Patent Description:
It is known, in the technical sector of small metal products that there is a need to produce bushes, in particular metal bushes, with an inner female thread designed to allow coupling together with the threading of components mounted on other parts, such as panels and the like, which must be fastened together in various ways.

Examples of a bush according to the preamble of Claim <NUM> are known from <CIT>, <CIT> and <CIT>. <CIT> describes a pin with a first end for insertion in a first bush, a second end with a threading for engaging a female thread of a second bush and annular reliefs on the shaft of the pin, for stably engaging with the first bush.

A particular example of use of these bushes consists in the application thereof to the backrests of chairs, which must be fastened to the uprights of the seat frame.

In this case, in fact, it is required that the bush must have a small thickness so that, once it has been inserted in the backrest, it remains flush with the surface thereof so as to allow operations involving painting and/or lining with fabric and/or the like without problems due to projections which are normally the cause of damage or require the operations to be repeated several times in order to complete the various coating/lining steps.

The technical problem which is posed, therefore, is that of providing a bush which is able to solve, or at least reduce, the aforementioned technical drawbacks, preferably, in such a way as not to leave visible screw components and is able to withstand high loads, in particular when applied to wooden parts.

In connection with this problem, it is also required that the bush should have small dimensions, be easy and inexpensive to produce and be able to be easily installed at high speed using normal standardized means.

These results are obtained according to the present invention by a bush according to the features of Claim <NUM> or Claim <NUM>.

The present invention relates furthermore to a fixing assembly according to Claim <NUM>, which are designed to allow the mounting thereof on different component parts for joining them stably together.

Preferred embodiments are provided by the dependent claims.

According to a preferred embodiment, the retaining means comprise an annular collar projecting towards the inside of the through-hole of the bush at the rear end of the body thereof. Said collar is preferably inclined towards the rear part of the bush.

According to a preferred further embodiment the retaining means comprise an elastic ring stably applied to the inside of the rear part of the through-hole in the bush body. The ring has preferably a coaxial hole and axial incisions extending radially from the said central hole and designed to provide the said ring with elasticity.

Such embodiments are particularly advantageous for receiving and retaining a first end of a pin, formed with a plurality of parallel annular reliefs, or with a roughness on the outer surface, or with a spherical head which may be inserted by means of a pushing force and does not have to be screwed in for engagement with the bush.

The insertion end with a spherical head advantageously allows also the disengagement and the extraction of the pin from the bush, by means of deformation of the elastic ring in a direction opposite to the direction of insertion.

According to a further preferred embodiment the retaining means comprise a female thread inside the through-hole of the body thereof, so that the bush is particularly advantageous for receiving a second end of a pin which has a thread.

The aforementioned pin is therefore configured with a second end comprising a thread, for mating with the retaining means of a second bush, in particular with the female thread of a bush according to the invention.

The means for engagement with a screwing/unscrewing tool may include a hexagonal profile or cross-shaped cut formed in the through-seat of the bush head. The hexagonal profile preferably has a diameter of the circumscribed circumference greater than the inner diameter of the coaxial through-hole of the cylindrical body, so that one end of the pin may be easily inserted.

In a further embodiment, forming the subject of Claim <NUM>, the bush is formed as a single piece with a pin which comprises a first end for insertion in another bush, formed with a plurality of parallel annular reliefs, or with a roughness on the outer surface, or with a spherical head, for engagement with respective retaining means of another bush according to the invention.

The outer thread of a bush according to the invention is preferably symmetrical and/or has preferably a profile angle α of between <NUM>° and <NUM>°.

The annular reliefs of the pin (whether it be formed as a separate body or as one piece with the bush) may preferably:.

The pin also has preferably a collar arranged in an intermediate position between the first end of the pin and the second end of the pin or between the first end of the pin and the rear end of the bush body and designed to form an end-of-travel stop for insertion inside the respective hole of a bush. The collar may be advantageously in the form of a polygonal, preferably hexagonal nut, shape so as to allow engagement with a corresponding tool for screwing/unscrewing the pin or the bush with pin. Alternatively or in addition, for screwing/unscrewing of the pin or the bush with pin, a cross-shaped incision may be provided on the head of the first end of the pin.

According to another advantageous aspect of the invention, the joining together of two component parts may be obtained by means of a fixing assembly, comprising a first bush according to the invention, designed to be screwed into a hole of a first component; and a second bush according to the invention, designed to be screwed into the second component.

The second bush is coupled with the second end of a pin, or it is a second bush formed as one piece with a pin according to the invention.

During use, the retaining means of the first bush are designed to engage with the first insertion end of the pin formed in the manner of a plurality of parallel annular reliefs, preferably arranged uniformly spaced along the longitudinal axis of the said pin, or with a surface roughness, so that the joining together of the two parts does not require the screwing of the first end of the pin into the first bush.

The second bush may instead comprise a female thread formed on the inner surface of the through-hole and suitable for mating with the thread of the second end of the pin.

Therefore, according to a further aspect of the invention, a method for fixing a first component together with second component to be joined together is provided, wherein a first bush according to the invention is screwed into a respective hole of the first component, and a second bush according to the invention is screwed into a respective hole of the second component.

The second bush is coupled (in particular by means of screwing) with a pin according to the invention, or is formed as one piece with the pin provided with a first insertion end according to the invention, while the first bush comprises retaining means for engagement with said first end of the pin. Therefore it is possible to perform insertion, by means of pushing, of the first end of the pin inside the through-seat of the first bush until locking by the retaining means occurs, resulting in stable joining together of the two component parts.

According to a particularly advantageous aspect of the present invention and owing to the small height of the bush, once screwing inside the respective component has been performed, the head of the first bush and/or of the second bush does not project from the respective surface of the component and is preferably arranged flush with the respective surface of the component.

The method is particularly, but not exclusively, suitable for the application where the first component is the upright of a chair and the second component is the backrest of a chair, or vice versa.

Further details may be obtained from the following description of non-limiting examples of embodiment of the subject of the present invention, provided with reference to the accompanying drawings, in which:.

As shown and assuming solely for the sake of easier description without any limiting meaning a pair of reference axes extending respectively in a longitudinal direction X-X, for the sake of simplicity shown coinciding with the axis of the bush, and transverse/radial direction Y-Y perpendicular to the first direction, as well as a front part "A" corresponding to the operating part of the bush and a rear part "P", opposite to the front part in the longitudinal direction, the bush according to the invention comprises essentially:.

According to a first embodiment, the bush according to the invention has a coaxial through-hole 10a which, in a position proximal to the rear opening thereof, has an annular collar <NUM> projecting radially towards the inside of the axial cavity with an inclination from the outside towards the inside and towards the exterior of the rear part of the bush.

In the axial direction the collar remains within the maximum dimension of the bush, without increasing the axial length thereof.

As will become clear below, the collar <NUM> forms a retaining means for a pin <NUM> which can be inserted inside the said bush and, in particular, are designed to form a functional non-return element for the pin <NUM>.

Advantageously, the head <NUM> has means designed to allow screwing/unscrewing of the bush by means of corresponding operating tools. Advantageously, said means have an internal coaxial through-seat with a hexagonal profile <NUM> or, alternatively, with a cross-shaped profile for screwing using a standard hex key or a cross-head spanner, which can be operated by means of a screwing tool.

Preferably, the hexagonal profile <NUM> has a diameter of the circumscribed circumference 14a greater than the internal diameter of the coaxial through-hole 10a of the cylindrical body <NUM>, allowing easy insertion of one end of a pin, as will become clear below.

In detail (<FIG>) preferred embodiments of the bush envisage:.

The broad profile angle α allows rapid screwing of the bush, while maintaining a high resistance to axial forces for extraction of the bush, which is particularly advantageous for low-density materials.

The cylindrical body generally has an axial length not greater than <NUM> and of between <NUM> and <NUM> and preferably between <NUM> and <NUM>.

Preferably, the bush is made of metal with a low content of carbon or other material such as aluminium or Zama.

<FIG> show a second example of embodiment of the bush which in this case has a coaxial through-hole 110a, with means of the female thread type <NUM> for retaining a pin <NUM>.

For the parts corresponding to the embodiment of <FIG> the same reference numbers are used.

As shown in <FIG> a pin <NUM>, according to the present invention, has a first end with parallel annular reliefs <NUM>, preferably arranged uniformly spaced along the longitudinal axis X-X, and a second opposite end with threading <NUM> suitable for mating with the corresponding female thread <NUM> of the second bush <NUM>.

Preferably, the reliefs <NUM> of the pin <NUM> have a frustoconical form with the larger base directed towards the pin; this form is designed to make it easier to pass over the collar <NUM> of the bush <NUM>, during coaxial insertion therein, but, on the other hand, to prevent the pin <NUM> from coming out as a result of pulling forces exerted in the opposite direction to the direction of insertion.

According to a preferred embodiment the pin <NUM> has an annular relief <NUM> arranged in an intermediate position between the two ends and designed to form an end-of-travel stop during insertion inside the respective hole 10a, 110a of one bush <NUM> or the other bush <NUM>.

As shown in <FIG> described below, it is envisaged that in a further embodiment the collar <NUM> has the form of a polygonal, for example hexagonal nut 201a, so as to allow engagement with a corresponding spanner for screwing/unscrewing the pin <NUM> onto/from the female thread 110a of the bush <NUM>.

Alternatively (<FIG>) a cross-shaped incision 201b may be provided on the end of the pin opposite to the threaded end, for allowing screwing by means of a corresponding tool.

According to a further embodiment of a bush <NUM> according to the invention, shown in <FIG>, it is envisaged that the means for retaining the pin <NUM> comprise an elastic ring <NUM> which is stably fitted inside the rear part of the through-hole 10a in the body <NUM> of the bush. The elastic ring may be made for example in the form of a washer made of spring steel.

Advantageously, the elastic ring <NUM> has a coaxial hole 315a and optionally incisions 315b extending radially from the said coaxial hole and designed to provide the ring <NUM> with further elasticity so as to allow a deformation towards the front part and/or rear part of the bush, designed to facilitate the coaxial insertion of the pin <NUM>, but at the same time prevent it from coming out, owing to the relative interference between the ring and the reliefs <NUM> on the said pin.

Although not shown, it is envisaged that, for this solution, the pin may have an end for insertion inside the bush without reliefs <NUM>; preferably the outer surface of the said end may advantageously have a certain roughness for increasing the friction with the ring <NUM> and therefore the resistance to any axial forces for extraction of the pin.

As shown in <FIG>, a further embodiment of a pin <NUM> according to the present invention has an end for insertion inside the bush, comprising a head <NUM> with a substantially spherical shape having a diameter greater than the diameter of the pin and smaller than the inner diameter of the coaxial hole of the bush.

Preferably, the diameter of the insertion end is greater than the diameter of the coaxial hole <NUM> of the elastic ring.

As shown in <FIG>, the pin <NUM> may be inserted through the elastic ring <NUM> which is deformed so as to allow the insertion of the spherical head. Once insertion has been performed, the elastic ring <NUM> returns into its original configuration ensuring a desired resistance to extraction of the pin <NUM>.

Advantageously, the pin with the spherical end <NUM> inserted inside the bush allows the subsequent disengagement, this being able to be performed by acting with an extraction force in the opposite direction to the insertion direction, said force causing deformation of the elastic ring <NUM> towards the front part, allowing the spherical head <NUM> to pass through.

As shown in <FIG>, the assembly formed by the two bushes <NUM>,<NUM> and the pin <NUM> allows two components to be joined together as follows:.

It is envisaged moreover that the second bush <NUM> and the pin <NUM> may be pre-assembled either by means of a screw/female thread connection, or else: by forming a single component which comprises as one piece the two parts as shown in <FIG>; in this case the hexagonal collar 201a and/or the cross-shaped cut 201b have the function of allowing operation of the bush for screwing thereof into the associated second component <NUM>, a hollow seat in the head of the bush therefore not being necessary.

It is therefore clear how the bushes according to the invention are designed to be mounted on components, in particular, but not exclusively wooden components, very rapidly and with optimum axial traction resistance characteristics, having moreover a head which remains flush with the respective surface of the component onto which it is mounted, thereby facilitating and reducing the cost of the finishing operations carried out on the said component, such as painting or lining with upholstery.

In addition, the assembly composed of the two bushes and the pin is such that the operation of coupling two components to be joined together, especially in the particularly complex case of the frame and backrest of a chair, is performed in an easier, rapid and low-cost manner.

Although described in connection with an example of application to chair parts, it is envisaged that the bush <NUM>;<NUM>;<NUM> and the bush/pin assembly may be likewise used on kitchen tops and/or lining/decorative panels to be fixed to a wall.

Claim 1:
Bush (<NUM>;<NUM>;<NUM>) comprising:
- a substantially cylindrical, hollow, body (<NUM>), with a front end face integral with:
- a substantially frustoconical head (<NUM>), with an inner through-seat, a front larger base (11a), comprising an annular edge (11b), and a rear smaller base connected to the larger base by a circular rim (11c) inclined towards the axis of the bush body;
- a coaxial hole (10a) passing through the body (<NUM>) and designed to receive a pin (<NUM>);
- a threading (<NUM>) formed on the outer side surface of the body (<NUM>);
- engagement means (<NUM>) for engaging with a corresponding tool for screwing/unscrewing the bush;
- retaining means (<NUM>;<NUM>) associated with the through-hole (10a;315a) and configured to allow retaining of a respective end of a pin (<NUM>;<NUM>);
Characterized in that said retaining means comprise: an annular collar (<NUM>) projecting towards the inside of the through-hole (10a) of the bush at the rear end of the body; or an elastic ring (<NUM>) stably applied to the inside of the rear part of the through-hole (10a) of the bush body (<NUM>); and
in that it has a height of no more than <NUM>.