GB2379257A

GB2379257A - Tube joints

Info

Publication number: GB2379257A
Application number: GB0121091A
Authority: GB
Inventors: Daniel Tutty
Original assignee: Sheffield Hallam University
Current assignee: Sheffield Hallam University
Priority date: 2001-08-31
Filing date: 2001-08-31
Publication date: 2003-03-05
Also published as: WO2003021113A1; GB0121091D0

Abstract

A joint is made between a first tube 10 and a second tube 12. The first tube 10 has an end wall which is perpendicular to the length of the first tube 10. The first tube 10 also includes a slot 16 which has generally parallel sides and extends down the length of the first tube 10 by an amount generally corresponding to, or slightly larger than the diameter of the second tube. The slot 16 can be formed by laser cutting or another suitable method. The second tube 12 is formed from the same size of tubing as the first tube 10, the second tube is a material removed therefrom corresponding to a projection of the end of the first tube 10 onto the second tube 12. The projection is made at an angle at which the first tube 10 and the second tube 12 are to be joined together. The joint is made by pushing the two tubes together.

Description

JOINTING TECHNIQUES This invention relates to a joint for use between two objects and to a method of joining two objects together.

Existing joins between pieces of material such as are used in carpentry and the like and also for joining elongate tubes and bars together typically involve the removal of material from one or both of the pieces to be joined together, one piece then being inserted into the other and fixing means being placed in the joint to hold the two pieces together.

Disadvantages arise with this existing technique because separate fixing means are needed in order to achieve a firm fit. It is an object of the present invention to address the above mentioned disadvantages.

According to a first aspect of the present invention a joint comprises a first tube section and at least one other, second, tube section, wherein the second tube section has an opening therein the shape of which is substantially a partial projection of the cross-section of the first tube onto the second tube and in which the joint is formed by engagement of the first tube in said opening.

The opening may correspond to a projection of the crosssection of the first tube onto the second tube at an angle at which the first and second tubes form the joint. The projection may be along the length of the first tube onto the second tube.

The partial projection may be a projection of a joint end of the first tube.

The first tube may include a slot at said joint end, thereby forming a partial cross-section of the tube. The slot may extend in the direction of the length of the tube. The slot may have a depth of at least the diameter of the second tube.

The joint end may have an end profile corresponding to an interior shape of the second tube. The joint end may be shaped to remain within, or only project slightly beyond, the exterior of the second tube.

The opening in the second tube may comprise at least one slot, preferably two slots. The opening may be bounded by at least one, preferably two, flange (s).

The opening may have two parts, preferably a part on one side of the second tube and a part on the opposite side of the second tube.

In the direction of the projection onto the second tube the opening may have a thickness approximately equal to or just greater than a wall thickness of the first tube.

The joint end of the first tube may include at least one, preferably two, projecting tabs. The or each tab may be receivable in a corresponding opening in the second tube.

The joint may include a third tube, in which case the opening may be an opening in the second and third tubes.

The opening may be a partial projection of the crosssection of the first tube onto the second and third tubes.

The second and third tubes may have an abutting relationship in the joint. The second and third tubes may have ends shaped to allow abutment of the two tubes at an angle to one another.

The opening in the second and third tubes may extend across a join between the two tubes. The opening may have at least two parts, resulting from at least two slots in the first tube. A single slot may be provided.

According to a second aspect of the invention an assembly comprises first and second tube sections arranged to form a joint, wherein the second tube section has an opening therein the shape of which is a partial projection of the cross-section of the first tube onto the second tube.

According to a third aspect of the present invention, a method of joining at least first and second tubes together comprises cutting from the second tube material to form an opening therein, which opening has a shape which is a partial projection of the cross-section of the first tube onto the second tube, the tubes being joined together by urging the tubes together.

All of the features described herein may be combined with any of the above aspects, in any combination.

Specific embodiments of the present invention will now be described, by way of example and with reference to the accompanying drawings, in which,

Figure 1 is a schematic perspective view of first and second tubular sections to be joined together; Figure 2 is a schematic perspective view of the tubular sections in figure 1 joined together; Figure 3a is a schematic perspective view of the tubular sections separated; Figure 3b is a further schematic, partially cut away, perspective view of the tubular sections joined together; Figure 4 is a schematic side view of the first tubular section; Figure 5 is a schematic side view of the first tubular section rotated 900 with respect to that in figure 4; Figures 6a, 6b and 6c show schematic perspective views of different types of joint; Figures 7a and 7b show different angles of joint between tubular sections; Figure 8 shows a diagrammatic perspective view of a joint between first, second and third tube sections; Figures 9a and 9b show schematic perspective views of a Tjoint between tubular sections before and after the joint has been made respectively; Figure lOa shows a schematic view from above of a joint between a circular cross-section tube and a square crosssection tube forming a 900 joint ; Figure 10b shows a perspective view of the circular crosssection and square cross-section pieces before the joint is made; Figure 10c shows a schematic perspective view from one side when the joint between the circular cross-section and square cross-section tubes has been made;

Figures lla-llb show similar views to those of figure 10a- 10c but between two circular cross-section tubes, also forming a 900 angle; Figures 12a-12c show views from above, during joining and joined of three tubular sections joined together at right angles to each other; Figures 13a-13c show schematic views from the side of three stages of the insertion of a first tubular section into a second tubular section at a shallow angle joint; Figures 14a-14c show schematic side views of three stages of insertion of a first tubular section into a second tubular section to form a narrow angled joint; Figures 15a-15c show schematic views from above and from the side of a joint between two circular cross section tubes of one diameter and another circular cross section tube of a larger diameter; and Figures 16a-16b show the formation of a joint between a circular cross section tube and a square cross section tube at right angles to one another.

Figures 1-5 show various views of a joint made between a first tube 10 and a second tube 12. The two tubes are made of steel and have a diameter of approximately 40cm with a wall thickness of approximately 2mm. Of course, other size of tube and thickness of wall can be used.

The first tube 10 has an end wall 14 which is perpendicular to the length of the first tube 10, as shown in figures 1 and 2. The first tube 10 also includes a slot 16 which has generally parallel sides and extends down the length of the first tube 10 by an amount generally corresponding to, or slightly larger than, the

diameter of the second tube 12. The slot 16 can be formed by laser cutting, or another suitable method.

The second tube 12 is formed from the same size of tubing as the first tube 10. The second tube 12 has material removed therefrom, preferably by laser cutting, or a similar method. The material removed corresponds to a projection of the end of the first tube 10 on to the second tube 12. The projection is made at an angle at which the first tube 10 and the second tube 12 are to be joined together. In the example shown in figures 1-5, the angle between the tubes is 900.

The projection onto the second tube 12 is of the end of the first tube 10 and so also includes the projection of the slot 16, as shown in figure 5. This results in a partial ring of material being cut from the second tube 12, with the exception of a portion 18 corresponding to the position of the slot 16 of the projection of the first tube 10 onto the second tube 12. The projection is best seen in figure 5, which has a view looking in the line of the projection onto the second tube 12. Figure 4 shows a view at right angles to the former view.

The first tube 10 and the second tube 12 are joined together by orientating the tubes with respect to each other at the angle at which they are to be joined and moving the tubes relative to one another along the axis of the first tube 10 so that the first tube 10 slides over the cut away section of the second tube 12 to thereby form the joint.

The machining of the first and second tubes 10 and 12 is performed very accurately which allows a close tolerance of the fit between the first and second tubes 10 and 12 to be achieved. The close tolerance also allows the first and second tubes 10 and 12 to join together very firmly, thereby making a solid joint. In view of the close tolerances achieved, no further fixing of the joint between the first and second tubes 10 and 12 is required.

If additional strength is required for the joint, then tabs (not shown) may be located at the points marked 20 in figures 3b and 4 may be provided on the second tube 12 at the end of flange portions 22 which remain after cutting of the second tube 12. The tabs are arranged to extend through openings (not shown), located at the points marked 24 in figure 3a. When the first and second tubes 10 and 12 are in their joined position, the tabs are arranged to extend through the openings to give extra strength. Extra force may be required to push the first and second tubes together to overcome any resistance caused by the tabs pushing against the interior of the first tube 10 before they project through the opening.

An important feature of the joint formed is that the projection of the first tube 10 onto the second tube 12 is a partial projection. By virtue of the projection being only partial, material is left which joins the flanges 22 to the body of the remainder of the second tube 12 by the area 18. The flanges 22 provide important extra strength for the joint between the first and second tubes 10 and 12 because the flanges 22 provide material which bears against the inside of the first tube 10, whereas the main body of the second tube 12 bears against the exterior of

the first tube 10 at slots 23. Thus, material of the second tube 12 bears against both the interior and the exterior of the first tube 10 by virtue of the projection of the first tube 10 on to the second tube 12 being only partial.

The joint shown in figures 1-5 is given strength by the second tube 12 making contact along all of the exterior length of the flange 22. Also, the two flanges 22 provides two points of contact along the length of the first tube 10, which provides strength in preventing relative turning of the first and second tubes 10 and 12 about an axis perpendicular to the lengths of both the first and second tubes 10 and 12. Relative turning of the first tube 10 relative to the second tube 12 about the longitudinal axis of the first tube 10 is prevented by the material at the edges of the slot 16 bearing against the area 18 of the second tube 12. Similarly, rotation of the second tube 12 relative to the first tube 10 about the longitudinal axis of the second tube 12 is prevented by material of the area 18 bearing against the edges of the slot 16 and by the slots 23.

Further features of the joint shown will be described in relation to the remaining figures. However, it should be borne in mind that each of the joints described herein is formed by a partial projection of a first tube 10 (and possibly a further tube) on to a second tube 12.

Figure 6c shows a similar arrangement to that shown in figures 1 to 5, but in which the second tube 12 has a square cross section.

Figures 6a, 6b, 9a and 9b show an example of a T-section joint, with figure 6b showing a joint similar to a Tsection, but with the"cross bar"slightly angled to the "upright"of the T.

As shown in figure 9a, the first tube 10 has an end profile shaped to correspond to the interior profile of the second tube 12. Thus, the end profile is convexly curved. Also, the first tube has a first slot 26 and a second slot (not shown) opposite the first slot 26. The first and second slots are bounded by flanges 22. From this example, it being a T-section, the first tube 10 cannot be pushed sideways into position over the end of the second tube 12. Thus, the partial projection of the first tube 10 on to the second tube 12 in this embodiment results in slots 28a and b being formed to receive the flanges 22 of the first tube 10. In this embodiment, the tubes are of the same diameter. However, it is possible that the tubes would be of a different diameter to each other, in which case if the first tube 10 is of a larger diameter than the second tube 12 care will be needed to ensure that the slots 28a and 28b have a section of material between them to ensure that the second tube remains intact and is not completely broken by the slots 28a/b. This may be achieved by rotation of the slots 28a/b compared to those shown in figure 9a, so that the sections of material between the slots 28a/b are arranged vertically above one another as opposed to side by side as shown in figure 9a.

The joint of this embodiment is prepared, as before, by pushing the first tube 10 into the second tube 12 until the end of the first tube abuts the interior of the second

tube. Tabs may also be provided on the ends of the flanges 22 to engage with corresponding openings on a face of the tube opposite the slots 28a/b.

Figures lOa-lOc show a further embodiment, in which the first tube 10 has a square cross-section and the second tube 12 has a circular cross-section.

The projection of the first tube 10 on to the second tube 12 is different to that described above by virtue of the first tube 10 having a square cross-section. Thus, the profile of the flanges 22 is square when viewed from the side, as required by a square cross-section first tube 10.

Otherwise, the preparation of the first and second tubes and the joining of the tubes is the same as described above.

One difference in the examples shown in the figures 10a- 10c is that the slot 16 has a rounded lower end to match with the rounded outer surface of the second tube 12 when the two tubes 10 and 12 are joined together. If the second tube 12 was of square cross-section then the base of the slot 16 would not need to be rounded and would be squaredoff.

Figures lla-lld show the joining at right angles of two circular cross-section tubes 10 and 12, in which the first tube 10 has a diameter approximately twice that of the second tube 12. The join is made by projection of the first tube 10 onto the second tube 12. In view of the first tube 10 being somewhat larger than the second tube 12, the amount of material which is removed from the second tube 12 is considerably less than is shown in, for

example, figures 1 to 5. The reason for this is that material does not need to be taken from the sides of the second tube 12, e. g. at areas marked 30 in Figures lialld. These areas 30 are the equivalents of the flanges 22 in the previous figures. Thus, in this example the only material cut away from the second tube 12 is to produce a slot 32 and to remove some material from the end 34 of the second tube 12.

In this embodiment, the tubes are slotted together as described above.

In Figures 8 and 12a-12c a triple joint made between a first tube 10, a second tube 12 and a third tube 36 is shown. The second and third tubes 12 and 36 make a right angle and have abutting sloping ends to form a right angled joint, onto which, and at right angles to which, the first tube 10 is projected and suitable areas of material are removed from the second and third tubes 12 and 36 respectively.

The first tube has two slots 16 extending lengthways along the tube and as shown from the end in Figure 12a, and from the side in Figure 12c. These provide the partial projection for the first tube 10 which is used in each of the embodiments herein. One slot 16 would also be an option.

As can be seen in Figures 12b and 12c the upper end of the first tube 10 is shaped to conform more smoothly and to make a tidier joint by removing two scallop shapes 42 from the tube.

The joint in Figures 12a-12c is assembled by abutting the second and third tubes 12 and 36 against one another and either pushing the first tube 10 down onto the joined second and third tubes 12 and 36 or pushing the joined second and third tubes onto the end of the first tube 10.

Figures 7b and 13a-13c show a joint between the first and second tubes 10 and 12 making a wide angle of approximately 1500.

The joint is made by projection of the first tube 10 onto the second tube 12. However, because of the wide angle of this particular joint a reasonable amount of material must be removed from the first tube 10 in order to prevent the first tube 10 projecting from the top side of the second tube 12 as shown in Figures 13a-13c.

The shape of the end of the first tube 10 can clearly be seen in Figure 13b.

As with previous embodiments discussed in relation to the preceding figures flanges 22 are formed. However, given the wide angle of the joint in this example a lower flange 22 projects further forward than the other, upper, flange to accommodate the joint and still produce a smooth outer surface as shown in Figure 13c.

In Figures 7a and 14a-14c first and second tubes 10 and 12

1 respectively are shown forming a joint with a narrow angle of approximately 450.

As mentioned in relation to the previous examples in Figures 13a-13c the flanges 22 produced in the second tube

12 project forward by different amounts to accommodate the angle of join.

As with the embodiment shown in Figures 13a-13c the end of the first tube 10 is shaped to prevent the first tube 10 protruding beyond the second tube 12 when the two are joined together, as shown in Figure 14c.

In Figures 15a-15c there is shown a joint between a first tube 10, a second tube 12 and a third tube 36. The three tubes are joined at right angles to each other and the first tube has a diameter approximately two to two and half times that of the second and third tubes 12 and 36.

The first tube 10 has two slots 16 to accommodate the second and third tubes 12 and 36 respectively. The second tube 12 is cut in the same way as the second tube described in relation to Figures lla-lld. The third tube 36 is shaped to abut the second tube 12 as shown in Figure 15a, and otherwise has a section removed to allow the tube to be placed over the slot 16 as shown in Figures 15a-15c.

In order to assemble the joint shown in Figures 15a-15c the third tube 36 is pushed up against the second tube 12, in the position shown in Figure 15a and the second and third tubes 12 and 36 are then pushed down onto the first tube 10 as shown in Figures 15b and 15c.

In Figures 16a-16d a join between a first tube 10 of circular cross-section and a second tube having a generally square cross-section with rounded corners is shown. Given the generally square cross-section of the second tube 12 the end of the first tube is shaped to match the shape of the second tube 12 so that the first

tube does not extend beyond the second tube 12 when the two are joined, as shown in Figure 16d. The first tube 10 has a slot 16 in its lower side as shown in Figure 16b. The second tube 12 has flanges 22 as shown in Figure 16b which abut the end of the first tube 10 as shown in Figure 16d, when the two tubes are joined together.

It will be appreciated from the foregoing examples of jointing, that many different types of joint are possible using the same general concept of joining potentially differently shaped tubes together by cutting away a partial projection from the other tube or tubes to be joined together.

Significant advantages with this method are achieved because a very accurately machined joint can easily be produced, for example by laser cutting, which offers an accurate and effective cutting method. Also the joints used are easily assembled, simply by pushing the parts together and are very strong given the tightness achievable in this type of joint and also given that contact across the width of the joined tubes is achieved.

The spaced points of contact between the tubes, being at different sides of one particular tube provide a resistance to the pivoting of the tubes about the joint.

The joints described have applications in a wide variety of fields, indeed any in which jointed tubes can be used. Examples include building frameworks, furniture, shelving or racking, vehicle chassis or superstructures, or frameworks generally.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS: 1. A joint comprises a first tube section and at least one other, second, tube section, wherein the second tube section has an opening therein the shape of which is substantially a partial projection of the cross-section of the first tube onto the second tube and in which the joint is formed by engagement of the first tube in said opening.
2. A joint as claimed in claim 1, in which the opening corresponds to a projection of the cross-section of the first tube onto the second tube at an angle at which the first and second tubes form the joint.
3. A joint as claimed in either claim 1 or claim 2, in which the projection may be along the length of the first tube onto the second tube.
4. A joint as claimed in any preceding claim, in which the partial projection is a projection of a joint end of the first tube.
5. A joint as claimed in any preceding claim, in which the first tube includes a slot at said joint end, thereby by forming a partial cross-section of the tube.
6. A joint as claimed in claim 5, in which the slot extends in the direction of the length of the tube.
7. A joint as claimed in either claim 5 or claim 6, in which the slot has a depth of at least the diameter of the second tube.

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8. A joint as claimed in any preceding claim, in which the joint end has an end profile corresponding to an interior shape of the second tube.
9. A joint as claimed in any preceding claim, in which the joint end is shaped to remain within, or projected slightly beyond, the exterior of the second tube.
10. A joint as claimed in any preceding claim, in which the opening in the tube comprises at least one slot.
11. A joint as claimed in any preceding claim, in which the'opening has two parts, including a part on one side of the second tube and a part on the opposite side of the second tube.
12. A joint as claimed in any preceding claim, in which in the direction of the projection onto the second tube the opening has a thickness approximately equal to or just greater than a wall thickness of the first tube.
13. A joint as claimed in any preceding claim, which includes a third tube, in which case the opening is an opening in the second and third tubes.
14. A joint as claimed in claim 13, in which the opening is a partial projection of the cross-sections of the first tube onto the second and third tubes.
15. A joint as claimed in either claim 13 or claim 14, in which the second and third tubes have an abutting relationship in the joint.

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16. A joint as claimed in any one of claims 13 to 15, in which the second and third tubes have ends shaped to allow abutment of the two tubes at an angle to one another.
17. A joint as claimed in any one of claims 13 to 16, in which the opening in the second and third tubes extends across a join between the two tubes.
18. An assembly comprises first and second tubes arranged to form a joint, wherein the tube section has an opening therein, the shape of which opening is partial projection of the cross-section of the first tube onto the second tube.
19. A method of joining at least first and second tubes together, comprises cutting from the second tube material to form an opening therein, which opening has a shape which is a partial projection of the cross-section of the first tube onto the second tube, the tubes being joined together by urging the tubes together.
20. A joint substantially as described herein with reference to the accompanying drawings.
21. A method of joining at least first and second tubes together substantially as described herein with reference to the accompanying drawings.