Kenmore 808353 - Manual (Page 52)

D. ELECTRICAL CONTROLS Timers
A Timer Operation
The limer is the central control point of the electrical componersis, All timers used on Kenmore Dishwashers are similar
in operation and design, The only difference is in complexity due to the variation in function and features of the various
models
FIGURE 54
All eieciromechanicai timers consists of two basic components; a motor, and cam switches, assembled into one unit,,
(Figure 54X To fully understand the function and relationship of these two components to one another, it is necessary
to examine'' each component in more detail
Timer motors may vary slightly in appearance, but each functions in the same manner, !t is a synchronous-type motor,
similar to those used in electric docks, vdth a small pinion which drives a cam through a gear arrangement.
The cam switches are enclosed in a case to protect them from damage and contamination by foreign particles which
may cause a malfunction. The nsimber of switch contacts and cams varies with the number of functions the dishwasher
performs.
The particular shape of the cam varies with the number of switch contacts it controls and the length of time each
switch contact is closed. Figure 55 shows a very simple cam that controls one switch contact, which is closed for
two increments of the limer cycle. Let's assume that this cam is designed for a timer that has an advancement of
six degrees (
6 °) evety sixty seconds. The cut-out portion of this cam, therefore, is twelve degrees, and the cam switch
contacts are dosed for only two minutes during the complete cyde.
A single metal strip, called a cam follower, (Figure 55) is anchored to each cam switch arm and as the cam turns,
this metal strip follows the contour of the outer circumference of the cam, thus causing the cam switch arm to make
and break contact at the proper time
In Figure 5B we see a more complicated cam. This cam was designed to corstrol one or possibly two switch arms that
have dual contacts. You wdl! rrote that this cam has raised, cut-out, and neutral portions . The raised portions
force the cam switch arm against the outer contact and the cut out portions allow the cam switch arm to make
contact with its inner contact,. Both contacts are open when the cam follower is on the neutral section of the cam
SWiTCHARrvr
OUTER
CONTACT-
CAM
FOLLOWER
CAM
INNER
contact —-V.
N
NEUTRAL
SECTION
INNER
CONTACT
CUT OUT
RAISED
PORTION
CAM
FOLLOWER
SWITCH ARM
FIGURE 56
4 9