Elevator disc brake

Abstract: An elevator disc brake 16 operates on a shaft 18 which drives an elevator sheave. The disc brake 16 comprises a rotating disc 44 and a non-rotating plate 46, the plate 46 being driven towards the disc by a plurality of springs 78 and moved away from the disc by means of an electromagnet 48. Gaps between the plate 46 and the disc 44, and between the electromagnet 48 and the plate 46, are readily adjustable by means of an adjustable spring seat 76.

Description: This invention relates to elevators, and more particularly to a disc brake for use therewith. Some elevators have a rope which attaches at one end to an elevator car, extends over a sheave disposed atop an elevator hoistway, and attaches at a second end thereof to a counterweight. In some elevator systems, the sheave is driven by a motor. The elevator car is raised or lowered by means of traction developed between the rope and the driven sheave. It is important to brake the movement of the car to register the car with a floor, as required, and for safety purposes. A brake may be attached to the motor to effectuate such control. Some motors utilize a brake drum and a pair of brake shoes. The brake shoes create friction with the drum thereby providing the braking force necessary to stop the sheave. Each shoe attaches to a first end of a lever, the lever being mounted upon a pivot. The second end of each lever reacts to spring and electromechanical forces to activate and release the brake by pivoting the brake shoes into and out of contact with the brake drum, as is known in the art. Drum brakes have several problems. In order to have sufficient area to create the friction forces necessary to stop the car, the brake drum may have to be of significant mass. Such drums may have a high moment of inertia thereby requiring more energy from the traction motor to accelerate and decelerate the car. Further, if one of the pivots holding the levers breaks, the drum brake may be rendered inoperative. The pivot arms also require a lot of space. Some elevators are known to utilize a disc brake. The motor shaft has a splined end upon which a brake disc is mounted for rotation therewith. The disc is disposed between a stationary plate and a counterplate. The plate moves axially towards the disc by means of a spring and away from the disc by means of an electromagnet. To actuate the brake, the electromagnet is turned off and the springs push the plate towards the counterplate. As the plate engages the disc, the disc moves axially along the splines towards the counterplate. The splines allow the disc to center itself between the plate and counterplate to develop friction forces between the disc and the plate and counterplate. This type of disc brake has several problems. The coupling between the brake disc and the shaft should be tight to permit the brake disc to rotate with the shaft with a minimum of wear. However, the brake disc must be free to move axially to center between the plate and the counterplate. The relatively loose connection required for free axial movement creates noise which is undesirable. Further, this type of brake is normally added on to the end of the rotating shaft of the motor. This requires more space, which is undesirable. US-A-4966255 describes an electromagnetic disc brake which automatically compensates for wear of the friction elements. The preamble to claim 1 is based on this document. It is an object of the invention to provide a brake for an elevator which utilizes a minimum of space. It is a further object of the invention to provide a reliable brake having a minimum of mass. It is a further object of the invention to provide a quiet brake. According to the invention, there is provided an elevator disc brake for use with a shaft which rotates as the elevator is raised or lowered, said elevator disc brake comprising: a non-rotating housing; a disc securely fastened to said shaft for rotation therewith; a non-rotating plate for cooperating with said disc to create sufficient friction to brake the rotation of said shaft; a guide means for guiding said plate into and out of contact with said disc; a spring assembly comprising spring means for urging said plate into contact with said disc, said spring assembly being attached to said housing; and an electromagnet disposed about said shaft and urging said plate out of contact with said disc when activated; characterized by said guide means being mounted to said housing such that said guide means is free to move parallel to the axis of said shaft. In the preferred embodiment, a disc brake is rigidly attached to a shaft which drives an elevator sheave. The disc brake comprises a rotating disc and a non-rotating plate, the plate being driven towards the disc by a plurality of springs and moved away from the disc by means of an electromagnet. Gaps between plate and the disc, and between the electromagnet and the plate, are readily adjustable by means of an adjustable spring seat, as is the frictional force between the plate and the disc. According to a further feature of the invention, the plate is guided towards and away from the disc by a plurality of jack screws which ensure proper axial movement of the plate and allow the disc brake to be disengaged in an emergency. An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawing. The Figure is a cross sectional, broken away, view of an embodiment of disc brake of the invention. Referring to the Figure, an embodiment of a disc brake used in an elevator drive system 10 is shown. The drive system 10 has three major sections: a motor 12, a gear box 14 and a disc brake 16 disposed between the motor and the gear box. A shaft 18 extends from the motor through the disc brake to the gear box. The shaft has an opening 20 disposed therein, as will be discussed infra. As is known in the art, the motor comprises a stator 22, and a rotor 24. The rotor has a central opening through which the shaft extends. The rotor is fixedly attached to the shaft 18 by means of a sleeve 26. The particular construction of the motor does not form a portion of this invention. The gear box 14 comprises: a housing 28 having an axial flange 30, the flange having a plurality of axial openings 32 passing therethrough; a plurality of bearings 34, 36 for allowing the free rotation of the shaft 18; an annulus 38 which seats the bearings 34 within the gear housing, the annulus being anchored to the housing by means of bolts 40; and gears (as represented by the helical screw 42 shown) as known in the art. The disc brake 16 comprises: a disc 44 which rotates with the shaft 18; a non-rotating brake plate 46; an annular, stationary electromagnet 48 having a square cross-section, the electromagnet encircling the shaft and interacting with the plate 46; a pair of rods 50 (one of which is shown for ease of illustration) for guiding the plate, the rods being disposed concentrically around the flange 30; and a plurality of spring assemblies 52 (three are desirable, one is shown for ease of illustration) for urging the plate into contact with the disc. The electromagnet 48 has a plurality of lugs 54 corresponding to the number of spring assemblies (one is shown for ease of illustration) having an interior threaded opening 56, as will be discussed infra. The disc 44 comprises a cylindrical body 58 having a radially extending flange 60. The flange has a flat annular portion 62 for engaging the plate 46 as will be discussed infra. The body 58 mates with the shaft and has a slot 64 which aligns with the opening 20 in the shaft 18. The body is attached to the shaft by: aligning the slot 64 and the opening 20, and inserting a close fitting key 66 through the slot and the opening. The plate 46 encircles the body 58 of the disc and is free to move coaxially therealong. The plate has an appropriate brake lining material 68 bonded thereto,as is known in the art. The brake lining material aligns with the flat annular portion 62 of the flange 60. The plate has a pair of openings 70 (one of which is shown for ease of illustration), each opening having a countersunk portion 72, as will be discussed infra. The spring assembly 52 comprises a first spring seat 74 fixedly attached to the plate 46, an adjustable spring seat assembly 76, and a spring 78. The adjustable spring seat assembly includes a bushing 80 which extends through one of the openings 32 in the housing 28, a first locking nut 82, a second locking nut 84, a second spring seat 86, and a threaded bolt 88, the bolt attaching to the second spring seat 86. The bushing 80 has an internal threaded portion 90 for cooperating with the threaded bolt, a first external threaded portion 92 for cooperating with the first locking nut 82, a second external threaded portion 94 for cooperating with the lugs 54 attached to the electromagnet, and an annular shoulder 96. The spring seat assembly is assembled as follows: the bolt 88 is threaded through the internally threaded portion 90 of the bushing 80; the bolt is then attached to the second spring seat 86 by conventional means; the bushing is then inserted into one of the openings 32 in the housing flange 30; the second threaded portion 94 of the bushing is screwed into the threaded opening 56 in one of the lugs 54 to attach the electromagnet 48 thereto, the bushing may be rotated to adjust the gap 98 between the electromagnet and the disc; the first locking nut 82 is threaded upon the first external threaded portion 92 of the bushing and tightened so the shoulder 96 of the bushing firmly abuts the geabox flange 30; the spring 78 is fitted between the first and second spring seats 74, 86; the bolt is then rotated within the bushing to set the frictional force between the plate and the disc; and, finally, the locking nut 84 is threaded over the bolt to prevent the bolt from moving after the frictional force has been adjusted. The rods 50 are arranged so as to be disposed within the gear box flange openings 32 at 180° around the circumference from each other. Each rod has a cylindrical body 102 having a region of increased diameter 104 and a region of decreased diameter 106. The region of increased diameter is seated within the countersunk portion 72 of the plate 46. The region of decreased diameter is disposed on the gearbox side of the flange. As may be required, a service person may insert a tool (not shown) into the region of reduced diameter to pull the plate, via the seating of the region of increased diameter in the countersunk portion, away from the disc.

Claims: An elevator disc brake (16) for use with a shaft (18) which rotates as the elevator is raised or lowered, said elevator disc brake comprising: a non-rotating housing (28); a disc (44) securely fastened to said shaft for rotation therewith; a non-rotating plate (46) for cooperating with said disc to create sufficient friction to brake the rotation of said shaft; a guide means (50) for guiding said plate into and out of contact with said disc (44); a spring assembly (52) comprising spring means (78) for urging said plate (46) into contact with said disc, said spring assembly being attached to said housing (28); and an electromagnet (48) disposed about said shaft and urging said plate out of contact with said disc when activated; characterized by: said guide means being mounted to said housing such that said guide means is free to move parallel to the axis of said shaft (18). The elevator disc brake of claim 1 wherein the axial position of said electromagnet (48) is adjustable. The elevator disc brake (16) of claim 1 or 2 wherein said electromagnet (48) is carried by said spring assembly (52). The elevator disc brake of any preceding claim wherein said spring assembly (52) further comprises: means (94) for adjusting an air gap between said disc (44) and said electromagnet (48). The elevator disc brake of any preceding claim wherein said spring assembly further comprises: means (88) for adjusting the frictional force, which is present when the magnet is deactivated, between the plate (46) and the disc (44). The elevator disc brake of any preceding claim wherein said guide means further comprises: means (104) for attaching said guide means to said plate, and means (106) for grasping and pulling said guide means for disengaging said plate from said disc. The elevator disc brake of any preceding claim wherein said housing (28) further comprises: a gearbox housing. The elevator disc brake (16) of any preceding claim wherein said spring assembly further comprises: a first spring seat (74) fixedly attached to said plate (46); a bushing (80) having an annular shoulder (46), an internally threaded portion (90) and two externally threaded portions (92,94), said bushing being insertable into an opening (32) in the non-rotating housing (28) and said second external threaded portion (94) cooperating with a lug (54) attached to the electromagnet; a bolt (88) threadably insertable into said bushing, said bolt being attached to a second spring seat (86); a spring (78) extending between said first and second spring seats; a first locking nut (82) for cooperating with said first external threaded portion (92) and said annular shoulder (96) of said bushing (80) to attach said bushing to said non-rotating housing; and a second locking nut (84) threadably attachable to said bolt (88).

Inventors: GARRIDO ALFONSO, SANCHEZ ANTONIO, SANDOVAL JOSE M, SEVILLEJA JOSE, GARRIDO, ALFONSO, SANCHEZ, ANTONIO, SANDOVAL, JOSE M., SEVILLEJA, JOSE
Applicants: OTIS ELEVATOR CO, OTIS ELEVATOR COMPANY
Application year: 1992
Main classification: B66B5
IPC codes: F16D55, F16D65, B66B5, F16D59, B66D5, B66B11