Fastener driving tool with improved piston return

Claim 2

A gas-operated fastener driving tool comprising: a housing adapted to contain gas under pressure; a cylinder disposed within said housing and defining with said housing a chamber adapted to receive gas under pressure; a piston slidably mounted within said cylinder and provided with a fastener driver on one side thereof facing one end of said cylinder, said cylinder defining spaced first and second ports communicating with said chamber, with said first port Being located immediately adjacent said one end of said cylinder and in communication with the driver side of said piston; valve means for controlling the introduction and exhaust of pressurized gas to and from said cylinder above said piston, said piston in response to said pressurized gas being driven from a retracted position at the other end of said cylinder to a driven position at said one end of said cylinder, said piston defining a first passageway communicating with said driving pressurized gas and positioned so that said driving gas is transmitted through said second port and into said chamber when said piston is in said driven position; and first check valve means on said piston for controlling said first passageway to prevent said gas in said chamber from returning into said passageway, whereby when said piston is in said driven position and pressurized gas moves into said chamber, said gas is constrained to move through said first port into said cylinder at said one end thereof, and upon the exhaust of said driving pressurized gas from above said piston, to act on said one side of said piston to return said piston to the retracted position; and said piston further provided with a second passageway communicating with said one side of said piston to release said pressurized gas from said one side of said piston to said other side of said piston when said piston is restored to said retracted position; and second check valve means on said piston for controlling said second passageway to prevent pressurized gas from flowing into said second passageway from said other side of said piston during the driving action.

Claim 3

A fastener tool as in claim 1, in which said first passageway opens at one end thereof on the periphery of the piston between said sides thereof.

Claim 4

A fastener tool as in claim 2, in which said first check valve is comprised of a groove about the periphery of said piston intersecting the opening of said first passageway together with an O-ring carried within said groove, said groove being enlarged whereby said O-ring moves away from the said passageway opening upon the arrival of the piston at the driven position to permit pressurized gas to flow into said chamber.

Claim 5

A fastener tool as in claim 1, in which said cylinder is enlarged in diameter at said other end thereof so as to define with a portion of said piston an annular space therebetween when said piston is in said retracted position, and in which said second passageway communicates with said annular space when said piston arrives at said retracted position to release said pressurized gas from said one piston side into said space.

Claim 6

A fastener tool as in claim 4, in which said second check valve is comprised of a groove about the periphery of said piston together with an O-ring carried within said groove and bearing against said cylinder, said groove intersecting one end of said second passageway and positioned adjacent said other side of said piston, said O-ring expanding into said annular space upon the restoration of said piston to said retracted position to release said pressurized gas from said one piston side.

Claim 7

A fastener tool as in claim 1, which further includes means for frictionally supporting said piston within said cylinder to restrain said piston from moving unless positively acted upon by pressurized gas.

Claim 8

A gas-operated fastener driving tool, comprising: a housing adapted to contain gas under pressure; an upstanding cylinder disposed within said housing and defining with said housing a chamber adapted to receive gas under pressure, said cylinder defining spaced first and second ports communicating with said chamber, with said first port being located immediately adjacent the lower end of said cylinder; a piston slidably mounted within said cylinder and provided with a fastener driver on the lower side thereof facing said lower cylinder end; valve means for controlling the introduction and exhaust of pressurized gas to and from said cylinder above said piSton, said piston in response to said pressurized gas being driven on the upper side thereof from a retracted position at the upper end of said cylinder to a driven position at said lower end of said cylinder, said piston defining a first passageway communicating with said driving pressurized gas and extending transversely across said piston to a first opening on the periphery of said piston between said upper and lower sides thereof, said opening being spaced from said lower side of said piston a lesser distance than the spacing between said first and second ports; bumper means associated with said lower cylinder end for stopping said piston at said driven position, said means being of a height such that said first passageway is at substantially the same level within the cylinder as said second port when said piston is stopped by said bumper means, said driving fluid thereupon flowing into said storage chamber; first check valve means on said piston for controlling said first passageway to prevent said gas in said chamber from returning into said passageway, whereby when said piston is in said driven position and pressurized gas moves into said chamber, said gas is constrained to move through said first port into said cylinder at said lower end thereof and upon the exhaust of said driving pressurized gas from above said piston to act on said lower side of said piston to return said piston to the retracted position; said cylinder being enlarged in diameter at the upper end thereof so as to define with a portion of said piston an annular space therebetween when said piston is in said retracted position, and said piston provided with a second passageway extending from said lower side thereof to a second opening on the periphery of said piston adjacent said piston upper side, said second opening being spaced from said piston upper side a lesser distance than the depth of said enlarged cylinder upper end; and second check valve means on said piston for controlling said second passageway to prevent pressurized gas from flowing into said second passageway from the upper side of said piston during the driving action, said second passageway communicating with said annular space when said piston is returned to said retracted position, whereby said pressurized gas acting on said lower side of said piston is exhausted.

Claim 9

A gas-operated fastener driving tool, comprising: a housing adapted to contain gas under pressure; an upstanding cylinder disposed within said housing and defining with said housing a chamber adapted to receive gas under pressure, said cylinder defining spaced first and second ports communicating with said chamber, with said first port being located immediately adjacent the lower end of said cylinder; a piston slidably mounted within said cylinder and provided with a fastener driver on the lower side thereof facing said lower cylinder end; valve means for controlling the introduction and exhaust of pressurized gas to and from said cylinder above said piSton, said piston in response to said pressurized gas being driven on the upper side thereof from a retracted position at the upper end of said cylinder to a driven position at said lower end of said cylinder, said piston defining a first passageway communicating with said driving pressurized gas and extending transversely across said piston to a first opening on the periphery of said piston between said upper and lower sides thereof, said opening being spaced from said lower side of said piston a lesser distance than the spacing between said first and second ports; bumper means associated with said lower cylinder end for stopping said piston at said driven position, said means being of a height such that said first passageway is at substantially the same level within the cylinder as said second port when said piston is stopped by said bumper means, said driving fluid thereupon flowing into said storage chamber; first check valve means on said piston for controlling said first passageway to prevent said gas in said chamber from returning into said passageway, whereby when said piston is in said driven position and pressurized gas moves into said chamber, said gas is constrained to move through said first port into said cylinder at said lower end thereof and upon the exhaust of said driving pressurized gas from above said piston to act on said lower side of said piston to return said piston to the retracted position; said cylinder being enlarged in diameter at the upper end thereof so as to define with a portion of said piston an annular space therebetween when said piston is in said retracted position, and said piston provided with a second passageway extending from said lower side thereof to a second opening on the periphery of said piston adjacent said piston upper side, said second opening being spaced from said piston upper side a lesser distance than the depth of said enlarged cylinder upper end; and second check valve means on said piston for controlling said second passageway to prevent pressurized gas from flowing into said second passageway from the upper side of said piston during the driving action, said second passageway communicating with said annular space when said piston is returned to said retracted position, whereby said pressurized gas acting on said lower side of said piston is exhausted.