Impact tools

Claim 2

An impact tool for generating percussive forces, said tool comprising: a housing have a bore, a piston disposed for oscillatory movement in said bore over a forward stroke toward and over a return stroke away from an impact position during each cycle of oscillation of said piston, said piston having faces which define the end boundaries of first and second variable column cavities in said bore, the volumes of which vary in opposite senses when said piston moves in said bore, the area of the one of said faces which defines said first cavity being greater than the area of the other of said faces which defines said second cavity, means in said housing whereby pressurized fluid is supplied thereto and returned therefrom, a valve mechanism associated with said first cavity having ports in said first cavity spaced from each other axially with respect to said bore and respectively in communication with said supply and said return of said last-named means, a valve element in said first cavity extending axially between said ports and movable with said piston for closing said supply port and opening said return port after displacement of said piston over a first predetermined distance in one direction during said forward stroke and for opening said supply port and closing said return port after displacement of said piston over a second predetermined distance in the opposite direction during said return stroke, said second predetermined displacement being substantially less than said return stroke whereby said return port is open for a shorter period of time than said supply port is open during each said cycle, and means in said housing providing communication between said supply and said second cavity for applying forces to said other piston face to drive it in a direction away from said impact position when said valve element opens said return port and closes said supply port.

Claim 3

The invention as set forth in claim 1 wherein said piston has a section of cross-sectional shape and size substantially equal to the cross-sectional shape and size of said bore, said faces being opposite ends of said piston section, said other of said faces being closer to said impact position than said one face.

Claim 4

The invention as set forth in claim 2 further comprising a shank in said bore presenting an impace surface to one end of said piston.

Claim 5

The invention as set forth in claim 1 wherein said valve element is a tubular member coaxial with said bore and encompassing said piston and is slidable along said bore across said ports, projections extending from one of said tubular member and said piston for directly engaging applying force to said tubular member for moving said tubular member.

Claim 6

The invention as set forth in claim 4 wherein said cavities are generally cylindrical chambers provided in said housing, and said ports are separate peripheral grooves in said chamber for said first cavity which are opened and closed by porting edges of said tubular member.

Claim 7

The invention as set forth in claim 1 including energy storage means associated with said second cavity and with said first cavity when said supply port is open.

Claim 8

The invention as set forth in claim 6 wherein said energy storage means is an accumulator.

Claim 9

The invention as set forth in claim 7 wherein said fluid is a hydraulic fluid and said accumulator has a fluid filled region and an adjoining region filled with a confined gas, said regions being separated by a yieldable member, said fluid filled region being in communication with said second cavity and said first cavity when saId supply port is open.

Claim 10

The invention as set forth in claim 7 including a second accumulator associated with said first cavity when said return port is open, and passage means in said housing presenting low inertance to the flow of said fluid between said second accumulator and said first cavity when said valve element closes said supply port and opens said return port.

Claim 11

The invention as set forth in claim 6 including a gallery in said housing encompassing said bore and spaced outwardly therefrom, said gallery extending between said supply port and said second cavity and being in communication therewith and with an accumulator which provides said energy storage means.

Claim 12

An impact tool for applying percussive forces to a load, said tool comprising a housing having a bore therein, a piston mounted in said bore for oscillatory movement axially of said bore in a first direction toward said load and in a second direction away from said load, said piston having a section having first and second faces at opposite ends of said section, said first face facing away from said load and defining the end boundary of a first cavity in said bore, said second face facing toward said load and defining the end boundary of a second cavity in said bore, the volumes of said cavities changing in opposite sense with movement of said piston in either of said directions, said first face being larger in area than said second face, pressurized hydraulic fluid supply and return passages in said housing, said second cavity being in communication with the supply passage for filling said second cavity with pressurized fluid which exerts force on said second face in the direction away from said load, a valve mechanism in said first cavity including a sleeve slidably mounted in said bore for movement axially thereof, means providing for moving said sleeve with said piston during final portions of its displacement in said first direction and during final portions of its displacement in said second direction for respectively communicating said first cavity with said return passage for causing said forces applied to said second face to move said piston in the direction away from said load and with said supply passage for applying forces to said first face in the direction toward said load, said final portion of said displacement in said second direction being a substantial portion of said displacement in said second direction, fluid energy storage means, and means communicating said energy storage means with said second cavity, with said supply means and also with said first cavity, when said valve mechanism communicates said supply with said first cavity, and for storing energy in said storage means when said piston is moving away from said load, thereby to bring said piston movement to a stop, said energy being returned to said piston as said piston accelerates back in the direction toward said load for applying said percussive forces thereto, said communicating means also providing an unrestricted passage for the exchange of fluid between said first and second cavities for reducing fluctuations in flow with respect to said storage means.

Claim 13

An impact tool for applying percussive forces to a load, said tool comprising a housing having a bore therein, a piston mounted in said bore for oscillatory movement axially of said bore in a first direction toward said load and in a second direction away from said load, said piston having a section having first and second faces at opposite ends of said section, said first face facing away from said load and defining the end boundary of a first cavity in said bore, said second face facing toward said load and defining the end boundary of a second cavity in said bore, the volumes of said cavities changing in opposite sense with movement of said piston in either of said directions, said first face being larger in area than said second face, pressurized hydraulic fluid supply and return passages in said housing, said second cavity being in communication with the supply passage for filling said second cavity with pressurized fluid which exerts force on said second face in the direction away from said load, a valve mechanism in said first cavity including a sleeve slidably mounted in said bore for movement axially thereof, means providing for moving said sleeve with said piston during final portions of its displacement in said first direction and during final portions of its displacement in said second direction for respectively communicating said first cavity with said return passage for causing said forces applied to said second face to move said piston in the direction away from said load and with said supply passage for applying forces to said first face in the direction toward said load, said final portion of said displacement in said second direction being a substantial portion of said displacement in said second direction, fluid energy storage means, and means communicating said energy storage means with said second cavity, with said supply means and also with said first cavity, when said valve mechanism communicates said supply with said first cavity, and for storing energy in said storage means when said piston is moving away from said load, thereby to bring said piston movement to a stop, said energy being returned to said piston as said piston accelerates back in the direction toward said load for applying said percussive forces thereto, said communicating means also providing an unrestricted passage for the exchange of fluid between said first and second cavities for reducing fluctuations in flow with respect to said storage means.