Abstract:
A blower supplies compressed air to a predetermined place. The blower is provided with a plurality of compressors, a common air tank for storing compressed air supplied from the compressors, a changeover valve for switching the compressed air taken in from the air tank between a first supply state and a second supply state, and a controller for controlling operations of the compressors and the switching operation of the changeover valve. The controller can select one operation pattern from among a plurality of operation patterns determined by combinations between the compressors and the changeover valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-167380, filed Jun. 14, 1999, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a blower, more particularly to a blower suitable for use in a septic tank of bio-filtration type. 
     In accordance with a rise in the awareness of environmental issues, more and more septic tanks have come into use. A septic tank is employed for the treatment of sewage, which is a water resource, i.e. one of the environmental resources. The septic tank is made up of: a settling separation tank into which sewage is supplied; a contact aeration tank into which the sewage is supplied after being cleared of the solid components in the settling separation tank; and a sedimentation tank to which the sewage is supplied after being treated with microorganisms in the contact aeration tank. In the sedimentation tank, the coagulated microorganisms (sludge) settle, and the supernatant liquid is disinfected and drawn off. 
     Inside the contact aeration tank, a contact filter medium is provided. Aerobic microorganisms attached on the surface of the contact filter medium propagate themselves in the presence of aerating air, which is supplied from a blower (air blower) by way of a pipe and an air diffuser. The organic matter included in the sewage is thus decomposed. Since the contact filter medium is contaminated in accordance with this decomposition, it is cleaned regularly or irregularly by supplying blowback air from the blower to the contact filter medium for a predetermined length of time of a day. 
     In the conventional art, a changeover valve is arranged in the pipe through which the compressed air from the blower flows. The changeover valve is provided for supplying aeration air or blowback air from the blower to the contact aeration tank. The valve is changed over between the aeration position and the blowback position. This type of prior art is disclosed in Jpn. Pat. Appln. KOKAI publication No. 10-196547, for example. 
     In general, the amount of blowback air supplied into a contact aeration tank per unit time is dependent on the type of that contact aeration tank. Regardless of the type, the amount of blowback air supplied must be controlled in relation to the amount of aeration air supplied during the same unit time. In the prior art, the amount of air supplied is controlled by using such a changeover valve as described above. Hence, the control of the changeover valve is complicated, and the amount of air supplied is hard to control with high accuracy. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a blower which has solved the problems described above and which enables easy switching of air supply states. An another object of the invention is to provide a blower which enables the entire apparatus incorporating it to be simple in structure, small in size, and low in manufacturing cost. 
     To achieve these objects, the present invention provides a blower comprising: 
     a plurality of compressors; 
     a common air tank for storing compressed air supplied from the compressors; 
     a switching device for switching the compressed air taken in from the air tank between a first supply state and a second supply state; and 
     a controller for controlling operations of the compressors and a switching operation of the switching device, the controller being capable of selecting one operation pattern from among a plurality of operation patterns determined by combinations between the compressors and the switching device. 
     The switching device of the present invention is a changeover valve having: an intake port from which the compressed air supplied from the air tank is taken in; a first discharge port used in the first supply state; and a second discharge port used in the second supply port. The changeover valve selects one of the first and second discharge ports and discharges the compressed air taken in from the intake port to the selected discharge port. 
     The controller of the present invention selectively drives the compressors. When the changeover valve is changed over to the second discharge port, the controller selects an operation pattern under which the compressors are driven momentarily in an overlap manner. 
     The controller of the present invention drives the compressors in parallel. Each time the changeover valve is changed over to the second discharge port, the compressors are alternately stopped in accordance with a period in which the second discharge port is used for air supply. The time when the changeover valve is changed over is shifted from the time when the compressors are selectively stopped. 
     The present invention also provides a blower comprising: 
     a compressor; 
     an air tank for storing compressed air supplied from the compressor; 
     a changeover valve including an intake port from which the compressed air supplied from the air tank is taken in, a first discharge port, a second discharge port, a valve body movable such that the intake port selectively communicates with one of the first and second discharge ports, a member for urging the valve body to a position where the valve body allows the intake port to communicate with the first discharge port, a back-pressure chamber for producing back pressure which enables the valve body to move, against the urging force of the urging member, to a position where the valve body allows the intake port to communicate with the second discharge port, and a back-pressure intake port from which the back pressure is taken into the back-pressure chamber, the valve body of the changeover valve being moved by the urging force of the member to the position where the valve body enables the intake port to communicate with the first discharge port, and when the back pressure is taken into the back-pressure chamber, the valve body is moved by the back pressure to the position where the valve body enables the intake port to communicate with the second discharge port; and 
     a valve including an intake port from which the compressed air supplied from the air tank is taken in, the compressed air taken in from the intake port being supplied to the back-pressure intake port of the changeover valve when the changeover valve supplies the compressed air of the air tank to the second discharge port. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a front view of an automatic blowback blower according to one embodiment of the present invention, the case of the blower being cut away to show the internal structure. 
     FIG. 2 shows an internal structure as viewed from line II—II of FIG.  1 . 
     FIG. 3 shows an internal structure as viewed from line III—III of FIG. 1, with the case being cut away. 
     FIG. 4 is an explanatory illustration showing the structure of an air tank, a changeover valve and a three-way valve. 
     FIG. 5 is a sectional view of an example of a changeover valve. 
     FIG. 6 is also a sectional view of an example of a changeover valve. 
     FIGS. 7A and 7B are block diagrams of a main-portion system configuration according to one embodiment of the present invention. 
     FIG. 8 is a timing chart illustrating operation pattern  1 . 
     FIG. 9 is a timing chart illustrating operation pattern  2 . 
     FIG. 10 is a timing chart illustrating operation pattern  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a front view of an automatic blowback blower according to one embodiment of the present invention. In FIG. 1, the case of the blower is cut away to show the internal structure. FIG. 2 shows an internal structure as viewed from line A—A of FIG.  1 . FIG. 3 shows an internal structure as viewed from line B—B of FIG. 1, with the case being cut away. 
     Two compressors  1  and  2  are located in the center of the automatic blowback blower, and an air tank  3  for storing the air compressed by the compressors  1  and  2  is arranged underneath the compressors. Arranged in front of the air tank  3  are a changeover valve  4  which communicates with the air tank  3 , and a three-way electromagnetic valve  5  which controls the changeover operation of the changeover valve. Pipes  6   a  and  7   a  are connected to the changeover valve  4 . Pipe  6   a  constitutes a normal aeration port  6 , and pipe  7   a  constitutes a blowback aeration port  7 . 
     As shown in FIG. 1, an air cleaner member  11  formed of a sponge or the like is provided on top of the automatic blowback blower. A cover  12  is placed on the air cleaner member  11 , so that the air cleaner member  11  does not separate from the case  10  of the automatic blowback blower. A control signal reception port  14  is provided on the right side of the automatic blowback blower. Through the control signal reception port  14 , control data for determining a blowback time and a blowback interval are supplied to a controller  13 . 
     FIG. 4 shows how the air tank  3 , the changeover valve  4  and the three-way electromagnetic valve  5  are connected together. The intake port  4   a  of the changeover valve  4  and the intake port  5   a  of the three-way electromagnetic valve  5  are connected to the air tank  3  directly, i.e., without connection hoses. Since no connection hose is provided between the air tank  3  and the changeover valve  4  or between the air tank  3  and the three-way electromagnetic valve, the structure surrounding the changeover valve  4  is simple and small in size, accordingly, and can be manufactured at low cost. The three-way electromagnetic valve  5  is provided with a supply port and a back-pressure port  5   b , as well as the intake port  5   a . The back-pressure port  5   b  is open in the atmosphere. 
     The structure of the changeover valve  4  will be described with reference to FIGS. 5 and 6. These Figures are sectional views of the changeover valve  4 . The changeover valve  4  has members for defining an intake port  4   a , an aeration port  4   b  (which serves as a first discharge port), a blowback port  4   c  (which serves as a second discharge port), and a back-pressure intake port  4   d . The members defining these ports are integral with a case  40 . The case  40  defines a valve chamber therein, and a first valve body  41 , a second valve body  42 , a spring  43  for urging the first and second valve bodies  41  and  42 , etc. are arranged in the valve chamber. The first and second valve bodies are flexible, and they are coupled together by a rigid member  44  in such a manner as to form one integral changeover valve body. In the valve chamber, a back-pressure chamber  47  communicating with the back-pressure intake port  4   d  is defined behind the first valve body  41 , and the spring  43  described above is arranged behind the second valve body  42 . The aeration port  4   b  and the blowback port  4   c  communicate with each other by way of a small-diameter hole  45 . When the aeration port  4   b  is closed by the valve body  41 , the hole  45  allows a certain amount of air to be supplied into the aeration port  4   b . Conversely, when the blowback port  4   c  is closed by the valve body  41 , the hole  45  allows a certain amount of air to be supplied into the blowback port  4   c . Thus, the hole  45  serves to prevent the clogging of an air diffuser. As shown in FIGS. 7A and 7B, the hole  45  may be provided with a valve functioning as a throttle valve  46 . In the case where this structure is adopted, the flow rate can be adjusted in the blowback mode. It should be noted that the hole  45  is not essential to the present invention. In other words, the present invention can be reduced to practice without any problems, even where the hole  45  is not provided. 
     In the normal aeration mode, the back-pressure air from the back-pressure intake port  4   d  is not supplied to the changeover valve  4 . As shown in FIG. 5, therefore, the second valve body  42  is moved, by the urging force of the spring  43 , to the position where it closes the blowback port  4   c.  Since the first valve body  41  opens the aeration port  5   b  then, the compressed air supplied to the intake port  4   a  is guided to the aeration port  4   b.    
     In the blowback aeration mode, the first valve body  41  is exerted with back pressure, as shown in FIG.  6 . Since this pressure is greater than the repulsive force of the spring  43 , the first and second valve bodies  41  and  42  move in one body to the leftward direction as viewed in FIG. 6 against the repulsive force of the spring  43 . As a result, the first valve body  41  closes the aeration port  4   b,  and the second valve body  42  opens the blowback port  4   c.  Hence, the compressed air supplied into the intake port  4   a  is guided to the blowback port  4   c.    
     FIGS. 7A and 7B are block diagrams of a main-portion system configuration according to one embodiment of the present invention. In FIG. 7A, the same reference numerals as used in FIGS. 1-3,  5  and  6  denote the same or equivalent structural elements, with the only exception of the reference numeral “ 46 ” assigned to a timer. In FIG. 7B, a modification of the system configuration is also indicated. According to the modification, a check valve  48  is arranged in series with the throttle valve  46 . In the normal aeration mode, this check valve  46  prevents air from flowing into the blowback tube by way of the throttle valve  46 . 
     The controller  13  controls the compressors  1  and  2  and the three-way electromagnetic valve  5  in accordance with data entered from a remote control (not shown) and supplied through the control signal reception port  14  (FIG.  1 ). The data include a blowback time (e.g., 5 minutes, 10 minutes, or 15 minutes), a blowback interval (e.g., once a day, once in two days, or once in three days), the execution or non-execution of a forcible blowback operation), etc. According to the present embodiment, three operation patterns  1  to  3 , examples of which will be described below, are prepared beforehand. The controller  13  selects one of the operation patterns, so that control suitable for the type of the septic tank can be easily performed. Examples of operation patterns executed by the controller  13  will be described with reference to FIGS. 8 to  10 . 
     Operation Pattern  1  (FIG. 8) 
     This is an operation pattern wherein a larger amount of air is used in the blowback aeration than in the normal aeration. The compressors  1  and  2  are switched from one to the other in accordance with the blowback timings. For example, if the blowback is executed once a day, the compressors  1  and  2  are switched from one to the other every day. At the time of switching, both the compressors  1  and  2  are driven simultaneously for the length of time corresponding to the blowback time, e.g., for five minutes. In addition, the three-way electromagnetic valve  5  is actuated by supplying an actuation signal. When the three-way electromagnetic valve  5  is in operation, the air from the air tank  3  passes through the electromagnetic valve  5  and flows into the back-pressure intake port  4   d  of the changeover valve  4 , causing the changeover valve  4  to be changed over in the manner shown in FIG.  6 . As a result, double-amount air, namely, the sum of the outputs of compressors  1  and  2 , is used for the blowback aeration. To execute a blowback operation at an arbitrary time, the compressor which is stationary then is driven for the blowback time, e.g., for five minutes, with the changeover valve  4  being changed over to the position for the blowback aeration. 
     According to this operation pattern, the control performed by the controller  13  is simple and yet enables the amount of air used in the blowback aeration to be twice the amount of air used in the normal aeration. In addition, since the compressors  1  and  2  are operated by turns, they withstand long use, contributing to the long life of the automatic blowback blower. 
     Operation Pattern  2  (FIG. 9) 
     This is an operation pattern wherein a smaller amount of air is used in the blowback aeration than in the normal aeration. The compressors  1  and  2  are operated in parallel in the normal operation mode. When blowback time comes, the changeover valve  4  is first changed over to the position for the blowback aeration by supplying a signal to the three-way electromagnetic valve  5 . A few seconds thereafter (e.g., two seconds thereafter), compressor  1  is stopped. After the elapse of a predetermined blowback time (e.g., five minutes), the changeover valve  4  is first changed over, and then compressor  1  is resumed a few seconds thereafter (e.g., two seconds thereafter). 
     When the blowback aeration is executed next, compressor  2  is stopped. The timings when the changeover valve  4  is changed over to the position for the blowback aeration and compressor  2  is stopped, and the timings when the changeover valve  4  is changed over to the position for the normal aeration and compressor  2  is resumed, are similar to those of the case of compressor  1 . According to operation pattern  2 , the forcible blowback is executed by stopping one of the compressors  1  and  2  at the timings similar to those described above. 
     According to this example, the changeover valve  4  is changed over before one of the compressors is stopped, and is thereafter changed over before that compressor is resumed. Hence, the first and second valves  41  and  42  can be moved in the state where the amount of air contained in the changeover valve  4  is stable. Owing to this, the changeover valve  4  can be changed over smoothly. 
     Operation Pattern  3  (FIG. 10) 
     This is an operation pattern wherein the amount of air used in the blowback aeration is the same as that used in the normal aeration. The compressors  1  and  2  are operated in parallel at all times. When the blowback time set for the controller  13  comes, the three-way electromagnetic valve  5  is operated for a predetermined blowback time (e.g., for five minutes), and thereafter the changeover valve  4  is changed over to the position used for the blowback aeration. 
     As can be understood from FIGS. 7A and 7B, the present embodiment is advantageous in that the three-way electromagnetic valve  5  is only required to control the ON/OFF of the back-pressure air to the changeover valve  5 . Hence, the electromagnetic valve  5  may be small in size and capacity. In comparison with the one used in the conventional system, the electromagnetic valve employed in the present invention is reduced about 5% in terms of the volume, about 10% in terms of the mass, about 10% in terms of the amount of current consumed, and about 20% in terms of the manufacturing cost. Needless to say, in the operation patterns  1 - 3  described above, a certain amount of air is kept supplied in the normal-aeration direction at all times, including the time when the blowback aeration is executed. 
     As can be seen from the foregoing, the embodiment of the present invention can switch the operation patterns determined for the compressors and the changeover means, in response to a command supplied from the controller. Hence, the amount of air used in the normal aeration mode and that used in the blowback aeration mode can be easily varied. For example, the amount of air used in the blowback aeration mode can be easily varied in three steps, namely, twice the amount of air supplied in the normal aeration mode, equal to this amount of air, and half the amount of air. 
     In the embodiment described above, the changeover means is made up of a three-way electromagnetic valve to which back-pressure air from a common air tank is supplied; and a changeover valve supplied with the back-pressure air from the three-way electromagnetic valve and changed over between the normal aeration position and the blowback aeration position. With this structure, the three-way electromagnetic valve can be small in size and capacity. Moreover, the changeover means can be connected to the common air tank directly, i.e., without using a hose. This structure is effective in providing a small-sized, low-priced automatic blowback blower. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.