Patent Description:
Mover systems utilizing linear drives can be used in a wide variety of processes (e.g. packaging, assembly automation, processes involving use of machine tools, etc.) and provide an advantage over conventional conveyor belt systems to provide flexible, extremely high speed movement, and mechanical simplicity. The mover systems provide a set of independently moveable "movers" supported on a track that holds individually controllable electric coils. Successive activation of the coils by drive electronics and a control system create a magnetic field that move and relocate the movers along the track. Sensors may be spaced at fixed positions along the track and/or on the movers to provide information about the position and speed of the movers.

High speed motion is available because the movers form part of a linear motor driven directly by the coils without the need for intervening mechanical elements. Sensors allow this movement to be extremely accurate providing submillimeter positioning. Mechanical simplicity is available because the linear motor design eliminates drives, gears, cams, and belts, used with traditional conveyor belt systems. In addition to high-speed and mechanical simplicity, the mover system provides another advantage over conventional conveyor belt systems in that the movers may be independently moved and positioned in contrast to the items on a conventional conveyor belt system, which remain in a single locked relationship. With the elimination of belts, gears, and cams used in traditional conveyor belt systems, changing the motion of the movers is accomplished through electronic/digital programming and is much faster and easier than changing physical components.

Mover systems typically comprise interconnected track sections of straight and curved tracks, for example, to provide for an oval shaped track. The movers may be supported over the track on lateral rails that engage wheels on the movers. The wheels include precision ball bearings to maintain a precise positional relationship between the movers and the track in close proximity for strong magnetic coupling white allowing relatively free movement of the moving elements along the track modules against the loads and forces of mechanical loads on the mover during motion. These forces will vary during motion to include downward forces caused by the weight of the loads on the movers, inward forces caused by centripetal force, and torsion caused by the offset of the track from the center of mass of the load. Accurate location of the movers with motion is obtained through the use of wheels with V-shaped circumferential grooves that engage with a corresponding track side to provide resistance against axial motion.

The high speed and large forces experienced by the movers together with the required close tolerances can create substantial wear and degradation on the mover wheel bearings and track.

<CIT> relates to a conveyor using a linear motor. The purpose of this document is to enable a distance to be kept constant between a linear motor on a car-body side and a guide-rail side. This objective is realized by moving a device vertically together with the linear motor on the car-body side, and by arranging rollers in contact with the guide rail.

<CIT> discloses a mover used on a track. The track comprises a mover support frame supporting a magnetic element for interacting with corresponding magnetic elements on the mover and supporting a first rail and a second rail wherein each rail provides two opposed parallel contact surfaces. The mover support frame further provides a first lateral face, a second lateral face parallel to the first lateral face, and a third transverse face extending between the first and second lateral face, the lateral faces defining a track attachment surfaces. The mover comprises a frame supporting a magnetic element for interacting with corresponding magnetic elements on the track and supports a first, a second and a third set of bearings, wherein each set of bearings provides two wheels being rotatable about a respective axis, the axes for the two wheels being parallel, and the wheels having peripheral contact surfaces opposed across a gap distance bisected by a center point between the contact surfaces, wherein the center points are displaced by a distance larger than the gap. In addition, the axes of the first bearing set and of the third bearing set are perpendicular to the axes of the second bearing set. In said document, a method of transporting the mover on the track along a transport direction comprises transporting the mover along the track assembly along the transport direction, and restraining movement of the mover in a normal direction perpendicular to a direction of motion of the mover along the track assembly and a vertical direction perpendicular to the transport direction and perpendicular to the normal direction.

It is the object of the present application to reduce the effects of thermal expansion and at the same time to accommodate track variations due to changes in curvature in a mover system.

This object is solved by the subject matter of the independent claims <NUM>, <NUM> and <NUM>.

The present inventors have determined that a significant factor in bearing and track degradation for moving systems is system dimensional variation of the track holding the rails such that it greatly increases the force on the bearings. This variation occurs during manufacture, assembly, and use, for example, caused by heating of the coils held in the track, which support the rails. Accordingly, the present invention provides a rail system in which opposed wheels are closely spaced so that the transition gap between the wheels and the track is minimized as the mover passes between the straight and curved track. In addition, the present invention eliminates the V-wheels and the resultant sliding wear caused by high tolerance V-wheels which contact the sides of the track on which they engage. Eliminating the V-wheels also eliminates all but the frictional component of the axial forces on the bearings.

Specifically, the invention provides a mover for use on a track providing a closed loop extending along a track circumferential path and having at least two rails extending along the circumferential path and displaced from each other in a direction perpendicular to the track circumferential path. The mover includes a frame supporting a magnetic element for interacting with corresponding magnetic elements on the track and supporting a first and second set of bearings. Each set provides two wheels each having peripheral contact surfaces rotatable about axes and in opposition across a gap distance bisected by a center point between the contact surfaces. The center points of the first and second bearing sets are displaced by a distance larger than the gap.

It is thus a feature of at least one embodiment of the invention to reduce the separation distance between opposed wheels to decrease the geometrical effect of passing through the straight to curved track transition that results in increased wheel clearance between the wheel and the rail and affects the loading of the bearings.

Each of the wheels is rotatable about a respective axis and the axes for the two wheels are parallel and the contact surfaces are displaced across the gap.

It is thus a feature of at least one embodiment of the invention to permit the use of tracks providing easily manufactured opposed parallel surfaces.

The axes of the first bearing set is perpendicular to the axes of the second bearing set.

It is thus a feature of at least one embodiment of the invention to provide resistance against forces directed in any of three directions constraining the mover except for in the direction of motion with a minimal set of bearings.

At least one of the wheels includes a compliant member adapted for variation of the gap distance. The compliant member may be a spring.

It is thus a feature of at least one embodiment of the invention to provide the benefits of reduced effects of thermal expansion together while accommodating track variations caused by changes in curvature of the track between straight and curved sections.

The wheels may be provided an outer cylindrical periphery having a hardened steel surface. The wheels may alternatively be provided with a barrel-shaped outer periphery.

It is thus a feature of at least one embodiment of the invention to reduce surface wear by hardening a rolling contact surface of a standard ball bearing. It is also a feature to allow the wheels to pivot while reducing the contact length.

Each set of bearings provides four wheels each having peripheral contact surfaces rotatable about axes and the axes for the four wheels are parallel and the contact surfaces for two wheels are opposed across a gap distance bisected by a center point between the contact surfaces of the other two wheels.

It is thus a feature of at least one embodiment of the invention to provide resistance to torsional loading parallel to the axes of the wheels.

The frame supports a third set of bearings wherein the third set provides two wheels each having peripheral contact surfaces opposed across a gap distance bisected by a center point between the contact surfaces; wherein the axes of the second bearing set is substantially perpendicular to the axes of the third bearing set and wherein the center points are displaced by a distance larger than the gap.

It is thus a feature of at least one embodiment of the invention to provide resistance to torsional loading about the track direction.

The center points are displaced by a distance substantially less than a height of the frame.

It is thus a feature of at least one embodiment of the invention to reduce the separation between bearing sets to reduce the effect of dimensional variation on the mover frame when there are multiple bearing sets with the same alignment displaced along the frame.

The present invention also provides a track used with a mover traveling along the track along a track circumferential path and having at least a first and second set of bearings having peripheral contact surfaces rotatable about axes and the axes for the two wheels of each first and second set of bearings are parallel and die axes of the first bearing set is substantially perpendicular to the axes of the second bearing set. The track includes a mover support frame having an electro-magnetic element for interacting with corresponding magnetic elements on the mover and supporting a first and a second rail extending along the circumferential path and displaced from each other in a direction perpendicular to the track circumferential path. Each track provides two opposed parallel contact surfaces and the first and second rail are displaced from each other a distance less than a length of the mover support frame.

It is thus a feature of at least one embodiment of the invention to provide a track compatible with a mover designed to minimize thermal expansion affects and a thin track geometry which reduces the necessary compliance caused by changing separation between the corresponding wheels on the inside and outside of the track. It is also a feature of at least one embodiment of the invention to provide a single track on a respective side of the mover with single directional loading on the track. The loading on the track is in the same direction as the thermal expansion and contraction of the linear motor. This track is less than a full length of the mover, on one end only, thus allowing a very short path for thermal expansion across the track.

The first and second rails are independently separable from the mover support frame and have a cross section with two parallel surfaces.

It is thus a feature of at least one embodiment of the invention to provide tracks that can be readily fabricated using standard materials and machining techniques at low cost.

The mover support frame further supports a third rail extending along the circumferential path and displaced from the first rail and second rail in a direction perpendicular to the track circumferential path.

It is thus a feature of at least one embodiment of the invention to use a three-track system to provide necessary support of the mover along the entire mover length. It is also a feature of at least one embodiment of the invention to control three independent directions of movement perpendicular to the motion of travel. The invention also allows for simple single directional loading on each bearing set.

The mover support frame provides a first lateral face, a second lateral face parallel to the first lateral face, and a third transverse face extending between the first and second lateral face, and defining a track attachment surface where the first rail is mounted to the first lateral face, the second rail is mounted to the third transverse face, and the third rail is mounted to the second lateral face.

It is thus a feature of at least one embodiment of the invention to provide spatial distance between the tracks for better control of the mover on the track.

A width of the rail is at least <NUM> times less than the length of the mover support frame.

It is thus a feature of at least one embodiment of the invention to provide thin tracks that are less affected by thermal expansion.

The opposed parallel contact surfaces of the first, second, and third rails are perpendicular to the first lateral face, second lateral face, and third transverse face respectively.

It is thus a feature of at least one embodiment of the invention to provide rectangular rails that are readily available and do not need to be fabricated using an extrusion process or another specialized method. However, the rails may take other forms or shapes consistent with the invention.

It is thus a feature of at least one embodiment of the invention to use a standard steel rail that may conform to the natural curvatures of the track attachment surface which may be curved.

The four wheels may form an isosceles trapezoid within inner wheels forming a shorter base of the trapezoid and outer wheels forming a longer base of the trapezoid parallel to the shorter base. The inner wheels may be formed outside of a triangle formed by joining a center of curvature of the track and the axes of the two outer wheels along their radii of curvature and a segment joining the axes of the two outer wheels.

It is thus a feature of at least one embodiment of the invention to align the wheels to minimize the transition gap while maintaining a tangential positioning of the wheels on the rail. It is also a feature of at least one embodiment of the invention to provide curved portions of the track that do not have a constant radius.

The present invention also provides a method of transporting a mover on a track along a transport direction and providing a track support frame providing a first face, a second face, and a third face defining a track attachment surface holding a plurality of individually controlled electromagnetic coils effective for creating electromagnetic fields, the track attachment surface carrying a first rail and second rail each having opposed parallel surfaces extending along the transport direction, the mover providing a first lateral arm communicating with the first wall, a second lateral arm communicating with the second wall, and a mounting platform extending between the first lateral arm and second lateral arm and holding magnetic elements positioned to interact with the electromagnetic fields of the track support frame, the mover carrying a first and second set of wheels contacting the opposed parallel surfaces of the first and second rails, respectively, in a direction perpendicular to the transport direction and in a direction perpendicular to an axis of rotation of the wheels, and the first and second rails separated on different faces of the track support frame. The method includes the steps of: mounting the mover to the track assembly; moving the mover along the track assembly along the transport direction; and restraining movement of the mover in a normal direction perpendicular to a direction of motion of the mover along the track assembly and a vertical direction perpendicular to the transport direction and perpendicular to the normal direction.

Turning now to the drawings, and referring first to <FIG>, a transport system <NUM> for moving articles or products includes a track <NUM> providing a generally closed loop supporting a set of movers <NUM> movable along the track in a transport direction <NUM> or circumferential path. In one embodiment, the loop of the track <NUM> may be positioned to lie in a horizontal plane as depicted and may be supported above the ground by a pair of vertically extending legs <NUM> extending downward from the track <NUM> toward the ground from diametrically opposed sides <NUM> and <NUM> of the track <NUM>.

In the illustrated embodiment, the track <NUM> may have a stadium shape, being a rectangle capped by semicircles, and may comprise of straight track modules <NUM> and curved track modules <NUM>. The straight track modules <NUM> provide linear open ended segments while the curved track modules <NUM> provide semicircle arched segments which connect at their ends to the straight sections to form closed loop tracks <NUM>. As illustrated, one or more straight track modules <NUM> extend along a front side <NUM> of the track <NUM> and one or more straight track modules <NUM> extend along a backside <NUM> of the track <NUM>. The two curved track modules <NUM> extend along the left <NUM> and right <NUM> ends of the track <NUM>, respectively, connecting with the front and back straight track modules <NUM> to form an elongated oval shaped platform. It is understood that the modules <NUM>, <NUM> are generally self-contained and mountable in various physical configurations.

Referring also to <FIG>, the modules <NUM>, <NUM> form a vertically extending wall <NUM> forming an oval loop extending around an outer periphery of the track <NUM>. The vertically extending wall <NUM> is defined by an inner surface <NUM> of the wall <NUM> opposite an outer surface <NUM> of the wall <NUM> connected at their upper ends by a top edge <NUM> and at their lower ends by a lower edge <NUM>. An interior of the track <NUM> is defined by a horizontally extending surface <NUM> forming an interior floor or platform within the track <NUM>. The horizontally extending surface <NUM> may extend inwardly from an approximate vertical center of the vertically extending wall <NUM> to form a ring along an inner perimeter of the track <NUM> while leaving a central opening <NUM> in the center of the track <NUM> free from vertical obstruction.

A series of parallel coils <NUM> are installed on the outer surface <NUM> of the vertically extending wall <NUM>, or between the outer surface <NUM> and inner surface <NUM> of the vertically extending wall <NUM>, and extending laterally about the outer periphery of the track <NUM>. Drive circuitry <NUM> may be included in each module <NUM>, <NUM> to allow for controlled power signals to be applied to the coils <NUM> in order to drive and position a plurality of movers <NUM> appropriately around the track <NUM>. In the illustrated embodiment, the track modules <NUM>, <NUM> are mounted end-to-end and interconnected with one another and/or with the power and control circuitry <NUM> to receive signals used to power the coils <NUM>.

The drive circuitry <NUM> provides signals to each track module <NUM>, <NUM>, and specifically individual coils <NUM> of the track modules <NUM>, <NUM> to create electromotive forces that interact with magnets <NUM> on the movers <NUM> to drive the movers <NUM> to specific locations, and at specific velocity and accelerations. This drive circuitry <NUM> may typically include inverter circuitry that makes use of power electronic switches to provide drive power to the individual coils <NUM> of each module in a controlled manner. In some embodiments, the drive circuitry <NUM> may be included in each individual module <NUM>, <NUM>, and signals provided to the drive circuitry <NUM> by power and control circuitry <NUM>. Various remote control and/or monitoring circuitry <NUM> may be provided and this circuitry may be linked to the system by one or more networks <NUM>. Such remote circuitry may generally allow for coordination of the operation of the transport system with other automation components, machine systems, and manufacturing and material handling machines.

Sensor arrays <NUM> may also be installed on the inner surface <NUM> of the vertically extending wall <NUM>, or between the outer surface <NUM> and inner surface <NUM> of the vertically extending wall <NUM>, and provided in each track module <NUM>, <NUM> to interact with sensor components of the movers <NUM>. The sensor arrays <NUM> will typically provide feedback that can indicate the position of the movers <NUM>, and can be used to derive velocity, acceleration, jerk and other motion parameters. The power and control circuitry <NUM> (and the drive circuitry <NUM>) may receive feedback from the movers <NUM> and/or from the sensor arrays <NUM> to detect the location, velocity, acceleration, and so forth of each mover <NUM>. The sensor arrays <NUM> may comprise permanent magnets, energized coils, Hall effect sensors, or any other suitable devices with one component of the sensor system <NUM> mounted on the movers <NUM>, while another component of the sensor system <NUM> is mounted at fixed locations around the track <NUM>.

The track modules <NUM>, <NUM> include a number of independently attached rails, as indicated by reference numerals <NUM>, <NUM>, <NUM>, respectively, mounted to the track modules <NUM>, <NUM> to allow for attachment of the movers <NUM> to the track <NUM>. The rails <NUM>, <NUM>, and <NUM> of the present invention are bars extending about the track <NUM> along and parallel to the transport direction <NUM> and providing a rectangular cross section. The rails <NUM>, <NUM>, and <NUM> generally conform to the curvature of the track <NUM> thus extending straight along the straight track modules <NUM> and curved along the curved track modules <NUM>. The rails <NUM>, <NUM>, and <NUM> may be constructed of hardened steel bent to conform to the outer curvature of the track <NUM>.

A first rail <NUM> may extend upwardly along a vertical axis <NUM> from the top edge <NUM> of the vertically extending wall <NUM> and running longitudinally along the top edge <NUM> of the wall <NUM> along the transport direction <NUM>. A second rail <NUM> extends transversely outward along an outwardly radial direction <NUM> from the outer surface <NUM> of the vertically extending wall <NUM> and runs longitudinally along the outer surface <NUM> of the wall <NUM> along the transport direction <NUM>. A third rail <NUM> extends downwardly along the vertical axis <NUM> from the lower edge <NUM> of the vertically extending wall <NUM> and runs longitudinally along the lower edge <NUM> of the wall <NUM> along the transport direction <NUM>. The rails <NUM>, <NUM>, <NUM> run generally parallel to one another, and parallel to the transport direction <NUM> to define a three rail system of mover <NUM> transport.

The rails <NUM>, <NUM>, <NUM> are generally thin and narrow encompassing only a partial width of the attachment edge of <NUM>, <NUM> or surface <NUM> on which it is attached. The rails <NUM>, <NUM>, <NUM> generally have a width in a first direction extending parallel to the attachment surface of the track modules <NUM>, <NUM> of approximately <NUM>-<NUM> inches (<NUM>-<NUM>) and preferably approximately <NUM> inch (<NUM>). The rails <NUM>, <NUM>, <NUM> have a height in a second direction extending perpendicular to the attachment surface of the track modules <NUM>, <NUM> of approximately <NUM>-<NUM> inches (<NUM>-<NUM>) and preferably approximately <NUM> inches (<NUM>). The rails <NUM>, <NUM>, <NUM> include a plurality of laterally spaced bores <NUM> extending through the rails <NUM>, <NUM>, <NUM> between the attachment surface and outwardly extending surface facilitating attachment of the rails <NUM>, <NUM>, <NUM> to the track modules <NUM>, <NUM>, for example using screws or bolts extending through the bores <NUM>.

Referring now to <FIG> and <FIG>, the system further comprises one or more movers <NUM> which are mounted to and movable along the track <NUM>. Each mover <NUM> comprises lateral mounting arms <NUM>, <NUM> extending along a top and bottom of the track <NUM> and engaging the track <NUM> to remain securely attached thereon. An upper mounting arm <NUM> having a generally rectangular section <NUM> tapering toward a rounded distal end <NUM> extends horizontally and substantially parallel to a generally rectangular lower mounting arm <NUM> connected at their rear ends <NUM>, <NUM>, respectively, by a rectangular vertical mounting platform <NUM> extending therebetween. The mounting platform <NUM> extends opposite an open front end <NUM> provided between distal ends of the upper mounting arm <NUM> and lower mounting arm <NUM>, respectively, and receiving an outer receiving edge of the track <NUM>. When mounted to the track <NUM>, the upper mounting arm <NUM> and lower mounting arm <NUM> extend in a radial direction <NUM> parallel to the top edge <NUM> and lower edge <NUM>, respectively, and the mounting platform <NUM> extends along the vertical axis <NUM> parallel to the outer surface <NUM>, so as to resemble a C-shaped frame extending around the three attachment edges or surfaces of the vertically extending wall <NUM>.

The mounting platform <NUM> is generally longer (the distance between the outermost ends of the mounting arms <NUM>, <NUM> defining a length of the mounting platform <NUM>) than the mounting arms <NUM>, <NUM>. The mounting platform <NUM> may be approximately <NUM>-<NUM> inches (<NUM>-<NUM>) long and the mounting arms <NUM>, <NUM> may be approximately <NUM>-<NUM> inches (<NUM>-<NUM>) long. In an actual implementation, various tools, holders, support structures, loads, and so forth may be mounted to the mounting platform <NUM> to be moved around the track <NUM>. The upper mounting arm <NUM> may be longer than the lower mounting arm <NUM> so that a distal end <NUM> of the upper mounting arm <NUM> may extend past the top edge <NUM> to interact with the inner surface <NUM> of the track <NUM> as described below.

The movers <NUM> interact with the coil <NUM> and sensor arrays <NUM> in or between an inner surface <NUM> and outer surface <NUM> of the track modules <NUM>, <NUM> as described below. A magnetic array <NUM> having a number of magnets therein and housed within a rectangular block <NUM> having a vertically extending front surface <NUM> opposite a vertically extending mounting surface <NUM> is mounted to an inner surface <NUM> of the mounting platform <NUM> by attaching the mounting surface <NUM> to the inner surface <NUM>. The rectangular block <NUM> is generally mounted toward a center of the mounting platform <NUM> and corresponds in width with the mounting platform <NUM>. The rectangular block <NUM> extends forwardly from the mounting platform <NUM> toward the open front end <NUM> such that the front surface <NUM> is parallel to the outer surface <NUM> of the track <NUM> when received thereon and a small air gap is provided between the magnetic array <NUM> and coils <NUM> of the track modules <NUM>, <NUM> described above. The magnetic array <NUM> will typically be permanent magnets, such as ferrite core.

The mover <NUM> further comprises a sensor component <NUM>, such as a permanent magnet, extending downwardly from the distal end <NUM> of the upper mounting arm <NUM>. The sensor component <NUM> may be a generally rectangular projection with a rounded distal tip <NUM> extending downwardly and contacting the horizontally extending surface <NUM> and interacting with the sensor array <NUM> provided in the inner surface <NUM> of each track module <NUM>, <NUM> described above. It should be noted, however, that the particular sensor component included in the mover <NUM> will depend upon the nature of the sensing strategy, the sensing resolution, and the position of the sensor on the mover (and cooperating components on the track module).

Again, the position, velocity, acceleration, and higher order derivative parameters are controllable for these movers <NUM> by appropriate control of the coils <NUM> of the system that are energized and de-energized as discussed above. In certain embodiments the movers <NUM> may be configured to be recognized by the power and control circuitry <NUM> as individual axes that are independently controlled, but with regulation of their position, velocity and acceleration to avoid conflicts, and collisions.

Referring also to <FIG>, a plurality of ball bearings or roller bearings having an outer race with a substantially cylindrical hardened steel surface, as indicated by wheels <NUM>, <NUM>, <NUM>, respectively, and associated components (e.g. flexible mounts <NUM>) are mounted to the mechanical structure of the mover <NUM> and serve to interact with the one or more rails <NUM>, <NUM> and <NUM>, respectively, of the track <NUM>. The wheels <NUM>, <NUM>, <NUM> are cylindrical wheels with a constant outer diameter. The wheels <NUM>, <NUM>, <NUM> may have an outer race with a crowned or barrel-shaped outer surface allowing the wheels to pivot while reducing the tangential contact length. The wheels <NUM>, <NUM>, <NUM> may have a generally similar hardness as the rails <NUM>, <NUM>, <NUM>. The thickness of the wheels <NUM>, <NUM>, <NUM> generally corresponds with the height of the rails <NUM>, <NUM>, <NUM> so that a full width of the wheels <NUM>, <NUM>, <NUM> contact the rails <NUM>, <NUM>, <NUM>.

A first set of four wheels 54a, 54b, 54c, 54d are mounted in a trapezoidal configuration to an inner surface <NUM> of the upper mounting arm <NUM> and correspond to rail <NUM> extending upwardly from the top edge <NUM> of the track <NUM>. The four wheels <NUM> are mounted to the upper mounting arm <NUM> such that an axial axis <NUM> of the wheels <NUM> extends substantially perpendicular to the inner surface <NUM> of the upper mounting arm <NUM> and parallel to vertical axis <NUM>. A first pair of lateral wheels 54a and 54b contacts a first sidewall <NUM> of the rail <NUM> and a second pair of lateral wheels 54c and 54d contacts a second sidewall <NUM> of the rail <NUM> opposite the first sidewall <NUM>. The first pair of wheels 54a and 54b are closely spaced from the second pair of wheels 54c and 54d allowing the narrow rail <NUM> to fit therebetween and slide between the first pair 54a and 54b and second pair 54c and 54d, respectively. For example, the first pair of wheels 54a, 54b may be spaced approximately <NUM> inch (<NUM>) from the second pair of wheels 54c, 54d which corresponds with a width of the rail <NUM>. A radial axis <NUM> of the wheels <NUM> in the outward radial direction <NUM> contacts the rail <NUM> in a direction perpendicular to the sidewalls <NUM>, <NUM> of the rail <NUM>. The distance between the first pair of wheels 54a, 54b, respectively, and second pair of wheels 54c, 54d, respectively, is described below with respect to <FIG>.

A second set of four wheels 56a, 56b, 56c, 56d are mounted in a similar rectangular formation to the inner surface <NUM> of the mounting platform <NUM> and correspond to rail <NUM> extending outwardly from the outer surface <NUM> of the track <NUM>. The four wheels <NUM> are shown mounted to the mounting platform <NUM> at a location above the magnetic array <NUM>; however, the wheels may also be located below the magnetic array <NUM> in a similar manner. The four wheels <NUM> are mounted to the mounting platform <NUM> so that an axial axis <NUM> of the wheels <NUM> extends substantially perpendicular to the inner surface <NUM> of the mounting platform <NUM> and parallel to outward radial direction <NUM>. A first pair of lateral wheels 56a and 56b contacts a top wall <NUM> of the rail <NUM> and a second pair of lateral wheels 56c and 56d contacts a bottom wall <NUM> of the rail <NUM> opposite the top wall <NUM>. The first pair of wheels 56a and 56b are closely spaced from the second pair of wheels 56c and 56d allowing the rail <NUM> to fit therebetween and slide between the first pair 56a and 56b and second pair 56c and 56d, respectively. For example, the first pair of wheels 56a, 56b may be spaced approximately <NUM> inch (<NUM>) from the second pair of wheels 56a, 56b corresponding with a width of the rail <NUM>. A radial axis <NUM> of the wheels <NUM> extending parallel to vertical axis <NUM> contacts the rail <NUM> in a direction perpendicular to the sidewalls <NUM>, <NUM> of the rail <NUM>. The distance between the first pair of wheels 56a, 56b, respectively, and second pair of wheels 56c, 56d, respectively, may be aligned such that the distance between the wheels 56a and 56b is substantially similar to the distance between the wheels 56c and 56d.

A third set of four wheels 58a, 58b, 58c, 58d are mounted in a trapezoidal formation to the inner surface <NUM> of the lower mounting arm <NUM> and correspond to rail <NUM> extending downward from the lower edge <NUM> of the track <NUM>. The four wheels <NUM> are mounted to the lower mounting arm <NUM> such that an axial axis <NUM> of the wheels <NUM> extends substantially perpendicular to the inner surface <NUM> of the lower mounting arm <NUM> and parallel to the vertical axis <NUM>. A first pair of lateral wheels 58a and 58b contacts a first sidewall <NUM> of the rail <NUM> and a second pair of wheels 58c and 58d contacts a second sidewall <NUM> of the rail <NUM> opposite the first sidewall <NUM>. The first pair of wheels 58a and 58b are closely spaced from the second pair of wheels 58c and 58d allowing the rail <NUM> to fit therebetween and slide between the first pair 58a and 58b and second pair 58c and 58d, respectively. For example, the first pair of wheels 58a, 58b may be spaced approximately <NUM> inch (<NUM>) from the second pair of wheels 58a, 58b corresponding with a width of the rail <NUM>. A radial axis <NUM> of the wheels <NUM> extending parallel to the outward radial direction <NUM> contacts the rail <NUM> in a direction perpendicular to the sidewalls <NUM>, <NUM> of the rail <NUM>. The distance between the first pair of wheels 58a, 58b, respectively, and second pair of wheels 58c, 58d, respectively, is described below with respect to <FIG>.

It is understood that although each set of wheels <NUM>, <NUM>, <NUM> provides four wheels, each set of wheels could also include two, three, or five or more wheels providing contact of the wheels on the rails <NUM>, <NUM>, <NUM> in a direction normal to the contact walls of the rails <NUM>, <NUM>, <NUM>.

In a similar manner, it is understood that the number of rails could also include two or four or more rails providing support along both the vertical axis <NUM> and outward radial direction <NUM>. For example, a first set of wheels may be mounted to the upper mounting arm <NUM> and a second set of wheels may be mounted to the mounting platform <NUM>. Correspondingly, the first set of wheels may contact two parallel walls of a first rail and the second set of wheels may contact two parallel walls of the second rail.

The wheels <NUM>, <NUM>, <NUM> will be mounted to the mover <NUM> via flexible mounts <NUM> of the mounting surfaces on which they are attached to allow the wheels <NUM>, <NUM>, <NUM> to adapt to track <NUM> variations, for example, when the mover <NUM> is transitioning between straight track modules <NUM> and curved track modules <NUM> of the track <NUM> and must account for "transition gaps" increasing a clearance between the wheels <NUM>, <NUM>, <NUM> and rails <NUM>, <NUM>,<NUM> and "lifting" the wheels off from the rail. The flexible mounts <NUM> allow the wheels <NUM>, <NUM>, <NUM> to shift inward and outward along radial axis <NUM>, <NUM>, <NUM>, respectively, while also allowing the wheels to retract or return to their original positions. The flexible mounts <NUM> provide an elastic material <NUM>, such as a flexible metal spring or other elastomeric material that allows an axle <NUM> of the wheels <NUM>, <NUM>, <NUM> to shift perpendicular to the axial axis <NUM>, <NUM>,<NUM> of the wheels. The elastic material <NUM> may also be a coil spring, a Bellville spring, or other flexible component. The flexible mounts <NUM> maintain the wheels <NUM>, <NUM>, <NUM> substantially parallel to the mounting surface on which they are attached. For example, all four wheels 54a, 54b, 54c, and 54d may include flexible mounts <NUM>.

Referring to <FIG>, the first set of four wheels 54a, 54b, 54c, 54d, and the third set of four wheels 58a, 58b, 58c, 58d are positioned with respect to rails <NUM>, <NUM>, respectively, to minimize a transition gap or jump that occurs when the mover <NUM> moves between the straight track modules <NUM> and curved track modules <NUM> given a fixed compliance of the wheel <NUM>, <NUM> provided by the flexible mounts <NUM>. The sets of wheels <NUM>, <NUM> can maintain contact with the contact surface of the track when the mover is wholly on the straight track module <NUM>, transitioning between straight <NUM> and curved <NUM> track modules, or wholly on the curved track module <NUM>.

With respect to curved track <NUM>, and referring to the first set of four wheels 54a, 54b, 54c, 54d, the inner wheels 54a, 54b will contact an inner circumference <NUM> of the curved rail <NUM> and outer wheels 54c, 54d will contact an outer circumference <NUM> of the curved rail <NUM>. The center points <NUM>, <NUM>, <NUM>, <NUM> of the wheels 54a, 54b, 54c, 54d, respectively, defined by the axes of rotation of the wheels form the corners of an isosceles trapezoid with the line segment joining the inner wheels 54a, 54b forming shorter base <NUM> parallel to the line segment joining outer wheels 54c, 54d forming the longer base <NUM>, and the line segment joining wheels 54a, 54c forming a first leg <NUM> and the line segment joining wheels 54c, 54d forming a second leg <NUM> equal in length to the first leg <NUM>.

The inner wheels 54a, 54b are positioned outside of a triangle having three vertices formed by a center of curvature <NUM> of the curved track <NUM> and the two center points <NUM>, <NUM> of the outer wheels 54c, 54d, respectively. The inner wheels 54a, 54b are also positioned inside a rectangle having straights sides formed by joining the center points <NUM>, <NUM> of the outer wheels 54c, 54d to form a first side <NUM> of the rectangle, second and third sides <NUM>, <NUM> extending from the center points <NUM>, <NUM>, respectively, toward and inward of the inner circumference <NUM>, and enclosed by a fourth side <NUM> tangent to the inner wheels 54a, 54b.

Similarly, the third set of four wheels 58a, 58b, 58c, 58d, inner wheels 58a, 58b are positioned along an inner circumference <NUM> of the curved rail <NUM> and outer wheels 58c, 58d are positioned along an outer circumference <NUM> of the curved rail <NUM>. The center points <NUM>, <NUM>, <NUM>, <NUM> of the wheels 58a, 58b, 58c, 58d, respectively, defined by the axes of rotation of the wheels form the corners of an isosceles trapezoid with the line segment joining the inner wheels 58a, 58b forming shorter base <NUM> parallel to the line segment joining outer wheels 58c, 58d forming the longer base <NUM>, and the line segment joining wheels 58a, 58c forming a first leg <NUM> and the line segment joining wheels 58c, 58d forming a second leg <NUM> equal in length to the first leg <NUM>.

The present inventors have determined that this positioning of the wheels <NUM> and <NUM> with different separations between the wheels on the inside of the tracks <NUM> and <NUM> than on the outside of the tracks <NUM> and <NUM> reduces the necessary compliance caused by changing separation between the corresponding wheels on the inside and outside of the track thus reducing a nearly imperceptible tendency of the wheels to leave the track on transitions between curved and straight track for a given compliance restoring force. The result is reduced track and bearing wear for a desired level of mechanical rigidity.

Referring to <FIG>, the wheels <NUM>, <NUM>, <NUM> and rails <NUM>, <NUM>, <NUM> allow the mover <NUM> to remain securely attached to the track modules <NUM>, <NUM> while allowing relatively free movement of the movers <NUM> along the track modules and supporting mechanical loads and forces encountered during motion. The wheels <NUM>, <NUM>, <NUM> are oriented such that loads are carried along their radial axes perpendicular to their axial axes. In this respect, the natural strength of the wheels <NUM>, <NUM>, <NUM> along the radial directions are utilized. For example, loads placed upon the mover <NUM> and creating a downward force along vertical axis <NUM> is carried by wheels <NUM>. The downward forces are placed along the radial axis <NUM> of wheels <NUM>. Centrifugal forces and torsion placed upon the mover <NUM> and creating an outward force along the outward radial direction <NUM> is carried by wheels <NUM> and <NUM>. The outward radial force is placed along the radial axis <NUM> and <NUM> of wheels <NUM> and <NUM>, respectively. Very little force is placed on the wheels <NUM>, <NUM>, <NUM> along their axial axis <NUM>, <NUM>, <NUM>, respectively, where the wheels are weakest.

The wheels <NUM>, <NUM> of the upper mounting arm <NUM> and lower mounting arm <NUM>, respectively, are positioned such that the mounting platform <NUM> is spaced from track <NUM> and so the rectangular block <NUM> of the magnetic array <NUM> is spaced from the inner surface <NUM> of the vertically extending wall <NUM> on the inner end and such that the sensor component <NUM> is spaced from the inner surface of the vertically extending wall <NUM> on the outer end. In a similar manner, the wheels 56a, 56b, 56c, 56d of the mounting platform <NUM> are positioned such that the upper mounting arm <NUM> and lower mounting arm <NUM> are spaced from the tracks <NUM>, <NUM>.

While a horizontal configuration is illustrated in <FIG>, other orientations may also be provided, such as ones in which the illustrated oval is generally stood on a side or end, or at any angle between. It should be noted that other configurations are equally possible. The configurations may form closed loops of various shapes, but may also comprise open-ended segments.

<FIG> illustrates an alternative configuration for a similar transport system. However, in this configuration, rather than motor coils <NUM> being positioned around the periphery of the outer surface <NUM> of the system, coils <NUM> are positioned around the top edge <NUM> of the system, in a generally planar arrangement. Magnet assemblies of each mover <NUM> face these coils <NUM> and are spaced from the coils <NUM> by a small air gap. It is understood that the illustrated embodiment may be adapted for use with the alternative configuration by rotating the mounting platform <NUM> to extend parallel to a top of the edge <NUM> of the system, and the mounting arms <NUM>, <NUM> extending parallel along an outer <NUM> and inner <NUM> surface of the track wall <NUM>.

As will be appreciated by those skilled in the art, in many applications, the transport system <NUM> will be configured to inter-operate with other machines, robots, conveyers, control equipment, and so forth (not shown) in an overall automation, packaging, material handling or other application. The transport system <NUM> may be a linear motor system as described in <CIT>, entitled "Controlled Motion System Having an Improved Track Configuration,".

Certain terminology is used herein for purposes of reference only. For example, terms such as "upper", "lower", "above", and "below" refer to directions in the drawings to which reference is made. Terms such as "front", "back", "rear", "bottom" and "side", describe the orientation of portions of the component within a consistent but arbitrary frame of reference, which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms "first", "second" and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. When elements are indicated to be electrically connected, that connection may be direct or through an intervening conductive element.

Claim 1:
A mover (<NUM>) for use on a track (<NUM>) providing a closed loop extending along a track (<NUM>) circumferential path and having a mover support frame supporting a magnetic element for interacting with corresponding magnetic elements on the mover (<NUM>) and supporting a first rail (<NUM>) and a second rail (<NUM>) extending along the circumferential path and displaced from each other a distance less than a length of the mover support frame in a direction perpendicular to the circumferential path, wherein each track (<NUM>) provides two opposed parallel contact surfaces, wherein the mover support frame further supports a third rail (<NUM>) extending along the circumferential path and displaced from the first (<NUM>) and second rails (<NUM>) in a direction perpendicular to the track circumferential path, the mover (<NUM>) comprising:
a frame supporting a magnetic element (<NUM>) for interacting with corresponding magnetic elements (<NUM>) on the track (<NUM>) and supporting a first, a second and a third set of bearings;
wherein each set of bearings provides two wheels (54a/54c, 56a/56c, 58a/58c) being rotatable about a respective axis (<NUM>, <NUM>, <NUM>) and the axes for the two wheels being parallel and the wheels having peripheral contact surfaces opposed across a gap distance bisected by a center point between the contact surfaces, wherein the center points are displaced by a distance larger than the gap; wherein the wheels (54a/54c, 56a/56c, 58a/58c) of each set of bearings are mounted to the mover (<NUM>) via flexible mounts (<NUM>) of mounting surfaces on which the wheels (54a/54c, 56a/56c, 58a/58c) are attached to allow the wheels (54a/54c, 56a/56c, 58a/58c) to adapt to track (<NUM>) variations, wherein the flexible mounts (<NUM>) provide an elastic material (<NUM>); and
wherein the axes (<NUM>, <NUM>) of the first bearing set and of the third bearing set are perpendicular to the axes (<NUM>) of the second bearing set.