Overshaft fluid transfer coupling and mounting arrangement

In one example embodiment, a fluid transfer coupling arrangement includes a hollow shaft that is arranged in a housing and rotatable about an axis. The hollow shaft is provided by a wall having radially spaced interior and exterior surfaces. A first passage extends through the wall and is configured to communicate fluid between the interior and exterior surfaces. A fluid coupling is located mid-shaft, sealed about the exterior surface, and aligns to the first passage. The fluid coupling provides a second passage that is in fluid communication with the first passage. The fluid coupling includes a locating feature configured to permit radial movement of the fluid coupling relative to the housing and allowing the fluid coupling to track subtle shaft movements.

BACKGROUND

This disclosure relates to an overshaft fluid transfer coupling and mounting arrangement for same.

Some machines include rotating hollow shafts through which fluid is transferred within the interior of the shaft. Often the fluid may be communicated from one end of the shaft to the other end of the shaft. However, some applications, which include spatial constraints at the shaft ends, may require fluid transfer through the radial wall of the shaft. A fluid coupling is arranged over the shaft and concentric annuli between close tolerance lands provide a transfer path between the fluid coupling and the rotating shaft. A bolted flange joint typically fastens the fluid coupling to the machine's housing.

SUMMARY

In one example embodiment, a fluid transfer coupling arrangement includes a hollow shaft that is arranged in a housing and rotatable about an axis. The hollow shaft is provided by a wall having radially spaced interior and exterior surfaces. A first passage extends through the shaft wall and is configured to communicate fluid between the interior and exterior surfaces. A fluid coupling is positioned about the exterior surface and straddles the first passage. The fluid coupling creates a second passage that is in alignment with the first passage and provides fluid communication. The fluid coupling includes a locating feature configured to permit compliance and radial movement of the fluid coupling relative to the housing.

In one example, the fluid transfer coupling has a sleeve with an interior surface providing sealing surfaces axially spaced from one another. The first and second sealing surfaces bound a portion of the second passages created between sleeve and shaft. A port is in fluid communication with the second passage portion. The locating feature configured to permit the sleeve to float is provided by a retaining ring on shaft exterior and a tab extending into the housing40from the exterior surface of the sleeve.

An example method of assembly of the fluid transfer coupling arrangement includes installing a sleeve about the exterior surface of the hollow shaft to provide a shaft assembly. The shaft assembly is inserted into the housing. The locating feature of the sleeve is positioned relative to a corresponding locating feature on the housing. The sleeve is permitted to float radially relative to the housing.

DETAILED DESCRIPTION

FIG. 1schematically illustrates an exemplary high speed vertical takeoff and landing (VTOL) rotary-wing aircraft10having a counter-rotating, coaxial rotor system12which rotates about an axis of rotation A. The aircraft10includes an airframe14that supports a drive system16(FIG. 2), which generally includes the rotor system12, a powertrain system24, a power plant system26, and a secondary thrust system30. The secondary thrust system30provides secondary thrust generally parallel to an aircraft longitudinal axis L while the main rotor system12operates in an unloaded reverse flow state during a high-speed forward flight profile. Although a particular aircraft configuration is illustrated and described in the disclosed embodiment, other configurations and/or machines, such as high speed compound rotary-wing aircraft with supplemental secondary thrust systems, dual contra-rotating, coaxial rotor system aircraft, turbo-props, tilt-rotor, tilt-wing aircraft and non-aircraft applications will also benefit from the disclosed planetary gear system.

The main rotor system12includes an upper rotor system18A and a lower rotor system18B. Each rotor system18A,18B includes multiple rotor blades20mounted to a respective rotor hub22A,22B for rotation about a rotor axis of rotation A. Any number of blades20may be used with the rotor system12.

With reference toFIG. 2, the powertrain system24interconnects the power plant system26, the rotor system12and the secondary thrust system30. The powertrain system24may include various gear systems such as main and combiner gearboxes. The power plant system26generates the power available for flight operations to power the main rotor system12and the secondary thrust system30through the powertrain system24. The power plant system26in the disclosed, non-limiting embodiment includes two engine packages ENG1, ENG2, however, single engine systems as well as multi-engine systems will also benefit from the disclosed planetary gear system.

The secondary thrust system30in one non-limiting embodiment may be mounted to the rear of the airframe14transverse to the axis of rotation A with a rotational axis T thereof oriented substantially horizontal and parallel to an aircraft longitudinal axis L to provide thrust for high-speed flight. It should be understood that other configurations of the secondary thrust system30such as a propeller system mounted to each side of the airframe, a lift fan system, or other system alternatively may be utilized. In this disclosed, non-limiting embodiment, the secondary thrust system30includes a pusher propeller system32including pusher blades34. Power is transmitted from an input shaft42of the drive system16through a gearbox38to an output shaft44to rotationally drive the pusher propeller system32.

In one example embodiment shown inFIGS. 3 and 4, a fluid transfer coupling sleeve46is used within the gearbox38. The fluid transfer coupling46includes a hollow shaft50that is arranged in the housing40and rotatable about an axis S. In one example, an input member48, which is operatively coupled to the input shaft42, is connected to the hollow shaft50by a splined connection86. The hollow shaft50is supported for rotation relative to the housing40by roller bearings54and a thrust bearing56in the example. An output member52is provided at one end of the hollow shaft50, for example, and is operatively coupled to the output shaft44.

The hollow shaft50has a wall58with radially spaced interior and exterior surfaces60,62. A first passage88extends through the wall58and is configured to communicate fluid between the interior and exterior surfaces60,62. A sleeve64provides the fluid coupling onto the hollow shaft50. Leakage is controlled by the use of close-tolerance lands at localized portions of the exterior surface62and the interior surfaces of the sleeve64. Annular voids created between the close tolerance seal lands provides a second passage90, which is annular, that aligns with first passage88to transfer fluid (fluid flow shown by small arrows) between an externally mounted controller device110and the interior of the hollow rotating shaft50.

As can be appreciated from the figures, more than one passage may be provided through the hollow shaft50. For example, first and second members82,84may be nested within the interior of the hollow shaft50and provide an annular passage83that communicates another fluid flow within the hollow shaft50. In the example, the fluid actuates a two-way hydraulic cylinder (not shown) mounted on the output shaft52.

In the example, the sleeve64is arranged axially at mid-span between the roller bearings54. Manufacturing runouts, bearing clearances and induced bending moments on the shaft flange52may result in the hollow shaft50having some undesired radial movements in the area of the coupling sleeve64. To this end, the fluid coupling46includes one or more locating features that maintain the sleeve64in desired circumferential, axial and radial positions while permitting some radial movement of the sleeve64to maintain a uniform gap and desired sealing engagement with the hollow shaft50.

The sleeve64includes a locating feature, provided by a tab66in one example, configured to permit nominal radial movement of the sleeve64relative to the housing40. The tab66, which acts as a key in the example, is received in a slot70provided by a boss68in the housing40. A nominally suitable tangential clearance is preserved in that key and slot arrangement. A radial clearance112is provided between the housing40and tab66to permit the sleeve64to float, best shown inFIG. 5B. The tab66extends an axial length T and includes a circumferential width W, best shown inFIG. 5A. The clearances aid in assembly and allow compliance of the sleeve unit during operation.

Returning toFIG. 3, the sleeve64includes a first side74. The hollow shaft50has a groove78that receives a retaining ring80, which provides an axial stop on the shaft body. In the example, the tab66is flush with a second side76of the sleeve64. The boss68provides an axial stop72for the sleeve64. Thus, the boss68and the retaining ring80axially locate the sleeve64within an allowable set of operating clearances.

Referring toFIG. 4, in one example, the sleeve64has an interior surface92providing first and second sealing surfaces. These surfaces can include features that improve sealing capability, such as grooves94, axially spaced from the edges and one another. The seal lands bound the annular passage90. The sleeve64includes a boss98that receives a transfer tube102, for example, which provides a port100(two shown). The port100supplies fluid communication with the annulus passage90. The housing40includes a clearance hole104(two exist, one is shown), best shown inFIGS. 5A and 5B. A transfer tube102extends through each hole104and is removably received in the port100. A controller110is secured to the housing40over the tubes102and selectively regulates fluid flow and pressure into the fluid coupling46. Three seals106,108, and114respectively seal between the transfer tube102, the sleeve64, housing40, and controller110. In this manner, and with its extended length and tangential entry into sleeve, the transfer tube102further accommodates some radial movement of the sleeve64during operation.

An example method of assembly of the fluid transfer coupling46is schematically shown inFIG. 3by the large block arrows. The assembly method includes installing the sleeve64about the exterior surface62of the hollow shaft50to provide a shaft assembly. In the example, the sleeve64slid over the hollow shaft50until the first side74abuts the retaining ring80. The shaft assembly is inserted into the housing40until the thrust bearing56bottoms on housing40. The tab66is positioned relative to the corresponding slot70, where the second side76maintains a nominal axial clearance to the stop72. The sleeve64is permitted to float radially relative to the housing40due to the radial clearance112(FIG. 5B). The transfer tubes102are inserted through the holes104and into the ports100. The actuator110is secured to the housing40to capture the tubes102. In this manner, the short, direct control loop is provided between the actuator and the hollow shaft50and components fluidly connected to the hollow shaft50.