1 SCREEN ASSEMBLY FIELD OF THE INVENTION [0001] THIS INVENTION relates to a screen assembly and in particular but not limited, a screen assembly for a door or window opening. BACKGROUND OF THE INVENTION [0002] Screen assemblies are generally used to screen insects from entering a building. Recently introduced screen assemblies have a closely woven steel screen which is strong enough so that this type of screen assemblies can serve as an insect screen and an intruder resistant screen, whiling allowing ventilation. . [0003] This type of screen assemblies have a frame formed of elongate frame members connected by corner stakes. Each frame member has an open channel for receiving corresponding edge of the woven screen. The screen is fixed to the frame members by wedging strips or clamping members. The wedging strips are forced into the open channels so that the screen edges are pressed against one the walls of the frame members. Inevitably, the wedging process causes deformation of the frame members as the walls forming the channels would be moved or tilted outwardly in order to receive the wedging strips. When fixed by clamping members, the edges of the screen are pressed by theses members and the edges are thereby deformed. The frame members are also deformed by the clamping process. [0004] The deformed screen and frame members cannot be reused. It is also difficult to remove the wedging strips and the clamping members if disassembly is required. Where the frame members are made of aluminium, in time corrosion would take place at the edges which contact with the frame members.
2 OBJECTS OF THE INVENTION [0005] An object of the present invention is to provide a screen assembly which alleviates or reduces to a certain level one or more of the above mentioned prior art problems. SUMMARY OF THE INVENTION [0006] In one aspect therefore, the present invention resides in a screen assembly comprising a frame configured to form an opening therein and a screen member arranged to cover the opening. The frame has frame members with open channel sections facing the opening. Each open channel section has a mouth between first wall and a second wall spaced from the first wall. The screen has edge portions which are positioned through the mouths into corresponding open channel sections. The edge portions are retained in position in the corresponding open channel sections by retention elements which penetrate though the first walls and the edge portions. Each of the retention elements have an enlarged head and a shaft extending from the head. The retention elements are configured so that when the head contacts said first wall the shaft is either spaced from the second wall or in contact with the second wall without penetration. [0007] Preferably, the assembly has non metallic members arranged in the open channel sections for spacing the edge portions from the frame members. The non metallic members may be plastic tapes or strips. In preference, the non metallic members are U-shaped plastic strip. [0008] The retention elements may have a threaded shaft and a head configured for engaging with a driving tool for driving the shaft through the first wall and the edge portion. The driving tool may have a driving bit for engaging a retention element and a 3 torque setting arrangement configured to be set to disengage from the driving bit when the head contacts the first wall [0009] The first wall of each frame member may have weakened zones or pre-drilled holes positioned for penetration by the retention elements. [0010] The first wall of each frame member may be formed in a recess and a removable cover strip is arranged to cover the recess. [0011] Each frame member may have a connection section outwardly of the channel section. The connection section has a passage for receiving a corner stake or spigot of an adjacent frame member. [0012] The screen may be formed of one or more woven steel wire panels or perforated metallic sheet panels. BRIEF DESCRIPTION OF THE DRAWINGS [0013] In order that the present invention may be more readily understood and be put into practical effect reference will now be made to the accompanying drawings which illustrate non-limiting preferred embodiments of the invention and wherein: Figure 1 is a schematic diagram showing an embodiment of the screen assembly according to the present invention; Figure 2 is a section view of a frame member for the assembly shown in Figure 1; Figure 3 shows the frame member in Figure 2 having retention screws; Figure 4 shows a screen about to be inserted into the frame member; and 4 Figure 5 shows the screen inserted and retained in the frame member. DETAILED DESCRIPTION OF EMBODIMENTS SHOWN IN THE DRAWINGS [0014] Referring to the drawings, and initially to Figure 1, there is shown an embodiment of the screen assembly 10 according to the present invention. The assembly has a frame 12 formed with an opening 14 therein and a screen 16 positioned to cover the opening. The screen as shown is partially cut away to reveal the opening. [0015] The frame 12 has spaced side frame members 18 and 20, a top frame member 22 and a bottom frame member 24 connected by corner stakes (not shown). Each of the frame members has a cover clip 26 which is shaped for snap fitting in a recess 28 (see Figure 4) formed in each frame member. [0016] As shown in Figure 2, each one of the frame members 18 to 24 has a lower hollow section 18 and an upper channel section 30. The hollow section has a passage 32 for receiving corner stakes or other connectors such as spigots (not shown). Raised strengthening ribs 34 are formed on the hollow section in order to improve structural strength of the frame members. The channel section 30 has a channel 36 formed between a first wall 38 in the recess 28 and a second wall 40. Corresponding edge portion of the screen is to be inserted into the channel 36 through its mouth 42. Retention screws 44 (see Figure 4) are used to retain the screen in position in the channels of the frame members. The cover clip 26 has snap fitting elements 27 for snap fitting onto correspondingly shaped grooves 46 on sides of the recess as shown in Figure 5. In this embodiment, the first wall 38 has weakened zones 48 for positioning and facilitating penetration by the screws 44. Alternatively, the weakened zones can be replaced by pre-drilled holes in the first wall.
5 [0017] Each of the retention screws 44 has an enlarged head 50 and a threaded shaft 52. The length of the shaft is configured so that when the head contacts the first wall the free end of the screw would contact the second wall without penetration. Thereby, the first wall and the second wall are not subject to any deforming action. The frame members can thus be reused. The screen can also be reused as it can be easily taken out of the channels without damage when the retention screws are removed during disassembling of the assembly. [0018] The inside face of each of the first and seconds walls 38 and 40 are serrated. The serrated faces assist in retaining a plastic or rubber strip 54 which wrapped along each of the edge portions of the screen as shown in Figure 4. An example of the strip is a 3M tape. In this embodiment the strip 54 also has serrated faces. [0019] As shown in Figure 4, the edge portions of the screen to be inserted into the corresponding channel 36 are wrapped in the strip 54. Figure 5 shows the screen 16 in the inserted position. As shown, insertion of the screen does not cause any deformation of the walls 38 and 40. [0021] A driving tool with settable torque, such as an electric or pneumatic drill, can be use to drive the screws 44. The torque for this application is set so that it would stop the driving action when the head 50 of the screw contacts the first wall 38 or when the free end of the shaft 52 contacts the second wall. Thus, there would be no deformation of the walls caused by use of such a driving tool. [0022] For disassembling, the cover clips 26 on the frame members can be removed by lifting from the recess 28 and the screw 44 unscrewed. The screen then can be separated from the frame members by pulling them away out of the screen portions. Both the frame members and the screen can be reused as they are not subject of deformation in the disassembling process.
6 [0026] Whilst the above has been given by way of illustrative example of the present invention many variations and modifications will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as herein set forth in the following claims.