Pushbuttons and Position or Limit Switches«

PUSHBUTTONS

They are auxiliary control devices provided with an element intended to be actuated by the force exerted by a part of the human body, generally the finger or the palm of the hand, and which has an accumulated return energy (spring).

However, due to the large number of manufacturers and the diversity of construction possibilities, in technical jargon it is common to see the following terms used:

• For the actuating element or push button: actuator, head, rosette, key, etc. Manufacturers strive to achieve a pleasing finish, also conditioned by the color, according to the function to be performed by the push button.
• The color of which can be the entire actuating element or, as is very common, the flush or protruding button that is press-fitted or threaded onto the head.
• For the control auxiliary or connection element: contact block, contact chamber, body, etc. Pushbuttons are manufactured for mounting on a base and for flush mounting.

Pushbuttons and their components

Pushbutton boxes and flush-mounted control units are equipped with contacts that, depending on the type of control head:

• They only connect or disconnect during the impulse, then take their original position (momentary contacts).
• They remain in position when acting on the control head (maintained or engaged contacts); in this case, a second intervention is necessary to cancel the previous one.

Types of pushbuttons

1. Intern: Avoid all unexpected maneuvers.
2. Outgoing: rapid intervention, emergency stop.
3. Rod: Rod maneuver in any direction (pendant pushbutton box).

Types of pushbuttons

Rotary knobs:

Of two or three positions held with automatic return and zero (selection of circuits or of a type of operation: manual operation, automatic operation and stop on a compressor or pump equipment, for example).

When the control is done by key (removable or locked in certain positions) only the authorized person can perform the maneuver.

POSITION SWITCHES OR “LIMIT SWITCHES”

Mechanical control contacts are used to control the position of a machine, allowing it to start, slow down, or stop at a specific location, or to control automatic operating cycles in modern machines.

Types of position switches

The main factors involved in choosing a mechanical control contact are:

• Protection against tampering, violent shocks, liquid splashes, and the presence of gas.
• Nature of the environment: humid, dusty, corrosive and the temperature that exist in the place of use.
• The available space to house and fix the device.
• The conditions of use: frequency of maneuvers, weight and speed of the mobile to be controlled, required precision and fidelity, effort required to activate the contact.
• Number and nature of contacts: slow or sudden breakage, possibility of regulation.
• Nature of the current, voltage value.

Symbol: