Patent Application
20050127764
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.
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.
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.
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.
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.
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.
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.
An apparatus for providing electrical coupling, comprising a motor having a hollow, rotational shaft, and an electrical conductor located within said shaft.
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.
As mentioned with respect to
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.
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
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.
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.
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.
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.
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.
