CA1336784C - Current to pressure transducer employing magnetic fluid - Google Patents
Current to pressure transducer employing magnetic fluidInfo
- Publication number
- CA1336784C CA1336784C CA 614828 CA614828A CA1336784C CA 1336784 C CA1336784 C CA 1336784C CA 614828 CA614828 CA 614828 CA 614828 A CA614828 A CA 614828A CA 1336784 C CA1336784 C CA 1336784C
- Authority
- CA
- Canada
- Prior art keywords
- current
- air
- diaphragm
- magnetic
- pressure transducer
- 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 - Fee Related
Links
- 239000011553 magnetic fluid Substances 0.000 title claims abstract description 29
- 239000012528 membrane Substances 0.000 claims description 15
- 239000012530 fluid Substances 0.000 claims description 8
- 238000006073 displacement reaction Methods 0.000 claims description 6
- 239000000696 magnetic material Substances 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 2
- 230000004044 response Effects 0.000 abstract description 4
- 230000035939 shock Effects 0.000 abstract description 4
- 239000003570 air Substances 0.000 description 54
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 239000000463 material Substances 0.000 description 5
- 230000004907 flux Effects 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 238000013016 damping Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000011554 ferrofluid Substances 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000006249 magnetic particle Substances 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229920002631 room-temperature vulcanizate silicone Polymers 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000004590 silicone sealant Substances 0.000 description 1
- 239000007779 soft material Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
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
- F15B5/00—Transducers converting variations of physical quantities, e.g. expressed by variations in positions of members, into fluid-pressure variations or vice versa; Varying fluid pressure as a function of variations of a plurality of fluid pressures or variations of other quantities
- F15B5/003—Transducers converting variations of physical quantities, e.g. expressed by variations in positions of members, into fluid-pressure variations or vice versa; Varying fluid pressure as a function of variations of a plurality of fluid pressures or variations of other quantities characterised by variation of the pressure in a nozzle or the like, e.g. nozzle-flapper system
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
- Nozzles (AREA)
- Reciprocating Pumps (AREA)
Abstract
A current-to-pressure transducer that is insensitive to shock employs a magnetic fluid that deforms a flexible diaphragm in response to an electrical input current that is applied to a coil and magnetic circuit. The deformed diaphragm varies the air space between the diaphragm and a nozzle connected to the air line so that the pressure within the air line is effectively controlled.
Description
s 7 FIELD OF THE I~VENTION
8 This invention relates to the regulation of air 9 pressure in response to electrical signals and in particular to a transducer for converting an electrical current to a 11 corresponding pressure in a system that uses compressed air.
14 Description of the Prior Art Compressed air is used in many systems for controlling 16 machinery because compressed air is immune to electrical 17 interference and is safe in explosive environments.
18 Compressed air is generally used, for example, to control 19 valves and other mechanical devices in industrial systems.
When using compressed air in a system, sensors are generally 21 provided that generate small electrical currents, in the 22 range of 4 to 20 milliamperes, for example. These currents 23 are used to establish a corresponding pressure of the 24 compressed air and to provide a sufficient volume of pressurized air for accomplishing the desired mechanical 26 task. In some systems, the conversion from electrical 27 current to a corresponding pressure is accomplished by use 28 of a current-to-pressure transducer that is capable of 29 regulating the pressure of a small volume of air, wherein the volume of air is amplified by using standard pneumatic 31 amplifiers. In the conventional current-to-pressure 32 transducer, a nozzle is supplied that directs compressed air 33 to the atmosphere at a rate determined by the proximity of a 34 flapper valve to a nozzle orifice. The flapper valve is generally mounted on a rotating suspension and is rotated by 36 magnetic forces that are generated by an electromagnet. The 37 flapper is rotated toward the nozzle so that the air that 38 escapes to the atmosphere is reduced. Such prior art -1- ~
devices are formed as delicate mechanical assemblies that require several adjustments during fabrication and are relatively expensive to produce.
It is highly desirable to employ a simple current-to-pressure transducer that lends itself to facile production at low cost without the need for individual mechanical adjustments.
A nozzle is a converging or converging-diverging tube attached to the outlet of a pipe, hose or pressure chamber. The purpose of the nozzle is to convert the pressure existing in a fluid into velocity efficiently. A nozzle allows a pressure to be carried in a pipe or hose adjacent to the nozzle.
Presently known nozzles used for controlling air flow generally terminate with an outer diameter slightly larger than the inner diameter. Typically, the outer diameter of a nozzle would be 0.035 inch and the inner diameter would be 0.02~ inch, by way of example. The current-to-pressure transducers that use such type nozzles usually incorporate a flapper, which is a pivotable paddle-shaped part, or a diaphragm to vary the flow of air through the nozzle. In either case, it is necessary that a good seal be provided at the end of the transducer from which there is the high flow of air or fluid. In order to achieve the required good seal, the flapper or diaphragm must be precisely aligned in a plane that is perpendicular to the axis of the nozzle. If the alignment is not proper, the flapper or diaphragm will first strike an edge of the nozzle end and will not advance further towards making an effective complete seal. It is relatively difficult to provide the desired orthogonal alignment of the flapper or diaphragm in a planar orientation relative to the nozzle axis.
SUMMARY OF THE INVENTION
An object of this invention is to provide a current-to-pressure transducer that regulates the air pressure within an air supply line. Henceforth, the word "pressure" will be used to mean the pressure relative to the environment.
Another object of this invention is to provide a transducer that is relatively efficient and has uniform characteristics so that individual adjustments need not be made.
Another object is to provide a current-to-pressure transducer that can be mass produced at low cost.
Another object is to provide a current-to-pressure transducer that is insensitive to shock and vibration.
In accordance with this invention, there is provided a current-to-pressure transducer comprising a baseplate or housing made of magnetic material; at least one chamber formed in said baseplate, said chamber having at least one open end; at least one flexible membrane or diaphragm for sealing said open end; a volume of magnetic fluid contained within said chamber;
air supply means disposed closely adjacent to said flexible membrane or diaphragm for supplying air; electromagnetic means comprising a magnetic circuit and a coil including permanent magnet means for receiving an input current to provide a magnetic field closely adjacent to said flexible membrane or diaphragm for displacing said flexible membrane or diaphragm relative to said air supply means so that the pressure of said air in said air supply means is regulated in accordance with said input current, wherein the displacement of said flexible membrane or diaphragm is accomplished with the volume of said magnetic fluid conserved and maintained constant and wherein said displacement is not opposed by ambient pressure.
In accordance with another aspect of this invention, there is provided a current-to-pressure transducer comprising means for supplying a flow of air; first and second chambers and a means connecting said chambers, each of said chambers having an open end; magnetic fluid disposed within the said chambers and said connection means; first and second flexible diaphragms respectively positioned against said open ends for containing said fluid within said chambers; and electromagnetic means energized by an input electrical current for coacting with said magnetic fluid to deform a selected one of said diaphragms thereby varying the air pressure in said supply means.
The transducer can regulate the air pressure within an air supply line so that the pressure differential between this line and ambient air pressure varies substantially linearly with an applied electrical current. In one - 3a -embodiment pressure sensing means and electronic feedback are used to achieve the desired linearity between the pressure within the line supplying air to the nozzle and the electrical input current.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail with reference to the drawing in which:
Figure 1 is a side cross-sectional view of a current-to-pressure transducer, made in accordance with this invention;
Figure 2 is a side cross-sectional view of an alternative implementation of the current-to-pressure transducer of this invention;
Figure 3 is a cross-sectional view, partly broken away, of another implementation of the invention;
Figure 4 is an enlarged isometric view, partly broken away, showing the relationship of a pole piece 11 to the nozzle 10 and the nozzle air supply line 24, as used in the transducer of this invention; and Figure 5 is a representative curve plotting pressure against current without electronic feedback to aid in the explanation of the operation of the current-to-pressure transducer.
Figure 6 is a side view of the nozzle and pole piece, made ln accordance with this invention;
Figure 7 is an end view at the slotted end of the nozzle and pole piece structure, such as illustrated in Fig. 6 ;
Figure 8A is an enlarged cross-sectional view, partly broken away, taken across lines A-A' of Fig.7 ;
Figure 8B is an enlarged cross-sectional view, partly broken away, taken across lines B-B' of Fig.7 ;
Figure 9 is an exploded view of an assembly drawing illustrating the housing which encloses the nozzle and pole piece structure; and Figurel0 is an isometric view illustrating an assembled housing which encloses the nozzle and pole piece structure of this invention.
Similar numerals refer to similar elements throughout the drawing.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to Fig. 1, the current-to-pressure transducer of this invention receives compressed air from a pneumatic amplifier 32. The current-to-pressure transducer includes an air supply line 24 having a nozzle 10 at one end and is coupled at the other end to the pneumatic amplifier 32.
A baseplate 19 made of magnetically soft material is joined to a magnetic member 20 by a screw 37 or other suitable means. A magnetic member 21 is attached to the member 20 by a screw 38 or other attachment means. A
cylindrical magnetic member 22 is positioned in contact with and partly within an aperture of the magnetic member 21. As 1 illustrated in Fig. 4, a pole piece 11 is provided at the 2 upper end of the tubular member 22.
8 This invention relates to the regulation of air 9 pressure in response to electrical signals and in particular to a transducer for converting an electrical current to a 11 corresponding pressure in a system that uses compressed air.
14 Description of the Prior Art Compressed air is used in many systems for controlling 16 machinery because compressed air is immune to electrical 17 interference and is safe in explosive environments.
18 Compressed air is generally used, for example, to control 19 valves and other mechanical devices in industrial systems.
When using compressed air in a system, sensors are generally 21 provided that generate small electrical currents, in the 22 range of 4 to 20 milliamperes, for example. These currents 23 are used to establish a corresponding pressure of the 24 compressed air and to provide a sufficient volume of pressurized air for accomplishing the desired mechanical 26 task. In some systems, the conversion from electrical 27 current to a corresponding pressure is accomplished by use 28 of a current-to-pressure transducer that is capable of 29 regulating the pressure of a small volume of air, wherein the volume of air is amplified by using standard pneumatic 31 amplifiers. In the conventional current-to-pressure 32 transducer, a nozzle is supplied that directs compressed air 33 to the atmosphere at a rate determined by the proximity of a 34 flapper valve to a nozzle orifice. The flapper valve is generally mounted on a rotating suspension and is rotated by 36 magnetic forces that are generated by an electromagnet. The 37 flapper is rotated toward the nozzle so that the air that 38 escapes to the atmosphere is reduced. Such prior art -1- ~
devices are formed as delicate mechanical assemblies that require several adjustments during fabrication and are relatively expensive to produce.
It is highly desirable to employ a simple current-to-pressure transducer that lends itself to facile production at low cost without the need for individual mechanical adjustments.
A nozzle is a converging or converging-diverging tube attached to the outlet of a pipe, hose or pressure chamber. The purpose of the nozzle is to convert the pressure existing in a fluid into velocity efficiently. A nozzle allows a pressure to be carried in a pipe or hose adjacent to the nozzle.
Presently known nozzles used for controlling air flow generally terminate with an outer diameter slightly larger than the inner diameter. Typically, the outer diameter of a nozzle would be 0.035 inch and the inner diameter would be 0.02~ inch, by way of example. The current-to-pressure transducers that use such type nozzles usually incorporate a flapper, which is a pivotable paddle-shaped part, or a diaphragm to vary the flow of air through the nozzle. In either case, it is necessary that a good seal be provided at the end of the transducer from which there is the high flow of air or fluid. In order to achieve the required good seal, the flapper or diaphragm must be precisely aligned in a plane that is perpendicular to the axis of the nozzle. If the alignment is not proper, the flapper or diaphragm will first strike an edge of the nozzle end and will not advance further towards making an effective complete seal. It is relatively difficult to provide the desired orthogonal alignment of the flapper or diaphragm in a planar orientation relative to the nozzle axis.
SUMMARY OF THE INVENTION
An object of this invention is to provide a current-to-pressure transducer that regulates the air pressure within an air supply line. Henceforth, the word "pressure" will be used to mean the pressure relative to the environment.
Another object of this invention is to provide a transducer that is relatively efficient and has uniform characteristics so that individual adjustments need not be made.
Another object is to provide a current-to-pressure transducer that can be mass produced at low cost.
Another object is to provide a current-to-pressure transducer that is insensitive to shock and vibration.
In accordance with this invention, there is provided a current-to-pressure transducer comprising a baseplate or housing made of magnetic material; at least one chamber formed in said baseplate, said chamber having at least one open end; at least one flexible membrane or diaphragm for sealing said open end; a volume of magnetic fluid contained within said chamber;
air supply means disposed closely adjacent to said flexible membrane or diaphragm for supplying air; electromagnetic means comprising a magnetic circuit and a coil including permanent magnet means for receiving an input current to provide a magnetic field closely adjacent to said flexible membrane or diaphragm for displacing said flexible membrane or diaphragm relative to said air supply means so that the pressure of said air in said air supply means is regulated in accordance with said input current, wherein the displacement of said flexible membrane or diaphragm is accomplished with the volume of said magnetic fluid conserved and maintained constant and wherein said displacement is not opposed by ambient pressure.
In accordance with another aspect of this invention, there is provided a current-to-pressure transducer comprising means for supplying a flow of air; first and second chambers and a means connecting said chambers, each of said chambers having an open end; magnetic fluid disposed within the said chambers and said connection means; first and second flexible diaphragms respectively positioned against said open ends for containing said fluid within said chambers; and electromagnetic means energized by an input electrical current for coacting with said magnetic fluid to deform a selected one of said diaphragms thereby varying the air pressure in said supply means.
The transducer can regulate the air pressure within an air supply line so that the pressure differential between this line and ambient air pressure varies substantially linearly with an applied electrical current. In one - 3a -embodiment pressure sensing means and electronic feedback are used to achieve the desired linearity between the pressure within the line supplying air to the nozzle and the electrical input current.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail with reference to the drawing in which:
Figure 1 is a side cross-sectional view of a current-to-pressure transducer, made in accordance with this invention;
Figure 2 is a side cross-sectional view of an alternative implementation of the current-to-pressure transducer of this invention;
Figure 3 is a cross-sectional view, partly broken away, of another implementation of the invention;
Figure 4 is an enlarged isometric view, partly broken away, showing the relationship of a pole piece 11 to the nozzle 10 and the nozzle air supply line 24, as used in the transducer of this invention; and Figure 5 is a representative curve plotting pressure against current without electronic feedback to aid in the explanation of the operation of the current-to-pressure transducer.
Figure 6 is a side view of the nozzle and pole piece, made ln accordance with this invention;
Figure 7 is an end view at the slotted end of the nozzle and pole piece structure, such as illustrated in Fig. 6 ;
Figure 8A is an enlarged cross-sectional view, partly broken away, taken across lines A-A' of Fig.7 ;
Figure 8B is an enlarged cross-sectional view, partly broken away, taken across lines B-B' of Fig.7 ;
Figure 9 is an exploded view of an assembly drawing illustrating the housing which encloses the nozzle and pole piece structure; and Figurel0 is an isometric view illustrating an assembled housing which encloses the nozzle and pole piece structure of this invention.
Similar numerals refer to similar elements throughout the drawing.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to Fig. 1, the current-to-pressure transducer of this invention receives compressed air from a pneumatic amplifier 32. The current-to-pressure transducer includes an air supply line 24 having a nozzle 10 at one end and is coupled at the other end to the pneumatic amplifier 32.
A baseplate 19 made of magnetically soft material is joined to a magnetic member 20 by a screw 37 or other suitable means. A magnetic member 21 is attached to the member 20 by a screw 38 or other attachment means. A
cylindrical magnetic member 22 is positioned in contact with and partly within an aperture of the magnetic member 21. As 1 illustrated in Fig. 4, a pole piece 11 is provided at the 2 upper end of the tubular member 22.
3 A coil 23 is wound around a portion of the magnetic 4 member 22. Baseplate 19, magnetic members 20, 21 and 22, the gap between pole piece 11 and the magnetic fluid 30 in 6 chamber 14 and the magnetic fluid 30 in chamber 14 form a 7 magnetic circuit. When current is applied to the coil 23, 8 the magnitude of the magnetic flux at the pole piece 11 is 9 varied in accordance with the magnitude of the current 10 signal.
11 The baseplate 19 is formed with two chambers 14 and 16 12 that are connected by a capillary tube 15. In keeping with 13 this invention, a magnetic fluid 30 which may be a colloidal 14 suspension of magnetic particles in a nonmagnetic carrier, such as Ferrofluid (a trademark of Ferrofluidics 16 Corporation, Nashua, New Hampshire) is provided to 17 chambers 14 and 16 and the capillary tube 15. The magnetic 18 fluid 30 may also be any composite, noncolloidal material 19 that is not capable of supporting shear forces and that exhibits a magnetic susceptibility. A plug 18 is provided 21 to enable filling the capillary tube 15 and chambers 14 and 22 16 with magnetic fluid 30.
23 In accordance with this invention, flexible membranes 24 or diaphragms 13 and 17 are located respectively at the lower open ends of the chambers 14 and 16 to seal the ends 26 of the chambers and to contain the magnetic fluid 30 within 27 the chambers. The flexible membranes 13 and 17 are retained 28 by a nonmagnetic retainer element or ring 25 which abuts the 29 diaphragms. The element 25 is fastened at its exposed surface to the baseplate 19 by screws or other suitable 31 means-32 In operation, the pneumatic amplifier 32 provides 33 compressed air through the air supply line 24 to the 34 nozzle 10. The air passes through the space between the diaphragm 13 and the surface of the nozzle 10. Escape 36 holes 12 or other suitable means are provided in the upper 37 portion of the magnetic member 22, as shown in Fig. 4 to 38 prevent undesirable pressure buildup between the pole 1 piece 11 and diaphragm 13. An air pressure sensor 26 senses 2 the pressure of the compressed air that is passing through 3 the air supply line 24 and generates a signal representative 4 of the pressure value. The signal is provided to an electronic feedback circuit 27, which also receives the 6 input current through lead 34. The input current and the 7 signal representative of the pressure value are compared in 8 the circuit 27 and a current representative of this 9 comparison is provided to the coil 23. The electronic feedback circuit 27 adjusts the actual current to the 11 coil 23 so that the pressure in the air line 24 is 12 substantially linear with the input current. The input 13 current during operation maintains the coil in an excited 14 state and as a result the pole piece 11 distributes magnetic flux in the area adjacent to the diaphragm 13. The 16 magnitude of the magnetic flux emanating from the pole 17 piece 11 varies with variations in the current supplied to 18 the coil 23. The magnetic fluid 30 in chamber 14 is 19 attracted towards the pole piece 11 and the diaphragm 13 is deformed to an extent directly related to the magnitude of 21 the current which is applied to the coil 23. The 22 diaphragm 13 deforms and moves partially towards the pole 23 piece 11 so that the space between the diaphragm 13 and the 24 nozzle 10 decreases. As a result, the pressure of air within the air line 24 supplying air to the nozzle 10 is 26 increased. During the deformation of the diaphragm 13 27 resulting from the magnetic fluid 30 being moved towards the 28 pole piece 11, the volume of magnetic fluid that is 29 displaced in chamber 14 associated with the displacement of diaphragm 13 is provided from chamber 16 to chamber 14. The 31 diaphragm 17 moves inwardly to the chamber 16 in an equal 32 and opposite direction to diaphragm 13.
33 With reference to Fig. 2, the air supply line 24 34 including the nozzle 10 is located under the chamber 16.
The coil 23 and the associated magnetic members 20, 21, 31, 36 baseplate 19 and pole piece 11 remain in association with 37 the chamber 14 for coaction with the diaphragm 13. An 38 increase in current to the coil 23 causes the diaphragm 13 1 to deform toward the pole piece 11 and the volume of 2 magnetic fluid that is displaced from chamber 16 to chamber 3 14 causes the diaphragm 17 to move away from the nozzle 4 10. Consequently, the pressure of the air in line 24 is decreased. In this embodiment of Fig. 2, the air line 24 is 6 made of nonmagnetic material such as aluminum, or 7 alternatively is magnetically isolated from the magnetic 8 circuit which includes the coil 23 and the magnetic 9 member 22, inter alia.
A feature of this invention is the insensitivity to 11 gravitational or acceleration forces. Because the magnetic 12 fluid 30 is relatively incompressible, the diaphragms 13 and 13 17 move equally in opposite directions. In those 14 embodiments in which the diaphragms are coplanar, the transducer is insensitive to forces that are applied 16 perpendicularly to the plane of the diaphragms. The 17 transducer is relatively insensitive to forces that are 18 applied perpendicularly to the plane of the drawing and a 19 line through the centers of the chambers, irrespective of whether the diaphragms are coplanar. Also the viscous 21 damping that is associated with the transport of the 22 fluid 30 through the capillary 15 causes the transducer to 23 be insensitive to shock in any direction. The damping is 24 enhanced as the viscosity of the magnetic fluid 30 is increased and the conductance of the capillary 15 is 26 decreased. Damping also can be used to limit the high 27 frequency response of the transducer.
28 As illustrated in Fig. 3 in another implementation of 29 the invention, a further increase in sensitivity is achieved by affixing an element 28 made of a solid, magnetically soft 31 material, such as iron, to the center of the diaphragm 13.
32 The element 28 is disposed within the magnetic fluid in 33 chamber 14 and has a higher saturation magnetization than 34 the magnetic fluid. The element 28 also can provide stiffness to the central portion of the diaphragm. To 36 preserve shock insensitivity, an element 29 is located in 37 the chamber 16 and is affixed to the diaphragm 17. The 38 element 29 may be substantially identical to the element 28, or may be of a nonmagnetic material with suitable size and shape to achieve the desired insensitivity.
Fig. 5 is a curve representing the changes in pressure (psi) as a function of current (milliamps). In an actual implementation of the invention, a 450 Gauss, 400 cp Ferrofluid was used. The element 28 is a steel slug of 3/8-inch diameter and 3/16-inch long cemented to the diaphragm 13 with RTV
silicone sealant. The air supply pressure is 18 psi. It should be understood that these parameters, materials and dimensions are exemplary and the invention is not limited thereby.
In an alternative approach the transducer comprises a single chamber and a single flexible diaphragm. In such case an air space is provided above the level of the magnetic fluid to allow displacement of the diaphragm.
It should be understood that chambers formed within a baseplate or housing are equivalent to chambers formed by concave diaphragms sealed against a flat baseplate.
In another approach, nozzle 10 is made of magnetic material and functions also as pole piece 11. In this approach, the outer coaxial member 11 and holes 12 shown in Figure 4 are eliminated.
The novel current-to-pressure transducer disclosed herein employs a magnetic fluid to coact with flexible diaphragms disposed in close juxtaposition to a nozzle of an air line. The transducer lends itself to mass production and low cost, is efficient in operation, and does not require individual adjustments.
In accordance with this invention, a nozzle and pole piece structure is formed from a rod 40 made of a magnetic material, such as Carpenter High Permeability "49" Alloy, for example. The rod 40 has a diameter of about 3/16 inch in this particular embodiment. As illustrated in Fig. 6, the magnetic rod 40 is formed with functional pole pieces 41 at a slotted end of the rod 40. Slots 43 allow the escape of excess air and are relatively easy to machine, with saw blades or slot cutters, as compared to the formation of individual bleed ~ _ 9 1 holes 12 and the associated deep circumferential groove 2 between elements 10 and 11 to which the holes connect, shown 3 in Fig. A-. The pole pieces 4~ provide magnetic flux for 4 coaction with electric current flowing through the electrical coil (not shown) of the electromagnetic circuit. Application 6 of electric current to the coil causes the magnetic fluid 30 7 to move which, in turn, causes the deformation of the flexible 8 diaphragm as explained heretofore thereby controlling air flow g through the nozzle .
11 The rod ~0 has a threaded part 42 for engagement with a 12 threaded cap 44 of a housing assembly, shown in Fig. ~ The 13 rod 40 also has a hexagonal part 46 formed at the end ddjacent 14 to the threaded part 42 to allow the rod to be turned so that the height of the nozzle relative to the diaphragm can be 16 adjusted for proper operation, and locked with nut 68.
18 Figure 4 shows an end view of the nozzle and pole piece 19 structure 40 viewed from the slotted end. The rod 40 is formed with one or more of the longitudinal slots 43, which 21 extend inwardly to at least the outer diameter of a relatively 22 shallow groove 46 formed within the end of the rod 40. The 23 slots 43 serve the same purpose as the holes 12 depicted in 24 Fig. 4 to allow the escape of excess air, but are easier to machine and fabricate than the transverse holes. Groove 46 26 may be eliminated if the slots 43 extend inward to the 27 proximity of the constricted passage 49.
29 As depicted in Figs. 8A and 8~B, an open channel 48 is formed within the interior of the nozzle tube 46 to allow the passage 31 and escape of air. The nozzle tube 46 may be tapered at the 32 end portion that faces the diaphragm so that a constricted 33 passage 49 is formed at the end of the nozzle channel 48. The 34 constricted portion 49 of the channel 48 (Figs. 8A and 8B) reduces the volume of air that escapes from the nozzle at a 36 given pressure. The amount of air flow from the channel 37 portion 49 is regulated by the position of the diaphragm 13, 38 which is con~ro~le~ by the action of the magnetic fluid in 39 response to the electric current supply to the coil of the 1 electromagnetic circuit.
3 The exploded view of ~ig.9 shows the main housing 50 for the 4 integral nozzle and pole piece structure which is made of soft iron. Diaphragms 52 and 54 are spaced by a soft iron spacer 6 56 formed with magnetic fluid chambers 58 and 60. O-ring 7 seals 62 and 64 are provided with the chambers. A threaded 8 aluminum retainer 66 is located adjacent to the diaphragm 54 g for connection to the spacer 56. A lock nut 67 is located against the retainer 66 and four cap screws 70 tie the spacer 11 56 and retainer 66 with the diaphragms 52 and 54 to the main 12 housing 50. A second nozzle ~not shown) may be threaded into 13 retainer 66 to coact with diaphragm 54, as described in the 14 referenced copending application.
16 At the other end of the housing 50, the threaded element 44, 17 which is made as a soft iron cap with internal threads for 18 engaging the nozzle, is joined with a lock nut 68 by means of 19 four Allen socket cap screws 72 to the main housing 50.
21 Fig.lO depicts the assembled unit which has a notch 74 in the 22 housing 50 to allow connection of electrical circuitry to the 23 electrical coil of the electromagnetic circuit and to permit 24 escape of excess air.
26 By virtue of the integral structure of a nozzle and pole piece 27 which are machined from a single magnetic rod, the end of the 28 nozzle tube 46 and the end of the pole piece 41 are 29 substantially coplanar. When the electromagnetic force is applied to the top surface of the diaphragm 13 by the magnetic 31 fluid 30, the lower surface of the diaphragm conforms to the 32 shape of the pole piece 41. Since the alignment of the ends 33 of the pole piece 41 and nozzle tube 46 are in substantial 34 planar alignment, the diaphragm will provide a complete seal at the face of the nozzle. Wlth the present design, the 36 torque applied to the flapper valve acts through a point 37 further from the noæzle than the point of first contact 38 between the flapper valve an~ nozzle 10, and if the flapper 39 valve does no~ contact the nozzle squarely, further torque 1 will only distort the flapper valve and worsen the incomplete ~ seal. With the nozzle and pole piece structure design as 3 disclosed herein, any canting of the diaphragm 13 is self-4 corrected because the force on the diaphragm acts between a point of first contact of the diaphragm 13 with the end of the 6 larger diameter pole piece 41 and the coplanar end of the 7 nozzie tube. The integral nozzle and pole piece structure 8 also is easier to fabricate with the slots 44 formed at the 9 end of the rod structure to allow the desired air escape instead of with transverse holes as used in prior nozzle 11 assemblies. Such transverse holes either require a difficult 12 process to machine a deep groove between the nozzle 10 and 13 pole piece 11, or require fabricating the nozzle 10 and pole 14 piece 11 separately, in which case it would be difficult to assemble these parts to achieve the desired coplanarity.
3&
11 The baseplate 19 is formed with two chambers 14 and 16 12 that are connected by a capillary tube 15. In keeping with 13 this invention, a magnetic fluid 30 which may be a colloidal 14 suspension of magnetic particles in a nonmagnetic carrier, such as Ferrofluid (a trademark of Ferrofluidics 16 Corporation, Nashua, New Hampshire) is provided to 17 chambers 14 and 16 and the capillary tube 15. The magnetic 18 fluid 30 may also be any composite, noncolloidal material 19 that is not capable of supporting shear forces and that exhibits a magnetic susceptibility. A plug 18 is provided 21 to enable filling the capillary tube 15 and chambers 14 and 22 16 with magnetic fluid 30.
23 In accordance with this invention, flexible membranes 24 or diaphragms 13 and 17 are located respectively at the lower open ends of the chambers 14 and 16 to seal the ends 26 of the chambers and to contain the magnetic fluid 30 within 27 the chambers. The flexible membranes 13 and 17 are retained 28 by a nonmagnetic retainer element or ring 25 which abuts the 29 diaphragms. The element 25 is fastened at its exposed surface to the baseplate 19 by screws or other suitable 31 means-32 In operation, the pneumatic amplifier 32 provides 33 compressed air through the air supply line 24 to the 34 nozzle 10. The air passes through the space between the diaphragm 13 and the surface of the nozzle 10. Escape 36 holes 12 or other suitable means are provided in the upper 37 portion of the magnetic member 22, as shown in Fig. 4 to 38 prevent undesirable pressure buildup between the pole 1 piece 11 and diaphragm 13. An air pressure sensor 26 senses 2 the pressure of the compressed air that is passing through 3 the air supply line 24 and generates a signal representative 4 of the pressure value. The signal is provided to an electronic feedback circuit 27, which also receives the 6 input current through lead 34. The input current and the 7 signal representative of the pressure value are compared in 8 the circuit 27 and a current representative of this 9 comparison is provided to the coil 23. The electronic feedback circuit 27 adjusts the actual current to the 11 coil 23 so that the pressure in the air line 24 is 12 substantially linear with the input current. The input 13 current during operation maintains the coil in an excited 14 state and as a result the pole piece 11 distributes magnetic flux in the area adjacent to the diaphragm 13. The 16 magnitude of the magnetic flux emanating from the pole 17 piece 11 varies with variations in the current supplied to 18 the coil 23. The magnetic fluid 30 in chamber 14 is 19 attracted towards the pole piece 11 and the diaphragm 13 is deformed to an extent directly related to the magnitude of 21 the current which is applied to the coil 23. The 22 diaphragm 13 deforms and moves partially towards the pole 23 piece 11 so that the space between the diaphragm 13 and the 24 nozzle 10 decreases. As a result, the pressure of air within the air line 24 supplying air to the nozzle 10 is 26 increased. During the deformation of the diaphragm 13 27 resulting from the magnetic fluid 30 being moved towards the 28 pole piece 11, the volume of magnetic fluid that is 29 displaced in chamber 14 associated with the displacement of diaphragm 13 is provided from chamber 16 to chamber 14. The 31 diaphragm 17 moves inwardly to the chamber 16 in an equal 32 and opposite direction to diaphragm 13.
33 With reference to Fig. 2, the air supply line 24 34 including the nozzle 10 is located under the chamber 16.
The coil 23 and the associated magnetic members 20, 21, 31, 36 baseplate 19 and pole piece 11 remain in association with 37 the chamber 14 for coaction with the diaphragm 13. An 38 increase in current to the coil 23 causes the diaphragm 13 1 to deform toward the pole piece 11 and the volume of 2 magnetic fluid that is displaced from chamber 16 to chamber 3 14 causes the diaphragm 17 to move away from the nozzle 4 10. Consequently, the pressure of the air in line 24 is decreased. In this embodiment of Fig. 2, the air line 24 is 6 made of nonmagnetic material such as aluminum, or 7 alternatively is magnetically isolated from the magnetic 8 circuit which includes the coil 23 and the magnetic 9 member 22, inter alia.
A feature of this invention is the insensitivity to 11 gravitational or acceleration forces. Because the magnetic 12 fluid 30 is relatively incompressible, the diaphragms 13 and 13 17 move equally in opposite directions. In those 14 embodiments in which the diaphragms are coplanar, the transducer is insensitive to forces that are applied 16 perpendicularly to the plane of the diaphragms. The 17 transducer is relatively insensitive to forces that are 18 applied perpendicularly to the plane of the drawing and a 19 line through the centers of the chambers, irrespective of whether the diaphragms are coplanar. Also the viscous 21 damping that is associated with the transport of the 22 fluid 30 through the capillary 15 causes the transducer to 23 be insensitive to shock in any direction. The damping is 24 enhanced as the viscosity of the magnetic fluid 30 is increased and the conductance of the capillary 15 is 26 decreased. Damping also can be used to limit the high 27 frequency response of the transducer.
28 As illustrated in Fig. 3 in another implementation of 29 the invention, a further increase in sensitivity is achieved by affixing an element 28 made of a solid, magnetically soft 31 material, such as iron, to the center of the diaphragm 13.
32 The element 28 is disposed within the magnetic fluid in 33 chamber 14 and has a higher saturation magnetization than 34 the magnetic fluid. The element 28 also can provide stiffness to the central portion of the diaphragm. To 36 preserve shock insensitivity, an element 29 is located in 37 the chamber 16 and is affixed to the diaphragm 17. The 38 element 29 may be substantially identical to the element 28, or may be of a nonmagnetic material with suitable size and shape to achieve the desired insensitivity.
Fig. 5 is a curve representing the changes in pressure (psi) as a function of current (milliamps). In an actual implementation of the invention, a 450 Gauss, 400 cp Ferrofluid was used. The element 28 is a steel slug of 3/8-inch diameter and 3/16-inch long cemented to the diaphragm 13 with RTV
silicone sealant. The air supply pressure is 18 psi. It should be understood that these parameters, materials and dimensions are exemplary and the invention is not limited thereby.
In an alternative approach the transducer comprises a single chamber and a single flexible diaphragm. In such case an air space is provided above the level of the magnetic fluid to allow displacement of the diaphragm.
It should be understood that chambers formed within a baseplate or housing are equivalent to chambers formed by concave diaphragms sealed against a flat baseplate.
In another approach, nozzle 10 is made of magnetic material and functions also as pole piece 11. In this approach, the outer coaxial member 11 and holes 12 shown in Figure 4 are eliminated.
The novel current-to-pressure transducer disclosed herein employs a magnetic fluid to coact with flexible diaphragms disposed in close juxtaposition to a nozzle of an air line. The transducer lends itself to mass production and low cost, is efficient in operation, and does not require individual adjustments.
In accordance with this invention, a nozzle and pole piece structure is formed from a rod 40 made of a magnetic material, such as Carpenter High Permeability "49" Alloy, for example. The rod 40 has a diameter of about 3/16 inch in this particular embodiment. As illustrated in Fig. 6, the magnetic rod 40 is formed with functional pole pieces 41 at a slotted end of the rod 40. Slots 43 allow the escape of excess air and are relatively easy to machine, with saw blades or slot cutters, as compared to the formation of individual bleed ~ _ 9 1 holes 12 and the associated deep circumferential groove 2 between elements 10 and 11 to which the holes connect, shown 3 in Fig. A-. The pole pieces 4~ provide magnetic flux for 4 coaction with electric current flowing through the electrical coil (not shown) of the electromagnetic circuit. Application 6 of electric current to the coil causes the magnetic fluid 30 7 to move which, in turn, causes the deformation of the flexible 8 diaphragm as explained heretofore thereby controlling air flow g through the nozzle .
11 The rod ~0 has a threaded part 42 for engagement with a 12 threaded cap 44 of a housing assembly, shown in Fig. ~ The 13 rod 40 also has a hexagonal part 46 formed at the end ddjacent 14 to the threaded part 42 to allow the rod to be turned so that the height of the nozzle relative to the diaphragm can be 16 adjusted for proper operation, and locked with nut 68.
18 Figure 4 shows an end view of the nozzle and pole piece 19 structure 40 viewed from the slotted end. The rod 40 is formed with one or more of the longitudinal slots 43, which 21 extend inwardly to at least the outer diameter of a relatively 22 shallow groove 46 formed within the end of the rod 40. The 23 slots 43 serve the same purpose as the holes 12 depicted in 24 Fig. 4 to allow the escape of excess air, but are easier to machine and fabricate than the transverse holes. Groove 46 26 may be eliminated if the slots 43 extend inward to the 27 proximity of the constricted passage 49.
29 As depicted in Figs. 8A and 8~B, an open channel 48 is formed within the interior of the nozzle tube 46 to allow the passage 31 and escape of air. The nozzle tube 46 may be tapered at the 32 end portion that faces the diaphragm so that a constricted 33 passage 49 is formed at the end of the nozzle channel 48. The 34 constricted portion 49 of the channel 48 (Figs. 8A and 8B) reduces the volume of air that escapes from the nozzle at a 36 given pressure. The amount of air flow from the channel 37 portion 49 is regulated by the position of the diaphragm 13, 38 which is con~ro~le~ by the action of the magnetic fluid in 39 response to the electric current supply to the coil of the 1 electromagnetic circuit.
3 The exploded view of ~ig.9 shows the main housing 50 for the 4 integral nozzle and pole piece structure which is made of soft iron. Diaphragms 52 and 54 are spaced by a soft iron spacer 6 56 formed with magnetic fluid chambers 58 and 60. O-ring 7 seals 62 and 64 are provided with the chambers. A threaded 8 aluminum retainer 66 is located adjacent to the diaphragm 54 g for connection to the spacer 56. A lock nut 67 is located against the retainer 66 and four cap screws 70 tie the spacer 11 56 and retainer 66 with the diaphragms 52 and 54 to the main 12 housing 50. A second nozzle ~not shown) may be threaded into 13 retainer 66 to coact with diaphragm 54, as described in the 14 referenced copending application.
16 At the other end of the housing 50, the threaded element 44, 17 which is made as a soft iron cap with internal threads for 18 engaging the nozzle, is joined with a lock nut 68 by means of 19 four Allen socket cap screws 72 to the main housing 50.
21 Fig.lO depicts the assembled unit which has a notch 74 in the 22 housing 50 to allow connection of electrical circuitry to the 23 electrical coil of the electromagnetic circuit and to permit 24 escape of excess air.
26 By virtue of the integral structure of a nozzle and pole piece 27 which are machined from a single magnetic rod, the end of the 28 nozzle tube 46 and the end of the pole piece 41 are 29 substantially coplanar. When the electromagnetic force is applied to the top surface of the diaphragm 13 by the magnetic 31 fluid 30, the lower surface of the diaphragm conforms to the 32 shape of the pole piece 41. Since the alignment of the ends 33 of the pole piece 41 and nozzle tube 46 are in substantial 34 planar alignment, the diaphragm will provide a complete seal at the face of the nozzle. Wlth the present design, the 36 torque applied to the flapper valve acts through a point 37 further from the noæzle than the point of first contact 38 between the flapper valve an~ nozzle 10, and if the flapper 39 valve does no~ contact the nozzle squarely, further torque 1 will only distort the flapper valve and worsen the incomplete ~ seal. With the nozzle and pole piece structure design as 3 disclosed herein, any canting of the diaphragm 13 is self-4 corrected because the force on the diaphragm acts between a point of first contact of the diaphragm 13 with the end of the 6 larger diameter pole piece 41 and the coplanar end of the 7 nozzie tube. The integral nozzle and pole piece structure 8 also is easier to fabricate with the slots 44 formed at the 9 end of the rod structure to allow the desired air escape instead of with transverse holes as used in prior nozzle 11 assemblies. Such transverse holes either require a difficult 12 process to machine a deep groove between the nozzle 10 and 13 pole piece 11, or require fabricating the nozzle 10 and pole 14 piece 11 separately, in which case it would be difficult to assemble these parts to achieve the desired coplanarity.
3&
Claims (17)
1. A current-to-pressure transducer comprising:
a baseplate or housing made of magnetic material:
at least one chamber formed in said baseplate, said chamber having at least one open end;
at least one flexible membrane or diaphragm for sealing said open end;
a volume of magnetic fluid contained within said chamber;
air supply means disposed closely adjacent to said flexible membrane or diaphragm for supplying air;
electromagnetic means comprising a magnetic circuit and a coil including permanent magnet means for receiving an input current to provide a magnetic field closely adjacent to said flexible membrane or diaphragm for displacing said flexible membrane or diaphragm relative to said air supply means so that the pressure of said air in said air supply means is regulated in accordance with said input current, wherein the displacement of said flexible membrane or diaphragm is accomplished with the volume of said magnetic fluid conserved and maintained constant and wherein said displacement is not opposed by ambient pressure.
a baseplate or housing made of magnetic material:
at least one chamber formed in said baseplate, said chamber having at least one open end;
at least one flexible membrane or diaphragm for sealing said open end;
a volume of magnetic fluid contained within said chamber;
air supply means disposed closely adjacent to said flexible membrane or diaphragm for supplying air;
electromagnetic means comprising a magnetic circuit and a coil including permanent magnet means for receiving an input current to provide a magnetic field closely adjacent to said flexible membrane or diaphragm for displacing said flexible membrane or diaphragm relative to said air supply means so that the pressure of said air in said air supply means is regulated in accordance with said input current, wherein the displacement of said flexible membrane or diaphragm is accomplished with the volume of said magnetic fluid conserved and maintained constant and wherein said displacement is not opposed by ambient pressure.
2. A current-to-pressure transducer as in claim 1 comprisng an integral nozzle and pole piece structure comprising:
a longitudinal rod made of magnetic material;
a nozzle tube formed in a central portion of said rod for allowing the passage of air received from an air supply;
one end of said rod forming a magnetic pole piece, said pole piece end being substantially coplanar with an end of said nozzle tube.
a longitudinal rod made of magnetic material;
a nozzle tube formed in a central portion of said rod for allowing the passage of air received from an air supply;
one end of said rod forming a magnetic pole piece, said pole piece end being substantially coplanar with an end of said nozzle tube.
3. A current-to-pressure transducer as in Claim 1, wherein said electromagnetic means comprises a magnetic tubular element and said coil is wound about said element.
4. A current-to-pressure transducer as in Claim 3, wherein said air supply means comprises a tube disposed coaxially within said magnetic tubular element, and a nozzle disposed at one end of said tube closely adjacent to said flexible membrane or diaphragm.
5. A current-to-pressure transducer as in Claim 1, including a magnetic piece positioned within said chamber adjacent to said membrane or diaphragm.
6. A current-to-pressure transducer as in Claim 1, wherein an air space is provided within said magnetic fluid.
7. A current-to-pressure transducer as in Claim 1, including a pressure sensing means, and an electronic feedback circuit for limiting the current to said electromagnetic means so that the pressure is substantially linearly related to the input current.
8. A current-to-pressure transducer as in Claim 1, including retainer means for maintaining said membrane or diaphragm in position at said open end of said chamber.
9. A current-to-pressure transducer comprising:
means for supplying a flow of air;
first and second chambers and a means connecting said chambers, each of said chambers having an open end;
magnetic fluid disposed within said chambers and said connection means;
first and second flexible diaphragms respectively positioned against said open ends for containing said fluid within said chambers; and electromagnetic means energized by an input electrical current for coacting with said magnetic fluid to deform a selected one of said diaphragms thereby varying the air pressure in said supply means.
means for supplying a flow of air;
first and second chambers and a means connecting said chambers, each of said chambers having an open end;
magnetic fluid disposed within said chambers and said connection means;
first and second flexible diaphragms respectively positioned against said open ends for containing said fluid within said chambers; and electromagnetic means energized by an input electrical current for coacting with said magnetic fluid to deform a selected one of said diaphragms thereby varying the air pressure in said supply means.
10. A current-to-pressure transducer as in Claim 9, wherein said electromagnetic means is positioned for coacting with said magnetic fluid in one of said chambers to deform a selected one of said diaphragms, and said air supply means is positioned for coacting with the other one of said diaphragms.
11. A current-to-pressure transducer as in Claim 9 wherein the diaphragms are coplanar.
12. A structure as in Claim 2, including longitudinal slots formed at said one end of said rod for allowing the escape of air.
13. A structure as in Claim 12,including a groove encompassing said nozzle tube, said slots being connected to said groove.
14. A structure as in Claim 2, including a threaded element seated on a portion of said rod adjacent to the other end of said rod, a housing cap for engaging said threaded element, and means formed integral with said rod for rotating said rod and said threaded element for adjusting the position of said nozzle tube.
15. A structure as in Claim 2, wherein said nozzle tube encompasses an air channel, said nozzle tube being tapered at one end to form a constricted portion of said air channel for changing the pressure of said air flow.
16. A structure as in Claim 2, including a housing for containing said nozzle and pole piece.
17. A structure as in Claim 16, including an opening formed in said housing for allowing access of electrical circuit connection and for permitting escape of excess air.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/281,125 | 1988-12-07 | ||
| US07/281,125 US4874005A (en) | 1988-12-07 | 1988-12-07 | Current to pressure tranducer employing magnetic fluid |
| US07/414,395 US4984600A (en) | 1989-09-29 | 1989-09-29 | Self correcting nozzle useful with current to pressure transducer |
| US07/414,395 | 1989-09-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1336784C true CA1336784C (en) | 1995-08-22 |
Family
ID=26960725
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 614828 Expired - Fee Related CA1336784C (en) | 1988-12-07 | 1989-09-29 | Current to pressure transducer employing magnetic fluid |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0380762B1 (en) |
| JP (1) | JP2539931B2 (en) |
| AU (1) | AU619927B2 (en) |
| CA (1) | CA1336784C (en) |
| DE (1) | DE68912562T2 (en) |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2939673A (en) * | 1953-12-23 | 1960-06-07 | Honeywell Regulator Co | Electromechanical elements |
| US2869818A (en) * | 1958-01-03 | 1959-01-20 | Fleuret Marcel | Electromagnetic metering valve |
| US3272078A (en) * | 1964-10-12 | 1966-09-13 | Honeywell Inc | Controlling apparatus |
| GB1140785A (en) * | 1966-07-29 | 1969-01-22 | Sperry Rand Corp | Improvements relating to control systems |
| DE1600840A1 (en) * | 1967-02-06 | 1970-02-05 | Licentia Gmbh | Control valve |
| US3426970A (en) * | 1968-03-25 | 1969-02-11 | Honeywell Inc | Vibration damping nozzle and flapper |
| US3817488A (en) * | 1971-10-04 | 1974-06-18 | Northeast Fluidics Inc | Electro-pneumatic device |
| US4053952A (en) | 1975-10-10 | 1977-10-18 | The United States Of America As Represented By The Secretary Of The Department Of Health, Education And Welfare | Magnetic fluid actuated control valve, relief valve and pump |
| US4579137A (en) | 1981-10-06 | 1986-04-01 | Inotek, Inc. | Electro-pneumatic current to pressure transducer and pneumatic and electronic control circuits therefor |
| GB2181818B (en) * | 1985-10-18 | 1989-10-25 | Ti Domestic Appliances Ltd | Fluid flow control valve |
| JP2621321B2 (en) * | 1988-03-31 | 1997-06-18 | 株式会社島津製作所 | Fluid pressure regulating valve device |
-
1989
- 1989-09-29 CA CA 614828 patent/CA1336784C/en not_active Expired - Fee Related
- 1989-10-24 DE DE1989612562 patent/DE68912562T2/en not_active Expired - Fee Related
- 1989-10-24 EP EP19890119767 patent/EP0380762B1/en not_active Expired - Lifetime
- 1989-12-01 JP JP1314132A patent/JP2539931B2/en not_active Expired - Lifetime
- 1989-12-06 AU AU45985/89A patent/AU619927B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| EP0380762B1 (en) | 1994-01-19 |
| DE68912562T2 (en) | 1994-05-05 |
| JPH02225803A (en) | 1990-09-07 |
| AU4598589A (en) | 1990-06-14 |
| JP2539931B2 (en) | 1996-10-02 |
| DE68912562D1 (en) | 1994-03-03 |
| EP0380762A1 (en) | 1990-08-08 |
| AU619927B2 (en) | 1992-02-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |