METHOD AND APPARATUS FOR MONITORING THE TEETH OF A COMB PLATE FOR A PASSENGER CONVEYOR

Abstract: An apparatus for automaticlly monitoring the structural integrity of comb plate teeth of a passenger conveyor by establishing an electrical or pressure signal path along each of the comb plate teeth. The signal parth is monitored by a controller and a damaged comb plate tooth is detected based on variation in the signal propagating through the signal path. Upon detection of a damaged tooth, the controller shuts off power to the passenger conveyor and/or indicates that service of the comb plate is needed.

Description: METHOD AND APPARATUS FOR MONITORING THE TEETH OF A COMB PLATE FOR A PASSENGER CONVEYOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to passenger conveyors and, more particularly, to a safety device for passenger conveyors. 2. Description of the Related Art A passenger conveyor, such as an escalator or a moving walk, is typically formed of a plurality of tread plates propelled between stationary pieces, i.e., landings, where passengers get on and off the conveyor. To prevent foreign objects from getting jammed at tlie gap or interface between the landing and the tread plates, a comb plate is attached to each landing for deflecting or pushing foreign objects away from that interface. The comb plate has a plurality of teeth shaped to mesh with longitudinal grooves in the tread plates. During die course of operation of the passenger conveyor, the teeth of the comb plate may break off or otherwise become damaged so that objects such as d e pointed heel of a shoe, miscellaneous refuse, or, more dangerously, a body .part of a passenger, may become lodged or entrapped between a tread plate and the comb plate. The comb plate teeth may be damaged due to cyclic stresses during use or impact loads by, for example, pebbles or screws wedged in the grooves of moving tread plates. A typical mode of failure is that one or more comb plate teeth break off thereby exposing tlie gap between the landing and a tread plate. Consequently, tlie comb plate becomes less effective in deflecting objects from the gap. If the drive mechanism is not immediately stopped, the passenger may suffer substantial injury or the conveyor drive mechanism may sustain substantial damage. Typically, comb plate teeth are visually inspected by building or service personnel. This dependency on human observation and intervention has sometimes led to damaged comb teeth remaining in service for extended periods of time, and thus exposed passengers to unnecessary risks. U.S. Patent No. 5,718,319 discloses a safety device for detecting objects stuck in an escalator or a moving walk. The device includes a high-strength flexible wire extending transversely through a series of holes formed in the teeth of a comb plate. The wire is connected to an actuator, which shuts off tlie motor operating the escalator when the wire is stretched or elongated. This device, however, cannot detect cracked or missing teeth as it is possible that a tooth can be broken off without causing the wire to stretch. Furthermore, this device requires increased maintenance as tlie wire traps and accumulates small foreign objects, which would have been deflected by tlie comb plate teeth. German reference DE 2 135 864 discloses a further safety device for escalators including an electrical conductor arranged in tl e comb teeth for establishing an electronic signal path through the comb tooth assembly. Similarly, International Publication No. WO 91/06501 discloses an escalator safety device in which tl e teeth comprise an electric conductor molded therein which is part of an electrical circuit. These safety devices are difficult to manufacture and therefore are expensive to manufacture. Yet another safety device is disclosed in Japanese Abstract No. JP 4-153195 in which optical means 24, 25, 26 are used to detect deformation or breaks in tl e comb teeth. Similarly, German reference DE 680 847 discloses a safety device for an escalator in which a light beam is projected through holes in the comb teeth and detected by a photoelectric device positioned on the side of the escalator. The manufacture of the optical means is also complex. Furthermore, dirt or other foreign objects may occlude the light path and produce a false signal. Accordingly, there is a need for a reliable method and apparatus for automatically detecting damaged comb plate teeth. SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for detecting damage to comb plate teeth of a passenger conveyor. According to an aspect of the invention, a missing or broken comb tooth can be detected by monitoring tlie continuity of an electrical or fluid circuit passing through or along each of the comb plate teeth, the circuit comprising part of a mechanism embedded in the comb plate. Thus, a break in tlie continuity of tlie circuit indicates a comb tooth has been damaged. In one embodiment, a signal line is arranged on a circuit board to extend along or through each of tlie comb plate teeti to form a series circuit so that when a comb tooth is damaged, the flow of electrical current through tlie series circuit is interrupted. If the conductor supplies power to a relay of a safety circuit of the passenger conveyor, a damaged comb tooth will result in a loss of power to the relay, causing tl e passenger conveyor to immediately stop so as to prevent further injury to the passenger or damage to tlie conveyor drive mechanism. Alternatively, tlie signal line forms a parallel circuit such that damage to a comb tooth results in a change or stoppage of electrical current through tlie circuit. A monitoring device detects the change in the electrical current and actuates a warning device and/or shuts off die conveyor's drive mechanism. Using Kirchoff s law, tlie number of broken comb teetii can be determined by measuring or monitoring changes in the equivalent resistance of tl e parallel circuit or the signal strengtli of tl e entire parallel circuit. Depending on tlie damage severity, tlie monitoring device may shut down the passenger conveyor or issue a warning signal indicating the comb plate has sustained damage. In anod er embodiment, the comb plate includes a continuous fluid channel formed in each of the comb plate teeth. The fluid chamber may be filled with an electrically conductive fluid such as, for example, a conductive gas or antifreeze liquid connected to a voltage source to form a circuit so that when a comb tooth breaks, the fluid leaks out thereby opening the circuit. Upon sensing an open circuit a detector informs a controller then actuates a warning device to indicate that a comb plate tooth has been damaged. Other objects and features of the present invention will become apparent from tl e following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be furtlier understood that the drawings are not necessarily drawn to scale and U at, unless od erwise indicated, they are merely intended to conceptually illustrate tlie structures and procedures described herein. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, wherein like reference characters denote similar elements throughout tlie several views: Fig. 1 depicts a prior art passenger escalator having a comb plate; Fig. 2 is a cross-sectional view of a comb plate and a tread plate; Fig. 3 is a plan view of two sections of a comb plate according to an embodiment of tlie present invention; Fig. 4 is a cross sectional view of a comb plate according to an embodiment of the present invention; Fig. 5 is a plan view as in Fig. 3 showing anodier embodiment of die present invention; Fig. 6 is a schematic view of yet another embodiment of the present invention; Fig. 7 is a schematic view of another embodiment of die invention incorporating a fluid chamber; and ' Fig. 8 schematically illustrates anodier embodiment of the invention having a pressure sensor disposed inside a fluid chamber. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS Fig. 1 illustrates a prior art escalator 10 including a treadway 12 formed by a plurality of tread plates 14 and risers 16. The tread plates 14 have longitudinally spaced tread grooves 18 formed on their top surfaces and are guided to slide beneath a comb plate 20 attached to a landing 22. Typically, the comb plate 20 is constructed of a plurality of sections arranged side by side and has teeth 24 shaped to project into die tread grooves 18. So arranged, the comb plate teeth 24 prevent debris deposited in the tread grooves 18 or a passenger's shoe or garment from becoming lodged at d e gap between the landing 22 and a tread plate 14 by deflecting it away from the gap. Fig. 2 depicts a cross-sectional view of an assembly of a landing 22, a comb plate 20, and a tread plate 14. As can readily be seen, die comb plate toodi 24 extends into a groove 18 of the tread plate 14 and is dimensioned to maintain a minimum clearance between the bottom surface 26 of the tooth 24 and die bottom wall 28 of die groove 18. Typically, d e comb plate tooth 24 has a sloping top surface extending from near die bottom wall 28 of die groove 18 to a distance above die tread plate 14 and shaped to deflect objects away from the interface 30 between die landing 22 and the tread plate 14. However, a comb plate tooth 24 can become damaged or broken due to fatigue or from collision with debris entrenched in the groove 18 of a tread plate 14. Without the sloping surface, the broken or damaged comb plate tooth 24 loses the ability to deflect debris trapped in the groove 18 of a tread plate 14 diercby increasing the likelihood that die debris becomes lodged under the landing. In accordance with the present invention, each of the comb plate teedi 24 can be monitored using an electrical and/or fluid mechanism embedded in die comb plate. Advantageously, the mechanism establishes a detectable physical variable such as, for example, the strength of an electrical signal or a level of fluid pressure for each of the comb plate teeth 24 so that when a tooth of die comb plate 20 becomes damaged, the value of the detectable physical variable changes. A detector senses the changed value of the detectable physical variable and generates a signal, preferably when the changed value varies from a predetermined direshold. A controller receives die signal from die detector and causes d e passenger conveyor 10 to shut down and/or issues a warning to d e passengcr(s) or operator(s) of the conveyor 10. Figs. 3 and 4 schematically illustrate an embodiment of an apparatus for detecting a damaged toodi of a comb plate 20 comprising two comb plate sections 44, 46 using a serial continuity check. Each comb plate section 44, 46 comprises a circuit board 31 comprising teeth 33 corresponding to the teeth 24 of the comb plate 20. A signal line 32 is arranged on die circuit board 31 using known circuit board printing technology and extends along and/or dirough each of the teedi 33 of die circuit board 31. The comb plate 20 is overmolded around die circuit board 31. As shown in Fig. 3, die signal line 32 may be connected to a signal generator 34 for generating a signal through the signal line 32 such that a damaged tooth 24 will disrupt or otherwise vary the signal transmitted through die signal line 32. The signal line 32 may, for example, be a conductive signal pad formed on the one-sided circuit board injection overmolded with an engineering plastic to form the comb plate 20 and comb plate teeth 24. The circuit board 31 may be formed of high temperature composite material such as, for example, polyimide, which has a higher processing temperature than the overmold material; in which case, the circuit board 31 and d e overmold material form separate layers. Alternatively, the circuit board 31 and the overmold material are the same; in which case, the circuit board 31 fuses with the overmold material. In any event, the conductive signal lines 32 are embedded in each of the comb plate teeth 24. A detector 36 connected to d e signal line senses d e signal disruption or variation and sends a warning message indicating die presence of a damaged tooth to a controller 38. In response to die message from the detector 36, the controller 38 may actuate a warning device or shut down the passenger conveyor 10. To avoid false readings, die detector 36 is preferably configured to transmit the warning message only when d e signal strengd is below a predetermined direshold. Alternatively, as depicted in Fig. 5, die detector 36 includes a relay 40 energized by a voltage source 42 connected to the signal line 32 so d at when a comb plate tooth 24 is broken, die relay 40 loses power and opens a safety circuit (not shown) of die conveyor 10 thereby shutting down d e conveyor 10 or actuates a warning-signaling device to issue a warning to the passengers or an operator of d e conveyor 10. Aldiough only two comb plate sections 44, 46 are shown in Figs. 3 and 5, it is contemplated that one or more sections can be used to construct a comb plate 20 of a desired width for these embodiments and d e embodiments described below. To connect the signal lines 32 of adjacent sections, a suitable connecting device such as for example spring contacts 48 disposed at corresponding locations of the adjacent sections may be used. Fig. 6 schematically depicts a comb plate 20 in which the circuit board 31 comprises a parallel circuit wherein a resistive element 60 is formed at each of d e comb plate teeth 24 such that damage to one or more comb teeth 24 results in a change of electrical current through die circuit. The detector 36 senses the change in electrical current and causes the controller 38 to actuate a warning device and/or shut off the conveyor drive mechanism. Additionally, using Kirchoff s law, d e number of broken comb teeth may be determined by measuring or monitoring changes in die equivalent resistance of the parallel circuit or d e signal strengdi of die entire parallel circuit. Depending on die damage severity, d e detector 36 may shut down die passenger conveyor 10 or issue a warning signal indicating the comb plate 20 has sustained damage. Fig. 7 schematically illustrates a comb plate 20 incorporating a fluid chamber 62 having a plurality of channels 64 extending into die comb plate teedi 24. The fluid chamber 62 and channels 64 may be filled widi a fluid (e.g., air, antifreeze liquid, etc.) and pressurized to a predetermined pressure by a pressure regulator 66 so diat when a comb plate toodi 24 is broken, fluid is lost and a pressure sensor 68 for sensing pressure in die fluid chamber sends a signal to die controller 38. The controller 38 responds to the signal from the pressure sensor 66 and causes a warning device to issue a warning to an operator of the passenger conveyor 10, and/or sends a control signal to a safety circuit to shut down the passenger conveyor 10. Alternatively, the fluid in die fluid chamber 62 and channels 64 may comprise an electrical conductive fluid. In diis alternative embodiment, the circuit of Figs. 3 and 5 may be connected to the ends of die fluid chamber 62 for conducting an electric signal through the fluid. When one of the comb fingers 24 breaks, the fluid drains from the comb plate section of that finger 24 and disrupts the signal. Optionally, as depicted in Fig. 8, a negative pressure may be created in the fluid chamber 62 so diat when a comb plate tooth 24 is broken, the fluid chamber 62 loses the negative pressure. A pressure sensor 68 (e.g., a micro pressure switch) disposed in die fluid chamber 62 then responds to the loss of negative pressure and sends a signal to d e controller 38. Upon receiving the signal from die pressure sensor 68, the controller 38 may shut down die passenger conveyor 10 (by, for example, opening a safety circuit) and/or actuate a warning device. The embodiments of Figs. 7 and 8 may be formed using gas-assisted injection molding technology. According to d is mediod, gas is injected into die plastic as the comb plate is being molded so as to form d e fluid chamber 62. Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in d e form and details of die devices illustrated, and in tiicir operation, may be made by tiiose skilled in d e art witiiout departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or mediod steps which perform substantially the same function in substantially the same way to achieve the same results are witiiin the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of die invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, dierefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims: CLAIMS We claim: 1. An apparatus for detecting one or more damaged teeth of a comb plate of a passenger conveyor, comprising: a comb plate having a plurality of teedi; a mechanism arranged in the comb plate having a detectable physical variable with a value which varies when one of d e plurality of teeth of die comb plate becomes damaged, said mechanism extending along each of the plural teedi and comprising one of a circuit board embedded in die comb plate having a signal line printed d ereon and a fluid arranged in a fluid chamber defined widiin die comb plate and including a plurality of channels extending dirough die plurality of teedi of the comb plate; and a detector opcratively connected to said mechanism for sensing die value of d e detectable physical variable and generating a signal when die value passes a predetermined direshold. 2. The apparatus of claim 1, wherein said mechanism comprises said circuit board and the signal line is connectable to a voltage source for supplying a reference voltage as the detectable physical variable. 3. The apparatus of claim 2, wherein the detector includes a relay connected to d e signal line such diat a damaged tooth results in an open circuit and a loss of power to the relay. 4. The apparatus of claim 1, further comprising a controller responsive to the signal from the detector for one of shutting down d e passenger conveyor and causing a warning to issue. 5. The apparatus of claim 2, wherein the signal line forms a series circuit such diat a damaged toodi results in a loss of signal dirough the signal line. 6. The apparatus of claim 2, wherein die signal line forms a parallel circuit including a resistive element disposed at each of die comb plate teedi such diat a damaged toodi results in a change in an equivalent resistance of die parallel circuit. 7. The apparatus of claim 1, wherein said mechanism comprises the fluid in the fluid chamber and the fluid chamber includes a pressure different from atmospheric pressure such that a damaged tooth results in a cliange of die pressure, the detectable physical variable being the pressure of the fluid chamber. 8. The apparatus of claim 7, wherein the pressure is above atmospheric pressure. 9. The apparatus of claim 7, wherein the pressure is below atmospheric pressure. 10. The apparatus of claim 7, wherein die detector includes a pressure sensor d at outputs a signal in response to die change of pressure in d e fluid chamber. 11. The apparatus of claim 10, wherein the detector is disposed inside d e fluid chamber. 12. The apparatus of claim 7, wherein die fluid in die fluid chamber is electrically conductive so as to form a signal padi dieredirough and an electrical signal source is connected to die fluid chamber for supplying an electrical signal to the fluid such that a damaged toodi results in a loss of die fluid and tiius an open circuit, the detector being responsive to a change in the electrical signal. . 13. The apparatus of claim 12, wherein the fluid includes a gas. 14. The apparatus of claim 12, wherein the fluid includes a liquid.

Inventors: CHIN GEEMING, ROBIBERO VINCENT P, THOMAS MICHAEL W, CHIN, GEEMING, ROBIBERO, VINCENT, P., THOMAS, MICHAEL, W.
Applicants: CHIN GEEMING, INVENTIO AG, ROBIBERO VINCENT P, THOMAS MICHAEL W, CHIN, GEEMING, ROBIBERO, VINCENT, P., THOMAS, MICHAEL, W.
Application year: 2001
Main classification: B66B29
IPC codes: B66B29