Abstract: A method for joining components using tensioning bolts, wherein the pressure is linearly increased over time when the tension bolt is hydraulically tensioned by means of a tensioning device. When a target value (Pmax) is reached, the volume is blocked so that no more hydraulic oil is supplied. The pressure decreases when the components show a setting behaviour during a holding time (tH). Pumping is resumed when a lower threshold value (PI) is reached, resulting in a pressure increase up to the target value (Pmax).

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: The invention relates to a hydraulic power wrench comprising a ratchet lever (16) driven by a hydraulic cylinder. According to the invention, said power wrench is provided with a friction brake (20) which operates continuously between the housing (10) and the output shaft (14). In this way, reversed rotations of the output shaft following the individual working strokes are avoided.

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: The invention relates to a method for joining components by means of tensioning bolts. According to said method, the pressure is linearly increased over time when the tensioning bolt is hydraulically tensioned by means of a tensioning device. When a target value (Pmax) is reached, the volume is blocked so that no more hydraulic oil is supplied. The pressure decreases when the components show a setting behavior during a holding time (tH). Pumping is resumed when a lower threshold value (Pi) is reached, resulting in a pressure increase up to the target value (Pmax). The invention prevents a setting process of the components from preventing that the projected pretension of the tensioning bolt is reached.

Abstract: The hydraulic aggregate comprises, within a container (10), a reservoir (11) for hydraulic oil. A pump (15) driven by a motor (18) is arranged in the reservoir (11). The motor (18) is a pneumatic motor. An electric control unit (30) for controlling a main valve (23) is mounted on the container (10). The main valve causes a reversal of the stroke direction of the hydraulic connections (13,14). The division into pneumatics and low power electronics leads to an explosion-proof embodiment of low weight and little technical complexity.

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.

Abstract: The invention relates to a hydraulic power wrench comprising a ratchet lever (16) driven by a hydraulic cylinder. According to the invention, said power wrench is provided with a friction brake (20) which operates continuously between the housing (10) and the output shaft (14). In this way, reversed rotations of the output shaft following the individual working strokes are avoided.

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.

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: The control of the pressure supply to a piston-cylinder unit (10) is effected by monitoring the pressure in the corresponding line (16) through a pressure sensor (22). This pressure is measured in fixed time intervals and the changes in pressure are determined. When the change in pressure has become zero, it is detected that the set terminal pressure has been reached so that the working operation is ended. A switching to the return stroke is effected when the pressure increase in at least one time interval is greater than in at least one of the previous intervals of the working operation. The control is independent from the type of piston-cylinder unit employed and requires no sensors at the piston-cylinder unit.

Abstract: In the method for controlling an intermittent screw process first a torque mode (DMM) is applied in which the torque is continuously measured. Upon attainment of a pre-torque (MF) a rotation angle mode (DWM) is carried out in which the rotation angle is measured. Proceeding from the rotation angle ?=0 (corresponding to the pre-torque (MF)) the rotation angle (?) is counted up during each stroke. In this connection that torque (MHE) is stored which has been reached at the end of the stroke. During the next stroke the angle (?) is continued to be counted only when the torque (MHE) at the stroke end of the previous stroke has been reached again. Upon attainment of a target angle (?z) the screw process is terminated.

Abstract: The control of the pressure supply to a piston-cylinder unit (10) is effected by monitoring the pressure in the corresponding line (16) through a pressure sensor (22). This pressure is measured in fixed time intervals and the changes in pressure are determined. When the change in pressure has become zero, it is detected that the set terminal pressure has been reached so that the working operation is ended. A switching to the return stroke is effected when the pressure increase in at least one time interval is greater than in at least one of the previous intervals of the working operation. The control is independent from the type of piston-cylinder unit employed and requires no sensors at the piston-cylinder unit.

Abstract: In the method for controlling an intermittent screw process first a torque mode (DMM) is applied in which the torque is continuously measured. Upon attainment of a pre-torque (MF) a rotation angle mode (DWM) is carried out in which the rotation angle is measured. Proceeding from the rotation angle &agr;=0 (corresponding to the pre-torque (MF)) the rotation angle (&agr;) is counted up during each stroke. In this connection that torque (MHE) is stored which has been reached at the end of the stroke. During the next stroke the angle (&agr;) is continued to be counted only when the torque (MHE) at the stroke end of the previous stroke has been reached again. Upon attainment of a target angle (&agr;z) the screw process is terminated.

Abstract: The power wrench comprises a housing (10) consisting of a head portion (11) and a driving portion (12). The driving portion (12) includes a cylinder bushing (21) which is introduced into the housing (10) through an opening (22) on the side facing away from the head portion (11). The cylinder bushing (21) with the piston (28) contained therein can easily be exchanged. With a lock connection, the piston rod (29) engages the pivotable lever (17) included in the head portion so that it can be pulled off by the lever (17).

Abstract: The power wrench comprises a housing (10) consisting of a head portion (11) and a drive portion (12). The drive portion (12) contains a cylinder sleeve (21) which is introduced into the housing (10) from the side facing away from the head portion (11). A pressure channel being connected to the hose connector (41) consists of a longitudinal bore (45) extending in the wall of the cylinder sleeve (21) to supply the high pressure required to the rearward cylinder chamber (36). Thereby, it is avoided that the housing (10), in the area of support, is additionally subject to hydraulic pressure. In case of bursting of the pressure duct, the cylinder sleeve (21) is still held together by the housing (10).

Abstract: The power wrench has a substantially T-shaped configuration and comprises a transversely extending housing (10) and a headpiece (11) extending centrally therefrom. The housing (10) comprises a working cylinder (17) and an additional cylinder (21). Both cylinders guide a unit (60) having at the one end a working piston (25) and at the other end an additional piston (29). The lever (41) of the headpiece (11) engages in a coupling member (27). The additional cylinder (21) drives the return stroke. Its area is substantially smaller than that of the working cylinder (17), so that the return movement does not require much hydraulic fluid. The headpiece (11) can easily be exchanged. Its lever (41) loosely engages in the coupling member (27) of the unit (60).

Abstract: The hydraulic power wrench is provided with a wrench head (10) including a rotatably supported ring member (14) to be connected for rotation with a bolt head. The ring member (14) is driven be a piston (40) accommodated in a cylinder housing (11). Mutual engagement of the wrench head (10) and the cylinder housing (11) is effected by a holding recess (32) and an insert member (33). Thus, the wrench head (10) is connected in such a manner to the cylinder housing (11) that it can be easily detached. The connection is secured by locking members (34). By this arrangement, the wrench head (10) can be selectively combined with different cylinder housings (11).