GB2443424A

GB2443424A - Camming element for a furniture jointing device

Info

Publication number: GB2443424A
Application number: GB0621794A
Authority: GB
Inventors: William Ernest Taylor Vallance; Valter Svara
Original assignee: Titus International Ltd
Current assignee: Titus International Ltd
Priority date: 2006-11-01
Filing date: 2006-11-01
Publication date: 2008-05-07
Anticipated expiration: 2026-11-01
Also published as: GB0621794D0; GB2443424B; WO2008053176A1

Abstract

A camming element for a furniture jointing device is made from a flat blank. The camming element is in the form of a generally cylindrical drum (10) having an aperture (13a) for receiving the head of a fastening element and is provided with eccentric camming surfaces (15a, 15b) to engage the head of a dowel when the camming element is rotated, in use. The camming surfaces (15a, 15b) are designed to have a degree of resilient flexibility towards the end of the rotational movement of the camming element.

Description

Improvements in fasteners This invention relates to fasteners and in

particular, though not exclusively, to fasteners for use in the furniture industry.

According to the invention there is provided a camming element for a device for forming a joint between two members, the camming element being designed to be rotatably mountable in use in a hole in one of the members and having at least one camming surface engageable in use with a head portion of a fastening element designed to be connectable in use to the other member, rotation of the cainming element in a first direction serving in use to draw the members together by action of the said at least one camming surface pulling on the head portion of the fastening element, the camming element being formed from a fiat blank with the said at least one camming surface having a resiliently defiectable portion to allow some attenuation of the pulling force applied to the head portion of the fastening element in use, at least towards the end of the range of rotational movement of the camming element in said first direction.

By way of example, an embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a camming element according to the invention, Figure 2 is a side view of the camming element of Figure 1, Figure 3 is a cross-sectional view through the caniming element along the lines 11 -U of Figure 2, Figures 4a and 4b show the blank from which the canning element of Figure 1 is formed in various stages of formation.

The camming element seen in Figure 11$ in the form of a cylindrical drum 10.

The drum lOis formed from a fiat blank 11, here of steel, seen in its original form in Figure 4a. The drum 10 is designed to be used together with a headed fastening element to join together two members, eg furniture panels, in the manner of a cam and dowel type of fastener. Cam and dowel fasteners are well known in the home-assembly furniture industry and an example can be seen in our UK patent No. 2305226.

The cam drum 10 is designed to be rotatably mounted in a hole in a panel, in known manner. One axial end Wa of the drum 10 is closed off, as seen in Figure 1, and is provided with a cutout feature 12 to receive the head of a screwdriver or similar tool. This is the means by which the drum 10 can be rotated. The drum 10 is open at its other axial end lob. It will be noted here that the formation of the cutout feature 12 allows the possibility for the tool to be operated over a range of angles (shown as sector A in Figure 2). This allows the possibility for the cam drum 10 to be located relatively near the panel edge, with the tool being used at an angle for rotating the drum to tighten the joint.

A slot 13 extends part way round the circumference of the drum 10. The slot 13 has an enlarged opening at one end 13a: this is to receive the head of a dowel by axial insertion thereof, in known manner. Otherwise, the slot 13 is of a width to receive the neck of the dowel, with the dowel head being located within the interior of the drum 10. The slot 13 may also be made accessible to the head of a dowel by means of a cutaway 14 (shown in dotted lines in Figure 1). This is to enable the dowel to be introduced optionally into engagement with the drum 10 by lateral movement.

It will be seen in Figure 1 that on its inside, the slot 13 has a ramped profile 15. The ramped profile 15 is formed by camming surfaces l5a, 15b to either side of the slot 13 which are designed to engage and act on the head of a dowel. In use, rotation of the cam drum 10 causes the dowel to be pulled towards the rotational axis of the drum by the action of the camming surfaces 15a, 15b on the head of the dowel.

In use, the cam drum 10 is mounted in a hole in one panel and engages the head of a dowel connected to another panel and the panels can be drawn together to form a tight joint by rotation of the drum, in the manner of a known cam and dowel type fastener.

Ideally, the panels will be drawn together in a tight joint at about the stage where the head of the dowel is near the inner end I 3b of the ramped profile 15, ie at the opposite end of the slot 13 to its enlarged opening 13a. By this stage, the drum 10 will be approaching the end of its range of rotation, the head of the dowel will have travelled along the ramped profile 15 and the dowel will have been pulled up its full distance. It will be appreciated, however, that the cam and dowel will only be able to interact properly if the holes in the panels for mounting the cam and dowel are drilled with reasonable accuracy. In particular, the edge-to-hole dimension in the panel in which the cam drum 10 is mounted is critical.

Steel is a relatively hard and unyielding material. Advantageously, therefore, a certain amount of elasticity is built into the design of the cam drum 10 here.

This is achieved by providing that the camming surfaces I 5a, I 5b are resiliently deflectable, at least in part. A slit 16 is formed in the blank (see Figure 4a) in a position near to what will become the inner end 13b of the ramped profile 15 in the finished article. When the cam drum 10 is formed, this slit 16 means that the inner end I 3b of the ramped profile 15 is separated from the main body of the cam. This allows the possibility for this portion of the ramped profile 15 to flex. The deflectable portion of the ramped profile 15 can flex in a radial direction, indicated by arrow B in Figure 3, which is the direction of pull on the dowel in use.

What this achieves is effectively some "give" in the interaction between the cam drum and dowel at the point where the joint is fully made, ie at so-called lock-up. Inaccuracies in the hole-to-edge dimension can be compensated for by the deflectability of the ramped profile 15. This allows there to be a greater tolerance in the drilling of the holes in the panel. Or, to put it another way, the cam drum 10 is able to operate satisfactorily over a wider range of inaccuracy in hole drillings.

It is known that joints made with a cam and dowel fastener can loosen if subjected to knocks or vibration. This is known as "backing off".

Advantageously, therefore, there is a mechanism to prevent backing off in the cam 10 here. This is provided in the form of formations 17 on the camming surfaces I 5a and 1 5b which engage the head of the dowel, and there are complementary formations on the head of the dowel. These formations 17 generally take the form of a series of depressions and/or projections on the respective engaging surfaces. The interengagement between the formations on the ramped profile and dowel head creates a resistance to backing off after lock-up. An example of such a feature can be seen in our UK patent No 2246826.

The cam drum 10 here is formed from its original blank 11 into its finished configuration essentially by rolling the side wall into a cylinder and bending the top over. Interfitting lugs and cutouts 18,19 are designed into the blank to hold the seams together and ensure that the blank retains its integrity once assembled. Alternatively, or additionally, a welding process could be used for this. Also, of course, the drwn may be made out of two or more separate pieces, rather than the single blank shown.

The cainming surfaces I 5a, I 5b which form the ramped profile 15 in the finished cam drum 10 are advantageously formed here as cut edges of the blank. This helps to allow the dimensional and positional accuracy of the ramped profile 15 in the finished drum 10 to be controlled. It also facilitates the making of the formations 17 on the camming surfaces 1 5a, I 5b described above.

The ramped profile 15 here is initially formed from the blank 11 by a pressing or stamping process. Figure 4b shows how in the region of the slit 16, the end portion of the ramped profile 15 becomes separated from the main body of the blank. This process, known as fine blanking, has the advantage that it enables close control to be kept on the dimensional and positional accuracy of the ramped profile 15 in the finished drum 10 and, in particular, its deflectable end portion. The desired degree of flexibility of this deflectable portion of the ramped profile 15 can be achieved by controlling the position and dimensions of the slit 16.

An advantage of making a camming element out of steel is its strength. In particular, it enables the camming element to be designed to have a greater potential range of rotational movement than is typically possible using other materials such as cast zinc. This is advantageous because it enables the camining element to be capable in use of pulling a dowel through a greater distance than in a conventional device. A steel cain therefore has the capacity to work effectively with a greater tolerance of inaccuracy in the drilling of the mounting holes in the panels than hitherto.

Claims

1. A camming element for a device for forming a joint between two members, the camming element being designed to be rotatably mountable in use in a hole in one of the members and having at least one camming surface engageable in use with a head portion of a fastening element designed to be connectable in use to the other member, rotation of the camining element in a first direction serving in use to draw the members together by action of the said at least one camming surface pulling on the head portion of the fastening element, the camming element being formed from a flat blank with the said at least one camming surface having a resiliently deflectable portion to allow some attenuation of the pulling force applied to the head portion of the fastening element in use, at least towards the end of the range of rotational movement of the camming element in said first direction.

2. A camming element as claimed in claim 1 wherein said at least one camming surface is formed as a cut edge of the blank.

3. A camming element as claimed in claim 1 or claim 2 wherein said blank is formed with a slit and the resiliently deflectable portion of said at least one camming surface is formed adjacent said slit using a fine blanking process.

4. A camming element as claimed in any preceding claim wherein said at least one camming surface comprises formations for co-operating with the head portion of a said fastening element in use to prevent rotation of the camming element in a direction opposite to said first direction.

5. A camming element as claimed in any preceding claim wherein the camming element is generally in the form of a cylindrical drum, the interior of which is accessible by the head portion of a said fastening element by movement of the fastening element either axially or laterally relative to the drum.

6. A camming element substantially as herein described with reference to the accompanying drawings.

7. A device for forming a joint between two members comprising a camining element as claimed in any preceding claim and a fastening element.

8. A device as claimed in claim 7 wherein said fastening element comprises formations on its head portion for co-operating with said at least one camming surface of the camming element in use to prevent rotation of the camming element in a direction opposite to said first direction.

9. A device for forming a joint between two members substantially as herein described with reference to the accompanying drawings.

tO. A piece of furniture comprising a camming element as claimed in any one of claims 1 to 6 or a device as claimed in any one of claims 8 to 9.