Fast Response Adjustable Brake

The invention arose during development efforts relating to brakes, including direct acting spring-set electromagnetically released brakes for electric motors.

The above type brake includes a magnetically permeable body having a pole face, an armature axially movable toward and away from the pole face, an energization coil energizable to magnetically attract the armature toward the pole face, biasing means biasing the armature away from the pole face, a pressure plate mounted to the body and axially spaced from the pole face, and a friction disc between the armature and the pressure plate and keyable to an axially extending rotary shaft, such as an electric motor shaft. Upon deenergization of the coil, the biasing means biases the armature to a braking position pushing the friction disc against the pressure plate to stop rotation of the disc and shaft. The armature in the braking position defines an air gap between the pole face and the armature. Upon energization of the coil, the armature is pulled through the air gap toward the pole face to a released position releasing the disc and permitting rotation of the shaft.

The present invention provides performance improvements for faster brake response. A plurality of magnetically permeable segments are provided in a housing shell and are separated and spaced from each other around the shell to break up eddy currents which oppose build-up of the magnetic field, to afford faster brake response. In preferred form, the segments are inserted into a mold followed by direct casting of the shell in-situ around the segments to form a housing shell providing the brake body.

The present invention provides an air gap adjustment mechanism adjustable to vary the axial distance from the pressure plate to the pole face to take up and compensate friction disc wear and maintain the air gap within a given tolerance as the friction disc wears with use.

The present invention provides a torque adjustment mechanism adjustable to vary the bias of the biasing means biasing the armature away from the pole face. In preferred form, a torque plate cams a plurality of biasing springs, increasing or decreasing compression of the latter.

The present invention further provides a simple, effective and reliable release mechanism for manually releasing the brake.

FIG. 1 is an isometric view of a brake in accordance with the invention mounted to an electric motor frame.

FIG. 2 is an isometric view of separated components of FIG. 1.

FIG. 3 is an exploded isometric view of the brake of FIG. 1.

FIG. 4 is an exploded perspective view of a portion of the structure of FIG. 3.

FIG. 5 is a side view partially in section of the brake of FIG. 1.

FIG. 6 is a bottom view partially in section of the brake of FIG. 1.

FIG. 7 is a view taken along line 7--7 of FIG. 6.

FIG. 8 is a view taken along line 8--8 of FIG. 6.

FIG. 9 is a bottom view of the brake of FIG. 1.

FIG. 10 is a view taken along line 10--10 of FIG. 9.

FIG. 11 is an enlarged view of a portion of the structure of FIG. 9 and shows an alternate position.

FIG. 12 is a view taken along line 12--12 of FIG. 11.

FIG. 13 is a top view of the brake of FIG. 1.

FIG. 14 is a view taken along line 14--14 of FIG. 13.

FIG. 15 is a view like FIG. 13 and shows another position.

FIG. 16 is a view taken along line 16--16 of FIG. 15.

FIG. 17 is a side view of the brake of FIG. 1.

FIG. 18 is a view taken along line 18--18 of FIG. 17.

FIG. 19 is a view of a portion of the structure of FIG. 17.

FIG. 20 is a view taken along line 20--20 of FIG. 19.

FIG. 21 is a view taken along line 21--21- of FIG. 20.

FIG. 1 shows a direct acting spring set electromagnetically released brake 30 mounted to the frame 32 of an electric motor 34 having a rotary shaft 36, FIG. 2, extending therefrom. The brake includes a magnetically permeable body 38, FIGS. 1-5, having a pole face 40. A magnetically permeable armature 42 is axially movable, i.e. right-left in FIG. 5, toward and away from pole face 40. An energization coil 44, provided by copper wire 46 wound on bobbin 48, is energizable at conductor lead 49 to magnetically attract armature 42 toward pole face 40 due to the magnetic flux field passing through body 38 and armature 42. Biasing means 50 provided by compression springs 52, 54, 56, 58, 60, 62, biases armature 42 away from pole face 40. Pressure plate 64 is mounted to the brake body and is axially spaced from pole face 40. Friction disc 66 is between armature 42 and pressure plate 64 and is keyable to axially extending rotary shaft 36. Friction disc 66 has an inner periphery 68, FIG. 2, of given toothed configuration mating with a like toothed outer configuration 70 of hub 72 mounted on shaft 36 by set screws 74 and 76 and keyed to rotate therewith by key 78. Upon deenergization of coil 44, biasing means 50 biases armature 42 to a braking position, leftwardly in FIG. 5, pushing friction disc 66 against pressure plate 64 to stop rotation of disc 66, hub 72 and shaft 36. Armature 42 in the noted braking position defines an air gap 80, FIG. 5, between pole face 40 and armature 42. Upon energization of coil 44, armature 42 is pulled rightwardly in FIG. 5 through air gap 80 to a released position releasing disc 66 and permitting rotation of hub 72 and shaft 36.

Body 38 is formed by a housing shell 82, FIG. 4, having a plurality of magnetically permeable segments 84, 86, 88. The segments are separated and spaced from each other around the shell to break up eddy currents which oppose build-up of the magnetic field, to afford faster brake response. Eddy currents circulate in the structure and oppose the build-up of the magnetic flux field. Segmenting the magnetized members breaks up the circular current flow path otherwise creating a circular magnetic field which opposes the build-up of the magnetic flux, i.e. a continuous current path allows much larger eddy currents to be produced. Shell 82 is composed of material which is thermally conductive and dissipates brake heat and is of lower magnetic permeability than segments 84, 86, 88, to break up eddy currents. Shell 82 is composed of a lower melting point material than segments 84, 86, 88, such that the shell may be cast around the segments inserted into a mold. In preferred form, segments 84, 86, 88 are sintered steel, and shell 82 is cast-in-situ aluminum. The segments are wedge-shaped sintered steel portions insert-molded in an aluminum casting providing the shell.

Segments 84, 86, 88 are arcuate and have a U-shape 90 in radial cross-section, FIG. 7. The brake body is an annulus having inner and outer circumferences 92 and 94, FIG. 3, and a U-shaped channel 96 therebetween in radial cross-section and aligned with the U-shape of arcuate segments 84, 86, 88, to provide a continuous U-shaped channel along the annulus. The brake body has a plurality of dividers 98, 100, 102 of U-shape in radial cross-section. The dividers have inner legs 104, 106, 108 on inner circumference 92, and outer legs 110, 112, 114 on outer circumference 94. The noted legs separate respective segments 84, 86, 88. Outer legs 110, 112, 114 provide a first set of axially extending posts. Shell 82 has a second set of axially extending posts 116, 118, 120 spaced around outer circumference 94 of the shell and interdigitated with the first set of posts 110, 112, 114. Segments 84, 86, 88 have respective outer slots 122, 124, 126 receiving a respective post 120, 116, 118. Inner legs 104, 106, 108 provide a third set of axially extending posts spaced around inner circumference 92 of shell 82. Each of the noted posts 110, 112, 114 of the first set, 116, 118, 120 of the second set, 104, 106, 108 of the third set, has an axially extending bore therein, shown respectively at 128, 130, 132, 134, 136, 138, 140, 142, 144. A first set of compression springs 58, 60, 62 of biasing means 50 extend axially in bores 128, 130, 132 of the noted first set of posts 110, 112, 114. A second set of compression springs 52, 54, 56 of the biasing means 50 extend axially in respective bores 140, 142, 144 of the noted third set of posts 104, 106, 108. A plurality of mounting bolts 146, 148, 150 extend through respective bores 134, 136, 138 of respective posts 116, 118, 120 of the noted second set for mounting the brake to electric motor frame 32 from which shaft 36 extends. Bolts 146, 148, 150 are threaded into respective threaded apertures 152, 154, 156 of motor frame 34, FIG. 2. Retainer clips 158, 160, 162 engage the threads of respective bolts 146, 148, 150 and engage the bottom side of pressure plate 64 and hold the brake in assembled condition until mounted to motor frame 32. A sealing O-ring gasket 164 is compressed between shell 82 and pressure plate 64. Armature 42 has outer peripheral slots 166, 168, 170 axially sliding along respective posts 120, 116, 118 and preventing rotation of the armature.

The brake includes an air gap adjustment mechanism 180, FIG. 5, adjustable to vary the axial distance from pressure plate 64 to pole face 40 to take up and compensate friction disc wear and maintain air gap 80 within a given tolerance as friction disc 66 wears with use. As friction disc 66 wears, its axial width such as 182, FIG. 10, decreases, for example to shorter dimension 184, FIG. 12. This in turn means that armature 42 moves further leftwardly in FIG. 5 to the braking position to engage friction disc 66, which in turn increases the axial width of air gap 80, FIG. 5. The greater the width of air gap 80, the greater magnetic force necessary to attract armature 42 through such gap toward pole face 40 and/or the slower the response time to release the brake upon energization of coil 44 and/or the greater the voltage necessary to apply across coil 44 to provide sufficient current to provide sufficient magnetic field to attract armature 42 rightwardly toward pole face 40. These changes in operation of the brake are not desirable as friction disc 66 wears. Instead, it is desired to maintain the width of air gap 80 within a given tolerance, to provide consistent fast brake response at consistent voltage requirements.

The noted axial distance between pressure plate 64 and pole face 40 is varied by partial rotation of pressure plate 64 along a given are about the axis of shaft 36. Pressure plate 64 is rotatable to a plurality of positions along the noted arc to progressively shorten the axial distance from pressure plate 64 to pole face 40 to compensate friction disc wear and maintain air gap 80 within a given tolerance. A plurality of spacers 186, 188, 190, FIG. 3, space pressure plate 64 from the brake body and are responsive to partial rotation of pressure plate 64 along the noted arc to shorten the axial spacing of pressure plate 64 and the brake body. Spacers 186, 188, 190 are provided by frustoconical washers each surrounding a respective bolt 146, 148, 150 and having a respective first end face 192, 194, 196 engaging the brake body, and a second distally opposite frustoconical end face 198, 200, 202 engaging a respective seat in pressure plate 64.

Pressure plate 64 has a first set of seats 204, 206, 208, FIG. 3, initially engaging and receiving respective frustoconical end faces 198, 200, 202 of respective spacer washers 186, 188, 190, and affording maximum spacing of pressure plate 64 from the brake body to afford initial friction disc width 182, FIG. 10. Pressure plate 64 has a second set of seats 210, 212, 214 engaging and receiving respective frustoconical end faces 198, 200, 202 of respective spacer washers 186, 188, 190 upon partial rotation of pressure plate 64 about the axis of shaft 36. This is accomplished by loosening bolts 146, 148, 150, and manually partially rotating pressure plate 64 by grasping tab 216 or otherwise grasping the outer periphery of the pressure plate. Seats 210, 212, 214 have a larger diameter than seats 204, 206, 208, such that the frustoconical spacer washers are received in seats 210, 212, 214 in deeper seating relation, to reduce the axial spacing of pressure plate 64 from the brake body, and compensate for wear of friction disc 66, to maintain air gap 80 within a given tolerance. Pressure plate 64 has a third set of seats 218, 220, 222 of larger diameter than seats 210, 212, 214 and spacing pressure plate 64 from the brake body by a third axial distance less than the axial distance spacing provided by the second set of seats 210, 212, 214. Pressure plate 64 has a fourth set of seats 224, 226, 228 of larger diameter than seats 218, 220, 222 and receiving the respective frustoconical spacer washers and spacing the pressure plate from the brake body by a fourth axial distance less than the noted third axial distance. Pressure plate 64 has a fifth set of seats 230, 232, 234 each of larger diameter than seats 224, 226, 228, and receiving respective spacer washers 186, 188, 190, and spacing the pressure plate from the brake body by a fifth axial distance less than the noted fourth axial distance. The plural sets of seats accommodate further friction disc wear with use, to provide closer and closer axial spacing of pressure plate 64 from the brake body to accommodate reduced axial width 184, FIG. 12, of the friction disc, and maintain air gap 80 within a given tolerance.

The noted seats in pressure plate 64 are arranged in first, second and third groups 236, 238, 240 separated and spaced from each other on a circular path concentric with the axis of motor shaft 36, each group having the noted plurality of seats and subtending an are about such axis. The first seats 204, 206, 208 of respective groups 236, 238, 240 define the noted first set receiving respective frustoconical spacer washers 186, 188, 190 and spacing pressure plate 64 from the brake body by a first axial distance. The second seats 210, 212, 214 of groups 236, 238, 240 form a second set spacing pressure plate 64 from the brake body by a second axial distance less than the noted first axial distance. The third seats 218, 220, 222 of groups 236, 238, 240 form a third set and space pressure plate 64 from the brake body by a third axial distance less than the noted second axial distance. The fourth seats 224, 226, 228 of groups 236, 238, 240 form a fourth set and space pressure plate 64 from the brake body by a fourth axial distance less than the noted third axial distance. The fifth seats 230, 232, 234 of the groups 236, 238, 240 form a fifth set and space pressure plate 64 from the brake body by a fifth axial distance less than the noted fourth axial distance. Pressure plate 64 is partially rotatable about the noted axis to disengage frustoconical end faces 198, 200, 202 of spacer washers 186, 188, 190 from the first set of seats 204, 206, 208 and engage such frustoconical end faces of the spacer washers with the second set of seats 210, 212, 214 to take up and compensate friction disc wear and maintain air gap 80 within a given tolerance. After further wear of the friction disc, pressure plate 64 is further rotated to disengage the spacer washers from the second set of seats 210, 212, 214, and engage the spacer washers with the third set of seats 218, 220, 222. As friction disc 66 continues to wear, pressure plate 64 is further rotated to engage the fourth set of seats 224, 226, 228 with the spacer washers, and then after further wear the pressure plate 64 is further rotated to engage the fifth set of seats 230, 232, 234 with the spacer washers. The sets of seats in each group have increasing diameters receiving the frustoconical spacer washers in deeper seating relation upon rotation of pressure plate 64 to engage the spacer washers with different sets of seats, to adjust air gap 80 and compensate for friction disc wear.

Pressure plate 64 is partially rotatable along a given arc subtended by each group 236, 238, 240. The seats of each group 236, 238, 240 are joined by a respective arcuate slot 242, 244, 246 each defining the given arc. Mounting bolts 146, 148, 150 extending axially through the brake body for mounting the brake to motor frame 32, as above described. Each bolt 146, 148, 150 extends through a respective arcuate slot 242, 244, 246 such that upon partial rotation of pressure plate 64 along the given arc, each arcuate slot slides along a respective bolt. The range of partial rotation of pressure plate 64 is limited by the arcuate length of the slots.

The above described air gap adjustment mechanism and method adjustably varies the axial distance from pressure plate 64 to pole face 40 by partially rotating pressure plate 64 about the axis of shaft 36, to take up and compensate friction disc wear and maintain air gap 80 within a given tolerance as friction disc 66 wears with use. The above described plurality of sets of seats in the pressure plate receive the spacer washers at different seated depths. Pressure plate 64 is partially rotated along a given arc about the noted axis to seat the spacer washers in different seats, to shorten the axial spacing of the pressure plate and brake body with deeper seatings of the spacer washers, to adjust air gap 80 and compensate for friction disc wear. The air gap is adjusted by loosening bolts 146, 148, 150, partially rotating pressure plate 64 about the noted axis to seat spacer washers 186, 188, 190 in different depth seats in pressure plate 64, and then retightening bolts 146, 148, 150.

A torque adjustment mechanism 250, FIG. 3, is provided and is adjustable to vary the bias of biasing springs 52, 54, 56 biasing armature 42 away from pole face 40. Biasing springs 52, 54, 56 extend axially through the brake body and have first ends 252, 254, 256 bearing against armature 42, and have distally opposite second ends 258, 260, 262. The torque adjustment mechanism includes a partially rotatable torque plate 264 and a plurality of spring plugs 266, 268, 270 engaging respective ends 258, 260, 262 of respective springs 52, 54, 56. Torque plate 264 is mounted on the brake body and is partially rotatable about the axis of shaft 36 to vary the compression of biasing springs 52, 54, 56.

Torque plate 264 has a plurality of arcuate slots 274, 276, 278 of tapered radial width each partially receiving a respective spring plug 266, 268, 270 at a respective rounded end 280, 282, 284. Torque plate 264 is partially rotatable in a counterclockwise direction in FIG. 13 to engage a respective spring plug 266, 268, 270 at a respective rounded end 280, 282, 284 with a respective slot 274, 276, 278 along a narrowing taper to push the respective spring plug 266, 268, 270 axially toward armature 42, which is leftwardly in FIG. 14, to increase the compression of the respective biasing spring 52, 54, 56, to increase braking torque. Torque plate 264 is partially rotatable in the opposite direction, clockwise in FIG. 15, such that each spring plug 266, 268, 270 at its respective rounded head end 280, 282, 284 engages its respective slot 274, 276, 278 along a widening taper to permit movement of the respective spring plug 266, 268, 270 axially away from armature 42, rightwardly in FIG. 16, to decrease the compression of the respective biasing spring 52, 54, 56, to reduce braking torque.

As seen in FIGS. 13-16, biasing spring 56, FIG. 14, is compressed to axial compression length 286 when rounded end 284 of spring plug 270 is in a narrow portion of tapered slot 278. Compression spring 56 is compressed to axial compression length 288, FIG. 16, when rounded end 284 of spring plug 270 is in a wider portion of tapered slot 278. Axial distance 286 is less than axial distance 288, whereby the rotated position of torque plate 264 in FIG. 13 provides greater axial compression of biasing springs 52, 54, 56 and hence greater braking torque than the rotated position of torque plate 264 in FIG. 15. Torque plate 264 has a set of arcuate slots 290, 292, 294 of constant radial width receiving respective bolts 296, 298, 300 extending therethrough and mounting torque plate 264 to brake body shell 82 and permitting partial rotation of torque plate 264 about the axis of shaft 36. The range of partial rotation of torque plate 264 is limited by the arcuate length of each of slots 290, 292, 294.

The combination of torque plate 264 and rounded end spring plugs 280, 282, 284 provides a torque adjusting camming mechanism engaging biasing springs 52, 54, 56 and camming the latter to vary the axial bias thereof, e.g. between different axial compression lengths 286 and 288. The apparatus and method thus adjustably varies the bias of the biasing springs biasing armature 42 away from pole face 40 to vary the bias of armature 42 in the braking position, to adjust braking torque.

The brake includes a release mechanism 310, FIGS. 3 and 17. The release mechanism includes a manually engageable handle 312 connected to a yoke 314 having pivot-bases 316 and 318, FIG. 3, mounted to the brake body on opposite distal sides of the axis of rotation of shaft 36. Pivot-bases 316, 318 have respective tabs 320, 322 extending through respective retention spacer clips 324, 326 and radially inwardly between pressure plate 64 and armature 42. Each tab 318, 320 is spaced radially outwardly of friction disc 66. Pivot-bases 316, 318 are pivotable about an axis perpendicular to the axis of shaft 36 such that tabs 316, 318 engage and push armature 42 toward pole face 40 and against the bias of biasing springs 52, 54, 56, 58, 60, 62. This releases the brake and allows rotation of friction disc 66, hub 72 and shaft 36.

Pivot-base 316 has pivot bosses 328, 330 on opposite sides of tab 320. Pivot-base 318 has pivot bosses 332, 334 on opposite sides of tab 322. Tab 320 has an inner edge 336 facing pivot boss 328 and then extending radially inwardly. Tab 320 has an inner edge 338 facing pivot boss 330 and then extending radially inwardly. Tab 322 has an inner edge 340 facing pivot boss 332 and then extending radially inwardly. Tab 322 has an inner edge 342 facing pivot boss 334 and then extending radially inwardly.

Upon rightward axial movement of handle 312 in FIG. 17 as shown at arrow 344, inner edges 336, 340 of tabs 320, 322 engage armature 42 as pivot-bases 316, 318 are pivoted about pivot bosses 330, 334, as shown in solid line in FIG. 19. When handle 312 is moved axially leftwardly in FIG. 17 as shown at arrow 346, inner edges 338, 342 of tabs 320, 322 engage armature 42 as pivot-bases 316, 318 pivot about pivot bosses 328, 332, as shown in dashed line in FIG. 19. Brake body shell 82 has distally opposite outer ledges 344, 346 cast on its outer periphery on opposite distal sides of the axis of rotation of shaft 36. Pivot bosses 328, 330 and 332, 334 pivot on respective ledges 344 and 346. When pivot-bases 316, 318 pivot about pivot bosses 330, 334, pivot bosses 328, 332 disengage ledges 344, 346 of the brake body, and inner edges 338, 342 disengage armature 42. When pivot-bases 316, 318 pivot about pivot bosses 328, 332, pivot bosses 330, 334 disengage respective ledges 344, 346, and inner edges 336, 340 disengage armature 42, FIG. 21. Handle 312 can thus be moved in either direction 344 or 346 to manually release the brake.

It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.