Crouzet MICROSWITCHES Basic Technical Concepts
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BASIC TECHNICAL CONCEPTS
INTRODUCTION
Our microswitches are high-precision, snap -action switches and these are the main features for which they are notable:
› Fast and reliable switching largely independent of actuating
speed
› High electrical ratings but small dimensions
› High repeat accuracy of switching points and forces
› Low operating force
MICROSWITCH CONSTRUCTION - ELECTRICAL FUNCTIONS
› Single-break changeover SPDT Microswitch (e.g. V3 83161)
› Short pre-travel but large overtravel
› Very long service life
› Extensive range of connections, xing means and actuators for
easy adaptation to numerous applications.
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Operating device (Plunger)
Return
spring
Fixing hole
Housing
Conductive pivot point
Snap-acting blade
Fixing hole
NC terminal (2)
Mobile contact
Fixed contact
NO terminal (4)
Common terminal C (1)
› Double-break changeover SPDT Microswitch (e.g. 83132)
Housing
NO terminal (3)
Mobile contact
NC terminal (1)
Fixing hole Fixing hole
NO and NC circuits must be used at same polarity.
Operating device (Plunger)
Snapacting
blade
Return spring
Fixed contact
NO terminal (4)
Mobile c ontact
NC terminal (2)
Changeover SPDT (Form C)
1 (C)
Normally Closed SPST-NC (Form B)
1 (C)
Normally Open SPST-NO (Form A)
1 (C)
Changeover SPDT (Form Za)
3 (NO)
1 (NC) 2 (NC)
Normally closed SPST-NC (Form Y)
1 (NC) 2 (NC)
Normally open SPST-NO (Form X)
3 (NO)
› Double-break changeover SPDT Microswitch with separated circuits (e.g. PBX 8324)
2 (NC)
4 (NO)
2 (NC)
4 (NO)
4 (NO)
4 (NO)
Operating device
(Plunger)
4 xed contacts
4 mobile contacts
NO terminal (13)
Snap-action
springs
NC terminal (21)
Return spring
NO and NC circuits are electrically separated, and can be used at opposite polarities.
Sealing membrane
NO blade
NO terminal (14)
Insulated mobile bracket
NC blade
NC terminal (22)
Changeover SPDT (Form Zb)
13 (N O) 14 (NO)
21 (N C) 22 (NC)
› Positive (or direct) opening operation according to IEC 60947-5-1 Annex K (depending on models)
An additional internal mechanism, made of non-resilient parts,
forces the opening of NC contacts in case of accidental welding
(overload, short-circuit, …) or snap-action mechanism failure.
Models tted with this function are particularly suitable for safety
related applications according to ISO 13849-1 or EN 60204-1.
To ensure proper functioning of positive opening operation, the
operating device must be depressed up to the positive opening position.
› Maintained action / Bistable reset variants
Double-break microswitches (Form Za, X, Y and Zb) are particularly
suitable for achieving this kind of “mechanical memory” function.
Return spring is removed, and operating device has special shape
for push/pull actuation.
Typical applications are level regulation, manual reset and position
contacts for bistable electromagnets.
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MECHANICAL CHARACTERISTICS
› Terminology: Forces - Positions - Travels
| 05/2016
PT
Actuation of operating device
*Depending on models
RP
OF Operating force
Force required to move
the operating device from
the rest position RP to the
operating position OP
Forces
RP Rest position OP Operating position
Position of the operating
device when no external
mechanical force is applied
Positions
Tra v els
Position of the operating
device at which the snapaction mechanism trips.
PT Pretravel
Distance between the
rest position RP and the
operating position OP
POF*
POT*
POF Positive opening force*
Force to be applied to the
operating device to achieve
the positive opening
operation
POP Positive opening position*
Position of the operating
device where the positive
opening of the NC contacts
is guaranteed
POT Positive opening travel*
Distance between the
rest position RP and the
positive opening position
POP
TTFOF
RF
DT
OT
TTPPOP*OP
TTF Total travel force RF Release force
Force required to reach total
travel position TTP (only
specified when higher than
operating force OF)
AOF Allowable overtravel
force
Maximum force which can
be applied to the operating
device without incurring
deterioration
TTP Total travel position RLP Release position
Position of the operating
device when the applied
force has moved it to the
effective end of the available
travel
OT Overtravel DT Differential travel
Distance between the
operating position OP and
the total travel position TTP
RLP
The level to which the
applied force must be
reduced to allow the snapaction mechanism to return
to its release position RLP
Position of the operating
device at which the snapaction mechanism trips back
to its original position
Distance between the
operating position OP and
the release position RLP
The reference po int for th e figur es given fo r travels an d forces i s a point F located on the top of th e plunger in the case of a plain microsw itch, or, generall y, 3 mm in from th e end of a
flat lever. The refere nce point for the po sitio ns is one of th e fixing h oles, unless oth erwis e indic ated.
› Force - Travel diagrams
On contactsOn operating device
N
OF
TTF
RF
RP RLP OP TTP
NC contact closed
open
NO contact closed
open
PT OT
DT
depression
return
mm
NC contact closed
NO contact closed
N
Force after tripping
return depression
NC
0
NO
PT OT
N
RP RLP OP TTP
DT
open
open
mm
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