Cutlery – Cutting tools – Saw
Reexamination Certificate
1999-11-01
2001-05-29
Payer, H. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S383000
Reexamination Certificate
active
06237229
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a guide bar for a chain saw of the type used, for example, for cutting down or trimming trees and, in particular, to a guide bar that incorporates a chain-tightening device which enables a user to readily and easily adjust the tightness of the saw chain.
Generally, when a chain saw is employed for a long period of time, the saw chain is caused to elongate due to the abrasion of the portions of the saw chain that engage the guide bar, thus loosening the saw chain and sometimes allowing disengagement of the saw chain from the driving chain sprocket wheel or the guide bar. Therefore, the saw chain is required to be re-tightened occasionally. Further, it is also required at the occasion of exchanging the saw chain for a new one to adjust the tightness of the new saw chain after the new saw chain is mounted on the driving chain sprocket wheel and guide bar.
Chain-tightening devices for adjusting the tightness of the saw chain have been conventionally provided on the main body and side guard of the chain saw. Examples of such a chain-tightening devices are described and shown in Japanese Utility Model Unexamined Publication S61-93201 and Japanese Patent Unexamined Publication H7-314402.
It is required, for the provision of the conventional chain-tightening device, to separately attach accessories to the main body and side guard of the chain saw and to configure the main body and side guard for mounting the chain-tightening device on the chain saw, thus making the chain saw complicated in construction, increasing the number of parts required for the provision of the chain-tightening device, and adding to the costs for manufacturing the chain saw. In addition, the maintenance and inspection of the chain-tightening device can be troublesome, and the chain-tightening device cannot be attached to an existing chain saw.
Additionally, since the conventional chain-tightening device is generally mounted on the main body and side guard of the chain saw, the tightening of the chain is required to be conducted by turning adjustment screws attached to the chain-tightening device using a tool such as a screwdriver. In this case, the adjustment screws are inevitably mounted close to one side wall of the main body of chain saw (generally, the right side wall as viewed from the proximal end of the chain saw), so that the operator is required, for the purpose of turning the adjustment screws, to manipulate a tool such as a screwdriver by directing it in the longitudinal direction of the main body of chain saw, in the direction perpendicular to the main body of chain saw, or in an intermediate direction thereof (or in an oblique direction) so as to position the tool to engage with the adjustment screw members. This often means that the operability for adjusting the tightness of saw chain is inferior and at the same time, it is difficult to confirm the degree of tightness of the saw chain while turning the adjustment screw members, thus making the adjustment of the chain tension rather difficult.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to overcome the aforementioned problems, and therefore an object of the present invention is to provide a guide bar of chain saw that incorporates a chain-tightening device, which makes it possible to avoid having to separately attach accessories to the main body and side guard of the chain saw or to configure the main body and side guard for mounting the chain-tightening device on the chain saw, thereby simplifying the construction of the chain saw and permitting the number of parts required for the provision of the chain-tightening device to be reduced, thus resulting in savings in manufacturing costs for the provision of the chain-tightening device and in the simplification of not only the assembling, but also the maintenance and inspection of the chain-tightening device. Another object of the present invention is to provide a guide bar of chain saw, which makes it possible to provide an existing chain saw with a chain-tightening function without requiring a modification of the chain saw. Yet another object is to enable a user to readily and easily perform the chain-tightening operation.
With a view to attaining the aforementioned objects, the present invention provides a chain saw guide bar that incorporates a chain-tightening device. A guide bar, according to the present invention, has a pair of elongated chain guide plates, which are superimposed with each other, which have proximal ends and distal ends, and which are adapted to receive a saw chain along portions of the peripheries thereof. Positioning slots formed adjacent the proximal ends of the chain guide plates extend in the longitudinal direction of the guide plates and are adapted to receive a pair of fixing stud bolts that project from the main body of the chain saw. A chain-tightening device carried by the guide bar includes an adjusting winding member carried by the guide plates in a fixed position distally of the guide slots for rotation about an axis. One end of a flexible wire is connected to the adjusting winding member. The other end of the flexible wire is connected to a circular ring that is slidably received between the guide plates with an opening thereof at least partly registering with the positioning slots. The ring is adapted to be received on one of the fixing stud bolts. A returning member is windingly engaged with an intermediate portion of the wire and stationarily located on a portion of the guide bar proximally of said one of the fixing stud bolts.
In a preferred embodiment of the present invention, an intermediate plate is fixedly interposed between and is engaged with the pair of guide plates and forms a space between the guide plates.
An advantageous embodiment of the present invention has a winding member in the form of a pulley having a barrel portion rotatably received in mounting holes formed in the guide plates and a flange portion radially projecting from the barrel portion and received for rotation in the space between the guide plates so as to be retained in the space by engagement with portions of the guide plates surrounding the mounting holes.
At the time of initially attaching the guide bar to the main body of the chain saw, the circular ring is at first fitted around the fixing stud bolt that projects from the main body of the chain saw. Then, for the purpose of fitting the saw chain around the guide bar, the guide bar is at first positioned on the main body of chain saw slightly rearwardly of the location that it occupies when the saw chain is in place and tightened for use.
Next, the saw chain is fitted around the driving sprocket that is connected with the drive motor inside the main body of chain saw and also around the guide plates of the guide bar. Thereafter, the side guard is set in position, and the fastening screws are hand-tightened onto the fixing stud bolts, thereby allowing the guide bar to be moved by the chain-tightening device in the longitudinal direction distally of the main body of the chain saw.
At this point, the adjusting winding member is turned clockwise by making use of a screw driver so as to adjust the tension of the saw chain. An end portion of the flexible wire is thereupon wound onto the adjusting winding member. Since the other end portion of the flexible wire is fixed by the circular ring to the fixing stud bolt and the intermediate portion of the flexible wire is wrapped around the turning member, the winding of the flexible wire onto the adjusting pulley causes the guide bar to move distally in a direction away from the main body of chain saw by a distance corresponding to half of the length of the flexible wire that is wound onto the adjusting pulley, the turning member serving as a working point for application of a force from the wire to the guide bar.
When the guide bar is moved distally in this manner, the distance between the driving sprocket of the main body of chain saw around which the saw chain is wound and the tip end portion of the guid
Igawa Hayato
Iizuka Akinori
Okochi Hiromi
Baker & Botts L.L.P.
Kioritz & Corporation
Payer H.
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