GB2576170A

GB2576170A - Letter plate

Info

Publication number: GB2576170A
Application number: GB1812800.9A
Authority: GB
Inventors: Johnson Dave
Original assignee: Era Home Security Ltd
Current assignee: Era Home Security Ltd
Priority date: 2018-08-07
Filing date: 2018-08-07
Publication date: 2020-02-12
Also published as: GB201812800D0

Abstract

A letter plate 1 for fitting to a letterbox aperture in a door or wall comprises a first closure portion 110 and a second closure portion 120. The first and second closure portions close at least a portion of an opening of the letter plate and apply a biasing force to an object inserted through the opening. The first and second closure portions may apply first and second biasing forces in first and second directions respectively. The letter plate may have a mounting portion 100 to which the first and second closure portions are hingedly connected. The letter plate may comprise third 130 and fourth 140 closure portions, wherein the third and fourth closure portion impede access through the opening to regions lateral of the letter plate. The third and fourth closure portions may be hingedly connected to the mounting portion such that they are located adjacent to the shortest edges of the opening. The hinge axes of the third and fourth closure portions may be parallel to each other and/or perpendicular to the hinge axes of the first and second closure portions. The letter plate aims to prevent thieves gaining access to an internal region of a building to steal objects.

Description

Letter Plate

Technical Field

The invention relates to a letter plate assembly for a door or wall for domestic or commercial installations.

Background

Letter plate assemblies are commonly fitted to doors or to parts of a skin of a building adjacent to a door for both domestic and commercial buildings in order to permit the delivery of post. Conventional letter plate assemblies comprise a letterbox aperture through the door, wall, or other area of the building skin. Letter plate assemblies typically comprise one or more pivoting letter flaps for closing the letterbox aperture. Exemplary letter plate assemblies comprise an external letter flap on an outer surface of the door and an internal letter flap on an inner surface of the door. The internal letter flap typically pivots inwards towards an internal region of the building.

It is known to provide security measures to reduce the risk of thieves gaining access to an internal region of a building to steal objects from a building by way of a letterbox aperture in a door. Such measures include security cowls that may be fitted to an internal side of a door over an internal letter flap, partially covering a letterbox aperture. The security cowls are configured to allow letters and other post to be delivered through the letterbox aperture, but to restrict access for a thief or other intruder to an interior region of a building above and to the side of the letterbox aperture. For example, thieves are known to insert a wire hook or rod through a letterbox opening to attempt to steal high value items, especially keys. Such attacks are known as “fishing”.

Summary

DHF Technical Specification TS008:2015 sets out a number of stringent criteria in order for letterboxes and letter plate assemblies to obtain their highest classification. In particular, a fishing test involves a test engineer attempting to pierce a target positioned in a specified region of the interior of the building through the letterbox aperture within 5 minutes. Should the target be successfully pierced then the target is replaced with a

75g weight and the test engineer is tasked with retrieval of the weight through the letter plate.

Many of the existing security products which conform to TS008:2015 suffer from poor aesthetics and are large and bulky, and are often removed by homeowners thus removing all security benefits.

The exemplary apparatus disclosed herein aim to solve or mitigate one or more problems with the prior art, including those discussed or arising from the above.

According to a first aspect of the invention, there is provided a letter plate for fitting to a letterbox aperture in a door or wall. The letter plate may comprise a first closure portion. The letter plate may comprise a second closure portion. The first and second closure portion define an opening therebetween. The first and second closure portions may be configured to close at least a portion of the opening. The first and/or second closure portions may be configured to apply a biasing force to an object inserted through the opening.

The letter plate may be an internal letter plate. For example, the letter plate may be configured to be fittable to a letterbox aperture on the interior side of a door or wall. A letterbox aperture typically extends horizontally through a wall or door as is well established in the art to allow items of mail to be delivered therethrough. The letter plate may comprise one or more mechanical fastener for attaching the letter plate to the wall or door. The mechanical fastener may connect to and/or engage with the mounting portion.

The letter plate according to the first aspect is particularly advantageous since it prevents or restricts the ability for attackers to steal items by inserting a tool through the letterbox aperture, what is typically known as ‘fishing’.

The first and/or second closure portions may be movable, e.g. hingedly movable. The first and/or second closure portions may be movable between a closed position wherein they close at least a portion of the opening and an open position wherein they do not close, or wherein they close a smaller area of, the opening. The first and/or second closure portions may comprise a biasing means. The biasing means may be configured to bias the first and/or second closure portions into their respective closed positions. The movement may be a rotation about a hinge, for example. The first and/or second closure portion may comprise a flap.

The first closure portion may be configured to apply a first biasing force in a first direction. The second closure portion may be configured to apply a second biasing force in a second direction. The first and second directions may be different to each other, and optionally, may be approximately opposite to each other. The first and second directions may be approximately upward and downward. The biasing forces may be the result of the rotation of the closure portions.

The first and second closure portions may apply the first and second biasing forces independently of each other. The first and second biasing force may be the same magnitude, or they may be different.

The letter plate may further comprise a sleeve. The sleeve may be configured to be inserted into a letterbox aperture in a wall or door. The sleeve may be configured to line the letterbox aperture i.e. to form at least part of the inner surface thereof. The sleeve may define at least part of a first channel. The mouth of the first channel may be the opening in the mounting portion. The sleeve may extend perpendicularly from the mounting portion. The sleeve may have an approximately rectangular cross section, and/or the first channel defined by the sleeve may have an approximately rectangular cross section. The sleeve may provide a simple way to align the letterplate with a letterbox aperture during installation and/or may provide weather resistance and restrict water ingress through the letterbox aperture.

The first and second closure portions may form or define opposite edges of the opening. Optionally, the first and second closure portions may form or define the longest edges of the opening. The first and second closure portions may have hinge axes parallel to the longest dimension of the opening, for example, the width of the opening. The first and second edges may be the longest edges of the opening. In use, the first and second edges may extend approximately horizontally.

The letter plate may further comprise a mounting portion fittable to the surface of a door or wall. The first and second closure portions may be hingedly connected to the mounting portion. In some embodiments, the opening may extend through the mounting portion and/or the mounting portion may extend at least partially around the opening.

The mounting portion may be fittable to a surface of a door or wall. The first and second closure portions may be hingedly connected to the mounting portion

The letter plate may further comprise a third closure portion and a fourth closure portion. The third and fourth closure portions may be configured to impede access through the opening to regions lateral of the letter plate.

The third and fourth closure portions may be hingedly connected to the mounting portion. The mounting portion may be configured so that the third and fourth closure portions are located adjacent to the shortest edges of the opening. The third and/or fourth closure portion may comprise a flap.

The hinge axes of the third and fourth closure portions may be parallel to each other and/or perpendicular to the hinge axes of the first and second closure portions.

The third and fourth closure portions may be configured to at least partially overlap the first and second closure portions when in the closed position.

The letter plate may further comprise limiting means configured to limit the movement of the first and/or second closure portion. The letter plate may further comprise limiting means configured to limit the movement of the third and/or fourth closure portion. The limiting means may comprise a block to physically limit movement. The limiting means may comprise a projection or cam on one or more of the first to fourth closure portions. The limiting means may be provided by a surface or edge of an adjacent part of the letter plate or other door furniture.

According to a second aspect of the invention, there is provided a letter plate assembly comprising a letter plate as previously described herein, and a housing. The letter plate may be attachable to a door or wall surface in use. The housing may be configured to be positioned over the letter plate and attachable to a door or wall surface.

The housing may comprise fasteners for engaging a door or wall surface adjacent to the letter plate. The housing may be attachable to the door or wall independently of the letter plate. In some embodiments, there may be no physical and/or mechanical connection between the housing and the letter plate e.g. the letter plate is freely retained within the housing.

The housing may be configured so that when installed, removal of the letter plate is restricted. By ‘installed’ it is intended that the housing is positioned over the letter plate and attached to a wall or door surface. In some embodiments, the housing portion may be configured to prevent removal of the mounting portion. The housing may be configured to cover or prevent access to the mechanical fastener(s) in the letter plate and/or mounting portion. The housing may be configured to substantially surround the letter plate. For example, the housing may comprise a volume for receiving the letter plate. The housing may be configured so that when installed, the letter plate is received in the volume and cannot be removed from the volume until the housing has been removed or detached from the door or wall surface.

In use, the housing may be configured to prevent removal of the letter plate and/or retain the letter plate therein if the attachment of the letter plate to the door or wall surface is broken or compromised. In some embodiments, the volume for receiving the letter plate may be larger than the letter plate. Thus, should the attachment of the letter plate to the door or wall be compromised, the letter plate would be able to move within the housing, but not be removed or extracted therefrom.

The housing may be configured to restrict the movement of one or more of the first or second closure portions if the attachment of the letter plate to the door or wall surface is broken or compromised. The housing may be configured to restrict the movement of one or more of the third or fourth closure portions if the attachment of the letter plate to the door or wall surface is broken or compromised.

The letter plate assembly may be configured so that the letter plate would become misaligned with the housing and one or more of the first to fourth closure portions would be prevented from moving by the housing.

The housing may comprise a housing aperture. The housing aperture may be configured so that when installed, the housing aperture is offset from the opening in the letter plate. For example, centre of the housing aperture may be offset relative to the centre of the opening. The housing aperture may be offset in a direction perpendicular to the plane of the opening. The opening and the housing aperture may be aligned for example, the opening and the housing aperture may together define at least part of a second channel which extends through the letter plate assembly. The housing aperture may be offset from the mounting portion.

The letter plate assembly may be configured so that if the attachment of the letter plate to the wall or door is compromised, the letter plate opening and the housing aperture may become misaligned. For example, the housing may be configured so that the letter plate can drop within the housing when the attachment is broken. When the letter plate attachment is broken, one or more of the first to fourth closure portion may become misaligned. When misaligned, the first to fourth closure portion may bear on the housing and be restricted from movement. In some embodiments, the third and/or fourth closure portions may be misaligned with the housing aperture, and/or be unable to extend through the housing aperture.

In embodiments comprising a sleeve, the first and second channel may be coaxial and/or continuous.

Optionally, the housing aperture may have a smaller area than the opening. The area may be defined as the cross-sectional area relative to the axis of the second channel.

The housing may form part of, or may comprise, a or the limiting means. The housing may be configured to restrict and/or limit the movement of any one or more of the first to fourth closure portions.

The housing may be configured to restrict the movement of the first and/or second closure portion. The housing may thus define the open position of the first and/or second closure portion. In the open position, the first and/or second closure portion may contact an inner surface of the housing. The housing and/or the first and/or second closure portions may be configured so that when the first and/or second closure portion are in the open position, they do not obstruct the opening.

The housing may be configured to restrict the movement of the third and/or fourth closure portion. The third and/or fourth closure portion may be configured to extend through the housing aperture when in the open position. The limiting means may comprise the perimeter of the housing aperture.

The housing may be configured to restrict the range of motion of the third and/or fourth closure portion to less than 90° e.g. between closed and open positions. In the closed position, the third and fourth closure portions may be coplanar and/or parallel to the plane of the opening. The housing may be configured to limit the open position so that the third and fourth closure portions are angled inwardly i.e. the leading edges of the closure portions are closer together than the hinged edges. The housing may be configured so that when in the open position, the angle between the plane of the opening and the third and/or fourth closure portion is less than 90°. When in the open position, the third and fourth may lie in or define coincident planes.

The housing may be configured to project from the surface of the door or wall by a distance less than or equal to the projection from the surface of a door handle or doorknob. For example, the housing may project from the surface of the door or wall by less than 50mm, and optionally less than 45mm or 40mm.

According to a third aspect of the invention, there is provided a security device for fitting to a door or wall comprising a letterbox aperture, the security device comprising a letter plate substantially as described herein or a letter plate assembly substantially as described herein, said letter plate or letter plate assembly for fitting to an internal side of the door or wall, the security device further comprising an external letter plate.

The security device may further comprise at least one mechanical fastener configured to extend through the door or wall and connect the letter plate and the external letter plate. In some embodiments, one or more of the at least one mechanical fasteners may extend through the letterbox aperture. In some embodiments, the at least one mechanical fastener may extend through a hole through the door or wall adjacent to the letterbox aperture.

The above described letter plate, letter plate assembly and security device are advantageous, since it is possible to provide a device which conforms to TS008:2015.

The first and second closure portions can apply a force to a ‘fishing’ tool, and thus make it difficult for an attacker to steal valuable items. The biasing force of the first and/or second closure portions thus prevents an attacker from controlling the fishing tool effectively.

A further advantage is that the letter plate, letter plate assembly and security device can be installed with a lower profile i.e. the components on the internal side or the door or wall surface project only a small distance. Such low profile assemblies are aesthetically pleasing, and reduce damage to adjacent walls caused due to the swing of the door. In some embodiments, the cowl can be configured to extend less than a conventional door handle, and thus the cowl will not strike adjacent surfaces. Subsequently, users are less likely to remove the cowl from their doors.

Brief Description of the Figures

Embodiments of the invention will now be described with reference to the following Figures in which:

Figure 1 is a perspective view of a security device;

Figure 2 is an exploded perspective view of a security device;

Figure 3 is a perspective view of a letter plate;

Figure 4 is a front view of a letter plate;

Figure 5 is a perspective view of a letter plate in an open position;

Figure 6 is a rear view of a letter plate;

Figure 7 is a front view of a security device;

Figure 8 is a top view of a security device;

Figure 9 is a cross section through the line A-A of Figure 7;

Figure 10 is a perspective view of a security device in an open position;

Figure 11 is a front view of a security device in an open position;

Figure 12 is a cross section through the line B-B of Figure 11; and

Figure 13 is a cross section through the line C-C of Figure 11.

Specific Description

Generally, disclosed herein are methods and apparatus for providing increased security to doors comprising letterbox apertures and letter plates. The methods and apparatus disclosed aim to provide a letter plate, letter plate assembly and security device having greater resistance to security threats and with a lower profile than known security cowls.

Figures 1 and 2 show a perspective view of a security device 10 in an assembled and exploded view. The security device 10 is formed from a letter plate 1, a housing 2 and an external letter plate 3. When installed, the letter plate 1 and external letter plate 3 will be mounted on opposite sides of a door or wall, so that the door or wall is sandwiched therebetween. The housing 2 is then mountable over the letter plate 1.

Turning now to Figures 3 to 5, there are shown a perspective and front view of a letter plate 1, and a perspective view of the letter plate 1 in an open position. The letter plate 1 comprises a mounting portion 100, a first closure portion 110 and a second closure portion 120. The first closure portion 110 and the second closure portion 120 define an opening between them.

The mounting portion 100 is substantially rectangular, and has a width W and height H larger than a conventional letterbox aperture. The mounting portion 100 is provided with a central opening which is formed at least partly by the opening defined by the first and second closure portions and which is configured to be aligned with a letterbox aperture in a door or wall. Each side 101, 102 of the mounting portion 100 is connected by elongate first and second rail portions 103, 104. The sides 101, 102 are mirror images of each other. The sides 101, 102, and the rail portions 103, 104 sit flush against the surface of a door or wall to which the mounting portion 100 is to be fitted.

The first and second closure portions 110, 120 are movable flaps. The first closure portion 110 is elongate and configured to extend widthwise across mounting portion 100 i.e. across the longest dimension of the mounting portion 100 and parallel to the first rail portion 103. Similarly, the second closure portion is elongate and extends widthwise across the mounting portion 100 and parallel to the second rail portion. The first and second closure portions are formed of a barrel section 111, 121 and a body portion 112, 122. The barrel portions 111, 121 each house a pair of hinge pins (not shown) in each end adjacent to and extending into the sides 101, 102 of the mounting portion 100. The hinge pins comprise torsion springs to apply a biasing force to the first and second closure portions 110, 120. In alternative embodiments a single elongate hinge pin may be used extending the length of each closure portion 110, 120 with each end being received in the sides 101, 102. The body portions 112 and 122 are substantially plate-like, and have reinforced leading edges 113, 123. The leading edges 113, 123 have a rounded shape, and the body portions 112, 122 have a gently curved profile extending between the leading edges 112, 123 and the barrel portions 111, 121.

The first and second closure portions 110, 120 are configured to extend largely across the full height H of the mounting portion 100. The leading edges 113, 123 of the closure portions 110, 120 meet in a central region of the mounting portion 100 to cover and substantially close the central opening within the mounting portion 100.

As best shown in Figure 5, the letter plate 1 is also provided with third and fourth closure portions 130, 140, each mounted on a side 101, 102 of the mounting portion 100. The third and fourth closure portions 130, 140 are approximately T-shaped, with a main body portion 131, 141 a pair of arm portions 132, 133, 142, 143 and a barrel portion 134, 144 extending along the third and fourth closure portions 130, 140 in the height direction H. The barrel portions 134, 144, receive a hinge pin 135, 145 which extends through corresponding side barrel portions 136, 146 located on the sides 101, 102 of the mounting portion 100. The barrel portions 134, 144 and the side barrel portions 136, 146 are aligned and thus form a hinge barrel connecting the third and fourth closure portions 130, 140 to the mounting portion 100. In an approximately central position of the hinge barrel are provided torsion springs 137, 147 to apply a biasing force to the third and fourth closure portions 130, 140.

The third and fourth closure portions 130, 140 are smaller than the first and second closure portions, and as shown in Figures 3 and 4, overlap across an approximately central region relative to the height H of the mounting portion 100.

Turning now to Figure 6, the rear of the letter plate 1 is shown. The sides 101, 102 and first and second rails 103, 104 form a back plate 109 for positioning against a door or wall surface. Projecting from the back plate 109 is a sleeve 105 which extends in the depth direction D transverse to the height H and width W of the mounting portion 100. The depth D is in the same direction as (and preferably parallel to) the axis of a letterbox aperture in a door or wall. The sleeve 105 is thus configured to extend into a door or wall to which the letter plate 1 is to be fitted and thus form an inner lining of a letterbox aperture. The sleeve 105 thus allows for easy location of the letter plate 1 in a letterbox aperture. The sleeve is shaped to have a curved rectangular cross section in order to minimise hard edges and corners on which items of mail could become caught or snagged. The dimensions of the sleeve 105 are configured to conform to the necessary standards and permit the passage of an item of standard mail.

The sleeve 105 extends to the back plate 109 and thus the central opening of the mounting portion 100. A small space is formed between the back plate 109 and the first and second closure portions 110, 120 in which can be provided weather seals such as brush seals (not shown) to close off the open end of the sleeve 105.

As best shown in Figure 2, the letter plate 1 is provided with four mechanical fasteners 107A-D which extend parallel to the sleeve 105 through fastener channels 108A. As shown, the mechanical fasteners 107A-D are screws or bolts, the head of which are retained by the back plate 109 (see Figure 5). In some embodiments, the mechanical fasteners 107A-D can be driven into the door or wall surface to retain the letter plate in place. Alternatively, for doors which comprise a relatively thin skin, such as UPVC doors, expansion nuts can be provided to receive the ends of the mechanical fasteners 107A-D. Even more preferred is for the mechanical fasteners 107A-D to engage anchor points 108B provided on the external letter plate 3 or a frame (not shown) provided on the external surface of the door or wall.

As shown in Figures 3 and 4, the first to fourth closure portions 110, 120, 130, 140 are in the closed position. Turning now to Figure 5, the first to fourth closure portions 110, 120, 130, 140 are in the open positions. Each of the closure portions 110, 120, 130, 140 has pivoted around their respective hinge pins to extend away from the mounting portion 110 in a direction opposite to the sleeve 105. Each of the closure portions comprises a biasing mechanism such as hinge pins (not shown) in the first and second closure portion 110, 120 or torsion springs 137, 147. Thus in the default state, the closure portions 110, 120, 130, 140 close the central opening and thus the sleeve 105.

Turning now to Figures 7 and 8, there is shown an assembled letter plate assembly in a front on and top view. Figure 9 shows a cross section through the line A-A of Figure 7.

In Figure 7, there is further shown a housing 2 located over the top of the letter plate 1. The housing has a first (upper) face 201, a second (front) face 202 and a third face 203. The second face 202 is joined to each of the first and third faces by first and second angled faces respectively 204, 205 to give a trapezium shaped cross section. The first face 201 and the third face project approximately perpendicularly from the surface of the wall or door. The second (front) face 202 is approximately parallel to the surface of the door or wall to which the housing 2 is fitted, and thus is offset from the surface of the door or wall. The faces 201-205 are typically formed from a sheet material, such as a metal sheet material in order to form a hollow box structure.

The housing 2 has a width W greater than the width W of the letter plate 1 and has housing sides 210, 212 at the lateral ends of the housing 2. The housing sides 210, 212 are provided with rear faces 215, 217 so as to form a complete loop. Preferably the rear faces 215, 217 are formed by bending tab portions extending from the first and third faces 201, 203. The housing sides 210, 212 are closed off by end caps 211, 213. The height H' of the housing 2 is greater than the height H of the letter plate 1. The rear faces 215, 217 are only provided at the housing sides 210, 212 and do not extend behind the letter plate 1, thus allowing the housing 2 to be directly fitted to the door or wall surface over the top of the letter plate 1.

The housing sides 210, 212 are connectable to the door or wall surface immediately adjacent to the sides 101, 102 of the mounting portion 100. Each of the housing sides 210, 212 are provided with a pair of mechanical fasteners 221 which extend from the rear faces 215, 217. The mechanical fasteners are preferably screws or bolts and configured to extend into the door or wall to which the housing is mounted. The mechanical fasteners 221 can either engage directly with the door or wall, or may be further provided with expansion nuts for engaging with thin skin materials. The mechanical fasteners 221 can be driven by a tool through fastener holes 219 in the second face 202, which can be closed off with fastener caps 220

In some embodiments, the housing sides 210, 212 may be reinforced, and could form a solid block. In such embodiments the mechanical fasteners can engage the second face 202 and extend through into the door or wall, or they may be held within a recess between the second face 202 and the rear faces 215, 217.

With additional reference to Figure 9, the second (front) surface 202 is provided with a housing aperture 216. The housing aperture 216 is aligned with the sleeve 105 of the letter plate 1 so as to define a passageway through which items of mail can be passed. Because the housing aperture 216 is offset from the surface of the door or wall, the length of the passageway from the exterior of the door or wall to the housing aperture 216 is significantly greater than if the housing 2 was not provided. The combination of the letter plate 1 and the housing 2 thus forms a letter plate assembly 10 which provides a significant restriction to access through the letterbox aperture without preventing mail be posted therethrough.

Figures 8 and 9 also show an external letter plate 3 connected to the letter plate 1 and fixable to an exterior side of a wall surface. Preferably the external letter plate 3 is provided with an inner sleeve 31 which is received within the sleeve 105 of the letter plate 1.

The installation of the letter plate assembly 10 is relatively simple. Firstly, if a letterbox aperture is not already provided, it must be formed in the door or wall by any suitable method. The sleeve portion 105 of the letter plate is then inserted into the letterbox aperture in order to quickly align the letter plate 1. Either the mechanical fasteners 107A-D are driven into the wall or door to secure it in place, or an external letter plate is provided on the opposite side of the door or wall and the fasteners 107A-D thus engage appropriate formations therein. Preferably the external letter plate is provided with an external sleeve which fits either within or around the outside of the sleeve 105 in a telescoping manner so as to provide a level of adjustability for different thicknesses of doors or walls. The housing 2 is then located over the top of the letter plate 1 and aligned so that the top and bottom edges of the letter plate 1 are received within and flush to the first 201 and third surfaces 203 of the housing 2. The fasteners 221 are then driven into the wall or door adjacent to the letterbox aperture and the whole assembly is installed.

The advantages of the invention will now be described with further reference to Figures 10 to 13.

Door and Hardware Federation TS008:2015 sets out a number of criteria for letter plate assemblies sold in the UK. In section 6.3.7 and as shown in Figure 4 of TS008:2015, one criteria is that the letter plate assembly must be able to withstand a manipulation test from a “fishing” type attack. This includes from an elongate rod to reach a target a specified distance from the letterbox aperture and from a curved tool attempting to reach through and around the internal letterplate to actuate a door handle.

Figure 10 shows the letter plate assembly from the internal side of a building with the flaps in their respective open positions. When an item of mail, or alternatively a fishing tool, is inserted into the security device, it will press against the first and second closure portions. The first and second closure portions in turn press against the inner surfaces of the third and fourth closure portions. Thus, all four closure portions are driven into their respective open positions, with the third and fourth closure portions projecting through the housing aperture.

Turning to Figure 12, with the third and fourth closure portions in the open position, access to regions adjacent to the letter plate on the internal side of the security device are restricted as shown by the line Z-Z. Because the flaps extend through the housing aperture and butt against the perimeter, they can open no further than the positions shown in Figure 12. This prevents a manipulation tool from being inserted through the security device to actuate a lock cylinder (provided with a thumb turn for example).

Turning to Figure 13, the lines X-X and Y-Y show the limits of accessibility through the security device. Since the fishing attacks are tested with an elongate linear tool, the line Y-Y shows the limit for the upward angle through the security device, and similarly X-X shows the maximum downward angle. This restriction drastically limits an attacker’s accessible region, while simultaneously would leave an item of mail inserted broadly horizontally unaffected.

More advantageously, the first and second closure portions are biased by springs into their closed positions, as discussed previously. Thus, when a tool is inserted through the security device, the first and second closure portions apply a biasing force to the tool. In Figure 13, the forces would be approximately upwardly and downwardly. These forces make controlling a fishing tool difficult, and means that an attacker can no longer accurately hook an item such as a pair of keys through the letter box. The forces of the first and second closure portion can be selected to be different so as to apply an imbalanced force and further increase the difficulty of controlling the fishing tool. A further advantage to this arrangement is that as the first and second closure portions rotate, their leading edge moves away from the mounting portion. Unless the fishing tool is held equidistant between the first and second closure portions, the first and second closure portions will have been opened by different amounts. Thus, the positions where the leading edges of the first and second closure portions contact a fishing tool are unlikely to be directly opposite to each other. The effect of this is that the forces apply a shear or twisting force to the fishing tool. This force is applied a large distance away from the exterior letter plate (where an attacker would be holding the tool) and thus the overall net effect is a tool which is very hard to control. Thus, attackers are considerably slowed and unable to obtain valuables and keys without detection.

A further advantage is provided by the way the housing and the letter plate interact. The letter plate is received within the housing, and when installed the first to fourth closure portions open without hindrance. An attacker may choose to break off the exterior letter plate (with a crowbar for example) in an attempt to improve their access through the letterbox aperture. As described above, in some embodiments the letter plate and external letter plate are fixed in position by mechanical fasteners which extend between the two plates. Thus, by breaking the external letter plate, the letter plate on the internal side of the door or wall is no longer reliably fixed in position. Typically, it will drop slightly under the effect of gravity. Because the letter plate is retained loosely within the housing, it remains approximately in position. However, when the letter plate drops, the third and fourth closure portion are no longer aligned with the housing aperture, and are thus prevented from opening by the arm portions 132, 133, 142, 143 contacting the inner surface of the housing such as the first and second angled faces 204, 205. The attacker is then unable to access the interior of the building at all unless they hold the letter plate in alignment, thus losing a hand with which to control the fishing tool.

The overall effect is of a security device which greatly reduces the likelihood of valuables being swiftly or easily stolen by way of either fishing or a manipulation attack of the lock cylinder itself.

Claims

CLAIMS:

1. A letter plate for fitting to a letterbox aperture in a door or wall, the letter plate comprising:

a first closure portion and a second closure portion defining an opening therebetween, and configured to close at least a portion of the opening, wherein the first and second closure portions are configured to apply a biasing force to an object inserted through the opening.

2. The letter plate according to claim 1, wherein the first closure portion is configured to apply a first biasing force in a first direction, and wherein the second closure portion is configured to apply a second biasing force in a second direction.

3. The letter plate according to claim 2, wherein the first and second closure portions apply the first and second biasing forces independently of each other.

4. The letter plate according to any one of the preceding claims, wherein the first and second closure portions form opposite edges of the opening.

5. The letter plate according to any one of the preceding claims, wherein the first and second closure portions have hinge axes parallel to the longest dimension of the opening.

6. The letter plate according to any one of the preceding claims, further comprising a mounting portion fittable to the surface of a door or wall, and wherein the first and second closure portions are hingedly connected to the mounting portion.

7. The letter plate according to claim 6, wherein the opening extends through the mounting portion and/or the mounting portion extends at least partially around the opening.

8. The letter plate according to any one of the preceding claims, further comprising a third closure portion and a fourth closure portion, wherein the third and fourth closure portions are configured to impede access through the opening to regions lateral of the letter plate.

9. The letter plate according to claim 8, when dependent on claim 6 or 7, wherein the third and fourth closure portions are hingedly connected to the mounting portion, and wherein the mounting portion is configured so that the third and fourth closure portions are located adjacent to the shortest edges of the opening.

10. The letter plate according to claim 8 or 9, wherein the hinge axes of the third and fourth closure portions are parallel to each other and/or perpendicular to the hinge axes of the first and second closure portions.

11. The letter plate according to any one of the preceding claims, further comprising limiting means configured to limit the movement of the first and/or second closure portion.

12. The letter plate according to claim 8, or any claim dependent thereon, further comprising limiting means configured to limit the movement of the third and/or fourth closure portion.

13. A letter plate assembly comprising:

a letter plate according to any one of the preceding claims, the letter plate attachable to a door or wall surface in use, and a housing configured to be positioned over the letter plate and attachable to a door or wall surface.

14. The letter plate assembly according to claim 13, wherein the housing is configured so that when installed, removal of the letter plate is restricted.

15. The letter plate assembly according to claim 13 or 14, wherein in use the housing is configured to prevent removal of the letter plate and/or retain the letter plate therein if the attachment of the letter plate to the door or wall surface is broken or compromised.

16. The letter plate assembly according to any one of claims 13 to 15, wherein the housing is configured to restrict the movement of one or more of the first or second closure portions if the attachment of the letter plate to the door or wall surface is broken or compromised.

17. The letter plate assembly according to any one of claims 13 to 16, when dependent on claim 8, wherein the housing is configured to restrict the movement of one or more of the third or fourth closure portions if the attachment of the letter plate to the door or wall surface is broken or compromised.

18. The letter plate assembly according to any one of claims 13 to 17, wherein the housing comprises a housing aperture, configured so that when installed, the housing aperture is offset from the opening in the letter plate.

19. The letter plate assembly according to claim 18, wherein the housing aperture has a smaller area than the opening.

20. The letter plate according to any one of claims 13 to 19, wherein the housing is configured to restrict the movement of one or both of the first and second closure portions.

21. The letter plate according to any one of claims 13 to 20, when dependent on claim 8, wherein the housing is configured to restrict the movement of the third and/or fourth closure portion.

22. The letter plate assembly according to claim 21, wherein the housing is configured to restrict the range of motion of the third and fourth closure portions to less than 90°.

23. The letter plate according to any one of claims 13 to 22, when dependent upon claim 8, wherein when in the open position, the third and fourth closure portions are angled inwardly so that the leading edges of the third and fourth closure portions are closer together than the hinged edges.

24. The letter plate assembly according to any one of claims 13 to 23, wherein the housing projects from the surface of the door or wall by a distance less than or equal to the projection from the surface of a door handle or doorknob. 5

25. A security device for fitting to a door or wall comprising a letterbox aperture, the security device comprising a letter plate according to any one of claims 1 to 12 or a letter plate assembly according to any one of claims 13 to 24 said letter plate or letter plate assembly for fitting to an internal side of the door or wall, and 10 an external letter plate.

26. The security device according to claim 25, further comprising at least one mechanical fastener configured to extend through a door or wall and connect the letter plate and the external letter plate.