Abstract:
A strut is provided for a three-point hitch device used to attach farm implements to an agricultural tractor. The strut is substantially symmetrical with respect to a longitudinal axis of symmetry, and has a system for adjusting its length along the axis. The adjusting system has fast, discrete length adjustment devices, and two infinite length adjustment devices. The two infinite length adjustment devices are located on opposite sides of a dividing member positioned crosswise to the axis of the strut.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to hitch devices for attaching farm implements to a tractor and, more particularly, to a strut for a farm implement hitch device.  
           [0002]    So-called “three-point hitches” normally comprise a top link and two bottom arms articulated to the tractor frame whereby each bottom arm is connected to a respective hydraulic lifting device. A farm implement, such as a plow or ripper, is fixed by known means to a three-point hitch of the above type.  
           [0003]    Hitches of the above type allow the bottom arms to swing laterally when the tractor is moving. Particularly during on-highway transfer and when the implement is raised, lateral swing of the bottom arms is extremely dangerous, and may result in serious damage and/or personal injury caused by collision with the implement and/or hitch components. In such conditions, therefore, steps should be taken to ensure that the hitch and attached implement swing as little as possible. To this end, side struts of a fixed length are provided which operate on the bottom arms of the hitch.  
           [0004]    On the other hand, when operating on a field, the strut should act as a stabilizer, since under these conditions it is often necessary to allow the implement to float to a certain extent. In other words, when actually working, it is often preferable to employ, as opposed to an overly rigid implement towing system, one allowing the implement to swing to a certain extent on encountering obstacles (such as stones) in the field.  
           [0005]    For this purpose, stabilizing struts have been proposed which are connected, at one end, to the tractor frame, and are fixed at the other end to one of the bottom three-point hitch arms.  
           [0006]    Stabilizing struts of this sort provide, in fact, for bracing the implement towing system, e.g. during on-highway transfer of the tractor, while at the same time allowing the three-point hitch and attached implement to swing to a certain extent when working on the field.  
           [0007]    The stabilizing struts employed so far, however, fail to provide for reliable adjustment of the degree of rigidity of the implement towing system.  
         SUMMARY OF THE INVENTION  
         [0008]    It is therefore an object of the present invention to provide a reliable strut for use in the hitch apparatus of agricultural tractors.  
           [0009]    It is a feature of this invention that a strut for a tractor three-point hitch includes a discrete length adjustment mechanism and two infinite length adjustment devices.  
           [0010]    It is another feature of this invention that the infinite length adjustment devices are located on opposite sides of a dividing member  
           [0011]    It is still another feature of this invention that the infinite length adjustment devices are positioned crosswise to the axis of the strut.  
           [0012]    It is an advantage of this invention that the adjustment of the axial length of the strut can be quickly and selectively accomplished.  
           [0013]    It is yet another feature of this invention that the adjustment of the length of the strut is accomplished through utilization of a number of through holes in the tubular member of the strut and a number of through holes in the sleeve of the strut.  
           [0014]    It is another advantage of this invention that a continuous fine adjustment of the length of the strut can be accomplished at both ends of the strut by manipulation of two rods with respective threaded shanks.  
           [0015]    It is still another advantage of this invention that the strut is free to swing within predetermined limits when required.  
           [0016]    It is yet another feature of this invention that the tubular member is allowed to float inside a cavity within the strut by lifting the spring member and removing a pin.  
           [0017]    It is yet another advantage of this invention that the strut can be preloaded using the fine-adjustment system to eliminate any slack caused by discrete adjustment using the pin.  
           [0018]    It is a further advantage of this invention that the degree of float can be adjusted according to the type of work to be performed by the implement attached to hitch device by allowing float on one side of the strut and setting a length at the other side of the strut.  
           [0019]    It is another object of this invention to provide a strut apparatus for a three-point hitch mechanism on an agricultural tractor such that the strut may replace the lifting arms of the conventional hitch which are connected to the lower arms of the hitch and which also require a length adjustment mechanism.  
           [0020]    These and other objects, features and advantages are accomplished according to the instant invention by providing a strut for a hitch device for attaching farm implements to a tractor. The strut is substantially symmetrical with respect to a longitudinal axis of symmetry, and has a system for adjusting its length along the axis. The adjusting system has fast, discrete length adjustment devices, and two infinite length adjustment devices. The two infinite length adjustment devices are located on opposite sides of a dividing member positioned crosswise to the axis of the strut. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings, wherein:  
         [0022]    [0022]FIG. 1 is a rear perspective view of a three-point hitch apparatus located at the rearward end of an agricultural tractor provided with a strut incorporating the principles of the instant invention, the strut being depicted as connected at one end to a tractor frame, and at the other to a bottom arm of the three-point hitch apparatus;  
         [0023]    [0023]FIG. 2 is a side elevational view of the strut depicted in FIG. 1;  
         [0024]    [0024]FIG. 3 is a cross-sectional view of the strut taken along lines A—A of the FIG. 1; and  
         [0025]    [0025]FIG. 4 is an end view of the strut depicted in FIGS.  1 - 3 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    As shown in FIG. 1, a strut  10  in accordance with the present invention is associated with a three-point hitch apparatus  100  used to connect a conventional farm implement (not shown), such as a wagon, baler or other harvesting implement, to be towed by an agricultural tractor to which the three-point hitch is mounted at the rearward end thereof. Though reference is made in the following description to use of the strut according to the present invention as a stabilizing strut for preventing lateral swing of the hitch, it may be used for replacing other components of the three-point hitch, which need adjustment. In the latter case, the floating capability may require elimination, as will be described in greater detail below. The strut also may be used on a three-point hitch apparatus, whether located at the rear or at the front of the agricultural tractor.  
         [0027]    The strut  10  is fitted by known means at one end to a bottom arm A of the hitch device  100 , and is supported at the other end by a supporting device S screwed to the frame F of the tractor. More specifically, in the FIG. 1 embodiment, the strut  10  is hinged by a pin P 1  at a first end to a bracket ST integral with the arm A, and is hinged by a pin P 2  at a second end to a fork FR integral with the support S.  
         [0028]    As shown in FIGS.  2 - 4 , the strut  10  comprises a substantially tubular outer body  11 . The tubular outer body  11  is divided by a wall  12  into two sleeves  11   a ,  11   b , each having a respective cavity  13 ,  14 . The outer body  111  may be formed by welding sleeves  11   a  and  11   b  to the wall  12 , which may comprise a projecting portion  12   a  in which an opening  12   b  is formed for housing a pin  19 , as will be described in greater detail below.  
         [0029]    Referring now to FIG. 3, the cavity  13  houses a tubular member  15 , at a first end  15   a  of which is formed a threaded seat  16  extending in the direction defined by a longitudinal axis of symmetry (a). The tubular member  15  also comprises a through hole  17  crosswise to the axis (a). As seen in FIGS. 2 and 3, a second end  15   b  of tubular member  15  rests against the wall  12 , and the transverse through hole  17  is aligned with a through hole  18  (FIG. 2) in the outer body  11 , so that the pin  19  need simply be inserted inside the coaxial holes  18  and  17  to connect the tubular member  15  integrally to the outer body  11 . The pin  19  is advantageously provided with a substantially U-shaped spring member  20  for preventing, in known manner, accidental withdrawal of the pin  19  from the holes  17 ,  18 . As stated, when not inserted inside the holes  17  and  18 , the pin  19  may be housed inside the opening  12   a.    
         [0030]    A threaded shank  21   a  of a rod  21  is screwed inside the threaded seat  16 . The rod  21  further comprises a head  21   b  having a seat  21   c  for housing a spherical joint  22  into which the pin P 2 , best seen in FIG. 1, is inserted, as stated, to connect one end of the strut  10  integrally to the support S.  
         [0031]    At the end near the spherical joint  22 , therefore, by lifting the spring member  20  and removing the pin  19  from the through holes  17 ,  18 , the tubular member  15  is allowed to float freely inside the cavity  13 . This capability is advantageously employed in certain operating modes of the tractor, as when working on a field.  
         [0032]    In a similar manner, the cavity  14  in the sleeve  11   b  houses a tubular member  24 . At a first end  24   a  of the member  24  a threaded seat  25  is formed, which extends in the direction defined by the longitudinal axis of symmetry (a). The tubular member  24  also comprises a number of through holes  26   a - 26   f  crosswise to the axis (a). As seen in FIGS. 2 and 3, a second end  24   b  of the tubular member  24  rests against the wall  12 , and the transverse through hole  26   f  is aligned with a through hole  27  (FIG. 2) forming part of a series of holes  27   a - 27   d  formed in the sleeve  11   b , so that a pin  28  (FIG. 2) need simply be inserted inside the coaxial through holes  26   f  and  27   d , such as depicted in FIG. 3, to connect the tubular member  24  integrally to the outer body  11 . The holes  26  differ in number from the holes  27 , and the series of holes  26  has a different spacing from that of the series of holes  27 , increasing the number of positions that the tubular member  24  may take up relative to the outer body  11 .  
         [0033]    The pin  28  is also advantageously provided, as depicted in FIG. 2, with a substantially U-shaped spring member  29  (identical with the spring member  20 ) for preventing, in known manner, accidental withdrawal of the pin  28  from the coaxial, aligned through holes.  
         [0034]    As shown in FIG. 3, the transverse holes  26   a - 26   f  formed in the tubular member  24  and aligned along the axis (a), the through holes  27   a - 27   d  formed in the sleeve  11   b , and the pin  28  form a system for rapidly adjusting the position of the tubular member  24  with respect to the wall  12  along the axis (a). Obviously, adjusting the position of the tubular member  24  along the axis (a) results in a variation of the overall length of the strut  10 .  
         [0035]    Accordingly, at the pin PI end (FIG. 1), by lifting the spring member  29  and removing the pin  28  from the through holes  26   f ,  27   d , the tubular member  24  can be shifted axially, and one of holes  27   a - 27   d  (in sleeve  11   b ) in combination with one of the other holes  26   a - 26   e  can be used to selectively and rapidly adjust the axial position of the tubular member  24  by sliding it inside the cavity  14 .  
         [0036]    A threaded shank  30   a  of a rod  30  is screwed inside the threaded seat  25 . The rod  30  further comprises a head  30   b  having a seat  30   c  into which the pin P 1  (FIG. 1) is inserted to fix the other end of the strut  10  to bracket ST, which, as already mentioned, is integral with arm A of the hitch device  100 .  
         [0037]    A finer length adjustment of the strut  10  can be made by rotating the tubular members  15 ,  24  (connected integrally to the outer body  11  by respective pins  19 ,  28 ) with respect to the rods  21 ,  30  using a plate  23  integral with the outer body  11 . In other words, once the strut  10  is mounted, the user can further adjust the length of the strut  10  by manually gripping the plate  23  and rotating the plate  23  about the axis (a) together with the outer body  11  and the tubular members  15 ,  24 . This serves to preload the strut  10  and eliminate any slack caused by using only the pin  28  as a discrete adjustment member.  
         [0038]    To be able to lengthen or shorten the strut  10  by rotation of the outer body  11  in the one or other sense, the shanks  21   a  and  30   a  of rods  21  and  30  have oppositely directed threads. The same applies to the respective nut screws inside the threaded seats  16  and  25 .  
         [0039]    Operation of strut  10  according to the present invention is easily deducible from the foregoing description. The main advantages of strut  10  when used as a stabilizing strut according to the present invention are a fast, selective adjustment of the axial length of the strut by means of a number of through holes  26   a - 26   f  in tubular member  24 , and a number of through holes  27   a - 27   d  in sleeve  11   b ; the continuous fine adjustment of the length of the strut at both ends with respect to the wall  12  by means of the two rods  21 ,  30  with respective threaded shanks  21   a ,  30   a ; and the degree of float can be adjusted according to the type of work to be performed by the implement attached to device  100 . The tubular member  15  can be allowed to float inside the cavity  13  by lifting the spring member  20  and removing the pin  19 , so that the apparatus  100  is free to swing within given limits when required. The strut  10  can be preloaded using the fine-adjustment system to eliminate any slack caused by discrete adjustment using the pin  28 . The degree of float can be adjusted by, on the one hand, allowing float on one side of the strut and, on the other hand, setting a length at the other side.  
         [0040]    In embodiments not shown, the strut  10  may advantageously replace the lifting arms B 1 , B 2  (FIG. 1) which are connected to the lower arms A and which also require a length adjustment mechanism. Obviously, for such an arrangement, the float condition would not be required as the arms A otherwise would fall onto the ground. Comparably, the principles of strut  10  also could be applied to top link B 3 .  
         [0041]    It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.