Patent Document

FIELD OF THE INVENTION  
       [0001]     The invention relates to a towing mechanism with an upper bracket, a lower bracket and a locking device.  
       BACKGROUND OF THE INVENTION  
       [0002]     A known towing mechanism is shown in U.S. Pat. No. 7,048,294, which issued in May 2006 and which is assigned to the assignee of this application. This mechanism is designed for use with a utility vehicle, such as an agricultural tractor. This known towing mechanism includes an upper bracket, a lower bracket and a locking device. Such lower brackets are also referred to as tractor drawbars, and such upper bracket are referred to as a hammerstrap.  
         [0003]     An implement drawbar is received between the two brackets and retained by a towing bolt which is received in bores in the brackets. The locking device includes a locking pin which slides axially in a pin bore. The locking pin projects from the pin bore and engages and prevents axial movement of the towing bolt. The locking pin includes a loop-shaped spring which prevents unintentional axial sliding of the locking pin. However, this spring is not designed to resist forces acting on the locking pin in the axial direction of the locking pin, such as caused by a foreign object. Such forces can bend the spring and move the locking pin to an unlocked position freeing the towing bolt. Thus, it would be desirable to provide such a towing mechanism which reduces the risk that a drawbar coupled to the towing mechanism could be released. In order to avoid this possibility, the spring could be made stronger, but this would make the operation of the locking arrangement considerably more difficult.  
       SUMMARY OF THE INVENTION  
       [0004]     Accordingly, an object of this invention is to provide a locking arrangement which is safe and easy to operate.  
         [0005]     A further object of the invention is to provide such a towing mechanism which is unlikely to unintentionally release the towing bolt.  
         [0006]     These and other objects are achieved by the present invention, wherein a towing mechanism includes an upper bracket spaced apart from a lower bracket for receiving a drawbar therebetween. The brackets have towing bolt bores therein for receiving a towing bolt, and a locking device releasably holding the towing bolt in the bores. The locking device includes a component with a pin bore extending therein for slidably receiving a locking pin. A spring is coupled to the locking pin. The locking device is mounted on the upper bracket so that the locking pin projects out of the pin bore and prevents an axial movement of the towing bolt.  
         [0007]     The towing mechanism is provided with a structure or blocking member which prevents a foreign object from acting upon the locking pin, and thereby prevents an unintentional release of a trailer attached to the towing mechanism. Preferably, the blocking member is a projection on the towing bolt which at least partially (preferably completely) covers the cross sectional area of the pin bore or the end of the locking pin with respect to the longitudinal direction of the locking pin or the axis of the bore. In any case, the projection is configured so that, when the vehicle is moving backwards, the projection will prevent an object (such as a branch or a part of a fence) from contacting the locking pin. Alternatively, the blocking member may be a projection which projects from the upper bracket.  
         [0008]     The towing bolt preferably includes a radially projecting collar which has a ring-shaped recess formed therein. The locking pin preferably has a groove which is engagable with the collar of the towing bolt to prevent movement of the locking pin caused by vehicle movements and/or vibrations. If the towing bolt contacts the locking pin, the groove on the locking pin engages the collar to limit movement of the locking pin, and thereby reduce the likelihood of an unintentional release of the connection between a towing mechanism and a drawbar.  
         [0009]     The locking pin may rotate about its longitudinal axis if it is not secured against rotation. Thus, at its end opposite the towing bolt, the locking pin has a head with a generally square or polygonal cross section. One side of the head can engage a component or the bracket to prevent rotation of the locking pin, and to prevent forces being transmitted to the spring.  
         [0010]     A portion of the spring which engages the end face of the locking pin is received in a small groove or recess in the end face of the locking pin, so that the spring is thereby protected against a deformation or destruction, if, for example, the locking pin is brought into its engaged or secured position by means of a hammer that is applied by an operator against the end face of the locking pin.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a first embodiment of a towing mechanism according to the invention; and  
         [0012]      FIG. 2  is a perspective view of a second embodiment of a towing mechanism according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     The towing mechanism of  FIG. 1  includes a lower bracket  40  with a locating bore  48  and an upper bracket  46  with a locating bore  50 . A towing bolt  52  can be inserted into the locating bores  48 ,  50 , in order to retain or couple to a drawbar (not shown) of a trailer (not shown). The left end (not shown) of the towing mechanism may be pivotally coupled to a vehicle (not shown). The upper bracket  46  is bolted to lower bracket  40 .  
         [0014]     The towing mechanism also includes a locking device  100 . Locking device has a locking pin  10  and a spring  14  with a loop  26 . The pin  10  has a cylindrical shaft section  16  that can be inserted into a bore  60  in component  56 . An end of the shaft section has a chamfer in order to simplify its insertion into the bore  60 . The locking pin may be configured as shown in U.S. Pat. No. 7,048,294, which is herein incorporated by reference.  
         [0015]     The component  56  is fastened to the upper surface of the upper bracket  46 , such as by bolting or welding. Or, the component  56  may be formed integrally with the upper bracket  46 . The component  56  has a generally rectangular shape and includes a bore  60  which extends generally parallel to the longitudinal axis of bracket  40 . The locking pin  10  is inserted into the bore  60  from the side opposite the towing bolt  52  (the left side) so that the chamfer faces the towing bolt  52 .  
         [0016]     The component  56  has a generally vertical front side  62  which faces the towing bolt  52 . The upper part of the component  56  has steps which forms a shoulder  64  which is parallel to the front side  62  and faces in the same direction. The upper surface of the component  56  forms an inclined ramp surface  66 . The spacing of ramp surface  66  from the axis of the bore  60  steadily increases in the direction towards the towing bolt  52  and towards shoulder  64 .  
         [0017]     A blocking member  102  is arranged relative to the locking device  100  to prevent the movement of the locking pin  10  into the free position. The blocking member  102  includes a shaft-shaped or journal-shaped component or neck  104 , that is formed by an upward extension of the towing bolt  52 . The neck  104  is located adjacent to or in the vicinity of the end surface of a shaft  16  of the locking pin  10 . Thereby, the neck  104  covers or overlaps the cross sectional area of the bore  60  of the locking device  100  almost completely, in the sense that the cross sectional area of the neck  104  can be projected upon the cross sectional area of the bore  60  along the longitudinal axis of the locking pin  10 . Therefore, an extended portion of the towing bolt  52  protects the end of the shaft  16  of the locking pin  10  from the effects of foreign object damage. In other words, the blocking member at least partially covers the pin bore  60  and prevents extraneous material from contacting the locking pin  10 .  
         [0018]     Alternatively, the blocking member may be a projection or overhang (not shown) which projects from bracket  46  so that the projection at least partially covers the cross sectional area of the bore  60  along the longitudinal axis of the locking pin  10 . Or, the projection (not shown) may be mounted on a side of the component  56 . The overhang (not shown) would be configured so that a vertical projection of the overhang at least partially (preferably completely) covers the cross section of the bore  60 . In any case, the projection or the overhang (not shown) should be configured so that a towing element (to which no drawbar has been coupled) cannot come into contact with an object during backwards movement the vehicle. The overhang (not shown) could be a one-piece metal component attached to the bracket  46 . Or, the overhang (not shown) could be attached to the component  56 . Preferably, the overhang would be mounted on the side of the component  56  which is opposite to the side of the component  56  in which the locking pin  10  is inserted.  
         [0019]     The towing bolt  52  includes a circular collar  106  which has a lower side which engages the upper side of the upper bracket  46 , when the towing bolt  52  is inserted into the locating bores  48 ,  50 . The collar  106  includes a ring-shaped recess  108  which surrounds the longitudinal axis of the towing bolt  52 . The towing bolt  52  also includes a shoulder  110  on its upper end. The shoulder  110  has a larger outside diameter than the neck  104 . The shoulder  110  is used primarily to simplify the handling of the towing bolt  52 , since it can very simply be grasped by an operator, particularly for extracting the towing bolt  52 .  
         [0020]     A recess or a groove  112  is formed near the end of the shaft  16  of the locking pin  10  along the longitudinal surface. Under certain circumstances the groove  112  may engage the collar  106  of the towing bolt  52 , if the towing bolt  52  is moved in its longitudinal direction due to vehicle motion (even if only over small distances). The recess  108  is generally complementary to the groove  112  and comes directly into contact or into engagement with the groove  112 . As a result, the locking pin  10  interacts with the collar  106  to prevent movement of the locking pin  10  to the left within the bore  16  into an unlocked position which allows upward of the towing bolt  52 . This prevents unintentional upward movement of the towing bolt  52 .  
         [0021]     At its end facing away from the towing bolt  52 , the locking pin  10  is provided with a square end or head  114 , which comes to rest against the upper surface  116  of the upper bracket  46 . The head  114  prevents rotation of the locking pin  10  about its longitudinal axis. This prevents rotation of the towing bolt  52  from causing a rotation of the locking pin  10 , and prevents deformation of the spring  14 . A small groove  118  is formed on the end face side of the head  114  and protects the part of the spring  14  which engages the head  114  from deformation or destruction, in case an operator would like to bring the locking pin  10  into the locked position by using a hammer against the head  114 .  
         [0022]     Referring now to  FIG. 2 , in an alternative embodiment, the towing bolt  52  includes a radially projecting generally rectangular shaped collar  120  which rests on an upper surface of the upper bracket  46 . The collar  120  is engagable with a shoulder surface  122  of the component  56  and therefore prevents rotation of the towing bolt  52 . In this embodiment the locking pin  10  does not have a groove near the end which faces towards the towing bolt  52 . However, a groove similar to groove  112  of  FIG. 1 , could be provided. Similarly, a rectangular recess (not shown) could be provided on the collar  120  to prevent unintentional movement of the locking pin  10  into the free position.  
         [0023]     The towing mechanism operates as follows. Initially, the chamfered end of pin  10  inserted (from the left) into the bore  60  of the component  56 . Then the spring  14  is lifted by the operator and deposited on the ramp  66  of the component  56 . Then the pin element  12  is slid further into the bore  60 . The spring  14  slides on the ramp  66  until the loop  26  reaches the end face  64  and snaps in the direction of the pin  10 . Now the pin  10  can no longer be retracted without lifting the spring  14 , which requires considerable application of force due to the height of the ramp  66 . Thereby the locking pin  10  is secured on the component  56  so that it cannot be lost.  
         [0024]     The towing bolt  52  is lifted and withdrawn from the locating bore  48 , so that a drawbar (not shown) can be inserted into the space  47 . At that point the locking pin  10  is in its unlocked position, in which the free end of the shaft section  16  does not project upward out of the component  56  and does not have any effect on the towing bolt  52 . When the opening of the drawbar is aligned with the locating bores  48 ,  50 , the towing bolt  52  is moved downward and inserted through the drawbar and into the locating bore  48 . Then the head  54  of the towing bolt  52  rests on the upper side of the upper bracket  46 . So that the drawbar cannot be released unintentionally, the towing bolt  52  is locked in this position. For this purpose the locking pin  10  need only be slid in the direction of the towing bolt  52 , until the spring  14  snaps behind the front side  62  of the component  56 . At that time the free end of the shaft section  16  slides will prevent upward movement of the towing bolt  52 .  
         [0025]     In order to unlock the towing bolt  52  the operator must lift the spring  14  with a certain effort and deposit it on the surface  68 . Now the locking pin  10  can be retracted until the spring  14  has reached the shoulder  64  and the free end of the pin  10  is drawn into the bore  60  and no longer interferes with movement of the towing bolt  52 . Now the towing bolt  52  can be extracted upward and the drawbar can be uncoupled from the towing mechanism.  
         [0026]     While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.

Technology Category: 7