Abstract:
An example apparatus includes a terminal block couplable to an electronics cabinet or mounting rail. The terminal block defines a first receptacle to receive a first circuit and a second receptacle to receive a second circuit. The terminal block includes an integral relay. The integral relay includes a first contact and a second contact. The first and second contacts are externally accessible relative to the terminal block. The integral relay further includes a first switch and a second switch. The first and second switches are electrically coupled between the first and second contacts. The first and second switches are respectively movable between corresponding open and closed positions. The first and second switches are independently testable to verify the respective operability of the first switch and the second switch.

Description:
RELATED APPLICATION 
     This patent arises from and claims priority to U.S. Provisional Patent Application No. 61/710,290, filed Oct. 5, 2012, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to terminal blocks and, more particularly, to terminal blocks including integral safety relays having independently testable contacts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an example termination module and first and second control circuits in accordance with the teachings of this disclosure. 
         FIGS. 2-4  depict different views of an example termination module in accordance with the teachings of this disclosure. 
         FIG. 5  depicts an example termination module and first and second I/O Cards in accordance with the teachings of this disclosure. 
         FIG. 6  depicts an example termination module and first and second control circuits in accordance with the teachings of this disclosure. 
         FIGS. 7-9  depict different views of an example termination module in accordance with the teachings of this disclosure. 
         FIG. 10  depicts an example termination module and first and second I/O Cards in accordance with the teachings of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain examples are shown above in the identified figures and described below in detail. In describing these examples, like or identical reference numbers are used to identify the same or similar elements. The figures are not necessarily to scale. Certain features and views of the figures may be exaggerated in scale or may be in schematic form for clarity or conciseness. Additionally, several examples have been described throughout this specification. Any features from any example may replace, be included with, or otherwise combined with other features from other examples. 
     Some safety instrumented systems may include safety relays, which may require a relatively high degree of diagnostic coverage and fault tolerance. For example, a hardware device fault tolerance of one implies that one component of the device could fail and the function would still be performed by the device. From these requirements, safety relays have been developed that provide multiple switching elements to break an electrical path between, for example, a power source or other signal source and a field device. Generally, these safety relays use multiple force-guided relays that have mechanically linked relay contacts. As a result, the relay contacts move together when one or more relay coils are energized or de-energized. 
     In some examples, a de-energize-to-fail circuit may include two relay contacts electrically coupled in series. In such examples, either of the relays may break the electrical path to a field device (e.g., a field actuator) to remove its power. In other examples (energize to actuate), two relays have coils electrically coupled in parallel such that when power is removed, both relays close. 
     The examples disclosed herein relate to terminations, termination modules and/or blocks including integral relays having independently testable contacts. In some examples, the example termination blocks include integral relays associated with a de-energize-to-fail circuit. In some such examples, the coils are powered from the same source and the relay contacts are electrically coupled in series. To enable a user to test the operability of the relay contacts during a proof test, in some examples, the example termination block includes a test point. To perform a proof test, a user may measure the resistance across the contacts (e.g., the voltage should be zero) and then actuate the relays and measure the voltage between the test point and the first and/or second relay contacts to verify that the contacts associated with the coil are not welded or otherwise unable to break an electrical path. 
     In other examples, the example termination blocks include integral relays associated with an energize-to-actuate circuit. Is some such examples, the coils are individually actuated and the relay contacts are electrically positioned in parallel. To perform a proof test, a user may measure the voltage across the contacts (e.g., the voltage should be non-zero) and then actuate the relays and measure the voltage between the relay contacts (e.g., field termination points) in sequence to verify that the contact associated with the coil is not welded or otherwise unable to break an electrical path. 
       FIG. 1  depicts an example termination module  100  and first and second control circuits  102 ,  104  coupled thereto. The termination module  100  and/or the control circuits  102 ,  104  may be coupled between one or more field devices and one or more controllers. In some examples, the termination module  100  protects the control circuits  102 ,  104  from, for example, a power surge. In some examples, the control circuits  102 ,  104  are I/O cards (e.g., CHARM I/O Cards of Emerson Process Systems) that translate information received from the field devices to a format compatible with the controllers and translate information from the controllers to a format compatible with the field devices. 
     In this example, the termination module  100  includes an integral relay module  106  and a fuse  107 . The relay module  106  includes first and second switches  108 ,  110  electrically coupled in series. In some examples, the switches  108  and  110  may respond to signals from coils and/or inductors  112 ,  114  to simultaneously open and/or close. In other examples, the switches  108  and  110  may not simultaneously open and, instead, may open and close independently. 
     The relay module  106  may be coupled to the control circuits  102 ,  104  to control the conveyance of power and/or other signals to the control circuits  102 ,  104 . Thus, in operation, the relay module  106  may be used to apply power to the control circuits  102 ,  104 , remove power from the control circuits  102 ,  104  and/or apply or remove any other signal(s) from the control circuits  102 ,  104 . 
     To enable the relay module  106  to be proof tested to ensure that the switches  108 ,  110  are operational and not welded, for example, the example relay module  106  includes a test point and/or area  116 . To perform the proof test, a user may measure the voltage between a first contact  118  and the test point  116  with the first switch  108  in the open and closed states and then measure the voltage between a second contact  120  and the test point  116  with the second switch  110  in the open and closed states. If the switches  108 ,  110  are operating properly, no voltage will be measured when the respective switches  108 ,  110  are closed and voltage will be measured when the respective switches  108 ,  110  are open. 
       FIGS. 2-4  depict different views of an example termination module  200  that can be used to implement the examples disclosed herein. The termination module  200  includes a fuse receptacle and/or aperture  201  and an integral relay module  202  with testable contacts  204 ,  206 , a test point  208  and switches  210 ,  212  in series. To enable the termination module  200  to be coupled to and/or receive the control circuits, the termination module  200  defines first and second receptacles  302 ,  304  ( FIG. 3 ). The termination module  200  further includes first and second latches  306 ,  308 . The first latch  306  is movable between a first position that enables a first control circuit to be secured within the first receptacle  302  and a second position that enables the first control circuit to be removed from the first receptacle  302 . The second latch  308  is movable between a first position that enables a second control circuit to be secured within the second receptacle  304  and a second position that enables the second control circuit to be removed from the second receptacle  304 . 
       FIG. 5  depicts an example termination module  500  and first and second control circuits and/or I/O cards  502 ,  504  coupled thereto via a baseplate  506 . The termination module  500  and/or the control circuits  502 ,  504  may be coupled between one or more field devices and one or more controllers. In some examples, the control circuits  502 ,  504  are I/O cards (e.g., CHARM I/O Cards of Emerson Process Systems) that translate information received from the field devices to a format compatible with the controllers and translate information from the controllers to a format compatible with the field devices. One or more of the control circuits  502 ,  504  may include current limiting circuitry and/or channel readback circuitry. 
     In this example, the termination module  500  includes an integral relay module  507  including first and second termination screws  508 ,  510 , switches  512 ,  514 , coils and/or inductors  516 ,  518 , a test point  520  and a fuse  522 . The relay module  507  may be coupled to the control circuits  502 ,  504  to control the conveyance of power from a power source  524  and/or other signals to the control circuits  502 ,  504  and/or a solenoid  526 . Thus, in operation, the relay module  507  may be used to apply power to the control circuits  502 ,  504  and/or the solenoid  526 , remove power from the control circuits  502 ,  504  and/or the solenoid  526  and/or apply or remove any other signal(s) from the control circuits  502 ,  504  and/or the solenoid  526 . While  FIG. 5  includes the solenoid  526 , the solenoid may be any other device such as a relay, a motor, a horn, a buzzer, etc. 
       FIG. 6  depicts an example termination module  600  and first and second control circuits  602 ,  604  coupled thereto. The termination module  600  and/or the control circuits  602 ,  604  may be coupled between one or more field devices and one or more controllers. In some examples, the termination module  600  protects the control circuits  602 ,  604  from, for example, a power surge. In some examples, the control circuits  602 ,  604  may be I/O cards (e.g., CHARM I/O Cards of Emerson Process Systems) that translate information received from the field devices to a format compatible with the controllers and translate information from the controllers to a format compatible with the field devices. 
     In this example, the termination module  600  includes an integral relay module  606  and a fuse  608 . The relay module  606  includes first and second switches  610 ,  612  electrically coupled in parallel that may respond to signals from coils  614 ,  616  to close. In some examples, the switches  610  and  612  may open and/or close independently at different times. However, in other examples, the switches  610  and  612  may open simultaneously. 
     The relay module  606  may be coupled to the control circuits  602 ,  604  to control the conveyance of power and/or other signals to the control circuits  602 ,  604 . Thus, in operation, the relay module  606  may be used to apply power to the control circuits  602 ,  604 , remove power from the control circuits  602 ,  604  and/or apply or remove any other signal(s) from the control circuits  602 ,  604 . 
     To proof test the relay module  606  to ensure that the switches  610 ,  612  are operational and not welded, fused, or otherwise unable to break an electrical path, for example, a user may open both switches  610 ,  612  and measure the voltage between first and second contacts  618 ,  620 . The voltage between first and second contacts  618 ,  620  is measured with the second switch  612  open and the first switch  610  closed. The voltage between first and second contacts  618 ,  620  is measured with the first switch  610  open and the second switch  612  closed. If the switches  610 ,  612  are operating properly, no voltage will be measured when one or both of the switches  610 ,  612  are closed and voltage will be measured when the switches  108 ,  110  are open. 
       FIGS. 7-9  depict different views of an example termination module  700  that can be used to implement the examples disclosed herein. The termination module  700  includes a fuse receptacle and/or aperture  701  and an integral relay module  702  with testable contacts and/or termination screws  704 ,  706  and switches  708 ,  710  electrically coupled in parallel. To enable the termination module  700  to be coupled to and/or receive the control circuits, the termination module  700  defines first and second receptacles  802 ,  804 . The termination module  700  further includes first and second latches  806 ,  808 . The first latch  806  is movable between a first position that enables a first control circuit to be secured within the first receptacle  802  and a second position that enables the first control circuit to be removed from the first receptacle  802 . The second latch  808  is movable between a first position that enables a second control circuit to be secured within the second receptacle  804  and a second position that enables the second control circuit to be removed from the second receptacle  804 . 
       FIG. 10  depicts an example termination module  1000  and first and second control circuits and/or I/O cards  1002 ,  1004  coupled thereto via a baseplate  1006 . The termination module  1000  and/or the control circuits  1002 ,  1004  may be coupled between one or more field devices and one or more controllers. In some examples, the control circuits  1002 ,  1004  may be I/O cards (e.g., CHARM I/O Cards of Emerson Process Systems) that translate information received from the field devices to a format compatible with the controllers and translate information from the controllers to a format compatible with the field devices. One or more of the control circuits  1002 ,  1004  may include current limiting circuitry and/or channel readback circuitry. 
     In this example, the termination module  1000  includes an integral relay module  1007  including first and second termination screws  1008 ,  1010 , switches  1012 ,  1014 , coils and/or inductors  1016 ,  1018  and a fuse  1020 . The relay module  1007  may be coupled to the control circuits  1002 ,  1004  to control the conveyance of power from a power source  1022  and/or other signals to the control circuits  1002 ,  1004  and/or a solenoid  1024 . Thus, in operation, the relay module  1007  may be used to apply power to the control circuits  1002 ,  1004  and/or the solenoid  1024 , remove power from the control circuits  1002 ,  1004  and/or the solenoid  1024  and/or apply or remove any other signal(s) from the control circuits  1002 ,  1004  and/or the solenoid  1024 . While  FIG. 10  includes the solenoid  1024 , the solenoid may be any other device such as a relay, a motor, a horn, a buzzer, etc. 
     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.