| 摘要 |
<p>A long retracting sootblower for boiler cleaning of the type having a lance tube which is advanced into and out of a boiler and simultaneously rotated, and having one or more nozzles discharging a jet of blowing medium which trace helical paths. An indexing mechanism is provided to change the positioning of the helical paths traced by the nozzles between successive actuation cycles to minimize boiler erosion and mechanical stress caused by repeated blowing medium impact against surfaces within the boiler. The indexing mechanism includes relatively slidable longitudinal advancement rack sections which cause the engaging pinion gears to index by one or more teeth upon each actuation cycle. A movable rack portion is biased by a compliant element to remain in a normal position until initial advancement of the lance carriage which causes the movable portion to be indexed with respect to the fixed portion of the rack. The movable rack portion returns to its normal position during other periods of the actuation cycle thereby providing said indexing.</p> |
