Cutting – With product handling means – By fluid current
Reexamination Certificate
2000-12-26
2003-06-17
Shoap, Allan N. (Department: 3724)
Cutting
With product handling means
By fluid current
C083S546000, C083S477200, C083S102100, C144S251100, C409S134000
Reexamination Certificate
active
06578460
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to safety equipment for table saws. More particularly, the present invention is directed to a blade guard assembly including a blade guard pivotally mounted to a portion of the table top by a parallelogram linkage and a lifter therefor that interlock to react lifting forces into one of the linkage elements.
Most table saws, if they have any guard at all, are equipped only with a plastic or light gauge sheet metal guard. These guards are pivoted to the splitter in a manner to provide movement that permits the guard to remain parallel to the table top. The only hold down force is provided by the weight of the guard, a minimal resistance force, indeed, when compared to the significant lifting force that can be produced in a workpiece. Further, any hold down pawls associated with such guards would prove ineffective since a significant downward force is essential for them to work.
The safety equipment of the present invention provides a suitable guard assembly for a table saw. The blade guard assembly includes a blade guard and a lifter for the blade guard. The blade guard is pivotally attached to the splitter by means of two primary links that are generally the same length, the two links being pivoted at each end and spaced by equal amounts at the top and bottom to form a parallelogram linkage that enables the blade guard to pivot upwardly about the pivot points and move rearward toward the splitter. A bearing protrudes laterally from side portions of the blade guard.
The lifter, formed by two interconnected identical plates, sandwiches the blade guard. The lifter is pivoted to the splitter by a secondary link that is considerably shorter than the two primary links. The secondary link is attached to the splitter at one of the two primary links' pivot points. This geometry produces forward movement of the lifter relative to the blade guard as the workpiece to be cut is shoved under the forward camming surface of the lifter. One of the rear portions of the lifter and the blade guard is equipped with a locking groove and the other with a locking rod. As the workpiece lifts the aft portion of the lifter, the secondary link causes the locking element on the lifter to move rearwardly engaging the locking element on the blade guard such that the lifter and blade guard become interlocked. The locking slot is equipped with serrated teeth to limit slippage between the locking rod and the slot. The interlocked unit will attempt to pivot about the secondary link's pivot point. Accordingly, any lifting force the workpiece experiences will be reacted into the primary link that does not share the pivot with the secondary link, i.e., the lifting force will be resisted by the stiffness of the primary link as the torsion of the workpiece attempts to axially compress the rigid primary link. The blade guard and lifter plates completely surround the saw blade and prevent accidental contact with person or property when no workpiece is being maneuvered toward the saw. A pair of platelets may be compressed by a bolt and wingnut to clamp the lifter and blade guard together to facilitate repetitive cutting of work pieces having identical thicknesses. Further, the table saw is provided with a dust removal system to reduce the effects of potentially hazardous dust resulting from currently compounded/treated materials. In addition, the dust removal system will minimize the cleanup needed following use of the saw.
In another embodiment of the saw guard, the saw blade is fixed in a fully elevated position. Some adjustable saws, at some of the lower blade positions, create a hazard to the user as a result of the teeth of the blade tending to project particles directly back toward the user's face. In the fully extended position, the teeth of the blade will tend to project the removed particulate matter downward below the table. Hence, by designing the guard and lifter to accommodate the blade in its fully extended position, and eliminating the raising, lowering and tilting mechanism associated with such a saw, the safety of the product is further enhanced. An additional advantage occurs in that the elimination of these mechanisms reduces the overall cost of the table saw. A single position table saw equipped with the blade guard of the present invention will provide a low cost, alternative to existing equipment that has maximum protection for the user. Such a saw will be ideal for school shops as well as some workplace and home uses.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.
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Prone Jason
Shoap Allan N.
Thomson Richard K.
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