Reading Rock manufactures concrete blocks—just like the ones used to build schools across the country for decades. Production Manager Phil Thacker figures that they’ve manufactured about 22 million of the industry-standard 8-in. blocks in the past four years alone.
One reason for this productivity is that Thacker and the Reading Rock team go to great lengths to eliminate downtime. Brakes and clutch-brakes that use oil shear technology have played a major role in improving Reading’s efficiency.
“Pretty much everything that has a motor on it is equipped with a Force Control clutch-brake or brake,” says Thacker. “I never worry about them going down.”
Reading Rock, like cement block plants across the country, has a single production line. That means that from the time that dry materials enter the mixer until pallets of formed and dried concrete blocks exit the facility, everything follows a single pathway. That also means that maintenance or service to any component will bring the entire production floor to a halt.
On the manufacturing line, the main drive is equipped with a Posidyne clutch-brake, which controls machine indexing. Pallets and molds are brought in, and concrete is dropped into the molds. After the mix is poured, vibrators shake the forms—ensuring proper density of the blocks. Then the main drive indexes again, and the cycle repeats.
Oil-shear technology plays a major role in ensuring that the cycle repeats flawlessly. Force Control clutch-brakes and brakes employ oil shear technology, which transmits torque between lubricated surfaces. The circulating fluid provides both cooling and lubrication of the friction surfaces—eliminating wear and dissipating heat. Because there is no direct contact between the friction surfaces during acceleration or deceleration, there is no wear—and thus no need for adjustment or replacement of discs.
Along with torque transmission and heat removal, the fluid also serves to continually lubricate all components—thus extending their service life. This also provides a “cushioned” stop that reduces shock to the drive system—further extending service life. Unlike dry clutch brakes, the totally enclosed oil shear system is impervious to external elements such as wet, dusty or dirty environments.
Reading Rock’s cement block production line has seen less downtime, due to the use of oil shear technology on its clutches and brakes.
Normal dry clutch brakes and brakes employ a sacrificial surface—the brake disc or pad—to engage the load. Without an adequate means of removing the heat caused from engagement between the disk and plate, this brake disc or pad must absorb the heat. These extremely high temperatures will eventually degrade the friction material. As the friction surface wears away and begins to glaze, the ensuing torque fade causes positioning errors, which require adjustment or replacement of the friction surface.
Posidyne oil shear clutch-brakes are also employed on Reading Rock’s vibrator drive to quickly settle the contents in the concrete block mold. Vibrator shafts can be fixed or variable—and are driven by the clutch-brake or motor with a motor-brake. The motor on a clutch-brake driven assembly runs constantly, eliminating the starting and stopping of the motor. The constant operation is smoother, so the motor will last longer.
A built-in neutral position is another benefit seen from the Posidyne clutch-brake driven assembly. At the completion of the vibration cycle, the brake is released and the weights can drop into the bottom position. This allows both weights to remain in synch during start-up, imparting vibration of predetermined amplitude into the shaft, as opposed to starting the cycle with weights in varying positions and imparting more (or less) severe amplitude. That would also cause shock to the system and shorten life of components, not to mention the effect it would have on the density of the blocks being formed.
Force Control Industries Inc.
Filed Under: Brakes • clutches, Mechanical, Motion control • motor controls