Abstract:
Elevators are maintained in level condition by four fixed ropes or cables passing diagonally across an elevator in angularly related opposite directions. The ropes extend from opposite corners of the elevator to fixed upper and lower ends. Moving the elevator causes equal and opposite changes in lengths of the portions of the ropes extending upward and downward from the pulleys on the elevator, keeping the elevator level.

Description:
BACKGROUND OF THE INVENTION 
   Elevators are raised and lowered in guideways using cables which are called ropes. Rollers on the elevators move along the guideways, keeping the elevators centered. 
   Uneven loads in elevators tend to tip the elevators. Undesirable tipping is controlled by simple or complex mechanisms. Occasionally when riding an unevenly loaded elevator a passenger is aware of sounds related to roller and guideway contact, particularly when starting. The problem of controlling tipping is particularly acute with large room-sized elevators. 
   Needs exist to maintain elevators level with simple and easy-to-install equipment. 
   SUMMARY OF THE INVENTION 
   Elevators are maintained in level condition by four fixed ropes or cables passing diagonally across an elevator in angularly related opposite directions. The ropes extend from opposite corners of the elevator to fixed upper and lower ends. Moving the elevator causes equal and opposite changes in lengths of the portions of the ropes extending upward and downward from the pulleys on the elevator, keeping the elevator level. 
   A preferred elevator levelling apparatus includes first and second rigidly connected cross beams extending at angles across an elevator. Eight pulleys on the beams include four pulleys on each beam. Paired pulleys are positioned on axles at opposite ends of each beam for freely rotating on the axles. four fixed ropes extend oppositely across the beams and upward and downward from opposite ends of the beams. Each beam has two oppositely extending ropes. Each rope extends downward from a fixed position near a top of an elevator guide around a first pulley, across the beam, around a second pulley and downward to a fixed position near a bottom of the elevator. Raising and lowering an elevator with the crossed beams, pulleys and ropes constrains the ends of the beams and the elevator for equal movement along the ropes and maintains the beams and elevator in constant relation with respect to horizontal. 
   A preferred elevator levelling apparatus uses an elevator having a rectangular planform. Pairs of pulleys are mounted near corners of the elevator. Ropes have upper ends fixed above the corners near an upper end of a guide and have lower ends fixed below diagonally opposite corners near a bottom of the guide. Each rope extends downward from its fixed upper end, passes around a pulley in one pair, extends diagonally across the elevator, passes around a pulley near a diagonally opposite corner of the elevator, and extends downward to its fixed lower end. Pairs of the ropes extend diagonally in opposite directions across the elevator. 
   Preferably four ropes are used. Each of the four ropes is connected above a different corner of the elevator and extends downward and corner to corner across the elevator and around the pulleys and downward to its fixed position under a diagonally opposite corner of the bottom of the elevator. 
   Stabilizing elevators for level operation fixes upper ends of ropes to diagonally opposite spaced positions above corners of an elevator. The ropes extend downward, and pass under and over pulleys at diagonally opposite corners of the elevator. Lower ends of the ropes are fixed to diagonally opposite and spaced anchor positions. 
   In one embodiment a vertical guideway has a rectangular cross-section, and each rope is connected to the anchor positions and to diagonally opposite upper frame positions. 
   Preferably an elevator has a rectangular planform. Four ropes extend downward to four corners of the elevator, across the elevator and to diagonally opposite anchors. 
   Eight pulleys and provided, two at each corner of the rectangular planform elevator. 
   Brakes connected to the elevator and to the ropes or the pulleys retard or stop the elevator. 
   Preferably the brakes are regenerative electric brakes. 
   In some embodiments, motors connected to the pulleys move the elevator. 
   Preferably, rigidly connected rigid cross-beams are connected across the elevator and extend from corner to corner of the elevator, and the pulleys are mounted in pairs at ends of the rigid cross beams. 
   These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic detail of a beam with four pulleys and two fixed ropes which constrain the beam to level up and down movements. 
       FIG. 2  is a schematic detail of four fixed ropes and two rigidly interconnected crossed rigid beams for attaching to an elevator and constraining the elevator to level raisings and lowerings. 
       FIG. 3  shows a prior art roller construction for rolling along a fixed channel or I-beam and resisting tipping of an elevator. 
       FIG. 4  is a schematic detail of an elevator moving in a guideway. 
       FIG. 5  is a schematic detail of one embodiment of the invention showing a guide I-beam and a guide attached to an elevator with four fixed ropes passing diagonally across the elevator around pulleys at diagonal and spaced positions on the elevator. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a schematic detail of a beam with four pulleys and two fixed ropes which constrain the beam to level up and down movements. 
     FIG. 1  shows a beam  1  and two ropes  2  and  3  extending around pulleys  5 ,  6  and  4 ,  7  respectively on the beam. The rope extremities are held fixed. 
   Ropes  2  and  3  are fixed at opposite ends  9 ,  10  and  8 ,  11  respectively. 
   The ropes and pulleys ensure that as beam  1  is raised or lowered, both ends of the beam must move equally. For example, moving the beam upward lengthens the portion  21  of rope  2  between fixed end  9  and pulley  5 , and shortens portion  33  of rope  3  between fixed end  8  and pulley  43 . Concurrently the lengthening of portion  21  shortens portion  23  of rope  2  between pulley  6  and fixed end  10 . At the same time, and by the same amount, portion  31  of rope  3  between pulley  7  and fixed end  11  is lengthened. All lengthenings and all shortenings of portions of the ropes are equal. The portions have equal changes or deltas, although changes to the upper portions  33 ,  23  have opposite signs or directions than the equal but opposite changes to the lower portions  21 ,  31 . The beam  1  is rigid. 
   Regenerative electric brakes  95  connected to the elevator and to the pulleys  4  and  6  retard or stop the elevator. 
   In  FIG. 2  a second rigid beam  41  is diagonally rigidly attached to the first beam  1  by a rigid interconnection  35  and bolts  36 . 
   Pulleys  44  and  45  at end  58  of beam  41  are similar to and function similarly to pulleys  4  and  5  at end  38  of beam  1 . 
   Pulleys  46  and  47  at end  59  of beam  41  are similar to and function similarly to pulleys  6  and  7  at end  39  of beam  1 . 
   Ropes  42  and  43  which pass around the pulleys on beams  41  are similar to and function similarly to ropes  2  and  3  which pass around the pulleys on beam  1 . Rope  42  is fixed at its upper end  50 , descends and passes around pulley  46 , extends across beam  41 , passes around pulley  45 , descends and is anchored and fixed at end  49 . 
   When the cross beams  41  and  1  are connected to an elevator, the elevator may be raised and lowered by cables attached to the central rigid interconnection  35 . 
   Rope  43  is fixed at upper end  48  and passes around pulley  44 , across beam  41 , and around pulley  47 . End  51  is anchored. 
   Moving any part of the rigidly connected frame upward or downward causes the frame to move in a level condition. 
     FIG. 3  shows a prior art roller construction for rolling along a fixed channel or I-beam and resisting tipping of an elevator. 
     FIG. 3  shows a prior art elevator guide system that uses two or more guide channels  61  or I-beams to guide rollers  63 ,  64 ,  67 ,  68 , which rotate on a mount  62  on connectors  65  extending outward from an elevator. 
     FIG. 4  is a schematic detail of an elevator moving in a guideway. 
     FIG. 4  schematically shows a guideway  70  with beams  71 ,  72  in which elevator  73  rides when hauled upward or lowered by cables  76 . The elevator is rigidified with rigid cross beams  74  between the floor  77  and ceiling  78 . 
     FIG. 5  is a schematic detail of one embodiment of the invention showing a guide I-beam and a guide attached to an elevator with four fixed ropes passing diagonally across the elevator around pulleys at diagonal and spaced positions on the elevator. 
     FIG. 5  shows an elevator  81  guided by a vertical I-beam guide  91  and a guide follower  92 . The elevator has a rigid upper frame forming a rectangular ceiling  83 , side walls  85  and floor  87 . Paired pulleys are mounted near upper corners of the rigid elevator box or roof or on crossed beams in, under or on the roof. The function of the ropes and pulleys is similar to that described with respect to  FIG. 2 . The elevator roof or base has fixed rigidly interconnected beams  1  and  41 . 
   Pulleys  44  and  45  at end  58  of beam  41  are similar to and function similarly to pulleys  4  and  5  at end  38  of beam  1 . 
   Pulleys  46  and  47  at end  59  of beam  41  are similar to and function similarly to pulleys  6  and  7  at end  39  of beam  1 . 
   Ropes  42  and  43  which pass around the pulleys on beams  41  are similar to and function similarly to ropes  2  and  3  which pass around the pulleys on beam  1 . Rope  42  is fixed at its upper end  50 , descends and passes around pulley  46 , extends across beam  41 , passes around pulley  45 , descends and is anchored and fixed at end  49 . 
   When the cross beams  41  and  1  are connected to an elevator, the elevator may be raised and lowered by cables attached to the central rigid interconnection  35 . 
   Rope  43  is fixed at upper end  48  and passes around pulley  44 , across beam  41 , and around pulley  47 . End  51  is anchored. 
   Moving any part of the rigidly connected frame upward or downward causes the frame to move in a level condition. 
   The elevator is raised or lowered by a series of cables  93  attached centrally to the elevator, or riding in cable guides along sides or corners, if the guideway is formed in a reinforced rectangular cross-section. 
   The pulleys may be driven by electric motors or brakes regeneratively or mechanically to control elevator movement. 
   While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.