Patent US4987823A successfully refreshed from Google Patents.
US4987823A
Expired / Lapsed
US
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Location of piston position using radio frequency waves
Assignee: Vickers Inc
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Filing: 1989-07-10
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Granted: 1991-01-29
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Expires: 2009-07-10
Abstract
Abstract An electrohydraulic control system includes an actuator having a cylinder and a piston variably positionable therewithin. An electrohydaulic valve is responsive to valve control signals for coupling the actuator to a source of hydraulic fluid. A coaxial transmission line extends through the actuator, and includes an outer conductor formed by the actuator cylinder and a center conductor operatively coupled to the piston, such that length of the coaxial transmission line is effectively directly determined by position of the piston within the cylinder. An rf generator is coupled to the coaxial transmission line for launching rf energy therewithin, and valve control electronics is responsive to rf energy reflected by the coaxial transmission line for indicating position of the piston within the cylinder and generating electronic control signals to the valve. A second coaxial transmission line of fixed length is connected the valve and actuator so that the hydraulic fluid flows therethrough. The rf energy is launched in the second transmission line and generator frequency is controlled as a function of phase angle at the second transmission line.
Inventors
- 👤 Lael B. Taplin
- 👤 Calman S. Sagady
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:57
CPC Classifications
F; F15; F15B; F15B15/00; F15B15/20; F15B15/28; F15B15/2815; F15B15/2869
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
168 words
An electrohydraulic control system that includes an actuator having a cylinder and a piston variably positionable therewithin, electrohydraulic valve means responsive to valve control signals for coupling said actuator to a source of hydraulic fluid, and means responsive to position of said piston within said cylinder for generating said valve control signals, characterized in that said position-responsive means comprises: a coaxial transmission line extending within said actuator and including an outer conductor formed by said cylinder and a center conductor operatively coupled to said piston such that length of said coaxial transmission line is determined directly by position of said piston within said cylinder, means for launching rf energy within said coaxial transmission line, said energy-launching means including an rf generator, and a stub antenna coupled to said generator and extending radially into said cylinder for capacitively coupling rf energy from said generator to said center conductor, and means responsive to rf energy reflected by said coaxial transmission line for indicating position of said piston within said cylinder.
Claim 2
Dependent Claim
168 words
An electrohydraulic control system that includes an actuator having a cylinder and a piston variably positionable therewithin, electrohydraulic valve means responsive to valve control signals for coupling said actuator to a source of hydraulic fluid, and means responsive to position of said piston within said cylinder for generating said valve control signals, characterized in that said position-responsive means comprises: a coaxial transmission line extending within said actuator and including an outer conductor formed by said cylinder and a center conductor operatively coupled to said piston such that length of said coaxial transmission line is determined directly by position of said piston within said cylinder, means for launching rf energy within said coaxial transmission line, said energy-launching means including an rf generator, and a stub antenna coupled to said generator and extending radially into said cylinder for capacitively coupling rf energy from said generator to said center conductor, and means responsive to rf energy reflected by said coaxial transmission line for indicating position of said piston within said cylinder.
Claim 3
Dependent Claim
63 words
The system set forth in claim 1 wherein said rf generator has a frequency control input, and wherein said energy launching means further includes means responsive to dielectric properties of said hydraulic fluid within said cylinder for providing a control signal to said frequency control input of said generator to automatically compensate frequency of said rf energy for variations in said dielectric properties.
Claim 4
Dependent Claim
39 words
The system set forth in claim 1 wherein said energy-launching means further comprises at least one stub tuner extending radially into said cylinder adjacent to said antenna for matching impedance of said coaxial transmission line to said energy-launching means.
Claim 5
Dependent Claim
28 words
The system set forth in claim 3 wherein said at least one stub tuner comprises a first tuning screw diametrically opposed to said stub antenna across said cylinder.
Claim 6
Dependent Claim
37 words
The system set forth in claim 4 wherein said at least one stub tuner further comprises second and third tuning screws positioned as a pair diametrically opposed to each other across said cylinder adjacent to said antenna.
Claim 7
Dependent Claim
20 words
The system set forth in claim 5 wherein all of said first, second and third tuning screws are radially adjustable.
Claim 8
Dependent Claim
22 words
The system set forth in claim 6 wherein said second and third tuning screws are positioned between said antenna and said piston.
Claim 9
Dependent Claim
46 words
The system set forth in claim 1 wherein said piston has an axial bore formed therein, and wherein said center conductor comprises means fixedly carried within said cylinder and slidably extending into said bore, said cylinder being electrically coupled to said fixedly-carried means within said bore.
Claim 10
Dependent Claim
67 words
The system set forth in claim 8 wherein said rf generator has a frequency control input, and wherein said energy-launching further includes means responsive to dielectric properties of said hydraulic fluid within said cylinder for providing a control signal to said frequency control input of said generator to automatically compensate frequency of said rf energy for variations in said dielectric properties so that operating wavelength remains constant.
Claim 11
Dependent Claim
88 words
The system set forth in claim 9 wherein said fixedly-carried means comprises a second coaxial transmission line that includes a hollow tube forming said inner conductor electrically coupled to said piston within said bore and a conductive element fixedly suspended within said tube, means in said tube for feeding hydraulic fluid within said cylinder through said tube, means for coupling said generator to said conductive element, and means responsive to phase angle of rf energy reflected at said second coaxial transmission line for providing said frequency control signal.
Claim 12
Dependent Claim
40 words
The system set forth in claim 1 wherein said piston is affixed to a piston rod extending from said cylinder, and wherein said stub antenna is positioned adjacent to said piston rod such that said rod forms said inner conductor.
Claim 13
Dependent Claim
63 words
The system set forth in claim 11 wherein said rf generator having a frequency control input, and wherein said energy launching means further includes means responsive to dielectric properties of said hydraulic fluid within said cylinder for providing a control signal to said frequency control input of said generator to automatically compensate frequency of said rf energy for variations in said dielectric properties.
Claim 14
Dependent Claim
77 words
The system set forth in claim 12 further comprising a second coaxial transmission line of fixed length and including a hollow outer conductor and an inner conductor suspended within said hollow outer conductor, means for feeding hydraulic fluid through said second coaxial transmission line, means for coupling said generator to said second coaxial transmission line, and means responsive to phase angle of rf energy reflected at said second coaxial transmission line for providing said frequency control signal.
Claim 15
Dependent Claim
173 words
An electrohydraulic control system that includes an actuator having a cylinder and a piston variably positionable therewithin, electrohydraulic valve means responsive to valve control signals for coupling said actuator to a source of hydraulic fluid, and means responsive to position of said piston within said cylinder for generating said valve control signals, characterized in that said position-responsive means comprises: an rf generator having a frequency control input, first and second coaxial transmission lines, said first coaxial transmission line being operatively coupled to said actuator such that length thereof varies as a function of position of said piston within said cylinder and said second coaxial transmission line having a fixed length, means for feeding said hydraulic fluid through said second transmission line such that impedance characteristics thereof vary with dielectric properties of said fluid, means for coupling output of said generator to said first and second coaxial transmission lines, and means responsive to phase angle of rf energy reflected at said second coaxial transmission line for providing said frequency control input to said generator.
Claim 16
Dependent Claim
173 words
An electrohydraulic control system that includes an actuator having a cylinder and a piston variably positionable therewithin, electrohydraulic valve means responsive to valve control signals for coupling said actuator to a source of hydraulic fluid, and means responsive to position of said piston within said cylinder for generating said valve control signals, characterized in that said position-responsive means comprises: an rf generator having a frequency control input, first and second coaxial transmission lines, said first coaxial transmission line being operatively coupled to said actuator such that length thereof varies as a function of position of said piston within said cylinder and said second coaxial transmission line having a fixed length, means for feeding said hydraulic fluid through said second transmission line such that impedance characteristics thereof vary with dielectric properties of said fluid, means for coupling output of said generator to said first and second coaxial transmission lines, and means responsive to phase angle of rf energy reflected at said second coaxial transmission line for providing said frequency control input to said generator.
Claim 17
Dependent Claim
57 words
The system set forth in claim 14 wherein said phase-angle-responsive means comprises a phase detector having an output and having inputs coupled to said generator and to said second coaxial transmission line, and an integrator having an input coupled to said output of said phase detector and an output coupled to said control input of said generator.
Claim 18
Dependent Claim
35 words
The system set forth in claim 14 wherein said first coaxial transmission line comprises an outer conductor formed by said cylinder, and a center conductor extending through said cylinder and operatively coupled to said piston.
Claim 19
Dependent Claim
49 words
The system set forth in claim 16 wherein said piston has an axial bore formed therein, and wherein said center conductor comprises means fixedly carried within said cylinder and slidably extending into said bore, said cylinder being electrically coupled by said piston to said fixedly-carried means within said bore.
Claim 20
Dependent Claim
49 words
The system set forth in claim 17 wherein said fixedly-carried means comprises said second coaxial transmission line including a hollow tube forming said center conductor and a conductive element fixedly suspended within said tube, and means in said tube for feeding hydraulic fluid within said cylinder through said tube.
Claim 21
Dependent Claim
25 words
The system set forth in claim 16 wherein said piston is affixed to a piston rod extending from said cylinder and forming said center conductor.
Claim 22
Dependent Claim
40 words
The system set forth in claim 19 wherein said second coaxial transmission line includes a hollow outer conductor and an inner conductor suspended within said hollow outer conductor, and means for feeding hydraulic fluid through said second coaxial transmission line.
Claim 23
Dependent Claim
37 words
The system set forth in claim 16 wherein said energy-launching means comprises a stub antenna coupled to said generator and extending radially into said cylinder for capacitively coupling rf energy from said generator to said center conductor.
Claim 24
Independent Claim
117 words
A system for monitoring position of a piston within a cylinder that comprises: a coaxial transmission line, including an outer conductor formed by said cylinder and a center conductor operatively coupled to said piston such that length of said coaxial transmission line is determined directly by position of said piston within said cylinder, means for launching rf energy within said coaxial transmission line, said energy-launching means including an rf generator and a stub antenna coupled to said generator and extending radially into said cylinder for capacitively coupling rf energy from said generator to said center conductor, and means responsive to rf energy reflected by said coaxial transmission line for indicating position of said piston within said cylinder.
Claim 25
Independent Claim
117 words
A system for monitoring position of a piston within a cylinder that comprises: a coaxial transmission line, including an outer conductor formed by said cylinder and a center conductor operatively coupled to said piston such that length of said coaxial transmission line is determined directly by position of said piston within said cylinder, means for launching rf energy within said coaxial transmission line, said energy-launching means including an rf generator and a stub antenna coupled to said generator and extending radially into said cylinder for capacitively coupling rf energy from said generator to said center conductor, and means responsive to rf energy reflected by said coaxial transmission line for indicating position of said piston within said cylinder.
Claim 26
Dependent Claim
39 words
The system set forth in claim 22 wherein said energy-launching means further comprises at least one stub tuner extending radially into said cylinder adjacent to said antenna for matching impedance of said coaxial transmission line to said energy-launching means.
Claim 27
Dependent Claim
28 words
The system set forth in claim 23 wherein said at least one stub tuner comprises a first tuning screw diametrically opposed to said stub antenna across said cylinder.
Claim 28
Dependent Claim
37 words
The system set forth in claim 24 wherein said at least one stub tuner further comprises second and third tuning screws positioned as a pair diametrically opposed to each other across said cylinder adjacent to said antenna.
Claim 29
Dependent Claim
20 words
The system set forth in claim 25 wherein all of said first, second and third tuning screws are radially adjustable.
Claim 30
Dependent Claim
22 words
The system set forth in claim 26 wherein said second and third tuning screws are positioned between said antenna and said piston.
Claim 31
Dependent Claim
46 words
The system set forth in claim 22 wherein said piston has an axial bore formed therein, and wherein said center conductor comprises means fixedly carried within said cylinder and slidably extending into said bore, said cylinder being electrically coupled to said fixedly-carried means within said bore.
Claim 32
Dependent Claim
40 words
The system set forth in claim 22 wherein said piston is affixed to a piston rod extending from said cylinder, and wherein said stub antenna is positioned adjacent to said piston rod such that said rod forms said inner conductor.
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) | 1994-01-28 | 1994-07-30 | 1995-01-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-01-28 | 1998-07-30 | 1999-01-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-01-28 | 2002-07-30 | 2003-01-29 | $7700.00 | Window Closed / Lapsed |