GB2083631A - Filter arrangement for diffusion gas composition measurement head - Google Patents

Abstract

A diffusion measurement head 1, for measuring the concentration in air of combustible gases and/or vapours, houses active and inactive gas detector elements having a sintered plate 4 between gas detector element space 2 and the surrounding atmosphere. A filter cap 6, comprising a replaceable filter chamber 7, is arranged on the diffusion measurement head 1, and retaining elements are located within the filter cap 6 at intervals, so that the filter chamber 7 can be plugged into the filter cap 6 and also for threading the latter over the diffusion measurement head 1. The retaining elements are elastic gastight seals. The filter chamber 7 may be constructed as a cartridge in which the filter materials 8 are secured by sieves covering the top and bottom ends thereof. <IMAGE>

Description

SPECIFICATION Diffusion measurement heads for gas metering appliances The present invention relates to diffusion measurement heads for gas metering appliances for measuring the concentration in air of combustible gases and/or yapours, said head housing an active and an inactive gas detector element and having a sintered plate between the gas detector element space and the surrounding atmosphere.

In diffusion measurement heads of this kind, it is known that the sintered plate of the diffusion measurement head may be covered externally by a charcoal filter to protect the gas detector elements against siliceous compounds which are contained in the gas concentration which is to be examined. The sensitivity of indication is impaired by these siliceous compounds.

It has now been determined in the case of other mensuration technology problems remaining to be resolved, that the mensuration signal of the substance which is to be detected is falsified by other disturbing components, in such manner that a precise determination of concentration is thus rendered impossible in practice, and also it is not possible to include means for ensuring safety. These troublesome components should be considered as catalyst contaminants and may, for example, be present as plumbic substances.

It is an object of the invention to provide a diffusion measurement head which does not include such troublesome components whilst measuring particular substances, so that unequivocal mensuration signals are available.

Accordingly, the invention consists in a diffusion measurement head for a gas metering appliance for measuring the concentration in air of combustible gases and/orvapours, said head housing an active and an inactive gas detector element having a sintered plate between a gas detector element space and the surrounding atmosphere comprises, wherein a filter cap comprising a replaceable filter chamber is insertibly arranged on the diffusion measurement head, retaining elements are locatable within the filter cap at appropriately specified intervals, for plugging the filter chamber into the filter cap on the one hand, and for threading the filter cap over the diffusion measurement head on the other hand, said retaining elements being constructed as gastight seals.

The filter chamber may be constructed as a cartridge in which the filter materials are secured by sleeves covering the ends of the cartridge, and the retaining elements may be constructed as elastic rings.

The invention also consists in a gas metering appliance including such a diffusion measurement head.

The advantages obtained by means of the invention consist, in particular, in that the diffusion measurement head provided with the filter cap referred to enables measurement gas preparation to be carried out even in the case of gas metering appliances which operate solely in accordance with the diffusion measurement principle without a foreconnected or post-connected gas conveying pump.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which show one embodiment thereof by way of example and in which Figure 1 shows a diffusion measurement head with the filter cap installed therein, and Figure 2 shows an enlarged illustration of the filter cap itself.

Referring now to the drawings, as will be seen in Figure 1, a diffusion measurement head 1 for a gas metering appliance which latter is not illustrated, comprises a space 2 divided by a web 3 and containing the gas detector elements, and which is covered externally by a sintered metal plate 4. A charcoal filter 5 may optionally be arranged over the plate 4. A filter cap 6 is insertibly arranged on the measuring head 1 for elimination of troublesome components upon measuring particular substances in accordance with the diffusion measurement principle. A replaceable cartridge-like filter chamber 7 in which appropriate filter materials 8 are placed either as loose material or as gas-permeable plates, is inserted in the filter cap.The filter cap itself has its external outlines appropriately formed so that a calibrating cap 9 may be placed thereon for the required calibration of the diffusion measurement head with test gas.

As will be apparent from Figure 2, O-rings 10 are located within the filter cap 6 at appropriate intervals, to act as retaining elements for insertion of the filter chamber 7 into the filter cap 6 on the one hand as well as for threading the filter cap 6 on to the diffusion measurement head 1, and on the other hand as gastight seals for the assembled components 1, 6 and 7. The filter material 8 is retained in the filter chamber 7 by sleeves 11 covering the top and bottom ends of the filter chamber. The O-rings 10 are preferably elastic.

1. A diffusion measurement head for a gas metering appliance for measuring the concentration in air of combustible gases and/or vapours, said head housing an active and an inactive gas detector element having a sintered plate between a gas detector element space and the surrounding atmosphere comprises, wherein a filter cap comprising a replaceable filter chamber is insertibly arranged on the diffusion measurement head, retaining elements are locatable within the filter cap at appropriately specified intervals, for plugging the filter chamber into the filter cap on the one hand, and for threading the filter cap over the diffusion measurement head on the other hand, said retaining elements being constructed as gastight seals.

2. A measurement head as claimed in Claim 1, wherein the filter chamber is constructed as a cartridge in which the filter materials are secured by sieves covering the ends of the cartridge.

3. A measurement head as claimed in Claim 1, wherein the retaining elements are constructed as

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Diffusion measurement heads for gas metering appliances The present invention relates to diffusion measurement heads for gas metering appliances for measuring the concentration in air of combustible gases and/or yapours, said head housing an active and an inactive gas detector element and having a sintered plate between the gas detector element space and the surrounding atmosphere. In diffusion measurement heads of this kind, it is known that the sintered plate of the diffusion measurement head may be covered externally by a charcoal filter to protect the gas detector elements against siliceous compounds which are contained in the gas concentration which is to be examined. The sensitivity of indication is impaired by these siliceous compounds. It has now been determined in the case of other mensuration technology problems remaining to be resolved, that the mensuration signal of the substance which is to be detected is falsified by other disturbing components, in such manner that a precise determination of concentration is thus rendered impossible in practice, and also it is not possible to include means for ensuring safety. These troublesome components should be considered as catalyst contaminants and may, for example, be present as plumbic substances. It is an object of the invention to provide a diffusion measurement head which does not include such troublesome components whilst measuring particular substances, so that unequivocal mensuration signals are available. Accordingly, the invention consists in a diffusion measurement head for a gas metering appliance for measuring the concentration in air of combustible gases and/orvapours, said head housing an active and an inactive gas detector element having a sintered plate between a gas detector element space and the surrounding atmosphere comprises, wherein a filter cap comprising a replaceable filter chamber is insertibly arranged on the diffusion measurement head, retaining elements are locatable within the filter cap at appropriately specified intervals, for plugging the filter chamber into the filter cap on the one hand, and for threading the filter cap over the diffusion measurement head on the other hand, said retaining elements being constructed as gastight seals. The filter chamber may be constructed as a cartridge in which the filter materials are secured by sleeves covering the ends of the cartridge, and the retaining elements may be constructed as elastic rings. The invention also consists in a gas metering appliance including such a diffusion measurement head. The advantages obtained by means of the invention consist, in particular, in that the diffusion measurement head provided with the filter cap referred to enables measurement gas preparation to be carried out even in the case of gas metering appliances which operate solely in accordance with the diffusion measurement principle without a foreconnected or post-connected gas conveying pump. In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which show one embodiment thereof by way of example and in which Figure 1 shows a diffusion measurement head with the filter cap installed therein, and Figure 2 shows an enlarged illustration of the filter cap itself. Referring now to the drawings, as will be seen in Figure 1, a diffusion measurement head 1 for a gas metering appliance which latter is not illustrated, comprises a space 2 divided by a web 3 and containing the gas detector elements, and which is covered externally by a sintered metal plate 4. A charcoal filter 5 may optionally be arranged over the plate 4. A filter cap 6 is insertibly arranged on the measuring head 1 for elimination of troublesome components upon measuring particular substances in accordance with the diffusion measurement principle. A replaceable cartridge-like filter chamber 7 in which appropriate filter materials 8 are placed either as loose material or as gas-permeable plates, is inserted in the filter cap.The filter cap itself has its external outlines appropriately formed so that a calibrating cap 9 may be placed thereon for the required calibration of the diffusion measurement head with test gas. As will be apparent from Figure 2, O-rings 10 are located within the filter cap 6 at appropriate intervals, to act as retaining elements for insertion of the filter chamber 7 into the filter cap 6 on the one hand as well as for threading the filter cap 6 on to the diffusion measurement head 1, and on the other hand as gastight seals for the assembled components 1, 6 and 7. The filter material 8 is retained in the filter chamber 7 by sleeves 11 covering the top and bottom ends of the filter chamber. The O-rings 10 are preferably elastic. CLAIMS

1. A diffusion measurement head for a gas metering appliance for measuring the concentration in air of combustible gases and/or vapours, said head housing an active and an inactive gas detector element having a sintered plate between a gas detector element space and the surrounding atmosphere comprises, wherein a filter cap comprising a replaceable filter chamber is insertibly arranged on the diffusion measurement head, retaining elements are locatable within the filter cap at appropriately specified intervals, for plugging the filter chamber into the filter cap on the one hand, and for threading the filter cap over the diffusion measurement head on the other hand, said retaining elements being constructed as gastight seals.

2. A measurement head as claimed in Claim 1, wherein the filter chamber is constructed as a cartridge in which the filter materials are secured by sieves covering the ends of the cartridge.

3. A measurement head as claimed in Claim 1, wherein the retaining elements are constructed as elastic rings.

4. A diffusion measurement head substantially as hereinbefore described with reference to the accompanying drawings.

5. A gas metering appliance including a diffusion measurement head as claimed in any of the preceding Claims.