Abstract:
A device for deflecting a detached cutting chain off the drive sprocket of a chain saw in order to deenergize and arrest it. A ramp provides a surface disposed below the chain guide bar, which surface is oblique with respect to the chain guide bar, slightly below a lower edge of the chain guide bar and obliquely angled with respect to a plane that contains the exterior surface of the chain guide bar, and distal to the drive sprocket. Sliding engagement of a detached cutting chain with the oblique surface moves the cutting chain exteriorly away from the chain guide bar and off the drive sprocket. A chain catcher is also provided to arrest the detached cutting chain and/or chain shot portions thereof.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application No. 61/853,717 for the same invention, entitled “Chain saw chain containment device,” filed on Apr. 10, 2013, by the same inventor, the disclosure of which is incorporated herein. 
     
    
     STATEMENT REGARDING FEDERALLY APPROVED RESEARCH OR DEVELOPMENT 
       [0002]    None. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    This invention relates generally to power chain saws and, more particularly, to safety devices for catching and containing a cutting chain that has become detached from the chain bar during operation of the saw. More specifically, the present invention pertains to a device for removing from the chain saw drive sprocket a cutting chain that has become detached from the chain bar during operation of the chain saw portion of a forest harvester to thereby deenergize the cutting chain, contain it, and render it harmless. 
         [0005]    2. Background Art 
         [0006]    Chain shot—i.e., flying fragments of a broken cutting chain of a power chain saw, as depicted, for example, in FIG.  1 —can be caused by improper chain tension, maintenance or repair, a damaged chain drive sprocket, chain guide bar and/or cutting chain, improper chain guide bar and chain lubrication, or excessive chain speed. Chain shot moves at high speed, usually in the plane of the chain bar and forwardly or rearwardly from the saw, and is an ever present danger to nearby personnel during operation of a power chain saw. In the case of a forest harvester, there is a direct hazard to the operator in the harvester cab when the chain bar is pointing toward the cab because chain shot has been known to penetrate the cab window under those circumstances and strike the operator within the cab. 
         [0007]    One approach to reducing the hazard presented by a broken cutting chain has been to deenergize and/or impose restrictions on the movement of broken chain ends and chain fragments. U.S. Pat. No. 5,101,567 issued to Cool disclosed a safety switch that deenergized the chain drive of a hand-held chain saw in the event of a break in the cutting chain, and also disclosed a chain braking mechanism and safety guard to effect stoppage of the cutting chain motion. U.S. Pat. No. 4,805,308 issued to Ritola disclosed a roller attachment to the handle of a hand-held chain saw. The roller was aligned with the chain guide bar so as to extend substantially perpendicularly through the plane defined by the chain guide bar in order to intercept the saw chain should it become derailed. U.S. Pat. No. 4,315,370 issued to Horne disclosed a finger piece that acted as a safety surface in the event of breakage of the cutting chain on a hand-held chain saw. The finger piece was located far enough forward from the chain drive to force the whipping length of the chain to pivot and catch the broken chain. 
         [0008]    The present invention, however, is primarily directed to improving the safety of chain saws mounted on forest harvesters, which are used in the commercial timber industry for felling and cutting the trunk of trees at suitable intervals. The present invention is particularly directed to deenergizing and restraining the cutting chain of a harvester-mounted chain saw when the cutting chain has become derailed—that is, detached from the chain guide bar and chain drive sprocket of the chain saw; see  FIG. 3 . In such a harvester chain saw, the cutting chain is looped around a drive sprocket and chain guide bar, similar to a hand-held chain saw, but, unlike a hand-held chain saw, which is typically powered by an internal combustion engine or electric motor, to achieve high-powered, rapid cutting, the drive sprocket is mounted to the output shaft of a hydraulic motor, and the chain saw itself is mounted for pivotal rotation about the motor shaft axis by a hydraulic cylinder within a shielding saw casing or saw box—all under the control of an operator seated within the cab of the harvester. The shielding provided by the saw box is only partial, of course, because the saw box must be sufficiently open to permit sawdust generated during cutting to exit the box, for maintenance access, and for the chain saw to pivot in and out of the box. 
         [0009]    For such a harvester-mounted chain saw, U.S. Pat. No. 7,690,407 B2 issued to Annala disclosed a protective wall positioned in the vicinity of the chain drive sprocket that was capable of receiving the movement of the tail of the broken cutting chain with the intent of guiding the broken chain in a desired direction. Annala&#39;s protective wall, depicted and labelled as “chain shot guard” in  FIG. 1 , was perhaps the most common device in use on harvester-mounted chain saws to intercept and restrain a broken cutting chain prior to my present invention. A chain shot guard has commonly been accompanied by a chain catcher, also illustrated in  FIG. 1 , in the form of a short, cylindrical extension attached to, and coaxially aligned with, the hydraulic motor shaft, and intended to intercept and receive in winding engagement a broken tail portion of a cutting chain. In an alternate version, the chain catcher has been bobbin-shaped, as depicted, for instance, in  FIG. 4 . In either case, the spring catcher of the prior art extended coaxially from, and rotated with, the hydraulic motor shaft. In extensive testing, I have observed that is counterproductive because, after a cutting chain broke or derailed, at the very time the cutting chain needed to be deenergized, the ongoing rotation of the chain catcher continued to add rotational energy to the broken tail of the cutting chain. In the case of a derailed cutting chain, the usual result was that the cutting chain would break up into three segments, creating chain shot instead of eliminating it. 
       SUMMARY OF THE INVENTION 
       [0010]    There thus remains a need for a device to deflect a cutting chain that has detached from the chain guide bar of a chain saw away from the chain guide bar and off the drive sprocket in order to deenergize the cutting chain and arrest it without releasing any chain shot into the environment. It is therefore an object of the invention to incorporate into a chain saw, and particularly a forest harvester-mounted chain saw, a chain containment device that comprises deflector means for deflecting, during operation of the chain saw, a detached or broken cutting chain exteriorly away from the chain saw drive sprocket in order to deneergize the cutting chain, as well as chain catcher means for catching and arresting the detached cutting chain after it has been deflected off the drive sprocket. The deflector means provides a ramp surface disposed below a lower edge of the chain guide bar, distal to the drive sprocket, and crossing a plane that contains the chain bar guide from a distal, entrance surface disposed slightly interior to the interior surface of the chain guide bar to a proximal exit, surface that is exterior to a plane that contains the exterior surface of the chain guide bar. That is the deflector means includes ramp means having an exterior surface that extends proximally and exteriorly at an oblique angle with respect to the plane that contains the exterior surface of chain guide bar. The deflector means further includes means for attaching the ramp means to the chain saw. The chain catcher is mounted to the chain saw and spaced apart exteriorly from the proximal ring of the chain bar mount. 
         [0011]    In a first embodiment of the device, the means for attaching the ramp means to the chain saw includes a first face plate that is shaped and dimensioned for attachment by fasteners to an exterior surface of the saw chain tensioner of the chain saw. An upper portion of a semiannular arm is attached to an upper, proximal end of the first face plate, which arm has a ramp extension that extends distally below and adjacent to a lower edge of the chain guide bar. The ramp extension has an exterior surface that extends proximally and exteriorly at an oblique angle with respect to the plane that contains the exterior surface of the chain guide bar. The semiannular arm is shaped and dimensioned for coaxial, surrounding engagement of the proximal ring of the chain bar mount. Accordingly, the semiannular arm, the drive sprocket, and the drive shaft of the motor that powers the chain saw all share a common axis A-A that is normal to a plane that contains the chain guide bar. The chain catcher means of the first embodiment of the device includes a flange at a proximal end of the first face plate, which flange protrudes exteriorly from the first face plate and extends from an upper edge to a lower edge of the first face plate. Optionally, the chain catcher means can include a second flange that protrudes exteriorly from an upper edge of the first face plate as well. In addition, an upper portion of the semiannular arm also acts to catch a detached or broken cutting chain and can, therefore, be considered as part of the chain catcher means. 
         [0012]    In a second embodiment of the device, the ramp means can include a horseshoe-shaped arm with a semiannular bight portion. The bight portion is shaped and dimensioned for coaxial, surrounding engagement of the ring of the bar mount. The second embodiment further includes a ramp that extends proximally from a lower, distal end portion of the horseshoe-shaped arm below the chain guide bar, and slightly interior (e.g., 1 cm) to a plane that contains the interior surface of the chain guide bar. The ramp has an exterior surface that extends proximally and exteriorly at an oblique angle with respect to the plane that contains the chain guide bar. Similar to an actual horseshoe, and except for its ramp, the thickness of the horseshoe-shaped arm preferably is more or less uniform throughout. A preferred means for attaching the horseshoe-shaped arm is a weld between a lower portion of the arm and the ring portion of the bar mount. The horseshoe-shaped arm enlarges the available surface area for attaching a ramp in the required location and may not be necessary on all chain saws. 
         [0013]    The chain catcher means of the second embodiment of the device includes a guard that is semiannular in exterior elevational view and is exteriorly spaced apart from the drive sprocket, and a chain catcher mounting plate that is shaped and dimensioned for close-fitting attachment by threaded fasteners to an exterior surface of the saw chain tensioner. A proximal end of the chain catcher mounting plate is attached to the distal ends of said guard. Preferably, the chain catcher mounting plate is coplanar with the guard, the guard is coaxial with the drive sprocket, the guard has an outer radius greater that the outer radius of the drive sprocket, but less that the outer radius of the proximal ring of the bar mount, and the bight portion of the guard is semitoroidal—that is, the shape of the guard comprises one-half of a torus defined by a plane through the center of the torus that bisects the torus into two, equal, opposite halves. 
         [0014]    Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  depicts a chain saw carried by a dangle head suspended from the main boom and jib boom of a forest harvester and cutting through the trunk of a felled tree; the arrows indicate possible directions of travel for chain shot if the cutting chain were to break. 
           [0016]      FIG. 2  is schematic, perspective view of a the exterior side of a proximal end portion of the chain saw of  FIG. 1 , showing a chain shot guard and chain catcher of the prior art. 
           [0017]      FIG. 3  is an enlarged, fragmentary, perspective view of an operating chain saw partially lowered out of a shielding saw casing carried by a dangle head; the cutting chain has become detached from the chain guide bar, a condition that, absent the installation of the present invention on the chain saw, portends impending chain shot. 
           [0018]      FIG. 4  repeats  FIG. 3 , but here the cutting chain has not detached and instead has remained within the groove of the chain guide bar, and the chain saw has been pivoted to a fully lowered position. 
           [0019]      FIG. 5A  is an exterior, elevational schematic view of the chain guide bar, bar mount, and drive sprocket of the chain saw of  FIGS. 1-4 , showing the meaning of the terms “distal,” “proximal,” “upper,” and “lower” as used herein; 
           [0020]      FIG. 5B  is a cross sectional view thereof taken along line  5 B of  FIG. 5A  and illustrating the meaning of “interior” and “exterior” as used herein. 
           [0021]      FIG. 6  is a further enlarged, perspective view of the following components of the chain saw of  FIGS. 1-4  after the saw has been removed from the shielding saw casing and has been partially disassembled: the chain bar mount; a proximal portion of the chain guide bar positioned adjacent to an exterior surface of the chain bar mount; and the drive sprocket disposed at an exterior side of the proximal ring portion of the chain bar mount and aligned for rotation about the motor drive shaft axis (A-A). The motor assembly, which attaches to an interior side of the chain bar mount, is omitted for clarity. 
           [0022]      FIG. 7  repeats  FIG. 6 , except that the cutting chain is shown looped around the drive sprocket and the groove of the chain guide bar, and the saw chain tensioner has been placed on the exterior surface of the chain guide bar with its bolt apertures aligned in registry with corresponding threaded bolt apertures of the bar mount; 
           [0023]      FIG. 8  is an exterior, elevational view of the partially assembled chain saw of  FIG. 7 , but showing a first embodiment of the chain containment device of the present invention mounted thereon, as follows: the first face plate of the device thereof is disposed adjacent to the exterior surface of the saw chain tensioner with corresponding openings for threaded fasteners of each aligned in registry; a semiannular arm of the device attached to an upper, proximal end of the first face plate and disposed in surrounding engagement around the periphery of the proximal ring portion of the chain bar; and a ramp extension that extends distally from a lower side of the semiannular arm to a free end; 
           [0024]      FIG. 9  is an elevational view of a proximal end thereof, with the cutting chain omitted for the sake of clarity; and 
           [0025]      FIG. 10  is a perspective view thereof as seen distally and from below the cutting chain. 
           [0026]      FIG. 11  is an exterior, elevational view of the first embodiment of the device, separate from the chain saw, wherein “W” indicates a weld. 
           [0027]      FIG. 12  is a perspective view of a proximal end portion of the chain saw of  FIG. 7 , with a second embodiment of the chain containment device of the present invention mounted thereon; 
           [0028]      FIG. 13  is a perspective view thereof as seen from the exterior side of the chain saw; and 
           [0029]      FIG. 14  is a bottom plan view thereof. 
       
    
    
       [0030]    Like numerals denote like parts throughout the several views. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Referring to  FIG. 1 , a chain saw  10  pivotally mounted for rotation within a shielding saw casing or saw box portion  12  of a dongle head  14  suspended from the main boom  16  and jib boom  18  of a forest harvester  20  is shown cutting through the trunk of a felled tree  22 . The arrows  24  indicate possible directions of travel for chain shot if the cutting chain  26  were to break. Prior to my present invention, the accepted way in the timber harvesting industry to contain chain shot has been to install on a forest harvester chain saw a chain shot guard  28  that partially surrounds a proximal end portion of the chain saw. It was intended that, should pieces of the cutting chain  30  break off, the chain shot would be captured within the convex, apposed surface of the chain shot guard. It was also common to further include a chain catcher  32 , as depicted in  FIG. 2 , as an axial, cylindrical stub extension (or bobbin-shaped, as in  FIGS. 3 and 4 ) of the drive shaft of the drive shaft of the hydraulic motor assembly  34 , with the intent that, if the cutting chain  30  were to become detached from the chain guide bar  36  of the chain saw (see, for example,  FIG. 3 ), the detached cutting chain would wrap itself around the chain catcher  32  and thereby be captured. Sometimes, however, the detached cutting chain  30  broke up into chain shot instead. 
         [0032]    The present invention dispenses with the chain catcher  32  ( FIGS. 2 ,  3  and  4 ) and chain shot guard  28  ( FIG. 2 ) of the prior art. To illustrate how one installs a first embodiment of my chain containment device  100  on a harvester chain saw  10 , selected component parts of a disassembled forest harvester chain saw of the prior art (e.g., a Keto 800 PHD Processor) are depicted in  FIG. 6 . Illustrated in  FIG. 6  are the chain bar mount  38 , which comprises a rectilinear, distal base portion  38 D joined to, and coplanar with it, a proximal ring portion  38 P; a proximal portion  36 P of the chain guide bar  36  disposed adjacent to an exterior surface  38 E of the chain bar mount  38 ; a drive sprocket  40  disposed at an exterior side  40  of the proximal ring portion  38 P of the chain bar mount and aligned for rotation about the hydraulic motor drive shaft axis (A-A); and a closed-loop, cutting chain  30  looped around the chain guide bar and the drive sprocket. The drive sprocket  42 , which attaches to the drive shaft  44  of the hydraulic motor assembly′  34 , has a first set of radially-directed teeth  42 A and, disposed on an opposite side of the sprocket, a coaxial second set of radially-directed teeth  42 B, such that, after excessive wear on the first set of teeth, the sprocket can be removed from the drive shaft, inverted, reattached to the drive shaft, and the second set of teeth can be used thereafter to drive the cutting chain  30 . The top  36 T, distal end  36 D, and bottom  36 B edges of the chain guide bar  36  has a continuous groove G, and, when the chain saw is operating, the cutting chain  30  moves through that groove. 
         [0033]    In  FIG. 7 , the cutting chain  30  has been installed on the disassembled chain saw  10  and a saw chain tensioner  46  has been positioned at the exterior surface  40  of the bar mount  38  and distally with respect to the drive sprocket  42 . The cutting chain  30  is looped around whichever of the two sets of sprocket teeth  42 A,  42 B, is currently flipped toward the interior side of the sprocket  42 , which, in the case of  FIGS. 6-9  happens to be the set that has been designated  42 A, and that currently interiorly-disposed set of sprocket teeth lies within the plane of the chain guide bar  36 . Thus, as it rotates around the chain guide bar  36  and the drive sprocket  42 , the cutting chain  30  remains within a plane that contains the chain guide bar (whereas, the unused set of sprocket teeth  42 B lies outside of, and exterior to, said plane). The proper positioning of the chain tensioner  46  is aided by a locating lug  48  that extends upward from an exterior side of the base portion of the bar mount and abuts a distal end  46 D of the chain tensioner as well as by a plurality of bores  49  in the tensioner for threaded fasteners  60  that align in registry with corresponding threaded bores in the bar mount  38  when the chain saw  10  is reassembled. The chain tensioner  36  includes a chain tension adjustment screw  46 S (e.g., Allen screw;  FIG. 10 ) within a longitudinal bore (not shown) that extends through the chain tensioner from the distal end  36 D thereof to a longitudinally slotted, proximal end portion  46 P thereof where it threads into a mating, threaded bore of a tensioner member (not shown) that is slidable within the slot and which attaches to a proximal end portion of the chain guide bar  36 , such that rotation of the screw  46 S permits adjustment of the tension in the cutting chain  30 . 
         [0034]    The present invention comprises deflector means, denoted generally by the numeral  50 , and chain catcher means, denoted generally by the numeral  52 . The purpose of the deflector means  50  is to deflect, during operation of the chain saw  10 , a detached or broken cutting chain  30  exteriorly away from the drive sprocket  42 , thereby preventing the drive sprocket from imparting additional kinetic energy to the cutting chain. In the first embodiment  100 , the deflector means  50  is disposed below the saw chain tensioner  46  and below the bottom edge  36 B of the chain guide bar  36 , such that the entrance surface S at a proximal end of the defector means is slightly interior (e.g., 1 cm to 3 cm) to a plane that contains the interior surface of the chain guide bar. The deflector means  50  includes ramp means  54  having an exterior surface (S to S′) that extends proximally and exteriorly at an oblique angle with respect to the plane that contains the exterior surface  36 E of the chain guide bar  36  and thus actually crosses over the chain guide bar  36 , and means  56  for attaching the ramp means to the chain saw  10 . 
         [0035]    In the first embodiment  100 , the ramp means  54  comprises a flat, first face plate  102  and a semiannular arm  106  attached to an upper, proximal end  104  of the first face plate. The first face plate  102  is apertured (openings  49 ′), shaped and dimensioned for attachment by threaded fasteners  60  to an exterior surface  46 E of the saw chain tensioner  46 , which fasteners extend through the above-described openings  49  in the chain tensioner. The ramp means  54  further includes a semiannular arm  106  attached to an upper, proximal end of the first face plate  102 . The semiannular arm  106  has a ramp extension  108  that extends distally from a lower portion  106 L of the semiannular arm below and adjacent to the lower edge of the chain guide bar  36 . The ramp extension  108  has an exterior surface S that extends proximally and exteriorly at an oblique angle with respect to the plane that contains the exterior surface  36 E of the chain guide bar  36 . Most detachments of a cutting chain  30  from the chain guide bar  36  are minimal deviations, temporary, and self-correcting, and we do not want the device  100  to derail the cutting chain for such minimal deviations. Accordingly, The entrance surface S is disposed at some minimal distance below the lower edge of the chain guide bar  36 . That minimal distance should be greater than the overall height of the cutting chain  36  in interior, elevational view; that is, the minimal distance will ordinarily be in the range of 4 to 6 cm, more or less for a three-quarter pitch cutting chain. The optimal minimum distance will vary somewhat among chain saws and with the design and dimensions of their cutting chains. In any case, the optimal minimum distance must be experimentally determined for each chain saw to prevent unnecessary derailings of the cutting chain  30 . 
         [0036]    The semiannular arm  106  coaxially surrounds and engages the semiannular periphery of the proximal ring  38 P of the chain bar mount. In the event that the cutting chain  30  detaches from the groove G of the chain guide bar  36  during operation of the chain saw  10 , the cutting chain would slide exteriorly along the oblique surface S to the exit surface S′ of the ramp extension  108 , which is preferably disposed well exteriorly from the drive sprocket  42 ; the inevitable result is that the cutting chain is thereby removed from the drive sprocket  42 , loses kinetic energy, and slows to a stop while still contained within the chain saw box  12 . 
         [0037]    In the first embodiment  100 , the chain catcher means  52  comprises a flange  110  at a proximal end portion  102 P of the first face plate  102 . The flange  110  extends from an upper edge to a lower edge of the first face plate  102  and protrudes exteriorly therefrom enough to be an effective barrier against a detached or broken chain flying distally past its location during operation of the chain saw  10 . In addition, an upper portion of the semiannular arm  106  also helps catch a detached or broken piece of cutting chain  30 . Accordingly, if any portion of a detached  30  moves from the semiannular arm  106  in the distal direction past the drive sprocket  42  it will hit the flange  110  and be stopped. Preferably, the face plate has a second flange  112  that is similar in shape and dimension to the flange  110 , but is disposed along an upper edge of the first face plate  102 P to further confine the movement of a detached chain or chain shot. 
         [0038]    A second embodiment of the device  200  is depicted in  FIGS. 12-14 . In the device  200 , for ramp means  54  there is provided a horseshoe-shaped arm  204  that includes a bight portion  204 B. The bight portion  204 B is dimensioned for coaxial, coplanar, close-fitting, surrounding engagement of the proximal ring portion  38 P of the bar mount  38 . The ramp means  54  further includes a ramp  206  that extends proximally and exteriorly from (or near) the lower, distal end  204 L of the arm  204 . The ramp  206  is disposed below the chain guide bar  36 , and has an entrance surface slightly exterior to a plane that contains the interior surface of the chain guide bar (e.g., 1 cm to 3 cm) and an exit surface that is exterior to the chain guide bar—that is, the ramp crosses over the chain guide bar  36 . With the ramp  206  so positioned, if, during operation of the chain saw  10 , the cutting chain  30  becomes detached from the groove G, the cutting chain swell into a more circular configuration and will be deflected off and exteriorly away from the drive sprocket  42 , depriving the cutting chain of additional kinetic energy. Previous comments regarding the minimum and maximum distances between the exterior surface of the chain guide bar  36  and the ramp extension  108  of the first embodiment of the device  100  apply as well to the ramp  206  of the second embodiment  200 . Preferably, the arm  204  is attached to a lower, ring portion of the bar mount by a weld or other suitable means. 
         [0039]    For chain catcher means  52 , the second embodiment of the device  200  provides a guard  208  that is semiannular in exterior elevational view and is exteriorly spaced apart from the drive sprocket  42 . The chain catcher means  52  of the second embodiment  200  further includes a chain catcher mounting plate  212  that is shaped and dimensioned for close-fitting attachment by fasteners to an exterior surface of the chain tensioner  46 . Preferably, the guard  208  is coaxial with the drive sprocket  42 , is semitoroidal as depicted in  FIGS. 12-14 , and has an outer radius greater that the outer radius of the drive sprocket, but less that the outer radius of the proximal ring  38 P of the bar mount  38 . 
         [0040]    As used herein, a first component of the device  100 ,  200  is “below” a second component of said device if, and only if, having reference to  FIG. 5A , the first component is disposed lower than the second component. All components of the device  100 ,  200  preferably comprise steel, but may comprise any substances having sufficient strength, hardness, and durability to adequately perform the functions required of those components by the invention. 
         [0041]    Although specific embodiments of the invention have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that modifications and changes in the devices  100 ,  200  set forth above will be possible without departing from the spirit and scope of the invention. Accordingly, it is intended that the following claims be interpreted to embrace all such modifications and changes, and equivalents thereof, as will be apparent to one having ordinary skill in this technology.