Rotary expansible chamber devices – Moving cylinder – Rotating
Reexamination Certificate
1999-04-02
2001-02-13
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Moving cylinder
Rotating
C418S166000, C029S888023
Reexamination Certificate
active
06186757
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an internal-gear machine such as a gear or pump.
BACKGROUND OF THE INVENTION
A typical form of internal-gear pump comprises a casing and a rotating unit or assembly which is accommodated therein and which comprises a rotatably mounted pinion and an internally toothed annular gear which meshes with the pinion. In such a machine the annular gear can be rotatably supported directly in a bore in the casing or in a bearing ring arranged in the bore. In other design configurations of an internal-gear machine, the annular gear is accommodated in the casing rotatably together with a running ring. A suction chamber and a pressure chamber are respectively formed between the tooth arrangements of the pinion and the annular gear, in which respect in particular the hydraulic pressure of the conveying medium, in the case of a pump, or operating medium, in the case of a motor, which prevails in the pressure chamber, determines the specific bearing loading obtaining between the outer peripheral surface of the annular gear and the bearing surface that co-operates therewith. That applies irrespective of whether the pressure chamber is respectively delimited from the suction chamber by a filling member, or whether the pressure chamber is defined by the teeth of the pinion on the one hand fully engaging into the gaps between the teeth of the annular gear and on the other hand, at a position in approximately diametrally opposite relationship with the region of engagement into the gaps between the teeth, they provide for a sealing contact with the tips of the teeth of the annular gear.
The annular gear is carried at its outer peripheral surface either in a plain bearing, in which case it is possible to set hydrostatic or hydrodynamic bearing conditions, or in a rolling bearing assembly. The permissible conveying or operating pressure of the internal-gear machine is determined by the load-bearing capability of the bearing arrangement. In the case of internal-gear machines with a low conveyor through-put, that is to say which operate at a low speed of rotation and/or which involve a tooth configuration of a small width, the conveying or operating pressure is frequently undesirably limited by the load-bearing capability of the annular gear bearing arrangement so that, in relation to the speed of rotation and/or the width of the tooth configuration, it is possibly necessary in structural terms to arrive at a compromise in order to be able to implement the required conveying or operating pressure, in a practical context.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an internal-gear machine which structurally affords greater freedom in terms of the choice of the conveying or operating pressure involved.
Another object of the present invention is to provide an internal-gear machine which can provide for a reduction in specific bearing loading at the outer periphery of the annular gear as a result of hydraulic forces obtaining in the pressure chamber of the machine.
Still another object of the present invention is to provide an internal-gear machine which, while being of a simple structure, affords satisfactory long-term wearing conditions at its bearing surfaces.
In accordance with the principles of the present invention the foregoing and other objects are attained by an internal-gear machine comprising a casing and a running assembly which is accommodated in the casing. The running assembly comprises a rotatably mounted pinion and an internally toothed annular gear meshing with the pinion. The annular gear is widened at its outer peripheral portion to form a running ring.
As will be seen from preferred embodiments of the invention described in greater detail hereinafter, as the annular gear is wider at its outer periphery than in the region of the tooth configuration thereof, the hydraulic forces which obtain between the co-operating tooth configurations of the pinion and the annular gear and by which the annular gear is pressed into its bearing arrangement are distributed over a larger bearing surface, thereby providing for a reduction in the specific bearing loading, as a result of hydraulic forces prevailing in the pressure chamber. The increase in the width of the annular gear at its outer periphery to constitute a bearing ring can be achieved in a number of different ways. The important consideration is that the part of the annular gear which forms the outer peripheral portion thereof, as a running ring, rotates as a unit together with the part which carries the internal tooth configuration of the annular gear. For that purpose the part of the annular gear which forms the running ring can be integral with the part having the internal tooth configuration, but alternatively the running ring can be a separately produced component which can be joined to the part having the internal tooth configuration, by a connection involving a form-locking or positively locking relationship and/or a force-locking relationship. An adequate force-locking relationship, for example involving frictional engagement, occurs in operation of the internal-gear machine when the part of the annular gear which carries the internal tooth configuration is pressed with its peripheral surface under the effect of the hydraulic forces acting in the tooth configuration against the inner periphery of the running ring. As in operation only the bearing frictional moment has to be overcome in order to cause the running ring to rotate together with the part of the annular gear which carries the internal tooth configuration, the frictional connection which is achieved in that way is sufficient. Therefore, it is also possible to conceive of an embodiment of the invention, for the annular gear which is increased in width at its outer periphery to form a running ring, in which a form-locking connection is afforded between the running ring and the part of the annular gear carrying the internal tooth configuration, only for the time when the internal-gear machine is starting up while still in a pressure-less condition.
Further objects, features and advantages of the invention will be apparent from the following description of preferred embodiments.
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Denion Thomas
Eckerle Industrie Elektronik GmbH
Hoffman & Baron LLP
Trieu Theresa
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