WO1997039267A1

WO1997039267A1 - Hygienic valve having leakage detection

Info

Publication number: WO1997039267A1
Application number: PCT/US1997/006305
Authority: WO
Inventors: Yutaka Kaneko; Bengt Andersson
Original assignee: Tetra Laval Holdings & Finance S.A.
Priority date: 1996-04-18
Filing date: 1997-04-17
Publication date: 1997-10-23
Also published as: AU2671197A

Abstract

A valve apparatus (20) includes a relatively simple yet effective way to monitor leakage in the valve apparatus (20) in accordance with one embodiment of the invention. The valve apparatus (20) comprises a housing (25) defining a product flow path therethrough. The housing (25) has at least one electrically conductive portion. The valve apparatus (20) also comprises a valve assembly (30) for controlling the flow of a product through the product flow path. The valve assembly (30) has at least one electrically conductive component that is electrically insulated (45) from at least one electrically conductive portion (45) of the valve assembly (30) during normal operation of the valve apparatus (30). A hygienic sealing member (40) is provided that is disposed between the housing (25) and the valve assembly (30). A continuity monitoring circuit (155) is provided for monitoring the status of the electrical conduction between the at least one conductive portion (45) of the housing (25) and the at least one electrically conductive portion (45) of the valve assembly (30).

Description

HYGIENIC VALVE HAVING LEAKAGE DETECTION

CROSS-REFERENCE TO RELATED APPLICATION

5 The present application is a continuation-in-part of the pending patent application of Rickard Franke, Yutaka Kaneko, and Per Brandstrom, U.S. Serial No. 08/315,408 (Attorney Docket No. 10570US01), filed September 28, 1994. The prior pending application is incorporated herein by reference.

10 TECHNICAL FIELD

The present invention relates generally to a valve apparatus that, for example, may be used in an automated filling machine for controlling the flow of a fluid product from a product reservoir to a container in a hygienic manner. More specifically, the present

15 invention relates to a hygienic valve apparatus that electrically detects a faulty seal that compromises the sterility of the fluid.

BACKGROUND A variety of dosing devices for fluid products are used in automated filling machines. The dosing devices typically employ

20 one or more valve apparatus that are disposed along a product flow path to control the product flow along a path beginning at a product supply reservoir and ending at a container.

Because the filling process must be carried out in a hygienic manner, the valves used in the automated filling

25 machines are particularly constructed with features that ensure such hygiene. These valves are generally of a piston valve type

and typically include a piston assembly disposed in an elongated, cylindrical housing, The housing includes an outlet and an inlet. The piston assembly generally includes a valve stem that is terminated in a plug. The inlet allows product to flow into the 5 housing and is separated from the outlet by a valve seat. In a closed position, the plug of the piston assembly rests against the outlet side of the valve seat. In an open position, the plug disengages the valve seat and allows product to flow through the housing from the inlet to the outlet. The plug is held open until a

10 desired amount of product has flowed through the valve.

The plug is moved relative to the valve seat by a mechanical drive assembly, such as a linear actuator, that is connected to drive the valve stem. To ensure the sterility of the filling environment, many of the moving components of the valve

15 assembly, including the mechanical drive assembly, are isolated from the product flowing through the housing. Isolation between the moving parts of the valve assembly from the product may be accomplished, for example, with a flexible diaphragm. The diaphragm may be placed around the valve stem and plug and

20 attached to the interior wall of the housing between the inlet and the moving mechanical portions of the valve. If the diaphragm remains intact, it provides is an effective seal. However, because the diaphragm is continually stretched, it tends to fatigue and may crack, tear, or break. If a breach develops in the diaphragm, the product may leak into the contact with non-sterile components of the valve apparatus and both the product and the valve apparatus may become contaminated. Therefore, it is desirable to monitor the valve apparatus to determine if a leak develops.

SUMMARY OF THE INVENTION

A valve apparatus is set forth that includes a relatively simple yet effective way in which to monitor leakage in the valve apparatus In accordance with one embodiment of the invention,

5 the valve apparatus comprises a housing defining a product flow path therethrough. The housing has at least one electrically conductive portion. The valve apparatus also comprises a valve assembly for controlling the flow of a product through the product flow path. The valve assembly has at least one electrically

10 conductive component that is electrically insulated from the at least one electrically conductive portion of the valve assembly during normal operation of the valve apparatus. A hygienic sealing member is provided that is disposed between the housing and the valve assembly. The sealing member facilitates electrical

15 isolation between at least one electrically conductive portion of the valve assembly and the at least one electrically conductive portion of the housing. A continuity monitoring circuit is provided for monitoring the status of electrical conduction between the at least one electrically conductive portion of the housing and the at least

20 one electrically conductive portion of the valve assembly. Upon a breach of the sealing member, the at least one electrically conductive portion of the valve assembly and the at least one electrically conductive portion of the housing are placed into electrical contact by the fluid passing through the breach. This

electrical continuity is detected by the continuity monitoring circuit to provide an indication that a breach of the sealing member has occurred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective sectional view of a valve in a closed position.

FIG. 2 is a perspective sectional view of a valve in an open position.

FIG. 3 is a perspective sectional view of a second embodiment of a valve according to the present invention.

FIG. 4 is a schematic block diagram of one embodiment of a circuit that can be used to monitor electrical continuity of selected components of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

One embodiment of the present invention is set forth in FIG. 1 and is in the form of a piston-type valve apparatus, shown generally at 20. The valve apparatus 20 includes a housing, 5 shown generally at 25, a valve assembly, shown generally at 30, a mechanism for operating the valve assembly, shown generally at 35, and a hygienic sealing member 40.

The housing 25 of the present embodiment may be discussed in connection with an upper housing portion 45 and a

10 lower housing portion 50. The lower housing portion 50 comprises an inlet 55 and an outlet 60. The lower housing portion 50 also includes sidewalls 65 that define a product flow channel extending between the inlet 55 and outlet 60. A valve seat 70 is disposed in the product flow channel.

15 The upper housing portion 45 may be formed as a separate piece from the lower housing portion 50, or, for example, may comprise a single, integrated piece with the lower housing portion 50. The upper housing portion 45 includes sidewalls that define a chamber 80 through which, as will be discussed in further detail

20 below, several components of the valve assembly 30 extend. The chamber 80 may also include one or more ports 85 and 90. Port 85 may be used to connect the chamber 80 with an underpressure source to place the chamber 80 at a pressure below the ambient pressure. Port 90 may contain a pressure sensor 95 that monitors

the pressure level within the chamber 80.

The valve assembly 30 comprises a valve stem 100 that passes through chamber 80 and the fluid flow channel to terminate in a plug 105. As illustrated, the plug 105 of the present embodiment is disposed on an outlet side of the valve seat 70, but may, if desired, be disposed on the inlet side thereof as well. The chamber 80 and the components therein are separated from the fluid flow channel of the lower housing portion 50 by the hygienic sealing member 40. The hygienic sealing member 40 of the illustrated embodiment is formed as an elastic diaphragm that envelops at least a portion of the valve stem 100 and plug 105.

The mechanism 35 for operating the valve assembly 30 may comprise a linear actuator that, for example, is fixed to one end of the upper housing portion 45. The linear actuator 35 includes a centrally disposed actuator rod 110 that is fixed to the valve stem

100 for moving the valve stem 100 and plug 105 between a first closed position, illustrated in FIG. 1 , and a second open position, illustrated in FIG. 2. The rod 110 is guided into the chamber 80 through an insulating collar 115. The rod 110 and valve stem 100 may be fixed to one another by, for example, a connection collar

120 or by any other mechanical connection type, such as by a thread and socket connection or the like. In the illustrated embodiment, the connection between the valve stem 100 and actuator rod 110 places these components in electrical contact

with one another.

The valve assembly 30 is provided with one or more components that are electrically conductive. Similarly, the upper housing portion 45 includes one or more components that are 5 electrically conductive. The electrically conductive portions of the upper housing portion 45 and the electrically conductive components of the valve assembly 45 are electrically insulated from one another under normal operating conditions.

In accordance with the illustrated embodiment, the

10 electrically conductive portion of the valve assembly 30 is the valve stem 100. The valve stem 100, in turn, is connected for electrical contact with the actuator rod 110 which is itself electrically conductive. The rod 110 is electrically isolated from electrical conduction with the upper portion of the housing 45. Electrical

15 isolation of the actuator rod 110 may be accomplished in any one of several manners. For example, the rod 110 may be surrounded by an insulating collar 125 as it extends through the body 130 of the linear actuator 35. Such a collar prevents electrical contact between the rod 110 and any electrically conductive components

20 of the linear actuator 35 that may result in an undesired electrical contact between the rod 110 and upper housing portion 45. Alternatively, or in addition to any insulating characteristics provided by the insulating collar 115, the body 130 of the linear actuator 35 may be insulated from the upper portion of the

housing 45 by insulating fasteners. For example, the screws 135 that secure the linear actuator 35 to the upper portion of the housing 45 may be formed from a non-conductive material. If a conductive material is used for the screws 135, insulating stand- 5 offs 140 may be used to interconnect the screws 135 to the upper portion of the housing 45.

Also in accordance with the illustrated embodiment, the electrically conductive member of the upper housing portion 45 is the upper housing portion itself. Thus, the upper portion of the

10 housing 45 is constructed from an electrically conductive material.

In operation, the linear actuator 35 is used to drive the valve stem 100 and plug 105 between the first and second positions illustrated in FIGs. 1 and 2. In the first position of FIG. 1 , the plug 105 engages the valve seat 70 thereby inhibiting flow of product

15 from the inlet 50 to the outlet 60. In the second position of FIG. 2, the plug 105 disengages from the valve seat 70 thereby allowing the product to flow from the inlet 55 to the outlet 60 through the product flow channel. In each instance, the valve stem 100, plug 105, rod 110, and chamber 80 are hygienically isolated from the

20 fluid product by the hygienic sealing member 40.

To facilitate the detection of a breach of the sealing member 40, the electrical conduction between the valve stem 100 /actuator rod 110 and the upper portion of the housing 45 is monitored. Although there are several manners of monitoring this conduction

condition, the illustrated embodiment employs a source of electrical potential 150 and an accompanying current monitor 155. The source of electrical potential 150 is connected, for example, so that a first end of the source 150 is connected to the portion of 5 the rod 110 extending outwardly from the body 135 of the linear actuator 35, while a second end is connected to ground potential. The upper portion of the housing 45 is likewise connected so that it is at ground potential. Upon the occurrence of a breach of the sealing member 40, the product fluid enters chamber 80 through

10 the breach thereby providing a current conduction path between the valve stem 100/actuator rod 110 and the upper portion of the housing 45. The resulting current flow is detected by the current monitor 155 which, in turn, provides an output signal along one or more lines 160 indicative of the breach condition. The signal at

15 line(s) may be supplied for detection by a controller 170, such as a programmable logic controller or the like, that, in turn, may process the signal to conduct the necessary machine actions

(e.g., shut down the machine, indicate the fault to a user, etc.).

It will be readily recognized that other manners of

20 monitoring the conductive state between the upper portion of the housing 45 and the valve stem/actuator rod are possible without departing from the scope of contribution that the present inventor has made to the art. For example, it is possible to reverse the polarity of the electrical signals provided by the source 150. It is

also possible to monitor the voltage between the upper portion of the housing 45 and the valve stem/actuator rod. In such instances, a drop in the potential is indicative of a breach of the sealing member 40. A still further manner of detecting a conductive condition resulting from the breach is set forth in U.S.

Patent No. 5,488,308.

FIG. 4 is a detailed block diagram of the circuit of the *308 patent, and further includes testing circuitry for testing the operation of the continuity checking circuit. As illustrated, the housing 45 and actuator rod 110 are connected to a continuity relay 270 by lines 210 and 230 respectively. The housing 45 and actuator rod 110 are also connected to a testing relay 270 by lines 210 and 230 respectively. The switched output of the continuity relay 270 is supplied to the SET input of a latching relay 310 by line 320. The switched output of the latching relay 310 on line

330, in turn, indicates the occurrence of a breach in the hygienic seal 40.

To assure reliability of operation, the circuit of FIG.4 utilizes test circuitry that includes testing relay 280 and PLC 170. Upon system initialization and/or periodically during the operation of the apparatus, the testing relay 280 is actuated by a signal output on line 350 of the PLC 340. Actuation of the testing relay results in an electrical continuity between the housing 45 and actuator rod 110 to thereby simulate a breach of the seal 40. This electrical

continuity actuates the continuity relay 270 which, in turn, actuates the latching relay 310 at its SET input. Upon detection of the actuation of the latching relay 310 by the PLC 340 along line 360, the PLC 340 returns the testing relay 280 to a non-actuated state 5 and resets latching relay 310 by sending a signal to the RESET input at line 370. If the PLC 340 fails to detect actuation of the latching relay 310, the PLC 340 may provide a fail signal output at line 380.

In the exemplary embodiment of the apparatus illustrated in

10 FIG. 4, the continuity relay 270 may be a continuity relay manufactured by and available from the Schiele Corporation. The latching relay 310 may be a HC2K-DC-24V relay manufactured by and available from Aeromat Corporation. The testing relay 280 may be any standard off-the-shelf relay. The PLC 340 may be a

15 PLC manufactured by and available from General Electric Fanuc, or any other PLC manufacturer.

Other circuits for monitoring continuity may also be employed, it being immaterial to the detection of a breach whether such circuits provide continuous or sampled conditions.

20 It should be noted that not all fluids are inherently electrically conductive. Consequently, when the valve apparatus 20 is used to control the flow of such a fluid, it may be necessary to provide a simple additive to the fluid to achieve the requisite conductivity. One such additive may be a small amount of sodium

chloride (NaCI). It will further be recognized that the present valve apparatus may be used with fluids of a wide range of resistivities, the principal limitation being the ability to detect the conduction in the particular environment in which the valve apparatus is employed.

In a second embodiment of the valve apparatus is set forth in FIG. 3. As illustrated, the plug 105' may be constructed of a nonconductive material such as plastic. If the plug 105' is non- conductive, the diaphragm 40 need not envelop the plug 105 and need only envelop the valve stem 100.

The valve apparatus 20 may be used in any number of machines to control fluid flow, but is particularly useful in the fluid flow paths of packaging machines requiring hygienic dosing. In such instances, the valve apparatus may be disposed anywhere along the product flow path between a fluid product reservoir and the container to be filled.

Those skilled in the art will recognize other modifications that may be made that nonetheless fall within the teachings of the present invention. Therefore, the present invention should not be limited to the embodiments described. Instead, the scope of the present invention should be consistent with the invention as described in the appended claims.

Claims

WE CLAIM:

1. A valve apparatus comprising: a) an electrically conductive housing having an inlet and an outlet defining a path through which a

5 fluid enters and exits the housing; b) a valve assembly disposed within the housing between the inlet and the outlet, the valve assembly being movable between an open and a closed position, the valve assembly having at least one

10 electrically conductive component, the electrically conductive housing being electrically insulated from the at least one electrically conductive component of the valve assembly during normal operation of the valve apparatus;

15 c) a hygienic sealing member within the housing separating the fluid flow along the fluid path from direct contact with the valve assembly; d) a continuity checking circuit for monitoring for a conduction condition between the housing and the

20 electrically conductive component to thereby provide an indication of the status of the hygienic sealing member .

2. A valve apparatus as claimed in Claim 1 wherein the valve assembly comprises:

a) an electrically conductive valve stem, the at least one electrically conductive component of the valve assembly comprising the electrically conductive valve stem; and 5 b) a plug member disposed at an end of the valve stem and shaped to engage a valve seat of the housing.

3. A valve apparatus as claimed in Claim 2 wherein the hygienic sealing member is a flexible diaphragm disposed

10 about the plug member and electrically conductive valve stem.

4. A valve apparatus as claimed in Claim 2 and further comprising a mechanical drive assembly attached to drive the valve stem and plug member between the open and

15 closed positions with respect to the valve seat.

5. A valve apparatus as claimed in Claim 2 wherein the electrically conductive valve stem and the mechanical drive assembly are in electrical contact with one another but electrically insulated from the housing and wherein the

20 continuity checking circuit comprises a first electrode electrically connected to the electrically conductive housing and a second electrode electrically connected to the mechanical drive assembly to thereby monitor conduction therebetween.

6. A valve apparatus comprising: a) a housing defining a product flow path therethrough, the housing having at least one electrically conductive portion; 5 b) a valve assembly for controlling flow of a fluid product through the product flow path, the valve assembly having at least one electrically conductive portion, the at least one electrically conductive portion of the housing being electrically insulated

10 from the at least one electrically conductive portion of the valve assembly during normal operation of the valve apparatus; c) a hygienic sealing member disposed between the electrically conductive portion of the housing and

15 the electrically conductive portion of the valve assembly, the hygienic sealing member hygienically preventing contact between non-hygienic components of the valve assembly and fluid flowing through the product flow path;

20 d) continuity means for monitoring electrical conduction between the at least one electrically conductive portion of the housing and the at least one electrically conductive portion of the valve assembly to determine whether a breach of the

sealing member has occurred.

7. A valve apparatus as claimed in Claim 6 wherein the valve assembly comprises a valve stem connected to a valve plug. 5

8. A valve apparatus as claimed in Claim 7 wherein the valve plug is formed from a polymer material and wherein the hygienic sealing member comprises a flexible diaphragm that has a first end connected to the plug and that envelops the valve stem. 10

9. A valve apparatus as claimed in Claim 7 wherein the hygienic sealing member comprises a flexible diaphragm that envelops the valve stem and plug.

10. A valve apparatus as claimed in Claim 6 and further comprising: 15 a) a linear actuator having an electrically conductive actuator rod that is insulated from electrical contact with the electrically conductive portion of the housing during normal operation of the valve apparatus; 20 b) the valve assembly comprising an electrically conductive valve stem connected to a plug, the electrically conductive portion of the valve assembly comprising the electrically conductive valve stem; and

c) the continuity means having a first electrode electrically connected to the actuator rod and a second electrode electrically connected to the electrically conductive portion of the housing.

5 11. In a valve apparatus for controlling the flow of a fluid product, the apparatus having a housing with an electrically conductive portion and a valve assembly with an electrically conductive portion that are separated by a hygienic sealing member, the electrically conductive portions of the housing

10 and the valve assembly being electrically insulated from one another, a method for detecting a breach in the hygienic sealing member comprising the steps of: a) monitoring electrical conduction between the electrically conductive portions of the housing and

15 valve assembly; and b) allowing the fluid product to provide electrical conduction between the electrically conductive portions of the valve assembly and the housing when the hygienic sealing member is breached.

20 12. A method as claimed in Claim 11 wherein the monitoring step is performed by monitoring a drop in voltage potential between the electrically conductive portions of the housing and valve assembly.

13. A method as claimed in Claim 11 wherein the

monitoring step is performed by monitoring an increase in current flow between the electrically conductive portions of the housing and valve assembly.

14. A method as claimed in Claim 11 and further comprising the step of providing an additive to the fluid product to render it conductive.