US4566868A
Expired / Lapsed
US
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Pressure source
Assignee: GEOTECHNICAL DIGITAL SYSTEMS Ltd
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Filing: 1981-09-11
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Granted: 1986-01-28
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Expires: 2001-09-11
Abstract
Abstract A liquid pressure source, e.g. for use in soil mechanics laboratories, has a piston-cylinder unit driven by a stepper motor: a pressure transducer indicates the liquid pressure and a digital feedback control unit responds to generate stepping pulses to maintain a desired pressure. A step counter can be included to provide an accurate indication of volume change, and backlash compensation may be provided by arranging that the counter, following a direction change, ignores motor steps until a pressure change occurs.
Inventors
- 👤 Bruce K. Menzies
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 01:31
CPC Classifications
F; F04; F04B; F04B35/00; F04B35/04; F04B49/00; F04B49/08; G; G05; G05D; G05D16/00; G05D16/20; G05D16/2006; G05D16/2066
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
235 words
A liquid pressure source comprising a piston and cylinder unit embodying a cylinder having at one end a pressure outlet, a piston in the cylinder movable reciprocally therein to generate a pressure at said outlet, a recirculating ball screw assembly at the other end of the cylinder, a threaded piston rod connected at one end to the piston, said threaded piston rod extending from the piston through said recirculating ball screw at said other end of the cylinder, a stepping motor, means non-rotatably supporting the stepping motor for rectilinear movement relative to the cylinder, said stepping motor including a rotor, means connecting the rotor to said piston rod such that rotation of the piston rod by way of the recirculating ball screw effects rectilinear movement of the stepping motor and piston, a pressure transducer at said one end of the cylinder operable to produce electric signals indicative of the fluid pressure generated at the outlet of the cylinder, means for generating signals representing the desired pressure, a digital feedback control means responsive to said transducer signals and to the signals representing said desired pressure to provide said stepping impulses to said stepping motor in a sense such as to reduce the difference between the actual and the desired pressure and a volume charge counter means coupled to said digital feedback control means to count said stepping pulses so as to indicate the change in volume.
Claim 2
Dependent Claim
235 words
A liquid pressure source comprising a piston and cylinder unit embodying a cylinder having at one end a pressure outlet, a piston in the cylinder movable reciprocally therein to generate a pressure at said outlet, a recirculating ball screw assembly at the other end of the cylinder, a threaded piston rod connected at one end to the piston, said threaded piston rod extending from the piston through said recirculating ball screw at said other end of the cylinder, a stepping motor, means non-rotatably supporting the stepping motor for rectilinear movement relative to the cylinder, said stepping motor including a rotor, means connecting the rotor to said piston rod such that rotation of the piston rod by way of the recirculating ball screw effects rectilinear movement of the stepping motor and piston, a pressure transducer at said one end of the cylinder operable to produce electric signals indicative of the fluid pressure generated at the outlet of the cylinder, means for generating signals representing the desired pressure, a digital feedback control means responsive to said transducer signals and to the signals representing said desired pressure to provide said stepping impulses to said stepping motor in a sense such as to reduce the difference between the actual and the desired pressure and a volume charge counter means coupled to said digital feedback control means to count said stepping pulses so as to indicate the change in volume.
Claim 3
Dependent Claim
38 words
A liquid pressure source according to claim 1, in which the control means is adapted in a selectable alternative mode of operation to provide stepping pulses in response to an electrical input representative of a desired volume change.
Claim 4
Dependent Claim
52 words
A liquid pressure source according to claim 1, in which the feedback control means includes means for computing whether or how many steps are required to be made, and in which, following a change in motor direction, the computation is suspended until a predetermined pressure change is detected by the pressure transducer.
Claim 5
Dependent Claim
22 words
A liquid pressure source according to claim 3, in which said predetermined pressure change increases on successive reversals of the motor direction.
Claim 6
Dependent Claim
58 words
A liquid pressure source according to claim 1, in which the feedback control means includes means for computing whether or how many steps are required to be made, the computing means being arranged to operate only when a predetermined number of motor steps have taken place since the last change in the direction of rotation of the motor.
Claim 7
Dependent Claim
57 words
A liquid pressure source according to claim 1 wherein the feedback control means includes means for computing whether or how many steps are required to be made, the computing means being arranged to operate only when a predetermined number of motor steps have taken place since the last change in the direction of rotation of the motor.
Claim 8
Dependent Claim
30 words
A liquid pressure source according to claim 1 wherein, following a change in motor direction, the computation is suspended until a predetermined pressure change is detected by the pressure transducer.
Claim 9
Dependent Claim
22 words
A liquid pressure source according to claim 7, in which said predetermined pressure change increases on successive reversals of the motor direction.
Claim 10
Dependent Claim
77 words
A liquid pressure source according to claim 1 comprising means arranged in operation when a motor step has been effected to compute the change between the transducer signal before and after the step and to supress further motor steps unless or until the difference between the target and transducer signals is least equal to half the said change and whenever said difference exceeds said change to a predetermined extent to generate a plurality of motor stopping pulser.
Claim 11
Dependent Claim
199 words
A liquid pressure source comprising a cylinder having at one end a pressure outlet, a piston in the cylinder, a threaded piston rod connected to the piston and extended therefrom through the other end of the cylinder, a stepping motor, means non-rotatably supporting the stepping motor for rectilinear movement relative to the cylinder, said stepping motor including a rotor, means connecting the rotor to the piston rod such that rotation of the rotor effects rotation of the piston rod, a ball screw mechanism at said other end of the cylinder through which the threaded piston rod extends operable in response to rotation of the piston rod to effect rectilinear movement of the stepping motor and the piston relative to the cylinder, a pressure transducer at said one end of the cylinder operable to produce an electric signal indicative of the fluid pressure at the outlet of the cylinder, means for generating a signal responsive to the desired pressure and digital feedback control means representing the transducer signal and to the signal representing the desired pressure to provide stepping pulses to the stepping motor in a sense such as to reduce the difference between the actual and the desired pressure.
Claim 12
Dependent Claim
199 words
A liquid pressure source comprising a cylinder having at one end a pressure outlet, a piston in the cylinder, a threaded piston rod connected to the piston and extended therefrom through the other end of the cylinder, a stepping motor, means non-rotatably supporting the stepping motor for rectilinear movement relative to the cylinder, said stepping motor including a rotor, means connecting the rotor to the piston rod such that rotation of the rotor effects rotation of the piston rod, a ball screw mechanism at said other end of the cylinder through which the threaded piston rod extends operable in response to rotation of the piston rod to effect rectilinear movement of the stepping motor and the piston relative to the cylinder, a pressure transducer at said one end of the cylinder operable to produce an electric signal indicative of the fluid pressure at the outlet of the cylinder, means for generating a signal responsive to the desired pressure and digital feedback control means representing the transducer signal and to the signal representing the desired pressure to provide stepping pulses to the stepping motor in a sense such as to reduce the difference between the actual and the desired pressure.
Claim 13
Dependent Claim
25 words
A liquid pressure source according to claim 10, in which the pressure transducer is an analogue pressure transducer followed by an analogue to digital converter.
Claim 14
Dependent Claim
66 words
A liquid pressure source according to claim 10 wherein said control means includes oscillation inhibiting means adapted, when a predetermined degree of motor movement has been effected, to compute the change between the transducer signal before and after the said movement, and to suppress further movement unless or until the difference between the target and transducer signals is at least equal to half the said change.
Claim 15
Dependent Claim
49 words
A liquid pressure source according to claim 12, in which the feedback control means additionally includes means arranged, whenever the said difference exceeds said change to a predetermined extent, to generate a plurality of motor stepping pulses at a rate greater than that at which single pulses are generated.
Claim 16
Dependent Claim
156 words
A liquid pressure source comprising a piston cylinder unit, a stepping motor arranged to actuate the piston cylinder unit by a predetermined amount for each of a series of received stepping pulses, a pressure transducer arranged to product an electrical signal indicating liquid pressure at the output of the piston cylinder unit, digital feedback control means responsive to the transducer signal and to signals representing the desired target pressure to provide said stepping pulses to said stepping motor in a sense such as to reduce the difference between the actual and the desired pressure, volume change counter means coupled to said digital feedback control means to count said stepping pulses so as to indicate change in volume, said feedback control means including backlash compensating means which, following a change in motor direction, applies pulses to the motor but not to the volume change counter means until a predetermined pressure change is detected by the pressure transducer.
Claim 17
Dependent Claim
156 words
A liquid pressure source comprising a piston cylinder unit, a stepping motor arranged to actuate the piston cylinder unit by a predetermined amount for each of a series of received stepping pulses, a pressure transducer arranged to product an electrical signal indicating liquid pressure at the output of the piston cylinder unit, digital feedback control means responsive to the transducer signal and to signals representing the desired target pressure to provide said stepping pulses to said stepping motor in a sense such as to reduce the difference between the actual and the desired pressure, volume change counter means coupled to said digital feedback control means to count said stepping pulses so as to indicate change in volume, said feedback control means including backlash compensating means which, following a change in motor direction, applies pulses to the motor but not to the volume change counter means until a predetermined pressure change is detected by the pressure transducer.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-01-27 | 1989-07-29 | 1990-01-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-01-27 | 1993-07-29 | 1994-01-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-01-27 | 1997-07-29 | 1998-01-28 | $7700.00 | Window Closed / Lapsed |