WO2012054984A1

WO2012054984A1 - Torque reversal and clutch gear coupling

Info

Publication number: WO2012054984A1
Application number: PCT/AU2011/001383
Authority: WO
Inventors: James Kwok
Original assignee: James Kwok
Priority date: 2010-10-27
Filing date: 2011-10-27
Publication date: 2012-05-03

Abstract

A clutch gear assembly adapted to engage and transmit rotation from an input shaft to an output shaft when the input shaft is subject to a predetermined amount of torque, and adapted to disengage when the input shaft is subject to less than a predetermined amount of torque.

Description

TORQUE REVERSAL AND CLUTCH GEAR COUPLING

FIELD OF THE INVENTION

The present invention relates to a clutch gear assembly. In some embodiments, the invention is directed to a torque reversal and clutch gear coupling, although the scope of the invention is not necessarily limited thereto.

BACKGROUND

Clutch gears such as roller-clutches, spragg gears, pinroller clutches, bicycle gear hubs and ratchet gears are available in the marketplace and are used to allow a drive shaft to free-wheel in the same direction as a power shaft

Existing clutch gears are limited in their ability to allow a drive shaft to 'freewheel'. A problem with existing clutch gears is that the drive shaft is unable to 'freewheel' (rotate) in a direction opposite to the torque direction of the power shaft when there is no torque applied to the power shaft.

In some instances the free-wheeling of a drive shaft in the same direction as the torque direction of . a power shaft may be undesirable while the power shaft is under torque. In these instances more complicated equipment is used leading to increased power consumption, emissions, maintenance and repairs.

Another disadvantage with existing clutch gears is that they cannot be used in large machinery such as cranes and air-compressor units and the like, these types of machines require the power shaft to be under torque in both directions without any free wheeling or may require an additional manually controlled clutch.

It is an aim of the invention to provide a clutch gear which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides the consumer with a useful or commercial choice.

It will be clearly understood that any reference herein to background material or information, or to a prior publication, does not constitute an admission that any material, information or publication forms part of the common general knowledge in the art, or is otherwise admissible prior art, whether in Australia or in any other country.

DESCRIPTION OF THE INVENTION

In one aspect, the present invention provides a clutch gear assembly comprising: a rotatable input shaft; a power frame mounted for rotation with the input shaft; a rotatable output shaft; a drive member mounted for rotation with the output shaft; at least one support frame mounted for rotation relative to either the input shaft or the output shaft; at least one spindle rotatably mounted to at least one of the at least one support frame; at least one first dog, each fixedly mounted to one of the at least one spindle; at least one second dog, each fixedly mounted to the spindle to which the at least one first dog is mounted, the at least one first dog moveable between a first disengaged condition and the second engaged condition by rotational separation between the power frame and the at least one support frame to which the at least one spindle is rotatably mounted, through the at least one second dog; a biasing means operatively associated with the spindle such that the at least one first dog is biased into a first disengaged condition where it is disengaged from the drive member; wherein when the input shaft is subject to a predetermined amount of torque in a first direction, the rotational separation between the power frame and the at least one support frame to which the at least one spindle is rotatably mounted motivates the at least one second dog against the biasing force of the biasing means to move the at least one first dog into the second engaged position, engaged with the drive member such that the rotation of the input shaft causes rotation of the output shaft.

Like most clutch gear assemblies, clutch gear assemblies in accordance with the present invention will typically operate to convey rotation generated by a prime mover at the input shaft to rotation at the output shaft or to disengage the output shaft from the relative rotation of the input shaft. .

It is envisaged that the kind of prime mover with which the invention will most often be used will be an internal combustion engine or an electric motor. However, the clutch gear assembly of the present invention could alternatively be used with any other form of prime mover capable of generating rotational motion, for example windmills, water wheels, manually rotated cranks etc or a combination thereof. Other possible prime movers which could be used to drive rotation of the clutch gear assembly will be recognized by those skilled in this area.

The clutch gear assembly will incorporate means for transmitting the rotation generated by the prime mover into a transmission system. Most typically, the prime mover will have a drive shaft, crankshaft or something similar which "outputs" the rotational motion generated by the prime mover. In these cases the clutch gear assembly may be provided with an input shaft which can be connected to the drive shaft of the prime mover, or linked with that drive shaft (possibly by way of a series of linkage components or some other mechanism) so that rotation is transmitted into the clutch gear assembly via the input shaft. Therefore, an input shaft is probably the most common form of "input" or "rotation input means" that will be used with the present invention.

However, input shafts are not the only means by which the transmission system can receive rotation from the prime mover. For example, the drive shaft of the prime mover could extend directly into the transmission system, in which case one of the internal components of the clutch gear assembly (such as an input gear or shaft etc) may incorporate a socket, slot or other aperture into which the drive shaft of the prime mover can insert, or to which the drive shaft can otherwise connect. Alternatively, an internal component in the clutch gear assembly may have a plug or protrusion of some kind which inserts into a socket in the end of the prime mover's drive shaft to thereby connect the drive shaft. In these cases, the socket, slot, plug, protrusion etc on or in the clutch gear assembly's internal component is the "input" or "rotation input means" which delivers rotation from the prime mover into the clutch gear assembly. Other rotation input means may be used as well, for example hydraulic linkages. Further possible rotation input means or mechanisms (or combination thereof) will be known to those skilled in the art, and any such means fall within the scope of the invention.

The clutch gear assembly will also incorporate means for "outputting" or delivering the rotation which has been transmitted and possibly converted by the clutch gear assembly. In other words, the clutch gear assembly will preferably have means for conveying the rotation to whatever rotational machine or other apparatus the clutch gear assembly is being used to drive. Similar considerations apply to this "output" or "rotation output means" as were discussed above in relation to the rotation input means. Therefore, the clutch gear assembly will most typically be provided with an output shaft which can be connected to the machine/apparatus which the clutch gear assembly is driving, or somehow linked with that machine/apparatus (possibly by way of a series of linkage components or some other mechanism) so that rotation is transmitted into the machine/apparatus. However, any of the possible mechanisms or arrangements discussed above in relation to the rotation input means may equally be used for the rotation output means.

In one embodiment, the input shaft and output shaft may be adapted to be rotatably mounted to each other. This type of arrangement may provide additional support to the input and output shafts. Typically, a male-female engagement is provided between the shafts. This engagement will normally be provided at a free end of each of the shafts. Alternatively, other mechanisms for supporting the shafts relative to each other may be provided. For example, the shafts may be provided with bearings such that the shafts are rotatably mounted relative to each other. However, other means to achieve the same results are envisaged including the use of bushes, surface finishes and/or the like. No particular limitation should be placed on the invention by the manner in which the input shaft and output shaft are rotatably mounted relative to each other.

The power frame is mounted for rotation with the input shaft and will typically be operatively associated with the input shaft. The power frame is typically formed with or engages with the input shaft. Preferably power frame is fixedly attached to the input shaft.

Normally the power frame will have at least one arm and preferably a plurality of arms extending radially outwardly terminating at a free end. Alternatively the power frame may be disc like. Normally the arms will radiate from a central collar which attaches to the input shaft according to a preferred embodiment.

Typically the power frame will comprise at least one aperture and normally a number of apertures defined by at least one wall. The at least one aperture is preferably located towards the periphery of the power frame.

According to the radially extending arm embodiment, each of the arms will preferably be provided with at least one aperture located towards the free end of each of the arms.

The apertures preferably extend into the power frame and are shaped and adapted to engage with one of the at least one second dog, through abutment of the at least one second dog with a periphery of the aperture in which the at least one second dog is preferably located, when the clutch gear assembly is in the second condition.

Alternatively, other mechanisms for engaging the at least one second dog may be provided. For example, the power frame may include at least one bearing surface such that the at least one second dog can engage with the power frame.

In one embodiment, more than one support frame is provided and a support frame may be mounted for rotation relative to either or both of the input shaft and/or the output shaft. Alternatively, other means for mounting the at least one support frame may be provided. For example, the at least one support frame may be mounted relative to an outer casing and/or other component of the clutch gear assembly. Normally the at least one support frame will have at least one arm extending to a free end. Alternatively the at least one support frame may be disc like.

Normally, each support frame is adapted to rotatably mount at least one spindle thereto. Each spindle is preferably mounted towards the free end of the support frame. If the at least one support frame comprises at least one arm, each of the at least spindle is preferably mounted towards the free end of each of the at least one arm. If the at least one support frame is configured as a disc, each spindle is preferably mounted towards an outer edge of the disc.

Each spindle is preferably operatively associated with one of the at least one second dogs and one of the at least one first dogs.- Each spindle is typically formed with or engages with the at least one second dog and/or the at least one first dog. Preferably, the dogs will be fixedly mounted to the spindle such that rotation of the spindle causes rotation of the dogs.

Typically, each spindle will be substantially rod-like in shape. Alternatively the at least one spindle may be any appropriate shape provided that the at least one spindle is rotatably mounted relative to the power frame and/or the at least one support frame. The spindle may be substantially identical to the shape of the at least one first dog and/or the at least one second dog such that the transition between the dogs and the spindle may not be noticeable.

Each spindle will preferably have at least one first dog and at least one second dog attached thereto. The dogs are preferably spaced from one another over the length of the spindle and may be spaced radially as well.

The biasing means may be at least one spring, magnet, resilient material and/or the like. Normally the biasing means is at least one torsion spring. The biasing means typically biases the at least one spindle into a first position where the at least one first dog is disengaged from the drive member. The biasing member normally provides a biasing force between the support frame and the spindle. However, other means to achieve the same results are envisaged including providing a biasing force between at least one of the at least one support frame and one of the at least one first and/or second dog. The biasing member may be adjustable to prevent the at least one first dog from moving into an engaged position with the drive member until a predetermined amount of torque is applied to the power frame.

A predetermined amount of torque can also be referred to as equal to or greater than a minimum amount of torque or a threshold torque ττ. In another embodiment, the at least one second dog is typically formed with or engages with the spindle. The dogs may be finger shaped, wedge shaped, cam shaped and/or the like. Dogs are well k ow in the art and no particular limitation should be placed on the invention by the shape of the at least one second dog.

In one embodiment, the at least one first dog is typically formed with, is attached to or engages with the spindle. The at least one first dog may be a clutch dog as used in dog clutches. The dogs may be finger shaped, wedge shaped, cam shaped and/or the like. Dogs are well know in the art and no particular limitation should be placed on the invention by the shape of the at least one first dog. Preferably, the at least one first dog is shaped to correspondingly engage with the drive member when in the second condition. For example, if the drive member is a gear, the part of the at least one first dog adapted to engage with the drive member may be substantially tooth shaped.

In another embodiment, the at least one first dog may be shaped to engage with the drive member in a third position. Typically in this embodiment the at least one first dog is V shaped. Alternatively, other shapes may be provided for the at least one first dog. For example, the at least one first dog may be X shaped, triangular and/or the like.

The at least one first dog may also be substantially gear shaped wherein the teeth of the gear shaped at least one first dog do not engage with the drive member in the first position. Typically, if the at least one first dog is shaped to engage with the drive member in a third position, the at least one second dog will also be shaped to engage with the power frame in a third position.

The at least one second dog may be similarly shaped to the at least one first dog. Alternatively the at least one second dog may be fin shaped and adapted to engage with the power frame in the second position at one end of the fin shape and in the third position at an opposed end of the fin shape.

Where the dog has a V-shape the dog may be used to engage with the drive member in a second position in either direction when the input shaft is subject to a predetermined amount of torque. In this embodiment, the first condition or position of the dog is typically located between the position of the dog when in either one or two second positions. In either second position, the dog will typically be engaged but engaged for rotation in the opposite direction. For example, rotation in a second direction such that the at least one second dog engages with the power frame and is rotated against the biasing force of the biasing means into an alternative second position causing the at least one first dog to rotate into the an alternative second position such that the rotation of the input shaft causes rotation of the output shaft.

Typically when the input shaft is subjected to less than a predetermined amount of torque the at least one second dog is biased by the biasing means into the first position causing the at least one first dog to rotate into the first position disengaging from the drive gear such that the rotation of the input shaft does not cause rotation of the output shaft. The input shaft may continue to rotate without any rotation of the output shaft until the threshold torque is applied to the input shaft. Normally when the at least one first dog is disengaged from the drive gear, the output shaft is free to rotate in any direction independently of the input shaft.

In one embodiment, the friction means may be a brake assembly and/or the like providing relative friction between the at least one support frame and a casing. Alternatively, other means for imparting friction on the at least one support frame may be provided. For example, the friction means may be the natural tendency of the support frames to rotate slower than the power frame when the power frame is subject to torque.

The friction means may be a fluid applied to at least one of the at least one support frame and/or the at least one spindle and/or the at least one second dog and/or the at least one first dog. Many means of applying friction are known in the art and no particular limitation should be placed on the invention by the means by which friction is applied. The friction means may be adjustable to prevent the at least one first dog from moving into an engaged position with the drive member until a predetermined amount of torque is applied to the power frame.

The drive member is preferably operatively associated with the output shaft.

Any portion of the drive member may be adapted to operatively engage with the at least one first dog. Usually, the engagement portion is provided circumferentially on the drive member. Normally, the engagement portion includes one or more teeth or similar engagement mechanisms. The teeth or engagement mechanisms may have any shape or configuration.

Normally, the engagement mechanism or teeth are provided around the entire circumference of the drive member. Alternatively the engagement mechanism or teeth may be provided around the drive member, wherein the engagement mechanism or teeth are oriented radially inwards towards the principal cylindrical axis of the drive member. The engagement mechanism or teeth are preferably shaped to engage with the at least one first dog. The drive member may be bevelled or U shaped in cross section when viewed side on. For example the drive member may be a bevelled gear.

If the drive member is bevelled or U-shaped, it is preferable that other components such as the power frame and the at least one support frame are also U- shaped in cross section when viewed side on. Typically if the drive member is ^■ bevelled, the at least one spindle will preferably extend through an intermediate shaft which is located between the input shaft and the output shaft. It will be appreciated that the clutch gear assembly will operate substantially as described herein even though some of the components may be mounted in different orientations.

Rotational separation between the power frame and the at least one support frame is typically created due to frictional forces which will cause the spindle to rotate to the second condition under a threshold torque.

In one embodiment, the clutch gear assembly may comprise a casing. The casing would typically form a shell around the clutch gear assembly, but with openings or connection means to allow the input shaft and. output shaft to connect to driving or driven components external of the casing. No particular limitation should be placed on the invention by the type of casing if any that is used.

In another embodiment, the at least one support frame may not be required. Alternatively, the power frame may be or include a support frame. If the support frames are not provided or if the power frame is or includes a support frame, other mechanisms for moving the at least one first dog into an engaged position may be provided. For example, the at least one first dog and/or the at least one second dog may be responsive to centrifugal forces and/or the like.

In another aspect, the present invention provides a clutch gear assembly comprising: an input shaft mounted for rotation; an intermediate shaft mounted for rotation; an engagement means between the input shaft and the intermediate shaft; a clutch means; a drive means; a driven means; an output shaft mounted for rotation operatively associated with the driven means; wherein when the input shaft is subjected to a predetermined amount of torque in a first direction, the engagement means is responsive to the predetermined amount of torque and causes the clutch means to operatively engage with the drive means such that rotation of the input shaft causes rotation of the drive means, the drive means is operatively associated to the driven means such that rotation of the drive means causes rotation of the driven means, which causes rotation of the output shaft.

In one embodiment, the input shaft is preferably provided with an abutment surface and/or the like. Abutment surfaces and/or the like which are known in the art can be utilised, for example, a collar mounted to the input shaft. However, other means to achieve the same results are envisaged including the use of circlips, locking pins and/or the like. No particular limitation should be placed on the invention by the type of abutment surface and/or the like that may be used. Preferably the abutment surfaces and/or the like are fixedly mounted to the input shaft in at least the longitudinal direction. The input shaft is typically formed with or engages with at least part of the engagement means. .

In another embodiment, the intermediate shaft is preferably provided with an abutment surface and/or the like. Abutment surfaces and/or the like which are known in the art can be utilised. For example, collars mounted to the input shaft. However, other means to achieve the same results are envisaged including the use of circlips, locking pins and/or the like. No particular limitation should be placed on the invention by the type of abutment surface and/or the like that may be used. Preferably the abutment surfaces and/or the like are fixedly mounted to the input shaft in at least the longitudinal direction. The intermediate shaft is typically formed with or engages with at least part of the engagement means.

In one embodiment, a friction means may provide friction to the intermediate shaft such that the input shaft and intermediate shaft are biased to engage and cause the clutch means to operatively engage with the drive means when the input shaft is subject to a predetermined amount of torque. The friction means may be a brake assembly and/or the like providing relative friction between the intermediate shaft and a casing (if present).

Alternatively, other means for imparting friction on the intermediate shaft may be provided. For example, the friction means may be the natural tendency of the intermediate shaft to rotate slower than the input shaft when the intermediate shaft is subject to torque. The friction, means may be a fluid applied to the intermediate shaft and/or to other components mounted to the intermediate shaft. Many means of applying friction are known in the art and no particular limitation should be placed on the invention by the means by which friction is applied. The friction means may be adjustable to prevent the intermediate shaft from engaging with the input shaft and causing the clutch means to operatively engage with the drive means until a predetermined amount of torque is applied to the input shaft.

In another embodiment, tho input shaft and the intermediate shaft are operatively engaged via the engagement means. The engagement means is preferably responsive to relative rotation between the input shaft and the intermediate shaft.

Normally when the input shaft is subject to rotation in a first direction relative to the intermediate shaft the engagement means will cause the abutment surfaces and/or the like of the input shaft and the intermediate shaft to move towards each other. Rotation of the input shaft in a second direction relative to the intermediate shaft will normally cause the abutment surfaces and/or the like of the input shaft and the intermediate shaft to move apart.

Typically once the abutment surfaces and/or the like of the input shaft and the intermediate shaft have moved towards each other a predetermined distance, the input shaft will not be rotating in a first direction relative to the intermediate shaft. Typically once the abutment surfaces and/or the like of the input shaft and the intermediate shaft have moved apart a predetermined distance, the input shaft will not be rotating in a second direction relative to the intermediate shaft.

Preferably the engagement means comprises a male and female threaded part. Normally one of the male and female threaded parts will be associated with the input shaft and the other of the male and female threaded parts will be associated with the intermediate shaft. The threading of the parts may be left handed threads or right handed threads depending on which direction the input shaft turns in a first direction. It will be appreciated that providing a male and female threaded part will enable the engagement means to operate as described above. However, other mechanisms may be provided. For example, ramp shaped splines, angled features and/or the like may be used to move the abutment surfaces and/or the like of the input shaft and the intermediate shaft apart or towards each other.

One of the male and female threaded parts is typically formed with or engages with the input shaft and the other of the respective male and female threaded parts is typically formed with or engages with the intermediate shaft. Alternatively, if other mechanisms are provided, one part of the engagement means may be formed with or engage with the input shaft and another part of the engagement means may be formed with or engage with the intermediate shaft. In one embodiment, the clutch means may be responsive to the engagement means. Typically the clutch means is responsive to the movement of the abutment surfaces and/or the like of the input shaft and the intermediate shaft. The clutch means is typically adapted to engage once the abutment surfaces and/or the like of the input shaft and the intermediate shait have moved towards each other a predetermined distance.

The clutch means is typically adapted to disengage once the abutment surfaces and/or the like of the input shaft and the intermediate shaft have moved apart a predetermined distance.

The clutch means is normally mounted on the input shaft and/or the intermediate shaft. The clutch means is normally mounted between the abutment surfaces and/or the like of the input shaft and the intermediate shaft.

Normally the clutch means will comprise clutch plates and/or disc pads to clutch the drive means to the input shaft and/or the intermediate shaft when the abutment surfaces and/or the like of the input shaft and the intermediate shaft have moved towards each other a predetermined distance. However, many clutch means are known in the art and no particular limitation should be placed on the invention by what type of clutch means is used to clutch the drive means to the input shaft and/or the intermediate shaft.

The clutch means may be adjustable to prevent the clutch means from operatively engaging with the drive means until a predetermined amount of torque is applied to the input shaft.

In another embodiment, the drive means may be mounted on the intermediate shaft and/or the input shaft. Normally the drive means is rotatably mounted relative to the intermediate shaft and/or the input shaft. When the clutch means operatively engages with the drive means, the drive means is typically clutched to the intermediate shaft and/or the input shaft such that rotation of the intermediate shaft and/or the input shaft causes rotation of the drive means. Any portion of the drive means may be adapted to operatively engage with the driven means. Usually, the engagement portion is provided circumferential on the drive means. Normally, the engagement portion includes one or more teeth or similar engagement mechanisms. The teeth or engagement mechanisms may have any shape or configuration. Normally, the engagement mechanism or teeth are provided around the entire circumference of the drive means. In one embodiment, the driven means is preferably operatively associated with the output shaft. Typically the driven means is fixedly mounted to the output shaft. Any portion of the driven means may be adapted to operatively engage with the drive means. Usually, the engagement portion is provided circumferential on the driven means. Normally, the engagement portion includes one or more teeth or similar engagement mechanisms. The teeth or engagement mechanisms may have any shape or configuration. Normally, the engagement mechanism or teeth are provided around the entire circumference of the driven means.

In another embodiment, gearing and/or the like may be applied at the output shaft and/or the input shaft. For example, gears, crown differentials, split torque involute gear drives and or the like may be applied to increase, decrease and/or change the direction of rotation. Alternatively such gearing and/or the like may be/additionally be applied between the drive means and the driven means

In one embodiment, a clutch device (not to be confused with the clutch means), ratchet device and/or the like, may be used between input shaft and intermediate shaft. Clutch devices, ratchet devices and/or the like which are known in the art may be utilised, alternatively a clutch assembly as described in one aspect of this invention may be used. No particular limitation should be placed on the invention by the type of clutch device, ratchet devices and/or the like, if any, that may be used.

Normally clutch device, ratchet devices and/or the like may be used to avoid the intermediate shaft from turning in a first direction relative to the input shaft unless the input shaft is rotated in a second direction. It will be appreciated that without a clutch device, ratchet devices and/or the like, that in use, when the input shaft is no longer under torque, the intermediate shaft may be subject to residual torque causing the intermediate shaft to rotate in a first direction relative to the input shaft causing the clutch means to release the drive means. The clutch device may be part of or engage with the clutch means.

In a further aspect, the present invention provides a clutch gear assembly comprising an input shaft mounted for rotation, an intermediate shaft mounted for rotation, a clutch means associated with the input shaft and the intermediate shaft, and an engagement means, wherein when the input shaft is subjected to a predetermined amount of torque in a first direction, the engagement means is responsive to the predetermined amount of torque and causes the input shaft to operatively engage with intermediate shaft via the clutch means such that rotation of the input shaft causes rotation of the intermediate shaft.

In one embodiment, the clutch gear assembly further comprises a drive means, a driven means and an output shaft mounted for rotation operatively associated with the driven means, wherein the intennediate shaft is operatively associated with the drive means hich is operatively associated to the driven means such that rotation of the drive means causes rotation of the driven means, which causes rotation of the output shaft.

In one embodiment, the input shaft is preferably provided with an abutment surface and/or the like. Abutment surfaces and/or the like which are known in the art can be utilised, for example, a collar mounted to the input shaft. However, other means to achieve the same results are envisaged including the use of circlips, locking pins and/or the like. No particular limitation should be placed on the invention by the type of abutment surface and/or the like that may be used. Preferably the abutment surface and/or the like is fixedly mounted to the input shaft.

In another embodiment, the intermediate shaft is preferably provided with an abutment surface and/or the like. Abutment surfaces and/or the like which are known in the art can be utilised. For example, a collar mounted to the intermediate shaft. However, other means to achieve the same results are envisaged including the use of circlips, locking pins and/or the like. No particular limitation should be placed on the invention by the type of abutment surface and/or the like that may be used. Preferably the abutment surface and/or the like is fixedly mounted to the intermediate shaft.

The engagement means is preferably responsive to relative rotation between the input shaft and an engagement member. Preferably the engagement member is an annular member. Typically the engagement member is rotatably mounted relative to a casing (if present). The engagement member is preferably mounted for linear movement relative to a casing (if present).

Preferably the engagement means comprises a male and female threaded part. Normally one the male and female threaded parts will be associated with the input shaft and the other of the male and female threaded parts will be associated with the engagement member.

The engagement member may be of any suitable shape. A skilled addressee will understand that typically any suitably shaped engagement member may be used provided that the engagement member is adapted to operatively engage with the input shaft such that the engagement means is responsive to relative rotation between the input shaft and an engagement/member. If the engagement member is an annular member, the annular member may be of any suitable shape. In this case, a skilled addressee will understand that any suitable annular member may be used such as a hollow body, collar, tube, pipe and/or the like.

The threading of the parts may be left handed threads or right handed threads depending on which direction the input shaft turns in a first direction. It will be appreciated that providing a male and female threaded part will enable the engagement means to operate as described above. However, other mechanisms may be provided. For example, ramp shaped splines, angled features and/or the like may be used to move the abutment surfaces and/or the like of the input shaft and the intermediate shaft apart or towards each other.

One of the male and female threaded parts is typically formed with or engages with the input shaft and the other of the respective male and female threaded parts is typically formed with or engages with the engagement member. Alternatively, if other mechanisms are provided, one part of the engagement means may be formed with or engage with the input shaft and another part of the engagement means may be formed with or engage with the engagement member.

The input shaft typically engages with at least part of the engagement member. In one embodiment, a friction means may provide friction to the engagement member such that the input shaft is biased to operatively engage with the intermediate shaft when the input shaft is subject to a predetermined amount of torque. The friction means may be a brake assembly and/or the like providing relative friction between the engagement member and a casing (if present).

Alternatively, other means for imparting friction on the engagement member may be provided. For example, the friction means may be the natural tendency of the engagement member to rotate slower than the input shaft when the input shaft is subject to torque. The friction means may be a fluid applied to the engagement member. Many means of applying friction are known in the art and no particular limitation should be placed on the invention by the means by which friction is applied.

The friction means may be adjustable to prevent the input shaft from operatively engaging with the intermediate shaft until .a predetermined amount of torque is applied to the input shaft. Normally when the input shaft is subject to rotation in a first direction relative to the engagement member the engagement means will cause the abutment surfaces and/or the like of the input shaft and the intermediate shaft to move towards each other. Rotation of the input shaft in a second direction relative to the engagement member will normally cause the abutment surfaces and/or the like of the input shaft and the intermediate shaft to move apart.

In one embodiment, the clutch means may be responsive to the engagement means. Typically the clutch mejans is responsive to the movement of the abutment surfaces and/or the like of the input shaft and the intermediate shaft. The clutch means is typically adapted to engage once the abutment surfaces and/or the like of the input shaft and the intermediate shaft have moved towards each other a predetermined distance.

The clutch means is typically adapted to disengage once the abutment surfaces and/or the like of the input shaft and the intermediate shaft haye moved apart a predetermined distance.

Normally the clutch means will comprise clutch plates and/or disc pads to clutch the input shaft to the intermediate shaft when the abutment surfaces and/or the like of the input shaft and the intermediate shaft have moved towards each other a predetermined distance. However, many clutch means are known in the art and no particular limitation should be placed on the invention by what type of clutch means is used to clutch the input shaft to the intermediate shaft. Alternatively, the abutment surfaces and/or the like may be the clutch means.

The clutch means may be adjustable to prevent the clutch means from operatively engaging the input shaft to the intermediate shaft until a predetermined amount of torque is applied to the input shaft. In another embodiment, the drive means may be mounted on the intermediate shaft and/or the input shaft. Normally the drive means is fixedly mounted relative to the intermediate shaft. Any portion of the drive means may be adapted to operatively engage with the driven means. Usually, the engagement portion is provided circumferential on the drive means. Normally, the engagement portion includes one or more teeth or similar engagement mechanisms. The teeth or engagement mechanisms may have any shape or configuration. Normally, the engagement mechanism or teeth are provided around the entire circumference of the drive means.

In one embodiment, the driven means is preferably operatively associated with the output shaft. Typically the driven means is fixedly mounted to the output shaft. Any portion of the driven means may be adapted to operatively engage with the drive means. Usually, the engagement portion is provided circumferential on the driven means. Normally, the engagement portion includes one or more teeth or similar engagement mechanisms. The teeth or engagement mechanisms may have any shape or configuration. Normally, the engagement mechanism or teeth are provided around the entire circumference of the driven means.

In another embodiment, gearing and/or the like may be applied at the output shaft, the intermediate shaft and/or the input shaft. For example, gears, crown differentials, split torque involute gear drives and or the like may be applied to increase, decrease and/or change the direction of rotation. Alternatively such gearing and/or the like may be/additionally be applied between the drive means and the driven means.

Normally the clutch device, ratchet devices and/or the like may be used to avoid the intermediate shaft from turning in a first direction relative to the input shaft unless the input shaft is rotated in a second direction. It will be appreciated that without a clutch device, ratchet devices and/or the like, that in use, when the input shaft is no longer under torque, the intermediate shaft may be subject to residual torque causing the intermediate shaft to rotate in a first direction relative to the input shaft. The clutch device, ratchet devices and/or the like may be part of or engage with the clutch means. If the clutch device, ratchet devices and/or the like is part of or engages with the clutch means, it will typically be used to avoid the intermediate shaft from turning in a first direction relative to a casing (if present).

In another embodiment, an input side clutch device (not to be confused with the clutch means), ratchet device and/or the like, may be engaged with or form part of the engagement member. Clutch devices, ratchet devices and/or the like which are known in the art may be utilised, alternatively a clutch assembly as described in one aspect of this invention may be used. No particular limitation should be placed on the invention by the type of clutch device, ratchet devices and/or the like, if any, that may be used.

Normally the input side clutch device, ratchet devices and/or the like may be used to avoid the engagement member from turning in a first direction relative to the input shaft unless the input shaft is rotated in a second direction. It will be appreciated that without an input side clutch device, ratchet devices and/or the like, that in use, the engagement member could turn in a first direction relative to the input shaft when the input shaft is not rotated in a second direction (for example substantial rotation of the engagement member in a first direction relative to a casing), thus causing the abutment surfaces and/or the like of the input shaft and the intermediate shaft to move apart when it is not desired for them to do so.

The input side clutch device, ratchet devices and/or the like is typically formed with or engages with the engagement member. For example, the input side clutch device, ratchet devices and/or the like may be a ratchet gear formed as part of the engagement member.

The present invention may also be used in a wide variety of fields not limited to what would normally be interpreted as the "mechanical arts" including the biomedical, bio-engineering and bio-science fields. The invention may be miniaturised. For example, the clutch gear assembly may be miniaturised to form a regulated-heart- pump that fits into existing artificial hearts and operates using blood flow. In this manner, the clutch gear assembly may require no batteries or external servo- connections.

The components of the present invention are normally made of a suitable metallic material. Alternatively the components may be made from an alloy, plastic, polymer, ceramic, composite and/or any material according to a suitable materials selection chart. BRIEF DESCRIPTION OF THE DRAWINGS

One or more preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a sectioned top view of a clutch gear assembly according to a preferred embodiment of the present invention.

Figure 2 is a sectioned end elevation view of a clutch gear assembly according to a preferred embodiment of the present invention.

Figure 3 illustrates a support frame according to a preferred embodiment of the present invention.

Figure 4 illustrates a power frame according to a preferred embodiment of the present invention.

Figure 4b illustrates various dogs according to preferred embodiments of the present invention.

Figure 5 is a sectioned top view of a clutch gear assembly according to a preferred embodiment of the present invention.

Figure 6 illustrates alternative drive gear configurations according to preferred embodiments of the present invention.

Figure 7 is a sectioned end elevation view of a clutch gear assembly according to a preferred embodiment of the present invention.

Figure 8 is a sectioned side view of a clutch gear assembly according to a preferred embodiment of the present invention.

Figure 9 illustrates a ratchet gear according to a preferred embodiment of the present invention

Figure 10 is a sectioned end elevation view of a clutch gear assembly according to a preferred embodiment of the present invention.

Figure 11 is a sectioned side view of a clutch gear assembly according to a further embodiment of the present invention.

Figure 12 is an end view of a power shaft according to a further embodiment of the present invention.

BEST MODE

With reference to Figures 1-4, there is shown a clutch gear assembly. A housing 14 encloses most of the components of the clutch assembly. The housing 14 can be opened by loosening a bolt 15 to allow access to the components. A power shaft 2 (which can also be referred to as an input shaft) is rotatably mounted in the housing 14. The power shaft 2 can be rotated by a power source (not shown). A power frame 3 is fastened to the power shaft 2. The power frame 3 has cutouts to accommodate second dogs in the form of dogs D2. The power shaft 2 is rotatably supported by a drive shaft 1 (which can also be referred to as an output shaft) by a male/female joint 5. Support frame 9 and support frame 8 are rotatably mounted on power shaft 2. Support frame 7 is rotatably mounted on drive shaft 1. Figure 2 shows the support frame 8 with four arms and figure 3 shows an alternative version of support frame 8 with two arms. Circlips 13 are used to keep the support frames 7, 8, 9 in position relative to shafts 1, 2. Spindles 10 are rotatably mounted to the support frames 7, 8, 9. First dogs in the form of dogs Dl , and dogs D2 are attached to the spindles 10, such that rotation of dogs D2 rotates the spindles 10 and dogs Dl . The spindles 10 are biased by biasing means in the form of springs 1 1 mounted to support frame 8 such that dogs Dl are biased into a first position where they are disengaged from a drive member in the form of a drive gear 4. Drive gear 4 is fastened to drive shaft 1. Item 6 signifies bushes, circlips and ball bearings used to mount the shafts 1, 2 to the housing 14. A friction assembly 12 is mounted between the housing 14 and the support frame 9. The friction assembly 12 is adjustable to adjust the amount of friction between the housing 14 and the support frame 9. When the power shaft 2 is under torque (indicated by Rl in figure 2), the friction assembly 12 causes the support frame 9 to lag behind the power frame 3 (this can also be referred to as rotational separation between support frame 9 and pcwer frame 3). This lag causes the cut outs in power frame 3 to push against the ends of dogs d2 rotating them in a clockwise direction, thus dogs Dl which are also connected to spindle 10 will rotate into a second position where the dogs Dl are engaged with drive gear 4. The springs 1 1 bias the spindle 10 in a counter clockwise direction such that when there is substantially no torque on shaft 2, the springs 11 overcome the force of the cut outs in power frame 3 pushing against the ends of dogs d2 such that the dogs d2 and dl are rotated in a counter clockwise direction to the first position, disengaging dogs dl from the drive gear 4. The power shaft 2 may also be -fitted with a ratchet gear or the like (not shown) as protection in the event that the power shaft has residual torque when the power source (not shown) has stopped rotating.

With reference to Figure 4b, there is shown a power frame 3 and two different embodiments of second dogs: fin shaped dogs in the form of tandem dogs D2 and V shaped dogs D2D. it will be appreciated that either type of dog can be used and that the dogs D2 and D2D do not have to be used in combination. In use, the dogs D2, D2D are biased by springs 11 (not shown) into a first position where they are disengaged from the drive gear 4(not shown). In this position, the drive shaft 1 (not shown) is completely 'freewheeling' and is able to rotate in any direction independently of the power shaft 2(not shown). When the power shaft 2 is under torque (indicated by Rl in figure 2), the friction assembly 12(not shown) causes the support frame 9(not shown) to lag behind the power frame 3. This lag causes the cut outs in power frame 3 to push against the ends of dogs D2, D2D rotating them in a clockwise direction, thus dogs Dl (not shown)( which may also have a similar shape to dogs D2 and D2D) which are also connected to spindle 10(not shown) will rotate into a second position where the dogs Dl(not shown) are engaged with drive gear 4(not shown). In this position, any rotational input from the power shaft 2(not shown) under torque will produce the same rotational output at the drive shaft l(not shown) due to dog arrangements depicted in figure 4b. When the power shaft 2 is under torque (in a direction opposite to that indicated by Rl in figure 2), the friction assembly 12(not shown) causes the support frame 9(not shown) to lag behind the power frame 3. This lag causes the cut outs in power frame 3 to push against the ends of dogs D2, D2D rotating them in a counter-clockwise direction, thus dogs Dl (not shown)(which may have a similar shape to dogs D2D) which are also connected to spindle 10(not shown) will rotate into a third position where the dogs Dl(not shown) are engaged with drive gear 4 (not shown). In this position, any rotational input from the power shaft 2(not shown) under torque will produce the same rotational output at the drive shaft l(not shown) due to dog arrangements depicted in figure 4b.

With reference to Figures 5-7, there is shown a clutch gear assembly. In this embodiment, the drive gear 4 is a bevelled gear. The shape of the bevel gear can take many forms including those depicted in figure 6. Dogs Dl are shaped accordingly such that they can engage with drive gear 4. A housing 14 encloses most of the components of the clutch assembly. The housing 14 can be opened by loosening a bolt 15 to allow access to the components. A power shaft 2 (which can also be referred to as an input shaft) is rotatably mounted in the housing 14. The power shaft 2 can be rotated by a power source (not shown). A power frame 3 is fastened to the power shaft 2. The power frame 3 has cutouts to accommodate dogs D2. The power shaft 2 is rotatably supported by a spindle shaft 20 which is rotatably supported by a drive shaft 1 (which can also be referred to as an output shaft) by a male/female joint 5. Support frame 8 is rotatably mounted on power shaft 2. Support frame 9 is rotatably mounted on drive shaft 1. Spindles 10 are rotatably mounted to the support frames 8, 9 and spindle shaft 20. Dogs Dl and dogs D2 are attached to the spindles 10, such that rotation of dogs D2 rotates the spindles 10 and dogs Dl. The spindles 10 are biased by springs 11 mounted to support frame 9 such that dogs Dl are biased into a first position where they are disengaged from drive gear 4. Drive gear 4 is fastened to drive shaft 1. A friction assembly 12 is mounted between the housing 14 and the support frame 8. The friction assembly 12 is adjustable to adjust the amount of friction between the housing 14 and the support frame 8. When the power shaft 2 is under torque, the friction assembly 12 causes the support frame 8 to lag behind the power frame 3. This lag causes cut outs in power frame 3 to push against the ends of dogs d2 rotating them, thus dogs Dl which are also connected to spindle 10 will rotate into a second position where the dogs Dl are engaged with drive gear 4. The springs 11 bias the spindle 10 such that when there is substantially no torque on shaft 2, the springs 1 1 overcome the force of the cut outs in power frame 3 pushing against the ends of dogs d2 such that the dogs d2 and dl are rotated to the first position, disengaging dogs dl from the drive gear 4. Figure 7 also shows mounting brackets 16 which are attached to the housing 14.

With reference to Figures 8 and 10, there is shown a . clutch gear assembly. In this embodiment, power shaft 2 has a threaded male end 2a which engages with a threaded female end la of an intermediate shaft 1. When power shaft 2 is under torque, engagement means in the form of threaded engagement between the male end 2a and the female end la (due to the friction assembly, 12 providing friction between > the intermediate shaft 1 and the housing 14) causes a relative compression between clutch disc 3a which is attached to power shaft 2 and circlip 13 which is attached to intermediate shaft 1. The relative compression can be adjusted by an adjustable collar 7a. The friction assembly 12 is adjustable through use of an adjustable collar 12a. The relative compression causes a clutch action by compressing clutch mechanisms 3b against disc pads 4a, drive gear 5a and assembly 6a thus locking drive gear 5a and assembly 6a to intermediate shaft 1. Assembly 6a may be a clutch gear assembly as shown in figures 1-7. Alternatively assembly 6a may be a ratchet assembly 17 as depicted in figure 9 or any type of ratchet/clutch assembly known in the art. The assembly 6a is held in position by support brackets 16a. As can be seen from the figures, when drive gear 5a is locked to intermediate shaft 1, rotation of drive gear 5a (by intermediate shaft 1) causes rotation of drive gear 5b which is attached to a drive shaft 11 a (which can also be referred to as an output shaft).

With reference to Figure 9, there is shown a ratchet assembly 17. Ratchet gear 8a is able to rotate in a first direction and prevented from substantial rotation in a second direction by a pin 9a. The pin 9a is biased into engagement with the ratchet gear by a magnet 10a. The pin 9a is adapted to rotate between a first position and a second position. In the first position, the pin 9a prevents the ratchet gear 8a from substantial rotation. When the pin 9a is in the second position, the ratchet gear 8a is able to rotate. Sufficient torque of the ratchet gear 8a in the first direction overcomes the biasing force of the magnet 10a acting on the pin 9a and the ratchet gear 8a rotates pin 9a into the second position. The ratchet assembly 17 has fixing brackets 13a which are adapted to attach to support brackets 16a.

With reference to Figures 11 and 12, there is shown a clutch gear assembly similar to the one shown in Figures 8 and 10. In this embodiment, an input shaft in the form of a power shaft 2 has a threaded portion which engages with a threaded bore 22 of an engagement member in the form of a ratchet gear 20. When the power shaft 2 is under torque, engagement means in the form of a threaded engagement between the power shaft 2 and the threaded bore 22 (due to friction applied between the ratchet gear 20 and the housing 14) causes a relative compression between the clutch disc 3b which is attached to power shaft 2 and the clutch disc 3b which is attached to the intermediate shaft 1. The friction between the ratchet gear 20 and the housing 14 is applied by a spring 18 biasing an adjustable collar T 2a which is connected to the ratchet gear 20 such that a compression disc 20a on the ratchet gear 20 is biased against a disc pad 4a which is biased against a stopper plate 19 which is attached to the housing 14. The friction between the ratchet gear 20 and the housing 14 can be adjusted by adjusting be position of the adjustable collar 12a relative to the ratchet gear 20. A compression bearing 17a is provided between the stopper plate 19 and the compression spring 18, such that the compression spring 18 can provide a biasing force between the adjustable collar 12a and the compression bearing 17a. Alternatively, the compression bearing 17a may be provided between the housing 14 and the compression spring 18. The ratchet gear 20 engages with a cog 21 such that the ratchet gear 20 is able to rotate in the first direction and prevented from substantial rotation in a second direction. When excess torque is provided to the power shaft 2, the engagement between the power shaft 2 and the threaded bore 22 causes the compression spring 18 to be compressed between the adjustable collar 12a and the compression bearing 17a, this results in the compression disc 20a disengaging from (or at least being less biased against) the disc pad 4a. In this manner, the ratchet gear 20 will rotate relatively freely with the power shaft 2 in the direction of torque. When the power shaft 2 is under sufficient torque, the relative compression between the clutch disc 3b which is attached to power shaft 2 and the clutch disc 3b which is attached to the intermediate shaft 1 will cause the power shaft 2 to transfer torque to the intermediate shaft 1 due to the clutch disc 3b which is attached to power shaft 2 engaging with a disc pad 4a, which engages with an assembly 6a, which engages with another disc pad 4a which engages with the clutch disc 3b which is attached to the intermediate shaft 1. The assembly 6a is provided to prevent any substantial reverse torque from being transmitted back to the power shaft 2 when there is a relative compression between the clutch disc 3b which is attached to power shaft 2 and the clutch disc 3b which is attached to the intermediate shaft 1. In this embodiment, the assembly 6a is a ratchet gear 6a which engages with a cog 21 such that the ratchet gear 6a is able to rotate in the first direction and prevented from substantial rotation in a second direction. When the intermediate shaft 1 is under torque and rotating, the drive gear 5a which is connected to the intermediate, shaft 1 causes rotation of the drive gear 5b which is connected to a secondary drive shaft l la(not shown). A compression bearing 17a prevents substantial longitudinal movement of the intermediate shaft 1 when there is a relative compression between the clutch disc 3b which is attached to power shaft 2 and the clutch disc 3b which is attached to the intermediate shaft 1. The power shaft 2 is rotatably supported by the intermediate shaft 1 by a male/female joint 23. conversely, the intermediate shaft 1 is rotatably supported by the power shaft 2 by the male/female joint 23. The male/female joint 23 allows the power shaft to move in the longitudinal direction relative to the intermediate shaft 1, such that relative compression between the clutch disc 3b which is attached to power shaft 2 and the clutch disc 3b which is attached to the intermediate shaft can be achieved.

In practice, the clutch gear in the drawings would also incorporate a number of other components which have not been shown. For example, bearings would normally be used to support the shafts. The bearings would typically be supported by the housing. The foregoing embodiments are illustrative only of the principles of the invention, and various modifications and changes will readily occur to those skilled in the art. The invention is capable of being practiced and carried out in various ways and in other embodiments. It is also to be understood that the terminology employed herein is for the purpose of description and should not be regarded as limiting.

In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to "one embodiment", or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

A clutch gear assembly comprising:

a rotatable input shaft;

a power frame mounted for rotation with the input shaft;

a rotatable output shaft;

a drive member mounted for rotation with the output shaft;

at least one support frame mounted for rotation relative to either the input shaft or the output shaft;

at least one spindle rotatably mounted to at least one of the at least one support frame;

at least one first dog, each fixedly mounted .to one of the at least one spindle;

at least one second dog, each fixedly mounted to the spindle to which the at least one first dog is mounted, the at least one first dog moveable, between a first disengaged condition and the second engaged condition by rotational separation between the power frame and the at least one support frame to which the at least one spindle is rotatably mounted, through the at least one second dog;

a biasing means operatively associated with the spindle such that the at least one first dog is biased into a first disengaged condition where it is disengaged from the drive member;

wherein when the input shaft is subject to a predetermined amount of torque in a first direction, the rotational separation between the power frame and the at least one support frame to which the at least one spindle is rotatably mounted motivates the at least one second dog against the biasing force of the biasing means to move the at least one first dog into the second engaged position, engaged with the drive member such that the rotation of the input shaft causes rotation of the output shaft.

A clutch gear assembly as claimed in claim 1 , wherein when the input shaft is subject to less than a predetermined amount of torque, the biasing means biases the at least one first dog into the first disengaged position, disengaging from the drive member such that rotation of the input shaft does not cause rotation of the output shaft.

A clutch gear assembly as claimed in any one of the preceding claims, wherein the at least one first dog is additionally adapted to engage with the drive member in a third engaged position, and wherein when the input shaft is subject to a predetermined amount of torque in a second direction, the rotational separation between the power frame and the at least one support frame to which the at least one spindle is rotatably mounted motivates the at least one second dog against the biasing force of the biasing means to move the at least one first dog into the third engaged position, engaged with the drive member such that the rotation of the input shaft causes rotation of the output shaft.

A clutch gear assembly comprising:

a rotatable input shaft;

a power frame mounted for rotation with the input shaft;

an rotatable output shaft;

a drive member mounted for rotation with the output shaft;

at least one spindle movably mounted to the power frame;

at least one first dog, each fixedly mounted to one of the at least one spindle;

at least one second dog, each fixedly mounted to the spindle to which the at least one first dog is mounted, the at least one first dog moveable between a first disengaged condition and a second engaged condition;

a biasing means operatively associated with the spindle such that the at · least one first dog is biased into the first disengaged condition where it is disengaged from the drive member;

wherein when the input shaft is subject to a predetermined amount of torque in a first direction, movement of the ;at least one first dog motivates the at least one second dog against the biasing force of the biasing means · to move the at least first dog into the second engaged position, engaged with the drive member such that the rotation of the input shaft causes rotation of the output shaft.

A clutch gear assembly as claimed in claim.4, wherein when the input shaft is subject to less than a predetermined amount of torque, the biasing means biases the at least one first dog into the first disengaged position, disengaging from the drive member such that rotation of the input shaft does not cause rotation of the output shaft.

A clutch gear assembly as claimed in claims 4 or 5, wherein the at least one first dog is additionally adapted to engage with the drive member in a third engaged position, and wherein when the input shaft is subject to a predetermined amount of torque in a second direction, the at least one second dog is motivated against the biasing force of the biasing means to move the at least one first dog into the third engaged position, engaged with the drive member such that the rotation of the input shaft causes rotation of the output shaft.

A clutch gear assembly comprising:

an input shaft mounted for rotation;

an intermediate shaft mounted for rotation;

an engagement means between the input shaft and the intermediate shaft;

a clutch means;

a drive means;

a driven means; and

an output shaft mounted for rotation operatively associated with the driven means;

wherein when the input shaft is subjected to a predetermined amount of torque in a first direction, the engagement means is responsive to the predetermined amount of torque and causes the clutch means to operatively engage with the drive means such that rotation of the input shaft causes rotation of the drive means, the drive means is operatively associated to the driven means such that rotation of the drive means causes rotation of the driven means, which causes rotation of the output shaft. A clutch gear assembly as claimed in claim 7 wherein the engagement means is a male-female thread arrangement.

A clutch gear assembly comprising:

an input shaft mounted for rotation;

an intermediate shaft mounted for rotation;

a clutch means associated with the input shaft and the intermediate shaft; and

an engagement means;

wherein when the; input shaft is subjected to a predetermined amount of torque in a first direction, the engagement means is responsive to the predetermined amount of torque and causes the input shaft to operatively engage with intermediate shaft via the clutch means such that rotation of the input shaft causes rotation of the intermediate shaft.

10. A clutch gear assembly as claimed in claim 9, further comprising:

a drive means;

a driven means; and

wherein the intermediate shaft is operatively associated with the drive means which is operatively associated to the driven means such that rotation of the drive means causes rotation of the driven means, which causes rotation of the output shaft.

1 1. A clutch gear assembly as claimed in claims 9 or 10, wherein the engagement means is between the input shaft and an engagement member.

12. A clutch gear assembly as claimed in claim 11 , wherein the engagement means is a male- female thread arrangement.

13. A clutch gear assembly as claimed in claim 12, wherein the male portion of the male-female thread arrangement is attached to the input shaft and the female portion of the male-female thread arrangement is attached to the engagement member.

14. A clutch gear assembly as claimed in claims 1 1, 12 or 13, wherein the engagement means is further responsive to friction applied to the engagement member.

15. A clutch gear assembly as claimed in claim 14, wherein friction is applied to the engagement member by a brake pad, brake pads, a brake disc and/or brake discs.

16. A clutch gear assembly as claimed in claim 15, wherein the brake pad, brake pads, the brake disc and/or brake discs are substantially tapered or conical in shape to provide a predetermined amount of friction.

17. A clutch gear assembly as claimed in claims 14, 15 or 16, wherein a biasing means is provided to bias the engagement member into engagement with a source of friction.

18. A clutch gear assembly as claimed in claim 17, wherein the biasing means is a compression and/or tension spring arrangement.

19. A clutch gear assembly as claimed in claims 17 or 18, wherein the biasing means is located outside and/or inside a housing for the clutch gear assembly.