Door Open Mechanism; Upper And Lower Latch Switches; Monitor Switch - Sharp R-771 OE Service Manual

DOOR OPEN MECHANISM

The door can be opened by pushing the open button on
the control panel, refer to Figure 4.
Pushing the open button, the open plate on the open
device pushes the door lever on the door.
Therefore, the lower and upper latch heads remove
upwards, and then those latch heads are released from the
lower and upper latch hooks.
Now, the door can be opened.

UPPER AND LOWER LATCH SWITCHES

The upper latch switch is mounted in the upper latch hook
and the lower latch switch is mounted in the lower latch
hook. They are activated by the latch heads on the door.
When the door is opened, the switches interrupt the circuit
to all components except the oven lamps and fan motor.
A cook cycle cannot take place until the door is firmly
closed thereby activating both switches.

MONITOR SWITCH

The monitor switch mounted on the upper latch hook is
activated (the contacts opened) by the latch head on the
door while the door is closed, refer to Figure 5. The switch
is intended to render the oven inoperative by means of
blowing the fuse when the contacts of the upper latch
switch fail to open when the door is opened.
Functions;
1. When the door is opened, the monitor switch contacts
close (to the ON condition) due to their being a
normally closed. At this time the upper latch switch is
in the OFF condition (contacts open) due to its being a
normally open contact switch.
2. As the door goes to a closed position, the monitor
switch contacts are first opened and then the upper latch
switch contacts close. (In case of opening the door, each
of the two switches operate inversely.)
3. If the door is opened and the upper latch switch con-
tacts fail to open, the fuse -blows simultaneously with
the closing of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE,
TEST THE UPPER LATCH SWITCH AND
MONITOR SWITCH FOR PROPER OPERA-
TION (REFER TO THE TEST PROCEDURE
ON PAGE 15 and 16.)
Figure 4. Door Open Mechanism
Latch
Head
Head
Figure 5. Latch Switches and Monitor Switch
10
Open
Button Device
Latch
Hook
Latch
Switch