US4874961A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical power generating system having parallel generator control
Assignee: Sundstrand Corp
•
Filing: 1988-10-31
•
Granted: 1989-10-17
•
Expires: 2008-10-31
Abstract
Abstract A power generation system (40), (120), is disclosed in which the phase and frequency of alternating current generated by one or more generators (14) is locked to the phase of alternating current generated by a master generator (12) or to an external power source (124). A master control unit (42), (122) contains a master count generator (52) which generates a synchronization count which is transmitted to each generator control unit (44). The synchronization count at any point in time of the master count generator is directly proportional to the phase of electrical current being generated by the master generator or the external power source. Each generator control unit (44) receives the synchronization count and compares the synchronization count with a locally generated synchronization count which is proportional to the phase of electrical current being generated by a generator controlled by the generator control unit receiving the synchronization count. The phase of the alternating current generated by the generators controlled by the each generator control unit receiving the synchronization count is adjusted as a function of the difference of the received and locally generated synchronization count to lock the phase and frequency of the alternating current with the phase and frequency of alternating current generated by the master generator or the phase and frequency of the external, power source.
Inventors
- 👤 Eric A. Henderson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:53
CPC Classifications
H; H02; H02J; H02J3/00; H02J3/38; H02J3/40; H02J3/44
Claims Analysis
Total Claims: 57
Claim 1
Independent Claim
328 words
An alternating current generating system having at least one slave generator with each slave generator being controlled by an associated slave generator control unit with alternating current generated by each slave generator being at least locked in phase to alternating current generated by a master generator controlled by a master generator control unit wherein: the master generator control unit includes a master count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of the alternating current generated by the master generator with the synchronization count being proportional at any time during a cycle of the alternating current to a phase of electrical current being generated by the master generator with respect to a time reference; each of the slave generator control units includes a slave count generator, each slave count generator generating a synchronization count varying from the minimum to the maximum during each cycle of the alternating current generated by the slave generator controlled by the slave generator control unit with the synchronization count of each slave count generator at any time during a cycle of alternating current generated by the slave generator controlled by the slave generator control unit being proportional to a phase of the generated alternating current measured with respect to a time reference; a transmission system is coupled to the master generator control unit and each of the slave generator control units for periodically transmitting the synchronization count from the master count generator to each slave generator control unit; each slave generator control unit has a processor for generating a correction count which is a function of a difference between the synchronization count received from the master control unit and the synchronization count of the slave count generator; and each slave generator control unit has a controller for adjusting at least the phase of the alternating current generated by the slave generator controlled by the slave generator control unit as a function of the correction count.
Claim 2
Dependent Claim
328 words
An alternating current generating system having at least one slave generator with each slave generator being controlled by an associated slave generator control unit with alternating current generated by each slave generator being at least locked in phase to alternating current generated by a master generator controlled by a master generator control unit wherein: the master generator control unit includes a master count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of the alternating current generated by the master generator with the synchronization count being proportional at any time during a cycle of the alternating current to a phase of electrical current being generated by the master generator with respect to a time reference; each of the slave generator control units includes a slave count generator, each slave count generator generating a synchronization count varying from the minimum to the maximum during each cycle of the alternating current generated by the slave generator controlled by the slave generator control unit with the synchronization count of each slave count generator at any time during a cycle of alternating current generated by the slave generator controlled by the slave generator control unit being proportional to a phase of the generated alternating current measured with respect to a time reference; a transmission system is coupled to the master generator control unit and each of the slave generator control units for periodically transmitting the synchronization count from the master count generator to each slave generator control unit; each slave generator control unit has a processor for generating a correction count which is a function of a difference between the synchronization count received from the master control unit and the synchronization count of the slave count generator; and each slave generator control unit has a controller for adjusting at least the phase of the alternating current generated by the slave generator controlled by the slave generator control unit as a function of the correction count.
Claim 3
Dependent Claim
38 words
A system in accordance with claim 1 wherein: each slave generator control unit controller also locks a frequency of alternating current generated by each slave generator to a frequency of the alternating current generated by the master generator.
Claim 4
Dependent Claim
37 words
A system in accordance with claim 2 wherein the correction count comprises: the synchronization count received from the master control unit less the sum of the synchronization count of the slave count generator and a compensation count.
Claim 5
Dependent Claim
43 words
A system in accordance with claim 3 wherein: the compensation count is a function of delay of the master generator control unit in providing the synchronization count of the master count generator to the transmission system for transmission to the generator control unit.
Claim 6
Dependent Claim
36 words
A system in accordance with claim 3 wherein: the compensation count is a function of delay of the transmission system in transmitting the synchronization count of the master count generator to the slave generator control unit.
Claim 7
Dependent Claim
37 words
A system in accordance with claim 3 wherein: the compensation count is a function of delay of the slave generator control unit in receiving the synchronization count of the master count generator and generating the correction count.
Claim 8
Dependent Claim
88 words
A system in accordance with claim 3 wherein: the compensation count is a function of delay of the master generator control unit in providing the synchronization count of the master count generator to the transmission system for transmission to the slave generator control unit, delay of the transmission system in transmitting the synchronization count of the master count generator to the slave generator control unit and delay of the slave generator control unit in receiving the synchronization count of the master count generator and generating the compensation count.
Claim 9
Dependent Claim
40 words
A system in accordance with claim 2 wherein: the transmission system transmits the synchronization count of the master count generator asynchronously, with respect to a frequency of the current generated by the master generator, to each slave generator control unit
Claim 10
Dependent Claim
94 words
A system in accordance with claim 8 wherein the transmission system comprises: a serial communication bus coupling the master generator control unit to each slave generator control unit; and a bus control unit controlling transmission of communications between the master generator control unit and each slave generator control unit, the bus control unit asynchronously with respect to the frequency of current generated by the master generator sampling the synchronization count of the master count generator and causing transmission of the sampled synchronization count to each slave generator control unit on the serial communication bus.
Claim 11
Dependent Claim
63 words
A system in accordance with claim 9 wherein: the bus control unit time multiplexes the transmission of the sampled synchronization count from the master generator control unit to each of the slave generator control units over the serial communication bus with transmission of other communications between the master generator control unit and the each slave generator control unit over the serial communication bus.
Claim 12
Dependent Claim
40 words
A system in accordance with claim 3 wherein: the transmission system periodically transmits the synchronization count of the master count generator, asynchronously with respect to a frequency of current generated by the master generator, to each slave generator control unit.
Claim 13
Dependent Claim
94 words
A system in accordance with claim 11 wherein the transmission system comprises: a serial communication bus coupling the master generator control unit to each slave generator control unit; and a bus control unit controlling transmission of communications between the master generator control unit and each slave generator control unit, the bus control unit asynchronously with respect to the frequency of current generated by the master generator sampling the synchronization count of the master count generator and causing transmission of the sampled synchronization count to each slave generator control unit on the serial communication bus.
Claim 14
Dependent Claim
61 words
A system in accordance with claim 12 wherein: the bus control unit time multiplexes the transmission of the sampled synchronization count from the master generator control unit to each slave generator control unit over the serial communication bus with transmission of other communications between the master generator control unit and the each slave generator control unit over the serial communication bus.
Claim 15
Dependent Claim
159 words
A system in accordance with claim 2 wherein the master generator control unit comprises: a reference clock for producing on an output pulses defining each cycle of the alternating current produced by the master generator; a counter having a reset input and a clock input which counts a predetermined count of pulses received on the clock input and an output which outputs the count of the counter as the synchronization count; a clock having an output coupled to the clock input of the counter for producing pulses on the output which are counted by the counter, the pulses on the output having a frequency higher than a frequency of the alternating current generated by the master generator; the output of the reference clock being connected to the reset input of the counter; and means, coupled to the output of the counter, for applying the count of the counter to the transmission system in response to a bus control signal.
Claim 16
Dependent Claim
34 words
A system in accordance with claim 14 wherein: the output pulses from the reference clock are applied to a frequency control which controls the frequency of the alternating current produced by the master generator.
Claim 17
Dependent Claim
124 words
A system in accordance with claim 2 wherein each slave generator control unit comprises: means for receiving the synchronization count transmitted from the master generator control unit and for generating an interrupt pulse in response to receipt of the synchronization count; the slave count generator having an enable input to which is applied the interrupt pulse to sample the synchronization count of the slave count generator, a clock input to which is applied clock pulses which are counted by the slave count generator, the pulses having a frequency higher than a frequency of the alternating current generated by the slave generator, and a reset input which is the time reference and an output which is the synchronization count of the slave generator control unit.
Claim 18
Dependent Claim
74 words
A system in accordance with claim 16 wherein: the controller includes a variable frequency clock to which is applied the correction count which has been integrated by a pair of integrators coupled in series to the correction count for controlling the frequency of pulses produced by the variable frequency clock, the variable frequency clock producing clock pulses having a frequency locked to the frequency of the alternating frequency current produced by the slave generator.
Claim 19
Dependent Claim
30 words
A system in accordance with claim 17 wherein: the clock pulses are applied to a frequency control which controls the frequency of the alternating current produced by the slave generator.
Claim 20
Dependent Claim
124 words
A system in accordance with claim 14 wherein each slave generator control unit comprises: means for receiving the synchronization count transmitted from the master generator control unit and for generating an interrupt pulse in response to receipt of the synchronization count; the slave count generator having an enable input to which is applied the interrupt pulse to sample the synchronization count of the slave count generator, a clock input to which is applied clock pulses which are counted by the slave count generator, the pulse having a frequency higher than a frequency of the alternating current generated by the slave generator, and a reset input which is the time reference and an output which is the synchronization count of the slave generator control unit.
Claim 21
Dependent Claim
41 words
A system in accordance with claim 2 wherein: the time reference of the master count generator is produced by a reference clock which controls the frequency of alternating current generated by the master generator and resetting of the master count generator.
Claim 22
Dependent Claim
27 words
A system in accordance with claim 2 wherein: the time reference of the master count generator is derived from the alternating current generated by the master generator.
Claim 23
Dependent Claim
41 words
A system in accordance with claim 2 wherein: the time reference of each slave count generator is produced by a reference clock which controls the frequency of alternating current generated by the slave generator and resetting of the slave count generator.
Claim 24
Dependent Claim
27 words
A system in accordance with claim 2 wherein: the time reference of each slave count generator is derived from the alternating current generated by the master generator.
Claim 25
Independent Claim
212 words
A method of at least phase locking alternating current generated by at least one slave generator to alternating current generated by a master generator comprising: periodically transmitting a synchronization count from a master generator control unit controlling the master generator to at least one slave generator control unit with each slave generator being controlled by a slave generator control unit, the synchronization count being proportional to a phase with respect to a time reference and, cyclically varying between a minimum and a maximum over each period of alternating current generated by the master generator; each slave generator control unit generating a synchronization count which varies between the minimum and the maximum over each period of alternating current generated by the slave generator controlled by the slave generator control unit; and each slave generator control unit generating a correction count which is a function of a difference between the received synchronization count and the synchronization count generated by the slave generator control unit and adjusting at least the phase of alternating current generated by the slave generator controlled by the slave generator control unit as a function of the correction count to cause the alternating current generated by the master and the at least one slave generator units to be locked in phase.
Claim 26
Independent Claim
212 words
A method of at least phase locking alternating current generated by at least one slave generator to alternating current generated by a master generator comprising: periodically transmitting a synchronization count from a master generator control unit controlling the master generator to at least one slave generator control unit with each slave generator being controlled by a slave generator control unit, the synchronization count being proportional to a phase with respect to a time reference and, cyclically varying between a minimum and a maximum over each period of alternating current generated by the master generator; each slave generator control unit generating a synchronization count which varies between the minimum and the maximum over each period of alternating current generated by the slave generator controlled by the slave generator control unit; and each slave generator control unit generating a correction count which is a function of a difference between the received synchronization count and the synchronization count generated by the slave generator control unit and adjusting at least the phase of alternating current generated by the slave generator controlled by the slave generator control unit as a function of the correction count to cause the alternating current generated by the master and the at least one slave generator units to be locked in phase.
Claim 27
Dependent Claim
48 words
A method in accordance with claim 24 further comprising: adjusting a frequency of alternating current generated by each slave generator as a function of the correction count to cause the alternating current generated by the master and at least one slave generator unit to be locked in frequency.
Claim 28
Dependent Claim
41 words
A method in accordance with claim 25 wherein: the periodic transmission of the synchronization count from the master generator control unit to each slave generator control unit is asynchronous with respect to a frequency of current generated by the master generator.
Claim 29
Dependent Claim
37 words
A method in accordance with claim 27 wherein: the correction count comprises the synchronization count received from the master control unit less the sum of the synchronization count of the slave count generator and a compensation count.
Claim 30
Dependent Claim
47 words
A method in accordance with claim 27 wherein: the compensation count is a function of delay of the master generator control unit in providing the synchronization count of the master count generator to the transmission system for transmission to the at least one slave generator control unit.
Claim 31
Dependent Claim
37 words
A method in accordance with claim 27 wherein: the compensation count is a function of delay of the transmission system in transmitting the synchronization count of the master generator control unit to the slave generator control unit.
Claim 32
Dependent Claim
37 words
A method in accordance with claim 27 wherein: the compensation count is a function of delay of the slave generator control unit in receiving the synchronization count of the master count generator and generating the correction count.
Claim 33
Dependent Claim
88 words
A method in accordance with claim 27 wherein: the compensation count is a function of delay of the master generator control unit in providing the synchronization count of the master count generator to the transmission system for transmission to the slave generator control unit, delay of the transmission system in transmitting the synchronization count of the master count generator to the slave generator control unit, and delay of the slave generator control unit in receiving the synchronization count of the master count generator and generating the correction count.
Claim 34
Dependent Claim
321 words
An alternating current generating system having at least one alternating current generator with each alternating current generator generating alternating current locked at least in phase to alternating current generated external to the system comprising: an input for receiving the alternating current external to the system; a master control unit, responsive to the alternating current external to the system, having a master count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of the alternating current external to the system with the synchronization count being proportional at any time during the cycle of the alternating current external to the system to a phase of the alternating current external to the system with respect to a time reference; a generator control unit associated with each alternating current generator, each generator control unit having a count generator, each count generator of each generator control unit generating a synchronization count varying from the minimum to the maximum during each cycle of alternating current generated by the generator controlled by the associated generator control unit with the synchronization count of each count generator of a generator control unit at any time during a cycle of alternating current generated by the generator being proportional to a phase of the generated alternating current with respect to a time reference; a transmission system coupled to the master generator control unit and each generator control unit for periodically sending the synchronization count from the master count generator to each generator control unit; and wherein each generator control unit has a processor for generating a correction count which is a function of a difference between the received synchronization count and the synchronization count generated by the generator control unit; and each generator control unit has a controller for adjusting at least the phase of the electrical current generated by the generator controlled by the generator control unit as a function of the correction count.
Claim 35
Dependent Claim
321 words
An alternating current generating system having at least one alternating current generator with each alternating current generator generating alternating current locked at least in phase to alternating current generated external to the system comprising: an input for receiving the alternating current external to the system; a master control unit, responsive to the alternating current external to the system, having a master count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of the alternating current external to the system with the synchronization count being proportional at any time during the cycle of the alternating current external to the system to a phase of the alternating current external to the system with respect to a time reference; a generator control unit associated with each alternating current generator, each generator control unit having a count generator, each count generator of each generator control unit generating a synchronization count varying from the minimum to the maximum during each cycle of alternating current generated by the generator controlled by the associated generator control unit with the synchronization count of each count generator of a generator control unit at any time during a cycle of alternating current generated by the generator being proportional to a phase of the generated alternating current with respect to a time reference; a transmission system coupled to the master generator control unit and each generator control unit for periodically sending the synchronization count from the master count generator to each generator control unit; and wherein each generator control unit has a processor for generating a correction count which is a function of a difference between the received synchronization count and the synchronization count generated by the generator control unit; and each generator control unit has a controller for adjusting at least the phase of the electrical current generated by the generator controlled by the generator control unit as a function of the correction count.
Claim 36
Dependent Claim
39 words
An alternating current generating system in accordance with claim 32 wherein: each generator control unit controller also locks a frequency of alternating current generated by the associated generator to a frequency of the alternating current external to the system.
Claim 37
Dependent Claim
43 words
A system in accordance with claim 33 wherein: the compensation count is a function of delay of the master generator control unit in providing the synchronization count of the master count generator to the transmission system for transmission to the generator control unit.
Claim 38
Dependent Claim
36 words
A system in accordance with claim 33 wherein: the compensation count is a function of delay of the transmission system in transmitting the synchronization count of the master count generator to the slave generator control unit.
Claim 39
Dependent Claim
37 words
A system in accordance with claim 33 wherein: the compensation count is a function of delay of the slave generator control unit in receiving the synchronization count of the master count generator and generating the correction count.
Claim 40
Dependent Claim
88 words
A system in accordance with claim 33 wherein: the compensation count is a function of delay of the master generator control unit in providing the synchronization count of the master count generator to the transmission system for transmission to the slave generator control unit, delay of the transmission system in transmitting the synchronization count of the master count generator to the slave generator control unit, and delay of the slave generator control unit in receiving the synchronization count of the master count generator and generating the correction count.
Claim 41
Dependent Claim
41 words
A system in accordance with claim 33 wherein: the transmission system periodically transmits the synchronization count of the master count generator asynchronously with respect to a frequency of the alternating current generated exterior to the system to each generator control unit.
Claim 42
Dependent Claim
92 words
A system in accordance with claim 38 wherein the transmission system comprises: a serial communication bus coupling the master generator control unit to each generator control unit; and a bus control unit controlling transmission of communications between the master generator control unit and each generator control unit, the bus control unit asynchronously with respect to the cycle of alternating current generated exterior to the system sampling the synchronization count of the master count generator and causing transmission of the sampled synchronization count to each generator control unit on the serial communication bus.
Claim 43
Dependent Claim
58 words
A system in accordance with claim 39 wherein: the bus control unit time multiplexes the transmission of the sampled synchronization count from the master generator control unit to each generator control unit over the serial communication bus with transmission of other communications between the master generator control unit and each generator control unit over the serial communication bus.
Claim 44
Dependent Claim
27 words
A system in accordance with claim 33 wherein: the time reference of the master count generator is derived from the alternating current generated external to the system.
Claim 45
Dependent Claim
47 words
A system in accordance with claim 33 wherein: the time reference of each count generator of each generator control unit associated with the generator is produced by a reference clock which controls the frequency of alternating current generated by the generator and resetting of the count generator.
Claim 46
Dependent Claim
31 words
A system in accordance with claim 42 wherein: the time reference of the count generator of each generator control unit is derived from the alternating current generated by the associated generator.
Claim 47
Independent Claim
211 words
A method of at least phase locking alternating current generated by at least one alternating current generator with each generator having an associated generator control unit for controlling the generator to alternating current generated external to a generating system comprising: periodically transmitting a synchronization count from a master control unit to each generator control unit in the system with the synchronization count varying from a minimum to a maximum during each cycle of the alternating current generated external to the generating system and being proportional to a phase of the alternating current generated external to the system with respect to a time reference; each generator control unit associated with a generator generating a synchronization count which varies between the minimum and the maximum over each period of a cycle of alternating current generated by the generator controlled by the associated generator control unit; and each generator control unit associated with a generator adjusting at least the phase of alternating current generated by the generator as a function of a difference between the received synchronization count and the synchronization count generated by the generator control unit to cause the alternating current generated by the generator to be locked at least in phase to the alternating current generated external to the generating system.
Claim 48
Independent Claim
211 words
A method of at least phase locking alternating current generated by at least one alternating current generator with each generator having an associated generator control unit for controlling the generator to alternating current generated external to a generating system comprising: periodically transmitting a synchronization count from a master control unit to each generator control unit in the system with the synchronization count varying from a minimum to a maximum during each cycle of the alternating current generated external to the generating system and being proportional to a phase of the alternating current generated external to the system with respect to a time reference; each generator control unit associated with a generator generating a synchronization count which varies between the minimum and the maximum over each period of a cycle of alternating current generated by the generator controlled by the associated generator control unit; and each generator control unit associated with a generator adjusting at least the phase of alternating current generated by the generator as a function of a difference between the received synchronization count and the synchronization count generated by the generator control unit to cause the alternating current generated by the generator to be locked at least in phase to the alternating current generated external to the generating system.
Claim 49
Dependent Claim
48 words
A method in accordance with claim 44 further comprising: adjusting the frequency of alternating current generated by each generator as a function of the correction count to cause the alternating current generated external to the generating system and at least one generator and to be locked in frequency.
Claim 50
Dependent Claim
27 words
A method in accordance with claim 45 wherein: the synchronization count is transmitted asynchronously with respect to a frequency of alternating current generated external to the system.
Claim 51
Dependent Claim
129 words
In an alternating current generating system having at least one slave generator with each slave generator being controlled by an associated slave generator control unit with alternating current generated by each slave generator being locked at least in phase to alternating current generated by a master generator controlled by a master generator control unit, the master generator control unit comprising: a master count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of alternating current generated by the master generator with the synchronization count being proportional at any time during a cycle of the generated alternating current to a phase of electrical current being generated by the master generator with respect to a time reference; and means for generating the time reference.
Claim 52
Dependent Claim
129 words
In an alternating current generating system having at least one slave generator with each slave generator being controlled by an associated slave generator control unit with alternating current generated by each slave generator being locked at least in phase to alternating current generated by a master generator controlled by a master generator control unit, the master generator control unit comprising: a master count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of alternating current generated by the master generator with the synchronization count being proportional at any time during a cycle of the generated alternating current to a phase of electrical current being generated by the master generator with respect to a time reference; and means for generating the time reference.
Claim 53
Dependent Claim
67 words
A master control unit in accordance with claim 47 wherein: the means for generating the time reference is a reference clock for producing output pulses on an output to the master unit generator defining the period of each cycle of the alternating current with the clock pulses also being applied to a frequency control which controls a frequency of the alternating current produced by the master generator.
Claim 54
Dependent Claim
137 words
In an alternating current generating system having at least one slave generator with each slave generator being controlled by an associated slave generator control unit with alternating current generated by each slave generator being locked at least in phase to alternating current generated by a master generator controlled by a master generator control unit, each slave generator control unit comprising: a slave synchronization count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of alternating current generated by the associated slave generator with the synchronization count of each slave count generator at any time during a cycle of alternating current generated by the associated slave generator being proportional to the phase of the generated alternating current measured with respect to a time reference; and means for generating the time reference.
Claim 55
Dependent Claim
137 words
In an alternating current generating system having at least one slave generator with each slave generator being controlled by an associated slave generator control unit with alternating current generated by each slave generator being locked at least in phase to alternating current generated by a master generator controlled by a master generator control unit, each slave generator control unit comprising: a slave synchronization count generator for generating a synchronization count varying from a minimum to a maximum during each cycle of alternating current generated by the associated slave generator with the synchronization count of each slave count generator at any time during a cycle of alternating current generated by the associated slave generator being proportional to the phase of the generated alternating current measured with respect to a time reference; and means for generating the time reference.
Claim 56
Dependent Claim
223 words
A slave control unit in accordance with claim 49 wherein each slave generator control unit further comprises: means for receiving a synchronization count transmitted from the master generator control unit which varies from a minimum to a maximum during each cycle of alternating current generated by the master generator with the synchronization count of the master generator control unit being proportional at any time during a cycle of the generated alternating current to a phase of electrical current being generated by the master generator with respect to a time reference and for generating an interrupt pulse in response to receipt of the synchronization count; an enable input to which is applied the interrupt pulse to sample the synchronization count of the slave count generator, a clock input to which is applied clock pulses which are counted by the slave count generator, the pulses having a frequency higher than a frequency of the alternating current generated by the slave generator; and wherein each slave generator control unit has a processor for generating a correction count which is a function of a difference between the compared counts; and each slave generator control unit has a controller for adjusting at least the phase of the electrical current generated by the slave generator controlled by the slave generator control unit as a function of the correction count.
Claim 57
Dependent Claim
40 words
A slave control unit in accordance with claim 50 wherein: the slave generator control unit controller also locks a frequency of alternating current generated by each slave generator to a frequency of the alternating current generated by the master generator.
References Cited (Backward Citations)
US3832713A
Cited
US3887820A
Cited
US4260947A
Cited
US4231029A
Cited
US4308465A
Cited
US4598257A
Cited
US4707142A
Cited
US4728806A
Cited
US4754161A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-16 | 1993-04-17 | 1993-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-16 | 1997-04-17 | 1997-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-16 | 2001-04-17 | 2001-10-17 | $7700.00 | Window Closed / Lapsed |