Abstract: A control system for a machine which includes a load handling apparatus for moving a load relative to a body of the machine. The machine includes a pivot about which a tipping moment is produced by the load. The load handling apparatus includes an actuator capable of moving the load to a position at which the tipping moment is at a threshold value. The control system is responsive to a tipping moment sensor to control operation of the actuator to progressively reduce the speed of movement of the load as the threshold value of the tipping moment is approached.

Abstract: The lifting gear comprises two motors (1, 1?) that are connected to a transmission (6) via respective drive shafts (2, 2?), couplings (3, 3?), with fitted brake disks (4, 4?) or brake drums, brakes (14, 14?) and transmission input shafts (5, 5?). The transmission (6) drives cable drums (9, 9?) via transmission output shafts (7, 7?) and couplings (8, 8?). The cable drums have a cable pull (12, 12?) and fitted brake disks (10, 10?) or brake drums and safety brakes (11, 11?). The inventive lifting gear is characterized by comprising, in the drive shafts (2, 2?), devices (13, 13?) that completely or partially disconnect the motors (1, 1?) from the transmission (6) when an excess load exceeds the predetermined load. They are monitored on both sides of the devices (13, 13?) and the brakes (14, 14?) and/or safety brakes (11, 11?) are activated in the event of disconnection.

Abstract: A control and regulation arrangement for protection of a conveyor or other hoisting or crane device that assures a safe reaction to overloading. A brake apparatus is provided that acts on the conveyor under control of an overload sensor. If the load approaches a predetermined threshold, a signal is emitted from the overload sensor and transmitted to a speed sensor that limits the conveyor speed. Simultaneously the control transmits a signal to the brake apparatus to actuate and stop the conveyor. Upon receipt of a subsequent signal that a load relief state is to be established, the control brakes the conveyor in accord with the speed signal such that the object in transport moves toward a safe position at a constant speed. A conveyor with multiple hoisting devices may include duplicate control and regulation arrangements for each hoisting device.

Abstract: A method is disclosed for controlling a crane which comprises a boom that may be raised or lowered by angular adjustment of the boom about a base portion of the crane. The method prevents operation of the crane in an undesired condition by continuously monitoring operation of the crane, including monitoring at least the position of the boom with respect to the base of the crane. If the crane approaches a limit of its operating range or any operational parameter, its operation will be controlled so as to selectively prohibit or permit a boom raising operation of the crane, depending on the cause of the condition, rather than uniformly prohibit such an operation.

Abstract: In a method for monitoring overstress conditions experienced by a crane component, a wireless signal is received. The wireless signal is indicative of an overstress condition experienced by a crane of which the crane component constitutes an assembled portion. In response to receiving the wireless signal, a record of the overstress condition is stored in a storage module mechanically coupled with the crane component. Information from the record is provided via a wireless communication to facilitate monitoring of occurrence of overstress conditions experienced by the crane component.

Abstract: A height sensor 26 and an image recognizing section 28 are installed in a teaching unit 24; the height sensor 26 contacts a pin 30a on a load port 4 to detect the height position of the pin 30a and the image recognizing section 28 recognizes a pin 30c and thus its horizontal plane position. A platform 16 of an overhead travelling carriage 8 grips and lowers the teaching unit 24 toward the load port 4. The height sensor 26 then detects the height of the load port 4. Then, the teaching unit 24 is slightly raised. The horizontal plane position of the pin 30c is recognized and averaged over a time equal to at least the vibration period of the platform 16. As a result, the position of the load port can be accurately taught to the overhead travelling carriage 8 without preparations such as the installation of marks on the load port.

Abstract: A mobile lift device having a load moving device capable of engaging a load is provided. The mobile lift device includes one or more systems for stabilizing the mobile lift device during operation of the load moving device. According to one exemplary embodiment, the mobile lift device is a heavy duty wrecker having a rotatable boom assembly. The heavy duty wrecker comprises a monitoring system for stabilizing the wrecker during operation of the boom assembly. The monitoring system comprises a plurality of sensors and a monitoring circuit coupled to the sensors to generate a force signal representative of at least one force being applied to the wrecker based upon the transmitted signals.

Abstract: A crane, in particular to an offshore crane, having a hoist rope winch, a hydraulic hoist winch drive and an overload protection which is connected to the hoist winch drive and which, when a predetermined permitted limit load is reached, permits a drawing off of the hoist rope from the hoist rope winch under a predetermined variable restoring force dependent on the radius and/or the permitted working load of the crane. A decoupling of the hoist winch drive and thus a mechanical separation of the powertrain between the hoist rope winch and the hoist winch drive is therefore dispensed with and instead the retention force varying in dependence on the radius and/or the respectively permitted working load of the crane is provided by the hoist rope winch drive motor.

Abstract: The present invention shows a crane control of a crane which includes at least one cable for lifting a load, wherein at least one sensor unit is provided for determining a cable angle relative to the direction of gravitational force. Furthermore, there is shown a crane control for driving the positioners of a crane which includes at least one first and one second strand of cables for lifting the load, with a load oscillation damping for damping spherical pendular oscillations of the load, wherein first and second sensor units are provided, which are associated to the first and second strands of cables, in order to determine the respective cable angles and/or cable angular velocities, and the load oscillation damping includes a control in which the cable angles and/or cable angular velocities determined by the first and second sensor units are considered. Furthermore, a corresponding crane and a method are shown.

Abstract: An integrated hoisting system includes a base structural component (BSC) assembled on a structural aperture and containing an opening compatible with a structural aperture. The integrated hoisting system further includes a plurality of primary hoisting components affixed to the BSC, wherein each primary hoisting component is disposed in an opposite diagonal corner on said BSC, and further includes a winch drum and at least one lead sheave and a plurality of load path assemblies, each containing a plurality of sheaves. The system further includes a plurality of hoisting lines, a plurality of termination components affixed to said BSC, each termination component including a monitoring unit and a load cell assembly for terminating the hoisting line, and a device configured to control the operation of the integrated hoisting system.

Abstract: A working boom with a rotating head on a frame, which rotates about a vertical axis, and boom arms that are each either pivotable or slideable by the use of a drive unit. The working boom includes a control device that controls boom movement with the aid of actuators assigned to each drive unit. Path or angular sensors are assigned to the boom arms, bending axes, vertical axis and/or or drive units. At least one of the drive units includes a hydraulic cylinder with a ground end and a rod-side end. A force or pressure sensor is disposed on the ground end or rod-side end of the hydraulic cylinder. A data storage device receives a pre-set data field of pressure and/or force limit values in connection with a respective path or measurement value assigned to the boom arms, the pre-set data field being analytical or in tabular form.

Abstract: The lifting gear comprises two motors (1, 1?) that are connected to a transmission (6) via respective drive shafts (2, 2?), couplings (3, 3?), with fitted brake disks (4, 4?) or brake drums, brakes (14, 14?) and transmission input shafts (5, 5?). The transmission (6) drives cable drums (9, 9?) via transmission output shafts (7, 7?) and couplings (8, 8?). The cable drums have a cable pull (12, 12?) and fitted brake disks (10, 10?) or brake drums and safety brakes (11, 11?). The inventive lifting gear is characterized by comprising, in the drive shafts (2, 2?), devices (13, 13?) that completely or partially disconnect the motors (1, 1?) from the transmission (6) when an excess load exceeds the predetermined load. They are monitored on both sides of the devices (13, 13?) and the brakes (14, 14?) and/or safety brakes (11, 11?) are activated in the event of disconnection.

Abstract: The present invention utilizes a hoist drum with a number of different diameter sections upon which the different ends of a lifting cable simultaneously spool on and off of as a function of counterclockwise and clockwise cable spooling. This combination reduces the amount of shaft torque required to raise or lower a load while increasing the number of hoist drum rotations required to raise or lower that load. These two features are incorporated into the operation of a main crane cable length adjusting device since they offer precise and rapid adjustment capabilities to be made with smaller sized electric motors and clutches.

Abstract: In an embodiment, a crane including a hoisting (i.e., load-lifting) mechanism is provided with a variable-speed load-dependent control system and method for operating functions of the crane. An exemplary control system includes an actuator subsystem for performing at least one function of the crane, a sensor for detecting the magnitude of the load lifted by the hoisting mechanism and a controller that communicates with the sensor, wherein, relative to a load signal from the sensor, the controller transmits a speed signal to vary an operating speed of at least one actuator of the actuator subsystem.

Abstract: The invention relates to a device for determining a load on a hoist of a crane for handling a container, including rope drum, drive motor as well as hoist transmission disposed between drive motor and rope drum and having a hoist transmission case which is swingably supported about an axis in parallel relationship to the rope drum axis and can be supported on its opposite end on at least one torque support, which a device for indirect determination of the load, suspended from the ropes, is assigned to.

Abstract: A crane installation, especially a container crane, includes at least one hoist mechanism provided with at least one motor for lifting and lowering a load suspended from the hoist mechanism. The operation of the hoist mechanism is controlled by a control unit which receives load-specific information signals from a device. The load-specific information signals are determined on the basis of load-dependent measuring signals generated by a load measuring assembly associated with the hoist mechanism.

Abstract: A stability measurement system is provided for a lifting vehicle including a vehicle frame, a turntable secured to the vehicle frame and supporting lifting components of the vehicle frame, and a turntable bearing disposed between the vehicle frame and the turntable. The stability measurement system includes a plurality of load sensors secured to the turntable bearing that measure vertical forces on the turntable bearing. A controller calculates a rotational moment applied to the vehicle frame from the turntable by processing the vertical forces on the turntable bearing measured by the plurality of load sensors. The forces are directly related to the stability of the machine. By monitoring the resulting moment according to a predetermined upper bound and lower bound, operation of the lifting machine can be controlled to substantially eliminate a tipping hazard.

Abstract: A programmable control system for a crane that senses a hydraulic pressure of the lift mechanism, and controls the movements of the crane apparatus as a function of the magnitude of the hydraulic pressure. As the status conditions of the crane change, sense switches relay such information to a programmable controller and error codes are generated and presented to the operator. The control system can respond to the states of the sense switches and override wireless command inputs to the control system.

Abstract: A measurement system uses dual axis force sensor pins to effectively assess the tipping moment of a load-bearing vehicle and anticipate imminent tipping in any direction. The pins are installed in the pivot points of the boom of a lift vehicle and its main lift cylinder, substituting the standard structural pins presently used. For non-traditional boom support arrangements, one sensor pin for each moving part attachment to non-moving turntable is required. Each of the sensors provides the actual force components acting on the sensor in two perpendicular axes. The output signals are then utilized to assess vehicle stability and detect when the machine is approaching instability in order to warn the operator and/or restrict vehicle movements.

Abstract: A material handler that includes a frame, first and second front wheels, first and second rear wheels, and a control system. The front and rear wheels define a generally horizontal plane. The control system determines the center of gravity of the material handler and displays the location of the center of gravity of the material handler within the plane.

Abstract: A load limiting device for a jib extension includes a pivotal insert adjacent the tip of the jib extension, a cable sheave mounted on the insert, a force measuring device for measuring forces imposed upon the insert by a load on the cable, an angle transducer for measuring the angle of orientation, and means for determining, based upon such force and angle of orientation, the load on the jib extension.

Abstract: A process for monitoring load conditions on a lifting machine having a rated load moment includes determining an actual load moment of the lifting machine due a weighted load. The actual load moment may be determined by measuring a tilt pressure within a hydraulic tilt cylinder of the lifting machine, and then calculating the actual load moment from the tilt pressure within the hydraulic tilt cylinder. The location of a center of gravity of the weighted load is also determined by measuring a lift pressure within a hydraulic lift cylinder of the lifting machine, and then calculating the weight of the weighted load from the lift pressure. Once the weight is determined, the location of the center of gravity of the weighted load may be found using the actual load moment and the calculated weight.

Abstract: A load limiting device for a jib extension includes a pivotal insert adjacent the tip of the jib extension, a cable sheave mounted on the insert, a force measuring device for measuring forces imposed upon the insert by a load on the cable, an angle transducer for measuring the angle of orientation, and means for determining, based upon such force and angle of orientation, the load on the jib extension.

Abstract: The present invention is directed to a material handler that includes a frame, a telescoping boom, a boom extension sensor, a boom angle sensor, and a control system. The telescoping boom is coupled to the frame, pivotable between a lowered and a raised position, and movable between a retracted and an extended position. The boom extension sensor generates a first signal that corresponds to the distance which the boom is extended. The boom angle sensor generates a second signal that corresponds to the angle which the boom is pivoted. The control system receives the signals and displays a cursor located at a position that is based on the first signal and the second signal.

Abstract: A side load detection and protection system (10) operable using pressure sensors (26, 28) to determine side load as a function of a difference in media pressure between two ports (40, 42) of a pneumatic/hydraulic rotation motor (22). When the side load exceeds a pre-established limiting value, the system (10) shuts off functions that could be causing the side load. The system (10) includes a visual display (34) to communicate the actual amount of side load and to present a warning when the limiting side load value has been reached or exceeded. The system (10) is able to differentiate between loads applied to the rotation mechanism through operation of the pneumatic/hydraulic rotation motor (22) and loads due to external forces acting directly or indirectly on the system (10). Furthermore, in order to account for different efficiencies, the system (10) can have separate set-points for side load in clockwise or counterclockwise directions.

Abstract: A stability measurement system is provided for a lifting vehicle including a vehicle frame, a turntable secured to the vehicle frame and supporting lifting components of the vehicle frame, and a turntable bearing disposed between the vehicle frame and the turntable. The stability measurement includes a plurality of load sensors secured to the turntable bearing that measure vertical forces on the turntable bearing. A controller calculates a rotational moment applied to the vehicle frame from the turntable by processing the vertical forces on the turntable bearing measured by the plurality of load sensors. The forces are directly related to the stability of the machine. By monitoring the resulting moment according to a predetermined upper bound and lower bound, operation of the lifting machine can be controlled to substantially eliminate a tipping hazard.

Abstract: The invention relates to a method for controlling the operation of a crane brake, the crane comprising an electric motor (2) controlled by means of a frequency converter (10) for hoisting and lowering movements of the crane; an electromechanical brake (9) having an impact on said movements, the brake being opened when the motor is started for a hoisting or lowering operation; a load sensor (8) weighing a load (7) to be handled; and an overload protection connected to the sensor, the frequency converter (10) being used for calculating the torque of the motor (2), which information is compared with the load information, or weight, obtained from the load sensor (8).

Abstract: The invention relates to a control monitoring device for tower cranes, in particular for small cranes, with integration of functions, and adapted for radio control. The device comprises, in respect of all the movements of the crane, such as hoisting, rotation, distribution and translation, a monitoring/control electronic unit (2) receiving at its inputs and processing the control signal (4) originating from the radio control box (3), and also receiving signals (5, 8, 9, 13, 15, 17, 19, 21) originating from sensors (6, 8, 11, 18, 20, 22, 23, 24) and from switches (14, 16). The electronic unit (2) delivers start and stop commands (27, 30, 31, 33, 34) at its outputs, while monitoring the action of the speed regulators (28) or other control members (35, 36) assigned to the movements, as well as the action of the crane's safety devices (32).

Abstract: The invention relates to a method for the overload protection of a mobile crane, in particular of a crawler-mounted crane, in which component-related geometrical data are stored in a memory. In accordance with a selected set-up, the geometrical data are put together to form a physical simulation model on a simulation computer. Taking into account real measurement data, the required geometrical data, centre of gravity data and forces are calculated, and from these the cut-off values. The crane is switched off when these cut-off values are reached.

Abstract: Two groups of test weights are stacked on a horizontal base frame transported to an aligned position underlying a crane to be tested for loading capacity. Such base frame is loaded with the test weights stacked thereon after assembly into a test apparatus by removable attachment through intermediate lift beams to an upper main lift beam through which such loading is transmitted directly to the crane.

Abstract: An load moment indicator, in a crane provided with hoist means of a main side and an auxiliary side, including a calculator in which a reference value if a rated load determined by the stability of a crane or the like is preset, a hoist load of the other side is converted into a load component of its own side, and the converted value is subtracted from a reference value of its own side to thereby obtain a rated load of own side, or in which a tolerant load that can be suspended by the other side is converted into a load component of its own side on the basis of a base of a reference value of the other side, and the converted value is compared with the reference value of its own side to select a lower value. Thereby, it is possible to make the most of the suspending ability of the main side and the auxiliary side and for an operator to grasp clearly a tolerance of the hoist load.

Abstract: The invention provides a load measurement in a crane hoist system. A parameter adaptation process uses a model of the system in order to measure the lifted load. A controller monitors hoist speed and hoist torque feedbacks that are input into the model and processed using a filter, as well as a previously determined load value. The model adapts automatically to determine the weight of the lifted load.

Abstract: A jib is supported for its luffing movement by a luffing rope mounted to a longitudinally intermediate portion of the jib. The jib has a truss structure with upper and lower beam members respectively overhanging upward and downward of load action line which connects a lifting point with a support pin.

Abstract: An electromechanical, remotely operated Auxiliary Hoist Control and Precision Load Positioner system and device is disclosed utilizing a Radio Frequency Hand Controller transceiver Unit distal to a Radio Frequency Hoist Controller Transceiver Unit for raising and lowering a large, heavy, bulky, fragile, or expensive piece of equipment by very gradual means to avoid hang ups that might otherwise destroy or seriously damage the equipment.

Abstract: The invention provides a load measurement in a crane hoist system. A parameter adaptation process uses a model of the system in order to measure the lifted load. A controller monitors hoist speed and hoist torque feedbacks that are input into the model and processed using a filter, as well as a previously determined load value. The model adapts automatically to determine the weight of the lifted load.

Abstract: An aerial work platform supported by a riser boom, a telescoping main boom, and a jib boom. Boom movement may be controlled by a platform control module or a ground control module connected to a controller by a controller area network (CAN). Movement of the platform and the jib boom are limited to a predefined envelope. If an operator attempts to move the platform outside the envelope, the controller automatically retracts the telescoping boom section or automatically levels the jib boom section in order to maintain the platform within the acceptable envelope. Boom section select switches permit the operator to select and move sequentially or simultaneously in different directions. Timers which are part of the system include various interlocks to accomplish safety and power saver features.

Abstract: A crane having a hydraulically actuated jib system, at least one cylinder for actuating the jib system and an apparatus for monitoring the pressure in the cylinder, which indicates the crane loading, wherein the feed flow of hydraulic fluid to the cylinder is controllable by varying the cross-section of a valve, and a signal is produced in dependence on the variation in pressure in relation to time which is detected in the cylinder or the variation in the loading of the piston guided in the cylinder in relation to time, which signal actuates the drive for adjusting the valve cross-section in the direction of a reduction in the detected variation in pressure or loading.

Abstract: An load moment indicator, in a crane provided with hoist means of a main side and an auxiliary side, including a calculator in which a reference value if a rated load determined by the stability of a crane or the like is preset, a hoist load of the other side is converted into a load component of own side, and the converted value is subtracted from a reference value of own side to thereby obtain a rated load of own side, or in which a tolerant load that can be suspended by the other side is converted into a load component of own side on the basis of a base of a reference value of the other side, and the converted value is compared with the reference value of own side to select a lower value. Thereby, it is possible to make the most of suspending ability of the main side and the auxiliary side and to grasp clearly a tolerance of the hoist load by an operator.

Abstract: A method for setting a safe work area and a rated load in a swing type work machine, as well as a swing type work machine which utilizes the said method, are disclosed. An area where a strength-based safe work area which is established taking the strength of a swing member into account and a stability-based safe work area which is established taking the stability of the work machine into account overlap each other, is set as a safe work area to be used actually. Likewise, out of a strength-based rated load which is set taking the strength of the swing member into consideration and a stability-based rated load which is set taking the stability of the work machine into consideration, the lower one is set as a rated load to be used actually. Using the safe work area and rated load thus obtained, there are made a safety control and an appropriate display.

Abstract: The present invention relates to a control device for a hoist mechanism of a crane, preferably for a crane with a jib which can be varied in length and be luffed, with a hydraulic motor driving the hoist mechanism drum which motor forms a closed hydraulic circuit together with a hydraulic pump driven by a motor, preferably by a diesel engine, and with a locking brake for the hoist mechanism drum.

Abstract: The automatic leveling and synchronization system for raising and lowering a counterweight includes at least a primary and secondary cylinder connected in series hydraulic communication. The primary cylinder includes a first rod connected to a first piston, and the first rod is attached to one end of a counterweight. The secondary cylinder includes a second rod connected to a second piston, and the second rod is attached to another end of the counterweight. A surface area of a bottom of the second piston is set equal to a surface area of a top of the first piston.

Abstract: A load measuring device for an aerial machine having a boom or jib which handles loads. A load bearing sheave has a winch line passed over it to raise and lower the load. A guide sheave maintains the winch line at a constant entry angle to the load bearing sheave. A dual axis load pin on which the load bearing sheave is mounted measures the force components of the load along two mutually perpendicular axes. Because the entry angle is constant, the load is dependent only on the two measurable force components and can be calculated and displayed. An overcenter machine has two load bearing sheave which are used alternately depending on whether the machine is overcenter or not. Each sheave in this case is mounted on a dual axis load pin.

Abstract: A replacement assembly is provided for retrofitting old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms with a hydraulically-operated fail-safe sideboom system. Conversion of discontinued, mechanically-operated, low-drive, Caterpillar sidebooms is accomplished by replacing the entire existing mechanical assembly with a single frame-mounted hydraulic assembly comprising a boom winch, a load winch, and preferably a single hand-operated joystick control. This single frame assembly is configured to be received by the existing foundation on discontinued Caterpillar sidebooms. Joystick technology is provided which negates cumbersome clutches and related multiple controls by affording a sideboom operator the ability to completely control the functions of both the boom and the load with a single joystick control which replaces the six conventional hand-operated mechanical controls that exist on the discontinued Caterpillar sidebooms.

Abstract: The boom length measurement includes a transmitting unit mounted on the fly section of a multi-section telescopic boom, and a receiving unit mounted on the base section of the multi-section telescopic boom. The transmitting unit transmits a first and second signal having first and second transmission speeds, respectively. The second transmission speed is less than the first transmission speed. Based on a difference in transit times of the first and second signals received by the receiving unit, a length determiner determines the length of the multi-section telescopic boom. A display displays the determined length.

Abstract: The present invention relates to a crane vehicle with a jib, preferably a telescoping jib, hinged to its superstructure which jib can be luffed by a luffing ram which is hinged to the jib and the superstructure, with extending sliding beams which are positioned at the end parts of the longitudinal sides of the carrier which face each other and which are provided at their ends with extending stabilizer bases, and with an overload safety unit which generates a signal and/or stops the crane operation when the crane reaches or exceeds limits which endanger its stability. In accordance with the invention a monitoring unit is provided which detects the extension state of the sliding beams and which feeds the signals corresponding to the relevant extension state of the individual sliding beams to the overload safety unit and the overload safety unit assumes the lowest extension length of one of the sliding beams for all sliding beams to determine the limits which endanger the stability.

Abstract: An overhead travelling carriage is provided wherein three drums are arranged on a base of a hoist unit along the sides of an imaginary equilateral triangle. Two motors and a brake are arranged along imaginary lines which join the imaginary center of the imaginary equilateral triangle where a hypoid gear of the hoist unit is positioned and the imaginary apices of the imaginary equilateral triangle. The rotation of the hypoid gear is transmitted to a spur gear on the drum side of the spur gear in order to drive the drum. As a result, the hoist unit of the overhead travelling carriage may be reduced in size.

Abstract: An object of this invention is to improve safety in a crane. A boom control signal .alpha.r and a winch control signal .beta.r are simultaneously outputted to, respectively, a boom drive portion and a winch drive portion of a driving portion 30 for obtaining, respectively, target values Xr, Yr, with current working radius X and lift Y that vary according to the flexure of boom 4 as feedback amounts, thereby a boom hoisting angle and a rope length being controlled simultaneously.

Abstract: The present invention relates to a suspension load and tipping moment calculating apparatus for a mobile crane which can calculate a suspension load and a tipping moment with high accuracy and use an excessive load prevention load while ensuring safety. For this reason, the apparatus is provided with sensors (50, 48, 46) for detecting a boom length, a boom angle, and an axle weight of a boom derricking cylinder (26) on a second boom (28) side, and is equipped with a controller (38) for calculating a suspension load (Wa) suspended from the second boom (28) based on signals from these sensors. In addition, for calculating a tipping moment, a boom length sensor (44) and a boom angle sensor (42) on a first boom (24) side are provided.

Abstract: A snag load protection system for a train including a guide frame, a sheave housing slidably received within the guide frame, and a hydraulic cylinder connected to the guide frame and to the sheave housing. The hydraulic cylinder serves to exert a compressive force against the sheave housing so as to resist relative movement between the guide frame and the sheave housing when forces exerted by the sheave housing are within a predetermined value. A relief valve is connected to the hydraulic cylinder for releasing hydraulic fluid from the hydraulic cylinder when the force is greater than the predetermined value. Pressure and position limit switches are connected to a motor so as to stop the movement of a hoist rope when forces exceed the predetermined value.

Abstract: In a vehicle mounted digger derrick or crane, the moment applied to the boom by a lift cylinder is controlled in a customized manner to more fully utilize the structural strength of the machine at different working positions of the boom. In one embodiment, the moment is controlled by controlling the moment arm through a pivot link which carries the base end of the lift cylinder and which is pivoted by an auxiliary cylinder. In another embodiment, the force component of the moment is controlled in response to changes in the boom angle or moment sensed by a linear position transducer or other sensor.