GB1593379A

GB1593379A - Insert for tubular members

Info

Publication number: GB1593379A
Application number: GB5414276A
Authority: GB
Original assignee: Comens A B; Comens C J
Current assignee: Comens A B; Comens C J
Priority date: 1977-12-22
Filing date: 1977-12-22
Publication date: 1981-07-15

Description

(54) INSERT FOR TUBULAR MEMBERS (71) We, ALBERT BERNARD COM ENS, of 95 Leighton Avenue, Swindon, Wiltshire, and CYRIL JAMES COMENS, of 20 Church Street, Wootton Basset, Wiltshire, both British Subjects, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is performed, to be particularly described in and by the following statement: This invention relates to devices for inserting into the end of tubular members, for example to plug the end of a tube or provide means for attaching the tube to another component.

According to one aspect of the present invention there is provided a nut for insertion into a tubular member, comprising a flat transverse portion with a central opening helically formed for mating with the thread of a screw, and substantially axially projecting peripheral portions at the ends of which are provided elements which are angled radially outwardly and axially in the same direction as the axial portions, edges of said elements remote from the transverse portion constituting the widest part of the nut, whereby the axial portions can engage the inside surface of the tube to keep the plane of the transverse portion at right angles to the axis of the tube while the nut is being forced down the tube, and said edges of the angled elements resist withdrawal of the nut from the tube.

The invention also provides an insert for tubular members comprising a nut as described in the foregoing paragraph in combination with a plug having a body for insertion into the end of a tubular member and a screw whose shank passes rotatably axially through the plug, the nut screwthreadedly engaging the shank so as to lie inside the tubular member, the peripheral elements of the nut occupying a transverse dimension slightly larger than the crosssection of the plug body so the nut will be a tight fit within the tube, the peripheral elements being angled radially outwardly and towards the plug so that they will deflect resiliently axially when the nut is forced into the tube from the plug end but will resist withdrawal of the nut from the tube.

The plug body preferably has a portion whose external cross-section increases progressively towards the outer end of the plug and is made of resilient material, so that it can resiliently deform to accommodate tubes with somewhat differing internal cross-sectional sizes. The plug may be provided with a radially directed flange at the outer end of the body for abutting the end of the tube.

The plug and nut are preferably adapted for insertion into a tube of circular crosssection, but they may alternatively be adapted for insertion into tubes having square, oblong or other cross-sections.

In order that the invention may be more clearly understood, various embodiments will now be described with reference to the drawings accompanying the Provisional Specification, wherein: Figure 1 shows a perspective view of a plug; Figure 2 shows a perspective view of a first form of nut; Figure 3 shows a cross-sectional view of the plug and nut being inserted into the end of a tube; Figure 4 shows a perspective view of a second form of nut; Figure 5 shows a side view of the nut of Figure 4; Figure 6 shows a top view of the nut of Figure 4; Figure 7 shows a cross-section view of the plug and second form of nut inserted in the end of a tube; Figure 8 shows an alternative arrangement of the screw in the end plug, and Figure 9 shows a perspective view of a nut suitable for conecting rectangular section tubes, and the manner of its use.

Referring to the drawings, and firstly to Figure 1; the plug is made from resilient plastics material and comprises a body 10 of circular cross-section and having a radially outwardly directed flange 12 at one end (the outer end). The hody 10 is slightly frustoconical, enlarging in cross-section towards the outer end. A central passage 14 passes axially through the plug to receive a screw.

Optionally, slots 16 may be formed in the body, extending axially from the inner end, to facilitate contraction of the pltig crosssection during the initial part of he insertion into the tube.

The nut l 18 shown in Figure 2 is of a known design. made of spring steel sheet and in the form of a dished washer. It has a central aperture 20 with a short radial cut 22 at one point, enabling the washer around the aperture to be given an axially helical form. By this means, it can be screwed onto the screw-threaded shaft. The dished marginal portion of the washer is provided with a number of slots 24 extending radially inwardly from the edge, thereby providing a number of scparate elements 16 which can be individually rcsilicntly axially deflected.

In usc, as shown in Figure 3, the shank 28 of a screw is passed through the passage 14 of the plug, with the head 3() of the screw at the outside end of the plug, and the nut 18 is screwed onto the shank, with the concave surface of the nut facing the plug. Then the nut is driven into the open end of the tube 32, by applying force to the heats of the screw, for example using a hammer. Engagement of the head of the screw with the plug forces the plug into the end of the tube until the flange 12 abuts the end of the tube.

In Figure 3, the nut is shown as having been screwed up against the inncr end of the plug prior to its insertion in the tube. However, this is not always necessary, and it could be located nearcr the end of the shank 28 of the screw, for example as shown in broken lincs. The body of the plug, being slightly frusto-conical, is selected so that it will be a tight fit within the tube. If the internal cross-section of the tube is somewhat smaller than the external cross-section of the plug body adjacent the flange, the excess material of the plug body will be compressed or cut back by the edge of the tube. it may be preferable to make the passage 14 in the plug appreciably larger than the diameter of the screw shank 28, so that the body of the plug docs not comprcss onto the shank when the plug is forced into the end of the tube. Howevcr, the portion 15 of the passage 14 at the outer end of the plug is preferably a rather closcr fit around the plug SO as to prevent any undue play.

It will be seen that the nut 18 can be forced into the tube because the elements 26 will deflect resiliently towards the end of the tube. However, if an attempt is made to withdraw the nut from the tube, the elements 26 cannot flex in the other direction, since this causes them to bite firmly into the surface of the tube. Thus, the nut can withstand the axial pressure when the screw is tightened.

One problem of the type of nut shown in Figure 2 is that it is sometimes difficult to ensure that it passes down the tube in a plane substantially at right angles to the axis of the tube. It it adopts an appreciable angle to this plane, it can be difficult to engage or remove the screw. Accordingly, an improved nut is shown in Figures 4 to 6. This nut 34 is also made from spring steel sheet, and has a face 36 with a central aperture 38 to take the screw shank. A radial slit 40 is provided at one point so that the edge of the opening 38 can be provided with an axial helical form for engagement with the screw, as in the nut of Figure 2. Two opposed sides of the face 36 may be straight, as shown, but the other two opposed sides are arcuate, forming part of a circle just a little smaller than the inside diameter of the tube into which the nut is to be fitted. From these two opposed edges two axial surfaces 42 project in one direction. Although these surfaces 42 extend essentially axially, they have a slight frusto-conical form, diverging slightly away from the face 36. This ensures that the nut will be a close fit inside tubes which are of slightly larger internal diameter than the nominal diameter for which the face 36 is designed. The surfaces 42 will resiliently deflect radially to the extent required for insertion of the nut inside the tube. At the two corners of each surface 42 remote from the face 36 are provided tooth-like elements 44, extending in the same direction as the surfaces 42 but inclined radially outwardly at a greater angle. These tooth elements bite into the surface of the tube to resist with drawl.

Figure 7 shows how the nut 34 is inserted into the tube. either engaged on the end of the screw shank 28, or preferably abutting the inner end of the plug body 40. The axial surfaces 42 engage the inside surface of the tube 32 as the nut is forced into the tube, and assist in maintaining the face 36 of the nut substantially at right angles to the tube axis.

Once the plug and nut are in position, the screw can be removed, and can then be used for attaching other components to the end of the tube. In the arrangement shown in Figure 8, the screw has been reversed prior to insertion of the plug. so that the head 30 of the screw is inside the tube and the shank projects from the outer end of the plug. The nut is screwed onto the shank and tightened against the head before insertion into the tube. The projecting shank 28 can then be used for attaching other components to the end of the tube. This arrangement may be particularly advantageous, for example, when the tube is to provide the leg of the table or the like; the leg being simply screwed into a recessed nut provided on the underside of the table top.

Referring to Figure 9; this nut 50 is made of spring steel and comprises a generally flat central part 52 with an aperture 54 and slit 56 similar to those in the other nuts described above. The ends of the central part are turned over to form a pair of limbs 58 at each end, each pair of limbs having toothlike elements 60 similar to the elements 44 in the nut of Figures 4 to 6, and for the same purpose. In addition, between one of the pairs of limbs is a prong 62 which extends beyond the limbs 58 and is rather nearer the centre of the nut.

In use the nut is inserted into a rectangular section tube 64, so that the prong 62 projects therefrom. A similar rectangular section tube 66 or other component is secured to the end of the tube 64 by a screw 68 which engages the nut 50. A small opening 70 is provided in the tube 64 to receive the prong 62, thereby preventing rotation of the tube 64 relative to the tube 66.

WHAT WE CLAIM IS: 1. A nut for insertion into a tubular member, comprising a flat transverse portion with a central opening helically formed for mating with the thread of a screw, and substantially axially projecting peripheral portions at the ends of which are provided elements which are angled radially outwardly and axially in the same direction as the axial portions, edges of said elements remote from the transverse portion constituting the widest part of the nut, whereby the axial portions can engage the inside surface of the tube to keep the plane of the transverse portion at right angles to the axis of the tube while the nut is being forced down the tube, and said edges of the angled elements resist withdrawal of the nut from the tube.

2. A nut according to claim 1 wherein a pair of diametrically opposed axial surfaces are provided, and each of these has a pair of tooth-like angled elements.

3. A nut according to claim 1 or claim 2 including an axial prong which extends beyond said axial portions.

4. A nut according to any one of claims 1, 2 and 3 made from hard resilient material.

5. A nut according to claim 4 made from spring steel sheet.

6. A nut for insertion into a tubular member, substantially as described herein with reference to Figures 4 to 6 or Figure 9 of the drawings accompanying the Provisional Specification.

7. An insert for tubular members, comprising a nut according to any one of the preceding claims in combination with a plug having a body for insertion into the end of a tubular member and a screw whose shank passes rotatably axially through the plug, the nut screw-threadedly engaging the shank so as to lie inside the tubular member, the peripheral elements of the nut occupying a transverse dimension slightly larger than the cross-section of the plug body so the the nut will be a tight fit within the tube, the peripheral elements being angled radially outwardly and towards the plug so that they will deflect resiliently axially when the nut is forced into the tube from the plug end but will resist withdrawal of the nut from the tube.

8. An insert according to claim 7 wherein the plug body has a portion whose external cross-section increases progressively towards the outer end of the plug and is made of resilient material, so that it can resiliently deform to accommodate tubes with somewhat differing internal crosssectional sizes.

9. An insert according to claim 7 or claim 8 wherein the plug is provided with a radially directed flange at the outer end of the body for abutting the end of the tube.

10. An insert for tubular members, substantially as described herein with reference to the drawings accompanying the Provisional Specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. nut is screwed onto the shank and tightened against the head before insertion into the tube. The projecting shank 28 can then be used for attaching other components to the end of the tube. This arrangement may be particularly advantageous, for example, when the tube is to provide the leg of the table or the like; the leg being simply screwed into a recessed nut provided on the underside of the table top. Referring to Figure 9; this nut 50 is made of spring steel and comprises a generally flat central part 52 with an aperture 54 and slit 56 similar to those in the other nuts described above. The ends of the central part are turned over to form a pair of limbs 58 at each end, each pair of limbs having toothlike elements 60 similar to the elements 44 in the nut of Figures 4 to 6, and for the same purpose. In addition, between one of the pairs of limbs is a prong 62 which extends beyond the limbs 58 and is rather nearer the centre of the nut. In use the nut is inserted into a rectangular section tube 64, so that the prong 62 projects therefrom. A similar rectangular section tube 66 or other component is secured to the end of the tube 64 by a screw 68 which engages the nut 50. A small opening 70 is provided in the tube 64 to receive the prong 62, thereby preventing rotation of the tube 64 relative to the tube 66. WHAT WE CLAIM IS:

1. A nut for insertion into a tubular member, comprising a flat transverse portion with a central opening helically formed for mating with the thread of a screw, and substantially axially projecting peripheral portions at the ends of which are provided elements which are angled radially outwardly and axially in the same direction as the axial portions, edges of said elements remote from the transverse portion constituting the widest part of the nut, whereby the axial portions can engage the inside surface of the tube to keep the plane of the transverse portion at right angles to the axis of the tube while the nut is being forced down the tube, and said edges of the angled elements resist withdrawal of the nut from the tube.

5. A nut according to claim 4 made from spring steel sheet.