WO2017001419A1

WO2017001419A1 - Joining device, particularly for joining a shelf to a wall of a piece of furniture

Info

Publication number: WO2017001419A1
Application number: PCT/EP2016/065044
Authority: WO
Inventors: Luca Carnelos; Simone Della Rosa; Giulio Durigon; Abramo Ivan; Davide Verziagi; Christian Zonta
Original assignee: Ferramenta Livenza - Societa' A Responsabilita' Limitata
Priority date: 2015-06-29
Filing date: 2016-06-28
Publication date: 2017-01-05

Abstract

A joining device (1), associable with a shelf (2) that in turn can be arranged against a wall (3) of a piece of furniture, comprising a cylindrical body (4) that can be associated in a first hole (5) adapted to be provided transversely in the shelf (2) and provided with a first axial seat (8) for the rotatable coupling of the first stem (9) of a screw (10) provided with a first crown-shaped head (11) that can be arranged rotatably within a second seat (12) that is adjacent to the first seat (8). The joining device (1) comprises an insert (37) that is accommodated within a second hole (28) adapted to be provided in the shelf (2), at right angles to the first hole (5), and is arranged substantially flush with or below the upper surface (29) of the shelf (2). On the insert (37) there is a seventh seat (38) for the rotatable coupling of a second head (22) of a pinion (21) that interacts with the first crown-shaped head (11). On the insert (37) there is also an eighth seat (39), which is adjacent and parallel to the seventh seat (38), for the passage of a tool for the optional adjustment of a foot associated with the piece of furniture.

Description

JOINING DEVICE, PARTICULARLY FOR JOINING A SHELF TO A WALL OF A PIECE OF FURNITURE

The present invention relates to a joining device, particularly for joining a shelf to a wall of a piece of furniture.

Currently, Italian utility model no. 262995, filed with application

PN2005U000035, is known which claims a joint, for the detachable connection of two structural elements of a piece of furniture that mutually abut at right angles, comprising an accommodation body that can be associated with a first structural element and is adapted to engage a fixing element that can be associated with a second structural element and an actuation element that is arranged in the accommodation body and is adapted to cooperate with said fixing element so as to mutually fix the structural elements; the fixing element comprises a toothed head that is in one piece with a stem of a screw, the head being coupled rotatably within the accommodation body and the screw stem protruding from the accommodation body, the actuation element comprising a crown gear that is adapted to actuate the head in order to screw the screw stem into the second structural element.

This solution suffers drawbacks: a high production and assembly cost is in fact noted, due to the structural complexity of the joint, the need to provide the joint in various sizes/dimensions as a function of the thickness of the panel, the need to use the joint on panels with high minimum thicknesses, a considerable aesthetic impact since the joint exposes the flat edge that must be applied so as to affect one edge of the panel, and the need to provide two holes/seats on the panel for the placement of the accommodation body and of the pin, the execution of which is complicated.

The accommodation body has a cylindrical shape and is divided diametrically into two components, which must be joined to each other in order to clamp the crown gear and the fixing element: a high degree of clamping might not allow optimum interaction between the gears, while clamping provided with the presence of plays might lead to difficulty in activating the gears due to possible mutual jamming of the teeth.

Furthermore, the crown gear and the fixing element are embedded in the accommodation body: in case of maintenance on the crown gear it is necessary to remove the entire accommodation body from the panel and then open, in practice breaking it, the accommodation body in order to access the internal components; in practice, in case of maintenance, it is necessary to replace the entire joint; moreover, the panel is also ruined in this case.

This solution makes it necessary to provide a further hole in the panel in order to be able to perform any adjustment of a leveling foot associated with the piece of furniture.

Finally, this structure is bulky and is therefore difficult to install if thin panels are used.

WO 2008/076089 is also known which discloses a solution for providing the connection of construction elements such as a panel; this solution comprises a threaded bush and a frame that can be arranged within a hole provided transversely to the panel; inside the frame there is a first screw, provided with a crown-shaped head, which interacts, according to a crown gear-pinion system, with the head of a second screw. A solution is shown in which a hole is provided in a panel to allow adjustment of the second screw.

This solution, also, suffers drawbacks: the second screw, once screwed to the frame, is fixed in its position and is no longer removable and therefore it is not possible to perform any maintenance in case of malfunctions or wear.

Furthermore, in this solution the head of the first screw works in contrast with an externally threaded bush that is associated rotatably with a complementary thread provided axially to the frame; if the bush loosens, optimum interaction of the head of the first screw with the head of the second screw is no longer permitted, thus making adjustment unattainable.

A similar remark can be made in relation to the rotatable connection of the second screw to the frame by means of the bush.

This solution is structurally complicated, requiring a preassembly of the various components to the frame, furthermore using a spring that is partially pre-compressed.

This solution, also, requires the provision of an additional hole in the panel in order to be able to perform any adjustment of a leveling foot associated with the piece of furniture.

Finally, this structure, too, is bulky and difficult to install in thin panels.

US5743670A is also known which discloses a joining device, accommodated within a body or structural housing or frame, which is constituted by: a ring gear; a shell that accommodates the stem of the ring gear; a helical spring; a pinion gear; a coupler shaft; a front support.

The coupler shaft is a multi-segment constituted by: a cylindrical segment, which is accommodated at one end inside the shell; a cylindrical central segment, which is provided with a longitudinal retainer slot for a key; a cylindrical collar; a cylindrical coupling segment, which is accommodated in the front support and comprises a longitudinal shaft with a non-threaded segment and a threaded end.

The assembly method of the present known solution provides for a large number of constructive steps and furthermore said solution is structurally complicated due to the large number of components that constitute the device, requiring a preassembly of the various components to the frame that is long and laborious, furthermore using a spring that is partially pre-compressed and additional mechanical means or welds or adhesives as elements for fixing the shell and the front support to the body.

This solution is also particularly expensive in terms of production costs, due to the large number of components required, and in terms of cost and time required for preassembly of the components.

Finally, in this background art document it is found that maintenance or replacement of the activation element, i.e., of the pinion gear, is long, complicated and laborious, since it requires the complete disassembly of the joint as the pinion gear is the first element that is assembled during assembly and since it is not possible to extract it from the opening as the head of the pinion gear has a larger diameter than the opening.

The aim of the present invention is to eliminate the drawbacks noted above, by providing a joining device that is structurally compact, can be used also on panels that have low thicknesses and requires, for its installation, limited work on the panel, so as to maximize the utilization of the space generated by the work on the panel to provide the joint according to the invention.

Within this aim, an object of the present invention is to provide a joining device that has a limited impact on the panel and the activation of which is simple and effective over time regardless of the machining tolerances both in the panel and in the joint.

Another object is to provide a joining device according to the invention on which it is possible to perform maintenance on the activation element rapidly and easily, preserving the integrity of the joint and of the panel.

Another object is to provide a joining device according to the invention that allows to achieve an optimum activation thereof, compensating the forces that tend to space the gears.

An object is to provide a joining device according to the invention that allows quick, easy and simple adjustment of a leveling foot associated with the piece of furniture in a region below the joint according to the invention itself.

Another object is to provide a joining device according to the invention that allows to reduce the dimensions of the components so as to allow application in particularly thin panels.

Another object is to provide a joining device according to the invention the assembly of which to the panel is simple and easy.

Another object is to provide a joining device according to the invention that has low manufacturing costs and can be provided with usual and known systems.

This aim and these and other objects that will become better apparent hereinafter, are achieved by a joining device, associable with a shelf that can be arranged against a wall of a piece of furniture, comprising a cylindrical body that can be associated in a first hole adapted to be provided transversely in said shelf and provided with a first axial seat for the rotatable coupling of the first stem of a screw provided with a first crown-shaped head that can be arranged rotatably within a second seat that is adjacent to said first seat, characterized in that it comprises an insert accommodated within a second hole adapted to be provided in said shelf, at right angles to said first hole, and is arranged substantially flush with or below the upper surface of said shelf, said insert being provided with a seventh seat for the rotatable coupling of a second head of a pinion that interacts with said first crown-shaped head, and an eighth seat, which is adjacent and parallel to said seventh seat, for the passage of a tool for the optional adjustment of a foot associated with said piece of furniture.

Further characteristics and advantages of the invention will become better apparent from the detailed description of a particular but not exclusive embodiment of the joining device according to the invention, illustrated by way of nonlimiting example in the accompanying drawings, wherein:

Figure 1 is an exploded view of a joining device with the cylindrical body constituted by two half-shells;

Figure 2 is a sectional view of the joining device;

Figure 3 is a view of a detail according to figure 2; Figure 4 is a side perspective view of the cylindrical body;

Figure 5 is a sectional view of the cylindrical body without the pinion and the screw with crown- shaped head;

Figure 6 is a view similar to Figure 1, with the cylindrical body composed of a single component;

Figure 7 is a view, similar to Figure 2, with the cylindrical body constituted by a single component.

Figure 8 is a side perspective view of the bushing of Figure 1 ;

Figure 9 is a side perspective view of the bushing of Figure 6;

Figure 10 is a view of a variation for the second wing of the insert;

Figures 11 and 12 are two side perspective views of a variation related to the arrangement and shape of the insert;

Figure 13 is a top view of the joining device;

Figure 14 is a view taken along the sectional line XIV-XIV of Figure 13;

Figure 15 is a front view of the shelf and of the wall;

Figure 16 is a view taken along the sectional line XVI-XVI of Figure

15.

In the exemplary embodiments that follow, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other exemplary embodiments.

Moreover, it is noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer.

With reference to the figures, the reference numeral 1 designates a joining device, particularly for joining a shelf 2 to a wall 3 of a piece of furniture.

The joining device 1 is constituted by a cylindrical body 4, which can be associated within a complementarily shaped first hole 5 that is adapted to be provided transversely to the shelf 2 through part of its thickness. The cylindrical body 4 can be composed of a single shell 6 or of a first half-shell and a second half-shell 7a, 7b which can be mutually coupled axially with front coupling.

In this last case, the first half-shell 7a has a substantially cylindrical and internally hollow shape, so as to define a first axial seat 8 for the rotary coupling of a first stem 9 of a screw 10 provided with a first crown-shaped head 1 1.

The first head 11 of the screw 10 can be arranged rotatably within a second seat 12 provided proximate to the first end 13, cut along a chord so as to define a flat portion 14, of the second half- shell 7b that is directed toward the first half- shell 7a.

The second seat 12 is provided along a plane that is perpendicular to the plane of arrangement of the first seat 8, has a substantially semicircular shape and lies between two partitions 15a, 15b, of which the front one 15a, directed towards the first half-shell 7a, has a semicircular opening 16 for the placement and passage of the first stem 9, along the same axis as the first seat 8.

Part of the first head 11 of the screw 10 therefore protrudes from the second seat 12 and lies below a first tab 17 that protrudes from the first half- shell 7a in the direction of the second half-shell 7b.

The first tab 17 is extended along a circular arc until it surmounts the first cut end 13 of the second half-shell 7b and therefore also the underlying first crown-shaped head 11 of the screw 10, once it is associated with the second half- shell 7b.

A third seat 18 is provided on the second half-shell 7b, at right angles to the axis of the first seat 8 and therefore to the axis of the first stem 9 and starting from the flat portion 14, and is open in a downward region and not connected to the adjacent second seat 12.

The distance between the flat portion (14) and the outer perimetric surface 19a, 19b of the first and second half-shells 7a, 7b is substantially equal to the height of the first head 11 of said screw 10, which thus does not protrude beyond the cylindrical body 4.

It is possible to arrange temporarily in the third seat 18 a second stem 20 of a pinion 21 provided with a second head 22 that protrudes outside the cylindrical body 4 and is adapted to couple kinematically with the first head 11 accommodated in the second seat 12.

The temporary interconnection of the second stem 20 occurs, in the solution in which the cylindrical body 4 is constituted by a first half- shell and by a second half-shell 7a, 7b, by way of the presence of an annular groove 23, which is provided proximate to its end and interacts selectively with an annular ridge 24 that protrudes proximate to the end of the third seat 18.

A stable temporary coupling of the pinion 21 to the second half-shell 7b is thus achieved.

The second half-shell 7b has, starting from the first cut end 13, and so as to surround the opening 16 provided on said front partition 15a, a second tab 25 that protrudes in the direction of the first half- shell 7a so as to trace a circular arc that is concentric to the first seat 8 so as to arrange itself, during the axial coupling of the first half-shell 7a to the second half-shell 7b, within the first seat 8 and adjacent to its internal lateral surface.

Part of the first stem 9 that protrudes from the first head 11 of the screw 10 rests rotatably on the second tab 25; advantageously, proximate to the part there is, in the region that is located on the opening 16, an annular recess 44 accommodated at the opening 16, so as to block the axial sliding of the screw 10.

On the second half-shell 7b there is, parallel to the axis of the third seat 18 and on the opposite side with respect to the first half-shell 7a, a separate sixth seat 36 that affects the entire diameter of the second half-shell 7b and therefore passes through it.

A second hole 28 is provided in the shelf 2, at right angles to the first hole 5 and connected thereto, and accommodates, substantially flush with or below the upper surface 29, an insert 37.

The insert 37 has a substantially cylindrical shape and has a height that is substantially equal to the distance that lies, once the joining device has been assembled, between the upper surface 29 of the shelf 2 and the outer lateral surface of the first and second half-shells 7a, 7b, so that the insert 37, once installed, is flush with the shelf 2.

A seventh through seat 38 is provided axially in the insert 37 and is axially offset with respect to the central axis of the insert 37 so as to lie along the same axis as the third seat 18.

The seventh seat 38 in fact has such a diameter as to accommodate rotatably the second head 22 of the pinion 21.

An eighth seat 39 is provided adjacent to the seventh seat 38 and parallel thereto and also is axially offset with respect to the central axis of the insert 37, so as to arrange itself along the same axis as the sixth seat 36.

The eighth seat 39 has such a diameter as to allow the passage of a tool, such as a hex key or a screwdriver, for the optional adjustment of a foot associated with the piece of furniture in a region that lies below, and is axially aligned with, the eighth seat 39.

The second head 22 of the pinion 21 protrudes from the flat portion

14 and is accommodated within the seventh seat 38, so as to be internal or substantially flush with the upper surface 29 of the shelf 2.

In this manner, the second head 22 of the pinion 21, in addition to providing motion to the first crown-shaped head 1 1 of the screw 10, also has the extraction-prevention or bolt function, since it is accommodated in the insert 37 that is located in the seventh seat 38, locking the cylindrical body 4, composed of the first and second half-shells 7a, 7b, within the shelf 2.

Means for the engagement of a pressure tool are provided on the second upper end 30 of the second head 22 of the pinion 21 and are constituted by a fifth seat 31 within which it is possible to arrange by pressing a tool such as a screwdriver or a specific tool that operates by pressure.

Figure 10 shows a variation for the insert 37, which comprises a second wing 41 that surrounds and defines the eighth seat 39 so as to affect only part of the depth of the sixth seat 36.

In this case, the second half-shell 7b is shortened with respect to the preceding solution, since the sixth seat 36 is not present.

In the constructive solution shown in Figures 6, 7 and 9, the insert 37 can be inserted in a third seat 18 and a sixth seat or hole 36, which is parallel to the seat 18 and is provided on the opposite side with respect to the first head 1 1 of the screw 10 so as to affect the entire diameter of the shell 6, such seats being provided on the cylindrical body 4, which is constituted by a single shell 6.

The insert 37 also has a first wing and a second wing 40, 41 which protrude downward from them.

The first wing 40 rests in a lower region on the first inner lateral surface 45 of said shell 6, protrudes at the side of the seventh seat 38 that is adjacent to the eighth seat 39, and is extended radially at the part of the seventh seat 38 that contains the second stem 20 of the pinion 21.

The flat lateral surface 53 of the first wing 40 that is directed toward the first head 11 of the screw 10 is partially hollow so as to provide a ninth seat 42 that is shaped complementarily to the second stem 20 of the pinion 21.

The rotary interconnection of the second stem 20 therefore occurs, in the solution in which the cylindrical body 4 is constituted by a single shell 6, by way of the presence of the ninth seat 42 provided on the first wing 40.

In this case, the extraction prevention or bolt function is provided both by the presence of the insert 37 and by the second head 22 of the pinion 21, which block the cylindrical body 4 with respect to the shelf 2 since the second head 22 is accommodated within the eighth seat 38 and the insert 37 is inserted within the second hole 28 adapted to be provided in the shelf 2.

The second wing 41 surrounds and defines the eighth seat 39, is located within the sixth seat 36 and is connected in a lower region to a complementarily shaped fifth hole 46 adapted to be provided in the cylindrical body 4.

The second wing 41 is slightly lower than the second hole 28.

Since the sixth seat 36 passes through the cylindrical body 4, there is an access for a tool adapted to allow the optional adjustment of a foot associated in a lower region with the shelf 2 if it acts as a bottom of the piece of furniture.

A third hole 32 is adapted to be provided transversely in the wall 3 and an internally threaded bush 33 can be arranged or screwed therein for the interconnection of the third end 34 of the first stem 9 of the screw 10.

The interconnection can also be achieved in a different manner: for example, the first stem 9 can have a thread for chipboard.

A fourth hole 35 is adapted to between provided on the lower surface of the shelf 2 that lies opposite the upper surface 29, is parallel to the third seat 18 and the sixth seat 36, and matches up with the second hole 28.

In the constructive solution shown in Figures 11, 12, 13, 14, 15 and

16, two centering tabs 56a, 56b protrude in the direction of the second half- shell 7b from the lower surface 55 of the insert 37, are mutually parallel and have a substantially circular transverse cross-section with a side obtained according to a chord.

On the outer perimetric surface 19b of the second half-shell 7b, at the pair of centering tabs 56a, 56b and along a plane that coincides with the diameter of the stem 22, there is a pair of complementarily shaped recesses 57a, 57b for removable coupling with the insert 37.

The distance between each of the centering tabs 56a, 56b is therefore substantially equal to the distance between the recesses 57a, 57b. Furthermore, the insert 37 is rotated, with respect to the previously illustrated solution, through 90° clockwise without altering the position of the pinion 21 , so as to axially offset the seventh seat 38 of the insert 37 with respect to the central axis of the insert 37 but axially align it with the third seat 18.

Furthermore, its eighth seat 39 also is axially offset with respect to the central axis of the insert 37 and is arranged along an axis that is parallel to the axis of the third seat 18.

The transverse axis of the cylindrical body 4 is therefore perpendicular to the axis of the seventh seat 38 of the insert 37 and of the second head 22 of the pinion 21 accommodated rotatably inside it, the height of the insert 37 being such as to arrange it internally or substantially flush with the upper surface 29 of the shelf 2.

The second hole 28 in which the insert 37 is located and the fourth hole 35 also are axially offset with respect to the axis of the pinion 21.

The eighth seat 39, furthermore, is obtained to the side of the centering tab 56b.

In its use, the invention is therefore constituted by a joining device 1 of the concealed type, in that it is entirely accommodated both in the shelf 2 and in the wall 3, only the second hole 28 being visible.

When the first and second half- shells 7a, 7b are axially mutually assembled in order to obtain the closed cylindrical body 4, with the screw 10 inside it, the cylindrical body 4 is inserted in the first hole 5.

Then the insert 37 is inserted through the second hole 28, adapted to be provided in the shelf 2, and the pinion 21 in the seventh seat 38 of the insert 37, thus locking temporarily the cylindrical body 4.

The rotation imparted to the pinion 21 through the second hole 28 thus allows to screw the first screw 10 to the threaded bushing 33 associated with the wall 3.

It has thus been found that the invention has achieved the intended aim and objects, a joining device 1 having been obtained which is structurally compact, can be assembled rapidly and simply, can also be used on low-thickness panels and requires, for its installation, limited machining on the panel, so as to maximize the utilization of the space generated by the machining on the panel to provide the invention, also avoiding spoiling it.

Furthermore, it has a scarce impact on the panel due to its concealed insertion, since the joining device 1 is accommodated entirely both in the shelf 2 and in the wall 3, only the second hole 28 being visible.

Furthermore, it has been observed that the seventh seat 38 of the insert 37 allows both to accommodate an activation element, i.e., the pinion 21, and to insert the pinion 2 after the insertion of the cylindrical body 4, with the screw 10 inside it, in the shelf 2, making the activation of the pinion 21 simple and effective over time regardless of the machining tolerances both in the panel and in the components of the device; the simple rotation imparted to the pinion 21 through the second hole 28 and through the seventh seat 38 of the insert 37 in fact allows to screw the first screw 10 into the threaded bushing 33 associated with the wall 3.

Furthermore, it has been found that the second head 22 of the pinion 21 and the insert 37 also perform the extraction-prevention or bolt function, by virtue of the fact that the second head 22 of the pinion 21 is accommodated within the eighth seat 38 of the insert 37 and the insert 37 is inserted within the second hole 28 adapted to be provided in the shelf 2, so as to be substantially flush with or below the upper surface 29 of said shelf 2, thus allowing to lock the cylindrical body 4 within the shelf 2.

Furthermore, it has been observed that maintenance of the pinion 21 can occur rapidly and easily, since it is simply removable from the cylindrical body 4 through the second hole 28 and through the seventh seat 38 of the insert 37 in which it is accommodated, without having to extract the cylindrical body 4 from the shelf 2, and is equally simply replaceable.

Moreover, it has been found that maintenance of the insert 37 also occurs rapidly and easily, since said insert can be simply removed from the cylindrical body 4 through the second hole 28 in which it is accommodated, without having to extract the cylindrical body 4 from the shelf 2 and is equally simply replaceable.

Finally, it has been found that the eighth seat 39 provided in the insert

37 acts as a passage seat for a tool for the optional adjustment of a foot associated with said piece of furniture, a single hole 28 having to be provided in the upper surface 29 of the shelf 2 and therefore achieving a quick, easy and simple adjustment of a leveling foot associated with the piece of furniture in a region below said invention.

The invention is of course susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. The materials used, as well as the dimensions that constitute the individual components of the invention, may of course be more pertinent according to the specific requirements.

The characteristics indicated as advantageous, convenient or the like may also be omitted or be replaced with equivalents.

The disclosures in Italian Patent Application No. 102015000028419 (UB2015A001767) from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A joining device (1), associable with a shelf (2) that can be arranged against a wall (3) of a piece of furniture, comprising a cylindrical body (4) that can be associated in a first hole (5) adapted to be provided transversely in said shelf (2) and provided with a first axial seat (8) for the rotatable coupling of the first stem (9) of a screw (10) provided with a first crown-shaped head (11) that can be arranged rotatably within a second seat (12) that is adjacent to said first seat (8), characterized in that it comprises an insert (37) accommodated within a second hole (28) adapted to be provided in said shelf (2), at right angles to said first hole (5), and is arranged substantially flush with or below the upper surface (29) of said shelf (2), said insert (37) being provided with a seventh seat (38) for the rotatable coupling of a second head (22) of a pinion (21) that interacts with said first crown-shaped head (1 1), and an eighth seat (39), which is adjacent and parallel to said seventh seat (38), for the passage of a tool for the optional adjustment of a foot associated with said piece of furniture.

2. The joining device according to claim 1, characterized in that said insert (37) is accommodated within said second hole (28) adapted to be provided in said shelf (2), at right angles to said first hole (5) and so as to be connected therewith, and is arranged substantially flush with or below said upper surface (29) of said shelf (2), said insert (37) having a substantially cylindrical shape and being as high as or lower than substantially the distance that lies, once the joining device has been assembled, between said upper surface (29) of said shelf (2) and the outer lateral surface of said cylindrical body (4).

3. The joining device according to claim 1 or 2, characterized in that a seventh through seat (38) is provided axially in said insert (37) and is axially offset with respect to the central axis so as to lie along the same axis as a third seat (18), provided in said cylindrical body (4), in which it is possible to arrange temporarily a second stem (20) of said pinion (21), the second head (22) of which protrudes outside said cylindrical body (4), is accommodated rotatably within said seventh seat (38) of said insert (37) and is adapted to couple kinematically with said first head (1 1) accommodated within said second seat (12).

4. The joining device according to one or more of the preceding claims, characterized in that a separate eighth seat (39) is provided adjacent to said seventh seat (38) and parallel thereto and also is axially offset with respect to the central axis of said insert (37), so as to arrange itself along the same axis as said sixth seat (36), said eighth seat (39) having such a diameter as to allow the passage of a tool for the optional adjustment of a foot associated with said piece of furniture in a region that lies below, and is axially aligned with, said eighth seat (39).

5. The joining device according to one or more of the preceding claims, characterized in that said insert (37) has a first wing and a second wing (40, 41), which protrude downward from it, said first wing (40) resting in a downward region on the first inner lateral surface (45) of said shell (6), protruding at the side of said seventh seat (38) that is adjacent to said eighth seat (39) and being extended radially at the part of said seventh seat (38) that contains said second stem (20) of said pinion (21).

6. The joining device according to one or more of the preceding claims, characterized in that the flat lateral surface (53) of said first wing (40) that is directed toward said first head (11) of said screw (10) is partially hollow so as to obtain a ninth seat (42) that is shaped complementarily to said second stem (20) of said pinion (21).

7. The joining device according to one or more of the preceding claims, characterized in that the extraction prevention or bolt function is provided both by the presence of said insert (37) and by said second head (22) of said pinion (21), which block said cylindrical body (4) with respect to said shelf (2) since said second head (22) is accommodated within said eighth seat (38) and said insert (37) is inserted within said second hole (28) adapted to be provided in said shelf (2).

8. The joining device according to one or more of the preceding claims, characterized in that said second wing (41) surrounds and defines said eighth seat (39), is located within said sixth seat (36) and is lower in height than said second hole (28), said second wing (41) being connected in a lower region to a complementarily shaped fifth hole (46) provided in said cylindrical body (4).

9. The joining device according to one or more of the preceding claims, characterized in that said sixth seat (36), which passes through said cylindrical body (4), forms an access for a tool adapted to allow the optional adjustment of a foot associated in a lower region with said shelf (2) if it acts as a bottom of the piece of furniture.

10. The joining device according to one or more of the preceding claims, characterized in that said cylindrical body (4) is constituted by a single shell (6) or by a first half-shell and a second half-shell (7a, 7b), which can be coupled to each other axially with front coupling, said first stem (9) protruding from the first head (11) of said screw (10) and having, in the region that is located on an opening (16) formed at a front partition (15a) directed toward said first half-shell (7a), an annular recess (44) which is accommodated at said opening (16) so as to block the axial sliding of said screw (10).

11. The joining device according to one or more of the preceding claims, characterized in that said insert (37) has a second wing (41) that surrounds and forms said eighth seat (39) so as to affect only part of the depth of said sixth seat (36).

12. The joining device according to one or more of the preceding claims, characterized in that said insert (37) is rotated through 90° (ninety degrees) clockwise or counterclockwise, without altering the placement of said pinion (21), so as to arrange said seventh seat (38) of said insert (37) so that it is axially offset with respect to the central axis of said insert (37) but is axially aligned with said third seat (18), said eighth seat (39) being axially offset with respect to the central axis of said insert (37) and being arranged along an axis that is parallel to the axis of said third seat (18), said eighth seat (39) being arranged in a free space that is arranged to the side of one of a pair of centering tabs (56a, 56b) that protrude downward from said insert (37), said second hole (28) on which said insert (37) is located and said fourth hole (35) being axially offset with respect to the axis of said pinion (21).

13. The joining device according to one or more of the preceding claims, characterized in that said pair of centering tabs (56a, 56b) protrudes from the lower surface (55) of said insert (37), in the direction of said second half-shell (7b), said tabs being arranged parallel to each other and having a substantially circular transverse cross-section with one side obtained according to a chord, on the outer perimetric surface (19b) of said second half-shell (7b), at said pair of centering tabs (56a, 56b) and along a plane that coincides with the diameter of said stem (22), there being a pair of complementarily shaped recesses (57a, 57b) for removable coupling with said insert (37), the distance between each of said centering tabs (56a, 56b) being substantially equal to the distance between said recesses (57a, 57b).