GB2147680A

GB2147680A - Connecting tube or rod members

Info

Publication number: GB2147680A
Application number: GB08326679A
Authority: GB
Inventors: James Brian O'hara
Original assignee: Hara J B O
Current assignee: Hara J B O
Priority date: 1983-10-05
Filing date: 1983-10-05
Publication date: 1985-05-15
Also published as: GB8326679D0

Abstract

A joint for connecting tube or rod members comprises a connector (2) engaged with a rod or tube (6) which is preferably formed in continuous lengths by extrusion of, for example, a resiliently deformable thermoplastics material in a generally circular cross-section with one or more longitudinal ribs or flats (8). The connector has socket portions (4) of complementary cross-section and provided with one or more corresponding flats or ribs (10), so that the joint can be assembled relatively loosely with the respective flats and ribs aligned and tightened by a cam- or wedge-locking effect when the ribs are moved away from the flats upon rotation of the rod or tube in the socket. <IMAGE>

Description

SPECIFICATION Joint for connecting tube or rod members This invention relates to joints for connecting tube or rod members and to structures comprising tube or rod members connected by such joints.

There are many occasions when it is desired to connect together tube or rod members and various means have been proposed for connecting such tube or rod members together. For light duty structures such as fruit cages for horticultural or agricultural use, light industrial or domestic racking or shelving systems, constructional toys and the like it is usual to use connector elements having sockets therein for tightly receiving end portions of the tube or rod members spigot-and-socket fashion.

The tightness of the fit of the tube or rod members in the sockets of the connector elements depends on the accuracy with which these parts are produced. Convenient manufacturing methods, such as extrusion, tend to produce variations in the cross-section of the rod or tube members that affect their fit in the sockets and so cause difficulties.

Moreover, when assembling structures as aforesaid, and particularly the larger structures such as fruit cages and racking systems, it is difficult with the known tube or rod members and connector elements to properly align the members and connector elements and so obtain a properly aligned structure which is not out of "true".

The present invention has as its object to enable the aforesaid difficulties to be overcome.

According to the present invention there is provided a joint comprising a rod or tube member and a connector member, the rod or tube member having at least an end portion comprising a spigot or socket and the connector member being provided with a complementary socket or spigot portion adapted to cooperate therewith to form the joint, wherein the spigot and socket cross-sections deviate from circularity such that at a first relative orientation the fit is relatively loose and the spigot can readily be inserted into and withdrawn from the socket, and the spigot can be rotated within the socket from the first to a second relative orientation at which the joint is relatively tight.

By providing a variation in tightness according to the relative orientations of spigot and socket, the invention enables a joint of a given tight fit to be formed without being critically dependent upon high dimensional accuracy in manufacturing the spigot and socket portions of the rod or tube member and the connector. Furthermore, the tightness of the joint need not be a compromise between ease of assembly and disassembly and firmness of the formed joint: the joint can be made relatively loose for assembly and disassembly and yet can be firm for reliability in use. In addition, the fact that the spigot and socket portions of the joint need to be in a particular relative orientation for easy assembly automatically ensures the alignment of the different components of a structure being assembled and so ensures the "trueness" of the structure.

Although clearly a large number of shapes are possible for the spigot and socket portions of the joint, their cross-sections (which term is applied herein to the internal wall of the socket portion and to the external wall of the spigot portion) are preferably substantially uniform along their lengths and the cross-sections are most preferably substantially circular over the greater part of their circumferences, the deviations from circularity being confined to distinct zones about their circumferences. Such zones may be raised and/or depressed relative to the circular regions of the cross-sections, and preferably extend parallel to the axes of the spigot and socket portions.In a preferred embodiment of the invention the rod or tube member forms the spigot and is of circular section with at least one flat thereon which extends the length thereof whilst the connector member provides a socket which has at least one longitudinally extending rib on the internal wall thereof, an end portion of the rod or tube member being relatively easily insertible into said socket when said at least one flat is aligned with said at least one rib and the joint being able to be tightened by relative rotation of the rod or tube member and the socket to produce a cam- or wedge-locking effect.

The rod or tube may be made by extrusion, since the joint of the invention can accommodate the slight variations in dimensions that can arise in this process, and accordingly a thermoplastic polymer is a particularly preferred and advantageous material for the rod or tube although, it could, if desired, be formed from metal, e.g., aluminium alloy, or other suitable material. The cross-section of the rod or tube may be unchanged throughout its length, so that it can be cut to any length and still exhibit end portions which have the necessary conformation to form a spigot, in the case of a rod, or either a spigot or a socket, as the case may be, in the case of a tube.

The present invention also provides a structure comprising a plurality of tube or rod members connected by joints in accordance with the invention. Preferred structures include fruit cages, racking and shelving systems, and constructional toys.

The invention is illustrated by way of example in the accompanying drawings, in which: Figure 1 is a perspective view of an assembled joint; Figure 2 is a cross-section through a tube member used in the joint of Fig. 1; Figure 3 is a cross-section through a socket of the connector member used in the joint of Fig. 1; Figure 4 is a cross-section through the tube and socket assembled in a first relative orientation; and Figure 5 is a cross-section through the tube and socket assembled in a second relative orientation.

The connector 2 shown in Fig. 1 has five socket portions 4. Four are angled at 90" intervals in a common plane, while the fifth extends perpendicularly thereto and is shown making a joint with a tube member 6. Clearly, other connectors with different number and arrangements of sockets may be used to form joints in accordance with the invention; it is not even necessary that the connec tors have more than one socket, since it may be used to connect a rod or tube member to part of a structure other than further rod or tube members.

The tube member 6 is generally cylindrical in form but is provided with four equiangularly spaced flats 8 on its outer surface which form narrow zones that are depressed relative to the wouldbe cylindrical surface and which extend the length of the tube member parallel with its axis.

Each socket 4 has a generally cylindrical inner surface of marginally greater diameter than the outer diameter of the tube member 6, and which is provided with four equiangularly spaced ribs 10 which form zones that are raised relative to the rest of the surface and which extend the length of the socket parallel with its axis.

Fig. 4 shows the relative orientations of the tube member and socket for easy assembly and disassembly of the joint. The ribs 10 of the socket are aligned with the flats 8 of the tube. The tube is held in the socket by light pressure between the ribs and flats and/or between the cylindrical walls of the tube member and the socket.

Fig. 5 shows the tube member turned through 45 relative to the connector to locate the flats 8 midway between ribs 10, causing the ribs to bear hard against the cylindrical walls of the tube member and giving the joint its greatest resistance to disassembly by increasing the frictional force between socket and tube member to a maximum to provide a cam- or wedge-lock effect.

The material of at least one of the tube member (or rod member) and socket should be capable of a degree of deformation to allow the joint to be locked into its tightened condition. Preferably the material is resiliently deformable to allow repeated use, while naturally retaining sufficient structural strength to suit its intended application. Many synthetic resins satisfy these requirements and also lend themselves to extrusion as a means of manufacturing the rod or tube members in continuous lengths to be cut as required.

The cross-sections of generally cylindrical sockets and rod or tube members may deviate from circularity at one or a plurality of zones, and the numbers of zones need not necessarily coincide: for example, a single rib 10 could suffice in the joint illustrated in the drawings. The shapes of the zones may vary from those illustrated, for example by providing a more tapering form to the crosssection of the ribs to facilitate a more gradual increase in resistance to rotation as the cam reaction between the socket and spigot portion increases and deformation occurs.

The joint illustrated in the drawings shows a particular advantage when a plurality of similar connector members are to be assembled on a single rod or tube member. The straight ribs 8 and flats 10 enable the joints of a structure to be assembled in the relatively loose first orientation shown in Fig. 4 with all the connectors 2 in alignment, after which all joints can be locked by partial rotation of the single rod or tube member to the second orientation without disturbing the alignment of rod or tube members fitted in the radial sockets of the several connector members.

The interior of a tube member can function as a socket and a connector member can be provided with spigot portions as well as or in place of sockets.

Claims

1. A joint comprising a rod or tube member and a connector member, the rod or tube member having at least an end portion comprising a spigot or socket and the connector member being provided with a complementary socket or spigot portion adapted to cooperate therewith to form the joint, wherein the spigot and socket cross-sections deviate from circularity such that at a first relative orientation the fit is relatively loose and the spigot can readily be inserted into and withdrawn from the socket, and the spigot can be rotated within the socket from the first to a second relative orientation at which the joint is relatively tight.

2. A joint according to claim 1 wherein the internal wall of the socket portion and the external wall of the spigot portion are substantially uniform along their lengths.

3. A joint according to claim 2 wherein the internal wall of the socket portion and the external wall of the spigot portion are substantially circular over the greater part of their circumferences.

4. A joint according to claim 3 wherein the internal wall of the socket portion and the external wall of the spigot portion deviate from circularity in distinct zones about their circumferences, which zones extend parallel to the axes of the spigot and socket portions.

5. A joint according to claim 1 wherein the rod or tube member forms the spigot and is of circular section with at least one flat thereon which extends the length thereof whilst the connector member provides a socket which has at least one longitudinally extending rib on the internal wall thereof, an end portion of the rod or tube member being relatively easily insertable into said socket when said at least one flat is aligned with said at least one rib and the joint being able to be tightened by relative rotation of the rod or tube member and the socket to produce a cam- or wedgelocking effect.

6. A joint according to any one of the preceding claims, wherein the rod or tube is made by extrusion.

7. A joint according to any one of the preceding claims, wherein the material of at least one of the rod or tube member and the socket portion of the connector member is resiliently deformable.

8. A joint according to any one of the preceding claims wherein the rod or tube is of a thermoplastic polymer.

9. A joint according to any one of the preceding claims, wherein the cross-section of the rod or tube is unchanged throughout its length.

10. A joint between a rod or tube member and a connector member, substantially as herein described with reference to and as illustrated in the accompanying drawings.

11. A structure comprising a plurality of tube or rod members connected by joints according to any one of the preceding claims.

12. A structure according to claim 11 including a plurality of said joints formed by a plurality of connector members assembled on a single rod or tube member.

13. A fruit cage, racking and shelving system or constructional toy comprising a structure according to claim 11 or claim 12.