Trigger valve apparatus for pneumatic tool

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve piston having a valve piston chamber therein for slidably accommodating said plunger and an axial bore into which said plunger is inserted, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an atmosphere via a clearance between said plunger and said axial bore of said valve piston;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve piston;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve piston to open said air passage, thereby allowing compressed air to exit from said valve piston chamber to the atmosphere under a condition where said plunger is engaged with said axial bore of said valve piston,
• wherein said seal member is coupled in an engaging recess of said axial bore of said valve piston,
• wherein said relief passage consists of axially extending and alternately arranged guides and grooves fanned on the cylindrical surface of said plunger, and
• wherein a total cross section of said grooves, formed when said plunger is guided by said seal member provided on said axial bore of said valve piston, defines an effective area of said relief passage.

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve piston having a valve piston chamber therein for slidably accommodating said plunger and an axial bore into which said plunger is inserted, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an atmosphere via a clearance between said plunger and said axial bore of said valve piston;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve piston;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve piston to open said air passage, thereby allowing compressed air to exit from said valve piston chamber to the atmosphere under a condition where said plunger is engaged with said axial bore of said valve piston,
• wherein said seal member is coupled around said plunger and guided along said axial bore of said valve piston, and
• wherein said relief passage consists of axially extending and alternately arranged guides and grooves formed on said axial bore of said valve piston.

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve bush having an axial bore into which said plunger is slidably inserted;
• a valve piston slidably supported by said valve bush to form a valve piston chamber for slidably accommodating said plunger, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an accumulator chamber via a clearance between said plunger and said axial bore of said valve bush;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve bush;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve bush to open said air passage, said relief passage including means for allowing compressed air to enter into said valve piston chamber from said accumulator chamber under a condition where said plunger is engaged with said axial bore of said valve bush.

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve bush having an axial bore into which said plunger is slidably inserted;
• a valve piston slidably supported by said valve bush to form a valve piston chamber for slidably accommodating said plunger, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an accumulator chamber via a clearance between said plunger and said axial bore of said valve bush;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve bush;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve bush to open said air passage, thereby allowing compressed air to enter into said valve piston chamber from said accumulator chamber under a condition where said plunger is engaged with said axial bore of said valve bush,
• wherein said seal member is coupled around said plunger and guided along said axial bore of said valve bush, and
• wherein said relief passage consists of axially extending and alternately arranged guides and grooves formed on said axial bore of said valve bush.

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve bush having an axial bore into which said plunger is slidably inserted;
• a valve piston slidably supported by said valve bush to form a valve piston chamber for slidably accommodating said plunger, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an accumulator chamber via a clearance between said plunger and said axial bore of said valve bush;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve bush;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve bush to open said air passage, thereby allowing compressed air to enter into said valve piston chamber from said accumulator chamber under a condition whore said plunger is engaged with said axial bore of said valve bush,
• wherein said seal member is coupled in an engaging recess of said axial bore of said valve bush,
• wherein said relief passage consists of axially extending and alternately arranged guides and grooves formed on the cylindrical surface of said plunger, and
• wherein a total cross section of said grooves, formed when said plunger is guided by said seal member provided on said axial bore of said valve bush, defines an effective area of said relief passage.

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve piston having a valve piston chamber therein for slidably accommodating said plunger and an axial bore into which said plunger is inserted, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an atmosphere via a clearance between said plunger and said axial bore of said valve piston;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve piston;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve piston to open said air passage, said relief passage provides means for allowing compressed air to exit from said valve piston chamber to the atmosphere under a condition where said valve piston is configured in the top-dead-center position and said plunger is engaged with said axial bore of said valve piston.

A trigger valve apparatus for a pneumatic tool driven by compressed air to drive a nail or similar member, said trigger valve apparatus comprising:

• a plunger shiftable in response to a trigger operation by a user;
• a valve bush having an axial bore into which said plunger is slidably inserted;
• a valve piston slidably supported by said valve hush to form a valve piston chamber for slidably accommodating said plunger, said valve piston being shiftable to control the compressed air supplied to or discharged from said pneumatic tool;
• an air passage connecting said valve piston chamber to an accumulator chamber via a clearance between said plunger and said axial bore of said valve bush;
• a seal member provided to seal said clearance between said plunger and said axial bore of said valve bush;
• and
• a relief passage formed on at least one of said plunger and said axial bore of said valve bush to open said air passage, said relief passage providing means for allowing compressed air to enter into said valve piston chamber from said accumulator chamber under a condition where said valve piston is configured in the top-dead-center position and said plunger is engaged with said axial bore of said valve bush.