Airborne dust mitigation system

A system for capturing airborne particles from a mixing apparatus for mixing mineral based building materials, particularly such materials containing a silica based material, wherein there is a hood assembly attachable to a mixing apparatus and positionable such that airborne particles generated in loading the mixing apparatus are drawn into the hood, the hood being operatively connectable to a vacuum/filtration apparatus.

FIELD OF THE INVENTION

The present invention relates to mitigation of airborne dust and, more particularly, to such dust generated by silica-containing building materials.

BACKGROUND OF THE INVENTION

Silica-containing powders, particulates and the like are considered by OSHA to be quite harmful when inhaled. Accordingly, in operations where silica-containing building materials are being prepared, precautions must be taken to reduce the amount of airborne silica dust. There are a variety of mineral-based building materials used in numerous different building applications. Many of these mineral-based building materials, e.g., concrete, mortar, grout, refractory, etc. do or can contain a silica or silica-type material. Depending on the composition being prepared, e.g., mortar, grout, etc. different types of mixers are employed. However, whatever the type of mixer, they have certain common features, namely, a mixing chamber or box having an entrance, a grate over the entrance, suitable mixing paddles, vanes, scrolls, or the like in the mixing box, the mixing paddles, vanes, etc., being driven by a motor connected in a well known fashion.

A common feature of these various mixers is the ingredients to be mixed are introduced into the entrance of the mixing chamber from bags although some are shoveled in, etc. Particularly in the case of bags of the material to be mixed, there are cutting elements connected to the grates which tear the bags as they are thrown or lifted onto the grate, the bag then being pulled apart and the ingredients falling through the grate into the mixing chamber. It will be readily apparent that this action can generate a significant amount of airborne particles of material. Likewise the use of a shovel to “throw” the building material ingredients into the mixing chamber through the grate also generates a significant amount of dust.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a dust mitigation system for use with mixers used to mix mineral based materials for building purposes.

In another aspect, the present invention relates to mixers for mixing mineral based materials into end products such as mortar, grout, masonry, refractory etc.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As used herein, the term “hood” shall mean and include an enclosure or canopy provided with a draft for carrying off fumes, sprays, smoke, or dust.

The term “adjacent” as used herein and with reference to the relationship of the hood/plenum assembly with a mixing chamber of any of the mixers is intended to mean that the hood/plenum of the hood/plenum assembly are attached to the mixers and positioned such that when the hood/plenum assembly is under suction, and the material to be mixed is being introduced into the mixing chamber through the entrance of the mixing chamber, any airborne dust generated will be drawn into the hood/plenum assembly preferentially as opposed to being released to the ambient surrounding the mixer. In other words, the proximity of the hood/plenum assembly to the mixing chamber will be such that the driving force of any airborne dust generated during the loading of the mixing chamber will be into the hood/plenum assembly and ultimately through the suction/ventilation system.

Referring now toFIG. 1, there is shown a mortar mixer, shown generally as10, is equipped with a hood assembly, shown generally as12in accordance with one embodiment of the present invention. Mortar mixer10has a rectangular frame14from which extends a cross-piece16, cross-piece16being connected to a stanchion18having a foot pad20. Mixer10is provided with a wheel assembly, shown generally as22, comprising first and second wheels24and26rotatably mounted on an axle28affixed to the rectangular frame portion14. There is a motor box30which houses a motor and other controls necessary to operate mixer10.

Mixer10further comprises a manually rotatable mixing drum32which, as shown in the drawings, is in a mixing position. As seen with reference toFIG. 3, a shaft40extends through drum32and is in turn connected to a motor contained in motor box30. Shaft40is connected to a mixing paddle assembly of drum32. Mixing drum32has an entrance overlaid by a grate44. It will be appreciated by those skilled in the art that when mixer10is being loaded, drum32will be rotated in the direction of arrow A until grate44and hence the entrance into drum32is displaced about 60° from the location shown inFIG. 3. In this position, grate44and the entrance there below will be positioned such that a worker could throw a sack of material to be mixed onto grate44and hence through the entrance into the drum32. Once loaded, drum32would again be rotated back to the position shown inFIGS. 1-3and the mixing process conducted. Again, as is well known to those skilled in the art, grate44covers an opening in drum32through which mixed material passes when drum32is rotated in the direction of arrow A whereby it can be loaded into a suitable carrier for transport to the work site.

As best seen inFIG. 1, hood assembly12comprises a generally open box-like structure having a top wall50, a front wall56, a back wall58, first side wall52, and second side wall54. As seen inFIG. 1, front wall56is at a slight acute angle to top wall50. Hood assembly12further includes a pair of struts60and62connected to the bottom end of side wall52and secured, as by welding or bolts, to stanchion18. Post70and a corresponding post not shown extend from the lower end of side wall54and are attached at their lower end to frame14. Thus it can be seen that hood assembly12is securely mounted to mixer10. It should be noted that hood assembly12can be fixedly or removably connected and in a preferred case it is removably secured, e.g., by the use of nuts and bolts, etc.

There is a vent74on top wall50of hood assembly12, vent74being connected to a duct76which, although not shown, but as well understood by those skilled in the art, is connected to a vacuum/filtration apparatus, whereby airborne particles generated in the loading and mixing of mixer10are drawn through hood assembly12, vent74, and duct76into the vacuum/filtration apparatus.

Referring now toFIGS. 4-6, there is shown another embodiment of the present invention in connection with a mixer which can be used for a variety of purposes including mixing mortar, grout, and other such materials. The mixer, shown generally as80, comprises a base82, a motor box84, and a mixing drum86. Mixing drum86can pivot about spaced pivot assemblies on either side of drum86only one of which,88, is shown. Paddle mixer92mounted on shaft93is driven by hydraulic motor90suspended form bracket91and which is drivingly connected to chute95.

Mixing drum86has a mouth94formed in part by a shaft93. Overlying mouth94is a grate96.

In the position shown inFIG. 4, hydraulic piston cylinder assembly89has pivoted drum86such that mouth94faces generally laterally outwardly. Accordingly, the materials to be mixed can be introduced to mouth94through grate96into mixing drum86. Once the necessary materials have been added, the hydraulic piston cylinder assembly89can pivot drum86to a position shown inFIGS. 5 and 6. In this position, grate96will be substantially horizontal. Once the materials have been mixed to the desired amount, drum86can then be pivoted again to the position shown inFIG. 4, whereupon the mixed material will fall through the chute95into a suitable receptacle.

Hood assembly82, which can be fixedly or removably attached to mixer80comprises a boxlike structure having a top wall100, front wall102, back wall104, first end1wall106, and second end wall108. The hood assembly82, as noted above, can be rigidly or removably attached to the frame82of mixer80. In this regard, vertical supports110,112,114, and116are connected to the four corners of the box-like structure formed by the side walls and the end walls and extend downwardly, the lower ends of the vertical supports110-116being connected to the frame82. As in the other cases described above, the hood assembly and/or components thereof can be releasably attached to mixer80. A vent120is connected to top wall100of hood assembly82and in turn is connected to a flexible vent hose122which is connected to a vacuum/filtration apparatus not shown, but well understood by those skilled in the art.

Referring now toFIGS. 7 and 8, there is shown another embodiment of the dust mitigation system of the present invention for use with a typical batch mixer shown generally as130. Batch mixer130has a generally cylindrical mixing housing134in which is contained rotating paddles (not shown) driven by a belt or chain (not shown) connected to a motor136mounted on a motor mount137. A hose138can be used to inject water or other liquid additives into the mixer housing134. As best seen inFIG. 8, the cylindrical mixing housing134has a top entrance140, a grate142overlying entrance140. In point of fact,FIG. 8substantially depicts a batch mixer without the mitigation system of the present invention, and in this regard it will be appreciated that the materials to be mixed would simply be lifted by a worker onto the grate142, the bags being cut open and the granulated material falling into the mixing chamber formed by cylindrical mixing housing134.

Referring now toFIGS. 7 and 8, the dust mitigation system used with the batch mixer comprises a generally rectangular chute150which can be removably attached to the top wall152of mixing housing134. In this regard, note that rivets or bolts154can be used to affix chute150to the housing134. Returning now toFIG. 8, there are suction plenums160and162connected to the bottom wall of chute150such that they are adjacent entrance140and grate142. Each of the suction plenums160,162is attached to a conduit164,166, respectively, conduits164,166being connected to a Y-coupling170having a leg172which is connected to a vacuum/filtration apparatus not shown but to those skilled in the art.

In operation, the bag of material to be mixed shown in phantom as180is positioned in chute150. To this end, flexible eye hooks182can be engaged by forklift tines, or other suitable lifting apparatus, and lowered into chute150. As the contents of bag180fall out of the bottom of bag180into mixing housing134through grate142, any dust generated is sucked into vacuum plenums160and162and transferred to the vacuum/filtration system of any various types well known to those skilled in the art.

It will be apparent from the above description and the drawings that the dust mitigation system of the present invention is both versatile and efficient. It is versatile in the sense that it can be retrofitted to existing mixers of various types as demonstrated above. Furthermore, it is efficient in the sense that it is connected to the various mixers in such a way that optimum removal of airborne dust is achieved. In this regard, as the bags of materials are opened and introduced into the various mixers, airborne dust generated in that step is almost immediately drawn by the hood through the conduits to the vacuum/filtration apparatus.

Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.