Abstract:
A standard ball and socket type of trailer hitch assembly is modified so as to provide means for automatically and positively locking the trailer hitch each time the trailer hitch ball is inserted into the trailer hitch socket. The socket receptacle of the trailer hitch is modified to receive a push rod which is actuated by contact with the ball of the hitch and in turn causes the latch to positively lock in place without requiring the operator to remember to move the latch into a positive locking position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to trailer hitch couplings of the ball and socket type and more particularly to an improved coupling wherein the two coupling members are automatically and positively locked against possible separation whenever they are interconnected and without the need for any intervention on the part of the user. 
     2. Description of the Prior Art: 
     A common and widely used coupling for trailer hitches consists of a ball member and a socket member having a recess adapted for receiving and engaging the ball member, with the ball member being attachable to the rear end of the hauling vehicle and the socket member to the tongue of the trailing vehicle. A latch is provided on the socket member which is manually movable to engage the ball member and to lock the members together when the coupling is in use. Likewise, the coupling can be disengaged by manual movement of the latch. Typical examples of such type trailer hitches may be found in U.S. Pat. No. 2,726,099 (reissued as U.S. Pat. No. RE. 24,362) and U.S. Pat. No. 2,971,777. 
     Although these prior trailer hitch couplings are quite satisfactory when properly used, there is always the danger that the user will forget to place the ball latch into final locking position before proceeding to his destination. When this occurs, the likelihood is that the coupling members will become disconnected while the vehicles are in transit which could result in a serious accident. 
     This problem has received attention but the means previously proposed for overcoming it have not been entirely satisfactory. For example, U.S. Pat. No. 2,855,222 describes a self-locking ball and socket coupling for trailers. However, the mechanism by which this was achieved is quite complicated and requires so many difficult to fabricate parts that construction would be difficult and costly. U.S. Pat. No. 2,726,099 also represents useful background art. 
     It is therefore an object of this invention to provide an improved self-locking ball and socket coupling for trailers in which the parts are few and simple in configuration and easily manufactured and assembled. 
     SUMMARY OF THE INVENTION 
     A trailer hitch of the type having a pressed metal housing with a forward ball receiving socket and a pivotal ball latch member, normally locked in position by a manually operable lever, is modified so that the entry of the ball into the ball socket causes the ball latch member to move automatically into a positive locking position. 
     In the modified trailer hitch according to the invention, a support arm is mounted on the top surface of the trailer hitch housing and incorporates a plunger rod at its forward end which passes through an aperture in the ball socket. Entry of the ball into the ball socket forces the plunger rod upward which in turn causes the support arm to raise and bring a ball retaining member into engagement with the ball while simultaneously causing a pivotal latch to move into a positive locking position to automatically secure the ball and socket coupling. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a coupling constructed in accordance with the invention showing an unlocked condition. 
     FIG. 2 is a side elevation view similar to FIG. 1 but showing the coupling members interconnected and self-locked. 
     FIG. 3 is a top plan view of the coupling of FIG. 2. 
     FIG. 4 is a partial elevation section view taken along the longitudinal center line of FIG. 3 with the coupling locked. 
     FIG. 5 is a partial elevation section view similar to FIG. 4 but showing the coupling members separated. 
     FIG. 6 is a partial elevation section view similar to FIGS. 4 and 5 but illustrating how the ball retainer and connecting rod may be moved into a locked position with the latch remaining in a non-locked position. 
     FIG. 7 is a bottom plan view of the coupling housing. 
     FIG. 8 is a bottom plan view similar to that of FIG. 7 but showing the push rod and ball retaining mechanism in locked position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention described and illustrated herein represents an improvement over prior constructions of the widely used ball and socket type trailer hitch coupling which is especially adapted for application to automobile bumpers or frames and trailer draft tongues. 
     Referring to the drawings, the improved trailer coupling shown therein by way of illustration includes a conventional stamped metal housing 20 having a tongue receiving portion 21 of channel shape in cross-section with appropriate apertures 22 to receive screws, bolts, and the like, for securement of the draft tongue of a trailer (not shown). The forward portion of the housing 20 includes a formed ball socket 25 adapted to receive a ball member 30 rigidly attached to a screw threaded mounting shank 31 which extends through a suitable opening in hitch member 33 of the towing vehicle and is engaged by a nut 34. Within the housing 20, there is provided a transverse rod 35 extending between the walls thereof which conveniently may be a bolt or rivet swaged in place. The head of such a rivet is seen at 36 and the swaged end at 37. Rod 35 pivotally mounts a ball retainer member designated generally as 38 and best shown in FIG. 5 in lowered position. 
     The ball retainer 38 which is movably suspended from the fixed pivot rod 35 has its forward wall provided with a spherical recess 39 which is adapted to snugly engage the lower portion of the ball when the ball and socket members 30 and 25 are interconnected. The top wall 40 of the ball retainer has a larger opening 41 and a connecting rod or linkage 42 passes through this opening. Its purpose is to permit raising or lowering of the ball retainer member 38. That portion of connecting rod 42 extending downward below top wall 40 of retainer 38 has its end threaded and mounts a transverse support plate 43 (best shown in FIG. 8) secured to connecting rod 42 by a nut 44. A coil spring 45 of relatively heavy construction is interposed around the rod 42 between the top surface of retainer plate 43 and the top wall 40 of ball retainer 38 and functions to snugly confine the ball member 30 within socket member 25 when the coupling is assembled for normal use. Another somewhat lighter coil spring 46 is interposed around rod 42 between the top wall 40 of the ball retainer 38 and top surface 23 of housing member 20 and serves to swing the retainer away from the ball member 30 when the coupling is disengaged. 
     In the conventional ball and socket coupling, the connecting rod or link 42 is raised and lowered by virtue of its connection to a manually movable latch member (see U.S. Pat. No. 2,726,099). However, according to the present invention, the upper end of rod 42 is attached by a bolt and nut arrangement 47 to a U-shaped arm member 48 spaced above and extending along the length of housing 20. Arm member 48 has a pivotal mount at the rear end thereof provided by brackets 49 and bolt-nut arrangement 50 with the brackets being welded or otherwise secured to the top surface of housing 20. Slot 55 operates false latching as later discussed. 
     A push rod 51 is rigidly attached to the forward end of arm member 48 and includes a lower portion designed to pass through an aperture 52 formed in the ball socket member 25 of housing 20. Thus, whenever the ball 30 is positioned within the socket receptacle 25, the top of the ball engages push rod 51 and forces arm member 48 to move in an upward direction. This, in turn, raises connecting rod 42 and causes ball retainer member 38 attached thereto to swing into active position and engage the lower surface of ball member 30 as it moves to a fully seated position (FIG. 4). 
     In order to automatically lock the coupling in the engaged position, a latch generally designated by the numeral 60 is provided. Latch 60 includes a crank arm having an upper portion 61, an integral handle member 62 and a lower portion 63 and pivots on pivot pin 67, which in turn mounts on pivotal arm member 48 and is retained by head 70 and cotter pin 69. A spring 64 is coiled around pivot pin 67 with one free end being secured to the lower portion 63 of latch member 60 and the other being secured to a transverse abutment 65, which is welded or otherwise securd to arm member 48. This spring functions to constantly urge the lower portion 63 of latch member 60 towards the abutment 65 when arm member 48 is in raised position following insertion of ball 30 in ball socket 25. The latch member 60, associated spring 64 and abutment 65 are best shown in FIGS. 4 and 5. It will also be observed on examination of these figures as well as from FIG. 1 and FIG. 2 that a wear plate 66 is positioned on the top surface of housing 20 to provide a wear surface for the lower end of latch 60 to slide on as it moves in and out of locking position. 
     It is apparent then from the foregoing description of the device that insertion of ball 30 into socket member 25 forces push rod 51 upward which in turn raises arm member 48 to which the push rod is attached. Likewise, retainer member 38 is brought into engagement with ball member 30 as arm 48 is rasied by virtue of its attachment to link rod 42 which in turn is connected to arm member 48 and moves upward therewith against the tension of its associated springs 45 and 46. Finally, the raising of arm member 48 causes latch member 60 to automatically rotate about transverse pivot pin 67 into a position which locks the coupling in place. Release of the lock to disengage the coupling is readily accomplished by merely grasping the handle member 62 of latch assembly 60 and moving it in an upward direction against the tension of spring 64. 
     In some instances, the operator may inadvertently place the ball 30 beneath ball retainer member 38 rather than in socket 25 as illustrated in FIG. 6. To avoid giving the operator a false latching indication in this situation the slot 55 in which the bolt and nut arrangement 47 is mounted allows the connecting rod 42 to rise, as in FIG. 6, but without causing latch member 60 to latch as in FIG. 6 and as could otherwise be the case. 
     Thus, it is seen that the invention provides a reliable and simple means for the self-locking of a ball and socket type of trailer coupling which can be conveniently released when it becomes necessary to disconnect the coupling members. Although the self-locking mechanism provides an efficient and safe securement of the coupling when engaged, in order to avoid any unauthorized tampering with locking latch 60, an aperture 71 is provided in the upper portion 61 thereof which aligns, when the latch is in locked position, with aperture 72 formed in arm member 48 to provide a passageway for receiving a padlock, or the like, to secure the locked latch against manual release. 
     It is believed that the invention will be understood from the foregoing without the need for further description and that while a preferred embodiment has been shown and described for illustrative purposes, the invention is limited only by the appended claims.