GB2047901A

GB2047901A - Electric Liquid Leakage Sensor

Info

Publication number: GB2047901A
Application number: GB8011262A
Authority: GB
Original assignee: Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Current assignee: Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Priority date: 1979-04-05
Filing date: 1980-04-03
Publication date: 1980-12-03
Also published as: IT8020414A0; DE2913813A1; IT1129700B; FR2453402A1

Abstract

The specification concerns a leakage sensor for an electronic liquid leak detector apparatus. The sensor comprises two electrodes 20, 28 respectively which are bridgable by leakage liquid, one of the electrodes 20 being an inverted pan or dish shaped member and the other electrode 28 being an extension of the central terminal 27 of a coaxial connector socket 24 secured in the base of the member 20. The extension 28 terminates slightly short of the plane containing the periphery 30 of the open end of the member 20. The member 20 has a substantially greater diameter than the socket 24 and is relatively massive compared to the latter, thus providing stability and strength in use. <IMAGE>

Description

SPECIFICATION Leakage Sensor for an Electronic Liquid Leak Detector Apparatus The present invention relates to a leakage sensor for an electronic liquid leak detector apparatus and having two electrodes which are bridgable by leakage liquid.

In the use of water-cooled scientific apparatus, vacuum systems and the like, as well as domestic appliances such as dish washer and washing machines the occurrence of a leak which is not quickly detected could result in considerable flood damage. This applies particularly to systems which must be operated without supervision, for example during the night. It is clear that similar problems arise in dealing with liquids other than water.

Electronic leakage detection apparatus is already known which exercises a switching function upon a change of electrical resistance between two electrodes; see for example "Guidebook of Electronic Circuits", published by McGraw-Hill Book Company, New York, 1974, chapter 56, pages 402 to 404.

Nevertheless, a problem to which a satisfactory solution has not been found is the design of the actual leakage sensor, that is to say the part of the apparatus containing the electrodes which are bridged by the leakage liquid and which is to be arranged at the position to be monitored for leaks.

The basic purpose of the present invention is to provide a leakage sensor which is particularly simple in construction, reliable in operation and convenient to manipulate.

According to the present invention there is provide a leakage sensor for an electronic liquid leak detector apparatus and having two electrodes which are bridgable by leakage liquid, wherein one of the two electrodes comprises a pan or dish shaped member and the other electrode comprises an extension of the central terminal of a coaxial connector socket, which extension terminates slightly short of a plane containing the periphery of the opening of the pan or dish shaped member.

The leakage sensor according to the invention can be manufactured very economically as a simple component produced by machine turning or pressing and a commercially available coaxial cable socket. The leakage sensor only requires to be set down upon the surface to be monitored, for example the floor, and remain securely at the required location in consequence of the advantageous design of the pan or dish shaped member as a relatively heavy component.

Moreover the functioning of the device is less likely to be impaired in the event of the leakage sensor suffering an inadvertent impact causing its displacement.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 shows a leak detection apparatus with a leakage sensor in accordance with one embodiment of the invention, Fig. 2 shows the individual components of a leakage sensor in accordance with a second embodiment of the invention, and Fig. 3 shows the assembled leakage sensor comprising the components of Fig. 2.

The leak detection apparatus shown in Fig. 1 comprises electronic equipment 10, a leakage sensor 12 according to one embodiment of the invention, and a connecting cable 14.

The equipment 10 is connectable to an alternating current supply as shown, and in the example shown includes a socket 1 6 for connecting thereto an apparatus which is to be switched on or switched off upon a leak being detected. The equipment 10 may include indicating lamps for the normal and alarm conditions and may include a conventional interlocking circuit which maintains the connected apparatus in its switched on or switched off condition even after the liquid which has caused the response of the device has flowed away. For the purpose of resetting this circuit a resetting button may be provided. The equipment 10 can be designed in a known manner and, since it forms no part of the present invention, needs no further detailed description herein.

The equipment 10 has a connector socket 18 by which it can be connected by the coaxial cable 14 to the leakage sensor 12. The connector socket 1 8 and the cooperating plug of the connecting cable 14 are preferably in the form of a commerically available coaxial cable plug and -socket connector, in particular a BNC bayonet cap connector.

The leakage sensor 12 comprises an inverted pan or dish shaped member 20 as one electrode, preferably a machine turned part of, for example, stainless steel, copper or other suitable electrically conducting material. The base of the pan shaped member 20 has a central hole 22 into which is fitted a coaxial cable connector socket 24 which is secured to the base by means of screws 26. The outer electrode of the socket 24 is thus electrically connected to the member 20.

The member 20 has a substantially greater diameter than the socket 24 and is relatively massive compared to the latter.

The connector socket 24 may advantageously be a BNC bayonet cap socket as shown in the drawing. The connector socket 24 has a central terminal 27, which is extended downwardly in the form of a wire or pin 28 of metal to form the second electrode of the sensor. The material of the pin should be relatively hard, for example spring wire, so that the pin cannot easily be permanently bent. The pin 28 terminates a short distance, for example 1 mm, from the plane which contains the peripheral edge 30 of the opening in the pan shaped member 20. The peripheral edge 30 of the pan shaped member may advantageously be provided with apertures 32, for example of semicircular shape, which permit the unimpeded entrance of liquid to the interior of the pan shaped member 20 when the latter is resting upon the surface 34 to be monitored for leaks, for example, the floor.

When in operation the connector socket 24 is connected by a suitable coaxial plug 36 of the connecting cable 14 to the equipment 10. Upon the occurrence of a leak, when liquid present upon the surface 34 flows into the pan shaped member 20 and reaches the pin 28, the electrical resistance between the pin forming one of the two measuring electrodes of the sensor and the pan shaped member 20 forming the other measuring electrode is reduced, thus causing a response in an electronic detection circuit in the equipment 10. This response may, for example, actuate an alarm, disconnect a cooling water pump, close a magnetic valve, set a bilge pump into operation or perform any other desired function.

The peripheral wall of the pan shaped member 20 may be made of magnetic material, in which case it is possible to attach the leakage sensor magnetically to the wall of a container which is to be monitored for leaks and over which leaking liquid must pass, for example as the result of an overflow.

It is possible to modify the design of the electronic detection circuit of the equipment 10 to enable it also to detect the presence of poorly conducting or practically non-conducting liquids, for example by making use of capacitance changes between the pin 28 and the pan shaped member 20. The embodiment of leakage sensor shown in Figs. 2 and 3 comprises an externally threaded BNC bayonet type equipment socket 24', a relatively massive annular metal plate 20a having an internally threaded central hole to receive the BNC bayonet type socket 24', and a short length of metal tubing 20b whose upper half is machine turned on the inside surface.The external diameter of the metal plate 20a and the internal diameter of the machined upper half of the metal tube 20b are so dimensioned that the metal plate 20a can be force fitted by pressure into the upper half of the metal tube 20b, thus forming a dish or pan shaped member 20' similar to the member 20 of Fig. 1.

The assembled leakage sensor is shown in Fig.

3. The central conductor of the BNC socket is extended by a piece of copper wire 28', for example a diameter 1.5 mm, which terminates just short of the plane containing the lower peripheral edge 30 of the metal tube 20 when the BNC socket 24' is fitted into the central hole of the metal plate 20a. As shown in Fig. 3, the upper rim of the pan shaped member 20' may be provided with a bevel 20c by machine turning or like operation after the parts 20a and 20b have been force fitted together.

The thickness of the metal plate 20a may, for example, be 10 mm and its diameter 66.5 mm.

Other corresponding dimensions may be inferred from Fig. 2. The weight of a practical example of the embodiment of leakage sensor according to Fig. 3 may be about 300 grams.

Claims

1. A leakage sensor for an electronic liquid leak detector apparatus and having two electrodes which are bridgable by leakage liquid, wherein one of the two electrodes comprises a pan or dish shaped member and the other electrode comprises an extension of the central terminal of a coaxial connnector socket, which extension terminates slightly short of a plane containing The periphery of the opening of the pan or dish shaped member.

2. A leakage sensor according to claim 1, wherein the pan or dish shaped member is a machine turned part which is relatively massive compared to the coaxial connector socket.

3. A leakage sensor according to claim 1 or 2, wherein the periphery of the opening of the pan or dish shaped member is provided with a series of spaced apertures.

4. A leakage sensor according to claim 1,2 or 3, wherein the coaxial connector socket is a BNC bayonet cap socket.

5. A leakage sensor according to any one of the foregoing claims, wherein the coaxial connector socket is secured in a central aperture in the base of the pan or dish shaped member.

6. A leakage sensor substantially as described with reference to Fig. 1 or Figs. 2 and 3 of the accompanying drawings.