FR2726650A1 - Detector for presence of specific material, esp. water, - Google Patents

Abstract

A detector for the presence of a material comprises a casing (1), two electric connectors (3) attached to the casing, and a unit (9) sensitive to the material. The unit has a first solid form corresp. to a first electric state of the link between the connectors in the absence of the material and a second, disintegrated, form corresp. to a second electric state of this link when the medium has a value of the material above a pre-determined. value. Passage from one electric state to the other is produced by a mechanical action caused by the change of shape of the unit causing displacement of a contact (5) between the connectors (3).

Description

 The present invention relates to a presence detector of a body intended to be integrated in an electrical or electronic monitoring circuit.

 The developed device makes it possible to open a circuit or trigger a signal when the rate of the body in the surrounding environment becomes greater than a predetermined level. The detected body can be water.

 Indeed, for many devices and technical installations, the presence of water is harmful as soon as it exceeds a predetermined threshold. The presence of water can be manifested either by a high relative humidity rate of the ambient air higher than a given value, or by a condensation of water, or by a accumulation of water.

While the relative humidity of the air can be tolerable up to a predefined rate, the presence of condensation water or accumulated water is generally not tolerable.

 To measure and monitor the presence of water in the various cases mentioned above, we have used up to now measuring instruments among which are for example: hair hygrometers comprising a synthetic fiber which is measured elongation; devices comprising at least one float, for measuring the accumulated water level; or else electronic measuring instruments comprising at least one amplifier and measuring the variation of the resistance of a hybrid component. These devices and their facilities are often expensive and at the very least, quite complex.

 Given the high number of detectors that often have to be installed to meet the requirements of the regulations in force, the use of such detectors sometimes represents fairly significant costs.

 Also the object of the invention is to overcome the aforementioned drawbacks of water presence detectors. More generally, it must be used to detect the presence of any body in a similar way.

 The object of the invention is particularly to provide a device of simple structure and feasible at low cost to detect the presence of a body.

 Another object of the invention is to provide a presence detector of a body which is connected to a measuring device or control by only two connectors.

 It is another object of the invention to provide a device for measuring and controlling the body's rate in the atmosphere, which is reliable and easy to manage.

 Another objective is to be able to use the detector directly in a circuit with usual voltages, such as 220 V.

 An additional object of the invention is to obtain an indefinitely reusable device by simple reset.

 The subject of the invention is a presence detector of a body comprising a housing, two electrical pins attached to the housing and a body-sensitive element. The element has a first solid form, corresponding to a first electrical state of the connection between the pins in the absence of the body, and a second disintegrated form, corresponding to a second electrical state when the atmosphere has a higher body rate at a predetermined level. The transition from one electrical state to another occurs by a mechanical action caused by the change in shape of the element, which causes the displacement of a contact means between the pins.

 According to a preferred embodiment of the invention, the contact means is a lamella which closes the contact between the pins in one of the two forms of the element, this lamella being actuated by a mechanical system. The detector then advantageously comprises a guide-slat which guides the slat relative to the housing, keeping it in contact with the pins in one of the two forms of the element and separated from them in the other form.

 In this embodiment, the housing preferably comprises a counterbore in which the pins are placed, the counterbore comprising at least one shoulder which serves as a stop for the lamella in the two electrical states, and the guidelamelle comprises a projection resting on the lamella, so that the latter is bent when it is in contact with the pins. It is then advantageous that the detector comprises a spring, between the housing and the guide-lamella, the spring exerting on the guide-lamella a force opposite to that exerted by the element.

 According to one embodiment of the invention, the body is water. The water-sensitive element is then advantageously composed of an agglomerated mineral salt in solid form which melts in contact with water or at a predetermined degree of hygrometry. It is advisable to choose the mineral salt from the following ones presented in ascending order of the moisture content constituting the detection salt: lithium bromide, lithium chloride, potassium acetate, magnesium chloride, potassium carbonate, nitrate of potassium, potassium iodide, sodium chloride, ammonium sulfate, potassium chloride, barium chloride, potassium nitrate, potassium dichromate.

 According to a preferred embodiment of the invention, the body-sensitive element has the shape of a pellet.

 On the other hand, the detector advantageously comprises a seal between the element and the pins. Preferably, the seal can be deformed to allow mechanical action and to absorb volume differences due to temperature and pressure variations.

 The housing is usefully equipped with a lid closing, letting the body into contact with the element and to replace the latter. It is advisable that the cover has a bore allowing the element to be evacuated in its second form.

 Other features and advantages of the invention will become apparent on reading the embodiment described below with reference to the drawings.

In these drawings:
Figure 1 shows the presence detector of a body in a longitudinal section in its first electrical state.

 Figure 2 shows the detector of Figure 1 in its second electrical state.

 Figure 3 shows the detector of Figures 1 and 2 in section A-A.

 Figure 4 shows the detector of Figures 1 and 2 in half section B-B.

 Figure 5 is a top view of the detector.

 Figure 6 is a bottom view of the detector with its lid.

 Figure 7 shows the presence detector of a body equipped with means of transport in longitudinal section.

 In the embodiment shown, the detected body is water. The water presence detector comprises a housing 1 having a countersink 20 in the center. This counterbore is filled with epoxy resin for sealing the device. Two electrical pins 3 are placed in holes at the bottom of the countersink 20. The pins 3 are connected to the outside by welded son and their spacing is determined by electrical standards. A lamella 5, made of beryllium bronze, makes contact between the pins 3 and gives their connection a first conductive electrical state. This slat 5 of rectangular shape has a thickness of 0.25 mm, these features allowing easy elastic deformation.

Its width 40 of 4 mm gives it a section of 1 necessary to be able to accept a current of 16 amperes.

Two shoulders 21 on the counterbore 20 serve as abutments to the lamella 5. In addition, a fillet on each shoulder 21 increases the contact with the lamella 5 and, as a result, reduces wear over time. The pins 3 can thus easily be interposed on a 220 V power line.

 A spring 2 is placed in a cylindrical slot 25 hollowed in the upper part of the housing 1. Flats 22 made on the cylindrical portions of the housing facilitate the positioning of the parts and prevent their driving in rotation.

 The housing 1 also has a shoulder 23 in its lower part serving as a stop for a seal 6.

 Grooves 24 formed on the outside of the shoulder 23 serve as slides to a cover 7. The outer diameter of the housing 1 is about 14 mm and its walls have a thickness of 1 mm. The water presence detector also comprises a guide-blade 4, which guides the blade 5 relative to the housing 1 and keeps it in contact with the pins 3 in the presence of an element 9 in its solid form. This piece has a cylindrical pin 26 in its upper part which is positioned in the cylindrical slot 25 of the housing 1.

 Interstices 31 provided between the guide-lamella 4 and the casing 1 make it possible to avoid a possible suction effect, thanks to good air communication, so that the guide-lamella 4 can easily play a role of piston. , moving in the housing 1.

 The guide-lamella 4 is provided with a longitudinal protrusion 27 rounded bearing on the lamella 5 by a linear contact, without risk of rapid wear. The guide-blade 4 also comprises a shoulder 28 in its lower part to reduce the height of the element 9 in solid form, and a countersink 29, in this shoulder 28, to keep constant thicknesses for molding. The thickness of the central round of the guide-lamella 4 measuring 1.5 mm serves as an insulator between the electrical part containing the pins 3 and the part where there can be water containing the element 9.

A seal 6 seals between the electrical part and that which may contain water. I1 is made of flexible plastic material without moisture recovery. The shape of the seal 6 allows it a vertical deformation necessary for the rise and fall of the guide-lamella 4, thanks to the presence of a bellows portion 42.

 The seal 6 also comprises a thick portion 41 whose inside diameter is smaller than the inside diameter of the housing 1 at the base of the shoulder 23. This thick portion 41 thus serves as a stop to the guide-lamella 4 when the element 9 is under its disintegrated form. The seal 6 also serves to absorb the differences in volume due to changes in temperature and atmospheric pressure.

 A washer 8 is mounted tightly in the housing 1 and presses the seal 6 against the housing 1. It has a shoulder to make it more solid.

 The water-sensitive element 9 is composed of an agglomerated mineral salt in the form of a pellet which melts in contact with water or at a predetermined degree of hygrometry. To detect the presence of a relative humidity of 98%, the mineral salt chosen is potassium dichromate. It is advantageous that the pellet 9 further comprises a binder and a dye for visually identifying the melt of the pellet.

 The cover 7 is positioned around the shoulder 23 of the casing 1. It is held by means of three pins 47 placed in the grooves 24 of the casing 1. The three pins 47 are distributed in a rotationally periodic manner, and thus spaced at an angle equals 120 '. The same is true of the grooves 24. The angular dimension p of the studs is equal to 30, and corresponds to the angle of rotation making it possible to fix the lid 7 to the casing 1 by sliding the studs 47 in the grooves 24.

The cover 7 also comprises a countersink 43 for placing the element 9 in the form of a pellet, so that the latter is as close as possible to the outside and substantially less than 1 mm of water height.

 On the other hand, the cover 7 comprises a central bore 44 at the bottom of the counterbore so that the element 9 is in contact with the outside and to allow its output in molten form. Three openings 45 and three grooves 46 of the cover 7 let the water pass. The shape of the perforations 45 is necessary to introduce the parts of the mold which serve for the construction of the three pins 47.

 For transport, the detector is advantageously provided with a cap 10 which is placed on the lower part of the device to make it waterproof. The height of this cap shown in Figure 7 is greater than the lower part of the apparatus so that there can be no leakage through the grooves 46 of the housing 1. An O-ring 11 provides the sealing between the device and the cap 10. These parts are disassembled after installation.

 The operation of the water presence detector according to the invention is as follows: the detector being fixed near an apparatus for which the presence of water can be detrimental, the ambient air circulates in the vicinity of the presence detector. water and enters through the bore 44, the perforations 45 and the grooves 46 of the cover 7. In the absence of water, the element 9 has the solid form of a pellet, as shown schematically in Figure 1.

 The pressure exerted by the element 9 on the guidelamelle 4 then keeps the strip 5 in contact with the two electrical pins 3. The electrical state is thus conductive.

 As soon as a certain humidity level is reached, the water of the air is absorbed by the element 9 in solid form which begins to melt. The force exerted by the spring 3 on the guidelamelle 4 then pushes the latter towards the element 9.

 The lamella 5 then loses contact with the pins 3, so that the electrical state is no longer conductive.

 The lateral surfaces 21, which serve as plate stops 5, play an important role and contribute to the safety of the use of the detector. Indeed, thanks to these staves, the contact remains open in all cases of predictable malfunction, for example when breaking a room.

 On the other hand, if by the effect of a bad contact during the passage of the current, a weld occurred on one of the pins 3, the stop 21 located on its side would act as lever arm. Moreover, the presence of the stops 21 avoids the support of the strip 5 on the cylindrical pin 26 of the guidelamelle 4, which may cause a blockage of the vertical sliding of the mechanism.

 Finally, the cumulative action of the abutments 21 and the longitudinal projection 27 causes the bending of the lamella 5, this deformation leaving a tolerance on the thickness of the element 9 in its solid form.

 The lid 7 fits and dislodges easily by rotation, which allows to reset the device by renewing the element 9.

 In the embodiment described so far, the mineral salt used is potassium dichromate for the detection of a moisture content of 98% at 25 C.

Different salts can be chosen and can be used to define the detected humidity threshold. For example, the following compounds make it possible to detect at 25 C each the indicated threshold:

<tb><SEP> Salt <SEP> Humidity Rate <SEP>
<tb><SEP> Threshold <SEP> detected
<tb> Bromide <SEP> of <SEP> Lithium <SEP> 6.4%
<tb> Chloride <SEP> of <SEP> Lithium <SEP> 11.3%
<tb> Acetate <SEP> of <SEP> potassium <SEP> 22.5%
<tb> Chloride <SEP> of <SEP> Magnesium <SEP> 32.2%
<tb> Carbonate <SEP> of <SEP> Potassium <SEP> 43.2%
<tb> Nitrate <SEP> of <SEP> potassium <SEP> 52.9%
<tb> Iodide <SEP> of <SEP> potassium <SEP> 68.9%
<tb> Chloride <SEP> of <SEP> sodium <SEP> 75.3%
<tb> Ammonium <SEP><SEP> 81%
<tb> Chloride <SEP> of <SEP> potassium <SEP> 84.3%
<tb> Chloride <SEP> of <SEP> barium <SEP> 90.1%
<tb> Nitrate <SEP> of <SEP> potassium <SEP> 93.6%
<tb> Dichromate <SEP> of <SEP> potassium <SEP> 98
<Tb>
As an alternative to the application of the water presence detector described so far, the latter may be disposed at a place likely to a passage or accumulation of water.

The water of which the presence is to be signaled may be a condensed water descending along a wall on which the water detector is installed, or a quantity of water which has accumulated, by example, at the bottom of an electronic cabinet. In both cases, the flow of condensation water or the amount of water accumulated, when it has reached a height of 1 mm, penetrates inside the lid 7, soaks the element 9 and melts it. The presence of water thus cuts off the electrical circuit, corresponding to the operation described above.

 Although the device has been described for water, it is conceivable that the detector can be used for any other body. The sensitive element must then be chosen such that it disintegrates in the presence of this body.

 The detector of presence of a body is a device for multiple and unlimited use, it suffices to replace the element 9 after each operation.

 The element in solid form need not be designed as a tablet. Although this arrangement is advantageous, any other geometric shape is conceivable.

 Instead of being made of beryllium bronze, the lamella 5 may be made of stainless steel or any other suitable material.

 Although in the embodiment shown, the pins 3 are fixed to the housing 1 and the lamella 5 is movable, it is conceivable that the contact means are fixed to the housing 1 and that the pins are actuated by the mechanism.

 It is also conceivable that the conductive electrical state is caused and not impaired by the melting of the element 9. It is sufficient for this reason that the lamella-guide 4 causes displacement of the lamella 5 towards the pins 3, in case of melting of element 9.

 Although the use of springs 3 seems particularly judicious, it is possible to replace them by any other means exerting a force opposite to that exerted by the element 9 on the guide-lamella 4. In particular, it is conceivable to use the action of gravity.

 The length of the pins can be increased so that they come out of the device to leave the free mounting to the user, who may, for example, use a fixing on printed circuit.

 Although the device (24, 47) for holding the cover 7 to the housing 1 described above is simple and practical to use, any other holding means is conceivable. In particular, the number of pins may be greater than three and therefore less than 120 °, and the angle p differ from 30. The number of perforations 45 and grooves 46 of the cover 7 may also be greater than 3.

 The reference signs inserted after the technical features mentioned in the claims, are intended only to facilitate the understanding of the latter, and in no way limit the scope.

Claims (13)

 1. A presence detector of a body comprising a housing (1), two electrical pins (3) fixed to said housing, and a member (9) responsive to said body, characterized in that said element has a first solid shape corresponding to a first electrical state of the link between the pins in the absence of the body, and a second disaggregated form corresponding to a second electrical state of said link when the environment has a rate of said body greater than a predetermined level, the passage of a electrical state to the other occurring by a mechanical action caused by the change of shape of the element causing the displacement of a contact means (5) between said pins (3).  2. Detector according to claim 1, characterized in that said contact means is a strip (5) which closes the contact between said pins in one of the two forms of said element, said strip being actuated by a mechanical system.  3. Detector according to claim 2, characterized in that it comprises a guide strip (4) guiding said strip (5) relative to said housing (1), which maintains it in contact with said pins (3) in one of two forms of said element and separated from them in the other form.  4. Detector according to claim 3, characterized in that said housing comprises a countersink (20) in which are placed the pins, said counterbore comprising at least one shoulder (21) which serves as a stop to said blade (5) in both electrical states, and in that said guide strip (4) has a projection (27) bearing on the strip, so that the latter is bent when it is in contact with the pins.  5. Detector according to any one of claims 3 to 4, characterized in that it comprises a spring (2) between said housing (1) and said guide strip (4), said spring exerting on the guide strip (4). a force opposite to that exerted by said element (9).  6. Detector according to any one of the preceding claims, characterized in that the body is water.  7. Detector according to claim 6, characterized in that said water-sensitive element is composed of an agglomerated mineral salt in solid form which melts in contact with water or at a predetermined degree of hygrometry.  8. Detector according to claim 7, characterized in that the inorganic salt is selected from lithium bromide, lithium chloride, potassium acetate, magnesium chloride, potassium carbonate, potassium nitrate potassium iodide, sodium chloride, ammonium sulfate, potassium chloride, barium chloride, potassium nitrate and potassium dichromate.  9. Detector according to any one of the preceding claims, characterized in that the element sensitive to said body has the shape of a pellet (9).  10. Detector according to any one of the preceding claims, characterized in that it comprises a seal (6) between said element (9) and said pins (3).  11. Detector according to claim 10, characterized in that said seal (6) can deform to allow said mechanical action and to absorb the differences in volumes due to temperature and pressure variations.  12. Detector according to any one of the preceding claims, characterized in that the housing is equipped with a cover (7), closing the housing, allowing said body to come into contact with said element and to replace said element.  13. Detector according to claim 12, characterized in that said cover (7) has a bore (44) for the evacuation of the element (9) in its second form.