Patent Abstract:
A fastener comprises a shank  10  for extending through an opening  60  from a near side  56  to a far side  58  of a wall and a catch  20  retained In the shank of the fastener, in which the catch has first and second orientations in which, respectively, it projects less and more beyond the profile of the shank, whereby the catch can pass through the opening in the first orientation but the catch engages the far side of the wall and prevents withdrawal of the shank from the opening in the second orientation, the catch being supported by a shoulder  42  when the shank is tensioned by a nut  50 . Swivelling of the catch is controlled by rotation of the shank.

Full Description:
FIELD OF THE INVENTION 
     This invention relates to fasteners, and in particular to fasteners suitable for fixing into a wall or other panel by passing though an opening in the wall and extending a catch member to prevent subsequent withdrawal, when access is restricted to one side of the wall. 
     SUMMARY OF THE INVENTION 
     A number of fastener designs of this general kind are known. The present invention has one object to provide an improvement in such designs, and in certain embodiments to provide a fastener which can withstand large withdrawal forces without damage, and also to provide a fastener which can be withdrawn even when there is no access to the catch mechanism. 
     Generally, this invention is concerned with a fastener comprising a shank for extending through an opening from a near side to a far side of a wall and a catch retained in the shank of the fastener, in which the catch has first and second orientations in which, respectively, it projects less and more beyond the profile of the shank, whereby the catch can pass through a suitably sized opening in the first orientation but the catch engages the far side of the wall and prevents withdrawal of the shank from the opening in the second orientation. Means are suitably provided for tensioning the shank in the opening by reaction against the near side of the wall. 
     In certain embodiments of the invention, the catch may be adapted to swivel from the first orientation to the second orientation, and/or from the second orientation to the first orientation, by means of gravity. In some embodiments of the invention, the catch may rely on the sides of the opening to retain it in the first orientation while the shank is inserted in through the opening. In some embodiments, it may not be possible to return the catch from the second orientation to the first orientation, but, especially in cases where the fastener is not being inserted vertically through an opening, the catch may be arranged to swivel under the action of gravity when the shank is rotated in the opening, according to the rotary position of the shank. 
     In a preferred embodiment, the catch may comprise a retaining arm mounted in the shank of the fastener, movable between a first orientation in which it lies substantially wholly within the profile of the shank, and a second orientation in which it extends beyond the profile of the shank, whereby it can engage the far side of the wall when the fastener is subjected to tension forces tending to withdraw it from the opening. 
     In particular preferred embodiments of the invention, the shank is provided with an abutment supporting the catch in its second orientation. 
     The shank may be provided with a slot extending diametrically through the shank. The arm may be swivel mounted on a pin extending across the slot. The aforesaid abutment may be formed by a shoulder at one end of the slot. 
     The catch may be adapted to pivot on an axis that is offset from its centre of gravity. In certain embodiments, intended for fixing the fastener with its shank vertical, the centre of gravity of the catch is offset from the pivot axis in a direction radially outwardly of the longitudinal axis of the shank when the catch is in its first orientation, contained within the profile of the vertical shank, so that gravity tends to turn the catch and swivel it into its second orientation. In other embodiments, intended for use with the shank horizontal, the centre of gravity of the catch may be displaced from its pivot axis in a direction parallel to the longitudinal axis of the shank, so that gravity tends to swivel the catch into its second orientation when the fastener is inserted horizontally through an opening. The centre of gravity may be offset both axially and radially of the shank to enable the fastener to be used in a variety of orientations, and in particular also to enable the catch to be switched between the first and second orientations by rotating the fastener on its longitudinal axis. 
     The movement of the retaining arm is desirably restricted by abutments or other means in order to permit it to swivel from the first orientation to the second orientation in one direction only, and/or to swivel from the second to the first orientation in one direction only, normally the opposite direction. By limiting the freedom of the swivel arm to rotate, it can more easily be controlled. 
     The tensioning means may comprise nut means in screw threaded engagement with the shank. Other means having equivalent effect may equally be used. 
     The fastener may be provided with marking whereby the orientation of the shank may be indicated, even when the part of the shank holding the catch is invisibly contained in or beyond the opening, so that a user can more conveniently control the orientation of a gravity operated catch by appropriately turning the fastener in the opening. Such marking may be on an end of the shank directed, in use, towards the near side of the wall. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two embodiments of the invention are illustrated, by way of example, in the accompanying drawings, in which: 
     FIG. 1 is a plan view of the shank of a first fastener according to the invention, showing a slot in which a catch can be mounted; 
     FIG. 2 is a side elevation of a catch for the fastener; 
     FIG. 3 is a diagrammatic side view of the shank with a near side of the slot cut away to show the catch in a first orientation in the slot, contained wholly within the profile of the shank; 
     FIG. 4 is a view corresponding to FIG. 3 but with the shank turned 180° on its axis to invert it, allowing the catch to turn 90° to a second orientation in which it extends beyond the profile of the shank; 
     FIG. 5 is a diagrammatic side view showing the complete first fastener assembled through an opening in a wall; 
     FIG. 6 is a plan view of the shank of a second fastener according to the invention, showing a slot in which a catch can be mounted; 
     FIG. 7 is a side elevation of a catch for the second fastener; 
     FIG. 8 is a diagrammatic side view of the shank with a near side of the slot cut away to show the catch in a first orientation in the slot, contained wholly within the profile of the shank; 
     FIG. 9 is a view corresponding to FIG. 8 but with the shank turned 180° on its axis to invert it, allowing the catch to turn 90° to a second orientation in which it extends beyond the profile of the shank; and 
     FIG. 10 is a diagrammatic side view showing the complete second fastener assembled through an opening in a wall. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The illustrated fasteners are constructed entirely of steel, for strength. In the illustrations of the first embodiment, FIG. 1 shows the shank  10  which consists of a steel rod having threads  12  on one end and slot  14  cut diametrically through the shank between the threaded potion of the rod and its far end. The end face of the threaded end of the shank is diametrically incised to form a groove  16  aligned with the slot, so that the orientation of the groove indicates the orientation of the slot. A suitable marker is applied at one end of the groove, as an indication of which way up the fastener shank is lying, to distinguish between the positions shown in FIGS. 3 and 4. 
     FIG. 2 shows a catch  20 , formed from a small steel plate of a width just less than the width of slot  14 . A dashed outlined indicates a rectangular shape to the plate from which material has been removed to form the catch, and on which a pair of nibs  22 , one on each end of the bottom edge  24  of the catch, have been formed. An aperture  26  for a pivot pin is provided through the plate centrally of the rectangular outline. The top edge  28  of the rectangle has been removed by an angled cut at one corner to leave an inclined edge portion  30 , and a central part in the region of the aperture  26  has been removed to a lesser extent to reduce weight and form a flat abutment portion  32 . The top corner opposite the inclined edge portion  30  has been retained to form an ear  34  to increase the weight differential between the two ends of the catch. These two ends form arms which, each with its nib  22 , may take up positions inside or outside of the profile of the shank according to the orientation of the catch. 
     As compared with the original rectangular outline, and dividing the catch by notional horizontal and vertical lines through the pivot aperture  26 , the lower half of the catch is heavier than the upper half, and the arm with the ear  34  is heavier than the arm with the inclined edge portion  30 , so that as seen in FIG. 2, the centre of gravity of the catch is in the lower right hand quadrant. 
     FIG. 3 shows how the catch is mounted in shank  10  by pivot pin  40  in slot  14 , which corresponds in shape substantially to the outline of catch  22 , except where additional material of the shank is removed in order to allow the catch to pivot on pin  40  from the position shown in FIG. 3 to the position shown in FIG.  4 . In particular, the slot is shorter at its upper opening than at its lower opening, as a result of conforming to the inclined edge portion  30  of the catch. Where the correspondingly inclined end of the slot emerges on the top of the shank, there is an abutment formed by a shoulder  42  which bears against the flat abutment portion  32  of the catch when the shank is inverted and the catch swings into the position shown in FIG.  4 . 
     It will be appreciated that, when the shank is as shown in FIG. 3, gravity tends to turn the catch clockwise and the catch is therefore retained in the slot wholly within the profile of the shank by the abutment of inclined edge portion  30  with the correspondingly shaped end of the slot. However, when the shank is turned axially through  180 ° to the inverted position shown in 
     FIG. 4, gravity turns the catch to the position there shown. Rotation of the shank through another 180° will of course return the catch to its FIG. 3 orientation. 
     In use, as shown in FIG. 5, a nut  50  is applied to the threaded end of the shank, preferably following a washer  52 . A wall  54  is illustrated, comprising a near panel  56  and a far panel  58  with a continuous opening  60  through both wall panels, drilled to allow the shank of the fastener to pass through from the rear side to the far side. This is done with the shank of the fastener in its FIG. 3 orientation, so that the catch does not contact the opening. The fastener is then rotated on its axis 180° so that the catch swivels into its second orientation, nibs  22  facing the far wall panel  58 . The shank is then withdrawn until the catch abuts the wall, whereupon nut  50  can be tightened to achieve the fastened arrangement shown in FIG.  5 . Groove  16  can be used as a screwdriver slot to turn the shank, and to hold it while nut  50  is tightened. A very substantial torque can be used on the nut, without overstressing the pivot pin  40 , because of the support provided by the shoulder  42  pressing against the flat abutment portion  32  of the catch. 
     The fastener can be withdrawn from the opening  60  by reversing the installation procedure, that is to say by slackening the nut  50 , pushing the fastener shank further into the opening, rotating 180° to drop the catch into the slot, and withdrawing the shank from the opening. 
     The second exemplary embodiment of the invention is illustrated in FIGS. 6 to  10  which are views corresponding to FIGS. 1 to  5  respectively. Comparison of the corresponding drawings will show the modifications that are incorporated into this second embodiment. The following description will concentrate on the differences between the two embodiments, and if no change to a feature of the fastener is mentioned, that feature may be assumed to be unchanged. 
     The fastener of the second embodiment has a shank  70  in which the flat, square shoulder  42  shown in FIG. 1 is replaced, for ease of manufacture, with a rounded concave shoulder  72  as shown in FIG.  6 . The orientation of slot  74  (corresponding to slot  14 ) is shown by a simple depression or punch mark  76  on the threaded end of the shank. 
     Catch  80 , as seen from the viewpoint shown in FIG. 7, has a greater weight bias towards the bottom half and towards the right hand half of the notional rectangular outline  88  into which it fits, and at the centre of which a pivot pin aperture  86  is located. This is achieved by omitting the nibs  22  of catch  20 , replacing inclined edge portion  30  by flat portion  90  and inclined transitional portion  91 , and by moving abutment portion  32  closer to the axis of the fastener, as abutment portion  92 . 
     FIGS. 8,  9  and  10  show that the action of the fastener is unchanged in principle, but that slot  74  has an internal shape that is adapted to the shape of catch edge portions  90 ,  91  and  92 . In particular, the abutment formed by shoulder  72  is longer than in shoulder  42 , which enables the forces experienced between the abutment portion  92  of the catch and the shoulder  72  to be distributed over a larger area, especially if the surface shape of portion  92  is curved to match shoulder  72 . 
     The absence of nibs  22  also allows a greater area of force distribution between catch  70  and wall panel  58 . Larger force distributions imply lower local pressures, which may be beneficial in terms of increasing the range of materials that can be used or fastened, or allowing higher forces to be used. 
     The same pivot pin  40  is used in the two embodiments. It should be noted that this pin transmits negligible force during operation of the fastener. As shown in FIGS. 5 and 10, when the fastener is tightened by means of the nut  50  to grip the panels  56 ,  58  of wall  54  between the catch and washer  52 , pin  40  becomes redundant. Catch  20  is pressed against the wall by shoulder  42  of shank  10 , and catch  80  is pressed against the wall by shoulder  72  of shank  70 . The purpose of pin  40  is to hold the catch in place in its slot while allowing it to swivel through approximately 90°, and It may suitably be made of a self-lubricating plastics material such as a polyamide, and preferably one that is flexible and resilient, so that any distortion is less likely to be permanent and stiffen the action of the catch. 
     Similar fasteners can be used in vertical orientations. According to whether the fastener is intended to be inserted upwardly or downwardly, the two ends of the slots  14 ,  74  and the catches  20 ,  80  can be as shown or reversed. The balance of the catches can be adapted as well, by altering the positions of the pivot pin apertures  26 ,  86 , or extending the length of either end. When the fastener is inserted vertically, the catch can be deployed by a sharp rotation of the shank, to use centrifugal force to pivot the out-of-balance catch. To remove a vertical fastener, it may be necessary simply to undo the nut and push the fastener inwardly through the opening, allowing it to fall away on the far side. 
     The invention is useful in many applications, but because the fastener is capable of exerting high pressures between two elements without failure, it can be used where great structural strength is required, or where relatively heavy materials, such as thick steel sheets, are to be fastened together.

Technology Classification (CPC): 5