EP0301845B1 - Sensing system - Google Patents
Sensing system Download PDFInfo
- Publication number
- EP0301845B1 EP0301845B1 EP19880306940 EP88306940A EP0301845B1 EP 0301845 B1 EP0301845 B1 EP 0301845B1 EP 19880306940 EP19880306940 EP 19880306940 EP 88306940 A EP88306940 A EP 88306940A EP 0301845 B1 EP0301845 B1 EP 0301845B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- piston
- magnetic
- cylinder
- magnetic particles
- proportion
- 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.)
- Expired
Links
- 239000000696 magnetic material Substances 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 10
- 230000005291 magnetic effect Effects 0.000 claims description 7
- 229910000859 α-Fe Inorganic materials 0.000 claims description 7
- 239000006249 magnetic particle Substances 0.000 claims description 6
- 239000004033 plastic Substances 0.000 claims description 6
- 229920003023 plastic Polymers 0.000 claims description 6
- 229910052712 strontium Inorganic materials 0.000 claims description 4
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 4
- 239000004677 Nylon Substances 0.000 claims description 3
- 229920001778 nylon Polymers 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 claims description 2
- KPLQYGBQNPPQGA-UHFFFAOYSA-N cobalt samarium Chemical compound [Co].[Sm] KPLQYGBQNPPQGA-UHFFFAOYSA-N 0.000 claims description 2
- 239000003302 ferromagnetic material Substances 0.000 claims description 2
- 239000011159 matrix material Substances 0.000 claims description 2
- 229910000938 samarium–cobalt magnet Inorganic materials 0.000 claims description 2
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 239000000945 filler Substances 0.000 description 2
- BGPVFRJUHWVFKM-UHFFFAOYSA-N N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] Chemical compound N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] BGPVFRJUHWVFKM-UHFFFAOYSA-N 0.000 description 1
- 235000014676 Phragmites communis Nutrition 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- YWJUZWOHLHBWQY-UHFFFAOYSA-N decanedioic acid;hexane-1,6-diamine Chemical compound NCCCCCCN.OC(=O)CCCCCCCCC(O)=O YWJUZWOHLHBWQY-UHFFFAOYSA-N 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000002991 molded plastic Substances 0.000 description 1
- 229910000889 permalloy Inorganic materials 0.000 description 1
Images
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
- F15B15/2807—Position switches, i.e. means for sensing of discrete positions only, e.g. limit switches
Definitions
- This invention relates to non-contact positional sensing systems and has particular reference to non-contact positional sensing systems for a piston movable longitudinally within a cylinder.
- Non-contact positional sensing of pneumatic cylinder pistons is common practice. Normally, a permanent magnet is fitted to the piston and a reed switch or magnetically sensitive proximity sensors are attached to the cylinder barrel around its diameter.
- the magnets which have been used heretofor have been of the ring type in various materials dependent upon the required field strength. Typical examples have been Samarium Cobalt, Ceramic Ferrite or a plastics material with a ferrite filler.
- the magnetic ring may be located between split piston halves.
- DE-A 3 424 461 A similar positional sensing system for a piston movable longitudinally within a cylinder is described in DE-A 3 424 461.
- the purpose of the piston in the device of DE-A 3 424 461 is to concentrate the indicative force produced by an external coil, thereby providing positional information by way of feedback.
- the specifc material disclosed in DE-A 3 424 461, namely Permalloy is of the type that is very effective in concentrating magnetic flex but that cannot be permanently magnetisesd to any appreciable extent.
- a present non-contact positional sensing system for a piston movable longitudinally within a cylinder, in which the cylinder is formed of non-ferromagnetic material, there is a magnetically sensitive proximity sensor on the outside of the cylinder and the piston incorporates a permanent magnet, characterised in that the piston is formed substantially entirely from permanently magnetic material.
- the piston may be moulded from magnetic material comprising magnetic particles in a non-magnetic matrix of plastics material.
- the piston may be moulded by injection moulding.
- the proportion of magnetic particles is preferably as high as practical and may be in the range 60-90%, preferably 70-90% and more preferably 80-90% by weight of the magnetic material.
- the plastics material may be nylon and is preferably nylon 6/10.
- the magnetic material may be a strontium ferrite filler. There may be present 88% by weight of strontium ferrite material.
- the piston may be provided with non-magnetic seals which may be of conventional form.
- the seals may be cup seals or '0' ring seals or disc seals.
- a piston comprising a pair of moulded plastics halves 1, 2 which are conjoined together by an inner sleeve 3.
- the two halves 1 and 2 trap between them a ring magnet 4.
- the pair of seals 5, 6 seal the piston within a cylinder.
- the cylinder and proximity sensors are well known and conventional and are not described herein.
- the magnetic piston comprises an injection moulded body 7 formed of 6/10 nylon and 88% by weight of strontium ferrite.
- the piston has a blind bore 8 permitting it to be attached to a piston rod, further piston or other piston follower.
- Cup seals 9 and 10 seal the piston within the cylinder.
- the piston may be a hollow piston as shown in Figure 3 in which the piston 11 is in the form of an injection moulded tubular member having cup seals 12 and 13.
- the piston is formed almost entirely of magnetic material, significant savings in the length of the piston can be achieved by using a moulded form of magnetic material.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Pistons, Piston Rings, And Cylinders (AREA)
Description
- This invention relates to non-contact positional sensing systems and has particular reference to non-contact positional sensing systems for a piston movable longitudinally within a cylinder.
- Non-contact positional sensing of pneumatic cylinder pistons is common practice. Normally, a permanent magnet is fitted to the piston and a reed switch or magnetically sensitive proximity sensors are attached to the cylinder barrel around its diameter.
- The magnets which have been used heretofor have been of the ring type in various materials dependent upon the required field strength. Typical examples have been Samarium Cobalt, Ceramic Ferrite or a plastics material with a ferrite filler. The magnetic ring may be located between split piston halves.
- Unfortunately, the magnetic materials which have a high strength tend to be very expensive and this makes the magnetic piston system expensive.
- A similar positional sensing system for a piston movable longitudinally within a cylinder is described in DE-A 3 424 461. The purpose of the piston in the device of DE-A 3 424 461 is to concentrate the indicative force produced by an external coil, thereby providing positional information by way of feedback. To that end, the specifc material disclosed in DE-A 3 424 461, namely Permalloy, is of the type that is very effective in concentrating magnetic flex but that cannot be permanently magnetisesd to any appreciable extent.
- By the present invention there is provided a present non-contact positional sensing system for a piston movable longitudinally within a cylinder, in which the cylinder is formed of non-ferromagnetic material, there is a magnetically sensitive proximity sensor on the outside of the cylinder and the piston incorporates a permanent magnet, characterised in that the piston is formed substantially entirely from permanently magnetic material.
- The piston may be moulded from magnetic material comprising magnetic particles in a non-magnetic matrix of plastics material. The piston may be moulded by injection moulding. The proportion of magnetic particles is preferably as high as practical and may be in the range 60-90%, preferably 70-90% and more preferably 80-90% by weight of the magnetic material. The plastics material may be nylon and is preferably nylon 6/10. The magnetic material may be a strontium ferrite filler. There may be present 88% by weight of strontium ferrite material.
- The piston may be provided with non-magnetic seals which may be of conventional form. The seals may be cup seals or '0' ring seals or disc seals.
- By way of example embodiment of the present invention will now be described with reference to the accompanying drawings of which
- FIGURE 1 is a cross section of a prior art piston with ring magnet
- FIGURE 2 is a cross section of one form of the invention, and
- FIGURE 3 is a cross section of a second form of the invention.
- In Figure 1 there is provided a piston comprising a pair of moulded plastics halves 1, 2 which are conjoined together by an inner sleeve 3.
- The two
halves 1 and 2 trap between them a ring magnet 4. The pair ofseals 5, 6 seal the piston within a cylinder. The cylinder and proximity sensors are well known and conventional and are not described herein. - In Figure 2, the magnetic piston comprises an injection moulded body 7 formed of 6/10 nylon and 88% by weight of strontium ferrite. The piston has a
blind bore 8 permitting it to be attached to a piston rod, further piston or other piston follower. Cup seals 9 and 10 seal the piston within the cylinder. - The piston may be a hollow piston as shown in Figure 3 in which the
piston 11 is in the form of an injection moulded tubular member having cup seals 12 and 13. - The use of an injection moulded piston assembly enables the complete piston to be produced from magnetic material. This permits a greater volume of magnetic material within the piston envelope (compared to conventional designs), which permits the use of weaker and hence cheaper magnetic material and also significantly cheaper plastics materials may be used.
- In the preferred embodiment in which the piston is injection moulded, very close tolerances can be held to the design and a very good surface finish can be provided.
- Because the piston is formed almost entirely of magnetic material, significant savings in the length of the piston can be achieved by using a moulded form of magnetic material.
Claims (8)
1. A non-contact positional sensing system for a piston movable longitudinally within a cylinder, in which the cylinder is formed of a non-ferromagnetic material, there is a magnetically sensitive proximity sensor on the outside of the cylinder and the piston incorporates a permanent magnet, characterised in that the piston (11) is formed substantially entirely from permanent magnetic material.
2. A system as claimed in claim 1 in which the piston (11) is moulded from magnetic material comprising magnetic particles in a non-magnetic matrix of plastics material.
3. A system as claimed in claim 2 in which the proportion of magnetic particles is in the range of 60% to 90% by weight of the magnetic material.
4. A system as claimed in claim 3 wherein said proportion is in the range of 70 to 90%.
5. A system as claimed in claim 3 wherein said proportion is in the range of 80 to 90%.
6. A system as claimed in any one of claims 2 to 5 in which the plastics material is nylon.
7. A system as claimed in any one of claims 2 to 6 in which the magnetic particles are of strontium ferrite.
8. A system as claimed in any one of claims 2 to 6 in which the magnetic particles are of samarium cobalt or ceramic ferrite materials.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8718173 | 1987-07-31 | ||
| GB878718173A GB8718173D0 (en) | 1987-07-31 | 1987-07-31 | Sensing system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0301845A1 EP0301845A1 (en) | 1989-02-01 |
| EP0301845B1 true EP0301845B1 (en) | 1990-12-05 |
Family
ID=10621614
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19880306940 Expired EP0301845B1 (en) | 1987-07-31 | 1988-07-28 | Sensing system |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0301845B1 (en) |
| DE (1) | DE3861224D1 (en) |
| GB (1) | GB8718173D0 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT404290B (en) * | 1996-10-28 | 1998-10-27 | Hygrama Ag | PISTON FOR A PNEUMATIC OR HYDRAULIC WORKING CYLINDER |
| DE102006006677A1 (en) * | 2006-02-14 | 2007-08-23 | Parker Hannifin Gmbh & Co. Kg | Magnetic piston for pneumatic cylinders |
| DE102006030999A1 (en) * | 2006-07-05 | 2008-01-17 | Zf Friedrichshafen Ag | Device for sensing the position, speed and / or the angle of rotation of a piston |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6013405U (en) * | 1983-07-05 | 1985-01-29 | 株式会社 東京衡機製造所 | actuator |
-
1987
- 1987-07-31 GB GB878718173A patent/GB8718173D0/en active Pending
-
1988
- 1988-07-28 EP EP19880306940 patent/EP0301845B1/en not_active Expired
- 1988-07-28 DE DE8888306940T patent/DE3861224D1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE3861224D1 (en) | 1991-01-17 |
| EP0301845A1 (en) | 1989-02-01 |
| GB8718173D0 (en) | 1987-09-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US20040227509A1 (en) | Position detector for a moving part in a pipe | |
| US6593734B1 (en) | Contactless position sensor with optimized magnetic volume and magneto sensitive probe | |
| JP3264929B2 (en) | Permanent magnet and magneto-sensitive probe position detector | |
| CN1828067B (en) | Actuator with position detecting mechanism | |
| JP3395402B2 (en) | Travel detector | |
| US20080231261A1 (en) | Hall-type sensor for measuring linear movements | |
| CN101532521B (en) | Hydraulic cylinder with information transmitter | |
| KR20030084639A (en) | Position sensing apparatus | |
| US20060113990A1 (en) | Linear position sensor | |
| CA2020787A1 (en) | Proportional electropneumatic solenoid-controlled valve | |
| EP0471073A4 (en) | CYLINDER CONSTRUCTION FOR USE IN POSITION MEASUREMENT. | |
| US6866127B2 (en) | Piston damper assembly, and dust tube subassembly, having a velocity sensor | |
| JPH03130615A (en) | High-resolution coder | |
| JPH02116719A (en) | Magnetic float for magnetic sensor | |
| US7308975B2 (en) | Velocity sensing system for a damper | |
| EP0301845B1 (en) | Sensing system | |
| EP0721067A3 (en) | Fluid-pressure actuator with a magnetic field sensor | |
| GB2164154A (en) | Magnetic velocity sensor | |
| US20030048100A1 (en) | Magnetic sensor of the position of a moving member over a trajectory followed by the moving member | |
| CA2408257A1 (en) | Stud welding head | |
| JPS5914305B2 (en) | Ram displacement detection device in die-casting machine | |
| DE3780001D1 (en) | POTENTIOMETER OR CHANGEABLE RESISTANCE. | |
| WO1991009277A3 (en) | Position sensor | |
| JPS6315727B2 (en) | ||
| JPH0416004Y2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB IT |
|
| 17P | Request for examination filed |
Effective date: 19890804 |
|
| 17Q | First examination report despatched |
Effective date: 19891106 |
|
| GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
| AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB IT |
|
| ITF | It: translation for a ep patent filed | ||
| REF | Corresponds to: |
Ref document number: 3861224 Country of ref document: DE Date of ref document: 19910117 |
|
| ET | Fr: translation filed | ||
| PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
| 26N | No opposition filed | ||
| ITTA | It: last paid annual fee | ||
| PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19980611 Year of fee payment: 11 |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY Effective date: 19990731 |
|
| REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |
|
| REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20050728 |
|
| PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20070726 Year of fee payment: 20 |
|
| PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20070725 Year of fee payment: 20 |
|
| REG | Reference to a national code |
Ref country code: GB Ref legal event code: PE20 Expiry date: 20080727 |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION Effective date: 20080727 |