Mechanical Limit Switches
RACO Linear Actuators are designed with either a Ball or ACME screw, of a certain overall length and with a screw diameter and pitch, to achieve the motion required to move its load in a specific application. When powered, the electrical controls will command the rod to move forward or reverse at a speed and for a desired distance. RACO Electric Actuators should always be ordered with internal end-of-travel limit switches, or consideration should be made for external limit switches to be mounted in the field.
A limit switch used in an actuator application acts as a safety mechanism to prevent over-travel. One type is a mechanical device that triggers a change in the actuator's electrical circuit, typically by cutting off power to the motor, when the actuator reaches its defined endpoint (either fully extended or fully retracted). This prevents damage to the actuator or the equipment it's connected to. Additional mechanical limit switches can also be used to stop the actuator at various midpoints throughout the available travel. RACO does offer electronic versions of limit switches (EPS 02 and EPS 06) and positioning devices, but sometimes harsh environments or even explosion proof atmospheres dictate the Type II mechanical limit switch to be used.
How Limit Switches should be selected
RACO can provide many internal and external mounting arrangements for limit switches, depending on the size and configuration of the actuator. An accessory housing will be supplied to the actuator assembly.
The Type II mechanical limit switches can either be mounted directly onto the back of the RACO motor or in a lateral accessory housing. When mounted in the lateral accessory housing, the rotation of the screw is translated via a timing belt into a switch set. Based on the number of revolutions on the screw, determined by the stroke of the actuator and the pitch of the screw, an appropriate gear reduction will be selected. An accurate, repeatable, absolute position signal can be obtained via the cam activated sealed micro switches, which are adjustable over the entire stroke length of the actuator.
Type II mechanical limit switches are typically used on the RACO MA series actuators and are available with up to 3 pairs of limit switches. This enables the user to assign two intermediate stroke positions in both the forward and reverse direction.
External limit switches, commonly used on the belt driven RACO LM series of Linear Actuators, are either proximity or snap action switches. Whether internal or external, Limit switches are positioned at the extreme ends of an actuator's travel (stroke).
Function and Benefits of RACO Mechanical Limit Switches
When the actuator's moving part, the screw or rod, reaches the limit switch, it physically actuates the switch. This switch engagement either breaks the electrical connection to the motor, stopping its motion, or triggers another action, such as activating a warning light or changing the direction of the actuator.
From a Safety standpoint, Limit switches are crucial for preventing the actuator from overextending or over-retracting, which could cause extensive damage to the actuator itself, bending the screw or further damage to the machinery it's controlling. RACO limit switches are adjustable, allowing users to define the exact point at which they want the actuator to stop within its full range of motion. Please consult with a RACO engineer to see how functioning limit switches can be integrated into your application.