Blind Aperture Fastener

1. Field of the Invention

This invention pertains to a fastener with a stud, an inner sleeve and a base member. The stud includes a post which fits into a blind aperture in the base member. The sleeve fits between the post and the base member and includes a boss structure which locks the post into the base member.

2. Description of the Prior Art

In the prior art, fasteners with a post which inserts into a blind aperture within the base member are known. However, to insure a tight fit between the post and the base member, relatively accurate manufacturing tolerances were required. Similarly, these fasteners frequently had intricate or complex shapes which had to be manufactured precisely. Additionally, many of these fasteners require complicated installation procedures, such as twisting, or specialized installation tools. All of these factors can add to the final total cost of such a fastener.

It is therefore an object of this invention to provide a fastener which has relatively relaxed manufacturing tolerances.

It is therefore a further object of this invention to provide a fastener which has a reduced complexity of structure.

It is therefore a still further object of this invention to provide a fastener which has a simple installation process.

It is therefore a final object of this invention to provide a fastener which reduces or eliminates the need for specialized tools in the installation process.

These and other objects are attained by providing a fastener with a base element including a blind aperture, a stud with a post element which fits into the blind aperture, and an inner sleeve which fits between the walls of the blind aperture and the post element. The inner sleeve includes inwardly and outwardly extending protrusions which function as boss elements against the post and base element, respectively. These protrusions ride smoothly on the walls of the blind aperture of the base element upon insertion of the post element into the blind aperture. Stamping of the stud into the aperture causes the protrusions to "cock" into a locked position. Additionally, the inner sleeve includes a longitudinally oriented slot in order to allow the sleeve to accommodate somewhat varying sizes of the blind aperture and post.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

FIG. 1 is an exploded partially cut-away perspective view of the fastener of the present invention.

FIG. 2 is a partially cut-away perspective view of the fastener of the present invention in the engaged position.

FIG. 3 is a cross-sectional view of the fastener of the present invention in the engaged position.

FIG. 4 is a perspective view of the inner sleeve of the fastener of the present invention.

Referring now to the drawings in detail wherein like numerals indicate like elements throughout the several views, one sees from FIGS. 1, 2 and 3 that fastener 10 includes stud 12, inner sleeve 14 and base element 16.

Stud 12 is radially symmetric and includes cylindrical post element 18 with chamfer 20 on tip 22 on distal end 24. Proximal end of cylindrical post element 18 includes enlarged stabilizing ring 26 (optional, as described hereinafter). Cylindrical base 28 is formed adjacent to stabilizing ring 26. Gripping element 30 is formed adjacent to cylindrical base 28 and, in the illustrated embodiment, consecutively includes frusto-conical portion 32, cylindrical portion 34 and partially hemispherical head 36 with outer planar surface 38.

Stud 12 is typically formed of glass-filled plastic, but those skilled in the art will recognize that other materials may be used. Stud 12 is typically molded as a single integral piece.

Inner sleeve 14 is typically formed from sheet metal or a similar material. As shown in FIG. 4, the sheet metal forms roughly cylindrical walls 40 with open ends 42, 44. However, longitudinal slot or gap 46 is formed between ends 48, 50 of the sheet metal. Longitudinal slot or gap 46 allows for flexure of cylindrical walls 40 during installation.

Boss structures 52, 54, 56 are formed about the periphery of cylindrical walls 40. Boss structures 52, 54, 56 include inwardly extending half-hemispherical bosses 58, 60, 62, respectively, which are formed immediately adjacent to outwardly extending half-hemispherical bosses 64, 66, 68, respectively. As can be seen from FIG. 4, in boss structure 52, outwardly extending half-hemispherical boss 64 shares substantially the same geometric center as inwardly extending half-hemispherical boss 58. Additionally, the exposed edge of outwardly extending half-hemispherical boss 64 is formed from a common original seam in inner sleeve 14 as the exposed edge of inwardly extending half-hemispherical boss 58. Boss structures 54, 56 are similarly formed. The shape and immediately adjacent structure of the inwardly extending half-hemispherical bosses 58, 60, 62 with the outwardly extending half-hemispherical bosses 64, 66, 68 allow for the formation of a sharp exposed edge on the bosses 58-68 with a simple sheet metal stamping process. Additionally, this structure allows the bosses 58-68 to maintain their shape under load and to be pushed into blind aperture 70 with the lowest possible friction and ease of manufacturing. However, a variety of shaped dimples would be possible such as a dimple with a radius equal to or less than the inner diameter radius of blind aperture 70, an oval, a triangle, a cone, a square, a rectangle or any other shape which would present an edge to grab the plastic when opposing force is applied. It is further important that the dimples do not inelastically or otherwise permanently deform the inner diameter of blind aperture 70 in such a way that the boss edges no longer have the ability of interfering with the inner diameter of blind aperture 70.

Base element 16 is typically formed of plastic or a similar material. Base element 16 is roughly cylindrical with blind aperture 70 formed about the longitudinal axis thereof. Blind aperture 70 includes enlarged portion 72 which forms mouth 74 in planar surface 76. Enlarged portion 72 has a diameter to accommodate stabilizing ring 26. This gives fastener 10 additional stability against lateral forces. Central portion 78 of blind aperture 70 is formed adjacent to enlarged portion 72 and is sized to allow inner sleeve 14 to fit therein and to be engaged by inner sleeve 14 when cylindrical post element 18 is inserted into inner sleeve 14. While stabilizing ring 26 and enlarged portion 76 are illustrated in the drawings and described herein, these elements should be considered optional in that it may be at least equally preferred to omit these elements. Cylindrical chamfered stop section 80 is formed adjacent to central portion 78 and serves to limit the insertion of inner sleeve 14 into blind aperture 70. Cylindrical chamfered stop section 80 leads to blind aperture portion 82 which has a diameter to receive cylindrical post element 18.

To use fastener 10, the installer typically inserts inner sleeve 14 into central portion 78 of blind aperture 70 as limited by cylindrical chamfered stop section 80 and aligns blind aperture 70 with the first side of an aperture in a panel or panels to be fastened (not shown). The user then pushes cylindrical post element 18 through the second side of the aperture in the panel or panels to be fastened (not shown) and into cylindrical sleeve 14 which is positioned within blind aperture 70. Stud 12 can then be stamped into position thereby driving post element 18 so that edges of inwardly extending half-hemispherical bosses 58, 60, 62 engage post element 18 and outwardly extending half-hemispherical bosses 64, 66, 68 engage the walls of blind aperture 70. The pressure exerted upon the insertion of stud 12 and the stamping into blind aperture 70 cause the inner diameter and the outer diameter of inner sleeve 14, along with inwardly extending half-hemispherical bosses 58, 60, 62 and outwardly extending half-hemispherical bosses 64, 66, 68, cause inner sleeve 14 to "cock" into position. Any subsequent forces attempting to withdraw stud 12 from base element 16 are opposed by the engagement of bosses 58-68 as described above. The final locked position of fastener 10 typically has planar surface 76 flush with a first side of the panel or panels to be fastened and cylindrical base 28 of stud 12 flush with a second side of the panel or panels to be fastened. The order of steps above is meant to be illustrative and those skilled in the art could have occasion to use a different order of steps of installation.

Thus the several aforementioned objects and advantages are most effectively attained. Although a single preferred embodiment of the invention has been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.