Wheel of belt sander, wheel set, and belt sander

Abstract

To provide a wheel of a belt sander which enables a feeding speed of a sanding belt to be changed with means other than changing of a rotation speed of a driving source, and to provide a wheel set and a belt sander.SOLUTION: A tube belt sander, one example of a belt sander, includes: an electric motor; and a first driving wheel and a second driving wheel 300 for attaching a sanding belt B. The second driving wheel 300 includes a planetary gear mechanism M which reduces a speed of rotational driving force from the electric motor. The second driving wheel 300 further includes an inner cylinder body 371 and a first shaft body 301. The inner cylinder body 371 is attached to a housing 10 of the belt sander. The first shaft body 301 has a receiving part 301R for receiving the rotational driving force from the electric motor and is disposed at a radial inner side of the inner cylinder body 371.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a wheel for a belt sander, such as a tube belt sander, on which a sanding belt is passed, a wheel set for changing the speed of a sanding belt, and a belt sander. [Background technology]

[0002] As shown in DE 10-2011-117412 A1 (Patent Document 1), a tube grinder is known that has a driving pulley (drive wheel) for driving a sanding belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 10-2011-117412 Summary of the Invention [Problem to be solved by the invention]

[0004] In belt sanders, including tube belt sanders, there is a demand for technology that allows the feed speed of the sanding belt to be changed by means other than changing the rotational speed of the drive source. [Means for solving the problem]

[0005] This specification discloses a wheel for a belt sander. The wheel may be a wheel for mounting a sanding belt in a belt sander having an electric motor. The wheel may be provided with a speed change mechanism for decreasing or increasing the speed of the rotational driving force from the electric motor. Effect of the Invention

[0006] The belt sander wheel, wheel set, and belt sander of the present disclosure allow the feed speed of the sanding belt to be changed by means other than changing the rotational speed of the drive source. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view of a tube belt sander according to an embodiment of the present disclosure; FIG. [Diagram 2] FIG. 2 is a left side view of FIG. 1, with a central vertical cross-sectional view of a portion of the view. [Diagram 3] FIG. 3 is a partial cross-sectional view taken along the line AA in FIG. 2. [Figure 4] 3 is a cross-sectional view taken along line EE in FIG. 2. [Diagram 5] FIG. 4 is a cross-sectional view taken along the line FF in FIG. [Figure 6] 2 is an exploded perspective view of the right side of a first drive wheel in the tube belt sander of FIG. 1. FIG. [Figure 7] FIG. 7 is an exploded perspective view of the left side of the first drive wheel of FIG. 6. [Figure 8] 2 is a right side perspective view of an attachment in the tube belt sander of FIG. 1. [Figure 9] FIG. 9 is a left perspective view of the attachment of FIG. 8. [Figure 10] 3 is a cross-sectional view taken along line CC in FIG. 2. [Figure 11] FIG. 3 is a cross-sectional view taken along line BB in FIG. [Figure 12] 3 is a cross-sectional view taken along line GG in FIG. 2. [Figure 13] 3 is a partial cross-sectional view taken along a line corresponding to line AA in FIG. 2 when a second drive wheel is attached in place of the first drive wheel. [Figure 14] FIG. 14 is an exploded perspective view of the right side of the second drive wheel of FIG. 13. [Figure 15] FIG. 14 is an exploded perspective view of the left side of the second drive wheel of FIG. 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In one embodiment of the present disclosure, the transmission mechanism may include gears. In this case, the transmission mechanism is more easily formed and mechanical loss in the transmission mechanism is suppressed. In one embodiment of the present disclosure, the transmission mechanism may include a planetary gear mechanism, which makes the transmission mechanism easier to form, more compact, and more well-balanced. In one embodiment of the present disclosure, the wheel of the belt sander may further include a mounting cylinder and a first shaft. The mounting cylinder may be attached to the housing of the belt sander. The first shaft may have a receiving portion for receiving a rotational driving force from the electric motor. The first shaft may be disposed radially inward of the mounting cylinder. In this case, the wheel can be more easily attached to the housing. Also, since the receiving portion for receiving the rotational driving force is disposed radially inward of the mounting portion of the wheel with respect to the housing, the wheel becomes more compact. In one embodiment of the present disclosure, the mounting tube may be cylindrical, which provides a stronger mounting strength to the housing and reduces the risk of the wheel becoming unbalanced relative to the housing. In one embodiment of the present disclosure, the wheel of the belt sander may further include a rotating cylinder. The rotating cylinder may be (1) disposed radially outward of the mounting cylinder. The rotating cylinder may be (2) rotatably supported relative to the mounting cylinder. The rotating cylinder may receive a sanding belt (3). In this case, the wheel has a triple structure in which the shaft, mounting cylinder, and rotating cylinder are stacked in order from the radial inside to the radial outside, making it more compact. In one embodiment of the present disclosure, the wheel of the belt sander may further include a second shaft. The mounting cylinder may be attached to the housing at a mounting portion arranged at the mounting portion side end, which is an end of the mounting cylinder. The rotating cylinder may have a wall portion at an end of the rotating cylinder opposite to the mounting portion side end. The second shaft may be connected to the first shaft via a speed change mechanism. The second shaft may be connected to the wall portion. The speed change mechanism may be arranged between the wall portion and the mounting portion. In this case, the efficiency of the arrangement of the speed change mechanism is improved. Thus, the wheel becomes more compact. In one embodiment of the present disclosure, the speed change mechanism may include a planetary gear mechanism. The first shaft may have a sun gear portion at an end opposite to the receiving portion. The second shaft may have a carrier portion supporting the planetary gears at an end opposite to the wall portion. The sun gear portion may mesh with the planetary gears. In this case, the receiving portion and the sun gear portion of the first shaft, and the wall portion and the carrier portion of the second shaft are more efficiently arranged. Thus, the wheel becomes more compact. In one embodiment of the present disclosure, the wheel of the belt sander may further include a first shaft body bearing, a second shaft body bearing, and a third shaft body bearing. The mounting cylinder may have a flange protruding radially inward from its inner surface. The first shaft body may be held by the mounting cylinder via the first shaft body bearing and the second shaft body bearing. The second shaft body may be held by the mounting cylinder via the third shaft body bearing. The second shaft body bearing and the third shaft body bearing may be in contact with the flange. In this case, the mechanism for rotatably holding the first shaft body and the mechanism for rotatably holding the second shaft body are more efficiently arranged in a state in which deviation of the rotation center axis can be suppressed. In one embodiment of the present disclosure, the third shaft bearing may be larger than at least one of the first shaft bearing and the second shaft bearing, in which case the third shaft bearing is more efficiently positioned while more adequately suppressing misalignment of the central axis of rotation.

[0009] Further disclosed herein is a belt sander, which may include the belt sander wheel described above. The present specification also discloses a wheel set for a belt sander, which may include a first wheel, which is the wheel of the belt sander described above, and a second wheel, which has a rotational speed faster than that of the first wheel. In one embodiment of the present disclosure, the second wheel in the wheel set of the belt sander may have one shaft body and a rotating cylinder body. The rotating cylinder body of the second wheel may have a wall portion. The shaft body may have a receiving portion for receiving a rotational driving force from the electric motor. The shaft body may have a connecting portion for connecting to the wall portion of the second wheel. In this case, the second wheel is more easily formed. The present specification further discloses a belt sander, which may be selectively mountable with a first wheel or a second wheel of the wheel set of the belt sander described above. EXAMPLES

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The description includes modified examples of the embodiments. The present disclosure is not limited to the embodiments and the modified examples. The front, back, up, down, left and right in the embodiments and modified examples are defined for the convenience of explanation and may change depending on at least one of the work situation and the movement of parts.

[0011] Fig. 1 is a perspective view of a tube belt sander 1 according to an embodiment of the present disclosure. Fig. 2 is a left side view of Fig. 1, with a central vertical cross-sectional view of a portion thereof. A tube belt sander 1, which is an example of a belt sander, has a main body 2 and an attachment 4. The tube belt sander 1 may also be called a pipe belt sander, a tube sander, or a pipe sander. The attachment 4 may also be called an assembly. In the tube belt sander 1, the attachment 4 is a working part that performs work such as polishing on a workpiece. Unlike the tube belt sander 1 described below, the working part may be incorporated into the main body 2 in a state in which it is difficult to separate, i.e., the attachment 4 does not have to be easily detachable from the main body 2. In Fig. 2, the left side is the front of the tube belt sander 1. Also, in Fig. 2, the top side is the top of the tube belt sander 1.

[0012] Fig. 3 is a partial cross-sectional view taken along line AA in Fig. 2. Fig. 4 is a cross-sectional view taken along line EE in Fig. 2. Fig. 5 is a cross-sectional view taken along line FF in Fig. 3. The main body 2 is cylindrical with its central axis extending in the front-rear direction. The main body 2 has a housing 10, a motor 12, a fan 14, a motor bearing 15, a battery mounting section 16, a battery 18, a controller 20, a switch main body 22, a speed adjustment dial 24, a switch operation section 26, a power transmission section 28, and a spindle 30 as an output section. In the main body 2, a battery 18, a battery mounting section 16, a controller 20, a switch body 22, a motor 12, a fan 14, a power transmission section 28, and a spindle 30 are arranged in this order from the rear. The battery 18 may not be a component of the main body 2 or the tube belt sander 1, but may be a component independent of the main body 2 or the tube belt sander 1. The spindle 30 may be a component of the power transmission unit 28. The spindle 30 may be a component of the output unit.

[0013] The housing 10 constitutes the outer shell of the main body 2 . The housing 10 directly or indirectly holds various members. The housing 10 includes a motor housing 40, a fan case 42, a gear housing 44, a bearing box 45, and an O-ring 47.

[0014] The motor housing 40 is made of plastic and has a left motor housing 40L and a right motor housing 40R. The left motor housing 40L has a plurality of screw bosses. The right motor housing 40R has a plurality of screw holes. The screw hole portions have screw holes corresponding to the screw bosses. The left motor housing 40L and the right motor housing 40R are fitted together by screws that enter the screw hole portions and the screw boss portions. The screws extend to the left and right and are inserted from the right side of the main body 2 to the left. The motor housing 40 is cylindrical. A front end of the motor housing 40 forms a front opening that opens forward. A rear end of the motor housing 40 forms a rear opening that opens rearward. The central portion of the motor housing 40 in the front-rear direction serves as a grip portion G that can be held by a user.

[0015] The fan case 42 is made of an aluminum die-cast alloy. The fan case 42 is ring-shaped. The fan case 42 is open at the front and rear. The fan case 42 has a plurality of exhaust ports 42E. Each exhaust port 42E extends in the front-rear direction. The plurality of exhaust ports 42E are arranged at the upper left, lower left, upper right, and lower right of the fan case 42.

[0016] The gear housing 44 is made of an aluminum die-cast alloy. The gear housing 44 is a bell-shaped member whose front portion is smaller in diameter than its rear portion. The rear end of the gear housing 44 is open to the rear. The left end of the gear housing 44 is open to the left. The gear housing 44 has a plurality of exhaust ports 48. The exhaust ports 48 are disposed at a front upper portion and a front lower portion of the gear housing 44. The gear housing 44 is fixed to the motor housing 40 via the fan case 42. The rear opening of the fan case 42 is aligned with the front opening of the motor housing 40. The rear opening of the gear housing 44 is aligned with the front opening of the fan case 42. The gear housing 44 and the fan case 42 are fixed by a plurality of screws 49 (four in this example) that extend forward and backward. The screws 49 are disposed at the upper right, lower right, upper left, and lower left of the rear of the fan case 42 and the gear housing 44. Each screw 49 is inserted from the front to the rear.

[0017] The bearing box 45 is made of an aluminum die-cast alloy. The bearing box 45 is cylindrical and extends to the left and right. The bearing box 45 is fixed to the gear housing 44. The right part of the bearing box 45 is inserted into the left opening of the gear housing 44. An O-ring 47 is interposed between the bearing box 45 and the gear housing 44.

[0018] The housing 10 can be modified in various ways. For example, the front and rear parts of the motor housing 40 may be separate bodies that can be assembled with each other. In the motor housing 40 that is split in half, at least one of the size and shape of the left motor housing 40L and the right motor housing 40R may be significantly different. Furthermore, the left motor housing 40L and the right motor housing 40R may be assembled by using a locking part such as a claw and a locked part such as a claw hole, without using screws. The gear housing 44 may be split in half. The fan case 42 may be omitted by being integrated with the motor housing 40 or the gear housing 44. The gear housing 44 may be integrated with the bearing box 45. The material of various parts of the housing 10 may be changed. In addition, at least one of the number and arrangement of the exhaust ports 42E, 48 may be appropriately changed.

[0019] The motor 12 is a brushless motor, a DC motor, and an electric motor. The motor 12 has a motor shaft 50 and a pinion 52 . The motor shaft 50 rotates about its own central axis and extends forward and backward. The pinion 52 is fixed integrally to the front end of the motor shaft 50 .

[0020] The fan 14 is fixed integrally to the motor shaft 50 . The fan 14 is a centrifugal fan, although other fans such as an axial flow fan may also be used as the fan 14. A fan case 42 disposed radially outward of the fan is provided with a plurality of exhaust ports 42E. Exhaust ports 48 of the gear housing 44 are disposed at the front upper and lower portions of the gear housing 44 .

[0021] The motor bearing 15 rotatably supports the motor shaft 50. The motor bearing 15 is disposed between the fan 14 and the pinion 52. The motor bearing 15 is disposed in front of the fan 14. The outer ring of the motor bearing 15 is held by the fan case 42. An O-ring 54 is interposed between the motor bearing 15 and the fan case 42.

[0022] The battery mounting section 16 is disposed at the rear end of the main body 2. The battery mounting section 16 extends vertically and horizontally relative to the front portion. A battery 18 is attached to the battery attachment section 16. The battery attachment section 16 has a main body side terminal that is connected to a terminal of the battery 18. The main body side terminal is disposed within a rear opening of the main body 2. The battery 18 is attached to the rear side of the battery attachment section 16. The battery 18 is attached by sliding downward from the top of the battery attachment section 16. The battery 18 may be slid in a direction other than from the top to the bottom. The battery 18 may also be attached in a manner other than sliding. The battery 18 is an 18V (volt) lithium ion battery. The battery 18 includes eight cells (not shown) in a plastic battery case. The cells are cylindrical and elongated in the axial direction, and face left and right when the battery 18 is attached. The battery 18 holds power for driving the motor 12. Any lithium ion battery of 10.8V, 14.4V, 25.2V, 28V, 36V, etc. may be used as the battery 18. A lithium ion battery with a voltage less than 10.8V or more than 36V may be used as the battery 18. Other types of batteries may be used as the battery 18. A plurality of batteries 18 may be used.

[0023] The controller 20 is held inside the battery mounting section 16 . The controller 20 controls the motor 12. The motor 12 is electrically connected to the controller 20 via a switch body 22. Furthermore, the main body side terminal of the battery mounting portion 16 is electrically connected to the controller 20. Further, a speed adjustment dial 24 and a switch body 22 are electrically connected to the controller 20.

[0024] The speed adjustment dial 24 is disposed at the top of the rear end of the motor housing 40 . The speed adjustment dial 24 extends in all directions and is rotatable around an imaginary axis in the front-rear direction. The upper end of the speed adjustment dial 24 is exposed.

[0025] The switch operating portion 26 is disposed at the upper front end of the motor housing 40 . The upper part of the switch operation unit 26 is exposed. The switch operation unit 26 can slide back and forth from a rear OFF position to a front maximum ON position. The switch operation unit 26 is connected to the switch main body 22 in a state in which the switch main body 22 can be switched. When the user performs a sliding operation on the switch operation unit 26 from the OFF position to the front, the switch operation unit 26 turns on the switch main body 22 after a predetermined amount of play. When the switch operation unit 26 is operated further forward from a state where the switch main body 22 is turned on, the switch main body 22 may change the state of the signal it issues in accordance with the amount of forward operation. In this case, the speed adjustment dial 24 may be omitted, and the controller 20 may change the rotation speed of the motor 12 in accordance with the state of the signal of the switch main body 22. The controller 20 may control the motor 12 so that the rotation speed of the motor 12 becomes faster as the switch operation unit 26 is operated further forward. Also, the play may be omitted, and the switch main body 22 may be immediately turned on when the switch operation unit 22 starts to be operated forward.

[0026] The power transmission unit 28 transmits the power of the motor 12 to the spindle 30. The spindle 30 is cylindrical. The spindle 30 extends left and right. A coupling unit 30C is disposed at the left end portion, which serves as the tip portion, of the spindle 30. The coupling unit 30C is a splined shaft. The power transmission unit 28 includes a bevel gear 60 , a right spindle bearing 62 , a left spindle bearing 64 , a circlip 65 , and a washer 66 . The power transmission portion 28 is disposed within a gear housing 44 and a bearing box 45 .

[0027] The bevel gear 60 is fixed integrally to the spindle 30. The bevel gear 60 is disposed around the upper portion of the spindle 30. The bevel gear 60 meshes with the pinion 52 . The bevel gear 60 reduces the rotation speed of the motor shaft 50 and transmits it to the spindle 30 .

[0028] A right spindle bearing 62 is disposed about the right end of the spindle 30 . Right spindle bearing 62 supports spindle 30 for rotation about its central axis. The right spindle bearing 62 is disposed on the right side of the bevel gear 60. The right spindle bearing 62 is held in the gear housing 44. The right spindle bearing 62 is disposed in front of the motor shaft 50 .

[0029] A left spindle bearing 64 is disposed about the center of the spindle 30 . The left spindle bearing 64 supports the spindle 30 for rotation about its central axis. The left spindle bearing 64 is disposed on the left side of the bevel gear 60. The left spindle bearing 64 is held in the bearing box 45 by a circlip 65.

[0030] The washer 66 is disposed to the left of the left spindle bearing 64 . A washer 66 is disposed between the inner ring of the left spindle bearing 64 and the large diameter portion in the center of the spindle 30 .

[0031] Fig. 6 is an exploded perspective view of the right side of the first drive wheel 70. Fig. 7 is an exploded perspective view of the left side of the first drive wheel 70. Fig. 8 is a perspective view of the left side of the attachment 4. Fig. 9 is a perspective view of the right side of the attachment 4. Fig. 10 is a cross-sectional view taken along line CC in Fig. 2. Fig. 11 is a cross-sectional view taken along line BB in Fig. 2. Fig. 12 is a cross-sectional view taken along line GG in Fig. 2. The attachment 4 has a first drive wheel 70, a base portion 100, a first joint portion 102, a base end arm 104 as an arm, a first wheel 106, a second joint portion 108, a tip end arm 110 as an arm, a second wheel 114, a grip 116, a guard 118, and a stopper mechanism 119. The first drive wheel 70 is replaceable with a second drive wheel 300 . 8 to 12, the first drive wheel 70 and the grip 116 are omitted. The drive wheel 70, 300 may be a component of the main body 2. The drive wheel 70, 300 may be an output part in place of the spindle 30 or together with the spindle 30. Furthermore, the drive wheel 70, 300 may be a component independent of the attachment 4. The drive wheel 70, 300 may be regarded as an attachment separate from the attachment 4.

[0032] The first drive wheel 70 serving as the first wheel has a cylindrical shape extending in the left and right directions. The first drive wheel 70 comprises an inner cylinder 71 as a mounting cylinder, two bolts 72, an outer cylinder 73 as a rotating cylinder, a first outer cylinder bearing 74, a second outer cylinder bearing 75, an outer cylinder circlip 76, a shaft 77, a first shaft bearing 78, a second shaft bearing 79, an inner cylinder circlip 80, an O-ring 81, two washers 82, and a shaft circlip 83.

[0033] The inner cylinder 71 has an inner cylinder main body 71B, two bolt holes 71H, a first flange 71F, and a second flange 71G. The inner cylinder main body 71B is cylindrical and extends left and right. Each bolt hole 71H, which serves as an attachment portion of the first drive wheel 70 to the main body 2, is disposed at the right end portion of the inner cylinder body 71B. Each bolt hole 71H extends in the radial direction of the inner cylinder body 71B. The angle between both bolt holes 71H is 90°. Note that the angle between both bolt holes 71H may be other than 90°. The first flange 71F is disposed in the center of the inner cylinder main body 71 B. The first flange 71F protrudes radially outward from the inner cylinder main body 71 B. The first flange 71F is ring-shaped. The second flange 71G is disposed on the left side of the inner cylinder body 71 B. The second flange 71G protrudes radially outward from the inner cylinder body 71 B. The second flange 71G is ring-shaped.

[0034] Each bolt 72 fits into a corresponding bolt hole 71H. The inner cylinder 71 is fixed to the bearing box 45 by each bolt 72. The right end of the inner cylinder 71 is inserted into the left opening of the bearing box 45. The left opening of the bearing box 45 is provided with bolt holes 45H corresponding to each bolt hole 71H. Each bolt 72 passes through the corresponding bolt hole 45H and enters the corresponding bolt hole 71H.

[0035] The outer cylinder 73 has an outer cylinder main body 73B and an outer cylinder outer shell portion 73A. The outer cylinder 73 is disposed radially outward of the inner cylinder 71. The outer cylinder body main body 73B is cylindrical and has a left wall portion 73W, and extends left and right. An outer cylinder body receiving portion 73R is formed in the center of the left wall portion 73W. The outer cylinder body receiving portion 73R is a spline hole. A ring-shaped recess 73P recessed rightward from the adjacent portion is provided on the left surface of the left wall portion 73W around the outer cylinder body receiving portion 73R. The outer cylinder outer shell portion 73A has an outer cylinder outer shell main body 73Y, a first flange 73F, a second flange 73G, and a plurality of (here, three) grooves 73V. The outer cylinder outer shell main body 73Y is cylindrical and extends left and right. The outer cylinder outer shell main body 73Y is fixed to the outer surface of the outer cylinder main body 73B. The first flange 73F protrudes radially outward from the right end of the outer cylinder outer shell main body 73Y. The second flange 73G protrudes radially outward from the left end of the outer cylinder outer shell main body 73Y. Each groove 73V is recessed radially inward from the outer surface of the outer cylinder outer shell main body 73Y. Each groove 73V extends in the circumferential direction of the outer cylinder outer shell main body 73Y. Each groove 73V is zigzag-shaped. The multiple grooves 73V are lined up left and right between the first flange 73F and the second flange 73G.

[0036] The first outer cylinder bearing 74 is fixed to the outer right side of the inner cylinder 71. The first outer cylinder bearing 74 supports the outer cylinder 73 so that the outer cylinder 73 is rotatable. The second outer cylinder body bearing 75 is fixed to the outside of the left portion of the inner cylinder body 71. The second outer cylinder body bearing 75 supports the outer cylinder body 73 so that it is rotatable.

[0037] The outer cylinder circlip 76 is fixed to a groove on the inner surface of the outer cylinder main body 73B. The first outer cylinder bearing 74 is sandwiched between the first flange 71F and the outer cylinder circlip 76. The second outer cylinder bearing 75 is sandwiched between the second flange 71G and a step on the inner surface of the outer cylinder main body 73B. The outer cylinder circlip 76 prevents the members inside the outer cylinder main body 73B from coming off.

[0038] The shaft body 77 has a shaft body main body 77B, a receiving portion 77R, and a connecting portion 77C. The shaft body 77 is disposed radially inward of the inner cylindrical body 71. The shaft body 77B is cylindrical and extends in the left and right directions. The receiving portion 77R is disposed inside the right portion of the shaft body 77B. The receiving portion 77R is a spline hole. The connecting portion 30C of the spindle 30 enters the receiving portion 77R and is connected to the receiving portion 77R by a spline connection. The connection between the spindle 30 and the shaft body 77 may be made by a means other than the spline connection between the connecting portion 30C and the receiving portion 77R. The connecting portion 77C is disposed outside the left portion of the shaft body 77B. The connecting portion 77C is a splined shaft. The connecting portion 77C is inserted into the outer cylinder body receiving portion 73R and is connected to the outer cylinder body receiving portion 73R by a spline connection. Note that the connection between the outer cylinder body 73 and the shaft body 77 may be made by a means other than the spline connection between the connecting portion 77C and the outer cylinder body receiving portion 73R.

[0039] The first shaft bearing 78 is fixed to the inside of the right portion of the inner cylinder body 71. The first shaft bearing 78 supports the shaft body 77 so that it is rotatable. The second shaft bearing 79 is fixed to the inside of the left portion of the inner cylinder body 71. The second shaft bearing 79 supports the shaft body 77 so that it is rotatable.

[0040] The inner cylinder circlip 80 is fixed to a groove on the inner surface of the inner cylinder main body 71B. The first shaft bearing 78 is sandwiched between a first step on the outer surface of the shaft 77 and an inner cylinder circlip 80 . The second shaft bearing 79 is sandwiched between a second step on the outer surface of the shaft 77 and a step inside the left end of the inner cylindrical body 71 . The inner cylinder circlip 80 prevents the members inside the inner cylinder 71 from coming off.

[0041] The O-ring 81 is disposed in the recess 73P of the left wall portion 73W of the outer cylindrical body 73. The multiple washers 82 are arranged on the left side of the O-ring 81 in a left-right stacked state. The shaft circlip 83 is fixed in a groove on the outer surface of the left end portion of the shaft 77. The shaft circlip 83 secures the O-ring 81 and the washers 82.

[0042] The first drive wheel 70 is attached to the main body 2 at the bolt hole 71H. The first drive wheel 70 is integrally connected to the spindle 30. Rotation of the spindle 30 is transmitted to the first drive wheel 70. The portion of the first drive wheel 70 other than the inner cylinder body 71 rotates around the drive wheel axis, which is its central axis. The first drive wheel 70 receives the sanding belt B. The sanding belt B is removably mounted on the first drive wheel 70. The first drive wheel 70 is for drivably mounting the sanding belt B.

[0043] The base portion 100 is made of metal, and has a fixing portion 120, a bearing portion 122, and a cover 123.

[0044] The fixing portion 120 is in the form of a plate extending in the front-rear and up-down directions, and has a central hole 124 and a plurality of (four in this example) screw holes 126. The central hole 124 extends to the left and right. The spindle 30 passes through the central hole 124. The screw holes 126 extend in the left-right direction and are disposed at a front upper portion, a front lower portion, a rear upper portion, and a rear lower portion of the fixing portion 120. The fixing part 120 is fixed integrally to the left part of the bearing box 45 by the left-right screws 128 that pass through the respective screw holes 126. In this way, the parts of the attachment 4 excluding the first driving wheel 70 are attached to the main body 2. The screws 128 are inserted from the left side to the right side. The fixed portion 120 is adjacent to the first drive wheel 70 .

[0045] The bearing portion 122 is disposed above the fixed portion 120 . The bearing portion 122 is bifurcated, having a left protruding portion 122L protruding upward from the left side in a plate shape and a right protruding portion 122R protruding upward from the right side in a plate shape. The left protruding portion 122L has a central hole. The right protruding portion 122R has a central hole.

[0046] The cover 123 is plate-like and has a "U" shape when viewed from the front to the rear. The cover 123 is fixed to the bearing portion 122 and covers the front side of the bearing portion 122 .

[0047] The first joint portion 102 has a shaft body 130, a torsion spring 132 which is an elastic body, and a circlip 134. The torsion spring 132 does not have to be a component of the first joint portion 102, and may be an independent component. The shaft body 130 is cylindrical and extends in the left and right directions. The torsion spring 132 is disposed around the shaft body 130. The torsion spring 132 biases the base-end arm 104 to assume a position facing the up-down direction. That is, the torsion spring 132 biases the base-end arm 104 in a rotational direction from a horizontal position to a vertical position. The circlip 134 is disposed at the left end of the shaft body 130 and prevents the shaft body 130 from coming off. The first joint portion 102 rotatably connects a base-end arm 104 to the base portion 100. The base-end arm 104 is rotatably coupled to the base portion 100.

[0048] The base-end arm 104 is made of metal and has an arc shape extending vertically. The base-end arm 104 is curved so as to be convex backward. The base-end arm 104 is disposed closer to the main body 2 than the tip-end arm 110, i.e., on the base-end side. The base end arm 104 has a lower bearing portion 140, a first wheel retaining portion 142, and an upper bearing portion 146.

[0049] The lower bearing portion 140 is disposed at the lower end portion of the base end arm 104 . The lower bearing portion 140 is bifurcated, having a left protruding portion 140L protruding downward from the left side in a plate shape, and a right protruding portion 140R protruding downward from the right side in a plate shape. The left protruding portion 140L has a central hole. The right protruding portion 140R has a central hole. The left protrusion 140L is disposed to the right of the left protrusion 122L of the base part 100. The right protrusion 140R is disposed to the left of the right protrusion 122R of the base part 100. The central holes of the left protrusion 122L, the left protrusion 140L, the right protrusion 140R, and the right protrusion 122R are aligned left and right and receive the shaft body 130 of the first joint part 102. The base end arm 104 is rotatable around the shaft body 130 relative to the base part 100. This allows the attachment 4 to have a first joint. The shaft 130 is prevented from coming off by a circlip 134 on the left side of the left protruding portion 122L. The torsion spring 132 is disposed between the left protruding portion 140L and the right protruding portion 140R.

[0050] The first wheel holding portion 142 is a left-right hole and its surrounding portion, and is disposed on the upper portion of the base-end arm 104. The upper bearing portion 146 is disposed at the upper end of the base-side arm 104. The upper bearing portion 146 is bifurcated, having a left protruding portion 146L protruding upward from the left side in a plate-like shape, and a right protruding portion 146R protruding upward from the right side in a plate-like shape. The left protruding portion 146L has a central hole. The right protruding portion 146R has a central hole.

[0051] The first wheel 106 has a first wheel shaft 150 as a driven wheel shaft, a bolt 151, a first wheel rotating portion 152, a right bearing 154, a left bearing 156, and a circlip 158. The first wheel shaft 150 is a cylindrical pin extending in the left-right direction. The first wheel shaft 150 is fixed integrally to a hole in the first wheel holding portion 142 by a bolt 151 extending in the left-right direction. The first wheel rotating part 152 is bobbin-shaped and has an inner hole extending left and right. The first wheel rotating part 152 has a first flange 152F and a second flange 152G. The first flange 152F is disposed at the right end of the first wheel rotating part 152 and protrudes radially outward from the adjacent part. The second flange 152G is disposed at the left end of the first wheel rotating part 152 and protrudes radially outward from the adjacent part. The right bearing 154 is held on the right portion of the first wheel shaft 150. The right surface of the inner ring of the right bearing 154 is engaged with a step portion on the outer surface of the first wheel shaft 150. The left surface of the outer ring of the right bearing 154 is engaged with a step portion on the inner surface of the inner hole of the first wheel rotating portion 152. The right bearing 154 rotatably supports the first wheel rotating portion 152. The left bearing 156 is held at the left end of the first wheel shaft 150. The left surface of the inner ring of the left bearing 156 is engaged by a circlip 158. The circlip 158 is engaged at the left end of the first wheel shaft 150. The right surface of the outer ring of the left bearing 156 is engaged with a step on the inner surface of the inner hole of the first wheel rotating part 152. The left bearing 156 rotatably supports the first wheel rotating part 152. A first wheel 106 is carried by the proximal arm 104 . The first wheel 106 receives the sanding belt B. The sanding belt B is removably attached to the first wheel 106. The first wheel 106 is a driven wheel that follows the driven sanding belt B. The first wheel 106 is for mounting the sanding belt B.

[0052] The second joint portion 108 has a shaft body 160, a torsion spring 162 which is an elastic body, and a circlip 164. The torsion spring 162 does not have to be a component of the second joint portion 108, and may be an independent component. The shaft body 160 is cylindrical and extends in the left and right directions. The torsion spring 162 is interposed between the base-end arm 104 and the tip-end arm 110. The torsion spring 162 biases the tip-end arm 110 to open forward and upward relative to the base-end arm 104. In other words, the torsion spring 162 can bias the tip-end arm 110 in a rotational direction to open it further relative to the base-end arm 104. The second joint portion 108 rotatably connects the tip side arm 110 to the base end arm 104. The tip side arm 110 is coupled to the base end arm 104 so as to be rotatable.

[0053] The tip side arm 110 is made of metal and extends in the front-rear direction. The tip side arm 110 has a shape that follows three sides of a trapezoid except for the bottom base side. The rear part of the tip side arm 110 is formed in a bifurcated shape and extends forward and upward. The tip side arm 110 is convex upward. The tip side arm 110 is disposed on the side farther from the main body unit 2 than the base side arm 104, i.e., on the tip side. The tip side arm 110 has a rear bearing portion 170, a second wheel holding portion 172, and a grip attachment portion 174.

[0054] The rear bearing portion 170 is disposed at the rear end portion of the tip side arm 110 . The rear bearing portion 170 is bifurcated, having a left protruding portion 170L protruding downward from the left side in a plate shape, and a right protruding portion 170R protruding downward from the right side in a plate shape. The left protruding portion 170L has a central hole. The right protruding portion 170R has a central hole. The left protrusion 170L is disposed to the left of the left protrusion 146L of the upper bearing 146 in the base-end arm 104. The right protrusion 170R is disposed to the right of the right protrusion 146R of the upper bearing 146 in the base-end arm 104. The central hole of the left protrusion 170L, the central hole of the left protrusion 146L of the base-end arm 104, the central hole of the right protrusion 146R of the base-end arm 104, and the central hole of the right protrusion 170R are aligned to the left and right and receive the shaft body 160 of the second joint portion 108. The tip-side arm 110 is rotatable around the shaft body 160 relative to the base-end arm 104. This allows the attachment 4 to have a second joint.

[0055] The second wheel holding portion 172 is a left-right hole and its surrounding portion, and is disposed at the front end portion of the tip side arm 110. The grip attachment portion 174 is a left-right hole and its surrounding portion, and is disposed at the upper end of the portion of the distal arm 110 that extends upward.

[0056] The second wheel 114 has a second wheel shaft 200 as a driven wheel shaft, a bolt 201, a second wheel rotating portion 202, a right bearing 204, a left bearing 206, and a circlip 208. The second wheel shaft 200 is a cylindrical pin extending in the left-right direction. The second wheel shaft 200 is fixed integrally to a hole in the second wheel holding portion 172 by a bolt 201 extending in the left-right direction. The second wheel rotating part 202 is bobbin-shaped and has an inner hole extending left and right. The second wheel rotating part 202 has a first flange 202F, a second flange 202G, and a plurality of (here, six) grooves 202V. The first flange 202F is disposed at the right end of the second wheel rotating part 202 and protrudes radially outward from the adjacent part. The second flange 202G is disposed at the left end of the second wheel rotating part 202 and protrudes radially outward from the adjacent part. Each groove 202V is recessed radially inward from the outer surface of the second wheel rotating part 202. Each groove 202V extends in the circumferential direction of the second wheel rotating part 202. Each groove 202V is ring-shaped. The plurality of grooves 202V are aligned left and right between the first flange 202F and the second flange 202G. The right bearing 204 is held on the right portion of the second wheel shaft 200. The right surface of an inner ring of the right bearing 204 is engaged with a step portion on the outer surface of the second wheel shaft 200. The left surface of an outer ring of the right bearing 204 is engaged with a step portion on the inner surface of the inner hole of the second wheel rotating part 202. The right bearing 204 rotatably supports the second wheel rotating part 202. The left bearing 206 is held at the left end of the second wheel shaft 200. The left surface of the inner ring of the left bearing 206 is engaged by a circlip 208. The circlip 208 is engaged at the left end of the second wheel shaft 200. The right surface of the outer ring of the left bearing 206 is engaged with a step on the inner surface of the inner hole of the second wheel rotating part 202. The left bearing 206 rotatably supports the second wheel rotating part 202. The second wheel 114 is held by the distal arm 110 . The second wheel 114 receives the sanding belt B. The sanding belt B is removably attached to the second wheel 114. The second wheel 114 is a driven wheel that follows the driven sanding belt B. The second wheel 114 is for mounting the sanding belt B.

[0057] The sanding belt B is a belt-shaped, ring-shaped, i.e., endless file. The sanding belt B has an abrasive surface that is used to abrade a workpiece. One sanding belt B is attached to the first drive wheel 70, the first wheel 106, and the second wheel 114 with the abrasive surface facing outward. When not sanding, the sanding belt B has a triangular shape with the first drive wheel 70, the first wheel 106, and the second wheel 114 as vertices when viewed from the left.

[0058] The grip 116 extends to the left and right and can be held by the user. The grip 116 is fixed integrally to the grip attachment portion 174 of the distal arm 110. The grip 116 is disposed on the left side of the grip attachment portion 174.

[0059] The guard 118 as an upright portion has a first guard body 220 and a second guard body 222 .

[0060] The first guard body 220 is made of metal. The first guard body 220 has a first guard body main body 224, a plurality of (here, two) screw holes 226, a plurality of (here, two) screws 227, and a plurality of (here, four) mounting holes 228. The first guard body 224 is plate-shaped. The lower part of the first guard body 224 extends in all directions. The upper part of the first guard body 224 has a cylindrical corner part and a part that extends in all directions. Each screw hole 226 is disposed on the right edge of the lower part of the first guard body 224. The two screw holes 226 are lined up one above the other. Each screw 227 enters a corresponding screw hole 226 and a corresponding screw hole of the base end arm 104. The base end arm 104 has a plurality of screw holes (two in this example) for the screws 227. The screw holes for the screws 227 each extend forward from the rear surface of the lower portion of the base end arm 104. The first guard body 220 is fixed to the base-end arm 104 by the screw holes 226 and the screws 227. The first guard body 220 is provided on the base-end arm 104 so as to stand thereon. Each mounting hole 228 is disposed in the lower part of the first guard body 224. The four mounting holes 228 are disposed at positions corresponding to the vertices of an imaginary rectangle. The first guard body 220 covers the upper and rear of the portion of the sanding belt B around the first wheel 106, and also covers the rear of the portion between the first wheel 106 and the first drive wheel 70. The first guard body 220 prevents the user from contacting the sanding belt B. The first guard body 220 also prevents sparks from the sanding belt B and the workpiece from reaching the user. The first guard body 220, which prevents sparks from the workpiece from reaching the user, is a spark guard. The first guard body 220 may be provided for purposes other than contact prevention and spark reach prevention, for example, it may be provided only for the purpose of installing the stopper mechanism 119.

[0061] The second guard body 222 is made of metal. The second guard body 222 has a second guard body main body 234, a plurality of screw holes (two in this case), a plurality of screws (two in this case), and a plurality of mounting holes 238 (four in this case). The second guard body 234 is plate-shaped. The screw holes are disposed on the right edge of the second guard body 234. The two screw holes are aligned front to back. Each screw enters a corresponding screw hole and a corresponding screw hole in the distal arm 110. The distal arm 110 has a plurality of screw holes (here, two) for the screws. The screw holes for the screws each extend upward from the lower surface of the distal arm 110. The second guard body 222 is fixed to the distal arm 110 by the respective screw holes and the respective screws. The second guard body 222 is provided on the proximal arm 104 so as to stand thereon. Each mounting hole 238 is disposed in the front portion of the second guard body 234. The four mounting holes 238 are disposed at positions corresponding to the vertices of an imaginary rectangle. The second guard body 222 covers the upper part of the sanding belt B between the first wheel 106 and the second wheel 114. The second guard body 222 prevents the user from coming into contact with the sanding belt B. The second guard body 222 also prevents sparks from the sanding belt B and the workpiece from reaching the user. The second guard body 222, which prevents sparks from the workpiece from reaching the user, is a spark guard. The second guard body 222 may be provided for purposes other than the prevention of contact and the prevention of sparks reaching the user, for example, it may be provided only for the purpose of installing the stopper mechanism 119.

[0062] The stopper mechanism 119 includes, as a stopper, a plurality of (eight in this example) rollers 240. In addition, four rollers 240 are illustrated in the drawing. Each roller 240 can rotate around its own central axis. Since each roller 240 is similar except for the mounting position, the following mainly describes one roller 240. The number of stoppers included in the stopper mechanism 119 may be seven or less, including one, or may be nine or more. The stopper mechanism 119 may also include a stopper that does not rotate around an axis. For example, the stopper may be a cylindrical or conical belt drop guard. Furthermore, the stopper mechanism 119 may also include two or more types of stoppers, such as a roller 240 and a belt drop guard.

[0063] The roller 240 includes a roller shaft 242 , a nut 244 , a roller rotating portion 246 , a first bearing 247 , a second bearing 248 , and a circlip 249 .

[0064] The roller shaft 242 is cylindrical. In the attached state, the roller shaft 242 extends vertically (see FIG. 12) or longitudinally. The following description will be given mainly with reference to the direction in FIG. The roller shaft 242 has a roller shaft main body 242B, a bolt portion 242T, and a bearing holding portion 242G. The roller shaft main body 242B is the part of the roller shaft 242 that has the largest diameter. The bolt portion 242T is disposed on the upper side of the roller shaft main body 242B. A thread groove is formed on the outer surface of the bolt portion 242T. The bearing holder 242G is disposed below the roller shaft main body 242B.

[0065] The nut 244 can enter the bolt portion 242T. The roller 240 is attached to the guard 118 by inserting the nut 244 into the bolt portion 242T from the side farther from the sanding belt B, with the bolt portion 242T passing through either of the mounting holes 228, 238 from the side closer to the sanding belt B to the side farther from the sanding belt B. The first guard body 220 or the second guard body 222 is sandwiched between the nut 244 and the roller shaft main body 242B. The roller 240 is installed in either of the mounting holes 228, 238, which serves as an installation portion. The rollers 240 may be attached by another attachment structure instead of the bolt portion 242T and the nut 244, or together with the bolt portion 242T and the nut 244. For example, the rollers 240 may be attached by engaging a locking portion such as a claw with a locked portion such as a groove in the first guard body 220 or the second guard body 222.

[0066] The roller rotating portion 246 has a roller rotating portion main body 246B and a flange portion 246F. The roller rotation part body 246B is made of heat-treated steel and has a hollow cone shape. The diameter of the roller rotation part body 246B increases from the top to the bottom, i.e., as it moves away from the guard 118. The roller rotation part body 246B has a tapered shape that narrows from the bottom to the top. Inside the roller rotation part body 246B, a protrusion 246J is provided that protrudes radially inward relative to the adjacent portion. The flange portion 246F is made of heat-treated steel and is disposed below the roller rotation portion body 246B. The flange portion 246F is held by the roller rotation portion body 246B. The flange portion 246F closes the lower end portion of the roller rotation portion body 246B. The roller rotating portion main body 246B and the flange portion 246F may be integrally formed.

[0067] The first bearing 247 is disposed outside the bearing holder 242G. The upper surface of the inner ring of the first bearing 247 contacts the lower surface of the roller shaft body 242B. The lower surface of the outer ring of the first bearing 247 contacts the upper surface of the protruding portion 246J. The first bearing 247 supports the roller rotation portion 246 rotatably around the roller shaft 242 . The second bearing 248 is disposed outside the bearing holder 242G. An upper surface of an outer ring of the second bearing 248 is in contact with a lower surface of the protruding portion 246J. A lower surface of an inner ring of the second bearing 248 is in contact with the circlip 249. The second bearing 248 supports the roller rotating portion 246 so that the roller rotating portion 246 is rotatable around the roller shaft 242 . The circlip 249 is fastened to the lower end of the bearing holder 242G. The circlip 249 fixes the first bearing 247 and the second bearing 248 to the roller shaft 242.

[0068] The roller 240 is detachably attached to either of the mounting holes 228,238. The attached roller 240 is disposed laterally on the side of the sanding belt B under normal conditions when no load other than the feed load is applied to the sanding belt B. The attached roller 240 does not normally contact the side of the sanding belt B. Note that the attached roller 240 may normally contact the sanding belt B. The extension direction of the roller 240 is perpendicular to the extension direction of the attached sanding belt B when viewed from the side. Note that the extension direction of the roller 240 may intersect with the extension direction of the attached sanding belt B at an angle other than 90°. The extension direction of the roller 240 is perpendicular to the extension direction of the first wheel shaft 150 and the second wheel shaft 200, which are the driven wheel shafts, when viewed from at least one of the above and the rear. More specifically, the extension direction of the roller 240 attached to the attachment hole 228 is the front-rear direction, and is perpendicular to the left-right direction, which is the direction of the driven wheel shaft, when viewed from above. Moreover, the extension direction of the roller 240 attached to the attachment hole 238 is the up-down direction, and is perpendicular to the left-right direction, which is the direction of the driven wheel shaft, when viewed from the rear. The extension direction of the roller 240 may intersect with the extension direction of the driven wheel shaft at an angle other than 90°.

[0069] The distal arm 110, the proximal arm 104, the guard 118, and the stopper mechanism 119 are elements of a working unit structure P1, which is a structure for preventing the sanding belt B from falling off from the attachment 4 as a working unit. Elements other than those described above may be added to the working section structure P1 for preventing the sanding belt B from falling off. Also, some of the elements described above may be omitted from the working section structure P1.

[0070] Fig. 13 is a partial cross-sectional view taken along the line corresponding to the line AA in Fig. 2 when the second drive wheel 300 is attached. Fig. 14 is an exploded perspective view of the right side of the second drive wheel 300. Fig. 15 is an exploded perspective view of the left side of the second drive wheel 300. The second drive wheel 300 as the second wheel has a cylindrical shape extending in the left and right directions. The second drive wheel 300 is similar to the first drive wheel 70, including modified examples, except for the structure inside the outer cylinder body 73. The same members and parts of the second drive wheel 300 as those of the first drive wheel 70 are denoted by the same reference numerals as those of the first drive wheel 70, and descriptions thereof will be omitted as appropriate. The second drive wheel 300 comprises an inner cylinder 371 as a mounting cylinder, two bolts 72, an outer cylinder 73 as a rotating cylinder, a first outer cylinder bearing 74, a second outer cylinder bearing 75, an outer cylinder circlip 76, a first shaft 301, multiple (six here) planetary gears 302, a second shaft 377, a first shaft bearing 378, a second shaft bearing 379, a third shaft bearing 303, a first inner cylinder circlip 380, a second inner cylinder circlip 304, an O-ring 81, two washers 82, and a shaft circlip 83.

[0071] The inner cylinder 371 has an inner cylinder main body 371B, two bolt holes 71H, a first flange 71F, a second flange 71G, a third flange 371E, and an internal gear portion 371N. The inner cylinder main body 371B is cylindrical and extends left and right. The third flange 371E protrudes radially inward from the inner surface of the inner cylinder main body 371B. The third flange 371E is disposed between the first flange 71F and the second flange 71G in the left-right direction. The third flange 371E is ring-shaped. The internal gear portion 371N is disposed on the inner surface of the inner cylinder main body 371B. The internal gear portion 371N has a plurality of teeth extending radially inward. The internal gear portion 371N meshes with each planetary gear 302.

[0072] The first shaft 301 has a first shaft main body 301B, a receiving portion 301R, and a sun gear portion 301C. The first shaft 301 is disposed radially inward of the inner cylindrical body 371. The first shaft main body 301B is cylindrical and extends left and right. The receiving portion 301R is configured similarly to the receiving portion 77R. The receiving portion 301R is disposed inside the right portion of the first shaft main body 301B. The receiving portion 301R is connected to the connecting portion 30C of the spindle 30 by spline connection. The sun gear portion 301C is disposed on the outside of the left portion of the first shaft main body 301B. The sun gear portion 301C has a plurality of teeth extending radially outward, and meshes with each of the planetary gears 302.

[0073] The second shaft 377 has a shaft main body 377B, a carrier portion 377R, and a connection portion 377C. The second shaft 377 is disposed radially inward of the inner cylindrical body 371. The shaft body 377B is cylindrical and extends in the left and right directions. The carrier portion 377R is disposed on the right side of the shaft body 377B. The carrier portion 377R has a disk-shaped carrier body extending vertically and longitudinally, and a plurality of shaft portions (six in this example) protruding to the right from the right surface of the carrier body. The diameter of the carrier body is larger than the diameter of the shaft body 377B. The carrier portion 377R rotatably supports the planetary gears 302 on the corresponding shaft portions. Each planetary gear 302 rotates around an axis in the left-right direction. Each planetary gear 302 is disposed around the sun gear portion 301C. The connecting portion 377C is configured similarly to the connecting portion 77C, and is disposed on the outside of the left portion of the shaft body 377B. The connection portion 377C is inserted into the outer cylinder body receiving portion 73R and is connected to the outer cylinder body receiving portion 73R by spline coupling.

[0074] The internal gear portion 371N, the sun gear portion 301C, the planetary gears 302, and the carrier portion 377R constitute a planetary gear mechanism M as a speed change mechanism. The planetary gear mechanism M is disposed between the left wall portion 73W and the bolt hole 71H in the left-right direction. The internal gear portion 371N is fixed to the internal cylinder body 371. The sun gear portion 301C is rotated by the spindle 30. Each planetary gear 302 rotates on its own axis and revolves following the carrier portion 377R. The planetary gear mechanism M reduces the rotation speed of the first shaft body 301 and transmits it to the second shaft body 377. The second shaft body 377 is connected to the first shaft body 301 via the planetary gear mechanism M. Note that the reduction in speed from the first shaft body 301 to the second shaft body 377 may be achieved by a mechanism other than the planetary gear mechanism M.

[0075] The first shaft bearing 378 is fixed to the inside of the right portion of the inner cylinder 371. The first shaft bearing 378 supports the first shaft 301 rotatably. The second shaft bearing 379 is fixed to the inside of the center portion of the inner cylinder 371. The second shaft bearing 379 supports the first shaft 301 rotatably. The third shaft bearing 303 is fixed to the inside of the right portion of the inner cylinder 371. The third shaft bearing 303 supports the second shaft 377 so that it is rotatable.

[0076] The first inner cylinder circlip 380 is fixed to a groove formed on the inner surface of the right end portion of the inner cylinder main body 371B. The first shaft bearing 378 is sandwiched between a first step on the outer surface of the first shaft 301 and the inner cylinder circlip 80 . The second shaft bearing 379 is sandwiched between a second step portion on the outer surface of the first shaft 301 and a third flange 371E of the inner cylinder 371. The second shaft bearing 379 is in contact with the third flange 371E. The inner cylinder circlip 80 prevents the members inside the inner cylinder 371 on the right side of the third flange 371E from coming off.

[0077] The second inner cylinder circlip 304 is fixed to a groove formed on the inner surface of the left end portion of the inner cylinder main body 371B. The third shaft bearing 303 is sandwiched between a step on the inner surface of the left end portion of the inner cylinder 371 and the second inner cylinder circlip 304. The third shaft bearing 303 contacts the third flange 371E. The third shaft bearing 303 is larger than the first shaft bearing 378 and the second shaft bearing 379. The third shaft bearing 303 is disposed on the left side of the carrier portion 377R. The second inner cylinder circlip 304 prevents the members inside the inner cylinder 371 on the left side of the third flange 371E from coming off.

[0078] The second drive wheel 300 is integrally connected to the spindle 30. The rotation of the spindle 30 is transmitted to the second drive wheel 300. The parts of the second drive wheel 300 other than the inner cylinder body 371 rotate around their own central axis. More specifically, the rotation of the spindle 30 is transmitted from the first shaft body 301 to the second shaft body 377 after being reduced in speed by the planetary gear mechanism M, and the second shaft body 377 and the outer cylinder body 73 connected to the second shaft body 377 rotate. The second drive wheel 300 receives the sanding belt B. The sanding belt B is removably mounted on the second drive wheel 300. The second drive wheel 300 is for drivably mounting the sanding belt B. The second drive wheel 300 rotates slower than the first drive wheel 70 and drives the sanding belt B at a slower speed.

[0079] The first drive wheel 70 and the second drive wheel 300 are elements of a working unit structure P2, which is a structure for changing the speed of the attachment 4. The first drive wheel 70 and the second drive wheel 300 are a set of wheels for changing the speed. In addition, elements other than those described above may be added to the working unit structure P2 or the wheel set for changing the speed. Also, some of the elements described above may be omitted from the working unit structure P2.

[0080] An example of the operation of the tube belt sander 1, the attachment 4, and the working unit structures P1 and P2 will be described. The user mounts the charged battery 18 in the battery mounting section 16 of the main body 2. The user mounts the attachment 4 on the main body 2. The user places the attachment 4 in a locked state. The user mounts the sanding belt B on the attachment 4. When the user operates the switch operation unit 26, the switch main body 22 is turned on. Then, the controller 20 controls and supplies power from the battery 18 to the motor 12 so that the motor shaft 50 rotates at a speed corresponding to the rotation position of the speed adjustment dial 24. As a result, the motor 12 is driven at a speed corresponding to the rotation position of the speed adjustment dial 24. The rotation direction of the motor shaft 50 may be switchable.

[0081] Rotation of the motor shaft 50 rotates the fan 14, and air is exhausted to the exhaust ports 42E and 48, forming an air flow (wind) within the main body 2. Such wind cools the internal mechanisms of the tube belt sander 1, including the motor 12.

[0082] Furthermore, the rotational force of the motor shaft 50 is reduced in speed by the bevel gear 60 and then transmitted to the spindle 30 . When the first drive wheel 70 is mounted on the spindle 30, the first drive wheel 70 drives the sanding belt B at a speed corresponding to the rotational speed of the spindle 30. The sanding belt B rotates in a caterpillar-like manner outside the first drive wheel 70, the first wheel 106, and the second wheel 114. On the other hand, when the second drive wheel 300 is attached to the spindle 30, the second drive wheel 300 feeds the sanding belt B at a speed corresponding to a rotational speed reduced from the rotational speed of the spindle 30 by the planetary gear mechanism M. The sanding belt B rotates in a loop-like manner outside the first drive wheel 70, the first wheel 106, and the second wheel 114 at a slower speed than when the first drive wheel 70 is attached. The tube belt sander 1 has a working section structure P2 including a first drive wheel 70 and a second drive wheel 300 interchangeably. Thus, a user can change the feed speed of the sanding belt B. For example, when grinding a pipe disposed in a building such as a residence or a store, the user selects the first drive wheel 70, which has a higher speed. On the other hand, for example, when grinding a welded portion of a pipeline disposed in a factory or an industrial complex, the user selects the second drive wheel 300, which has a lower speed.

[0083] The user holds the grip portion G of the main body 2 with his / her right hand and holds the grip 116 of the attachment 4 with his / her left hand. Then, the user places the underside of the portion of the sanding belt B between the first wheel 106 and the second wheel 114 on the workpiece, such as the outer surface of a pipe. The sanding belt B then polishes the workpiece.

[0084] At this time, the route of the sanding belt B between the first wheel 106 and the second wheel 114 is recessed upward along the processed part in a "U" shape when viewed from left to right in response to the pressing force against the processed part. When the recess in the route of the sanding belt B occurs, the route of the sanding belt B changes from a triangular shape to a rectangular shape. Due to such a recess in the route of the sanding belt B, the processed part is wrapped in the sanding belt B. Therefore, the polishing of the processed part is performed more effectively. Since the length of the sanding belt B does not change, the second wheel 114 approaches the first wheel 106 by an amount corresponding to the recess in the route of the sanding belt B. The approach of the second wheel 114 to the first wheel 106 is mainly caused by the rotation of the distal arm 110 relative to the proximal arm 104. The rotation of the distal arm 110 relative to the proximal arm 104 is caused by the torsion spring 162 in an elastic state. Furthermore, the base end arm 104 rotates relative to the base portion 100 under the action of elastic force from a torsion spring 132 . The tube belt sander 1 is a two-joint type having a first joint portion 102 and a second joint portion 108 that can rotate while elasticity is acting, so that the sanding belt B contacts the workpiece better than a one-joint type without the first joint portion 102. Therefore, the tube belt sander 1 can polish the workpiece better.

[0085] The user can appropriately change the way in which the sanding belt B contacts the processed part, that is, the position and range at which the sanding belt B contacts the processed part, depending on the overall shape of the processed part. Depending on how the sanding belt B hits the workpiece, the sanding belt B may attempt to climb over at least one of the first flange 73F and the second flange 73G of the outer cylinder 73, the first flange 152F and the second flange 152G of the first wheel 106, and the first flange 202F and the second flange 202G of the second wheel 114, and may attempt to come off at least one of the outer cylinder 73, the first wheel 106, and the second wheel 114. In particular, when the sanding belt B hits a curved workpiece, the sanding belt B is more likely to fall off the attachment 4 due to a reduction in the tension of the sanding belt B. In response to this, the tube belt sander 1 uses the working section structure P1 including the stopper mechanism 119 to prevent the sanding belt B from falling off the attachment 4. That is, the roller 240 attached to the left mounting holes 228, 238 blocks the leftward movement of the sanding belt B that is about to fall off to the left. Also, the roller 240 attached to the right mounting holes 228, 238 blocks the rightward movement of the sanding belt B that is about to fall off to the right. Although this rarely occurs, the lateral movement of the sanding belt B that is about to fall off to the left and right simultaneously due to twisting or meandering of the sanding belt B is blocked by the roller 240 attached to the left mounting holes 228, 238. Furthermore, in the tube belt sander 1, a roller 240 that is rotatable around an axis is used as the stopper mechanism 119. Therefore, the roller 240 rotates together with the sanding belt B that contacts it, and can make gentle contact with the sanding belt B. Furthermore, if a plurality of rollers 240 are provided, the falling off of the sanding belt B is further suppressed. Furthermore, if the rollers 240 are disposed on both the left and right sides of the sanding belt B, the falling off of the sanding belt B is suppressed in two directions.

[0086] In order to prevent the sanding belt B from falling off, it is conceivable to increase the protruding height of each of the first flanges 73F, 152F, 202F and the second flanges 73G, 152G, 202G. In this case, the sanding belt B becomes more difficult to install because the protruding height is increased. The first flanges 73F, 152F, 202F and the second flanges 73G, 152G, 202G are disposed on the side of the curved portion in the route of the sanding belt B. Therefore, it is more difficult for the user to install the sanding belt B when the protruding height is increased, compared to when the user installs the sanding belt B while avoiding the roller 240 disposed on the side of the straight portion in the route of the sanding belt B. Moreover, the greater the protruding height, the greater the possibility that the first flanges 73F, 152F, 202F and the second flanges 73G, 152G, 202G will come into contact with the workpiece. In particular, the first flanges 73F and 73G of the outer cylinder 73 and the first flanges 202F and 202G of the second wheel 114 are closer to the workpiece, and therefore more likely to come into contact with the workpiece. In the tube belt sander 1, the sanding belt B can be sufficiently prevented from falling off even if the protruding heights are not so large. In the tube belt sander 1, at least one of the protruding heights may be sufficiently large. In this case, the possibility of the sanding belt B falling off is further reduced. Furthermore, the possibility that the first flange 73F, 152F, 202F and the second flange 73G, 152G, 202G come into contact with the user's arm or the like increases by the amount of the protruding height. The roller 240 can be made smaller than the first flange 73F, 152F, 202F and the second flange 73G, 152G, 202G, and is not limited to being disposed at a corner portion in the route of the sanding belt B. Therefore, the possibility that the stopper mechanism 119 comes into contact with the user's arm or the like is further reduced. The stopper mechanism 119 is disposed on the opposite side of the grip portion G in the guard 118. Therefore, the stopper mechanism 119 is prevented from coming into contact with the user's arm or the like.

[0087] When sanding is completed, the user stops the forward sliding operation of the switch operation unit 26 to turn off the motor 12. At this time, the sanding belt B stops. The user removes the sanding belt B, the attachment 4, and the battery 18 as appropriate.

[0088] The embodiments of the present disclosure are not limited to the above and the modified examples, and further modifications such as those described below can be made as appropriate. At least one of the rollers 240 and the mounting holes 228, 238 may be provided only on the left or right side, i.e., only on one side. Also, one or more rollers 240 may be provided in a non-detachable manner. One or more rollers 240 may be provided directly on at least one of the base arm 104 and the tip arm 110. At least one of the first flanges 73F, 152F, 202F and the second flanges 73G, 152G, 202G may be omitted. Three or more types of drive wheels for changing the speed may be provided. In transmitting the rotation from the first shaft 301 to the second shaft 377 in the second drive wheel 300, the rotation may be increased rather than decreased, or may be transmitted at the same rotational speed.

[0089] The speed reduction mechanism from the motor shaft 50 to the first drive wheel 70 in the tube belt sander 1 may be replaced with a speed reduction mechanism other than the pinion 52 and the bevel gear 60 . The tube belt sander 1 may be AC-powered with a commercial power source by having a power cord instead of the battery mounting portion 16. At least any of the materials of the various cases and housings may be changed to resin, metal, a composite of these, etc. The classification of the housing 10 may be changed from that described above. At least any of the various members, number of parts, installation or non-installation, materials, treatment or non-treatment such as heat treatment, arrangement, structure, and type, etc. may be appropriately changed.

[0090] Furthermore, the above embodiment or its modified example may be applied to other tube belt sanders. For example, the above embodiment or its modified example may be applied to a single-joint type tube belt sander. The single-joint type tube belt sander may be a bifurcated single-joint type. Alternatively, the above embodiment or its modified example may be applied to a tube belt sander having three or more driven wheels. Alternatively, the above embodiment or its modified example may be applied to a tube belt sander having a plurality of drive wheels. Alternatively, the above embodiment or its modified example may be applied to a tube belt sander having three or more joints. Alternatively, the above embodiment or its modified example may be applied to other belt sanders. For example, the above embodiment or its modified example may be applied to a belt sander in which a track-shaped sanding belt is disposed at the lower end of a block-shaped main body. [Explanation of symbols]

[0091] 1··tube belt sander (belt sander), 4··attachment (working part), 10··housing, 12··motor (electric motor), 70··first driving wheel (component of wheel set), 71, 371··inner cylinder (mounting cylinder), 71H··bolt hole (mounting part), 73··outer cylinder (rotating cylinder), 73W··left wall part (wall part), 77··shaft, 77C, 377C··connection part, 77R, 301R··receiving part, 104··base end arm (arm), 106··first wheel (driven wheel), 110··tip end arm (arm), 114··second wheel (driven wheel), 118··guard (standing part, spark guard), 240··roller (stopper), 300··second driving wheel wheel (wheel, component of wheel set), 301··first shaft body, 301C··sun gear portion (gear, component of planetary gear mechanism M), 302··planetary gear (gear, component of planetary gear mechanism M), 303··third shaft body bearing, 371E··third flange (flange with which second shaft body bearing 379 and second shaft body bearing 303 contact), 371N··internal gear portion (gear, component of planetary gear mechanism M), 377··second shaft body, 377R··carrier portion (component of planetary gear mechanism M), 378··first shaft body bearing, 379··second shaft body bearing, B··sanding belt, M··planetary gear mechanism (speed change mechanism), P1··working section structure (for preventing sanding belt B from falling off).

Claims

1. A wheel for mounting a sanding belt in a belt sander having an electric motor, comprising: A speed change mechanism that reduces or increases the rotational drive force from the electric motor. Equipped with A belt sander wheel characterized by:

2. The speed change mechanism includes gears.

2. A wheel for a belt sander according to claim 1.

3. The speed change mechanism includes a planetary gear mechanism.

3. A wheel for a belt sander according to claim 2.

4. The device further includes a mounting cylinder and a first shaft, The mounting cylinder is attached to a housing of the belt sander, The first shaft has a receiving portion for receiving a rotational driving force from the electric motor, and is disposed radially inward of the mounting cylinder. A wheel for a belt sander according to any one of claims 1 to 3.

5. The mounting cylinder is cylindrical.

5. A wheel for a belt sander according to claim 4.

6. Further, the rotating cylinder is provided, The rotating cylinder is (1) disposed radially outward of the mounting cylinder, (2) supported rotatably relative to the mounting cylinder, and (3) configured to receive the sanding belt. A wheel for a belt sander according to claim 4 or 5.

7. Further, a second shaft body is provided, The mounting cylinder is attached to the housing at a mounting portion disposed at an end portion of the mounting cylinder, the mounting portion being an end portion of the mounting cylinder. the rotating cylinder has a wall portion at an end portion of the rotating cylinder opposite to the attachment portion side end portion, the second shaft is connected to the first shaft via the speed change mechanism and is connected to the wall portion, The speed change mechanism is disposed between the wall portion and the mounting portion. A wheel for a belt sander according to claim 6.

8. the speed change mechanism includes a planetary gear mechanism, The first shaft has a sun gear portion at an end opposite to the receiving portion, The second shaft has a carrier portion that supports a planetary gear at an end opposite to the wall portion, The sun gear portion is in mesh with the planetary gear. A wheel for a belt sander according to claim 7.

9. Further, the bearing includes a first shaft bearing, a second shaft bearing, and a third shaft bearing, The mounting cylinder has a flange protruding radially inward from its inner surface, the first shaft is held by the mounting cylinder via the first shaft bearing and the second shaft bearing, The second shaft is held by the mounting cylinder via the third shaft bearing, The second shaft bearing and the third shaft bearing are in contact with the flange. A wheel for a belt sander according to claim 7 or 8.

10. The third shaft bearing is larger than at least one of the first shaft bearing and the second shaft bearing. A wheel for a belt sander according to claim 9.

11. The belt sander wheel according to any one of claims 1 to 10 is provided. A belt sander characterized by:

12. A first wheel, which is a wheel of a belt sander according to any one of claims 1 to 10; a second wheel having a rotational speed faster than that of the first wheel; Equipped with A belt sander wheel set characterized by:

13. The second wheel has one shaft body and a rotating cylinder body, The rotating cylinder of the second wheel has a wall portion, The shaft body has a receiving portion for receiving a rotational driving force from the electric motor and a connecting portion for connecting to the wall portion of the second wheel.

13. A wheel set for a belt sander as claimed in claim 12.

14. The first wheel or the second wheel of the wheel set of the belt sander according to claim 12 or 13 can be selectively mounted. A belt sander characterized by:

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