PUMP PROVIDED WITH A SYSTEM FOR COMPENSATING THE INTERNAL PRESSURE

Abstract

The present document describes a pump (10) comprising a casing (12) that encloses a pumping group (14). On the casing (12) at least one inlet conduit for inletting a fluid (F) and at least one outlet conduit for outletting the fluid (F) are obtained. The pumping group (14) comprises a pair of mutually coupled gears, each mounted on a respective support shaft. The relative movement of a first gear with respect to the second gear defines a pumping chamber having variable volume inside the pumping group (14), so as to suck the fluid (F) from the suction conduit to expel it through the delivery conduit. A first support shaft (16) is operatively connected to an actuator assembly (18) so that the first gear can operate as a driving gear to set the second gear in rotation. The pump (10) comprises at least one element (20) for compensating the increase in volume of the fluid (F) and/or the increase in the pressures inside such a pump (10). The element (20) for compensating the pressure/volume is at least partially manufactured from a shape memory metal alloy having superelastic properties.

Claims

1. Pump (10) comprising a casing (12) enclosing a pumping group (14), at least one inlet conduit for inletting a fluid (F) and at least one outlet conduit for outletting said fluid (F) being obtained on said casing (12), said pumping group (14) comprising a pair of mutually coupled gears, each mounted on a respective support shaft, wherein the relative movement of a first gear with respect to the second gear defines a pumping chamber having variable volume inside the pumping group (14), so as to suck the fluid (F) from the suction conduit and to eject it through the delivery conduit, a first support shaft (16) being operatively connected to an actuator assembly (18) so that the first gear can operate as driving gear to set the second gear in rotation, the pump (10) comprising at least one element (20) for compensating the increase in volume of the fluid (F) and/or the increase in the pressures inside said pump (10), the pump (10) being characterized in that said element (20) for compensating the pressure/volume is at least partially manufactured from a shape memory metal alloy having superelastic properties.

2. Pump (10) according to claim 1, characterized in that said at least one element (20) for compensating the pressure/volume comprises a first wall (22), manufactured from a shape memory metal alloy having superelastic properties and configured to be placed in direct contact with the fluid (F) circulating inside the casing (12).

3. Pump (10) according to claim 2, characterized in that said at least one element (20) for compensating the pressure/volume further comprises a second wall (24) manufactured from a non-deformable material, a chamber (26) being obtained between the first deformable wall (22) and the second non-deformable wall (24) arranged to form a hollow cavity, inside which the superelastic material forming the first wall (22) can deform under critical load conditions.

4. Pump (10) according to claim 3, characterized in that the second non-deformable wall (24) is configured to be placed in direct contact with an inner wall of the casing (12).

5. Pump (10) according to claim 3, characterized in that said non-deformable material is a metal material.

6. Pump (10) according to claim 5, characterized in that said metal material is steel.

7. Pump (10) according to claim 3, characterized in that both the first deformable wall (22) and the second non-deformable wall (24) are made in the shape of discs mutually coupled by calking.

8. Pump (10) according to claim 7, characterized in that at least one sealing ring (28) of the O-ring type is interposed between said two discs.

9. Pump according to claim 1, characterized in that said actuator assembly (18) is housed inside the casing (12).

10. Pump according to claim 1, characterized in that said actuator assembly (18) is of the magnetic type.

Description

[0026] The characteristics and advantages of a gear pump provided with a system for compensating the internal pressure according to the present invention will become clearer from the following description, given as an example and not for limiting purposes, referring to the attached schematic drawings, in which:

[0027] FIG. 1 is a schematic section view of a gear pump made according to the prior art;

[0028] FIG. 2 is a schematic section view of a gear pump made according to the present invention;

[0029] FIG. 3 shows a detailed view of a component of the pump of FIG. 2; and

[0030] FIG. 4 is a stress-strain diagram typical of classes of materials, in particular shape memory alloys, having superelastic properties.

[0031] It should be noted that, in the different attached figures, the same reference numerals indicate elements that are the same or equivalent to one another. It should also be noted that, in the following description, numerous components of the gear pump will not be mentioned, since they are well known components to the skilled in the art.

[0032] With reference in particular to FIG. 1, a gear pump made according to the prior art is shown, wholly indicated with reference numeral 10. The pump 10 comprises a casing 12 that encloses a pumping group 14 and on which at least one inlet conduit (not shown) for inletting a fluid F and at least one outlet conduit (not shown) for outletting such a fluid F are obtained.

[0033] The pumping group 14 comprises a pair of perfectly mutually coupled toothed-wheels or gears, each mounted on a respective support shaft. The relative movement of the first gear with respect to the second gear defines a pumping chamber having variable volume inside the pumping group 14, so as to suck the fluid F from the suction conduit to expel it through the delivery conduit. In other words, the pressurisation of the fluid F takes place inside the pumping group 14.

[0034] The support shafts are oriented along respective axes that are parallel to one another. One of the support shafts, for example the shaft 16, is operatively connected to an actuator assembly 18, for example of the magnetic type, so that the respective gear can operate as a driving gear to set the other gear in rotation, which thus acts as driven gear. The actuator assembly 18 is preferably housed inside the casing 12.

[0035] Since the pump 10 is specifically designed for applications in which the fluid F is subject to the phenomenon of expansion of volume due to freezing, at least one deformable element 20 is also housed inside the casing 12 and arranged in direct contact with the fluid F. This deformable element 20 operates as an element for compensating the increase in volume of the fluid F and/or the increase in pressure inside the pump 10 due to the freezing of the fluid F itself.

[0036] The deformable element 20 can be manufactured with a compact elastomer or with a closed-cells foamed one, as disclosed in document WO 2009/029858 A1. However, it should immediately be noted that, in order to obtain acceptable performance, it is necessary for the deformable element 20 to have considerable thickness and volume, using a substantial amount of elastomeric material, all at the expense of the compactness of the pump 10 and of the pumping system in which it is inserted.

[0037] Now with reference to FIGS. 2 and 3, a gear pump made according to the present invention is shown, still wholly indicated with reference numeral 10. The pump 10 comprises most of the technical components of known magnetically-driven gear pumps described so far.

[0038] According to the present invention, the pump 10 is provided with at least one element 20 for compensating the pressure/volume at least partially manufactured with a shape memory metal alloy having superelastic properties. In detail, as shown in FIG. 3, the element 20 for compensating the pressure/volume comprises a first wall 22, manufactured with a shape memory metal alloy having superelastic properties and configured to be placed in direct contact with the fluid F flowing inside the casing 12.

[0039] The element 20 for compensating the pressure/volume also comprises a second wall 24 manufactured with a non-deformable material, typically metallic, like for example steel. Between the first deformable wall 22 and the second non-deformable wall 24 a chamber 26 is obtained that is configured to form a hollow cavity, inside which the superelastic material that constitutes the first wall 22 can deform in critical load conditions. As shown in FIG. 3, the second non-deformable wall 24 is configured to be placed in direct contact with a wall inside the casing 12.

[0040] Preferably, both the first deformable wall 22, and the second non-deformable wall 24 are made in the form of discs mutually coupled through calking. At least one sealing ring 28 of the O-ring type is interposed between the two discs.

[0041] It has thus been seen that the gear pump provided with a system for compensating the internal pressure according to the present invention achieves the purposes outlined earlier, being advantageous particularly in terms of size with respect to known deformable elements. The element 20 for compensating the pressure/volume according to the present invention does not indeed impact upon the normal operation of the pump 10 and, thanks to the ability of the superelastic disc 22 to carry out large deformations whilst being manufactured with a metal alloy, the system is particularly strong and reliable.

[0042] Moreover, the system for compensating the internal pressure according to the present invention is simple to make, because it is made up of three elements: a disc 22 made of superelastic alloy, a sealing O-ring 28 and a drawn and calked counter-disc 24, manufactured in simple steel. In this way a small hollow cavity 26 is formed, ensured by the static O-ring seal, inside which the superelastic disc 22 can deform, compensating for the increase in volume due to the expansion of the fluid by freezing. Therefore, the uncontrolled rise in pressure is avoided through a reliable and compact system, which still remains rigid in the operating steps at nominal pressure of the pump 10.

[0043] The gear pump provided with a system for compensating the internal pressure of the present invention thus conceived can in any case undergo numerous modifications and variants, all of which are covered by the same inventive concept; moreover, all of the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the shapes and sizes, can be whatever according to the technical needs.

[0044] The scope of protection of the invention is therefore defined by the attached claims.