Piston made of ceramic material

Abstract

A piston (1) comprising a first portion (10) suitable for coupling with an actuator member (53) and a second portion (20) made of ceramic material suitable for sliding in a cylinder (51). The first portion (10) and the second portion (20) are axially connected along a longitudinal axis (L) of the piston (1). The second portion (20) has an elongated shape along the longitudinal axis (L) of the piston (1), with an interface base (21) proximal to the first portion (10) and a free base (23) distal from the first portion (10). Moreover, the free base (23) is closed and entirely defines a piston crown.

Claims

1. Piston (1) comprising a first portion (10) couplable with an actuator member (53) and a second portion (20) made of ceramic material slidable in a cylinder (51), the first portion (10) and the second portion (20) being axially connected along a longitudinal axis (L) of the piston (1), wherein the second portion (20) has an elongated shape along the longitudinal axis (L) of the piston (1) with a proximal interface base (21) to the first portion (10) and a free base (23) distal from the first portion (10), the free base (23) being closed and overall defines a piston crown, wherein the second portion (20) has a cup shape and comprises a cavity (25) elongated along the longitudinal axis (L) of the piston (10) accessible through an opening (211) on the interface base (21), and wherein the first portion (10) comprises a stem (15) elongated along the longitudinal axis (L) of the piston (10) inserted axially into the cavity (25) of the second portion (20), the stem (15) of the first portion (10) comprising a first through hole (17) with an axis transversal to the longitudinal axis (L) of the piston (1), and wherein the second portion (20) comprises a second through hole (27) formed facing the cavity (25) and coaxial with the first through hole (17), and wherein a pin (40) is inserted axially into the first through hole (17) and in the second through hole (27).

2. The piston (1) according to claim 1, wherein a longitudinal extension of the cavity (25) of the second portion (20) is greater than a longitudinal extension of the stem (15) of the first portion (10).

3. The piston (1) according to claim 1, wherein the first portion (10) and the second portion (20) are mutually constrained by an adhesive element (30) arranged in contact with a surface of the stem (15) of the first portion (10) and an inner surface (251) of the second portion (20) which delimits the cavity (25).

4. Pump (50) comprising: a cylinder (51), an actuator member (53), and the piston (1) according to claim 1, wherein the first portion (10) is connected to the actuator member (53) in order to move the piston (1), and wherein the second portion (20) of the piston (1) is slidingly inserted axially into the cylinder (51), with the free base (23) of the second portion (20) which delimits a pumping chamber (517) within the cylinder (51).

5. The pump (50) according to claim 4, wherein a longitudinal extension of the second portion (20) is greater than, or equal to, a stroke of the piston (1) inside the cylinder (51).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will be more apparent after reading the following description provided by way of a non-limiting example, with the aid of the accompanying drawings.

(2) FIG. 1 is a side view of a piston according to an embodiment of the present invention.

(3) FIG. 2 is a schematic view of a pump comprising the piston of FIG. 1.

(4) FIGS. 3A to 6B are side views of the piston, with partial cut-out and/or cross-sectioned parts, and of a portion thereof according to different embodiments of the present invention.

IMPROVED METHOD FOR IMPLEMENTING THE INVENTION

(5) With particular reference to such drawings, a piston is indicated as a whole with number 1.

(6) The piston comprises a first portion 10 and a second portion 20 which are axially connected to each other along a longitudinal axis L of the piston 1.

(7) The first portion 10 may be made of metal material, for example of steel.

(8) The second portion 20 may be made, for example entirely made, of ceramic material or equivalently, may be made of composite material comprising a ceramic material, for example alumina.

(9) The first portion 10 has an elongated shape along the longitudinal axis L of the piston and comprises a connecting end 11 and an opposite interface end 13. In detail, the connecting end 11 is suitable for coupling with a (rotatory or linear) actuator member which may allow moving the piston 1 with reciprocating motion along the longitudinal axis L thereof. For example, the connecting end 11 may comprise a through hole 111. The interface end 13 is suitable for coupling with the first portion 20.

(10) The second portion 20 has an elongated shape along the longitudinal axis L of the piston 1, with an interface base 21 proximal to the first portion 10 and a free base 23 distal from the first portion 10. For example, the second portion has a cylindrical or prismatic shape, with the free base 23 and the interface base separated by a shell 24 comprising the side surface of the cylinder or the side faces of the prism. Advantageously, the shell is smoothed so as to minimize a respective friction coefficient during use.

(11) The free base 23 is closed in the embodiments of the present invention. In this manner, the free base 23 entirely defines a piston crown 1. Advantageously, the free base 23 of the second portion 20 is a surface which substantially is transversal to the longitudinal axis L and has no openings in the direction of the longitudinal axis L, thus forming a barrier for a fluid in contact therewith. In other words, the shape of the free base 23 prevents a passage of fluid in direction of the longitudinal axis towards the interface base 21.

(12) Preferably, although without limitation, the shell 24 and the free base 23 of the second portion 20 are formed in a single body, i.e. they are integral, as a single piece of ceramic material, for example by means of a single gluing operation.

(13) In a first and second embodiment (shown in FIGS. 3A and 3B and in FIGS. 4A and 4B, respectively), the second portion 20 has a cup shape. Preferably, the second portion 20 comprises a cavity 25 elongated along the longitudinal axis L. Preferably, the cavity 25 has circular section. In the examples considered, the cavity 25 is accessible through an opening 211 formed on the interface base 21. Moreover, the cavity 25 is delimited by an inner surface 251 of the second portion 20.

(14) Otherwise, the interface end 13 of the first portion 10 comprises a stem 15, which is elongated along the longitudinal axis L of the piston 1. Advantageously, the stem 15 is suitable for being axially inserted into the cavity 25 of the second portion 20. Preferably, transverse sizes of the stem 15 and transverse sizes of the cavity 25—i.e. the respective diameters in cross section in the case of cylindrical stem 15 and cavity 25—substantially are formed in corresponding manner so that stem 15 is inserted into the cavity 25 with a highly reduced clearance.

(15) Advantageously, a longitudinal extension of the cavity 25 of the second portion 20 is greater than a longitudinal extension of the stem 15 of the first portion 10.

(16) In the first embodiment, the first portion 10 and the second portion 20 are mutually constrained by an adhesive element 30, for example an adhesive paste. The adhesive element 30 is arranged in contact with an (outer) surface of the stem 15 of the first portion 10 and of the inner surface 251 of the second portion 20 that delimits the cavity 25. In this manner, it is possible to firmly fasten the first portion 10 and the second portion 20.

(17) Preferably, the surface of the stem 15 and the inner surface 251 of the second portion 20 are formed with respective predetermined roughness values—for example, much greater than a roughness of the shell 24—such as to ensure a reliable adhesion of the adhesive element thereto.

(18) In the second embodiment (shown in FIGS. 4A and 4B), the stem 15 of the first portion 10 comprises a first through hole 17. Preferably, the first through hole 17 is formed with an axis transversal to the longitudinal axis L. In addition, the second portion 20 comprises at least one second through hole formed facing the cavity 25 and aligned to a respective axis transversal to the longitudinal axis L. In the example considered, the second portion 20 comprises two axially-formed through holes 27.

(19) Advantageously, the first through hole 17 and the second through holes 27 are arranged coaxial when the stem 15 is inserted into the cavity 25. In addition, the piston 10 comprises a pin 40, which is suitable for being axially inserted into the first through hole 17 and into the second through holes 27 so as to axially block the first and the second portion, 10 and 20, of the piston 1.

(20) In a third and in a fourth embodiment (shown in FIGS. 5A and 5B and in FIGS. 6A and 6B, respectively), the first portion 10 comprises a receptacle 19, which extends along the longitudinal axis L (inside the first portion 10). Otherwise, the second portion 20 comprises a coupling shank 29, which projects from the interface base 21 along the longitudinal axis L. The coupling shank 29 may be formed in a single body with the rest of the second portion 20. Alternatively, the coupling shank 29 may be made independently—for example, of a different material, such as steel or aluminum—and therefore coupled to the interface base 23 of the second portion 20.

(21) Advantageously, the coupling shank 29 is suitable for being axially inserted into the receptacle 19.

(22) Preferably, the transverse sizes of the receptacle 19 and the transverse sizes of the coupling shank 29—i.e. the respective diameters in cross section in the case of cylindrical receptacle 19 and coupling shank 29—are formed substantially corresponding.

(23) In the third embodiment in particular, the coupling shank 29 and the receptacle 19 are sized to mutually couple with mechanical interference. In this manner, a stable coupling is obtained between the first portion 10 and the second portion 20 of the piston 1.

(24) Otherwise, in the fourth embodiment, an outer side surface 291 of the coupling shank 29 and an inner lateral surface 191 of the first portion 20 delimiting the receptacle 19 are threaded such that they become screwed one to another.

(25) The piston 1 according to the embodiments disclosed above is suitable for use in an operating machine, such as a (volumetric) pump 50 shown in the schematic example of FIG. 2.

(26) In the case considered, the pump 50 comprises a cylinder 51, an actuator member 53 and the piston 1.

(27) The second portion 20 of the piston 1 is coaxially inserted into the cylinder 51, for example through a corresponding opening 515, in such a manner that the free base 23 delimits a pumping chamber 517 inside the cylinder 51.

(28) In detail, the pumping chamber 517 is delimited by the free base 23 and by the inner surface of the cylinder 51. Advantageously, the free base 23 defines a movable wall of the pumping chamber 517, made uniformly and only of ceramic material.

(29) The cylinder 51 comprises a suction mouth 511, a delivery mouth 513, which are in communication with the pumping chamber 517 of the cylinder 51. The suction mouth 511 comprises a first valve 61 configured to allow only a flow of fluid with direction entering the pumping chamber 517. Similarly, the delivery mouth 513 comprises a second valve 63 configured to allow only a flow of fluid with direction leaving the pumping chamber 517.

(30) The first portion 10 of the piston 1 projects outside the cylinder 51 and is connected to the actuator member 53, which is configured to move the piston 1 so it slides along the longitudinal axis L coinciding with the axis in the cylinder. In the example considered, the actuator member 53 may comprise a crank 531 and a connecting rod 533, in which the connecting rod 533 has a first end hinged to the crank 531 and a second end (opposite to the first end) hinged to the connecting end 11 of the first portion 10 of the piston 1. For example, the second end of the connecting rod 533 may be hinged to the first portion 10 of the piston 1 by means of a pin inserted into the through hole 111 of the connecting end 11.

(31) In the preferred embodiment, the longitudinal extension X of the second portion 20 of the piston 1 is greater than, or equal to, a stroke C of the piston inside the cylinder 51.

(32) In use, the activation of the actuator member 53 causes a reciprocating axial movement of the piston 1 inside the cylinder 51, which alternately causes suction steps and expelling steps of a fluid into/from the cylinder 51. In detail, a distancing movement of the second portion 20 of the piston 1 from a closed end of the cylinder 51 causes a vacuum in the pumping chamber 517, the opening of the first valve 61 and a suction of the fluid from a first portion of hydraulic circuit (not shown) connected to the suction mouth 511. Otherwise, an approaching movement of the second portion 20 of the piston 1 from the closed end of the cylinder 51 causes an increase of pressure in the pumping chamber 517, the opening of the second valve 63 and the expulsion of the fluid into a second portion of hydraulic circuit (not shown) connected to the delivery mouth 513.

(33) The invention thus conceived is susceptible to several modifications and variations, all falling within the scope of the inventive concept. For example, although the free base is illustrated with a curved shape, nothing prevents the same from being shaped with a different profile, such as a flat, frustoconical, inclined, concave, etc. profile, so as to obtain a piston having a crown corresponding to contingent needs.

(34) Moreover, all the details can be replaced by other technically equivalent elements.

(35) In practice, any materials and also any contingent shapes and sizes may be used, depending on the needs, without departing from the scope of protection of the following claims.