Levitators: A new concept for elevators

© 2007, Rajaram Pejaver, Patent Pending


This document describes an elevator system that operates multiple elevator cars per elevator shaft, i.e., there will be more elevator cars than there are elevator shafts.  As in traditional systems, elevator cars transport people by going up and down shafts.  The unique concept here is that, when the paths of two cars interfere with each other, with one car going up and the other going down in the same shaft, then one of the cars will move sideways to an adjacent shaft and continue on to its destination floor.

This innovative system avoids the use of counterweights which are used in traditional elevator designs.  Instead, the system balances cars against each other so that there are an approximately equal number of cars going up and going down at any time in a bank of shafts

The primary benefits of this system are to increase the number of operating elevator cars in an existing building and to reduce the number of elevator shafts required during the design of a new building.  It results in reduced passenger wait times and increased utilization of space inside a tall building.  The design allows a number of other benefits which are also described.


Levitators: A new concept for elevators. 1

Abstract 1

Background. 2

Summary. 3

Drawings. 4

Detailed description. 5

Vertical motion. 5

Drive Assembly. 8

Balancing the load. 9

Vertical transitions. 10

Switching shafts. 14

Stacked drive segments. 17

Computer control system.. 18

Slanted operation. 19

Horizontal travel 20

Personal sized elevator cars. 20

Splicing cars together 21

Tilting cars during horizontal acceleration. 21

Power supply and communications. 21

Claims. 21

Appendix A: Previously granted relevant US patents. 22


First, some terminology to explain traditional elevator systems:

à        Car, Cab, Cage: the compartment used to transport passengers between floors.

à        Shaft, Well, Hoistway, Hatchway: The vertical passage way in the building through which the car travels.

à        Bank, Group: A set of adjoining shafts.

à        Counterweight: A weight that serves to balance the car.

à        Cable, Hoist, Rope: The cable that supports the car by connecting it to the counterweight.

à        Pulley, Sheave: A wheel that guides the cable at the top of the shaft.  This is usually driven by a motor.

à        Control system: A set of computers that control the smooth operation of the system.

à        Algorithm, Program: The software that runs on the Control system.

There is always a need for improved elevator service in tall buildings.  Today, the prevailing trend is towards tall and thin buildings.  As the number of floors increase, there is a need for more cars because there are more passengers and each car will be slower because there are more floors to stop at.  At the same time, with thinner buildings, there is a less room for elevator shafts.  These shafts use up valuable space on each floor, regardless of whether or not they service that floor.  It is estimated that more than 30% of the floor space in a 100 story building would be dedicated to the elevator system.

Today, most elevators operate by dedicating one car per shaft.  A pulley is placed on top of each shaft.  The elevator car and a counterweight are connected by a cable and balance each other over the pulley.  A motor drives the pulley and causes the car to move up and down the shaft.  The counter weight serves to reduce the effort required by the motor to move the car up and down, since power would be needed to lift only the difference in the weights of the counterweight and the car.  This basic engineering design has survived decades of technical improvements.

While using counterweights, it is not practical to operate more than one independent car per shaft.  The support cable stretches all the way from the car to the top of the shaft.  It occupies the center of the shaft and precludes the possibility of another car in that space.  It is possible to move the support cables to the sides, but it is hard to imagine an extensible design where the cables and counterweights do not get tangled during operation.

Prior inventions have addressed this problem in simple ways.  One idea has “double-decker” cars where a car simultaneously serves two adjacent floors.  Another idea has multiple independent cars in a shaft, but the cars are not able to pass each other.  In a different direction, a Paternoster elevator employs a train of cars that continually operate in a cyclic path so that they move up one shaft and down another.  Some systems propose the use of Linear Induction Motors for propulsion; however such systems will not be commercially economical for the foreseeable future.

The most common practical solution today in tall buildings is to have multiple groups of elevators, with each group serving a range of floors.  For example, a group would serve floors 1 through 20, another would serve floors 21 through 40, and yet another for floors 41 through 60, and so on.  This arrangement usually reduces service times for passengers.  The main problem with this idea is that the shafts for all groups extend through all floors below the service range, regardless of whether or not the car stops at that floor.  This consumes valuable floor space on floors that are not serviced by the elevator bank.  Also, in practice, the shafts usually extend all the way to the top of the building.

Another problem is that the weight of the support cable becomes significant in tall buildings with long shafts.  This affects the balance between the car and the counterweight as the car moves from the top to the bottom of the shaft.  When the car is at the top of the shaft, the weight of the cable is on the side of the counterweight.  This weight shifts to the other side as the car moves to the bottom of the shaft.  All in all, the conclusion is that the concept of counterweights is not suited for tall buildings.  An annotated list of relevant patents is included in Appendix A.

With modern architectural designs, there will be a need for elevators that move in slanted or curved paths.  Buildings are no longer simple cuboids (shaped like a box).  The Luxor hotel in Las Vegas resembles a giant pyramid.  It would not be possible to have a traditional vertical shaft that provided service from a bottom edge to the top of the building.  It is also useful to have elevators that follow complex paths, with some vertical segments, some horizontal segments and other slanted or curved segments.  There will be situations, for example, in large cruise ships, where a straight vertical shaft is not feasible because of structural components or critical functional areas that block a straight run.  There is also a need for elevator cars that move horizontally from one bank of elevators to another.  Workers in buildings that cover a large area of ground often need to ride an elevator to a crossover floor, walk to a different elevator bank and take that to their destination.  The Time-Warner building in New York City covers an entire city block.  The Pentagon is another extreme example.

While some of the requirements described above are ambitious and exotic, the design described in this note supports all of them.  Most importantly, it will require fewer elevator shafts in tall buildings, thus increasing the useful floor space.


The solution described here allows multiple cars to operate simultaneously in each shaft.  This increases the utilization of the shaft and improves the service provided to the riders.

Imagine a four lane highway between two places that are about a mile apart.  If we were to dedicate one lane for each vehicle that travels between the two places, then we would have a grand total of four vehicles at any time on this highway.  Clearly, this sounds unacceptable.  There typically are far more than four vehicles on the road.  When a slow vehicle obstructs a faster one in a lane, then one of them changes lanes and the faster vehicle goes ahead.  Similarly, the solution to the problem being addressed here lies in allowing elevator cars to switch shafts.  When the paths of two cars threaten to intersect, one of the elevator cars simply switches to an adjoining shaft and proceeds to its destination floor.  If there is a lot of traffic, then the car may have to switch several times before it reaches its destination.  Switching will also be necessary when a car moving upwards or downwards comes across a stationary car that is loading or unloading passengers at a floor.  The computer based control system would track all cars and route them so that switching is minimized.  While switching sounds quite simple, the difficulty lies in designing a system that allows cars to safely and smoothly move between shafts while being as efficient as today’s systems.

The first requirement for the solution is that there should be more than one elevator shaft, and that they must be in ‘banks’ so that they are located next to each other.  There should also be adequate openings between the shafts so that the cars can move from one shaft to another.  This is usually not a problem, both for existing buildings and in new designs.

The next requirement is for an efficient way to move the cars up and down.  Today’s designs use a hoist cable that connects a car to its counterweight.  Since this cable stretches from the car to the top of the shaft, it would interfere with any other car that was operating above the lower car.  The seemingly simple solution is to eliminate the counterweight and the hoist cable.  However, we still need the function of the counterweight, since without it powerful driving motors would have to be installed in each car.  The solution for this is to mechanically link the motions of all the cars so that downward moving cars would serve to balance the upward moving cars.  The computer based control system would ensure that roughly the same number of cars is going up and down at any given time.  The balancing concept is not obvious and will be explained in detail below.

Next, there needs to be a reliable and safe mechanism that allows cars to move freely between shafts.  This is accomplished using a slide assembly which allows the car to move to the adjacent shaft.  The switch can be made while the car is moving or while it is stationary.  Switching shafts involves a 5 step operation that will be detailed below.  The switching operation can be repeated so that the car can move to any shaft in the elevator bank.  The paths of all cars are managed by a computer system that monitors and controls all the operations.

Now that the counterweights have been eliminated, the car is no longer statically tethered to the support cable.  This allows a number of new capabilities, like extended horizontal motion between elevator banks, which can be accomplished by mounting the car on rollers and propelling it sideways.


Figure 1 shows the basic parts of a traditional elevator.

Figure 2 shows an abstracted view of a drive. 

Figure 3a and 3b show the positioning of twelve Drive Assemblies in elevator bank with three shafts.  Figures 3c and 3d show a bank of three shafts with a car in shaft 1 and another in shaft 3.

Figure 4a shows an embodiment of a Drive Track where links are connected to form a track.  Figure 4b shows how the track goes over the upper pulley.  Figures 4c and 4d show additional views of this embodiment.

Figure 5a shows one Drive Assembly balancing 2 cars.  Figure 5b shows two linked Assemblies balancing two cars.  Figure 5c shows three linked Assemblies balancing four cars.

Figure 6 shows a pair of Clamp Runners.

Figure 7a shows the clamp in detail.  Figure 7b shows the lower clamp caliper in the engaged position and the upper clamp caliper (on the upper runner) in the disengaged position.

Figure 8a shows the upper runner starting to extend to the right to latch on to tracks in the adjoining shaft.  Figure 8b, it has almost fully extended.

Figure 9a shows the lower clamp runner extending before switching shafts.  Figure 9a shows the car switching shafts by retracting lower runner and extending the upper runner.

Figure 10a shows how stacked Drive Assemblies involves the installation of a second set of four assemblies in the same portion of the shaft.  Figure 10b shows the switching process in more detail.

Figure 11 shows two cars with their clamp runners extended for slanted operation.

Detailed description

The solution consists of multiple concepts that work together.  For simplicity, each concept will be introduced sequentially and details will be abstracted till later.  The construction and operation of each part will be described.

First, we will describe how cars move up and down in a shaft and how the system stays balanced.  Then we describe how cars move sideways.  Lastly, we describe the finer details that make this system work.

Vertical motion

This section describes how elevator cars move up or down.  The Drive Assembly is introduced as the mechanism that propels the cars upwards or downwards.

 A Drive Assembly consists of two pulleys and an endless loop stretched over them.  Figure 2 shows an abstract view of a drive.  There are several embodiments of this drive, as will be described later.

The pulleys drive the loop at a steady and constant speed.  One segment of the track is constantly moving upwards and the other segment is moving downwards.  Arrows on the tracks indicate their direction.  Additionally, there is one more track installed between the two tracks.  This track will be stationary. 

Drive Assemblies are installed vertically along the sides of each shaft.  Elevator cars will move up by clamping on to the upward moving track and move down by clamping on to the downward moving track.  Cars will clamp on to the stationary track when they are not moving.

Figure 2 shows a Drive Assembly spanning a 20 floor building.  Note that the figure is not drawn to scale. As the pulley turns in the direction shown, the track on the left moves upwards and the track on the right moves downward.  In between the two moving tracks, there is the stationary track that is used for braking.  The lower pulley is housed in a shaft well that extends below floor 1, and the upper pulley is in a space above floor 20.  The assembly can be driven by motors at the top, at the bottom, or both.

There will be four Drive Assemblies installed per shaft, one at each corner, i.e. left-front, right-front, left-rear, right-rear.  Two assemblies are placed on the front wall of the shaft and the other two are on the rear wall. Note that only the front assemblies are shown in the diagrams.  The rear assemblies are located directly behind the front assemblies.  A bank of elevators will have multiple shafts, and each shaft will have four Drive Assemblies.  The horizontal spacing between the left and right assemblies will be the same in all shafts in a bank.  Also, the spacing between the up, stationary and down tracks in an assembly will be the same for all assemblies in the bank.  Figures 3a and 3b show the positioning of twelve Drive Assemblies in elevator bank with three shafts. 

Figures 3c and 3d show a bank of three shafts with a car in shaft 1 and another in shaft 3.  Note that the sides of the shaft are clear so that cars can move sideways between adjacent shafts.

To summarize, a Drive Assembly consists of three tracks: one moving up, one moving down and one stationary.  There are four Drive Assemblies per shaft.  Cars move up by latching on to the upward moving tracks in the shaft, and move down by latching on to the downward moving tracks.  In figure 4a, the car in the left shaft is clamped to the upward moving track and is moving upwards.  The car in the right shaft is clamped to the downward moving track.  When a car is stationary, it will be clamped to the stationary tracks.

Drive Assembly

This section shows a few embodiments of the Drive Assembly.  The requirements are that the assembly should be able to propel, guide and stabilize multiple cars in the shaft.  They must also provide for safety and emergency operation.

In the first embodiment, the drive track is made up of a sequence of links that are connected by hinges.  This resembles the track tread on a battle tank and is referred to as a Drive Assembly Track.  Figure 4a shows how the links are connected to form a track.  Figure 4b shows how the track goes over a sprocket which is the upper pulley.

The upward and downward moving tracks are stabilized and guided by a set of vertically spaced rollers attached to the Drive Assembly.    Figures 4a and 4b show the placement of the rollers.  Each link has a flange.  One pair of rollers goes over the flange and another pair goes over the body of the link.  Without stabilization the tracks may vibrate horizontally or twist.  This would cause unwanted problems for the clamping systems on the cars.  These rollers also allow the Drive Assembly to be curved or slanted.

The stationary track is firmly connected to the shaft wall.  It has the same thickness as the other tracks.  But, unlike them, it is a solid plate; it is not composed of hinged links.  This track functions as the brake and as the guide rail to stabilize the cars.  Figures 4c shows the up and down tracks in relation to the fixed guide rail.


In the second embodiment, the drive track consists of links like a bicycle chain.  The pulleys at the top and bottom are toothed sprockets.  Flanges are added so that rollers can guide and stabilize them.  Figure 4e shows two views.  The operation of this track is described later.

Balancing the load

The next important concept to be described is how the system operates efficiently without a counterbalancing deadweight.

All the Drive Assemblies in a bank are mechanically linked so that they are driven by one set of motors.  This allows cars to act as counterweights for each other.  A load on an upward moving segment is balanced by an equal load on a downward moving segment, even if the segments are on different drive assemblies.  Figure 5 explains this concept.  In figure 5a, it is easy to see that the two weights balance each other in the single drive assembly.  In figure 5b, assume that the two drive assemblies shown are located in adjacent shafts.  They are linked by the horizontal belt which transfers loads between the assemblies.  The two weights shown on the different segments will balance each other.  In the actual implementation, there will be several assemblies in different shafts that will be linked together.  There will also be multiple cars on the assemblies.  In figure 5c, the two upward moving cars in the leftmost shaft are being balanced by the downward moving two cars in the other shafts.  Counterbalancing is important because it reduces the load on the drive motors.

It is important to keep the system balanced so that approximately equal weights are moving up and moving down at the same time.  If these two weights are not balanced, then an excessive load will be placed on the drive motors.  The control system will schedule the movement of cars so that the system is balanced.  It may move empty cars up or down, or delay the movement of loaded cars, for the sake of maintaining balance.  Note that the system does not have to be perfectly balanced; it just has to be balanced sufficiently so that the total load on the motors is within acceptable limits. 

Besides keeping the system balanced, linking the Drive Assemblies together ensures that all the drives are moving at exactly the same speed.  As will be explained later, all drives need to be synchronized for the cars to stay leveled and to transition smoothly between shafts.

Vertical transitions

This section describes how a car transitions from being stationary to moving upwards (or downwards), and how it transitions back from moving to being stationary.  The Clamp Runner is introduced as the device that allows the elevator car to latch on to any one of the tracks in the Drive Assembly.

A Clamp Runner has a horizontal bar with a mechanism at each end that allows it to latch on simultaneously to tracks in two Drive Assemblies. 

Clamp Runners come in pairs.  They are placed vertically next to each other as shown in Figure 6.  They will be referred to as the Upper and Lower runner.  The two are identical but operate independently of each other.

Figure 6 also shows how a runner can slide sideways.  The lower runner has moved a little to the left.  Runners resemble the slides in a kitchen drawer, except that they can extend in either direction.  The runner consists of bars that can slide lengthwise.  Roller bearings fit into slots along the bars keep them aligned linearly.  Though the diagrams show three slider bars, there may be more sliders in a runner to allow it to extend as necessary.

The rearmost bar is firmly attached to the elevator car.  The front-most bar has a clamp at each of its two ends.  The sideways motion is motorized so that the control system can accurately position the clamps over the appropriate tracks of the Drive Assembly.  The clamp can then latch on to the selected track.  The horizontal spacing between the clamps is the same as the spacing between the left and right Drive Assemblies in a shaft, thereby allowing the left and right clamps to engage simultaneously.  In the diagrams, a clamp that is in the engaged (latched) state is shown as a darkened circle, and a disengaged clamp is shown as a clear circle.

Each elevator car has four pairs of Clamp Runners, two located in the front and two at the back, at the top and bottom of the car.  Figure 4a (elevation view) shows two front pairs of Clamp Runners on each car and their position relative to the Drive Assembly.  Note that there are two more pairs of Clamp Runners that are directly behind the ones shown.  They are visible in figure 4b (plan view.)

As mentioned, each of the four pairs of runners on a car has an Upper and Lower runner.  The control system operates the four upper runners on a car simultaneously as a set and the four lower runners as a separate set.  The sets will be referred to as the “Upper Runner Set” and the “Lower Runner Set”.  Hence, the Upper Runner Set consists of four runners, one from each of the four Clamp Runner pairs.  All the eight clamps in a set engage or disengage simultaneously.  At most times, only one runner set will be in an engaged state.  The other set will be inactive (free) waiting to be used for the next transition, which could be starting to move vertically, stopping, or moving between shafts.  The two sets of runners take turns in being active and in being inactive.  In figure 4a, the upper set or runners is being used on the left elevator and the lower set is being used on the elevator on the right.  The free runners are shown positioned over the stationary track, but are shown as not clamped.  The clamped state is shown by the darkened circle over the track.

When a car is stationary, all the clamps on one set of runners will be latched on to the stationary track.  So, the car will be connected to the stationary track in four separate Drive Assemblies.  There will be eight clamps engaged, four at the upper corners and four at the corners of the car.  The other set of runners will be free.

Figure 7a shows the clamp in more detail.  The figure shows a clamp latched on to a track segment.  The track is being gripped by pads on a hydraulically driven piston.  The pistons are mounted on a caliper.  The caliper is hinged so that it can swivel away when the clamp is not engaged.  The swivel action is also hydraulically driven.  Figure 7b shows the lower clamp caliper in the engaged position and the upper clamp caliper (on the upper runner) in the disengaged position.

Besides being able to firmly latch on to the track in the Drive Assembly, the clamp has another major function: it has to be able to smoothly accelerate and decelerate the car when it is starting or stopping its vertical motion.  The clamp cannot abruptly lock on to a track; it should smoothly increase traction over a few seconds (acting like a clutch) until the car is moving at the same speed as the track. 


In general, the clamping action on all clamps will not be precisely the same.  The clamps on one corner may grip more than the others and the cab may tend to tilt.  The tilt may be left to right, or front to back, or both.  Sensors will detect the tilt and an on-board control system will cause appropriate clamps to slip a bit so the cab remains horizontal.  Strain gauge sensors on the clamp will determine the load borne by each clamp. The on-board control system will precisely modulate the clamping force individually for each clamp to ensure smooth transitions, keep the car level and align a stopped car with the landing floor.  The Clamp Runner may be attached to the car with a “suspension” (not shown) that consists of springs and dampers.  This will further reduce the jerks that passengers may feel during transitions.

When the car needs to transition from stationary to upward motion, the following steps happen:

1.      The free set of runners slide over and position so the clamps are aligned with the upward moving track segments.  All four free runners in the set move in unison.

2.      Then the eight clamps would simultaneously engage and latch on to the moving segment.  The control system ensures a smooth transition without excessive acceleration or jerks. 

3.      At the same time as the above step, the eight clamps previously latched to the stationary track start to disengage.  The control system ensures that the car is not simultaneously latched on to the stationary track and the upward moving one.

4.      When the car reaches full upward speed, the clamps on the runner set that was previously latched to the stationary segment fully disengage and swivel away.  The set will now be free for the next operation.

While a car is in motion, it will be connected to a moving track in four separate Drive Assemblies.  Again, there will be eight clamps engaged, one at each corner of the car.

Transitioning from upward motion to stationary is accomplished in a similar way. 

1.      First, the free runner set is slid so its clamps are positioned over the stationary track segments.

2.      The eight clamps start to latch on to the stationary track segments

3.      The clamps on the previously active set simultaneously disengage from the upward moving segments.  Again, the transition happens smoothly to avoid jerks. 

4.      When the car stops, the clamps on the runner set that was previously latched to the moving segment fully disengage and the set will be free for the next operation.

Transitioning from stationary to downward and from downward to stationary is similar.

Clamp runners also have a two Guide Rollers (figures 7c and 7d) installed on each end.  When the clamp is engaged on one of the moving tracks, one of the rollers will be engaged against the associated stationary track.  The rollers stabilize the car.  The rollers are installed in the same swivel housing as the clamp and can swivel away when not engaged.  The rollers and the clamp swivel independently and are engaged only as needed.  Note that rollers engage only on the stationary track (which doubles as the guide rail.)  It will not engage on a moving track.


The guide rollers will also house a spring loaded mechanical emergency brake .  When this brake (not shown) is engaged, the rollers will clamp on to the stationary tracks, thereby bringing the car to a halt.  The brake will automatically engage if the hydraulic system fails.

An optional safety lock (not shown) can be part of the swiveling caliper.  It is engaged after the clamp fully latches on to the track and the car is leveled.  The lock causes a pin to extend into one of the holes in the drive track.  In case there is a hydraulic failure and the clamp releases unexpectedly, then the pin will remain engaged and will prevent the car from falling.  In normal operation, the pin will be disengaged fully before the clamp starts to disengage from the track.

In the second embodiment of the Drive Assembly, a chain is used as the drive track.  A different clutch mechanism will be needed here.  As before, it is mounted on the swivel housing.  It consists of a pair of sprockets that engage into the chain, as shown in figure 7e.  The sprocket is attached coaxially to a disk brake.  Hydraulically driven calipers are positioned so that they can clamp on to the disks.  If the cable is moving at a different speed from the car, then the sprocket and the rotor will spin.  The calipers engage and press on to the spinning rotors thereby slowing them down.  This causes the weight of the car to be slowly and smoothly transferred to the drive.  When the calipers are fully engaged, the rotor stops spinning and the car is then fully connected to the cable.

Switching shafts

This section describes how a car moves from a shaft to an adjoining shaft.  The extended use of the Clamp Runner is described.

Moving from one shaft to an adjacent shaft is accomplished by making the free clamp runner slide over all the way to the adjacent shaft and latching on to the appropriate Drive Assembly track there.  The runners are strong enough to resist bending even when fully extended.  However, it will be seen that they will never have to bear the full weight of the car when extended.

Figure 6 shows the upper runner in a fully retracted position.  Figure 8 shows the upper runner extending to latch on to tracks in the adjoining shaft.  In figure 8a, the upper runner is starting to extend to the right, and in figure 8b, it has almost fully extended.  All runners in a set extend simultaneously.  In both figures, the lower runner set is shown latched on to a track.  The upper set is currently not engaged and is moving as part of the transition.

Moving from one shaft to the adjoining one involves the following steps.  Assume that the car is moving upwards and the upper Clamp Runner set is active.  Figures 9a and 9b show the car moving right from shaft 1 to shaft 2.

1.      The runners on the lower (free) set extend until the clamps are positioned next to the upward moving track segments in the adjoining shaft, as in figure 9a.

2.      The lower clamps then latch on.

3.      The car moves from one shaft to the other, as in figure 9b.  While it is moving, the fully extended lower runners retract while the upper runners start extending.  During this sideways motion, the car is attached to four drive assemblies in the originating shaft and four drive assemblies in the adjoining shaft.  Clamp in both sets are engaged; i.e. all sixteen clamps are being used.  Note that the upper clamps are still latched to tracks in the originating shaft and the lower clamps are latched to tracks in the adjoining shaft.  Also, the car is still moving upwards because it is latched to the upward moving tracks.  Hence, the car is moving in an upward-right diagonal direction. All tracks are moving upwards at the same speed.

4.      When the car has moved all the way over to the destination shaft, the clamps attached to the tracks in the originating shaft are disengaged

5.      The upper runner set is retracted and is now free.  The lower runner set is now active.

After the car has moved to the adjoining shaft and has retracted its clamp runner, it can immediately initiate a move to the next shaft.  The runner is designed so that it can extend in either direction.  Hence, the runner that just retracted can extend the other way to initiate movement into the next shaft.

The horizontal move can be made while the car is stationary, or while moving upwards or downwards.  The control system ensures that adjacent shaft is clear before initiating the move.

In buildings today, there usually are no structural barriers between shafts.  Occasionally, structural beams may be located every so often.  The control system would be aware of the location of these beams and would ensure that the cars do not bump into them while switching shafts.

Stacked drive segments

The description so far has implied that the drive assemblies would extend the entire length of an elevator shaft.  However, it will not always be practical to have such long runs, especially in very tall skyscrapers.  Very long Drive Assemblies will be hard to maintain.  There will be a need to reduce the length of individual assemblies and yet allow the smooth motion of cars up and down the elevator shaft.  This section describes how the Drive Assemblies are placed so that the entire height of a building can be covered using many shorter assemblies.  This technique can also be used to vary the vertical speed of a car, thus resulting in “express” and “local” speeds.

Figure 10a shows how stacked Drive Assemblies involves the installation of a second set of four assemblies in the same portion of the shaft.  The second set is installed at an offset and there is some vertical overlap in the coverage of floors.  The set covering the middle floors are offset to the right.  Two adjacent shafts are shown.  The thick black vertical lines depict the tracks of the Drive Assemblies.  The assemblies overlap in areas that are marked as “transition zones.” 

As cars move through the transition zone, they switch from one set of tracks to the other.  The transition would be made very smoothly since both sets of tracks would typically be moving at the same speed.  Thus, a car could start at the bottom floor and switch drive assemblies as many times as necessary to go all the way to the top of the shaft.  A car can even move from one shaft to another while moving through the transition zone.  Note that all the drives would be mechanically linked so that they share loads and maintain the overall balance.

Figure 10b shows the switching process in a little more detail.  It shows a car moving upwards through a transition zone.  Before the car entered the zone, the upper clamp runner sets were latched on to the upward moving tracks in the left set of Drive Assemblies.  As the car enters the transition zone, the clamps in the lower runner set position themselves and latch on to the upward moving tracks of the right set of Drive Assemblies.  For a brief moment, as shown in the figure, the car is attached to both sets of Drive Assemblies.  Then the upper clamp set will disengage before the car exits the transition zone, and the car will continue upwards connected to the right-most set of Drive Assemblies.

The computer control system is aware of the locations of the transition zones and manages the timings of the transitions and the movement of the clamp runners.  The system also tracks the precise position and velocity of each car, and maintains a plan for the motion of each car.  A beneficial side-effect is that individual drive mechanisms can be taken out of service for maintenance without shutting down the entire elevator shaft.  The computer system can divert cars around the sections that are not in service.

An extension of this idea allows for express zones.  A few sets of drives can be configured to move at faster speeds.  This can be used to create a “highway” where cars can quickly move through several floors.  It would be useful to dedicate segments of shafts for express zones.  The Drive Assemblies in the express zone can be linked to the rest of the bank.  However, note that cars in this zone will impose a proportionally higher load on the system.  For example, if the express tracks are moving 50% faster, then the weight of cars in this zone should be adjusted to be 50% more while determining the balance of the system.

Computer control system

The computer system controls all aspects of the operation of this elevator system.  It has to be highly redundant and failsafe.  Specifically, it deals with:

1.      Handling calls and requests from elevator passengers

2.      Operating the clamps smoothly to start and stop the vertical motion of elevator cars

3.      Operating the extension of clamp assemblies to switch shafts as necessary

4.      Timing the shaft switching of cars to avoid obstructions

5.      Operating the clamp assemblies to switch between stacked drive mechanisms in a shaft

6.      Balancing the loads so as to not overload the drive motors

7.      Planning and scheduling car movements to optimize smoothness and utilization

8.      Managing emergency and custom situations

Sensors in each car measure the weight of the car and report it to the control system.  A computer algorithm considers the weight of each car, its direction of movement and then schedules car movements so that an acceptable level of overall balance is maintained.  If necessary, a car may be halted in the middle of its transit until another car is available to balance the load.  Whenever possible, such halts will be made at a location so that the car doors can be opened if the expected delay is too long.  Empty cars may be moved up and down to maintain the required balance.

Slanted operation

Though this system supports vertical and horizontal motion, there may be buildings where the elevator shaft needs to be curved or at a slant.  The system described here can be easily adapted to that requirement by installing drive assemblies along the slanted shaft. 

Slanted operation relies on the ability of the Drive Assembly to propel the cars while inclined.  Rollers placed along the moving drive tracks force them to follow a specific path.  They allow the path to be curved.  These rollers are shown in figures 2b and 2c.  As before, the stationary track functions as a guide rail and as the brake.

The clamp runners on cars will extend as required so that the car itself is in a vertical orientation.  The passengers will not be aware that they are moving in a slated direction.  Figure 11 shows two cars with their clamp runners extended.  Note that, unlike previous operations, the clamp runners within a set extend unequally.  The upper and lower runners may have to extend in different directions.  Note that the upper clamp runner is being used on the car on the left which is moving upwards.  The other (lower) clamp runner is free and will be used to stop moving and to move between shafts. It is shown fully retracted.  All aspects of the operation would be similar to that described earlier, except that the clamp runners may have to extend further while switching shafts.

If the elevator is to move in a curved path, then the inclination of the tracks will vary from point to point.  Care should be taken to ensure that the horizontal spacing between the Drive Assemblies remains constant.  Further, the clamps and guide rollers on the runners should be free to rotate around their axis so that the runners can remain horizontal.  They should also be pre-positioned to the correct angle before they swivel in to engage the tracks.

Because the drive assemblies would obstruct the normal location of the car doors, landing doors would have to be placed on the two sides of the car.  Passengers would enter and exit the car when it stops at either the leftmost or rightmost shaft of an elevator bank.  The car would slide over as necessary so that the doorway on the landing would not obstruct the normal operation in the shaft.  The dashed line shows the clearance necessary for normal operation.  The car on the right is shown stopped and aligned with a landing doorway.  Note that it is out of balance and is placing unusual loads on the stationary track.

Horizontal travel

So far, the movement of cars have been restricted to a single plane; cars can move vertically (up and down) and horizontally (left and right).  This section describes how a car can move in the third dimension (front and back) as well.

Since the cars are not statically connected to any counterweight, they can be detached from the system and allowed to travel between elevator banks.  There will be Transfer Points at specific locations in the shafts where causeways are available so that cars can move horizontally to different banks.  For example, at the transfer point in Bank 1, a car can be placed on a wheeled platform and moved to a transfer point in Bank 2.  It then would latch on to the Drive Assemblies in bank 2 and continue its vertical movements.  Multiple banks can be stacked, front to back, allowing for better utilization of space. 

Personal sized elevator cars

This system enables smaller cars that can take passengers to their specific destinations.  Smaller cars will be less likely to stop at intermediate floors to load or unload other passengers.  This speeds up transit times and improves utilization as a whole.  Also, the statistical load balancing algorithm is more efficient driving a large number of small cars rather than a small number of large cars.

Newer buildings with many offices or apartments can be designed so that these small cars go directly to the inside of a specific office or apartment, without stopping at any intermediate floors.  Security features will ensure that the car will not unload unauthorized passengers at private stops.  With proper design, it may be possible to completely eliminate the shared elevator lobby area on each floor, thus further improving the utilization of floor space in the building.

Splicing cars together

Occasionally, there will be a need for larger cars, say, while carrying stretchers bearing injured people.  The control system can be configured to allow two or more cars to be joined together temporarily so that they move in tandem in adjoining shafts.  Sliding doors on the sides of the elevator open to unify the spaces.  Other passenger carrying cars will be routed around this custom configured car.  Clearly, this feature can be activated only if there are no obstructions between the shafts in the relevant range of floors.

Tilting cars during horizontal acceleration

Elevator passengers are accustomed to vertical accelerations.  In this system, the cars move sideways and passengers may be subjected to horizontal forces as well.  To reduce this unexpected discomfort, the entire car can be tilted slightly in the direction of the sideways acceleration.  The car will be tilted the other way during deceleration.  If the tilting is timed correctly, passengers will not feel any sideways forces.

The tilting mechanism would be hydraulically operated and would be located in the suspension between the elevator car and the Clamp Runners.

Power supply and communications

Elevator cars need a constant supply of power to operate lights, fans and control systems.  Further, the control systems and the onboard emergency communications systems need data signal connections with corresponding systems outside the shafts.  Both these requirements are addressed by power distribution using the Drive Assemblies.  There will be a low voltage (say 48 volts) potential difference between the tracks on the front Drive Assemblies and the tracks on the rear.  This voltage will be adequate to drive the lights, air conditioning, hydraulics and other electronic systems.  A battery will be on board for emergency use.

Control data, digitized voice channels and music will be multiplexed on a carrier and transmitted over the power supply using existing technology.  Data and voice transmission will be bi-directional.  Use of wireless communications systems for control data is strongly discouraged for security reasons.


This section lists the unique claims that are new and not previously patented.

1)      Drive Assembly for elevators that allows operation in slanted and curved shafts

2)      Clamp Assembly and clutch mechanism for smooth transitions

3)      Use of extension slides to allow arbitrary transfers of cars between adjacent shafts

4)      Moving of cars between elevator banks

5)      Multiple drive zones and express zones

6)      Statistical balancing of cars in a bank of elevators

7)      Control system for collision avoidance and car trajectory

8)      Dynamic joining of cars to form a larger car

9)      Tilting of cars to reduce rider discomfort

Appendix A: Previously granted relevant US patents

6955245, Oct 18, 2005, Thomas Dünser, Romeo Deplazes (Inventio AG)

Elevator installation comprising a number of individually propelled cars in…

Summary: Self propelled cars.  Cars switch shafts at specific crossing points. 

Similarities: Shaft switching.

Dissimilarities: No drive mechanism.  No counterbalances.  No slant operation.


6871727, Mar 29, 2005, Simo Jokela, et al (Kone Corporation)

Elevator system with one or more cars moving independently in a same shaft

Summary: A way of dividing shafts into zones so that cars can ??  RE-READ!!!


6786305, Sep 7, 2004, Kosei Kamimura, Ikuo Asami (Toshiba Elevator Kabushiki Kaisha)

Double-deck elevator

Summary: Double decker car with adjustable spacing between them.


6672431, Jan 6, 2004, Matthew E. Brand, Daniel N. Nikovski (Mitsubishi Electric Research Laboratories)

Method and system for controlling an elevator system

Summary: Scheduling algorithm for conventional elevator


6508333,  Jan 21, 2003, Miroslav Kostka, Kurt Steinmann (Inventio AG)

Method of controlling elevator installation with multiple cars

Summary: Double-deck elevator


6360849, Mar 26, 2002, Shiro Hikita (Mitsubishi Denki Kabushiki Kaisha)

Elevator system, including control method for controlling, multiple cars in a single shaft

Summary: Control system for Double decker cars and for and multi-cage (independent) cars in a shaft that do not cross each other.


6273217, Aug 14, 2001, Shiro Hikita (Mitsubishi Denki Kabushiki)

Elevator group control apparatus for multiple elevators in a single elevator shaft.

Summary: Algorithm for avoiding collisions in situations with multiple cars per shaft.  It does not mention the mechanics.  It does not consider the horizontal movement of cars.


5924524, Jul 20, 1999, Frederick H. Barker, et al (Otis Elevator Company)

Integrated, multi-level elevator shuttle


5877462, Mar 2, 1999, Patrick Chenais (Inventio AG)

Safety equipment for multimobile elevator groups

Summary: Collision avoidance system for multiple cars per shaft.


5865274, Feb 2, 1999, Junichi Kiji, Shoji Nakai,, et al (Kabushiki Kaisha Toshiba)

Elevator group management control apparatus and elevator group management control method

Summary: for system with multiple elevators per shaft and horizontal movement.


5861586, Jan 19, 1999, Richard C. McCarthy, Joseph Bittar, et al (Otis)

Horizontal and vertical passenger transport


5823299, Oct 20, 1998, Gilbert W. Wierschke (Otis Elevator Company)

Shuttle elevators feeding local elevators


5,816,368, Oct 6, 1998, David W. Barrett, John F. Cassidy, Jr., et al (Otis)

Elevator cars switch hoistways while traveling vertically

Summary: Slanted operation in transition section. 


5,773,772, June 30, 1998,.McCarthy ,   et al. 

Transferring elevator cabs between non-contiguous hoistways



5758748,.Jun 2, 1998, Frederick H. Barker, et al (Otis)

Synchronized off-shaft loading of elevator cabs


5752585, May 19, 1998, Joseph Bittar, et al (Otis)

Elevator shuttle with auxiliary elevators at terminals


5749441, May 12, 1998, Joseph Bittar, et al (Otis Elevator Company)

Extra deck elevator shuttle


5663539, Sep 2, 1997, Bruce A. Powell, et al (Otis Elevator Company)

Passenger transfer, double deck, multi-elevator shuttle system


5660249, Aug 26, 1997, Bruce A. Powell, Joseph Bittar, et al (Otis)

Elevator cabs transferred horizontally between double deck elevators



5657835, Aug 19, 1997, Joseph Bittar (Otis Elevator Company)

Elevator shuttle employing horizontally transferred cab


5651426, Jul 29, 1997, Joseph Bittar, et al (Otis)

Synchronous elevator shuttle system


5584364, Dec 17, 1996, Masami Sakita

Elevator system

Summary: Extension of 5,419,414.  Multiple elevators per shaft.  No switching shafts.  Cars cannot pass each other.  Cabs counterbalance each other with fixed pairing.


5501295, Mar 26, 1996, Wolfgang Muller, Viktor Wunderlin (Inventio AG)

Cableless elevator system


5482143, Jan 9, 1996, Takaharu Saito (Mitsubishi Denki Kabushiki Kaisha)

Method of controlling a plurality of elevators moving in a common hoistway

Summary: Scheduling algorithm to minimize operation noise


5,464,072, Nov 7, 1995, Wolfgang Muller (Inventio AG)

Self-propelled elevator system

Summary: Self-propelled elevator car for vertical and horizontal travel in an elevator shaft.  No counterbalances .  Uses friction from wheels to move up and down.  Each car has to have the horsepower to haul its full weight up.  Friction drive is unreliable.  Shaft walls have to be strong to bear outward force.  Horizontal travel is mentioned but not described.


5419414, May 30, 1995, Masami Sakita

Elevator system with multiple cars in the same hoistway

Summary: Sakita describes a scheme where upto 3 cars can share a shaft.  They are balanced by counterweights.  However, the cars cannot pass each other and do not switch shafts.


5107962, Apr 28, 1992, Ralf Ekholm (Kone Elevator GmbH)

Vertical transport system in a building


5,090,515, February 25, 1992, Takahashi, Tastuhiko et al.

Passenger transport installation, vehicle for use therein, and method of

Summary: A system where passengers get into wheeled ‘vehicles’, which are horizontally loaded on to ‘frames’, which move up and down by the elevator passages.  Also describes a Paternoster system for moving frames..

Similarities: Detachable cars.  Detached cars can move horizontally.

Dissimilarities: The frame has to stop to load a car.  No counterbalancing cars.


3896736, Jul 1975, Norbert Hamy (rebron Holdings)


Summary: No counterweights.  Paternoster like continuous loop drive.  Cars are detachable from main drive.  Allows multiple cars per shaft, but they flow in the same direction, one shaft is dedicated for upward and another for downward flow.

Dissimilarities: Envisions a loading/unloading area away from the path of cars.  No shaft switching.  No balancing.


3750849, Aug 1973, Harry Berkovitz (Westinghouse Electric Corporation)

UPPER TERMINAL / Duplex counterweightless shuttle elevator system

Summary: Two cars counterbalance each other in separate shafts.  Cars are fixed to rope. 

Similarities: No counterweights. 


3658155, Apr 5, 1972, William G. Salter


Summary: Multiple self propelled cars per shaft.  All cars go up one shaft and down another.  Cars can stop at a floor by moving out of the shaft to a ‘loading/unloading’ area. 


2704609, Mar 1955, Zeckendorf et al.



1943119, Jan 9, 1934, James, H D (Westinghouse Electric Corporation)


Summary: Paternoster like.

Similarities: No counterweights. 


1939729, Dec 1933, A. D. STARK


Summary: Cars fit inside “Conveyors”.  Conveyors go up and down using hoists.  Cars slide horizontally out of one conveyor into another in an adjoining shaft.  Adjoining shaft goes higher.  No mention of counterweights.


1,914,128, June 13, 1933, James, Henry D., Boozer, Douglas G. (Hitachi)

Multi-cage elevator

Summary: Double-decker cars. The vertical distance between the cars is adjustable. 

Similarities: Two cars counterbalance each other within a carriage.

Dissimilarities: The carriage needs a counterbalance.  Cars are fixed to rope.


1458881, Jun 12, 1923, WOLFGANG GBOMER.


Summary: Paternoster. 


Other Prior Art: Eiffel Tower.  Elevator moves along slated tracks.  Cars counterbalance each other.

Dissimilarities: Cars are statically attached to rope.