Abstrict A fluid flow meter of fluid-tight, sandwiched assembly of three
flat faced plates with transparent, fluid impervious sheets interposed
between the plates. The central plate is symmetrically tapered to
be wider at the upper end than at the lower end. Each of the three
plates has at least one elongated slot cut therethrough with the
slots in coplanar alignment in the sandwiched assembly. The central,
tapered plate has extensions at either end of the slot cut less
than all the way through from the same side of the plate. The plate
and transparent sheet adjacent to the side of the tapered plate
containing the slot extension have perforations therethrough aligned
to permit passage of fluid from the outside of the meter through
the extensions to the slot in the central plate. A plummet is inserted
in the slot in the second plate.
Claims I claim:
1. A fluid flow meter comprising a fluid-tight, sandwiched assembly
of a first flat faced plate; a first sheet of transparent, fluid
impervious material; a second flat faced plate; a second sheet of
transparent, fluid impervious material; and a third flat faced plate;
all co-extensive in face size;
(a) each of said plates having at least one elongated slot cut
therethrough, said slots of the same length and width and said plates
assembled with slots in coplanar alignment;
(b) said second plate symmetrically tapered to be wider at the
upper end than the lower end; and having extensions of said slot
cut less than all the way through said second plate with a perforation
extending through the second plate into said extension at each end
of the second plate;
(c) the sheet assembled adjacent to a perforation in the second
plate having a perforation therein aligned with the perforation
of said second plate;
(d) the plate assembled adjacent a perforated sheet having a perforation
therein aligned with the perforation in said sheet thereby forming
passage for fluid from outside the meter to the slot in said second
plate; and
(e) a plummet inserted in the slot in the second plate.
2. A fluid flow meter of claim 1 wherein said plummet in the slot
of the second plate is a weighted ball.
3. A fluid flow meter of claim 1 wherein each plate has one slot.
4. A fluid flow meter of claim 1 wherein each plate has a multiplicity
of slots in coplanar alignment with the corresponding slots of the
other plates.
5. A fluid flow meter of claim 1 wherein the extensions of the
slot are cut about half way through said second plate.
6. A fluid flow meter of claim 1 wherein the perforations in the
plates are machined and threaded to receive similarly threaded connections.
7. A fluid flow meter of claim 6 wherein the threaded connections
are screwed in the perforations in said plates pressing against
a transparent, fluid impervious material sheet.
8. A fluid flow meter of claim 1 wherein the slot extensions are
both on the same side of the second plate.
Description BACKGROUND OF THE INVENTION
This invention relates to fluid flow meters. In one of its aspects
this invention relates to the construction of fluid flow meters.
In another of its aspects this invention relates to fluid flow meters
of the variable area type (rotameter).
Fluid flow meters of the variable area type having plummet cavities
of rectangular cross-section are well known in the art. The present
invention provides a construction for such a fluid flow meter in
which there is a rectangular cross-section through the flow cavity
with the cavity having two parallel sides and two sides forming
a wedge-shaped opening so that the plummet sits loosely in the base
of the rectangular space at the bottom of the cavity. The body of
the cavity diverges upward in the shape of a truncated pyramid so
that a plummet placed in this chamber can be carried by fluid flowing
upwardly through the chamber and the flow of the fluid is indicated
by the height attained by the plummet. Such devices have been produced
by milling appropriately tapered cavities in solid blanks, but such
production requires expensive procedures. The fluid flow meter of
the present invention incorporates ease of construction with uncomplicated
design to provide a relatively inexpensive fluid flow meter having
a wedge-shaped plummet cavity.
It is, therefore, an object of this invention to provide a fluid
flow meter having a wedge-shaped plummet cavity. It is another object
of this invention to provide a fluid flow meter of comparatively
simple and economical construction.
Other objects, aspects, and the various advantages of this invention
will be apparent upon study of this specification, the drawing,
and the appended claims.
STATEMENT OF THE INVENTION
A fluid flow meter is provided comprising a fluid-tight, sandwiched
assembly of a first flat faced plate; a first sheet of transparent,
fluid impervious material; a second flat faced plate; a second sheet
of transparent, fluid impervious material; and a third flat faced
plate. All of the plates and transparent sheets are co-extensive
in the size of their faces. Each of the plates has at least one
elongated slot cut entirely through the plate with the slots of
each plate being the same length and width. On assembly the plates
are arranged with the corresponding slots in coplanar alignment.
The second plate is symmetrically tapered so that it is wider at
the upper end than at the lower end and has extensions cut at either
end of the slot less than all the way through the plate. The extensions
can be on opposite sides of the plate, but are preferably on the
side of the plate that is assembled adjacent to the second sheet
of transparent, fluid impervious material. The sheet of fluid impervious
material and the plate assembled adjacent to an extension in the
second plate have perforations therein that are positioned to be
aligned with the extensions of the slot in the second plate in the
sandwiched assembly. These perforations aligned with the extensions
of the slot in the second plate provide a passage for fluid from
the outside of the flow meter to the slot in the second plate. A
plummet is inserted in the slot in the second plate.
In a preferred embodiment of the invention a perforation in an
outside plate is machined and threaded to receive a similarly threaded
piping connection. The connection provides passage from the outside
into the meter. For use in processes in which particularly corrosive
fluid is to be measured, the threaded connections and the tapered
plate can be made of metal that is not corroded by the fluid being
measured, eliminating excessive costs often experienced when the
whole body of a fluid flow meter must be made of exotic material
to combat corrosion. In the apparatus set forth herein the corrosive
material can be contained within threaded connections on the inlet
and outlet of an outside plate and within the slot and slot extensions
of the tapered plate with the outside plates, i.e., the first and
third plates, being protected by the transparent, fluid impervious
material sheets that are sandwiched on either side of the tapered
plate.
It is easily seen that the material of construction of the three
flat faced plates can be any material that has sufficient structural
strength to be formed into the plates and have slots cut therethrough.
The usual material of construction would be metal although rigid
plastic or glass are also useful.
Any material that can be formed into a transparent sheet that is
impervious to the fluid contemplated for measurement can serve as
the sheeting that is sandwiched between the plates to provide observation
ports in the meter. For general purposes the thickness of the sheeting
will depend upon the strength of the sheeting material. Such materials
as transparent plastics of polyolefin film, acetate film, Lucite,
or Kel-f fluorocarbon polymer are exemplary. If relatively high
pressure is to be withstood the plastic sheets can be reinforced
with glass plates or, depending upon the fluid being measured, glass
plates can be substituted entirely.
The plummet also can be made of any material commonly used for
plummets which is resistant to the fluid that will be passed through
the flow meter. The plummet can be made of metal, teflon, poly(arylene
sulfide), or other fluid-resistant materials.
The sandwiched assembly of plates and transparent sheet can be
held together by clamping plates arranged around the edges of the
assembly or holes may be drilled through the sandwiched assembly
for the insertion of bolts which can be locked with nuts on either
end. The arrangement of threaded bolts to hold the sandwiched assembly
together in fluid-tight alignment would be apparent to anyone skilled
in the art.
Some of the advantages of the device described include the fact
that the flow meter can easily be mass produced using simple, inexpensive
machining operations in which blanks can be punched or broached
to rough dimensions and then ground, burnished, or polished to final
tolerances. The tolerances in machining the central, tapered plate
and in machining the slot within this plate are not as critical
as would be necessary in producing a conical bore; for instance,
a 2 percent error in the width of the slot would result in only
a 2 percent cross-sectional error while a 2 percent error in the
diameter of the conical bore would yield 4 percent error in the
circular cross-sectional area of the conical bore. The transparent
sheets sandwiched between the plates can be punched out to size
for easy production and can be changed without affecting the calibration
of the fluid conducting tube. The sandwiched assembly can be made
fluid-tight without the use of seals or O-rings since the sealing
of ports is accomplished using straight-threaded fittings that can
be screwed through the outer pressure plate to bear against the
transparent sheet, pressing this sheet firmly against the body of
the central plate. These fittings can be screwed in place by such
simple devices as jam-nuts run up tightly against the pressure plate.
One of the outstanding features of this device is that a multiplicity
of slots can be cut in parallel alignment through a tapered plate
and sandwiched with transparent sheets and slotted pressure plates
to provide a bank of fluid flow meters within a single apparatus
body. Such an apparatus could be of distinct usefulness in the measurement
of flows for test apparatus or laboratory apparatus such as chromatographs.
The apparatus and method of this invention can best be understood
by studying this specification in conjunction with the drawing.
In the drawing FIG. 1 is an exploded view of the apparatus showing
an exaggerated taper for the central plate;
FIG. 2 is a front elevation of a sandwiched assembly; and
FIG. 3 is an isometric view of a device according to this invention
containing three plummet cavities.
Referring now to FIG. 1 and FIG. 2 the first plate 1 is a rigid
flat faced plate having a rectangular face and of sufficient thickness
to provide the strength necessary to serve as a pressure plate.
This first plate has cut therethrough a slot 3.
Assembled next to the first plate is a first sheet 5 of transparent,
fluid impervious material. This sheet is co-extensive in face size
with the first plate.
The second plate 7 is assembled with the first transparent sheet
5 and the first plate 1 so that the first transparent sheet 5 is
sandwiched between the plates. The second plate is located centrally
in the sandwiched assembly and is pierced by elongated slot 9. Slot
9 is co-extensive with slot 3 in the first plate 1 and in the assembled
apparatus the slots are coplanar. The second plate also has extensions
11 13 of slot 9 cut less than all the way through the plate. These
extensions of the slot are on the side of the plate next to the
first transparent sheet 5 and in conjunction with perforations 12
and 14 extending through the second plate to the side adjacent the
second sheet provide in the assembled apparatus access of fluid
through the slot 9. The diameter of perforations 12 and 14 is no
larger than the inside diameter of fittings 29 and 31 hereinafter
described. Perforations 12 and 14 provide access to extensions 11
and 13 respectively.
The second plate 7 has as its most important feature a symmetrical
taper so that the upper part of the plate is wider than the lower
part of the plate. The taper of this central plate is important
because it provides an increase in the size of the bore created
by the slot cut through the plate that enables measurement of fluid
flow by lifting a plummet in a bore of increasing transverse cross-section.
The walls of the slot cut through the plate are parallel. The increase
in cross-sectional area for the plummet bore is provided by the
increase in the width of the plate from the bottom to the top of
the plate.
A second sheet of transparent, fluid impervious material 15 is
assembled adjacent to the side of the second plate 7 opposite the
side of that plate that contains the extensions 11 13 of the slot
9. The second transparent sheet has perforations 17 19 which are
aligned with, and of no greater diameter than, the perforations
12 and 14 of the second plate 7. These perforations 17 19 in the
sheet provide access of fluid through the sheet, through perforations
12 and 14 in the second plate into the cavity in the second plate.
The third plate 21 is assembled adjacent to the second transparent
sheet 15 so that the second sheet is sandwiched between the third
plate 21 and the second plate 7. The third plate also contains a
slot 23 cut therethrough which is co-extensive with the slot 9 of
the second plate 7 and the slot 3 of first plate 1. In the assembled
apparatus the three slots are in coplanar alignment. The third plate
also has perforations 25 27 cut therethrough which are aligned
with the perforations 17 19 in the second transparent sheet to
permit the passage of fluid through the plate and second sheet into
perforations 12 and 14 of the second plate.
In a preferred embodiment of the invention, connections 29 31
comprising threads 33 35 along a length of the connection at least
sufficient to pass through the perforations 25 27 in the third
plate 21 are provided for insertion into the perforations 25 27
of the third plate. This requires that the perforations in the third
plate be machined and threaded to mate with the threads on the connections.
The connections are inserted through the third plate and jammed
against the second sheet to seal the second sheet against the second
plate in fluid-tight alignment.
The final element of the apparatus is a plummet 37 or ball float
which is inserted in the slot 9 or cavity in the second plate 7
during the assembly of the apparatus. The ball float is sized to
fit within the base of the cavity formed by the sides of slot 9
and the sandwiching of the transparent sheets 5 15 against the
faces of second plate 7. The extensions 11 13 in the slot 9 of
the second plate 7 are of sufficiently less depth than the slot
to prevent escape of the plummet 37 from the slot 9.
In FIG. 2 which is a view of the face of the assembled apparatus,
it can be seen that the slots 23 9 3 of the third plate 21 the
second plate 7 and the first plate 1 are aligned to provide with
the two transparent sheets 15 5 a view through the slots of the
cavity containing the plummet 37. In this view the alignment of
the connections 29 31 through the perforations into the extensions
11 13 of the slot 9 can also be seen.
Referring now to FIG. 3 an assembled device containing three plummet
cavities 41 is shown. Each of the cavities 41 is formed by the juxtaposition
of transparent sheets 15 5 with the slot 9 of tapered plate 7.
A plummet 37 rests within each cavity. Pressure plates 21 1 form
the outside protective cover for the sandwiched assembly. All of
the elements of the assembly are pierced by a multiplicity of holes
through which threaded bolts 43 are passed with nuts 45 on either
end tightened to provide fluid-tight assembly.
Referring now to all the drawings, in operation, fluid is passed
through the threaded connection 31 at the base of a plummet cavity
39 which passes through the perforation 27 in the third plate 21
and the perforation 19 in the second transparent sheet 15 to give
access to perforation 14 and to the extension 13 of slot 9 in the
second plate 7. Fluid passes through the extension 13 into the plummet
cavity 39 formed by the walls of slot 9 and the sandwiched transparent
sheets 15 5 cut through the upper extension 11 of slot 9 and perforation
12 and through the perforation 17 in the upper portion of sheet
15 and the perforation 25 in the upper portion of the third plate
21 by means of the threaded connection 29. The fluid passing through
the cavity 39 lifts the plummet 37 to a height dependent on the
volume of fluid flowing therethrough. Calibration of flow can be
carried out by methods well known in the art with the calibration
being performed after assembly of the apparatus or the size of the
cavity can be designed to a specific calculated calibration dependent
on the weight of the plummet.
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