Metal working – Method of mechanical manufacture – Impeller making
Reexamination Certificate
1999-02-26
2001-04-10
Rosenbaum, I. Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Impeller making
C029S458000, C029S460000
Reexamination Certificate
active
06212770
ABSTRACT:
TECHNICAL FIELD
This invention relates to a stator assembly for an axial flow rotary machine and more particularly to structure for actuating a device for selectively flowing air from a working medium flowpath of the machine. While the invention was conceived in the field of axial flow, gas turbine engines for bleeding air at a point between two compressor rotor assemblies, it has application to other devices in such engines that employ an actuating ring.
BACKGROUND OF THE INVENTION
Axial flow gas turbine engines include a compression section, a combustion section and a turbine section. A flowpath for medium gases extends through these sections of the engine. During operation, the gases are pressurized in the compression section and fuel is added in the combustion section. The fuel is burned to add energy to the pressurized gases. The hot, pressurized gases are expanded through the turbine section to provide the work of compression and hot, high pressure gases for subsequent use.
U.S. Pat. No. 4,827,713 issued to Paterson et al entitled “Stator Valve Assembly for a Rotary Machine” is an example of such a gas turbine engine. In Paterson, the compression section of the engine is provided with two independent mechanical compressors. During transient operating conditions, one compressor can provide more flow than can be accommodated by the second compressor. Accordingly, the compression section is provided with a plurality of passages extending about the working medium flowpath to allow a portion of the air to escape form the compression section. In particular, the engine has a housing extending circumferentially about the axis of the engine. The housing has a plurality of openings. Each opening is covered or uncovered by an axially translating valve ring having circumferentially extending seal surfaces axially which move to engage resilient seal members. The valve ring is moved from an opened to a closed position by actuating means and includes guide roller assemblies in one ring and guide slots in the other ring.
The engine has circumferentially extending resilient seal members which extend axially. In the closed position, the seal members extend between a valve ring and the seal surface. The valve ring is urged by simple actuating means from an open position to a closed position to axially compress the resilient seal members on either side of the openings to provide a gas tight seal.
The valve ring is movable between an opened and a closed position and being guided by a slot and guide pin combination for urging the valve ring axially against resilient sealing members, the slots being contoured to provide a mechanical advantage as the axial compressive force is applied to the resilient sealing members.
The valve ring is movable between an open position and a closed position. The ring is guided by a slot and pin (cam follower) configuration, the slot having a preselected contour as the ring compresses the resilient seal members such that an inclined plane effect is provided during compression. In one embodiment, a feature is a bushing which engages the cam follower and the adjacent stator structure as the valve ring is moved to the open position.
As will be realized, the loss of working medium gases through the openings under steady state conditions when the compressors are operating at their design point will cause a decrease in the efficiency of the engine. Accordingly, it is desirable to insure that flow does not occur through these openings under conditions which do not require the diversion of flow from the flowpath.
Another problem is wear on the surface of the track opening and fracture failures of the pin which holds the hardface roller assembly in engagement with the track opening. A particular concern of the prior art design shown in
FIG. 10
is the potential failure of the roller assembly occasioned by the shank breaking or by the thrust element at the head of the pin coming free and allowing the rotatable element of the roller to fall into the engine and degrade the performance of the engine. For example, the roller assembly has a thrust element which is bonded or mechanically attached to the pin. Experience has shown that this thrust element has the capability to become separated from the pin.
The above art notwithstanding, scientists and engineers working under the direction of Applicant's assignee have sought to decrease leakage through such seals by improving the sealing effectiveness of the seals and decreasing the effect that distortion resulting from operative load has on seal components.
SUMMARY OF THE INVENTION
According to the present invention, a method for forming a roller assembly having a pin includes forming a race on the head of the pin by forming an outwardly facing surface on the pin and an axially facing surface on the pin to bound the bottom and the side of the race and forming at least a portion of the third side of the race by pressing a collar against the pin.
In accordance with one embodiment of the present invention, the method includes trapping the collar between the head of the pin and a support and pressing the collar against the head of the pin and the support by creating a tensile force in the pin.
In accordance with one detailed embodiment of the present method, the method includes spacing the interior of the collar away from the pin adjacent the support and pressing the interior of the collar against the pin adjacent the area of the race and resisting bending forces from the external forces in the race region of the pin with a turning moment exerted by the support through the collar at a location in proximity to the race.
A primary feature of the present method is forming the race for a rotatable element on a roller assembly by pressing a trapped collar against one side of the pin. Another feature of the present method is forming the race with a thrust element which is one piece with the remainder of the pin such that the thrust element is not bonded nor mechanically attached to the pin. Another feature is using a collar for shifting the turning moment exerted by a support on the pin from the support to a location closer to the race.
A primary advantage of the present is the durability of a machine having a roller assembly which results from trapping the collar of the roller assembly with the remainder of the roller assembly and avoiding the use of a detachable thrust element which might separate and enter the machine. Another advantage is the durability of the roller assembly which results from decreasing bending stresses in the pin of the roller assembly by transferring loads from the support to the roller assembly to a location closer to the race region of the roller assembly. Still another advantage is the durability of the roller assembly which results from disposing a self lubricating coating between the rotatable element of the roller assembly and the remainder of the roller assembly, whether the material is bonded to a portion of the structure forming the race, bonded to the rotatable element or disposed as an independent structure between the rotatable element such that the material is in faying contact with the rotatable element and structure forming the race.
REFERENCES:
patent: 4827713 (1989-05-01), Peterson et al.
patent: 5380151 (1995-01-01), Kostka et al.
Honda Keith T.
Sandini Francis J.
Walton Kevin A.
Cuda Rosenbaum I.
Fleischhauer Gene D.
United Technologies Corporation
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