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2. Apply a gram scale at the center of the contact tip, on the back contact springs,
to just barely move the flexible bronze spring away from the curved stop
member. The stop member should be bent if necessary, not the spring, in
obtaining this adjustment. In order to make this check on the front contact
springs, using the gram scale, the spring assembly will have to be checked in the
inverted position and the pressure should be 18 grams (9 grams each tip), to
compensate for the weight of-the contact tip. The contact buttons of the
bifurcated springs should close at the same instant.
3.7.5.2.2. Heel Contacts
1. The design of heel contact provides a flexible hinge arrangement with a rigid
assembly on the outer part of the member. The thin center spring should be
straight and the projection on the upper and lower pressure plates should both
bear against the thin center spring. This heel spring assembly should deflect
through its full motion - with very slight pressure from the operating arm. The
heel spring has to be handled carefully in order not to distort the thin center
member.
2. Adjust the heel springs so that when the relay is held with the base horizontal
and the contact springs pointing downward, the heel spring will take a free
position when not connected to the operating arm without appreciable bias either
toward the front or back contacts.
3.7.5.3. Final Contact Adjustment Procedure
The normal contact adjustment provides 0.031" compression of the front contacts with
the vane just touching the upper roller stop, 0.025" compression of the back contacts
when the vane just touches the lower roller stop, and 0.025" opening of the back
contacts with the fronts just barely closed. These adjustments can be obtained by using
the proper section of three-way bending tool N451151-2401 applied as shown in Figure
3-4.
1. Align the front and back contact springs with their associated heel springs using
alignment tool J397164-0020 as explained for the heel contact springs.
2. Adjust the front contacts to have 0.055" opening with the vane resting against
the lower roller stop.
3. Adjust the back contacts so that they have 0.025" opening with the fronts just
barely closed.
4. Move the vane up against the upper roller stop, the opening of the back contacts
should be approximately 0.055". As a further check, each front contact spring
should have approximately 0.010" opening from its stop spring.
5. Move the vane to touch the lower roller stop. Each back contact spring should
have approximately 0.010" opening from its stop spring.
Copyright 2019
SM 4574F, Rev. 4, March 2019
PV-250 Track Relay
3-15
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