Title:
Flapper wheel
United States Patent 3890746
Abstract:
Method and apparatus employs pads of multiple abrasive sheets equally spaced on a rotary flapper wheel. The method includes arranging the working edges of the abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges. The apparatus provides slidably mounted holders for the pads and keyhole-shaped or trapezoidal-shaped grooves for easy insertion and removal of the pad holders.
US Patent References:
Rotary abrading tool
Hall - January 1958 - 2819567
CARTRIDGE WORK WHEEL
McAleer - June 1969 - 3451093
Rotary abrading tool
Hall - January 1958 - 2819567
CARTRIDGE WORK WHEEL
McAleer - June 1969 - 3451093
Inventors:
Saegusa, Kyuji (Ohta-ku, Tokyo, JA)
Sonobe, Eitetsu (Ageo-shi, Saitama-ken, JA)
Sudo, Susumu (Sawa-gun, Gunma-ken, JA)
Sonobe, Eitetsu (Ageo-shi, Saitama-ken, JA)
Sudo, Susumu (Sawa-gun, Gunma-ken, JA)
Application Number:
05/483848
Publication Date:
06/24/1975
Filing Date:
06/27/1974
View Patent Images:
Export Citation:
Primary Class:
International Classes:
B24D13/06; B24D13/08; B24D13/00; B24B9/02
Field of Search:
51/332-337 15/179-187
Primary Examiner:
Simpson, Othell M.
Claims:
What is claimed is
1. A flapper wheel comprising a rotary wheel member having a centrally positioned longitudinal axis, said wheel member having parallel planar sides, said wheel member having a plurality of segmental areas being divided by a plurality of longitudinal grooves circumferentially and equally spaced around its cylindrical surface, the longitudinal grooves being located parallel to the centrally positioned longitudinal axis of the rotary wheel member; a plurality of abrasive pad units, each of which being inserted into one of said longitudinal grooves, each of said abrasive pad units including multiple superimposed sheets of abrasive covered material, the planar surfaces of said superimposed abrasive sheets being arranged substantially parallel to the planar sides of the rotary wheel member, each of said superimposed sheets having an inner clamped end and an outer working end; a plurality of slidably mounted holder means, each of which clamps and maintains together the inner ends of said superimposed abrasive sheets in a laminar relationship to each other with said inner ends being substantially aligned, the outer working end of each of said superimposed abrasive sheets having an arcuate configuration, said arcuate working edges of said superimposed abrasive sheets being arranged substantially parallel to the direction of the grinding track operatively created by the contacts between a workpiece and said arcuate working edges of the superimposed abrasive sheets.
2. A flapper wheel as set forth in claim 1 wherein each of said longitudinal grooves has its peripheral entrance of substantially less width than its maximum width dimension.
3. A flapper wheel as set forth in claim 1 wherein each of said holder means includes at least one movably mounted side plate portion providing in its open position ingress and egress for each of said abrasive pad units in and out of its respective longitudinal groove and preventing axial movement of said respective abrasive pad unit when said side plate portion is in its closed position.
4. A flapper wheel as set forth in claim 1 wherein each of said longitudinal grooves has a cross-sectional configuration of a keyhole.
5. A flapper wheel as set forth in claim 1 wherein each of said longitudinal grooves has a trapezoidal cross section and is of progressively decreasing width from its innermost end adjacent said centrally positioned longitudinal axis to its outermost end at the periphery of said rotary wheel member.
6. A flapper wheel as set forth in claim 1 wherein each of said multiple superimposed sheets has a U-shaped configuration with the flat part of said letter U constituting the inner edge thereof.
7. A flapper wheel as set forth in claim 4 wherein the inner portion of said side plate portion of each of said holder means has a keyhole configuration to conform with the keyhole configuration of said respective longitudinal groove for insertion therein and wherein the outer portion adjacent the periphery of said rotary wheel member of said side plate portion of each of said holder means has an enlarged portion for the retention of said respective abrasive pad unit therein.
8. A flapper wheel as set forth in claim 5 wherein the inner portion adjacent the centrally located hub of said side plate portion of each of said holder means has a trapezoidal cross section to conform with the trapezoidal configuration of said respective longitudinal groove for slidably insertion and removal of said holder means and wherein the outer portion adjacent the periphery of said rotary wheel member of said side plate portion of each of said holder means constitutes an enlarged area for the retention of said respective abrasive pad unit therein.
9. A flapper wheel as set forth in claim 7 wherein said inner portion of said side plate portion of each of said holder means is hingedly mounted at its innermost edge to provide in its open position a pivotable movement of said side plate portion away from the peripheral of said rotary wheel member and to provide in its closed position ingress and egress to and from the entrance of said respective longitudinal groove for insertion and removal of said respective abrasive pad unit.
10. A flapper wheel as set forth in claim 9 wherein said holder means has a plurality of upstanding pin members position parallel to said axis of said rotary wheel member and located on said outer portion of said side plate portion of said rotary wheel member, said pin members adapted to be inserted into apertures of both said outer portion of said side plate portion of said holder means and said inner ends of said respective pad of multiple superposed sheets.
1. A flapper wheel comprising a rotary wheel member having a centrally positioned longitudinal axis, said wheel member having parallel planar sides, said wheel member having a plurality of segmental areas being divided by a plurality of longitudinal grooves circumferentially and equally spaced around its cylindrical surface, the longitudinal grooves being located parallel to the centrally positioned longitudinal axis of the rotary wheel member; a plurality of abrasive pad units, each of which being inserted into one of said longitudinal grooves, each of said abrasive pad units including multiple superimposed sheets of abrasive covered material, the planar surfaces of said superimposed abrasive sheets being arranged substantially parallel to the planar sides of the rotary wheel member, each of said superimposed sheets having an inner clamped end and an outer working end; a plurality of slidably mounted holder means, each of which clamps and maintains together the inner ends of said superimposed abrasive sheets in a laminar relationship to each other with said inner ends being substantially aligned, the outer working end of each of said superimposed abrasive sheets having an arcuate configuration, said arcuate working edges of said superimposed abrasive sheets being arranged substantially parallel to the direction of the grinding track operatively created by the contacts between a workpiece and said arcuate working edges of the superimposed abrasive sheets.
2. A flapper wheel as set forth in claim 1 wherein each of said longitudinal grooves has its peripheral entrance of substantially less width than its maximum width dimension.
3. A flapper wheel as set forth in claim 1 wherein each of said holder means includes at least one movably mounted side plate portion providing in its open position ingress and egress for each of said abrasive pad units in and out of its respective longitudinal groove and preventing axial movement of said respective abrasive pad unit when said side plate portion is in its closed position.
4. A flapper wheel as set forth in claim 1 wherein each of said longitudinal grooves has a cross-sectional configuration of a keyhole.
5. A flapper wheel as set forth in claim 1 wherein each of said longitudinal grooves has a trapezoidal cross section and is of progressively decreasing width from its innermost end adjacent said centrally positioned longitudinal axis to its outermost end at the periphery of said rotary wheel member.
6. A flapper wheel as set forth in claim 1 wherein each of said multiple superimposed sheets has a U-shaped configuration with the flat part of said letter U constituting the inner edge thereof.
7. A flapper wheel as set forth in claim 4 wherein the inner portion of said side plate portion of each of said holder means has a keyhole configuration to conform with the keyhole configuration of said respective longitudinal groove for insertion therein and wherein the outer portion adjacent the periphery of said rotary wheel member of said side plate portion of each of said holder means has an enlarged portion for the retention of said respective abrasive pad unit therein.
8. A flapper wheel as set forth in claim 5 wherein the inner portion adjacent the centrally located hub of said side plate portion of each of said holder means has a trapezoidal cross section to conform with the trapezoidal configuration of said respective longitudinal groove for slidably insertion and removal of said holder means and wherein the outer portion adjacent the periphery of said rotary wheel member of said side plate portion of each of said holder means constitutes an enlarged area for the retention of said respective abrasive pad unit therein.
9. A flapper wheel as set forth in claim 7 wherein said inner portion of said side plate portion of each of said holder means is hingedly mounted at its innermost edge to provide in its open position a pivotable movement of said side plate portion away from the peripheral of said rotary wheel member and to provide in its closed position ingress and egress to and from the entrance of said respective longitudinal groove for insertion and removal of said respective abrasive pad unit.
10. A flapper wheel as set forth in claim 9 wherein said holder means has a plurality of upstanding pin members position parallel to said axis of said rotary wheel member and located on said outer portion of said side plate portion of said rotary wheel member, said pin members adapted to be inserted into apertures of both said outer portion of said side plate portion of said holder means and said inner ends of said respective pad of multiple superposed sheets.
Description:
BACKGROUND OF THE INVENTION
This invention relates to method and apparatus directed to a surface finishing rotary wheel and in particular to method and apparatus directed to a finishing rotary wheel of the flapper wheel type.
The prior art flapper wheels have the working outer edges of the abrasive sheets perpendicularly arranged to the direction line of the grinding track that is operatively created by the contacts between the workpiece and the working outer edges of the abrasive sheets. The present invention, on the hand, has the working outer edges of the abrasive sheets arranged to be substantially parallel to the direction line of the grinding track.
The prior art flapper wheels involve elastic or resilient grinding, and namely, such characteristics as conventional pliability, flexibility and tenacity are achieved to their utmost degree. The grinding of the surfaces is performed by the prior art on a straight line basis similar to the techniques involved in connection with working sheets, discs, rolls and belts. This results in an impact grinding on the workpiece in an interrupting manner and at right angles to the grinding track line of the workpiece. A workpiece which receives a manually applied grinding pressure from such multiple sheet pads is intermittently impacted and grounded with grinding abrasive surfaces which are the outer edges of the overlapped portion of the pad which edges are perpendicular to the rotating track line of the pad. In the operation, the workpiece is abraded by its contact with the abrasive sheets by virtue of the external pressure applied by the operator. With the bending movement of the pads, a grinding function commences and the discharge of chips and the like takes place. With repetition of this action by a plurality of pads, the final result of grinding can be eventually expected. However, in accordance with such prior art teachings a workpiece in an unsatisfactory condition is obtained. Various examples, such as removal of scales from steel and stainless sheets, removal of welding bead and ball formed on large diameter pipes, removal of white lanes on roads and removal of welding scale and the like are performed in many cases by grinding wheels but such grinding operations involve considerable work.
Further, many of the conventional prior art flapper wheels are formed with an integral and permanent securing means for holding the abrasive pads. Such pads may be repeatedly flexed relatively sharply near the periphery of the wheel and thus such flexture can substantially reduce the life of the pads. In other prior art abrasive wheels, the abrasive pads are pivotably mounted on their inner ends to render a degree of flexibility to the abrasive pads. With such pads having freedom of swing through a substantial range of angles, the pads simply follow and conform to the resultants of the forces to which they are subjected.
Consequently, with the use of the foregoing prior art flapper wheels such operations as removing and cleaning of annealed scale, oxide film, welding scale, welding bead, welding ball, burr resulting from cutting by torch and the like have been considered the most difficult work in the grinding and polishing arts. In grinding and polishing work, in general, a grinding wheel, grinding belt, flap wheel and the like have been employed as the tools. For example, in performing the grinding operation with a grinding belt and in order to achieve satisfactory results, the frequent exchange of belt units is required. Such exchanges require complicated structures and the like and necessitate interruptions of time. Further, the use of multiple abrasive belts involves an expenditure of excessive expense. Furthermore, in grinding with a single abrasive tool, complete grinding may be sometimes obtained, however the dissipation of the generated heat is not rapidly effected. In polishing, for example a stainless steel sheet, a discoloration and a change in quantity may occur in the overheated portion. In such a situation, the metal's inherent tenacity is lost and it becomes brittle.
Under the foregoing circumstances and as a result of extensive research and development in the grinding and polishing arts, the present inventors have succeeded in developing method and apparatus relating to flapper wheels having the function of removing heavy stock from the surface of the metal with a minimum of effort.
SUMMARY OF THE INVENTION
This invention relates to method and apparatus directed to a finishing rotary wheel of the flapper wheel type.
The method of the present invention involves the abrading of a workpiece with abrasive sheet pads equally spaced on a rotary flapper wheel and includes the steps of providing pad holders at circumferentially and equally spaced positions on the cylindrical surface of the rotary flapper wheel, positioning a plurality of superimposed abrasive sheets into each of the pad holders, and arranging the working edges of the superimposed abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges of the superimposed abrasive sheets.
The apparatus relates to a flapper wheel in which the rotary wheel member is provided with a plurality of segmental areas being divided by a plurality of longitudinal grooves circumferentially and equally spaced around its cylindrical surface. The configuration of each groove is one having its peripheral entrance of substantially less width than its maximum width dimension. The inner ends of the corresponding holder for clamping and maintaining the abrasive pad unit has a configuration which substantially corresponds with that of the longitudinal groove. At least one side plate portion of the holder is movably mounted at its inner end thereof for providing ingress and egress for each of the abrasive pad units in and out of its respective longitudinal groove. Such side plates prevent axial movement of the respective abrasive pad unit when the side plates are located in their operative closed position.
Accordingly, it is an object of the present invention to provide a method and apparatus directed to a flapper wheel having pads of multiple superimposed abrasive coated sheets in the circumferentially and equally spaced grooves on its cylindrical surface and having the working edges of the abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges.
Another object of the present invention is to provide a pivotally mounted side plate on each pad holder to retain the pad holder in the respective groove and restrain the pad holder against axial movement during rotation of the rotary wheel member.
These and other objects and aspects of the invention will be more clearly understood from the following descriptions of the embodiments of the invention shown, by way of examples only, in the accompanying drawings in which like reference numerals denote corresponding parts throughout the several views.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a workpiece contacting a pad of multiple abrasive sheets in accordance with the teachings of the prior art;
FIG. 2 is a similar view of FIG. 1, but in accordance with the teachings of the present invention;
FIG. 3 is a perspective view of a flapper wheel according to an embodiment of the present invention;
FIG. 4 is a side elevational view of FIG. 3; and
FIG. 5 is a perspective view of a flapper wheel according to another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
As shown in the prior art disclosure of FIG. 1, a plurality of abrasive sheets 10 constitutes one of the pad units 11 for a flapper wheel. A workpiece 12 (material to be grounded) which receives a grinding pressure P from the pad unit 11 is intermittently impacted and grounded with the grinding surfaces which are the outer edges of the overlapped portion of the pad unit 11 which edges are peripendicular to the rotating track line of the pad unit 11. In the operation, the workpiece 12 is abraded by its contact with the abrasive sheets 10 by virtue of the external pressure P applied by the operator. With the bending movement of the pad units 11, a grinding function commences and the discharge of chips and the like takes place. With repetition of this action by the plurality of pad units, the final result of grinding can be eventually expected. However, in accordance with such prior art teachings a workpiece in an unsatisfactory condition is easily obtained.
As shown in the present invention disclosure of FIG. 2, a plurality of abrasive sheets 13 constitutes one of the pad units 14 for the flapper wheel. It is to be noted that the abrasive sheets 13 in FIG. 2 have, in essence, been moved 90 degrees with respect to the position of the sheets 10 in FIG. 1. The teaching of the method of the present invention is that the longitudinal edges of the multiple abrasive sheets receive the applied pressure from the workpiece whereby the edges do not bend longitudinally as illustrated in the prior art disclosure of FIG. 1. With the arrangement of the present invention, rigidity, abrasive grain content percentage, tenacity, hardness and pliability, which are characteristics of a abrading pad of the instant type, can be obtained at their desired levels. A feature of the present invention is that the pad unit 14 having a desired tenacity and hardness can be obtained by using the outer edges of the abrasive sheets 13 as the grinding surface, which edges are in parallel with the grinding track direction line or substantially in parallel therewith. As a result, a flapper wheel structural arrangement completed according to method disclosed herein, is readily capable of performing, for example, stock removal of a material whose stock is normally barely removable with the use of grinding pressures of 40-100 kg/cm 2 on the workpiece.
Accordingly, the present invention broadly provides a method of abrading the workpiece with abrasive sheet pads equally spaced on the rotary flapper wheel and comprises the steps of providing pad holders at circumferentially and equally spaced positions on the cylindrical surface of the rotary flapper wheel, positioning a plurality of superimposed abrasive sheets into each of the pad holders, and arranging the working edges of the superimposed abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges of the superimposed abrasive sheets. Further, the present invention more specifically provides a method of abrading the workpiece with abrasive sheet pads equally spaced on the rotary flapper wheel and comprises the steps of providing the rotary flapper wheel with parallel planar sides and a centrally positioned longitudinal axis, inserting removable-type pad holders into circumferentially and equally spaced longitudinal grooves formed in the cylindrical surface of the rotary flapper wheel, the longitudinal grooves being located parallel to the centrally positioned longitudinal axis of the rotary flapper wheel, positioning a plurality of superimposed abrasive sheets with arcuate-shaped working edges into each of the pad holders, arranging the planar surfaces of the superimposed abrasive sheets to be substantially parallel to the planar sides of the rotary flapper wheel and arranging the arcuate-shaped working edges of the superimposed abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the arcuate-shaped working edges of the superimposed abrasive sheets.
In an embodiment of the flapper wheel as shown in FIGS. 3 and 4, the numeral 21 is a sheet of coated abrasive material of substantially rectangular shape and has side edges 22 and front or outer grinding edges 27. A suitable number of sheets 21 is assembled into a pad 28 and these sheets are clamped and maintained in rigid and firm positions by a holder 23 having at least one movably mounted side plate 24.
A rotary wheel member 25 comprises a centrally located hub portion 29 which is mounted on a power-actuated shaft (not shown). The wheel member 25 is made from a suitable metal such as aluminum or plastic material such as nylon. The wheel member 25 is formed with a plurality of segmental areas 30 being divided by a plurality of longitudinal grooves 26 which are circumferentially and equally spaced around the outer cylindrical surface of the wheel member 25. The grooves 26 are described as having a keyhole cross-sectional configuration in that each groove has a peripheral entrance 31 that is of substantially less width than the maximum width dimension of the groove. In this structural form of the invention, the groove has a longitudinal portion commencing at the entrance 31 on the peripheral of the wheel member 25 and terminating in an enlarged substantial circular portion which is adjacent to the centrally located hub portion 29.
As illustrated in FIG. 3, the side plate 24 of holder 23 is pivotally mounted at its innermost edge adjacent the centrally located hub 29. Each of the side plates 24 in its open position provides an ingress for the insertion of the abrasive pad 28 into the groove 26. Each of the side plates 24 also in its open position provides an egress for the removal of an abrasive pad 28 from the groove 26. Accordingly, the side plate 24 in its closed position retains the pad holder in its respective groove and restrains the pad holder against axial movement during rotation of the rotary wheel member 25.
The particularity of this feature is that the edges of the abrasive sheet material rotates in circumferential directions, provided that each longitudinal grinding edge of the sheet coincides with said direction. Accordingly, the grinding sheet material of the present invention contacts the workpiece edgewise in a perpendicular manner and thus the edges of the sheets are not positioned as conventionally practiced. Rather the outer working sheet edges of the present invention are edgewisely urged against the surface of the workpiece as the edges are directed toward the rotating direction. That is, the working edges 27 of the abrasive sheets 21 are arranged to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges 27 of the abrasive sheets 21.
FIG. 5 illustrates another embodiment which is similar to the above-described embodiment in FIGS. 3 and 4. In this embodiment, a rotary wheel member 35 comprises a centrally located hub portion 39. The wheel member 35 has a plurality of segmental areas 40 divided by a plurality of longitudinal grooves 36 circumferentially and equally spaced around its outer cylindrical surface. Each of the grooves 36 has a trapezoidal cross section and is of progressively decreasing width from its innermost end adjacent the centrally located hub 39 to its outermost end at the periphery of the wheel member 35.
A plurality of abrasive pad units 38 is provided with multiple superimposed sheets 41 having a U-shaped configuration with the flat part of the letter U constituting the inner edge of the respective sheet. A plurality of slidable mounted holders 33 clamps and maintains together the inner ends of the multiple superimposed sheets 41 in a laminar relationship to each other with the inner ends being substantially aligned. Each of the holders 33 includes at least one movably mounted side plate 34 for providing ingress and egress in its open position for each of the abrasive pads 38 in and out of its respective groove. The side plate 34 in its closed position prevents axial movement of the respective pad when inserted in the respective groove. An inner portion 42 of the side plate 34 of each of the holders 33 has a trapezoidal cross section to conform with the trapezoidal configuration of the respective groove for slidably insertion therein. The outer portion 43 of the side plate 34 constitutes an enlarged area for the retention of the respective abrasive pad unit inserted in the respective holder. The holder 33 has two upstanding pins 44 that are positioned parallel to the axis of the wheel member 35 and that are located on the bottom of outer portion 43 of the side plate 34 of the holder 33 as illustrated in FIG. 5. The top of outer portion 43 has two holes 45 for the insertion of the pins 44 therethrough. Further, the U-shaped pads 38 have two holes to correspond with the two holes 45 of outer portion 43 for insertion therethrough. Accordingly, the trapezoidal cross section ends of holders 33 together with the pin inserted ends of holders 33 clamp and maintain the U-shaped pads 38 in rigid and firm positions.
It should also be understood that other shapes of grooves, wherein each has its peripheral entrance of substantially less width than the maximum width dimension of the groove, may also be used in practicing the invention.
When the rotary wheel member is to be used, the operator will bring the workpiece into proximity of the wheel member and thus, the working edges of the abrasive sheets will be substantially parallel to the direction line of the grinding track that is operatively created by the contacts between the workpiece and the working edges.
The holder may be of any suitable construction and may be of any suitable material but it is contemplated that the holder will be resilient to a desirable degree to permit the holder to be flexed slightly to permit the inner portion of the holder to be axially slid in and out of its respective groove and also to permit the ingress and egress of the pad of multiple superimposed sheets into the outer portion of the holder.
The coated abrasive of the sheet to be used is predetermined. Also, the backing material, the type of abrasive grains and the adhesive are selected according to a predetermined ratio. A coated abrasive sheet may be formed of a single layer or double layers of abrasive grains. A coated abrasive sheet of more than double layers is not generally manufactured unless there is a requirement for same. However, in the use of the flapper wheel of the present invention, higher density of abrasive grains may be applied and thus permit greater stock removal. After establishing the required density of the abrasive grains, the weight formation of the adhesive with respect to the weight of the abrasive grains is decided to maintain a certain safety factor as well as providing a protective bonding that is capable of sufficiently withstanding the centrifugal force and continuous intermittent impact type grinding.
High speed rotation of a flapper wheel generates a high speed flow of air around the wheel especially between the pads of the coated abrasive sheets, and this flow of air together with the flow of air between coated abrasive sheets provides very effective air cooling during the operation. Therefore, the temperature rise on the surface of the workpiece is relatively small and thus there is little chance that discoloration will occur on the surface.
In practicing the present invention, the grinding has produced good results with respect to white aluminum oxide, aluminum oxide and aluminum zirconium oxide. Regarding the difference of the grain size 24, 30, 40, 50, 60 at the peripheral speed of 1,500 to 2,000 meters per minute, undesirable roughness may appear on the finished surface. However, the degree of roughness is minor; for example, welding can be performed without applying further finishing operation. In an atmosphere where no coolant is used, the feasibility of continuous operation removing 60 to 100 microns by one pass grinding with a minimum of heat generation is difficult to obtain so far as conventional grinding wheels are concerned. It is to be noted that with the use of the instant flapper wheel, as the grain size changes from 120, 150, 180 to finer particles and minute particles, the grinding and polishing effects produce a fine and smooth finish on the surface, and thus the selection of the grain size can be predetermined depending upon the thickness of the annealed scale of the metal.
While these embodiments of the invention have been shown and described, it will be appreciated that these are for the purpose of illustration and that modifications may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.
This invention relates to method and apparatus directed to a surface finishing rotary wheel and in particular to method and apparatus directed to a finishing rotary wheel of the flapper wheel type.
The prior art flapper wheels have the working outer edges of the abrasive sheets perpendicularly arranged to the direction line of the grinding track that is operatively created by the contacts between the workpiece and the working outer edges of the abrasive sheets. The present invention, on the hand, has the working outer edges of the abrasive sheets arranged to be substantially parallel to the direction line of the grinding track.
The prior art flapper wheels involve elastic or resilient grinding, and namely, such characteristics as conventional pliability, flexibility and tenacity are achieved to their utmost degree. The grinding of the surfaces is performed by the prior art on a straight line basis similar to the techniques involved in connection with working sheets, discs, rolls and belts. This results in an impact grinding on the workpiece in an interrupting manner and at right angles to the grinding track line of the workpiece. A workpiece which receives a manually applied grinding pressure from such multiple sheet pads is intermittently impacted and grounded with grinding abrasive surfaces which are the outer edges of the overlapped portion of the pad which edges are perpendicular to the rotating track line of the pad. In the operation, the workpiece is abraded by its contact with the abrasive sheets by virtue of the external pressure applied by the operator. With the bending movement of the pads, a grinding function commences and the discharge of chips and the like takes place. With repetition of this action by a plurality of pads, the final result of grinding can be eventually expected. However, in accordance with such prior art teachings a workpiece in an unsatisfactory condition is obtained. Various examples, such as removal of scales from steel and stainless sheets, removal of welding bead and ball formed on large diameter pipes, removal of white lanes on roads and removal of welding scale and the like are performed in many cases by grinding wheels but such grinding operations involve considerable work.
Further, many of the conventional prior art flapper wheels are formed with an integral and permanent securing means for holding the abrasive pads. Such pads may be repeatedly flexed relatively sharply near the periphery of the wheel and thus such flexture can substantially reduce the life of the pads. In other prior art abrasive wheels, the abrasive pads are pivotably mounted on their inner ends to render a degree of flexibility to the abrasive pads. With such pads having freedom of swing through a substantial range of angles, the pads simply follow and conform to the resultants of the forces to which they are subjected.
Consequently, with the use of the foregoing prior art flapper wheels such operations as removing and cleaning of annealed scale, oxide film, welding scale, welding bead, welding ball, burr resulting from cutting by torch and the like have been considered the most difficult work in the grinding and polishing arts. In grinding and polishing work, in general, a grinding wheel, grinding belt, flap wheel and the like have been employed as the tools. For example, in performing the grinding operation with a grinding belt and in order to achieve satisfactory results, the frequent exchange of belt units is required. Such exchanges require complicated structures and the like and necessitate interruptions of time. Further, the use of multiple abrasive belts involves an expenditure of excessive expense. Furthermore, in grinding with a single abrasive tool, complete grinding may be sometimes obtained, however the dissipation of the generated heat is not rapidly effected. In polishing, for example a stainless steel sheet, a discoloration and a change in quantity may occur in the overheated portion. In such a situation, the metal's inherent tenacity is lost and it becomes brittle.
Under the foregoing circumstances and as a result of extensive research and development in the grinding and polishing arts, the present inventors have succeeded in developing method and apparatus relating to flapper wheels having the function of removing heavy stock from the surface of the metal with a minimum of effort.
SUMMARY OF THE INVENTION
This invention relates to method and apparatus directed to a finishing rotary wheel of the flapper wheel type.
The method of the present invention involves the abrading of a workpiece with abrasive sheet pads equally spaced on a rotary flapper wheel and includes the steps of providing pad holders at circumferentially and equally spaced positions on the cylindrical surface of the rotary flapper wheel, positioning a plurality of superimposed abrasive sheets into each of the pad holders, and arranging the working edges of the superimposed abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges of the superimposed abrasive sheets.
The apparatus relates to a flapper wheel in which the rotary wheel member is provided with a plurality of segmental areas being divided by a plurality of longitudinal grooves circumferentially and equally spaced around its cylindrical surface. The configuration of each groove is one having its peripheral entrance of substantially less width than its maximum width dimension. The inner ends of the corresponding holder for clamping and maintaining the abrasive pad unit has a configuration which substantially corresponds with that of the longitudinal groove. At least one side plate portion of the holder is movably mounted at its inner end thereof for providing ingress and egress for each of the abrasive pad units in and out of its respective longitudinal groove. Such side plates prevent axial movement of the respective abrasive pad unit when the side plates are located in their operative closed position.
Accordingly, it is an object of the present invention to provide a method and apparatus directed to a flapper wheel having pads of multiple superimposed abrasive coated sheets in the circumferentially and equally spaced grooves on its cylindrical surface and having the working edges of the abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges.
Another object of the present invention is to provide a pivotally mounted side plate on each pad holder to retain the pad holder in the respective groove and restrain the pad holder against axial movement during rotation of the rotary wheel member.
These and other objects and aspects of the invention will be more clearly understood from the following descriptions of the embodiments of the invention shown, by way of examples only, in the accompanying drawings in which like reference numerals denote corresponding parts throughout the several views.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a workpiece contacting a pad of multiple abrasive sheets in accordance with the teachings of the prior art;
FIG. 2 is a similar view of FIG. 1, but in accordance with the teachings of the present invention;
FIG. 3 is a perspective view of a flapper wheel according to an embodiment of the present invention;
FIG. 4 is a side elevational view of FIG. 3; and
FIG. 5 is a perspective view of a flapper wheel according to another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
As shown in the prior art disclosure of FIG. 1, a plurality of abrasive sheets 10 constitutes one of the pad units 11 for a flapper wheel. A workpiece 12 (material to be grounded) which receives a grinding pressure P from the pad unit 11 is intermittently impacted and grounded with the grinding surfaces which are the outer edges of the overlapped portion of the pad unit 11 which edges are peripendicular to the rotating track line of the pad unit 11. In the operation, the workpiece 12 is abraded by its contact with the abrasive sheets 10 by virtue of the external pressure P applied by the operator. With the bending movement of the pad units 11, a grinding function commences and the discharge of chips and the like takes place. With repetition of this action by the plurality of pad units, the final result of grinding can be eventually expected. However, in accordance with such prior art teachings a workpiece in an unsatisfactory condition is easily obtained.
As shown in the present invention disclosure of FIG. 2, a plurality of abrasive sheets 13 constitutes one of the pad units 14 for the flapper wheel. It is to be noted that the abrasive sheets 13 in FIG. 2 have, in essence, been moved 90 degrees with respect to the position of the sheets 10 in FIG. 1. The teaching of the method of the present invention is that the longitudinal edges of the multiple abrasive sheets receive the applied pressure from the workpiece whereby the edges do not bend longitudinally as illustrated in the prior art disclosure of FIG. 1. With the arrangement of the present invention, rigidity, abrasive grain content percentage, tenacity, hardness and pliability, which are characteristics of a abrading pad of the instant type, can be obtained at their desired levels. A feature of the present invention is that the pad unit 14 having a desired tenacity and hardness can be obtained by using the outer edges of the abrasive sheets 13 as the grinding surface, which edges are in parallel with the grinding track direction line or substantially in parallel therewith. As a result, a flapper wheel structural arrangement completed according to method disclosed herein, is readily capable of performing, for example, stock removal of a material whose stock is normally barely removable with the use of grinding pressures of 40-100 kg/cm 2 on the workpiece.
Accordingly, the present invention broadly provides a method of abrading the workpiece with abrasive sheet pads equally spaced on the rotary flapper wheel and comprises the steps of providing pad holders at circumferentially and equally spaced positions on the cylindrical surface of the rotary flapper wheel, positioning a plurality of superimposed abrasive sheets into each of the pad holders, and arranging the working edges of the superimposed abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges of the superimposed abrasive sheets. Further, the present invention more specifically provides a method of abrading the workpiece with abrasive sheet pads equally spaced on the rotary flapper wheel and comprises the steps of providing the rotary flapper wheel with parallel planar sides and a centrally positioned longitudinal axis, inserting removable-type pad holders into circumferentially and equally spaced longitudinal grooves formed in the cylindrical surface of the rotary flapper wheel, the longitudinal grooves being located parallel to the centrally positioned longitudinal axis of the rotary flapper wheel, positioning a plurality of superimposed abrasive sheets with arcuate-shaped working edges into each of the pad holders, arranging the planar surfaces of the superimposed abrasive sheets to be substantially parallel to the planar sides of the rotary flapper wheel and arranging the arcuate-shaped working edges of the superimposed abrasive sheets to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the arcuate-shaped working edges of the superimposed abrasive sheets.
In an embodiment of the flapper wheel as shown in FIGS. 3 and 4, the numeral 21 is a sheet of coated abrasive material of substantially rectangular shape and has side edges 22 and front or outer grinding edges 27. A suitable number of sheets 21 is assembled into a pad 28 and these sheets are clamped and maintained in rigid and firm positions by a holder 23 having at least one movably mounted side plate 24.
A rotary wheel member 25 comprises a centrally located hub portion 29 which is mounted on a power-actuated shaft (not shown). The wheel member 25 is made from a suitable metal such as aluminum or plastic material such as nylon. The wheel member 25 is formed with a plurality of segmental areas 30 being divided by a plurality of longitudinal grooves 26 which are circumferentially and equally spaced around the outer cylindrical surface of the wheel member 25. The grooves 26 are described as having a keyhole cross-sectional configuration in that each groove has a peripheral entrance 31 that is of substantially less width than the maximum width dimension of the groove. In this structural form of the invention, the groove has a longitudinal portion commencing at the entrance 31 on the peripheral of the wheel member 25 and terminating in an enlarged substantial circular portion which is adjacent to the centrally located hub portion 29.
As illustrated in FIG. 3, the side plate 24 of holder 23 is pivotally mounted at its innermost edge adjacent the centrally located hub 29. Each of the side plates 24 in its open position provides an ingress for the insertion of the abrasive pad 28 into the groove 26. Each of the side plates 24 also in its open position provides an egress for the removal of an abrasive pad 28 from the groove 26. Accordingly, the side plate 24 in its closed position retains the pad holder in its respective groove and restrains the pad holder against axial movement during rotation of the rotary wheel member 25.
The particularity of this feature is that the edges of the abrasive sheet material rotates in circumferential directions, provided that each longitudinal grinding edge of the sheet coincides with said direction. Accordingly, the grinding sheet material of the present invention contacts the workpiece edgewise in a perpendicular manner and thus the edges of the sheets are not positioned as conventionally practiced. Rather the outer working sheet edges of the present invention are edgewisely urged against the surface of the workpiece as the edges are directed toward the rotating direction. That is, the working edges 27 of the abrasive sheets 21 are arranged to be substantially parallel to the direction line of the grinding track operatively created by the contacts between the workpiece and the working edges 27 of the abrasive sheets 21.
FIG. 5 illustrates another embodiment which is similar to the above-described embodiment in FIGS. 3 and 4. In this embodiment, a rotary wheel member 35 comprises a centrally located hub portion 39. The wheel member 35 has a plurality of segmental areas 40 divided by a plurality of longitudinal grooves 36 circumferentially and equally spaced around its outer cylindrical surface. Each of the grooves 36 has a trapezoidal cross section and is of progressively decreasing width from its innermost end adjacent the centrally located hub 39 to its outermost end at the periphery of the wheel member 35.
A plurality of abrasive pad units 38 is provided with multiple superimposed sheets 41 having a U-shaped configuration with the flat part of the letter U constituting the inner edge of the respective sheet. A plurality of slidable mounted holders 33 clamps and maintains together the inner ends of the multiple superimposed sheets 41 in a laminar relationship to each other with the inner ends being substantially aligned. Each of the holders 33 includes at least one movably mounted side plate 34 for providing ingress and egress in its open position for each of the abrasive pads 38 in and out of its respective groove. The side plate 34 in its closed position prevents axial movement of the respective pad when inserted in the respective groove. An inner portion 42 of the side plate 34 of each of the holders 33 has a trapezoidal cross section to conform with the trapezoidal configuration of the respective groove for slidably insertion therein. The outer portion 43 of the side plate 34 constitutes an enlarged area for the retention of the respective abrasive pad unit inserted in the respective holder. The holder 33 has two upstanding pins 44 that are positioned parallel to the axis of the wheel member 35 and that are located on the bottom of outer portion 43 of the side plate 34 of the holder 33 as illustrated in FIG. 5. The top of outer portion 43 has two holes 45 for the insertion of the pins 44 therethrough. Further, the U-shaped pads 38 have two holes to correspond with the two holes 45 of outer portion 43 for insertion therethrough. Accordingly, the trapezoidal cross section ends of holders 33 together with the pin inserted ends of holders 33 clamp and maintain the U-shaped pads 38 in rigid and firm positions.
It should also be understood that other shapes of grooves, wherein each has its peripheral entrance of substantially less width than the maximum width dimension of the groove, may also be used in practicing the invention.
When the rotary wheel member is to be used, the operator will bring the workpiece into proximity of the wheel member and thus, the working edges of the abrasive sheets will be substantially parallel to the direction line of the grinding track that is operatively created by the contacts between the workpiece and the working edges.
The holder may be of any suitable construction and may be of any suitable material but it is contemplated that the holder will be resilient to a desirable degree to permit the holder to be flexed slightly to permit the inner portion of the holder to be axially slid in and out of its respective groove and also to permit the ingress and egress of the pad of multiple superimposed sheets into the outer portion of the holder.
The coated abrasive of the sheet to be used is predetermined. Also, the backing material, the type of abrasive grains and the adhesive are selected according to a predetermined ratio. A coated abrasive sheet may be formed of a single layer or double layers of abrasive grains. A coated abrasive sheet of more than double layers is not generally manufactured unless there is a requirement for same. However, in the use of the flapper wheel of the present invention, higher density of abrasive grains may be applied and thus permit greater stock removal. After establishing the required density of the abrasive grains, the weight formation of the adhesive with respect to the weight of the abrasive grains is decided to maintain a certain safety factor as well as providing a protective bonding that is capable of sufficiently withstanding the centrifugal force and continuous intermittent impact type grinding.
High speed rotation of a flapper wheel generates a high speed flow of air around the wheel especially between the pads of the coated abrasive sheets, and this flow of air together with the flow of air between coated abrasive sheets provides very effective air cooling during the operation. Therefore, the temperature rise on the surface of the workpiece is relatively small and thus there is little chance that discoloration will occur on the surface.
In practicing the present invention, the grinding has produced good results with respect to white aluminum oxide, aluminum oxide and aluminum zirconium oxide. Regarding the difference of the grain size 24, 30, 40, 50, 60 at the peripheral speed of 1,500 to 2,000 meters per minute, undesirable roughness may appear on the finished surface. However, the degree of roughness is minor; for example, welding can be performed without applying further finishing operation. In an atmosphere where no coolant is used, the feasibility of continuous operation removing 60 to 100 microns by one pass grinding with a minimum of heat generation is difficult to obtain so far as conventional grinding wheels are concerned. It is to be noted that with the use of the instant flapper wheel, as the grain size changes from 120, 150, 180 to finer particles and minute particles, the grinding and polishing effects produce a fine and smooth finish on the surface, and thus the selection of the grain size can be predetermined depending upon the thickness of the annealed scale of the metal.
While these embodiments of the invention have been shown and described, it will be appreciated that these are for the purpose of illustration and that modifications may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.