Patent Application
20110094832
This invention relates to enhancements in the safety of elevators, particularly the detection of the unauthorised presence of a person on top of an elevator car.
It is becoming increasingly common in elevator installations to provide very little space above the ordinary travel of the elevator car as this reduces building costs and increases the available flexibility in building design. However, there is a risk of injury in low overhead elevator installations as there is less refuge space for a person riding on top of the elevator car as the car approaches the uppermost landing. It is therefore necessary to provide a series of safety systems such as a retractable balustrade and a special inspection mode for the elevator controller which prevent the car from travelling to the top of the hoistway. These permit authorised inspections to be carried out safely by an engineer riding on top of the car. However, if these safety measures are not all properly employed or are inadvertently or deliberately overridden, there is an increased risk of injury. This could result from an engineer not adhering to an approved procedure for carrying out inspection or could result from an unauthorised person gaining access to the top of the car.
In view of the above, it is desirable automatically to prevent the elevator car moving to the uppermost end of its travel if a person is present on top of the car.
When viewed from a first aspect the present invention provides an elevator system comprising a hoistway and an elevator car arranged to travel vertically within the hoistway, the hoistway being further provided with a sensing arrangement for detecting the presence of a person on top of the car as the car approaches the top of the hoistway, the elevator system being arranged so as to limit further upward movement of the car in the event that a person is detected.
When viewed from a second aspect the invention provides a method of preventing injury to a person riding on top of an elevator car in a low-overhead elevator system the method comprising detecting the presence of a person on top of the car as the car approaches the top of a hoistway using means provided in the hoistway and limiting further upward movement of the car in the event that a person is detected.
Thus it will be seen by those skilled in the art, that in accordance with the invention a person at risk of being injured at the top of the hoistway as the elevator car moves up will be detected and the elevator system will limit upward movement of the car to reduce the risk of injury to that person.
The means for detecting a person on top of the car could be one that is able to distinguish between a living person and an inanimate object so that it does not sense the presence of the car itself during normal operation. For example, the sensing arrangement could comprise a passive infrared sensor for sensing the body heat of the person on top of the car. Preferably, however, the sensing arrangement is adapted to detect the presence of an object at the relevant vertical point of the hoistway.
A point in the hoistway above the normal travel of the elevator could be chosen but in very low overhead installations this may not give sufficient distance in which to stop the car safely without causing injury to the person on top of it. In accordance with preferred embodiments therefore the sensing point is within the normal travel of the car and the elevator system is arranged to be able to distinguish between a person riding on top of the car and the car itself having traveled to the vertical sensing point during normal operation. Whilst there are many ways of achieving this, it is preferred to use an existing position reference system to determine the position of the car and to limit upward movement of the car in accordance with the invention only if it is determined via the position reference system that the elevator car is not intended to be in a position where it will be detected by the sensing arrangement. One way of doing this would be for the sensing arrangement to send a signal to the elevator controller and for the elevator controller to be arranged to limit upward movement of the car based on the signals from the sensing arrangement and the position reference system.
Alternatively, the sensing arrangement may be enabled when the elevator car is towards the top of the hoistway but still low enough that there is sufficient space between the top of the car and the top of the hoistway to accommodate a person. For example, the sensing arrangement could be activated when the elevator car is at the landing below the uppermost landing. By positioning the sensing arrangement above the position of the elevator car when the sensing arrangement is activated, the sensing arrangement will only detect an object on top of the car rather than the car itself. Of course, if the position of the sensing arrangement is such that it will be passed by the elevator car during normal operation, this should not set off the safety system to limit movement of the car. One possibility would be for a second position signal to be used to deactivate the sensor. Alternatively the sensing arrangement could be enabled when the elevator car is above the penultimate landing a time measurement made to determine whether an object is detected before it would be expected for the car itself to be detected.
Upon detection of an unauthorised person on top of the car there are a number of possibilities for taking action to prevent injury to that person. For example the elevator controller may immediately prevent any further upward movement of the car by interrupting power to the elevator motor and applying the brake. Additionally, or alternatively, a physical safety device may be automatically employed.
In a preferred set of embodiments the sensing arrangement comprises means for emitting a sensing radiation and means for detecting the emitted radiation so as to enable the presence of an object in the path of the radiation to be detected. The sensing arrangement could be such that radiation reflected from the detected body is sensed but preferably the arrangement is such that the radiation travels across the hoistway to be detected so that the presence of a body at that vertical point in the hoistway interrupts the sensing of the radiation. Most preferably the sensing arrangement comprises a plurality of beams spanning the hoistway and one or more sensors arranged to detect said beam(s).
The radiation employed may be of any convenient nature such as ultrasound, microwave or visible light but preferably infrared radiation is employed since the associated sensors and emitters are relatively easily available and inexpensive whilst being reliable.
A preferred embodiment of the present invention will now be described, by way of example only with reference to the accompanying drawings in which:
a and 2b are front and perspective views respectively of an elevator system embodying the invention showing activation of the infrared curtain;
a and 3b are front and perspective views respectively showing detection of an unauthorised person on top of the car; and
In low overhead systems such as that shown, a series of safety measures is required to ensure that the car cannot reach the uppermost landing 6 with someone riding on top of it. Normally such systems are linked to certain conditions like putting the elevator in a special inspection mode or the detection of unauthorised opening of a hoistway door indicating access to the top of the car by an unauthorised person.
However, it is not impossible that detection elements can be overridden or the elevator not properly put into inspection mode. Specifically, a door detection system can be overridden by an unauthorised user who can then ride on top of the car in normal mode. As will be seen from
According to the embodiment of the invention described herein, in the uppermost part of the hoistway 2 there is provided an infrared sensor and emitter arrangement comprising an elongate emitter array 10 and a corresponding elongate sensor array 12 disposed horizontally within the elevator shaft by being attached to the respective guide rails 14. In the embodiment shown in the Figures the emitter array 10 comprises a plurality of separate emitters which emit-infrared beams spanning the hoistway at a number of different angles to be sensed by a corresponding plurality of sensors at the sensor array 12 on the other side of the hoistway. By having a plurality of independent emitters and sensors the probability of spurious detection e.g. from small pieces of debris or flying insects in the hoistway may be reduced. However, it is envisaged that a single beam could be employed which could span the hoistway just once or alternatively which could be reflected one or more times to provide a greater spatial extent.
It will be seen that the sensor and emitter arrays 10,12 are provided approximately one third of the way up the uppermost landing space 6. The sensing arrangement 10,12 is activated when the elevator car 2 is adjacent the landing 16 below the uppermost landing 6. As will be seen now with reference to
If there is no unauthorised person on top of the car, the top of the car itself will eventually break the beam between the emitter array 10 and sensor array 12 as the car moves up to the uppermost landing 6. However, this does not lead to suspension of operation of the car since the position reference system (PRS) signal indicates that the car is expected to be at a position such that it breaks the beam.
It will be appreciated by those skilled in the art that variations and modifications to the described embodiment may be made without departing from the scope of the invention. For example, other means for sensing the presence of a person on top of the car may be provided such as visible light, ultrasonic, microwave or other sensors. Moreover timing signals could be used rather than position signals to distinguish between the car and an unauthorised person on top of it.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2004/004249 | 12/21/2004 | WO | 00 | 6/14/2007 |
