WO2006125259A1

WO2006125259A1 - Magnetically actuated valve

Info

Publication number: WO2006125259A1
Application number: PCT/AU2006/000688
Authority: WO
Inventors: George Osborne
Original assignee: Adelaide Research and Innovation Pty Ltd
Current assignee: Innovation and Commercial Partners Pty Ltd
Priority date: 2005-05-24
Filing date: 2006-05-24
Publication date: 2006-11-30
Anticipated expiration: 2007-11-24

Abstract

A magnetically actuated valve is provided having a body with at least first and second orifices. The valve includes a magnetic actuating means having first and second valve members each associated with a respective magnetic field, the interaction of the magnetic fields being such that the valve members are normally urged away from each other to close the first and second orifices respectively. The magnetic actuating means also includes at least one supplementary magnetic field capable of interacting with either or both of the first and second magnetic fields to move one or both of the valve members to open a respective orifice.

Description

MAGNETICALLY ACTUATED VALVE

Field of the Invention

The present invention relates to a magnetically actuated valve. The valve is envisaged to be particularly useful for use with pneumatically actuated mechanisms, such as pneumatically actuated artificial muscles in robotics and mechatronics. While much of the following description will be limited to discussions of those applications, the invention is not to be so limited. For example, the magnetically actuated valve of the present invention may find use in pneumatically actuated transport systems of industrial assembly lines, fast acting automatic door mechanisms, or pneumatically operated musical instruments. For closed-loop control applications, the valve can be fitted with an integrated miniature pressure sensor.

Background of the Invention

While pneumatically actuated artificial muscles are known in the robotics field, they are still only a small part of the fairly recent advances in robotic technology. Indeed, difficulties are still being encountered in operating and manipulating these artificial muscles, many of which relate to the suitable delivery and control of air to the muscle. One such difficulty lies in the use of suitable valving to control that delivery.

Typically, robotics technology requires the development of equipment that tends to be lightweight yet strong, relatively simple in its construction, and capable of delivering the required force and load outputs with relatively low power consumption requirements. Physical size is also an issue, with the need for most equipment to be relatively small in size.

It is an aim of the present invention to provide a valve that is capable of being used to actuate a pneumatically actuatable artificial limb, specifically via an artificial muscle. The valve is ideally mechanically simple, and relatively lightweight and small. However, the valve may find use in other applications that have similar requirements. It is envisaged that most pneumatic control environments would provide suitable uses.

Summary of the Invention

According to the present invention there is provided a magnetically actuated valve having a body with at least first and second orifices, the valve including a magnetic actuating means having first and second movable valve members each associated with a respective magnetic field, the interaction of the magnetic fields being such that the valve members are normally urged away from each other to close the first and second orifices respectively, the magnetic actuating means also including at least one supplementary magnetic field capable of interacting with both of the first and second magnetic fields to move one or both of the valve members to open a respective orifice.

The first and second magnetic fields will ideally be provided by permanent magnets, such as by rare earth magnets. The first and second magnetic fields in this form are thus ideally static magnetic fields that are not variable.

With reference to the first and second valve members each being "associated with" a respective magnetic field, it should be appreciated that the valve members are ideally either partly or wholly a permanent magnet, or they may interact with another valve part that is itself either partly or wholly a permanent magnet. For example, the valve member may be a valve piston or valve stem that provides the closing of the respective orifice as mentioned above, and there may be a permanent magnet arranged so as to interact with the valve piston or valve stem to provide its movement. It is with this in mind that use is made of the term "associated with", with respect to the association of a valve member with a magnetic field. The at least one supplementary magnetic field will preferably be provided electromagnetically by any suitable electromagnetic field generating device, and thus will ideally be variable in that it is capable of being switched on or off, of being modulated, and also of being reversed. For example, known types of inductors can be used, preferably that permit reversal of the polarity of the supplementary magnetic field, such as by reversing the current direction in a coil.

Preferably, there will only be one coil, located substantially between the valve members, to provide whatever electromagnetic fields are required to interact with either or both of the first and second magnetic fields to move either of the valve members to open a respective orifice. However, ideally the coil will be wound in a manner that permits maximization of the variable magnetic force where it is most effective, reducing the power required to operate the valve. Low-power devices are required in many robotics applications where the weight of the battery pack is often a limiting factor.

Preferably, the valve will include one coil that is wound to provide three parts, each capable of generating its own electromagnetic field. This allows three pairs of electromagnetic north and south poles to be placed substantially in between those of the permanent magnets. The additional electromagnetic poles exercise an additional push-pull effect where it is most effective (near the ends of the permanent magnets). An overall stronger electromagnetic force is thus able to act on the magnetic force of the permanent magnets while the field generating current remains unaltered. Alternatively, the same electromagnetic force can be produced with a lower current, thereby leading to additional energy savings and a reduced level of heat generation within the coil.

It will be appreciated that the configuration and interaction of the static and variable magnetic fields described above avoids the need for an iron core, which in turn avoids the need to counteract any residual magnetism during continuous operation of the valve. The magnetically actuated valve of the present invention is thus not subject to the adverse effects of hysteresis losses caused by the presence of such iron cores.

However, where coils are used to generate the supplementary magnetic field, heat is generated inside the windings of the coil whenever the valve is operated. Thus, the coil is preferably cooled during operation by configuring the chambers, porting and air passageways such that air flowing through the valve is directed to pass over the coil. In one such form, upon actuation of the valve inlet, air is able to flow past the valve seat and through a small passage into a coil chamber, from where it can proceed through an outlet into the device to be actuated (e.g. a pneumatic muscle).

The present invention thus also provides a magnetically actuated valve having a body with at least first and second orifices, the valve including a magnetic actuating means having a housing, first and second opposed movable valve members providing first and second static magnetic fields, and a means for externally generating at least one supplementary magnetic field about the valve members, the valve members being at least partially constrained within the housing such that they are both capable of reciprocal axial movement, whereby the first and second valve members are normally urged away from each other by the interaction of their respective static magnetic fields to close the first and second orifices respectively, and whereby the at least one supplementary magnetic field interacts with the static magnetic fields such that one of the first and second valve members retracts in response thereto to open its respective orifice.

The valve of the present invention, in its most preferred form, thus only requires a single electrical connection for operation. The two permanent magnets are ideally arranged with like poles adjacent each other, and close enough to each other, so as to provide the bias required between the two valve members to ensure the orifices are closed in the absence of a supplementary magnetic field and thus when the magnetic actuating means is at rest. It is thus the interaction of the static magnetic fields of the two permanent magnets that permits this, without any reliance on attraction to an iron core or the like.

By then introducing the third magnetic field (the supplementary and preferably variable magnetic field), a further interaction of magnetic fields is provided that results in one of the permanent magnets (and thus its valve member) moving.

By suitably configuring the valve members in conjunction with the orifices, this movement can be advantageously used to open and close the orifices in response to the introduction of the supplementary magnetic field (and thus merely in response to the passing of a current through a coil).

Furthermore, it will be appreciated that the valve may additionally be provided with suitable chambers, passageways and porting in order to provide the required valve operation. For example, the valve may simply require one inlet and one outlet, and thus only need to provide opening and closing of the inlet and outlet in order to provide its full functionality. Alternatively, exhaust ports may be required in order to vent expelled gases, or additional operational outlets may be required.

Finally, although this specification will generally refer the valve operating with, or due to, air, it is to be appreciated that any suitable gas (and possibly some liquids) may be used with the magnetically actuated valve of the present invention.

Description of the Drawings

The magnetically actuated valve of the present invention will now be described in relation to various preferred embodiments as illustrated in the accompanying drawings. Of course, the following description of preferred embodiments is not to limit the broad nature of the above description of the invention. In the drawings:

Figure 1 is a schematic representation of a magnetically actuating valve in accordance with the present invention, shown in an at rest position;

Figure 2 is a schematic representation of a first embodiment of the magnetically actuating valve of Figure 1 , shown with a supplementary magnetic field of a first type being generated to operate the valve;

Figure 3 is a schematic representation of the first embodiment of the magnetically actuating valve of Figure 1 , shown with the supplementary magnetic field of the first type being generated to further operate the valve;

Figure 4 is a schematic representation of a second embodiment of the magnetically actuating valve of Figure 1 , shown with a supplementary magnetic field of a second type being generated to operate the valve;

Figure 5 is a schematic representation of the second embodiment of the magnetically actuating valve of Figure 1 , shown with the supplementary magnetic field of the second type being generated to further operate the valve;

Figures 6, 7 and 8 are sequential schematic representations showing the operation of a preferred type of valve member for use with the magnetically actuated valve of any of Figures 1 to 5;

Figure 9 is a section view through a magnetically actuated valve embodying the electromagnetic field and valve member illustrated schematically in Figures 4 to 8; and

Figure 10 is a section view through a magnetically actuated valve embodying the electromagnetic field illustrated schematically in Figures 4 and 5 with a combination of valve members. Description of the Preferred Embodiments

The magnetically actuated valve 10 of the preferred embodiment illustrated schematically in Figure 1 uses two opposing permanent (rare earth) magnets Mi and M₂ (having respective static magnetic fields 12 and 14 respectively) to keep both the first orifice 16 and the second orifice 18 closed, via respective valve stems 17 and 17' and valve heads 19 and 19'. In this embodiment, it is the combination of a permanent magnet, a valve stem and a valve head that is regarded as the valve member referred to above, the valve members in Figure 1 being generally identified as Vi and V₂. Thus, the permanent magnet (Mi and M₂) is merely a part of the valve member (\Λ and V₂), but still results in there being a magnetic field (12 or 14) associated with a valve member (Vi or V₂). The two additional ports shown in Figure 1 are the mains air supply port 18' and the outlet exhaust into atmosphere 16'.

It can be seen that the valve members (Vi and V₂) are held with a generally cylindrical housing in a manner that generally constrains them both to permit only axial movement. Both of the valve members are thus operative valve members in that they are both capable of movement to open or close the respective orifices.

The permanent magnets (Mi and M₂) eliminate the need for return springs, as the force exercised by the opposing poles of the two magnets (Mi and M₂) hold both valve members (V₁ and V₂) closed (as is shown in Figure 1 ) in the at rest position, this being the interaction between the first and second magnetic fields (12 and 14) as generally indicated by arrow A. On the inlet side, this process is assisted by the chamber pressure on the mains side of the valve member. Also, this configuration avoids the need for an iron core, or any other type of iron member, which might sometimes be used to provide an attractive force for one or both of the permanent magnets. The general valve configuration and arrangements shown in Figure 1 are the same configuration adopted for the first and second embodiments of coil configurations that provide the first and second types of supplementary magnetic field briefly mentioned above. The first type is shown in Figures 2 and 3 and the second type is shown in Figures 4 and 5, both of which will now be described.

In Figures 2 and 3, a common coil 20 is illustrated placed about the cylindrical housing 22 within which the two permanent magnets (M₁ and M₂) are arranged. This coil 20 is ideally located substantially between the valve members such that the magnetic field that is capable of being generated by the coil 20 (that is supplemental to the static magnetic fields of the permanent magnets (Mi and M₂), and is thus generated externally of them) is able to interact with (and modify) both the first and second magnetic fields (12 and 14) as described below.

When a current is applied in the forward direction (see Figure 2), the coil generates an electromagnetic field (shown as arrow B pointing to the right of the page with N-S polarity) that interacts with the magnetic field 14 of the permanent magnet M₂, causing the permanent magnet M₂ to move towards the centre barrier 24 of the cylindrical housing 22, thereby moving the valve member V₂ to open the orifice 18. The permanent magnet M₁ is urged away from the centre barrier 24 by the generated electromagnetic field, towards the orifice 16 adjacent the valve member V-i, holding the valve member Vi closed even more firmly.

Reversing the direction of the current to the coil (see Figure 3) causes the generated electromagnetic field (now shown as arrow C pointing to the left of the page with S-N polarity) to interact with the magnetic field of the permanent magnet M-i, causing it to move towards the centre barrier 24 of the cylindrical housing 22, thereby moving the valve member V₁ and causing the orifice 16 to be opened. The permanent magnet M₂ is urged towards the orifice 18 adjacent the valve member V₂ by the generated electromagnetic field, holding it closed even more firmly.

The illustrations of Figures 4 and 5 show a similar operation to that of Figures 2 and 3, with the exception of the configuration of the coil and thus the manner of generation of the supplementary magnetic field (the variable electromagnetic magnetic field).

With respect to Figures 4 and 5, a common coil 26, this time with three distinct sections (28, 30 and 32) is placed substantially between the pair of permanent magnets (Mi and M₂). The outer sections (28 and 32) of the coil 26 are wound in the opposing direction to the inner section 30, which effectively produces a set of three electromagnets from a single coil. Energizing the coil 26 with a forward current thus generates three electromagnetic fields with the polarity as shown by the three arrows D, E and F in Figure 4. In this state, the permanent magnet M₂ moves towards the centre barrier 24 of the cylindrical housing 22, thereby moving the valve member V₂ and causing the orifice 18 to be opened. Again, the permanent magnet Mi is pushed outwards onto the seat of the valve member V-i, holding the orifice 16 closed even more firmly.

Reversing the direction of the current causes the reversal of the polarity of all three of the electromagnetic fields, as is shown by the three arrows G, H and J in Figure 5. The permanent magnet Mi therefore moves towards the centre barrier 24 of the cylindrical housing 22, moving the valve member V₁, and opening the orifice 16, while the permanent magnet M₂ is again pushed outwards onto the seat of the valve member V₂, holding the orifice 18 closed even more firmly.

As mentioned above, the chambers, porting and air passageways shown in Figures 1 to 5 may be altered as required, depending upon the application in which the valve will be used. Indeed, the chambers into which the respective orifices open may themselves be ported into the chambers above the coil (indicated generally in Figure 5 by reference numeral 30) or may open directly to the bore of the cylindrical housing 22 within which the permanent magnets (Mi and M₂) are located.

With further reference to the chambers, porting and air passageways, the magnetically actuated valve of the present invention can be configured, for example, in two different ways. Firstly, an orifice-type inlet and/or outlet can be used to reduce the flow of air into and out of an artificial muscle to which the valve is attached. This may be important in applications in which fast actuation can cause damage or instability to the operation of the artificial muscle. For example, many haptic devices and servomechanism applications might benefit from a reduced actuation speed. Secondly, on-off control requires a maximally quick increase/decrease of the pressure inside an artificial muscle, which can be achieved by fitting the valve with, for example, a diaphragm. Fortunately, and as will be seen below, the simplicity of the valve design makes it very easy to swap these modules.

The magnetically actuated valve can thus be easily optimized to any particular task. For example, in a robotics application involving the pneumatic actuation of a bipedal autonomous mobile robot, the accurate switching of five different pneumatic muscles is required, following a complex timing sequence. In this case, the switching time requires adjustment to the range from 100 ms to 200 ms. As faster switching would make the robot motion become unstable, the first mentioned configuration (the orifice type outlet) would be preferred.

The sequential operation of one type of valve configuration is shown in Figures 6 to 8. In each of these Figures, the same general configuration is shown throughout, so suitable reference numerals have been shown in Figure 6 and only where needed for an understanding of the operation in Figures 7 and 8.

Illustrated is a valve member including a permanent magnet 40 in the bore of a cylindrical housing 42 (similar to the cylindrical housing 22 mentioned above), with the housing including a centre barrier 44, the permanent magnet being constrained within the cylindrical housing 42 for reciprocal axial movement. The permanent magnet 40 abuts against a hollow valve stem 46 that includes a centrally arranged valve head 48 located between the ends of the valve stem 46. The outer surface (the outlet side, towards the left of the page) of the valve head 48 abuts against a valve seat 52, the valve seat 52 being provided by the open end of a valve stem receiving chamber 53. The valve stem receiving chamber 53 is in fluid communication at its closed end 55 with the valve outlet 54.

The permanent magnet 40 is urged against the interior end 50 of the valve stem 46 by virtue of the interaction of its magnetic field with the magnetic field of an adjacent permanent magnet (not shown) via arrow K, much like the urging apart of the permanent magnets (Mi and M₂) via arrow A in Figure 1. This in turn urges the valve head 48 onto the valve seat 52 to close off the valve outlet 54. Although not illustrated in these Figures, it will be appreciated that the engagement of the permanent magnet 40 with the valve stem 46 and of the valve head 48 with the valve seat 52 may be via a suitable type of seal, such as a rubber seal.

The valve head 48 includes a flexible diaphragm 56 that extends across the full internal width of the valve and is secured at edges 58 to the outer wall thereof. The operation of the diaphragm 56 will be described below in relation to the sequential operation of the valve itself.

In operation, a small hole 60 near the centre of the diaphragm 56 allows air to pass from the valve inlet 62 to the inner surface of the diaphragm 56 (the inlet side, towards the right of the page), thereby firmly pressing the valve head 48 (and thus the diaphragm 56) against the valve seat 52 to close the valve.

Upon energizing the coil (not shown), reversing the effect of the interaction of the permanent magnets (as shown by arrow L in Figure 7), the permanent magnet 40 starts moving away from the interior end 50 of the valve stem 46. This allows some of the air to pass through the hollow interior of the valve stθm 46 (Figure 7). The build-up of pressure on the front of the diaphragm 56 (the outlet side, towards the left of the page) causes the diaphragm 56 to flex and move in the direction of the permanent magnet 40 (away from the valve seat 52). Then, as soon as a small air gap has developed across the valve seat 52, high pressure air from the valve inlet 62 can pass directly over the valve seat 52 and to valve outlet 54, pushing the valve open even faster using positive force feedback (see Figure 8). The valve therefore opens maximally fast.

To close the valve, the current through the coil needs to be switched off. This causes the permanent magnet 40 to again urge the valve stem 46 and thus the valve head 48 against the valve seat 52, thereby closing the air gap as well as sealing off the hollow interior of the valve stem 46. The valve is then held shut.

A description of two embodiments of the magnetically actuated valve of the present invention will now be described in relation to the illustrations in Figures 9 and 10.

Mains air enters the valve assembly at port 60 in the embodiments of both Figure 9 (diaphragm type) and Figure 10 (orifice type), thereby pressurising the chamber 62 on the inlet side of the valve seat. In the case of the diaphragm type (Figure 9), the pressure builds up to the same level (mains) on both sides of the diaphragm 64.

As soon as the permanent magnet member 66 begins to move towards the centre of the valve assembly, air can flow through the hollow valve stem (68 and 68'), with the airflow directed from interior end of the valve stem (70 and 70') towards the connecting port (72, out of plane) into the coil chamber 74. From there it enters the device to be inflated (e.g. the bladder of the pneumatic muscle) via a port which is not visible in Figures 9 or 10. Similarly, the outlet valve is supplied with air through port 76. The same mechanism lets air pass through the hollow valve stem (78 and 78') at that end of the valve assembly and then over the opening valve seat (80 and 80') into the venting exhaust port 82.

The air flow at the inlet and/or outlet can be restricted as required by the application by fitting the valve assembly with different sized (and/or different types of) valve members, generally referred to by reference numerals 84 or 84', with the numeral 84 designating a diaphragm based mechanism and the prime numeral 84' designating an orifice based mechanism. Maximally fast actuation can be achieved by fitting the inlet and/or outlet with a diaphragm based mechanism 84. This has the additional advantage of a reduced current consumption as the valve can be operated using very short actuation pulses (as opposed to the longer pulses required to actuate the orifice based mechanism 84').

It is possible to combine both actuation methods (as is illustrated in Figure 10) by using the diaphragm based mechanism 84 while fitting the supply line port 60 (inlet) and/or the exhaust port 76 (outlet) with a variable size orifice. The latter restricts the flow into and out of the device to be inflated or deflated, while still retaining the advantage of fast low-current actuation provided by the diaphragm mechanism.

With reference to the operation of the valve assemblies illustrated in Figures 9 and 10, an electrical current is switched onto the coil 90 through a push-on connector 92 and solder-less contact electrodes 94. This ensures minimal assembly time of the device as everything can be put together in three simple steps. The coil 90 sits on a small coil former 96 which is held between the two main members (98 and 100) of the body of the valve assembly. The coil former may be of any suitable material but ideally will be a hard, engineering plastic such as the acetal resin Delrin™, or may be aluminium. The outer housing 102 simply slides over the body of the valve assembly and then screws onto the muscle sided member 98 of the body of the valve assembly. A small grub screw 104 is then used to firmly push the inlet sided member 100 of the body of the valve assembly onto the coil former 96. Rubber O-ring seals 108 ensure an airtight seal of the entire assembly. The artificial (and pneumatically operated) muscle 110 is clamped onto the inner member 98 of the main body of the valve assembly via a clamping ring 112.

Finally, it will be appreciated that other variations and modifications may be made to the various configurations described herein that are also within the scope of the present invention.

Claims

We claim:

1. A magnetically actuated valve having a body with at least first and second orifices, the valve including a magnetic actuating means having first and second movable valve members each associated with a respective magnetic field, the interaction of the magnetic fields being such that the valve members are normally urged away from each other to close the first and second orifices respectively, the magnetic actuating means also including at least one supplementary magnetic field capable of interacting with both of the first and second magnetic fields to move one or both of the valve members to open a respective orifice.

2. A valve according to claim 1, wherein the first and second magnetic fields are provided by permanent magnets, such as by rare earth magnets.

3. A valve according to claim 1 or claim 2, wherein the first and second magnetic fields are static magnetic fields that are not variable.

4. A valve according to any one of claims 1 to 3, wherein the valve members are either partly or wholly a permanent magnet, or they may interact with another valve part that is itself either wholly or partly a permanent magnet.

5. A valve according to any one claims 1 to 4, wherein the at least one supplementary magnetic field is provided electromagnetically by an electromagnetic field generating device.

6. A valve according to any one of claims 1 to 5, wherein the at least one supplementary magnetic field is variable in that it is capable of being switched on or off, of being modulated, or of being reversed.

7. A valve according to any one claims 1 to 6, wherein the at least one supplementary magnetic field is a variable electromagnetic field in the form of an inductor that permits reversal of the polarity of the supplementary magnetic field by reversing the current direction in a coil.

8. A valve according to claim 7, wherein there is one coil to provide the electromagnetic fields required to interact with either or both of the first and second magnetic fields to move one or both of the valve members to open a respective orifice, the coil being arranged to be substantially between the valve members.

9. A valve according to claim 8, wherein the valve includes one coil that is wound to provide three parts, each part being capable of generating its own electromagnetic field, the coil being arranged to be substantially between the valve members.

10. A valve according to claim 8 or claim 9, wherein the coil is cooled during operation by configuring the air passageways such that air flowing through the valve is directed to pass over the coil.

11. A valve according to any one of claims 1 to 10, the valve including a housing, the valve members being at least partially constrained within the housing for reciprocal axial movement.

12. A valve according to claim 11 , wherein the valve members include a hollow valve stem having a centrally arranged valve head located between the ends thereof, and a flexible diaphragm extending across the valve housing, the diaphragm having an inlet side and an outlet side.

13. A valve according to claim 12, the valve head having an outer surface that, at rest, abuts against a valve seat, the valve seat being provided by the open end of a valve stem receiving chamber that is in fluid communication at its closed end with a valve outlet.

14. A valve according to claim 13, wherein each valve member includes a respective permanent magnet urged at rest against the valve stem by virtue of the interaction of its magnetic field with the magnetic field of an adjacent permanent magnet, which in turn urges the valve head onto the valve seat to close off the valve outlet.

15. A valve according to claim 14, wherein the diaphragm includes a hole therethrough that allows air to pass from its inlet side to its outlet side, thereby firmly pressing the valve head against the valve seat to close the valve.

16. A magnetically actuated valve having a body with at least first and second orifices, the valve including a magnetic actuating means having a housing, first and second opposed movable valve members providing first and second static magnetic fields, and a means for externally generating at least one supplementary magnetic field about the valve members, the valve members being at least partially constrained within the housing such that they are both capable of reciprocal axial movement, whereby the first and second valve members are normally urged away from each other by the interaction of their respective static magnetic fields to close the first and second orifices respectively, and whereby the at least one supplementary magnetic field interacts with the static magnetic fields such that one of the first and second valve members retracts in response thereto to open its respective orifice.

17. A magnetically actuated valve according to claim 1 , substantially as herein described in relation to the accompanying Figures.

18. A magnetically actuated valve according to claim 16, substantially as herein described in relation to the accompanying Figures.