GB2577441A

GB2577441A - Air tool

Info

Publication number: GB2577441A
Application number: GB1918473.8A
Authority: GB
Inventors: Azuma Takanori
Original assignee: Nitto Kohki Co Ltd
Current assignee: Nitto Kohki Co Ltd
Priority date: 2017-06-23
Filing date: 2018-05-29
Publication date: 2020-03-25
Anticipated expiration: 2038-05-29
Also published as: KR20200018646A; DE112018003194T5; CN110785266A; KR102338966B1; GB201918473D0; JPWO2018235541A1; GB2577441B; WO2018235541A1; TW201919829A; TWI677411B; JP6864741B2; CN110785266B

Abstract

[Problem] To provide an air tool configured in such a way that an operator can easily recognize a state in which a release valve is in a released position, and a switching valve is in a neutral position. [Solution] A belt-type grinding tool (100) is provided with: an air motor (112) capable of forward rotation and reverse rotation; an opening and closing valve (126) which opens and closes an air supply passage (144); and a switching valve (124) which switches the air supply passage (144). When the switching valve (124) is in a neutral position between a forward rotation position and a reverse rotation position, first and second branch air supply passages (154, 156) are caused to communicate with the air supply passage (144), and the first and second branch air supply passages (154, 156) are caused to communicate with an exhaust passage. Compressed air reaches the first and second branch air supply passages (154, 156) from the air supply passage (144), and either passes through the air motor (112) from first and second motor air supply ports of the air motor (112) and reaches the exhaust passage, or reaches the exhaust passage without passing through the air motor (112), and is exhausted to the outside. An exhaust sound is generated at this time together with the exhaust.

Description

Title of Invention: Air Tool

Technical Field:

[00011 The present invention relates to air tools including an air motor and, more particularly, to an air tool configured to allow the rotational direction of an air motor to be switched between forward rotation and reverse rotation.

Background Art:

[0002] Among air tools including an air motor such as a torque wrench, a. belt-type grinding tool, etc., there is known an air tool configured to allow the rotational direction of the wrench or the belt to be changed by switching between supply paths for supplying compressed air to the air motor to thereby switch the rotational direction of the air motor between fin-ward rotation and reverse rotation. In this type of air tool, the air motor usually has two air supply ports, and an air supply path extending from an air supply port connected to an external compressed air supply source is branched at a halfway point into two branch air supply paths, which extend to the two air supply ports, respectively, of the air motor. At the branch point of the air supply path, a switching valve for switching between the branch air supply paths is provided. the switching valve is displaceable between a forward rotation position and a reverse rotation position. When the switching valve is placed in the forward rotation position, the air supply path and one branch air supply path are communicated with each other, so that compressed air is supplied to the air motor from one air supply port. Consequently, the air motor rotates forward. When the switching valve is placed in the reverse rotation position, the air supply path and the other branch air supply path are communicated with each other, so that compressed air is supplied to the air motor from the other air supply port. Consequently, the air motor rotates reversely. The air tool further includes an open-close valve for opening and closing the air supply path, separately from the switching valve. When the open-close valve is displaced to an open position, compressed air from the external compressed air supply source is supplied to the supply path, and the

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air motor is driven in a direction set by the switching valve (Patent Literatures I and 2). Citation List: Patent Literature: [00031 Patent Literature 1: Japanese Utility Model Registration Application Publication No. Hei 2-145971 Patent Literature 2: Japanese Patent Application Publication No. 2005-28533 Patent Literature 3: Japanese Examined Utility Model Application Publication No. Sho 48-43670

Summary of Invention:

Technical Problem: [0004] With the above-described air tool capable or switching the rotational direction, when the switching valve is placed in a neutral position between the forward rotation position and the reverse rotation position, the air supply path is not communicated with either of the branch air supply paths. Accordingly, compressed air will not flow beyond the switching valve irrespective of the state of the open-close valve and therefore cannot be supplied to the air motor. Consequently, the air motor does not rotate. Therefore, if the worker actuates the open-close valve without being aware of that the switching valve is in the neutral position, the air motor will not be driven, and no other change will occur in the air tool. Accordingly, the worker may misunderstand that the air tool is broken, or that compressed air is not supplied to the air tool. With the air tools of Patent Literatures 1 and 2, if a ring-shaped operating member for actuating the open-close valve is configured to be held in a drive position where the open-close valve is placed in an open position as in the air tool of Patent Literature 3, the air motor may be driven unexpectedly when the switching valve is actuated to the forward or reverse rotation position to set the driving direction of the air motor for the air tool which has been stopped in a state where the switching valve is in the neutral position and the open-close valve is in the open position. This may lead to an unexpected accident. -2 -

[0005] Accordingly, an object of the present invention is to provide an air tool configured to allow a worker to readily recognize a state where the open-close valve is in the open position and the switching valve is in the neutral position.

Solution to Problem: [0006] That is, the present invention provides an air tool including an air motor having a first motor air supply port and a second motor air supply port. The air motor is configured to rotate forward when compressed air is supplied thereto from the first motor air supply port and to rotate reversely when compressed air is supplied thereto from the second motor air supply port. The air tool includes the following: an air supply port configured to he connected to an external compressed air supply source; an air supply path extending from the air supply port; a first branch air supply path extending to the first motor air supply port of the air motor; a second branch air supply path extending to the second motor air supply port of the air motor; an exhaust path for discharging compressed air to the outside; an open-close valve disposed halfway in the air supply path, the open-close valve being displaceable between an open position for opening the air supply path and a closed position for closing the air supply path; an operating member for actuating the open-close valve to open and close, the operating member being displaceable between a drive position where the open-close valve is placed in the open position and a stop position where the open-close valve is placed in the closed position; and a switching valve disposed between the air supply path and the first and second branch air supply paths, the switching valve being displaceable among a forward rotation position where the first branch air supply path is communicated with the air supply path and where the second branch air supply path is cut off from the air supply path, a neutral position where the first and second branch air supply paths arc communicated with the air supply path, and a reverse rotation position where the first branch air supply path is cut off from the air supply path and where the second branch air supply path is communicated with the air supply path. When the open-close valve is in the open position and the switching valve is in the neutral position, compressed air -3 -supplied from the air supply port reaches the first and second branch air supply paths from the air supply path and is discharged through the exhaust path substantially without rotating the air motor.

[0007] In the above-described air tool, when the open-close valve is in the open position and the switching valve is in the neutral position, compressed air is discharged through the exhaust path; therefore, exhaust sound is generated when compressed air is discharged. The exhaust sound allows the worker to readily recognize that the switching valve is in the neutral position and the open-close valve is in the open position.

[0008] Specifically; the arrangement may be as follows. When the switching valve is in the neutral position, the first and second branch air supply paths are communicated with the exhaust path, and when the open-close valve is in the open position and the switching valve is in the neutral position, at least part of compressed air reaching the first and second branch air supply paths from the air supply path is passed through the exhaust path from the first and second branch air supply paths without passing through the air motor.

[0009] The following arrangement may be adopted in place of or in addition to the above: the air motor is a vane motor having a circular columnar motor chamber of circular cross-section and a rotor rotatably provided in the motor chamber. The air motor has a motor exhaust port located at substantially equal circumferential distances from the first and second motor air supply ports opened into the motor chamber adjacently to each other, the motor exhaust port being communicated with the exhaust path. When the open-close valve is in the open position and the switching valve is in the neutral position, at least part of compressed air reaching the first and second branch air supply paths from the air supply path enters the motor chamber from the first and second motor air supply ports, and compressed air entering the motor chamber from the first motor air supply port and compressed air entering the motor chamber from the second motor air supply port flow around the rotor in mutually opposite directions, respectively, to reach the motor exhaust port and are passed through the exhaust path. [0010] Further, the operating member may be configured to be capable of being held in the drive position.

[0011] When the operating member is configured to he capable of being held in the drive position, particularly, the air motor is likely to be unexpectedly driven when the switching valve is actuated to use the air tool which has been stopped in a state where the switching valve is in the neutral position and the open-close valve is in the open position. In this regard, however, the relevant air tool can allow the worker to readily recognize by exhaust sound that the open-close valve is in the open position; therefore, it is possible to prevent the air motor from being unexpectedly driven as described above.

[0012] Preferably, the arrangement may be as follows. The air tool has a first body part including the air motor and the switching valve, and a second body part including the open-close valve and the operating member and rotatably attached to the first body part. One of the first body part and the second body part has a first locking portion, and the other of the first and second body parts has a plurality of second locking portions fittable to the first locking portion. When the second body part is rotated relative to the first body part, the first locking portion is fitted to one of the plurality of second locking portions at one of a plurality of relative rotational positions, thereby holding the rotational direction position of the second body part relative to the first body part.

[0013] The above-described arrangement makes it possible to change the circumferential position of the operating member as desired. Accordingly, even when the worker changes the direction of his or her hand gripping the air tool or the gripping direction in accordance with the nature of work to be done, the position of the operating member can be changed according to the direction of the hand or the gripping direction, which allows an improvement in operability [0014] Preferably, the arrangement may be as follows. 1'he operating member is a -5 -lever pi votably attached to the second body part. The air tool further includes a lever locking member for preventing the lever from being displaced to the drive position. [0015] The above-described arrangement makes it possible to prevent the air motor from being undesirably driven which might otherwise be caused by the worker mistakenly displacing the lever to the drive position when rotating the second body part, for example.

[00161 Embodiments of the air tool according to the present invention will be explained below on the basis of the accompanying drawings.

Brief Description of Drawings:

[0017] Fig. 1 is a top view of a belt-type grinding tool according to a first embodiment of the present invention.

Fig. 2 is a side view of the belt-type grinding tool shown in Fig. 1.

Fig. 3 is a sectional top view taken along the line A-A in Fig. 2.

Fig. 4 is a. sectional side view taken along the line B-B in Fig. 3.

Fig. 5 is a sectional side view taken along the line C-C in Fig. 3.

Fig. 6A is an enlarged sectional view of a switching valve and its vicinities, showing a state where the switching valve is in a forward rotation position.

Fig. 68 is an enlarged sectional view of the switching valve and its vicinities, showing a state where the switching valve is in a neutral position.

Fig. 6C is an enlarged sectional view of the switching valve and its vicinities, showing a state where the switching valve is in a reverse rotation position.

Fig. 7 is a top view of a belt-type grinding tool according to a second embodiment of the present invention.

Fig. 8 is a side view of the belt-type grinding tool shown in Fig. 7.

Fig. 9 is a sectional top view taken along the line D-D in Fig. 8.

Fig. 10 is a sectional side view taken along the line E-E in Fig. 9.

Fig. 11 is a side view of the belt-type grinding tool in Fig. 7, showing a state where a second body part has rotated through 45 degrees.

Fig. 12 is a sectional top view taken along the line F-17 line in Fig. 11.

Fig. 13 is an illustration showing a rear end face of a first body part as seen from the line 0-0 in Fig. 12.

Fig. 14 is an illustration showing a forward end face of the second body part as seen from the line H-II in Fig. 12.

Fig. 15 is a side view of the belt-type grinding tool in Fig. 7, showing a state where the second body part has rotated through 180 degrees.

Description of Embodiments:

[0018] An air tool according to a first embodiment of the present invention is, as shown in Figs. 1 to 3, a belt-type grinding tool 100 which includes a tool body 110 including an air motor 112, a drive pulley 116 secured to a drive shaft 114 of the air motor 112, a pulley support bar 118 longitudinally displaceably attached to the tool body 110, and an idle pulley 120 rotatably attached to a forward end portion of the pulley support bar 118. An endless grinding belt 122 is wound around between the drive pulley 116 and the idle pulley 120 and driven to rotate by the drive of the air motor 112. In the belt-type grinding tool 100, the rotational direction of the endless grinding belt 122 can be changed by changing the driving direction of the air motor 112 by using a switching valve 124, and the air motor 112 is driven and stopped by controlling the supply of compressed air to the air motor 112 by opening and closing an open-close valve 126, as will be described later.

[0019] The air motor 112 is, as shown in Figs. 4 and 5, a vane motor having a motor housing 130 defining a. circular columnar motor chamber 128 of circular cross-section, a rotor 132 rotatably provided in the motor chamber 128, and a plurality of vanes 134 disposed to be radially displaceable relative to the rotor 132. The motor housing 130 is, as shown in Fig. 4, provided with a first motor air supply port 136 and a second motor air supply port 138 which are opened into the motor chamber 128 adjacently to each other. The motor housing 130 further has, as shown in Fig. 5, a motor exhaust port 140 provided at a position at which the circumferential distances from the first -7 -motor air supply port 136 and the second motor air supply port 138 are substantially equal to each other.

[00201 The tool body 110 is, as shown in Fig. 3, formed with an air supply path 144 extending from an air supply port 142 that is configured to be connected to an external compressed air supply source (not shown). An open-close valve 126 for opening and closing the air supply path 144 is disposed halfway in the air supply path 144. The open-close valve 126 is urged by a spring 146 toward a closed position for closing the air supply path 144. The open-close valve 126 is displaced to an open position for opening the air supply path 144 by pushing in an operating shaft 148, which extends to the outside of the tool body 110, against the urging force of the spring 146. The tool body 110 further includes an operating ring (operating member) 150 for actuating the open-close valve 126 to open and close. The operating ring 150, when in the position shown in the figure, is restrained from rotating in the circumferential direction. The operating ring 150 is enabled to rotate in the circumferential direction when displaced forward (leftward as seen in the figure) against the urging force of a spring 152. When the operating ring 150 is rotated in the circumferential direction after being displaced forward, a sliding inner peripheral surface 150a of the operating ring 150 cam-engages the operating shaft 148 of the open-close valve 126 and presses the operating shaft 148 radially inward, thus causing the open-close valve 126 to be displaced to the open position. By actuating the operating ring 150 from the stop position where the open-close valve 126 is placed in the closed position to the drive position where the open-close valve 126 is placed in the open position, as described above, the air supply path 144 is opened. It should be noted that the operating ring 150 is configured to be held in any rotational position when the worker releases the operating ring 150, and hence the position of the operating ring 150 is held also in the drive position. Therefore, it is unnecessary to continuously hold the operating ring 150 by hand while driving the belt-type grinding tool 100.

[0021] The tool body 110 is further formed with, as shown in Fig. 4, a first branch air supply path 154 extending to the first motor air supply port 136 of the air motor 112, and a second branch air supply path 156 extending to the second motor air supply port 138 of the air motor 112, and a switching valve 124 is disposed between the air supply path 144 and the first and second branch air supply paths 154 and 156. The switching valve 124 is rotatably disposed in a cylindrical valve housing 158. The switching valve 124 has an operating knob 160 (Figs. 2 and 3) located outside the tool body 110. By actuating the operating knob 160, the switching valve 124 can be displaced from a forward rotation position shown in Fig. 6A through a neutral position shown in Fig. 6B to a reverse rotation position shown in Fig. 6C. When the switching valve 124 is in the forward rotation position (Fig. 6A), the first branch air supply path 154 is communicated with the air supply path 144 through an air supply communication path 162 in the switching valve 124, and the second branch air supply path 156 is cut off from the air supply path 144. Accordingly, compressed air supplied from the air supply path 144 passes through the first branch air supply path 154 and is supplied into the motor chamber 128 of the air motor 112 from the first motor air supply port 136, thus rotating the rotor 132 forward (counterclockwise as seen in Fig. 4). When the switching valve 124 is in the reverse rotation position (Fig. 6C), the first branch air supply path 154 is cut off from the air supply path 144, and the second branch air supply path 156 is communicated with the air supply path 144 through the air supply communication path 162. Accordingly, compressed air supplied from the our supply path 144 passes through the second branch air supply path 156 and is supplied into the motor chamber 128 of the air motor 112 from the second motor air supply port 138, thus rotating the rotor 132 reversely (clockwise as seen in Fig. 4). When the switching valve 124 is in the neutral position (Fig. 6B), both the first branch air supply path 154 and the second branch air supply path 156 are communicated with the air supply path 144 through the air supply communication path 162. At this time, compressed air supplied from the air supply port 142 reaches the first branch air supply path 154 and the second branch air supply path 156 and is discharged from the belt-type grinding tool -9 -substantially without rotating the air motor 112, as will be described later. [0022] The tool body 110 is further formed with an exhaust path 164 for finally discharging compressed air supplied from the air supply port 142 to the outside. The exhaust path 164 has, as shown in Fig. 5, an annular first portion 164a extending from the motor exhaust port 140 of the air motor 112 to the periphery of the motor housing 130, a second portion 164b extending rearward from the first portion 164a, and an annular third portion 164e contiguous with the second portion 164b. The exhaust path 164 further has, as shown in Fig. 3, a fourth portion 164d extending from an exhaust communication path 166 of the switching valve 124 to the third portion 164c, and a fifth portion 164e (shown by the broken lines in Fig. 3) extending rearward from the third portion 164c to an exhaust port 168.

[0023] if the operating ring 150 is placed in the drive position to bring the open-close valve 126 into the open position in a state where the switching valve 124 is in the forward rotation position (Fig. 6A), compressed air supplied to the air supply port 142 from the external compressed air supply source reaches the switching valve 124 through the opened air supply path 144. The compressed air further passes through the first branch air supply path 154 communicated with the air supply path 144 through the air supply communication path 162 of the switching valve 124 and is supplied into the motor chamber 128 of the air motor 112 from the first motor air supply port 136, thus rotating the rotor 132 forward. Part of compressed air having rotated the rotor 132 is discharged from the air motor 112 through the motor exhaust port 140, and the remaining compressed air is discharged from the air motor 112 through the second motor air supply port 138. Compressed air discharged from the air motor 112 through the motor exhaust port 140 further passes through the first portion 164a, second portion 164b, third portion 164c and fifth portion 164e of the exhaust path 164 in order and is finally discharged to the outside from the exhaust port 168. On the other hand, compressed air discharged from the air motor 112 through the second motor air supply port 138 passes through the second branch air supply path 156 and through the fourth portion 164d of the exhaust path 164 communicated through the exhaust communication path 166 of the switching valve 124 and further passes through the third portion 164c and fifth portion 164c of the exhaust path 164, before being finally discharged from the exhaust port 168.

[00241 If the operating ring 150 is placed in the drive position to bring the open-close valve 126 into the open position in a state where the switching valve 124 is in the reverse rotation position (Fig. 6C), compressed air supplied from the air supply path 144 passes through the second branch air supply path 156 communicated with the air supply path 144 through the air supply communication path 162 of the switching valve 124 and is supplied into the motor chamber 128 of the air motor 112 from the second motor air supply port 138, thus rotating the rotor 132 reversely. Part of compressed air having rotated the rotor 132 is discharged from the air motor 112 through the motor exhaust port 140 and discharged through the exhaust path 164 in the same way as in the case of forward rotation. The remaining compressed air is discharged from the air motor 112 through the first motor air supply port 136 and passes through the first branch air supply path 154 and further through the fourth portion 164d of the exhaust path 164 communicated through the exhaust communication path 166 of the switching valve 124. Thereafter, the compressed air is discharged through the same route as in the case of forward rotation. Thus, when the belt-type winding tool 100 rotates forward, the second motor air supply port 138 serves as a motor exhaust port, and the second branch air supply path 156 constitutes a part of exhaust path. When the belt-type grinding tool 100 rotates reversely, the first motor air supply port 136 serves as a motor exhaust port, and the first branch air supply path 154 constitutes a part of exhaust path.

[0025] Thus, in response to displacement of the switching valve 124 between the forward rotation position and the reverse rotation position, the rotational direction of the air motor 112 is switched between forward rotation and reverse rotation, and consequently, the rotational direction of the endless grinding belt 122 is changed. It should be noted that the area of opening between the air supply communication path 162 and the first branch air supply path 154 or the second branch air supply path 156 can be changed by controlling the rotational position of the switching valve 124 in the forward rotation position and in the reverse rotation position, and that the rotational speed of the air motor 112 can be controlled by adjusting the amount of compressed air to be supplied to the air motor 112 by changing the above-described opening area. [0026] If the operating ring 150 is placed in the drive position to bring the open-close valve 126 into the open position in a state where the switching valve 124 is in the neutral position (Fig. 6B), compressed air from the air supply path 144 reaches the first branch air supply path 154 and the second branch air supply path 156 which are communicated with the air supply path 144 through the air supply communication path 162 of the switching valve 124. Part of the compressed air enters the motor chamber 128 from each of the first and second motor air supply ports 136 and 138.

Compressed air entering the motor chamber 128 from the first motor air supply port 136 and compressed air entering the motor chamber 128 from the second motor air supply port 138 flow around the rotor 132 in opposite directions to each other through between the inner peripheral surface 128a of the motor chamber 128 and the vanes 134 and are discharged from the motor exhaust port 140 and further through the exhaust path 164. At this time, in the motor chamber 128, substantially the same amounts of compressed air flow in opposite directions to each other, and forces of substantially the same magnitude act on the rotor 132 in mutually opposite rotational directions, respectively. Accordingly, the rotor 132 substantially does not rotate. In addition, the area of opening between the air supply communication path 162 of the switching valve 124 and each of the first and second branch air supply paths 154 and 1.56 is narrow as shown in Fig. 6B. Therefore, even if there is a difference between the amount of compressed air supplied from the first motor air supply port 136 and the amount of compressed air supplied from the second motor air supply port 138 and hence the forces acting on the rotor 132 are not equal to each other, the difference between the forces acting on the rotor 132 is not so great as to rotate the air motor 112 and the drive pulley 116, etc. connected to the air motor 112. That is, the air motor 112 does not rotate either. The remaining compressed air passes through the first branch air supply path 154 and the second branch air supply path 156 and is discharged from the exhaust path 164 through the exhaust communication path 166 of the switching valve 124 without passing through the air motor 112. Thus, when the switching valve 124 is in the neutral position, compressed air is discharged through the exhaust path 164 substantially without rotating the air motor 112. At this time, exhaust sound is generated when compressed air is discharged through the exhaust path 164; therefore, the worker can readily recognize that the open-close valve 126 is in the open position in a state where the switching valve 124 is in the neutral position. It should be noted that there are two routes through which compressed air is discharged: a route passing through inside the air motor 112; and another route not passing through the air motor 112, as has been described above. However, compressed air may be discharged through only one of the routes. For example, in a case where the vanes 134 of the air motor 112 are in abutting contact with the inner peripheral surface 128a of the motor chamber 128 without any gap therehetween, compressed air cannot pass through the rotor 132 chamber. Consequently, substantially all compressed air is discharged through the route passing through the exhaust communication path 166 of the switching valve 124. Which of the routes compressed air will take when discharged or in what flow ratio compressed air will flow through the two routes depend on the magnitude of the flow path resistance of each route.

[0027] An air tool according to a second embodiment of the present invention is, as shown in Figs. 7 to 10, a belt-type grinding tool 200 having a lever 250 as an operating member for actuating an open-close valve 226. Pivoting the lever 250 causes an operating shaft 248 of the open-close valve 226 to be pressed inward, and thus the open-close valve 226 is displaced from the closed position to the open position. [0028] The belt-type grinding tool 200 has a tool body 210 comprising a first body -13 -part 210-1 including an air motor 212 and a switching valve 224, and a second body part 210-2 including an open-close valve 226 and a lever 250. The second body part 210-2 is disposed in coaxial relation to the first body part 210-1 and rotatably attached to the first body part 210-1. By rotating the second body part 210-2 relative to the first body part 210-1, the lever 250 can he changed in position between the position shown in Fig. 8 and the position shown in Fig. 15, which is reached by turning over the second body part 210-2 through 180 degrees. The first body part 210-1 has, as shown in Fig. 13, a rear end face 270 foamed with a plurality of locking recesses (second locking portion) 272 circumferentially spaced at 45 degrees. The second body part 210-2 has, as shown in Figs. 12 and 14, a forward end face 271 equipped with a ball plunger (first locking portion) 274 having a ball urged by a spring. In the state shown in Figs. 11 to 14, the second body part 210-2 has been rotated through 45 degrees relative to the first body part 210-1, and the ball plunger 274 has been fitted into one of the locking recesses 272, thereby allowing the second body part 210-2 to be held in a rotational direction position of 45 degrees relative to the first body part 210-1. Similarly, when the rotational position of the second body part 210-2 relative to the first body part 210-1 is 0 degree, 90 degrees, 135 degrees, or 180 degrees also, the ball plunger 274 is fitted into a corresponding one of the plurality of locking recesses 272 to hold the rotational direction position of the second body part 210-2. Changing the rotational direction position of the second body part 210-2 in this way allows the direction of the lever 250 to be changed in accordance with the nature of work to be done or the worker's preference. Thus, it is possible to improve operability. It should be noted that the rotation range of the second body part 210-2 may be limited to a narrower range, or that the second body part 210-2 may he configured to be rotatable 360 degrees unlimitedly. In addition, the spacing of the locking recesses 272 may be changed appropriately, i.e. may be narrowed so that the position can be adjusted more finely, for example. It should be noted that, of an air supply path 244, a first portion 244a formed in the first body part 210-1 and a second portion 244b formed in the second body part 210-2 are -14 -always in communication with cach other irrespective of the rotational direction position of the second body part 210-2 relative to the first body part 210-1. Similarly, of an exhaust path 264, a second portion 264h and a fourth portion 264d, which are formed in the first body part 210-1, are always in communication with a fifth portion 264e Thrmed in the second body part 210-2 through a third portion 264c between the first body part 210-1 and the second body part 210-2 irrespective of the rotational direction position of the second body part 210-2 relative to the first body part 210-1. [0029] The lever 250 has, as shown in Fig. 10, a lever locking member 276 for locking the lever 250 in a stop position where the open-close valve 226 is placed in the closed position, thereby preventing the lever 250 from being displaced to a drive position. By locking the lever 250 in the stop position by the lever locking member 276, it is possible to prevent the lever 250 from being mistakenly displaced to the drive position, which might otherwise cause the air motor 112 to be undesirably driven. In particularly, when rotating the second body part 210-2 relative to the first body part 210-1, the worker is likely to cause the lever 250 to be pivoted undesirably, and hence it is likely that the air motor 112 may be driven unexpectedly. In this regard, however, it is possible to adjust the rotational direction position of the lever 250 safely by locking the lever 250 in the stop position by the lever locking member 276.

[0030] Although some embodiments of the present invention have been described above, the present invention is not limited to the described embodiments. For example, the invention of the present application is not limited to the belt-type grinding tool but also applicable to other air tools, e.g. a torque wrench. Further, it is not always necessary to have two routes for discharging compressed air when the switching valve is in the neutral position. The air tool may have only either one of the routes.

List of Reference Signs: [0031] Belt-type grinding tool (air tool according to first embodiment) 100; tool body 110; air motor 112; drive shaft 114; drive pulley 116; pulley support bar 118; idle pulley 120; endless grinding belt 122: switching valve 124; open-close valve 126; motor -15 -chamber 128; inner peripheral surface 128a; motor housing 130; rotor 132; vanes 134; first motor air supply port 136; second motor air supply port 138; motor exhaust port 140; air supply port 142; air supply path 144; spring 146 (of open-close valve); operating shaft 148; operating ring (operating member) 150; sliding inner peripheral surface 150a; spring 152 (of operating ring); first branch air supply path 154; second branch air supply path 156; valve housing 158; operating knob 160; air supply communication path 162; exhaust path 164; first portion 164a; second portion 164b; third portion 164c; fourth portion 164d; fifth portion 164e; exhaust communication path 166; exhaust port 168; belt-type grinding tool (air tool according to second embodiment) 200; tool body 210; first body part 210-1; second body part 210-2; air motor 212; switching valve 224; open-close valve 226; air supply path 244; first portion 244a; second portion 244b; operating shaft 248; lever (operating member) 250; exhaust path 264; second portion 264b; third portion 264c; fourth portion 264d; fifth portion 264e; rear end face 270; forward end face 271; locking recesses (second locking portion) 272; ball plunger (first locking portion) 274; lever locking member 276.

-16 -

Claims

Claims 1. An air tool including an air motor having a first motor air supply port and a second motor air supply port, the air motor being configured to rotate forward when compressed air is supplied thereto from the first motor air supply port and to rotate reversely when compressed air is supplied thereto from the second motor air supply port, the air tool comprising: an air supply port configured to be connected to an external compressed air supply source; an air supply path extending from the air supply port; a first branch air supply path extending to the first motor air supply port of the air motor; a second branch air supply path extending to the second motor air supply port of the air motor; an exhaust path for discharging compressed air to an outside; an open-close valve disposed halfway in the air supply path, the open-close valve being displaceable between an open position for opening the air supply path and a closed position for closing the air supply path; an operating member for actuating the open-close valve to open and close, the operating member being displaceable between a drive position where the open-close valve is placed in the open position and a stop position where the open-close valve is placed in the closed position; and a switching valve disposed between the air supply path and the first and second branch air supply paths, the switching valve being displaceable among a forward rotation position where the first branch air supply path is communicated with the air supply path and where the second branch air supply path is cut off from the air supply path, a neutral position where the first and second branch air supply paths are communicated with the air supply path, and a reverse rotation position where the first branch air supply path is cut off from the air supply path and where the second branch -17 -air supply path is communicated with the air supply path; wherein when the open-close valve is in the open position and the switching valve is in the neutral position, compressed air supplied from the air supply port reaches the first and second branch air supply paths from the air supply path and is discharged through the exhaust path substantially without rotating the air motor.
2. The air tool of claim 1, wherein when the switching valve is in the neutral position, the first and second branch air supply paths are communicated with the exhaust path, and when the open-close valve is in the open position and the switching valve is in the neutral position, at least part of compressed air reaching the first and second branch air supply paths from the air supply path is passed through the exhaust path from the first and second branch air supply paths without passing through the air motor.
3. The air tool of claim 1 or 2, wherein the air motor is a vane motor having a circular columnar motor chamber of circular cross-section and a rotor rotatable provided in the motor chamber, the air motor having a motor exhaust port located at substantially equal circumferential distances from the first and second motor air supply ports opened into the motor chamber adjacently to each other, the motor exhaust port being communicated with the exhaust path; wherein when the open-close valve is in the open position and the switching valve is in the neutral position, at least part of compressed air reaching the first and second branch air supply paths from the air supply path enters the motor chamber from the first and second motor air supply ports, and compressed air entering the motor chamber from the first motor air supply port and compressed air entering the motor chamber from the second motor air supply port flow around the rotor in mutually opposite directions, respectively, to reach the motor exhaust port and are passed through the exhaust path.
4. The air tool of any one of claims 1 to 3, wherein the operating member is capable of being held in the drive position.
-18 - 5. The air tool of any one of claims 1 to 4, further comprising: a first body part including the air motor and the switching valve; and a second body part including the open-close valve and the operating member and rotatably attached to the first body part; wherein one of the first body part and the second body part has a first locking portion, and an other of the first body part and the second body part has a plurality of second locking portions fittable to the first locking portion; and wherein when the second body part is rotated relative to the first body part, the first locking portion is fitted to one of the plurality of second locking portions at one of a plurality of relative rotational positions, thereby holding the rotational direction position of the second body part relative to the first body part.
6. The air tool of claim 5, wherein the operating member is a lever pivotably attached to the second body part; the air tool further comprising: a lever locking member for preventing the lever from being displaced to the drive position.-19 -