Grinding wheel dressing tool with hollow spheres

Abstract

A grinding wheel dressing tool with hollow spheres preferably includes a tool shank and a dressing portion. The tool shank preferably includes a shank portion and a tool body. The shank portion extends from one end of the tool body and a dressing portion cavity is formed in an opposing end. The dressing portion preferably includes a quantity of diamond grit, metal bond powder, binder and a plurality of hollow spheres. The dressing portion cavity is preferably filled to a top with metal bond powder. The diamond grit, the metal bond powder and the binder are mixed together to form a grit mixture. A tubular mold is slipped over a top of the tool body. The dressing portion is created by forming alternative layers of grit mixture and hollow spheres in the tubular mold. The tubular mold is heated and the grit mixture pressed with a plunger.

Claims

1. A grinding wheel dressing tool with hollow spheres, comprising: a tool shank includes a shank portion and a tool body, said shank portion extends from one end of said tool body; and a dressing portion formed on a top side of said tool body including a quantity of diamond grit, metal bond powder, binder and a plurality of hollow spheres, said diamond grit, said metal bond powder and said binder are mixed together to form a grit mixture, wherein said plurality of hollow spheres includes a first layer of hollow spheres adjacent to the tool shank and including at least two hollow spheres centered along a first horizontal axis, said plurality of hollow spheres further including a second layer of hollow spheres offset from the first layer of hollow spheres in a vertical direction and including at least two hollow spheres centered along a second horizontal axis which is perpendicular to the first horizontal axis, wherein an area around the plurality of hollow spheres is filled with said grit mixture.

2. The grinding wheel dressing tool with hollow spheres of claim 1, wherein: a diameter of said hollow spheres is at least 3 mm.

3. The grinding wheel dressing tool with hollow spheres of claim 1, further comprising: said dressing portion includes at least one additional layer of hollow spheres.

4. A grinding wheel dressing tool with hollow spheres, comprising: a tool shank includes a shank portion and a tool body, said shank portion extends from one end of said tool body, wherein a dressing portion cavity is formed in an opposing end of said tool body; a dressing portion formed on said opposing end of said tool body including a quantity of diamond grit, metal bond powder, binder and a plurality of hollow spheres, said dressing portion cavity is filled with metal bond powder, wherein said diamond grit, said metal bond powder and said binder are mixed together to form a grit mixture, wherein said plurality of hollow spheres includes a first layer of hollow spheres adjacent to the tool shank and including at least two hollow spheres centered along a first horizontal axis, said plurality of hollow spheres further including a second layer of hollow spheres offset from the first layer of hollow spheres in a vertical direction and including at least two hollow spheres centered along a second horizontal axis which is perpendicular to the first horizontal axis, wherein an area around the plurality of hollow spheres is filled with said grit mixture wherein said grit mixture and hollow spheres are heated and cured to form the dressing portion.

5. The grinding wheel dressing tool with hollow spheres of claim 4, wherein: a diameter of said hollow spheres is at least 3 mm.

6. The grinding wheel dressing tool with hollow spheres of claim 4, further comprising: said dressing portion includes at least one additional layer of hollow spheres.

7. A grinding wheel dressing tool with hollow spheres, comprising: a tool shank includes a shank portion and a tool body, said shank portion extends from one end of said tool body; a dressing portion formed on a top side of said tool body including a quantity of diamond grit, metal bond powder, binder and a plurality of hollow spheres, said diamond grit, said metal bond powder and said binder are mixed together to form a grit mixture, wherein said plurality of hollow spheres includes a first layer of hollow spheres adjacent to the tool shank and including at least two hollow spheres centered along a first horizontal axis, said plurality of hollow spheres further including a second layer of hollow spheres offset from the first layer of hollow spheres in a vertical direction and including at least two hollow spheres centered along a second horizontal axis which is perpendicular to the first horizontal axis, wherein an area around the plurality of hollow spheres is filled with said grit mixture, wherein when said dressing portion is brought in contact with a grinding wheel, said hollow spheres break causing a groove to be formed on a surface of the grinding wheel.

8. The grinding wheel dressing tool with hollow spheres of claim 7, wherein: a diameter of said hollow spheres is at least 3 mm.

9. The grinding wheel dressing tool with hollow spheres of claim 7, further comprising: said dressing portion includes at least one additional layer of hollow spheres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a top perspective view of a hollow sphere dressing tool in accordance with the present invention.

(2) FIG. 2 is a cross sectional view of a hollow sphere dressing tool with a tubular mold applied thereto, illustrating multiple layers of a dressing portion in accordance with the present invention.

(3) FIG. 3 is a top view of a first layer of hollow spheres of a hollow sphere dressing tool in accordance with the present invention.

(4) FIG. 4 is a top view of a second layer of hollow spheres of a hollow sphere dressing tool in accordance with the present invention.

(5) FIG. 5 is a top view of a second layer of hollow spheres of a hollow sphere dressing tool in accordance with the present invention.

(6) FIG. 6 is a top view of a grinding machine with a hollow sphere dressing tool retained in a dressing arm and the dressing arm treating a lower grinding wheel of the grinding machine in a start position and in an end position.

(7) FIG. 7 is an enlarged side view of a dressing arm retaining two hollow sphere dressing tools in accordance with the present invention.

(8) FIG. 8 is an enlarged end view of a dressing tool holder arm retaining two hollow sphere dressing tools in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) With reference now to the drawings, and particularly to FIG. 1, there is shown a perspective view of a hollow sphere dressing tool 1. The hollow sphere dressing tool 1 preferably includes a tool shank 10 and a dressing portion 12. The tool shank 10 preferably includes a shank portion 14 and a tool body 16. With reference to FIG. 2, the shank portion 14 extends from one end of the tool body 16 and a dressing portion cavity 18 is formed in an opposing end of the tool body 16. A center drill bit is preferably used to create the dressing portion cavity 18, but other tools could also be used. The dressing portion 12 preferably includes a quantity of diamond grit 20, metal bond powder 22, binder 24 and a plurality of hollow spheres 26. A diameter of the spheres 26 preferably has a range of between 3-5 mm, but other dimensions could also be used. The spheres 26 are preferably fabricated from aluminum oxide, but other materials could also be used, such as glass.

(10) With reference to FIGS. 3-5, the dressing portion cavity 18 is preferably filled to a top with the metal bond powder 22. The diamond grit 20 and the metal bond powder 22 are mixed together and wetted with the binder 24 to form a grit mixture 28. Satisfactory results have been achieved, when using Isopropyl alcohol for the binder 24, but other fluids may also be used. The percentage of weights of the diamond grit 20, the metal bond powder 22 and the binder 24 is dependent upon the piece part ground on the grinding wheel. Creating grit mixtures 28 is within the ability of one skilled in the art. A size of the diamond grit 20 is dependent upon the grinding wheel to be dressed. A tubular mold 30 is slipped over a top of the tool body 16. The tubular mold 30 includes a through bore 32, which is the same diameter as an outer diameter of the dressing portion cavity 18, and a counterbore 34 sized to receive an outer diameter of the tool body 16.

(11) The grit mixture 28 is applied to a top of the metal bond powder 22 in a first layer 36. A plurality of hollow spheres 26 are applied to a top of the first layer 36 of the grit mixture 28 in a first pattern. A second layer 38 of the grit mixture 28 is applied to a top of the first layer of spheres 26. The grit mixture layers 36, 38, 40 preferably have a height, which is about equal to a diameter of the hollow spheres 26. A second layer of the hollow spheres 26 is applied to a top of the second layer 38 of the grit mixture 28. The second layer of the hollow spheres 26 is applied to the second layer 38 of the grit mixture 28 in a second pattern, which is offset from the first pattern of spheres 26. A third layer 40 of the grit mixture 28 is applied over the second layer of the hollow spheres 26. A third layer of the hollow spheres 26 is applied on top of the third layer 40 of grit mixture 28 in a third pattern, which is offset from the second pattern. The grit mixture 28 is applied around the third layer of hollow spheres 26 to finish a top of the dressing portion 12. The shank portion 14 is inserted into a bore 46 of a holding block 44. The tool body 16, the uncured dressing portion 12 and the tubular mold 30 are heated to about 1800 degrees Fahrenheit for a period of about five minutes and pressed with a plunger 42. The plunger 42 has a slip fit with the through bore 32. The tubular mold 30 and the plunger 42 are preferably made from graphite, but other materials may also be used. The heating cures the dressing portion 12 and fuses the dressing portion 12 to the tool body 16. A volume of the dressing portion 12 will be reduced by about 50%, which effectively stacks the hollow spheres 26 on top of each other, after the heating and pressing.

(12) With reference to FIGS. 6-8, the shank portion 14 of the hollow sphere dressing tool 1 is held in a dressing arm 102. The dressing arm 102 includes a dressing tool holder 104. The dressing tool holder 104 includes at least one dressing tool bore 105 and at least one set screw 107, which communicates with the dressing tool bore 105. The shank portion 14 is inserted into the dressing tool bore 105 and the set screw 107 is tightened against the shank portion 14 to secure the hollow sphere dressing tool 1 in the dressing tool holder 104. The dressing tool holder 104 will also retain a star cutter tool. The dressing arm 102 is a movable fixture, similar to a tone arm of a record player. The hollow sphere dressing tool 1 acts like a stylus of a record player that holds the needle and moves across a surface of a record. The hollow spheres 26 in the dressing portion 12 break during the dressing process and create voids in a contact surface of the dressing portion 12. The voids have the unexpected result to impart grooves 108 into the grinding wheel 106 similar to the grooves in a vinyl record. The diamond grit 20 in the dressing portion 12 cuts away dull areas in the grinding wheel 106 as opposed to breaking out the grains by force, which creates a flatter grinding surface without the deformity of a fractured surface. The grooves 108 in the grinding wheel 106 provide an open structure necessary for heavy material removal. Because the grinding wheel 106 is dressed flat, the length of time between dresses increases significantly, thus reducing the cost of dressing from a reduced down time standpoint.

(13) For example, on a grinding job where tolerances are tight, the difference between one dress per production shift with the hollow sphere dressing tool 1, as opposed to 5-6 dresses per shift with the prior art star cutter tool. The length of time required to dress the grinding wheel 106 is also significantly reduced. The time required to dress a grinding wheel 106 varies with the hardness of the grinding wheel 106 and the amount of surface area of the grinding wheel 106 that needs to be dressed to make it flat. With the prior star cutter tool, the dressing process can take anywhere between 20-60 minutes. Dressing with the hollow sphere dressing tool 1 takes between 5-10 minutes. The star cutter tool is made as an assembly, with the stars spinning freely on a shaft with bearings. When the stars need to be replaced, it takes about an hour to remove the stars from a star cutter tool. More time is required, if the shaft or bearings are worn and need machined or replaced. When the hollow sphere dressing tool 1 needs to be replaced the set screw 107 is loosened and the hollow sphere dressing tool 1 replaced. The replacement of the hollow sphere dressing tool 1 only takes a few minutes to replace. Additionally, the hollow sphere dressing tool 1 does not rotate relative to the dressing arm 102.

(14) There is another advantage to the hollow sphere dressing tool 1 over the star cutter tool. Dressing with the star cutter tool creates a tremendous amount of stress on the dressing arm 102 of the grinding machine 100. Over time the force of the dressing process with the star cutter tool creates wear on the bearings of the dressing arm 102 and the points where it is attached to the grinding machine 100. The rebuilding of the dressing arm 102 can result in extensive machine downtime and be costly. For example, the minimum cost of rebuilding the dressing arm 102 is $10,000 for a 30 Besly double disc grinder. Because the hollow sphere dressing tool 1 cuts away the grinding wheel 106, there is a negligible amount of stress on the dressing arm.

(15) Additionally, the purpose of a dressing tool is to cut away dull abrasive grains of a grinding wheel to obtain a desired shape to expose sharp grains on the surface of the grinding wheel. The hollow sphere dressing tool opens up the structure of the grinding wheel surface by creating a continuous spiral groove 108 in a top surface of the grinding wheel 106.

(16) A grinding wheel operator trained to use diamond dressing tools will use the hollow sphere dressing tool 1 in the same manner. An operator trained to use the star cutter tool will need to adapt to a different process. The star cutter tool applies force to the grinding wheel in order to break out the grains of the grinding wheel to expose sharp grains. The hollow sphere dressing tool 1 is designed to cut or abrade the grains away with the cutting edges of the diamond grit 20. It would be accurate to compare the hollow sphere dressing tool 1 to using sandpaper as opposed to hammer and chisel to chisel out dull grains with the star cutter tool.

(17) The operator should locate the high point of the grinding wheel to be dressed and begin the dress there. The first pass should be a shallow cut of 0.002 to 0.003 inches and the tool should traverse the surface at a rate where the hollow sphere dressing tool 1 is effectively removing grains in the grinding wheel 106 without force or motor load. The depth of cut is relative to the exposed cutting edges of the diamond grit 20. The larger the diamond grit 20, the greater the depth of cut. When a grinding wheel dressing operator is familiar with the hollow sphere dressing tool 1, the operator will determine the optimum depth of cut and rate of traverse of the dressing arm 102 appropriate to the specification of the grinding wheel 106. The type and size of grain, the hardness and structure of the bond and the size of the grinding wheel 106 will all have a bearing on the dressing process. Dressing the grinding wheel 106 at an appropriate speed will produce the spiral groove 108 in the grinding wheel similar to a needle groove in a vinyl record. The spiral groove 108 is necessary in that it opens the structure of the grinding wheel 106 to prepare the surface for coarse grinding.

(18) While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.