Abstract:
An anti-pinch chainsaw bar assembly for enabling the extraction of chainsaw bars when bound or pinched during cutting includes rolling bearing members integrated into outer surfaces of the bar. The bearings are arranged in groups of at least two bearings in rolling contact with one another. At least one bearing in each group extends outwardly from each outer surface of the bar. The assembly preferably also includes wedge structures mounted on the distal end of the bar for spreading out the sides of a cut.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to bars used to support the cutting chain of a chainsaw, and more specifically to an anti-pinch chainsaw bar assembly designed to facilitate extraction of a chainsaw bar bound or pinched during the cutting of timber. 
     2. Description of the Related Art 
     Chainsaws are typically used to fell timber and to trim branches from trees. Afterwards, the trunk and branches are typically cut into smaller sections for ease of handling and use as firewood. While cutting timber or other material with a chainsaw, care should be taken to avoid pinching or binding the chainsaw bar within the gap formed by the cut. Nevertheless, binding may occur due to unexpected material movement and, in particular, may be difficult to avoid when cutting limb wood which is subject to twisting, due to wind and to movement under force of gravity, including rotational forces exerted upon the limb from associated branches. In addition, limb wood is known to contain internal forces that may be released as the limb is cut causing the gap to close upon the bar. 
     Since the bar generally has opposing flat sides that each typically present a relatively large surface area, the bar may be quite difficult to remove from the gap when binding occurs. To remove the bar, it may be necessary to reposition the material being cut or to pry the gap open using separating mechanisms. While these solutions may be time-consuming but useful when cutting timber to length on the ground, they may not be practical when binding occurs within a large branch still attached to the trunk and suspended high above ground. 
     It would be advantageous, therefore, to have a chainsaw with a bar adapted to be more readily withdrawn from material being cut even when pinched or bound. 
     SUMMARY OF THE INVENTION 
     The present invention is an anti-pinch chainsaw bar assembly for enabling the extraction of a chainsaw from a cut when the bar is pinched or bound. In a preferred embodiment, the bar is a laminate structure comprising a pair of outer plates and an inner plate sandwiched therebetween. Formed between the inner and outer plates are a plurality of pockets which each receive a respective rotatable cylindrical roller bearing. Each roller bearing extends outwardly from an outer face of the respective outer plate to present a bearing surface to the material being cut. The roller bearings are arranged in bearing groups of at least two, and preferably three, cylindrical roller bearings wherein each roller bearing in a bearing group is in rolling contact with at least one other bearing in the group such that rotation of a first roller bearing in the bearing group facilitates rotation in a second, and preferably a third roller bearing. The roller bearings in each bearing group are arranged such that the bearing surface of at least one roller bearing in each bearing group is presented on each outer plate of the bar. Typically, the bearing groups are arranged along the bar in a pattern that optimizes the withdrawal of the bar from the gap in a rearward direction (towards the user) without excessively compromising bar stiffness and strength. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a left side elevational view of a chainsaw bar assembly embodying the present invention. 
         FIG. 2  is a cross-sectional view of the chainsaw bar assembly taken generally along line  2 - 2  in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the chainsaw bar assembly taken generally along line  3 - 3  in  FIG. 1 . 
         FIG. 4  is a cross-sectional view of the chainsaw bar assembly taken generally along line  4 - 4  in  FIG. 1 . 
         FIG. 5  is an enlarged fragmentary cross-sectional view similar to  FIG. 2  showing a single bearing group. 
         FIG. 6  is an enlarged fragmentary left side elevational view similar to  FIG. 1  showing a wedge structure which forms a part of the present invention. 
         FIG. 7  is an enlarged fragmentary cross-sectional view similar to  FIG. 2  showing a wedge structure which forms a part of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words “upwardly,” “downwardly,” “rightwardly,” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of a similar import. 
     Referring to the drawings in more detail, and in particular to  FIGS. 1 and 2 , the reference number  1  generally designates an anti-pinch chainsaw bar assembly  1  including an elongate bar  3  having a peripheral slot  5  for receiving and guiding a saw chain (not shown) around the bar  3 . The bar  3  is a laminate structure formed by sandwiching an inner plate  7  between first and second opposing outer plates  9  and  11 , respectively. Each outer plate  9  and  11  includes a respective outer surface  12  which also comprises an outer surface of the bar  3 . The bar  3  has a mounting end  13  for connection to a chainsaw drive assembly (not shown) and a nose or distal end  15 . The mounting end  13  may include a slot  17  and holes  19  for alignment and adjustable attachment to the drive assembly. The chain forms a closed loop that encircles the perimeter of the bar  3  and includes inwardly extending drivers which extend into the peripheral slot  5 . The chain extends past the mounting end  13  of the bar  3  to engage a drive sprocket (not shown) powered by a motor of the drive assembly. The distal end  15  of the bar  3  typically includes a nose sprocket  21  rotatably mounted between the outer plates  9  and  11  and positioned to be drivingly engaged by the drivers of the saw chain. 
     As best seen in  FIGS. 3 and 5 , the bar assembly  1  further includes a plurality of roller bearings  23  set into pockets  25  in the bar  3 . Referring in particular to  FIG. 5 , each pocket  25  includes a semi-cylindrical trough  27  formed in the inner plate  7  and a respective aperture  29  formed in one of the outer plates  9  or  11 . Each trough  27  is sized and shaped to rotatably receive the respective roller bearing  23  and to seat approximately one longitudinal half of the roller bearing  23  therein. Each aperture  29  is also generally semi-cylindrical in shape, but extends through the outer plate  9  or  11  so as to be open to the outer surface  12  of the respective outer plate. A portion of the roller bearing  23  positioned in the pocket  25  thus extends outwardly from the respective outer surface  12  to present a rolling bearing surface to the material being cut. Less than half of each roller bearing  23  extends out of the respective pocket  25  through the aperture  29 , thus the roller bearings  23  are captured between the inner plate  7  and the respective outer plate  9  or  11  so that they cannot be dislodged from the bar  3 . As best seen in  FIGS. 1 and 4 , the outer plates  9  and  11  are attached to the inner plate  7  using dowel pins  31  to insure proper alignment of the apertures  29  with the respective troughs  27  to prevent binding of the rollers  23  within the pockets  25 . 
     Referring to  FIGS. 1 and 5 , the roller bearings  23  and pockets  25  are organized into bearing groups  33 . The bearing groups  33  each include at least two roller bearings  23  and preferably at least three roller bearings  23  (three shown). Within each bearing group  33 , at least one roller bearing  23  extends outwardly from each of the opposed outer surfaces  12  of the outer plates  9  and  11 . The troughs  27  of the pockets  25  within each bearing group  33  intersect such that the respective roller bearings  23  are each in rolling contact with at least one other roller bearing  23  within the same bearing group  33 . In an embodiment with three roller bearings  23  in each bearing group  33 , a center roller bearing  23   a  will be in rolling contact with two outside roller bearings  23   b . Rotation of any one of the roller bearings  23  in a bearing group  33  thus facilitates rotation of at least one other roller bearing  23  in the same bearing group  33 . 
     The bearing groups  33  are preferably arranged along the bar  3  in a pattern that optimizes the withdrawal of the bar from the gap in a rearward direction (towards the user). For example, the groups are shown in  FIG. 1  as being arranged in two parallel longitudinal rows  35 , including an upper row  35   a  positioned above a longitudinal centerline  37  of the bar  3  and a lower row  35   b  positioned below the longitudinal centerline  37 . Each roller bearing  23  is oriented generally perpendicular to the longitudinal centerline  37 . 
     The bearing groups  33  are shown as being groups of three roller bearings  23  and the orientation of the bearing groups  33  is alternated such that the center bearings  23   a  in adjacent groups  33  in each row  35  extend outward from opposite outer surfaces  12  of the bar  3 . In this arrangement, the outside roller bearings  23   b  in adjacent groups  33  also extend outward from opposite outer surfaces  12  of the bar  3 . The rows  35  are also shown as having bearing groups  33  which are aligned in vertical pairs  39  across the longitudinal centerline. In each vertical pair  39 , one bearing group  33  has its respective center bearing  23   a  extending outward from one outer surface  12  of the bar  3  and the other bearing group  33  has its respective center bearing  23   a  extending outward from the opposite outer surface  12 . Consequently, each vertical pair  39  has one bearing group  33  with its outside roller bearings  23   b  extending outwardly from each of the outer surfaces  12  of the bar  3 . 
     In another aspect of the present invention, best seen in  FIGS. 6 and 7 , the bar  3  includes a pair of wedge structures  41  positioned on the outer surfaces  12  of the outer plates  9  and  11  proximate the distal end  15 . Each wedge structure  41  has a thin end  43  and a thicker end  45 . The wedge structures are oriented with their thicker ends  45  nearest the distal end  15  of the bar  3 . When the bar  3  is pinched in a cut and the bar  3  is pulled toward the operator, the wedge structures bear against the edges of the cut and act to spread the sides of the cut apart and thereby assist in extracting the bar. The wedge structures  41  may be integrally formed with the outer plates  9  and  11 , or formed separately and attached to the plates  9  and  11 , such as by welding or by the use of fasteners (not shown). 
     It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown. For example, it is foreseen that the bearing groups  33  may each contain two, three, or more roller bearings  23 . All that is required is that there be at least two roller bearings  23  in at least one bearing group  33 , that the roller bearings  23  in the bearing group  33  be in rolling contact with one another, and that at least one respective roller bearing  23  in the group  33  extend outwardly past each outer surface  12  of the bar  3 . 
     Furthermore, it is to be understood that the pattern in which the bearing groups  33  are arranged on the bar  3  may be modified. For example, there may be more or less than two rows  35  of bearing groups  33 , or the bearing groups may not be arranged in parallel rows at all. It is also to be understood that bearing groups  33  need not be vertically aligned. It is also foreseen that the individual roller bearings  23  may not be oriented perpendicular to the centerline of the bar  3 ; for example, a herringbone pattern (not shown) of bearings is foreseen. In addition, it is foreseen that bearing groups or assemblies could be incorporated into the structure forming the wedge. 
     It is also to be understood that the bar  3  may be formed of more or less than the three plates described above. For example the bar  3  may be formed of only two plates with a space maintained therebetween, or a laminate of more than three plates may be employed. In an application using only two plates, spacers (not shown) may be used to maintain the two plates in spaced relation to one another. 
     As used in the claims, identification of an element with an indefinite article “a” or “an” or the phrase “at least one” is intended to cover any device assembly including one or more of the elements at issue. Similarly, references to first and second elements is not intended to limit the claims to such assemblies including only two of the elements, but rather is intended to cover two or more of the elements at issue. Only where limiting language such as “a single” or “only one” with reference to an element, is the language intended to be limited to one of the elements specified, or any other similarly limited number of elements.