US3749203A

US3749203A - Elevator floor leveling system

Info

Publication number: US3749203A
Application number: US00170841A
Authority: US
Inventors: W Hoelscher
Original assignee: US ELEVATOR CORP
Current assignee: United States Elevator Corp; US ELEVATOR CORP
Priority date: 1971-08-11
Filing date: 1971-08-11
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31
Also published as: CH554804A; IT963527B; FR2148598A1; DE2234312A1; ES406301A1

Abstract

A system for landing and leveling elevators or otherwise controlling the spacial relationship between two relatively movable objects. The system incorporates a pair of vanes that include a light transmitting opening along their long dimension. A light bulb movable with the elevator car traverses the space between the two light vanes and a pair of light sensors view the light bulb through the openings in the vanes. The vane openings are tapered from a relatively large to a relatively narrow end and this taper is in opposite directions on opposite ones of the pair of vanes. The relative displacement position between the light vane and the sensor-bulb position, that produces an equal signal on each sensor, comprises a null, and this null position is set to correspond to the desired location for the car. The null is developed by comparing the signals in a differential amplifier, any deviation from the null position will produce an amplified error signal that may be used to input an electronic elevator drive control means or other means for controlling relative motion. Also incorporated in the system is an error modifying means for increasing the error signal when there is a relative acceleration between the parts of the system. The signal is also increased and at an increasing rate with the persistence of an error for a period of time. Thus, the system closely follows the movement of the elevator with respect to the hoistway and maintains its position accurately at the desired floor level through inputs to the elevator drive means.

Description

United States Patent 1191' Hoelscher i 111 3,749,203 451 July 31,1973

1521 user.

[ 1 ELEVATOR 1 110011 LEVELING SYSTEM [75] inventor: William R. Hoelscher, La Mesa,

Calif. I v t [73] Assignee: United States Elevator Corporation,

. Spring Valley, Calif. 22 Filed: Aug. 11, 1971 [21] Appl. No.: 170,841

Primary Examiner-Bernard A. Gilheany Assistant Examiner-W. E. Duncanson, Jr. Attorney-Carl R. Brown et al.

[5 7 ABSTRACT A system for landing and leveling elevators or otherwise controlling the spacial relationship between two relatively movable objects. .The system incorporates a pair of vanes that include a light transmitting opening bulb position, that produces an equal signal on eachsensor, comprises a null, and this null position is set to correspond to the desired location for the car. The null is developed by comparing the signals in a differential amplifier, any deviation from the null position will produce an amplified error signal that may be used to input an electronic elevator drive control means ,or other means for controlling relative motion; Also incorporated in the system is an error modifying means for increasing the error signal when there is a relative acceleration between the parts of the system. The signal is also increased and at an increasing rate with the persistence of an error for a period of time. Thus, the system closely follows the movement of the elevator with respect to the hoistway and maintains its position accurately at the desired floor level through inputs to the elevator drive means. 1

9 Claims, 6 Drawing Figures PAIENIEUJULB 1 M5 3.749.203

SNEU 1 BF 2 INVENTOR. WILLIAM R. HOELSCHER 03mmx mm ATTORNEYS PAIENIEU Jul. 31 I975 SNEHZUFZ R M. m L 2 T L 5% 9 mam W T M 7& 4 RN H 9/ D m w R. T\ M A A G .L m w 0 WM 7 T E B m V}- O T 8 2 l vn 6 .m 0 4 F N 4 4 w 8 L 4 ole Ill u A R 6 H E 4 l E m v R E m. G IA D ATTORNEYS 1 ELEVATOR FLOOR LEVELING SYSTEM BACKGROUND OF THE INVENTION In the elevator field a common problem, for which many different solutions have been proposed, is the problem of causing the elevator car to slow down and reach 'zero velocity and stop atthe precise point where the elevator car is level with the desired floor. An additional and related problem in this art, is the requirement that the elevator be maintained in the level position during the period while it is at rest at a given floor, despite changesin loading the elevator or other variables.

Prior art systems for elevator stop and leveling con-- trol have employed microswitches or other remote means of producing a signal corresponding to the elevators position. These systems are frequently inaccurate, especially in the higher buildings in which they are installed, and consequently it is most often necessary, that an elevator slow down to a very slow speed, well in advance of reaching the floor at which it is to stop. The elevator then creeps towardthe floor and an electromechanical or electronic sensor shuts the system down and sets a brake as the car reaches the predetermined level point. Such systems are not only slow but induce acceleration changes .that are noticeable and objectionable to the passengers, both the transition between running and creeping as well' as stopping point. An additional accelerationtransientis felt by the passengers when the elevator takes off, since the elevator load cannot be sensed by the system with the brake on, and the elevator may therefore descend slightly before ascending or may ascend prior todescending, until the system sense the elevator motion and compensates accordingly.

Various systems have been proposed for contouring the descent curve to produce minimum passenger sensation during the deceleration from fastruns to a precise landing at the elevator floor. However, these systems are excessively complicated and require too high a level of maintenance to make them practical for most installations. Further, these systems frequently cannot be eliminated by a differential comparison. The light transmitting openings in the instant embodiment are capable of varying the amount of light transmitted to the sensor, in accordance with the displacement of the light vane with respect to the light bulb and sensors, by incorporating a slot having a width that varies in the direction of movement of the elevator car. Thus, with the light bulb and sensor opposite the wide end of the slot, a relatively large amount of radiation is transmitted. Decreasing amounts of radiation reach the sensor as the slot progresses past the sensor toward its'narrow end. This technique of varying the amount of light reaching the sensor has particular advantages when utilized with this system. One advantage of such a method is its simplicity and applicability to a plurality of materials, for example the opening may consist of a transparent Plexiglas mounting having an overlay of opaque material or opaque paint thereon. Additionally, such a method of varying the amount of light transmitted is easily adaptable to developing various functions of light transmittal. For example, in the exemplary embodiment a portion of relatively higher slope is located near thecenter of the slot to produce a higher degree of sensitivityas the elevator nears its null position. i

It should be understood that other methods of pro- I ducing variable amounts of light transmittal would be applicable to the system. For example, it may be possi ble to employ a surfacevarying from opaque at one end to transparent at the other.

It should also be understood that while light radiation has the advantages of low cost and easy maintenance,

other forms of radiation may also be utilized with the principles of the invention. For example, it may be desirable to use a radioactive source and to incorporate a vane of shielding material having a slot to pass'the radiation to a nuclear radiation sensor.

It is advantageous with the system of the invention, to incorporate a conventional light bulb, having an elongated filament for the light source. The elongated filament reduces the criticality of the horizontal position of the light bulb and it is possible to obtain-extremely high service life from such a bulb by operating compensate for many of the variables in day to day operation and therefore do not produce an accurate floor position, or induce objectionable acceleration changes on the passengers.

It would therefore be desirable if an elevator landing and leveling control system could be provided to produce an accurate signal corresponding to the displacement of the elevator from the desired point of landing, together with appropriate sensors and electronics to transfer that signal into a form where it may control the power source to produce a smooth landing and hold the elevator in its level position without brakes.

SUMMARYOF THE INVENTION An exemplary embodiment of the invention utilizes a pair of opposed light vanes having light transmitting openings located along their length. These vanes are mounted on the hoistway adjacent the path of travel of an elevator car. The elevator car mounts a light source and a pair of light sensors. A single light source is employed so that both sensors see precisely the same amount of radiation under similar conditions. In this manner local voltage variations or changes in condition of the bulb will produce corresponding changes in both of the light sensors and the error thus developed may it at a low voltage. The purposes of operating the lamp at a low voltage are two fold. First, such a lamp is subject to a much lower likelihood of filament failure due to the high temperatures reached by lamps at their normal operating temperatures. Secondly, the operation of a bulb at an extremely low relative voltage greatly increases the resistance of the filament to failure under vibrational environments. Additionally, a bulb operated at such low temperatures has a nearly infrared radiation characteristic. It is therefore possible to utilize sensors that are primarily sensitive to infrared radiation. Such a concentration of the sensitivity in the infrared range reduces the likelihood that the sensor will be inadvertently triggered by ambient light within the hoistway without the necessity of elaborate shroudin or other light shielding techniques.

When the output of the two sensors are combined in a differential amplifier to produce an output that is representative of the difference between the two sensors, any variation caused by such occurances, as local line voltage variations will be cancelled out, and the summation will remain substantially constant. Thus, the output of the differential amplifier will represent an error or analog of the distance from the present elevator position to null or floor level. This error signal may be utilized to input an elevator drive control system'and cause a reduction or increase in the elevator power to produce proper slowing of the elevator without overshoot, and landing precisely at the level point. An additional important function of the system is to produce an error signal representative of the displacement from null for use in systems maintaining the floor of the elevator level after the elevator has reached a stop. When utilized in this mode, the system of the invention produces a signal whenever a disturbance has caused the car to leave its assigned position. For example, if an individual steps onto the car, adding to the load therein, the car will have a tendency to drop a small amount depending on the length of cable by which the car is supported. With the system of the invention, the tendency toward a displacement will be countered, when the error signal senses the displacement and increases the power to the drive control system. While such a system without more, would produce a leveling effect, this effect would not prevent significant displacement from the floor, and could leave residual errors uncompensated. Therefore, the invention employs sensing acceleration of the car away from the null point. The effect of the amplifier is to produce an additive output to the error signal before significant displacement has taken place.

An additional feature of theinvention is its ability to eliminate residual errors. An integral amplifier, integrates the error signal over time and is reset, to start a new integration cycle each time the elevator stops at a level. Thus, if an error has existed for a given period of time, the integral amplifier will produce an additive output to create additional input and additional power from the drive means. Should the error persist for a still longer time, the integral output would increase and with further time duration would increase at an increasing rate, until it produces a sufficient power increase to the power means to result in a level floor position.

It is therefore an object of the invention to provide a new and improved automatic elevator floor leveling system.

It is another object of the invention to provide a new and improved system for reducing relative displacement between movable objects.

It is another object of the invention to provide a new and improved elevator leveling system incorporating sensors responsive to a variation in level of radiation caused by displacement of an elevator car from a designated point in the hoistway.

It is another object of the invention to provide a new and improved system for leveling elevators that has a high degree of reliability.

It is another object of the invention to provide a new and improved elevator leveling system that is relatively insensitive to ambient light.

It is another object of the invention to provide a new and improved elevator leveling system that produces a smooth transition from running to landing at a floor.

It is another object of the invention to provide a new It is another object of the invention to provide a new and improved elevator leveling system that is relatively insensitive to variations on site.

It is another object of the invention to provide a new and improved elevator leveling system that requires no electronic components at each floor level.

It is another object of the invention to provide a new and improved elevator leveling system that may be easand improved elevator leveling system that produces a ily tailored to provide custom descent characteristics for a given requirement.

Other objects and many attendant advantages of the invention willbecome more apparent upon a reading of the following detailed description together with the drawings in which like reference numerals refer to like parts throughout and in which:

FIG. 1 is a side elevation view of a portion of an elevator car, showing an installation of the elevator floor leveling system.

FIG. 2 is a top plan view of the structure, of FIG. 1.

FIG. 3 is an enlarged side view of a vane element of the sensing means.

FIG. 4 is a sectional view taken on line 4 -4 of FIG. 3.

FIG. 5 is a perspective view of the vane means sensors and light source.

FIG. 6 is a block diagram of the system and its connection to anelevator control system.

Referring now to the drawings, there is illustrated generally an elevator car 10 supported in a hoistway on a cable 12. The structure 14 mounted in the hoistway mounts an incremental position detector 16 and a displacement signal means or vane means 18.

The configuration of the vane means is most clearly illustrated in FIG. 5 wherein the

plural vanes

20 and 22 are illustrated as being mounted on a supporting-portion 24. Each vane means comprises a substantially opaque planar elongated member with a transparent opening or slot. The long dimension of the slot corresponds to the long dimension of the vane and the slot has a width that varies with the distance from either end of the vane. The vane is mounted and permanently fixed in position after initial adjustment to the hoistway structure 14. The light bulb 28 illustrated in FIG. 5 and the

photosensitive element

30 and 32 illustrated therein are carried on a supporting frame 33 mounted on a portion of the elevator car for movement therewith. The photoelectric sensors are selected to have a range of sensitivity that includes the range of radiation from the light bulb 28 at its operating voltage. In the preferred embodiment, the light bulb 28 is operated at a fraction of its normal operating voltage, for example, for a light bulb that is normally operated at 117 volts A. C., a voltage below 40 would be selected. Operations at this voltage produce a long life for the lamp and. therefore it is not necessary to change it at frequent intervals. The lamp life is enhanced, both by the operation of the filament below the temperature at which thermionic deterioration and other high temperature failure takes place, and because the operation of the bulb at these lower temperatures greatly increases its resistance to vibration due to increased mechanical strength for the filament at these lower temperatures.

When operated at the desired voltages, the light bulb 28 produces a dull red visible radiation and has a substantial part of its radiation in the infrared range. For this reason, and because of their ready availability, light sensors sensitive to radiation in this range are incorporated. The sensors are therefore relatively insensitive to ambient light within the elevator hoistway, and the chance of their being inadvertently activated is reduced.

Referring now to FIG. 3, the configuration of the transparent slot is illustrated. In particular a slot 37 having a generally triangular configuration is employed with the width of the slot narrowing from one end at substantially a straight line rate over its entire length. The slope of the straight line is constant over a substantial portion of the length, however, the section near the vane midpoint, where the elevator null position would be located, is provided with sides 38 of increasing slope. Thus there is provided a variable characteristic to the slot narrowing function, and this has the effect of providing increased system sensitivity in the range of displacement very close to the null point. The area of this increased sensitivity is indicated by the dotted circle 39.

The cross section view of FIG. 4 illustrates the manner in which the vane, incorporated in the preferred embodiment, is built up of a base of transparent Plexiglas material 34, overlaid by an opaque layer 36, that may be, for example; opaque paint, silk screened onto the Plexiglas. [t is specifically contemplated that it may be desirable, in some instances, to use a vane having an cut out opening rather than utilizing a transparent material.

Referring now to FIG. 6, the

output

40 and 42 of the

light cell

30 and 32 respectively are shown to be connected to a differential amplifier 44. The differential amplifier subtracts one signal from the other and thus produces an output that is representative of the difference between the light received in one sensor as compared with that received by the other. Further, the output is provided with a positive or negative sense to determine whether the car is displaced upwardly or downward "from the desired null point.

The-output of the differential amplifier is connected by lines 46 to gate 48. Gate 48 is normally gated closed and is opened only as the elevator approaches in close proximity of the selected floor. An appropriate signal for gating open the gate 48 may be provided by a plurality of discrete position sensors, such as those illustrated in FIG. 1. The sensors in the discrete systems measuring system 16, are spaced vertically along a support 49 carried by car 10. The sensors include a door zone sensor 50 as well as level up sensor 52, leveled down sensor 54, intermediate down sensor 56, and intermediate up sensor 58. These sensors are normally illuminated by a plurality of corresponding light sources, an exemplary one of which is indicated by the numeral 59. An opaque fixed vane 60 is aligned to pass between the light sources and sensors and intercept the light path between the corresponding pairs of sensors and light sources to produce a signal at the moment the light is cut off. With appropriate circuitry, it is therefore possible to determine the elevators precise position at a plurality of points as it approaches the floor from either the up or the down direction. A selected discrete position may be utilized to gate on gate 48 and pass the signal from the differential amplifier to the error modification circuit 70. In this manner, the error modification circuit will be activated only when the elevator is in close proximity to the appropriate floor.

The error signal modification circuit processes the raw error signal from the differential amplifier output,

6 by inputing this signal into a plurality of amplifiers. The proportional amplifier 72 is effective to increase the amplitude of the error signal to that level utilizable by the drive control. The output of the proportional amplifier K3 connected to the summing junction 74 is therefore, substantially proportional to the displacement of the car from its level position. The second amplifier, in the error signal modification circuit, is the differentiating amplifier 76. The effect of this amplifier is to produce an immediate output whenever an acceleration away from the null position is present. Thus, it is not necessary for the system to wait for significant displacement before correction can be made, but when the car is accelerated away from null, as when the load in the car is increased, an immediate corrective measure will be instituted. Additionally, there is provided an integrating amplifier 78. This amplifier is reset to zero by reset line 80, each time the car reaches its null position after a run. From that time forward, any error which continues to exist in the system, will result in an output from the integrating amplifier 78. Further, an error which continues to exist for an additional increment of time, will receive an increased output from the integrating amplifier, and thereby, residual errors are reduced or eliminated. Where other means are provided to transition the elevator from its run to floor level the gate is gated on, only after the elevator has reached a complete stop and leveling action is to be initiated. After gate 90 is gated open, the output of the three amplifiers, summed at junction 74, is connected by line 92 to drive control means 94. The drive control means may constitute any system capable of responding to an electrical error signal to produce a corrective variation in the power delivered to the motive means for the elevator.

OPERATION When the system of the invention is utilized to provide an error signal in transitioning an elevator from a run to a stop at a floor, the system will be gated on by gate 48 at a predetermined distance of the elevator from the level position, for the selected floor. Since the initial output from the system will take place with the sensors and source near the extremes of the light transmitting slots, there will be a large difference in the signal between the two that will result in a large output from the differential amplifier. The positive or negative sense of the differential amplifier output will be determined by the direction the floor is being approached.

The raw signal from the differential amplifier is representative of the displacement error of the system. As the spread between the present elevator position and level reduces, so does the error signal from the differential amplifier, and this signal may be utilized to cause the elevator drive control system to effect decreasing elevator velocity, thereby providing a smooth deceleration characteristic, and avoiding any jerking. Finally, as the elevator nears the level or null position, the throat of the opening will be encountered, where small displacement movement results in a larger reduction in the differential between the two sensors output thereby causing less rapid velocity reduction so that the zero velocity point is reached relatively gradually and so that no jerking or bouncing is detectable.

In the leveling mode the sensitivity of the system to displacements immediately adjacent the level position is put to good effect, to maintain the elevator in that position, under the influence of the motor. The rapid initial response and resistance to residual errors previously described for the systems, ensures that relatively little displacement from the level floor position will take place, and no bouncing sensation will be experienced by the passengers. Similarly, when it is desired to accelerate to the next floor, since the elevator is already under load, no sensation will be encountered by the motor taking up the load and the acceleration will proceed smoothly.

Having described my invention, 1 now claim:

1. A system for automatically stopping or leveling the floor of an elevator car with respectto a predetermined point in the elevator hoistway comprising:

displacement signal means for varying the amount of radiation reaching sensor means from a source means when said sensor means is moved relative to said displacement signal means; said sensor means having an output that is substantially proportional to the amount of said radiation; sense means for determining the direction said source means is displaced from said displacement signal means; and I drive control means for controlling the velocity of said car in response to the output of said sensor means.

2. The system of claim 1 wherein:

said displacement signal means comprises a vane means having an opening that transmits a variable amount of radiation at a plurality of relative locations of said source means and said vane means.

3. The system of claim 2 wherein:

said vane means comprises a pair of relatively planar vanes having openings that generally taper along their length; 7 the narrow end of said openings being located at opposite ends of said pair of vanes.

4. The system of claim 3 wherein:

said source comprises a light bulb with an elongated filament, the filament being substantially parallel to the width dimension of said opening.

5. The system of claim 4 wherein:

said sensor means comprises a pair of photosensitive elements mounted on said car;

said light bulb being mounted on said car;

and said vanes being mounted on said hoistway to straddle the path of travel of said light bulb.

6. The system of claim 1 wherein:

said sensor means comprises a pair of sensors;

said displacement signal means for causing the amount of radiation reaching one of said pair of sensors to vary in amplitude in the opposite direction of the variation in amplitude of the other of said sensors.

7. The system of claim 6 wherein:

the difference in the amplitude of said signals comprises an error signal;

and said drive control means for responding to said error signal to reduce said signal by causing relative movement'between said displacement signal means and said sensors.

8. The system of claim 7 including:

error signal modifying means for producing an increase in said error signal when the signal displacement means and said sensor means are'relatively accelerated.

9. The system of claim 7 including:

error signal modifying means for increasing said error signal by increasing amounts, if said error signal persists for a period of time.

1.! i 1 II t

Claims

1. A system for automatically stopping or leveling the floor of an elevator car with respect to a predetermined point in the elevator hoistway comprising: displacement signal means for varying the amount of radiation reaching sensor means from a source means when said sensor means is moved relative to said displacement signal means; said sensor means having an output that is substantially proportional to the amount of said radiation; sense means for determining the direction said source means is displaced from said displacement signal means; and drive control Means for controlling the velocity of said car in response to the output of said sensor means.

2. The system of claim 1 wherein: said displacement signal means comprises a vane means having an opening that transmits a variable amount of radiation at a plurality of relative locations of said source means and said vane means.

3. The system of claim 2 wherein: said vane means comprises a pair of relatively planar vanes having openings that generally taper along their length; the narrow end of said openings being located at opposite ends of said pair of vanes.

4. The system of claim 3 wherein: said source comprises a light bulb with an elongated filament, the filament being substantially parallel to the width dimension of said opening.

5. The system of claim 4 wherein: said sensor means comprises a pair of photosensitive elements mounted on said car; said light bulb being mounted on said car; and said vanes being mounted on said hoistway to straddle the path of travel of said light bulb.

6. The system of claim 1 wherein: said sensor means comprises a pair of sensors; said displacement signal means for causing the amount of radiation reaching one of said pair of sensors to vary in amplitude in the opposite direction of the variation in amplitude of the other of said sensors.

7. The system of claim 6 wherein: the difference in the amplitude of said signals comprises an error signal; and said drive control means for responding to said error signal to reduce said signal by causing relative movement between said displacement signal means and said sensors.

8. The system of claim 7 including: error signal modifying means for producing an increase in said error signal when the signal displacement means and said sensor means are relatively accelerated.

9. The system of claim 7 including: error signal modifying means for increasing said error signal by increasing amounts, if said error signal persists for a period of time.