Cutlery – Cutting tools – Saw
Reexamination Certificate
1999-07-20
2001-05-29
Rada, Rinaldi I. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S386000
Reexamination Certificate
active
06237228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates, generally, to improvements in chain saws. More particularly, it relates to an improvement that enables the chain of a chain saw to be loosened or tightened without requiring loosening of locking nuts that secure a chain-carrying blade of the saw to the motor housing of the saw.
2. Description of the Prior Art
Chain saws include an elongate flat blade having a peripheral edge about which a cutting element, also known as a chain, extends in a continuous, endless loop. The distal free end of the chain is used for cutting. The proximal end of the chain extends around a sprocket gear that engages the chain and causes it to rotate around the peripheral edge of the elongate flat blade when the sprocket gear is rotated. The sprocket gear is attached to the output shaft of a motor means that is housed in a motor housing, and the proximal end of the elongate flat blade is secured to the motor housing.
More specifically, an elongate slot is formed in the proximal end of the elongate flat blade, and a pair of externally threaded post members that are secured to the motor housing respectively extend through the apertures. Each post member has an unthreaded base having a diameter greater than the diameter of the threaded part of the post, and the respective bases are recessed with respect to the elongate slot formed in the elongate flat blade. A pair of internally threaded locking nuts respectively screw threadedly engage the threaded part of the post members and securely lock the elongate flat blade against movement when the nuts are tightly seated. The nuts do not contact the respective base members of the posts due to their recessed position.
A worm gear means is employed as a part of a blade position adjustment means that displaces the elongate flat blade in a first direction to loosen the chain and in a second, opposite direction to tighten the chain. However, when the elongate flat blade is tightly secured against movement by the locking nuts, the blade position adjustment means cannot perform its function because the elongate flat blade cannot be displaced when said locking nuts are firmly seated.
Accordingly, to tighten or loosen the chain, both locking nuts must be loosened. After a tool such as a screw driver is used to manipulate the blade position adjustment means until the chain is loosened or tightened to a desired tautness, the locking nuts must then be tightened again.
It can take several minutes to perform the above-described procedure. The locking nuts are very tight, and must be loosened and re-tightened with a socket wrench or other high torque tool. There are many times, such as when a firefighter is in the field and fighting a fast-moving fire, where a quick loosening or tightening of the chain is imperative. Conventional chain saws, however, are designed as described above and thus do not enable such quick adjustment.
In view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how a chain saw could be modified to enable quick loosening or tightening of the cutting element of the saw with respect to the elongate flat blade around which the cutting element extends.
SUMMARY OF THE INVENTION
The long-standing but heretofore unfulfilled need for an apparatus that overcomes the limitations of the prior art is now met by a new, useful, and nonobvious invention. The present invention includes a chain position adjustment means for enabling adjustment of a chain saw cutting element. A conventional, elongate flat blade has a peripheral edge about which the cutting element extends. The elongate flat blade has a distal free end used for cutting and a proximal end that is slidingly secured to a housing for a motor means that drives the chain about the peripheral edge of the elongate flat blade when the saw is activated. An elongate slot is formed in the proximal end of the elongate flat blade and extends completely therethrough. A pair of longitudinally spaced apart, externally threaded post members are mounted to the motor means housing. The posts have threaded parts that extend through the elongate slot formed in the proximal end of the elongate flat blade and unthreaded bases of greater diameter than the threaded parts. The respective bases are recessed with respect to the elongate slot formed in the proximal end of the elongate flat blade.
A blade position adjustment means is rotatably mounted to the motor housing and includes a peg means, driven by a worm gear, for displacing the elongate flat blade in a distal-to-proximal direction to loosen the cutting element and to displace the elongate flat blade in a proximal-to-distal direction for tightening the cutting element. The elongate slot formed in the flat blade means in registration with the peg means accommodates the distal-to-proximal and proximal-to-distal displacement of the elongate flat blade.
A spacer plate having a predetermined thickness has a longitudinal extent sized to fit within the elongate slot. The spacer plate is apertured at its opposite ends and sits atop shoulders formed at the juncture of the threaded posts and their respective unthreaded bases.
The spacer plate also has a cut-out formed in it, mid-length thereof, to provide access to the blade position adjustment means.
The predetermined thickness of the spacer plate positions an external or away-from-the motor housing surface thereof above an external or away-from-the motor housing surface of the elongate flat blade. A clearance space is therefore provided between the external or away-from-the motor housing surface of the spacer plate and the internal or facing-the-motor housing surface of the elongate flat blade when locking nuts are respectively loosely screw-threadedly engaged with the externally threaded posts. The nuts cause the internal or motor housing-facing side of a motor housing cover to seat lightly against the spacer plate and not against the proximal end of the elongate flat blade when the nuts are loosely tightened.
In the prior art, when firmly seated the nuts cause the internal or motor housing-facing side of the motor housing cover to seat tightly against the external or away-from-the motor housing surface of the proximal end of the elongate flat blade because the respective bases of the nuts are recessed with respect to the elongate slot formed in said proximal end. Thus, there is nothing to prevent the nuts from driving the internal, motor housing-facing surface of the motor housing cover into tightly abutting relation to the external, away-from-the motor housing surface of said proximal end.
In the novel assembly, the spacer plate provides a clearance space between the inner surface of the motor housing cover and the outer surface of the elongate flat blade when the nuts are loosely tightened, as aforesaid. However, when the nuts are firmly tightened, the clearance space disappears due to the compressability of the facing-the-motor housing side of the motor housing cover, it being understood that said cover is formed of a high impact plastic. The internal or facing-the-motor housing side of the motor housing cover therefore abuts the proximal end of the elongate flat blade. However, the presence of the spacer plate prevents the abutting contact from being firm. The amount of contact is sufficient to prevent vibration of the blade, but not enough to prevent adjustment of the blade position by using a blade position adjustment tool in a well-known standard way. The light abutting contact thus enables displacement of the elongate flat blade by the blade position adjustment means to loosen or tighten the cutting element with respect to the peripheral edge of the elongate flat blade even when the nuts are tightly seated.
It is a primary object of this invention to enable adjustment of a chain saw chain even when the locking nuts of a chain saw are firmly seated.
In other words, it is the primary object of this invention to provide the first chain saw having a chain adjustment me
Flores-Saánchez Omar
Rada Rinaldi I.
Smith Ronald E.
Smith & Hopen , P.A.
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