Abstract:
A ball latch  46  is reciprocally mounted in a latch slot  44  and is biased downwardly by coil compression spring  68  until the semi-spherical recess at its lower end becomes coextensive with the spherical surface of the ball socket  36 . When the trailer hitch  16  is placed on the hitch ball  26 , the force applied by the hitch ball against the ball latch  46  moves the ball latch upwardly against the bias of its spring  68  to make room for the hitch ball to enter the ball socket  36 . Once the hitch ball is fully inserted in the ball socket  36 , the spring  68  pushes the ball latch  46  back to its locked position about the hitch ball.

Description:
FIELD OF THE INVENTION 
     This invention generally comprises a trailer hitch that is used to connect a towed trailer to the hitch ball of a towing vehicle. More particularly, the invention concerns a trailer hitch that automatically locks itself to the hitch ball of a towing vehicle. 
     BACKGROUND OF THE INVENTION 
     Trailer hitches for small vehicles usually include a socket that connects to a hitch ball mounted on the rear end of a towing vehicle. The trailer usually includes a forwardly extending trailer draft tongue that includes a coupler having the downwardly facing ball socket that is to be placed over and pivotally connects to the hitch ball. 
     When the towing vehicle is to be connected to the trailer, the operator typically elevates the trailer tongue so that the socket of the coupler is at a slightly higher level than the level of the hitch ball that is carried by the towing vehicle. The operator backs the towing vehicle toward the anticipated position of the socket of the coupler until the operator estimates that the hitch ball is aligned below the socket of the coupler. The operator then stops the vehicle, exits the vehicle and lowers the trailer tongue until the socket of the hitch registers with the hitch ball and the trailer is mounted to the hitch ball. 
     It is important that the ball socket of the coupler is properly mounted on and is locked to the hitch ball, and most trailer hitches include a lever actuated latch that is movable to extend a locking element from the trailer hitch to a position in abutment with the neck of the hitch ball, below the larger lateral breadth of the hitch ball for locking the trailer hitch to the hitch ball of the towing vehicle. Without this type of lock, there is a hazard that the trailer hitch will tend to bounce off the hitch ball upon the vehicle and/or the trailer passing over bumps in the road, or upon braking or accelerating, or upon side forces received from winds, or turns of the towing vehicle, etc., or upon the trailer being out of balance. Accordingly, the driver of a towing vehicle, when in the driver&#39;s position within the vehicle, is not likely to remain in the vehicle and to allow someone else to lock the trailer hitch to the hitch ball of the towing vehicle. This means that the driver is likely to apply the emergency brakes to the towing vehicle, exit the truck, and then make sure that the lock is secure between the trailer and the towing vehicle. While this operation is likely to increase the safety of the connection between the towing vehicle and the trailer, it leaves the towing vehicle and the trailer unattended for accidental movement during the locking procedure. Also, it is possible that the conventional latch device used to connect the trailer top to the ball hitch might be inadvertently left open or could be accidently engaged by another obstacle that causes the latch to open. 
     It is to the above described problem that the following disclosure is directed. 
     SUMMARY OF THE DISCLOSURE 
     Briefly described, the present disclosure concerns a trailer hitch for mounting the draw bar of a trailer to a conventional hitch ball of a towing vehicle. The hitch ball includes a substantially dome shaped upper portion and a lower portion that converges beneath the larger lateral breadth of the dome shaped upper portion to a stem of a smaller breadth. The trailer hitch may include a socket housing that defines a downwardly facing ball socket for mounting on the upwardly facing hitch ball. The ball socket may define a downwardly facing substantially semi-spherical upper interior surface that corresponds in size and shape to the substantially semi-spherical hitch ball. 
     A ball latch may be supported by the socket housing adjacent the ball socket for engaging the hitch ball at the stem of the hitch ball below the larger intermediate lateral breadth of the hitch ball for locking the trailer hitch to the hitch ball of the towing vehicle. 
     The trailer hitch herein disclosed may include a ball latch with a concave surface that is substantially coextensive with the semi-spherical interior surface of the ball socket when engaging the hitch ball at the stem of the hitch ball below the larger lateral breadth of the hitch ball. 
     The concave surface of the ball latch may include an arcuate surface, and a biasing means may be supported by the socket housing for urging the ball latch toward the hitch ball at the stem of the hitch ball for locking the ball latch to the hitch ball. 
     The biasing means may include a coil compression spring that engages the ball latch, and a latch pin may be connected to the ball latch with a coil compression spring surrounding the latch pin for urging the ball latch toward its locked position. 
     A latch slot may be formed in the socket housing, with the ball latch movable along the latch slot into and out of the locking position with respect to the hitch ball, with the spring positioned in the latch slot for urging the ball latch toward the hitch ball at the stem of the hitch ball below the larger lateral breadth of the hitch ball for locking the trailer hitch to the hitch ball of the towing vehicle. 
     The above described features of this disclosure, as well as the others hereinafter described, provide a trailer hitch that, when applied to the hitch ball, is self-locking. The trailer hitch has a latch that is urged out of the way when the hitch socket is lowered onto the hitch ball to allow the socket to become properly placed on the hitch ball, and once properly positioned on the hitch ball, the latch is biased into locking engagement with the hitch ball. 
     This provides the vehicle operator with the knowledge that once the trailer hitch is mounted to the hitch ball, it is locked in place and does not require his personal attention to properly secure the trailer hitch to the hitch ball. This reduces the hazard of improper locking of the trailer hitch to a hitch ball. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a towing vehicle and a trailer connected thereto with the trailer hitch that mounts the draw bar of the trailer to the hitch ball of the towing vehicle. 
         FIG. 2  is a perspective view of the trailer hitch of  FIG. 1 . 
         FIG. 3  is a side cross-sectional view of the trailer hitch of  FIG. 2 , with a hitch ball shown spaced beneath the trailer hitch. 
         FIG. 4  is a front view of the ball latch. 
         FIG. 5  is a side cross-sectional view of the ball latch of  FIG. 4 , taken along lines  5 - 5  of  FIG. 4 . 
         FIG. 6  is a perspective view of the ball latch of  FIGS. 4 and 5 . 
         FIG. 7  is a top view of the ball latch of  FIGS. 4-6 . 
         FIG. 8  is a side cross-sectional view of the trailer hitch of  FIG. 2 , as the hitch is moved down onto the hitch ball, showing the latch being pushed out of the way to allow the hitch ball to enter the socket of the hitch. 
         FIG. 9  is a side cross-sectional view of the trailer hitch of  FIG. 8 , with a hitch ball positioned in the socket and the latch closed about the bottom portion of the hitch ball. 
         FIG. 10  is a side cross-sectional view of the trailer hitch of  FIGS. 8 and 9 , showing the lever lifted to withdraw the latch from the hitch ball and the hitch ball moved down out the socket. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now in more detail to the drawings, in which like numerals indicate like parts throughout the several views,  FIG. 1  illustrates a towing vehicle, such as a pickup truck  10  and a trailer  12  that includes a draft draw bar  14  extending between the trailer and the towing vehicle, and a trailer hitch  16  mounted on the front end of the draw bar  14  that engages a conventional hitch ball mounted to the rear of the towing vehicle  10 . 
     Trailer hitch  16  is shown in more detail in  FIGS. 2 and 3  of the drawings. As shown in  FIG. 2 , the trailer hitch  16  includes a mounting sleeve  18  that is mounted to the forward end of the draw bar  14 . The mounting sleeve typically will be formed in an inverted U-shape, with a horizontal top wall  20  and opposed vertically oriented side walls  22  and  24 . Mounting sleeve  18  supports at its forward end the trailer hitch  16  and also supports the brake cylinders, electrical wiring and other components not further described herein. 
     As shown in  FIG. 3 , the trailer hitch  16  is to be mounted on a conventional hitch ball  26 . The hitch ball includes a semi-spherical shape that includes a dome-shaped upper portion  28  that expands downwardly to the large lateral intermediate breadth  30  at the dash line, then to a lower portion that contracts to a smaller breadth  29 , and is mounted on a vertical stem  32 . This is conventional in the art. 
     As shown in  FIG. 3 , trailer hitch  16  includes a hitch body  34  that includes a socket housing  35  and a rear mounting portion  33 . The socket housing  35  is telescopically received in mounting sleeve  18 . 
     Socket housing  35  has a downwardly facing ball socket  36  for mounting on a hitch ball  26 . The ball socket  36  defines a substantially semi-spherical interior surface  38  that expands outwardly from its upper portion to a large intermediate lateral breadth  40  as represented by a dash line in  FIG. 3 , then converges inwardly and terminates at the downwardly facing horizontal opening  42 . The opening  42  of the ball socket  36  is of smaller breadth than the large lateral intermediate breadth  30  of the hitch ball  26 . The size and shape of the ball socket  36  corresponds to the size and shape of the hitch ball  26  so that the ball socket may snugly fit over the hitch ball and the trailer hitch may rotate on the hitch ball. 
     A latch slot  44  extends diagonally in the socket housing  35  and at its lower end intersects a side of the ball socket and forms a latch opening  50  ( FIGS. 8 and 10 ) that extends from above the large lateral breadth  40  of the ball socket, downwardly through the edge of the socket opening  42 . The latch opening  50  is formed in the rear side and lower portion of the ball socket  36 . 
     Ball latch  46  is positioned in latch slot  44  and is movable along the length of latch slot  44  toward and away from the latch opening  50 . 
     Ball latch  46  is shown in more detail in  FIGS. 4-7 . Ball latch  46  is generally rectangular and includes a through bore  52 , and a counter bore  54  at the upper end of the through bore. A semi-spherical recess  56  is formed on the front face of the ball latch  46 , with the recess intersecting the front face and the bottom surface of the ball latch. The rear surface of the ball latch includes a step  58  that faces downwardly. A beveled edge  60  faces upwardly. 
     As shown in  FIGS. 8 and 9 , latch pin  62  is pivotally connected to latch lever  64  by pivot pin  66 , and latch pin  62  extends from latch lever  64  through the upper portion of latch slot  44  and is connected at its lower portion to ball latch  46 . The lower portion of the latch pin  62  extends through the counter bore  54  and into the through bore  52  and is connected to the through bore. Coil compression spring  68  extends into the counter bore  54  and about the latch pin  62  and the upper end of the spring  68  engages the upper interior surface of the latch slot  44  and functions as a biasing means for urging the ball latch  46  downwardly in the latch slot  44  until its step  58  engages a flange  70  of the socket housing  35 . When the ball latch  46  is in its lowermost position, its semi-spherical recess  56  will be coextensive with the spherical shape of the ball socket  36 , as shown in  FIG. 3 . However, when the latch lever  64  is tilted upwardly as shown in  FIG. 10 , it withdraws the ball latch  46  from the lower portion of the latch slot  44 , which opens the latch opening  50 . 
     As shown in the sequence of  FIGS. 8-10 , when the socket housing  35  is moved downwardly as indicated by arrow  72  onto the hitch ball  26  ( FIG. 8 ), the ball latch  46  engages the hitch ball  26 , and the hitch ball urges the ball latch against the bias of its spring to move out of the way of the hitch ball as the hitch ball moves into the ball socket  36 . 
     Once the ball socket  36  rests upon the hitch ball  26 , the complementary shapes of the spherical hitch ball  26  and the semi-spherical recess  56  of the ball latch  46  allow the ball latch to move under the bias of spring  68  from its upward withdrawn position in  FIG. 8  to its downward locking position as shown in  FIG. 9 . It will be noted that the semi-spherical recess  56  extends below the large lateral breadth  40  of the hitch ball. Also, the remaining lower edge of the horizontal opening  42  of the ball socket  36  is lower than the position of the large lateral breadth  40  of the hitch ball. Therefore, the hitch ball  26  and the ball socket  36  become connected and any vertical motion that tends to separate the hitch ball  26  and the ball socket  36  is resisted. 
     It can be seen from the above description and the associated drawings that the trailer hitch  16  is automatically locked to the hitch ball  26  by simply moving the trailer hitch down onto the hitch ball. The hitch ball engages and pushes the ball latch out of its way until the ball latch passes the large lateral breadth of the hitch ball, whereupon the spring pushes the ball latch into its locking position. 
     When the trailer hitch is to be separated from the hitch ball, the operator will lift the latch lever  64 , as shown in  FIG. 10 . This lifts the ball latch  46  out of the way of the hitch ball  26  so that the trailer hitch may be lifted as indicated by arrow  74  away from the hitch ball. 
     As an additional safety feature, the side of the latch slot  44  includes a semi-cylindrical pin opening  76  and a rectilinear safety pin  78  may be inserted through the pin opening  76 . The safety pin  78  is positioned and sized to engage the beveled edge  60  of the ball latch  46  to prevent any inadvertent upward movement of the ball latch. When the safety pin  78  is removed from the pin opening  76 , the ball latch  46  is free to move against the bias of its spring in an upward direction upon tilting the lever  64  indicated in  FIG. 10 . 
     Although preferred embodiments of the invention have been disclosed in detail herein, it will be obvious to those skilled in the art that variations and modifications of the disclosed embodiments can be made without departing from the spirit and scope of the invention as set forth in the following claims.