Abstract:
A direct current contactor having at least one low current terminal and at least two high current terminals is disclosed. The low current terminal is connected to a spring, which is nested in a chimney-shaped receptacle, where it is coupled to the contactor&#39;s coil. The chimney shaped receptacle also has a slot that receives a terminal blade that electrically connects the spring to the coil. The housing of the solenoid is designed with longitudinally extending channels that receive the receptacles, which prevents the assembly from rotating within the housing unit. Each terminal is provided with ribbed and knurled areas to restrict rotation of the terminal in the housing and the mating connection while tightening.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to contactors and more specifically to a direct current contactor for selectively closing the connection between a fixed pair of high current terminals by supplying a low current to the contactor. 
     Direct current contactors include a high current switch and a solenoid in a single enclosure. The switch provides the desired function, to turn current flow on and off. The solenoid serves as the actuator for the switch, thereby allowing the switch to be controlled remotely via a low current control device. 
     Most commonly, the switch portion is a normally open switch of the single pole single throw variety. In operation, the switch contacts are open with no power applied to the solenoid and are actuated to the closed condition when power is applied to the solenoid. 
     Direct current contactors are commonly used to supply power between a battery and starter for various over-the-road and off-road vehicles such as automobiles, trucks, tractors, construction machinery and the like. The contactor and solenoid are connected in a circuit between the battery, electric starter and starter switch. The contactor is connected in series with the battery and starter in a high current environment. 
     During the manufacturing process of a contactor, numerous components must be assembled in sequence. It is a further requirement that the components be retained from dislodgement and/or rotation during assembly and use. It is also desirable that the assembly gives the installer a tactile confirmation that the installation was completed without damage to the unit. 
     SUMMARY OF THE INVENTION 
     The present invention provides a reliable contactor that may be reconfigured to be grounded to a mounting bracket or a separate terminal. The contactor comprises a housing unit having at least two high current terminals and at least one low current coil terminal located and sealed within the surface of the housing unit, with one end of the terminal protruding into the housing unit, and one end of the terminal extending outward from the surface. The terminals are designed with a ribbed or knurled center area that prevents the terminals from rotating within the housing surface. Also included are several steps along the terminals axes to assist in seal integrity. The terminals further have a knurled surface on the outward connecting end of the terminal. The knurled surface assists in connecting to an external wire, cable, or other device, since the knurled surface also restricts terminal rotation. 
     The solenoid also comprises a bobbin with a conductive coil wrapped around the bobbin. The bobbin has a plurality of projections located on the outer edges of the bobbin&#39;s ends. The projections each have a chimney structure or retaining receptacle that permits holding of a spring within the chimney. The projections also have a slot that may receive a conductive terminal blade or coupling means. The spring retained in the chimney is in connection with the low current terminal or terminals, and possibly a contactor cover for a solenoid that is grounded to its mounting surface. The terminal blade connects the coil to the spring and allows a current to flow through the solenoid coil. The design of the chimneys allows for easy assembly of the solenoid with the contactor housing. 
     The housing unit of the contactor is designed to receive the bobbin in a mating arrangement that will prevent the bobbin from rotating within the housing once assembled. The housing design, which has preformed, longitudinally extending channels to receive the projections on the bobbin, also makes it easier to properly align the bobbin when inserting the solenoid assembly into the housing unit. 
     The overall design of the contactor allows for a more efficient assembly than prior contactor arrangements. These and other features will become evident in the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a contactor according to the present invention. 
         FIG. 2  is a cut-away view of the contactor shown along line  2 — 2  of  FIG. 1 . 
         FIG. 3  is an exploded view of the contactor according to the present invention. 
         FIG. 4  is an interior bottom view of the solenoid housing. 
         FIG. 5  is a close-up perspective view of a high current terminal or stud used in the present invention for current transfer showing the top of the stud. 
         FIG. 6  is a close-up side view of a high current terminal or stud used in the present invention for current transfer showing the side of the stud. 
         FIG. 7  is an exploded view of the solenoid used in the present invention. 
         FIG. 8  is close-up sectional view of the projection area of the bobbin. 
         FIG. 9  is a cross-sectional view of a first embodiment of the contactor according to the present invention taken along the line  9 — 9  of  FIG. 1 . 
         FIG. 10  is a cross-sectional view of a second embodiment of the contactor according to the present invention taken along line  10 — 10  of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     A direct current contactor  10  according to the present invention can be seen generally in  FIG. 1 . The contactor  10  is shown having a pair of high current studs or power terminals  12  and a pair of low current studs or terminals  14 . In the embodiment shown, the contactor is a normally open contactor of the single pole single throw variety. The contactor  10  may operate with more or fewer studs  12  and  14  as in, for example only, a single pole double throw contactor. This variety of contactor typically has three or four high current studs  12  whereby one set is normally open and the other is normally closed. 
     The high current stud  12  and the lower current stud  14  will be referred to in the description as single items for the sake of clarity and not as a limitation on the invention. The studs  12  and  14  each sit within a housing unit  16 , which is attached to an end plate, cover, or mounting bracket  18 . While the mounting bracket  18  is shown to be a unitary piece, it is conceivable that a cover without mounting structure may replace the mounting bracket  18 . In such an instance, separate attaching or clamping means would be used to secure the contactor  10  in place. Provided that the end plate or cover  18  secures the required elements within the housing unit  16 , any suitable structure may act as the mounting bracket  18 . 
       FIG. 2  is a cross-sectional perspective view of the contactor  10 . The studs  12  and  14  are nestled within the surface of the housing  16 . A portion of the outer surface of the low current stud  14  has a knurled surface  15  located where the stud  14  sits within the housing  16 , thereby restricting rotation of the stud  14  within the housing  16 . A similar design located on the high current stud  12  will be discussed with respect to  FIGS. 5 and 6 . The high current studs  12  make contact with a contact disc  20 , which is attached to an armature or plunger rod  22 . The plunger rod  22  is biased against the housing  16  by way of a headspring  24 . The headspring is nestled within a well  60  that holds the headspring  24  in proper alignment. A seal spring  26  maintains the static position of the contact disc  20  and allows the solenoid to over-travel to its internal stopping point thereby providing the contact disc  20  with a predefined load on the high current studs  12 . The coil  30  allows a magnetic flux to pass to the plunger  78 , which is forced upward and persuades the plunger rod  22  upward which in turn moves the contact disc  20  to make a connective bridge between the high current studs  12 . The seal spring  26  preferably is of a high force design that provides for a low milivolt drop between the high current studs  12 . The seal spring  26  is also preferably an inverted conical design to provide for a stable platform for the contact disc  20  to rest upon. 
     Still referring to  FIG. 2 , at least one low current terminal  14  is connected to a coil spring  32 , which is in contact with a coupling means or terminal blade  34 . The coil spring  32  is shown to be helical in shape, but any conductive connecting means that will transfer a current from the terminal  14  to the coil  30  via the terminal blade  34  will suffice. The terminal blade  34  is connected to the coil  30 , thereby allowing an electrical connection for the low current coil terminal  14  through the spring  32  to the coil  30 . As also shown in  FIG. 2 , in one contactor embodiment a similar lower spring  36  may be placed on the opposite side of the bobbin  28 , thereby allowing the coil assembly to be grounded to a grounding means through its mounting cover  18 . 
       FIG. 3  is an exploded view of the contactor  10 . The various elements of the contactor  10  are designed to easily fit within the housing  16 . The headspring  24  and the contact disc  20 , which is supported by the seal spring  26 , sit on the plunger rod  22 . The headspring  24  is fitted onto and mates with a ridged end  38  of the plunger rod  22 , while a C-clip  40  that fits into a groove  42  holds the contact disc  20  in place. The mating of the headspring  24  and the ridged end  38  allows placement of the headspring  24  into the well  60  (see  FIGS. 2 and 4 ) when the assembly is inverted, without needing to independently hold the headspring  24  in place. Such an arrangement eases manufacturing and allows for a less frustrating assembling process. The seal spring  26  slides over the plunger rod  22  and sits between a shoulder on the plunger rod  22  and the contact disc  20 . Insulating washers  44  and  46  sandwich the seal spring  26 . 
     Still referring to  FIG. 3 , the bobbin  28  has a pair of bobbin ends  47  with a plurality of projections  47   a  extending from the bobbin ends  47 . In a preferred embodiment, the upper bobbin end  47  will have two projections  47   a  located on it, while the bottom bobbin end  47  will have one projection  47   a  located on it. The bobbin  28 , bobbin ends  47 , flanges  47   a , and receptacles  48  may be molded as one piece or as individual pieces and secured together afterwards. The coil springs  32  are slid into respective chimneys or receptacles  48  that are attached to the projections  47   a . The receptacles  48  hold the coil springs  32  in place, even if the bobbin  28  is inverted for insertion into the housing  16 . The chimneys  48  also provide an efficient way for the coil springs  32  to contact the terminal blades  34 . Similarly, and for the same purpose as the coil springs  32 , the lower spring  36  sits within a chimney or receptacle  48 . The lower spring  36  will also be held in place within the receptacle  48 , without needing an exterior force when the lower spring  36  is pointing downwards in a normal position. While  FIG. 3  shows the two coil springs  32  and also the lower spring  36  being present at the same time, this is only for illustration purposes. While such an arrangement is feasible, normally, there will only be two springs, either one coil spring  32  and the lower spring  36 , or two coil springs  32 , used in the contactor  10  at one time. Likewise, the terminal blades  34  will only be present when a corresponding spring is located within a corresponding chimney. While any springs or other similar devices may be used, the headspring  24 , the coil springs  32 , and the lower springs  36  are preferably of the same shape and design, thereby easing assembly and inventory. 
       FIG. 3  also shows a steel housing  50  sitting on the bobbin  28  around the coil  30  (see  FIG. 7 ). The plunger rod  22  goes through the center of the plunger  78  (not shown), in turn the bobbin  28  and is held in place by a plunger washer  52 . The bobbin  28  and the plunger rod  22  will be described in more detail with respect to  FIG. 7 . A compression washer  54  sits below the bobbin  28 . The compression washer  54  is preferably a one-piece design that is either molded or cut from stock material. It preferably includes a recess so that it will not interfere with the chimney  48  located on the lower bobbin end  47 . The compression washer  54  is preferably made from a resilient, flexible material such as neoprene. A gasket  56 , preferably made of cork, rubber or a cork/rubber composite, sits between the housing  16  and the cover  18 . The cover  18  is secured to the housing unit  16  by a plurality of rivets  58 . While any fastening means may be used to secure the cover  18  to the housing unit  16 , it is preferred that the rivets or fastening means  58  are arranged in an evenly spaced circular arrangement for equal loading of the gasket  56  for more efficient sealing purposes. 
       FIG. 4  shows an interior bottom view of the housing unit  16 . At the center of the housing sits the well  60  that allows the headspring  24  (not shown) to be situated within the housing  16 . The well  60  provides a surrounding structure for the headspring  24  so that it will be properly biased against the plunger rod  22  (see  FIG. 2 ) and will not slide around within the housing  16 . The housing  16  has a pair of longitudinally extending channels  62 , which correspond to the size and shape of the chimneys  48  (see  FIGS. 2 and 3 ). The low current stud  14  is located in an end wall  61  of the housing  16  within the area defined by one of the longitudinally extending channels  62 . The high current studs  12  can be seen situated in the end wall  61  on either side of the well  60 . The mating effect of the chimneys  48  and the longitudinally extending channels  62  prevents the bobbin  28  (not shown) from rotating within the housing, which provides for an easier and more efficient assembly for locating the proper arrangement of the solenoid assembly and to further insure that the low current stud  14  will make contact with the coil spring  32 . 
       FIGS. 5 and 6  show views of the high current terminal or stud  12 . A ribbed area  64  and a lip  66  provide for a design that secures the stud  12  within the molded housing  16  (see  FIG. 2 ). The ribbed area  64  restricts rotation of the stud when it is sealed within the end wall  61  of the housing  16 . Above the ribbed area  64  is a knurl feature  68 . When sealed within the end wall  61 , the knurled area  68  will be located externally of the contactor housing  16 . The knurl  68  assists in the mating of the stud  12  with an exterior wire or cable connector or other interconnecting hardware (not shown). A connected terminal wire or cable will be restrained from rotating by the knurl  68  during tightening of the nut (not shown). The stud  12  also has an end or contact pad  70  that is crowned. The crowned end  70  provides a more efficient mating surface for the contact disc  20 , which results in a more consistent and reliable current passing through the stud  12 . 
     An exploded view of the bobbin  28  and the plunger rod  22  is shown in  FIG. 7 . As previously stated, the C-clip  40  holds the contact disc  20  and the seal spring  26  on the plunger rod  22 . The C-clip  40  allows the contact disc  20  and the plunger rod  22  to be mechanically connected to one another. It should be noted that any securing means, such as bolts, clasps, clips, pins, or other similar means, may be utilized in place of the C-clip  40 , provided the means do not interfere with the assembly process. The plunger rod  22  will pass through the center of a top flux washer  72 , the bobbin  28 , and a bottom flux washer  74 . The top flux washer  72  and the bottom flux washer  74  are separate structures from the bobbin flanges  47  of the bobbin  28 . The plunger rod  22  also passes through a plunger casing  78  and a pole piece  76 , both of which are situated within the center of the bobbin  28 . The plunger rod  22  is connected to the plunger washer  52 , which is located below the bottom flux washer  74 . The plunger rod  22 , the plunger casing  78  and the plunger washer  52  are designed as separate pieces and then staked or connected to one another. It should be noted that any securing means, such as threads, clasps, clips, pins, or other similar means, may be utilized in place of the staking process. While the pieces could be cut from raw material as a single piece, machining them as separate pieces is more cost effective, since there will be less scrap raw material. The plunger is also preferably of a geometry that is optimized for short stroke operating conditions, which will be used in shaping the solenoid force curve required for a predetermined level of performance. This is accomplished by allowing a larger diameter section of the plunger to operate outside the main coil assembly. 
     Still referring to  FIG. 7 , the top flux washer  72  and the bottom flux washer  74  are designed with notches  80  that fit around a corresponding projection  47   a  and chimney  48 . The notches  80  loosely fit around the projections  47   a  and prevent the washers  72  and  74  from rotating separately of the bobbin  28  when assembled. The chimneys  48 , projections  47   a , bobbin flanges  47 , and the bobbin  28  are preferably molded from a single piece of plastic, but could be designed as separate pieces and fastened together. The wound coil  30  sits on the bobbin  28  and is connected at its respective ends to the respective terminal blades  34 . The coil  30  is wrapped with a protective insulating layer  82 , which sits between the coil  30  and the steel housing  50 . The elements shown in  FIG. 7  are assembled as an independent subassembly, which allows the elements to be assembled and visually verified for accuracy prior to being placed within the housing  16  (not shown). Such an arrangement also allows for the critical components to be assembled outside of the housing unit  16 . 
     As shown in  FIG. 7 , the steel housing  50  is designed of two halves,  50   a  and  50   b . The halves  50   a  and  50   b  are preferably substantially identical sections assembled symmetrically around the bobbin  28 . Such an arrangement provides for an efficient flux path for the coil  30 , since no gap is needed in the housing  50  to clear the bobbin  28  during assembly. Furthermore, the housing  50  has an advantage over a rolled, single section housing in that the housing  50  does not have to be compressed to be fit properly around the bobbin  28  and to also fit within the housing unit  16 . The halves  50   a  and  50   b , along with the bobbin  28 , may be easily slipped into the housing unit  16  without any additional reshaping or reforming of the steel housing  50 , which is normally necessary with single piece designs. While the invention would work with a single section housing unit, it is advantageous to have the arrangement described above. 
       FIG. 8  is a close-up exploded view of the projection  47   a , the chimney  48  and the terminal blade or coupling means  34 . A slot  84 , which is located within the projection  47   a , receives the terminal blade  34 . The slot  84  extends inwardly past the area of the projection where the chimney  48  is located, allowing the terminal blade  34  to be in solid contact with one of coil springs  32 / 36  (not shown). Preferably, the end of the coil  30  is attached to the terminal blade  34  by welding, soldering or other attachment means that will allow a current to pass from the coil  30  to the terminal blade  34 . The arrangement of the projection  47   a , the chimney  48 , and the blade  34  allows for easy assembly and connection of the coil  30  to the blade  34 . As previously stated, the projections  47   a  and the chimneys  48  are preferably molded as one piece, but it is possible that they could be molded individually and then later joined together. Likewise, the chimneys  48  are shown to be cylindrical so that they are in mating relationship with the coil springs  32 / 36 . However, it is within the realm of this invention for the chimneys  48  to be of any shape that will provide a mating relationship with the springs  32  and  36 , which may also be of other shapes and designs than the currently shown springs. 
     After the bobbin  28 , the projection  47   a , and the chimney  48  are assembled or formed, the blade  34  may then be slid into the slot  84 , preferably extending the entire length of the slot with a small lip  85  located outside of the slot  84 . The lip  85  will provide an area for the end of the coil  30  to be secured to the blade  34 . Because the lip  85  is located outside of the bobbin  28 , less manipulation is required in securing the separate parts, which results in an easier and more efficient assembly process. 
       FIG. 9  is a side view of a contactor  10  showing the solenoid being connected to two low current studs  14 . In this arrangement, two coil springs  32  are present. Each spring  32  is connected to one of the low current studs  14 , with one stud  14  connected to the positive polarity of a voltage source and the other stud  14  connected to the negative polarity of a voltage source or chassis ground. The low current studs  14  include a post  86 , which the coil spring  32  will mate around to further insure a secure contact between the spring  32  and the stud  14 . As current enters the solenoid through the low current stud  14 , it flows through the coil springs  32 , the terminal blade  34 , and into the coil  30 . The result is the contact disc  20  is forced upward from the magnetic flux produced from the coil  30 , and the disc  20  makes contact with each contact pad  70 , thereby providing a bridge for the high current terminals  12 . The lower spring  36  is not present in this arrangement. Also, there is no terminal blade  34  located in the chimney  48  that would normally house the lower spring  36 . 
       FIG. 10  is a side view of a contactor  10  having a single low current stud  14  mounted in the housing  16 . This single stud  14  receives the input current. The coil spring  32  is connected to the stud  14  and the post  86  and makes a connection to the upper terminal blade  34 . Power is transferred across the high current terminals  12  in the same fashion as in  FIG. 9 . However, in this arrangement, the lower spring  36  is present and connected to the lower terminal blade  34 . The lower spring  36  is in contact with the cover  18 , which provides one of the coil connection paths, usually via chassis ground. The second coil spring  32  that was present in  FIG. 9  is not present, and the respective projection  47   a  for the second coil spring  32  does not have the terminal blade  34  connected to it, either. 
     The design of the housing unit  16  is such that the end wall  61  (see  FIGS. 1 and 2 ) is portrayed as being opposite of where the cover  18  is located. However, the end wall  61  should be construed broadly as an area of the housing unit  16  where the terminals  12  and  14  are located. For instance, if the terminals were located in the cylindrical portion of the housing  16 , that should also be considered as the end wall  61 . Likewise, the longitudinally extending channels  62 , terminals  12 , and terminals  14 , are shown to be diametrically opposed. While such a design may be advantageous for manufacturing and design purposes, it is not critical for the present invention. Provided there is sufficient insulation between the different electrical contacts, any arrangement will be within the scope of the present invention. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.