GB1563197A - Detector for fluid material - Google Patents

Description

(54) DETECTOR FOR FLUID MATERIAL (71) I, JOSE ALVAREZ VALEUZUELA, of 72, Fulbourne Road, London, E17 4E6, of Chilean nationality, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to detectors for fluid materials which are to some extent electrically conducting, e.g. rain.

In accordance with the invention a detector for fluid materials comprises an array of two groups of electrically conducting thin plates (as hereinafter defined) assembled face to face and having an edge exposed for contact with a fluid material to be detected, the plates of one group being insulated from and inter-leaved between the plates of the other group; and means for detecting electrical conductance between the two groups of plates. By thin plate is meant a foil or other plate substantially less than a quarter of an inch thick. When a detectable fluid material contacts plates of both groups increased electrical conductance is detectable therebetween, i.e. the impedance is reduced.

Means sensitive to the electrical impedance between the two groups of plates may be provided by a solenoid or relay connected in a series circuit with the two groups of plates. Connection of the series circuit across an electrical supply, e.g. a battery, allows the solenoid or relay to respond to electrical conduction between the two groups of plates produced by the reduction in impedance when a detectable fluid material contacts plates of both groups. The solenoid or relay may be arranged to operate an indicator or an alarm.

A preferred embodiment of the invention is a rain detector. However the invention may be embodied in other forms, for example water or river level detectors.

The preferred embodiment of the invention, given by way of example, will now be described with reference to the accompanying drawings, in which: Figure 1 is an exploded schematic plan view of a rain detector embodying the invention; Figure 2 is a schematic section also exploded, of another detector embodying the invention; Figure 3 shows a detail of the construction of another rain detector embodying the invention; Figures 4 and 5 show, in plan and end elevation respectively, one of the components of the rain detector of Figure 3; Figure 6 shows, schematically, a front view of apparatus for manufacturing the component of Figures 4 and 5; and Figure 7 is a section on arrows VII--VII of Figure 6.

The rain detector illustrated in the Figure 1 has two groups of electrically conducting thin plates 2 and 4. The plates 2 in one group are connected together as by lead 6. The plates 4 in the other group are connected as by lead 8.

The plates 2 and 4 are arranged in an array with the plates 2 interleaved between the plates 4.

Plastics insulators 10 are disposed between adjacent plates 2 and 4 to insulate one group of plates from the other.

Although for clarity Figure 1 is an exploded view, in practice the insulators and plates are assembled closely together to be impervious and may for example, be stuck together by adhesive to provide a unitary assembly.

Figure 2 shows an arrangement in which the plates 2 of one group have insulators 10' in the form of self-adhesive insulating material, stuck to both of their two opposite faces. Figure 2 shows a rain drop 12 having settled on the rain detector. Edges 14 of the plates are exposed to be contacted by the drop 12. The electrical conductivity between the group of plates 2 and the group of plates 4 is normally very low. When a drop of rain bridges a number of plates as illustrated in Figure 2, the natural conductivity of the rain increases the conductivitv substantially.

Means 18 are provided to detect electrical conductance between the group of plates 2 and the group of plates 4. The means 18 are connected in a series circuit with the conductor array by leads 6 and 8 and an electrical supply such as battery 20.

The conductance detecting means 18 comprises a relay having a winding 22 in the series circuit. Normally, the conductance between the group 2 and 4 of the plates being very low, the relay is not operated.

However when the conductance is raised by the presence of a rain drop 12, (Figure 2) there is sufficient current allowed in the series circuit to operate the relay which closes a normally-open contact 24 so providing current from battery 20 to operate a utilisation circuit for example an alarm such as a bell or an indicator. Alternatively, the utilisation circuit may automatically act responsive to the rain detection for example to operate windscreen wipers or to close a drying room roof or greenhouse doors. The utilisation circuit may be powered by its own mains or battery supply (not shown) separate from the battery 20. The relay has a further self latching contact 26 arranged to latch the relay in its operating condition until it is switched off, even if the rain drop disappears.

In one experimental arrangement conductor plates 2 and 4 in the form of aluminium foil by plastics insulators were stacked about 12 in 1 inch.

The battery 20 provided 18 volts and the relay had a 300 ohm winding. The arrangement was sensitive to one drop of rain. In order to provide a substantial chance of catching a rain drop the conductor array is thought to be required about 4 inches square. Alternatively a funnel having a mouth of those approximate dimensions could be provided. In another arrangement a reed-relay was found sensitive to the conductance produced across the array between the plates 2 and the plates 4. by one drop of rain when the battery 20 produced 6 volts.

In order to prevent the rain detector becoming so wet during rain fall as to be unable to respond to subsequent rain fall for a prolonged period until dried off, the utilisation circuit may include means, for example a solenoid, for moving an impervious cover (not shown) over the detector particularly over the conductor array. The solenoid may be interlinked to a switch in the self latching circuit of the relay. The solenoid and the switch are manually reset when it has stopped raining, withdrawing the cover and enabling the detector to respond to further rainfall.

Additionally, to prevent the rain detector becoming saturated, the planar array is impervious to rain. This may be achieved by, use of adhesive as already mentioned or, for example. by bolting the assembly tightly together. Such construction is illustrated in Figure 2. As mentioned above the group of plates 2 has an insulative film 10' stuck to its two faces. Aligned holes 28 and 30 are provided through all the plates 2 and 4 respectively. The holes (holes 30) in one group of plates (plates 4) are smaller than the other holes. A bolt 32 passes through the aligned holes 28 and 30 and the plates are bolted up tight by the bolt 32 and a nut 34.

The bolt 32 is located by the smaller of the holes 30 thus remaining clear of the edges of the larger holes 30. This ensures that the plates 2 and 4 are not shorted together bv the bolt 32. Two or more bolts 32 are preferably spaced along the length of the plates.

A part assembled arrangement for receiving three bolts 32 is illustrated in perspective in Figure 3. The group of plates 2 and the group of plates 4 are each formed integrally in a single sheet 36 of conductive material in this case aluminium, see Figure 4. The plates 2 or 4 are joined along one edge of the sheet and, in the sheet as illustrated in Figure 4, are separated by slots 40 which extend to the opposite edge 42 of the sheet.

Each of the plates is formed with three spaced holes 28 or 30. The edge 38 of each sheet is bound with a flexible binding which may comprise an inner conductive layer 44 and an outer plastics layer 46 as illustrated in Figure 4. The edge 38 is folded between adjacent plates 2 or 4, successive folds being in alternate directions as illustrated in Figure 3. The binding helps to prevent fracture at the fold and. in the conductive layer 44, to maintain electrical connection between the plates even if the sheet 36 does fracture at the fold.

The part folded sheets are arranged as illustrated in Figure 3 with their plates 2 and 4 interleaved. The arrangement is then pushed up together as indicated by arrow 'A' to complete the folding and to bring the plates into the face to face relationship illustrated in Figure 2. Rigid end plates 48 are then added and the assembly is bolted up tight.

A sheet in the form illustrated in Figure 4, can conveniently be prepared by means of the apparatus of Figures 6 and 7. The apparatus has a bed 50 in which are formed a line of three die holes 52 (only one being visible in the drawings) and a slot 54. A guide plate 56 is positioned over the bed 50 and contains holes 57 each to guide a ram 58. Each ram cooperates with one of the die holes 52 to punch a hole in a sheet 36 placed on the bed 50. To this end a lever arrangement 60, pivoted at 62, is provided to enable the rams 58 to be operated simultaneously. The rams 58 are returned by springs 64.

For cutting the slots 40 in a sheet 36, a double blade 66 is mounted pivotally at 68 for movement into the slot 54 in the bed 50.

As seen in section in Figure 7, the double blade 66 has two component blades 70. The blades 70 are somewhat flexible and are joined together as by rivets 72 but not entirely rigidly. A cutting edge 74 is provided on each blade, the cutting edges being bevelled slightly and oppositely so as to provide a shallow V-shaped groove as between the two blades 70. The slot 54 is a width such that its edges 76 cooperate with the cutting edges 74 of the blades 70. During cutting, the bevel forces the blades 70 away from each other tightly against the cooperating edge 76 so as to provide a clean out.

In order to cut the pattern of alternating holes and slots as illustrated in Figure 4, two sheets 36 overlapping as illustrated in Figure 6 are fed between the guide plate 56 and the bed 50. One of the two sheets is conveniently already coated on both faces with insulative material. The double blade 66 is preferably positioned in, and extending from the slot 54 to facilitate positioning of the sheets 36 which are fed through until they abut the blade 65. The lever arrangement 60 is then operated driving the ram 58 to punch a line of holes 28 in the sheets 36 in cooperation with the die holes 52.

The double blade 62 is raised and the sheets are fed through until the holes 28 each locate on a respective stud 78 provided on the base plate 50. The double blade 66 is then operated to cut a slot 40 in each sheet.

The blade 66 has two notches 80 suitably positioned to leave the edge 38 of each sheet 36 uncut. The lever arrangement is then operated to punch another line of holes, the sheets are fed forward until the holes locate on the studs 78 and the process is repeated.

The holes in one or other of the two sheets can then be enlarged to prevent shorting by bolts 32 after assembly.

The detector may be used to detect the presence of other fluid materials besides rain. For example water could be detected at a dangerous level in rivers or in mines.

Further the fluid might be gaseous or a flowable solid such as a powder.

WHAT I CLAIM IS: 1. A detector for fluid materials comprising: an imperious array of two groups of electrically conducting thin plates as hereinbefore defined assembled face to face and having an edge exposed for contact with a fluid material to be detected, the plates of one group being insulated from and interleaved between the plates of the other group; and means for detecting electrical conductance between the two groups of plates.

2. A detector as claimed in claim 1, wherein the assembly of plates is bolted together.

3. A detector as claimed in claim 1 or 2, wherein each group of plates is formed integrally in a single sheet of conductive material and joined to each other along an edge of the sheet, the sheet being folded at that edge between adjacent plates, successive folds being in alternate directions.

4. A detector as claimed in claim 3, wherein the insulation is provided by insulative coating on one or both of the sheets.

5. A detector as claimed in claim 4, wherein the insulative coating is self adhesive insulative film.

6. A detector as claimed in any preceding claim, including an impervious cover for the array of plates.

7. A detector as claimed in claim 6, including means for closing the cover over the array of plates responsive to detection of a predetermined electrical conductance between the groups of plates.

8. A detector as claimed in any preceding claim, including an alarm responsive to detection of a predetermined electrical conductance between the groups of plates.

9. A detector for fluid materials substantially as hereinbefore described with reference to Figure 1 or 2 or Figures 3, 4 and 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. to enable the rams 58 to be operated simultaneously. The rams 58 are returned by springs 64. For cutting the slots 40 in a sheet 36, a double blade 66 is mounted pivotally at 68 for movement into the slot 54 in the bed 50. As seen in section in Figure 7, the double blade 66 has two component blades 70. The blades 70 are somewhat flexible and are joined together as by rivets 72 but not entirely rigidly. A cutting edge 74 is provided on each blade, the cutting edges being bevelled slightly and oppositely so as to provide a shallow V-shaped groove as between the two blades 70. The slot 54 is a width such that its edges 76 cooperate with the cutting edges 74 of the blades 70. During cutting, the bevel forces the blades 70 away from each other tightly against the cooperating edge 76 so as to provide a clean out. In order to cut the pattern of alternating holes and slots as illustrated in Figure 4, two sheets 36 overlapping as illustrated in Figure 6 are fed between the guide plate 56 and the bed 50. One of the two sheets is conveniently already coated on both faces with insulative material. The double blade 66 is preferably positioned in, and extending from the slot 54 to facilitate positioning of the sheets 36 which are fed through until they abut the blade 65. The lever arrangement 60 is then operated driving the ram 58 to punch a line of holes 28 in the sheets 36 in cooperation with the die holes 52. The double blade 62 is raised and the sheets are fed through until the holes 28 each locate on a respective stud 78 provided on the base plate 50. The double blade 66 is then operated to cut a slot 40 in each sheet. The blade 66 has two notches 80 suitably positioned to leave the edge 38 of each sheet 36 uncut. The lever arrangement is then operated to punch another line of holes, the sheets are fed forward until the holes locate on the studs 78 and the process is repeated. The holes in one or other of the two sheets can then be enlarged to prevent shorting by bolts 32 after assembly. The detector may be used to detect the presence of other fluid materials besides rain. For example water could be detected at a dangerous level in rivers or in mines. Further the fluid might be gaseous or a flowable solid such as a powder. WHAT I CLAIM IS:

1. A detector for fluid materials comprising: an imperious array of two groups of electrically conducting thin plates as hereinbefore defined assembled face to face and having an edge exposed for contact with a fluid material to be detected, the plates of one group being insulated from and interleaved between the plates of the other group; and means for detecting electrical conductance between the two groups of plates.

2. A detector as claimed in claim 1, wherein the assembly of plates is bolted together.

3. A detector as claimed in claim 1 or 2, wherein each group of plates is formed integrally in a single sheet of conductive material and joined to each other along an edge of the sheet, the sheet being folded at that edge between adjacent plates, successive folds being in alternate directions.

4. A detector as claimed in claim 3, wherein the insulation is provided by insulative coating on one or both of the sheets.

5. A detector as claimed in claim 4, wherein the insulative coating is self adhesive insulative film.

6. A detector as claimed in any preceding claim, including an impervious cover for the array of plates.

7. A detector as claimed in claim 6, including means for closing the cover over the array of plates responsive to detection of a predetermined electrical conductance between the groups of plates.

8. A detector as claimed in any preceding claim, including an alarm responsive to detection of a predetermined electrical conductance between the groups of plates.

9. A detector for fluid materials substantially as hereinbefore described with reference to Figure 1 or 2 or Figures 3, 4 and 5 of the accompanying drawings.