Abstract:
A self locking apparatus is disclosed having a housing, a load initiating element located within the housing, a spring located adjacent to the load initiating element and configured to expand in compression against the housing in response to a compressive load, and a compression member slideably disposed within the housing and configured to compress the spring from a side opposite the load initiating element. The load initiating element, spring and compression member are slideable within the housing in a first axial direction and in a second opposite axial direction in response to an axial load on the load initiating element, and lockable within the housing in the second axial direction in response to an axial load on the compression member in the second axial direction.

Description:
TECHNICAL FIELD 
     The presently disclosed apparatus relates to a self locking apparatus. 
     BACKGROUND OF THE INVENTION 
     Self locking apparatuses that can be positioned through a continuum of locations may be utilized in many applications. Some of these applications may fall into what might be described as temporary structures with telescoping elements. Among these are jack stands, extendable tripods, and canopies with telescoping legs. 
     If, in addition, such a self locking apparatus will stroke and absorb energy in a controlled fashion, if the loading on the self locking apparatus exceeds a design threshold, then such self locking apparatuses may find use in a number of automotive applications. These automotive applications include, but are not limited to: (1) an extendable/retractable bumper used to increase an automobile&#39;s energy absorbing space; (2) an extendable/retractable knee bolster used to help restrain vehicle occupants and absorb their kinetic energy during a rapid deceleration; and (3) a seatbelt pretensioner/load-limiter where a stroking distance is used to limit load and absorb energy. Accordingly, manufacturers continue to seek improved self locking apparatuses for a variety of reasons. 
     SUMMARY OF THE INVENTION 
     The disclosed apparatus relates to a self locking apparatus comprising: a housing; a load initiating element located within the housing; a spring located adjacent to the load initiating element, and configured to expand in compression against the housing; and wherein the load initiating element and spring are slideable within the housing until the spring is loaded into a self locking mode. 
     The disclosed apparatus also relates to a self locking apparatus comprising: an outer tube; an inner tube located within the outer tube; a load initiating element located within the outer tube and around a portion of the inner tube; a spring located adjacent to the load initiating element and around a portion of the inner tube and configured to expand in compression against the inner tube; and the load initiating element, spring and outer tube are slideable about the inner tube until the spring is loaded into a self locking mode. 
     In addition, the disclosed apparatus relates to a self locking apparatus comprising: an outer tube; a cylindrical body, with a plurality of slotted surfaces forming a plurality of load transfer segments, and with a bottom annulus, the cylindrical body located within the outer tube; a spring located adjacent to the bottom annulus and configured to expand in compression against the load transfer segments; and the slotted cylindrical body and spring are slideable within the outer tube in the absence of the spring being loaded into a self locking mode. 
     Additionally, the disclosed apparatus relates to a self locking apparatus comprising: an inner tube; a cylindrical body, with a plurality of slotted surfaces forming a plurality of load transfer segments, and with a bottom annulus, the cylindrical body located adjacent to an inner tube; a spring located adjacent to the bottom annulus and configured to expand in compression against the load transfer segments; and the inner tube is slideable with respect to the slotted cylindrical body and spring in the absence of the spring being loaded into a self locking mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the figures, which are exemplary embodiments, and wherein like elements are numbered alike: 
         FIG. 1  is a top sectional view of one embodiment of a self locking apparatus; 
         FIG. 2  is top sectional view of the self locking apparatus from  FIG. 1  with the inner tube axially moved towards the left; 
         FIG. 3  is a top view of an outwardly biased conic spring; 
         FIG. 4  is a cross-sectional side view of the conic spring from  FIG. 3 ; 
         FIG. 5  is a top view of an inwardly biased conic spring; 
         FIG. 6  is a cross-sectional side view of the conic spring from  FIG. 5 ; 
         FIG. 7  is a top sectional view of one embodiment of a self locking apparatus with a conic spring; 
         FIG. 8  is top sectional view of another embodiment of the self locking apparatus with a conic spring from  FIG. 7  with the inner tube axially moved towards the left; 
         FIG. 9  is a top sectional view of self locking apparatus with an initiator wave spring and multiple additional wave springs. 
         FIG. 10  is a top sectional view of the self locking apparatus of  FIG. 9 , with the wave springs in a compressed state; 
         FIG. 11  is a top sectional view of one embodiment of the self locking apparatus with an initiator conic spring and intermediate load conic springs and primary load conic springs; 
         FIG. 12  is a top sectional view of the self locking apparatus of  FIG. 11 , with the conic springs in a compressed state; 
         FIG. 13  is a top sectional view of one embodiment of a self locking apparatus with wave springs and a load transfer spring; 
         FIG. 14  is a top sectional view of one embodiment of the self locking apparatus with conic springs and a load transfer spring; 
         FIG. 15  is a top sectional view of one embodiment of the self locking apparatus with inwardly biased conic springs; 
         FIG. 16  is a perspective sectional view of one embodiment of a load transfer element for use in self locking apparatuses; 
         FIG. 17  is a top sectional view of an embodiment of the load transfer embodiment in a self locking apparatus; and 
         FIG. 18  is a top sectional view of an inertial loading embodiment of a self locking apparatus. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , a top sectional view of one embodiment  8  of a self locking apparatus is shown. A housing  10  is shown with a load initiating element  14  located within the housing  10 . The housing may be a tube. The load initiating element  14  may be a friction element. A friction element may include o-rings, piston rings, or any devices that will provide an axial frictional force acting between the load initiating element  14  and the inner surface of the housing  10 . An inner tube  18  is shown located within the housing  10 . Positioned between the inner tube  18  and the load initiating element  14  is a wave spring  22 . Although a wave spring is shown here, any spring that expands upon compression may be used, including, but not limited to a conic spring.  FIG. 2  is a top sectional view of the embodiment  8  of the self locking apparatus from  FIG. 1  with the inner tube  18  axially moved towards the left. As the inner tube moves to the left, the wave spring  22  is compressed between the load initiating element  14  and the inner tube  18 . A wave spring when compressed will expand radially outward. Thus, if one or more wave springs are installed in a tube  10  with minimal radial clearance and compressed, expansion will occur and radial loading will result between the outer circumference of the wave spring  22  and the inner surface of the enclosing housing  10 . With proper selection of wave spring and tubing stiffness, the friction resulting from the interference between the wave spring  22  and the housing  10  wall can be significantly greater than the axial loading necessary to initially compress the wave spring  22 . When the friction resulting from the interference between the wave spring  22  and the housing  10  is significantly greater than the axial loading, then the self locking apparatus is in a self locking mode. 
     In one non-limiting embodiment of the self locking apparatus shown in  FIGS. 1 and 2 , the wave spring  22  may have three waves, an inner diameter of about 9.0 mm, an outer diameter of about 12.5 mm, a height of about 0.9 mm, a thickness of about 0.18 mm, and a nominal deflection of about 0.3 mm at a load of about 24 Newtons. The housing  10  may be a tube with an inner diameter of about 12.58 mm, a radial tube thickness of about 2.0 mm, and a friction of coefficient of about 0.57 for steel on steel. With the above specified wave spring installed in the above specified tube, if the spring is compressed with a load of about 40 Newtons, the resulting radial load between the spring and tube would be about 280 Newtons, with a frictional load of about 160 Newtons. With the resisting load being greater than the applied load, the spring would not move within the tube, thus it would be in a self locking mode. With the use of a stack of six such wave springs, a load resistance of approximately 1000 Newtons would be obtained. Alternate dimensions and loadings may be employed for alternative designs. 
     The disclosed self locking apparatus is not limited to a wave spring for providing the radial expansion. A conic spring, also known as a Belleville washer, when axially compressed will expand both radially outward and inward.  FIG. 3  shows a top view of a conic spring  26  with a plurality of slots  30  located near the outer edge of the conic spring  26 .  FIG. 4  shows a cross-sectional side view of the conic spring  26 . By introducing slots  30  near the outer edge of the conic spring  26 , one can bias the expansion in a radially outward direction.  FIG. 5  shows a conic spring  34  with a plurality of slots  38  located near the inner edge of the conic spring  34 . By introducing slots  38  near the inner edge, one can bias the expansion in a radially inward direction.  FIG. 6  shows a cross-sectional side view of the conic spring  34 .  FIGS. 7 and 8  show how a conic spring can be arranged in a similar arrangement as the wave spring shown in  FIGS. 1 and 2 . In  FIG. 8 , the conic spring  26  expands in compression and creates a frictional force between the conic spring  26  and the inner surface of the housing  10 , which locks the inner tube  18 , conic spring  26  and load initiating element  14  in place relative to the housing  10 . 
       FIG. 9  shows a top sectional view of another embodiment  40  of the disclosed apparatus where the load initiating element  14  enables compression of an initiator wave spring  42 . Additional wave springs  22  may be added to increase the friction area and axial load bearing capability of the embodiment  40  of the self locking apparatus. Also, by adding some additional hardware such as a pin  46  that is fixedly coupled to the inner tube  18  and is slideably coupled to a piston  50  such that when a force pulls the piston to the left, and the piston is restrained by the pin  46 , then the pin  46  and piston  50  are not sliding with respect to each other, but when the piston  50  is pushed to the right, the pin  46  may slide into the piston  50 . By pushing or pulling the piston to the right or to the left, one can position the load initiating element  14 , pin  46 , wave springs  22 ,  42  and the inner tube  18  in the housing. Additionally, if one moves the inner tube  18  to the right, the load initiating element  14 , pin  46 , and wave springs  22 ,  42  may also be re-positioned within the housing  10 . However, if the inner tube  18  is moved to the left, the initiator wave spring  42  expands in compression and creates a frictional force between the initiator wave spring  42  and the inner surface of the housing  10  as shown in  FIG. 10 . As the axial force of the inner tube increases, the other wave springs  22  expand in compression, which locks the inner tube  18 , wave springs  22  and  42  and load initiating element  14  in place relative to the housing  10 , thus putting the apparatuses in a self locking mode. 
       FIGS. 11 and 12  show a similar embodiment to the one shown in  FIGS. 9 and 10 , but with conic springs used instead of wave springs. An initiator conic spring  54 , intermediate load conic springs  58  and primary load conic springs  62  are used with separators  66  separating the types of springs. The separators  66  may be washers, very stiff wave springs, or any other device that will separate the initiator conic spring  54 , intermediate conic spring  58  and primary conic springs  62 . The primary load springs  62 , as a group, are stiffer than the intermediate load springs  58 , which in turn are stiffer than the initiator conic spring  54 . Thus as the inner tube  18  is moved to the left, the initiator conic spring  54  expands in compression and creates a frictional force between the wave spring  54  and the inner surface of the housing  10 . As the axial force of the inner tube increases, the intermediate wave springs  58  expand in compression. As the axial force of the inner tube continues to increase, the primary wave springs  62  expand in compression. As the wave springs  54 ,  58 ,  62  compress and expand, they lock the inner tube  18 , wave springs  54 ,  58 ,  62  and load initiating element  14  in place relative to the housing  10 . 
     In  FIG. 13 , another embodiment  70  of the disclosed apparatus is shown. In this embodiment, a load transfer spring  74  allows forces used to position the springs  42 ,  54 , pin  46  and inner tube  18  within the housing  10  to bypass the initiator wave spring  42 . This embodiment therefore avoids the situation where the initiator wave spring  42  is prematurely compressed from a force from a piston rod  78  used to move and position the springs  42 ,  54 , pin  46  and inner tube  18  within the housing  10 . Thus, if the piston rod  78  is used to position the springs  42 ,  54 , pin  46  and inner tube  18  within the housing  10  by moving the embodiment to the right, the moving force will travel from the piston rod  78 , through the load transfer spring  74  through a piston head  82 , through the pin  46  to the inner tube  18 , thereby bypassing the wave springs  42 ,  22 . 
       FIG. 14  shows a similar arrangement to that shown in  FIG. 13 , but with conic springs  54 ,  58  and  62  instead of wave springs. 
       FIG. 15  shows another embodiment  86  of the self locking apparatus, but this embodiment  86  uses conic springs that have been biased for inward expansion, like the conic spring  34  shown in  FIG. 6 . With this type of spring, one can create a resisting force between the internal circumference of the springs  90 ,  94  and the outside circumference of an inner tube  18  passing through the center of the springs  90 ,  94 . Similar to the other embodiments, a load initiating element  14  provides the resistance necessary to compress the initiator internally biased conic spring  90  that, in turn, supplies sufficient resistance to compress the next stage of internally biased springs  94 . In  FIG. 15 , only two stages of springs  94  are shown, but a person skilled in the art would recognize that one may incorporate as many spring stages as are necessary to handle a specified design load. 
     All shown and previously discussed embodiments have used the interface friction directly between spring elements and a housing  10 . Referring now to  FIG. 16 , a load transfer element  96  embodiment is shown which would be used as an intermediate element between the spring and the housing surface. This would enable the independent optimization of the spring characteristics and the interface friction characteristics. One possible form of this intermediate element would be a cylindrical body  98  with a bottom annulus  102  against which the spring elements (not shown) would be positioned, and multiple vertical cuts in the cylindrical side wall to form load transfer segments  106  which can transfer the force from the expansion of the spring elements to an outer tube (not shown) that encloses the cylinder  98 . The friction force between the outer surfaces of the load transfer segments  106  and the inner surface of an outer tube would lock the embodiment  96  in place with respect the outer tube. This embodiment may be configured such that the cylindrical body locks by inwardly applying a radial force on an inner tube which the cylindrical body fits around. This would be accomplished by having an inwardly biased conic spring adjacent to a annular surface that is on the outside of the cylindrical body. 
       FIG. 17  shows a self locking apparatus using an embodiment of the load transfer element  96 . A spacer washer  110  is located between the initiator conic spring  54  and the load transfer element  96 , and the load transfer element is located between the washer  110  and the piston  50 . The load transfer element  96  allows for the efficient load transfer from the wave springs  22 ,  54  to the outer tube. The spacer washer  110  is used to locate the initiator wave spring  54  in a radially compliant region of the load transfer element  96 . In another embodiment, the load transfer element bottom annulus  102  may have a single radial cut to enable more radial load transfer near the bottom annulus  102 . 
       FIG. 18  shows an inertial loading embodiment  114  of a self locking apparatus. At least one mass element  118 , slideably attached to the pin  46 , provides sufficient inertial load such that the initiator wave spring  54  compresses and locks when the inner tube  18  exceeds design acceleration threshold in the direction of the arrow. Numerous other means of creating the resistance necessary to initiate compression of a spring stack, such as a direct mechanical connection or a viscous design to enable a velocity dependent actuation, are possible and will generally depend on the specific application. 
     The embodiments of the self locking apparatus disclosed in this document provide a simple and low cost means for self locking an apparatus within a housing. In addition, some embodiments also provide a simple and low cost means for positioning such an apparatus in a housing. 
     It will be appreciated that the use of first and second or other similar nomenclature for denoting similar items is not intended to specify or imply any particular order unless otherwise stated. 
     While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.