Abstract:
A household lift is provided with a stationary base and rack, wherein the movement of the drive gears and an associated movable portion is supported for linear motion parallel to the rack by at least a pair of extensible slides that are oriented at approximately right angles to one another.

Description:
FIELD OF THE INVENTION 
     The invention relates to a light weight lift system wherein the lift mechanism is separate from stabilizing elements. 
     BACKGROUND OF THE INVENTION 
     Lifting apparatus for televisions and monitors have been commercially available for more than 20 years. Most vendors of such lifting apparatus have designed lifting systems that were appropriate when large televisions and monitors weighed in the range of 100 pounds or more. The cost of such systems is substantial and as a result, these legacy lift apparatus have been most commonly deployed in custom installations for the wealthy and business enterprises. The expense of these legacy mechanisms is directly related to the cost to manufacture these relatively bulky, heavy and inefficient systems designed to lift weights in excess of 100 pounds. 
     Manufacturers have failed to revisit their legacy mechanisms&#39; basic structure and design in light of the recent drastic changes in television designs and the reduction in weight of even relatively large screen televisions. This failure is understandable because: 
     (1) manufacturers continue to enjoy sales and profits from their legacy lift systems; 
     (2) manufacturers&#39; costs for legacy lift designs are fully amortized, yielding handsome profit margins, and 
     (3) competitive entrants to the market place for lift systems have been sparse. 
     The continued existence of high cost lift systems demonstrates the customer need and desirability to be able to hide a television or monitor. This need is also established by the extent and range of expensive armoires available that allow televisions to be hidden behind closed doors. 
     Prior art motorized lift systems would generally be classified into three distinct categories: 
     (1) Telescoping steel screw lift columns with multiple attachment brackets to anchor a ridged lift structure to a cabinet or support wall, as exemplified by Moebel TV lift products. 
     (2) Steel rectangular frames with integral heavy duty slides and complex metal rack and pinion gear or chain drive arrangements. The heavy duty steel frames provide fixed box-like stability after being anchored to a cabinet or support wall, as shown in the Nexus 21 TV Lift System Model L-27. 
     (3) Large box-like modular platforms driven at both edges by metal rack and pinion or metal screw mechanisms. The box-like structure provides stability as shown in the Auton Motorized Systems Standard Lifts. 
     These three arrangements described above typically weigh in excess of 40 pounds, have numerous functional components, and are insufficient both in their use of materials and energy. Insufficiencies result both because a part of the heavy structure moves up and down with the monitor and must be driven by the motor, and because it is necessary to use a larger motor for the resulting heavier load. 
     In summary, lifts available today for televisions, monitors, ergonomic desks, projectors, kitchen appliances, hidden safes, motion furniture, and other devices are either cumbersome, noisy, unstable, erratic, expensive, complex, heavy, inefficient, or a combination of some or all of these. There is a need for an efficient, economical, precision, smooth, quite, compact, light weight, simple, and preferably environmentally sound, lift mechanism which may be conveniently sized to fulfill a range of lifting needs from small to large and from light to heavy. 
     SUMMARY OF THE INVENTION 
     To achieve the design objective of producing an improved lift mechanism, it is necessary to analyze the basic mechanical functions that a lift system needs to accomplish and then combine the best solution to fulfill the functional needs for resulting lift weight and economical performance. Desirable mechanical and electrical functions include:
         Power with little or no back-drive,   Smooth operation, and   Stability during and after the lifting process.       

     These objectives may be respectively achieved by:
         Selecting a suitably sized and geared motor,   Selecting one of a number of lift means, including cable drives, scissor drives, linear actuators, rack and pinion, and dual rack and pinion drive systems, and   Selecting and placing sufficient guides or slides or a combination of both, and creating a self-contained box-like structure.       

     A novel class of lifts is achieved by using a worm gear motor to power a dual rack and pinion drive which is coupled with angled ball bearing extensible slides to achieve stability. To achieve the most cost effective, efficient system, the stability and lifting may be treated independently. Lifting may be achieved by positioning and operating a single powered dual rack and pinion system at or near the center of mass of the object to be lifted, thereby minimizing torque and unwanted moments. Stability may be independently realized by selecting, spacing and positioning a minimum number of ball bearing slides to achieve the stability objective. Angling the ball bearing slides may increase the realized stability. Lifting and ensuring stability for objects of different shapes requires the selection of two or more angled slides and the number of slides may vary according to the shape in accordance with the following general guidelines:
         Flat screen television or monitor (narrow rectangular lift profile) and   Compact Circle (diameter≦about 24 inches) or Compact Square (≦about 24×24 inches)—2 slides;   Medium circular profile (diameter≦about 60 inches) and   Medium Square (≦60×60 inches) or Medium rectangular profile (≦about 24×60 inches)—4 slides;   Large rectangular profile (≧about 24×60 inches)—6 slides;   Large squares (≧about 60×60 inches) and   Large circular profiles (diameters≧about 60 inches)—8 slides.       

     Most other shapes can be accommodated with between 2 to 8 slides. 
     To demonstrate and teach principles of the invention, two particular cases will be discussed in detail. The first is a lift designed to raise and lower flat screen television monitors, which the second is a lift design to raise and lower a coffee table so that it becomes a dining table. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following description in conjunction with these accompanying drawings: 
         FIG. 1  is an exploded perspective view of an exemplary lift according to the invention optimized for raising and lowering an object with a narrow rectangular profile such as a television or monitor. 
         FIG. 2A  is a perspective view of the lift system of  FIG. 1  in fully extended or raised position. 
         FIG. 2B  is a perspective view of the lift system of  FIG. 1  intermediate its extended and retracted positions. 
         FIG. 3  is a perspective view of the back plate of the lift system of  FIG. 1 . 
         FIG. 4A  is a perspective view of the rack and gear box of  FIG. 1 . 
         FIG. 4B  is a reverse angle perspective view of the gear box of  FIG. 4A  shown in isolation. 
         FIG. 5  is a perspective view of the moving front plate of the lift system of  FIG. 1 . 
         FIG. 6  is a perspective view of the mount plate of the lift system of  FIG. 1 . 
         FIG. 7A  is a side plan view of the motor bracket plate of the lift system of  FIG. 1 . 
         FIG. 7B  is a front plan view of the motor bracket plate of the lift system of  FIG. 1 . 
         FIG. 8  is a perspective view of the cable mount plate of the lift system of  FIG. 1 . 
         FIG. 9  is a perspective view of the safety plate of the lift system of  FIG. 1 . 
         FIG. 10A  is a perspective view of a lid support bracket of the lift system of  FIG. 1 . 
         FIG. 10B  is a perspective view of the lid bracket of the lift system of  FIG. 1 . 
         FIG. 10C  is a perspective view of the stop bracket of the lift system of  FIG. 1 . 
         FIG. 11A  is an exploded perspective view of an exemplary table lift system according to the present invention. 
         FIG. 11B  is a perspective view of the table lift system of  FIG. 11A  in a fully extended position. 
         FIG. 11C  is a perspective view of the table lift system of  FIG. 11A  in a fully collapsed position. 
         FIG. 12A  is a perspective view of a first outer wrap bracket of the lift assembly of  FIG. 11A . 
         FIG. 12B  is a perspective view of a second outer wrap bracket of the lift assembly of  FIG. 11A . 
         FIG. 13  is a perspective view of the rack support bracket of the lift assembly of  FIG. 11A . 
         FIG. 14  is a perspective view of the inner slide bracket of the lift assembly of  FIG. 11A . 
         FIG. 15  is a perspective view of the motor bracket of the lift of  FIG. 11A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Televisions and monitors come in a wide variety of sizes and weights. The lift system illustrated in  FIG. 1  is designed for use with flat screen televisions and monitors, and it will be understood that a range of lift sizes might be advantageously provided to cover the entire spectrum of television and monitors that are available. The illustrated example is selected to cover the mid-range sizes of flat screen televisions, generally ranging from about 32 inches to 46 inches in screen diameter. Televisions are not universally constructed to have the same structural framework or core rigidity; consequently, it is more convenient to raise and lower televisions by “hanging” the televisions through attachments to the back vertical surface or vertical sides rather than by “pushing” the televisions from their bases. Thin flat screen televisions are generally provided with a sizable vertical rectangular viewing surface and a narrow or slim rectangular base profile. For efficiency, the lift dimensions should be generally analogous to this rectangular shape, in a fashion that imparts stability to the lift and television assembly while minimizing the depth and space required for installation. 
     Turning then to  FIG. 1 , the functional assembly of a lift system is illustrated. The principle components include a base cage in the form of a stationary back plate  13 , a rack  24 , two angled slides  20 , an inner cage in the form of a moving front plate  14 , a mount plate  15 , a cable mount plate  17 , and a motor cover  25 . As shown in  FIG. 1 , a motor  23  is positioned between the motor cover  25  and the motor bracket plate  16 . Further, the motor engages with a gearbox  26 . The stationary back plate  13  also serves as the mounting point for stop bracket  19  and safety plate  18  connected by a folding hinge. 
       FIG. 2A  shows the lift at full extension and  FIG. 2B  shows the lift at mid-extension. Each of the principal components may be examined in greater detail in isolation. In particular,  FIG. 3  shows the stationary back plate  13  which is comprised of five principal segments. At either side of back plate  13  is an angled slide holder section  31 ,  32 . These sections are preferably angled at approximately 45° from the planar orientation of back plate  13 . The center portion  35  of back plate  13  serves as mounting surface for dual rack  24 . To either side of the central rack mounting section  35  is a spacing section  36 ,  37  that provides additional clearance behind the mounted television and sufficient spacing from the rack to the angled portions  31 ,  32  for the slides mounted on the angle portions to serve their own stabilizing function. In the central section  35  there are openings  29  to facilitate mounting the rack  24 . Other apertures on back plate  13  are used to mount ball bearing extensible slides on angled portions  31 ,  32  and to attach the back plate  13  to a stationary wall or support in the spacing sections  36 ,  37 . Because the back plate is a securely fastened to a support or wall, the back plate itself need not be made of heavy gauge materials. Furthermore, the folds in the connecting sections, that are preferably at an angle of about 45°, between spacing sections  36 ,  37  and center portion  35  provide additional rigidity. 
     Turning then to  FIGS. 4A and 4B , the rack  24  is illustrated with dual racks  40 ,  41  to engage with a pinion gear. An open gearbox  26  is shown at the lower end of rack  24  with apertures  51 ,  52  that are used to the join the gearbox to the moving front plate  14  shown in detail in  FIG. 5 .  FIG. 4B  illustrates the driven pinion gear  47  which with its teeth  48  engages with a matching spur gear  49 . The gear teeth  48 ,  50  of the pinion gear  47  and spur gear  49  engage with the teeth in racks  40 ,  41  as the racks are received in channels  53 ,  52  of the gear housing. 
     The moving front plate  14  has apertures  66  near its lower edge through which fasteners are attached to secure the moving front plate  14  to the gearbox  26 . In this fashion, the moving front plate  14  will ride with the gearbox along the rack  24  as the gear wheels  47 ,  49  are turned by the motor  23 . Also of note on the moving front plate  14  are two rows of slots  65  which can receive tabs from the mount plate  15  shown in  FIG. 6 . In addition, the moving front plate  14  has rearward angled wings  61 ,  62  which are bent through a range of approximately 135° from the planar surface of moving front plate  14  at angle lines  63 ,  64 . Angle wings  61 ,  62  are attached to the ball bearing extensible slides that are mounted on the angled edges  31 ,  32  of the stationary back plate  13 . It will be seen that by positioning the slides between the moving front plate  14  and stationary back plate  13  at approximately a 45° angle, not only is rigidity added to the plates  13 ,  14 , but the slides also are positioned at approximately 90° to each other in such a fashion as to simultaneously resist movement in both the front to back and side to side directions. Thus the angled slide connections provide stability in all directions while minimizing any friction or lack of smoothness in the movement of the lift system when it is raised or lowered. Finally the slots  67  on the moving front plate  14  are adapted to receive a horizontal portion  91  of stop bracket  77  to lock the moving front plate  14  in a vertical position. 
     Turning then to  FIG. 6 , the mount plate  15  is shown with four rearwardly extending feet  56  each having a downwardly extending tab  57  defined by upward channel  58 . These tabs  57  are adapted to fit in the slots  65  of the moving front plate  14  shown in  FIG. 5 . However, before attaching the mount plate  15  to the slots  65  of the moving front plate  14 , a monitor or television is first attached to apertures  59  which are positioned according to a mounting interface standard of the Video Electronics Standards Association (VESA). In addition, a fixed screw is placed in an aperture  60 . Once the television and mounting plate  15  are connected to moving front plate  14 , this screw is secured in a central slot on the moving front plate  14  as a security and safety precaution. Generally, when the mount plate  15  is attached to slots  65  of moving front plate  14  the relatively smaller monitors or televisions will be mounted in the lower slots  65  while larger televisions or monitors would be mounted in higher slots  65  so that a fixed stroke of travel will position the center of either size television to be at the correct height in the up position for optimum viewing of the central area of the television screen. This mechanical positioning simplifies the design of the electronic control necessary to automatically operate the television. 
     The electronic controls are further simplified by the choice of slides with up and down stops that insure stopping and avoid the need for the additional cost and complexity of micro-switches. The use of modulated current and time controls built into the automated controls for operating the motor can minimize the load sustained at the full up and down positions. 
       FIGS. 7A and 7B  illustrate the motor bracket plate  16  which allows the motor to be securely positioned and attached to the bottom of the moving front plate  14  and the associated gearbox  26 .  FIG. 8  illustrates the cable mount plate  17  with some apertures to attach to the bottom of the moving front plate  14  and slots  44  that together may receive ties to attach or pass through cables to the cable mount plate  17 . Securing cables such as signal and power connections to the television mounted on the lift using ties will avoid an inadvertent loosening of those electrical connections by repeated operation of the lift. 
     Two additional features of the lift system are a hinged stop plate  18  and a self locating lid mechanism. The hinged safety plate  18  shown in  FIG. 9  is hingedly connected through apertures  43  to apertures on section  37  of the stationary back plate  13 . Generally this stop plate  18  will remain folded flush against the stationary back plate, however, should the motor malfunction then the stop plate  18  can be used to manually position the television at a usable height. In the case of a motor malfunction, then the attachment of the of motor and gearbox through apertures  66  of the moving front plate  14  is undone so that plate  14  is movable separate from the motorized drive. Then the front plate  14  and television can be lifted to a usable height and the hinge operated to move the stop plate  18  so that it is in a position normal to the stationary back plate  13  and the television will rest in the channel  42  on stop plate  18 . When it is no longer desired to have the television in the raised position, the stop plate  18  may be folded inward and the front plate  14  and television lowered back into its recessed position. 
     As a television exits a cabinet, a suitably sized lid either has to hinge back by approximately 90° or alternatively be lifted with the television. For a television lift capable of raising and lowering different sized televisions with a single stroke, the lid lifting and lowering must be self and independently positioning from the raising and lowering lift mechanism. This is achieved by fixedly mounting a lid lift bracket  22  (shown in  FIG. 10A ) to two vertically aligned independently adjustable slides  21  (shown in  FIG. 10B ) fixedly attached to the back side of the front moving plate  14 . The slots in slides  21  are used to position the attached lid bracket  22  at the proper weight when an aesthetically appropriate lid is fixed on bracket  22 . 
     To minimize the cost and weight of the lift system, the dual rack  24  and gears  47 ,  49  can advantageously be made of thermoplastic materials. Similarly, other components such as the motor cover  25  and cable mount plate  17  may also be made of thermoplastic materials. Generally the thermoplastic materials are preferred to have antistatic or non-dust attractant qualities, as by the incorporation of amorphous or crystalline carbon materials. The dual rack  24  and gears  47 ,  49  are advantageously made of crystalline or semi-crystalline polymers. In particular, polymers such as polyamide, polyester, polyolefin, and polyphenylene sulfide are suitable examples. In addition, the polymers may advantageously be self lubricating, as by incorporating one or more of silicone, polytetrafluoroethylene, carbon fiber, or molybdenum disulfide. To provide additional reinforcement to the thermoplastic materials the inclusion of glass fiber, carbon fiber or reinforcing filler materials may be advantageously employed. 
     To minimize torque moments associated with movement and operation of the lift system, it is preferable that the teeth  48 ,  50  of gears  47 ,  49  engaging with rows of teeth  40 ,  41  in the dual rack  24  are aligned central of the angled slides  20  attached between the angled end sections of the stationary back plate  13  and moving front plate  14 . Torque is minimized when the center vertical plane of the two slides is also the plane of lifting. 
     It will also be understood that the motor  23  of the lift is operable by radiofrequency, infrared, or other communications typically implemented in audiovisual remote control systems. Furthermore, the electronics of the lift system may advantageously include a solenoid actuated shaft attached to the moving front plate  14  and capable of engaging the stationary back plate  13  when the television is in its full up position to help support the weight of the television. Electronics may also include detection of an amperage level that when exceeded will cut off the motor to prevent motor damage and/or a time shutoff control for the motor after it has operated for the length of time necessary to move from the full-up to full-down position or vice-versa. In addition, the on/off control of the television may be synchronized with the operation of the lift system so that the television is turned on when reaching the full up position and the television is turned off when the lift is operated to lower the television from its raised and visible position. 
     The lift of  FIG. 1 , adapted for use with flat screen televisions, is effectively a two-dimensional example of the present lift system which is generalized to a three-dimensional example in the lift system depicted in  FIGS. 11A ,  11 B and  11 C. Turning then to these figures, the lift system is shown with a base cage formed of a pair of outer wrap brackets  70 ,  71 , a central rack support bracket  72 , a moving inner cage or bracket  73 , a motor bracket plate  76 , a rack  24 , a gearbox  26 , a motor  23 , and a plurality of slides  78 . This illustrated lift system is particularly adapted for a coffee table or small dining table, perhaps of 45 inches square. Coffee tables typically have a top surface height of about 18 to 20 inches, while dining tables have a top surface height of approximately 29 to 31 inches. The objective of the lift therefore, is to raise the tabletop approximately 1 foot, or about 10 to 14 inches, while providing stability without shaking or jarring during the raising and lowering motion. The table should also have sufficient stability in the up position to avoid toppling under an uneven load, as might be applied by a person leaning or sitting upon an edge or corner of the table. 
     The design chosen for this square table with 45 inch sides, utilizes four slides  78  that are angled and positioned at the corners of the lift. The movement is operated by a worm gear motor driven dual rack and pinion drive positioned beneath the center of mass of the table. The dual rack  24  is attached to the rack support bracket  72  that together with the outer wrap brackets  70 ,  71  are mounted to a stationary base or other structure. Stationary components of slides  78  are attached to outer wrap brackets  70 ,  71 . The motor (not shown) is mounted upon the motor bracket plate  76  and to the gearbox  26 . The motor bracket plate  76  is also connected to the moving inner brackets  73 ,  74  which has angled or beveled corners that are connected to the sliding portions of angled slides  78 . The moving bracket  73  has horizontal tables  74  and the motor bracket plate  76  has horizontal tabs  75 . These horizontal tabs  74 ,  75  are fastened to the bottom surface of the table top (not shown). 
     When the motor is energized, the pinion drive lifts the tabletop to the extended position shown in  FIG. 11B  while the plurality of angled slides  78  independently provide stability. The drive motor may be plugged into a household power supply, however, to facilitate the positioning of the lift table, it is desirable to provide a drive motor attached to a dry cell rechargeable battery pack, that is in turn attached to a renewable power supply. The drive motor may be energized either by a spring-loaded toggle switch or a remote control manually operated button. 
     For the tabletop with 45 inch sides, the spacing of the slides  78  approximately 9 inches apart, results in a very stable lift in both fixed up and down positions and during its intermediate movement. The slide spacing may be increased or decreased depending upon the load to be lifted, the material and thickness of the individual components, and the loadbearing capability of the slides. As with the television lift, ball bearing slides produce the most advantageous results. Coupling of the angled slides to a single lift mechanism produces very smooth action throughout the start, stop and intermediate movement of the lift. In contrast, the use of prior art multiple drives as disclosed in the Nexus 21 TV Lift System Model DL-3 results in non-synchronized motion, is jarring to the lift surface, and is relatively costly. As previously mentioned, the position of the rack and pinion drive mechanism is preferably central to the center of mass of the tabletop that is being lifted, and the positioning of the extensible slides  78  is also designed to minimize torque moments. By minimizing torque associated with the rack and pinion drive mechanism and the slide stabilizing mechanism, a fluid and continuous movement of the lift is facilitated with little jarring or wobbling action. 
     Turning to  FIG. 12A  it can be seen that the first outer wrap bracket  70  has a center panel  80  and on either side an angled slide holding panel  81 ,  82  set at approximately a 45° angle from the plane of the center panel  80 . The angled panels  81 ,  82  have a plurality of apertures  85  to secure the nonmoving portion of attached slides  78 . In  FIG. 12B , the second outer wrap bracket  71  has a very similar structure. Lugs  87  are fixed along the bottom edge of the outer wrap brackets  70 ,  71  and fasteners are placed through openings  88  to secure the outer wrap brackets to a table base. To either side of the angled panels  81 ,  82  are edge tabs  83 ,  84  with apertures  86  for fastening purposes. 
       FIG. 13  shows the rack support bracket  72  in isolation, including a rack mounting surface  93  with mounting apertures  94 . To either side of the rack mounting surface  93  is a sidewall  95 ,  96 . Although not shown, to the bottoms of each sidewall  95 ,  96  may be attached tab sections with tab apertures for fastening purposes. An exemplary moving bracket  73  is shown in  FIG. 14  with a center panel  100  and angled pairs of side panels  101 ,  102  at either side and at a 45° angle to the plane of the center panel  100  and approximately 90° to one another. Pairs of angled side panels  101  are separated by wall  104  while pairs of side angles  102  are separated by wall  105 . Apertures  103  are provided in the side panels  101 ,  102  in order to attach the moving portion of slides  78 . Horizontal tabs  74  are provided with openings to facilitate fastening to the bottom of a table top. 
       FIG. 15  illustrates the motor bracket plate  76  which has a central aperture  115  to permit the motor to connect and drive the pinion gear. Apertures  117  allow the motor to be mounted to the motor bracket plate  76  while apertures  116  permit the motor bracket plate  76  to be fastened to the gearbox  26 . The edge tabs  118  and  119  are used to connect the motor bracket plate  76  to the moving bracket  73  with fasteners passing through apertures  105  of tab  118  and  89  of bracket  73 . The motor may be of the worm type driving a single gear that in turn drives a slave gear. Alternatively, the motor may be of a double ended worm type with opposite rotational helix that drives both gears engaging the double rack  24 . In yet another alternative, structure, the motor may be a worm type motor with an elongated shaft that comprises to opposite rotational helix aligned to drive both gears along the rack. The worm helix angle may be selected to impart little or no back drive. As described in connection with the lift of  FIG. 1 , the dual rack  24 , gears and gearbox can advantageously be formed of thermoplastic material, with crystalline or semi-crystalline polymers being a preferred class of materials. Such polymers including polyamide, polyester, polyolefin, and polyphenylene sulfide. These thermoplastics may also be formulated to be a self lubricating as previously described. 
     All publications, patents and patent documents are incorporated by reference herein as though individually incorporated by reference. Although preferred embodiments of the present invention have been disclosed in detail herein, it will be understood that various substitutions and modifications may be made to the disclosed embodiment described herein without departing from the scope and spirit of the present invention as recited in the appended claims.