Abstract: A hydraulic crane comprising: —a rotatable column (7); —a crane boom system (10) comprising two or more liftable and lowerable crane booms (11, 13); and —an electronic control device (25), which is configured to prevent an execution of crane boom movements that would make the lifting moment of the crane exceed the maximum allowed lifting moment of the crane, and to continuously establish position information as to the prevailing position of the load suspension point (P) of the crane boom system. When the lifting moment of the crane has reached a limit value at a given level below the maximum allowed lifting moment, the electronic control device is configured to prevent the execution of any combination of crane boom movements that would increase the horizontal distance between the load suspension point and said vertical axis of rotation and at the same time allow the execution of any combination of crane boom movements that keeps said horizontal distance unchanged or reduces said horizontal distance.

Abstract: A hydraulic crane comprising: —a rotatable column (7); —a crane boom system (10) comprising two or more liftable and lowerable crane booms (11, 13); and—an electronic control device (25), which is configured to prevent an execution of crane boom movements that would make the lifting moment of the crane exceed the maximum allowed lifting moment of the crane, and to continuously establish position information as to the prevailing position of the load suspension point (P) of the crane boom system. When the lifting moment of the crane has reached a limit value at a given level below the maximum allowed lifting moment, the electronic control device is configured to prevent the execution of any combination of crane boom movements that would increase the horizontal distance between the load suspension point and said vertical axis of rotation and at the same time allow the execution of any combination of crane boom movements that keeps said horizontal distance unchanged or reduces said horizontal distance.

Abstract: A hydraulic crane comprising: —a rotatable column (7); —a crane boom system comprising a first crane boom (11) connected to the column; and —an electronic control device for controlling the movement of the column and the crane boom system on the basis of control signals from a manoeuvring unit and a calculation model for boom tip control. The control device is configured to switch from a first control mode into a second control mode when the first crane boom is about to interfere with an obstacle. In the first control mode, the control device controls the crane boom movements in accordance with an ordinary control strategy. In the second control mode, the control device makes the load suspension point (P) of the crane boom system move along the trajectory defined by said control signals while controlling the crane boom movements in accordance with an auxiliary control strategy in which the first crane boom is prevented from interfering with the obstacle.

Abstract: A hydraulic crane comprising: —a rotatable column (7); —a crane boom system comprising a first crane boom (11) connected to the column; and —an electronic control device for controlling the movement of the column and the crane boom system on of the basis of control signals from a manoeuvring unit and a calculation model for boom tip control. The control device is configured to switch from a first control mode into a second control mode when the first crane boom is about to interfere with an obstacle. In the first control mode, the control device controls the crane boom movements in accordance with an ordinary control strategy. In the second control mode, the control device makes the load suspension point (P) of the crane boom system move along the trajectory defined by said control signals while controlling the crane boom movements in accordance with an auxiliary control strategy in which the first crane boom is prevented from interfering with the obstacle.

Abstract: A method of providing by a laser beam on a bright metal surface (1) areas discernible from the surrounding surface as darker areas for producing for instance optically readable marks (5) and a metal surface provided in this manner. The procedure for producing marks not weakening the general properties of the metal surface is that the metal surface (1) is exposed to a laser beam pulse, the energy of which is 1 to 10 J/cm.sup.2, preferably 3 to 5 J/cm.sup.2 and the duration 5 ns to 1 .mu.s, preferably 15 to 30 ns; a spot of impact (7) of the laser beam pulse on the metal surface (1) is changed in such a way that a new spot of impact (8) overlaps the earlier spot of impact (7) and the metal surface (1) is exposed to a new laser beam pulse, such that an area (7a) of the metal surface, where the pulses do not overlap each other and which abuts on the spot of impact of the new pulse, gets a color contrasting with the original metal surface (1).

Abstract: A location scale and an optical reading sensor for reading the location scale. The location scale comprises bars with a first edge and a second edge, wherein either the first edges or the second edges are located at regular intervals to form an incremental scale. To provide both incremental data and absolute data on the same scale, the bars are of at least two different widths, and any n successive bars on the scale form a unique individual code indicating the absolute location of those n bars on the scale.