Magnetic spring actuator device
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.
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 INVENTIONPrior 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 INVENTIONIn 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:
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- 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:
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- 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 DRAWINGSFor 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:
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.
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.
In
As seen in
Referring now to
An alternative embodiment, in which the piston 66 is magnetic, is shown in
In
It is appreciated that in
It is also appreciated in both
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
Referring to
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).
In
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
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
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
In
As shown in
When the electrical current is turned on (shown as I=i), the coil is induced to contract (
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.
Type: Application
Filed: Sep 14, 2005
Publication Date: Mar 16, 2006
Inventors: Moshe Gombinsky (Bat Yarn), Amir Porat (Savyon)
Application Number: 11/224,947
International Classification: F04B 17/00 (20060101); F01B 23/08 (20060101);