Hydraulically powered impact device

A hydraulic impact device comprising

• a cylinder having lower and upper gland portions defining the ends of a cylinder bore,
• a hammer member reciprocally disposed in the cylinder bore having lower and upper rod portions sealingly received in the lower and upper gland portions respectively and including a piston portion disposed in the cylinder bore having a diameter significantly less than that of the cylinder bore to permit fluid to bypass the piston within the cylinder,
• a sleeve valve reciprocally disposed in the cylinder bore above the piston portion for sealingly engaging the upper surface of the piston portion and dividing the cylinder bore into a lower high pressure chamber and an upper low pressure chamber,
• hydraulic port means for applying high pressure fluid to the high pressure chamber and for exhausting fluid from the low pressure chamber,
• the sleeve valve being totally exposed only to said high pressure fluid and exhaust pressure fluid and having effective hydraulic areas exposed only to said high pressure and said low pressure such that hydraulic fluid continually biases the sleeve valve toward the piston portion to tend to maintain sealing engagement between the sleeve valve and the piston portion to thereby divide the cylinder into high and low pressure chambers,
• means for separating the sleeve valve from the piston portion when the sleeve valve has reached a predetermined position of its stroke toward the upper gland to allow high pressure fluid to bypass the piston within the cylinder from the high pressure chamber to the low pressure chamber,
• energy storage means engaging one of the rod portions which is charged with energy by upward movement of the hammer member for rapidly driving the hammer member downwardly when the sleeve valve is separated from the piston portion to allow high pressure fluid in the high pressure chamber to bypass the piston to the low pressure chamber.

A hydraulic impact device comprising

• a cylinder member having a lower gland portion, a center portion having a stepped bore with an upper section having a diameter less than a lower section, and an upper gland portion,
• a hammer member reciprocally disposed in the cylinder having lower and upper shaft portions slidably and sealingly received in the lower and upper gland portions, respectively, and a piston portion disposed generally in the center portion, the piston portion having a diameter less than the maximum diameter of the stepped bore to permit fluid to bypass the piston within the bore and permit the hammer member to be driven downwardly by an external biasing force,
• a sleeve valve reciprocally disposed within the cylinder member around the upper shaft portion, the sleeve valve having a first peripheral seal with the upper section of the stepped bore and a second peripheral seal with the lower section of the stepped bore to form an annular cavity between the first and second peripheral seals, the sleeve valve and the cylinder member, and a first annular seal with the upper face of the piston section, the effective diameter of the first annular seal being less than the diameter of the lower section of the stepped bore and greater than the diameter of the upper section of the stepped bore,
• high pressure port means continually communicating with the interior of the cylinder below the second peripheral seal and with the annular cavity formed by the first and second peripheral seal means, the sleeve valve, and the cylinder member,
• low pressure port means communicating with the interior of the sleeve valve between the first peripheral seal and the first annular seal, and
• means for reversing the balance of hydraulic forces acting on the sleeve valve for separating the sleeve valve from the piston portion at the top of the stroke of the piston to break the first annular seal and bypass fluid around the piston portion and within the bore to allow the piston portion to be driven downwardly by the external biasing force applied to the piston, said means comprising
• a second annular seal formed on the lower face of the sleeve valve for sealingly engaging the piston portion when the first annular seal is formed, and having an effective diameter less than the diameter of the upper stepped portion to form a control chamber between the first and second annular seals, and
• port means for directing high pressure fluid to the control chamber when the piston and sleeve valve have reached the top of the stroke to change the balance of hydraulic forces acting on the sleeve valve and move the sleeve valve away from the piston portion.

A hydraulic impact device comprising

• a cylinder having lower and upper gland portions defining the ends of a cylinder bore,
• a hammer member reciprocally disposed in the cylinder bore having lower and upper rod portions sealingly received in the lower and upper gland portions respectively and including a piston portion disposed in the cylinder bore having a diameter significantly less than that of the cylinder bore to permit fluid to bypass the piston within the cylinder,
• a sleeve valve reciprocally disposed in the cylinder bore above the piston portion for sealingly engaging the upper surface of the piston portion and dividing the cylinder bore into a lower high pressure chamber and an upper low pressure chamber,
• hydraulic port means for aplying high pressure fluid to the high pressure chamber and for exhausting fluid from the low pressure chamber,
• the sleeve valve being totally exposed to either high pressure fluid or exhaust pressure fluid and having effective hydraulic areas proportioned such that hydraulic fluid continually biases the sleeve valve toward the piston portion to tend to maintain sealing engagement between the sleeve valve and the piston portion to thereby divide the cylinder into high and low pressure chambers,
• means for separating the sleeve valve from the piston portion when the sleeve valve has reached a predetermined position of its stroke toward the upper gland to allow high pressure fluid to bypass the piston within the cylinder from the high pressure chamber to the low pressure chamber,
• energy storage means engaging one of the rod portions which is charged with energy by upward movement of the hammer member for rapidly driving the hammer member downwardly when the sleeve valve is separated from the piston portion to allow high pressure fluid in the high pressure chamber to bypass the piston to the low pressure chamber, and
• means for limiting the movement of the sleeve valve toward the lower gland portion at a point such that the valve member cannot engage with the piston portion until the hammer member has been moved upwardly a distance.