AU2010202502A1 - Clip - Google Patents

Description

Clip (71 This invention relates to a bistable clip suitable for clasping or clamping together two or more items. This clip has numerous possible applications, and is particularly well suited to joining together sheets of paper. Many different kinds of paperclip are already known in the prior art. In particular, W0200600341 5 discloses a bistable clip which derives considerable benefit from having a corrugated 'spine'. The main features ofthis clip are: I. a corrugated spine; 2. a corrugated lower surface; 3. a bistable upper surface; 4. a pair of lower teeth to grip the bottom sheet of paper; CI 5. a pair ofupper teeth to grip the top sheet offpaper. These features are shown in figures I and 3, which show a clip disclosed in W0200600341 5. The bistable upper surface can be toggled by the user between a first stable 'open' position (to insert and remove papers) and a second stable 'closed' position (to grip the papers). Ihe corrugated spine is an important feature for reasons described in WO2006003415, which also describes methods for manufacturing the corrugated spine. The corrugated spine is described as comprising a number of'bumps Figure I shows a clip disclosed in W02006003415 comprising two bumps. W02006003415 describes a method for manufacturing a clip comprising two bumps and proposes manufacturing first one bump, then the other bump, in consecutive processes. W02006003415 suggests that this may be done in a multi stage die in a progressive die machine. The operation ofsuch machines is typically as follows: A continuous strip of steel is fed into one side of the die; holes are punched into one side ofthe strip, and that side ofthe strip is used to feed the steel along the die, indexing it from one station to the next. [his side ofthe strip is commonly known as the 'ladder'; the parts are formed in a succession of stages, all the while attached to the ladder by one or more 'tags The final stage is that the finished parts are 'parted-off from the tags. The tags remain as part ofthe ladder, which becomes scrap, In the case ofWO200600341 5 it is best for the tags to be located on the 'tail' ofthe clip (at the extreme end ofthe lower surface of the clip, at the furthest point from the spine). The manufacturing method described in W02006003415 has been found to be unsuitable for volume manufacture, as the asymmetry ofthe first and second bump-forming stages causes unpredictable deformations 2 C throughout the clip and beyond, causing the part to twist relative to the ladder. This makes it very difficult to manufacture the two-bump embodiment in high volume. A further problem with clips as described in W0200600341 5 is that the optimum location for the tags is at the tail of the clip, and the clip in W02006003415 is corrugated in this region. These corrugations make it more difficult to part the clip offfrom the ladder without causing burrs, because the tooling to cut the clips from the ladder must be curved to conform with the shape ofthe corrugations. The parting-offtooling is also more expensive than a flat parting-offtool would be, and since this tooling suffers wear this increases the unit cost of 0 the clip. A further problem with clips as described in W02006003415 is that the lower teeth are formed in the corrugated lower surface, which means that they point at an angle (according to their location in the C corrugation) instead offpointing directly towards the upper surface. A further problem with clips as described in W020060034 15 is that the upper teeth do not have a flat surface against which to bear, because they bear against the corrugated lower surface which is not flat. The main embodiment described in W02006003415 is the two-bump embodiment, but it is difficult to manufacture the two bumps. f the bumps are both made at the same time then the material between the bumps tends to buckle - and if one bump is made before the other then the asymmetry of the manufacturing process causes the clip to twist relative to the ladder which make it very hard to manufacture in high volume. W02006003415 also describes a one-bump embodiment, but the performance of this is unsatisfactory because the spheroidal curvature in the spine does not significantly increase the stiffness of the spine. When forces are applied between the nose and tail of the one-bump embodiment (as would happen when the clip is used on a sheafofpapers), the main effect of these forces is to increase the curvature in the bump ofthe spine and to reduce the curvature around the axis of the spine - so the spine is not effective at resisting forces tending to open it. In other words, when there is only one bump the bump comprises material curved spheroidally in two orthogonal directions (around the axis of the spine, and also to form the corrugation) and the curvature can be transferred between these two directions. Ihis means that the clip's clamping force is low, because it can open easily by transferring the curvature about the axis of the hinge into a deeper bump. [he present invention provides a clip comprising three bumps or more in the spine, a method for manufacturing this clip with three bumps, improvements to the corrugated lower surface and improvements to the design ofthe teeth. In particular, according to an embodiment ofthe present invention there is provided a bistable clip substantially as described in WO200600341 5 but having three or more bumps in the spine. [he clip described in W02006003415 comprises a single piece ofmaterial folded around a bend axis extending in a first direction to form first and second members, said clip arranged to receive an item or items to be held between said first and 3 second members, said first member having an aperture therein with at least some ofthe material around said =O aperture being plastically deformed whereby said first member has a first position ofstability in which at least the free end ofsaid first member has a generally convex shape and a second position ofstability in which at least the free end of said first member has a generally concave shape, in which said fold comprises a first cross section orthogonal to said first direction and a second cross-section parallel to said first cross-section and displaced in said first direction from said first cross-section, characterised in that said first cross-section has a greater radius ofcurvature about axes parallel to said first direction than the radius ofcurvature about said axes of said second cross-section. C1 CO The present invention is similar and provides a bistable clip substantially as described in W02006003415 but Co having three or more bumps in the spine and preferably having one central corrugation in the lower surface, and o a pair oftapering corrugations in the lower surface. IN Also according to the present invention there is provided a method of manufacture for bistable clips substantially as described in W02006003415 but having three or more bumps in the spine. To be more precise, the present invention provides a clip comprising a member folded about a bend axis to form a first portion, fold portion and second portion, the clip arranged to receive an item or items to be held between the first and second portions, the first portion being deformable in order to have a first position ofstability and a second position ofstability, and wherein the fold portion comprises three or more bumps. The present invention also preferably provides a clip wherein the bumps extend in a direction relative to or substantially perpendicular to the bend axis to form one or more corrugations in the second portion, and one wherein the second portion comprises a central corrugation and a pair ofoutermost corrugations tapering from the end nearest the fold portion to the free end ofthe second portion to form flat regions. One advantage of the present invention is that it significantly increases the stiffness ofthe spine because there is much more resistance to the complex mode ofelastic deformation in a clip, and that it can be manufactured symmetrically. A further advantage ofthe present invention over W02006003415 is that a clip with three bumps can be designed with one central corrugation running the entire length ofthe spine and an outer pair oftapered corrugations, which run out to leave flat regions outside the central corrugation and beyond the end ofthe tapered corrugations. This creates three additional advantages. Firstly, the flat regions are an ideal location for the lower teeth, which are easier to form on a flat surface, and which can point directly upwards at the upper surface, rather than being angled according to their location on the corrugations.

4 Secondly, the flat regions create an ideal 'anvil' against which the upper teeth can act. Iis allows the upper Ct teeth to act directly against a flat surface instead of acting against an angled surface. These two advantages combine to enable the papers to be kept flatter than would be possible without the flat regions created by the tapered corrugations. This advantage is increased ifthe teeth are manufactured as barbs, by being partially pierced from the flat region ofthe lower surface and inside the crimps of the upper surface. Thirdly, the flat regions make it easier to part the clip from the tags and the ladder during the final parting-off operation. This reduces the tool cost and also makes it much easier to manufacture the clips without any burrs which might otherwise be caused during the final parting-off stage. It will be appreciated that the present invention offers considerable manufacturing and functional advantages over the clips described in W020060034 15. The present invention will be better understood from the following C description ofthe preferred embodiment which is given by way of example and with reference to the accompanying drawings in which: Figure I shows a perspective view ofa prior art clip disclosed in W02006003415. Figure 2 shows a perspective view ofa preferred embodiment of the present invention. Figure 3 shows a plan view of the prior art clip of Figure 1. Figure 4 shows a plan view ofthe preferred embodiment shown in Figure 2. Figure 5 shows a view of the underside ofthe preferred embodiment shown in Figure 2. Figure 6 shows a series of cross sections through the lower surface of the preferred embodiment shown in Figure 4. Figure 7 shows a strip layout illustrating the manufacturing process for a clip according to an alternative embodiment ofthe present invention where the teeth are formed differently to those in the preferred embodiment. The preferred embodiment ofthe present invention will now be described by reference to the accompanying figures Figures 2, 4 and 5 show a bistable clip in a closed position. The clip is formed by folding a piece of sheet metal about a bend axis to form a lower surface I and an upper surface 2, joined by a spine 3 comprising an inner bump 4 and a pair ofouter bumps 5. The upper surface comprises a pair of holes 6 separated by a strut 7. The region ofthe upper surface furthest from the spine is the nose 8 and the region ofthe lower surface furthest from 5 C the spine is the tail 9. The nose is joined to the spine not only by the strut but also by a pair ofarms 10. The C nose comprises a pair oferimps I I in which are located a pair ofupper teeth 12. [he lower surface comprises a central corrugation 13 and a pair oftapered corrugations 14, and in the tail it comprises a pair oflower teeth 15 which are located in a pair of flat portions 16 ofthe lower surface, outside the central corrugation and beyond where the tapered corrugations have run out. [he clip is manufactured from a single piece ofsheet material which has two surfaces and after the material is folded the clip can be seen to comprise an inner surface 21 and an outer surface 22. Figure 6 shows four sections through the lower surface ofthe preferred embodiment ofthe preferred invention, C the locations ofthese sections being shown in figure 4. Section A shows the form ofthe central corrugation and the flatness ofthe tail in the flat portions. Section B shows where the tapered corrugations are diminishing into flatness. Section C shows the tapered corrugations just beginning to taper down from their full form. Section D shows all three corrugations having their full form, which is the same form that they maintain as they become the bumps in the spine. It will be apparent from these diagrams that by tapering we mean that the cross section of the lower surface on either side of the central corrugation at the end of the lower surface nearest to the spine has a greater amplitude than at the tail of the lower surface where there is no curvature in the flat portions either side ofthe central corrugation. In this embodiment, the central corrugation is ofa constant curvature such that the inner side ofthe curve faces towards the upper surface 2; in other words, such that the inner surface ofthe clip comprises the inner side ofthe curve and the outer surface ofthe clip comprises the outer side ofthe curve. Figure 7 shows how the alternative embodiment ofthe present invention might be manufactured from a continuous strip of steel on a progression tool. Figure 7 shows the ladder 17 and the tags 18. Figure 7 also shows a different kind ofupper teeth 19 which are simply formed from tabs 20 by a process ofbending. Whilst stage 5 shows the corrugated blank, stage 6 shows the corrugations having been eliminated within the spine by the spine bending process. stage 7 shows the formation ofthe inner bump and stage 8 shows the formation of the pair ofouter bumps. Stages 6-8 show the clip bent to 150 degrees (on account ofspringback) and stage 9 shows the clip after it has been finally squeezed closed. The operation of the preferred embodiment will now be described by reference to the figures. When the bistability of the clip is used to toggle the clip into its open position by pressing it on the strut, it adopts an open configuration in which it can accept a generous sheafofpapers. The upper surface and in particular the strut become substantially concave. [he clip can easily be placed around the papers until the edge ofthe papers reaches the spine which acts as an end-stop for the papers. The clip can then be closed onto the papers simply by pressing on the nose of the clip. This pressure causes the clip to toggle from its stable open configuration into its stable closed configuration. When the clip is in its closed configuration, the upper surface and in particular the strut become substantially convex as shown in figure 2.

6 The upper teeth and lower teeth are designed to grip the papers securely when the clip is in its closed configuration. Ideally the tipper teeth and lower teeth should just pierce the papers, making the clip as secure as a staple but doing minimal damage to the papers. Figure 7 shows a possible strip layout for the alternative teeth embodiment, in which the stages shown are as follows: I. Blanking. The two-dimensional shape is pressed out from sheet steel. 2. Lower Tooth forming. The material is partially pierced to form the lower teeth. 3. Crimp Forming. The crimps are formed in the nose ofthe clip using appropriately shaped punches and dies. This creates the bistability in the upper surface. 4. Upper Teeth forming. The upper teeth are formed by bending the tabs on the nose ofthe clip. 5. Corrugating. The central corrugation and tapered corrugations in the lower surface are made by plastic deformation using a punch and a die. 6. Spine Bending. The spine is bent plastically around a cylindrical former. The Spine Bending process removes the corrugations from the spine area, but will leave some residual stresses from these earlier plastic deformations. The spine should be bent to about 180 degrees, but springback leaves a final angle of about 150 degrees at this stage. 7. Forming Inner Bump. [he inner bump is formed using 'holding' tooling in the region ofthe spine where the outer bumps will later be formed, to prevent buckling. 8. Forming Outer Bumps. The two outer bumps are formed using 'holding' tooling in the inner bump to prevent buckling. 9. Spine squeezing. At this stage, the clip is still quite wide open due to the springback from the spine bending, although the exact angle may have been affected by subsequent operations. The final stage is therefore to squeeze the spine ofthe clip to the correct angle. This is best done with the clip toggled into its open position. In some circumstances, the sequence ofthese stages may be altered to suit manufacturing requirements. In high volume manufacture, these stages may all be completed in a multi stage die in a progressive die machine. In this case, the unit cost ofeach clip can be very low. It will be understood that the present invention is not limited to embodiments with three bumps, and that the advantages ofthe present invention may equally well be achieved with any odd number of bumps. Furthermore, the advantages may be achieved with any even number ofbumps except 2. For example, a four bump embodiment could be made by forming the inner pair of bumps first (while holding the part ofthe spine which will later become the outer pair ofbumps). then forming the outer pair of bumps while holding the material which then comprises the inner pair of-bumps.

7 C) Although the lower surface ofthe preferred embodiment ofthe present invention comprises a central O corrugation throughout the full length ofthe lower surface and a pair oftapered outer corrugations which run out to flat before the tail, it will be understood that the central corrugation may be tapered also, without significantly impairing the design. Although the present invention is primarily intended as a paper joining device, it will be understood that the clip described may be used in other applications. Most notably, it may also be used on its own or combined with other components to make products suitable for at least the following applications: 1. As a money clip, for securely and releasably holding banknotes together; CA O 2. As a tagged clip (in combination with a suitably slotted piece ofeard), eg for use as a subject divider in Cl a document; 3. As a suspension file tag (when configured as a tagged clip); CA 4. As a name badge holder for conference delegates etc. (when configured as a tagged clip or otherwise): 5. As a hanging clip (in combination with a suitably bent piece ofwire); 6. As a folder or binder for documents (in combination with a suitable presentation cover); 7. As a clipboard (in combination with a suitable board); 8. As a fridge magnet (in combination with a suitable magnet).

Claims (15)

1. A clip comprising a member folded about a bend axis to form a first portion, fold portion and second portion, the clip arranged to receive an item or items to be held between the first and second portions, the first portion being deformable in order to have a first position of stability and a second position of stability, wherein the fold portion comprises three or more bumps and the bumps extend in a direction substantially perpendicular to the bend axis to form one or more corrugations in the second portion.

2. A clip according to claim 1 wherein the second portion comprises a central corrugation and a pair of outermost corrugations tapering from the end nearest the fold portion to the free end of the second portion to form flat regions.

3. A clip according to claim 2 wherein the central corrugation extends along the entire length of the second portion.

4. A clip according to claim 2 or 3 wherein the central corrugation is curved such that the inner surface of the clip comprises the inner side of the curve and the outer surface of the clip comprises the outer side of the curve.

5. A clip according to any preceding claim, further comprising one or more lower teeth formed by partially piercing the member and located in the second portion.

6. A clip according to claim 5 wherein the lower teeth are formed in the flat regions of the second portion.

7. A clip according to any preceding claim, wherein the first portion is crimped in or near the free end of the first portion to form one or more crimps.

8. A clip according to claim 7 further comprising one or more upper teeth formed by partial piercing in the crimps.

9. A clip according to claim 8 wherein the one or more upper teeth are positioned in the first portion so as to act against the flat regions.

10. A clip substantially as hereinbefore described with reference to the accompany drawings.

11. A method of manufacturing a clip comprising providing a sheet member, folding the member about a bend axis to form a first portion, fold portion, and second portion, and forming three or more bumps in the fold portion, wherein the bumps are formed so as to provide one or more corrugations in the second portion, extending in a direction substantially perpendicular to the bend axis.

12. A method according to claim 11 wherein the method includes providing a central corrugation and a pair of outermost corrugations tapering from the end nearest the fold portion to the free end of the second portion.

13. A method according to claim 11 or 12 further comprising forming one or more lower teeth by partially piercing the member in the second portion.

14. A method according to any of claims 11 to 13 further comprising crimping the free end of the first portion to form one or more crimps.

15. A method according to claim 14, further comprising partially piercing the crimps to form one or more upper teeth.