Abstract:
A trailer tongue jack system which in an exemplary embodiment has separable upper and lower housings which must be coupled together to form a complete operable system, and a driveshaft with a recessed non-standard coupling which must be coupled in order to allow the housings to be coupled.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to instruments for applying pressure and more particularly to jacks for trailer tongues. 
     Standard trailer tongue jacks sometimes pose two significant problems, interference with lowering of tailgates of towing vehicles and lack of effective security against theft. A trailer jack that allows for lowering of a tailgate while the trailer is attached to the vehicle is known. See, for example, U.S. Pat. No. 3,314,692. A vehicle jack with anti-theft features is known. See, for example. U.S. Pat. No. 5,782,115. It would be desirable to have a trailer jack with both features in a convenient combination. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment, a trailer jack system for a trailer tongue is provided with convenient tailgate non-interference and convenient anti-theft features in a single package. The trailer jack system includes separable top and bottom housings which must be aligned and engaged to render the system operable for raising or lowering of a trailer tongue. The bottom housing is adapted to be permanently affixed to a trailer tongue. The top housing is rapidly and easily separable from the bottom housing for allowing a motor vehicle tailgate to be lowered while the trailer is attached to the motor vehicle and for providing security against theft of the trailer when the trailer is left unattached and unattended. 
     The top housing has a rotary driveshaft therein, a first coupling on a lower end of the driveshaft, the coupling having a first set of engagement surfaces of a non-standard shape. The bottom housing has a selectively downwardly extendable and retractable jack having a jackscrew with an upper end within the housing. A second coupling is provided on the upper end of the jackscrew. The second coupling has a second set of engagement surfaces of a non-standard shape configured to mate with and engage the first set of engagement surfaces. A releasable connector is provided for selectively, and rapidly connecting and disconnecting the upper and lower housings so as to securely maintain the engagement of the first and second couplings and yet allow for rapid disconnection to conveniently disengage the first and second couplings Optionally, a lockable cover for the bottom housing is provided to prevent unauthorized access to the second coupling 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a trailer jack system according to a first embodiment of the invention, 
     FIG. 2 is a side view of a top portion of the jack system of FIG. 1, 
     FIG. 3 is top view of the drive coupling of FIG. 1, 
     FIG. 4 is a bottom view of the drive coupling of FIG. 3, 
     FIG. 5 is a side view of an exemplary bottom portion of the jack system of FIG. 1, with portions cut away, 
     FIG. 6 is a top view of the bottom portion of FIG. 5, 
     FIG. 7 is a top view of an exemplary cover plate for the bottom portion of FIG. 5, and 
     FIG. 8 is a side view of the exemplary jack system of FIG. 1 installed on a trailer tongue with the top portion removed and a tossing vehicle attached. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a side elevational view of an exemplary, trailer jack system  10 . System  10  includes a top portion  12  and a bottom portion  14 . Top portion  12  has a tubular cylindrical housing  16  with a first connector plate  18  at a lower end and provides rotary drive power for system  10 . Bottom portion  14  has a tubular housing  20  having a second connector plate  22  at an upper end  24 , an attachment flange or plate  26  and a jack  28 . Bottom portion  14  receives rotary drive force from top portion  12  and converts that force into vertical force to extend or retract jack  28  from housing  20  for raising or loitering a trailer tongue (not shown) attached to flange  26 . Attachment flange  26  is slightly below upper end  24 , but could be at or near upper end  24 , if desired. Housing  20  contains a jack  28 . Jack  28  projects from a lower end  30  of housing  20 . A plurality of tabs  32  are provided on connector plate  22  to assist in holding first connector plate  18  and second connector plate  22  together and thus top portion  12  on bottom portion  14 . A locking pin  34  attached to top portion be a chain  36 , further assists in holding plates  22  and  24  together and preventing lateral movement of plates  22  and  24  relative to each other. A longitudinal centering groove  38  on an exterior of jack  28  and a corresponding longitudinal centering rib (not shown) projecting inwards from housing  20  assist in preventing rotation of jack  28  within lower housing  20 . A handle  40  of top portion  12  is turned by a user (not shown) to provide rotational force to power the jack. An electrical motor or other source of rotational drive force could be substituted for handle  40 , if desired. 
     FIG. 2 is a side elevational view of top portion  12 . Top portion  12  includes housing  16 , handle  40 , a driveshaft  42 , a top bearing  44 , a bottom bearing  46 , first connector plate  18 , and a non-standard female drive coupling  48 . Housing  16  is a cylindrical body with a longitudinal axial bore  50  adapted to hold driveshaft  42 . Bore  50  is enlarged at each end to produce annular recesses  52  and  54  adapted to hold bearings  44 . Driveshaft  42  has an upper end  60  and a lower end  62  that extend out of a top  64  and a bottom  66  of housing  16 . A mounting collar  68  of handle  40  is fastened to upper end  58  by a pin  70  or other fastening means such as threads, bolt, set screw, glue or weld. Coupling  48  is a cylindrical body with an upper socket  72 , configured to receive lower end  60 , and a lower socket  74 , configured to receive a male coupling (described below) of bottom portion  14 . Collar  68  and coupling  48  prevent driveshaft  42  from moving upwardly or downwardly out of housing  14 . Snap rings (not shown) could be added to engage peripheral grooves in driveshaft  42 , if desired, to hold shaft  42  and bearings  44  in bore  50  even if coupling  48  or collar  68  were removed. Lower socket  74  is of a non-standard configuration, such as pentagonal. Coupling  48  is mounted on lower end  48  by forcing a pin (not shown) through a first transverse pinhole  76  in lower end  62  and a pair of second transverse pinholes  78  in coupling  48 . 
     FIG. 3 is top view of exemplar drive coupling  48 . Upper socket  72  is cylindrical to match lower end  62  and pinholes  78  are diametrically aligned. 
     FIG. 4 is a bottom view of drive coupling  48 . Lower socket  74  is pentagonal. Other non-standard socket configurations could be utilized in place of pentagonal socket  74 , to reduce the chance that a socket  74  from one jack system  10  would fit another jack system similar to system  11 . For example, ten different socket designs might be used, so that there is only a ten percent chance that a top portion from system  10  would function in another similar system or vice versa. Coupling  48  serves to engage lower end  62  with coupling  98 . Lower socket  74  is pentagonal. Pentagonal sockets are not readily available to the general public, and standard socket wrenches do not readily work on a polygonal nut width an odd number of surfaces, such as 3,5,7,9, etc. sides. Accordingly pentagonal sockets are examples of non-standard sockets, as would triangular, heptagonal or nonagonal sockets. Likewise any oddly lobed socket (not shown) would be non-standard all with the intention of making standard sockets and standard tools not couple sufficiently to allow any such coupling substituted for coupling  48  to engage coupling  98 . 
     FIG. 5 is a side, partially in cross-section, of bottom portion  14  with portions cut aa, v. A bearing plate  80  divides the interior of housings  20  into an upper coupling chamber  82  and a lower jackscrew chamber  84 . Jack  28  comprises a jackscrew  86 , an intermediate telescoped screw sleeve  88 , and an outer screw sleeve  90 , which are engaged for extension and retraction in conventional manner upon the rotation of jackscrew  86 . Jack  28  has an upper portion  92  which projects upwardly through an opening  94  in bearing plate  80  into upper chamber  82 . A snap ring  96  locks into a corresponding groove (not shown) in upper portion  92  to prevent jack  28  from dropping out of housing  20 . A male coupling  98 , having a pentagonal outer surface matching pentagonal lower socket  74  is pinned by a pin  100  to upper portion  92 . Upper chamber  82  is provided with an access hole  102  to allow pin  100  to be inserted through male coupling  98  and upper portion  92  in similar manner to that described previously for coupling  48 . Access hole  102  also allows moisture to drain from upper chamber  82 . A bottom portion  104  of jack  28  projects out of bottom  30  of housing  20  with the remainder of jack  28  contained within lower chamber  84 . A central circular drive opening  106  in second connector plate  24  allows coupler  48  to pass into upper chamber  82  to engage coupler  98  to provide rotary powter to jack  28 . Wall  108  of chamber  82  and second connector plate  22  help block an attempt to raise or lower jack  28  using any common tool such as a wrench or pliers. Wall  108  and plate  22  thus deter operation of jack  28  by anone not having top portion  12 . 
     FIG. 6 is a top view of the bottom portion  14 . Snap ring  96  engages upper portion  90  and male coupling  98  is pinned to upper portion  90  over snap ring  96 . Connector plate  18  extends radially inward from tabs  32  to a circular access opening  106 . Access opening  106  is only slightly larger in diameter than the outer diameter of female coupling  48  to minimize tinanted or unauthorized access to coupling  98 . Coupling  48  can be passed through opening  106  and over and around male coupling  98  to provide rotational drive force to jackscrew  86  but wrenches, pliers and other lateral gripping devices are thwarted by plate  18 . Attachment plate  26  has four bolt holes  108  for attaching plate  26  to a trailer tongue. Plate  26  could instead be welded or otherwise permanently attached to a trailer if preferred. 
     FIG. 7 is a top view of an exemplary cover plate  110  configured to cover upper end  24  and opening  106  while underlying tabs  32 . Cover plate  110  has four locking holes  112  configured to receive locking pin  34  or a padlock (not shown) to further deter theft. Cover plate  110  has rounded corners  114  to allow plate  110  to be placed on second connector plate  18  with corners  114  between tabs  32  and then rotated so that corners  114  are under tabs  32 . One locking hole  112  of cover plate  110  then aligns with a corresponding locking hole  116  in plate  18  to allow plate  110  to be locked onto plate  18 . Plate  110  also assists in keeping debris and moisture out of chamber  82 . First connector plate  18  has the same rounded corners as corners  114  and the same locking holes  112  and the same outside dimensions as plate  110  so that plate  18  and plate  110  each fit securely under tabs  34 . 
     FIG. 8 is a side view of bottom portion  14  of jack system  10  installed on a trailer tongue  116  with a tailgate  118  of a tossing vehicle  120  lowered over portion  14 . Top portion  12  has been removed. Access to the rear interior of vehicle  120  is thus facilitated and damage to tailgate  118  from being lowered onto the top portion is prevented. 
     In operation, attachment plate  26  is attached permanently to trailer tongue  116  or other similar object to be raised and lowered. Handle  40  is rotated about the axis of housing  16  to rotate shaft  42 , coupling  48  and  98 , and jackscrew  86  to extend or retract lower end  104  to raise or lower tongue  116 . When the desired extension or retraction of lower end  104  is obtained, locking pin  34  is removed from holes  112  and  116  and plate  18  is rotated relative to plate  22  and top portion  12  is removed from bottom portion  14 . If additional security is desired, cover plate  110  is then placed atop second connector plate  18  and rotated to place corners  114  under tabs  32 . A padlock (not shown) or locking pin  34  is then placed through holes  112  and  116  to block opening  106  and help prevent access to second coupling  98 . This process is reversed to reactivate system  10  for subsequent raising or lowering 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.