Hydraulic crane

1. A hydraulic crane comprising:

a crane base ( 6 );

a column ( 7 ) which is rotatably mounted to the crane base ( 6 ) to be rotatable in relation to the crane base about an essentially vertical axis of rotation (A 1 );

an actuating device ( 8 ) for rotating the column ( 7 ) in relation to the crane base ( 6 );

a crane boom system ( 10 ) comprising two or more liftable and lowerable crane booms ( 11 , 13 ) which are articulately connected to each other and hydraulic cylinders ( 12 , 14 ) for lifting and lowering the crane booms ( 11 , 13 ), wherein a first crane boom ( 11 ) of the crane boom system is articulately connected to the column ( 7 ) and a second crane boom ( 13 ) of the crane boom system is articulately connected to the first crane boom ( 11 );

an electronic control device ( 25 ) for controlling said actuating device ( 8 ) and the hydraulic cylinders ( 12 , 14 ) of the crane boom system ( 10 ) to thereby control the rotation of the column ( 7 ) and the positioning of the crane booms ( 11 , 13 ); and

a manoeuvring unit ( 24 ) with one or more maneuvering members (S 1 , S 2 , S 3 ) configured to be manoeuvrable by a crane operator to control the position of a load suspension point (P) of the crane boom system ( 10 ), wherein the manoeuvring unit ( 24 ) is configured to supply the electronic control device ( 25 ) with control signals related to the manoeuvring of said one or more maneuvering members (S 1 , S 2 , S 3 ), wherein

the electronic control device ( 25 ) is configured to control the crane boom movements on the basis of said control signals and a calculation model for boom tip control,

the electronic control device ( 25 ) in a first control mode is configured to make the load suspension point (P) move along a trajectory defined by said control signals while controlling the crane boom movements in accordance with an ordinary control strategy,

the electronic control device ( 25 ) is configured to switch from the first control mode into a second control mode when it is established by the electronic control device ( 25 ) that the first crane boom ( 11 ) is about to interfere with a predefined safety zone associated with a known obstacle ( 18 ) or about to interfere with an obstacle detected by one or more sensors ( 45 ) of the hydraulic crane ( 1 ), and

the electronic control device ( 25 ) in this second control mode is configured to make the load suspension point (P) move along said trajectory while controlling the crane boom movements in accordance with an auxiliary control strategy in which the first crane boom ( 11 ) is prevented from interfering with the safety zone or the detected obstacle.

2. A hydraulic crane according to claim 1 , wherein

said safety zone is defined as a set of limit values (Vαlimit) for the angle of inclination (α) of the first crane boom ( 11 ), and

each limit value (Vαlimit) of the set of limit values is associated with a given slewing angle (θ) of the column ( 7 ) and represents a limit for the allowed inclination of the first crane boom ( 11 ) in a vertical plane downwards or upwards at the associated slewing angle (θ) of the column ( 7 ).

3. A hydraulic crane according to claim 1 , wherein the hydraulic crane ( 1 ) is a lorry crane mounted to the chassis of a lorry ( 4 ), and said safety zone is associated with a driver's cab ( 18 ) of the lorry.

4. A hydraulic crane according to claim 1 , wherein the second crane boom ( 13 ) is telescopically extensible to enable an adjustment of the extension length (L) thereof.

5. A hydraulic crane according to claim 1 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

6. A hydraulic crane according to claim 2 , wherein the hydraulic crane ( 1 ) is a lorry crane mounted to the chassis of a lorry ( 4 ), and said safety zone is associated with a driver's cab ( 18 ) of the lorry.

7. A hydraulic crane according to claim 6 , wherein the second crane boom ( 13 ) is telescopically extensible to enable an adjustment of the extension length (L) thereof.

8. A hydraulic crane according to claim 3 , wherein the second crane boom ( 13 ) is telescopically extensible to enable an adjustment of the extension length (L) thereof.

9. A hydraulic crane according to claim 2 , wherein the second crane boom ( 13 ) is telescopically extensible to enable an adjustment of the extension length (L) thereof.

10. A hydraulic crane according to claim 9 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

11. A hydraulic crane according to claim 8 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

12. A hydraulic crane according to claim 7 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

13. A hydraulic crane according to claim 6 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

14. A hydraulic crane according to claim 4 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

15. A hydraulic crane according to claim 3 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.

16. A hydraulic crane according to claim 2 , wherein the electronic control device ( 25 ) is configured to stop presently executed crane boom movements when it has been established by the electronic control device that the crane booms ( 11 , 13 ) of the crane boom system ( 10 ) cannot be positioned to move the load suspension point (P) along said trajectory without the first crane boom ( 11 ) interfering with the safety zone or the detected obstacle.