Abstract: A hydraulic valve (3) includes an actuation device (1, 1 a, 1 b) for a control piston (2). The valve (3) is simple, robust, and insensitive to dirt. The is an actuation device (1, 1 a, 1 b) has a flexurally rigid metal plate (5), with an outer region fixed to the housing (4) in a stationary manner. A piezoelectric actuator (6) can bend a central region of the metal plate (5); and a pressure chamber (7) is filled with a pressurized liquid during operation. The pressure chamber (7) is delimited by the housing (4), the metal plate (5), and the control piston (2). The metal plate (5) seals the pressure chamber (7), and the pressure chamber (7) acts on the control piston (2). A surface area AP of the metal plate (5) over the pressure chamber (7) is larger than the cross-sectional area AK of the control piston (2).

Abstract: A hydraulic valve (3) includes an actuation device (1, la, lb) for a control piston (2). The valve (3) is simple, robust, and insensitive to dirt. The is an actuation device (1, 1a, 1b) has a flexurally rigid metal plate (5), with an outer region fixed to the housing (4) in a stationary manner. A piezoelectric actuator (6) can bend a central region of the metal plate (5); and a pressure chamber (7) is filled with a pressurized liquid during operation. The pressure chamber (7) is delimited by the housing (4), the metal plate (5), and the control piston (2). The metal plate (5) seals the pressure chamber (7), and the pressure chamber (7) acts on the control piston (2). A surface area AP of the metal plate (5) over the pressure chamber (7) is larger than the cross-sectional area AK of the control piston (2).

Abstract: An apparatus is described for needling a non-woven material with at least one needleboard (23) which is connected with push rods (26) guided in the needle-penetration direction and with at least one drive for the needleboard (23) acting upon the push rods (26). In order to provide advantageous drive conditions it is proposed that the drive is arranged as a hydrostatic resonance drive which comprises at least one working cylinder (1) with a piston (2) pressurized on both sides by a hydraulic spring (4, 5) each and a device for pressurizing the piston (2) with a frequency which corresponds to the resonance frequency of the oscillation system obtained from the moved masses and the hydraulic springs (4, 5).

Abstract: An apparatus is described for needling a non-woven material with at least one needleboard (23) which is connected with push rods (26) guided in the needle-penetration direction and with at least one drive for the needleboard (23) acting upon the push rods (26). In order to provide advantageous drive conditions it is proposed that the drive is arranged as a hydrostatic resonance drive which comprises at least one working cylinder (1) with a piston (2) pressurized on both sides by a hydraulic spring (4, 5) each and a device for pressurizing the piston (2) with a frequency which corresponds to the resonance frequency of the oscillation system obtained from the moved masses and the hydraulic springs (4, 5).