Whether mounted in the hopper or on the conveyor the paddles work in essentially the same way. When material pushes against the paddle it shuts the conveyor or auger off. When material does not push against the paddle the conveyor or auger operates until material pushes against the paddles again and the system turns off.
Other pavers offer noncontact conveyor sensors to slow or stop the conveyor. Sensors are adjustable and when material coming through the conveyor reaches a predetermined height the sensor slows and stops the conveyor. "When the height of material falls, the sensor conveyors are turned on to keep that predetermined height of material," Spring says.
At least one manufacturer has moved away from slat conveyors, opting instead for screw conveyors. These are mounted lengthwise and rely on the rotating screw motion of an auger to do the same job as slat conveyors.
The conveyor moves the hot mix asphalt from the hopper to the auger assembly. The augers, which operate perpendicular to the conveyor, look a little like threads on a screw. As the augers turn they pick up mix in their "threads" and carry it from the conveyor to either the left or the right side of the rear of the paver.
"The biggest problem is keeping an even, steady head of material from the conveyor to the auger to the screed," Spring says. "Augers should run slow and continuously and should not be constantly sped up or slowed down to maintain the head of material at the screed."
Spring recommends relying on automatic sensors as opposed to making manual adjustments if the paver has automatic sensors. "When using manual sensors people tend to overfeed the material and then let it run down too low so there's very little material; then they crank it back up again to get it where it should be; then they back off and let it fall down. And with a free-floating screed, as the head of material changes the depth of the mat changes."
In addition to the augers pavers offer auger extensions which enable the contractor to pave widths wider than the width of the paver. Hood says that on many highway class pavers the auger extensions are bolted on and mix is pushed from the auger into the extension and then forced to the edge of the extension by the other mix in the auger. Hood says this approach works well for roadway paving where the pulls are long and there are no obstructions that might cause an operator to narrow the width of his paving.
"On commercial jobs, however, bolt-on auger extensions can be impractical because paving passes are affected by islands, light poles, and other obstacles," Hood says. "So commercial pavers offer extensions connected to the screed so as the screed extends or is retracted the auger extensions move with it."