Abstract:
A gear assembly for a tree felling head having a frame securable to a manipulator arm of a tree cutting carrier, the gear assembly includes a final gear securable to the frame and rotatably engageable over a bearing-like member mounted to the manipulator arm for pivotally mounting the frame to the manipulator arm; and a driving gear generating a torque, the torque of the driving gear being applied to at least two intermediate gears drivingly connected with the final gear.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 USC§119(e) of U.S. provisional patent application 61/267,851 filed on Dec. 9, 2009, the specification of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The technical field relates to a tree harvesting machine and, more particularly, to a felling head securable on a manipulator arm of a tree cutting carrier. It also relates to a gear assembly for a tree felling head having a frame securable to a manipulator arm of a tree cutting carrier. 
     DESCRIPTION OF THE PRIOR ART 
     Felling heads, mounted to an end of a hydraulic crane or manipulator arm of a tractor or tracked vehicle, are used to restrain, cut, and manipulate trees. Tilting felling heads are well-suited for manipulating the cut trees since they provide greater maneuverability and increase the productivity potential. 
     Depending on the mechanism used for side tilting, the tilting motion can be limited to about 180 degrees or can reach 360 degrees. In several embodiments, the tilting motion is obtained through a gear assembly. 
     However, the relatively slow rotation speed of the felling head combined with relatively important loads create significant torque when rotation is imparted. The internal and superficial stresses on the gear teeth often exceed the prescribed limits and create premature wear or gear breakage. Furthermore, the radial stresses on the mechanical components which actuate idler gears of the gear assembly are too high. To reduce stress applied on the gear assembly components, additional gear assemblies including motor and associated driving gears and idler gears are added. By adding gear trains, the forces are divided to reach the prescribed limits. However, the weight of the resulting felling head carried by the manipulator arm significantly increases. 
     There is thus a need for a gear assembly for a tree felling head which has internal and superficial stress within the prescribed limits, which reduces the radial stress on the mechanical components of the gear assembly, and which reduces the additional weight associated with the gear assembly. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore an aim of the present invention to address the above mentioned issues. 
     According to a general aspect, there is provided a felling head securable to a manipulator arm of a tree-cutting carrier. The felling head comprises: a frame with a final gear mounted thereto; a bearing-like member mounted to the manipulator arm and engageable with the final gear for mounting the frame to the manipulator arm, the final gear being rotatable about the bearing member; a motor having a driving output; a driving gear disposed externally to the final gear and drivingly mounted to the driving output of the motor and being drivingly connected to the final gear; and at least two intermediate gears drivingly engaged with the driving gear and drivingly connected to the final gear, the final gear rotating upon rotation of the driving output of the motor. 
     According to another general aspect, there is provided a felling head for mounting to a manipulator arm of a tree-cutting carrier. The felling head comprises: a frame having a holder connecting the frame to the manipulator arm and a gear train including a final gear secured to the frame, a driving gear, and at least two intermediate gears, each being located on a respective side of the driving gear and operatively engaged therewith and operatively connected to the final gear, a bearing member secured to the holder and engaged with the final gear, the final gear being rotatable about the bearing-like member; and a motor operatively connected to the driving gear, the final gear being externally driven. 
     According to a further general aspect, there is provided a gear train for a tree felling head having a frame securable to a manipulator arm of a tree cutting carrier. The gear train comprises: a final gear securable to the frame and rotatably engageable over a bearing-like member mounted to the manipulator arm for pivotally mounting the frame to the manipulator arm; and a driving gear generating a torque, the torque of the driving gear being applied to at least two intermediate gears drivingly connected with the final gear. 
     According to a further general aspect, there is provided a felling head securable to a manipulator arm of a tree-cutting carrier, the felling head comprising: a frame with a final gear secured thereto; a bearing member mounted to the manipulator arm and engageable with the final gear for mounting the frame to the manipulator arm, the final gear being rotatable about the bearing-like member; a motor having a driving output; a driving gear disposed externally to the final gear and drivingly mounted to the driving output of the motor and being drivingly connected to the final gear; and at least two intermediate gears drivingly engaged with the driving gear and drivingly connected to the final gear, the final gear and the frame rotating upon rotation of the driving output of the motor. 
     According to another general aspect, there is provided a tree cutting carrier comprising the felling head described above. 
     According to still a further general aspect, there is provided a felling head for mounting to a manipulator arm of a tree-cutting carrier, the felling head comprising: a saw blade supporting frame; a holder secured to the manipulator arm and connecting the saw blade supporting frame to the manipulator arm; a gear assembly including a final gear secured to the saw blade supporting frame, a driving gear, and at least two intermediate gears, each being located on a respective side of the driving gear and operatively engaged therewith and operatively connected to the final gear, a bearing-member secured to the holder and engaged with the final gear, the final gear being rotatable about the bearing-like member; and a motor operatively connected to the driving gear, the final gear being externally driven. 
     According to still another general aspect, there is provided a tree cutting carrier having a manipulator arm, comprising: a felling head having a saw blade supporting frame, a holder connecting the saw blade supporting frame to the manipulator arm, a slewing bearing including a final gear secured to the saw blade supporting frame and a bearing member secured to the holder and engaged with the final gear, the final gear being rotatable about the bearing-like member, and a first gear assembly including a driving gear and at least two intermediate gears, each being located on a respective side of the driving gear and operatively engaged therewith and operatively connected to the final gear, the final gear being externally driven. 
     According to a further general aspect, there is provided a gear assembly for a tree felling head having a saw blade supporting frame securable to a manipulator arm of a tree cutting carrier, the gear assembly comprising: a final gear securable to the saw blade supporting frame and rotatably engageable over a bearing member mounted to the manipulator arm for pivotally mounting the saw blade supporting frame to the manipulator arm; and a driving gear generating a torque, the torque of the driving gear being applied to at least two intermediate gears drivingly connected with the final gear. 
     According to still another general aspect, there is provided method for rotating a tree felling head having a saw blade supporting frame securable to a manipulator arm of a tree cutting carrier. The method comprises: rotating a driving gear actuator to engage in rotation a driving gear; transmitting the rotation movement of the driving gear to at least two intermediate gears mounted on a respective side of the driving gear; and transmitting the rotation movement of the at least two intermediate gears to a final gear secured to the saw blade supporting frame, the rotation movement being transmitted externally to the final gear, the rotation movement of the final gear engages in rotation the saw blade supporting frame of the tree felling head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a tree cutting carrier with a felling head mounted to a manipulator arm in accordance with an embodiment; 
         FIG. 2  is a side elevation view of the felling head shown in  FIG. 1  mounted to a tilting holder in accordance with an embodiment; 
         FIG. 3  is a perspective view, exploded, of the felling head, a gear assembly and the tilting holder shown in  FIG. 2 ; 
         FIG. 4  is a perspective view, partly sectioned, of a slewing bearing of the gear assembly in accordance with an embodiment; 
         FIG. 5  is a front elevation view of a gear train for the felling head and the tilting holder shown in  FIG. 2  in accordance with an embodiment, including one driving gear and two intermediate gears driving a final gear; 
         FIG. 6  is a perspective sectional view, fragmented, of the final gear attached to a frame of the felling head and an inner ring of the gear assembly attached to the tilting holder shown in  FIG. 5 ; 
         FIG. 7  is a front elevation view of a gear train for the felling head and the tilting holder shown in  FIG. 2  in accordance with another embodiment, including two driving gears and three intermediate gears driving the final gear; and 
         FIG. 8  is a front elevation view of two gear trains for the felling head and the tilting holder shown in  FIG. 2  in accordance with another embodiment, including two driving gears, each being mounted on a respective side of the final gear and engaged with two intermediate gears. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , there is shown a tree felling head  20  adapted to grip, cut, and manipulate trees and designed for tilting and rotation movements. 
     The tree felling head  20  includes a tilting holder  22  mounted to a manipulator arm  24  of a tree cutting carrier  26 , or other such vehicle. The tilting holder  22  is secured to an end of the manipulator arm  24 . 
     The felling head  20  also includes a frame  28  on which is mounted a saw blade  30  for cutting trees. The saw blade  30  is usually located at the base of the frame  28 . The frame  28  is secured to the tilting holder  22  through a gear assembly  32  including a gear train  34 , a slewing bearing  36 , and a motor-reducer  38 , as it will be described in more details below. 
     Referring to  FIGS. 3 to 6 , there is shown that the slewing bearing  36  includes an external portion  40  mounted to the frame  28  and an internal portion  42  mounted to the tilting holder  22 . The external portion  40  includes a final gear  44  (or outer ring) having external peripheral teeth  46 . The internal portion  42  includes an inner ring  48  mounted to the tilting holder  22  and a bearing member  50  mounted about the inner ring  48  and concentric therewith. The final gear  44  is mounted to the bearing-member  50 , outwardly thereof, and is rotatable thereabout, as it will be described in more details below. The final gear  44 , the inner ring  48 , and the bearing member  50  are thus concentric. The frame  28  rotates simultaneously with the final gear  44  since the latter is secured to the frame  28 , i.e. the final gear  44  does not rotate relatively to the frame  28 . As it will be described in more details below, the rotational movement is induced by the other components of the gear train  34 . 
     As shown in  FIG. 6 , the inner ring  48  is secured to the tilting holder  22  through fasteners  80  inserted in both the inner ring  48  and the tilting holder  22 . Similarly, the final gear  44  is secured to the frame  28  through fasteners  82  inserted in both the final gear  44  and the frame  28 . One skilled in the art will appreciate that the inner ring  48  can be secured to the tilting holder  22  and the final gear  44  can be secured to the frame  28  by any other suitable method. 
     In the embodiment shown, the components of the slewing bearing  36  including the final gear  44 , the inner ring  48 , and the bearing member  50  are annular members. 
     As shown in  FIG. 5 , the gear assembly  32  also includes the gear train  34 . The gear train  34  includes a driving gear  52  secured to a drive shaft  54  operationally connected to the motor-reducer  38  and two intermediate (or idler) gears  60 . The external and peripheral teeth  56  of the driving gear  52  are engaged with the external and peripheral teeth  58  of two intermediate gears  60 , each being mounted on a respective side of the driving gear  52 . 
     The gear train  34  including the motor-reducer  38 , the drive shaft  54 , the driving gear  52 , and the two intermediate gears  60  is mounted to the tilting holder  22 , externally to the slewing bearing  36 . The external and peripheral teeth  58  of the intermediate gears  60  are engaged with the external and peripheral teeth  46  of the final gear  44 . Thus, the motor-reducer  38  imparts a rotational movement to the drive shaft  54 , which in turn imparts the rotational movement to the driving gear  52 . The driving gear  52  engages in rotation both intermediate gears  60 , which rotate the final (or driven) gear  44 . Each intermediate gear  60  is mounted on a respective side of the driving gear  52  and is simultaneously engaged with the driving gear  52  and the final gear  44 . The final gear  44  being secured to the frame  28 , the latter rotates simultaneously with the components of the gear train  34 . The final gear  44  is externally driven. The rotation axis  62  of the final gear  44  corresponds to its center and is spaced apart from the drive shaft  54  and from the rotation axis of the driving gear  52 . 
     The torque of the driving gear  52  is transferred to both intermediate gears  60 , which, in turn, transfer their torque to the final gear  44 . The torque applied to the intermediate gears  60  is reduced since the torque of the driving gear  52  is applied to two intermediate gears  60 . 
     Arrows  64  show the tangential strains applied to the final gear  44  by the intermediate gears  60 . Arrows  66  in  FIG. 5  show that radial strains are eliminated or significantly reduced. The intermediate gear torque is applied at two gearing points  68 . Each intermediate gear  60  transfers half of the torque to the final gear  44 , as shown by arrows  64 . Consequently, the total strain on the intermediate gears  60  is reduced. Adding two intermediate gears  60  is advantageous for power transfer. 
     In the embodiment shown, the motor-reducer  38 , the drive shaft  54 , the driving gear  52 , and the two intermediate gears  60  are mounted to the tilting holder  22 . However, in alternate embodiments, these components or portions thereof can be mounted to the frame  28 . 
     It is appreciated that the gear train  34  can be mounted either to the left or to the right side of the tilting holder  22 . 
       FIG. 7  shows an alternative embodiment of the gear assembly wherein the features are numbered with reference numerals in the 100 series which correspond to the reference numerals of the previous embodiment. The gear assembly includes two motor-reducers (not shown), two drive shafts  154 , two driving gears  152 , and three intermediate gears  160 , all mounted to the tilting holder  122 , on a same side of the slewing bearing  136 , and interconnected to one another as described in further details below. 
     The driving gears  152  are secured to a respective drive shaft  154  operatively connected to a respective motor-reducer. The peripheral and external teeth  156  of each driving gear  152  are engaged with the peripheral and external teeth  158  of two intermediate (or idler) gears  160 , each being mounted on a respective side of the respective driving gear  152 . Thus, each one of the driving gears  152  is interposed between two intermediate gears  160 . The peripheral and external teeth  158  of one of the intermediate gears  160  are engaged with the peripheral and external teeth  156  of both driving gears  152 , i.e. one of the intermediate gears  160  is interposed between both driving gears  152 . 
     As for the previously described embodiment, the motor-reducer (not shown), the drive shafts  154 , the driving gears  152 , and the three intermediate gears  160  are mounted to the tilting holder  122 , externally to the slewing bearing  136 . The peripheral and external teeth  158  of the intermediate gears  160  are engaged with the peripheral and external teeth  146  of the final gear  144 . Thus, the motor-reducer imparts a rotational movement to the drive shafts  154 , which in turn impart the rotational movement to the driving gears  152 . The driving gears  152  engage in rotation the three intermediate gears  160 , which rotate the final (or driven) gear  144 . Each intermediate gear  160  is mounted on a respective side of their respective driving gear  152  and is simultaneously engaged with at least one of the driving gears  152  and the final gear  144 . The final gear  144  being secured to the frame  28 , the latter rotates simultaneously with the components of the gear train  134 . As for the previously described embodiment, the final gear  144  is externally driven and its rotation axis is spaced apart from the drive shafts  154  and their respective rotation axis. 
     The torque of each driving gear  152  is transferred to two intermediate gears  160 , which, in turn, transfer their torque to the final gear  144 . The torque applied to the intermediate gears  160  is reduced since the torque of each driving gear  152  is applied to two intermediate gears  160 . 
       FIG. 8  shows another alternative embodiment wherein the features are numbered with reference numerals in the 200 series which correspond to the reference numerals of the previous embodiments. The tilting holder and felling head assembly includes two gear trains  234   a ,  234   b , each having one motor-reducer (not shown), one drive shaft  254 , one driving gear  252 , and two intermediate gears  260 , all mounted to the tilting holder  222 . Each gear train  234   a ,  234   b  is mounted on a respective side of the slewing bearing  236 , with one gear train  234   a  mounted on a right side of the slewing bearing  236  and the other gear train  234   b  mounted on the left side of the slewing bearing  236 . 
     The interconnection between the motor-reducer, the drive shaft  254 , the driving gear  252 , the intermediate gears  260 , and the final gear  244 , within one gear train  234 , is similar to the one of the embodiment described above in reference to  FIG. 5 . The driving gears  252  are secured to their respective drive shaft  254 , which in turn are operationally connected to their respective motor-reducer. The external and peripheral teeth  256  of the driving gears  252  are engaged with the external and peripheral teeth  258  of their respective intermediate gears  260 , each are mounted on a respective side of their respective driving gear  252 . The external and peripheral teeth  258  of the intermediate gears  260  are engaged with the external and peripheral teeth  246  of the final gear  244 . Thus, the motor-reducers impart a rotational movement to their respective drive shafts  254 , which in turn impart the rotational movement to the driving gears  252 . The driving gears  252  engage in rotation the intermediate gears  260 , which rotate the final (or driven) gear  244 . The final gear  244  being secured to the frame  28 , the latter rotates simultaneously with the components of the gear trains  234 . The final gear  244  is externally driven. The rotation axis of the final gear  244  corresponds to its center  262  and is spaced apart from the drive shafts  254 . 
     As for the previously described embodiments, the motor-reducers, the drive shafts  254 , the driving gears  252 , and the intermediate gears  260  are mounted to the tilting holder  222 , externally to the slewing bearing  236 . 
     The torque of each driving gear  252  is transferred to the intermediate gears  260 , which, in turn, transfer their torque to the final gear  244 . The torque applied to the intermediate gears  260  is reduced since the torque of each driving gear  252  is applied to two intermediate gears  260 . 
     It is appreciated that any number of gear trains can be engaged with the final gear  244  for driving the latter in rotation. 
     In the embodiment shown in  FIG. 8 , the gear trains  234  are symmetrically mounted to the tilting holder  222 , on a respective side of the slewing bearing  236 . However, it is appreciated that, in an alternative embodiment (not shown), the gear trains  234  can be mounted in an asymmetrically manner to the tilting holder  222  and/or the frame  228  of the felling head  220 . 
     In the illustrated embodiment, the gear trains  234  are mounted to and engaged with the superior half of the slewing bearing  236 . However, one skilled in the art will appreciate that the gear trains  234  can be mounted anywhere around the slewing bearing  236 . 
     As for the embodiments shown in  FIG. 7 , the torque applied to the final gear  244  for rotating the felling head  120  is higher than with the embodiment shown in  FIG. 5 . 
     In alternative embodiments, a motor can include more than one reducer section, each reducer section being operatively connected to a respective drive shaft. 
     It is appreciated that, in alternative embodiments (not shown), the gear assembly(ies) can include other gear components interposed between the driving gear and the intermediate gears and/or the intermediate gears and the final gear. 
     Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.