Sliding two-piece fastener

Abstract: A fastening assembly for securing plastics panels (50) to metallic substrates (52) is provided in which a metallic nut (14) is mounted in snap-fit relationship on a plastics insert (12), which is in turn engaged in snap-fit relationship on the metallic substrate (52). The nut (14) slidably engages the plastics insert (12) to permit limited movement along an axis perpendicular to the axis of the insert (12) to provide thermal compensation for the mounted plastics panel (50). The nut (14) itself utilises the same guide lug structure (26) of the insert member (12) to both effect snap-fit retention of the nut (14) on the insert (12) and to guide the sliding movement of the nut (14) with respect to the insert (12).

Description: Field of the Invention The present invention relates generally to automotive fastener assemblies, and more specifically to fastener assemblies for securing plastics finish panels to metallic substrates, according to the preamble of claim 1. Description of the Related Art As part of the overall effort of automotive manufacturers to improve fuel economy of automotive vehicles, plastics finish panels have come into widespread use and even broader use is planned for the future. Most of the uses of plastics finish panels in the automotive vehicle arts require that a plastics sheet or panel be secured to an underlying metallic substrate through suitable fasteners. As in most mechanical joining applications, one of the primary fastening systems of choice is the use of a threaded fastener spanning the two components to be secured together and exerting a clamping load between them. In the target application for the automotive industry, the mounting of a plastics body panel on a metallic substrate such as a frame or underbody, certain impediments to the presentation of a finish panel of good quality and appearance have been experienced. The significant difference in coefficient of thermal expansion between the plastics panel and the metallic substrate tends to result in displacement between these two components, and when a fastener is arranged to hold the panel fast with respect to the substrate, distortion can result. The automotive industry has addressed this problem by providing fastener mechanisms which permit some relative movement between the panel and the substrate. U.S. Patent 5,098,765 to Bien is an example of solutions suggested in the industry, providing mounting blocks engageable in the substrate to permit fore and aft movement which mounts a fastener receiving plate through agency of laterally extending wings. This and other solutions have been found to be disadvantageously complex and expensive to produce and also fail to provide directly for movement of a fastener receiving device or nut in response to thermal growth of the plastics panel. This direct compensation for thermal growth is, at least in some applications, the most reliable way to provide for the desired compensating movement. French Patent 2554522 A describes an adjustable assembly fixing for joining on support to a panel-shaped component consisting of a box-shaped element which fits into a rectangular aperture in the panel and contains a wedging element for a screw. The box-shaped element has ribs and flexible shoulders so it can grip the edges of the rectangular aperture and grooves along its sides which enable the wedging element to slide in it. The wedging element has a threaded hole for the screw and an expanding base to anchor it to the box-shaped element. The teaching of French Patent 2554522 is acknowledged in the preamble of claim 1. Summary of the Invention It is an advantage of the fastener assembly of the present invention that the engagement between insert member and nut is improved. This is achieved through the features of the caracterising portion of claim 1. Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is an exploded perspective view of a fastener assembly according to the present invention; Figure 2 is a cross-sectional view of the fastener assembly illustrating the fixed securement of a plastics finish panel to a metallic substrate; and Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2. Description of the Preferred Embodiment In Figure 1, a fastener assembly 10 is illustrated as generally including an insert member 12, a nut member 14, and an externally threaded fastener such as a screw 16. As may best be seen in Figure 2, the insert member 12 is a plastics moulded part of generally T-shaped cross-section. It includes a lower plug portion 18 of generally box-like configuration and an upper nut mounting portion 20, likewise of generally box-like configuration, of larger cross-section than the plug portion 18. As used herein, the terms upper and lower, inner and outer, and other terms of direction, will be as illustrated in this Figure 2. An annular face 22 is formed on the underside of the nut mounting portion 20 and a plurality (four shown) of barbs 24 are formed integrally with plug portion 18 on its outer peripheral surfaces in spaced relationship with respect to the annular face 22 measured along the longitudinal extent of the plug portion 18. The plug portion 18 is referred to as defining a longitudinal axis notwithstanding its box-like rectangular configuration, its downwardly extending axis of symmetry being inferred. The nut mounting portion 22 also has a plurality (two shown) of generally triangular projections or barbs 26 projecting from two slide surfaces 28, 30 formed on the longer sides of the nut mounting portion 20, as viewed in Figure 1. Centring tabs indicated generally at 30, 32 in Figure 1 project perpendicularly from the ends of the slide surfaces 28, 30 to assist in locating the nut 16 with respect to the insert 12. The nut 14 is preferably formed as a generally C-shaped member having a base portion 34 having a dished, internally threaded aperture 36 formed through it and terminating at laterally spaced, downwardly projecting slide arms 38, 40. The nut 14 is fabricated as a metallic member and includes longitudinally extending slots 46, 48 formed through the slide arms 38, 40, respectively. Turning next to Figure 2, the fixed securement of a plastics finish panel 50 to a metallic substrate 52 through the agency of the fastening assembly 10 is illustrated. The insert member 12 is inserted through an aperture 54 formed in the metallic substrate 52 and the barbs 24 slide through the aperture 54 and snap back to retain the insert 12 in snap-fit retention with respect to the metallic substrate 52. The nut 14 is likewise presented to the nut mounting portion 20 of the insert 12, and by the agency of the projections 26 co-operating with the guide slots 46, 48, snap-fit retention in the axial direction of the nut 14 with respect to the insert 12 is effected. The screw 16 may then be introduced through a clearance hole 56 provided in the finish panel 50 to engage the threaded aperture 36 in the nut 14 and clampingly secure the finish panel 50 with respect to the metallic substrate 52. If thermal growth of the plastics panel 50 is experienced in a direction parallel to the slots 46, 48, the screw 16 can be carried along with the deflecting panel 50 and can be permitted to move the nut 14 a limited amount in the direction of the slots 46, 48 until the projection 26 contacts either end of the slots 46, 48. It will be noted that a hollow cavity 58 is formed in the insert 12 for receiving a portion of the nut 16 being sized to permit the certain movement described.

Claims: A fastening assembly for securing a plastics finish panel (50) to a metallic substrate (52), the substrate having a mounting aperture (54) extending perpendicular from an external face thereof, the fastening assembly (10) comprising: a nut (14) being generally C-shaped and including a base (34) portion having threads (36) formed therethrough and a pair of laterally spaced side portions (38,40) projecting perpendicularly from said base portion (34) and extending longitudinally of the base portion (34); an insert member (12) having a generally box-like plug portion (18) receivable in snap-fit relationship in said substrate mounting aperture (54), an enlarged nut mounting portion (28) formed of generally rectangular cross-section at one end of said plug portion (18) and integrally formed therewith, the nut mounting portion being of larger cross section than said plug portion (18) to define a generally T-shaped stepped configuration of said insert member (12), means defining longitudinally extending slide surfaces on said nut mounting portion (28) receiving said nut for sliding engagement therebetween and a threaded fastener (16) received in said nut (14) and operatively engageable with said panel (50) to attach said panel (50) to said substrate (52); characterised by said nut (14) comprising an elongated guide slot (46,48) formed through each of its said side portions (38,40) and by a means (26) formed on said means defining slide surfaces on said nut mounting portion (28) and being operatively engaged with said nut slot (46,48) and effecting snap-fit engagement between said nut and said insert for both limiting relative movement in two opposed directions between said nut (14) and said insert (12). A fastening assembly as claimed in claim 1, wherein said insert plug portion (18) includes a plurality of barbs (24) projecting outwardly from the periphery for effecting said snap-fit retention in said substrate aperture (54.) A fastening assembly as claimed in claim 1 or 2, wherein said means for limiting and effecting engagement comprises at least one lug (26) formed with said insert member nut mounting portion (28) and projecting through said nut guide slot (46,48). A fastening assembly as claimed in any one of the preceding claims, wherein said insert member (12) is fabricated from a plastics material and said nut member (14) is fabricated from metal.

Inventors: GAW WILLIAM JR, GAW, WILLIAM, JR.
Applicants: FORD MOTOR CO, FORD MOTOR COMPANY
Application year: 1995
Main classification: F16B5
IPC codes: F16B37, F16B1, F16B5