Note: Descriptions are shown in the official language in which they were submitted.
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RA~K~ROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piston-type quantity
meter including a metering chamber having a bottom, a
cylindrical chamber shell, a cover, a central journal, a guide
ring, a separation wall located in a chamber interior, two
inlet opening formed, respectively, in the chamber bottom and
the chamber cover, and a radial outlet opening formed in the
chamber shell; and an annular piston located in the chamber
interior and having a cylindrical piston skirt, a piston cap,
piston journal means, guide slot means formed in the piston
skirt and corresponding to a width of the separation wall for
pinning the piston on the separation wall, and a radial outlet
opening associated with the outlet opening formed in the
chamber shell.
2. Description of the Prior Art
Piston-type quantity meters, which belong to volume
meters, have a metering chamber through which an entire amount
of fluid is forcefully flown. At that, a portion of a
potential energy of a to-be-measured fluid is lost for driving
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the meter. The resulting pressure reduction is designated as --
a pressure loss as delta p. It results from deviations of the
fluid flow path, cross-sectional changes along the flow path,
from driving the annular piston of the meter, ets...
In the metering chamber, an annular piston is arranged
which during the measuring process, is displaced from a high
pressure side to a lower pressure side. This displacement
takes place automatically as a result of flow of the fluid
through the meter. During rotation of the piston, two
different volumes having, respectively, the same predetermined
value are transported. During the transportation, the annular
piston internal journal rotates about the central journal of
the metering chamber.
The skirt of the annular piston is slotted over its
entire height. The slot reciprocate once along a separation
wall provided in the metering chamber with each revolution of
the piston. The advantage of the oscillating movement of the
piston consists in that the piston automatically returns into
its initial position without any additional control elements,
valves, slides, ets...
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The annular piston has an upper journal for supporting
a driver which transmits the rotary movement of the journal to
a counter. A piston-type quantity meter of the above-
described type is disclosed in a publication of Orlicek et
al., "Zur Technik der Mengen - und Durchflu~ Messung von
Flussigkeiten" (Technique for measuring volume and flow rate
of fluid), R. Oldenbourg Verlag, Munchen-Wien, 1971,p.p. 44-
57.
The measurement precision of the piston-type quantity
meters depends to a great extent on the dimensional accuracy
of portions of the metering chamber. The greater is the slit
between the annular piston and the metering chamber the
greater is the amount of fluid that can pass through the
chamber without being measured and the greater is the
measurement error. Anyway, the slit between the chamber and
the piston should be as small as possible but have a size
which would prevent jamming of the piston. A typical size of
a slit between movable relative to each other parts should be
no more than 10~m. It is clear the smaller is the to-be-
measured discharge flow the more the slit leakage would affect
the measurement accuracy. The slot leakage is calculated
according to the following equation:
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Qspalt = Aspalt ~2-g-(delta p)
whereln ~-ASpalt~ ls a sum of all sllt surfaces, "g" is
acceleration due to gravlty, and "delta p" ls, as dlscussed
above, a pressure loss.
There exlst three ways of flowlng a to-be-measured
fluld through a plston-type quantlty meter.
Accordlng to a flrst varlant, the fluld flows through a
slckle-shaped openlng ln the bottom of the meterlng chamber lnto
the chamber and ls dlscharged through another slckle-shaped
openlng ln the chamber bottom. In thls case, the plston ls
sub~ected to one-slded forces whlch leads to an lncreased
frlctlon and wear of the plston. Both the frlctlon and the wear
adversely affect the measurement preclslon.
In a second case, the to-be-measured fluld flows
through a slckle-shaped openlng ln the chamber bottom and ls
dlscharged through a llkewise slckle-shaped openlng ln the
chamber cover. At that, the posltlon of the lnlet and the outlet
can be changed. In thls case llkewlse, one-slded
21182-316
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forces act on the piston, unfavorably influissing the
measurement accuracy.
In a third case, an inlet opening is provided in both
the bottom and the cover of the metering chamber, with a half
of the volume of the to-be-measured fluid passing through each
inlet opening. Rectangular slots, which are formed in the
chamber shell and in the annular piston skirt, form outlet
openings. With this flow of fluid through the metering
chamber, in an ideal case, the axial flow forces acting on the
piston are automatically balanced. See French Patent
Publication FR-A 454609 and the article of Orlicek et al.
'Zur Technique der Mengen-un Durchfusmessung von
Flussigkeiten," r. Oldenbourg Verlag, 1971, p.p. 44-57.
The present invention relates to a piston-type quantity
meter of the third type.
Because in the third type of piston-type quantity
meters, the axial forces, which act on the piston, are
automatically balanced, the meters of this type should have a
greater measurement accuracy than the meters of the first two
types. Actually, opposite is the case. The smaller
measurement accuracy of the piston-type quantity meters of the
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- third type is caused by formation of slits between the piston
and the inner surface of the chamber shell and between the
guide ring and the inner surface of the piston. Because of
the slits, the chamber shell and the piston skirt could not
perform their sealing functions. Therefore, when the piston
and the guide ring reach the region of respective slits, a
noticeable increase of the effective slit width takes place,
and this leads to a high slit leakage. For this reason, the
piston-type quantity meter of the third type could not be used
up to the present.
Accordingly, an object of the present invention is to
reduce the measurement error in the piston-type quantity
meters of the third type.
SUMMARY OF THE INVENTION
This and other objects of the present invention, which
will become apparent hereinafter, are achieved by providing a
seal strip for sealing at least one of a slit formed between a
chamber edge, which is defined by an intersection between a
side wall of the outlet opening formed in the chamber shell
and an inner wall of the chamber shell, and a piston edge,
which is defined by an intersection between a side wall of the
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outlet opening formed in the piston skirt and an outer surface
of the piston, and a second slit formed between a piston edge,
which is defined by an intersection between a side wall of the
outlet opening formed in the piston skirt and an inner wall of
the piston, and an outer wall of the guide ring.
According to the present invention, the seal strip can
be secured, for sealing the outer slit, either to the chamber
shell, projecting into the outlet opening formed in the piston
skirt, or to the piston skirt, projecting into the outlet
opening formed in the chamber shell.
For sealing, the inner slit, the seal strip is secured
either to the guide ring, projecting into the outlet opening
formed in the piston skirt, or to the piston skirt, projecting
into a groove formed in the guide ring.
The seal strip can be formed integrally with an element
to which it is secured by being sprayed thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and objects of the present invention will
become more apparent, and the invention itself will be best
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understood from the following detailed description of the
preferred embodiments when read with references to the
accompanying drawings, wherein:
Fig. 1 shows a conventional piston-type quantity
meter with an annular piston having radial
outlet slots;
Fig. 2 shows the piston-type quantity meter shown in
Fig. 1 with a displaced annular piston;
Fig. 3 shows the piston-type quantity meter shown in
Fig. 1 with an outer seal according to the
present invention;
Fig. 4 shows the piston-type quantity meter shown in
Fig. 1 with an alternative embodiment of the
outer seal according to the present
invention;
Fig. 5 shows the piston-type quantity meter shown in
Fig. 1 with the annular piston being further
displaced by 180~;
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Fig. 6 shows the piston-type quantity meter shown in
Fig. 5 with a displaced annular piston;
Fig. 7 shows the piston-type quantity meter shown in
Fig. 5 with inner and outer seals according
to the present invention; and
Fig. 8 shows a cross-sectional view of a standard
piston-type quantity meter in which the flow
of fluid is shown.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 shows a plan view of a piston-type quantity
meter with elements necessary for explaining the present
invention. The meter includes a metering chamber 10 with a
bottom 11, a chamber shell 12, a central journal 13, a guide
ring 14, and a separation wall 15. On the left, adjacent to
the separation wall 15, there is provided a sickle-shaped
inlet opening 16u for the measured water. An identical inlet
opening 160 (see Fig. 8) is formed in a metering chamber cover
24 which is not shown in Fig. 1 for the sake of clarity.
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On the opposite side of the separation wall 15, an
outlet opening 17 having a shape of a rectangular slot is
provided in the chamber shell 12.
Inside the metering chamber 10, there is provided an
annular piston 30 formed of a cylindrical piston skirt 31,
piston cap 32, and a guide journal 33. The guide journal 33
rotates about the central journal 13.
A radial slot 34 is formed in the piston skirt 31 and
the piston cap 32. With the radial slot 34, the annular
piston 30 is pinned onto the separation wall 15. The linear
movement imparted by the separation wall 15 and a circular
movement, which imparted by the central journal 13 and the
guide ring 14, in combination, provide for the known
oscillating movement of the annular piston 30. A relief
passage 35 is formed in the piston skirt 31.
As shown in Fig. 1, not only the metering chamber 12
but also the piston skirt 31 has an outlet opening designated
with a reference numeral 36. This outlet opening 36 is
necessary for discharging a partial metered volume inside the
annular piston 30.
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In the region of the outlet slot 17 and the outlet
opening 36, respective portions of the chamber shell 12 and
the piston skirt 31 are absent. As soon as the annular piston
30 reaches an angular position, which is defined by an
angle ~, as shown in Fig. 2, an additional slit is formed
which attains its maximum size A1 in the position of the
piston 30 shown in Fig. 3. The slit A1 is formed between a
chamber edge 18, which is formed by an intersection between a
side wall 19 of the outlet opening 17 and the inner wall 20 of
the chamber shell 12, and a first piston edge 37, which is
formed by an intersection between a side wall 38 of the outlet
opening 36 and a piston outer wall 39. Only a small portion
of the chamber volume VI, which remains unmeasured, flows
through the slit A1. Fig. 3 shows a first solution for
eliminating the additional slit A1. A seal strip 1 is formed
on the inner wall 20 of the chamber shell 12 in the region of
the side wall 19. The seal strip 1 forms an extension of the
side wall 19. It extends into the outlet opening 36
immediately adjacent to the side wall 38 of the outlet opening
36 which is, as discussed above, is formed in the piston skirt
31. Thereby a labyrinth-type seal is formed which seals the
slit A1.
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Fig. 4 shows another solution for sealing the
additional slit A1'. A seal strip 2 is formed on the side
wall 38 of the outlet opening 36, forming an extension of the
side wall 38, and projects into the outlet opening 17 formed
in the chamber shell 12. This solution provides an additional
advantage which consists in that the seal strip 2 deflects the
stream of the outer measured volume in the direction toward
the outlet opening 17 so that not only slit losses but also
flow losses are reduced.
Fig. 5 shows a piston-type quantity meter, which is
shown in Fig. 1, but with the piston having been displaced by
180~. As soon as the piston reaches an angular position ~',
as shown in Fig. 6, an additional slit is formed which attains
its maximal size A1l in the angular position shown in Fig. 2.
An unmeasured portion of the chamber volume V2 flows through
the slit A11. The slit A11 is formed between a second piston
edge 40, which is formed by an intersection of the side wall
38 and an inner wall 41 of the piston 30, and an outer wall 21
of the side guide ring 14.
Fig. 7 shows a solution with which the second
additional slit A' can be sealed with a seal strip 3 which is
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formed on the inner side of the piston skirt 31. The seal
strip 3 extends into a groove 22 formed in the guide ring 14.
The extension of the inner seal strip 3 forms the outer
seal strip 2. With such a combined solution, both slits A1
and A1' can be sealed with the formed labyrinth seal, without
in any way adversely affecting the functioning of the quantity
counter. It should be obvious that sealing of the inner slit
A11 with a seal strip, which is provided on the outer side of
the guide ring 14 and which projects into the outlet opening
36 in the piston skirt 31, is also possible.
Fig. 8 shows schematically a cross-sectional view of
the metering chamber 10 and the annular piston 30 of a
standard piston-type quantity meter. The lower inlet opening
16u in the bottom 11 and the upper inlet opening 160 in the
cover 24 can be clearly seen. The fluid stream 5 separates in
upper and lower partial streams 50 and 54. In the region of
the outlet openings 17 and 36, both partial streams 50 and 54
are combined again and leave the metering chamber 10.
Thereby, the forces acting on the annular piston 30 are
automatically balanced, which positively influences the
measurement precision and reduces wear.
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Though the present invention was shown and described
with references to the preferred embodiments, various
modifications thereof will be apparent to those skilled in the
art and, therefore, it is not intended that the invention be
limited to the disclosed embodiments or details thereof, and
departure can be made therefrom within the spirit and scope of
the appended claims.
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