1. A method of creating a digital certificate revocation list (CRL), comprising:
creating a list of digital certificates satisfying at least one inactive criterion;
identifying a latest CRL in which changes have been made to the list; and
storing an attribute indicating the CRL as being the latest as a part of the latest CRL.
2. The method according to claim 1, further comprising formatting as an ASN.1 format CRL with the attribute of the latest CRL as an extension to the format.
3. The method according to claim 1, wherein the identifying comprises comparing the list with entries in a previously generated CRL.
4. The method according to claim 1, wherein the creating, identifying and storing are carried out at regular time intervals.
5. The method according to claim 1, further comprising applying a digital signature to the CRL.
6. An electronic storage medium storing instructions which when executed on a programmed processor carry out the method of creating a digital certificate revocation list according to claim 1.
7. The method according to claim 1, wherein the at least one inactive criterion comprises at least one of a hold status criterion, an expired status criterion and a revoked status criterion.
8. The method according to claim 1, further comprising transmitting the CRL to a recipient over an electronic communication medium.
9. A method of using a digital certificate revocation list (CRL), comprising:
storing a first CRL, the first CRL comprising a list of digital certificates satisfying at least one inactive criterion, a first CRL identifier, and a first attribute for indicating if the first CRL is the latest CRL;
carrying out a processing operation on the first CRL;
receiving a second CRL, the second CRL comprising a list of digital certificates satisfying the at least one inactive criterion, a second CRL identifier, and a second attribute for indicating whether the second CRL is the latest CRL wherein the second CRL is the latest CRL if changes have been made to the list of the second CRL compared to the list of first CRL; and
carrying out the processing operation on the second CRL only if the second attribute of the second CRL indicates that the second CRL is the latest CRL.
10. The method according to claim 9, wherein the processing operation comprises storing the list of digital certificates satisfying the inactive criterion.
11. The method according to claim 9, wherein the processing operation comprises storing the list of digital certificates satisfying the inactive criterion as a part of a database.
12. The method according to claim 9, wherein the processing operation comprises filtering the list of digital certificates based on inactive criteria.
13. The method according to claim 9, wherein the processing operation comprises authenticating a digital certificate against the second CRL.
14. The method according to claim 9, wherein the at least one inactive criterion comprises at least one of a hold status criterion, an expired status criterion and a revoked status criterion.
15. The method according to claim 9, wherein the first and second CRL are received over an electronic communication medium.
16. An electronic storage medium storing instructions which when executed on a programmed processor carry out the method of using a digital certificate revocation list according to claim 9.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A multispeed drive unit comprising:
a rotary input positioned to be driven by a power source and disposed at an input side of the drive unit;
a rotary output positioned to drive a driven unit and disposed at an output side of the drive unit;
a transmission operably interposed between said rotary input and said rotary output, said transmission having a gear moveable between a high-reduction configuration and a low-reduction configuration;
a first friction clutch operable to fix said gear in said high-reduction configuration, whereby said transmission is operable to reduce a speed of said rotary output relative to said rotary input when said first friction clutch is engaged; and
a second friction clutch operable to fix said gear in said low-reduction configuration, whereby said transmission is not operable to reduce the speed of said rotary output relative to said rotary input when said second friction clutch is engaged.
2. The multispeed drive unit of claim 1, further comprising an actuator and a biasing element, wherein:
said gear is acted upon by said actuator which urges said gear into one of said low-reduction configuration and said high-reduction configuration when said actuator is actuated; and
said gear is acted upon by said biasing element which urges said gear into the other of said low-reduction configuration and said high-reduction configuration when said actuator is not actuated.
3. The multispeed drive unit of claim 2, wherein:
said actuator is configured to cause engagement of said second friction clutch while simultaneously allowing said first friction clutch to disengage when said actuator is actuated; and
said biasing element is configured to cause engagement of said first friction clutch while simultaneously allowing said second friction clutch to disengage when said actuator is not actuated.
4. The multispeed drive unit of claim 2, wherein said actuator comprises a hydraulic actuator.
5. The multispeed drive unit of claim 1, wherein said gear is moveable between a first position toward the input side of the drive unit and an opposed second position toward the output side of the drive unit,
said gear in said high-reduction configuration at one of said first position and said opposed second position, and
said gear in said low-reduction configuration at the other of said first position and said opposed second position.
6. The multispeed drive unit of claim 1, wherein said first friction clutch comprises a plurality of clutch plates frictionally engageable with one another, said plurality of clutch plates alternately rotationally fixed to said gear and a rotationally fixed component of the multispeed drive unit, such that said gear and said rotationally fixed component are rotationally fixed to one another when said first friction clutch is engaged such that said gear is in said high-reduction configuration.
7. The multispeed drive unit of claim 6, wherein said rotationally fixed component comprises a housing of the multispeed drive unit interposed between the input side and the output side.
8. The multispeed drive unit of claim 1, wherein said second friction clutch comprises a plurality of clutch plates frictionally engageable with one another, said plurality of clutch plates alternately rotationally fixed to said gear and a component of said transmission, such that said gear and said component of said transmission are rotationally fixed to one another when said second friction clutch is engaged such that said gear is in said low-reduction configuration.
9. The multispeed drive unit of claim 1, wherein said transmission comprises a planetary transmission assembly comprising:
a sun gear having sun gear teeth formed on an outer surface thereof;
at least one planet gear having planet gear teeth formed on an outer surface of said planet gear, said planet gear teeth intermeshingly engaged with said sun gear teeth such that rotation of said sun gear is capable of rotating said at least one planet gear;
a planet gear carrier rotatably supporting said at least one planet gear, such that said at least one planet gear is independently rotatable with respect to said planet gear carrier; and
said gear moveable between said high-reduction configuration and said low-reduction configuration comprising a ring gear having ring gear teeth formed on an inner surface of said ring gear, said ring gear teeth intermeshingly engaged with said planet gear teeth, said planet gear disposed between said ring gear and said sun gear such that torque is transmissible from said sun gear to said planet gear carrier via said planet gear.
10. The multispeed drive unit of claim 9, wherein said ring gear is rotationally secured to said planet gear carrier when in said low-reduction configuration.
11. The multispeed drive unit of claim 9, further comprising a rotationally fixed housing interposed between the input side and the output side, said ring gear rotationally secured to said housing when said ring gear is in said high-reduction configuration.
12. The multispeed drive unit of claim 1, wherein said rotary output rotates at the same speed as said rotary input when said gear is in said low-reduction configuration.
13. The multispeed drive unit of claim 12, wherein said rotary input rotates at between 2 and 10 times faster than said rotary output when said gear is in said high-reduction configuration.
14. A multispeed drive unit comprising:
a rotary input positioned to be driven by a power source and disposed at an input side of the drive unit;
a rotary output positioned to drive a driven unit and disposed at an output side of the drive unit;
a planetary transmission assembly operably interposed between said rotary input and said rotary output, said planetary transmission assembly comprising:
a sun gear having sun gear teeth formed on an outer surface thereof;
at least one planet gear having planet gear teeth formed on an outer surface of said planet gear, said Planet gear teeth intermeshingly engageable with said sun gear teeth such that rotation of said sun gear is capable of rotating said at least one planet gear;
a planet gear carrier rotatably supporting said at least one planet gear, such that said at least one planet gear is independently rotatable with respect to said planet gear carrier; and
a ring gear comprising ring gear teeth formed on an inner surface of said ring gear, said ring gear teeth intermeshingly engageable with said planet gear teeth, said planet gear disposed between said ring gear and said sun gear such that torque is transmissible from said sun gear to said planet gear carrier via said planet gear,
said ring gear selectively configurable into a high-reduction configuration and a low-reduction configuration by moving said ring gear toward one of the input side of the drive unit and the output side of the drive unit;
a housing interposed between the input side and the output side, said housing stationary with respect to said planetary transmission assembly;
a first clutch pack comprising:
a first clutch plate rotatably fixed to an outer surface of said ring gear; and
a second clutch plate rotatably fixed to an inner surface of said housing,
said second clutch plate engageable with said first clutch plate to rotatably fix said ring gear to said housing when said ring gear is in said high-reduction configuration, said planetary transmission assembly operable to reduce a speed of said rotary output relative to said rotary input when said first and second clutch plates are engaged; and
a second clutch pack comprising:
a third clutch plate rotatably fixed to said inner surface of said ring gear; and
a fourth clutch plate rotatably fixed to said planet gear carrier,
said third clutch plate engageable with said fourth clutch plate to rotatably fix said ring gear to said planet gear carrier when said ring gear is in said low-reduction configuration, said planetary transmission assembly rotating as a single unit when said third and fourth clutch plates are engaged.
15. The multispeed drive unit of claim 14, further comprising:
a biasing element urging said first and second clutch plates into engagement with one another, whereby said biasing element urges said ring gear into said high-reduction configuration; and
a gearshift piston moveable between an actuated position and a non-actuated position, said gearshift piston allowing said first and second clutch plates to engage when in said non-actuated position, said gearshift piston urging said second clutch pack into engagement when in said actuated position, whereby said gearshift piston cooperates to toggle said ring gear between said high-reduction configuration and said-low reduction configuration.
16. The multispeed drive unit of claim 15, further comprising a fluid inlet leading to a fluid chamber, said gearshift piston urged into said actuated position when pressurized fluid is received in said fluid chamber.
17. The multispeed drive unit of claim 15, wherein said biasing element acts on said ring gear such that a shoulder of said ring gear is positioned to abut one of said first clutch plate and said second clutch plate to engage with the other of said first clutch plate and said second clutch plate when said gearshift piston is in the non-actuated position.
18. The multispeed drive unit of claim 15, further comprising a low-friction interface between one of said third and fourth clutch plates and said gearshift piston, whereby rotation therebetween is facilitated when said second clutch pack is engaged.
19. The multispeed drive unit of claim 14, wherein said first clutch pack is disposed radially outwardly of said second clutch pack, whereby said first clutch pack comprises an outer clutch pack and said second clutch pack comprises an inner clutch pack.
20. The multispeed drive unit of claim 14, wherein said at least one planet gear circumnavigates said sun gear when said ring gear is in said high-reduction configuration, and said ring gear rotates at the same speed as with said sun gear when said ring gear is in said low-reduction configuration.
21. A multispeed drive unit comprising:
input means for receiving power from a power source, said input means disposed at an input side of the drive unit;
output means for driving a driven unit, said output means disposed at an output side of the drive unit;
transmission means for selectively toggling between a high-reduction configuration and a low-reduction configuration, said transmission means including a moveable gear interposed between said input means and said output means;
means for fixing said moveable gear in said high-reduction configuration during operation of said multispeed drive unit, such that said transmission means is operable to reduce a speed of said output means relative to said input means; and
means for fixing said moveable gear in said low-reduction configuration during operation of said multispeed drive unit, such that said transmission means is not operable to reduce the speed of said output means relative to said input means.
22. The multispeed drive unit of claim 21, further comprising:
biasing means for biasing said moveable gear into one of said high-reduction configuration and said low-reduction configuration; and
hydraulic means for selectively urging said moveable gear into the other of said high-reduction configuration and said low-reduction configuration, said hydraulic means operating against a biasing force provided by said biasing means.
23. The multispeed drive unit of claim 21, wherein said means for fixing said moveable gear in said high-reduction configuration and said means for fixing said moveable gear in said low-reduction configuration each comprises means for frictionally rotationally fixing one component to another.