Research Details

Abstract: A shop assembled drag-type conveyor is provided with means for shortening its length and width and the conveyor is placed in assembled, but shortened form in a dust hopper of an electrostatic precipitator. When the conveyor is in place it is lengthened to its operating length and its width is expanded and attached to the side walls of the dust hopper with a minimum of on-site construction. Claims: 1. A drag conveyor and hopper assembly characterized by a hopper having a generally quadrangular base and vertical side walls, a conveyed material receiving trough along one side of the base, and a drag conveyor, said drag conveyor having a main frame comprising at least a pair of spaced apart longitudinal frame members telescopically extendable at one end, means for extending and retracting said telescopically extendable end, at least a pair of longitudinally spaced transverse members rigidly connected to said frame members and extending transversely therebeyond, hopper wall engaging support members telescopically mounted at the outboard ends of the at least one pair of transverse members, an idler shaft and a drive shaft each carrying a pair of transversely spaced chain sprockets mounted at opposite ends of the frame members, a pair of drag chains mounted between said sprockets and a plurality of drag bars connected between said pair of chains.
2. The invention defined in claim 1, wherein the hopper wall engagable support members are welded to the walls of said hopper after the drag conveyor has been inserted in the hopper and leveled.
3. The invention defined in claim 2, wherein the length of the drag conveyor is telescopically extended to its operating length after insertion of the drag conveyor in said hopper and the conveyor is attached to the side walls of said hopper.
4. The invention defined in claim 2, wherein the hopper is provided with a transverse bulkhead dividing the hopper into a pair of conveyor pan spaces, and a drag conveyor is installed in each of said conveyor pan spaces.
5. The invention defined in claim 4, wherein the drive shafts of said pair of drag conveyors are connected and a single drive unit means, drives said connected drive shafts.
6. The invention defined in claim 5, wherein the drive means for the drag chains is mounted externally of one of the side walls of said hopper to thereby simplify the maintenance of the drive assembly.
<>   Description:
The use of drag conveyors in dust hoppers of electrostatic precipitators can eliminate dust re-entrainment 100 percent. The present invention is directed to a drag conveyor which has better reliability and shorter field construction hours as the conveyor per se is manufactured in the shop under tightly controlled conditions.

BACKGROUND OF PRIOR ART
Drag scrapers or conveyors have been used in electrostatic precipitators of the dry type for a number of years as the use of drag conveyors eliminate dust re-entrainment. Historically, the drag conveyor mechanisms consisted of a pair of parallel shafts set at opposite ends of the precipitator's shell. The shafts hold sprockets that pull scraper bars attached to large chains across the bottom of the precipitator hopper, scraping the accumulated collected particulate material into a small hopper carrying, for example, a screw conveyor. The drag conveyor thus consists of a number of individual components, parts, and pieces which were assembled inside of the precipitator at the job sight. Such fabrication was time consuming and the cramped work area made assembling difficult. Further, most of the labor required for the assembly of various components of the drag conveyor had to be done by highly skilled millwrights due to the precise alignment required of the moving parts.

BRIEF SUMMARY OF THE INVENTION
The present invention is directed to a drag conveyor which is shop assembled, and lowered in its fully erected, and telescoped condition into a precipitator hopper at a convenient stage of construction. The drag conveyor is then extended to its fully operative size and welded to the hopper walls to complete the assembly. Thus, the invention may be defined as a drag conveyor and hopper assembly characterized by a hopper having a generally quadrangular base and vertical side walls, with a conveyed material receiving trough along one side of the base and a drag conveyor mounted in the hopper. The drag conveyor is characterized by having a main frame comprising at least a pair of spaced-apart longitudinal frame members, telescopically extendable at one end with means for extending and retracting the telescopically extendable end.  The transverse members are provided with hopper wall engaging support members which are telescopically mounted at the outboard ends of the pair of transverse members. The assembly also includes an idler shaft and a drive shaft, each carrying a pair of transversely spaced chain sprockets mounted at opposite ends of the frame members, and a pair of drag chains mounted between the sprockets with a plurality of drag bars connected between the pair of chains.