Detailed Mechanical Structure
1.1 Suspension (Item 1)
The suspension unit serves as the connecting interface between the two closing ropes and the lifting rope. The crane hook is directly engaged with the pre-fabricated oval suspension eye provided on the suspension assembly.
Important Safety Note: For operational safety, the crane hook must be equipped with a securing device (anti-drop latch) to prevent accidental disengagement of the hook from the suspension eye, which could otherwise lead to a catastrophic drop.
Grab Head (Item 2)
Housed within the remote control grab head is the upper roller block, which features a three-fold reeling arrangement to achieve a mechanical advantage multiplication effect for the wire rope system. At both ends of the head, screwed rope bell mouths made of hardened steel are fitted. These components serve as precision guides for the closing ropes, effectively minimizing abrasion and extending the service life of the wire ropes.
Pressure Rods (Item 3)
The pressure rods establish a rigid connection between the scoops and the grab head, thereby forming the mechanical counterpoint (fulcrum) in the closing-force transmission path. The tensile forces from the closing ropes are transmitted through the remote control grab head to the pressure rods and subsequently act upon the scoops to generate the required closing/gripping force.
Mobile Traverse (Item 4)
The mobile traverse houses the lower roller block of the lifting block system. Together with the upper roller block in the remote control grab head, these two assemblies constitute a complete movable/fixed pulley system. The closing rope forces are transmitted via the lower roller block to the mobile traverse, and from there are transferred-through bolted connections-to the piston rods of the locking cylinders.
3.5 Rope Compensation Frame (Item 5)
The extremities of the two closing ropes are anchored to the rope compensation frame, which is connected to the mobile traverse in a pendulum fashion. The primary function of this frame is as follows: if the grab assumes a tilted orientation during operation, the compensation frame automatically equalizes the tension between the two closing ropes, ensuring that the closing force remains centrally transmitted to the mobile traverse. This design prevents uneven loading that could otherwise cause pulley blockage or rope derailment.
3.6 Traverse (Item 6)
The traverse serves as the pivotal connection point for the scoops, around which the scoops rotate to perform opening and closing motions. Additionally, the traverse functions as the mounting base for both the hydraulic system (Item 10) and the electrical system (Item 9).
Hydraulic System (Item 10) and Locking Cylinders (Item 7)
2.1 Hydraulic System Configuration
The hydraulic system is fully enclosed within the traverse and comprises the following main components:
Oil tank - for hydraulic fluid storage
Control block (valve manifold) - for directional and flow control
Hydraulic hoses - serving as flexible connections between the locking cylinders, the oil tank, and the control block
2.2 Operating Logic of the Locking Cylinders
The locking cylinders mechanically link the mobile traverse (Item 4) and the traverse (Item 6). Their primary function is to transmit the closing rope forces through the traverse to the scoops of the single-rope remote control grab.
Grab Opening Principle:
When the grab is to be opened, the hydraulic system hydraulically unlocks the locking cylinders.
In the unlocked state, the combined weight of the traverse, the scoops, and the bulk material causes the piston rods to extend. This extension motion drives the scoops to pivot about their hinge points until the grab is fully opened.
The engineering ingenuity of this design lies in the following: the closing force is provided by the wire ropes, while the opening force relies on gravity - the hydraulic system acts solely as an "unlocking" mechanism rather than actively applying opening force. This approach significantly reduces both the power requirement and the energy consumption of the hydraulic system.
2.3 Emergency Manual Operation
In the event of a remote control failure or electrical system malfunction, the hydraulic system (specifically, the solenoid valve) can be manually actuated via an emergency switch system, enabling forced opening of the remote control grab. This redundant safety feature ensures that the equipment can still discharge its load under fault conditions, thereby preventing jamming accidents and safeguarding operational continuity.
3. Electrical System (Item 9)
The electrical system is housed within a steel plate enclosure, providing robust protection against atmospheric influences such as moisture, dust, and saline corrosion - making it particularly suitable for outdoor port and dockyard environments.
Power Supply Scheme:
A nickel-cadmium (Ni-Cd) battery supplies power to both the wireless transmitter and the solenoid valve.
Depending on the switching rate (frequency of actuation), a single charge supports up to 24 hours of continuous grab operation.
4. Radio Remote Control System (Item 11)
4.1 System Composition
The radio remote control system consists of two principal components: a transmitter and a receiver.
Receiver: Housed together with the electrical system within the steel plate enclosure, ensuring an equivalent level of environmental protection.
Transmitter: Can either be carried by the operator via a neck strap (portable mode) or be permanently installed in a stationary position within the crane cabin (fixed mode).
4.2 Power Supply and Charging
The transmitter is also powered by a nickel-cadmium battery, providing a maximum operating time of approximately 24 hours, depending on the switching rate.
For fixed-installation applications, the transmitter can be additionally equipped with an external power pack (optional extra equipment), enabling continuous operation without battery constraints.
A battery charger is included within the scope of supply, capable of simultaneously recharging both the transmitter and receiver batteries.
The recharging time is approximately 12 to 14 hours.
The charger accommodates either 110 V or 220 V mains supply voltages, with an automatic voltage adaptation feature that eliminates the need for manual voltage selection.
5. Scoops (Item 8) and Overload Protection
The scoops are the direct material-engaging components responsible for picking up bulk materials. When handling heavy bulk materials, the remote control grab and the lifting appliance can be protected against overload conditions through the incorporation of spill plates provided within the scoops.
Operating Logic:
When the weight of the grasped material exceeds the designed rated capacity, the spill plates automatically open, allowing a portion of the bulk material to overflow. This action effectively limits the actual load to within the safe operational range.
This constitutes a purely mechanical overload protection mechanism, requiring no electrical or hydraulic intervention. Its response is immediate and highly reliable, making it particularly suitable for harsh working environments.
6. Summary of System Synergistic Operation (Closed-Loop Sequence)
Closing/Grabbing: The crane hoists the closing ropes → the closing force is transmitted through theremote control grab head, pulley blocks, mobile traverse, and locking cylinders to the traverse → the scoops pivot about their hinge points and close, securing the bulk material.
Locking/Holding: The locking cylinders remain in the locked state, maintaining the scoops in the closed position and securely retaining the material.
Opening/Discharging: The operator actuates the "open" command on the remote control → the receiver decodes the signal and energizes the solenoid valve → the hydraulic system unlocks the locking cylinders → the combined weight of the traverse, scoops, and material extends the piston rods → the scoops pivot open and discharge the material.
Emergency Condition: In the event of remote control or electrical failure, the operator manually actuates the solenoid valve via the emergency switch, enabling forced load discharge.
