A SELF-LOCKING SEAL

Abstract: There is disclosed a self-locking seal which comprises a flexible strip (10) having a locking box (11) secured to one end and a profiled tongue-defining slot at its other end (12) which is adapted, following insertion into the locking box, to be engaged lockingly so as to prevent subsequent withdraw­ al of the slotted end (12) of the strip.

Description: This intention relates to a self-lock¯Ph0 4 288 sea) comprising a flexible strip with a locking box secured to one end , the other end of the strip being formed with a profiled tongue-defining slot which is adapted, following insertion into the yocking box, to be engaged lockingly in the box so as to prevent subsequent withdrawal of the slotted end of the strip. Seals of this kind are well known, and have, as primary objective, to provide an indication of unauthorised tampering with the seal. It is known from our United Kingdom Patent Specification 1 085 185 to provide a seal of the above kind, and this has provided a generally satisfactory operating performance over the years. However, there has developed a need to further improve this knounseal, so as to provide even greater resistance to unauthorised tampering withthe seal. Thus, one essential operating requirement for the known seal has been the necessity to exert a strong pull on the slotted end of the strip, immediately after insertion of the slotted end into the locking box, before locking engagement of the slotted end can be ensured. but it has not been readily apparent that this has been done. The present invention seeks generally to further improve the known seal, and particularly to overcome the above drawback. According to one aspect the invention provides a self-locking seal comprising a flexible strip having a locking box secured to one end and a profiled tonguedefining slot at its other end which is adapted, following insertion into the locking box, to be engaged lockingly so as to prevent subsequent withdrawal of the slotted end of the strip, in which the slotted end of the strip has a generally I-shaped tongue comprising a first transversely extending bar connected to the strip, a second transversely extending bar, and a stem which connects the secondbar to the first bar; a deflecting tooth is provided in the locking box, in the path of insertion of the tongue into the locking box; ; and a locking recess is arranged in the locking box to cooperate with the deflecting tooth whereby, upon insertion of the I-shaped tongue, the latter is deflected by the tooth into said recess and the second bar of the tongue is guided into a plane different from the stem)and subsequent attempted withdrawal of the tongue is resisted by engagement of said first bar of the tongue with the root of the tooth and attempted further movement in the direction of insertion is resisted by locking engagement between said second bar and said locking recess. Preferably, the tooth andi;the locking recess are formed in an end portion of the strip which is secured in the locking box, the tooth being T-shaped and having a bar (forming said todth root), by which the tooth is connected to the strip and the locking recess being defined by the shape left following formation of the tooth. The end portion of the strip may be anchored to the locking box by means of a mating projection and hole arrangement, preferably provided by an inward projection in the locking box and a hole in the strip end portion, or by holding the end of the strip between the two halves of the locking box when they are fastened:together. However, the strip may be doubled back if desired, in the manner of the flexible strip shown in our United Kingdoms; Patent Specification 1 085 185. While the self-locking seal according to said one aspect of the invention has improved resistance to tampering, the seal may be further improved by the provision of means whereby the interengaging parts of the seal can readily be observed, and particularly that the tongue has been pulled into the fully locking position. Although this might illustrate part of the nature of the locking mechanism to unauthorised personnel, the parts cannot become unlocked by normal manipulation, and only the application of excessive force could unlock the parts - by rupturing them, and this fact would be readily apparent during routine inspection of the seal. It would not be possible to re-assemble the parts without exhibiting the ruptured parts. Means for enabling observation of the inter-engaged parts within the locking box may be provided in any suitable way. Thus, a viewing aperture may be provided in the form of an appropriately positioned aperture or apertures, or a window. Indeed, one side of the locking box may be formed in transparent plastics material, and particularly suitably a plastics material which gives a visible indication when it is subjected to pressure. There are available commercially plastics which turn opaque white when subjected to pressure. According to a further aspect of the invention there is provided a self-locking seal comprising a flexible strip having a locking box secured to one end and a profiled tongue-defining slot at its other end which is adapted, following insertion into the locking box, to be engaged lockingly so as to prevent subsequent withdrawal of the slotted end of the strip; in which the locking box is provided with means to enable visual observation of the lockingly engaged parts of the seal Conveniently, said means comprise a suitably positioned viewing aperture formed in a wall of the locking box, or it may comprise a transparent cover portion arranged in, or forming all or part of a wall of the locking box. Preferably, the transparent cover portion is made of plastics material. Embodiments of self locking seal according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of a flexible strip forming part of the self-locking seal , a locking box of the seal being shown in dash-dot lines attached permanently to one end of the strip; Figure 2 is a plan view corresponding to Figure 1; Figure 3 is a detail view, to an enlarged scale, illustrating the manner by which a tongued end of the flexible strip can be inserted into the locking box; Figure 4 is a plan view illustrating the outer surface of one part of a two part locking box; Figure 5 is a longitudinal sectional view of the locking box, showing in more detail the manner by which one end of the flexible strip may be permanently secured in position in the locking box; ; Figure 6 is a plan view showing in more detail the construction of both ends of the flexible strip, arranged one upon the other after partial insertion but before locking; Figure 7 is a side view, similar to Figure 5, illustrating both ends of the flexible strip received by the locking box and fully locked; shows Figure 8 / part of the locking box, similar to Figure 4, illustrating a modification comprising means for enabling visual observation of the lockingly-engaged ends of the seal inside the locking box; Figure 9 is a plan view of the inside surface of one part of the locking box, illustrating a further modification to improve the retention in position of one end of the sealing strip; Figure 10 is a plan view of the outer surface of a part of the locking box which cooperates with the part shown in Figure 9; ; Figure 11 is a longitudinal sectional view of the parts, shown in Figure 9 and 10, which are assembled in inverted form to the illustration in Figures 9 and 10; Figure 12 is a plan view of a modification to the end of the sealing strip which is normally attached permanently to the locking box; Figure 13 is a plan view of a modification to the end of the sealing strip which is initially unconnected to the locking box; and Figure 14 is a plan view of a locking box assembled from the parts shown in Figures 9 to 12. Referring now to#Figures 1 to 3 of the drawings, there is shown a self-locking seal which comprises a flexible strip 10 having a locking bo 11 secured to one end portion 18 and a profiled tongue defining slot at its other end 12 which is adapted, following insertion into the locking box 11, to be engaged lockingly so as to prevent subsequent withdrawal of the slotted end of the strip. The slotted end 12 has a generally I-shaped tongue 13 (tongue 12 is normally in the plane of the strip until deformed by the locking action) which comprises a first transversely extending bar 14 connected to the strip 10, a second transversely extending bar 15, and a stem 16 which connects the second bar 15 to the first bar 14. The slotted end 12 is shown, in Figure 2, prior to insertion in the locking box 11, whereas the end portion 18 is shown occupying its engaged position within the locking box 11. A deflecting tooth is provided in the locking box, in the path of insertion of the strip end 12 into the locking box, and comprises a generally T-shaped tooth 17 which is formed by stamping-out from the end portion 18 of strip 10 which is permanently anchored in the locking box 11. End portion 18 is anchored in position by means of a projection 19 provided in the locking box 11 which is taken through a hole 20 in the end portion 18. A T-shaped locking recess 22 is arranged in the locking box 11 to cooperate with the deflecting tooth 17 whereby, upon insertion of the I-shaped tongue 13, the latter is deflected by the tooth 17 into the locking recess. The locking recess 22 is formed in the, end portion 18 by virtue of the stamping-out of the tongue 17 and is similarly, generally T-shaped. Referring to Figure 3, which shows the tongue 13 partly engaged with tooth '17, once the tongue hds entered the locking recess 22 subsequent attempts to withdraw the the tongue 13 are resisted by engagement of the first bar 14 of the tongue 13 with a root portion 21 of the tongue 17 (the bar of the T-shaped tongue), and attempts at further movement in the direction of insertion is resisted by locking engagement between the second bar 15 of tongue 13 and edges of locking recess 22 (the edges which define the shape of the stem of the T-shaped recess 22). The locking box 11, as shown in Figures 1 to 3, comprises a base cover 23 and an upper cover 24 which are crimped together along their sides and ends by overlapping flanges 25. As indicated above, the flexible strip is shown in Figure 2 with the tongued end 12 of the strip ready for insertion into the locking box 11 whereas Figure 3 shows the tongued end 12 inserted in the locking box and partly in locking engagement therein. Full locking engagement is achieved when the tongued end 12 and the end portion 18 lie substantially alongside each other, with the tongue 13 fully received in the locking recess 22 and with the bar 15 parallel to the strip end 18. The construction and interengagement of the locking parts is shown somewhat schematically in Figures 1 to 3, and is shown in more detail in Figures 4 to 8, and corresponding parts are designated by the same reference numerals. Referring to Figures 4 and 5, there is shown the end portion 18 of the sealing strip attached permanently in position in the locking box, during initial manufacture of the sealing strip and locking box. As described above, projection 19 at one end of cover 23 is taken. through hble 20 in the end 18, and the opposite end of the cover 23 has an inturned flange 28 which is received by a transverse groove 29 provided on the end portion 18. A blister-type projection 30 is provided on the upper surface of the end portion 18 to locate the strip and provide a space into which the tongue 13 can be received when the initially free end 12 of the strip enters the locking box and engages lockingly with the end portion 18 and to help in bending bar 15 into a plane different from stem 16. In Figure 6, there is shown the ends 12 and 18 of the sealing strip arranged one above the other in the locking box, and illustrating the construction of the parts 14, 15 and 16Of tongue 13 in more detail, and prior to engagement with the tooth 17 and locking recess 22 of the end 18. In Figure 7, there is shown the locked engagement between tongue 13 of end 12 and tooth 17 and the locking recess of the end 18 with the bar 15 being substantially alongside end portion 18 and in a plane different from stem 16. Referring to Figure 8, there is shown a modification to the cover 23 of the locking box, which is provided with means for enabling visual observation of the state of locked (or otherwise) engagement between the ends 12 and 18. This comprises a pair of viewing apertures 27 formed in the cover 23 at a position in which the outline 26 of the second bar 15 of tongue 13 can be observed, when the ends 12 and 18 of the sealing strip are properly interlocked. Although not illustrated, other means may be provided to enable observation of #a correct, or incorrect, locking status of the ends-12 and 18. For example one or both of the covers 23, 24 may be provided with a transparent window, formed by a block of plastics material which may be incorporated in, or form all or f#art- of one wall of the-locking box. Conveniently, the window is made of a transparent plastics material of a known type, which turns opaque white when subjected to pressure. This would then give an indication of any attempt at tampering with the seal. Referring now to Figures 9 to 14, there is shown a modified locking box having improved retention of the end of the sealing strip wbich is permanently attached to the locking box during manufacture. The interlocking parts of the sealing strip may be as already disclosed, and will not be described in detail again. Parts corresponding with the previously described components will be designated by similar reference numerals, but with the addition of 100 in each case. Referring first to Figures 9 to 11, there is shown a modified two-part locking box, comprising cover part 123 which has its inside 'surface (with respect to the locking box) shown in plan view in Figure 9, and cover part 124 which has its outer surface shown in plan view in Figure 10. The cover parts 123 and 124 fit together in the manner shown in Figure 11 along overlapping peripheral flanges 125, which are formed by turningin the upstanding edges 123a (see Figure '9) over the side edges 124a (see Figure '10) of cover part 124. Referring'now to Figures 12 and 13, the sealing strip has end 118 which is permanently secured in the locking box during initial manufacture, and has tongue .117 and locking recess 122. The other end 112.of the sealing strip has an I-shaped tongue '113, composed of first transverse bar 114, second transverse bar 115,, and stem 116 which interconnects the bars 114 and 115, The tongue 113 makes locking engagement ir the locking recess 122, and with tooth 117, in similar manner to that already described above with reference to tongue 13, tooth 17. and locking recess 22. However, in addition, end 118 is provided with a saddle 131 which is arranged forwardly of tooth 117, with respect to the direction of insertion of end 112 into the locking box and over the tooth 117. The saddle 131 comprises a narrow strip extending transversely of the end 118, which is formed from the material of the strip so as to be upstanding from the general surface of the end 118. The first bar 114 of the tongue 113 slides over the tongue 117 and 'the saddle 131, during locking-assembly. As described above, the tongue 113 is then pulled in the opposite direction, so as to engage with the underside of tooth 117, and enter into engagement in the locking recess 122. This engagement holds the ends 112 and 118 of the strip more closely together so that only a small movement in the direction of insertion is possible before it is obstructed by saddle 131, and any attempt to separate"the strips to pass saddle 131 engages the tongue 113 more strongly lm the locking recess 122. In the previously described embodiments, the end 118 of the sealing strip is secured in position in the locking box by means of projection 19 and inturned flange 28 of the cover 23. However, in the arrangement shown in Figures 9 to 14, an alternative, and strengthened means of retention is provided. This retention means comprises a hole 132 which is formed in the cover part 123, by formation of an annular collar 133 which projects perpendicularly inwardly of the general plane of the cover part 123. The cover part 124 is also formed with a hole 134 which is defined by an annular collar 135 which extends, as shown in Figure 11, in opposite direction to the collar 133. Figure 11 shows how the collar 133 is located within the collar 135, and has an outwardly turned flange 136 which Jocks the assembly together. The end 118 of the sealing strip is retained in position in the locking box by positioning of a mounting aperture 137 around the collars 133 and 135, prior to formation of the flange 136. Thereafter, the flange '136 is formed, so as to complete the retention in position of the sealing strip. The formation of the locking box is completed by pinching-together the flanges 125 of the cover parts 123 and 124. Referring to Figure '14, the end 118 is illustrated occupying its permanently secured position within the locking box. The end 112 is engaged lockingly with the end 118-, by interengagement of the locking parts of the strip ends, as described above. The manner by which the strip end 112 enters the locking box will now be described, with reference to Figures 11 and 14. The cover part -124 is provided with a raised transverse flange 138 which defines a narrow entry aperture 139 into which the leading end (first bar 114) of the strip end 112 can be received. A further raised flange '140 is provided on the cover part 124, defining a further' entrance aperture '141 via which the strip end 112 can enter the locking box proper. Although not shown in Figure '11, the strip end 118 will already be located within the locking box, and I-shaped tongue 113 can engage tooth 117, and locking recess 122 in the manner described above. Once the ends 112 and 118 hÅave become locked together, it will be evident that the' strip end 112 will overlie the flange 136 and the collars 133 and 135, thereby preventing access to this means of retention of the strip to any attempts at unauthorised tampering with the seal. When the locking. parts have become fully interengaged, this status of the seal may be observed via inspection through the viewing apertures 127. In addition, when the parts are fully locked together, register holes 142 and 143 formed in the strip ends 118 and 112 respectlvely should be substantially in alignment with each other.

Claims: CLAIMS: 1. A self-locking seal comprising a flexible strip having a locking box secured to one end and a profiled tonguedefining slot at its other end which is adapted, following insertion into the locking box, to be engaged lockingly so as to prevent subsequent withdrawal of the slotted end of the strip, in which: : the slotted end of the strip has a generally I-shaped tongue comprising a first transversely extending bar connected to the strip, a second transversely extending bar, and a stem which connects the second bar to the first bar; a deflecting tooth is provided in the locking box, in the path of insertion of the tongue into the locking box; ; and a locking recess is arranged in the locking box to co-operate with the deflecting tooth whereby, upon insertion of the 'I-shaped tongue, the latter is deflected by the tooth into said recess and the second bar of the tongue is guided into a plane different from the stem, and subsequent attempted withdrawal of the tongue is resisted by engagement of said first bar of jhe tongue with the root of the tooth and attempted further movement in the direction of insertion is resisted by locking engagement between said second bar and said locking recess. 2. A self-locking seal according to claim 1, in which #he tooth and the locking recess are formed in an end portion of the strip which is secured in the locking box, the tooth being T-shaped and having a bar (forming said tooth root), by which the tooth is connected to the strip and the locking recess being defined by the 'shape left following formation of the tooth. 3. A self-locking seal according to claim 1 or 2, in which the end portion of the strip is anchored to the locking box by means oS a mating projection and hole arrangement. 4. A self-locking seal according to claim 3, in which an inward projection is provided in the locking box and a hole is formed in said end portion of the strip. 5. A self-locking seal according to claim 1 or 2, in which the end portion of the strip is secured in the locking box between two halves of the locking box when said halves are joined together. 6. A self-locking seal according to claim 1 or 2, in which the locking box is secured to the strip by retention means comprising an inwardly extending collar which is taken through a hole in the strip, and is turned-over in order to retain the strip on said collar. 7. A self-locking seal according to claim 6, in which the locking box comprises two cover parts which are joined together, and in which the collar extends inwardly from one of said cover parts, through the hole in the strip and through a hole in the other cover part, before being turned-over to retain the strip on the collar. 8. A self-locking seal according to any'one of the preceding claims, including means provided on the locking, box to enable visual inspection of the interengaging parts of the strip within the 'locking box. 9. A self-locking seal according to claim 8, including one or more viewing aperture formed in a wall of the locking-box. 10. A self-locking seal according to claim 8, including a window formed in, or forming part of a--wall of the locking box. 11. A self-locking seal according to claim 10, in which the window is formed of transparent plastics material. 12. A self-locking seal according to claim 11, in which the window is formed of plastics material which is of the type which turns opaque white when subjected to pressure. 13. A self-locking seal comprising a flexible strip having a locking box secured to one end and a profiled tongue-defining slot at its other end which is adapted following insertion into the locking box, to be engaged lockingly so as to prevent subsequent withdrawal of the slotted end of the strip; in which the locking box is provided with means to enable visual observation of-the lockingly engaged parts of the seal. 14. A self-locking seal according to claim 13, in which said means comprises a suitably positioned viewing aperture formed in a wall of the locking box. 15. A self-locking seal according to claim 13, in which said means comprises a transparent cover portion arranged'in, or forming part of a wall of the locking box. 16. A self-locking seal according to claim 15, in which all or part of the transparent cover portion is made of plastics material. 17. A Aself-locking seal according to claim 16, in all or part of the transparent cover portion is made of plastics material which turns opaque white when subjected to pressure.

Inventors: DYSON, KEITH, HEDGER, JAMES
Applicants: ACME SEALS LIMITED, DYSON, KEITH, HEDGER, JAMES
Application year: 1982
Main classification: G09F3
IPC codes: G09F3