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 for selectively sending a wind either in forward direction or in a reverse direction, comprises a cylindrical casing (3), an impeller (16) having airfoil blade rotors with camber provided in the casing (3), a drive motor (15) for driving the impeller (16) and wind-direction selecting means (19) for driving the casing (3) to rotate so that an inlet (3a) and an outlet (3b) of the wind path is reversed in accordance with the desired wind direction.

Description: The present invention relates to a bi-directional axial-flow blower which can be mounted, for example, near the ceiling of a road tunnel to ventilate the tunnel. Such blowers are often used in places which underlie certain restrictions of space, for instance road tunnels or parking decks. In these places, it is often necessary to reverse the air flow direction of the blower depending on environmental conditions such as the direction of natural wind flowing through the tunnel or the occurrence of fire in the tunnel. With respect to the height of vehicles passing the tunnel or to be parked on the deck and the fact that the air blower has to be arranged at a certain distance away from the wall to work properly, there exists a need for small and highly efficient air blowers because enlarging the diameter of a tunnel tube or the height of a parking deck would be very costly. In conventional air blowers, the direction of air flow is reversed by simply reversing the drive motor of the rotor or by reversing the rotor in its casing. There exists two types of blowers which are generally referred to as jet fan and which are commonly used. In the simple contrarotating type, an impeller having a rotor cascade is connected to a reversible drive motor and housed in a casing. As the orientation of the rotors is fixed, the drive motor can be operated in either direction to produce air flow in the respective axial direction. In the 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 plates. An automatic rotor reversing mechanism is provided that reverses the orientation of the rotor by 180°. The entire assembly is housed in a casing. The air flow direction can be changed by operating the drive motor in either direction while at the same time the orientation of the rotor is changed. An air blower of this type is known from DE-A-72180. In both cases, the casing has to be fixed to the ceiling in order to provide a sufficient stability. As in the simple contrarotating type, the impeller is usually provided with a rotor having camber, the blowing efficiency of the blower in the forward rotation mode of the impeller will be better than in the reverse rotation mode which also exhibits increased noise emission. Thus, this type of blower is not suited for bi-directional air blowing. If on the other hand a flat plate type rotor without camber is used, the same blowing performance in both directions can be achieved which however is not expected to be very high. In the adjustable rotor-direction contrarotating type high blower efficiency can be achieved in both the forward and reverse direction. However, this type requires a complicated rotor reversing mechanism which deteriorates the reliability of the air blower. Further, from FR-A-2 531 501 an air distribution device is known which is constituted by an outer casing accommodating a cylindrical casing having a through opening to define a wind path in which an impeller and a drive motor for driving the impeller are mounted. The wind path is perpendicular to the axis of the cylinder of the cylindrical casing which can be rotated about the axis of the cylinder to change the air flow direction. Another bi-directional air blower is known from BE-A-484 254. It has a reversible casing which houses a ventilator. The casing is suspended by a complicated outer support structure. From BE-A-484 254, it can be concluded that in view of the weight of the casing and the ventilator and its motor, and the possibility of forces acting laterally on the casing, a rigid support structure for the casing is necessary. The same idea is manifested in FR-A-2 531 501 by the rigid outer housing. However, in reversible air blowers for the above-mentioned applications such a rigid support structure would require a large space. The present invention therefore intends to provide a bi-directional air blower which has a high blowing efficiency and which is small in size and therefore particularly suited for tunnels or parking decks. This problem is solved by a bi-directional air flow blower for selectively sending a wind either in a forward direction or in a reverse direction, said blower includes a hollow cylindrical casing defining a wind path coaxial with the axis of the cylinder, an impeller provided in the casing, a drive motor for driving said impeller, a wind direction selecting means having a motor and a drive shaft which is connected to the casing, the wind direction selecting means being adapted to reverse the orientation of the casing, and hence that of the drive motor and the impeller, wherein said casing is held by a one-arm-suspension which is formed by the drive shaft of the wind direction selecting means. According to a preferred embodiment of the present invention, the impeller is disposed upstream of the wind path and the drive motor is disposed downstream of the wind path in the casing, and the drive motor is secured to the casing by means of stay vanes having a cross section such that an angle with respect to the center axis of the casing gradually decreases from the front edge toward the rear edge. According to a further preferred embodiment of the bi-directional axial-flow blower, a stationary casing is disposed adjacent to the casing in which the impeller and drive motor are incorporated and the stationary casing defines a wind path communicating with the latter casing and has at the central axis thereof a conical wind guide. According to another preferred embodiment of the invention the impeller has airfoil blades with camber. The airfoil type rotors having camber to provide high blower efficiency in both air flow directions. According to the present invention, the impeller is driven into rotation in the same direction regardless of the desired wind direction. With the blower operating, when the casing is turned around in response to the command of changing wind direction so as to change the orientation of wind path, the impeller and drive motor are also turned around together with the casing so that the wind flow is reversed. According to a further preferred embodiment of the invention, the stay vane converts a high rotating dynamic pressure produced at the outlet of the impeller into a static pressure for pressure recovery as well as controls the separation on the surface of stay vane. Thus, the wind pressure of blower is increased achieving highly efficient and low noise operation of the blower. According to still another preferred embodiment of the invention, the conical wind guide provided within the stationary casings forms a wind path whose cross section continuously grows smaller(upstream) toward and larger(dowstream) from the boss of impeller and the drive motor which are incorporated within the casing adjacent to the fixed casing. This permits the smooth acceleration and deceleration of the air flowing through the bore of casing, retarding the occurrence of separation. Further, the conical wind guide in the stationary casing arranging is separated from the casing in which the impeller and drive motor are incorporated, thus achieving a short and small casing that rotates in accordance with the desired wind direction. This is particularly advantageous in that adjacent casings will not interfere each other during rotation even if a plurality of blowers for ventilation are suspended from the tunnel ceiling side by side in a narrow space. (Brief Description of the Drawings) Fig. 1 and 2 are cross-sectional views of a preferred embodiment showing different operating conditions of a blower; Fig. 3 shows the positional relation of the rotor and stay vane shown in Fig. 2; Fig. 4 is a cross-sectional view of a further embodiment; Fig. 5 is a top view of Fig. 4; and Fig. 6 is a front elevational view showing the manner in which the blower may be installed in a tunnel. Embodiments of the present invention will now be described with reference to the drawings. The rotor 8a of the impeller 16a and has a camber shown in Figs. 3 (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). Figs. 1 to 3 show an embodiment according to a prefered embodyment of the invention. Within a hollow cylindrical casing 3 are housed a drive motor 15 supported by means of a stay vane 14 and an impeller 16 coupled to the output shaft of the drive motor 15. The casing has a wind inlet 3a, a wind outlet 3b, an impeller 16 disposed upstream of the drive motor 15. A cone 17 for guiding the wind is mounted at the front end of the impeller 16 and a cone 18 at the rear end of the drive motor 15. The casing 3 is mounted to a motor shaft 19a of a wind-direction selecting motor 19 for selecting the wind direction such that the casing is suspended from the motor 19 mounted on the ceiling. The casing 3 is rotated about the shaft 19a in the direction of the arrow C. As shown in Fig. 3, the impeller 16 has an airfoil type rotor 16a having a camber. The orientation of rotor blades relative to the rotational direction a is that shown in Fig. 3. As shown, the stay vane 14 aligned downstream of the rotor 16a is formed with a curved surface, so that the cross section of the stay vane is such that the angle  with respect to the central axis O of the casing 3 decreases from front edge to rear edge. The wind-direction selecting operation of the blower 1 of the aforementioned construction will now be described. When the wind is delivered from left to right in the tunnel 2, having the inlet 3a of the casing 3 directed to the left as shown in Fig. 1, the motor 15 drives the impeller 16 into rotation in the direction of the arrow a. Thus, within the casing 3 is produced an air flow in the direction of the arrow A. When the wind is delivered from right to left with the drive motor 15 rotated in the direction a , the casing 3 is rotated by the wind-direction selecting motor 19 so as to change the orientation of the casing 3 by 180 degrees from the position in Fig. 1 to that in Fig. 2. Thus, the inlet 3a of the casing 3 is oriented to the right and an air flow is produced in the direction B within the casing 3. The stay vane 14 holding the motor 15 is formed to have the aforementioned cross section so that the stay vane 14 retards the separation of wind flowing along the stay vane 14 and absorbs the dynamic pressure due to the rotating velocity produced by the impeller 16 to convert it into the static pressure. The cones 17 and 18 provided at the front end of the impeller 16 and at the rear end of the drive motor 15, respectively, allow the smooth change of flow rate of air flow contributing to the retardation of separation. Figs. 4 and 5 show a variation of the third embodiment as an embodiment of the fifth aspect of the invention. The drive motor 15 and impeller 16 are assembled just as in the third embodiment. A stationary casings 20 are suspended from the ceiling by means of wires 21 such that the stationary casings 20 are in line with the casing 3 and are disposed at the front of and at the rear of the casing 3. In the middle of each of the casings 20, a long conical wind guide 22 is mounted by means of the stays 23 so that the cross section of the wind path varies continuously toward the drive motor 15 and the front end of impeller 16. As shown in Fig. 5, the inlet and outlet of the casing 3 and the ends of the stationary casings 20 opposing the casing 3 are formed in an arcuate shape in concentric relation with the motor shaft 19a of the wind-direction selecting motor 19. The casings are opposing each other with slight clearances therebetween. By this arrangement, the conical wind guide mounted to the stationary casing 20 smooths out the change in wind velocity just as in the third embodiment so as to control the occupance of separation. The casing 3 is allowed to rotate free in the direction of the arrow C without interfering with the stationary casings 20. Mounting the long conical wind guide 22 to the stationary casing 20 separately from the casing 3 permits a smaller size of the casing 3 which incorporates the drive motor 15 and impeller 16 therein. This minimizes the projection of the casing 3 to the sideway when the casing 3 is rotated. Thus, where a plurality of blowers 1 are provided side by side near the ceiling within the tunnel as shown in Fig. 6, the adjacent blowers may be spaced apart only by short distance between them without interference. A bi-directional type axial-flow blower according to the present invention is of the aforementioned constructed and has the following advantages. With the construction according to the present invention, the orientation of the casing in which the impeller and drive motor are assembled, is reversed in accordance with the desired wind direction. Thus, a complex mechanism for changing the orientation of rotor blade is not required while the wind direction can be switched between the forward and reverse directions by rotating the casing with both the direction of rotor blade cascade and the motor direction unchanged. With the construction according to a further aspect of the invention, the impeller is disposed upstream of the wind in the casing and the drive motor downstream while at the same time the drive motor is mounted to the casing by means of a stay vane whose cross section is such that the angle with respect to the center axis of casing decreases from front edge to rear edge. This arrangement reduces the separation of wind and converts the dynamic pressure produced by the whirling velocity caused by the impeller into the static pressure to achieve high efficiency and low noise. With the construction according to a prefered further development, the stationary casing having a wind path is disposed adjacent the casing, which has the impeller and drive motor assembled therein, in such a away that the wind path communicates with the casing. Then, the conical wind guide is provided within the stationary casing on the central axis. This allows the change in wind velocity to be smoothed out for high efficiency and low noise as well as achieves the smallest possible casing that is rotated to be oriented in accordance with the wind direction. The blower is advantageous in that if the blower is used for the ventilation in the tunnel where a plurality of blowers are to be aligned in a small space near the ceiling, the casings of adjacent blowers will not interfere each other when the casings are rotated.

Claims: A bi-directional axial-flow blower for selectively sending a wind either in a forward direction or in a reverse direction, said blower includes: a hollow cylindrical casing (3) defining a wind path coaxial with the axis of the cylinder, an impeller (16) provided in the casing (3), a drive motor (15) for driving said impeller (16), a wind direction selecting means having a motor (19) and a drive shaft (19a) which is connected to the casing (3), the wind direction selecting means being adapted to reverse the orientation of the casing (3), and hence that of the drive motor (15) and the impeller (16), wherein said casing (3) is held by a one-arm-suspension which is formed by the drive shaft (19a) of the wind direction selecting means. A bi-directional axial-flow blower according to claim 1, characterised in that said impeller (16) is disposed upstream of the wind path and the drive motor (15) is disposed downstream of the wind path in the casing (3), and the drive motor (15) is secured to the casing (3) by stay vane means (14) having a cross section such that an angle with respect to the center axis of the casing gradually decreases from the front edge toward the rear edge of the stay vane (14). A bi-directional axial-flow blower according to claim 1, characterised in that a stationary casing (20) is disposed adjacent to the casing (3) in which the impeller (16) and drive motor (15) are incorporated and said stationary casing (20) defines a wind path communicating with the latter casing (3) and has at the central axis thereof a conical wind guide (22). A bi-directional axial-flow blower according to claim 1, characterised in that a pair of stationary casings (20) is provided which are disposed on both ends of said cylindrical casing (3) in line with the latter. A bi-directional axial-flow blower according to claim 4, characterised in that the inlet and the outlet of the casing (3) and the respective ends of the stationary casings (20) are formed in an arcuate shape. A bi-directional axial-flow blower according to claim 5, characterised in that the cylindrical casing (3) and the respective stationary casing (20) oppose each other with a slight clearance therebetween. A bi-directional axial-flow blower according to one of claims 1 and 4 to 6, characterised in that in the middle of each casing (20) there is mounted a long conical wind guide (22). A bi-directional axial-flow blower according to claim 7, characterised in that said conical wind guide (22) is mounted by means of stays (23). A bi-directional axial-flow blower according to one of claims 1 to 8, characterized in that the impeller (15) has airfoil blades with camber.

Inventors: NIIKURA YOSHIYUKI, NISHI MICHIHIRO, NOGUCHI YOKIHIRO, SUZUKI RYOJI, TSUKAMOTO TADASHI, NIIKURA, YOSHIYUKI, NISHI, MICHIHIRO, NOGUCHI, YOKIHIRO, SUZUKI, RYOJI, TSUKAMOTO, TADASHI, NIIKURA, YOSHIYUKI, C/O FUJI ELECTRIC CO., LTD., 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