Abstract:
A connector cable assembly has first and second plugs wired to permit plugging into a first pair of electrical plugs with a pair of terminals in a first configuration to place the terminals of those plugs in parallel connection, and to permit plugging into a second pair of electrical plugs with a pair of terminals in a second configuration, to place the terminals of those plugs in series connection. In a commercial embodiment, such a cable assembly can be used to provide power to electrical devices such as gas valves connected to receive power in parallel from the first pair of electrical plugs, and to connect in series, safety switches connected to plugs with a pair of terminals in the second configuration. By using an adapter with specialized connections between two sets of terminals it is possible to use additional cable assemblies to connect in excess of two switches in series.

Description:
BACKGROUND 
     Two types of components are used in certain electrical systems. Two or more of a first type must be connected in parallel with each other. Two or more of a second type must be connected in series with each other. One such electrical system is that for controlling flow of gaseous fuel to a burner. An electronic controller provides the operating power to the various components of the burner control system. Burners, particularly larger ones, have a number of operating requirements for safety. For example, startup must proceed according to a prescribed series of steps involving combustion chamber purging and proving pilot flame. During normal combustion, it is important to constantly monitor the output of a flame detector. If flame is not present, then the flow of fuel to the combustion chamber must be immediately stopped to prevent dangerous accumulations of unburned fuel. 
     Because the potential for harm when fuel flows uncontrollably is so great, it is customary to have two valves in series flow relationship so if one fails in the open position, the other will still be closed to prevent flow of fuel to the combustion chamber. These valves typically have electrical operators or solenoids to open and close them, with the power for operating them provided by the controller. While the valves are in series flow relationship, their operators are in parallel electrical connection, so that the controller can provide operating power at a single source for simultaneously opening and closing them. 
     In operating a burner, a number of operating conditions must be present for safety. For the burner itself, proper fuel pressure, sufficient combustion air, and presence of flame are necessary. In a case where the burner is used to heat water or generate steam, other conditions must also be present, such as proper water temperature and water pressure. It is customary to sense many of these conditions with safety or limit switches that open if the condition is not within the preset range. All of these safety switches are connected in series to provide power to the controller or to provide power for the valve operators when all are sensing conditions within the preset limits. If any condition is outside its prescribed limit, the associated switch opens, removing power to the valve operators, and causing the fuel valves to close. For example high and low pressure sensor switches sense fuel pressure. If the fuel supply pressure is below the low-pressure limit setting or above the high-pressure limit setting, the associated switch opens. 
     Proper installation is a concern with these burner control systems. For example, if the safety switch for a particular condition is omitted or by-passed by mistake or is wired in parallel with another switch, the safety test is absent. Where a number of switches are present in a burner installation, it is relatively easy to miswire one or more switches and relatively difficult to detect the miswires. Accordingly, the fewer switches that must be individually wired by the installer the better. 
     Limiting the number of parts and wiring present in a burner installation saves cost. If it is possible to use identical parts for different purposes in an installation, returns to scale reduce cost of that part. Further, internal point-to-point wiring within a component of the system is time consuming and thus relatively expensive, so replacing this wiring with more standardized wiring reduces cost. 
     One way to accomplish this is by combining related safety switches and the fuel valve sets in a single package. First of all, this is less costly because a large number of a few identical devices can be made in a factory setting. Secondly, by combining many of these components in the same package, the space required is reduced. Space in many installations is limited, so by combining a number of required or common components in a single package, the installation process is simplified and less likely to have errors. We find that one particularly advantageous package combines fuel pressure safety switches and two fuel valves with their operators. We will call a package containing both a pair of pressure safety switches mounted to sense out of range inlet fuel pressure and a pair of fuel valves in series, each with their own operator, a fuel control module. 
     BRIEF DESCRIPTION OF THE INVENTION 
     We have developed a universal cable assembly that can be used either for connecting components in serial or parallel. This cable assembly has particular advantage for wiring or connecting fuel control modules. Such a cable assembly comprises a (usually) flexible cable with first and second ends, and having at least first and second internal conductors insulated from each other. A first connector plug is mechanically attached to the first end of the cable. The connector plug has at least first, second, and third terminals. By “terminal” we mean a conductive element designed to make electrical contact with another conductive element carried on a separate connector plug, and which may be but not necessarily is, electrically connected to a conductor in the cable. The first plug&#39;s first and third terminals are electrically connected with each other and with the first conductor. The first plug&#39;s second terminal is electrically connected with the second conductor. 
     A second connector plug is mechanically attached to the second end of the cable and also has at least first, second, and third terminals. The first terminal is electrically connected to the first conductor, and the second terminal is electrically connected to the second conductor. A third terminal is not connected to either conductor. 
     A cable assembly conforming to nothing more than this broad statement of the invention has little use. In a preferred embodiment, each of the first and second plugs includes first through third slots, for respectively receiving first through third connecting pins and within each of which is respectively the first through third terminal. The terminals within the slots are shaped and positioned to make electrical contact with the connecting pin within the slot. Further, this preferred cable assembly has for each of the second plug&#39;s terminals, a projecting connecting pin. Since usually these components will be assembled in a factory environment, the likelihood of proper connection from the component terminals to the plug terminals is quite high. 
     The slots in the two plugs and the connecting pins of the second plug should all have what we call “predetermined polarized geometry”. By this we mean that all of the pins in the second plug will simultaneously mate with their respective slots of either plug in only one orientation of the pins with respect to the slots and while mated, make electrical connection with the terminals within the slots, first pin in first slot, second pin in second slot, etc. Such a cable assembly can be used either to connect in series two safety switches each having two connecting pins mounted to match the predetermined polarized geometry, or to connect two valve operators in parallel, each operator having two connecting pins mounted to match the predetermined polarized geometry. 
     The design makes it irrelevant which plug of the assembly is connected to a particular one of the switches or the operators, and which to the other. Of course, the switches and the operators must be properly connected to their connector pin sets for the proper connection of the individual components to each other, and to the controller. 
     In one embodiment of the invention, the connecting pins of each of the safety switches must connect to the second and third terminals of each plug. 
     By using a special adapter, two or more of these cable assemblies can be used to connect more than two devices in series. Such an adapter comprises a plug having a first surface having therein first through third slots having a predetermined polarized geometry. The respective one of first through third conductive pins may be inserted into each of these slots. A first terminal is mounted in the first slot to make electrical contact with an inserted connecting pin. A third terminal is mounted in the third slot to make electrical contact with an inserted connecting pin. A second surface of the adapter has at least second and third conductive pins projecting therefrom and has the predetermined polarized geometry of the second and third slots. The second pin is electrically connected to the first terminal and said third pin is electrically connected to the third terminal. This arrangement creates the situation where the two devices connected in series by the first cable assembly appear across the adapter&#39;s second and third pins as a single two-terminal switch or other device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective drawing of a universal cable assembly comprising the invention. 
     FIG. 2 is an elevation view of a first side of the cable assembly. 
     FIG. 3 is an elevation view of a second side, opposite to the first side, of the cable assembly. 
     FIG. 4 is a wiring diagram of the cable assembly connecting a pair of valve operators in parallel. 
     FIG. 5 is a wiring diagram of the cable assembly connecting a pair of safety switches in series. 
     FIG. 6 is a perspective drawing of two universal cable assemblies similar to that of FIG. 1, and an adapter block for allowing three switches to be placed in series connection using these universal cable assemblies. 
     FIG. 7 is a wiring diagram of a part of a universal cable assembly and the adapter block. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning first to FIGS. 1-3, the universal cable assembly  10  is shown with a first plug  20  and a second plug  30  electrically and mechanically connected by a short length of flexible two or three-conductor cable  40 . One suitable type of plug for use as plugs  20  and  30  is that designated as DIN 43650. Plugs  20  and  30  shown are intended to replicate the 43650 and similar units. Plug  20  has first through third slots or sockets  13 ,  14 , and  15  (sharing the  1 ,  2 ,  3  labeling) on a surface  18  and arranged in a predetermined polarized geometry as defined above. The term “slot” is intended to include various shapes of sockets or apertures. Electrical contacts or terminals  13   a ,  14   a , and  15   a  are located within sockets  13 - 15  respectively to allow electrical contact with conductive pins entering the slots. This sort of arrangement of course has been well known for literally many decades-consider the ubiquitous wall plug for electrical power connection. 
     Plug  30  has three slots or sockets  23 ,  24 , and  25  on a surface  28  and preferably arranged in the same predetermined polarized geometry as are the slots or sockets  13 - 15 . Electrical slot contacts or terminals  23   a ,  24   a , and  25   a  are located within slots  23 - 25  respectively and are similar to terminals  13   a ,  14   a , and  15   a  to allow electrical contact with conductive pins entering these slots. 
     As shown in FIGS. 1 and 3, plug  30  also has conducting pin terminals  33 - 35  projecting from a surface  38  opposite surface  28 . Pin terminals  33 - 35  are electrically connected to slot terminals  23   a ,  24   a ,  25   a  respectively. It is best if pins  33 - 35  have the predetermined polarized geometry of slots  13 - 15  and  23 - 25 . That is, the projective pattern or footprint of pin terminals  33 - 35  as shown in FIGS. 1 and 3 preferably matches the pattern of the slots  13 - 15  or  23 - 25 , and in only one angular orientation where all of the pins  33 - 35  are mated or aligned with corresponding slots. This allows pin terminals  33 - 35 , or a set of pin terminals that are identical, to enter a set of slots similar to those at  13 - 15  and  23 - 25 . While slots and pins are far and away the most common and desirable types of terminals, other types of terminals such as surface conductive patches are not excluded by this disclosure. 
     First and second conductors  42  and  43  in cable  40  electrically connect terminals in plug  20  to slot and pin terminals in plug  30 . First conductor  42  is electrically connected to terminal  23   a  of plug  30  and to both terminals  13   a  and  15   a  in plug  20 . A jumper  44  within plug  20  connects terminals  15   a  and  13   a . Presence of jumper  44  allows for the alternative serial and parallel connection using the same cable assembly  10 . Second conductor  43  is electrically connected to terminal  24   a  of plug  30  and to terminal  14   a  in plug  20 . 
     One non-essential alternative is the ground terminal  4   16   a  in plug  20  and ground terminal  4   26   a  in plug  30 . Terminals  16   a  and  26   a  are mounted within slots  16  and  26  respectively to make contact with connector pins, and are electrically connected to each other by a third conductor  46  in cable  40  shown as a dashed line in FIG.  2 . As a general observation, it may be convenient to mold all of the terminal, plug, and conductor components as a single unit for cost savings rather than as the separate components implied in the drawings. 
     FIG. 3 shows the cable assembly  10  of FIG. 2 with the surface  38  from which terminals  33 - 35  project, in elevation view. This view shows the predetermined polarized geometry for the pin set  33 - 35 , which also duplicates the geometry of the slot sets  13 - 15  and  23 - 25 . Of course, each set of slots and pins may use a unique geometry, but there is little reason to do so. 
     The circuit or wiring diagrams of FIGS. 4 and 5 show distinguishing features of the invention. As has already been explained, a connector cable incorporating this invention can be used to electrically connect two two-terminal system components having properly constructed connection pin sets in either series or in parallel irrespective of the plugs  20  and  30  making the connections to the components. In FIGS. 4 and 5 the schematic of the individual plugs  20  and  30  shows each pin terminal  33 - 35  as an inverted “V” or arrowhead representing a male terminal terminating the conductor connected to the corresponding slot terminal  13   a - 15   a  and  23   a - 25   a . Slot terminals  13   a - 15   a  and  23   a - 25   a  are also shown as inverted “V&#39;s”, but with the conductor involved exiting from the tip of the inverted “V” to thereby represent a female terminal. The numeric labels  1 - 3  on the terminals in FIGS. 4 and 5 track the labels in FIGS. 2 and 3. 
     In FIG. 4, the components to be connected in parallel to receive power are valve  1   50  and valve  2   51 . Two-terminal components to be connected in parallel with each other may be referred to as type A components. A controller and cable, not shown, supply power for both valves  50  and  51  to terminals ( 1  and  2 )  33  and  34  of cable assembly  10 . In this parallel configuration, terminals  3   15   a ,  25   a , and  35  are unused. Valves  50  and  51  must have pin terminals  53 - 54  and  56 - 57  arranged with the predetermined polarized geometry as pins  1  and  2  to fit in slots  13 - 14  and  23 - 24 . Of course a dummy pin  3  on either or both of valves  50  and  51 , to fit in slots  15  and  25  may be present. Connected as shown, pins  1   53  and  56  and pins  2   54  and  57  are electrically connected in parallel across pins  33  and  34 . The pins  33 - 34  can be used without regard to selection or orientation of such cable assemblies  10  to piggyback or daisy chain many valve operators using additional cable assemblies  10  identical as to terminal connections but perhaps of differing cable  40  lengths. 
     In FIG. 5, normally closed safety switches ( 1  and  2 )  60  and  61  are to be electrically connected in series across pin  1   33  and pin  3   35  of a cable assembly  10  identical to that of FIG.  4 . Such two-terminal components to be connected in series may be referred to as type B components. Switches  60  and  61  in this application are intended to sense insufficient pressure and excessive pressure in a fuel supply whose flow is to be regulated by valves  1  and  2   50  and  51 . If out-of-range pressure is detected by either one of the switches  60  and  61 , that switch opens, removing the electrical connection between pins  33  and  35 . Pins  33  and  35  are to be used to conduct power to a device such as a burner during normal conditions, and remove power from that device when either switch  60  or  61  detects an abnormality. Of course, many other conditions besides abnormal pressure may also be checked using such switches. In this use, terminals  1   13   a  and  23   a  and pin  34  are not used. 
     A problem that can arise with the use of assembly  10  is where more than two type B components are to be connected in series. In the context of a burner control system&#39;s valves and switches, certain applications may require more than two switches. For example, if the burner is used to heat water or make steam, testing for water pressure or temperature within preselected limits may be important. Such limit testing may require a string of more than two limit switches. We find that it is-useful to include more than two switches while still using additional cable assemblies  10 . 
     However, two or more cable assemblies  10  cannot be directly connected to achieve a series connection of more than two switches. We find that an adapter  70  shown in FIG. 6 can be devised that allows assemblies  10  to connect more than two switches (or other type B components) in series. Adapter  70  has a specific internal structure that allows daisy chaining of assemblies  10 . 
     FIG. 6 shows adapter  70  in exploded view positioned to form an interface between cable assemblies  10 ′ and  10 ″ thereby allowing connecting additional switches in series. Two switches are to be plugged into the slots of plugs  20 ″ and  30 ″ as is shown in FIG.  5 . A third switch is to be plugged into the slots of plug  30 ′. When so connected and with the pins  73 - 75  of adapter  70  plugged into the slots of plug  20 ′ and the pins of plug  30 ″ plugged into slots  83 - 85 , the three switches will be connected in series with each other, and across pins  1  and  3  of plug  30 ′. 
     An adapter  70  suitable for connecting cable assemblies for this purpose comprises a rectangular block  78  having on a first surface thereof a set of slots or sockets  83 - 85  whose geometry precisely matches the pins of plug  30 ″. Adapter  70  further includes a set of pins  73 - 75  whose geometry precisely matches the slots of plug  20 ′. 
     Internally, as shown in FIG. 7, adapter  70  has the connection between the slot  1   83  terminal and pin  1   73  broken. The connection between the slot  2   84  terminal and pin  2   74  within adapter  70  is also broken. The slot  1   83  terminal is internally connected to pin  2   74 . The slot  3   85  terminal is directly connected electrically to pin  3   75 . This wiring arrangement causes a cable assembly  10 ″ connecting two type B components, and into which an adaptor  70  is plugged as shown in FIG. 6, to appear to be a single switch whose pin terminals  2 - 3   74  and  75  can be connected by another cable assembly  10  to another single switch or other type B device. For this reason it is immaterial into which of the plugs  20 ′ or  30 ′ the adapter pins  1 - 3   73 - 75  are inserted. 
     As a result of these internal connections (or lack thereof), adapter  70  allows any desired number of switches or other devices to be daisy-chained in series connection. One adapter  70  and one cable assembly  10  is required for each additional switch to be daisy-chained in series connection. While the length of the cable  40 ′ connecting the two plugs of assembly  10 ′ can be of a standard short length as shown in FIG. 7, it can also be of any convenient greater length to accommodate type B components located at various places within the installation. 
     Some safety issues involved should be briefly discussed. If an adapter  70  is mistakenly included in a parallel connection of type A devices, the result is that some or all devices connected to receive power through such a misinstalled adapter  70  will not function because of the break in connectivity between terminal pairs  73  and  83 , and  74  and  84  in adapter  70 . No power intended to flow through pin  73  to terminal  83  can in fact do so, because pin  73  is not electrically connected to terminal  83  or any other conductor, nor is terminal  84  connected to any other conductor other than a pin  34  that might be plugged into it. This results in a safe failure when adapter  70  is misused, in that a fuel valve  50  or  51  cannot receive power when an adapter  70  is improperly included in the connection. Testing during installation should always reveal such a significant wiring error. 
     Similarly, if an adapter  70  were to be installed directly on the terminals of a switch  1   60  or switch  2   61  (FIG. 5) when connecting type B components in series, a safe condition also occurs. In this case, the open circuit between slot terminal  84  and every other terminal in adaptor  70  causes the connection to slot terminals  3   85  and  2   84  to appear as an open circuit. This is a safe failure with no power applied to the type B components attached to plugs  20  and  30 , and should also be corrected by a competent installer during the normal checkout that occurs at installation. 
     However, if in the daisy-chained series connection situation (FIG.  6 ), one cable assembly  10  is directly connected to another without adapter  70  interposed, the switch or other type B components connected to plugs  20 ″ and  30 ″ will be placed in parallel with each other. This parallel switch group will then be in series with the type B component plugged into plug  30 ′. Because of this possibility, we feel that it is wise to apply on every cable assembly  10 , a suitable warning label advising against omitting adapter  70  when daisy-chaining assemblies  10  in the series situation. In addition, a competent installer will check out every safety feature for proper function before completing the installation. 
     From one standpoint, the availability of an adaptor  70  provides added safety by implying that daisy-chaining two or more cable assemblies  10  for connecting type B components should only be done using adaptor  70 . That is, availability of an adaptor  70  for use in with type B components suggests that the procedure for daisy-chaining type B components differs from that of daisy-chaining type A components. Nevertheless, since type B components are often safety-related devices, it is well to provide adequate notice of the importance of including an adaptor  70  between each cable assembly  10  to be daisy-chained. 
     Accordingly, it is possible to safely use two or more of the universal cable assembly  10  along with an adapter  70  between each to daisy chain as many type B components as is desirable in series connection.