Bretec Oy

Sandvik Mining and Construction Oy

Sandvik Tamrock Oy

Tamrock Oy

Esko Juvonen

Kauko Juuri

Arvo Hurskainen

Jouni Salo

A hydraulic rock breaking device, a protection valve and a method of operating a hydraulic rock breaking device. The rock breaking device comprises a percussion device to which pressure fluid is fed along an inlet channel. The inlet channel is provided with a protection valve arranged to monitor the volume flow of pressure fluid flowing through it. If the flow is larger than what has been preset, the protection valve closes, at least partly, the connection through it, protecting thus the percussion device against too high an input power. The protection valve comprises a throttle which generates a pressure difference the magnitude of which is dependent on the fed volume flow. Information on the pressure difference is utilized in controlling the protection valve.

Rock breaking device, protection valve and a method of operating a rock breaking device

A hydraulic hammer having a sealing bushing includes a percussion piston that delivers strokes to a tool. A lower part of the percussion piston is sealed with respect to a frame by the sealing bushing, which includes one or more lower seals. The sealing bushing does not contribute to the bearing of the percussion piston and it is arranged in place through the lower end of the hydraulic hammer.

Hydraulic hammer having a sealing bushing

A hydraulically operated percussion hammer comprising a percussion piston that reciprocates by means of the pressure of the pressure fluid, a main valve that is controlled by the position of the percussion piston and that guides the pressure fluid to the percussion piston in order to provide a reciprocating motion, and a pressure control valve that is placed in an outlet duct for pressure fluid and that prevents the flow of the pressure fluid from the percussion apparatus before the pressure of the pressure fluid in the inlet duct exceeds the set value of the pressure control valve. The percussion apparatus comprises a separate by-pass duct which allows the pressure fluid to flow from the pressure chamber of the percussion piston past the pressure control valve to the outlet duct until the percussion piston has reached a certain point during its return motion.

Hydraulically operated percussion hammer

Hydraulic percussion hammer, in which a motion of a percussion piston (1) is controlled by a main valve (3), the control motion of which is controlled by a separate control valve (9) in such a way that the main valve changes its state, when the pressure acting on the control valve (9) rises to a predetermined value. The percussion hammer comprises a controller (21) mounted in its return duct (13), by which controller an outflow of pressure fluid from the percussion hammer can be adjusted in such a way that the filling rate of a pressure accumulator (7) and thus the length of a return motion of the percussion piston (1) are proportional to the flow resistance provided by the controller (21).

Hydraulic percussion hammer

The invention relates to a hydraulic percussion hammer comprising a piston (1), a pressure accumulator (7) in the high pressure circuit, a main valve (8) alternately conducing a high and low pressure to at least one of the pressure surfaces (2,4) of the piston (1) for making the piston (1) move reciprocally, and a tool (3) which the piston (1) strikes, and, for the purpose of controlling the main valve (8), a control pressure valve (9) which opens when the pressure exceeds a set value. According to the invention, the control pressure valve (9) is placed in such a way that the spindle (27) of the control pressure valve (9) is connected from one end to the high pressure circuit of the hydraulic percussion hammer. Furthermore, for the purpose of adjusting the maximum and minimum operating pressure of the hydraulic percussion hammer the other end of the spindle (27) of the control pressure valve (9) comprises a control space (29) connected through the hydraulic ducts to at least two pressure control devices (30,31,32,33) connected hydraulically in parallel or in series.

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Lahti, Finland

Esko Juvonen