Abstract:
Disclosed is a safety stop that is operatively connected to the existing rotatively mounted front handle of a chain saw to independently actuate such safety stop to its actuated position to stop the rotation of the cutting chain upon rotation of such rotatively mounted front handle either automatically when &#34;kick-back&#34; occurs or upon such rotation by the operator at his option.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to a chain saw cutting chain safety stop that is operatively connected to an existing rotatively mounted front handle of a chain saw and is independently actuated by the rotative action of such front handle to stop the cutting chain. 
     2. Background Art 
     The prior art, U.S. Pat. No. 3,664,390 discloses safety means for power driven chain saws; U.S. Pat. No. 3,776,331 discloses a brake device for power saws; U.S. Pat. No. 3,934,345 discloses a snap-acting over-center chain saw safety brake and method of operation thereof; U.S. Pat. No. 3,964,333 discloses a safety braking mechanism for a portable chain saw; U.S. Pat. No. 3,991,469 discloses a safety braking mechanism for a portable chain saw; U.S. Pat. No. 3,991,864 discloses a motor saw, especially motor chain saw; U.S. Pat. No. 3,992,779 discloses a chain brake for chain saws; U.S. Pat. No. 4,026,392 discloses a snap-acting over-center chain saw safety brake and method of operation thereof; U.S. Pat. No. 4,121,339 discloses a safety brake mechanism for chain saws; U.S. Pat. No. 4,156,477 discloses a braking system of a chain saw; U.S. Pat. No. 4,324,045 discloses a motor chain saw with dynamic safety braking device; U.S. Pat. No. 4,334,357 discloses a safety braking apparatus for a portable chain saw; U.S. Pat. No. 4,426,563 discloses a chain saw safety switch. 
     The following discussion focuses on the problems inherent in the prior art and how this invention contributes to the solution of such prior art problems. 
     &#34;Kick-Back&#34; means that the outgoing run of the cutting chain is jammed, caught or otherwise encounters resistance thereby causing the cutter bar, mounting such cutting chain to be thrown back towards the operator, causing serious injury or even death. For example, a right handed operator grasps and holds the chain saw with his left hand holding a cross-wise, gripping front handle and his right hand holding a rear control handle aligned with the front to rear longitudinal axis of such chain saw. When &#34;Kick-Back&#34; occurs, the operator&#39;s left hand, holding such cross-wise front handle rotates on such front handle as the chain saw rotates towards him, thus sending the cutter bar in his direction. In certain circumstances, the operator of a chain saw may loose his balance and fall on his running chain saw, the result being very serious injury or possibly even death. 
     The prior art; U.S. Pat. No. 3,664,390; U.S. Pat. No. 3,776,331; U.S. Pat. No. 3,934,345; U.S. Pat. No. 3,964,333; U.S. Pat. No. 3,991,469; U.S. Pat. No. 3,991,864; U.S. Pat. No. 3,992,779; U.S. Pat. No. 4,026,392; U.S. Pat. No. 4,121,339; U.S. Pat. No. 4,156,477; U.S. Pat. No. 4,324,045 and U.S. Pat. No. 4,334,357 relate to chain stopping devices to prevent injuries related to &#34;Kick-Back&#34;. The drawback of said proposals being the loss of time between the start of the &#34;Kick-Back&#34; or &#34;Throw&#34; of the cutter bar and the actuation of said chain stopping devices. Also, these proposals are intended for the occurance known as &#34;Kick-Back&#34;, but are not designed to prevent injury to the operator in other accident situations, such as an operator falling on his running chain saw. U.S. Pat. No. 4,426,563 relates to a hand held, rotatively mounted front handle of a chain saw to shut off the ignition to the power source of such chain saw, either automatically, as in &#34;Kick-Back&#34; or at the operator&#39;s option in other accident situations. Although this proposal puts control to shut off the power source of the saw in the operator&#39;s hand, which is holding the front handle, it is understood that even though the driving force to the cutting chain is removed, said cutting chain may continue to freely rotate for a short period of time as it comes to a stop. In this situation, it is possible for the operator to come in contact with the cutting chain as it is coming to a stop. 
     It is the object of this invention to contribute to the solution of such prior-art problems by providing a safety chain stopping device that is operatively connected to an existing rotatively mounted front handle of a chain saw. Said chain stopping device being actuated to quickly stop the cutting chain by the rotative action of said rotatively mounted front handle. It is understood that, since this invention is actuated to stop the cutting chain by the action of the front handle, while being held by the operator, said actuation takes place instantly. It is the further object of this invention to provide a means of quickly stopping the cutting chain of a chain saw that is uncomplicated in design and can be adapted to either gasoline engine powered chain saws or electric motor powered chain saws. After the safety stop has been actuated to its chain stopping position, it must be reset to its &#34;Run&#34; position before the cutting chain will freely rotate. 
     It is another object of the present invention to provide the operator with a great amount of control to quickly stop the cutting chain in various accident situations. Present invention is actuated automatically by the rotatively mounted front handle when kick-back causes the front handle to rotate in the operator&#39;s hand or by the operator manually rotating the front handle at his option. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, there is provided a chain saw cutting chain safety stop device that is operatively connected to an existing rotatively mounted front handle of a chain saw to quickly stop the cutting chain upon rotation of said rotatively mounted front handle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This object and other objects of the invention should be discerned and appreciated by reference to the drawings, wherein like reference numerals refer to similar parts throughout the several views, in which; 
     FIG. 1 Provides a side fragmentary, partial elevational view of that portion of a chain saw (with cover removed) immediately associated with the safety chain stopping mechanism of the present invention and showing the cutter chain in a braked condition; 
     FIG. 1a provides a top fragmentary, partial view of a chain saw immediately associated with the safety chain stopping mechanism of the present invention and showing the stopping mechanism in a braking posture; 
     FIG. 2 is a view similar to FIG. 1 wherein the cutter chain is in a non-braked condition. 
     FIG. 2a is a view similar to FIG. 1a wherein the chain stopping mechanism is in a non-braking posture. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To facilitate understanding of the invention, a nomenclature list is herewith provided: 
     1 generally refers to the invention 
     3 saw housing 
     4 elongated opening in saw housing 3 
     5 chain cutter bar 
     7 cutting chain carried on cutter bar 5 
     9 cable sheath 
     11 cable operatively connected to rotatively mounted front handle 50 
     13 linkage 
     14 curved end of linkage 13 
     15 fixed plug carried on cable 11 
     16 mounting aperture in trigger leg 39 
     17 brake band reset grip operatively connected to brake band 21 
     19 torsion spring 
     21 flexible brake band 
     22 looped end of flexible brake band carried on actuating shaft 36 
     23 mounting bracket 
     24 looped end of brake band carried on anchor shaft 34 
     25 brake band anchor shaft mounting pedistal fixed to mounting bracket 23 
     27 actuating shaft trigger mounting pedistal fixed to mounting bracket 23 
     29 actuating shaft guide fixed to mounting bracket 23 
     30 centrifugal clutch 
     32 outer drum of centrifugal clutch 30 
     34 threaded fixed end anchor shaft 
     36 partically threaded brake band actuating shaft 
     38 actuating shaft trigger 
     39 leg of actuating shaft trigger 38 
     40 recess incorporated in actuating shaft guide 29 
     42 actuating shaft trigger mounting bolt 
     44 front handle pedistal mount fixed to saw housing 3 
     46 torsion spring connecting aperture on front handle pedistal 44 
     48 torsion spring connecting aperture on brake band reset grip 17 
     50 rotatively mounted front handle 
     51 operator&#39;s hand holding front handle 50 
     52 washer carried on trigger mounting bolt 42 
     54 washer carried on trigger mounting bolt 42 
     56 locking nut carried on trigger mounting bolt 42 
     58 foot of actuating shaft trigger 38 
     60 machine screws (two) afixing mounting bracket 23 to housing 3 
     62 fixed end anchor shaft head 
     64 locking nut carried on fixed end anchor shaft 34 
     66 locking nut carried on fixed end anchor shaft 34 
     68 locking nut carried on fixed end anchor shaft 34 
     70 locking nut carried on threaded end of actuating shaft 36 
     72 locking nut carried on threaded end of actuating shaft 36 
     Reference numeral 1 generally refers to the invention of the chain saw cutting chain safety stop. 
     In FIG. 1 there is depicted a preferred form of the invention embodied in a portable chain saw which carries a rotatively mounted front hande. Shown is the present invention operatively connected to said rotatively mounted front handle. 
     A chain saw includes a housing 3. Fixed to housing 3 is a pedistal mount 44, on which is carried a rotatively mounted front handle 50 that operatively carries a cable 11 freely received in cable sheath 9. The rotatively mounted front handle 50 is grasped and held by the operator&#39;s hand 51. 
     A chain cutter bar 5 projects forwardly from the housing 3 and freely carries a cutter chain 7 for endless movement therearound. The cutter chain 7 is driven by the power source of the chain saw, be it electric motor or gasoline engine. Driving force is administered from the power source to the cutter chain 7 by means of the centrifugal clutch 30. 
     Shown in FIG. 1 is the mounting bracket 23 of the present invention. Mounting bracket 23 fixedly carries as parts thereof an anchor shaft mounting pedistal 25, a trigger mounting pedistal 27 and a actuating shaft guide 29. A complimental recess 40 is shown formed in the end of actuating shaft guide 29 that faces the rear of housing 3. Recess 40 is engageable by the partially threaded brake band actuating shaft 36 to releaseably lock actuating shaft 36 in its pre-actuation posture. 
     Carried on the threaded end of actuating shaft 36 by means of locking nut 70 and locking nut 72 is a looped end 22 of flexible brake band 21 and a reset grip 17 via drilled hole (not shown). Reset grip 17 being non-pivotly mounted by means of extended lips (not shown) abutting each side of looped end 22. 
     As shown in FIG. 2 and 2a the brake band 21 extends through the elongated opening 4 in housing 3 and is disposed around the peripheral surface of the clutch outer drum 32. The torsion spring 19 is shown broken away to reveal the brake band 21 anchored at one end to the threaded anchor shaft 34 by means of looped end 24, locking nut 66 and locking nut 68. Said anchor shaft 34 being afixed to mounting pedistal 25 via drilled hole (not shown) with with anchor shaft head 62 on one side of pedistal 25 and locking nut 64 on the other side. The threaded anchor shaft 34 allows appropriate lateral adjustment of brake band 21 and easy removal thereof for maintenance. 
     The brake stopping mechanism includes a spring 19 which continually biases the actuating shaft 36, which carries one end of brake band 21, towards a braking posture. The spring composes a torsion spring 19 that is mounted relatively to the actuating shaft 36. This spring includes a brake activation end that is connected to the reset grip 17 which is carried on actuating shaft 36 by being hooked through aperture 48 to continuously urge the actuating shaft 36 forwardly. The other end of spring 19 is connected to front handle pedistal mount 44 by being hooked through aperture 46. 
     Depicted in FIGS. 1 and 1a is an actuating shaft trigger 38 which comprises leg 39 and foot 58, pivotly mounted on mounting pedistal 27 by mounting bolt 42 via drilled hole (not shown) in pedistal 27 and drilled hole (not shown) in trigger leg 39. Carried on mounting bolt 42 in a position on one side of trigger 38 is washer 52, carried on the opposite side of trigger 38 is washer 54 with locking nut 56. 
     Shown is a cable sheath 9 which freely receives in reciprocable relationship therein a cable 11. Cable 11 being operatively connected to rotatively mounted front handle 50. Actuating shaft trigger 38 is operatively connected to cable 11 by linkage 13 and fixed plug 15. Actuating shaft trigger 38 operatively carries a curved end 14 of linkage 13 in aperture 16. The other end of linkage 13 is fixedly connected to cable 11 by means of fixed plug 15. 
     As the rotatively mounted front handle 50 is rotated clockwise, either automatically in a &#34;kick-back&#34; situation or manually by the operator at his option, cable 11 is reciprocated toward said handle 50 in an upward direction. Such upward movement being caused by the elevated mounting position of handle 50. This movement of cable 11 causes fixed plug 15, which carries one end of linkage 13, to move in relationship with cable 11. The result of said action being that linkage 13 is moved in a forwardly and upwardly direction and exerts a lifting force on trigger 38 to operatively lift said trigger to an elevated position. It is understood that the end of linkage 13, which is connected to trigger leg 39 is allowed to swivel in aperture 16 as linkage 13 is moved in a forward or backward direction. 
     FIGS. 1 and 1a show the present invention in a braking posture with the brake band 21 tigthened around the periphery of the clutch outer drum 32 by the biasing force of the torsion spring 19 to impose frictional forces against drum 32 and stop the cutter chain 7. 
     FIGS. 2 and 2a show the present invention in a non braking posture. The actuating shaft 36 is releasably received in recess 40 with its unthreaded end resting on the trigger foot 58, as a biasing force is being exerted by torsion spring 19 to dispose the actuateing shaft 36 toward its braking posture. The invention, being in this posture, the brake band 21 is disposed loosely around the outer drum 32 so that no braking forces are exerted. 
     FIG. 2a shows the mounting bracket 23 of the present invention afixed to the saw housing 3 by means of cap (machine) screws 60, of which there are two, via drilled holes (not shown) in bracket 23 and tapped holes (not shown) in housing 3. 
     OPERATION 
     In utilizing the chain saw invention described herein, the housing 3 is manually supported by an operator who grasps a rotatively mounted front handle 50 during operation of the chain saw. The handle 50 is in its appropriate normal position. While in this position, the invention is set in a non-braking condition with actuating shaft 36 releaseably held by being received in recess 40 and resting on the foot 58 of trigger 38 as forwardly biasing force is being exerted on actuating shaft 36 by torsion spring 19. 
     In the event that the rotatively mounted front handle 50 is rotated clockwise, either automatically as by the twisting action of &#34;kick-back&#34; or manually by the operator at his option, the following will occur. Cable 11 is reciprocated toward the handle 50 in a upward direction to cause fixed plug 15 to move accordingly and by means of linkage 13 elevate trigger foot 58. This movement correspondingly lifts and releases actuating shaft 36 from recess 40. Being biased forward by torsion spring 19, actuating shaft 36 is positively moved forward along the surface of actuating shaft guide 29 to instantly dispose and tighten brake band 21 around clutch outer drum 32 which causes frictional forces to bring the cutter chain 7 to a complete stop. It will be understood that once the cutter chain has been halted, operation of the chain saw may be resumed by manually resetting the invention to its non-braking posture. Front handle 50 is rotated counterclockwise, correspondingly, by means of cable and linkage, trigger 38 is pivoted to its lowered position. The operator, by grasping with one finger, reset grip 17, retracts rearward actuating shaft 36 along the surface of actuating shaft guide 29 and lowers said actuating shaft into receivership with recess 40 to rest on trigger foot 58. Brake band 21 is now released from it&#39;s frictional grip on clutch outer drum 32. 
     SUMMARY OF MAJOR ADVANTAGES AND SCOPE OF THE INVENTION 
     Those skilled in the chain saw art and familiar with the present disclosure may well envision alternative arrangements in addition to those described and will recognize that the invention may be practiced in a variety of structural formats. In short, while additions, deletions, substitutions or modifications in relation to the disclosed embodiments may be effective in practicing the invention, such changes would be deemed to fall within the purview of the present invention to the extent encompassed by the appended claims.