Note: Descriptions are shown in the official language in which they were submitted.
Background of the Invention
This invention relates to filters and more particu-
larly to a magnetic filter element for removing magnetic par-
ticles from fluids used as a lubricant or in hydraulic systems.
Magnetic filters have been used for many years in
fluid systems in combination with a pleated paper filter ele-
ment for removing microscopic ferrous particles that pass
through the paper element thereby increasing the life of the
hydraulic system components. However, heretofore such magnetic
filters have been constructed with conventional bar or ring
magnets and are difficult to clean. Furthermore, the bar and
ring magnets increase the cost of the filter such that it be-
comes too expensive to be replaced on the same replacement
schedule of standard oil filters.
In accordance with the invention, a magnetic filter
element for removing ferromagnetic particles from a fluid com-
prises a tubular cylinder of flexible permanently magnetised
sheet material having a multiplicity of holes formed therein
for the fluid to pass through, each hole having a diameter
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within the range from 0.25 inches to 0.38 inches and the holes
providing a hole circumference to filter area ratio in the
range from 5 inches to 7 inches per square inch.
This new magnetic filter element may be inexpensive
to manufacture and could be used as a "throw-away" type of
filter to be replaced at regular intervals. The element could
be used as a separate filter for filtering ferromagnetic par-
ticles from a fluid in combination with a conventional oil ;
filter which filters the nonmagnetic particles from the fluid.
Alternatively, it could be used as an integral part of a fil-
ter assembly which includes a conventional porous filtering
element.
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Some examples of filter elements constructed in
accordance with the invention are illustrated in the accom-
panying drawings in which:-
Fig. 1 is a vertical section through one magnetic5 filter element in association with a filter assembly;
Fig. 2 is an elevation of the magnetic filter ele-
ment at an intermediate step in its construction; and,
Fig. 3 is another example of magnetic filter element.
Referring now to the drawings, a magnetic filter
10 element embodying the principles of the present invention is ~ -~
generally indicated by the reference numeral 10 in association
with a filter assembly 11. The filter assembly includes a
housing 12 having a generally cylindrical sidewall 13, an end
wall 14 integrally secured at one end of the sidewall and a
cover 16 removably secured to the opposite end of the sidewall
by a plurality of bolts 17. A pair of centrally disposed pro-
jections 18 and 19 extend inwardly from the end wall and cover,
respectively. A first port 21 extends through the end wall
and projection 18 and receives the end of a tube 22 while a
second port 23 extends through the sidewall adjacent to the
cover and receives the end of a tube 24. An elongated pleated
paper filter element 25 is disposed within the housing with
its opposite ends disposed in sealing engagement with the end
wall and cover. The filter element 25 has an axially extend-
ing passage 26 formed therein.
1~
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1'7~
The magnetic filter element 10 of the present
invention includes an elongated tubular member 27 of flexible
magnetic material having a relatively thin wall thickness.
The tubular member is disposed within the passage 26 of the
filter element 25 with the pro~ections 18 and 19 sealingly
protruding into ~he opposite ends of the tubular member. A
multiplicity of holes 28 extend through the wall of the
tubular member.
One method of making the magnetic filter element
is to machine a multiplicity of holes 28 in a flat strip or
sheet of the ~lexible magnetic material as shown in Fig. 2.
The sheets of flexible magnetic material are commonly formed
by dispersing magnetically anisotropic particles in a non-
magnetic immobilizing matrix material such as rubber, plastic
or the like. One method of making the flexible magnetic
; material is described in the U.S. Patent 2,999,275 issued to
W. S. Blume, Jr. on September 12, 1961. After the holes
have been machined in the strip, it is formed into a cylindrical
shape with its ad~acent edges then fastened together in any
suitable manner such as rivetting, stapling, or the like.
In one type of filtering operation, the fluid to
be filtered is pumped through the tube 22 into the center of
the tubular member 27 where it passes radially outwardly
through the holes 28. The magnetic attraction of the tubular
member attracts and retains any ferrous particles carried by
the fluid. The fluid then passes through the pleated paper
filter element 26 which filters out the nonmagnetic particles
with the filtered fluid then being exhausted through the
port 23 and tube 24. Alternately, the fluid flow could be
reverséd so that the fluid enters through the port 23,
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passes through the paper filter element and the holes in the
tubular member with the fluid then being exhausted through
the port 21 and tube 22. Thus, the magnetic filter element
would attract only the microscopic ferrous particles that
pass through the pleated paper element.
An alternate embodiment of the magnetic filter
element 10 of the present invention is disclosed in Fig. 3.
In this embodiment, however, the magnetic filter element is
in the form of a perforated wrapper constructed from the
flexible magnetic material with the wrapper encircling a
pleated paper filter element 32 as an integral part of a
; fluid filter 33. The fluid filter may be employed within a
housing similar to that described above.
The magnetic filter element 10 of the present
invention may also be utilized in the flat form shown in
; Fig. 2 by placing it in the flow path so that the fluid
passes through the holes 28. One example of such use would
be to insert such a flat magnetic filter element within the
fluid tank between the inlet and outlet ports.
The size of the holes 28 is selected to maintain a
minimal pressure drop in the fluid passing through the
filter element 10 and is dependent upon flow rate of the
fluid. Typically, the diameter d of the holes will be
withln the range of from approximately 0.25 inches to Q.38
inches with the hole pattern selected to provide a hole
circumference length to filter area ratio within the range
of approximately 5 to 7 inches per square inch. The filter
area includes the area of the holes plus the surface area of
the magnetic material. For example, the hole pattern shown
in Fig. 2 provides a circumference length to area ratio of
_5_
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0
5.99 inches per square inch when the diameter d is 0.31
inches, the dimension A is 0.43 and the dimension B is 0.38.
In view of the foregoing, it is readily apparent
that the structure of the present invention provides an
improved magnetic filter element which can be economically
manufactured to provide a throw-away magnetic filter. The
magnetic filter element is made from a flexible magnetic
material which is commercially available in inexpensive
sheet form. The flexible magnetic material can be readily
formed into a tubular shape as an independent filter element
or as a wrapper which is an integral part of a fluid filter.
Since all the fluid passes through the holes in the filter
element, any magnetic particles carried in the fluid is
forced to pass through the magnetic field of the magnetic
filter element and is attracted thereto. Thus, the magnetic
filter element is very efficient in removing magnetic particles
from the fluid.
While the invention has been described and shown
with particular reference to the preferred embodiments, it
will be apparent that variations might be possible that
would fall within the scope of the present invention which
i5 not intended to be limited except as defined in the
following claims.
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