Note: Descriptions are shown in the official language in which they were submitted.
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A GAS METER PROVIDED WITH IMPROVED GUIDE MEANS
The invention relates to a gas meter comprising a
plurality of deformable diaphragm measurement chambers, a
distributor element mounted to rotate about a "rotation"
axis on a distribution surface in which there are
provided a plurality of orifices each of which is
connected to a respective measurement chamber, said
distributor element enabling gas to enter and to leave
the measurement chambers in alternation during its rotary
movement, and means for guiding said distributor element
in rotation.
Such gas meters comprising rotary guide means for
the distributor element are known, and Figure 1 shows an
embodiment thereof.
In Figure 1, a structure given overall reference 1
comprises a frame 3 in which two bearing-forming housings
5 and 7 are formed (the gas meter and the distributor
element are not shown).
The guide means comprise a guide piece 9 in the form
of a crank having a portion 11 that is constituted by a
brass cylinder having the same diameter over its entire
height and engaged in the two openings 5 and 7 of the
frame 3. The cylinder 11, and thus the guide piece 9,
are guided in rotation at the bearings 5 and 7 by
cylindrical regions of the cylinder 11 that are spaced-
apart from each other.
A handle 13 of sheet metal is disposed
perpendicularly to the axis of the cylinder 11 and is
crimped on the end 11a thereof. This handle includes a
finger 15 extending parallel to the axis of the cylinder
11 but offset therefrom. The finger 15 is designed to
co-operate with the distributor element (situated below)
in order to guide its rotary movement.
The top portion llb of the cylinder 11 has a
plastics washer 17 provided to hold the guide piece 9
axially and prevent it from exerting a downward thrust
force on the distributor element.
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That guide piece suffers from the drawback of being
difficult to assemble and it would consequently be
advantageous to find a solution that is simpler.
The present invention seeks to remedy that problem
by proposing a gas meter comprising a plurality of
deformable diaphragm measurement chambers, a distributor
element mounted to rotate about a "rotation" axis on a
distribution surface in which there are provided a
plurality of orifices each of which is connected to a
respective measurement chamber, said distributor element
enabling gas to enter and to leave the measurement
chambers in alternation during its rotary movement, and
means for guiding said distributor element in rotation
comprising firstly a guide piece having at least a
portion of generally elongate shape along the axis of
rotation with two cylindrical regions spaced apart from
each other, and secondly two bearings in which said
cylindrical regions are mounted to rotate freely, the
meter being characterized in that the guide piece is made
of a thermoplastic material and in that the cylindrical
regions are of different diameters.
The fact of using a thermoplastic material makes it
possible to obtain the entire guide piece in a single
unmolding operation so there is no longer any need to
assemble said guide piece using a complicated method.
The Applicant has also found that it is necessary to
have two cylindrical regions of different diameters for
the guide piece made of thermoplastic material so that
head loss problems do not arise due to the mechanical
wear of the portions that come into contact.
If, as in the prior art, the guide piece were to
conserve the same diameter over its entire height, e.g.
15 mm, then, because of the unmolding operation and thus
the need to have draft on the pieces that are to be
unmolded, it would be technically impossible for said
guide piece and the other portion of the guide means
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including the bearings to have identical amounts of
draft, given the height involved.
As a result there would necessarily be unequal
mechanical clearance over the full height of the guide
piece, giving rise to premature mechanical wear and to
inevitable problems of head loss in the meter.
With cylindrical regions of different diameters, and
for a given height of the guide piece, the draft of said
cylindrical regions is fully under control and the same
draft can be obtained for corresponding bearings which
guarantees identical mechanical clearance over the full
height of the guide piece.
In addition, thermoplastic material presents the
advantage of being low in cost, so the increase in the
diameter of the cylindrical regions of the guide piece
has little repercussion on the cost of manufacturing such
a piece.
By performing the operation of unmolding the guide
piece in a direction that is parallel to the longitudinal
direction of said guide piece, it can be guaranteed that
the two cylindrical regions remain accurately on the same
axis.
This means that clearance in the bearings can be
reduced, thus leading to a reduction in wear and in head
losses in the meter.
According to a characteristic, the larger diameter
cylindrical region is closer to the distributor element.
In a variant, the guide piece may have a
frustoconical region interconnecting the two different-
diameter cylindrical regions.
More particularly, the guide piece is in the form of
a crank having one end constituted by the cylindrical
regions engaged in the bearings, and whose other end is
constituted by finger parallel to the axis of rotation
and offset therefrom, which finger co-operates with a
cavity formed in the distributor element.
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According to a characteristic of the invention, the
gas meter includes a U-shaped carrier structure whose
inside faces towards the distributor element so as to
surround it, and supporting the guide piece, the elongate
portion of said guide piece being engaged in a housing
provided in the structure via one end of said housing
which is disposed at the same end as the distributor
element, the bearings being arranged inside said housing.
Furthermore, the gas meter of the invention
comprises an axial retaining member for the guide piece
to prevent said guide piece from exerting a vertical
downward force on the distributor element.
For example, the axial retaining member for the
guide piece is a peg engaged in an axial sheath provided
inside the guide piece from its end opposite from the
housing, said peg being fixed to said guide piece in
removable manner and being provided on the outside of
said sheath with a shoulder forming a head which bears
against the carrier structure so as to retain said guide
piece axially.
The peg is fixed to the inside of the sheath by snap
fastening, for example.
More precisely, the peg has an annular groove on one
of its diameters to co-operate with an annular bead
formed on the inside surface of the sheath.
In addition, the head of the peg bears against the
carrier structure by means of an annular surface
extending perpendicularly to the axis of rotation.
The gas meter of the invention also comprises a
display totalizer and the guide piece includes a
gearwheel for transmitting the rotary movement of the
distributor element to said totalizer via a gear train.
For example, the gearwheel is disposed at the end of
the elongate portion of the guide piece which is closest
to the distributor element, and is perpendicular to said
portion.
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The guide piece may comprise a turntable which
carries the gearwheel on one of its faces.
The turntable carries on its opposite face the
finger which co-operates with the distributor element.
5 More particularly, the U-shaped structure is
constituted by a central portion parallel to the
distribution surface and two side portions forming the
branches of the U-shape, said central portion including a
base of generally circular shape disposed in a plane Pl
extending parallel to the distribution surface and
provided at its periphery with a collar disposed
perpendicularly to said base in such a manner as to
define a cavity situated facing the distributor element
and designed to receive its gearwheel.
On either side of the base, the central portion of
the U-shaped structure includes two regions situated in a
plane P2 parallel to the distribution surface and offset
from the plane P1 by a distance that is greater than the
thickness of the gearwheel, one of said regions carrying
a pivot capable of receiving another gearwheel of the
gear train, and a recess being provided in said base and
in said collar so that the gearwheels can co-operate with
each other.
The other region of the central portion carries a
pivot capable of likewise receiving another gearwheel of
the gear train, and another recess being formed in the
base and the collar on the side opposite to the first
recess so that the gearwheels can co-operate with each
other.
Other characteristics and advantages of the
invention appear from the following description given
purely by way of non-limiting example and made with
reference to the accompanying drawings, in which:
- Figure 1 shows guide means for a distributor
element of a prior art diaphragm gas meter;
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- Figure 2 is a perspective view of a gas meter of
the invention, showing passages 30 to 38 for admitting
gas into the meter and for evacuating it therefrom;
- Figure 3 is a perspective view of the gas meter of
the invention showing a diaphragm 28 and a cover 24
fitted to the central block 22;
- Figure 4 is a perspective view from above of the
gas meter of the invention in the same position as that
shown in Figure 2, but having the distribution cover 42,
the plate 40, and the pins 66 and 68 added thereto;
- Figures 5 and 6 show the distributor element 64
respectively in a perspective view and in a view from
beneath;
- Figure 7 is on a larger scale showing the top
portion of the gas meter of the invention and in
particular the distributor element 64, the carrier
structure 80, and the transmission means 70, 72, 74, and
76;
- Figure 8 is an exploded view showing the guide
piece 84 and the carrier structure 80; and
- Figure 9 shows the guide piece in section when
mounted in the carrier structure 80.
As shown in Figures 2 and 3 and given overall
reference 20, the gas meter of the invention comprises
firstly a central block referenced 22 and two side
covers, only one of which 24, is visible in Figure 3.
The central block 22 defines two chambers, only one
of which 26 is shown in Figure 2. Each chamber is
defined firstly by the central block 22 and secondly by a
deformable diaphragm (diaphragm 28 in Figure 3). When
the covers are fitted to the central block 22, they co-
operate with the respective deformable membranes to
define two other measurement chambers. Thus, there are
two measurement chambers situated on either side of each
deformable diaphragm and the volumes of these chambers
vary depending on the positions of the diaphragms.
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As shown in Figure 2, the central block 22 defines
four passages 30, 32, 34, and 36 in its internal
structure, each passage communicating with a respective
one of the measurement chambers. For example, the
passage 30 communicates with the measurement chamber 26
and the passage 34 communicates with a measurement
chamber (not shown in Figure 2) which is symmetrical to
the measurement chamber 26 about the central block 22.
The central block 22 also defines a fifth passage
referenced 38 which enables gas to be evacuated from said
central block.
In Figures 3 and 4, a sheet metal plate 40 has been
placed over the passages 30 to 38 and a piece referred to
as a "distribution cover", referenced 42, is placed on
said plate 40. The cover 42 has four openings or ports
44, 46, 48, and 50 each in the form of a quarter sector
of a circle, and they are separated from one another by
radial sealing strips 42a, 42b, 42c, and 42d.
In the central portion of the distribution cover 42,
a circular ring 42e co-operates with the radial strips
42a-d to define four orifices 52, 54, 56, and 58. Each
of these orifices communicates with the outlet passage 38
and the outlet passage is terminated by an opening 60
formed through the closure plate 40.
In the center of the distribution cover 42, a pivot
62 is mounted on an axis perpendicular to the top surface
42f of the distribution cover 42, which surface is
referred to as the "distribution" surface. The pivot is
designed to receive a distributor element that is also
referred to as a "distributor".
The distributor 64 is mounted to rotate on the
distribution surface 42f of the distribution cover 42 and
it slides on said surface. The distributor is
constituted by four circular sectors which are arranged
in such a manner as to form an orifice 64a and a setback
zone 64b (Figure 5) separated by two plane zones 64c and
64d. Each of these four zones occupies an angle of 90°.
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The distributor also has a hollow central zone 64e
(Figure 6) which communicates with the hollow setback
zone 64b.
In the light of Figures 5 to 7, it will readily be
understood that the orifice 64a serves to put each of the
ports 44, 46, 48, and 50 successively into communication
with the outside of the central block 22, that the
setback zone 64b and the central zone 64e are to put the
outlet passage 38 into communication with one of said
ports while isolating the assembly from the outside of
the central block, and that the plane zones 64c and 64d
close the remaining ports.
As is well known, rotation of the distributor serves
to control the admission and the evacuation of gas into
and from the various measurement chambers. Meters having
four chambers and a rotary distributor are well known in
themselves, e.g. from US patent No. 3 161 049. There is
therefore no need to describe the operating details of
such a meter, i.e. the relationships between the position
of the rotary distributor 64 and the positions of the
membranes in the measurement chambers. Reference can be
made to the above-cited document.
Nevertheless, it is appropriate to mention that the
gas meter has transmission means for dynamically
connecting the distributor to the deformable membranes.
As shown in Figures 3, 4, and 7, the transmission
means comprise two pins 66 and 68 passing through the
block 22 over a fraction of its height, and communicating
with the measurement chambers of the meter. In Figure 4,
a portion of the pin 66 can be seen in the chamber 26.
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.
As shown in Figure 7, the transmission means also
comprise two sets of levers 70, 72, and 74, 76. These
sets of levers connect each of the pins 66, 68 to another
pin 78 (Figure 8) which is engaged in an opening 79
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(Figure 5) formed in the distributor 64. Thus, the
movement of the deformable diaphragms during admission
and evacuation of gas into and out from the measurement
chambers is communicated by the transmission means to the
distributor 64 which performs corresponding rotary
motion.
As shown in Figure 7, a structure 80 is mounted on
the central block 22 immediately above the distributor
element 64. This carrier structure 80 is generally U-
shaped, with the inside of the U facing towards the
distributor element so as to contain it.
The U-shaped structure 80 is constituted by a
central portion parallel to the distribution surface 42f
and two side portions 80a and 80b forming the branches of
the U-shape. The central portion of the structure has a
base 80c of generally circular shape lying in a plane P1
parallel to the distribution surface 42f and provided at
its periphery with a collar 80d disposed perpendicularly
to said base so as to define a cavity 81.
The central portion of the structure has two plane
regions 80e and 80f on either side of the base 80c and
lying in a plane P2 parallel to the distribution surface
but axially offset from the plane P1.
One of the regions 80f carries a pivot 82 for
receiving a gearwheel 84, as shown in Figure 7.
A recess 86 is formed in the base 80c and in the
collar 80d so as to enable the gearwheel 84 to engage in
the cavity 81.
The other region 80e of the central portion of the
structure 80 carries a pivot 88, likewise designed to
receive another gearwheel (not shown in the figures) when
the gearwheel 84 is not present, and another recess 90 is
formed in the base of the collar on its side opposite to
the first recess, thus enabling said other gearwheel, if
any, to penetrate into the cavity 81.
The branches 80a, 80b of the carrier structure 80
are provided at their free ends remote from their ends
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connected to the central portion with fixing tabs 80g,
80h which are designed to co-operate with the top portion
92 of the central block 22.
Rotary guide means for the distributor element 64
5 are provided and are shown in Figures 8 and 9.
Figure 8 is an enlarged side view of the central
portion of the carrier structure 80, with the guide means
being shown in section on a plane including the axis of
rotation of the distributor element 64 which coincides
10 with the axis of the pivot 62. The remainder of the
central portion is not shown in section. These guide
means comprise a crank-shaped piece 94 (Figure 8). The
guide piece 94 has a generally elongate portion which is
constituted by two cylinders of different diameters, a
first cylinder 96 of relatively small height, e.g. about
6 mm, and a second cylinder 98 of greater height than the
first cylinder, e.g. about 14 mm.
The guide piece also has a circular turntable 100
and a gearwheel 102 mounted on one of the faces of the
turntable 100.
The elongate portion of the guide piece 94
constituted by two cylinders 96 and 98 is mounted
centrally relative to the gearwheel 102 so that the end
of the elongate portion carrying the larger diameter
cylinder 96 is connected to said gearwheel.
As shown in Figure 9, the central portion of the
guide piece is hollow.
The turntable 100 also carries, on its opposite
face, a finger 78 (described above) which is parallel to
the axis of rotation of the distributor element 64 and
which engages in the opening 79 of said element, as shown
in Figure 5.
To simplify manufacture, the guide piece 94 is made
as a single piece.
The central portion of the carrier structure 80 has
a cylindrical piece 104 (Figures 7 to 9) mounted on the
base 80c and in which a housing 106 is provided in
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alignment on the axis of rotation of the distributor
element 64.
As shown in Figure 9, the guide piece 94 is engaged
by means of its elongate portion in the housing 106
provided for this purpose. Thus, when the piece 94 is
engaged in the housing 106, the cylindrical region 96 co-
operates with a first bearing 104 and the gearwheel 102
is received in the cavity 81.
The cylinder 98 has two cylindrical regions 98a and
98b, and the second cylindrical region 98b co-operates
with a second bearing 104b of the piece 104. Thus, the
spaced-apart cylindrical regions 96 and 98b of different
diameters serve to provide guidance inside the bearings
104a and 104b.
The piece 94 is made of a thermoplastic material.
Thus, this piece is easy to make by molding and
unmolding, and its cost of manufacture is cheaper than
the cost of manufacturing the above-described prior art
piece, which is built of different materials.
In addition, this guide piece can easily be
assembled with other pieces, e.g. by heat sealing.
In a variant, the guide piece can also have a
frustoconical region interconnecting the two cylindrical
regions 96 and 98b which participate in providing
guidance, thus replacing the cylindrical region 98a.
Given that while guiding the distributor element 64
in rotation, the guide piece 94 and the piece 104 are
subjected to large mechanical forces, it is possible to
provide ribs 108 to reinforce the central portion of the
structure 80.
To ensure that the guide piece 94 does not exert
downward axial forces on the distributor element 64, an
axial retaining member 110 is provided.
As shown in Figures 8 and 9, the axial retaining
member for the guide piece is a cylindrical peg 110
engaged in a cylindrical sheath 112.formed in the central
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portion of the guide piece 94, level with the cylindrical
regions 96 and 98a,b.
The peg 110 is provided at its end opposite from the
end engaged in the sheath 112 with a head-forming
shoulder 114 which bears against the carrier structure
and, more particularly, against the plane top portion
104a of the piece 104 so as to hold the gmide piece 94
axially.
The peg 110 is fixed inside the sheath 112 in
removable manner, e.g. by snap fastening. For snap-
fastening purposes, the peg has an annular groove 116
(Figure 8) on one of its diameters for co-operating by
engaging an annular bead 118 formed on the inside surface
of the axial sheath 112 (Figure 9).
The head 114 of the peg rests on the top portion
104a of the piece 104 via an annular surface 120. This
configuration provides better contact by friction than
would be obtained if the peg was placed with its head
extending downwards towards the distributor element,
since under such circumstances friction contact would be
made via the snap-fastening.
It is appropriate to observe that it is particularly
simple to assemble the guide piece 94 and the~peg 110,
since it suffices to engage the guide piece in the
housing 106 and to force the peg 110 into the axial
sheath 112 until the two elements snap fasten together.
The prior art guide piece (Figure 1) is made up of a
plurality of parts and provision is made to mount a worm
screw (not shown in Figure 1) on the cylinder 11 for
meshing with one or more gearwheels of a gear train, thus
considerably complicating the prior art guide means and
assembly thereof compared with the guide means of the
invention. The gear train is connected to the totalizer
of the meter.
In the invention, the gas meter includes in
conventional manner a display totalizer for displaying
the volume of gas measured by the meter.
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In order to avoid overcrowding the figures, the
totalizer is not shown.
The guide piece 94 has a gearwheel 102 which serves
to transmit rotary movement from the distributor element
64 to the totalizer via a gear train. L~ecau~e of the
recess 86 provided in the central portion of the carrier
structure 80, the gearwheel 102 meshes with the other
gearwheel 84 mounted on the pivot 82. This gearwheel co-
operates in turn with a third gearwheel 112 placed
perpendicularly to the first two gearwheels and which is
mounted on a stud 124 (Figure 8) formed on the outside
portion of the branch 80b of the carrier ;structure 80.
The gearwheel 122 co-operates in turn (not shown in
the figures) with the display totalizer.
The presence of the recesses 86, 90 and of the
pivots 82, 88 on the central portion of the carrier
structure serves advantageously to make it simple to
mount the gearwheels of the gear train, and their
symmetrical disposition as shown in Figures 7 to 9 makes
it possible to mount the gearwheel 84 either on the pivot
82 or on the pivot 88 depending on the desired
configuration.
Another stud 126 formed on the outside portion of
the branch 80a of the carrier structure 80 is also
provided symmetrically to the stud 124 so as to receive
the wheel 122 when the wheel 84 is mounted on the pivot
88.
