Patent Application
20220258305
This invention relates to power tools, stationary or portable, and more particularly to abrasive wheels and discs used with bench or floor-mounted grinders.
A bench grinder is a benchtop type of grinding machine used to drive abrasive wheels. A pedestal grinder is a similar and usually larger version of grinder that is mounted on a pedestal and stands from the floor. These grinders have removable grinding wheels and are used to hand-grind various workpieces. Bench grinders can be mounted at a permanent location in a shop or carried on a mobile platform such as a work truck.
Examples of conventional uses of bench grinders are sharpening cutting tools and shaping metal pieces. Bench grinders are standard equipment in metal fabrication shops and machine shops.
Bench and pedestal grinders are designed for placing the workpiece against the periphery of the grinding wheel. Conventional bench grinder wheels are designed for grinding on the periphery only. “Side grinding” on a bench grinder wheel is considered to be unsafe and runs the risk of wheel explosion.
The grinding performed on the periphery of a grinding wheel of a bench grinder is in contrast to grinding with a “disc” of a handheld grinder, such as an angle grinder. These tools are designed to do grinding on one side of the disc. The workpiece is in a secured fixed position, such as in a vice. The handheld grinder is held in the operator's hands, and the operator presents and uses the grinding disc at an angle to the workpiece.
This description is directed to a “double-sided flap disc” for use with a bench or pedestal grinder. As explained below, the double-sided flap disc has abrasive flaps on both sides. It is designed for situations in which it is desired to have a stable grinding surface on two sides of a rotating disc.
An example of use of the double-sided flap disc is in farrier work, where the farrier shapes the heel portion of a horseshoe by grinding the horseshoe on the inside of both ends. The farrier holds the horseshoe with the open end presented to the grinder and moves the horseshoe from side to side during grinding to ensure a symmetrical result.
As stated in the Background, conventional bench grinders and pedestal grinders have a grinding wheel and are designed for grinding on the periphery of the wheel. In contrast, hand-held grinders have thinner discs that are designed for grinding on one side.
For purposes of this description, bench and pedestal grinders are referred to as “wheel-type” grinders as distinguished from hand-held grinders. A particular advantage of a wheel-type grinder is that it is mounted on a secure platform and thereby provides a stable grinding surface. The operator may easily hold the workpiece in hand while producing the desired shape or surface with the grinder.
In conventional farrier work, the horseshoe 10 must be awkwardly and unsafely held against the wheel periphery of a bench grinder. However, as explained below, the double-sided flap disc of this invention makes this task much safer, easier, and accurate.
Grinder 20 is a “mounted” grinder, in the sense that it is not hand-held and is mounted on a platform 21. Various means such as bolts are used to securely mount grinder 20 to platform 21.
Grinder 20 may be any one of various commercially available wheel-type grinders but adapted for use with disc 22. Conventional bench grinders are characterized by having removable and replaceable grinding wheels. However, in
Grinder 20 is powered by an electric motor (not shown), which drives an arbor 25 (also sometimes referred to as a spindle) that rotates. The motor is housed within a durable rigid housing 27. Grinder 20 further has various control features and power connections (battery or line voltage) such as are found on conventional grinders.
Disc 22 is mounted on arbor 25, typically by having a center hole which is slid onto the end of arbor 25. Disc 22 is securely attached so that it rotates as arbor 25 rotates and resists pressure applied to disc 22 by a workpiece being held against it during use. A nut 26 holds disc onto arbor 25 and facilitates removal and replacement of a disc 22 when it becomes worn from use.
In the example of
In operation, flap disc 22 is quiet, long lasting, and smooth running. It allows for stock removal (abrading) of metals or other hard materials, using both sides of the disc 22. The object to be ground may be held in the operator's hand. Using both sides of disc 22, the operator can grind areas of objects, such as the inside heels of a horseshoe as shown in
A feature of the invention is that the arbor 25 of grinder 20 is sufficiently long to allow disc 22 to be spaced a distance from the body of grinder 20. Specifically, disc 22 is typically mounted with sufficient space between disc 22 and the main body of grinder 20 so as to allow a workpiece to be moved back and forth horizontally relative to the plane of disc 22. Various bushings and bolts may be used to vary this distance if desired, as well as to adjust the size of the central hole in disc 22 to the diameter of arbor 25.
Depending on the application and expected dimensions of the workpiece, disc 22 is expected to be mounted along arbor 25 at least two inches from the main body of grinder 20. For example, where the workpiece is a horseshoe, allowance for several inches of side-to-side motion of the workpiece is desired. This is in contrast to conventional bench grinders, where a minimal gap between its grinding wheel and the body of the grinder is desired.
Double-sided flap disc 22 comprises a carrier plate 30 to which are attached abrasive “flaps” 31 on each side. Carrier plate 30 is planar, round, and flat on both faces. In the example of this description, carrier plate 30 has a diameter of 7 inches, which is the same as the diameter of the grinding wheels for which many conventional bench grinders are designed. However, carrier plate 30 may have other diameters for varying sizes of grinders. The carrier plate 30 may be made from a variety of rigid and strong materials, with a suitable material being fiberglass.
In the example of this description, carrier plate 30 is 0.125 inches in thickness. Other thicknesses may be used. Because the function of carrier plate 30 is for attachment of flaps 31 and not for grinding, it need only be sufficiently thick to provide structural support for flaps 31.
Carrier plate 30 has a center hole, which is sized so that carrier plate 30 may be slid onto the arbor of grinder 20. In the example of this description, center hole is 0.6250 inches. However, like the diameter of the carrier plate, the size of the center hole may vary to fit a particular type or size of grinder. The center hole allows disc 22 to be mounted onto the arbor 25 of the grinder using appropriate nuts, flanges, and bushings.
Around the perimeter of both sides of carrier plate 30 are arranged individual pieces of overlapping abrasive sheets known as “flaps” 31. Each flap is a cloth polyester backing, known as X or Y type, coated with abrasives. Examples of suitable abrasives for flaps 31 are ceramic alumina, aluminum oxide, or zerconia alumina in grit sizes 36 to 60.
In the example of
If disc 22 is viewed toward on side, mounted on a grinder, the flaps 31 are attached to carrier plate 30 overlapping each other in a clockwise direction. Looking at the left side, the flaps are attached to carrier plate 30 overlapping one another in a counterclockwise direction.
In other words, and as particularly shown in
Referring to
The degree of overlap of flaps 31 may vary. In the example of this description, the flaps edges are close together for a large degree of overlap, such that the flaps are lifted from the surface of carrier plate at about 45 degrees.
The flaps completely surround the circumference of carrier plate 30 on each side but need cover only the outer perimeter of carrier plate 30 on each side. The coverage of flaps 31 toward the center of the disc may vary. In the example of this description, the flaps 31 cover approximately the outer edges of carrier plate 30 inward about ⅓ of the radius of carrier plate 30.
