Fluid filter cartridge

A filter cartridge for filtering fluid, such as air, within an enclosed housing, such as a disk drive, comprises a toroidal body having a pair of mating confronting halves fastened together. A pair of annular sheets of filter media are sandwiched between the halves and are separated by a ring member to engage each sheet of filter material against a respective one of the confronting halves. Fluid to be filtered flows radially through the cartridge to flow through at least two portions of the filter media. Optionally, a third sheet of filter material may be supported by the ring member to provide additional filtering.

This invention relates to fluid filters, and particularly to air filter 
cartridges for use in disk drives. 
In U.S. Application Ser. No. 255,311, filed Apr. 17, 1981, now U.S. Pat. 
No. 4,377,830, for "Air Filter System for a Magnetic Disk Housing" by D. 
C. Patel, and assigned to the same assignee as the present application, 
there is described a filter system for a disk drive wherein air is 
continuously recirculated through a filtering system to reduce foreign 
particle contamination in the shroud area of a magnetic disk unit. 
Rotational movement of the disks within the shroud coact with the filter 
to circulate and filter the air within the disk housing. 
In U.S. Pat. No. 4,308,041, there is described an air filter cartridge for 
use within a disk drive. The filter cartridge described therein comprises 
a pair of mating halves with a filter element sandwiched therebetween, 
formed in such a way as to form a toroidal filter capable of filtering air 
flowing radially through the filter. One problem associated with the 
filter cartridge described in U.S. Pat. No. 4,308,041 results from the 
fact that the confronting halves of the filter cartridge are of different 
design, thereby requiring separate tooling to fabricate each half thereof. 
Furthermore, the single filter element contained in the cartridge is not 
altogether adequate for filtering particulate matter from air within the 
disk drive. 
It is an object of the present invention to provide a filter cartridge 
wherein having a plurality of filter media through which fluid being 
filtered must pass. 
It is another object of the present invention to provide a filter cartridge 
having confronting halves of identical design to thereby reduce the 
fabrication costs of the filter. 
In accordance with the present invention, an air filter cartridge comprises 
a rigid body formed by a pair of separate confronting halves. First and 
second sheets of annular filter media are placed between the confronting 
halves of the cartridge body, and a toroidal ring is nested between the 
two halves to separate the sheets of filter media. Fluid being filtered 
flows radially through apertures in the cartridge body, through the filter 
media, through the apertures in the toroidal ring, through the filter 
media again, and through opposite apertures in the body of the cartridge. 
One feature of the present invention resides in the fact that the toroidal 
ring provides compressive strength to the filter cartridge to provide a 
good seal between the cartridge body and the portions of the disk drive in 
which it is placed. 
Another feature of the present invention resides in the fact that an 
additional sheet of filter media may be wrapped around the toroidal ring 
to additionally filter fluid passing through the filter.

Referring to FIG. 1, there is diagramatically illustrated a disk drive 
having a filter cartridge in accordance with the presently preferred 
embodiment of the present invention. The disk drive comprises an enclosed 
housing 10 having a door 12 mounted to be opened to permit the insertion 
or removal of a disk cartridge generally illustrated at 20. The disk 
cartridge includes a cartridge housing 22 having one or more apertures 24, 
a hub arrangement 26, and a disk 28. Permanently mounted within the disk 
drive is a hub 30 to which a fixed disk 32 is attached. Disk 32 is 
enclosed within housing 34, which itself has one or more apertures 36. 
Shaft 38 is arranged to impart rotational movement to hub 30, and to hub 
26 when attached thereto, thereby rotating disks 28 and 32. Filter 40, 
which is the subject of the present invention, is positioned on the top 
surface of separator plate 42. Means 44 is provided to bear against the 
top surface of housing 22 of cartridge 20 so that when cartridge 20 is in 
place, means 44 presses housing 22 against filter 40, thereby separating 
the lower portion of housing 22 from hub 26. A more detailed explanation 
of the structure of the disk drive and its relationship to cartridge 20 
may be found in the aforementioned Patel application. When cartridge 20 is 
in place and disks 28 and 32 are rotated, the rotational movement of the 
disks causes fluid, such as air, within housing 10 to circulate toroidally 
and radially in the direction of arrows 46 through apertures 24 and 36 and 
filter 40. 
With reference particularly to FIGS. 2 and 3, there is illustrated a filter 
cartridge in accordance with the presently preferred embodiment of the 
present invention. The cartridge comprises a body constructed of a pair of 
confronting toroidal halves 50 and 52 mated together. Halves 50 and 52 are 
of essentially identical shape and design. For sake of convenience, the 
reference numerals associated with half 52 bear primes whereas the 
reference numerals associated with half 50 do not. As is shown 
particularly in FIg. 3, the cross section of each half 50 and 52 is 
essentially cap-shaped with an outer ring portion 54 and an inner ring 
portion 56. Annular portion 58 includes an internal annular groove 60 
adapted to receive toroidal ring member 62 to be described in further 
detail. Preferably, portion 58 includes a raised section 64 to give 
strength to the annular portion 58 in the region of annular groove 60. 
Raised section 64 also provides a flat ring surface against which the 
cartridge housing 22 and separator plate 42 may bear. Thus raised section 
64 provides a region of strength for supporting the compression forces and 
provides a fluid seal against the cartridge housing and separator plate. A 
frustoconical portion comprising an outer sloped member 65 and an inner 
sloped member 67 joins annual portion 58 to ring portions 54 and 56, 
respectively. A plurality of apertures 66 and 68 are disposed annularly 
through the inner and outer sloped portions of halves 50 and 52. 
Preferably, apertures 66 and 68 are disposed opposite to each other around 
the periphery of the body. Typically, there may be thirty-six of each such 
apertures on each such half centered at 10.degree. intervals about the 
circumference of the halves. Mounting tabs 55 may be conveniently formed 
in each half 50, 52 to provide for mounting of the filter to the fixed 
portions of the disk drive. Halves 50 and 52 are essentially identical in 
design, and hence may be fabricated by the same tooling equipment and 
techniques. Halves 50 and 52 are preferably constructed of a suitable 
rigid plastic such as ABS (copolymers made from acrylonitrile, butadiene 
and styrene). 
A pair of annular sheets 70 and 72 of filter material are sandwiched 
between the respective rings portions 54, 54' and 56, 56' within the 
cavity formed by the confronting portions of halves 50 and 52. Toroidal 
ring 62 is positioned within the cavity to nest within the grooves 60 and 
60' in the respective halves 50 and 52, so as to separate filter sheets 70 
and 72 into substantially conical cross-sectional shapes and to sandwich 
the filter sheets between the ring member 62 and the respective half 50 or 
52. Ring member 62 is preferably constructed of rigid plastic, such as 
ABS, and has a plurality of apertures 74 exposed about its periphery, 
conveniently at the same 10.degree. positioning of apertures 66 and 68. 
Optionally, an additional sheet of filter material 76 fastened to the 
outside surface of toroidal ring 62 over apertures 74 to provide 
additional filtering of air passing radially through the filter. 
Halves 50 and 52 and toroidal ring 62 are dimensioned so that the parts may 
be readily assembled to sandwich the filter material between ring 62 and 
the respective halves 50 and 52. After the elements have been assembled in 
the manner essentially indicated in FIG. 3, they are permanently joined in 
that relationship by conventional techniques such as adhesives or 
ultrasonic welding of the plastic ring portions 54, 54' and 56, 56'. 
The present invention thus provides a filter cartridge which is easily 
assembled and inexpensively manufactured, and which effectively filters 
contaminants from air being filtered therethrough. The inclusion of ring 
62 provides added strength to the filter to enable the filter to react 
against the compressive forces occasioned by the positioning of a disk 
cartridge thereagainst as illustrated in FIG. 1. Also, annular portion 64 
provides support for the filter and seals the filter against the disc 
cartridge 22 and separator plate 42. 
This invention is not to be limited by the embodiment shown in the drawings 
and described in the description, which is given by way of example and not 
of limitation, but only in accordance with the scope of the appended 
claims.