GB2033526A - Joints - Google Patents

Abstract

A corner joint between three sections 1, each of which includes two channel-shaped portions 4 and 5 arranged perpendicular to one another and extending along two sides of each section 1 comprises a connecting element having a body 2 including abutment surfaces 12 lying in three mutually perpendicular planes and at least three screwthreaded members 10 passing through the body 2 and being screwed into the sections 1 to pull the ends of the sections 1 into engagement with their corresponding abutment surfaces 12. The connecting element also includes a cap 3 arranged to be fitted over the outside of the body 2 to cover the body 2 and the heads of the screw- threaded members 10. Preferably the body 2 of the connecting element also includes locating spigots 14 and which locate the body 2 with respect to the sections 1 and prevent them rotating on tightening of the screwthreaded members 10. <IMAGE>

Description

SPECIFICATION Improvements relating to joints Joints between three mutually perpendicular sections particularly where the sections are extruded from aluminium, or an aluminium alloy, are used in the frames of furniture, for example showcases, and in frames for, for example, exhibition stands. Fre quentlythe sections include two channel-shaped portions arranged perpendicular to one another and extending along two sides of the section. A strip is usually placed in each channel-shaped portion to accommodate a glass or solid panel which fills in the space enclosed by the frame.

At present joints between three mutually perpen dicularsections are made using a single piece knuckle having spigots received in portions of each section and often received in the channel-shaped portions of each section. In this case the spigots are locked into the channel-shaped portions by screwthreaded members which extend transverse to the channel-shaped portions and the bases of the channel-shaped portions. Since the spigots of the knuckle joint occupy part of the channel-shaped portions of the sections, the glass or other solid panel which fills the frame, and the strip to be inserted in the channel-shaped portions is cut away at its corners so that the spigots are accommodated.

Sometimes the spigots of the knuckle fit into hollow portions of each section and in this case, they are also fixed in place by transverse screws or alternatively, by each spigot being longitudinally split and expanded in a direction transverse to the axis of the sections to drive the two parts of each spigot into tight engagement with its section.

With all of these previous arrangements as the joint between each section is tightened the tighten ing force is applied in a direction transverse to the axis of each section. With such joints it is difficult to obtain a clean, tight joint between the end of the section and the edge of the knuckle since there is no pre-loaded tension in the joint acting in the axial direction. Often, the framework has to be assembled from the inside and this is particularly difficult and unsatisfactory when the panel has to be fitted inside the framework as the framework is assembled.

According to this invention a corner joint between three sections comprises three sections each of which includes two channel-shaped portions arranged perpendicular to one another and extend ing along two sides of each section, a connecting element having a body including abutment surfaces lying in three mutually perpendicular planes, and at least three screwthreaded members passing through the body and being screwed into the sections to pull ends of the sections into engage ment with their corresponding abutment surfaces, the connecting element also including a cap arranged to be fitted over the outside of the body to cover the body and the heads of the screwthreaded members.

With the joint arranged in this way, as the screwthreaded members are tightened they exert tensional force in the axial direction of each section.

Thus the end of each section is pulled into tight engagement with its corresponding abutment surface to provide a strong effective joint with a pre-loading in the axial direction. This results in a joint which has a clean tight external appearance, which does not obstruct the channel-shaped portions of the sections, and which can be made from the outside of the frame, so enabling a solid panel to be fitted inside the frame as the sections forming the frame are fixed together.

With sections of small size there may be only a single screwthreaded member in engagement with each section although, with sections of larger size it is preferred that at least two screwthreaded members are engaged with each section. Preferably, the body of the connecting element also includes locating spigots arranged to engage with parts of each of the sections other than the channel-shaped portions.

The provision of the locating spigots ensures accurate location of each of the sections with respect to the connecting element and with respect to one another and, particularly in the case where only a single screwthreaded member is provided for each section, prevents the sections from rotating relative to the connecting element as the screwthreaded member is tightened. Preferably, each section includes a hollow portion extending between the two channel-shaped portions and the spigots on the body of the connecting element are arranged to fit into this hollow portion.

The sections may have a generally square or rectangular cross-section with the channel-shaped portions arranged on adjacent sides of the section.

However, the sections may have an L-shaped crosssection with the channel-shaped portions arranged along the edges of the section. Preferably, the section has a curved cross-section and is quadrantshaped with the channel-shaped portions extending along the adjacent flat sides of the quadrant-shaped section or alternatively the section may be formed as an annular quadrant with the channel-shaped portions extending along the edges of the annular quadrant-shaped section. The curvature of the quadrant or annular quadrant-shaped section may be generally elliptical or parabolic rather than strictly circular. It is also possible for the sections to have an inverse annular quadrant shape with the channelshaped portions extending along the edges of the section with the open sides of both channel shaped portions opening away from the centre of curvature of the section.

The cap may be a snap-fit onto the body of the connecting element but preferably it is arranged to be fixed in place by a screwthreaded member extending outwards from the inside of the body.

Preferably the body of the connecting element includes lands arranged to engage the periphery of the cap to ensure a precise location of the periphery of the cap and in turn precise registry between the periphery of the cap and the outer profile of the sections. The outer profile of the cap will usually be matched to that of the three sections to give the appearance of the three sections merging into one another to provide a clean and unbroken appearance for the outer profile of the completed framework.

However it is also possible to provide the cap with an outer profile of any particular required shape to enhance the aesthetic appeal of the completed framework. For example, the cap may have a part spherical outer profile to give the appearance of a "ball" at each joint.

Preferably the body and the cap of the connecting element are pressure diecast and the may be made from mazak 3. Whilst the sections will usually be extruded in aluminium and the connecting element diecast in metal it is possible for both to be made of ,astics material and even forthe connecting elernent to be wholly or partly made from plastics material when it is used with aluminium sections The successful operation of the joint in accordance with the first aspect of this invention relies upon the strength of the connection between the screwthreaded members and the sections. Provided that the screwthreaded members are bolts and each of the sections includes a tapped hole or holes into which the bolts can be screwed, the strength of the connection between the screwthreaded members and the sections is no problem.However, the provision of tapped holes in the ends of the sections is time consuming and thus expensive.

It is common practice to use self-tapping screws when making connections and it is also common practice to provide a portion of arcuate cross-section in an extruded metal section which subtends an angle of at least 2400. Self-tapping screws are then driven axially into this portion having an arcuate cross-section. Difficulty is experienced using such a technique particularly when such a technique is used to provide a fixing in a joint in accordance with this invention. As the self-tapping screw is screwed into the portion of arcuate cross-section the free ends of the portion tend to splay apart. This leads to the axis of the self-tapping screw moving and changing its location as the screw is tightened and also leads to little penetration of the crown of the screwthread of the self-tapping screw into the walls of the portion of arcuate cross-section.In general, the penetration of the screwthread into the side wall is rarely more than 15% and this is insufficient for strong fixings such as are required for this invention.

If the arcuate portion is made more rigid, for example, if it is made of much heavier gauge or if its cross-section is formed as a closed circle this does not solve the problem. Whilst both of these solutions can lead to a greater penetration of the screwthread into the wall and overcome the problem, there is then considerable difficulty in obtaining sufficient torque to drive the self-tapping screw into the section. A wrench is needed rather than a screwdriver and frequently it is impossible for the screw to be driven in manually. Also, the self-tapping screws tend to shear off before they have been driven fully home and this leads to the entire section having to be replaced.

Preferably, each of the three sections includes a portion which is generally arcuate in cross-section subtending an angle of at least 240 having at least three inwardly directed ribs on its inner surface and the screwthreaded members are all formed by self-tapping screws, in use, the self-tapping screws biting into the ribs to provide a fixing which is strong in the axial direction. Preferably the ribs are equiangularly spaced around the arcuate portion and, when three ribs are provided they are preferably spaced at 1200 to one another. Since the screws bite into the ribs as the screws are inserted and tightened, the axis of the screw does not move during tightening.

Such joints can be made readily and efficiently on site with the use of manual tools only.

Two examples of a joint in accordance with this invention will now be described with reference to the accompanying drawings; in which: Figure 1 is an exploded perspective view of a first example seen from the outside; Figure 2 is an exploded perspective view of the joint seen from the inside; Figure 3 is a partly sectioned plan of the com pleted joint; Figure 4 is a cross-section through the section used in the first example; Figure 5 is a partly cutaway perspective view of the cap; Figure 6 is a section through the cap; Figure 7 is a cross-section through the section used in a second example; Figure 8 is a perspective view of a connecting element used in the second example.

A joint is formed between three mutually perpendicular sections 1 using a connecting element having a body 2 and a cap 3. Each section 1 is generally quadrant-shaped and includes two channel-shaped portions 4 and 5 arranged on adjacent sides of a quadrant-shaped portion 6. The channel-shaped portions 4 and 5 are arranged to receive an in-fill panel 7 made from timber or glass which, in use, forms the side panels of a piece of furniture such as a showcase. The in-fill panels may be held in place in the channel-shaped portions 4 and 5 by a strip of resilient plastics material 8 as shown in Figure 3. An arcuate portion 9 is located on the inside face of the quadrant-shaped portion 6 and is arranged to receive a self-tapping screw 10.The arcuate portion 9 subtends an angle of approximately 240 and the inside surface of the arcuate portion 9 includes three inwardly facing ribs 11, as shown most clearly in Figure 4.

The body 2 of the connecting element includes three abutment surfaces 12 lying in three mutually perpendicular planes. Holes 13 are provided in the abutment surfaces 12 and L-shaped spigots 14 extend outwards away from the abutment surfaces 12. A continuous land 15 extends around the outside periphery of the body 2 and a further hole 16 is provided in the centre of the body 2. The cap 3 has a partly spherical outer profile and an internal boss 17.

The cap 3 fits over the outside of the body 2 and engages the land 15 to provide a smooth external finish to the completed joint. The cap 3 is held in place by a self-tapping screw, not shown, passing through the hole 16 and into the boss 17.

The joint is made by cutting the sections 1 to the appropriate length and ensuring that their end faces are normal to their longitudinal axes then, inserting the L-shaped spigots 13 of the connecting element 2 into the quadrant-shaped portions 6 of the sections 1 with the L-shaped spigots 14 resting against the inside faces of the quadrant-shaped portion 6. The end faces of the sections 1 are then against the abutment surfaces 12. Self-tapping screws 10 are inserted through the holes 13 and screwed into the arcuate-shaped portion 9. As the self-tapping screws 10 are driven into the arcuate-shaped portion 9 the grounds of the screwthread on the self-tapping screws 10 bites into the raised ribs 11 on the inside surfaces of the arcuate portion 9.As the self-tapping screws 10 are tightened home the end surfaces of the sections 1 are urged tightly against the abutment faces 12 on the body 2 of the connecting element. As the sections 1 are joined together the in-fill panel 7 and its resilient strips 8 are inserted into the channel-shaped members 4 and 5. The cap 3 is screwed into place to complete the joint. Since the sections 1 are pulled tightly towards one another along their longitudinal axes a tight clean joint is ensured between the edges of the cap 3 and the outer profile of the sections 1. The self-tapping screws 10 also provide an initial pre-loading to the joint which resists forces attempting to separate the various components of the joint.Thus, the insides of the channel-shaped portions 4 and 5 are left completely free in the completed joint, as shown in Figure 3 and this means that the corners of the in-fill panel 7 do not need to be cut away.

A second example of joint in accordance with this invention uses sections 1 having a cross-section as shown in Figure 7. The sections are similar to those used in the first example in that they are generally arcuate in shape and include channel-shaped portions 4 and 5 on the adjacent flat faces of a quadrant-shaped portion 6. However, in this example the arcuate portion 9 to receive the self-tapping screw 10 is located at the join between the two adjacent flat faces of the quadrant-shaped portion 6 instead of on the inside of the curved face. To accommodate this section the body 2 of the connecting element is modified as shown in Figure 8. The L-shaped projecting spigots 14 are replaced by curved spigots 18 projecting forwards from the abutment surfaces 12. The curved spigots 18 rest against the inside curved face of the quadrantshaped portions 6.

Both the L-shaped spigots 14 and the curved spigots 18 fulfil the same function in that both of them locate the sections 1 with respect to the body 2 of the connecting element and prevent the sections 1 from rotating with respect to the body of the connecting element when the self-tapping screws are tightened.

Claims (10)

1. A corner joint between three sections comprising three sections each of which includes two channel-shaped portions arranged perpendicular to one another and extending along two sides of each section, a connecting element having a body including abutment surfaces lying in three mutually perpendicular planes, and at least three screwthreaded members passing through the body and being screwed into the sections to pull ends of the sections into engagement with their corresponding abutment surfaces, the connecting element also including a cap arranged to be fitted over the outside of the body to cover the body and the heads of the screwthreaded members.

2. A corner joint according to claim 1, in which the body of the connecting element also includes locating spigots arranged to engage with parts of each of the sections other than the channel-shaped portions.

3. A corner joint according to claim 2, in which each section includes a hollow portion extending between the two channel-shaped portions and in which the spigots on the body of the connecting element are arranged to fit into this hollow portion.

4. A corner joint according to any one of the preceding claims, in which each section has a curved cross-section and is quadrant-shaped with the channel-shaped portions extending along the adjacent flat sides of the quadrant-shaped section.

5. A corner joint according to any one of the preceding claims, in which the cap is connected to the body of the connecting element by a screwthreaded member extending outwards from the inside of the body.

6. A corner joint according to any one of the preceding claims, in which the body of the connecting element includes lands arranged to engage the periphery of the cap to ensure a precise location of the periphery of the cap.

7. A corner joint according to any one of the preceding claims, in which the body and the cap of the connecting element are pressure diecast from mazak 3 and the sections are extruded from aluminium.

8. A corner joint according to any one of the preceding claims, in which each of the three sections includes a portion which is generally arcuate in cross-section subtending an angle of at least 240 having at least three inwardly directed ribs on its inner surface, and in which the screwthreaded members are all formed by self-tapping screws, in use, the self-tapping screws biting into the ribs to provide a fixing which is strong in the axial direction.

9. A corner joint according to claim 8, in which the ribs are equiangularly spaced around the arcuate portion.

10. A corner joint according to claim 1, constructed substantially as described with reference to the accompanying drawings.