Abstract:
An electric motor apparatus in a direct drive positioning device for positioning for example a television camera or a robot arm along X-Y-Z axes, which provides a direct drive which permits a free and unobstructed continuous rotation over 300° in horizontal, vertical and any other angular axes with no electrical wires or cables twisting or flexing. The apparatus includes a motor which has a hollow central shaft connected to a rotary member for mounting thereon a robot arm or television camera of the direct drive positioning device. The central shaft encloses a rotating slip ring assembly coupled to respective wires for connecting to the television camera. Electric power is supplied through the wires which are not twisted or flexed while the rotating member is being directly driven by the motor and is rotating.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electric motor apparatus used for positioning a device such as robot arm along X-Y-Z axes, and more particularly, for a positioning device used for a television camera. 
     2. Description of the Prior Art 
     Positioning devices such as pan-tilt heads for television cameras or robot arms include a fixed body to be attached to a wall, a pole or a table and employs motors and power transmission assemblies consisting of gears or rollers or belts and pulleys or chains, and the like. Such pan-tilt heads or robot arm mechanisms are generally constructed so that the television cameras or the robot arm rotate angularly about their vertical and horizontal and/or other angular axes. In some cases electrical wires or a cable assembly are used for connecting the rotating television camera or the robot arm circuits to the fixed base of the positioning device. Such electrical wires or a cable are commonly known as a flexible cable assembly that spans between the fixed and the rotatable members, or between two rotatable members of the positioning device. The cable assembly thereby rotates and repeatedly twists or flexes along with the movement of the positioning device, and this eventually causes the cable to break. This requires a frequent cable replacement which is costly; moreover such cable assembly spanning across a joint of the positioning device prevents the positioning device from rotating over 360° about its axis, which limits the free rotation of the positioning device. 
     Some positioning devices use slip-ring or rotating contact assemblies which are positioned at the individual rotating axis center, thereby eliminating the cable assemblies from spanning across the rotating joints. However, such slip ring assembly occupies the center of the rotating axis, thereby preventing the use of a direct drive motor, such as stepping motors, which are very efficient, accurate and require no power transmission mechanism. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a direct drive positioning device with a direct drive motor and a slip-ring mechanism mounted inside or along a main shaft of the motor. When such direct drive motor is positioned with its shaft at each axis, it permits a free unobstructed and continuous rotation, over 360° in both horizontal and. vertical axes and/or other angular axes, with no cables twisting or flexing. 
     According to the present invention a direct drive positioning device comprises at least one rotating member for rotating about horizontal or vertical or any other angular axes of the positioning device. Each such rotating member is provided with means to mount a television camera or a robot arm and/or for mounting another member for incorporating a further joint positioning mechanism. 
     A direct drive motor has its central shaft connected to a rotating member for directly driving the rotating member wherein its central shaft comprises a rotating or slip ring assembly. The rotating contacts or the slip ring assembly provides for connecting the television camera, or the robot arm circuits and/or the direct drive motor circuit to a control circuit and other peripheral/ancillary equipment, thereby eliminating the problems associated with the use of flexing cables and providing for a continuous uninterrupted rotation about the rotating axis over 360°. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and features of the invention will become apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a television camera inside a domed cover incorporating direct drive motors of the preferred embodiment; 
     FIG. 2 is a schematic side view of a robot arm incorporating direct drive motors of the preferred embodiment of the invention; 
     FIG. 3 is a schematic side view of a television camera mounted onto a remote positioning device incorporating direct drive motors of the preferred embodiments of the present invention; 
     FIG. 4 is an axial sectional view of a stepping motor incorporating a slip ring assembly of the preferred embodiment of the invention; 
     FIG. 5 is an axial sectional view of another stepping motor incorporating a slip ring of a preferred embodiment of the present invention; 
     FIG. 6 is an axial sectional view of yet another motor incorporating a slip ring assembly of still another preferred embodiment; 
     FIG. 7A is a top view of an example of a slip ring used in FIGS. 4-6; and 
     FIG. 7B is an axial sectional view of the slip ring example used in FIGS.  4 - 6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A television camera apparatus  1  shown in FIG. 1 is a well known dome-shaped camera enclosure  3  used in surveillance systems comprising a portion having transparent or semi-transparent dome  3 A, a base plate  4  which is fixedly attached to the upper portion of the camera enclosure  3 , a panning motor  2  which is fixedly attached to the surface of the base plate  4 , a camera holder bracket  7  attached to a rotor  14  of the panning motor  2  to be rotatable about horizontal axis H (pan) extending through the center of the base plate  4  and orthogonal to the base plate  4 . 
     A tilting motor  10  is fixedly mounted onto one side of the camera holder bracket  7  which is formed as an inverted U-shape fork-like holder. A television camera  12  is attached to a rotor  16  of the tilting motor  10 , so that the camera can be rotatable about the vertical axis-V (tilt), while on the opposite side the camera is mounted to the camera holder bracket  7  via a well known pivoted rotating joint  15  extended along the V axis. 
     The V axis (tilt) which is orthogonal to the H axis (pan) along with the L axis (lens) which is orthogonal to the V axis (tilt) and the H axis (pan) all intersect at the center core of the dome shaped cover portion  3 A so as to provide for the all-round unobstructed panning and tilting movement within the dome sphere. The panning motor  2  incorporates rotary contacts or a slip ring assembly  6  inside its rotor  14  shown also in FIGS. 4 &amp; 5. The slip ring assembly  6  per se is a well known assembly of rotating conductive metal rings along with complementary mounted conductive metal brushes that provide pressure for a continuous current flow through the metal rings during the rotation of the metal rings. 
     Connecting wires  5  including wires for feeding power and control signals to the camera and a video signal, an audio signal and data signals from the camera pass through an opening in the domed closure or case  3  and the base plate  4  for connecting the rotating ring of the slip ring assembly  6 . Wires  13  feeding power to the panning motor  2  may be fed through a separate opening  13 A directly to the panning motor if the panning motor  2  is an inner rotor type or should be connected along with the connecting wires  5  if the panning motor  2  is an outer rotor type. 
     Wires  8  connected at one ends to the brushes of the slip ring assembly  6  are fed through an opening in the holder bracket  7  and are connected at their other ends to the rotating rings of a slip ring assembly  9  mounted inside the shaft of the rotor  16  of the tilting motor  10 . 
     Wires  11  connected to the brushes of the slip ring assembly  9  are further connected at the other ends to the camera  12  and to control circuits (not shown). It is obvious from FIG. 1 that in this arrangement the camera can rotate endlessly about its panning H axis or its tilting V axis without causing the wires to flex or twist. Furthermore, it is obvious that the camera holder bracket  7  which is mounted directly onto the rotor  14  of the panning motor  2  is directly driven by the drive motor without any power transmission mechanism. Similarly, it is obvious from FIG. 1 that the rotor  16  of the tilting motor  10  can drive the camera tilting position directly, using no power transmission mechanism. 
     The elimination of power transmission devices and assemblies reduces the size of the dome-shaped camera enclosure  3 , simplifies the construction and improves upon the efficiency and the accuracy of the positioning device, as well as improves its reliability. 
     A robot arm  20  shown in FIG. 2 has a fixed body  24  attached to a table  21 . A motor  25  affixed to the upper surface of the fixed body  24  incorporates a rotary contact or slip ring assembly inside its rotor shaft  26  and the rotor is affixed to one end of a horizontally rotating arm  28  of the robot arm  20 . The control and power wires  22  are directly connected to the slip rings of the slip ring assembly inside the rotor shaft  26  (not shown) while power to the motor  25  can be fed directly through wires  23  since the motor  25  is an inner rotor type. 
     Wires  27  are connected at the side A of the horizontally rotating arm  28  to the brushes of the slip ring assembly (not shown) mounted inside the rotor shaft  26  and at the side B of the horizontally rotating arm  28  to the rings of a slip ring assembly (not shown) inside the rotor shaft  30  of a motor  29  and to the motor  29 . The motor  29  is affixed to the end B of the horizontally rotating arm  28  and the rotor shaft  30  is affixed to an horizontally rotating joint  31 . 
     Wires  35  are connected at one ends thereof to the brushes of the slip ring assembly positioned inside the rotor  30  while the other ends of wires  35  are connected to the rings of a slip ring assembly incorporated inside the shaft of the rotor  32  of the motor  33 . The brushes of the slip ring assembly inside the rotor  32  are connected by wires (not shown) to a robot arm finger  34  and its circuitry. It is obvious from FIG. 2 that the horizontally rotating arm  28 , the horizontally rotating joint  31  and the vertically rotating finger  34  can all rotate endlessly without flexing or twisting any of the wires connecting power and/or control signals to the respective motors and control circuits. It is also obvious that the construction of the robot arm is greatly simplified by the use of direct drive motors incorporating slip ring assemblies inside the rotor shafts. 
     A television camera apparatus  40  shown in FIG. 3 is another well known television camera  51  mounted on a well known pan-tilt positioning device consisting of a fixed member  42  and a horizontally rotating member  49 . The fixed number  42  is affixed to the top of a wall  41  and comprises a motor  44  which is attached to the top of the fixed member  42  while a rotor  45  is affixed to the horizontally rotating member  49 . Wires  43  are connected to the rings of the slip ring assembly located inside the shaft of the rotor  45  and to the motor  44 . A motor  47  is affixed to the arm of the horizontally rotating member  49  and a rotor  50  is affixed to the camera  51 . Wires  46  are connected at one ends thereof to the brushes of the slip ring assembly inside the shaft of the rotor  45  and at the other ends thereof to a ring of the slip ring assembly  48  inside the shaft of rotor  50 . 
     The wires connected to the brushes of the slip ring assembly  48  (not shown) feed power and control signals to the camera  51  and video/audio signals from the camera. It is apparent from FIG. 3 that the pan-tilt positioning device of the camera apparatus  40  can endlessly rotate in any horizontal and vertical direction without flexing or twisting a plurality of wires carrying power, control and video signals. It is also apparent that such positioning device employing direct drive motors with built-in slip rings inside the rotor&#39;s shafts provide a simplified mechanical construction. 
     A motor assembly  55  shown in FIG. 4 combines a well known stepping motor with an inner rotor and rotating contacts or a slip ring assembly. A plate  60  is a portion of a fixed or a rotating joint of a positioning device such as the base plate  4  of FIG.  1 . The plate  60  is affixed to a first cover  61  of the stator portion of the motor assembly  55  using a plurality of screws  79 . 
     The stator portion of the motor assembly  55  includes a stator coil assembly  62 , magnetic metal laminates  63 , first cover  61  and a second cover  64 . The stator coil assembly  62  is connected to power and control circuits (not shown) via wires  71  passing through an opening in the first cover  61  and plate  60 . 
     Dual ball bearings  80  are provided for supporting the rotor assembly between the first cover  61  and second cover  64  to ensure a smooth rotor movement. 
     A rotor assembly includes a hollow rotor shaft  82  surrounded by a magnetic ring  81  and a slip ring assembly embedded inside the rotor shaft. 
     The rotor shaft  82  is attached to a plate  66  by a plurality of screws  79 . The plate  66  is a portion of a fixed member or of a rotating joint of a positioning device such as the camera holder bracket  7  shown in FIG.  1 . 
     A well known slip ring assembly has the rings holder assembly  73  which rotate inside a slip ring body  72  and a printed circuit board assembly  76 . A ring holder assembly  73  includes multiple conductive rings  74  all spaced and insulated from each other and all electrically connected to a connector  77 . 
     The printed circuit board assembly  76  is fixedly attached to the slip ring body  72  and comprises multiple conductive electrical brushes  75  positioned and spaced to compliment the multiple conductive rings  74  for providing a constant electrical contact by their brushing action against the conductive rings  74  and a connector  78  for providing electrical connections to the wire assembly  69 . 
     The slip ring body  72  is fixedly attached to the rotor shaft  82  and the ring holder assembly  73  which rotates about the central axis of the slip ring body  72  is fixedly attached to plate  60 . 
     The wire harness or assembly  67  and connector  68  provide electrical connections to a plurality of the conductive rings  74  while the wire assembly  69  and the connector  70  provide complimentary electrical connections to the conductive electrical brushes  75 . 
     It becomes obvious from FIG. 4 that the wires of the wire assembly  67  and wire assembly  69  are electrically connected through the conductive rings  74  and the conductive electrical brushes  75  regardless of whether the motor is idle or it is energized through its power and control wires  71  and is rotating. 
     A motor assembly  56  of FIG. 5 combines a well known stepping motor with the outer rotor and rotating contacts or slip ring assembly. A plate  60  similarly to the plate  60  of FIG. 4 is affixed to the first cover  61 A of the outer rotor portion of the motor assembly  56 , using screws  79 . The outer rotor portion of the motor assembly  56  consists of magnetic metal laminates  81 A, first cover  61 A and second cover  64 A. 
     Dual ball bearings  80  are provided between a stator shaft  83 , first cover  61 A and second cover  64 A for supporting the rotor and to ensure a smooth rotor rotation. A stator assembly includes the hollow stator shaft  83  surrounded by and fixedly attached to magnetic metal laminates  63 , a stator coil assembly  62 A and a slip ring assembly embedded inside the stator shaft. The stator coil assembly  62 A is connected to power and control circuits (not shown) via wires  71 A passing through an opening in the stator shaft  83  and a plate  66 . 
     The stator shaft  83  is attached to the plate  66  by a plurality of screws  79 . Plate  66  is a portion of a fixed member or of a rotating joint of a positioning device such as the camera holder bracket  7  shown in FIG.  1 . 
     A well known slip ring assembly includes a ring holder assembly  73  rotating inside the slip ring body  72  and a printed circuit board assembly  76 . The ring holder assembly  73  consists of multiple conductive rings  74  all spaced and insulated from each other and all electrically connected via a wire harness  67 . 
     The printed circuit board assembly  76  includes multiple conductive electrical brushes  75  positioned and spaced to compliment the multiple conductive rings  74  for providing constant electrical contact by their brushing action against the conductive rings  74  and a wire harness  69  for providing electrical connections. 
     The slip ring body  72  is fixedly attached to the stator shaft  83  and the ring holder assembly  73  which rotates about the central axis of the slip ring body  72  is fixedly attached to plate  60 . 
     The wire harness  67  provides electrical connections to the plurality of the conductive rings  74  while the wire harness  69  provides the complimentary electrical connections to the plurality of the conductive electrical brushes  75 . 
     It becomes obvious from FIG. 4 that the wire harness  67  and the wire harness  69  are electrically connected through the conductive rings  74  and the conductive electrical brushes  75  regardless of whether the motor is idle or it is energized through its power and control wires  71  and is rotating. 
     Instead of attaching the plate  60  of FIG. 5 to the first cover  61 A it is possible to attach plate  60 A to the second cover  64 A, thereby providing for mounting the motor assembly  56  to a positioning device such as motor  25  or motor  29  of FIG. 2 or motor  42  of FIG. 3 the same why as they are shown to be mounted to the respective members of the positioning devices. Similarly, it will be possible to mount the motor assembly  55  shown in FIG. 4 to a member of the positioning device by affixing the second cover  64  of FIG. 4 to the member of the positioning device instead of the plate  60  attached to first cover  61  of motor assembly  55  shown in FIG.  4 . 
     It is apparent from FIG.  4  and FIG. 5 that regardless of whether the motor is an inner or an outer rotor type it can incorporate the slip ring assembly inside its main shaft and provide a through passage for power, control and other signals without flexing or twisting the wires connected to the opposing sides of the rotating joint and such motor assembly can endlessly rotate about its rotating axis. 
     The motor assemblies  55  and  56  shown in FIG.  4  and FIG. 5 are large diameter type motors which can be made with a shaft diameter large enough to incorporate the slip ring assembly inside the shaft. On occasions there may be a need for slim motors which cannot be provided with the slip ring assembly inside a small diameter shaft. For such motors it is possible to provide a hollow shaft and mount the slip ring assembly at the end of the shaft. 
     A motor assembly  57  shown in FIG. 6 combines a well known stepping motor with the inner rotor and rotating contacts or a slip ring assembly. A plate  90  is a portion of a fixed joint or of a rotating joint of a positioning device; the plate  90  is affixed to the first cover  89  of the stator portion of the motor assembly  57  using screws  79 . 
     The stator portion of the motor assembly  57  consists of a coil assembly  62 , magnetic metal laminates  88 , a first cover  89  and a second cover  87 . The stator coil assembly  62  is connected to power and control circuits (not shown) via wires  71  passing through an opening in the first cover  89  and plate  90 . 
     Dual ball bearings  80  are provided for supporting the rotor assembly between the first cover  89  and second cover  87  to ensure the smooth rotor movement. The rotor assembly comprises a hollow rotor shaft  86  surrounded by a magnetic ring  95  and a ring holder assembly  97  mounted at one end of the rotor shaft. 
     The other end of the rotor shaft  86  is attached to a plate  85  by screws  96 . The plate  85  is a portion of a fixed member or of a rotating joint of a positioning device (not shown). 
     The slip ring assembly includes the ring holder assembly  97  attached to the rotor shaft  86  and a printed circuit board assembly  93  affixed to plate  90 . The ring holder assembly  97  includes multiple conductive rings  74  all spaced and insulated from each other and all electrically connected to the wire harness  67 . All the wires of wire harness  67  are fed through the hollow rotor shaft  86  and through the opening in the plate  85  to exit from the other end of the rotor shaft, opposite to the end of the ring holder assembly  97 . 
     The printed circuit board assembly  93  is fixedly attached to the plate  90  and/or to the first cover  90  by a holder  92  and screws  91  and comprises multiple conductive electrical brushes  75  positioned and spaced to compliment multiple conductive rings  74  for providing constant electrical contact by their brushing action against the conductive rings  74  and wire harness  69  for providing electrical connections. 
     The ring holder assembly  97  is fixedly attached to the rotor shaft  86  for rotating about the central axis of the shaft  86 . 
     The wire harness  67  provides electrical connections to the plurality of the conductive rings  74  while the wire harness  69  provides the complimentary electrical connections to the plurality of the conductive electrical brushes  75 . 
     It becomes obvious from FIG. 6 that the wires of the wire harness  67  and the wire harness  69  are electrically connected through the conductive rings  74  and the conductive electrical brushes  75  regardless of whether the motor is idle or it is energized through its power and control wires  71  and is rotating. 
     It is also obvious from FIG. 6 that it is possible to mount a slip ring assembly to the shaft of the motor of a positioning device even though the motor is slim, to thereby provide a through passage for power, control or other signals without flexing or twisting the wires connected to the opposing sides of the rotating joint. 
     FIGS. 7A and 7B show details of the slip ring assembly of FIG.  4 . The slip ring assembly  58  includes a slip ring body  72 , a printed circuit board assembly  76  and a ring holder assembly  73 . The ring holder assembly  73  has a plurality of conductive rings  74  all spaced and insulated from each other and all electrically connected via metal wires to form a connector  77  at one end of the slip ring assembly  58 . 
     The ring holder assembly is constructed to fit into the slip ring body  72  and to be freely rotatable around the rotating axis of the longitudinal center of the slip ring body. 
     The printed circuit board assembly  76  comprises a plurality of conductive brushes  75  mounted and connected to a printed circuit board conductive pattern; the brushes  75  are positioned and spaced to compliment the conductive rings  74  for providing constant electrical contact by their brushing action against the conductive rings  74 , and a connector  78  for providing electrical connections at the other end of the slip ring assembly  58 . The printed circuit board assembly  76  which is secured to the slip ring body  72  by screws  98  can be directly connected to a wire harness instead of using the connector  78 . Similarly, instead to forming connector  77  the conductive rings can be connected via a wire harness. 
     FIG. 7A illustrates conductive brushes  75  in contact with conductive rings  74 . The use of brushes at both sides of the conductive rings improves continuity and reliability of the brushing action. 
     Other well known rotating contacts or slip ring assemblies can be used instead of the slip ring assembly shown in FIG. 7 and, regardless of the type of slip rings or other rotating electric coupling means used it is clearly seen that the apparatus of the present invention provides extremely simple means for directly driven positioning devices such as pan-tilt head of a television camera, robot arms or any other rotating joints by a motor incorporating rotating electric coupling means in its central shaft, without flexing or twisting the wires associated with both sides of the rotating joint. 
     It will, of course, be understood by those skilled in the art that the particular embodiment of the invention here presented is by way of illustration only, and is meant to be in no way restrictive, therefore, numerous changes and modifications may be made, and the full use of equivalents resorted to, without departing from the spirit or scope of the invention as outlined in the appended claims.