US3503725A - Continuous method of making abrasive finishing materials - Google Patents

Description

March 31, 1970 F. P. LEIPOLD 3,503,725

CONTINUOUS METHOD OF MAKING ABRASIVE FINISHING MATERIALS Filed Sept. 19, 1967 2 Sheets-Sheet l l l i i u l I n L. l l

l l I I INV ENT OR Forrest P LeI'po/d ATTORNEY.

CONTINUOUS METHOD OF MAKING ABRASIVE FINISHING MATERIALS Filed Sept. 19. 1967 March 31, 1970 F. P. LEIPOLD 2 Sheets-Sheet 2 INV ENT OR Forrest P Lelpold ATTORNEY} United States Patent US. Cl. 51-298 4 Claims ABSTRACT OF THE DISCLOSURE A method of making resin-bonded abrasive finishing material for use in vibratory finishing, tumbling, and the like, comprising the steps of providing a mixture of a particulate abrasive material with a curable resin, the resin being in a fluid state, depositing the mixture onto a movable web contoured to a desired cross-sectional shape, moving the web including the mixture along a predetermined path, partially curing the resin in the mixture during said movement along said predetermined path, separating the partially-cured resin-abrasive mixture at a point in said movement while said mixture is still in a gelatinous or uncured state from the moving web, cutting the partially-cured resin-abrasive mixture into suitable segments While in the uncured or gelatinous state, and curing the individual resin-abrasive segments thus-produced.

BACKGROUND OF THE INVENTION The use of abrasives in the finishing of metal, ceramic, plastic, wood and other parts by subjecting the part to be finished to the action of a particulate abrasive in the finishing chamber of a tumbling machine or vibratory finishing machine has long been known. Various types and forms of abrasive have been employed. Such abrasive has also been used with or incorporated into other media, such as p astic, and the abrasive material is sometimes variously referred to as finishing media or finishing chips. Incorporation of such particulate abrasive material into a resin binder has become popular in the finishing industry. Such popularity is desired because the size and form of the finishing chip can, in such case, be varied widely to suit the individual requirements for dimensions, hardness, and the like, not only of the resin binder but also of the abrasive material incorporated therein. Such resin-bonded abrasive chips can obviously be tailor-made to fit any finishing requirement, within the limits of available resin and finishing materials. Although such finishing chips are not always especally tailor-made to suit a particular finishing situation, it is obviously possible to provide the same in quantity or bulk in a great variety of forms, types, hardnesses, etc., by producing the finishing chips in this manner and from these materials, so that at least a considerable choice or selection of various resin-bonded abrasive finishing chips is available to the operator in any particular finishing situation. The provision of such resinbonded abrasive finishing chips has without question been a forward stride in the industry. The production of such resin-bonded finishing chips has, however, also been an area of the industry which has invited improvement. Up until the present time, such resin-bonded finishing chips have been individually cast or molded, with the obvious disadvantages in economy, waste of material, excess labor, and limitation on the size and contour ranges of the finishing chips produced. When cast or molded in the form of bars of cured stock, additional labor and the necessity of providing a saw for cutting the bars into selected lengths or chip thicknesses, together with the obvious deterioration of the blade of any saw thus provided, are

Patented Mar. 31, 1970 further disadvantages of an obvious nature. It is apparent that a simpler, more expeditious, and more economically feasible method of producing resin-bonded abrasive finishing chips would be highly desirable and advantageous to the industry.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel method for the production of resin-bonded abrasive finishing chips which is not subject to the aforementioned disadvantages. It is a further object to provide such a method wherein the particulate abrasive material is admixed with the resin, either before or after formation of the resin (as with the components reacted to produce the resin), but in any event before it is cured and while it is in the fluid state, the fluid mixture deposited into a preformed movable web having a desired cross-section, the said web moved along a predetermined path, the resinabrasive mixture partially cured while moving the same along said predetermined path, resin-abrasive mixture cut to provide appropriately-sized resin-bonded abrasive finishing chips while said mixture is in an uncured or gelatinous state, and the cut-off segments constituting the individual resin-bonded abrasive finishing chips thereafter cured. An additional object of the invention is to provide such a process which is particularly adapted for making triangular-shaped resin-bonded finishing chips. Still an additional object is the provision of such a process which can be operated continuously, is more economically feasible than previous processes for producing the same type of product, which is capable of producing said product with substantially no waste, without the necessity of a saw or deterioration of the blade of any saw, and which requires little or no labor from beginning to end of the process. Further objects will become apparent hereinafter and additional objects will be apparent to one skilled in the art.

It has now been found that the foregoing objects of the invention can be accomplished by providing a method of making resin-bonded abrasive finishing material for use in vibratory finishing, tumbling, and the like, comprising the steps of providing a mixture of a particulate abrasive material with a curable resin, the resin being in a fluid state, depositing the mixture onto a movable web contoured to a desired cross-sectional shape, moving the web including the mixture along a predetermined path, partially curing the resin in the mixture during said movement along said predetermined path, separating the par tially-cured resin-abrasive mixture at a point in said movement while said mixture is still in a gelatinous or uncured state from the moving Web, cutting the partially-cured resin-abrasive mixture into suitable segments while in the uncured or gelatinous state, and curing the individual cutoff resin-abrasive segments.

The cross-section of the web may take any desired shape capable of being formed and maintained, and is preferably triangular, but may also be rectangular, halfoval, half-circular, half-octagonal, circular, or oval, and is mainly dependent upon the structure employed for holding and shaping the moving 'web, as will become apparent hereinafter. The web may obviously be in the form of an open trough or may be closed on all sides, including the top.

The types of abrasive which may be employed are particulate solids, including aluminum oxide, silicon carbide, amorphous silicas, crystalline silicas, bauxite, bentonite, rouge pumice, flint, volcanic ash, granite, limestone, emery, garnet, zirconium oxides, and crushed rock.

The resin may be preformed but uncured or unset at the time of admixing with the particulate abrasive, or the components may be admixed with the abrasive and the resin then produced in the presence of the particulate abrasive. The exact mode of operation is immaterial so long as, at the proper stage in the process, the uncured or unset resin and the particulate abrasive are present together in admixture, the resin being in the fluid state.

The resin may be any suitable thermosettable or otherwise curable resin, which is curable by contact with the air, catalyst action, heat, or the like, all as is well known in the art. Suitable resins include polyesters, epoxies, alkyds, allyls, aminos, phenolics, and urethanes, and other standard types. Suitable catalysts include benzoyl peroxides, methyl ethyl ketone peroxide, acids, other organic peroxides, and other standard types, depending on the type of resin employed.

The particle size of the particulate abrasive material may be varied greatly, but is generally less than 60 mesh screen size and is preferably between about 2 microns and about 100 microns.

When a catalyst is employed, it is generally employed in approximately 2% by weight of the resin, although other proportions, such as /2 to by weight, or even greater, may be employed, again as is well known in the art.

The amount of abrasive in relation to the amount of the resin may be varied over wide ranges, depending upon the intended application of the finishing chips thus pro duced, but is advantageously approximately a 50/50 weight basis, especially when a polyester type of thermosetting resin material is employed. A combination of a polyester type of thermosetting resin and abrasive, of particulate size between about 60 microns and about 75 microns, has been found especially advantageous.

Among the many advantages of the method of the present invention may be mentioned that perfect triangles may be made with no draft angle whatever for mold release, that no release sheet or media is required although the stripped web may be reused again in the process if desired, that an infinite size range of triangularly shaped finishing chips may be produced using the same equipment, that substantially no waste of resin or abrasive either in the raw form or in the form of the finishing chip product is involved, that no casting or molding equipment of any complex nature is required, that no saw is required for cutting a cured stock bar into desired lengths or thicknesses and that no deterioration of any saw blade is involved, and that little or no labor is required from start to finish of the process of the invention when operated continuously.

According to the method of the invention, a final resinbonded abrasive finishing chip product is produced from a fluid mixture of a curable resin and particulate abrasive, the resin being settable in any one of various ways, by utilizing a continuously moving web of predetermined cross section, depositing the fluid resin-abrasive mixture into the continuously moving web, moving the web along a predetermined path until the resinous material has reached the gelatinous state, and stripping the strippable web from the gelatinous resin-abrasive mixture, thus removing the form from the hardening (curing or setting) but still gelatinous resin-abrasive material. The continuously-moving rod of gelatinous resin-abrasive material is then guided through a suitable cutting device which cuts the gelatinous rod into desired lengths or widths, at any rate into individual segments, which are then converted into the final polymerized, set, or cured condition by any one of several currently accepted standard practices, such as by allowingto stand in the air at room temperature, by heating, or by utilizing radio-frequency energy. The finally set segments constitute the desired resin-bonded abrasive finishing chip product.

BRIEF DESCRIPTION OF THE DRAWINGS The invention in its preferred embodiments is illustrated by the accompanying drawings which show apparatus suitable for carrying out the process of the invention and the process in various of its stages, and in which:

FIG. 1 is a side view, partially schematic, showing the process of the invention in various of its stages and a side elevational view of apparatus suitable for carrying out the said process.

FIG. 2 is a top plan view of the apparatus shown in FIG. 1 and again shows the process of the invention in various of its stages.

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 1.

FIG. 4 is a cross-sectional view taken on line 44 of FIG. 1.

FIG. 5 is a cross-sectional view taken on line 55 of FIG. 1.

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 1.

FIG. 7 is a cross-sectional view taken on line 7-7 of FIG. 1, and

FIG. 8 is a cross-sectional view taken on line 8-8 of FIG. 1.

SPECIFIC DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying drawings for a better understanding of the invention, wherein all the parts are numbered and wherein the same numbers are used to refer to the same parts throughout.

Referring now to FIGS. 1 and 2, these show production of a gelatinous rod 17 of triangular cross section which is then cut into gelatinous segments 18 which, upon curing, constitute the finished resin-bonded abrasive finishing chip product.

The strippable web 3, in this case of paper, is stored in suitable coiled form on web-storage coil 1 and is caused to move through web guide 2 and form 4, which may take any suitable cross-section desired, web-contouring device 5, and web contour block 6, by means of webdriving drum 11, which is in turn powered by web-driving drum motor 13. A positive drivingaction on web 3 by web-driving drum 11 is ensured by web pinch roll 12. Subsequent to passing over web-driving drum 11, the used web material 19 is discarded or, if desired, may be reused either by rewinding on a rewind drum (not shown) or by establishing the web 3 as an endless type of web with constant recirculation through form 4.

Web-contouring device 5, as shown, comprises a narrow spring-loaded wheel which operates by folding web 3 to the approximate angle necessary to fit the cross section of form 4. Web-contouring block 6 completes the final shaping of the web contour to that of the form 4. Web contour block 6 rests on top of web 3 and is prevented from moving along the predetermined path with web 3 by web contour block retainer 7.

A stationary dam 8 is provided for preventing the fluid resin-abrasive mixture from flowing out of the web 3 in the wrong direction, i.e., backwardly, and movable dam 10 as shown is affixed to the web for purposes of enabling a proper commencement of the continuous casting of the resin-abrasive mixture which is here involved.

For purposes of cutting gelatinous resin-abrasive rod 17 into segments 1-8 which ultimately harden into the desired resin-abrasive finishing chips, flywheel cutter 15 is provided. Cutter guide bushings 14 provide support for the relatively thin flywheel cutter blade 16, and also serve to guide the gelatinous rod of resin-abrasive material 17 to the flywheel cutter blade 16.

The settable fluid resin-abrasive mixture is fed to the web 3 from any suitable storage tan-k or mixing device (not shown) through filler tube 9'.

FIG. 3 shows the cross section of the form 4 and the web 3, FIG. 4 shows the same plus the web contouring device, FIG. 5 shows the same plus the web contouring block, FIG. '6 shows the same plus the stationary darn, FIG. 7 shows the same plus the filler tube 9, and FIG. 8 shows the same plus the resin-abrasive rod in the gelatinous state, downstream from the movable darn 10 and after operation has commenced. It should be apparent that the movable dam is only present in the device at the commencement of operations and before the resinabrasive mixture has commenced to solidify, at which time the web is actuated for downstream movement and the dam removed, the partially solidified resin-abrasive mixture thereafter acting as a dam for succeeding portions of the fluid resin-abrasive mixture deposited on web 3.

In operation continuously, the process of the invention is commenced by feeding a suitable resin-abrasive mixture, e.g., a catalyzed polyester resin-abrasive mixture, from a source thereof (not shown) which can provide not only for continuous catalyzation thereof but also dispensing of the material at a controllable rate through the filler tube 9 into the space between stationary dam 8 and movable dam 10. During initial filling of this space between stationary dam 8 and movable dam 10' from filler tube 9, web 3 remains stationary. When the fluid catalyzed thermosetting resin-abrasive material has reached the required level or height necessary for production of finishing chips having a desired cross section in form 4, web 3 is actuated by activating web-driving drum motor 13 and drum 11, which in turn moves web 3 along form 4. Movable dam 10 moves along with web 3. In this manner the space between stationary dam 8 and movable dam 10 is increased, and this additional space is filled to the desired level by metering a suitable amount of resin-abrasive mixture thereinto through filler tube 9. Fluid level in web 3 is kept constant by control of the rate of flow of the catalyzed resin-abrasive mixture from filler tube 9 and control of the lineal speed of web 3 along form 4. Both of these aspects are readily controllable. As movable dam 10 movesdownstream once the process gets under way, fluid input through filler tube 9 maintains the desired level of fluid resin-abrasive mixture in the web 3, in turn within form 4. The length of the form 4 and web 3 are selected so as to provide ample time for the lineal movement of web 3 between filler tube 9 and cutter 15, so that the resin-abrasive mixture attains a satisfactory state, i.e., the form of a gelatinous bar 17, before it reaches the cutter 15. This in turn depends upon the amount of catalyst, heat, type of resin, and other considerations which are all well known to one skilled in the art. At such time as sufiicient gelation of the catalyzed resinabrasive mixture has occurred, with formation of bar 17, movable dam 10 is removed from the web 3 and the gelatinous rod 17 thereafter acts as the dam for subsequent fluid resin-abrasive mixture flowing into web 3 from filler tube 9. After strippable web 3, which may contain a coating of release material, is stripped from the gelatinous rod of resin-abrasive material 17, the rod is guided through cutter guide bushings 14 to cutter blade 16, whereby it is cut into segments of desired width or length. The Width or length of the uncured gelatinous segments 18 can be controlled by simple variation of the speed of flywheel cutter 15. After the segments 18 have been produced, they are collected and cured to provide the desired cured resin-abrasive finishing chips. When a catalyzed polyester resin is employed as the resinous material, this is accomplished merely by allowing the gelatinous segments 18 to stand for a suitable period in the air, for example approximately 60 minutes.

The catalyst when a polyester resin is employed may be any one of various suitable types, but in this case was a 60% solution of methyl ethyl ketone peroxide in dibutyl phthalate. The polyester resin in the process just described was a promoted rigid isophthalic type. The abrasive employed in the process just described was silica sand having a particle size of approximately 75 microns. The distance between the filler tube 9 and the cutter was approximately 50 feet and the time for the web 3 to traverse this distance was approximately 10 minutes.

The chips thus produced, upon hardening, were collected and were found to be entirely suitable for use in the finishing of parts, and in this particular case were used to finish the surface of zinc die castings by either tumbling or vibratory finishing, as in a Spiratron (TM) helical vibratory finishing device. Additional runs according to the same process produced chips of a similar nature which were employed for finishing the surface of various parts, including aluminum casting, aluminum machined parts, steel stampings, punchings and forgings, various steel machined parts, and ceramics.

Other combinations found suitable include numerous types of polyester or other resin combinations with numerous silica sand, aluminum oxide, silicon carbide, bauxite, volcanic ash, and tripoli abrasive grains.

Production runs were made according to the process of the invention using an approximately 50-50 weight ratio of polyester resin [promoted rigid isophthalic polyester resin; viscosity 160:10 cps., acid number 18-20, specific gravity 1.06, non-volatiles 50:1% (TM- Guardsman 49-0257)] and abrasive filler [Silica sand- #1250 Agsco (TM)]; abrasive dimensions approximately 75 microns. The resin was catalyzed with 1 to 2% by weight of a sixty percent solution of methyl ethyl ketone peroxide in dimethyl phthalate. The catalyzed mixture was fed into the paper web 3 contained in an extruded aluminum angular form 4. The procedure described in the foregoing was followed, whereafter the abrasive-filled gelatinous objects 18 were permitted to air cure to their final condition and employed in processing as already described. The dimensions of the finishing chips thus prepared were varied and included triangles of 1/2! X 3/4! X 1/2n 1/2 X %n X 14!! and 7/8 X 7/16 X 1A.

It is to be understood that the invention is not limited to the exact details of construction, operation or exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art, and the invention is therefore to be limited only by the scope of the appended claims.

I claim:

1. A method of making resin-bonded abrasive finishing chips for use in vibratory finishing, tumbling, and the like, comprising the steps of providing a mixture of particulate abrasive material and a curable resin, the resin being in the fluid state, depositing the mixture onto a movable web contoured to a desired cross-sectional shape, moving the web including the resin-abrasive mixture along a predetermined path, partially curing the resin in the mixture during said movement along said predetermined path, separating the resin-abrasive mixture at a point in said movement while said mixture is still in the gelatinous or uncured state from the moving web, cutting the partially-cured resin-abrasive mixture into suitable segments While in the uncured or gelatinous state, and curing the individual resin-abrasive segments thus-produced.

2. The method of claim 1, which includes the steps of providing a strippable web, forming the strippable web into a desired cross-sectional shape, and stripping the web from the partially-cured resin-bonded abrasive mixture while partially cured and before cutting.

3. The method of claim 2, wherein the web is a paper Web.

4. The method of claim 1, wherein the web is shaped to have a triangular cross-section, with an apex of the triangle downwardly disposed.

References Cited UNITED STATES PATENTS 2,339,072 1/ 1944 Herzog et al. 264163 2,449,876 9/1948 Calvert et a1 264-- 3,102,011 8/1963 Bellinger 51298 3,183,071 5/1965 Rue et a1. 51307 3,387,957 6/1968 Howard 51298 DONALD J ARNOLD, Primary Examiner US. Cl. X.R. 51293

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