Patent Publication Number: US-7905378-B2

Title: Trigger valve for nail gun

Description:
BACKGROUND 
     The present invention relates to a trigger valve for a pneumatic nail gun, and more particularly to a trigger valve, which is capable of controlling hitting-nail action of a pneumatic nail gun with the trigger valve according to a thickness of a workpiece. 
     Generally, when an operator wants to use a pneumatic nail gun to join one workpiece (e.g., gasket, etc) with a through hole to another workpiece, a nail is required to be aimed at the through hole in advance, so that the nail can be exactly extended through the through hole and nailed into the another workpiece. For easily aiming the nail at the through hole, a nail gun with a nail exposed outside of a gunpoint thereof, has been developed in the related art. 
     The thickness of the one workpiece is usually varied. To make the nail gun capable of automatically selecting the one workpiece of suitable thickness, a main air passage between a trigger valve and a main air valve typically has a control vale, which is actuated to set the nail gun in the status of hitting nails when a hitting base on a bottom end of a safety slide rod of the nail gun downwardly moves into a predesigned height range above the one workpiece. The predesigned height includes a thickness and a depth of a through hole of the one workpiece of suitable thickness. Thus, the conditions when the control vale to be actuated, are designed according to a displacement of the movement of the hitting base to the predesigned height. That is, the operator can insert into the through hole a tip of the nail exposed outside of a gunpoint of the nail gun, and the tip contacts a surface of the another workpiece, and the hitting base moves along a hitting-nail direction to press the one piece. The displacement of the hitting base represents (reflects or implicates) the relative distance between the tip of the nail and the hitting base, which is the thickness and the depth of the through hole of the one workpiece. When the thickness and the depth of the through hole of the one workpiece measure up the predesigned height range, the control valve is actuated to help the trigger valve to drive the high pressure air, so as to open the main air valve and power the nail gun to hit nails. 
     In the related arts, a pneumatic nail gun with a hitting-nail control device equivalent to the above control valve can be found in US Public No. 2007/0075113. The hitting-nail control device includes a swinging rod driven by a safety slide rod, and a valve rod braked or released by the swinging rod. The safety slide rod indirectly brakes or releases the valve rod, so as to control the high pressure air to drive a main air valve to open and then power the nail gun to hit nails. However, the pneumatic nail gun disclosed in US Public No. 2007/0075113 has several disadvantages: the valve rod is driven to move by the limited volume of high pressure air from main air valve and is indirectly braked or released by the swinging rod, thus, the nail gun has poor control stability. Further, the swinging rod is positioned between the valve rod and the safety slide rod, which makes the structure of the nail gun unduly complicated and it is bad for maintaining stability after long-time use. Moreover, the installation of the hitting-nail control device or a valve body on the nail gun having the trigger valve, will unduly increase the complexity in air passage design and hitting-nail control and the weight of the nail gun, and decrease space of the nail gun for continuously gathering high pressure, and makes the cost unduly high. Accordingly, the nail gun is urgently needed to be improved. 
     BRIEF SUMMARY 
     A trigger valve of a pneumatic nail gun is provided, and can be used in a pneumatic nail gun, which is capable of controlling hitting-nail action according to a thickness of a workpiece. Structures such as drives for hitting nails and controls of hitting nails are integrated into the single trigger valve, this simplifies the nail gun and improves stability after long-time use of the nail gun. Furthermore, the safety slide rod is directly driven to locate, this improves control stability. 
     The trigger valve of a pneumatic nail gun includes: 
     a valve base disposed at a gun body of the nail gun between a compressed chamber and a main air valve of the nail gun; 
     a valve rod sliding received in the valve base, being capable of being driven by a trigger of the nail gun to move so as to open or close high pressure air from the compressed chamber into the valve base; 
     a sliding portion sliding received in the valve base, being capable of being driven by high pressure air to move to cause a safety slide rod of the nail gun producing a displacement along a hitting-nail direction; and 
     a shuttle valve sliding received in the valve base and nested with the sliding portion, the shuttle valve being capable of being driven to move under control of the displacement of the sliding portion so as to open or close high pressure air from the valve base into the main air valve. 
     With these configurations, when the trigger is pressed, the valve rod is driven to move causing the higher pressure air in the compressed chamber flowing into the valve base. The sliding portion in the valve base is then driven by the high pressure air to move, and this causes the safety slide rod producing a displacement along a hitting-nail direction. The shuttle valve is actuated to open under control of the displacement of the sliding portion so that the high pressure air in the valve base flows into the main air valve so as to power the nail gun to hit nails. 
     Thus, structures such as drives for hitting nails and controls of hitting nails are integrated into the single trigger valve, this simplifies the nail gun and improves stability after long-time use of the nail gun. Furthermore, the safety slide rod is directly driven to locate, this improves control stability. 
     Furthermore, the trigger valve further includes following features. 
     The valve base is disposed at an end of the gun body. The valve base includes a top guide groove and a bottom guide groove defined therein, the bottom guide groove connecting with the top guide groove. A first valve hole is disposed in a top end of the valve base, the first valve hole connecting with the compressed chamber and the top guide groove. The valve rod is sliding received in the top guide groove and includes an air-guiding passage defined therein, the air-guiding passage connecting the first valve hole and the bottom guide groove. The valve rod further includes a first valve stopper formed on an outer peripheral surface of a top end thereof. The first valve stopper is capable of controlling the first valve hole to open or close. 
     The air-guiding passage includes at least one air inputting passage, which is formed in the outer peripheral surface of the top end of the valve rod below the first valve stopper. The first valve stopper is located in the top guide groove and closes the first valve hole. When the trigger is pressed, the valve rod with the first valve stopper is driven to move along a direction opposite to the hitting-nail direction, and the first valve stopper moves to an outside of the top guide groove to open the first valve hole. 
     A second valve hole is defined in a connecting portion between the top guide groove and the bottom guide groove. The valve base further includes at least one travel slot defined in a side portion of the top end thereof, the at least one travel slot connecting with the top guide groove and the atmosphere. A second valve stopper is disposed at an outer peripheral of the valve rod, which is located between the top and bottom guide grooves, the second valve stopper can open or close the second valve hole. 
     The second valve stopper is located outside of the top guide groove and opens the second valve hole. When the trigger is pressed, the valve rod with the second valve stopper is driven to move along a direction opposite to the hitting-nail direction, and the second valve stopper moves into the top guide groove to close the second valve hole. 
     The valve rod includes a pole disposed at an end thereof. The pole is sliding received in the travel slot and exposed outside of side end portions of the valve base. The pole is capable of being driven by the trigger to drive the valve rod to move. 
     A first elastic element is nested with the sliding portion, for inducing the sliding portion to move along a direction opposite to the hitting-nail direction to keep the sliding portion elastically and sliding locating in the bottom guide groove. A bottom portion of the valve rod extends into the bottom guide groove. An axial hole is formed in a top portion of the sliding portion and is nested with the bottom portion of the valve rod. 
     The air guiding passage includes at least one air exhausting passage, which is formed in an outer peripheral surface of the bottom portion of the valve rod. The sliding portion is connected with the safety slide rod. 
     A second elastic element is located between the shuttle valve and an inner wall of the bottom guide groove, for inducing the shuttle valve to move along the hitting-nail direction to keep the shuttle valve elastically and sliding locating in the bottom guide groove. 
     The valve base includes at least one air exhausting hole defined in a side portion of a bottom portion thereof, the at least one air exhausting hole connecting with the bottom guide groove and the main air valve. The shuttle valve divides the bottom guide groove into a first air room and a second air room. The first air room connects with the top guide groove. The shuttle valve includes a guide hole defined therein, which connects with the first air room and the second air room. The shuttle valve further includes at least one through hole defined in side portions thereof. The through hole connects with the guide hole and the air exhausting hole. A third valve hole is defined in a connecting portion between the guide hole and the first air room. The sliding portion is sliding received in the guide hole and includes a third valve stopper formed on the outer periphery thereof. The third valve stopper is capable of controlling the third valve hole to open or close. 
     The third valve stopper is located in the guide hole above the through hole and closes the third valve hole. The sliding portion is driven by high pressure air to cause the third valve stopper moving into the guide hole below the through hole along the hitting-nail direction so that the third valve hole is opened to connect with the through hole and the air exhausting hole. 
     The sliding portion is driven by high pressure air to cause the third valve stopper moving away from the guide hole along the hitting-nail direction, so as to open the third valve hole to connect with the second air room, so that the shuttle valve is driven by high pressure air to move along a direction opposite to the hitting-nail direction so as to block the air exhausting hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a cross-sectional view of several elements of a nail gun according to an exemplary embodiment of the present invention; 
         FIG. 2  is a perspective view of the nail gun of  FIG. 1 ; 
         FIG. 3  is a schematic view of a safety slide rod and a hitting base of the nail gun of  FIG. 1 ; 
         FIG. 4  is a three-dimensional view of a trigger valve of the nail gun of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of  FIG. 4 ; 
         FIG. 6  is a cross-sectional view of a valve base of the nail gun of  FIG. 1 ; 
         FIG. 7  is a cross-sectional view of a shuttle valve of the nail gun of  FIG. 1 ; 
         FIG. 8  is a cross-sectional view of a main air passage of the nail gun of  FIG. 1 ; 
         FIG. 9  is a partly enlarged view of  FIG. 1 ; 
         FIG. 10  is an enlarged, cross-sectional view of the trigger valve; 
         FIG. 11  is a view similar to  FIG. 9 , showing the operating status thereof; 
         FIG. 12  is an enlarged view of the trigger valve of  FIG. 11 , showing the operating status thereof; 
         FIG. 13  is a schematic, enlarged view of the hitting base of  FIG. 1 , showing the operating status thereof; 
         FIG. 14  is a view similar to  FIG. 13 , showing the continuously operating status thereof; 
         FIG. 15  is a view similar to  FIG. 13 , showing another continuously operating status thereof; 
         FIG. 16  is a view similar to  FIG. 9 , showing another operating status thereof; 
         FIG. 17  is an enlarged view of the trigger valve of  FIG. 16 , showing the operating status thereof; 
         FIG. 18  is a view similar to  FIG. 17 , showing a status of the sliding portion having a shortened displacement; 
         FIG. 19  is a view similar to  FIG. 17 , showing a status of the sliding portion having a lengthened displacement; 
         FIG. 20  is a view similar to  FIG. 19 , showing the continuously operating status thereof; and 
         FIG. 21  is a view similar to  FIG. 19 , showing another continuously operating status thereof. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a cross-sectional view of a trigger valve of a nail gun according to an exemplary embodiment of the present invention is shown. The trigger valve  30  includes a valve base  3 , a valve rod  4 , a sliding portion  5  and a shuttle valve  6 . The valve base  3  is disposed at an end of a gun body  1  of the nail gun  10  (as shown in  FIGS. 2 ,  4 , and  5 ), adjacent to a grip  11  disposed at an end of the gun body  1 . Further, the valve base  3  connects between a compressed chamber  12  and a main air valve  2  of the nail gun  10 . The valve rod  4  is sliding received in the valve base  3 , and is capable of being driven to move by a trigger  13  of the nail gun  10  (as shown in  FIG. 11 ), so that the high pressure air in the compressed chamber  12  can be guided or prevented from flowing into the valve base  3 . The sliding portion  5  is sliding received in the valve base  3 , and is capable of being driven by the high pressure air to move. The sliding portion  5  moves together with a safety slide rod  14  of the nail gun  10  and a hitting base  15  disposed on a bottom end of the safety slide rod  14  along a hitting-nail direction, and a displacement h 1  is produced (as shown  FIGS. 12-14 ). The shuttle valve  6  is sliding received in the valve base  3 , and nested with an outer periphery of the sliding portion  5 . The shuttle valve  6  is capable of moving under control of the displacement of the sliding portion  5  (as shown  FIGS. 18-20 ), so that the high pressure air in the valve base  3  can be guided or prevented from flowing into the main air valve  2 . 
     The gun body  1  includes a cylinder  7  disposed therein (as shown in  FIG. 1 ). The main air valve  2  is disposed in the gun body  1  above the cylinder  7 . The compressed chamber  12  is disposed outside of the main air valve  2  and the cylinder  7 , and also disposed in the grip  11 . The compressed chamber  12  is for concentrating air and maintain a certain high pressure therein. The gun body  1  has a main air passage  16  formed therein (as shown in  FIG. 8 ). The gun body  1  has a receiving groove  17  formed in an end portion thereof and extending along the hitting-nail direction. The main air passage  16  is divided into a first air passage  161  and a second air passage  162 , and the first air passage  161  and the second air passage  162  connect with the receiving groove  17 , respectively. The valve base  3  is installed in the receiving groove  17  so that the first air passage  161  connects the compressed chamber  12  with the valve base  3  and the second air passage  162  connects the valve base  3  and the main air valve  2 . The trigger  13  is elastically and sliding mounted on an end of the grip  11  via a spring  131 , for fingers pressing. The safety slide rod  14  is sliding disposed on the gun body  1 . A top end portion of the safety slide rod  14  is connected with a bottom portion of the sliding portion  5 . A bottom end portion of the safety slide rod  14  is connected with the hitting base  15 . The hitting base  15  extends to beyond a distal end of a gunpoint  18 , which is located at a bottom portion of the gun body  1 . The hitting base  15  is capable of moving along the hitting-nail direction to press a working piece  81  (as shown in  FIGS. 13-14 ). The main air valve  2  is capable of being actuated to be driven by the high pressure air in the main air passage  16 , so that the high pressure air in the compressed chamber  12  can be guided or prevented from flowing into the cylinder  7  (as shown in  FIG. 9  and  FIG. 11 ) to power the nail gun  10  to hit nails. 
     The main air valve  2  includes a main air chamber  20  (as shown in  FIG. 1  and  FIG. 8 ). The main air chamber  20  connects with the second air passage  162 . The main air chamber  20  is capable of concentrating high pressure air from the second air passage  162  to actuate the main air valve  2  to open a top portion of the cylinder  7  (as shown in  FIG. 11 ), so that the high pressure air in the compressed chamber  12  are guided into the cylinder  7 . The cylinder  7  has a piston  70  slinding received therein. The piston  70  divides an inner portion of the cylinder  7  into a top cylinder chamber  71  and a bottom cylinder chamber  72 . The cylinder  7  has a drive rod  73  connected to a bottom portion thereof. A spring  141  (as shown in  FIG. 3 ) is disposed between an end of the safety slide rod  14  and a bottom end of the gun body  1 . The spring  141  drives the safety slide rod  14  with the hitting base  15  to upwardly move, so that a nail  9 , installed in a drive track at the bottom end of the gun body  1 , is exposed outside of the gunpoint  18  and the hitting base  15 . 
     Of course, the illustrated embodiment of the main air valve  2  and the cylinder  7  is only a preferred embodiment of the present invention, and not intended to be limiting in any way. In other words, other arrangements which can use high pressure air to actuate the main air valve  2  so as to drive high pressure air into the cylinder  7 , and which includes main air valves and cylinders with same functions in the related art, can be adopted in other embodiments of the present invention. 
     The preferred embodiment will be described in more details. 
     The valve base  3  includes a top guide groove  31  and a bottom guide groove  32  defined therein, the bottom guide groove  32  connecting with the top guide groove  31  (as shown in  FIG. 6  and  FIG. 10 ). The valve base  3  includes a first valve hole  33  disposed in a top end thereof. The first valve hole  33  connects with the first air passage  161 , the compressed chamber  12  and the top guide groove  31 . The valve rod  4  is sliding received in the top guide groove  31 , and has an air-guiding passage  40  defined therein (as shown in  FIG. 5 ). The air-guiding passage  40  connects the first valve hole  33  and the bottom guide groove  32 . The valve rod  4  includes a first valve stopper  41  formed on an outer peripheral of a top end thereof. The valve rod  4  can control the first valve hole  33  (as shown in  FIG. 12 ) to open or close. The air-guiding passage  40  includes at least one air inputting passage  401 , which is formed in the outer periphery of the top end of the valve rod  4  below the first valve stopper  41 . In this embodiment, the at least one air inputting passage  401  includes several air inputting passages  401 . The first valve stopper  41  is located in the top guide groove  31  when the trigger  13  is not pressed, and closes the first valve hole  33 . 
     In a connecting portion between the top guide groove  31  and the bottom guide groove  32 , a second valve hole  34  is defined (as shown in  FIG. 6  and  FIG. 10 ). At a side portion of a top portion of the valve base  3 , at least one travel slot  35  is defined and connects with the top guide groove  31  and the atmosphere (as shown in  FIGS. 4-5 ). In this embodiment, two travel slots  35  are defined in opposite side portions of the top portion of the valve base  3 . A second valve stopper  42  is disposed at the outer periphery of the valve rod  4 , which is located between the first and second guide grooves  31 ,  32 . The second valve stopper  42  can open or close the second valve hole  34  (as shown in  FIG. 12 ). The second valve stopper  42  is located outside of the top guide groove  31  when the trigger  13  is not pressed, and opens the second valve hole  34 . The first and second valve stoppers  41 ,  42  each may be an air tight ring. An air tight ring  403  is disposed at the outer periphery of the top end of the valve rod  4 , which is located below the air input passage  401 . The air tight ring  403  prevents the high pressure air following from the first valve hole  33  from exhausting toward the atmosphere through the bottom guide groove  32  and the travel slot  35 . 
     Two end slots  171  are defined in opposite end portions of the receiving groove  17  (as shown in  FIGS. 8-10 ). The end slots  171  are corresponding to the travel slots  35  of the valve base  3 , respectively. The valve rod  4  includes a pole  43  disposed at an end thereof (as shown in  FIGS. 4-5 ). The pole  43  is sliding received in the travel slots  35  and extends exposed outside of side end portions of the valve base  3 . In this embodiment, the pole  43  is extended through the valve rod  4  with opposite ends of the pole  43  exposed outside of opposite sides of the valve rod  4 . Further, the opposite ends of the pole  43  are respectively received in the travel slots  35  and extended through the end slots  171  to expose outside of side portions of the gun body  1 . The trigger  13  includes two side plates  132 , which extend to two side portions of the valve base  3 , respectively, and located outside of the gun body  1  (as shown in  FIG. 2 ). The pole  43  is pivotally attached between the two side plates  132 . The pole  43  is capable of being driven by the trigger  13  to drive the valve rod  4  to move (as shown in  FIGS. 11-12 ). 
     A portion of the pole  43  extending in the air-guiding passage  40 , has an air-guiding channel  431  defined therein to make the air-guiding passage  40  unobstructed (as shown in  FIG. 10 ). Two air tight rings  432 ,  433  are disposed at an outer wall of the pole  43  at opposite sides of the air-guiding channel  431 , and the air tight rings  432 ,  433  are embedded in the valve rod  4  to prevent the high pressure air in the air-guiding passage  40  from exhausting toward the atmosphere through leakage between the valve rod  4  and the pole  43 . 
     A first elastic element  51  is nested with the sliding portion  5  (as shown in  FIG. 10 ). The first elastic element  51  may be a spring and is used for inducing the sliding portion  5  to move along a direction opposite to the hitting-nail direction, so as to keep the sliding portion  5  elastically and sliding locating in the bottom guide groove  32 . A bottom portion of the valve rod  4  extends into the bottom guide groove  32 . An axial hole  52  is formed in a top portion of the sliding portion  5 , and is nested with the bottom portion of the valve rod  4 . The air-guiding passage  40  includes at least one air exhausting passage  402 , which is formed in an outer periphery of the bottom portion of the valve rod  4 . In this embodiment, the at least one air exhausting passage  402  includes several air exhausting passages  402 . 
     A second elastic element  61  is located between the shuttle valve  6  and an inner wall of the bottom guide groove  32  (as shown in  FIG. 10 ). The second elastic element  61  may be a spring and is used for inducing the shuttle valve  6  to move along the hitting-nail direction, so as to keep the shuttle valve  6  elastically and sliding locating in the bottom guide groove  32 . 
     The valve base  3  includes at least one air exhausting hole  36  defined in side portions of a middle portion thereof (as shown in  FIG. 6  and  FIGS. 9-10 ). In this embodiment, the at least one air exhausting hole  36  includes several air exhausting holes  36 , which connect with the bottom guide groove  32 , the second air passage  162  and the main air valve  2 . Furthermore, the shuttle valve  6  divides the bottom guide groove  32  into a first air room  321  and a second air room  322 . The first air room  321  connects with the top guide groove  31 . The shuttle valve  6  includes a guide hole  62  defined therein, which connects with the first air room  321  and the second air room  322  (as shown in  FIG. 7 ). The shuttle valve  6  further includes at least one through hole  63  defined in side portions thereof, and the through hole  63  connects with the guide hole  62  and the air exhausting hole  36 . In this embodiment, the at least one through hole  63  includes several through holes  63 . Two air tight rings  631 ,  632  are disposed at an outer periphery of the shuttle valve  6  and located at opposite top and bottom sides of the through hole  63 , respectively, so as to communicate the air exhausting hole  36  with the through hole  63 . In a connecting portion between the guide hole  62  and the first air room  321 , a third valve hole  64  is defined. The sliding portion  5  is sliding received in the guide hole  62 . Furthermore, the sliding portion  5  has a third valve stopper  53  formed on the outer periphery thereof. The third valve stopper  53  is capable of controlling the third valve hole  64  to open or close (as shown in  FIG. 12 ). The third valve stopper  53  is located in the guide hole  62  above the through hole  63  when the trigger  13  is not pressed (as shown in  FIG. 10 ), and closes the third valve hole  64 . The distance h 3  that the third valve stopper  53  has moved along the hitting-nail direction before it gets away from the guide hole  62 , defines the range of the above described displacement h 1 . 
     Based on the above description, the operation of the present invention will be described herein with reference to  FIGS. 11-22 . 
     When an operator wants to use the nail gun  10  to join one workpiece  81  with a through hole  811  to another workpiece  82 , a tip of the nail  9  which is exposed outside of the gunpoint  18  and the hitting base  15 , is first inserted into the through hole  811  (as shown in  FIG. 13 ) and contacts with a surface of the another workpiece  82 . At this time, the hitting base  15  does not contact with a surface of the workpiece  81 . When the operator presses the trigger  13  (as shown in  FIGS. 11-12 ), the side plates  132  of the trigger  13  together with the pole  43  and the valve rod  4  move along the direction opposite to the hitting-nail direction, this causes the first valve stopper  41  to move along the direction opposite to the hitting-nail direction to the outside of the top guide groove  31 , and the first valve hole  33  is opened. The second valve stopper  42  are also driven to move along the direction opposite to the hitting-nail direction into the top guide groove  31 , and the second valve hole  34  is closed. At this time, the high pressure air in the compressed chamber  12  flows into the first air room  321  of the bottom guide groove  32  through the first air passage  161 , the first valve hole  33 , the top guide groove  31 , the air inputting passage  401 , the air-guiding passage  40  and the air exhausting passage  402 . As a result, the sliding portion  5  together with the safety slide rod  14  and the hitting base  15  moves along the hitting-nail direction, and the hitting base  15  on the bottom end portion of the safety slide rod  14  moves into a range of the predesigned height h 2  above the another workpiece  82 , and then contacts with the surface of the one workpiece  81  (as shown in  FIGS. 13-14 ). The predesigned height h 2  includes a thickness and a depth of a through hole  811  of the one workpiece  81 . The distance h 3  (as shown in  FIG. 10 ) that the third valve stopper  53  moves in the guide hole  62  along the hitting-nail direction is designed according to the predesigned height h 2 . Thus, the displacement h 1  that the safety slide rod  14  and the hitting base  15  move along the hitting-nail direction, represents (reflects or implicates) the relative distance between the tip of the nail  9  and a bottom surface of the hitting base  15  as shown in  FIG. 13 , so as to check the thickness and the depth of the through hole  811  of the one workpiece  81 . When the thickness and the depth of the through hole  811  of the one workpiece  81  measure up the predesigned range of the predesigned height h 2 , the sliding portion  5  produces a displacement h 1  along the hitting-nail direction, so that the third valve stopper  53  moves into the guide hole  62  below the through hole  63  along the hitting-nail direction and the third valve hole  64  is opened to connect with the guide hole  62 , the through hole  63  and the air exhausting hole  36 . Therefore, the high pressure air in the first air room  321  are guided into the main air chamber  20  through the third valve hole  64 , the guide hole  62 , the through hole  63 , the air exhausting hole  36  and the second air passage  162 , and the main air valve  2  is actuated to open the top portion of the cylinder  7  so that the high pressure air in the compressed chamber  12  are guided into the top cylinder chamber  71 . As a result, the piston  70  drives the drive rod  73  to downwardly move to hit the nail  9 , and the nail  9  is hit into the surface of the another workpiece  82  so as to join the workpieces  81 ,  82  together (as shown in  FIG. 15 ). 
     Thus, the present invention can feedback the thickness and the depth of the through hole  811  of the one workpiece  81  via the safety slide rod  14  and the hitting base  15 , and then checks the feedback height of the safety slide rod  14  via the sliding portion  5  of the trigger valve  30  to control the compressed chamber  12  to close or open, so as to control the high pressure air in the compressed chamber  12  to power the nail gun  10  to hit the nail  9 . 
     When the operator releases the trigger  13  (as shown in  FIGS. 16-17 ), the spring  131  drives the side plates  132  of the trigger  13  with the pole  43  and the valve rod  4  to reposit to original positions. Meanwhile, the high pressure air in the compressed chamber  12  also drives the valve rod  4  to reposit to original position, and the first valve stopper  41  are driven to move into the top guide groove  31  along the hitting-nail direction to close the first valve hole  33 . The second valve stopper  42  are driven to move outside of the top guide groove  31  to open the second valve hole  34 . As a result, the high pressure air in the compressed chamber  12  can not be continuously guided into the trigger valve  30  and the main air chamber  20  via the first valve hole  33 , and the high pressure air in the main air chamber  20 , the second air passage  162  and the bottom guide groove  32  is exhausted to the atmosphere via the second valve hole  34 , the top guide groove  31 , the travel slot  35  and the end slots  171 , so that the main air valve  2  is driven by the high pressure air from the compressed chamber  12  to close the top portion of the cylinder  7  so as to cause the piston  70  upwardly moving to reposit. At the same time, the spring  141  (as shown in  FIG. 3 ) drives the safety slide rod  14  and the hitting base  15  to reposit again. 
     Additionally, when a thickness or a depth of a through hole of one workpiece is larger than the predesigned height h 2  (as shown in  FIG. 13 ), the displacement h 1  of the safety slide rod  14  and the sliding portion  5  is shortened. At this time, when the operator presses the trigger  13  (as shown in  FIG. 18 ), the valve rod  4  is driven to open the first valve hole  33  and close the second valve hole  34 . The high pressure air in the compressed chamber  12  flows into the first air room  321  of the bottom guide groove  32  via the first valve hole  33  and then drives the sliding portion  5  and the safety slide rod  14  to move along the hitting-nail direction. As a result, the hitting base  15  is driven to move to contact a surface of one workpiece at a position, which is above the workpiece  82  and does not reach the range of the predesigned height h 2 . Therefore, the sliding portion  5  is driven by the high pressure air to move, and this causes the third valve stopper  53  moving into the guide hole  62  above the through hole  63  along the hitting-nail direction, so as to prevent the third valve hole  64  from connecting with the through hole  63 . Then, the nail gun  10  can not hit the nail  9 . 
     Moreover, when a thickness or a depth of a through hole of one workpiece is smaller than the predesigned height h 2  (as shown in  FIG. 13 ), the displacement h 1  of the safety slide rod  14  and the sliding portion  5  is lengthened. At this time, when the operator presses the trigger  13  (as shown in  FIG. 19 ), the valve rod  4  is driven to open the first valve hole  33  and close the second valve hole  34 . The high pressure air in the compressed chamber  12  flows into the first air room  321  of the bottom guide groove  32  via the first valve hole  33  and then drives the sliding portion  5  and the safety slide rod  14  to move along the hitting-nail direction. As a result, the hitting base  15  is driven to move to contact a surface of one workpiece at a position, which is above the workpiece  82  and exceeds the range of the predesigned height h 2 . Therefore, the sliding portion  5  is driven by the high pressure air to move, and this causes the third valve stopper  53  moving away from the guide hole  62  along the hitting-nail direction and entering into the second air room  322 , so as to open the third valve hole  64  to connect with the second air room  322 . Then, the high pressure air in the first air room  321  flows into the second air room  322  via the third valve hole  64  and the guide hole  62 , so as to concentrate high pressure air therein for driving the shuttle valve  6  to move along the direction opposite to the hitting-nail direction (as shown in  FIG. 20 ). As a result, the through hole  63  is prevented from connecting with the air exhausting holes  36 , and the nail gun  10  can not hit the nail  9 . When the operator releases the trigger  13  (as shown in  FIG. 21 ), the spring  131  and the high pressure air drive the valve rod  4  to reposit to original positions. The first valve stopper  41  is driven to close the first valve hole  33  so as to prevent the high pressure air from entering into the trigger valve  30  and the main air room  20 . The second valve stopper  42  are driven by the valve rod  4  to open the second valve hole  34 , then the high pressure air in the second air room  322  is exhausted to the atmosphere via the guide hole  62 , the third valve hole  64 , the second valve hole  34 , the top guide groove  31 , the travel slot  35  and the end slots  171 . The spring  141  (as shown in  FIG. 3 ) drives the safety slide rod  14  and the hitting base  15  to reposit again. 
     When the operator wants to nail the nail  9  into only the another workpiece to cause the hitting base  15  downwardly moving to the position, which is on the surface of the another workpiece and exceeds the range of the predesigned height h 2 , or the operator wrongly touches the trigger  13  to cause the hitting base  15  downwardly moving to the position, which is above the workpiece and exceeds the range of the predesigned height h 2 , the shuttle valve  6  will be driven to move along the direction opposite to the hitting-nail direction (as shown in  FIG. 20 ) so as to prevent the through hole  63  from connecting with the air exhausting holes  36 , and the nail gun  10  can not hit the nail  9 . 
     As described above, structures such as drives for hitting nails and controls of hitting nails are integrated into the single trigger  13 , this simplifies the nail gun and improves stability after long-time use of the nail gun. Furthermore, the safety slide rod  14  is directly driven by the sliding portion  5  to locate, this improves control stability. 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations ways of the recessed portions and materials and/or designs of the attaching structures. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.