Abrading – Work holder – Clamp
Reexamination Certificate
2001-11-29
2003-11-11
Nguyen, Dung Van (Department: 3723)
Abrading
Work holder
Clamp
C451S509000
Reexamination Certificate
active
06645058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of rotary power tools. In particular the present invention relates to a tool-free mechanism for clamping interchangeable rotary tool accessories, such as grinding discs, circular saw blades, etc.
2. Discussion
Various types of rotary power tools require a user to selectively attach a tool accessory, such as a grinding disc. Over the course of a particular project or work period it may be necessary to employ a variety of such accessories and to replace worn or broken ones. Convenient removal and replacement of the interchangeable tool accessories is therefore desirable.
Various methods are employed for clamping such accessory discs. For example, in current grinder designs a replaceable grinding disc has a center hole. The hole in the grinding disc fits over the end of the grinder's output shaft or drive spindle, with the plane of the grinding disc transverse to the axis of the shaft. For some radial distance the interior surface of the disc hub rests against a flat shoulder of the shaft or an inner washer connected to the shaft.
Conventionally, the grinding disc is clamped in place against the shoulder or inner washer with a retaining-nut threaded down over a threaded end of the drive spindle. An outer washer may be placed between the nut and the hub of the grinding disc. When changing grinding discs, the nut must be loosened and removed. The tightening and loosening of the nut may be partially performed by hand, but the size and shape of the nut make it difficult and/or uncomfortable to properly tighten and then initially loosen using hands alone. Therefore, it is necessary to use a hand wrench or similar tool in order to apply sufficient torque to the retaining nut.
Additionally, when tightening or loosening the nut, the shaft/spindle must be prevented from rotating or else it would be difficult to achieve relative motion between the nut and the rotatable spindle. Conventionally, the loosening and tightening process requires that the operator simultaneously grip both the shaft/spindle and the nut with two separate hand wrenches or the like. Then a torque is applied to the nut while the shaft is held in place. This is an awkward process and made even more so by the necessity to support the weight of the tool itself.
More recently, tools have been designed that incorporate a locking mechanism that locks the shaft/spindle relative to the tool housing. Thus, the rotation of the shaft can be prevented, simply by employing the built in shaft lock. For such a power tool, only one hand wrench is required to loosen or tighten the nut.
The need to use even one hand tool to change grinding discs, however, is still inconvenient. For example, when a replacement disc is required, the tool operator has to stop what he is doing to find a wrench, which may not be readily at hand.
To make the replacement of a grinding disc a tool free process, a number of clamping devices that can be tightened and loosened by hand have been invented. Such prior art devices have had several drawbacks including: the clamping device height interferes with use of the grinding tool; the clamping device does not self tighten during operation or, if it does self tighten, it cannot be readily released by hand; and incorporation of a slip clutch effect to prevent over-tightening.
An example of such a quick acting clamping device is described in U.S. Pat. No. 5,707,275 to Preis et al., which is embodied in the FIXTEC® Rapid Locking Nut manufactured by INA Wälzlager Schaeffler oHG. The clamping device according to the U.S. Pat. No. 5,707,275, patent has a slip clutch function that, while preventing over tightening of the clamping device, unnecessarily limits the usable torque of the grinding machine.
SUMMARY OF THE INVENTION
It is, therefore, one object of the invention to provide an improved device for simple and reliable axial clamping of a tool accessory disc, such as a circular grinding disc, without the use of any hand tools. Further objectives of the present invention include:
A compact, low height design;
Simply shaped and easy to manufacture parts;
Low manufacturing cost;
Provides for self-tightening under load, but without loss of the ability to loosen by hand.
These and other objects of the invention are accomplished according to the present invention in a clamping device constructed of stacked components that can be manipulated from a first position having a first stack height to a second position having a second stack height less than the first stack height. The clamping assembly is installed and tightened in the first position with the greater stack height. After tightening, the axial reaction load on the camping assembly would require significant torque to unscrew. By first manipulating the assembly into the second position and consequently reducing the stack height of the assembly, however, the axial reaction load is significantly reduced. Thus, the torque required to unscrew the device is reduced to levels that can be applied by hand.
In order to so function, the clamping assembly includes a clamp flange positioned axially inward against the hub of the grinding disc. Stacked axially outward of the clamp flange is a first roller cage. The roller cage is pierced by a plurality of angularly spaced perforations. Rotatably mounted in the perforations is a first set of rolling elements. The rolling elements may be needle bearings, which distribute the axial load and minimize the overall stack height of the clamping assembly, but may include other types of bearings. Stacked axially outward of the first roller cage is a center thrust plate, also pierced by a plurality of angularly spaced perforations, equivalent in number to the rolling elements. Equivalently, instead of perforations, appropriately sized and spaced indentations could be located on the opposed sides of the center thrust plate.
Stacked axially outward of the center thrust plate is a second roller cage pierced by a plurality of angularly spaced perforations. Located in the perforations of the second roller cage is a second set of rolling elements. The first and second roller cages are connected so as to rotate together with the two sets of rolling elements in axial alignment. Said connection may be by means of a tab and slot combination on the outer circumference of the roller cages.
The center thrust plate is sandwiched in between the roller cages and can rotate relative thereto. A biasing means, rotationally biases the center thrust plate into a ready or locked position, relative to the roller cages, wherein the two sets of rolling elements rest on the opposite flat surfaces of the center thrust plate, rather than in the perforations of the center thrust plate. The biasing means may include springs.
Stacked axially outward of the second roller cage is a flange nut with an axially projecting hub. The hub threadably engages the shaft of the grinding tool. The clamp flange is rotationally locked with the flange nut, but they have limited axial movement between them. The rotational engagement of the clamp flange and the flange nut may be accomplished by use of mating double—D surfaces near the radially inner perimeters of the two elements.
Sandwiched rotatably between the clamp flange and the flange nut is a ring collar, which surrounds the stacked center thrust plate and roller cages. The outer circumference of the ring collar has a grippable surface. Within the inner circumference of the ring collar, the interlocked roller cages can rotate. The center thrust plate is connected to the ring collar, so that the thrust plate will turn when the surrounding ring collar is turned. Said connection can be accomplished by means of a tab and slot combination between the inner circumference of the ring collar and the outer circumference of the center thrust plate.
In its ready or locked position the springs have rotationally biased the center thrust plate so that the rolling elements, while inside their respective perforations in the roller cages, ar
Baron Michael P.
O'Banion Michael L.
Puzio Daniel
Black & Decker Inc.
DelPonti John D.
Leary Michael P.
Nguyen Dung Van
Yocum Charles E.
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