1. Carefully grind out the entire length, width and depth
of the crack, being careful to go a little beyond the extremes so that
the entire crack is removed.
The resulting cavity should be rounded in the bottom,
with the upper edges slightly curled inward. The significance of this
is to help "hold" the patching material in the cavity.
The belt surface should be lightly polished with the grinding
tool 1/4 to 3/8 inches (6 to 10 mm) all around the edge of the ground
Absolute cleanliness is necessary throughout this operation. All tools
should be cleansed with Toluol. Hands must also be thoroughly cleaned
to insure removal of natural skin oils.
2. MIX EQUAL AMOUNTS
of the SHIELDâ Rubber Patch Sheeting and Toluol. (Generally this is a
small amount of both products, as a little bit goes a long way. The viscosity
should be about 500 centipoise, which is the equivalent of typical house
paint.) When thoroughly dissolved, use the resulting cement or adhesive
to paint the entire prepared cavity. After about 15 minutes, paint a second
coat of adhesive onto the entire cavity surface being sure to cover the
entire surface, including the lightly ground area around the cavity. Allow
the cement to fully dry before proceeding (it will take approximately
3. Cut pieces of patching material that conform to both
the length and width of the cavity. Using the 1/4 inch (6 mm) diameter
steel rod, carefully press each piece (one at a time) into the cavity.
Be very careful to remove all air bubbles or trapped air. Continue
this operation using as many strips as necessary to fill the cavity to
about 1/8-inch (3 mm) above the level of the surrounding rubber belt.
4. Sprinkle the surface lightly with talc and place a
square of Aluminum foil or Teflon coated fiberglass over the patched area.
5. Set the thermostat and heat the shoe or iron to a minimum
temperature of 220° F (104° C) and a maximum temperature of 240° F (115°
C); place the shoe over the patched area and attach it in place using
a weight or clamp load of about 100 lbs. (45 kgs.) NOTE:
We recommend not placing the heated shoe on the blanket until it reaches
a minimum of 200° F (93° C). Be sure that the heated shoe continues to
heat up to the 220-240° F (104 -115° C) range if the shoe is applied at
200° F (93° C).
6. Two (2) hours minimum curing time is recommended for
a cavity depth of up to 1/4-inch (6 mm). An additional hour cure time
is recommended for each additional 1/4 inch (6 mm) of depth.
7. When the necessary cure time has passed, shut off the
current to the electrically heated shoe; remove the shoe from the patched
area and allow a few hours for cooling of the patch.
8. Carefully remove any excess rubber from the patch being
careful not to go below the level of the belt surface. A disc or belt
sander may be used for this purpose; 60 to 80 grit abrasive is suitable.
9. It is usually necessary to regrind the belt surface
to achieve uniformity. If the patch is outside of the cloth line, this
may not be necessary.
10. Patch hardness should be about 40° Shore "A".