Anti-tamper device

Abstract

An anti-tamper component 50a 50b, to retain a panel of a window or door in its frame, comprises a base (52 Fig 5) for location on an edge surface of one of the panel or frame, and a retaining edge (60 Fig 5) for engaging a structure on the respective other of the panel or frame, wherein the retaining edge is carried on a return structure (62 Fig 5) of the anti-tamper component. The retaining edge 60 is provided by an edge structure of a sheet structure that is configured to yield by plastic deformation when exposed to a break-in force, thus allowing the component to take up stresses under load by deformation or stretching. The retaining edge may be a hook. The component may be a metal, for example hot rolled steel or case hardened steel, various case hardness values are disclosed. The component may have a specific elongation at faction value of 15%, 17.5%, 20% or 22.5%.

Description

Referring to the Figures, Figures 1 to 4 each show a section through a portion of a frame system 10 showing a hinged side of a panel 12 and a frame 32. In the Figures, different conditions of the frame system 10 will be denoted by suffices, as 10A, 10B, 10C and 10D, wherein identical components of the system 10 are identified by the same numerals without repeating the description thereof. In Figure 1, the panel 12 is illustrated in a closed condition 10A, seated in a frame 32. In Figure 2, the panel 12 is illustrated in an open condition 10B, wherein the panel 12 is opened about a hinged axis (hinges not shown) and angled in a part-opened, ajar condition relative to the frame 32. In Figure 3, the panel 12 is in shown in a partially dislodged configuration 10C in which a force is applied sufficient to dislodge the panel 12 from the hinged side of the frame 32. In Figure 4, the panel 12 is shown in a condition in an unhinged condition 10D in which the hinged side of the panel 12 was levered out of the frame 32. The panel 12 comprises a panel frame 14 formed from elongate members to hold a glass pane (not shown) or other structure, wherein the panel frame 14 is typically rectangular and comprises a circumferentially extending panel edge 16, providing an edge surface of the panel, corresponding generally to the thickness of the panel. The panel edge 16 comprises, here, a panel lip 18 and an edge interface 20 comprising an edge profile 22 of an elongate member including a groove 24 (here: in the form of a so-called Eurogroove). The frame 32 is, typically, mounted in a building structure (not shown) to provide an opening, such as a window and to be closed by the panel 12. The frame 32 comprises a frame structure 34 of typically rectangular shape formed from elongate members with an inner frame edge 36 providing an edge surface of the frame and facing, when closed by a panel 12, the panel edge 16. The inner frame edge 36 comprises a frame lip 38 and a frame interface 40 comprises a frame profile 42. As shown herein, both the panel frame 14 and the frame structure 34 are made from elongate members formed from extrusions comprising hollow channels, however it will be appreciated that other panel and frame structures may be made from solid material or composite material. The profiles of the panel frame 14 and the frame structure 34 are such that in a normally closed condition 10A a free space 30 remains between the edge interface 20 and the frame interface 40, the free space 30 closed at one side by the panel lip 18 and on the other (outer) side by the frame lip 38. The panel 12 and the frame 32 are each provided with an anti-tamper device 50 constituting an anti-tamper component. For the purpose of the present disclosure, Figures 1 to 4 show an arrangement comprising two elements 50a, 50b each constituted by the same anti-tamper device 50, and so only one anti-tamper device 50 is described herein. One anti-tamper device 50a is located on the edge interface 20, positioned relative to the groove 24 and affixed using screws 26 engaged in the panel frame 14 (only one screw 26 shown in section). Another anti-tamper device 50b is located on the frame interface 40, positioned relative to the frame profile 42, and affixed using screws 28 engaged in the frame structure 34 (only one screw 28 shown in section). The anti-tamper devices 50a and 50b are arranged relative to each other such that, during normal opening and closing of the panel 12, they remain in a pre-inhibitory configuration in which they do not come into engagement, and usually are not expected to come into contact with each other, as illustrated in Figures 1 and 2. However, if subjected to a sufficiently strong force, as illustrated in Figures 3 and 4, the panel 12 may be dislodged so much that the two anti-tamper devices 50a and 50b come into engagement, as illustrated in Figure 4, to thereby impede a further opening or further dislodging of the panel 12. As will be appreciated, more than one anti-tamper device may be located along the extension of the frame 32 and / or along the extension of the panel 12. The arrangement of Figures 1 to 4 shows two identical anti-tamper devices 50a, 50b, one each arranged at a hinged side of a panel and frame, such that one retaining edge of one component 50a provides an engaging structure for the retaining edge of the other component 50b. However, it will be appreciated that embodiments may use two differently shaped components arranged such that a retaining edge of one component engages an engaging structure such as lip, edge or other suitable profile of the other component. Likewise, in some embodiments, only one of the panel and frame is provided with an anti-tamper device 50, the retaining edge of the anti-tamper device 50 being arranged to engage an integral structure, of the other of the panel and frame. To provide illustrative examples, an integral structure may be provided, for instance, by an edge of a groove 24, or by an edge of a profile 42, provided these provide a suitable geometry for engaging a retaining edge of an anti-tamper device. Figure 5 shows a retainer hook 50 constituting an anti-tamper component comprising a base plate 52 of generally rectangular profile with rounded edges, having an elongate dimension with a long side of about 60 mm length and a short side of about 15 mm width, and a sheet thickness of 1.5 mm. The dimensions of the base plate are understood to represent exemplary embodiments and may differ depending on the profile of the panel and frame on which they are intended to be installed. In use, the base plate 52 is affixed to an interface such as the edge interface 20 or the frame interface 40 with the elongate dimension oriented along the extension of the interface. The base plate 20 comprises an arrangement of, here: two, holes 54a, 54b for fastening means such as screws. Along one of the elongate edges of the base plate, the retainer hook 50 comprises a hook structure extending from the plane of the base plate 52, the hook structure comprising a neck 58 and a return 62 constituting a return structure, and a free end constituted by an edge structure 60, providing a retaining edge. In a transition region between base plate 52 and the neck 58, the base plate 52 comprises two cut-outs 56 laterally of the neck 58. Anti-tamper components of this style have, to the best of the inventor’s knowledge, hitherto been made from spring steel materials having a high tendency to resiliently resist a forcible abutment by an engaging component, and to spring back into a rest position to resume a pre-inhibitory configuration. An observation underlying a development of the invention was that spring steel material can in some situations fail. Specifically in colder temperatures, the steel may exhibit a somewhat more brittle behaviour. Figure 6 shows a failed reference test component 1 made from spring steel, having a neck 2 with a free end providing a retaining edge that was stress tested by subjecting the retaining edge of the neck 2 to force until failure. As can be seen, a fragment 3a broke from the base plate 3 of the test component 1. Due to the resilient properties of the spring steel material, the base 3 of the failed component 1 is practically planar, despite the force applied to cause the breaking of the base 3, and the neck 2 has maintained, or resumed, its original rest position. The suggestion made in this disclosure is that the material used for the anti-tamper component is, counterintuitively, a material with a relatively high elongation at fracture value, exceeding 15%, 17.5% 20%, 22.5%, and even 25%. Also counterintuitively, the material may have a relatively low yield strength lower limit, of no more than 600 N / mm2, 550 N / mm2, 500 N / mm2, 450 N / mm2, or 400 N / mm2. The yield strength is lower than typically expected from spring steel having a yield strength with a lower limit of over 700 N / mm2 or higher. The embodiments of the invention are thought to be typically made from a unitary sheet material shaped (stamped) and plastically deformed as desired, and typically having a plate thickness of around 1.5 mm, typically no more than 2 mm or no more than 3 mm. An exemplary material used for this purpose as S355MC steel with a yield strength of >355 N / mm2 and having an elongation at fracture (Aso Lo = 80mm, thickness <3mm) of 19% and (As Lo = 5.65mm, thickness >3mm) of 23%. In one test batch, the S355MC hot rolled steel was tested to have an elongation at fracture (Lo = 80mm) higher than nominally expected, of 24%. Figure 7 illustrates comparative test component 1b manufactured from steel with high yield strength and relatively thin sheet thickness of less than 1.5 mm, the test component 1b comprising a neck 2b extending from a base plate 3b. The test component 1b was subjected to a break-in force under test conditions and shows a stretch behaviour deforming (elongating) the neck 2b and also deforming the base in a region 4b. The deformation at the base 4b resulted in a lifting of several millimetres, and a corresponding extension of the retaining edge of the neck 2b, causing the test component 1b to fail. Figures 8 and 9 show a front view and side view, respectively, of a prototype embodiment 50a that was subjected to a break-in load. The base plate 52 of the prototype 50a has plastically deformed in several areas, including a corner region 55 that has been deformed out of the plane of the base plate 52 and in the neck region, where a deformation from the original shape (as in Figure 5) can be discerned specifically in a transition zone 53. The deformation of the prototype 50a is a consequence of plastic deformation properties and practically irreversible, by which is meant that the component remains deformed after removal of a deforming load. The component once deformed in this manner is believed to eventually require replacement for repair of the panel, as it may interfere with the normal opening and closing of the panel 12. Compared to Figure 6, the base plate 52 and the neck 58 are deformed considerably stronger than the base 3 and the neck 2. However, an observation was that the prototype 50a, despite its deformation, continued to perform as an anti-tamper device during the application of test forces, by continuing to impede the forcible opening of the panel 12 out of the frame 32. The observation was surprising because the elongation properties specifically of thin sheet metal, with a thickness of no more than usually 2 or 3 mm, were believed to yield too much to be able to maintain an effective anti-tamper function, as illustrated in Figure 7. To further improve the resilience of a component using a sheet of only a few millimetres sheet thickness, the embodiment comprises a case-hardened surface. As may be appreciated from Figures 8 and 9, the “stretching” of the prototype 50a is still relatively small in absolute numbers, and may be in the region of a millimetre. Deformed in this manner, the prototype device 50a is believed to be able to continue to frustrate a forcible entry attempt. Particularly, the observed amount of deformation D of the base 52 was relatively compared to the earlier prototype component 1b of Figure 7. To provide illustrative example values, typical tests of such anti-tamper devices may be carried out on a test installation of a panel in a frame, fitted with the anti-tamper device. A typical test protocol may involve the application of a force representative of a break-in force, for a predetermined period of time and in progressively increasing increments, e.g. 3.0 kN for 10 seconds, 3.5 kN for 10 seconds, 4.0 kN for 10 seconds, and so on, until a panel is prised out of its frame, or until a test is discontinued after reaching maximum load. Using spring steel, a sample such as the Figure 6 component 1 failed at around 4.5 to 5 kN, due to snapping. A non-spring steel embodiment such as the Figure 7 component 1b comprising a thin sheet material of around 1 mm thickess failed, due to deformation. In contrast, a prototype component 50a illustrated in Figures 8 and 9 eventually started to deform plastically but remained functional to frustrate a forcible opening of a panel in excess of 5kN. Test protocols were carried out using prototypes with different case hardness depths. The case hardness depth (CHD) was tested on samples that had been cut to expose a cross-section, and the test area polished to 1 pm to provide a flat surface for Vickers Hardness testing. The Vickers Hardness testing was carried out with a micro hardness test force of 300g (2.94N), Vickers scale HV0.3, in 0.05 mm increments to confirm the case hardness depth. Prototype embodiments passing the test protocol, and exceeded a load of 4.5kN, had a case hardness depth of 0.25 mm for a hardness in a region of 400 to 500 HV. Comparative prototype samples with larger case hardness depth, and a Vickers Hardness HV800, performed poorer and surprisingly snapped at loads of 3kN or higher. As such, it is believed that relatively shallow case hardness depths, of around 0.20 mm to 0.30 mm, are providing a good anti-tamper performance, while allowing the anti-tamper component to be made from relatively thin sheet material comprising a sheet thickness of no more than 3 mm, no more than 2 mm, or no more than 1.5 mm. In some embodiments, sufficient anti-tamper performance may be achieved by a case-hardened component comprising with a sheet thickness of 1 mm. Figure 10 shows an alternative embodiment that may be used with other panel profiles or frame profiles. A retainer plate 70 comprises a plate portion 72 of generally rectangular form provided with an arrangement of holes 74a, 74b laterally of an elongate slot 76. The elongate slot 76 extends along an elongate extension of the plate portion, off-centre, separating a ledge region 78 from the remainder of the plate portion 72. The elongate slot 76 constitutes an aperture or eye, comprising an inner circumferential edge, whereas the ledge region 78 may be understood as being structurally connected with the main body of the plate portion 72 via two lateral corners 77a, 77b each providing a return structure, and an edge structure 80 of the ledge region 78 providing a retaining edge. As will be appreciated, if the retainer plate 70 is affixed to a surface underneath, a structure engaging the edge structure 80 in a direction away from the holes 74a, 74b may initially be retained by the edge structure 80 and its anchoring to a structure underneath via the holes 74a, 74b. Continued application of a sufficiently strong force F in the direction of the edge structure 80 may be expected to result in plastic deformation in the form of elongation and / or twisting of the ledge region 78 and / or the lateral corners 77a, 77b. The retainer plate 70 may be no more than 2mm, 3mm or 4mm thick. It may be made from a material such as hot rolled steel having an elongation at fracture value of at least 15%, or higher, e.g. at least 17.5%, 20%, 22.5%, or at least 25%. An exemplary material is S355MC hot rolled steel. The retainer plate 70 may be case-hardened, with a case hardness depth in the region of 0.20 mm to 0.30 mm, e.g. with a case hardness depth of around 0.25 mm, comprising a Vickers Hardness in a range of 400HV to 500HV. As will be appreciated, the degree to which case hardening improves anti-tamper performance may depend on the sheet thickness and geometry of the anti-tamper component. Tests made with components of elongation properties revealed that such components tend to start to deform sooner, sometimes under lower stress loads, in a less reversible manner than spring steel components. However, despite the yield properties, the elongation behaviour was found to provide a ‘stretchiness’ that continued to present an obstacle to forcibly removing a panel component out of its frame. Thus, surprisingly, the deformation of the component of did not affect the required performance as a security device. Furthermore, the higher elongation value is believed to make the device more suited to colder temperature ranges. The use of case hardening allows thinner sheet material to be used compared to anti-tamper components of otherwise same geometry. A security component may be formed from sheet metal material. Embodiments subjected to test loads typically comprised a return structure or ledge oriented in a manner allowing them to take up some of the forces that may contribute to folding, unfolding, bending or unrolling, of a ledge or hook structure, thereby reducing the likelihood of the anti-tamper component breaking. In embodiments, comprising an edge carried on a neck structure, some stress loads are believed to be taken up by deformation or stretching of the neck structure, in addition to stresses under load taken up by other portions of the anti-tamper component. The ability to absorb at least some of the load by unfolding, unrolling, bending or stretching is believed to help to frustrate a forcible entry attempt. While the security component deformed in this way may impede the normal closed of a panel after a failed break-in attempt, this can be addressed by repair or refitting. The anti-tamper device may be treated with a finishing process such as plating. While the description of an embodiment relates to panels for window frames, the antitamper mechanism may also be used for door panels, hatch panels and the like, as well as for panels that may not typically be intended to be opened, such as ‘blind’ or so-called ‘dummy’ panels fitted into frame structures. Whilst the principle of the invention has been illustrated using exemplary embodiments, it will be understood that the invention is not so limited, and that the invention may be embodied by other variants defined within the scope of the appended claims.

Claims

1. An anti-tamper component to assist with the retaining of a panel of a window or door in its frame, the anti-tamper component comprising a base for location on an edge surface of one of the panel or frame, wherein the anti-tamper component further comprises a retaining edge for engaging a structure on the other of the panel or frame, the retaining edge being carried on a return structure of the anti-tamper component, wherein the retaining edge is provided by an edge structure of a sheet structure, and wherein the sheet structure is configured to yield by plastic deformation when exposed to a break-in force.

2. The component according to claim 1, wherein the retaining edge is provided by a hook structure.

3. The component according to claim 2, wherein the retaining edge is provided by an inner edge of an aperture within the sheet structure.

4. The component according to any one of the preceding claims, wherein the retaining edge is carried on a neck structure extending from the base.

5. The component according to claim 4, wherein the retaining edge is carried on a neck structure protruding out of a plane of the base.

6. The component according to claim 4 or 5, wherein the base comprises one or more recesses where the neck structure extends from the base.

7. The component according to any one of claims 4 to 6, wherein the base comprises fixing holes positioned laterally of the neck structure.

8. The component according to any one of claims 4 to 7, wherein the base comprises one or more fixing holes positioned laterally within the extent of the neck structure and offset from the neck structure.

9. The component according to any one of the preceding claims, configured to allow elongation of the neck structure when exposed to a break-in force.

10. The component according to any one of the preceding claims, configured to allow elongation of the edge structure when exposed to a break-in force.

11. The component according to any one of the preceding claims, wherein the base and the edge structure are different regions of a unitary component.

12. The component according to any one of the preceding claims, formed from metal.

13. The component according to any one of the preceding claims, formed from hot rolled steel.

14. The component according to any one of the preceding claims, formed from case-hardened steel.

15. The component according to claim 14, wherein case-hardened portions comprise a case hardness in the region of 400HV to 550HV and a case hardness depth of no more than 0.3 mm.

16. The component according to claim 14 or 15, wherein case-hardened portions comprise a case hardness in the region of 400HV to 550HV and a case hardness depth of no less than 0.1 mm.

17. The component according to any one of claims 14 to 16, wherein case-hardened portions comprise a case hardness in the region of 400HV to 550HV and a case hardness depth in a region between 0.20 mm and 0.28 mm.

18. The component according to any one of the preceding claims, formed from a material with an elongation at fracture value of no less than 15%.

19. The component according to any one of the preceding claims, formed from a material with an elongation at fracture value of no less than 17.5%.

20. The component according to any one of the preceding claims, formed from a material with an elongation at fracture value of no less than 20%.

21. The component according to any one of the preceding claims, formed from a material with an elongation at fracture value of no less than 22.5%.

22. The component according to any one of the preceding claims, having a sheet thickness of no more than 4 mm.

23. The component according to any one of the preceding claims, having a sheet thickness of no more than 3 mm.

24. The component according to any one of the preceding claims, having a sheet thickness of no more than 2 mm.

25. A door or window frame system comprising a panel fixed in a frame, the panel removable from the frame in a removal direction and closable into the frame in a seating direction, wherein the system is provided with one or more anti-tamper components according to any one of the preceding claims, the one or more anti-tamper components being located at an interface between the panel and the frame, the base being affixed to one of the panel and the frame, and oriented such that forcible movement of the panel out of the frame results in abutment of the retaining edge with a structure of the other of the panel and the frame, and such that further application of force of the structure against the retaining edge results in plastic deformation of the anti-tamper component.

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