Abstrict A fluid flow meter has a housing within which inlet and outlet
displacement rotors flank a blocking rotor. The end plates of the
housing rotatably support all three rotors which rotate in a timed
sequence in response to the passage of fluid through the meter.
The cylindrical blocking rotor has a pair of disk-shaped endwalls
joined by a rectangular, centrally-positioned web, and a pair of
arcuate sidewalls which, with the endwalls and web define a pair
of rotor cavities. Recesses in the housing end plates fit the blocking
rotor endwalls and provide an added fluid seal. Use of the rotor
endwalls makes it possible to manufacture the blocking rotor with
a smaller diameter and thinner body portions, saving weight and
rotational mass.
Claims What is claimed:
1. A blocking rotor for a rotary fluid displacement device, said
device of the type having at least one displacement rotor, said
blocking rotor being a one-piece unified structure comprising:
a generally hollow cylindrical body including opposing circular
end walls and diametrically opposing substantially quarter-round
arcuate side walls extending between said end walls defining opposing
substantially quarter-round side wall openings in said generally
hollow cylindrical body; a diametrical interior web extending between
and substantially bisecting said opposed substantially quarter-round
arcuate side walls and between said opposing circular end walls;
a pair of opposing journals, each positioned externally of respective
ones of said opposing circular end walls coaxially therewith.
2. The blocking rotor as defined in claim 1 wherein said diametrical
interior web includes opposed flat side surfaces extending between
said opposing circular end walls defining opposing semicylindrical
pockets in said body, and for providing clearance for any displacement
rotor sweeping through one of said semicylindrical pockets.
3. The blocking rotor as defined in claim 1 wherein each of said
opposing end walls include a pair of substantially flat semicircular
inside surfaces for providing clearance for any displacement rotor
sweeping through one of said semicylindrical pockets.
4. In an end plate for use on a trefoil cavity type housing for
a rotary fluid displacement device, said end plate of the type having
a generally flat working surface, a pair of displacement rotor mounting
apertures formed perpendicularly through said end plate in spaced
relation to each other and a blocking rotor mounting aperture formed
perpendicularly through said end plate positioned equidistant from
said pair of displacement rotor mounting apertures in spaced triangular
relation thereto; and improvement comprising:
a cylindrical recess on said substantially flat working surface,
said blocking rotor mounting aperture positioned on an end wall
of said cylindrical recess and being coaxial therewith, said cylindrical
recess being for receiving an end segment of a blocking rotor having
a disk-shaped end wall with an inside surface of said end wall being
co-planar with said substantially flat working surface.
5. In a rotary fluid displacement device of the type including
a housing having a trefoil shape cavity therein, a pair of vaned
displacement rotors mounted in spaced relation in said housing for
rotary movement in like direction therein, and a blocking rotor
mounted for rotary movement in triangulated relation to said pair
of displacement rotors, said blocking rotor comprising:
a generally hollow cylindrical body including opposing circular
end walls and diametrically opposing substantially quarter-round
arcuate side walls extending between said end walls defining opposing
substantially quarter-round side wall openings in said generally
hollow cylindrical body; a diametrical interior web extending between
and substantially bisecting said opposed substantially quarter-round
arcuate side walls and between said opposing circular end walls;
said diametrical web and said quarter round arcuate sidewalls defining
opposing semicylindrical pockets on said blocking rotor, the length
of said semicylindrical pockets being greater than the length of
said displacement rotor vanes for providing clearance when said
displacement rotors sweep through respective ones of said semicylindrical
pockets.
6. The rotary fluid displacement device as defined in claim 5 further
including a pair of end plates mountable on opposed open ends of
said housing, each said end plate including:
a generally flat working surface, a pair of displacement rotor
mounting apertures formed perpendicularly through each end plate
in spaced relation to each other and a blocking rotor mounting aperture
formed perpendicularly through each said end plate positioned equidistant
from said pair of displacement rotor mounting apertures in spaced
triangular relation thereto;
a cylindrical recess on said substantially flat working surface,
said blocking rotor mounting aperture positioned on an end wall
of said cylindrical recess and being coaxial therewith, said cylindrical
recess being for receiving an end segment of said blocking rotor
that is axially longer than the length of a vane of one of said
displacement rotors with an interior surface of said end segment
of said blocking rotor being co-planar with said generally flat
working surface.
7. The rotary fluid displacement device as defined in claim 5 further
including a pair of end plates mountable on opposed open ends of
said housing, each said end plate including:
a generally flat working surface, a pair of displacement rotor
mounting apertures formed perpendicularly through each end plate
in spaced relation to each other and a blocking rotor mounting aperture
formed perpendicularly through each said end plate positioned equidistant
from said pair of displacement rotor mounting apertures in spaced
triangular relation thereto;
a cylindrical recess on said substantially flat working surface,
said blocking rotor mounting aperture positioned on an end wall
of said cylindrical recess and being coaxial therewith, said cylindrical
recess being for receiving an end segment of said blocking rotor
that is axially longer than the length of a vane of one of said
displacement rotors, and
said cylindrical recesses includes at least one vent hole positioned
therethrough for receiving any fluid buildup between an end wall
of said blocking rotor and said cylindrical recess.
8. The rotary fluid displacement device as defined in claim 5 further
including a pair of end plates mountable on opposed open ends of
said housing, each said end plate including:
a generally flat working surface, a pair of displacement rotor
mounting apertures formed perpendicularly through each end plate
in spaced relation to each other and a blocking rotor mounting aperture
formed perpendicularly through each said end plate positioned equidistant
from said pair of displacement rotor mounting apertures in spaced
triangular relation thereto;
a cylindrical recess on said substantially flat working surface,
said blocking rotor mounting aperture positioned on an end wall
of said cylindrical recess and being coaxial therewith, said cylindrical
recess being for receiving an end segment of said blocking rotor
that is axially longer than the length of a vane of one of said
displacement rotors, and
a substantial seal is formed between an outer circumference of
a circular end wall on one end of said blocking rotor and an inner
cylindrical surface on said cylindrical recess on one of said pair
of end plates.
9. In a rotary fluid displacement device of the type including
a housing having a trefoil shape cavity therein, a pair of vaned
displacement rotors positioned in spaced relation in said housing
for rotary movement in like direction therein, a blocking rotor
mounted for rotary movement in triangulated relation to said pair
of displacement rotors, and a pair of opposing end plates for covering
the opposing sides of said trefoil shape cavity on said housing
and for rotatably mounting the ends of said pair of vaned displacement
rotors and said blocking rotor, respectively; thereon,
an improvement comprising,
a radius of a hub of said displacement rotor plus a radius of said
blocking rotor are substantially equal to a radial length of a blade
of said displacement rotor plus one-half the thickness of a web
on said blocking rotor, wherein a thickness of said web on said
blocking rotor is substantially thinner than a diameter of a journal
on said blocking rotor.
10. In a rotary fluid displacement device of the type including
a housing having a trefoil shape cavity therein, a pair of vaned
displacement rotors positioned in spaced relation in said housing
for rotary movement in like direction therein, a blocking rotor
mounted for rotary movement in triangulated relation to said pair
of displacement rotors, drive means adjacent one end of each of
said rotors for continuing the relative rotary movement therebetween,
a pair of opposing end plates for covering the opposing sides of
said trefoil shape cavity on said housing and for rotatably mounting
thereon the ends of said pair of vaned displacement rotors and the
end of said blocking rotor, respectively, and two end covers for
mounting on opposing sides of said housing and covering each of
said end plates, and said drive means adjacent one of said end plates,
an improvement comprising,
said end plates and said two end covers including substantially
complementary mating surfaces for substantially minimizing any voids
around said ends of said rotors and said drive means.
Description BACKGROUND OF THE INVENTION
This invention relates to improvements in positive displacement
fluid flow meters, and more particularly to a blocking rotor and
meter housing for such meters.
Industrial fluid flow meters, such as those used in the petrochemical
and natural gas industries, are generally the reverse of a positive
displacement pump. That is, the fluid, flowing through a gasoline
storage tank facility, gasoline transport truck, underground natural
gas delivery system, or other storage or delivery system, generally
has a positive displacement meter connected in line in the fluid
delivery system such that movement of fluid, whether gas or liquid,
through the delivery line causes movement of the rotors in the meter
which drives a mechanical or electrical counting device to measure
precisely the volume of flow through the delivery system. Such a
meter is described in detail in U.S. Pat. No. 5513529 assigned
to the assignee of the present invention. As set forth in the '529
patent, another typical industrial meter is a plastic rotary fluid
displacement meter suitable for use in the food industry is disclosed
at U.S. Pat. No. 3465683.
The meter described in the '529 patent has a housing defining a
generally trefoil-shaped cavity within which a trio of rotors are
rotatably mounted, a pair of displacement rotors flanking a blocking
rotor. As the blocking rotor rotates, it combines with first one
displacement rotor then the other to close off a part of the cavity
to define a flow path along which the fluid must pass, thereby rotating
the displacement rotors and creating a motion that can be correlated
to fluid volume passing through the meter, making it possible to
translate the rotation of the displacement rotor into a meter reading
showing fluid volume flow. Meters of this type are also described
in U.S. Pat. Nos. 3457835 and 3465683 also assigned to the
predecessor of the assignee of the present invention.
Typically, the entire fluid flow through a conduit is diverted
through the flow meter in order to provide a flow rate reading.
Because of this, it is desirable that the meter add as little flow
impedance as possible to minimize energy losses and to maintain
as high a flow rate as possible. To that end, it is desirable to
provide a flow meter with movable components of as little mass as
possible while maintaining sufficient strength for a long and accurate
service life.
It is also desirable to provide housings for flow meters that are
as compact as possible. For minimizing pressure loss, minimizing
a retention of fluid in the meter, and for ease of installation
and flexibility of location and orientation when placed in service.
A continuing need then exists to provide flow meters of the type
utilizing blocking rotors with rotors of lightweight yet strong
construction. A further need exists for rotor housings designed
to complement the improved blocking rotor design while providing
a compact and low profile construction with minimum pressure loss.
SUMMARY OF THE INVENTION
The invention resides in an improvement of a rotary fluid displacement
device of the type having a housing within which a pair of displacement
rotors are rotatably mounted within a fluid chamber, and a blocking
rotor positioned between the displacement rotors. The invention
resides in an improved additionally elongated blocking rotor having
walls that enclose the distal end and both sides of any displacement
rotor blade as it rotates by the blocking rotor in a meter housing.
Modified housing end caps include recesses to receive the ends of
the blocking rotors. The invention is further found in an improvement
wherein the blocking rotor has a relatively thin cross-section for
overall weight reduction, maximum displacement rotor penetration,
smallest possible blocking rotor displacement, and has circular
end walls integrally formed therewith for improved structural rigidity.
dr
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention which are believed to be
novel are set forth with particularity in the appended claims. The
invention, together with further objects and advantages thereof,
may best be understood by reference to the following description
taken in connection with the accompanying drawings, wherein like
reference numerals identify like elements throughout and in which:
FIG. 1 is a lateral sectional view, constructed in accordance with
the present invention, showing the placement of the displacement
and blocking rotors within the meter housing;
FIG. 2 is a top plan view of the blocking rotor of FIG. 1;
FIG. 3 is a perspective view of the blocking rotor of FIG. 2;
FIG. 4 is a front elevational view of the blocking rotor of FIG.
2;
FIG. 5 is a right end elevational view of the blocking rotor of
FIG. 2;
FIG. 6 is a blade-on elevational view of one of the displacement
rotors of FIG. 1 with portions of the opposing end journals shown
in section;
FIG. 7 is an end-on elevational view of the rotor of FIG. 6;
FIG. 7a is a bottom plan view of the rotor of FIG. 6;
FIG. 8 is a perspective view of the first and second housing end
plates assembled to the displacement and blocking rotors of FIG.
1;
FIG. 9 is a partial perspective view of the assembly of FIG. 8;
FIG. 10 is an edge-on view representative of both housing end plates
of FIG. 8;
FIG. 11 is a front elevational view of the exterior of the first
housing end plate of FIG. 10;
FIG. 12 is a perspective view of the exterior of the second end
plate of FIGS. 8 and 9;
FIG. 13 is a perspective view representative of the interior of
both end plates of FIG. 10; and
FIG. 14 is an exploded perspective view of the exterior of the
first end plate of FIG. 10 showing the rotor timing gears on the
outer side of the end plate, and the blocking rotor of FIG. 2 and
displacement rotors of FIG. 6 on the inner side of the end plate;
FIG. 15 is a perspective view, with portions cut away, of a second
embodiment of the meter of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to FIG. 1 the numeral 10 indicates generally a flow
meter having a meter housing 11 an inlet port 12 a fluid chamber
13 and an outlet port 14. Disposed and rotatably supported within
housing 11 are inlet displacement rotor 15 blocking rotor 16 and
outlet displacement rotor 17. Housing 11 is of a generally trefoil
shape, with a first arcuate chamber 18 with a curved inner surface
19 having a radius of curvature R.sub.1 measured from the axis of
rotation 20 of rotor 15. As seen in FIG. 1 rotor 15 has a generally
rectangular vane 21 extending normal to axis 20 and terminating
in a vane end 22. Preferably, the distance between axis 20 and vane
end 22 approximates R.sub.1 allowing vane end 22 to "wipe"
along inner surface 19 during rotation of rotor 15. This wiping
contact helps to keep fluid from leaking past vane 15 during its
rotation. In like fashion, a second arcuate chamber 23 is formed
proximate outlet port 14 having an inner surface 24 with a radius
of curvature R.sub.2 as measured from an axis 25 of rotor 17. A
generally rectangular vane 26 extends normal to axis 25 and terminates
at a vane end 27 with the distance from axis 25 to vane end 27
approximating R.sub.2 allowing end 27 to wipe along surface 24.
As seen in FIGS. 1-5 blocking rotor 16 constructed in accordance
with the present invention is formed in a generally cylindrical
configuration having first and second circular end walls 28 and
29 between which extend a pair of arcuate, substantially quarter-round
side walls 30 and 31 parallel one to the other and an interior,
generally rectangular web 32 joined integrally to end walls 28 and
29 and to side walls 30 and 31 bisecting said side walls as seen
in FIG. 5. Web 32 end walls 28 and 29 and side walls 30 and 31
combine to define a pair of rotor cavities 35a and 35b, as seen
in FIG. 5. Web 32 as it extends between end walls 28 and 29 is
longer than the length of vanes 21 and 26 of displacement rotors
15 and 17 for reasons discussed in more detail below. Use of end
walls 28 and 29 allows web 32 and side walls 30 and 31 to be made
relatively thin in cross-section, producing a blocking rotor with
not only reduced mass and, thereby, reduced resistance to rotation,
but with increased structural rigidity as well.
End wall 28 has a journal 33 formed thereon, while end wall 29
has a journal 34 formed thereon, said journals rotatably supporting
blocking rotor 16 within housing 11 as described below. As seen,
journal 33 is longer than journal 34.
Referring now to FIGS. 6 7 and 7a, displacement rotor 15 is illustrated
in detail, it being understood that in a preferred embodiment of
the present invention, displacement rotors 15 and 17 are identical
in construction and the following description of rotor 15 is also
descriptive of rotor 17. Details of the structure and function of
displacement rotors in general may be found in U.S. Pat. Nos. 3457835
and 3465683 owned by the predecessor of the assignee of the present
application.
Rotor 15 consists of a rotor hub 36 formed integrally with vane
21 and a pair of rotor journals 37 and 38 formed at opposite ends
of hub 36. Journals 37 and 38 rotatably support rotor 15 within
housing 11 as described below and, as seen in FIGS. 6 7 and 7a,
journal 37 is longer than journal 38.
Rotor hub 36 is generally semi-circular in cross-sectional configuration,
with each displacement rotor having a curved outer surface (surface
39 of rotor 15 and surface 40 of rotor 17) as best seen in FIG.
1. In like fashion, each sidewall 30 and 31 of blocking rotor 16
also has a curved outer surface (41 and 42 respectively) which
successively contact and roll against outer surfaces 39 and 40 in
a manner to be described below. To that purpose, hub 36 is shaped
and dimensioned to contact outer sidewall surfaces 41 and 42 when
rotors 15 and 17 are installed in housing 11. The axial length of
vane 21 is such that vane 21 fits inside blocking rotor cavities
35a and 35b, with vane side surfaces 21a and 21b wiping, respectively,
inner end wall surfaces 28a. 28b, 29a and 29b, and web surfaces
32a and 32b as seen in FIGS. 4 8 and 9.
Referring now to FIGS. 8 and 9 details of housing 11 and the mounting
of rotors 15 16 and 17 are illustrated. Shown in FIG. 8 are first
housing end plate 43 and second housing end plate 44 assembled to
support blocking rotor 16 and displacement rotors 15 (not visible)
and 17. For purposes of illustration, the remaining portions of
housing 11 have been omitted to allow details of the rotor placement
and assembly to be observed. In service, housing 11 completely and
fluid-tightly encloses the rotor assemblies. In FIG. 9 a portion
of end plate 43 has been removed to illustrate the details of how
blocking rotor 16 is mounted within housing 11.
Preferably, end plates 43 and 44 are identical and interchangeable,
and end plate 43 will be described in detail, it being understood
that the same configuration and structure is present in end plate
44 as well. As seen in fuller detail in FIGS. 10 11 and 13 end
plate 43 has an interior working surface 45 and an exterior surface
46. Formed on each end plate 43 are bearing support structures 47
48 and 49 with apertures 47a and 49a therethrough within which
are mounted, respectively, bearings 50 51 and 52 (FIGS. 8 and 9).
In FIG. 12 it can be seen that end plate 44 has bearing support
structures 53 54 and 55 formed thereon, with bearings 56 57 and
58 respectively, inserted into the bearing apertures.
As seen in FIG. 8 bearing 50 rotatably supports journal 37 of
inlet displacement rotor 15 bearing 51 rotatably supports journal
33 of blocking rotor 16 and bearing 52 rotatably supports journal
59 of outlet displacement rotor 17 (note that journal 59 corresponds
in size and configuration to journal 37). In like fashion, end plate
44 rotatably supports blocking rotor journal 34 in bearing 57 while
inlet displacement rotor journal 38 is rotatably supported by bearing
56 and outlet rotor journal 59 (not herein shown, but identical
to inlet displacement rotor journal 38) is rotatably supported by
bearing 58.
FIG. 13 illustrates interior work surface 45 of end plate 43 it
being understood that end plate 44 has an identically configured
work surface referred to for convenience as work surface 60. As
seen in FIG. 13 in another aspect of the present invention, a cylindrical
recess 61 is formed as part of end plate 43 with a face 62 and a
sidewall 63 that extend "below" or are set into work surface
45. An identically configured recess 64 is formed in end plate 44.
Recesses 61 and 64 are concentric with, respectively, bearing apertures
48a and 54a and are sized to enclose the opposing end walls 28 and
29 of blocking rotor 16. The opposing cylindrical surfaces 63 on
end plate 43 64a on end plate 44 (FIGS. 8 and 9) and 30-31 plus
the outer portions of end walls 28 and 29 form fluid seals between
the blocking rotor 16 and the end plates 43 44 respectively. Within
limits, the rotor 16 is allowed to float along its axis and holes
such as 64b on plate 44 (FIG. 12) receive any pressure buildup between
the end plate recess 64 and the rotor end wall 28.
Referring to FIGS. 1 4 6 8 and 9 the operation and arrangement
of meter 10 may now be described. Fluid entering meter 10 via inlet
12 moves along flowpath A to impinge upon vane 21 of inlet displacement
rotor 15 rotating rotor 15 about axis 20 in direction B. Rotors
15 16 and 17 rotate in a timed sequence, with blocking rotor 16
rotating in direction C, to allow vane 21 to enter, sweep through
and clear cavity 35a. As rotor 15 sweeps through cavity 35a, the
vane side surfaces 21a, 21b closely pass along the inside surfaces
28a, 29a of endwalls 28 and 29. Although the vane and cavity surfaces
are rotating in opposite angular directions, during a part of the
time vane 21 is in cavity 35a, the linear directions of their movements
temporarily approximate one another. For example, as seen in FIG.
1 although blocking rotor 16 is rotating clockwise and inlet displacement
rotor 15 is rotating counterclockwise, vane 21 and cavity 35a are
both moving toward inlet 12. The relative movement between vane
side 21a and cavity side wall surface 28a is very small during that
portion of their rotation. This similar relative movement provides
for more efficient passage of fluid through the meter than heretofore
known.
As seen in FIG. 1 when vane 21 is fully within cavity 35a, arcuate
hub 40 of outlet displacement rotor 17 contacts and rolls along
arcuate web sidewall outer surface 41 as rotor 17 rotates about
axis 25 in direction B. As flow continues, vane 21 clears cavity
35a as blocking rotor 16 rotates to bring outer surface 41 into
contact with the outer arcuate surface 39 of rotor 15. During this
sequence, rotor 17 rotates to bring vane 26 into cavity 35b. As
can be appreciated, continued flow serves to repeat the foregoing
sequence, with vanes 21 and 26 intermittently entering, sweeping
through and clearing cavities 35a and 35b. The presence of blocking
rotor 16 and the close movement of vane ends and sides 21a, 21b
and 27 respectively, along respective cavity side surfaces 28a,
29a, 28b and 29b, the close movement of end wall rims 65 and 66
along sidewalls 63 of recesses 61 and 64 the close movement of
blocking rotor end walls 28 and 29 along faces 62 of recesses 61
and 64 and the rolling movement of rotor hub surfaces 39 and 40
along blocking rotor outer surfaces 41 and 42 keeps the process
fluid substantially confined to and moving forward along flow path
A from inlet 12 to outlet 14 in a more efficient and less restrictive
manner than heretofore known.
Timed rotation of rotors 15 16 and 17 is described in U.S. Pat.
Nos. 3457835 and 3465683 and is accomplished in the present
invention as seen in FIG. 14 by mounting a timing gear 68 to journal
37 of inlet displacement rotor 15 as journal 37 protrudes through
bearing 50 mounting a timing gear 69 to blocking rotor journal
33 as it protrudes through bearing 51 and mounting a timing gear
70 to journal 53 of outlet displacement rotor 17 as it protrudes
through bearing 52. Rotation of rotors 15 16 and 17 are kept in
timed sequence to prevent jamming of vanes 21 and 26 with blocking
rotor 16.
As can clearly be seen when comparing FIG. 1 in this application
with FIG. 1 in the aforementioned U.S. Pat. No. 5513529 the diameter
of the blocking rotor has decreased relative to the radial length
of the displacement rotor blades. As a consequence, the housing
has a lower profile than housings of prior trefoil cavity type positive
displacement meters or pumps. In the embodiments shown in FIG. 1
and FIG. 5 of the '529 patent, with the blocking rotor and displacement
rotor blade being of the same axial length, the radial length of
the displacement rotor blade is limited by the radial dimension
of the blocking rotor hub. Those two dimensions add up to the distance
between the displacement rotor axis and the blocking rotor axis.
In the present embodiment of the invention, with the blocking rotor
being longer than the displacement rotor, the radial length of the
displacement rotor blade is limited only by one half the thickness
of the blocking rotor web. In other words, the radial length of
the displacement rotor blade may extend to the blocking rotor axis
minus one half the blocking rotor web thickness. The blocking rotor
journals and adjacent strengthening structures are now positioned
completely axially outwardly of the displacement rotor blade so
they are no longer a limitation on radial blade length.
As one can see in FIG. 1 the other dimensions which must add up
to the perpendicular distance between the blocking rotor axis and
the displacement rotor axis, are the hub radius of the displacement
rotor and the blocking rotor radius. The sums of each of those two
sets of dimensions must be equal. Given these design limitations,
both the displacement rotor hub radius and the radial blade length
may be increased if the blocking rotor radius and web thickness
are correspondingly decreased. Therefore, the positive displacement
device of the invention has a smaller blocking rotor diameter than
found in such heretofore known devices.
Referring to FIG. 15 a second embodiment of the meter of the invention
is generally indicated at 110 with the housing removed for clarity.
In this second embodiment, the meter is rotated 90 degrees for mounting
with the axes of the displacement rotor 17 and blocking rotor 16
positioned vertically. In this orientation the top and bottom end
plates 143 144 have differing thicknesses of construction for differing
reasons. First, in order to lessen rotor drag, the top bearings
150 151 152 (not shown) are ball or needle bearings. The bottom
bearings, such as shown at 156 are bushings as in the first embodiment.
The rotors are mounted vertically in the housing by means of shims
such as shown at 157 positioned between the rotor and the bottom
end plate. The bushings 156 etc., are more able to withstand a
dirtier environment at the bottom of the meter caused by any sediment
in the fluid. The ball bearings 150 151 etc., perform well and
longer with less drag in the cleaner environment at the top of the
meter.
Additionally, in order to prevent or lessen any potential for contamination
if differing fluids are passed through the meter at differing times,
the amount of fluid retained in the meter outside of the normal
fluid flow path must be minimized. For example, such events may
occur in commercial tank transport trucks carrying differing grades
of gasoline at differing times. Fluid may be retained in the meter
between the end plates 143 144 and end covers (not shown) that
are mounted over the end plates. Such end covers are shown in FIG.
3 at 12 and 13 of U.S. Pat. No. 5513529 issued to the predecessor
of the assignee of the present invention, and are incorporated herein
by reference. Since the bottom end plate 144 does not have gears
mounted thereadjacent, the spaces where those gears would have been
needed to be filled in on the end plate. Also, an end cover may
be reshaped to lessen the size of or eliminate any cavity in the
bottom of the meter.
At the top of the meter, the wall thickness of end plate 143 should
be increased and the spaces denoted at 143a, 143b, 143c on the top
of end plate 143 should be filled in to closely surrounds the gears
(not shown) when they are mounted on journals 133 137 153. The
top end cover may also be modified to eliminate internal cavities.
In this manner, most of the cavity space in the end plates will
be eliminated and the amount of residual fluid in the meter will
be substantially lessened. The meter will be easier to flush or
clear and the purity of fluids passed therethrough will also be
enhanced.
While the foregoing has presented a description of two embodiments
of the present invention, it is to be understood that this description
is presented by way of example only and is not intended to limit
the scope of the present invention. It is expected that others skilled
in the art will perceive variations which, while differing from
the foregoing, do not depart from the spirit and scope of the invention
as herein described and claimed. |