Abstract:
A display lifting device is provided which is mounted within a ceiling plenum and is arranged for concealing a support framework, lifting arm and display within the ceiling area. A support arm for the display is pivotally mounted within the framework and is biased in the downward position and supported by a cable mounted on a cable drum drivingly connected to a reversible motor. The support arm comprises at least two telescoping sections with the cable connected to the end of the inner lower most section so that as the cable is extended the arm pivots downward with the telescoping sections extending through gravity to their fullest extent. In this way, the display can extend a considerable distance from the ceiling for viewing by the audience while in the retracted position a very small opening and space within the plenum is required for concealment. Mechanical stops and limit switches are provided at both extremes of the movement of the display and support arm to restrict the angular movement of the arm. A cover matching the opening in the ceiling is attached to the support arm and is pivoted from the ceiling to close the ceiling opening when the arm is raised into the upper concealed position. Actuation of the display lifting device can be made with a wired control panel or a remote control device.

Description:
FIELD OF THE INVENTION:  
         [0001]    This invention is directed to a concealed ceiling mount for a large screen display. It is more specifically directed to a pivotal mount for storing within a ceiling a large screen display which can be pivotally and telescopically extended to an exposed position for use.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the design and construction of auditoriums or theaters, it is very desirable to conceal the components of the audio/visual equipment that is to be used in those locations. One of the ways of doing this is to position the equipment in the ceiling or sidewalls with a panel covering the equipment to prevent it from being seen. Upon use, the panel is then either removed or moved aside so that the equipment can perform its function.  
           [0003]    In other situations, the equipment has been concealed within the ceiling and provides the capability of lowering the equipment from the ceiling to a use position, whereby a video projector or film projector can be used to show videos or motion pictures on an auxiliary screen positioned at the front portion of the auditorium or theater. Some of these systems include a cable lift or a telescoping column that allows the equipment to be lowered from the concealed position within the ceiling structure.  
           [0004]    In recent years, video screens and computer monitors have been redesigned in a relatively flat configuration with large size dimensions. Some of these screens utilize fibre optics to provide the displayed picture, while others use projection of a video image through mirrors and lenses to provide a large scale image. In recent years plasma screen technology has been developed which can provide a flat screen televison display of large proportions. These screens can be as big as 3′×6″ or larger, depending upon the application that is intended. It has been found highly desirable to conceal this screen out of sight when it is not being used. At the time that it is needed, it can be exposed or moved into position for use.  
           [0005]    The present inventor is a pioneer in the effort to solve these problems by concealing the display unit in a ceiling or wall when it is not being used. As part of that effort, the inventor has devised lift structures, which can be attached in the ceiling area and which can allow a video or movie projector to be remotely raised or lowered from the ceiling surface by a cable lift. In addition, the projector can be lowered to a position which is easily accessible from the floor of the area for maintenance or replacement purposes.  
           [0006]    One of the major problems with concealing a mechanism of this type in a ceiling area is the fact that there is usually a very small dimensional clearance available in the plenum area between the ceiling of the auditorium, theater or presentation room and the above floor or roof structure. In many cases, this clearance is no more than 15″-18″ and, in many cases, this limited clearance prevents any type of lifting mechanism from being mounted or concealed within the ceiling area. The present patent application is directed to a new invention to eliminate the problems which have been encountered in the past with this type of mechanism and to provide a unique high strength, lifting mechanism which is compatible with a flat screen type of display panel.  
         INFORMATION DISCLOSURE STATEMENT  
         [0007]    This statement is provided in order to comply with the inventor&#39;s acknowledged duty to inform the Patent and Trademark Office of any pertinent information of which he is aware that would be of any value or have importance in the Examination of this application. The following patents are known to the applicant and may have some applicability to the present invention and the examination of this application.  
           [0008]    The Huffman patents (U.S. Pat. Nos. 5,261,645 and 5,366,203) disclose a remote control, ceiling mounted lifting device which is provided for concealing, supporting and allowing convenient access to audio/visual equipment, such as video/data projectors. The lifting device has an outer mounting framework. A support carriage is arranged within the framework and is suspended by cables and its lateral movement is restricted by a scissor-like stabilizer mechanism. The cables are mounted on a motor driven drum assembly which is laterally positioned within the support framework. An emergency lever brake assembly is provided in conjunction with the cable drum to prevent the carriage from dropping out of control in an emergency situation.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides a lifting mechanism for supporting and moving relatively large flat panel displays. It is primarily intended for concealment of the display within the ceiling area when not in use. Since there is a relatively low structural clearance in the plenum area above the ceiling surface found in most auditoriums, theaters or presentation rooms, the present mechanism has an extremely flat profile which allows it to be installed within the ceiling structure for the purpose of this concealment.  
           [0010]    The lifting mechanism, according to the present invention, uses a number of new and novel elements to provide a lifting device having long extensions for relatively large flat objects. Although the object in the present invention is intended to be a type of display such as, a flat screen T.V. or monitor, it can also cover a number of other objects, such as a projection screen for movies or for a video/data projector. In some cases, the video projector utilizing the concealed flat screen can also be supported in the ceiling structure or in a side wall.  
           [0011]    The present invention incorporates a relatively compact flat framework mounted within the ceiling cavity with a pivotally extended support arm having a flat screen T.V. mounted at the end of the arm. In the raised or upper position the screen and arm is positioned within the ceiling cavity. A ceiling cap or cover which matches the required ceiling opening is mounted on the underside of the arm and can be aligned to be flush with the existing ceiling surface when the lift is in the raised position. To lower the arm and the attached screen to the lower view position, a wired control switch or a suitable type of remote control device using infrared or UHF can be utilized. Upon command, the arm is pivoted downward to a substantially perpendicular viewing position. As part of the present invention the actual angular position of the screen can be adjusted minutely to position the screen in the correct and proper angular position for viewing by the audience. Thus, the arm can move either less or greater than the 90° vertical position to obtain the desired angular position.  
           [0012]    The support arm is pivotally mounted on a shallow, rigid framework which is adequately positioned and mounted within the ceiling cavity or plenum. The pivotal support arm is biased by a suitable device, such as a helical spring attached to the supporting shaft or one or more coiled springs attached to an extension of the arm which can be leveraged beyond the pivot mounting of the arm. This force biases the arm and display in the downward direction and position. A cable wound on a laterally positioned cable drum assembly mounted within the framework has its free end threaded over a pulley and down through the support arm. The end of the cable is secured to the end of the arm. A reversible drive motor properly geared or drivingly connected to the cable drum assembly is provided for extending or retracting the cable as required.  
           [0013]    A suitable safety lock can be provided in conjunction with the drum or cable to arrest the rapid downward movement of the cable and arm in an emergency situation. The cable lock can be a lever type lock mounted in conjunction with the cable drum. The lock can be controlled by an over-speed governor attached to the drum to sense the rotational velocity of tie drum. At an exceedingly high rate of rotational speed the drum lock can be activated to arrest and stop the rotation of the drum and, thus, the cable and arm. By the same token, a cable brake, such as an automatic clamp can be positioned adjacent to or surrounding the cable so that the cable itself can be clamped and stopped if its velocity exceeds a predetermined rate. It is to be understood that any type of suitable brake which will arrest the downward movement of the arm in an emergency situation can be used.  
           [0014]    It is intended that stops will be placed in proper position to restrict the overall movement of the support arm in the up or down position. The up position stop limits the movement of the arm in the retracted ceiling concealed position. The stop for the lowered position restricts the pivotal movement of the arm past a limited arc beyond vertical to control the overall movement of the support arm.  
           [0015]    In order to make the lift device as compact as possible, the support arm is arranged in a telescoping configuration wherein the arm is made up of two or more telescoping sections or channels which have an essentially hollow rectangular cross-section. The lower or inner sections of tile arm can slidably fit within the dimensions of the upper or base section of the arm. Although the sections of the arm can be mechanically biased into the extended position, it has been found that gravity is suitable for this purpose, with the end of the support cable secured within tie inner portion of the end section. Thus, the arm can be lowered by releasing and extending the cable which is guided across a pulley mounted on the side of the arm and down into the interior of the end section. In this way, the lower end section is held in the contracted position within the upper section until the support arm is fully extended with further extension of the cable allowing the end section or sections to lower into a downward extended position with the screen or display object. In the reverse, the cable, upon retracting, first raises the lower or end section of the arm and the attached display into a contracted position within the upper section and then further pivots the arm upward into the concealed raised position within the ceiling. In this way, a relatively long yet compact, heavy duty lifting device is provided for storing and concealing the entire lifting mechanism and display within the ceiling cavity. A ceiling cover can be pivotally mounted from the ceiling and arranged to move with the downward movement of the pivoting support arm or it can be mounted directly on the arm, whereby the entire cover moves with the arm. The attachment for supporting the cover is arranged to move with the arm extension. As can be seen in the present invention, the length of the support arm and the positioning of the screen can be greatly extended to compensate for the height of the ceiling in the auditorium, theater or presentation room and the positioning of the audience within the room.  
           [0016]    One of the objects of the present invention is to provide a heavy duty lifting device that can extend a flat screen television or monitor, or the like, from a concealed position within the ceiling of a structure to a lower viewable position which is properly positioned and aligned with respect to the audience.  
           [0017]    It is a further object of this invention to provide a lifting device for a flat screen T.V. wherein the position of the screen can be angularly adjusted.  
           [0018]    It is a still further object of the present invention to provide a display lift whereby the display can be extended to a position close to the level of the audience and then retracted to a compact configuration before being concealed within the structure.  
       
    
    
       [0019]    Other objects and features of this invention will be seen and explained through the following drawings and descriptions.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a perspective view showing a video display screen concealed within a ceiling structure of an auditorium or presentation area;  
         [0021]    [0021]FIG. 2 is a perspective view showing the auditorium of FIG. 1 with the screen extended to a lowered viewing position;  
         [0022]    [0022]FIG. 3 is an enlarged perspective view showing the display screen and supporting arm in the lowered extended position;  
         [0023]    [0023]FIG. 4 is an enlarged perspective view showing the display screen being raised in relation to the support arm;  
         [0024]    [0024]FIG. 5 is an enlarged perspective view showing the display screen and support arm being pivoted into the raised position;  
         [0025]    [0025]FIG. 6 is an enlarged perspective view showing the display screen and support arm in the raised ceiling concealed position;  
         [0026]    [0026]FIG. 7 is an enlarged perspective view showing the support framework and cable mechanism for the pivotable support arm according to the present invention;  
         [0027]    [0027]FIG. 8 is a side sectional view showing the screen and support arm in the lowered extended position;  
         [0028]    [0028]FIG. 9 is a partial cross-section view taken along lines  9 - 9  of FIG. 8;  
         [0029]    [0029]FIG. 10 is a bottom plan view of the support and pivoting mechanism for the display screen lift;  
         [0030]    [0030]FIG. 11 is a partial cross-sectional view taken along lines  11 - 11  of FIG. 9;  
         [0031]    [0031]FIG. 12 is a partial cross-sectional view taken along lines  12 - 12  of FIG. 9;  
         [0032]    [0032]FIG. 13 is a cross-sectional view taken along lines  13 - 13  of FIG. 9;  
         [0033]    [0033]FIG. 14 is a partial side cross-sectional view of the lift mechanism according to the present invention showing the support arm being retracted as part of the pre-pivotal movement;  
         [0034]    [0034]FIG. 15 is a partial cross-sectional view taken along lines  15 - 15  of FIG. 14;  
         [0035]    [0035]FIG. 16 is a partial cross-sectional view taken along lines  16 - 16  of FIG. 5; and  
         [0036]    [0036]FIG. 17 is a partial cross sectional view taken along lines  17 - 17  of FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]    Turing now more specifically to the drawings, FIGS. 1 and 2 show a perspective view of an open auditorium versus the same auditorium with the flat video screen and the support lift extended into the lowered viewing position. The auditorium or presentation room A, includes a plurality of seats S and speaker&#39;s podium D. This shows the contrast between the open cleared auditorium or presentation room A as shown in FIG. 1 and the appearance of the audio visual device, such as a flat screen TV  12  mounted on a support arm  14  which is part of the pivotal screen lifting device  10  which is the present invention. The lifting device  10  is arranged to be concealed within the ceiling C structure where it cannot be seen and blends into the existing ceiling surface when not in use. Anytime that the display  12  is to be used, the lifting device  10  is then pivoted, usually by remote control, so that the support arm  14  pivots downward out of the ceiling along with the screen  12  and the concealment cover  16 . In this way, the display lift can be extended and used as needed.  
         [0038]    FIGS.  3 - 6  show the operation of the ceiling display lift  10 . There is a cavity or plenum found immediately above the ceiling of most commercial buildings. This same plenum usually exists throughout the building and most especially, is found in the ceiling areas of auditoriums, conference rooms and presentation rooms. The problem with the plenum found in most commercial buildings is that it is very shallow, usually not being more than 15″-18″ in depth. These are the usual dimensions whether it is a false ceiling, such as a suspended acoustical tile ceiling or a structural ceiling having a solid gypsum board surface. The upper part of the plenum is the roof structure or the floor structure for the next story.  
         [0039]    In the present invention, a support framework  20  is rigidly and securely mounted within the plenum P of the ceiling structure of the auditorium, theater, conference room or presentation room. Usually the display lift of the present invention is mounted in the forward or front portion of the presentation area so that it can be viewed by the entire audience. The framework  20  is securely mounted and supported within the ceiling structure by any suitable means which is well known in the art.  
         [0040]    [0040]FIG. 3 shows the ceiling display lift according to the present invention in the extended exposed position. The ceiling plenum is exposed with the lift support structure  20  visible in the plenum area. The support arm  14  has the display  12  attached to its lower end. The ceiling concealment cover  16  can be hinged at one end  22  to the ceiling structure C with the opposite end moveably attached to the support arm  14 . In this way, the cover  16  is held essentially parallel to the arm  14  when in the extended or the retracted position.  
         [0041]    [0041]FIG. 4 shows the display screen  12  and support arm  14  being raised into alignment with the ceiling cover  16  as a first step in the storing of the ceiling display lift  10 . Once the display  12  has reached its contracted position with respect to the support arm  14 , the raising mechanism which includes cable  24  starts to pivotally raise the combination of the display  12 , support arm  14 , and cover  16 . This movement is shown in FIG. 5 where the support arm  14 , display  12  and cover  16  is partially raised or pivoted towards the ceiling C and plenum P. Once these components have been raised completely into the retracted or concealed position, the cover  16 , as shown in FIG. 6, fits the outline of the opening  26  which is present within the ceiling surface C. Thus, the display, supporting arm and support framework are completely concealed within the plenum P of the ceiling C; leaving a flush, unobstructed surface at the ceiling C.  
         [0042]    FIGS.  7 - 9  show a closeup of the display lifting device  10  including the base  20 , support arm  14 , ceiling cover portion  16  and display device  12  attached to the end of the support arm  14 . The display device  12  is shown as a dotted line, since it is not part of the actual invention, but is supported and displayed by the lifting device  10 . A mounting plate  28  is securely attached to the end of the support arm  14  for mounting and supporting the display  12 .  
         [0043]    The support frame or framework  20  includes an inverted U-shaped support pan  30  having a base plate  32  with substantially perpendicular downwardly extending legs or sides  34 ,  36 . The downward dimension of legs  34 ,  36  are considerably less than the width of the base plate  32 . Suitable mounting holes can be provided within the legs and/or base plate for the mounting of the support pan  30  securely within the ceiling structure  38 . The support legs  34 ,  36  can extend perpendicular to the base plate  32  and are arranged substantially parallel to each other.  
         [0044]    A pair of support stanchions are provided adjacent to each of the downwardly extending legs  34 ,  36 . Each stanchion can be fabricated from a short length of a hollow box girder, or it can be formed as illustrated by nesting two U-shaped panels  44 ,  46  to form an enclosed column or girder. As shown in FIG. 7, the outer panels can be attached to the downwardly extending legs  34 ,  36 , respectively, and can be secured to the legs by any suitable means, such as bolts or by welding. The inner complementing panel is nested within the outer panel and can be adjustably positioned with respect to the outer panel. In other words, the inner panels  46  can be moved inwardly or outwardly with respect to the opposite panel and also can be adjusted in the vertical direction as needed. The two panels  44 ,  46  can then be securely attached by any suitable fastening device, such as bolts.  
         [0045]    The display support arm  14  can be pivotally mounted, as desired, between the two stanchions  40 ,  42 . A rotatable shaft or bar  48  mounted between two bearing supports  50 ,  52  attached respectively to the inner mounting plates  46  is suitably arranged for mounting the support arm  14 . The bearing supports  50 ,  52  are permanently attached to the inner surfaces of the inner plates  46  forming part of the stanchions  40 ,  42 . The shaft  48 , in most cases, will be arranged parallel to the outer ends of the support pan  30 .  
         [0046]    The support arm  14  can be fabricated from a plurality of elongated channels. For the sake of illustration, the present drawings will show an arrangement which incorporates two individual channels  54 ,  56  making up the support arm  14 . The channels are formed, usually from hollow box type structures with the upper channel  54  having larger inner dimensions than the outer dimensions of the lower channel  56  and arranged so that the inner channel  56  slides freely within the upper outer channel  54 . In this way, the two channels are arranged in a telescoping configuration. It has been found that a much more stable and stronger supporting arm  14  can be provided if the depth d dimension of the channels have a ratio of approximately 2:1 with respect to the width W of the channels. In this way, additional rigidity will be provided in the lifting arm to provide adequate support strength for the raising and lowering of the display  12 . As stated above, the supporting arm  14  can be made up of any number of individual channels which are arranged in a telescoping configuration. The number of channels and the length and cross-sectional thickness of the channels is designed to accommodate various ceiling heights and the anticipated weight of the display. A long thin slot  60  can be provided along the outer side of the channels  54 ,  56 . The purpose of this slot will be explained below.  
         [0047]    The support arm  14  is pivotally mounted on the shaft  48  by a U-shaped flanged clamp  64  securely attached to the backside  62  of the upper elongated channel  54 . The clamp is attached to the channel  54  by means of bolts or other suitable fastening devices. The clamp position is spaced downwardly from the end of the channel  54  a predetermined amount to provide a lever arm for the movement of the support arm  14 . This arrangement will be explained later.  
         [0048]    A pair of coiled springs  66  can be used to bias the support arm  14  in the downward pivoted position. The springs  66  are anchored at one end by bolts  70  attached to the base plate  32  of support pan  30 . The other end of the springs are connected to an anchor bar  70  mounted at the end of the upper channel  54  of the support arm  14 . Flanges  72  can be provided on the ends of the anchor bar  70  in order to retain the ends of the springs and prevent them from becoming displaced. The length of the springs  66  and their strength is predetermined for the force that is necessary to bias the support arm  14  in the downward pivoting position. These springs hold the support arm  14  rigidly in the downward most position when the arm is extended. It is also understood that any other type of biasing device can be used, which would bias the support arm in the lowered or downward position.  
         [0049]    A stop bracket  74  is arranged on the base plate  32  of the support pan  30 . The stop bracket  74  is aligned in the pivotal plane of the support arm  14 . A threaded stop bolt having an enlarged flat head and a locking nut is threadedly positioned in the side of the stop bracket  74 . A resilient pad  78  can be suitably fastened to the front face of the upper end of the upper channel  54  of the support arm  14  and positionally aligned with the stop bolt  76  for restricting the maximum movement of the downward positioning of the channel  54  and, in turn, the support arm  14 . The stop bolt  76  can be threadedly adjusted to establish the maximum lowered position of the support arm  14 .  
         [0050]    An electrically controlled linear actuator  76   a  can be substituted for the stop bolt  76 . In the lowered position, the support arm  14  is still under slight tension force from the springs  66 , movement of the linear actuator away from the arm or towards the arm will cause the arm to angularly move in order to provide a final adjustment to the actual position of the display with respect to the audience.  
         [0051]    The movement of the support arm  14  is controlled by a cable drum  80  and reversible drive motor  82 . The cable drum  80  is mounted on shaft  84  which is supported between the legs  34 ,  36  by bearing supports  86 ,  88 . The drive motor  82  and cable drum  80  are drivingly connected by sprockets  90 ,  92  and an interconnecting drive chain  94 . Although this description has been illustrated with a sprocket and chain drive arrangement, any other type of direct gear drive or other suitable drive can be substituted.  
         [0052]    Cable  24  is wound around the drum  80 . The cable  24  can be braided steel rope having a {fraction (3/16)} or ¼ inch diameter which has been found to be suitable for this purpose. The size of the cable is determined by the strength and load requirements that are placed upon the cable by the lifting arm  14  and display  12 . The longitudinal placement of the cable drum with respect to the support pan  30  is determined by the position of the downward feeding cable with respect to the support arm  14 . A pulley  18  is mounted longitudinally along the upper channel  54  of the support arm  14 . In the present structure, the pulley  18  is mounted with brackets provided on both sides of the upper channel  54  in order to provide a closed area for guiding the cable  24 . The pulley  18  is mounted at the upper end of the elongated slot  60 . The cable is fed from the cable drum  80  across the inner surface of the pulley  18  and down through the slotted channel  60  to an attachment point at or near the end of the lower channel  56  of the support arm  14 . The anchor for the cable  24  can be a threaded bolt  96  extending through the sides of the lower channel  56 . The head and nut of the anchor bolt  96  located on the outer sides respectively of the lower channel  56  provide a stop when they engage the lower end  98  of the upper channel  54  when the lower channel  56  is raised.  
         [0053]    An electrical control box  73  for connecting the input power to the motor  82  is provided within the support pan  30 . Suitable wiring is provided throughout the lift for performing the intended functions. A control panel for controlling the extension and retraction of the support arm  14  can be wired directly from the control box  73  to a convenient location for the control panel (not shown). This panel can be located at any location within the auditorium or a control room for the auditorium. It is also to be understood that, instead of using a wired control panel, a wireless arrangement can be provided which could include a portable remote control that could be used to control the movement of the display lift from within or near the auditorium or presentation area.  
         [0054]    A bracket  102  mounted at the outer end of the support pan  30  and positioned in the pivotal plane of the support arm  14  can be provided. The length of the bracket  102  is predetermined to provide a stop for the upward movement of the upper channel  54  and the support arm  14 . A limit switch  104  is provided in conjunction with the end of the bracket  102  which will automatically disengage the motor  82 . The bracket  102  provides the upper stop for the pivotal movement of the arm  14  while the stop  74 ,  76  limits the pivotal movement of the arm  14  in the downward position.  
         [0055]    An electrical limit switch  55 , such as a Microswitch, is mounted on the outward side of upper channel  54 . An aperture provided through the channel  54  allows the contact pin for the switch to contact the channel  56  and a plastic glide  57  which is adjustably positioned in the upper end of lower channel  56 . When the support arm  14  is raised the lower channel  56  is telescoped within channel  54  causing the limit switch  55  to make electrical contact to permit operation of the cable motor  82 . As the lift arm  14  is lowered and channel  56  slides downward with respect to upper channel  54  the glide  57  passes the limit switch  55  shutting off the motor  82 . The positioning of the glide  57  determines the extended length of lift arm  14  which is usually seven feet.  
         [0056]    A suitable arresting brake or locking mechanism  75  can be included in conjunction with the cable drum  80  to arrest the rotational movement of the drum if an emergency situation should occur. This type of emergency could be caused by the chain  94  breaking or the motor  92  malfunctioning. A lever type locking mechanism, as shown and described in U.S. Pat. No. 5,261,645, would be satisfactory for this purpose. It is also understood that a cable clamp mechanism (not shown) could also be used in conjunction with the cable  24  to arrest the cable movement and provide a safety feature for the lift.  
         [0057]    Since the cable  24  is the only component that is holding the support arm  14  in the upper position, it is possible to provide a mechanical locking device, such as a pin operated solenoid suitably mounted on the framework support pan  30 . In this way, a solenoid actuated pin can engage an aperture in the side of the lifting arm  14  which can physically lock it when it is in the upper or retracted position. In this way, the arm cannot extend without applying an electrical signal to the solenoid to retract the pin before the lift arm is to be lowered.  
         [0058]    The ceiling cover  16  can include reinforcing strips  106 ,  108  which can be used to reinforce and improve the lateral rigidity of the cover  16 . A pair of attachment brackets  110 ,  112  are pivotally connected at one end to the cover  16  and at the other end to the upper channel  54  of the support arm  14 . The brackets  110 ,  112  are pivotally attached at each end to accommodate the differences between the radial movement of the lift support arm  14  and the cover  16 . Elongated slots  114  can be provided in each of the brackets  110 ,  112  with adjusting screws provided for adjustment of the space between the arm  14  and cover  16  when in the raised or concealed position. During the movement of the arm  14  the brackets  110 ,  112  will pivot backward with respect to the cover  16  in order to accommodate the pivotal movement of the cover and raise it into the closed position in the ceiling C.  
         [0059]    Operation:  
         [0060]    It is to be understood that, for the sake of illustration, the operation of the display lifting device will be described from the extended or lowered position to the upper concealed position. The movement of the support arm and display to the lowered position would be the reverse of the following description.  
         [0061]    With the support arm  14  in the lowered extended position as shown in FIG. 13 the display  12  can be easily mounted on the mounting bracket  28  on the end of the lower channel  56  of the support arm  14 . With the display securely mounted, the motor  82  is actuated by a control panel or a remote control suitable for this purpose. With the rotation of the motor  82  turning the drive chain  94  through the sprockets  82 ,  90  the cable drum  80  is rotated in the clockwise position as seen in FIG. 13 to wind and retract the cable  24 . The end of the cable is suitably clamped to the anchor bolt  96  provided at the end of the lower channel  56 . Upon retraction of the cable  24  the lower channel  56  is pulled upward into the interior of the upper channel  54  contracting the anchor bolt  96  and the lower channel  56  of the support arm  14  as shown in FIG. 14. Once the anchor bolt  96  or display mount  28  comes in contact with the lower end  98  of the upper channel  54  the telescoping movement is stopped. Further retraction of the cable  24  causes the upper and lower channel  54 ,  56  and display  12  to start pivoting towards the ceiling opening  26 . The support arm  14  continues to pivotally rise with the cable  24  passing over the pulley  18  which acts as an attachment point for the upward movement. Since the ceiling cover  16  is pivoting from a different hinge  22  location, than the support shaft  48  of the support arm  14  the brackets  110 ,  112  start to pivot to accommodate the radial difference between the components. Further retraction of the cable  24  by the cable drum  80  causes the arm to be raised to the upper or concealed position to the point that the arm  14  and display  12  come in contact with the cutoff switch  104  which stops the motor  82  and the rotation of the cable drum  80 . At this point, with proper adjustment, the ceiling cover  16  will fit within the opening  26  and align with the surface of the ceiling C to conceal the display lifting arm and actuation mechanism.  
         [0062]    As the lifting arm  14  is raised into its upper retracted position, the biasing springs  66  are extended so as to provide a constant bias force on the lifting arm in the downward or extended position. Thus, when the support arm  14  is extended the relaxation and extension of the cable  24  allows the lower channel  56  to slidably extend from the end of the upper channel  54  to the fully extended downward position due to gravity. As previously mentioned, the stop bracket  74  and stop  76  come in contact with the resilient pad  78 . It is possible to substitute an electrically operated linear actuator for the stop  74 ,  76  so that the final downward position of the support arm  14  can be angularly adjusted to provide the optimum viewing position of the display  12  with respect to the audience.  
         [0063]    Materials used throughout this display lifting device can be chosen as desired to provide the desired strength characteristics and rigidity. It is to be understood that any suitable materials which provide these characteristics can be utilized. It is also understood that any display device, whether passive or active can be attached to the end of the support arm  14  for viewing purposes.  
         [0064]    While a display lifting device for active or passive displays has been shown and described in detail, it is to be understood that this invention is not to be limited to the exact form or structure disclosed and changes in detail and construction of the invention may be made without departing from the spirit thereof.