초록 ▼

Disclosed is a safety system for use in a pneumatic impact tool for driving a fastener, for preventing accident or injury to personal body. Particularly, the injury to personal body, which often occurs at the instant of connection of the tool to a compressed air source, is completely eliminated. The

Disclosed is a safety system for use in a pneumatic impact tool for driving a fastener, for preventing accident or injury to personal body. Particularly, the injury to personal body, which often occurs at the instant of connection of the tool to a compressed air source, is completely eliminated. The safety system is automatically turned into operative state when the tool is disconnected from the compressed air source, and the fastener driving work cannot be started unless the safety system is turned into inoperative state by a manual operation.

대표청구항 ▼

1. In a safety system incorporated in a pneumatic impact tool, the tool having an impact cylinder accomodating an impact piston to which rigidly connected is a driver for directly impacting a fastener, said impact piston defining in said impact cylinder an upper chamber of the impact cylinder at the

1. In a safety system incorporated in a pneumatic impact tool, the tool having an impact cylinder accomodating an impact piston to which rigidly connected is a driver for directly impacting a fastener, said impact piston defining in said impact cylinder an upper chamber of the impact cylinder at the same side as the top dead center of said impact piston; a compressed air storage chamber adapted to be charged with compressed air when it is connected to a compressed air source and to discharge the same when it is disconnected from the compressed air source; a differential pressure type head valve having a head valve cylinder and a head valve piston accomodated by the latter, said head valve piston being adapted to interrupt, when it takes the bottom dead center, a communication between said upper chamber of the impact cylinder and said compressed air storage chamber, and to establish said communication when it moves from said bottom dead center to the top dead center; and a control air passage interconnecting said compressed air storage chamber and a control chamber of said head valve, said control air passage having a manual trigger valve adapted to change the air pressure in said control air passage to cause a movement of said head valve piston between said top and bottom dead centers; the improvement comprising: a first control air passage and a second control air passage constituting said control air passage, said first control air passage always communicating with said control chamber, said second control passage having said trigger valve and adapted to be communicated with said compressed air storage chamber when said trigger valve 15 is not manually operated; and a self-holding type safety valve having a safety valve cylinder (13, 56 or 73) accomodating a valve spring (42, 65a or 100) and a safety valve piston (27, 57 or 74) provided with a manually operable stem (34, 68a or 88), said safety valve (25, 55 or 72) having a mis-discharge prevention air introduction port (32, 60 or 77) always communicating with said compressed air storage chamber (7) and adapted to prevent mis-discharge of said impact piston (4), a first connection port (31, 59 or 77) always communicating with said first control air passage (12), and a second connection port (30, 58 or 75) always communicating with said second control air passage (14), wherein, when said compressed air storage chamber (7) is disconnected from said compressed air source, said safety valve piston (27, 57 or 74) is moved, by the resetting force of said valve spring (42, 65a or 100), to the operative position of said safety system in which said mis-discharge prevention air introduction port (32, 60 or 77) is communicated with said first connection port (31, 59 or 76) and, at the same time, said first connection port (31, 59 or 76) is interrupted in communication with said second connection port (30, 58 or 75), and, also when said compressed air storage chamber (7) is brought into connection with said compressed air source, safety valve piston (27, 57 or 74) is still maintained at said operative position of safety system, due to the differential force between the resetting force of said valve spring (42, 65a or 100) and the total pressure of compressed air introduced into said safety valve cylinder (13, 56 or 73) through said mis-discharge prevention air introduction port (32, 60 or 77) and through said second connection port (30, 58 or 75) to act on said safety valve piston (25, 57 or 74) and further, when said manually operable stem (34, 68a or 88) is operated, said safety valve piston (27, 57 or 74) is moved to and self-held at inoperative position of said safety system in which the communication between said mis-discharge prevention air introduction port (32, 60 or 88) and said first connection port (31, 59 or 76) is interrupted and the communication between said first connection port (31, 59 or 76) and said second connection port (30, 58 or 75) is completed. 2. A safety system as claimed in claim 1, wherein said manually operable stem (34) has a reduced diameter portion (45) for locking purpose defined by shoulders (46 and 47), said manually operable stem (34) being adapted to be engaged by a lock mechanism (43) including a lock cylinder (29), a lock piston (49) accomodated by said lock cylinder (29) and slidable in the transverse direction of said manually operable stem (34), a manually operable unlocking stem (54) rigidly connected to said lock piston (49) and a spring 54a adapted to bias said lock piston (49) either to the top or bottom dead center of the lock piston (49), said lock piston (49) having a retaining opening (48) adapted to freely pass said manually operable stem (34) and having a diameter slightly greater than that of said manually operable stem (34), said lock cylinder (29) having a self-holding air introduction port (33) always communicating with said compressed air storage chamber (7) and adapted to supply compressed air acting in the direction opposite to the biasing force of said spring (54a), whereby, when said safety valve piston (27) takes said inoperative position of said safety system, said lock piston (49) is moved, by the compressed air introduced into said lock cylinder (29) through said self-holding air introduction port (33), overcoming the force of said spring (54 a) of said lock mechanism (43), thereby to bring the opening lower edge (52) or the opening upper edge (51) of said retaining opening (48) into engagement with said reduced diameter portion (45) thereby to lock said safety valve piston (27) at the inoperative position of said safety system, while, when said compressed air storage chamber (7) is disconnected from said compressed air source, said opening lower edge (52) or opening upper edge (51) of said retaining opening (48) is disengaged from said reduced diameter portion (45) due to the resetting force of said spring (54a) of said lock mechanism (43). 3. A safety system as claimed in claim 1, wherein said safety valve piston (57) has a large diameter piston (65) and a small diameter piston (64) interconnected and spaced at a certain distance by a connecting stem (68), and "O" ring (69) being fitted to the side (65b) of said large diameter piston (65) confronting the top dead center of said safety valve piston (57), said safety valve cylinder (56) being provided at its intermediate portion with an intermediate valve seat (61) having one surface (61a) confronting the top dead center of said safety valve piston (57) and the other surface (61b) confronting the bottom dead center of the same, said large diameter piston (65) and said "O" ring (69) being positioned at the same side as said other side (61b) of said intermediate valve seat (61), said small diameter piston (64), said mis-discharge prevention air introduction port (60), said first connection port (59) and said second connection port (58) being positioned at the same side as said one surface (61a) of said intermediate valve seat (61), said "O" ring (69) being adapted to be brought into and out of contact with said other side (61b) of said valve seat (61) in accordance with the movement of said safety valve piston (57). 4. A safety valve system as claimed in claim 1, wherein said safety valve piston (74) has a large diameter piston (83) adapted to divide the space in said safety valve cylinder (73), said manually operable stem (88) having a small diameter stem (88a) connected at its one end to said large diameter piston (83) and a large diameter stem (88b) connected to the other end of said small diameter stem (88a), said safety valve cylinder (73) further having an opening (89) adapted to be communicated with or incommunicative to the atmosphere in accordance with the movement of said manually operable stem (88) in said opening (89), and a self-holding air introduction port (78), an "O" ring (90) being fitted to the inner wall of said opening (89), said "O" ring (190) being adapted to cooperate with said manually operable stem (80) in establishing and interrupting communication between the atmosphere and a top chamber (98a) which is defined by said large diameter piston (73) and positioned at the same side as the top dead center of said safety valve piston (74) corresponding to said operative position of said safety system, whereby, when said safety valve piston (74) is in said inoperative position of said safety system, said top chamber (98a) is sealed against the atmosphere due to mutual engagement of said "O" ring (90) and said large diameter stem (88b), so that compressed air supplied through said self-holding air introduction port (78) to said top chamber (98a) acts to hold said safety valve piston (74) in said inoperative position of said safety system overcoming the force which is the sum of the force of compressed air supplied through said first connection port (76), mis-discharge prevention air introduction port (77) and second connection port (75), and the force of said valve spring (96). 5. A safety system as claimed in claim 4, wherein an exhaust valve (80) is disposed between the atmosphere and said top chamber (98a), said exhaust valve (80) being adapted to be operated manually independently of said opening (89) to establish the communication between said top chamber (98a) and the atmosphere, the amount of air discharged to the atmosphere through said exhaust valve (80) being set to be greater than that of compressed air supplied to said top chamber (98a) through said self-holding air introduction port (78), and wherein, when said top chamber (98a) is brought into communication with the atmosphere through said exhaust valve (80), said safety valve piston (83) commences its movement to said operative position of said safety system due to a pressure drop in said top chamber (98a), the movement of said safety valve piston (83) being continued because of the disengagement of said large diameter stem (88b) from said "O" ring (90), said safety valve piston (83) then being held at said operative position of said safety system because of the force of compressed air supplied into said safety valve cylinder (73) via said mis-discharge prevention air introduction port (77) and the force of said valve spring (96) acting on the safety valve piston (83). 6. In a safety system incorporated in a pneumatic impact tool, the tool having an impact cylinder accomodating an impact piston to which rigidly connected is a driver for directly impacting a fastener, said impact piston defining in said impact cylinder an upper chamber of the impact cylinder at the same side as the top dead center of said impact piston; a compressed air storage chamber adapted to be charged with compressed air when it is connected to a compressed air source and to discharge the same when it is disconnected from said compressed air source; a differential pressure type head valve having a head valve cylinder and a head valve piston accomodated by the latter, said head valve piston being adapted to interrupt, when it takes the bottom dead center, a communication between said upper chamber of the impact cylinder and said compressed air storage chamber, and to establish said communication when it moves from said bottom dead center to the top dead center; and a control air passage interconnecting said compressed air storage chamber and a control chamber of said head valve, said control air passage having a manual trigger valve adapted to change the air pressure in said control air passage to cause a movement of said head valve piston between said top and bottom dead centers; the improvement comprising: a safety cylinder device (101 or 121) disposed in the vicinity of said head valve (8), said safety cylinder device (101 or 121) including a safety cylinder (102 or 122) and a safety plunger (103) or safety piston (123) accomodated by said safety cylinder (102 or 122), said safety plunger (103) or safety piston (123) having a lock stem (105 or 125) which can move into and out of said control chamber (11) and adapted to make contact with the top face (10c) of said head valve piston (10) resting at the bottom dead center thereby to prevent said head valve piston (10) from moving toward the top dead center, as well as a manually operable stem (107 or 128), said safety cylinder device (101 or 121) further including a spring (120 or 127) adapted to reset said safety plunger (103) or said safety piston (123) to the operative position of said safety system in which said lock stem (105 or 125) is projected into said control chamber (11), and a self-holding air introduction port (115 or 138) for supplying compressed air for holding said safety plunger (103) or safety piston (123) at said inoperative position of said safety system in which said lock stem (105 or 125) is retracted from said control chamber (11), said self-holding air introduction port (115 or 138) being always communicated with said compressed air storage chamber (7); whereby, when said compressed air storage chamber (7) is disconnected from said compressed air source, said safety plunger (103) or said safety piston (123) is moved to said inoperative position of said safety system due to the resetting force of said spring (120 or 127), while, when said compression air storage chamber (7) is connected to said compressed air source, said safety plunger (103) or said safety piston (123) is still held at said operative position of said safety system due to the resetting force of said spring (120 or 127) and further, when said safety plunger (103) or said safety piston (123) is moved to said operative position of said safety system by means of said manually operable stem (107 or 128), said safety plunger (103) or said safety piston (123) is maintained at said operative position by the force of compressed air supplied through said self-holding air introduction port (115 of 138). 7. A safety system as claimed in claim 6, wherein said manually operable stem (107) is provided with a reduced diameter portion (108) for locking purpose demarked from other portion by both shoulders (110 and 111), said manually operable stem (107) being adapted to be engaged by a lock mechanism (104) including a lock cylinder (116), lock piston (113) accomodated by said lock cylinder (116) and slidable transversely of said manually operable stem (107), manually operable unlocking stem (118) rigidly connected to said lock piston (113) and a spring (119) adapted to bias said lock piston (113) toward either the bottom or top dead center of said lock piston (113), said lock piston (113) being provided with a retaining opening (112) adapted to freely pass said manually operable stem (107) and said retaining opening (112) having a diameter slightly larger than that of said lock piston (113), said self-holding air introduction port (115) being provided in said lock cylinder (113) so as to apply said compressed air to said lock piston (113) in the direction opposite to the force of said spring (119) of said lock mechanism (104), whereby, when said safety piston (123) is held stationary at said inoperative position of the safety system, said lock piston (113) is moved by the compressed air supplied to said lock cylinder (116), through said self-holding air introduction port (115) overcoming the resetting force of said spring (119) of said lock mechanism (104) thereby to bring the opening lower edge (112b) or opening upper edge (112a) of said retaining opening (112) into engagement with said reduced diameter portion (108) to lock said safety piston (123) in said inoperative position of said safety system, and, when said compressed air storage chamber (7) is disconnected from said compressed air source, said opening lower edge (112b) or opening upper edge (112a) of said retaining opening (112) is disengaged from said reduced diameter portion (108) due to the resetting force of said spring (119) of said lock mechanism (104). 8. A safety system as claimed in claim 6, wherein said manually operable stem (128) is provided with a reduced diameter portion (129) for locking purpose demarked from other portions of said manually operable stem (128) by both shoulders (131 and 132), said manually operable stem (128) being adapted to be engaged by a lock mechanism (124) including a lock cylinder (116), a lock plunger (134) accomodated by said lock cylinder (116) and slidable in the transverse direction of said manually operable stem (128) and a spring (136) adapted to bias said lock plunger (134) either toward the bottom or top dead center, said lock plunger (134) having a retaining opening (133) adapted to be freely pass said manually operable stem (128) and said retaining opening (133) having a diameter somewhat greater than that of said manually operable stem (128), said self-holding air introduction port (138) being formed in said safety cylinder (122) so as to apply a force to said safety piston (123) in the direction opposite to the force of said spring (127) in said safety cylinder (122), whereby, when said safety piston (123) is in the inoperative position of said safety system, the compressed air supplied into said safety cylinder (122) through said self-holding air introduction port (138) holds said safety piston (123) in said inoperative position of said safety system, overcoming the resetting force of said spring (127) in said safety cylinder (122), so that, when said compressed air storage chamber (7) is disconnected from said compressed air source, the opeing lower edge (112b) or opening upper edge (112a) of said retaining opening (133) is brought into engagement with said reduced diameter portion (129) by the resetting force to said spring (127 and 136).