Technical Guide for Limit Switches
Stroke Settings vs. Dog Movement Distance
•
The following information on stroke settings is based on the
movement distance of the dog instead of the actuator angle.
The following is the optimum stroke of the Limit Switch.
Optimum stroke: PT + {Rated OT
×
(0.7 to 1.0)}
In terms of angles, the optimum stroke is expressed as
θ
1
+ θ
2
.
•
The movement distance of the dog based on the optimum stroke is
expressed by the following formula.
Movement distance of dog
φ
: Dog angle
θ
: Optimum stroke angle
R: Actuator length
X: Dog movement distance
•
The distance between the reference line and the bottom of the dog
based on the optimum stroke is expressed by the following formula.
Y = a + b + r (mm)
a: Distance between reference line and actuator fulcrum
b: R cos
θ
r: Roller radius
Y: Distance between reference line and bottom of dog
Dog Surface
The surface of dog touching the actuator should be 6.3 S in quality
and a hardness of approximately HV450.
For smooth operation of the actuator, apply molybdenum disulfide
grease to the actuator and the dog touching the actuator. This is ideal
for Limit Switches of drip-proof construction and Multiple Limit
Switches.
Maintenance and Repairs
The user of the system must not attempt to perform maintenance and
repairs. Contact the manufacturer of the system concerning
maintenance and repairs.
Other
•
The standard material for the switch seal is nitrile rubber (NBR),
which has superior resistance to oil. Depending on the type of oil or
chemicals in the application environment, however, NBR may
deteriorate, e.g., swell or shrink. Confirm performance in advance.
•
The correct Switch must be selected for the load to ensure contact
reliability. Refer to precautions for micro loads in individual product
information for details.
•
When using a Limit Switch with a long lever or long rod lever, make
sure that the lever is in the downward direction.
•
Wire the leads as shown in the following diagram.
•
Reduced ambient temperature tends to result in hardening of the
actuator's rubber seal. Therefore, reset may be delayed or reset
may fail if the Switch is used with the actuator continually pressed
in. Contact your OMRON representative if the Switch is to be used
for this type of environment or application.
X = Rsin
θ
+
R (1–cos
θ
)
(mm)
tan
φ
70% to 100% of rated OT
PT: Pretravel
OT: Overtravel
φ
Dog
Reference line
Mounting hole
Y
Dog
Crimp terminal with insulating sheath
Terminal screw
Terminal
screw
Terminal
Terminal
Crimped location facing up Lead
Lead
Correct Wiring
Crimp terminal with insulating sheath
Terminal screw
Terminal
screw
Terminal
Terminal
Too close to maintain dielectric strength
Crimped location facing down Lead
Lead
Incorrect Wiring
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C-8
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