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Title: Impact tool
Claims: We claim: 1. A hydraulic impact tool for use in a hydraulic system comprising a pump, hydraulic fluid, and reservoir, said tool comprising: A. a housing defining a cylindrical bore having a central portion of increased section, B. a ram slidable in the housing between stored energy and impact positions. C. an energy storage means for biasing the ram toward the impact position, D. said ram having lift and closure cylindrical pistons secured thereto so that the housing, the ram and the pistons define at least two chambers, one between the pistons having a fixed volume and an expansible volume lift chamber, E. said ram between said pistons having two cylindrical portions of different cross section, F. axially spaced ports comprising: at least one main transfer port opening into said fixed volume chamber, at least one main exhaust port opening to said fixed volume chamber, at least one slid valve exhaust port opening to said fixed volume chamber but closable by said lift piston on said ram, at least one main inlet port opening to said fixed volume chamber, at least one lift chamber transfer port opening into said expansible volume lift chamber, all said main transfer and lift chamber transfer ports being in direct communication, G. a cylindrical valve sleeve positioned within the said fixed volume chamber and movable relative to the ram and housing, 1. said sleeve having a radial end surface having an area A.sub.1, 2. 2. said sleeve having another radial end surface having an area A2 such that the area A.sub.1 is less than the area A.sub.2, 3. said sleeve having transfer means thereon for connecting either the main exhaust port with the main transfer port or the main inlet port with the main transfer port, the aforesaid ram, valve sleeve and axially spaced ports arranged such that the sleeve is carried mechanically in one direction by the lift piston until the surface A.sub.2 enters the main inlet port and thereafter the sleeve is moved relative to the ram by hydraulic pressure and such that the slide is carried mechanically in the other direction until the ram lift piston opens the slide valve exhaust port and thereafter, the valve sleeve is moved relative to the ram by hydraulic pressure. 2. A hydraulic impact tool for use in a hydraulic system comprising a pump, hydraulic fluid, and reservoir, said tool comprising: A. a housing defining a cylindrical bore having a central portion of increased section, B. a ram slidable in the housing between stored energy and impact positions, C. an energy storage means for biasing the ram toward the impact position, D. said ram having lift and closure cylindrical pistons secured thereto so that the housing, the ram and the pistons define three chambers, one between the pistons having a fixed volume, an expansible volume swallow chamber which increases in volume as the ram moves to the impact position, an expansible volume lift chamber that increases in volume as the ram moves to the stored energy position, the combined volume of said lift and swallow chambers being constant for all positions of said ram, E. said ram between said pistons having two cylindrical portions of different cross section, F. axially spaced ports comprising: 1. at least one swallow chamber exhaust port opening to said expansible swallow chamber and said hydraulic reservoir, 2. at least one valve sleeve inlet port opening to the fixed volume chamber, 3. at least one main transfer port opening into said fixed volume chamber, 4. at least one main exhaust port opening to said fixed volume chamber, 5. at least one valve sleeve exhaust port opening to said fixed volume chamber when the ram is approaching or just at the impact position but otherwise sealed by the ram, 6. at least one main inlet port opening to said fixed volume chamber, 7. at least one lift chamber transfer port opening into said expansible volume lift chamber, said main transfer and lift chamber transfer ports being in direct communication, G. a cylindrical valve sleeve positioned within the said fixed volume chamber, 1. said sleeve having a portion of reduced thickness arranged to slide between the cylindrical bore and the portion of the ram having a larger section, said portion terminating with a radial end surface having an area A.sub.1, 2. said sleeve having another portion for sliding between the cylindrical bore and the portion of the ram having the smaller section, said portion terminating with a radial end surface having an area A.sub.2 such that the area A.sub.1 is less than the area A.sub.2, 3. said sleeve having transfer means thereon for connecting either the main exhaust port with the main transfer port or the main inlet port with the main transfer port, the aforesaid ram, valve sleeve and axially spaced ports arranged such that the valve sleeve is carried mechanically toward the stored energy position by the lift piston until the surface A.sub.2 communicates with the main inlet port and thereafter the sleeve is moved relative to the ram by hydraulic pressure to connect the main transfer port with the main exhaust port enabling rapid transfer of hydraulic fluid from the expansible volume lift chamber to the expansible volume chamber which in turn enables the energy storage means to accelerate the ram toward the impact position, and such that the sleeve is carried mechanically toward the impact position by the closure piston until the ram opens the valve sleeve exhaust port and thereafter, the sleeve is moved relative to the ram by hydraulic pressure to connect the main transfer port to the main inlet port thereby connecting the pump pressure to the expansible volume lift chamber to cushion the movement of the ram past the impact position and to initiate the movement of the ram toward the stored energy position. 3. A hydraulic impact tool for use in a hydraulic system comprising a pump, hydraulic fluid, and reservoir, said tool comprising: A. a housing defining a cylindrical bore having a central portion of increased section, B. a ram slidable in the housing between stored energy and impact positions, C. an energy storage means for biasing the ram toward the impact position, D. said ram having lift and closure cylindrical pistons secured thereto so that the housing, the ram and the pistons define three chambers, one between the pistons having a fixed volume, an expansible volume swallow chamber adjacent the closure piston which increases in volume as the ram moves to the impact position, an expansible volume lift chamber adjacent the lift piston that increases in volume as the ram moves to the stored energy position, the combined volume of said lift and swallow chambers being constant for all positions of said ram, E. said ram between said pistons having two cylindrical portions of different cross section, the larger section being near the closure piston, F. seven axially spaced ports comprising: 1. at least one swallow chamber exhaust port opening to said expansible swallow chamber and the hydraulic reservoir, 2. at least one valve sleeve inlet port opening to the fixed volume chamber in the vicinity of the closure piston, 3. at least one main transfer port opening centrally into said fixed volume chamber, 4. at least one main exhaust port opening to said fixed volume chamber axially between said valve sleeve inlet port and said main transfer port, 5. at least one valve sleeve exhaust port opening to said fixed volume chamber when the ram is approaching or just at the impact position but otherwise sealed by said lift piston, 6. at least one main inlet port opening to said fixed volume chamber axially between said main transfer port and said valve sleeve outlet port, 7. at least one lift chamber transfer port opening into said expansible volume lift chamber, said transfer and main lift chamber transfer ports being in direct communication, G. a cylindrical valve sleeve positioned within the said fixed volume chamber, 1. said sleeve having a portion of reduced thickness arranged to slide between the cylindrical bore and the portion of the ram having a larger section, said portion of the sleeve terminating with a radial end surface having an area A.sub.1, 2. said sleeve having another portion for sliding between the cylindrical bore and the portion of the ram having the smaller section, said portion of the sleeve terminating with a radial end surface having an area A.sub.2 such that the area A.sub.1 is less than the area A.sub.2, 3. said sleeve having transfer means thereon for connecting either the main exhaust port with the main transfer port or the main inlet port with the main transfer port, the aforesaid ram, valve sleeve and ports ports arranged such that the sleeve is carried mechanically toward the stored energy position by the lift piston until the surface A.sub.2 enters the main inlet port and thereafter the sleeve is moved relative to the ram by hydraulic pressure to connect the main transfer port with the main exhaust port enabling rapid transfer of hydraulic fluid from the expansible volume lift chamber to the expansible volume swallow chamber which in turn enables the energy storage means to accelerate the ram toward the impact position, such that the sleeve is carried mechanically toward the impact position by the closure piston until the lift piston opens the valve sleeve exhaust port and thereafter the sleeve is moved relative to the ram by hydraulic pressure to connect the main transfer port to the main inlet port thereby connecting pump pressure to the expansible volume lift chamber to cushion the movement of the ram past the impact position and to initiate the movement of the ram toward the stored energy position. 4. A hydraulic impact tool for use in a hydraulic system including a pump, hydraulic fluid and reservoir comprising: A. a housing defining a cylindrical bore having a central portion of increased diameter forming a cylinder, B. a ram including piston surfaces slidable in the housing, A lift chamber formed by the ram and housing, C. means at one end of said bore to store energy as the ram is moved thereto, D. means at the other end of said bore to be impacted by said ram, E. a hollow cylindrical valve sleeve in the cylinder moveable relative to the ram and housing, the valve sleeve having an end of small area constantly in communication with the hydraulic pump pressure and an end of larger area which may be brought into communication alternately with either pump pressure or the reservoir, F. inlet, outlet and transfer porting which cooperate with the valve sleeve to direct the hydraulic fluid from the pump to the lift chamber to move the ram to the stored energy position and to release fluid from the lift chamber to permit the ram to accelerate toward the impact position, the aforesaid ram, valve sleeve and porting arranged such that the ram carries the valve sleeve mechanically in one direction until the large area end of the sleeve is in communication with pump pressure at which time the sleeve is hydraulically actuated in the direction in which it was being mechanically carried and such that the ram carries the valve sleeve mechanically in the other direction until the large area end of the sleeve is in communication with the reservoir at which time the sleeve is hydraulically actuated in the direction in which it was being mechanically carried. Other info: Inventors: Barthe, Henry P. (Pittsburgh, PA, US) Schroeder, John S. (Sewickley, PA, US) Application Number: 561419 Filing Date: 1975-03-24 Publication_date: 1977-03-15 Assignee: Schroeder Brothers Corporation (Pittsburgh, PA) Primary Class(es): 91/286 91/165, 91/320, 91/328, 91/329, 92/134 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Maslousky, Paul E. Assistant Examiner: Attorney: Webb, Bunden, Robinson & Webb |
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