US3579988A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydrostatic transmission control system
Assignee: NAT RES DEV
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Filing: 1969-03-24
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Granted: 1971-05-25
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Expires: 1989-03-24
Abstract
Abstract A hydrostatic pump-and-motor transmission system, e.g. for a vehicle, in which the pump and the motor can have their displacement volumes varied in discrete steps to give a number of predetermined fixed ratios. The pump is either a swashplate or variable eccentric pump adjustable to and between predetermined settings, or, a plurality of fixed displacement pumps switchable on the hydraulic side between, e.g. small pump alone, large pump alone, both pumps together. The motor is either a multibank piston/cylinder motor with valving arrangements for cutting out one bank of cylinders from the fluid supply, or several separate motors - some disconnectable. A hand selector sets up the various conditions e.g. three alternative pump displacement values with the motor at maximum displacement and two conditions with the motor at minimum displacement and the pump at two of the three pump displacement values. Instead of using multibank motors and cutting out one bank, four motors on four wheels of a vehicle may give the maximum motor displacement condition, the motors of either the front or the rear wheels being cut off from the pump, for the minimum motor displacement condition.
Inventors
- 👤 Donald Firth
- 👤 Roger Harvey Yorke Hancock
- 👤 James Mccallum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:24
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/38; F16H61/40; F16H61/46; F16H61/462; F16H61/66; F16H2061/6604; F16H2061/6615; F16H2061/6616
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
205 words
A hydrostatic transmission system in which positive displacement pumping means, adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement in discrete steps of said pumping means and said motor means, said control means being operable first to increase the displacement of the pumping means in a number of discrete steps in succession, and then to decrease the displacement of the motor means in at least one discrete step, whereby the transmission ratio is increased, and in which the displacement of the motor means may thereafter be first increased, followed by the decrease, in a number of discrete steps, of the displacement of the pumping means, whereby the transmission ratio is lowered, the control means being further operative, when a change in the displacement of the motor means takes place, to change the displacement of the pumping means by a smaller amount in the same direction, whereby the overall change in the transmission ratio, on such change in the displacement of the motor means, is reduced as compared with the change of overall ratio which would result from changing only the displacement of the motor means.
Claim 2
Dependent Claim
205 words
A hydrostatic transmission system in which positive displacement pumping means, adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement in discrete steps of said pumping means and said motor means, said control means being operable first to increase the displacement of the pumping means in a number of discrete steps in succession, and then to decrease the displacement of the motor means in at least one discrete step, whereby the transmission ratio is increased, and in which the displacement of the motor means may thereafter be first increased, followed by the decrease, in a number of discrete steps, of the displacement of the pumping means, whereby the transmission ratio is lowered, the control means being further operative, when a change in the displacement of the motor means takes place, to change the displacement of the pumping means by a smaller amount in the same direction, whereby the overall change in the transmission ratio, on such change in the displacement of the motor means, is reduced as compared with the change of overall ratio which would result from changing only the displacement of the motor means.
Claim 3
Dependent Claim
101 words
A hydrostatic transmission system in which positive displacement pumping means, adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the pumping means or the motor means, and said motor means comprising at least one motor having two groups of piston and cylinder combinations, each cooperating with cam means, and with valve means for disconnecting one group of piston and cylinder combinations from the pumping means to reduce the displacement of the motor.
Claim 4
Dependent Claim
101 words
A hydrostatic transmission system in which positive displacement pumping means, adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the pumping means or the motor means, and said motor means comprising at least one motor having two groups of piston and cylinder combinations, each cooperating with cam means, and with valve means for disconnecting one group of piston and cylinder combinations from the pumping means to reduce the displacement of the motor.
Claim 5
Dependent Claim
68 words
A transmission system as claimed in claim 2, and including means for retaining liquid leaking past the pistons in the space between the pistons and the cam means and for regulating the pressure in such space to a value a little above atmospheric pressure whereby the pistons of the piston/cylinder group put out of communication with the pumping means are held out of contact with the cam means.
Claim 6
Dependent Claim
174 words
A hydrostatic transmission system in which positive displacement pumping means, adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the pumping means or the motor means, and with a bypass valve capable of interconnecting the high-pressure and the low-pressure lines from the pumping means, said bypass valve having an obturator normally engaging a seating to block the said interconnection, and piston/cylinder means coupled to the obturator having a larger effective piston area on one side acting to close the obturator upon said seating, and a smaller piston area on the other side acting to lift the obturator from said seating, a restrictor orifice permitting flow from one side of the piston to the other whereby the obturator is normally held to its seating, and including means for exhausting the space on the large area side of the piston to lift the obturator off its seating.
Claim 7
Dependent Claim
174 words
A hydrostatic transmission system in which positive displacement pumping means, adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the pumping means or the motor means, and with a bypass valve capable of interconnecting the high-pressure and the low-pressure lines from the pumping means, said bypass valve having an obturator normally engaging a seating to block the said interconnection, and piston/cylinder means coupled to the obturator having a larger effective piston area on one side acting to close the obturator upon said seating, and a smaller piston area on the other side acting to lift the obturator from said seating, a restrictor orifice permitting flow from one side of the piston to the other whereby the obturator is normally held to its seating, and including means for exhausting the space on the large area side of the piston to lift the obturator off its seating.
Claim 8
Dependent Claim
78 words
A transmission sYstem as claimed in claim 4 wherein said exhausting means comprises a valve resiliently urged to an open, or exhausting, condition and with means for closing the valve such means comprising an auxiliary pump coupled to the said pumping means, a piston/cylinder combination connected to the output of the said pump, and coupled mechanically to the said valve, the whole being so adjusted that the valve is closed when the said pump reaches a predetermined speed.
Claim 9
Dependent Claim
195 words
A hydrostatic transmission system in which positive displacement pumping means adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the said pumping means or the said motor means, the control means being operable first to increase the displacement of the pumping means in a number of discrete steps in succession and then to decrease the displacement of the motor means in at least one discrete step, whereby the transmission ratio is increased, whereafter the displacement of the motor means is first increased, followed by the decrease, in a number of discrete steps, of the displacement of the pumping means whereby the transmission ratio is lowered, said motor means comprising at least four motors each directly coupled to a wheel of a vehicle, and means for reducing the displacement of the motor means comprising valve means for disconnecting from the pumping means the motors coupled to wheels at one end of the vehicle, whereby the aggregate displacement of the motors connected to the pumping means is reduced.
Claim 10
Dependent Claim
195 words
A hydrostatic transmission system in which positive displacement pumping means adapted for connection to a prime mover, supplies fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the said pumping means or the said motor means, the control means being operable first to increase the displacement of the pumping means in a number of discrete steps in succession and then to decrease the displacement of the motor means in at least one discrete step, whereby the transmission ratio is increased, whereafter the displacement of the motor means is first increased, followed by the decrease, in a number of discrete steps, of the displacement of the pumping means whereby the transmission ratio is lowered, said motor means comprising at least four motors each directly coupled to a wheel of a vehicle, and means for reducing the displacement of the motor means comprising valve means for disconnecting from the pumping means the motors coupled to wheels at one end of the vehicle, whereby the aggregate displacement of the motors connected to the pumping means is reduced.
Claim 11
Dependent Claim
189 words
A hydrostatic transmission system in which positive displacement pumping means adapted for connection to a prime mover, supplied fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the said pumping means or the said motor means, the control means being operable first to increase the displacement of the pumping means in a number of discrete steps in succession and then to decrease the displacement of the motor means in at least one discrete step, whereby the transmission ratio is increased, whereafter the displacement of the motor means is first increased, followed by the decrease, in a number of discrete steps, of the displacement of the pumping means, whereby the transmission ratio is lowered, the control means comprising a motor control actuator coupled to the motor means to change the displacement thereof and a hand-operated selector operable to any one of a number of predetermined settings in at least one of which settings valving passages, associated with the selector, control the flow of pressurized fluid to the motor actuator.
Claim 12
Dependent Claim
189 words
A hydrostatic transmission system in which positive displacement pumping means adapted for connection to a prime mover, supplied fluid under pressure to positive displacement motor means adapted for connection to a load, with control means for varying the displacement, in discrete steps, of at least one of them, the said pumping means or the said motor means, the control means being operable first to increase the displacement of the pumping means in a number of discrete steps in succession and then to decrease the displacement of the motor means in at least one discrete step, whereby the transmission ratio is increased, whereafter the displacement of the motor means is first increased, followed by the decrease, in a number of discrete steps, of the displacement of the pumping means, whereby the transmission ratio is lowered, the control means comprising a motor control actuator coupled to the motor means to change the displacement thereof and a hand-operated selector operable to any one of a number of predetermined settings in at least one of which settings valving passages, associated with the selector, control the flow of pressurized fluid to the motor actuator.
Claim 13
Dependent Claim
52 words
A transmission system as claimed in claim 7, and including other valving passages associated with the selector controlling the flow of pressurized fluid to an actuator coupled to the pumping means to change the displacement thereof in discrete steps each corresponding to one of the said predetermined settings of the said selector.
Claim 14
Dependent Claim
114 words
A transmission system as claimed in claim 7, and including a mechanical linkage from the said selector to a servo valve controlling the displacement of the pumping means in discrete steps each corresponding to one of the said predetermined settings of the selector, valving passages associated with the selector to control flow of pressurized fluid to an actuator adapted for changing the displacement of the motor means and a mechanical connection from the actuator to a fulcrum of the linkage for the servo valve to operate the servo valve in a direction to reduce the displacement of the pumping means on operation of the said actuator to reduce the displacement of the motor means.
Claim 15
Dependent Claim
62 words
A transmission system as claimed in claim 7 comprising a dump valve operable to interconnect the high-pressure and low-pressure fluid conduits from the pumping means and valving passages controlled by the selector operable to actuate the dump valve to interconnect the said conduits when the selector is at a setting intermediate between at least one adjacent pair of the said predetermined settings.
Claim 16
Dependent Claim
95 words
A transmission system as claimed in claim 2 in which the motor means comprises a motor of the cam operated ball-piston type having two banks of cylinders radially extending through a cylinder block from an internal pintle valve towards an encircling cam for each bank of cylinders, with means for translating the said pintle valve axially of the cylinder block to move supply ports of the valve and of one bank of cylinders out of register with one another whilst leaving the supply ports of the valve and of the other bank of cylinders undisturbed.
Claim 17
Dependent Claim
93 words
A transmission system as claimed in claim 11 having an enclosure surrounding the zone of engagement of the pistons with the cams, and a pressure relief valve maintaining the pressure in the said zone above atmospheric pressure in the presence, in the said zone, of working fluid leaking past the pistons, whereby, when a bank of cylinders is cut off from the supply of pressure fluid from the pumping means, on translation of the pintle valve as aforesaid, the pistons are held out of engagement with the cam with which they normally cooperate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-24 | 1974-11-23 | 1975-05-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-24 | 1978-11-23 | 1979-05-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-24 | 1982-11-23 | 1983-05-25 | $7700.00 | Window Closed / Lapsed |