GB2340669A

GB2340669A - Rolling Rotor Motor

Info

Publication number: GB2340669A
Application number: GB9918506A
Authority: GB
Inventors: Kevin Ross Inkster
Original assignee: Arbortech Industries Ltd
Current assignee: Arbortech Industries Ltd
Priority date: 1998-08-05
Filing date: 1999-08-05
Publication date: 2000-02-23
Also published as: AUPP509198A0; FR2782205A1; JP2000060104A; GB9918506D0; DE19936021A1

Abstract

A motive power apparatus including a stationary member (1) and a movable member (2), one said member having an inner contact surface (20, 27, 33), the other said member having an outer contact surface (21, 28, 30) located adjacent the inner contact surface, the inner and outer contact surfaces contacting along a point contact, wherein propulsion means (3) are provided on one said member for urging the other said member in a rolling orbital motion relative to the one said member. Commutation switches 25 may be provided and pole structure is disclosed. The rotor may direct drive a cutting tool. Contact may be improved by magnetic/electro magnetic means and the contact surfaces may be toothed.

Description

2340669 MQTIVE POWEB APPARATUS The present invention is directed to

apparatus used to supply motive power for various small and large scale mechanical applications. The present invention will be described with respect to apparatus that are electrically powered. It Is however to be appreciated that the present Invention is not restricted to being electrically powered, and that the use of other power sources such as compressed air Is also envisaged.

Conventional electric motors are used to drive many different forms of mechanical equipment. The usual operating characteristics of such electric motors is that they are generally Inefficient at high torques and low rotational speeds. Therefore, in applications where the mechanical equipment needs to be driven at relatively low speeds and/or where the maximum torque is required at low speeds, speed reduction units such as gear boxes or belt or chain drives are required between the electric motor and the driven component. For example, In power tools such as electric drills and saws, a gear box Is typically provided between the electric motor and the driven component of the power tool.

The provision of such speed reduction units Inevitably results in some power loss between the electric motor and the driven component resulting in less than optimurn power transfer efficiency. Furthermore, the requirement for a speed reduction unit can also be disadvantageous where there are weight and space limitations as in the case of hand held power tools. The use of speed reduction units can also make it more difficult to control the torque delivered to the device being driven, In particular, this can lead to excessive or insufficient torque being applied to the driven device, Furthermore, there is a greater potential for electric motors used In low rotational speed applications to stall when the torque applied to the output shaft of the motor is sufficiently high to stop the rotational movement of the rotor of the motor. This will lead to the overheating of the motor which is likely to result in permanent damage or destruction of the motor.

It would therefore be preferable to have a motive power apparatus which provides relatively high torques at low rotational speeds without the need for 2 any speed reduction unit as would typically be the case with electric motors, Furthermore, it Is preferable to have a motive power apparatus having a self limiting torque output. In addition, it is also preferable that the motive power apparatus can be staffed without leading to any damage or the destruction of 5 that apparatus.

It is therefore an object of the present invention to provide an improved motive power apparatus providing at least one of the above noted operating characteristics.

With this in mind, the present invention provides a motive power apparatus Including a stationary member and a movable member, one said member having an inner contact surface. the other said member having an outer contact surface located adjacent the inner contact surface, the inner and outer contact surfaces contacting along a point contact, wherein propulsion means are provided on one said member for urging the other said member in a rolling 16 orbital motion relative to the one said member.

The term "point contact includes contact along a contact fine between the Inner and outer contact surfaces.

It should also be noted that the rolling orbital motion is a 'relative" motion between the said members. Therefore, in addition to the situation where only the movable member moves, the stationary member may also move to an extent. In particular, the movable could wobble' with little to no rotational movement while the stationary member can move in a purely rotational movement.

The propulsion means may preferably be provided on the stationary member for urging the movable member in the rolling orbital motion relative to the stationary member.

The propulsion means may include electromagnetic means for providing an attractive or repulsive force on the movable member. It is however also envisaged that alternative propulsion means such as electrostatic, hydraulic or pneumatic or other means be used to provide the motive force for urging the motion of the movable member. For example, a series of compressed air jets could be used to apply force to the contact surface of the movable membr.

The stationary and movable members may be held in contact by centrifugal forces as a result of the movement of the movable member relative to the stationary member. Other forces may also act to hold in contact the members, for example, magnetic, electrostatic or hydraulic or pneumatic pressure forces in dependence on the configuration of the motive power apparatus. The rolling orbital motion of the movable member may be Induced as a result of frictional forces between the Inner and outer contact surfaces. It is also envisaged that there be a positive interaction between the inner and outer contact surfaces to ensure that the movable members moves in the rolling orbital motion. For example, the inner and outer surfaces may include gear teeth t hat mesh together during movement of the movable member.

In a first preferred embodiment, the stationary member may have the outer contact surface and the movable member may have the Inner contact surface. The propulsion means may urge the movable member In a said rolling orbital motion about the outer contact surface of the stationary member. The inner contact surface of the movable member therefore rolls over the outer contact surface of the stationary member. In this embodiment. the movable member moves in a similar fashion to the movement of a hula hoop" about the outer contact surface of the stationary member with the point contact between the movable and stationary members travelling along the outer contact surface of the stationary member during the rolling orbital motion.

Alternatively. according to a second preferred embodiment, the stationary member may have an inner contact surface and the movable member may have an outer contact surface. The _movable-member may be urged in the roWing orbital motion against the Inner contact surface of the stationary member by the propulsion means. The outer contact surface of the movable member therefore rolls along the inner contact surface of the stationary member. The motion of the movable member relative to the stationary member is similar to the movement of the planet wheel relative to the outer annular track within an epicyclic gear set.

The Inner and outer contact surfaces may be at least generally cylindrical in configuration. The movable member may generally float without support about the stationary member when the motive power apparatus Is not iri use In 4 the first preferred embodiment. Alternatively, the movable mmber may float within the confines of the stationary member In the second preferred embodiment.

Alternatively, according to a third preferred embodiment of the present 5 Invention. one said member may have an at least generally frustoconical outer contact surface, and the other said member may have an at least generally frustoconical inner contact surface. Preferably, the movable member may have the at least generally frustoconical outer contact surface, with the stationary member having the at least generally frustoconical inner contact surface. The movable member may be pivotally supported about a single pivot point, and may pivot about said point when undergoing said rolling orbital motion. The single pivot point may be located at or adjacent an apex of the conical plane within with the outer contact surface is located. The cone angle at the conical plane apex, being the angle between a central axis of the cone and the surface of the cone, may be within the range of 0 to 90. Therefore, when the cone angle approaches 00, the outer contact face of the movable member is almost cylindrical. However, when the cone angle at the conical plane apex approaches 9011, the outer contact surface of the movable member approaches the form of a flat disk- Such a configuration could be applicable for, for example, a rotatable platform. Of course. the cone angle could also be any intermediate angle within the abovenoted range.

A plurality of electromagnetic means may be provided along the periphery of the stationary member. Each electromagnetic means may be sequentially energised about the periphery thereof to thereby urge the portion of the movable member closest to the electromagnetic means towards or away from it. Three or more electromagnetic means may preferably be provided along the periphery of the stationary member. The electromagnetic means may be energised in sequence whereby the next electromagnetic means immediately forward of the point contact between the stationary and movable members is energised. This sequential energising of the electromagnetic means thereby urges the movable member in the required rolling orbital motion.

The electromagnetic rneans may be In the form of a solenoid assembly having a solenoid coil. A pole assembly may also be provided around the solenoid coil. The pole assembly may provide opposing pole pieces across which a magnetic field may be generated when the solenoid coil Is energised. The pole pieces may be provided within or adjacent the contact surface of the stationary member andlor may form part of said contact surface. The opposing pole pieces may be spaced such that they are aligned generally along the elongate extent of the contact surface. Alternatively. the pole pieces may be spaced such that they are aligned laterally relative to the elongate extent of the contact surface.

Switch means may be provided along the elongate extent of the contact surface of the stationary member for controlling the energisation of each solenoid coil. The switch means may be a contact switch which may contact the movable member as it orbits relative to the stationary member. The switch may be located to thereby control the energisatign of the solenoid assembly located immediately to the front of the switch in the direction of the orbit of the movable member.

Alternatively, the switching means may be provided by the solenoid assemblies. the switching occurring when the pole pieces of the solenoid assembly are bridged or substantially bridged by the movable member when In contact. This switching energises the next solenoid assembly in the direction of movement of the orbit of the movable member. It is also envisaged that the switching means may be provided by electronic circuitry for actively controlling the switching.

It Is also envisaged that electromagnetic means be provided on both members to reinforce the attraction forces between the movable and stationary members. Permanent magnetic means may also or alternatively be provided on both members to assist the operation of the electromagnetic means.

Transfer means may be provided to transfer the power induced by the rolling orbital motion of the movable member to a drive shaft of the motive power apparatus. Gear teeth may for example be provided on an outer periphery or inner cavity of the movable member. A cooperating gear member may engage the movable member, with the gear member in turn driving the drive shaft.

6 Alternatively, the movable member may be connected to the drive shaft by means of a flexible coupling which compensates for the orbital rolling motion of the movable member.

In the Applicant's Australian Patent Application No. 56275198, there is described a cutting apparatus wherein a cutting member is driven in a rolling orbital motion. As this motion is the same as the motion of the movable member of the motive power apparatus according the present invention, this apparatus may be used to drive the cutting member. To this end. the cutting member may be directly secured to or be integral with the movable member and may therefore rnove together with the said movable member. This arrangement provides a compact assembly wherein the only moving part is the movable member of the motive power apparatus and the cutting member secured thereto.

The motive power apparatus according to the present invention provides relatively high torque at low rotational spqeds and is thereby particularly applicable for the above noted cutting apparatus. In particular, this allows the cutting member to be rotated at a relatively low rotational speed while at the same time providing sufficient torque to allow the cutting member to cut through hard materials. The slow rotation of the cutting member also makes the cutting apparatus safer to use. It should be noted that the motive power apparatus can be readily adapted for use in a variety of different applications. The motive power apparatus can be sized to suit small device applications such as hand held power tools as previously described. Larger versions of the motive power apparatus could be used to drive large scale equipment such as automobiles, industrial and mining equipment, and so on.

The torque output of the motive power apparatus according to the present Invention can be readily varied by varying the size of the electromagnetic means andlor permanent magnetic means thereby varying the force on the movable member. It should noted that the high torque is in part achieved because of the distance between the contact point of the movable member with the stationary member and the energised electromagnetic means. This provides a leverage advantage which results in said high torques at"rlativeiy low rotational speeds of the movable member.

7 The motive power apparatus according to the present Invention has significant advantages over conventional apparatus such as electric motors. Firstly. the motive power apparatus according to the present Invention can provide high torque at low rotational speeds without the need for any speed reduction unit. This leads to potential cost and weight savings. Furthermore, the motive power apparatus according to the present invention allows for more accurate control of the torque, partly because no speed reduction unit is required.

Operationally, the motive power apparatus provides a self limiting torque output which prevents excessive torque being delivered. Furthermore, unlike conventional electric motors, the apparatus can be stalled or even back driven without any damage to the apparatus.

The motive power apparatus, when compared with conventional electric motors, is simpler In construction, with the need for shaft bearings and brushes being eliminated.

It will be convenient to further descnibed the Invention by reference to the accompanying drawings which Illustrate preferred embodiments of the present invention. Other embodiments of the Invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the Invention.

In the drawings:

Figure 1 is a front cross-sectional view of a first preferred embodiment of a motive power apparatus according to the present invention; Figure 2 is a side cross-sectional view of the motive power apparatus of Figure 1; Figure 3 is a front cross-sectional view of a second preferred embodiment of a motive power apparatus according to the present invention; Figure 4 is a side cross-sectional view of a third preferred embodiment of a motive power apparatus according to the present invention; and Figure 5 is a side cross-sectional view of a fourth preferred embodiment of a motive power apparatus according to the present invention.

The following description refers to a number of preferred embodinients of

8 the motive power apparatus according to the present invention. The same reference numerals have therefore been used for corresponding features in each embodiment for clarity reasons.

Referring initially to Figure 1 and 2. the motive power apparatus includes a stationary member or "stator' 1 and a movable -member or "rotor' 2. The movable member 2 has a cylindrical inner contact surface 20 for contacting a cylindrical outer contact surface 21 of the stationery member 1, with the movable member 2 moving about the exterior of the stationary member 1 In a rolfir)g orbital motion, The movable member 2 Is shown supporting a cutting member 3 which is secured to or integral with the movable member 2 in Figure 2. This cutting member 3 operates in a manner described In the Applicants Australian Patent application No. 56275198, details of which are incorporated herein by reference. Alternative uses of the motive power apparatus are also envisaged, and the present invention Is not restricted to this application.

is The stationery member 1 includes a central portion 4. The central portion 4 supports the propulsion means for the apparatus In the form of four separate solenoid assemblies 5 spaced about the central portion 4. Each solenoid assembly 5 includes a solenoid coil 6 supported on a pole assembly 7. The pole assembly 7 includes a solenoid core piece 8 located within the solenoid coil 6. The core piece 8 is secured to or integral with a base portion 9, the base portion 9 engaging the central portion 4 of the stationery member 1. An outer pole piece 10, a portion of which is shown in Figure 2, extends to either side of and behind the solenoid coil 6. A magnetic field is generated in the space between and around the solenoid core 8 and the outer pole piece 10 when the_ solenoid coil 6 is energised.

In the arrangement shown In Figure 1 and 2, the outer contact surface 21 of the stationary member 1 may be provided by the exposed upper surface of each outer pole piece 10. It is also envisaged that the stationary member 1 provide an cylindrical shoulder upon which the movable member 2 can roll.

Contact switches 25 may be provided between each pair of solenoid assemblies 5. Each contact switch 25 energises the next solenoid assembly 5 in the direction of orbit of the movable member 2 when the movable member 2 9 contacts the respective contact switch 25. Alternatively, the contact switches 25 may be eliminated, and the "switching" requirement provided directly by the solenoid assemblies 5. In particular the bridging of the pole assembly 7 as a result of contact with andlor the proximity of movable member 2 can provide the switching signal to energise the next solenoid assembly 5 in the direct of orbit of the movable member 2. it is also envisaged that the switching be electronically controlled.

Sequential energisation of the solenoid assemblies 5 urges the movable member 2 to in a rolling orbital motion about the central portion 4 of the stationary member 1. The cutting member 3 is also caused to move In the same rolling orbital motion because it is an Integral part of the movable member 2. The advantages of such a motion is explained in detail in the Applicant's Patent Application No. 56275198. Furthermore, because the motive power apparatus according to the present invention can provide high torque at low rotational speeds, this enables the cutting member 3 to cut through a variety of material including hard substances such as brick and stone.

The use of the motive power apparatus of the present invention in a cutting apparatus also has the advantages that only one movable component is required in the cutting apparatus. Furthermore. the cutting apparatus can be kept relatively compact in size because there is no requirement for complicated mechanical assemblies to drive the cutting member 3.

Figure 3 shows an alternative preferred embodiment of the motive power apparatus according to the present invention. This embodiment differs from the embodiment shown In-Figures 1 and 2 in that the positions of the stationary and movable members 1,2 are reversed, the movable member 2 now moving within the confines of the stationary member 1. The stationary member 1 is therefore provided with an internal cylindrical contact surface 27, whereas the movable member 2 is provided with an outer cylindrical contact surface 28. The movable member 2 moves In a rolling orbital motion within the stationary member 1.

Solenoid assemblies 5 are also spaced about the stationary member 5 and operate in the same general manner as for the previously described embodiment to provide the propulsion for the movable member 2.

In both of the above described embodiments, the contact surfaces of both the stationary and movable members are cylindrical shape. Furthermore, the movable member 2 is allowed to 'float" around or within the stationary member I with no other support. Figure 4 shows another altemative preferred embodiment where the motive power apparatus according to the present invention Is provided With a single point support, This embodiment is similar to the embodiment shown In Figure 3 in that the movable member 2 Is located within the confines of the stationary member 1. The movable member 2 however has an outer contact surface 30 which Is frustoconical in shape. The conical plane 38 within which the frustoconical contact surface 30 of the mova ble member 2 is located has an apex 32, and the single point support is located at the apex 32'. The stationary member 1 has an inner frustoconical surface 33 for cooperating with the outer frustoconical contact surface 30 of the movable member 2. Solenoid assemblies 5 are provided about the periphery of the stationary member 1 and operate in the same manner as previously described.

A shaft extends from the movable member 2, and a pivot coupling 35 supports the opposing end of the shaft 39 at a pivot connection 37 therebetween. This allows the motion of the movable member 2 to be transferred through the shaft 39 to the coupling 35. The movable member 2 is at the same time supported by the coupling about the pivot connection 37. The rolling orbital motion of the movable member 2 results in a constantly varying angular deviation b of the axis of rotation of the shaft 39 relative to the single point support at the pivot connection 37. The coupling 35 can however provide a simple rotational output to, for example, an output shaft (not shown) without any such angular deviation being transferred.

The cone angle a of the conical plane of the movable member contact surface 30, being the angle between the central axis of the conical plane and the conical plane, is shown in Figure 4 to be about 150. This cone angle can however be anywhere within the range of 00 to 900.

The further preferred embodiment of the present invention shown in Figure 5 is similar to the embodiment shown in Figure 4 in having a rovable member 2 with an outer frustoconical contact surface 30 In contact with the inner frustoconical surface 33 of a stationary member 1. The cone angle a of the movable member outer contact surface 30 is however much greater than the cone angle a of the embodiment in Figure 4. In the embodiment of Figure 5, the cone angle Is almost 90 such that the movable member 2 is in the form of a disc. One side 41 of the movable member 2 supports the frustoconical contact surface 30, whereas the opposing side 43 of the movable member 2 canbe flat. This embodiment can be used to provide, for example a rotatable platform for rotating support applicaons.

12

Claims

CLAIMS;

1 1 A motive power apparatus including a stationary member and a movable member, one said member having an inner contact surface, the other said member having an outer contact surface located adjacent the inner contact surface, the inner and outer contact surfaces contacting along a point contact, wherein propulsion means are provided on one said member for urging the other said member In a rolling orbital motion relative to the one said member, 2. A motive power apparatus according to claim 1, wherein the propulsion means are provided on the staflonary member for urging the movable member in the rolling orbital motion relative to the stationary member.

3. A motive power apparatus according to claim 2, the stationary member having the outer contact surface and the movable member having the Inner contact surface, wherein In use the propulsion means urges the movable member in a said rolling orbital motion against and about the outer contact surface of the stationary member such that the inner contact surface of the movable member rolls along the outer contact surface of the stationary member.

4. A motive power apparatus according to claim 2, the stationary member having the inner contact surface and the movable member having the outer contact surface, wherein in use the propulsion means urges the movable member In the rolling orbital motion against and within the Inner contact surface of the stationary member such that the outer contact surface of the movable member rolls along the Inner contact surface of the stationary member.

5. A motive power apparatus according to claim 4, wherein one said member has an at least generally frustoconical outer contact surface, and the other said member has an at least generally frustoconical inner contact surface, the movable member being pivotally supported about a single pivot point, and pivoting about said point when undergoing said rolling orbital motion.

13 6. A motive power apparatus according to claim 5, wherein the movable member has an at least generally frustoconical outer contact surface, and the stationary member has an at least generally frustoconical inner contact surface.

7. A motive power apparatus according to claim 6, wherein the single pivot point may be located at or adjacent an apex of the conical plane within With the outer contact surface of the movable member Is located.

8. A motive power apparatus according to claim 7, wherein the conical plane apex has a cone angle measured between a central ayJs of the conical plane and the conical plane, the cone angle being within the range of 011 to 9011.

91 A motive power apparatus according to any one of the preceding claims, wherein the propulsion means Includes electromagnetic means for providing an attractive or repulsive force on the other said member.

10. A motive power appadtus according to claim 9, wherein a plurality of said electromagnetic means are provided along the periphery of the stationary member, each electromagnetic means in use being sequentially energised about the periphery thereof to thereby urge the portion of the movable member closest to the electromagnetic means towards or away from said electromagnetic means.

11. A motive power apparatus according to claim 10, wherein in use the electromagnetic means Is energised in sequence whereby the next electromagnetic means Immediately forward of the point contact between the stationary and movable members Is energised to thereby urge the movable member in the required rolling orbital motion.

12. A motive power apparatus according to any one of claims 9 to 11, wherein the electromagnetic means are in the form of a solenoid assembly having a solenoid coil.

14 13. A motive power apparatus according to claim 12, wherein the solenoid assembly further includes a pole assembly, the pole assembly providing opposing pole pieces across which a magnetic field is generated when the solenoid coil is energised.

14. A- motive power apparatus according to claim 13, wherein the pole pieces are provided within or adjacent the contact surface of the stationary member andlor form part of said contact surface.

15. A motive power apparatus according to claim 14, wherein the opposing pole pieces are spaced'such that they are aligned generally along the elongate extent of the contact surface.

16. A motive power apparatus according to claim 14, wherein the pole pieces are spaced such that said pole pieces are aligned laterally relative to the elongate extent of the contact surface.

17. A motive power apparatus according to any one of claims 12 to 16, further including switch means provided along the elongate extent of the contact surface of the stationary member for controlling the energIsation of each solenoid coil.

18. A motive power apparatus according to claim 17, wherein the switch means Is a contact switch for contacting the movable member as h orbits relative to the stationary member, each said switch being located to thereby control the energisation of the solenoid assembly located immediately to the front of the switch in the direction of the orbit of the movable member.

19. A motive power apparatus according to any one of claims 12 to 16, further including switch means provided by the solenoid assemblies for controlling the energisation of each solenoid coil, a switching being provided by the switch means occurring when the pole pieces of the solenoid assembly are bridged or substantially bridged by the movable member when In contact, the switching energising the next solenoid assembly in the direction of movement of the orbit of the movable member.

20. A motive power apparatus according to any one of claims 12 to 16 further including electronic switch means for controlling the energisaflon of the solenoid coils.

21. A motive power apparatus according to any one of claims 9 to 20, further including electromagnetic andlor permanent magnetic means provided on the movable member to reinforce the attracdon or repulsion forces between the movable and stationary members.

22. A motive power apparatus according to any one of claims 10 to 21, further including permanent magnetic means provided on the stationary member to assist the operation of the electromagnetic means.

23. A motive power apparatus according to any one of the preceding claims, ineJuding transfer means for transferring the power Induced by the rolling orbital motion of the movable member to a drive shaft of the motive power apparatus.

24. A motive power apparatus according to claim 23, wherein the transfer means Includes gear teeth provided on an outer periphery or inner cavity of the movable member, and a cooperating gear member for engaging the movable member, the gear member in turn driving the drive shaft.

16 25. A motive power apparatus according to claim 23, wherein the transfer rneans includes a flexible coupling connecting the movable member to the drive shaft.