Imperforate bowl: centrifugal separators – Rotatable bowl – Driven by energy of material supplied
Reexamination Certificate
2002-01-15
2003-09-16
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Rotatable bowl
Driven by energy of material supplied
C494S083000, C494S084000
Reexamination Certificate
active
06620090
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of international patent application no. PCT/EP00/05598, filed Jun. 17, 2000, designating the United States of America, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Federal Republic of Germany patent application no. DE 199 33 040.9, filed Jul. 15, 1999.
BACKGROUND OF THE INVENTION
The invention relates to a free-jet centrifuge suitable, for instance, for cleaning the lubricating oil in an internal combustion engine.
Freejet centrifuges of this type are known in the art. German Utility Model application no. DE 296 09 980 U1 proposes a rotor of a centrifuge suitable for mass production in large numbers. It comprises a plurality of sheet metal cups that are connected by common flanging (see
FIG. 1
of the cited document). This unit has a center tube
30
into which sleeves
31
,
32
are inserted. These sleeves rotatably support the centrifuge rotor on a housing shaft
16
and limit the axial play of the rotor within the clearance. During operation, the rotor can move back and forth between the axial limits of the housing. Due to the oil pressure and any downward tilt of the nozzles
28
, the rotor tends to rise inside the housing.
If the oil pressure drops below a predetermined value, valve
40
closes, thus preventing the oil from passing through the centrifuge rotor. Due to bearing friction of the slide bearings, the rotor then comes to a stop. Bearing friction is increased because the centrifuge rotor is lowered to the lower axial limit stop within the housing, which increases the bearing surface of the slide bearing.
Despite the use of integrated components, e.g., pressure valve
40
, the described rotor module is highly complex. This makes it difficult to produce the rotor in an economical manner. In particular, the axial position of the rotor is not precisely defined during operation. Sudden pressure fluctuations can, for instance, cause the rotor to strike against one of the axial limit stops even during operation. As a consequence, these limit stops must be equipped with similarly favorable frictional properties as the radial area of the slide bearings.
A further problem is the run-on behavior of the centrifuge when the oil supply is interrupted. In such a case, the centrifuge should come to a stop as quickly as possible. The kinetic energy of the rotor is reduced through bearing friction. To obtain the highest possible rotational speeds, however, bearing friction should be as low as possible. In other words, the more successful the reduction of bearing friction, the longer the centrifuge will run on.
If oil centrifuges are used in passenger cars, the requirements for smooth running characteristics of the engine are particularly high. At the same time, frequent load variations, e.g., if the car is used in densely populated areas, cause the centrifuge to be continuously turned on and off. When the internal combustion engine is idling, long run-on of the centrifuge rotor is unacceptable due to noise, since it is louder than the quiet engine noise in this operating state and is perceived as disagreeable by the driver.
SUMMARY OF THE INVENTION
The object of the invention is to provide an improved centrifuge with a rotor that achieves a good centrifuge result by realizing high rotational speeds
A further object of the invention is to provide a centrifuge with a rotor which has short run-on times after being turned off.
These and other objects have been achieved in accordance with the present invention by providing a free-jet centrifuge comprising a rotor having an oil inlet, at least one drive nozzle as an outlet, and a deposition surface interiorly of the rotor; a housing in which the rotor is rotatably disposed to shield the rotor against the environment, and bearing means for rotatably supporting and limiting the axial play of the rotor inside the housing; in which a fixed, externally actuated power source is provided on the free-jet centrifuge, the power source exerting a force which acts on the rotor in an axial direction counter to axial forces created by rotor operation, the power source being dimensioned such that the centrifuge can be pushed against the axial play limit by actuation of the power source to brake the centrifuge from any operating state.
In accordance with a further aspect of the invention, the objects are achieved by providing a rotor for use with a free-jet centrifuge comprising a housing in which the rotor is rotatably mounted to shield it from the environment, the rotor comprising an oil inlet, at least one drive nozzle as an outlet, a deposition surface interiorly of the rotor, and rotor bearing means for engagement with mating housing bearing means to rotatably mount the rotor in the housing; wherein the rotor bearing means interacts with the housing bearing means to limit axial play of the rotor within the housing; and the rotor comprises a rotor friction surface outside the rotor bearing means for engagement with a housing friction surface to brake the rotor upon actuation of a power source.
The free-jet centrifuge according to the invention comprises a rotor with an inlet and at least one drive nozzle, which simultaneously serves as the outlet. The deposition surface for the separated suspended solids contained in the fluid is formed, for instance, by the rotor shell. The housing shields the rotor against the environment. This is necessary because the spray of the drive nozzles must be collected. Within the scope of the invention the term “housing” should be understood to refer to any type of casing protecting the environment. It is not necessary to provide a separate housing for the centrifuge. It is also feasible, for instance, to build the centrifuge into cavities of an internal combustion engine that forms part of the oil circuit. The support of the centrifuge rotor inside the housing simultaneously allows its rotation and limits its axial play.
According to the invention the free-jet centrifuge is provided with a power source, which is fixed inside the centrifuge housing and the force of which acts on the rotor. This power source can, for instance, be a prestressed helical spring, the ends of which are supported on the rotor bearing and on the housing, respectively. The force of the power source acts against the axial forces created during rotor operation. As a result, an equilibrium of forces is established between the power source and the rotor in operation. The rotor, within its axial range of movement, migrates into the position of this equilibrium of forces without contacting either of the axial limit stops. This permits low-friction operation of the centrifuge at high rotational speeds. The power source simultaneously acts as a buffer when there are pressure fluctuations that shift this equilibrium of forces, but it does not cause the rotor to rub against one of the axial limit stops.
As soon as the oil pressure falls below a certain value, the power source pushes the rotor against one of the axial limit strops. This creates a braking torque, which is capable of braking the rotor until it comes to a stop. Prolonged run-on is prevented, so that there are no audible running noises of the centrifuge, e.g., when the internal combustion engine is idling. The power source further has the positive effect that the bearing partners are kept under tension. As the centrifuge continues to rotate, this prevents knocking of the bearings due to the bearing play, which can also cause a disagreeable noise. Furthermore, the risk of bearing damage due to knocking, which shortens the life of the bearings, is avoided. This is necessary particularly if roller bearings are used to support the rotor. But slide bearings also benefit from the decreased run-on times. Due to the low oil pressure in this operating state, lubrication of the bearings is no longer fully assured. Prolonged run-on would therefore cause increased bearing wear.
Normally, the external support by the power source will act in the direction of the gravitational fo
Fischer Helmuth
Frehland Peter
Cooley Charles E.
Crowell & Moring LLP
Filterwerk Mann & Hummel GmbH
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