Abstract:
A testing interface provides rapid, temporary connections to individual signal relays used in railroad signal systems when testing is required, and otherwise permits normal operation of railroad signal vital circuits through its connections. A connectivity block provides contacts that are used to isolate the relay from its application circuit and provide connectivity to the relay coils for testing when a connection paddle is inserted into the block. The interface allows fully automated or manual testing of installed relays without requiring removal from the relay rack.

Description:
[0001]    This invention relates to an improved method and apparatus for connecting the signal relays used in railroad signal systems to test equipment for periodic testing and, in particular, to a testing interface that permits normal operation of vital circuits through its connections, rapidly temporarily disconnects a relay under test from its application circuit without requiring physical removal of the relay, and during testing both isolates the relay from its application circuit and establishes connections to automatic or manual test equipment.  
         BACKGROUND OF THE INVENTION  
         [0002]    Railroad signal relays have been in use for 100 years or more. Many installations in use today have been in service for over sixty years. Typically, signal relays are installed in bungalows or field cases alongside the tracks. As these enclosures are neither heated nor air-conditioned, the relays are thus exposed to temperature extremes as well as vibration from passing trains. Therefore, rugged design is essential.  
           [0003]    Furthermore, safety and fail-safe operation concerns are of prime importance in the design and operation of railroad signaling systems. To meet the fail-safe requirements, most relays are of the gravity type, meaning that the armature falls to a de-energized position under the force of gravity when the coil is not energized. An energized coil overcomes the gravity force and picks up the armature. Both normally open and normally closed contacts are employed. Contacts are relatively massive due to current carrying requirements and exposure to current and voltage surges from lightning strikes and other transients.  
           [0004]    As part of the fail-safe design of vital circuits, many relays are normally in the energized, or picked, state. Any interruption of power in the coil circuit, whether due to power supply failure or a signal wire break, causes the relay to open. This results in a more restrictive and safer condition.  
           [0005]    Gravity relays are mounted in a particular orientation to work properly, and are typically designed as either shelf-mounted or rack-mounted. Shelf-mounted relays are usually mounted on shock mounts fastened to a shelf within a wayside bungalow. Connection wires with soldered or crimped ring terminals are bolted to studs on top of the relay. Shelf relays are individually installed along many shelves.  
           [0006]    Rack mounted relays are designed to interface with standard blocks mounted on a vertical frame in horizontal rows. Blocks come in different sizes depending upon relay type and relay manufacturer. A commonly used block system uses two size blocks. The B-1 block has a width of 2.5 inches while the B-2 block has a width of 5 inches. The mounting design and hardware for these blocks is identical, allowing them to be intermixed in rows according to the design requirements of the signaling system.  
           [0007]    Connections from the field wiring are made to the rear of the B-1 or B-2 blocks. Connections are either fastened to studs using ring terminals or inserted into slots using special crimped terminals with retaining clips. These terminals may be removed using a special tool and re-inserted into another connection slot as desired.  
           [0008]    A B-1 or B-2 type relay is mounted to the front of the B-1 or B-2 block. The mating surface of the relay has spring contacts that mate with the wiring terminals inserted in the slots from the rear. Two rods are used as guides for the relay during insertion. These rods are threaded on the ends and are further used to firmly retain the relay in place with knurled nuts and lock nuts. Other mounting and retention designs by other manufacturers perform the same functions using slightly different mechanisms.  
           [0009]    On the most commonly used relay block system, the coil connections are brought out to the front of the block below the relay. Two stud connections are provided. One connection (called the 1E post) provides the low side or DC return side of the circuit. The other connection (called the 3E post for B-1 relays and the 5E post for B-2 relays) provides the control signal or energizing side of the circuit. This connection is made through a special stud with a nonconductive shoulder that isolates a ring terminal placed around the shouldered stud from the stud itself. A barrel nut is screwed down over the stud to make contact with the ring terminal and thereby connect the control signal to the high side of the coil. The barrel nut may be opened (unscrewed) to disconnect the circuit from the relay for testing purposes without removing any wires, and is frequently used by maintenance personnel to drop a given relay.  
           [0010]    Although the barrel nut may be loosened to drop a particular relay, there is no easy way to test an individual relay in a rack. Due to the safety issues involved in railroad signaling, regulatory requirements dictate periodic testing of relays employed in vital signaling circuits. These tests are typically performed on a two-year cycle.  
           [0011]    Testing requires that a relay first have its coil saturated. The coil current is then slowly decreased until the relay drops. The current at which the drop occurs is recorded as the drop current. The current is further reduced to zero and then slowly increased until the relay picks up. This current is recorded as the pick current. Close observation of the armature is required to determine the drop and pick points. Careful and slow increase and decrease of the coil current is necessary in order to obtain accurate and repeatable readings of pick-up and drop-away currents.  
           [0012]    Prior art as practiced in some Union Switch and Signal relays incorporates a pair of test contacts on the front surface of the installed relay. These contacts are placed in series with the coil circuit and are normally closed to maintain a circuit through the coils. A test probe may be inserted that separates the contacts and opens the coil circuit. At the same time, conductive surfaces on each side of the test probe each make contact with one of the contacts. Two conductive leads from the probe provide the ability to connect test equipment to the circuit or to the coil as required. A separate connection must be made by another means to the low side of the coil (or DC return) to complete a test circuit through the relay coil.  
         SUMMARY OF THE INVENTION  
         [0013]    The testing interface of the present invention includes a connectivity block provided with contact assemblies that provide connections to external test equipment, and quickly and easily installs under the barrel nut on the 3E or 5E post. A connection paddle, having leads extending therefrom to the test equipment, is inserted into one or more contact assemblies in the block associated with a relay under test. The paddle may be instantly withdrawn when the test is complete, and inserted into the block installed on the next relay to be tested. Upon withdrawal of the paddle, the conductivity block reestablishes the circuit to the relay coil.  
           [0014]    Each connectivity block may be installed only for the duration of the test and then removed, since the labor time for installation is only a few seconds, typically 5 to 10 seconds. Alternatively, the connectivity blocks may be installed on the relays and then left in place permanently, further shortening test time when the two-year test cycle is repeated.  
           [0015]    The testing interface permits a better and more efficient test methodology by facilitating the utilization of a software-controlled system to perform the test measurements. A computer controlled ramp voltage (or current) is generated to drive the relay coil via the connection to the relay through the connection paddle and conductivity block. The voltage is carefully monitored during the ramp. As the armature picks or drops, it interacts magnetically with the coil and causes back electromotive forces (EMFs) that are detectable and measurable by the system. The electronic measurement system can therefore accurately and repeatedly detect the drop-away and pick-up points of the relay without the need to remove the relay from the rack.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a perspective view of the connectivity block of the present invention;  
         [0017]    [0017]FIG. 2 is a perspective view of another embodiment of the connectivity block of the present invention;  
         [0018]    [0018]FIG. 3 is a diagrammatic front elevational view of the connectivity block of FIG. 1;  
         [0019]    [0019]FIG. 4 is a diagrammatic rear elevational view of the connectivity block of FIG. 1;  
         [0020]    [0020]FIG. 5 is a diagrammatic side elevational view of the double contacts of the connectivity block, shown removed from the body of the block and somewhat reduced in scale as compared with FIGS. 3 and 4;  
         [0021]    [0021]FIG. 6 is a diagrammatic side elevational view of the single contact of the connectivity block, shown removed from the body of the block and on the same scale as FIG. 5;  
         [0022]    [0022]FIG. 7 is a diagrammatic top plan view of the connection paddle;  
         [0023]    [0023]FIG. 8 is a diagrammatic bottom plan view of the connection paddle;  
         [0024]    [0024]FIG. 9 is a diagrammatic front end view of the paddle prongs, the thickness of the conductive pads being enlarged for clarity;  
         [0025]    [0025]FIG. 10 is a diagrammatic partial front view of the paddle prongs engaged with the connectivity block contacts, parts being broken away and the body of the block removed for clarity;  
         [0026]    [0026]FIG. 11 is a diagrammatic partial side view of a paddle prong engaged with the double contacts of the connectivity block;  
         [0027]    [0027]FIG. 12 is a diagrammatic partial side view of a paddle prong engaged with the single contact of the connectivity block;  
         [0028]    [0028]FIG. 13 is a side elevational view of a connectivity block installed on a relay block;  
         [0029]    [0029]FIG. 14 is a front elevational view of FIG. 13;  
         [0030]    [0030]FIG. 15 is a circuit diagram of the paddle and connectivity block and an associated relay;  
         [0031]    [0031]FIG. 16 is an exploded perspective view of connectivity block and relay block posts of FIG. 13.  
     
    
     DETAILED DESCRIPTION  
       [0032]    Referring to FIGS. 1 and 3- 6 , a connectivity block  20  of the present invention includes a body  21  having two side-by-side slots  22  and  24  in the front surface  26  of body  21  that provide connectivity access to respective contact bracket assemblies  28  and  30  within the block  20 . The slots  22  and  24  extend in parallel through the body  21  from front to rear as is evident from a comparison of FIGS. 3 and 4. The body  21  is composed of an insulating material such as a durable, extruded plastic.  
         [0033]    The contact assembly  28  comprises a pair of generally L-shaped elements as seen in FIG. 5. As viewed, the upstanding portions thereof present a pair of spade lugs  32  and  34  separated by an insulation layer  36 . The other legs  33  and  35  extend into slot  24  from the rear (FIG. 4), the assembly  28  being secured to block body  21  by a screw  46  or other fastening means.  
         [0034]    Legs  33  and  35  are provided with spaced, redundant contacts  38  and  40 , respectively (see FIG. 10). Leg  33  is bifurcated to present a pair of resilient arms each carrying an associated contact  38 , the purpose of which is described below. The contacts  38  and  40  are low-resistance, high-current contacts that provide a reliable and safe connection for the vital circuit to which lugs  32  and  34  are connected in use.  
         [0035]    Connectivity block  20  also has a single spring contact bracket assembly  30  that is positioned within the narrower slot  22 . Assembly  30  is also of generally L-shaped configuration and presents a spade lug  42  projecting from the rear end of slot  22 , and a low-resistance, high-current contact  44  disposed within slot  22  for access from the front of block  20 . A screw  48  or other suitable fastening means secures assembly  30  to body  21 .  
         [0036]    Referring to FIGS.  7 - 12 , a test paddle or probe  50  is designed to be inserted into the two slots  22  and  24  and make connections to the contacts  38 ,  40 , and  44 . The head  51  of the paddle  50  may be fabricated from a nonconductive substrate material  52 , such as printed circuit board material for example, and shaped with a beveled leading edge  54  and a longitudinal slot  56  in the paddle  50 . The slot  56  in the paddle  50  essentially separates the paddle into two sections or prongs  58  and  60  that simultaneously insert into the two slots  22  and  24  respectively in the connectivity block  20 . As the paddle  50  is grasped by its handle  53  and inserted into connectivity block  20 , the beveled leading edge  54  separates the two pairs of contacts  38  and  40  of the contact assembly  28  and engages the contact  44  of the spring contact assembly  30 .  
         [0037]    Conductive surfaces  62 ,  64  and  66  on the paddle  50  make separate electrical contact with the internal contacts  44 ,  38  and  40  respectively. The wiping action of the insertion process ensures a good electrical connection between the conductive surfaces and the contacts. Wires  68 ,  70  and  72  in the paddle  50  extend through the handle  53  and connect to the contact surfaces  62 ,  64  and  66  respectively, and thus provide electrical connections to the relay (discussed hereinbelow).  
         [0038]    Referring to FIGS.  13 - 16 , in use the connectivity block  20  makes three connections through contacts  38 ,  40  and  44  to a relay  79  mounting block  80 , one each to the relay circuit  82 , the high side  84  of the relay coil  86 , and the low side  88  of the relay coil  86  (DC return or 1E post  90 ). The connections to the relay circuit  82  and the high side of the relay coil are made at the 3E (or 5E) post  92 . The barrel nut  94  on post  92  is first loosened using the standard railroad barrel nut tool. As the barrel nut  94  is loosened, the connection between the relay circuit  82  and the high side  84  of the relay coil  86  is opened (FIG. 15) as the barrel nut  94  is withdrawn from contact with the ring terminal component  95  of the terminal. A slot  96  (see FIGS. 3 and 4) presented by the insulated spade lugs  32 ,  34  is slightly wider than the diameter of the 3E stud  92 , and allows the lugs to slide up onto the 3E stud  92  and under the barrel nut  94 . The barrel nut  94  is then tightened to firmly secure the connectivity block  20  in place. This connects the top contacts  38  (as viewed in FIG. 5) to the barrel nut  94 , thereby establishing contact with the stud  92  and the high side of the relay coil  84 . The bottom contacts  40  are connected to the ring terminal component  95  and the relay circuit  82 . The slot  96  in the bottom contact lug  34  is wider than that in the upper contact lug  32  and designed so that it fits over the nonconductive shoulder washer  97  around the stud  92  and is prevented from contacting the 3E stud  92 .  
         [0039]    The third contact  44  in connectivity block  20  is located in slot  22  separated from the contacts  38  and  40 . In the B-1 connectivity block  20  implementation (FIG. 1), spade lug  42  is positioned under the hex nut  98  on the 1E post  90 , thereby connecting contact  44  with the low side  88  of the coil  86  and DC return.  
         [0040]    The 1E post  90  contact may be a spring terminal fashioned in such a way that the terminal hooks over the end of the 1E post  90 . When the barrel nut  94  on the 3E post  92  is tightened, it applies pressure to the entire block resulting in spring tension on the terminal  95  hooked over the 1E post, providing the electrical connection. This method would most likely be used when the connectivity block  20  is installed temporarily for testing, rather than permanently.  
         [0041]    Referring to FIG. 2, in an alternate implementation, such as for the B-2 relay block (not shown) where the 1E post is not located under the terminal, a short wire  100  connected to the spring contact  44  (FIG. 6) is used to connect to the 1E post. This wire  100  has a ring terminal  102 , which is placed under the 1 E post nut and tightened. Alternatively, a clip lead or other temporary connection may be used for those situations where the user does not intend to leave the connectivity block  20  in place.  
         [0042]    Alternate configurations for shelf relays utilize the same principles as the B2 relay block application for shelf relays with horizontal posts. For shelf relays with vertical posts, and adapter arm is utilized for the 3E connection to transition the vertical post to a horizontal connection. In all shelf relay applications, wires and ring terminal extend from the 1E terminal of the block to the negative side of the relay coil.  
         [0043]    Once the connectivity blocks are installed, the relay may be connected to the test equipment for test by the simple insertion of the paddle  50  on the test cable. This operation may be accomplished in one or two seconds, isolating the relay under test from the circuit and connecting it to the test equipment. When inserted as shown in FIGS.  10 - 12 , the paddle  50  opens the connection between the relay circuit (FIG. 15) and the high side of the relay coil  86  so that the relay is isolated from the circuit.  
         [0044]    Connections to the high side  92  and low side  90  of the relay coil  86  allow full testing of the relay disconnected from the circuit but not removed from the rack. Since all three connections are wired back to the test equipment from the paddle  50 , the connection from the relay circuit to the high side of the relay may be restored within the test equipment to allow train operation without requiring the removal of all the paddles. This feature is provided by the test equipment, however not without additional safety tests that are automatically run as the cables and paddles are first installed to ensure that all the cables have connectivity and that none of the wires are shorted to each other or to the ground.  
         [0045]    Once this safety test has been satisfied, a multi-pin connector at the test equipment that supports up to eight paddles connected to different relays may be removed from the test connection and placed on a normal connection. Wires within the normal connector reconnect the high side of the relay coil to the relay circuit and allow safe operation of trains with the test equipment paddles installed. In this manner, testing personnel may stop testing and release track time to the dispatcher. This allows a train to pass through the side under test without requiring the removal of the test equipment. When the train is clear and track time has been returned to the maintenance personnel, the multi-pin connectors are returned to the TEST connection and the testing resumed.  
         [0046]    When testing is finished, the paddles  50  are quickly removed and the relays are reconnected to the relay circuits by the contacts within the connectivity blocks  20 . Since no wires within the signaling circuit have been disconnected or removed, none have to be reconnected. There is no possibility of disarrangement or mis-wiring. Railroad safety rules require a complete test of the signaling system if more than one wire is removed at a time, opening the possibility of disarrangement when the wires are reconnected. Thus, the connectivity blocks  20  allows the isolation of as many as 64 or 128 relays for example from their circuits for thorough automatic testing without violating the wire disarrangement rule and requiring a retest of the signaling system.  
         [0047]    In addition to the test paddle  50  inserted in the connectivity block  20  to connect to the automatic test equipment, other paddles may be inserted into the block  20 . A paddle with three wires provides temporary access to the relay coil isolated from its circuit and allows an immediate manual test of the relay or measurement of the circuit input voltage. Trouble shooting of the signaling system often requires maintenance personnel to drop a relay by opening the barrel nut  94  to disconnect the relay from the circuit. This is typically done to a track relay, since dropping the track relay  79  indicates the presence of a train in the block and will activate the appropriate signals and safety locks. With the connectivity block  20  installed, a blank paddle  50  may be inserted into the connectivity block  20 . This paddle  50  separates the contacts of the sandwiched contacts  38  and  40  and isolates the relay from the circuit. Inserting and removing the paddle  50  is much simpler than loosening the barrel nut  94 . The task is accomplished in much less time and precludes the potential problems that might result if the barrel nut  94  is not retightened properly or not at all.  
         [0048]    It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and allowable equivalents thereof.