Electrically actuated disc stack having low response time due to reduced residual magnetism for use in drives, brakes and combinations thereof

• US 5,533,425 A
• Filed: 11/16/1994
• Issued: 07/09/1996
• Est. Priority Date: 03/05/1992
• Status: Expired due to Term

• Current Assignee: Force Control Industries, Inc.
• Original Assignee: Easom Engineering and Manufacturing Corporation
• Inventors: Mabee, Brian D.
• Primary Examiner(s): Lorence, Richard M.
• Application Number:
  US08/340,220
• Time in Patent Office: 601 Days
• Field of Search: 192/18 B, 192/12 D, 192/70.14, 192/70.19, 192/70.28, 192/84 R, 192/84 C, 192/90, 192/107 M, 74/625, 74/661, 188/161, 188/164, 188/171
• US Class Current: 74/661
• CPC Class Codes: F16D 2121/22 for releasing a normally applied brake
• CPC Class Codes: F16D 55/36 Brakes with a plurality of rotating discs all lying side by side
• CPC Class Codes: F16D 67/06 electromagnetically actuated
• CPC Class Codes: Y10T 74/19014 Plural prime movers selectively coupled to common output

Abstract

The present invention is an electrically actuated disc stack for drives, brakes and combinations thereof having minimized residual magnetism. Residual magnetism is minimized by the following features being provided, singly or in combination, in a drive, brake or combination thereof. 1) A non-magnetic material is located between the clutch armature plate and the clutch electromagnetic coil assembly, and a non-magnetic material is located between the brake armature plate and the brake electromagnetic coil assembly. The non-magnetic material serves as a spacer to add reluctance to the magnetic circuit and may be for example a wafer for instance composed of aluminum or stainless steel or may be a coating. 2) A driver circuit for energizing the primary and secondary electromagnetic coils, wherein the self-induced EMF produced when current is shut-off is rapidly dissipated. 3) Non-magnetic drive components are used in the path of the magnetic circuit of the clutch and brake electromagnetic coil assemblies. For example, the portion of the drive shaft concentric with respect to the clutch electromagnetic coil assembly is composed of a non-magnetic metal, such as aluminum. This has the effect to reduce residual magnetism in that the drive shaft will not be contributing its own permanent magnetism acquitted during energization of the primary electromagnetic coil.

Claims

1. A device selected from at least one of a clutch, a brake and a combination thereof, said device comprising:

a housing;

a first component connected with said housing;

a second component connected with said housing so as to be rotatable with respect to said first component;

a disc stack comprising;

a first set of annular discs; and

a second set of annular discs, said second set of annular discs being interleaved with said first set of annular discs in a prearranged order;

first connection means for connecting said first set of annular discs with said first component, wherein said first set of annular discs is nonrotatable with respect to said first component, wherein further said first set of annular discs is axially slidable with respect to said first component;

second connection means for connecting said second set of annular discs with said second component, wherein said second set of annular discs is nonrotatable with respect to said second component, wherein further said second set of annular discs is axially slidable with respect to said second component; and

biasing means connected with said housing for selectively biasing said first set of annular discs with respect to said second set of annular discs to thereby regulate relative rotation between said first component and said second component, wherein said biasing means comprises an electromagnetically actuated biasing means comprising;

an armature plate having a coil face portion constructed of a magnetic material, said armature plate being slidably connected with said housing;

a first thrust surface connected with said armature plate for abutably contacting a first side of said disc stack;

a second thrust surface connected with said second component for abutably contacting a second side of said disc stack opposite with respect to said first side thereof;

spring biasing means connected with said housing for biasing said armature plate to thereby selectively bias said first thrust surface with respect to said disc stack to thereby selectively clamp said first and second annular discs together between said first and second thrust surfaces;

electromagnetic coil means comprising an electromagnetic coil, said electromagnetic coil means being connected with said housing f or magnetically attracting said coil face portion of said armature plate in response to energization of said electromagnetic coil; and

substantially non-magnetic shim mean s located between said coil face portion and said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said armature plate;

wherein energization of said electromagnetic coil magnetically attracts said armature plate thereto against said biasing of said spring biasing means.

2. The device of claim 1, wherein at least a portion of said first component which is concentrically disposed with respect to said electromagnetic coil means is substantially non-magnetic.

3. The device of claim 2, further comprising a thrust plate rotatably connected to said armature plate, said thrust plate having said first thrust surface;

wherein said thrust plate is substantially non-magnetic.

4. The device of claim 3, further comprising coil driver circuit means for providing rapid de-energization of said electromagnetic coil.

5. The device of claim 4, wherein said coil driver circuit means comprises:

rectifier means for converting an alternating current input thereto to a direct current output therefrom for driving said electromagnetic coil;

solid state coil driver means for providing disconnection of said electromagnetic coil from said rectifier when electrical current to said electromagnetic coil is switched off;

low voltage detector means for providing a saturated operation state of said solid state coil driver means; and

output coil surge protector means for protecting said coil driver circuit means from transients generated by said electromagnetic coil.

6. The device of claim 1, further comprising driver circuit means for providing rapid de-energization of said electromagnetic coil.

7. The device of claim 1, wherein each annular disc of said first set of annular discs has a first inner substantially circular periphery and a first outer substantially circular periphery, wherein further each annular disc of said second set of annular discs has a second inner substantially circular periphery and a second outer substantially circular periphery, said first inner periphery defining a first diameter, said second inner periphery defining a second diameter, said first diameter being less than said second diameter, said first outer periphery defining a third diameter, said second outer periphery defining a fourth diameter, said third diameter being less than said fourth diameter;

and wherein said alignment pin means comprises;

a plurality of alignment pins, each alignment pin of said plurality of alignment pins having a first end and an opposite second end; and

abutment means located at said first end and said second end of each said alignment pin for providing an abutment at each of said first and second end thereof;

wherein each annular disc of said second set of annular discs is provided with a plurality of circumferentially disposed alignment holes, an alignment pin of said plurality of alignment pins extending through each alignment hole of said plurality of alignment holes, said first and second sets of annular discs being captured on said plurality of alignment pins by said abutment means.

8. The device of claim 7, further comprising driver circuit means for providing rapid de-energization of said electromagnetic coil.

9. The device of claim 7, further wherein at least a portion of said first component which is concentrically disposed with respect to said electromagnetic coil means is substantially non-magnetic.

10. A device selected from at least one of a clutch, a brake and a combination thereof, said device comprising:

a housing;

a first component connected with said housing;

a second component connected with said housing so as to be rotatable with respect to said first component;

a disc stack comprising;

a first set of annular discs; and

a second set of annular discs, said second set of annular discs being interleaved with said first set of annular discs in a prearranged order;

first connection means for connecting said first set of annular discs with said first component, wherein said first set of annular discs is nonrotatable with respect to said first component, wherein further said first set of annular discs is axially slidable with respect to said first component;

second connection means for connecting said second set of annular discs with said second component, wherein said second set of annular discs is nonrotatable with respect to said second component, wherein further said second set of annular discs is axially slidable with respect to said second component; and

biasing means connected with said housing for selectively biasing said first set of annular discs with respect to said second set of annular discs to thereby regulate relative rotation between said first component and said second component, wherein said biasing means comprises an electromagnetically actuated biasing means comprising;

an armature plate having a coil face portion constructed of a magnetic material, said armature plate being slidably connected with said housing;

a first thrust surface connected with said armature plate for abutably contacting a first side of said disc stack;

a second thrust surface connected with said second component for abutably contacting a second side of said disc stack opposite with respect to said first side thereof;

spring biasing means connected with said housing for biasing said armature plate to thereby selectively bias said first thrust surface toward said disc stack to thereby selectively clamp said first and second annular discs together between said first and second thrust surfaces;

electromagnetic coil mean s comprising an electromagnetic coil, said electromagnetic coil means being connected with said housing for magnetically attracting said coil face portion of said armature plate in response to energization of said electromagnetic coil, said electromagnetic coil having a magnetic circuit; and

substantially non-magnetic material means located in said magnetic circuit of said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said clutch armature plate;

wherein energization of said electromagnetic coil magnetically attracts said clutch armature plate thereto against said biasing of said spring biasing means.

11. The device of claim 10, wherein said substantially non-magnetic material means comprises substantially non-magnetic shim means located between said coil face portion and said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said brake armature plate.

12. The device of claim 10, wherein said substantially non-magnetic material means comprises at least a portion of said primary clutch shaft which is concentrically disposed with respect to said primary electromagnetic coil means being substantially non-magnetic.

13. The device of claim 12, further comprising a thrust plate rotatably connected to said armature plate, said thrust plate having said first thrust surface;

wherein said thrust plate is substantially non-magnetic.

14. The device of claim 10, further comprising coil driver circuit means for providing rapid de-energization of said electromagnetic coil.

15. The device of claim 14, wherein said coil driver circuit means comprises:

rectifier means for converting an alternating current input thereto to a direct current output therefrom for driving said electromagnetic coil;

solid state coil driver means for providing disconnection of said electromagnetic coil from said rectifier when electrical current to said electromagnetic coil is switched off;

low voltage detector means for providing a saturated operation state of said solid state coil driver means; and

output coil surge protector means for protecting said coil driver circuit means from transients generated by said electromagnetic coil.

16. A two-speed drive, comprising:

a stationary housing;

an output shaft;

primary drive means connected with said stationary housing and said output shaft for providing high speed driving of said output shaft;

secondary drive means connected with said stationary housing for providing low speed driving of said output shaft;

clutch means connected with said primary drive means and said secondary drive means for selectively engaging said secondary drive means to said output shaft, said clutch means comprising;

a first pre-assembled disc stack having a first predetermined cross-section within a first preset tolerance, said first pre-assembled disc stack comprising;

a first set of annular discs, each annular disc of said first set of annular discs having at least one first thickness within at least one second preset tolerance, said first set of annular disks being connected with said primary drive means so as to be rotatable therewith and axially slidable with respect thereto;

a second set of annular discs, each annular disc of said second set of annular discs having at least one second thickness within at least one third preset tolerance, said second set of annular discs being connected with said secondary drive means so as to be rotatable therewith and axially slidable with respect thereto, said second set of annular discs being interleaved with said first set of annular discs in a prearranged order such that said at least one first thickness of each annular disc of said first set of annular discs and said at least one second thickness of each said annular disc of said second set of annular discs cumulatively equals the first predetermined cross-section within the first preset tolerance; and

first alignment pin means connected with said second set of annular discs for capturing each annular disc of said second set of annular discs and for capturing each annular disc of said first set of annular discs so as to provide the pre-assembled disc stack having the first predetermined cross-section within the first preset tolerance; and

first biasing means connected with said stationary housing for selectively biasing said first set of annular discs with respect to said second set of annular discs so as to selectively clamp said first set of annular discs with respect to said second set of annular discs, thereby engaging said secondary drive means with respect to said primary drive means; and

brake means connected with said stationary housing means and said secondary drive means for selectively engaging said secondary drive means with respect to said stationary housing, and, in combination with said clutch means, for selectively engaging said primary drive means with respect to said stationary housing, said brake means comprising;

a second pre-assembled disc stack having a second predetermined cross-section within a fourth preset tolerance, said second pre-assembled disc stack comprising;

a third set of annular discs, each annular disc of said third set of annular discs having at least one third thickness within at least one fifth preset tolerance, said third set of annular disks being connected with said secondary drive means so as to be rotatable therewith and axially slidable with respect thereto;

a fourth set of annular discs, each annular disc of said fourth set of annular discs having at least one fourth thickness within at least one sixth preset tolerance, said fourth set of annular discs being connected with said stationary housing so as to be nonrotatable therewith and axially slidable with respect thereto, said fourth set of annular discs being interleaved with said third set of annular discs in a prearranged order such that said at least one third thickness of each annular disc of said third set of annular discs and said at least one fourth thickness of each said annular disc of said fourth set of annular discs cumulatively equals the second predetermined cross-section within the fourth preset tolerance; and

second alignment pin means connected with said fourth set of annular discs for capturing each annular disc of said fourth set of annular discs and for capturing each annular disc of said third set of annular discs so as to provide the second pre-assembled disc stack having the second predetermined cross-section within the fourth preset tolerance; and

second biasing means connected with said stationary housing for selectively biasing said third set of annular discs with respect to said fourth set of annular discs so as to selectively clamp said third set of annular discs with respect to said fourth set of annular discs, thereby engaging said secondary drive means and, selectively through said clutch means, said primary drive means with respect to said stationary housing;

wherein said clutch means further comprises;

a primary clutch shaft rotatably mounted to said stationary housing and connected with said primary drive means, said primary clutch shaft being provided with splines; and

a secondary clutch shaft rotatably mounted to said stationary housing and connected with said secondary drive means, said secondary clutch shaft being provided with a plurality of lugs oriented parallel with respect to said secondary clutch shaft;

wherein said first inner periphery is provided with a plurality of teeth for engaging said splines of said primary clutch shaft, and said second outer periphery is provided with a plurality of notches for engaging said plurality of lugs of said secondary clutch shaft;

wherein said first biasing means comprises;

a thrust plate having a first clutch thrust surface for abutably contacting one side of said first pre-assembled disc stack;

a second clutch thrust surface connected with said secondary clutch shaft for abutably contacting a side of said first pre-assembled disc stack opposite with respect to said one side thereof;

a clutch armature plate having a coil face portion constructed of a magnetic material, said clutch armature plate being rotatably connected with said thrust plate for transmitting force on said clutch armature plate axially with respect to said primary clutch shaft to said thrust plate;

a plurality of clutch springs, said stationary housing being provided with a plurality of clutch spring cavities for locating each clutch spring of said plurality of clutch springs in a respective clutch spring cavity;

a plurality of shoulder bolts, a shoulder bolt being anchored in each of said clutch spring cavities, said armature plate being slidably connected with said plurality of shoulder bolts so as to be slidable axially with respect to said primary clutch shaft;

clutch electromagnetic coil means comprising a primary electromagnetic coil, said clutch electromagnetic coil means being connected with said stationary housing for magnetically attracting said coil face portion of said clutch armature plate in response to energization of said primary electromagnetic coil, said clutch electromagnetic coil means having a magnetic circuit; and

substantially non-magnetic material means located in said magnetic circuit of said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said clutch armature plate;

wherein said plurality of clutch springs bias said clutch armature plate against said thrust plate, thereby causing said first and second clutch thrust surfaces to bias against said first pre-assembled disc stack so as to clamp said first set of annular discs with respect to said second set of annular discs;

wherein further, energization of said primary electromagnetic coil magnetically attracts said clutch armature plate so as to relieve said biasing of said thrust plate against said first pre-assembled disc stack; and

wherein upon de-energization of said electromagnetic coil, said spring biasing means rapidly thereafter biases said thrust plate against said disc stack.

17. The two-speed drive of claim 16, wherein said brake means further comprises:

a brake hub connected with a gear reduction means for rotating with said secondary drive means, said brake hub being provided with splines; and

threaded seat means in said stationary housing for threadably receiving said double threaded nut of each said second alignment

wherein said third inner periphery is provided with a plurality of teeth for engaging said splines of said brake hub, and said double threaded nuts of each of said second alignment pins is threadably received in said threaded seat means; and

wherein said second biasing means comprises;

a brake armature plate having a first brake thrust surface for abutably contacting one side of said second pre-assembled disc stack, said brake armature plate being provided with a coil face portion constructed of a magnetic material;

a second brake thrust surface connected with said stationary housing for abutably contacting a side of said second pre-assembled disc stack opposite with respect to said one side thereof;

a plurality of brake springs, said stationary housing being provided with a plurality of brake spring cavities for locating a brake spring of said plurality of brake springs in a respective brake spring cavity;

a plurality of shoulder bolts, a shoulder bolt being anchored in each of said brake spring cavities, said armature plate being slidably connected with said plurality of shoulder bolts so as to be slidable axially with respect to said brake hub;

brake electromagnetic coil means comprising a secondary electromagnetic coil, said brake electromagnetic coil means being connected with said stationary housing for magnetically attracting said coil face portion of said brake armature plate in response to energization of said secondary electromagnetic coil; and

substantially non-magnetic shim means located between said coil face portion and said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said brake armature plate;

wherein said plurality of brake springs bias said brake armature plate against said second pre-assembled disc stack thereby causing said first and second brake thrust surfaces to bias against said second pre-assembled disc stack so as to clamp said third set of annular discs with respect to said fourth set of annular discs;

wherein further, energization of said secondary electromagnetic coil magnetically attracts said brake armature plate so as to relieve said biasing of said brake armature plate against said second pre-assembled disc stack; and

wherein upon de-energization of said secondary electromagnetic coil, said brake springs rapidly thereafter bias said brake armature plate against said disc stack.

18. The two-speed drive of claim 17, wherein said substantially non-magnetic material means comprises substantially non-magnetic shim means located between said coil face portion and said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said brake armature plate.

19. The two-speed drive of claim 18, wherein further said substantially non-magnetic material means comprises at least a portion of said primary clutch shaft which is concentrically disposed with respect to said primary electromagnetic coil means being substantially non-magnetic.

20. The two-speed drive of claim 19, wherein further said substantially non-magnetic material means comprises said thrust plate being substantially non-magnetic.

21. The two-speed drive of claim 20, further comprising coil driver circuit means for providing rapid de-energization of each of said primary and secondary electromagnetic coils.

22. The two-speed drive of claim 21, wherein each said coil driver circuit means comprises:

rectifier means for converting an alternating current input thereto to a direct current output therefrom for driving a respective electromagnetic coil of said primary and secondary electromagentic coils;

solid state coil driver means for providing disconnection of said respective electromagnetic coil from said rectifier when electrical current to said respective electromagnetic coil is switched off;

low voltage detector means for providing a saturated operation state of said solid state coil driver means; and

output coil surge protector means for protecting said coil driver circuit means from transients generated by said respective electromagnetic coil.

23. The two-speed drive of claim 22, wherein said first and second alignment pin means comprise:

a plurality of first alignment pins, each first alignment pin of said plurality of first alignment pins having a head at a first end thereof and a threaded opposite end;

a plurality of first double threaded nuts, a first double threaded nut being threadably engaged on said threaded opposite end of each said first alignment pin;

a plurality of second alignment pins, each second alignment pin of said plurality second of alignment pins having a head at a first end thereof and a threaded opposite end; and

a plurality of second double threaded nuts, a second double threaded nut being threadably engaged on said threaded opposite end of each said second alignment pin;

wherein each annular disc of said first set of annular discs has a first inner substantially circular periphery and a first outer substantially circular periphery, wherein each annular disc of said second set of annular discs has a second inner substantially circular periphery and a second outer substantially circular periphery, said first inner periphery defining a first diameter, said second inner periphery defining a second diameter, said first diameter being less than said second diameter, said first outer periphery defining a third diameter, said second outer periphery defining a fourth diameter, said third diameter being less than said fourth diameter; and

further wherein each annular disc of said second set of annular discs is provided with a plurality of circumferentially disposed first alignment holes, a first alignment pin of said plurality of first alignment pins extending through each first alignment hole of said plurality of first alignment holes, said first and second sets of annular discs being captured between said head and said double threaded nut of each said first alignment pin; and

wherein each annular disc of said third set of annular discs has a third substantially circular inner periphery and a third outer substantially circular periphery, wherein further each annular disc of said fourth set of annular discs has a fourth inner substantially circular periphery and a fourth outer substantially circular periphery, said third inner periphery defining a fifth diameter, said fourth inner periphery defining a sixth diameter, said fifth diameter being less than said sixth diameter, said third outer periphery defining a seventh diameter, said fourth outer periphery defining an eighth diameter, said seventh diameter being less than said eighth diameter; and

further wherein each annular disc of said fourth set of annular discs is provided with a plurality of circumferentially disposed second alignment holes, a second alignment pin of said plurality of second alignment pins extending through each second alignment hole of said plurality of second alignment holes, said third and fourth sets of annular discs being captured between said head and said double threaded nut of each said second alignment.

24. An electrical actuation system for at least one of a clutch and a brake having a housing and further having at least one disc stack mounted within the housing, the disc stack having a first side and a second side, a first thrust surface being provided within the housing adjacent the first side of the disc stack, the disc stack being composed of at least two sets of annular discs which are mutually interleaved, said electrical actuation system comprising:

an electromagnetic coil assembly located within and connected to the housing, said electromagnetic coil assembly comprising an electromagnetic coil and a pole piece, said pole piece being located with respect to said electromagnetic coil so as to be magnetizable thereby, said electromagnetic coil having a magnetic circuit; and

an armature assembly located within the housing, said armature assembly comprising;

armature plate means selectively locatable within a first predetermined distance from said pole piece;

substantially non-magnetic material means located in said magnetic circuit of said electromagnetic coil for reducing magnetic flux of said electromagnetic coil with respect to said armature plate means;

armature connection means for slidably connecting said armature plate means with respect to the housing so that said armature plate means may slide reciprocably between a first location whereat said armature plate means contacts said pole piece to a second location whereat said armature plate means is at said first predetermined distance from said pole piece;

spring take-up plate means resiliently connected with said armature plate means;

armature spring means for resiliently connecting said spring take-up plate means to said armature plate means, said armature spring means having a first end and a second end, said first end of said armature spring means being connected with said armature plate means, said second end of said armature spring means being slidably connected with said spring take-up plate means; and

second thrust surface means for selectively contacting the second side of the disc stack, said second thrust surface means being connected with said spring take-up plate means, said second thrust surface means being selectively locatable within a second predetermined distance from the second side of the disc stack;

wherein an excitation current supplied to s aid electromagnetic coil causes said armature plate means to be magnetically attracted to said pole piece and as a result thereof slide on said armature connection means toward said pole piece until contact therewith has been made whereupon said excitation current is reduced by a predetermined amount which provides sufficient magnetism to keep said armature plate means in contact with said pole piece, and wherein said first predetermined distance is longer than said second predetermined distance;

wherein further, the movement of said armature plate means into contact with said pole piece causes said armature spring means, said spring take-up plate means and said second thrust surface means to move with said armature plate means until said second thrust surface means forcibly abuts the second side of the disc stack, wherein still further, said armature spring means resiliently compresses in order to accommodate the difference between said first and second predetermined distances thereby supplying a predetermined biasing force to said second thrust surface means with respect to the second side of the disc stack so as to clamp the at least two sets of annular discs between the first thrust surface and said second thrust surface means.

25. The electrical actuation system of claim 24, wherein said substantially non-magnetic material means comprises substantially non-magnetic shim means located between said coil face portion and said electromagnetic coil means for reducing magnetic flux of said electromagnetic coil with respect to said brake armature plate.

26. The electrical actuation system of claim 25, wherein further said substantially non-magnetic material means comprises at least a portion of said primary clutch shaft which is concentrically disposed with respect to said primary electromagnetic coil means being substantially non-magnetic.

27. The electrical actuation system of claim 26, wherein further said substantially non-magnetic material means comprises said thrust plate being substantially non-magnetic.

28. The electrical actuation system of claim 27, further comprising coil driver circuit means for providing rapid de-energization of each of said primary and secondary electromagnetic coils.

29. The electrical actuation system of claim 28, wherein each said coil driver circuit means comprises:

rectifier means for converting an alternating current input thereto to a direct current output therefrom for driving a respective electromagnetic coil of said primary and secondary electromagentic coils;

solid state coil driver means for providing disconnection of said respective electromagnetic coil from said rectifier when electrical current to said respective electromagnetic coil is switched off;

low voltage detector means for providing a saturated operation state of said sold state coil driver means; and

output coil surge protector means for protecting said coil driver circuit means from transients generated by said respective electromagnetic coil.

30. The electrical actuation system of claim 29, wherein said armature connection means further comprises means for biasing said armature plate means away from said pole piece when no excitation current is supplied to said electromagentic coil.