"DOSING PISTON"

The present invention relates to a piston for food product dosing devices, applicable particularly, but not limited to, the field of liquid and semi- liquid dairy products, such as, for example, milk and yogurt .

The packaging of food products in general involves several issues. In addition to the need to ensure a precise and repeatable dosing, one of the most felt problems is to ensure a high level of asepticity to the working environment. This can be achieved only if the several parts composing the system, particularly the dosing device directly contacting the food, can be suitably periodically hygienized during maintenance interventions.

In addition, if the packaging relates to liquid or semi-liquid products, such as milk and yogurt, the sealing of the piston-cylinder assembly of the dispensing device is another extremely important element. In fact, the poor sealing leads to the deposition of food residues in the inner recesses of the device, with consequent bacterial pollution risk. This makes the hygienization intervention still more troublesome . No dosing devices of the prior art are optimal in addressing all the problems set forth above.

The problem addressed by the present invention is to provide an integral dosing piston for a food product dosing device which solves the drawbacks of the prior art.

Such a problem is solved by an integral dosing piston for a food product dosing device as set forth in the appended claims, the definitions of which are an integral part of the present disclosure.

Therefore, an object of the invention is an integral dosing piston for a food product dosing device, which ensures a high precision and repeatability of the dispensed dose of food product.

A further object of the invention is an integral dosing piston for a food product dosing device, which ensures a high sealing against leakages through the dosing cylinder.

A still another object of the invention is an integral dosing piston for a food product dosing device, which allows an easy and efficient hygienization .

Further characteristics and advantages of the present invention will be more apparent from the description of some embodiment examples, given herein below by way of illustrative, non-limiting example, with reference to the following figures:

Fig. 1 represents a longitudinal sectional view of an integral piston according to the present invention;

Fig. 2 represents a sectional view of a detail of the integral piston of the invention according to an embodiment ;

Fig. 3 represents a perspective view of a part of the integral piston of Fig. 1.

With reference to the figures, the integral dosing piston for a food product dosing device, generally indicated with the number 1, comprises an inner body 2, an outer head member 3, and a position abutment member 4.

The inner body 2, made of a substantially rigid material, is in a substantially cylindrical shape and comprises a side surface 5 and a head surface 6.

The head surface 6 has a relief central portion 7 and a contour portion 8. A step is thus formed between the central portion 7 and the contour portion 8.

The side surface 5 has a front portion 9, which is proximal to the head surface 6, having a first diameter dl, and a rear portion 10 having a second diameter d2, wherein the diameter dl is less than the diameter d2. A step 12 is thus formed between the front portion 9 and the rear portion 10, which composes a seat for at least one, preferably two, elastic rings 11, 11' (Fig. 1) .

In a more retracted position with respect to the step 12, the side surface 5 comprises, in the order moving away from the step 12, a first annular recess 13a and a second annular recess 13b. The second annular recess 13b composes the seat for a gasket ring 14.

The inner body 2 comprises coaxially a hole 15, typically a threaded hole, for securing the piston 1 to the actuator member of a dosing system.

The outer head member 3 comprises, in turn, a head portion 16 and a mantle 17.

In preferred embodiments, the connecting corner 16a between the head portion 16 and the mantle 17 is beveled ( Fig . 1 ) .

In preferred embodiments, the head portion 16 is planar .

The mantle 17 comprises a front portion 18 and a rear portion 22.

Two annular ridges 19, 19' are arranged on the front portion 18, which ensure the interference seal against the surface of the cylinder (not shown) in which the piston 1 operates. The annular ridges 19, 19' have a sectional profile having the side 20 facing inwardly inclined and the side 21 facing outwardly substantially perpendicular to the mantle 17 surface.

The rear portion 22 comprises a first relief length 22a, which is flush with the annular ridges 19, 19' and diametrically calibrated to act as a guide for such annular ridges, and a second length 22b forming a step with the first relief length 22a and has a profile facing downwardly, so as to form a snap-fitting profile 23 intended to interfere with the first annular recess 13a of the inner body 2. In this manner, it is possible to create a biunivocal position abutment between the outer head member 3 and the inner body 2.

The inner surface of the mantle 17, i.e., the one facing the inner body 2, has a front portion 24 and a rear portion 25, wherein the rear portion 25 has a diameter substantially corresponding to the diameter of the rear portion 10 of the inner body 2. Vice versa, the front portion 24 of the inner surface of the mantle 17 has a larger diameter, so as to create a gap so that the elastic rings 11, 11' insist simultaneously on both the surface of the step 12 and the inner surface of the mantle 17.

The position abutment member 4 has a portion that is proximal to the mantle 17 and a distal portion (not visible in the drawing) , which is secured to the actuator member of the dosing system. The proximal portion has an inner surface with a diameter substantially corresponding to the outer diameter of the second length 22b of the rear portion 22 of the mantle 17.

On the inner surface of the proximal portion of the position abutment member 4, in the order starting from the end of said proximal portion, a seat 26 for a gasket ring 27 and a tooth 28 engaging with the second annular recess 13b of the inner body 2 are arranged .

In a preferred embodiment, shown in Fig. 2, the seat 26 has a coupling geometry with the gasket ring 27, i.e., it has an arc-of-a-circle-shaped profile, so as to avoid straight-angled profiles. This type of geometry, which in the technical jargon is referred to as "3A cavity", allows avoiding the product build ^¬ up which can possibly penetrate the seat, if for any reasons the sealing of the mantle 17 against the corresponding cylinder has failed. In this manner, the washing and hygienization of the piston 1 is facilitated .

As stated above, the inner body 2 is made of a substantially rigid material. In preferred embodiments, by the term "substantially rigid material" is meant a material having an elastic module E (Young's module) >2000 MPa, as determined according to the method ASTM D790. More preferably, such material will be a plastic with a module E >2000 MPa.

Vice versa, the material of which the outer head member 3 is made is a medium rigidity material. In preferred embodiments, by the term "medium rigidity material" is meant a material having an elastic module E ranging between 50 and 1000 MPa. More preferably, such material is selected from plastic materials, such as, for example, polytetrafluoroethylene (PTFE) , polyethylene (PE) , and polyurethanes (PU) . PTFE is particularly preferred by virtue of its reduced friction properties .

Instead, the elastic rings 11, 11' and the constraint rings 14, 27 are made of a flexible material. In preferred embodiments, by the term "flexible material" is meant a material having a hardness Shore A 40-70, as determined by the method ISO 868. Preferably, such material will be a silicone elastomer .

The position abutment member 4 is also made of a substantially rigid material. In preferred embodiments, by the term "substantially rigid material" is meant a material having a module E >2000 MPa. More preferably, such material will be a plastic material with a module E >2000 MPa.

The piston 1 according to the invention is auto- adaptive, since it increases the sealing strength as the pressure to which the head portion 16 of the outer head member 3 is subjected increases. In fact, as shown by the arrows in Fig. 1, an overpressure onto the surface of the head portion 16 results in a compression of the elastic rings 11, 11', which consequently deform by elongating in the radial direction. In this manner, the elastic rings 11, 11' exert a pressure onto the inner surface 24 of the outer head member 3 which causes the radial expansion of the mantle 17 and thus a higher sealing pressure of the annular ridges 19, 19' onto the surface of the dosing cylinder. This change in the piston geometry, which is allowed by the configuration of the head surface 6 of the inner body 2 which provides for a relief central portion 7 with respect to the contour portion 8, results in a self-adaptation of the seal of the piston 1 following an increase in the axial pressure onto the piston itself without perceivably altering the head volume of the cylinder, i.e., the volume determining the amount of product to be dosed. In this manner, the dosing of the product is always precise and repeatable.

Therefore, the piston 1 according to the invention efficiently addressed the needs of the dosing in particular of food products.

As stated above, the above-described self- adaptive system allows keeping the head volume of the cylinder of the dosing pump substantially unaltered, allowing a precise dosing. At the same time, the fact that the higher sealing pressure against the cylinder is obtained only as the pressure to which the piston is subjected increases, creates a lesser wear of the mantle 17 with respect to the prior art pistons, which provide for a radially pre-loaded system.

Therefore, the piston of the invention achieves an optimal sealing in all situations.

Furthermore, the snap-anchoring system between the mantle 17 and the position abutment member 4, having a simplified geometry and the substantial absence of undercut profiles, is simpler and easier to be hygienized than the conventional pistons, which provide for couplings which can be difficult to be sanitized.

It is apparent that only some particular embodiments of the present invention have been described, to which those skilled in the art will be able to make all the modifications that are necessary of the adaptation thereof to particular applications, without anyhow departing from the protection scope of the present invention.