Internal loading cylindrical filter with unsupported tubular filter fabric

An internal loading cylindrical air filter apparatus having a circular tubular knit pile fabric filter element extending unsupported between end plates to provide an essentially full length unobstructed filter area, and having a rotating internal suction cleaning nozzle therefor. The tubular filter element is supported at its entry end by a detachable angle ring having a cylindrical ring flange extending through an opening in the entry end plate of the apparatus to permit endwise assembly and disassembly of the fabric filter element into the apparatus. Annular or helical strands may extend in circumferential engagement with the filter element for restraining it from ballooning out of effective cleaning distance with respect to the rotating suction nozzle under heavy filtering conditions, and a crank may be provided for adjusting the extending length of a helically extending restraining strand for controlling the degree of restaint imposed on the filter element.

BACKGROUND OF THE INVENTION 
Internal loading cylindrical filters are well known, and U.S. Pat. No. 
4,154,588 is exemplary of current developments in the art. This patent 
discloses a knit pile fabric filter element which is stretched in tubular 
form over a helically-wound metal rod support frame. The pile of the 
fabric is on the inside, and a lengthwise zipper is provided in the 
tubular fabric filter element for ease of assembly over the helical 
support. The small helically-travelling cleaning nozzle of the filter 
apparatus has been found not to be entirely suitable in applications where 
large quantities of fine wood and paper fiber are being recaptured for 
reuse after the fiber has been concentrated in smaller amounts of air by 
passage through a cyclone separator. 
U.S. Pat. Nos. 1,944,267 and 1,944,268 disclose the only known unsupported 
cylindrical fabric filter elements with self-cleaning nozzles; however, in 
these patents the nozzles are of annular configuration and move lengthwise 
through the cylindrical filter elements, piston-like, and the axes of the 
cylindrical filter elements are in a vertical position for a "bag-house" 
application whereby it might be assumed that the long, narrow, heavy, 
woven, woolen tubular filter elements used for filtering purposes at that 
time would be relatively rigid, and that the piston-like movement of the 
cleaning nozzles therefore had no tendency to disturb the original 
cylindrical form of the filter element, but rather to maintain it. 
Moreover, the vertical disposition of the filter elements did not result 
in any tendency of such elements to bow at the center if not supported, as 
would be the case if the filter elements were arranged horizontally 
between two end plates. 
Two additional U.S. Pat. Nos. 1,995,648 and 2,057,446, having the same 
inventor as the last-mentioned pair of patents, disclose vertical 
cylindrical filter elements in which the filter medium is a fibrous 
material such as steel or mineral wool, and the medium is fastened to a 
supporting screen or wire mesh cover for greater strength, rigidity, and 
durability of the filter element. In both of these patents, the 
cylindrical proportions of the filter elements are those of conventional 
drum filters, unlike bag house filter elements, and full length rotating 
suction nozzles serve to clean the filtered-out waste material from the 
interior of the filter element, with biasing means being provided to 
assure that the filter elements and suction nozzles stay in contact. 
The present invention provides the advantage of a relatively inexpensive, 
very flexible knit fabric filter medium having a pile component which 
provides a "surface loading" filter effect wherein the pile fibers lie 
down as the dirty air passes through the filter element from the pile 
side, thereby trapping the waste dust or fibers on the surface; then, as 
the suction nozzle passes, the pile fibers are sucked up perpendicular to 
the filter element and the waste material is easily and thoroughly sucked 
therefrom. The knit filter element in tubular form is quite flexible and 
can be readily stretched taut between the end plates of the filter 
apparatus to assume a cylindrical shape in which the internal rotating 
cleaning nozzles are adjacent the knit fabric, and the filter element may 
be assembled in place from the ends of the filter apparatus without need 
for access from the sides thereof (which are usually inaccessible due to 
the typical "built-in" arrangement of the filter apparatus), with a unique 
end support structure being provided for the filter element to permit this 
ease of assembly. In some cases of extremely heavy waste build-up inside 
the filter element, the force of air passing through the knit fabric 
element causes it to have a tendency to "balloon" out of its normal taut 
cylindrical shape, and, in accordance with a further feature of the 
present invention, restraining circumferential flexible strands may be 
used to restrain the filter element from such ballooning tendencies so 
that the rotating nozzle may clean it suitably. 
SUMMARY OF THE INVENTION 
More specifically, the present invention provides an internal loading 
cylindrical air filter apparatus that includes a pair of end plate members 
arranged in spaced relation to one another, a rotating cleaner nozzle 
mounted between the end plate members for rotation about a horizontal axis 
in engagement with bearing means located on said apparatus for said 
rotation and including radially extending suction conduits drive means for 
rotating said nozzle, and a fabric filter element disposed in generally 
circular tubular form to extend between the end plate members and about 
the rotating cleaner nozzle adjacent the radially extending conduits, the 
filter element being supported solely at the end plate members and 
extending tautly therebetween with the portion of the filter element 
between the end plate members being unsupported and unencumbered for 
providing an unobstructed filtering area internally thereof for air passed 
outwardly therethrough between the end plate members, the area being 
thoroughly cleaned during the rotation of the rotating cleaner nozzle. 
Preferably, as noted above, the filter apparatus includes restraining 
strand means extending in generally external circumferential restraining 
engagement with the tubular filter element for restraining the element 
against excessive ballooning as a result of the passage of air 
therethrough, and the strand means may extend annularly or helically 
relative to the tubular filter element, which is preferably formed from 
knit pile fabric. Means may also be provided for adjusting the extending 
length of the helically extending restraining strand means for controlling 
the degree of the restraint imposed upon the tubular filter element 
thereby, and the adjusting means may include a fixed anchoring means 
disposed on one of the end plate members for anchoring attachment thereat 
of one end of the strand and a rotating crank means disposed on the other 
end plate member for attachment at the other end of the strand whereby 
rotation of the crank means will adjust the extending length of the 
strand. 
In the preferred embodiment of this invention, the end of the tubular 
filter element adjacent one of the end plate members finds support on 
annular means extending inwardly of the end plate member from ring means 
having means for retention thereof at the end plate member, and the 
apparatus has means for attaching the filter element to the inwardly 
extending annular support means during temporary disposition of the 
support means exteriorly of the end plate member for permitting assembly 
of the filter element into the filter apparatus endwise thereof where the 
interior of the filter apparatus is inaccessible laterally thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An internal loading cylindrical air filter apparatus 20 according to the 
present invention is typically assembled with three others into a module 
22 as shown in FIG. 1. The module 22 usually rests on a floor with top and 
sides enclosed, such enclosures being omitted for clarity of illustration, 
or a number of the modules may be assembled side-by-side or stacked 
vertically to form filter walls of any desired shape and size. In any 
case, a front end plate 24 is left exposed for the entry of air through 
circular openings 26 therein. 
At each opening 26, an annular angle ring 28 is provided, each ring 28 
having an extending flange 30 for attachment or retention flat against the 
front plate 24 by means of headed screws 32 extending through holes 34 
provided in the flanges 30 and matching mounting holes 36 provided in the 
front plate 24. Cylindrical flanges 38 are provided on the rings 28 for 
extending inwardly through the plate 24 for support of the entry ends 40 
of circular tubular fabric filter elements 42 which are stretched 
therearound. 
The rear structural framework 44 of the module 22 has attached thereto four 
circular end cover plates 46 having annular flanges 48 thereon extending 
inwardly of the module 22. The end cover plates 46 are disposed in axial 
alignment with, and at suitable spacing from, the openings 26 in the front 
plate 24. Hose clamps 50 of suitable size are used to encircle the ends 40 
of the filter elements 42 for securing them over the annular flanges 38, 
and the filter elements 42 may then be stretched tautly through the module 
22 and over the annular flanges 48 of the end cover plates 46 for 
securement there by additional hose clamps 50. 
A tubular bearing member 52 is supported in coaxial relation with each 
angle ring 28 by support bars 54 attached therebetween, as by welding. The 
bearing member 52 supports the front end of a tubular suction manifold 56 
which extends coaxially for horizontal rotation about its axis between the 
ring 28 and the end cover 46 and has a smaller, extending, end-plugging 
portion 58 which extends through an opening 60 in the cover 46 to carry at 
the end thereof a suitable sprocket 62 attached thereto for rotary drive 
of the manifold 56, the end portion being supported in the opening 60 by a 
bearing (not shown). 
Two radially extending suction conduits 64 are attached to each manifold 56 
in communicating relation with the hollow bore of the manifold 56 and 
extending therefrom in opposite directions for dynamic balance of the 
rotating cleaner nozzle apparatus 66 formed thereby. The conduits 64 are 
elongated in the axial direction of the manifold 56, are hollow, and 
extend radially therefrom so that the open ends thereof are located 
adjacent (in contact or in close proximity with) the internal surface of 
the filter element 42 thereby forming rotating cleaner nozzles therefor. 
Suction slots 68 at the extending ends of the conduits 64 extend parallel 
to the axis of the conduit 56 and are of suitable length such that upon 
rotation of the manifold 56, the two oppositely disposed suction slots 
will cover and clean essentially the entire interior surface of the filter 
element 42 during each revolution of the manifold 56 when suction is 
applied thereto. 
Suction may be applied to the manifolds 56 by flexible suction hoses 70 
suitably attached to the bearing members 52 and extending therefrom to a 
suction header (not shown) which may be connected to any convenient source 
of suction, such as the central suction system of a manufacturing plant. 
The manifolds 56 are rotated in unison by a chain drive 72 engaging each 
of the sprockets 62 and entrained also around an idler sprocket 80 mounted 
on the framework 44 for free rotation and around a drive sprocket 74 
affixed to the shaft 76 of an electric gearmotor 78 mounted on the rear 
framework 44 of the module 22. 
Annular restraining strands 82 may be sewn-in or otherwise arranged in 
circumferential engagement with the tubular filter elements 42 to restrain 
the filter elements 42 from ballooning excessively as a result of air 
passing therethrough. While the strands may be formed of any material that 
provides the necessary restraint for the filter elements, it has been 
found that heavy denier nylon is particularly effective with filter 
elements formed of knit pile fabric. 
As an alternative to the annular strands 82, helically extending strands 84 
may be wrapped around or intertwined with the filter elements 42 as 
illustrated in FIG. 4 so that the length of helical strands 84 may be 
adjusted to control the degree of restraint imposed on the filter elements 
42. One end of each strand 84 is anchored under a screw head 86 fixed to 
the cylindrical flange 38, and the other end is attached to a wind-up 
crank means 88 mounted for rotating on a clamp screw 90 engaged with the 
end cover 46 as shown in FIGS. 4, 5 and 6. Counter-clockwise rotation of 
the handle 92 of the reel 88 (to some other position as exemplified in 
broken lines at the numeral 92' in FIG. 5) adjusts the extending length of 
the strand 84 for controlling the degree of restraint imposed upon the 
tubular filter element 42 by the strand 84 to control the ballooning 
thereof; and when the strand 84 has been adjusted to a desired length, the 
crank means 88 may be locked in place by tightening the clamp screw 90. 
In normal operation, air containing waste dust or fibers is blown or sucked 
against the front plate 24 and thereby caused to pass through the openings 
26 to the interior of the filter elements 42, which are unsupported, 
unencumbered, and unobstructed for essentially their full lengths between 
the end plates 24 and 46. The air then passes through the unobstructed 
area of the filter elements 42 in a radial direction, thereby causing the 
pile fibers on the inner surface of each filter element 42 to lie down 
flat and form the aforesaid surface loading filter medium. After passing 
through the filter element 42, the now clean air may pass out through the 
rear framework of the module 22 or laterally thereof, depending on the 
particular installation. If the air is heavily loaded with dust or fibers, 
the rotating nozzle apparatus 66 may be operated continuously, and suction 
may be applied thereto continuously; but if the loading is not heavy, 
automatic controls (not shown) may be used to operate the suction source 
and the nozzle apparatus 66 only as required, to reduce power consumption, 
in which case the build up of waste inside the filter element may result 
in even better filtering. In cases where the waste build up is extremely 
heavy and rapid within the filter element, or unusually high air 
velocities are maintained, it may be desirable to provide the reinforcing 
and restraining strands 82 or 84 in order to prevent the filter element 42 
from ballooning out to the extent that the suction nozzles are no longer 
close enough to clean the interior surface of the element 42. 
A drawback to previous cylindrical cell internal loading filters, such as 
those disclosed in the aforesaid U.S. Pat. No. 4,154,588, has been the 
difficulty of assembling and disassembling a filter element into and out 
of the apparatus, and the aforesaid patent discloses a zipper running 
lengthwise of the tubular knit fabric filter element so that the filter 
element can be handled in flat form and wrapped around the helical support 
structure and then be zipped-up to keep it in place. In the apparatus of 
the present invention, it is a simple matter to disassemble the filter by 
loosening the hose clamp 50 at the end cover 46 from the open rear portion 
of the module 22, and then, from the front side of the module 22, to 
remove the angle ring 28 from the front plate 24, withdrawing it 
sufficiently to allow removal of the hose clamp 50 from the entry end of 
the filter element 42. Assembly is readily accomplished by reversing the 
process, assembling the clamp 50 over the entry end 40 of the filter 
element 42 while it is stretched over and supported by the cylindrical 
flange 38 of the angle ring 28 and while the flange 38 is temporarily 
disposed exteriorly of the end plate 24. The clamp 50 having been 
tightened to hold the filter element end 40, the angle ring 28 may be 
reassembled with the plate 24 to support the filter element end 40 
adjacent the inside of plate 24. Then, working from the rear end of the 
module 22, the filter element 42 with another hose clamp 50 thereover may 
be pulled out and stretched over the annular flange 48 of the end cover 46 
and the clamp 50 lightly tightened thereabout to hold the filter element 
42 in place while it is pulled through between the clamp 50 and the flange 
48 to smooth out any wrinkles and achieve suitable tautness in the tubular 
filter element 42 before final tightening of the hose clamp 50. This ease 
of assembly and disassembly is quite advantageous in that lateral access 
to the filter apparatus 20 and the filter element 42 may be effectively 
blocked by the other filter apparatus in the module 22, adjacent modules 
22, or by whatever enclosing walls may surround the module 22. 
The structural elements of the present invention work together to provide 
outstanding commercial advantages in that the use of the knit pile filter 
fabric permits the use of a simple relatively inexpensive support and 
housing structure for small internal-loading filter units which are 
ideally suited for multi-filter modules that may be built into building 
structures to form filter walls of varying sizes and shapes. The effective 
filter area in these filter walls is more concentrated, and such filter 
walls are more adaptable to existing structures than the conventional, 
large, cylindrical drum filters, yet they generally require less floor 
space. 
Since the knit pile fabric may be stretched taut to support itself, the 
filter elements need be supported only at the ends, thereby providing a 
significant increase in effective filtering area as compared to 
conventional screen-supported elements, or even the helically-wound 
support of the aforesaid U.S. Pat. No. 4,154,588, where the supporting 
members cover a significant area of the filter element that cannot be 
utilized for filtering purposes and also interfere with the cleaning of 
the element. Also, whereas there was no convenient way to attach the knit 
pile fabric of the aforesaid patent to the helical support to prevent 
ballooning, the circumferential restraint strands disclosed herein provide 
simple and effective restraint in a way which could not be achieved in 
external-loading filters. 
Elimination of any support structure except at the ends of the tubular 
filter element makes it possible to provide an end support structure which 
permits assembly and disassembly of filter elements to and from the filter 
units or modules thereof by endwise access alone, thereby providing a 
considerable maintenance advantage; and it also permits forming the filter 
elements permanently into tubular form, without need for the lengthwise 
zippers which were required for the aforesaid U.S. Pat. No. 4,154,588. 
The details of the preferred embodiment described herein are for disclosure 
purposes only and are not intended to represent the only apparatus for 
internal loading cylindrical air filters which might lie within the scope 
of this invention, but the scope is to be determined only by the claims 
appended hereto.