Dual spring hold down for wood working tools

Details Dual spring hold down for wood working tools Dual spring hold down for wood working tools

1998-12-21

2001-01-09

Rada, Rinaldi I. (Department: 3724)

Cutting

Rotatable disc tool pair or tool and carrier

With means to support work relative to tool

C083S421000, C083S431000, C083S438000, C083S440200, C083S450000, C083S477200, C083SDIG001, C144S253100, C144S250120, C144S251100, C144S286100, C269S058000, C269S317000

Reexamination Certificate

active

06170372

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a dual spring hold down for a wood working tool such as a table saw, shaper or router, and, more particularly, to such a hold down which attaches to a table and which is positioned to securely hold a wood panel as it is being shaped and to act as a barrier to minimize the operator's exposure with the working tool. The inventive hold down is adjustable for different thicknesses of wood stock, and includes a hold down bar which drops down into contact with the table surface, guide or depth stop position when no wood stock is present, but which easily lifts to a height just below the stock thickness to facilitate placement of the wood panel beneath the hold down for wood working operations.
BACKGROUND OF THE INVENTION
Designers and manufacturers of professional wood working tools, such as table saws, routers and shapers, are constantly looking for ways to improve the efficiency and safety of their products. One improvement which has been widely adopted is the use of “hold downs” which are spring loaded bars or blocks which provide downward pressure on a wood panel as it is being pushed or pulled past a saw blade, router or shaper. One example of such a hold down is illustrated and described in U.S. Pat. No. 4,063,612 to Richard Atkins. In the Atkins patent, a housing includes a pair of legs which straddle a rip fence and a spring biased hold down arm is attached to the housing and extends downward at an angle therefrom to engage a wood panel being cut by a table saw. The housing can be pushed along the rip fence to urge the wood panel into the saw blade while keeping the operator's fingers clear.
Another example of a hold down is illustrated and described in U.S. Pat. No. 4,026,173 to Livick. In the Livick patent, again, the hold down device is attached to and is movable along a rip fence so that an operator's hand are kept clear of the saw blade.
Hold downs are also known which attach to a shaper work table andiextend over the shaper blade to engage a wood panel being shaped. An example of such a hold down, which is offered on the assignee's machines, is illustrated in
FIG. 1
, labeled as “PRIOR ART”. The hold down of
FIG. 1
which is described in detail below, includes a U-shaped bar which fits over the shaper blade and which is spring biased downward by a coil spring to apply downward pressure against a wood panel being shaped. The working height of the hold down is adjustable via a crank arm to allow for different thicknesses of wood panels.
The rip fence mounted hold downs of Livick and Atkins are suitable for use with table saws equipped with rip fences, but not with shapers or routers, and not for sawing lumber of a width such that it will not fit within a rip fence. Assignee's prior art hold down design, as represented in
FIG. 1
, has worked satisfactorily as a hold down, but, particularly for wood panels of larger thicknesses, does not provide as effective of a barrier for minimizing the exposure of an operator to a working tool.
It is clear, then, that a need exists for an improved hold down device for use with wood working tools, such as table saws, routers and shapers. Such an improved hold down should provide downward pressure against a wood panel being shaped or cut and should allow an operator to feed the wood panel through the wood working tool while minimizing the exposure of the operator to the operating tool. Finally, such a hold down should be easily adjustable to accommodate different thicknesses of wood stock.
SUMMARY OF THE INVENTION
The present invention is directed to a hold down for use with wood working tools, such as table saws, routers and shapers. The inventive hold down includes a base with a flat plate which is removably secured to the wood working table behind the tool and which forms a part of a bracket including opposing side plates connected by a bracket cross plate. Each bracket side plate has a slot extending there through and a rigid bracket extension arm is attached to and extends outward from the bracket cross plate. A hold down mechanism includes a pair of hold down legs which are sized to go on respective sides of the wood working tool and each hold down leg is bolted through a respective slot of one of the bracket side plates such that the hold down legs are pivotable relative to the bracket. A hold down cross plate connects between the two hold down legs behind the wood working tool and the hold down cross plate includes a slot extending there through. A hold down bar connects between the two hold down legs arms in front of the wood working tool. An externally threaded rod is threaded into and extends upward from a threaded bore in the rigid bracket arm and through the slot in the hold down cross plate where a first washer is positioned. A first coil spring surrounds the threaded rod immediately above the first washer and extends upward to a second washer and a second coil spring surrounds the threaded rod above the second washer and extends upward to a third washer. A cylindrical sleeve surrounds the first coil spring, with the sleeve being somewhat shorter than an extended length of the first coil spring. The first coil spring is of considerably smaller gauge, and is thus quite a bit weaker, than the second coil spring. The hold down bar is free to drop down to the table surface, guide, or position of depth stop when not in use. Then, initial lifting of the hold down bar by a wood panel is against the relatively light downward bias of the first coil spring until the sleeve is lifted a distance sufficient to compress the first coil to the length of the surrounding sleeve, i.e. until the top of the sleeve contacts the second washer at a hold down height. Further lifting of the hold down bar is then against the considerably stronger downward bias of the second coil spring as the sleeve pushes upward against the second washer. It is the second, larger gauge coil spring which provides most of the hold down pressure against the wood panel. The hold down height of the hold down bar is adjustable by threading the threaded rod upward or downward. A first embodiment of hold down mechanism is designed for use with raised panel shapers while a second embodiment is designed for use with table saws and the like.
OBJECTS AND ADVANTAGES OF THE INVENTION
The objects and advantages of the invention include: providing an improved hold down for wood working tools; providing such an improved hold down which greatly reduces the exposure of the wood working tool and applies the proper pressure to a wood panel as it is being fed through a wood working tool; providing such a hold down which uses a first coil spring surrounding a threaded shaft connected to a hold down bracket arm, which first coil spring is surrounded by a cylindrical sleeve such that the first coil spring provides a minimal downward bias against a hold down bar until the hold down bar has been lifted to a preset hold down height; providing such an improved hold down with a second, larger gauge coil spring positioned above the first coil spring and surrounding sleeve on the threaded shaft which second coil spring provides a significant downward bias against the wood panel secured beneath the hold down bar after the hold down bar has been raised to the hold down height; providing such a hold down in which the hold down height is conveniently adjustable; and providing such a hold down which is economical and which is particularly well suited for its intended purpose.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.
The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.


REFERENCES:
patent: 2100455 (1937-11-01), Souther et al.
patent: 2155730 (1939-04-01), Miller
patent: 2642902 (1953-06-01), Carey
patent:

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