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  Axial flow fan improvementsUSPTO Application #: 20060286924Title: Axial flow fan improvements Abstract: An energy efficient and compact axial fan with a housing comprising a fan assembly comprising a drive motor and a propeller coupled thereto. The inlet opening and/or the outlet opening of the fan housing are provided with a shutter assembly positioned adjacent the propeller and having a plurality aerodynamically shaped pivoted louvers working in tandem for less air obstruction and noise. The propeller comprises a plurality of radial blades comprising means for straitening the air flow and reducing the vortex flow of the propeller thereby permitting the shutter to be mounted adjacent the propeller to lessen the dept of the fan housing for making the fan more compact. (end of abstract)
Agent: Angelo Milana - Montreal, QC, CA Inventor: Angelo Milana USPTO Applicaton #: 20060286924 - Class: 454259000 (USPTO) Related Patent Categories: Ventilation, Having Inlet Airway, Including Backdraft Preventer The Patent Description & Claims data below is from USPTO Patent Application 20060286924. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention disclosed herein relates generally to axial flow fans improvements and, more particularly to axial flow fans having a shutter operated by a centrifugal mechanism for maintaining a controlled environment in buildings such as poultry houses, greenhouses, steel-plants, foundries, etc. [0003] 2. Description of the Related Art [0004] Axial flow fans are used to move high volume of air at low static pressure. An application in which they are beneficially used involves the ventilation of poultry house buildings which often are shaped like a tunnel. Intensive rearing of birds (typically more than 10 000) imposes severe demands on the fans which are provided for removing moisture, heat, carbon dioxide and other contaminants from said buildings. [0005] Hot summer days often cause indoor conditions to become much hotter than desired, temperatures above 25 degree Celsius have an adverse effect on production of said birds. The high temperatures can be controlled effectively with large exhaust fans and with water-wetted cooling pads. Typically eight to twelve (48'') propeller fans are installed in one end wall of the building and water-wetted cooling pads are installed on the opposite end wall of said building. When the fans work create a small negative pressure in the building causing outside warm air to pass across the water-wetted cooling pads causing some water to evaporate and extract some heat from the air, thereafter fresh air passes throughout the building cooling said birds. [0006] Most of the conventional fans for use in poultry house buildings applications are propeller type fans comprising a shutter assembly with gravity shutters or vanes extending horizontally across the intake or the exhaust of the fans. Said vanes do not open to a position where they are perfectly horizontal, i.e., the vanes have a slight downward angle thereto because of their weight. In additions the fans are too sensitive to added resistance therefore, a small increase of static pressure causes a substantial reduction of the air flow of the fans. As a result, when wind blows against the fans, the air flow decreases substantially and will not be sufficient to cool the birds which will suffer of heat stress. [0007] To overcome the detrimental effect of the insufficient airflow, a larger number of fans are used. However, the solution is not satisfactory because increases the capital cost and the operating cost due to an increase of energy consumption. [0008] In general, a conventional axial flow fan for agricultural applications includes a housing made of galvanized steel enclosing a drive motor and a propeller which is running adjacent to a venturi or orifice. The fan comprises a shutter assembly provided for preventing infiltration of outside air into the building and back flow through idle fans. Said shutter assembly typically is composed of a myriad of horizontally mounted pivoted vanes connected with cranks and at least one tie rod. As it can be imagined, the large number of vanes constitutes an obstruction to air flow and raise the cost of the fan, which is also increased by the cost of labor required to assemble the large quantity of vanes and elements connecting them. [0009] For maintaining a controlled environment on those poultry house buildings, the fans need to provide an appropriate and precise airflow. Any reduction in needed air flow can reduce bird performance and increases mortalities of the birds. In a conventional axial flow fan with gravity shutters used in a poultry house building dirt can build up on the shutters as fast as a 1/4 pound per day and after few days of operation said accumulation of dust causes a reduction of at least 30% of the air flow of the fan and a reduction of air speed in the building of 30%. The lower air velocity causes a significant less cooling for birds. [0010] The shutters or vanes of the fans can be located at the fan intake where ambient air passes across the vanes with low turbulence or can be located at the fan discharge where air flow is more turbulent therefore causing more vibrations and noise. In north climates, for protection from stormy weather the vanes are mounted at the fan intake therefore they open inwardly the fan housing interior therefore the housing is deeper. [0011] In addition, in order to limit the vibrations and noise said vanes must be mounted away from the propeller, of at least of 1/3 of the diameter of the propeller. As a result, the fans are bulkier and heavier and the manufacturing and shipping costs are significantly higher. [0012] The vibrations and noise of said vanes is caused by the interference between the vanes and the vortex flow produced by the propeller, said interference creates a large head pressure that may be prevented providing propellers comprising means producing less turbulent air flow and vanes designed to be less affected by the turbulent air flow. The applicant provides shutter assemblies with a plurality of aerodynamically shaped vanes mounted adjacent the propeller and extending vertically across the intake and/or the exhaust of the fan. The vanes comprise leading edges connected together by a continuous hinge, therefore the vanes work in tandem. [0013] As the vanes are vertically pivoted gravitational dust is prevented from accumulating thereon. As the vanes work in tandem their drag and noise is reduced. However, said vertical vanes have to be operated by an actuator as a centrifugal shutter device. When the fan operates any pressure and energy is required to keep the vanes in their wide open position. [0014] In contrast to prior art fans with shutters comprising a myriad of vanes, the fan of the present invention comprises few vertical pivoted vanes working in tandem therefore the fan is able to move consistently and quietly at least 20% more than the prior art fans. The poultry house fans may operate continuously generating also undesirable noise and vibrations. As such, the fans collectively represent a significant energy drain and source of noise therefore it is important to pay more attention to energy efficiency and reduction of noise level in the design of such fans. [0015] Vibrations and excessive noise of the fans mainly are caused by the air pushed by the propeller and passing across the vanes which oscillate. Another important source of noise is caused by the blades of the propeller which during its rotational movement over obstacles produce a pressure variation on the obstacle which results in noise emission. [0016] As the drive motor is energized, the movement of rotation of the propeller blades imparts to the air a great deal of centrifugal force generating a turbulent air flow that quickly and erratically disperses upon exiting the orifice or venturi that normally surrounds the propeller blades. The turbulent air flow not only comprises a velocity component that is parallel to the propeller blades rotation axis but also a swirl comprised of variable velocity components of various obliquities to the propeller blades rotational axis. Since the function of the propeller blades is to move air in a direction parallel to a rotational axis, velocities imparted in other directions represent degradation in efficiency, increase of the noise and cost to operate the fan. [0017] In particular, the air flow around the tip region of said propeller blades creates a very noisy and strong vortex trailing downstream from the blade tips. To reduce this vortex, it is important to have a very close and uniform clearance between the propeller blade tips and the venturi, so as to minimize the air "leakages" and back air flow. [0018] The applicant solves the problem of vortex production by providing a propeller comprising a hub and plurality of airfoil shaped blades comprising a plurality of fins positioned at the pressure side of the blades. For each propeller blade the applicant provides a radially slidably adjustable shoe comprising a fin extending circumferentially for preventing radial components of the air flow from moving radially toward the venturi, for guiding the air flow substantially axially toward the fan discharge and for preventing air from flowing back around the blades tips. This results in a somewhat more efficient fan capable of operating quietly at a relatively higher static pressure. [0019] The applicant provides also a propeller with a hub and a plurality of airfoil shaped blades comprising a plurality of fins and an outer duct or band secured to the tips of the blades for co-rotation therewith; the blades are pivotally attached to both the duct and the hub. As the duct is attached to the blades tips the creation of vortices and vibrations is reduced. As the vortex generation of the propeller is reduced, if not eliminated, noise is reduced, the problems of air flow interference with the vanes are minimized therefore the vanes can be mounted in proximity of the propeller of the fan. As a result, the novel fan is more compact than prior art fans and it can be delivered to the end user totally assembled. Heretofore, it was necessary to ship a large amount of "air" in the assembled fans at a cost that became significant especially with overseas shipments. [0020] The overall effect of the combination of the improved propellers and improved vanes working in tandem is a noticeable reduction of back pressure on the propeller and a noticeable increase of the efficiency and performance of the fan. [0021] A lower vortex emission also implies that a lower amount of the energy provided to the fan is being spent in the vortex production so that a greater amount of energy can be used to produce useful work in the fluid. Hence, the reduction in the noise level comes with an increase in the fan efficiency. [0022] Another problem encountered with axial flow fans used in poultry house buildings includes the drive belt. Over time, a typical V-belt will eventually wear and the tension transmitted by the belt will vary causing slippage and reduction of fan air flow. Therefore the applicant provides toothed gears and timing belts. End users never have to worry about belt slippage and reduction of the airflow of the fans. [0023] To solve some of prior art problems of the shutters, the applicant previously provided a fan described in U.S. Pat. No. 6,276,895 issued on Aug. 21, 2001, and its teachings are incorporated herein by reference. The fan described in that patent had an exhaust shutter assembly with vanes that did not have insulation or protection from the elements. Continue reading... Full patent description for Axial flow fan improvements Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Axial flow fan improvements patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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