专利汇可以提供Chainsaw throttle and brake mechanisms专利检索，专利查询，专利分析的服务。并且A chainsaw is provided having a brake band disposed about a drum that rotates during advancement of the saw chain about the saw bar. An end of the brake band is biased to a position that draws the brake band tight about the drum to prevent advancement of the saw chain, and the throttle trigger of the chainsaw is associated with this biased end to push the band against the bias and release the drum when the throttle trigger is squeezed to drive the elements of the chainsaw that serve to advance the saw chain. Also provided are new concepts for associating throttling and braking elements with the throttle trigger.，下面是Chainsaw throttle and brake mechanisms专利的具体信息内容。
The present invention generally relates to chainsaws, and, more particularly, relates to braking mechanisms for providing added safety features to typical chainsaws. This invention is focused on handling chain run down.
Chainsaws are potentially dangerous tools even when operators exercise extreme caution during their use. Over the years, chainsaws have been manufactured to include braking mechanisms that are intended to function to stop the rotation of the saw chain about the saw bar in the event that the saw bar and the chain thereabout kick backwards toward the operator. These “kickback” brakes operate either through centrifugal forces or through impact of a front hand guard with the operator's support arm used to support and maneuver the chainsaw. In either case, the kickback brakes operate through the movement of various elements from active positions, where the saw chain is permitted to rotate about the chain guide, to brake positions, where the saw chain is braked. When the kickback brakes are activated, the saw chain is stopped through well-known typically spring biased mechanisms.
Chainsaws typically operate in such a manner that the saw chain may continue to rotate about the saw bar when the operator has let up on the throttle. This is known as “chain run down.” Even when the throttle is fully released, there is a chance that the saw chain may be moving at a rate fast enough to be dangerous. Attempts have therefore been made to associate components of the braking mechanism with the throttle to brake the saw chain upon release of the throttle and release the saw chain from the braked state upon squeezing the throttle. It is believed that these attempts have failed, because they provided a chainsaw having a throttle that was too difficult to squeeze and keep depressed, causing finger fatigue and shock to the finger squeezing the throttle trigger, when the front hand guard is activated. An example is provided in U.S. Pat. No. 4,683,660, wherein a link extends from components of the brake mechanism to the throttle such that squeezing the throttle pulls on the brake mechanism to release its braking of the saw chain, and letting up on the throttle allows the brake mechanism to return to a position that stops the moving saw chain. Similar chainsaw embodiments are provided in U.S. Pat. No. 4,594,780; 4,753,012; 5,813,123; and 6,842,987.
Although the prior art has addressed the inherent dangers in operating a chainsaw and has provided mechanisms in an attempt to make chainsaw operation safer, a need still exists for improved safety mechanisms that deal with chain run down. A further need exists for chainsaw mechanisms that reduce finger fatigue.
This invention provides advantages in a chainsaw comprising a brake drum; a saw bar; a saw chain disposed about said saw bar, wherein rotation of said brake drum at sufficient velocity causes said saw chain to be advanced about said saw bar; and a brake band disposed around said brake drum for braking the same. In accordance with this invention, the brake band includes a first movable end that is associated with a first biasing member and an independent second movable end that is biased by a second biasing member to draw said brake band against said brake drum and thereby prevent the rotation of said brake drum, i.e., chain run down. A throttle control trigger is operatively associated with said second movable end of said brake band and has an off throttle position and an on throttle position, wherein, when said throttle control trigger is moved from said off throttle position to said on throttle position, said second movable end moves against said second biasing member, thereby loosening said brake band from said brake drum and permitting the rotation of said brake drum, and, when said throttle control trigger is moved from said on throttle position to said off throttle position, said second movable end is moved by said second biasing member to draw said brake band against said brake drum and thereby prevent the rotation of said brake drum, i.e., chain run down.
For a complete understanding of the objects, embodiments and structure features of the present invention, reference should be made to the following detailed description and accompanying drawings wherein
Referring now to
Chainsaws are primarily provided in two well-known configurations, termed “inboard” and “outboard,” which refer to the location of the brake band and the kickback brake mechanisms that are associated with the front hand guard. In inboard configurations, the brake band and kickback brake mechanisms are secured in the main body of the saw, behind the cover plate. In outboard configurations, the brake band and brake mechanisms are secured to the backside of the cover plate. It will be readily apparent how this invention will be practiced with either the inboard or outboard configuration, although it is intended that the outboard configuration be shown here. Additionally, it will be appreciated that different kickback braking mechanisms are provided in different chainsaws, and, although a particular configuration is shown, it will be readily apparent how this invention will be practiced with other braking mechanisms. Typically, these braking mechanisms work through the movement of lever arms and spring biased members when the kickback brake is activated through the movement of the front hand guard.
In the prior art, the saw chain is operatively connected to a brake drum, and the brake drum is rotated to cause the saw chain to be advanced around the saw bar. Typically, the brake drum is rotated by a centrifugal clutch to advance the saw chain around the chain guide, but the present invention is not limited thereto or thereby. As known, the centrifugal clutch is activated by squeezing the throttle trigger. The brake band is disposed around the brake drum, and is fixedly secured to the main body of the saw at one end, while being secured at its other end to movable braking mechanism components associated with the kickback braking mechanism and the front hand guard. In the prior art, when the kickback braking mechanism is not activated, the brake band is loose around the brake drum, allowing the brake drum to rotate and permitting the advancement of the saw chain about the saw bar. When the kickback braking mechanism is activated through movement of the front hand guard, the braking mechanisms pull on the movable end of the brake band to tighten the brake band about the brake drum and prevent further advancement of the saw chain about the saw bar. Again, this is all well-known to those of ordinary skill in the art, and it is from these well-known configurations that the present invention departs in order to provide benefits heretofore never realized in the chainsaw arts.
The present invention significantly alters the functioning of the brake band, particularly in relation to the brake drum and the throttle control trigger that is squeezed to power and advance the saw chain about the saw bar. More particularly, a spring bias acts on the typically stationary end of the brake band, and the brake band is associated to move when the throttle control mechanism is manipulated. Through practice of the present invention, the brake band is tightened or loosened about the brake drum according to the position of the throttle control trigger. Thus, the tightening of the brake band around the brake drum (and resultant braking of the chain) is not dependant only upon the activating of the kickback braking mechanism. Rather, in the present invention, the tightening and loosening of the brake band around the brake drum is dependant upon the squeezing and releasing of the trigger, when the kickback braking mechanism is not activated. However, the mechanisms used to associate the brake band with the trigger are independent of and do not frustrate the normal operation of the kickback braking mechanism. Even when the brake band is associated with the trigger as taught by this invention, the brake band may be caused to engage the brake drum and prevent the advancement of the saw chain about the saw bar by activating the kickback braking mechanism. Beneficially, in this invention, when the kickback braking mechanism is activated, there is no resultant shock to the trigger finger while the chainsaw is being operated in the on throttle position.
With reference to
Second movable end 34 is biased from support 42 by spring 44, which urges second movable end 34 in the direction of arrow B. Spring 44 is strong enough to pull brake band 30 against brake drum 28 with enough force to prevent the movement of brake drum 28. Thus, when trigger 20 is in the normal off throttle position, saw chain 12 simply cannot be advanced about saw bar 11. This is much different than in the prior art, wherein it is common for an idling chainsaw to be seen with the saw chain advancing around the saw bar. By preventing such chain run down, this invention provides a safety benefit beyond that provided by the prior art.
Second movable end 34 is functionally associated with trigger 20 such that movement of trigger 20 from the normal off throttle position (trigger not squeezed) to an on throttle position (trigger squeezed) will allow chain 12 to be advanced around saw bar 11 (i.e., will loosen brake band 30 from brake drum 28). Particularly, actuator bar 46 engages second movable end 34 to move the same when trigger 20 is squeezed by a chainsaw operator. Actuator bar 46 is secured to cover plate 24 at pivot point 48, and is secured to cable 50 at an opposite end 52 of actuator bar 46. Cable 50 is preferably a Bowden cable. Brake band 30 engages actuator bar 46 at some point between pivot point 48 and cable 50 such that movement of cable 50 in the direction of arrow C causes actuator bar 46 to press up against the bias of spring 44 against second movable end 34. It will be appreciated that this movement will loosen brake band 30 from brake drum 28. With reference to
By connecting cable 50 to trigger 20, the on throttle position, wherein chain 12 may be advanced about saw bar 11, is achieved upon squeezing trigger 20 to provide the driving force to chain 12, and the braking position is achieved upon release of trigger 20. As known, throttle rod 51 is associated with trigger 20 and a carburetor 53 such that squeezing trigger 20 moves rod 51 and opens carburetor 53, and releasing trigger 20 moves rod 51 to close carburetor 53. Assuming that the kickback brake mechanism has not been activated, brake band 30 engages brake drum 28 to stop chain run down as the system is being throttled down, and the life of brake band 30 is thus extended, as wear on brake band 30 is reduced.
It should be appreciated that “actuator bar” is to interpreted very broadly because virtually any structure rotating about a pivot point may be used to press against the second movable end of the brake band. And although a particular pivot point and orientation was chosen for disclosure, other orientations and pivot points could be used to cause the actuator bar to contact the second movable end as desired.
In particularly preferred embodiments, the connection between throttle control mechanism 20 and cable 50 is configured to provide advantages over prior art connections.
Referring now to
It should be appreciated that the focus of this arced brake control is on pulling the cable around a periphery of the arced brake control, and, thus, it is not absolutely necessary that the cable be secured at the perimeter of the arced brake control so long as the length of cable is pulled by winding the length about the controller. “Winding,” in this context, entails any length of cable extending around the periphery, and it does not require that it actually wind 360 degrees around the arced brake control. Additionally, while a circular arced brake control is shown and is sufficient, other arcs, including cycloidal arcs, could be used and should be understood as being covered by the terms “arc” or “arced.” A cycloidal arc may lessen the finger fatigue to an even greater extent.
While a full and complete description of the invention has been set forth in accordance with the dictates of the patent statutes, it should be understood that modifications can be resorted to without departing from the spirit hereof or the scope of the appended claims.