Hydraulic rock drill

An hydraulic rock drill comprising a housing, an anvil slidable in the housing having an external portion adapted to be coupled to a drill string, a hammer piston hydraulically reciprocable in the housing to pound the anvil, a cylinder for the piston, a reservoir of pressurized hydraulic fluid in the housing, a return shoulder on the piston under constant pressure of the reservoir fluid urging the piston in a return direction, the piston having within the cylinder a relatively greater diameter area than that of the shoulder, a supply port connecting the reservoir with the cylinder for applying reservoir fluid to the greater diameter area to drive the piston on a power stroke, a return port for relieving said reservoir fluid from the cylinder, an open ended cylindrical valve means slidable back and forth in the cylinder relative to the supply and return ports to effect alternate opening and closing of the supply and return ports, said valve means being periodically engaged by the piston, and means for developing differential pressures alternately at opposite ends of the valve means for sliding the latter back and forth relative to the supply and return ports.

An hydraulic rock drill comprising a housing, a reservoir in the housing of constantly pressurized fluid, a piston cylinder at a rear end of the housing, a bore at an opposite forward end of the housing, a hammer piston having a head portion reciprocable in the cylinder and a shank portion extending through the fluid of the reservoir and slidably supported at a front end in the bore, a shoulder area of the shank portion disposed within the fluid of the reservoir and subject to pressure of the fluid to constantly urge the piston in a return stroke direction, the head portion having a greater diameter surface area than that of the shoulder adapted upon application to it of pressure fluid from the reservoir to move the piston on a power stroke, a supply port for admitting pressure fluid from the reservoir to the cylinder, a relief port for allowing relief of said fluid from the cylinder, valve means slidable back and forth in the cylinder relative to the supply and relief ports for causing alternate opening and closing of said ports to effect reciprocation of the piston, said valve means being periodically engaged by the piston, and means responsive to motion of the piston for developing differential pressures over the valve means to cause said back and forth slidable movement of the valve means.

The combination of a reservoir of constantly pressurized hydraulic fluid, a piston cylinder surrounded by the reservoir, a piston having a head reciprocable in the cylinder and having a shank of reduced diameter extending through the fluid constantly subject to pressure of the fluid urging the piston in a return direction, a supply port for admitting the fluid to the cylinder for application to the head to drive the piston on a power stroke, a return port for relieving the admitted fluid to a sump to allow return of the piston under pressure of fluid over the reduced diameter shank, an elongated peripheral groove in the piston defining a forward end shoulder and a rear end shoulder, a sleeve valve means movable in the groove between the shoulders relative to the supply and return ports, means responsive to movement of the piston on a return stroke to cause the valve means to progressively cover the return port and to uncover the supply port and responsive to movement of the piston on a power stroke to progressively cover the supply port and to uncover the return port.

A rock drill including a piston constantly pressured in a return direction having a head portion hydraulically reciprocable in a piston cylinder subject to admission of pressurized hydraulic fluid to the cylinder to move on a power stroke and adapted upon relief of said fluid from the cylinder to be pressured in a return direction, a supply port for admitting the fluid to the cylinder, a return port for relieving the fluid from the cylinder, sleeve valve means within the cylinder in surrounding relation to the head portion controlling alternate opening of one port and closing of the other, a driving shoulder on the piston having cooperation with the valve means on a return stroke of the piston to initially slide the valve means rearwardly to progressively open the supply port and to close the return port, a rear shoulder on the piston having cooperation with the valve means on a forward power stroke of the piston to slide the valve means forwardly to progressively close the supply port and to open the return port, and means responsive to an initial return movement of the valve means to accelerate the valve means ahead of the piston during the return stroke of the latter and responsive to an initial forward movement of the valve means to retard the movement of the valve means relative to the movement of the piston during the power stroke of the piston.

A sleeve valve unit comprising an outer sleeve valve member having first and second inner diameters the first being greater than the second, an inner sleeve member having first and second outer diameters respectively slidably mating with the first and second inner diameters of the valve member, an annular expandible cavity formed in the valve member at the juncture of its first inner diameter with its second inner diameter, a plurality of angular holes extending from the cavity through the body of the valve member to the periphery of the latter, and an annular groove in the periphery of the valve member common to the angular holes, the cavity being adapted to expand as it is pressurized with hydraulic fluid and as a consequence causing the valve and sleeve members to be hydraulically extended in opposite directions, and the valve and sleeve members being retractible relative to one another upon relief of the hydraulic fluid from the cavity as a consequence of differential pressures being applied to opposite ends of the sleeve and valve members.