This invention relates to joint forming devices and in particular, though not exclusively, to such devices for use in the furniture industry.
Joint forming devices are used extensively in the flat-pack furniture industry for connecting panels together. Such panels are customarily pre-drilled with a standard pattern of holes for receiving the joint forming devices. Often, drilling jigs are used to drill a multiplicity of holes at once. With larger panels, this can sometimes lead to quite significant inaccuracies in hole positions. This in turn can make assembly of the panels into furniture problematic. The present invention aims to try and alleviate this problem.
The invention provides a fastening element for a joint forming device, comprising an elongate dowel and a sleeve for the dowel, the dowel having a head portion at one end thereof which is engagable in use with a tightening element, the dowel being adapted at the other end thereof to co-operate with the sleeve to cause radial expansion of an expandable end section of the sleeve upon relative axial movement between the sleeve and dowel, the expandable end section of the sleeve being insertable axially into a mounting hole in a first panel, the head of the dowel being insertable axially into a mounting hole in a second panel whereby to enable engagement with said tightening element, and the sleeve being configured to allow the position of the dowel within its mounting hole in the second panel to be adjusted to enable insertion of the expandable end section of the sleeve into its mounting hole in the first panel, in use, even if the axes of the two mounting holes are out of axial alignment.
By way of example, an embodiment of the invention will now be described with reference to the accompanying drawings, in which:
An embodiment of a fastening element according to the present invention, shown in
As will be seen, the sleeve 11 has a generally conical profile leading up to its expandable end section 14. This contrasts with the normally cylindrical profile of prior art sleeves. The conical profile extends fully between the end 15 of the sleeve 11 and its expandable end section 14 and is indicated by reference 16 in the drawings. The maximum outer diameter of the sleeve 11 is at its end 15 and this roughly equates to the bore size of the mounting hole 105 in the panel 104. At the narrowest point of the conical profile 16, adjacent the expandable end section 14, the sleeve is reduced to about 75% of its diameter at the end 15.
As seen in
If there is any inaccuracy in the position in which the mounting holes 105 and 109 have been drilled in the two panels 104 and 110, they will not match up when the panels are brought together. In
As will be seen, the conical profile 16 of the sleeve 11 allows the fastening element some freedom of movement in order to be able to adjust its position within its mounting hole 105 in the panel 104. In particular, the fastening element can tilt so that its axis lies at an angle to the axis of its mounting hole 105. It can do this whilst the head 12 of the dowel 10 remains in engagement with the cam 102. The effect of such an adjustment will be to offset the protruding end of the fastening element, ie the expandable end section 14, relative to the axis of the mounting hole 105.
Prior art fastening elements are typically not expected to be able to tolerate inaccuracies in hole positionings of any more than about 0.5 mm. With the fastening element described above, it should be possible to increase the tolerance to nearly 2 mm of allowable inaccuracy.
It is important that the fastening element has some means to retain it in position in its hole 105 in the panel 104, for assembly and also possibly transit purposes. This is achieved here by a pair of fins 17 extending out from sleeve 11 adjacent to the expandable end section 14. The fins 17 are narrow in section and flexible. At pre-assembly, that is to say, before the two panels are brought together into engagement, the fins 17 are able to locate the sleeve 11 in its mounting hole 105 with sufficient grip to keep it there. However, the fins 17 are designed to flex and/or bite into the panel 104 in the event that the position of the fastening element has to be adjusted in order to take up a misalignment.
A further feature of the sleeve here is that it has a resiliently collapsible region 18. This allows for a controlled reduction in the length of the sleeve when the fastening element is used in practice. This is needed to allow the panels to be brought up together (so as not to leave a gap between them) and then to put them under load so as to create a tight joint. This technology is known from the applicant's own earlier GB patent No. 2335245.
Number | Date | Country | Kind |
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0520450.8 | Oct 2005 | GB | national |