Cutting – Tool or tool with support – Joint or connection
Reexamination Certificate
1999-08-13
2001-10-02
Bray, W. Donald (Department: 3725)
Cutting
Tool or tool with support
Joint or connection
C083S543000, C083S698410, C192S055100, C192S150000, C192S048300, C081S476000
Reexamination Certificate
active
06295910
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to circular saws and in particular to clutch assembly positioned between the blade shaft and the shaft rotated by the saw's motor.
2. Scope of the Prior Art
Circular saws use a saw blade to cut materials such as wood. A shaft having a gear or pinion at the distal end that is powered by the saw's motor rotates a blade shaft. Traditionally, the bolt and washer are used to secure the blade into a hole provided in the blade shaft. A wrench is required to tighten the bolt and washer is that the blade remains secured to the shaft. As it can be appreciated, the bolt must be tightened enough to secure the blade for rotation. A user is instructed, however, not to over tighten the bolt and is told to tighten the bolt with the wrench only a one-eighth turn past finger tight. The need to use a wrench can be cumbersome, and it requires that the tool be available.
The material cut by the saw can lock saw blades. Accordingly, the blade will not rotate even though the motor is rotating the shaft and gear. The bolt and washer that secures the blade to the rotating blade shaft therefore functions as a clutch so that the motor does not burn out. If the bolt is over tightened, however, the bolt-and-washer clutch arrangement may not function properly. The saw therefore may tend to kick and the motor may be damaged.
Other power tools that have rotating parts, such as table saws and, power drills etc., also use bolts and other mechanisms to secure the blade or bit to a rotating shaft. These power tools also must protect the motor when the blade or bit is locked. Table saws use the same bolt and washer arrangement. Chucks can be used by other tools such as drills.
It has long been known to use various types of friction-type washers as clutch arrangements for automobiles, agricultural equipment, and other devices. Those clutches drive a member and include an arrangement of Belleville washers and friction plates. When the member is locked, the clutch arrangements allow the motor and engine to continue rotating while the member remains stationary. These clutches tend to be heavy-duty because of the forces involved and the torque required by the equipment.
SUMMARY OF THE INVENTION
The present invention relates to a clutch assembly that is used with a circular saw in which the assembly overcomes the deficiencies of the prior art. The circular saw includes a motor driven shaft that includes a pinion at one end. The pinion drives the clutch assembly that rotates a blade shaft. A blade is secured to the end of the blade shaft.
The clutch assembly of the present invention includes a clutch gear that has a longitudinal hole through its rotating axis. The clutch gear fits over an end of the blade shaft opposing the blade. A bearing function is provided between clutch the clutch gear and the blade shaft. A cylindrical bearing can be served as the bearing friction and as a slip surface. A bearing can be positioned between the clutch gear and the blade shaft. To rotate the blade shaft, the clutch assembly includes a shaft washer on either side of the clutch gear. Belleville, or spring-type, washers bias the shaft washers against the clutch gear. A press-fit washer fits over the end of the blade shaft to hold the clutch assembly against a ledge formed on the shaft. In one embodiment, the shaft washer is made of a suitable friction material that will not bond or weld to the clutch gear, such as bronze. Preferably, the shaft washers include a frictional substrate layered to the side of the washer pressed against the clutch gear. In another embodiment, an assembly of gear washers and shaft washers are arranged on at least one side of the clutch assembly.
In operation, the pinion engages in teeth formed on the outer side of the clutch gear. When the blade is not locked by any means, the clutch gear rotates the gear washers that in turn rotate the blade shaft. Accordingly, the blade cuts the material. When the blade is locked in a position for any reason, the clutch assembly permits the pinion to rotate while the blade holds the blade shaft. The pinion continues to rotate the clutch gear while the torque provided on the blade shaft overcome the friction, which is the result of the clamping force, coefficient of friction, and effective radius, of the surfaces between the clutch gear and the gear washers. Alternatively, the torque is overcome between the faces of the laminated gear washers and the shaft washers.
The use of the clutch assembly of the present invention with a circular saw, or other power tool, overcomes the concerns of over-tightening the bolt to the blade shaft. In addition, the present invention orients the clutch assembly directly between the gear that rotates the shaft and the shaft itself. This provides for increased performance of the clutch assembly, prevents premature motor problems and reduces the chance that the clutch friction fails when the blade is locked. Moreover, the present invention can be modified by provided different coefficient of friction to the surfaces on the gear washers or increasing the number of gear washers and shaft washers to provide different friction between the shaft and the gear. The present invention provides these advantages while maintaining the dimension and weight of the saw. The clutch assembly is also built within the same volume as the gear assembly used by the prior art.
REFERENCES:
patent: 1564342 (1925-12-01), Gebhardt et al.
patent: 2427153 (1947-09-01), Mossberg
patent: 2482387 (1949-09-01), Veneman
patent: 2675835 (1954-04-01), Kiekhaefer
patent: 2917147 (1959-12-01), Finn
patent: 3038576 (1962-06-01), Simpson
patent: 3214773 (1965-11-01), Benjamin et al.
patent: 3315773 (1967-04-01), Aschauer
patent: 3498434 (1970-03-01), Richmond
patent: 3503478 (1970-03-01), Neumann
patent: 4496136 (1985-01-01), Maeda
patent: 4776442 (1988-10-01), Young
patent: 4883152 (1989-11-01), Froment
patent: 4949587 (1990-08-01), Oka
patent: 5107737 (1992-04-01), Tagliaferri
Childs Daniel K.
Holzer Michael
Houben Jan P.
Bray W. Donald
Gardner Carton & Douglas
S-B Power Tool Company
LandOfFree
Clutch assembly for use with a circular saw does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Clutch assembly for use with a circular saw, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clutch assembly for use with a circular saw will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590054