Abstract:
A low profile standoff with tool stop is disclosed for attaching surfaces in fixed proximity to each other. The low profile standoff with tool stop includes a main body having a threaded bore, a threaded stem for threading a nut, and an intermediate section of narrower cross section than the main body that admits a portion of the threaded bore. The intermediate section extends within the thickness of the mounting surface while the main body stays on one side and the threaded stem extends wholly through to the opposite side of the surface. Some embodiments further comprise a tool stop on the exterior of the main body. Other embodiments dispense with the threaded stem. The low profile standoff with tool stop is particularly useful for overcoming the strength disadvantages of reduced height standoffs known in the art, and of minimizing tool head damage to the mounting surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to low profile standoffs and more specifically to low profile standoffs maximizing the thread purchase for mounting screws. 
       BACKGROUND OF THE INVENTION 
       [0002]    Standoffs are used to establish and maintain a required distance between two objects. A common use of standoffs in electronics technology is to act as mounting spacers between a circuit board and an enclosure. 
         [0003]    A particular type of commonly used standoff may be seen in perspective view in  FIG. 1A . The standoff has a main body  100  of a generally cylindrical shape and a main axis  102 . A threaded bore  104 , parallel and generally centered on the main axis  102  penetrates the main body  100 . A threaded stem  106  extends, again parallel and generally centered on the main axis  102 , at the opposite end of the main body  100  from the threaded bore  104 . In some versions, main body  100  is provided with faceted sides for ease of coupling to wrench tool heads. 
         [0004]    Referring now to  FIG. 1B , the standoff may be seen in sectional view with main body  110 ; main axis  112 ; threaded bore  114 ; and threaded stem  116 . 
         [0005]    In operation the standoff is used in a manner depicted in  FIG. 1C  where circuit board  128  has a hole through which threaded stem  126  is inserted until main body  120  comes to rest on circuit board  128 . As is obvious to those skilled in the art, the hole through circuit board  128  is sufficiently large enough to admit threaded stem  126 , yet small enough to preclude main body  120  from falling through the hole. In operation a nut and possibly a washer is threaded over threaded stem  126  anchoring the resultant assembly to circuit board  128 . The threaded bore in main body  120  may then accept a bolt or machine screw which can be used to secure a second circuit board (not shown) to the top of main body  120  and “stood-off” from circuit board  128 . 
         [0006]    In some applications threaded stem  126  is used to affix an appropriately threaded mechanical part, for example a heat sink, to circuit board  126 , thus serving the double function of standoff and anchoring bolt. 
         [0007]    With the increased packing density being achieved in modern circuit assemblies there is a requirement for lower profile standoffs. This presents a problem as may be seen in the section drawing of a standoff in  FIG. 2 . In the standoff shown in  FIG. 2  main body  200  has been reduced in height above circuit board  208 . This has the result of shortening the threaded length of threaded bore  204 . As a certain reduced standoff height, the threaded length of threaded bore  204  provides insufficient mechanical strength to meet vibrational and shock performance requirements for the assembly. Threaded bore  204  cannot be further extended along main axis  202  because the bore will compromise the strength of threaded stem  206 , and in the extremis result in the detachment and failure of stem  206 , again compromising the integrity of the standoff assembly. 
         [0008]    Therefore there is a need for a standoff of reduced height, with standard threaded dimensioning that maintains an adequate mechanical strength. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the invention to provide a reduced height standoff with standard threaded dimensioning that maintains adequate mechanical strength. 
         [0010]    According to an aspect of the invention there is provided a standoff for mounting on a surface having a thickness, the standoff having a proximal end having a threaded bore; a distal end having a threaded stem generally parallel to the threaded bore; and an intermediate section between proximal and distal ends, wherein the intermediate section is narrower in cross section than the proximal end, and wherein the intermediate section is wider in cross section than the threaded stem; and wherein the threaded bore extends through the proximal end and into the intermediate section. 
         [0011]    In some embodiments of the invention the standoff has flat sidewalls on the proximal end. In some of these embodiments the flat sidewalls are six in number and comprise a regular hexagon in cross-section. 
         [0012]    In other embodiments of the invention the intermediate section is of length less than the thickness of the mounting surface. 
         [0013]    According to another aspect of the invention there is provided a tool stop on the exterior of the proximal end of the standoff. In some embodiments the tool stop has a surface which precludes a driving tool from encompassing the length of the proximal end. In some of these embodiments the tool stop is a circumferential ridge around the proximal end of the standoff. 
         [0014]    In other embodiments of this aspect of the invention the standoff has flat sides wherein the flat sides commence at the threaded bore end of the proximal end and terminate at an intermediate point along the length of the proximal end, and a tool stop is formed by a ledge at the bottom of the flat sides. 
         [0015]    In yet other embodiments of this aspect of the invention the tool stop is a non-circumferential projection from the side surface of the proximal end. In some of these embodiments the non-circumferential projection is a nub, while in other of these embodiments the non-circumferential projection is a plurality of nubs equidistant from the bore end of the proximal end. In some of these embodiments the plurality of nubs is symmetrically disposed around the circumference of the proximal end. 
         [0016]    In some embodiments of this aspect of the invention the threaded bore has a helical thread, while in other embodiments the threaded bore has a circumferential thread. Similarly, in some embodiments of the invention the threaded stem has a helical thread, while in other embodiments the threaded stem has a circumferential thread. 
         [0017]    According to another aspect of the invention there is provided a standoff for mounting between a first surface having a first thickness and a second surface having a second thickness, the standoff having a first shoulder section at a first end of the standoff; a second shoulder section at the end opposite to the first end; an intermediate section between the first and second shoulder sections wherein the intermediate section is wider in cross section than the first shoulder section and wider in cross section than the first shoulder section; and wherein a threaded bore extends continuously through the first shoulder section, and the intermediate section, and the second shoulder section. 
         [0018]    In some embodiments of this aspect of the invention the first should section is of length less than the first thickness. 
         [0019]    In some embodiments of this aspect of the invention the threaded bore has a helical thread, while in other embodiments the threaded bore has a circumferential thread. 
         [0020]    Note: in the following the description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The present invention will be further understood from the following detailed description of embodiments of the invention, with reference to the drawings in which like reference numbers are used to represent like elements, and: 
           [0022]      FIG. 1A  illustrates a perspective view of a standoff according to the prior art; 
           [0023]      FIG. 1B  illustrates a sectional view of the standoff of  FIG. 1A ; 
           [0024]      FIG. 1C  illustrates an elevation view of the standoff of  FIG. 1A  in mounted position on a circuit board; 
           [0025]      FIG. 2  illustrates a sectional view of a reduced height standoff in position on a circuit board; 
           [0026]      FIG. 3A  illustrates a sectional view of a reduced height standoff in position on a circuit board according to an embodiment of the invention; 
           [0027]      FIG. 3B  illustrates an elevation view of the standoff of  FIG. 3A  in mounted position on a circuit board; 
           [0028]      FIG. 4A  illustrates an elevation view of a reduced height standoff according to an embodiment of the invention in mounted position on a circuit board and having adjacent components; 
           [0029]      FIG. 4B  illustrates an elevation view of a reduced height standoff according to an alternative embodiment of the invention in mounted position on a circuit board and having adjacent components; 
           [0030]      FIG. 5  illustrates an elevation view of a reduced height standoff according to another embodiment of the invention in mounted position on a circuit board and having adjacent components; 
           [0031]      FIG. 6  illustrates an elevation view of a reduced height standoff according to yet another embodiment of the invention in mounted position on a circuit board and having adjacent components; and 
           [0032]      FIG. 7  illustrates a sectional view of a reduced height standoff in position on a circuit board according to an alternative embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    In the following description, references in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation. 
         [0034]    In the following description, like reference numbers refer to similar features. 
         [0035]    Referring to now to  FIG. 3A  there may be seen an embodiment of the invention in sectional view mounted on circuit board  308 . According to this embodiment, main body  300  has a threaded board  304 , and a threaded stem  306 . Below main body  300 , shoulder section  303  of narrower cross-sectional width than main body  300  and wider cross-sectional width than threaded stem  306  provides a zone wherein threaded bore  304  may be extended. The extension of threaded bore  304  provides additional threads for the top-side faster, while the increased cross-sectional width as compared to threaded stem  306  provides for sufficient material strength at the lower point of threaded bore  304 . 
         [0036]    In some versions of the embodiment, shoulder section  303  is dimensioned so that in position it does not penetrate fully through circuit board  308 , stopping short of the lower surface as shown at gap  307 . The gap  307  precludes any interference between shoulder section  303  and the nut and washer assembly normally affixed to threaded stem  306 , as such interference could prevent adequate tightening of the nut. Alternatively, shaped washers such as stepped washers or concave washers known in the art could be used to bridge any penetration of shoulder section  303  through circuit board  308 , thereby allowing operation without the presence of gap  307 . 
         [0037]    Referring now to  FIG. 3B , there may be seen the standoff of  FIG. 3A  in elevation view, having main body  310 , circuit board  318 ; threaded stem  316 ; and shoulder section gap  317 . The standoff in this embodiment has faceted sides. A preferred version has six sides to accommodate hexagonal nut drivers. 
         [0038]    Referring now to  FIG. 4A  there may be seen a low profile standoff in accordance with an embodiment of the invention mounted in circuit board  408 . Adjacent to the standoff are components  401   a  and  401   b.  Driving tool head  405  fits over the top of the faceted main body  400  of the standoff, preparatory to anchoring the main body while a nut or nut and washer combo is applied to the threaded stem  406 . As may be seen in  FIG. 4A , driving tool head  405  has the possibility of descending and impacting components  401   a  and  401   b,  or of causing abrasion damage to the surface of circuit board  408 . 
         [0039]    Referring now to  FIG. 4B  there may be seen an alternative embodiment of the invention. As in  FIG. 4A  a low profile standoff in accordance with an embodiment of the invention is mounted in circuit board  418 . Adjacent to the standoff are components  411   a  and  411   b.  Driving tool head  415  fits over the top of the faceted main body  410  of the standoff, preparatory to anchoring the main body while a nut or nut and washer combo is applied to the threaded stem  416 . This embodiment further comprises tool stop  429  which serves to limit the depth that tool head  415  may encompass main body  410 . In this embodiment tool stop  419  comprises a ridge or ring extending outward from the sides of main body  410  to an extent that interrupts the downward motion of tool head  425 . The presence of the tool stop prevents tool head  425  from coming into contact with either components  411   a  and  411   b,  or with the surface of circuit board  418 . The net result is to allow closer placement of components to the standoff, thus realizing the use of more of the surface of circuit board  418 . As well, the prevention of abrasion damage to the surface of circuit board  418  enhances the reliability of the circuit board and circuit traces thereon. 
         [0040]    Referring now to  FIG. 5 , there may be seen an alternative embodiment of the invention which also possesses a tool stop feature. In this embodiment, main body  500  has a cylindrical form at its base portion adjacent to circuit board  508 , and the faceted sides are formed via a relieving of the cylinder walls to define the facets. The bottom ledge of the relieved portions at  509  acts as the bearing surface for tool stop purposes. Note, the term “relieving” refers to the absence of material as opposed to implying the specific type of operation forming the relief. In practice any of the embodiments of the invention could be formed by machining, casting, forging, molding, or a combination thereof. 
         [0041]    Referring now to  FIG. 6 , there may be seen yet another embodiment of the invention which also possesses a tool stop feature. According to this embodiment which has the low profile standoff inserted in circuit board  608  and having adjacent component  601 , the main body  600  of the standoff has a series of projections  609  extending outward therefrom. These projections may take the form of pins or nubs. In quantity the number of nubs would be sufficient to withstand the expected forces from use of a tool head, a quantity that would vary dependent upon the strength of the material from which the standoff was made. Standoffs are commonly manufactured in plastic, nylon being a common material, as well as metals, brass being a common material. The metal standoffs have the advantage of increased strength whereas the plastic standoffs possess an insulative property. In preferred embodiments the projections are arranged symmetrically around the main axis of the standoff so as to minimize the generation of lateral forces as the tool head comes to bear on the standoff. 
         [0042]    Referring now to  FIG. 7 , there may be seen a sectional view of yet another embodiment of the invention. According to this embodiment which has the main body  700  of the low profile standoff inserted between circuit boards  708   a  and  708   b,  there may be seen a shoulder section  703   a  at one end of main body  700  and shoulder section  703   b  at the other end of main body  700 . In some embodiments the length of shoulder section  703   a  is less than the thickness of circuit board  708   a,  and in other embodiments the length of shoulder section  703   b  is less than the thickness of circuit board  708   b.  This embodiment represents a form of standoff characterized as type “female-female” representing the apertures at each end of the main body  700  produced by the threaded bore  704 . By way of contrast the previously described embodiments would be characterized as “female-male” embodiments according to the aperture produced by the threaded bore at one end and the threaded stem at the other end. 
         [0043]    In the various embodiments described, the term “threaded” may refer to a helical thread which would engage a bolt in the case of the threaded bore, or would engage a nut in the case of the threaded stem; or alternatively could refer to a circumferential thread of the kind intended for engagement with a push-on barbed fitting. 
         [0044]    In the various embodiments described, the threaded bore and threaded stem are generally parallel to the main axis of the standoff and generally collinear with the main axis. In certain applications it may be advantageous to offset either the threaded stem or the threaded bore, and so nothing in the foregoing discussion is to be construed to preclude this. In general however, for both ease of manufacturing and ease of fastening, the threaded bore and threaded stem will be generally coaxial with the main axis of the main body of the standoff. 
         [0045]    In the various embodiments described, the low profile standoff has been described in relation to an application in relation to a circuit board. The circuit board is representative of any appropriate surface in which the low profile standoff would be used. Other typical, but not limiting examples of surfaces in which the low profile standoff could find application include circuit board faceplates, electronics enclosures, and subcircuit assemblies. 
         [0046]    According to the foregoing, various exemplary embodiments provide for a standoff of reduced height, with standard threaded dimensioning that maintains an adequate mechanical strength. In particular by providing a shoulder section beneath the main body of the standoff, the depth of the threaded bore may be increased and the attachment area of the threaded stem not substantially weakened. In addition, the provision of a tool stop integral to the main body of the low profile standoff acts to prevent damage to the surface upon which the low profile standoff is mounted, and provides the opportunity to place components in closer proximity to the standoff. 
         [0047]    Although the various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be affected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims.