US20060056993A1

US20060056993A1 - Magnetic spring actuator device

Info

Publication number: US20060056993A1
Application number: US11/224,947
Authority: US
Inventors: Moshe Gombinsky; Amir Porat
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-09-14
Filing date: 2005-09-14
Publication date: 2006-03-16
Also published as: WO2006030434A3; WO2006030434A2

Abstract

A magnetic spring actuator comprising a ring, a piston movably disposed inside of the ring, and a-non-magnetic holding cylinder. At least one of the ring and the piston is magnetic. Due to a magnetic force caused by at least one of the ring and the piston, the piston is initially located in a first position with respect to the ring. Application of an outside force results in movement of the piston to a second position with respect to the ring. The magnetic force produces a return force for causing the piston to return to the first position with respect to the ring. Alternatively, the piston can be fixed and the ring can be adapted for moving with respect to the piston in a similar manner. A bi-metal coil spring may be wound around the piston.

Description

FIELD OF THE INVENTION

The present invention relates to a magnetic spring actuator device. The invention can be used as a common spring in almost every application in which springs are employed, under the condition that the magnetism does not disturb other aspects of the technology. The magnetic spring actuator is especially useful in the fields of pneumatic and electromagnetic actuation.

BACKGROUND OF THE INVENTION

Prior art patent EP1420164 describes a simplified magnetizable piston slidable in a cylinder and moved by magnetic coupling to an external magnetic element which moves along the cylinder and is actuated via an external actuator.
Prior art patent DE 10147064 describes a vibrator for a mobile telephone with an oscillating mass provided by a magnetic core that is displaced within electromagnetic coil. The magnetic core or piston is moved back into the electromagnet by a spring.
Prior art publication WO2004038741 describes a flat voice coil actuator having planar coils and having spring-type characteristics. The coil employs a few groups of magnets that create magnetic flux in an air gap where the coil is moveable.
Prior art publication US2004099784 describes an hybrid pneumatic magnetic isolator actuator wherein pneumatic and magnetic forces are applied to a single carriage. The invention relates to a magnetic actuator that operates in parallel to a pneumatic actuator. The magnetic actuator capability is affected by a current supplied to a coil surrounding the magnetic actuator body. The current is controlled so as to be proportional to the instantaneous error in the pressure servo, i.e. the difference between the commanded pressure and the actual pressure. The magnetic force makes up for this difference and thus corrects the error.
All the above publications disclose actuators in which the return force applied on the magnetic piston comes from sources such as pneumatic forces, an external actuator, or a spring.
Surprisingly, using a magnetic piston or ring as a source for creating a return force saves energy and permits better control. Also, the magnetic force does not change over time in contrast to springs which can change over time thus resulting in compromised or altered performance.
Prior art publication US2001003802 describes a magnetic spring wherein magnets are moved by magnetic forces created by a plurality of spaced-apart stationary magnetized segments dispersed along a circle about an axis, defining a first plurality of spaced apart gaps. The magnets move along the gaps of the stationary magnets. This device is adapted as a heart ventricle assist device, but is very complicated since it uses many magnets.

SUMMARY OF THE INVENTION

In the present invention, the term “ring” is used to refer to a component having a central opening into which a piston can enter. This component may take the form of a toroidal element, or may have any other shape, as long as a central bore is present to allow advancement of the piston into the central bore. Additional shapes other than a ring, which may be used, include (but are not limited to): a hollowed open-faced cube, a rectangular element with central bore, a U-shape, a cup-shape, or an ellipse.
The present invention relates to a magnetic spring actuator device comprising:

- a) a piston and a ring arranged so that one of them is a fixed part and the other is a moving part;
- b) a non-magnetic holding cylinder having each of said fixed and moving parts disposed therein.

In the invention, at least one of the fixed and moving parts is magnetic. Due to a magnetic force caused by at least one of the fixed and moving parts, the moving part is initially located in a first position with respect to the fixed part. Upon application of an outside force on the magnetic spring actuator, the moving part moves to a second position with respect to the fixed part, such that the magnetic force produces a return force causing the moving part to return to the first position with respect to the fixed part.
According to one embodiment of the present invention, the piston is movably disposed inside of said ring. According to another embodiment of the invention, the ring is moveably engaged around the piston.
According to preferred embodiments of the present invention, the outside force is an electromagnetic force. Alternatively, the outside force is a pneumatic force, or any other suitable force for providing an initial force for causing displacement of the ring or the piston.
Further according to preferred embodiments of the present invention, the piston is magnetic and the ring is magnetizable.
Additionally according to preferred embodiments of the present invention, the ring is magnetic and one end of the piston is positioned substantially inside of the ring.
Still further according to preferred embodiments of the present invention, the ring is magnetic and piston has the same width as the ring. In this case, the piston is positioned inside of the ring. This preferred embodiment provides a magnetic spring unit having a very strong magnetic force on the piston. Additionally, increasing the thickness of the ring further increases the magnetic holding force on the piston. This will be described in more detail below.
Moreover according to preferred embodiments of the present invention, the magnetic spring actuator further comprises a second ring engaged around said piston.
Further according to preferred embodiments of the present invention, said second ring is magnetizable and each of said rings contain an opposite end of said piston disposed therein.
Additionally according to preferred embodiments of the present invention, the ring is a magnet and the piston is magnetizable.
Still further according to preferred embodiments of the present invention, both said ring and said piston are magnetic.
Moreover according to preferred embodiments of the present invention, the distance between the first position and the second position is up to half of the width of the piston.
Additionally according to preferred embodiments of the present invention, the distance between the first position and the second position is up to half of the width of the ring.
Further according to preferred embodiments of the present invention, the magnetic spring actuator also comprises a stopper. The stopper ensures that the magnetic holding force in the unit is not reduced to zero due to the exterior applied force. This will be described in more detail below.
Moreover according to preferred embodiments of the present invention, the magnetic spring actuator further comprises a non-magnetizable shaft connecting between the piston and the cylinder. Connecting means are provided for connecting between the piston and the shaft. The connecting means can be, for example, a screw fit, or any other suitable connection.
Additionally, according to a preferred embodiment, the invention further comprises a bi-metal coil spring wound around the piston, wherein one free end of said bi-metal coil spring is connected to the non-magnetic holding cylinder, and a second free end of the bi-metal coil spring is connected to the piston. The bi-metal coil spring is inducible to contract or expand in response to a stimuli selected from: a change in temperature, or application of an electrical current to the bi-metal coil spring. Preferably, the bi-metal coil spring is formed from an alloy of at least two metals selected from the group consisting of nickel, titanium, copper, chrome and iron.
According to certain embodiments, the bi-metal coil spring is connected to an operable electrical circuit containing a power source, for inducing contraction or expansion of the bi-metal coil spring upon closure of the electrical circuit and activation of the power source. Alternatively, the actuator further comprises a heating element adjacent to or surrounding the actuator, for inducing contraction or expansion of the bi-metal coil spring upon activation of the heating element.
Moreover, in certain embodiments, the invention further comprises an external actuator for inducing contraction or expansion of the bi-metal coil spring.
There is additionally provided by the invention, a method of activation of the bi-metal coil spring actuator, comprising the steps of:

- a. applying a stimuli selected from: a change in temperature or electrical current, to said bi-metal coil spring to induce expansion or contraction of the bi-metal coil spring and cause movement of the piston from the initial starting position to a second position; and
- b. discontinuing said stimuli to allow the piston to return to the initial starting position.

Other features and advantages of the invention will become apparent from the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention in regard to the embodiments thereof, reference is made to the following drawings, not shown to scale, in which:
FIG. 1 a is a schematic cross-sectional drawing of the actuator comprising an iron ring and a magnetic piston disposed within, illustrated in a starting position;
FIG. 1 b is identical to FIG. 1 a, however the piston appears in a second position with respect to the ring, following application of an external force;
FIG. 2 is a schematic cross-sectional drawing of a magnetic actuator composed of a magnetic ring and an iron piston;
FIG. 3 a is a schematic cross-sectional drawing of a magnetic actuator comprising a magnetizable ring and a magnetic piston;
FIG. 3 b is identical to FIG. 3 a, but in this case, the magnetic spring actuator comprises two magnetizable rings;
FIG. 4 is a schematic cross-sectional drawing of a magnetic spring actuator comprising a magnetic ring and a magnetizable piston slidably disposed inside of the ring;
FIG. 5 is a schematic cross-sectional drawing of an electromagnetic spring actuator, having an electric coil for applying an initial force for displacing the piston with respect to the ring;
FIG. 6 a is a schematic cross-sectional drawing of an actuator in which the piston does initially not protrude from the ring;
FIG. 6 b is identical to FIG. 6 a, except that the piston is connected to a shaft;
FIG. 6 c is a schematic drawing of the piston/shaft component of FIG. 6 b;
FIG. 6 d is a schematic drawing of a similar piston/shaft component, however in this embodiment the piston is magnetic;
FIG. 7 is a schematic cross-sectional drawing of an actuator comprised of a magnetic ring and a shorter iron piston disposed inside of the ring;
FIG. 8 is a schematic cross-sectional drawing of an actuator comprised of a long iron ring and a shorter magnetic piston disposed inside of the ring;
FIG. 9 a is a schematic cross-sectional drawing of a pneumatic actuator comprised of a movable magnetic ring, a fixed magnetizable piston, and a cylinder housing the ring and the piston. The piston is fixed by a non-magnetizable shaft to the cylinder;
FIG. 9 b is identical to FIG. 9 a, except that the magnetic ring has a smaller thickness than the ring of FIG. 9 a;
FIG. 10 a is a schematic cross-sectional drawing of a magnetic spring composed of a magnetic ring and a magnetic piston.
FIG. 10 b is identical to FIG. 10 a, except that the magnetic ring is positioned differently with respect to the magnetic piston, due to the polarity of the magnets;
FIG. 11 is a schematic cross-sectional drawing of an actuator comprising a fixed magnetic piston and a movable magnetizable ring positioned inside of a cylinder; the piston is fixed to the cylinder via a non-magnetizable shaft;
FIG. 12 is a schematic cross-sectional drawing of an electromagnetic spring actuator comprising a fixed magnetic piston, a movable magnetizable ring, and a cylinder including an electric coil. The piston is fixed to the cylinder via a non-magnetizable shaft;
FIGS. 13 a-13 d are schematic cross-sectional drawings illustrating the magnetic field lines of magnetic rings. In FIG. 13 a, a magnetic ring is illustrated. In FIG. 13 b, a magnetic ring is illustrated with a piston inside, the piston having a width that is larger than the ring. In FIG. 13 c, the magnetic ring and the piston have the same width. In FIG. 13 d, the magnetic ring and the piston both have the same width, and said width is shorter than that of FIG. 13 c;
FIG. 14 a is a schematic cross-sectional drawing of a bi-metal magnetic coil actuator illustrated in a starting position, and piston is covered with a bi-metal coil;
FIG. 14 b is identical to FIG. 14 a, except that the piston is shown in a second position, following application of force due to a contracting bi-metal coil spring;
FIG. 14 c is similar to FIG. 14 a yet describes the magnetic field of the N pole of piston 146 and the field lines bending into the magnetizable (iron) ring 142;
FIG. 14 d is similar to FIG. 14 b, yet describes the magnetic field of the N pole of piston 146;
FIG. 14 e describes an actuator having a bi-metal coil, with the piston comprised one short magnetic portion, and one lengthened non-magnetic and non-heat-retentive portion;
FIG. 14 f describes the same bi-metal magnetic actuator as in FIG. 14 e, with the magnetic piston shown in a second position with respect to the iron ring;
FIG. 15 a is a schematic cross-sectional drawing of a bi-metal actuator including a non-magnetizable cylinder and a magnetic piston illustrated in a starting position and covered with a bi-metal coil spring. The magnetic piston is connected to a non-magnetic shaft moving through an independent iron ring attached to an actuator arm;
FIG. 15 b is identical to FIG. 15 a, except that the piston is shown in a second position with respect to the non-magnetizable cylinder, following application of force due to a contracting bi-metal coil spring;
FIG. 16 a describes a non-magnetic piston covered with a contracted bi-metal coil spring; the spring and a magnetic piston are attached to the covered piston. The piston is in a first position;
FIG. 16 b describes the magnetic piston in a second position with respect to the magnetizable ring after the bi-metal coil spring is expanded; and
FIGS. 17 a and 17 b illustrate the bi-metal coil spring being part of an electrical circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention discloses a magnetic spring actuator comprising a ring, a piston movably disposed inside of the ring, and a non-magnetic holding cylinder. At least one of the ring and the piston is magnetic. Due to a magnetic force caused by at least one of the ring and the piston, the piston is initially located in a first position with respect to the ring. Application of an outside force results in movement of the piston to a second position with respect to the ring. The magnetic force produces a return force for causing the piston to return to the first position with respect to the ring.
Alternatively, the piston can be fixed and the ring can be adapted for moving with respect to the piston in a similar manner.
The term “a.p.” appearing in the drawings refers to air pressure. “N” and “S” refer to north and south magnetic poles. The arrows in the Figures indicate directions of the initial applied force and of the magnetic return force, and, consequently, the direction of the movement of the ring or piston. “V” refers to a vacuum force.
FIG. 1 represents a simple magnetic spring actuator 10 comprising an iron ring 12 firmly attached to a nonmagnetic cylinder 14 and a long magnetic piston 16 having a stopper 18 that is also employed as a handle. Piston 16 is illustrated in the starting position with respect to ring 12, with the north magnetic pole end of the piston 16 disposed inside of ring 12. A force f applied in the direction indicated results in movement of piston 16 within cylinder 14. Magnetic return force m induced by the magnetism of N pole of piston 16 causes piston 16 to return to the initial starting position.
It is appreciated that piston 16 is maintained in the initial starting position due a magnetic holding force. The force f applied to the unit goes against the magnetic holding force, causing the piston to move. As force f is applied, the magnetic holding force diminishes, approaching zero. However, force f must be stopped before the magnetic holding force reaches zero, or else the piston would become released from the ring. This is the function of the stopper. Once force f is suspended, the magnetic return force m returns the piston to its starting position. FIG. 1 b illustrates the position of piston 16 following application of force f. Piston 16 is prevented from escaping from inside ring 12 due to stopper 18. It is appreciated that the length of movement of piston 16 can be regulated depending on the length of cylinder 14.
FIG. 2 represents a simple magnetic spring 20 comprised of a magnetic ring 22 and an iron piston 24 that protrudes from ring 22. While in FIG. 1 the piston was magnetic and the ring was non-magnetic, in FIG. 2 the ring is magnetic and the piston is non-magnetic. An initial applied force causes piston 24 to become displaced from its original starting position (the starting position resulting from the magnetic force created by the ring on the piston). Subsequently, the magnetic return force induced by magnetic ring 22 causes piston 24 to return to its starting point.
FIG. 6 a is similar to FIG. 2, except that in this case, magnetic ring 60 has a width “w” that is equal to the length “r” of magnetizable piston 62, so that in the initial starting position the piston does not protrude from the ring. The preferred embodiment illustrated in this Figure provides a magnetic spring unit wherein the magnetic ring exerts a very strong magnetic force on the piston. This can be more clearly understood from FIGS. 13 a-13 d.
In FIG. 13 a, the magnetic field lines of magnetic ring 130 are illustrated. At the central bore of the ring there are straight magnetic field lines. In FIG. 13 b, a piston 132 occupies the central bore of ring 130. As seen in this Figure, at the south magnetic pole end of the ring, a closed magnetic force is exerted on the piston end. At the north magnetic pole of the ring, no magnetic force is exerted on the piston end protruding from the ring. In FIG. 13 c, piston 134 has a length that is equal to that of ring 130 so that at the starting position shown in FIG. 13 c, the piston is present entirely within the ring. Thus, at both ends of piston 134, a strong closed magnetic force is exerted.
As seen in FIG. 13 d, the magnetic force can be increased by shortening the length of the piston in regard to the ring, or by increasing the thickness of the ring. Referring to FIG. 13 d, the thickness “d” of the piston is larger than the thickness “d” of the piston seen in FIG. 13 c. Increasing the piston thickness produces more magnetic field lines in the ring bore, and thus a greater magnetic force is exerted on a piston held inside of the ring.
Referring now to FIG. 6 b, piston 62 is attached to a non-magnetizable shaft 64 for facilitating attachment to an external actuator. It is important that shaft 64 be non-magnetizable so that the strong magnetic spring unit formed by ring 60 and piston 62 having the same length as ring 60 is not weakened. The piston 62/shaft 64 component is also seen in FIG. 6 c.
An alternative embodiment, in which the piston 66 is magnetic, is shown in FIG. 6 d with magnetic piston 66 connected to shaft 64. It is appreciated that a non-magnetizable shaft is preferably provided in each of the embodiments described, for connecting between the piston and the cylinder (the cylinder will be described in relation to FIGS. 9 a, 9 b, 11, 12).
FIG. 3 a illustrates a magnetic piston 30 located in a starting position. The end of piston 30 which corresponds to the north pole is disposed inside of ring 32. Ring 32 can be composed of any magnetizable material such as iron or nickel. Air pressure is applied towards the end of piston 30 as indicated. Magnetic return force (indicated by arrow m) works in the direction opposite from air pressure so as to return piston 30 to its starting position with respect to the ring 32.
FIG. 3 b is similar to FIG. 3 a, with the exception that the actuator comprises two magnetizable rings 32 a, 32 b positioned as shown. Due to the presence of two rings 32 a 32 b, the starting position of piston 30 is substantially in between the two rings. A stronger initial force is required to displace piston 30.
FIG. 4 represents a magnetizable piston 40 slidably engaged inside of magnetic ring 42. The piston can be formed, for example, from iron. An initial force, in this case, vacuum V causes displacement of piston 40 with respect to ring 42. Magnetic return force m causes piston 40 to return to the initial starting position shown in the Figure.
FIG. 5 is similar to FIG. 4, but in this embodiment, an electric coil 50 supplies the initial force for displacing piston 52 disposed within the magnetic ring 54. This is an example of an electromagnetic actuator. Piston 52 is comprised of three portions. The first portion is an iron segment 58, held inside of magnetic ring 54 due to the magnetic force of ring 54. The second is a non-magnetizable segment 56. Segment 56 can formed, for example, from copper or aluminum. The third portion is a magnetizable segment 59 that enables application of an electromagnetic force to piston 52 from electric coil 50.
FIGS. 7 and 8 represent further preferred embodiments of the present invention. In FIG. 7, an iron piston 70 is disposed inside of a magnetic ring 72 in the starting position indicated, at the north magnetic pole end of ring 72. The width of piston 70 is shorter than that of ring 72.
In FIG. 8, a long iron ring 80 is illustrated with a shorter magnetic piston 82 disposed therein. This embodiment does not provide a magnetic force that is as strong as that of FIG. 7, because the magnet, in this case, the piston, comprises a smaller area.
It is appreciated that in FIGS. 7 and 8, the ring itself comprises the cylinder. A stopper can be incorporated onto one end of the ring in order to stop the piston from escaping from the ring. (Alternatively, as in FIG. 1, a longer non-magnetizable unit is securely attached to the ring.)
It is also appreciated in both FIGS. 7 and 8, that the piston is held by magnetic force at the north magnetic pole end of the unit. When an external force is applied, the piston cannot be allowed to move more than half the width of the ring, or else the holding force will have been reduced to zero.
FIG. 9 a illustrates a pneumatic actuator wherein magnetic ring 90 is slidably disposed on a static iron piston 92 that is attached to cylinder 94 via a non-magnetizable shaft 96. Air pressure is applied in the direction indicated, causing ring 90 to move from its original position (shown in the diagram) with respect to piston 92 to a second position in which ring 90 is slightly displaced (to the right) with respect to piston 92. The magnetic return force thereafter causes ring 90 to return to the original position.
FIG. 9 b is the same as FIG. 9 a, with the exception that ring 95 has a smaller width than ring 90 (shown in FIG. 9 a), and thus ring 95 moves a shorter distance when air pressure is applied.
FIG. 10 a and FIG. 10 b illustrate magnetic springs that include both magnetic rings and magnetic pistons. In FIG. 10 a, due to the polarity of the two magnets, one end of magnetic piston 100 is positioned inside of magnetic ring 102. In FIG. 10 b, due to the polarity of the magnets, magnetic piston 100 is positioned with its center inside of magnetic ring 102. It is emphasized that in FIG. 10 a, the piston may only move a distance equal to less than half of the width of the magnetic ring, since, if it were to go any farther (and thus the magnetic holding force would be zero), the piston would escape from inside the ring because the north and south magnetic poles of the piston and the ring would repel one another. Likewise, in FIG. 10 b, piston 100 is held with its center inside of ring 102. If ring 102 were to be moved a distance of more than half of the width of the piston, then the magnetic holding force on piston 100 would be totally overcome and piston 100 would escape from inside of ring 102.
FIG. 11 illustrates a magnetic spring actuator comprising a fixed magnetic piston 110 and a movable magnetizable ring 112 engaged around piston 110 and inside of cylinder 119. An applied force f causes movement of ring 112 along piston 110. The magnetic return force induced by piston 110 causes ring 112 to return to its starting position shown.
FIG. 12 is similar to FIG. 11, but in this case, an electric coil 120 supplies the initial force for moving ring 112 with respect to magnetic piston 110. Magnetic piston 110 is connected to cylinder 114 via a non-magnetizable shaft 116 (also illustrated in FIG. 6 d).
Another embodiment central to the invention makes use of the tendency of a coiled spring formed from an alloy of two metals, to contract or expand in response to passage of an electric current through the coil, or in response to a significant change in the surrounding temperature. Such an alloyed coil, termed a “bi-metal coil spring”, a “bi-metal spring” or a “shape-memory alloy (SMA)” is usually made from nickel and at least one other metal. Most often, nickel-titanium is used, but optionally additional metals are included in the alloy in addition to nickel and titanium, such as copper, iron or chrome. Depending on the identity of the two metals in the alloy, the coil will either contract, or expand in response to one of the aforementioned stimuli (heat or application of an electrical current).
In the second central embodiment of the invention, a bi-metal coil spring is wound around the piston of the actuators described above. The initial force applied to the actuator which acts to move the piston, is not a physical force in this case, rather it is either a raise in the temperature surrounding the actuator, or the closing of a circuit in which the bi-metal coil takes part of. When the initial force is discontinued, the magnetic force will act to return the piston to its starting position.
In the following description of FIGS. 14-15, the bi-metal coil is described as tending to contract in response to heat or to electrical current. This is not intended to limit the scope of the invention, rather is thus described for illustrative purposes. Depending on the metals used in the alloy from which the bi-metal coil spring is formed, the coil may tend to expand in response to these stimuli, and then contract when these stimuli are removed. One can envision any of the embodiments of the invention, in which expansion of the bi-metal coil spring in response to these stimuli induces movement of the piston, rather than contraction of the bi-metal coil spring inducing movement of the piston.
FIG. 14 a represents a bi-metal magnetic spring actuator 140 comprising an iron ring 142 firmly attached to a nonmagnetic cylinder 144 and a long magnetic piston 146 covered with a bi-metal coil spring 148. The bi-metal coil spring 148 is attached at one end to the magnetic piston 146 through a cover/stopper 143. The other end of the bi-metal coil spring 147 is attached to the nonmagnetic cylinder 144. Piston 146 is illustrated in the starting position with respect to ring 142, with the north magnetic pole end of the piston 146 disposed inside of ring 142.
Referring to FIG. 14 b, heating the bi-metal coil spring either through a heating element (not shown), surrounding and contacting the actuator or directly via an electric current (flowing into the spring) results in contraction of the bi-metal coil spring against cover 143 and movement of piston 146 within cylinder 144. Magnetic return force m induced by the magnetism of N pole of piston 146 causes piston 146 to return to the initial starting position (shown in FIG. 14 a).
It is appreciated that piston 146 is maintained in the initial starting position due a magnetic holding force. The bi-metal coil spring contraction force (resulting from the application of heat or electric current) goes against the magnetic holding force, causing the piston to move. As the contraction force is applied, the magnetic holding force diminishes, approaching zero. However, the contraction force must be stopped before the magnetic holding force reaches zero, to permit a magnetic return force m. This is achieved due to the fact the contracting bi-metal coil spring reaches a minimal compression before the magnetic holding force reaches zero.
Once the contraction force is suspended, the magnetic return force m returns the piston 146 to its starting position and at the same time recompresses or stretches the bi-metal coil spring to its starting length. It should be noted that the bi-metal coil spring must be allowed to return to ambient temperature prior or during the above stretching process (depending on the identity of the metals in the alloy). FIG. 14 b illustrates the position of piston 146 following application of bi-metal coil spring contraction force. Piston 146 is prevented from escaping and exiting entirely through the ring 142 due to cover 143 which functions as a stopper. It is appreciated that the length of movement of the piston 146 can be regulated depending on the length of cylinder 144. The piston may maximally move up to half the length of the piston 146.
FIG. 14 c describes the magnetic field of the N pole of piston 146 and how the field lines bend into the magnetizable (iron) ring 142. This creates a closure mechanism or a magnetic locking between the magnetic piston 146 and the iron ring 142. The contraction of bi-metal coil spring creates a force that acts against the above magnetic locking therefore moving the magnetic piston to a second position as described in FIG. 14 b.
In FIG. 14 d, the magnetic piston 146 is shown with half of its length projecting out of the ring 142 therefore most of the magnetic field of pole N is far from the ring and only a few field lines bend towards the ring. These few lines create a return magnetic force “m” as shown and mentioned in relation to FIG. 14 b. Force “m” moves the piston 146 back to the first position shown in FIG. 14 a, and FIG. 14 c.
When the entire piston is formed from a material that is magnetizable, and the actuator is submitted to heat to provide the initial force for contraction and movement of the piston, the heat tends to lower the magnetic force necessary for returning the piston to its starting position. Additionally, a piston made of a heat-retaining material will absorb heat and lengthen the time needed for the bi-metal coil to return to ambient temperature and to thus expand and return the piston to its starting position. In order to overcome these disadvantages, in the embodiments described in FIG. 14 e, FIG. 14 f, the piston comprises two portions, one of which is a short magnetic portion, and one of which is a lengthened non-magnetic and non-heat-retentive portion.
FIG. 14 e describes a piston comprised of a non-magnetic portion 149 covered with a bi-metal coil spring 148, and a magnetic portion 146 attached to the non-magnetic portion 149 in proximity to a magnetizable ring 142.
This arrangement permits protection of the magnet from the hot bi-metal coil spring 148. In preferred embodiments the piston 149 is made from non-heat conducting materials or having a low thermal coefficient, for better protection of the magnet 146 and fast cooling of 148.
In FIG. 14 f, after heating the bi-metal coil spring 148 using a heat source or after application of an electric current, the coil contracts and applies a force on 149 via cover 143. This force acts against the magnetic locking force of 146 and moves piston 149 and magnetic portion 146 to a second position with respect to ring 142.
FIG. 15 represents a bi-metal magnetic spring actuator 150, in which the iron ring 152 is not attached to the nonmagnetic cylinder 154 as previously described, rather it is attached to an outside actuator via moveable arm 155. The actuator comprises a nonmagnetic cylinder 154 and a piston having a lengthened magnetic portion 156 covered with a bi-metal coil spring 158. The bi-metal coil spring 158 is attached to the magnetic portion of the piston 156 through a cover/stopper 153 and is attached at its other side 157 to the nonmagnetic cylinder 154. Piston 156 is illustrated in FIG. 15 a in the starting position with respect to nonmagnetic cylinder 154 with the north magnetic pole end of the piston 156 located far from iron ring 152. The iron ring 152 is attached to an outside actuator via arm 155. This arrangement ensures zero magnetic holding force when the piston is at the starting position of FIG. 15 a.
When heat is applied to the bi-metal coil spring either through a heating element (not shown) which contacts the actuator 150, or directly via an electric current (flowing into the spring), this results in contraction of the bi-metal coil spring against cover 153 and movement of piston 156 within nonmagnetic cylinder 154, as shown in FIG. 15 b. Piston 156 is connected to a non-magnetic shaft portion 151 moving through an iron ring 152. Following the movement of piston 156 the nonmagnetic shaft 151 moves through iron ring 152 guiding magnetic piston 156 towards the iron ring 152.
FIG. 15 b illustrates the position of piston 156 following application of bi-metal coil spring contraction force. Since pole N of magnetic piston 156 is now near iron ring 152 a magnetic force is induced. Application of force f via an outside actuator causes arm 155 to advance the iron ring 152 towards the magnetic portion of the piston 156, creating a magnetic return force on magnetic piston 156 to return to it's initial starting position, and at the same time stretches the bi-metal coil spring to it's starting length. It should be noted that the bi-metal coil spring must be allowed to cool to ambient temperature prior to or during the return to the starting position induced by the stretching process.
FIG. 16 describes another version of a bi-metal coil magnetic spring actuator. The bi-metal coil spring 168 is in a contracted state (FIG. 16 a) before heating. The magnetic piston 166 is magnetically locked to ring 162 as in FIG. 16 a due to pole N that is located inside the ring.
In FIG. 16 b the bi-metal coil spring expands after heat is applied to the spring.
As shown in FIG. 16 b, the non-magnetic piston 169 has entered and progressed into the non-magnetic cylinder 164 due to the expansion of bi-metal coil 168. In FIG. 16 b piston 166 is unlocked from ring 162 due to the spreading force of spring 168. When spring 168 cools it contracts, and the piston is further induced to return to the starting position shown in FIG. 16 a, due to the magnetic attraction between piston 166 and ring 162.
FIG. 17 illustrates the bi-metal coil spring being part of an electrical circuit. In FIG. 17 a, the current is turned off, and the actuator is in the starting position.
When the electrical current is turned on (shown as I=i), the coil is induced to contract (FIG. 17 b). When the current is turned off (I=0), the magnetic force “m” present between magnetic piston 146 and ring 142 propels the expansion of the coil and movement of the piston to the starting state (FIG. 17 a).
It is appreciated that the magnetic force in each embodiment can be controlled in accordance with the initially applied pressure in order to produce the desired effect (i.e., the extent of displacement of the piston or ring). Moreover, varying the size and thus the magnetic force of the piston and/or the ring will also produce corresponding effects. It will also be appreciated that the magnetic spring actuator of the present invention is useful in a wide variety of applications.
Having described the invention with regard to certain specific embodiments thereof, it is to be understood that the description is not meant as a limitation, as further modifications will now become apparent to those skilled in the art, and it is intended to cover such modifications that are within the scope of the appended claims.

Claims

1. A magnetic spring actuator device comprising:

a) a piston and a ring arranged such that one of said piston and ring is a fixed part and the other is a moving part;

b) a non-magnetic holding cylinder having each of said fixed and moving parts disposed therein;

wherein at least one of said fixed and moving parts is magnetic and wherein due to a magnetic force caused by at least one of said fixed and moving parts, said moving part is initially located in a first position with respect to said fixed part, and wherein upon application of an outside force on said magnetic spring actuator, said moving part moves to a second position with respect to said fixed part, such that said magnetic force produces a return force causing said moving part to return to said first position with respect to said fixed part.

2. The actuator device of claim 1, wherein said piston is movably disposed inside of said ring.

3. The actuator device of claim 1, wherein said ring is moveably engaged around said piston.

4. The actuator device of claim 1, wherein the outside force is an electromagnetic force.

5. The actuator device of claim 1, wherein the outside force is a pneumatic force.

6. The actuator device of claim 1, wherein the piston is magnetic and the ring is magnetizable.

7. The actuator device of claim 1, wherein the ring is magnetic and wherein one end of the piston is positioned inside of the ring.

8. The actuator device of claim 1, wherein the ring is magnetic and wherein the piston has the same width as the ring, said piston being positioned inside of said ring.

9. The actuator device of claim 3, further comprising a second ring engaged around said piston.

10. The actuator device of claim 9, wherein said second ring is magnetizable and wherein each of said rings contains an opposite end of said piston disposed therein.

11. The actuator device of claim 1, wherein the ring is a magnet and the piston is magnetizable.

12. The actuator device of claim 1, wherein both of said ring and said piston are magnetic.

13. The actuator device of claim 1, wherein the distance between the first position and the second position is up to half of the width of the piston.

14. The actuator device of claim 1, wherein the distance between the first position and the second position is up to half of the thickness of the ring.

15. The actuator device of claim 1, further comprising a stopper.

16. The actuator device of claim 1, further comprising a non-magnetizable shaft connecting between said piston and said cylinder.

17. The actuator device of claim 16, further comprising connecting means for connecting between the piston and the shaft.

18. The actuator device of claim 1, further comprising a bi-metal coil spring wound around the piston, wherein one free end of said bi-metal coil spring is connected to the non-magnetic holding cylinder, and a second free end of said bi-metal coil spring is connected to the piston; said bi-metal coil spring being inducible to contract or expand in response to a stimuli selected from: a change in temperature, or application of an electrical current to the bi-metal coil spring.

19. The actuator device of claim 18, wherein the bi-metal coil spring is formed from an alloy of at least two metals selected from the group consisting of nickel, titanium, copper, chrome and iron.

20. The actuator device of claim 18, wherein the bi-metal coil spring is connected to an operable electrical circuit containing a power source, for inducing contraction or expansion of said bi-metal coil spring upon closure of said electrical circuit and activation of said power source.

21. The actuator device of claim 18, further comprising a heating element adjacent to or surrounding said actuator, for inducing contraction or expansion of said bi-metal coil spring upon activation of said heating element.

22. The actuator device of claim 18, further comprising an external actuator for inducing contraction or expansion of the bi-metal coil spring.

23. A method of activation of the actuator of claim 18, comprising the steps of:

a. applying a stimuli selected from: a change in temperature or electrical current, to said bi-metal coil spring to induce expansion or contraction of the bi-metal coil spring and cause movement of the piston from the initial starting position to a second position;

b. discontinuing said stimuli to allow the piston to return to the initial starting position.

24. The method of claim 23, wherein the maximal movement of the piston equals half the length of the piston.

25. The method of claim 23, further comprising a bi-metal coil spring, wherein one end of said bi-metal coil spring is connected to the piston; said bi-metal coil spring being capable of contracting or expanding in response to a stimuli selected from: a change in temperature, or application of an electrical current to the bi-metal coil spring.