It is aimed to enable an easier attachment of a lower spreader to a machine main body. The mast 30 is tiltably attached to the machine main body 13, and operable to lie over the machine main body 13. The lower spreader retainer 40 is fixedly attached to the machine main body 13, and adapted for retaining the lower spreader 50. The connector 60 connects the mast 30 and the lower spreader 50 with each other so that the mast 30 holds the lower spreader 50. The lower spreader 50 and the lower spreader retainer 40 are arranged at a position that allows the lower spreader retainer 40 to retain the lower spreader 50 in a state where the mast 30 holding the lower spreader 50 is lowered.

A hydraulic system for operating a hydraulic fall-back support of a work machine including at least one hydraulic fall-back support cylinder for tracking and limiting movements of a boom of the work machine and a hydraulic pump by means of which the fall-back support cylinder and at least one further hydraulic consumer can be supplied with hydraulic fluid. A stop valve having a blocking position and a passage position is connected between the hydraulic pump and the fall-back support cylinder, by means of which the stop valve and a load-bearing cylinder space of the fall-back support cylinder is blockable and a hydraulic store connected to the load-bearing cylinder space is provided between the stop valve and the fall-back support cylinder.

A hydraulic system for operating a hydraulic fall-back support of a work machine including at least one hydraulic fall-back support cylinder for tracking and limiting movements of a boom of the work machine and a hydraulic pump by means of which the fall-back support cylinder and at least one further hydraulic consumer can be supplied with hydraulic fluid. A stop valve having a blocking position and a passage position is connected between the hydraulic pump and the fall-back support cylinder, by means of which the stop valve and a load-bearing cylinder space of the fall-back support cylinder is blockable and a hydraulic store connected to the load-bearing cylinder space is provided between the stop valve and the fall-back support cylinder.

A crane for use on an offshore vessel is provided with a boom restrainer, wherein the boom restrainer is a hydro-pneumatic boom restrainer, for reducing upward pivoting of the boom, when the boom is in the top zone, wherein the boom restrainer includes: multiple hydraulic cylinders, each having a hydraulic circuit and a cylinder rod with a cylinder head, wherein the cylinders are mounted on the crane structure with the cylinder heads directed towards the boom of the crane, preferably are mounted on a stay of the crane structure, a catcher for each hydraulic cylinder, wherein each catcher is mounted on the boom and is configured for receiving the cylinder head of the corresponding hydraulic cylinder, and to lock the cylinder head, preferably pivotable locks the cylinder head, relative to the boom, when the boom pivots upwards in the top zone; a gas buffer for each hydraulic cylinder, wherein each gas buffer is mounted to the corresponding hydraulic cylinder, and is connected to the hydraulic circuit of the corresponding hydraulic cylinder via a medium separator, wherein the gas buffer forces the hydraulic cylinder in an extended position, and wherein the volume ratio between the hydraulic cylinder and the gas buffer is such that the hydraulic cylinder acts as a progressive spring, e.g. the gas buffers each have a size in the range of 1000-1400 litre, for example 1200 litre and the hydraulic cylinders each have a size in the range of 800-1000 litre, for example 900 litre, and preferably the ratio between the volume of the gas buffer and the volume of the associated hydraulic cylinder is 4:3.

A crane for use on an offshore vessel is provided with a boom restrainer, wherein the boom restrainer is a hydro-pneumatic boom restrainer, for reducing upward pivoting of the boom, when the boom is in the top zone, wherein the boom restrainer includes: multiple hydraulic cylinders, each having a hydraulic circuit and a cylinder rod with a cylinder head, wherein the cylinders are mounted on the crane structure with the cylinder heads directed towards the boom of the crane, preferably are mounted on a stay of the crane structure, a catcher for each hydraulic cylinder, wherein each catcher is mounted on the boom and is configured for receiving the cylinder head of the corresponding hydraulic cylinder, and to lock the cylinder head, preferably pivotable locks the cylinder head, relative to the boom, when the boom pivots upwards in the top zone; a gas buffer for each hydraulic cylinder, wherein each gas buffer is mounted to the corresponding hydraulic cylinder, and is connected to the hydraulic circuit of the corresponding hydraulic cylinder via a medium separator, wherein the gas buffer forces the hydraulic cylinder in an extended position, and wherein the volume ratio between the hydraulic cylinder and the gas buffer is such that the hydraulic cylinder acts as a progressive spring, e.g. the gas buffers each have a size in the range of 1000-1400 litre, for example 1200 litre and the hydraulic cylinders each have a size in the range of 800-1000 litre, for example 900 litre, and preferably the ratio between the volume of the gas buffer and the volume of the associated hydraulic cylinder is 4:3.

Provided is a lifting device with a force-absorbing base to which a boom with hoisting cable for lifting a load in substantially vertical direction is tiltably connected. The lifting device is provided with an auxiliary device for counteracting tipover of the boom in the case of sudden loss of load. The auxiliary device is connected to the base of the lifting device, provides a contact surface which is in permanent contact with a contact surface of the boom or comes into contact therewith in the case of tipover, and further comprises a drive and control system which is configured to stop the boom movement when a predetermined force between the contact surfaces is exceeded as a result of the boom tipping over. The described auxiliary device can take an autonomous form and can be arranged on a lifting device.

Provided is a lifting device with a force-absorbing base to which a boom with hoisting cable for lifting a load in substantially vertical direction is tiltably connected. The lifting device is provided with an auxiliary device for counteracting tipover of the boom in the case of sudden loss of load. The auxiliary device is connected to the base of the lifting device, provides a contact surface which is in permanent contact with a contact surface of the boom or comes into contact therewith in the case of tipover, and further comprises a drive and control system which is configured to stop the boom movement when a predetermined force between the contact surfaces is exceeded as a result of the boom tipping over. The described auxiliary device can take an autonomous form and can be arranged on a lifting device.

A changing device easily and safely changes the posture of the backstop of a crane between a support posture and a storage posture. The backstop posture changing device is provided with a first support member, a second support member, a push-up mechanism, and a connection member. The first support member and the second support member are rotationally connected to a backstop and a lower boom respectively. When a cylinder rod of the push-up mechanism is extended with respect to a cylinder body, a push-up member pushes up the first support member and the posture of the backstop is changed from a storage posture on the lower boom to a support posture in which it is possible to support a boom while the crane is in a working posture.

A changing device easily and safely changes the posture of the backstop of a crane between a support posture and a storage posture. The backstop posture changing device is provided with a first support member, a second support member, a push-up mechanism, and a connection member. The first support member and the second support member are rotationally connected to a backstop and a lower boom respectively. When a cylinder rod of the push-up mechanism is extended with respect to a cylinder body, a push-up member pushes up the first support member and the posture of the backstop is changed from a storage posture on the lower boom to a support posture in which it is possible to support a boom while the crane is in a working posture.

There is provided a crane including a front member capable of derricking, a backstop disposed on a rear surface side of the front member so as to limit a standing operation of the front member, an angle sensor that detects an angle of the front member, an operation detection unit that detects whether or not the backstop is operated, and a controller that controls a derricking operation of the front member. In a case where the controller determines that the angle of the front member is equal to or larger than a predetermined angle, based on a detection signal output from the angle sensor, and determines that the backstop is not operated, based on a detection signal output from the operation detection unit, the controller stops the standing operation of the front member.