FIXING SYSTEM

Abstract: The invention discloses a system for fixing two components together utilising undercut recesses (14) and headed or expandable plugs. Special tools (11) for forming the undercut recesses are disclosed. The undercut recess is formed by forming a straight walled cylindrical recess (12) and then moving the tool laterally to form single or multiple keyways or circular undercut recesses (14).

Description: "FIXING SYSTEM" THIS INVENTION relates to a system for fixing two components together. It is particularly useful for fixing slabs or panels to surfaces and particularly vertical surfaces. There are innumerable methods for fixing slabs - marble, granite, ceramic tiles, concrete, aluminium and other metals, or timber - to any surface. But the cost of fixing slabs to buildings is high because of the ever- increasing cost of site labour. In addition, each material poses its own special problem in the application of the fixing elements to the slabs. The site fixing cost can only be reduced by a system which provides PRECISE and SYNCHRONISED fixing elements on both the surfaces to which the slabs have to be fixed, and the slabs " themselves. Test panel installations done with aluminium, lightweight concrete, marble and granite slabs indicate a substantial site-labour saving which could, in many instances, be over 50%. The factory operation is simple, fast and more foolproof than the welding, gluing or drilling presently being done in the workshops. A known method which well illustrates and which attempts to overcome the problem is the fixing of big ceramic tiles to an aluminium frame, which is fastened to a building and which corresponds with the fasteners attached to the tiles. These fasteners are factory-fixed to the tiles in a separate firing process. Whilst the system works well with these special tiles, it would be hard to adapt it economically to granite slabs or aluminium panels. Today, gluing is an obvious method for fixing fasteners to slabs, but the accurate gluing on of fixing points to panels on site presents a number of technical problems, and the same applies to welding or screwing them on. Anything protruding from the slabs as .a result of fixing in the factory creates extra cost in packing and transport. Even the above described fixing system for tiles has this disadvantage. The present invention provides a system which can be used for fixing flat materials to each other or for fixing slabs to walls or ceilings and ■ allows the fixing of fasteners, on site, to any material, into anchorage points provided in the factory in a precision operation where exact, and adjustable r drill positions and movements determine the location and depth of the anchorage points. Thus the present invention resides in a system for fixing two components together utilising a headed fixing member or an expanding plug and an undercut recess formed in one of the components, the head of the headed fixing member or the expanded portion of the plug being of a shape and dimension complementary to the undercut, and the fixing being concealed with respect to at least one of the components characterised in that:- (1) The undercut is formed by (a) forming a straight walled cylindrical recess at a predetermined location in one of the components away from the periphery of the component with a hole forming tool, (b) moving the hole forming tool laterally with respect to the axis of the recess to form an undercut portion, and (c) returning the tool to the recess and withdrawing it vertically; and (2} The head of the fixing member or the expanding portion of the plug is inserted into the cylindrical recess and moved laterally to engage the undercut, the fixing member or plug being fixed to the other component by any suitable means either before or after the engagement of the head on the plug with the undercut portion. The invention will be better understood by reference to the following description when read in conjunction with the accompanying diagrammatic drawings wherein:- Figs la, lb, and lc illustrate the forming of the undercut recess; Figs laa, lbb, and lcc are plan views corresponding to Figs la, lb and lc; Figs 2a and 2b show the positioning of the fixing member; Figs 3a and 3b show fixing of two slab-like components together; Figs 3aa and 3bb are plan views corresponding to Figs 3a and 3b; Fig 4 shows one means to prevent tilting of the hole forming tool; and controlling depth when a manual tool is used; Fig 5 is an elevation partly sectioned of one form of hole forming tool suitable for the purposes of this invention; Fig 6 is an elevation partly sectioned of an alternative form of tool; Fig 7 is an elevation partly sectioned of a further alternative form of tool; Fig 8 is an elevation of a fourth form of tool; Fig 9 is an end view of the upper end of the tool of Fig 8; Fig 10 is an end view of the lower end of the tool of Fig 8; Figs 11, 12 and 13 are plan views showing alternative arrangements of undercuts; Fig 14 is a fragmentary sectional elevation showing the use of a protective collar; and Figs 15a and 15b are sectional elevations showing one form of a fixing member. By using drill bits specifically desired for each material, it is possible to produce an undercut recess in any material, the steps being: i) Penetration the material from the back face 10 with a special hole forming tool or drill 11, to form a cylindrical walled recess 12 without damaging the visible face of the material as shown in Figures la and laa; ii) When a predetermined depth is reached by the drill, moving the tool sideways in a predetermined direction and for a predetermined distance - the shape of the tool creates an undercut 14 as shown in Figures lb and Ibb; iii) Returning the tool to the original position and lifting it out of the hole as shown in Figures lc and lcc. Referring now to Figures 5, 6, and 7 the hole forming tool comprises a shank 21 provided at its lower end with a frusto-conical portion 22 the side and end face being covered with diamond particles or other suitable abrasive material. The nature of the abrasive material used will depend on the degree of hardness of the slab. The end face 23 of the tool shown in Figure 5 is flat. As shown in Figure 6 it may be concave or it may be concave as shown in Figure 7 (the degree of concavity shown in the drawings being exaggerated for the sake of clarity) . Instead of covering the working surfaces of the tool as in the tool of Figures 5, 6 and 7 the abrasive material may be applied in the form of strips on the side face and end face of the tool. In the embodiment of the tool shown in Figures 8, 9 and 10 of the drawings the frusto-conical portion 31 is substantially hollow and is divided into three by radial slots 32. Both the inner and outer faces of the tool are coated with abrasive material. With the initial operation of the tool the recess will have a vertical wall with a conical portjion in the centre. When lateral pressure is applied to the tool it will be evident that the wall will be undercut in the direction of the lateral pressure whilst the height of the central conical portion will be reduced. By applying lateral pressure in the opposite direction a further portion of the recess wall will be undercut and the remainder of the conical portion will be cut away. An accurately shaped plug or fixing member is provided for each keyway. One such plug 34 is shown in Figures' 2a and 2b of the drawings. The plug is provided with a portion 35 which is shaped and dimensioned so that it can pass into the straight sided part of the recess 12 and then be moved laterally to engage in the keyway 14 with a wedging action. If desired an adhesive may be used to lock the plug in position. The outer portion of the plug 34 is provided with a threaded hole 36 to enable it to be fixed to the cladding material. Any other suitable attachment means may be substituted for the threaded hole. If desired the threaded hole may be covered with a cover 37 which when removed can be inserted into the recess to lock the plug in place as shown in Figure 2a. Alternatively after the plug has been positioned the recess may be filled with a suitable material. If the keyway is to formed with a manual tool it is preferable that it be fitted with a guide to prevent tilting of the tool and to control the depth of cut. One such guide is shown in Figure 4 of the drawings and comprises a bell shaped shroud 31 fitted to the shank of the tool with the bell facing towards the surface 10 of the panel or slab. In order to protect the upper edge of the recess from damage when the tool is moved laterally to form the undercut and annular metal collar 46 may be positioned around the shank 11 of the tool as shown in Fig. 14 of the drawings. The inner edge of the collar is provided with a small downwardly projecting flange 46 which fits into the recess 12 whilst the collar sits on the face of the component. The diameter of the inner hole of the collar may be varied to control the dimensions of the undercut. To ensure accuracy it is desirable that the position and the formation of the keyway in the surface of the slab or panel be done utilising suitable machine tools which are controlled mechanically, hydraulically and/or electronically. Whilst the invention has thus far been described with reference to_a single keyway it is possible to use two or more keyways projecting laterally from a single recess as is shown in Figures 11 and 12 of the drawings. The undercut may be circular as shown in Fig. 13 of the drawings. This is achieved by moving the tool laterally and then with a circular motion. The circular undercut is particularly advantageous as it provides greater strength. The tool may be moved in a curvilinear path to form an undercut which is elliptical or of any desired curvilinear shape. It is possible to cut matching keyholes 41, 42 in two matching flat or curved surfaces 43, 44 place a twin plug 45 in the lined up keyholes and, by moving the materials in opposite directions, achieve a locking effect as is shown in Figures 3a, 3b, 3aa and 3bb. If glue is used on the plugs or surfaces, these come under pressure and remain compressed. As the keyhole is always cut into the back of the panel, the face remains intact. For example, in a 4mm aluminium panel the cut would be only approximately 3mm deep, and whereas today a 25mm marble panel is used mainly to provide sufficient thickness for edge fixing one could use a panel only 15mm thick while still leaving sufficient external wall thickness with a keyhole of 11mm depth. The undercut-keyhole fixing method can thus give considerable savings in material by requiring a reduced thickness of material. The location of fixing points can be determined by the optimum structural configuration. The elimination of fixing on edges (as is done now in all stone and aluminium cladding fixing systems) will also simplify the waterproofing problem. In some materials, e.g. glass, the thickness at fixing points may be increased by laminating a small slab onto the back of a larger one and drilling in these positions. The strength of the keyhole in holding the plugs has proved to be beyond expectations. In 15mm Brescia marbles with a 4mm face depth, the perpendicular pull on a 22mm diam. base plug (22.5 degree angle) was taken up to 250kg, and parallel to the long axis of the hole, up to 250kg, without breakage of the marble fixing. It should be noted that these marbles were of the most fragile kind. The system of the present invention thus consists of several basic elements: (a) the drillheads, (b) the drilling benches with adjustable - preferably multiple - drill positions which can be controlled to 0.1mm or less accuracy in location, depth and movement of the drillheads, (c) the precision-manufactured plugs, including braces and (d) the accurate fixing grounds, which may be a new system or one of those already existing, or some other means of locating precisely the fixing positions, e.g. for ceilings or for fixing together two materials. In the alternative form of fixing member shown in Figs. 15a and 15b a cylindrical plug 50 having an external diameter corresponding to that of the straight walled portion of the recess has the tip of a small wedge 51 inserted into the end thereof as shown in Fig. 15a. When a downward pressure is applied to the plug the wedge forces the bottom portion of the plug into contact with the undercut portion of the recess to lock the plug in place. The outer end of the plug may be attached to another component by any suitable means. This form of plug is particularly suitable for use with a circular undercut recess as shown in Fig.13. In another form of plug suitable for the purposes of the invention the plug is provided with an axial recess terminating in a conical portion. A straight sided screw is screwed into the recess so that its inner end bears against the conical portion. When the screw is screwed home the lower end of the plug is expanded into contact with the undercut.

Claims: THE CLAIMS defining the invention are as follows:- 1. A system for fixing two components together utilising a headed fixing member or an expanding plug and an undercut recess formed in one of the components, the head of the headed fixing member or the expanded portion of the plug being of a shape and dimension complementary to the undercut, and the fixing being concealed with respect to at least one of the components characterised in that:- (1) The undercut is formed by (a) forming a straight walled cylindrical recess at a predetermined location in one of the components away from the periphery of the component with a hole forming tool, (b) moving the hole forming tool laterally with respect to the axis of the recess to form an undercut portion, and (c) re-aligning the tool with the axis of the recess and withdrawing it vertically; and (2) The head of the fixing member or the expanding portion of the plug is inserted through the straight walled portion of the cylindrical recess to engage the undercut, the fixing member or plug being fixed to the other component by any suitable means either before or after the engagement of the head or the plug with the undercut portion. 2. A system as claimed in claim 1 wherein the hole forming tool is a rotary tool having a shank provided at one end with a frusto-conical portion, the side and end face of the frus o-conical portion being faced with abrasive cutting material such as diamond or tungsten carbide. 3. A system as claimed in claim 2 wherein the end of the frusto-conical portion of the tool is concave. 4. A system as claimed in claim 2 wherein the end of the frusto-conical portion of the tool is convex. 5. A system as claimed in claim 2,3 or 4 wherein the abrasive material is applied to the side face and end face of the tool in strips. 6. A system as claimed in claim 2 wherein the frusto- conical portion is substantially hollow and is divided into sections by one or more radial slots. 7. A system as claimed in claim 1 wherein the hole forming tool is a rotary tool having a shank provided at one end with a frusto-conical portion, the side face and end of the frusto-conical portion being provided with one or more cutting edges as in a normal drill. 8. A system as claimed in any one of the preceding claims wherein the tool is moved laterally in one direction to form a keyway. 9. A system as claimed in any one of claims 1 to 8 wherein the tool is moved laterally in two or more directions to form two or more keyways projecting laterally from a single recess. 10. A system as claimed in any one of claims 1 to 8 wherein the tool is moved laterally with a circular or other curvilinear motion to form an undercut which is circular or other curvilinear shape. 11. A system as claimed in any one of the preceding claims wherein an annular metal collar is fitted around the shank of the tool, the inner periphery of the collar being provided with a small downwardly projecting flange which engages the upper edge of the straight walled portion of the recess to protect the component from damage when the tool is moved laterally to form the undercut. 12. A system as claimed in any one of the preceding claims wherein an undercut recess is formed in both components which are connected together by inserting a double headed fixing member into the recesses and moving the components in opposite directions to enable the heads to engage the respective undercuts. 13. A rotary tool for forming an undercut recess comprising a shank having a frusto-conical portion at one end, the side and end face of the frusto-conical portion being faced with having abrasive material. 14. A tool as claimed in claim 13 wherein the abrasive material is applied in strips. 15. A tool as claimed in claim 13 or 14 wherein the end of the frusto-conical portion is concave. 16. A tool as claimed in claim 13 or 14 wherein the end of the frusto-conical portion is convex. 17. A tool as claimed in claim 13 wherein the frusto- conical portion is substantially hollow and is divided into two or more sections by one or more radial slots, the inner and outer faces of the frusto-conical portion being faced with the abrasive material. 18. A rotary tool for forming an undercut recess comprising a shank having a frusto-conical portion at one end, the side face and end being provided with one or more cutting edges as in a normal drill. 19. A rotary - tool for forming an undercut recess substantially as herein described and as shown in Fig. 5 or Fig. 6 or Fig. 7 or Figs. 8, 9 and 10 of the accompanying drawings. 20. A system for fixing two components together substantially as herein described with reference to the accompanying drawings.

Inventors: ELISCHER JULIUS WILLIAM, ELISCHER, JULIUS, WILLIAM
Applicants: ELISCHER JULIUS WILLIAM, ELISCHER, JULIUS, WILLIAM
Application year: 1989
Main classification: F16B5
IPC codes: B23C3, B24B19, F16B3, F16B5, F16B17, F16B21