Patent Publication Number: US-6703724-B1

Title: Electric machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 09/196,274, filed on Nov. 19, 1998, now U.S. Pat. No. 6,160,328, which claims the benefit of Australian Provisional Application filed on Nov. 13, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The applicant is knowledgeable of the design and operation of pulverizing mills used to grind mineral samples into a fine powder. The pulverizing mill together with many other types of machines require an orbital or vibratory motion in order to work. These machines include for example screens for screening particles, cone crushers for crushing rocks, and shakers and stirrers for shaking and stirring laboratory solutions, biological/medical products and specifications, and the like. 
     The invention relates to an electric machine operable as a motor to provide motion required to drive a pulverizing mill but which can alternatively be operated as a generator to provide electricity or an electrical load. 
     2. Description of the Related Art 
     Traditionally, the orbital or vibratory motion required on such machines is imparted to an object by attaching the object to a spring mounted platform to which is coupled an eccentrically weighted shaft driven by a motor; or, via bearings to an eccentric shaft driven by a motor. A mechanical coupling such as a gear box, belt, or universal joint is used to couple the output of the motor to the shaft. 
     However, the very motion that these machines are designed to produce also leads to their inevitable and frequent failure. Specifically, the required orbital or vibratory motion leads to fatigue failure in various components of the machines including mechanical couplings, transmissions, bearings, framework and mounts. The cost of repairing such failures is very high. In addition to the cost of repairing the broken component(s) substantial losses can be incurred due to down time in a larger process in which the failed machine performs one or more steps. A further limitation of such machines is that they produce fixed orbits or motions with no means of dynamic control (i.e. no means of varying orbit path while machine is running). 
     The present invention has evolved from the perceived need to be able to generate orbital or vibratory motion without the limitations and deficiencies of the above described prior art. 
     It is also well known in the art that an electric machine can operate as a motor when driven by electricity to provide a mechanical output such as a rotation of a shaft and, can operate as an electricity generator or electrical load when a mechanical input is provided such as a rotation of a shaft by crank, water wheel, or similar means. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided an electric machine having a magnet producing lines of magnetic flux extending through an air gap in a first direction. The air gap is formed by oppositely disposed magnetic poles. A support capable of at least two-dimensional motion relative to the magnet in a single plane contains the support. The support is provided with at least two electrically conductive paths, each having a current carrying segment which extends with a circumferential aspect relative to a center of the support, and the segments are disposed in and extend across the lines of magnetic flux within the air gap in a second direction substantially perpendicular to the first direction. Thus, interaction of an electric current flowing through a particular segment and the lines of magnetic flux produces a thrust force to cause motion of the support relative to the magnet. 
     Preferably, the support is made of an electrically conductive material and is provided with a plurality of apertures disposed inboard of an outer peripheral edge of the support wherein at least one of the electrically conductive paths is constituted by the portions of the support that extend about the apertures. Also, preferably, the support is in the form of a wheel having a central portion hub with spokes extending radially outwardly from the central portion hub and an outer rim joining the spokes, respectively. Each aperture is thus defined in the wheel by the space formed between adjacent spokes and sectors of the central portion of the hub and rim. Each conductive path comprises two pairs of adjacent spokes and respective sectors of the central portion of the hub and rim extending between the two spokes. 
     In another aspect, the electric machine further includes an induction device for inducing an electric current to flow through the electrically conductive paths. Preferably, the induction device is supported separately from the support. Also, preferably, the induction device comprises a plurality of transformers, each having a primary coil and a core about which the primary coil winds. The core of each transformer interlinks with adjacent apertures so that an electric current flow in the primary coil of a transformer can induce an electric current to flow through the electrically conductive paths about the corresponding adjacent apertures. 
     In one embodiment, the induction device includes a transformer having a core formed into a closed loop and provided with a plurality of windows through which respective spokes of the support pass, each window bound by opposed branches of the core that extend in the same plane as the support and opposed pairs of legs of the core that extend in a plane perpendicular to the support. Also, with a plurality of primary coils, a primary coil wound about at least one of the branches of the core of each window. Thus, in use, when an alternating current is caused to flow through the primary coils, lines of magnetic flux are created that circulate about the windows in the core, the majority of the flux being shared in legs of the core between adjacent windows so that the lines of magnetic flux circulating about a particular window induce a current to flow through the spoke passing through that window and the conductive paths containing that spoke. 
     The number of segments can be equal to the number of electric phases supplied to the support. Also, preferably, the magnet is shaped as a closed loop magnet and provides a common polarity flux in the air gap. The device can include a coupling for mechanically coupling the support to a mechanical input that moves the support two-dimensionally in the single plane to induce an electric current to flow in the conductive paths. Thus, the machine can operate as an electric generator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1A is a schematic representation of the first embodiment of the electric machine; 
     FIG. 1B is an enlarged view of section A—A of FIG. 1A; 
     FIG. 1C is a graphical representation of a three-phase AC voltage/current supply; 
     FIG. 2 is a partial cut away perspective view of a second embodiment of the electric machine; 
     FIG. 3 is a partial cut away perspective view of a third embodiment of the electric machine; 
     FIG. 4 is a partial cut away perspective view of a fourth embodiment of the electric machine; 
     FIG. 5 is a partial cut away perspective view of a fifth embodiment of the electric machine; 
     FIG. 6 is a partial cut away perspective view of a sixth embodiment of the electric machine; 
     FIG. 7 is a partial cut away perspective view of a seventh embodiment of the electric machine; 
     FIG. 8A is a partial cut away perspective view of an eighth embodiment of the electric machine; 
     FIG. 8B is a perspective view of a support incorporated in the embodiment shown in FIG. 8A; 
     FIG. 9 is a schematic representation of the machine depicted in FIG. 1A showing the invention as an electricity generator; 
     FIG. 10 is a schematic representation of a further simplified version of the machine depicted in FIG. 9; and 
     FIG. 11 is a perspective view of a portion of the machine depicted in FIG. 5 showing the invention as an electricity generator. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1A and 1B, a first embodiment of the machine operates as an electric motor  10 ; includes magnetic field means in the form of three separate magnets  12 A- 12 C (referred to in general as “magnets  12 ”) each producing a magnetic field having lines of flux B extending in the first direction perpendicularly into the page. A support in the form of disc  14  is provided that is capable of two-dimensional motion relative to the magnets  12  in the plane or the page. The disc  14  is provided with a minimum of two, and in this particular case three, electrically conductive paths in the form of conductor coils C A , C B  and C C  (referred to in general as “conductive paths”; “coils”; or “paths” C). 
     Throughout this specification and claims the expression “the disc (or support) . . . is provided with . . . electrically conductive paths” is to be construed as meaning that either the disc (support) has attached, fixed or otherwise coupled to it electrical conductors forming the paths, as shown for example in FIGS. 1-4; or, that the disc (support) is made of an electrically conductive material and does by itself provide or constitute the electrically conductive paths as shown for example in FIGS. 5-8B. 
     Consider for the moment the conductor path or coil C A  and its corresponding magnet  12 A. The path C A  as a segment  16 A that extends through the magnetic field B produced by the magnet  12 A in a second direction preferably, but not essentially, perpendicular to the first direction, i.e. perpendicular to the lines of flux produced by the magnet  12 A in a second direction preferably, but not essentially, perpendicular to the first direction, i.e. perpendicular to the lines of flux produced by magnet  12 A. If a current with a positive polarity is caused to flow in coil C A  say in the clockwise direction then the interaction of that current and magnetic field will produce a transverse thrust force T A  that acts on the disc  14  via the segment  16 A. In this instance the precise direction of the thrust force T A  is provided by the right hand rule, assuming the flux B is in a direction into the page and thus, in this scenario will be directed in the upward direction in the plane of the page. The direction of thrust can also be determined with this right hand rule if the current is flowing counter clockwise in the coils or if the flux B is flowing upwards into the plane of the page. If in a further arrangement the current is provided with a negative polarity then a left-hand rule is used to determine the direction of thrust forces. The remaining coils or paths C B  and C C  likewise have corresponding segments  16 B and  16 C that extend in a direction perpendicular to the lines of magnetic flux of corresponding magnets  12 B and  12 C. Therefore, if electric currents are caused to flow in paths C B  and C C , say in the clockwise direction, then similarly thrust forces T B  and T C  will be produced that act on the disc  14  via the respective segments  16 B and  16 C and in directions as dictated by the right hand rule. The segments  16 A and  16 B (and indeed in this instance also segment  16 C) are located relative to each other so that their respective thrust forces T A  and T B  do not lie on the same axis or line. By having two thrust forces directed along different axes or lines, two-dimensional motions of the disc  14  can be achieved. Moreover, the path of motion of the disc  14  can be controlled by varying the magnitude and/or phase relationship of the electric currents flowing through the segments  16 A- 16 C (referred to in general as “segments  16 ”). 
     In its simplest form, consider the situation where electric current is supplied to coil C A  only in the clockwise direction. Thrust force T A  is produced which causes the disc  14  to move in the direction of the thrust force. If coil C A  is now de-energized and coil C B  energized the disc  14  will move in a direction parallel to thrust force TB which is angularly offset by 120° from the direction of thrust force T A . If coil C B  is de-energized and coil C C  energized the disc  14  will move in the direction of corresponding thrust force T C  which is angularly offset by a further 120° from thrust force T B . By repeating this switching process, it can be seen that the disc  14  can be caused to move in a triangular path in a plane, i.e. it can move with two-dimensional motion in a plane. A digital controller (not shown) can be used to sequentially provide DC currents to coils C A -C C  at various switching rates and various amplitudes for control of the motion of the disc  14 . Also, the path or motion can be modified by causing an overlap in currents supplied to the segments. For example, current can be caused to flow in both coils C A  and C B  simultaneously, perhaps also with modulated amplitudes. 
     In this embodiment, three separate coils C A , C B , and C C  are shown. However, as is clearly apparent to produce two-dimensional motion in a plane a minimum of two coils, for example C A  and C B , only is sufficient, provided the respective thrust forces T A  and T B  do not act along the same axis or line. Stated another way, what is required for a two-dimensional motion is that there is a minimum of two coils relatively disposed so that when their thrust forces are acting on the disc  14  they cannot produce a zero resultant thrust force on the disc (except when both the thrust forces themselves are zero). 
     Rather than the triangular motion described above, the disc  14  can be caused to move with a circular orbital motion by energizing the coils C A , C B  and C C  with AC sinusoidal currents that are 120° (electrical) out of phase with each other. 
     It is to be appreciated that the circular orbital motion is not a rotary motion about an axis perpendicular to the disc  14 , i.e. the disc  14  does not act as a rotor in the conventional sense of the word. In the present embodiment, if each of the coils C A , C B , and C C  were connected to different phases in the three phase sinusoidal AC current supply, of the type represented by FIG. 1C, the disc  14  would move in a circular orbital motion. This arises because the total resultant force, i.e. the combination of T A , T B  and T C  is of constant magnitude at all times. The difference in phase between the coils C A , C B  and C C  leads to the direction of the resultant force simply rotating about the center of the disc  14 . This is an angular linear force, not a torque. The frequency of the motion of disc  14  is synchronous with the frequency of the AC current to the coils C A , C B  and C C . Thus, the motion frequency of disc  14  can be varied by varying the frequency of the supply voltage/current. A non-circular orbit can be produced by providing coils C A , C B , and C C  with currents that are other than 120° out of phase and/or of different amplitude. 
     In the embodiment shown in FIGS. 1A and 1B, the disc  14  is made of a material that is an electrical insulator and the coils C A , C B  and C C  are wire coils that are fixed for example by glue or epoxy to the disc  14 . The coils C A , C B  and C C  have separate leads (not shown) that are coupled to a voltage supply (not shown). The magnets  12  have a C-shaped section as shown in FIG. 1B providing an air gap  18  through which lines of flux B extend. The segments  16  of each of the coils C are located in the air gap  18  of their corresponding magnets  12 . 
     FIG. 2 illustrates an alternate form of the motor  10   ii  which differs from the embodiment shown in FIG. 1 by replacing the separate magnets  12 A,  12 B and  12 C with a single magnet  12  in the form of a Cockcroft ring and in which the disc  14  is provided with six conductive paths or coils—C A -C F . In order to reduce weight, the disc  14  is provided with six apertures or cut-outs  20  about which respective ones of conductive paths C extend. A multi-conductor cable  22  extends from a six phase power supply (not shown) to a central point  24  on the disc  14  where respective conductor pairs fan out to the coils C. The six phases required for the coils C A -C F  can be obtained from a conventional star of delta three phase power supply by tapping off the reverse polarities of each phase. 
     In the motor  10   ii  shown in FIG. 2, each conductive path or coil C has a segment  16  that is disposed in the air gap  18  of the magnet  12 . As with the previous embodiment, when current is caused to flow through the segments  16 , a transverse force is created due to the interaction between the current and the magnetic flux B, the transverse force is acting on the disc  14  via the respective segments  16 . It will be recognized that many segments are relatively located to each other so that their respective thrust forces are not parallel to each other in the plane of motion of the disc  14 , i.e. their respective thrust forces do not lie along the same axis or line. For example the thrust force arising from current flowing through segment  16 A lies on a different line to the thrust force arising from current flowing through segment  16 F. The same holds for say segments  16 A and  16 C; and  16 B and  16 D. Consequently, the disc  14  is again able to move in a two-dimensional planar motion. The fact that thrust forces produced on diametrically-opposed segments are parallel does not negate the existence of other thrust forces that do not act along the same axis or line to enable the generation of the two-dimensional planar motion. 
     In order to avoid rubbing of components and reduce friction, the disc  14  may be supported on one or more resilient mounts, e.g. rubber mounts or springs so that it is not in physical contact with the magnet  12 . 
     It would be understood that a conventional grinding head can be attached to the disc  14  of the machine  10   ii  in FIG. 2 for grinding a mineral sample. The orbital motion of the disc  14  would produce the required forces to cause a puck or grinding rings within the grinding head to grind a mineral sample. However, unlike conventional pulverizing mills, the frequency of the orbital motion can be changed at will by varying the frequency of the AC supply to the coils C. Further, the actual path and/or diameter of motion can be varied from a circular orbit to any desired shape by varying the phase and/or magnitude relationship between the currents in the coils C while the machine is in motion. 
     A further embodiment of the electric motor  10   iii  is shown in FIG.  3 . In the electric motor  10   iii  instead of each coil C being physically connected by a conductor to a current supply through multi-connector cable  22 , current for each coil C is produced by electromagnetic induction using transformers  26 A- 26 E (referred to in general as “transformers  26 ”). Further, the conductive paths (i.e. coils C) are now multi-turn closed loops. The disc  14  includes in addition to the apertures  20 , a plurality of secondary apertures  28 A- 28 F (hereinafter referred as “secondary apertures  28 ”), one secondary aperture  28  being located adjacent a corresponding primary aperture  20  with the apertures  20  and  28  being separated by a portion of the coils C extending about the particular primary aperture  20 . Each transformer  26  has a core  30  and a primary winding  32 . The primary winding  32  may be in the form of two physically separated though electrically connected coils located one above and one below the plane of the disc  14 . The core  30  of each transformer links with one of the coils C so that coil C acts as secondary windings. This interlinking is achieved by virtue of the core  30  looping through adjacent pairs of apertures  20  and  28 . It will be appreciated that a current flowing through the primary winding  32  of a transformer  26  will induce the current to flow about the linked coil C. The apertures  20  and  28 , and core  30  are relatively dimensioned to ensure that the disc  14  does not impact or contact the core  30  as it moves in its two-dimensional planar motion. The transformers  26  are supported separately from the disc  14  and thus do not add any inertial effects to the motion of the disc  14 . By using induction to cause currents to flow through the coils C the need to have a physical cable or connection as exemplified by multiconductor cable  22  in the motor  10   ii  is eliminated. This is seen as being particularly advantageous as cables or other connectors may break due to fatigue caused by motion of the disc  14  and also add weight and thus inertia to the disc  14 . 
     FIG. 4 illustrates a further embodiment of the electric motor  10   iv . This motor differs from motor  10   iii  by forming the respective conductive paths C with a single turn closed loop conductor rather than having multiturn coils as previously illustrated. Replacing a multi-turn wire coil with a single solid loop has no adverse effects. The single solid loop behaves the same as the multi-turn coil with the same total cross-sectional area, where the current in the single loop equals the current in each turn of the coil multiplied by the number of turns, thereby giving the same resultant thrust force. Again, as with the previous embodiments, the motion of the disc  14  can be controlled by the phase and/or magnitude relationship of electric currents flowing through the segments  16  of each conductive path, i.e. conductive loop C. 
     FIG. 5 illustrates yet a further embodiment of the electric motor  10   v . This is a most remarkable embodiment as the conductive paths C are electrically connected together. In the motor  10   v , the disc  14  is now in the form of a wheel having a central portion in the form of a hub  34 , a plurality of spokes  36  extending radially outwardly from the hub  34  and an outer peripheral rim  38  joining the spokes  36 . Apertures  20  similar to those of the previous embodiments are now formed between adjacent spokes  36  and the sectors of the hub  34  and rim  38  between the adjacent spokes  36 . The disc  14  is made of an electrically conductive and most preferably non-magnetic material such as aluminum. The current paths are constituted by the parts of the disc  14  surrounding or bounding an aperture  20 . For example, conductive path C A  (shown in phantom) comprises the spokes  36 A and  36 B and the sectors of the hub  34  and  38  between those two spokes. Conductive path C B  is constituted by spokes  36 B and  36 C and the sectors of the hub  34  and  38  between those two spokes. The sector of the rim  38  between adjacent spokes form the segment  16  for the conductive path containing those spokes. It is apparent that adjacent conductive paths C share a common spoke, (i.e. have a common run or log). Each transformer  26  links with adjacent apertures  20  and has, passing through its core  30  one of the spokes  36 . Consider for the moment transformer  26 B. The core of this transformer passes through adjacent apertures  20 A and  20 B with the spoke  36 B extending transversely through the core  30  of the transformer  26 B. The current induced into spoke  36 B by the transformer  26 B is divided between current paths C B  and C A . Thus the transformer  26 B, when energized, induces a current to flow through both paths C A  and C B . In like fashion, each of the transformers  26  can induce the current to flow in respective adjacent conductive paths C. The state of the transformers will determine the current division between adjacent conductive paths C. Hence, the sectors of the rim  38  between adjacent spokes  36  and the currents flowing through them act in substance the same as the segments  16  in the motors  10   i - 10   iv . 
     FIG. 6 illustrates a further embodiment of the electric motor  10   vi . This motor differs from electric motor  10   v  by replacing the separate transformers  26  with a multi-phase toroid shaped transformer dubbed a “transoid”  40 . The transoid  40  can be viewed as a ring of magnetically permeable material formed with a number of windows  42  and arranged so that separate conductive spokes  36  pass through individual different windows  42 . Each window  42  is bound by opposed branches  44  and  46  that extend in the plane of the disc  14  and opposed legs  48  and  50  that extend perpendicularly to and join the opposed branches  44  and  46 . Primary windings  32  are placed on each of the opposed branches  44  and  46  for every window  42 . (Although it should be understood that primary winding can be placed anywhere within the window i.e.,  44 ,  46 ,  48 ,  50  with one or more primary windings being utilized in various embodiments). Primary windings  32  are coupled to a six phase current supply in a manner so that the windings  32  for each window  42  are coupled to a different phase. Current flowing through the primary windings  32  sets up lines of magnetic flux circulating about the windows  42 . This flux in turn induces the current to flow in the spoke  36  passing through that window  42  and the conductive path C to which that spoke  36  relates. It will be recognized that the majority of the flux generated about adjacent windows  42  will circulate through the common adjacent leg  48 . 
     In comparison with the electric motor  10 , shown in FIG. 5, the use of the transoid  40  makes more efficient use of its core because flux is shared from one or more primary coils. That is, magnetic flux induced by currents in primary coils about adjacent windows  42  can be shared through the common leg  48 . Indeed more distant primary coils can contribute to the flux in that leg. 
     A further embodiment of electric motor  10   vii  is shown in FIG.  7 . This embodiment differs from the motor  10   v  shown in FIG. 5 in the configuration of the Cockcroft ring  12 . In this embodiment, the air gap  18  of the Cockcroft ring is on the outer circumferential surface of the Cockcroft ring rather than on the inside surface as shown in FIG.  5 . Additionally, a plurality of radially extending slots  52  are formed in the Cockcroft ring  12  through which the spokes  36  can pass. The slots  52  must be sufficiently wide to not inhibit the motion of the disc  14 . 
     In the embodiment of the electric motor  10   ii - 10   vii  there are six segments  16  through which current flows to produce respective transverse forces that act on the disc  14 . However, this can be increased to any number. Conveniently however the number of segments  16  will be related to the number of different phases available from a power supply used for driving the motor  10 . For example, the motor  10  can be provided with twelve segments  16  through which current can flow by use of a twelve-phase supply. In this instance, therefore, transformers are used to induce currents to flow in each segments, there will be required either twelve separate transformers  26  as shown in FIGS. 4,  5 , and  7  or alternately a twelve window transoid  40 . 
     In the afore-described embodiments, the motion of the support  14  is a two-dimensional motion in one plane. However, motion in a second plane or more nonparallel planes can also be easily achieved by the addition and/or location of further segments  16  in the second or additional planes and, further means for producing magnetic fields perpendicular to the currents flowing through those additional segments. An example of this is shown in the motor  10   viii  in FIGS. 8A and 8B in which the support  14  has one set of segments  16   i  and a first plane (coincident with the plane of the support  14 ) and a second set of segments  16   ii  that extend in a plane perpendicular to the plane of the support  14 . The motor  10   viii  has first magnet  12   i  having an air gap  18   i  in which the segments  16   i  reside, and a second magnet  12   ii  having an air gap  18   ii  in which the second set of segments  16   ii  reside. Thus, in this embodiment, the support  14  can move with a combined two-dimensional motion in the plane of the support  14  and an up and down motion in a second plane perpendicular to the plane of the support  14 . Thus, in effect, in this embodiment, the support  14  can float in space by action of the thrust forces generated by the interaction of the current flowing through segments  16   ii  and the magnetic field in the air gap of the magnet  12   ii . It is also apparent from the previous motor embodiments  10   i - 10   vii  that the segments  16   i  and  16   ii  of the motor  10   viii  can be individually supplied with electrical currents. In such instances the motion of the support  14  in the second plane is not just limited to a perpendicular up and down movement but can include motion with two degrees of freedom. As is apparent from FIG. 8B the support  14  need not be circular in shape but can be square (as in FIG. 8B) or any other required/desired shape. For the sake of clarity the means for supplying current to the segments  16   i ,  16   ii  have not been shown. The currents may be provided by direct electrical connection to a current source as in the embodiments  10   i  and  10   ii  or via induction as in embodiments  10   iii  to  10   vii . 
     From the above description it will be apparent that embodiments of the present invention have numerous benefits over traditional machines used for generating vibratory or orbital motion. Clearly, as the motion of the disc  14  is non-rotational, there is no need for bearings, lip seals, gear boxes, eccentric weights or cranks. In addition, the inertial aspects of rotation, such as a time to accelerate to speed and gyroscopic effects are irrelevant. In the embodiments of the machine  10   ii - 10   vii  induction is used to cause current to flow in the segments  16  and thus commutators, brushes, and flexible electric cables are not required. It will also be apparent that the only moving part of the machine  10  is either the support  14  or the magnetic field means  12 . When it is the support  14  itself that carries the electric current as shown in embodiments  10   v - 10   vii  this support  14  may be made from one piece only say by punching or by casting. In these embodiments the disc  14  must be made from an electrically conductive material and most preferably a non-magnetic material such as aluminum copper or stainless steel. When the machine  10  is used to generate an orbital motion from imparting to another object (for example a grinding head) there can be a direct mechanical coupling by use of bolts or screws. 
     The motor  10  is a force driven machine and the force it delivers is essentially unaltered by its movement. There is a small degree of back EMF evident, however the tests indicate that this is almost negligible, especially when compared with conventional rotating motors. As such, the motor  10  is able to deliver full force regardless of whether the disc  14  is moving or not. For this reason, current drawn by the motor  10  is relatively unaffected by the motion of the disc  14 . This enables the motion of the disc  14  to be resisted or even stalled with negligible increase in current draw and therefore negligible increase in heat build-up. 
     In the conventional mechanical orbital or vibratory machines, the orbital or vibratory motion is usually fixed with no variation possible without stopping the machine to make suitable adjustments. With the motor  10   i  the orbit diameter is proportional to the force applied, which in turn is proportional to the currents supplied. Therefore the orbit diameter can be controlled by varying the supply voltage that regulates the current in the segment  16 . This results in a linear control with instant response available, independent of any other variable. As previously mentioned, the orbit frequency is synchronous with the frequency of the supply voltage, so that orbit frequency can be varied by varying the supply frequency. The motor  10  also allows one to avoid undesirable harmonics. A common problem with conventional out of balance drive systems is that as the motor builds up speed it can pass through frequency bands coinciding with the actual harmonic frequencies of various attached mechanisms that can then lead to uncontrolled resonance that can cause damage to the machine or parts thereof. The disc  14  however is able to start at any desired frequency and does not need to ramp up front zero speed to a required speed. In this way any undesired harmonics can be avoided. Particularly, the motor  10  can be started at the required frequency with a zero voltage (and hence zero orbit diameter) and then the voltage supply can be increased until the desired orbit diameter is reached. 
     If no control over the orbit diameter or frequency is required, the motor  10  can be connected straight to a mains supply so that the frequency will be fixed to the mains frequency. Nevertheless, full control is not difficult or costly to achieve. Existing motor controllers which utilize relatively simple electronics with low computing requirements can be adapted to suit the motor  10 . Because voltage supplies can be controlled electronically, the motor  10  can be computer driven. This enables preset software to be programmed and for safety features to be built into the supply controller allowing its operation to be reprogrammed at any time. The addition of feedback sensors can allow various automatic features such as collision protection. When the disc  14  is mounted on rubber supports, it can be considered as a spring-mass system. As such, it will have a harmonic or resonance frequency at which very little energy is required to maintain orbital motion at that frequency. If the machine  10  is only required to run at one frequency, the stiffness of the rubber supports can be chosen such that resonance coincides with this frequency to reduce the power losses and hence improve the machines efficiency. 
     While the description of the preferred embodiments mainly describes the disc  14  as moving in an orbit, depending on the capabilities of the controller for the supply, i.e. the ability to vary phase relationships and amplitudes of the supply current, the disc  14  can produce any shaped motion within the boundaries of its maximum orbit diameter. 
     Embodiments of the motor  10  can be used in many different applications such as pulverizing mills as previously described, cone crushers, sieve shakers, vibrating screens, vibratory feeders, stirrers and mixers, orbital sanders, orbital cutting heads, polishers and specific tools requiring a non-rotational motion, blood product agitators for blood storage systems, motion and stirring device for cell culture fermentors and bioreactors, tactile devices and motion alarms for personal pagers and mobile communication devices, planetary drive system for digital media storage systems or read heads for digital media system, friction welders for plastic components, dynamic vibration input device for testing components and structures, dynamic vibratory material feeder for hoppers and chutes, vibration device for seismic surveying, vibration cancellation platform for sensitive equipment and vibration cancellation device included for pipe-work attached to pumps, orbital/planetary motion device for acoustic speakers. 
     Further in the described embodiments the motion of the support/disc  14  relative to the magnetic field means  12  is achieved by having the support/disc  14  movable and the magnetic field means  12  fixed. However this can be reversed so that the support/disc  14  is fixed or stationary and the magnetic field means  12  moves. This may be particularly useful when it is required to impart and maintain, for example a vibratory motion to a large inertial mass. Also, it is preferred that the segments  16  extend through the magnetic field B at right angles to maximize the resultant thrust force. Clearly embodiments of the invention can be constructed where the segments  16  are not at right angles, though it is preferable to have some components of their direction at right angles to the field B to produce a thrust force. 
     Referring now to FIG. 9, the invention can also operate as an electricity generator  100 . In FIG. 9, the mechanical input is represented schematically by the vector  102 . 
     The mechanical input  102  is attached to the disc  14  through a conventional connection. The input  102  and the disc  14  are connected such that the movement of the disc  14  is coextensive with the plane of the disc  14 . The mechanical input  102  is provided by a conventional apparatus capable of producing a two-dimensional motion, such as a triangular or circular orbital motion. Electrical leads  104 A- 104 C connect the coils C A -C C  to a junction  106 , to which is connected a multi conductor cable  108 . The movement of the input  102  will create a corresponding movement of the disc  14 . Movement of the disc  14  within the flux B of the magnets  12 A- 12 C will induce a current in the coils C A -C C  which will be carried through the leads  104 A- 104 C, junction  106 , and cable  108 . 
     A more basic version of the machine  100   i  is depicted in FIG.  10 . The machine  100   i  differs from the machine  100  of FIG. 9 by the provision of a single electrical path only constituted by coil C A . It would be appreciated that the motion provided by input  102  causing movement of the disc  14  in a plane would also lead to the induction of a current in the coil C A  which is carried through lead  104 A, junction  106 , and cable  108 . 
     In a further variation of the embodiment shown in FIG. 10 a second electrically conductive path or coil can be provided on disc  14  diametrically opposed to coil C A . All other parameters being equal, the currents induced in coils C A  and the diametrically opposed coil would have the same wave form but be out of phase by 180° with each. If such currents were added they will produce a nil result. However, the currents from the coils can be tapped individually. This is in contrast to the situation where the machine having diametrically opposed coils is operated as a motor in which case the thrust forces rising from currents flowing through the coils would be diametrically opposed and, if of the same magnitude, would result in no motion, and if not of same amplitude, would cause a reciprocating motion rather than a orbital motion as ordinarily required for a pulverizing mill. 
     FIG. 11 illustrates how the machine  100   ii  of FIGS. 5 and 6 can be operated as a generator by coupling of the disc  14   i  to a mechanical crank  110 . The disc  14   i  differs marginally from the disc  14  depicted in FIGS. 5 and 6 by forming the hub support as a solid web  112  to provide for coupling of the crank  110 . The crank  110  is attached to a central axis  114  of the disc  14   i  which is offset by distance D by a crank arm  116  from a drive axis  118 . The crank  110  is rigidly attached to the disc  14   i  so that the application of torque about the axis  118  causes an orbital motion in a plane of the support  14   i . 
     As with the machine depicted in FIGS. 5 and 6 individual wound cores or the “transoid” (depicted in FIG. 6) can be associated with the disc  14   i  to effectively tap off currents induced in the separate paths C A -C F  constituted by the support  14   i . 
     The machine when configured as a generator illustrated in FIGS. 9-11 can be mechanically directly coupled to the motor form of the machine depicted in FIGS. 1-8 by a mechanical linkage between the respective discs  14 . Indeed such coupling has been made in order to allow measurement of the efficiency of the motor by comparing electrical power, output and output current/voltage waveform in the generator with the electrical input to the motor. 
     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.