TECHNICAL FIELD

[0001 ] One aspect of the present invention relates to a pad for supporting a grinding disk.

BACKGROUND

[0002] Grinding machines of various types are known conventionally and one such grinding machine is a portable grinder. For example, Patent Document 1 describes an orbital sander drive device in which a drive shaft having a first end rotatably connected to a rotary shaft with eccentricity relative to the rotary shaft extending from a drive source provided on a drive unit eccentrically moves around a shaft core of the rotary shaft by the rotation of the rotary shaft to obitally move a base plate supported by the drive unit via a support column composed of an elastic member and affixed to a second end of the drive shaft.

[0003] Patent Document 1 : Japanese Unexamined Patent Application Publication

No. H8-309653

SUMMARY OF THE INVENTION

[0004] A grinding disk is attached to a grinding machine such as the orbital sander drive device described above. The grinding disk, generally, is a component obtained by affixing particles or fine powder of an abrasive on a surface of a flexible base material made of cotton cloth, paper, or the like with an adhesive (glue, gelatin, synthetic resin, and the like). Therefore, there is a possibility that the adhering portion of the grinding disk or a portion of the base material portion may expand due to heat generated in the grinding disk during grinding, thereby lowering grinding efficiency and shortening the life of the grinding disk. There is also a possibility that the expansion may cause an undesirable vibration in the grinding disk during operation, rendering use of the grinding machine difficult. Thus, suppressing an increase in heat generated in the grinding disk during grinding is desired.

[0005] The pad according to one aspect of the present invention is a pad supporting a grinding disk by being affixed to a shaft of a grinding machine together with the grinding disk, the pad including a support surface opposing the grinding disk, a back surface opposing the support surface, and a plurality of air passages formed at a predetermined spacing along a circumferential direction of the support surface, wherein at least a portion of each of the air passages penetrates from the support surface to the back surface and each of the air passages is formed to a peripheral portion of the support surface. [0006] With such aspect, because air passages penetrating from the support surface to the back surface and extending to the peripheral portion of the support surface are provided, air flows continuously through the passage by centrifugal force, discharging at least a portion of the heat generated in the grinding disk by the flow of air when the grinding disk and the pad rotate as the grinding machine operates. Therefore, an increase in heat generated in the grinding disk during grinding can be suppressed.

[0007] According to one aspect of the present invention, an increase in heat generated in the grinding disk during grinding can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a diagram illustrating an appearance of a portable grinder provided with a pad according to an embodiment.

FIG. 2 is an exploded perspective view for describing the attachment of the pad according to the embodiment.

FIG. 3 is a perspective view illustrating a support surface of the pad according to the embodiment.

FIG. 4 is a perspective view illustrating a back surface of the pad according to the embodiment.

FIG. 5 is a front view illustrating a support surface of the pad according to the embodiment.

FIG. 6 is a graph showing cumulative grinding amounts in Working Examples and Comparative Examples.

FIG. 7 is a graph showing the grinding amount for every 30 seconds in Working Examples and Comparative Examples.

DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention is described below with reference to the attached drawings. Note that the same reference numerals are assigned to the same or equivalent constituents in the following description and overlapping descriptions are omitted.

[0010] A structure of a pad 10 according to the embodiment is described using

FIGS. 1 to 5.

[001 1 ] The pad 10 is a component for supporting a grinding disk 20 to be attached to a portable grinder (grinding machine) 1 illustrated in FIG. 1. A hard resin such as nylon is selected as the material for the pad 10 in consideration of heat resistance but the material of the pad 10 is not limited thereto. Also, the type of the grinding machine is not limited and the pad 10 can be applied to any grinding machine.

[0012] The grinding disk 20 is a grinding tool in a circular plate shape and is used by attaching to the portable grinder 1 and rotating. The grinding disk 20 is obtained by evenly affixing particles or fine powder of an abrasive onto the surface of the flexible base material of cotton cloth, paper, or the like with an adhesive such as glue, gelatin, synthetic resin, and the like. Therefore, the grinding disk 20 has a certain degree of flexibility. It is preferred that the base material of the grinding disk 20 be a material that has sufficient strength and heat resistance.

[0013] The pad 10 and the grinding disk 20 are removably attached to the main body of the portable grinder 1. As illustrated in FIG. 2, a through hole 10a is formed in the pad 10 through which a shaft 2 extending from the main body of the portable grinder 1 passes. A user inserts the pad 10 first into the shaft 2 and inserts the grinding disk 20 next. Then, the user affixes the pad 10 and the grinding disk 20 to the shaft 2 by tightening a nut 3 on a male screw formed on an end portion of the shaft 2. The surface of the pad 10 opposed to the grinding disk 20 functions as a support surface 1 1 for supporting the grinding disk 20 during grinding. The surface of the pad 10 opposed to the support surface 1 1 is referred to as a back surface 12.

[0014] The pad 10 and the grinding disk 20 rotate at a high speed around the shaft 2 when the portable grinder 1 is activated by the user. The user can grind a surface by applying the grinding disk 20 to the surface of the grinding object. Note that the term "grinding" is a concept that also includes grinding down.

[0015] When the grinding force of the grinding disk 20 has degraded, the user removes the nut 3 from the shaft 2, replaces the grinding disk 20 to a new one, and re-tightens the nut 3 on the shaft 2. Meanwhile, the pad 10 is reusable and the user does not need to replace the pad 10 each time together with the grinding disk 20. Note that the pad 10 may be provided in a fixed manner to the shaft 2.

[0016] The center portion of the support surface 1 1 surrounding the through-hole

10a is recessed in a circular shape, and this portion is hereinafter referred to as a recess 10b. The portions other than the recess 10b in the support surface 1 1 are flat. In such a flat portion, a plurality of air passages 14 is formed in a spiral shape as a whole, in other words, each of the air passages 14 is formed obliquely to a radial direction of the support surface 11. Each air passage 14 is formed in an arc shape that is convex in the rotation direction of the pad 10 rather than in a linear shape.

[0017] In the example illustrated in FIG. 3 and FIG. 5, each air passage 14 is formed so that it becomes convex in the counterclockwise direction, but of course, the air passage 14 may be formed to become convex in the clockwise direction. The degree of curvature of the air passage 14 may be set as desired. Also, the number of the air passages 14 formed on the support surface 1 1 and the spacing between the air passages 14 may also be set as desired.

[0018] Each air passage 14 is formed to the peripheral portion of the support surface 1 1 from the recess 10b or from the vicinity of the recess 10b. In the embodiment, as illustrated in FIG. 3 to FIG. 5, a majority of each air passage 14 is a groove and an end portion Therefore, both ends of the air passage 14 are not blocked even when disposing the grinding disk 20 on the support surface 11 , and the air can flow to the end portion 14b of the peripheral side from the end portion 14a of the back surface 12 side by rotating the pad 10.

[0019] As described above, the pad according to one aspect of the present invention is a pad supporting a grinding disk by being affixed to a shaft of a grinding machine together with the grinding disk, the pad including a support surface opposing the abrasive disk, a back surface opposing the support surface, and a plurality of air passages formed at a

predetermined spacing along the circumferential direction of the support surface, wherein at least a portion of each of the air passages penetrates from the support surface to the back surface, and each of the air passages is formed to the peripheral portion of the support surface.

[0020] With such aspect, because air passages penetrating from the support surface to the back surface and extending to the peripheral portion of the support surface are provided, air flows continuously through the passage by centrifugal force, discharging at least a portion of the heat generated in the grinding disk by the flow of air when the grinding disk and the pad rotate as the grinding machine operates. Therefore, an increase in heat generated in the grinding disk during grinding can be suppressed. As a result, it is possible to further extend the usable time or the grinding amount of one of the grinding disks.

[0021 ] Also, because the pad and the grinding disk are independent of each other, when the grinding disk is no longer usable, only the grinding disk may be replaced.

Therefore, it is possible to save resources compared to a product in which the pad and the grinding disk are integrated.

[0022] With the pad according to another aspect, each air passage may be formed in a spiral form. Forming the air passage in this manner allows heat to be discharged more effectively because the flow of air in this passage is further improved during the rotation of the pad.

[0023] With the pad according to another aspect, each of the air passages may be in an arc shape that is convex in the rotation direction. It is possible to discharge heat more effectively because the flow of air in this passage is further improved during the rotation of the pad by forming the air passage in this manner.

EXAMPLES

[0024] Although the present invention is described more specifically based on working examples, the present invention is not limited thereto.

[0025] As a working example, a pad corresponding to the pad 10 described above is prepared. The pad was made of a polyamide-based synthetic resin and the outer diameter thereof was 96 mm. The length of the air passage was 33 mm, and the width and depth of the groove of the air passage was 3 mm and 2.5 mm, respectively. The length and width of

4 the through-hole was 10 mm and 3 mm, respectively. The spacing of the adjacent air passages was 6 mm. Meanwhile, as a comparative example, a pad identical to the working example was prepared having the through-holes of each air passage sealed with a seal on the back surface. Other than the pad, all configurations and the grinding object were common between the working example and the comparative example.

[0026] A PDA 100D (rotation speed of 12000 rpm) produced by Hitachi machine

Co. Ltd. was used as the main body of the portable grinder, and a fiber disk 987C60+ (outer diameter of 101.6 mm) produced by 3M was used as the grinding disk. A flat plate of SUS304 which is a kind of austenitic stainless steel was prepared as the grinding object.

[0027] First, in the working example and the comparative example, the temperature of the pad during grinding of the flat plate with the portable grinder was measured using a thermochromic member. A thermo label 5E- 120 produced by NiGK Corporation was used as the thermochromic member, and the thermochromic member was adhered to the back surface of the pad. The grinding time was 60 seconds and the grinding load applied to the grinder by the worker was from 1 to 5 kg.

[0028] The temperature measurement results for the working examples and the comparative examples are shown in Table 1. The black circle in Table 1 means that the pad reached a temperature indicating the highest level during grinding, and the hyphen means that the pad did not reach that temperature. Therefore, Table 1 shows that the temperature of the pads in the working examples did not reach 125°C whereas the temperature of the pads in the comparative examples reached 160°C.

[Table 1 ]

[0029] Next, the grinding amount when grinding the flat plate using the portable grinder was measured for the working examples and the comparative examples. This measurement was performed every 30 seconds until grinding was no longer possible. In each of the working examples and the comparative examples, the measurement of the grinding amount was performed twice by exchanging the grinding disk and the grinding object (sample). Table 2 and FIG. 6 show the transition of the cumulative grinding amount (g) for the four total samples of the working example and the comparative example. The horizontal axis and the vertical axis of the graph in FIG. 6 are the elapsed time (seconds) and the cumulative grinding amount (g) from the start of grinding, respectively. In FIG. 6, the solid line shows the results of the working example and the broken line shows the results of the comparative example. Table 3 and FIG. 7 show the transition of the grinding amount per 30 seconds (g/30 seconds) calculated from the results of Table 2. The horizontal axis and the vertical axis of the graph of FIG. 7 are the elapsed time (seconds) and the grinding amount per about 30 seconds (g/30 seconds) from the start of grinding, respectively. Even in FIG. 7, the solid line shows the results of the working example and the broken line shows the results of the comparative example.

[Table 2]

[0030] The present invention has been described in detail with reference to the embodiment. However, the present invention is not limited to the above embodiments. The present invention can be modified in various ways without departing form the scope of the invention.

[003 1 ] In the above embodiment, the through-hole was formed in the end portion

14a of the air passage 14, but this through-hole can be formed in the middle of the air passage. Alternatively, the through-hole to the back surface may be formed in a plurality of locations of the air passage, for example, it is possible to form a through-hole in two locations such as the end portion of the center side of the pad and a portion in the middle. Also, the air passage 14 included a groove portion, but the entire air passage may penetrate from the support surface to the back surface (that is, the groove portion may be absent).

[0032] The air passage 14 had an arc shape in the above embodiment, but the air passage may be formed in a linear shape.

[0033] A plurality of air passages 14 was formed in a spiral shape in the above embodiment, but the aspect of forming an air passage is not limited thereto and, for example, the plurality of air passages may be formed radially. Even when the air passages are provided radially, each air passage may be formed in an arc shape that is convex in the rotation direction, or they may be formed in a linear shape.

[0034] Thus, with the pad according to another aspect, each air passage may be formed substantially radial.

[0035] Even in this case, because the air flows through the passage by centrifugal force, at least a portion of the heat generated in the grinding disk is discharged by the flow of air, thereby enabling the increase in heat generated in the grinding disk during grinding to be suppressed.

[0036] The width of the air passage 14 is constant in the above embodiment, but it is also possible to form each air passage so that the width becomes wider toward the peripheral portion from the center portion of the support surface.

[0037] That is, with the pad according to another aspect, the width of each air passage may be wider from the center portion of the support surface toward the peripheral portion. Widening the outlet side of the air in this way allows air to easily flow by the rotation of the pad and discharge the heat more efficiently. [0036]

[0038] The portable grinder was illustrated as an example of the grinding machine in the above embodiment, but the type of grinding machine is not limited.

[0039] The pad according to the present invention is applicable to any grinding machine using a grinding disk.