Abstract:
A system includes a slip ring plate and a pair of brush assemblies mounted on each side of a housing. The disk-shaped slip ring plate is mounted to a first gimbal member and has a plurality of concentric, truncated circular shaped electrical conductive segments disposed on one surface thereof, the electrical conductive segments being electrically insulated from each other and divided (truncated) into half circular segments by discontinuities on each side of the slip ring plate. Pins ( 22 ) are fixed to a cylinder ( 152 ) on the gimbal ( 22 ). The pins ( 22 ) pass through acruate slots ( 40 ) in the slip ring ( 18 ). Motors ( 14, 16 ) are used to cause rotation of the gimbal with the slip ring remaining stationary until the pins engage ends of the slots ( 40 ), the slip ring then rotating with the gimbal, the rotation being limited by slip ring stops engaging housing stops. The brush assembly has a like plurality of brushes, each of the brushes being positioned in electrical contact with a corresponding one of the plurality of conductive segments while the brush assembly and disk-shaped ring platter rotate with respect to each other about an axis common to the concentric, truncated circular shaped conductive segments.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to gimbal systems and more particularly to gimbal systems adapted for use in guided missile seekers. 
     As is known in the art, gimbal system are used in a wide range of applications. One such application is in guided missile seekers. More particularly, guided missiles typically include in the frontal portion thereof a seeker, such as a radar, infrared, or electro-optical seeker, disposed within the missile&#39;s body behind a dome (i.e., a radome or IR dome, for example). The seeker is mounted to the interior body of the missile, by a gimbal system, such as a three-degree of freedom pitch-yaw gimbal system or a six-degree of freedom pitch-yaw-roll gimbal system. 
     The seeker includes a sensor, such as a radar antenna, on IR detector, or a laser energy detector, and associated electronics, such as hybrids, A/D converters. amplifiers, etc, and additional support devices, such as body rate sensors (i.e, gyros), torque motors, and resolvers, etc. Further, the gimbals are driven by motors in response to signals supplied by the missile&#39;s guidance system and fed to the sensors, associated electronics, additional support devices, and motors through cables. In some applications, as many as 70 cables are required for the seeker/gimbal system. 
     Typically, these cables, or electrical wires, are harnessed and such harness wraps around a gimbal axis to provide a “service loop” configuration to accommodate large gimbal angles. A harness of this size is relatively inflexible; a condition which worsens at cold temperature. Further, there is relatively little space for the harnessed cables. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a system is provided including a slip ring plate and a brush assembly. The disk-shaped slip ring plate is mounted to a first gimbal member and has a plurality of concentric, truncated circular shaped electrical conductive segments disposed on one surface thereof, the electrical conductive segments being electrically insulated from each other. The brush assembly has a like plurality of brushes, each of the brushes being positioned in electrical contact with a corresponding one of the plurality of conductive segments while the brush assembly and disk-shaped ring platter rotate with respect to each other about an axis common to the concentric, truncated circular shaped conductive segments. 
     In accordance with another embodiment of the invention, a gimbal system is provided including a slip ring plate and a brush assembly. The disk-shaped slip ring plate is mounted to a first gimbal member and has a plurality of truncated circular shaped electrical conductive segments disposed on one surface of thereof, such circular shaped conductors having a common central axis, a plurality of the electrical conductive segments being disposed along a common radius from the central axis, the conductive segments being electrically insulated from each other. The brush assembly has a like plurality of brushes, each of the brushes being positioned in electrical contact with a corresponding one of the plurality of conductive segments while the brush assembly and disk-shaped ring platter rotate with respect to each other about an axis common to the concentric, truncated circular shaped conductive segments. 
     In accordance with another embodiment of the invention, a gimbal system is provided. A disk-shaped slip ring plate is mounted to a first gimbal member having a plurality of electrically isolated sectors, each one of the sectors having truncated circular shaped electrically insulated conductive segments disposed on the surface, the circular shaped conductors having a common central axis. The system also includes a like plurality of brush assemblies, each one of the assemblies being positioned to electrically contact the segments in a corresponding one of the sectors while the brush assembly and disk-shaped ring platter rotate with respect to each other about an axis common to the concentric, truncated circular shaped conductive segments. Each one of the assemblies includes a plurality of brushes, each of the brushes being positioned in electrical contact with a corresponding one of the conductive segments in the sector associated with such brush assembly. 
     In accordance with another embodiment of the invention, a system is provided including a housing, a motor, a bearing, a slip ring, a gimbal, an elongate member, a plurality of conductive wires, and a brush assembly. The motor is mounted to the housing, the motor for providing torque to a rotatable portion thereof that is rotatable relative to the housing along an axis. The bearing is mounted to the housing and includes a rotatable portion that is rotatable relative to the housing about the axis. The disk-shaped slip ring includes a surface on which a plurality of arcuate conductors are disposed, the plurality of arcuate conductors being concentric about the axis and separated by at least one electrically insulative discontinuity extending radially from the axis, the slip ring defining an arcuate opening that is concentric about the axis and that is partially defined by endwalls. The gimbal is nonrotatably coupled to the rotatable portion of the motor and to the rotatable portion of the bearing. The elongated member is attached to the gimbal and extends through the arcuate opening. The plurality of conductive wires are each electrically connected to one of the plurality of arcuate conductors. The brush assembly is fixedly attached to the housing and includes a plurality of conductive brushes each electrically contacting one of the plurality of arcuate conductors. When the motor rotates the gimbal, the slip ring is substantially stationary while the elongated member is displaced from the endwalls of the arcuate opening and is urged to rotate about the axis when the elongated member is forced against an endwall of the arcuate opening. 
     In accordance with another embodiment of the invention, an assembly is provided. The assembly includes a gimbal and a slip ring defining an axis and including a plurality of arcuate conductors that are concentric about the axis, the slip ring further defining an arcuate opening that is concentric about the axis and that is partially defined by endwalls. A elongated member extends from the gimbal through the arcuate opening, the elongated member being configured to move angularly within the arcuate opening when the gimbal and slip ring are rotated with respect to each other about the axis, and to engage the endwalls of the arcuate opening. 
     In accordance with another embodiment of the invention, an assembly is provided. A gimbal includes a first gimbal engaging surface and a second gimbal engaging surface. An electrically insulative disk is coupled to the gimbal and defines an axis, the disk being rotatable relative to the gimbal about the axis. The disk includes a plurality of arcuate conductors that are concentric about the axis and are disposed on a surface of the disk, a first disk engaging surface, and a second disk engaging surface angularly displaced about the axis from the first disk engaging surface. The first disk engaging surface is disposed to interfere with the first gimbal engaging surface to induce rotation of the gimbal relative to the disk in a first angular direction, and the second disk engaging surface is disposed to interfere with the second gimbal engaging surface to induce rotation of the gimbal relative to the disk in a second angular direction. 
     Various aspects of the invention may include one or more of the following advantages. Large amounts of conductor runs can pass from one axis to another without typical wire bundling, service loop coiling, or along-axis feed through. Wide angle field of view (FOV) capabilities are provided while also providing low friction to inertia, and accommodating for environmental requirements such as acceleration and vibration, and accommodating look angle and packaging constraints. Large wire counts are provided in highly flexible, non-binding flex prints that can accommodate large rotation angles without requiring a large volume. Conductor runs can be shielded to reduce electromagnetic interference in easily-producible flex print cabling that provides reliable, high-quality performance. Small angle (e.g., 5-10°) rotation is provided for without significant, if any, slip ring rotation. Slip ring wear is reduced and lifetime lengthened compared to traditional slip rings. Noise between brush contacts and slip ring conductors is reduced, if not eliminated, compared to traditional slip rings. Larger arcuate slip ring travel is provided than the arcuate length of a sector of conductors on a slip ring. Brush contacts slide very little, if at all, on corresponding slip ring conductors during small-angle rotation stabilization of a gimbal. Freely flexible, shielded wiring for a yaw axis is provided. Mechanical flexibility and rotation of the yaw axis of approximately ±25° using a freely flexing, shield cable are provided. Freely flexing, shielded cabling is provided for the pitch axis. Gimbal system cabling is electromagnetically shielded. A slip ring arrangement can be used with less than a four-inch circumferential conductor length of unshielded conductor. A slip ring is provided that has a more modular, conformed packaging with improved ease of installation and repair, producibility and reliability than traditional slip ring gimbal systems. Electrical contact with conductors of the slip ring can be maintained even if a contact to a conductor breaks or otherwise fails. Wide angle FOV is attainable for the pitch axis with little, if any, wiring restriction or induced cabling torque. An increased number of connector runs can be provided compared to traditional slip ring designs. Yaw cables provide a more flexible, less motion restricted, lower torque, and improved ease of assembly, compared to traditional slip ring gimbal systems. Friction to inertia of the slip ring and brush contacts is reduced compared to traditional slip ring designs, improving performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention, as well as the invention itself, will become more readily apparent when taken together with the following detailed description and the accompanying drawings, in which: 
     FIG. 1 is an exploded isometric view of a gimbal assembly; 
     FIG. 2 is an exploded view of a portion of a gimbal, a slip ring, a portion of a housing, two motors, and several elongated fastening members all shown in FIG. 1; 
     FIG. 3 is a top view of the slip ring shown in FIG. 2; 
     FIGS. 4-5 are isometric views with portions of the housing and the gimbal shown in dashed lines; 
     FIG. 6 is a top view of the slip ring shown in FIG. 2 with brush assemblies, shown in cross section, disposed adjacent the slip ring similar to the configuration shown in FIGS. 4-5. 
     FIG. 7 is a schematic diagram of electrical connections for the assembly shown in FIG. 1; and 
     FIG. 8 is a partially-exploded perspective view of a missile employing the gimbal system shown in FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-2 show a gimbal system  10  comprising a housing  12 , two motors  14  and  16 , a disc-shaped slip ring  18 , a gimbal ring  20 , four elongated members  22 , a yaw axis flex cabling  24 , a pitch axis flex cabling  25  and two brush assemblies  26 . As shown, the motors  14  and  16  can be mounted to the housing  12  and can provide torque to portions  28  and  29  of the motors  14  and  16 , respectively, that are rotatable relative to the housing  12  along an elevational, or pitch, axis  30 . The rotatable portions  28  and  29  are fixed to the gimbal  20 . The slip ring  18  includes a surface  34  on which a plurality, e.g., thirty, arcuate conductors  36   25  are disposed. The conductors  36  are concentric about the axis  30  in two sets of fifteen conductors  36  with pairs of conductors being disposed equidistant from the axis  30  and electrically insulated from each other by two electrically insulating discontinuities  38 . The slip ring  18  provides  30  four arcuate openings or slots  40  centered about the axis  30  and disposed equidistant therefrom, and partially defined by end walls  42  and  44  respectively (FIGS.  2 - 3 ). The gimbal  20  is nonrotatably coupled to the rotatable portions  28  and  29  of the motors  14  and  16  by screws  23 . The elongated members  22  have arcuate widths that are less than the arcuate widths of the corresponding arcuate openings  40  in the slip ring  18 . The elongated members  22  are attached to the gimbal  20  through the arcuate slots  40  in the slip ring  18 . The yaw axis cabling  24  includes a plurality of conductive wires each electrically connected to one of the arcuate conductors  36 . The brush assemblies  26  are fixedly attached to the housing  12  and each includes a plurality of conductor brushes  46  and  48  that, when the system  10  is assembled, each contact one of the arcuate conductors  36  (or  37 , FIG.  4 ), respectively. With this arrangement, when the motors  14  and  16  rotate the gimbal  20 , the slip ring  18  is substantially stationary while the elongated members  22  are displaced from the end walls  42  and  44  of the arcuate openings  40  and is urged to rotate about the axis  30  when the elongated members  22  are forced against the end walls  42  or  44  of the arcuate openings  40 . 
     Referring to FIG. 2, the motor  16  is mounted to the housing  12  and fixedly attached to the gimbal  20 . The motor  16  is fixedly mounted to the housing  12 , e.g., with screws (not shown). The rotatable portion  29  of the motor  16  is fixedly attached to the gimbal  20  with screws  23 . The screws  23  extend through holes  21  in the gimbal  20 , an opening  27  in the slip ring  18 , and an opening  15  in the housing  12  and are received by mating threaded holes  19  in the portion  29 . The motor  14  is similarly attached to the housing  12  and to the gimbal  20 . 
     As shown, the slip ring  18  is disposed between the housing  12  and the gimbal  20 , and mates with the gimbal  20 . A circular recess  150  in the slip ring  18  is centered along the pitch axis  30 . The recess  150  is sized and shaped to receive a cylinder  152  extending from the gimbal  20  along the pitch axis  30 . The cylinder  152  and the recess  150  help to align the slip ring  18  while permitting the slip ring  18  to rotate relative to the gimbal  20  about the pitch axis  30 . 
     The elongated members  22  help retain the relationship of the gimbal  20  relative to the slip ring  18 , with the cylinder  152  received by the recess  150 . The elongated members  22  are screws with threaded ends  50  for threadedly engaging threaded holes  52  in the gimbal  20 . The elongated members  22  have smooth cylindrical portions  54  that can be made, or coated, with, e.g., teflon. The cylindrical portions  54  extend through the arcuate openings  40  in the slip ring  18 . The cylindrical portions  54  are sized such that they have a width, or subtend and arc measured from the axis  30 , that is less than the arcuate length (i.e., the arc subtended as measured from the axis  30 ), of the arcuate openings  40 . The cylindrical portions  54  are also sized such that the elongated members  22  can slide within the arcuate openings  40  in the slip ring  18 . The elongated members  22  have a length such that when they are tightened into the holes  52  in the gimbal  20 , the recess  150  of the slip ring  18  receives the cylinder  152  of the gimbal  20  while allowing relative rotational motion between the gimbal  20  and the slip ring  18 . 
     As shown in FIG. 3, the surface  34  of slip ring  18  has a number, here fifteen, concentric truncated circular, or arcuate, electrical conductors  36  centered about the axis  30 . The electrical conductors are circular about the axis  30  and are truncated and arranged in two sectors  56  and  58 . Each of the sectors  56  and  58  contains fifteen electrical conductors  36  that are each about 0.0003 inch gold deposited in an approximately 0.025 inches wide, 0.009 inches deep, “V” groove in the slip ring  18 . Sector  56  contains electrical conductors  36   1 ,  36   2 , . . .  36   15  while sector  58  contains conductors  36   16    36   17 , . . .  36   30 . Pairs of the conductors  36 , one from each of the two sectors  56  and  58 , are equidistant from the axis  30 . In other words, conductors  36   1  and  36   16  are equidistant from the axis as are conductors  36   2  and  36   17  . . . , and conductors  36   15  and  36   30 . More or fewer conductors  36  can be provided on the slip ring  18  depending on the application. The slip ring  18  is made of an electrically insulating material such as glass epoxy and has a circumference of about four inches. 
     The surface  34  of slip ring  18  also includes the two electrically insulating discontinuities  38 . The discontinuities  38  are equispaced about the axis  30  and electrically isolate the sectors  56  and  58  by providing an arcuate expanse of the insulating material separating the conductors  36  along a radial strip on the surface  34  of the slip ring  18 . More sectors can be provided by forming more discontinuities  38  on the slip ring  18 . Although the sectors  56  and  58  are shown of equal angular extent, the discontinuities  38  can be unevenly spaced to provide sectors of unequal angular extent. This directly impacts available gimbal travel and field of view. 
     A similar arrangement is provided on the opposite side  35  of the slip ring  18 , with conductors  37   1 - 37   30  separated by discontinuities  39  (FIG.  4 ). 
     The slip ring  18  also includes the four arcuate slots  40  centered about the axis  30 . The arcuate slots  40  each subtend an arc of about 5-10° plus the arcuate width of the elongated members  22 . 
     Other features are included in the slip ring  18 . A rectangular cutout  60  (FIGS. 1 and 2) is provided in the slip ring  18  to accommodate the yaw axis cabling  24  (FIG.  1 ). Internal groundplanes (not shown) are provided inside the slip ring  18  between surfaces  34  and  35 . 
     FIGS. 4-5 show the slip ring  18 , the brush assemblies  26 , the yaw axis cabling  24  and the pitch axis cabling  25  as assembled with the gimbal  20  and the housing  12 , although the housing  12  is not shown for clarity and the gimbal  20  is only partially shown in dash lines for clarity. The gimbal  20  is mounted as described above through the slip ring  18  with the elongated members  22  (FIGS.  1 - 2 ). The brush assemblies  26  are mounted to the housing  12  along ledges  62  using screws  64 . 
     Each of the brush assemblies  26   1  and  26   2  have twice as many brush contacts  66  and  68 , and  70  and  72 , respectively, per sector  56  and  58  as there are electrical conductors  36  per sector  56  and  58 . The brush contacts  66 ,  68 ,  70 , and  72  are arranged redundantly such that two brush contacts  66 ,  68 ,  70 , or  72  touch or contact each one of the electrical arcuate conductors  36  and  37 . The brush contacts  66 ,  68 ,  70  and  72  extend from the respective brush assemblies  26  and are angled toward the respective electrical conductors  36  and  37  such that the brush contacts  66 ,  68 ,  70 , and  72  are spring biased into electrical contact with the respective electrical arcuate conductors  36  and  37 . The redundant brush contacts  66 ,  68 ,  70 , and  72  have different lengths and different natural frequencies. This helps to maintain contact between the brush contacts  66 ,  68 ,  70 , and  72  with the conductors  36  and  37  in vibrational environments. The brush contacts  66 ,  68 ,  70  and  72  are made of a gold alloy, e.g., gold, silver, and nickel, to provide good electrical contact, good wear resistance and low Coulombic friction. Total friction between the brush contacts  66 ,  68 ,  70  and  72  and the electrical conductors  36  is approximately 5 inches-ounce. This friction inhibits rotation of the slip ring  18  when the elongated members  22  are not in contact with at least one end wall  42  or  44  of the arcuate slots  40 , thus allowing the gimbal  20  to rotate relative to the slip ring  18 . The brush contacts  66 ,  68 ,  70  and  72  are electrically coupled to the yaw axis cabling  24  through the arcuate electrical conductors  36  and  37  and the slip ring  18 . The brush contacts  66 ,  68 ,  70  and  72  are electrically coupled to the brush assemblies  26  and to one end of the pitch axis cabling  25 . 
     The pitch axis cabling  25  includes a brush block assembly connecting portion  80  and a regulator board connecting portion  82 . The portion  80  electrically couples to the outputs from the brush contacts  66 ,  68 ,  70  and  72  and to the portion  82 . The portions  80  and  82  contain one electrical conductor for each of the arcuate conductors  36  within a flexible layer of kapton that insulates the conductors and provides electromagnetic interference (EMI) shielding. The portions  80  and  82  can contain the conductors therein between two 0.001 inch thick kapton layers bonded with an acrylic adhesive. The conductors in the portions  80  and  82  are 0.5 or 1.0 ounce copper traces (0.0007 or 0.0014 inches thick) with 15 conductors spaced within a 0.025 inch pitch. The conductors associated with each sector of the slip ring  18  can be contained in its own kapton-enclosed flexible cabling. Thus, there are four kapton-enclosed flexible cablings in each of the portions  80  and  82 . Thus, the portions  80  and  82  are layered with conductors in conductive layers enclosed therein with shielding layers disposed between the conductive layers. The end of the portion  82  displaced from the portion  80  splits and is connected to two connectors  84  and  86 . The conductors in the portion  82  are electrically coupled to connector pins (not shown), e.g., by soldering, and encapsulated. The connectors  84  and  86  are adapted to be coupled through mating connectors (not shown) to circuitry, such as a regulator board (FIG.  7 ), for electrical processing. 
     The yaw axis cabling  24  is electrically coupled to, and extends from, the slip ring  18 . The yaw axis cabling  24  is made of a flexible cabling of kapton shielding surrounding layers of electrical conductors similar to the portion  82  of the pitch axis cabling  25 . Four sets of conductors (not shown) are electrically coupled through the slip ring  18  to the four sets of arcuate electrical conductors  36  and  37  of the slip ring  18 . A portion  88  of the cabling  24  extends through an opening  90  (FIG. 1) in the gimbal  20 . A portion  92  of the cabling  24  disposed within the gimbal  20  extends upwardly to a bend  94  and then downwardly to a circular portion  96  that transverses the interior of the gimbal  20 . The bend  94  provides a service bend area for mechanical flexibility and rotation of the gimbal in the yaw axis (FIG. 8) of approximately ±25°. The flex cabling  24  splits and is connected to two connectors  98  and  100 , with the conductors in the cabling  24  being soldered to connector pins (not shown) of the connectors  98  and  100 . The connectors  98  and  100  are adapted to be coupled through mating connectors (not shown) to circuitry, such as a sensor assembly, for electrical processing. 
     The slip ring  18 , brush assemblies  26 , and cablings  24  and  25  are adapted to conduct approximately two amps continuously or up to three amps for up to approximately 400 milliseconds. 
     The kapton shieldings are terminated to ground planes within the slip ring  18 , to shield pins within the connectors  98 ,  100 ,  84 , and  86 , and to external connector shells of these connectors to help adhere to the Electromagnetic Environmental Effects (E 3 ) design guidelines. 
     The system  10  can be assembled as shown in FIGS. 1-2. The motor  14  is fixedly attached, e.g., with screws, to the housing  12  and the rotatable portion  28  is screwed to the gimbal  20  with screws  23 . The elongated members  22  are inserted through the arcuate slots  40  in the slip ring  18 , and tightened into the threaded openings  52  in the gimbal  20 . The motor  16  is fixedly attached, e.g., with screws, to the housing  12 , and the gimbal  20  is fixedly attached to the portion  29  with screws  23 . The brush assemblies  26  are screwed into the housing  12  and arranged such that the brush contacts  66 ,  68 ,  70  and  72  are in electrical contact with the electrical conductors  36  and  37  of the slip ring  18 . The yaw axis cabling  24  is threaded through the opening  90  in the gimbal  20  and the connectors  98  and  100  are connected to appropriate mating connectors (not shown). Similarly, connectors  84  and  86  of the pitch axis cabling  25  are connected to appropriate mating connectors (not shown). 
     As shown in FIG. 6, the slip ring  18  includes two slip ring stops  132 ,  134  (FIG. 4) and the brush assemblies  26  and  262  include brush assembly stops  402 ,  404  with corresponding engaging surfaces  406 ,  408  and  410 ,  412 , respectively. The slip ring  18  includes engaging surfaces  414 ,  416 ,  418 , and  420  arranged so that when the slip ring  18  rotates with respect to the brush assemblies  26  about the pitch axis  30 , the surfaces  414 ,  416 ,  418 , and  420  will contact the corresponding engaging surfaces  406 ,  410 ,  412 , and  408  of the brush assemblies  26  to inhibit further rotation of the slip ring  18 . The stops  130 ,  132  are shown in phantom in position for contacting the surfaces  408  and  420 . 
     The limits on the rotation of the slip ring  18  about the pitch axis  30  are determined by the locations of the stops  132 ,  134  and  402 ,  404 . These stops  132 ,  134 ,  402 ,  404  are preferably arranged in accordance with the slip ring sectors  56  and  58  so that the brush contacts  66 ,  68 ,  70  and  72  do not extend into the discontinuities  38  and  39  when the gimbal  20  is rotated about the pitch axis  30  relative to the housing  12 . This inhibits loss of electrical contact with the arcuate electrical conductors  36  and  37 . 
     The gimbal  20  can rotate about the pitch axis  30  further than the slip ring  18 . The slip ring  18  cannot exceed 180° of travel (in this embodiment) in order to maintain continuity and stay within the subtended angles of the sectors  56  and  58 , assuming that the discontinuities  38  and  39  are of minimal width. The gimbal  20  is permitted to rotate further than the slip ring  18  approximately the arcuate length of the arcuate slots  40 . 
     The permissible angle of rotation of the gimbal  20  relative to the housing  12  is reduced by the width of the discontinuities  38 ,  39 , and the separation of the redundant brush contacts  66 ,  68 ,  70  and  72 , assuming that none of the brush contacts  66 ,  68 ,  70  or  72  are allowed to lose electrical contact with the conductors  36  or  37 , respectively. Thus, the arcs subtended by the arcuate slots  40 , the width of the discontinuities  38 ,  39 , and the angular separation of the brush contacts  66 ,  68 ,  70  and  72  will limit the amount of effective rotation about the pitch axis  30  that the gimbal  20  will preferably have. The amount of allowable rotation by the gimbal  20  is approximately equal to the angle subtended by the sectors  56 ,  58  (which inherently includes the width of the discontinuities  38 ,  39 ), plus the angle subtended by the arcuate slots  40 , minus the angle subtended by the elongated members  22 , minus the separation of redundant pairs of the brush contacts  66 ,  68 ,  70 ,  72 . 
     Thus, if the sectors  56 ,  58  subtend angles of approximately 180° (assuming that the discontinuities  38  and  39  are of minimal width) and the arcuate slots subtend arcs of approximately 20°, plus a semicircular portion to accommodate the elongated members  22 , and the separation of redundant pairs of brush contacts  66 ,  68 ,  70 ,  72  is 10°, then the gimbal  20  can rotate approximately 190° in each direction. Effectively there is 380° of travel from a disk of 360°. 
     As shown in FIG. 7, the slip ring  18  provides electrical connections between components for the system  10 . The pitch axis cabling  25  and yaw axis cabling  24  are connected to the slip ring  18 , with the yaw axis cabling  24  splitting into four cables with  15  electrical lines each. The connections provide communication for a roll slip ring  200 , a pitch motor  202 , a pitch motor/resolver  204 , a yaw motor  206 , and a yaw motor/resolver  208 . As shown, some wires connected to the motors and resolvers  202 ,  204 ,  206 ,  208  are off of the gimbal  20  and some are on the gimbal  20 . This helps facilitate installation/removing motors, resolvers, etc. 
     As shown in FIG. 8, the gimbal system  10  can be mounted, e.g., in a missile  102 . As shown, the gimbal system  10  is mounted at the front of a body  104 , and inside a infrared dome  106 , of the missile  102 . A seeker is pivotable and/or rotatable about a yaw axis  110 , a roll axis  112 , and the pitch axis  30 . About pitch axis  30 , the gimbal  20 , and therefore the seeker, is rotatable in directions  114  and  116 . 
     In operation, the motors  14  and  16  can rotate the gimbal  20  about the pitch axis  30  in directions  114  and  116 . As the gimbal  20  rotates; the elongated members  22  will move within the arcuate slots  40 . The elongate members  22  can move within the slots  40  through the entire arcuate lengths subtended by the slots  40  without causing the slip ring  18  to rotate about the pitch axis  30 . Thus, the gimbal  20  can rotate (i.e., dither) back and forth approximately ±10° without causing rotation of the slip ring  18 . Slight adjustments in the pitch angle of the gimbal  20  therefore do not cause rotation of the slip ring  18 . 
     Significant rotation, e.g., in direction  114 , of the gimbal  20  about the pitch axis  30  will cause the slip ring  18  to rotate. Once the motor  14  has rotated the gimbal  20  far enough that one or more of the elongated members  22 , and in particular the smooth cylindrical portions  54 , engages and is forced against an end wall  42  or  44  of the arcuate slots  40 , the slip ring  18  will rotate. Thus, the outer surfaces of the smooth cylindrical portions  54  of the elongated members  22  act as engaging surfaces to engage and press against complimentary engaging surfaces  42  or  44  of the slip ring  18 , to induce rotation of the slip ring  18  about the pitch axis  30 . 
     As the slip ring  18  rotates, the redundant brush contacts  66 ,  68 ,  70  and  72  remain in electrical contact with corresponding ones of the arcuate electrical conductors  36  and  37  of the slip ring  18 . This helps maintain electrical continuity in the gimbal system  10 . 
     The slip ring  18  can rotate about the pitch axis  30  in direction  114  until surfaces  414 ,  418  of the slip ring stops  132 ,  134  contact the surfaces  406 ,  412  of the brush assembly stops  402 ,  404 . This defines the limit of rotation of the slip ring about the pitch axis  30  in direction  114 . 
     The motors  14  and  16  can also rotate the gimbal  20  about the pitch axis in the opposite direction  116 . The slip ring  18  will not be rotated until one or more of the elongated members  22  contacts the other one of the end walls  42  or  44  of the arcuate slots  40 . The motors  14  and  16  can rotate the gimbal  20  in the opposite direction  116  until the slip ring  18 , as forced by the elongated members  22 , reaches its other maximum rotated position when the surfaces  416 ,  420  of the slip ring stops  132 ,  134  contact the surfaces  410 ,  408  of the brush assembly stops  402 ,  404 . 
     Other embodiments are within the scope of the appended claims. For example, instead of mechanical stops provided on the slip ring  18  and the brush assemblies  26  to inhibit rotation of the slip ring  18  about the pitch axis  30 , mechanical or electrical stops may be implemented in the motor area. The stops  132 ,  134 ,  402 , and  404  provide safeguards in case of failures. If stopping commands are programmed into software control of the motor  14 , and if this software fails, or if motor circuitry fails, then the mechanical and electrical hardware of the system  10  is protected by the stops  132 ,  134 ,  402 , and  404  inhibiting rotation of the slip ring  18  as described. A slip ring stop  160  (shown in dashed lines in FIG. 4) and two housing stops  162 ,  164  (shown in dashed lines in FIG. 2) can be used to limit or inhibit rotation of the gimbal  20  relative to the housing  12 .