Compact filter mounted in a cassette frame

A bag-type filter having a removable filter element, said element being mounted in a cassette frame which may be inserted and removed from the filter housing. The filter element has a plurality of tubular sleeves which are open at the top and closed at the bottom to provide elongated gas passsageways surrounded by filter material. The cassette frame includes stiffening members positioned within said sleeves and a rectangular frame surrounding the top of the filter element. The filter element is suspended from said rectangular frame and is releasably clamped to the frame. The cassette frame has a lower structure which may support the cassette outside the housing and provide reinforcement for the cassette. The filter element is clamped to the frame portion of the cassette by collar means extending from the open top of the filter element over the frame portion, and locking rods operable to interlock the collars with the frame portion of the cassette.

This invention relates to a device for mounting a compact filter in a 
cassette frame. More particularly, the invention provides a cassette 
having a rectangular frame engaging the upper part of a filter element 
formed into a plurality of bags having a common gas opening at the top. 
Filter means of this kind are used for cleaning gases from dust. The 
compact filter is clamped in a cassette frame, which is inserted in a 
filter housing. The dust-loaded gas is introduced into a raw-gas chamber 
and passes through the filter material whereby the dust is deposited on 
the surface of said material. The cleaned gas leaves the filter housing 
via a clean-gas chamber, which can be common to several compact filters. 
Between the cassette frame and filter housing an efficient sealing must be 
provided to ensure that all gas on its way from the raw-gas chamber to the 
clean-gas chamber passes through the filter material. For ensuring 
efficient operation of the filter, the dust collected on the filter 
material must be removed regularly. 
According to known technique, the dust is removed by subjecting the filter 
material to vibration movements, which usually are brought about by 
pressure pulses of a suitable gas, usually air. The filter material in 
operation is exposed to varying wear in response to gas load, dust 
concentration, dust type and cleaning process. Satisfactory operation of 
the filter presupposes regular inspections and, if necessary, exchange of 
the filter material. It is, therefore, essential that the inspection can 
be carried out easily and the filter tubes be exchanged simply and 
rapidly, so that the filter section concerned must not be taken out of 
operation for a long period. Conventional filters do not meet these 
requirements. In such known installations, the exchange of filters is a 
tedious and heavy work, which often requires several persons, and the 
manufacturing, transportation and storage costs for the filters and their 
spare parts are high in view of their complicated, bulky and heavy 
structural design. Owing to these factors, the filter process on the whole 
often requires large resources or does not operate satisfactorily. 
The present invention has the object to eliminate the aforesaid 
disadvantages and produce a filter means of the above kind, which is of 
simple and lightweight design, the parts of which are nonexpensive to 
manufacture, transport and store, and the filter bags of which, if 
necessary, can be exchanged rapidly and easily by one man. This object is 
achieved by a device of the present invention, including the several 
embodiments thereof. The design of the cassette frame, compact filter 
element and locking rod ensures a very efficient and well-defined 
attachment of the compact filter element to the cassette frame. The 
mounting can easily be carried out by one man, because one side at a time 
is fastened. During filter exchange, the locking rods can be released and, 
thus, the filter element can be removed from the cassette frame, in a very 
simple way. When mounting, the filter collar is folded over the upper side 
of the frame and serves both as a fastening means and simultaneously as a 
sealing means between the cassette frame and the filter housing when the 
frame, rigid by design, is pressed upward against the connecting frame of 
the filter housing. Said sealing is very efficient, and due to the absence 
of loose packings a safe sealing effect always is ensured during filter 
exchange, because the filter collar portion serving as packing for a new 
filter element automatically is intact. The absence of loose packings 
apparently provides advantages also from a handling and storing aspect.

In FIG. 1, the numeral 1 designates a compact filter element comprising a 
plurality of filter bags 2, which constitute clean-gas passageways 3 for 
the cleaned gas. The passageways are closed at the lower portion 4 of the 
filter bags and at the upper portion of the filter element form a common 
clean-gas opening 5. The compact filter element is mounted in a cassette 
frame 30 (FIG. 3) consisting of a rectangular frame 31, which comprises 
means for mounting the compact filter element in the cassette frame. The 
configuration of cassette frame and compact filter element is adapted to 
suitably be inserted in a filter housing (not shown) where the common 
clean-gas opening of the filter element sealingly is connected to the 
clean-gas passageways of the filter housing. It is apparent that one or 
more cassette frames with associated filters can be connected to the same 
filter housing. The numeral 50 (FIG. 1) designates means for stiffening 
the filter bags. 
In FIG. 2 a view of the compact filter element separated from the cassette 
frame is shown. The filter element shown consists of filter material 
formed with two deep folds. From said folds two rows 6 and 7 of filter 
bags 2 have been formed by sewing together the folds with seams 8 in 
parallel with each other. At the end surfaces 9 and 10 of each row members 
11 are provided to clamp the filter element in the cassette frame. Said 
members preferably have the form of longitudinal sleeves. The compact 
filter element at its upper portion has a clean-gas opening 5 common to 
all filter bags and interconnecting the clean-gas passageways formed by 
the respective filter bags. The filter bags are closed at their lower 
portion 4 by an end portion. At the upper portion of the compact filter 
element, i.e. surrounding the common clean-gas opening 5, collars 12a-d 
are provided which on at least two sides are formed with sleeves 16 and 
17. The compact filter element can also be formed with one row or with 
more than two rows of filter bags. 
In FIG. 2a the design of two adjacent collars 12c and 12d of the compact 
filter is shown in detail. The collars are sewn together at a right angle 
relative to each other and formed as sleeves 16 and 18 being open at their 
short sides. The dashed lines 14 indicate seams, by which the collars are 
connected to the remaining parts of the compact filter element and by 
which the sleeves are formed. 
In FIG. 3 a view of the cassette frame 30 is shown. The upper portion of 
the frame is a rectangular frame 31, at the opposite ends of which end 
wall pieces 32 and 33 are provided. Said end wall pieces include clamping 
means 35 and 36 to detachably clamp each row of filter bags at the opposed 
end surfaces. The clamping means 35 and 36 preferably are bars adapted to 
be inserted through the longitudinal sleeves at the ends of the filter bag 
rows. The two opposed end wall pieces 32 and 33 are rigidly interconnected 
at their lower end by a bottom beam 34, which may be formed as shown in 
the Figure, i.e. the beam, or preferably the tubular section, is attached 
to the ends of the frame 31 and constitutes an integrated part of the end 
wall pieces 32 and 33, froming a bow at the lower portion of the cassette 
frame. This bow serves as a support element for the cassette frame before 
its positioning in the filter housing and also renders it possible to 
apply a relatively great clamping pressure to the clamping of the filter 
bag rows, i.e. without thereby bending the end wall pieces toward each 
other. Surrounding the upper end of the filter element, the rectangular 
frame 31 consists of four channel elements 37a through d of U-shaped 
cross-section which form an outwardly open U-shaped groove 41 extending 
about the frame. In the Figure also two L-shaped locking rods 60 are shown 
which are used for fixing the filter elements in the cassette frame. 
In FIGS. 4a and 4b the design of the U-shaped channel elements 37 
constituting the rectangular frame 31 is shown in detail. Two sides 
thereof, preferably the opposed long sides (37b and d in FIG. 3) are 
formed by elements with a cross-section as shown in FIG. 4a. The 
U-section, thus, faces with its groove 41 open faces to the side, while 
the two flanges 42a and 42b of the section are horizontal. The web 43 of 
the section is vertical. The outer ends of the flanges are provided with 
lips 38 and 39 directed toward each other and forming an open gap 40 
therebetween. The remaining two elements of the frame (37a and c in FIG. 
3) also are formed with horizontal flanges 42a, and b and upstanding webs 
43, but these elements have no lips. 
The cassette frame is inserted in the filter housing and locked thereto in 
a way not described here in detail. As can be seen in FIGS. 5a, b, and c a 
packing 13 is attached to the filter collar 12 and provides a more 
efficient sealing between the filter housing and cassette frame. The 
packing preferably is attached to the collar by seams 14. The packing 13 
according to FIGS. 5a and 5b extends along the upper flange 42a of the 
element 37, while the packing 13 according to FIG. 5c also extends along 
the web 43 of the element 37. The packing also serves as a reinforcement 
of the collar at the portion where it is folded over the frame element and 
where substantial wear can be expected. It is also apparent from said 
lastmentioned Figure, how the collar 12 is connected to the remaining 
compact filter by a seam 15. 
In FIGS. 5a-c is shown in detail how the attachment of the compact filter 
to the elements 37 of the frame is effected. The collar 12 of the compact 
filter which is formed with a sleeve 16 is inserted in the groove in the 
elements 37b and 37d provided with lips. From the lateral edge of the 
elements thereafter one leg 60a of the locking rod 60 is introduced 
through the sleeve 16 located in the groove. The total thickness of the 
locking rod and sleeve exceeds the size of the gap 40, so that an 
efficient locking of the flange 12 to the element 37b and d is obtained. 
This is apparent from FIG. 5a. The adjacent collars 12a and 12c are placed 
about the other leg 60b of the locking rod before this is pressed into the 
open groove of the adjacent element 37a, c. This is shown in FIG. 5b. The 
total thickness of the locking rod 60 and collar 12a and 12c respectively, 
preferably is adjusted so that also said leg 60b remains in the groove of 
the element. The thickness of the legs 60a and 60b is less than the width 
of the groove 41. When both locking rods 60 have been introduced in the 
manner intended, an efficient releasable retention of the compact filter 
in the cassette frame has been obtained. When the collar of the filter is 
folded over the upper flange 42a of the elements 37, the filter material 
serves as a sealing means between the cassette frame and the connecting 
frame 80 of the filter housing (see FIG. 5c). 
The filter device according to the invention operates as follows. For 
mounting the compact filter element in the filter cassette, the cassette 
is placed with the bottom beam 34 on the floor or on a floor plane 
provided at the filter housing. The compact filter element, which can be 
delivered in folded-together state, is then positioned in the cassette 
frame, but with its collars folded over the upper flange of the U-section. 
The filter collars are fastened in the frame by inserting the locking rods 
60 in the sleeves of the collars when the sleeves are in the opening of 
the U-beam. When the two longsides have been fixed, the other leg of the 
respective locking rod is pressed into the adjacent U-beam opening, and 
due to the location of the filter collar wrapped partially around the leg, 
the filter element is efficiently locked to the cassette frame. As one 
side is fastened at a time, also this moment apparently can be carried out 
easily by one person. The filter material is clamped in the end walls of 
the cassette by threading the bars 32 and 33 through holes in the end wall 
pieces and the sleeves 11. During this moment, the filter material is in 
slack state, which renders said clamping easy. The stiffening elements 50 
are thereafter introduced into the respective filter bags, which thereby 
assumes a rhombic or square configuration, seen by way of horizontal 
section, which is highly advantageous, because the planes of the lateral 
surfaces of adjacent filter bags form a substantially right angle to each 
other. The filter surfaces hereby do not cover each other, and there is no 
risk of dust migration from one surface to an adjacent one in connection 
with the cleaning operations. When all stiffening elements have been 
mounted, the entire compact filter element is very stably fastened in the 
cassette frame, i.e. the filter material can withstand variations in the 
raw-gas flow and it can be subjected to cleaning operations without 
jeopardizing its attachment to the cassette frame. Thereafter the cassette 
frame with the filter element is inserted in the filter housing and 
connected to the clean-gas passageway of the filter housing by pressing 
the frame of the cassette with intermediate collars, which serve as 
packing, against the connecting frame of the filter housing and then 
locking it by a suitable means. The filter can be dismounted by carrying 
out the above operations reversed and in inverse order. It is apparent, 
that the invention also renders possible simple and rapid dismounting of 
the filter element. 
The invention, of course, can be applied to filters of different 
dimensions. The filter cassettes, however, must not be so large and heavy 
that they are difficult to handle, nor must they be so small as to have 
low capacity, because then a great number of cassettes are required for a 
definite capacity demand. According to an embodiment, the cassette frame 
has a length of 0.95 m, a width of 0.25 m and a height of 1.55 m. The 
filter surface amounts to 7.5 m.sup.2. The weight of the cassette frame is 
15 kg, and the total weight of a compact filter element mounted in the 
cassette frame is 20 kg. Filters having said weight and designed according 
to the invention, as may be pointed out again, can easily be handled by 
one man. Four to eighteen cassette frames with filter elements are 
positioned in a common filter housing.