GB2297345A

GB2297345A - Laths for shutters and shutters made therefrom

Info

Publication number: GB2297345A
Application number: GB9501398A
Authority: GB
Inventors: John Hamilton
Original assignee: AMBER DOORS Ltd
Current assignee: AMBER DOORS Ltd
Priority date: 1995-01-25
Filing date: 1995-01-25
Publication date: 1996-07-31
Anticipated expiration: 2015-01-25
Also published as: GB2297345B; GB2324113B; GB2324113A; GB9501398D0; GB9814805D0

Description

Laths for Securitv Shutters and Securitv Shutters Made Therefrom The present invention relates to laths for security shutters, to security shutters made therefrom and more particularly but not exclusively to laths for security shutters of the sort used to protect business premises out of trading hours by covering the fronts of doorways and windows and which are rolled up, folded or otherwise retracted when the premises are in use.

Security shutters comprise shutter curtains made of interlocked laths mounted on mounting means. The mounting means may include a stand, vertical uprights including slide guides for the curtain and retracting/storing means, such as a roller, for holding the curtain in its retracted position.

Shutter curtains are available in a number of forms, mostly comprising an assembly of elongated laths placed horizontally and connected by hinge joints above and below to adjoining laths. Such laths may be manufactured by extruding single skin members.

Such a curtain, made of interlocked laths, may have a bottom rail attached by a hinge joint to the lowest lath. The shutter curtain runs in two vertical side guides from the retracted position to the in-use position in which it covers the doorway etc. Means are conventionally provided for locking the shutter curtain in its in-use position by locking the bottom rail to the base of the shutter apparatus.

When not in use the curtain may be folded or rolled up depending on the construction of the hinge joints and the method of mounting the curtain. Thus, when not in use, it may take the form of a stack or roll. When in use the laths form a screen or curtain and thus protect the premises. Laths of the prior art are made from sheet steel or extruded aluminium. A shutter curtain made of extruded laths is described in UK patent no. 2011512. In this case double skin laths are disclosed. These are made by joining together several elongated skin members and a hollow space is formed within.

Such curtains are widely used to prevent burglary but a number of shortcomings have been noted. Two particular methods of penetrating such security curtains are known. The first is the use of high power cutting equipment and the second is the use of a vehicle to drive into the curtain, the so-called "ram raid". The curtain is sufficiently damaged by the impact to make entry into the premises possible.

In respect of the first problem, UK patent application no. 2254356 provides a method for protecting against such cutting apparatus as motorised abrasive disc cutters. A shutter curtain as described above is provided and a cut resisting body is either bonded to the back of a single skin lath or is placed in a hollow within a double skin lath. The cut resisting body comprises a polymer matrix and a plurality of hard particles of silicon carbide or like material. This development has had some success against the cutting apparatus of the type envisaged because the hard particles are inclined to rotate with the cutter or absorb impact by deformation of the matrix thus lengthening the cutting process. However this development has proved ineffectual in the face of large-toothed cutters such as rotating saws.

In connection with the problem of ram-raiders, the inventor could find no indication that there was any possibility of adapting shutters of the above-mentioned variety for dealing with the problem.

It is thus an object of the present invention to provide laths, which may be formed into shutter curtains which are resistant to cutting by high power cutting tools.

It is a further object of the present invention to provide a shutter curtain that is resistant to sudden and heavy impact such as that of a vehicle used in ramraiding.

In accordance with a first aspect of the present invention there is provided a lath for an interlocking lath shutter curtain, the lath comprising an outer skin, interlocking means for attachment to adjacent laths and an internal void substantially along the length of the lath, at least one rigid body within the void and compression means acting to place the rigid body under compression.

In an embodiment the rigid body may be a bar of any suitably solid material. Steel, and in particular case-hardened steel, is especially favoured.

Alternatively aluminium may be considered. The compression means may be a steel spring which may be inserted in the interior of the lath along with the rigid body. The extent of compression may be such as to trap any cutting blade that may insert itself into the lath.

In accordance with a second aspect of the present invention there is provided a lath for an interlocking lath shutter curtain which lath comprises an outer skin, interlocking means adapted to engage corresponding means on adjacent laths, an internal void along the whole length of the lath and a linking means disposed therein, an attachment means adapted to attach the lath to vertical side guides and fixedly attached to respective ends of the linking means, wherein the linking means is adapted to absorb force without breaking.

In a preferred embodiment the linking means is made of a strong but deformable substance and any material which allows the absorption of force without breaking is suitable. In a particular example this is malleable steel. Again, aluminium may be considered as an alternative. The linking means may be in the form of a bar. Alternatively it may be a cable.

The attachment means at each end are 'T' sections in a embodiment and slide freely along vertical side guides. The 'T' shape ensures that they cannot be pulled out of the guides by means of lateral force. In a particularly preferred embodiment the attachment means are deformable so as to absorb, at least in part, the force of an impact on the lath.

In accordance with a third aspect of the present invention there is provided an interlocking lath shutter curtain for a security shutter having interlocked laths for running down vertical side guides of the security shutter to a bottom rail thereof, wherein the laths comprise an external skin and an internal void and wherein at least a proportion of the internal voids contain rigid bodies and compression means operative to place the rigid bodies in compression.

In accordance with a fourth aspect of the present invention there is provided an interlocking lath shutter curtain for a security shutter comprising a plurality of interlocked laths, laths forming at least a proportion of the curtain each comprising an outer skin and an internal void along its entire length, interlocking means adapted to engage corresponding means on adjacent laths and attachment means at each end of the lath adapted to attach the lath slidably to vertical side guides of the security shutter, at least one lath comprising further a linking means disposed within the void linking the attachment means at each end of the lath, the linking means being adapted to absorb force without breaking. Again, the attachment means may also be deformable.

In accordance with a fifth aspect of the present invention there is provided a lath for an interlocking lath shutter curtain, the lath comprising an outer skin, interlocking means for attachment to adjacent laths and an internal void along the length of the lath, a linking means provided within the void and attachment means fixedly attached to respective ends of the linking means and adapted to attach the lath to vertical side guides, the attachment means being compressible to absorb force. In an embodiment the linking means is rigid.

A disadvantage of the earlier embodiment in which the linking means is deformable is that whilst the linking means itself is stretched by the impact, the lath skin is not. Thus lengths of linking means may become exposed and are rendered easy to cut. This disadvantage is obviated by the present embodiment in which the deformation is substantially enclosed within the guide rails.

In accordance with a sixth aspect there is provided an interlocking lath shutter curtain for a security shutter comprising a plurality of interlocked laths, laths forming at least a proportion of the curtain each comprising an outer skin and an internal void along its entire length, interlocking means adapted to engage corresponding means on adjacent laths and attachment means at either end of the lath adapted to attach the lath slidably to vertical side guides of the security shutter, each said lath further comprising a linking means disposed within the void linking the attachment means at each end of the lath, the attachment means being adapted to absorb force without breaking. In an embodiment the linking means is itself substantially rigid.

In all six aspects of the invention the void inside the lath is utilised by filling it with a bar of homogenous material with the aim of protecting the shutter against attempts to break the laths.

In a particularly favoured embodiment the two types of lath are provided alternately in the shutter curtain. In a further embodiment the bars held under compression are compressed by springs or like compression means and the springs may be located at different points in different laths. Thus the security of the system cannot be overcome by learning the position of the spring and thus cutting through the spring rather than the bar.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which: Figure la shows a longitudinal cross section through a part of a lath according to an embodiment of the invention.

Figure 1b shows a transverse cross section of the lath in Figure 1.

Figure 2a shows a lath according to an embodiment of the invention in situ seen from above.

Figure 2b shows a longitudinal cross-section of the lath in Figure 2a.

Figure 2c shows a transverse cross-sectional view of the lath in Figure 2a.

Figure 3 is a side elevation of a shutter curtain apparatus mounted on a test rig for use in the invention.

Figure 4 is a front elevation of the apparatus in Figure 3.

Figure 5 is a transverse cross section of a part of the device in Figure 3.

Figure 6 is a front elevation of part of the device of Figure 3.

Figure 7 is a front elevation of part of the device of Figure 3.

Figure 8 is a perspective view of a modification of the embodiment of Figure 2.

Figure 9 is a cross-sectional plan view of the device in Figure 8.

Figure 3 shows a side elevation of a shutter curtain apparatus suitable for use in the invention mounted on a test rig comprising an endpiece 15, two vertical sections 16 and a stand 17. A plurality of interlocked laths forming a curtain 20 are rolled up on a steel tube 14. Attached to the lower side of the final lath on the roll is the end piece 15 which is shown in detail in Figure 5. The steel tube 14 is rotatably mounted on its axis across the top of the two vertical sections 16 which themselves are rigidly attached to the stand 17 fixedly attached to the ground. Thus a fixed frame is provided as a mounting.

Vertical guides 13 are placed on the insides of the vertical sections 16. The interlocked laths are held by attachment means 21 at each end to the vertical guides 13 and slide along the guides 13. The laths may thus be unrolled and lowered to the ground to form a protective screen or curtain in front of the premises as they are left unattended. The end piece 15 is then locked to fix the shutter curtain in position. The end piece may then simply be unlocked and the curtain retracted to provide access during business hours.

Figure 4 is a view from in front of the shutter apparatus and, like Figure 3, shows the shutter curtain in its rolled up position.

Figure 6 is a view from above of the roller and shows how it is rotatably mounted to the vertical sections 16. Figure 7 is a view from above of the lath of Figure 1 fitted into the vertical guides.

Figure 1 shows a lath of the invention for use in the curtain. At the top and bottom of the lath are hooks 9 and 10 for attachment to adjacent laths of the curtain. The lath is of constant cross-section and is made by extrusion of aluminium or a similar material.

In the particular construction illustrated, a front face 1 and a rear face 2 are joined together by frontto-rear walls 3 and 4 so as to form a box configuration enclosing a void 5. Other constructions known to those skilled in the art are also suitable, provided that the lath includes an internal void.

An infil bar 6 is inserted within the void 5.

This bar may be of aluminium but as an alternative it can be made of harder materials such as steel. The infill bar extends through most of the lath and in the remaining space a spring 7 is inserted to provide compression means to act on the infil bar 6. At either end of the lath anchor blocks 8 are fixed. The compressing force from the spring is transmitted to the infill bar 6. Thus, when a blade is inserted to cut the lath, the infill bar will tend to trap the cutting blade used. As the cutting blade is withdrawn the spring 7 pushes the infill bar 6 to fill the gap made by the intruding cutting blade.

The positioning of the spring is not always as shown but is varied in different laths. It is important that the position of the spring is unpredictable. This is because, if the position of the spring can be easily discovered, there arises the possibility of cutting through the spring as a means of overcoming the security of the system. Thus, the spring 7 need not be placed at one end of the lath as illustrated but instead the infill bar 6 may be made in two parts and the spring 7 placed in between.

Furthermore, the lath may include a plurality of springs and infill bars as desired.

Figure 2 shows a lath according to a second aspect of the invention. In this case the void 5 within the lath is filled by a continuous bar 11 of aluminium, steel or other suitable material which extends right through the lath and protrudes at each end. The bar 11 is deformable so as to absorb the force of an impact applied to the bar and malleable steel is a particularly effective material. An alternative to a bar that enhances flexibility is a cable. 'T' sections 12 are formed on those parts of the bar or cable which protrude at each end of the lath and these fit into the vertical guide rails 13. This construction allows the laths to slide up and down along the guide rails 13.

However, the laths are prevented from being pulled out of the guide rails by means of lateral force because the 'T' sections, which provide the attachment means, are linked by the bar 11. Furthermore, the bar 11 that extends through the lath resists fracture of the lath itself. Thus a shutter curtain made of such laths is highly resistant to ram-raid attack. Figure 2a is a view from above of a single lath in situ in the guide rails 13. Figure 2b is a longitudinal cross sectional view and Figure 2c is a lateral cross sectional view of the same lath.

Figures 8 and 9 show a modification of the embodiment of Figure 2. In this modification the T bar 12 is replaced by a generally triangular end section 30 to whose truncated apex 31 the continuous bar 11 or cable is attached. The vertical guide rails 13 are formed so that the end sections 30 slide easily up and down. The base 32 of the triangle is firmly abutted to an inner layer 33 of the inward face of the guide rail and thus the end section 30 serves to wedge the continuous bar 11 into the guide rails.

The triangular end sections 30 are preferably made of aluminium and are rigid but deformable. The triangular shape is chosen partly for its rigidity in normal use of the shutter, partly for its economy in terms of use of materials and partly because of the presence of a flat base to abut against the guide rail 13. Other shapes or other materials, which deform in an appropriate manner, may also be used. During an impact on the laths the bar 11 is pulled in the direction of arrow 34. As the bar 11 is attached only to the apex 31 and the base 32 of the triangle is firmly abutted to the layer 33 of the guide rail, the side walls 35 and, in a heavy impact also the base 32, of the end section 30 are forced to deform.

Consequently the end section 30 is compressed and the force of the impact is more gradually absorbed reducing the possibility of the breaking strain of the bar 11 being exceeded at any time. The compression of the end piece absorbs the energy of the impact.

In an embodiment the bar is substantially rigid.

This has the advantage that the deformation is confined to the interior of the vertical guide rails 13.

In an example high tensile EN24T steel with a breaking load of 55 to 65 tonnes/sq.in was used. The diameter of the bar was 8mm giving a breaking strain of 2.53 tonnes per bar.

The advantage of confining deformation to the interior of the guide rails 13 by allowing end sections 30 to compress is that an impact does not lead to exposure of lengths of the bar 11 outside the skin of the lath where they would be easy to cut.

A preferred embodiment of the shutter curtain contains a proportion of the laths according to Figure 1 and a proportion of the laths according to Figure 2 or Figure 8. In one example each type of lath is provided alternately along the shutter curtain, thus providing a composite curtain which is resistant to both the forms of attack discussed above.

Claims

CLAIMS:

1. A lath for an interlocking lath shutter curtain, the lath comprising; an outer skin, interlocking means for attachment to adjacent laths, an internal void extending substantially along the length of the lath, a core provided within the void, and attachment means fixedly attached to respective ends of the core and adapted to attach the laths to vertical side guides, the attachment means being deformable to absorb force

2. A lath according to claim 1 wherein the core is substantially rigid.

3. A lath according to claim 1 or claim 2 wherein the attachment means has a base facing the centre of the lath and adapted to be wedged within a guide rail, the core being attached to the opposite end of the attachment means away from the base.

4. A lath according to claim 3 wherein the attachment means is substantially triangular and wherein the core is attached to the apex of the triangle.

5. A lath according to claims 1, 2, 3 or 4 wherein the attachment means is comprised substantially of aluminium.

6. A lath according to any one of claims 3 to 5, wherein the lath skin is attached to the base of the attachment means.

7. A lath for an interlocking lath shutter curtain, the lath comprising; an outer skin, interlocking means adapted to engage corresponding means on adjacent laths, an internal void extending substantially along the length of the lath, at least one rigid body within the void, and compression means acting to place the rigid body under compression.

8. A lath according to claim 7 wherein the compression means and the rigid body are located adjacently within the void along its length.

9. A lath according to claim 7 or claim 8 wherein the compression means is a steel spring.

10. A lath according to claim 7, 8 or 9 wherein the rigid body is made substantially of steel or of case-hardened steel or of aluminium.

11. A lath, for an interlocking lath shutter curtain, the lath comprising; an outer skin, interlocking means adapted to engage corresponding means on adjacent laths, an internal void extending substantially along the length of the lath, a linking means disposed within the void and extending along the length of the void, attachment means adapted to attach the lath to vertical side guides and fixedly attached to respective ends of the linking means, and wherein the linking means is adapted to absorb force by deformation.

12. A lath according to claim 11 wherein the linking means is a bar.

13. A lath according to claim 11 wherein the linking means is a cable.

14. A lath according to claim 11, 12 or 13 wherein the linking means is comprised of malleable steel.

15. A lath according to claim 11, 12, 13 or 14 wherein the attachment means are 'T' sections.

16. A lath according to claim 11, 12, 13, 14 or 15 wherein the attachment means are deformable.

17. An interlocking lath shutter curtain for a security shutter, having interlocked laths for running down vertical guide rails of a security shutter to a bottom rail thereof wherein at least a proportion of the laths are in accordance with any one of claims 1 to 6.

18. An interlocking lath shutter curtain for a security shutter having interlocked laths for running down vertical guide rails of a security shutter wherein at least a proportion of the laths are in accordance with any one of claims 7 to 10.

19. An interlocking lath shutter curtain for a security shutter, comprising a plurality of interlocked laths, at least a proportion of the laths being in accordance with any one of claims 11 to 16.

20. A shutter curtain apparatus comprising vertical side guides and a curtain according to claim 17 arranged to slide therethrough.

21. An interlocking lath shutter curtain according to claim 20 wherein deformation of the laths is substantially confined within vertical guide rails of the shutter.

22. Attachment means for slidably attaching a lath having a void and a linking means in the void, to the vertical guide rail of a shutter curtain apparatus, the attachment means being substantially triangular, having a base facing the centre of the lath and arranged to abut against a wall of the guide rail, and an apex to which the linking means is attachable.

23. A lath substantially in accordance with any one of the embodiments hereinbefore described with reference to the accompanying drawings.

24. A shutter curtain substantially in accordance with any one of the embodiments hereinbefore described with reference to the attached drawings.

25. A shutter curtain apparatus substantially in accordance with any one of the embodiments hereinbefore described with reference to the accompanying drawings.

26. An attachment means substantially as hereinbefore described with reference to Figures 8 and 9 of the accompanying drawings.