Patent Description:
As is known, a furniture unit typically comprises two vertical panels (commonly called "flanks" or "shoulders"), a horizontal bottom panel (commonly called "base") and a top panel which is also horizontal (commonly called "lid"). Furthermore, the furniture unit may comprise a number of horizontal intermediate panels, otherwise known as "shelves".

During assembly of the furniture unit, the shoulders are typically joined together with the bottom panel of the furniture unit and with the top panel. Furthermore, the intermediate panels are usually joined to the shoulders of the furniture unit so as to form shelves and/or to reinforce the furniture unit.

In particular, a shelf of a furniture unit may be a shelf with a single visible edge (also called "single-face" or "blind" shelf) or a shelf with double visible edge (also called "double-face" shelf). In the first case it consists of a shelf where, when the furniture unit is assembled, only the front edge is visible and the rear edge normally rests against a panel or a wall behind the furniture unit. In the second case instead it consists of a shelf which, when the furniture unit is assembled, may have visible both the front edge and the rear edge.

<CIT>, in the name of the same present Applicant, discloses an expansion joint for joining together two panels.

<CIT> discloses another joint known in the state of the art.

The joint disclosed in <CIT> is very efficient and provides an efficient system for joining together two panels, typically in order to assemble a furniture unit.

The Applicant has defined the general object of providing an expansion joint for joining together two panels, in particular for panels made of wood or chipboard or a non-homogeneous material, which is even better than the known joint described in <CIT> or <CIT>.

In particular, the Applicant has defined the object of providing a joint, which has similar performance features, while obtaining a reduction in the production and assembly cost.

The Applicant has defined the object of finding an alternative to the solution formed by the fixing pin which is configured to engage stably with the fixing member.

According to the Applicant, in order to provide stable engagement between the joint and panel, the body of the joint must be knurled.

According to a first aspect of the invention, a joint for joining a first panel together with a second panel is provided, the joint comprising:.

According to the invention, the joint also comprises an expansion plug which is configured to engage with the outer surface of the body when the joint is completely inserted inside a recess in the thickness of a panel, for example a shelf, of a furniture unit.

According to embodiments, the joint further comprises a hexagonal element for rotating the body.

According to embodiments, the joint comprises a slot for a screwdriver at the outer end for rotating the body.

According to embodiments, the threaded pin comprises a metric thread or a self-tapping thread.

According to embodiments, the joint further comprises a pin for engaging with the transverse shaft, wherein the pin comprises a hexagonal shank and a head having a circular cross-section with a hexagon socket.

According to another aspect, the present invention provides a method for joining a first panel, for example a shelf of a furniture unit, to a second panel, for example an upright of a furniture unit, wherein said first panel comprises a recess in its thickness and a transverse hole and said second panel comprises a threaded bush, or a hole or a recess, the method comprising:
providing a joint of the aforementioned type, inserting the joint completely inside the recess of the first panel, rotating the transverse shaft so as to cause the rotation of the longitudinal shaft and the rotation of the threaded pin, such that the threaded pin passes from the configuration inside the body to the configuration at least partially outside the body and engages inside a threaded hole in the bush or a hole formed directly in the second panel.

According to embodiments, the method further comprises the step of fully inserting the joint comprises the step of pushing the joint so that the expansion plug expands on the outer surface of the body.

According to embodiments, the method further comprises the step of rotating the joint body with a tool for example a hex wrench or a screwdriver, so as to adjust its position or extract it from the recess.

The present invention will become clearer from the following detailed description, provided by way of a non-limiting example, to be read with reference to the attached drawings in which:.

The joint according to the present invention is particularly suitable for being inserted in a milled opening formed in a panel of a furniture unit or the like. In particular, it is suitable for being inserted in the side thickness of a shelf of a furniture unit in order to connect said shelf to a side of the said furniture unit. The joint according to the present invention is suitable for use in any material, but is particularly effective when the shelf is made of a non-homogeneous material, such as a chipboard panel or a laminated chipboard panel. These panels are formed by bonding together wood chips.

With reference initially to <FIG> and <FIG>, the main components of a first joint according to the present invention are shown.

A joint <NUM> according to the present invention typically comprises a body <NUM> and a plug <NUM>.

The body <NUM> has a roughly cylindrical shape with a first end (also called outer end) <NUM> and a second end <NUM> (also called inner end since, during use, it is located close to the bottom of the hole inside which the joint is inserted). Preferably, the body <NUM> is formed by two half-shells 10A and 10B which, when they are joined together, form a substantially hollow body. The interior of the body <NUM> and any gearing inside it will be described further below. The half-shells may be joined together by means of pins and holes. The half-shell 10A is also called male half-shell because it has pins, while the half-shell 10B is also called female half-shell because it has holes for receiving the pins.

The body <NUM> has a roughly circular cross-section, but preferably comprises two longitudinal strips <NUM> which are diametrically opposite to each other and form two flat surfaces. The longitudinal strips <NUM> extend substantially along the whole length of the body <NUM>. The body <NUM> has a transverse through-hole <NUM> in the vicinity of the inner end <NUM> of the body <NUM>.

Preferably, the inner end <NUM> of the body <NUM> is tapered and has a pair of diametrically opposite reliefs <NUM> for retaining the plug <NUM>, as will be clarified below.

The outer end <NUM> of the body <NUM> has preferably a longitudinal hole <NUM>. Preferably, it also has a centring slot <NUM> for the head of a screwdriver or another similar tool.

The outer end <NUM> of the body <NUM> also comprises a hexagonal element <NUM> for rotating the body <NUM>, when necessary. As will be clarified below, it may also be required to rotate the joint in order to insert it into a cavity <NUM> of the panel, in order to adjust its position or extract it.

The outer surface of the body <NUM> comprises raised ridges which form a knurling <NUM>. According to the invention, the knurling <NUM> has a substantially helical progression. Preferably the knurling <NUM> is interrupted in the region of the longitudinal strips <NUM>.

The body <NUM> may be made of a metallic material such as steel, aluminium, zamak or alloys thereof. Alternatively, the body <NUM> may be made of structural plastics such as glass-fibre reinforced nylon.

The plug <NUM> has preferably a roughly cylindrical shape with a proximal end <NUM>, a distal end <NUM> and a side surface <NUM>. The terms "distal" and "proximal" relate to the inner end <NUM> of the body <NUM>.

The proximal end <NUM> comprises preferably a collar <NUM> configured to engage with the reliefs <NUM> of the inner end <NUM> of the body <NUM> so that, in a preassembled configuration (<FIG>), the body <NUM> and the plug <NUM> are stably connected. The collar preferably has a pre-weakened point for favouring breakage thereof in a substantially predictable manner.

Preferably, the side surface of the plug <NUM> comprises a plurality of parallel fins <NUM>. Preferably the side surface <NUM> of the plug <NUM> has a pair of longitudinal diametrically opposite openings <NUM> with a size and shape similar to that of the longitudinal flat surfaces <NUM> of the body <NUM>.

The plug <NUM> is preferably made of a thermoplastic material and is preferably obtained by means of moulding. Preferably it has a thickness of the side surface which is small, for example less than <NUM>. Preferably, the thickness at the distal end <NUM> is greater.

The various views of <FIG> show the joint <NUM> with the plug <NUM> in the non-expanded configuration. This is typically the configuration which the joint <NUM> has before being inserted into a recess <NUM> in the thickness of a panel (for example a shelf) of a furniture unit.

The various <FIG> show instead the joint <NUM> with the plug <NUM> in the expanded configuration, completely fitted over the body <NUM>. This is typically the configuration which the joint <NUM> has after it has been fully inserted inside a recess <NUM> in the thickness of a panel (for example a shelf) of a furniture unit.

<FIG> shows the components inside the body <NUM>. The components comprises a transverse shaft <NUM> with a first bevel gear wheel <NUM> and a longitudinal shaft <NUM> with a second bevel gear wheel <NUM> in engagement with said first bevel gear wheel <NUM>. The first shaft <NUM> preferably comprises a cylinder having a through-cavity with a hexagonal cross-section so that it may be rotated by means of a hex wrench of the Allen key type <NUM>. The hexagonal through-cavity is situated opposite the transverse through-hole <NUM> of the body <NUM>.

The longitudinal shaft <NUM> preferably comprises an internal shaft with a hexagonal cross-section connected to the second bevel gear wheel <NUM> and a tie-piece <NUM> concentric with the internal shaft and in engagement with it so that rotation of the internal shaft <NUM> causes the rotation of the tie-piece <NUM>. The tie-piece <NUM> comprises a threading <NUM> and terminates in an externally threaded section which forms said threaded pin <NUM>. According to one embodiment, the threading of the threaded pin <NUM> may be an M4 or M6 threading. An end stopper plug <NUM> may be provided in order to prevent scratching of the panels with which the threaded pin <NUM> comes into contact.

A nut <NUM> which acts as a shoulder is preferably provided in an intermediate position along the tie-piece <NUM>. The thread <NUM> has the function of allowing the tie-piece <NUM> to be moved backwards and forwards. Preferably, a cylindrical spring <NUM> is mounted around said tie-piece <NUM> and is retained between said nut <NUM> and a rib <NUM> (see <FIG>) inside the half-shells 10A and 10B of the body <NUM>. The spring <NUM> tends to push the nut <NUM> which in turn pushes the tie-piece <NUM>, causing the threaded pin <NUM> to move outwards. The nut <NUM> is preferably screwed onto a threading of the tie-piece <NUM>.

The threaded pin <NUM> may assume (i) the position where it is fully retracted, i.e. not projecting from the outer end of the body, (ii) the position where it is fully extended, namely fully projecting from the outer end of the body, or (iii) any intermediate position. The displacement of the threaded pin <NUM> occurs when the transverse shaft <NUM> (accessible via the transverse hole <NUM> in the body <NUM>) is rotated. This rotation causes the rotation of the first bevel gear wheel <NUM>, the second bevel gear wheel <NUM>, the internal shaft <NUM> and the tie-piece <NUM>.

The joint <NUM> of <FIG> is entirely similar to the joint <NUM> of <FIG> and a detailed description thereof will not be repeated. The difference consists in the fact that the joint <NUM> in <FIG> does not have an expansion plug and is not forming part of the invention.

The gripping action is ensured by the knurling <NUM> on the surface of the body <NUM>. The joint <NUM> is also shown in the various views of <FIG>.

<FIG> shows in schematic form the main steps for joining a first panel (shelf) <NUM> to a second panel (upright or shoulder) <NUM> by means of the joint <NUM> according to the first embodiment. The shelf <NUM> is provided with a recess <NUM> for housing the joint <NUM> according to the invention and the upright <NUM> has, inserted inside it, a bush <NUM> with a threaded hole for receiving the pin <NUM> of the joint <NUM> according to the invention. The shelf <NUM> also has a transverse hole <NUM> formed therein beforehand in a suitable position. <FIG> shows a portion of the shelf <NUM>, the recess <NUM>, the transverse hole <NUM> and the joint <NUM> according to the first embodiment. The joint <NUM> is preassembled and the threaded pin <NUM> is substantially in its completely retracted position. The joint <NUM> is about to be inserted inside the recess <NUM>. Then (<FIG>) the preassembled joint <NUM> is pushed fully inside the recess <NUM>. With a further axial pushing force, the body <NUM> is pushed inside the plug <NUM> and this movement causes a substantially uniform radial expansion of the plug <NUM> inside the recess <NUM> (<FIG>). Advantageously, with this movement, the knurling <NUM> of the body <NUM> engages with the inner surface of the plug <NUM>. Owing to this engagement, the extraction force which would be required to extract the body <NUM> from the recess <NUM> is greatly increased. This is extremely advantageous in all cases, but in particular when the material is not compact, but is an agglomerated material. <FIG> show the joint completely inserted inside the recess. An enlarged detail is also shown encircled for each figure.

<FIG> shows the threaded pin <NUM> partly extracted and therefore partly screwed inside the hole of the bush <NUM> in the shoulder <NUM>. In <FIG> the pin is fully extracted. In order to extract the threaded pin <NUM>, the assembler inserts an Allen key <NUM> inside the transverse hole <NUM> in the shelf <NUM> and engages it with the transverse shaft <NUM> of the joint <NUM>.

As shown in <FIG>, the joint <NUM> is preassembled so that the two openings in the plug are aligned with the two flat surfaces of the body. The two openings also allow full access to the transverse hole <NUM> inside the body <NUM>. Obviously it is also necessary for the transverse hole in the body to be aligned with the transverse hole <NUM> in the shelf <NUM>. If a slight misalignment after assembly is noticed, the assembler could rotate the joint by means of the hexagonal element <NUM>. The assembler could also decide to extract the joint from the recess by rotating it by the amount required.

The joint <NUM> according to the first embodiment is very advantageous and practical. Firstly it ensures a strong gripping action because it acts over a broad surface area. Another advantage which it has is that it may be inserted at the factory by means of special machinery and need not be assembled on-site. Advantageously, the threaded pin <NUM> is kept fully retracted. The fact that it does not project facilitates storage and assembly and prevents the risk of the threaded pin <NUM> scratching or damaging other parts of the furniture unit. It also allows assembly of a furniture unit inside a niche.

Advantageously, the joint may be assembled only by exerting a pressure in the axial (longitudinal) direction of the body. Rotational movements are not necessary.

Another advantage is that the joint is completely reversible and the shelf in which it is mounted may be used as a middle shelf, as a base or as a lid.

Owing to the spring <NUM>, the threaded pin <NUM> is pushed so as to engage in an efficient manner with the threading of the bush <NUM> in the shoulder <NUM>.

<FIG> shows in schematic form the main steps for joining a first panel (shelf) <NUM> to a second panel (upright or shoulder) <NUM> by means of the joint <NUM> not forming part of the invention, according to <FIG>. The shelf <NUM> is provided with a recess <NUM> for housing the joint <NUM> according to the invention and the upright <NUM> has, inserted inside it, a bush <NUM> with a threaded hole for receiving the pin <NUM> of the joint <NUM>. The shelf <NUM> also has a transverse hole <NUM> formed therein beforehand in a suitable position. <FIG> shows a portion of the shelf <NUM>, the recess <NUM>, the transverse hole <NUM> and the joint <NUM>, before it is inserted inside the recess <NUM>. Then (<FIG>) the joint <NUM> is pushed fully inside the recess <NUM>. Advantageously, with this movement, the knurling <NUM> of the body <NUM> is made to engage with the inner surface of the recess <NUM>. Owing to this engagement, the extraction force which would be required to extract the body <NUM> from the recess <NUM> is greatly increased. <FIG> show the joint <NUM> fully inserted inside the recess. An enlarged detail is also shown encircled for each figure.

<FIG> shows the threaded pin <NUM> partly extracted and therefore partly screwed inside the hole of the bush <NUM> in the shoulder <NUM>. In <FIG> the pin <NUM> is fully extracted. In order to extract the threaded pin <NUM>, the assembler inserts an Allen key <NUM> inside the transverse hole <NUM> in the shelf <NUM> and engages it with the transverse shaft <NUM> of the joint <NUM>.

<FIG> shows an accessory <NUM> which may be used in association with the joint <NUM> or the joint <NUM>. The accessory <NUM> is essentially a circular ring which is split, namely open on one side. Internally it has a substantially hexagonal shape. The size of the hexagon substantially corresponds to the hexagonal element <NUM>. The accessory has the main function of closing off the space between the inner surface of the recess <NUM> and the hexagonal element <NUM>, as shown in <FIG>. This, in order to preserve the material around the joint as well as for aesthetic purposes.

The example <NUM> not forming part of the invention (<FIG>) is similar to the preceding example <NUM>. The difference consists in the fact that the hexagonal element <NUM> is not present, but there is a slot <NUM> for a screwdriver. As regards the rest, the body <NUM> (with the knurling <NUM>) is substantially the same. The components inside the joint are also substantially the same.

The second embodiment <NUM> of the joint <NUM> (<FIG>) is similar to the first embodiment <NUM>. The difference consists in the fact that the threaded pin <NUM> has a European thread (i.e. triangular for wood screws) instead of a metric thread. This allows the threaded pin <NUM> to engage directly inside a hole <NUM> of the upright <NUM>. A bush inside the upright is not required, as shown in <FIG>.

The example <NUM> of the joint not forming part of the invention is shown in <FIG> and is similar to the second embodiment. Unlike the joint <NUM>, the joint <NUM> does not comprise a plug, but has only the knurling <NUM> on the surface of the body <NUM>.

The example <NUM> (<FIG>) is not forming part of the invention and is entirely similar to the first embodiment <NUM>, but is of the female type, namely without the threaded pin <NUM>. Whereas the body <NUM> is entirely similar to the body <NUM> of the first embodiment, it does not contain gears and parts. It contains only a nut <NUM>. In <FIG> the plug is shown fully expanded on the body <NUM>.

The example <NUM> (<FIG>) is not forming part of the invention and is entirely similar to the preceding example <NUM>. The difference consists in the fact that the joint <NUM> does not have an expansion plug.

In <FIG> a possible use of the female joint <NUM> according to <FIG> is schematically shown. The female joint <NUM> is used to engage with a male joint <NUM> according to the first embodiment. In this way two panels may be joined together in an end-to-end configuration.

<FIG> show different views of a pair of joints <NUM> not forming part of the invention, which are rotatably connected so as to join together two panels in a hinged manner. Each joint <NUM> comprises a body <NUM> with knurling <NUM> and a plug <NUM>.

<FIG> show different views of a pair of joints <NUM> not forming part of the invention, which are rotatably connected so as to join together two panels in a hinged manner. Each joint <NUM> comprises a body <NUM> with knurling <NUM>, but does not comprise a plug <NUM>.

<FIG> show two panels which are joined together by means of the joints <NUM>. The panels may be joined together end-to-end (<FIG>), at an angle other than <NUM>° (<FIG>) or at right angles (<FIG>).

<FIG> show a pin <NUM> designed to be inserted inside the transverse hole <NUM> of the panel <NUM>. The pin <NUM> comprises a hexagonal shank <NUM> and a head <NUM> with a circular cross-section. The head <NUM> comprises a hexagon socket <NUM>. The hexagonal shank <NUM> also comprises a ridge <NUM> for firmly retaining the hexagonal shank <NUM> inside the shaft <NUM>, which also has a hexagonal cross-section.

<FIG> shows the pin <NUM> before it is inserted inside the hole <NUM>. Finally, <FIG> shows the pin <NUM> after it has been inserted inside the hole <NUM>.

Claim 1:
A joint (<NUM>, <NUM>, <NUM>, <NUM>) for joining a first panel (<NUM>) together with a second panel (<NUM>, <NUM>), comprising:
a substantially hollow body (<NUM>) having substantially a cylindrical shape with an outer end (<NUM>) and an inner end (<NUM>), and
gearing for rotatably displacing a threaded pin (<NUM>) from a position retracted within the body (<NUM>) to a position at least partially extracted from the body (<NUM>);
wherein said gearing comprises a transverse shaft (<NUM>) with a first bevel gear wheel (<NUM>) and a longitudinal shaft (<NUM>) with a second bevel gear wheel (<NUM>) in engagement with said first bevel gear wheel (<NUM>), wherein the rotation of the transverse shaft (<NUM>) causes the rotation of the longitudinal shaft and the rotation of the threaded pin (<NUM>),
wherein said body (<NUM>) comprises an outer surface and wherein said outer surface comprises raised ridges forming a knurling (<NUM>),
characterised in that
the knurling (<NUM>) has a substantially helical progression,
and in that the joint further comprises an expansion plug (<NUM>) which is configured to engage with the outer surface of the body (<NUM>) when the joint is fully inserted inside a recess (<NUM>) in the thickness of a panel (<NUM>), for example of a shelf, of a furniture unit.