Centrifugal filter with external service indicator

A centrifugal separator for separating contaminants from contaminated oil is disclosed. The centrifugal separator has a shroud which defines a first chamber and has a hollow rotor mounted for rotation therewith in the first chamber and defining a second chamber. Oil under pressure is admitted to the second chamber through a rotatable, hollow spindle on which the rotor is fixed. The oil flows into the first chamber through tangential reaction nozzles in the rotor to cause contaminants to migrate toward the sidewall of the second chamber under the influence of centrifugal force. The spindle is axially movable in the shroud, and is biased toward the upper end of the shroud by a spring. An indicator pin extends through the top of the shroud and is biased against the top of the spindle so that it follows movements of the spindle. As the contaminants build up on the sidewalls of the rotor, the spindle, and therefore the indicator pin, move downwardly so that an inspection of the indicator pin will inform the observer as to the build up of contaminants within the rotor without disassembling the separator.

BACKGROUND OF THE INVENTION 
Conventional fluid filters, such as oil filters, are basically mechanical 
strainers which include a filter element having pores which trap and 
segregate dirt from the fluid. Since the flow through the filter is a 
function of the pore size, filter flow will decrease as the filter pack 
becomes clogged with dirt. Since the filtration system must remove dirt at 
the same rate at which it enters the oil, a clogged conventional pack 
cannot process enough oil to keep the dirt level of the oil at a 
satisfactory level. A further disadvantage of some mechanical strainer 
type filters is that they tend to remove oil additives. Furthermore, the 
additives may be depleted to some extent by acting upon trapped dirt in 
the filter and are rendered ineffective for their intended purpose on a 
working surface in the engine. 
Prior art centrifugal filters have been proposed which do not act as 
mechanical strainers but, rather, remove contaminants from a fluid by 
centrifuging. For example, such a filter is shown in U.S. Pat. No. 
3,432,091 granted to Beazley. In the Beazley patent, there is illustrated 
a hollow rotor which is rotatably mounted on a spindle. The spindle has an 
axial passageway which conducts oil into the interior of the rotor. 
Tangentially directed outlet ports are provided in the rotor so that the 
rotor is rotated upon issuance of the fluid therefrom. Solids, such as 
dirt, are centrifuged to the sidewalls of the rotor and the dirt may be 
later removed by disassembling the rotor and scraping the filter cake from 
the sidewalls. 
Such centrifugal filters have oil inlets and outlets through the base of 
the filter, since access to the rotor for cleaning purposes is provided by 
removing a shroud cover and by then removing the rotor from the spindle. 
Such a maintenance operation is frequently not necessary, but the user of 
the filter has no way of knowing this until after the filter is 
disassembled. 
SUMMARY OF THE INVENTION 
This invention relates to a centrifugal separator which has an external 
indicator to provide information as to the condition of the filter bowl or 
rotor. More specifically, the invention pertains to a centrifugal filter 
having a shroud which defines a first chamber and a vertically extending 
spindle within the shroud having a hollow rotor mounted for rotation 
therewith. The rotor defines a second chamber for receiving contaminated 
fluids, such as oil, to be separated. There is provided an inlet port at 
one end of the spindle and passage means through the spindle to the second 
chamber. The rotor is rotated by tangential outlet ports and such rotation 
causes contaminants within the second chamber to migrate toward a sidewall 
of that chamber under the influence of centrifugal force. 
The spindle, and therefore the rotor, are axially movable within the first 
chamber and the spindle is biased toward one end of the first chamber by a 
spring. There is also provided an indicator pin extending through the end 
of the shroud toward which the spindle is biased and adapted to follow 
movement of the spindle. Thus, as particulate matter accumulates in the 
second chamber, the weight increase of the rotor causes the rotor to 
settle at lower positions when at rest. The indicator pin is therefore 
drawn deeper and deeper into the rotor to give a visual indication of the 
degree to which the second chamber has become contaminated.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawing, there is illustrated a centrifugal separator 
10 having a sealed shroud 11. The sealed shroud 11 includes a base 12 and 
a top cover 13. The interior of the shroud 11 constitutes a first chamber 
14. The base 12 further includes a flanged foot structure 15 which defines 
an outlet port 16. The foot structure 15 is adapted to be connected to an 
engine or other mechanism to be lubricated by bolting the flanged foot 
structure 15 to a valve cover, an oil filler tube, the crankcase, or 
sideplates with suitable fittings. The cover 13 is sealed against the base 
12 by an O-ring 17, and the cover 13 and the base 12 are clamped together 
by a V-shaped band 18. An inlet port 19 is bored into the base 15 and 
communicates with an axial passage 20 bored in a vertical spindle 21 by 
way of a passageway 22 in the base 12. Since the centrifugal filter is a 
bypass filter, an isolating valve 23 is provided between the inlet port 19 
and the passageway 22, and is adapted to cut off flow to the filter if the 
supply of pressure drops below a predetermined level to assure maximum oil 
flow to the engine under startup and low idle speed conditions. The lower 
end of the spindle 21 is mounted in a bearing 24 which is press-fitted 
within a counterbore 25 in the base 12. The spindle 21 is rotatably and 
axially slidably mounted in the bearing 24. The other end of the spindle 
21 is rotatably and axially slidably mounted in a bearing 26 which is 
press-fitted into a recess 27 in the cover 13. 
Carried by the spindle 21 and fixed thereto by a key (not shown) is a rotor 
assembly 28 which consists of an upper body section 29 and a lower body 
section 30. The body sections 29 and 30 are clamped together by a nut 31 
threaded onto the upper end of the spindle 21 and are sealed by a gasket 
32. 
Oil is fed into a second chamber 33 within the rotor assembly 28 through at 
least one passageway 34 and egresses through reaction nozzles 35 provided 
at the lower end of the rotor. In order to reach the reaction nozzles 35, 
the oil passes through a cup-shaped baffle 36 which tends to direct the 
contaminated oil out toward the sidewalls of the rotor assembly 28 to 
encourage the contaminants to be deposited on the sidewalls of the rotor 
assembly. To ensure that large particles will not clog the reaction 
nozzles, a screen 37 surrounds the spindle 21 and extends from the 
cup-shaped baffle 36 to a conical baffle 38. Since oil under pressure 
substantially fills the second chamber 33, the upper bearing 26 is 
lubricated by oil passing through inlet ports 39 in the spindle 21 and 
then through an axial passageway 40. Oil is expelled from the second 
chamber 33 through the tangentially mounted outlet ports 35 and, since 
those ports are oppositely directed, they cause the rotor assembly to 
rotate according to the principle of Hero's engine. 
As the rotor assembly 28 rotates, suspended solids migrate to and are 
retained at the sidewalls of the rotor assembly with a force which is 
dependent upon the running oil pressure of the engine, which is typically 
between 50 and 80 psi for a diesel engine. The rotor speed usually exceeds 
5000 rpm and the force on the dirt particles exceeds 1800 g's. In time, 
the dirt particle and sludge form a rubbery mass at the rotor sidewalls. 
As has been previously noted, the spindle 21 is mounted for limited axial 
movement relative to the bearings 24 and 26. When the rotor assembly is 
uncontaminated, it is biased upwardly to its solid outline position by a 
conical coil spring 41. An indicator pin 42 extends through an aperture 43 
at the top of the cover 14 and is biased by a coil spring 44 against a 
spider member 45 which is press-fitted into the passage 40. Thus, as the 
rotor assembly accumulates contaminants, its weight increase will cause 
the rotor assembly to approach the phantom outline position illustrated in 
FIG. 1. As the rotor assembly 28 approaches this position, the indicator 
pin 42 follows and its apparent length is shortened, thus giving a visual 
indication of the condition of the rotor. Of course, a reading should be 
made when the filter is at rest with the engine off, since there exists a 
hydraulic imbalance which tends to hydraulically shift the spindle 21 
upwardly when the system is pressurized. 
An alternate spindle biasing spring is illustrated in FIG. 3. In that 
figure, the lower end of the spindle 21 is provided with a counterbore 50 
which receives a cylindrical coil spring 51 to bias the spindle 21 
upwardly. 
Although the preferred embodiment of this invention has been shown and 
described, it should be understood that various modifications and 
rearrangements of parts may be resorted to without departing from the 
scope of the invention as disclosed and claimed herein.