There are many heavy-duty vehicles like excavators, forklifts, trucks, cranes, etc… that are designed to serve various industries. Reach stacker is one such vehicle used for handling containers, semi-trailers, and loose goods. The major contributions of this mobile machinery can be found in small terminals or medium-sized ports for handling intermodal cargo containers. The popular features of a reach stacker include speed, power, precision, low operational cost, efficiency, and more. This vehicle will help to transport large containers weighing tons to a shorter distance and also for stacking/unstacking the containers in rows based on the access. Flexibility, versatility, higher stacking, user-friendliness, strength, safe operation, and storage capacity are other key benefits of using reach stackers.
The appearance and operation of the reach stacker are similar to that of forklifts. But, reach stackers are more effective and safe for transporting heavy containers while comparing them with forklifts. The design of reach stackers consists of a boom, comfortable cabin, chassis, rotator, engine, hydraulic system, combi attachment, and more. The extended boom nose is a type of attachment that will help the reach stacker to easily pick containers below ground level. The auxiliary components like steering system, cooling circuit, braking circuit, and spreader actuators are also necessary to reach stacker working.
Reach stackers are available in the market with varying specifications. Lifting capacity, wheelbase, turning radius, and reach are some of those specifications that need to be considered while selecting one. The lifting capacity indicates how much load this mobile machine can carry and transport safely. The distance between the front and rear axles is known as the wheelbase. The radius of the smallest circle that can be created by this vehicle is the turning radius and it denotes how flexible and convenient the machine is. The reach of this vehicle is calculated by measuring the difference between the fully-retracted and fully-extended positions of the boom.
Hydraulics in Reach Stacker Boom
The boom is the most essential part of the reach stacker that carries the heavy load and helps the vehicle to reach the required height. The telescopic boom of the reach stacker will provide the extended horizontal reach that simplifies the overall load handling task. The boom is constructed with high tensile steel with minimum welds and this will improve the overall strength of the structure. The boom uses hydraulics for producing the required power for lifting and holding the loads. Let’s discuss more details on the hydraulic working of this boom.
The primary energy source of the reach stacker is the Internal Combustion Engine(ICE). The power required to translate, lock, and lift heavy load is provided by this ICE. The two variable displacement pumps used for producing hydraulic energy is equipped with a load sensing(LS) system and it is powered by ICE. The pump will pressurize the fluid in the reservoir and is supplied to the lifting and telescoping cylinders with the help of proportional control valves. The control valves will regulate the flow rate, pressure, and direction of oil flow. The hydraulic circuit in the boom uses wider hoses for reducing pressure drops, producing a lower flow rate, minimizing friction, and controlling heat development.
The rotators used by reach stackers for providing rotational motion to containers is also operated by hydraulics. The rotator contains an upper and a lower yoke connected together with a powerful bearing and this part is attached in the inner boom. The two hydraulic motors will drive the gear-ring and this will produce the required rotation of the container. The circuit will also include hydraulic dampers to prevent the swinging of containers.
Also Read: Hydraulics in Mobile Heavy Equipment
Reach Stacker Spreader Mechanism
What is a spreader in reach stacker and how it works? The spreader is the attachment fixed on to the reach stacker for safely handling large containers. A spreader connected to the boom will lock the four top corners of the cargo container and enables the operator to lift the load easily. The spreader will include a side-shift mechanism, rotation mechanism, and forward-backward tilt mechanism for accurately positioning the container.
The spreader can be controlled from the operator cabin over serial communication(CANopen) or parallel wiring. An Electronic Control Unit will process these signals and create the desired mechanical output with the help of hydraulics power. The proximity switches are mounted to the grapple arms for sensing contact with the cargo container. The integrated twist locks located at the corners will control the locking and unlocking functions. Also, this locking mechanism will prevent premature locking and accidental unlocking.
The twist-lock system, telescoping system, and side shift system are hydraulically activated using cylinders. The side shift system contains an independently adjustable hydraulic cylinder on the yoke beam that helps for shifting or inclining containers. Each of the side flippers is equipped with two hydraulic cylinders. The telescoping system contains hydraulic cylinders that can be extended with pressurized hydraulic oil.