive sprocket 16 in Figure 8 and that the chain sprockets 16 and 20 have a chain drive radius of R, = 25mm. It is also assumed that the chain foot elements 42 of the chain track 50 can be positioned to produce a chain support radius, R, that varies from 60mm to 100mm. It is further assumed that the chain 22 has a link length of Lie, = 19mm and a total length of 38 links or Tie, = 19-38mm = 722mm.

In high ratio (top gear) the chain sprocket 16 will drive the chain 22 at a constant linear velocity,

Vin, of: 2.71-R,-V,, 2-n-100025 y

Vien z= —————————=261m's 60000 60000

With a chain track 50 chain support radius of R; = 60mm, as shown in Figures 1 and 8, the chain 22 will travel at a constant angular velocity, Vou, of

V,, -60000 2.61-60000

Vout skh To Te 415.39rpm in the direction of the arrow on the 2-7-R, 2.7.60 output shaft 14 in Figure 8 but only for the duration of 2-0 in Figure 8 relatively only to the input shaft 14.

On any other section of the chain 22 the angular velocity of the chain, relatively to the output shaft 14, is less than the constant angular velocity of the chain in the 2-6 section since any radius drawn from the output shaft 14 to any section of the chain 22 other than the above 2-0 section, will be larger than the chain track 50 radius R;.

The sprag clutch 24 on each arm 26 is set up to engage the output shaft 14 only if its outer race is rotated, by the arm 26 to which it is attached, faster than the output shaft 14 in the direction of the arrow on the output shaft 14 in Figure 8.

Thus whenever an arm 26 is travelling in the 2-0 section the sprag clutch will engage the respective sliding arm with the output shaft 14 and release it when out of the 2-6 section.

Since all the arms 26 are attached to the chain 26 by the chain holders 28 the respective arm 26 will be driven by the chain 22. A sufficient number of arms 26 are utilised to ensure that at all times at least one arm 26 operates in the 2-0 section.

In the low ratio configuration (low gear) the chain velocity will remain 2.61m-5". "With a chain track 50 chain support radius of R, = 100mm as shown in Figures 2 and 9 the chain will travel at a constant angular velocity, Vou, of

Vou = — = ———————— = 240.23rpm in the direction of the output shaft 2.-n-R, 2-7-100 arrow in Figure 9 but again only for the arm travel duration of 2-0 relatively only to the output shaft 14. ] As with the high ratio configuration, on any section of the chain 22 which is not in the 2-6 section the angular velocity of the chain, relative to the output shaft 14, is less than the constant angular velocity of the chain in the 2.0 above section since any radius drawn from the output shaft 14 to any section of the chain 22 other than the above 2-0 section, will be larger than the chain track 50 radius R;.

Erom the above it will be appreciated that because of the output shaft 14 sprag clutch 24 and arm 26 drive arrangement the use of highly advanced traction fluid, as required by the prior art machines, is eliminated in the IVT machine of this invention and therefore no fimitations exist within the machine kilowatt or torque output ranges and high power applications above 130kw are easily accommodated.

The invention is not limited to the precise details as herein described. For example:

The arms 26 could be made telescopic, to make the machine more space economical, and the arm holders 28 could be eliminated with the ends of the arms being directly connected to the chain 22.

The drive sprocket 16 could be fixed in the frame 10 with the idler sprocket 20 being located on a longer and perhaps spring biased arm to cater for chain slack.

The illustrated track arrangement could be replaced by the track arrangement illustrated in

Figure 17 in which the guide plate 38 remains substantially unchanged except that its boss 55 is

Claims

1. An infinitely variable transmission machine including a frame (10) which carries: ] an endless flexible driven element (22), a circular track arrangement (12) which is variable in diameter and on which the driven element (22) bears in use means (34,106) for varying the diameter of the track arrangement (12), an angular velocity output shaft (14) which passes centrally through the track arrangement (12), a driven angular velocity input wheel (16) which is engaged with the driven element (22), and means (20) for holding the driven element (22) in tension as the diameter of the track arrangement (12) is varied to vary the ratio of rotation of the output shaft (14) relatively to that of the input wheel (16). Characterised in that the machine includes: a plurality of extraction devices (24) which are fixed adjacent to each other to the output shaft (14), an arm (26) which is connected to and extends in a radial direction from each of the extraction devices (24) with all of the arms (26) being rotatable about the output (14) shaft in a common plane with the driven element (22) being connected to each of the arms (26) at spaced intervals over its length in such a manner that the driven element (22) is movable in the axial direction of the arms (26) so that the output shaft (14) will be engaged and partially rotated by each of the extraction devices (24) in turn to cause a single revolution of the output shaft (14) when the arm (26) to which it is connected achieves a greater angular velocity than that of the output shaft (14) as the driven element (22) is driven over the track arrangement (12).

2. A transmission machine as claimed in claim 1 wherein the track arrangement (12) comprises a radially slotted guide disc (38), which is fixed to the machine output shaft (14), foot elements (42) in each of the disc (38) slots (40) with each element (42) including a body (44) which is slidably engaged in the slot (40), a foot (46) on the body (44) which projects outwardly from one face of the disc (38) so that the feet (46) collectively define a circular track (50) for the driven element (22) and a drive formation (48) on the body (44) which projects from the opposite face of the disc (38), and means (34,106)for concomitantly moving the foot element (42) drive formations (48) radially inwardly and outwardly in the disc slots (40) to vary the diameter of the circular track (50).

3. . A transmission machine as claimed in claim 2 wherein the foot element (42) moving means (34,106) is a control disc (34) which is rotatable about the machine output shaft (14) and carries a continuous spiral groove (36) in which the drive formations of the foot . elements (42) are slidably located in a circle which is concentric with the machine output shaft (14) axis about which the foot elements (42) are moved inwardly and outwardly in the guide disc (38) slots(40) on rotation of the control disc (34) relatively to the guide disc (38).

4, A transmission machine as claimed in claim 2 wherein the guide disc (38) is fixed to the machine output shaft (14) and the foot element (42) moving means is a control disc (106) which is rotatable by and with the guide disc (36), is movable towards and away from the guide disc (38) and has a radially grooved frusto conical face which faces the guide disc (38), the foot element (108) drive formations (109) are elongated in the axial direction of the control disc (108) with their free ends engaged with and slidably located in the control disc (106) slots (110) so that relative movement of the guide (38) and control discs (106) toward and away from each other in the axial direction of the machine output shaft (14) will cause the foot elements (108) to move radially inwardly and outwardly in the slots (110) of the guide (38) and control discs (1086) to vary the diameter of the circular track.

5. A transmission machine as claimed in claim 1 wherein the track arrangement (12) comprises two discs which have facing frusto conical faces with at least one of the discs being rotated by the machine output shaft, a composite driven element which consists of two driven elements (22) which are each located over one of the conical faces of the discs and are held in a parallel spaced relationship by pins which pass through them with the extraction device (24) arms (26) being located, at equally spaced intervals of the composite drive element, in spaces between the pins between the two driven elements (22) and means for holding each of the driven elements in tension as the diameter of the track arrangement (50) is varied.

6. A transmission machine as claimed in any one of the above claims wherein the or each : driven element (22) is a chain and the input wheel is a sprocket (16) which is driven by an angular velocity input shaft (14).

7. A transmission machine as claimed in claim 6 wherein the or each chain tensioning means is a movable idler sprocket (20) which is engaged with the chain (22) between the track arrangement (12) and the driven input sprocket (186).

8. A transmission machine as claimed in claim 7 wherein the input (16) and idler (20) sprockets are carried on cranked arms (62,64) which are each rotatably mounted in a ’ frame component (66,68) of the machine and are movable between a first position in which the sprockets (186,20) are adjacent each other and a second position in which they are spaced from each other at a position further from the track arrangement (12) than they are in their first position and the machine includes control means (180) for moving the cranked arms (62,64) between their two position of operation, as the diameter of the track arrangement (12) is varied, to hold the chain (22) in tension.

9. A transmission machine as claimed in claim 3 wherein the track arrangement (12) diameter varying means is a differential gear arrangement (90), in which one of the bevel wheels (92) is gear (80) driven from the machine output shaft (14)and the opposite bevel

15 . wheel (92) is driven in the opposite direction by a gear (54) on the control disc (34) with the control disc (34) being rotated relatively to the guide disc by causing a differential angular velocity across the differential gear (90) by rotating the differential gear cage (91) by a controller.

10. a transmission machine as claimed in claim 9 wherein a suitable machine controller controls both the chain (22) tensioning (16,20) and differential gear (90) controllers (80,98) to hold the driven chain (22) in tension as the diameter of the chain track (50) is varied.

11. A Transmission machine as claimed in any one of the above claims wherein the or each flexible drive element (22) is a transversely ribbed belt and the or each angular velocity input wheel is a wheel having a ribbed tread surface.

©

12. A transmission machine as claimed in any one of the above claims wherein the extraction device (24) arms (26) are telescopic in length with their free ends connected at spaced intervals to the flexible drive element (22).