Rotary Bridge Break Helps Dose Poor-Flowing Materials

A pneumatically operated device that is deployed inside one of the hoppers in a gravimetric blender reportedly makes possible accurate dosing of regrind, recycled plastics, and other ingredients that tend to agglomerate or “bridge,” obstructing flow through the dispense valve of the hopper.

Maguire Products Inc. has introduced the new “bridge breaker” for its three largest blender series, those with maximum throughput capacities of 5,000 kg/hr, (11,000 lb/hr) and capability of blending up to twelve ingredients. The bridge breaker consists of a hopper insert that directs material straight down onto the dispensing valve; and a rotary device that operates automatically while the dispense valve is open. The device rapidly pulses between clockwise and counter-clockwise movement, enhancing material flow through the dispense valve.

The hopper insert, which provides a vertical alternative to the sloping wall of the hopper, can be retrofitted in any blender currently in operation. To make up for the space occupied by the insert, the complete hopper assembly includes an extension to accommodate the desired quantity of material.

“The new bridge breaker addresses the growing demand for recycled content in plastic products and the increasing use of regrind as a means of reducing production costs,” notes Frank Kavanagh, v.p. of sales and marketing. “More and more processors have been finding it a challenge to keep such materials flowing consistently. In fact, we developed the bridge breaker to help one of our customers solve a problem with trim scrap.”

The three large-capacity Maguire blender families, the 1200, 2400, and 3000 Series, blend up to 12 ingredients, using a wide range of removable hopper and feeder configurations and numerous dispensing devices. The blenders handle raw materials in a variety of forms, including regular pellets and regrind, bulk powders, flake, and ingredients that are especially bridge-prone, such as wood flour.

As with other Maguire weigh scale blenders, once all ingredients are dosed into the weigh chamber, the batch falls into a mixing chamber. A microprocessor makes corrections from batch to batch, including adjustments to compensate for variations in extrusion rate or bulk density, maintaining overall batch accuracy to within ±0.1%.