BACKGROUND OF THE INVENTION Mechanical transmissions have generally relied upon gears, planetary devices, belts, chains, clutch packs and the like to transmit torque from a power source to an apparatus. Such transmissions are usually complex requiring a substantial number of components which are often expensive to manufacture and/or assemble. Another disadvantage of such traditional mechanical transmissions is that the complex componentry causes significant power loss due to friction, heat and/or vibration. Moreover, such transmissions permit generally only a limited number of stepped ratios.

Variable ratio power transmissions have been disclosed which produce substantially continuous variation of ratios between an input and an output means, for example by the VARIOMATIC™ belt drive transmission adopted in DAF™ motorcars and the Perbury type transmission which utilises disc rollers bearing against toroidal members. Both transmissions rely on friction for their drive and their continuous variability of drive ratio. However, operation of these transmissions at relatively high torque generally causes the belts associated therewith to stretch and hence only very limited torque can be transmitted therewith.

OBJECT OF THE INVENTION It is therefore an object of the present invention to provide a continuously variable ratio power transmission to enable high torque levels to be transmitted between a power source and an apparatus.

Other objects will become apparent from the following description.

SUMMARY OF THE INVENTION According to one aspect of the present invention, there is provided a continuously variable power transmission comprising: an input means and an output means operatively associated with a disc member therebetween; said input means comprising a cone-shaped driving member rotatable about an axis thereof, and having a contact surface adapted to contact said disc member; said output means comprising at least one cone-shaped driving member which is rotatable about an axis thereof and which has a contact surface adapted to contact said disc member, said drive member of said input means and said at least one drive member of said output means being spaced from each other; and said disc member rotatable about an axis thereof and in releasable driving engagement with the contact surface of said drive member of said input means and the contact surface(s) of said at least one drive member of said output means to effect transmission of rotation from said input to said output means, and being moveable across said contact surfaces to vary the transmission ratio between said input and said output means.

Preferably, one of said driving members is adapted to provide reversible transmission. For example, one of said driving members may have two frusto-conical portions: a first frusto-conical portion adapted to provide forward transmission; and a second frusto-conical portion adapted to provide reversible transmission.

Suitably, the first and second frusto-conical portions converge in the same direction.

Preferably, the first and second frusto-conical portions are

operatively associated with an output shaft.

Preferably, the second frusto-conical portion is operatively associated with a planetary gear which is adapted to rotate the output shaft in an opposite direction to the direction of rotation of the second frusto-conical portion.

Suitably, the planetary gear is operatively associated with the output shaft.

The disc member preferably comprises a raised portion adapted to be engaged with the contact surfaces of said input and said output means.

In preference, the raised portion is a peripheral edge portion of the disc member.

The disc member preferably comprises a frictional material capable of high inter-frictional engagement with the contact surfaces of said input and said output means in use. It will be appreciated that the type of frictional material used will vary in accordance with the material used for said contact surfaces.

For example, the frictional material may be asbestos, leather, a metal, a plastics material, a ceramic or a fibre-reinforced material such as, for example, a woven carbon or metal fibre-reinforced material, or a combination of any two or more of these.

Preferably, the frictional material is a deformable frictional material.

Preferably, the raised peripheral edge portion comprises a plurality of spaced teeth. In such a case, it will be appreciated that use of spaced teeth in engagement with the contact surfaces of said input and said output means may substantially reduce wear of the frictional material.

The contact surfaces of said input and output means, for example, may be comprised of a metal, a ceramic or a plastics material or a combination of any two or more of these.

Preferably, the contact surfaces of said input and said output

means are comprised of metal and the frictional material is a fibre- reinforced material such as, for example, a metal fibre-reinforced material.

Preferably, said driving members have a substantially smooth peripheral surface. Preferably, apexes of said driving members are directed towards each other.

Alternatively, bases of said driving members are directed towards each other.

Preferably, the output means comprises one driving member.

The driving members preferably comprise a plurality of capillaries adapted to be charged with a fluid. In such a case, it will be appreciated that charging the plurality of capillaries with the fluid, such as a transmission fluid, may substantially increase the dissipation of heat from said driving members in use.

Suitably, said driving members are fixed to, or formed integrally with a respective shaft.

The driving members of said input and said output means may have any suitable dimension. Suitably, the dimensions of said driving members are substantially identical.

The driving members are preferably of substantially equivalent axial length.

Where frictional contact between the disc member and the contact surfaces of said input and said output means is relied upon for transmission of power between the input to the output means, the engagement of said disc member must provide sufficient loading of the disc member against the respective contact surfaces to transmit adequately the available power in the required ratio and through the required range of ratios.

Such loading may be effected by any suitable means. For

example, the disc member may be operatively associated with an actuating means such as, for example, a hydraulic or pneumatic ram, for reversible engagement of the disc member with the contact surfaces of said input and said output means. In such a case, the actuating means is preferably adapted to vary the loading of the disc member against said contact surfaces.

Movement of the disc member across the contact surfaces of said input and said output means may be effected by any suitable means to vary the transmission ratio between the driving members of said input and said output means.

Preferably, movement is effected by mechanical, electrical, magnetic, or hydraulic means. Alternatively, movement is effected by manual operation.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be readily understood and put into practical effect, preferred embodiments will now be described with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of a housing in which a continuously variable ratio power transmission according to the present invention is located therewithin;

FIG. 2 is a top plan view of the housing of FIG. 1 showing input and output shafts protruding outwardly of the housing;

FIG. 3 is a side plan view of the housing of FIG. 1 taken normal to the longitudinal axis of the housing; FIG. 4 is a side plan view of the housing of FIG. 1 taken along the longitudinal axis of the housing;

FIG. 5 is a longitudinal cross-sectional view taken along line A-A of FIG. 2 showing the transmission of FIG. 1 wherein an input cone- shaped driving member and an output cone-shaped driving member are mounted such that the bases thereof are directed towards each other;

FIG. 6 is a perspective view of an internal housing in which

input and output cone-shaped driving members of the variable ratio power transmission of FIG. 1 are mounted therewithin;

FIG. 7 is a longitudinal cross sectional view of the internal housing of FIG. 6 taken along line A-A of FIG. 2; FIG. 8A is a part cross-sectional view of the disc carriage of the transmission according to FIG. 1 ;

FIG. 8B is a cross sectional view of another embodiment of a raised peripheral edge portion of the disc member according to the invention; FIG. 8C is a cross sectional view of yet another embodiment of a raised peripheral edge portion of the disc member in accordance with the invention;

FIG. 9 is a perspective view of the output cone-shaped driving member of the variable ratio power transmission of FIG. 1 showing a planetary gear assembly of the output driving member.

FIG. 10 is a schematic perspective view of an alternative embodiment of the variable ratio power transmission according to the invention depicting rotational movement of the input cone-shaped driving member, the output cone-shaped driving member and a disc member therebetween;

FIG. 11 is a longitudinal cross sectional view of the transmission of FIG. 10.

FIG. 12 is a side plan view of an alternative embodiment of the input and output driving members according to the invention; FIG. 13 is a cross sectional view of an alternative embodiment of a continuously variable ratio power transmission according to the invention showing an input cone-shaped driving member and an output cone-shaped driving member being mounted such that the bases thereof are directed towards each other. DETAILED DESCRIPTION

Referring now to the figures and more particularly to FIGS.

1-5, there is illustrated an embodiment of the continuously variable power transmission according to the invention. The transmission shown generally at 10 comprises a housing 11 having cover 12 releasably engagable with box 13. Cover 12 has an upper wall 14, side walls 15, 16, 17, 18 and continuous flange 19 extending along side walls 15-18 as shown. Box 12 has a base 20, side walls 21 , 22, 23, 24 and a continuous flange 25 extending along side walls 21-24 as shown. Cover 12 is releasably engagable with box 13 through apertures 12A, 12B, 12C, 12D of continuous flange 19 and corresponding coaxially aligned apertures (not shown) of continuous flange 25.

Complementary surfaces (not shown) of flanges 19 and 25 abut each other and act as sealing surfaces. Accordingly, these surfaces may be used, for example, in concert with a sealing gasket to seal the housing 11 and thereby substantially prevent leakage of fluids such as transmission fluids therefrom.

Upper wall 14 comprises an opening covered by circular plate 26 which provides access into a compartment in which is disposed a disc member 56 on disc carriage 56A of the transmission 10 described in more detail hereinafter. The circular plate 26 is releasably mounted over this opening through apertures 26A, 26B, 26C, 26D. Substantially towards the centre of plate 26, there is also provided a channel in which is slidably mounted hydraulic cut-off switch 27.

Closely adjacent the peripheral boundary of upper wall 14 adjacent side walls 15 and 17 are channels 28, 29, 30, 31 which communicate with hydraulic rams 63, 64 (described hereinafter) which, in use, vary the loading of the disc member against input and output driving members 40, 41 of the transmission 10 (as shown in FIG. 5).

Side wall 15 comprises channels 32, 33 in which seal bearings 32A and 33A are mounted respectively. Drive screws 34, 35 are mounted in bearings 32A, 33A for displacing the disc member in a direction parallel to the longitudinal axis of the housing 10.

Side walls 21 and 23 of container 13 comprise elongate slots 21 A and 23A through which main output shaft 36 and main input shaft 37 protrude outwardly therefrom for engagement to an apparatus and a power means respectively. Now turning to FIG. 5-8, the transmission 10 is shown in more detail. With particular reference to FIG. 5-7, the transmission 10 comprises input cone-shaped driving member 40 and output cone-shaped driving member 41 mounted in W-shaped internal housing 42 disposed inside box 13. Input and output drive members 40, 41 are fixed respectively on intermediate shafts 43, 44. Respective terminal portions 43A, 44A of intermediate shafts 43, 44 are rotatably engagable with bearings 45, 46 anchored in boss 47 of internal housing 42. Coaxially mounted on terminal portions 43B, 44B of intermediate shafts 43, 44 are bevelled gears 48, 49 which rotatably engage bevelled gears 50, 51 coaxially mounted on terminal portions 37A, 36A of input shaft 37 and output shaft 36 respectively. Input and output shafts 37, 38 extend outwardly from housing 42 through seal bearings 38, 39 operably connected to underside of plate 42A of internal housing 42.

Each of the input and output driving members 40, 41 has a substantially smooth peripheral surface. The input driving member 40 has an input contact surface 52 and the output driving member 41 has an output contact surface 53. The input and output driving members 40, 41 are spaced from each other and are mounted such that the apexes thereof are directed towards each other and respective contact regions 54, 55 of the input and output contact surfaces 52, 53 in engagement with disc member 56 (to be hereinafter described) are in substantially co¬ planar contact.

The output driving member 41 has two frusto-conical portions 41 A, 41 B which converge in the same direction. Whereas frusto- conical portion 41 A provides forward transmission, frusto-conical portion 41 B provides reverse transmission by way of a planetary gear assembly

57 operatively associated therewith and adapted to rotate shaft 44 in an opposite direction to the direction of rotation of frusto-conical portion 41 B. Referring now to FIG. 8A, the disc carriage 56A is shown with disc member 56 releasably engaging contact regions 54, 55 of input and output contact surfaces 52, 53. Disc member 56 is rotatable about an axle 58 disposed substantially normal to contact regions 54, 55. Axle 58 is mounted in block housing 69 operably connected to hub 91 of disc member 56. Block housing 69 is also operably connected to sleeve 90 slidably mounted on load shaft 65 extending substantially parallel to the longitudinal axis of housing 11. Accordingly, disc member 56 is adapted to be laterally displaced across input and output contact surfaces 52, 53 in order to change the transmission ratio between input and output drive members 40, 41.

Disc member 56 comprises a bottom surface 59 and an upper surface 60. The bottom surface 59 comprises a raised peripheral edge portion 61 which, in use, engages the input and output contact surfaces 54, 55. The raised peripheral edge portion 61 comprises a frictional material 62 capable of high inter-frictional engagement with the input and output contact surfaces 54, 55 in use. In this embodiment, frictional material 62 is formed of a metal fibre-reinforced material having a substantially planar surface engaging contact surfaces 54, 55. In a preferred embodiment shown in FIG. 8B, the frictional material 62 is formed with a plurality of spaced teeth 62A which are adapted to substantially reduce wear of frictional material 62. Alternatively, the frictional material shown in FIG. 8C may comprise a deformable woven fibre-reinforced material 62C adapted to be charged with transmission fluid to increase dissipation of heat from the fibre-reinforced material 62C and, in use, maximizing surface contact with contact surfaces 54, 55.

In order to effect sufficient loading of the raised peripheral edge portion 61 against the input and output contact surfaces 54, 55 such that the available power is transmitted in the required ratio and through

the required range of ratios, there is also provided hydraulic rams 63, 64 which communicate with a suitable hydraulic system (not shown) through channels 28-31 mentioned above. In use, hydraulic rams 63, 64 effect upright displacement of end blocks 81 A, 81 B operably connected to terminal portions of load shaft 65 thereby varying the loading of the raised peripheral edge portion 61 against the input and output contact surfaces 54, 55.

At terminal portions 90A, 90B of sleeve 90 are operably connected conical bearings 66, 67 rotatably engaging an elevated peripheral flange 68 of upper surface 60 of disc member 56.

Block housing 69 comprises lobe 80 operatively associated with hydraulic cut-off switch 27 of a hydraulic cut-off mechanism (not shown). This mechanism effects upward displacement of rams 63, 64 thereby disengaging the raised peripheral edge portion 61 from the input and output contact surfaces 54, 55 when the raised peripheral edge portion 61 is displaced laterally from frusto-conical portion 41A to frusto- conical portion 41 B and vice-versa. Thus, the cut-off mechanism effects a neutral gear intermediate forward and reverse transmission. It will be appreciated that an electrical cut-off switch may be used in substitution of the hydraulic cut-off mechanism.

To vary the transmission ratio between the input and output driving members 40, 41 , disc member 56 is displaced laterally across the input and output contact surfaces 54, 55 by use of an actuating means in operative association with drive screws 34, 35 operably connected to block housing 69.

In use, disc member 56 is laterally displaced so that its points of contact with input and output contact surfaces 54, 55 are varied. As the input and output driving members 40, 41 are inversely convergent, this varies the ratios of circumferential contact between input and output driving members 40, 41 and disc member 56 and thereby the transmission ratio between the minimum and maximum circumferences of

input and output driving members 40, 41.

With reference to FIG. 9, the planetary gear assembly 57 is more clearly shown comprising outer ring gear 74, sun gear 76 and planetary gears 77, 78, 79. In use, gears 77, 78, 79 rotate in planetary relationship with sun gear 76 and outer ring gear 74 such that shaft 44 rotates in an opposite direction to frusto-conical portion 41 B. This effects reverse transmission which is communicated to an apparatus through bevelled gear 49 in operative association with bevelled gear 51 and output shaft 36. In another embodiment of the continuously variable ratio power transmission of the invention, there is shown in FIGS. 10 and 11 a transmission 100 which is substantially similar to transmission 10 except that hydraulic rams 63, 64 are operatively associated with corresponding spring members 101 , 102 for upwardly displacing shaft 65 to effect a neutral gear by disengaging the raised peripheral edge portion 61 from the input and output contact surfaces 54, 55. Hydraulic rams 63, 64 are in fluid communication with a hydraulic cut-off mechanism 120 in operative association with cut-off switch 27.

Also shown are drive screws 34, 35 extending through complementary threaded channels of block housing 69 operably connected to hub 91 of disc member 56. At terminal portions of drive screws 34, 35 are coaxially mounted cogs 34A, 35A having chain 110 rotatably connected therebetween. Lateral displacement of disc member 56 is effected by synchronous rotation of drive screws 34, 35 by electric servo motor 111.

It will be appreciated that hydraulic rams 63, 64 and electro servo motor 111 may be operably connected to a computer or microprocessor to effect respectively automatic control of the loading of the raised peripheral edge portion 61 against the input and output contact surfaces 54, 55 and automatic control of the transmission ratio between the input and output driving members 40, 41.

Turning now to FIG. 12, there is shown an alternative embodiment of the input and output driving members in accordance with the invention. In this embodiment, respective input and output driving members 301 , 302 comprise a plurality of capillaries 303 extending internally of contact surfaces 304, 305 of driving members 301 , 302. In use, capillaries 303 are charged with a transmission fluid which effects a substantial increase in dissipation of heat from driving members 301 , 302. Referring now to FIG. 13, there is illustrated a cross sectional view of an alternative embodiment of a continuously variable ratio power transmission 201 according to the invention wherein the respective orientations of input and output cone-shaped driving members 202, 203 have been inverted with respect to those of the previous embodiments such that the bases of the driving members 202, 203 are directed towards each other. Otherwise, transmission 201 is substantially the same as transmission 10 described above in that it comprises disc member 56 in releasable engagement with input and output cone-shaped driving members 202, 203 and being movable across contact surfaces 204, 205 of driving members 202, 203 to vary the transmission ratio therebetween. Output driving member 203 has two frusto-conical portions 203A, 203B; frusto-conical portion 203A effecting forward transmission and frusto-conical portion 203B effecting reverse transmission by use of planetary gear assembly 57. Disc member 56 is rotatably mounted on disc carriage 56A which is laterally displaceable along load shaft 65. Input and output shafts 37, 36 are operatively associated with a power means and an apparatus respectively.

In comparison to the orientation of the cone-shaped driving members in the previous embodiment, the orientation of driving members 202, 203 provides a more compact arrangement of parts which may be useful in applications where an economy of space is required. The present invention provides a simple, yet efficient, means to provide a continuously variable ratio power transmission to enable high

torque levels to be transmitted between a power source and an apparatus. The gearing ratio of the transmission can be changed on a continuous basis within a stepless range.

Intended applications for the transmission include vehicle transmissions, machinery drives and the like.

While the invention has been described with respect to preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention. Accordingly, it is intended that all matter contained in the above description, or shown in the accompanying drawings shall be interpreted as illustrative and not in limiting sense.