The invention disclosed in this application is directed generally to a rotary valve used to input particulate material into a pneumatic conveying system, and particularly to a rotor configuration that reduces air leakage across the individual rotor vanes which results in less air consumption caused by air leaking past the rotor and further results in an improved operating efficiency measured by increased capacity.
Rotary valves are well known in the art as a mechanism for introducing a flow of particulate material into a pressurized pneumatic conveying system. The pneumatic conveying system utilizes a flow of pressurized air through a pipe or tubular conduit to establish a fluidized flow of the particulate material fed into the conduit to move the particulate material from one place to another. The rotary valve has a housing defining an opening at the top for the introduction of particulate material and an opening at the bottom to discharge the particulate material flowing through the rotary valve into the pneumatic conveying system conduit. The housing rotatably supports an internal rotor for movement about a transverse axis of rotation. The rotor is formed with a plurality of radially extending vanes that define chambers therebetween.
Each respective chamber receives a supply of particulate material when rotated to be opened to the upper inlet opening and then deposits the particulate material into the conduit when the chamber is rotated around the axis of rotation and opens to the conduit. The interior of the housing is, therefore, formed in a generally cylindrical shape so that the outer tips of the radially extending vanes pass in close proximity to the interior cylindrical surface of the housing to restrict leakage of pressurized air from the conduit around the rotor.
Conventional manufacturing methods for the rotary valve utilize welding techniques to secure the individual vanes to a central shaft that corresponds to the axis of rotation of the rotor. Conventional welded rotors are machined and grinded to proper tolerances for utilization in a rotary valve housing, but welding techniques have limitations with respect to the number of vanes that can be welded onto a central shaft. Thus, the number of vanes on the rotor are limited from a practical sense to the space needed at the central shaft to affect the welding. Limiting the number of vanes results in limiting the number of pockets between the vanes for the transportation of the particulate material around the rotor from the supply hopper to the pneumatic conduit. In order to add more pockets in the rotor structure, the depth of the pockets from the other tip of the vanes would have to be reduced to provide sufficient room to affect the welding process. If the depth of the pockets is decreased, the volume of the pockets is decreased, resulting in lower capacity for the rotary valve.
Air leakage in rotary valves is a common problem. If the rotary valve has a severe air leakage problem, the leaking of air around the rotor into the supply hopper restricts the movement of the particulate material into the pockets of the rotor. For light particulate material, this restriction on movement into the rotor pockets can be a severe problem. Accordingly, the air leakage problem will reduce operating efficiency because the pockets in the rotor will not be able to fill completely. Furthermore, less air leakage means that the air compressor supplying pressurized air for the pneumatic conveying system has to produce sufficient quantities of air into the pneumatic conduit to make up for the air loss through the rotary valve. By substantially reducing the air leakage, the size of the compressor can be reduced and less energy can be utilized, saving in operating costs.
Air leakage problems can be reduced by increasing the thickness of the vanes as the corresponding increased width of the tips helps to restrict the passage of air around the vanes. The leakage problem can be reduced by increasing the number of vanes, which is a conventional solution to the air leakage problem. Simply increasing the number of vanes to reduce the air leakage problem results in reducing the depth of the pockets and the overall capacity of the rotary valve to accommodate the welding techniques. Increasing vane thickness can also be accomplished when utilizing welding techniques to manufacture the rotor to reduce air leakage problems; however, the increased thickness in the vanes results in a corresponding reduced size in the chambers located between the radially extending vanes and lowers the operating capacity of the rotary valve in the feeding of particulate material into the conduit.
Accordingly, it would be desirable to provide a rotary valve that reduces air leakage without detracting from the operating capacity of the valve and without increasing the power consumption thereof. It would also be desirable to provide a rotary valve configuration that is conducive to manufacturing techniques other than welding.
It is an object of this invention to overcome the aforementioned disadvantages of the prior art by providing a rotary valve having a rotor construction that will reduce air leakage through the rotary valve during operation thereof.
It is another object of this invention to provide a rotary valve having a rotor configuration that includes flared tips at the distal ends of the vanes of the rotor.
It is a feature of this invention that the rotor is configured with flared tips that move along the cylindrical surface of the valve housing.
It is an advantage of this invention that the rotor having flared tips increases air leakage resistance during operation of the rotary valve to meter particulate material into a pneumatic conveying system.
It is another feature of this invention that the thickness dimension of the flared tips is approximately twice the thickness dimension of the vane extending between the flared tip and the central hub.
It is another advantage of this invention that the rotor can be formed through a precision casting process.
It is still another feature of this invention that the flared tip of each vane extends toward the direction of rotation of the rotor within the valve housing, such that the trailing side of the vane is linear to the terminus of the flared tip.
It is still another advantage of this invention that the precision casting process will enable the rotor to be constructed with a larger number of radially extending vanes than can be constructed using welding techniques for the manufacturing process.
It is yet another advantage of this invention that the wider surface area of the flared tip adjacent the interior surface of the valve housing restricts the passage of pressurized air from the pneumatic conveying system around the flared tip.
It is yet another feature of this invention that the valve housing incorporates a release port extending across substantially the entire length of the pocket formed between adjacent rotor vanes to provide a release of the pressurized air trapped in the pocket with the discharge of the particulate material from the pocket into the pneumatic conveying system.
It is a further advantage of this invention that the elongated release port provides a more complete release of the air pressure within the pocket than is known from conventional single round port release ports.
It is still a further advantage of this invention that the elongated release port provides an enhanced operating efficiency for the rotary valve.
It is a further object of this invention to provide a rotary valve that is operable to meter the flow of particulate material into a pneumatic conveying system, which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use.
These and other objects, features and advantages are accomplished according to the instant invention by providing a rotary valve for metering the flow of particulate material from a supply source into the air stream of a pneumatic conveying system that includes a central rotor manufactured through a precision casting process. The rotor is formed with a plurality of radially extending vanes terminating in tips that are flared circumferentially into the leading side of the vane to provide a flared vane tip that is preferably at least twice the thickness of the vane itself. The valve housing is formed with an elongated release port that has an overall length approximately equal to the length of the pockets formed between adjacent vanes to provide a more complete release of pressurized air from the pocket after the particulate material has been dropped into the pneumatic conveying system. The angled leading edge of the flared tips provides a less aggressive engagement with the particulate material to reduce damage thereto.
The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:
Referring to
The housing 16 is formed in a generally cylindrical shape to support the rotational movement of the internal rotor assembly 20, as will be described in greater detail below. The housing 16 is formed with a mounting flange 17 at the top of the cylindrically-shaped housing 16 to permit the supply hopper 12 to be coupled thereto so that particulate material will be efficiently fed into the rotary valve 10. The housing 16 is also formed with a mounting flange 18 at the bottom of the cylindrically-shaped housing 16 to be coupled to an infeed opening 15a in flow communication with the top of the conduit 15 so that particulate material can flow by gravity from the filled pockets 27 into the pressurized conduit 15 of the pneumatic conveying system. The opposing sides of the cylindrically-shaped housing 16 are also formed with mounting flanges 19a that allow the coupling of bearing caps 19 that support respective bearings (not shown) that rotatably support the central shaft 21 of the rotor assembly 20.
The rotor assembly is best seen in
The rotor 22 is cast with a central hub 24 defining the central opening 23 for the passage of the shaft 21 from which vanes 25 extend radially. The vanes 25 have a uniform length and terminate in a tip 26 that is flared with respect to the radially extending vane 25, as is best seen in
To further support the radially extending vanes 25, the rotor casting has attached thereto an end plate 28 that can be separately welded onto the opposing ends of the rotor casting, attaching the vanes thereto, or as part of the precision casting. The support of the respective opposing ends of the vanes 25 at the end plates 28 help stabilize the vanes 25 and increase rigidity in the rotor assembly 20. The flared tip 26 is preferably constructed such that the increased width of the tip 26, compared to the thickness of the corresponding vane 25, projects only from one side of the vane 25, as is best seen in
The rotation of the rotor assembly 20 conveys the particulate material received from the supply hopper 12 when the pocket 27 is rotated to the top position to receive particulate material from the supply hopper 12. The pocket 27 is then rotated about the central shaft 21 until the pocket 27 opens into the pneumatic conduit 15 where the particulate material drops by gravity into the conduit 15. Once the pocket 27 is opened to the conduit 15, the higher air pressure present in the pneumatic conduit 15 fills the emptied pocket 27 with air. Further rotation of the pocket back toward the top position to receive another supply of particulate material from the supply hopper 15 traps that quantity of high pressure air in the emptied pocket against the interior surface of the rotor.
A release port 30 is built into the housing to be in communication with the pockets 27 as they rotate from the bottom position to the top position. The release port 30 is preferably coupled to a conduit (not shown) that connects the release port 30 to the supply hopper 12 above the rotary valve 10 to release the air pressure from being trapped in the pocket 27 to being fed into the supply hopper 12 to urge particulate material down into the open pocket 27 at the top position. Without the release port 30 the high pressure air in the pocket 27 would continue around to the top position and release into the supply hopper 12 which would urge the particulate material away from the pocket and limit the flow of particulate material into the pocket 27 to be conveyed into the pneumatic conduit 15. In the rotary valve 10 incorporating the principals of the instant invention, the release port 30 preferably extend across substantially the entire width of the pockets 27, as opposed to conventional release ports which is simply a single round port in the middle of the housing 16. As a result, the release port 30 provides a more complete release of the air pressure within the pockets 27 rotating toward the top position and, thus, increases operating efficiency and capacity.
It will be understood that changes in the details, materials, steps and arrangements of parts, which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles of the scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly, as well as in the specific form shown.
This application claims domestic priority on U.S. Provisional Patent Application Ser. No. 61/161,401, filed on Mar. 18, 2009, the contents of which are incorporated herein by reference.
Number | Date | Country | |
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61161401 | Mar 2009 | US |