Patent Description:
Reference is made to International Patent Application publication number <CIT>, which describes an intruder resistant screen. <CIT> describes an intruder resistant screen including a frame comprising elongate frame members, each having a channel section engaging a respective corner stake in each end thereof. A woven wire intruder resistant mesh covers an opening enclosed by the frame. There is a clamping member co-acting with respective fasteners and each frame member to thereby clamp the mesh to the frame. The intruder resistant screen described in <CIT> is known in the market as the Crimsafe® Security System.

The Crimsafe® Security System achieves intruder resistance, at least in part, due to leveraged clamping between the clamping members and the frame members. The clamping members are held in place by fasteners that are screwed into the frame members. The clamping members extend for the full length of the frame members. To assemble the Crimsafe® Security System holes are drilled in the clamping members, mesh and frame and then screws are screwed into the frame members through the holes in the clamping members.

As far as possible the Crimsafe® Security System uses lightweight components, but the mesh is formed from woven wire. The frame members and clamping members are formed from extruded aluminium. Nonetheless, a standard sized door can be quite heavy and the effort required in construction can be taxing.

<CIT> discloses a security door system having a door that includes a door frame comprising elongate door frame members, each having a first holding channel formed therein, and a clamping portion spaced from the first holding channel. The door further includes a mesh covering and an opening enclosed by the frame. The security door system includes a wall frame comprising elongate wall frame members operably coupled to the door frame by one or more hinge members, the hinge members facilitating pivotable movement of the door between open and closed positions and one or a plurality of security members configured to prevent levering of the door relative to the wall frame.

<CIT> discloses a method of enhanced security for fixing a security screen assembly.

<CIT> discloses a countersunk head screw for the attachment of accessories and hardware on a metal wall.

The invention resides in an improved intruder resistant screen according to claim <NUM>.

The frame members are preferably extruded aluminium each having a channel section. The corner stakes suitably engage the channel sections and are held by fixing means, such as screws. The corner stakes may be injection moulded plastic or extruded aluminium.

The clamp elements are suitably carbon fibre reinforced polymer. The carbon fibre reinforced polymer is suitably injection moulded. As an alternative the clamp elements may be die cast aluminium or extruded aluminium. Each clamping member may be relatively short compared to the length of a frame member.

The fasteners are suitably self-drilling screws and preferably have a pan head or countersunk head. The thread preferably extends the length of the shank portion and the drilling portion.

Each clamping member has one or more holes for receiving corresponding fasteners. The holes are preferably countersunk.

Suitably the frame member includes a lip portion and the clamping member includes a complementary hook portion such that engagement of the clamping member to the frame member is by engagement of the complementary hook and lip portions.

In a further form, the invention resides in a method of assembling an improved intruder resistant screen according to claim <NUM>.

Further features and advantages of the present invention will become apparent from the following detailed description.

To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, in which:.

Embodiments of the present invention reside primarily in an improved intruder resistant screen. Accordingly, the elements of the screen have been illustrated in concise schematic form in the drawings, showing only those specific details that are necessary for understanding the embodiments of the present invention, but so as not to obscure the disclosure with excessive detail that will be readily apparent to those of ordinary skill in the art having the benefit of the present description.

In this specification, adjectives such as first and second, left and right, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Words such as "comprises" or "includes" are intended to define a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed, including elements that are inherent to such a process, method, article, or apparatus.

Referring to <FIG> there is a shown an intruder resistant screen <NUM> having a frame <NUM> formed from elongate frame members <NUM>. For the door shown there are four elongate frame members forming a rectangle, but other shapes are possible for specific applications. An intruder resistant mesh <NUM> is held in the frame <NUM> by a clamping system, as described below. The mesh is suitably woven from stainless steel wire as described in <CIT>. Suitable wire dimensions have been found to be anywhere between about <NUM> and <NUM>. The wire spacing (in weft or warp) is suitably anywhere from about <NUM> to <NUM>.

Referring to <FIG>, an exploded view of the intruder resistant screen <NUM> is shown to display the details of construction. An enlarged portion of <FIG> is shown in <FIG> to assist understanding. The elongate frame members <NUM> are suitably aluminium extrusions having a channel section <NUM> of a size and shape to receive a corner stake <NUM>. The elongate frame members <NUM> are cut to an appropriate length to fit the opening to be covered and are joined together by inserting the corner stakes <NUM> into the channel sections <NUM> and fixing with screws <NUM>.

The mesh <NUM> is clamped to the frame members <NUM> by a plurality of short clamp elements such as <NUM> which are held in place by self-drilling screws <NUM>. A cover <NUM> clips over the clamp elements <NUM> to provide a clean appearance. A pair of seals 27a, 27b reduce the ingress of moisture along the mesh <NUM> and thereby minimise galvanic corrosion.

As clearly seen in <FIG>, the clamp elements <NUM> are short compared to the frame members <NUM>. For instance, for a typical domestic door of dimensions <NUM> high by <NUM> wide (6ft x 3ft) there are seven clamp elements on the long side, each about <NUM> long on about <NUM> centre spacing and four clamp elements on the short side with approximately the same size and spacing. As seen on the short sides in <FIG>, the spacing may be varied to accommodate the door dimensions. Although a length of <NUM> is preferred for the clamp elements <NUM>, other lengths may also be suitable such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. Other lengths in the range <NUM> to <NUM> may be used. Similarly, other spacings may also be used in the range from <NUM> to <NUM> including but not limited to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

<FIG> displays a portion of an intruder resistant screen showing hidden detail to make clear how the elements are assembled. Clamp elements <NUM> are located adjacent each corner and additional clamp elements <NUM> are spaced along the frame member <NUM>. The location of the clamp elements <NUM> is described in greater detail by reference to <FIG>.

The construction can be seen clearly in the cut away end view of <FIG>. The elongate frame member <NUM> is extruded to include a flange <NUM> that has a serrated surface 51a with serrations that are of a size to restrain the mesh <NUM>. There is also a seal channel <NUM> that receives the seal 27a. It is convenient for the seal 27a to slide or press into the seal channel <NUM>.

The clamp element <NUM> may also have a surface 24a with serrations that are of a size to restrain the mesh <NUM>. The clamp element <NUM> engages the frame member <NUM> as described in detail below. The cover <NUM> clips onto the frame member <NUM> and the clamp element <NUM>. An edge of the cover <NUM> includes another seal channel <NUM> which receives seal 27b.

The nature and location of the clamp element <NUM> is shown more clearly in <FIG>. Part of the cover <NUM> has been removed in <FIG> to make the whole of clamp element <NUM> visible. The clamp element <NUM> is relatively short compared to the length of the elongate frame member <NUM>. This is in sharp contrast to the prior art arrangements referenced above. In the prior art system of <CIT>, for instance, the clamping member extends the full length of the elongate frame member. For the current invention there are multiple short clamp elements <NUM> distributed along the elongate frame member <NUM>, as seen in <FIG>. In the preferred embodiment, each clamp element <NUM> is made from carbon fibre reinforced polymer, aluminium extrusion or die-cast aluminium. A suitable carbon fibre reinforced polymer is obtainable from Toray Industries of Japan. However, the clamp element <NUM> may be produced from other materials with similar tensile strength and flexural strength properties. In some embodiments the clamp elements <NUM> may be aluminium or an aluminium alloy.

As seen in <FIG>, the clamp element <NUM> terminates at one edge with a hook <NUM> that is captured by a lip <NUM> formed on the elongate frame member <NUM>. The clamp element <NUM> is leveraged against the flange <NUM> to grip the mesh <NUM>. The leverage is provided by a self-drilling screw <NUM> which passes through a hole <NUM> in the clamp element <NUM> and drills through the mesh <NUM> into the flange <NUM>.

Turning now to <FIG>, it can be seen that in the preferred embodiment clamp elements <NUM> are placed close to each corner of the frame <NUM> as well as being distributed between the corners. It will be noted that in the preferred embodiment each clamp element <NUM> has more than one hole <NUM> for screw <NUM>, and suitably three holes. A length of the clamping element <NUM> of about <NUM> is sufficient to fit three holes and provide adequate clamping. For clamp elements <NUM> located near the corners of frame <NUM> it has been found to be advantageous to use the hole 62a closest to the corner but for the other clamp elements <NUM> it is preferable to use the middle hole 62b. The provision of multiple holes <NUM> is for convenience and is not essential to the invention. However, the inventor has found that having multiple holes offers advantages that result in less inventory and more flexibility in manufacturing. Which of the holes <NUM> is selected depends on the situation. For a corner fixing the hole closest to the corner is used whereas the middle hole is used for clamps away from the corner.

To fully understand the advantages of the improved intruder resistant screen, reference is made to <FIG>, <FIG> and <FIG> showing the nature and order of assembly. Looking particularly at <FIG>, the elongate frame member <NUM> comprises the channel section <NUM>. A wall <NUM> of the channel section <NUM> extends to form one side of a clamping assembly. The flange 51extends away from the wall <NUM> and includes serrated surface 51a. Extending from another wall <NUM> is a lip <NUM> having a groove <NUM> that forms a catch for the hook <NUM> of the clamp element <NUM>. At an end of wall <NUM> is a channel <NUM> that receives a seal element 27a that coacts with seal element 27b to form a seal to inhibit ingress of moisture along the mesh <NUM>. The clamp element <NUM> has a serrated surface 24a that is similar to the serrated surface 51a. A hole <NUM> in the clamp element <NUM> receives screw <NUM>. A cover <NUM> has at one side an edge <NUM> that engages a rim <NUM> on the frame member <NUM> and towards an opposite side a hook <NUM> that engages a clip <NUM> on the clamp element <NUM>. At an edge of the cover <NUM> is a channel <NUM> that receives seal element 27b.

<FIG> shows the elements of <FIG> assembled together. The hook <NUM> of the clamp element <NUM> is engaged with the lip <NUM> of the frame member <NUM>. The screw <NUM> urges the clamp element <NUM> towards the flange <NUM> so as to hold the mesh <NUM> in place by leveraged clamping. The cover <NUM> clips under the rim <NUM> and the clip <NUM>. The seal elements 27a, 27b cooperate to seal against the mesh <NUM> to inhibit ingress of moisture and therefore minimise galvanic corrosion between the stainless steel mesh and the aluminium frame. For completeness a screw <NUM> is shown holding the corner stake <NUM>. Screw <NUM> is a conventional round head metal thread screw as is known.

A sequence of assembly is shown in <FIG>. As shown in <FIG> the first step is to fit the seal element 27a, which is fitted to the channel <NUM>. Then, as seen in <FIG> the mesh <NUM> is located against the seal element 27a. The clamp element <NUM> is then located with the hook <NUM> under the lip <NUM> as shown in <FIG> and the screw <NUM> is drilled through the hole <NUM> into the flange <NUM>. The seal element 27b is fitted to the cover <NUM> which is then fitted to the elongate frame member <NUM> as shown in <FIG>, The cover <NUM> is snapped in place by pushing as showing <FIG> shows the finally assembled intruder resistant screen <NUM>.

The inventor has found that it is useful to use a screw <NUM> of the type shown in <FIG>. Unlike known screws the screw <NUM> is self-drilling with a thread 25a that extends from the head 25b to the tip 25c, including along the drill portion 25d. This screw design is unknown since it is generally considered that the drill portion 25d cannot make a contribution to the holding strength of the screw <NUM>. However, at least part of the thread in the drill portion 25d engages the flange <NUM>, thus providing additional holding strength to the intruder resistant screen <NUM>.

Also relevant is that the screw head 25b is a round head with a flat underside 25e although the hole <NUM> in the clamp element <NUM> is countersunk. It has been found that the combination of a thread on the drill portion together with a round head screw and a countersunk hole provides additional strength compared to the absence of these features. The inventors have found that flat underside 25e when seated against the countersunk part gives the required impact performance, as shown in <FIG>. They speculate that part of the extra strength is provided by the additional holding strength of the thread 25d engaging the flange <NUM>, but also that the flat underside 25e of screw head 25b with the countersunk hole <NUM> allows for additional flexure. The additional flexure permits some movement of the clamp member <NUM> before failure, thus providing additional strength against impact.

Claim 1:
An improved intruder resistant screen (<NUM>) comprising:
a frame comprising multiple elongate frame members (<NUM>) joined by corner stakes (<NUM>);
a woven wire intruder resistant mesh covering an opening enclosed by the frame;
a plurality of clamp elements (<NUM>) engaging with the elongate frame members (<NUM>) to hold the mesh by a leveraged clamping action; and
at least one fastener holding each clamping element (<NUM>) to the elongate frame member (<NUM>);
wherein there are two or more clamp elements (<NUM>) engaging each elongate frame member (<NUM>);
characterized in that: each clamp element (<NUM>) is elongate in the direction of the respective elongate frame member (<NUM>); and
each fastener has a drilling portion, a shank portion, a head and a thread.