Claims:We claim: -

1. A retrofit type safety device (100) for a braking apparatus (10) of an elevator, comprising a hydraulic unit (70), said hydraulic unit (70) comprises a valve (80) to regulate supply of oil to a hydraulic cylinder (90); said hydraulic cylinder (90) is couplable to a plunger (30) of an electro-magnetic brake (20) of said elevator for actuating said plunger (30), characterized in that,
? a controller (75) for controlling operation of said valve (80) based on at least one of a weight of an elevator car, a position of said elevator car, acceleration of said elevator car and direction of movement of said elevator car selected by an elevator user.
2. The retrofit type safety device (100) as claimed in claim 1, wherein the controller (75) compares the weight of the elevator car with a counterweight.
3. The retrofit type safety device (100) as claimed in claim 1, wherein the controller (75) compares the position of the elevator car with the position of the counterweight.
4. The retrofit type safety device (100) as claimed in claim 1, wherein the controller (75) checks at least one of a destination floors selected by said elevator user and checks if the direction of movement of said elevator car is upwards/downwards.
5. The retrofit type safety device (100) as claimed in claim 1, wherein the controller (75) compares said acceleration with a threshold.
6. The retrofit type safety device (100) as claimed in claim 1, comprises a set of brake springs (60) for driving a set of brake arms (40) to press against a drive axle (50) of said elevator to apply the brake, when power supply to said electro-magnetic brake (20) is stopped.
7. The retrofit type safety device as claimed in claim 6, where the controller (75) controls said valve (80) to selectively supply oil to said hydraulic cylinder (90) to control the movement said plunger (30) and also the braking force applied by said brake springs (60) and said brake arms (40).
8. The retrofit type safety device as claimed in claim 6, wherein controller (75) controls the valve (80) such that the force of the brake springs (60) is applied on the drive axle (50) in a controlled manner without any jerk.
9. A method of controlling braking apparatus (10) of an elevator, said braking apparatus (10) comprises an electro-magnetic brake (20) with a plunger (30), said plunger (30) is actuated to control movement of set of brake arms (40), said method comprises
? evaluating at least one of a weight of an elevator car, a position of said elevator car, acceleration of said elevator car and direction of movement of said elevator car selected by an elevator user; and
? regulating a valve (80) to control supply of oil to a hydraulic unit (70) based on said evaluation result for controlling movement of said plunger (30) of an electro-magnetic brake (20).
10. The method as claimed in claim 9, wherein said evaluation step involves comparing the weight of the elevator car with a counter-weight.
11. The method as claimed in claim 9, wherein said evaluation step involves comparing position of the elevator car with the position of the elevator car.
12. The method as claimed in claim 9, wherein said evaluation step involves checking at least one of a destination floors selected by said elevator user and checking if the direction of movement of said elevator car is upwards/downwards.
13. The method as claimed in claim 9, wherein said evaluation step involves comparing said acceleration of elevator car with a threshold.
14. The method as claimed in claim 9, comprises controlling said valve (90) to selectively supply oil to said hydraulic cylinder (70) to control the movement said plunger (30) and the braking force applied by said brake arms (40).

, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:
Field of the invention:
[0001] The present invention relates to retrofit type safety device for an elevator. More specifically, it relates to a method of controlling braking apparatus of an elevator
Background of the invention:
[0002] Elevators in multi-story buildings come with lot of interesting and sophisticated features. However, in a small and mid-sized building, there is a limitation to have sophisticated systems. There is still a challenge to stop the elevator car or cage in a safe floor without any physical discomfort or jerk, when the mains power supply goes off.
[0003] JP10095580 A2 discloses an emergency operation device for an elevator. If the power is not supplied by a power failure, an external power source is connected to the external power source connector and then the electromagnetic brake is released by the electromagnetic brake releasing switch to move down a car to the nearest floor by its self- weight.
Brief description of the invention:

[0004] This invention related to a retrofit type safety device for an elevator. The retrofit type safety device comprises a hydraulic unit having a valve to regulate supply of oil to a hydraulic cylinder. The hydraulic cylinder is couplable to a plunger of an electro-magnetic brake of the elevator for actuating the plunger. A controller controls operation of the valve based on one or more of weight of an elevator car, a position of the elevator car, acceleration of the elevator car and direction of movement of the elevator car selected by an elevator user.
[0005] The controller performs one or more of the following checks for controlling the operation of the valve. The controller compares the weight of the elevator car with a counter-weight. The controller compares the position of the elevator car with the position of the elevator car. The controller checks at least one of a destination floors selected by the elevator user and checks if the direction of movement of the elevator car is upwards/downwards. The controller compares the acceleration of the elevator car with a threshold. The retrofit type safety device comprises a set of brake springs for driving a set of brake arms to press against a drive axle of the elevator to apply the brake, when power supply to the electro-magnetic brake is stopped. The controller controls the valve to selectively supply oil to the hydraulic cylinder to control the movement the plunger and the braking force applied by the brake springs and the brake arms. The controller controls the valve such that the force of the brake springs is applied on the drive axle in a controlled manner without any jerk.
[0006] A method of controlling braking apparatus of an elevator. The braking apparatus comprises an electro-magnetic brake with a plunger. The plunger is actuated to control movement of a set of brake arms. The method involves evaluating at least one of a weight of an elevator car, a position of the elevator car, acceleration of the elevator car and direction of movement of the elevator car selected by an elevator user. A valve is regulated to control supply of oil to a hydraulic unit based on the evaluation result for controlling movement of the plunger of an electro-magnetic brake. The evaluation step involves comparing the weight of the elevator car with a counterweight. The evaluation step involves comparing position of the elevator car with the position of the counterweight. Destination floor selected by the elevator user is detected and if the direction of movement of the elevator car is upwards/downwards is also checked in the evaluation step. In an embodiment of the invention, acceleration of elevator car is compared with a threshold. The valve is controlled to selectively supply oil to the hydraulic cylinder to control the movement the plunger and the braking force applied by the brake arms
Brief description of the accompanying drawings:
[0007] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0008] Fig. 1 illustrates a schematic block diagram of a retrofit type safety device for an elevator, according to an embodiment of the present invention;
[0009] Fig. 2 shows a schematic block diagram of a hydraulic unit implemented in a safety device for a braking system of an elevator, according to an embodiment of the present invention; and
[0010] Fig. 3 shows a flow chart of a method controlling braking apparatus of an elevator, according to an embodiment of the present invention.
[0011] Detailed description of the embodiments:
[0012] Fig. 1 shows a schematic block diagram of a retrofit type safety device 100 for a braking apparatus 10 of an elevator. The braking apparatus 10 comprises an electro-magnetic brake 20 or electric brake with a plunger 30. The plunger 30 is movable between a braking position and a release position. A set of brake arms 40 are coupled to the plunger 30 and are actuated by the plunger 30. In the braking position of the plunger 30, the brake arms 40 press-against a drive-axle 50 of the elevator to restrict the movement of the drive-axle 50 and thereby stop the movement of an elevator cage or car. Similarly, the release position of the plunger 30, the set of brake arms 40 move away from the drive axle 50 for releasing the brake.
[0013] In an embodiment of the invention, the plunger 30 is moved vertically up and down between the release position and the braking position. By electromagnetic force, the plunger 30 is moved upwards to the release position, in which the brake arms 40 move away from the drive axle 50, thereby permitting the movement of the elevator. Similarly, the plunger 30 is moved downwards to the braking position, in which the brake arms 40 press-against the drive-axle 50 of the elevator.
[0014] When power supply to the electro-magnetic brake 20 is stopped, the brake arms 40 are driven by a set of brake springs 60 to press against the drive-axle 50 to apply the brake. When the power supply is stopped, the plunger 30 goes up towards the release position, because of the absence of the electro-magnetic force. However, in order to ensure safety to the passengers, a set of brake springs 60 are provided in the braking system 20.
[0015] By default, the brake arms 40 are pressed against the drive-axle 50 by the force of the brake springs 60. When the elevator needs to be moved, the plunger 30 is moved to the release position by the electromagnetic force, against the force of the brake springs 60. As a result, the elevator cage/car is movable to different floors. When the power supply is stopped, there is no electro-magnetic force, hence the plunger 30 is not moved to braking position. However, the brake arms 40 are driven by the brake springs 60 suddenly to apply brake to the drive-axle 50, which may cause jerks or unintentional oscillations. This invention helps in avoiding such jerks or oscillations. The retrofit type safety device 100 comprises a hydraulic unit 70 and a controller 75 connected to the hydraulic unit 70.
[0016] Fig. 2 shows a schematic block diagram of a hydraulic unit implemented in a safety device for a braking system of an elevator, according to an embodiment of the present invention. The hydraulic unit 70 having a valve 80 to regulate supply of oil to a hydraulic cylinder 90. The hydraulic cylinder 90 is couplable to the plunger 30 of an electro-magnetic brake 20 of the elevator for actuating the plunger 30. The controller 75 controls operation of the valve 80 based on one or more of weight of an elevator car, a position of the elevator car, acceleration of the elevator car and direction of movement of the elevator car selected by an elevator user.
[0017] Weight of the elevator car in comparison to a counterweight of the elevator, the direction of movement of the elevator car, the selected floor, the acceleration/speed of the elevator car, position of the elevator car with respect to the next lower/upper level are considered for controlling the hydraulic cylinder 90. This is further explained in the below paragraphs.
[0018] In an embodiment of the invention, the controller 75 compares the weight of the elevator car with a counterweight. Weight of the elevator car is measured using sensors and output to the controller 75. The weight of the counterweight is stored beforehand and known to the controller 75.
[0019] In another embodiment of the invention, the controller 75 compares the position of the elevator car with the position of the counterweight.
[0020] In yet another embodiment of the invention, the controller 75 checks at least one of a destination floors selected by the elevator user and checks if the direction of movement of the elevator car is upwards/downwards.
[0021] Also, the controller 75 compares the acceleration of the elevator car with a threshold. Acceleration or speed of the elevator car is also measured by a sensor and output to the controller 75. The threshold value is pre-decided and can be set according to the variations or models of the elevator.The controller 75 performs one or more of the above checks for controlling the operation of the valve 80.
[0022] For example, when the weight of the elevator car is more than the counterweight, hydraulic cylinder 90 is controlled (i.e. oil is not supplied by controlling the valve 80), so that the brake is applied slowly to bring the elevator car to next lower level which is closer to the destination floor (when the user selected direction of movement is downwards). Similarly, hydraulic cylinder 90 is controlled (oil is not supplied by controlling the valve 80), so that the brake is applied slowly to bring the car to next upper level, which is closer to the destination floor, when the selected direction of movement is up. This happens, when the elevator car can move upward because of the inertia. Otherwise, the elevator car stops at the floor at the next below level.
[0023] For example, when the weight of the elevator car is lesser than the counterweight, the counterweight tends to pull down the elevator car, when there is no power supply. The hydraulic cylinder 90 is controlled (oil is not supplied), so that the brake is applied slowly to bring the car to next lower level, which is closer to the destination floor, when the selected direction of movement is down.
[0024] Similarly, hydraulic cylinder 90 is controlled (oil is not supplied by regulating the valve 80), so that the brake is applied slowly to bring the car to next upper level, which is closer to the destination floor (when the selected direction of movement is up). This happens when the elevator car moves upwards due to inertia. Otherwise, the elevator car stops at the next below level (lower floor)
[0025] Thus, when power supply to the electro-magnetic brake is stopped, the controller 75 controls the valve 80 to selectively supply oil to the hydraulic cylinder 90 to control the movement the plunger 30 and also the braking force applied by the brake springs 60 and the brake arms 40. The controller 75 controls the valve 80 such that the force of the brake springs 60 is applied on the drive axle 50 in a controlled manner without any jerk and abrupt movements while braking, especially during power off conditions.
[0026] Instead of allowing the brake arms 40 to forcedly and abruptly dash against the drive-axle 50, the valve 80 is controlled to control the brake application by the braking springs 60 in a smooth manner. Therefore, jerky stop of the elevator cage/car is avoided.
[0027] Fig. 3 shows a flow chart of a method controlling braking apparatus of an elevator, according to an embodiment of the present invention. The braking apparatus 10 comprises an electro-magnetic brake 20 with a plunger 30. The plunger 30 is actuated to control movement of a set of brake arms 40. The method involves evaluating one or more of the following parameters such as weight of an elevator car, a position of the elevator car, acceleration of the elevator car and direction of movement of the elevator car selected by an elevator user (step S1). A valve 80 is regulated to control supply of oil to a hydraulic unit 70 based on the evaluation result for controlling movement of the plunger 30 of an electro-magnetic brake 20 (step S2).
[0028] The evaluation step (S1) involves comparing the weight of the elevator car with a counter-weight. The evaluation step (S1) involves comparing position of the elevator car with the position of the counterweight. Further, the destination floor selected by the elevator user is detected and if the direction of movement of the elevator car is upwards/downwards is also checked in the evaluation step (S1). In an embodiment of the invention, acceleration of elevator car is compared with a threshold.
[0029] Based on the one or more evaluation results, the valve 80 is selectively controlled by the controller 75 during the power OFF condition in order to regulate the braking (S2). The valve 80 is coupled to a relay 250. Based on the input from the relay 95, the valve 80 regulates the discharge of oil to the hydraulic cylinder 90 when the power supply to the electro-magnetic brake 20 is stopped. The valve 80 is controlled to selectively supply oil to the hydraulic cylinder 70 to control the movement the plunger 30 and the braking force applied by the brake arms 40, based on the evaluation result.
[0030] As a result, braking is applied smoothly without any harm or discomfort to the users. Both safety as well as comfort are ensured to the elevator users even when power is cut off. As the safety device is retrofit type, existing elevators can be upgraded with higher safety and comfort features at less cost. The invention obviates the need for expensive power source for moving the elevator car during the mains power off condition. Energy saving is achieved as the inertia of the elevator car is selectively used.
[0031] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.