Abstract:
A fast-adjust trailer jack has three telescoping tubular segments, an upper, an intermediate and a lower. A lead screw is used to operatively couple the upper to the intermediate and a tension spring is coupled between the intermediate and the lower to normally urge the retraction of the lower into the intermediate. A spring-biased pin and hole based detent mechanism is employed to allow setting of the degree of extension of the lower tubular segment with respect to the intermediate tubular segment.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    I. Field of the Invention 
         [0002]    This invention relates generally to trailer jacks used to support the tongue of a trailer when the trailer is not coupled to a towing vehicle, and more particularly to a trailer jack allowing for rapid deployment. 
         [0003]    II. Description of the Prior Art 
         [0004]    A typical trailer jack is used to support the tongue weight of a trailer when the trailer hitch is not fastened to a towing vehicle and generally comprises an upper, outer tube adapted to be coupled to the trailer tongue and a lower inner tube coupled in telescoping relation to the upper outer tube and incorporating a lead screw member that is journaled for rotation in the upper, outer tube about a longitudinal axis thereof. The lead screw is threaded into a traveling nut that is welded to the inner wall of the lower, inner tube so that when the lead screw is rotated by a crank, the lower inner tube can be made to project further from or retract back into the lumen on the upper outer tube, depending on the direction of rotation of the crank. A disadvantage of this type of jack is that it takes many rotations of the crank to move the lower tube between a retracted disposition needed to provide ground clearance when the trailer is being towed and an extended disposition needed to elevate the trailer tongue when decoupling the trailer tongue receiver from the ball hitch of the towing vehicle. 
         [0005]    The Ryan U.S. Pat. No. 2,939,679 addresses this problem by providing a tension spring that is operatively coupled between the upper and lower tubes, allowing a user to step down on a footplate affixed to a bottom end of the lower tube to rapidly move the footplate against the ground and lock the lower tube in its extended position. At this point, only a few turns of the crank are needed to raise the trailer tongue sufficiently to uncouple the trailer from the towing vehicle. When it is desired to retract the lower tube into the upper one, when the lock is released, the tension spring works against gravity to lift the foot sufficiently to provide the needed ground clearance. Because the jack of the &#39;679 patent comprises only two telescoping tubes, it is unduly long and cumbersome. 
         [0006]    The McMahan U.S. Pat. No. 8,091,922 teaches another way of obtaining a fast initial adjustment of the jack, followed by a final adjustment using a lead screw where the final adjustment makes it only necessary to make a few turns of the screw to achieve a desired elevation. The jack is comprised of an inner tubular member nested within an outer tubular member, a collar, a housing and a pin. The inner member is threadedly connected to the outer member with a bolt having a crank attached at one end. The bolt enables incremental adjustments in the trailer height by extension and refraction of the inner member with respect to the outer member. The connected outer and inner members are secured to the trailer with a pin inserted through the housing, a hole in the collar and one of a plurality of longitudinal holes in the outer member. To create rapid gross adjustment in the trailer height, the pin is retracted, a different hole in the outer member is registered with the hole in the collar and the pin is then reinserted. Having a plurality of longitudinally spaced holes in the outer member necessarily weakens the structural integrity of the jack. 
         [0007]    The Wilson U.S. Pat. No. 4,769,864 describes a trailer jack having a tubular outer housing adapted to be attached to a trailer vehicle with second and third tubular members slidably disposed therein. A locking mechanism is provided adjacent an aperture in a wall of the second tubular member for positioning a pin in selectively alignable apertures in a wall of the third tubular member, thereby preventing relative movement between the second and third tubular members. A tension spring engages both the second and third tubular members, the spring being located within the third tubular member. It functions to bias the third tubular member toward a retracted position with respect to the second tubular member. A crank is provided for rotating a threaded screw member for moving the second tubular member with respect to the tubular outer housing. 
         [0008]    The present invention is deemed to be an advancement over the prior art in affording an improved releasable locking arrangement that affords greater selectivity over the initial positioning of the lower tubular member with respect to the intermediate member. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention comprises a trailer jack adapted for connection to a tongue of a trailer that comprises an upper tubular member of a predetermined cross-sectional shape, an intermediate tubular member of the same cross-sectional shape that is telescopingly received within the upper tubular member. A lower tubular member is telescopingly received within the intermediate tubular member and an elongate tension spring is disposed within the lower tubular member and operatively coupled for normally urging at least a portion of the lower tubular member into the intermediate tubular member. 
         [0010]    A swivel bracket is affixed to the exterior of the upper tubular member and is adapted to attach the trailer jack to the tongue of a trailer in a way that permits the jack to be rotated between a vertical and a horizontal orientation with respect to the trailer tongue. A threaded rod is journaled for rotation about a central longitudinal axis of the upper tubular member and cooperates with a traveling nut affixed to the interior of the intermediate tubular member such that rotation of the threaded rod by a hand crank displaces the upper tubular member with respect to the intermediate tubular member and the lower tubular member. 
         [0011]    A plurality of regularly, longitudinally-spaced detent holes are formed on an exterior wall of the lower tubular member. A latch is pivotally secured to a lower end portion of the intermediate tubular member and comprises a pin with a flat plate affixed intermediate its ends and that is normally urged by a compression spring into engagement with a selected one of the regularly longitudinally spaced holes on the lower tubular member for releasably locking the lower tubular member with respect to the intermediate tubular member. The latch further comprises a pedal plate positioned such that depression thereof against a force provided by the same compression spring for the pin disengages the pin from a selected one of the holes allowing the elongate tension spring to retract the lower tubular member into the intermediate one. For increased safety against inadvertent tripping of the jack&#39;s release, a locking pin can be inserted that cooperates with the flat plate to prevent movement of the spring-biased pin. 
         [0012]    The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which like numerals in the several views refer to corresponding parts. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a rear elevation view of the trailer jack comprising a preferred embodiment of the present invention; 
           [0014]      FIG. 2  is a side elevation thereof; and 
           [0015]      FIG. 3  is a partial view showing the spring biased detent employed. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    This description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top” and “bottom” as well as derivatives thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “connected”, “connecting”, “attached”, “attaching”, “join” and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece, unless expressively described otherwise. 
         [0017]    As seen in  FIG. 1 , the trailer jack  10  comprises three telescoping segments, namely, an upper, outer tubular member  12  of rectangular cross-section, an intermediate tubular member  14  also of rectangular cross-section but having an outer dimension capable of being slidingly fit within the lumen of the upper, outer tubular member  12 . Fitting telescopically into the central lumen of the intermediate tubular member  14  is a lower tubular member  16  at the lower end of which is secured a footplate  18 . The footplate  18  has a rectangular collar  20  dimensioned to fit about the lower end of the lower tubular member  16 . A bolt  22  passes through aligned apertures in the collar  20  and the lower tubular member  16  as a mode of attachment. 
         [0018]    Welded to the upper tubular member  12  is a swivel mounting bracket assembly indicated generally by numeral  24 . It comprises a base member  26  having arms, as at  28 ,  30 , that straddle and are welded to opposed side surfaces of the upper, outer tubular member  12  and secured to the base member  26  is a swivel plate  34 . The swivel plate  34  has a cylindrical sleeve  35  ( FIG. 2 ) rotatably secured in a circular aperture  32  in the base member  26 . A wire ring retainer  33  prevents uncoupling of the sleeve  35  from the base member  36 . 
         [0019]    The swivel plate  34  is adapted to be connected to a trailer tongue by suitable fasteners, such as bolts  37  that pass through clamping bars  39 . The jack mounting bracket assembly  24  thus permits the jack to be swung between a vertical disposition when supporting the trailer tongue to a horizontal position when the trailer is being towed. A U-shaped handle  41  extends through the arms  28  and  30  of the mounting bracket  26  and a pair of compression springs  43  surround portions of the legs of the U-shaped handle  41  and apply a biasing force urging end portions of the U-shaped handle through aligned apertures in the base portion of the mounting bracket and the swivel plate  34 . This serves to releasably lock the jack assembly in either a horizontal disposition with respect to the tongue of a trailer or in a vertical disposition depending upon which of the aperture pairs on the swivel plate  34  (A-A or A-B) are brought into alignment with the legs of the U-shaped handle  41 . 
         [0020]    As can be seen in the partial, cut-away view of  FIG. 2 , journaled for rotation in a bearing  36  mounted close to the top of the jack is a threaded lead screw  40  that is threaded through a traveling nut  42  welded to the inside wall of the intermediate tubular member  14 . Thus, by turning the crank  44  that is joined to the upper end of the lead screw  40  by a bevel gear connection  38 , the lead screw  40  is rotated, causing the intermediate tubular member  14  to be drawn into the lumen of the upper, outer tubular member  12  or moved outward so as to project further out from the lower end of the upper tubular member  12 , depending upon the direction of rotation of the crank  44 . 
         [0021]    Contained within the lumen of the lower tubular member  16  is a tension spring  48  whose lower end is hooked about the bolt  22  used to fasten the foot member  18  to the lower end of the tubular member  16 . The spring extends upward through the lumen of the lower tubular member  16  and hooks about a pin  50  that extends transversely through opposed side walls of the intermediate tubular member  14 . Thus, the spring  48  normally tries to retract the lower tubular member  16  into the intermediate member  14 . A cable  49  is also connected between the bolts  22  and  50  whose length prevents the lower tubular member  16  from coming free of the lumen of the intermediate tubular member  14 . 
         [0022]    As seen in the partial detail view of  FIGS. 1 and 3 , there is formed in one side surface of the lower tubular member  16  a series of longitudinally spaced holes  52  that are spaced apart approximately ½ inch although this spacing is not critical and can be as small as ¼inch and as large as ¾inch. The holes  52  thus form a detent surface along the length dimension of the lower tubular member  16  that is made to cooperate with a spring-loaded pin  54 . More particularly, welded or otherwise affixed to an outer wall of the intermediate tubular member  14  proximate its lower end is a block-like housing  56  in which is disposed a spring biased pin, the end of which can best be seen in  FIG. 3 . Pivotally joined to the housing  56  is a pedal member  58  that pivotally joins to the housing  56  by means of a hinge pin  60 . The pedal member  58  has opposed arms  62  that straddle the lower end portion of the intermediate tubular member  14  and the pin  54  is operatively coupled to the ends of the arms  62 . More particularly, an angled plate  63  is welded to the opposed arms and a rear end portion thereof wraps down over the housing  56 . The portion of the angled plate  63  that wraps down is identified by the numeral  65  and as seen in  FIG. 1 , it includes a U-shaped cutout  67  through which a rear end of the pin  54  extends. A roll pin  69  extends through the pin  54  and its length is such that it extends beyond the opposed side edges of the cutout  67 . It can be seen then that downward depression of the pedal member  58  pivots the pedal arms about the hinge pin  60  and in doing so forces the pin  54  rearward against the force of its biasing spring  71  to the point where the pin  54  no longer engages one of the holes  52 . 
         [0023]    With continued reference to  FIG. 3 , there can be observed a steel plate  72  affixed to the pin  54  intermediate its ends and with compression spring  71  pressing on it. A locking bolt, as at  74 , when inserted through aligned apertures in the housing  56 , abuts the plate  72  to block the ability of the pin  54  to move, thus providing a safety feature preventing inadvertent release of the jack. 
         [0024]    Having described the constructional features of the jack of the present invention, consideration will next be given to its mode of operation. 
         [0025]    Let it be assumed that the trailer had been traveling over the road and has arrived at a spot where the trailer is to be parked. At this point, the longitudinal axis of the jack will be generally horizontal and aligned with the tongue of the trailer. The lower tubular member  16  will be retracted within the intermediate tubular member  14  under action of the tension spring  48 . The operator will first pull the U-shaped handle  41  that secures the jack in its horizontal disposition and will rotate the jack about the cylindrical swivel  32  that connects the base member  26  to the swivel plate  34 , the swivel plate  34  being joined to the tongue of the trailer. Next, by placing one&#39;s foot on the plate  18  and stepping down, the lower tubular member  16  will be displaced outward from the lower end of the intermediate tubular member  14  against the force of the tension spring  48 . The pin  54  will click through the holes  52  and will ultimately stop in one of the holes determined by the length of travel of the lower tubular member needed before the footpad  18  abuts the ground. The operator may now insert the safety locking bolt  74  to prevent release of the lower tubular member from its engagement with the intermediate tubular member and turn the crank  44  only a few turns in a direction that will elevate the trailer tongue by displacing the intermediate tubular member from the lumen of the upper, outer tubular member  12 . This decouples the trailer&#39;s hitch receiver from the ball hitch on the towing vehicle. 
         [0026]    Later, when it is desired to again transport the trailer, the operator will maneuver the towing vehicle so that a hitch ball on the towing vehicle will be positioned directly beneath the hitch ball receiver on the end of the trailer tongue and then the crank  44  may again be rotated only a few times in a direction to lower the trailer tongue so that the receiver will engage the hitch ball. Now, by simply removing the locking bolt  74  so that it no longer prevents movement of the plate  72  and the spring-biased pin  54  and then stepping on the pedal  58  or otherwise pushing it down, the spring-biased pin  54  will become disengaged from the hole  52  in which it resided, allowing the tension spring  48  to rapidly draw the lower tubular member  16  into the intermediate tubular member  14  to thereby provide sufficient ground clearance to permit over-the-road travel. If it is contemplated that the trailer is to be taken off-road, additional ground clearance can be achieved by again rotating the jack about the swivel  32  so that the longitudinal axis of the jack will again be horizontally disposed alongside the trailer&#39;s tongue. 
         [0027]    This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.