Abstract:
A plastic push-in or drive fastener having a enlarged head and a shank is disclosed. The fastener is configured to allow the shank to be pushed through a complementary shaped aperture or opening in an article using a relatively low insertion force. A helical screw or rib formation on the fastener shank provides a retention force opposing the fastener from being axially withdrawn from the article while readily permitting withdrawal of the fastener from the article in response to rotation of the fastener about its axis. Moreover, the fastener shank is configured to prevent inadvertent separation of the fastener from the article through which it passes.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims benefit of provisional patent application Ser. No. 60/327,491, filed Oct. 5, 2001. 

   FIELD OF THE INVENTION 
   The present invention generally relates to the fastener art, and more particularly, to a fastener of the type generally referred to as a “push-in” or “drive” fastener but which is rotatably removable so as to permit the fastener to be reused. 
   BACKGROUND OF THE INVENTION 
   “Push-in” or “drive” fasteners of a variety of types and styles are well known in the fastener art. Typically, such fasteners have a shank with series of vertically spaced flexible tabs or wing-like members extending away from an axis of the fastener. As such, fasteners of this variety are also referred to as tree fasteners. 
   Such fasteners are driven axially into preformed openings or holes in a workpiece article with the flexible tabs or wings-like members engaging the article and flexing as they move through opening or hole in the article The workpiece article into which the fastener is introduced or inserted may be a panel of a shipping container of a particular type, with the fastener being used to secure another panel, i.e., nameplate, strip of molding, or the like to such container. 
   The flexible tabs or wing-like members on the shank of the fastener are specifically designed such that the force required to install or push the fastener through the hole or opening is relatively low thereby facilitating ergonomic considerations. Ideally, it is desirable in many situations to further design the fastener such that the force required to remove the fastener from the hole is relatively high. The relatively high retention force securely holds the article or nameplate to the shipping container during transport and other rough handling conditions. 
   A problem arises, however, when the nameplate or article held by the fastener is to be removed from the container. Since conventional tree fasteners are typically designed to exert high retention force following their insertion, extensive efforts are often required when the nameplate or article held by the fastener is to be removed. As will be appreciated, such extensive efforts at replacing the nameplate or the like is not conducive to repetitive use of such containers along with required timely turn around of the product stored and transported therewithin 
   Accordingly, the nameplate or article held by the fastener is typically torn or pulled from the container often resulting in destruction of the nameplate, container, or both, as well as destruction of the fastener. Of course, requiring a new or replacement nameplate adds to the transportation costs of the product. Moreover, when the nameplate or article is torn from the container, such action frequently results with the fastener head being broken off from the shank. Thus, when the new nameplate is to be attached to the container, the remaining shank of the broken fastener must be drilled or otherwise removed from the container. As will be appreciated, this requires a labor intensive effort resulting in the waste of valuable time in a highly competitive market. Moreover, forcible removal of the broken fastener frequently results in the hole through which the fastener is inserted to become enlarged, thus, adversely effecting the holding ability of the replacement fastener used to secure a replacement nameplate to the container. 
   Thus, there is a continuing need and desire for a push-in type fastener requiring a relatively low insertion force and offering a relatively high retention force after the fastener is inserted into an opening or hole in an article while providing for quick and easy non-destructive removal of the fastener. 
   SUMMARY OF THE INVENTION 
   In view of the above, and in accordance with the present invention, there is provided a push-in type fastener which solves the heretofore known problems associated with these type fasteners. The fastener of the present invention has an enlarged head and a shank. The fastener is configured to allow the shank to be pushed through a complementary shaped aperture or opening in an article using a relatively low insertion force. A series of convolutions form a helical screw or rib formation on the fastener shank which opposes the fastener from being axially withdrawn from the article while readily permitting withdrawal of the fastener from the article in response to rotation of the fastener about its axis. Moreover, the fastener shank is configured to prevent inadvertent removal or separation of the fastener from the article through which it passes. 
   Preferably, the convolutions are configured such that the helical screw or rib formation on the fastener shank has an incomplete formation extending about the peripheral edge thereof. In one form, one or more convolutions comprising the helical screw or rib formation on the fastener shank are each configured with at least one recess or serration which opens to a crest diameter of the screw formation. An innermost edge of each recess or serration, however, preferably terminates radially outwardly from a root diameter of the respective screw or rib convolution. Besides resisting inadvertent rotation of the fastener about its axis, a threaded fastener shank so configured advantageously reduces fastener installation force by approximately twenty-five percent as comparted to fully threaded fasteners. 
   In another form of fastener, and besides configuring the fastener shank with a helical screw or rib formation, a pair of resilient wings or elements are joined and extend outwardly from opposed sides of the fastener shank free end. Each wing or element extends outwardly relative to the fastener axis a further radial distance than does the helical screw or rib formation on the fastener shank and, preferably, is inclined or slants toward the fastener head. Each wing or element is flexible in a direction toward the fastener head but is resistant to deflection in a direction away from the fastener shank whereby resisting inadvertent removal of the fastener from the opening in the article through which it passes. In a most preferred embodiment, guide structure is provided toward the free end of the threaded shank to facilitate self-centering of the threaded shank and the opening through which it is adapted to pass 
   Regardless of the particular fastener shank structure utilized to resist inadvertent removal or separation of the fastener from the opening through which it passes, the terminal end of the fastener shank is preferably configured with a pilot. That is, the distal end of the fastener shank is preferably configured to facilitate insertion and alignment of the fastener shank relative to the hole or opening within which the shank is to be inserted. 
   The head of the fastener is configured to promote rotation of the fastener about the axis through use of a tool. In a preferred embodiment, the head of the fastener has a relatively low profile to benefit reduced clearance applications. Additionally, the shank is joined to an underside of the fastener head across an area preferably having a cross-section equal to or greater than the crest diameter of the screw or rib formation. 
   Accordingly, one feature of the present invention involves the provision of a fastener of the above-described type which is of simple one-piece construction whereby permitting economical and mass production of the fastener. 
   Another feature of the present invention is to provide a push-in fastener which requires reduced insertion forces while offering relatively high axial retention forces and yet readily permits removal of the fastener as by turning about a fastener axis, thus, minimizing adverse impacts on the article or workpiece through which the fastener is inserted. 
   Still another feature of the present invention relates to providing a fastener easily insertable into an opening in an article and which can be removed and reused without loss of effectiveness while applying an advantageous retention force to reduce the likelihood of rattling. 
   Yet another feature of the present invention relates to the provision of a an affordable, push-in removable fastener which resolves the heretofore chronic broken fastener problem while yet securely retaining an article in place during use and handling. 
   These and other features, objects, aims and advantages of the invention will become more readily apparent from the following detailed description, appended claims, and accompanying drawings. 

   
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an enlarged side view of one form of fastener according to the present invention; 
       FIG. 2  is a sectional view taken along line  2 — 2  of  FIG. 1 ; 
       FIGS. 3 and 4  are fragmentary views showing alternative serration designs; 
       FIG. 5  is a top plan view of one fastener head design; 
       FIG. 6  is a perspective view of an alternative form of fastener according to the present invention; 
       FIG. 7  is a side view of the fastener shown in  FIG. 6 ; 
       FIG. 8  is another side view of the fastener shown in  FIG. 6 ; 
       FIG. 9  is a bottom plan view of the fastener shown in  FIGS. 7 and 8 ; 
       FIG. 10  is an elevational view showing the fastener of the present invention used to secure a panel to a container; and 
       FIG. 11  is an enlarged plan view of a serration on an outer edge of a fastener shank after the fastener is inserted through an opening in an article or panel. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While the present invention is susceptible of embodiment in multiple forms, there is shown in the drawings and will hereinafter be described preferred embodiments of the invention, with the understanding the disclosure is to be considered as setting forth exemplifications of the invention which are not intended to limit the invention to the specific embodiments illustrated and described. 
   Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views, in  FIG. 1  there is shown one form of fastener, which embodies principals of the present invention, and is generally identified by reference numeral  10 . Fastener  10  is preferably formed in one piece and comprises an axially elongated shank  12  defining an axis  14  for the fastener  10  and which depends from one side of an enlarged head  16 . Fastener  10  can be injection molded from any of the polymeric resins, or plastic materials commonly used for the manufacture of these fasteners types and known by those of ordinary skill in the art. Nylon is but one example of a suitable material. 
   The fastener shank  12  is provided with a rib formation  20  comprised of a series of convolutions  22  which combine to provide the rib formation  20  with an aggressive helical thread form. The majority of convolutions extend 360° about the fastener shank  12  and radially away from the fastener axis  14 . 
   As shown, the screw or rib formation  20  has an outer crest diameter  24  defining an outer diameter of the fastener shank  12 . Moreover, the screw or rib formation  20  has an inner root diameter  26 . As will be appreciated from an understanding of the present invention, and as shown in  FIG. 1 , the outer crest diameter  24  and inner root diameter  26  of the screw or rib formation  20  on the fastener shank  12  are sized relative to the complementary article or workpiece opening or aperture  30  through which the fastener  10  is configured to pass. 
   In the illustrated embodiment, the convolutions  22  along the length of the fastener shank  12  are substantially identical relative to each other and equally extend away from axis  14 . Accordingly, in a preferred embodiment, the screw formation  20  and, thus, the fastener shank  12  has a substantially constant outer diameter along the length thereof. 
   The outer crest diameter  24  of the threaded formation  20  is sized slightly greater than the diameter of the article or workpiece hole or opening  30  through which fastener  10  passes. Moreover, the inner root diameter  26  of the threaded or rib formation  20  is sized slightly less than the diameter of the article or workpiece hole or opening  30  through which the fastener  10  passes. 
   In the exemplary embodiment, the free end of the fastener shank  12  opposite from the fastener head  16  has a pilot  32  configured to facilitate introduction of the fastener shank  12  into the article or workpiece hole or opening  30 . In one form, the pilot  32  has a conically tapered shape preferably defining a generally round pointed end  34 . 
   Notably, the fastener shank  12  is structured to prevent inadvertent removal of the fastener  10  from the article through which it passes. To accomplish such result, and in one form, the fastener shank  12  is configured to resist inadvertent turning or rotation of the fastener  10  about axis  14 . As shown in  FIGS. 1 and 2 , one or more of the convolutions  22  forming the helical screw formation  20  on fastener shank  12  is configured with at least one recess or notch  36  opening to the crest diameter  24  of the respective convolution. Preferably, each convolution  22  forming the helical rib  20  is provided with at least one notch or serration  36  every 360 degrees about the crest diameter  24  of the respective convolution. Although the exemplary embodiment illustrates the notches or serrations  36  on the various convolutions  22  in generally vertically aligned relation relative to each other, it will be appreciated the notches or serrations  36  on the various convolutions  22  can be radially displaced relative to each other while accomplishing the same function and objective without detracting or departing from the spirit and scope of the present invention. 
   In a most preferred form, the majority of convolutions  22  forming the helical rib  20  are provided with a plurality of notches or serrations  36  spaced every 120 degrees or so about the outer edge or crest diameter  24  of the respective convolutions  22  comprising helical rib or thread  20 . As shown in  FIG. 2 , a radial innermost edge  38  of each serration or notch  36  preferably terminates radially outwardly of the root diameter  26  of the helical thread or rib formation  30 . 
   The notches or serrations  36  can take any of a myriad of different designs. One form of serration  36  is illustrated in  FIG. 2 . Alternative forms or designs for such serrations  36  are illustrated in  FIGS. 3 and 4 . It should be appreciated, the different designs of serrations  36  illustrated in  FIGS. 2 through 4  are not intended to be exhaustive of all the possible serration designs but are merely examples of but a few serration designs which have proven useful in combination with the thread or rib formation  20 . 
   In the illustrated embodiment, the convolutions  22  are joined to each other to form a continuous helically shaped rib or thread formation  20  extending about and along the fastener shank  12 . Alternatively, the helical convolutions  22  can be configured such that a relatively narrow radial gap or opening can be provided between an ending portion of one convolution and a lead-in or beginning portion of an adjacent helical convolution. Yet the convolutions, when combined together, form a thread formation equivalent allowing the fastener shank  12  to be rotated about axis  14  and, thus, forcibly removed from opening  30  ( FIG. 1 ) in the article. It should be appreciated, configuring the helically shaped rib or thread  20  from a series of individual but radially spaced helical convolutions will provide the peripheral edge of screw or rib  20  with an incomplete surface configuration functionally analogous to the serration  36  described above. 
   In the exemplary embodiment illustrated in  FIG. 1 , the fastener head  16  is larger in diameter than the fastener shank  12  and preferably has a generally round cross-sectional configuration whereby providing a generally circular and, preferably, planar shape to an engaging face  40  of the fastener head  16 . It will be appreciated by those skilled in the art, however, fasteners, as contemplated by the present invention, can have a head with differing configurations from that shown without departing or detracting from the spirit and scope of the present invention. Moreover, and as shown in  FIG. 1 , the fastener head  16  is preferably configured with a relatively low vertical profile. 
   Fastener head  16  is furthermore configured to promote purposeful rotation of the fastener  10  about axis  14  as with a tool or the like. As shown in  FIG. 5 , the fastener head  16  preferably has a slotted configuration  44  to allow a tool T ( FIG. 1 ) to be arranged in operable driving relation relative to the fastener  10 . As will be appreciated, the slotted configuration  44  defined by the fastener head  16  can take any of a myriad of shapes and sizes other than that shown for exemplary purposes. 
   Returning to  FIG. 1 , the shank  12  of the fastener  10  is preferably joined to the head  16  across and area having a cross-section generally equal to or greater than the outer crest diameter of the helical rib  20 . This design reinforces the head  16  and reduces the likelihood of breakage between the shank  12  and the head  16 . 
   An alternative form of fastener is illustrated in  FIGS. 6 through 9 . The alternative form of fastener is designated generally by reference numeral  110 . The elements of this alternative form of fastener that are identical or functionally analogous to the structure of fastener  10  discussed above are designated by reference numerals identical to those used above with the exception this embodiment of fastener uses reference numerals in the one-hundred series. 
   In this form, fastener  110  includes an axially elongated shank  112  defining an axis  114  and depending from one side of an enlarged head  116 . The fastener shank  112  is provided with a rib formation  120  comprised of a series of convolutions  122  which combine to provide the rib formation  20  with an aggressive helical thread form. The majority of convolutions  122  extend 360° about the shank  112  and radially away from the fastener axis  114 . 
   A free end of the fastener shank  112  opposite from the enlarged head  116  preferably has a frusto-conically shaped section  123  depending from the last helical screw convolution  122 . In the embodiment shown in  FIGS. 7 and 8 , a narrowed elongated pilot  132  extends axially away from the free end of the fastener shank  112 . In the exemplary embodiment, and as shown in  FIG. 9 , the pilot  132  has a generally rectangular cross-sectional configuration. Preferably, the pilot  132  has a tapered or chamfered extremity  133  to facilitate insertion of the fastener shank  112  into the hole or aperture accommodating the fastener  110 . 
   Like fastener  10 , fastener  110  is structured to prevent inadvertent separation or removal of the fastener  110  from the article through which it passes. In the exemplary embodiment, a pair of wings or elements  135  radially project to opposite sides of axis  114  for a distance exceeding the diameter of the bore or opening in the article through which fastener  110  is adapted to pass. 
   Each wing or element  135 , in the exemplary embodiment, is configured to provide the fastener  110  with a cam-like lead-in to the aperture in the article into which it is inserted. As shown, each wing  135  is preferably provided with a first surface  137  extending outwardly from axis  114  and inclined toward the head  116  of the fastener  110  and a second tapered surface  139  extending outwardly and inclined toward the head  116 . The wings or elements  135  are each inclined toward the fastener head  116  at generally the same angle ranging between about 25° and about 60° relative to a generally horizontal plane. In a most preferred embodiment, each wing  135  angles or is inclined toward the fastener head  116  at an angle of about 45° relative to a generally horizontal plane. 
   Each wing or element  135  is preferably formed integral with the fastener pilot  132 . In a preferred form, each wing or element  135  is joined to the fastener pilot  132  along a relatively narrow and straight edge. Such connection provides a straight line hinge or bend point which facilitates ready flexing of the wings or elements  135  during insertion within the aperture or bore and flexure outwardly behind a surface of the article through which the fastener is inserted thereby preventing inadvertent axial removal of the fastener  110  from the article. The second or free end of each wing  135  preferably has a wider configuration than does the first end. 
   In this alternative fastener embodiment, the fastener shank  112  is furthermore preferably provided with guide structure to facilitate self-centering of the fastener shank  112  within the bore or opening in the article through which the fastener  110  is inserted. In the illustrated embodiment, such guide structure includes a pair of guide tabs  141  radially extending from opposite sides of axis  114  and preferably formed integral with the fastener shank  112 . 
   In a most preferred form, the guide tabs  141  are disposed in diametrically opposed relation relative to each other and extend outwardly from that end of fastener section  123  disposed closet to the free end of the fastener shank  112 . As viewed in  FIGS. 7 and 9 , the guide tabs  141  are preferably shown radially disposed between the wings or elements  135  on the fastener shank  112 . As shown, each guide tab  141  preferably includes a first surface  143  extending outwardly and toward the head  116  of the fastener  110  and a second tapered surface  145  extending outwardly and toward the head  116  to provide fastener  110  with a self-centering function as it is inserted into the aperture in the article. 
   As shown in  FIG. 8 , and although not necessarily required to inhibit inadvertent axial removal of the fastener  110 , one or more of the convolutions  122  forming the helical screw formation  120  on fastener shank  112  can each be configured with at least one recess or notch  136  opening to the crest diameter  124  of the respective convolution. The notches or serrations  136  formed on the helical screw formation  120  can be like those described above. 
   Fasteners according to this invention are versatile and can be used in a variety of different places and find multiple uses. For example, and as shown in  FIG. 10 , fasteners of the type described above are particularly useful to secure a panel or nameplate  50  to a container  60 . 
   Suffice it to say, the material into which fastener  10  is inserted is preferably a material, i.e., plastic, which is subject to cold flow characteristics. Moreover, the material from which the fastener is formed is preferably harder than the material into which the fastener is to be inserted. As such, and as schematically illustrated in  FIG. 11 , the softer material surrounding the fastener and through which the fastener shank passes will tend to cold flow, over time, at least partially between opposed sides of and into the opening defined by the serrations on the helical rib whereby inhibiting free rotation or turning of the fastener about its axis and, thus, resisting inadvertent removal of the fastener from the article through which it passes. Moreover, and without purposeful unscrewing of the fastener from the article, the wings or elements on the fastener shank are configured to resist inadvertent removal or separation of the fastener from the article but which resiliently deflect or bend to readily permit insertion of the fastener shank into and through the opening in the article. 
   It will be apparent to those skilled in the art, the instant invention contemplates an economical and simple push-in fastener that can be readily installed into an apertured panel or hole  30  with a relatively low insertion force while an axially directed removal force, far in excess of the insertion force, would be required to axially remove the fastener from such panel. Thus, superior retention is provided by the fastener of the present invention. Moreover, the elongated helical screw or rib formation on the fastener shank will accommodate and work well with a large range of panel or sheet thicknesses. Additionally, the helical screw or rib formation allows the fastener to be released as through a simple turning action. As such, the fastener design set forth above allows for reliable reuse of the fastener any number of times without any real loss of efficiency or effectiveness while reducing the likelihood the fastener will loosen as a result of shock or, vibration during rough conditions. Furthermore, the preferred low profile design of the fastener head promotes use of the fastener in reduced clearance applications. 
   From the foregoing it will be readily appreciated and observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended to set forth exemplifications of the present invention which are not intended to limit the invention to the specific embodiments illustrated. The disclosure is intended to cover by the appended claims all such modification and colorful variations as fall within the spirt and scope of the claims.