Abstract: Depending on the working and application conditions, it may be desirable to equip fluid-operated percussion devices with a mechanism that protects against no-load strokes, particularly in the interest of avoiding undesired stress. In the present case, this protection mechanism is configured such that the control unit that influences the movements of the percussion piston is blocked by a safety element in the form of a multiple-position valve, and the percussion device is halted if the percussion piston overshoots the extended position occurring in normal operation by a defined distance, thereby assuming a no-load-stroke position. The safety element (21) that acts on the control unit (5) of the percussion device (1) is automatically controlled, notably such that it is not switched to be active until some time after the startup of the percussion device (1) acted on by the working pressure. The percussion device (1) can therefore start up without being influenced by the safety element (21).

Abstract: An apparatus having a housing (5) that shields a front of a percussion drive (1) against the environment, and into which a drive driven tool (3) projects. An exchangeable outer seal (10) is disposed at the housing opening (6c) for the tool (3), surrounds the tool transversely to its longitudinal axis (3a) with spacing, and is moveable in this transverse direction. An inner seal (11) is disposed behind the outer seal (10), and rests elastically against the tool (3) outside of its tool guide (2). The inner seal (11) is exchangeably secured to an elastic extension (12) of the tool guide (2) that surrounds the percussive tool (3) in the region of the inner seal (11) with a spacing larger than the largest transverse displacement of the tool (3). The extension (12) is an independent, elastic support that forms a detachable connection with the tool guide (2) at one end.

Abstract: Depending on the working and application conditions, it may be desirable to equip fluid-operated percussion devices with a mechanism that protects against no-load strokes, particularly in the interest of avoiding undesired stress. In the present case, this protection mechanism is configured such that the control unit that influences the movements of the percussion piston is blocked by a safety element in the form of a multiple-position valve, and the percussion device is halted if the percussion piston overshoots the extended position occurring in normal operation by a defined distance, thereby assuming a no-load-stroke position. The safety element (21) that acts on the control unit (5) of the percussion device (1) is automatically controlled, notably such that it is not switched to be active until some time after the startup of the percussion device (1) acted on by the working pressure. The percussion device (1) can therefore start up without being influenced by the safety element (21).