Patent Publication Number: US-2022212326-A1

Title: Pneumatic tool

Description:
TECHNICAL FIELD 
     The present disclosure relates to a pneumatic tool. 
     BACKGROUND ART 
     In the related art, widely used is a nailing machine that includes a main body having a cylinder, a piston provided to be slidable in the cylinder, and a driver connected to the piston, and is configured to drive the piston by compressed air to strike a nail into a to-be-struck member. 
     The nailing machine using the compressed air includes a head valve configured to control actuation of the piston, a trigger valve configured to actuate the head valve, a trigger mechanism configured to actuate the trigger valve, and a contact arm protruding from a nose part provided on a tip end-side of the main body. The nailing machine is configured so that, when the contact arm is pressed against the to-be-struck member in a state where a trigger lever is pulled, a striking operation (hereinafter, referred to as ‘contact striking’) of striking out a nail to the to-be-struck member by a driver can be enabled. 
     In the contact striking, after striking a nail, nails can be continuously struck each time the contact arm is pressed against the to-be-struck member while the trigger is pulled, which is suitable for a quick operation. On the other hand, suggested is a technology where when a predetermined time elapses without the contact arm being pressed against the to-be-struck member after the trigger is pulled, the head valve is put into non-actuation, so as to regulate a careless operation (refer to PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese examined utility model application publication No. H06-32308 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the nailing machine of the related art disclosed in PTL 1 has following problems. A general nailing machine is configured to allow any pressure of the compressed air to be selected between a low pressure and a high pressure, depending on an application where the nailing machine is used. In a timing valve of the related art, an actuation control is performed using the compressed air supplied to a main chamber. Therefore, when a pressure of the compressed air that is used varies, a variation also occurs in time measurement of the timing valve, so that an operation of the timing valve is not stable. 
     Therefore, in order to solve the above problems, the present disclosure provides a nailing machine capable of stabilizing an operation of a timer mechanism by making the timer mechanism less susceptible to an influence of compressed air that is used to drive a drive mechanism. 
     Solution to Problem 
     A pneumatic tool according to one aspect of the present disclosure includes a drive mechanism configured to drive by an air pressure of compressed air, a head valve configured to control supply of the compressed air to the drive mechanism, a trigger valve configured to actuate the head valve, a control valve configured to disable actuation of the trigger valve or the head valve, and a timer valve configured to be actuated based on an operation on a trigger and to disable actuation of the trigger valve or the head valve by actuating the control valve at a predetermined timing, wherein the timer valve has a valve body configured to act on the control valve and is provided with a throttle portion configured to regulate a flow rate of a fluid generated in conjunction with movement of the valve body. 
     A pneumatic tool according to one aspect of the present disclosure includes a drive mechanism configured to drive by an air pressure of compressed air, a head valve configured to control supply of the compressed air to the drive mechanism, a trigger valve configured to actuate the head valve by receiving an operation on a trigger, a control valve configured to disable a trigger operation, and a timer valve configured to be actuated based on the operation on the trigger and to disable actuation of the head valve by actuating the control valve at a predetermined timing, wherein the timer valve has a valve body configured to press the control valve and a damper mechanism configured to regulate a moving speed of the valve body, and wherein the valve body is configured to press the control valve after a predetermined time elapses from start of movement by an operation on the trigger. 
     Advantageous Effects of Invention 
     According to the pneumatic tool of one aspect of the present disclosure, a moving speed of the timer valve is controlled using the throttle portion. Therefore, it is possible to prevent a variation in time until the control valve is actuated, so that an operation of the timer valve can be stabilized. 
     In addition, according to the pneumatic tool of one aspect of the present disclosure, the moving speed of the valve body is controlled by the damper mechanism that is less susceptible to an influence of the compressed air that is used to drive the drive mechanism. Therefore, it is possible to prevent a variation in time until the control valve is actuated, so that an operation of the timer valve can be stabilized. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side sectional view of a nailing machine according to a first embodiment. 
         FIG. 2  is a side sectional view of a trigger valve and a switch valve according to the first embodiment. 
         FIG. 3  is a side sectional view of a timer valve and a control valve according to the first embodiment. 
         FIG. 4  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 5  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 6  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 7  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 8  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 9  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 10  is an operation view upon striking in the nailing machine according to the first embodiment. 
         FIG. 11  is a side sectional view of a nailing machine according to a second embodiment. 
         FIG. 12  is a side sectional view of a timer valve according to the second embodiment. 
         FIG. 13  is a side sectional view of a nailing machine according to a second embodiment. 
         FIG. 14  is a side sectional view of a control valve, a trigger valve and a switch valve according to the third embodiment. 
         FIG. 15  is a side sectional view of a timer valve according to the third embodiment. 
         FIG. 16  is a view during a striking operation in the nailing machine according to the third embodiment. 
         FIG. 17  is a view during the striking operation in the nailing machine according to the third embodiment. 
         FIG. 18  is a view during the striking operation in the nailing machine according to the third embodiment. 
         FIG. 19  is a view during the striking operation in the nailing machine according to the third embodiment. 
         FIG. 20  is a view during the striking operation in the nailing machine according to the third embodiment. 
         FIG. 21  is a view during the striking operation in the nailing machine according to the third embodiment. 
         FIG. 22  is a view during the striking operation in the nailing machine according to the third embodiment. 
         FIG. 23  is a side sectional view of a nailing machine according to a fourth embodiment. 
         FIG. 24  is a side sectional view of a timer valve according to the fourth embodiment. 
         FIG. 25  is a side sectional view of a control valve according to the fourth embodiment. 
         FIG. 26  is a view during a striking operation in the nailing machine according to the fourth embodiment. 
         FIG. 27  is a view during the striking operation in the nailing machine according to the fourth embodiment. 
         FIG. 28  is a view during the striking operation in the nailing machine according to the fourth embodiment. 
         FIG. 29  is a view during the striking operation in the nailing machine according to the fourth embodiment. 
         FIG. 30  is a view during the striking operation in the nailing machine according to the fourth embodiment. 
         FIG. 31  is a view during the striking operation in the nailing machine according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, favorable embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that, in the specification and drawings, the constitutional elements having substantially the same functional configurations are denoted with the same reference signs, and the overlapping descriptions are omitted. 
     First Embodiment 
     [Configuration Example of Nailing Machine  100 ] 
       FIG. 1  is a side sectional view of a nailing machine  100  according to a first embodiment.  FIG. 2  is a side sectional view of a trigger valve  50  and a switch valve  70  according to the first embodiment.  FIG. 3  is a side sectional view of a tinier valve  80  and a control valve  40  according to the first embodiment. 
     The nailing machine  100  is an example of the pneumatic tool, and includes a main body  1  having a nose part  2 , a grip part  4  that is gripped by an operator, and a magazine part  6  in which nails to be struck into a to-be-struck member are loaded. Housings of the main body  1  and the grip part  4  are integrally formed by a housing  1   a , for example. The nailing machine  100  also includes a head valve  30 , a trigger mechanism  10 , a trigger valve  50 , a switch valve  70 , a timer valve  80  and a control valve  40 . 
     Note that, in the present embodiment, the nose part  2 -side of the nailing machine  100  is referred to as a lower side of the nailing machine  100 , and an opposite side thereto is referred to as an upper side of the nailing machine  100 . Also, the main body  1 -side of the nailing machine  100  is referred to as a front side of the nailing machine  100 , and the grip part  4 -side of the nailing machine  100  is referred to as a rear side of the nailing machine  100 . 
     An inside of the main body  1  is hollow, and a striking mechanism (drive mechanism) configured to drive by an air pressure of compressed air is arranged in the main body  1 . The striking mechanism  20  has a driver  22 , a piston  24 , and a cylinder  26 . The driver  22  is configured to reciprocally move in an upper and lower direction (axial direction) in the cylinder  26 , and to impact a head portion of a nail delivered from the magazine part  6 , thereby striking the nail into a to-be-struck member. The piston  24  is connected to an upper end portion of the driver  22 , and is configured to reciprocally move in the cylinder  26 , in response to the compressed air flowing into a piston upper chamber  24   a  provided on an upper side of the cylinder  26 . The cylinder  26  is a cylindrical body, is arranged in the housing  1   a  constituting the main body  1 , and is configured to accommodate the driver  22  and the piston  24  to be reciprocally movable in the upper and lower direction. An annular locking part  25  configured to regulate upward movement of the piston  24  is provided between the piston  24  and the head valve  30 . 
     A lower end portion of the main body  1  is provided with the nose part  2 . The nose part  2  protrudes downward from the lower end portion of the main body  1  by a predetermined length. The nose part  2  is formed with an ejection port  3  for striking out the nail delivered by the driver  22  to an outside. The ejection port  3  is arranged coaxially with the driver  22  and the cylinder  26 . 
     A main chamber  5  in which the compressed air is filled is provided between an inner wall on an upper side of the main body  1  and an outer peripheral part on an upper side of the cylinder  26  and in the grip part  4 . A blow back chamber  28  for returning the piston  24  to a top dead center is provided between an inner wall on a lower side of the main body  1  and an outer peripheral part on a lower side of the cylinder  26 . One end portion of a first connection passage  29  configured to communicate with the switch valve  70  is connected to the blow back chamber  28 . 
     A plurality of small holes  27  is formed at predetermined intervals in a substantially intermediate position in the axial direction of the cylinder  26  and in a circumferential direction of the cylinder  26 . The plurality of small holes  27  is formed to communicate with the blow back chamber  28  via a check valve  27   a  provided to the cylinder  26 . Note that, when the piston  24  is located at a bottom dead center below the small holes  27 , the compressed air of the cylinder  26  is caused to flow into the blow back chamber  28  via the small holes  27 , and when the piston  24  is located at the top dead center, the compressed air in the blow back chamber  28  is discharged to the atmosphere, so that the inside of the blow back chamber  28  becomes an atmospheric pressure. 
     The head valve  30  is configured to perform supply and shut-off of the compressed air to the cylinder  26 , and to drive the striking mechanism  20  by using the compressed air supplied from the main chamber  5 . The head valve  30  has a base part  32  and a movable part  34 . The base part  32  is arranged on an upper end-side in the main body  1 , and the movable part  34  is arranged below the base part  32 . The movable part  34  is urged toward the cylinder  26  at a predetermined interval from the base part  32  by an urging spring  36  interposed between the base part  32  and the movable part  34 . A lower surface of the movable part  34  is in contact with an upper surface of the locking part  25  in an urging state (a state where the head valve  30  is off), so that the main chamber  5  and the piston upper chamber  24   a  are shut off therebetween. 
     The interval between the base part  32  and the movable part  34  is configured to function as a head valve chamber  38  to which the compressed air in the main chamber  5  is supplied. One end portion of a second connection passage  39  is configured to communicate with the head valve chamber  38 , and the other end-side of the second connection passage  39  is configured to communicate with the control valve  40 . The movable part  34  is configured to slide along an inner wall of the housing  1   a  constituting the main body  1  and to open/close between the piston upper chamber  24   a  and the main chamber  5 , according to a state of the compressed air in the head valve chamber  38 . The piston upper chamber  24   a  is configured to communicate with an outside via an opening portion  1   b  formed in the housing  1   a.    
     The grip part  4  is attached to a side part on the rear side of the main body  1  in a direction substantially orthogonal to an extension direction of the main body  1  (a moving direction of the striking mechanism  20 ). A rear end portion of the grip part  4  is provided with an air plug  8 . One end portion of an air hose (not shown) is connected to the air plug  8 , and the other end portion of the air hose is connected to a compressor (not shown). The air compressor is configured to generate the compressed air for driving the striking mechanism  20  and to supply the generated compressed air into the main chamber  5  via the air hose and the air plug  8 . 
     The trigger mechanism  10  has a trigger lever  11 , a contact lever  12 , a contact arm  14  and a pressing member  15 . The trigger lever  11  is a lever for turning on (actuating) the switch valve  70 , and is attached to a side surface on the rear side of the main body  1  and a lower side of the grip part  4  so as to be rotatable about a shaft part as a fulcrum. The contact lever  12  is arranged in the trigger lever  11  and is configured to rotate about a rear side as a fulcrum in conjunction with the trigger lever  11 . A front end portion of the contact lever  12  is urged downward by, for example, a spring provided on a rear end-side, and is in contact with an upper end face of the pressing member  15 . Note that, the contact lever  12  may not be urged by the spring. 
     The contact arm  14  is attached to an outer peripheral part of the nose part  2  in a state of protruding downward from a lower end portion of the nose part  2 . The contact arm  14  is urged downward by a spring (not shown), and is configured to reciprocally move in the upper and lower direction relative to the nose part  2  in conjunction with a pressing operation against the to-be-struck member. The pressing member  15  is connected to the contact arm  14 , and is configured to push up a front end-side of the contact lever  12  in conjunction with upward movement of the contact arm  14 . When the trigger lever  11  is pulled, a trigger valve stem  58  of the trigger valve  50  is pushed up, so that the trigger valve  50  is actuated (turned on). 
     The magazine part  6  is configured so that a series of connected connecting nails can be loaded therein, and is provided on a lower side of the grip part  4 . A front end-side of the magazine part  6  is connected to the nose part  2 , and a rear end-side of the magazine part  6  is connected to the grip part  4  via an attaching arm part  7 . The connecting nails loaded in the magazine part  6  are guided to the ejection port  3  of the nose part  2  by a feeding claw provided to be slidable with respect to the nose part  2 , and is struck into the to-be-struck member by the descending driver  22 . 
     The trigger valve  50  is configured to actuate the head valve  30 , based on an operation on the trigger lever  11  and a pressing of the contact arm  14 . As shown in  FIGS. 1 and 2 , the trigger valve  50  is arranged near the switch valve  70  on the front end-side of the grip part  4 . The trigger valve  50  has a housing  52 , a pilot valve  54 , a cap  53  and a trigger valve stem  58 . 
     The housing  52  has a passage  53  provided in a substantially intermediate portion in the upper and lower direction. The passage  53  is configured to communicate with one end portion of a third connection passage  49  configured to connect the head valve  30  and the trigger valve  50  each other. The passage  53  is also configured to be able to communicate with an air exhaust passage  59  upon turning-on of the trigger valve  50 . 
     The pilot valve  54  is arranged at a gap S 1  on an inner side of the housing  52 . O-rings  54   a  and  54   b  are attached at a predetermined interval in the upper and lower direction to a peripheral edge portion on a lower side of the pilot valve  54 . The O-ring  54   a  is configured to shut off a passage between the passage  53  and the air exhaust passage  59  to thus prevent the compressed air in the head valve chamber  38  from being leaked from the passage  53  to an outside, during turning-off of the trigger valve  50 . In addition, the O-ring  54   a  is pressed against an inner wall of the housing  52  to regulate upward movement of the pilot valve  54 . The O-ring  54   b  is configured to shut off between an empty chamber  55 , which will be described later, and the air exhaust passage  59 . 
     The cap  56  is attached on an inner side of the housing  52  with an empty chamber  55  being interposed between the cap and the pilot valve  54  on the upper side. The empty chamber  55  is configured to communicate with the main chamber  5  via a gap S 2  between the pilot valve  54  and the trigger valve stem  58  and a passage  54   c  of the pilot valve  54  and to function as a chamber in which the compressed air is filled, during non-actuation of the trigger valve  50 . 
     The trigger valve stem  58  is arranged on inner sides of the pilot valve  54  and the cap  56 , and is provided to be movable in the upper and lower direction from the cap  56  as a point of origin. An upper end-side of the trigger valve stem  58  is urged toward the contact lever  12  (toward the lower side) by a compression spring  57 . The compression spring  57  is interposed between the pilot valve  54  and the trigger valve stem  58 , and is adapted to expand and contract, in response to pressing of the trigger valve stem  58 . A lower end portion of the trigger valve stem  58  protrudes from a lower surface of the cap  56  by a predetermined length, and can come into contact with the contact lever  12  (refer to  FIG. 1 ). O-rings  58   a  and  58   b  are attached at a predetermined interval in the upper and lower direction to a peripheral edge portion of a substantially intermediate position in the upper and lower direction of the trigger valve stem  58 . The O-rings  58   a  and  58   b  are configured to prevent the compressed air in the empty chamber  55  from being leaked from a gap S 3  between the trigger valve stem  58  and the cap  56  to an outside, during non-actuation of the trigger valve  50 . 
     The air exhaust passage  59  is provided between the housing  52  and the cap  56 . When the empty chamber  55  is closed due to push-up of the trigger valve stem  58  during actuation of the trigger valve  50 , the air exhaust passage  59  communicates with the passage  53  to exhaust the compressed air in the head valve chamber  38  to the atmosphere. 
     As shown in  FIGS. 1 and 2 , the switch valve  70  is arranged in the vicinity of a rear side of the trigger valve  50 , and is configured to actuate the timer valve  80  based on an operation on the trigger lever  11 . The switch valve  70  has a cylinder  72  and a switch valve stem  74 . 
     The cylinder  72  is a hollow cylindrical body extending in the upper and lower direction, and is configured to accommodate the switch valve stem  74  so as to be slidable in the upper and lower direction. An upper side of the cylinder  72  is formed with a passage  72   a . The passage  72   a  is configured to communicate with the main chamber  5 , and the compressed air in the main chamber  5  is caused to flow into the cylinder  72  via the passage  72   a.    
     One end portion of a fourth connection passage  79  is configured to communicate in a substantially intermediate position of the cylinder  72 , and the other end portion of the fourth connection passage  79  is configured to communicate with the timer valve  80 . The fourth connection passage  79  is configured to connect the switch valve  70  and the timer valve  80  therebetween, and the compressed air can be supplied or exhausted with respect to the timer valve  80  via the fourth connection passage  79 . One end portion of the first connection passage  29  is configured to communicate on a further lower side than the fourth connection passage  79  of the cylinder  72 , and the other end portion of the first connection passage  29  is configured to communicate with the blow back chamber  28 . The first connection passage  29  is configured to connect the switch valve  70  and the blow back chamber  28  therebetween, and the compressed air can be supplied to the switch valve  70  or the compressed air can be exhausted from the switch valve  70  via the first connection passage  29 . 
     The switch valve stem  74  is accommodated in the cylinder  72 , and is urged toward the trigger lever  11  (toward the lower side) by the compression spring  76 . The compression spring  76  is interposed between an upper end face of the switch valve stem  74  and a top surface in the cylinder  72 , and is adapted to expand and contract, in response to a pulling operation on the trigger lever  11 . Mower end portion of the switch valve stem  74  protrudes downward from the lower surface of the cylinder  72 , and comes into contact with the contact lever  12  at the time when the trigger lever  11  (refer to  FIG. 1 ) is pulled. 
     An O-ring  74   a  for close contact with an inner wall of the cylinder  72  is mounted to a peripheral edge portion of a substantially intermediate position of the switch valve stem  74 . Upon non-pulling operation of the trigger lever  11 , the switch valve stem  74  is configured to close a path between the fourth connection passage  79  and the first connection passage  29  by the O-ring  74   a  and to communicate the passage  72   a  and the fourth connection passage  79  each other. On the other hand, upon pulling operation of the trigger lever  11 , the switch valve stem  74  is configured to be pushed up against the elastic force of the compression spring  76  by the contact lever  12  and to close a path between the passage  72   a  and the fourth connection passage  79  by the O-ring  74   a  and to communicate the fourth connection passage  79  and the first connection passage  29  each other. 
     As shown in  FIGS. 1 and 3 , in a state where the trigger lever  11  is pulled, after a prescribed time elapses, and when the contact arm  14  is pressed against the to-be-struck member, the timer valve  80  actuates the control valve  40  to disable an operation of the head valve  30 , thereby limiting the striking operation. The timer valve  80  has a cylinder  81 , a timer piston  84 , and a piston shaft part  85 . 
     The cylinder  81  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the timer piston  84  so as to be slidable in the front and rear direction. In the present embodiment, a part of the cylinder  81  has a structure sharing a part of the housing  1   a.    
     The timer piston  84  is a cylindrical body having substantially the same diameter as an inner diameter of the cylinder  81 , and is arranged to be slidable along an inner wall of the cylinder  81 . A peripheral edge portion of the timer piston  84  is formed with a concave portion  84   a  along a circumferential direction thereof. In the concave portion  84   a , an O-ring  86  for close contact with the inner wall of the cylinder  81  is mounted. Thereby, an inside of the cylinder  81  is partitioned into a first space  81   a  on a rear side of the O-ring  86  and a second space  81   b  on a front side of the O-ring  86 . The first space  81   a  and the second space  81   b  are isolated from each other by the O-ring  86 . The timer piston  84  is urged toward the control valve  40  (toward the front side) by a compression spring  89 . The compression spring  89  is interposed between a concave portion formed on a base end-side thereof and a rear wall in the cylinder  81 . The compression spring  89  is compressed by the compressed air that is supplied to the second space  81   b  of the cylinder  81 , and is expanded in response to the atmospheric air that is supplied to the first space  81   a  of the cylinder  81 . 
     One end portion of the fourth connection passage  79  is configured to communicate with a lower surface-side and the second space  81   b  of the cylinder  81 , so that the compressed air can be supplied to the timer valve  80  and the compressed air can be exhausted from the timer valve  80  via the fourth connection passage  79 . 
     On the rear side of the cylinder  81 , a first passage  82   a  and a second passage  82   b  extending in the front and rear direction are provided side by side in the upper and lower direction. One end portion of the first passage  82   a  is configured to communicate with the inside of the cylinder  81 , and the other end portion of the first passage  82   a  is configured to communicate with a third passage  82   c . One end portion of the second passage  82   b  is configured to communicate with the inside of the cylinder  81 , and the other end portion of the second passage  82   b  is configured to communicate with the third passage  82   c . The third passage  82   c  has an opening on the housing-side, and is configured to communicate with an outside of the housing  1   a  via the opening. In this way, since the timer piston  84  of the timer valve  80  is actuated using the atmospheric air that is supplied from the third passage  82   c , not the compressed air, the timer valve  80  can be actuated in a stable pressure state all the time. Note that, in the present embodiment, the first passage  82   a  and the second passage  82   b  are configured to communicate with the common third passage  82   c . However, separate passages may also be provided to the first passage  82   a  and the second passage  82   b , respectively. In addition, the opening of the third passage  82   c  may be provided with a filter. Thereby, even when the atmospheric air contains trash, dust and the like, the air after trash, dust and the like are removed by the filter can be caused to flow into the cylinder  81 , so that the stabilization of the moving speed of the timer piston  84  can be further improved. 
     A check valve  87  is provided in the middle of the path of the first passage  82   a . The check valve  87  has a ball  87   a  for opening/closing the first passage  82   a , for example, and a spring  87   b  provided on a rear side of the ball  87   a  for urging the ball  87   a  toward the timer piston  84 . When the timer piston  84  is retreated in the cylinder  81 , the ball  87   a  is urged against an elastic force of the spring  87   b  by the atmospheric air, so that the first passage  82   a  opens and the atmospheric air flows from the inside of the cylinder  81  to the outside. On the other hand, when the timer piston  84  is advanced in the cylinder  81 , the ball  87   a  is urged forward by the atmospheric air from the outside and the spring  87   b , so that the first passage  82   a  is closed by the ball  87   a  and back-flow of the atmospheric air from the outside into the cylinder  81  is prevented. 
     A throttle portion  88  is provided in the middle of the path of the second passage  82   b . The throttle portion  88  is constituted by reducing a cross-sectional area (narrowing a width) of a path of a part of the second passage  82   b , and is configured to restrict a flow rate per unit time of the atmospheric air, which is caused to flow into the cylinder  81  from the outside, to be constant. Thereby, it is possible to control the moving speed until the piston shaft part  85  presses a control valve stem  44  of the control valve  40 . In the present embodiment, the example where the moving speed of the timer piston  84  is regulated by the air entering via the throttle portion  88  and the compression spring  89  has been described. However, a configuration where the moving speed of the timer piston  84  is regulated by the air flowing out via the throttle portion  88  and the compression spring  89   
     In addition, a prescribed time at the time when the timer piston  84  moves from an initial position in the cylinder  81  to an actuation position in which the control valve  40  is actuated is determined by a flow rate passing through the throttle portion  88  of the timer valve  80 , a spring coefficient of the compression spring  89 , and the like. In the present embodiment, the prescribed time is, for example, 3 seconds to 10 seconds. In the present embodiment, a time for which the control valve  40  moves from the actuation position to a position in which the passage between the head valve chamber  38  and the trigger valve  50  is shut off is set to a time considerably shorter than the prescribed time. For this reason, when the prescribed time elapses, the passage between the head valve  30  and the trigger valve  50  is immediately shut off by the control valve  40 . In addition, in the present embodiment, the initial position is a position in which the timer piston  84  is most retreated in the cylinder  81  upon set or reset of the timer piston  84 , and the actuation position is a position in which the timer piston  84  presses the control valve  40  on the front end-side in the cylinder  81  after the trigger lever  11  is pulled. 
     The piston shaft part  85  is a rod-shaped columnar body, and a rear end portion thereof is formed integrally with a front end portion of the tinier piston  84 . The piston shaft part  85  is slidably arranged in a through-hole  4   a  formed between the cylinder  81  and the control valve  40 , and can appear and disappear with respect to an inside of a cylinder  42  that constitutes the control valve  40 . The piston shaft part  85  is configured to press against a rear end face of the control valve stem  44  to actuate the control valve  40  at the time when the prescribed time in the timer valve  80  elapses and the timer piston  84  reaches the actuation position. 
     As shown in  FIGS. 1 and 3 , the control valve  40  is configured to disable actuation of the head valve  30  that is actuated in conjunction with actuation of the trigger valve  50 . Specifically, the control valve  40  is configured to switch the passage between the head valve chamber  38  and the trigger valve  50  from a communication state to a shut-off state by control of the timer valve  80 , thereby disabling actuation of the head valve  30 . The control valve  40  is arranged in a position near the timer valve  80  ahead of the timer valve  80 , between the head valve chamber  38  and the trigger valve  50 . The control valve  40  has a cylinder  42  and a control valve stem  44 . Note that, a part of the cylinder  42  has a structure sharing a part of the housing  1   a . In the present embodiment, an example where the control valve  40  disables actuation of the head valve is described. However, a configuration where actuation of the trigger valve  50  configured to be actuated in conjunction with an operation on the trigger is disabled may also be adopted. 
     The cylinder  42  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the control valve stem  44  so as to be slidable in the front and rear direction. An upper surface-side of the cylinder  42  is configured to communicate with one end portion of the second connection passage  39  configured to communicate with the head valve chamber  38 . A lower surface-side of the cylinder  42  is configured to communicate with one end portion of the third connection passage  49  configured to communicate with the trigger valve  50 , and is formed with a passage  42   c  configured to communicate with the main chamber  5 . 
     The control valve stem  44  is a cylindrical body extending in the front and rear direction and is arranged in the cylinder  42 . The control valve stem  44  is urged toward the timer valve  80  (toward the rear side) by a compression spring  46 . The compression spring  46  is interposed between a front wall in the cylinder  42  and a front end face of the control valve stem  44 , and is adapted to expand and contract, in response to pressing by the timer valve  80 . O-rings  44   a  and  44   b  are attached at a predetermined interval in the front and rear direction to a peripheral edge portion of a substantially intermediate position in the front and rear direction of the control valve stem  44 . 
     The control valve stem  44  is located on a rear end-side in the cylinder  42 , and closes a path between the second connection passage  39  and the passage  42   c  by the O-ring  44   b  and opens a path between the second connection passage  39  and the third connection passage  49 , upon non-pressing of the timer valve  80 , i.e., before timeout. Thereby, the head valve chamber  38  and the trigger valve  50  are connected to each other. On the other hand, the control valve stem  44  is moved to a front end-side in the cylinder  42 , and opens the path between the second connection passage  39  and the passage  42   c  and closes the path between the second connection passage  39  and the third connection passage  49  by the O-ring  44   a , upon pressing of the timer valve  80 , i.e., after timeout. Thereby, the head valve chamber  38  and the trigger valve  50  are shut off therebetween. Since a pressure of the main chamber  5  acts on the control valve  40 , a sliding resistance of the control valve stem  44  varies due to variation in pressure in the main chamber. However, it is preferably to make movement of the timer valve  80  configured to press the control valve stem  44  less susceptible to an influence of variation in the sliding resistance of the control valve stem  44 . For example, a setting of an area to receive a spring load and a pressure should be considered. 
     As shown in  FIGS. 1 and 3 , the timer valve  80  is arranged in the grip part  4  so that a moving direction of the timer piston  84  is different from, in the present embodiment, orthogonal to, an axial direction of the cylinder  26  (a moving direction of the driver  22 ). In addition, the timer valve  80  is arranged in the grip part  4  so that the moving direction of the timer piston  84  is along the extension direction of the grip part  4 , i.e., is parallel to the extension direction of the grip part  4 . 
     [Operation Example of Nailing Machine  100 ] 
     Subsequently, an example of a striking operation of the nailing machine  100  according to the first embodiment is described.  FIGS. 4 to 10  show a striking operation in the nailing machine  100  according to the first embodiment. 
     In a case of performing a striking operation by using the nailing machine  100 , when the air hose is connected to the air plug  8  shown in  FIG. 1 , the compressed air is supplied into the main chamber  5 , as shown in  FIG. 4 . The compressed air supplied into the main chamber  5  is supplied to the second space  81   b  of the timer valve  80  via the inside of the switch valve  70  and the fourth connection passage  79 . 
     Along with this, the front surface-side of the timer piston  84  is pushed backward by the compressed air, and the timer piston  84  and the piston shaft part  85  are retreated against the elastic force of the compression spring  89 . At this time, the atmospheric air in the first space  81   a  is compressed and the compressed atmospheric air is caused to flow into the first passage  82   a . The ball  87   a  of the check valve  87  is pushed against the elastic force of the spring  87   b  by the inflow atmospheric air, thereby opening the first passage  82   a . Thereby, the atmospheric air flowing into the first passage  82   a  passes through the check valve  87  and the third passage  82   c  and is exhausted to the outside of the housing  1   a . Note that, in the second passage  82   b , since the flow resistance of the throttle portion  88  increases, the compressed air hardly passes, as compared to the first passage  82   a.    
     As shown in  FIG. 5 , when the supply of the compressed air into the second space  81   b  of the timer valve  80  continues, the timer piston  84  reaches the initial position in the cylinder  81 , specifically, the base end portion of the timer piston  84  reaches the rear end portion of the first space  81   a  by compression of the compression spring  89 . Thereby, the timer valve  80  becomes in a standby state. 
     As shown in  FIG. 6 , when the trigger lever  11  is pulled by an operator, the switch valve stem  74  of the switch valve  70  is pushed up by the contact lever  12 , so that the switch valve  70  is actuated. By the push-up of the switch valve stem  74 , the O-ring  74   a  (refer to  FIG. 2 ) is also moved upward, so that while the communication state between the passage  72   a  of the switch valve  70  and the fourth connection passage  79  is shut off, the fourth connection passage  79  and the first connection passage  29  communicate with each other. Along with this, the compressed air in the second space  81   b  of the timer valve  80  is exhausted to the blow back chamber  28  at the atmospheric pressure via the fourth connection passage  79 , the inside of the switch valve  70  and the first connection passage  29 . 
     In addition, when the compressed air in the second space  81   b  in the cylinder  81  is exhausted, the urging force of the compression spring  89  acts on the timer piston  84 . Along with this, the atmospheric air is caused to flow into the first space  81   a  of the timer valve  80  through the third passage  82   c , the second passage  82   b  and the throttle portion  88 . The flow rate of the atmospheric air that is supplied to the first space  81   a  is restricted to be constant by the throttle portion  88 . The compression spring  89  gradually expands, according to the flow rate of the atmospheric air that is caused to flow into the first space  81   a . Along with this, the timer piston  84  is slowly advanced from the initial position in the cylinder  81  and the timer (time measurement) of the timer valve  80  starts. Note that, since the first passage  82   a  is not closed by the ball  87   a , the atmospheric air does not flow into the cylinder  81  via the first passage  82   a.    
     As shown in  FIG. 7 , when the contact arm  14  is pressed against the to-be-struck member in a state where the trigger lever  11  is pulled and before timeout of the timer valve  80 , the pressing member  15  is pushed up. Along with this, when the front end-side of the contact lever  12  is pushed up, the trigger valve stem  58  of the trigger valve  50  is pushed up, so that the trigger valve  50  is actuated. When the trigger valve stem  58  is pushed up, the O-rings  58   a  and  58   b  are also moved upward, as shown in  FIG. 2 , so that the compressed air in the empty chamber  55  is exhausted from the gap S 3  between the cap  56  and the trigger valve stem  58  to the outside. The pilot valve  54  is pushed down against the elastic force of the compression spring  57  by the compressed air in the main chamber  5 , so that the lower surface of the pilot valve  54  comes into contact with the upper surface of the cap  56 . Thereby, the passage  53  and the air exhaust passage  59  communicate with each other, and the compressed air in the head valve chamber  38  is exhausted to the atmosphere (outside) via the second connection passage  39 , the control valve  40 , the third connection passage  49 , the inside of the trigger valve  50  and the air exhaust passage  59 . 
     When the compressed air in the head valve chamber  38  is exhausted, the movable part  34  of the head valve  30  is pushed up by the compressed air in the main chamber  5  and the movable part  34  and the locking part  25  are opened therebetween, so that the compressed air in the main chamber  5  is caused to flow into the piston upper chamber  24   a  and the piston  24  rapidly descends in the cylinder  26 . 
     As shown in  FIG. 8 , when the piston  24  further descends, the nail is struck into the to-be-struck member by the driver  22  connected to the piston  24 . In addition, when the piston  24  descends to the lower part-side in the cylinder  26 , the compressed air in the cylinder  26  is caused to flow into the blow back chamber  28  via the small holes  27 . The inflow compressed air is supplied to the second space  81   b  of the timer valve  80  via the first connection passage  29 , the inside of the switch valve  70  and the fourth connection passage  79 . Thereby, the timer valve  80  is again retreated to the initial position in the cylinder  81 , so that the timer valve  80  is reset. As the timer valve  80  is retreated, the atmospheric air in the first space  81   a  is exhausted to the outer side of the housing  1   a  via the first passage  82   a  and the third passage  82   c.    
     As shown in  FIG. 9 , when the contact arm  14  is not pressed against the to-be-struck member, i.e., the striking operation is not executed within the prescribed time from the time point when the switch valve  70  shown in  FIG. 6  is actuated, the timer valve  80  times out. Specifically, the timer valve  84  of the timer valve  80  is moved to the actuation position in which the control valve  40  on the front end-side in the cylinder  81  is pressed. 
     The control valve stem  44  of the control valve  40  is pushed by the piston shaft part  85  and is moved toward the front end-side of the cylinder  42 . When the control valve stem  44  is advanced, the O-rings  44   a  and  44   b  are also advanced, so that while the path communicating the second connection passage  39  and the third connection passage  49  each other is shut off, a gap S 4  is formed. Thereby, the head valve chamber  38  is switched from the communication state with the trigger valve  50  to the communication state with the main chamber  5  via the second connection passage  39 , the gap S 4  and the passage  42   a  of the control valve  40 . 
     As shown in  FIG. 10 , when the contact arm  14  is pressed against the to-be-struck member in a state of the switch valve  70  shown in  FIG. 6  being actuated and after timeout of the timer valve  80 , the pressing member  15  is accordingly pushed up. The front end-side of the contact lever  12  is pushed up by the pressing member  15 , and the trigger valve stem  58  of the trigger valve  50  is pushed up by the pushed-up contact lever  12 . Thereby, the trigger valve  50  is actuated. When the trigger valve stem  58  is pushed up, the O-rings  58   a  and  58   b  are moved upward, as shown in  FIG. 2 , so that the compressed air in the empty chamber  55  is exhausted from the gap S 3  between the cap  56  and the trigger valve stem  58  to the outside. The pilot valve  54  is pushed down against the elastic force of the compression spring  57  by the compressed air in the main chamber  5 , so that the lower surface of the pilot valve  54  comes into contact with the upper surface of the cap  56 . Thereby, the passage  53  and the air exhaust passage  59  communicate with each other. 
     However, in a timeout state of the timer valve  80 , while the path between the second connection passage  39  and the third connection passage  49  is shut off by the control valve  40  shown in  FIG. 9 , the second connection passage  39  and the main chamber  5  communicate with each other. For this reason, the compressed air in the head valve chamber  38  is left remaining in the head valve chamber  38  without being exhausted to the outside via the air exhaust passage  59  provided to the trigger valve  50 . Thereby, when the timer valve  80  times out, the head valve  30  is not actuated even though the contact arm  14  is pressed against the to-be-struck member in a state where the operator pulls the trigger lever  11 . Therefore, the striking operation is not executed after timeout of the timer valve  80 . 
     As described above, according to the first embodiment, the atmospheric air with no variation in pressure outside the housing  1   a  is restricted to a constant flow rate by the throttle portion  88  and is caused to flow into the cylinder  81 , and the timer piston  84  is advanced (actuated) using the atmospheric air and the compression spring  89 . Thereby, since the moving speed of the timer valve  80  can be controlled without using the compressed air with variation in pressure, the variation in prescribed time until the control valve  40  is actuated can be prevented. Specifically, even when the pressure of the compressed air that is used in the nailing machine  100  varies, the time measurement of the timer valve  80  can be maintained constant. Thereby, the operation of the timer valve  80  can be stabilized. Note that, even though it is not configured so that the compressed air in the housing  1   a  does not completely act on the timer piston  84 , it goes without saying that if it is configured so that the generated force of the compression spring sufficiently acts (dominates), the similar effects are obtained because it is less susceptible to the variation in pressure. In addition, in the first embodiment, when an operator&#39;s finger detaches from the trigger lever  11  after timeout of the timer valve  80 , the timer valve  80  is reset by the compressed air in the main chamber  5 , so that a follow-up striking operation can be performed. Further, after the usual striking operation, since the timer valve  80  is reset by the inflow compressed air from the blow back chamber  28 , a follow-up striking operation can be performed by the pressing of the contact arm  14  in the state where the trigger lever  11  is pressed. 
     Further, according to the present embodiment, since the timer valve  80  is arranged in the grip part  4  so that the moving direction of the timer piston  84  of the timer valve  80  is orthogonal to the moving direction of the striking mechanism  20 , it is possible to prevent the timer valve  80  from receiving a shock that is generated upon the striking operation of the striking mechanism  20 . Thereby, it is possible to prevent an erroneous operation of the timer valve  80 , so that it is possible to stabilize the operation of the timer valve  80 . 
     Second Embodiment 
     In a timer valve  280  of a second embodiment, a mechanical configuration different from the timer valve  80  of the first embodiment is adopted. Note that, the other configuration, function and operation of a nailing machine  200  are common to the configuration and the like of the nailing machine  100  of the first embodiment. Therefore, the detailed descriptions thereof are omitted, and only the configuration and the like of the timer valve  280  of the second embodiment are described. 
     [Configuration Example of Nailing Machine  200 ] 
       FIG. 11  is a side sectional view of a nailing machine  200  according to a second embodiment.  FIG. 12  is a side sectional view of a timer valve  280  according to the second embodiment. 
     As shown in  FIG. 11 , the nailing machine  200  is an example of the pneumatic tool, and includes the piston  24  configured to be slidable in the cylinder  26 , the striking mechanism  20  having the driver  22  attached to the piston  24  and configured to strike a nail into the to-be-struck member, the head valve  30  configured to drive the striking mechanism  20  by using the compressed air that is supplied from the main chamber  5 , the trigger valve  50  configured to actuate the head valve  30 , and the control valve  40  configured to disable actuation of the head valve  30  configured to be actuated in conjunction with actuation of the trigger valve  50 . 
     The nailing machine  200  also includes a timer valve  280  configured to restrict a striking operation by actuating the control valve  40  to disable actuation of the head valve  30  when a predetermined time elapses in a state where the trigger lever  11  is pushed. The timer valve  280  has a first cylinder  281 , a first timer piston  284 , a first piston shaft part  285 , a second cylinder  291 , a second timer piston  294 , and a second piston shaft part  295 . 
     The first cylinder  281  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the first timer piston  284  so as to be slidable in the front and rear direction. In the first cylinder  281 , oil O for attenuating a moving speed of the first timer piston  284  is filled. The first cylinder  281  and the oil O constitute an example of an oil-type damper mechanism. In the present embodiment, the first cylinder  281  is fitted to the second cylinder  291  that constitutes the housing  1   a , and a front end-side thereof is configured to communicate with an inside of the second cylinder  291 . 
     Note that, the damper mechanism is not limited to the oil-type damper mechanism. For example, well-known technologies such as a damper mechanism using a friction resistance between solid members and a damper mechanism using an attenuation force of a member such as rubber configured to be elastically deformed can be adopted as appropriate. 
     The first timer piston  284  is a cylindrical body having substantially the same diameter as an inner diameter of the first cylinder  281 , and is configured to slide in the front and rear direction in the first cylinder  281 . A moving speed of the first timer piston  284  in the front and rear direction is controlled by a resistance due to viscosity and the like of the oil O. A peripheral edge portion of the first timer piston  284  is formed with an annular through-hole  284   a  penetrating in a thickness direction (front and rear direction). A front surface of the through-hole  284   a  is provided with a check valve  284   b  configured to open/close an opening of the through-hole  284   a . The check valve  284   b  is urged toward the first timer piston  284  (toward the rear side) by a compression spring  284   c , and is configured to move toward or away from the first timer piston  284 , according to a moving direction of the first timer piston  284 . 
     The first timer piston  284  is urged toward the control valve  40  (toward the front side) by a compression spring  289 . The compression spring  289  is interposed between a rear end face of the first timer piston  284  and a spring retainer plate  286  provided on a rear side of the inside of the first cylinder  281 , and is adapted to expand and contract, according to a position of the first timer piston  284 . 
     The first piston shaft part  285  is a rod-shaped columnar body, and a rear end portion thereof is attached to the first timer piston  284 . The first piston shaft part  285  extends into the second cylinder  291  from the inside of the first cylinder  281 , and a front end portion of the extending first piston shaft part  285  is attached to a rear end portion of the second tinier piston  294 . Thereby, an operation of the first timer piston  284  can be transmitted to the second timer piston  294  via the first piston shaft part  285 . When the time measurement of the timer valve  280  starts, the first piston shaft part  285  presses forward the second timer piston  294 . 
     A rear part-side of the first cylinder  281  is formed with a first flow path  281   a  configured to reduce a resistance at the time when the first timer piston  284  moves in the first cylinder  281 . The first flow path  281   a  is formed by cutting an inner wall of the first cylinder  281  in a concave surface shape in a circumferential direction around the initial position that is a start end of a moving range of the first timer piston  284 . An inner diameter of the first cylinder  281  at which the first flow path  281   a  is located is made larger than an inner diameter of the first cylinder  281  at which a second flow path  281   b , which will be described later, is located. 
     A second flow path  281   b  configured to increase a load at the time when the first timer piston  284  moves in the first cylinder  281  is formed between the first flow path  281   a  of the inner wall of the first cylinder  281  and a third flow path  281   c , which will be described later. The second flow path  281   b  is formed to have a convex surface shape in the circumferential direction of the inner wall of the first cylinder  281 . An inner diameter of the first cylinder  281  at which the second flow path  281   b  is located is made smaller than the inner diameter of the first cylinder  281  at which the first flow path  281   a  is located. 
     A front part-side of the first cylinder  281  is formed with a third flow path  281   c  configured to reduce a load at the time when the first tinier piston  284  moves in the first cylinder  281 . The third flow path  281   c  is formed by cutting an inner wall of the first cylinder  281  in a concave surface shape in the circumferential direction around the operation position that is a terminal end of the moving range of the first timer piston  284 . An inner diameter of the first cylinder  281  at which the third flow path  281   c  is located is made larger than the inner diameter of the first cylinder  281  at which the second flow path  281   b  is located. 
     A diaphragm  287  is arranged between the spring retainer plate  286  and a rear wall in the first cylinder  281 . The diaphragm  287  is made of a resin material such as elastically deformable rubber, and is configured to be deformed according to a length of the first piston shaft part  285  arranged in the first cylinder  281 . Thereby, even when a volume in the first cylinder  281  changes by a volume of the first piston shaft part  285  arranged in the first cylinder  281 , the volume in the first cylinder  281  can be maintained constant. 
     The second cylinder  291  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the second timer piston  294  so as to be slidable in the front and rear direction. In the present embodiment, a part of the second cylinder  291  has a structure sharing a part of the housing  1   a.    
     The second timer piston  294  is a cylindrical body having substantially the same diameter as an inner diameter of the second cylinder  291 , and is configured to be advanced and retreated in the second cylinder  291 , according to the pressing by the first piston shaft part  285 . A peripheral edge portion of the second timer piston  294  is mounted with an O-ring  296  for sealing between the peripheral edge portion and an inner wall of the second cylinder  291 . Thereby, the second cylinder  291  is further partitioned into a first space  291   a  on a rear side of the O-ring  296  and a second space  291   b  on a front side of the O-ring  296 . 
     The first space  291   a  is formed with a passage  290   a  configured to communicate with an outside of the housing  1   a . One end portion of the fourth connection passage  79  configured to communicate with the switch valve  70  is connected to the second space  291   b , so that the compressed air can be supplied to the timer valve  280  or the compressed air can be exhausted from the timer valve  280  via the fourth connection passage  79 . 
     The second piston shaft part  295  is a rod-shaped columnar body, and a rear end portion of the second piston shaft part  295  is attached to a front end portion of the second timer piston  294 . The second piston shaft part  295  can move in the front and rear direction in a through-hole  290   b  formed between the second timer piston  294  and the control valve  40 . A front end portion of the second piston shaft part  295  is provided to appear and disappear with respect to the inside of the cylinder  42  of the control valve  40 , and is configured to actuate the control valve  40  by pressing the rear end face of the control valve stem  44  constituting the control valve  40 . 
     As shown in  FIGS. 11 and 12 , the timer valve  280  is arranged in the grip part  4  so that a moving direction of the first timer piston  284  is different from, in the present embodiment, orthogonal to, the axial direction of the cylinder  26  (the moving direction of the driver  22 ). In addition, the timer valve  280  is arranged in the grip part  4  so that the moving direction of the first timer piston  284  is along the extension direction of the grip part  4 , i.e., is parallel to the extension direction of the grip part  4 . 
     [Operation Example of Nailing Machine  200 ] 
     Subsequently, an example of the striking operation of the nailing machine  200  is described with reference to  FIGS. 11 and 12 , and the like. In a case of performing a striking operation by using the nailing machine  100 , when the air hose is connected to the air plug  8  shown in  FIG. 11 , the compressed air is supplied into the main chamber  5 . The compressed air supplied into the main chamber  5  is supplied to the second space  291   b  of the timer valve  280  via the inside of the switch valve  70  and the fourth connection passage  79 . 
     Along with this, the second timer piston  294  is urged backward by the compressed air, so that the first tinier piston  284  is retreated to the initial position in the first cylinder  281 . 
     In this case, the oil O flows from the rear side toward the front side with respect to the first timer piston  284  that is retreated. For this reason, the oil O enters from the front side of the through-hole  284   a , so that the check valve  284   b  is pressed forward by the entering oil O and the compression spring  284   c  is compressed. Along with this, the check valve  284   b  separates from the front surface of the first timer piston  284 , so that the through-hole  284   a  opens. For this reason, the oil O can path through the through-hole  284   a  and the resistance by the oil O at the time when the first timer piston  284  moves is reduced, so that the first timer piston  284  is retreated to the initial position in the first cylinder  281  at relatively high speed. 
     Continuously, when the trigger lever  11  is pulled by the operator, the switch valve stem  74  of the switch valve  70  is pushed up by the contact lever  12 , so that the switch valve  70  is actuated. Thereby, the compressed air in the timer valve  280  is exhausted to the blow back chamber  28  at the atmospheric pressure via the fourth connection passage  79 , the inside of the switch valve  70  and the first connection passage  29 . 
     When the compressed air in the second space  291   b  of the second cylinder  291  is exhausted, the first timer piston  284  is advanced against the resistance of the oil O and the like by the urging of the compression spring  289 . 
     Specifically, when the first timer piston  284  is advanced, the oil O flows from the front side toward the rear side with respect to the first timer piston  284 . At this time, since the oil O collides with the front surface of the check valve  284   b , the through-hole  284   a  is closed by the check valve  284   b . For this reason, when the first timer piston  284  is advanced, a collision area of the oil O with the first timer piston  284  increases, so that the resistance due to the oil O increases. Thereby, the first timer piston  284  is slowly advanced while receiving the resistance due to the oil O. 
     In addition, when the first timer piston  284  is located in the first flow path  281   a  inside the first cylinder  281 , an interval between the inner peripheral surface of the first cylinder  281  and the outer peripheral surface of the first timer piston  284  becomes a wide first interval. For this reason, the resistance due to the oil O at the time of flowing in the first flow path  281   a  is reduced, and the load at the time when the first timer piston  284  is advanced is also reduced. In the below, in this case, the moving speed of the first timer piston  284  is referred to as ‘first speed’. 
     Continuously, the first timer piston  284  is moved from the first flow path  281   a  to a position facing the second flow path  281   b  in the first cylinder  281 . In this case, the interval between the inner peripheral surface of the first cylinder  281  and the outer peripheral surface of the first timer piston  284  becomes a second interval narrower than the first interval. For this reason, the resistance of the oil O at the time of flowing in the third flow path  281   c  is slightly increased, and the load at the time when the first timer piston  284  is advanced is also slightly increased. Thereby, the first timer piston  284  is moved at a second speed slightly slower than the first speed while receiving the resistance due to the oil O. 
     Continuously, the first timer piston  284  is moved from the second flow path  281   b  to a position facing the third flow path  281   c  in the first cylinder  281 . The interval between the inner peripheral surface of the first cylinder  281  and the outer peripheral surface of the first timer piston  284  becomes the first interval wider than the second interval. For this reason, the resistance of the oil O at the time of flowing in the third flow path  281   c  is reduced, and the load at the time when the first timer piston  284  is advanced is also reduced. Thereby, the first timer piston  284  is slowly moved at the first speed slightly faster than the second speed while receiving the resistance due to the oil O. 
     In this way, the load at the time when the first timer piston  284  is moved is reduced immediately before actuation of the control valve  40 , so that the moving speed of the first timer piston  284  and the like can be increased and the control valve stem  44  can be pushed with a strong force by the second piston shaft part  295 . Thereby, the control valve  40  can be actuated securely and with high accuracy. 
     As described above, according to the second embodiment, since the moving speed of the first timer piston  284  is controlled by the damper mechanism using the oil O filled in the first cylinder  281 , the variation in prescribed time until the control valve  40  is actuated can be prevented, so that the actuation of the timer valve  280  can be stabilized. Specifically, even when the pressure of the compressed air that is used for drive of the striking mechanism  20  of the nailing machine  200  varies, the time measurement of the timer valve  280  can be maintained constant. Thereby, the operation of the timer valve  280  can be stabilized. 
     Further, since the timer valve  280  is arranged in the grip part  4  so that the moving direction of the first timer piston  284  of the timer valve  280  is orthogonal to the moving direction of the striking mechanism  20 , it is possible to prevent the timer valve  280  from receiving a shock that is generated upon the striking operation of the striking mechanism  20 . Thereby, it is possible to prevent an erroneous operation of the timer valve  280 , so that it is possible to stabilize the operation of the timer valve  80 . 
     Note that, the technical scope of the present invention is not limited to the above-described embodiments, and the above-described embodiments can be variously changed without departing from the gist of the present invention. Specifically, in the above embodiments, the nailing machines  100  and  200  have been described as an example of the pneumatic tool. However, the present invention is not limited thereto. For example, as the pneumatic tool, the present invention can be applied to a screw fastening tool, a screw driving tool and the like. 
     In addition, in the first and second embodiments, the example where the control valve  40  is arranged between the head valve  30  and the trigger valve  50  has been described. However, the present invention is not limited thereto. For example, the control valve  40  may also be arranged in the trigger valve  50 . In addition, in the first and second embodiments, the passage between the head valve  30  and the trigger valve  50  is shut off by the control valve  40 . However, the present invention is not limited thereto. For example, a structure where the actuation of the head valve  30  is mechanically disabled by the control valve  40  and  240  can be adopted. Further, in the first and second embodiments, when the prescribed time by the timer valve  80  elapses, the control valve  40  is pressed and actuated by the timer valve  80 , so that the passage between the head valve  30  and the timer valve  50  is completely shut off when the predetermined time elapses. However, the present invention is not limited thereto. For example, a configuration where the control valve  40  is actuated in a state of being pressed from a first stage by the timer valve  80  and the passage between the head valve  30  and the timer valve  50  is completely shut off when the predetermined time elapses may also be adopted. Further, in the first and second embodiment, the control valve  40  is actuated by being pressed. However, the present invention is not limited thereto. For example, the control valve  40  may also be actuated by being pulled. 
     Third Embodiment 
     [Configuration Example of Nailing Machine  1100 ] 
       FIG. 13  is a side sectional view of a nailing machine  1100  according to a third embodiment.  FIG. 14  is a side sectional view of a trigger valve  1050 , a switch valve  1070  and a control valve  1040  according to the third embodiment.  FIG. 15  is a side sectional view of a timer valve  1080  according to the third embodiment. 
     The nailing machine  1100  is an example of the pneumatic tool, and includes, as shown in IG.  13 , a main body  1001  having a nose part  1002 , a grip part  1004  that is gripped by an operator, and a magazine part  1006  in which nails to be struck into a to-be-struck member are loaded. Housings of the main body  1001  and the grip part  1004  are integrally formed by a housing  1001   a , for example. The nailing machine  1100  also includes a head valve  1030 , a trigger mechanism  1010 , a trigger valve  1050 , a switch valve  1070 , a timer valve  1080  and a control valve  1040 . 
     Note that, in the present embodiment, the nose part  1002 -side of the nailing machine  1100  is referred to as a lower side of the nailing machine  1100 , and an opposite side thereto is referred to as an upper side of the nailing machine  1100 . Also, the main body  1001 -side of the nailing machine  1100  is referred to as a front side of the nailing machine  1100 , and the grip part  1004 -side of the nailing machine  1100  is referred to as a rear side of the nailing machine  1100 . 
     An inside of the main body  1001  is hollow, and a striking mechanism (drive mechanism)  1020  configured to drive by an air pressure of compressed air is arranged in the main body  1001 . The striking mechanism  1020  has a driver  1022 , a piston  1024 , and a cylinder  1026 . The driver  1022  is configured to reciprocally move in the upper and lower direction (axial direction) in the cylinder  1026 , and to impact a head portion of a nail delivered from the magazine part  1006 , thereby striking the nail into a to-be-struck member. The piston  1024  is connected to an upper end portion of the driver  1022 , and is configured to reciprocally move in the cylinder  1026 , in response to the compressed air flowing into a piston upper chamber  1024   a  provided on an upper side of the cylinder  1026 . The cylinder  1026  is a cylindrical body, is arranged in the housing  1001   a  constituting the main body  1001 , and is configured to accommodate the driver  1022  and the piston  1024  to be reciprocally movable in the upper and lower direction. An annular locking part  1025  configured to regulate upward movement of the piston  1024  is provided between the piston  1024  and the head valve  1030 . 
     A lower end portion of the main body  1001  is provided with the nose part  1002 . The nose part  1002  protrudes downward from the lower end portion of the main body  1001  by a predetermined length. The nose part  1002  is formed with an ejection port  1003  for striking out the nail delivered by the driver  1022  to an outside. The ejection port  1003  is arranged coaxially with the driver  1022  and the cylinder  1026 . 
     A main chamber  1005  in which the compressed air is supplied and filled is provided between an inner wall on an upper side of the main body  1001  and an outer peripheral part on an upper side of the cylinder  1026  and in the grip part  1004 . A blow back chamber  1028  for returning the piston  1024  to a top dead center is provided between an inner wall on a lower side of the main body  1001  and an outer peripheral part on a lower side of the cylinder  1026 . One end portion of a first connection passage  1029  configured to communicate with the switch valve  1070  is configured to communicate with the blow back chamber  1028 . 
     A plurality of small holes  1027  is formed at predetermined intervals in a substantially intermediate position in the axial direction of the cylinder  1026  and in a circumferential direction of the cylinder  1026 . The plurality of small holes  1027  is formed to communicate with the blow back chamber  1028  via a check valve  1027   a  provided to the cylinder  1026 . Note that, when the piston  1024  is located at a bottom dead center below the small holes  1027 , the compressed air in the cylinder  1026  is caused to flow into the blow back chamber  1028  via the small holes  1027 . In addition, when the piston  1024  is located at the top dead center, the compressed air in the blow back chamber  1028  is discharged to the atmosphere, so that the inside of the blow back chamber  1028  becomes an atmospheric pressure. 
     The head valve  1030  is configured to perform supply and shut-off of the compressed air to the cylinder  1026 , and to drive the striking mechanism  1020  by using the compressed air supplied from the main chamber  1005 . The head valve  1030  has a base part  1032  and a movable part  1034 . The base part  1032  is arranged on an upper end-side in the main body  1001 , and the movable part  1034  is arranged below the base part  1032 . The movable part  1034  is urged toward the cylinder  1026  at a predetermined interval from the base part  1032  by an urging spring  1036  interposed between the base part  1032  and the movable part  1034 . A lower surface of the movable part  1034  is in contact with an upper surface of the locking part  1025  in an urging state (a state where the head valve  1030  is off), so that the main chamber  1005  and the piston upper chamber  1024   a  are shut off therebetween. 
     The interval between the base part  1032  and the movable part  1034  is configured to function as a head valve chamber  1038  to which the compressed air in the main chamber  1005  is supplied. One end portion of a second connection passage  1039  is configured to communicate with the head valve chamber  1038 , and the other end-side of the second connection passage  1039  is configured to communicate with the control valve  1040 . The movable part  1034  is configured to slide along an inner wall of the housing  1001   a  constituting the main body  1001  and to open % close between the piston upper chamber  1024   a  and the main chamber  1005 , according to a state of the compressed air in the head valve chamber  1038 . The piston upper chamber  1024   a  is configured to communicate with an outside via an opening portion  1001   b  formed in the housing  1001   a.    
     The grip part  1004  is attached to a side part on the rear side of the main body  1001  in a direction substantially orthogonal to an extension direction of the main body  1001  tan axial direction of the cylinder  1026 ). A rear end portion of the grip part  1004  is provided with an air plug  1008 . One end portion of an air hose (not shown) is connected to the air plug  1008 , and the other end portion of the air hose is connected to a compressor (not shown). The air compressor is configured to generate the compressed air for driving the striking mechanism  1020  and to supply the generated compressed air into the main chamber  1005  via the air hose and the air plug  1008 . 
     The trigger mechanism  1010  has a trigger lever  1011 , a contact lever  1012 , a contact arm  1014  and a pressing member  1015 . The trigger lever  1011  is a lever for turning on (actuating) the switch valve  1070 , and is attached to a side surface on the rear side of the main body  1001  and a lower side of the grip part  1004  so as to be rotatable about a shah part as a fulcrum. The contact lever  1012  is arranged in the trigger lever  1011  and is configured to rotate about a front end-side as a fulcrum in conjunction with the trigger lever  1011 . A front end portion of the contact lever  1012  is urged downward by, for example, a torsion spring provided on a rear end-side, and is in contact with an upper end face of the pressing member  1015 . Note that, the contact lever  1012  may not be urged by the spring. 
     The contact arm  1014  is attached to an outer peripheral part of the nose part  1002  in a state of protruding downward from a lower end portion of the nose part  1002 . The contact arm  1014  is urged downward by a spring (not shown), and is configured to reciprocally move in the upper and lower direction relative to the nose part  1002  in conjunction with a pressing operation against the to-be-struck member. The pressing member  1015  is connected to the contact arm  1014 , and is configured to push up a front end-side of the contact lever  1012  in conjunction with upward movement of the contact arm  1014 . When the trigger lever  1011  is pulled, a trigger valve stem  1058  of the trigger valve  1050  is pushed up, so that the trigger valve  1050  is actuated (turned on). 
     The magazine part  1006  is configured so that a series of connected connecting nails can be loaded therein, and is provided on a lower side of the grip part  1004 . A front end-side of the magazine part  1006  is connected to the nose part  1002 , and a rear end-side of the magazine part  1006  is connected to the grip part  1004  via an attaching arm part  1007 . The connecting nails loaded in the magazine part  1006  are guided to the ejection port  1003  of the nose part  1002  by a feeding claw provided to be slidable with respect to the nose part  1002 , and is impacted and struck into the to-be-struck member by the descending driver  1022 . 
     As shown in  FIGS. 13 and 14 , the trigger valve  1050  is configured to actuate the head valve  1030  based on a pressing state of the contact arm  1014  against the to-be-struck member. The trigger valve  1050  is arranged near the switch valve  1070  on a front end-side of the grip part  1004 . The trigger valve  1050  has a housing  1052 , a pilot valve  1054 , a cap  1056  and a trigger valve stem  1058 . 
     The housing  1052  has a passage  1053  provided in a substantially intermediate portion in the upper and lower direction. The passage  1053  is configured to communicate with one end portion of a third connection passage  1049  configured to connect the control valve  1040  (head valve  1030 ) and the trigger valve  1050  each other. The passage  1053  is also configured to be able to communicate with an air exhaust passage  1059  upon turning-on of the trigger valve  1050 . 
     The pilot valve  1054  is arranged at a gap S 1001  on an inner side of the housing  1052 . O-rings  1054   a  and  1054   b  are attached at a predetermined interval in the upper and lower direction to a peripheral edge portion on a lower side of the pilot valve  1054 . The O-ring  1054   a  is configured to shut off a passage between the passage  1053  and the air exhaust passage  1059  to thus prevent the compressed air in the head valve chamber  1038  from being leaked from the passage  1053  to an outside, during non-actuation of the trigger valve  1050 . In addition, the O-ring  1054   a  is pressed against an inner wall of the housing  1052  to regulate upward movement of the pilot valve  1054 . The O-ring  1054   b  is configured to shut off between an empty chamber  1055 , which will be described later, and the air exhaust passage  1059 . 
     The cap  1056  is attached on an inner side of the housing  1052  with an empty chamber  1055  being interposed between the cap and the pilot valve  1054  on the upper side. The empty chamber  1055  is configured to communicate with the main chamber  1005  via a gap S 1002  between the pilot valve  1054  and the trigger valve stem  1058  and a passage  1054   c  of the pilot valve  1054  and to function as a chamber in which the compressed air is filled, during non-actuation of the trigger valve  1050 . 
     The trigger valve stem  1058  is arranged on inner sides of the pilot valve  1054  and the cap  1056 , and is provided to be movable in the upper and lower direction from the cap  1056  as a point of origin. An upper end-side of the trigger valve stem  1058  is urged toward the contact lever  1012  (toward the lower side) by a compression spring  1057 . The compression spring  1057  is interposed between the pilot valve  1054  and the trigger valve stem  1058 , and is adapted to expand and contract, in response to pressing of the trigger valve stem  1058 . A lower end portion of the trigger valve stem  1058  protrudes from a lower surface of the cap  1056  by a predetermined length, and can come into contact with the contact lever  1012  (refer to  FIG. 13 ). O-rings  1058   a  and  1058   b  are attached at a predetermined interval in the upper and lower direction to a peripheral edge portion of a substantially intermediate position in the upper and lower direction of the trigger valve stem  1058 . The O-rings  1058   a  and  10586  are configured to prevent the compressed air in the empty chamber  1055  from being leaked from a gap S 1003  between the trigger valve stem  1058  and the cap  1056  to an outside, during non-actuation of the trigger valve  1050 . 
     An air exhaust passage  1059  is provided between the housing  1052  and the cap  1056 . When the empty chamber  1055  is closed due to push-up of the trigger valve stem  1058  during actuation of the trigger valve  1050 , the air exhaust passage  1059  communicates with the passage  1053  to exhaust the compressed air in the head valve chamber  1038  to the atmosphere. 
     As shown in  FIGS. 13 and 14 , the switch valve  1070  is arranged in the vicinity of a rear side of the trigger valve  1050 , and is configured to actuate the timer valve  1080  based on an operation on the trigger lever  1011 . The switch valve  1070  has a cylinder  1072  and a switch valve stem  1074 . 
     The cylinder  1072  is a hollow cylindrical body extending in the upper and lower direction, and is configured to accommodate the switch valve stem  1074  so as to be slidable in the upper and lower direction. An upper side of the cylinder  1072  is formed with a first passage  1072   a . The first passage  1072   a  is configured to communicate with the main chamber  1005 , and the compressed air in the main chamber  1005  is caused to flow into the cylinder  1072  via the first passage  1072   a.    
     One end portion of a fourth connection passage  1079  is configured to communicate in a substantially intermediate position in the upper and lower direction of the cylinder  1072 , and the other end portion of the fourth connection passage  1079  is configured to communicate with the timer valve  1080 . The fourth connection passage  1079  is configured to connect the switch valve  1070  and the timer valve  1080  each other, and the compressed air can be supplied or exhausted with respect to the timer valve  1080  via the fourth connection passage  1079 . One end portion of the first connection passage  1029  is configured to communicate on a further lower side than the fourth connection passage  1079  of the cylinder  1072 , and the other end portion of the first connection passage  1029  is configured to communicate with the blow back chamber  1028 . The first connection passage  1029  is configured to connect the switch valve  1070  and the blow back chamber  1028  therebetween, and the compressed air can be supplied to the switch valve  1070  or the compressed air can be exhausted from the switch valve  1070  via the first connection passage  1029 . 
     The switch valve stem  1074  is accommodated in the cylinder  1072 , and is urged toward the trigger lever  1011  (toward the lower side) by a compression spring  1076 . The compression spring  1076  is interposed between an upper end face of the switch valve stem  1074  and a top surface in the cylinder  1072 , and is adapted to expand and contract, in response to a pulling operation on the trigger lever  1011 . A lower end portion of the switch valve stem  1074  protrudes downward from the lower surface of the cylinder  1072 , and comes into contact with the contact lever  1012  at the time when the trigger lever  1011  (refer to  FIG. 13 ) is pulled. 
     An O-ring  1074   a  for close contact with an inner wall of the cylinder  1072  is mounted to a peripheral edge portion of a substantially intermediate position in the upper and lower direction of the switch valve stem  1074 . Upon non-pulling operation of the trigger lever  1011 , the switch valve stem  1074  is configured to close a path between the fourth connection passage  1079  and the first connection passage  1029  by the O-ring  1074   a  and to communicate the first passage  1072   a  and the fourth connection passage  1079  each other. On the other hand, upon pulling operation of the trigger lever  1011 , the switch valve stem  1074  is configured to be pushed up against the elastic force of the compression spring  1076  by the contact lever  1012  and to close a path between the first passage  1072   a  and the fourth connection passage  1079  by the O-ring  1074   a  and to communicate the fourth connection passage  1079  and the first connection passage  1029  each other. 
     As shown in  FIGS. 13 and 15 , in a state where the trigger lever  11  is pulled, after a preset prescribed time elapses, when the contact arm  1014  is pressed against the to-be-struck member, the timer valve  1080  actuates the control valve  1040  to disable the striking operation Specifically, the timer valve  1080  is configured to be actuated based on an operation on the trigger lever  1011  and to actuate the control valve  1040  at a predetermined timing, thereby disabling actuation of the head valve  1030 . 
     The timer valve  1080  has a cylinder  1090 , a first timer piston  1084 , a first piston shaft part  1085 , a second timer piston  1094 , and a second piston shaft part  1095 . 
     The cylinder  1090  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the first timer piston  1084  and the second timer piston  1094  so as to be slidable in the front and rear direction. An inside of the cylinder  1090  is partitioned into a first chamber  1081  and a second chamber  1091 , which are an example of the accommodation part, via a partition portion  1090   a  The first chamber  1081  is constituted by a sealed closed space (closed circuit) and is isolated from the second chamber  1091 , which is another space, the main chamber  1005  and the like. In addition, the first chamber  1081  is also isolated from an outside air. In the first chamber  1081 , the atmospheric air (air) that is used when actuating the timer valve  1080  is filled in advance. Thereby, it is possible to prevent impurities such as trash and oil from flowing into the first chamber  1081  from other spaces. 
     The first timer piston  1084  is a cylindrical body having substantially the same diameter as an inner diameter of the cylinder  1090 , and is arranged to be movable along the inner wall of the cylinder  1090  in the extension direction of the grip part  1004 . The first timer piston  1084  is urged toward the control valve  1040  (toward the front side) by a compression spring  1089 . The compression spring  1089  is interposed between a concave portion formed on a base end-side of the first timer piston  1084  and a rear wall in the first chamber  1081 , and is adapted to expand and contract, according to advance or retreat of the first timer piston  1084 . 
     A peripheral edge portion of the first timer piston  1084  is formed with a concave portion  1084   a  along a circumferential direction thereof. In the concave portion  1084   a , an O-ring  1086  for sealing between the concave portion and the inner wall of the cylinder  1090  is mounted. Thereby, the first chamber  1081  is further partitioned into a first space  1081   a  on a rear side of the O-ring  1086  and a second space  1081   b  on a front side of the O-ring  1086 . The first space  1081   a  and the second space  1081   b  are isolated from each other by the O-ring  1086 . 
     On a lower side in the cylinder  1090 , a first passage  1082   a  and a second passage  1082   b  extending in the front and rear direction are provided side by side in the upper and lower direction. A front end portion of the first passage  1082   a  is configured to communicate with the second space  1081   b , and a rear end portion of the first passage  1082   a  is configured to communicate with the first space  1081   a . A front end portion of the second passage  1082   b  is configured to communicate with the second space  1081   b , and a rear end portion of the second passage  1082   b  is configured to communicate with the first space  1081   a.    
     A check valve  1087  is provided in the middle of the path of the first passage  1082   a . The check valve  1087  has a ball  1087   a  for opening closing the first passage  1082   a , for example, and a spring  1087   b  for urging backward the ball  1087   a . When the first timer piston  1084  is retreated in the first chamber  1081 , the ball  1087   a  is moved forward against the elastic force of the spring  1087   b  by the atmospheric air flowing into the first passage  1082   a  from the first space  1081   a , so that the first passage  1082   a  opens and the atmospheric air in the first space  1081   a  of the first chamber  1081  is caused to flow into the second space  1081   b . When the first timer piston  1084  is advanced in the first chamber  1081 , the atmospheric air flowing into the first passage  1082   a  from the second space  1081   b  and the spring  1087   b  act on the ball  1087   a  and the first passage  1082   a  is closed by the ball  1087   a , so that the atmospheric air in the second space  1081   b  of the cylinder  1090  does not flow into (flow back to) the first space  1081   a  through the first passage  1082   a.    
     A throttle portion  1088  is provided in the middle of the path of the second passage  1082   b . The throttle portion  1088  is constituted by reducing a cross-sectional area (narrowing a width) of a path of a part of the second passage  1082   b . The throttle portion  1088  is configured to restrict a flow rate per unit time of the atmospheric air, which is caused to flow into the second passage  1082   b  from the second space  1081   b , to be constant, so that the moving speed of the first timer piston  1084  is regulated. Thereby, it is possible to control the moving speed until the second piston shaft part  1095  presses a control valve stem  1044  of the control valve  1040 . In addition, a prescribed time at the time when the first timer piston  1084  moves from an initial position (bottom dead center) in the first chamber  1081  to an actuation position (top dead center) in which the control valve  1040  is actuated is determined by a flow rate of the air passing through the throttle portion  1088  of the timer valve  1080 , a spring coefficient of the compression spring  1089 , and the like. In the present embodiment, the prescribed time is, for example, 3 seconds to 10 seconds. However, the present invention is not limited thereto. In addition, in the present embodiment, a time for which the control valve  1040  moves from the actuation position to a position in which the passage between the head valve chamber  1038  and the trigger valve  1050  is shut off is set to a time considerably shorter than the prescribed time. For this reason, when the prescribed time elapses, the passage between the head valve  1030  and the trigger valve  1050  is immediately shut off by the control valve  1040 . 
     The first piston shaft part  1085  is a rod-shaped columnar body, and a rear end portion of the first piston shaft part  1085  is attached to a front end portion of the first timer piston  1084 . The first piston shaft part  1085  is inserted in a through-hole  1090   b  formed in the partition portion  1090   a , and a front end-side thereof extends from the inside of the first chamber  1081  into the second chamber  1091 . A front end portion of the first piston shaft part  1085  is attached to a rear end portion of the second timer piston  1094  and is configured to be able to transmit the pressing force of the first timer piston  1084  to the second timer piston  1094 . An O-ring  1090   c  is attached to the partition portion  1090   a  to secure a sealed state of the first chamber  1081 . 
     The second timer piston  1094  is a cylindrical body having substantially the same diameter as an inner diameter of the cylinder  1090 , and is configured to be advanced and retreated in the second cylinder  1091 , according to the pressing by the first piston shaft part  1085 . A peripheral edge portion of the second timer piston  1094  is formed with a concave portion  1094   a  along a circumferential direction thereof. In the concave portion  1094   a , an O-ring  1096  for sealing between the concave portion and the inner wall of the cylinder  1090  is mounted. Thereby, the second chamber  1091  is further partitioned into a first space  1091   a  on a rear side of the O-ring  1096  and a second space  1091   b  on a front side of the O-ring  1096 . 
     The first space  1091   a  is formed with a passage  1090   e  configured to communicate with an outside of the housing  1001   a . One end portion of the fourth connection passage  1079  configured to communicate with the switch valve  1070  is connected to the second space  1091   b , so that the compressed air can be supplied to the timer valve  1080  or the compressed air can be exhausted from the timer valve  1080  via the fourth connection passage  1079 . 
     The second piston shaft part  1095  is a rod-shaped columnar body, and a rear end portion of the second piston shaft part  1095  is attached to a front end portion of the second timer piston  1094 . The second piston shaft part  1095  can move in the front and rear direction in a through-hole  1090   d  formed between the second timer piston  1094  and the control valve  1040 . A front end portion of the second piston shaft part  1095  is provided to appear and disappear with respect to the inside of the cylinder  1042  of the control valve  1040 , and is configured to actuate the control valve  1040  by pressing the rear end face of the control valve stem  1044  constituting the control valve  1040 . 
     In the present embodiment, as shown in  FIGS. 13 and 15 , the timer valve  1080  is arranged in the grip part  1004  so that moving directions of the first timer piston  1084  and the second timer piston  1094  are different from, in the present embodiment, orthogonal to, the axial direction of the cylinder  1026  (the moving direction of the driver  1022 ). In addition, the timer valve  1080  is arranged in the grip part  1004  so that the moving directions of the first timer piston  1084  and the second timer piston  1094  are along the extension direction of the grip part  1004 , i.e., are parallel to the extension direction of the grip part  1004 . 
     As shown in  FIGS. 13 and 14 , the control valve  1040  is configured to disable actuation of the head valve  1030  that is actuated in conjunction with actuation of the trigger valve  1050 . Specifically, the control valve  1040  is configured to switch the passage between the head valve chamber  1038  and the trigger valve  1050  from a communication state to a shut-off state by control of the timer valve  1080 , thereby disabling actuation of the head valve  1030  by. The control valve  1040  is arranged in a position near the front side of the timer valve  1080 , between the head valve chamber  1038  and the trigger valve  1050 . The control valve  1040  has a cylinder  1042  and a control valve stem  1044 . Note that, a part of the cylinder  1042  has a structure sharing a part of the housing  1001   a.    
     The cylinder  1042  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the control valve stem  1044  so as to be slidable in the front and rear direction. An upper surface-side of the cylinder  1042  is configured to communicate with one end portion of the second connection passage  1039  configured to communicate with the head valve chamber  1038 . A lower surface-side of the cylinder  1042  is configured to communicate with one end portion of the third connection passage  1049  configured to communicate with the trigger valve  1050 , and is formed with a passage  1042   c  configured to communicate with the main chamber  1005 . 
     The control valve stem  1044  is a columnar body extending in the front and rear direction and is arranged in the cylinder  1042 . The control valve stem  1044  is urged toward the timer valve  1080  (toward the rear side) by a compression spring  1046 . The compression spring  1046  is interposed between a front wall in the cylinder  1042  and a front end face of the control valve stem  1044 , and is adapted to expand and contract, in response to pressing by the timer valve  1080 . O-rings  1044   a  and  1044   b  for close contact with the inner wall of the cylinder  1042  are attached at a predetermined interval in the front and rear direction to a peripheral edge portion of a substantially intermediate position in the front and rear direction of the control valve stem  1044 . 
     The control valve stem  1044  is located on a rear end-side in the cylinder  1042 , and closes a path between the second connection passage  1039  and the passage  1042   c  by the O-ring  1044   b  and opens a path between the second connection passage  1039  and the third connection passage  1049 , upon non-pressing of the timer valve  1080 , i.e., before timeout. Thereby, the head valve chamber  1038  and the trigger valve  1050  are connected to each other. On the other hand, the control valve stem  1044  is moved to a front end-side in the cylinder  1042 , and opens the path between the second connection passage  1039  and the passage  1042   c  and closes the path between the second connection passage  1039  and the third connection passage  1049  by the O-ring  1044   a , upon pressing of the timer valve  1080 , i.e., after timeout. Thereby, the head valve chamber  1038  and the trigger valve  1050  are shut off therebetween. 
     [Operation Example of Nailing Machine  1100 ] 
     Subsequently, an example of a striking operation of the nailing machine  1100  according to the third embodiment is described.  FIGS. 16 to 22  show a striking operation in the nailing machine  1100  according to the third embodiment. 
     When the air hose is connected to the air plug  1008  of the nailing machine  1100  shown in  FIG. 13 , the compressed air is supplied into the main chamber  1005 . As shown in  FIG. 16 , the compressed air supplied into the main chamber  1005  is supplied into the second space  1091   b  of the second chamber  1091  of the timer valve  1080  via the first passage  1072   a  of the switch valve  1070 , the inside of the switch valve  1070  and the fourth connection passage  1079 . 
     Along with this, the front surface of the second timer piston  1094  is pushed backward by the compressed air, and the first timer piston  1084  and the first piston shaft part  1085  are retreated against the elastic force of the compression spring  1089 . At this time, the atmospheric air in the first space  1081   a  is compressed and the compressed atmospheric air is caused to flow into the first passage  1082   a . The ball  1087   a  of the check valve  1087  is moved forward against the elastic force of the spring  1087   b  by the inflow atmospheric air, thereby opening the first passage  1082   a . Thereby, the air in the first space  1081   a  is caused to flow into the second space  1081   b  via the first passage  1082   a . Note that, in the second passage  1082   b , since the flow resistance of the throttle portion  1088  is high, the compressed air hardly passes through the second passage  1082   b.    
     As shown in  FIG. 17 , when the supply of the compressed air into the second chamber  1091  of the timer valve  1080  continues, the first timer piston  1084  reaches the initial position in the cylinder  1090 , specifically, the base end portion of the first timer piston  1084  reaches the rear part of the first chamber  1081  by compression of the compression spring  1089 . Thereby, the timer valve  1080  becomes in a standby state. 
     As shown in  FIG. 18 , when the trigger lever  1011  is pulled by an operator, the switch valve stem  1074  of the switch valve  1070  is pushed up by the contact lever  1012 , so that the switch valve  1070  is actuated. By the actuation of the switch valve  1070 , the O-ring  1074   a  (refer to  FIG. 14 ) is also moved upward, so that while the first passage  1072   a  of the switch valve  1070  and the fourth connection passage  1079  are isolated from each other, the fourth connection passage  1079  and the first connection passage  1029  communicate with each other. Along with this, the compressed air in the second space  1091   b  of the second chamber  1091  of the tinier valve  1080  is exhausted to the blow back chamber  1028  at the atmospheric pressure via the fourth connection passage  1079 , the inside of the switch valve  1070  and the first connection passage  1029 . 
     In addition, when the compressed air in the second space  1091   b  of the cylinder  1090  is exhausted, the first timer piston  1084  is advanced in the first chamber  1081  by the urging force of the compression spring  1089 . Along with this, the atmospheric air in the second space  1081   b  of the first chamber  1081  is caused to flow into the first space  1081   a  through the second passage  1082   b  and the throttle portion  1088 . The flow rate of the atmospheric air that is supplied to the first space  1081   a  is restricted to be constant by the throttle portion  1088 . The compression spring  1089  expands, according to the flow rate of the atmospheric air that is caused to flow into the first space  1081   a . Thereby, the first tinier piston  1084  is slowly advanced from the initial position in the first chamber  1081  and the time measurement (timer) of the timer valve  1080  starts. Note that, since the first passage  1082   a  is closed by the ball  1087   a , the atmospheric air does not flow into (flow back to) the first space  1081   a  via the first passage  1082   a.    
     As shown in  FIG. 19 , when the contact arm  1014  is pressed against the to-be-struck member in a state where the trigger lever  1011  is pulled and before the prescribed time of the timer valve  1080  elapses, the pressing member  1015  is pushed up. Along with this, the front end-side of the contact lever  1012  is pushed up and the trigger valve stem  1058  of the trigger valve  1050  is pushed up, so that the trigger valve  1050  is actuated. When the trigger valve  1050  is actuated, the O-rings  1058   a  and  1058   b  are also moved upward, as shown in  FIG. 14 , so that the compressed air in the empty chamber  1055  is exhausted from the gap S 1003  between the cap  1056  and the trigger valve stem  1058  to the outside. The pilot valve  1054  is pushed down against the elastic force of the compression spring  1057  by the compressed air in the main chamber  1005 , so that the lower surface of the pilot valve  1054  comes into contact with the upper surface of the cap  1056 . Thereby, the passage  1053  and the air exhaust passage  1059  communicate with each other, and the compressed air in the head valve chamber  1038  is exhausted to the atmosphere (outside) via the second connection passage  1039 , the inside of the control valve  1040 , the third connection passage  1049 , the inside of the trigger valve  1050  and the air exhaust passage  1059 . 
     When the compressed air in the head valve chamber  1038  is exhausted, the movable part  1034  of the head valve  1030  is pushed up by the compressed air in the main chamber  1005  and the movable part  1034  and the locking part  1025  are opened therebetween, so that the compressed air in the main chamber  1005  is caused to flow into the piston upper chamber  1024   a  and the piston  1024  rapidly descends in the cylinder  1026 . 
     As shown in  FIG. 20 , when the piston  1024  further descends, the nail is struck into the to-be-struck member by the driver  1022  connected to the piston  1024 . In addition, when the piston  1024  descends to the lower part-side in the cylinder  1026 , the compressed air in the cylinder  1026  is caused to flow into the blow back chamber  1028  via the small holes  1027 . The inflow compressed air is caused to flow into the second  1091  of the timer valve  1080  via the first connection passage  1029 , the inside of the switch valve  1070  and the fourth connection passage  1079 . Thereby, the timer valve  1080  is again retreated to the initial position in the first chamber  1081 , so that the timer valve  1080  is reset. As the timer valve  1080  is retreated, the atmospheric air in the first space  1081   a  is caused to flow into the second space  1081   b  via the second passage  1082   b  and the check valve  1087 , as described in  FIG. 16 . 
     On the other hand, as shown in  FIG. 21 , when the contact arm  1014  is not pressed against the to-be-struck member, i.e., the striking operation is not executed within the prescribed time set in advance from the time point when the switch lever  1011  shown in  FIG. 18  is pulled by the operator. Specifically, the second piston shaft part  1095  of the timer valve  1080  is moved to the actuation position in which the control valve  1040  is pressed when the prescribed time elapses, the timer valve  1080  times out. 
     The control valve stem  1044  of the control valve  1040  is pushed forward by the second piston shaft part  1095  and is moved toward the front end-side of the cylinder  1042 . When the control valve stem  1044  is advanced, the O-rings  1044   a  and  1044   b  are also advanced, so that while the path communicating the second connection passage  1039  and the third connection passage  1049  each other is shut off, a gap S 1004  is formed. Thereby, the head valve chamber  1038  is switched from the communication state with the trigger valve  1050  to the communication state with the main chamber  1005  via the second connection passage  1039 , the gap S 1004  and the passage  1042   a  of the control valve  1040 . 
     As shown in  FIG. 22 , when the contact arm  1014  is pressed against the to-be-struck member after timeout of the timer valve  1080  in a state where the trigger lever  1011  shown in  FIG. 18  is pulled by the operator, the pressing member  1015  is accordingly pushed up. Along with this, the front end-side of the contact lever  1012  is pushed up and the trigger valve stem  1058  of the trigger valve  1050  is pushed up by the push-up of the contact lever  1012 , so that the trigger valve  1050  is actuated. When the trigger valve  1050  is actuated, the O-rings  1058   a  and  1058   b  are moved upward, as shown in  FIG. 14 , so that the compressed air in the empty chamber  1055  is exhausted from the gap S 1003  between the cap  1056  and the trigger valve stem  1058  to the outside. The pilot valve  1054  is pushed down against the elastic force of the compression spring  1057  by the compressed air in the main chamber  1005 , so that the lower surface of the pilot valve  1054  comes into contact with the upper surface of the cap  1056 . Thereby, the passage  1053  and the air exhaust passage  1059  communicate with each other. 
     However, in a timeout state of the timer valve  1080 , while the path between the second connection passage  1039  and the third connection passage  1049  is shut off by the control valve  1040  shown in  FIG. 21 , the second connection passage  1039  and the main chamber  1005  communicate with each other. For this reason, the compressed air in the head valve chamber  1038  is left remaining in the head valve chamber  1038  without being exhausted to the outside via the air exhaust passage  1059  provided to the trigger valve  1050 . Thereby, when the timer valve  1080  times out, the head valve  1030  is not actuated even though the contact arm  1014  is pressed against the to-be-struck member in a state where the operator pulls the trigger lever  1011 . Therefore, the striking operation is not executed after timeout of the timer valve  1080 . 
     As described above, according to the third embodiment, the first chamber  1081  of the cylinder  1090  for reserving the atmospheric air for actuating the timer valve  1080  is constituted by the closed space that is isolated from the other spaces, and the atmospheric air that is used when actuating the timer valve  1080  is not supplied from the outside. Therefore, it is possible to prevent oil, trash and the like from entering the first chamber  1081  of the timer valve  1080 . Thereby, it is possible to measure the prescribed time of the timer valve  1080  correctly and with high accuracy, and to prevent an erroneous operation of the tinier valve  1080  due to attaching of attachments such as oil and trash. 
     Fourth Embodiment 
     In a timer valve  1280  of a fourth embodiment, a configuration different from the timer valve  1080  of the third embodiment is adopted. Similarly, also for a control valve  1240  and the switch valve  1070  of the fourth embodiment, configurations different from the control valve  1040  and the switch valve  1070  of the third embodiment are adopted. Note that, since the other configuration, function and operation of a nailing machine  1200  are common to the configuration and the like of the nailing machine  1100  of the third embodiment, the detailed descriptions thereof are omitted. 
     [Configuration Example of Nailing Machine  1200 ] 
       FIG. 23  is a side sectional view of a nailing machine  1200  according to a fourth embodiment.  FIG. 24  is a side sectional view of a tinier valve  1280  according to the fourth embodiment.  FIG. 25  is a side sectional view of a control valve  1240  according to the fourth embodiment. 
     The nailing machine  1200  is an example of the pneumatic tool, and includes the piston  1024  configured to be slidable in the cylinder  1026 , the striking mechanism  1020  having the driver  1022  attached to the piston  1024  and configured to strike a nail into a to-be-struck member, the main chamber  1005  to which the compressed air for driving the striking mechanism  1020  is supplied, the head valve  1030  configured to drive the striking mechanism  1020  by using the compressed air that is supplied to the main chamber  1005 , and the trigger valve  1050  configured to actuate the head valve  1030 . The nailing machine  1200  also includes a control valve  1240  configured to disable actuation of the head valve  1030  configured to be actuated in conjunction with actuation of the trigger valve  1050 , a timer valve  1280  configured to disable actuation of the head valve  1030  by actuating the control valve  1240 , and a switch valve  1070  configured to actuate the timer valve  1280  based on an operation on the trigger lever  1011 . 
     As shown in  FIG. 23 , the switch valve  1070  is arranged in the vicinity of a rear side of the trigger valve  1050 , and is configured to actuate the timer valve  1280  based on an operation on the trigger lever  1011 . The switch valve  1070  has a cylinder  1072  and a switch valve stem  1074 . 
     The cylinder  1072  is a hollow cylindrical body extending in the upper and lower direction, and is configured to accommodate the switch valve stem  1074  so as to be slidable in the upper and lower direction. An upper side of the cylinder  1072  is formed with a first passage  1072   a  configured to communicate with the main chamber  1005 . One end portion of the fourth connection passage  1079  is configured to communicate in a substantially intermediate position of the cylinder  1072 , and the other end portion of the fourth connection passage  1079  is configured to communicate with the timer valve  1280 . A second passage  1072   b  configured to communicate with the outside of the housing  1001   a  at the atmospheric pressure is formed below the fourth connection passage  1079  of the cylinder  1072 . 
     During a non-pulling operation of the trigger lever  1011 , the switch valve stem  1074  is configured to communicate the fourth connection passage  1079  and the second passage  1972   b  each other, and to close a path between the first passage  1072   a  and the fourth connection passage  1079  by the O-ring  1074   a . On the other hand, during a pulling operation of the trigger lever  1011 , the switch valve stem  1074  is configured to be pushed up against the elastic force of the compression spring  1076  by the contact lever  1012 , so that the first passage  1072   a  and the fourth connection passage  1079  communicate with each other and the path between the fourth connection passage  1079  and the second passage  1072   b  is closed by the O-ring  1074   b.    
     As shown in  FIGS. 23 and 24 , the nailing machine  1200  includes the timer valve  1280  that disables the striking operation by actuating the control valve  1240  when the contact arm  1014  is pressed against the to-be-struck member in a state where the trigger lever  1011  is pulled and the prescribed time elapses. 
     The timer valve  1280  is provided outside the housing  1001   a , is connected to the control valve  1240  via a connection passage  1249 , which will be described later, is connected to the switch valve  1070  via the fourth connection passage  1079 , and is connected to the blow back chamber  1028  via the first connection passage  1029 . 
     As shown in  FIG. 24 , the timer valve  1280  has a housing  1281  for valve, a timer valve stem  1282 , a piston  1285  and a seal member  1286 . The housing  1281  for valve is provided with a first accommodation part  1281   a  configured to accommodate the timer valve stem  1282 , a second accommodation part  1281   b  configured to accommodate the piston  1285 , a third accommodation part  1281   c  configured to accommodate the seal member  1286 , and a space part  1281   d  configured to reserve compressed air for measuring a prescribed time until the control valve  1240  is actuated. 
     A lower end-side of the first accommodation part  1281   a  is configured to communicate with one end portion of the fourth connection passage  1079 , so that the compressed air in the main chamber  1005  can be supplied into the first accommodation part  1281   a  via the fourth connection passage  1079 . An upper end-side of the first accommodation part  1281   a  is configured to communicate with one end portion of a first passage  1281   u , and the other end portion of the first passage  1281   u  is configured to communicate with the space part  1281   d.    
     An upper end-side of the second accommodation part  1281   b  is configured to communicate with one end portion of a third passage  1281   w  and the other end portion of the third passage  1281   w  is configured to communicate with one end portion of the first connection passage  1029 , so that the compressed air in the blow back chamber  1028  can be supplied into the second accommodation part  1281  via the third passage  1281   w.    
     A lower end-side of the third accommodation part  1281   c  is configured to communicate with one end portion of a second passage  1281   v  and the other end portion of the second passage  1281   v  is configured to communicate with one end portion of the fourth connection passage  1079 , so that the compressed air in the main chamber  1005  can be supplied into the third accommodation part  1281   c  via the second passage  1281   v.    
     A fifth passage  1281   y  configured to communicate with an outside of the housing  1281  for valve is provided between the second accommodation part  1281   b  and the third accommodation part  1281   c . A sixth passage  1281   z  configured to communicate between the first accommodation part  1281   u  and the second accommodation part  1281   b  is provided therebetween. A fourth passage  1281   x  branching from a middle of the third passage  1281   w  is provided between the third passage  1281   w  and the first accommodation part  1281   a.    
     The timer valve stem  1282  is a substantially columnar body extending in the upper and lower direction, and is arranged to be slidable in the upper and lower direction along an inner wall of the first accommodation part  1281   a . The timer valve stem  1282  is urged downward by a compression spring  1284 . The compression spring  1284  is interposed between a support portion  1281   s  provided to the housing  1281  for valve and an upper side of the timer valve stem  1282 , and is adapted to expand and contract, in response to the compressed air that is supplied from the main chamber  1005 . 
     The timer valve stem  1282  has a throttle portion  1282   a  configured to control a flow rate of the compressed air that is used when actuating the control valve  1240 . The throttle portion  1282   a  is formed continuously to an upper end portion of the timer valve stem  1282  having a columnar shape, and is constituted by a tapered columnar body whose outer diameter gradually decreases toward the upper side. The throttle portion  1282   a  is configured to ascend in the first accommodation part  1281   a  by the compressed air entering in response to a pulling operation on the trigger lever  1011 , thereby fitting (engaging) to a to-be-throttled portion  1281   u   1  provided on a lower end-side of the first passage  1281   u  to close the first passage  1281   u . That is, a gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  is closed. The to-be-throttled portion  1281   u   1  is configured so that a passage diameter increases from an upper end-side toward a lower end-side, and has such a shape that the throttle portion  1282   a  can be fitted therein. At this time, a circumferential surface of the throttle portion  1282   a  comes into close contact with a wall surface of the to-be-throttled portion  1281   u   1 . However, in the present embodiment, the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  are configured to form a slight gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  so that the compressed air supplied from the main chamber  1005  can pass therethrough. Thereby, it is possible to regulate a flow rate of the compressed air, which is caused to flow into the space part  1281   d , to be constant by adjusting an area of the gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1 . 
     The space part  1281   d  of the housing  1281  for valve is constituted by a space having a volume capable of reserving a predetermined amount of compressed air, and has a rear wall with which one end portion of the first passage  1281   u  communicates and a front wall with which one end portion of the connection passage  1249  communicates. The volume of the space part  1281   d  is designed based on the prescribed time (timeout) for which the control valve  1240  is actuated by the timer valve  1280 . Therefore, in the present embodiment, the prescribed time by the timer valve  1280  is determined based on the volume of the space part  1281   d  and the area of the slight gap formed between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1 . Note that, for the volume of the space part  1281   d , volumes of the connection passage  1249 , the first passage  1281   u  and the like may also be considered. 
     The piston  1285  has a columnar body  1285   a  having substantially the same diameter as an inner diameter of the second accommodation part  1281   b , and a pressing portion  1285   b  smaller than the diameter of the columnar body  1285   a  and protruding downward from the second accommodation part  1281   b . The columnar body  1285   a  of the piston  1285  is configured to descend in the second accommodation part  1281   b , in response to the compressed air that is supplied from the blow back chamber  1028 , during the striking operation by the striking mechanism  1020 . The pressing portion  1285   b  is configured to press the seal member  1286  arranged on the lower side, as the columnar body  1285   a  descends. 
     The seal member  1286  is made of a resin material such as rubber, and is arranged in the third accommodation part  1281   c  below the second accommodation part  1281   b . The seal member  1286  is integrally attached to an attachment member  1287 , and is urged upward by a compression spring  1288 . The compression spring  1288  is interposed between the attachment member  1287  and a bottom surface in the third accommodation part  1281   c , and is adapted to expand and contract, in response to the pressing of the piston  1285 . 
     During the pressing by the piston  1285 , the seal member  1286  is configured to communicate a sixth passage  1281   z  configured to communicate with the space part  1281   d  and a fifth passage  1281   y  configured to communicate with the outside, thereby exhausting the compressed air in the space part  1281   d  to the outside. On the other hand, during the non-pressing of the piston  1285 , the seal member  1286  is configured to communicate the second passage  1281   v  configured to communicate with the main chamber  1005  and the sixth passage  1281   z  configured to communicate with the space part  1281   d , there causing the compressed air in the main chamber  1005  to flow into the space part  1281   d.    
     As shown in  FIGS. 23 and 25 , the nailing machine  1200  includes the control valve  1240  configured to disable actuation of the trigger valve  1050  after the prescribed time of the timer valve  1280  elapses. The control valve  1240  has a cylinder  1241 , a control valve piston  1242  and a control valve stem  1245 . 
     The cylinder  1241  is a cylindrical body opening on an upper side and having a bottom surface on a lower side, and an upper end portion thereof is attached to a support portion  1   c  via an O-ring  1248 . A lower portion of a rear wall of the cylinder  1241  is configured to communicate with one end portion of a connection passage  1249  configured to communicate with the timer valve  1280 . 
     The control valve piston  1242  is arranged in the cylinder  1241 , and is configured to slide in the upper and lower direction along an inner wall of the cylinder  1241 . An O-ring  1243  for close contact with the inner wall of the cylinder  1241  is mounted to an attaching portion  1242   a  provided on a lower side of the control valve piston  1242 . The control valve piston  1242  is urged downward by a compression spring  1244 . The compression spring  1244  is interposed between the attaching portion  1242   a  and a support portion  1001   d  constituting the housing  1001   a , and is adapted to expand and contract, in response to the compressed air that is supplied from the timer valve  1280 . When the compressed air is supplied between the lower surface of the control valve piston  1242  and the bottom surface in the cylinder  1241  via the connection passage  1249 , the control valve piston  1242  ascends from the bottom surface in the cylinder  1241 . On the other hand, when the compressed air between the lower surface of the control valve piston  1242  and the bottom surface in the cylinder  1241  is exhausted via the connection passage  1249 , the control valve piston  1242  descends from an ascending position in the cylinder  1241  and comes into contact with the bottom surface. 
     The control valve stem  1245  is arranged in an accommodation part  1001   e  formed in the housing  1001   a  on an upper side of the control valve piston  1242 . The control valve stem  1245  is urged downward by a compression spring  1247 , and a lower surface of the control valve stem  1245  is in contact with an upper surface of the control valve piston  1242 . The compression spring  1247  is interposed between a top surface in the accommodation part  1001   e  and an upper surface of the control valve stem  1245 , and is adapted to expand and contract, in response to the ascending or descending of the control valve piston  1242 . 
     Two O-rings  1246   a  and  1246   b  are mounted in substantially intermediate positions in the upper and lower direction of the control valve stein  1245  along a circumferential direction thereof. The O-ring  1246   a  is configured to open/close a path between the second connection passage  1039  and the third connection passage  1049 , thereby communicating or shutting off the second connection passage  1039  and the third connection passage  1049 . The O-ring  1246   b  is configured to open/close a path between the second connection passage  1039  and a passage  1241   a , thereby communicating or shutting off the second connection passage  1039  and the passage  1241   a.    
     [Operation Example of Nailing Machine  1200 ] 
     Subsequently, an example of a striking operation of the nailing machine  1200  according to the fourth embodiment is described.  FIGS. 26 to 31  show a striking operation in the nailing machine  1200  according to the fourth embodiment. 
     When the air hose is connected to the air plug  1008  of the nailing machine  1200  shown in  FIG. 23 , the compressed air is supplied into the main chamber  1005 . As shown in  FIG. 26 , in the initial state until the switch valve  1070  is actuated, the first passage  1072   a  and the fourth connection passage  1079  are shut off by the O-ring  1074   a , so that the compressed air in the main chamber  1005  is not supplied to the timer valve  1280  at this stage. On the other hand, the space part  1281   d  of the timer valve  1280  communicates with the outside at the atmospheric pressure via the fourth connection passage  1079  and the second passage  1072   b  of the switch valve  1070 . 
     As shown in  FIG. 27 , when the trigger lever  1011  is pulled by an operator, the switch valve stem  1074  of the switch valve  1070  is pushed up by the contact lever  1012 , so that the switch valve  1070  is actuated. When the switch valve  1070  is actuated, the O-ring  1074   a  is also moved upward, so that the first passage  1072   a  of the switch valve  1070  and the fourth passage  1079  communicate with each other. Along with this, the compressed air in the main chamber  1005  is supplied to each of the first accommodation part  1281   a  and the second passage  1281   v  of the timer valve  1280  via the first passage  1072   a , the inside of the switch valve  1070  and the fourth connection passage  1079 . 
     When the timer valve stem  1282  is pressed upward by the compressed air flowing into the first accommodation part  1281   a , the timer valve stem  1282  ascends at a stretch in the first accommodation part  1281   a  and reaches the top dead center. Thereby, the throttle portion  1282   a  is fitted to the to-be-throttled portion  1281   u   1  of the first passage  1281   u . At this time, a slight gap through which a fluid can pass is formed between the circumferential surface of the throttle portion  1282   a  and the wall surface of the to-be-throttled portion  1281   u   1 . 
     In addition, the compressed air flowing into the second passage  1281   v  passes through the third accommodation part  1281   c , the sixth passage  1281   z , the gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  and the first passage  1281   u  and flows into the space part  1281   d . In the space part  1281   d , the compressed air is gradually accumulated, so that the internal pressure of the space part  1281   d  rises. Thereby, the time measurement of the prescribed time until the control valve  1240  is actuated starts. 
     As shown in  FIG. 28 , when the contact arm  1014  is pressed against the to-be-struck member in a state where the trigger lever  1011  is pulled and before timeout of the timer valve  1280 , the pressing member  1015  is pushed up. Along with this, the front end-side of the contact lever  1012  is pushed up and the trigger valve stem  1058  of the trigger valve  1050  is pushed up by the push-up of the contact lever  1012 , so that the trigger valve  1050  is actuated. 
     When the trigger valve  1050  is actuated, the O-rings  1058   a  and  1058   b  are also moved upward, as shown in  FIG. 14 , so that the compressed air in the empty chamber  1055  is exhausted from the gap S 1003  between the cap  1056  and the trigger valve stem  1058  to the outside. The pilot valve  1054  is pushed down against the elastic force of the compression spring  1057  by the compressed air in the main chamber  1005 , so that the lower surface of the pilot valve  1054  comes into contact with the upper surface of the cap  1056 . Thereby, the passage  1053  and the air exhaust passage  1059  communicate with each other, so that the compressed air in the head valve chamber  1038  is exhausted to the atmosphere (outside) via the second connection passage  1039 , the control valve  1240 , the third connection passage  1049 , the trigger valve  1050  and the air exhaust passage  1059 . 
     When the compressed air in the head valve chamber  1038  is exhausted, as shown in  FIG. 28 , the movable part  1034  of the head valve  1030  is pushed up by the compressed air in the main chamber  1005  and the movable part  1034  and the locking part  1025  are opened therebetween, so that the compressed air in the main chamber  1005  is caused to flow into the piston upper chamber  1024   a  and the piston  1024  rapidly descends in the cylinder  1026 . 
     As shown in  FIG. 29 , when the piston  1024  further descends, the nail is struck into the to-be-struck member by the driver  1022  (refer to  FIG. 23 ) connected to the piston  1024 . In addition, when the piston  1024  descends to the lower part-side in the cylinder  1026 , the compressed air in the cylinder  1026  is caused to flow into the blow back chamber  1028  via the small holes  1027 . The inflow compressed air is caused to flow into the second accommodation part  1281   b  via the first connection passage  1029  and the third passage  1281   w  of the timer valve  1280 . 
     The piston  1285  is urged downward by the inflow compressed air and descends in the second accommodation part  1281   b , thereby pushing down the seal member  1286 . The seal member  1286  is pushed down against the elastic force of the compression spring  1288 . Thereby, the fifth passage  1281   y  configured to communicate with the atmosphere and the control valve  1240  communicate with each other via the sixth passage  1281   z , the first passage  1281   u , the space part  1281   d  and the connection passage  1249 . 
     The compressed air flowing into the third passage  1281   w  also is caused to flow into the first accommodation part  1281   a  via the fourth passage  1281   x . The timer valve stem  1282  descends to the initial position (bottom dead center) of the first accommodation part  1281   a  by the inflow air and the urging force of the compression spring  1284 . In the present embodiment, a pressure receiving area of the compressed air at a portion of the position of the timer valve stem  1282  in which the fourth passage  1281   x  is provided is set greater than a pressure receiving area of the compressed air on the lower end-side of the timer valve stem  1282 . For this reason, the timer valve stem  1282  descends with receiving the compressed air entering from the blow back chamber  1028  via the fourth passage  1281   x . Thereby, the gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  provided on the upper end-side of the timer valve stem  1282  is expanded. 
     In this state, the compressed air in the space part  1281   d  and the compressed air on the lower part-side of the control valve  1240  flow back and are exhausted to the outside via the fifth passage  1281   y . At this time, in the present embodiment, the compressed air flowing from the control valve  1240  and the space part  1281   d  vigorously passes through the gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  while colliding with the circumferential surface of the throttle portion  1282   a  and the wall surface of the to-be-throttled portion  1281   u   1 . Thereby, impurities such as trash and oil attached to the circumferential surface of the throttle portion  1282   a , and the like are removed. 
     As shown in  FIG. 30 , when the contact arm  1014  is not pressed against the to-be-struck member, i.e., the striking operation is not executed within the prescribed time from actuation of the timer valve  1280  shown in  FIG. 27 , the control valve  1240  is actuated by timeout of the timer valve  1280 . 
     Specifically, when the compressed air in the space part  1281   d  of the timer valve  1280  reaches a prescribed pressure value, a part of the compressed air is caused to flow between the lower surface of the control valve piston  1242  and the bottom surface in the cylinder  1241 . Along with this, the control valve piston  1242  ascends from the bottom surface in the cylinder  1241 , so that the control valve stem  1245  is also pushed up. By the push-up of the control valve stem  1245 , the O-rings  1246   a  and  1246   b  are also moved upward, so that while the second connection passage  1039  and the passage  1241   a  communicate with each other, the second connection passage  1039  and the third connection passage  1049  are isolated from each other. Thereby, the head valve chamber  1038  is switched from the communication state with the trigger valve  1050  to the communication state with the main chamber  1005 . 
     As shown in  FIG. 31 , when the contact arm  1014  is pressed against the to-be-struck member after timeout of the timer valve  1280  in a state where the trigger lever  1011  is pulled by the operator, the pressing member  1015  is accordingly pushed up. When the front end-side of the contact lever  1012  is pushed up by the push-up of the pressing member  1015 , the trigger valve stem  1058  of the trigger valve  1050  is pushed up, so that the trigger valve  1050  is actuated. When the trigger valve  1050  is actuated, the O-rings  1058   a  and  1058   b  are moved upward, as shown in  FIG. 14  and the like, so that the compressed air in the empty chamber  1055  is exhausted from the gap S 1003  between the cap  1056  and the trigger valve stem  1058  to the outside. The pilot valve  1054  is pushed down against the elastic force of the compression spring  1057  by the compressed air in the main chamber  1005 , so that the lower surface of the pilot valve  1054  comes into contact with the upper surface of the cap  1056 . Thereby, the passage  1053  and the air exhaust passage  1059  communicate with each other. 
     However, in a timeout state of the timer valve  1280 , while the second connection passage  1039  and the third connection passage  1049  are isolated from each other by the control valve  1240 , the second connection passage  1039  and the main chamber  1005  communicate with each other. For this reason, the compressed air in the head valve chamber  1038  is left remaining in the head valve chamber  1038  without being exhausted to the outside via the air exhaust passage  1059  provided to the trigger valve  1050 . Thereby, when the timer valve  1280  times out, the head valve  1030  is not actuated even though the contact arm  1014  is pressed against the to-be-struck member in a state where the operator pulls the trigger lever  1011 . Therefore, the striking operation is not executed after timeout of the timer valve  1280 . 
     As described above, according to the fourth embodiment, every striking operation by the striking mechanism  1020  of the nailing machine  1200 , the compressed air that is used when actuating the control valve  1240  is caused to flow back to the gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1  from the space part  1281   d . Therefore, the impurities such as trash and oil attached to the throttle portion  1282   a  and the like can be securely removed. Thereby, it is possible to measure the prescribed time of the timer valve  1280  correctly and with high accuracy, and to prevent an erroneous operation of the timer valve  1280  due to attaching of attachments such as oil and trash. 
     In addition, in the fourth embodiment, the compressed air from the blow back chamber  1028  is supplied to the timer valve stem  1282  to move the timer valve stem  1282  toward the lower side of the first accommodation part  1281   a , in conjunction with the striking operation by the striking mechanism  1020 , thereby spacing the throttle portion  1282   a  from the to-be-throttled portion  1281   u   1 . Therefore, it is possible to increase an area of the gap between the throttle portion  1282   a  and the to-be-throttled portion  1281   u   1 . Thereby, when causing the compressed air in the space part  1281   d  to flow to the throttle portion  1282   a , an area of the compressed air that collides with the circumferential surface of the throttle portion  1282   a  and the wall surface of the to-be-throttled portion  1281   u   1  can be increased, so that it is possible to easily remove the impurities attached to the throttle portion  1282   a  and the like. 
     Note that, the technical scope of the present invention is not limited to the above-described embodiments, and the above-described embodiments can be variously changed without departing from the gist of the present invention. Specifically, in the above-described embodiments, the nailing machines  1100  and  1200  have been described as an example of the pneumatic tool. However, the present invention is not limited thereto. For example, as the pneumatic tool, the present invention can be applied to a screw fastening tool, a screw driving tool and the like. 
     In addition, in the third and fourth embodiments, the example where the control valve  1040 ,  1240  is arranged between the head valve  1030  and the trigger valve  1050  has been described. However, the present invention is not limited thereto. For example, the control valve  1040 ,  1240  may also be arranged in the trigger valve  1050 . Further, in the third and fourth embodiments, the passage between the head valve  1030  and the trigger valve  1050  is shut off by the control valve  1040 ,  1240 . However, the present invention is not limited thereto. For example, a structure where the actuation of the head valve  1030  is mechanically disabled by the control valve  1040 ;  1240  can be adopted. Further, in the third embodiment, when the prescribed time by the timer valve  1080  elapses, the control valve  1040  is pressed and actuated by the timer valve  1080 , so that the passage between the head valve  1030  and the trigger valve  1050  is completely shut off when the predetermined time elapses. However, the present invention is not limited thereto. For example, a configuration where the control valve  1040  is actuated in a state of being pressed from a first stage by the timer valve  1080  and the passage between the head valve  1030  and the timer valve  1050  is completely shut off when the predetermined time elapses may also be adopted. Further, in the third and fourth embodiments, the control valve  1040 ,  1240  is actuated by being pressed. However, the present invention is not limited thereto. For example, the control valve  1040 ,  1240  may also be actuated by being pulled. 
     &lt;Additional Statement&gt; 
     The present technology can also take following aspects. 
     (1) 
     A pneumatic tool including: 
     a drive mechanism configured to drive by an air pressure of compressed air, 
     a chamber to which the compressed air for driving the drive mechanism is supplied; 
     a head valve configured to control supply of the compressed air supplied to the chamber to the drive mechanism; 
     a trigger valve configured to actuate the head valve; 
     a control valve configured to disable actuation of the trigger valve or the head valve; and 
     a timer valve configured to be actuated based on an operation on a trigger and to disable actuation of the trigger valve or the head valve by actuating the control valve at a predetermined timing, 
     wherein the timer valve has an accommodation part configured to reserve air for actuating the timer valve, and 
     wherein the chamber and the accommodation part are constituted by spaces isolated from each other. 
     (2) 
     The pneumatic tool according to the above (1), wherein the control valve is configured to disable actuation of the head valve configured to be actuated in conjunction with the actuation of the trigger valve. 
     (3) 
     The pneumatic tool according to the above (1), wherein the accommodation part is isolated from an outside air. 
     (4) 
     The pneumatic tool according to any one of the above (1) to (3), wherein the timer valve includes: 
     a valve body configured to move in the accommodation part and to act on the control valve, and 
     a throttle portion configured to regulate flow of air generated by movement of the valve body. 
     (5) 
     The pneumatic tool according to any one of the above (1) to (3), further including: 
     a main body having the drive mechanism provided thereto, and 
     a grip part attached to a side part of the main body and extending in a direction intersecting with a moving direction of the piston of the drive mechanism, 
     wherein the timer valve is arranged in the grip part. 
     (6) 
     The pneumatic tool according to the above (4), wherein the valve body is arranged to be movable along an extension direction of the grip part. 
     (7) 
     A pneumatic tool including: 
     a drive mechanism configured to drive by an air pressure of compressed air; 
     a first chamber to which the compressed air for driving the drive mechanism is supplied; 
     a head valve configured to control supply of the compressed air supplied to the first chamber to the drive mechanism; 
     a trigger valve configured to actuate the head valve; 
     a control valve configured to disable actuation of the trigger valve or the head valve; and 
     a timer valve configured to be actuated based on an operation on a trigger and to disable actuation of the trigger valve or the head valve by actuating the control valve at a predetermined timing, 
     wherein the timer valve has a throttle portion configured to regulate flow of the compressed air for actuating the control valve, and is configured to cause the compressed air to flow to the throttle portion at a predetermined timing interlocking with a striking operation by the drive mechanism. 
     (8) 
     The pneumatic tool according to the above (7), wherein the throttle portion is configured to regulate the flow of the compressed air by displacing an area of a gap between the throttle portion and a to-be-throttled portion, and to increase the area of the gap at the time when the compressed air is supplied in conjunction with the striking operation. 
     (9) 
     The pneumatic tool according to the above (8), further including a second chamber configured to accommodate compressed air for returning the drive mechanism to an initial position after the striking operation, 
     wherein the throttle portion is configured to move relative to the to-be-throttled portion by the compressed air supplied from the second chamber, thereby increasing the area of the gap. 
     The nailing machine of the related art disclosed in PTL 1 has following problems. The timing valve uses the compressed air from the main chamber and the like. For this reason, oil, drain, minute trash and the like contained in the compressed air supplied to the nailing machine are attached to the flow path (throttle portion), so that the flow rate of the compressed air may vary. As a result, the time measurement of the timer mechanism varies, so that the actuation of the tinier mechanism is not stabilized. 
     In order to solve the above problems, the aspect of the above (1) provides the pneumatic tool capable of stabilizing the actuation of the timer mechanism by excluding an influence of oil, drain, minute trash and the like contained in the compressed air supplied to the nailing machine. 
     According to one aspect of the present disclosure, the timer valve is actuated using the air in the accommodation part isolated from the chamber, without using the compressed air that is used for driving of the drive mechanism. Therefore, it is possible to prevent trash, oil and the like from entering the timer valve. 
     In addition, according to one aspect of the present disclosure, the compressed air is caused to flow to the throttle portion in conjunction with the striking operation. Therefore, it is possible to remove impurities such as trash and oil attached to the throttle portion by the compressed air. Thereby, the time of the timer valve until the control valve is actuated can be stabilized. 
     The present application is based on Japanese Patent Application Nos. 2019-086669 filed on Apr. 26, 2019, and 2019-086670 filed on Apr. 26, 2019, the contents of which are incorporated herein by reference. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : main body 
               4 : grip part 
               11 : trigger lever (trigger) 
               20 : striking mechanism (drive mechanism) 
               22 : driver 
               24 : piston 
               26 : cylinder 
               30 : head valve 
               40 : control valve 
               50 : trigger valve 
               80 : timer valve 
               84 : timer piston (valve body) 
               85 : piston shaft part (valve body) 
               88 : throttle portion 
               89 : compression spring 
               100 ,  200 : nailing machine (pneumatic tool) 
               280 : timer valve 
               281 : first cylinder (damper mechanism) 
               284 : first timer piston (valve body) 
               285 : first piston shaft part (valve body) 
               294 : second timer piston (valve body) 
               295 : second piston shaft part (valve body)  0 : oil (damper mechanism) 
               1001 : main body 
               1004 : grip part 
               1005 : main chamber (first chamber) 
               1011 : trigger lever (trigger) 
               1020 : striking mechanism (drive mechanism) 
               1022 : driver 
               1024 : piston 
               1026 : cylinder 
               1028 : blow back chamber (second chamber) 
               1030 : head valve 
               1040 : control valve 
               1050 : trigger valve 
               1080 : timer valve 
               1081 : first chamber (accommodation part) 
               1084 : first timer piston (valve body) 
               1085 : first piston shaft part (valve body) 
               1088 : throttle portion 
               1089 : compression spring 
               1100 ,  1200 : nailing machine (pneumatic tool) 
               1282 : timer valve stem 
               1281   u   1 : to-be-throttled portion 
               1282   a : throttle portion