AU757219B2 - Method for making a gas meter and gas meter obtained by said method - Google Patents

Description

A METHOD OF MANUFACTURING A GAS METER AND A GAS METER MANUFACTURED BY SUCH A METHOD The invention relates to a method of manufacturing a gas meter of the type comprising a plurality of deformable diaphragm measurement chambers and a central body defining a plurality of communication channels serving to feed gas from the outside of said central body into the respective measurement chambers and to evacuate the gas from the central body, said method consisting in making said central body by injection molding and then in unmolding it.

The invention also relates to a gas meter manufactured by the method.

BACKGROUND OF THE INVENTION Figures 1 to 4 shows a portion only of a known gas meter 10 which has four measurement chambers (not shown) separated in pairs by respective deformable diaphragms, and a central body 12 defining four communication channels 14, 16, 18, 20 serving to feed gas into respective ones of the measurement chambers and to evacuate it from the central body.

Via its two opposite ends, each communication channel connects a chamber to a common face 22 of said meter which is situated in the top of the meter.

In Figure 1, which is a plan view parallel to the top face of the meter, the four channels visible from above are distributed around a central portion 24.

A fifth channel 28 is provided between two adjacent channels 18 and 20 and extends radially, from one of its ends 28a which constitutes a central portion, towards its opposite end 22b which is situated at the periphery of the top face 22. This fifth channel 28 evacuates gas from the central body of the meter.

As can be seen in Figure 2 which is a section view in a plane perpendicular to that of Figure 1, the fifth channel 28 is generally U-shaped and only its two 2 opposite ends 28a and 28b open out into the top face 22 of the meter.

The channel 28 has three portions constituting the Ushape: a vertical first portion 28c extending from the end 28a coinciding with the central portion and going towards the inside of the central body 12; a horizontal second portion 28d which extends towards the periphery of the central body, and a vertical third portion 28e which connects the second portion to the opposite end.

The central body 12 of meters of that type is traditionally injection molded.

When the central body of the meter is unmolded, mold pieces 30, 32, 34 forming the fifth communication channel are unmolded in two stages, in a first direction 15 represented by arrows B in Figure 3 for the first and third portions 28c and 28e of the fifth communication channel 28, and in a second direction represented by arrow *o C for the second portion 28d of the channel.

Once unmolding has been finished, an unmolding plug 36 (Figure 4) is fixed in definitive manner to one of the ends of the second portion 28d of the fifth communication channel situated at the periphery of the central body so i as to guarantee that it is gastight during operation of the meter.

OBJECTS AND SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a method of manufacturing a gas meter of the type comprising a plurality of deformable diaphragm measurement chambers and a central body defining a plurality of communication channels serving to feed gas from the outside of said central body into the respective measurement chambers and to evacuate the gas from the central body, said method consisting in making said central body by injection molding and then in unmolding it, the method consisting in unmolding all of the communication channels in a single operation.

\\melbfiles\hoeS\Priyanka\geep\speci\39313-99 Amendmentsr.doc 20/11/02 3 According to another aspect of the invention there is provided a gas meter made by the above method, the meter being of the type comprising a plurality of deformable diaphragm chambers and a central body defining a plurality of communication channels serving to feed gas from the outside of said central body into respective measurement chambers and to evacuate the gas from said central body, all of the communication channels opening out into the same face of the central body, wherein each channel is visible in full from said face of the central body.

BRIEF DESCRIPTION OF THE DRAWINGS Characteristics and advantages of the invention S• 15 appear from the following description given by way of nonlimiting example, and made with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic plan view of the central body of a prior art gas meter; Figure 2 is a diagrammatic fragmentary section on AA of the top portion of the gas meter shown in Figure 1; Figure 3 is a diagrammatic fragmentary section analogous to that of Figure 2 and showing the various pieces of the mold required for making the fifth communication channel; Figure 4 is a diagrammatic fragmentary section analogous to that of Figure 2 and showing the fifth communication channel fitted with its unmolding plug after manufacture; Figure 5 is a perspective view of the gas meter of an example of the invention showing the communication channels for feeding and evacuating gas; Figure 6 is a perspective view of the gas meter of the example of showing a diaphragm and a cover fitted to the central body of the meter; \\melbfiles\homeS\Priyanka\Keep\speci\39313-99 PmendmenCsr.doc 20/11/02 4 Figure 7 is a perspective view of the gas meter in the same position as in Figure 5, but with the distribution cover, the plate, and the pins added thereto; Figures 8 and 9 are respectively a diagrammatic perspective view and a diagrammatic bottom view of the distributor; Figure 10 is a perspective view from above showing the various mold pieces used in forming the communication channels; and Figure 11 is a section view on a larger scale of the fifth communication channel and of the corresponding mold piece.

MORE DETAILED DESCRIPTION 15 As shown in Figures 5 and 6 and given overall reference 38, the gas meter of the invention comprises firstly a central block referenced 40 and two side covers, only one of which 42, is shown in Figure 6.

The central block 40 defines two chambers, only one of which 44, is shown in Figure 5. Each chamber is defined firstly by the central block 40 and secondly by a deformable diaphragm (diaphragm 46 in Figure When the covers are fitted to the central block 40, they co-operate with respective deformable diaphragms to form additional measurement chambers. Thus, two measurement go \\oelbbfiles\home$\Priyanka\Keep\speci\39313-99 Amendmentsr.doc 20/11/02 Page 5 has been intentionally left blank.

0 000000 0 0 0* 0* 00 00 0 0 00 0 00 00 0 0000 000000 0 000000 0 \\melb-files\home$\Priyanka\Keep\speci\39313-99 Amendmentrsr.doc 20/11/02 chambers are situated on either side of each deformable diaphragm.and the volumes of the chambers vary depending on the positions of the diaphragms.

As shown in Figure 5, the central block 40 defines in its internal structure four channels 48, 50, 52, and 54, each of which communicates with a respective measurement chamber. For example, the channel 48 communicates with the measurement chamber 44 and the channel 50 communicates with a measurement chamber (not shown in Figure 5) which is symmetrical to the measurement chamber 44 about the central block The channels 48-54 are distributed around a central portion.

The central block 40 also defines a fifth communication channel referenced 56 which enables gas to be evacuated from said central block.

The channel 58 is arranged between two adjacent channels 52 and 54 and it extends radially from one of its ends 56a which constitutes the central portion towards its opposite end 56b which is situated at the periphery of the central block All five communication channels have one end opening out in a common face 58 of the central body.

As shown in Figure 5, each channel is free of any obstacle that could mask a portion of said channel from said face 58, and it is therefore visible from said face.

As shown in Figure 7, the top face 58 of the meter receives a plane metal plate 60 which is stuck thereto to make it gastight and which obstructs the open ends of the communication channels 48 to 56.

An opening is formed through the metal plate centered on the end 56a of the fifth channel 56 which coincides with the central portion.

The diameter of the opening is greater than the diameter of the end of the fifth channel so as to leave uncovered a portion of the open end of each of the four other communication channels 48 to 54.

A substantially circular piece 62 known as a "distribution cover" is mounted on the metal plate over the opening.

The cover 62 has four ports 64, 66, 68, and 70, each in the form of a circular quarter sector and separated from one another by radial sealing strips 64a-d.

Each of the ports communicates with the uncovered open end of a respective one of the four communication channels 48 to 54.

In the central portion of the distribution cover 62, a circular ring 64e co-operates with the radial strips 64a-d to define four orifices 72, 74, 76, and 78 situated immediately over the end 56a of the fifth channel 56 that coincides with the central portion, and that communicates with each of them.

As shown in Figure 5, a cylindrical support 80 of axis perpendicular to the top face 58 of the meter is secured to the central block 40 and is disposed inside the fifth communication channel, at its end 56a.

At the center of the cover 62, a pivot 82 is mounted in the support 80 on the axis thereof in order to receive a gas distributor element 84 referred to as a "distributor", as shown in Figures 8 and 9.

The distributor 84 is mounted to rotate on the surface of the distribution cover 62 and has four circular sectors arranged so as to form an orifice 84a and a setback zone 84b which are separated by two plane zones 84c and 84d, each of which covers an angle of 900.

The distributor 84 also has a hollow central zone 84e which communicates with the hollow setback zone and which includes a bearing 84f for being engaged on the pivot 82.

The orifice 84a defined by the distributor serves to put each of the ports 64-70, and thus each of the four communication channels 48-54, successively into communication with the outside of the central body 40 so as to cause gas to penetrate into the corresponding measurement chamber.

The setback zone 84b and the central zone 84e of the distributor serve to put one of the four channels 48-54 into communication with the fifth channel 56 via the corresponding port and orifice of the distribution cover, while isolating the assembly from the outside of the central body and with the two plane zones 84c and 84d obstructing the remaining ports.

Thus, the gas present in one of the measurement chambers leaves it along the corresponding communication channel, passes through the corresponding port, passes into the setback zone 84d of the distributor and then into its central zone 84e, passes through the four orifices 72-78 of the cover, flows along the fifth communication channel 56, and escapes therefrom via an opening 86 formed through the metal plate 60 and coinciding with the opposite end 56b of said channel.

The cover 62 also has a piece 87 which extends from either side of the radial sealing strip 64c in that portion thereof which is placed between the two ports 68 and The piece 87 thus obstructs a portion of each of the open ends so as.to provide sealing between the fifth channel-and the communication channels 52 and 54 whose open ends in the face 58 communicate with the ports 68 and As is well known, rotation of the distributor controls gas admission and evacuation into and from the various measurement chambers. Gas meters having four chambers and a rotary distributor are well known per se, e.g. from American patent No. 3 161 049. There is therefore no need to describe the operation of such a meter in detail herein, i.e. to describe the relationships between the positions of the rotary distributor 64 and the positions of the diaphragms in the measurement chambers. It suffices to refer to the abovecited document.

Nevertheless, it should be mentioned that the gas meter has transmission means for connecting the distributor dynamically to the deformable diaphragms.

As shown in Figures 5 and 7, the transmission means comprise two pins 88 and 90 which pass through the central block 40 over a fraction of its height and which communicate with the measurement chambers of the meter.

In Figure 7, a portion of the pin 88 can be seen in the chamber 44. Each of these pins is connected to a deformable diaphragm, and under the effect of the displacement of said diaphragm it performs corresponding pivoting motion.

The transmission means also comprise (in manner.not shown in the figures) two sets of levers each connecting one of the pins 88, 90 to another pin which is engaged in an opening 92 formed in the distributor 84. The movement of the deformable diaphragms during admission and evacuation of gas into and from the measurement chambers is communicated by said transmission means to the distributor 84 which performs corresponding rotary motion.

The central body 40 of the gas meter is made using conventional techniques of injecting liquid aluminum, for example under pressure 1000 bars) under drive from a piston, into a metal mold constituted by a plurality of mold pieces.

After allowing sufficient time for the aluminum to solidify, the various mold pieces are withdrawn (unmolding operation) and in particular, as shown in Figure 10, the pieces 94, 96, 98, 100, and 102 are withdrawn that have served to form the communication channels 48 to 56.

The mold pieces 94-102 are withdrawn in a single operation in the direction marked by the arrow referenced 10 by the letter D, which direction is perpendicular to the face 58 of the central body 40 (Figure Such an unmolding operation is particularly simple to perform.

However, it should be observed that the pieces 94-102 could equally well be constituted by a single piece.

Each of the mold pieces 94-102 is artificially linked to the corresponding communication channel 48-56 by a line to show its location in the central block Figure 11 is a highly diagrammatic section view in a plane perpendicular to the face 58 of the central block and containing the support 80, showing the mold piece 102 which is withdrawn from the fifth communication channel 56.

S* 15 This view serves to emphasize the simplification provided by the invention compared with the prior art as shown in Figures 3 and 4 where two unmolding directions are required, and also subsequent installation of a sealing plug 36.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

For the purposes of this specification it will be clearly understood that the word "comprising" means "including but not limited to", and that the word "comprises" has a corresponding meaning.

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