Load detector for elevator car

Abstract: A load detector for an elevator having a cage moving up and down in a shaft for transporting passengers and a cable hanging the cage, including a relative position detector configured to detect a relative position of the cage against the shaft; and a calculator configured to calculate a change of the relative position between the position of the cage just after landing at a floor and the position of the cage just before leaving the floor, and a load of the cage on the basis of the change of the relative position caused by an expansion and contraction of the cable.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a load detector for an elevator cage. DESCRIPTION OF THE BACKGROUND An ordinary traction type elevator is composed as shown in FIG. 1 and FIG. 2. In FIG. 1, one terminal of a cable 2 is connected to a cage 1 and the other terminal of the cable 2 is connected to a counter weight via a sheave 31 of a hoisting machine 3 and deflector sheave 4. The hoisting machine is composed of the sheave 31 and a motor 32. The sheave 31 is driven by the motor 32, and the cable 2 is driven by the traction between the sheave 31 and the cable 2. Eventually, the cage 1 is moved up and down via the cable 2. As shown in enlarged FIG. 2, the cage 1 moves up and down along guide rails 7 by means of guide devices 6 attached to the cage 1. The cage 1 is composed of a cage frame 1A including a crosshead 1Aa, an upright 1Ab and a plank 1Ac, and a cab 1B mounted in the cage frame 1A. That is, construction of the cage 1 is in effect doubled by providing the cage frame 1A around the cab 1B, and the cab 1B is supported by vibration-proof materials 1C such as a rubber. The vibration-proof materials 1C reduce vibration transfer from the cage frame 1A to the cab 1B and improve passenger comfort during travel of the cage 1. Further, a deformation detector 1D is installed between the cage frame 1A and the cab 1B. The vibration-proof materials 1C is pressed by the load of the cab 1B, and the amount of the deformation of the vibration-proof materials 1C is detected by the deformation detector 1D. The amount of the deformation is transmitted to a calculator 11 in an elevator control panel via a transmitting cable 8, a connector box 91 attached on a shaft wall 9a of a shaft 9, and a transmitter 10. The calculator 11 calculates the load of the cab 1B or the load of passengers on the basis of the amount of the deformation from the deformation detector 1D. The calculator 11 also calculates a necessary torque to drive the motor 32 so as to move the cage 1 smoothly at the start time, and outputs the torque signal to a drive controller 12. Accordingly, even if the cage 1 is filled with many passengers, the cage 1 does not move down suddenly at the start time when a brake is off. On the other hand, even if the cage 1 has no passengers, the cage 1 does not move up suddenly at the start time. That is, the drive controller 12 applies a necessary torque to the motor 32 before the brake is off so as to move the cage 1 smoothly at the start time. In the above described traction type elevator, both the cage frame 1A and the cab 1B need a proper strength. It is not easy for the cage 1 to meet both the requirements of the proper strength and the capacity of the cab 1B. As the efficiency of the hoisting machine 3 improves, the vibration of the cage 1 has been reduced. Therefore, all cages are not required to be constructed in double in order to improve comfort of a ride in the cab 1B. But if the cage 1 has a single construction, that is to say, the cab 1B is integrated with the cage frame 1A, the deformation detector 1D cannot be installed between the cage frame 1A and the cab 1B. As a result, since a load of the cab 1B cannot be detected properly, the elevator has difficulty in controlling the torque applied to the motor 32 at the start time in accordance with change in the load. In EP-A-0 755 894 there is described a method and apparatus for the measurement of a load in an elevator cage supported by spring elements mounted to a carrying frame and movable in an elevator shaft by a hoist cable guided over a drive pulley. The elevator is of a double construction with a cage and a carrying frame. In JP 08076845 there is disclosed an automatic carrier device which can automatically stop a carrier part at a prescribed position. A light-emitting element is provided on one part and a mark comprised by a phosphor is provided on the other part. The light from the light-emitting element excites the phosphor and fluorescent light from the phosphor is received by a light receiving element. In US-A-4,299,309 there is disclosed an elevator system which determines if there are passengers present in the elevator car from the activity of passenger-actuatable switches within the car. Summary of the Invention Accordingly, an object of the invention is to provide a load detector for an elevator which can detect the passenger load if a cab is integrated with a cage frame. According to the present invention, there is provided a load detector for an elevator having a cage, which is constructed in a single construction, moving up and down in a shaft for transporting passengers and a cable hanging said cage, comprising: (1) a relative position detector configured to detect a relative position of said cage against said shaft, wherein said relative position detector includes: (a) a plurality of reflecting plates attached on said shaft near floor levels; (b) a light source attached to said cage for irradiating a light with a predetermined wavelength toward said reflecting plates; (c) a lens attached to said cage for gathering reflected light from said reflecting plates; and (d) a plurality of photoconductive cells arranged in a moving direction of said cage so as to output respective voltage signals on the basis of gathered light from said lens; and (2) a calculator configured to calculate a change of said relative position between the position of said cage just after landing at a floor and the position of said cage just before leaving said floor, and a load of said cage on the basis of said change caused by an expansion and contraction of said cable, and wherein said calculator is configured to calculate said relative position on the basis of said voltage signals from said photoconductive cells. Brief description of the drawings A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: FIG. 1 is a schematic overview of a conventional traction type elevator; FIG. 2 is a side view of a conventional traction type elevator in Fig. 1; FIG. 3 is a schematic overview of a load detector for an elevator cage of an embodiment of the present invention; and FIG. 4 is a side view of an optical position sensor shown in Fig. 3. Detailed description of the preferred embodiments Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views and more particularly Fig. 3 thereof, Fig. 3 shows a load detector for an elevator cage of an embodiment of the present invention. In FIG. 3, a cage 1 for passengers moves up and down by the movement of a cable 2. The cage 1 has a optical position sensor 13. Reflecting plates 14 are attached on a shaft 9 near each floor level and arranged to face the optical position sensor 13 at the time the cage 1 lands at the floor. Thus, a relative position detector is composed of the optical position sensor 13 and the reflecting plate 14. The position sensor 13, as shown in FIG. 4, is composed of a light source 132 in a box 131 for irradiating a light with a predetermined wavelength toward the reflecting plates 14, a lens 134 in the box 131 for gathering a reflected light from one of the reflecting plates 14, and photoconductive cells such as PSD ( Position Sensitive Device) elements 133 arranged in the moving direction of the cage. Each of the PSD elements 133 transforms a gathered light from the lens 134 into a voltage signal, and the PSD elements 133 are arranged to output respective different voltage signals in accordance with the position of the cage 1. If the cage 1 shifts up or down at the landing floor, the voltages produced by the PSD elements 133 of optical position sensor 13 also shift up or down. In other words, a relative position of the cage 1 against the reflecting plate 14 on the shaft 9 changes and the voltage signals from the PSD elements 133 also change on the basis of the relative position of the cage 1 against the reflecting plate 14. The voltage signals are transmitted to a filter 135 in order to extract and output a constituent signal corresponding to the light with the predetermined wavelength. That is, the filter 135 eliminates noise from the voltage signals. The constituent signal is transmitted to a transmitter 10 via a cable 8 and a connector box 91 on a shaft wall 9a. A field of vision of the lens 134 is set greater than a field of reflected light from the reflecting plate 14. Reflected light from the shaft wall 9a except the reflected light from the reflecting plate 14 is scattered and is not detected by the PSD elements 133 effectively. When the cage I lands on a floor level, the voltage signals from the PSD elements are outputted corresponding to the vertical position of the cage 1 and transmitted to a calculator 11 via the transmitter 10. The calculator 11 has a timer 11a and manages the voltage signals in order of the input time. The calculator 11 calculates a passed time after closing a cage door, if there is no call, i.e., either a destination call or a hall call. The destination call is a call by which passengers order the destination in the cage 1, the hall call is a call by which passengers call the cage 1 to a floor. If the passed time exceeds a predetermined time and the cage 1 does not move during the passed time, the calculator 11 resets a load value to zero on the assumption that there is no passenger in the cage 1. If a destination call is made, the cage 1 goes up or down and lands at the destination floor. The operation of detecting a load of cage 1 is as follows. First, as the cage 1 approaches to land at a floor level, the optical position sensor 13 detects the reflecting plate 14 of the destination floor. Before the cage door opens, the relative position Yb of the cage 1 against the reflecting plate 14 is detected by the optical position sensor 13. At this time, the cage 1 stops at the landing floor, because the sheave 31 is locked by a brake device (not shown ). However, since the cable 2 itself has elasticity, the cable 2 expands and contracts corresponding to a load change of the cage 1. As a result, the vertical position of the cage 1 changes, even if the cage 1 lands and stops on the floor. Consequently, when passengers finish getting on and off, the vertical position of the cage 1 could change corresponding to the load change of the cage 1. Therefore, after passengers get on and off and the cage door closes, the optical position sensor 13 detects the relative position Ya of the cage 1 against the reflecting plate 14. The calculator 11 then calculates the current load Mn of the cage 1 on the basis of the relative positions Ya and Yb, an elastic coefficient k of the cable 2, and the previous load Mo of the cage 1, and the current load Mn is calculated as follows: Mn = Mo + k x (Yb - Ya) The elastic coefficient k can be changed corresponding to the vertical position of the cage 1. Because the length of the cable 2 between the sheave 31 and the cage 1 changes corresponding to the vertical position of the cage 1. Therefore, the elastic coefficient k is applied corresponding to location of the cage 1. The calculator 11 calculates a necessary torque to drive the motor 32 so as to start the cage 1 smoothly on the basis of the load Mn, and outputs the torque signal to a drive controller 12. According to the embodiment, the cage 1 has a "single" construction, that is to say, the cab 1B is integrated with the cage frame 1A in Fig. 1, and a load of the cage 1 can be calculated on the basis of the difference of the relative position of the cage 1 against the shaft wall 9a, between a vertical position of the cage 1 just after landing at a floor and a vertical position of the cage 1 just before leaving the floor. Further, if the no call time exceeds a predetermined time and the cage 1 does not move for the no call time, the calculator 11 resets the load value to zero indicating that there is no passenger in the cage 1. Therefore, a cumulative error of a load of the cage 1 can be automatically adjusted. Furthermore, since the optical position sensor 13 detects the relative position of the cage 1 against the reflecting plate 14, the load detector can be used as a landing position detector of the cage 1. Moreover, since the optical position sensor 13 detects the relative position of the cage 1 against the reflecting plate 14 without mechanical contact and the filter 135 eliminates noise due to other light sources, the precision of the load detector can be improved. In the embodiment, the optical position sensor 13 and the reflecting plate 14 can be changed. A camera having an image sensor which can recognize light and shade can be substituted for the position sensor 13 and a plate having a geometric or other pattern can be substituted for reflecting plate. The camera can then be provided with an image processor (not shown) to recognize an image of the geometric or other pattern, or a portion of this pattern, picked up by the camera, and output different signals corresponding to the position of the cage 1. Various modifications and variations are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.

Claims: A load-detector for an elevator having a cage (1), which is constructed in a single construction, whereby the cab (1B) is integrated with the cage frame (1A), moving up and down in a shaft (9) for transporting passengers and a cable (2) hanging said cage, comprising: (1) a relative position detector (13) configured to detect a relative position of said cage against said shaft, wherein said relative position detector includes: (a) a plurality of reflecting plates (14) attached on said shaft near floor levels; (b) a light source (132) attached to said cage for irradiating a light with a predetermined wavelength toward said reflecting plates; (c) a lens (134) attached to said cage for gathering reflected light from said reflecting plates; and (d) a plurality of photoconductive cells (133) arranged in a moving direction of said-cage so as to output respective voltage signals on the basis of gathered light from said lens; and (2) a calculator (11) configured to calculate a change of said relative position between the position of said cage just after landing at a floor and the position of said cage just before leaving said floor, and a load of said cage on the basis of said change caused by an expansion and contraction of said cable, and wherein said calculator is configured to calculate said relative position on the basis of said voltage signals from said photoconductive cells. The load detector for an elevator as recited in Claim 1, wherein: said calculator is configured to reset a load value as a no load of said cage in case a time of no destination call being made exceeds a predetermined time after said cage stops.

Inventors: KAMIMURA KOSEI, MIZUTANI KENJI, SUZUKI SATOSHI, KAMIMURA, KOSEI, MIZUTANI, KENJI, SUZUKI, SATOSHI
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1999
Main classification: B66B1
IPC codes: B66B3, B66B1, B66B5