WO1990008695A1

WO1990008695A1 - Retractable brush block

Info

Publication number: WO1990008695A1
Application number: PCT/US1989/000449
Authority: WO
Inventors: Jon H. Young
Original assignee: United Technologies Corporation
Priority date: 1989-02-06
Filing date: 1989-02-06
Publication date: 1990-08-09

Abstract

Electric power is transferred to a rotating member (14) by a rotating conductive ring (24) and a retractable carrier (20). At least one brush (26) in the carrier (20) contacts the conductive ring (24) when transferring electric power. When the carrier (20) is retracted, the brush (26) and conductive ring (24) are separated.

Description

RETRACTABLE BRUSH BLOCK

FIELD OF THE INVENTION

The present invention relates to a device for transferring electrical power between a stationary frame and a rotating component, such as a propeller.

BACKGROUND

Propeller driven aircraft require, on occasion, the application of heat to the surfaces of the propeller blades and spinner for removing or preventing the formation of ice. One such method of ice removal is by means of electrically heated elements on or beneath the surfaces and powered as required by a source of electrical energy carried on the main body of the aircraft. The electric power is transferred to the rotating propeller assembly by means of a brush block or carrier holding one or more conductive carbon brushes which are resiliently urged against corresponding conductive rings disposed in the rotating propeller assembly and concentrically about the propeller shaft.

This prior art arrangement, while effective, is subject to wear of the carbon brushes caused by the friction of sliding between the brushes and the conductive rings. It is important to note that such wear is independent of the frequency or duration of electric deicer operation, being primarily a function of the propeller run time.

As will be appreciated by those skilled in the art, the reduction of a scheduled maintenance task on an aircraft translates directly into reduced materials and services costs for the aircraft operator. What is needed is an arrangement for transferring intermittently required electrical power across a rotating gap which is also able to achieve extended periods of time between replacement as compared with the prior art.

SUMMARY OF THE INVENTION

The present invention provides a retractable brush block which establishes electrical contact with a rotating component only during periods wherein the transfer of electric power across the rotating gap is required.

The brush block according to the present invention is mounted on a movable support which is selectively driven out of contact with the rotating component by a solenoid or other actuator. In the preferred embodiment, a biasing means is provided for continually urging the brush block toward one or more annular conductive surfaces on the rotating component for the purpose of achieving a fail-safe condition in the event of a failure of the withdrawing actuator.

By withdrawing the brush block from contact with the rotating component, the present invention provides a longer total operating period between replacement of the contacting brushes thereby reducing the costs of service and lost availability. Both these and other features and advantages of the apparatus according to the present invention will become apparent to those skilled in the art following a review of the following specification and the appended claims and drawing figures. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a view of a brush block according to the present invention installed in a propeller driven aircraft. Figure 2 shows a cross section of one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a brush block energy transfer arrangement 10 according to the present invention as installed in an aircraft 12 having a propeller assembly 14 driven by a shaft 16 rotating about an axis 18. The brush block 20 is disposed adjacent the propeller assembly 14, and more specifically adjacent the rear bulkhead 22 of the assembly 14. Included in the rear bulkhead 22 are one or more annular conductive copper surfaces 24 which contact, at least during periods wherein it is desired to transfer electrical power to the propeller assembly 14, corresponding carbon brushes 26 carried by the brush block 20.

The arrangement of carbon brushes 26 within a carrier or brush block 20 is well known, with such brushes 26 being resiliently mounted or spring loaded so as to press firmly but flexibly against the rotating conductive surfaces 24. As also noted above, such brushes 26, being essentially solid carbon blocks, are subject to wear due to the frictional action of the rotating surfaces 24.

The brush block 20 according to the present invention is shown in Figure 1 as being pivotally mounted 28 to the nonrotating portion 30 of the aircraft 12. The brush block 20 is pivoted about the pivot point 28 by means of a linear or other actuator 32 which selectively positions the brush block 20 as required.

During periods wherein it is desirable to transfer electric power across the rotating gap 34 the actuator 32 positions the brush block 20 proximate the rotating bulkhead 22 such that the brushes 26 contact the corresponding conductive rings 24. Direct electrical contact between the rotating propeller assembly 14 and the nonrotating portion 30 of the aircraft 12 is thus established. A relay (not shown) or other power interrupting device may optionally be provided for ensuring that the brushes and conductive rings do not "arc over" as the brush block is reciprocated between the operating and retracted positions.

It should be noted that although there may be a plurality of brushes 26 and corresponding conductive rings 24 as shown in Figure 1, the retractable brush block arrangement 10 according to the present invention is equally effective in circumstances or arrangements wherein there is a need for only one conductive ring 24 and corresponding brush 26. The use of multiple rings 24 and brushes 26 follows typical practice of utilizing a plurality of blade surface heating circuits (not shown) for sequentially deicing individual or opposing pairs of propeller blades 36.

During periods wherein there is no requirement to supply deicing electrical energy to the rotating propeller asssembly 14, actuator 32 is selectively operated to retract the brush block 20 away from the bulkhead 22 and conductive rings 24, thereby separating the brushes 26 and rings 24 and eliminating frictional wear therebetween.

Figure 2 shows a more detailed cross section of another embodiment 38 of the retractable brush block according to the present invention. In the Figure 2 embodiment, the brush block 38 includes a carrier 40 supported by a sliding mount 42 which is in turn secured to the nonrotating airframe 30. Individual brushes 26 are disposed in the carrier 40 and selectively positioned so as to contact corresponding annular conductive rings 24 disposed concentrically about the axis of rotation 18 (not shown in Figure 2) in the bulkhead 22.

An actuator 44 is provided for selectively withdrawing the carrier 40 axially away from the bulkhead 22 thereby separating the brushes 26 and surfaces 24. Also included in this second embodiment 38 are biasing means 46 in the form of coil springs or the like for continually urging the carrier 40 axially toward the conductive surfaces 24. The actuator 44, preferably an electrically operated solenoid, is of sufficient size to overcome the spring force 46 when energized, thus withdrawing the carrier 40 and separating the surfaces 24 and brushes 26. When it is desired to provide electric power across the rotating gap 34, solenoid actuator 44 is deenergized and the biasing means 46 operates to drive the carrier 40 axially toward the surfaces 24 establishing contact with the brushes 34. The carrier 40 may be retained within the sliding mount 42 by any of a variety of methods or structures, such as the interfering shoulders 48, 50 shown in Figure 2. Electrical power is transferred between the nonrotating structure 30 and the carrier 40 by flexible wiring 52, etc.

Although disclosed and claimed in terms of a rotating propeller in an aircraft application and for the purpose of providing intermittent electrical energy to the blades of such propeller assembly for deicing, it will readily be apparent to those skilled in the art that the retractable connector according to the present invention is well suited for any of a variety of applications wherein it is desired to establish intermittent direct electrical contact between two members across a rotating gap.

The foregoing disclosure and referenced drawings are thus intended solely to illustrate certain embodiments of the retractable connector according to the present invention and should not be interpreted as limiting the scope or application thereof, except as specifically recited in the claims presented hereinbelow.

Claims

1. In an aircraft having an intermittently electrically heated propeller assembly rotating about a central axis, the propeller assembly further including a rotating annular conductive surface and the aircraft further including a nonrotating brush carrier having at least one brush means for contacting said annular surface and transferring electric power thereto, the improvement comprising: means, operable during periods wherein the propeller assembly is not heated, for withdrawing the brush carrier away from the annular surface and separating the contacting brush means from the annular surface.

2. The aircraft as recited in Claim 1, wherein the withdrawing means is an electrically operated solenoid.

3. The aircraft as recited in Claim 2 wherein the withdrawing means includes means for continually urging the brush carrier toward the annular surface, and wherein the solenoid is energized to withdraw the brush carrier and deenergized to establish contact between the contacting brush means and the corresponding annular surface.

4. A device for intermittently and selectively establishing direct electrical contact between a rotating member and a nonrotating member, comprising: a rotating annular surface disposed in the rotating member, the surface being coaxial with the axis of rotation and oriented so as to face toward the nonrotating structure, a brush carrier including at least one resiliently mounted brush, said brush electrically connected to a source of electric power, means, operable during periods wherein no electrical transfer is desired, for withdrawing the brush carrier away from the annular surface, the withdrawing means further adapted to separate the brush and corresponding annular surface, and further including means for biasing the brush carrier toward the annular surface.

5. Apparatus for intermittently transferring electric current between a rotating member and a fixed member, comprising an annular conductive surface, disposed on the rotating member concentric with the axis of rotation, a carrier having a brush disposed therein, said carrier supported from the fixed member, and means for moving said carrier toward the conductive surface to establish electrical contact between the surface and the brush and for withdrawing said carrier from the conductive surface and separating the brush therefrom.