Abstract: The invention relates to a method and a an apparatus for processing various materials, the apparatus including at least two annular feed gaps placed one within the other. The beginning of each feed gap is provided with a grinding section (5), which is followed in the apparatus by a mixing section (10). The materials are processed in the grinding section (5), whereafter they are mixed in the mixing section (10), and the mixture is extruded into a product.

Abstract: A film is extruded from plastic material by an extruder. The film is orientated after extrusion. Material is mixed into the plastic so that when the plastic film is stretched, cavitation bubbles are formed in the material particles mixed into the plastic. During the orientation, gas is arranged to the plastic film under high pressure so that the gas diffuses in the cavitation bubbles and causes overpressure in them. Thus, it is possible to make a thin foamed film with a foaming degree over 70%.

Abstract: An electromechanic film intended for transforming electric energy into mechanical energy and transforming mechanical energy into electric energy. The film (1) is dielectric and formed of cells (3), the ratio of the height and width of which cells is between 3:1 and 1:3. By joining two such films together and controlling them in such a way that in the first film (1) the electric field strength decreases and in the second film (1) the electric field strength increases, a bending acoustic element is provided.

Abstract: An electromechanical transducer comprising at least one transducer element which has a multilayer structure comprising at least two layers such that the transducer element is capable of changing its thickness. The transducer element allows air to flow inside the transducer element in the direction of thickness thereof and inside and out of the transducer element through at least one surface of the transducer element in the direction of thickness of the transducer element. The transducer element can be used e.g. for transforming energy from mechanical energy into electric energy and/or vice versa.

Abstract: A method and an apparatus for extruding material, the material being extruded with an apparatus comprising at least one rotatable rotor and at least one stator, the rotor and the stator comprising grooves, whereby the grooves make the material move through the apparatus when the rotor is rotated. The rotor and stator surfaces facing each other have a wavelike cross-section, and the grooves are so arranged that at the ridge of a wave the depth of a groove reaches its maximum, and at the bottom of a wave the depth reaches its minimum. The bottom of the wave in the rotor is at the ridge of the wave in the stator and vice versa. This makes the material move alternately from a rotor groove to a stator groove, and back.

Abstract: The invention relates to a method and an apparatus for sound processing, where sound is attenuated by measuring it and by producing with an actuator a sound field of opposite sign in view of the original sound field. A desired value signal (I) is supplied to the actuator which reproduces the signal. To the actuator is attached a sensor, measuring sound pressure, and the difference of the sensor signal (B) and the desired value signal (I) is applied as high gain feedback to the actuator. As a consequence, sound not pertaining to the desired value signal (I) can be attenuated in a simple manner, and sound in accordance with the desired value signal (I) can be produced simultaneously with the same apparatus.

Abstract: In an extrusion method and an extruder, an annular material flow is created by extruding material into an annular extrusion channel (6). The extruder has a tubular filtering unit (7) arranged to the annular extrusion channel (6), whereby the annular material flow flows through the tubular surface of the filtering unit (7).

Abstract: An apparatus for manufacturing an extruded plastic product, the apparatus including at least one rotor and at least one stator defining a clearance having a feed gap between them, the rotor and stator collectively including a groove for moving material to be extruded from a feed zone of the apparatus to a shear zone of the apparatus upon rotation of the rotor and a countergroove for facilitating the extrusion of the material, the groove and countergroove being disposed on opposite sides of the feed gap, the countergroove having a thread that is opposite in direction to a thread of the groove, the groove having a cross-section that is substantially unchanging, the countergroove being disposed substantially along an entire length of the shear zone, the groove, countergroove and clearance forming a processing cavity having a volume that is the volumes of grooves, countergrooves and the clearance, the processing cavity having a cross-sectional area that decreases continuously along at least a part of an axis of t

Abstract: The invention relates to a method of and an arrangement for damping a wall movement. In the invention, the strength of an electric field between a surface of a wall and an air-permeable mass plate parallel with the surface is controlled to provide a force opposite to the wall-moving force. A sound wave, for instance, may cause a force moving a wall back and forth, which force is cancelled by the opposite force by means of the method and arrangement of the invention, whereby the movement applied to the wall by the sound wave can be stopped.

Abstract: An extrusion method and an extruder, the material to be extruded being fed with a material feeding device (1) into a radial pump unit included in the equipment. The radial pump unit comprises conical gearwheels (2) which are adjacently positioned and rotate in opposite directions. The radial pump unit transfers the material in an annular flow into the extruder's nozzle (4). Additional material (20) can be supplied into the product through the radial pump unit.

Abstract: The present invention relates to an electroacoustic transducer where the voltage of a capacitive acoustic element is controlled by charging and discharging the charge of the element via an inductance (L) by fast switches (K1, K2). In the case energy unconverted into the acoustic energy of the transducer can be transferred to an energy storage of an electrical circuit formed by the inductance (L) and the capacitance (C1, C2, C0) during each control sequence and in this way the transducer can be made to operate with a good coefficient of efficiency.

Abstract: An extrusion method and an extruder, the material to be extruded being fed with a material feeding device (1) into a radial pump unit included in the equipment. The radial pump unit comprises conical screws (2) which are adjacently positioned and rotate in the same direction. The radial pump unit transfers an annular flow of the material into the extruder's nozzle (4). Additional material (20) can be supplied into the product through the radial pump unit.

Abstract: An extrusion method and an extrusion device, whereby at least two different flows of material are supplied from the extrusion device to a nozzle. The nozzle comprises at least two nozzle chambers such that the material flowing through the first nozzle chamber forms an outer part of a product, and the material flowing through the second nozzle part forms an inner part of the product. The capacity of the nozzle chambers is changed, whereby the relative proportion of the different parts of the product can be varied. When the capacity of the nozzle chamber is decreased, the amount of material flowing therethrough increases at the outlet of the nozzle, and when the capacity of the nozzle chamber is increased, the amount of material flowing out there-through decreases at the outlet of the nozzle.

Abstract: The invention relates to a method and an arrangement for cooling an extruded hollow product. According to the invention, the extruder (1) is provided with means for sucking air through the pipe (2). The air to be sucked is thus in contact with the inner surface of the pipe (2), cooling the pipe from the inside. Therefore the cooling of the pipe (2) can be realized in an efficient and simple manner. By arranging the sucking to occur from the middle of the conical extruder (1), no weld line will be formed in the extruded product, and the extruder (1) can be cooled effectively from the inside. According to the invention, the heat contained by the air that has been sucked through the pipe (2) can also be utilized.

Abstract: A method and an apparatus for extruding material, the material being extruded with an apparatus comprising at least one rotatable rotor and at least one stator, the rotor and the stator comprising grooves, whereby the grooves make the material move through the apparatus when the rotor is rotated. The rotor and stator surfaces facing each other have a wavelike cross-section, and the grooves are so arranged that at the ridge of a wave the depth of a groove reaches its maximum, and at the bottom of a wave the depth reaches its minimum. The bottom of the wave in the rotor is at the ridge of the wave in the stator and vice versa. This makes the material move alternately from a rotor groove to a stator groove, and back.

Abstract: An electromechanic film intended for transforming electric energy into mechanical energy and transforming mechanical energy into electric energy. The film (1) is dielectric and formed of cells (3), the ratio of the height and width of which cells is between 3:1 and 1:3. By joining two such films together and controlling them in such a way that in the first film (1) the electric field strength decreases and in the second film (1) the electric field strength increases, a bending acoustic element is provided.

Abstract: A method of steering an aircraft, and an aircraft comprising a supporting structure, at least one utility space, at least two propellers whose axles are arranged horizontally, and a driving mechanism to rotate each propeller. The blade angles of at least one propeller of the aircraft are adjusted as a function of a rotation angle of the propeller such that the blow power of the propellers provides the aircraft with a lifting force, and after take-off of the aircraft the blade angles of the propellers are adjusted such that the blow power of the propellers provides the aircraft with horizontal flight.

Abstract: An acoustic element comprising a platelike active element. The platelike active element comprises creases. The creases can be produced such that the platelike active element forms a space comprising at least one opening and/or gap, whereby the space and the opening and/or the gap constitute a Hemholz resonator.

Abstract: The invention relates to an acoustic element and method for sound processing. The acoustic element (1) is made of a porous stator plate (2) which is either electrically conductive or plated on at least one of its surfaces to be conductive. A moving diaphragm (3, 3a, 3b) has been attached to the stator plate (2). To measure as well as produce sound pressure and particle velocity, the equipment comprises two pairs of aforementioned acoustic elements (1). Elements serving as sensors control elements serving as actuators to attenuate and absorb sound.

Abstract: A method and an apparatus for treating waste material. The apparatus has a conical rotatable rotor (3) placed between stators (1, 2). At least the stators (1, 2) have recesses (9) from which the material in the apparatus can be discharged when the rotor (3) is rotating. The rotor (3) has several openings (8a, 8b) in the axial direction of the apparatus through which openings at least some of the waste material passes. The edges of the recesses (9) and the openings (8a, 8b) of the rotor (3) are sharp so that the waste material supplied to the apparatus is ground by means of the sharp edges when it passes through the openings (8a, 8b).