CN110966425B

CN110966425B - Expansion valve

Info

Publication number: CN110966425B
Application number: CN201811152284.0A
Authority: CN
Inventors: 单宇宽; 宋治国
Original assignee: Zhejiang DunAn Hetian Metal Co Ltd
Current assignee: Zhejiang DunAn Hetian Metal Co Ltd
Priority date: 2018-09-29
Filing date: 2018-09-29
Publication date: 2021-12-07
Anticipated expiration: 2038-09-29
Also published as: CN110966425A

Abstract

The present invention provides an expansion valve, comprising: the valve comprises a valve body, a first valve cavity and a second valve cavity, wherein the valve body is provided with a first valve port and a second valve port which are communicated with the first valve cavity; the valve core seat is arranged at the first valve port and is provided with a through hole; the diaphragm is arranged at the top of the first valve cavity; the valve core assembly comprises a valve needle, a first elastic element and a guide piece, the guide piece is fixed in a first valve cavity, a stop flange is arranged on the periphery of the valve needle, the valve needle is installed on the guide piece, one end, close to the membrane, of the valve needle abuts against the membrane, the first elastic element is sleeved on the valve needle, two ends of the first elastic element abut against the stop flange and the valve core seat respectively, and the valve needle has an opening position for opening the through hole and a closing position for plugging the through hole. The expansion valve is not provided with structures such as an electromagnetic coil and a stop ring, and the cost and the noise of the expansion valve are reduced conveniently.

Description

Expansion valve

Technical Field

The invention relates to the technical field of switch valves, in particular to an expansion valve.

Background

Electronic expansion valves are important components in cooling/heating systems, primarily for regulating the flow of refrigerant fluid. The conventional electronic expansion valve is generally controlled by a stepping motor, and generally comprises a driving mechanism (stepping motor), an actuating mechanism (threaded screw mechanism), a throttling mechanism (valve needle seat) and related auxiliary mechanisms.

In the field, there is a need to integrate the self-closing characteristic of the solenoid valve after power failure into the electronic expansion valve skillfully through mechanical structure design so as to realize the power failure self-protection function of the electronic expansion valve, and there is a need to develop a new reliable and effective threaded screw mechanism (threaded pair connection) in compliance with the power failure self-protection function of the electronic expansion valve.

Most of existing electronic expansion valves need to be opened and closed by using structures such as electromagnetic coils, the cost of the electronic expansion valves is high, circumferential limiting parts such as stop rings need to be arranged in the actual design process, mechanical expansion is serious, and noise is high.

Disclosure of Invention

The invention mainly aims to provide an expansion valve which is low in cost and low in noise.

In order to achieve the above object, the present invention provides an expansion valve comprising: the valve comprises a valve body, a first valve cavity and a second valve cavity, wherein a first valve port and a second valve port which are communicated with the first valve cavity are arranged on the side wall of the valve body; the valve core seat is arranged at the first valve port and is provided with a through hole; a diaphragm disposed at a top of the first valve chamber; the valve element assembly comprises a valve needle, a first elastic element and a guide piece, the guide piece is fixed in the first valve cavity, a stop flange is arranged on the periphery of the valve needle, the valve needle is installed on the guide piece, one end, close to the diaphragm, of the valve needle abuts against the diaphragm, the first elastic element is sleeved on the valve needle, two ends of the first elastic element respectively abut against the stop flange and the valve element seat, and the valve needle is provided with an opening position for opening the through hole and a closing position for plugging the through hole.

Further, the guide piece is provided with a mounting hole, and the valve needle is mounted in the mounting hole.

Further, the membrane is a metal sheet.

Further, the expansion valve also comprises a valve cover, and the valve cover is arranged on the top of the valve body and surrounds the diaphragm to form a second valve cavity.

Furthermore, a positioning part and a second elastic element are arranged in the center of the interior of the valve cover, the second elastic element is installed at the positioning part, and two ends of the second elastic element respectively abut against the valve cover and the diaphragm.

Further, the diaphragm includes an outer flange that rides on top of the valve body; the diaphragm is fixed on the top of the valve body through the pressing ring in a pressing mode.

Further, the diaphragm includes an outer flange, a central reinforcing portion, and a flexible deformation portion connected between the outer flange and the central reinforcing portion.

Further, the outer flange and the central reinforcing portion are both made of a metal material.

Further, the valve cover comprises a ring sleeve and an end cover in threaded connection with the ring sleeve, the pressing ring is arranged on the inner wall surface of the ring sleeve, and the positioning portion is arranged on the end cover.

Furthermore, the positioning part is a positioning column integrally formed on the valve cover.

Furthermore, the positioning part is a positioning column which is processed separately from the valve cover and then fixed on the valve cover.

Further, the positioning part is a positioning groove arranged on the valve cover.

Further, a detachable part is arranged on the valve cover.

Further, the dismounting part is a polygonal column body, a multi-deformation groove or a long-strip groove.

Further, the expansion valve further comprises a first pipeline and a second pipeline, the first pipeline is connected with the second valve port, and the second pipeline is connected with the first valve port.

By applying the technical scheme of the invention, in the actual work, the expansion valve can realize bidirectional circulation, when the expansion valve works reversely, the diaphragm is welded and fixed at the top of the first valve cavity, the top end of the valve needle is abutted against the diaphragm, the diaphragm applies an initial pretightening force F to the valve needle, when fluids such as refrigerants and the like enter the first valve cavity from the first pipeline, the fluid flowing into the first valve cavity applies an upward pressure b to the diaphragm, and if F + b is less than or equal to F, F is the deformation critical force of the diaphragm, and the valve needle does not act. When the fluid in the first valve cavity is increased continuously, b is increased continuously, when F + b is larger than F, the diaphragm is stressed and deformed, the valve needle moves upwards under the action of the first elastic element, the valve needle can open the through hole to be at an opening position, and the fluid such as refrigerant and the like in the first valve cavity flows to the second pipeline from the first valve port.

When the expansion valve works in the forward direction, fluid such as refrigerant enters the through hole in the valve core seat from the second pipeline to drive the valve needle to move upwards, after the diaphragm deforms upwards due to the force applied by the valve needle to the diaphragm, the valve needle moves upwards under the action of the first elastic element, gas enters the first valve cavity, and the fluid such as the refrigerant enters the second valve port through the first valve cavity and flows out from the first pipeline.

Therefore, the expansion valve is not provided with structures such as an electromagnetic coil and a stop ring, and the cost and the noise of the expansion valve are reduced conveniently.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 schematically shows a partly sectional view of an expansion valve according to a first embodiment of the invention;

fig. 2 schematically shows a partly sectional view of an expansion valve according to a second embodiment of the invention;

fig. 3 schematically shows a partial cross-sectional view of an expansion valve according to a third embodiment of the invention;

FIG. 4 schematically illustrates a bottom view of the valve cover of FIG. 3;

FIG. 5 schematically illustrates a cross-sectional view of the valve cover of FIG. 4;

FIG. 6 schematically shows a cross-sectional view of the diaphragm of FIG. 3;

FIG. 7 schematically illustrates a top view of the diaphragm of FIG. 3;

fig. 8 schematically shows a partial cross-sectional view of an expansion valve according to a fourth embodiment of the invention;

fig. 9 schematically shows a partial cross-sectional view of an expansion valve according to a fifth embodiment of the invention;

FIG. 10 schematically illustrates a cross-sectional view of a first embodiment of an end cap of the present invention;

FIG. 11 schematically illustrates a top view of the end cap of FIG. 10;

FIG. 12 schematically illustrates a bottom view of a second embodiment of an end cap of the present invention;

FIG. 13 schematically illustrates a cross-sectional view of the end cap A-A of FIG. 12;

FIG. 14 schematically illustrates a bottom view of a third embodiment of an end cap of the present invention;

FIG. 15 schematically illustrates a cross-sectional view of the end cap of FIG. 14;

FIG. 16 schematically illustrates a bottom view of a fourth embodiment of an end cap of the present invention;

FIG. 17 schematically illustrates a cross-sectional view of the end cap of FIG. 16;

FIG. 18 schematically illustrates a cross-sectional view of a fifth embodiment of an end cap of the present invention;

FIG. 19 schematically illustrates a bottom view of the end cap of FIG. 18;

FIG. 20 schematically illustrates a cross-sectional view of a sixth embodiment of an end cap of the present invention;

FIG. 21 schematically illustrates a top view of the end cap of FIG. 20;

FIG. 22 schematically illustrates a cross-sectional view of a seventh embodiment of an end cap of the present invention;

FIG. 23 schematically illustrates a top view of the end cap of FIG. 22;

FIG. 24 schematically illustrates a cross-sectional view of an eighth embodiment of an end cap of the present invention;

FIG. 25 schematically illustrates a top view of the end cap of FIG. 24;

FIG. 26 schematically illustrates a front view of a ninth embodiment of the end cap of the present invention;

fig. 27 schematically illustrates a top view of the end cap of fig. 26.

Wherein the figures include the following reference numerals:

10. a valve body; 11. a first valve chamber; 12. a first valve port; 13. a second valve port; 14. a second valve cavity; 20. a valve core seat; 21. a through hole; 30. a membrane; 31. an outer flange; 32. a central reinforcing portion; 33. a flexible deformation portion; 40. a valve core assembly; 41. a valve needle; 411. a stop flange; 42. a first elastic element; 43. a guide member; 431. mounting holes; 50. a valve cover; 51. a positioning part; 52. pressing a ring; 53. sleeving a ring; 54. an end cap; 55. a detachable portion; 60. a second elastic element; 70. a first conduit; 80. a second conduit.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Referring to fig. 1 to 27, according to an embodiment of the present invention, an expansion valve is provided, in which the expansion valve is a bidirectional flow expansion valve that is opened or closed by a purely mechanical structure, and the expansion valve is not provided with a solenoid coil, a stopper ring, and the like, so that the cost and noise of the expansion valve can be reduced.

Specifically, referring to fig. 1, according to a first embodiment of the present invention, there is provided an expansion valve including a valve body 10, a valve cartridge seat 20, a diaphragm 30, a valve cartridge assembly 40, a first conduit 70, and a second conduit 80.

The valve body 10 is provided with a first valve cavity 11, the side wall of the valve body 10 is provided with a first valve port 12 and a second valve port 13 which are communicated with the first valve cavity 11, a first pipeline 70 is connected with the second valve port 13, and a second pipeline 80 is connected with the first valve port 12, so that fluids such as refrigerant and the like can be conveniently conveyed; the valve core seat 20 is arranged at the first valve port 12, and a through hole 21 is arranged on the valve core seat 20; the diaphragm 30 is arranged on top of the first valve chamber 11; the valve core assembly 40 includes a valve needle 41, a first elastic element 42 and a guide 43, the guide 43 is fixed in the first valve cavity 11, a stopping flange 411 is provided on the periphery of the valve needle 41, the valve needle 41 is mounted on the guide 43, one end of the valve needle 41 close to the diaphragm 30 abuts against the diaphragm 30, the first elastic element 42 is sleeved on the valve needle 41, two ends of the first elastic element 42 respectively abut against the stopping flange 411 and the valve core seat 20, and the valve needle 41 has an opening position for opening the through hole 21 and a closing position for closing the through hole 21.

In actual operation, the expansion valve in this embodiment can realize bidirectional circulation, when the expansion valve works in reverse direction, the diaphragm 30 is welded and fixed on the top of the first valve cavity 11, the top end of the valve needle 41 abuts against the diaphragm 30, the diaphragm 30 applies an initial pretightening force F to the valve needle 41, when a fluid such as a refrigerant enters the first valve cavity 11 from the first pipeline 70, the fluid flowing into the first valve cavity 11 applies an upward pressure b to the diaphragm 30, and if F + b is less than or equal to F, F is a deformation critical force of the diaphragm 30, and the valve needle 41 does not act. When the fluid in the first valve chamber 11 increases, b increases, and when F + b > F, the diaphragm 30 is deformed by force, the needle 41 moves upward under the action of the first elastic element 42, the needle 41 can open the through hole 21 to be in the open position, and the fluid such as the refrigerant in the first valve chamber 11 flows from the first valve port 12 to the second pipe 80.

When the expansion valve works in the forward direction, a refrigerant or other fluid enters the through hole 21 in the valve core seat 20 from the second pipe 80 to drive the valve needle 41 to move upward, and after the diaphragm 30 is deformed upward by the force exerted by the valve needle 41 on the diaphragm 30, the valve needle 41 moves upward under the action of the first elastic element 42, gas enters the first valve cavity 11, and the refrigerant or other fluid enters the second valve port 13 through the first valve cavity 11 and flows out from the first pipe 70.

It can be seen that the expansion valve in this embodiment is not provided with the electromagnetic coil and the stop ring, which is convenient for reducing the cost and noise of the expansion valve.

The first pipeline 70 and the second pipeline 80 in this embodiment are both copper pipes, and have simple structure and low cost, and are not easy to corrode.

In order to support and guide the needle 41, the guide 43 in this embodiment is provided with a mounting hole 431, and the needle 41 is mounted in the mounting hole 431. In addition, in order to facilitate exerting force on the diaphragm 30, the guide member 43 in this embodiment is provided with a yielding through hole, so that the refrigerant and the like can flow to the diaphragm 30 conveniently, and the diaphragm 30 can exert force conveniently.

Preferably, the diaphragm 30 in this embodiment is a metal sheet, and in actual assembly, the diaphragm 30 is directly mounted on the valve body 10, so that the structure is simple and the implementation is convenient.

Of course, in other embodiments of the present invention, the membrane 30 may be provided with other sheet-like structures for facilitating deformation, and any other deformation method under the concept of the present invention is within the protection scope of the present invention.

The first elastic element 42 in this embodiment is preferably a spring, but of course, in other embodiments of the present invention, the first elastic element 42 may be configured as an elastic rubber pad, and other modifications under the concept of the present invention are within the protection scope of the present invention.

Referring to fig. 2, according to a second embodiment of the present invention, an expansion valve is provided, the structure of which is substantially the same as that of the first embodiment, except that the expansion valve further comprises a valve cover 50, and the valve cover 50 is arranged on the top of the valve body 10 and surrounds the diaphragm 30 to form the second valve chamber 14. The diaphragm 30 is protected by the valve cover 50.

In the first embodiment of the present invention, since the diaphragm 30 is made of a metal sheet, the structural strength is high and the stability is good, and therefore, the valve cover 50 may not be provided.

Of course, in the second embodiment of the present invention, even if the diaphragm 30 is provided as a metal sheet, the valve cover 50 may be provided, so as to improve the structural stability of the expansion valve of the present invention.

Referring to fig. 3 to 7, according to a third embodiment of the present invention, there is provided an expansion valve, which has a structure substantially identical to that of the expansion valve of the second embodiment, except that a positioning portion 51 and a second elastic member 60 are centrally provided in the interior of a valve cover 50 of the present embodiment, the second elastic member 60 is mounted on the positioning portion 51, and both ends of the second elastic member 60 abut against the valve cover 50 and the diaphragm 30, respectively. The diaphragm 30 jacked up by the valve needle 41 is reset by the action of the second elastic element 60, and the structure is simple and convenient to realize.

The second elastic element 60 in this embodiment is a spring, but it is understood that in other embodiments of the present invention, the second elastic element 60 may be configured as an elastic rubber pad, and other modifications within the spirit of the present invention are within the scope of the present invention.

Referring again to fig. 3-7, for ease of installation and positioning, the diaphragm 30 in this embodiment includes an outer flange 31 that rides on top of the valve body 10; correspondingly, a press ring 52 is arranged on the inner peripheral wall of the valve cover 50, the valve cover 50 is screwed on the valve body 10, and the diaphragm 30 is pressed and fixed on the top of the valve body 10 through the press ring 52, so that the diaphragm 30 is fixed conveniently.

In actual design, the pressing ring 52 in this embodiment may be integrally formed with the valve cover 50 (as shown in fig. 3), or may be separately formed from the valve cover 50 and then assembled into a whole (as shown in fig. 5), and in actual assembly, the valve cover 50 and the pressing ring 52 may be connected by a screw, a locking screw, a snap, or other structures, and any other modifications within the scope of the present invention are within the spirit of the present invention.

Referring to fig. 6 and 7, the diaphragm 30 in this embodiment includes an outer flange 31, a central reinforcing portion 32, and a flexible deformation portion 33 connected between the outer flange 31 and the central reinforcing portion 32, and in actual use, the top end of the needle 41 contacts the central reinforcing portion 32, the outer flange 31 is set on the top of the valve body 10, and by the action of the central reinforcing portion 32 and the outer flange 31, not only is the assembly of the diaphragm 30 facilitated, but also the service life and the structural stability of the entire diaphragm 30 are improved.

In order to further prolong the service life of the diaphragm 30 in this embodiment, the outer flange 31 and the central reinforced portion 32 in this embodiment are made of metal materials, so that the structural strength is high and the service life is long. Correspondingly, the flexible deformation portion 33 may be made of rubber or the like, so as to be easily deformed to switch between the open position and the closed position using the needle 41.

Referring to fig. 8, a fourth embodiment of the present invention provides an expansion valve, which has a structure identical to that of the third embodiment, except that the valve cover 50 of the present embodiment includes a ring sleeve 53 and an end cover 54 screwed on the ring sleeve 53, the compression ring 52 is disposed on an inner wall surface of the ring sleeve 53, and the positioning portion 51 is disposed on the end cover 54, and the valve cover 50 of the present embodiment is configured in such a manner that the ring sleeve 53 and the end cover 54 are assembled in a matching manner, so that an installation error of the second elastic element 60 can be easily eliminated by adjusting an installation position of the end cover 54.

Referring to fig. 8, 10, 11, 12, 13, 20 to 27, in a preferred embodiment of the present invention, the positioning portion 51 is a positioning column integrally formed on the end cover 54 of the valve cover 50.

Referring to fig. 14 to 17, in another embodiment of the present invention, the positioning portion 51 may be a positioning column that is processed separately from the valve cover 50 and then fixed to the valve cover 50.

Referring to fig. 9, in a fifth embodiment according to the present invention, an expansion valve is provided, which is substantially the same as the fourth embodiment, except that the positioning portion 51 is a positioning groove provided on the valve cover 50 to facilitate positioning of the second elastic member 60.

As shown in fig. 20 to 27, the valve cap 50 of the present embodiment is provided with a detachable portion 55 to facilitate the detachment of the valve cap 50.

As shown in fig. 20 to 23, the detachable portion 55 in the present application may be provided as a polygonal cylinder, such as a quadrangular prism or a column with a cut edge.

As shown in fig. 26 to 27, the detachable portion 55 may also be provided with a multi-changeable groove, such as a hexagonal groove or a quadrangular groove.

As shown in fig. 24 to 25, the detachable portion 55 may be provided with a long groove or the like, and any other modifications within the spirit of the present invention are within the scope of the present invention.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

1. the expansion valve has bidirectional circulation capacity, and an electromagnetic coil (a stator coil) is not needed, so that the product cost is reduced;

2. the expansion valve in some embodiments of the invention is adjusted without screw thread, thus avoiding product failure caused by entering impurities;

3. the expansion valve has no stop ring and other circumferential limiting parts, has no mechanical collision, and avoids the mechanical collision noise of the expansion valve.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An expansion valve, comprising:

the valve comprises a valve body (10), wherein a first valve cavity (11) is arranged on the valve body (10), and a first valve port (12) and a second valve port (13) which are communicated with the first valve cavity (11) are arranged on the side wall of the valve body (10);

the valve core seat (20), the valve core seat (20) is arranged at the first valve port (12), and a through hole (21) is arranged on the valve core seat (20);

a diaphragm (30), said diaphragm (30) being arranged on top of said first valve chamber (11);

the valve core assembly (40) comprises a valve needle (41), a first elastic element (42) and a guide piece (43), the guide piece (43) is fixed in the first valve cavity (11), a stop flange (411) is arranged on the periphery of the valve needle (41), the valve needle (41) is installed on the guide piece (43), one end, close to the diaphragm (30), of the valve needle (41) abuts against the diaphragm (30), the first elastic element (42) is sleeved on the valve needle (41), two ends of the first elastic element (42) respectively abut against the stop flange (411) and the valve core seat (20), and the valve needle (41) has an opening position for opening the through hole (21) and a closing position for blocking the through hole (21);

the diaphragm (30) comprises an outer flange (31), a central reinforcing portion (32), and a flexible deformation portion (33) connected between the outer flange (31) and the central reinforcing portion (32).

2. An expansion valve according to claim 1, wherein the guide (43) is provided with a mounting hole (431) and the valve needle (41) is mounted in the mounting hole (431).

3. An expansion valve according to claim 1, wherein the membrane (30) is a metal sheet.

4. An expansion valve according to claim 1, further comprising a valve cover (50), wherein the valve cover (50) covers the top of the valve body (10) and encloses the membrane (30) to form a second valve chamber (14).

5. An expansion valve according to claim 4, wherein the valve cover (50) is centrally provided with a positioning portion (51) and a second resilient member (60) at the inner part thereof, the second resilient member (60) being mounted at the positioning portion (51), the two ends of the second resilient member (60) abutting against the valve cover (50) and the membrane (30), respectively.

6. An expansion valve according to claim 5, wherein the membrane (30) comprises an outer flange (31) overlapping the top of the valve body (10);

the valve is characterized in that a pressing ring (52) is arranged on the peripheral wall of the inner side of the valve cover (50), the valve cover (50) is in threaded connection with the valve body (10), and the diaphragm (30) is pressed and fixed on the top of the valve body (10) through the pressing ring (52).

7. An expansion valve according to claim 6, wherein the outer flange (31) and the central reinforcement portion (32) are both made of a metallic material.

8. An expansion valve according to claim 6, wherein the valve cover (50) comprises a collar (53) and an end cap (54) screwed to the collar (53), the pressing ring (52) is provided on an inner wall surface of the collar (53), and the positioning portion (51) is provided on the end cap (54).

9. An expansion valve according to claim 5, wherein the positioning portion (51) is a positioning post integrally provided on the valve cover (50).

10. An expansion valve according to claim 5, wherein the positioning portion (51) is a positioning post that is machined separately from the valve cover (50) and then fixed to the valve cover (50).

11. An expansion valve according to claim 5, wherein the positioning portion (51) is a positioning groove provided on the valve cover (50).

12. An expansion valve according to claim 4, wherein the valve cover (50) is provided with a detachable portion (55).

13. An expansion valve according to claim 12, wherein the dismounting part (55) is a polygonal cylinder or a polygonal groove or an elongated groove.

14. An expansion valve according to any of claims 1-13, further comprising a first conduit (70) and a second conduit (80), the first conduit (70) being connected to the second valve port (13), the second conduit (80) being connected to the first valve port (12).