Gripper for petroleum pipes

1. A gripper for petroleum pipes, the gripper including:

a housing;

two gripper arms, wherein the gripper arms are provided, at first end portions, with gripping surfaces and are pivotable, at opposite end portions, around respective first axes;

first pivotal links connecting each of the gripper arms to the housing, each of the first pivotal links being pivotably connected to the respective gripper arm around a second axis which is between the gripping surface and the first axis, and each of the first pivotal links being pivotably connected to the housing around a third axis; and

second pivotal links around the first axis connecting each of the gripper arms to the housing,

wherein each of the second pivotal links is pivotably connected to the housing on a respective fourth axis fixed relative to the housing, the two first pivotal links being independently pivotable from the two second pivotal links;

wherein the distance between the first axis and the fourth axis is shorter than the distance between the second axis and the third axis; and

wherein the housing includes an abutment surface for the petroleum pipe.

2. The gripper in accordance with claim 1 , wherein the gripper includes two gripper arms which are arranged on opposite sides of the housing.

3. The gripper in accordance with claim 1 , wherein the petroleum pipe is moved against the abutment surface when the gripper is in its active position.

4. The gripper in accordance with claim 1 , wherein the distance between the first axis and the second axis is different from the distance between the third axis and the fourth axis.

5. The gripper in accordance with claim 1 , wherein a fourth axle which is concentric with the fourth axis is provided with a toothed wheel which is in mesh with a movable pitch rack, the fourth axle being arranged to transmit torques between the toothed wheel and the second pivotal link.

6. The gripper in accordance with claim 5 , wherein the pitch rack is connected to a piston rod belonging to a linear actuator.

7. The gripper in accordance with claim 6 , wherein the linear actuator is between the third axis and the fourth axis in the housing.

8. A gripper for petroleum pipes, the gripper including:

a housing;

two gripper arms, wherein the gripper aims are provided, at first end portions, with gripping surfaces and are pivotable, at opposite end portions, around respective first axes;

first pivotal links connecting each of the gripper arms to the housing, each of the first pivotal links being pivotably connected to the respective gripper arm around a second axis which is between the gripping surface and the first axis, and each of the first pivotal links being pivotably connected to the housing around a third axis; and

second pivotal links around the first axis connecting each of the gripper arms to the housing,

wherein each of the second pivotal links is pivotably connected to the housing on a respective fourth axis fixed relative to the housing, the two first pivotal links being independently pivotable from the two second pivotal links; and

wherein a fourth axle which is concentric with the fourth axis is provided with a toothed wheel which is in mesh with a movable pitch rack, the fourth axle being arranged to transmit torques between the toothed wheel and the second pivotal link.

9. The gripper in accordance with claim 8 , wherein the pitch rack is connected to a piston rod belonging to a linear actuator.

10. The gripper in accordance with claim 9 , wherein the linear actuator is provided between the third axis and the fourth axis in the housing.