Figure 2-16.--Sensitive switch.

switch or located in a remote space and

The types of mechanically operated switches are

connected to the switch by a capillary tube. The

the push-action (type A-S) and the cam-action (types

temperature range at which the switches

P and P41). The push-operated switch, provided for

operate is adjustable at X (fig. 2-15).

bulkhead mounting, is a single-throw or multiple-

throw, momentary action, normally open push

switch. The push-action mechanism uses a straight-

Temperature-operated switches are used with

line movement of the shaft to operate the electrical

the circulating-water, high-temperature alarm

contacts. The cam-action switch consists of two SPDT

system; cruising-turbine exhaust alarm system;

sensitive switches operated by two adjustable cams

and generator-air, high-temperature alarm

mounted on the rotor shaft (fig. 2- 17).

system.

The cam-action mechanism uses a rotary motion of

Mechanical Switches

the shaft to move cams, which in turn operate

sensitive switches. The points of operation of the

Mechanically operated switches are used in

sensitive switches are varied by adjusting the

many types of installations, such as wrong-

angular positions of the cams with respect to the

direction alarms and valve-position indicators.

shaft on which they are mounted. Mechanical

switches are used with the following systems:

Widely used because of their small size and

excellent dependability, they are commonly

Air-lock indicator

called "micro switches, " or properly called

sensitive switches. ("MICRO SWITCH" is a

Clutch-position indicator

trademark

of MICRO

SWITCH

Division,

Honeywell Inc.)

Shaft-position alarm

These switches will open or close a circuit

Submersible steering-gear alarm

with a very small movement of the tripping

device. They are usually of the push-button

DW Wrong-direction alarm

variety, and depend on one or more springs for

their snap action. For example, the heat of the

Hull-opening indicator

sensitive switch is a beryllium copper spring,

heat-treated for long life and unfailing action.

Valve-position indicator

The

simplicity

the

one-piece

spring

contributes to the long life and dependability of

Water Switch

this switch. The basic sensitive switch is shown

in figure 2-16.

A water switch consists of a pair of terminals

mounted in an insulated base within a cast

fitting (fig. 2-18). T h e r e i s a 7 0 0 0 - o h m , 5 - w a t t

resistor connected across the two terminals,

which limits the current to the required

value for the supervisory circuit when the

140.6

Figure 2-16.--Sensitive switch.

Figure 2-17.--Cam-action mechanical switch.

2-10