Patent Description:
Bushings with elastic absorption of radial stress are used to connect a pin to an axis of a mechanical component, where the pin is subject to angular displacements with respect to said axis. They are also used in various sectors, including the field of heavy goods vehicles. Here they are used, for example, to connect the leaf spring eyes of the rear suspensions to the chassis of the vehicle, or to connect the supporting arms of the front wheels to the chassis and to the hub of these wheels, respectively, or yet again to connect connecting rods, arms, etc..

There are known bushings of the type with elastic absorption of radial stress comprising:.

Said reinforcing sleeve is coupled to the inner surface of said elastic outer ring, usually by vulcanization, while said reinforcing ring is freely inserted over said inner ring made of self-lubricating material.

Said first and second cut are useful for assembly of the bushing and its mounting in a leaf spring eye of the suspensions, as they facilitate temporary deformation of the components on which they are produced when they must be inserted with force with respect to one another.

In particular, said first cut is useful for insertion of said inner ring mad of lubricating materials inside the reinforcing sleeve on which the elastic outer ring is normally already vulcanized; while said second cut is useful for insertion of the entire bushing into the eye of the leaf spring of the suspension.

The European patent no. <CIT> by the same applicant discloses an elastic bushing as described above.

Further prior art is disclosed by the document <CIT>, which describes a bearing (for example for supporting a rotating shaft) comprising a tubular body made of rubber, a bushing made of polyamide reinforced with fiberglass, arranged inside and connected to said body made of rubber, and a sleeve made of self-lubricating material inserted into said bushing, to receive an axis or shaft to be connected to the bearing. The bushing and the body made of rubber are firmly connected by a dovetail coupling, or by vulcanization of the body made of rubber to the bushing, while also in this case the sleeve made of self-lubricating material is freely inserted inside the bushing.

Similarly, document <CIT>, which discloses the features of the preamble of claim <NUM>, discloses an elastic bushing for the support of motor vehicle parts, comprising:.

In this document, there is no reference to how the bushing is assembled, other than indication that the elastic outer ring is connected to the inner ring in a form-coupled, force-coupled, and/or material-coupled (vulcanized) manner.

Therefore, in general in both cases the reinforcing ring coupled to the outer elastic ring is freely inserted on the inner ring made of self-lubricating material, without the interposition of any locking means and is thus free to rotate thereon by a few degrees during use of the bushing.

Disadvantageously, during mounting of the bushing, if particular attention is not paid, said first and second cut can be aligned and superimposed, creating a weak point in the bushing. If the two cuts are superimposed, the bushing has a line without the reinforced part, hence without the thickness both of the sleeve and of the inner ring, but resistant only with the rubber of the elastic outer ring.

It is clear that this line forms a weak point facilitating cracking and breakage of the elastic ring subjected to continuous deformations due to the radial stresses.

Disadvantageously, these bushings therefore have the drawback of not being particularly suitable for applications that require high radial rigidity and the capacity to withstand considerable radial loads.

To avoid these problems, the mounting step of conventional bushings requires a great deal of attention and lengthy times.

Moreover, as there are no anti-rotation locking means, during use of bushing the inner ring made of self-lubricating material can, albeit slightly, rotate inside the reinforcing sleeve, and therefore alignment and superimposing of the two cuts can occur even after mounting.

The object of the present invention is to eliminate the drawbacks mentioned above.

In particular, the object of the present invention is to produce an elastic bushing with an oriented structure that is simple and quick to mount, that is safe and reliable over time, that can reliably withstand considerable radial loads and that is inexpensive to manufacture.

The objects are achieved by an elastic bushing with an oriented structure comprising:.

characterized in that it comprises guaranteed orientation means of the mutual position between said inner ring and said reinforcing sleeve, adapted to define therebetween a definite mounting position so that said first longitudinal cut of said inner ring and said second longitudinal cut of said reinforcing sleeve are not superimposed, and adapted to prevent the risk of unwanted rotations between the parts, wherein said guaranteed orientation means comprise form-fitting coupling means of male-female type.

According to a possible embodiment, said coupling means comprise at least one tooth protruding from the outer surface of said inner ring and at least one corresponding seat present on the inner surface of said reinforcing sleeve, where said at least one tooth is adapted to occupy said at least one seat to couple said inner ring and said reinforcing sleeve in a definite position.

so that, when the bushing is assembled, said first and second cut are staggered by <NUM>°.

Advantageously, said at least one seat is formed directly on said reinforcing sleeve by means of the same material thereof, and said at least one tooth is formed directly on said inner ring by means of the same material thereof.

According to a further aspect of the invention, said at least one tooth and said at least one seat have a complementary truncated pyramid shape.

In particular, the area of the cross section of said at least one tooth is smaller than the area of the corresponding cross section of said at least one seat.

Advantageously, said at least one tooth and said at least one seat are arranged on the edge of said inner ring and of said reinforcing sleeve, respectively, so as to be visible from the outside.

Moreover, said inner ring and said elastic outer ring are provided with stop collars.

The invention also relates to a motor vehicle characterized in that it comprises at least one elastic bushing with an oriented structure as described above.

The main advantage of the present invention concerns the reliability and duration of the installed bushing obtained through a suitable mounting step of the bushing itself.

The orientation means between said inner ring and said reinforcing sleeve ensure therebetween a definite mounting position: the orientation of the components during mounting is in fact guaranteed by cooperation between the respective form-fitting coupling means of male-female type.

Positioning of the ring made of self-lubricating material inside the reinforcing sleeve, inserting the protruding tooth into the corresponding seat, ensures that said first longitudinal cut of said inner ring and said second longitudinal cut of said reinforcing sleeve are not superimposed but are staggered by a definite angle, which can be chosen appropriately based on the application of the bushing.

In this way the rigidity given to the elastic bushing by the inner ring and by the reinforcing sleeve is in fact even more uniform and does not have discontinuous points that could facilitate deformation and cutting of the elastic outer ring made of rubber of the bushing.

Due to the staggering of the two cuts, preferably by <NUM>°, the deformation of the bushing when it is stressed in radial direction is uniform along the whole of the circumference.

The coupling means are clearly visible and easily connectable: advantageously, it is not necessary to pay attention to positioning of the cuts during mounting of the bushing, which in fact takes place in an entirely automatic way.

The dimensions of tooth and protrusion are such as not to create problems of interference.

Said coupling means also act as locking element between the inner ring made of self-lubricating material and the reinforcing sleeve during operation of the bushing, when it is inserted into the leaf spring eye and in use, without the risk of unwanted rotations between the parts.

The advantages of the invention will be more apparent in the description below, in which a preferred embodiment is described by way of non-limiting example, with the aid of the figures, wherein:.

With reference to the drawings, the elastic bushing <NUM> with an oriented structure according to the invention essentially comprises an inner ring <NUM>, made of self-lubricating plastic material, an elastic outer ring <NUM>, made of rubber, an annular reinforcing sleeve <NUM>, of suitable thickness, fixed to the inner cylindrical surface of said outer ring <NUM> made of rubber, made of a substantially rigid material, such as nylon.

The coupling between said elastic outer ring <NUM> and said reinforcing sleeve <NUM> is advantageously produced with a vulcanization process.

Said inner ring <NUM> made of self-lubricating material comprises a first longitudinal cut <NUM>.

Said reinforcing sleeve <NUM> comprises a second longitudinal cut <NUM>.

Said elastic bushing <NUM> comprises orientation means of the mutual position between said inner ring <NUM> and said reinforcing sleeve <NUM>.

Said orientation means comprise form-fitting coupling means <NUM>, <NUM> of male-female type.

Said orientation means are adapted to define between said inner ring <NUM> and said reinforcing sleeve <NUM> a definite mounting position so that said first longitudinal cut <NUM> of said inner ring <NUM> and said second longitudinal cut <NUM> of said reinforcing sleeve <NUM> are not superimposed, but staggered by a predetermined angle.

In the variant illustrated, said orientation means comprise a tooth <NUM> protruding from the outer surface <NUM> of said inner ring <NUM> and a corresponding seat <NUM> present on the inner surface <NUM> of said reinforcing sleeve <NUM>.

When the bushing <NUM> is assembled, said tooth <NUM> engages said seat <NUM> to stably couple said inner ring <NUM> and said reinforcing sleeve <NUM> in a definite position.

In particular, said tooth <NUM> is arranged staggered by <NUM>° with respect to said first cut <NUM> of said inner ring <NUM>, while said seat <NUM> is arranged staggered by <NUM>° with respect to said second cut <NUM> of said reinforcing sleeve <NUM>.

In this way, when the bushing <NUM> is assembled, said first <NUM> and second cut <NUM> are staggered by <NUM>°.

Said seat <NUM> is formed directly on said reinforcing sleeve <NUM> by means of the same material thereof, just as said tooth <NUM> is formed directly on the outer surface <NUM> of said inner ring <NUM> made of lubricating material by means of the same material thereof.

With particular reference to <FIG>, said tooth <NUM> and said seat <NUM> have a complementary truncated pyramid shape.

The area of the cross section of said tooth <NUM> is smaller than the area of the cross section of said seat <NUM> so that the tooth <NUM> can enter the seat without interference and friction.

The truncated pyramid shape of the seat <NUM> and of the tooth <NUM>, with the inclined faces creating a guide, facilitate self-centring of the components so that assembly of the bushing <NUM> is rapid and easy.

Said tooth <NUM> and said seat <NUM> are arranged on the edge of said inner ring <NUM> and of said reinforcing sleeve <NUM>, respectively, so as to be visible from the outside and further facilitate the operator in coupling of the parts.

It is clear that, although a bushing <NUM> with a tooth <NUM> and a seat <NUM> has been illustrated, the presence of a plurality of teeth and corresponding seats allows the same advantages of the invention to be achieved.

Moreover, in the example of embodiment illustrated, the inner ring <NUM> and ring <NUM> made of rubber are provided with stop collars <NUM>, <NUM>, which allow the bushing <NUM> to withstand compression forces parallel to the axis of the bushing itself.

Assembly of the elastic bushing <NUM> with an oriented structure according to the invention takes place by centring the tooth <NUM> of the inner ring <NUM> in the seat <NUM> of the reinforcing sleeve <NUM>, on which the outer ring <NUM> made of rubber was previously vulcanized, while the inner ring <NUM> is inserted into the sleeve itself. Said first <NUM> and second <NUM> cut will be automatically staggered from each other.

Subsequent mounting of the bushing <NUM> takes place by forcing the outer surface of the rubber elastic outer ring <NUM> into the seat of the bushing. The bushing <NUM> is thus fixed in its seat by the friction present between the rubber and the inner surface of the housing seat. A pin is mounted free to rotate on the inner surface of the inner ring <NUM>.

Claim 1:
Elastic bushing (<NUM>) with an oriented structure, comprising:
- an inner ring (<NUM>) made of self-lubricating material comprising a first longitudinal cut (<NUM>);
- an elastic outer ring (<NUM>);
- a reinforcing sleeve (<NUM>) made of a substantially rigid material, interposed between said inner ring (<NUM>) and said elastic outer ring (<NUM>), where said reinforcing sleeve (<NUM>) is coupled to the inner surface of said elastic outer ring (<NUM>) and comprises a second longitudinal cut (<NUM>),
characterized in that it comprises guaranteed orientation means of the mutual position between said inner ring (<NUM>) and said reinforcing sleeve (<NUM>), adapted to define therebetween a definite mounting position so that said first longitudinal cut (<NUM>) of said inner ring (<NUM>) and said second longitudinal cut (<NUM>) of said reinforcing sleeve (<NUM>) are not superimposed, and adapted to prevent the risk of unwanted rotations between the parts, wherein said guaranteed orientation means comprise form-fitting coupling means (<NUM>, <NUM>) of male-female type.