Differential pressure sensor and detection device comprising such a sensor

Abstract

The present invention relates to a differential pressure sensor for a leak detection device, comprising: - at least two bodies in which cavities are formed; - a diaphragm which is arranged between the two bodies and separates the cavities so as to define test chambers in each of the bodies; - at least one electrode which is arranged in each of the test chambers and faces the diaphragm so as to form a capacitor therewith; characterized in that the sensor comprises at least two seals arranged between each of the bodies and the diaphragm.

Description

Field of the Invention

[0001] The present invention relates to the field of devices for detecting leaks or measuring tightness. More precisely, the present invention relates to a differential pressure sensor intended to be installed in such devices. Background Art

[0002] In fact, in many industries, it is necessary to be able to check whether manufactured parts, packages, products... have leaks (or otherwise be configured to check that parts are tight) and be able to quantify said leaks.

[0003] There are different methods for detecting and quantifying leaks, such as the tracer gas method, the swimming pool (or water tank) method or the pressure change method.

[0004] However, if the leak is associated with a pressure difference greater than 0.1 Pa / s, then the pressure change method is the fastest and most economical method. In fact, unlike the tracer gas method, there is no need to make the gas cylinder airtight for measurement. Additionally, unlike the water tank method, the pressure change method is fast and can be implemented during an industrial process (e.g., on a production line).

[0005] Thus, in the pressure change method, the object to be tested undergoes a controlled pressure change, and after a determined time (stable phase), the pressure is measured again, for example, in the chamber containing the object, and if the object has a leak, the pressure will change.

[0006] Therefore, it is crucial to have a pressure sensor capable of measuring small pressure changes and thus indirectly measuring small leaks. Summary of the Invention

[0007] Accordingly, the present invention is a new type of differential pressure sensor for a leak detection device, comprising:

[0008] - at least two bodies fastened to each other, in which a cavity is formed;

[0009] - a diaphragm, which is arranged between the two bodies and separates the cavity so as to define a test chamber in each of the bodies;

[0010] - at least one electrode, which is arranged in each of the test chambers and faces the diaphragm so as to form a capacitor therewith;

[0011] characterized in that the sensor comprises at least two seals arranged between each of the bodies and the diaphragm.

[0012] The seals allow ensuring the tightness of the test chambers from the outside. Additionally, the seals are preferably arranged concentrically, allowing minimizing any change in the volume of the test chambers.

[0013] According to a possible feature, each of the bodies includes at least one fluid conduit opening between the seals.

[0014] The fluid conduit opening between the seals precisely allows for changing the pressure existing between the seals and bringing it into equilibrium with the pressure existing in the adjacent test chamber (i.e., the test chamber whose seals ensure tightness). Thus, the inner seal directly defining the test chamber does not undergo a pressure change (and thus does not move).

[0015] According to another possible feature, at least one of the body and / or the diaphragm includes a groove for receiving the seal.

[0016] Advantageously, a shape for receiving the seal is provided (e.g., a groove or any other suitable shape), which precisely facilitates the positioning of the seal during the manufacture of the sensor and also limits the radial movement of the seal and optimizes the seal provided by the latter.

[0017] According to another possible feature, each of the pair of seals is arranged on both sides of the diaphragm.

[0018] According to another possible feature, each of the pair of seals is in contact with at least one of the diaphragm and the body of the sensor.

[0019] According to another possible feature, at least one of the bodies includes a component for tensioning the diaphragm.

[0020] The tensioning component is in the shape of, for example, a projection or a washer, which bears on the diaphragm to preferably tension the diaphragm in a uniform manner.

[0021] According to another possible feature, the diaphragm and the body are made of materials having substantially equal coefficients of thermal expansion. The materials are, for example, bronze, beryllium bronze alloy, and / or stainless steel, etc.

[0022] According to another possible feature, at least one of the electrodes has, on the one hand, two opposite end faces, one facing the diaphragm and the other fastened to one of the bodies, and, on the other hand, a lateral face connecting the end faces.

[0023] More precisely, the electrode has a substantially cylindrical or disc shape and is made of, for example, a conductive material (e.g., brass, bronze, or copper alloy...).

[0024] According to another possible feature, at least one of the electrodes includes a through hole whose end opens at the (opposite) end face of the electrode.

[0025] According to another possible feature, at least one electrode includes a lateral housing intended to receive an electrical contact rod.

[0026] According to another possible feature, the through-hole and the lateral housing communicate with each other, specifically in a fluidic manner.

[0027] According to another possible feature, at least one of the bodies is produced by die stamping.

[0028] The fact that one of the bodies is produced by die stamping improves the mechanical stiffness of the part, and specifically, enables the sensor to withstand greater pressure values while allowing for fewer large parts. Additionally, die stamping is a more ecological method as it produces less material waste than conventional machining.

[0029] According to another possible feature, the sensor includes (especially at the lateral housing formed in the electrode) an electrical contact bar that contacts the electrode.

[0030] According to another possible feature, the sensor includes an electrical connector.

[0031] The electrical connector is connected on the one hand to the electrical contact bar and on the other hand to an electronic entity for measuring electrical quantities (such as capacitance, resistance, etc.).

[0032] According to another possible feature, the bar includes an end having a polygonal shape, such as square or rectangular.

[0033] The polygonal shape of the end of the bar is intended to be closely fitted (or pressed) into the lateral housing of the electrode and ensure good electrical contact between the electrode and the bar.

[0034] According to another possible feature, each of the bodies includes a fluid channel that opens into its corresponding test chamber.

[0035] The channel preferably opens tangentially to the wall defining the test chamber.

[0036] According to another possible feature, the sensor includes an interface part that is mounted on the body and includes a fluid channel in which at least one water collector (or water retention device) is arranged.

[0037] The present invention also relates to a leak detection device, characterized in that the leak detection device includes a sensor as described above. Description of the Drawings

[0038] During the following description of specific embodiments of the present invention, which is given only by way of illustration and not limitation, reference is made to the accompanying drawings, and the present invention will be better understood, and other objects, details, features, and advantages of the present invention will become clearer, wherein:

[0039] Figure 1 is a schematic perspective representation of a differential pressure sensor according to the present invention; ​

[0040] Figure 2 is the cross-sectional view of the sensor of Figure 1 ;

[0041] Figure 3 is the schematic perspective view of the sensor body of the sensor of Figure 1 ;

[0042] Figure 4 is the enlarged cross-sectional view of a part of the sensor of Figure 1 ;

[0043] Figure 4a is the enlarged and partial view of Figure 3 ; Detailed Description of the Invention

[0044] Figure 1 is a schematic perspective representation of the differential pressure sensor 1 according to the present invention.

[0045] More specifically, the sensor 1 includes at least two bodies 3a and 3b fastened to each other by fastening members 5 (e.g., screws). The sensor 1 also includes interface parts 6 and electrical connectors 10 fastened to the bodies 3a and 3b.

[0046] Each of the bodies 3a and 3b is hollow, such that in the installed position, the bodies 3a and 3b define a cavity 7 (the cavity inside the sensor), and this configuration is more clearly visible in Figure 2 which is Figure 2 the cross-sectional view of the sensor 1 shown in Figure 1 ;

[0047] It can also be seen in Figure 2 that the sensor 1 includes a diaphragm 9 inserted between the two bodies 3a and 3b to divide the cavity 7 into two sub-parts, and the two sub-parts respectively define a test chamber 7a and a test chamber 7b.

[0048] In addition, each of the bodies 3a and 3b includes fluid channels 8a and 8b that open into their respective test chambers 7a and 7b, which are 8a (the channel 8a is more clearly visible in Figure 3 ) and 8b (the latter is not shown in the figure).

[0049] It should be noted that in a variant embodiment not shown, at least one of the bodies 3a and / or 3b is produced by die stamping.

[0050] The channels 8a and 8b allow the fluid in the test chambers 7a and 7b to enter or exit respectively.

[0051] ​​​​Each of the channels 8a and 8b preferably opens tangentially to the wall of the body 3a or 3b that defines the test chamber 7a or 7b (an air flow opening tangentially to the wall limits the appearance of turbulent patterns, thus facilitating filling and stability).

[0052] The sensor 1 also includes two electrodes 11a and 11b housed respectively in the test chambers 7a and 7b.

[0053] The electrodes 11a and 11b are arranged on the one hand facing the diaphragm 9 so as to form a capacitor therewith, and on the other hand are respectively fastened to the bottom walls of the bodies 3a and 3b (the bottom wall of the housing is the wall opposite the diaphragm). The electrical connector 10 is in turn intended to transmit information on the physical quantities (e.g., capacitance value) of the electrodes 11a and 11b of the sensor 1 to an electronic entity (not shown) capable of processing them.

[0054] In the present embodiment, the electrodes 11a and 11b are substantially cylindrical or disc-shaped and are made, for example, of a conductive material (e.g., brass, bronze, copper alloy...).

[0055] Thus, each of the electrodes 11a and 11b has two opposite end faces and a lateral face connecting the two end faces.

[0056] The electrodes 11a and 11b are advantageously fastened to the bodies 3a and 3b here using a suitable glue (thus one of the end faces of the electrode is glued to the bottom wall of the body). Each of the bodies 3a and 3b has through openings 14a and 14b that open respectively at the electrodes 11a or 11b, more precisely facing the glued end faces of the electrodes 11a or 11b. This configuration thus allows the operator to more easily separate the electrodes 11a or 11b from the bodies 3a or 3b during maintenance and / or repair operations. After checking that the electrodes have been correctly installed, the through openings 14a and 14b are respectively closed by plugs 15a and 15b (the plugs ensure the tightness of the body).

[0057] The sensor 1 includes at least two sets 13 of seals, namely 13a1, 13a2 and 13b1, 13b2, each set of seals being arranged between one of the bodies 3a or 3b and the diaphragm 9.

[0058] The seals 13a 1-2 and 13b 1-2 (usually O-ring seals) are thus inserted between each of the bodies 3a and 3b and the diaphragm 9 (thus on each side of the diaphragm) to ensure the respective tightness of the test chambers 7a and 7b. More precisely, circular grooves 4 are provided in the bodies 3a and 3b to receive the seals 13a 1-2 and 13b 1-2, thereby facilitating the installation of the seal and also restricting the radial movement of the seal (in a variant embodiment not shown, the groove is formed in the diaphragm). It should be noted that there are two seals (or seal pairs) 13a arranged on both sides of the diaphragm 9 1-2 or 13b 1-2 . One seal pair 13a 1-2 thus contacts the first body 3a, while the other seal pair 13b 1-2 contacts the second body 3b. Thus, it is possible to define the volume between the seals bounded by the diaphragm 9, the seal pair 13a 1-2 or 13b 1-2 and one of the bodies 3a or 3b.

[0059] In addition, one of the bodies 3a has a member 17 for tensioning the diaphragm 9 (projecting from the surface of the body), and the member 17 abuts against the diaphragm 9 and keeps it under tension. The diaphragm 9 includes, for example, a groove or at least one shape that cooperates with the tensioning member of the body 3a. It should be noted that the member 17 can also be a part separate from the body 3a, such as a washer inserted between the body 3a and the diaphragm 9.

[0060] In addition to the channels 8a and 8b for supplying fluid to the test chambers 7a and 7b, the bodies 3a and 3b also each include fluid conduits 12a and 12b (the latter not shown in the figure) that open between the seals 13a 1-2 or 13b 1-2 respectively. The channels 8a, 8b and the conduits 12a and 12b are connected, for example, to valves (not shown), thereby allowing the management of pressure changes applied to different parts of the sensor 1.

[0061] In fact, the channels 8a and 8b precisely allow changing the pressure existing between the seals 13a 1-2 or 13b 1-2 and balancing it with the pressure existing in the test chamber 7a or 7b.

[0062] It should be noted that the channels 8a and 8b can also include secondary branches that open at the seals 13a1 and 13b2 respectively, and the secondary branches are, for example, substantially perpendicular to the channels 8a or 8b (the secondary branch 8a1 of the channel 8a of the body 3a is more clearly illustrated in Figure 3 ).

[0063] The diaphragm 9 and the bodies 3a and 3b are preferably made of materials having substantially equal coefficients of thermal expansion, such as bronze, beryllium bronze alloy and / or stainless steel...

[0064] Figure 4 Also Figure 1Schematic cross-section and enlarged representation of the electrode 11a of the sensor, but the following description (similar to the previous one) also applies to the other electrode 11b of the sensor 1.

[0065] The sensor 1 thus includes an electrical contact rod 21, which is inserted into the electrode 11a (or 11b) and passes through the body 3a (or 3b).

[0066] The rod 21 is preferably arranged on the same side of the sensor 1 in order to have a single electrical connector 10 (e.g., a card board with electrical tracks) for connecting the rod 21, and thus limit the length of the wires and / or tracks. In fact, the pressure difference between the two chambers 7a and 7b can cause a very small movement of the diaphragm 9, which is converted into a capacitance value (expressed in farads) via the electrodes 11a and 11b. Therefore, it is advantageous to have circuits that are as identical and as short as possible, especially for measurements on the order of nanofarads.

[0067] More precisely, the electrode 11a includes a through-hole 22 extending from one end face 111 to the other end face 112, and a transverse housing 23 extending from the radial face 113 of the electrode 11a to the through-hole 22 (so that the through-hole 22 and the transverse housing 23 are fluidly connected).

[0068] More precisely, as Figure 4a can be seen, the radial housing 23 has different parts. The inlet 23a of the housing 23 is beveled to guide the insertion of the rod 21 into the electrode 11a, followed by an intermediate straight part 23b, and then an intermediate beveled part 23c (acting as a physical stop), which extends to a straight end part 23d opening into the through-hole 22.

[0069] The rod 21 thus has an end 21a inserted into the housing 23, and the end 21a has a polygonal section 211a, such as a square, which is tightly fitted in the housing 23, more precisely, in the right end part 23d. It should be noted that it is advantageous for the polygonal section (thus including a section with several edges) to be tightly fitted in the cylindrical end part in order to ensure good electrical contact.

[0070] In addition, the end 21a of the rod 21 includes a crown 211b arranged upstream of the polygonal section 211a, which acts as a stop by abutting against the intermediate beveled part 23c, and in addition promotes the electrical contact between the rod 21 and the electrode 11a.

[0071] The rod 21 also includes a sleeve 21b, which surrounds a part of the rod 21 and is intended to close the through-hole 31 formed in the body 3a or 3b so that the rod 21 can be inserted into one of the electrodes 11a or 11b.

[0072] The sleeve 21b is generally made of plastic material and fastened with glue to prevent the movement of the rod 21 and also ensure the tightness of the main body 3a or 3b.

[0073] The other end 21c of the rod 21 is also fastened to the electrical connector 10.

[0074] The interface part 6 mounted on the main bodies 3a and 3b includes fluid channels connected to the channels 8a and 8b formed in the main bodies 3a and 3b and opening into the test chambers 7a and 7b. In addition, the fluid channels of the interface part include a water collector (or water retention device) arranged in the channels. However, it should be noted that the interface part 6 is an optional part that allows the sensor 1 according to the present invention to be mounted in the leak detection device, and it does not necessarily have a housing structure (orientation of the fluid channels, electrical connector, etc.) suitable for the sensor.

[0075] Therefore, when a tightness test of the parts is required, each of the test chambers is connected to the test housing via a fluid supply channel, where the parts to be tested and the reference parts are respectively arranged. The housing is exposed to a pressure change, and after a determined duration, if the part to be tested has a leak, then each of the test chambers isolated from each other will have a different pressure.

[0076] Subsequently, there is a higher pressure in one of the test chambers compared to the other, and under the influence of this pressure difference, there is a movement of the diaphragm.

[0077] The movement of the diaphragm then modifies the distance between the diaphragm and the electrodes arranged in the test chamber. Therefore, it is possible to measure the change (more precisely, the difference) in the capacitance of the capacitor formed by the electrodes and the diaphragm via the contact rod. This configuration allows the measurement of a very small movement of the diaphragm and thus the measurement of a small pressure change, which is in turn related to the leak (or the tightness level of the part being tested).

[0078] Therefore, it is important to limit the volume of the test chamber and / or the change in the volume inside the test chamber, because these volume changes can be assimilated or confused with leaks.

[0079] Therefore, the fluid pipes 12a or 12b arranged between the two seals allow the pressure between the test chambers 7a and 7b and the volume between the seals to be balanced during the pressure change applied to the part - test chamber assembly to measure the leak.

[0080] In fact, if there is only one seal to ensure the tightness of the test chamber, during a pressure change, one of the facing layers is exposed to the atmospheric pressure while the other facing layer is under a reduced pressure or overpressure with respect to the atmospheric pressure. This pressure difference experienced by the seal can cause its deformation and / or its movement over a long period of time, which will result in a modification of the volume of the test chamber (and thus a change in the pressure present in the test chamber).

[0081] Furthermore, connecting the housing for accommodating the rod to the through-hole and connecting the volume located between the electrode and the bottom wall of the body to the main volume of the test chamber allows avoiding the formation of restricted or enclosed volumes that are difficult to access. Due to their limited accessibility, these volumes can be slowly filled and / or emptied and can thus cause a change in the volume (and pressure) of the test chamber, thereby mimicking a leak in the part to be tested and distorting the leak measurement performed.

Claims

1. A differential pressure sensor (1) for a leak detection device, comprising: - At least two bodies (3a, 3b) fastened to each other, with a cavity (7) formed in the at least two bodies; - A diaphragm (9) arranged between the two bodies (3a, 3b) and separating the cavity (7) so as to define test chambers (7a, 7b) in each of the bodies (3a, 3b); - At least one electrode (11a, 11b) arranged in each of the test chambers (7a, 7b) and facing the diaphragm (9) so as to form a capacitor therewith; Wherein the sensor (1) comprises at least two seals (13a1, 13a2, 13b1, 13b2) arranged between each of the bodies (3a, 3b) and the diaphragm (9), And wherein at least one of the electrodes (11a, 11b) has on the one hand two opposite end faces, one facing the diaphragm (9) and the other fastened to one of the bodies (3a, 3b), and on the other hand a lateral face connecting the end faces, Characterized in that, At least one of the electrodes (11a, 11b) comprises a through hole (22) whose end opens at the end face of the electrode (11a, 11b); at least one of the electrodes (11a, 11b) comprises a lateral housing (23) intended to receive an electrical contact rod (21); the through hole (22) and the lateral housing (23) are in fluid communication with each other; each of the bodies (3a, 3b) comprises at least one fluid conduit (12a, 12b) opening between the seals (13a1, 13a2, 13b1, 13b2).

2. The sensor according to claim 1, wherein At least one of the bodies (3a, 3b) is produced by die stamping.

3. The sensor according to claim 1, wherein The sensor comprises an electrical contact rod (21) in contact with the electrodes (11a, 11b).

4. The sensor according to claim 1, wherein The electrical contact rod (21) comprises an end (21a) having a polygonal shape.

5. The sensor according to claim 1, characterized in that At least one of the bodies (3a, 3b) comprises fluid channels (8a, 8b) opening into the test chambers (7a, 7b).

6. The sensor according to claim 1, wherein The sensor comprises an interface part (6) mounted on the bodies (3a, 3b) and comprising a fluid channel in which at least one water collector is arranged.

7. A leak detection device, characterized in that The leak detection device comprises the sensor according to any one of claims 1 - 6.

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