PUSH-ON FASTENER

Abstract: A molded plastic, push-on fastener (10) for connection to threaded studs (24) or the like comprises first and second cylindrical collar members (12, 14). The first collar (12) has a resilient side wall and threads are formed on the interior thereof in a form and size for positive engagement with the threads on the associated threaded stud (24). The second collar member (14) has a relatively rigid side wall (30) with an open interior diameter which is greater than the diameter of the first collar member (12) to permit the second member (14) to be received over and surround the first member (12). A thin frangible, connecting web is provided for temporarily connecting the collar members in axial alignment. Cooperating interengaging thread forms are formed on the exterior of the first collar member (12) and the interior of the second collar member (14).

Description: The subject invention is directed toward the fastener art and, more particularly, to a push-on fastener for connection to elongate elements having external threading, such as threaded studs and the like. The invention is particularly suited for attaching decorative panels or insulation to a base frame having threaded studs welded thereon and will be described with particular reference to such use. As will become apparent, however, the invention is capable of broader application and could be used for attaching many different structures or components to bolts, studs and similar threaded elements. In the automotive industry, insulation and sound proofing materials must be installed on both horizontal and vertical panels. The installation is sometimes made by the use of nuts or similar fasteners received on threaded stud members welded to substructure or panels in the application area. It would be desirable in most instances if a push-on type fastener or nut could be used for such installation rather than a nut or fastener which must be rotatably threaded onto the threaded studs. In US -A- 4,756,654 there is disclosed a push-on fastener for connection to an elongate element having external threading comprising: a member push fittably connectable to the elongate element, the member having an aperture with an entrance end for receiving the elongate element and a formation extending within the aperture for engaging the external threading of the elongate element. This fastener has a low push-on force and a very high pull-off force when used with threaded studs. To achieve a desirable high range pull-off forces, the thread form on the studs should have a preferred shape. Often, however, the studs encountered in use have a shallow, widely spaced and/or inconsistent 60° form which does not provide ideal mating with the fastener of the noted patent. Consequently, the desirable high levels of pull-off force are sometimes not achieved. An object of this invention is to provide a push-on fastener which overcomes the noted problems, achieves an extremely high resistance to pull-off, but is, however, capable of being readily disconnected through a standard unthreading operation. The invention provides a,fastener for connection to an elongate element having external threading comprising: a member push fittably connectable to the elongate element, the member having an aperture with an entrance end for receiving the elongate element and a formation extending within the aperture for engaging the external threading of the elongate element, characterised in that said member comprises; a first collar portion having first and second open ends and a relatively resilient side wall, said side wall defining said aperture, said entrance end thereof being at said first end of said first collar portion, and said formation comprising threading formed on the interior of said resilient side wall of a form and size for positive engagement with the external threading of said elongate element; a second collar portion having a relatively rigid side wall, said second collar portion having an entrance end for receiving the first collar portion and an open interior diameter greater than the exterior diameter of said first cylindrical collar portion to permit said second collar portion to be received over and surround said first collar portion; connecting means for temporarily joining the second end of said first collar portion to the entrance end of said second collar portion with said collar portions in axial alignment; and, cooperating interengaging means on the exterior of the resilient side wall of said first collar portion and the interior of said rigid side wall of said second collar portion for preventing radial expansion of said first collar portion while simultaneously preventing axial withdrawal of said second collar portion in a direction off the second end of said first collar portion after the second collar portion has been moved from the temporarily connected position to a position received over and surrounding said first collar portion. In use, the resilient wall of the first collar portion allows it to be readily pushed on over the end of the associated elongate element. As the second collar portion is pushed over the first collar portion, the interengaging means interlock and act to prevent radial expansion or deflection of the first collar portion thereby locking it firmly to the elongate element. Because the threading formed on the interior of the first collar portion is arranged to correspond to the shape of the threading on the elongate element, a full positive engagement is achieved between the element and the first collar portion. Preferably, the connecting means comprises a frangible web extending between the first and second collar portions. The cooperating interengaging means may comprise mating sets of thread forms formed on the exterior of the resilient side wall of said first collar portion and the interior of said second portion. At least one set of said mating sets of thread forms comprise resilient finger-like members. The second collar portion may have a closed end opposite the entrance end thereof, said closed end carrying thereon a radially extending head. The head allows the second collar portion to function in the nature of a nut or the like for retaining material in position on the elongate element. In order that the invention may be well understood, an embodiment thereof which is given by way of example only, will now be described, with reference to the accompanying drawings, in which: Figure 1 is a side elevational view of a push-on type fastener; Figure 2 is a cross-sectional view taken on line 2-2 of Figure 1; Figure 3 is a somewhat enlarged cross-section view taken on line 3-3 of Figure 1; Figure 4 is a vertical cross-sectional view taken through the fastener of Figure 1 at a 45° angle as best illustrated by line 4-4 of Figure 2; and, Figure 5 is a cross-sectional view showing the fastener of Figures 1 through 4 installed on a threaded stud member. Referring to Figures 1 through 4 there is illustrated the overall arrangement of a push-on type fastener 10 which is molded as an integral, one-piece structure from a suitable resinous plastic material such as nylon, polyethylene, or the like. The fastener 10 is designed to be received on the end of a threaded stud, rod, bolt or similar threaded or groove element with a simple axial push-on motion. That is, the fastener can be moved into its connected position merely by axially pushing the fastener onto the threaded element associated therewith. As more particularly illustrated in the drawings, the fastener 10 comprises cooperating first and second generally cylindrical collar portions, or members, 12 and 14, respectively. The collar member 12 includes a resilient, radially deflectable or expansible side wall 16 which extends from a first, entrance end 18 to a second end 20. The radial flexibility and/or expansibility of the side wall 16 is enhanced by four vertically extending slots or openings 22. In the embodiment under consideration, the first collar member 12 is designed to be closely received over an associated threaded stud or the like 24 (see Figure 5). For this reason, the internal diameter of the central aperture, or opening, 26 of the collar member 12 defined by the side wall 16 is only slightly larger than the exterior diameter of the associated stud or bolt 24. Carried on the interior of the side wall 16 is a thread form 25 which is sized and shaped to closely mate with threads on the stud or bolt 24. As can be appreciated, the radial flexibility or expansibility of the first collar 12 allows it to be placed on the associated stud or bolt 24 by a simple axial pushing action. Of course, it should be understood that the same radial flexibility allows the first collar to be readily removed from the stud by a simple axial pull-off operation. For this reason, the second collar member 14 is arranged to function in a manner to prevent radial expansion of the first collar member 12 after it has been installed in position on the associated threaded stud. Consequently, the second collar member 14 has a relatively rigid side wall 30 which is also of generally cylindrical configuration. Access openings 31 are formed through diagonally opposite sides of the wall 30. These openings result from the tooling used in molding the fastener and form no part of the invention. A central opening 32 extends axially of the collar 14 and the side wall 30. The opening 32 is sized to relatively closely receive collar member 12. In the embodiment illustrated, the first or upper end of the side wall 30 is generally closed by an enlarged radially extending head member 34. It should, of course, be understood that the head member 34 could have a variety of designs or configurations or comprise a separate element or assembly such as a pipe or wire holder depending upon the intended use for the fastener 10. In the subject embodiment, the head 34 includes a transversely extending slot 36 adapted to receive a screw driver or the like. The first and second collar members 12, 14, respectively, are joined at their respective second ends in a manner to permit them to at least temporarily retain the aligned position illustrated in Figure 4. Many different types of temporary connecting means could be provided to perform this function. In the subject embodiment, however, the connecting means comprise a thin frangible web of plastic 40 which is molded in place simultaneously with the molding of the fastener 10 and which extends radially outwardly from the second end 20 of the collar member 12 into engagement with the lower, or entrance, end of the collar member A. The web 40 is sized and arranged such that after the first collar member 12 has been moved into position on the end of the threaded stud as shown in Figure 5, further axial force applied to the second collar member 14 causes the web to break and the member 14 to move into located position over the collar 12 as shown in Figure 5. In order to maintain the second collar member locked in position on the first collar member in the assembled relationship shown in Figure 5, the two collar members are provided with cooperating interengaging means. The interengaging means could have many designs but in the subject embodiment comprise cooperating thread forms which are generally of the type shown and described in U. S. -A- 4,756,654. In particular, the exterior of the collar member 12 is provided with a first continuous spiral of threads 42 which preferably have somewhat of a buttress shape with a generally horizontal first wall 42a and an inclined mating wall 42b (See Figure 4). The interior of the collar member 14 is provided with a continuous cooperating thread form in the configuration best shown in Figures 1 and 4. The threads 46 formed on the interior of the side walls 30 are relatively resilient and are inclined in a direction away from the second or lower end of the opening 32. As noted earlier, the preferred form and shape for these resilient finger like threads is more fully described and shown in the aforementioned U. S. -A- 4,756,654. Generally, however, they include a first face 46a which is inclined somewhere in the range of approximately 30° relative to the axis of the fastener. A second wall 46b inclined at an angle in the range of approximately 45° joins wall 46a at the apex of the thread form. The arrangement allows the threads to readily flex in a direction away from the lower end of the fastener. Thus, as the fastener is pushed on to the threaded stud the position shown in Figure 5, the individual thread forms 46 can deflect upwardly and pass over the individual threads 42 on the exterior of the collar member 12. However, once the threads 46 have passed over the individual threads 42, attempts at axially withdrawing the sleeve member 14 are strongly resisted. Additionally, while in the final located position shown in Figure 5, the threads 46 and the rigid side walls 30 of the collar member 14 maintain the first collar member 12 firmly locked in engagement with the threaded stud 24. Thus, axial withdrawal of the push-on fastener 10 is generally not possible and removal can be accomplished only by a conventional unthreading operation. During the rotation or unthreading of the member 10 the greater surface contact between the interior of the collar member 12 and the exterior of the threaded stud 24 produce a greater friction than is present between the exterior of collar member 12 and the interior of collar member 14. Thus, during the unthreading operation, the collar member 12 remains in position on the stud. Of course, after the collar member 14 has been removed the collar member 12 can be removed either by axially pull-off or unthreading from the stud. As can be seen from the foregoing, the subject fastener has the ability to work on standard thread forms and produce a high resistance to pull-off. In addition, the fastener can be molded in one piece and after installation can be removed by a simple unthreading operation. Further, the individual components of the fastener can be separated to facilitate subsequent serviceability of the assembly.

Claims: A push-on fastener for connection to an elongate element (24) having external threading comprising: a member (12) push fittably connectable to the elongate element, the member having an aperture with an entrance end (18) for receiving the elongate element and a formation (25) extending within the aperture for engaging the external threading of the elongate element, characterised in that said member comprises; a first collar portion (12) having first and second open ends (18, 20) and a relatively resilient side wall (16), said side wall defining said aperture, said entrance end thereof being at said first end of said first collar portion, and said formation comprising threading formed on the interior of said resilient side wall of a form and size for positive engagement with the external threading of said elongate element; a second collar portion (14) having a relatively rigid side wall (30), said second collar portion having an entrance end for receiving the first collar portion and an open interior diameter greater than the exterior diameter of said first cylindrical collar portion to permit said second collar portion to be received over and surround said first collar portion; connecting means (40) for temporarily joining the second end (20) of said first collar portion to the entrance end of said second collar portion with said collar portions in axial alignment; and, cooperating interengaging means (42, 46) on the exterior of the resilient side wall (16) of said first collar portion (12) and the interior of said rigid side wall (30) of said second collar portion (14) for preventing radial expansion of said first collar portion (12) while simultaneously preventing axial withdrawal of said second collar portion (14) in a direction off the second end (20) of said first collar portion after the second collar portion has been moved from the temporarily connected position to a position received over and surrounding said first collar portion. A push-on fastener as defined in claim 1, wherein said second collar portion has a radially extending head portion (34) formed on an end opposite the entrance end thereof. A push-on fastener as defined in claim 1, wherein said second collar portion has a closed end opposite the entrance end thereof, said closed end carrying thereon a radially extending head. A push-on fastener as defined in claim 1, 2 or 3, wherein said connecting means comprises a frangible web (40) extending between said first and second collar portions (12, 14). A push-on fastener as defined in claim 1, 2 or 3, wherein said connecting means comprises a thin, frangible wall extending radially outwardly from the second end (20) of said first collar portion (12) into engagement with said entrance end of the second collar portion (14). A push-on fastener as defined in any one of the preceding claims, wherein said cooperating interengaging means comprise thread forms (42, 46) formed on the exterior of the resilient side wall (16) of said first collar portion and the interior of the second collar portion. A push-on fastener as defined in claim 6 wherein the thread form formed on the interior of the second collar portion comprises a series of resilient finger members (46) which are inclined in a direction away from said entrance end of said second collar portion. A push-on fastener as defined in any one of claims 1 to 5, wherein said cooperating interengaging means comprise mating sets of thread forms (42, 46) formed on the exterior of the resilient side wall of said first collar portion and the interior of said second portion. A push-on fastener as defined in claim 8, wherein at least one set of said mating sets of thread forms (42, 46) comprise resilient finger-like members. A push-on fastener as defined in any one of the preceding claims wherein said first collar portion has a cylindrical exterior. A push-on fastener as defined in any one of the preceding claims, wherein said second collar portion is generally cylindrical in shape.

Inventors: CLOUGH, MELVYN JOHN LEACH, LEWIS, JEFFREY CHARLES, MACKOWIAK, STEPHEN PAUL
Applicants: TRW INC.
Application year: 1989
Main classification: F16B17
IPC codes: F16B37