Abstract:
A magnetic spring utilizing spatially modulated magnetic field patterns of magnetic regions for both stator and slider, allowing custom force curves over the range of motion. Also disclosed is a magnetic spring whose slider can be rotated relative to the stator on the axis, such that the alignment of the spatially modulated magnetic field patterns of the slider and the stator is altered, resulting in changeable force curve for the spring, selected by rotating the slider.

Description:
BACKGROUND 
     Magnetic springs offer benefits of compactness and high energy density, similar to fluidic springs, but without the disadvantages of leakage and temperature dependence. In addition, magnetic springs offer the possibility of constant force over the operating range, as opposed to mechanical springs, which feature a force that varies linearly according to displacement. 
     SUMMARY 
     The present invention provides a magnetic spring based on spatially modulated magnetic field patterns and having a customized force curve over the operating range. Additional embodiments of the invention provide a magnetic spring with multiple force curves, such that the active force curve is selected according to the azimuthal angular position of the spring&#39;s sliding shaft relative to the stator. 
     Therefore, according to embodiments of the present invention, there is provided a magnetic spring comprising: (a) a stator having a first spatially modulated magnetic field pattern of magnetic regions; and (b) a slider having a second spatially modulated magnetic field pattern of magnetic regions; wherein the stator and the slider are mechanically constrained to have a spatial relationship such that: (i) the slider and stator are mechanically free to undergo an axial movement relative to one another along a predefined axis over a predefined axial range, resulting in an axial displacement of the slider and stator relative to one another; (ii) the first spatially modulated magnetic field pattern and the second spatially modulated magnetic field pattern interact magnetically to have a magnetic interaction according to the spatial relationship and the axial displacement, so that an axial force arising from the magnetic interaction exists between the stator and the slider; and (iii) the axial force between the stator and the slider is a function of the axial displacement of the slider and the stator relative to one another along the predefined axis within the predefined axial range. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
         FIG. 1  is an exploded isometric view illustrating the components of a magnetic spring according to an embodiment of the present invention. 
         FIG. 2  shows axial views separately illustrating the stator and slider of the magnetic spring of  FIG. 1 . 
         FIG. 3  illustrates a non-limiting example of a spatially modulated magnetic field pattern of regional magnetic orientation in a magnetic spring stator according to the present invention. 
         FIG. 4  shows axial views separately illustrating the stator and slider of a magnetic spring according to another embodiment of the present invention. 
         FIG. 5  illustrates a non-limiting example of a force curve for a magnetic spring according to an embodiment of the present invention. 
         FIG. 6A  is an axial view illustrating a magnetic spring according to another embodiment of the present invention with a slider in a first azimuthal orientation. 
         FIG. 6B  is an axial view illustrating the magnetic spring of  FIG. 6A , with the slider in a second azimuthal orientation. 
         FIG. 7  illustrates a non-limiting example of two respective force curves for the magnetic spring of  FIG. 6A  and  FIG. 6B  in the two azimuthal orientations. 
     
    
    
     It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. 
       FIG. 1  illustrates the components and makeup of a magnetic spring  100  according to an embodiment of the present invention. A stator  101  has a protective outer casing  103  and a thin low-friction inner bearing  105  around a recess  109  inside which a slider  111  fits and slides in and out in directions  115  along a longitudinal axis  117 . Between casing  103  and bearing  105  is a magnetic material having a spatially modulated magnetic field pattern of magnetic regions, such as in representative regions  107 A,  107 B,  107 C,  107 D, and  107 E. Spatially modulated magnetic field patterns of magnets and magnetic regions are known in the art, and techniques of creating predetermined spatially modulated magnetic field patterns of magnetic regions are also known in the art. According to embodiments of the present invention, such techniques may be utilized to create spatially modulated magnetic field patterns of magnetic regions in the components of a magnetic spring as described herein. 
     In certain embodiments of the invention, stator  101  and slider  111  feature patterns which are spatially-modulated both axially and azimuthally. 
     Slider  111  contains a magnetic material, also having a spatially modulated magnetic field pattern of magnetic regions, such as in representative regions  113 A,  113 B,  113 C,  113 D, and  113 E.  FIG. 2  shows enlarged axial views of stator  101  and slider  111 . The magnetic interaction between the spatially modulated magnetic field pattern of magnetic regions in stator  101  and the spatially modulated magnetic field pattern of magnetic regions in slider  111  give rise to an axial force between stator  101  and slider  111 , which is a function of the axial displacement of slider  111  relative to stator  101 . 
       FIG. 3  shows a non-limiting example of a spatially modulated magnetic field pattern of magnetic regions in representative regions  107 A,  107 B,  107 C,  107 D, and  107 E, according to an embodiment of the present invention. The arrows in the representative regions shown in  FIG. 3  represent the respective magnetic moment vectors of the regions, with the arrows pointing according to the common convention, from the respective south poles to the respective north poles. The term “spatially modulated magnetic field pattern” denotes that the specific pattern of magnetic orientations in the magnetic regions is according to a predetermined arrangement. 
     In some embodiments of the present invention, slider  111  may be mechanically free to be rotated inside stator  101  in directions  119  ( FIG. 1 ) to change azimuthal orientation. In other embodiments, slider  111  may be constrained to a particular range or set of values of azimuthal orientation. In specific embodiments, constraints may be imposed magnetically, by the particular spatially modulated magnetic field patterns of the magnetic regions; in other specific embodiments, constraints may be imposed mechanically, such as by a keyed channel, or by the geometry of the stator and slider. For example, instead of using a cylindrically-symmetrical geometry for the slider and its recess, as in  FIG. 1  and  FIG. 2 , a prismatic geometry lacking continuous rotational symmetry can be used.  FIG. 4  shows axial views of a non-limiting example of a prismatic stator  401  with a square cross-section and having an outer casing  403  and an inner bearing  405  for a corresponding slider  411 . In this example, stator  401  contains a spatially modulated magnetic field pattern of magnetic regions, such as in representative regions  407 A,  407 B, and  407 C; and slider  411  also contains a spatially modulated magnetic field pattern of magnetic regions, such as in representative regions  413 A,  413 B, and  413 C. In still other embodiments of the present invention, the geometry of the slider and the stator recess can be such that there is no rotational symmetry at all, in which case the slider-stator azimuthal angular alignment is fixed so long as the slider remains inserted in the stator. If the slider is removable from the stator, however, the azimuthal angular alignment can be changed by removal, reorientation, and re-insertion. 
       FIG. 5  illustrates a non-limiting example of a force curve  505  for a magnetic spring according to an embodiment of the present invention. Stator  101  and slider  111  are mechanically free to undergo an axial movement relative to one another along axis  117  ( FIG. 1 ) over a predefined range in a direction  507  or in a direction  509 . Slider  111  and stator  101  have a spatial relationship with a magnetic interaction between the spatially modulated magnetic field pattern of magnetic regions in slider  111  with the spatially modulated magnetic field pattern of magnetic regions in stator  101 . The magnetic interaction results in axial force curve  505 , which is a function of the axial displacement of slider  111  relative to stator  101 . Axial force  505  is plotted according to a force axis  501  against an axial displacement axis  503 . The precise form of force curve  505  depends on the specific properties of the spatially modulated magnetic field patterns of magnetic regions. In this non-limiting example, a portion  515  exhibits a relatively constant force over a portion of the displacement range, and another portion  517  exhibits a different relatively constant force over another portion of the displacement range. Embodiments of the present invention provide different force curves by having different spatially modulated magnetic field patterns of magnetic regions in the slider and/or stator. 
       FIG. 6A  is an axial view illustrating a magnetic spring according to another embodiment of the present invention that provides different force curves in the same magnetic spring, which are selected by rotating the slider to different predetermined angular positions relative to the angular position of the stator. A stator  601  has an index mark  609  in one angular position, and another index mark  617  in another angular position. A slider  611  has an indicator  615  showing an azimuthal angular alignment with index mark  609 , so that representative magnetic regions  613 A,  613 B, and  613 C of slider  611  align with representative magnetic regions  607 A,  607 B, and  607 C, respectively, of stator  601 .  FIG. 6B  is an axial view illustrating the magnetic spring of  FIG. 6A , but with slider  611  rotated azimuthally so that indicator  615  shows an azimuthal angular alignment with index mark  617 , whereupon representative magnetic regions  613 A,  613 B, and  613 C of slider  611  do not align with representative magnetic regions  607 A,  607 B, and  607 C, respectively, of stator  601 . Instead, a different set of magnetic regions  623 A,  623 B and  623 C on slider  611  align with the set of magnetic regions  607 A,  607 B and  607 C respectively.  FIG. 7  illustrates non-limiting examples of a force curve  711  corresponding to the slider-stator azimuthal angular displacement of  FIG. 6A , and a force curve  713  corresponding to the slider-stator azimuthal angular displacement of  FIG. 6B . Both curve  711  and curve  713  are plotted according to a force axis  701  against an axial displacement axis  703  for displacement in a direction  619 . 
     A single magnetic spring according to this embodiment of the present invention can provide different spring characteristics for a particular application simply by rotating the slider to a different position relative to the stator. Since the rotation is relative to the slider, this embodiment can be used in a configuration where the slider has a fixed rotational position, and it is the stator which is rotated instead, to select the spring characteristics. 
     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.