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| LIMIT AND FOOT SWITCHES | |
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Can the so-called “position” limit switches be used for safety purposes? |
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They can be used but it is imperative the break (NC) contacts have direct opening operation capability  , that is with direct action, without non-resilient
members, and there is no direct or easy access to the actuator, moved by the direct opening
travel, to consent the simple overriding of this safety function.
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How do slow-break contacts, mounted on the LOVATO ELECTRIC K series limit switches, operate? |
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The
movement of the contacts is bound to the contact carrier travel. The
contact speed is directly proportional to the actuator speed. |
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Limit switches can be equipped with snap or slow break action contacts. What does "snap action contact" mean? |
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The switching of the contacts is obtained abruptly when the contact carrier moves, at a speed not related to the one of the operating head, and reaches the engage point, also called the snap action point. The movement of the operating head does not affect the contact carrier until the snap action point is engaged. |
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Is it true all limit switches must have a metric thread entry for conduits as of 2001? |
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The
European standard EN 50262 prescribes all new models must have cable
entry with metric thread. LOVATO ELECTRIC has complied with this
current standard prescription so the new limit switches are equipped
with M20 thread cable entry. |
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What colour do safety switches have to be? |
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Standards do not
impose any specific colour for safety switches. Nonetheless, it is normal practice of OEMs to prefer this red colour. In fact, it provides for easy and immediate identification of the limit switch on board machines. With this in mind, LOVATO Electric has selected the red colour for the "key", "hinge" and "slotted lever" versions. |
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What type of limit switch must be used for safety applications? |
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The
limit switches with direct opening operation of contacts must be
used. The contacts to connect to the safety circuit are the NC (Normally Closed) type. There are three dedicated types of operating heads for the safety and control of mobile protections: "key", "hinged" and "slotted lever" versions. |
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What does direct opening operation mean? |
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There is a direct
connection between the mobile contacts and the operating head
on which the operating force is applied, without the use of
non-resilient members, i.e. not dependent on springs. The principle of direct opening operation assures the full contact opening of the break-contact elements even in case of welding or fault. |
