Portable polishing machine

Abstract

To provide a portable polishing machine which can reduce at least one of mass and size of a weight.SOLUTION: A portable polishing machine comprises: a rotatable output shaft which extends in an axial direction; a polishing part which performs an eccentric circular motion in accompany with rotation of the output shaft; a dust collection fan which is fixed to the output shaft surrounding the output shaft in a circumferential direction; a motor which is arranged in an opposite side of the polishing part relative to the dust collection fan in the axial direction to provide the output shaft with rotation driving force; a motor cooling fan which is arranged between the dust collection fan and the motor in the axial direction; a first weight which is attached to one of the dust collection fan and the motor cooling fan and whose relative density is larger than the one of the fans; and a second weight which is arranged at a position different from the first weight in the axial direction.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a portable grinder.

Background Art

[0002] As a portable grinder, an orbital sander has been conventionally known. The orbital sander causes a pad connected to one end of an output shaft (for example, a motor shaft) to perform an eccentric circular motion (orbital motion). A sanding paper is attached to the pad. By pressing the sanding paper against the workpiece to be polished, a polishing operation can be performed.

[0003] In such an orbital sander, vibrations occur along with the eccentric circular motion of the pad. In order to reduce the occurrence of such vibrations, a weight (counterweight) is directly or indirectly attached to the output shaft to eliminate static imbalance and couple imbalance. For example, Patent Document 1 below discloses a fan attached to an output shaft and having two thick portions acting as weights. This fan has the functions of a dust collection fan and a motor cooling fan.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the sander described in Patent Document 1 still has room for improvement. Specifically, the positions of the two weights (thickened parts) in the axial direction are close together, and they overlap when including the disc part, so the centrifugal forces acting on the two weights cancel each other out. For this reason, a large mass is required to eliminate the accidental imbalance. Also, the fan, including the weight, is a single molded product (completely single part) made of a single material, and there is no difference in specific gravity between the weight and the other parts. For this reason, the weight cannot efficiently generate a large centrifugal force to eliminate the accidental imbalance. As a result, a large weight is required, which may lead to a larger fan and, consequently, a larger sander. This problem is not limited to orbital sanders, but is common to various portable polishing machines that involve eccentric circular motion. For these reasons, it is desirable to provide a portable polishing machine that can reduce at least one of the mass and size of the weight. [Means for solving the problem]

[0006] This specification discloses a portable polishing machine. This portable polishing machine may comprise an output shaft, a polishing section, a dust collection fan, a motor, a motor cooling fan, a first weight, and a second weight. The output shaft may extend axially and be rotatable. The polishing section may be configured to perform eccentric circular motion as the output shaft rotates. The dust collection fan may be fixed to the output shaft so as to surround it circumferentially. The motor may be positioned axially opposite the polishing section to the dust collection fan and configured to provide rotational driving force to the output shaft. The motor cooling fan may be positioned axially between the dust collection fan and the motor. The first weight may be attached to one of the fans, the dust collection fan and the motor cooling fan, and may have a higher specific gravity than the other fan. The second weight may be positioned axially different from the first weight.

[0007] According to the above configuration, since the first weight and the second weight are positioned at different axial positions, the centrifugal forces acting on each of the first and second weights can be prevented from canceling each other out. Therefore, the mass of the first and second weights required to eliminate the extra-excessive imbalance can be reduced. Moreover, by ensuring a large difference in specific gravity between the first weight and the fan to which the first weight is attached (dust collection fan or motor cooling fan), the centrifugal force required to eliminate the extra-excessive imbalance can be efficiently generated. Consequently, the size of the first weight can be reduced. Furthermore, the fan to which the first weight is attached can be made lighter. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of a sander according to the first embodiment. [Figure 2] This is a left side view of the sander. [Figure 3] This is a plan view of the sander. [Figure 4] This is a cross-sectional view along line AA in Figure 3. [Figure 5] This is a magnified view of a portion of Figure 4. [Figure 6] This is a partial cross-sectional view along line BB in Figure 3. [Figure 7] This is a perspective view of the Sanda with some of its equipment removed. [Figure 8] This is a perspective view of the dust collection fan, motor cooling fan, first weight, and second weight. [Figure 9] This is a perspective view of the dust collection fan, motor cooling fan, first weight, and second weight. [Figure 10] This is an exploded perspective view of the dust collection fan, motor cooling fan, first weight, and second weight. [Figure 11] This is a schematic diagram showing the arrangement of the first weight and the second weight according to the second embodiment. [Figure 12] This is a schematic diagram showing the arrangement of the first and second weights according to the third embodiment. [Figure 13] This is a schematic diagram showing the arrangement of the first and second weights according to the fourth embodiment. [Modes for carrying out the invention]

[0009] Representative and non-limiting examples of the present invention will be described in detail below with reference to the drawings. This detailed description is intended simply to show those skilled in the art details for carrying out preferred examples of the present invention and is not intended to limit the scope of the invention. In addition, the additional features and inventions disclosed below may be used separately from or in conjunction with the other features and inventions to provide further improved apparatus, methods for manufacturing and using the same.

[0010] Furthermore, the combinations of features and processes disclosed in the following detailed description are not essential for carrying out the present invention in the broadest sense, and are described solely to illustrate representative examples of the present invention. Moreover, the various features of the representative examples described above and below, as well as the various features described in the independent and dependent claims, do not necessarily have to be combined in the same way as the examples described herein or in the order listed, in order to provide additional and useful embodiments of the present invention.

[0011] All features described herein and / or in the claims are intended to be disclosed individually and independently of each other, as limitations to the original disclosure and claimed specifics, separate from the configurations of features described in the embodiments and / or in the claims. Furthermore, all descriptions relating to numerical ranges and groups or clusters are intended to disclose intermediate configurations therein, as limitations to the original disclosure and claimed specifics.

[0012] In one or more embodiments, the first weight and the second weight may be axially spaced apart via a spacer. According to this configuration, the axial distance between the first weight and the second weight is ensured to be large by the spacer. Therefore, the masses of the first weight and the second weight required to eliminate the even imbalance can be further reduced.

[0013] In one or more embodiments, the dust collecting fan and the motor cooling fan may be axially spaced apart. According to this configuration, the motor cooling fan can be arranged closer to the motor. Therefore, the motor cooling performance by the motor cooling fan can be improved.

[0014] In one or more embodiments, the dust collecting fan and the motor cooling fan may be axially spaced apart via a spacer. According to this configuration, the separation distance between the dust collecting fan and the motor cooling fan can be ensured to be large. Therefore, the motor cooling fan can be further closer to the motor, and the motor cooling performance can be further improved.

[0015] In one or more embodiments, the first weight may be attached to the dust collecting fan and may have a specific gravity greater than that of the dust collecting fan. The motor cooling fan may be fixed to the output shaft so as to surround the output shaft in the circumferential direction. The second weight may be attached to the motor cooling fan and may have a specific gravity greater than that of the motor cooling fan. According to this configuration, a large specific gravity difference can be ensured both between the first weight and the dust collecting fan and between the second weight and the motor cooling fan, and the centrifugal force required to eliminate the even imbalance can be efficiently generated. Therefore, the sizes of the first weight and the second weight can be reduced. Moreover, both the dust collecting fan and the motor cooling fan can be lightened.

[0016] In one or more embodiments, the dust collection fan may be made of light metal. The first weight may be made of heavy metal. According to this configuration, the masses of the dust collection fan and the first weight can be optimized. In other words, the dust collection fan can be lightened, and while ensuring the function of the first weight, the first weight can be lightened and compacted.

[0017] In one or more embodiments, the first weight may be attached to the dust collection fan by screwing. According to this configuration, it becomes easy to attach the first weight and the output shaft of the dust collection fan.

[0018] In one or more embodiments, the motor cooling fan may be made of synthetic resin. The second weight may be made of metal. According to this configuration, the masses of the motor cooling fan and the second weight can be optimized. In other words, the motor cooling fan can be lightened, and while ensuring the function of the second weight, the second weight can be lightened and compacted.

[0019] In one or more embodiments, the second weight may have a through hole through which the output shaft passes. According to this configuration, the radial positioning of the second weight with respect to the output shaft can be accurately performed. Also, even if the motor cooling fan is made of synthetic resin, the motor cooling fan will not be deformed by the centrifugal force acting on the second weight.

[0020] In one or more embodiments, the first weight may have a through hole through which the output shaft passes. According to this configuration, the radial positioning of the first weight with respect to the output shaft can be accurately performed.

[0021] In one or more embodiments, the spacer may be in the form of a first bearing that rotatably supports the output shaft. With this configuration, the bearing originally required to rotatably support the output shaft can be used as a spacer, eliminating the need to separately arrange a spacer. Therefore, the portable polishing machine can be made more compact and manufacturing costs can be reduced.

[0022] In one or more embodiments, the dust collection fan, motor cooling fan, first weight, and second weight may be fixed to the output shaft by fastening them together. This configuration simplifies the manufacturing process.

[0023] In one or more embodiments, the dust collection fan may include a shaft portion that extends axially toward the opposite side of the output shaft and is eccentric with respect to the output shaft. The polishing section may be fixed to the shaft portion via a second bearing that rotatably supports the shaft portion. This configuration allows for the eccentric circular motion of the polishing section to be achieved with a simple configuration.

[0024] Hereinafter, with reference to the drawings, an orbital sander (hereinafter simply referred to as "sander") 10 as an exemplary embodiment will be described in more detail. The sander 10 exemplified in this embodiment is also called a finishing sander.

[0025] As shown in Figures 4 and 5, the sander 10 comprises an electric motor 60, a motor shaft 61, and a polishing section 30. One end of the motor shaft 61 is connected to the polishing section 30 via other components. As will be described in more detail later, the sander 10 is configured such that the polishing section 30 performs a polishing motion due to the rotation of the electric motor 60 (motor shaft 61).

[0026] In the following explanation, the direction in which the motor shaft 61 extends is defined as the vertical direction of the sander 10. Within the vertical direction, the side where the polishing section 30 is located is defined as the lower side, and the opposite side is defined as the upper side. The longitudinal direction of the sander 10, perpendicular to the vertical direction, is defined as the front-to-back direction of the sander 10. Within the front-to-back direction, the side where the polishing section 30 is located is defined as the front side, and the opposite side is defined as the rear side. The direction perpendicular to both the front-to-back direction and the vertical direction is defined as the left-to-right direction of the sander 10. Within the left-to-right direction, the right side when viewed from the rear to the front is defined as the right side of the sander 10, and the opposite side is defined as the left side of the sander 10.

[0027] As shown in Figures 1-3, the sander 10 is equipped with a housing 20. The housing 20 comprises a front housing section 21, a grip section 22, and a rear housing section 23. The front housing section 21 and the rear housing section 23 are connected in the front-rear direction by a bifurcated shape that is separated vertically, and the upper connecting section functions as the grip section 22. A power cord 26 extends from the rear end of the rear housing section 23 to supply commercial AC power to the electric motor 60. The power source for the electric motor 60 may be a battery that is detachably attached to the sander 10 instead of commercial power.

[0028] As shown in Figure 4, a controller 65 is housed in the lower part of the rear housing 23. The controller 65 is electrically connected to the power cord 26 and the electric motor 60, and controls the operation of the electric motor 60 by controlling the power supplied to the electric motor 60. As shown in Figure 1, a switch 27 is provided at the front of the front housing 21 for starting and stopping the electric motor 60. The switch 27 is electrically connected to the controller 65.

[0029] As shown in Figure 5, the front housing portion 21 houses an electric motor 60. The motor shaft 61 of the electric motor 60 extends in the vertical direction and is rotatably supported by bearings 62 and 63 fixed to the front housing portion 21. Bearing 62 supports the upper end of the motor shaft 61, and bearing 63 supports the area near the lower end of the motor shaft 61.

[0030] A motor cooling fan 40 is positioned below the electric motor 60. The motor cooling fan 40 is fixed to the motor shaft 61 so as to surround the motor shaft 61 in the circumferential direction (the fixing method will be described later). As the motor shaft 61 rotates, the motor cooling fan 40 rotates, and air flows from the outside to the inside of the housing 20 through the intake ports 24 (see Figures 1 and 2) formed in the front housing portion 21 and the grip portion 22. This air flows axially (in the direction in which the motor shaft 61 extends) through the electric motor 60, is directed radially outward at the motor cooling fan 40, and is discharged to the outside of the housing 20 through the exhaust port 25 (see Figures 1 and 2) formed in the front housing portion 21. The electric motor 60 is cooled by this airflow.

[0031] A dust collection fan 50 is positioned below the motor cooling fan 40. The dust collection fan 50 and the motor cooling fan 40 are spaced apart in the axial direction via a bearing 63. This axial separation allows the motor cooling fan 40 to be positioned closer to the electric motor 60. As a result, motor cooling performance can be improved.

[0032] The dust collection fan 50 is fixed to the lower end of the motor shaft 61 so as to surround the motor shaft 61 in the circumferential direction (the fixing method will be described later). As shown in Figures 5 and 9, the dust collection fan 50 comprises a substantially disc-shaped faceplate 51, a shaft portion 52, and a plurality of blades 53. The shaft portion 52 protrudes cylindrically downward from the faceplate 51 near the center of the faceplate 51. A hole 54 is formed inside the shaft portion 52. The plurality of blades 53 extend radially outward from the shaft portion 52 on the lower surface of the faceplate 51. A shaft insertion hole 55 is formed in the faceplate 51 so as to communicate with the hole 54. The shaft insertion hole 55 has a larger inner diameter than the hole 54.

[0033] The dust collection fan 50 is fixed to the motor shaft 61 with the lower end of the motor shaft 61 inserted into the shaft insertion hole 55. At this time, the hole 54 of the shaft portion 52 is coaxial with the motor shaft 61, but the shaft portion 52 is eccentric with respect to the motor shaft 61. The shaft portion 52 is rotatably supported by a bearing 64. For this reason, the bearing 64 is eccentric with respect to the motor shaft 61.

[0034] The space housing the dust collection fan 50 is in communication with a dust collection passage 28 that extends in the front-rear direction from the lower part of the rear housing section 23. A dust collection bag 29 is detachably attached to the rear end of the rear housing section 23. When the dust collection bag 29 is attached, the dust collection passage 28 and the inside of the dust collection bag 29 are in communication.

[0035] As shown in Figures 1 and 2, the polishing section 30 is located at the bottom of the sander 10 and comprises a pad 31 and a base 32 positioned on top of the pad 31. The pad 31 and base 32 have a roughly triangular shape with a pointed front when viewed in the vertical direction. As shown in Figure 6, the pad 31 and base 32 are joined by bolts 33 that extend in the vertical direction. As shown in Figure 5, the bottom surface of the pad 31 has multiple through holes 34 that penetrate the pad 31 in the vertical direction (only one through hole 34 is visible in the cross-section shown in Figure 5). A space 35 is formed between the pad 31 and the base 32, communicating with the through holes 34. This space 35 communicates with the dust collection passage 28. Sanding paper (not shown) is attached to the bottom surface of the pad 31. Holes are formed in this sanding paper at positions corresponding to the through holes 34 of the pad 31.

[0036] As the motor shaft 61 rotates, the dust collection fan 50 rotates, causing air to flow into the dust collection bag 29 through the holes in the sanding paper, the through-holes 34, the space 35, and the dust collection passage 28. This airflow allows the dust generated during sanding with the sanding paper to be collected in the dust collection bag 29.

[0037] As shown in Figure 5, a bearing 64 supporting the shaft 52 of the dust collection fan 50 is fixed to the polishing section 30. Therefore, the polishing section 30 is connected to the motor shaft 61 via the bearing 64 and the dust collection fan 50. Furthermore, as shown in Figures 5 to 7, the polishing section 30 is connected to the front housing section 21 via a connector 70 that extends in the vertical direction. As shown in Figure 7, the connector 70 is located at the front and rear of the front housing section 21, respectively.

[0038] As shown in Figures 6 and 7, each of the connectors 70 comprises six foot portions 71, an upper plate portion 75, and a lower plate portion 76 (a total of 12 foot portions 71). The foot portions 71, the upper plate portion 75, and the lower plate portion 76 are joined together as a single molded product from a single material, which is TPE (thermoplastic elastomer). The upper plate portion 75 and the lower plate portion 76 are rectangular in shape, elongated from left to right and flat from top to bottom, while the foot portions 71 are roughly columnar in shape, extending vertically. Three foot portions 71 are unevenly distributed at each of the left and right ends. The six foot portions 71 are arranged in a single row. Each foot portion 71 comprises a top portion 72, a bottom portion 73, and an intermediate portion 74. The top portion 72 and bottom portion 73 are conical in shape, and the intermediate portion 74 is cylindrical in shape. The upper plate portion 75 is held immovably in the front housing portion 21. The lower plate portion 76 is held immovably by the base 32.

[0039] The sander 10 described above operates as follows. First, when the user operates the switch 27 to drive the electric motor 60, the motor shaft 61 starts to rotate. Here, as described above, the bearing 64 connecting the motor shaft 61 and the polishing section 30, and the shaft 52 of the dust collection fan 50 are eccentric with respect to the motor shaft 61. Therefore, when the motor shaft 61 rotates, the polishing section 30 performs eccentric circular motion (orbital motion) while changing the horizontal relative position of the top 72 and bottom 73 of the foot section 71. Here, the intermediate section 74 is in an inclined position connecting the top 72 and bottom 73. As the top 72 and bottom 73 rotate relative to each other, the intermediate section 74 also rotates while deforming in the direction of inclination. That is, the polishing section 30 does not rotate itself, but moves in a circular motion along the horizontal plane while maintaining its position. In this state, when the sanding paper attached to the bottom surface of the pad 31 is pressed against the object to be polished, polishing is performed. The dust collection fan 50 is equipped with an eccentric shaft portion 52, and the shaft portion 52 is supported by a bearing 64, thereby enabling eccentric circular motion with a simple configuration.

[0040] Such eccentric circular motion of the polishing section 30 generates vibration. Therefore, the sander 10 is equipped with a configuration to reduce vibration by eliminating static and accidental imbalances using counterweights (first weight 80 and second weight 90). Such a configuration will be described below.

[0041] As shown in Figures 5, 8 to 10, a first weight 80 is attached to the dust collection fan 50. As shown in Figure 10, the first weight 80 has a substantially semi-circular disc shape and is provided with an annular portion 81 at the center of its arc. The annular portion 81 has a shaft through-hole 82 through which the motor shaft 61 passes. Therefore, the radial positioning of the first weight 80 with respect to the motor shaft 61 can be performed with high precision.

[0042] Furthermore, as shown in Figure 10, an annular portion 56 is formed around the shaft insertion hole 55 of the dust collection fan 50, protruding upward from the faceplate 51 in an annular shape. As shown in Figure 5, when the first weight 80 is attached to the dust collection fan 50, the annular portion 56 is fitted inside the annular portion 81. This spigot structure allows for precise radial positioning of the first weight 80 relative to the dust collection fan 50.

[0043] Furthermore, as shown in Figure 10, the faceplate 51 of the dust collection fan 50 has a shape in which approximately half of its outer edge is bent upward along the circumferential direction. This bent portion corresponds to the portion to which the first weight 80 cannot be attached. Therefore, as shown in Figure 8, when the first weight 80 is attached to the dust collection fan 50, the circumferential ends of this bent portion come into contact with the end faces of the first weight 80 that extend in the diametrical direction. Thus, the circumferential positioning of the first weight 80 relative to the dust collection fan 50 can be performed with high precision.

[0044] In this embodiment, the first weight 80 is attached to the dust collection fan 50 by screwing a screw 58 (see Figure 5) into the screw hole 57 of the dust collection fan 50 and the screw hole 83 (see Figure 10) of the first weight 80. This makes it easy to attach the first weight 80 and the dust collection fan 50 to the motor shaft 61. However, the first weight 80 and the dust collection fan 50 may be separate components until they are finally attached to the motor shaft 61.

[0045] The materials of the first weight 80 and the dust collection fan 50 are selected such that the specific gravity of the first weight 80 is greater than that of the dust collection fan 50. By ensuring a difference in specific gravity between the first weight 80 and the dust collection fan 50, the centrifugal force necessary to eliminate the imbalance can be efficiently generated. In other words, the mass of the first weight 80 can be reduced.

[0046] In this embodiment, the dust collection fan 50 is made of a light metal (for example, aluminum, magnesium, titanium, or an alloy containing any of these). This ensures the necessary strength for the dust collection fan 50, which is subjected to the load of the polishing section 30, while making the dust collection fan 50 as lightweight as possible. In this embodiment, the first weight 80 is made of a heavy metal (for example, iron, zinc, copper, or an alloy containing any of these (for example, brass)). This configuration ensures a large difference in specific gravity between the first weight 80 and the dust collection fan 50, and generates the centrifugal force necessary to eliminate the imbalance very efficiently. This leads to a lighter and more compact first weight 80. However, the materials of the first weight 80 and the dust collection fan 50 can be arbitrarily selected, as long as the specific gravity of the first weight 80 is greater than the specific gravity of the dust collection fan 50.

[0047] As shown in Figures 5,8 to 10, a second weight 90 is attached to the motor cooling fan 40. In this embodiment, the motor cooling fan 40 and the second weight 90 are separate components, but in this specification, if the motor cooling fan 40 and the second weight 90 are inseparably in contact when the motor cooling fan 40 and the second weight 90 are finally attached to the motor shaft 61, such a contact state is intended to be included in the state in which the second weight 90 is attached to the motor cooling fan 40.

[0048] As shown in Figure 10, the second weight 90 has a sector shape and is provided with an annular portion 91 at the center of its arc. The annular portion 91 has a shaft through hole 92 through which the motor shaft 61 passes. Therefore, the radial positioning of the second weight 90 relative to the motor shaft 61 can be accurately performed. The second weight 90 is positioned opposite the first weight 80, with the motor shaft 61 in between, when viewed in the axial direction.

[0049] As shown in Figure 10, the motor cooling fan 40 comprises a substantially partially disc-shaped faceplate 41, a plurality of blades 42, and a base 44. A shaft through-hole 43 is formed at the center of the arc of the faceplate 41 through which the motor shaft 61 passes. The base 44 protrudes upward in an arc shape from the faceplate 41, radially outward from the shaft through-hole 43. The plurality of blades 42 extend radially outward from the base 44 on the upper surface of the faceplate 41.

[0050] As shown in Figure 8, the base portion 44 has a shape that fits the annular portion 91 of the second weight 90. Therefore, the radial positioning of the second weight 90 relative to the motor cooling fan 40 can be performed with high precision. Furthermore, as shown in Figures 8 and 9, when the second weight 90 is attached to the motor cooling fan 40, the circumferential ends of the base portion 44 of the motor cooling fan 40 and the circumferential ends of the second weight 90 come into contact with each other. Therefore, the circumferential positioning of the second weight 90 relative to the motor cooling fan 40 can be performed with high precision.

[0051] The materials of the second weight 90 and the motor cooling fan 40 are selected such that the specific gravity of the second weight 90 is greater than that of the motor cooling fan 40. By ensuring a difference in specific gravity between the second weight 90 and the motor cooling fan 40, the centrifugal force necessary to eliminate the imbalance can be efficiently generated. In other words, the mass of the second weight 90 can be reduced.

[0052] In this embodiment, the motor cooling fan 40 is made of synthetic resin. This allows for weight reduction of the motor cooling fan 40. In this embodiment, the second weight 90 is made of metal. The second weight 90 may be made of heavy metal, similar to the first weight 80. This configuration allows for a large difference in specific gravity between the second weight 90 and the motor cooling fan 40, enabling the generation of centrifugal force necessary to eliminate the imbalance very efficiently. This leads to weight reduction and compactness of the second weight 90. However, the materials of the second weight 90 and the motor cooling fan 40 can be arbitrarily selected, as long as the specific gravity of the second weight 90 is greater than that of the motor cooling fan 40. As mentioned above, the motor shaft 61 passes through the shaft through hole 92 of the second weight 90. Therefore, a reaction force acts on the motor shaft 61 against the centrifugal force acting on the second weight 90, so even if the motor cooling fan 40 is made of synthetic resin, the motor cooling fan 40 will not deform due to the centrifugal force acting on the second weight 90.

[0053] In this embodiment, the dust collection fan 50, the motor cooling fan 40, the first weight 80, and the second weight 90 are fixed to the motor shaft 61 by fastening them together. Specifically, as shown in Figure 5, the motor shaft 61 has a screw hole 66 that extends upward from its lower end. The screw hole 66 communicates with the hole 54 of the dust collection fan 50. The inner diameter of the screw hole 66 is smaller than the inner diameter of the hole 54. The motor shaft 61 also has a flange 67. The flange 67 has an outer diameter larger than the inner diameter of the annular portion 91 of the second weight 90, and the flange 67 and the annular portion 91 are in contact in the axial direction. Below the motor shaft 61, a plate 69 is brought into contact with the lower end of the bearing 64. A conical hole is formed in the center of the plate to match the screw head of the countersunk screw 68. In this state, when a countersunk screw 68 that engages with the screw hole 66 is inserted into the hole 54 and the screw hole 66 and tightened, the dust collection fan 50, the first weight 80, the bearing 63, the motor cooling fan 40, and the second weight 90 are tightened axially between the bolt head, which engages with the lower end of the shaft portion 52, and the flange 67. As a result, the dust collection fan 50, the motor cooling fan 40, the first weight 80, and the second weight 90 are fixed to the motor shaft 61. This configuration simplifies the manufacturing process.

[0054] In this embodiment, the motor cooling fan 40 and the second weight 90 are separate components until they are fastened together as described above, but they may be integrated during the manufacturing process. For example, the motor cooling fan 40 and the second weight 90 may be joined by bolting, or they may be manufactured integrally by insert molding.

[0055] As described above, with respect to the sander 10, the first weight 80 and the second weight 90 are positioned at different axial positions, so that the centrifugal forces acting on each of the first weight 80 and the second weight 90 do not cancel each other out. Therefore, the mass of the first weight 80 and the second weight 90 required to eliminate the extra-excessive imbalance can be reduced. In particular, in this embodiment, the first weight 80 and the second weight 90 are spaced apart in the axial direction via the bearing 63, so that a large axial distance can be secured between the first weight 80 and the second weight 90. Therefore, the mass of the first weight 80 and the second weight 90 required to eliminate the extra-excessive imbalance can be further reduced.

[0056] Furthermore, the bearing 64 functions as a spacer to separate the first weight 80 and the second weight 90 in the axial direction. In other words, the bearing 64, which is originally necessary to rotatably support the motor shaft 61, can be used as a spacer, so there is no need to separately place a spacer. Therefore, the sander 10 can be made more compact and manufacturing costs can be reduced. However, a separate spacer may be prepared and placed between the first weight 80 and the second weight 90.

[0057] The second embodiment will now be described with reference to Figure 11. The second embodiment differs from the first embodiment in that a balancer 180 is attached to the lower end of the motor shaft 61 instead of the first weight 80 attached to the dust collection fan 50. The balancer 180 has its center of gravity on the opposite side of the motor shaft 61 from the second weight 90. Even with this configuration, the same effect as in the first embodiment can be obtained because the second weight 90 and the balancer 180 are spaced apart in the axial direction. Although not shown, the first weight 80 may be attached to the dust collection fan 50 instead of the second weight 90 being attached to the motor cooling fan 40.

[0058] The third embodiment will now be described with reference to Figure 12. The third embodiment differs from the first embodiment in that the motor cooling fan 40 and the dust collection fan 50 are not spaced apart in the axial direction. The first weight 80 is attached to the lower side of the dust collection fan 50, and the second weight 90 is attached to the upper side of the motor cooling fan 40. Therefore, the first weight 80 and the second weight 90 are positioned at different axial positions. Even with this configuration, the mass of the first weight 80 and the second weight 90 required to eliminate the slight imbalance can be reduced compared to the case where the first weight 80 and the second weight 90 are positioned at the same axial position.

[0059] The fourth embodiment will now be described with reference to Figure 13. The fourth embodiment differs from the first embodiment in that the spindle 368 is arranged parallel to the motor shaft 61. The motor shaft 61 and the spindle 368 are connected by an endless belt 369 to enable power transmission. Although not shown in the figure, a polishing section 30 is connected to the tip of the spindle 368. A motor cooling fan 40 and a second weight 90 are attached near the upper end of the spindle 368, and a balancer 380 is attached to the lower end of the spindle 368. The balancer 380 has its center of gravity on the opposite side of the spindle 368 from the second weight 90. Even with this configuration, the same effect as in the first embodiment can be obtained because the second weight 90 and the balancer 380 are spaced apart in the axial direction.

[0060] While embodiments of the present invention have been described above, these embodiments are provided to facilitate understanding of the present invention and do not limit it. The present invention can be modified and improved without departing from its spirit, and equivalents thereof are included. Furthermore, any combination or omission of the elements described in the claims and specification is possible to the extent that at least some of the above-described problems can be solved or at least some of the effects can be achieved.

[0061] Furthermore, the above-described embodiment is applicable not only to orbital sanders but also to various portable polishing machines that involve eccentric circular motion. For example, the above-described embodiment is applicable to random orbit sanders, polishers, and the like.

[0062] The correspondence between each component of the above embodiment and each component of the present invention is shown below. However, each component of the embodiment is merely an example and does not limit the components of the present invention. Sander 10 is an example of a "portable polishing machine". Motor shaft 61 and spindle 368 are examples of "output shafts". Polishing section 30 is an example of a "polishing section". Dust collection fan 50 is an example of a "dust collection fan". Motor cooling fan 40 is an example of a "motor cooling fan". Electric motor 60 is an example of a "motor". First weight 80 is an example of a "first weight", and second weight 90 is an example of a "second weight". However, it is also possible to consider the second weight 90 as an example of a "first weight" and the first weight 80 as an example of a "second weight". Balancers 180, 380 are examples of "second weights". Bearing 64 is an example of a "spacer" and a "first bearing". Shaft section 52 is an example of a "shaft section". Bearing 64 is an example of a "second bearing". [Explanation of Symbols]

[0063] 10... Orbital Sander 20... Housing 21...Front housing section 22... Grip section 23...Rear housing section 24...Inlet 25... Exhaust port 26...Power cord 27...Switch 28... Dust collection passage 29... Dust collection bag 30...Polishing section 31...pad 32...bass 33...volts 34...Through hole 35...space 40...Motor cooling fan 41...face plate 42...feathers 43...Shaft through hole 44...Base 50... Dust collection fan 51...face plate 52...Shaft 53...feathers 54...hole 55... Shaft insertion hole 56... Ring section 57...Screw holes 58... Screws 60... Electric motor 61...Motor shaft 62, 63, 64... bearings 65... Controller 66... ​​Screw holes 67...Flange 68... Countersunk head screws 69...plate 70... Connectors 71...Foot part 72...Top 73...bottom 74...Middle section 75... Upper plate section 76...Lower plate section 80...First weight 81... Ring section 82...Shaft through hole 83...Screw holes 90... Second weight 91... Ring section 92...Shaft through hole 180...Balanza 368...Spindle 369...Endless belt 380...Balanza

Claims

1. A portable polishing machine, comprising: a rotatable output shaft extending axially; and a grinding unit configured to perform eccentric circular motion in association with rotation of the output shaft; a dust collection fan fixed to the output shaft so as to surround the output shaft in a circumferential direction; a motor disposed on an opposite side of the polishing unit with respect to the dust collecting fan in the axial direction and configured to provide a rotational driving force to the output shaft; a motor cooling fan disposed between the dust collection fan and the motor in the axial direction; a first weight attached to one of the dust collection fan and the motor cooling fan and having a specific gravity greater than that of the one of the dust collection fan and the motor cooling fan; a second weight disposed at a position different from that of the first weight in the axial direction; A portable polishing machine comprising:

2. 2. The portable grinder of claim 1, The first weight and the second weight are spaced apart from each other in the axial direction via a spacer. Portable grinder.

3. 3. The portable grinder according to claim 1 or 2, The dust collection fan and the motor cooling fan are disposed apart from each other in the axial direction. Portable grinder.

4. A portable polishing machine according to claim 3, which includes claim 2 as a dependent element, The dust collection fan and the motor cooling fan are disposed apart from each other in the axial direction via the spacer. Portable grinder.

5. A portable grinder according to any one of claims 1 to 4, the first weight is attached to the dust collection fan and has a specific gravity greater than that of the dust collection fan; the motor cooling fan is fixed to the output shaft so as to surround the output shaft in a circumferential direction, The second weight is attached to the motor cooling fan and has a specific gravity greater than that of the motor cooling fan. Portable grinder.

6. 6. The portable grinder of claim 5, The dust collection fan is made of light metal. The first weight is made of a heavy metal. Portable grinder.

7. 7. The portable grinder of claim 6, The first weight is attached to the dust collection fan by a screw. Portable grinder.

8. A portable grinder according to any one of claims 5 to 7, The motor cooling fan is made of synthetic resin. The second weight is made of metal. Portable grinder.

9. A portable grinder according to any one of claims 5 to 8, The second weight has a through hole through which the output shaft passes. Portable grinder.

10. A portable grinder according to any one of claims 1 to 9, The first weight has a through hole through which the output shaft passes. Portable grinder.

11. A portable grinding machine according to claim 2 and any one of claims 3 to 10 which depend on claim 2, The spacer is in the form of a first bearing that rotatably supports the output shaft. Portable grinder.

12. A portable grinder according to any one of claims 1 to 11, The dust collection fan, the motor cooling fan, the first weight, and the second weight are fixed to the output shaft by being fastened together. Portable grinder.

13. A portable grinder according to any one of claims 1 to 12, the dust collection fan includes a shaft portion extending in the axial direction toward an opposite side to the output shaft and eccentric with respect to the output shaft, The grinding unit is fixed to the shaft portion via a second bearing that rotatably supports the shaft portion. Portable grinder.

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