Patent Publication Number: US-2007119218-A1

Title: Adaptive engaging assembly

Description:
TECHNICAL FIELD  
      The present application relates, in general, to shape memory alloys and to fasteners.  
     SUMMARY  
      An embodiment provides an apparatus that includes a first piece, a stop, and an assembly that includes a shape memory alloy. In addition to the foregoing, other embodiments are described in the claims, drawings, and text forming a part of the present application. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1   a  shows a first embodiment of the apparatus in a first configuration.  
       FIG. 1   b  shows a first embodiment of the apparatus in a second configuration.  
       FIG. 2  shows a second embodiment of the apparatus.  
       FIG. 3   a  shows a third embodiment of the apparatus in a first configuration.  
       FIG. 3   b  shows a third embodiment of the apparatus in a second configuration.  
       FIG. 4  shows a first embodiment of the assembly.  
       FIG. 5  shows a second embodiment of the assembly.  
       FIG. 6  shows a third embodiment of the assembly.  
       FIG. 7  shows a fourth embodiment of the assembly.  
       FIGS. 8   a - 8   f  show different perspectives and configurations of a fourth embodiment of the apparatus.  
       FIG. 9  is a diagrammatic representation of a key having local resistive regions. 
    
    
     DETAILED DESCRIPTION  
      A shape memory alloy is a material that can change shape or attempt to change shape upon transfer (including loss or gain) of energy, such energy including thermal, electrical, magnetic, electromagnetic, mechanical, or a different form of energy. Properties of shape memory alloys are summarized in METALS HANDBOOK, Eds. J. R. Davis, Davis and Associates; Desk Edition, Second Edition; ASM International: Materials Park, Ohio, 1998; pp 668-669, which is incorporated herein by reference. Note that, in some contexts herein, shape memory alloy may respond to directly applied energy such as heat or may respond to indirectly provided energy, as may be the case for example where energy is provided via a magnetic field or through local heating from an applied current.  
      Shape memory alloys may be useful in the fabrication of a fastener, latch, or hinge, as described, for example, in U.S. Pat. No. 6,889,411 entitled SHAPE MEMORY METAL LATCH HINGE DEPLOYMENT METHOD to Hinkley, et al.; U.S. Pat. No. 6,875,931 entitled RETAINER FOR CIRCUIT BOARD ASSEMBLY AND METHOD FOR USING THE SAME to Combs, et al.; U.S. Pat. No. 6,860,689 entitled FASTENING ASSEMBLIES AND COMPONENTS THEREOF to Attanasio; and U.S. Pat. No. 6,840,700 entitled MECHANICAL CONNECTING ELEMENT to Nusskern, et al., each of which is incorporated herein by reference.  
       FIGS. 1   a  and  1   b  show the cross section of a first embodiment of an apparatus  100  where an assembly  108  includes a shape memory alloy that is configured proximate to a segment  104  of a first piece  102 , where  FIG. 1   a  shows a first configuration and  FIG. 1   b  shows a different configuration of the same apparatus shown in  FIG. 1   a . The assembly  108  may include an assembly aperture  109  that is large enough to allow the first piece  102  to pass.  
      The shape memory alloy may include NiTi, CuZnAl, CuAlNi, FeMnSi, or a different material having shape memory properties. As is described in W. H. Zou, C. W. H. Lam, C. Y. Chung, J. K. L. Lai, “Microstructural Studies of a Cu-Zn-Al Shape-Memory Alloy with Manganese and Zirconium Addition”, Metallurgical and Materials Transactions A, Volume 29A, July 1998, 1865, which is incorporated herein by reference, materials may be added in order to improve the memory of the shape memory alloy. The transition temperatures of the material depends on the particular alloy, and may be tuned by varying the elemental ratios. The transition temperatures of the material may also depend on stresses applied to the material, and the material shape may vary according to varying stresses applied as is described in István Mihálcz, “Fundamental Characteristics and Design Method for Nickel-Titanium Shape Memory Alloy”, Periodica Polytechnica Ser. Mech. Eng. Vol. 45, No. 1, PP. 75-86 (2001), which is incorporated herein by reference. In another aspect, the shape memory alloy may be a ferromagnetic shape memory alloy that may change shape in response to an applied magnetic field as well as to temperature and stress changes as in other shape memory alloys, as described in E. Cesari, J. Pons, R. Santamarta, C. Segui, V. A. Chemenko, “Ferromagnetic Shape Memory Alloys: An Overview”, Archives of Metallurgy and Materials, Volume 49, Issue 4, 2004, which is incorporated herein by reference.  
      The assembly  108  may be configured to transfer thermal, electrical, electromagnetic, or a different form of energy, in some cases to or from an energy bank  112 . The energy bank  112  may be a circuit configured to exchange electrical energy with the assembly  108 , an electromagnetic field, a material such as water that may be configured to exchange thermal energy with the assembly  108 , a heat source or a heat sink, a magnetic field, or a different configuration designed to exchange energy with the assembly  108 . In a relatively straightforward illustrative case, the energy bank may be a battery powered current source. The assembly  108 , upon transfer of said energy, may change shape, causing the first piece  102  to move in a direction  110  relative to the assembly  108 .  
      In the embodiment shown in  FIGS. 1   a  and  1   b , the first piece  102  is configured so that lateral dimensions of the assembly  108  in  FIG. 1   a  increase upon transfer of energy. The perimeter of the first piece  102  engages the assembly  108  non-perpendicularly. As the assembly  108  attempts to expand, force increases between the first piece  102  and the assembly  108 . Because the engagement is non-perpendicular, the force includes a vector component that urges the first piece  102  in the direction  110 . The stop  106  is configured with an aperture  107  having a size and location such that when the first piece  102  is urged in the direction  110 , the perimeter of the first piece  102  engages with the perimeter of the stop  106 , which limits the motion of the first piece  102  in the direction  110 . In one embodiment, the first piece  102  may be mateable, and may be attached to, another object at a mounting site.  
      In one embodiment, the stop  106  may comprise a shape memory alloy such as those listed previously for the assembly  108 , where the stop  106  may be configured to change shape to adjust the position of the first piece  102  relative to the stop  106 . In this case the stop may be configured to transfer energy to or from an energy bank  114 , where the energy bank  114  may include those listed as examples previously for the energy bank  112 .  
      The energy banks  112 ,  114  may be controlled by a control system  116  that may establish the amount and timing of energy transfer. Further, the control system  116  may include a sensor to affect the amount of control signal, where the sensor may be an optical, force, pressure, resistance, or other type of sensor.  
      In one embodiment,  FIGS. 1   a  and  1   b  show cross sections of an apparatus  100  having substantially circular symmetry where the apertures  107  and  109  are substantially round apertures. In other embodiments,  FIGS. 1   a  and  1   b  show cross sections of an apparatus  100  that does not have circular symmetry. For example, the assembly  108  may comprise rods that are configured to increase in length to exert a force on the first piece  102 , or the stop  106  may comprise rods that are configured to change in length to control the position of the first piece  102 .  
      Although the illustrative example of  FIGS. 1   a  and  1   b  has the first piece  102  with an hourglass shape, one skilled in the art may extend the embodiment to other configurations, such as a substantially double-hourglass, or an even more complex shape potentially resembling a key structure, where the assembly  108  and the stop  106  may be positioned at a number of different places along the first piece  102 . Further, the first piece  102  may have portions having substantially parallel sides, portions where the slope of the sides is substantially constant, or portions of the sides where the side is not smooth, for example to increase friction between the first piece  102  and the assembly  108  or the stop  106 .  
      The illustrative example of  FIGS. 1   a  and  1   b  has been described such that  FIG. 1   a  represents the rest state and  FIG. 1   b  represents a state achieved after energy transfer. However, the initial rest state and activated states may be reversed such that  FIG. 1   b  represents the rest state and  FIG. 1   a  represents a state achieved after energy transfer.  
      In some cases it may be desirable to increase the force between the assembly  108  and the first piece  102  and/or the force between the stop  106  and the first piece  102  after they have already made contact and are not in motion relative to each other. For example, in situations where it is desirable to maximize the force between the assembly  108  and the stop  106  and the first piece  102 , energy may be supplied or withdrawn from the system to provide the desired amount of force. Further, the apparatus  100  may include one or more components or devices that may provide additional force or control, which may be a clamp, pliers, or other such device. Such components may provide mechanical gain or concentrate forces locally or provide other spatial distributions of force. In such approaches, mechanical structures allow the vector of force provided by the assembly  108  may be parallel to, opposite to, at an acute or obtuse angle relative to, or even perpendicular to the direction at which force is applied to the first piece.  
       FIGS. 1   a  and  1   b  also show an exemplary embodiment of the stop  106  as including the stop aperture  107  that engages the periphery of the first piece  102 , however other configurations may also limit the relative motion between the first piece  102  and the assembly  108 . For example, as shown in  FIG. 2 , the first piece  102  does not pass through the stop  106 . In this embodiment, the stop  106  is shown as a substantially solid plane with apertures  202 ,  204  that accept protrusions  206 ,  208 . The apertures  202 ,  204  are shown as being too small to allow the first piece  102  to pass. In still another approach, the stop  106  may include the protrusions  206 ,  208  and the assembly may include the apertures  202 ,  204 . In another embodiment, the protrusions  206 ,  208  may engage a solid face of the stop  106  or may engage other structures configured to mate with the protrusions.  
       FIGS. 3   a  and  3   b  show another embodiment, where  FIG. 3   a  shows a first configuration and  FIG. 3   b  shows a different configuration of the same apparatus shown in  FIG. 3   a . In  FIGS. 3   a  and  3   b  the stop  106  includes a rod  304  that passes through the first piece  102 . In one embodiment, the rod may be permanently affixed to the first piece  102 , and in another embodiment, the rod  304  may be configured to pass through the first piece  102 . In this case, the rod  304  may comprise a shape memory alloy that may be configured to expand according to conditions. The assembly  108  is configured with a shape memory alloy that responds to input energy by expanding. The assembly  108  is shaped such that, as it expands it places a force on the first piece  102  urging the first piece  102  to move in a direction  302 . The stop  106  limits motion of the first piece  102 , such that the first piece  102  is held in place against the stop  106 . Once again, as described with respect to  FIGS. 1   a  and  1   b , the selection of rest state and activated state can be reversed. Thus,  FIG. 3   a  may represent the activated state and  FIG. 3   b  may represent the rest state in some applications. The selection of which state to select as the rest or activated state can be a design choice depending upon the application.  
      In an embodiment, a top view of which is shown in  FIG. 4 , each of two assemblies  108  includes a respective handle  402 ,  403  at its distal end. The assemblies are responsive to input energy to move the handles  402 ,  403  toward each other in directions  404 ,  406  to grip the first piece  102 .  
      While  FIG. 4  shows two handles  402 ,  403  being shaped as semicircles to grip the first piece  102 , which, in this embodiment, has a substantially round cross-section, a variety of other configurations and shapes may be implemented. For example, other embodiments may have a different number of handles, handles of different shapes, other mating surfaces, or other geometrical placements of the assemblies. Further, the handles may be carried by the stop  106 , or both the assembly  108  and the stop  106  may include handles.  
      In a similar embodiment, the top view of which is shown in  FIG. 5 , the assembly  108  includes four arms  508 ,  510 ,  512 ,  514  having respective distal ends  509 ,  511 ,  513 ,  515  that are configured to move in directions  516 ,  518 ,  520 ,  522  responsive to input energy. As the distal ends move, they make contact with the first piece  102 .  FIG. 5  shows four substantially rod-shaped arms  508 ,  510 ,  512 ,  514  configured to make contact with the first piece  102 , which, in this embodiment, is round, but in other embodiments there may be a different number of arms and they may have a different shape. Further, the stop  106  may include arms similar to those in  FIG. 5 , or both the assembly  108  and the stop  106  may include the arms.  
      In a similar embodiment, the top view of which is shown in  FIG. 6 , the assembly  108  includes an encircling portion  602  configured to tighten to make contact with the first piece  102 , thereby acting as a cinch.  FIG. 6  shows one encircling portion  602  configured to make contact with the first piece  102 , which, in this embodiment, is round, but in other embodiments the first piece  102  and the encircling portion  602  may have a different shape and may be substantially rectilinear or irregularly shaped. Further, the encircling portion  602  is shown in  FIG. 6  and entirely enclosing the first piece  102 , however in some cases the encircling portion  602  may not completely enclose the first piece  102 , as is the case in  FIG. 7 . Moreover, while the inner surface of the encircling portion  602  is shown as smooth, the surface may be adapted to mate to the first piece  102 . For example, the inner surface may include pins, teeth, serrations, bevels or other shapes and the first piece may include complementary features. Such features may increase retention strength in some applications.  
       FIG. 7  shows an embodiment where a partially encircling portion,  702 , is configured to close around the first piece  102  in a grasping fashion. The embodiments shown in  FIGS. 6 and 7  (as well as structures corresponding to other embodiments) may be configured such that the encircling portion  602  and/or the partially encircling portion  702  may be substantially helical rather than confined to a single plane. Further, although  FIGS. 6 and 7  show one encircling portion  602  and one partially encircling portion  702 , in some embodiments the apparatus may comprise more than one encircling portion  602  or partially encircling portion  702 . Further, although  FIGS. 6 and 7  show the assembly  108  including an encircling portion  602  or partially encircling portion  702 , in other embodiments the stop  106  may include an encircling portion  602  or partially encircling portion  702 . Additionally, each of these embodiments may be adapted to implement features described with respect to any of the other embodiments, such as types of energy applied, mating features or other aspects.  
       FIGS. 8   a - f  show one embodiment where the first piece  102  (the “key”) is a structure sized and shaped to enter the apertures  107 ,  109 , and the assembly  108  (which, in this embodiment, forms the “lock”) is a structure configured with a shape memory alloy. In one state, the key  102  can turn to position it relative to the lock  108  and the stop  106  (which, in this embodiment, forms the “retainer”).  FIGS. 8   a ,  8   b , and  8   c  show top views of the apparatus  800  and  FIGS. 8   d ,  8   e , and  8   f  show side views of the apparatus  800 .  FIGS. 8   a  and  8   d  show the apparatus  800  after the key  102  has entered the apertures  107 ,  109 . The  FIGS. 8   b  and  8   e  show the apparatus  800  after the key  102  has been rotated relative to the lock  108  and the retainer  106 . In  FIGS. 8   b  and  8   e , the apparatus  800  is shown with the key  102  and the retainer  106  in contact, however it may be that rotating the key  102  is not sufficient for the key  102  to make contact with the retainer  106 , and the retainer  106  may be configured with a shape memory alloy configured to change in shape to make contact with the key  102  upon transfer of energy.  FIGS. 8   c  and  8   f  show the apparatus  800  in the final “locked” position, where energy has been transferred to the lock  108  to change its shape such that it has made contact with the key  102 .  
      While the representation of  FIGS. 8   a - f  show a simple structure having rectangular and hourglass cross sections, other more complex structures can be implemented as well. For example, the key  102  may include a series of indentations and projections of various sizes, shapes and depths, rather than an hourglass shape. Further, the key  102  may comprise a shape memory alloy, where the height or depth of the respective indentations or projections would be a function of the energy input to the key. The corresponding lock  108  would then include a number of surfaces that mate to corresponding indentations and projections. The configuration may or may not include the retainer  106 . In a simple implementation, each of the mating surfaces is at a distal end of a respective pin. For a given energy input, the heights and depths of the respective indentations and projections correspond to a key structure that will drive the pins to the proper position to permit the key to turn to a second position, as in a conventional lock.  
      In one embodiment, opening the lock involves rotating the key  102  from the second position to a third position. However, the depths and heights of the indentations and the projections to rotate from the second position to the third position are different from those to rotate from the input orientation to the second position.  
      To establish the new depths and heights, a new level of input energy is applied to the key. Local regions, or in a simple case, the entire key, expand or contract, to set new depths and heights. At a selected temperature or other energy state, the new depths and heights correspond to the depths and heights that permit the key to turn from the second position to the third position.  
      While the illustrative embodiment includes input energy at two positions, the process can be extended to establish three or more sets of depths and heights. Moreover, the key  102  may be configured to rotate from the initial position to the second position, the second position to the third position or other stages at the rest state. Further, energy states may be repeated in some cases. For example, rotation from the initial position to the second position and from the third position to a fourth position may both be established at the rest state.  
      Also, as noted above, the key may include a plurality of regions that may each receive a respective energy input different from those of the other regions. As shown in  FIG. 9 , the key  102  may include a set of N sections  902  proximate to respective projections  916   a  and indentations  918   a , where the section  902  and its corresponding projection  916   a  and/or indentation  918   a  form a region of the key. Each section  902  is electrically coupled to a power source  904 , that may include a battery  906 , microprocessor  908 , and/or other electrical circuitry  910 . The regions  916   a  may be substantially isolated from each other, electrically and/or thermally. For example, where the input energy is electrical energy insulative gaps or barriers may provide electrical isolation. The regions may also be electrically insulated from the main portion of the key.  
      In one approach, the power source  904  provides energy input in the form of an electrical current having a respective amplitude that heats a resistive segment  912  at each respective region  902  to provide localized heating. The amount of heating energy may be established by controlling the current and/or by the magnitude of the local resistance.  
      In one simple embodiment, the energy input may be a DC input, such as may be applied by a battery, other DC source, or AC source having a substantially constant amplitude. The voltage applied can be defined through a variable resistance or similar structure for regulating voltages. Where the input is DC or constant amplitude AC, the relative current, and thus the amount of resistive heating at each region  902  is established by the relative magnitudes of the resistances  912 . As represented by the broken line  914  in  FIG. 9 , segments of the key  102  expand differentially corresponding to the amount of local heat energy to establish a new set of projections  916 b and indentations  918   b.    
      In use, the first set of projections  916   a  and indentations  918   a  engage pins  920  or other typical lock features. If the heights and depths of the projections  916   a  and indentations  918   a  correspond to the proper pin locations, the lock (main body not shown) permits rotation from an initial position to a second position. Note that the pins  920  are shown slightly separated from the projections  916   a  and indentations  918   a  for clarity of presentation, although in operation, the pins  920  would typically contact the projections  916   a  and indentations  918   b.    
      After rotation to the second position, the power source  904  provides energy and the key  102  assumes the shape represented by the broken line  914  to establish the new set of projections  916   b  and indentations  918   b . The new set of projections  916   b  and indentations  918   b  engages a second set of pins (not shown). Once again if the heights and depths of the projections  916   b  and indentations  918   b  correspond to the proper pin positions, the key can rotate to a third position. As noted previously, in some embodiments, a larger number of rotational positions and energy levels can be established to provide even more control.  
      Note that although the structures in the illustrative embodiments of  FIGS. 8   a - 9  are described herein as a key and a lock, other structures that provide interactive activation may also be implemented. For example, the structure corresponding to the lock may be an electrical switch, such as an automobile ignition switch or a secure activation switch for an electrical device. Similarly, the structure corresponding to the lock may be a release mechanism having features similar to or dissimilar to a lock.  
      In some applications, the approaches shown herein may be implemented at very small scales, for example on the micron scale or even smaller. For example, a 150 μm shape memory alloy is described in H. B. Brown, Jr., J. M. Vande Weghe, C. A. Bererton, and P. K. Khosla, “Millibot Trains for Enhanced Mobility”, IEEE/ASME Transactions on Mechatronics, Volume 7, Number 4, December 2002, which is incorporated herein by reference.  
      The embodiments described singularly may also be configured in arrays where multiple apparatuses are employed. The apparatuses may be connected to individual circuits and each controlled separately, or they may be connected to a common circuit and controlled simultaneously. In this case, they may all transfer substantially the same amount of energy or they may transfer different amounts of energy. The energy transferred to or from the apparatuses may be controlled by a computer or by another apparatus. Further, the apparatuses may be configured in such a way that they must be assembled in a certain order, in which energy may be transferred to or from the apparatuses in this order.  
      Although the embodiments in  FIGS. 1-9  are generally described as having a rest state where the assembly  108  and the stop  106  are not engaged with the first piece  102 , it may be that for any of the embodiments the assembly  108  and/or the stop  106  are engaged with the first piece  102  in the rest state, and may be configured to become disengaged upon transfer of energy.  
      Although only the embodiment shown in  FIGS. 1   a  and  1   b  include energy banks  112  and  114  and a control system  116 , one or more energy banks or their equivalent and a control system may be included in any of the embodiments shown in  FIG. 1-9 . Such control system may include electrical circuitry that establishes the amount, location, or other features of the input energy. Additionally, such electrical circuitry may interact with forms of feedback, such as sensing rotation of a lock, local temperature, absolute or relative movement of objects, or other aspects, to provide additional control of various aspects of operation.  
      The apparatus described above may have a variety of applications. For example, it may be configured as a fastener in a variety of environments, including for quick-assembling furniture. It may also be used in situations where it is desirable to assemble and dissemble something quickly, such as in assembly line operations. In this configuration, something such as a circuit board may pass to a position on an assembly line to a position where the board is to be worked on, and the apparatus may be used to keep the board in a fixed position during this operation. Further, the apparatus may be useful in situations where a fastener is needed and electrical energy or another form of energy is more easily supplied to the apparatus than mechanical energy. It may be used in situations where two parts assemble and dissemble frequently and quick assembly or dissembly is desired, such as on skis. It may be used as a connector in places that are difficult to access such as for braces on teeth or within a body. Or, it may be included in a lock and key configuration, where turning a key creates an electrical connection which assembles or dissembles the apparatus. The apparatus may be incorporated in toys that are configured to be assembled by the user, or the apparatus may be included in the design of a toy similar to legos.  
      The foregoing detailed description has set forth various embodiments of the apparatuses and/or processes via the use of block diagrams, diagrammatic representations, and examples. Insofar as such block diagrams, diagrammatic representations, and examples contain one or more functions and/or operations, it will be understood as notorious by those within the art that each function and/or operation within such block diagrams, diagrammatic representations, or examples can be implemented, individually and/or collectively, by a wide range of hardware, materials, components, or virtually any combination thereof.  
      Those skilled in the art will recognize that it is common within the art to describe apparatuses and/or processes in the fashion set forth herein, and thereafter use standard engineering practices to integrate such described apparatuses and/or processes into elements, processes or systems.  
      While particular embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more ”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).