Patent Description:
Mechanical seals are devices that can be applied to rotating shafts to prevent fluid leakage and can withstand high pressure and mechanical stress.

Mechanical seals are used, for example, in centrifugal pumps and in motor boats in which a shaft transmits rotational motion from an engine, located inside a boat, to a propeller, which is completely submerged in water, to prevent liquid from entering the boat through the shaft.

Nowadays, a mechanical seal is realised by a pair of annular bodies, one stationary and one rotating sealing body, placed around a drive shaft and in relative motion with respect to each other when the drive shaft is driven; the two annular bodies are coaxial and coupled frontally so that a circular crown face of one is in contact with that of the adjacent annular body.

The rotating annular body is kept in contact with the stationary one by elastic means that push it axially against the stationary body. Preferably, such elastic means consist of a wave spring with a substantially annular profile.

During rotation, a minimal amount of fluid, sufficient to lubricate and prevent overheating, seeps through the two annular bodies without, however, escaping into the environment to be insulated.

With particular reference to the rotating part, it generally comprises a sealing element, presenting the sealing surface, and an annular body integrally connectable to a rotating shaft in such a way as to ensure a seal thereon.

In order to allow for mutual flotation of the sealing element and the annular body, they are coupled with clearance along the rotation axis of the shaft, so that they are free to make a limited and controlled translation in the axial direction. The wave spring, having a substantially annular profile, is placed between the sealing element and the annular body to absorb such axial movements and maintain mutual pressure between the coupling surfaces.

In order to enable the transfer of rotational motion from the annular body to the sealing element, it is known to make a shape coupling between the two. In particular, two teeth are made on the annular body at the level of the annular head surface and away from it. These teeth have an axial extension equal to the axial extension of the sealing element and are diametrically opposed. Corresponding counter-seats for such teeth are formed on the sealing element in order to transfer rotational motion from the annular body to the sealing element by means of a rotational shaped coupling between such teeth formed on the annular body and such counter-seats formed on the sealing element.

Disadvantageously, the teeth have a large extension, so this solution is excessively costly due to the process of obtaining these teeth on the annular body, which are in fact obtained by removal of material, generating considerable waste of the material removed, and therefore considerable costs.

Even more disadvantageously, these teeth, being subject to considerable mechanical stress, must undergo a process of ion nitriding or hardening in order to make them stronger. Unfortunately, this process is expensive and, together with the costs related to the manufacturing process by material removal, results in an uneconomical product.

In order to obviate the costs of the material removal procedure for obtaining teeth at the level of the annular body, it is known to transfer the rotational motion from the annular body to the sealing element by means of the elastic means between them, as described in <CIT>. In particular, such elastic means comprise a wave spring, interposed between the annular body and the sealing element, having a substantially annular profile and presenting a plurality of teeth, one for each wave of the spring, diametrically opposed and extending on the surface in which the spring itself lies, alternating teeth projecting towards the inside and towards the outside of the annular profile defined by the spring. In <CIT> there are two diametrically opposite teeth protruding inwards and two diametrically opposite teeth protruding outwards.

In more detail, the teeth protruding towards the inside of the annular profile defined by the spring are configured to engage respective radially through recesses made in the annular body, while the teeth protruding towards the outside of the annular profile defined by the spring are configured to engage respective recesses made in the sealing element.

Disadvantageously, during assembly of the seal, the annular body and the sealing element can become axially detached, creating problems and forcing the assembly actions to be repeated several times before the correct configuration is achieved.

Furthermore, disadvantageously, the teeth protruding towards the outside of the annular profile defined by the spring rest in the respective recesses made in the sealing element, thus generating a distribution of the forces generated by the wave spring that is not uniform, but rather concentrated in the limited support areas. In addition to the above, the inner and outer teeth of the wave spring have sharp edges, which can disadvantageously cause potential injuries during assembly and disassembly of the mechanical seal.

Finally, known mechanical seals are generally made of AISI <NUM> steel, which is particularly resistant to corrosion. In this case, the stationary body is generally made of silicon carbide and it is necessary to place an insert of sacrificial material, usually graphite, between the stationary and the rotating sealing body. However, this solution is not very environmentally friendly as the graphite insert must be sealed on a circular crown surface of the sealing element using a polluting agent. In addition, graphite, which is also a polluting agent, being porous, needs to be impregnated with antimony, a material that is toxic and polluting even though it withstands high temperatures. Even more disadvantageously, the rotating part, comprising a graphite insert sealed to it, requires a separation of the graphitic portion from the metal portion during disposal.

A further mechanical seal, comprising an annular body, a sealing element and a wave spring, whereby the wave spring is rotationally constrained to the annular body and and the sealing element is rotationally constrained to the wave spring, is known from <CIT>.

In this context, the technical task underlying the present invention is to propose a mechanical seal that overcomes at least some of the drawbacks of the prior art mentioned above.

In particular, it is the purpose of the present invention to provide a mechanical seal that ensures versatile and safe assembly for the operator.

A further aim of the present invention is to provide a mechanical seal that ensures environmental sustainability in production and disposal.

The defined technical task and the specified aims are substantially achieved by a mechanical seal comprising the technical characteristics set forth in one or more of the appended claims.

In particular, there is an initial rotationally-shaped constraint between the annular body, integral with a drive shaft, and the wave spring. There is also a second rotationally-shaped constraint between the wave spring and the sealing element.

By means of the aforementioned first and second rotational constraints, it is therefore possible to transfer the rotation of the annular body, integral with a drive shaft, to the wave spring and thus to the sealing element.

According to an aspect of the present invention, the aforementioned first rotational constraint between the annular body and the wave spring is defined by a bayonet coupling.

The bayonet coupling also defines an axial restraint between the annular body and the wave spring aimed at preventing them from detaching from each other along the rotation axis.

More specifically, the axial constraint is configured to be reversibly activated by a relative rotation between the wave spring and the annular body.

In this way, the annular body and the spring, which is integral with the sealing element, are not only rotationally, but also axially, constrained, thus providing greater versatility when installing the seal.

The dependent claims correspond to possible embodiments of the invention.

Preferably, the sealing element has at least one outer recess, preferably one for each wave of the wave spring, and the wave spring has at least one outer tooth, preferably one for each wave of the wave spring, protruding away from the rotation axis and configured to engage the outer recess to define the mentioned second rotationally-shaped constraint. Even more preferably, the outer recess has a depth greater than the radial extension of the outer tooth so that an area of the wave spring adjacent to the outer tooth defines an extended support surface between the wave spring and the sealing element in the deformed condition of the wave spring itself. Therefore, the outer tooth is free to move within the outer recess, resulting in a uniform and extended distribution of the forces generated by the wave spring over a section of the wave spring itself. Preferably the annular body is made of AISI <NUM>, while the sealing element when integral, i.e. without the graphite or silicon insert, is preferably made of chromium steel. This makes it possible to realise an environmentally friendly mechanical seal that avoids the pollution caused by the use of the graphitic insert between the rotating part and the stationary body.

Further features and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but non-exclusive, embodiment of a mechanical seal.

Such description will be set forth herein below with reference to the accompanying drawings, provided for merely indicative and therefore non-limiting purposes, wherein:.

With reference to <FIG>, a mechanical seal is referred to generically with the numerical reference <NUM> and will be referred to hereafter with the notation "mechanical seal <NUM>".

The mechanical seal <NUM> is applicable to a fixed wall "P" and a non-illustrated rotatable shaft passing through an opening in the wall "P", so as to generate a fluid seal through that opening, in particular to isolate a first side of the wall "P" from a fluid present at an opposite second side thereof. The wall "P" forms, for example, part of the hull of a boat and the rotating shaft passes through an opening in it to transmit motion from the engine, located on board the boat, to the propeller, located outside the hull. In this type of application, the mechanical seal <NUM> isolates the inside of the hull from the water on the outside of the hull.

In the context of this description, the outer side "E" is indicated as the side of the mechanical seal <NUM> exposed to the fluid to be contained, and the inner side "I" as the side opposite the outer side "E".

The mechanical seal <NUM> comprises a rotating part <NUM> and a fixed part <NUM>. The rotating part <NUM> is connected integrally to a rotating shaft via a first fluid-tight coupling and the fixed part <NUM> is integrally connectable to the wall "P" via a second fluid-tight coupling.

The rotating part <NUM> and the fixed part <NUM> have respective coupling surfaces, in particular a rotating coupling surface <NUM> and a static coupling surface <NUM>, which are arranged in abutment and pressed against each other so as to slide mutually during the rotation of the rotating shaft and generate a fluid seal.

The rotating part <NUM> comprises an annular body <NUM> and a sealing element <NUM>, both of which are essentially bushed bodies, extending around a rotation axis "R" and essentially coaxial.

In particular, the annular body <NUM> can be integrally connected to the rotating shaft and rotates together with it about the rotation axis "R".

More specifically, the diameter of the annular body <NUM> is smaller than the diameter of the sealing element <NUM>, so that the first body can be inserted into the second element.

The rotating part <NUM> also comprises elastic means <NUM> interposed between the annular body <NUM> and the sealing element <NUM>.

The sealing element <NUM>, illustrated in <FIG>, <FIG>, <FIG> and <FIG>, has a central cavity "C" adapted to accommodate the rotating shaft and the annular body <NUM> integral with it.

The sealing element <NUM> comprises the rotating coupling surface <NUM> described above and is coupled to the annular body <NUM> so as to be movable with respect to it (and with respect to the rotating shaft) along the rotation axis "R". It is thus possible to maintain contact of the rotating coupling surfaces <NUM> and static coupling surfaces <NUM> following a translation of the rotating shaft and the annular body <NUM> connected thereto.

Preferably, the sealing element <NUM> has a cylindrical mouth <NUM> for access to the central cavity "C" adapted to accommodate at least a portion of the annular body <NUM>.

Moreover, the sealing element <NUM> preferably has a channel <NUM>, in communication with the mouth <NUM>, defining a portion of the cavity "C" having a smaller diameter than the mouth <NUM> and preferably dimensioned so as to allow a flush or fluid-tight coupling with the rotating shaft.

Preferably, the sealing element <NUM> has an inner annular groove <NUM> facing the rotation axis "R" and preferably interposed between the mouth <NUM> and the channel <NUM>.

Preferably, the annular groove <NUM> has a larger diameter than the mouth <NUM> and the channel <NUM>, so as to define an annular surface <NUM> extending around the rotation axis "R", a hitting shoulder <NUM> extending normal to the rotation axis "R" and arranged between the annular surface <NUM> and the channel <NUM> and, preferably, a containment shoulder <NUM> arranged between the annular surface <NUM> and the mouth <NUM>.

The sealing element <NUM> also has at least one external recess <NUM>, preferably two and diametrically opposed.

In the preferred embodiment, illustrated in <FIG>, the outer recesses <NUM> are partially obtained at the hitting shoulder <NUM> and the annular surface <NUM>, these recesses are also inclined in relation to the hitting shoulder <NUM>.

The mechanical seal <NUM> further comprises elastic means active between the annular body <NUM> and the sealing element <NUM> to keep the rotating coupling surface <NUM> pressed against the static coupling surface <NUM>.

These elastic means are also configured to allow a mutual position adjustment along the rotation axis "R" between the annular body <NUM> and the sealing element <NUM>, for example as a result of translational movements of the rotatable shaft along the rotation axis "R" with respect to the wall "P".

Advantageously, the elastic means comprise a wave spring <NUM> illustrated in two different embodiments in <FIG>. The wave spring <NUM> has a substantially annular shape, preferably two-wave and preferably shaped like a closed loop.

The wave spring <NUM> is preferably housed in the sealing element <NUM>, even more preferably in the annular groove <NUM>, and has an outer profile, thus distal from the rotation axis "R", substantially countershaped to the annular surface <NUM>. Preferably, the wave spring <NUM> has an inner diameter at least coincident with the diameter of the containment shoulder <NUM> and the mouth <NUM> so as to protrude with respect to them towards the rotation axis "R".

Preferably, the containment shoulders <NUM> and hitting shoulders <NUM> are configured to engage the wave spring <NUM> in a fully extended configuration to define a maximum, or limit stop, extension along the rotation axis "R" coincident with the width of the annular groove <NUM>.

In the preferred embodiment, the width of the annular groove <NUM> is less than the axial extension of the wave spring <NUM> in the unloaded configuration, resulting in pre-compression.

In addition, in the preferred embodiment shown in <FIG>, the hitting shoulder <NUM> has an inclination of less than <NUM>°, preferably equal to <NUM>°, to the rotation axis "R", as can be seen in figure 9b. In other words, the hitting shoulder <NUM> is inclined with respect to a plane X, orthogonal to the rotation axis "R", by an angle α comprised between <NUM>° and <NUM>°, preferably <NUM>°.

Advantageously, the aforementioned technical feature promotes lower stress on the wave spring <NUM>, thus allowing for a longer service life thereof.

Even more advantageously, the aforementioned inclination of the hitting shoulder <NUM> avoids edge contact between the spring <NUM> and the shoulder <NUM> itself, thus limiting possible notching and wear of the sealing element <NUM>.

The wave spring <NUM> also has at least one outer tooth <NUM>, preferably one for each wave of the wave spring <NUM>, protruding away from the rotation axis "R". Preferably, this external tooth <NUM> has a curvilinear profile.

Each outer tooth <NUM> is made along an outer perimeter edge of the wave spring <NUM>.

Each outer tooth <NUM> is also configured to fit within a respective outer recess <NUM> of the sealing element <NUM>.

The annular body <NUM> is preferably a substantially bushed body extending around the rotation axis "R" as illustrated, in two of its embodiments, in <FIG>.

The annular body <NUM> has a side surface "SP" proximal to the rotation axis "R", a side surface "SD" distal to the rotation axis "R" and two annular head surfaces "ST", one external, exposed to the fluid to be contained, and one internal, its opposite. In particular, the head surfaces ST extend around the rotation axis "R".

The annular body <NUM> is configured to fit inside the cavity "C" of the sealing element <NUM>, more precisely in its mouth <NUM>. In other words, considering the mechanical seal <NUM> in its entirety, the annular body <NUM>, by means of its distal lateral surface "SD", is smoothly inserted into the sealing element <NUM>, and the wave spring <NUM> is interposed between the two.

In addition, the annular body <NUM> preferably has an abutment shoulder <NUM> formed on its distal side surface "SD" and adjacent to the outer portion of the mechanical seal <NUM>. The annular body <NUM>, when inserted into the sealing element <NUM>, is free to slide inside the same until it comes to rest at the abutment shoulder <NUM>.

Considering the rotating part <NUM> in its entirety, the wave spring <NUM> is interposed between an annular head surface "ST" of the annular body <NUM> and the hitting shoulder <NUM> of the sealing element <NUM>: the wave spring <NUM> is therefore arranged to be pressed against them to be_compressed during a mutual approach of the annular body <NUM> and the sealing element <NUM> along the rotation axis "R".

Even more preferably, as shown in <FIG>, the annular body <NUM> is coupled to the sealing element <NUM> so that the distal side surface "SD" faces the annular groove <NUM> to define, in cooperation therewith, an at least partially closed housing volume "V" for the wave spring <NUM>.

The rotating part <NUM> comprises sealing means <NUM>, e.g. one or more O-rings, interposed between the annular body <NUM> and the sealing element <NUM> to advantageously seal the housing volume "V" of the wave spring <NUM> at least with respect to the fluid present on the outer side "E" to the mechanical seal <NUM>.

The wave spring <NUM> has a first rotationally-shaped coupling with the annular body <NUM> configured to rotationally constrain the wave spring <NUM> to the annular body <NUM> around the rotation axis "R".

Advantageously, such a first rotationally-shaped coupling is able to transfer the rotation of the annular body <NUM>, integral with a drive shaft, to the wave spring <NUM>.

In addition, the wave spring <NUM> has a second rotationally-shaped coupling with the sealing element <NUM> configured to rotationally constrain the sealing element <NUM> to the wave spring <NUM> around the rotation axis "R".

Specifically, such a second rotationally-shaped coupling results in the insertion of an outer tooth <NUM> of the wave spring <NUM> into a respective outer recess <NUM> of the sealing element <NUM>.

In other words, an outer tooth <NUM> is configured to engage an outer recess <NUM> in order to define such a second rotationally-shaped coupling between the wave spring <NUM> and the sealing element <NUM>.

The outer recess <NUM> has a greater depth than the radial extension of an outer tooth <NUM>. In other words, the wave spring <NUM>, instead of resting with one end of the outer tooth <NUM> inside the cavity defined by the outer recesses <NUM>, rests at the level of the hitting shoulder <NUM>. Consequently, the wave spring <NUM> rests on the hitting shoulder <NUM> with an area adjacent to at least one outer tooth <NUM>, the latter thus remaining free from mechanical stress.

When the spring <NUM> is in a deformed configuration, i.e. when the annular body <NUM> and the sealing element <NUM> are in close proximity along the rotation axis "R", this feature is convenient allowing the definition of a support surface between the wave spring <NUM> and the sealing element <NUM> coinciding with an area of the wave spring <NUM> adjacent to its outer tooth <NUM> and varying with the degree of compression thereof.

Advantageously, it is therefore possible to achieve a distribution of the forces generated by the wave spring <NUM> that is uniform and promotes homogeneous wear at the rotating coupling surface <NUM> between the rotating <NUM> and fixed <NUM> parts.

Considering the mechanical seal <NUM> in its entirety therefore, the first rotationally-shaped coupling results in a rotational constraint between the annular body <NUM> and the spring <NUM> which, being constrained to the sealing element <NUM> by the second rotationally-shaped coupling, results in a rotational constraint between the annular body <NUM> and the sealing element <NUM>.

In other words, thanks to the interposition of the wave spring <NUM> between the annular body <NUM> and the sealing element <NUM>, these are both constrained to rotate about the rotation axis "R" integrally with a rotating shaft.

Furthermore, thanks to the interposition of the wave spring <NUM> between the annular body <NUM> and the sealing element <NUM>, they can move mutually along the rotation axis "R", however counteracted by the axial action of the wave spring <NUM>.

The wave spring <NUM> also has an axially-shaped coupling with the annular body <NUM>, which is configured to axially constrain the wave spring <NUM> and the annular body <NUM> so as to prevent them from detaching from each other along the rotation axis "R".

More specifically, this axially-shaped coupling is configured to be reversibly activated upon relative rotation between the wave spring <NUM> and the annular body <NUM>.

In detail, this axially-shaped coupling is a bayonet coupling defined by a circumferential housing <NUM> obtained in the annular body <NUM> as illustrated in <FIG>, the latter relating to two different embodiments.

The axially-shaped coupling between the wave spring <NUM> and annular body <NUM> results in a bayonet coupling between the two and is achieved by keeping the annular body <NUM> stationary and rotating the sealing element <NUM>, in which the spring <NUM> is inserted, or vice versa.

In accordance with the first and second embodiments of the mechanical seal <NUM> according to the present invention, illustrated in <FIG> respectively, the axially-shaped coupling is realised by means of a housing <NUM> formed in the annular body <NUM> and a respective recess <NUM> formed in the wave spring <NUM>, as illustrated in <FIG> and <FIG> respectively.

In particular, with reference to <FIG>, the annular body <NUM> in its first embodiment has at least one tooth <NUM>, preferably two and diametrically opposed.

The tooth <NUM> extends axially and away from the respective annular head surface "ST" of the annular body <NUM>.

Preferably, the tooth <NUM> has a radial thickness less than a radial thickness of the annular head surface "ST" from which it extends. Even more preferably, the tooth <NUM> is arranged proximal to the rotation axis "R".

Advantageously, the tooth <NUM> has at least one appendage 115a extending in a circumferential direction with respect to the rotation axis "R", defining the circumferential housing <NUM>. More specifically, the appendage 115a appears to be positioned distally with respect to an annular head surface "ST".

Conveniently, the tooth <NUM> has a lower axial extension than the axial extension of the sealing element <NUM>.

With reference to <FIG>, the wave spring <NUM> in a first embodiment has at least one axially pass-through recess <NUM> formed in a portion of the wave spring <NUM> facing the rotation axis "R", the recess <NUM> also being open towards the rotation axis "R". Preferably, the wave spring <NUM> has a recess <NUM> for each of its waves; even more preferably, there are two such recesses, square in shape and diametrically opposed.

Each recess <NUM> is obtained along an inner perimeter edge of the wave spring <NUM>, preferably by defining a counter-seat for a respective tooth <NUM>.

In the preferred embodiment illustrated in <FIG>, the wave spring <NUM> has two inner recesses <NUM>, diametrically opposite the centre of extension of the wave spring <NUM>, and two outer teeth <NUM>, also diametrically opposite the centre of extension of the wave spring <NUM> and angularly spaced <NUM>° apart from the inner recesses <NUM>.

Considering the mechanical seal <NUM> subject matter of the present invention in its first (<FIG>) and second (<FIG>) embodiments, the housing <NUM> of the annular body <NUM> is configured to engage the wave spring <NUM> in a portion thereof adjacent to a recess <NUM> thereof as a result of relative rotation between the wave spring <NUM> and the annular body <NUM>.

More specifically, following a relative rotation between the wave spring <NUM> and the annular body <NUM>, the appendage 115a of the annular body <NUM> is able to oppose the mutual axial detachment between the wave spring <NUM> and the annular body <NUM>.

In other words, the housing <NUM> is configured to define a bayonet coupling with the area adjacent to the recesses <NUM> formed in the wave spring <NUM>.

The axial coupling just described is also useful in defining the aforementioned first rotationally-shaped coupling between the annular body <NUM>, integral to a drive shaft, and the wave spring <NUM>.

The aforementioned second rotationally-shaped coupling between the wave spring <NUM> and the sealing element <NUM> is achieved by inserting the outer teeth <NUM> of the wave spring <NUM> into respective outer recesses <NUM> of the sealing element <NUM>.

As far as construction materials are concerned, the first embodiment is traditional and shown in <FIG>. This has an annular body <NUM> and a sealing element <NUM> both made of AISI <NUM>, a particularly corrosion-resistant steel, while the fixed part <NUM> is made of silicon carbide. This first traditional embodiment also includes a sealed graphite insert <NUM> on the sealing element <NUM> of the rotating part <NUM> to accommodate the front coupling between the rotating part <NUM> and the fixed part <NUM>.

In other words, the front coupling between the rotating part <NUM> and the fixed part <NUM> occurs between the graphite insert <NUM> of the sealing element <NUM> and the silicon carbide of the fixed part <NUM>.

The second embodiment is innovative and can be realised with the mechanical seal configuration <NUM> described here and is shown in <FIG>. This second innovative embodiment includes an annular body <NUM> and a sealing element <NUM> made entirely of chromium steel (Y1), while the fixed part <NUM> is made of graphite. This would result in an integral sealing element <NUM> as shown in <FIG>. An integral sealing element is defined as a sealing element without a graphite or silicon insert and preferably made of chromium steel. This type of sealing element, being composed of only one piece, is environmentally friendly.

In accordance with the third embodiment of the mechanical seal <NUM> according to the present invention illustrated in <FIG>, the axially-shaped coupling results in a bayonet coupling made by means of a housing <NUM> formed in the annular body <NUM> and a respective inner tooth <NUM> of the wave spring <NUM>, illustrated in <FIG> and <FIG> respectively.

In particular, with reference to <FIG>, the annular body <NUM> in a second embodiment has at least one radially pass-through inner recess <NUM>, preferably two and diametrically opposed.

Preferably, the annular body <NUM> comprises an inner annular portion <NUM> adjacent to the annular head surface "ST" and comprising the aforementioned inner recess <NUM>.

Even more preferably, the inner annular portion <NUM> has a radial thickness less than a radial thickness of the respective annular head surface "ST" and is preferably arranged proximal to the rotation axis "R".

Advantageously, the recess <NUM> has within it at least one appendage 315a extending in a circumferential direction with respect to the rotation axis "R", defining the circumferential housing <NUM>. More specifically, the appendage 315a appears to be positioned proximally with respect to an annular head surface "ST".

With reference to <FIG>, the wave spring <NUM> in a second embodiment has at least one inner tooth <NUM> formed in a portion of the wave spring <NUM> facing the rotation axis "R".

In other words, the inner tooth <NUM> protrudes towards the rotation axis "R". Preferably, the wave spring <NUM> has an inner tooth <NUM> for each of its waves; even more preferably, there are two such inner teeth, square in shape and diametrically opposed.

Each tooth <NUM> is obtained along an inner perimeter edge of the wave spring <NUM>.

In the preferred embodiment illustrated in <FIG>, the wave spring <NUM> has two inner teeth <NUM>, diametrically opposite the centre of extension of the wave spring <NUM>, and two outer teeth <NUM>, also diametrically opposite the centre of extension of the wave spring <NUM> and angularly spaced <NUM>° apart from the inner teeth <NUM>.

Considering the mechanical seal <NUM> according to the present invention in its third (<FIG>) embodiment, the inner tooth <NUM> of the wave spring <NUM> is configured to engage the recess <NUM> of the annular body <NUM> so as to define the aforementioned first rotationally-shaped coupling between the annular body <NUM>, integral with a drive shaft, and the wave spring <NUM>.

On the other hand, the circumferential housing <NUM> formed in the recess <NUM> of the annular body <NUM> is configured to engage the wave spring <NUM> at its inner tooth <NUM> as a result of a relative rotation between the wave spring <NUM> and the annular body <NUM>, defining a bayonet coupling.

By means of this relative rotation, the appendage 315a defining the circumferential housing <NUM> opposes the mutual detachment of the wave spring <NUM> and the annular body <NUM>, thus realising the aforementioned bayonet coupling, i.e., an axially-shaped coupling.

In other words, following a relative rotation between the wave spring <NUM> and the annular body <NUM>, the appendage 315a of the annular body <NUM> is able to oppose the mutual axial detachment between the wave spring <NUM> and the annular body <NUM>.

In other words, the housing <NUM> is configured to define a bayonet coupling with the wave spring <NUM>, which is also useful to define the aforementioned first rotationally-shaped coupling between the annular body <NUM>, integral with a drive shaft, and the wave spring <NUM>.

The second rotationally-shaped coupling between the wave spring <NUM> and the sealing element <NUM> is achieved by inserting the outer teeth <NUM> of the wave spring <NUM> into respective outer recesses <NUM> of the sealing element <NUM>.

As far as construction materials are concerned, the third embodiment is traditional and shown in <FIG>. This has an annular body <NUM> and a sealing element <NUM> both made of AISI <NUM>, a particularly corrosion-resistant steel, while the fixed part <NUM> is made of silicon carbide. This third traditional embodiment also includes a sealed graphite insert <NUM> on the sealing element <NUM> of the rotating part <NUM> to accommodate the front coupling between the rotating part <NUM> and the fixed part <NUM>.

In other words, the front coupling between the rotating part <NUM> and the fixed part <NUM> occurs between the graphite insert <NUM> of the sealing element <NUM> and the silicon carbide of the stationary part <NUM>.

A fourth embodiment not illustrated is innovative and can be implemented with the configuration of the mechanical seal <NUM> described herein. This fourth innovative embodiment includes an annular body <NUM> and a sealing element <NUM> made entirely of chromium steel (Y1), while the fixed part <NUM> is made of graphite. This would result in an integral sealing element <NUM>. An integral sealing element is defined as a sealing element without a graphite or silicon insert and preferably made of chromium steel. This type of sealing element, being composed of only one piece, is environmentally friendly.

A further embodiment not illustrated concerns a bayonet coupling defined between the inner teeth <NUM> of the wave spring and the housing <NUM> formed in the tooth <NUM> of the annular body <NUM>. In this case, the housing <NUM> is configured to engage the wave spring <NUM> at its inner tooth <NUM> as a result of a relative rotation between the wave spring <NUM> and the annular body <NUM> so as to define the aforementioned axially-shaped and first rotationally-shaped coupling.

The present invention achieves the proposed aim, overcoming the drawbacks complained of in the prior art.

Advantageously, the shape of the wave spring <NUM> and its coupling, with the annular body <NUM> and the sealing element <NUM>, in particular the first and second rotationally-shaped couplings described here, allow for mutual rotational drive between the two elements.

The main purpose achieved by the mechanical seal <NUM> described herein relates to assembly versatility: the reversible axial constraint between annular body <NUM> and wave spring <NUM> ensures easy assembly for the operator by preventing axial separation between sealing element <NUM> and annular body <NUM>, thus preventing an operator from having to repeat the assembly actions several times before reaching the correct configuration.

Even more advantageously, the curved profile of the outer teeth <NUM> of the spring <NUM> aids the operator during assembly, preventing any injuries caused by sharp edges.

Conveniently, the conformation of the coupling between the outer recesses <NUM> in the sealing element <NUM> and the outer teeth <NUM> of the wave spring <NUM> allows an even distribution of the forces generated by the wave spring <NUM> and transmitted to the front coupling surface between the rotating <NUM> and fixed <NUM> parts. More specifically, the spring <NUM>, resting on the hitting shoulder <NUM> in an area adjacent to its outer teeth <NUM>, generates a uniform distribution of forces that promotes homogeneous wear at the front coupling surface between the rotating <NUM> and fixed <NUM> parts. In addition, this allows the support surface of the wave spring <NUM> to vary consistently with the compression of the wave spring <NUM>.

Claim 1:
Mechanical seal (<NUM>), comprising a rotating part (<NUM>) connectable to a rotating shaft and a fixed part (<NUM>) connectable to a fixed wall (P); said rotating part (<NUM>) comprising:
- an annular body (<NUM>) integrally connectable to a rotating shaft about a rotation axis (R);
- a sealing element (<NUM>) substantially coaxial with said annular body (<NUM>) and having a rotating coupling surface (<NUM>) configured to abut against a respective static coupling surface (<NUM>) of said fixed part (<NUM>); and
- elastic means comprising a wave spring (<NUM>) having a substantially annular profile, said elastic means being active between said annular body (<NUM>) and said sealing element (<NUM>) to maintain said rotating coupling surface (<NUM>) pressed against said static coupling surface (<NUM>) and to allow a mutual position adjustment along said rotation axis (R) between the annular body (<NUM>) and the sealing element (<NUM>);
- a first rotationally-shaped coupling configured to rotationally constrain said wave spring (<NUM>) to said annular body (<NUM>) about said rotation axis (R) and a second rotationally-shaped coupling configured to rotationally constrain said sealing element (<NUM>) to said wave spring (<NUM>) about said rotation axis (R),
characterised in that it comprises
an axially-shaped coupling configured to axially constrain said wave spring (<NUM>) and said annular body (<NUM>) so as to prevent them from disengaging from each other along said rotation axis (R), wherein said axially-shaped coupling is configured to be reversibly activated upon relative rotation between said wave spring (<NUM>) and said annular body (<NUM>).