Bi-directional axial-flow blower

Abstract: A bi-directional axial-flow blower which requires no complex mechanism such as a rotor-reversing mechanism and employs a proper shape of rotor to enables air-blowing operation with high efficiency and low noise both in the forward and reverse directions. The bi-directional axial-flow blower (1) for selectively sending a wind either in forward direction (A) or in a reverse direction (B), comprises a cylindrical casing (3), a forwardly-rotating impeller (8) and a reversely-rotating impeller (9) having airfoil blade rotors (8a, 9a) with camber, and a forward drive motor (6) for driving the forwardly-rotating impeller (8) and a reverse drive motor (7) for driving the reversely-rotating impeller (9), in which the forwardly-rotating impeller (8) is operated whereas the reversely-rotating impeller (9) is made free to rotate when the blower (1) is in the forward wind mode, and the reversely-rotating impeller (9) is operated and the forwardly-rotating impeller (8) is made free to rotate in the reverse wind mode.

Description: (Field of the Invention) The present invention relates to a bi-directional axial-flow blower which is mounted, for example, near the ceiling of the tunnel of an automobile road for ventilating the tunnel. (Background of the Invention) It is required of the blower used for ventilating a tunnel that the wind direction is reversed depending on environmental conditions such as the direction of natural wind flowing through the tunnel and the occurrence of fire in the tunnel. Thus, a bi-directional axial-flow blower generally referred to as a jet-fan is commonly used. Such type of well-known bi-directional blower is grouped in the following categories. (1) Simple contrarotating type: An impeller having a rotor cascade is connected to a reversible drive motor and is housed in a casing. With the direction of the rotors fixed, the drive motor operates in either directions to produce air flow in either axial directions. (2) Adjustable rotor-direction contrarotating type: A reversible drive motor is connected to an impeller having in the boss thereof an airfoil rotor with camber such as circular-arc plate and an automatic rotor-reversing mechanism that reverses the orientation of the rotor by 180 degrees. Then, the entire assembly is housed in a casing. The air-flow can be set in either direction by operating the drive motor in either direction while at the same time changing the direction of rotor. (Problems to be Solved by the Invention) The aforementioned well-known bi-directional axial-flow blowers have the following drawbacks in terms of performance and reliability. (1) In the simple contrarotating type, the impeller provided with a rotor having camber exhibits different performance for the forward rotation mode of impeller and the reverse rotation mode, showing poor efficiency and noise characteristic particularly in the reverse rotation mode. Thus, this type of blower is not suitable for use as a bi-directional axial-flow blower. If the rotor is of a flat plate type not having camber so that the same blower performance is achieved in either directions, then high performance is not expected in either directions. (2) In the adjustable rotor-direction contrarotating type, high blower efficiency can be achieved in either of the forward and reverse directions. However, a complex rotor-reversing mechanism is required which makes it difficult to obtain high reliability. From DE-C-431 682 there is known a bi-directional axial-flow blower for selectively sending a wind either in forward direction or in a reverse direction, comprising a cylindrical casing for defining a wind path, a forwardly-rotating impeller and a reversely-rotating impeller serially aligned in said casing, said impellers having airfoil blade rotors with camber. According to this bi-directional axial-flow blower of DE-C-431 682, there is provided a motor being coupled to both impellers, each of them being coupled to the motor or uncoupled depending of the wind direction. This, however, renders the configuration of the drive motor very complicated and bulky, leading to a reduced flow section of the wind. It is, therefore, an object of the present invention to provide a bi-directional axial-flow blower which requires no complex mechanism to enabling air-blowing operation with high efficiency and low noise both in the forward and reverse directions. This object is achieved by the characterizing features of the single claim. According to the present invention, the bi-directional axial-flow blower comprises a forward drive motor for driving the forwardly-rotating impeller and a reverse drive motor for driving the reversely-rotating impeller, wherein the forward drive motor is operated whereas the reverse drive motor is stopped with the reversely-rotating impeller left free to rotate when the blower is in the forward wind mode, and the reverse drive motor is operated and the forward drive motor is stopped with the forwardly-rotating impeller left free to rotate in the reverse wind mode. (Operation) According to the invention, the wind is controlled to flow either in the forwardly direction or in the reverse direction by selectively operating one of the forward or reverse drive motor in accordance with the command for changing wind directions. The airfoil type rotors having camber suitable for the respective wind directions provide high blower efficiency in either directions. Additionally, the impeller of the inoperative motor side is left free, so that the inoperative impeller receives air flow produced by the operative impeller to rotate free without adversely affecting the ventilation performance. (Brief Description of the Drawings) Fig. 1 is a cross-sectional view of a first embodiment of the invention; Figs. 2 is a front elevational view showing the manner in which the blower of the first embodiment is installed in a tunnel; Fig. 3(a)-3(b) show the orientation of the forwardly-and reversely-rotating rotors of Fig. 1; Figs. 4(a)-4(b) show the orientation of rotors of a modified embodiment; (Embodiment) Embodiments of the present invention will now be described with reference to the drawings. Figs. 1 - 3 show an embodiment according to the invention. In the figures, reference numeral 1 denotes a blower supported from the ceiling of tunnel 2. The blower 1 comprises a hollow cylindrical casing 3 opening at two ends thereof, an inner hollow cylinder 5 mounted in the middle of the casing 3 by means of a stay 4, a forward drive motor 6 and a reverse drive motor 7 housed in the inner hollow cylinder 5 on the same axis thereof, and a forwardly-rotating impeller 8 and a reversely-rotating impeller 9 coupled to the output shafts of the respective motors 6 and 7, respectively. Reference numeral 10 denotes a controller for controlling the wind direction, 8a and 9a denote rotors of the impellers, and 8b and 9b denote cones enclosing the ends of the impellers. The rotors 8a and 9a of aforementioned impellers 8 and 9 have a camber shown in Figs. 3(a) and 3(b) (curved rotor whose thickness grows thinner toward the rear edge of the rotor plate or circular-arc plate whose thickness is constant along the camber line of rotor), and are disposed with respective orientation in accordance with the rotational directions of the forward and reverse motors 6 and 7 as shown by arrows a and b . With this construction, when the wind is delivered from left to right in the direction of the arrow A, upon the command from a controller 10, the forward drive motor 6 is operated to drive the forwardly-rotating impeller 8 into rotation in the direction of the arrow a of Fig. 3(a) while the reverse drive motor 7 is deenergized. Thus, within the casing 3 is produced an air flow in the direction of the arrow A. The impeller 9 directly coupled to the inoperative motor 7 is free, so that it receives the wind flow A to rotate free without disturbing the wind flow. On the other hand, when the wind is delivered from right to left in the direction of the arrow B, the command is supplied to the controller 10 so as to change the wind direction. The forward drive motor 6 is stopped and the reverse drive motor 7 is started so as to drive the reversely-rotating impeller 9 into rotation in the direction of the arrow b of Fig. 3(b). Thus, within the casing 3 is produced an air flow in the direction of the arrow B. The impeller 9 directly coupled to the inoperative motor 8 is free, so that it receives the air flow B to rotate free. In Fig. 1, the inner hollow cylinder 5 may be omitted and the forward drive motor 6 and the reverse drive motor 7 may be mounted within the casing 3 by the means of the stay 4. The dual-rotor type motor in which two rotors are assembled into a common stator may be used in place of two independent motors such as the motor 6 for driving the forwardly-rotating impeller and the motor 7 for driving contrarotating impeller. Where the dual-rotor type motor is used, the inner hollow cylinder 5 may be omitted and the drive motor may be directed mounted in the casing 3 by means of the stay 4. In the figure, the cones 8b and 9b are mounted to the impellers 8 and 9, the cones may be separated from the impellers and fixed in the casing 3. In Fig. 3, the rotor 8a of the forwardly-rotating impeller 8 and the rotor 9a of the reversely-rotating impeller 9 are oriented 180 degrees opposite to each other and the drive motor 6 runs in the direction of a and the drive motor 7 in the direction of b . A modification can be made such that the rotors 8a and 9a are oriented differently as shown in Fig. 4 and the drive motors 6 and 7 may be rotated in the same direction, a and b . (Advantages of the Invention) A bi-directional type axial-flow blower according to the present invention is of the aforementioned construction and has the following advantages. With the construction according to the invention, the rotor of impeller is constructed of the airfoil blade having a camber and the forward and reverse drive motor is selectively operated to achieve the forward and reverse flow of wind for high efficiency wind production. The impeller requires no complex mechanism for changing the orientation of rotor blades ensuring high reliability.

Claims: A bi-directional axial-flow blower (1) for selectively sending a wind either in forward direction or in a reverse direction, comprising: a cylindrical casing (3) for defining a wind path; a forwardly-rotating impeller (8) and a reversely-rotating impeller (9) serially aligned in said casing (3), said impellers (8, 9) having airfoil blade rotors (8a, 9a) with camber; characterised by a forward drive motor (6) for driving the forwardly-rotating impeller (8) and a reverse drive motor (7) for driving the reversely-rotating impeller (9); wherein the forward drive motor (6) is operated whereas the reverse drive motor (7) is stopped with the reversely-rotating impeller (9) left free to rotate when the blower (1) is in the forward wind mode, and the reverse drive motor (7) is operated and the forward drive motor (6) is stopped with the forwardly-rotating impeller (8) left free to rotate in the reverse wind mode.

Inventors: NIIKURA YOSHIYUKI C O FUJI ELE, NISHI MICHIHIRO, NOGUCHI YOKIHIRO C O FUJI ELEC, SUZUKI RYOJI C O FUJI ELECTRIC, TSUKAMOTO TADASHI C O FUJI ELE, NIIKURA, YOSHIYUKI, C/O FUJI ELECTRIC CO., LTD., NISHI, MICHIHIRO, NOGUCHI, YOKIHIRO, C/O FUJI ELECTRIC CO., LTD., SUZUKI, RYOJI, C/O FUJI ELECTRIC CO., LTD., TSUKAMOTO, TADASHI, C/O FUJI ELECTRIC CO., LTD.
Applicants: FUJI ELECTRIC CO LTD, FUJI ELECTRIC CO., LTD.
Application year: 1991
Main classification: F04D19
IPC codes: F04D19, F04D25