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(11) | EP 0 106 507 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Means and methods for abrading a work surface |
| (57) The invention relates to honing, polishing, reducing, or otherwise abrading, in which
improved means and methods are employed for abrasion of workpieces (10) in general,
and at least selected internal portions (16) of workpieces (10) such as bores, passages,
and cavities in particular. In general, the abrasion is accomplished by the use of
a flowable abrasive medium (18), with particular embodiments using a visco-elastic,
rheopectic abrasive medium. The abrasive medium (18) is in the form of a plastic or semisolid matrix containing abrasive particales (120) distributed substantially uniformly throughout the matrix. The matrix transports the particles (120) through or across selected portions of a workpiece (122) being reated in order to permit the abrasive particles (120) to remove upraised metal and to round or radius comers as it passes, or to otherwise uniformly remove or finish these portions. Uniform distribution and maximised abrasive effect of the particles (120) is obtained by use of the matrix which also provides a relatively firm backing for the abrasive when the medium is subjected to high pressure. |
[0001] This invention relates to honing, polishing, reducing, or otherwise abrading, in which improved means and methods are employed for abrasion of workpieces in general, and at least selected internal portions of workpieces such as bores, passages, and cavities in particular. In general, the abrasion is.accomplished by the use of an abrasive medium, and more particularly by the use of a visco-elastic, abrasive medium.
[0002] In one embodiment, this abrasive medium comprises a visco-elastic, rheopectic matrix, having the consistency of putty (at room temperature and with no pressure applied) which is permeated with finely divided and evenly dispersed abrasive particles. When passed-across and against a work surface in the proper manner, this abrasive medium provides maximum abrasive action and uniformity of finish. In the context of this invention, "rheopectic" defines the property of a composition in which the viscosity increases with time under shear or a suddenly applied stress. Stated another way, this property of the abrasive medium is exactly opposite of "thixotropy".
[0003] The invention also deals with the discovery that visco-elastic materials adhere strongly to porous or roughened surfaces and to silicone rubber. When using an abrasive medium comprising a mixture of a visco-elastic matrix and abrasive particles, this "bonding" property allows adherence of at least a portion of the matrix to such a surface to provide resistance to abrasion by the particles or grit. This "bonding" property also may be utilized for articles of manufacture such as belts for belt sanders, abrasive pads for manual use, and devices for increasing the abrasion of selected work surface areas--particularly selected work surface areas of internal bores.
[0004] The invention further deals with selectively masking a work- piece with a ceramic or the like in order to control surface finishing by a flowable abrasive. Due to such masking, abrasion of selected areas of the workpiece may be reduced controllably, or prevented, while normal abrasion is allowed to occur on other areas of the workpiece.
[0005] It is known to extrude a visco-elastic abrasive medium through workpieces to accomplish abrasive finishing of selected surfaces of the work, as disclosed in U.S. Patent No. 3,634,973 - McCarty. Other references directed to this approach are U.S. Patent Nos. 3,802,128 - Minear, Jr., et al.; 3,819,343 - Rhoades; and 3,521,412 - McCarty. The disclosures of the above patents are hereby incorporated by reference.
[0006] It is also known,- as in Japanese Utility Model Publication 55-53320, to space a work surface opposite from a deformable, elastic member and force a flowable abrasive mixture therebetween, with the elastic member deforming to reduce flow restriction caused by the work.
[0007] It is also known to hone or lap gears, as in U.S. Patent No. 3,618,272 - Whalen, et al., in which a thickened, flowable abrasive medium is used. Other references disclosing this same general approach are U.S. Patent Nos. 3,293,805 - Davis; 3,955,327 - Franco; 2,986,856 - Fehr; and 3,169,349 - Findley. A meshing (usually driving) relationship is required between two surfaces, whether or not one or both are the work surfaces to be treated.
[0008] It is also known, as in U.S. Patent No. 3,593,410 - Taylor, to chemically alter the surface of one of a pair of generally mating die surfaces, to place abrasive grains or grits between the die pair, and to impart relative notion between the die pair to remove any protuberances from the chemically altered surface.
[0009] It is also known, as in Japanese Utility Model Publication 50-29197, to abrade a workpiece cavity by use of a mating mandrel having an elastic, deformable surface attached thereto and abrasives applied to the elastic surface.
[0010] Other known processes of finishing surfaces employ: vapor blasting, sand blasting, shot blasting, and vibratory finishing. Vapor blasting incorporates an abrasive slurry which is forced against the product at relatively high velocity. The impingement of the abrasive particles on the surface of the product erodes or abrades away the surface. This process has almost no effect on surfaces located interiorly of the product. Sandblasting involves the use of abrasive particles thrown at high speed by compressed air or a mechanical flinger. This process also has little value for interior surface finishing. Shot blasting uses cast iron shot, steel shot, or glass beads at high velocities as in the case of sand blasting. This operation is more nearly a peening over of burrs or the like rather than a clean removal. Vibratory finishing agitates the product in a mixture of abrasive particles, stones, or jacks, and is carried out at low pressure. The more exposed surfaces receive the.most action. Here again, interior surfaces receive little or no abrasive effect.
[0011] U.S. Patent Nos. 2,799,789 - Wolfskill and 3,247,572 - Hunk disclose prior methods of masking of small objects, such as piezoelectric crystals and miniature magnetic cores for microcircuits, in order that surfaces of the devices may be selectively abraded by the above-mentioned sandblasting, tumbling, shot-peening, or the like. The material used to mask these small objects comprises a lacquer, varnish, paint, ink, or the like which provides a resilient covering having doubtful masking capabilities when used with a flowable, visco-elastic abrasive material. Also this masking material was required to be diluted to assure "a surface tension of appropriate magnitude so that the resulting coating on the objects pulls away from ... sharp projections and collects on (the) broad surfaces of (the) objects ..."
[0012] Further, these patents disclose abrasive processes which do not provide for good abrasion of internal work surfaces or cavities.
[0013] The present invention.incorporates the use of an abrasive medium having a plastic or semisolid matrix containing abrasive particles distributed substantially uniformly throughout. The purpose of the semisolid matrix is to transport the abrasive particles through or across selected portions of a workpiece being treated in order to permit the abrasive particles to remove upraised metal and to round or radius corners as it passes, or to otherwise uniformly remove or finish these portions.
[0014] Another purpose of the semisolid matrix is to hold the abrasive particles in suspension so that they will be pressed firmly against the workpiece, as taught hereinafter, so that the abrasive effect is at a maximum and is uniformly distributed, over the surface or edge being treated.
[0015] Another purpose of the semisolid matrix is to provide a relatively firm backing for the abrasive when the medium is under pressure, in order to increase the cutting action of the abrasive against the workpiece portion being treated, while still being plastic enough to flow through or across the product in order to reach all required surfaces and edges. Although abrasion of the workpiece is only accomplished by the abrasive particles which come in contact with it, the other, non-contacting particles, and their flow, are just as important as the particles that actually do the abrading of the workpiece.
[0016] It should be noted that a liquid slurry carrying an abrasive material and pumped through the same kind of workpiece as treated by this invention, would not have the required abrasive action nor would it strike all surfaces uniformly. Such a liquid slurry would require high flow velocity to provide maximum impingement of the abrasive particles against the treated surface. Under such conditions some areas requiring abrasion would receive no abrasion at all.
[0017] One embodiment of the instant invention is especially useful in polishing mold cavities of complex shapes in which the internal peripheral surface to be worked or polished is of a varying radius. One such workpiece is the internal surface of a plastic injection mold for a telephone receiver. These mold cavities are usually polished manually by a skilled die maker at a time consuming rate of approximately 1-4 hours per square inch of work surface. Additionally, piece-by-piece, manual polishing of these mold cavities is not constantly repeatable, and human error accounts for workpiece wastage. On the contrary, the invention provides a time-wise and materials-wise efficient method and means for repeatably abrading, honing, or polishing such workpieces in an inexpensive manner. By this embodiment, the abrasive medium is displaced positively against and across a portion of a workpiece which is utilized as the displacement chamber or as the displacer, or as both. In this context, the abrasive medium acts as a positively displaced abrading tool. There is no need for engagement, such as meshing, between the opposed surfaces, nor is there a need for mating of these surfaces although, in practice, it may be desirable to use such an arrangement. Further, there is no need to chemically alter the work surface prior to or during the abrading thereof.
[0018] Throughout the description of the invention, the term "relative motion" between the opposed surfaces is used to indicate that either or both surfaces may be moved to accomplish positive displacement of the flowable abrasive medium. Further, this movement may be gyratory, orbital, reciprocatory, or any combination of these, so long as positive displacement of the abrasive medium is accomplished against and across the work portion to be treated in a manner allowing the uniform abrasion offered by a flowable, preferably visco-elastic, abrasive media.
Figures 1-4 are partial cross-sectional views of an internal passageway of a workpiece, illustrating various means of practic-ing one embodiment of the invention.
Figures 5 and 6 are isometric views, partially broken away, Lllustrating another embodiment of the invention.
Figure 7 is a schematic side elevation of a belt sander incorporating another feature of the invention.
Figure 8 is a partial isometric, with parts broken away, illustrating still another embodiment of the invention.
Figure 9 is a side cross-sectional view of another embodiment and illustrating a reciprocatable mandrel within a mold cavity.
Figure 10 is a side, cross-sectional view illustrating an alternate embodiment of Figure 9.
Figure 11 is a top view taken along the lines 11-11 of figure 10.
Figures 12-14 are top views depicting various opposed surface profiles and arrangements.
Figure 15.is a plan view of another embodiment of the invention.
Figure 16 is a plan view, partially in section, illustrating still another embodiment of the invention.
Figure 17 is an approximate cross-sectional view, as viewed in the direction of arrows 17-17 of Figure 16.
Figure 18 is a front plan view of a machine suitable for use in the invention.
Figures 19-21 are schematic cross-sections illustrating flow of a visco-elastic abrasive medium through a workpiece.
Figures 22 and 23 are partial schematic cross-sections of a workpiece to illustrate masking and selective protection of one surface of a workpiece which would be directly subjected to abrasion during treatment of an adjacent portion of the workpiece.
Figure 24 is a schematic cross-section of a workpiece to illustrate masking and protection of surfaces which are indirectly subjected to abrasion during treatment of an adjacent portion of the workpiece.
[0020] Referring to Figure 1, a workpiece 10 having internal bore 12 is provided with a protrusion 14 formed of or coated with silicone rubber or the like and is secured or held in place by any of various means within the skill of the art, opposite from a selected portion of the internal surface of bore 12, to form a restriction. Due to this restriction and the properties of a visco-elastic abrasive medium used in the invention, the internal surface may be selectively reduced, as indicated in phantom lines at 16. Because of the property of bonding to silicone rubber of the matrix of some of the media used in this invention, a surface layer of the matrix, as indicated at 18, adheres strongly to protrusion 14 to further restrict bore 12. It has been found that layer 18 also provides abrasion resistance to silicone rubber.
[0021] A change of flow direction of the medium tends to increase the abrasive action at a conjunction of surfaces. Since protrusion 14 is protected from abrasion by layer 18, the increased abrasive action of the medium is directed against the portion of the internal surface of bore 12 which is opposite of protrusion 14. Arrows 20 indicate the flow of the medium without protrusion 14, and phantom-lined arrows 22 indicate the altered flow of the medium due to protrusion 14.
[0022] Protrusion 14 may be composed in its entirety of a silicone rubber-like material, as shown in Figure 1, or it may be coated with a layer of silicone rubber-like material. Figure 2 discloses a molded silicone rubber plug 30 which is opposite the selected area of abrasion. Although plug 30 is shown in Figure 2 as protruding into bore 12, it may also be "even" with or slightly "recessed" relative to the internal surface of bore 12, so long as a surface layer 18 of the matrix adheres strongly to the plug so as to provide a restriction of bore 12. In this regard, it should be mentioned that the invention is applicable to increased or directed abrasion for surfaces other than internal bores, such as selected portions of cavities or even external surfaces.
[0023] Additionally, as indicated generally at 42 in Figure 3, the material for causing the restriction of the passageway may also be any porous material 40, such as woven fibers or material with a porous surface, such as an oxidized iron or steel, since it has been found that some of the matrices used in the invention adhere strongly to such surfaces also.
[0024] Figure 4 illustrates a restrictor 50 for finishing or undercutting a bore 12 peripherally at 13.
[0025] Figures 5 and 6 illustrate hand tools such as abrasive pads or blocks, generally indicated at 60, with the abrasive medium adhered thereto. In Figure 5, substrate 62 is provided with a silicone rubber coating 64 to which visco-elastic matrix 66 adheres. Alternatively, substrate 62 could be silicone rubber material in its entirety, and coating 64 could be eliminated. In Figure 6, a porous substrate 68 is covered with the matrix 66 as by dipping. The various substrates used may have varying degrees of stiffness or flexibility, according to the use intended.
[0026] Figure 7 schematically illustrates a porous, or silicone rubber, or silicone rubber coated belt 72 for a portable belt sander 70. A supply reservoir 74 is provided for periodical or continual resupply of a visco-elastic abrasive medium to the work engaging portion of the belt 72. With this arrangement, the useful life of the belt 72 as an abrader.is greatly, if not .indefinitely, extended.
[0027] Figure 8 depicts one blade 82 of a turbine 80, the surface of which must be finished to a required tolerance, as by extruding or otherwise passing a flowable abrasive medium between blade 82 and guides 84 of a tooling jig. Prior to the invention, guides 84 were subject to abrasion during the extrusion process, thus causing continuous widening of the gap between guides 84 and blade 82 and reduction in abrasion.of subsequently treated blades 82 due to this widening gap. This presented a costly problem in the finishing of workpieces such as blades 82.- However, by molding guides 84 of a silicone rubber-like material 86 or coating portions 88 of guides 84 with silicone rubber, and.by using an abrasive medium which is a mixture of a visco-elastic matrix and abrasive particles, a film of the-matrix adheres to the silicone rubber and protects the surfaces of guides 84 such that a reliable, repeatable finishing of a multitude of blades is realized while using the same tooling jig. Because of the relative in- expense in molding guides 84 from a silicone rubber-like material, they are easily replaceable if eventually abraded out of the required tolerance.
[0028] The spacing between the work surface and the opposed working surface (protrusion 14 of Figure 1 or guides 84 of Figure 8) is selectable according to such parameters as: matrix viscosity, grit size, work surface finish desired, input energy, and amount of relative displacement normal to the opposed surfaces. This spacing should be at least greater than the diameter of the largest abrasive grit when using a generally non-deformable working surface; and a spacing of at least four times the grit diameter is preferable. Although not necessary, the profiles of the opposed surfaces may be substantially mating in shape.
[0029] Figures 9-15 disclose alternate embodiments for treating, polishing, or abrading internal and external three-dimensional work surfaces. As with the other embodiments, an abrasive medium comprising a visco-elastic matrix permeated with abrasive particles or grit is used. A preferred abrasive medium for use in the invention has a visco-elastic, rheopectic matrix of silicone bouncing putty (borosiloxane) interspersed with abrasive particles.
[0030] In the embodiment of Figure 9, the abrasive medium is used to treat the internal surface 12 of a mold 10 by utilizing a mandrel 14 having a profile smaller than (and generally mating with) that of the mold cavity. External surface 16 of mandrel 14 is spaced from internal surface 12 of mold 10 to define a gap 22 through and across which the abrasive medium is displaced positively in the general direction of arrows 24 by relative movement between mold 10 and mandrel 14. This relative movement may take the form of reciprocation, oscillation, rotation, orbital motion, or any combination of these motions of either or both of the mold 10 and mandrel 14. In this particular embodiment, mandrel 14 includes a passage 18 through which the abrasive medium is fed into the cavity as indicated by arrow 20. After a sufficient amount of abrasive medium has been fed into the mold cavity, passage 18 may be sealed before imparting the relative movement between mold 10 and mandrel 14. In Figure 9, mandrel 14 is illustrated as the working displacer formed from or coated with an abrasion-resistant material such as a polyurethane. Alternatively, when using an abrasive medium having a visco-elastic matrix, the working surface may be composed of or coated with a .silicone rubber-like material or the surface of the "working surface may be roughened or porous such that a portion of the visco-elastic matrix adheres or "bonds" thereto to provide this abrasion resistance. Although Figure 9 illustrates external surface 16 as the working surface and internal surface 12 as the work surface, it should be understood that these roles could be changed such that either or both of the opposed surfaces 12, 16 receive treatment by the abrasive medium.
[0031] In Figure 10, passageway 18 has been eliminated and a removable cavity sealing member 30 has been added. Sealer 30 and/or mandrel 14 may be raised or removed to allow introduction of the abrasive medium (generally indicated at 40) into the cavity. As may be appreciated by reference to Figures 10 and 11 (Figure 11 is a cross-section in the direction of arrows 11-11 of Figure 10) arrows 32 are meant to indicate relative reciprocatory, rotary, oscillatory, or orbital movement, or any combination thereof, between the mandrel 14 and mold 10.
[0032] Figures 12-14 are cross-sections illustrating various profiles of work surfaces 12 and working surfaces 16 which are applicable to practice of the invention. In Figure 13, external surface 12 is the work surface and internal surface 16 is the working surface. It is thought that this substantial likeness in profiles enhances the positive displacement and abrasive action of the medium when relative movement is imparted between the two surfaces.
[0033] Figure 15 illustrates another structural embodiment of the invention in which a screw conveyor 50 is rotated about and/or reciprocated along longitudinal axis 52. Surrounding conveyor 50 is a coaxial tubular enclosure-60 comprising an internal surface facing and opposed to the external surface of screw conveyor 50. The edges of flights 54 of conveyor 50 may be spaced from or in rubbing contact with the internal surface of enclosure 60. As in the other embodiments of the invention, either or both the internal and external surfaces may be the work surface and all or selected portions of the working surface may be provided with the abrasion resistance as taught by this invention. Additionally, the conveyor 50 or the enclosure 60, or both, may be tapered or have varying radii and still be within the scope of the invention when the abrasive medium is used for polishing or honing or the like.
[0034] In the embodiments of Figures 9-14, it is generally preferred that there is always a gap between the opposed surfaces of sufficient spacing that the largest abrasive grit being used cannot bridge this gap and engage both surfaces simultaneously, and there is no need for the gap to be any smaller when using a visco-elastic 'matrix as taught by the invention. However, as may be appreciated from Figure 11, working surface 16 may be temporarily deformable by the abrasive grit and the spacing between the work and working surfaces may be smaller than the largest abrasive grit being used. With such a deformable working surface, any flowable abrasive medium may be used, according to the desired treatment of the work surface.
[0035] A still further embodiment of the invention is disclosed in Figures 16 and 17, in which workpiece 90 has a cavity 92 which is to be polished, honed, or the like by means of the abrasive medium of the instant invention. In this embodiment, a plurality of tubes 94 are loosely held together such that they may conform substantially to the cavity 92, as by assuming various vertical heights according to engagement of their lower ends with cavity 92.- Having substantially conformed to this surface, they are then tightly held or clamped together as by metal strap 96 and adjustable machine screw 97 such that they may be removed from cavity 92 while still retaining the general shape thereof at their lower ends. Although Figure 17 discloses tubes 94 to be of varying diameters, it is contemplated also that all of the tubes 94 may have the same general diameters. In implementing this embodiment, the clamped together tubes are then again lowered into cavity 92 such that they are slightly spaced from the surface of cavity 92 and workpiece 90 is moved in a plane generally perpendicular to the vertical axes of tubes 94 by imparting orbital, reciprocating, rotational, or any combination of these movements to a table or the like upon which workpiece 90 is mounted. Alternatively, workpiece 90 could remain stationary with the same general type of motion imparted to the clamped together group of tubes 94. It is also contemplated that both the workpiece 90 and clamped together tubes 94 could have motion imparted thereto. The purpose of the tubes 94 is to provide flow passages for the abrasive medium of the instant invention. The abrasive medium is caused to flow, as by an applied pressure through the tubes 94 into the gap between the lower ends of tubes 94 and cavity 92. Although tubes 94 are illustrated as having circular cross-sections, various other cross-sections, including rectangular and triangular, are contemplated. Additionally, relative vertical reciprocation between the clamped tubes 94 and workpiece 90 may be imparted. Although Figure 16 illustrates tubes 94 as only partially covering the internal surface of cavity 92, it is contemplated that a sufficient number of tubes 94 may be provided such that substantially the entire surface of cavity 92 is covered by tubes 94. Although Figure 16 discloses this embodiment as used upon a generally concave work surface, it is also contemplated that a generally convex, or outwardly protruding, work surface may be treated using the same general concept. Further, when more than one cavity of the same three-dimensional shape is to be abraded, polished, honed, or the like, such an arrangement of tubes 94 may be permanently attached together as by braising, adhesives, or the like.
[0036] Figure 18 illustrates a machine suitable for imparting relative motion between opposed surfaces during machining of at least Jne of the surfaces while using a visco-elastic, preferably rheopectic, abrasive medium. The machine includes two vertically opposed platens 102 and 104, either or both of which are provided with means for imparting reciprocating motion in the vertical direction and orbitinq, gyrating, oscillating, reciprocating and the like motions in a generally horizontal direction. Platen 104 has workpiece 106 attached thereto, with workpiece 106 having a work surface 105 to be machined. Fastened to platen 102 is a complementary model 103 which is generally a mirror image of work surface 105. Rather than imparting the relative motion to platens 102 and 104, suitable devices (not shown) may be attached to platens 102 and 104, with these suitable devices supporting complementary model 103 and workpiece 106 and imparting the relative motion therebetween. Devices for imparting relative motion between two surfaces are generally known to be old in the art and are not, per se, the invention. A visco-elastic abrasive medium is fed from a supply 108 via supply tube 110 to the interface between surfaces 103 and 105. Working surface 103 is formed from a plurality of tubes or is provided with pre-drilled holes througr which the abrasive medium is transported to the interface. In operation, top platen 102 is lowered into contact with platen 104 according to the accepted method in such machines. Relative motion commences with the two platens 102, 104 slowly being forcec further toward each other as the work surface 105 is machined. During the course of this operation, the abrasive medium is replaceable by advancing refeed piston 112, with the older, used medium simply being forced out of the work surface 105 and onto platen 104 for collection by the operator of the machine.
[0037] It should be noted that the opposed surfaces 103, 105 need not be exact complements as suggested by the figure. Rather, by using a visco-elastic, rheopectic abrasive medium, the working surface needs to be only a rough approximation of the work surface. Use of such a machine combines the full, three-dimensional machining capabilities of orbital abrasion with the uniform abrasion offered by a visco-elastic abrasive medium.
[0038] Previously, the basic technique of having two opposed surfaces undergo relative motion while in contact relied upon a "working" surface being embedded with an abrasive grit to form, polish, or in some way machine the work surface. Machining methods utilizing visco-elastic abrasive mediums previously achieved the abrasive action only by hydraulically forcing the media through or across the work surfaces. In contrast, the machine and method of use described above and illustrated in Figure 18 allows gyrating, orbiting, reciprocating, or any combination of these motions to be imparted between opposed surfaces while using a visco-elastic abrasive medium and thus facilitating a smooth and uniform abrasion of a workpiece.
[0039] In certain instances, a workpiece will include areas that must be abraded or machined and which lie directly adjacent to other areas that, due to critical tolerances, must be left intact and untouched by the abrasive medium. Prior to another embodiment of this invention, it was necessary to protect certain areas of the workpiece from abrasion by means of fixtures and mandrels designed specifically for the workpiece. These fixtures and mandrels represented a tooling cost, in both time and money, beyond that of the actual abrasive flow machining. Additionally, particular areas of a workpiece were very difficult, if not impossible, to protect from abrasion during such flow machining. To overcome these vast difficulties, the instant invention also involves masking of these particular areas of a workpiece in order to selectively protect and abrade various workpiece portions as explained hereinafter.
[0040] Referring to Figure 19, abrasive grains 120 are carried in a semi-solid matrix (not shown) and forced to flow across or through a workpiece 122. By way of example, a particular abrasive grain 121 contained in the matrix cuts into or abrades workpiece 122 to remove a small, yet predictable, portion of the workpiece surface as the abrasive medium is caused to flow in the general direction of arrow 124. Thousands of these particles 120 act together to evenly abrade the surfaces of a workpiece. In this respect, arrow 130 illustrates the force of the abrasive grain generally parallel to flow direction 124 and arrow 132 illustrates an angled force that determines the depth of cut of the abrasive grain 121 into the workpiece. Angled force 132 is determined by the restriction of the passageway through the workpiece and the pressure with which the abrasive medium is forced to flow. As seen in Figure 20, the abrasive medium should be made to flow evenly through the passageway to uniformly polish passageway surfaces 126, with the evenness of flow indicated by parallel lines 128. However, when it is desired to radius an entrance to a passageway, as at 134, then the flow of the abrasive medium should be faster through the center of the passageway than at . the edges thereof, as illustrated by curved flow lines 129, wherein edges 134 at the passageway entrance are abraded more than surfaces 126 of the passageway.
[0041] However, there are instances in which particular edges or surfaces of a workpiece must be abraded or machined while other surfaces lying directly adjacent thereto must not be machined because of critical tolerances. As applied to Figure 21, this would be a situation where edges or corners 134 must be radiused ut the distance between adjacent surfaces 126 must be held constant. Accordingly, surfaces 126, although directly in the flow path of the abrasive medium, must not be abraded. In this embodiment of the invention, a ceramic mask is applied to the area to be protected, such as surfaces 126 of Figure 21. After the mask cures, the workpiece is machined by a flowable abrasive medium. When subjected to the abrasive action, the mask remains relatively intact to protect surfaces 126 while surfaces 134 are subjected routinely to the machining operation. One manner in which such selective machining may be accomplished will be better understood by reference to Figures 22 and 23. In Figure 22, a workpiece 140 has a passageway similar to that illustrated in Figure 20 with an edge or corner 142 at the entrance to the passageway which needs to be radiused or abraded while surface 148 of the passageway must be left unabraded. Accordingly, a ceramic mask 146 is applied to surface 148 and, due to the natural characteristics of the abrasive flow, or other abrading process to provide more abrasive action at the corner 142 than along the remaining portion of surface 148. Although ceramic mask 146 resists abrasion during machining of the workpiece by this abrasive process, some of mask 146 will be removed abrasively such that corner 142 will be radiused, as indicated by phantom lines, at. 144 in Figure 22. Accordingly, there is a smooth blend between radius 144 and unabraded surface 148, as illustrated in Figure 23. After the machining process, mask 146 is removed by soaking the workpiece in a detergent suitable for removal of the ceramic coating.
[0042] There are other instances, as in Figure 24, in which the corners and internal walls of a passageway (generally indicated is 152) must be machined while other surfaces 150 which are in- iirectly subjected to the abrasive action of the flowable abrasive nedium should not be machined. Surfaces 150 are sometimes very difficult, if not impossible, to protect from such abrasive tction. By the instant invention, it is only necessary to apply the ceramic mask 146 to surface 150 in order to provide the necessary protection.
[0043] Other uses for this embodiment of the invention include the prevention of abrasion where a special finish has been placed on the surface or where the abrasive medium would leave a cosmetically unacceptable mark on the workpiece. As may be appreciated from the above description, the mask provides protection of workpiece areas which are subjected to both direct and indirect flow machining. This protective mask could also be used in vibratory, spindel, tub, barrel, or gyro finishing processes, all of which use an abrasive medium to finish a workpiece. The mask may be comprised of ceramic, silicone, or similar substances which may be painted or dipped onto critical areas to protect them, while allowing other areas of a workpiece to be abraded normally.
[0044] Typical parameter ranges for the embodiments of Figures 9-14, and 18 include: grit sizes of 6 microns to 16 mesh, gap distances of 0.002-0.500 inches, time of treatment of '5-60 minutes, vibra- tions per minute of 20-2,000, and amplitude of vibration of 0.025- J.500 inches. Specifically, after substantially filling the gap with a rheopectic abrasive medium, the mandrel of Figure 9 could be operated at 500 vibrations per minute with an amplitude of 0.05 inches for 5 minutes and a gap of 0.005 inches would be sufficient for a grit size of 10 microns.
[0045] It is preferable that the plastic carrier matrix have sufficient body at moderate pressure and low velocity to press the abrasive particles against the work surface with sufficient force to produce the result desired. One mixture successfully used in the invention is MV70 Extrude-Hone media, comprising 50% by volume of silicon carbide abrasive grit and 50% by volume of silicone bouncing putty (borosiloxane) carrier (matrix) having a ratio of approximately 2:1 by weight.
[0046] By definition, silicone bouncing putty (borosiloxane) exhib- its many of the characteristics of a fluid. Under suddenly applied pressure it becomes less flowable and more like a solid. It conforms exactly to the shape of whatever confines it and this helps in abrading intricate shapes and details. It should be noted that silicone bouncing putty (borosiloxane) is particularly useful in the invention as it is well known that this material becomes harder when subjected to sudden shear force such as when squeezed in the gap between the opposed surfaces as they are moved relative to one another. This increased stiffness enhances abrasion of the work- piece by holding the abrasive particles more firmly in place and transferring the driving force of the working member to the abrasive grains at the work surface.
[0047] A non-rheopectic abrasive medium suitable for use in some situations is that described in U.S. Patent No. 3,819,343 - Rhoades.
[0048] This invention may be utilized to hone or abrade machined parts, die castings, forgings, sand castings, investment castings and extruded shapes. It is applicable to all materials such as steel, aluminum, brass, bronze, plastics, glass and other compositions and materials as needed.
[0049] Obviously, the abrasive used in the carrier matrix will be varied to suit the job. A satisfactory abrasive to use in working on steel is boron carbide (BC) which is readily obtainable from the Norton Company in standard grit sizes. Another abrasive which is useful for many applications is aluminum oxide. Other abrasives might include diamond dust, silicon carbide, rouge, corrundum, garnet, alundum, glass or, in some unusual operations, softer material such as fiber or shell material. Commonly, the abrasive will vary from about 2 to 4 pounds of abrasive particles per pound of the matrix material.
[0050] The above-mentioned visco-elastic honing mediums act as a surface abrading tool and are unique for the reason that the abrasive grit is held or contained in a random repositioning arrangement in a plastic matrix. The grain particles in use in the process of this invention are sharp until the sum of all points or edges have been exposed many times, as opposed to the traditional concept of an abrasive "stone" or lap wherein the grain particle is fixed and presents one cutting point or edge which is maintained until dulling causes removal by means of a dressing operation.
[0051] The fastest cutting action, which is also consistent with the most uniform results, occurs when the medium exhibits an oily nonadhering contact with the work surface. It would appear that when in this condition the medium has the greatest opportunity, to pass through the gap at a constant cross-sectional pace. This is contrary to a fluid flow which is greatest through the center and supposedly "zero" along the wall.
[0052] It is to be understood that the present invention is not limited to the preferred embodiments disclosed herein, and that many modifications in construction, arrangement, use and operation are possible within the true spirit of the invention. Accordingly, the present invention is to be considered as including all such modifications and variations coming within the scope of the appended claims.
forming a backing surface having a profile generally the same as said work surface;
coating said backing surface with an abrasion resistant material;
facing said backing surface opposite.from and in spaced relation to said work surface to form a gap therebetween; and
introducing a visco-elastic, abrasive medium under pressure into said gap and guiding said medium against and across said work surface and abrading said work surface, said medium comprising a mixture of a visco-elastic, rheopectic matrix and abrasive particles.
forming an abrasion resistant material to provide a backing surface having a profile at least a portion of which is generally the same as said work surface profile;
facing said backing surface opposite from and in spaced relation to said work surface to form a gap therebetween; and
introducing a visco-elastic, abrasive medium under pressure into said gap; bonding a portion of said medium to said material and reducing abrasion of said backing surface; and guiding with said backing surface and bonded medium, at least a portion of said medium which is not bonded to said backing surface against and across said work surface during said treatment.
applying a silicone rubber-like material to said wear surface; and
bonding a portion of said medium to said material during abrading of said work surface with said abrasive medium.
applying a porous material to said wear surface; and bonding a portion of said medium to said porous material during abrading of said work surface with said abrasive medium.
providing at least an outer surface portion of said backing with a silicone rubber-like material; and
applying said medium to said silicone rubber-like material; whereby said medium is bonded to said silicone rubber-like material.
providing at least an outer surface portion of said backing with a porous material; and
applying said medium to said porous material such that said medium is bonded to said porous material.
providing a porous substrate; and
applying a visco-elastic reheopectic abrasive medium to said porous substrate to bond said medium to said substrate.
coating a substrate with a silicone rubber-like material.; and
applying a visco-elastic abrasive medium to said material to bond said medium to said substrate.
providing at least a portion of said internal surface with a silicone rubber-like material; and
feeding said medium against and across said portion whereby a portion of said medium is bonded to said material and forms a restriction in said passageway.
directing said medium by said restriction against said work surface; and
treating said work surface with said medium.
continuing said treating for time sufficient to form a cavity in said work surface.
providing a silicone rubber-like material within said passageway in opposed, facing relationship to said selected portion;
feeding said abrasive medium into said passageway and against and across said material;
bonding a portion of said medium to said material;
restricting said passageway at said material with said bonded medium: and
abrading said selected portion with a portion of the medium which is not bonded to said-material and is fed through said restriction.
providing an abrasion resistant portion in said passageway speced from and in facing opposition to said selected portion to form a restriction of said passageway opposite said selected portion;
feeding a flowable abrasive medium into said passageway and past said restriction;
increasing the working of said abrasive medium on said selected portion by said restriction; and
reducing said selected portion due to said icreased working.
a flowable abrasive medium for abrading said work surface during flow of said medium against and across said work surface;
guide means spaced from and in facing, opposition to said work surface and having a portion engageable by said medium for guiding said medium against and across said work surface during said abrading; and
portection means for resisting abrasion of said guide means by said medium.
an abrasion resistant polyurethane material; and
at least a portion of said guide means is formed from said polyurethane material, or wherein said protection means comprises:
an abrasion resistant coating on said portion of said guide means engageable by said medium.
means for supplying said abrasion resistant coating to said guide means continuously.
means for supplying said abrasion resistant coating periodically to said guide means.
a mixture of a visco-elastic matrix and abrasive particles.
said guide means having at least said medium engaging portion comprising a means for bonding a portion of said matrix thereto.
a silicone rubber-like material, or wherein said bonding means comprises:
a porous surface.
a substrate having a bonding area; and
a visco-elastic abrasive medium bonded to said substrateat said bonding area.
means for increasing the working of said medium on said selected portion such that said medium is caused to reduce said internal surface at said selected portion.
means for restricting the flow of said medium past said selected portion.
build-up means, spaced from and in facing opposition to said selection portion, for engagement by said medium flow such that a portion of said matrix bonds to saoid build-up means and,restricts the flow of said medium past said selected portion.
a porous material, or wherein said.build-up means comprises:
a silicone rubber-like coating, or wherein said build-up means comprises:
a formed silicone rubber-like plug.
providing opposed surfaces in facing, spaced relationg to provide a gap therebetween, at least one of said opposed surfaces comprising a work surface to be treated;
introducing a visco-elastic abrasive medium into said gap;
imparting relative motion between said opposed surfaces and working said medium positively against nd across said opposed surfaces and abrading at least said work surface.
imparting relative orbital motion between said opposed surfaces to positively work said medium against and across said work surface, or
imparting relative reciprocal motion between said opposed surfaces along a line of reciprocation to positively work said medium agains and across said work surface, or importing relative rotational motion between said opposes surfaces to positively work said medium against and cross said work surface.
varying the angle of said line of reciprocation relative to an instantaneous point on said work surface to vary the positive work of said medium.
abrading both said opposed surfaces, or further comprising the step of:
confining said medium in said gap during said abrading, or further comprising the step of:
introducing more of said medium into said gap to replace medium displaced.from said gap during said treatment.
providing at least a portion of said working surface with means for resisting abrasion.
coating said working surface portion with a polyurethane, or forming said working surface portion of a polyurethane.
roughening said working surface portion;
contacting said working surface portion with said abrasion medium; and
bonding said abrasive medium portion to aid roughening during said contact, or the steps of:
providing said working surface with a porous material;
contacting said working surface portion with said abrasive medium portion; and
bonding said abrasive medium portion to said porous material during said contct, or the steps of:
coating said working surface portion with a silicone rubber-like material;
contacting said silicone rubber-like material with said abrasive medium portion; and
bonding said abrasive medium portion to said silicone rubber-like material during said contact, or the steps of:
forming said working surface portion from a silicone rubber-like material;
contacting said silicone rubber-like materialwith said abrasive medium portion: and
bonding said abrasive medium portion tos aid silicone rubber-like material during said contact.
means for abrading said work surface when positively displaced against and across said work surface, said abrading means comprising a visco-elastic matrix having abrasive grit interspersed therein;
opposed surfaces spaced to define a gap therebetween for reception of said abrading means, at least a portion of at least one of said opposed surfaces comprising said work surface to be treated, and said gap defining a displacement chamber for said abrading means;
means for introducing said abrading means into said gap; and
means for imparting relative motion between said opposed surfaces and positively working said abrading means against and across said work surface for abrasion thereof.
a visco-elastic, rheopectic material.
said gap being greater than said largest grit size, such that said working surface engages said grit with said work surface indirectly via said matrix.
said gap being at least as small as said largest grit size, such that said working surface engages·said grit with said work surface directly.
an abrading means engaging surface comprising a temporarily deformable, abrasion resistant elastomer.
a polyurethane.
means for resisting abrasion.
an abrasion resistant polyurethane.
a coating of said polyurethane on said displacer.
means for bonding a portion of said matrix to said displacer and resisting abrasion of said working surface by said grit.
a roughened working surface, or wherein said bonding means comprises:
a porous working surface, or wherein said bonding means comprises:
a silicone rubber-like working surface.
a medium mover comprising a mandrel and genrally helical-shaped flights and having an external surface;
a confiner coaxial with and surrounding at least a portion of said medium mover along said longitudinal axis thereof and having an internal surface;
at least one of said external and internal surfaces comprising said work surface to be treated:
an abrasive medium comprising a visco-elastic matrix material having abrasive grit interspersed therein:
means for introducing said medium between aid internal and external surfaces; and
means for imparting relative motion between said medium mover and said confiner to positively work said medium against and across said work surface for abrasion thereof.
a visco-elastic, rheopectic material.
providing a plurality of tubes for directing said medium to said work surface;
grouping said tubes loosely together and engaging said work surface with one end of each of said tubes such that a bottom of said grouping generally conforms to a profile of said work surface;
securing said grouping together and fixing each of said tubes relative one to the other;
spacing said bottom from said work surface to provide a gap;
introducing said medium through said tubes into said gap: and
imparting relative motion between said grouping and said work surface such that said medium is worked across and in engagement with said work surface.
a plurality of tubes for directing said medium to said work surface;
means for grouping said tubes loosely together and engaging said work surface with one end of each of said tubes such that a bottom of said grouping generally conforms to a profile of said work surface;
means for securing said grouping together and fixing each of said tubes relative one to the other:
means for spacing said bottom from said work surface to provide a gap;
means for introducing said medium through said tubes into said gap; and
means for imparting relative motion between said grouping and said work surface such that said medium is worked across and in engagement with said work surface.
applying a ceramic material selectively on said work-piece;
curing said ceramic material;
masking a first portion of said workpiece with said ceramic material to prevent abrasion o said first portion;
masking a second portion of said workpiece with said ceramic material to reduce abrasion of said second portion;
forcing a visco-elastic, rheopectic, abrasive medium against and across said workpiece;
abrading a thrid portion of said workpiece and said ceramic material masking said second portion to provide a smooth transition between said second and thrid portions; and
removing all remaining ceramic materialfrom said workpiece.
applyign a ceramic material selectively onto a first portion of said workpiece;
curing said ceramic material and masking said first portion to reduce abrasion of said first portion by an abrasive treatment; and
subjecting said workpiece to said abrasive treatment and abrading a second portion of said workpiece, such that said first portion s subject to a lesser degree of abrasion than said second portion.
applying a ceramic material selectively onto a first portion of said workpice;
curing said ceramic material to prevent abrasion of said first portion by an abrasive treatment; and
subjecting said workpiece to said abrasive treatment and abrading a second portion and preventing abrasion of said first portion.
forcing a visco-elastic, abrasive medium against and across said workpiece.
applying an abrasion resistant material onto a first portion of said workpiece;
curing said abrasion resistant material to bond said material to said first portion;
subjecting said workpiece to abrasive treatment with a visco-elastic abrasive medium and abrading a second portion of said workpiece and protecting said first portion from abrasion by said medium.
abrading an edge of said first portion to a lesser degree than said second portion is abraded such that a smooth transition is provided between said first and second portions.
applying an abrasion-resistant material onto the surfaces of a workpiece to be abraded and protected
subjecting the workpiece to abrasive treatment so tht more abrasive action occurs at selected areas, such as corners and progressively less occurs at adjacent and other areas;
continuing the abrasive treatment·until at selected areas the applied abrasive resistant material is abraded away and these areas of the workpiece itself are abraded, such as corners being rounded; yet other selected areas of the workpice have not seem sufficient abrasive action to fully remove the applied abrasive resistant material and consequently not abrading these areas of the workpiece itself at all; and between these areas providing a smooth uniform transistion;
subsequently removing the applied abrasion resistant material remaining on the workpiece by other means.