Patent Application
20060180949
This invention relates to an impeller shroud, for a propeller, the shroud allows some water to flow over the propeller. The shroud is mounted on a draft tube, which allows both a propeller shaft to rotate the propeller and air to enter the shroud. The arrangement aerates water, especially contaminated water, and speeds aerobic digestion or decomposition of the contaminants. It is believed that this is achieved by micro sized air bubbles generated by the impeller, which maximizes absorption of air into the water. The shroud has apertures allowing water to be drawn into the shroud, where the propeller is believed to cavitate the water creating a strong vacuum which draws air down the draft tube into the propeller which mixes the air and water uniformly. The propeller then propels the air water mixture into the surrounding water causing a gentle mixing action. The propeller shaft is attached by a bearing box to a motor. Preferably the device is mounted on a frame attached to a float or floats. In use it aerates water, such as but not limited to hog barn effluent and other lagoons for industrial effluents. Application of such aerators greatly reduces the smell and effluents present, to such an extent that complaints about smell vanish, the water in the lagoons is odorless and usable for industrial applications. It is conjectured that this is due to the aerator supplying air and oxygen to satisfy biological oxygen demand and prevent or reduce anaerobic digestion and decomposition. An aerator incorporating shroud and propeller is environmentally beneficial in that it reduces the effects of pollution and contamination.
Aerators are known. An aerator is known locally to applicant of which only a single example exists without printed publication, which has a shroud with a rear aperture for a shaft to rotate a propeller, parallel to the shaft are two pipes or tubes to support the shroud and two bearings for the shaft. One tube has an end bend connecting through an aperture to the shroud to supply air down the tube, water is supplied through the shaft aperture. Two transverse plates welded to the tubes have the shaft bearings bolted to them. A motor drives the shaft mounted on the longer air supplying tube, which itself is mounted on another pipe pivoted on a frame connecting two pontoons. The motor was coupled to the shaft by a rubber coupling. When tested this aerator was less effective than current invention, probably because the propeller suction was less effective down the side tube, dissolving less air. It also vibrated substantially wearing the bearings so they needed replacement every seven or eight weeks or two months. The device also seized when the temperature fell below −7 or −8° C. There was substantial room for improvement.
The problem with lagoons used to store pollutants and contaminants is that generally the initial aerobic digestion or decomposition removes the dissolved oxygen from the lagoon water and anaerobic digestion or decomposition begins, the products of anaerobic decomposition often include vapors and gasses of horrible odor. It is known that aeration both stops anaerobic digestion and decomposition and encourages and initiates aerobic digestion and decomposition. Obviously a steady supply of oxygen is required to maintain dissolved oxygen for aerobic digestion or decomposition. Typically it is provided by passing air through the water, where it dissolves. Many such devices have been patented and many are commercially available.
Applicants had a 2½ million gallon (11 million liter) lagoon which was used for waste water from a truck wash. It produced a horrible odor which was a nuisance and made applicants very unpopular with the local community. Two devices of the present invention were installed and within fourteen days, the smell had vanished and the lagoon water seemed clean, at least for washing, solving applicants' problem, and improving local community relations. Local authorities using a crude quantitative test rated the treated lagoon odor as 1, acceptable, at the edge of the lagoon, roughly 0 is no noticeable smell, 10 is the maximum detectable, hog barn lagoons rate between 7 and 8.
In a separate instance, a hog barn stage-one lagoon for liquid excrement after removal of solids from 4,000 hogs and 100 dairy cattle, flow estimated at 80,000 gallons every two weeks, was treated with three aerators of the invention. Previously there were intense odors and endless complaints from neighbours. Within seven days of installation of the aerators of the invention, there was very little noticeable odor around the lagoon, within fourteen days the odor was almost completely eliminated. Further there are now no complaints from neighbours. Not only did the odor vanish for practical purposes, but the sludge build up around the outside edge of the lagoon had disappeared and the liquid of the lagoon itself was much cleaner. Previously two other types of aerators were tried by comparison only the aerators of the invention were effective. One ½ horsepower aerator tested had no effect. The other aerator, which had the same horsepower, 5, as applicants' aerator, did far less than applicants' aerator, and used three times as much electricity.
In view of the observed deficiencies of commercially available prior art aeration devices, the present invention provides a new impeller shroud for aeration devices for industrial waste water lagoons. The shroud has a front aperture for outward aerated water flow and rear apertures for inward water access. It is also connected to a draft tube which has an aperture for inward air access. When assembled a propeller rotates in the shroud, driven by a propeller shaft passing through the draft tube. The propeller sucks water in through the rear apertures, which cavitates in the shroud and sucks air down the draft tube to produce microbubbles of air which dissolve in the water. The absence of a shaft or propeller bearing in the shroud is significant because otherwise the suction effect of the propeller would be eliminated or at least greatly reduced. The aerated water then mixes smoothly with the water in the lagoon. The shroud draft tube has an aperture for air access, and a motor connected through a bearing box to the propeller shaft. Preferably the draft tube-motor assembly is mounted on a frame so that the propeller impeller is submerged in the water, while the draft tube aperture, bearing box and motor are in the air. Preferably the device is mounted on a frame, which may be pivotable from a horizontal position above water, to an angled position with propeller and shroud submerged. The frame may be mounted on a raft, which may include floats. Generally the motor is electric, although it is not so limited, and may be connected by an electric cable to a power supply. The cable may extend to the raft, which is typically moored in a lagoon, although not so limited.
There has thus been outlined, rather broadly, the more important features of the invention in order that the description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and that will form the subject matter of the claims appended thereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practised and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.
It is a principal object of the invention to provide a shroud for a propeller that overcomes the shortcomings of prior art aerators. It is a principal object of the invention to provide a shroud with a front aperture for outward aerated water flow and rear apertures for inward water access. It also a principal object to provide a shroud with a rear draft tube allowing inward air access. It is a further principal object of the invention that the draft tube provides access for a propeller shaft to rotate a propeller within the shroud. It is a further principal object to provide that rotation of the propeller within the shroud, sucks water through the rear shroud aperture and sucks air down the draft tube and expels aerated water from the forward aperture of the shroud. It is a subsidiary object that the propeller cavitates the water in the shroud and sucks air down the draft tube into the cavitating water to produce microbubbles of air which dissolve in the water. It is a further principal object of the invention to provide no propeller bearing or shaft bearing in the shroud and draft tube, to affect, reduce or eliminate the suction effect of the propeller in the shroud. It is a further principal object of the invention to provide aerated water which mixes smoothly with the water surrounding the shroud. It is a further object of the invention to provided an air access aperture in the draft tube. It is a further subsidiary object of the invention to provide a motor to drive said propeller shaft. It is also a further subsidiary object of the invention to provide a bearing box to connect the motor to the propeller shaft. It is a subsidiary object to provide a frame to mount the draft tube-motor assembly is mounted on a frame so that the propeller impeller is submerged in the water, while the draft tube aperture, bearing box and motor are in the air. It is a further subsidiary object of the invention that the frame is pivotable from a horizontal position with propeller, shroud, shaft, draft tube, bearing box and motor above water, to an angled position with propeller and shroud submerged. It is a further subsidiary object of the invention to provide the frame mounted on a raft. It is a further subsidiary object of the invention to provide an electric motor for driving the bearing box. It is a further subsidiary object to provided a raft mounting the frame, propeller, shroud, shaft, draft tube, bearing box and motor, moored in a lagoon. Other objects and advantages of the present invention will become obvious to those skilled in the art, from the following specification, accompanying drawings and appended claims, and it is intended that these objects and advantages are within the scope of the present invention.
To accomplish the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, not limiting, and that changes may be made in the specific construction illustrated and described within the scope of the appended claims.
In one broad aspect the invention is directed to a draft tube for an impeller extending from a front end for connection to a shroud to accommodate a freely rotating propeller, to a rear end to accommodate a shaft to drive the propeller, and to pass air around the shaft. The tube is straight and has sufficient cross sectional area to permit the shaft and air to pass freely from the rear end to the front end. Generally the draft tube has a side aperture for air ingress toward its rear end. Preferably the draft tube has a rear attachment plate at right angles to the said draft tube. More preferably the side aperture has a stub tube protruding therefrom.
In an alternate broad aspect the invention is directed to a shroud for impeller to accommodate a freely rotating propeller. The shroud has a first aperture of sufficient size to receive a shaft to drive said propeller and to pass air into the shroud around the shaft, and at least one second aperture to pass water into the shroud. The shroud preferably has a front portion for a freely rotating propeller and a rear portion comprising the first aperture axially aligned with the position of the propeller, and the at least one second aperture is rearward of the propeller position. Usually the front portion is cylindrical and the rear portion is a disc which has the first aperture centrally therein. The disc usually has the at least one second aperture therein spaced radially apart from the first aperture. Often there are several second apertures. Conveniently the front portion is joined to the rear portion by a frustroconical mid portion.
In a second broad aspect the invention is directed to a shroud for impeller comprising a front portion for a freely rotating propeller and a rear portion having a first aperture axially aligned with the position of the propeller. The first aperture us of sufficient size to receive a shaft to drive the propeller and to pass air into the shroud around the shaft, and at least one second aperture in the shroud rearward of the propeller position to pass water into the shroud. A draft tube extends rearward from the rear portion and the first aperture. The draft tube is axially aligned with the position of the propeller, and of sufficient size to accommodate the shaft and to pass air into the shroud. Usually the at least one second aperture is rearward of said propeller position. Typically the tube and first aperture have the same i.d. The draft tube usually has a side aperture for air ingress toward its rear end. The draft tube usually has a rear attachment plate at right angles to the draft tube. Typically the draft tube has a stub tube protruding therefrom. The shroud typically has a front cylindrical portion and a rear disc portion, which has the first aperture centrally therein, and also the at least one second aperture therein spaced radially apart from the first aperture. Often there are several second apertures. Conveniently the front portion is joined to the rear portion by a frustroconical mid portion.
In a further broad aspect the invention is directed to an impeller for aeration comprising in combination front to rear shroud, propeller, propeller shaft, draft tube and motor. The propeller shaft is driven by the motor and passes through the draft tube to drive the propeller in the shroud. The propeller shaft is generally coupled by a socket in the propeller shaft which snugly receives the motor shaft, the motor shaft is usually secured in the socket by set screws. The shroud has a first aperture for the propeller shaft and air ingress into the shroud around the shaft, and at least one second aperture for water ingress into the shroud. The draft tube has a side aperture for air ingress toward its rear. Usually the front portion is cylindrical to accommodate ther propeller and the rear portion is a disc which has the first aperture centrally therein. The disc usually has the at least one second aperture therein spaced radially apart from the first aperture. Often there are several second apertures. Conveniently the front portion is joined to the rear portion by a frustroconical mid portion. The draft tube usually has a rear attachment plate at right angles to the draft tube. Typically the draft tube has a stub tube protruding therefrom. The impeller usually additionally comprising a bearing box between the draft tube and the motor. The bearing box contains a bearing for the shaft, which passes through the bearing box, and the bearing. Suitably the impeller is mounted by its bearing box on a swivel arm pivotally mounted on a frame, which itself is mounted on a floatable substrate, typically a raft. It can also be pivotally or fixedly mounted on a fixed substrate. Usually the front portion of the shroud is cylindrical to accommodate ther propeller and the rear portion is a disc which has the first aperture centrally therein. The disc usually has the at least one second aperture therein spaced radially apart from the first aperture. Often there are several second apertures. Conveniently the front portion is joined to the rear portion by a frustroconical mid portion. The draft tube usually has a rear attachment plate at right angles to the draft tube. Typically the draft tube has a stub tube protruding from the side aperture. The bearing box, when present, is attached at its front to ther draft tube by the attachment plate. The bearing is held within the bearing box by a retainer. The motor is mounted upon a motor mount plate attached to the bearing box at its rear. The impeller can be mounted by its bearing box on a swivel arm pivotally mounted on a frame. The frame itself is preferably mounted on paired parallel pontoons. The impeller is mounted on the frame between and parallel to the pontoons. The impeller is pivotable angularly through a right angle from horizontal to vertical through a plurality of angular positions. The swivel arm has mounted thereon an adjustment arm at right angles to the swivel arm and at right angles to the impeller. The frame has mounted thereon an adjustment plate cooperating with the adjustment arm. The adjustment arm has a single aperture. The adjustment plate has a plurality of apertures corresponding to the angular positions of the impeller, each aperture is registrable with the adjustment arm aperture. The impeller can be secured in angular position by passing a retaining pin through the adjustment arm aperture and one of the adjustment plate apertures.
Nearly all elements of shroud, shaft, draft tube bearing box, swivel arm and frame are preferably stainless steel, except the propeller which is aluminum.
Numeral 10 indicates shroud 12 with attached draft tube 14 of an embodiment of the invention. Shroud 12 has forward cylindrical portion 16, 10″ diameter, 5″ deep, middle frusto conical portion 18 10″ forward diameter tapering to 7″ rear diameter, also 5″ deep and rear disc portion 20 with water access slots 22 and rear draft tube access aperture 24. Water access slots 22 are made by drilling eight 1″ diameter apertures equispaced around draft tube access aperture 24, centered on a circle 5⅛″ diameter, adjacent pairs are then joined to form slots 22. Draft tube 14 has 3″ o.d., 2¾″ i.d., and is 2′ long excluding or including rear plate 26, which is 5½″ or 5⅞″ square and ¼″ or ⅜″ thick, which has corner apertures for attachment to a bearing box. Centered 2¼″ or 3″ forward from the rear end of draft tube 24 is threaded pipe ferrule 28, 1″ diameter and projecting ¾″, for air access. When assembled impeller 29 has shroud 12, containing propeller 31 with hub 32 and blades or vanes 34, hub 32 is mounted on threaded spindle 33 of drive shaft 30. Propeller 31 is a Michigan Machine #012109 9X9 three-bladed propeller of diameter 9 inches. Shaft 30 extends through draft tube 14 into bearing box 36. Shaft 30 is about 45¾″ long, including spindle 33, 4″ long, the bulk of the shaft is 1¾″ diameter. Bearing box 36 is 6½″ square in cross section and extends about 1′3″ along shaft 30, it is of 12 gauge steel plate and has a front or lower end plate 38 for attachment to draft tube attachment plate 26 and a rear or upper end plate 40 for attachment of motor 48, it also has a side removable access plate, not shown. Shaft 30 is contained in bearing 42 held in place by retainer 44, note that bearing 42 avoids the necessity of having an end bearing in shroud 12 for shaft 30, which would virtually eliminate the suction effect of propeller 31. Shaft 30 narrows slightly in bearing box 36 to 1 45/64″ diameter, at its upper or rear end it engages motor drive shaft 46, 3″ long, 1⅛″ diameter, secured by set screws 94 in fitted socket 92, of i.d. 1.127″ (
In use the shroud bottom is typically between 1′ and 1½′ below water level. The propeller turns at 1750 rpm, the set speed of the motor, which is not adjustable, and as a result there is essentially no water in the draft tube. As a further result the propeller does not seize, because there is no water in the draft tube to freeze, the water in the shroud being in constant motion also does not freeze. The impeller operates reliably down to at least −30° C. or −31° C. without freezing, a significant advantage in much of North America. It aerates through 5 or 6″ of ice, producing a frozen white foam in the hole through the ice. In time this frozen foam covers the entire aerator, including draft tube and motor, resembling an igloo, through which the motor can be heard humming away. It is believed that as air incoming through the draft tube is at −30° C. or −31° C., while the water in the shroud is probably between 0 and 4° C., that the turning of the drive shaft, at about 1750 rpm, in the draft tube prevents freezing and seizing of the impeller. The device was observed to seize at −38° C. In warmer weather, when there is no surface ice, the impeller generates a foam which eventually dissipates covering the entire lagoon with a white foam about ¼″ thick or deep. After prolonged use the lagoon gives positive oxygen readings using an oxygen reading device, no positive oxygen readings were noted when testing the truck wash lagoon before aeration. No competitor's aerator was observed to produce the same amount of foam as of the impeller of the invention, nor was one as effective as instant impeller to applicants' knowledge. Larger 20 or 25 horsepower aerators produced patches of foam around the aerators, but didn't cover the slough. It is believed that the smaller bubbles of instant impeller produce much better aeration than the larger bubbles observed in other aerators. It is also considered that the motor shaft-propeller shaft coupling and the bearing box coupling which greatly reduce vibration and hence bearing wear, avoids the need for a bearing in the impeller shroud, which if present would incommode aeration by the propeller. Such bearings are normally a sleeve mounted by vanes in the shroud, which obviously affects the flow around the propeller. It is also believed that the air flowing down the draft tube is evenly distributed by the propeller in the shroud, and that the absence of bearings in the propeller enhances air flow which is central around the shaft, better distributed and creates better suction. Similarly the water flows evenly into the shroud and mixes better with the air to produce a foam, some of which dissolves into and aerates the water surrounding the shroud.
As those skilled in the art would realize these preferred described details and materials and components can be subjected to substantial variation, modification, change, alteration, and substitution without affecting or modifying the function of the described embodiments.
Although embodiments of the invention have been described above, it is not limited thereto, and it will be apparent to persons skilled in the art that numerous modifications and variations form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.
