Abrading – Tool support for flexible-member tool
Reexamination Certificate
1998-05-27
2002-04-09
Hail, III, Joseph J. (Department: 3725)
Abrading
Tool support for flexible-member tool
C451S527000
Reexamination Certificate
active
06368199
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to the field of abrasive or sanding disks, and in particular this invention relates to backing plates for abrasive disks and accessories for angle grinders and means for making them.
BACKGROUND
Abrasive disks, or sanding disks are widely used on portable electric drills and (at a more professional level) on hand-held angle grinders. When used on these machines the disk is held by its centre against a backing plate and is rotated at generally a high speed while pressed in front of a backing plate against the work. The abrasive surface wears down the surface of the work by, in effect, a cutting action. Angle-grinder mounted sanding disks are commonly used (for example) in automotive panel beating, where body filler is to be sanded back to conform to the original contours of a remodelled car part. It is said that millions of sanding disks suitable for use with angle grinders are sold each year. There are some problems related to the use of sanding disks, such as:
(a) The relatively rigid backing plates commonly used with angle grinder sanding disks force the sanding disks into an unsatisfactory mode of operation when the angle grinder is tilted towards the work during use—such as that primarily the edge engages with the work, resulting in local, intense action rather than an even, gradual action over a wider area. There is a tendency for the work surface to develop an unsatisfactory scalloped surface which requires hand sanding block treatment. The disks cannot be used for finely controlled work such as preparation of surfaces in a state ready for painting.
(b) Sometimes the material being abraded tends to melt at the high cutting speeds involved, and if this happens it is particularly likely to clog the sanding disk in a quick and effective manner so that the disk has to be discarded. Melting may also lead to the tool biting in and as a result the surface of the work may be inadvertently destroyed. Heating also adversely affects the life of the sanding disk.
(c) The operator cannot see the material being sanded during the actual operation; he/she can only see material that is not covered by the blade. It is difficult to carry out a precise operation without repeatedly inspecting the work in progress and more closely reaching an approximation to the desired result. Hand-held tools cannot be re-applied precisely so that repeated inspection is not a good option for careful work.
It is a well known phenomenon that a disk having perforations becomes semi-transparent when spun at a moderate to high speed because of the persistence of image on the retina in the human eye—the “persistence of vision” effect. The image seen through a perforated spinning disk is further enhanced if there is a contrast in light and/or colour between the spinning disk and its background and/or foreground. To increase the width of the “window” or see-through viewing effect when a disk is spun, perforations are usually designed to overlay each other. There are many abrasive and rasping disks that make use of this phenomenon. Examples are those of F. Reidenback filed Aug. 31, 1953 U.S. Pat. No. 2,749,681 or J. C. Schwartz filed Mar. 26, 1985 U.S. Pat. No. 4,685,181.
Because of the presumed catastrophic consequences of protrusions into large apertures of perforated disks these inventions to date have relied on using many small perforations in the disk in relation to total disk size.
DEFINITIONS & NOTES
Although we relate the invention to angle grinders in particular, the invention is also applicable to sanding disks used in some other power tools, such as ordinary electric drills, even though the usual types of electric drills do not spin at such a high speed.
“Aperture” means a channel or hole passing completely through an object, and is surrounded on all sides by the material of the object. It is not limited to apertures having a circular profile.
“Dished” means that a disk has been formed into a convex shape (like a saucer) and for this invention the abrasive would usually be found on the base, or convex side, of the saucer.
“Disk” refers to a flat piece of relatively rigid material (though having some resilience) which is adapted for mounting on a rotatable spindle or arbor. It is not limited here to purely circular shapes and the materials used can be any of those known for use in the production of abrasive disks for rotary grinders.
“Gap” means an indentation or invagination which is incompletely surrounded by the material of the object. It would include therefore configurations in which the circular periphery of a disk has had a segment, (defined below), removed or the configuration obtained by (notionally) moving an “aperture” until a portion extended beyond the periphery of the disk.
“Sanding” is used herein to refer to any abrading or finishing operation in which the surface of a workpiece is treated to remove material or alter the roughness.
“Segment” means that portion of a circle which lies between the perimeter and a chord.
STATEMENT OF THE INVENTION
In a first broad aspect the invention comprises a backing plate for use as part of a sanding system for use with an angle grinder or the like, comprising a backing plate and a disk bearing at least one abrasive surface, the disk being adapted for mounting upon an arbor of the angle grinder in conjunction with a matching backing plate, characterized in that the sanding disk is modified by being provided with at least one non-concentric aperture adapted for viewing and ventilation which aperture is capable in use of being substantially in alignment with at least one similarly adapted viewing and ventilation gap or aperture constructed within the backing plate, so that in use the work surface and the sanding disk are cooler as a result of air movement, abraded material is moved tangentially away, and the user can see the work through the at least one non-concentric apertures.
The term “non-concentric” as applied to apertures in this Application means that the aperture is displaced from the axis of rotation along a radius of the disk. A preferred number of non-concentric apertures adapted for viewing and ventilation is between one and nine. A more preferred number of non-concentric apertures is between three and five.
Preferably the non-concentric apertures adapted for viewing and ventilation are placed at varying distances from the centre of rotation of the disks, so that when the disk is rotated, a substantial proportion of the area beneath the disk can be seen.
The Abrasive Disk Component
The abrasive disk component of the sanding system is the subject of PCT/US96/19191 but is described herein to assist in understanding the invention claimed herein which relates to the backing plate used in conjunction with such abrasive disks.
The sanding disk as described previously, can be modified to provide that at least one edge of the or each non-concentric aperture adapted for viewing and ventilation is formed in order to serve as a cutting edge.
In a further aspect the viewing or ventilation apertures may also be regarded as means to intermittently interrupt the abrading action of the disk as it turns, thereby providing a “rest time” during which time the work surface may become cooler.
In another aspect the sanding disk may be provided with one or more apertures primarily intended for alignment with alignment features upon the backing plate, so that the sanding disk can on installation be aligned so that apertures within the sanding disk are matched with apertures within the backing plate.
Optionally the one or more alignment apertures may also serve as engagement means to mate with drive pins extending from the backing plate.
Optionally, one or more apertures are provided in the sanding disk in positions capable of matching air extraction apertures within a backing plate.
In a preferred aspect the perimeter of the sanding disk may be distorted from a circular shape by the provision of one or more gaps, most preferably in the form of segments, around from the circumference of the disk. Where a plurality
Bennett David
Hail III Joseph J.
Saint-Gobain Technology Company
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