JP2003048175A - Safety device for air impact driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an air impact driver. SOLUTION: A slidable contact nose 12 is mounted on a nose 5 of the air impact driver 1, and a contact valve 23 above the contact nose is switched by the contact nose. An AND circuit for pilot-operating a pilot valve 39 for controlling an air motor and a pilot valve 41 for controlling a piston is constituted by a trigger valve 8 operated by a trigger lever 9 and the contact valve 23. When the contact nose is pressed in and the trigger lever is pulled, the pilot valve for controlling the air motor and the pilot valve for controlling the piston are switched to a start position to start the air impact driver. A lateral width of a body can be reduced more than a conventional mechanical safety device provided with a contact arm reaching a trigger lever along outer periphery of the body from the nose so that the workability in a corner part and in a place where a width is small where the work has been difficult conventionally is improved.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for preventing activation of an air impact driver due to an erroneous operation, and more particularly to a safety device for an air impact driver constituted by a pneumatic circuit. It concerns safety devices. 2. Description of the Related Art An air impact driver provided for screwing a construction material such as a gypsum board is equipped with a mechanical safety device using a contact arm like a nailing machine. The contact arm is an arm formed into a crank shape along the nose of the air impact driver and the outer shape of the cylinder housing, and is slidable in parallel with the nose, the tip of which protrudes forward from the nose, and the other end. Has reached the front of the trigger lever of the air impact driver body. A swingable free arm is attached to the trigger lever, and when the contact arm is pushed into the air impact driver body, the tip of the free arm attached to the trigger lever is pushed by the contact arm. Approach the trigger valve stem. In this state, when the trigger lever is pulled, the free arm rotates together with the trigger lever in the direction of the trigger valve with the tip portion as a fulcrum, and the stem of the trigger valve is pushed by the free arm to activate the air impact driver. Further, even if the contact arm is pressed against the screw tightening target surface after the trigger lever is first pulled, the free arm pushes the stem of the trigger valve and the air impact driver is activated in the same manner as the above-described operation. As described above, the trigger lever and the contact arm cooperate to turn on the trigger valve. When only the trigger lever is operated, the free arm does not reach the position of the stem of the trigger valve. In this case, the air impact driver cannot be started, thereby preventing the air impact driver from being started due to erroneous operation of the trigger lever. [0005] In the conventional mechanical safety mechanism, since the contact arm passes through the side surface of the cylinder housing, the width of the entire air impact driver is wide, and the corners and width are narrow. It may be difficult to drive the screw into place. In a configuration in which the contact arm is slid to push up the tip of the free arm attached to the trigger lever, and furthermore, the trigger lever is pulled to move the entire free arm, thereby pushing the trigger valve stem, the contact arm pushing stroke However, there is a problem that the operability is not good and the speed of one cycle of work is lacking. Further, as another problem, between the slide arm supporting the long contact arm and the contact arm, gypsum powder generated at the time of screw tightening may be clogged and the contact arm may not slide. If the trigger cannot be returned to the initial position, the air impact driver is activated when the trigger lever is erroneously operated, so that there is a problem that the air impact driver does not function as a safety mechanism. [0007] Therefore, there is a technical problem to be solved in order to provide an air impact driver in which it is difficult to tighten a screw in a corner or a narrow place, and the overall workability is improved and safety is improved. Therefore, an object of the present invention is to solve the above problems. SUMMARY OF THE INVENTION The present invention proposes to achieve the above object, in which a slidable contact nose is attached to a nose of an air impact driver, and a contact valve is attached to the contact nose. A trigger valve operated by a trigger lever and a pneumatic logic circuit for controlling a start control valve of an air impact driver by the contact valve, and a contact nose is pushed in, and the trigger lever and the contact valve are pulled by pulling the trigger lever. Is switched to the ON position, the air impact driver is activated, and the contact valve has a secondary outlet communicating with the primary inlet at the ON position and a secondary outlet communicating with the atmosphere at the OFF position. The present invention provides a safety device for an air impact driver, which is a switching valve that performs a switching operation. An embodiment of the present invention will be described below in detail with reference to the drawings. FIGS. 1 to 4 show an air impact driver 1, and a housing in which an air motor housing 2, a clutch housing 3, a cylinder housing 4, and a nose 5 are connected in a row from above, and a grip 6 extending in a direction perpendicular to the clutch housing 3 is attached. It has a structure. Although illustration is omitted, an air plug is attached to the end of the grip 6 like an ordinary pneumatic tool, and an air hose is connected to the air plug to supply high-pressure air from an air compressor to an air chamber 7 in the grip 6. At the base of the grip 6, a trigger valve 8 and a trigger lever 9 are provided, and by operating the trigger lever 9 to open and close the trigger valve 8,
Starts and stops the air impact driver 1. A known connecting screw feeder comprising a spring offset type air cylinder 10 and a feed claw 11 connected to its piston rod is provided on the back (right side in the figure) of the nose 5. The feed claw 11 is moved backward and forward in conjunction with the operation of one cycle, so that the connection screw in the connection screw magazine (not shown) is nosed.
Send into 5. In the drawing, the upper right portion A is a cross-sectional view of the trigger valve 8 as viewed from the right, and the lower left B portion is a cross-sectional view of the contact nose 12 provided in the nose 5 as viewed from the left.
The air piping is indicated by a chain line. The piston 14 of the air cylinder 13 built in the cylinder housing 4 has a driver bit 15 attached to the front (lower in the figure) and the rear (upper in the figure).
A hexagonal shaft 16 is attached to the. The clutch housing 3 has a built-in centrifugal mesh type impact mechanism 17, and a hexagonal hole is formed at the center of a driven rotating body 18 (hereinafter referred to as anvil) having a butterfly-shaped horizontal cross section disposed at the center. The hexagonal shaft 16 passes through the hexagonal hole. The rotor 20 of the air motor 19 disposed on the impact mechanism 17 has a center hole having a diameter larger than that of the hexagonal shaft 16, and the upper part of the hexagonal shaft 16 enters the center hole. Hex shaft with piston 14 and driver bit 15
16 rotates around the axis together with the anvil 18 of the impact mechanism 17 and can move up and down inside the air cylinder 13. The impact operation by the air motor 19 and the impact mechanism 17 is well known, and the rotor 20 of the air motor 19 is connected to the outer rotor 21 of the impact mechanism 17 and both rotate integrally. As shown in FIG.
A lever type hammer 21a is swingably attached to the outer rotor 21. When the outer rotor 21 starts rotating clockwise in the drawing, the hammer 21a rotates in the rotational direction rearward toward the center of rotation due to static inertia, and the rear corner contacts the anvil 18 as shown in FIG. As shown in ()), it is pushed on the convex portion of the anvil 18 and is pushed outward in a direction opposite to the start time. As a result, as shown in (d), the corner portion on the front side in the rotation direction rotates toward the center of rotation and meshes with the convex portion of the anvil 18, so that the anvil 18 is impacted and rotated. Then, as the anvil 18 rotates, the front corner of the hammer 21a comes off the anvil 18 as shown in (e), and the rear corner contacts the anvil 18 as shown in (b). Hereinafter, the hammer 21a swings from (b) to (e) at a high speed and circulates at high speed to continuously apply a rotational impact to the anvil 18,
The hex shaft 16 and the piston 14 and the driver bit 15 are rotated. Next, the contact nose 12 of FIG. 1 will be described. The contact nose 12 fitted on the outer peripheral surface of the tip of the nose 5 can slide upward with respect to the nose 5. Rod on contact nose 12
A tip of the rod 22 enters a rod guide hole of a contact valve 23 provided at a lower portion of the cylinder housing 4 and is in contact with a stem 24 in the rod guide hole. At the center of the front surface of the contact nose 12, a stroke adjusting dial 25 is mounted. A stopper 26 formed on the nose 5 is located above the stroke adjusting dial 25. A cam portion 27 whose radius from the center of rotation changes stepwise (eight steps in the illustrated example) according to the rotation angle is formed on the back surface of the stroke adjustment dial 25.
An eight-stage click stop mechanism is formed by a spring (not shown) and a ball 28 inserted into a hole on the back surface of the stroke adjusting dial 25, and a ball receiving hole 29 arranged in an annular shape on the front surface of the contact nose 12. The stroke adjustment dial 25 is fixed at a constant rotation angle. The stopper 26 provided on the nose 5 is opposed to the outer peripheral surface of the cam portion 27 of the stroke adjusting dial 25. When the contact nose 12 is slid upward, the outer peripheral surface of the cam portion 27 is moved to the stopper 26. The contact nose 12 stops. As described above, since the radius of the cam portion 27 that hits the stopper 26 varies depending on the rotation angle of the stroke adjustment dial 25, the upward stroke of the contact nose 12 is reduced by rotating the stroke adjustment dial 25 to an arbitrary click position. It can be adjusted step by step, so that the tightening depth of the screw can be adjusted. Next, a pneumatic circuit and an operation process of the air impact driver 1 will be described. FIG. 1 shows a standby state, in which the stem 30 of the trigger valve 8 is lowered to the closed position by a spring, and the poppet 31 coaxial with the stem 30 is raised by the spring and the air pressure acting on the lower surface. An air motor switching valve 33 is connected to an intake port 32 of the air motor 19, an input port 34 of the air motor switching valve 33 is connected to an upper output port 35 of the trigger valve 8, and an upper pilot port 36 is connected to an A portion. The upper output port 37 of the trigger valve 8 shown is connected to the lower pilot port 38, and the lower pilot port 38 is connected to the air motor control pilot valve 39. An upper pilot port 40 of the air motor control pilot valve 39 and an upper pilot port 42 of the left piston control pilot valve 41 are connected to an upper output port 37 of the trigger valve 8 shown at A. The upper port 43 of the air cylinder 13 and the front port 44 of the spring-offset air cylinder 10 of the connecting screw feeder are connected to the lower port 45 of the piston control pilot valve 41, and the lower port 46 of the air cylinder 13 is connected. Is connected to the lower port 47 of the trigger valve 8 shown in section A. The lower port 48 of the contact valve 23 arranged at the lower part of the cylinder housing 4 is connected to the upper port 49 of the piston control pilot valve 41. The upper port 50 of the contact valve 23 It is connected to the chamber connection port 51. As shown in FIG. 6, a small poppet valve 52 arranged next to the contact valve 23 and a contact valve
The lower port 48 of the valve 23 communicates with a gap on the outer periphery of the contact valve 23, and the poppet valve 52 opens and closes a passage 54 to the upper port 53 of the pilot valve 39 for air motor control. The spool 23a of the contact valve 23 has an exhaust passage 23b formed from the outer peripheral surface of the intermediate portion to the bottom surface on the stem 24 side.
At the initial position shown in FIG. 6, the lower port 48, which is the secondary passage, communicates with the atmosphere through the exhaust passage 23b of the spool 23a. As shown in FIGS. 1 and 6, in an initial state in which the trigger valve 8 is in the closed position and the contact nose 12 is lowered, high-pressure air in the air chamber 7 flows from the lower port 47 of the trigger valve 8 to the air. The air is supplied to the lower air chamber through the lower port 46 of the cylinder 13, and pushes the piston 14 to the upper standby position. FIGS. 2 and 7 show a state in which the contact nose 12 is pressed against the surface to be screwed.
The spool 23a of the contact valve 23 is pushed up by the twelve rods 22, and the upper port 50 communicates with the lower port 48, and pressurized air is supplied to the air chamber of the piston control pilot valve 41 through the lower port 48, as shown in FIG. So that the spool of the pilot control pilot valve 41 rises and the upper port
49 and lower port 45 are blocked. At the same time, the pressurized air pushes up the poppet valve 52 through the passage on the outer periphery of the contact valve 23, and the pressurized air is supplied to the air chamber of the air motor control pilot valve 39 through the outlet passage 54,
The spool is kept up to keep the upper port 53 and the lower port 55 shut off. Subsequently, as shown in FIG. 3, when the trigger lever 9 is pulled, the stem 30 of the trigger valve 8 rises to communicate the upper ports 35 and 37 of the trigger valve 8 with the air chamber 7 and the poppet 31 The pressure air acting on the lower surface is exhausted downward from around the stem 30 and the poppet 31 descends,
The air in the lower air chamber of the air cylinder 13 is discharged to the atmosphere through the trigger valve 8. The pressurized air is supplied to the input port 34 of the air motor switching valve 33 through the upper port 35 of the trigger valve 8, and the upper pilot port 36 of the air motor switching valve 33 and the pilot port of the air motor control pilot valve 39. Pilot pressure is applied to 40 and a pilot port 42 of a piston control pilot valve 41. As a result, the spool of the air motor switching valve 33, the spool of the air motor control pilot valve 39, and the spool of the piston control pilot valve 41 are lowered, and the piston is moved from the lower port 48 of the contact valve 23 at the bottom of the cylinder housing 4 to the piston. Pressurized air is supplied to the upper air chamber of the air cylinder 13 through the control pilot valve 41, and the piston 14, the driver bit 15, and the hexagonal shaft 16 start descending. Further, pressure air is supplied to the lower pilot port 38 of the air motor switching valve 33 through the lower port 55 of the air motor control pilot valve 39, the spool 56 of the air motor switching valve 33 rises, and the air motor 19 Is activated, and the piston 14, the driver bit 15 and the hexagonal shaft 16 start rotating. When the air motor 19 starts, the anvil 18, the hexagonal shaft 16, the piston 14, and the driver bit 15 are rotated by the high-speed impact operation of the impact mechanism 17, and the screw is fastened to the screw tightening target. FIG. 4 shows a state in which screw tightening is completed, and the piston 1
4 reaches the lower end of the movable range and pushes down the bumper 57 in the air cylinder 13 and the poppet valve 52 at the bottom. Poppet valve 52
Is lowered, the pilot valve for air motor control
The pressurized air supplied to the lower air chamber of the air motor switching valve 33 through 39 is discharged from the trigger valve 8 through the poppet valve 52 and the lower port 46 of the air cylinder. As a result, the air pressure acting on the lower surface of the spool 56 of the air motor switching valve 33 decreases, the spool 56 descends, the input port 32 of the air motor 19 and the air chamber 7 are cut off, and the air motor 19 stops rotating. When the trigger lever 9 is turned off after the screw tightening is completed, the stem 30 of the trigger valve 8 is lowered to the initial position, pressurized air enters the lower surface of the poppet 31, and the poppet 31 is raised. Pressurized air is supplied to the lower air chamber of the air cylinder 13 through the lower port 47, and the piston 14 rises and returns to the initial position. Next, a case where only the trigger lever 9 is turned on in the initial state shown in FIG. 1 will be described. When the trigger valve 8 is turned on by operating the trigger lever 9, pilot pressure is applied to the upper pilot ports 36, 40, and 42 of the air motor switching valve 33, the air motor control pilot valve 39, and the piston control pilot valve 41, and the air motor control is performed. Pilot valve 39 and piston control pilot valve 41
The respective spools are lowered to the open position. At this time, since the contact valve 23 operated by the contact nose 12 is in the initial state, no compressed air is supplied to the air motor control pilot valve 39 and the piston control pilot valve 41, and the air motor 19 is stopped. Remains. Further, since pressure air is not supplied from the piston control pilot valve 41 to the lower pilot port 38 of the air motor switching valve 33, the spool 56 of the air motor switching valve 33 is lowered by the pilot pressure applied to the upper pilot port 36, and the input of the air motor 19 is reduced. Since the port 32 and the air chamber 7 are shut off, the air motor 19 does not start, so that the start of the air impact driver due to an erroneous operation of the trigger lever can be prevented as in the conventional mechanical safety device. Next, safety measures in the case where the contact nose 12 is once pushed in and then returned to the initial position will be described. When the contact nose shown in FIG. 7 is released from the pressed state and the spool 23a of the contact valve 23 returns to the initial state shown in FIG. 6, the air chamber of the piston control pilot valve 41 and the air motor control pilot valve 39 are returned. The pressure air supplied to the air chamber is discharged to the atmosphere through the exhaust passage 23b of the spool 23a of the contact valve 23.
As a result, even when the trigger lever 9 is operated, the air cylinder 13 and the air motor 19 are not activated, as in the case where only the trigger lever 9 is turned on. On the other hand, unlike the above-mentioned contact valve 23,
The operation in the case where the secondary-side pressure air is not exhausted when the contact valve is turned off will be described with reference to FIGS. Here, the passage is not provided in the spool 62 of the contact valve 61, and when the contact valve 61 is opened from the initial state of FIG. 8 as shown in FIG. 9, the piston is moved in the same manner as the contact valve 23 of FIGS. 6 and 7. Pressurized air is supplied to the air chamber of the control pilot valve 41 and the air chamber of the air motor control pilot valve 39. When the contact nose, which has been pushed once, is released and returned to the initial position, the contact valve 61 is closed as shown in FIG. 10, and the air chamber of the piston control pilot valve 41 and the air motor control are controlled. Air supplied to the air chamber of the pilot valve 39 is not exhausted. Therefore, when the trigger lever is turned on in this state, the piston control pilot valve 41
Then, the air motor control pilot valve 39 and the air motor switching valve 33 are turned on, and the air cylinder 13 and the air motor 19 are activated and the screw is fired.
As shown in (2), when the contact valve 23 is in the off position, the secondary side pressure air is discharged to the atmosphere to eliminate the danger of violence. FIGS. 11 and 14 show another embodiment of the contact valve according to the present invention.
The inner diameter of the lower portion of the cylinder portion 72 is larger than the outer diameter of the spool 73. Therefore, when the spool 73 returns to the initial position, the pressure air remaining in the air chamber of the piston control pilot valve 41 and the air chamber of the air motor control pilot valve 39 is reduced by the lower portion of the cylinder portion 72 and the spool 73. Is discharged to the atmosphere through an exhaust passage in the gap. As shown in FIG. 12, when the contact nose is pushed in and the spool 73 is raised, the lower exhaust passage of the cylinder portion 72 is blocked by the spool 73, and the air chamber of the piston control pilot valve 41 and the air motor control pilot valve 39. Is supplied to the air chamber and the air chamber is activated by a trigger operation. The contact valve 81 shown in FIGS. 13 and 14 has a vent 83 formed in the lower part of the cylinder part 82, and as shown in FIG. 13, when the spool 84 returns to the initial position, The pressure air remaining in the air chamber of the pilot valve 41 and the air chamber of the pilot valve 39 for air motor control is:
It is discharged to the atmosphere through the vent 83. As shown in FIG. 14, the contact nose is pushed in so that the spool 84 is
When it rises higher, the vent 83, the lower port 48, and the outlet passage 54 are shut off, and compressed air is supplied from the upper port 50 to the air chamber of the piston control pilot valve 41 and the air chamber of the air motor control pilot valve 39. Then, it can be activated by the trigger operation. As described above, also in the contact valves 71 and 81 shown in FIGS. 11 to 14, safety is achieved when the contact nose is once pushed in and then returned to the initial position. It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible within the technical scope of the present invention, and it goes without saying that the present invention extends to those modifications. is there. As described above, the safety device for an air impact driver according to the present invention comprises a trigger control valve operated by a trigger lever and a contact control valve slidably operated by a contact nose. The conventional mechanical safety device eliminates the need for a long contact arm from the nose to the trigger lever, making it possible to reduce the width of the air impact driver, which was difficult in the past. It can be used for corners and narrow places. Also, unlike a mechanism in which a relay member such as an arm or a lever is moved by a contact nose, the contact nose operates a valve, so that the stroke of the contact nose is extremely short, and operability and work efficiency are improved. I do. In addition, by disposing the contact nose and the contact valve close to each other, a guide for guiding the connecting member between the contact nose and the contact valve is not required, and the possibility that the guide portion is clogged with gypsum powder and the like and a sliding failure is eliminated. And various other effects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an embodiment of the present invention and showing a standby state of an air impact driver. FIG. 2 is a sectional view showing a state where a contact nose of an air impact driver is turned on. FIG. 3 is a cross-sectional view illustrating a state where a contact nose and a trigger lever of an air impact driver are turned on. FIG. 4 is a cross-sectional view illustrating a state when screw tightening of the air impact driver is completed. FIGS. 5A to 5E are cross-sectional views showing operation steps of the impact mechanism. FIG. 6 is a sectional view of an initial state of the contact valve. FIG. 7 is a cross-sectional view of the ON state of the contact valve. FIG. 8 is a cross-sectional view showing an initial state of a contact valve to which no erroneous start prevention measures are taken. FIG. 9 is a sectional view showing an ON state of the contact valve of FIG. 8; FIG. 10 is a cross-sectional view showing a state where the contact valve in FIG. 8 has returned to an initial state from ON. FIG. 11 shows another embodiment of the present invention, and is a sectional view of an initial state of a contact valve. FIG. 12 is a sectional view showing the ON state of the contact valve of FIG. 11; FIG. 13 shows another embodiment of the present invention, and is a cross-sectional view of an initial state of a contact valve. FIG. 14 is a sectional view showing an ON state of the contact valve of FIG. 13; [Description of Signs] 1 Air Impact Driver 5 Nose 8 Trigger Valve 9 Trigger Lever 12 Contact Nose 13 Air Cylinder 14 Piston 15 Driver Bit 16 Hex Shaft 17 Impact Mechanism 19 Air Motor 22 Rod 23 Contact Valve 23a Spool 33 Air Motor Switching Valve 39 Air Motor Control Pilot valve 41 Piston control pilot valve 52 Poppet valve 71 Contact valve 72 Cylinder 73 Spool 81 Contact valve 82 Cylinder 83 Vent 84 Spool

Claims (1)

Claims 1. A slidable contact nose is attached to a nose of an air impact driver, a contact valve is connected to the contact nose, and air is generated by a trigger valve operated by a trigger lever and the contact valve. A pneumatic logic circuit for controlling the activation control valve of the impact driver, a logic configuration in which the air impact driver is activated when the contact nose is pushed in and the trigger lever is pulled to switch the trigger valve and the contact valve to the ON position. The safety device for an air impact driver, wherein the contact valve is a switching valve in which an outlet on the secondary side communicates with the inlet on the primary side at the ON position and a secondary outlet communicates with the atmosphere at the OFF position.