Abstrict
A duplex filter cloth for chamber type filters has two initially
separate pieces secured together, as by stitching, around circumferential
terminal edges of turned-down collar portions of the respective
pieces, which portions are closely and smoothly interlapped to provide
a barrel neck for the duplex filter cloth. Turning down of the collar
portions is accomplished by an elongate conical mandrel of a jig
press which operates relative to mandrel-receiving openings in pairs
of bed plates, inserted in turn in such jig press, to effectively
turn-down circumferential marginal portions of filtrate feed openings
of respective flat filter cloth sheets.
Claims
I claim:
1. A duplex filter cloth product for use on chamber type filter
presses, comprising two initially separate pieces of a filter cloth
material each having a filtrate feed opening intermediate its periphery,
the opening of one being of less diameter than that of the other
and each having the circumferential margin of such opening turned
down and interlapped as component collar parts of a barrel neck
for such product, the piece with feed hole opening of lesser diameter
having its turned-down margin closely and smoothly fitted over and
against the turned-down margin of the other and defining the filtrate
feed hole of the final product; and means attaching said turned-down
interlapped margins to each other to retain the close and smooth
fit.
2. A duplex filter cloth product according to claim 1, wherein
the means attaching the turned-down margins to each other comprise
circular lines of stitching around the terminal edges of the respective
turned-down margins at opposite circumferential portions of the
barrel neck.
3. A duplex filter cloth product according to claim 1, wherein
the turned-down circumferential margin of the one filter cloth piece
overlaps substantially fully the margin of the other when the two
pieces are placed together in interlapping relationship.
4. A method of fabricating a duplex filter cloth product for use
on chamber type filter presses, comprising cutting out from sheet
filter cloth material two separate flat sheets having respective
filtrate feed openings intermediate the periphery thereof, the opening
of one being of less diameter than that of the other; turning down
the circumferential margin of the feed opening of said sheets of
filter cloth material to provide two filter cloth pieces having
respective turned-down margins that will interlap when the two pieces
are placed together with the interlapped margins serving as component
parts of a barrel neck for the duplex filter cloth product; placing
the so-formed pieces together so that the turned-down margin of
the one with filtrate feed opening of less diameter is closely and
smoothly fitted over and against the turned-down margin of the other
to define the filtrate feed hole and the barrel neck of the final
product; and attaching said turned-down margins to each other so
as to achieve the close and smooth fit.
5. A method according to claim 4, wherein the turned down margins
are attached to each other by sewing around the terminal edges of
the respective turned-down margins at opposite circumferential portions
of the barrel neck.
6. A method according to claim 4, wherein the turned-down circumferential
margin of the filtrate feed opening of the one filter cloth piece
overlaps substantially fully the margin of the other when the two
pieces are placed together in interlapping relationship.
7. A method according to claim 4, wherein margins bordering the
filtrate feed openings of the respective flat filter cloth sheets
are turned down by placing said sheets on corresponding bed plates,
respectively, in a jig press having an open bed for supporting the
bed plates in turn, said plates having respective, appropriately
sized, mandrel-receiving openings, said sheets being placed with
the centers of their openings coincident with the centers of the
openings of the respective bed plates; by forcing, in turn, an appropriately
sized, conical, mandrel plunger into the respective filtrate feed
openings of said flat filter cloth sheets, small end first; and
by advancing, in turn, said mandrel plunger into said filtrate feed
openings until the circumferential marginal portions bordering said
filtrate feed openings of the respective sheets are turned down
against the bed plate by pressure of said mandrel plunger.
Description BACKGROUND OF THE INVENTION
1. Field
The invention is in the field of fabricated filter cloths for installation
on chamber type filter presses prior to passing a solids-containing
liquid therethrough to remove the solids from the liquid. Such filter
cloths are commonly called "duplex" filter cloths.
2. State of the Art
Duplex filter cloths in the form of double pieces of sheet filter
cloth material with interconnecting collar about the circumferential
margins of the filtrate-feed openings of the two otherwise separate
pieces are well known and widely used in chamber type filter presses.
The individual filter cloth pieces are conventionally fabricated
from felted filter cloth material by cutting flat sheets, usually
of equal size, from the sheet filter cloth material, inturning inner
margins bordering the respective filtrate-feed openings thereof,
and sewing such inturned margins to corresponding circular margins
of a separate collar, usually made of a strong material such as
a length of a coarsely woven fabric tape. Fabricated in this way,
however, the so-called "barrel neck" collar joining the
two filter cloth pieces together around their filtrate-feed openings
do not fit snugly and smoothly against the supporting structure
of the filter press in which they are installed.
SUMMARY OF THE INVENTION
In accordance with the present invention, a duplex filter cloth
product of the type concerned and of given dimensions to fit a given
size of filter press is fabricated by cutting, from a sheet of conventional
filter cloth material, two individual pieces of similar shape but
of slightly unequal size in that, while their outer peripheries
are normally the same, the diameters of their filtrate feed openings
are not. One is enough less in diameter than the other to allow
its inturned margin to overlap the inturned margin of the other,
such margins being of respective widths that provide for preferably
substantially complete interlap in any of the various sizes in which
such filter cloths are made.
When these margins are inturned and interlapped in the assembly
of the two pieces, circular seams are preferably sewn around opposite
edge portions, respectively, of the composite collar so formed.
It has been found that the resulting double thickness collar, of
the same material of which the duplex filter cloth product is made
and firmly secured together by the seaming or other securing means,
overcomes the difficulties in fit and operative effectiveness of
duplex filter cloths as conventionally made and used.
The duplex filter cloth product of the invention is fabricated
by a unique method of forming the collar portion of each of the
two pieces, preferably utilizing apparatus which, in itself, is
unique. Thus, each piece is cut to the required outer and inner
dimensions and then placed in a jig press equipped with interchangeable
stationary bed plates. The bed plates have central circular openings
differing, respectively, in diameter, there being pairs of such
plates in which the central openings are closely but slightly differently
dimensioned for the same size of the duplex filter cloth product.
The jig press includes a conical plunger serving as a mandrel and
having different diameters intermediate its length adapted to cooperate,
respectively, with the slightly differently dimensioned center openings
of the respective bed plates of a pair to properly turn down the
defining margins of the center openings of the two separate flat
sheet filter cloth pieces used in the assembling of a particular
duplex filter cloth product.
Sewing of the interlapped collar portions of the two filter cloth
pieces about respective terminal edge portions of such collar portions
is ordinarily accomplished by manual operation of a suitable industrial
type of sewing machine, but other securement means may be utilized.
THE DRAWINGS
The best mode presently contemplated for carrying out the invention
in practice is illustrated in the accompanying drawings, in which:
FIG. 1 represents a fragmentary, perspective view of a completely
fabricated, duplex filter cloth product of the invention, looking
into the space between joined, but otherwise separate, filter cloth
pieces to show the smooth interior face of the barrel neck collar;
FIG. 2, a diametric vertical section taken along the line 2--2
of FIG. 1;
FIG. 3, a view in vertical axial section of a jig press preferably
utilized in the forming of the separate filter cloth pieces used
in the fabrication of the duplex filter cloth product of FIGS. 1
and 2, the mandrel plunger being in raised position and a flat,
annular sheet of filter cloth material being shown on a selected
bed plate of the apparatus prior to turn-down of the collar portion;
FIG. 4, a similar but fragmentary view showing the mandrel in a
downward, collar-portion-turn-down position; and
FIG. 5, a schematic showing of the pneumatic work-piece-hold-down
and plunger-operating system of the jig press of FIGS. 3 and 4.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
In its illustrated form, the duplex filter cloth product of the
invention as shown in FIGS. 1 and 2 comprises two filter cloth pieces
10 and 11, each cut from usual sheet filter cloth material and provided
with turned-down collar portions 10a and 11a, respectively, defining
the respective inner, central, filtrate feed openings of the two
pieces 10 and 11, which, together, provide a filtrate feed hole
12 for the duplex product. The turned-down collar portions 10a and
11a are formed from circumferential portions of the respective filter
cloth pieces marginal to the filtrate-feed openings thereof, in
a manner explained hereinafter.
The turned-down collar portions 10a and 11a are interlapped as
shown and secured together in any suitable manner, as by sewing
circular lines of stitching 13 and 14, FIG. 2, around the terminal
edges 15 and 16 of the respective collar portions. As closely and
smoothly interlapped and attached together, these collar portions
form an improved version of what is known in the art as a "barrel
neck" 17.
Interlapping of the turned-down collar portions 10a and 11a of
filter cloth pieces 10 and 11, respectively, is made possible by
the fact that the filtrate feed opening of one of the flat sheets
of filter cloth material, see the opening 18 of the sheet 19, FIG.
3, is of slightly less diameter than is the other and that the turned-down
collar portion, See 19 as of that sheet and of the resultant annular
filter cloth piece, here the piece 10 and the collar portion 10a
thereof overlaps and is fitted closely and smoothly against the
turned-down collar portion of the other, here the piece 11 and the
collar portion 11a, see FIGS. 1 and 2.
The extent of turn-down of the circumferential margins of the feed
holes of the respective flat sheets of filter cloth material is
preferably such that the resulting collar portions interlap substantially
fully when the two filter cloth pieces are placed together.
Each of the two filter cloth pieces 10 and 11 are advantageously
made by placing a properly dimensioned, flat sheet of filter cloth
material, such as the sheet 19, on bed plate, such as shown at 20,
with the center of its filtrate feed opening 18 coincident with
the center of the corresponding but larger opening 20a of the bed
plate. The particular bed plate will be selected from pairs of bed
plates corresponding to given sizes of duplex filter cloth products
for given sizes of filter presses, and one bed plate of each pair
will have the diameter of its opening less than the diameter of
the opening of the other member of the pair by an amount that will
provide for overlapping of the turned down collar portion of the
filter cloth piece, made on the other bed plate of the pair, by
the turned-down collar portion of the filter cloth piece made on
the one bed plate of the pair. This amount will depend on the thickness
of the sheet of filter cloth material from which the individual
flat sheets are cut.
The special jig press comprises a conical plunger 21, FIGS. 3 and
4, working (small end first) within a receiving opening, here 20a,
of a selected bed plate, here 20, and serving as a mandrel. The
large end of the mandrel plunger is attached to the lower end of
an extendable and retractable part 22a of an elongate, vertically
placed, pneumatic cylinder 22 for down and up movement relative
to a framework 23 having horizontal frame members 23a and 23b that
support a bed-plate-receiving bed 24 of the jig press.
The bed plate, 20, fits into a receiving recess 24a of jig press
bed 24, where it remains immovable during operation of the press.
A flat filter cloth sheet, here the sheet 19, FIG. 3, is placed
on its corresponding bed plate, 20, of the selected pair, that has
been fitted into the receiving recess 24a of the bed 24 of the filter
press, being properly aligned therewith and being below a clamping
plate 27 that is placed upon such sheet, 19, and below a series
of pneumatic power cylinders 28, respectively, which plate and power
cylinders serve to clamp such sheet firmly in place during operation
of the press. Power cylinders 28 are mounted on frame members 23c
and 23d of framework 23.
As previously indicated, the conical formation of plunger mandrel
21 has a cross-sectional circumference and diameter at some point
along its length that is adapted to cooperate with the diametric
edge of the opening, 20a, of the selected bed plate, 20, so as to
properly turn down the circumferential margin of the filtrate-feed
opening, 18, 19a, defining the flat filter cloth sheet for interlapping
with the turned-down circumferential margin of its companion filter
cloth sheet in the final fabrication of the duplex filter cloth
product of the invention.
Control of press operation may be effected in numerous ways, but,
as illustrated in FIG. 5, control is manually accomplished through
electrical on and off witches 29 and 30 controlling respective solenoid
operated, pneumatic valves 31 and 32, which control flow of air
through a main line 33 from a suitable source of air pressure, such
as the storage tank of an air compressor (not shown), through a
pressure regulating valve 34 and branch line 35 and sub-branch lines
35a and 35b to top and bottom, respectively, of sheet hold-down,
pneumatic power cylinders 28 and through branch line 36 and sub
branch lines 36a and 36b to the top and bottom of the elongate pneumatic
power cylinder 22.
Valves 31 and 32 may be those produced by Aro Corporation of Bryan,
Ohio, and designated K313FD-120A-109 and 6212FF-120A-1278, respectively.
The conical mandrel plunger 21 of the filter press and the bed
plates, here represented by bed plate 20, are advantageously of
wood so as to yield somewhat as the mandrel plunger is pressed into
the receiving opening of the bed plate and wedged against the turned-down
circumferential margin of the flat filter cloth sheet, here represented
by the sheet 19.
Whereas this invention is here illustrated and described with specific
reference to an embodiment thereof presently contemplated as the
best mode of carrying out such invention in actual practice, it
is to be understood that various changes may be made in adapting
the invention to different embodiments without departing from the
broader inventive concepts disclosed herein and comprehended by
the claims that follow.
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