Abstract:
A breakaway switch assembly for detecting the unintended separation of a pair of connected vehicles or the like, of the type having a housing enclosure which slidably receives a pin-type actuator that operates an internal switch when pulled from the housing upon separation of the connected vehicles etc., incorporates a fully assembled, self-contained switch unit of a commercially known type, rather than a special switch assembly having long, resilient contact-carrying spring arms that must be carefully and tediously mounted in specially designed housings, as was the most prevalent practice heretofore. The self-contained switch unit so utilized preferably has an enclosing outer housing or body which protects the interior switch mechanism, contacts, etc., from the elements and also provides protruding flanges or the like which facilitate easy and fast mounting of the entire unit within the housing. Instead of being disposed between the conventional spring-arm electrical contact carriers, and retained in place thereby, the pull-pin operator is self-retained within a tubular receiver passage extending through the housing wall, preferably by resiliently deformable elastomer members such as O-rings, or by spring arms extending from the side of the pull-pin and integrally made as a part thereof. The O-rings when used are mounted on the pull-pin and must compress to pass over ridges formed in the tubular receiver when the pin is pulled out to actuate the switch unit, thus providing an alternative form of resilient biasing between the pin and the housing.

Description:
FIELD OF THE INVENTION 
     Breakaway switch devices have long been used to detect the unintended separation of a pair of mutually coupled vehicles or other such machines, for example, the separation of a towed vehicle from a towing vehicle such as a trailer and an automotive vehicle pulling the trailer. Various different forms of such devices have been used or considered over time, but the most widely accepted type is one which uses a “pull-pin” or the like that is connected to the towing vehicle and normally carried in an inserted position in a switch housing mounted on the trailer, in which position the pin is disposed between a pair of electrical contacts located inside the housing, to prevent them from contacting one another and allowing current to flow through them. Since the pin is connected to the towing vehicle, the accidental decoupling of the towed vehicle will immediately pull the pin out of the switch housing, allowing the electrical contacts to touch and thereby complete an electrical circuit that can actuate an alarm and/or provide some other such desired result, including the application of brakes on the towed vehicle, as an automatic response. 
     BACKGROUND OF THE INVENTION 
     Many or most such breakaway switch devices used in the past have included electrical contacts that are either attached to or comprise an integral part of long, specially shaped blade-type electrically conductive members which not only carried the electrical contacts but also acted as springs. These were specially mounted and retained inside a switch housing so that their end extremities or other contact portions would normally be spring-biased into mutual contact were it not for the pull-pin actuator, which when inserted pushed the two self-biased spring contacts apart to prevent their engagement and thereby maintain the same in open-circuit configuration until the pin was withdrawn. 
     Switch assemblies of the type just described are expensive to produce since the long spring-type electrical contacts are relatively expensive to manufacture, and they are also difficult and labor-intensive to assemble within the switch housing, as they do not lend themselves to automated assembly and typically require manual assembly. Furthermore, they often do not provide optimal switching operation due to their size, shape, and manner of operation, and are often subject to exposure to the elements, since their corresponding switch housings may not be well sealed. Consequently, the switch contacts may rust and corrode over time, sometimes becoming unreliable and even inoperative at the time upon when they are finally needed. In addition, such spring-contacts may lose their resiliency over time and are also subject to distortion by bending in use, due to the insertion and withdrawal of the pull-pin actuator each time a trailer is coupled and uncoupled. Numerous other disadvantages also attended the use and manufacture of such switch assemblies. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a unique and effective solution for problems such as those noted above in connection with previous types of breakaway switches, providing a new type of breakaway switch assembly of high reliability and long life which is at the same time extremely economical to manufacture and also easy to use. 
     In a first aspect, the breakaway switch assembly comprises a housing enclosure having a self-contained switch unit disposed inside it which has an internal switch mechanism and an externally accessibly operating member. The self-contained switch unit has an outer body with mounting surfaces that engage switch-retention members inside the housing enclosure to hold the switch unit in predetermined placement therewithin. Input and output conductors are connected to corresponding terminals of the switch unit to carry an electrical current which is switched through the switch unit, such signal conductors extending out of the housing enclosure. An externally accessible actuator extends into the housing enclosure in alignment with the switch-operating member of the switch unit, and the actuator is movable from at least a first position to a second position whereby it moves the switch-operating member into and out of a position causing electrical conduction through the switch unit. 
     In a preferred embodiment, the self-contained switch unit to be mounted inside the housing enclosure comprises a standard off-the-shelf push-button or rocker-type switch, with integral flanges or the like which are rapidly and easily insertable into place between opposing such flanges provided inside the housing, and the switch unit includes spade-type or other such quick-connect electrical terminals extending from it, by which the electrical conductors used to form the related electrical circuit may be quickly and easily connected to the switch unit during manufacture. In addition, a preferred pull-pin actuator for the assembly comprises an integral one-piece member, preferably molded of non-conductive or other such polymer, to provide a very economically manufactured member of high reliability and easy utilization, and having a structural configuration which includes a portion for directly engaging the switch unit operator (push-button or rocker), to hold it in predetermined position actuating the switch in a desired manner dependent upon the position of the pull-pin. 
     The foregoing general and preferred attributes of the invention will become increasingly apparent and better understood following consideration of the ensuing specification and claims, taken in conjunction with the attached drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a frontal perspective view of a preferred breakaway switch assembly embodiment in accordance with the invention; 
     FIG. 2 is an exploded perspective view of the embodiment shown in FIG. 1; 
     FIG. 3 is an exploded overhead plan view of the apparatus shown in FIGS. 1 and 2, showing the pull-pin in withdrawn position; 
     FIG. 4 is a bottom view of,the top closure member for the switch housing; 
     FIG. 5 is an overhead plan view similar to FIG. 3 but showing the pin in fully engaged position; 
     FIG. 6 is an enlarged central sectional view of the structure shown in FIG. 5; 
     FIG. 7 is an enlarged side view of the pull-pin, showing a first side thereof; 
     FIG. 8 is an enlarged side view of the pull-pin rotated 90° from the position shown in FIG. 7; 
     FIG. 9 is an enlarged fragmentary perspective view showing a second embodiment of the pull-pin and switch unit, with the pin disposed in a first position; 
     FIG. 10 is a view like FIG. 9 showing the same structure but with the pull-pin in a second position; 
     FIGS. 11,  12 , and  13  are fragmentary cross-sectional views similar to FIG. 6 but showing a third of the pull-pin in various positions of partial and full insertion; and 
     FIG. 14 is a perspective view of the pull-pin embodiment shown in FIGS. 11-13 inclusive. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a breakaway switch assembly  10  in accordance with the invention, shown in fully assembled condition. Basically, switch assembly  10  comprises a partially enclosing main housing  12  and a top closure member  14  therefore, with which it forms a complete housing enclosure. Main housing  12  includes a rearwardly extending portion  16  which is preferably integral with the main housing and which preferably includes a mounting hole  18  by which the housing may be readily mounted to a trailer or the like by a bolt or the like, which if not fully tightened will provide a pivotal mounting for the switch assembly. In addition to the attachment extension  16 , a pair of electrical conductors  20  exit the housing enclosure  12 ,  14  at its rearward extremity, and at the front a pull-pin actuator  22  is seen in fully engaged position. As illustrated, pull-pin  22  preferably includes an open-centered loop-like bail  24  by which it may be secured to a cord or chain, etc. attached to the towing vehicle. 
     FIG. 2 illustrates the housing top  14  lifted from the main housing  12  to reveal the interior of the latter, and also shows pull-pin  22  withdrawn from housing  12 . In addition, FIG. 2 illustrates the preferred type of self-contained switch unit  26 , which is easily but securely mountable inside housing  12  by interfitting it between wall-like flanges  28 ,  28 A, and  30  inside housing  12 , as further illustrated in FIG.  3 . It will be noted that switch unit  26  includes a pair of laterally extending flanges  26   a ,  26   b  at opposite sides. Flange  26   b  nests between housing flanges  28  and  28   a , and flange  26   a  rests flush against housing flange or wall  30 . Switch  26  is a self-contained unit, preferably of a type commercially available on an economical basis, such as that sold by CW Industries of Southamton, Pa. and identified as part no. GRS-4011C-XXX (SP/ST, momentary/NC). Preferably, this switch unit includes an outer enclosure or body  32  which integrally forms the mounting flanges  26   a ,  26   b . On opposite sides of switch body  32 , adjacent the mounting flanges  26   a ,  26   b , a pair of resiliently deflectable or deformable spring arms  34  may be provided which help secure the switch  26  in a receiving opening, such as that provided between housing flanges  28  and  30 . As will be understood by those skilled in the art, switch units such as that just described, including the various physical attributes just noted, are well known in the art and readily available commercially. Of course, the selected switch must have adequate current-carrying capacity for the intended purpose, and where it must carry vehicle brake-actuating current that will likely be in the range of fifteen to thirty amps. 
     In the mounted position of switch unit  26 , shown in FIGS. 3,  5 , and  6 , the self-contained unit is securely held in the illustrated position by the various flange walls referred to above, which are disposed in mutual contact, with the spring arms  34  exerting at least light spring force against the end extremities of flanges  28  and  30 . Switch body  32  includes a rearwardly projecting shelf-like extremity  36 , and this rests upon an upwardly projecting flange wall  38  (FIGS. 2 and 6) that forms an integral part of the main housing  12 . The bottom of switch unit  26  (body  32 ) rests upon the bottom inside surface of main housing  12 , and the housing top  14  preferably includes a downwardly projecting wall-like flange whose end extremity bears against the top of switch body  32  when housing top  14  is mounted in place upon the main housing  12  (FIG.  6 ). Thus, switch unit  26  is securely and reliably captured in place inside the housing enclosure, and has no freedom of movement in any direction. As illustrated, switch unit  26  has a pair of rearwardly extending terminals located directly above the shelf-like projection  36 , which may in the form of spade terminals that slidably receive closely fitting C-shaped crimped-on conductor terminals  21  for easy attachment of the electrical conductors  20  to the switch unit. Conductors  20  are preferably separated along substantially their entire length inside housing  12  by an upright partition wall  13 , and the conductors exit housing  12  at the rear, over the top of the rearwardly extending portion  16 , in a manner described in more detail subsequently. 
     Preferably, the partition line between housing top  14  and main housing  12  in the area adjacent pull-pin  22  occurs at a point well above a cylindrically tubular receiver portion  38 , which is therefore entirely defined by, or part of, main housing  12  (FIG.  6 ). Accordingly, receiver  38  is not subject to deformity or irregularity in shape due to manufacturing tolerances or manufacturing processes (e.g., molding), and is smoothly and regularly tubular inside. Therefore, pull-pin  22  slides smoothly and freely inside receiver  38  and maintains a generally uniform retention force therewithin caused by resilient deflection of a pair of spring arms  40  which preferably comprise an integral part of pull-pin  22 . Further, both the top  14  and main housing  12  define opposing walls  42 ,  44  respectively which project toward one another when the top  14  is mounted in place upon the main housing  12  (FIG.  6 ). Walls  42  and  44  preferably have centrally located semicircular reliefs or cutouts to provide a passage way for the end extremity of pull-pin  22 , but otherwise directly are in contact with one another on each side of pin  22  when top  14  is in place upon the main housing  12 . This helps rigidify the assembled housing structure and also provides an impediment to the passage of moisture or contaminants inside the housing enclosure through the tubular interior of receiver  38 . 
     The mutual alignment and initial securement of housing top  14  with respect to the main housing  12  is preferably accomplished by complementary and interengaging pins and recesses  12   a ,  12   b , and  14   a ,  14 B which may be seen by reviewing FIG. 2-6 inclusive. More particularly, upstanding tubular column  12   a  defines an internal recess that receives a downwardly-projecting pin  14  formed on top member  14 ; similarly, main housing  12  has an upstanding post  12   b  that is receivable within a central recess defined by a downwardly projecting tubular column  14   b  comprising part of top  14 . Once so mounted in place, the top closure  14  and main housing  12  are preferably welded ultrasonically or otherwise joined permanently along their adjoining edges, which extend the entire periphery around the two such housing members except for a pair of very small openings at the rear through which the electrical conductors  20  exit the housing enclosure. These passageways are preferably made sufficiently small to closely accommodate (and preferably slightly pinch) conductors  20 , to thereby provide strain relief for them as well as reduce the likelihood of moisture migration into the interior of the housing enclosure, but they are also preferably sealed in a positive manner as well by injecting a sealant (e.g., silicone gel, etc.) into a tubular cavity  46  (see in particular FIG. 6) which surrounds a short length of the conductors  20  at the point where they exit the housing enclosure. Sealant cavity  46  is formed by correspondingly mating channel-shaped walls  46   a ,  46   b  formed on a the main housing  12  and top closure  14 , respectively, which come into mating registry with one another when top  14  is secured in place. 
     Pull-pin  22  is preferably an integral one-piece member made by injection molding or the like and formed of a non-conductive generally rigid polymer such as acetal polymer. As already indicated, pull-pin  22  includes an externally accessible bail  24  on one end, by which it may readily be secured (as by a lightweight rope, wire, cable, or other such tether) to the towing vehicle or other such device (referred to broadly as a joined member or component which is joined to another such member or component and whose relative motion is to be detected). In addition, pull-pin  22  preferably includes a circular collar  48  adjacent bail  24  which fits snuggly against the outer end surface of receiver  38  when the pull-pin is fully inserted into the receiver and, adjacent collar  48 , a pair of cylindrical sections  50  and  52 , the first of which fits snugly inside the end of receiver  38  and the second of which slides inside the latter with minimal clearance when the pull-pin is fully inserted therein (as shown in FIG. 5 for example). Further, pull-pin  24  includes the previously mentioned spring arms  40 , which may be formed on opposite sides of the pin and extend part way along its length. Along the major portion of its length, this embodiment of pull-pin  22  has a generally X-shaped or cruciform cross section defined by a pair of mutually orthogonal elongated wall sections  22   a ,  22   b  (FIGS. 2-8 inclusive), which may provide longitudinal guiding surfaces with respect to the tubular interior of receiver  38  and the circular central opening defined in housing walls  42  and  44  mentioned previously, through which pin  22  passes to access the self-contained switch unit  26 . 
     In the first embodiment of pull-pin  22  (illustrated and described in FIGS.  2 - 8 ), this member has a somewhat conically tapered end extremity  54  which, in the fully inserted position of pin  22 , bears directly against and operatively moves an operating member  56  of switch unit  26 . In the illustrated embodiment, operating member  56  comprises a rocker member but it could in a broader sense be practically any analogous push-type component, all of which are collectively referred to herein as “a push button.” This movement of operating member  56  actuates switch  26  to its normal operating condition which prevails during times when there is no unexpected breakaway or relative motion between the joined components (e.g., towing and towed vehicles). That is, as will be understood, the switch unit  26  includes an internal switching mechanism, e.g., a pair of contacts or the like, which operate to complete or interrupt a path for current flow through the switch unit via conductors  20 . Upon relative movement of the joined components, however, pin  22  will be pulled longitudinally outwardly with respect to receiver  38  directly in accordance with the extent to which the joined components (e.g., towing and towed vehicles) have moved apart. If pull-pin  22  is so retracted, at least to the extent shown in FIG. 6 (or further, even to the extent it is fully withdrawn from switch assembly  10 ), the switch operating member (rocker, etc.  56 ) immediately moves to its opposite position, in which it actuates the internal switch mechanism to an opposite condition of conductivity, i.e., to either complete or interrupt a circuit path through the switch unit. (As will be understood, switch unit  26  may of either a “normally closed” or “normally opened” circuit configuration, and the operating member  56  should be spring-biased so as to automatically return to its original position (i.e., as shown in FIG. 3) when pin  22  is so withdrawn.) 
     In this operation, it will be noted that the integral spring arms or fingers  40  of pull-pin  22  function to maintain a positive and predetermined retention force with respect to receiver  38  whereby inadvertent withdrawal of the pull-pin during operation is substantially precluded. No part of pull-pin  22  actually touches or operates the electrical switch contacts or any related electrical switch mechanism inside switch unit  26 , contrary to the conventional practice followed heretofore. Thus, switch unit  26  may be of a conventional nature which may be purchased economically in the market place and which has both well-established and consistent actuation characteristics and current-carrying capabilities, unlike the essentially custom-made, complicated spring-like internal contacts heretofore conventionally used in breakaway switches. In addition, switch unit  22  preferably has an enclosing body  32  which protects the internal contacts/switch mechanism of switch unit  26  from moisture or the like even if it does enter the adjacent area, unlikely as that may be due the closely interfitting character of the pull-pin  22  and receiver  38 , the adjoining internal housing walls  42  and  44 , and the housing flanges or walls  28 ,  28   a , and  30  which interfit closely with the extending flange portions  26   a ,  26   b  of switch unit  26 . In this regard, an O-ring (not shown in FIGS. 1-8) may be used on pin  22  at the point where it enters receiver  38 , to positively seal that area when the pin is in place. As already pointed out, there is little or no likelihood that moisture or other contamination will enter the housing past the electrical terminals  21 , since they are disposed within the sealed cavity formed by the closely interfitting housing and top walls  46   a ,  46   b , as well as by the sealant injected into sealant cavity or pocket  46 . 
     FIGS. 9 and 10 illustrate a modified form or alternative embodiment of the pull-pin, designated by the numeral  122 , which may be used in a component configuration wherein switch unit  26  is positioned differently within housing  12  (by appropriately reconfigured internal walls, not specifically shown), such that the switch unit  34  is rotated essentially 90° from its position as shown in FIGS. 3-6 inclusive, i.e., with the switch operating member (e.g. rocker  56 ) disposed essentially parallel to the longitudinal axis of the pull-pin and receiver  38 . In this configuration, pin  122  slides across the switch operating member rather than meeting it directly at right angles. In this form, pull-pin  122  has the indicated conical sections  154  which enable it to approach rocker  56  in the manner shown in FIG.  9  and move across it to the position shown in FIG. 10, in which rocker  56  moves from one of its alternative positions to the other, and the opposite happens as pull-pin  122  is withdrawn. 
     FIG. 11-14 inclusive illustrate another modified form or alternative embodiment of the pull-pin, designated by the numeral  222 , which is shown in a configuration analogous to that depicted in FIGS. 1-8 inclusive but also directly usable in the configuration of pull-pin  122 , referred to in the preceding paragraph, for use with switch units mounted in the alternative position discussed therein. In the form illustrated, pull-pin  222  comprises an elongated circularly cylindrical member having a rounded protruding forward end  62  for directly abutting contact with switch unit rocker (or push button)  56  in the same manner as pull-pin  22 , discussed in connection with FIGS. 1-8 inclusive. Unlike pull-pin  22 , pull-pin  222  does not spring arms  40  or the like but instead incorporates a pair of resiliently flexible O-rings  66  and  72  which cooperate with the interior of a slightly different receiver  38   a  to hold the pull-pin in place therewithin. 
     That is, as seen in FIGS. 11,  12 , and  13 , receiver  38   a  includes an inwardly projecting annular wall portion  72  which is sized in relation to the outside diameter of pull-pin  222  and its forwardmost O-ring  64  such that O-ring  64  must be compressed (as shown in FIG. 12) in order to slide over the diametral constriction represented by annular flange  72 . Upon further insertion of pull-pin  222 , O-ring  64  clears the innermost edge of annular flange  72  (as shown in FIG. 13) and at this point its rounded forward end  62  depresses switch unit rocker  56  to cause switching operation of switch unit  26 . In this position, pull-pin  222  is resiliently but firmly locked in place in its switch-actuating position, and it will retain itself in this position until forcibly withdrawn from receiver  38   a  through resilient compression of O-ring  64 . 
     Preferably, pull-pin  22  also includes an outer O-ring  66  which seats in an annular groove formed in the larger cylindrical portion  52  of pull-pin  222  located adjacent its outer flange  48 . O-ring  66  compressively fits within a chamber  70  formed immediately inside the outer end extremity of receiver  38   a , whose diameter is sized to require resilient compression of O-ring  66  in order to seat it in place therein. To facilitate this process, the entrance to recess  70  in the end of receiver  38   a  is preferably chamfered or angularly relieved, as indicated by numeral  68 . The resilient compression of O-ring  66  when seated within recess  70  also serves a retaining function for pull-pin  222 , but its principal purpose is to seal the interior of housing unit  12 ,  14  from moisture and foreign elements which might otherwise move past the outside of the pull-pin in actual usage. As in the case of pull-pins  22  and  122 , pin  222  also preferably includes an outer bail designated  224 , by which the pull-pin may readily be connected to the towing vehicle for forced retraction from receiver  38   a  upon decoupling of the towed vehicle. 
     The above description is considered that of the preferred embodiments only. Modifications and variations of this and other such embodiments may well occur to those skilled in the art and to those who make or use the invention after learning of it through access to such preferred embodiments. Accordingly, it is to be understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and should not be used to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.