POLISHING METHOD

Background

[0001] The present disclosure relates to a polishing cushion, a polishing apparatus, a polishing method, and an article including an object polished by the polishing method.

[0002] Polishing apparatuses for polishing metal materials or the like are conventionally known. For example, polishing apparatuses provided with a polishing disk or a polishing wheel are in common use. UK Unexamined Patent Application Publication No. 813963 describes a contact element for supporting a polishing belt and applying the polishing belt onto a work piece. This contact element has a series of ridged sections with a serrated shape and a material which is softer than the ridged sections is packed into grooves separating the individual ridged sections. U.S. Patent No. 7,824,248 describes a driving apparatus for an orbital sander which, by eccentrically moving a drive shaft, which is eccentric with respect to a rotating shaft extending from a driving source provided in a driving section and of which one end is rotatably coupled with the rotating shaft, around the shaft core of the rotating shaft in proportion to the rotation of the rotating shaft, causes a base plate, which is supported on the driving section via a support pillar formed of an elastic member and fixed to the other end of the drive shaft, to make an orbital motion.

Summary

[0004] It is useful to be able to perform various types of polishing with a single polishing apparatus (in other words, for example, with one polishing disk or endless polishing belt). For example, it is useful to be also able to intensively polish a workpiece surface by pressing a polishing surface onto an object with a relatively high pressure and, at the same time, to finely finish the workpiece surface by pressing the polishing surface onto the object with a relatively low pressure. In order to realize a broad range of types of polishing with one single polishing apparatus, disposing a cushioning material on a rear side of the polishing surface may be considered. However, it is difficult to obtain a desired polishing effect simply by adopting the conventionally available cushioning materials. Therefore, there is a demand to realize a plurality of types of polishing with a single polishing apparatus as described above.

[0005] A polishing cushion according to one aspect of the present invention includes: a first outer layer facing one out of a polishing member and a support member; a second outer layer facing the other out of the polishing member and the support member; an inner layer positioned between the first outer layer and the second outer layer; and a plurality of spaces formed in the second outer layer which the inner layer is able to enter, wherein a hardness of the inner layer is lower than both of the hardness of the first outer layer and the hardness of the second outer layer.

[0006] In this aspect, when pressure is applied to the polishing member during polishing, a part of the soft inner layer enters the spaces due to the pressure. In a case where the polishing member is applied to the object at a pressure of a degree at which the spaces are not entirely packed with the inner layer (that is, at a relatively low pressure), it is possible to finely finish the surface by lightly applying the polishing member to the workpiece surface since the inner layer acts as a buffer for the pressure. On the other hand, in a case where the polishing member is applied to the object at a pressure of a degree at which the individual spaces are packed with the inner layer (that is, at a relatively strong pressure), the workpiece surface is intensively polished by transferring almost all of the pressure to the polishing member since the inner layer is almost completely crushed and substantially does not act as a buffer for the pressure. In this manner, it is possible to realize a plurality of types of polishing with a single polishing apparatus by providing spaces into which the soft inner layer enters in the outer layer.

[0007] According to one aspect of the present invention, it is possible to realize a plurality of types of polishing with a single polishing apparatus.

Brief Description of the Drawings

[0008] FIG. 1 is a perspective diagram of a polishing cushion according to an embodiment.

FIG. 2 is an exploded perspective diagram which shows an example of the polishing cushion according to the embodiment.

FIG. 3 is an exploded perspective diagram which shows another example of the polishing cushion according to the embodiment. FIG. 4 is a perspective diagram which shows still another example of spaces in the polishing cushion.

FIG. 5 is a perspective diagram which shows yet another example of spaces in the polishing cushion.

FIG. 6 is a perspective diagram which shows yet another example of spaces in the polishing cushion.

FIG. 7 is a perspective diagram which shows yet another example of spaces in the polishing cushion.

FIG. 8 is a perspective diagram which shows yet another example of spaces in the polishing cushion.

FIG. 9 is a perspective diagram which shows yet another example of spaces in the polishing cushion.

FIG. 10 is a perspective diagram which shows yet another example of spaces in the polishing cushion.

FIG. 11 is a diagram of a portable grinder provided with the polishing cushion according to the embodiment.

FIG. 12 is an exploded perspective diagram which shows attachment of the polishing cushion in the portable grinder.

FIG. 13 is a perspective diagram of a polishing wheel provided with the polishing cushion according to the embodiment.

FIG. 14 is exploded perspective diagram which shows attachment of the polishing cushion in the polishing wheel.

FIG. 15 is a diagram of a single action sander provided with the polishing cushion according to the embodiment.

FIG. 16 is a diagram of a double action sander provided with the polishing cushion according to the embodiment.

FIG. 17 is an exploded perspective diagram which shows attachment of the polishing cushion in the single action sander or the double action sander.

FIG. 18 is a cross sectional diagram which schematically shows states where the polishing cushion according to the embodiment is changed by being pressed.

FIG. 19 is a table which shows the results of polishing amounts and surface finishing in a working example and a comparative example.

Detailed Description

[0009] Embodiments of the present invention will now be described in detail with reference to the attached drawings. In the description of the drawings, identical or equivalent elements are labeled with the same symbols and not repeatedly described.

[0010] First, a structure of a polishing cushion 10 according to an embodiment will be described using FIGS. 1 to 10. The polishing cushion 10 is an article disposed between a polishing member and a support member which are constituent components of the polishing apparatus. In general, the number of purposes of the polishing is not limited to one and examples of purposes include various types of polishing such as greatly shaving away a surface of an object (a workpiece surface) and finely finishing the surface. The polishing cushion 10 is used for realizing a plurality of types of polishing with a single polishing apparatus.

[0011] Note herein that the term "polishing" in the present specification is a concept which also includes grinding. Furthermore, the term "polishing member" in the present specification is a component which has a polishing surface which contacts a surface of the object. In addition, the term "support member" in the present specification is a component which directly or indirectly supports the polishing member and the polishing cushion 10 during polishing.

[0012] The polishing cushion 10 as shown in FIG. 1 includes at least three layers. Specifically, the polishing cushion 10 includes a first outer layer 11 facing one out of the polishing member and the support member, a second outer layer 12 facing the other out of the polishing member and the support member, and an inner layer 13 positioned between these two outer layers. The first outer layer 11 , the second outer layer 12, and the inner layer 13 are all flat and these three layers are stacked using an adhesive. The thickness of each of the layers may be determined in consideration of the dimensions of the polishing member, the type and dimensions of the polishing apparatus, and the like.

[0013] The first outer layer 11 and the second outer layer 12 are manufactured, for example, with natural rubber or synthetic rubber (for example, urethane rubber or chloroprene rubber) as a main raw material. On the other hand, the inner layer 13 is, for example, a foam body obtained from natural rubber or synthetic rubber. A closed cell foam is more preferable than an open cell foam as the foam body in consideration of the buffering property and the elasticity of the inner layer 13. However, an open cell foam type of foam body may of course be used. Alternatively, the main raw material of the inner layer 13 may be natural rubber or synthetic rubber with a lower hardness than those of the first outer layer and the second outer layer 12. [0014] The hardness of the inner layer 13 is lower than those of both of the hardness of the first outer layer 11 and the hardness of the second outer layer 12. The hardness of each layer is measured in accordance with

"Determination of Hardness of Vulcanized Rubber and Thermoplastic Rubber (JIS K 6253 (2012 Edition))" which is a standard for measuring the hardness of rubber. For example, when the inner layer 13 is a material which is so soft that the hardness is difficult to measure with a Type A durometer, the hardness of the inner layer 13 may be measured using a Type E durometer hardness tester. As long as the relationship described above is satisfied, the hardness of the inner layer 13 and the hardnesses of the two outer layers are not limited to any specific numerical values. As an example, the hardnesses of the first outer layer 11 and the second outer layer 12 may be 70 according to the Type A durometer and the hardness of the inner layer 13 may be five according to the Type E durometer. Alternatively, the hardnesses of the first outer layer 11 and the second outer layer 12 may be 50 according to the Type A durometer and the hardness of the inner layer 13 may be ten according to the Type E durometer. Note that the first outer layer 11 and the second outer layer 12 may differ in hardness.

[0015] A plurality of spaces 14 is formed in one (the second outer layer

12 in the present specification) of the two outer layers. The spaces 14 may be holes (spaces with no bottoms) 14a penetrating from one surface of the second outer layer 12 through the opposite surface as shown in FIG. 2. Alternatively, the spaces 14 may be recesses (bottomed spaces) 14b formed in one surface of the second outer layer 12 as shown in FIG. 3. In all cases, the surface which has the opening sections of the spaces 14 out of the surfaces of the second outer layer 12 is bonded with the inner layer 13.

[0016] In FIGS. 2 and 3, the circular spaces 14 are arranged in a staggered manner; however, the shapes and arrangement of the spaces 14 are not limited thereto. Some modified examples of the spaces are shown in FIGS. 4 to 10. Note that the spaces are through-holes in the modified examples of FIGS. 4 to 9; however, the spaces may of course be recesses. The spaces are recesses in the modified example of FIG. 10.

[0017] The spaces 14 with a triangular shape are arranged in a staggered manner in FIG. 4 and the spaces 14 with a square shape are arranged in a staggered manner in FIG. 5. Naturally, the staggered arrangement is not essential and, for example, the spaces 14 may be arranged in a grid pattern. In FIGS. 6 to 10, the individual spaces are slits. In FIG. 6, the spaces 14 which extend along one side of the second outer layer 12 are arranged in a staggered manner. In FIG. 7, the spaces 14 which extend from along one side of the second outer layer 12 are aligned with a side orthogonal to this side. In FIG. 8, the spaces 14 which extend obliquely with respect to the outer edge of the second outer layer 12 are aligned. In FIG. 9, the spaces 14 with a zigzag shape are aligned. In FIG. 10, the spaces 14 which extend obliquely with respect to the outer edge of the second outer layer 12 are arranged in a network.

Naturally, the shapes of the spaces 14 are not limited these examples. For example, various shapes such as hexagons, stars, ellipses, waveforms, arcs, and fans may be considered.

[0018] The spaces 14 with different shapes may be mixed in one second outer layer 12. For example, the spaces 14 with a triangular shape may be mixed with the spaces 14 with a square shape or the spaces 14 with a circular shape may be mixed with the spaces 14 with a slit shape. Furthermore, through-holes and recesses may be mixed in one second outer layer 12.

Moreover, the sizes of the individual spaces 14 in one second outer layer 12 may be different. For example, the circular spaces 14 with a diameter of 1 cm may be mixed with the circular spaces 14 with a diameter of two cm.

[0019] The ratio of the region of the spaces 14 to the entirety of the second outer layer 12, that is, the porosity, is not limited. The porosity may, for example, be in a range of 50 to 80%. Since there may also be cases where the shapes or sizes of the spaces 14 in one second outer layer are different, the porosity may change according to the position of the region which is the target of the calculation. For example, the porosity in the vicinity of a peripheral section in one second outer layer 12 may possibly be 50% whereas the porosity in the vicinity of the center may possibly be 70%.

[0020] Next, an application example of the polishing cushion 10 will be shown using FIGS. 11 to 14. FIGS. 11 and 12 are an example where the polishing cushion 10 is applied to a portable grinder 20. In this example, the polishing member is a polishing disk 21 and the support member is a pad 22. The polishing cushion 10 is processed to match shapes of the polishing disk 21 and the pad 22 and a through-hole is formed in the center thereof. The polishing cushion 10 is detachably attached to the portable grinder 20 in the same manner as the polishing disk 21 and the pad 22. As shown in FIG. 12, a user plugs these three components into a shaft 23, which extends from the main body of the portable grinder 20, in order of the pad 22, the polishing cushion 10, and the polishing disk 21. Thereafter, the user fixes the pad 22, the polishing cushion 10, and the polishing disk 21 to the shaft 23 by tightening a nut 24 onto a male screw which is formed at an end section of the shaft 23. [0021] FIGS. 13 and 14 are an example where the polishing cushion 10 is attached to a polishing wheel 30. In this example, the polishing member is an endless polishing belt 31 and the support member is a wheel 32. FIG. 14 shows a plurality of the polishing cushions 10 shorter than the outer circumference of the wheel 32 (for example, eight polishing cushions 10 whose length is 1/8 of the outer circumference). However, the polishing cushions 10 may be endless (that is, ring-shaped). The polishing cushion 10 is detachably attached onto the outer circumferential surface of the wheel 32. If the plurality of polishing cushions 10 are attached as shown in FIG. 14, an adhesive layer or a bonding layer is further formed on the outer layer (second outer layer 12 in FIG. 14) of the polishing cushion 10 facing the wheel 32. In such a case, the user attaches the endless polishing belt 31 to the wheel 32 after the polishing cushion 10 is affixed to the outer circumferential surface of the wheel 32. If the polishing cushion 10 is endless (ring-shaped), the user first fits the polishing cushion 10 into the wheel 32 and then attaches the endless polishing belt 31 to the wheel 32.

[0022] It is also possible to apply the polishing cushion 10 to a single action sander 40 A shown in FIG. 15 or a double action sander 40B shown in FIG. 16. These polishing apparatuses 40A and 40B each include a common polishing pad 41 shown in detail in FIG. 17. In the polishing pad 41 , the polishing member is a polishing disk 42 and the support member is a pad 43. The polishing cushion 10 is processed to match the shapes of the polishing disk 42 and the pad 43. The polishing cushion 10 is detachably attached to the single action sander 40A or the double action sander 40B. As shown in FIG. 17, the user attaches the pad 43 to a shaft 44 extending from the main body of the polishing apparatus 40 A or 40B, the polishing cushion 10 is affixed to the pad 43, and the polishing disk 42 is affixed to the polishing cushion 10. Note that it is possible to realize the affixing using a surface fastener or an adhesive. Through these series of operations, the pad 43, the polishing cushion 10, and the polishing disk 42 are fixed to the shaft 44.

[0023] Regardless of the type of polishing apparatus, the polishing cushion 10 is used in two ways. As shown in FIGS. 11 to 17, one is in a method for attaching the polishing cushion 10 to the polishing apparatus such that the second outer layer 12 where a plurality of the spaces 14 are formed faces the support member (the pad 22, the wheel 32, or the pad 43), and such that the first outer layer 11 which does not have the spaces 14 faces the polishing member (the polishing disk 21 , the endless polishing belt 31 , or the polishing disk 42). The other is in a method for attaching the polishing cushion 10 to the polishing apparatus such that the second outer layer 12 faces the polishing member and such that the first outer layer 11 faces the support member.

[0024] In this manner, the types of the polishing apparatus and the ways of using the polishing cushion are varied. In any cases, the user polishes an object using the polishing apparatus where the polishing cushion 10 is arranged between the polishing member and the support member. The polished object is provided as it is as an article or as a part of an article.

[0025] When the user polishes the workpiece surface by applying the surface of the polishing member against the object, the inner layer 13 of the polishing cushion 10, which is disposed between a polishing member 50 and a support member 60, enters the spaces 14 which are formed in the second outer layer 12 as shown in FIG. 18. As shown in the middle part of FIG. 18, in a case where the user applies the polishing member 50 against the object at a pressure of a degree at which the spaces 14 are not completely packed (that is, a relatively low pressure), it is possible to weakly apply the polishing member 50 against the workpiece surface since the inner layer 13 acts as a buffer for this pressure and it is possible to finely finish the surface as a result. On the other hand, as shown in the lower part of FIG. 18, in a case where the user applies the polishing member 50 against the object at a pressure of a degree at which the spaces 14 are completely packed with the inner layer 13 (that is, a relatively high pressure), the inner layer 13 substantially does not act as a buffer for the pressure since the inner layer 13 is almost completely crushed between the first outer layer 11 and the second outer layer 12 and the spaces 14 are packed with the inner layer 13. As a result, it is possible to intensively polish the surface of the object by transferring almost all of the pressure to the polishing member 50.

[0026] Since the inner layer substantially does not change shape in the polishing cushion which does not have spaces which the soft inner layer is able to enter, the result is that the inner layer substantially does not act as a buffer for the pressure. As a result, even though it is possible to intensively polish the object, it is difficult to finely finish the workpiece surface. On the other hand, according to the present embodiment, it is possible to realize a plurality of types of polishing with the single polishing apparatus by providing the spaces 14 which the soft inner layer 13 enters in the second outer layer 12.

[0027] As described above, a polishing cushion according to one aspect of the present invention includes: a first outer layer facing one out of a polishing member and a support member; a second outer layer facing the other out of the polishing member and the support member; an inner layer positioned between the first outer layer and the second outer layer; and a plurality of spaces formed in the second outer layer which the inner layer is able to enter, in which a hardness of the inner layer is lower than both of the hardness of the first outer layer and the hardness of the second outer layer.

[0028] Furthermore, a polishing apparatus according to one aspect of the present invention includes: the polishing cushion; the polishing member; and the support member described above.

[0029] Moreover, a polishing method according to one aspect of the present invention is a polishing method which uses the polishing apparatus and includes: polishing an object using the polishing apparatus where a polishing cushion is arranged between the polishing member and the support member, in which the polishing cushion includes a first outer layer facing one out of the polishing member and the support member; a second outer layer facing the other out of the polishing member and the support member; an inner layer positioned between the first outer layer and the second outer layer; and a plurality of spaces formed in the second outer layer which the inner layer is able to enter, and a hardness of the inner layer is lower than both of the hardness of the first outer layer and the hardness of the second outer layer.

[0030] Furthermore, an article according to an aspect of the present invention includes an object which is polished using the polishing method described above.

[0031] In this aspect, when pressure is applied to the polishing member during polishing, a part of the soft inner layer enters the spaces due to the pressure. In a case where the polishing member is applied to the object at a pressure of a degree at which the spaces are not entirely packed with the inner layer (that is, at a relatively low pressure), it is possible to finely finish the surface by lightly applying the polishing member to the workpiece surface since the inner layer acts as a buffer for the pressure. On the other hand, in a case where the polishing member is applied to the object at a pressure of a degree at which the individual spaces are packed with the inner layer (that is, at a relatively strong pressure), it is possible to intensively polish the workpiece surface by transferring almost all of the pressure to the polishing member since the inner layer is almost completely crushed and substantially does not act as a buffer for the pressure. In this manner, it is possible to realize a plurality of types of polishing with a single polishing apparatus by providing spaces which the soft inner layer enters in the outer layer.

[0032] In another aspect of the present invention, the first outer layer which does not have the spaces which the inner layer is able to enter may face the polishing member, and the second outer layer may face the support member. By providing no spaces in the first outer layer facing the polishing member, it is possible to polish the workpiece surface without patches since the pressure which is applied to the polishing cushion is transferred from the first outer layer to the polishing member almost uniformly.

[0033] In another aspect of the present invention, the surface of the second outer layer where opening sections of a plurality of spaces are formed may be bonded with the inner layer. In such a case, since nothing is interposed between the inner layer and the opening sections, it is easy for the inner layer to enter the spaces and it is easy to adjust the thickness of the inner layer for this part.

[0034] In another aspect of the present invention, the plurality of spaces may be through-holes. Since it is possible to increase the volume of the inner layer which enters the spaces to the maximum by setting the spaces as through- holes, it is easy to apply a relatively low pressure to the polishing member. Furthermore, since it is easy to form the through-holes in comparison with a case of forming the recesses, it is possible to easily manufacture the polishing cushion in this respect.

Examples

[0035] While the present invention is described more specifically based on a working example hereinafter, the present invention is not at all limited thereto.

[0036] As the working example, a polishing cushion with three layers equivalent to the polishing cushion 10 described above was prepared. The main raw material of the first outer layer and the second outer layer was a chloroprene rubber and the main raw material of the inner layer was also chloroprene rubber. In the working example, the hardnesses of both of the first outer layer and the second outer layer were 50 according to the standards of the Type A durometer and the hardness of the inner layer was five according to the standards of the Type E durometer. Furthermore, the thicknesses of the first outer layer and the second outer layer were 2 mm and the thickness of the inner layer was 3 mm. A plurality of spaces formed in the second outer layer were circular through-holes and the through-holes were lined up in a staggered manner. The porosity was set to 50 to 80%.

[0037] On the other hand, as a comparative example, a polishing cushion with two layers formed of one outer layer which did not have spaces (equivalent to the first outer layer 11 in the embodiment described above) and an inner layer was prepared. The main raw material and the hardness of each of the layers were the same as those of the comparative example.

[0038] The configuration apart from the polishing cushion and the polishing target object were common to the working example and the comparative example. As the polishing apparatus, a centerless polishing machine, Nisshinbo Hammond OD-2, manufactured by Hammond Roto-Finish Co., Inc. of Kalamazoo, Michigan, USA was used. As a polishing belt, Trizact (trademark) 363FC A35 manufactured by the 3M Company of St. Paul, Minnesota, USA was adopted. The width of the polishing belt was 5.08 cm (two inches). A carbon steel bar with a diameter of 5.08 cm (two inches) was used as the polishing target object. The pressure during the polishing was determined by a load current (amperes) from the centerless polishing machine.

[0039] In the working example and the comparative example, the bar was polished by the centerless polishing machine twice; once in a case where the pressure was increased (a load current of 4 amperes) and once in a case where the pressure was lowered (a load current of 0.5 amperes). Note herein that the high pressure was a pressure of a degree at which the spaces inside the second outer layer are completely packed with the inner layer in the working example (refer to the lower part of FIG. 18) and that the low pressure was a pressure of a degree at which a part of the spaces inside the second outer layer are not packed with the inner layer in the working example (refer to the middle part of FIG. 18). In both of the working example and the comparative example, the polishing time was 1.5 seconds per 5.08 cm (two inches, that is, length equivalent to the width of the polishing belt) in the length direction of the bar. FIG. 19 shows the results of the polishing with two aspects of the polishing amount and the surface finishing. The polishing amounts were determined according to the reduction amount in the diameter of the bar and the finishing of the surface was determined by the surface roughness (specifically, the arithmetic mean roughness (Ra)).

[0040] The present invention has been described in detail with respect to the embodiments thereof. However, the present invention is not limited to the embodiments described above. Various modifications may be made to the present invention to the extent that they do not depart from the gist of the present invention.

[0041] In the embodiment described above, the polishing cushion 10 has a three-layer structure; however, the polishing cushion may have four or more layers. However, an adhesive layer for affixing the first outer layer to the inner layer and an adhesive layer for affixing the second outer layer to the inner layer are not included as layers. That is, a separate layer apart from the adhesive layer may be present between the first outer layer and the inner layer or between the second outer layer and the inner layer. However, it is necessary for a layer which is present between the outer layer where the spaces are formed and the inner layer to be thinned or softened to an extent that the layer does not interfere with the entry of the inner layer into the spaces.

Alternatively, a separate layer may be stuck to the outer side of the first outer layer and a separate layer may be stuck to the outer side of the second outer layer.

[0042] In the embodiment described above, the spaces 14 are only formed in the second outer layer 12. However, the spaces into which the inner layer enters may be formed in both of the first outer layer and the second outer layer. In such a case, the shapes, dimensions, and locations of the spaces may be the same in the first outer layer and the second outer layer or may be different.

[0043] When using the polishing cushion 10, a separate member may be interposed between the polishing cushion 10 and the polishing member, or a separate member may be interposed between the polishing cushion 10 and the support member. That is, the outer surface of the polishing cushion 10 need not contact the polishing member or the support member.

REFERENCE NUMERALS

[0044]

10 POLISHING CUSHION

11 FIRST OUTER LAYER

12 SECOND OUTER LAYER

13 INNER LAYER

14 SPACE

14a through-hole (SPACE)

14b RECESS (SPACE)

21 POLISHING DISK (POLISHING MEMBER)

22 PAD (SUPPORT MEMBER)

31 ENDLESS POLISHING BELT (POLISHING MEMBER)

32 WHEEL (SUPPORT MEMBER)

42 POLISHING DISK (POLISHING MEMBER)

43 PAD (SUPPORT MEMBER)

50 POLISHING MEMBER

60 SUPPORT MEMBER