WO2000008356A1

WO2000008356A1 - Method and apparatus for engaging and disengaging a body from a shaft about which it is provided

Info

Publication number: WO2000008356A1
Application number: PCT/AU1999/000629
Authority: WO
Inventors: William Wesley Martin
Original assignee: Preload International Limited
Priority date: 1998-08-04
Filing date: 1999-08-04
Publication date: 2000-02-17

Abstract

An apparatus for engaging and disengaging a rotatable body (18) with or from a shaft (12) about which the rotatable body is provided, the apparatus being characterised by one or more electromagnetic field generating means (30) and one or more magnetically susceptible elements (38, 40), wherein the or each electromagnetic field generating means (30) is arranged with respect to the or each magnetically susceptible element (38, 40) so as to allow the or each electromagnetic field generating means (30) to act on the or each magnetically susceptible element (38, 40), causing such to move relative thereto, and thereby causing the actuation or deactuation of one or more means for actuable engagement (20, 22) of the rotatable body (18) with the shaft (12).

Description

METHOD AND APPARATUS FOR ENGAGING AND DISENGAGING A BODY FROM A SHAFT ABOUT WHICH IT IS PROVIDED

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for engaging and disengaging a rotatable body from a shaft about which it is provided. More particularly, the present invention relates to a method and apparatus for engaging and disengaging a rotatable body from a shaft, at least in part by a magnetic field.

BACKGROUND ART

Existing means for the engaging and disengaging a rotatable body from a shaft at least in part by a magnetic field, as discussed in International Applications PCT/AU98/00181 (WO 98/41779) and PCT/AU97/00024 (WO 97/26268) , use either permanent magnets exclusively, or a solenoid assembly.

Existing methods using exclusively permanent magnets are reliant on the movement of a roving permanent magnet assembly, and thus speed with which rotatable bodies can be engaged and disengaged from the shaft is limited by the speed with which the roving permanent magnet assembly can be appropriately located.

Further, rotatable bodies provided about a shaft are typically provided with several means for actuable engagement of the rotatable body with the shaft in the rotational direction, and several means for actuable engagement of the rotatable body with the shaft in the counter-rotational direction. It is highly advantageous to ensure that all means for actuable engagement of the rotatable body with the shaft in the rotational direction are activated simultaneously, and all means for actuable engagement of the rotatable body with the shaft in the counter-rotational direction are also activated simultaneously.

If a solenoid is used, there are broadly three methods by which simultaneous actuation of the means for actuable engagement may be achieved. Firstly, simultaneous actuation may be achieved by the action of a non-rotating solenoid assembly on one or more rotating lock rings, as disclosed in International Patent Application PCT/AU98/00181 (WO 98/41779).

Secondly, rotatable bodies may be engaged or disengaged from the shaft by way of one or more rotating solenoid assemblies that maintain their position relative to the means for actuable engagement. This approach necessitates the incorporation of one or more slip ring assemblies into the shaft system to enable current to be delivered to the solenoid or solenoids.

Thirdly, rotatable bodies may be engaged or disengaged by way of one of several static solenoid assemblies situated about the circumference of the rotating shaft such that the means for actuable engagement integral therewith may be actuated as an actuating device passes by the core of a coil. This method necessitates complicated windings.

The existing methods of actuation of means for actuable engagement unnecessarily introduce a level of complication to the actuation system, which is disadvantageous in the context of high speed mechanical parts as in a gear box in that they provide more potential sources of mechanical failure and complicate repair.

The method and apparatus for engaging and disengaging rotatable bodies of the present invention have, as one object thereof, to substantially overcome the above-mentioned problems associated with the prior art.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. DISCLOSURE OF THE INVENTION

In accordance with the present invention there is provided an apparatus for engaging and disengaging a rotatable body with or from a shaft about which the rotatable body is provided, the apparatus being characterised by one or more electromagnetic field generating means and one or more magnetically susceptible elements, wherein the or each electromagnetic field generating means is arranged with respect to the or each magnetically susceptible element so as to allow the or each electromagnetic field generating means to act on the or each magnetically susceptible element, causing such to move relative thereto, and thereby causing the actuation or deactuation of one or more means for actuable engagement of the rotatable body with the shaft.

Preferably, there is provided at least one electromagnetic field generating means per rotatable body.

In one form of the invention there is provided one electromagnetic field generating means per rotatable body. In an alternate form of the invention there are provided two electromagnetic field generating means per rotatable body.

Preferably, each means for actuable engagement has associated therewith a counterweight assembly, the counterweight assembly being radially opposed to the means for actuable engagement and adapted to substantially balance the weight of such.

Preferably, the or each means for actuable engagement has associated therewith one or more permanent magnets adapted, in the absence of an electromagnetic field generated by the or each electromagnetic field generating means, to maintain the means for actuable engagement in a deactuated condition.

Preferably still, the means for actuable engagement of the rotatable body with the shaft comprises at least one means for actuable engagement in a rotational direction, and at least one means for actuable engagement in a counter-rotational direction, such that actuation of both the or each means for actuable engagement in the rotational direction and the or each means for actuable engagement in the counter-rotational direction causes the rotatable body to rotate in conjunction with the shaft and prevents such from counter-rotating relative to the shaft, deactuation of both the or each means for actuable engagement in the rotational direction and the or each means for actuable engagement in the counter-rotational direction allows the rotatable body to rotate independently of the shaft and counter-rotate relative to the shaft, actuation of the or each means for actuable engagement in the rotational direction and deactuation of the or each means for actuable engagement in the counter-rotational direction causes the rotatable body to rotate in conjunction with the shaft and allows such to counter rotate relative to the shaft, and actuation of the or each means for actuable engagement in the counter- rotational direction and deactuation of the or each means for actuable engagement in the rotational direction allows the rotatable body to rotate relative to the shaft, but prevents the rotatable body from counter-rotating relative to the shaft.

Further and still preferably, there is provided at least one magnetically susceptible element relative to the means for actuable engagement in the rotational direction, and at least one magnetically susceptible element relative to the means for actuable engagement in the counter-rotational direction.

In one form of the invention, the electromagnetic field generating means is provided in the form of an electromagnetic coil.

In one form of the invention, the or each magnetically susceptible means is provided in the form of a permanent magnet. In an alternate form of the invention, the or each magnetically susceptible means is provided in the form of a portion of magnetically susceptible material or an alloy containing such.

Where there is provided one electromagnetic field generating means per rotatable body in the form of an electromagnetic coil, and the or each magnetically susceptible element is provided in the form of a permanent magnet, the or each permanent magnet is preferably located adjacent a face of the electromagnetic coil, such that the magnetic dipole of the or each permanent magnet is substantially parallel to the axis thereof.

Where there are provided two electromagnetic field generating means in the form of electromagnetic coils, and the or each magnetically susceptible element is provided in the form of a permanent magnet, the or each permanent magnet is preferably located adjacent a circumference one of said electromagnetic coils, such that the magnetic dipole of the or each permanent magnet is substantially parallel to the axes thereof.

In one form of the invention, where each rotatable body is provided both with means for actuable engagement in the rotational direction and means for actuable engagement in the counter-rotational direction, and a single electromagnetic field generating means is provided per pawl gear wheel in the form of an electromagnetic coil, and the or each magnetically susceptible element is provided in the form of a permanent magnet, the electromagnetic coil is interposed between the or each permanent magnet associated with the means for actuable engagement in the rotational direction and the or each permanent magnet associated with the means for actuable engagement in the counter- rotational direction, and the magnetic dipoles of the or each permanent magnet associated with the means for actuable engagement in the rotational direction are of opposite direction relative to the magnetic dipoles of the or each equivalent permanent magnet associated with means for actuable engagement in the counter-rotational direction, whereby the application of current through the electromagnetic coil in a first direction causes the simultaneous actuation of the means for actuable engagement in the rotational direction and deactuation of the means for actuable engagement in the counter-rotational direction, whilst application of a current through the electromagnetic coil in a second direction, opposite to the first direction, causes simultaneous actuation of the means for actuable engagement in the counter-rotational direction orientation and deactuation of the means for actuable engagement in the rotational direction.

In an alternate form of the invention, where each rotatable body is provided with both means for actuable engagement in the rotational and the counter-rotational directions, the electromagnetic coil is interposed between the or each permanent magnet associated with the means for actuable engagement in the rotational direction and the or each permanent magnet associated with the means for actuable engagement in the counter-rotational direction, and the magnetic dipoles of the or each permanent magnet associated with the means for actuable engagement in the rotational direction are of the same direction as the magnetic dipoles of the or each equivalent permanent magnet associated with the means for actuable engagement in the counter-rotational direction, whereby the application of current through the electromagnetic coil in a first direction causes the simultaneous actuation of the both the means for actuable engagement in the rotational and counter-rotational directions, whilst application of a current through the electromagnetic coil in a second direction, opposite to the first direction, causes simultaneous deactuation of the means for actuable engagement in the rotational and counter-rotational directions.

Where each gear wheel is provided with two electromagnetic coils and where each gear wheel is provided both with means for actuable engagement in the rotational direction and means for actuable engagement in the counter-rotational direction, the or each permanent magnet associated with the means for actuable engagement in the rotational direction is preferably located about a circumference of one electromagnetic coil, whilst the or each permanent magnet associated with the means for actuable engagement in the counter rotational direction is located about a circumference of the other electromagnetic coil.

Preferably, where each rotatable body has associated therewith two or more means for actuable engagement in the rotational direction, the actuation of the means for actuable engagement in the rotational direction is at least partially governed by a mechanical synchronisation means. Preferably still, where each rotatable body has associated therewith two or more means for actuable engagement in the counter-rotational direction, the actuation of means for actuable engagement in the counter-rotational direction is at least partially governed by a mechanical synchronisation means. ln one form of the invention, or each the means for actuable engagement is provided in the form of one or more pawl members, provided in the shaft or in the rotatable body and adapted to engage a complimentary recess in an opposed surface.

Preferably, the means for actuable engagement in the rotational direction is provided in the form of one or more forward pawl members, and the means for actuable engagement in the counter-rotational direction is provided in the form of one or more reverse pawl members, wherein the or each forward pawl member is adapted to engage a leading surface of a substantially complimentary recess in an opposed surface positively during rotation of that opposed surface with respect to the pawl member, and the or each reverse pawl member is adapted to engage a trailing surface of a substantially complimentary recess in an opposed surface positively during rotation of that opposed surface with respect to the pawl member.

In one form of the invention, there are provided two permanent magnets for the or each forward or reverse pawl member. Preferably, the two permanent magnets associated with the or each forward or reverse pawl member are held in fixed position relative to one another. Where each gear wheel is provided with one electromagnetic coil, the permanent magnets are preferably located on opposite sides of the axis of the electromagnetic coil and such that their magnetic dipoles are opposite, and substantially parallel to, the axis of the electromagnetic coil.

In an alternate form of the invention, there is provided one permanent magnet for the or each forward or reverse pawl member. Preferably, where the means for actuable engagement in the rotational and counter-rotational directions are provided in the form of forward and reverse pawls respectively, where the or each forward or reverse pawl has one permanent magnet associated therewith, and where each forward or reverse pawl has associated therewith a counterweight assembly, the permanent magnet is provided in the counterweight assembly, the counterweight assembly associated with each forward or reverse pawl member being located on the opposite side of the axis of the electromagnetic coil to the forward or reverse pawl member and being operatively connected therewith. Preferably, the counterweight assembly is formed separately from the forward or reverse pawl member, and is adapted to at least partially receive such.

Preferably still, the counterweight assembly is adapted to partially receive the forward or reverse pawl member, with a leading portion of the forward or reverse pawl member projecting therefrom.

Where each gear wheel is provided with two electromagnetic coils, where each gear wheel is provided with means for actuable engagement in the rotational direction, and means for actuable engagement in the counter-rotational direction in the form of forward and reverse pawl members respectively, and where each forward or reverse pawl member has two permanent magnets associated therewith held in fixed position relative to one another, the permanent magnets associated with a single forward or reverse pawl member are preferably located adjacent to the circumference the same electromagnetic coil.

An apparatus according to claim 28 characterised in that the two permanent magnets associated with each forward or reverse pawl member have magnetic dipole moments of opposite direction, and are held in fixed position relative to each other on opposite sides of a pivot means. Where each gear wheel has associated therewith two or more forward pawl members, and two or more reverse pawl members, the actuation of the forward pawl members and the reverse pawl members is preferably governed at least partially by a mechanical synchronisation means, the or each mechanical synchronisation means comprises a connector pin, fixed to each counterweight assembly, and a synchronising plate in which there are provided a number of slots equal to the number of connecting pins wherein the connecting pins are slidably engaged within the slots.

In a highly preferred form of the invention, the permanent magnets are Samarium- Cobalt type magnets.

In one form of the invention, the means for actuable engagement comprises a roller clutch arrangement whereby engagement between the rotatable body and the shaft about which such is provided is achieved in both rotational and counter- rotational directions.

In a highly preferred form of the invention, the rotatable body is provided in the form of a gear wheel.

In accordance with the present invention, there is further provided a method for engaging and disengaging a rotatable body with or from a shaft about which the rotatable body is provided by way of the apparatus described herein, the method comprising the steps of:

selectively powering at least one electromagnetic field generating means; and

causing an assembly housing one or more magnetically susceptible elements to move relative thereto, the movement induced in the assembly causing actuation or deactuation of one or more means for actuable engagement.

Where the rotatable body is provided in the form of a gear wheel, and both means for actuable engagement in the rotational direction, and means for actuable engagement in the counter-rotational direction are provided, when changing up from a first gear to a second gear under acceleration, the method more specifically comprises steps of: -

powering the or each electromagnetic field generating means of the first gear in such a manner that both the means for actuable engagement in the rotational direction and the means for actuable engagement in the counter- rotational direction of the first gear would be retracted if not for the fact that that the means for actuable engagement in the rotational direction of the first gear is loaded and will not retract;

powering the or each electromagnetic field generating means of the second gear in such a manner that both the means for actuable engagement in the rotational direction and the means for actuable engagement in the counter- rotational direction of the second gear would be deployed;

allowing the means for actuable engagement in the rotational direction of the second gear to be loaded before means for actuable engagement in the counter-rotational direction of the second gear, due to the relative speeds of the shaft and gear wheel; and

allowing the forward means for actuable engagement in the rotational direction of the first gear to spontaneously disengage due to overdrive.

Where the rotatable body is provided in the form of a gear wheel, and both means for actuable engagement in the rotational direction, and means for actuable engagement in the counter-rotational direction are provided, when changing down from a second gear to a first gear whilst engine braking, the method more specifically comprises the steps of:-

poweπng the or each electromagnetic field generating means of the second gear in such a manner that both the means for actuable engagement in the rotational and counter-rotational directions of the second gear would be retracted if not for the fact that that the means for actuable engagement in the counter-rotational direction of the second gear are loaded and will not retract;

powering the or each electromagnetic field generating means of the first gear in such a manner that both the means for actuable engagement in the rotational and counter-rotational directions of the second gear would be deployed;

allowing the means for actuable engagement in the counter-rotational direction of the first gear to be loaded before the means for actuable engagement in the rotational direction of the first gear, due to the relative speeds of the shaft and gear wheel; and allowing the means for actuable engagement in the counter-rotational direction of the second gear to spontaneously disengage due to overdrive.

BRIEF DESCRIPTION OF THE DRAWINGS

The method and apparatus for engaging and disengaging a rotatable body of the present invention will now be described, by way of example only, with reference to two embodiments thereof and the accompanying drawings, in which:

Figure 1 is a simplified diagrammatic representation of an axial cross section of an apparatus for the engaging and disengaging of a rotatable body in accordance with a first embodiment of the present invention, showing in particular the location of forward and reverse pawl actuator assemblies adjacent to the faces of an electromagnet assembly;

Figure 2 is a representation of a radial cross section of the apparatus of Figure 1 , showing in particular the arrangement of forward pawl actuator assemblies about a central wiring conduit;

Figure 3 is a simplified diagrammatic representation of an axial cross section of an apparatus for the engaging and disengaging of a rotatable body in accordance with a second embodiment of the present invention, showing in particular the location of forward and reverse pawl actuator assemblies about the circumference of first and second electromagnet assemblies;

Figure 4 is a representation of a portion of a radial cross section of the apparatus of Figure 3, showing in particular an actuator assembly containing permanent magnets pivotally attached to a flange;

Figure 5 is a partial perspective view of an apparatus for the engaging and disengaging of a rotatable body in accordance with a third embodiment of the present invention, showing forward and reverse pawls in an engaged position; Figure 6 is a partial perspective view of the apparatus of Figure 5, showing the forward and reverse pawls in a disengaged position; and

Figure 7 is an exploded view of an actuator assembly of the apparatus of Figures 5 and 6.

BEST MODE(S FOR CARRYING OUT THE INVENTION

In Figures 1 and 2, there is shown an apparatus for engaging and disengaging a rotatable body 10, comprising a shaft 12 having a hollow central bore 14, located coaxially within which is a static wiring conduit 16. A series of rotatable bodies in the form of gear wheels 18 are provided about the shaft, such that the gear wheels 18 may rotate freely and independently thereabout, as can best be seen in Figure 1.

Referring now to Figure 2, provided within the shaft 12 and spaced approximately equidistantly about the circumference thereof are a number of means for actuable engagement in the rotational direction in the form of forward pawls 20, corresponding to three per gear wheel 18. Interposed between the forward pawls 20 about the circumference of the shaft 12 are a number of means for actuable engagement in the counter-rotational direction in the form of reverse pawls 22, also corresponding in number to three per gear wheel 18. The reverse pawls 22 are oriented in the opposite manner to the forward pawls 20. The forward and reverse pawls 20 and 22 are pivotally attached to the shaft 12 by known means.

Provided in the inner surface 24 of each gear wheel 18 are a series of three arcuate recesses 26, each adapted to receive a forward pawl 20. Interposed between the arcuate recesses 26 in the inner surface 24 of each gear wheel 18 are three further arcuate recesses 28, each adapted to receive a reverse pawl 22.

Located about the wiring conduit 16 such that their magnetic dipole moments are substantially parallel thereto are a series of electromagnetic field generating means in the form of electromagnet assemblies 30, each comprising a wound copper coil and a former assembly. The number of electromagnet assemblies 30 corresponds to one per gear wheel 18. Current reaches the electromagnet assemblies 30 by way of wiring 32 situated within the wiring conduit 16, as can best be seen in Figure 1.

Adjacent to a face 29 of each electromagnet assembly 30, and situated about the wiring conduit 16 although in no way fixed thereto, are three forward pawl actuator assemblies 34, each connected to a single forward pawl 20 by way of a connecting rod 36.

As shown in Figure 2, each forward pawl actuator assembly 34 in turn comprises magnetically susceptible elements in the form of a first permanent magnet 38 and a second permanent magnet 40, held in fixed position relative to each other by a framework 42. Each framework 42 is adapted to allow radial movement of the forward pawl actuator assemblies 34 without interference by the wiring conduit 16. The distribution of mass within the frameworks 42 is such that centrifugal forces generated by the rotation of such with the shaft 12 are evenly balanced.

Further, each framework 42 positions the first and second permanent magnets 38 and 40 in a radially opposed manner relative to the dipole moment of the electromagnet assembly 30, and such that the dipole moments of the first and second permanent magnets 38 and 40 are substantially parallel to the dipole moment of the electromagnet assembly 30. However, the first and second permanent magnets 38 and 40 are fixed within the framework 42 such that the dipole moments thereof, whilst substantially parallel, are in opposite direction.

Adjacent to an opposing face 43 of each electromagnet assembly 30, on the opposite side thereof to the forward pawl actuator assemblies 34 are three reverse pawl actuator assemblies 44, each connected to a single reverse pawl 22 by way of a connecting rod 46.

Each reverse pawl actuator assembly 44 in turn comprises a first permanent magnet 48 and a second permanent magnet 50, held in fixed position relative to each other by a framework 52. Each framework 52 is adapted to allow radial movement of the reverse pawl actuator assemblies 44 without interference by the wiring conduit 16.

Further, each framework 52 positions the first and second permanent magnets 48 and 50 in a radially opposed manner relative to the dipole moment of the electromagnet assembly 30, and such that the dipole moments of the first and second permanent magnets 48 and 50 are substantially parallel to the dipole moment of the electromagnet assembly 30. However, the first and second permanent magnets 48 and 50 are fixed within the framework 52 such that the dipole moments thereof, whilst substantially parallel, are in opposite direction.

The dipole moments of the permanent magnets 48 and 50 of the reverse pawl actuator assemblies are of opposite the same configuration and orientation to those of the permanent magnets 38 and 40 of the corresponding forward pawl actuator assemblies.

Distributed about the inner circumference of the shaft 12 are a series of further permanent magnets 53. The permanent magnets 53 are circumferentially spaced to coincide with the frameworks 52 and 42 and are adapted to hold such in position in the absence of an electromagnetic field generated by the electromagnet assembly 30.

The temporary application of current in a particular direction through a selected electromagnet assembly 30 thus enables simultaneous engagement of the forward pawls 20 with the arcuate recesses 26 in the inner surface 24 of a selected gear wheel 18, and disengagement of the reverse pawls 22 from the arcuate recesses 28 in the inner surface 24 of the same gear wheel 18. Application of the current in the opposite direction will have the opposite effect.

For example, and with reference to Figures 1 and 2, application of a current in a clockwise direction through the electromagnet assembly 30, as represented in Figure 2, induces a magnetic field which attracts the first permanent magnet 30 of each of the forward pawl actuator assemblies 34 radially inward, due to the attraction of the south pole thereof with the north pole of the induced dipole, whilst at the same time causing the second permanent magnet 40 of the forward pawl actuator assembly 34 to move radially outward, the north pole of which being repelled by the north pole of the induced dipole. The effect of the magnetic interactions is thus the action of the forward pawl actuator assemblies on the connecting rods 36, causing the connecting rods 36 to in turn cause the forward pawls 20 to engage with the arcuate recesses 26 in the inner surface 24 of the selected gear wheel 18. The forward pawls 20 are maintained in position by way of centrifugal forces.

Simultaneously, the reverse pawl actuator assemblies 44 are caused to retract the reverse pawls 22. Being located at the opposite pole of the temporary dipole induced by the application of current to the electromagnet assembly 30, the south pole of the first permanent magnet 48 is repelled radially outward, whilst the north pole of the second permanent magnet is attracted radially inward, causing the reverse pawl actuator assemblies 44 to act on the connector rods 46 and thereby retract the reverse pawls 22.

Alternatively, and also with reference to Figures 1 and 2, application of a current in an anticlockwise direction through the electromagnet assembly 30 will cause the retraction of the forward pawls 20 and engagement of the reverse pawls 22 with the arcuate recesses 28 in the inner surface of each gear wheel 24.

When no current is applied through the electromagnet assembly 30, the permanent magnets 53 ensure the forward and reverse pawls 20 and 22 are maintained in a retracted position.

It is to be understood that the engagement and disengagement of the forward and reverse pawls 20 and 22 of each of the gear wheels 18 is substantially similar.

In Figures 3 and 4 there is shown an apparatus for engaging and disengaging gear wheels 54 in accordance with a second embodiment of the present invention. The means for engaging and disengaging gear wheels 54 is substantially similar to the means for engaging and disengaging gear wheels 10 hereinbefore described, and like numerals denote like parts. Each gear wheel 18 has associated therewith first and second electromagnet assemblies 56 and 58 Each electromagnet assembly 56 or 58 is capable of independent activation by way of current delivered by way of the wiring 32 passing through the wiring conduit 16.

Associated with each forward pawl 20, and integral with the shaft 12 is an internal flange 60, pivotally attached to which is a forward pawl actuator assembly 62, having first and second ends 64 and 66. Provided about the first end 64 of the forward pawl actuator assembly 62 is a first permanent magnet 70, and situated about the second end 66 is a second permanent magnet 72, such that the point of attachment of the forward pawl actuator assembly 62 to the internal flange 60 is interposed between the first and second permanent magnets 70 and 72 The distribution of mass within the forward pawl actuator assembly 62 is such that centrifugal forces generated by the rotation of such with the shaft 12 are evenly balanced

Each forward pawl actuator assembly 62 is adapted so as to align first and second permanent magnets 64 and 66 with the circumference of the first electromagnet assembly 56, such that their dipole moments are parallel to the axis thereof, although in opposite directions.

Attached to the second end 66 of each forward pawl actuator assembly 62 is a connecting rod 74, linking each forward pawl actuator assembly 62 with a forward pawl 20 The temporary application of current in a particular direction through a selected first electromagnet assembly 56 thus enables engagement of the forward pawls 20 with the arcuate recesses 26 in the inner surface 24 of a selected gear wheel 18, whilst application of the current in the opposite direction will cause the forward pawls 20 to be retracted therefrom The forward pawls 20 are maintained in position by way of centrifugal forces

For example and with reference in particular to Figure 4, application of a current in a clockwise direction through the first electromagnet assembly 56 induces a magnetic field which repels the first permanent magnet 70 of each of the forward pawl actuator assemblies 62 radially outward, whilst at the same time causing the second permanent magnet 72 of the forward pawl actuator assembly 62 to be attracted radially inward.

Thus the magnetic interactions cause the forward pawl actuator assemblies 62 to pivot about the internal flanges 60, and thereby act on the connecting rods 74, causing the connecting rods 74 to in turn act on the forward pawls 20 and cause them to engage with the arcuate recesses 26 in the inner surface 24 of the selected gear wheel 18.

Alternatively, and also with reference to Figure 4, application of a current in an anticlockwise direction through the first electromagnet assembly 56 will reverse the magnetic effect and cause the retraction of the forward pawls 20 from the arcuate recesses 28 in the inner surface of each gear wheel 24.

It is to be understood that the reverse pawls 22 can be controlled by way of the second electromagnet assembly 58 by analogous means.

Whilst it is acknowledged that the placement of the permanent magnets 38, 40, 48 and 50 relative to the magnetic fields produced by the electromagnet assemblies 30, 56 and 58 in the apparatus for engaging and disengaging gear wheels 10 and 54 does not result in the most efficient use of power provided to the electromagnet assemblies 30, 56 and 58, this is not perceived as problematic as the power is applied only on a momentary basis, with the pawls 20 and 22 being maintained in position by way of centrifugal forces.

It is envisaged that the apparatus for engaging and disengaging gear wheels 10 and 54 may be provided without the second permanent magnets 40, 50 and 66.

In Figures 5 to 7 there is shown an apparatus for engaging and disengaging gear wheels 76 in accordance with a third embodiment of the present invention. The means for engaging and disengaging gear wheels 76 is substantially similar to the apparatus 10 and 54 hereinbefore described, and like numerals denote like parts.

As for the apparatus 10, the apparatus 76, comprises a shaft 12 having a hollow central bore 14, about which are provided gear wheels 18, such that the gear wheels 18 may rotate freely and independently about the shaft, as can best be seen in Figure 5.

Provided within the shaft 12 and spaced approximately equidistant about the circumference thereof are a number of forward pawls 20, corresponding to three per gear wheel 18. Interposed between the forward pawls 20 about the circumference of the shaft 12 are a number of reverse pawls 22, also corresponding in number to three per gear wheel 18. The reverse pawls 22 are oriented in the opposite manner to the forward pawls 20.

Located in the hollow central bore 14 of the shaft 12, such that their magnetic dipole moments are substantially parallel thereto, are a series of electromagnet assemblies 30, each comprising a wound copper coil and a former assembly. The number of electromagnet assemblies 30 corresponds to one per gear wheel 18.

Adjacent to a face 29 of each electromagnet assembly 30, and situated about the wiring conduit 16 although in no way fixed thereto, are three forward pawl actuator assemblies 34, each in communication with a single forward pawl 20. Adjacent to an opposing face (not shown) of each electromagnet assembly 30, on the opposite side thereof to the forward pawl actuator assemblies 34 are three reverse pawl actuator assemblies 44 of identical configuration to the forward pawl actuator assemblies 34.

As can best be seen in Figure 7, each forward and reverse pawl actuator assembly 34 or 44 comprises a counterweight 78, pivotally attached to a pawl seat 80 by way of an actuating rod 82. Each counterweight 78 is provided with a connector pin 84, and contains a Samarium-Cobalt permanent magnet (not shown) configured such that the dipole moment of the permanent magnet is substantially parallel to that of the electromagnet assembly 30.

The dipole moments of the permanent magnets of the counterweights 78 of the forward pawl actuator assemblies 34 are of opposite direction to those of the reverse pawl actuator assemblies 44, such that the temporary application of current through the electromagnet assembly 30 causes the counterweights 78 thereof to simultaneously be drawn to, or repelled from such.

The counterweights 78 of each of the forward pawl actuator assemblies 34 are operatively interconnected by way of their connector pins 84 engaging slots 86 in a first synchronising plate 80, ensuring the simultaneous deployment or retraction of the forward pawls 20. Similarly, the counterweights 78 of each of the reverse pawl actuator assemblies 44 are operatively interconnected by way of their connector pins 84 engaging slots (not shown) in a second synchronising plate (not shown), ensuring the simultaneous deployment or retraction of the reverse pawls 22.

The pawl seat 80 of each forward or reverse pawl actuator assembly 34 or 44 comprises a hinge pin 86, by which the pawl seat 80 is pivotably attached to the shaft 12, and is adapted to partially receive a forward or reverse pawl 20 or 22 such that a leading portion 88 thereof extends therefrom.

In use, a user (not shown) who wishes to change up from a first gear to a second gear under acceleration, where the engagement of at least one gear wheel of each of the gear wheel pairs comprising the first and second gears both the first gear and the second gear is controlled by the apparatus for engaging and disengaging gear wheels 76, first applies a current to the electromagnet assembly 30 of the first gear in such a direction that the counterweights 78 of both the forward and reverse pawl actuator assemblies 34 and 44 are attracted radially inward.

The reverse pawls 22 are not under load, and are drawn inward, disengaging from the arcuate recesses 28 in the inner surface 24 of the gear wheel 18 of the first gear However, the forward pawls 20 are under load and, despite the attraction, remain engaged with the arcuate recesses 26 The user then applies current to the electromagnet assembly 30 of the second gear in such a direction that the counterweights 78 of both the forward and reverse pawl actuator assemblies 34 and 44 are repelled radially outward

Due to the relative speeds of the gear wheel 18 and the shaft 12, the forward pawls 20 will engage the arcuate recesses 26 prior to the reverse pawls 22 engaging the arcuate recesses 28 Finally, once the forward pawls 20 of the second gear are bearing load, the forward pawls 20 of the first gear will be overdriven and spontaneously retract

It is to be understood that the engagement and disengagement of the forward and reverse pawls 20 and 22 of each of the gear wheels 18 is substantially similar

It is envisaged that the forward and reverse pawl actuator assemblies 34 and 44 be formed from an inexpensive material such as cast alloy The forward and reverse pawls 20 and 22, on the other hand, should be formed of a precision ground, heat treated material

It is further envisaged that the apparatus for engaging and disengaging gear wheels 10, 54 and 54 70 may be used in conjunction with an apparatus for controlling the engagement and disengagement of gear wheels, such as that described in our co-pending International Application titled "METHOD AND APPARATUS FOR CONTROLLING THE ENGAGEMENT AND DISENGAGEMENT OF GEAR WHEELS", filed contemporaneously with this application

Modifications and variations as would be apparent to the skilled addressee are considered to fall within the scope of this invention

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS

1 . An apparatus for engaging and disengaging a rotatable body with or from a shaft about which the rotatable body is provided, the apparatus being characterised by one or more electromagnetic field generating means and one or more magnetically susceptible elements, wherein the or each electromagnetic field generating means is arranged with respect to the or each magnetically susceptible element so as to allow the or each electromagnetic field generating means to act on the or each magnetically susceptible element, causing such to move relative thereto, and thereby causing the actuation or deactuation of one or more means for actuable engagement of the rotatable body with the shaft.

2. An apparatus according to claim 1 characterised in that there is provided at least one electromagnetic field generating means per rotatable body.

3. An apparatus according to either of claims 1 or 2 characterised in that there is provided one electromagnetic field generating means per rotatable body.

4. An apparatus according to either of claims 1 or 2 characterised in that there are provided two electromagnetic field generating means per rotatable body.

5. An apparatus according to any one of the preceding claims characterised in that each means for actuable engagement has associated therewith a counterweight assembly, the counterweight assembly being radially opposed to the means for actuable engagement and adapted to substantially balance the weight of such.

6. An apparatus according to any one of the preceding claims characterised in that the or each means for actuable engagement has associated therewith one or more permanent magnets adapted, in the absence of an electromagnetic field generated by the or each electromagnetic field generating means, to maintain the means for actuable engagement in a deactuated condition.

. An apparatus according to any one of the proceeding claims characterised in that the means for actuable engagement of the rotatable body with the shaft comprises at least one means for actuable engagement in a rotational direction, and at least one means for actuable engagement in a counter- rotational direction, such that actuation of both the or each means for actuable engagement in the rotational direction and the or each means for actuable engagement in the counter-rotational direction causes the rotatable body to rotate in conjunction with the shaft and prevents such from counter-rotating relative to the shaft, deactuation of both the or each means for actuable engagement in the rotational direction and the or each means for actuable engagement in the counter-rotational direction allows the rotatable body to rotate independently of the shaft and counter-rotate relative to the shaft, actuation of the or each means for actuable engagement in the rotational direction and deactuation of the or each means for actuable engagement in the counter-rotational direction causes the rotatable body to rotate in conjunction with the shaft and allows such to counter rotate relative to the shaft, and actuation of the or each means for actuable engagement in the counter-rotational direction and deactuation of the or each means for actuable engagement in the rotational direction allows the rotatable body to rotate relative to the shaft, but prevents the rotatable body from counter-rotating relative to the shaft.

8. An apparatus according to claim 7 characterised in that there is provided at least one magnetically susceptible element relative to the means for actuable engagement in the rotational direction, and at least one magnetically susceptible element relative to the means for actuable engagement in the counter-rotational direction.

9. An apparatus according to any one of the preceding claims characterised in that the electromagnetic field generating means is provided in the form of an electromagnetic coil.

10. An apparatus according to any one of the preceding claims where the or each magnetically susceptible means is provided in the form of a permanent magnet.

1 1 . An apparatus according to any one of claims 1 to 10 where the magnetically susceptible means is provided in the form of a portion of magnetically susceptible material or an alloy containing such.

12. An apparatus according to either of claim 2 or 3, where the electromagnetic field generating means is provided in the form of an electromagnetic coil, and the or each magnetically susceptible element is provided in the form of a permanent magnet, characterised in that the or each permanent magnet is located adjacent a face of the electromagnetic coil, such that the magnetic dipole of the or each permanent magnet is substantially parallel to the axis thereof.

13. An apparatus according to either of claim 2 or 4, where the electromagnetic field generating means are provided in the form of electromagnetic coils, and the or each magnetically susceptible element is provided in the form of a permanent magnet, characterised in that the or each permanent magnet is located adjacent a circumference one of said electromagnetic coils, such that the magnetic dipole of the or each permanent magnet is substantially parallel to the axes thereof.

14. An apparatus according to claim 12 characterised in that, where each rotatable body is provided both with means for actuable engagement in the rotational direction and means for actuable engagement in the counter- rotational direction, the electromagnetic field generating means is provided in the form of an electromagnetic coil, and the or each magnetically susceptible element is provided in the form of a permanent magnet, characterised in that the electromagnetic coil is interposed between the or each permanent magnet associated with the means for actuable engagement in the rotational direction and the or each permanent magnet associated with the means for actuable engagement in the counter-rotational direction, and the magnetic dipoles of the or each permanent magnet associated with the means for actuable engagement in the rotational direction are of opposite direction relative to the magnetic dipoles of the or each equivalent permanent magnet associated with means for actuable engagement in the counter-rotational direction, whereby the application of current through the electromagnetic coil in a first direction causes the simultaneous actuation of the means for actuable engagement in the rotational direction and deactuation of the means for actuable engagement in the counter-rotational direction, whilst application of a current through the electromagnetic coil in a second direction, opposite to the first direction, causes simultaneous actuation of the means for actuable engagement in the counter-rotational direction orientation and deactuation of the means for actuable engagement in the rotational direction.

15. An apparatus according to claim 12 characterised in that, where each rotatable body is provided with both means for actuable engagement in the rotational and the counter-rotational directions, and the electromagnetic field generating means is provided in the form of an electromagnetic coil, the electromagnetic coil is interposed between the or each permanent magnet associated with the means for actuable engagement in the rotational direction and the or each permanent magnet associated with the means for actuable engagement in the counter-rotational direction, and the magnetic dipoles of the or each permanent magnet associated with the means for actuable engagement in the rotational direction are of the same direction as the magnetic dipoles of the or each equivalent permanent magnet associated with the means for actuable engagement in the counter-rotational direction, whereby the application of current through the electromagnetic coil in a first direction causes the simultaneous actuation of the both the means for actuable engagement in the rotational and counter-rotational directions, whilst application of a current through the electromagnetic coil in a second direction, opposite to the first direction, causes simultaneous deactuation of the means for actuable engagement in the rotational and counter-rotational directions.

16. An apparatus according to claim 13 characterised in that, where each gear wheel is provided both with means for actuable engagement in the rotational direction and means for actuable engagement in the counter-rotational direction, the or each permanent magnet associated with the means for actuable engagement in the rotational direction is located about a circumference of one electromagnetic coil, whilst the or each permanent magnet associated with the means for actuable engagement in the counter rotational direction is located about a circumference of the other electromagnetic coil.

17. An apparatus according to any one of claims 7 to 16 characterised in that, where each rotatable body has associated therewith two or more means for actuable engagement in the rotational direction, the actuation of the means for actuable engagement in the rotational direction is at least partially governed by a mechanical synchronisation means.

18. An apparatus according to any one of claims 7 to 17 characterised in that, where each rotatable body has associated therewith two or more means for actuable engagement in the counter-rotational direction, the actuation of means for actuable engagement in the counter-rotational direction is at least partially governed by a mechanical synchronisation means.

19. An apparatus according to any one of the preceeding claims characterised in that the means for actuable engagement is provided in the form of one or more pawl members, provided in the shaft or in the rotatable body and adapted to engage a complimentary recess in an opposed surface.

20. An apparatus according to either of claims 7 or 8 characterised in that the means for actuable engagement in the rotational direction is provided in the form of one or more forward pawl members, and the means for actuable engagement in the counter-rotational direction is provided in the form of one or more reverse pawl members, wherein the or each forward pawl member is adapted to engage a leading surface of a substantially complimentary recess in an opposed surface positively during rotation of that opposed surface with respect to the pawl member, and the or each reverse pawl member is adapted to engage a trailing surface of a substantially complimentary recess in an opposed surface positively during rotation of that opposed surface with respect to the pawl member.

21 . An apparatus according to claim 20 characterised in that there are provided two permanent magnets for the or each forward or reverse pawl member.

22. An apparatus according to claim 21 characterised in that the two permanent magnets associated with the or each forward or reverse pawl member are held in fixed position relative to one another.

23. An apparatus according to claim 22, where each gear wheel is provided with one electromagnetic coil, characterised in that the permanent magnets are located on opposite sides of the axis of the electromagnetic coil and such that their magnetic dipoles are opposite, and substantially parallel to, the axis of the electromagnetic coil.

24. An apparatus according to claim 20 characterised in that there is provided one permanent magnet for the or each forward or reverse pawl member.

25. An apparatus according to claim 5, where the means for actuable engagement in the rotational and counter-rotational directions are provided in the form of forward and reverse pawls respectively and where the or each forward or reverse pawl has one permanent magnet associated therewith, characterised in that the permanent magnet is provided in the counterweight assembly, the counterweight assembly associated with each forward or reverse pawl member being located on the opposite side of the axis of the electromagnetic coil to the forward or reverse pawl member and being operatively connected therewith.

26. An apparatus according to claim 25 characterised in that the counterweight assembly is formed separately from the forward or reverse pawl member, and is adapted to at least partially receive such.

27. An apparatus according to claim 26 characterised in that the counterweight assembly is adapted to partially receive the forward or reverse pawl member, with a leading portion of the forward or reverse pawl member projecting therefrom.

28. An apparatus according to claim 13, where each gear wheel is provided with means for actuable engagement in the rotational direction, and means for actuable engagement in the counter-rotational direction in the form of forward and reverse pawl members respectively, and where each forward or reverse pawl member has two permanent magnets associated therewith held in fixed position relative to one another, characterised in that the permanent magnets associated with a single forward or reverse pawl member are located adjacent to the circumference the same electromagnetic coil.

29. An apparatus according to claim 28 characterised in that the two permanent magnets associated with each forward or reverse pawl member have magnetic dipole moments of opposite direction, and are held in fixed position relative to each other on opposite sides of a pivot means.

30. An apparatus according to any one of claims 25 to 27, where each gear wheel has associated therewith two or more forward pawl members, and two or more reverse pawl members, the actuation of the forward pawl members and the reverse pawl members being governed at least partially by a mechanical synchronisation means, characterised in that the or each mechanical synchronisation means comprises a connector pin, fixed to each counterweight assembly, and a synchronising plate in which there are provided a number of slots equal to the number of connecting pins wherein the connecting pins are slidably engaged within the slots.

31 . An apparatus according to any one of the proceeding claims characterised in that the permanent magnets are Samarium-Cobalt type magnets.

32. An apparatus according to any one of claims 1 to 18 characterised in that the means for actuable engagement comprises a roller clutch or ratchet re arrangement whereby engagement between the rotatable body and the shaft about which such is provided is achieved in both rotational and counter- rotational directions.

33. An apparatus according to any one of the preceeding claims in which the rotatable body is provided in the form of a gear wheel.

34. A method for engaging and disengaging a rotatable body with or from a shaft about which the rotatable body is provided by way of the apparatus of claims 1 to 33, the method comprising the steps of:

selectively powering at least one electromagnetic field generating means; and

35. A method according to claim 29, where the rotatable body is provided in the form of a gear wheel, for engaging and disengaging a gear wheel by way of the apparatus of claim 7, characterised by, when changing up from a first gear to a second gear under acceleration, by the steps of:-

36. A method according to claim 29, where the rotatable body is provided in the form of a gear wheel, for engaging and disengaging a gear wheel by way of the apparatus of claim 7, characterised by, when changing down from a second gear to a first gear whilst engine braking, by the steps em¬

powering the or each electromagnetic field generating means of the second gear in such a manner that both the means for actuable engagement in the rotational and counter-rotational directions of the second gear would be retracted if not for the fact that that the means for actuable engagement in the counter-rotational direction of the second gear are loaded and will not retract;

allowing the means for actuable engagement in the counter-rotational direction of the first gear to be loaded before the means for actuable engagement in the rotational direction of the first gear, due to the relative speeds of the shaft and gear wheel; and

allowing the means for actuable engagement in the counter-rotational direction of the second gear to spontaneously disengage due to overdrive.

37. A method according to any one of claims 29 to 31 characterised in that the means for actuable engagement in the rotational direction is provided in the form of one or more forward pawl members, and the means for actuable engagement in the counter-rotational direction is provided in the form of one or more reverse pawl members.

38. An apparatus substantially as hereinbefore described with reference to Figures 1 and 2, Figures 3 and 4 or Figures 5 to 7.