HK1135080B - An elevator system and a method of operating the elevator system - Google Patents

Description

Elevator system and method of operation

Technical Field

The invention relates to a plurality of elevators operating in a single elevator shaft, and the current safe stopping distance between adjacent cages is determined for all possible speeds of two cages during braking and stopping by a safety device; periodically or continuously comparing the actual distance between adjacent cars therewith; the brakes of one or more of the cars are engaged in response to determining that the other separation fuse fails, and the safeties of those cars are engaged in response to determining a possible brake failure or when the cars are in a free fall.

Background

It is known to reduce the space required for elevator service in a building by moving more than one elevator car within each elevator hoistway. If the call assignment is restricted and incomplete, collision avoidance between elevator cars can be guaranteed. Such a system does not increase the effective service performance since many calls cannot be assigned. Examples are described in us patents 5419914, 6360849 and 2003/0164267.

In us patent 5877462, elevator stopping requests are processed to ensure that one car does not reach a landing while the other is still at that landing, according to a speed versus position profile applicable to both cars.

In order for the service achieved by several cars in one hoistway to approach the level of service achievable by cars in several hoistways, it is necessary to not only ensure that the cars remain separated, but also to allow the cars to have the maximum amount of movement in response to a service call.

Disclosure of Invention

The objects of the present invention include: safely maximizing elevator service provided by more than one car traveling in a single elevator hoistway; multiple cars answering calls in a single elevator hoistway are free to move while ensuring car separation; stopping multiple cars in an elevator hoistway if one car is in free fall; and improving elevator service with multiple cars traveling in the same hoistway.

According to the invention, an indication of a safe stopping distance is determined for all speed combinations of a pair of adjacent cars moving in the same elevator hoistway; continuously comparing the actual distance between adjacent cars with a predetermined safety distance; a first level indication occurs when the separation software (or hardware) of the other car has failed; this may cause the brakes of one or more cars to engage; a second level of indication occurs when the brake does not prevent adjacent cars from forming closer spacing, typically due to brake failure; the safeties of both cars are now engaged.

The comparison may be made by one or more tables made by a certain formula, or by processing the data in real time, if desired.

Although the disclosure herein refers to engaging the brakes of the cars only when the speed of the cars exceeds a threshold, the invention may be practiced with one or another criterion for determining that the brakes should only be applied when one or more cars respond to the first level indication.

Further in accordance with the present invention, an acceleration sensor detects a car in free fall and engages the safeties of all cars in a multi-car elevator hoistway.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawings.

Drawings

Fig. 1 is a partial perspective view of a pair of elevator cars traveling in the same hoistway and associated block diagram that may incorporate the apparatus of the present invention.

Fig. 2 is a functional block diagram illustrating the working principle of the present invention.

Detailed Description

Referring to fig. 1, an elevator system 8 having an elevator hoistway 9 includes an upper car 10 and a lower car 11 both traveling in the elevator hoistway 9. Within the hoistway is a durable strip of coded steel, such as stainless steel 14 with the code punched thereon. The stainless steel belt 14 extends between two fixed parts 16, 17 of the elevator shaft. Each car has conventional two-way safeties 18, 18a, 19, 19a which operate in a conventional manner relative to two guide rails (not shown). However, a weighted safety device may be used in place of the lower safety devices 18, 19, or other forms of safety devices may be employed.

There are two position sensors on each elevator car: the upper car 10 has an upper (U) position sensor 20 and a lower (L) position sensor 21, and the lower car 11 has an upper position sensor 22 and a lower position sensor 23. Each position sensor and corresponding associated circuitry 29-32 provides upper car and lower car position information 35-38 to redundant processors 41, 42 and upper car controller 45 and lower car controller 46. As shown in fig. 2, the redundant processors 41, 42 operate the brakes of the motor/brake systems 49, 50 of each car or the safeties that engage the upper and lower cars whenever the cars are in a dangerous spacing/speed relationship. Position/speed feedback is provided by means mounted on the car, without steel belts, by magnetically or optically reading blades mounted on the hoistway or platform. A form of position/velocity feedback may be employed.

Referring to fig. 2, an upper car position signal upos (u) on line 35 is sent from the upper position sensor 20 on the upper car 10 to the differentiator 60, and a signal upos (l) on line 37 indicative of the lower car position is sent from the upper position sensor 22 on the lower car 11 to the differentiator 62. This provides an upper car speed signal v (u) on line 64 and a lower car speed signal v (l) on line 65.

Now make such a convention: an upward travel corresponds to a positive speed and a downward travel corresponds to a negative speed, the positions in the elevator shaft being positive. Of course, there is no danger when the cars move away from each other in opposite directions or when one car moves away from the other car and the other car stops.

The disclosed embodiments of the invention assume that the dispatching of cars (call assignment to cars) and motion control of cars traveling in the same hoistway are designed to normally run multiple cars without interfering with each other, i.e., without colliding. The present invention takes into account that a software or hardware failure may result in an unsafe operation of the car as designed, which the present invention will detect and adjust by means of the car's brake or safety device.

The embodiment described here is presented in a simple form, in which a table is generated as described below to determine the minimum braking distance, stopping distance (B), for identifying a fault in the normal control of the elevators which leads to the cars being too close to each other. If the cars are close by a distance less than this braking distance, the brakes of one or both of the adjacent cars will be applied. These tables are a function of a plurality of fixed values, and as a function of upper car speed and lower car speed. As shown in the following equation, it can be indicated that the stopping distance (B) to apply the brake is determined using a factor, Δ t, for all possible combinations of upper and lower car speeds, where the factor Δ t is a time period, typically on the order of hundreds of milliseconds, indicating the time required to engage the brake after a safety issue is determined. Which is a fixed factor in generating the above table.

Stopping distance (B) ═ v (u) # t +1/2a (u) # t²+[V(U)+A(U)Δt]²/2D(U)+V(L)Δt+1/2A(L)Δt²+[V(L)+A(L)Δt]²/2D(U)+K(B)

Where k (b) is a brake distance deviation constant, which is selectable,

velocity V ═ velocity

A is the acceleration, set according to the over-balance of the car,

d ═ deceleration ═ f (b) -W. M

Wherein F (B) is the force applied by the brake

W is added. Overbalanced (net) weight of car

mass of car with counterweight

The first term is the upper car speed times Δ t. The second term uses the factor a (u) which represents the assumed acceleration of the upper car when its motor looses control of the car, even though the car is still going through the sheave to the counterweight. This factor is a function of the weight overbalance difference between the empty car and the counterweight, which is assumed to be the same as the weight difference between the full car and the counterweight. The second term is 1/2 of the upper car acceleration a (u) multiplied by the square of the elapsed time factor.

The third term of the equation is the sum of the velocity of the upper car, v (u), and the acceleration of the upper car, a (u), multiplied by the delay factor, Δ t, squared divided by twice the acceleration d (u), taken by the upper car. The resulting deceleration is derived from the stopping force f (b) that the brake can apply, which can be determined empirically for the car or analytically based on the difference between the stopping force f (b) of the brake and the over-balance or net weight (W) of the car and counterweight divided by the total mass m of the car and counterweight.

The next three terms are the same as the first three terms except they utilize values associated with the lower car (L).

In the seventh term of the equation, k (b) is the brake distance deviation constant, i.e. the distance measure added to the value calculated from the first six terms of the equation, in order to further ensure safety. The term "safety braking distance" does not exclude a distance which is a predetermined amount greater than the minimum safety braking distance with or without the deviation constant. This fact is inherent in the need to safely brake once the cars approach each other less than the "safe braking distance".

The safe braking distance, stopping distance (B), is determined by the aforementioned formula for all possible combinations of the speeds of the upper car and the lower car and is used to form a table which can be used to determine the current safe braking distance at any time as a function of both the current speed of the upper car and the current speed of the lower car. Fig. 2 shows such a table 66, which represents the operations in the redundant processor 41.

The safe stopping distance required to stop the car when the safety gear is engaged, stopping distance (S), is calculated in the same way with respect to braking distance, except that the force used to calculate deceleration is the force f (S) that will be applied when the safety gear is engaged, and a different deviation constant k (S) may be used or omitted. If the brake is applied and the cars do not respond normally, the cars will approach each other closer than the stopping distance (S); this can be considered a brake failure and a safety device must be used to prevent the cars from moving any further towards each other. In the foregoing manner, the stopping distance (S) for all possible combinations of upper and lower car speeds is calculated and the results are listed in table 67 of fig. 2.

The position sensors 20, 22 and the position sensors 21, 23 are separated by a distance between adjacent cars. If the safety braking distance and the safety stopping distance are considered to be about zero when the cars are close to each other to the distance allowed by the separation insurance function, the sensor position must be calculated by subtracting the separation distance from the actual distance Δ P between the cars. This can be adjusted by a constant H on line 71 in adder 75. Using this constant H facilitates incorporating the comparison with the above equation into the software (see below) while easily modifying the allowed separation distance within the software.

The distance between the cars is obtained by subtracting the position of the lower car from the position of the upper car in an adder 75 to provide the actual distance signal deltap on line 76. The actual distance signal on line 76 is fed to a pair of comparators 77, 78 for comparison with the outputs 79, 80 of the tables 66, 67. This may be done continuously or periodically about every 0.15 to 1.0 seconds. In fact, the comparison means may be located within the software, and may be incorporated within the results of the calculations if desired.

In this embodiment, conditional engage brake signals on line 85 may be applied to one or both of the upper and lower cars depending on the current speed of each car. To this end, each speed signal V (U) on line 64 and each speed signal V (L) on line 65 may be applied to a respective bi-directional threshold detection function 88, 89, and when the respective speed is above the threshold, the associated signals on lines 92, 93 cause the corresponding AND gates 94, 95 to generate an engage brake signal ENGBRK (U) on line 98 or ENGBRK (L) on line 99, respectively. The signals on lines 98, 99 are applied to upper controller 45 (fig. 1) and lower controller 46, respectively. In response to these signals, the respective controller will cause the holding current to the respective brake 49, 50 to terminate, for example by opening a conventional safety chain, thus disengaging the associated brake.

The conditions under which the brake-engaging signals on lines 98 and 99 are provided may differ from the previously described speed thresholds as appropriate for any given implementation of the invention.

For the stopping distance of the safety device, the output of the table 67 can be applied to the comparator 78, the output of which can be used directly to engage the safety device by activating the corresponding and gate 103 and 106 to generate the signal 82 in dependence on the indication of car going up or down from the bi-directional level detectors 109, 110. A positive output from one of the level detectors 109, 110 indicates that the car is moving upwards and the lower safety devices 18 and 19 should be engaged. Conversely, a negative output from the level detector 109, 110 indicates that the corresponding car is moving downwards and therefore the upper safety gear 18a, 19a should be engaged.

The engage safety signal on line 81 is shown as being applicable to the or gate 112, the other inputs on lines 113, 114 being from respective vertical acceleration sensors 117, 118 (fig. 1) which provide a signal when the downward acceleration of the respective car reaches a threshold amount, while maintaining that amount for a period of time sufficient to eliminate a false trip. This feature of the invention can detect a free falling car and thereby cause the safety devices of all cars in the hoistway to engage. Since a car that is not in free fall is likely to travel to the stopped car, past the point where the dispatch and motion control software recognizes as safe, all cars must be stopped. This aspect of the invention can be utilized without regard to the safe stopping distance aspect of the invention and vice versa. If desired, acceleration can be determined by differentiating the velocity, but the sensors 117, 118 can respond more quickly.

Redundant processor 42 is as described in fig. 2, except that signals from lower sensors lpos (u), lpos (l) are used.

The signal on line 98 from either of the redundant processors 41, 42 may alone affect the fall of the safety chain in the controller of the upper car; similarly, the signal on either line 99 may independently affect the dropping of the safety chain in lower car controller 46. Engaging a safety signal on either line 82 from either redundant processor 41, 42 drives the corresponding safety device 18, 19 when the car is up and the corresponding safety device 18a, 19a when the car is down.

If desired, instead of the two-dimensional tables 66, 67 followed by the respective comparators 77, 78, a three-dimensional table may be used, which comprises as input the actual distance Δ P. Or the invention may be practiced in other ways.

The car brake as described herein may be a conventional disc or drum brake, a rope grab or other stopping device. If there are more than two cars in one elevator hoistway, the invention can be implemented with respect to each pair of adjacent cars; but each car involves more than one separation assurance comparison, except for the highest and lowest cars in the elevator hoistway.

When desired, instead of deriving the relative velocity from the absolute position of the two cars, the relative velocity and distance can be detected more directly, for example by integrating the instantaneous position over a short interval involving the actual position reading by doppler effect of the relative velocity, by means of acoustic, infrared or radio frequency devices mounted in the cars.

Claims (10)

1. An elevator system comprising:

at least one elevator hoistway;

a plurality of elevator cars traveling within the at least one elevator hoistway, each car having a brake and a safety device;

means for determining car speeds of cars within the elevator hoistway;

the method is characterized in that:

means corresponding to each car in said elevator hoistway for providing a signal indicative of downward vertical acceleration of the associated car;

means for generating a braking distance (B) for all possible combinations of speeds of each adjacent car pair in the elevator hoistway that is greater than a safe braking distance for stopping one or both cars in each adjacent car pair by a predetermined amount to maintain proper separation; for generating a stopping distance (S) for all possible combinations of the speeds of each of said pairs of adjacent cars, said stopping distance being greater than a safe stopping distance for stopping both cars of each of said pairs of adjacent cars by means of a safety device by a predetermined amount; for periodically or continuously determining the actual distance between the cars of each said adjacent car pair; for providing at least one signal to cause the brake of one or more cars in a particular pair of adjacent cars to be activated when the actual distance between the particular pair of adjacent cars is less than the braking distance (B) corresponding to the simultaneous speed of the particular pair of adjacent cars; to provide an engaged safety signal indicating that the actual distance is less than the stopping distance (S) corresponding to a speed at which adjacent car pairs are simultaneously occurring; and to provide a signal to engage the safety devices of all of the cars in the elevator hoistway in response to a signal indicative of a downward vertical acceleration of any of the cars indicating that the respective car is in free fall or in response to the engage safety device signal.

2. A method of operating an elevator system having at least one elevator hoistway and a plurality of elevator cars traveling in the at least one elevator hoistway, each car having a brake and a safety device, the method comprising:

determining a car speed for each car in the elevator hoistway,

the method is characterized in that:

providing a signal indicative of a downward vertical acceleration of the associated car to each car in the elevator hoistway;

generating a braking distance (B) that is a predetermined amount greater than a safe braking distance used to park one or both cars in each of the adjacent car pairs for all possible combinations of speeds of each adjacent car pair in the elevator hoistway to maintain proper separation;

generating a stopping distance (S) greater by a predetermined amount than a safe stopping distance for stopping both cars of each of the adjacent car pairs with a safety device for all possible combinations of the speeds of each of the adjacent car pairs;

periodically or continuously determining the actual distance between the cars of each said adjacent car pair;

providing at least one signal to cause a brake of one or more cars in a particular adjacent car pair to be activated when the actual distance between the particular adjacent car pair is less than the braking distance (B) corresponding to a concurrent speed of the particular adjacent car pair;

providing an engaged safety signal indicating that the actual distance is less than the stopping distance (S) corresponding to a speed at which adjacent car pairs are simultaneously occurring; and

providing a signal to engage the safeties of all of the cars in the elevator hoistway in response to a signal indicative of any downward vertical acceleration of the car indicating that the respective car is in free fall or in response to the engage safeties signal.

3. A method of operating an elevator system, the system having at least one elevator hoistway and a plurality of elevator cars traveling in the at least one elevator hoistway, each car having a brake and a safety device, the method comprising:

determining a car speed of each car in the elevator hoistway, characterized in that:

generating a stopping distance (B) for all possible combinations of speeds of each adjacent car pair in the elevator hoistway, the stopping distance (B) being greater than a safe stopping distance for stopping one or both cars in each of the adjacent car pairs by a predetermined amount to maintain proper separation;

generating a stopping distance (S) for all possible combinations of the speeds of each of said pairs of adjacent cars, said stopping distance (S) being greater than a safe stopping distance for stopping both cars of said each pair of adjacent cars by a safety device by a predetermined amount;

periodically or continuously determining the actual distance (Δ Ρ) between the cars of each of said pairs of adjacent cars;

providing at least one signal to cause a brake of one or more cars in a particular adjacent car pair to be activated when the actual distance between the particular adjacent car pair is less than the braking distance (B) corresponding to a contemporaneous speed of the particular adjacent car pair;

providing an engaged safety signal indicating that the actual distance is less than the stopping distance corresponding to a speed at which adjacent car pairs are simultaneously occurring; and

providing a signal to engage the safety devices of all of the cars in the elevator hoistway in response to the engage safety device signal.

4. The method of claim 3, wherein the stopping distance (B) is derived as

Braking distance (B) ═ v (u) # t +1/2a (u) # t²+[V(U)+A(U)Δt]²/2D(U)+V(L)Δt+1/2A(L)Δt²+[V(L)+A(L)Δt]²2D(U)+K(B)

Wherein k (b) is a braking distance deviation constant, which is selectable,

velocity V ═ velocity

A is the acceleration, set according to the over-balance of the car,

d ═ deceleration ═ f (b) -W. M

Wherein F (B) is the force applied by the brake

W is added. Unbalanced (net) weight of the car

mass of car with counterweight

The stopping distance (S) is derived in the same way as the braking distance (B), except that the force (f (S)) exerted by the safety device replaces the braking force (f (B)), and the safety device braking distance deviation constant may be the same as the braking distance deviation constant (k (B)), different from the braking distance deviation constant (k (B)), or the braking distance deviation constant (k (B)) is omitted.

5. An elevator system, the system comprising:

at least one elevator hoistway;

a plurality of elevator cars traveling in the at least one elevator hoistway, each car having a safety device;

the method is characterized in that:

means corresponding to each car in the elevator hoistway for providing a signal indicative of downward vertical acceleration of the associated car; and

means responsive to the signal indicative of any one or more of the cars being in a free fall indicating that the respective car is in a free fall for providing a signal to engage safety devices of all of the cars in the elevator hoistway.

6. An elevator system comprising:

at least one elevator hoistway;

a plurality of elevator cars traveling within the at least one elevator hoistway, each car having a brake and a safety device;

means for determining car speeds of cars within the elevator hoistway;

the method is characterized in that:

means for generating a stopping distance (B) for all possible combinations of speeds of each adjacent car pair in the elevator hoistway, the stopping distance being greater than a safe stopping distance for stopping one or both cars in each of the adjacent car pairs by a predetermined amount to maintain proper separation; for generating a stopping distance (S) for all possible combinations of the speeds of each of said pairs of adjacent cars, said stopping distance being greater than a safe stopping distance for stopping each of said pairs of adjacent cars by a safety device by a predetermined amount; for periodically or continuously determining the actual distance between the cars of each said adjacent car pair; for providing at least one signal to activate a brake of one or more cars of a particular pair of adjacent cars when the actual distance between the particular pair of adjacent cars is less than the braking distance (B) corresponding to a contemporaneous speed of the particular pair of adjacent cars; to provide an engaged safety signal indicating that the actual distance is less than the stopping distance (S) corresponding to a speed at which adjacent car pairs are simultaneously occurring; and which provides a signal to engage safety devices of all of the cars in the elevator hoistway in response to the engage safety device signal.

7. The elevator system of claim 6, wherein the means for determining the speed and the means for generating the stopping distance (B) are duplicated for redundant safety devices.

8. The elevator system of claim 6 wherein:

the braking distances (B) and the stopping distances (S) for all of the speed combinations are stored in one or more tables accessible for concurrent speeds of cars of adjacent car pairs to provide respective braking distances (B) and respective stopping distances (S).

9. The elevator system of claim 8 wherein:

the respective stopping distance (B) is compared to the actual distance to provide the at least one signal.

10. The elevator system of claim 8, wherein

The respective stopping distance (S) is compared with the actual distance to provide the engaged safety device signal.