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Cam-follower levers are particularly well suited for use with plastic actuating cams. Abrupt actuation or release of Microswitch actuators shortens the life of the microswitch. For this reason the cam should preferably provide a continuous movement. Ideally they should be of cyclodal form.
Various lever types are available for use with the Saia-Burgess Microswitch. They are generally stainless steel. If roller or cam- follower levers are approached in the reverse direction, care must be taken to ensure that the angle of approach is small enough not to jam the lever.
The electrical life is based on laboratory controlled tests. In practice, freguency, speed of operation, type of load, suppression, actuator travel used, ambient humidity, temperature, and other environmental conditions can have a major effect on life. Individual assessments are welcome at our Saia-Burgess Test Laboratory.
The figures relate to the number cycles made without electrical load.
Electrical ratings are ratings according to UL 1054, CSA22.55 or IEC61058-1. Where these are not available a general rating is given based on in-house laboratory testing. The rating tables should be considered as safe working maximum for most applications. However, Microswitch performance is influenced by a variety of factors, including: Frequency of operation, Type of Load, Amount of Travel Used, Temperature, Humidity. Please contact us about your specific application.
These can generate very high peak currents which can cause contact welding. Applications should be subject to individual assessment.
Force applied in a straight line to the plunger to move it to operating position.
That part of a machine, appliance or device which moves or exerts force to actuate a Microswitch.
Direct current (DC) ratings where shown should not be exceeded if destructive arcing and contact welding are to be avoided. Some form of arc suppression is recommended when Microswitches are used in DC circuits containing inductive devices wired in series with the switch and the supply.
Actuating plungers should be operated in the direction of their axis. Where this is not possible the use of actuating levers is recommended. For direct actuation the attack angle should not exceed 30*.
The general ratings tables provide data for switches used to control inductive circuits at a power factor of 0.5 (EN 0.6; UL 0.7 means HP-Rating 0.5)
Because of the very high inrush currents associated with incandescent lamps, applications should be subject to individual assessments.
If switches are likely to be subjected to shock and vibration, select models with the highest available actuating force. Saia-Burgess switches feature low mass mechanisms which are inherently resistant to shock and vibration. If possible, the Microswitch should be mounted so that the line of acceleration is at right angles to the travel of the plunger. The maximum available over-travel should be used.
Temperature of the medium surrounding the switch. Most switches are suitable for use in ambient temperatures between -10* and 85*C, but certain switches are designed and constructed in special materials to withstand temperatures to150*C.
Any force used intentionally to influence the switch actuator. Both actuating and release forces are applied forces.
The posture of a switch when mounted in an application. While virtually all switches will operate in any attitude, certain operating characteristics may be affected by the direction of the gravity, and for this reason they are specified when the switch is in the upright position.
The time taken by the moving contact in Microswitch mechanisms to move from one stable position to another.
The distance in air between current carrying parts of opposite polarity or between any current carrying part and an earthed (grounded) metal plate to which the switch is attached.
The force exerted by the moving contact on the fixed contact.
The electrical resistance measurable across closed contacts.
Or "contact gap". The distance in air between two open contacts. The gap achieved when a Microswitch is actuated is a function of its design, but it is dependant on the amount of actuator movements in positive action switches.
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| Considerations when designing a Microswitch into your application: |
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The path along the surface of insulating material between current carrying parts of opposite polarity or between any current carrying part and an earthed(grounded) metal plate to which the Microswitch is attached.
The inevitable separation of contacts achieved when a positive snap action Microswitch is actuated.
The difference between the values of actuating and release forces.
The position of the actuator when not subjected to applied force. Also known as the "rest position".
Resistance as measured between the normally-open and normally-closed terminals, or between all terminals connected together and a metal plate to which the switch is mounted. In dry conditions the value would be expected to be greater than 5000 megohms.
Applicable only to positive snap action Microswitches. It is the position of the actuator when contact separation commences. When this is not quoted as an operating characteristic it is because the contacts begin to separate immediately the actuator is moved from its free position
The movement of the microswitch actuator between operating position and release position during the return stroke to rest position.
More than two poles.
A feature of certain lever-actuated Microswitches where the lever bears upon a plunger and causes it to move in the same direction as itself.
Terminals which protrude from the Microswitch and therefore are exposed. It is good installation practice to screen these if they are accessible to the operator.
The point in a snap action switch's cycle of operation where the moving contact leaves one fixed contact and makes with the other. It is carefully specified as an actuator position as it is a switch characteristic fundamental to good installation.
Movement of the microswitch actuator beyond the operating position. For some switches available over-travel is quoted as a nominal dimension, and it is important that this should not be exceeded. For other microswitches over-travel is identified by the expression depress to case", meaning that the actuator may be moved until it reaches the switch case or plunger boss.
Ascribed to a normally-closed only Microswitch which has moving contacts aligned or linked to the actuator so that movement of the latter must produce a corresponding movement of the contacts to cause a forced break without the aid of springs. Snap action mico switches of this type are mainly used in safety applications.
The sort of installation, considered necessary in high risk safety applications, where a positive snap action microswitch is opened positively by direct mechanical action, as by the rising profile of a cam or the opening motion of a guard.
Movement of the Microswitch actuator between free and operating positions. Quoted only for switches with adjustable lever actuators which do not have a fixed free position. It can be calculated for other microswitches by deducting operating position from free position.
The lowest force applied to the Microswitch actuator which can be Overcome by the return force inherent in the mechanism to allow The actuator to return to its release position.
The point in the switch cycle where decreasing applied force allows changeover to occur so that the contacts can assume their un-operated relationship.
The degree to which switch characteristics are maintained throughout the life of the Microswitch.
A feature of certain lever-actuated snp action Microswitches where the lever in its free position holds the plunger depressed. Depression of the lever allows the plunger to assume its un-operated position. The relationship between lever and plunger movements is the reverse of normal and, because of this, the positions of the normally open and normally closed terminals is the reverse of normal.
The cause of wear on plunger actuator and its guide when force is applied in any direction not aligned to the plunger axis. A lever or roller interposed between plunger and actuating medium will absorb side thrust and deliver a correctly aligned force to the plunger.
A microswitch mechanism which opens or closes the conductor at one point only.
One complete switching operation, from free position through operating position into over-travel and back through release position to free position. Mechanical life estimates reflect the number of switching cycles expected to be accomplished before operating characteristics become impaired.
The total resistance offered by a microswitch in a circuit, as measured from terminal, through mating contacts, to terminal.
The sum of pre-travel and available over-travel. Total travel force is the applied force necessary to achieve this movement.
See creepage distance.
The time taken by the moving contact in snap action Microswitch mechanisms to move from one stable position to another |
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