Abstract:
A split slip ring assembly formed from first and second halves of a slip ring having a contact surface for rotational engagement with a stationary brush element for transferring electrical signals there between. The contact surface has a smooth surface at the junction of the first and second halves. A fastener locates the first and second halves to form a ring shape. An electrical contact on the ring carries electrical signals between the slip ring and the brush element. An alignment element aligns the first and second halves to form the smooth surface at their junction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims priority to U.S. Provisional Pat. App. No. 61/134,896 filed Jul. 15, 2008, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    This invention relates generally to a assembly used to provide electrical power and communication signals operating on a rotating portion of an aircraft. More particularly, the present invention relates to a slip ring used with an aircraft rotating component such as a propeller, and specifically attached to the aft portion of the propeller hub. 
         [0003]    Present propeller designs are connected to the gearbox output shaft using a bolted flange on the propeller hub. The flange connection adds weight to the aircraft. An alternative to a bolted flange is hub that is integral with the gearbox output shaft. The slip ring assembly conventionally employed provides electrical connections between the rotating and non-rotating components of the propeller. Conventional slip rings have non-rotating brushes conductively coupled to one side of each connection and slidingly engaging rotating rings that are conductively coupled to the other side of each connection. In time, the brushes become worn and need to be replaced. Removal of the slip ring, for maintenance or replacement, requires complete removal of the propeller, or in the case of an integral hub and gearbox shaft replacement requires complete removal of the gearbox. 
         [0004]    Not providing maintenance and service for slip ring assemblies is not an option since failure of the slip ring, such as by brush failure, may result in the inability of the deicing equipment to properly function. 
       SUMMARY 
       [0005]    A slip ring is formed from two parts that form a smooth surface for the brushes to ride on. The two halves are assembled apart from the propeller hub and are machined to give a uniform surface with a tolerance between the diameters of the two parts being less than 0.1 micron. Thus the smooth surface at the junction when the two components are assembled together has essentially no step that would adversely affect the wear on the stationary brushes. 
         [0006]    The two parts are held together by a fastener such as a pair of bolt and nut assemblies at the junction of the two parts. A guide such as a dowel may be used to effectively align the two components to maintain the smooth junction. The slip ring can then be easily attached to a propeller hub or other rotating element. The electrical connections to the slip ring and the stationary brushes are made to transmit the electrical power for deicing the propeller, or another appropriate signal that slip rings are designed to transmit. Due to the split design a jumper wire or other electrical connection is required between the first half of the slip ring and the second half. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a section view of the nose of an aircraft propeller assembly showing the location of the present invention. 
           [0008]      FIG. 2  is an enlarged view of the components shown in circle  17  in  FIG. 1 . 
           [0009]      FIG. 3  is a rear elevational view of the assembly of this invention. 
           [0010]      FIG. 4  is an alternative view of a portion of the assembly in  FIG. 3 . 
           [0011]      FIG. 5  is a view of a part of the assembly in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The present invention is useful for most aircraft propellers, particularly those that have a deicing feature. Slip rings are used to transfer a signal or electric current to or from a stationary component to a rotating component, where the ring rotates and the brushes remain fixed or stationary. The use of a slip ring that could be disassembled separately would permit assembly or replacement of the ring in the field and would eliminate the need for the conventional flange now being used to connect the propeller and gearbox shaft allowing the hub to be integrated with the gearbox shaft. 
         [0013]    A typical aircraft propeller assembly  10  is shown in  FIG. 1 , with parts cut away. Blade  11 , also cut away, is driven by a shaft  13  that drives blade  11  in a conventional manner. Shaft  13  takes the rotation of the gas turbine engine, which may operate at 20,000 rpm, and reduces it to a useable rotation for the blades to 1,200 rpm or the like.  FIG. 1  shows where the slip ring assembly  17  is located. Slip ring assembly  17  is attached to the hub using a suitable connection like bolts. Spinner  15  is an aerodynamic shell that houses blade counterweight  21 . Blade counterweight  21  serves as a safety device when the system hydraulics, not shown, fail, and aligns blade  11  in a position of least drag, rather than allowing blade  11  to turn to the greatest drag. Other conventional elements in the spinner  15  are blade retention assembly  23 , spinner support bulkhead  25 , hub  27  and actuator  29 . Actuator  29  controls the pitch angle of blade  11 . 
         [0014]    The slip ring transmits electrical power for blade deicing, and can be used for other purposes such as transmitting control signals.  FIG. 2  illustrates the slip ring assembly  17  in greater detail. Three slip rings  31   a ,  31   b  and  31   c  are mounted in a non-conductive slip ring housing  33 . Housing  33  is attached to support  19  with a structural slip ring housing  35 . Housing  35  is made of aluminum in this assembly though any conductive structural material is suitable. Heater leads  37  are connected to the slip ring housing with threaded studs  39  which are electrically and structurally attached to the back of the slip rings, and retention nuts  41 , and the heater leads  37  transmit the electrical current to the de-icer unit, not shown, in a conventional manner. The brushes  43   a  for slip rings  31   a ,  31   b  and  31   c  are mounted in a housing  43  and attached to the gearbox front housing by bracket  45 . Brushes  43   a  are shown spaced a bit from slip rings  31   a,    31   b  and  31   c  to illustrate their separate shapes, but in operation, rings and brushes are in contact to function in a normal manner. Housing  35  is rotated by support  19  as the entire propeller assembly  10  rotates. Slip rings  31   a,    31   b  and  31   c  transmit or receive electrical signals to or from stationary brushes  43   a . For example, brushes  43   a  may transmit electrical energy to slip rings  31   a ,  31   b  and  31   c  to power a de-icer unit. 
         [0015]      FIG. 3  is a rear view of the slip ring assembly with slip rings  31   a ,  31   b  and  31   c  joined together at junction  49  inside non-conductive housing  35  and conductive housing  33 . Split line bolts  51  and nuts  53  hold a matched set of bulkheads  55  and  57  to support slip rings  31   a ,  31   b  and  31   c  in place in housings  33  and  35 . Bulkheads  55  and  57  are aligned with one or more alignment dowels  59 . Not shown in  FIG. 3  are jumper wires between each slip ring half to maintain electrical continuity. Prior to assembly and use in an aircraft, the split rings  31   a,    31   b  and  31   c  are assembled and the inner surfaces are machined to virtually zero tolerance at junction  49  so that the junctions  331   a ,  331   b  and  331   c  have no step or misalignment and present a smooth running surface to the brushes  43   a . When reassembled, split rings  31   a,    31   b  and  31   c  present that smooth running surface to the brushes  43   a  and function as if the split ring junctions shown as  331   a ,  331   b  and  331   c  were formed from a solid ring rather than from two halves, with smooth running surfaces so the life of the brushes is not affected. Accordingly, when the slip ring assembly  17  is installed in an aircraft or other location where slip rings are used, slip rings  31   a,    31   b  and  31   c  of  FIG. 2  function as any slip ring does. When the rings have become worn or damaged, however, it is a simple matter to remove nuts  53  from bolt  51  without having to disassemble anything else, and they can be repaired or replaced at a substantial savings in time and labor. 
         [0016]      FIG. 4  illustrates a different orientation for split slip rings  131   a ,  131   b  and  131   c  which are mounted on non-conductive housing  133 , which is in turn mounted by bolts  139  and nuts  141  on hub  135 . Conductive housing  135 , split slip rings  131   a ,  131   b  and  131   c  operate in a conventional manner with brushes  143   a , which are mounted in housing  143  and attached to gearbox  147  with bracket  145 . Again split slip rings  131   a ,  131   b  and  131   c  are first assembled outside the location of use, and junction  149  is machined to have a smooth running surface. Then split slip rings  131   a,    131   b  and  131   c  are put into location and they function as other slip rings do and are in contact with brushes  143   a , rather than spaced as shown for illustration purposes. 
         [0017]      FIG. 5  shows how the junction  149  mates the two halves of split slip rings  131   a,    131   b  and  131   c . They are held in place with bolts  139  (in  FIG. 4 ) and nuts  141 . Junction  149  has been machined to join the two halves of split slip rings  131   a ,  131   b  and  131   c  to function as conventional solid rings. Jumper wires are required between each slip ring half. 
         [0018]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.