Abstract:
A towing device for selectively locking a towing load has a support member that pivotably supports a link member at a first pivotal point near the first proximal end. A stopper is located on the support member for regulating a pivotal movement of the link member. A joint member is pivotably coupled to the link member near the first proximal end at a second pivotal point and has a tendency to pivot about the second pivotal point toward the first pivotal point to contact the stopper as the first proximal end pivots toward the stopper about the first pivotal point. A coupling member is connected to the second distal end of the joint member. An interference avoiding unit is located near the joint member for guiding the joint member to maintain a certain distance from the stopper as the link member pivots about the first pivotal point.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a towing device for selectively locking a towing load.  
           [0002]    A towing tractor generally includes one of towing devices. Referring to FIGS. 8 through 10, a towing device of a towing tractor generally has a support member  3 , a shaft C, a first link member  5 , a second link member  15 , an operational member  6 , a drawbar pin  16  and a drawbar bracket  17 . The support member  3  is erected near the rear side of a vehicle body  2  and pivotably supports the shaft C. The proximal end of the first link member  5  and the proximal end of the operational member  6  are fixedly connected to the shaft C so that the shaft C, the first link member  5  and the operational member  6  integrally pivot. The second link member  15  is pivotably coupled to the distal end of the first link member  5  at its one end and is also pivotably coupled to a head  16   a  of the drawbar pin  16  at the other end. The drawbar bracket  17  is fixedly connected to the rear end and lower side of the vehicle body  2 . The drawbar pin  16  is fitted in the drawbar bracket  17  to be raised or lowered. The drawbar pin  16  is coupled with a drawbar of a carriage so that the carriage is towed. The first and second link members  5  and  15  constitute a link mechanism.  
           [0003]    A stopper or a rotation regulating member includes a stopper bracket  10  and a stopper bolt  11 . The stopper bracket  10  is fixedly connected to the support member  3 . The stopper bolt  11  is fitted into a through hole of the stopper bracket  10  and is adjustable in its level to regulate the maximum upward rotational distance of the first link member  5 . The stopper bolt  11  is supported by the stopper bracket  10  and is located under the operational member  6  so as to correspond with the rotational range of the operational member  6 . The stopper bolt  11  contacts the operational member  6  as the drawbar pin  16  is raised upward through the link mechanism.  
           [0004]    A clevis  7  is coupled to the distal end of the operational member  6  at its one end and is connected to a cable  8  at the other end. The cable  8  travels near a rear axle of the vehicle body  2  and is ultimately coupled to a link lever  13  of a drawbar operation lever  14  that is located near an operator seat through a clevis  12 . When the drawbar operation lever  14  is manipulated to raise the drawbar pin  16 , the cable  8  is tensioned to pull the clevis  7  so that the clevis  7  pivots about a pivotal point between the clevis  7  and the operational member  6 . As a result, the clevis  7  does not contact the stopper bracket  10 .  
           [0005]    When an operator holds a grip portion  5   a  of the first link member  5  and manually lifts up the first link member  5  to raise the drawbar pin  16 , since the operation lever  14  is not manipulated, the cable  8  is not tensioned. Only the operational member  6  pivots about the shaft C in the counterclockwise direction in the drawings. Then, the operational member  6  pushes the cable  8  downward to bend the cable  8  so that the clevis  7  tends to pivot toward the stopper bracket  10  and the stopper bolt  11 . In this case, since the length of the clevis  7  is shorter than the distance between the operational member  6  and the stopper bolt  10 , the clevis  7  gets entangled with the stopper bolt  11  or the stopper bracket  10  so that a contact surface  6   a  of the operational member  6  does not move to contact the upper end surface of the stopper bolt  11 . As a result, the drawbar pin  16  cannot completely be raised, and the manually raising operation is interrupted. The clevis  7  needs to be moved in the operator&#39;s hand to remove interference between the clevis  7  and the stopper bracket  10  and between the clevis  7  and the stopper bolt  11 . Thus, the operation is complicated. Therefore, it is desired that a towing device that does not interrupt the drawbar operation by overcoming the interference between the clevis  7  and the stopper bracket  10  and between the clevis  7  and the stopper bolt  11 .  
         SUMMARY OF THE INVENTION  
         [0006]    In accordance with the present invention, a towing device for selectively locking a towing load has a support member, a link member, a stopper, a joint member, a coupling member and an interference avoiding unit. The link member has a first proximal end and a first distal end and is movably pivoted by the support member at a first pivotal point near the first proximal end. The stopper is located on the support member for regulating a pivotal movement of the link member by contacting the link member between the first pivotal point and the first proximal end. The joint member has a second proximal end and a second distal end and is pivotably coupled to the link member near the first proximal end at a second pivotal point. The joint member has a tendency to pivot about the second pivotal point toward the first pivotal point to contact the stopper as the first proximal end of the link member pivots toward the stopper about the first pivotal point. The coupling member is connected to the second distal end of the joint member for controlling the pivotal movement of the link member. The interference avoiding unit is located near the joint member for guiding the joint member to maintain a certain distance from the stopper as the link member pivots about the first pivotal point.  
           [0007]    Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
         [0009]    [0009]FIG. 1 is a side view of a towing device according to a first preferred embodiment of the present invention;  
         [0010]    [0010]FIG. 2 is an enlarged end view of an interference avoiding unit according to the first preferred embodiment of the present invention;  
         [0011]    [0011]FIG. 3 is a side view of a towing device according to a second preferred embodiment of the present invention;  
         [0012]    [0012]FIG. 4 is an enlarged end view of an interference avoiding unit according to the second preferred embodiment of the present invention;  
         [0013]    [0013]FIG. 5 is an enlarged side view of an interference avoiding unit according to a third preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 6 is an enlarged end view of an interference avoiding unit according to the third preferred embodiment of the present invention;  
         [0015]    [0015]FIG. 7 is an enlarged end view of an interference avoiding unit according to an alternative embodiment of the present invention;  
         [0016]    [0016]FIG. 8 is a side view of a towing tractor according to a prior art;  
         [0017]    [0017]FIG. 9 is a side view of a towing device according to the prior art; and  
         [0018]    [0018]FIG. 10 is a plan view of a towing device according to the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    A first preferred embodiment of the present invention will now be described in reference to FIGS. 1 and 2. Components irrespective of a drawbar operation mechanism are substantially identical to those of the prior art. Therefore, the description of the above components will briefly be described.  
         [0020]    Now referring to FIG. 1, a diagram illustrates a side view of a towing device according to the first preferred embodiment of the present invention. A support member  3  is erected on the rear side of a vehicle body  2 . A shaft C is pivotably supported near the upper end of the support member  3 . The proximal end of a first link member  5  is fixedly connected to the shaft C. The proximal end of an operational member  6  is also fixedly connected to the shaft and the proximal end of the first link member  5 . The distal end of the operational member  6  extends from the shaft C toward the front side of the vehicle body  2  or toward an operator seat. The shaft C, the first link member  5  and the operational member  6  integrally pivot.  
         [0021]    A link mechanism includes the first link member  5  and a second link member  15  through which a drawbar pin or a locking portion  16  is raised or lowered. The first link member  5  includes a grip portion  5   a,  and the distal end of the first link member  5  is coupled to the second link member  15  through an oblong hole  5   b.  The second link member  15  is coupled to a head  16   a  of the drawbar pin  16 . As the first link member  5  pivots about the shaft C, the drawbar pin  16  moves vertically up and down along a drawbar pin hole  17   a  of a drawbar bracket  17 . The drawbar pin  16  couples a drawbar of a carriage or a towing load therewith when it is lowered so as to tow the carriage.  
         [0022]    A stopper or a rotation regulating member includes a stopper bracket  10  and a stopper bolt  11 . The stopper bracket  10  is fixedly connected to the support member  3 . The stopper bolt  11  is fitted into a through hole of the bracket  10  and is adjustable in its level to regulate the maximum upward rotational distance of the first link member  5 . The stopper bolt  11  is supported by the stopper bracket  10  and is located under the operational member  6  so as to correspond with the rotational range of the operational member  6 . The stopper bolt  11  contacts the operational member  6  as the drawbar pin  16  is raised upward through the link mechanism. A clevis or a joint member  7  is pivotably coupled to the operational member  6  through a coupling pin  18 . A cable or a coupling member  8  is connected to the clevis  7 . The other end of the cable  8  travels near a rear axle of the vehicle body  2  and is coupled to an operation lever  14  that is located near the operator seat through a clevis  12 , as shown in FIG. 8. A guide member or an interference avoiding member  19  includes a plate bracket  19   a  and a plate portion  19   b.  The proximal end of the plate bracket  19   a  is rotatably coupled to the coupling pin  18 . The plate portion  19   b  is fixedly connected to the plate bracket  19   a  and is L-shaped in side view.  
         [0023]    Now referring to FIG. 2, a diagram illustrates an enlarged end view of a towing device according to the first preferred embodiment of the present invention. The proximal end of the clevis  7  is pivotably coupled to the distal end of the operational member  6  through the coupling pin  18 . The distal end of the clevis  7  includes a through hole  7   a  for inserting a cable or a coupling member  8 . One end of the cable  8  is inserted through the through hole  7   a  and is connected to the clevis  7  by a fixing holder  20 .  
         [0024]    Referring back to FIG. 1, when the first link member  5  is raised to rotate around the shaft C by holding the grip portion  5   a  that is secured to the first link member  5 , the cable  8  tends to pliantly bend toward the support member  3  so that the clevis  7  together with the cable  8  also tends to pivot toward the support member  3 , that is, a counterclockwise direction in the drawing. Meanwhile, the plate portion  19   b  of the guide member  19  is in contact with an edge  10   a  of the stopper bracket  10 , and the plate portion  19   b  contacts the clevis  7  to prevent the clevis  7  from further pivoting toward the stopper bracket  10 . Since the guide member  19  itself is rotatably coupled to the operational member  6  through the shaft C, the guide member  19  slides on the stopper bracket  10  as the first link member  5  pivots. In the meantime, the clevis  7  is in contact with the guide member  19  and is not caught by the stopper bolt  11  and the stopper bracket  10 . Similarly, the cable  8  that is connected to the clevis  7  is not caught by the stopper bolt  11  and the stopper bracket  10 .  
         [0025]    According to the first preferred embodiment, the following advantageous effects are obtained.  
         [0026]    (1) Even if the first link member  5  is directly pivoted by hand to raise the drawbar pin  16  so that the cable  8  pliantly bends, the lower end of the clevis  7  and the cable  8  are not caught by the stopper. As a result, the first link member  5  smoothly pivots without any interference.  
         [0027]    (2) The guide member  19  and the clevis  7  slides on the stopper bracket  10 . Due to the slide, the guide member  19  not only prevents the stopper from interfering with the clevis  7  and the cable  8  but also guides the clevis  7  and the cable  8 .  
         [0028]    (3) Since the lower end of the guide member  19  forms a rounded surface in such a manner that the lower end of the guide member  19  is bent away from the cable  8 , even if the cable contacts the lower end of the guide member  19 , the cable  8  is not damaged.  
         [0029]    A second preferred embodiment of the present invention will now be described in reference to FIGS. 3 and 4. In the first preferred embodiment, the plate portion  19   b  of the guide member  19  is located between the clevis  7  and the stopper bracket  10 . Instead, in the second preferred embodiment, the shape of the clevis  7  is changed to obtain the same advantageous effects. The same reference numerals in the second preferred embodiment denote the corresponding components in the first preferred embodiment, and description of the substantially identical components is omitted.  
         [0030]    Now referring to FIG. 3, a diagram illustrates a side view of a towing device according to the second preferred embodiment of the present invention. The guide member  19  in the first preferred embodiment is not provided in the second preferred embodiment. Instead, the clevis  70  functions as an interference avoiding member by elongating the clevis  7 . Where h is a distance between a pivotal axis of the coupling pin  18  and the support member side edge of the lower end of the clevis  70 , and where k is the longest distance between the pivotal axis of the coupling pin  18  and the edge  10   a  of the stopper bracket  10 , the distance h is longer than the distance k.  
         [0031]    Now referring to FIG. 4, a diagram illustrates an enlarged end view of a towing device according to the second preferred embodiment of the present invention. Where d is a width of the stopper bracket  10 , and where f is a distance between longitudinally extending portions of the clevis  70 , the width d is longer than the distance f.  
         [0032]    Referring back to FIG. 3, when the first link member  5  is raised by holding the grip portion  5   a,  the cable  8  pliantly bends so that the clevis  70  tends to pivot about the axis of the coupling member  18  toward the support member  3 , that is, a clockwise direction in the drawing. However, since the longitudinally extending portion of the clevis  70  contacts the stopper bracket  10 , the longitudinally extending portion prevents the clevis  70  from further pivoting so that the clevis  70  slides on the stopper bracket  10 .  
         [0033]    Incidentally, the clevis  70  is illustrated to avoid interference with the stopper bracket  10  in the drawing for easier understanding. However, interference with the clevis  70  is also avoided by changing the shape of the stopper bolt  11 .  
         [0034]    According to the second preferred embodiment, the following advantageous effects are obtained.  
         [0035]    (1) The lower end of the clevis  70  avoids interference with the stopper without increasing the number of components.  
         [0036]    (2) Since the clevis  70  extends in a longitudinal direction of the cable  8 , the cable  8  is remotely located from the stopper so that the cable  8  avoids interference with them.  
         [0037]    A third preferred embodiment of the present invention will now be described in reference to FIGS. 5 and 6. In the above preferred embodiments, the guide member  19  is located between the clevis  7  and the stopper bracket  10  in the first preferred embodiment, and the shape of the clevis  7  itself is changed in the second preferred embodiment. In the third preferred embodiment, a compression spring or an urging member  25  urges the clevis  7  away from the stopper to obtain the same advantageous effects. The same reference numerals in the second preferred embodiment denote the corresponding components in the first preferred embodiment, and description of the substantially identical components is omitted.  
         [0038]    Now referring to FIG. 5, a diagram illustrates an enlarged side view of an interference avoiding unit according to the third preferred embodiment of the present invention. The compression spring or an interference avoiding member  25  winds around the coupling pin  18  that couples the clevis  7  and the operational member  6 . The compression spring  25  urges the clevis  7  away from the stopper, that is, a direction indicated by an arrow in the drawing.  
         [0039]    Now referring to FIG. 6, a diagram illustrates an enlarged end view of the interference avoiding unit according to the third preferred embodiment of the present invention. The compression spring  25  is located between the clevis  7  and the operational member  6 . One end  25   a  of the compression spring  25  is secured to the operational member  6 , and the other end  25   b  is secured to the clevis  7 .  
         [0040]    Referring back to FIG. 5, when the first link member  5  is raised by holding the grip portion  5   a  to loosen the tension of the cable  8 , the clevis  7  pivots about the axis of the coupling pin  18  away from the stopper due to urging force of the compression spring  25 .  
         [0041]    According to the third preferred embodiment, the following advantageous effect is obtained.  
         [0042]    (1) Only one simple additional component, which is the urging member such as the compression spring  25 , is merely provided to avoid interference between the lower end of the clevis  7  and the stopper.  
         [0043]    The present invention is not limited to the above preferred embodiments but may be modified into the following alternative embodiments.  
         [0044]    In alternative embodiments to the above preferred embodiments, a chain is employed as a coupling member instead of the cable  8 .  
         [0045]    In alternative embodiments to the above first and third embodiments, an interference avoiding member, such as the guide member  19  and the compression spring  25 , is located on the stopper bolt  11  or the vehicle body  2 .  
         [0046]    In alternative embodiments to the above first preferred embodiment, an interference avoiding member is integrated with a joint member. For example, referring to FIG. 7, a plate  7   b  is secured to the clevis  7 .  
         [0047]    In alternative embodiments to the above second preferred embodiment, a portion of the clevis  70  facing the stopper bracket  10  includes a sufficient length for avoiding interference.  
         [0048]    In alternative embodiments to the above third preferred embodiment, a pair of the compression springs  25  is located on both sides of the operational member  6 , and each of the compression springs  25  couples the operational member  6  and the clevis  7 .  
         [0049]    In alternative embodiments to the above third preferred embodiment, an urging member is not limited to the compression spring  25 . In addition, a position of the urging member is not limited. As far as the urging member urges the clevis  7  away from the stopper, any positions are applicable.  
         [0050]    Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.