EP3926179A1 - Surveillance de course de piston dans des cylindres de vérin hydrauliques - Google Patents

Surveillance de course de piston dans des cylindres de vérin hydrauliques Download PDF

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Publication number
EP3926179A1
EP3926179A1 EP21171189.0A EP21171189A EP3926179A1 EP 3926179 A1 EP3926179 A1 EP 3926179A1 EP 21171189 A EP21171189 A EP 21171189A EP 3926179 A1 EP3926179 A1 EP 3926179A1
Authority
EP
European Patent Office
Prior art keywords
piston
barrier
ram
cylinder
around
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21171189.0A
Other languages
German (de)
English (en)
Inventor
Patrick Byrne
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Burnside Autocyl Tullow Ltd
Original Assignee
Burnside Autocyl Tullow Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Burnside Autocyl Tullow Ltd filed Critical Burnside Autocyl Tullow Ltd
Publication of EP3926179A1 publication Critical patent/EP3926179A1/fr
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2869—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using electromagnetic radiation, e.g. radar or microwaves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/1423—Component parts; Constructional details
    • F15B15/1447—Pistons; Piston to piston rod assemblies
    • F15B15/1452—Piston sealings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/1423—Component parts; Constructional details
    • F15B15/1471—Guiding means other than in the end cap
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2215/00—Fluid-actuated devices for displacing a member from one position to another
    • F15B2215/30—Constructional details thereof

Definitions

  • the invention relates to monitoring of travel of a piston in a cylinder of a hydraulic ram.
  • electromagnetic waves are suitable for measuring the linear stroke of a piston.
  • the linear measurement of stroke can be determined within a hydraulic cylinder by sending an electromagnetic signal from an antenna/receiver that is mounted either on the full-bore side of the cylinder to reflect off the piston face or on the annular side of the cylinder to reflect off the rear of the piston.
  • Electromagnetic waves are chosen which have high penetration abilities through many non-metallic or non-conductive substances such as hydraulic oil.
  • the invention is directed towards achieving more accurate piston position measurement.
  • a fluid ram having a piston mounted in a cylinder, an electromagnetic wave sensor mounted to detect movement of the piston in its travel within the cylinder, characterized in that, the piston comprises an electromagnetic wave barrier of electrically conductive material mounted to the piston around at least part of its circumference to prevent passage of electromagnetic waves past the piston.
  • the fluid is hydraulic oil.
  • the barrier is of a material selected from aluminium, phosphor bronze, malleable cast iron, a metal alloy with impregnated graphite, and a conductive plastics material.
  • the barrier is annular, extending fully or substantially fully around the piston, and the barrier has a natural position lightly pressing against the cylinder internal surface.
  • the barrier has at least one circumferential gap.
  • the barrier gap is at a taper angle to longitudinal, for example about 45°.
  • the barrier has only one gap.
  • the barrier is mounted in a circumferential groove around the piston.
  • the barrier has a natural size providing a radial gap between the barrier and the groove base.
  • the radial gap between the barrier and the groove base has a radial dimension in the range of 0.5mm and 1.0mm.
  • the barrier is around the piston adjacent an end of the piston closest to the sensor.
  • the ram further comprises a seal around the piston at a location axially separate from the barrier, and a guide ring around the piston at a location axially separate from the barrier.
  • the piston comprises or supports, in order in the axial direction from the sensor, the barrier, a guide ring, a seal, and a guide ring.
  • the barrier is shorter in the longitudinal dimension than the groove, so that it is mounted in the groove in a manner to allow a gap on both longitudinal sides of the barrier and radially inwardly of the barrier, and the relative dimensions of the barrier and the groove are such as to allow flow of pressurized fluid in the longitudinal direction through said gaps and past the barrier to a piston seal.
  • the barrier is shorter than the groove in the longitudinal direction by a distance in the range of 0.5mm to 1.0mm.
  • a piston for mounting in a cylinder with an electromagnetic wave antenna sensor to detect movement of the piston in its travel within the cylinder, wherein the piston comprises an electromagnetic wave barrier of any example described herein mounted to the piston around at least part of its circumference to prevent passage of electromagnetic waves past the piston.
  • a fluid ram having a piston mounted in a cylinder, an electromagnetic wave antenna sensor mounted to detect movement of the piston in its travel within the cylinder, wherein the piston comprises an electromagnetic wave barrier mounted to the piston around at least part of its circumference to prevent passage of electromagnetic waves past the piston.
  • the fluid is in one example hydraulic oil.
  • the barrier is of an electrically conductive material, and preferably the barrier is of a material selected from aluminium, phosphor bronze, malleable cast iron, and a conductive plastics material.
  • the barrier is of aluminium.
  • the barrier is annular, extending fully or substantially fully around the piston.
  • the barrier is mounted in a circumferential groove in the piston.
  • the barrier has a natural size providing a gap between the barrier and the groove base, allowing radial movement of the barrier within the groove.
  • the gap has a radial dimension in the range of 0.5mm and 1.0mm.
  • the barrier has a natural position lightly pressing against the cylinder internal surface.
  • the barrier is around the piston adjacent an end of the piston closest to the sensor.
  • the ram further comprises a seal around the piston at a location axially separate from the barrier.
  • the ram further comprises a guide ring around the piston at a location axially separate from the barrier.
  • the piston comprises, in order in the axial direction from the sensor, the barrier, a guide ring, a seal, and a guide ring.
  • the barrier is shorter in the longitudinal dimension than the groove, so that it is mounted in the groove in a manner to have a gap on one or both longitudinal sides of the barrier.
  • the relative dimensions of the barrier and the groove are such as to allow flow of pressurized fluid in the longitudinal direction past the barrier to a piston seal.
  • the barrier is shorter in the longitudinal direction to allow a gap on both longitudinal sides in the range of 0.5mm to 1.0mm.
  • piston for mounting in a cylinder with an electromagnetic wave antenna sensor to detect movement of the piston in its travel within the cylinder, wherein the piston comprises an electromagnetic wave barrier mounted to the piston around at least part of its circumference to prevent passage of electromagnetic waves past the piston.
  • the piston may have any or all of the piston features set out above.
  • the ram has a sensor for very accurate measurement of longitudinal position of the piston face, the sensor having an electromagnetic wave transmitter and receiver in the end cap and facing the piston face. Accuracy of the measurements is excellent by ensuring that almost all radiation which is emitted is reflected back to the receiver.
  • the radiation comprises HF electromagnetic waves. Excellent accuracy is achieved despite the fact that the piston wall does not touch the cylinder wall in operation. This gap avoids damage to the cylinder wall surface, avoids failure of the high-pressure seals between the piston and the cylinder, and allows for thermal expansion and contraction.
  • a ram 1 has a cylinder 2 and an end cap or head 3.
  • a piston 4 is on a piston rod 5. This provides an annular space 6 around the rod 5 and behind the piston 4, and there is a space 12 in front of the piston face 8.
  • a distance sensor is in this example an electromagnetic transceiver antenna 10 is mounted in the cylinder head 3, arranged to direct HF electromagnetic waves towards the piston 4 face 8.
  • the antenna 10 comprises a metallic core, surrounded by an insulating plastics housing, and fitted with high pressure hydraulic seals. There is an annular electromagnetic wave barrier 30 around the piston 4, in the gap between the piston and the cylinder internal wall.
  • the dimensions of the cylinder and the piston are 95mm bore cylinder with 70mm rod.
  • the antenna 10 emits HF electromagnetic waves in the direction of the piston 4, the waves are then reflected back in the opposite direction by the piston 4 and the barrier 30.
  • the piston has front and rear guide rings 20 of type C10 phenolic resin size 95mm outer diameter x 89mm inner diameter x 20mm wide, which assist accurate travel on-axis. Between the guide rings 20 in the axial direction there is a high-pressure seal 21 of type Hallite 735 TM (95mm outer diameter x 80mm inner diameter x 11mm wide).
  • the barrier 30 is mounted in an annular groove 33 around the piston 4.
  • the barrier 30 is configured with an excess internal diameter so that a small gap 32 exists between the barrier's internal radially inwardly facing surface and the piston.
  • the seal 21 is a main pressure seal, which has the function of creating a hydraulic seal around the piston. It is of a material other than metal as it is in direct contact with the cylinder 2 inner surface and must not damage it and must not leak oil.
  • the seal 21 may be of rubber, polyurethane, or PTFE for example as is known in the art.
  • each guide ring 20 there are two guide rings 20, however in other examples there may be only one.
  • the function of the guide rings is to ensure that the (metal) piston 4 does touch the inner surface of the cylinder 2. They resist all side loads that are induced into the piston 4 from external forces, under both low and high temperatures.
  • the material of each guide ring 20 is such that it does not scratch or score the cylinder 2 surface, and they may for example be plastics or phenolic based materials, also as is known in the art.
  • the material of the barrier 30 is preferably a good electrical conductor. Examples are aluminium, phosphor bronze, malleable cast iron, a conductive plastics material, or a combination of any of these. Other suitable materials are Grey Cast Iron, also known as Flake Graphite Iron. In this example there is impregnated graphite to assist sliding with reduced friction against the cylinder bore. The impregnated graphite is considered to provide self-lubrication of the barrier. Aluminium is particularly preferred because of its mechanical and conductive properties. The configuration and material of the barrier is such that it will not damage the inner surface of the cylinder, and will substantially block electromagnetic waves without affecting operation of the high-pressure seal 21 and the guide rings 20.
  • the barrier 30 is of GD250/EN-GJL-250 to DIN EN 1561 (Grey cast Iron) material with a tensile strength of 250 to 350 N/mm2.
  • another preferred material is an iron alloy with impregnated graphite, one example being Flake Graphite Iron.
  • Fig. 1 Detail A
  • the barrier 30 is shown in more detail in Fig. 2 .
  • the dimensions of the barrier 30 are 95mm diameter x 3mm wide x 4mm deep (radial dimension).
  • the barrier is in the form of a ring which is not closed, having a circumferential gap 31 at a taper angle to longitudinal.
  • the gap is in this example 1.5mm in width.
  • the barrier 30 has a natural shape as illustrated with the gap 31 present. This outside diameter is very slightly larger than that of the cylinder bore, providing for a very small bias radially outwardly against the cylinder bore. If there are distortions arising from, for example, temperature changes, then the barrier 30 can contract slightly by closing the gap 31.
  • the barrier 30 is mounted in the groove 33 such that it has its own built-in bias to remain with a diameter equal to or greater than the cylinder bore.
  • the cylinder bore will vary in size due to tolerances, temperature change, and distortion among others. Therefore, the barrier 30 is able to change its outer diameter accordingly.
  • the space is of radial dimension between 0.5mm and 1mm. This space 32 is very advantageous to allow the free movement of the barrier 30 to accommodate cylinder and piston expansion and contraction, but this feature does not allow the electromagnetic waves to pass, as they reflect off the piston 4 side walls.
  • the gap 32 extends also in a preferred embodiment around one or both sides of the barrier in the longitudinal direction. This allows entry of pressurized fluid in a manner which does not allow localized build-up of pressure which might damage the barrier 30. It is most preferred to that the gap extend on both longitudinal sides, thereby allowing passage of pressurized fluid past the barrier and all of the way back to the high-pressure seal 21. This allows the seal to take the applied pressure, preventing damage to the barrier, and allowing it to perform its function of blocking electromagnetic waves.
  • the pressurized fluid has a path to the high-pressure seal 21, but this path does not allow any significant passage of electromagnetic waves, due to the orthogonal faces of the groove 32 and the barrier 30. It is preferred that the gap on the longitudinal sides is in the range of 0.5mm and 1.0mm. For illustration purposes, the size of the gap 32 is exaggerated in Fig. 1 .
  • a ram 100 has a cylinder 102, a piston 104, and a piston rod 105. Like parts are given the same reference numerals.
  • a sensor 110 is mounted on the inner face of a gland 115, emitting electromagnetic waves towards the rear side of the piston in an annular space 106.
  • the piston 104 has a pair of guide rings 20 and a high-pressure seal 21 similar to those of the ram 1.
  • the annular barrier 30 is in a piston circumferential groove 33 around the rear end of the piston 104. In this position it performs the same function as the barrier 30 in the ram 1, and the gap 32 is present for the same purpose, in this case allowing passage of pressurized fluid to the left as viewed in this drawing.
  • a barrier 200 has an axial length of 20mm, and two gaps 201 at 45°.
  • the material of the barrier 200 is in this example is an aluminium alloy, Grade 6082T6, with a tensile strength of 250 to 300 N/mm 2 .
  • the barrier 200 is in two pieces which interface together at the gaps 201 to make it easy to fit around the piston. In this case there isn't a spring effect toward a larger diameter to press against a cylinder bore, however because it is in two pieces the manufacturing tolerance can be very tight for optimum placement with an effect of brushing or rubbing along against the cylinder bore.
  • the arrangement of the barrier 30 (with only one gap, 31), is preferred because of the natural bias outwards.
  • the gaps 201 allow movement to cater for distortion and to provide a gap between the barrier and the piston for the same purpose as the gap 32 of the barrier 30.
  • the fact that the gaps 201 are at an angle to longitudinal, 45° in this case, means that electromagnetic waves can do not have a path in the longitudinal direction.
  • Any barrier irrespective of its longitudinal length, may be manufactured as one piece with a single cut and stretched over the piston for fitting.
  • the barrier may also perform the function of a guide ring, as the selected material already has bearing capabilities and load resisting properties, hence the selection of the high strength aluminium alloy grade 6082T6.
  • the material of the blocker or barrier may be a dynamic metallic or semi-metallic or metallic-composite suitable to block electromagnetic waves emitted by the sensor. It fulfils the function of blocking low to very high frequency microwaves, thus greatly reducing the extent of echoes re-entering the measuring space from the opposite side of the cylinder. It is estimated that the improvement in sensing accuracy is about 50% to 70%.
  • the blocker 30/200 also fulfils all dynamic mechanical/environmental requirements to be found inside pressurised hydraulic cylinders. It operates dynamically without affecting the performance of the hydraulic cylinder. It also allows the use of high frequency microwaves in the range S-band 2-4 as against medium frequency in the range L-band 1-2 thus increasing measuring accuracy to stroke lengths of beyond 6000 mm.
  • the invention solves the problem of sensor signals, such as an ultrahigh frequency signal, directed towards the face of the piston will also penetrate the piston seals and enter the annular side of the cylinder.
  • the invention prevents such a signal from being reflected by the inner wall of the gland, the cylinder rod, the cylinder wall and any other metallic features. Hence, it prevents such an errant HF from arising and hence prevents the consequent problem of such an errant signal passing back through the piston seals and creating an echo that disturbs the signal quality being received from the signal target (the piston face). It will be appreciated that this benefit is surprisingly achieved without affecting normal operation of the ram.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Electromagnetism (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Toxicology (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)
EP21171189.0A 2020-06-15 2021-04-29 Surveillance de course de piston dans des cylindres de vérin hydrauliques Pending EP3926179A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP20180110 2020-06-15

Publications (1)

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EP3926179A1 true EP3926179A1 (fr) 2021-12-22

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EP21171189.0A Pending EP3926179A1 (fr) 2020-06-15 2021-04-29 Surveillance de course de piston dans des cylindres de vérin hydrauliques

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4207800A (en) * 1978-11-02 1980-06-17 Homuth Kenneth C Single directional sealing piston ring
US5222429A (en) * 1992-05-11 1993-06-29 Caterpillar Inc. Piston assembly for a hydraulic cylinder
US5540137A (en) * 1994-10-11 1996-07-30 Caterpillar Inc. Electrical contacting in electromagnetic wave piston position sensing in a hydraulic cylinder
US5560278A (en) * 1994-10-11 1996-10-01 Caterpillar Inc. Hydraulic cylinder with an electrical contacting and sealing ring
DE102007020046A1 (de) * 2007-04-27 2008-10-30 Astyx Gmbh Abstandsmessvorrichtung und Verfahren zur Bestimmung eines Abstands und ein geeigneter Reflexionskörper
US20100011954A1 (en) * 2007-01-23 2010-01-21 Festo Ag & Co. Kg Actuator with Position Sensing Device
US8362788B2 (en) 2007-08-16 2013-01-29 Astyx Gmbh Double piston rod
US10436889B2 (en) 2013-11-11 2019-10-08 Astyx Gmbh Measuring device for determining a distance in a conducting structure

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4207800A (en) * 1978-11-02 1980-06-17 Homuth Kenneth C Single directional sealing piston ring
US5222429A (en) * 1992-05-11 1993-06-29 Caterpillar Inc. Piston assembly for a hydraulic cylinder
US5540137A (en) * 1994-10-11 1996-07-30 Caterpillar Inc. Electrical contacting in electromagnetic wave piston position sensing in a hydraulic cylinder
US5560278A (en) * 1994-10-11 1996-10-01 Caterpillar Inc. Hydraulic cylinder with an electrical contacting and sealing ring
US20100011954A1 (en) * 2007-01-23 2010-01-21 Festo Ag & Co. Kg Actuator with Position Sensing Device
DE102007020046A1 (de) * 2007-04-27 2008-10-30 Astyx Gmbh Abstandsmessvorrichtung und Verfahren zur Bestimmung eines Abstands und ein geeigneter Reflexionskörper
US8362788B2 (en) 2007-08-16 2013-01-29 Astyx Gmbh Double piston rod
US10436889B2 (en) 2013-11-11 2019-10-08 Astyx Gmbh Measuring device for determining a distance in a conducting structure

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