Abstract:
A multi-pole switch with a neutral position is provided with an efficient mechanical layout. Such switch is suitable for use in relay format in an automatic battery booster cable system to be used to connect a polarized source and a polarized load, eg. two batteries together in parallel, with automatically correct polarity. The relay switch in the booster cable application is driven by an electronic controller which senses the polarity of the two batteries and connects the two batteries with the correct polarity. The electronics provides features for setting the relay to neutral, thereby disconnecting the source from the load when any of the cables are disconnected, while maintaining current flow under high load conditions. The booster cable system also employs direct inter-connections between the cable conductors and the relay contacts thus simplifying the construction of the relay. The relay makes use of resilient polymeric elements instead of coiled springs to minimize relay re-bound.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a multi-pole format electrical switch. It further addresses an automatic polarity adjusting switching system. For example, it is useful for connecting batteries in parallel, as well as other applications. In particular, it relates to a switching arrangement forming an integral part of a booster cable which assembly enables the operator to connect the cables to two batteries in parallel without having to worry about finding the correct polarity. It can also be used wherever a heavy duty, electronically actuated, multi-pole, single or double-throw switch is required.  
       BACKGROUND OF THE INVENTION  
       [0002]     Using the booster cable situation as an example, it is desirable to provide an automatic switching system that can transfer high current of the correct polarity between two batteries with a minimum voltage drop. In order for correct polarity connections to be established, the system must determine the relative polarities of the two batteries and do so automatically. In the case of the discharged battery, its polarity may only be indicated by a very low voltage level. At the same time, the system must distinguish the case when the cables on the discharged battery side of the switch are not connected at all, i.e., are receiving a zero-level voltage input.  
         [0003]     Further, once the switch has been actuated to supply current to a discharged battery, the system should thereafter detect a disconnected condition and switch the charging-side cables to a “dead” condition. Otherwise, disconnected cables that have been activated, if they were to touch each other could cause a high current short.  
         [0004]     These and other issues have already been addressed by prior art in this field.  
         [0005]     In the previous art, several patents teach methods of automating the battery boosting process using as a supply source a supply battery to provide current to a discharged battery. These methods address the issue of providing a polarity adjusting switching system that ensures that the positive poles are connected to each other, and the negative poles are connected to each other to ensure that a parallel connection format is established.  
         [0006]     U.S. Pat. No. 4,400,658 by Yates is an example of an impractical automatic booster cable arrangement. An improvement was described in U.S. Pat. No. 5,103,155 and Canadian Pat. No. 2,056,645 by myself, which is an improvement over the Yates patent because it uses amplifiers to detect the voltage of the dead battery. In this way, the dead battery can have a very small voltage, down to approximately 0.03 volts and the system will still work. However, the mechanical aspect of the U.S. Pat. No. 5,103,155 patent as described has the disadvantage that it calls for coil spring elements which are liable to rebound when the solenoid is released and can momentarily connect the batteries the wrong way.  
         [0007]     Another pertinent patent is U.S. Pat. No. 6,262,494 to Shian-Fang Sheng, in which a more practical arrangement is described but which is more complicated, using four ordinary solenoids and a complex digital circuit to drive them. Another complication is that it calls for special cables which contain sensing wires inside the heavy current wires to enable the device to sense when the clamps are disconnected from the batteries in order to switch the system off.  
         [0008]     The present invention addresses a booster cable system which improves upon these prior art designs. It does so through use of a double-pole, double-throw switch of a novel structure.  
         [0009]     The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following thereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.  
       SUMMARY OF THE INVENTION  
       [0010]     The objects of this invention include providing both a multi-pole, single or double-throw automatic switch having a neutral position of novel design. As such it is readily adaptable to a double-pole, double-throw polarity reversing switch with a neutral position wherein the switching can either be mechanically operated or electrically activated by a solenoid. The switch according to the invention includes the features of: 
    a) employing simplified solenoid construction;     b) using resilient rubber instead of springs in the relay to avoid rebound of the contacts when the relay releases into its neutral position; and     c) using heavy duty conductors that are efficiently coupled to the switch in fixed, immobile orientations; 
 
 Further, this switch is ideally suited to a polarity reversing application such as an automatic booster cable system when combined with: 
    d) an electrical circuit which can sense the voltage and polarity of the dead, to-be-charged battery down to very low levels, and     e) an electrical circuit which can sense when not all of the cables are connected, and will correspondingly deactivate the relay, while ensuring that the circuit will deliver current continuously when all batteries are fully connected.    
 
         [0017]     More particularly, according to one aspect of the invention, a double or multi-pole, single or double-throw switch with a neutral position is provided wherein a solenoid-actuated construction is provided in the form of a series of fixed, parallel, contactor bars connected to heavy duty conductors and supported in a non-conductive frame. Such contactor bars are interspaced with shiftable contactors. The shiftable contactors are preferably generally washer-shaped and have central support openings for mounting, through such support openings, on an alignment shaft. The shiftable contactors are slideably positioned on the alignment shaft to effect contact with the contact bars in a “closed” configuration, or to be withdrawn into an “open” condition.  
         [0018]     In one variant the contactor bars and shiftable contactor are assembled in combinations that will constitute switch closures for either of the two conducting configurations of a multi-pole, double-throw switch. Additionally, the shiftable contactors may assume an intermediate, neutral position providing an “open” condition. Solenoids are preferably used to displace the shiftable contactors along the alignment shaft upon activation of at least one of the solenoids. Alternately, the switch may be mechanically activated by suitable drive means.  
         [0019]     Resilient polymeric spring means are preferably employed along the alignment shaft. These are installed towards the ends of the alignment shaft and between the shiftable contactors in the relay and the contactor bars. Their function is to cushion the closing of the switch and to bias the positioning of such shiftable contactors into a neutral position while avoiding or minimizing rebound of the shiftable contactors when, upon deactivation of the solenoids or mechanical activation, the relay returns into a neutral condition.  
         [0020]     According to a further aspect of the invention, the heavy duty conductors in a set of jumper cables are directly coupled to the fixed contactor bars of the switch. This connection is achieved without imposing any curvature on the conductors as they engage with such contactor bars, or even as they approach such contactor bars. Further, this connection and the cable conductors remain immobile during switching operation. The contactor bars are punched at one end to form an opening in such end into which the stripped cable ends are pressed and the extended ends of the opening are then squeezed onto the cable conductors to become crimped in place.  
         [0021]     According to a further feature of the invention in its booster cable application, an electrical circuit is provided which can sense the polarity of a heavily discharged battery down to very low voltage levels through the power cables. Thus the system has a sensing capacity which allows it to distinguish the polarity of a discharged battery that provides only a low level of voltage. This is achieved through use of a differential circuit which compares the voltage on the discharged battery to the voltage of the supply battery.  
         [0022]     According to a further feature of the invention an electrical circuit is provided which can sense, after an initial connection has occurred and the switch has been activated, whether one of the cables has become dis-connected. This is achieved by a circuit which momentarily deactivates the switch returning the discharge side cables to a “dead” condition. During the period of disconnection, the voltage sensing circuit “polls” for the presence of voltage, and if the voltage is not there the relay will stay in its neutral position.  
         [0023]     This polling circuit incorporates a pulse generator the output of which provides a positive test pulse with, for example, a 10 percent duty cycle and a suitable sampling frequency, conveniently in the range of 0.5 to 2 cycles per second. Each pulse disables activation of the solenoids for the duration of the pulse. This places the relay in a neutral position. If any of the clamps are at that time disconnected, then the relay will stay in its neutral position. This occurs because there will either be no voltage at the dead-battery side of the system, allowing the “connected” sensing circuitry to maintain an “open” condition; or the cables on the good battery or supply side power supply side will go to zero disabling the connection circuitry. In this manner the system remains switched OFF following a test pulse when any clamp is disconnected from a battery.  
         [0024]     As the last procedure leads to repeated opening and closing of the switch while the “connected” status of the cables is being polled, such repeated cycling can be wearing on the switch if the switch is carrying a high current. To avoid such wear, the system may include a sensing means which suspends the polling activity while the switch is carrying high current.  
         [0025]     The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIGS. 1   a ,  1   b  and  1   c  depict the double-pole, double-throw switch of the invention in its respective two connected and one neutral positions.  
         [0027]      FIG. 1   d  is a schematic drawing showing the electrical/electronic solenoid control circuitry of the system.  
         [0028]      FIG. 2  shows a cross section of the relay in its neutral position.  
         [0029]      FIG. 3  shows the reversing switch of  FIG. 2  displaced in one direction.  
         [0030]      FIG. 4  shows the reversing switch of  FIG. 2  displaced in the other direction.  
         [0031]      FIG. 5  shows a pictorial view of the reversing relay with the contactors crimped onto the cables to form the interconnections with the relay contacts.  
         [0032]      FIG. 5   a  shows a typical switch contactor which is formed with an opening to be fitted around the conductor core of a cable but before crimping.  
         [0033]      FIG. 5   b  shows a partial pictorial view of two electrode contact bars crimped to an exposed conductor core of the cable.  
         [0034]      FIG. 6  shows a pictorial view of a receptacle in which the cables can be fastened with the solenoids, alignment shaft and a printed circuit board arranged in the case.  
         [0035]      FIG. 7  shows the whole booster cable assembly wherein the cables to be connected to the good battery during boosting are shorter than the ones to be connected to the weak battery.  
         [0036]      FIG. 8  shows a complete case containing the booster cable system without the cables attached, wherein the cables can be attached to the system by available set-screws.  
         [0037]      FIG. 8   a  shows a detailed view of the attachment mechanism for the cables. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0038]      FIGS. 1   a ,  1   b  and  1   c  depict the layout of a preferred embodiment of the switch of the invention wherein fixed contactor bars  36  to  43  are contacted by moveable contactors  27 ,  29 . The solenoids Sol  1  and Sol  2  displace the shiftable contactors  27 ,  29  along the alignment shaft against the fixed contactor bars  36  to  43  to effect switch closures, cf  FIGS. 1   a ,  1   b . Resilient compressible sleeves  30 ,  35  ( FIG. 4 ) restore the shiftable contactors  27 ,  29  to a neutral “open” position ( FIG. 1   c ) when neither of the solenoids Sol  1 , Sol  2  are activated.  
         [0039]      FIGS. 3 and 4  show these sleeves in their two compressed conditions.  FIG. 3  shows the sleeves in a first compressed configuration occurring when Sol  1  is activated.  FIG. 4  shows a second compressed configuration that occurs when Sol  2  is activated.  
         [0040]     For the purpose of describing the operation of the control circuitry, we will describe the particular case in which the “load” presented at connectors  5 , 6  is a “weak” battery, and the “source” presented at connectors  1 ,  2  is a charging device, in particular a “strong” or “good” 12 volt battery (see  FIG. 1   d ).  
         [0041]     It should be appreciated that this is a particular example. DC devices of higher or lower voltages could be handled and the load and source may be other than batteries.  
         [0042]     Referring to the circuit diagram of  FIG. 1   d  clamps  1 , 2  are to be attached to the good battery, and clamps  5 ,  6  are to be attached to the weak battery to be charged. While reference is made to a “good battery” this supply-side power supply can be a generator or other equivalent power source. Rectifier diodes D 5  to D 8  provide the proper polarity to supply lines or “rails” 15+ and 16−, irrespective of the polarity of the terminals to which the battery clamps  1 ,  2  are connected. Supply lines 15+ and 16− provide battery voltage (example 12 volts) and current to the rest of the electronic driver circuits.  
         [0043]     The weak battery connected to clamps  5  and  6  provides a differential voltage to amplifier A 1  and to the voltage divider network Ra. While reference is made to a “weak battery” this is exemplary of any polarized load that presents a voltage that can be sensed. Amplifier A 1  provides a positive output or a negative output with respect to the voltage at point O, which has a potential of half the voltage between lines 15+ and 16− (e.g., 6 volts). Differential comparator A 2  has its positive input connected to a point between resistors  9  and  10 . Such input may be at a potential of about, for example, 9 volts. Differential comparator A 3  has its positive input connected between resistors  11  and  12  and maybe at a potential of, for example, 3 volts. The negative inputs of both comparators A 2 , A 3  are connect to the output of amplifier A 1 , which is at 6V potential when there is a zero input to A 1  from cables  7 ,  8 . This is the condition when there is no battery to be charged connected to clamps  5 ,  6 .  
         [0044]     All resistors  9 ,  10 ,  11  and  12  have equal values. Therefore, depending on the output voltage of A 1 , if it is positive and more than, for example, 9 volts, (the threshold value set between resistors  9 ,  10 ), A 2  and A 3  will output a negative output. This output will switch transistors T 3  and T 5  ON but nothing will then happen to T 4  and T 6 , which require a positive input to switch ON. If amplifier A 1  outputs a negative output, then A 2  and A 3  output a positive voltage, which will turn ON T 4  and T 6  without affecting T 3  and T 5 . Note that if A 1  outputs no voltage with respect to point O, or a voltage below, for example, 3 volts, then A 2  outputs a positive output and A 4  outputs a negative output. In this case, no power transistor is turned ON.  
         [0045]     Feedback resistor R 20  on amplifier A 1  controls the gain of this amplifier and therefore the sensitivity of the circuit as to the threshold level of voltage on the discharged battery below which the system will not operate to effect closing of the switch. Sufficient voltage must be present to establish the polarity of the battery and enable the switch to operate appropriately. Threshold values as low as 0.03 volts have been tested successfully.  
         [0046]     When T 3  and T 5  are turned ON, either solenoid Sol  1  or solenoid Sol  2  will operate, depending on the polarity at clamp  1  and clamp  2 . If clamp  2  is negative, only solenoid Sol  1  will operate and if clamp  1  is negative, only solenoid sol  2  will operate. Similarly, reversing the polarity at clamps  5  and  6  will cause T 4  and T 6  to turn ON and again, depending on the polarity at clamps  1  and  2 , the solenoid connected to the positive clamp will operate.  
         [0047]     The two solenoids Sol  1 , Sol  2  operate mechanical contacts which connect the two batteries correctly no matter what the polarity is at the clamps, based upon a double-pole, double-throw switching system.  
         [0048]     While solenoids Sol  1 , Sol  2  are shown, any form of “drive means” which will displace the shiftable contactors  27 ,  29  may be employed. This may include mechanical buttons or levers etc. that are manually operated  
         [0049]     Another aspect of the invention is the method by which the relay goes to neutral when any of the battery terminals are disconnected. In  FIG. 1   d , differential amplifier A 4  is connected as a pulse generator that produces produce a positive pulse with a duty cycle of about, for example, 10 percent at a convenient sampling rate. The output of A 4  is then coupled to the base of transistor T 1  to switch it ON 10 percent of the time. When T 1  is switched ON, the negative inputs of comparators A 2  and A 3  are connected to point Q of the circuit which is at 6 volt potential, the same value as point O. During this instant, the output of A 2  goes positive and the output of A 3  goes negative, which is the state of the circuit when the voltage between clamp  5  and clamp  6  is zero, i.e., disconnected. During this time, both solenoids are not operating, putting the relay in the neutral position. If any of the clamps are disconnected, the relay will then stay in its neutral position because either there will be no voltage at the dead battery side of the system, or the power supply lines will, through clamps  1 , 2 , be at zero. In this way the system switches OFF when any clamp is disconnected, without resorting to extra sensing wires embedded in the current carrying cables.  
         [0050]     In order to prevent heavy arcing during this 10 percent interruption, such as when the vehicle with the weak battery is trying to start its engine, a pulse suppression circuit may be built into the system that senses a high current flow through a drop of voltage at clamps  1 , 2  and prevents the pulse generator from pulsing. This allows the relay to stay ON continuously. This pulse suppression circuit may consist of zener diode D 9 , resistor  14 , transistor T 2 , resistor  13 , capacitor C, and diode D 4 . When the voltage between lines 15+ and 16− is 12 volts or greater, the voltage drop of the zener diode D 9 , which is at say 10 volts, leaves a voltage across resistor  14  sufficient enough to keep enough current in the base of T 2  to keep the transistor conducting. Then, since the voltage across the transistor is close to zero and diode D 4  is back-biased, this allows the pulse generator A 4  to pulse.  
         [0051]     When the voltage between line 15+ and 16− is lower than say 10 to 11 volts, for example, then transistor T 2 , does not have enough current in its base and it switches OFF. This causes resistor  13  to allow current to flow through diode D 4  (forward biasing it) and thus stopping A 4  from pulsing because capacitor C 1  is made to increase its voltage and cut-off oscilation.  
         [0052]      FIG. 2  shows diagrammatically the mechanical layout of the reversing relay, which is operated by the two solenoids Sol  1  and Sol  2  described above. The relay is shown in its neutral position in  FIG. 2 . Plungers  20 ,  21  are positioned within the respective solenoids. The plungers  20 ,  21  have an opening  22  where alignment shaft  23  is accommodated. Solenoids Sol  1  and Sol  2 , when respectively energized, attract plungers  20  and  21  which bear against sleeves  24   a  and  24   b  compressing resilient tubes  30  to  35 . Sleeves  24   a  and  24   b  are fixed on shaft  23  and carry alignment shaft  23  with them when they are displaced. Mandrel  26  slidingly supports a moveable contactor, e.g. copper washer  27 ; and mandrel  28  slidingly supports a second moveable contactor, e.g. copper washer  29 . Washers  25   a ,  25   b  and  25   c  are fixed along shaft  23  bounded and interspersed by resilient tubes  30 ,  31 ,  32 ,  33 ,  34  and  35  made of silicon rubber or a similar material of suitable resilience. Strips of copper serving as contactor bars  36  to  43  are crimped on the exposed portion of the conductors of cables  44  to  47 . Copper washers  27  and  29  and copper contactor strips  36  to  43  form the relay contacts. Copper is used as a preferred, low cost, highly conductive metal with good contact resistance. Silver, e.g. silver plated contacting surfaces may also be employed.  
         [0053]     The relay described in  FIG. 2  above is wired to provide a polarity reversing relay. (Also, refer to  FIG. 5  for a more detailed description of an alternate physical arrangement or layout for the relay). It operates as a double-throw, double-pole reversing switch. In  FIG. 2 , cables  44  and  45  are connected to the good battery optionally with polarity as shown. In its neutral position in  FIG. 2 , neither of the solenoids Sol  1 , Sol  2  are energized and copper washers  27 ,  29  do not contact any of the other copper strips or bars (electrodes)  36  to  43  and therefore cables  46  and  47  have no voltage across them.  
         [0054]      FIG. 3  shows the case where solenoid Sol  1  is energized. In this state plunger  20  is pulled into solenoid Sol  1  and pushes sleeve  24   a  against washer  25   a , which pushes against mandrel  26 , washer  25   b , mandrel  28 , and washer  25   c . Copper washers  27  and  29  are free to move along mandrels  26  and  28 . As a result, resilient tube  31  pushes against washer  27 , which, in turn, is squeezed against copper bars or contactor strips  37  and  41 . Similarly, resilient tube  33  squeezes washer  29  against copper bars or strips  39  and  43 . In this state, cable  44  makes connection to cable  46  and cable  45  makes connection to cable  47 . Insulator  48 , which need not be very thick, e.g., 0.01 inches of MYLAR™, is used to prevent strip  37  from touching strip  38 .  
         [0055]      FIG. 4  shows the case where solenoid Sol  2  is energized. In this case the above events are correspondingly reversed and cable  44  connects to cable  47  while cable  45  connects to cable  46 . Resilient tubes  30 ,  35  are seated on cap ends  59  on the respective solenoids SoL  1 , SoL  2 . In other words, the polarity of the connection to cables  46  and  47  is reversed. The function of resilient tubes  30  and  35  is to open the switch to a neutral state by centering washers  27  and  29  as in  FIGS. 1   c  and  2 , and such tubes,  30 ,  35  are dimensioned accordingly. The function of tubes  31  to  34  is to ensure that the shiftable contactors  27 ,  29  bear intimately against the contactor bars  36 - 43  with a low resistance contact.  
         [0056]     The reason resilient polymeric tubes  30  to  35  are used instead of coil springs is that resilient tubes, when deformed and released, have a reduced tendency to over-respond or bounce back compared to coiled springs. Further these tubes  30  to  35  may be made of a material, such as silicon rubber for instance, which does not significantly change its resiliency with temperature.  
         [0057]     In the operation of the relay, it is advantageous to minimize the total moving mass which the solenoids Sol  1 , Sol  2  displace. The smaller this mass is, the faster the relay operates and the more the rebound is minimized. To achieve lower mass, plungers  20 ,  21  are not fixed to shaft  23 , and openings  22  allow room for the alignment shaft  23  to move within the plungers  20 ,  21 . In this way, when any of the plungers  20 ,  21  are released, they do not carry the opposite plunger with it.  
         [0058]      FIG. 5  shows a convenient arrangement for effecting connections to the cables of the reversing relay. The four cables  44  to  47  connect to the copper bars or strips  36  to  43  which form the fixed relay contacts. These bars or contractors are shown as extending past the center line in  FIG. 5  (as opposed to  FIG. 4 ) as this is permissible due to the vertical offset. FIGS.  2  to  4  have been simplified for ease of presentation. Also the cable connections to bars  36  to  43  are repositioned in  FIG. 5  as opposed to  FIG. 4  for convenience of layout, but with the same electrical effects.  
         [0059]      FIG. 5   a  shows a typical copper contactor strip  49  prior to assembly. The strips are punched at one end to form an opening  49   c  into which the stripped conductors at the cable ends are pressed. The extended ends  49   a ,  49   b  of the openings  49   c  are then squeezed onto the cable conductors as shown in  FIG. 5   b . This crimping procedure makes it easy to assemble the relay. It also provides a direct connection between the conductors of cables  44  to  47  and the contactor strips  36 - 43 .  
         [0060]     Conveniently, these connections and the cables  44  to  47  do not move at any time during the operation of the relay. Further, the conductors lie straight, without curvature both between multiple contactor connections and approaching such connections. This is an especially desirable feature when heavy gauge conductors are employed.  
         [0061]     The relay assembly is preferably mounted within and enclosed by a plastic casing  60 , which is partly shown in  FIG. 6  and fully shown in  FIG. 7 . A non-conductive frame of supports  61 ,  62  seated on case  60  serves as a holder for the contactor bars  36  to  43 . The electronics are conveniently mounted on a circuit board  64  positioned beneath this frame. Four ports  63  are provided in the case  60  for cable entry.  
         [0062]      FIG. 7  shows the complete booster cable system. Note that cables  7  and  8  that are to be connected to the good battery are visibly shorter than cables  3  and  4  that are to be connected to the weak battery. This serves as an indicator that makes it easier to recognize the two sets of cables and ensures that the voltage developed across lines 15+ and 16− is the full, good battery voltage. Other indicia, such as markings, may alternately be employed to identify the cables to be connected to the good battery.  
         [0063]      FIG. 8  shows the relay portion of the automatic booster cable system in its case without the cables  53  being directly attached.  FIG. 8   a  shows a detail for a method whereby the cables  53  can be attached to the system. In  FIG. 8   a , a conductor end  50  extending within the relay is attached to hollow member or sleeve  51  for example either by soldering or staking. Sleeve  51  features a threaded hole and screw  52 . The screw is a set-screw to hold the core conductor of the external cable  53  firmly inside member  51 . Other user-accessible connection means can be employed. In this way, the assembly of the relay portion of the booster system can be sold separately and completed by assembly with external cables at a later time.  
       CONCLUSION  
       [0064]     The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest, and more specific aspects, is further described and defined in claims which now follow.  
         [0065]     These claims, and the language used therein, are to be understood in terms of the variants of the invention which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as it is implicit within the invention and the disclosure that has been provided herein.