Patent Publication Number: US-10784058-B2

Title: Sealed electrical contact system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional patent application No. 62/333,605 entitled “Sealed Electrical Contact System”, filed on May 9, 2016, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to electrical contacts, and more particularly to electrical contacts that include features to protect the electrical contacts from debris, corrosion and moisture. 
     BACKGROUND 
     Platform screen doors are used in light and heavy railway stations to separate travelers from the trains. Platform screen doors also provide the primary ingress and egress threshold to and from the trains. Oftentimes, an automatic sliding door in the train station aligns with a corresponding sliding door of the train when the train is in position for loading and unloading. For safety reasons, when these sliding doors are open, a signal is sent to the train control center, and the train is prevented from moving. The train may only move when the platform screen doors are fully closed. In this manner, there can be no movement of the train while passengers are attempting to board or depart from the train. 
     If a railway system malfunctions, the railway car may enter the station but a malfunction prevents the train from aligning with the sliding doors of the platform screen door system. In this case, passengers on the train still need to exit the train, especially if there is an emergency situation on the train, such as a fire. To facilitate exit of a railway car when the train is misaligned with the sliding doors of the platform screen door system, the platform screen door is equipped with an emergency swinging door adjacent the sliding doors. In the event of an emergency with a misaligned train, the train doors open and the passengers can exit through the emergency swinging door. Oftentimes, a bar releases the emergency swinging door similar to a fire door of a building. 
     The emergency swinging door is equipped with an electrical sensor or switch that communicates to the train control system that the door is in a closed position, and thus, if the sliding doors are also closed and this condition is sensed by the system, then the train can move. However, if the emergency swinging door is opened, the electrical sensor sends a signal that overrides the all clear signal and prevents movement of the train. Magnetic switches are not used in connection with railways because the power lines associated with the trains create large magnetic fields that may interfere with a magnetic switch. 
     There are different types of electrical sensors that can provide the signal for the emergency swinging door of the platform screen door system. For example, a plunger switch or a lever switch may be used. However, if either a plunger switch or a lever switch is damaged, an electrical connection may not be made or the connection may be weak such that it may send a false signal that stops operation of the train. To make the system more robust, multiple plunger switches or multiple lever switches may be employed in parallel. Thus, if one switch fails, the other switch may continue to be operational. 
     Elevators sometimes employ positive operation door contacts to communicate when an elevator is in a proper position to allow opening of the elevator doors and/or the doors of the elevator lobby. In these contacts, a pair of pins is received in a pair of receptacles. If the pins are properly in position in the receptacles, an electrical signal travels from one pin to the second pin and the corresponding electrical signal communicates that the elevator is in the proper position to allow operation of the doors. K. A. Schmersal GmbH &amp; Co. KG d/b/a Schmersal of Wuppertal, Germany provides positive-operation elevator contacts of the type described. 
     These pin/receptacle elevator contacts may not be as reliable when used in a railroad environment because parts of the pins may be exposed to the environment. Moisture, debris and other environmental conditions can cause part of the pins to corrode such that the electrical signal is impeded from traveling from one pin to the other. Although, this is a fail-safe type of failure mode in that breaking the electrical path with corrosion causes the system to interpret the elevator out of position and therefore not allow the doors to operate, it is still inconvenient, inefficient, and costly to investigate, repair, and/or replace the positive door contacts such that the system functions normally. 
     What is needed is a positive electrical contact system that has increased reliability when used in a railroad environment because it is protected from moisture and corrosion. 
     SUMMARY 
     A sealed electrical contact system includes at least one male electrical contact with at least one annular flange and a male conductive contact. At least one female electrical contact includes a receptacle and a female conductive contact disposed in the receptacle. The at least one annular flange is configured to contact an inner surface of the receptacle when the male conductive contact contacts the female conductive contact and closes a circuit. 
     According to one embodiment, a pair of male electrical contacts are secured to a trailing edge of a door, and a pair of female electrical contacts are secured to a door jamb. The door may rotate on an offset pivot. When the door is closed, the male electrical contact is received in the female electrical contact and respective conductive contacts are electrically coupled with each other and a circuit is closed. The female electrical contacts may be disposed at each end of an open circuit, and the male electrical contacts are electrically coupled to each other. Closing the circuit sends a signal to a train control system that the door is closed and the train may be safely operated. The annular flanges create a seal with the inner surface of the female receptacle where the seal is analogous to a seal formed by a plunger and a barrel of a syringe. 
     Technical advantages of the sealed electrical contact system include a prong/receptacle type electrical contact system where the conductive portions are sealed with a water-tight seal that prevents water, debris, and corrosion from interfering with the electrical coupling of the prong/receptacle type electrical contact system, which would otherwise falsely signal that an emergency door of a platform screen door system is not fully closed, and thereby prevent normal operation of a train. 
     Other technical advantages will be readily apparent to one of ordinary skill in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
         FIG. 1  is a perspective view of an environment including a sealed electrical contact system according to an embodiment of the present disclosure; 
         FIG. 2A  is a partial section view of the sealed electrical contact system of  FIG. 1  illustrating an open circuit; 
         FIG. 2B  is a partial section view of the sealed electrical contact system of  FIG. 2A  illustrating a closed circuit; 
         FIG. 3A  is a partial section view of an alternate embodiment of a sealed electrical contact system according to the teachings of the present disclosure illustrating an open circuit; and 
         FIG. 3B  is a partial section view of the electrical contact system of  FIG. 3A  illustrating a closed circuit. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental view of a sealed electrical contact system  10  where the electrical contacts are not in electrical communication which each other so the details of the respective contacts can be shown. The sealed electrical contact system  10  according to the teachings of the present disclosure is suitable for any male/female electrical contact that completes a circuit or otherwise communicates a signal. For example, the sealed electrical contact system  10  may indicate positioning of doors (i.e. whether the door is open or fully closed), such as elevator doors, sliding doors, swinging doors, and the like. The sealed electrical contact system  10  may also be used to sense the positioning of an elevator car. 
     According to one embodiment, the sealed electrical contact system  10  may be employed on a platform screen door. More specifically, the sealed electrical contact system  10  may be employed on an emergency swinging door of a platform screen door system. The seal created by the electrical contacts may be water tight to prevent corrosion and other debris from interfering with the electrical connection and falsely indicating that the swinging doors are open. This sealing function may be particularly beneficial in a railway environment where moisture, debris, and other unwanted material are virtually unavoidable. 
     The sealed electrical contact system  10  includes a pair of male electrical contacts  12  and a pair of female electrical contacts  14 . A first male electrical contact  12   a  is electrically connected to a second male electrical contact  12   b  by any suitable electrically conductive means, such as a conductive wire  16 . Each of the female electrical contacts  14   a  and  14   b  are ends of an open circuit, and therefore each is connected to a respective conductive wire  18  that runs within (and/or along) a door jamb  20 . In certain embodiments, the conductive wires  18  are electrically coupled to a railroad control system (not illustrated). Thus, when the pair of male electrical contacts  12  are electrically coupled to the pair of female electrical contacts  14 , the circuit is closed and the railroad control system receives a signal that is interpreted as indicating that an emergency swinging door  22  of the platform screen door system is closed and it is safe to operate the train, provided all other safety signals indicate the train may be safely operated, for example the signal indicating that the sliding door, which is the primary entrance and exit from the train car, is fully closed. 
     According to certain embodiments, the male electrical contacts  12  may be secured to either the door  22  or the door jamb  20 , and the female electrical contacts are secured to either the door  22  or the door jamb  20 , whichever the male electrical contacts are not secured to. The male/female electrical contacts  12 ,  14  may be secured to either the leading side or the trailing side of the door  22  and the corresponding leading or trailing side of the door jamb  20 .  FIG. 1  illustrates the male electrical contacts  12  secured to a trailing side of the door  22  proximate a hinge  23  and the female electrical contacts  14  secured to a door jamb  20 . The door  22  may include an offset pivot to facilitate more direct insertion of the male electrical contact  12  into the female electrical contact  14 . Other embodiments contemplate any combination of male/female electrical contacts. For example, the door  22  may include one male and one female electrical contact and the door jamb  20  may include one male and one female electrical contact, provided that when all of the electrical contacts (male/female) are in electrical communication with each other, a circuit is closed. And, when one of the four electrical contacts is not in electrical communication with the others, then the circuit is open and the door  22  is indicated as not fully closed. 
     The female electrical contacts  14  each include a receptacle  24 . The receptacle  24  is generally frustoconically-shaped and hollow with an open distal end. In certain embodiments, the receptacle  24  may be formed of a substantially rigid polymer material and may generally be a thin-walled part. The receptacle  24  may be formed using any suitable polymer forming process, such as injection molding. 
       FIG. 2A  is a section view of the sealed electrical contact system  10  showing an open circuit, and  FIG. 2B  is a section view of the sealed electrical contact system  10  showing a closed circuit. Each male electrical contact  12  includes a conductive contact  26 , typically formed of metal, disposed at a distal end of the male electrical contact  12 . The conductive contact  26  is electrically coupled to the wire  16 , which connects to the other conductive contact  26 . The wire  16  runs through a cone portion  28  of the male electrical contact  12 . The cone portion  28  supports at least one and preferably a plurality of annular flanges  30 , where each annular flange  30  surrounds, the cone portion  28 . The cone portion  28  may be a generally rigid, thin walled part formed of a suitable polymer material, similar to the receptacle  24 . According to an alternate embodiment, the cone portion  28  may be omitted and the annular flanges  30  may surround the wire  16 . The annular flanges  30  are formed of a resilient material, such as natural or synthetic rubber. This disclosure is not limited to conically-shaped electrical contacts, but rather contemplates electrical contacts of any suitable shape provided a prong-shaped portion is inserted into a receptacle. For example, the male electrical contact  12  may be generally cylindrical and be inserted into a generally cylindrical, hollow female receptacle.  24 . 
     When the male electrical contacts  12  are inserted into the female electrical contacts  14  such that the circuit is closed, as illustrated in  FIG. 2B , the annular flanges  30  contact an inner surface  32  of the receptacle  24  and form a seal. The annular flanges  30  are elastically deformed by the contact with the inner surface  32  of the receptacle  24  and the resilient material of the flanges  30  opposes this elastic deformation, such that a seal is formed between the annular flanges  30  and the inner surface  32  of the rigid receptacle  24 . The seal formed is analogous to a seal formed in a syringe between the barrel and the plunger. According to certain embodiments, a diameter of the annular flanges  30  may increase from a smallest diameter proximate the conductive contact  26  to a largest diameter furthest from the conductive contact  26 . 
     Each of the female electrical contacts  14  include a conductive contact  34 , and each of these conductive contacts  34  may be coupled to a biasing element  36 . The biasing element  36  may be a single piece of resilient material, such as rubber or a closed-cell foam. According to an alternate embodiment, the biasing element may be a coil spring. The biasing element  36  biases the female conductive contact  34  toward the male conductive contact  26 . In this manner, manufacturing tolerances and shifting structures are accommodated. In addition, the biasing element  36  allows electrical contact and a closed circuit condition to be maintained even under vibrating conditions associated with train movement. The biasing element  36  also allows an electrical connection to be made if the male electrical contact  12  is less than fully inserted into the female electrical contact  14 . 
       FIG. 3A  is a section view of an alternate embodiment of a sealed electrical contact system  40  showing an open circuit, and  FIG. 3B  is a section view of the sealed electrical contact system  40  showing a closed circuit. The electrical contact system  40  includes a pair of receptacles  42  that may be recessed into a door or a door jamb  44 . The receptacles  42  receive a pair of male electrical contacts  46  to close the circuit and indicate a properly closed emergency swing door, and thus a safe condition for train operation. The pair of male electrical contacts  46  is secured to either a door  48  or the door jamb  44 , as discussed above with the embodiment shown in  FIGS. 1-2B . The male electrical contacts  46  include cone portion  50  that supports a plurality of annular flanges  52 . The annular flanges  52  are formed of a resilient material, and when the annular flanges  52  are elastically deformed by the inner surface  54  of the receptacle  42 , a water-tight seal is created, as described above with respect to sealed electrical contact system  10 , and the male and female conductive contacts  56 ,  60  are protected from debris and corrosion. 
     The male conductive contact  56  is disposed on an outer conical surface of the conical portion  50 . Similarly, the female conductive contact  60  is disposed on an inner conical surface of the receptacle  42 . In this manner, less than full insertion of the male electrical contact  46  into the receptacle  42  of the female electrical contact will still electrically couple the contacts  56 ,  60  and close the circuit. In addition, positioning the male and female electrical contacts  56 ,  60  on respective conical surfaces allows electrical contact to be maintained even under vibrating conditions associated with train movement or shifting structural members. 
     Although preferred embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.