WO1995015876A1

WO1995015876A1 - Electric brake

Info

Publication number: WO1995015876A1
Application number: PCT/US1994/014046
Authority: WO
Inventors: Thomas J. Carlson, Jr.
Original assignee: Midwest Brake Bond Company
Priority date: 1993-12-06
Filing date: 1994-12-05
Publication date: 1995-06-15
Also published as: AU1398695A

Abstract

An electric motor brake (10) has a printed circuit board (76) which circumferentially locates and retains a plurality of electromagnetic coils (68) within a coil housing (34). The circuit board (76) simplifies both the assembly and wiring associated with the electric motor brake.

Description

ELECTRIC BRAKE

Field of the Invention The present invention relates to motor brake assemblies. More particularly, the present invention relates to motor brake assemblies incorporating a printed circuit board which simplifies the assembly of the motor brake assembly.

Background and Summary of the Invention A typical brake assembly for an electric motor comprises a stationary brake housing, a brake pack and an actuating mechanism. The brake housing is a stationary housing normally bolted directly to the motor or it is bolted to the motor through an adaptor plate. The brake pack is usually positioned within the brake housing and comprises a rotating member which rotates with the drive shaft of the motor and a fixed portion which is fixedly secured to the brake housing. The brake pack further includes a plurality of driving friction discs which are secured to the rotating member and interleaved with a plurality of driven friction discs which are secured to the fixed member. The actuating mechanism selectively moves the brake pack between an applied condition where the driving and driven discs are compressed together and a released condition where the driving discs are allowed to rotate relative to the driven discs. Thus, the rotation of the shaft of the motor can be stopped or prohibited when the driving and driven friction discs are compressed together by the actuating mechanism.

The actuating mechanism normally comprises an actuating disc which is longitudinally movable within the brake housing between the applied condition and the released condition. In the applied condition, the actuating disc compresses the plurality of driving and driven friction discs between two abutment surfaces to effectively lock the drive shaft of the motor to the stationary brake housing. In the released condition, the actuating disc releases the compressive load on the plurality of driving and driven friction discs and the drive shaft of the motor is allowed to rotate relative to the stationary brake housing. The movement of the actuating disc within the stationary brake housing is typically controlled by a plurality of electromagnetic coils fixedly secured to the stationary brake housing. The electromagnetic coils magnetically attract the actuating disc which then moves longitudinally against a biasing force. The biasing force is normally provided by a plurality of springs which bias the actuating disc away from the electromagnetic coils and into an applied condition for safety reasons although it would be possible to bias the actuating disc into a released condition if desired. When power is supplied to the electromagnetic coils, the actuating disc is magnetically attracted against the biasing load to release or apply the brake depending on its position of the brake due to the biasing load.

The above described prior art motor brake assemblies have been designed to either run dry or they have been designed to be submerged in a cooling fluid operating under the oil shear principle. In simple terms, the oil shear principle is based on the use of multiple interleaved discs bathed in oil. A positive oil film is maintained between each of the disc surfaces. When the interleaved discs are compressed together, torque is transmitted by the viscous shearing of this oil film. The result is that the wear of the friction surfaces on the discs is greatly reduced. In addition, heat is dissipated by the circulating oil for fast cyclic capability.

Prior art motor brake assemblies have the electromagnetic coils circumferentially arranged in an annular recess provided in a coil housing which forms a part of the stationary brake housing. Each individual electromagnetic coil is held in place by a bolt and once located the electromagnetic coils are wired together with power being supplied to the plurality of electromagnetic coils through an access hole extending through the coil housing. In some motor brake assemblies, instead of bolting each electromagnetic coil to the coil housing, the plurality of electromagnetic coils can be wired together and be potted into the annular recess of the coil housing by a non-conductive material such as epoxy. The epoxy will entirely fill the annular recess and cover the electrical connection between the coils.

While these prior art motor brake units are effective, especially when using the oil shear principle, the assembly of the motor brake units has proven to be an especially time consuming and expensive operation. This is particularly true when considering the assembly and wiring of the plurality of electromagnetic coils into the annular recess of the coil housing. Accordingly, what is needed is a cost effective assembly method for locating and wiring the plurality of electromagnetic coils within the coil housing which forms a part of the stationary brake housing.

The present invention provides the art with a simplified and cost effective method of locating and wiring the plurality of electromagnetic coils within the coil housing. The present invention utilizes an annular shaped printed circuit board which includes the wiring required to interconnect the plurality of electromagnetic coils. Each individual coil is fixedly secured and electrically connected to the annular circuit board. This assembled circuit board is then located relative to the coil housing. Once provisions have been made for providing connection to an external power source, the assembly of the circuit board and the electromagnetic coils can be bolted to or potted within the coil housing. The use of the printed circuit board thus eliminates both the circumferential locating of the individual electromagnetic coils as well as the tedious task of wiring each individual electromagnetic coil. Thus the assembly of the brake unit is simplified and the reliability is significantly improved. Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.

Brief Description of the Drawings In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

Figure 1 is a longitudinal side elevational view, partially broken away, of a motor brake unit embodying the principles of the present invention;

Figure 2 is a cross-sectional view of the motor brake shown in Figure 1 taken in the direction of Arrow 2-2; Figure 3 is a plan view of the top side of the printed circuit board shown in

Figures 1 and 2 prior to the assembly of the electromagnetic coils;

Figure 4 is a plan view of the bottom side of the printed circuit board shown in Figures 1 and 2 prior to the assembly of the electromagnetic coils; and

Figure 5 is an electrical circuit diagram provided by the utilization of the circuit board shown in Figures 4 and 5.

Detailed Description of the Preferred Embodiment

Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in Figure 1 a motor brake assembly embodying the principles of the present invention which is designated generally by the reference numeral 10. For exemplary purposes, motor brake assembly

10 is shown bolted directly to motor 16 by a plurality of bolts 18. Motor brake assembly

10 could be bolted to an adaptor plate (not shown) which would in turn be bolted to motor 16 assuming the bolt patterns on the two components were not the same. Motor

16 includes a rotatable motor shaft 20 extending axially or longitudinally into motor brake assembly 10 to provide for the interface between motor brake assembly 10 and motor 16.

Motor brake assembly 10 comprises a main stationary brake housing 30, a rotatable sleeve 32, an electromagnetic coil housing 34 and an oil shear brake pack 36.

Stationary brake housing 30 is an annular housing having a central hub 40 defining a centrally located bore 42 for mounting a roller bearing 44. Roller bearing 44 rotatably mounts rotatable sleeve 32 within brake housing 30 as will be described later herein. A plurality of mounting flanges 46 extend radially outwardly from one end of central hub 40 and are adapted to provide for the attachment of brake housing 30 to motor 16 or the adaptor plate by the plurality of bolts 18. Brake housing 30 is shown bolted directly to motor 16 using flanges 46 and bolts 18. The adaptor plate could be provided in applications where the two bolt patterns do not match. An L-shaped annular section 48 extends radially outwardly from the end of central hub 40 opposite to the plurality of flanges 46. L-shaped section 48 provides clearance for oil shear brake pack 36 and is adapted with a plurality of circumferentially spaced bosses 50 for the attachment of electromagnetic coil housing 34. Rotatable sleeve 32 extends into motor brake assembly 10 through bore 42 in stationary brake housing 30. Sleeve 32 is rotatably supported by roller bearing 44 and is secured against rotation relative to motor shaft 20 by means of a suitable longitudinally extending keyway 52. The end of sleeve 32 that extends into motor brake assembly 10 is provided with an expansion plug 54 which provides a fluid seal between the interior of sleeve 32 and the interior of stationary brake housing 30. An additional seal 56 is disposed between stationary brake housing 30 and the exterior of sleeve 32 to provide a fluid tight connection between the interior and the exterior of stationary brake housing 30. The exterior surface of sleeve 32 which extends into motor brake pack 10 is provided with a plurality of axially extending splines 58 for interfacing with oil shear brake unit 36 as will be described later herein.

Electromagnetic coil housing 34 includes a plurality of flanges 60 extending radially outwardly from its exterior surface. The plurality of flanges 60 coincide with the plurality of circumferentially spaced bosses 50 within brake housing 30 to provide for the attachment of coil housing 34 to brake housing 30 using a plurality of bolts 62. Stationary brake housing 30, rotatable sleeve 32 and coil housing 34 define a sealed internal cavity 64. Internal cavity 64 is sealed by expansion plug 54, seal 56 and a seal 66 located between brake housing 30 and coil housing 34.

A plurality of electromagnetic coils 68 are located within an annular chamber 70 located within coil housing 34 radially inward from the plurality of flanges 60. Annular chamber 70 is open to internal cavity 64 and includes an interior tapered wall 72 and an external tapered wall 74. Walls 72 and 74 are tapered towards each other to provide for the retention of the plurality of electromagnetic coils 68 as will be described later herein. Each of the plurality of electromagnetic coils 68 is fixedly secured to and electrically connected to a printed circuit board 76. A first pair of pins (not shown) secure each coil 68 to circuit board 76 and a set of four pins 80 electrically connect each coil 68 to circuit board 76. Circuit board 76 is an annular circuit board which is provided with a plurality of mounting holes 82 for mating with the pins for mounting and circumferentially spacing the plurality of coils 68. An additional plurality of holes 84 are provided through circuit board 76 to mate with pins 80 to provide for the electrical connection of the plurality of coils 68. A plurality of printed circuits 86 interconnect the appropriate plurality of holes 84 and a terminal location 88 such that once the plurality coils 68 are mounted and electrically connected to circuit board 76, all that is required is to connect terminal location 88 to an external power source and the plurality of coils 68 will become active. The printed circuits are best shown in Figures 3 and 4 with Figure 5 showing the overall electrical circuit provided by utilizing circuit board 76.

Positioned radially inwardly from annular chamber 70 are a plurality of bores 90. Bores 90 extend axially into coil housing 34 and receive a plurality of coil springs 92 which bias oil shear brake pack 36 into an applied condition as will be described later herein. An oil fill port 94 extends through coil housing 34 and is provided with a removable plug 96 for providing access to internal cavity 64. A cylindrical cavity 98 is provided at the center of coil housing 34. Cavity 98 is open to internal cavity 64 and allows for an increased quantity of oil to be supplied to oil shear brake unit 36.

Oil shear brake pack 36 is disposed within interior cavity 64 and comprises a plurality of driving discs 100, a plurality of driven discs 102 and an actuating disc 104. The plurality of driving discs 100 are splined on their interior surface to mate with the plurality of splines 58 located on rotatable sleeve 32. Thus, discs 100 are mounted for rotation with sleeve 32 but are allowed to move axially along sleeve 32 due to their engagement with splines 58. The plurality of driven discs 102 are disposed interadjacent or interleaved between the plurality of driving discs 100. Each of the plurality of driven discs 102 is formed with a plurality of notches (not shown) which are adapted to slidingly engage a plurality of axially extending dowels 108. Each dowel 108 is press fit into a respective bore 110 located within central hub 40 of stationary brake housing 30. Dowels 108 support the plurality of driven discs 102 for longitudinal sliding movement, yet prevent any relative rotation of discs 102 with respect to stationary housing 30. Actuating disc 104 is an annular disc which is disposed between coil housing 34 and the plurality of driving and driven discs 100 and 102, respectively. Actuating disc 104 is located within internal cavity 64 and has a plurality of locating tabs 112 for positioning disc 104 within cavity 64. The exterior diameter which is formed by locating tabs 112 is sized to be slidingly received within the internal diameter formed by L-shaped section 48 of stationary brake housing 34 as shown in Figure 1. Actuating disc 104 is movable from an applied condition to a released position. In the applied position (to the left as shown in Figure 1) actuating disc 104 compresses the driving and driven plates 100 and 102 between a first abutment face 114 located on stationary brake housing 30 and a second abutment face 116 located on actuating disc 104. In this position, rotatable sleeve 32 and thus motor shaft 20 are locked to stationary brake housing 30, thus preventing rotation of motor shaft 20. In the released position (to the right as shown in Figure 1) the driving and driven discs 100 and 102 are allowed to rotate relative to one another thus allowing sleeve 32 and motor shaft 20 to rotate freely. A spring seat 120 is provided at the radial interior of actuating disc 104 and provides a seat for the plurality of coil springs 92 located within the plurality of bores 90. The plurality of coil springs 92 are sized in conjunction with the depth of bores 90 to bias actuating disc 104 to the left as shown in Figure 1 thus applying oil shear brake 34 and locking sleeve 32 and motor shaft 20 to stationary brake housing 30.

Actuating disc 104 further defines an annular chamber 122 which opposes annular chamber 70 located within coil housing 34. Disposed within annular chamber 122 are circular steel laminations 124. Circular steel laminations 124 are attached to a plurality of circumferentially spaced magnetic plates 126. The attachment of circular steel laminations 124 with the plurality of plates 126 allows the components to be cast into annular chamber 122 during the manufacture of actuating disc 104 to reduce the amount of machining required after forming. Circular steel laminations 124 provide for the magnetic material which is to be attracted by the plurality of coils 68 thus permitting the remainder of actuating disc 104 to be made from a lighter non-magnetic material preferably aluminum.

Referring now to the overall operation of motor brake unit 10. The initial conditions are that the interior of cavity 64 is properly filled with a cooling fluid and the plurality of coil springs 92 will function to bias actuating disc 104 toward the left in Figure 1 whereby the plurality of driving and driven discs will be compressed between first and second abutment faces 114 and 116 so that an effective braking action is exerted against motor shaft 20. At such time as it is desired to operate the motor, the braked condition is relieved by connecting the source of electricity to coils 68 approximately the same time that the current is connected to motor 16 to start motor operation. Coils 68 will magnetically attract actuating disc 104 longitudinally to the right as shown in Figure 1 against the resistance of the plurality of coil springs 92. This movement will disengage the plurality of driving and driven discs 100 and 102 thereby releasing motor shaft 20. When it is again desired to effect braking of motor 16, coils 68 are deactivated with the result that the plurality of coil springs 92 will again bias actuating disc 104 toward the left as shown in Figure 1 again compressing the plurality of driving and driven discs 100 and 102 between first and second abutment stops 114 and 116 thereby effecting the braking of motor shaft 20. Motor brake assembly 10 may be provided with a manual release 130 which is comprised of a cylindrical shaft 132 rotatably supported within a bore 134 extending through stationary housing 30. A seal 136 maintains the integrity of sealed cavity 64. The end of shaft 132 which extends outside of brake housing 30 is provided with a release lever 138 while the end of shaft 132 extending into cavity 64 is provided with a cam 140. Manual release 130 is positioned in relationship to actuating disc 104 such that rotation of shaft 132 by moving release lever 138 causes cam 140 to push against actuating disc 104 and move actuating disc 104 to the right as shown in Figure 1 against the load exerted by the plurality of coil springs 92. Rotation of shaft 132 in the opposite direction will release actuating disc 104 and again apply braking to motor shaft 20. The present invention thus provides a unique and simplified assembly for the plurality of coils 68 within stationary coil housing 34. The plurality of coils 68 are first mounted and electrically connected to circuit board 76. This assembly of coils 68 with circuit board 76 locates coils 68 circumferentially as well as connecting them electrically with the remainder of the coils and the external power source. This assembly is then located within annular chamber 70. A plurality of stand offs 150 space circuit board 76 from coil housing 34 to prevent any shorting of the plurality of circuits 86. Terminal location 88 of circuits 86 is positioned adjacent an access hole 152 extending through coil housing 34 and the appropriate connections for interfacing with the exterior power source are provided. Annular chamber 70 is then filled with a non-conductive epoxy which secures coils 68 and circuit board 76 within annular chamber 70 due to the taper of walls

72 and 74. The taper in walls 72 and 74 creates an annular chamber which is wider at the base than at the opening. Thus, once the epoxy cures, it is not possible to remove coils

68 and circuit board 76 from annular chamber 70 without destroying the epoxy structure.

Thus it can be seen that circuit board 76 significantly reduces the labor associated with manually wiring each individual coil 68. In addition, the positioning and locating of the plurality of coils 68 within annular chamber 70 during the introduction of the epoxy is simplified and accuracy is improved with the utilization of circuit board 76. Finally, the integrity and reliability of the entire system is significantly improved.

While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.

Claims

What is claimed is:

1. A brake unit for an apparatus, said brake unit comprising: a main housing defining a cavity, said main housing being adapted to be mounted to said apparatus; a coil housing fixedly secured to said main housing, said coil housing further defining said cavity; a sleeve member rotatably supported relative to said main housing, said sleeve at least partially disposed within said cavity and adapted to engage a rotatable member of said apparatus; a plurality of driving friction discs disposed within said cavity and rotatable with said sleeve; a plurality of driven friction discs disposed within said cavity and non- rotatably supported by said main housing; an actuating disc axially translatable within said cavity for selectively engaging and disengaging said plurality of driving and driven friction discs; and a plurality of electromagnetic coils fixedly secured to said coil housing; said plurality of electromagnetic coils electrically communicating with a printed circuit board.

2. The brake unit according to Claim 1 wherein said cavity is sealed and at least partially filled with a cooling fluid.

3. The brake unit according to Claim 1 wherein said plurality of electromagnetic coils are fixedly secured to said circuit board.

4. The brake unit according to Claim 3 wherein said circuit board circumferentially locates said plurality of electromagnetic coils.

5. The brake unit according to Claim 1 further comprising a biasing member for urging said actuating disc such that said plurality of driving and driven discs are engaged.

6. The brake unit according to Claim 1 wherein said circuit board and said plurality of electromagnetic coils are disposed within an annular chamber defined by said coil housing.

7. The brake unit according to Claim 6 wherein said annular chamber is at least partially filled with an epoxy.

8. The brake unit according to Claim 6 wherein said circuit board provides for the wiring necessary to electrically interconnect said plurality of electromagnetic coils.

9. A brake unit for an apparatus, said brake unit comprising: a main housing defining a cavity, said main housing being adapted to be mounted to said apparatus; a coil housing fixedly secured to said main housing, said coil housing further defining said cavity; a sleeve member rotatably supported relative to said main housing, said sleeve at least partially disposed within said cavity and adapted to engage a rotatable member of said apparatus; a plurality of driving friction discs disposed within said cavity and rotatable with said sleeve; a plurality of driven friction discs disposed within said cavity and non- rotatable supported by said main housing; an actuating disc axially translatable within said cavity for selectively engaging and disengaging said plurality of driving and driven friction discs; a printed circuit board disposed within an annular chamber located in said coil housing, said annular chamber being open to said cavity; and a plurality of electromagnetic coils fixedly secured to said printed circuit board, said plurality of electromagnetic coils communicating electrically with said printed circuit board.

10. The brake unit according to Claim 9 wherein said cavity is sealed and at least partially filled with a cooling fluid.

11. The brake unit according to Claim 9 further comprising a biasing member for urging said actuating disc such that said plurality of driving and driven discs are engaged.

12. The brake unit according to Claim 9 wherein said annular chamber is at least partially filled with an epoxy.