Abstract:
An apparatus for providing electrical coupling, comprising a motor having a hollow, rotational shaft; and, in one embodiment, an electrical conductor located within said shaft for providing electrical signals through the motor.

Description:
I. FIELD  
       [0001]     The present invention pertains generally to the field of motors and electrical circuits, and more specifically to a motor for providing an electrical feed-through to a rotating object.  
       II. BACKGROUND  
       [0002]     Electric motors have been used for many years, for instance, to rotate antenna platforms. In many instances, antennas are mounted to a structure commonly known as a turntable. An electric motor is mounted underneath the turntable and attached thereto, and is used to rotate the turntable and, hence, the antenna, to maximize the antenna signal strength.  
         [0003]     The turntable rotates with respect to the motor and any circuitry not located on the turntable. Hence, there is a need to couple electrical signals to the rotating antenna platform. Traditionally, this has been accomplished by use of a rotational coupler, which is a device that rotates with respect to fixed circuitry yet allows electrical signals to be transmitted from the fixed circuitry and onto one end of a rotating member of the rotational coupler. The other end of the rotational coupler is typically fixed to, for instance, circuitry located on the turntable.  
         [0004]     The use of a rotary coupler typically demands that the motor be located off-axis from the central axis about which the turntable rotates. One or more belts, gears, or similar devices is used to couple rotational energy from the motor to a pulley attached to the turntable, thereby causing the turntable to rotate.  
         [0005]     Generally, the location of the motor off-axis presents several problems. Often, there is limited space for a motor to be mounted anywhere in an antenna structure, so it becomes a challenge to fit all necessary electrical components and the motor onto the surface of the base. Locating the motor along the central rotating axis of the turntable would be ideal, however it is necessary to locate the rotational coupler in that particular area, due to the physical constraints of the rotational coupler.  
         [0006]     Additionally, the reliability of such an antenna system is diminished somewhat, due to the use of the belt or gears, which can wear out, break, or slip in relation to the motor or the pulley to which it is attached.  
         [0007]     What is needed is a way to locate the motor along the turntable central axis and attach it directly to a turntable, platform, or antenna, while still providing electrical signals to and from the turntable, platform, or antenna.  
       SUMMARY  
       [0008]     An apparatus for providing electrical coupling, comprising a motor having a hollow, rotational shaft, and an electrical conductor located within said shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  illustrates an isometric, exploded, cutaway view of an antenna assembly using a feed-through motor;  
         [0010]      FIG. 2  illustrates a close-up, isometric, exploded, cutaway view of one embodiment of the feed-through motor of  FIG. 1 ; and  
         [0011]      FIG. 3  illustrates the antenna assembly of  FIG. 1 , shown in a cross-sectional view. 
     
    
     DETAILED DESCRIPTION  
       [0012]     The embodiments described herein are described with respect to an electric motor, commonly used to rotate antenna platforms. However, it should be understood that the motor could alternatively comprise any type of motor, including those driven by means other than electrical signals. In addition, the embodiments described herein may be used in applications other than antenna assemblies, such as in automotive applications, computer applications, or any other application where it is desirous to transmit an electrical signal to a rotatable platform.  
         [0013]      FIG. 1  illustrates an isometric, exploded, cutaway view of an antenna assembly  100 , comprising motor  102 , antenna horn  104 , platform  106 , and circuit board  108 . Motor  102  is mounted against circuit board  108  and is used to rotate platform  106  and antenna horn  104  when assembled. Motor  102  comprises shaft  110  which, in one embodiment, comprises conductor  112 . One end of conductor  112  is electrically connected to circuit board  108  while the other end of conductor  112  extends into a cavity formed by platform  106  and antenna horn  104  when assembled. Shaft  110  is connected to platform  106 , enabling platform  106  and antenna horn  104  to rotate about an axis around shaft  110 . Conductor  112  resides within shaft  110  and, in this embodiment, is not connected to shaft  110 . Therefore, conductor  112  remains stationary as shaft  110  rotates about its axis.  
         [0014]      FIG. 2  illustrates a close-up, isometric, exploded, cutaway view of one embodiment of the feed-through motor of  FIG. 1 . In this embodiment, a semi-rigid coaxial cable  200  is housed inside shaft  110 . Shaft  10  is rotated about a central axis by an electromagnetic force generated by exciting windings of motor  102 . Shaft  110  is additionally connected to platform  106  which in turn provides a bottom portion of a horn antenna assembly (not shown). Coaxial cable  200  extends past a top portion of shaft  110 , exposing coaxial cable  200  to a cavity formed by the platform  106  and the horn antenna assembly. The other end of coaxial cable  200  extends past a lower portion of shaft  110 , through motor  102 , and through circuit board  108  where it is electrically connected to electronic circuitry used to generate and receive high frequency electronic transmissions.  
         [0015]      FIG. 3  illustrates the antenna assembly  100  of  FIG. 1 , shown in a cross-sectional view, including motor  102  in accordance with one embodiment of a feed-through motor. Motor  102  in this example comprises a stepper motor, however any type of motor could be used alternatively, including a D.C. brush or brushless motor, a servo motor, a brushless servo motor, and others, including motors that are driven by means other than electricity, such as a gasoline-powered motor.  
         [0016]     As mentioned with respect to  FIG. 1 , the antenna assembly  100  comprises motor  102 , antenna horn  104 , platform  106 , and circuit board  108 . The antenna horn  104  rotates about an axis  300  as shown to allow it to maximize the signal strength of high-frequency signals received by antenna horn  104 . It should be understood that any other type of rotatable assembly could be used in place of antenna horn  104 , such as a circuit board for receiving electric signals through motor  102  or any other type of mechanical assembly.  
         [0017]     Motor  102  comprises stator  202 , hollow shaft  110 , and, in one embodiment, conductor  112 . Shaft  110  is rotated with respect to stator  302  using principles well-known in the motion-control art. For example, shaft  110  may be rotated to any position using motor-control circuitry (not shown) in accordance with generally-known stepper motor principles.  
         [0018]     Shaft  110  comprises a hollow, cylindrical member, able to rotate with respect to stator  302 . Shaft  110  may be formed by drilling or by any other means known in the art. In one embodiment, motor  102  is constructed with conductor  112  located within shaft  110 . In other embodiments, motor  102  is constructed without conductor  112 , the conductor  112  inserted or otherwise introduced through shaft  110  during a later time, such as the mounting of motor  102  onto circuit board  108 . Conductor  112  functions to provide electrical signals from circuit board  108  to antenna horn  104 . For example, in one embodiment, shaft  110  comprises a conductor which is used to pass electrical signals. In the example of  FIG. 3 , one end of conductor  112  is connected to circuit board  108  by any convenient means, such as soldering. Alternatively, or in addition, conductor  112  is electrically coupled to circuitry located on circuit board  108 . The other end of conductor  112  extends into a cavity of antenna horn  104  and, in this embodiment, remains unconnected from any physical portion of antenna horn  104 .  
         [0019]     In one embodiment, conductor  112  is not connected to shaft  110  so that conductor  112  remains stationary as shaft  110  rotates, and therefore antenna horn  104 , about axis  300 . In another embodiment, conductor  112  is affixed to shaft  110  and rotates along with shaft  110  around axis  300 . In this embodiment, at least one end of conductor  112  comprises a rotary coupling. For example, a rotary coupling is needed at the juncture of a signal source located on or within circuit board  108  (such as a circuit trace, microstrip, or waveguide coupler) and conductor  112 . In other applications where both ends of conductor  112  are connected to a mechanical structure, such as a circuit board, two rotational couplers are needed, one located at the juncture of a signal source located on or within circuit board  108  (such as a circuit trace, microstrip, or waveguide coupler) and one needed at the opposite end of conductor  112  where conductor  112  attaches to a mechanical structure, such as a turntable, platform, or directly to antenna horn  104 .  
         [0020]     In embodiments where conductor  112  is affixed to the shaft and rotates therewith, conductor  112  may comprise a flexible, rigid, or semi-rigid coaxial cable. Such a coaxial cable typically comprises a non-conductive sleeve surrounding a conductor, dielectric, and shield. The sleeve may be held fixedly within shaft  110  by an adhesive, by press fitting, or by any other means generally known in the art. In an embodiment where a non-conducting sleeve is not used, such as the case of some rigid or semi-rigid coaxial cables, the shield may be connected directly to the shaft from within, held in place by an adhesive, by press fitting, soldering, welding, or any other means generally known in the art. In still another embodiment, shaft  110  forms the shield of the coaxial cable, wherein a dielectric and center conductor are located within shaft  110 . In yet another embodiment, shaft  110  comprises a waveguide.  
         [0021]     Conductor  112  comprises any electrical conductor known in the art including an insulated or non-insulated wire, a coaxial cable, a waveguide, or a combination thereof. Electrical signals carried by conductor  112  may comprise digital or analog signals, from D.C. to microwave frequencies and beyond.  
         [0022]     The advantages of this design allows motor  102  to be located along an axis of rotation of platform  106 /antenna horn  104 , thereby freeing space on circuit board  106  for other components. In addition, one or more drive belts, used in applications where a motor is located off-axis, are eliminated, adding to the reliability of antenna assembly  100 .  
         [0023]     The preferred embodiments of the present invention have thus been shown and described. It would be apparent to one of ordinary skill in the art, however, that numerous alterations may be made to the embodiments herein disclosed without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited except in accordance with the following claims.