Snap fastener assembly

Abstract: A snap fastener assembly (10) includes a cylindrical C-shaped spring retainer member (14) having a hollow open core with an exterior longitudinal slit aperture extending into the core. The spring retainer member is mounted on a stud member (12) having an enlarged head (24) at one end, a retaining head (28) at the other end, and a longitudinal shaft (26) that is dimensioned to be substantially enclosed by the spring retainer member. The stud member (12) can be used for both the insertion and retraction of the cylindrical spring retainer member. The retainer member can be actively fastened to a hole, for example, to hold panels on a wall.

Description: 1. Field of the Invention The present invention is directed to a fastener assembly that permits the mounting of panels in the cargo bay of aircraft and, more particularly, a two-part fastener assembly that can be quickly mounted and demounted to release the panel. 2. Description of Related Art The interior walls of cargo planes, for example, as used by the military, can be subject to wear, such as abrasions and scrapes, that can occur as the maximum amount of cargo is attempted to be loaded into the bay of the cargo hold. The cargo plane walls are typically formed of approximately .06 inch thick composite surface panels. There has been a desire to use sheets of a protective plastic having various thickness ranges, for example, .04 inches in thickness, which should be easily mounted and demounted from the spars and stringers of the cargo bay. The conventional approach to this installation, has been the use of titanium bolts that extend through both a protective cover panel and the interior wall panel of the cargo bay. A clip nut is mounted in appropriate spars and stringers to enable the bolt to be threaded into the nut assembly. Since in large planes as many as 20,000 fastener assemblies are utilized to hold the panels/liners, a substantial issue of labor in installation and removal of the panels is created. As can be appreciated, a plane can be subject to vibrations and the protective panels and its fasteners should be securely fastened. Balanced against this operational requirement is the desirability to reduce the labor time in both installing and demounting of the panels. The prior art is still seeking an optimum solution to these opposing requirements. US-A-2336153 discloses a fastener having a spring clip with a longitudinal slit which is positioned within a hole, the clip also having a number of prongs. A rod member is then inserted into the spring clips through a sheet to be fastened, the sheet pressing down on the clip to force the prongs into engagement with the rod member and lock it in position. The present invention provides a removable two-part fastener for extending through and removably holding an apertured panel to extend over a wall having a bore of a predetermined dimension for receiving the fastener and providing a friction fit with the fastener, the fastener comprising: a cylindrical C-shaped spring retainer member having a longitudinal hollow open-ended core with an exterior longitudinal slit aperture extending into the core, the exterior surface including an annular tapering section with a central enlarged portion of a greater dimension than the tapering section; and a stud member having an enlarged head at one end and a retaining head at the other end which is interconnected by a longitudinal shaft that is dimensioned to be substantially enclosed by the spring retainer member, and to have a larger length than the spring retainer member, width dimensions of the enlarged head and the retaining head are larger than the longitudinal shaft and the open-ended core of the spring retainer member, whereby the enlarged head and the retainer head prevent the spring retainer member from being released along the longitudinal axis while the spring retainer member can be compressed during insertion into an opening to provide a locking friction force with the walls of the opening, and the spring retainer member can slide along the longitudinal shaft during extraction to permit the retaining head to exert an extraction force on the spring retainer member. Preferably, the exterior surface of the spring retaining member has a first and a second annular tapering section that meet at a central enlarged portion of a greater diameter than the tapering sections. The enlarged head of the stud member can have an annular groove adjacent the base of the longitudinal shaft that is dimensioned to receive one end of the spring retaining member. The enlarged head and retainer head of the stud member prevent the spring retainer member from being released along the longitudinal axis whereby the spring retainer member can be compressed during insertion into an opening or bore and then can expand to provide a locking friction force for holding the protective cover to the bulkhead of a cargo bay. The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings. Figure 1 is a perspective view disclosing protective covers mounted on the bulkhead of a cargo bay; Figure 2 is a perspective view of the fastener assembly of the present invention; Figure 3 is a perspective view of the spring retainer member of the present invention; Figure 4 is a perspective view of the stud member of the present invention; Figure 5 is a cross-sectional view of the fastener assembly under compression as it is being mounted on the bulkhead skin of a cargo plane; Figure 6 is a cross-sectional view of the fastener assembly installed; Figure 7 is a schematic cross-sectional view of the fastener assembly being released with a hand tool; and Figure 8 is a cross-sectional view of an alternative embodiment of the invention, incorporating a threaded joint. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide a cargo panel fastener. Referring to Figure 1, a schematic partial perspective view of a cargo bay of a plane is disclosed wherein panels, for example, having a .04 inches thickness of plastic sheets are mounted onto the bulkhead 8 of a plane by the fastener assembly of the present invention. The panels 2 have appropriately positioned holes or bores 4, which are juxtapositioned to align with corresponding holes or bores 6 in the bulkhead flanges 9. The fastener assembly 10 of the present invention can be quickly mounted by a force application so that the insertion operation can be performed manually by laborers, either by hand or with hand tools. A perspective view of the fastener assembly 10 can be seen in Figure 2. The fastener assembly 10 includes a stud member 12 and a spring retainer member 14. The spring retainer member, as seen in a perspective view in Figure 3, can comprise a substantially cylindrical C-shaped metallic body, for example, made of stainless steel, such as a formable AISI 430, having a longitudinal hollow open ended core section. An exterior slit aperture 16 extends the length of the retainer member 14 to thereby enable a compression movement of the spring retainer member 14 during insertion and extraction. The exterior surface has a first annular tapering section 18 and a second annular tapering section 20. The degree of taper can be 5° relative to a longitudinal axis through the core section. A central enlarged portion or rim 22 of a greater diameter than the tapering sections and positioned between the respective tapering sections is provided. By appropriate selection of the type of material and the heat treating procedure, the spring constant of the retainer member 14 can be adjusted to provide a particular insertion force. For example, a 3/8-inch fastener can be set to have an insertion force between 25 and 35 pounds in a hole diameter of about .31 inches with a 430 stainless steel. Referring to Figure 4, a perspective view of the stud member 12 is disclosed. The stud member has an enlarged head 24 with a hollow longitudinal shaft 26 terminating in a retaining head or flange 28. An annular groove 30 is formed in the enlarged head 24 at its interface with the longitudinal shaft 26. As seen in Figure 5, the stud member 12 can be machined from a unitary piece of metal, such as a 430 stainless steel. While not shown, an alternative embodiment of the present invention could have the longitudinal shaft 26 and retainer head 28 formed as one piece of material with the enlarged head 24 formed from another piece of material having a central opening. A portion of the longitudinal shaft could extend through the central opening to be cold-worked for an interconnection with the enlarged head. Other forms of manufacturing the stud member can be employed. Again, referring to Figure 5, the spring retainer member 14 is mounted on the longitudinal shaft 26 and the open-ended portion of the longitudinal shaft 26 could be cold-worked to form the retainer head 28 for locking the spring retainer member 14 to the fastener assembly. The provision of the annular groove 30 is dimensioned to assist in centering the spring retainer member 14 and to also assist in enabling a hand-operated retraction tool to be inserted beneath or between the enlarged head 24 and a panel 2 for a simplified extraction. The relative distance between the base of the groove 30 and the enlarged head 28 keep the spring retainer member 14 within the groove 30 and permit sufficient longitudinal movement while minimizing any rattling movement of the head relative to the spring retainer member 14. The enlarged head 24 also has a tapered edge 32 to further facilitate the insertion of a removal tool 34. In Figure 5, the spring retainer member 14 has been compressed as it is passing through a hole that is juxtapositioned between the panel 2 and the bulkhead wall or flange 9. The spring retainer member 14 is compressed during the insertion and then, as seen in Figure 6, the spring retainer member can be somewhat released, although it is still in compression, due to the dimensioning of the hole 4. Referring to Figure 7, a removal tool 34 has been slid underneath the enlarged head 24 of the stud member 12 so that the fastener assembly can be pried from the panel 2. As can be readily appreciated, the stud member 12, in essence, is a carrier or insertion component of a fastening assembly with the exterior of the enlarged head 24 receiving the insertion force and the underside of the enlarged head 24 receiving an extraction force as a result of a lever pivoting motion by a removal tool 34. The spring retainer member 14 compresses in a direction perpendicular or traverse to the longitudinal axis of the fastener assembly and it is driven into place by the stud member 12 and then removed also by the stud member 12. The stud member 12 does not perform an active role after the retainer member has been installed, that is, the retainer member 14 is the locking member for holding the panel 2 in place. An alternative embodiment of the present invention is disclosed in Figure 8, wherein the opening bore section 36 of the longitudinal shaft 26 can be further threaded so that it can receive a threaded bolt member 40. This embodiment of the invention would, in essence, provide an arrangement for inserting a nut through a panel so that it would receive a threaded bolt 40 from the other side of the panel to thereby provide a locking assembly. The enlarged head 24 has a slot 42 for receiving a screwdriver blade to prevent the modified stud member from turning when the bolt member 40 is inserted. As can be appreciated, any use of this embodiment of the invention would require access to both sides of the panel. As disclosed in the preferred embodiment, shown in Figure 1, only one-sided access is required for assembly and extraction of the present fastening assembly with a minimum of labor.

Claims: A removable two-part fastener for extending through and removably holding an apertured panel to extend over a wall having a bore of a predetermined dimension for receiving the fastener and providing a friction fit with the fastener, the fastener comprising: a cylindrical C-shaped spring retainer member (14) having a longitudinal hollow open-ended core with an exterior longitudinal slit aperture extending into the core, the exterior surface including an annular tapering section with a central enlarged portion of a greater dimension than the tapering section; and a stud member (12) having an enlarged head (24) at one end and a retaining head (28) at the other end which is interconnected by a longitudinal shaft that is dimensioned to be substantially enclosed by the spring retainer member, and to have a larger length than the spring retainer member, width dimensions of the enlarged head and the retaining head are larger than the longitudinal shaft and the open-ended core of the spring retainer member, whereby the enlarged head and the retainer head prevent the spring retainer member from being released along the longitudinal axis while the spring retainer member can be compressed during insertion into an opening to provide a locking friction force with the walls of the opening, and the spring retainer member can slide along the longitudinal shaft during extraction to permit the retaining head to exert an extraction force on the spring retainer member. A fastener as claimed in claim 1, wherein the enlarged head (24) has an annular groove (30) extending around the longitudinal shaft and dimensioned to receive the spring retainer member. A fastener as claimed in claim 2, wherein the spring retainer member (14) can move longitudinally along the longitudinal shaft to extend into and out of the annular groove (30). A fastener as claimed in any of the preceding claims, wherein the spring retainer member (14) and stud member (12) are formed of AISI 430 stainless steel. A fastener as claimed in any of the preceding claims, wherein the enlarged head (24) has tapered edges. A fastener as claimed in any of the preceding claims, wherein the stud member (12) has a hollow threaded opening. A fastener as claimed in any of the preceding claims, wherein the enlarged head (24) has a tapered edge extending inwardly towards the spring retainer member of a dimension to enable an extraction tool to pry the stud member away from a fastened position. A fastener according to any of the preceding claims. wherein the spring retainer member (14) has a substantially cylindrical outer surface with at least one annular tapering section and a central enlarged portion of a greater diameter than the tapering section, the only opening along the cylindrical outer surface is the longitudinal slit aperture. A fastener according to claim 8, wherein the tapering section has a taper angle of approximately 5° relative to a longitudinal axis. A wall with removable apertured panels and a removable two-part fastener according to any of the preceding claims for extending through and removably holding an apertured panel to extend over the wall, the wall having a bore of a predetermined dimension for receiving the fastener and providing a friction fit with the fastener. An aircraft having a wall according to claim 10. A method of mounting and removing apertured panels to a surface having a bore with a two-part fastener assembly (10) including a cylindrical spring retainer member (14) having a longitudinal hollow open-ended core with an exterior longitudinal slit aperture extending into the core, the exterior surface including an annular tapering section and a stud member (12) having an enlarged head (24) at one end and a retaining head (28) at the other end which is interconnected by a longitudinal shaft that is dimensioned to be substantially enclosed by the spring retainer member, the spring retainer member can slide along the longitudinal shaft from the enlarged head to the retaining head during insertion and retraction of the fastener assembly, comprising the steps of: aligning an aperture of a predetermined dimension smaller than the enlarged head in the panel with the bore in the surface, the bore having a predetermined dimension to interact with the spring retainer member; inserting the fastener in the aperture and the bore; applying an insertion force to the enlarged head of the stud member to force the spring retainer member to compress as the spring retainer member is forced into the bore by contact with the enlarged head, whereby a frictional retention of the spring retainer member with the bore can be achieved with the enlarged head holding the panel; and applying an extraction force to the enlarged head of the stud member to permit the stud member to slide along the longitudinal shaft until the retaining head engages the spring retaining member and force the spring retainer member to compress as it is extracted and releases the panel. A method according to claim 12, wherein the fastener is constructed according to any of claims 1 to 9.

Inventors: MCCORKLE DANIEL J, REHBURG HEINDRICH, WAITS ROBERT L, MCCORKLE, DANIEL J, REHBURG, HEINDRICH, WAITS, ROBERT L
Applicants: SHUR LOK CORP, SHUR-LOK CORPORATION
Application year: 1996
Main classification: F16B5
IPC codes: F16B21, F16B5, F16B37