Patent Description:
See <CIT>, disclosing a device according to the state of the art.

It is well known that in order to produce the compressed air required to perform operations such as painting industrial products, such as cars or earth-moving machines, reciprocating volumetric compressors are used, which compress air flow rates that vary according to application requirements.

Such reciprocating volumetric compressors generally comprise:.

Such reciprocating volumetric compressors, although well known and appreciated, have aspects that can be refined.

A first aspect to be refined is the fact that the connecting rod, through the first hinge means, acts on the rigid translating body according to directions transverse to the translation axis of the same rigid translating body; this causes the two piston guide and sliding rings near the first hinge means to be heavily stressed in the radial direction, resulting in wear, where such wear causes a progressive lack of tightness between the cylinder and piston and a consequent drop in the performance of the volumetric compressor itself.

A second aspect that can be refined relates to the compressor compactness in the direction of the axis of the movement of the pistons, as even in this technical field a reduction in overall dimensions is always sought, as well as a reduction in the number of components to the benefit of simplicity and speed of assembly thereof.

The task of the present invention is to develop a reciprocating volumetric compressor structure capable of obviating the aforementioned drawbacks and limitations of the prior art.

In particular, an object of the invention is to develop a reciprocating volumetric compressor structure capable of maintaining the same high efficiency for longer than similar compressors of the known type.

Another object of the invention is to develop a reciprocating volumetric compressor structure with an improved pneumatic sealing.

A further object of the invention is to develop a reciprocating volumetric compressor structure more compact than similar volumetric compressors of the known type.

The above-mentioned task and objects are achieved by a reciprocating volumetric compressor structure according to claim <NUM>.

Further characteristics of the reciprocating volumetric compressor structure according to claim <NUM> are described in the dependent claims.

The aforesaid task and objects, together with the advantages that will be mentioned hereinafter, are indicated by the description of an embodiment of the invention, which is given by way of non-limiting example with reference to the attached drawings, where:.

With reference to the mentioned figures, a reciprocating volumetric compressor structure according to the invention is indicated as a whole by number <NUM>. This reciprocating volumetric compressor structure <NUM> comprises:.

The peculiarity of the reciprocating volumetric compressor structure <NUM> according to the invention lies in the fact that at least one of said pistons <NUM> and <NUM> comprises at least two guide and sliding rings <NUM>, 32a, preferably three guide and sliding rings <NUM>, 32a, 32b, as clearly shown in <FIG>.

In particular, such a piston comprising at least two guide and sliding rings <NUM>, 32a is the second piston <NUM>, closer to the first hinge means <NUM>.

In particular, in the embodiment of the invention described herein by way of illustrative and non-limiting example of the invention itself, a first piston <NUM>, further away from the first hinge means <NUM>, comprises a single first guide and sliding ring <NUM>, while a second piston <NUM>, closer to the first hinge means <NUM>, comprises four second guide and sliding rings <NUM>, 32a, 32b, 32c placed side by side.

It is not excluded, however, that in different embodiments of the invention these second guide and sliding rings may be two in number, preferably three or more than four.

Advantageously, according to any embodiment of the invention just described, at least one of said second guide and sliding rings <NUM>, 32a, 32b, 32c is positioned so as to surround said first hinge means <NUM>.

This last characteristic allows the radial forces transmitted from the connecting rod <NUM> to the piston <NUM> to be well distributed at least on the second rings <NUM>, 32a, 32b, making the wear of the individual second rings <NUM>, 32a, 32b, 32c much slower and thus leading to an important extension of the operational life of the volumetric compressor structure <NUM>.

At the same time, the presence of the at least two second guide and sliding rings <NUM>, 32a, 32b, of which at least one is positioned so as to surround said first hinge means <NUM>, determines an equally important improvement in the sealing between cylinder <NUM> and piston <NUM>, resulting in improved overall efficiency of the reciprocating volumetric compressor structure <NUM>.

In particular, such at least one of the second guide and sliding rings <NUM>, 32a, 32b, 32c positioned so as to surround the first hinge means <NUM> is designed to be mounted so that it is at the point of maximum thrust and return angle during the swinging movement of the hinged connecting rod <NUM>.

The first hinge means <NUM> comprise, by way of example, a pin 17a, a needle roller bearing 17b and two opposite annular seals 17c, positioned in a corresponding annular seat 16a defined at one end of the connecting rod <NUM>, where the pin 17a is simultaneously arranged with its ends in corresponding holes 13a defined on the rigid translating body <NUM>.

In particular, the second piston <NUM> comprises a fixing head <NUM>, fixed to the rigid translating body <NUM>, to which a cup-shaped cap <NUM> is in turn fixed.

This cup-shaped cap <NUM> comprises a circular base 35a and a cylindrical wall <NUM>.

This cup-shaped cap <NUM> comprises a cylindrical wall <NUM> bearing as many annular cavities <NUM> as there are second guide and sliding rings <NUM>, 32a, 32b, 32c.

In the present embodiment, three second guide and sliding rings <NUM>, 32a and 32b, as clearly visible in <FIG> and <FIG>, surround, supported by the cup-shaped cap <NUM>, the first hinge means <NUM>.

In the present embodiment, the annular cavities <NUM> all have the same width in the direction of the axis of the cup-shaped cap <NUM>.

The second guide and sliding rings <NUM>, 32a, 32b, 32c have therefore also the same width.

Thanks to this peculiar configuration, the forces that the connecting rod <NUM> transmits to the second piston <NUM>, causing the friction of the latter against the inner surface of the corresponding cylinder <NUM>, are better distributed among the four second guide and sliding rings <NUM>, 32a, 32b, 32c if compared to known compressors comprising one or two rings, which rings, in known configurations, are also distant from the first hinge means, i.e. they do not surround the pin between the connecting rod and the rigid translating body. The second guide and sliding rings <NUM>, 32a, 32b and 32c are annular and their axis of symmetry is parallel to a translation direction Z of the rigid translating body <NUM>.

In the present embodiment, the rigid translating body <NUM> has a symmetrical structure, as clearly visible in <FIG>.

Such a rigid translating body <NUM> has a circular central part with a centre C; a plane of transverse symmetry P1 and a plane of longitudinal symmetry P2 pass through this centre C.

The dotted line representing the plane of longitudinal symmetry P2 is the same as that representing the translation direction Z.

A first distance A1 between the centre C and a first end of a first piston <NUM> is substantially the same as a second distance A2 between the centre C and a second end of the second piston <NUM>, as is well schematised in <FIG>.

The translation direction Z is, for example, orthogonal to the rotation axis X2 of said drive shaft <NUM>.

In particular, the second guide and sliding rings <NUM>, 32a, 32b and 32c are annular and their axis of symmetry is orthogonal to the first rotation axis X1 of the first hinge means <NUM>.

This peculiar reciprocating volumetric compressor structure <NUM> allows the radial forces transmitted from the connecting rod <NUM> to the piston <NUM> to be well distributed over at least the three first second rings <NUM>, 32a, 32b, making the wear of the individual second rings <NUM>, 32a, 32b, 32c much slower and thus leading to a significant extension of the service life of the volumetric compressor structure <NUM>.

At the same time, the presence of at least three second guide and sliding rings <NUM>, 32a, 32b leads to an equally important improvement in the sealing between cylinder <NUM> and piston <NUM>, resulting in an improvement in the overall efficiency of the reciprocating volumetric compressor structure <NUM>.

Each of said first <NUM> and second <NUM> pistons comprises:.

A similar perimetral elastic gasket <NUM> is well shown in the section of <FIG>; the perimetral elastic gaskets <NUM> and <NUM> are to be understood as equal.

The perimetral elastic gasket <NUM> and <NUM> comprises:.

The sealing portion 41b is configured to be in contact with the inner surface of the corresponding suction and compression chamber <NUM> and <NUM>.

The sealing portion 41b and said cover <NUM> and <NUM> are configured in such a way that a compression gap <NUM> is defined between them, as visible in <FIG>.

In the compression steps, i.e. during the movement of the first <NUM> and second <NUM> piston towards the respective head <NUM> and <NUM>, this compression gap <NUM> allows air to interpose itself between the sealing portion 41b and the cover <NUM> and <NUM>, so as to act pushing against the sealing portion 41b in an outward radial direction; thereby, the sealing portion 41b increases its sealing efficiency against the inner surface of the suction and compression chamber <NUM> and <NUM>. More in particular, the cover <NUM> and <NUM> comprises a pinch relief 40a configured to press the annular base portion 41a against the cover <NUM> or <NUM> in a variant embodiment not shown, or against the circular base 35a of the cup-shaped cap <NUM>, as shown in <FIG>.

The pinch relief 40a determines an improved clamping of the annular base portion 41a of the perimetral elastic gasket <NUM> and <NUM>.

Each of said one-way valve means <NUM> and <NUM>, which are well represented in <FIG>, comprises:.

In particular, in this embodiment, two second suction openings <NUM> are defined in the base portion 22a and 23a, each defined by a through-hole.

Said at least one second delivery opening <NUM> consists of an opening having a substantially U-shaped profile with a diverter plane 55b tilted towards the inside of the head <NUM> and <NUM>.

The one-way valve means <NUM> and <NUM> also comprise:.

The first shutter foil <NUM> consists, for example, of a metal foil shaped to include a fixing portion 60a from which two side-by-side and independent shutter appendages 60b develop.

The second shutter foil <NUM> consists, for example, of a metal foil shaped to include a fixing portion 61a from which two side-by-side and independent shutter appendages 61b develop.

In each of said heads <NUM> and <NUM> they are defined:.

Such at least one suction passage <NUM> is schematised in hatching in <FIG> and is clearly represented and visible in <FIG>; in the embodiment herein shown, the head <NUM> comprises two suction passages <NUM>, defined by two channels made in the body of the head <NUM> and communicating with the filtering chamber <NUM> via a corresponding through opening 64a.

Each of the cylinders <NUM> and <NUM> comprises a tubular wall <NUM> wherein at least one suction channel <NUM> is defined extending in a direction parallel to a translation direction Z of said pistons <NUM>, <NUM> in the respective compression chamber.

The suction channels <NUM> can be, for example, two for each cylinder <NUM> and <NUM>. The suction channels <NUM> are in communication with a corresponding suction passage <NUM> by means of a corresponding first opening <NUM> defined on said inner plate <NUM> and an adjacent second opening <NUM> defined on said shaped gasket <NUM>.

Practically, it has been established that the invention achieves the intended task and objects.

In particular, the invention developed a reciprocating volumetric compressor structure capable of maintaining the same high yield for longer than similar compressors of the known type.

In addition, the invention developed a reciprocating volumetric compressor structure with improved pneumatic sealing.

In addition, the invention developed a reciprocating volumetric compressor structure more compact than similar volumetric compressors of the known type.

The invention thus conceived is susceptible of numerous modifications and variations within the scope of the appended claims.

In practice, the components and materials used, provided they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.

Claim 1:
Reciprocating volumetric compressor structure (<NUM>) comprising:
- two opposite pistons (<NUM>, <NUM>) fixed coaxially to each other to a same rigid translating body (<NUM>);
- two cylinders (<NUM>, <NUM>), one for each of said pistons (<NUM>, <NUM>);
- a connecting rod (<NUM>), hinged to said rigid translating body (<NUM>) with first hinge means (<NUM>) defining a first rotation axis (X1);
- an electric motor (<NUM>) with a drive shaft (<NUM>) having a second rotation axis (X2);
- an eccentric body (<NUM>) fixed to said drive shaft (<NUM>) and rotatably constrained to said connecting rod (<NUM>) with second hinge means (<NUM>) defining a third rotation axis (X3);
- two heads (<NUM>, <NUM>), each configured and positioned to close a corresponding cylinder (<NUM>, <NUM>), each head (<NUM>, <NUM>) having suction and delivery one-way valve means (<NUM>, <NUM>);
- two suction and compression chambers (<NUM>, <NUM>), each defined within a cylinder (<NUM>, <NUM>), between a corresponding piston (<NUM>, <NUM>) and a facing head (<NUM>, <NUM>);
- at least one guide and sliding ring (<NUM>, <NUM>) for each piston (<NUM>, <NUM>), said at least one guide and sliding ring (<NUM>, <NUM>) being fixed to the respective piston (<NUM>, <NUM>) so as to be in contact with the inner surface of the corresponding cylinder (<NUM>, <NUM>);
- a casing (<NUM>), on which said cylinders (<NUM>, <NUM>) and said electric motor (<NUM>) are fixed, said rigid translating body (<NUM>), said connecting rod (<NUM>) and said eccentric body (<NUM>) being positioned within said casing (<NUM>),
wherein a first piston (<NUM>), further away from the first hinge means (<NUM>), comprises at least one first guide and sliding ring (<NUM>), and a second piston (<NUM>), closer to the first hinge means (<NUM>), comprises at least two second guide and sliding rings (<NUM>, 32a, 32b, 32c) placed side by side, preferably three second guide and sliding rings (<NUM>, 32a, 32b, 32c), placed side by side, characterised in that at least one of said second guide and sliding rings (<NUM>, 32a, 32b) is positioned so as to surround said first hinge means (<NUM>).