Abstract:
A pivot connection for a grapple having a link member with a journal-bore at one end, a yoke member with spaced-apart parallel arms receiving the one end of the link member therebetween bores in the arms, and a pivot pin mounted through the bores in the arms in the yoke member and the journal-bore in the link member to pivotally connect the two members together. Tapered, counter-bored brake surfaces are provided in each side of the link member concentric with the journal-bore. Tapered brake cores are slidably mounted on the pivot pin and located in the counter-bores facing each other, each core located between an arm of the yoke and the link member, in such a way that the break cores are not load bearing structures in the pivot connection. A mechanical connection applies pressure to one of the cores to force both cores against the brake surfaces to brake the link member relative to the yoke member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is directed toward an improved, snubbed, pivot connection. 
     2. Description of the Prior Art 
     Grapples are employed in loading or skidding logs in the forest industry. The grapple has a pair of grapple arms pivotally suspended from the end of a boom, the arms operable to grapple or grab a load of logs. The pivot connection connecting the grapple arms to the boom comprises two pivots, with the axis of the two pivots at right angles to each other to permit universal movement of the grapple arms. To prevent the grapple arms from swinging uncontrollably about the pivots, which swinging could cause damage and/or injury, and which causes excessive wear on the pivots, dampers or snubbers are provided in the pivots to dampen the swinging movement. 
     Each pivot usually employs a link member pivotally connected by a pivot pin between the arms of a yoke member. The snubber employed is usually a dual snubber having a pair of opposed brake means in the pivot to balance the braking load and reduce wear. Examples of such dual snubbers are shown in U.S. Pat. No. 4,572,567, Johnson, issued Feb. 25, 1986, and in U.S. Pat. No. 4,573,728, Johnson, issued Mar. 4, 1986, by way of example. These dual snubbers are usually operated by hydraulic means. The use of fluid to actuate the brake means in the dual snubber presents a problem in that the fluid leaks. Leakage of fluid changes the braking effect. In addition, the hydraulic actuating means employed in these dual snubbers are often complicated in construction and thus expensive. The known dual snubbers also have wear problems due to the type of brake means employed. Brake disks, as employed in U.S. Pat. No. 4,573,728, for example, wear unevenly because it is difficult to apply pressure uniformly. Often the brakes are quite small, as in U.S. Pat. No. 4,572,567, for example, and thus tend to wear out quite quickly because of the load applied. 
     It is known to provide snubbers that are mechanically rather than hydraulically operated. These single snubbers employ a tapered brake sleeve in the brake means cooperating with a tapered braking surface. These brake means increase the braking efficiency because of their size, and being self-centering, braking force is applied more evenly, thus reducing wear of the brake means. The tapered brake sleeve, being operated mechanically rather than hydraulically, ensures that the braking force remains more constant. Examples of such snubbers are shown in U.S. Pat. No. 5,451,087, Beaulieu, issued Sep. 19, 1995. However, these single snubbers do not provide balanced braking and thus have excessive wear. In addition, the adjustment means employed to control their braking force are still quite complicated and thus expensive. Further, the single snubbers require enlarged yokes to be properly used in some embodiments, and in other embodiments, the single snubbers are exposed to damage. 
     Other examples of double mechanically operated snubbers are found in U.S. Pat. No. issued Feb. 3, 1998. These double snubbers are an integral part of the load bearing structure at the pivot connection and subject to uneven wear of the breaking surfaces leading to a reduced dampening ability of the snubber. 
     SUMMARY OF THE INVENTION 
     It is the purpose of the present invention to provide a dual snubber for a pivot connection, employing a link member within a yoke member, which dual snubber is mechanically operated in a simple and easy manner. 
     It is another purpose of the present invention to provide a mechanically operated dual snubber in which the braking force is easily adjusted. 
     It is another purpose of the present invention to provide a dual snubber employing tapered brake cores which are mounted in a compact manner in a protected environment. 
     It is another purpose of the present invention to provide a dual snubber for a pivot connection, wherein the load is not borne by the brake cores. 
     In accordance with the present invention, there is provided a pivot connection having a pivot pin member between the arms of a yoke member and a link member having a journal-portion journalled on the pivot pin between the arms of the yoke member. Tapered brake cores are provided adjacent each side of the journal-portion of the link member, mounted for axial sliding movement on the pivot pin. Recesses are provided on each side of the journal portion of the link for receiving the respective brake cores. The recesses define conical brake surfaces to be contacted by the brake cores. The recesses in the link member for receiving the cores provide a compact mounting for the cores and also protect the cores. 
     The improved pivot connection also includes mechanical means on the pivot pin at one end of the pin for biasing the brake core adjacent the one end into contact with the link member, which biasing action simultaneously biases the other brake core into contact with the other side of the link member. The braking force is easily adjusted by the mechanical means and remains the same, once set, except for wear of the brake surfaces. The location of the mechanical means provides easy access for adjustment of the braking force. 
     The invention is particularly directed toward a pivot connection having a link member with a journal-bore at one end, a yoke member with spaced-apart parallel arms receiving the one end of the link member therebetween, bores in the arms, and a pivot pin mounted through the bores in the arms in the yoke member and the journal-bore in the link member to pivotally connect the two members together. Tapered, counter-bored brake surfaces are provided in each side of the link member concentric with the journal-bore. Tapered brake sleeves are slidably mounted on the pin and located in the counter-bores facing each other, each core located between an arm of the yoke and the link member. A nut, threaded on the end of the pin outside the yoke, applies axial pressure through a mechanical connection to one of the cores to force both cores against the brake surfaces to brake the link member relative to the yoke member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood by an examination of the following description, together with the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of the pivot connection according to an embodiment of the present invention; 
     FIG. 2 is a front exploded view, in partial cross-section, of the pivot connection; 
     FIG. 3 is a partial cross-sectional view of the link member used in the pivot connection; 
     FIG. 4 is a cross-sectional view of one of the brake cores; and 
     FIG. 5 is a cross-sectional view of the pivot connection according to another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to an embodiment of the present invention, the pivot connection  1 , as shown in FIGS. 1,  2  and  3 , has a link member  3  having a journal-bore  5  in its lower portion  3 a that is transverse to an upper pivot opening on the upper portion of the member. The upper pivot bore  7  can be used to rotatably mount the link member  3  on the end of a boom (not shown), or to another pivot connection (not shown). The sides  9 ,  11  of the link member  3 , which are transverse to the axis of the journal-bore  5 , have tapered, countersunk recesses  13 ,  15  concentric with the journal-bore  5 . The opposed recesses  13 ,  15  each define tapered brake surfaces  17 ,  19  within the link member  3 . 
     The pivot connection  1  includes a bottom yoke member  25  having a pair of parallel arms  27 ,  29  with aligned pivot bores  31 ,  33  defined coaxially through the arms  27 ,  29 . The lower journal-portion of link member  3  fits between the arms  27 ,  29  and a pivot pin  37  passes through the aligned bores  5 ,  31 ,  33 . The mechanical connection between pivot pin  37  and the journal-bore  5  is made through a replaceable wear bushing  6 . The pivot pin  37  has a head  39  on one end that abuts one side  41  of the arm  29 , and the other end is threaded as shown at  43 . A nut  45  is threaded on the threaded end of the pin  37  to retain it in place. 
     Brake means are provided on the pin  37  for cooperating with the brake surfaces  17 ,  19  on the link member  3 . The brake means comprise a pair of tapered brake cores  51 ,  53  slidably mounted on the pin  37  with one core  51  located between arm  27  and the link member  3  and the other core  53  located between the other arm  29  and the link member  3 . Each core  51 ,  53  is provided with an outer conical friction sleeve  55 ,  57  respectively. The cores  51 ,  53  are sized to fit snugly within the tapered brake surfaces  17 ,  19  in the link member  3 . 
     Means are provided for fixing the brake cores  51 ,  53  against rotation relative to the pin  37  and yoke  25 . O-rings  16  are provided to seal the cores  51 ,  53  to the pin  37 . The rotation preventing means can comprise first rotation preventing means  59  for preventing rotation of the pivot pin  37  relative to the yoke member  25  and brake core  53  relative to pin  37 ; and second rotation preventing means  61  for preventing rotation of the brake core  51  relative to the yoke member  25 . The first rotation preventing means  59  can comprise a set of pins  63  (two shown) that project from the head  39  of the pin  37 , parallel to the axis of the pin  37 , through holes  65  in arm  29  of the yoke member  25 . As shown, the rotation preventing means for core  53  is accomplished by pins  63  which extend through holes  65  of arm  29  into blind holes  75  formed in the outer side  77  of core  53 . The second rotation preventing means  61  can comprise a slot  71  (only one shown) provided on the outer periphery of the brake core  51 . The stop tab  73  (only one shown) is part of the yoke member  25  adjacent the base of arm  27 . 
     Mechanical means are provided for forcing the brake cores  51 ,  53  against the brake surfaces  17 ,  19  and to provide brake movement of the link member  3  relative to the yoke member  25 . The mechanical brake applying means has a thrust sleeve  81  mounted on the pivot pin  37  at its threaded end  43 . The threaded end  43  of the pivot pin  37  can be reduced in diameter, as shown at  83 , to receive the sleeve  81 . The sleeve  81  fits snugly between the pin  37  and the arm  27  in the bore  31  and is slidable on the reduced diameter portion  83  of the pin  37 . The mechanical brake applying means includes a Belleville-type spring washer  87  and the nut  45 . The washer  87  is mounted within a shallow counter-bore  89  on the outer face  91  of the brake core  51  with the outer peripheral edge  93  of the washer  87  bearing against the inner surface  95  of the counter bore  89  and the inner peripheral edge  97  of the washer  87  bearing against the inner end  99  of the sleeve  81 . The nut  45  on the pin  37  bears against the outer end  101  of the sleeve  81 . 
     When the nut  45  is tightened on the pin  37 , it pushes the sleeve  81  against the washer  87 , the washer  87  resiliently biasing the brake core  51  against the brake surface  17 . This tends to push the link member  3  to the side, as seen in FIG.  1 . However, this causes the brake core  53  on the other side to be also biased against its brake surface  19  on the other side of the link member  3  since the core is prevented from moving to the side by the arm  29  of the yoke member  25 . Thus, braking is provided equally from both brake cores  51 ,  53 . The braking force is controlled by the position of the nut  45  on the threaded end of the pivot pin  37 . 
     According to another embodiment (not shown), the rotation preventing means for both cores  51  and  53  can comprise slots  71  and stop tabs  73 . 
     According to yet another embodiment of the present invention as shown in FIG. 5, a pivot connection  2  has a link member  3  having a journal-bore  5  in its lower portion  3 a, that is transverse to an upper pivot opening  7  on the upper portion of the link member  3 . Side  9  of the link member  3  has a tapered, countersunk recess  13  concentric with the journal-bore  5 . The recess  13  defines a tapered brake surface  17  within the link member  3 . 
     The pivot connection  2  includes a bottom yoke member  25  having a pair of parallel arms  27 ,  29  with aligned pivot bores  31 ,  33  defined coaxially through the arms  27 ,  29 . The lower journal-portion of link member  3  fits between the arms  27 ,  29 , and a pivot pin  37  passes through the aligned bores  5 ,  31 , and  33 . The pivot pin  37  has a head  39  on one end that abuts one side  41  of the arm  29 . The other end of the pin  37  is threaded as shown at  43 . A nut  45  is threaded on the threaded end of the pin  37  to retain it in place. 
     Brake means are provided on the pin  37  for cooperating with the brake surfaces  17  on the link member  3 . The brake means comprise a tapered brake core  51  slidably mounted on the pin  37  with the core  51  located between arm  27  and the link member  3 . The core  51  is provided with an outer conical friction sleeve  55 . The core  51  is sized to fit snugly within the recessed, tapered brake surface  17  in the link member  3 . 
     Means are provided for fixing the brake core  51  against rotation relative to yoke  25  shown at  61 . The rotation preventing means  61  comprise a slot  71  (only one shown) provided on the outer periphery of the brake core  51 , and a stop tab  73  (only one shown) is part of the yoke member  25  adjacent the base of arm  27 . 
     Mechanical brake-applying means are provided for forcing the brake core  51  against the brake surfaces  17  and to provide snubbing effect of the link member  3  relative to the yoke member  25 . The mechanical brake-applying means includes a thrust sleeve  81  mounted on the pivot pin  37  at its threaded end  43 . The threaded end  43  of the pivot pin  37  can be reduced in diameter, as shown at  83 , to receive the sleeve  81 . The sleeve  81  fits snugly between the pin  37  and the arm  27  in the bore  31  and is slidable on the reduced diameter portion  83  of the pin  37 . The mechanical brake-applying means includes a Belleville-type spring washer  87  and the nut  45 . The washer  87  is mounted within a shallow counter-bore  89  on the outer face  91  of the brake core  51  with the outer peripheral edge  93  of the washer  87  bearing against the inner surface  95  of the counter-bore  89  and the inner peripheral edge  97  of the washer  87  bearing against the inner end  99  of the sleeve  81 . The nut  45  on the pin  37  bears against the outer end  101  of the sleeve  81 . 
     According to this embodiment, when the nut  45  is tightened on the pin  37 , it pushes the sleeve  81  against the washer  87 , whereby the washer  87  resiliently biases the brake core  51  against the brake surface  17 . This tends to push the link member  3  to the side, as seen in FIG.  5 . However, this causes a pressure plate  202  on the other side of the link member  3  to be also biased against side  10  of the link member  3  since side  206  of pressure plate  202  abuts against the arm  29  of the yoke member  25 . Side  204  of pressure plate  202  has a countersunk groove  208  in which thrust bearing  210  is positioned to provide frictionless contact between side  10  of link member  3  and side  204  of pressure plate  202 . Braking is provided by brake core  51 . The braking force is controlled by the position of the nut  45  on the threaded end of the pivot pin  37 . 
     The contact surface between the friction sleeve  55  on the brake core  51  and the brake surface  17  can be greased, if desired, to increase the life of the brake means. Alternatively, the friction sleeves and the brake surfaces can be made from composite materials which increase the life of the contact surfaces. 
     It is noted that link  3  includes a relatively broad central portion  3 a, journalled directly to the pin  37 , in order that the load of the grapple is transferred directly from the yoke arms through the pin  37  and to the link  3 . This avoids undue wear on the brake core  51  and friction sleeve  17 . 
     The described arrangement provides a compact, yet effective, single acting snubber on a grapple. The mechanical operation of the snubber is simple and easy as is adjustment of the braking force.