Grinding wheels, disc grinders
Patent Information
- Application Number
- JP2025059678
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2026-10-14
Smart Images
Figure 2026166622000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a grinding wheel for grinding a workpiece, and a disc grinder provided with the grinding wheel.
Background Art
[0002] Conventionally, a workpiece is ground by pressing a grinding wheel against the workpiece while rotating the grinding wheel in the circumferential direction, and FIG. 35 shows a conventional disc grinder provided with the above grinding wheel (the disc grinder 101 shown in FIG. 35 is disclosed in Non-Patent Document 1). The disc grinder 101 shown in FIG. 35 includes a grinding wheel 102, a main grip 103, a sub grip 104, and a switch 105. An operator can rotate the grinding wheel 102 in the circumferential direction by gripping the main grip 103 and the sub grip 104 with the right hand and the left hand respectively, and pressing the switch 105 with the right hand to drive a motor (not shown). When grinding a workpiece, the operator presses the grinding wheel 102 against the workpiece while rotating the grinding wheel 102.
Prior Art Documents
Non-Patent Document
[0003]
Non-Patent Document 1
Summary of Invention
Problems to be Solved by the Invention
[0004] When the grinding wheel 102 described above is used, the workpiece is ground by rotating the grinding wheel 102 and pressing the workpiece mainly with the bottom surface, sides, or lower corners (the corners forming the boundary between the bottom surface and the sides) of the grinding wheel 102. In this manner of using the grinding wheel 102, the upper surface 102a of the grinding wheel 102, which is not pressed against the workpiece, is the part of the grinding wheel 102 that is most likely to cause injury to the worker if they come into contact with it due to carelessness or other reasons.
[0005] The present invention has been made in view of the above problems, and the object of the present invention is to provide a grinding wheel that is pressed against a workpiece while being rotated in the circumferential direction for grinding the workpiece, which reduces the risk of injury to the worker even if the worker comes into contact with the upper surface of the grinding wheel, and a disc grinder equipped with the grinding wheel. [Means for solving the problem]
[0006] To achieve the above objectives, the present invention encompasses the subject matter described in the following sections.
[0007] Item 1. A grinding wheel that is pressed against a workpiece while being rotated in the circumferential direction for grinding the workpiece, It has a structure in which the grinding plate and the pad are stacked in the vertical direction. The grinding wheel plate is made of abrasive grains bonded together by a binder, and the grinding wheel plate contains general abrasive grains or superabrasive grains as the abrasive grains. The pad is formed from a polymer material or plant fiber and constitutes the upper surface of the grinding wheel.
[0008] Item 2. The pad comprises a disc and an annular wall projecting downward from the outer circumference of the disc. The grinding wheel according to item 1, wherein the pad is arranged such that the disc covers the upper surface of the grinding wheel plate and the annular wall covers the upper side of the grinding wheel plate, the disc constitutes the upper surface of the grinding wheel, the annular wall constitutes the upper side of the grinding wheel plate, and the grinding wheel plate constitutes the lower side of the grinding wheel and the lower surface of the grinding wheel.
[0009] Item 3. The pad comprises a disc and an annular wall projecting downward from the outer circumference of the disc. The grinding wheel according to item 1, wherein the pad is arranged such that the disc covers the upper surface of the grinding wheel plate and the annular wall covers the side surface of the grinding wheel plate, so that the disc constitutes the upper surface of the grinding wheel, the annular wall constitutes the side surface of the grinding wheel plate, and the grinding wheel plate constitutes the lower surface of the grinding wheel.
[0010] Item 4. The pad comprises a disc and an annular wall projecting downward from the outer circumference of the disc. The grinding wheel according to item 1, wherein the pad is positioned above the grinding wheel plate, and the annular wall is positioned between the disc and the grinding wheel plate in the vertical direction, so that the disc constitutes the upper surface of the grinding wheel, the annular wall constitutes the upper side surface of the grinding wheel, and the grinding wheel plate constitutes the lower side surface of the grinding wheel and the lower surface of the grinding wheel.
[0011] Item 5. The pad further comprises a plurality of linear projections and an annular projection, The plurality of linear protrusions and the annular protrusion project downward from the disc on the inside of the annular wall, Each of the aforementioned linear projections extends radially to the disk, and the annular projection extends circumferentially to the disk so as to intersect with each of the linear projections. The grinding wheel according to item 4, wherein the pad is positioned above the grinding wheel plate, and the pad is arranged such that, in the vertical direction, the annular wall, the plurality of linear protrusions, and the annular protrusions are positioned between the disc and the grinding wheel plate.
[0012] Item 6. The pad is disc-shaped and comprises a central portion that forms the center of the pad and an annular surrounding portion that surrounds the outside of the central portion. The vertical thickness of the surrounding portion is greater than the vertical thickness of the central portion. The grinding wheel according to item 1, wherein the pad is positioned above the grinding wheel plate, so that the pad constitutes the upper surface of the grinding wheel and the upper side surface of the grinding wheel, and the grinding wheel plate constitutes the lower side surface of the grinding wheel and the lower surface of the grinding wheel.
[0013] Item 7. The grinding wheel described in Item 1, wherein the outer diameter of the pad is larger than the outer diameter of the grinding plate.
[0014] Item 8. The grinding wheel according to Item 1, wherein the inner circumference of the grinding wheel plate and the inner circumference of the pad are joined together such that the outer circumference of the grinding wheel plate and the outer circumference of the pad are separated in the vertical direction.
[0015] Item 9. Further comprising an annular body joined to the pad so as to surround the outer circumference of the pad, The grinding wheel according to item 1, wherein the annular body is formed from a polymer material or plant fiber, and the Rockwell hardness of the annular body is lower than the Rockwell hardness of the pad.
[0016] Item 10. The grinding wheel according to Item 1, wherein the pad has through holes for air circulation.
[0017] Item 11. The pad is a grinding wheel according to Item 1, formed from a transparent material.
[0018] Item 12. A grinding wheel as described in any of items 1 to 11, Equipped with a grinder body, The grinding wheel is rotatably suspended from the grinder body with the pad forming the upper surface of the grinding wheel. The aforementioned grinder body is a disc grinder in which a motor for rotating the grinding wheel is built in. [Effects of the Invention]
[0019] According to the grinding wheel and the disc grinder of the present invention, even if an operator comes into contact with the upper surface of the grinding wheel, the risk of the operator getting injured can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] [Figure 1] It is a perspective view showing the disc grinder according to the embodiment of the present invention. [Figure 2] It is an image showing the grinding wheel according to the embodiment of the present invention. [Figure 3] It is a cross-sectional view showing a state where the grinding wheel according to the embodiment of the present invention is cut in the vertical direction. [Figure 4] It is a schematic side view showing a state where a workpiece is being ground using the grinding wheel according to the embodiment of the present invention. [Figure 5] It is an image showing a reinforcing material. [Figure 6] It is a schematic diagram showing an example of a circuit configuration for driving a motor. [Figure 7] It is an image showing a grinding wheel according to a modified example of the present invention. [Figure 8] It is an image showing a grinding wheel according to a modified example of the present invention. [Figure 9] It is a perspective view showing a pad included in a grinding wheel according to a modified example of the present invention. [Figure 10] It is a perspective view showing another example of the pad included in the grinding wheel according to the modified example of the present invention. [Figure 11] It is a perspective view showing another example of the pad included in the grinding wheel according to the modified example of the present invention. [Figure 12] It is a perspective view showing another example of the pad included in the grinding wheel according to the modified example of the present invention. [Figure 13] (A) and (B) show a grinding wheel according to a modified example of the present invention, where (A) is a side view and (B) is a bottom view. [Figure 14] It is a perspective view showing a grinding wheel according to a modified example of the present invention. [Figure 15] It is a side view showing a grinding wheel according to a modified example of the present invention. [Figure 16] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 17] This is a side view showing a grinding wheel according to a modified example of the present invention. [Figure 18] This is a schematic side view showing a state in which a workpiece is being ground using a grinding wheel according to a modified example of the present invention. [Figure 19] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 20] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 21] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 22] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 23] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 24] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 25] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 26] This is a perspective view showing a grinding wheel according to a modified example of the present invention. [Figure 27] This is a side view showing a grinding wheel according to a modified example of the present invention. [Figure 28] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 29] This is a perspective view showing a grinding wheel according to a modified example of the present invention. [Figure 30] This is a side view showing a grinding wheel according to a modified example of the present invention. [Figure 31] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 32] This is a perspective view showing a grinding wheel according to a modified example of the present invention. [Figure 33]This is a side view showing a grinding wheel according to a modified example of the present invention. [Figure 34] This is a cross-sectional view showing a grinding wheel according to a modified example of the present invention, cut in the vertical direction. [Figure 35] This is a perspective view showing a conventional disc grinder. [Modes for carrying out the invention]
[0021] Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, and various modifications are possible without departing from its spirit.
[0022] Figure 1 is a perspective view showing a disc grinder 1 according to an embodiment of the present invention. Figure 2 is an image showing a grinding wheel 2 according to an embodiment of the present invention. Figure 3 is a cross-sectional view showing the grinding wheel 2 according to an embodiment of the present invention cut in the vertical direction E. Figure 4 is a schematic side view showing the grinding of a workpiece W using the grinding wheel 2 according to an embodiment of the present invention.
[0023] An embodiment of the present invention, the disc grinder 1 (Figure 1), is a handheld power tool comprising a grinding wheel 2, a grinder body 3, a main grip 4, a sub-grip 5, a switch 6, and a disc guard 7. The disc grinder 1 can grind a workpiece W (Figure 4) by rotating the grinding wheel 2 in its circumferential direction D while pressing the grinding wheel 2 against the workpiece W. The workpiece W is, for example, a steel material such as carbon steel or stainless steel. In the following, the terms "up," "down," "front," "back," "left," and "right" are used based on the state in which the grinding wheel 2 is used for grinding the workpiece W (more specifically, the state in which the grinding wheel 2 is suspended from the grinder body 3 in order to use the grinding wheel 2 for grinding the workpiece W). In the following, "circumferential direction D of the grinding wheel 2" will be abbreviated as "circumferential direction D," and "radial direction F of the grinding wheel 2" will be abbreviated as "radial direction F."
[0024] The grinding wheel 2 is a grinding wheel with a circular outer circumference. The grinding wheel 2 is positioned below the grinder body 3 (Figure 1) and is suspended from the grinder body 3 so as to be rotatable in the circumferential direction D, with the center of the grinding wheel 2 as the axis. With the grinding wheel 2 suspended from the grinder body 3, the grinding wheel 2 can be rotated in the circumferential direction D by turning on the switch 6 and driving the motor 10.
[0025] The grinding wheel 2 has a structure in which a grinding plate 30 and a pad 31A are stacked in the vertical direction E, and is suspended from the grinder body 3 such that the pad 31A is positioned above the grinding plate 3 (so that the pad 31A constitutes the upper surface of the grinding wheel 2). The pad 31A constitutes the upper surface 2a and the upper side 2d of the grinding wheel 2, and the grinding plate 30 constitutes the lower side 2d and the lower surface 2b of the grinding wheel 2.
[0026] In the illustrated example, the grinding wheel 30 and the pad 31A are disc-shaped with the same outer diameter (i.e., the outer circumferences of the grinding wheel 30 and the pad 31A are circular with the same outer diameter), but the grinding wheel 30 and the pad 31A may be disc-shaped with different outer diameters, or they may have a shape other than a disc (i.e., the outer circumferences of the grinding wheel 30 and the pad 31A may be circular with different outer diameters, or they may have a shape other than a circle). The thickness E in the vertical direction of the grinding wheel 30 is, for example, 2 mm or more and 7 mm or less. The thickness E in the vertical direction of the pad 31A is, for example, 5 mm or more. However, the present invention does not limit the thickness E in the vertical direction of the grinding wheel 30 and the pad 31A to the above values. In this application, a "plate with a circular outer circumference" is referred to as a "disc".
[0027] Furthermore, as shown in Figure 3, it is preferable to form a projection 43 that protrudes upward from the center of the grinding wheel plate 30, and to fit this projection 43 into a recess 44 formed in the center of the pad 31A. In this way, misalignment of one of the grinding wheel plate 30 and the pad 31A relative to the other can be prevented.
[0028] The grinding wheel plate 30 is a layer in which abrasive grains are bonded together by a binder. In addition to the abrasive grains and binder, the grinding wheel plate 30 may also contain fillers and reinforcing materials.
[0029] The abrasive grains described above are sand-like particles that act as "blades." When grinding a workpiece W using the grinding wheel 2, the grinding wheel 2 is rotated in the circumferential direction D while the grinding wheel plate 30 is pressed against the workpiece W. This causes the abrasive grains protruding from the surface of the grinding wheel plate 30 to come into contact with the workpiece W, resulting in a continuous phenomenon where a very small amount of the workpiece W is scraped away.
[0030] The grinding wheel plate 30 contains general abrasive grains or superabrasive grains as the abrasive grains mentioned above.
[0031] As general abrasive grains to be contained in the grinding wheel plate 30, for example, alumina-based abrasive grains, silicon carbide-based abrasive grains, or ceramic abrasive grains can be used. As the above alumina-based abrasive grains, for example, A abrasive grains (brown alumina) or WA abrasive grains (white alumina) can be used. As the above silicon carbide-based abrasive grains, for example, C abrasive grains (black silicon carbide) or GC abrasive grains (green silicon carbide) can be used.
[0032] For example, CBN abrasive grains (Cubic Boron Nitride abrasive grains) or diamond abrasive grains can be used as the superabrasive grains to be contained in the grinding wheel plate 30.
[0033] The above-mentioned binder is a material used to bond abrasive grains together. A binder containing phenolic resin can be used as a binder to form the grinding wheel plate 30. As an example of this type of binder, a resin bond (an organic binder mainly composed of phenolic resin) can be used. To improve the bonding strength between materials, it is preferable to use a binder containing liquid phenolic resin as the above-mentioned binder. In addition, a binder mainly composed of nickel, a vitrified bond (an inorganic binder mainly composed of glass or ceramics), or a metal bond (a binder mainly composed of bronze-based metals) can also be used as the above-mentioned binder.
[0034] The above-mentioned binder is brittle and easily wears away upon contact with the workpiece W. Due to the properties of this binder, when the grinding wheel 30 comes into contact with the workpiece W, abrasive grains are detached from the surface of the grinding wheel 30, exposing a new surface of the grinding wheel 30, thereby maintaining the grinding performance of the grinding wheel 2. For example, the Rockwell hardness of the above-mentioned phenolic resin is about 100 HRR, which is significantly lower than the Rockwell hardness of carbon steel and stainless steel, which can be used as the workpiece W. For this reason, the binder containing the above-mentioned phenolic resin easily wears away upon contact with carbon steel or stainless steel.
[0035] The above-mentioned fillers are additives that affect the appearance and performance of the grinding wheel 2. The fillers to be included in the grinding wheel plate 30 can include those that suppress deformation of the grinding wheel plate 30 and improve its strength, those that increase the fluidity of the material, those that increase the volume of the grinding wheel plate 30, those that have a cooling effect on the grinding wheel plate 30, those that improve the flexibility of the material, and those that suppress molding defects. The above-mentioned fillers may also contain colorants. For example, carbon-based colorants or iron oxide-based colorants can be used as colorants.
[0036] The above-mentioned reinforcing material is provided to increase the strength of the grinding wheel plate 30. Nonwoven fabric or glass cloth coated with phenolic resin can be used as the reinforcing material. Figure 5 shows an example of glass cloth that can be used as the above-mentioned reinforcing material. The glass cloth 34 shown in Figure 5 is a cloth made of bundled transparent glass fibers and has a yellow coating of phenolic resin applied to its surface.
[0037] The pad 31A is formed from a polymer material or plant fibers. For example, plastic or rubber can be used as the polymer material for forming the pad 31A. For example, polypropylene, nylon 6, polystyrene, acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), or polycarbonate can be used as the plastic for forming the pad 31A. In order to improve the visibility of the grinding plate 30, it is preferable to form the pad 31A from a transparent material, and polycarbonate can be used as the transparent material. When plant fibers are used as the material for the pad 31A, the pad 31A is formed using, for example, paper or cloth made of plant fibers.
[0038] The hardness of the polymer materials (plastics and rubbers) and plant fibers used as the material for pad 31A is significantly lower than the hardness of the general abrasive grains and superabrasive grains contained in the grinding wheel plate 30. Therefore, the grinding performance of pad 31A is significantly lower than that of grinding wheel plate 30.
[0039] Table 1 below shows the hardness of general abrasive grains that can be used as materials for the grinding plate 30, including A abrasive grains (brown alumina), WA abrasive grains (white alumina), C abrasive grains (black silicon carbide), and GC abrasive grains (green silicon carbide). It also shows the hardness of superabrasive grains that can be used as materials for the grinding plate 30, including cubic boron nitride abrasive grains and diamond abrasive grains. Furthermore, it shows the hardness of plastics (polymer materials) that can be used as materials for the bat 31A, including polypropylene, nylon 6, and polystyrene. Finally, it shows the hardness of carbon steel and stainless steel that can be used as workpieces W (objects to be ground).
[0040] [Table 1]
[0041] The "Vickers hardness" shown in Table 1 above is the amount of indentation when a diamond piece of a predetermined shape is pressed against a material (although "Knoop hardness" is not shown in Table 1 above, each of the materials shown in Table 1 above exhibits a Knoop hardness equivalent to that of Vickers hardness). The "Rockwell hardness" shown in Table 1 above is the amount of indentation when an indenter such as a rigid ball or diamond piece of a predetermined size is pressed against a material. Generally, the expression of the indentation amount for "Rockwell hardness" differs depending on the indenter and test load. In this application, "Rockwell hardness" is shown in HRC as the result measured with a test load of 150 kg using an indenter made of a diamond piece, and in HRR as the result measured with a test load of 60 kg using an indenter made of a rigid ball with a diameter of 1 / 2 inch.
[0042] As is clear from Table 1, the A abrasive grains (brown alumina), WA abrasive grains (white alumina), and C abrasive grains (black silicon carbide) and GC abrasive grains (green silicon carbide) exhibit significantly higher Vickers hardness and Rockwell hardness than carbon steel and stainless steel, respectively. Furthermore, cubic boron nitride abrasive grains and diamond abrasive grains are so hard that their Rockwell hardness cannot be measured. Although the Rockwell hardness of cubic boron nitride abrasive grains and diamond abrasive grains is not shown in Table 1 above, cubic boron nitride abrasive grains and diamond abrasive grains have significantly higher Vickers hardness than carbon steel and stainless steel, respectively. For this reason, A abrasive grains (brown alumina), WA abrasive grains (white alumina), C abrasive grains (black silicon carbide), GC abrasive grains (green silicon carbide), cubic boron nitride abrasive grains, and diamond abrasive grains can be said to be suitable materials for grinding carbon steel and stainless steel, respectively.
[0043] Regarding Rockwell hardness, the test load used in measuring HRC is overwhelmingly larger than the test load used in measuring HRR. Therefore, according to the Rockwell hardness values shown in Table 1, it is clear that the hardness of the plastic contained in pad 31A is significantly lower than the hardness of the abrasive grains contained in grinding plate 30.
[0044] When manufacturing the grinding wheel 2 described above, a grinding wheel plate forming step is performed to form the grinding wheel plate 30, a pad forming step is performed to form the pad 31A, and a polymerization step is performed to overlap the grinding wheel plate 30 obtained in the grinding wheel plate forming step and the pad 31A obtained in the pad forming step.
[0045] The grinding wheel plate forming process involves a first step of mixing and drying "abrasive grains, binder, and filler" to form the grinding wheel plate 30; a second step of alternately placing the dried material obtained in the first step and a reinforcing material into a mold; a third step of creating an intermediate for the grinding wheel plate 30 by pressing the material placed in the mold in the second step using a press machine; and a fourth step of obtaining the grinding wheel plate 30 by firing the intermediate obtained in the third step in a furnace.
[0046] The above-mentioned fillers and reinforcing materials are not necessarily required, and the grinding wheel 30 may be manufactured without using them (i.e., the grinding wheel 30 may be a layer containing only abrasive grains and a binder, and not containing fillers or reinforcing materials). In this case, when manufacturing the grinding wheel 30, the following steps are performed: a first step of mixing and drying the "abrasive grains and binder" to form the grinding wheel 30; a second step of putting the dried material obtained in the first step into a mold; a third step of creating an intermediate for the grinding wheel 30 by pressing the material put into the mold in the second step using a press machine; and a fourth step of obtaining the grinding wheel 30 by firing the intermediate obtained in the third step in a furnace.
[0047] In the pad formation process described above, for example, the pad 31A is formed by injection molding.
[0048] In the polymerization process described above, the grinding wheel plate 30 and the pad 31A are bonded together, for example, by using an adhesive to bond them. As the adhesive, for example, an adhesive mainly composed of epoxy resin or an adhesive mainly composed of cyanoacrylate can be used. Alternatively, in the polymerization process described above, the grinding wheel plate 30 and the pad 31A may be bonded together using anchors or screws while they are stacked on top of each other.
[0049] As shown in Figure 1, the main grip 4 extends to the rear from the grinder body 3, and the sub-grip 5 extends to the left from the grinder body 3. The operator uses the disc grinder 1 by gripping the main grip 4 with their right hand and the sub-grip 5 with their left hand. The sub-grip 5 may also extend to the right from the grinder body 3. In this case, the operator uses the disc grinder 1 by gripping the main grip 4 with their left hand and the sub-grip 5 with their right hand.
[0050] Switch 6 is located on the main grip 4, and the operator can switch between the on and off states by operating the switch 6 with the fingers of the hand gripping the main grip 4. In this embodiment, the switch 6 is located on the underside of the main grip 4, but the position of the switch 6 is not particularly limited as long as it is in a position where the operator can operate it. For example, the switch 6 may be located on the sub-grip 5. In this case, the operator can switch between the on and off states by operating the switch 6 with the fingers of the hand gripping the sub-grip 5. It is also preferable that the switch 6 is a paddle switch that is on only when pressed and always off when not pressed.
[0051] The grinder body 3 contains a motor 10 (Figure 6, described later) that rotates the grinding wheel 2. The motor 10 is a rotational power source that is either an electric motor or a pneumatic fluid machine. When the switch 6 is turned on, power is supplied to the motor 10, which drives the motor 10 and causes the grinding wheel 2 to rotate in the circumferential direction D. When the switch 6 is turned off, power is no longer supplied to the motor 10, the motor 10 stops driving, and the rotation of the grinding wheel 2 stops. In the illustrated example, the grinding wheel 2 is connected to the rotation shaft of the motor 10 by inserting the rotation shaft of the motor 10 through a through hole 41 (Figure 3) formed in the center of the grinding wheel 2. When the switch 6 is turned on, the rotation shaft of the motor 10 rotates in its circumferential direction, causing the grinding wheel 2 to rotate in the circumferential direction D. Figure 2 shows an example in which a metal cylinder 42 through which the rotating shaft of the motor 10 is inserted is fitted into the through hole 41 (Figure 3) (although the cylinder 42 is not shown in Figure 3). However, a non-metallic cylinder through which the rotating shaft of the motor 10 is inserted may be fitted into the through hole 41, or the cylinder may be omitted and the rotating shaft of the motor 10 may be inserted directly into the through hole 41.
[0052] Figure 6 is a schematic diagram showing an example of a circuit for driving the motor 10. In the example shown in Figure 6, the motor 10 is a universal motor and is driven by power supplied from the power supply 11. Switch 6 is provided between the motor 10 and the power supply 11. When switch 6 is turned ON, power from the power supply 11 is supplied to the motor 10, driving the motor 10 and rotating the grinding wheel 2. When switch 6 is turned OFF, power is no longer supplied to the motor 10, the motor 10 stops driving, and the rotation of the grinding wheel 2 stops. The power supply 11 is provided in the grinder body 3 or an external device. When the power supply 11 is provided in an external device, for example, the external device and the grinder body 3 are connected via wires, and when switch 6 is turned ON, power from the power supply 11 is supplied to the motor 10 via the wires, driving the motor 10 and rotating the grinding wheel 2.
[0053] The present invention does not limit the circuit for driving the motor 10 to the above example. Various circuits can be applied to the disc grinder 1 of the present invention as a circuit for driving the motor 10, such as one in which the grinding wheel 2 is rotated when the switch 6 is turned on and the grinding wheel 2 is stopped when the switch 6 is turned off.
[0054] As shown in Figure 1, the disc guard 7 comprises an upper guard portion 20 and an outer guard portion 21. The upper guard portion 20 has an arc shape in plan view, and the outer guard portion 21 extends downward from the outer circumference of the upper guard portion 20. The above "plan view" means "a view of the disc grinder 1 in the vertical direction of the grinding wheel 2".
[0055] The disc guard 7 is attached to the outer circumference of the grinder body 3 such that the upper guard portion 20 is located above the rear region of the grinding wheel 2, and the outer guard portion 21 is located outside the rear region of the grinding wheel 2 in the radial direction F. The front region 2e of the grinding wheel 2 is exposed and not covered by the disc guard 7. The attachment of the inner circumference of the upper guard portion 20 to the outer circumference of the grinder body 3 can be achieved, for example, by providing a protruding plate that projects radially outward from the outer circumference of the grinder body 3, and bonding, welding, or fastening the inner circumference of the upper guard portion 20 to the protruding plate. However, the present invention is not limited to the above method for attaching the inner circumference of the upper guard portion 20 to the outer circumference of the grinder body 3. In the disc grinder 1 of the present invention, various methods can be applied to attach the inner circumference of the upper guard portion 20 to the outer circumference of the grinder body 3 such that the upper guard portion 20 is located above the rear region of the grinding wheel 2 and the outer guard portion 21 is located outside the radial direction F of the rear region of the grinding wheel 2.
[0056] When grinding a workpiece W, as shown in Figure 4, the operator presses the grinding wheel 30 against the workpiece W while rotating the grinding wheel 2 in the circumferential direction D. This pressing is performed each time a grinding operation is performed, causing the grinding wheel 30 to wear down and its thickness to gradually decrease. As shown in the bottom diagram of Figure 4, when the grinding wheel 30 is worn down to the point where the pad 31A contacts the workpiece W, the hardness of the material of the pad 31A (plastic or plant fiber) is lower than the hardness of the general abrasive grains or superabrasive grains contained in the grinding wheel 30, and the grinding performance of the pad 31A is inferior to that of the grinding wheel 30. This prompts the operator to stop using the grinding wheel 2 and replace it with a new one. In Figure 4, an example is shown in which the workpiece W is ground by pressing the lower surface 2b of the grinding wheel 30 or the lower corner 2c of the grinding wheel 30 (i.e., the corner 2c that forms the boundary between the lower surface 2b and the side surface 2d of the grinding wheel 30) against the workpiece W. However, the side surface 2d of the grinding plate 30 can also be pressed against the workpiece W for grinding purposes.
[0057] According to the above embodiment, since the upper surface 2a of the grinding wheel 2 is made of a pad 31A formed from a low-hardness polymer material (e.g., plastic or rubber) or plant fiber, the risk of injury to the worker is reduced even if the worker comes into contact with the upper surface 2a of the grinding wheel 2.
[0058] Furthermore, according to the above embodiment, since the upper side of the side surface 2d of the grinding wheel 2 is made up of a pad 31A, even if an operator comes into contact with the side surface 2d of the grinding wheel 2, the grinding wheel 2 is less likely to cause deep injury to the operator's body.
[0059] The present invention is not limited to the embodiments described above and can be modified in various ways. Modifications of the present invention are described below. In the following description, components corresponding to those shown in the embodiments above are denoted by the same reference numerals as in the embodiments above, and detailed descriptions are omitted.
[0060] The grinding wheel 2 described above may be equipped with a pad 31B, as shown in Figures 7, 8, and 9, instead of pad 31A (i.e., the grinding wheel 2 may have a laminated structure in which the grinding wheel plate 30 and the pad 31B are stacked in the vertical direction E). The pad 31B, like pad 31A, is formed from a polymer material or plant fiber. In order to improve the visibility of the grinding wheel plate 30, it is preferable to form the pad 31B from a transparent material, and polycarbonate can be used as such a transparent material.
[0061] As shown in Figure 9, the pad 31B comprises a disc 50, an annular wall 51 projecting downward from the outer circumference of the disc 50, and a plurality of linear protrusions 52 projecting downward from the disc 50 inside the annular wall 51, with each of the linear protrusions 52 extending in the radial direction of the disc 50 (the radial direction F of the grinding wheel 2).
[0062] The pad 31B is positioned above the grinding wheel plate 30, and in the vertical direction E, the annular wall 51 and the plurality of linear protrusions 52 are positioned between the disc 50 and the grinding wheel plate 30. With this arrangement, the disc 50 constitutes the upper surface 2a of the grinding wheel 2, the annular wall 51 constitutes the upper side 2d of the grinding wheel 2, and the grinding wheel plate 30 constitutes the lower side 2d of the grinding wheel 2 and the lower surface 2b of the grinding wheel 2.
[0063] In the illustrated example, multiple linear protrusions 52 are arranged radially at equal angular intervals in the circumferential direction of the disc 50 (circumferential direction D of the grinding wheel 2), but the angular intervals of the multiple protrusions 52 do not have to be equal. Also, in the illustrated example, one end of each protrusion 52 is connected to the annular wall 51, but there may be a gap between each protrusion 52 and the annular wall 51. It is preferable that the height E in the vertical direction of each protrusion 52 is less than or equal to the height E in the vertical direction of the annular wall 51. Also, in the illustrated example, the outer circumferences of the grinding wheel plate 30 and the pad 31B are circular with the same outer diameter, but the outer circumferences of the grinding wheel plate 30 and the pad 31B may be circular with different outer diameters, or may have a shape other than a circle.
[0064] Through holes 54 for air circulation are formed in the disc 50. In the illustrated example, one through hole 54 is formed between two adjacent protrusions 52, 52 in the circumferential direction of the disc 50, but the number and position of the through holes 54 can be set arbitrarily.
[0065] When manufacturing a modified version of the grinding wheel 2 described above, a grinding wheel plate forming step is performed to form the grinding wheel plate 30, a pad forming step is performed to form the pad 31B, and a polymerization step is performed to overlap the grinding wheel plate 30 obtained in the grinding wheel plate forming step and the pad 31B obtained in the pad forming step. The grinding wheel plate forming step is the same as the step in the above embodiment. In the pad forming step, for example, the pad 31B is formed by injection molding. In the bonding step, for example, the grinding wheel plate 30 and the pad 31B are bonded together by bonding them using an adhesive. As the adhesive, for example, an adhesive mainly composed of epoxy resin or an adhesive mainly composed of cyanoacrylate can be used. In the polymerization step, the grinding wheel plate 30 and the pad 31B may be fixed together using anchors or screws while they are overlapped.
[0066] In the modified grinding wheel 2 shown in Figures 7 to 9, a hole for inserting the rotating shaft of the motor 10 is formed in the center (the hole 55 shown in Figure 9 is part of the above hole and is formed in the center of the pad 31B). When the switch 6 is turned on, the rotating shaft of the motor 10 rotates in its circumferential direction, causing the grinding wheel 2 to rotate in the circumferential direction D. Figure 7 shows an example in which a metal cylinder 48 for inserting the rotating shaft of the motor 10 is fitted into the above hole, but a non-metallic cylinder for inserting the rotating shaft of the motor 10 may be fitted into the above hole. Alternatively, the above cylinder may be omitted, and the rotating shaft of the motor 10 may be directly inserted into the hole of the grinding wheel 2.
[0067] When the grinding wheel 2 is equipped with the pad 31B described above, the grinding wheel 2 is suspended from the grinder body 3 such that the pad 31B is positioned above the grinding wheel plate 3 (so that the pad 31B forms the upper surface of the grinding wheel 2). When grinding a workpiece W, the operator rotates the grinding wheel 2 in the circumferential direction D while pressing the grinding wheel plate 30 against the workpiece W. When the grinding wheel plate 30 is worn down to the point where the pad 31B contacts the workpiece W, the hardness of the pad 31B is lower than that of the grinding wheel plate 30, and the grinding performance of the pad 31B is inferior to that of the grinding wheel plate 30, prompting the operator to stop using the grinding wheel 2 and replace it with a new one.
[0068] If the grinding wheel 2 is equipped with the pad 31B described above, the upper surface 2a of the grinding wheel 2 is made of a pad 31B formed from a low-hardness polymer material (e.g., plastic or rubber) or plant fiber, so even if the worker comes into contact with the upper surface 2a of the grinding wheel 2, the risk of injury to the worker can be reduced.
[0069] Furthermore, since the upper side of the side 2d of the grinding wheel 2 is made up of a pad 31B, even if the worker comes into contact with the side 2d of the grinding wheel 2, it is less likely that the grinding wheel 2 will deeply injure the worker's body.
[0070] Furthermore, if the grinding wheel 2 is equipped with the pad 31B described above, the pad 31B can be made hollow to reduce the weight of the grinding wheel 2 and lower the material cost of the grinding wheel 2. In addition, the projection 52 can be formed on the disc 50 to increase the strength of the pad 31B. Note that the projection 52 is not necessarily required and does not have to be formed on the pad 31B. In this case, the pad 31B is positioned above the grinding wheel plate 30, and the annular wall 51 is positioned between the disc 50 and the grinding wheel plate 30 in the vertical direction E. As a result, the disc 50 constitutes the upper surface 2a of the grinding wheel 2, the annular wall 51 constitutes the upper side 2d of the grinding wheel 2, and the grinding wheel plate 30 constitutes the lower side 2d of the grinding wheel 2 and the lower surface 2b of the grinding wheel 2.
[0071] Furthermore, if the grinding wheel 2 is equipped with the pad 31B described above, the through hole 54 is formed in the disc 50, allowing the heat generated in the grinding wheel plate 30 by contact with the workpiece W to be released through the through hole 54. This allows the temperature of the grinding wheel 2 to be kept low. It is preferable that the outer circumference of the grinding wheel plate 30 be visible from above the grinding wheel 2 through the through hole 54. In this way, the degree of wear of the grinding wheel plate 30 can be determined (the "outer circumference of the grinding wheel plate 30" refers to the area of the grinding wheel plate 30 that includes the outer circumference and has a predetermined width in the radial direction F, in the state before the grinding wheel 2 is put into use (i.e., when no wear due to grinding has occurred on the grinding wheel 2)).
[0072] The pad 31B of the grinding wheel 2 (Figures 7 and 8) can be changed to the one shown in Figure 10. The modified pad 31B shown in Figure 10 is disc-shaped and comprises a central portion 56 that forms the center of the pad 31B and an annular surrounding portion 57 that surrounds the outside of the central portion 56. The thickness of the surrounding portion 57 in the vertical direction E is greater than the thickness of the central portion 56 in the vertical direction E (i.e., the surrounding portion 57 is thicker than the central portion 56).
[0073] When the grinding wheel 2 is equipped with the modified pad 31B (Figure 10) described above, the pad 31B is positioned above the grinding wheel plate 30 (Figures 7 and 8). The pad 31B constitutes the upper surface 2a of the grinding wheel 2 and the upper side of the side surface 2d of the grinding wheel 2, while the grinding wheel plate 30 constitutes the lower side of the side surface 2d of the grinding wheel 2 and the lower surface 2b of the grinding wheel 2.
[0074] In the modified pad 31B (Figure 10) described above, through holes 54 for air circulation are also formed. In the illustrated example, the through holes 54 are formed in the surrounding portion 57, but the through holes 54 may also be formed in the central portion 56. In the illustrated example, multiple through holes 54 are formed at angular intervals equal to the circumferential direction D of the grinding wheel 2, but the position and number of through holes 54 can be set arbitrarily. Furthermore, even when the grinding wheel 2 (Figures 7 and 8) is equipped with the modified pad 31B (Figure 10) described above, it is preferable that the outer periphery of the grinding wheel plate 30 (Figure 9) be visible from above the grinding wheel 2 through the through holes 54 (Figure 10) (the "outer periphery of the grinding wheel plate 30" refers to the area of the grinding wheel plate 30 that includes the outer periphery of the grinding wheel plate 30 and has a predetermined width in the radial direction F, in the state before the grinding wheel 2 is put into use (i.e., when no wear due to grinding has occurred on the grinding wheel 2)).
[0075] Even when the grinding wheel 2 is equipped with the modified pad 31B (Figure 10) described above, the grinding wheel 2 has a hole in the center for inserting the rotation shaft of the motor 10, and a part of this hole is formed by the hole 55 formed in the center of the pad 31B (Figure 10). When the switch 6 is turned on, the rotation shaft of the motor 10 rotates in its circumferential direction, causing the grinding wheel 2 to rotate in the circumferential direction D.
[0076] The through-holes 54 shown in Figures 9 and 10 are not necessarily required and do not need to be formed in the pad 31B. In this case, for example, it is preferable to form the pad 31B from a transparent material in order to make the grinding wheel plate 30 visible from above the grinding wheel 2. For example, polycarbonate can be used as the transparent material for forming the pad 31B.
[0077] Figures 11 and 12 are perspective views showing modified examples of the pad 31B formed from the transparent material described above.
[0078] The modified pad 31B shown in Figure 11 comprises a disc 50, an annular wall 51, a plurality of linear protrusions 52, and an annular protrusion 58. The annular wall 51 protrudes downward from the outer circumference of the disc 50. The plurality of linear protrusions 52 and the annular protrusion 58 protrude downward from the disc 50 inside the annular wall 51. Each of the plurality of linear protrusions 52 extends in the radial direction of the disc 50 (radial direction F of the grinding wheel 2). The annular protrusion 58 extends in the circumferential direction of the disc 50 (circumferential direction D of the grinding wheel 2) so as to intersect with each of the linear protrusions 52.
[0079] In the modified pad 31B shown in Figure 11, a plurality of linear protrusions 52 are arranged radially at equal angular intervals in the circumferential direction of the disc 50 (circumferential direction D of the grinding wheel 2), but the angular intervals of the plurality of linear protrusions 52 do not have to be equal. Also, in the illustrated example, one end of each linear protrusion 52 is connected to the annular wall 51, but there may be a gap between each linear protrusion 52 and the annular wall 51. It is preferable that the height E in the vertical direction of each linear protrusion 52 and the height E in the vertical direction of the annular protrusion 58 be less than or equal to the height E in the vertical direction of the annular wall 51. Furthermore, the outer circumference of the grinding wheel plate 30 and the pad 31B may be circular with the same outer diameter, circular with different outer diameters, or have a shape other than a circle.
[0080] The pad 31B shown in Figure 11 is positioned above the grinding wheel plate 30 (Figures 7-8), and in the vertical direction E, the annular wall 51, the multiple linear protrusions 52, and the annular protrusion 58 are positioned between the disc 50 and the grinding wheel plate 30. With this arrangement, the pad 31B shown in Figure 11 constitutes the upper surface 2a of the grinding wheel 2 and the upper side of the side surface 2d of the grinding wheel 2, while the grinding wheel plate 30 (Figures 7 and 8) constitutes the lower side of the side surface 2d of the grinding wheel 2 and the lower surface 2b of the grinding wheel 2.
[0081] The modified pad 31B shown in Figure 12 comprises a disc 50, an annular wall 51, a plurality of linear protrusions 52, an annular protrusion 58, and a plurality of reinforcing protrusions 59. The disc 50, linear protrusions 52, and annular protrusions 58 have the same characteristics as those shown in Figure 11.
[0082] Multiple reinforcing protrusions 59 project downward from the disc 50 inside the annular protrusion 58. Two reinforcing protrusions 59 are provided for each linear protrusion 52. In each pair of reinforcing protrusions 59, 59, one reinforcing protrusion 59 is provided on one side of the disc 50 in the circumferential direction (one side of the circumferential direction D of the grinding wheel 2) relative to the linear protrusion 52, and the other reinforcing protrusion 59 is provided on the other side of the disc 50 in the circumferential direction (the other side of the circumferential direction D of the grinding wheel 2) relative to the linear protrusion 52. The side edge of the other side of the disc 50 in the circumferential direction (the other side of the circumferential direction D of the grinding wheel 2) of the one reinforcing protrusion 59 is connected to the linear protrusion 52, and the side edge of the other reinforcing protrusion 59 is connected to the linear protrusion 52 on one side of the disc 50 in the circumferential direction (one side of the circumferential direction D of the grinding wheel 2) of the other reinforcing protrusion 59. As a result, each of the linear projections 52 is reinforced by the one and the other reinforcing projections 59, 59 described above.
[0083] In the modified version of the pad 31B shown in Figure 12, in order to reduce weight, each reinforcing projection 59 has a shape in which the width in the vertical direction E becomes narrower as it moves away from the linear projection 52. In the illustrated example, each reinforcing projection 59 forms a right-angled isosceles triangle when viewed in the radial direction of the disc 50 (radial direction D of the grinding wheel 2), with the edge 59a of one equal side of the right-angled isosceles triangle being connected to the disc 50, and the edge 59b of the other equal side of the right-angled isosceles triangle being connected to the linear projection 52. Note that the shape of each reinforcing projection 59 is not limited to the shape shown in the illustrated example, and can be various shapes that connect to the disc 50 and the linear projection.
[0084] The pad 31B shown in Figure 12 is positioned above the grinding wheel plate 30 (Figures 7-8), and in the vertical direction E, the annular wall 51, a plurality of linear protrusions 52, an annular protrusion 58, and a plurality of reinforcing protrusions 59 are positioned between the disc 50 and the grinding wheel plate 30. With this arrangement, the pad 31B shown in Figure 12 constitutes the upper surface 2a of the grinding wheel 2 and the upper side of the side surface 2d of the grinding wheel 2, while the grinding wheel plate 30 (Figures 7, 8) constitutes the lower side of the side surface 2d of the grinding wheel 2 and the lower surface 2b of the grinding wheel 2.
[0085] Even when the grinding wheel 2 is equipped with the pad 31B shown in Figures 11 and 12, the grinding wheel 2 is suspended from the grinder body 3 such that the pad 31B is positioned above the grinding wheel plate 3 (so that the pad 31B constitutes the upper surface of the grinding wheel 2). To perform this suspension, the grinding wheel 2 is connected to the rotating shaft of the motor 10 by passing the rotating shaft of the motor 10 through a hole formed in the center of the grinding wheel 2. The hole 55 shown in Figures 11 and 12 constitutes a part of the above hole and is formed in the center of the pad 31B.
[0086] Each time the workpiece W is ground, the grinding wheel 30 is pressed against the workpiece W, causing it to wear down. However, since the pad 31B shown in Figures 11 and 12 is made of a transparent material, the operator can visually inspect the grinding wheel 30 from above the grinding wheel 2 and check the degree of wear on the grinding wheel 30. It should be noted that the present invention is not limited to forming the pad 31B shown in Figures 11 and 12 from a transparent material; the pad 31B shown in Figures 11 and 12 may be made from an opaque material.
[0087] Furthermore, in the example of the grinding wheel 2 described above, the outer diameter of the pad 31A or 31B may be larger than the outer diameter of the grinding wheel plate 30, as shown in Figure 13. In this way, even if an operator accidentally comes into contact with the rotating grinding wheel 2, the pad 31A or 31B with lower grinding performance will come into contact with the operator, while the grinding wheel plate 30 with higher grinding performance will not come into contact with the operator. Thus, serious injury to the operator can be avoided.
[0088] Furthermore, in the example of the grinding wheel 2 described above, in order to prevent misalignment of one of the grinding wheel plate 30 and the pad 31 relative to the other, a protrusion that protrudes upward from the center of the grinding wheel plate 30 may be formed, and this protrusion may be fitted into a recess 61 formed in the center of the pad 31 (in the examples shown in Figures 14 to 16 and Figure 17, a protrusion 60 that protrudes upward from the center of the grinding wheel plate 30 is formed, and this protrusion 60 is fitted into a recess 61 formed in the center of the pad 31A).
[0089] Furthermore, in the example of the grinding wheel 2 described above, as shown in Figure 17, the outer diameter of the grinding wheel 2 may be made to increase as the outer diameter of the grinding wheel 2 increases towards the top, by increasing the outer diameter of the grinding wheel 30 and the pad 31A or 31B as they move upwards, so that the outer diameter of the upper end 30x of the grinding wheel plate 30 matches the outer diameter of the lower end 31x of the pad 31A or 31B.
[0090] Furthermore, in the example of the grinding wheel 2 described above, the grinding wheel plate 30 and the pad 31A or 31B may be separated in the vertical direction E, as shown in Figure 18. In this way, as shown in the bottom figure of Figure 18, even when the diameter of the grinding wheel plate 30 has decreased due to wear, the workpiece W can be ground by the grinding wheel plate 30, which has high grinding performance, without the workpiece W coming into contact with the pad 31A or 31B, which has low grinding performance.
[0091] As described above, separating the grinding wheel 30 and the pad 31 in the vertical direction E can be achieved, for example, by placing a resin or metal spacer (not shown) between the grinding wheel 30 and the pad 31A or 31B. In this case, for example, the grinding wheel 30 and the pad 31 are joined via the spacer by bonding both the grinding wheel 30 and the pad 31 to the spacer using an adhesive.
[0092] Furthermore, in the example of the grinding wheel 2 described above, the inner circumference of the grinding wheel 30 and the inner circumference of the pad 31A or 31B may be joined so that the outer circumference of the grinding wheel 30 and the outer circumference of the pad 31A or 31B are separated in the vertical direction E (Figures 19 and 20 show an example of a grinding wheel 2 in which the inner circumference 30b of the grinding wheel 30 and the inner circumference 31b of the pad 31A are joined so that the outer circumference 30a of the grinding wheel 30 and the outer circumference 31a of the pad 31A are separated in the vertical direction E). In this way, even when the diameter of the grinding wheel 30 has decreased due to wear of the grinding wheel 30, the workpiece W can be ground with the grinding wheel 30, which has high grinding performance, without bringing the workpiece W into contact with the pad 31A or 31B, which has low grinding performance. Furthermore, from the viewpoint of preventing the workpiece W from coming into contact with the pad 31A or 31B, which has low grinding performance, it is preferable to make the thickness of the pad 31A or 31B thinner than the thickness of the grinding wheel plate 30 (in the example shown in Figure 20, the thickness of the pad 31A is thinner than the thickness of the grinding wheel plate 30).
[0093] Furthermore, in the example of the grinding wheel 2 described above, a recess may be formed on the upper surface of the pad 31A or 31B from the viewpoint of reducing weight (Figures 21 and 22 show an example of a grinding wheel 2 in which a recess 62 is formed on the upper surface of the pad 31A). The recess may be formed in the center of the upper surface of the pad 31, or on the outside of the upper surface of the pad 31. The number of recesses formed on the upper surface of the pad 31 may be one or any number.
[0094] Furthermore, in the example of the grinding wheel 2 described above, the outer circumference of the grinding wheel plate 30 may be in contact with the outer circumference of the pad 31A or 31B, the inner circumference of the grinding wheel plate 30 may be in contact with the inner circumference of the pad 31A or 31B, and the grinding wheel plate 30 and the pad 31A or 31B may be joined together such that there is a gap between the intermediate portion between the outer circumference and the inner circumference of the grinding wheel plate 30 and the intermediate portion between the outer circumference and the inner circumference of the pad 31A or 31B (Figure 2). Figures 2-24 show an example of a grinding wheel 2 in which the grinding wheel 30 and the pad 31A are joined together such that the outer circumference 30a of the grinding wheel 30 and the outer circumference 31a of the pad 31A are in contact, the inner circumference 30b of the grinding wheel 30 and the inner circumference 31b of the pad 31A are in contact, and the intermediate portion 30c between the outer circumference 30a and the inner circumference 30b of the grinding wheel 30 and the intermediate portion 31c between the outer circumference 31a and the inner circumference 31b of the pad 31A are separated.
[0095] Furthermore, the example of the grinding wheel 2 described above may also include an annular body joined to the pad 31A or 31B so as to surround the outer circumference of the pad 31A or 31B (Figures 24 and 25 show an example of the grinding wheel 2 including an annular body 63 joined to the pad 31A so as to surround the outer circumference of the pad 31A).
[0096] If the grinding wheel 2 includes the above-mentioned annular body, the annular body is formed from a polymer material or plant fiber, and the Rockwell hardness of the annular body is lower than the Rockwell hardness of the pad 31A or 31B. For example, as the polymer material for forming the annular body, Teflon®, urethane rubber, polypropylene, or acrylonitrile butadiene styrene (abbreviated as ABS) can be used. It is preferable that the annular body be formed from a transparent material.
[0097] As described above, if the grinding wheel 2 is equipped with an annular body, the annular body, which has lower grinding performance than the pad 31A or 31B, surrounds the pad 31A or 31B, thereby further reducing the risk of injury to the worker from contact with the grinding wheel 2.
[0098] Furthermore, if the grinding wheel 2 includes the annular body described above, it is preferable to make the outer diameter of the annular body larger than the outer diameter of the grinding wheel plate 30 (in the example shown in Figure 25, the outer diameter of the annular body 63 is larger than the outer diameter of the grinding wheel plate 30). In this way, even if an operator comes into contact with the rotating grinding wheel 2, the annular body 63 with low grinding performance will come into contact with the operator, while the grinding wheel plate 30 with high grinding performance will not come into contact with the operator.
[0099] In the example of the grinding wheel 2 described above, a projection that protrudes upward from the center of the grinding wheel plate 30 may be formed, and a bowl-shaped projection that protrudes upward from the center of the pad 31A or 31B may be formed, and the projection 70 of the grinding wheel plate 30 may be fitted into the recess 72 of the projection of the pad 31A or 31B (Figures 26 to 28 show an example of a grinding wheel 2 in which a projection 70 that protrudes upward from the center of the grinding wheel plate 30 is formed, and a bowl-shaped projection 71 that protrudes upward from the center of the pad 31A is formed, and the projection 70 is fitted into the recess 72 of the projection 71). Even in this manner, misalignment of one of the grinding wheel plate 30 and the pad 31A or 31B relative to the other can be prevented.
[0100] The grinding wheel 2 described above may be equipped with a pad 31C, as shown in Figures 29 to 31, instead of pads 31A and 31B (i.e., the grinding wheel 2 may have a laminated structure in which the grinding plate 30 and the pad 31C are stacked in the vertical direction E). The pad 31C, like pads 31A and 31B, is formed from a polymer material or plant fiber. To improve the visibility of the grinding plate 30, it is preferable to form the pad 31C from a transparent material, and polycarbonate can be used as the transparent material.
[0101] The pad 31C comprises a disc 80 and an annular wall 81 that protrudes downward from the outer circumference of the disc 80.
[0102] The pad 31C is positioned such that the disc 80 covers the upper surface 30d of the grinding wheel plate 30, and the annular wall 81 covers the upper side of the side surface 30e of the grinding wheel plate 30. With this arrangement, the disc 80 constitutes the upper surface 2a of the grinding wheel 2, the annular wall 81 constitutes the upper side of the side surface 2d of the grinding wheel plate 30, and the grinding wheel plate 30 constitutes the lower side of the side surface 2d of the grinding wheel 2 and the lower surface 2b of the grinding wheel 2.
[0103] When manufacturing a modified version of the grinding wheel 2 described above, a grinding wheel plate forming step is performed to form the grinding wheel plate 30, a pad forming step is performed to form the pad 31C, and a polymerization step is performed to overlap the grinding wheel plate 30 obtained in the grinding wheel plate forming step and the pad 31C obtained in the pad forming step. The grinding wheel plate forming step is the same as the step in the above embodiment. In the pad forming step, for example, the pad 31C is formed by injection molding. In the bonding step, for example, the grinding wheel plate 30 and the pad 31C are bonded together by using an adhesive. As the adhesive, for example, an adhesive mainly composed of epoxy resin or an adhesive mainly composed of cyanoacrylate can be used. In the polymerization step, the grinding wheel plate 30 and the pad 31C may be fixed together using anchors or screws while the grinding wheel plate 30 and the pad 31C are overlapped.
[0104] In the modified grinding wheel 2 shown in Figures 29 to 31, a hole 82 for inserting the rotating shaft of the motor 10 is formed in the center. When the switch 6 is turned on, the rotating shaft of the motor 10 rotates in its circumferential direction, causing the grinding wheel 2 to rotate in the circumferential direction D. A metal or non-metallic cylindrical body for inserting the rotating shaft of the motor 10 may be fitted into the hole 82. Alternatively, the above cylindrical body may be omitted, and the rotating shaft of the motor 10 may be inserted directly into the hole 82.
[0105] When the grinding wheel 2 is equipped with the pad 31C described above, the grinding wheel 2 is suspended from the grinder body 3 such that the disc 80 of the pad 31C is positioned above the grinding wheel plate 30 (so that the disc 80 of the pad 31C forms the upper surface of the grinding wheel 2). When grinding a workpiece W, the operator rotates the grinding wheel 2 in the circumferential direction D while pressing the grinding wheel plate 30 against the workpiece W. When the grinding wheel plate 30 is worn down to the point where the pad 31C contacts the workpiece W, the hardness of the pad 31C is lower than that of the grinding wheel plate 30, and the grinding performance of the pad 31C is inferior to that of the grinding wheel plate 30, prompting the operator to stop using the grinding wheel 2 and replace it with a new one.
[0106] According to the modified grinding wheel 2 shown in Figures 29 to 31, the upper surface of the grinding wheel 2 is made of a pad 31C formed from a low-hardness polymer material (e.g., plastic or rubber) or plant fiber, thus reducing the risk of injury to the worker even if they come into contact with the upper surface of the grinding wheel 2.
[0107] Furthermore, according to the modified grinding wheel 2 shown in Figures 29 to 31, the upper side of the side surface 2d of the grinding wheel 2 is made up of a pad 31A, so even if an operator comes into contact with the side surface 2d of the grinding wheel 2, the grinding wheel 2 is less likely to cause deep injury to the operator's body.
[0108] The pad 31C of the grinding wheel 2 (Figures 29 to 31) can be changed to the one shown in Figures 32 to 34. The pad 31C shown in Figures 32 to 34 differs from the one shown in Figures 29 to 31 in that the height of the annular wall 81 in the vertical direction E is different, and the height of the annular wall 81 in the vertical direction E is set to be hard enough to cover the entire side surface 30e of the grinding wheel plate 30.
[0109] In the modified grinding wheel 2 shown in Figures 32 to 34, the disc 80 is arranged to cover the upper surface 30d of the grinding wheel plate 30, and the annular wall 81 is arranged to cover the entire side surface 30e of the grinding wheel plate 30. Thus, the disc 80 constitutes the upper surface 2a of the grinding wheel 2, the annular wall 81 constitutes the entire side surface 2d of the grinding wheel plate 30, and the grinding wheel plate 30 constitutes the lower surface 2b of the grinding wheel 2.
[0110] According to the modified grinding wheel 2 shown in Figures 32 to 34, since the upper surface of the grinding wheel 2 is made up of a pad 31C, the risk of injury to the worker is reduced even if the worker comes into contact with the upper surface of the grinding wheel 2. Furthermore, since the entire side surface 2d of the grinding wheel 2 is made up of a pad 31C, the risk of injury to the worker is further reduced if the worker comes into contact with the side surface 2d of the grinding wheel 2.
[0111] Furthermore, the grinder body of the disc grinder 1 of the present invention is not limited to the grinder body 3 shown in Figure 1. Various devices can be used as the grinder body for the disc grinder 1 of the present invention, which can rotatably suspend the grinding wheel 2 with the pads 31A, 31B, and 31C forming the upper surface of the grinding wheel 2, and which incorporate a motor for rotating the grinding wheel 2. [Explanation of Symbols]
[0112] 1. Angle grinder 2. Grinding Wheel 2a Upper surface of the grinding wheel 2b Lower surface of the grinding wheel 2d Side view of a grinding wheel 3. Grinder body 30 Sharpening Stones 30d Top surface of the grinding stone 30e Side of the grinding stone 31A, 31B, 31C pads 50,80 disk 51,81 Ring Wall 52 Linear process 54 Through hole 56 Central part 57 Enclosing part 58 Annular projection 63 Ring-shaped body D Circumferential direction of the grinding wheel E Vertical direction
Claims
1. A grinding wheel that is pressed against a workpiece while being rotated in the circumferential direction in order to grind the workpiece, It has a structure in which the grinding plate and the pad are stacked in the vertical direction. The grinding wheel plate is made of abrasive grains bonded together by a binder, and the grinding wheel plate contains general abrasive grains or superabrasive grains as the abrasive grains. The pad is formed from a polymer material or plant fiber and constitutes the upper surface of the grinding wheel.
2. The pad comprises a disc and an annular wall protruding downward from the outer circumference of the disc. The grinding wheel according to claim 1, wherein the pad is arranged such that the disc covers the upper surface of the grinding wheel plate and the annular wall covers the upper side of the grinding wheel plate, the disc constitutes the upper surface of the grinding wheel, the annular wall constitutes the upper side of the grinding wheel plate, and the grinding wheel plate constitutes the lower side of the grinding wheel plate and the lower surface of the grinding wheel.
3. The pad comprises a disc and an annular wall protruding downward from the outer circumference of the disc. The grinding wheel according to claim 1, wherein the pad is arranged such that the disc covers the upper surface of the grinding wheel plate and the annular wall covers the side surface of the grinding wheel plate, so that the disc constitutes the upper surface of the grinding wheel, the annular wall constitutes the side surface of the grinding wheel plate, and the grinding wheel plate constitutes the lower surface of the grinding wheel.
4. The pad comprises a disc and an annular wall protruding downward from the outer circumference of the disc. The grinding wheel according to claim 1, wherein the pad is positioned above the grinding wheel plate, and the annular wall is positioned between the disc and the grinding wheel plate in the vertical direction, so that the disc constitutes the upper surface of the grinding wheel, the annular wall constitutes the upper side surface of the grinding wheel, and the grinding wheel plate constitutes the lower side surface of the grinding wheel and the lower surface of the grinding wheel.
5. The pad further comprises a plurality of linear protrusions and an annular protrusion, The plurality of linear protrusions and the annular protrusion project downward from the disc on the inside of the annular wall, Each of the aforementioned linear projections extends radially to the disk, and the annular projection extends circumferentially to the disk so as to intersect with each of the linear projections. The grinding wheel according to claim 4, wherein the pad is positioned above the grinding wheel plate, and the pad is arranged such that, in the vertical direction, the annular wall, the plurality of linear protrusions, and the annular protrusions are positioned between the disc and the grinding wheel plate.
6. The pad has a disc shape and comprises a central portion that forms the center of the pad and an annular surrounding portion that surrounds the outside of the central portion. The vertical thickness of the surrounding portion is greater than the vertical thickness of the central portion. The grinding wheel according to claim 1, wherein the pad is positioned above the grinding wheel plate, so that the pad constitutes the upper surface of the grinding wheel and the upper side surface of the grinding wheel, and the grinding wheel plate constitutes the lower side surface of the grinding wheel and the lower surface of the grinding wheel.
7. The grinding wheel according to claim 1, wherein the outer diameter of the pad is larger than the outer diameter of the grinding plate.
8. The grinding wheel according to claim 1, wherein the inner circumference of the grinding wheel plate and the inner circumference of the pad are joined together such that the outer circumference of the grinding wheel plate and the outer circumference of the pad are separated in the vertical direction.
9. The pad further comprises an annular body joined to the pad so as to surround the outer circumference of the pad, The grinding wheel according to claim 1, wherein the annular body is formed from a polymer material or plant fiber, and the Rockwell hardness of the annular body is lower than the Rockwell hardness of the pad.
10. The grinding wheel according to claim 1, wherein the pad has through holes for air circulation.
11. The abrasive wheel according to claim 1, wherein the pad is formed from a transparent material.
12. A grinding wheel according to any one of claims 1 to 11, Equipped with a grinder body, The grinding wheel is rotatably suspended from the grinder body with the pad forming the upper surface of the grinding wheel. The aforementioned grinder body is a disc grinder in which a motor for rotating the grinding wheel is built in.