Electric chain hoists are being increasingly widely used in both industrial and everyday applications. But do you really know what an electric chain hoist is at its core? In the 1950s, Japan developed the chain-type electric hoist and, building on its highly developed economy, put it to efficient use in lifting and material-handling operations, achieving significant progress. Although subsequently affected by the oil crisis, the industry responded to diverse market demands by developing differentiated products, leading to a steady expansion of end-user adoption. To meet the varied requirements of electric chain hoists, it is essential that their performance and quality reach a high standard and that their application scope continue to broaden.

1. Structure and Characteristics of Electric Chain Hoists

Electric chain hoists are available in two basic series: standard and high-speed. These models can be used as standalone units or combined with small vehicle traveling mechanisms (manual trolleys, manual trolleys, manual trolleys, and electric trolleys) to function as cranes.

Overall Structure

The electric chain hoist consists of a high-performance steel plate frame that supports the winch assembly. The motor is mounted on the right side, while the gear and brake are located on the left. To enhance maintainability, the power supply and the cable for the hand-held control box are designed as plug-in connectors. The lifting limit is implemented via a mandatory start limit switch. The main frame is constructed from a fully welded, all-steel structure, offering a compact footprint, light weight, and high productivity. The following is an overview of the key components.

(1) Round-link chain

Chains are used in high-speed sprocket engagement under frequent dynamic loading, making tensile strength, fatigue strength, toughness, and wear resistance critical. Therefore, the materials used for chains must exhibit both hardenability (surface hardening) and toughness, and alloy steels that offer good formability, weldability, and resource efficiency need to be developed. In addition, to ensure the chain’s balanced mass, the manufacturing process is automated, and the chain undergoes load testing.

(2) Brakes

To accommodate high-speed, frequent operation, high-speed chain electric hoists are equipped with a dual-braking system consisting of an automatically adjustable primary brake and an auxiliary brake integrated within the motor.

The primary brake is a braking method that operates when power is cut. When power is simultaneously supplied to the motor and the brake, the movable iron core is attracted, releasing the braking surface. Upon power failure, spring force presses against the brake wheel, generating braking torque. As the brake is applied repeatedly and absorbs energy, wear gradually reduces the braking force, increases slippage, and extends the travel of the electromagnet; therefore, periodic adjustment is required. This brake features automatic adjustment: any increase in the electromagnet’s travel caused by wear of the brake wheel can be compensated for by the adjusting lever (or follower). If the travel becomes excessive, the adjusting screw can be rotated to restore the brake to its original, normal setting. Should the primary brake fail, the secondary brake will ensure a steady descent at a constant speed, preventing accelerated lowering under load. This is achieved through the use of a centrifugal brake—a compact, energy-efficient device that remains stationary unless an abnormal drop occurs.

The manual pushbuttons in the control circuit are designed for 24-volt low voltage and feature a drop-resistant (water- and oil-proof) cartridge, ensuring reliable operation. In addition, when a three-phase power supply is used, if the wiring sequence is incorrect, the lift limit switch will fail to operate properly; therefore, a reverse-polarity protection device has been incorporated. The principle behind this protection is to employ a phase-shifting circuit that uses relays to disconnect the control circuit in the forward, reverse, and reverse directions. Adjustments also include accounting for the increased air gap in the electromagnet due to wear on the brake wheel, as well as fine-tuning the screw by one inch.

2. Overload protection device

To prevent accidents caused by overload, the chain electric hoist is equipped with a dual-function mechanical–electrical safety device. A load-sensing element is mounted on the reduction gear, clamped between the gear and its shaft, and utilizes spring-induced displacement to detect the load torque. The control unit transmits this displacement signal to a switch in the hoisting control circuit; if the load exceeds the rated capacity, the spring-induced displacement triggers the switch to halt the lifting motion. This device serves as an effective means of detecting and controlling overloads, even for sudden, transient loads such as those resulting from hook misalignment or other abnormal conditions. It complies with the “overload protection device” requirements stipulated in the Structural Standards for Cranes and Related Equipment.

A. Under normal load conditions, the spring force and the load torque are balanced, and the gear and the countershaft gear engage to transmit torque. At this time, the sensing device remains stationary and operates normally.

B. In the overload condition, when the load torque exceeds the spring force, the pinion on the auxiliary shaft disengages from the main shaft gear, the ball is ejected from the tapered bore, and the stop plate is pushed outward. As the stop plate actuates the lever, the microswitch in the control circuit opens, thereby shutting down the system.