Fastening arrangement

Abstract: A fastening arrangement comprises a support (10,68) for a substrate (224,236) and resilient coupling means (204,212) connectable, in use, between the support and the substrate (224,236) to fasten the substrate (224,236) under tension to the support, in use. The coupling means each comprise a resilient tension spring (210,220) attached at one end to a block (206,216), with its other end adapted to engage a tension bar (240) through a hole (218,242) in the substrate, the blocks being slidable in a groove in each side of the support.

Description: This invention relates to a fastening arrangement, and particularly to a fastening arrangement for tensioning flexible substrates/sheets, hereinafter referred to as 'substrates'. It also relates to a method of fastening a substrate to a support under tension, preferably using the fastening arrangement of the invention. Flexible substrates, such as Panonflex (TM), are becoming increasingly popular for signage due to their inherent advantages over acrylic substrates. In high winds an acrylic substrate may flex to such a degree that it may become dislodged from its support frame, with the resultant safety risk of it shattering. The fastening of such flexible substrates in their support frames is currently achieved by the use of clamps and/or bolts to set the tension over the surface of the substrate. This tensioning of flexible substrates is very labour intensive, often requiring repeated and frequent adjustments in order to achieve a uniform tension over the substrate surface, thus leaving the substrate smooth and free from 'wrinkles'. A further disadvantage of such a clamp/bolt tensioning arrangement is the large depth of mounting required for such fastening mechanisms and the consequent large weight of such a mounting. This large weight limits the nature of the surfaces to which such a mounting can be affixed. It is an object of the present invention to mitigate these disadvantages. US Patent Specification No. 4580361 shows a frame device for holding and displaying sign panels, the panels being held in tension along the edges thereof by spring-biased slide means. In one embodiment the slide member has an upright post which is received through an elongate opening in the sign panel. The slide member is resiliently mounted by a coil spring which is attached at one end directly to the slide member and at its other end to a wall of a base member of the frame. The sign panel is tensioned as a flat planar sheet and each slide can move only backwards and forwards. US Patent Specification No. 5044102 shows a tensioned display sign having a rigid frame on which a flexible vinyl sign face is stretched. The sign face has hems on its top and bottom edges with rigid rods being inserted in the hems, and tension springs extended through notches in the hems and hooked to the rods. The other ends of the springs are hooked on lips projecting from extrusions which extend along the top and bottom of the face frame, with the springs holding the sign face taut on the sign cabinet frame. A hinged end section is pivoted on the frame to permit the sign face to be placed under the proper lateral tension as a result of the lever action resulting from swinging the hinged section inwardly and then bolting it in place on the sign cabinet frame. European Patent Specification No. 0132953 shows a frame for mounting a photographic print, by the use of a display sheet incorporating the print which has eyelets along its edges. The display sheet is mounted under tension in the frame using springs connected between the eyelets and runners. The display sheet is held as a plane parallel to the front of the frame, with the springs in the same plane as the display sheet. According to the present invention there is provided a fastening arrangement for tensioning flexible substrates comprising a support for a substrate and coupling means connectable, in use, between said support and said substrate so as to fasten the substrate under tension to said support, the coupling means comprising a multiplicity of resilient coupling elements, said support comprising a number of sides, each of which has a groove therein along its length in which respective supports for the coupling elements are received for longitudinal sliding of the supports and respective associated resilient coupling elements therealong, each side defining an arm with a nose part, and the resilient coupling elements being disposed non-parallel to a front plane of the support at which, in use, a visible part of the substrate is held under said tension with each of its respective side parts extending around the nose part of its associated support side. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a transverse cross-section through a support of a first embodiment of a fastening arrangement of the present invention, Figure 2 is a transverse cross-section, on an enlarged scale, through a top plate for the support of Figure 1, Figure 3 is a transverse cross-section through a support of a second embodiment of a fastening arrangement of the present invention, Figure 4 is a schematic side view of a first embodiment of coupling means of a fastening arrangement of the present invention, Figure 5 is a schematic side view of a second embodiment of coupling means of a fastening arrangement of the present invention, Figure 6 is a schematic side view of a prespacer, fitted to a third embodiment of coupling means, Figure 7 is a fragmentary, schematic, perspective, cross-sectional view of how a fastening arrangement comprising the support of Figure 1 fitted with the top plate of Figure 2 and the coupling means of Figure 4, fastens a substrate, in use, and Figure 8 is a fragmentary, schematic, perspective view of a fastening arrangement of the invention fastening a substrate. A particular application of the invention will now be described in relation to an advertising sign. The sign has a casing of square or rectangular shape in plan, and each casing side 10 has the transverse cross-section shown in Figure 1. The sides 10 can each be an aluminium extrusion, or alternatively could each be a metal fabrication. The casing side 10, of unitary construction, comprises a hollow box-like body portion 12, from a lower front part of which upwardly extends a cantilever arm 14 and from an upper front part of which normally extends a projecting arm 16. In an alternative embodiment the arm 14 need not be cantilevered, i.e. it could extend normally from a surface of the body portion which is vertical, in use. The body portion 12 has a rear wall 18, which is intended to be vertical, in use, and a downwardly, forwardly sloping front wall 20. A lower wall 22 of the body portion 12 comprises an inverted generally 'U'-shaped channel section 24, the rear limb 24a of which forms a co-planar continuation of the rear wall 18, whilst the front limb 24b of which is joined by an upwardly sloping wall section 26 to the lower end of the front wall 20. Extending upwardly at an angle from said lower end of the front wall 20, and being coplanar with the wall section 26 is a wall section 28 of the cantilever arm 14. An L-shaped wall section 30 projects rearwardly normally from the top of the rear wall 18 and is connected to a top wall 32, which is horizontal, in use, so as to provide an inner ledge 33. A pair of rectangular ledges 34, 36, project normally inwardly from each of respective limbs 24a, 24b, of the inverted 'U'-shaped channel section 24, adjacent the base thereof. A rectangular projection 38, which depends normally downwardly from the L-shaped wall section 30 adjacent the rear wall 18, is provided for engagement with a connecting member (not shown) to couple two casings, thereby providing dual faced signage. An inner rectangular ledge 40 projects from the front wall 20, at the level of the top of the rear wall 18. The lower part of front wall 20 forms a rear wall of the hollow cantilever arm 14, whilst its lower wall section 28 terminates at a forward nose part 44 to which an upwardly sloping upper wall 42, extending from wall 20, also terminates. The nose has an arcuate exterior surface 46. Within the hollow arm 14 a step 48 is provided at the rear of the nose part 44, the step having an upper surface 50. Within the hollow arm 14, a rectangular ledge 52 projects from the front wall 20 parallel to the upper wall 42. The spacing of the ledge 52 from the upper wall 42 is such that the upper surface of the ledge 52 is co-planar with the upper surface 50 of the step 48. A rectangular projection 54, parallel to and adjacent the front wall 20 of the body portion 12, extends upwardly from the upper wall 42 of the cantilever arm 14. The top wall 32 extends beyond the front wall 20 to form part of the projecting arm 16 which has a downwardly depending projection 56 which is parallel to the front wall 20, such that the rear surfaces of projections 54, 56 are co-planar, defining therebehind a generally rectangular groove. A ledge 58, which is horizontal, in use, extends from the front surface of the projection 56 at a level slightly below the lower surface of the top wall 32. A rear portion of the ledge 58 defines one arm of a sidewardly disposed 'U'-shaped groove 60 with the other arm being defined by an end section 32a of the top wall 32 which extends over the rear portion of the ledge 58 and is approximately half the thickness of the remainder of the top wall 32. A ledge 62, which is parallel to ledge 58, extends forwardly from the end of the projection 56 and has a top surface which is co-planar with a ledge 64 of an L-shaped projection 66 which depends downwardly from the underside of the ledge 58 just inwards of its free end. The ledges 62, 64 define with the ledge 58 an inverted, generally rectangular lipped channel section groove. The ledges 33 and 40 are provided so as to be engagable by bracing members (not shown) which can be inserted within the casing side 10 in order to give added rigidity when joining respective sections of the casing side 10 at right angles or in the case of a particularly long section of the casing side 10. It will be appreciated that this function is also provided by the pair of ledges 34,36, the ledges 62, 64, and the upper surface 50 of the step 48 with the ledge 52. Referring now to Figure 2, a substantially L-shaped top plate 68, having a longer limb 70 which is approximately six times the length of a shorter limb 72 thereof, is provided so as, in use, substantially to cover the space bounded by the front wall 20, upper wall 42 and projecting arm 16, and will be described fitting to the casing side of Figure 1 when said side is horizontal, in use. A step 74 at the end of the top plate 68 remote from the limb 72 engages in the groove 60. Similarly, one arm 76,which is intended to be horizontal, in use, of a downwardly depending inverted T-shaped projection 78, proximal the step 74, engages the underside of the ledge 58 so as to, in use, effect a fixing between the top plate 68 and the casing side 10. The other arm 79,which is intended to be horizontal, in use, faces the limb 72. An L-shaped projection 80 depends downwardly from the underside of the limb 70 with an arm 82,which is intended to be horizontal, in use, directed away from the limb 72. The upper surfaces of the arms 79 and 82 are co-planar, defining, with the limb 70, an inverted lipped channel section groove for reception of one or more bracing members, if required. An end portion 84 of the limb 72 has a concave inner surface 86 of a similar radius of curvature as the surface 46 of the cantilever arm 14 such that, in use, the inner surface 86 sits adjacent the underside of surface 46 defining therebetween a narrow channel 88 (indicated schematically in Figure 7). The end portion 84 is shaped to prevent ingress of moisture/dirt into the assembly, in use. Reference is now made to Figure 3, which shows a second embodiment of a casing side of the present invention. Parts similar to those of the first embodiment of the present invention, shown in Figure 1, will be accorded the same reference numerals, in the one hundred series, as those of the first embodiment. The side will be described as when it forms an upper horizontal part of the casing, in use. The casing side has a rear wall 118, which is intended to be vertical, in use, and a top wall 132 extending normally forwardly thereof. A pair of ledges 190, 192,which are intended to be horizontal, in use, project inwardly of the body portion 112 adjacent the top wall 132 from the rear wall 118 and a front wall 120 respectively. A lower wall 122 of the body portion 112 includes an inverted 'U'-shaped channel section 124, one of the limbs of which 124a is shared with the rear wall 118, and a lower wall section 194, which is intended to be horizontal, in use, extending between the inverted 'U'-shaped channel section 124 and the sloping wall section 126. The wall section 194 has an opening 196 therethrough, the opening 196 being encompassed internally of the body 112 by an inverted 'U'-shaped channel 198 such that a pair of ledges 200 and 202 are defined which project inwardly of downwardly depending limbs of the channel 198. The ledges 190,192 and 200,202 can support bracing members, if required. The top plate of Figure 2, suitably sized, can be fitted to the Figure 3 section in the same manner as described with the Figure 1 section. The cavity within the casing side 110 is enlarged as compared to the equivalent cavity within casing side 10, in order that electrical supplies and circuitry (not shown) required for the lighting of a fastened substrate, in use, can be mounted therein. Referring now to Figure 4, there is shown a first embodiment of coupling means for connecting a substrate under tension to the casing of the advertising sign. In this first embodiment the coupling means is in the form of a linking element 204 which comprises a substantially rectangular support block 206 with a convex region 208 situated about the mid-point of one of the larger faces of the block 206. A right angled end section 209 of a coiled tension spring 210 passes through the centre of the convex region 208 into the interior of the block 206 so as to be encapsulated therein, e.g. by moulding. The angle between the spring 210 and the surface of the block 206, in the example shown 90°, is substantially fixed, with the spring anchored to the block 206. The spring 210 has a curved hook section 210a at its free end remote from the block 206. Referring now to Figure 5, a second embodiment of coupling means, in the form of a linking element 212, comprises a substantially rectangular support block 214 with an outwardly convex ledge 216 projecting normally from one of the larger faces of the block 214, and extending over the width thereof. The ledge 216 has a circular passageway 218 therethrough parallel to the larger faces of the block 216. A first curved hook end section 219 of a coiled tension spring 220 passes through said passageway 218, the spring 220 having a second curved hook end section 222 remote from said block 216. Connection of a substrate to the sign casing by the use of the coupling means is described below. Although such connection can be carried out using a multiplicity of the coupling means alone, accurate centring and perfect tensioning of the sign face are in fact facilitated by the use of a number of prespacers 228, one of which is shown in Figure 6 in use with a linking element generally in the form of the element 204 shown in Figure 4. Preferably the prespacers are of stainless steel. From Figure 6 it can be seen that the prespacer 228 is in the form of a wire having a curved hook end part 230, an elongate straight main body part 232 and a tail part 234, which is inclined inwardly of part 232, like the part 230 which it faces, all the parts lying in a common plane. In use, the tail of the prespacer is received into the end of the coiled spring part of element 204 nearest block 206, which spring part is in its relaxed state. The body part 232 passes over the upper surface of spring part 210 and extends beyond it so that end part 230 is spaced from curved hook section 210a of element 204 by typically 12mm. Referring now to Figure 7, the casing side 10 and associated top plate 68 are shown in an interlocked arrangement, with a block 206 being closely but slidably engaged in the groove defined between the wall 20 and the projections 54,56. A flexible substrate 224, which in this embodiment carries advertising material on its outer face, has its edge section passed through the channel 88. A row of regularly spaced holes 225 with respective eyelets 226 are provided in said edge section, for example at every 200mm starting 60mm in from a corner edge. Figure 7 shows the substrate in its final, tensioned form, with the spring 210 extended. In this state, the extended spring passes over the edge section of the substrate up to the holes 225 and the curved hook section 210a is received in the one of the holes aligned with the position of the block 206 in the groove of the casing in which it is received. The angle of the spring relative to its block is such as to match or substantially to match the angle of the cantilever arm and thus this angle for the linking element 204 shown in Figure 7 is more typical than the 90° angle shown for illustration purposes in Figure 4. The linking element 212 could of course be used instead of linking element 204, but again this would have the spring 220 angled relative to the block 214 at other than the 90° shown, so as to match the angle of the cantilever arm. The use of prespacers 228, described in relation to Figure 8, to connect the substrate to the casing, would preferably be used with the Figure 7 arrangement in a similar manner. It will be appreciated that the Figure 7 fixing arrangement by use of the linking elements is repeated at the other three sides of the substrate and of the casing, to complete the tensioning and attachment of the rectangular sign. The dimensions of the flexible substrate 224 are chosen such that the attachment of the spring 210 to the eyelet 226 places the spring 210, and consequently the flexible substrate 224, under tension, assuming the flexible substrate 224 is held in at least one other position. It is this restorative force which flattens the surface of the flexible substrate 224 to cause it to lie smooth, i.e. unwrinkled, across the area bounded within the four sides of the casing. In use, in one assembly method, a multiplicity of blocks 206 are slid to one end of a horizontal side, and also to the adjacent end of a vertical side. The substrate 224 is then attached by its eyelets 226 to the spring ends 210a and thus the blocks 206, before they are slid along the sides of the casing to open out the substrate 250. The spring ends 210a on the adjusted blocks 206 on the other two sides are then attached to the respective eyelets 226 of the substrate 224 in order to tension it fully and pull it smooth within the casing. In a further assembly method, in use, a multiplicity of blocks 206 on opposing casing sides 10, for example the horizontal sides, are slid to one end of the casing sides 10, the spring ends 210a attached to the eyelets 226 upon the respective opposite edges of the substrate 250, tensioning the substrate 224 in the vertical direction. The blocks 206 are then slid along the horizontal casing sides 10 in order to open the substrate 224 out, the vertical pair of edges of the substrate 224 are then attached by their respective eyelets 226 to spring ends 210a in order to tension the substrate in the horizontal direction. The slidable engagement of the blocks 206 within the casing sides 10 allows the removal of 'wrinkles' upon the surface of the flexible substrate 224 by slidably adjusting the position of the blocks 206 within the casing sides 10. In both assembly methods the elements 212 could replace the elements 204. Referring now to Figure 8, an alternative form of substrate 236 has each of its edges turned back on itself and sewn or glued as a seam 237 to the main part of the substrate 236 to provide an envelope or pocket 238 along the edge. A continuous tension rod or bar 240, for example of aluminium, of circular section, and having a diameter of typically 5mm, is received within said envelope 238 formed along each edge of the substrate 236. At spaced positions along the envelope 238 are pairs of holes 242 therethrough, which may or may not be reinforced with eyelets. The pairs of holes 242 are aligned, one in the upper surface of the envelope 238 and the other in the lower surface. Each pair of holes 242 is spaced from the inner periphery of the envelope by a distance only slightly greater than the diameter of the rod 240. As described for the holes 225, pairs of holes 242 typically have a maximum separation of 200mm and the pairs of holes 242 nearest the corners of the substrate 236 are typically at least 60mm therefrom. In order to ensure that the substrate 236 to be mounted is held in place and centred accurately during the connection of the springs 210 thereto, and tensioned correctly thereafter, prespacers 228 are attached along two adjacent edges of the substrate 236 through specific pairs of holes, including the corner pairings 242 prior to the attachment of the springs 210 to the substrate. The prespacers will be fitted to a linking element 204 (or a linking element 212) as shown in Figure 6. This connection is best made once the linking element is received in its groove in the casing, but could be made prior to fitting in said groove. All the linking elements are initially slidably engaged in their respective grooves in the casing sides. Typically, for a small rectangular substrate, there will be two prespacers 228 adjacent the respective corners of the substrate 236 on one short side and four prespacers 228 along an adjacent long side thereof, including two adjacent corners of the substrate 236. The prespacers 228 may or may not be equispaced along said long side of the substrate 236. For each such prespacer its hook end part 230 will be received around the rod 240, as for the two prespacers shown at opposite ends of the top edge of the substrate in Figure 8, with the hook section 210a of the associated spring 210 being 'loose' at the outer boundary of the envelope 238. Once said six prespacers have been attached to the substrate, it will be held in place whilst the springs of all the other linking elements are attached thereto. Firstly the six springs of linking elements, without prespacers, have their respective hook end sections 210a attached to the appropriate rods 240, these linking elements being positioned directly opposite the six prespacers respectively. The spring end sections 210a of the remaining linking elements are then attached to said rods in sequence working side to side (i.e. in opposite pairs) downwardly along the short sides, and then up and down from left to right along the long sides, along the sign. Finally the prespacers are unhooked from the rods and the sections 210a of the spring 210, to which springs the prespacers were attached, are then hooked onto said rods. The prespacers can be removed, or left 'loosely' attached to a spring 210 by their tail parts 234 for future use. Figure 8 shows an intermediate stage in the assembly, with the prespacer having been removed from the linking element 204 at the top of a substrate vertical short side, the section 210a thereof now having been hooked onto the rod. However two prespacers along the top side of the substrate are still attached to rod 240, with three linking elements being ready to be attached to said rod during said sequential fastening process. This arrangement around the edges of the substrate produces maximum pressure, and thus maximum stretch, on the substrate in order to avoid over-pull on the springs. The arrangement has the effect of applying a distributed pressure over the length/width of the substrate, thus eliminating any possible localised wrinkling in the region of the point of attachment, such as in the previously described fixing arrangement using the eyelets 226, which can be omitted, if desired, in this arrangement. In the case of a large sign, small lengths of the rod can be inserted into the envelope, for example through a series of lengthwise spaced slits therein, (preferably between the spring connection positions). The rods can have a spacing between their ends of 25mm and this allows for the folding of the sign for ease of transport and installation. Typically a short rod could have a length of 500mm, with the spring connections being spaced apart at 200mm. For a large sign, the prespacers can be up to 2 metres apart. If a spring becomes damaged/overstretched after assembly of the sign has been completed, and it is not possible or not wished to effect disassembly to replace it, the damaged spring alone can still however effectively be 'replaced'. This involves drilling a hole through the wall 54 or 154 at a position adjacent the damaged spring and attaching a 'replacement' tension spring which merely comprises a central coil with opposite identical hooked ends. One hooked end is passed through the drilled hole and the other hooked end is engaged with the substrate, either merely in a hole therein or onto a tension rod. It will be appreciated that the resilient means need not be a spring but could be merely an elastic member. It will further be appreciated that the fixing means for the spring or other resilient member need not be slidable but may be fixed location points upon the front wall 20. Preferably the substrate is a laminate, possibly of polymeric material. It could be of PVC material with an inner layer of nylon scrim. Alternatively, it could be of a single polymer type material.

Claims: A fastening arrangement for tensioning flexible substrates comprising a support (10,68) for a substrate (224,236) and coupling means (204,212) connectable, in use, between said support and said substrate so as to fasten the substrate under tension to said support, the coupling means comprising a multiplicity of resilient coupling elements (210,220), said support comprising a number of sides, each of which has a groove therein along its length in which respective supports (206,214) for the coupling elements are received for longitudinal sliding of the supports and respective associated resilient coupling elements therealong, each side defining an arm (14,114) with a nose part (44,144), and the resilient coupling elements being disposed non-parallel to a front plane of the support (10,68) at which, in use, a visible part of the substrate is held under said tension with each of its respective side parts extending around the nose part (44,144) of its associated support side. An arrangement as claimed in Claim 1, wherein each coupling element has a first end (210a,222) and a second end (209,219), said first end being adapted to engage, in use, in a selected one of a multiplicity of holes (225,242) in the substrate (224,236). An arrangement as claimed in Claim 2, wherein said second ends (209,219) of the coupling elements are connected to respective ones of said longitudinally slidable supports (206,214). An arrangement as claimed in Claim 3, wherein said second end (219) is hooked through an opening (218,242) in said support (214). An arrangement as claimed in Claim 3, wherein said second end (209) is fixedly encapsulated in said support (206). An arrangement as claimed in any one of Claims 1 to 5, wherein each of the resilient coupling elements (210,220) comprises a tension spring. An arrangement as claimed in any one of the preceding claims, wherein each side has a main casing part (10) and a cover plate (68) fitted to the main casing part. An arrangement as claimed in Claim 7, wherein an opening (88) is defined between said main casing part and the cover plate for receiving said substrate therethrough, in use. An arrangement as claimed in Claim 8, wherein the opening is defined between said nose part (44) and the shorter limb (72) of an L-shaped member constituting said cover plate. An arrangement as claimed in any one of Claims 7 to 9, wherein said main casing part (10) includes said arm (14,114). An arrangement as claimed in any one of the preceding claims, wherein said arm (14,114) is a cantilever arm. An arrangement as claimed in any one of the preceding claims, wherein each groove is defined between a front surface (20,120) of a box-like section (12) of the side and at least one projection (54,56:154,156) spaced forwardly thereof. An arrangement as claimed in Claim 12, wherein said one protection extends from said arm (14,114) which extends forwardly from said front surface (20,120). An arrangement as claimed in any one of the preceding claims, in which said support comprises at least one elongated channel to receive bracing means, in use. . An arrangement as claimed in any one of the preceding claims, wherein said support comprises projection means (38) for use in coupling it to a further support. An arrangement as claimed in any one of the preceding claims, wherein each of said sides of the support is formed as an extruded section. An arrangement as claimed in any one of the preceding claims, in which the support is square or rectangular. . A method of fastening a substrate (224,236) under tension to a support (10,68) utilising a fastening arrangement as claimed in any one of Claims 1 to 17, the method comprising sliding the supports (206,214) for the coupling elements along said grooves in the sides respectively to position them in alignment with respective openings along respective edge surfaces of the substrate (224,236). A method as claimed in Claim 18, wherein a number of prespacer elements (228) are attached to the substrate (224,236) to hold it in place prior to connection of the coupling means to the substrate. A method as claimed in Claim 18 or Claim 19, wherein the coupling means engage tension bars (240) adjacent respective edges of the substrate. A method as claimed in Claim 20, wherein the tension bars (240) are in envelopes (238) defined along said respective edges of the substrate.

Inventors: BICKLEY STUART, BICKLEY, STUART
Applicants: KESTREL SIGNS MIDLANDS LTD, KESTREL SIGNS (MIDLANDS) LTD.
Application year: 2000
Main classification: G09F15
IPC codes: G09F15