Multi-stage filter frame assembly

A multi-stage filter assembly having a number of filter media layers, at least one of which is removably mounted to a filter frame, utilizes a retaining clip to hold the filter media in place. The retaining clip is in the form of an elongated strip that extends across the filter media and has its ends disposed within channels formed in the frame. The elongated strip is provided with a centrally located bend that causes the ends of the clip to be urged upwardly into engagement with the framework and causes a portion of the clip to be urged downwardly into engagement with the filter media.

BACKGROUND OF THE INVENTION 
Non-removably mounted particulate and gaseous filter media have been housed 
in more or less conventional permanent frame constructions for many, many 
years. Such frames generally consist of metal channel members forming the 
four sides of a rectangular configuration with the edges of the filter 
media being disposed within the channels. Typically the side walls of the 
channel members are bent inwardly to firmly engage and fix the outer edges 
of a layer of filter media in position within the frame. 
While this is generally a satisfactory construction for particulate filter 
media of relatively long life or which can be cleaned and re-used, it 
represents a considerable expense in those applications wherein the filter 
media is relatively short-lived. In such situations, a disposable and 
replaceable media is desirable. 
In applications wherein a combination of particulate and gaseous filter 
media are required, it is not unusual for one or more types of such media 
to be relatively shortlived. In this situation, a less expensive 
disposable filter media held by an inexpensive throwaway frame 
construction is desirable. 
However, most prior frame constructions of the stronger permanent type do 
not readily permit removal and replacement of layers of filter media held 
therein and the less expensive disposable frame constructions are less 
sturdy, weak and otherwise not satisfactory for certain applications. This 
type of prior art incorporated all filter media within a singular frame 
which must be thrown away when one or more of the filter media has served 
its useful life or to employ a separate filter frame for each type of 
media used. 
Other prior art filter assemblies such as that in U.S. Pat. No. 4,737,147 
utilized a plurality of clips to removably retain layers of filter media, 
but the clips had an awkward shape that was complex to manufacture and 
whose installation was less than simple. The clips also could not readily 
accept and accommodate multiple layers of removable filter media. 
It is an object of the present invention to provide a filter assembly 
having one or more disposable layers of filter media removably retained 
within a filter frame by a plurality of elongated clips that are easily 
manufactured and installed. 
SUMMARY OF THE INVENTION 
A multi-stage filter assembly includes a first filter layer having its 
outer edges disposed within a channel defined by the top, bottom and side 
walls of a metal frame. 
In accordance with one aspect of the invention, at least one additional 
filter layer is disposed in a freely overlying relationship to the first 
filter layer. 
In accordance with another aspect of the invention, a plurality of 
elongated retaining clips extend across the overlying filter layer and 
have a first end removably disposed within a channel in the frame and a 
second end removably disposed within an opposite channel in the frame. 
In accordance with still another aspect of the invention, the top and/or 
bottom walls of the metal frame is/are provided with a lip that is 
integral with the wall and extends from the inner edge of the wall into 
engagement with the first filter layer. 
In accordance with another aspect of the invention, the lip is provided 
with notches that help locate and position the retaining clips in the 
channels. 
In accordance with yet another aspect of the invention, the retaining clip 
has a centrally located bend disposed along its length so that the ends of 
the clip are urged upwardly into engagement with a frame wall while a 
portion of the retaining clip is urged into contact with the second filter 
layer. The centrally disposed bend causes the retaining clip to assume a 
flattened V shape when the clip is not disposed within the frame. 
The present invention thus provides a filter assembly in which at least one 
of the layers of filter media is removable and disposable and is retained 
within the filter frame by a plurality of retaining clips that are easily 
manufactured and installed.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in FIG. 1, a multi-layered filter assembly 10 includes a generally 
rectangular metal frame 12 in which one or more layers of filter media 14 
are permanently disposed. 
The metal frame 12 includes a top wall 16 and a bottom wall 18 which are 
connected by a side wall 20. Walls 16, 18 and 20 define a channel 22 in 
which the edges of filter media 14 are disposed. Walls 16 and 18 are 
provided with an integral lip 19 that extends from the inner edge of walls 
16 and 18 and into engagement with filter media 14. 
At least one removable and replaceable filter media layer 24 is disposed in 
a freely overlying relationship with filter media layer 14. 
Removable filter media layer 24 is held in place against filter media layer 
14 by a plurality of retaining clips 26. 
Retaining clips 26 are in the form of elongated strips which could be made 
from a number of different materials, but the applicant has found that 
thin metal strips are well suited for this purpose. Elongated clips 26 
have a first end 28 disposed within channel 22 of frame 12 and a second 
end 30 disposed within a channel 22 on the opposite side of frame 12. To 
facilitate the locating and positioning of clips 26, lips 19 are provided 
with notches 31 through which clip ends 28 and 30 extend into channel 22. 
Each of retaining clips 26 is provided with a centrally located bend 32 
which causes clip ends 28 and 30 to be urged upwardly into contact with 
top walls 16 of frame 12 and which causes the central portion 34 of the 
retaining clip to be urged downwardly into contact with removable filter 
layer 24. 
As seen in FIG. 2, the centrally located bend 32 causes retaining clip 26 
to assume the shape of a flattened V when retaining clip 26 is removed 
from frame 12. 
FIG. 5 illustrates an alternate embodiment for retaining clip 26. In this 
embodiment, elongated clip 26 is provided with a pair of bends 36 which 
urge the ends of clip 26 upwardly into contact with top wall 16 of frame 
12 and cause a pair of pressure points 38 to come into contact with 
removable filter layer 24. 
As seen in FIG. 5, bends 36 cause retaining clip 26 to assume the shape of 
a flattened U when retaining clip 26 is removed from frame 12. 
In larger filter assemblies it is also possible to use clips having three 
or more bends. 
FIGS. 6-9 illustrate yet another embodiment for retaining clip 26. In this 
embodiment, elongated clip 26 is provided with multiple bends 40 which 
result in multiple pressure points 42 in contact with removable filter 
layer 24. 
In this embodiment, each of the ends of clip 26 is provided with a 
downwardly extending flange 44 that is substantially parallel to side wall 
20 and engageable with lip 19. A leg 46 is integral with and extends 
outwardly from flange 44 substantially parallel to top wall 16. When clip 
26 is positioned in frame 12, leg 46 will be disposed in channel 22. 
Removable filter layers 24 and 24a are dimensioned so that filter layer 
edges 48 and 48a extend beyond and/or overlap metal frame 12. In this 
regard, filter layers 24 and 24a are provided with a notch 50 that 
accommodates clip flange 44 and leg 46. The length of flange 44 can be 
varied to accommodate various numbers of removable filter layers. 
The present invention thus provides a filter assembly having a removable 
and disposable filter layer that is retained in the filter frame by 
retaining clips that are easily manufactured and installed. 
Various modes of carrying out the invention are contemplated as being 
within the scope of the following claims particularly pointing out and 
distinctly claiming the subject matter regarded as the invention.