Limit Switch Manufacturers for EOT Cranes in India

A limit switch is operated by a mechanical actuator or sensor which detects the presence or absence of an object. There are full contact or contactless limit switches . A limit switch typically cuts power or sends a control signal to cut power to the moving equipment such as an overhead crane or robot.

A limit switch is used to contain the movement or motion of a machine such as a crane. A limit switch can also be used to bring the machine to its starting position or to a previously known location . A limit switch prevents damage to nearby equipment or injury to people by limiting the motion of a moving overhead crane . In an industrial environment , a limit switch is necessary in each direction a machine can travel.

Rotary limit switches are directly attached to the gearbox of the motor with a shaft and a coupling. The coupling helps in relieving stress to the shaft of the limit switch in case of Misalignment . The movement of the gearbox rotates the shaft of the limit switch . Rotary limit switch contains the movement of a hoist machinery in the vertical direction where the upper vertical limit and the lower vertical limit of the movement of the hook of the hoist is set.

Gravity Limit Switch for EOT Cranes

Gravity limit switch works on the basic principle of weight balance scale where One counter weight is mounted at one side of the lever and another suspended weight is tied at another end of the lever.

Working principle of Gravity limit switch

At the center of the lever a Shaft is present with attached Coaxial cams . The lever shaft and cams , all rotate simultaneously at the same angle.
These cams are responsible for changing the state of electrical contacts position, placed inside the limit switch enclosure. Electrical Output wire is fed to crane control panel.

The suspended weight is directly connected to the hoist wire rope (as shown in below image) at the predetermined point where it prevents the hoist from reaching the upper block and wire drum.

Suspended weight is a little heavier than the counter weight ,so due to gravity effect suspended weight wire become stiff and it makes counter weight lift upward.During normal operation the limit switch normally remains closed. A gravity limit Switch will not have a spring return mechanism .

Gravity limit switch operates when the hoist reaches its predetermined point. In this condition the suspended weight rests on the surface of the hoist and suspended weight wire sags and counter weight changes the position and electrical contactor cut off power to stop the hoist motor. Gravity limit switches can be used parallelly with rotary limit switch in a vertical type motion such as hoisting .

If the rotary limit switch fails to activate at the correct number of turns, the gravity limit switch will be operated to provide an emergency stop .

Applications of Gravity Limit Switch:

Since Gravity Limit Switches work on the principle of gravity , they are always used in Vertical Movement such as

• Crane Hoists

• Hoists Machinery

• Main hoists of EOT Cranes

• Auxiliary Hoist of EOT Cranes

• Electric Hoists