MOLYBDENUM COATED ELEVATOR SAFETY BRAKES

Abstract

An elevator safety brake for stopping an elevator car, the brake including a brake shoe including a base, and a brake pad disposed on the base, wherein the brake pad includes a rail contacting friction surface for contacting an elevator guide rail surface, wherein the brake pad is fuse bonded to the base, wherein the brake pad is chosen from a group consisting of: molybdenum and molybdenum alloys.

Claims

1. An elevator safety brake for stopping an elevator car, the brake comprising: a brake shoe including a base; and a brake pad disposed on the base, wherein the brake pad includes a rail contacting friction surface for contacting an elevator guide rail surface, wherein the brake pad is fuse bonded to the base; wherein the brake pad is chosen from a group consisting of: molybdenum and molybdenum alloys.

2. The elevator safety brake of claim 1, wherein the base comprises a high compressive strength structural alloy.

3. The elevator safety brake of claim 2, wherein the high compressive strength structural alloy is chosen from a group consisting of: steel and cast iron.

4. The elevator safety brake of claim 2, wherein the brake pad is fuse bonded to the brake base via a fusion welding process.

5. The elevator safety brake of claim 4, wherein the fusion welding process comprises an arc welding process.

6. The elevator safety brake of claim 1, further comprising an interface layer disposed between the base and the brake pad, wherein the interface layer is fuse bonded to the base and the brake pad.

7. The elevator safety brake of claim 1, wherein the interface layer is chosen from a group consisting of: chrome, iron, nickel, nickel alloys, cobalt, and cobalt alloys.

8. The elevator safety brake of claim 1, wherein the rail contacting friction surface includes surface features disposed thereon, wherein the surface features are configured to provide at least one of increased friction of the brake pad and wear indication of the brake pad.

9. The elevator safety brake of claim 8, wherein the surface features include at least one raised feature deposited onto at least one of the brake pad and the base.

10. The elevator safety brake of claim 9, wherein the at least one raised feature is non-continuously applied to at least one of the brake pad and the base.

11. The elevator safety brake of claim 9, wherein the at least one raised feature includes a plurality of dots.

12. The elevator safety brake of claim 9, wherein the at least one raised feature includes a plurality of line segments.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The embodiments and other features, advantages and disclosures contained herein, and the manner of attaining them, will become apparent and the present disclosure will be better understood by reference to the following description of various exemplary embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein:

[0016] FIG. 1 is a schematic diagram of an elevator safety brake system according to an embodiment of the present disclosure;

[0017] FIG. 2 is a schematic diagram of an elevator safety brake according to an embodiment of the present disclosure;

[0018] FIG. 3 is a schematic diagram of an elevator safety brake including a cross-hatch pattern;

[0019] FIG. 4 is a schematic diagram of an elevator safety brake according to another embodiment of the present disclosure;

[0020] FIG. 5 is a schematic diagram of an elevator safety brake including a raised feature; and

[0021] FIG. 6 is a schematic diagram of an elevator safety brake including a raised feature.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0022] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended.

[0023] FIG. 1 provides a simplified schematic illustration of a known elevator safety brake system, generally indicated at 10. The brake system 10 includes a pair of actuators 12 which are attached to an elevator car 14 and positioned in an opposing relationship about a guide rail 16 supported in an elevator hoistway (not shown). The actuators 12 are formed, in part, by a wedge shaped guide shoe 18 which is movable within housing 20 in a direction which is generally perpendicular to the guide rail 16. The guide shoe 18 is biased towards the guide rail 16 by spring 22. The guide shoe 18 has an inclined cam surface 24. A wedge shaped brake shoe 25 having base 26 is provided so as to have an inclined cam surface 28 which is complimentary to the inclined cam surface 24 of the guide shoe 18. In an embodiment, the base 26 includes a high compressive strength structural alloy. In on embodiment, the high compressive strength structural alloy is chosen from a group consisting of steel and cast iron. It will be appreciated that other high compressive strength structural alloys may be chosen. The brake shoe 25 is also provided with a rail facing surface 30. The brake shoe 25 is positioned between the guide shoe 18 and the guide rail 16.

[0024] A brake pad 32 having a high friction material is disposed on the rail facing surface 30 of the brake shoe base 26. A roller cage assembly containing a plurality of rollers 34 is positioned between the inclined cam surface 24 of the guide shoe 18 and the complimentary inclined guide shoe facing surface 28 of the brake shoe 25. The rollers 34 provide a low friction contact between the complimentary inclined adjacent surfaces 24 and 28 of the guide shoe 18 and the brake shoe 25, respectively. The guide shoe 18, biased by spring 22, applies normal force F.sub.N in the direction of the guide rail 16 on brake shoe 25 through rollers 34.

[0025] In an emergency or overspeed situation wherein the application of the brake system 10 is desired, a force F.sub.A in the direction parallel to the guide rail 16 is applied to the wedge shaped brake shoes 25 which cause the brake shoes 25 to move towards the elevator car 14. Ordinarily, force F.sub.A is supplied by a rope, cable or mechanical linkage connected to a governor (not shown). The inclined complimentary cam surfaces 24 and 28 of the guide shoe 18 and the brake shoe base 26, respectively, cause the brake shoe 25 to move towards the rail 16 until contact between the brake pad 32 and the guide rail 16 is made. For a brief moment, the brake pads 32 stop (friction on rail 16) while elevator car 14 continues down (via gravity). As those skilled in the art will appreciate, when engaged (e.g., the elevator car 14 now dragging the brake pad 32 on the guide rail 16), the brake pad 32 is applied to the guide rail 16 with normal force F.sub.N supplied by the spring 22. The amount of braking force developed by normal force F.sub.N is substantially and directly proportional to the friction coefficient .sub.k between the high friction material used in the brake pad 32 and the guide rail material. As braking occurs, heat tends to become accumulated in the brake pad 32 which can deleteriously reduce the friction coefficient .sub.k between the pad material and guide rail material. If the heat becomes high enough for a given material, a substantial reduction in the hardness, as well as deformation or fusion of the high friction material may occur, which in turn may cause brake failure.

[0026] FIG. 2 illustrates an embodiment of a brake shoe 25, wherein the brake pad 32 is fuse bonded to brake shoe base 26, wherein the brake pad 32 is chosen from a group including molybdenum and molybdenum alloys, such as TZM to name one non-limiting example. In an embodiment, the coating of brake pad 32 is fuse bonded to the brake shoe base 26 via a fusion welding process. In one embodiment, the fusion welding process includes an arc welding process. It will be appreciated that the arc welding process may include a process in which the added metal is delivered through a metal or a powder to name a couple of non-limiting examples. It will further be appreciated, in other embodiments; the fusion welding process includes laser beam or electron beam welding process. The laser beam or electron beam welding process may include a process in which the added metal is delivered through a metal or a powder to name a couple of non-limiting examples.

[0027] In embodiment, as shown in FIG. 3, surface features 36 may be added to the brake pad friction surface 38 during the fusion welding process, the surface features 36 are configured to provide at least one of increased friction of the brake pad 32 and wear indication of the brake pad 32. For example, the surface features 36 may include cross hatch patterns, tiles, and buttons to name a few non-limiting examples.

[0028] The surface features 36 of an embodiment include one or more raised features 50. The raised features 50 may be non-continuously applied to the brake pad 32 and/or the base 26 in one or more embodiments. As illustrated in FIG. 5, the raised features 50 include a plurality of dots 52 in one embodiment. As illustrated in FIG. 6, the raised features 50 include a plurality of line segments 54 in an embodiment. In particular embodiments, the dots 52, the line segments 54, and/or any other raised feature 50 may be finished, machined, or otherwise modified to form an even or flat rail facing surface 30. In additional embodiments, the dots 52, the line segments 54, and/or any other raised feature 50 is not finished, machined, or otherwise modified following formation and/or deposition. It will be appreciated that any combination of different surface features 36 and methods of forming the various surface features 36 may be included in a brake pad 32 of an embodiment, and such combinations form part of the present disclosure.

[0029] In some embodiments, the surface features 36 may be added to the brake pad friction surface 38 by machining (i.e., cutting the brake pad friction surface 38 into the desired surface feature). In other embodiments, the brake shoe base 26 may be pre-machined to have the desired surface features 36 disposed thereon. As the brake pad material is fuse bonded onto the flat surfaces and into the grooves of the brake shoe base 26, the desired surface features 36 are created on the brake pad friction surface 38.

[0030] In an embodiment, as shown in FIG. 4, an interface layer 40 is fuse bonded between the brake shoe base 26 and the brake pad 32. In an embodiment, the interface layer 40 is chosen from the group consisting of chrome, iron, nickel, nickel alloys, cobalt, and cobalt alloys. The interface layer 40 is configured to provide metallurgical compatibility for the fuse bonded brake pad 32.

[0031] It will therefore be appreciated that the present embodiments include a molybdenum alloy based brake pad 32 fuse bonded to a brake shoe base 26 to reduce the amount of high friction material required for effective operation to stop the elevator car 14; thus, reducing the costs of the elevator system 10.

[0032] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.