Note: Descriptions are shown in the official language in which they were submitted.
CA 02332288 2000-11-14
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.
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
opposite ends 28a and 28b open out into the top face 22
of the meter.
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The channel 28 has three portions constituting the
U-shape: 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
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 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
as to guarantee that it is gastight during operation of
the meter.
The present invention seeks to simplify the method
of manufacturing that type of gas meter.
The present invention thus provides 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 being
characterized in that it consists in unmolding all of the
communication channels in a single operation.
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Thus, where the prior art required two distinct
operations for unmolding, the method of the invention
requires only one.
Furthermore, given that gas meters are products that
are manufactured in very large quantities, any
simplification to the method of manufacture gives rise to
a reduction in manufacturing cost.
More precisely, the method of the invention provides
for unmolding all of the communication channels of the
meter in a single direction.
In an embodiment of the invention, all of the
communication channels of the meter open out into a
single face of the central body, and the unmolding
direction is perpendicular to said face of the central
body.
As a result, it is not necessary as in the prior art
to provide an additional operation of fixing an
additional sealing piece (plug) on a portion of one of
the communication channels that has been formed by
unmolding in a direction other than the direction in
which all the other channels were unmolded.
The method of manufacture is thus simplified, and
its economic cost is likewise reduced.
The present invention also provides a gas meter
obtained by the above-described 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, the meter
being characterized in that each channel is visible in
full from said face of the central body.
The gas meter manufactured in this way is simpler
and more reliable than the prior art gas meter since it
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avoids any risk of gas leakage being caused by faulty
fixing of the sealing plug.
More precisely, the distribution cover comprises
firstly four ports each in the form of a circular quarter
sector and separated from one another by radial sealing
strips, each of the ports communicating with the
uncovered open end of a respective one of the four
communication channels connected to the measurement
chambers, and secondly a circular ring co-operating with
the radial trips to define four orifices all
communicating with the uncovered open end of a fifth
channel which is for evacuating the gas.
Furthermore, the cover further includes a piece
which extends on either side of one of the radial strips
in a portion thereof which is situated between two ports
so as to obstruct a portion of the uncovered open end of
the fifth channel so as to provide sealing between said
fifth channel and the communication channels whose open
ends communicate with said two ports.
Preferably, the fifth communication channel is
disposed between two adjacent communication channels and
one of its ends is disposed in a central portion around
which the other four communication channels are
distributed.
Other characteristics and advantages of the
invention appear from the following description given by
way of non-limiting 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;
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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;
5 ~ Figure 5 is a perspective view of the gas meter of
the invention showing the communication channels for
feeding and evacuating gas;
Figure 6 is a perspective view of the gas meter of
the invention showing a diaphragm and a cover fitted to
the central body of the meter;
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.
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 6). 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
chambers are situated on either side of each deformable
diaphragm and the volumes of the chambers vary depending
on the positions of the diaphragms.
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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 40.
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 40.
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 60
over the opening.
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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 90°.
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
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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 G4c in that
portion thereof which is placed between the two ports 68
and 70.
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 70.
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 above-
cited document.
Nevertheless, it should be mentioned that the gas
meter has transmission means for connecting the
distributor dynamically to the deformable diaphragms.
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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 (e. g. 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
by the letter D, which direction is perpendicular to the
face 58 of the central body 40 (Figure 10).
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.
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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 40.
Figure 11 is a highly diagrammatic section view in a
plane perpendicular to the face 58 of the central block
40 and containing the support 80, showing the mold piece
102 which is withdrawn from the fifth communication
channel 56.
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.
