A bi-stable pin actuator includes a soft magnetic core and having a first central portion and a second central portion spaced apart from the first central portion. The first central portion has a first passage extending there-through and the second portion has a second passage extending there-through which is coaxial with the first passage. A first coil is wound about the first central portion and a second coil is wound about the second central portion. A pair of permanent magnets are located in the space between the first central portion and second central portion and attached to the core. An armature is movably positioned between and spaced apart from the permanent magnets. A pin is attached to the armature and extends into the first passage and second passages such that movement of the armature results in movement of the pin within the first passage and second passage. The armature moves between a first position wherein the armature is adjacent to the first central portion of the core and a second position wherein the armature is adjacent to the second central portion of the core. The armature is in one stable state when in the first position and in another of the stable state when in the second position. The magnets generate magnetic flux having a magnetic flux density sufficient to hold the armature in either of the stable states when neither of the coils is energized. When the armature is in the first stable state, only a first end of the pin protrudes from the core. When the armature is in the second stable state, only an opposite second end of the pin protrudes from the core. Energizing at least one of the coils generates a magnetic flux in one section of the actuator that opposes the magnetic flux holding the armature in a current stable state and supplements the magnetic flux in another section of the actuator so as to shift the armature into another stable state.

CROSS REFERENCE TO OTHER PATENT APPLICATIONS

FIELD OF THE INVENTION

The present invention relates to a bi-stable pin actuator.

BACKGROUND

Actuator devices are used in all types of industries, e.g. space, aerospace, automotive, etc. There are many types and sizes of actuator devices. The size of the actuator device is a critical issue especially in applications where there is limited space. One commonly used actuator device is a solenoid. Solenoids are used in many industries. However, small-sized solenoids typically cannot produce the required forces and also require electrical power to hold the solenoid in one state or the other. Other common actuator devices are Frangibolts and other Shaped Memory Alloy (SMA) devices. However, both of these devices rely on heating a fairly large piece of SMA. As a result, these two devices have relatively slow actuation times and require significant energy to actuate and generate significant heat. Burn-wires and pyrotechnic bolts are two other types of actuator devices. However, these devices produce contaminants upon activation. What is needed is a new and improved actuator device that does not have the aforementioned disadvantages of conventional actuator devices.

SUMMARY OF THE INVENTION

The present invention is directed to a bi-stable pin actuator. The bi-stable pin actuator is an electromagnetic device that actuates an output pin between a first position and a second position. The bi-stable pin actuator includes a core made of a soft magnetic material. In an exemplary embodiment, the core includes a first portion and a second portion that is attached to the first portion wherein the first portion and second portion are mirror images of each other. The bi-stable pin actuator includes an armature that is movable within the core and between the first position and the second position. The armature is made from soft magnetic material. The bi-stable pin actuator further includes a pair of permanent magnets attached to the core. The permanent magnets do not move and are oriented such that like poles of the magnets face each other. The armature is located between and spaced apart from the permanent magnets. An output pin is attached to the armature and thus moves with the armature. The first portion of the core includes a first winding and a second portion of the core includes a second winding. The core, permanent magnets and armature cooperate to create a bi-stable magnetic structure. The armature is naturally forced to either the first position or the second position due to the nature of the magnetic fields created by the bi-stable magnetic structure. When the armature is in the first position, it is in one stable state and when the armature is in the second position, it is in another stable state. When the armature is in one stable state, the output pin protrudes from one end of the bi-state pin actuator. When the armature is in another stable state, the output pin protrudes from an opposite end of the bi-state pin actuator. When the armature is in one of the two stable states, substantially all of the magnetic flux is constrained to the section of the bi-stable magnetic structure where the armature is positioned. The magnetic flux in the other section of the bi-stable magnetic structure does not have the strength to pull the armature over to the stable state. In order to shift the armature to the second position, and thus the other stable state, an electrical current is applied to one or both windings in order to oppose the magnetic flux holding the armature in the current stable state and supplementing the magnetic flux in the other section of the bi-stable magnetic structure in order to “steer” flux to that other section of the bi-stable magnetic structure. As a result, the armature is pulled into the second position and thus, the other stable state. If a sufficient electrical current is used, only one winding need be energized in order to shift the armature to the other stable state. Optionally, both windings may be energized to produce flux that increases the holding force on the armature in order to hold the armature in its current stable state until it is desired to shift the armature to the other stable state.

In an exemplary embodiment, the bi-stable pin actuator of the present invention includes a core made from soft magnetic material. The core includes a first central portion and a second central portion that is separated from the first central portion by a space. The first central portion has a first passage extending there-through and the second portion has a second passage extending there-through. The second passage is coaxial with the first passage. A first conductive coil is wound about the first central portion of the core. A second conductive coil is wound about the second central portion of the core. A first permanent magnet is located within the space between the first central portion and second central portion and attached to the core. A second permanent magnet is located within the space between the first central portion and second central portion and is attached to the core. The second permanent magnet is located across from the first permanent magnet. The first permanent magnet and the second permanent magnet have horizontally aligned North (N) and South (S) poles. The first permanent magnet and the second permanent magnet are aligned such that like poles face each other. A soft magnetic armature is movably positioned within the space between the first central portion and the second central portion. The armature is positioned between and spaced apart from the first permanent magnet and the second permanent magnet. The armature has a third passage that is coaxial with the first passage and the second passage and is movable between a first position wherein the armature is adjacent to the first central portion of the core and a second position wherein the armature is adjacent to the second central portion of the core. The armature is in one stable state when in the first position and in another stable state when in the second position. The first permanent magnet and the second permanent magnet generate magnetic flux having a magnetic flux density sufficient to hold the armature in either stable state when neither conductive coil is energized. The bi-stable pin actuator includes a pin that has a first end and an opposite second end. The pin extends through the third passage of the armature and is attached to the armature. The pin extends into the first passage of the first central portion of the core and into the second passage of the second central portion of the core such that movement of the armature causes the pin to longitudinally move within the first passage and the second passage. When the armature in in one stable state, only the first end of the pin protrudes from the core. When the armature is in another stable state, only the opposite second end of the pin protrudes from the core. Energizing at least one of the conductive coils generates in a first section of the bi-stable pin actuator a magnetic flux that opposes the magnetic flux holding the armature in the current stable state and supplements the magnetic flux in a second section of the bi-stable pin actuator so as to magnetically pull the armature into the other stable state.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring toFIGS. 1-5, there is shown bi-stable pin actuator10in accordance with an exemplary embodiment. Actuator10has a first section11A, second section11B and core12. In a preferred embodiment, core12is made from a soft magnetic material. Examples of suitable soft magnetic materials include iron, silicon steel and Vanadium Permendur. Core12includes first section14and second section16. First section14and second section16are mirror images of each other and are identical in construction and structure. First section14and second section16are attached together by bolts18and nuts20which are further described in the ensuing description. First section14has widthwise end portion22and leg portion24which extends from widthwise end portion22. In an exemplary embodiment, leg portion24is generally “L” shaped. Leg portion24includes outwardly extending lip24A which has thru-hole25for receiving bolt18. First section14further includes leg portion26which extends from widthwise end portion22. In an exemplary embodiment, leg portion26is generally “L” shaped. Leg portion26includes outwardly extending lip portion26A which has thru-hole27for receiving bolt18. First section14includes central portion28which extends from widthwise end portion22. Space30separates central portion28and leg portion24. Space32separates central portion28and leg portion26. Central portion28includes end36. First section14further includes internal passage38that extends through widthwise end portion22and central portion28. Internal passage38has opening39in widthwise end portion22and another opening (not shown) in end36of central portion28. Second section16has widthwise end portion40and leg portion42which extends from widthwise end portion40. In an exemplary embodiment, leg portion42is generally “L” shaped. Leg portion42includes outwardly extending lip portion42A which has thru-hole43for receiving bolt18. Thru-hole43is coaxial with thru-hole25of lip portion24A. Second section16further includes leg portion44which extends from widthwise end portion40. In an exemplary embodiment, leg portion44is generally “L” shaped. Leg portion44includes outwardly extending lip portion44A which has thru-hole45. Thru-hole45is coaxial with thru-hole27of lip portion26A. Second section16includes central portion46which extends from widthwise end portion40. Space50separates central portion46and leg portion42. Space52separates central portion46and leg portion44. Second section16further includes internal passage56that extends through widthwise end portion40and central portion46. Internal passage56has opening58in widthwise end portion40and another opening (not shown) in end54of central portion46. Internal passage56is coaxial with internal passage38in central portion28.

Referring toFIGS. 1-4A, 4B and 5, actuator10includes a pair of spools60and61. Spools60and61are identical in construction. Spool60has central opening62that is sized to receive central portion28of core12. Spool60includes ends64and65. Spool61also has a central opening (not shown) that is sized to receive central portion46of core12. Spool61includes ends66and67. In an exemplary embodiment, spools60and61are made from fiberglass. In one embodiment, the fiberglass is G10 fiberglass. It is to be understood that spools60and61may be fabricated from other materials having properties similar to G10 fiberglass. Actuator10includes electrically conductive coil or winding68that is wound about spool60. Winding68includes ends (not shown) that are connected to an electrical current source. In an exemplary embodiment, winding68is made from copper. In an exemplary embodiment, the electrical current source is a battery. However, it is to be understood that other suitable electrical current sources may be used. A flux is generated when an electrical current flows through winding68. Actuator10includes electrically conductive coil or winding72that is wound about spool61. Winding72includes ends (not shown) for connection to the electrical current source. In an exemplary embodiment, winding72is made from copper. A flux is generated when an electrical current flows through winding72. Applying an electrical current to windings68and72energizes the windings thereby generating a magnetic flux.

It is to be understood that in some embodiments, actuator10is configured without spools60and61. In such an embodiment, windings68and72are wound directly on central portions28and46, respectively.

In an exemplary embodiment, bolts18and nuts20are made from stainless steel. However, it is to be understood that bolts18and nuts20may be made from other metals as well. Referring toFIGS. 2 and 4A, when first section14and second section16are attached together with bolts18and nuts20, central portion28and central portion46are spaced apart by a space80. Actuator10further includes permanent magnet90and permanent magnet92that are located in space80and are attached to core12. Permanent magnet90is attached to a portion of first section14of core12and to a portion of second section16of core12. In an exemplary embodiment, permanent magnet90is bonded to the portions of first section14and second section16. However, other suitable techniques may be used to attach permanent magnet90to the portions of first section14and second section16. Similarly, permanent magnet92is attached to a portion of first section14and to a portion of second section16. In an exemplary embodiment, permanent magnet92is bonded to the portions of first section14and second section16. However, other suitable techniques may be used to attach permanent magnet92to the portions of first section14and second section16. Permanent magnet90and permanent magnet92each have horizontally aligned North (N) and South (S) poles. Permanent magnet90and permanent magnet92are aligned and oriented such that like poles face each other. In an exemplary embodiment, permanent magnets90and92are made from Neodymium-Iron-Boron (rare earth) or Samarium Cobalt. However, permanent magnets90and92may be made from other suitable materials.

Referring toFIGS. 1, 2 and 4A, bi-stable pin actuator10further includes armature100that is located within space80. Armature100is positioned between and spaced apart from permanent magnets90and92. Armature100is made from soft magnetic material. Suitable soft magnetic materials include iron, silicon steel and Vanadium Permendur. In an exemplary embodiment, armature100includes internal passage102therein. Bi-stable pin actuator10further includes pin or central rod104that is positioned in internal passage102and attached or joined to armature100such that pin104moves along with armature100. Pin104also extends through internal passage38of first section14and through internal passage56of second section16. Pin104can freely move longitudinally within internal passages38and56. In an exemplary embodiment, pin104is made from stainless steel because it is non-magnetic and has the requisite strength. However, pin104made be made from other suitable materials as well.

Referring toFIGS. 1, 2 and 5, first section14includes through-holes110and second section16includes through-holes112. Through-holes110and112are sized to receive bolts or screws116. Nuts118are fastened to bolts116. Each bolt116has a predetermined length that allows actuator10to be attached to any surface, structure or apparatus so that windings60and72are spaced apart from such surface, structure or apparatus. In an exemplary embodiment, bolts116and nuts118are made from stainless steel.

Armature100moves between a first position and a second position. When armature100is in either of these positions, armature100is in a stable state. For example, when armature100is in the first position, it is in one stable state and when armature100is in the second position, it is in another stable state. Armature100is in the first position when it is adjacent to central portion46and winding70. Armature100is in second position when it is adjacent to central portion28and winding68. In order to move between the first position and the second position, the armature100must pass through the center of space80. Armature100enters an unstable state as it passes through the center of space80.

FIG. 6shows armature100in an initial first position and in a first stable state. Armature100is adjacent to central portion46and winding72and pin104protrudes from opening58in portion40of core12. At this time, windings68and72are not energized, therefore all flux is generated by permanent magnets90and92. Substantially all of the permanent magnetic flux density, indicated by arrows204and206, is in section11A of actuator10due to the lower reluctance of these flux paths. As result, this strong permanent magnet flux density holds armature100in this initial first position. The permanent magnetic flux in section11B of actuator10is indicated by arrows200and202is the relative weak and does not have the strength to pull armature100through the unstable center of space80and over to the second position that is adjacent to central portion28and winding68.

Referring toFIG. 7, when it is desired to shift armature100from the first position into the second position and thus to the second stable state, electrical current is applied to winding68and/or winding72in order to energize the winding. Arrows220and222indicate the flux generated by energizing either or both windings68and72. Flux220and222opposes the permanent magnet flux204and206that holds armature100in the first position and supplements permanent magnet flux200and202so as to steer flux into section11B of actuator10in order to pull armature100away from the first position. Referring toFIG. 8, as a result in the decrease in the magnetic flux density in section11A and an increase in magnetic flux density in section11B, the permanent magnetic flux previously holding armature100in the first position is significantly reduced and is now indicated by reference numbers260and262. As a result, the total magnetic flux density250and252in section11B has sufficient strength to pull armature100through the unstable state and into the second position and thus, the second stable state. As a result, pin104is withdrawn from opening58in widthwise end40and now protrudes through opening39in widthwise end22. InFIG. 9, the energization of windings68and72has ceased and magnetic flux300and302in section11B is permanent magnet flux and is sufficient to hold armature100in the second position and thus, the second stable state. The permanent magnet flux260and262in section11A is too weak to pull armature100back to the first position.

It is to be understood that is sufficient electrical current is used, only one of the windings68and72need be energized to generate a flux that supplements the permanent magnet flux in one section of actuator10while simultaneously opposing the flux in an another section of actuator10. Otherwise, a lower electrical current could be applied to both windings68and72to supplement the permanent magnet flux in one section of actuator10and oppose the permanent magnet flux in another section of the actuator.

If it is desired to move armature100back to the first position, then one or more windings68and72are energized to oppose the permanent magnet flux in section11B and supplement the permanent magnet flux in section11A. Armature100is then pulled from the second position back through the unstable state and into the first position wherein the armature is adjacent to central portion46and winding72(seeFIG. 6). As a result of the movement of armature100, pin104is withdrawn from opening39and now once again protrudes through opening58.

Bi-stable pin actuator10provides many advantages and benefits. Pin actuator10is bi-directional due to its symmetric structure and therefore can be fired and reset by actuating in opposite directions. Pin actuator10can be fired repeatedly. With respect to the movement of armature100and pin104, pin actuator10provides a short stroke with high force. The short strike occurs within 1/10thsecond from the command. Power is only applied during actuation thereby conserving energy. Therefore, armature100is held in either stable state without the application of electrical current to the windings68and72. A relatively small amount of energy is needed to actuate pin actuator10. Specifically, a battery is sufficient to provide the electrical current to the windings68and72. Actuator10dissipates negligible heat and does not release any contaminants when activated. Actuator10is relatively small in size making it suitable for applications where there is limited space.

Prototype testing has confirmed many of the aforesaid advantages and superior operating characteristics. For example, when windings68and72are not energized, the permanent magnet flux can hold armature100in either the first position or second position with up to twenty-four (24) pounds-force applied to armature100. The actuation time is less than 100 milliseconds. A prototype fit within a 1.5″×2.0″×0.7″ rectangular volume.

Although the foregoing description is in terms of the deployable multi-section boom being used with spacecraft, it is to be understood that the multi-section boom may be used with other devices including, but not limited to, vehicles, robots including robotic devices used by law-enforcement or military bomb-disposal units and fail-safe laboratory equipment, etc.

The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. Various modifications to these embodiments will readily be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein. Any reference to claim elements in the singular, for example, using the articles “a”, “an” or “the” is not to be construed as limiting the element to the singular.