Frame Work Joints

This invention relates to joints for connecting together members of, for example, a framework.

There are many constructions in which two or more members must be secured to one another in a simple and reliable manner. Examples of such constructions are shelving systems, frameworks for display and other cabinets and partition systems.

Many proposals have been made which involve the use of a pair of locking arms which are received within the hollow interior of one of the members to be joined. The arms protrude from one end of said one member and the protruding portions of the arms are entered in an aperture or slot in the wall of the other member. The protruding portions each have an outwardly directed tooth thereon. The protruding portions are forced apart so that they engage with the wall parts which bound the slot, the teeth hooking behind said wall parts to prevent the protruding portions being withdrawn from the slot or aperture. In many forms, screws are employed to force the arms apart so that the protruding portions engage said wall parts.

In a structure developed by applicant, the arms are of elongate form with curved surfaces at each end. The arms are presented to the slot or aperture in a diverging relationship, the arms touching at one end and being spaced apart at the other. It is the touching ends of the arms which are presented to and enter the slot or aperture. When the spaced ends are sqeezed together, said surfaces of the arms at said one end roll on one another and said portions move apart into engagement with said wall parts. Such rolling action continues until the arms are parallel and back-to-back. Said one member, which is hollow, is then slid over the arms to hold them in their parallel relationship.

It is sometimes desirable to be able to connect together three members, two of the members being spaced apart, and the third member spanning the gap between these two members. In structures of the form described above, this would be achieved by using two pairs of arms, each pair connecting the third member to a respective one of the other members.

An object of the present invention is to provide a joint which includes a single pair of arms connecting two spaced members to one another.

According to one aspect of the present invention there is provided, in a construction including first and second members which are spaced apart and each of which has an opening therein bounded by wall parts, a joint comprising a pair of arms spanning between said members and having the end portions thereof entered in said openings in the first and second members, there being teeth on said end portions which teeth engage behind said wall parts to prevent the arms being withdrawn from said openings, and means for forcing said arms apart and into engagement with said wall parts.

To enable the arms to be forced apart into engagement with said wall parts, one of said arms can have a tapped bore therein, there being a screw in said bore which bears on the other arm to force the arms apart and into engagement with said wall parts.

If desired a second tapped bore and a second screw can be provided, the screws being spaced apart along the arms.

To prevent slipping of the arms with respect to one another, those surfaces of the arms which face one another can each be formed with a rib and a groove, the groove of each arm receiving the rib of the other arm when the arms are in juxtaposed relationship.

A difficulty with a number of the prior art constructions of which applicant is aware is that they are difficult to manipulate as they comprise at least the two members to be joined, the two arms and quite often springs and other components. A screw is provided which, when tightened, urges the arms apart. Where springs are provided, these urge the arms together as the screw is slackened so that the arms move together and can be removed from, or inserted in, the aperture or slot.

Another object of the present invention is to provide a joint in which manipulation is simpler than in the prior art proposals.

According to another aspect of the present invention there is provided, in a construction including a member which has an opening therein bounded by wall parts, a joint comprising a pair of arms each having one end portion thereof entered in said opening, each of said one end portions including a tooth and the teeth engaging behind said wall parts to prevent withdrawal of said one end portions from said opening, the other end portion of each arm including a further tooth, the further teeth being directed away from one another and there being a clip engaged with said other end portions and preventing said other end portions from moving apart, the clip including two end sections and a connecting section joining said end sections, the end sections each having a recess therein and one of said further teeth being in each recess.

In one form said clip is of resilient material and further includes a central portion received between those surfaces of said arms which face one another, said central portion including a pair of diverging limbs which bear one on each arm and are deflected towards one another to reduce the angle between them when said one end portions are displaced towards one another.

The construction can further include a hollow member, said clip and arms, apart from said one end portions, being within said hollow member.

It is also possible for said other end portions of the arms to have grooves in those surfaces thereof which are directed away from one another, each of said further teeth lying between the other end of the respective arm and the groove of that arm, and said end sections of the clip including projections which seat in said grooves.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:

FIG. 1 is a top plan view of a joint between two members of a framework which members are at right angles to one another;

FIG. 2 is a side elevation of the joint of FIG. 1;

FIG. 3 is a view of the joint of FIG. 1 taken in the direction of the arrow A in FIG. 1;

FIG. 4 is a top plan view of the joint of FIG. 1 with the horizontal member removed;

FIG. 5 is a detail, to a larger scale, of the joint of FIGS. 1 to 4;

FIG. 6 is a top plan view of a joint between two parallel members;

FIG. 7 is a rear elevation of the joint of FIG. 5; and

FIG. 8 is a plan view of a further joint between two parallel members.

Referring firstly to FIGS. 1 to 4, a vertical member 10 and a horizontal member 12 are shown. The vertical member 10, which is preferably an aluminium extrusion, has a central core 14 with four arms 16 radiating from the core. Each arm 16 is at right angles with respect to the adjacent arms. At the outer end of each arm 16 there is a right angled element 18, each limb of each right angled element having a lip 20 extending along the free edge thereof. This structure provides four cavities 22 and a slot-like entrance 24 to each cavity. The entrances 24 are bounded by those edges of the elements 18 which have the lips 20 extending therealong.

The member 12, which is also preferably constituted by an aluminium extrusion, comprises (see particularly FIG. 3) a vertical web 26 and two vertically spaced, horizontal flanges 28 protruding from one face of the web 26. The web 26 extends both above the top flange 28 and below the bottom flange 28 and has, along each of the free edges thereof, an element 30. The elements 30 are at right angles to the web 26 and each has a lip 32 along the free edge thereof.

Along the free edge of each flange 28 there is an element 34 which, in section, is of right angled form. Along one free edge of each element 34 there is a lip 36. It will be seen that the lips 32 and 36 bound two slot-like entrances 38 leading to two cavities 40. Portions 42 of the elements 34 protrude towards one another and bound a slot-like entrance 44 to the main cavity 46 of the member 12.

Turning now to FIG. 4, reference numerals 48 designate two locking arms which join the members 10 and 12. One of these arms can also be seen in FIG. 2 and a small portion of each arm can be seen in FIG. 1. Each arm 48 comprises an outer face 50 and an inner face 52. In the faces 50 there are horizontally spaced, re-entrant grooves 54. By `re-entrant` is meant that the grooves 54 have slot-like entrances which are narrower than inner parts of the grooves. Between each groove 54 and the adjacent end of the arm 48 there is a further groove 56 (see particularly FIG. 5). Each groove 56 has one bounding face 58 which intersects the face 50 at right angles and a face 60 which is oblique to the face 50, the faces 58 and 60 being so arranged that the mouth of each groove 56 is wider than its base. Protrusions 62 are provided where the faces 58 intersect the faces 50. The faces 60 of the grooves 56 intersect curved end faces 64 of the arms 48 to form teeth 66. It will be noted that the apex of each tooth 66 is set back with respect to the face 50.

Each face 52 has therein a groove 68 of rectangular cross section and each groove 68 lies just to one side of the centre of its arm. On the other side of the centre of each arm there is a rib 70. The rib 70 has side faces which are at right angles to the face 52 and a top face which is arcuate when viewed in section. The groove 68 of each arm 48 receives the rib 70 of the other arm.

It will be noted from FIG. 4 that the arms 48 are of the same cross sectional shape, one being rotated through 180.degree. about a transverse central axis with respect to the other. The arms can be produced by extruding an aluminium bar of the desired cross sectional form and then cutting it transversely.

A spring clip 72 (see particularly FIG. 5) of resilient synthetic plastics material secures the arms 48 to one another at the end remote from the member 10 and prevents these ends of the arms 48 moving apart. The clip 72 comprises a central portion 76 which lies between the faces 52 and a connecting section in the form of two hook portions 78. The hook portions 78 extend from the central portion 76 to beyond the ends of the arms 48 and curve around to join end sections 80 of the clip. The end sections 80 lie outwardly of the arms 48 and each includes a projection which seats in the groove 56 and a recess which receives one of the teeth 66. The central portion 76 includes two diverging limbs 82 which bear one on each arm 48.

One of the arms 48 is drilled and tapped at 84 and 86 (see FIG. 2) so that it is capable of receiving two Allen screws one of which is shown at 88. As will be described in more detail hereinafter, the single Allen screw, when tightened, is normally sufficient to cause the members 10 and 12 to be secured to one another but there are instances where two Allen screws are preferred.

To connect the members 10 and 12, the arms 48 are pushed into the main cavity 46 of the member 12. The member 12 is orientated with respect to the arms 48 so that the Allen screw moves along the entrance 44 to the main cavity 46 (see particularly FIGS. 2 and 3).

To attach the arms 48 to the member 10, the Allen screw 88 is turned until its inner end lies within the arm 48. The ends of the arms 48 remote from the clip 72 are then squeezed towards one another so that the arms converge and the tips thereof adjacent the teeth 66 touch. Where the arms 48 are within the member 12 as shown in FIG. 2, squeezing is achieved by pressing on the screw 88. Squeezing causes the limbs 82 to be deflected and reduces the angle between them so that a restoring force tending to displace the arms 48 back to their parallel condition comes into existence. The arms 48 are then presented to one of the entrances 24. In their converging condition, the width of the pair of arms, measured across the crests of the teeth 66, is less than that of the entrance 24. Thus the teeth 66 enter the cavity 22. When the pressure holding the arms 48 in their converging condition is released, the portions 82 force the arms apart so that the lips 20 enter the grooves 56. The force exerted by the limbs 82 of the clip 72 is such that there is sufficient friction between the member 10 and the arms 48 to prevent the arms 48 from slipping down the member 10. The Allen screw 88 is then tightened so that its inner end moves across the gap between the arms 48 and bears on the other arm to force them apart. This has the effect of forcing the arms 48 into engagement with the elements 18 of the member 10.

If the web 26 has a hole drilled in it at a suitable point, the member 12 can be rotated through 180.degree. about its longitudinal axis with respect to the position shown in FIG. 3. When the drilled hole is aligned with the tapped bore 84 the Allen screw is inserted.

In any circumstance where the frictional force exerted by the deflected limbs 82 is not required, the portion 76 and the limbs 82 can be omitted. In such circumstances, resilient material is not required and a short length of an aluminium or non-resilient synthetic plastics material extrusion suffices. A clip of this nature prevents the end portions of the arms 48 from moving apart but exerts no significant restoring force. It will be understood that all the forms of clip disclosed protect the teeth 66 with which they are associated. Should the left hand teeth in FIGS. 1, 2 and 4 be damaged, then the arms 48 can be turned around and the teeth 66 previously covered by the clip brought into use.

In FIGS. 6 and 7, the clip 72 has been omitted and the arms 48 join two members 10.1 and 10.2. It will be noted that the relationship between the arms 48 and the members 10.1 and 10.2 is the same as that between the arms 48 and the member 10 in FIG. 1. For extra security against slipping, a second Allen screw 90 is inserted in the tapped bore 86. When the Allen screws 88 and 90 are tightened, the ends of the arms 48 are forced apart into engagement with the elements 18 of the members 10.1 and 10.2.

There can be several pairs of arms 48 joining the members 10.1 and 10.2. For example, the members 10.1 and 10.2 can be elongate columns and there can be a series of vertically spaced pairs of arms 48 joining the columns. To conceal the arms 48 a cover strip 92 (FIG. 6) can be provided. The cover strip 92 has two ribs 94 on the rear face thereon, the cross sectional shape of the ribs 94 being compatible with that of the grooves 54 so that the ribs 94 can snap into the grooves 54 and hold the cover strip 92 in place.

In FIG. 8 the arms are enclosed by a member designated 96. The cross section of the member 96 can be the same of that as the member 12 and the member can be of a length such that only those portions of the arms 48 which lie outwardly of the faces 58 protrude therefrom.

It will be understood that the illustrated and described cross sectional shapes of the members 10 and 12 are by way of example only. Provided the vertical member has a cavity with a slot like entrance into which the arms 48 can be inserted, then the cross sectional shape of the remainder of the vertical member can be of any desired form. Simply by way of example, the lips 32 and 36 of the member 12, which define the entrance 38, will also receive the arms 48. Thus the members 10.1 and 10.2 in FIG. 6 could, if desired, be replaced by two members having the cross sectional shape of the member 12. Furthermore, provided the member 12 has a main cavity 46 which is capable of receiving the two arms 48, the remaining features of the member can be varied depending on the additional functions that the member is to perform.

It will be understood that the grooves 68 and ribs 70 are not essential and can be omitted. Likewise, if no cover strip 92 is to be used, then the grooves 54 are not required.

The arms 48 can, as described, be cut from extruded stock or can be cast in `left` and `right ` hand forms. For some purposes a single tapped bore 84 or 86 is adequate and this bore can be at the centre of the arm.

In the angle between the face 58 of each groove 56 and its bottom wall there can be a protruding tooth 56.1 (FIG. 5). This tooth can only be provided in the die cast form. When the arms 48 are forced apart, the teeth 56.1 bite into the lips 20 to further improve the grip. The tooth, measured at right angles to the section of FIG. 5, is relatively narrow to enhance its ability to bite into the lip. Two or more teeth 56.1 can be provided in each groove 56, the teeth 56.1 being spaced apart across the groove 56.

The illustrated member 12 can be replaced by a tube of rectangular cross section. A hole drilled in its walling receives the Allen screw.

To enable the members 10 and 12 to intersect at other than 90.degree., the arms 48 are cut from two pieces of extruded stock. Before cutting, a further extrusion having the cross-sectional shape of the clip 72 is used to hold the two pieces of extruded stock together. When cutting takes place it does so at, for example, 30, 45 or 60 degrees to the edge of the extruded stock. The end of the member 12 is cut at the same angle.