Patent Application
20060066014
Not Applicable
1. Field of Invention
The present invention relates to an apparatus for feeding or loading fine particulate material into industrial plant equipment and to a portable dust collector for filtering and removing of dust and particulate materials that are generated in industrial plants, such as foundry furnaces. The present invention more particularly relates to an apparatus for feeding and loading fine particulate material, such as fine silica powder, into foundry furnaces and to a portable dust collector for removing such dust and fine particulate materials during relining operations of foundry furnaces.
2. Description of the Related Art
Generation of dust and fine particulate materials, e.g., fine silica powder, in industrial plants is a particular vexing and serious health problem. The U.S. Department of Labor's Occupational Safety and Health Administration (OSHA) has established regulations that set forth safety guidelines and industrial standards that are required to be met owners in the operation of industrial plants for the protection of employee's health and safety. For example, OSHA has established guidelines in the U.S. metal-casting industry, which includes foundry furnace industry, for exposure to silica in the workplace and includes a maximum exposure limit of 20 parts per million (ppm) for crystalline silica in an 8-hour day.
Recently, attesting to the significance of silica as a workforce safety hazard, the America Foundry Society (AFS) and OSHA the signed a two year new alliance agreement to continue joint efforts to promote safer and more healthful workplaces in the U.S. metal-casting industry that will help AFS members protect employee's health and safety, particularly focusing on workplace issues, including personal protective equipment, ventilation and reducing and preventing exposure to silica.
Exposure to silica particulates is especially seen as hazardous in the foundry industry, such as the coreless induction furnaces, which require frequent installing of the refractory (e.g., silica) liners. Heretofore, the fine silica powder was delivered in bags, which were then opened by workers by slitting the bag and dumping the fine silica powder into the annulus formed by a sacrificial metal liner (furnace form) and the furnace exterior wall. This technique is quite dirty and generates large amounts of very fine silica powder and dust particulates that float around in the air and may create health problems for the workers. Typically, foundry furnace operators pull a vacuum over the furnace freeboard above the open reactor vessel to reduce the level of silica powder and dust particulates exposure to their workers. Workers also typically wear personal protective equipment, including respirators, masks, etc., to attempt to filter out the fine silica powder and dust particulates but the silica powder and dust particulates are so pervasive that they continue to present health hazards due to ingestion of fine silica powder and dust particulates, which can lead to silicosis an incurable lung disease.
Other more conventional feed devices include one, for example, described in U.S. Pat. No. 2003/0015812 A1, which involves a method for installing a refractory lining in coreless or channel electric induction furnaces by adding dry refractory material between a liner form and an inner wall of the furnace. There, a simple funnel is used for placement of the refractory material in a coreless electric furnace. While the use of a funnel is possibly beneficial in better directing the dry refractory material into the annulus formed by the liner form and the inner wall of the furnace, it obviously generates dust and fine particulate material into the atmosphere surrounding the furnace, which creates a hazardous condition for the foundry workers installing the refractory liners.
Another feed apparatus for loading particulate material into foundry furnaces, such as cylindrical coreless electric furnaces, is described in U.S. Pat. No. 5,058,776. This patent discloses an apparatus for dispensing particulate material for foundry furnaces into an annulus formed by the furnace wall and an expendable cylindrical form. In particular there is provided a cylindrical platform covering the top of the expendable metal form and adapted to rotate around the center line axis of the metal form by a carriage rotatably mounted on the platform and riding on wheels that travel along a circular track that is inboard and concentric with the annulus formed between the furnace wall and the metal expendable form. The cylindrical platform includes a circular rim that fits about the open top of the expendable liner to position the apparatus. A hopper is carried on the top of the cylindrical platform having an opening in the lower end for discharging the particulate material into the annulus. A motor is also provided for rotating the cylindrical platform around the top of the cylindrical metal form. While this apparatus provides a delivery system for particulate material into foundry furnaces, such as coreless electric furnaces, it is expensive and complex to operate.
As noted above, these prior art feed apparatuses and designs provide little or no protection for workers who are dispensing the particulate material in foundry furnaces, such as a coreless electric furnace. Viewing U.S. Pat. No. 5,058,776, above, there is noted that the feed dispensing apparatus disclosed therein is open to the atmosphere and any particulate dust would be carried into the atmosphere that surrounds the operator and like conventional prior art apparatuses, e.g., funnels, provide no reduction of the particulate dust formed in the furnace re-lining operation. Thus, while these prior art devices address apparatuses for the introduction of particulate material into foundry furnaces during the re-lining operation, they offer little or no abatement of the generated dust or fine particulate material, such as fine silica powder, during the critical furnace re-lining operation which depending on the size and through-put (as measured in tons) of metal must be repeated every 2-4 weeks.
Thus, it may be seen that there is a need to provide a simple, less costly feed apparatus for use in delivering particulate materials, such as fine silica powders, into foundry furnaces, e.g., coreless electric furnaces. There also is a need to provide a cost effective and efficient dust collector for use in removing fine dust and particulate materials (e.g., fine silica powders) in foundry operations, such as in re-lining operations of coreless electric furnaces.
In view of the above needs, it is a primary objective of the present invention to provide a simple and efficient feed apparatus for feeding or loading fine particulate material into industrial plant equipment, such as coreless electric furnaces.
Another objective of the invention is to provide a cost-effective and efficient portable dust collector for filtering and removing of dust and particulate materials that are generated in industrial plants, such as coreless electric furnaces.
Other and further objects of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the invention together with the appended claims and by reference to the accompanying drawings.
In one aspect of the invention there is provided a feed apparatus for delivering particulate material to a foundry furnace having disposed therein a furnace form defining an annulus with the furnace exterior wall for receipt of the particulate material. The novel feed apparatus broadly includes a cover, having a top end, side wall, and a bottom end, the latter of which is adapted to fit on top of the furnace ring or melt deck floor; a rotatable tabletop that is adapted to fit on the top end of the cover while permitting air ingress into the cover and having at least one access port for delivering the particulate material into the interior of the cover; a form top that is adapted to fit within the cover on top of the furnace form to facilitate delivery of said particulate material into the annulus made by the furnace form and the furnace exterior wall; means for rotating the tabletop about the centerline of the cover; and means for centering the tabletop as it rotates about the centerline of the cover.
In another aspect of the present invention there is provided a portable dust collector for filtering and removing of dust and particulate materials that are generated in industrial plants, such as coreless electric furnaces. The portable dust collector broadly includes a cover, having a top end, side wall, and a bottom end, the latter of which is adapted to fit on top of the furnace ring or melt deck floor; a rotatable tabletop that is adapted to fit on the top end of the cover while permitting air ingress into the cover and having at least one access port for delivering the particulate material into the interior of the cover; a form top that is adapted to fit within the cover on top of the furnace form to facilitate delivery of said particulate material into the annulus made by the furnace form and the furnace exterior wall; means for rotating the tabletop about the centerline of the cover; means for centering the tabletop as it rotates about the centerline of the cover; and means for filtering the dust and particulate materials that are generated within the cover during plant operations and collecting same for ultimate removal and disposition thereof.
These and other embodiments of the invention provide for a number of advantages over the prior art devices. First, the feed apparatus of the present invention is a simple and straightforward design for delivering particulate material, e.g., fine silica powder, to a foundry furnace, such as a coreless electric furnace, during re-lining operations. As may be seen from the drawings and detailed description of the invention, the particulate material may be introduced through an access port, such as either a spout or a centrally disposed access port located in the rotatable tabletop and allowed to fall onto a form top, which is of an inwardly tapered design that fits on top of the furnace form located within the cover to thereby direct the introduced particulate material into the annulus formed by the furnace form and the furnace exterior wall. Advantageously, in the design using the spout, the rotatable tabletop, which is easily rotated about the center line of the furnace, facilitates the uniform introduction of the particulate material into the annulus as the spout is continuously moved around the arc defined by the annulus with respect to the centerline of the furnace. As such, a continuous layer of the particulate material is delivered into the annulus which provides for a more uniform packing and density of the particulate material, resulting in less tamping of the particulate material.
Second, the design of the present invention provides a portable dust collector that achieves a marked reduction in airborne dust and fine particulate material, such as fine silica powder, over prior art devices, resulting in a safer, less hazardous work environment for foundry workers. In several tests, airborne silica dust and particulates were reduced in a range of from a low of about 60% and up to a high of about 80% (as determined by standard air sampling techniques) over the conventional approach of delivering the silica powder or particulate material via a slit-bag and pouring of the silica powder or particulate material into the annulus formed between the form liner and the exterior furnace wall. It is believed that no other prior art collection and/or filtration device achieves anywhere near these significant reductions in airborne dust and fine particulate material as has been demonstrated by the novel portable dust collector of the present invention. Thus, it is believed that the present invention will, during the process of re-lining a typical foundry furnace, such as a coreless induction electric furnace, enable the furnace operator closer to the OSHA limits for airborne crystalline silica and provide a safer workplace for its employees.
a is a top plan view that illustrates the tabletop (without the access ports shown) and the eight spaced-apart casters that provides the means for rotating the table top around the centerline of the cover.
The present invention can best be described with reference to the attached drawings and photographs. The reference characters refer to the same parts throughout the various views. The drawings are not to scale and are presented to help illustrate the principles of the present invention in a clear manner. While the invention may be used in various foundry furnace applications (e.g., ABB Furnaces, Electric Melt Furnaces, Ajax Inducterthurm Furnaces, etc.), it will be illustrated in connection with a coreless electric furnace. This type of foundry furnace has an expendable metal furnace form that is disposed within the furnace that forms an annulus with the furnace exterior wall for receipt of said particulate material. The re-lining operation for furnaces of this type briefly includes removing the dome of the furnace and removing the old insulation liner (e.g., silica), which typically is removed by the use of a jackhammer or the use of a specially designed push rod to push the old hardened refractory insulation liner out of the furnace. After the old liner is completely removed from the furnace, a new expendable metal furnace form, such as a mild steel, is next inserted into position in the cavity of the furnace after an initial charge of the refractory lining material (e.g., silica powder) is poured (by hand) into the furnace along the bottom to a desired depth. The expendable metal form holds the silica material in place until the silica material is heated to an elevated temperature sufficient to harden or fuse the silica powder into a hardened refractory state to enable the silica material to remain in place as an insulating liner during the melting process; thus, protecting the exterior furnace wall. The furnace is now ready to have the feed apparatus of the present invention positioned over the top of the opened furnace with the bottom end of the cover resting or sitting on the furnace ring or melt deck floor.
In one embodiment of the present invention as shown schematically in
The feed apparatus of the preset invention may be constructed, as known by those in the foundry furnace art, of conventional structural materials, such as mild steel. For example, rotatable tabletop 10 may comprise a 3/16 inch mild steel checker plate rolled to a diameter, for example, of 68 inches. The side wall of cover 4 may be constructed out of 14 gauge mild steel plate. While the cover 4 may be any convenient height that will accommodate form top 14 it has been found that a height of about 24 inches is preferred. This height provides a convenient height for the foundry workers to easily lift the bags of silica powder for pouring into material spout 11 or where central port 12 is used to easily accommodate an overhead crane for positioning Supersacks of silica powder for delivery into the interior of the cover during the re-lining operation. The skeleton or framework to which the side wall is affixed may be constructed out of 2″×2″ angle iron. The form top 14 may be constructed out of 26 gauge mild steel and formed into a cone shape having, for example, a 40 inch diameter at the bottom which will just fit over a typical coreless induction electric furnace that has a 39.5 inch ID expendable metal furnace form, thus, insuring that the silica powder is directed into the annulus. The spaced-apart casters are readily available as a commercial item.
In another embodiment of the present invention, which is shown schematically in
An additional feature of the present invention is the provision of wetting the silica dust and particulate material in the catch pan to further eliminated airborne silica dust and particulate material during disposal of the filtered materials. In this way, a small quantity of water may be added (for example by pouring the water into the catch pan) to turn the silica dust and particulate material into mud, thus, minimizing or eliminating airborne particles being released into the atmosphere.
It has been found, quite surprisingly, that the portable dust collector of the present invention can achieve such a marked reduction in airborne dust and particulate materials, such as fine silica particulates, generated in furnace re-lining operations. For example, in several tests airborne silica dust and particulates were reduced by greater than 60% (as determined by standard air sampling techniques) and as high as 80% over the conventional approach of delivering the silica powder or particulate material via a slit-bag and pouring of the silica powder or particulate material into the annulus formed between the furnace form liner and the exterior furnace wall. Such a marked reduction in airborne dust and particulate materials, may enable foundry operators during re-lining of, for example a coreless furnace, to better meet OSHA standards for silica of 20 ppm per 8-hour day, resulting in a safer, less hazardous work environment for foundry workers.
Referring to
It is to be understood that the invention is not limited to the details give as described above but that it may be modified within the scope of the appended claims.
