HK1087390B - Elevator with variable drag for car and counterweight - Google Patents

Description

Elevator with variable traction of car and counterweight

Background

The present invention relates to improvements for changing the traction of an elevator car and counterweight, particularly when near the ends of its operating range.

An elevator typically has a car that moves up and down on an elevator shaft, as is known and schematically illustrated in fig. 1, with a car 12 balanced by a counterweight 14. The two are connected by a rope 16. Pulleys 18 and 20 guide the rope.

In the prior art, particularly when the car or the counterweight reaches the end of travel, one of the two is lighter than the other. The hoisting ropes are more on one side and therefore the hoisting ropes add more weight to the lower of the hoisting car and counterweight. This causes trouble and challenges in the smooth operation of the car 12. In particular, in very high rise applications, sufficient counterweight balancing force is challenging at extreme positions of the counterweight or car. Therefore, the compensating ropes 22 are sometimes used. It is desirable to eliminate compensating ropes, such as rope 22.

Other problems with controlling the weight of the elevator car and counterweight include a problem known as "rebalancing" in which the car can move slightly once stopped at a floor. Furthermore, if the car or counterweight hits a buffer in the pit, a "counterweight jump" or "car jump" condition can occur at the end of travel. The other of the car or counterweight may continue to move in an upward direction due to inertia. The rope tension on the lower element is low so that its rope can become slack and cause slippage on the traction sheave. As the counterweight then descends, the rope is again tensioned.

The present invention therefore does not require compensating ropes and provides smooth operation of the elevator particularly at the extremes of operation.

Disclosure of Invention

The invention provides an elevator system, comprising an elevator car; a counterweight; a rope connecting the elevator car and the counterweight; the traction element is connected with at least one of the car and the counterweight, and the controller controls the traction force between the car and the counterweight through the traction element so as to control the movement of the car and the counterweight.

In one embodiment of the present disclosure, variable traction is applied to the car and counterweight. When the two elements reach the extreme end of their travel, the traction of the lighter increases. At the same time, the other element is driven. Thus when the counterweight reaches a lower point of travel, and conversely the car reaches a higher point of travel, the car is lighter relative to the counterweight due to the hoist ropes. The traction of the car will be lighter than the traction of the counterweight. The rope portion of the counterweight is driven. Thereby, the weight difference can be solved.

In a particularly useful embodiment in a 2: 1 arrangement, the counterweight and lower sheave of the car have a brake/drive motor. The brake motor thus provides variable traction on the pulley as described above while driving the other pulley.

The controller monitors the position and/or speed of the car and counterweight and controls traction accordingly.

The invention is particularly useful for compensating for weight differences between a counterweight and a car in operation, and the traction control element can also be used to hold the car in a selected position, for example, at a stop on a floor.

The present invention provides another feature if the car or counterweight encounters a buffer in the pit. The other of the car and counterweight continues to move upward due to the stored inertia. At this point the tension of the rope of the element moving upwards is reduced, causing a temporary slackening of the rope and possibly causing a slip on the traction sheave, and the rope is again tensioned after a possible shock impact of the subsequent lowering of the element. The invention also allows the control feature of activating traction control if a collision is sensed. This reduces the dynamic forces of the suspension ropes and the building.

In another embodiment, a 1: 1 elevator setup is used, with magnetically controlled elements with variable magnetic force guiding the car and counterweight on guide rails. By controlling the magnetic force, the magnitude of the traction on the car and counterweight can be controlled in relation to each other. This embodiment does not require a compensating rope and provides the "hold" and "bump" features described above.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Drawings

FIG. 1 is an arrangement of a prior art elevator;

FIG. 2 is a schematic view of the inventive system;

FIG. 3 is another embodiment;

fig. 4 is a cross-sectional view of a portion of the embodiment of fig. 3.

Detailed Description

Fig. 2 shows an embodiment 50, which is a 2: 1 arrangement between the car 60 and the counterweight 56. As shown, in this arrangement, the ropes 52 pass over sheaves 54 and 58 associated with a corresponding counterweight 56 and car 60, respectively. Pulleys 54 and 58 have brake/drive motors 62 and 64 under the control of an elevator controller, such as controller 42. The brake/drive motor operates to provide variable traction on the rolling pulleys 54 and 58 to achieve the following control functions.

Controller 42 controls motors 54 and 58. In the position shown, the counterweight 56 is moving lower than the car 32. By this movement, the counterweight 56 will reach a higher weight than the car 60. In this case, the counterweight is not functioning to provide the counterweight advantage substantially as if the car and counterweight were in more equal vertical positions. In very high rise applications, this problem becomes acute. Thus, if the counterweight is below the car, the motor 64 is controlled to brake the sheave 54 to compensate for the greater weight of the counterweight 56. At the same time, the other motor 62 brakes the pulley 58 to compensate for the imbalance. Conversely, when the car is near the bottom of the path of travel, the control motor 62 will be controlled to brake the sheave 58, while the motor 64 brakes the sheave 54. Similarly, motors 62 and 64 on the car and counterweight can drive the sheaves 54 and 58 as the car or counterweight moves up and down the hoistway, thereby equalizing the rope tension on the car and counterweight. Such control may be based on the position or speed of the counterweight 56 or the car 60. It will be apparent to those skilled in the art that controller 42 determines the amount of tractive effort to compensate for the imbalance in height. Further, position and/or speed information is typically used to control the elevator, and thus it will be apparent to those skilled in the art that the necessary inputs to controller 42 are provided to operate control motors 62 and 64.

This embodiment thus allows varying traction forces exerted on the counterweight and car to control weight imbalances due to extreme differences in the vertical positions of the counterweight and car. This contributes to the prior art. Brake/drive motors 62 and 64 are used to hold the car in the desired position and remove rebalancing. Variable traction can be used to hold the car at a floor. In this way, the car can be held in an exact desired position while stopping at the floor.

The invention proposes another feature for the buffer where the car and counterweight hit the pit. The other of the car and counterweight continues to move upward due to the stored inertia. In this case, the rope tension on the upwardly moving element is reduced, causing the rope to slacken temporarily and possibly causing slippage at the traction sheave and possible impact when the element is subsequently lowered, the rope again being tensioned. The present invention also allows the control feature of activating traction control if a crash is sensed. This reduces the dynamic forces of the suspension ropes and the building.

The elevator system 30 is shown in fig. 3 with a car 32 with traction elements 33 to be guided on guide rails 34. It is known that the car is guided on guide rails of a standard elevator system. However, as will be shown in detail below, the traction elements 33 are operated to control the amount of traction between the elements and the rails. A similar guide rail 36 guides a counterweight 38 via a similar traction element 40.

Only though it is preferred that the traction element is connected to both the car and the counterweight, said control is also obtained with a single traction element connected to the car or to the counterweight.

As shown in FIG. 4, in one embodiment, the rails 36 receive the sides 44 of the traction elements 40. These sides comprise magnetic material that can be controlled by an electric current to control the magnitude of the magnetic force. In this way, the traction forces generated by the elements 33 and 40 along the guide rails 36 and 34, respectively, can be varied and controlled.

The second embodiment shown in fig. 3 and 4 solves the above-mentioned problems of rebalancing and counterweight car bouncing.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (8)

1. An elevator system comprising an elevator car; a counterweight; a rope connecting the elevator car and the counterweight; the elevator comprises a traction element and a controller, wherein the traction element is respectively connected with the car and the counterweight, the controller controls the traction element based on the vertical position of the car and the counterweight, and the traction element controls the traction force between the car and the counterweight so as to control the movement of the car and the counterweight, wherein the controller controls the traction element to ensure that the vertically lower person in the car and the counterweight is provided with lower traction force than the vertically higher person in the car and the counterweight.

2. The elevator system of claim 1, wherein the traction element includes a magnetizable member that is guided along a guide rail for the one of the car and the counterweight.

3. The elevator system of claim 1, wherein the car and the counterweight are coupled together in a 2: 1 arrangement, a sheave is coupled to the car and the counterweight, and the traction element is coupled to at least one of the car and the counterweight via the sheave.

4. The elevator system of claim 3, wherein the traction element is a brake/drive motor.

5. The elevator system of claim 1, wherein a controller monitors for a potential "jump" condition when one of the car and the counterweight reaches a run position endpoint and activates the traction element if a jump condition is identified.

6. The elevator system of claim 1, wherein the traction element is to hold the car at a floor.

7. A method of controlling operation of an elevator car comprising the steps of:

(1) connecting the elevator car with a counterweight through a rope;

(2) coupling a traction element to at least one of the car and the counterweight, the traction element providing variable traction under control of a control element;

(3) detecting a vertical position of at least one of the car and the counterweight, and controlling a variable traction of the traction element such that a vertically lower one of the car and the counterweight has a higher traction resistance.

8. The method of claim 7, wherein step (2) includes providing a traction element for each of the car and the counterweight.