SERVICE AND INSTALLATION INSTRUCTIONS
I. GENERAL DESCRIPTION AND OPERATION
The “Power Flo” shoe brake product line consists of five sizes of spring applied/air released brakes. These brakes are engaged with two coil springs which force the shoes together against a drum resulting in braking torque, This torque is reacted through a pin which anchors the shoes to the machine structure. The brake is released when an air cylinder is pressurized and overcomes the spring force to spread the shoes apart. The brakes are self-energizing in one direction, so forward and reverse braking torques are substantially different. The engaged torque can be adjusted by changing the spring compressed height with adjusting nuts.
The anchor pin should be made of material of stock diameter that will give a slip fit in the mounting pin hole. The center distance between the mounted anchor pin and the center line of the shaft must be within the range of adjustment on the eccentric bushing. The anchor pin must be mounted so that it is parallel to the shaft. Mount the drum on the shaft and set screw it in place. Remove the adjustment nuts and springs from the shoe brake. Remove the spring studs and open the secondary shoe to allow the brake over the shaft. Slide the pin hole over the anchor pin and position the brake over the drum. Loosen the two set screws holding the eccentric bushings in place. Close the secondary shoe over the drum and rotate the eccentric bushing until the shoes are concentric with the drum. Open the secondary shoe and tighten the set screws on the bushing. Close the secondary and reassemble the studs, springs and adjustment nuts. Torque the spring studs in the shoe to – (20 FT. LB. – 7SB), (50 FT. LB. – 10 & 14SB), (100 FT. LB. – 18 & 24SB).
FAILURE TO TIGHTEN THESE STUDS COULD RESULT IN SUDDEN FRACTURE AND COMPLETE LOSS OF BRAKE CAPACITY.
Tighten the adjustment nuts so that there is 1/4″ compression on the springs when the shoes are contacting the drums. Tighten the jam nut on the spring plate. Loosen the locknut on the piston rod and turn the adjustment bolt so that it comes out of the piston rod. Continue extending the bolt until it just begins to separate the shoes. Now the piston is bottomed on the back of the cylinder. Back the bolt off 1/8″ from the pad and tighten the locknut on the piston rod. The unit is now adjusted for proper release and should not need further adjustment until there is a total of 1/8″ lining wear. Final torque adjustment is done by increasing or decreasing the spring compression with the adjustment nuts. If using an 18″ or 24″ unit, be sure to use an oiler dryer in the air lines as these units use an O-ring seal and require dry lubricated air.
As the linings wear, the spring compression will have to be tightened to make up the wear dimension. Also as the lining wears, the release cylinder will open the shoes farther than needed and may not retract enough to allow the shoes to engage the drum. To correct this, readjust the piston adjustment bolt as described in the installation section. Check that the spring studs are tightened to the correct torque every 3 months of operation.
Failure to maintain this preload could result in sudden spring stud fracture and complete loss of brake capacity.
Periodically, the brake should be checked for situations requiring repair. These might include excessive lining wear or failure to release due to air leakage.
V. LINING REPLACEMENT
The most common repairable problem encountered in a normal application will be lining wear. When the shoes bottom against each other or the lining is worn down to the screw heads, the lining should Be replaced. Remove the adjustment nuts, springs and spring studs to allow the secondary shoe to open. Remove the four screws holding each lining and install the replacement linings. Close the shoe and re-install the springs and studs. Readjust the piston adjustment bolt as described in the installation section and readjust the spring compression.
VI. AIR LEAKAGE
The 7″, 10″ and 14″ shoe brakes have an air cylinder which uses a diaphragm. If air leakage is heard or the unit fails to hold pressure, remove the six head cap screws from the cap. Removing the cap will expose the diaphragm. Check the diaphragm for holes or damage and if it is defective, replace it. Re-tighten the cap screws to 100 in/lb.
The 18″ and 24″ shoe brakes have an air cylinder which uses a piston and O-ring seal. If air leakage is heard or if the unit fails to hold pressure, remove the six hex head cap screws from the cap, pull the cap off the piston and check the condition of the O-ring and the cylinder wall. If there are any defects, replace the parts and reassemble the
VII. ORDERING INFORMATION
Replacement parts can be obtained from an authorized “Power Flo” distributor or from The Carlson Company, Inc., 6045 North Broadway, Wichita, Kansas 67219. Any service problems should be handled through the original equipment manufacturer or the distributor from whom the equipment was purchased. When ordering parts or requesting service information, give the serial number of the unit. An identification plate with the serial number can be found on the primary shoe just under the air cylinder. Also, when ordering parts, state how shipments are to be routed. The Carlson Company, Inc. Will not be responsible for any charges incurred by this procedure. All shipments will be made F.O.B. Wichita, Kansas.
SERVICE BULLETIN 68F