Abstract:
The present invention is directed toward a stabler leveling mechanism for tree harvesters. The present invention utilizes many of the same components of conventional leveling mechanisms for tree harvesters, but it alters the pivot axis of a swing-house assembly. A conventional swing-house assembly pivots about an axis parallel to the top surface of a carriage on level ground. That conventional assembly can be deleterious, therefore, applicant has altered the pivot axis of the swing-house assembly. Admittedly, merely moving the pivot axis seems simple but it is difficult. The components had to be constructed differently to obtain the desired results and simultaneously make the device stable within the working environment.

Description:
FIELD OF THE INVENTION 
     This invention relates to a mechanism that stabilizes a boom swing-house assembly of a forestry machine by leveling the swing-house in uneven or sloping terrain. 
     DISCUSSION OF THE PRIOR ART 
     Forestry machines, such as feller bunchers for harvesting standing trees, are well known. In one type of feller buncher, a saw head which is used to sever the tree is mounted at the end of a boom which has its other end mounted to a turntable so as to be pivotable about a lateral axis relative to the turntable. The turntable is mounted to a turntable support so as to be pivotable about a vertical axis (when the support is vertical). A carriage, which can have tracks or wheels for conveying the turntable support, has a frame to which the turntable support is mounted by a leveling mechanism. The leveling mechanism is operable to vary the position and orientation of the turntable support relative to the carriage, depending upon the slope of the terrain and the orientation of the carriage on the terrain. For example, if trees are being cut on a hillside, the machine will typically be driven onto the hillside so the trees are within reach of the boom and the leveling mechanism adjusted so as to make the axis of the turntable generally vertical. The center of gravity of the swing-house assembly; which includes the boom and the cutting head attached, the engine of the machine and the operator cab; mounted on the turntable, should be in a predetermined positioned. That position should be relative to the carriage so that the machine does not tip forward or backward when the tree is cut and its weight comes to rest on the butt plate of the head. 
     Such a mechanism has been made using linkages and hydraulic cylinders for moving the linkages as described in U.S. Pat. No. 4,679,803. In that mechanism, one set of links is provided forwardly and another set is provided rearwardly, and hydraulic cylinders connect the links both laterally and longitudinally to tilt the turntable relative to the carriage both about a lateral axis and a longitudinal axis. Other mechanisms for positioning and orienting the swing-house assembly relative to the carriage are also discussed in U.S. Pat. Nos. 4,679,803, and 6,173,973. The latter patent sets forth and confirms that other leveling devices for tree-harvesters require that the swing-house pivot about an axis parallel to the carriage, when the carriage is on a planar surface as shown in FIG.  6 . This type of pivot action can be deleterious because the center of gravity is extremely high when a tree is being harvested. 
     This invention solves that problem by directing the center of gravity of the complete swing house assembly  12  away from the tip axis of the complete machine. The invention is successful because, for at least one reason, of the unique orientation of the side pivot axis  170 . 
     In Timberjack&#39;s Canadian patent application 2276515 claim 5 (a dependent claim), there is a reference to a similar obtuse angle being formed between the turntable major axis  34  and the side tilt axis  170 . The present invention improves the angle to achieve better weight transfer and does it without the use of complicated linkages, used in Timberjack&#39;s application, to achieve this obtuse angle. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a stable leveling mechanism for tree harvesters. The present invention utilizes many of the same components of conventional leveling mechanisms for tree harvesters, but it alters the pivot axis of a swing-house assembly. A conventional swing-house assembly pivots about an axis parallel to the top surface of a carriage on level ground. That conventional assembly can be deleterious, therefore, applicant has altered the pivot axis of the swing-house assembly. Admittedly, merely moving the pivot axis seems simple but it is difficult. The components had to be constructed differently to obtain the desired results and simultaneously make the device stable within the working environment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a harvesting device illustrated on a slope, with the swing-house assembly tilted forwardly, with a portion of the track broken away; 
     FIG. 2 is an enlarged isometric cross-sectional view of the carriage and the present invention of FIG. 1 showing the turntable slew bearing in a position parallel to the ground; 
     FIG. 3 is an isometric view of the FIG. 1 without the swing-house assembly showing the turntable slew bearing in a position tilt full forward to the ground; 
     FIG. 4 is an alternative embodiment of FIG. 2 showing the present invention tilting rearwardly; 
     FIG. 5 is a schematic showing the pivot axes of the present invention compared to the prior art devices using no linkages; and 
     FIG. 6 a  illustrates the tip axis of the prior art and FIG. 6 b  illustrates the tip axis of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a forestry machine  10 , particularly a feller buncher, which includes a carriage  14  and a swing-house assembly  12 . The carriage  14  includes tracks  16  and  18  (not shown). The tracks  16 ,  18  (not shown) engage the ground G and are mounted to a carriage frame  20  so as to propel the vehicle  10  when driven. The drive mechanism of the tracks  16  and  18  and the general structure of the frame are conventional, may be of any suitable type and are not discussed in detail here. 
     The swing-house assembly  12  includes a cab  22  in which the vehicle operator sits and controls the vehicle, an engine  24  that provides power for driving the carriage and the hydraulic systems of the vehicle  10 , and a boom  26 , all of which are mounted to a turntable  30 . At the end of the boom opposite from the cab  22 , a cutting head  28  is mounted for harvesting a tree. Many different types of cutting heads are available, a high speed disc saw felling head being illustrated. These instruments are well known to those skilled in the art. 
     As with most turntables, the turntable  30  is mounted to a turntable slew bearing  32  so as to be rotatable about a turntable major axis  34 . A ball bearing connection may be used to provide this rotary connection. An internal gear is fixed relative to the turntable slew bearing  32  and a hydraulic motor is fixed to the turntable  30  so as to rotate a pinion which meshes with the internal gear. Driving the pinion along the internal gear serves to rotate the swing-house assembly  14  360° in either direction relative to the turntable support  32 . The connection of the turntable to the turntable support and the driving of the turntable about the turntable major axis relative to the turntable support are all conventional, and may be performed in any suitable way to practice the invention. 
     Turning to FIG. 2, the turntable slew bearing  32  is secured into position over the carriage  14  through a upper pivot support  130  and an intermediate pivot support  270 . The upper pivot support  130  and the turntable slew bearing  32  are secured together by conventional methods, such as by bolts  131 . 
     The upper pivot support  130  has at least four flanges, two pairs of rod end lugs  132   a ,  132   b , and two side pivot axis lugs  134   a ,  134   b . The side pivot axis lugs  134  are at or near a 100° angle in relation to the upper pivot support  130  and the turntable slew bearing  32 , and extend toward the carriage  14 . Each side pivot axis lug  134  has a first aperture  136 , as shown in FIG.  3 . Assuming the carriage  14  has a front end  77  that is always 12:00 in relation to the upper pivot support  130 , then the side pivot axis lugs are at or near  12  and 6 o&#39;clock in relation to the upper pivot support  130 . These lugs are at or near the end of the upper pivot support  130 . 
     In contrast, the rod end lugs  132  are positioned at or near 3 and 9 o&#39;clock  172  in relation to the upper pivot support  130 . Moreover, the rod end lugs  132  are positioned to allow the full range of motion for the swing-house assembly  12  to be optimized. In particular, the rod end lugs are positioned at an obtuse angle from the turn table major axis toward the rear  76  of the carriage  20  and the ground G. Each rod end lug  132  has a second aperture  138  and each rod end lug  132  is spaced from its corresponding pair by a predetermined distance (D) to allow a force to move between the pair of lugs  132 . 
     The intermediate pivot support  270  provides the female lugs  234   a ,  234   b  to receive the side pivot lugs  134   a ,  134   b  from the upper pivot support. Two suitable bearing and pin arrangements are use to connect the upper pivot support and the intermediate pivot support  270  and this forms the means for a side to side pivot axis  170 . 
     The intermediate pivot support also provides a fore/aft pivot axis  275  at or near 90° to the side pivot axis  170  and on a plane below the top tangential horizontal level of the front idler wheel  276  and forward of the turntable major axis  34 . A suitable bearing connection is made between both outside members  277   a  &amp;  277   b  of the intermediate pivot support  270  and the undercarriage  14 . Preferably, the angle of the side pivot axis  170  is at an obtuse angle  250  less than 130° from the turn table major axis. The obtuse angle  250  is in the direction of a predetermined working zone of the leveling mechanism (defined in the drawings) to provide maximum effect on the relocation of the center of gravity of the swing-house assembly relative to a side tip axis of the leveling mechanism. 
     The predetermined force  140   a,b  is applied by, in this embodiment illustrated as, a hydraulic cylinder  142   a, b.  The hydraulic cylinder  142  is a conventional unit that is interconnected to the engine  24  and controlled by the user in the cab  22 , in the conventional manner known to those of ordinary skill in the art. As with all hydraulic cylinders  142 , there is a distal end  144  and a proximal end  146 . The distal end  144  pivotally connects between each set of rod end lugs  132  that allows for non-planer movement between the hydraulic cylinder axis  280  and the plane of the turntable  30 . The method of pivotally interconnecting the distal end  146  to the set of rod end lugs  132  is done in the conventional method known to those skilled in the art. 
     In contrast, the proximal end  146  pivotally connects to the carriage  14 . This pivotal interconnection must occur on a plane below the top tangential horizontal level of the front idler wheel  276  and behind the turn table major axis  34 . The method of pivotally interconnecting the proximal end  146  to the carriage  14  is done in the conventional method known to those skilled in the art. This is referred to as the location of fore/aft pivot. 
     By being pivotally interconnected to the carriage  14  and allowing the distal end to move within the pair of lateral flanges  132 , the hydraulic cylinders  142   a, b  can lift and alter the plane of the swing-house assembly  12  to a desired position. In relation to the lower level of the tracks  148 , the swing house assembly  12  can be tilted anywhere from +26° to −10° in the x,y plane and +22° to −22° in the z,y plane (see FIG. 2) in relation to when the swing-house assembly  12  is parallel to the carriage  14  on level ground, as shown in FIG.  2 . 
     When the cylinders  143   a, b  are extended or retracted in unison, the swing-house assembly  12  and upper pivot support  130  pivots about the fore/aft axis  275  either forwardly as illustrated in FIG. 1, or rearwardly as illustrated in FIG.  4 . Likewise, when the cylinders  143   a, b  are extended or retracted in a non-unison manner, the swing-house pivots about the axis  170 . 
     The side axis stabilizes the device by moving the center of gravity  171  to a position away from the tip axis  251   a , as shown in FIG. 6 b , in relation to prior art devices, as shown in FIGS. 5 and 6 a.    
     A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to those skilled in the art. Therefore, the invention should not be limited to the embodiment described, but should be defined by the claims which follow.