Abstract:
A fastener for releasably securing a pram wheel to its axle and similar applications includes a groove in the axle and a post extending tangentially of the axle and which is resilient to deflect about its root so that it can snap engage in the groove. The post is carried in a cap secured to the wheel. A pin is located parallel to the axle in the cap to displace the post to enable the parts to be separated when required.

Description:
This invention relates to fasteners comprising two parts which are adapted to be secured together. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention a fastener comprises a locking plate and a stud with a lateral recess, the plate including a frame element and at least one post projecting from the frame to extend generally laterally of the stud and engage in the recess when the plate and stud are connected, said post being resilient so that when deflected out of the recess for release or disengagement, it will return to the engaged position. 
     Preferably a pair of said posts are provided side by side and are arranged to be deflected away from one another for release, the stud including a peripheral groove forming the recess. This feature allows the two parts to be relatively rotatable in the engaged position, when the posts maintain their engagement in the groove but rotate relative to the stud. Hence the one part may be provided on a wheel while the other part forms or is provided on the axle. 
     Preferably also in the case of rotatable parts, the frame comprises an endless loop located in a cover, the cover being adapted to be fixed to one of the rotatable parts, and the frame and cover being held against relative angular movement of one with respect to the other. 
     The fastener may be adapted for release by a separate tool, but preferably incorporates release means adapted to be displaced manually, for example by a coin, and to this end a release plate is provided with a number of pegs arranged to deflect the post or posts when the release plate is turned, and in the case when two posts are provided the pegs will be located between the posts, and possibly one on either side of the stud when the posts have their roots (which are connected to the frame) located generally diametrically of the axis of the stud. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view showing a fragmentary portion of a pram wheel and axle and a securing means therefor; 
     FIG. 2 is a sectional elevation of the assembly of FIG. 1; 
     FIGS. 3 and 4 are sections taken on the line 3--3 and 4--4 respectively of FIG. 2; 
     FIG. 5 is a view similar to FIG. 2 showing parts in a &#34;release&#34; condition; and 
     FIG. 6 is a view similar to FIG. 2 of a modification. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning first to FIGS. 1 to 5 and initially to FIG. 1, the pram wheel comprises a tubular hub 10 with spokes 12 and on its outer face (in use) the hub includes a base member in the form of an annulus 14. The latter has a peripheral bead 16 which serves to confine the rim of a cover member 20 which is snap engaged with the annulus by means of a number of headed prongs 18 passed through slots 22 in the annulus. Located between the cover 20 and the annulus is a locking plate 24 and externally of the cover is a release plate 26. Axle 28 constitutes a stud including a frusto conical end 30 with a peripheral groove or recess 32 behind the same. 
     The locking plate 24 includes an annular frame 34, see FIG. 2, which is confined within the skirt 36 of the cover (although as an alternative it could seat within the bead 16 and annulus 14) and it is held against rotation by a peg 38 engaged in recess 40 in the cover. Alternatively the cover, which peg constitutes means for holding the plate angularly captive and frame could be non-circular to like effect. Projecting generally chord-wise from the frame is a pair of locking posts 42 each integral with the frame at one end and extending generally parallel to and on opposite sides of a diameter of the frame, and conveniently these have curved edges 44 midway along their length and towards the axis of the frame, the curved edges being located towards one another so as to embrace the periphery of the axle when located between them. 
     All of the parts 10 to 26 inclusive may be made of suitable synthetic resinous products, thus removing or avoiding problems from corrosion and failures as a result, and in the case of plate 24 one with a suitable resilience to allow the posts 42 to be deflected from the FIG. 2 position to the FIG. 5 position and automatically returned to the FIG. 2 position, as described hereinafter, is an acetal such as the material sold under the Registered Trade Mark DELRIN. However a nylon would also be suitable, and the plate could even be made of metal with suitable dimensions for the cross-section of the posts to give the required deflection and return result, if so required. It will also be appreciated that the other components described could be made of metal if wished. 
     The release plate 26 comprises a pair of pegs 46 projecting parallel to the axis of the assembly, that is parallel to the axle, and located between the two posts 42. The cover 20 includes an annular portion 48 extending radially outwards from a central sleeve 50 and portion 48 has two arcuate slots 52 therethrough and the pegs project through those slots. Each peg includes a lateral projection 54 and the slots have enlarged ends 56; this arrangement permits the pegs to pass through the enlargements in assembly, and then when the plate 26 is turned, for example via a transverse recess 58 in its outer face and by means of a coin engaged in that recess and used to turn the plate, the projections prevent withdrawal of the pegs through the narrower portion of the slots. 
     The angular position of the peg 38 and recess 40 relative to the slots 52 is such that in the assembled position, FIG. 2, release pegs 46 are held out of alignment with the enlarged slot portions. Any attempt to turn the release plate clockwise in FIG. 3 is prevented by the locking posts which, in such direction, would be contacted near to their roots where they are stiff and where the leverage is poor. In the opposite direction however, anti-clockwise in FIG. 2, the pegs engage the posts near their free ends with good leverage and in movement of the pegs to the ends of the slots the posts are deflected to the FIG. 5 position where overtravel is prevented by the posts engaging the frame, or by the pegs reaching the ends of the slots. In this preferred embodiment the frame is itself confined by the skirt of the cover. 
     The release plate and locking plate are assembled to the cover, and the latter to the hub, in the manner described and by virtue of the tapered end of the axle, and the guiding afforded by the tubular hub, the wheel may be offered up to the axle so that the axle enters the hub and is aligned with the centre of the locking plate, and pressed home when the tapered end of the axle will enter between the two posts, spring them apart, and as they recover resiliently they will engage in the groove 32. This will hold the wheel axially captive, and leave it rotationally free. If desired the curvature of the edges 44 may be such as to create a clearance between then and the base of the groove 32, so as to minimise friction in rotation, but the preferred materials have a low co-efficient of friction and contact between the posts and the axle is then not important. It will be appreciated that where a part equivalent to the wheel is secured by such a fastener, but rotation is not required, interference between the posts and the walls and base of the groove will be immaterial. 
     Removal of the wheel is effected simply by turning the release plate and moving the wheel axially. The plate 26 may bear an arrow or other indicia to show the direction in which it should be turned. 
     It will be understood that the fastener of FIGS. 1 to 5 may be used for other purposes. For example a short stud may be provided as the equivalent to the axle, and the part to be fixed thereto may be a panel or sheet of material with an apertured plate as the equivalent of the hub fixed to that panel or sheet. One instance of such use may be in holding panels in place on machinery, vehicles or aircraft. 
     Instead of fixing the cover by prongs it may be secured by other means such as adhesives or welding, and when both components (hub or equivalent and cover) are of suitable materials, ultra sonic vibrations may be used to &#34;weld&#34; the parts together. 
     It will be noted that the fastener described is effectively fail-safe, for in the event of loss of the release plate it is merely release which becomes more difficult and the locking plate remains in place. Even if the cover is lost the locking plate may remain functional. If one post breaks at its root, the other is effective alone, and indeed it is possible or even likely that if both posts were to break they would be constrained between the face of the annulus 14 and the annulus 48 to remain in the plane of the groove 32 and would remain in locking engagement with the groove. 
     In a modification, not shown, the release plate comprises a push button having a pair of frusto-conical stems located so as to pass between the parts and urge them apart, and the edges of the posts may be bevelled complementarily to give a smooth action. 
     FIG. 6 shows a view similar to FIG. 2 of a modified version in which the posts have their roots adjacent one another instead of being diametrically opposed. Further, in this embodiment the release plate is omitted and the cover includes an axially offset aperture 60 to admit a screw-driver blade which may be turned angularly to separate the posts for release. This fastener may comprise only a headed stud and the locking plate, and may be adapted for mass production for use for example in holding motor vehicle components in place such as for holding wheel trims to wheels when the studs may be secured to the wheels by adhesive or may be metal components electrically welded to the metal wheels, and the cover plates may be formed by the trims (or secured to them), the apertures 60 being disguised by being ones of a series of apertures forming an ornamental pattern in the trim. 
     In the case of FIG. 6 or any other arrangement in which the posts extend from adjacent roots, the modification of using a push button to deflect the posts can be employed using only a single frusto-conical or like stem to act on both posts.