Abstract: A method for controlling a screwdriver that has an electromotor, the electromotor having a clear ratio of rotational speed (n) to torque (M) at a defined effective voltage (Ueff soll), involving the following method step: —defining an effective voltage (Ueff soll) for operating the electromotor, —defining a cut-off rotational speed (nab) that corresponds to a pre-defined cut-off torque (Msoll) at the pre-defined effective voltage (Ueff soll), —operating the screwdriver under load with the pre-defined effective voltage (Ueff soll), —during operation of the screwdriver: —determining the rotational speed (n), —shutting down the electromotor when the cut-off rotational speed (nab) is attained.

Abstract: A method for rotating a rotatable part using a hydraulic piston-cylinder drive operated by a hydraulic pressure source and having at least one piston and a ratchet, wherein a torque is applied to the rotatable part during a loading stroke and the piston is moved into a starting position via a return stroke. The loading stroke ends when an end position of the piston is reached and subsequently the return stroke is started, wherein the end position is a position of the piston before the piston abuts against an end stop.

Abstract: The screw tensioning device comprises a support tube (12), a cylinder member (15) and a piston section (17). The piston section serves for moving a tensioning bolt (20) screwed onto the thread of a threaded bolt (31). Provided according to the invention is a depth measuring device (35), which presents an externally visible indication of the screw-in depth (ET) of the threaded bolt (31). This ensures that, when the threaded bolt (31) undergoes extension under strain, there is a threaded engagement with the tensioning bolt (20) along a sufficiently long distance. This avoids the hazard that the screw tensioning device might break off from the threaded bolt.

Abstract: A method for controlling a screwdriver that has an electromotor, the electromotor having a clear ratio of rotational speed (n) to torque (M) at a defined effective voltage (Ueff soll), involving the following method step:—defining an effective voltage (Ueff sollfor operating the electromotor,—defining a cut-off rotational speed (nab) that corresponds to a pre-defined cut-off torque (Msoll) at the pre-defined effective voltage (Ueff soll,—operating the screwdriver under load with the pre-defined effective voltage (Ueff soll,—during operation of the screwdriver:—determining the rotational speed (n),—shutting down the electromotor when the cut-off rotational speed (nab) is attained.

Abstract: In a power wrench having a power unit part containing a drive cylinder, an output part, wherein the output part includes an output shaft that is mounted in a housing and rotated at intervals by the drive cylinder, and a support part, which is disposed on the housing and can be placed against an abutment of a screwing site, it is provided that the housing includes a holding system for fixing the power wrench at the screwing site, wherein the holding system includes at least one holding magnet, which cooperates with the screwing site and prevents the power wrench from rotating away from the abutment.

Abstract: The screw tensioning device comprises a support tube (12), a cylinder member (15) and a piston section (17). The piston section serves for moving a tensioning bolt (20) screwed onto the thread of a threaded bolt (31). Provided according to the invention is a depth measuring device (35), which presents an externally visible indication of the screw-in depth (ET) of the threaded bolt (31). This ensures that, when the threaded bolt (31) undergoes extension under strain, there is a threaded engagement with the tensioning bolt (20) along a sufficiently long distance. This avoids the hazard that the screw tensioning device might break off from the threaded bolt.

Abstract: A method for rotating a rotatable part using a hydraulic piston-cylinder drive operated by a hydraulic pressure source and having at least one piston and a ratchet, wherein a torque is applied to the rotatable part during a loading stroke and the piston is moved into a starting position via a return stroke. The loading stroke ends when an end position of the piston is reached and subsequently the return stroke is started, wherein the end position is a position of the piston before the piston abuts against an end stop.

Abstract: A hydraulic aggregate for supplying a hydraulic cylinder in consecutive load strokes is monitored for its working load in order to determine the condition of the aggregate automatically. For this purpose, the time integral of the pressure is determined for each load stroke. The pressure and duration are processed into a characteristic number which indicates the wear. This makes it possible to diagnose the condition of the hydraulic aggregate at any time.

Abstract: A hydraulic aggregate comprises a container, a reservoir for hydraulic oil, and a pump driven by a motor arranged in the reservoir. The motor is a pneumatic motor. An electric control unit for controlling a main valve is mounted on the container. The main valve causes a reversal of the stroke direction of the hydraulic connections. The division into pneumatics and low power electronics leads to an explosion-proof embodiment of low weight and little technical complexity.

Abstract: The invention relates to a hydraulic group comprising a reservoir (28) for oil, in which a multiple piston pump (60) is arranged. The individual pumps (61) are cyclically driven by an eccentric ring (29). In order to ensure a permanent immersion of the individual pumps in the reservoir (28), an auxiliary reservoir (47) providing oil for refilling the reservoir (28) is arranged above the reservoir. The auxiliary reservoir (47) is connected to an additional tank (45) by means of a connection line (48).

Abstract: A power wrench (10) for turning a screw is supplied by a hydraulic unit (25) that contains a positive displacement pump (26) and supplies a defined rate of flow. The pressure in a hydraulic pressure line (28) is measured by a pressure sensor (32) and provided to a control unit (31). The volume flow of the hydraulic unit (25) is determined in amount per unit of time. The piston stroke per unit of time can be determined due to the fact that the filling volume of the hydraulic cylinder is known. The piston acts upon a lever system that turns the moving part. The turning angle per unit of time can be determined due to the fact that the lever length is known. This makes it possible to dispense with an angle measuring device and to determine the turning angle merely by measuring pressure.