HK1195041B - Permanent magnet centering system for brake - Google Patents

Description

Permanent magnet centering system for brake

Technical Field

The present disclosure relates generally to brake systems and, more particularly, to centering of a caliper (caliper) with respect to a rotor in a disc brake system.

Background

Disc brakes are widely used to slow or stop the rotation of a moving object. One application of disc brakes is elevator systems, and in particular traction-based elevator systems. Such elevator systems generally include an elevator car connected to a counterweight via a hoisting rope that is drawn (trained) around a traction sheave. The traction sheave is driven by a motor such that rotation of the traction sheave moves the hoist rope, causing the desired movement of the elevator car. To slow or stop movement of the elevator car (e.g., by actuating the brake), the traction sheave is connected to a disc brake.

The traction sheave may have a flange coupled to each side, the flange serving as a rotating disc or rotor for the disc brake. The traction sheave and the rotor rotate together to facilitate movement of the elevator car. When friction is applied to both sides of the rotor, the rotor and the traction sheave slow or stop, slowing or stopping the movement of the elevator car. Friction with the rotor is applied by a caliper having at least one set of brake pads, brake coils, and springs on each caliper. When the brake is actuated, the brake coils are disengaged and the spring applies a force to the brake pads, which contact the rotor, causing a tangential frictional force opposing the movement of the rotor and the traction sheave.

The caliper is mounted such that it is fixed in tangential and radial directions, but is allowed to have some degree of translation or float in axial direction with respect to the rotor. While this amount of float is required to allow for the range of axial motion encountered in operation and proper braking operation under load, such float still contributes to the eccentricity of the caliper with respect to the rotor. The centering of the caliper and rotor helps prevent brake pads from contacting the rotor when the brake is released. Ideally, the caliper will always be centered by itself on the rotor with a consistent clearance between each brake pad and the rotor braking surface of the rotor. However, this is not generally true. Therefore, several techniques have been proposed in the past to specifically center the caliper and ensure that the brake pads do not contact the rotor when the brake is released.

While effective, such conventional techniques still have several drawbacks. For example, in most conventional techniques, mechanical devices such as sensors are used to center the caliper and rotor. These sensors maintain a large physical contact with the rotor, resulting in static friction (stiction) and friction losses. Typically, such techniques also require a power supply or other closed loop system operation, which not only increases the overall cost and maintenance of the disc brake, but is also prone to failure and shorter life. Furthermore, such sensors cannot accommodate differential thermal expansion between the mounting unit of the sensor and the rotor.

Therefore, it would be beneficial if a reliable, robust, and/or inexpensive system were developed that facilitated caliper centering with respect to the rotor. Additionally or alternatively, it would be beneficial if such a system would minimize static and frictional losses, accommodate any thermal expansion, and/or eliminate the need for a separate power supply system.

Disclosure of Invention

According to one aspect of the present disclosure, a brake assembly is disclosed. The brake assembly may include a rotating element, a stationary element mounted in operative association with the rotating element, and a positioning device connected to the stationary element. The positioning device may also magnetically interface with the rotating element to facilitate centering of the fixed element with respect to the rotating element.

In some refinements, the rotating element may be a rotor, the stationary element may be a caliper assembly, and the positioning device may optionally comprise two side portions and a permanent magnet. The permanent magnet may alternatively be sandwiched between two side portions, which in turn may be made of ferromagnetic material.

In a further refinement, each of the two side portions may optionally have a first abutment surface and the rotary element may have a second abutment surface, such that the first and second abutment surfaces may abut each other to magnetically abut the positioning device with the rotary element.

In an additional refinement, the first abutting surface may optionally have a first plurality of teeth with a first plurality of tips, and the second abutting surface may have a second plurality of teeth with a second plurality of tips. The first plurality of teeth may optionally magnetically interface with the second plurality of teeth, and the first plurality of tips may be aligned with the facing second plurality of tips when the fixed element is centered with the rotating element, and the first plurality of tips may optionally be offset from the facing second plurality of tips when the fixed element is eccentric to the rotating element.

In still further refinements, the positioning device may optionally generate a magnetic flux concentrated at the first plurality of tips and the second plurality of tips.

In other refinements, the second abutment surface may be machined into an annular groove of the rotating element, and the annular groove may optionally include a non-magnetic stop.

In accordance with another aspect of the disclosure, a machine for an elevator system is disclosed. The machine may include a traction sheave and an electric motor that drives the traction sheave. The machine may also include a brake assembly for braking the traction sheave, the brake assembly having a caliper assembly and a positioning device having a permanent magnet, the positioning device being connected to the caliper assembly and magnetically interfacing with the traction sheave.

In some refinements, the positioning device may optionally be positioned between the caliper assembly and the rotor of the traction sheave. The positioning device may also optionally include a first plurality of teeth having a first plurality of tips, and the rotor may include a second plurality of teeth having a second plurality of tips, the first and second plurality of tips being alignable with one another to center the caliper assembly and the rotor.

In other refinements, the positioning device may optionally generate a magnetic flux that may be concentrated at the first and second plurality of tips to align the first and second plurality of tips.

In still further refinements the positioning device may optionally have a first abutment surface that abuts a second abutment surface of the traction sheave.

According to yet another aspect of the present disclosure, a method of centering a stationary element and a rotating element is disclosed. The method may include providing a brake assembly having a rotating element, a stationary element connected in operative association with the rotating element, and a positioning device connected to the stationary element and magnetically interfacing with the rotating element. The method may also include generating a magnetic flux by the positioning device, and sending the magnetic flux via the rotating element to restore the centered position of the stationary element and the rotating element. The method may further comprise repeating the generating step after each braking operation.

In some refinements, generating the magnetic flux may optionally include defining a closed loop magnetic flux path from the positioning device to the rotating element and back.

In other refinements, defining the magnetic flux path may optionally include restricting the magnetic flux from moving laterally into the rotating element.

Other advantages and features will become apparent from the following detailed description when read in conjunction with the accompanying drawings.

Drawings

For a more complete understanding of the disclosed method and apparatus, reference will now be made to exemplary embodiments illustrated in greater detail in the accompanying drawings, in which:

fig. 1 is a simplified schematic illustration of an elevator system using a machine having a disc brake system of the present disclosure;

FIG. 2 is a perspective view of the machine of FIG. 1 with the disc brake system in greater detail;

FIG. 3 is an enlarged perspective view of a portion of the disc brake system of FIG. 2 in greater detail;

FIG. 4 is an enlarged perspective view of the disc brake system of FIG. 3 with the caliper assembly of the disc brake system removed;

FIG. 5 is a cross-sectional view of the disc brake system taken along line 5-5 in FIG. 3;

FIG. 6 illustrates the magnetic flux path through the magnetic means employed in the disc brake system of FIGS. 2-5; and

fig. 7A and 7B are vector diagrams of magnetic flux densities of the magnetic device of fig. 6.

While the following detailed description is given and provided with respect to certain specific exemplary embodiments, it is to be understood that the scope of the disclosure is not to be limited to such embodiments, but is only provided for the purpose of implementation and best mode. The breadth and spirit of the present disclosure are broader than the embodiments specifically disclosed and encompassed within the claims appended hereto and their equivalents.

Detailed Description

Referring now to fig. 1, a simplified schematic diagram of an elevator system 2 is shown, according to at least some embodiments of the present disclosure. Although all of the components of the elevator system 2 have been illustrated and/or described in detail herein, a typical elevator system may include an elevator car 4 connected to a counterweight 6 via hoisting ropes (not shown). The hoisting ropes may extend over a traction sheave 10 driven by an electric motor within the traction sheave (e.g., the traction sheave 10 may be the rotor of the electric motor) to move or stop the elevator car 4 as desired. A disc brake system (described below) on the traction sheave 10 helps slow or stop the elevator system 2. The electric motor, traction sheave 10, and disc brake system are collectively referred to herein as an elevator machine 12. The elevator system 2 with the counterweight 6 operates in a known manner and is therefore not described in detail for the sake of brevity. However, it will be understood that components other than those described above, such as an elevator car frame, guide assembly, drive assembly, and the like, are contemplated and considered within the scope of this disclosure.

Turning now to fig. 2, an exemplary embodiment of the elevator machine 12 according to the present disclosure is shown in more detail. As shown, the elevator traction machine 12 may include various structural components to, for example, assist in positioning or installing the elevator traction machine in a machine room above a hoistway (e.g., a hoist rope). For example, the structural member may include a base plate 16, the base plate 16 having a plurality of struts (e.g., steel struts or channels) 18. The structural members may also include a pair of racks 20 mounted to the floor 16 and extending from the floor 16.

Further, each of the racks 20 may be identical (or substantially identical) to each other in shape, size, and form. The elevator traction machine 12 can also include a shaft (with an electric motor stator mounted thereon) extending between the two frames 20 and through the traction sheave 10. Thus, the frame 20 can be used to secure the ends of the shaft to carry the weight of the stator and any rotating parts. Other components, such as encoders, typically used in combination with or in conjunction with such frame and/or disc brake systems, although not shown and/or described, are contemplated and considered within the scope of the present disclosure.

Flanges mounted on either side of the traction sheave 10 serve as the rotating element or rotor 30 of the brake assembly 22. Brake assembly 22 may also include one or more stationary elements or caliper assemblies 34, one or more of which may be mounted to a respective one of frames 20 by way of suitable fasteners, such as pins 24, and may also abut a respective one of rotors 30. Although not visible in fig. 2, brake assembly 22 may also include a positioning device 36 (see fig. 3) for centering each caliper assembly 34 with respect to each respective rotor 30. The positioning device 36 is described in more detail in fig. 3-7 below.

In operation, the brake assembly 22 may be electrically actuated. When the brakes (not shown) of the elevator system 2 are energized (in a known manner), brake coils (not visible) positioned within the caliper assembly 34 generate a magnetic field, moving the brake pads (also not visible, and positioned within the caliper assembly) away from the rotor 30 and allowing rotation thereof for moving the traction sheave 10 (through the electric motor) to move the elevator car 4. Upon de-energizing, the brake coils in the caliper assembly 34 no longer affect the brake pads, and the springs in the caliper assembly move the brake pads toward the rotor 30 and into contact with the rotor 30 to stop its rotation and stop movement of the elevator car 4.

Further, during operation of brake assembly 22, some or all of caliper assemblies 34 may be fixed to frame 20 in the tangential and radial directions, but may have some degree of translation or float in the axial direction as described below. For example, axial float helps accommodate size variations in the elevator machine 12 due to temperature, etc. For example, all of the caliper assemblies 34 on one end of the elevator traction machine 12 may be allowed to float axially. This axial floating of caliper assembly 34 is illustrated by arrow 37 in fig. 3. To account for the float and to ensure that the caliper assembly 34 returns to a centered position with respect to the respective rotor 30 after a braking operation, a positioning device 36, described below, may be employed.

Referring now to fig. 3-4, the positioning device 36 is shown and described in greater detail. Specifically, FIG. 3 shows a portion of the brake assembly 22 having the positioning device positioned between a caliper assembly 34 and a rotor 30 in greater detail, while FIG. 4 shows a portion of the brake assembly with a caliper assembly removed. For simplicity of illustration, the positioning device 36 is described below with respect to only one caliper assembly 34 (also referred to below simply as caliper assembly 34) and one rotor 30 (also referred to below simply as rotor 30). However, it should be understood that the same teachings may be applied to other caliper assemblies 34 and other rotors 30 within the elevator traction machine 12, each of those caliper assemblies 34 and rotors 30 having a positioning device 36 positioned therebetween.

The positioning device 36 may be embodied as a magnetic positioning device, and more specifically a passive permanent magnet device, which is connected to the caliper assembly (stationary element) 34 and magnetically interfaces with the rotor (rotating element) 30. In at least some embodiments, the positioning device 36 can be mechanically attached (or mounted) to the caliper assembly 34 by way of fasteners such as nuts, bolts, screws, or the like, or by adhesive and glue. In other embodiments, the positioning device 36 may be magnetically mounted to the caliper assembly 34, or also mounted to the caliper assembly 34 by other types of mechanisms. The connection (magnetic docking) between the positioning device 36 and the rotor 30 is described in more detail below. By virtue of the positioning device 36 being connected between the caliper assembly 34 and the rotor 30 and magnetically interfacing the positioning device with the rotor, the caliper assembly can be centered on the rotor with a consistent clearance (e.g., positioned equidistant) between each brake pad and the rotor braking surface of the rotor to ensure that the brake pads do not contact the rotor (e.g., the rotor braking surface) when the brake is released (e.g., energized).

To facilitate centering of the caliper assembly 34 and the rotor 30, the positioning device 36 may include side portions 38 that clamp permanent magnets 40 (see FIG. 4). In at least some embodiments, each side portion 38 can be made of a ferromagnetic material, such as steel, although in other embodiments other types of ferromagnetic materials can be used. Relatedly, to magnetically interface with the permanent magnets 40, the rotor 30 may be constructed of a ferromagnetic material such as cast iron (e.g., gray iron), although other types of ferromagnetic materials commonly used to construct disc brake rotors may be employed.

By virtue of the side portions 38 and the rotor 30 being constructed of ferromagnetic material, a magnetic flux path (described below in FIG. 6) may be established from the permanent magnets 40 through the side portions 38 and the rotor 30 for centering the rotor and caliper assembly 34. Further, the permanent magnets 40 may be positioned in an orientation or direction in order to establish a magnetic flux path. For example, in at least some embodiments and as shown, the permanent magnet 40 can be oriented such that the north pole of the permanent magnet faces the direction shown by arrow 41 and magnetic flux flows from the north pole to the south pole of the permanent magnet. In other embodiments, the north pole may face in a direction opposite to the direction of arrow 41, and the magnetic flux may then flow in a direction opposite to that described below in fig. 6.

Despite the fact that in the embodiment of fig. 3 and 4, each side portion 38 has been shown to be similar (or substantially similar) in shape and size to the permanent magnet 40 to be positioned centrally (or substantially centrally) between the side portions, this need not always be the case. Rather, in other embodiments, each side portion 38 may take on a different configuration (e.g., shape and size) than the other, and/or the permanent magnet 40 may be positioned off-center between the two asymmetric side portions. Further, while only one permanent magnet 40 has been shown, it will be understood that in other embodiments, multiple of those permanent magnets and/or multiple positioning devices each having one or more permanent magnets may be used between caliper assembly 34 and rotor 30.

The shape, size, and material of the permanent magnets 40 and the positioning of the positioning device 36 between the caliper assembly 34 and the rotor 30 may also vary in other embodiments. Specifically, the shape, size, and arrangement of the positioning device 36 may vary depending on several factors, such as the size of the elevator traction machine 12, the size and weight of the caliper assembly 34, and the axial force (F) required to center the caliper assembly and the rotor. The above parameters may also vary as long as permanent magnets 40 are arranged to generate a magnetic flux through positioning device 36 and through rotor 30 (as described below) such that any change in the relative positions of caliper assembly 34 and the rotor is sensed by the positioning device and a magnetic shear force (e.g., a restoring axial force) is used to restore brake assembly 22 to its centered position.

Referring now to fig. 5 and 6 in conjunction with fig. 3 and 4, the positioning device 36 may be connected to magnetically dock the rotor 30 by way of a first docking surface 42 and a second docking surface 44, respectively. A first abutment surface 42 may be machined on each side portion 38 and a second abutment surface 44 may be machined within an annular groove 46 of the rotor 30. In addition, each of the first and second abutment surfaces 42 and 44, respectively, may be machined with a plurality of corresponding teeth 48 and 50, the teeth 48 and 50 having tips 52 and 54, respectively, with a small clearance between those tips.

To magnetically interface the positioning device 36 with the rotor 30, the side portion 38 may be inserted into the annular groove 46 such that the teeth 48 on the first interface surface 42 interface with the teeth 50 on the second interface surface 44. Specifically, the magnetic interface between the first interfacing surface 42 and the second interfacing surface 44, respectively, is established such that the tip 52 of the tooth 48 is aligned with (e.g., directly contacts or mates with) the tip 54 of the tooth 50. By virtue of the magnetic interface of the positioning device 36 with the rotor 30, any substantially direct physical contact between the positioning device and the rotor is avoided, thereby minimizing stiction and friction losses. Further, while in the present embodiment a single positioning device 36 has been disclosed that magnetically docks the rotor 30 through the annular groove 46, in at least some embodiments, multiple annular grooves each having a positioning device may be employed.

The aligned position of tips 52 and 54 presents a centered position of caliper assembly 34 and rotor 30. Any deviation from alignment of tips 52 and 54 (caused by axial movement of the caliper assembly in the direction of arrow 37) results in an eccentric position of caliper assembly 34 and rotor 30. This off-center position may be corrected by positioning device 36, and in particular, by permanent magnet 40 of the positioning device, which generates a magnetic flux to restore alignment between tips 52 and 54, thereby returning caliper assembly 34 and rotor 30 to the centered position in a manner described below.

With particular respect to teeth 48 and 50, each of those pairs of teeth may be a mating tooth, which may be made of a ferromagnetic material (e.g., steel), and may take a trapezoidal or triangular configuration with tips 52 and 54, respectively, and may or may not have chamfered end portions. Preferably, the number of teeth 48 on the first abutment surface 42 may be equal to the number of teeth 50 on the second abutment surface 44, but this need not always be the case. Further, in at least some example embodiments, fifteen teeth 48 and 50 on each of the first and second abutment surfaces 42 and 44, respectively, may be employed. In other embodiments, the number of teeth may vary. Also, in some exemplary embodiments, a tooth-to-tooth pitch (e.g., the distance between two consecutive tips) of 1.67 millimeters for each tooth 48 and 50 may be employed. In other embodiments, the tooth-to-tooth pitch of the teeth 48 and 50 may vary.

Referring now to fig. 6 and 7A-7B, the magnetic flux path 56 of the permanent magnet 40 is shown in fig. 6, while the flux density vector diagrams 58 and 60 of the magnetic flux 62 are shown in fig. 7A and 7B, respectively. As described above, the positioning device 36 with permanent magnets 40 and the rotor 30 are set up such that the tips 52 and 54 of the teeth 48 and 50 are in aligned positions corresponding to the centered positions of the caliper assembly 34 and the rotor 30, respectively. During operation, when an axial force (F), shown by arrow 37 in fig. 3, acts on the caliper assembly 34 or rotor 30 and eccentricities those components, a magnetic flux (e.g., magnetic field) 62 (shown by the various arrows in fig. 7A and 7B) generated by the permanent magnet 40 generates a restoring axial force (e.g., in a direction opposite the axial force F) to restore alignment between the tips 52 and 54 and return the caliper assembly and rotor to a stable centered position. As described further below, magnetic flux 62 tends to follow magnetic flux path 56 to maintain a position of minimum reluctance (reluctant), and any increase in reluctance is counteracted by restoring axial force to return the magnetic flux to the position of minimum reluctance.

With respect to the magnetic flux path 56 corresponding to the magnetic flux 62 generated by the permanent magnet 40, it extends in the direction of arrow 41 (from north to south pole) and enters the rotor 30 along the side portion 38 passing through the positioning device 36 and returns to the closed loop 38 of permanent magnets via the other of the side portions. In addition, the magnetic flux path 56 attempts to take the shortest path from the positioning device 36 to the rotor 30 and back. The shortest distance and minimum reluctance of the magnetic flux 62 and the magnetic flux path 56 is achieved when the tip 52 of the tooth 48 is directly aligned with the tip 54 of the facing tooth 50. Thus, the magnetic flux 62 flows from each of the tips 52 of the teeth 48 of the positioning device 36 to each corresponding tip 54 of the teeth 50 of the rotor 30, as shown by the ring portion 64 of the magnetic flux path 56 in FIG. 6. Thus, the magnetic flux 62 is concentrated between the tips 52 and 54 of the facing or corresponding pairs of teeth 48 and 50.

Such aligned (or centered) positions of tips 52 and 54 correspond to centered positions of caliper assembly 34 and rotor 30. This position is shown in map region 58, where the corresponding tips 52 and 54 are aligned with each other and have a zero (0) millimeter offset. If tip 54 of tooth 50 of rotor 30 moves laterally away from tip 52 of tooth 48 of positioning device 36 (e.g., an offset caused by axial movement of caliper assembly 34), resulting in an eccentric position of caliper assembly 34 and rotor 30, the reluctance in magnetic flux 62 increases. To restore the minimum reluctance position of tips 52 and 54, magnetic flux 62 creates an opposing axial restoring force and forces offset tip 54 back into alignment with tip 52. The plot area 60 shows the displacement of one quarter (0.25) millimeter of the tips 52 and 54 of the teeth 48 and 50, respectively, and the restoring force generated by the permanent magnet 40.

Thus, magnetic flux 62 tends to maintain the position of minimum reluctance at all times, and any increase in reluctance (caused by the offset of tips 52 and 54) causes permanent magnet 40 to try and minimize reluctance and maintain the alignment of tips 52 and 54, thereby maintaining the centered position of caliper assembly 34 and rotor 30. Further, to prevent direct contact between the positioning device 36 and the rotor 30, a non-magnetic stop 66 is located within the annular groove 46 of the rotor and in the path of the magnetic flux path 56. The inner semi-circular shape of the stop 66 and the positioning device 36 creates a non-magnetic barrier to prevent the magnetic flux 62 from flowing to the disk, and the teeth 48 and 50 are omitted.

Industrial applicability

In general, the present disclosure sets forth a brake assembly connected in operative association with a traction sheave. The brake assembly may include a rotating element or rotor, a stationary element or caliper assembly, and a positioning device positioned between each respective caliper assembly and the rotor. Each positioning device may comprise a permanent magnet arranged to generate a magnetic flux through each rotor to centre each respective caliper assembly therewith.

By virtue of centering the caliper assembly and rotor through the use of permanent magnets (in the form of the positioning devices described hereinabove), the present disclosure provides several advantages over conventional centering mechanisms. For example, there is no substantial physical contact between the sensor (positioning device) and the portion (rotor) whose position is sensed, thereby eliminating or at least substantially reducing any frictional losses. In addition, the positioning device provides passive control, thereby eliminating the need for a power supply and closed loop control system of conventional solutions. Furthermore, the positioning device overcomes the typical problems of mechanical centering devices involving static friction (static friction) and friction, and provides the ability to accommodate differential thermal expansion between the object (sensor mounting) and the sensing part (rotor). Thus, the positioning device provides a brake assembly and, therefore, a disc brake system that is robust, easy to maintain and use, results in a long life with minimal maintenance, and is inexpensive to install and operate.

Further, while the above disclosure has in fact been described with reference to elevator systems, it will be understood that disc brake systems may be used with other types of machines and systems that also employ disc brakes.

While only a few embodiments have been set forth, alternatives and modifications will be apparent to those skilled in the art from the foregoing description. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.

Claims (18)

1. A brake assembly (22) comprising:

a rotating element (30);

a fixed element (34) mounted in operative association with said rotating element (30); and

a positioning device (36) connected to the stationary element (34) and magnetically interfacing with the rotating element (30) to facilitate centering of the stationary element (34) with respect to the rotating element (30), the positioning device (36) comprising two side portions (38) and a permanent magnet (40) sandwiched between the two side portions (38), wherein the permanent magnet (40) is arranged to generate a magnetic flux through the positioning device (36) and through the rotating element (30) such that any change in the relative position of the stationary element (34) and the rotating element is sensed by the positioning device and magnetic shear forces are used to restore the brake assembly (22) to its centered position.

2. The brake assembly (22) of claim 1 wherein the rotating element is a rotor (30) and the stationary element is a caliper assembly (34).

3. The brake assembly (22) of claim 1, wherein each of the two side portions (38) is made of a ferromagnetic material.

4. The brake assembly (22) of claim 1, wherein each of the two side portions (38) has a first abutment surface (42) and the rotary element (30) has a second abutment surface (44), the first and second abutment surfaces abutting each other to magnetically abut the positioning device (36) with the rotary element (30).

5. The brake assembly (22) of claim 4 wherein the first abutment surface (42) has a first plurality of teeth (48) with a first plurality of tips (52) and the second abutment surface (44) has a second plurality of teeth (50) with a second plurality of tips (54).

6. The brake assembly (22) of claim 5, wherein the first plurality of teeth (48) magnetically interface with the second plurality of teeth (50).

7. The brake assembly (22) of claim 5, wherein the first plurality of tips (52) are aligned with the facing second plurality of tips (54) when the stationary element (34) is centered with the rotating element (30).

8. The brake assembly (22) of claim 5, wherein the first plurality of tips (52) are offset from the facing second plurality of tips (54) when the fixed element (34) is eccentric from the rotating element (30).

9. The brake assembly (22) of claim 5, wherein the positioning device (36) generates a magnetic flux (62) concentrated at the first and second plurality of tips (52, 54).

10. The brake assembly (22) of claim 4, wherein the second abutment surface (44) is machined in an annular groove (46) of the rotating element (30).

11. The brake assembly (22) of claim 10 wherein the annular groove (46) further includes a non-magnetic stop (66).

12. A machine (12) for an elevator system (2), comprising:

a traction sheave (10);

an electric motor driving the traction sheave (10); and

a brake assembly (22) for braking the traction sheave (10), the brake assembly (22) having a caliper assembly (34) and a positioning device (36) having a permanent magnet (40), the positioning device (36) connected to the caliper assembly (34) and magnetically interfacing with the traction sheave (10), the positioning device (36) positioned between the caliper assembly (34) and a rotor (30) of the traction sheave (10), wherein the permanent magnet (40) is arranged to generate a magnetic flux through the positioning device (36) and through the rotor (30) such that any change in the relative position of the caliper assembly (34) and the rotor is sensed by the positioning device and magnetic shear forces are used to restore the brake assembly (22) to its centered position.

13. The machine (12) of claim 12, wherein the positioning device (36) has a first plurality of teeth (48) with a first plurality of tips (52) and the rotor (30) has a second plurality of teeth (50) with a second plurality of tips (54), the first and second pluralities of tips (52, 54) being aligned with one another to center the caliper assembly (34) and the rotor (30).

14. The machine (12) of claim 13, wherein the positioning device (36) generates a magnetic flux (62), the magnetic flux (62) being concentrated at the first and second pluralities of tips (52, 54) to align the first and second pluralities of tips (52, 54).

15. The machine (12) of claim 12, wherein the positioning device (36) has a first abutment surface (42) that abuts a second abutment surface (44) of the traction sheave (10).

16. A method of centering a stationary element (34) and a rotating element (30), the method comprising:

providing a brake assembly (22) having a rotary element (30), a stationary element (34) connected in operative association with the rotary element (30), and a positioning device (36) connected to the stationary element (34) and magnetically interfacing with the rotary element (30), the positioning device (36) comprising two side portions (38) and a permanent magnet (40) sandwiched between the two side portions (38), wherein the permanent magnet (40) is arranged to generate a magnetic flux through the positioning device (36) and through the rotary element (30) such that any change in the relative position of the stationary element (34) and rotary element is sensed by the positioning device and magnetic shear forces are used to restore the brake assembly (22) to its centered position;

generating a magnetic flux (62) by the positioning device (36) and sending the magnetic flux (62) via the rotating element (30) to restore the centered position of the stationary element (34) and the rotating element (30); and

the generating step is repeated after each braking operation.

17. The method of claim 16, wherein generating a magnetic flux (62) includes defining a closed loop magnetic flux path (56) from the positioning device (36) to the rotating element (30) and back.

18. The method of claim 17, wherein defining the closed loop magnetic flux path (56) further comprises restricting lateral movement of the magnetic flux (62) into the rotating element (30).