Patent Publication Number: US-2022219300-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 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 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). 
     CTIATION 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. For a timer mechanism, a control using compressed air is generally adopted. However, in most cases, a structure of controlling actuation of the head valve configured to control inflow of the compressed air into the cylinder is used. In the head valve, a flow rate of the compressed air that is caused to flow in or to be exhausted with respect to a chamber increases. As a result, a changing valve configured to control actuation of the head valve is also enlarged. In addition, as the switching valve is enlarged, responsiveness upon actuation of the switching valve is also lowered. 
     In order to solve the above problems, the present disclosure provides a pneumatic tool capable of miniaturizing a control valve and improving response performance. 
     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 having a first chamber configured to reserve compressed air that is supplied from an air source, and configured to drive the drive mechanism, according to a state of the compressed air in the first chamber, a trigger valve configured to actuate the head valve by exhausting the compressed air in the first chamber, and a control valve configured to disable actuation of the trigger valve. 
     In addition, 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 chamber to which the compressed air for driving the drive mechanism is supplied, a head valve configured to drive the drive mechanism by using the compressed air supplied to the chamber, 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 disable actuation of the trigger valve or the head valve by actuating the control valve at a predetermined timing, based on an operation on a trigger, wherein the timer valve has a valve body capable of moving to an actuation position in which the valve body acts on the control valve when a predetermined time elapses, wherein a moving range of the valve body includes a first section in which the predetermined time is measured and a second section in which the valve body acts on the control valve, and wherein a resistance to the valve body is different between the first section and the second section. 
     Advantageous Effects of Invention 
     According to the pneumatic tool according to one aspect of the present disclosure, the actuation of the head valve can be controlled by disabling the actuation of the trigger valve by the control valve, so that the control valve can be made small. In addition, the control valve is made small, so that responsiveness of the actuation can be improved. 
     According to the pneumatic tool according to one aspect of the present disclosure, since the moving range of the valve body configured to actuate the control valve is divided into the first section and the second section between which the resistance to the valve body is different, the time measurement can be stabilized in the first section and the control valve can be securely actuated in the second section. 
    
    
     
       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 second control valve according to the first embodiment. 
         FIG. 3  is a side sectional view of a switch valve and a first control valve according to the first embodiment. 
         FIG. 4  is a side sectional view of a timer valve according to the first embodiment, 
         FIG. 5  is an enlarged view of main parts showing a striking operation in the nailing machine according to the first embodiment. 
         FIG. 6  is an enlarged view of main parts showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 7  is an enlarged view of main parts showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 8A  is a view showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 8B  is an enlarged view of main parts showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 9A  is a view showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 9B  is an enlarged view of main parts showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 10  is an enlarged view of main parts showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 11  is an enlarged view of main parts showing the striking operation in the nailing machine according to the first embodiment. 
         FIG. 12A  is a view showing an operation of the trigger valve during the striking operation in the nailing machine according to the first embodiment. 
         FIG. 12B  is a view showing the operation of the trigger valve during the striking operation in the nailing machine according to the first embodiment. 
         FIG. 12C  is a view showing the operation of the trigger valve during the striking operation in the nailing machine according to the first embodiment. 
         FIG. 12D  is a view showing the operation of the trigger valve during the striking operation in the nailing machine according to the first embodiment. 
         FIG. 12E  is a view showing the operation of the trigger valve during the striking operation in the nailing machine according to the first 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 trigger valve, a switch valve and a control valve according to the second embodiment. 
         FIG. 15A  is a side sectional view of a timer valve according to the second embodiment. 
         FIG. 15B  is a view for illustrating a first section and a second section of the timer valve according to the second 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 second control valve  60  according to the first embodiment.  FIG. 3  is a side sectional view of a switch valve  70  and a first control valve  40  according to the first embodiment.  FIG. 4  is a side sectional view of a timer valve  80  according to the first embodiment. 
     The nailing machine  100  is an example of the pneumatic tool, and includes, as shown in  FIG. 1 , 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 second control valve  60 , a switch valve  70 , a first control valve  40 , and a tinier valve  80 . 
     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)  20  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 the 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 supplied and 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 configured to communicate with 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 in the cylinder  26  is caused to flow into the blow back chamber  28  via the small holes  27 . In addition, 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 of 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 trigger valve  50 . 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  (an axial direction of the cylinder  26 ), 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 front end-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 torsion 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 . Thereby, 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 
     As shown in  FIGS. 1 and 2 , the trigger valve  50  is configured to actuate the head valve  30  based on a pressing state of the contact arm  14  against the to-be-struck member. The trigger valve  50  is arranged on a front end-side of the grip part  4  and near the switch valve  70 . 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 the second connection passage  39  configured to communicate with the head valve  30 . The passage  53  is also configured to be able to communicate with an air exhaust passage  56   a  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  56   a  to thus prevent the compressed air in the head valve chamber  38  from being leaked from the passage  53  to an outside, during non-actuation 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  56   a.    
     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 stern  58  and a passage  54   c  of the pilot valve  54  and to function as a chamber in which the compressed air is tilled, during non-actuation of the trigger valve  50 . Note that, in the present embodiment, a volume of the empty chamber  55  of the trigger valve  50  for reserving the compressed air is configured smaller than a volume of the head valve chamber  38  of the head valve  30  for reserving the compressed air. For this reason, the inflow and outflow amounts of the compressed air with respect to the empty chamber  55  of the trigger valve  50  are smaller than the inflow and outflow amounts of the compressed air with respect to the head valve chamber  38  of the head valve  30 . 
     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  56   a  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  56   a  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 second control valve  60  is incorporated into the trigger valve  50 , and is configured to disable actuation of the trigger valve  50  after the prescribed time by time measurement of the timer valve  80  elapses. The second control valve  60  has a cylinder  61 , a control valve stem  62 , and a seal member  65 . 
     The cylinder  61  is a hollow cylindrical body extending in the upper and lower direction, and is arranged at a lower part on a rear side of the trigger valve  50  and in a position near the trigger valve stem  58 . A first passage  61   a  configured to communicate with the empty chamber  55  of the trigger valve  50  is formed in a substantially intermediate position in the upper and lower direction of a front wall of the cylinder  61 . A second passage  61   b  configured to communicate with an air exhaust passage  61   d  is formed in a substantially intermediate position in the upper and lower direction of a rear wall of the cylinder  61 . A lower part of the rear wall of the cylinder  61  is configured to communicate with one end portion of a fourth connection passage  69  configured to communicate with the first control valve  40 . A support portion  61   c  for supporting a spring  64 , which will be described later, is provided on an inner wall of the cylinder  61 . 
     The control valve stem  62  is a columnar body extending in the upper and lower direction and can slide in the upper and lower direction in the cylinder  61 . An attaching portion  62   a  provided on a lower side of the control valve stem  62  is mounted with an O-ring  63  for shutting off between the fourth connection passage  69  and the first passage  61   a  and second passage  61   b  along a circumferential direction thereof. The control valve stem  62  is urged downward by a spring  64 . The spring  64  is interposed between the attaching portion  62   a  and the support portion  61   c,  and is adapted to expand and contract, in response to the compressed air that is supplied from the timer valve  80 . For the spring  64 , for example, a compression spring or a coil spring can be used. When the compressed air is supplied between a bottom surface in the cylinder  61  and a lower surface of the control valve stem  62  from the fourth connection passage  69 , the control valve stem  62  ascends against an elastic force of the spring  64 , with respect to the bottom surface in the cylinder  61 . On the other hand, when the compressed air between the bottom surface in the cylinder  61  and the lower surface of the control valve stem  62  is exhausted via the fourth connection passage  69 , the control valve stem  62  descends from an ascending position in the cylinder  61  and comes into contact with the bottom surface. 
     The seal member  65  is arranged in the cylinder  61  and above the control valve stem  62 . The seal member  65  is integrally attached to an attachment member  67 , and is urged downward by a spring  66  inserted between the attachment member  67  and a top surface in the cylinder  61 . The seal member  65  is configured to be pushed up against an elastic force of the spring  66  as the control valve stem  62  ascends, thereby opening the first passage  61   a  to communicate the first passage  61   a  and the second passage  61   b.  Thereby, the empty chamber  55  and the air exhaust passage  61   d  communicate with each other via the first passage  61   a  and the second passage  61   b.  In addition, the seal member  65  is configured to be pushed down as the control valve stem  62  descends, thereby closing the first passage  61   a  to shut off a path between the first passage  61   a  and the second passage  61   b.    
     The switch valve  70  is arranged between the first control valve  40  and the second control valve  60 , and is configured to actuate the timer valve  80  based on a pulling operation on the trigger lever  11 . The switch valve  70  has a cylinder  71 , a switch valve stem  72 , a pressing member  74 , a diaphragm  75 , and a seal member  76 . 
     The cylinder  71  is a hollow cylindrical body extending in the upper and lower direction, and is configured to accommodate the switch valve stem  72  so as to be slidable in the upper and lower direction. The cylinder  71  is fitted with a front end-side of a common cylinder  81  and is connected with one end portion of a third connection passage  49  formed in the common cylinder  81 . An inside of the cylinder  71  is configured to communicate with an outside, and is at the atmospheric pressure. A lower surface-side of the common cylinder  81  constituting the switch valve  70  is configured to communicate with one end portion of a sixth connection passage  89  configured to communicate with the timer valve  80 . An upper surface-side of the common cylinder  81  constituting the switch valve  70  is configured to communicate with the other end portion of the first connection passage  29  configured to communicate with the blow back chamber  28 . 
     The switch valve stem  72  is a columnar body extending in the upper and lower direction and is arranged to be slidable in the upper and lower direction in the cylinder  71 . The switch valve stem  72  is urged toward the trigger lever  11  (toward the lower side) by a compression spring  73  inserted between a lower end-side of the switch valve stem  72  and a lower surface of the cylinder  71 . A lower end portion  72   a  of the switch valve stem  72  protrudes downward from the lower surface of the cylinder  71 , and is provided to be able to come into contact with the contact lever  12  (refer to  FIG. 1 ). The switch valve stem  72  is configured to be pushed up by the contact lever  12  and to ascend against an elastic force of the spring  73  in the cylinder  71 , during a pulling operation of the trigger lever  11 . 
     The pressing member  74  is a columnar body extending in the front and rear direction, and a front end portion thereof is provided to protrude from the common cylinder  81 -side into the cylinder  71 . The pressing member  74  facing toward the inside of the cylinder  71  collides with an upper end portion  72   b  of the switch valve stem  72  by push-up of the switch valve stem  72  and is pressed backward. Specifically, in the pressing member  74 , an operation in the upper and lower direction of the switch valve stem  72  is converted into an operation in the front and rear direction. A rear end-side of the pressing member  74  is locked by a fixing member  74   a,  so that the pressing member  74  is not separated toward the cylinder  71 . 
     The diaphragm  75  is an elastically deformable thin film made of a resin material such as rubber, and separates an atmospheric pressure region on the switch valve stem  72 -side and a compressed air region on the seal member  76 -side. The diaphragm  75  is attached to a rear end-side of the pressing member  74 , and is configured to move in the front and rear direction in the cylinder  71  in conjunction with an operation of the pressing member  74 . A peripheral edge portion of the diaphragm  75  is attached in a state of being sandwiched by fixing members  74   a  and  74   b.    
     The seal member  76  is made of a resin material such as rubber, for example, and is integrally attached to an attachment member  77 . The attachment member  77  is urged forward by a spring  78  inserted between a rear end-side of the attachment member  77  and a common support part  48 . A to-be-sealed member  79  is provided to be able to come into contact with the seal member  76  configured to move in the front and rear direction, and is configured to regulate forward movement of the seal member  76 . 
     During pressing of the pressing member  74 , the seal member  76  is configured to move backward against an elastic force of the spring  78 , thereby shutting off between a common passage CP configured to communicate with the main chamber  5  and a sixth connection passage  89  configured to communicate with the tinier valve  80  and communicating the sixth connection passage  89  configured to communicate with the timer valve  80  and the first connection passage  29  configured to communicate with the blow back chamber  28  at the atmospheric pressure each other. On the other hand, during non-pressing of the pressing member  74 , the seal member  76  is configured to connect the common passage CP configured to communicate with the main chamber  5  and the sixth connection passage  89  configured to communicate with the timer valve  80  each other and to shut off between the sixth connection passage  89  configured to communicate with the timer valve  80  and the first connection passage  29  configured to communicate with the blow back chamber  28 . 
     An empty chamber SP is provided in the common cylinder  81  and between the seal member  76  of the switch valve  70  and a seal member  44  of the first control valve  40 . The empty chamber SP is configured to communicate with one end portion of the common passage CP configured to communicate with the main chamber  5 . The empty chamber SP can communicate with each of the common passage CP, the fourth connection passage  69  and the sixth connection passage  89 . 
     As shown in  FIGS. 1 and 3 , the first control valve  40  is configured to be actuated by the timer valve  80 , and to control supply of the compressed air for actuating the second control valve  60 . In the present embodiment, the first control valve  40  is arranged in the common cylinder  81  that is common to the switch valve  70  and the timer valve  80 . The first control valve  40  has a pressing member  42 , a diaphragm  43 , and a seal member  44 . The respective components such as the pressing member  42  of the first control valve  40  have configurations that are common to the respective components such as the pressing member  74  of the switch valve  70 , and are arranged in symmetrical positions, respectively. 
     A lower surface-side of the common cylinder  81  constituting the first control valve  40  is configured to communicate with the other end portion of the fourth connection passage  69  configured to communicate with the second control valve  60 . An upper surface-side of the common cylinder  81  constituting the switch valve  70  is configured to communicate with the other end portion of the third connection passage  49  configured to communicate with the inside of the cylinder  71  of the switch valve  70 . 
     The pressing member  42  is a substantially columnar body extending in the front and rear direction, and is configured to move forward as a rear end face is pressed by the timer valve  80 , which will be described later. A front end-side of the pressing member  42  is locked by a fixing member  41   a,  so that the pressing member  42  is not separated toward the timer valve  80 . 
     The diaphragm  43  is constituted by an elastically deformable thin film made of a resin material such as rubber, for example. The diaphragm  43  is attached to a tip end-side of the pressing member  42 , and is configured to move in the front and rear direction in the common cylinder  81  in conjunction with an operation of the pressing member  42 . A peripheral edge portion of the diaphragm  43  is attached in a state of being sandwiched by fixing members  41   a  and  41   b.    
     The seal member  44  is made of a resin material such as rubber, for example, and is attached to an attachment member  45 . The attachment member  45  is urged forward by a spring  46  inserted between a front end-side of the attachment member  45  and the common support part  48 . A to-be-sealed member  47  is provided to be able to come into contact with the seal member  44  configured to move in the front and rear direction, and is configured to regulate backward movement of the seal member  44 . 
     During non-pressing of the pressing member  42 , the seal member  44  is configured to come into contact with the to-be-sealed member  47 , thereby connecting the common passage CP configured to communicate with the main chamber  5  and the fourth connection passage  69  configured to communicate with the second control valve  60  each other. On the other hand, during pressing of the pressing member  42 , the seal member  44  is configured to move forward against an elastic force of the spring  46  and to separate from the to-be-sealed member  47 , thereby connecting the fourth connection passage  69  configured to communicate with the second control valve  60  and the third connection passage  49  configured to communicate with the inside of the cylinder  71  of the switch valve  70  each other. 
     As shown in  FIGS. 1 and 4 , when the prescribed time elapses in a state where the trigger lever  11  is pulled, the timer valve  80  actuates the first control valve  40 , the second control valve  60  and the like, thereby restricting the striking operation. Specifically, the tinier valve  80  is configured to be actuated based on an operation on the trigger lever  11  and to actuate the first control valve  40  and the second control valve  60  at a predetermined timing, thereby disabling actuation of the head valve  30 . The timer valve  80  has a common cylinder  81 , a first timer piston  84 , a first piston shaft part  85 , a second timer piston  86 , and a second piston shaft part  87 . 
     The common cylinder  81  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the first timer piston  84  and the second timer piston  86  so as to be slidable in the front and rear direction. An inside of the common cylinder  81  is partitioned into a first chamber  82  and a second chamber  83 , via a partition portion  81   a.  The first chamber  82  is constituted by a sealed closed space, and an inside of the first chamber  82  is filled with an atmospheric air. Thereby, the compressed air, trash and the like cannot flow into the first chamber  82  from other spaces. 
     The first timer piston  84  is a cylindrical body having substantially the same diameter as an inner diameter of the common cylinder  81  and is configured to slide in the front and rear direction in the common cylinder  81 . The first timer piston  84  is urged toward the first control valve  40  (toward the front side) by a compression spring  99 . The compression spring  99  is inserted between a concave portion formed on a base end-side of the first timer piston  84  and a rear wall in the first chamber  82 , and is adapted to expand and contract, in response to the compressed air flowing in or flowing out with respect to the common cylinder  81 . A peripheral edge portion of the first 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  88   a  for sealing between the concave portion and an inner wall of the common cylinder  81  is mounted. Thereby, the first chamber  82  is further partitioned into a first space  82   a  on a rear side of the O-ring  88   a  and a second space  82   b  on a front side of the O-ring  88   a.    
     The O-ring  88   a  is mounted in a state where the O-ring  88   a  can move in the front and rear direction in the concave portion  84   a,  i.e., in a state where a play is provided. The concave portion  84   a  is formed with a bypass passage  84   b  for causing the atmospheric air in the second space  82   b  to flow to the first space  82   a  when the O-ring  88   a  is in close contact with a front wall in the concave portion  84   a.    
     In the present embodiment, when the first timer piston  84  is advanced, the O-ring  88   a  is moved backward in the concave portion  84   a  to seal between the O-ring and the rear wall in the concave portion  84   a.  For this reason, in this case, the atmospheric air does not flow from the second space  82   b  into the first space  82   a  via the concave portion  84   a.  On the other hand, when the first timer piston  84  is retreated, the O-ring  88   a  is moved forward in the concave portion  84   a  to seal between the O-ring and the front wall of the concave portion  84   a.  However, since the bypass passage  84   b  is opened, the atmospheric air flows from the first space  82   a  into the second space  82   b  via the concave portion  84   a.  In this way, in the present embodiment, the O-ring  88   a,  the concave portion  84   a  and the bypass passage  84   b  function as a check valve. 
     The concave portion  84   a  of the first timer piston  84  is formed with a passage  84   c  penetrating in the front and rear direction (thickness direction) of the first timer piston  84 , so that the atmospheric air can flow from the second space  82   b -side into the first space  82   a -side via the passage  84   c.  The passage  84   c  is provided with a throttle portion  84   d.  The throttle portion  84   d  is constituted by reducing a cross-sectional area (narrowing a width) of a path of a part of the passage  84   c,  and is configured to restrict a flow rate per unit time of the atmospheric air, which flows from the second space  82   b  into the first space  82   a,  to be constant. Thereby, it is possible to control the moving speed of the first timer piston  84  until the first control valve  40  can be actuated. 
     The first piston shaft part  85  is a rod-shaped columnar body, and a rear end portion of the first piston shaft part  85  is integrally formed with a front end portion of the first timer piston  84 . The first piston shaft part  85  passes through a through-hole  81   b  formed in the partition portion  81   a,  and extends from an inside of the first chamber  82  into the second chamber  83 . A front end face of the first piston shaft part  85  is attached to a rear end face of the second timer piston  86  and is configured to be able to transmit the pressing force of the first timer piston  84  to the second timer piston  86 . An O-ring  88   b  is provided to the partition portion  81   a  to secure a sealed state of the inside of the first chamber  82 . 
     The second timer piston  86  is a cylindrical body having substantially the same diameter as an inner diameter of the common cylinder  81 , and is arranged to be slidable in the second chamber  83 . A peripheral edge portion of the second timer piston  86  is formed with a concave portion  86   a  along a circumferential direction thereof. In the concave portion  86   a,  an O-ring  88   c  for sealing between the concave portion and the inner wall of the common cylinder  81  is mounted. Thereby, the second chamber  83  is further partitioned into a first space  83   a  on a rear side of the O-ring  88   c  and a second space  83   b  on a front side of the O-ring  88   c.    
     One end portion of the sixth connection passage  89  configured to communicate with the switch valve  70  is configured to communicate with the second space  83   b,  so that the compressed air can be supplied into the second space  83   b  or the compressed air can be exhausted from the second space  83   b.    
     The second piston shaft part  87  is a rod-shaped columnar body, and a rear end portion of the second piston shaft part  87  is integrally attached to a front end portion of the second timer piston  86 . A front end-side of the second piston shaft part  87  is arranged to be slidable in a through-hole  81   c  formed between the second timer piston  86  and the first control valve  40 . A front end portion of the second piston shaft part  87  is provided to appear and disappear with respect to the inside of the common cylinder  81  of the first control valve  40 , and is configured to actuate the first control valve  40  by pressing a rear end face of the pressing member  42  constituting the first control valve  40 . 
     [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. 5 to 11  show a striking operation in the nailing machine  100  according to the first embodiment.  FIGS. 12A to 12E  show an example of an operation of the trigger valve  50  during the striking operation in the nailing machine  100  according to the first embodiment. 
     When an air hose (not shown) is connected to the air plug  8  of the nailing machine  100  shown in  FIG. 1  and the compressed air is supplied into the main chamber  5  via the air hose or the like, the compressed air is caused to flow from the common passage CP into the empty chamber SP, as shown in  FIG. 5 . The inflow compressed air is supplied to the second space  83   b  of the second chamber  83  of the timer valve  80  via the sixth connection passage  89 . Along with this, the front surface of the second timer piston  86  is pushed backward by the compressed air, and the first timer piston  84  and the like are retreated against the elastic force of the compression spring  99 . That is, the timer valve  80  becomes in a timer setting state. 
     At this time, the atmospheric air in the first space  82   a  of the first chamber  82  of the timer valve  80  is compressed and the compressed atmospheric air is caused to flow from the first space  82   a  toward the second space  82   b,  so that the O-ring  88   a  is moved forward in the concave portion  84   a.  Thereby, a gap Sa between an outer peripheral surface of the first tinier piston  84  and the inner wall of the common cylinder  81 , a gap Sb between the rear wall of the concave portion  84   a  and the O-ring  88   a  and the bypass passage  84   b  communicate one another, so that the atmospheric air in the first space  82   a  flows into the second space  82   b  via the gaps Sa and Sb and the bypass passage  84   b.  Note that, since the resistance of the throttle portion  84   d  becomes high, the atmospheric air hardly passes through the passage  84   c.    
     In addition, the compressed air flowing into the empty chamber SP is supplied into the cylinder  61  of the second control valve  60  via the fourth connection passage  69 . The control valve stem  62  and the seal member  65  of the second control valve  60  ascend by the compressed air supplied between the bottom surface in the cylinder  61  and the lower surface of the control valve stem  62 , so that the second control valve  60  is actuated. Thereby, the first passage  61  a is opened, so that the first passage  61   a  and the second passage  61   b  communicate with each other. 
     Note that, as shown in  FIG. 2 , the compressed air in the main chamber  5  is supplied to the empty chamber  55  of the trigger valve  50  via the passage  54   c.  In addition, the compressed air in the main chamber S is supplied to the head valve chamber  38  via the gap S 1  and the passage  53 . 
     As shown in  FIG. 6 , when the supply of the compressed air into the second chamber  83  of the tinier valve  80  continues, the rear end face of the first timer piston  84  comes into contact with the rear wall in the first chamber  82 . Thereby, the first timer piston  84  reaches the initial position in the common cylinder  81  and the timer valve  80  becomes in a standby state. 
     As shown in  FIG. 7 , when the trigger lever  11  is pulled by an operator, the switch valve stern  72  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  72 , the pressing member  74  is pressed backward, and the seal member  76  is moved backward by the pressing member  74 . Thereby, the sixth connection passage  89  is closed, so that the communication state between the connection passage CP and the sixth connection passage  89  is shut off. Note that, by the backward movement of the seal member  76 , the sixth connection passage  89  and the first connection passage  29  communicate with each other. Along with this, the compressed air in the second space  83   b  of the second chamber  83  of the timer valve  80  is exhausted to the blow back chamber  28  at the atmospheric pressure via the sixth connection passage  89  and the first connection passage  29 . As the compressed air in the timer valve  80  is exhausted, the first timer piston  84  and the second timer piston  86  are advanced toward the first control valve  40  by the urging force of the compression spring  99  and the time measurement (timer) by the timer valve  80  starts. 
     At this time, the atmospheric air in the second space  82   b  of the first chamber  82  of the timer valve  80  is compressed and flows into the first space  82   a  through the throttle portion  84   d  and the passage  84   c.  Since a flow rate of the atmospheric air flowing into the first space  82   a  is restricted to be constant by the throttle portion  84   d,  a flow rate of the atmospheric air flowing in the first space  82   a  is also reduced. For this reason, the first tinier piston  84  is slowly advanced based on the flow rate of the atmospheric air passing through the throttle portion  84   d  and the urging force of the compression spring  99 . The prescribed time of the timer valve  80  becomes under time measurement. 
     Note that, in the concave portion  84   a  of the first timer piston  84 , the O-ring  88   a  is moved backward in the concave portion  84   a  by the atmospheric air entering from the second. space  82   b,  so that a passage between the O-ring  88   a  and the rear wall of the concave portion  84   a  is closed. For this reason, the atmospheric air in the second space  82   b  does not flow into the first space  82   a  via the concave portion  84   a.    
     As shown in  FIGS. 8A and 8B , 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 the prescribed time of the timer valve  80  elapses, the pressing member  15  is pushed up. Along with this, when the front end-side of the trigger lever  11  is pushed up, the trigger valve stem  58  of the trigger valve  50  is also pushed up by the trigger lever  11 , so that the trigger valve  50  is actuated. 
     As shown in  FIG. 12C , when the trigger valve stem  58  is pushed up, the O-rings  58   a  and  58   b  are also moved upward, so that the compressed air in the empty chamber  55  passes through the first passage  61   a  of the second control valve  60  from the gap S 3  between the trigger valve stem  58  and the outer wall surface of the cylinder  61 . The compressed air passing through the first passage  61   a  passes through the inside of the cylinder  61  and is exhausted to the outside via the second passage  61   b  and the air exhaust passage  61   d.    
     Along with this, as shown in  FIGS. 8A and 12D , 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  56   a  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 inside of the trigger valve  50  and the air exhaust passage  56   a.    
     When the compressed air in the head valve chamber  38  is exhausted, as shown in  FIG. 8A , 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 is caused to flow from the main chamber  5  into the piston upper chamber  24   a  and the piston  24  rapidly descends in the cylinder  26 . 
     As shown in  FIG. 9A , when the piston  24  further descends, the nail is struck into the to-he-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 . As shown in  FIG. 9B , the inflow compressed air is caused to flow into the switch valve  70  under actuation via the first connection passage  29 , and is also caused to flow into the second space  83   b  of the second chamber  83  of the timer valve  80  via the sixth connection passage  89 . Thereby, the first timer piston  84  and the first piston shaft part  85  of the timer valve  80  are again retreated in the common cylinder  81 , so that the timer valve  80  is reset. 
     As shown in  FIG. 10 , when the contact arm  14  is not pressed against the to-be-struck member within the prescribed time from the time point when the trigger lever  11  shown in  FIG. 7  is pulled (the timer valve  80  is actuated), the second timer piston  86  of the timer valve  80  is moved to the actuation position in which the first control valve  40  can be pressed when the prescribed time elapses, and is further moved to the front end portion of the second chamber  83 . At this time, the compressed air in the second chamber  83  of the timer valve  80  is exhausted into the blow back chamber  28  via the sixth connection passage  89 , the inside of the switch valve  70  and the first connection passage  29 . 
     The pressing member  42  of the first control valve  40  is pressed from the rear side by the second piston shaft part  87 . The pressing member  42  is advanced in the common cylinder  81  to press the seal member  44  via the attachment member  45 , thereby moving forward the seal member  44 . When the seal member  44  is moved forward, while the communication state between the fourth connection passage  69  and the common passage CP is shut off, the fourth connection passage  69  and the third connection passage  49  communicate with each other. Along with this, in the state shown in  FIG. 12B , the compressed air between the lower surface of the control valve stem  62  of the second control valve  60  and the bottom surface in the cylinder  61  is exhausted from the blow back chamber  28  to the outside via the fourth connection passage  69 , the inside of the first control valve  40  and the third connection passage  49 . Thereby, as shown in  FIG. 12A , the control valve stem  62  of the second control valve  60  and the seal member  65  descend, so that the first passage  61   a  is closed by the seal member  65  and the communication between the first passage  61   a  and the second passage  61   b  is shut off. 
     As shown in  FIG. 11 , when the contact arm  14  is pressed against the to-be-struck member after the prescribed time of the timer valve  80  elapses in a state where the trigger lever  11  shown in  FIG. 7  is pulled, the pressing member  15  is accordingly 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. As shown in  FIG. 12E , when the trigger valve stem  58  is pushed up, the O-rings  58   a  and  58   b  are also moved upward. However, since the first passage  61   a  of the second control valve  60  is closed by the seal member  65 , the compressed air in the empty chamber  55  remains as it is, without being exhausted to the outside. That is, the filled state of the compressed air in the empty chamber  55  is maintained. In addition, the empty chamber  55  and the air exhaust passage  56   a  are isolated from each other by the O-ring  54   a.  Therefore, the compressed air in the head valve chamber  38  is not exhausted to the outside via the air exhaust passage  56   a.  For this reason, even when the contact arm  14  is pressed against the to-be-struck member in a state where the operator pulls the trigger lever  11 , the head valve  30  is not actuated, so that the striking operation is not executed. 
     As described above, according to the first embodiment, the filling or exhaust of the compressed air with respect to the empty chamber  55  of the trigger valve  50  is controlled by the second control valve  60 . Thereby, since the volume of the empty chamber  55  of the trigger valve  50  is smaller than the volume of the head valve chamber  38  of the head valve  30  and the flow rate of the compressed air caused to flow in and flow out is smaller in the empty chamber  55  of the trigger valve  50  than in the head valve chamber  38  of the head valve  30 , the second control valve  60  can be made small. As a result, the second control valve  60  is made small, so that the nailing machine  100  can be made small. In addition, the second control valve  60  is made small, so that responsiveness of the actuation of the second control valve  60  can also be improved. 
     Second Embodiment 
     In the structure of the timer mechanism of the nailing machine of the related art disclosed in PTL 1, it is configured in many cases so that a constant resistance is applied to maintain the moving speed of the timer valve constant and the switching valve is actuated after a preset prescribed time elapses. For this reason, at a stage of actuating the switching valve, a load (pressing force) of the timer valve becomes insufficient, so that the switching valve cannot be controlled in a stable state. Therefore, in order to solve the above problems, a configuration of a nailing machine  200  according to a second embodiment is adopted. 
     In a timer valve  280  according to the second embodiment, a configuration different from the timer valve  80  of the first embodiment is adopted. Similarly, also for a switch valve  270  and a control valve  240  of the second embodiment, configurations different from the switch valve  70  and the second control valve  60  and the like of the first embodiment are adopted. Note that, since the other configuration, function and operation of the nailing machine  200  are common to the configuration and the like of the nailing machine  100  of the first embodiment, the detailed descriptions thereof are omitted. In addition, since the trigger valve  50  of the second embodiment is substantially common to the trigger valve  50  of the first embodiment in terms of the configuration and the like, except that the control valve is not arranged in the trigger valve  50 , the detailed descriptions thereof are omitted. 
     [Configuration Example of Nailing Machine  200 ] 
       FIG. 13  is a side sectional view of a nailing machine  200  according to a second embodiment.  FIG. 14  is a side sectional view of a trigger valve  50 , a switch valve  270  and a control valve  240  according to the seventh embodiment.  FIG. 15A  is a side sectional view of a timer valve  280  according to the second embodiment, and  FIG. 15B  is a view for illustrating a first section R 1  and a second section R 2 . 
     As shown in  FIG. 13  and the like, the nailing machine  200  includes the piston  24  capable of sliding in the cylinder  26 , the striking mechanism  20  having the driver  22  attached to the piston  24  and configured to strike a nail into a to-be-struck member, the head valve chamber  38  to which compressed air for driving the striking mechanism  20  is supplied, the head valve  30  configured to drive the striking mechanism  20  by using the compressed air supplied to the head valve chamber  38 , the trigger valve  50  configured to actuate the head valve  30 , a control valve  240  configured to disable actuation of the head valve  30  configured to be actuated in conjunction with actuation of the trigger valve  50 , a timer valve  280  configured to disable actuation of the head valve  30  after a predetermined time elapses by actuating the control valve  240 , and a switch valve  270  configured to actuate the timer valve  280  based on an operation on the trigger lever  11 . 
     As shown in  FIGS. 13 and 14 , the switch valve  270  is arranged in the vicinity of a rear side of the trigger valve  50 , and is configured to actuate the timer valve  280  based on an operation on the trigger lever  11 . The switch valve  270  has a cylinder  272  and a switch valve stem  274 . 
     The cylinder  272  is a hollow cylindrical body extending in the upper and lower direction, and is configured to accommodate the switch valve stem  274  so as to be slidable in the upper and lower direction. An upper side of the cylinder  272  is formed with a passage  272   a.  The passage  272   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  272  via the passage  272   a.    
     One end portion of a fifth connection passage  59  is configured to communicate in a substantially intermediate position in the upper and lower direction of the cylinder  272 , and the other end portion of the fifth connection passage  59  is configured to communicate with the timer valve  280 . The fifth connection passage  59  is configured to connect the switch valve  270  and the tinier valve  280  each other, and the compressed air can be supplied or exhausted with respect to the timer valve  280  via the fifth connection passage  59 . One end portion of the first connection passage  29  is configured to communicate on a further lower side than the fifth connection passage  59  of the cylinder  272 , 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  270  and the blow back chamber  28  therebetween, so that the compressed air can be supplied to the switch valve  270  or the compressed air can be exhausted from the switch valve  270  via the first connection passage  29 . 
     The switch valve stem  274  is accommodated in the cylinder  272 , and is urged toward the trigger lever  11  (toward the lower side) by a compression spring  276 . The compression spring  276  is interposed between an upper end face of the switch valve stem  274  and a top surface in the cylinder  272 , and is adapted to expand and contract, in response to a pulling operation on the trigger lever  11 . A lower end portion of the switch valve stem  274  protrudes downward from the lower surface of the cylinder  272 , and comes into contact with the contact lever  12  at the time when the trigger lever  11  is pulled. 
     An O-ring  274   a  is mounted to a peripheral edge portion of a substantially intermediate position in the upper and lower direction of the switch valve stem  274 . During non-pulling operation of the trigger lever  11 , the switch valve stem  274  is configured to close a path between the fifth connection passage  59  and the first connection passage  29  by the O-ring  274   a  and to communicate the passage  272   a  and the fifth connection passage  59  each other. On the other hand, during a pulling operation of the trigger lever  11 , the switch valve stem  274  is configured to be pushed up against an elastic force of the compression spring  276  by the contact lever  12 , and to close a path between the passage  272   a  and the fifth connection passage  59  by the O-ring  274   a  and to communicate the fifth connection passage  59  and the first connection passage  29  each other 
     As shown in  FIGS. 13 and 14 , the control valve  240  is configured to communicate or shut off a path between the head valve chamber  38  and the trigger valve  50  by control of the timer valve  280 . The control valve  240  is arranged in a position near the front side of the tinier valve  280 , between the head valve chamber  38  and the trigger valve  50 . The control valve  240  has a cylinder  242  and a control valve stem  244 . Note that, a part of the cylinder  242  has a structure sharing a part of the housing  1   a.    
     The cylinder  242  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the control valve stem  244  so as to be slidable in the front and rear direction. An upper surface-side of the cylinder  242  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  242  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  242   c  configured to communicate with the main chamber  5 . 
     The control valve stem  244  is a columnar body extending in the front and rear direction and is arranged in the cylinder  242 . The control valve stem  244  is urged toward the tinier valve  280  (toward the rear side) by a compression spring  246 . The compression spring  246  is interposed between a front wall in the cylinder  242  and a front end face of the control valve stem  244 , and is adapted to expand and contract, in response to pressing by the timer valve  280 . O-rings  244   a  and  244   b  for close contact with the inner wall of the cylinder  242  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 stein  244 . 
     The control valve stem  244  is located on a rear end-side in the cylinder  242  and closes a path between the second connection passage  39  and the passage  242   c  by the O-ring  244   b,  and opens a path between the second connection passage  39  and the third connection passage  49 , upon non-pressing of the timer valve  280 , 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 stein  244  is moved to a front end-side in the cylinder  242 , and opens the path between the second connection passage  39  and the passage  242   c  and closes the path between the second connection passage  39  and the third connection passage  49  by the O-ring  244   a,  upon pressing of the timer valve  280 , i.e., after timeout, Thereby, the head valve chamber  38  and the trigger valve  50  are shut off therebetween. 
     As shown in  FIGS. 13, 15A and 15B , in a state where the trigger lever  11  is pulled, after a preset prescribed time elapses, when the contact arm  14  is pressed against the to-be-struck member, the timer valve  280  actuates the control valve  240  to disable the striking operation. 
     The timer valve  280  has a cylinder  290 , a first timer piston  284 , a first piston shaft part  285 , a second tinier piston  294 , and a second piston shaft part  295 . 
     The second cylinder  290  is a hollow cylindrical body extending in the front and rear direction, and is configured to accommodate the first timer piston  284  and the second timer piston  294  so as to be slidable in the front and rear direction. An inside of the cylinder  290  is partitioned into a first chamber  281  and a second chamber  291 , which are an example of the accommodation part, via a partition portion  290   a.  The first chamber  281  is constituted by a sealed closed space (closed circuit) and is isolated from the second chamber  291 , which is another space, the main chamber  5  and the like. In the first chamber  281 , the atmospheric air (air) that is used when actuating the timer valve  280  is filled in advance. Thereby, it is possible to prevent impurities such as trash and oil from flowing into the first chamber  281  from other spaces. 
     The first timer piston  284  is a cylindrical body having substantially the same diameter as an inner diameter of the cylinder  290 , and is configured to slide along an inner wall of the cylinder  290 . The first timer piston  284  is urged toward the control valve  240  (toward the front side) by a compression spring  289 . The compression spring  289  is interposed between a concave portion formed on a base end-side of the first timer piston  284  and a rear wall in the first chamber  281 , and is adapted to expand and contract, according to advance or retreat of the first timer piston  284 . The first timer piston  284  can move to the actuation position in which the control valve  240  is pressed when the time measurement by the timer valve  280  elapses for a predetermined time. 
     A peripheral edge portion of the first timer piston  284  is formed with a concave portion  284   a  along a circumferential direction thereof. In the concave portion  284   a,  an O-ring  286  for sealing between the concave portion and the inner wall of the cylinder  290  is mounted. Thereby, the first chamber  281  is further partitioned into a first space  281   a  on a rear side of the O-ring  286  and a second space  281   b  on a front side of the O-ring  286 . The first space  281   a  and the second space  281   b  are shut off from each other by the O-ring  286 . 
     On a lower side in the cylinder  290 , a first passage  282   a  and a second passage  282   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  282   a  is configured to communicate with the second space  281   b,  and a rear end portion of the first passage  282   a  is configured to communicate with the first space  281   a.  A front end portion of the second passage  282   b  is configured to communicate with the second space  281   b,  and a rear end portion of the second passage  282   b  is configured to communicate with the first space  281   a.    
     A check valve  287  is provided in the middle of the path of the first passage  282   a.  The check valve  287  has a ball  287   a  for opening/closing the first passage  282   a,  for example, and a spring  287   b  for urging backward the ball  287   a.  When the first tinier piston  284  is retreated in the first chamber  281 , the ball  287   a  is moved forward against an elastic force of the spring  287   b  by the atmospheric air flowing into the first passage  282   a  from the first space  281   a,  so that the first passage  282   a  opens and the atmospheric air in the first space  281   a  of the first chamber  281  is caused to flow into the second space  281   b.  When the first timer piston  284  is advanced in the first chamber  281 , the atmospheric air flowing into the first passage  282   a  from the second space  281   b  and the spring  287   b  act on the ball  287   a  and the first passage  282   a  is closed by the ball  287   a,  so that the atmospheric air in the second space  281   b  of the cylinder  290  does not flow into (flow back to) the first space  281   a  via the first passage  282   a.    
     A throttle portion  288  that is an example of the compression generation part is provided in the middle of the path of the second passage  282   b.  The throttle portion  288  is constituted by reducing a cross-sectional area (narrowing a width) of a path of a part of the second passage  282   b.  The throttle portion  288  is configured to restrict a flow rate per unit time of the atmospheric air, which is caused to flow into the second passage  282   b  from the second space  281   b,  to be constant, thereby generating the compressed air for moving the first timer piston  284  and the like. Thereby, it is possible to control the moving speed until the second piston shaft part  295  presses the control valve stem  244  of the control valve  240 . In addition, a prescribed time at the time when the first timer piston  284  moves from an initial position in the first chamber  281  to an actuation position in which the control valve  240  is actuated is determined by a flow rate passing through the throttle portion  288  of the timer valve  280 , a spring coefficient of the compression spring  289 , 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  240  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  240 . 
     As shown in  FIG. 15A , a bypass passage  282   c  penetrating a partition wall  290   e  constituting the cylinder  290  in a thickness direction (upper and lower direction) is formed between a substantially intermediate position of the second passage  282   b  and the cylinder  290  in a position in which the first timer piston  284  is accommodated. The bypass passage  282   c  is a passage different from the second passage  282   b  for causing the atmospheric air to flow from the second space  281   b  into the first space  281   a  of the cylinder  290 . 
     As shown in  FIG. 15B , a moving range of the first timer piston  284  includes a first section R 1  for measuring a prescribed time after the trigger lever  11  is pulled until the control valve  240  is actuated, and a second section R 2  for pressing the control valve  240 . In the present embodiment, based on a rear end portion  284   e  of the first timer piston  284  configured to move in the cylinder  290 , the first section R 1  is a section between the initial position of the first timer piston  284  and a rear edge of the bypass passage  282   c.  In addition, the second section R 2  is a section between the rear edge of the bypass passage  282   c  and the actuation position in which the control valve  240  is pressed. 
     In the present embodiment, a resistance (second resistance) to the first timer piston  284  in the second section R 2  is configured smaller than a resistance (first resistance) to the first timer piston  284  in the first section R 1 . Specifically, in the first section R 1 , a passage through which the atmospheric air passes from the second space  281   b  to the first space  281   a  becomes the throttle portion  288  of the second passage  282   b.  In the second section R 2 , a passage through which the atmospheric air passes from the second space  281   b  to the first space  281   a  becomes the bypass passage  282   c  whose cross-sectional area is greater and flow resistance is smaller than the throttle portion  288 . 
     Back to  FIG. 15A , the first piston shaft part  285  is a rod-shaped columnar body, and a rear end portion of the first piston shaft part  285  is attached to a front end portion of the first timer piston  284 . The first piston shaft part  285  is inserted in a through-hole  290   b  formed in the partition portion  290   a,  and a front end-side thereof extends from the inside of the first chamber  281  into the second chamber  291 . A front end portion of the first piston shall part  285  is attached to a rear end portion of the second tinier piston  294  and is configured to be able to transmit the pressing force of the first timer piston  284  to the second timer piston  294 . An O-ring  290   c  is attached to the partition portion  290   a  to secure a sealed state of the first chamber  281 . 
     The second timer piston  294  is a cylindrical body having substantially the same diameter as an inner diameter of the cylinder  290 , 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 formed with a concave portion  294   a  along a circumferential direction thereof. In the concave portion  294   a,  an O-ring  296  for sealing between the concave portion and the inner wall of the cylinder  290  is mounted. Thereby, the second chamber  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   f  configured to communicate with an outside of the housing  1   a.  One end portion of the fifth connection passage  59  configured to communicate with the switch valve  270  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 fifth connection passage  59 . 
     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 tinier piston  294 . The second piston shaft part  295  can move in the front and rear direction in a through-hole  290   d  formed between the second timer piston  294  and the control valve  240 . 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  242  of the control valve  240 , and is configured to actuate the control valve  240  by pressing the rear end face of the control valve stem  244  constituting the control valve  240 . 
     In the present embodiment, as shown in  FIGS. 13 and 15A , the timer valve  280  is arranged in the grip part  4  so that moving directions of the first timer piston  284  and the second timer piston  294  are 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 directions of the first timer piston  284  and the second timer piston  294  are along the extension direction of the grip part  4 , i.e., are parallel to the extension direction of the grip part  4 . 
     [Operation Example of Nailing Machine  200 ] 
     Subsequently, an example of a striking operation of the nailing machine  200  according to the second embodiment is described with reference to  FIGS. 13 to 15B , and the like. 
     When the air hose is connected to the air plug  8  of the nailing machine  200  shown in  FIG. 13 , 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  270  and the fifth connection passage  59 . 
     Along with this, the second timer piston  294  is urged backward by the compressed air, so that the first timer piston  284  is retreated to the initial position in the cylinder  290 . 
     Continuously, when the trigger lever  11  is pulled by the operator, the switch valve stem  274  of the switch valve  270  is pushed up by the contact lever  12 , so that the switch valve  270  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 fifth connection passage  59 , the inside of the switch valve  270  and the first connection passage  29 . 
     When the compressed air in the second space  291   b  of the cylinder  290  is exhausted, the first timer piston  284  is advanced by the urging of the compression spring  289 . As shown in  FIGS. 15A and 15B , when the rear end portion  284   e  of the first timer piston  284  passes through the first section R 1 , the atmospheric air caused to flow from the second space  281   b  into the second passage  282   b  is caused to flow into the first space  281   a  through the throttle portion  288  of the second passage  282   b.  The flow rate of the atmospheric air that is supplied to the first space  281   a  is restricted to be constant by the throttle portion  288 . Thereby, the first timer piston  284  is slowly advanced from the initial position in the first chamber  290  and the time measurement (timer) of the timer valve  280  starts. The timer valve  280  measures the set prescribed time until reaching the second section R 2 . 
     Continuously, when the rear end portion of the first timer piston  284  starts to pass through the bypass passage  282   c  of the second section R 2 , a communication destination of the bypass passage  282   c  is switched from the second space  281   b  to the first space  281   a.  In the present embodiment, the cross-sectional area of the bypass passage  282   c  is designed greater than the cross-sectional area of the throttle portion  288 , and the flow resistance of the bypass passage  282   c  is set smaller than the flow resistance of the throttle portion  288 . For this reason, the atmospheric air entering from the second space  281   b  passes through the bypass passage  282   c,  not the throttle portion  288  of the second passage  282   b,  and flows into the first space  281   a.  In this case, the flow rate of the atmospheric air caused to flow from the second space  281   b  into the first space  281   a  is larger in the second section R 2  than in the first section R 1 . Therefore, the moving speed of the first timer piston  284  also further increases in the second section R 2  than in the first section R 1 . 
     As described above, according to the second embodiment, the load at the time when the first timer piston  284  is moved is reduced in the second section R 2  immediately before actuation of the control valve  240 , so that the moving speed of the first timer piston  284  and the like can be increased and the control valve stem  244  can be pushed with a strong force by the second piston shaft part  295 . Thereby, the control valve  240  can be actuated securely and with high accuracy. In addition, according to the second embodiment, since the first chamber  281  configured to accommodate the first timer piston  284  is constituted by the closed space, it is possible to apply the constant resistance to the first timer piston  284  all the time in the first section R 1 . Thereby, the moving speed of the first timer piston  284  can be maintained constant, so that the time measurement 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  280 . 
     Note that, in the second embodiment, the means for making the resistance to the first timer piston  284  in the second section R 2  smaller than the resistance to the first timer piston  284  in the first section R 1  is not limited to changing the area of the passage. For example, a plurality of bypass passages  282   c  whose cross-sectional areas are greater than the throttle portion  288  may be provided. 
     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 second embodiment, the example where the control valve  240  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  240  may also be arranged in the trigger valve  50 . In addition, in the second embodiment, the passage between the head valve  30  and the trigger valve  50  is shut off by the control valve  240 . 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  240  can be adopted. Further, in the second embodiment, the moving range of the control valve  240  is divided into the first section R 1  and the second section R 2 . However, the present invention is not limited thereto. For example, a configuration where the control valve  240  is actuated in a state of being pressed from a first stage by the timer valve  280  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 embodiments, the second control valve  60  and the control valve  240  are actuated by being pressed. However, the present invention is not limited thereto. For example, the second control valve  60  and the control valve  240  may also be actuated by being pulled. In the second embodiment, the example where the control valve  240  disables actuation of the head valve  30  has been described. However, instead of this, a configuration where the control valve  240  disables actuation of the trigger valve  50  may also be adopted. 
     The present application is based on Japanese Patent Application No. 2019-086671 filed on Apr. 26, 2019, the contents of which are incorporated herein by reference. 
     REFERENCE SIGNS LIST 
       1 : main body 
       4 : grip part 
       5 : main chamber 
       11 : trigger lever (trigger) 
       20 : striking mechanism (drive mechanism) 
       22 : driver 
       24 : piston 
       26 : cylinder 
       28 : blow back chamber 
       30 : head valve 
       38 : head valve chamber (first chamber) 
       40 : first control valve 
       50 : trigger valve 
       60 : second control valve 
       55 : empty chamber (second chamber) 
       80 : timer valve 
       84 : first timer piston 
       85 : first piston shaft part 
       88   a:  O-ring 
       100 ,  200 : nailing machine (pneumatic tool) 
       280 : timer valve 
       282   c:  bypass passage 
       284 : first timer piston (valve body) 
       285 : first piston shaft part (valve body) 
       288 : throttle portion 
     R 1 : first section 
     R 2 : second section