Automatic solution dispensing apparatus

Abstract: An automatic solution mixing apparatus is provided with a plurality of solution distributors 101 and 201 located on either side of the common base plate 302 on the supporting block 305 which is movable right-to-left with the pistons 101b and 201b of the solution distributors 101 and 201 connected to the common base plate 302, so that dual solution mixing operations can be performed in the solution distributors 101 and 201 arranged bilaterally with an improved solution mixing accuracy which is common for the respective ingredient solutions. Moreover, a stepping motor is utilized as a driving motor, and the control of the operation thereof can be performed by controlling the number of pulses of the pulse signal supplied to the driving motor 310, without using a rotary encoder.

Description: The present invention relates to an automatic solution dispensing apparatus for use with dying, developing, etching solutions and the like. DESCRIPTION OF THE PRIOR ART The applicant of this invention has previously proposed an automatic solution dispensing apparatus in the Japanese Patent Laid Open 026980/1990. The automatic solution dispensing apparatus disclosed in the above-mentioned patent application comprises, as shown in Fig. 1, a plurality of solution distributors 1-1, 1-2, ..., 1-n (hereinafter represented by the solution distributors 1) which suck and discharge solutions by the reciprocal movement of pistons 1-1b, 1-2b, ..., 1-nb (hereinafter represented by 1-b) inserted in cylinders 1-1a, 1-2a, ..., 1-na (hereinafter represented by 1-a) are arranged in a row. The solution distributors 1-1, 1-2, ..., 1-n are respectively connected to three-way solenoid valves 3-1, 3-2, ..., 3-n (hereinafter represented by three-way solenoid valves 3) through common ports (COM) thereof. The three-way solenoid valves 3 are connected to solution tanks (not shown) through solution intake pipes 15-1, 15-2, ..., 15-n respectively for intaking solutions from the solution tanks. Also, the three-way solenoid valves 3 are connected to a solution receiver 5 respectively through injection pipes 2-1, 2-2, ..., 2-n for discharging solutions from the solution distributors 1 to the solution receiver 5. The pistons 1-1b, 1-2b, ..., 1-nb of the solution distributors 1 are respectively coupled through couplings 6-1, 6-2, ..., 6-n to an actuating arm 7 for driving all the pistons by the same amount of stroke in the same direction. The movement of the arm 7 in the direction as indicated with an arrow A, i.e., back and forth movement is performed by the normal and reverse rotation of a driving motor 8, and the amount of the back and forth movement is controlled by the number of pulses of the pulse signal fed from a rotary encoder 14 which detects the number of revolutions of the motor 8. Accordingly, since the back and forth movement of the actuating arm 7 corresponds to that of the pistons 1-b, the amount of movement of the pistons 1-b can be controlled by controlling the amount of the back and forth movement of the arm 7, i.e., the number of pulses fed from the rotary encoder 14. Moreover, since the amount of movement of the pistons 1-b corresponds to the amount of the solution discharged from the distributors 1, by obtaining the above-mentioned number of pulses per unit discharge amount in advance, the amount of solution discharged from the cylinders 1-a can be controlled. The operation of such an automatic solution mixing apparatus will now be hereinafter described. In the first step, with the three-way solenoid valves 3 having their valve passages opened toward the solution tanks, the driving motor 8 is so operated as to move the pistons 1-b in a direction of extending the pistons from the cylinders 1-a, i.e., to move the actuating arm 7 backward. Accordingly, the solution is sucked from the solution tank into each distributor 1 and filled therein. The number of pulses corresponding to the amount of solution to be discharged from each distributor 1 is then set in a control section (not shown), so that the control section will control the operation of the driving motor 8 based upon the number of the above-mentioned set pulses and the number of the pulses supplied from the encoder 14. Subsequently, the driving motor 8 is rotated to move the actuating arm 7 forward, i.e., to actuate the pistons 1-b in a direction of insertion thereof into the cylinders 1-a to eject air bubbles therefrom, and thereafter, performing an operation for dispensing a plurality of solutions. In the solution mixing operation, the solutions are discharged in the order of increasing the amount of solutions to be discharged from the distributors 1, i.e., increasing the number of the pulses set in the control section, and the control section operates the driving motor 8 to move the actuating arm 7 forward until the discharge amount of the solution reaches to the specified amount of discharge for each distributor 1 set in the control section. For the distributor 1 in which the solution discharge of a desired amount has been completed, the three-way solenoid valve 3 located on the discharge side of the cylinder is opened toward the solution tank and the solution remained in the cylinder 1-a (hereinafter called as the residual solution) is ejected into the solution tank. This operation is repeated for every solution distributor 1 to mix the solutions. Although the automatic solution dispensing apparatus described above is capable of mixing many kinds of solutions accurately, these solution distributors 1 must be arranged in a row to install a driving gear including the actuating arm 7, driving motor 8 and so on behind the distributors 1, and the number of the solution distributors 1 connected to the driving gear is limited because of the limited length of the actuating arm 7. Therefore, when a large number of solution distributors 1 are required, a plurality of sets of the driving gears and the solution distributors 1 have to be prepared, which arises a problem to make the automatic solution dispensing apparatus large in size. A solution dispensing apparatus comprising the features of the precharacterizing part of claim 1 is known from US-A-3 765 605. This dispensing apparatus comprises a pair of solution distributors disposed on either side of an actuating member, each distributor comprising a cylinder and a piston. The pistons of both distributors are connected to a piston of a double-acting hydraulic actuating member such that their movements are opposite to each other. While one piston sucks into its corresponding cylinder a liquid solution from a solution tank, the other piston ejects from its cylinder a solution that has been previously sucked in. The actuating member is controlled by a control valve that is manually operable via a solenoid. From US-A-4 145 165, an automatic solution dispensing apparatus is known, wherein cylinders are situated on both sides of a driving member. The driving member for driving pistons comprises a shifting screw which, when rotated, extends one piston and retracts the other one. It is an object of the present invention to provide an automatic solution dispensing apparatus which may be provided with a large number of solution distributors without making the size thereof large and which is capable of dispensing the solutions accurately. This object is solved, according to the invention, with an automatic solution dispensing apparatus having the features of claim 1. According to a feature of the present invention, the automatic solution dispensing apparatus comprises: one or plural pairs of solution distributors for sucking solutions into their cylinders or discharging therefrom by the movement of pistons in the cylinders, the distributors being substantially disposed face to face each other in pairs to place their pistons in opposite directions; piston connecting mechanism for connecting both pistons in pairs in such a way that the movement of the pistons in the cylinders located in one side is opposite to that of the pistons in the cylinders located in the other side; and piston driving means for driving the pistons to suck the solutions into the solution distributors and discharge a predetermined amount of solutions therefrom. According to another feature of the present invention, the automatic solution dispensing apparatus further comprises one or plural pairs of solution distributors for sucking solutions into their cylinders or discharging therefrom by the movement of the pistons in the cylinders, the distributors being substantially disposed face to face each other in pairs to place their pistons in opposite directions; plural pairs of solution tanks provided corresponding to the respective solution distributors for containing ingredient solutions to be mixed; one or plural pairs of solution receivers for containing mixed solutions; three-way solenoid valves for communicating the solution distributors with the solution tanks or with the solution receivers depending on the control signal; piston connecting means for connecting both pistons in pairs in such a way that the movement direction of the pistons in the cylinders located in one side is opposite to that of the pistons in the cylinders located in the other side and their movement amounts are equal; piston driving means for driving the piston connecting means to suck the solutions into the solution distributors and to discharge a predetermined amount of solutions therefrom; solution intake means for feeding a signal to open each valve passage of the three-way solenoid valve toward each solution tank and for feeding a signal to move the piston driving means in the direction of removing the piston from the cylinder of each solution distributor in one side connected to the above-mentioned three-way solenoid valve having its valve passage opened toward the solution tank; calculation means for calculating the quantity of a solution to be discharged into the receiver through each of the distributors; discharge switching means feeding a signal to actuate the piston driving means until the quantity of condensed solutions discharged from the respective distributors provided in one side reaches to the target discharge amount predetermined for the solution distributors and to switch the valve passages of the three-way solenoid valves connected to the distributors to the tank side when the target discharge amount of the solutions is reached; and control means for controlling the operation of the solution intake means and the discharge switching means and for stopping the piston driving means. Thus constructed, the piston connecting means connects the pistons respectively located in the individual solution distributors in which the pistons are placed face to face each other in pairs in such a manner that the movement of the piston in each distributor in one side is opposite to that of the piston in each distributor in the other side and both of the movement amounts are equal. The piston driving means reciprocates the piston connecting means in a direction in which the piston can be moved within the range of the cylinder of the distributor. In this way, when those pistons of a group of solution distributors in one side which are placed face to face to a group of solution distributors in the other side are moved in a direction to insert them into their cylinders for example, those pistons of the group of the solution distributors in the other side will be moved in a direction to remove them from their cylinders. And when the situation is reversed, the respective groups of the solution distributors will then be operated in reverse. Thus, the automatic solution dispensing apparatus according to the present invention will perform the solution dispensing operation by operating at least two groups of solution distributors in one operation thereof, in which the distributors located in one group suck solutions, while the distributors located in the other group discharge the same. As a result, a solution dispensing operation is effected in accuracy without making the automatic solution dispensing apparatus large in size. The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention together with further objects and advantages thereof may best be understood with reference to the following detailed description, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing a construction of a conventional automatic solution dispensing apparatus; Fig. 2 is a perspective view showing a construction of an embodiment of an automatic solution dispensing apparatus according to the present invention; Fig. 3 is a partial cross sectional view showing the main portion of the apparatus shown in Fig. 2; Fig. 4 is a perspective view shown in a coupling portion of the apparatus shown in Fig. 2; and Fig. 5 is a block diagram showing a construction of an embodiment of a control unit for the automatic solution dispensing apparatus according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In Figs. 2 and 3 depicting one embodiment of an automatic solution dispensing apparatus according to the present invention, there are fixed a plurality of solution distributors 101-1, 101-2, ..., 101-n and 201-1, 201-2, ..., 201-n of two groups for sucking and discharging solutions by the backward and forward movement of their respective cylinders in parallel and spaced apart appropriately along the extending direction on a pair of flat bases 301a and 301b which are fixed to extend in parallel to each other so that their respective pistons 107 and 207 are installed face to face each other with their coaxial lines in alignment, the cylinders being mounted in a horizontal state. It is noted that, for representing the respective solution distributors 101 and 201 fixed on the bases 301a and 301b, they may be indicated as the solution distributors 101 and 201 respectively. The solution distributors 101 and 201 mentioned above are respectively composed of cylinders 101a and 201a, and pistons 101b and 201b reciprocating in these cylinders. The pistons 101b and 201b of the solution distributors 101 and 201 are respectively connected with a common movable base plate 302 through connecting rods 107 and 207. With this construction, the solution distributors 101 discharge solutions and the solution distributors 201 suck the same when the common base plate 302 is moved to the left in the figures, whereas the solution distributors 201 discharge solutions and the solution distributors 101 suck the same when the common base plate 302 is moved to the right in the figures. Each of the solution distributors 101 and 201 has a solution intake/discharge port A located and vertically protruding upward from the closed end of the cylinders 101a and 201a respectively. Three-way solenoid valves 103-1, 103-2, ..., 103n (represented by the valves 103 hereinafter) are respectively connected to the solution intake/discharge ports A of the distributors 101 through intake/discharge pipes 155-1, 155-2, ..., 155-n (represented by pipes 155 hereinafter). Similarly, three-way solenoid valves 203-1, 203-2, ..., 203-n (represented by valves 203 hereinafter) are respectively connected to the solution intake/discharge ports A of the distributors 201 through intake/discharge pipes 255-1, 255-2, ..., 255-n (represented by pipes 255 hereinafter). Each of the three-way solenoid valves 103 has a normally open port (NO), common port (COM) and normally closed port (NC), wherein the normally open ports NO are respectively connected to solution tanks 104-1, 104-2, ..., 104-n (represented by solution tanks 104 hereinafter) through solution pipes 115-1, 115-2, ..., 115-n (represented by solution pipes 115 hereinafter), and the common ports COM are respectively connected to the cylinders 101a through intake/discharge pipes 155, and the normally closed ports NC are respectively connected to solution receivers 105-1, 105-2, ..., 105-n (represented by receivers 105 hereinafter) through injection pipes 102-1, 102-2, ..., 102-n (represented by injection pipes 102 hereinafter). When the solenoid of the valve is energized (turned on), the passage (COM-NC) will open to communicate the injection pipes 102 for the respective receivers 105 with the solution distributors 101, whereas when the solenoid of the valve is de-energized (turned off), the passage (COM-NO) will open to communicate the pipes 115 for the tanks 104 with the solution distributors 101. Similarly, each of the three-way solenoid valves 203 has the same construction as those of the three-way solenoid valves 103. In each of the tanks 104 (204), there is provided an agitator 152 (252) which agitates a condensed solution contained in the tank. The receivers 105 (205) are respectively mounted on a turn table or belt conveyer (not shown) so that they are moved along the nozzles of the injection pipes 102 (202). For example, the first receiver 105 receives a desired amount of the first solution through the injection pipe 102-1 of the solution distributor 101-1, and this receiver 105-1 is moved to the second position corresponding to the injection pipe 102-2 of the solution distributor 101-2 to receive a desired amount of the second solution therefrom. In this way the receivers 105 (205) are respectively filled with different condensed solutions for mixing the solutions by moving the receivers to the injection pipes of desired solution distributors so as to receive their individual solutions. Although, in this embodiment shown in Fig. 2, the solution distributors 101 (201) are individually provided with solution receivers 105 (205) connected thereto for receiving solutions, a pair of solution receivers may be arranged as shown in Fig. 1, in other words, one solution receiver is provided in the side of the solution distributors 101 for receiving the solutions injected through the respective injection pipes 102 and the other solution receiver is provided in the side of the solution distributors 201 similarly. Moreover, although there are individually provided ingredient solution tanks 104 (204) corresponding to each of the solution distributors 101 (201), there may be provided a single ingredient solution tank 104 (204′) for containing solutions fed from a plurality of solution distributors 101 (201) through a plurality of solution pipes 115 (215). As shown in Figs. 3 and 4, there are provided metal rings 101c (201c) mounted on the end portions of the pistons 101b (201b) and provided coupling mechanisms 106 (206) for coupling the metal rings 101c (201c) with the connecting rods 107 (207) which are fixed with the common base plate 302 by rod linkage metal fittings 108 (208). It is noted that, although Fig. 4 shows these parts only on the side of the solution distributors 101, their arrangement is identical with that of those on the side of the solution distributors 201 and the explanation thereof is omitted for brevity. Each coupling 106 is composed of a forked U character member 50 to be fixed on the end surface of the metal ring 101c and a joint member 51 connected to the connecting rod 107. The forked member 50 is composed of two arms 50a and 50b appropriately spaced apart from each other, each having oval cutting portion 50c with its longer axis running perpendicularly to the extending direction of each of the arms 50a and 50b and opened at one end thereof. The joint member 51 has a flat connecting plate 51b which is removably inserted in the space between the arm plates 50a and 50b and attached thereto. The connecting plate 51b of the joint member 51 has a cylindrical stem rod 51c fixed passing through the center of the connecting plate 51b perpendicularly thereto. The cylindrical stem rod 51c is slidingly movable in close contact with the cut portions 50c defined in the arm plates 50a and 50b. That is to say, the forked member 50 and the joint member 51 thus constructed are engaged with each other in such a way that the connecting plate 51b is inserted in the space between the arm plates 50a and 50b of the forked member 50 with the stem rod 51c engaged in the cut portion 50c. By providing the coupling mechanism 106 thus constructed, there is an advantage that the flexibility of the setting angle of the solution distributors 101 with respect to the connecting rod 107 fixed onto the common base plate 302 through the rod linkage metal fitting 108 is increased to facilitate to adjustment of setting the solution distributors 101. The connecting rod 107 is a round bar with its both ends threaded and has a hexagon nut 52 fixed at the intermediate portion thereof through which the round bar is passed. The connecting rod 107 has one threaded end portion engaged in a threaded hole provided at an end surface 51d of the joint member 51 opposite to the connecting plate 51b and has the other threaded end portion engaged in a threaded hole formed at an end surface of the rod linkage metal fitting 108 fixed on the common base plate 302. In this way the piston 101b of each of the solution distributors 101 is connected to the common base plate 302 through the coupling mechanism 106 and the connecting rod 107. In addition, by turning the hexagon nut 52 fixed on the intermediate portion of the connecting rod 107, the length of the portion of the connecting rod 107 inserted in the joint member 51 and the length of the portion thereof inserted in the rod linkage metal fitting 108 can be adjusted to perform a fine adjustment of the relative position of the piston 101b with respect to the cylinder 101a of the solution distributor 101. As shown in Figs. 2 and 3, the common base plate 302 is supported by a supporting block 305 which is movable longitudinally in the figures. Through a base member 320 of the supporting block 305, there are provided two guide bars 303 extending horizontally in parallel with an appropriate space therebetween, whereby the supporting block 305 is moved right-to-left in the figures. In the middle portion of the base member 320, there is formed a threaded hole 321 through which a shifting screw 304 made of ball screw is inserted, so that the supporting block 305, i.e., the common base plate 302 is moved right and left in the figures by rotating the shifting screw 304. On the top surface of the supporting block 305 are provided two posts 305a vertically standing at the both ends thereof and the common base plate 302 is fixed on the posts 305a on the supporting block 305. On the common base plate 302, the rod linkage metal fittings 108 and 208 are fixed face to face each other. A plurality of these metal fittings 108 (208) are arranged in the positions corresponding to the solution distributors 101 (201) installed on the base 301a (301b). In this embodiment, the solution distributor 101, connecting rod 107, rod linkage metal fittings 108 and 208, connecting rod 207 and solution distributor 201 are disposed on the same line in alignment. Since the common base plate 302 is flat, there is an advantage that the rod linkage metal fittings 108 (208) can be easily fixed on the base plate 302 and detached therefrom so that parts including the solution distributors 101 (201) can be easily maintained. When providing an additional rod linkage metal fitting which is free to adjust the relative angle with respect to the common base plate 302 in addition to the rod linkage metal fitting 108 shown in Fig. 2, the solution distributors can be arranged in four directions and the like. In this case, it is necessary to compensate the amount of the movement of the pistons corresponding to that of the supporting block 305. At one end of the shifting screw 304, there is provided a pulley 308 which is linked with a pulley 309 mounted on a driving shaft of a driving motor 310 through a belt for example. The driving motor 310 is a reversible stepping motor whose operating time is controlled by the number of pulses supplied from a controller 30 to be described later. Thus, by operating the driving motor 310, the shifting screw 304 is rotated so as to move the supporting block 305 and the common base plate 302 right and left along the extending direction of the guide bars 303. The supporting block 305 is moved right and left in the figures in the space between the opposingly directed pistons 101b and 201b of the solution distributors 101 and 201. In this embodiment, the supporting block 305 is moved longitudinally in an opening 307 formed in a substrate 301 to which the solution distributors 101 and 201 are fixed. In order to detect the limit positions of the longitudinal movement of the supporting block 305, there are provided limit switches 311a and 311b on a fixed frame (not shown) for sending signals to stop the rotation of the driving motor 310. And there are provided detection bars 312 protruding from the supporting block 305 in the longitudinal direction for actuating the limit switches 311a and 311b when the supporting block 305 reaches the specified movement limit positions thereof. The limit positions are set within a range in which the pistons 101b and 201b can be moved in the cylinders 101a and 201a of the solution distributors 101 and 201 fixed on the both sides on the substrate 301. In order to lubricate the backward and forward movement of the pistons 101b (201b) within the cylinders 101a (201a), lubricant such as water or oil will be dropped from a portion above the pistons 101b (201b) when the pistons are pulled out from the cylinders of the solution distributors 101 (201), and there are provided lubricant receivers 109 and 209 on the substrate 301 for receiving the lubricant. In this embodiment, there is provided a shifting unit 313 integrally including the guide bars 303, shifting screw 304 and supporting block 305 under a lower surface 301c of the substrate 301 so as to constitute the automatic solution dispensing apparatus as an integrated unit including the substrate 301. In this arrangement as mentioned above, when the supporting block 305 is shifted to the left in the figures for example, the pistons 101b will move in a direction to be inserted into the cylinders 101a (forward) in the side of the solution distributors 101, and at the same time, the pistons 201b will move in a direction to be removed from the cylinders 201a (backward) in the side of the solution distributors 201. When the supporting block 305 is shifted to the right, the pistons 101b and 201b are reversely operated from the operation thereof mentioned above. Accordingly, when the pistons 101b is moved in a direction to be removed from the cylinders 101a for example, since the three-way solenoid valves 103 are opened toward the ingredient solution tanks 104, the solution distributors 101 will suck the solution contained in the solution tanks 104 into the cylinders 101a through the three-way solenoid valves 103 and intake/discharge ports A. At the same time, the solution distributors 201 will discharge the solution remained in the cylinders 201a through the intake/discharge ports A to the solution receivers 205 by inserting the pistons 201b into the cylinders 201a. Conversely, when the pistons 201b are moved in a direction to be removed from the cylinders 201a, since the three-way solenoid valves 203 are opened toward the ingredient solution tanks 204, the solution distributors 201 will suck the solution contained in the solution tanks 204 into the cylinders 201a through the three-way solenoid valves 203 and intake/discharge ports A. At the same time, the solution distributors 101 will discharge the ingredient solution remained in the cylinders 101a through the intake/discharge ports A by inserting the pistons 101b into the cylinders 101a. The operation of this embodiment of the automatic solution dispensing apparatus constructed as mentioned above will now be described with reference to Figs. 2, 3 and 5. To help one understand the operation, it is noted that the explanation will be performed on the assumption that the solution distributors for distributing the solutions to be used are arranged on both of the right and left sides of the common base plate 302 in Fig. 2. In the discussion, suffixes L and R depict items relating to the solution distributors 101 and 201 on the left and right respectively. For the number of the pulses of the signal to be fed to the driving motor 310, the relation between the number of revolutions of the driving motor 310 depending on the number of the pulses supplied to the motor 310 and the amount of the ingredient solution discharged from each of the solution distributors 101 and 201 corresponding to the movement of the supporting block 305 driven by the rotation of the driving motor 310 has been previously obtained from an experiment, so that the numbers of the pulses per a unit discharge amount of the solution by each of the solution distributors 101 and 201, i.e., P0iL and P0iR (pulses/milliliter) are respectively registered in a first memory 31 in the controller 30 as shown in Table 1. The numbers of input pulses PmL and PmR corresponding to the largest strokes of each of the respective pistons 101b and 201b of the solution distributors 101 and 201, i.e., the largest distance among those in which the pistons 101b and 201b can be moved from end to end in the cylinders 101a and 201a are set and registered in a third memory unit 34 in the controller 30. The sums of the content volume of the intake/discharge pipes from the intake/discharge ports A to the three-way solenoid valves, the remaining content volume of the three-way solenoid valves, the content volume of the ingredient solution pipes between the three-way solenoid valves and the solution tanks and some extra content volume for safety are individually obtained for the solution distributors 101 and 201. In connection with the solution distributor having the largest sum among those obtained, the numbers of pulses PnL and PnR to be fed to the driving motor 310 which correspond to the movement amount of the piston required for discharging the solution of the content volume mentioned above are registered in a fourth memory 35 in the controller 30. The numbers of the pulses PnL and PnR may also be obtained from an experiment. The numbers of pulses PnL and PnR registered in the fourth memory unit 35 are fed to a first comparator unit 37 for comparing the numbers of pulses PnL and PnR with the counted values PiL and PiR fed from an adder 42 to be described later. When the data of the names of solutions and their respective target injection amounts QiL and QiR are fed to the controller 30, the numbers of pulses P0iL and P0iR per unit discharge amount of the ingredient solution of the solution distributor connected to the solution tank which contains the solution in question are entered in the first memory unit 31, and the numbers of pulses PQiL and PQiR corresponding to the target injection amounts QiL and QiR are calculated in a first calculation unit 32 by equations as follows: PQiL = P0iL x QiL, and PQiR = P0iR x QiR In addition, in the first calculation unit 32, the calculated target numbers of pulses PQiL and PQiR are divided by the produced pulse numbers PmL and PmR respectively corresponding to the largest distances mentioned above for the pistons to be moved, and subsequently, the respective quotients as the numbers of injections nL and nR and their residuals as the numbers of the last injection pulses PqiL and PqiR are registered in the second memory 33 as shown in Table 2. The numbers of injections nL and nR are positive integers 0, 1, 2, ... an n = 0 means the first injection. Accordingly, when the numbers of injections nL and nR are 0, the target pulse numbers PQiL and PQiR become equal to the last injection pulse numbers PqiL and PqiR. The largest values of the counted numbers of injections nL and nR are registered in an injection number memory unit 43, and the pistons 101b and 201b of all the solution distributors 101 and 201 perform the reciprocal movements that number of times. In Table 2, it is indicated that each of ingredient solutions A3L and A3R is not injected. Moreover, the solution distributors 101 and 201 are moved approximately the same distance, and the diameters thereof may be different from each other. By increasing the calibers of one or more solution distributors 101 and 201, a large amount of ingredient solutions can be sucked and discharged by the same movement amount of the pistons 101b and 201b, thereby reduction of period of time required for sucking and discharging the ingredient solution. On the other hand, by reducing the calibers of the solution distributors 101 and 201, a smaller amount of ingredient solutions can be sucked and discharged by the same movement amount of the pistons 101b and 201b, thereby improvement of the accuracy of the sucking or discharging amount of the solution. That is, since the accuracy of the moving distance of the pistons 101b and 201b is fixed, a smaller sectional area across the calibers of the solution distributors 101 and 201 enables the smallest distribution amount of the solution to be decreased so that a higher degree of distribution amount can be obtained. Therefore, by selecting a suitable caliber for the solution distributors 101 and 201 corresponding to the ingredient solution used and the distribution amount thereof, a desired solution mixing can be performed by a smaller times of reciprocal movement of the pistons 101b and 201b. Generally speaking, in order to cover a wide range of solution concentration by plural solution distributors of the same caliber, it is necessary to prepare several kinds of concentration for ingredient solutions to be sucked into the solution distributors since the range of the injection amount of the solution of the distributors is limited. However, by preparing a plurality of solution distributors having different calibers for ingredient solutions of the same concentration, a wide range of discharging amount can be covered without increasing the number of solution tanks, so that a wide range of solution concentration can be covered. Therefore, there is an advantage that the times of solution dispensing operations required for one kind of ingredient solution can be decreased and more kinds of solutions can be used in one automatic solution dispensing apparatus. The automatic solution dispensing operation actually performed by each of the solution distributors 101 and 201 will be now described hereinafter for each operating step. In the following description, it is noted that the solution distributors 101 represent all the solution distributors disposed on the left side in Fig. 2, while the solution distributors 201 indicate all the solution distributors disposed on the right. [1] SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; DISCHARGE IN THE SIDE OF SOLUTION DISTRIBUTOR 201 When an operation start-up signal is fed in the controller 30, the driving motor 310 is operated (in a counterclockwise rotation for example) so as to move the supporting block 305 to the right in Figs. 2 and 3. At this time, the three-way solenoid valves 103 are in de-energized condition to open the valve passages toward the solution tanks 104. Accordingly, the pistons 101b of the solution distributors 101 are moved backward according to the right-hand movement of the supporting block 105, namely, the common base plate 302, so that the ingredient solutions in the solution tanks 104 are sucked and fed into the cylinders 101a of the solution distributors 101. At this time, the three-way solenoid valves 203 in the side of the solution distributors 201 opposing to the solution distributors 101 are in de-energized condition to open the valve passages toward the solution tanks 204. Accordingly, the pistons 201b of the solution distributors 201 are moved forward according to the right-hand movement of the common base plate 302, so that the ingredient solutions (air if the solution is nct present) in the cylinders 201a are discharged and fed into the solution tanks 204. The driving motor 310 is rotated to move the supporting block 305 to the right until the detecting bar 312 fixed to the supporting block 305 comes in touch with the limit switch 311b. When the supporting block 305 reaches the limit position on the right hand and the limit switch 311b is operated by the detecting bar 312, a right-hand movement completion signal is transmitted from the limit switch 311b to a calculation control unit 36 in the controller 30. Then, the calculation control unit 36 interrupts power supply to the driving motor 310 through a driving motor control unit 40 so as to stop the rotation of the motor 310 and set the movement amount count value Pi of the supporting block 305 stored in the adder 42 to zero. The movement amount count value Pi is a value obtained by counting the number of pulses of the pulse signal fed to the driving motor 310 to control the operation thereof. The calculation control unit 36 sends a signal for setting the number of injections to zero to the injection number memory unit 43. [2] AIR BUBBLE EJECTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 201 Next, the controller 30 reverses the driving motor 310 (clockwise rotation for example) through the driving motor control unit 40 so as to move the supporting block 305 to the left. The pulse signal fed to the driving motor 310 is at the same time fed to the adder 42 from the driving motor control unit 40, and the number of pulses fed to the adder 42 is additively accumulated therein. In this case, since all of the three-way solenoid valves 103 associated with the solution distributors 101 are held in de-energized condition, the valve passages are opened toward the solution tanks 104. At this time, the three-way solenoid valves 203 of the solution distributors 201 opposing to the solution distributors 101 are in de-energized condition with the valve passages opened to the solution tanks 204. Accordingly, the pistons 201b of the solution distributors 201 are moved backward, in other words, moved in a direction to be removed from the cylinders according to the left-hand movement of the supporting block 305, so that the ingredient solution in the solution tanks 204 are sucked into the cylinders 201a of the respective solution distributors 201. The count value Pi added in the adder 42 in accordance with the operation of the driving motor 310 is successively fed to the first comparator 37 through the calculation control unit 36, and the first comparator 37 compares the count value Pi with the pulse number PnL fed from the fourth memory unit 35. When the count value Pi becomes equal to the pulse number PnL, the first comparator 37 sends out the signal for stopping the rotation of the driving motor 310 so as to once stop the rotation of the driving motor 310. In addition, the calculation control unit 36 sets the added value added in the adder 42 to zero according to the signal supplied from the first comparator 37. The purpose of moving the pistons 101b of the solution distributors 101 once to the left is to push back all of the air bubbles mingled in the solution distributors 101 during the solution sucking operation to the solution tanks 104 so as to ensure that there is no air bubble present between the intake/discharge ports A of the solution distributors 101 and the three-way solenoid valves 103. Such an air bubble ejection may be performed from end to end of the piston moving distance, and the solutions ejected from the cylinders can be either returned to the solution tanks or disposed. In this case, the ingredient solutions must be supplied to the cylinders 101a of the solution distributors 101 again. [3] INDIVIDUAL DISTRIBUTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 201 In response to the signal transmitted from the calculation control unit 36, the second comparator unit 39 energizes the three-way solenoid valves 103 associated with one or more solution distributors 101 which are required to discharge the solutions into the receivers 105, based on the data signals fed to the second memory unit 33 from the first calculation unit 32 so as to open the valve passages of the three-way solenoid valves 103 to communicate the solution distributors 101 with the receivers 105. Accordingly, when the pistons 101b of the solution distributors 101 are moved forward, that is, when inserted into their cylinders 101a, the ingredient solutions in the solution distributors are discharged into the receivers 105. At this time, the three-way solenoid valves 203 of all the distributors 201 located on the right oppositely to the solution distributors 101 are in de-energized condition and the valve passages thereof are opened toward the solution tanks 204. Accordingly, when the pistons 201b of the solution distributors 201 are moved backward according to the left-hand movement of the common base plate 302, the ingredient solutions in the solution tanks 204 are sucked into the cylinders 201a of the solution distributors 201. Subsequently, the calculation control unit 36 operates the driving motor 310 through the driving motor control unit 40 so as to move the common base plate 302 to the left. Therefore, the ingredient solutions are discharged from the corresponding solution distributors 101 to the receivers 105, and at the same time, the pulse signal supplied to the driving motor 310 is fed to the adder 42, which accumulates the number of pulses and sends the accumulated value to the calculation control unit 36 successively. The second comparator unit 39 compares the target number of pulses of the solution distributors 101 with the number of pulses supplied from the adder 42. When the smallest value PQiL of the target number of pulses becomes equal to the number of pulses produced from the adder 42, the second comparator unit 39 sends a signal for stopping the rotation of the driving motor 310 temporarily to the driving motor control unit 40. The second comparator unit 39 further de-energizes the three-way solenoid valve 103-i connected to the solution distributor 101-i corresponding to the target number of pulses PQiL through a three-way solenoid valve control unit 38. Accordingly, the ingredient solution in the solution distributor 101-i is prevented from being discharged to the receiver 105-i, and thereafter, the ingredient solution in the solution distributor 101-i is discharged to the solution tank 104-i. In this embodiment, although the valve passages of the three-way solenoid valves 103 are switched after the driving motor 310 has been temporarily stopped, it is also possible to switch over the valve passages of the three-way solenoid valves 103 without temporarily stopping the rotation of the driving motor 310. In this case, the time required for distributing the solution can be shortened. On the other hand, at this time, since all the three-way solenoid valves 203 of the solution distributors 201 are in de-energized condition, the valve passages of thereof are opened toward the solution tanks 204, and even when the flow of the discharged solution from the three-way solenoid valve 103-i of the solution distributor 101-i is changed, the pistons 201b are moved backward in accordance with the left-hand movement of the supporting block 305 as mentioned above, the ingredient solutions in the solution tanks 204 are successively sucked into the cylinders 201a of the solution distributors 201. Subsequently, the calculation control unit 36 operates the driving motor 310 again to move the common base plate 302 to the left. Like as mentioned above, the second comparator unit 39 compares the next smallest value PQiL of the target number of pulses with the number of pulses produced from the adder 42. When the next smallest value PQiL is equal to the number of pulses produced from the adder 42, the rotation of the driving motor 310 is temporarily stopped again and the associated three-way solenoid valve 103-i' is de-energized. On this occasion too, since the three-way solenoid valves 203 associated with the solution distributors 201 are in de-energized condition, their valve passages are opened toward the solution tanks 204. Therefore, even when the flow of the solution in the three-way solenoid valve 103-i' associated with the solution distributor 101-i' is changed, the pistons 201b are moved backward in accordance with the left-hand movement of the common base plate 302 as mentioned above, and the ingredient solutions in the solution tanks 204 are successively sucked into the cylinders 201a of the solution distributors 201. In this way, starting from the solution distributor which has attained the solution dispensing operation corresponding to the target number of pulses set in the second memory unit 33, the valve passages of the three-way solenoid valves 103 associated with the corresponding solution distributors are switched to be opened to the solution tanks 104 so as to complete the discharge of the solutions into the receivers 105. [4] DISCHARGE OF REMAINING SOLUTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 201 The third comparator unit 41 compares the number of pulses supplied from the adder 42 with the number of pulses PmL for the largest piston movement of the solution distributor set in the third memory unit 34, and when the pulse numbers are coincident with each other, the rotation of the driving motor 310 for moving the supporting block 305 to the left is stopped and all the three-way solenoid valves 103 associated with the solution distributors 101 are de-energized and the valve passages thereof are switched to be opened to the solution tanks 104. The number of pulses PmL indicates the number of pulses which corresponds to the movement amount of the detection bar 312 to actuate the limit switch 311a at the left side for sending the detection signal when the pistons 101b are completely inserted into the cylinders 101a of the solution distributors 101. Therefore, the limit switch 311a nay be omitted by using the number of pulses PmL corresponding to the largest distance of the movement of the pistons 101b. At this time, the three-way solenoid valves 203 associated with the solution distributors 201 oppositely located are held in de-energized condition and their valve passages are opened to the solution tanks 204. Accordingly, the pistons 201b of the solution distributors 201 are moved backward in accordance with the left-hand movement of the common base plate 302, and the ingredient solutions in the solution tanks 204 are continuously sucked into the cylinders 201a of the solution distributors 201 until the left-hand limit switch 311a is turned on so as to stop the common base plate 302. When the pistons 201b reach the backward limit position and the limit switch 311a is actuated by the detection bar and sends out the signal for stopping the rotation of the driving motor 310, the number of injections to be stored in the injection number memory unit 43 is replaced with a value subtracted by 1 from the current number of pulses stored in the memory unit 43. [5] SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; AIR BUBBLE EJECTION, MEASUREMENT AND RETURN IN THE SIDE OF SOLUTION DISTRIBUTOR 201 Next, in the case the data of injection number sent out from the injection number memory unit 43 is not zero, the calculation control unit 36 reverses the rotation of the driving motor 310 and operates the driving motor 310 until the right-hand limit switch 311b is turned on. In this case, the supporting block 305 does not move from the left end to the right end but moves as to be described later. Accordingly, since the common base plate 302 connected to the pistons 101b of the solution distributors 101, i.e., the supporting block 305 is moved to the right, the ingredient solutions are sucked from the solution tanks 104 into all the solution distributors 101. In addition, by turning on the limit switch 311b as mentioned above, the calculation control unit 36 sets to zero the count value Pi for the movement amount of the supporting block 305 to be stored in the adder 42. The operation from the time when the left-hand limit switch 311a is turned on to the time when the right-hand limit switch 311b is turned on will be hereinafter described on the solution distributors 201 oppositely located in the right side. [5-1] SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; AIR BUBBLE EJECTION IN THE SIDE OF SOLUTION DISTRIBUTOR 201 When the limit switch 311a is turned on, the pistons 201b of the solution distributors 201 are in fully pulled out to the leftmost position with the three-way solenoid valves 203 opened to the solution tanks 204, so that every cylinder 201 is filled with each ingredient solution. Then the controller 30 reverses the rotation of the driving motor 310 (counterclockwise rotation for example) to move the supporting block 305 to the right. The pulse signal fed to the driving motor 310 from the driving motor control unit 40 is at the same time fed to the adder 42 and the number of pulses fed to the adder 42 is additively accumulated in the adder 42. The count value Pi added in the adder 42 is successively fed to the first comparator unit 37 through the calculation control unit 36. The first comparator unit 37 compares the count value Pi with the number of pulses PnR supplied from the fourth memory unit 35. When the count value Pi becomes equal to the number of pulses PnR, the first comparator unit 37 sends out the signal to the driving motor control unit 40 for stopping the rotation of the driving motor 310. Thus, the rotation of the driving motor 310 is temporarily stopped. In addition, in response to the output signal of the first comparator unit 37, the calculation control unit 36 sets the added value in the adder 42 to zero. The purpose of moving the supporting block 305 temporarily to the right is to push out all the air bubbles mingled in the solution distributors 201 during the solution sucking operation to the solution tanks 204 so as to ensure that there is no air bubble present between the solution distributors 201 and the three-way solenoid valves 203. [5-2] SUCTION IN THE SIDE OF SOLUTIONS DISTRIBUTOR 101; INDIVIDUAL DISTRIBUTION IN THE SIDE OF SOLUTION DISTRIBUTOR 201 Next, in response to the signal transmitted from the calculation control unit 36, the second comparator unit 39 energizes the three-way solenoid valves 203 associated with the solution distributors 201 required to discharge the solutions into the receivers 205 based on the data supplied to the second memory unit 33 so as to communicate the solution distributors 201 with the receivers 205. Accordingly, when the pistons 201b of the solution distributors 201 are moved to the right, the solutions in the solution distributors 201 are discharged into the receivers 205. Next, the calculation control unit 36 sends the signal to the driving motor control unit 40 for operating the driving motor 310 to move the supporting block 305 to the right again. Therefore, the solutions are discharged from the corresponding solution distributors 201 into the receivers 205, and at the same time, the pulse signal supplied to the driving motor 310 is fed from the driving motor control unit 40 to the adder 42 which accumulates the number of pulses and sends out the accumulated value to the calculation control unit 36 successively. The second comparator unit 39 compares the target numbers of pulses of the solution distributors 201 with the number of pulses supplied from the adder 42. When the smallest value PQiR of the target numbers of pulses becomes equal to the number of pulses produced by the adder 42, the signal is transmitted from the second comparator unit 39 to the driving motor control unit 40 for temporarily stopping the rotation of the driving motor 310. Then, the second comparator unit 39 sends a signal to the three-way solenoid valve control unit 38 for de-energizing the three-way solenoid valve 203-i associated with the solution distributor 201-i which is corresponding to the target number of pulses PQiR. By this operation, the solution in the solution distributor 201-i is not discharged into the receiver 205 thereafter, but is discharged into the solution tank 204-i. Moreover, in this operation, since all the three-way solenoid valves 103 associated with the solution distributors 101 are in de-energized condition, the valve passages of the three-way solenoid valves 103 are opened to the solution tanks 104. Therefore, even when the flow of the solution through the three-way solenoid valve 203-i associated with the solution distributor 201-i is changed, the pistons 101b are moved backward, namely, moved in a direction to be removed from the cylinders 101a in accordance with the right-hand movement of the supporting block 305 as mentioned above, so that the solutions in the solution tanks 104 are being sucked on into the cylinders 101a of the solution distributors 101. Subsequently, the calculation control unit 36 sends the signal to the driving motor control unit 40 again for operating the driving motor 310 to move the common base plate 302 to the right. Like as mentioned above, the second comparator unit 39 compares the next smallest value of the target number of pulses PQiR′ with the number of pulses produce by the adder 42. When the next smallest value PQiR′ becomes equal to the number of pulses produced by the adder 42, the rotation of the driving motor 310 is temporarily stopped again and the three-way solenoid valve 203-i′ corresponding to the next smallest target number of pulses PQiR' is de-energized. By this operation, the solution in the solution distributor 201-i′ is prevented from being discharged into the receivers 205, and thereafter, the solution is discharged into the solution tank 204-i′. Also, in this operation, since all the three-way solenoid valves 103 associated with the solution distributors 101 are in de-energized condition, their valve passages are opened to the solution tanks 104. Therefore, as mentioned above, even when the direction of the flow of the solution through the three-way solenoid valve 203-i′ associated with the solution distributor 201-i′ is changed, the pistons 101b are moved backward, namely, moved in a direction to be removed from the cylinders 101a in accordance with the right-hand movement of the common base plate 302, so that the solutions in the solution tanks 104 are being sucked on into the cylinders 101a of the solution distributors 101. In this way, the second comparator unit 39 switches the valve passages of the three-way solenoid valves 203 sequentially corresponding to the solution distributors opened to the solution tanks 204 in the order starting from one of the solution distributors 201 which has attained the target number of pulses set in the second memory unit 33, thereby completion of the discharge of the solutions into the receivers 205. [5-3] SUCTION IN THE SIDE OF SOLUTION DISTRIBUTOR 101; REMAINING SOLUTION DISCHARGE IN THE SIDE OF SOLUTION DISTRIBUTOR 201 The third comparator unit 41 compares the number of pulses supplied from the adder 42 with the number of pulses PmR for the largest piston movement of the solution distributor set in the third memory unit 34, and when the both pulse numbers are coincident with each other, the rotation of the driving motor 310 for moving the supporting block 305 to the right is stopped and all the three-way solenoid valves 203 associated with the solution distributors 201 are de-energized and their valve passages are switched to be opened to the solution tanks 204. The number of pulses PmR indicates the number of pulses which corresponds to the movement amount of the detection bar 312 to actuate the limit switch 311b at the right side for sending the detection signal when the pistons 201b are completely inserted into the cylinders 201a of the solution distributors 201. Therefore, the limit switch 311b may be omitted by using the number of pulses PmR corresponding to the largest distance of the movement of the pistons 201b. When the limit switch 311b sends out the signal for stopping the rotation of the driving motor 310, the number of injections to be stored in the injection number memory unit 43 is replaced with a value subtracted by 1 from the current number of pulses stored in the memory unit 43. In this way, when the supporting block 305 is moved to the right in Fig. 2 until the limit switch 311b is operated, the first solution dispensing operation with respect to the solution distributors 201 is completed, and at the same time, the solution sucking operation with respect to all the solution distributors 101 is completed. [6] REPETITION OF THE PROCEDURES [1] TO [5] The automatic solution dispensing operation mentioned above will be started again from this stage. That is, the first comparator unit 37 operates the driving motor 310 to move the supporting block 305 to the left for ejecting air bubbles mingled in all the solution distributors 101 until the added count value PiL of the number of pulses of the pulse signal supplied to the driving motor 310 becomes equal to the number of pulses PnL stored in the fourth memory unit 35 in the automatic solution dispensing operation with respect to the solution distributors 101. In this operation, since every three-way solenoid valve 103 associated with the solution distributors 101 is in de-energized condition, the solutions in the solution distributors 101 are discharged into the solution tanks 104. Also, in the solution distributors 201, like as mentioned above, the three-way solenoid valves 203 are in de-energized condition with their valve passages opened to the solution tanks 204. Accordingly, the pistons 201b of the solution distributors 201 are moved backward in accordance with the left-hand movement of the supporting block 305 i.e. common base plate 302, so that the ingredient solutions in the solution tanks 204 are fed into the cylinders 201a. Similarly to the operation mentioned above, when the air bubble ejection in the solution distributors 101 has been completed, the second comparator unit 39 sends the signal to the three-way solenoid valve control unit 38 for switching on the three-way solenoid valves 103 associated with the solution distributors 101 having the number of injections n which is equal to or more than 1, thereby opening their valve passages for discharging the solutions into the receivers 105. The second comparator unit 39 operates the driving motor 310 to move the supporting block 305 to the left until the number of pulses produced by the adder 42 reaches the smallest number of pulses among the numbers of pulses corresponding to the remaining solution discharge amount. When the number of pulses produced by the adder 42 reaches the smallest number of pulses mentioned above, the second comparator unit 39 temporarily stops the rotation of the driving motor 310 so as to switch off the three-way solenoid valves 103 associated with the corresponding solution distributors 101 with their valve passages opened to the solution tanks 104. The second comparator unit 39 operates the driving motor 310 again to move the supporting block 305 further to the left. Also in this operation, the three-way solenoid valves 203 associated with the solution distributors 201 are held in off condition, and their valve passages are opened to the solution tanks 204. Accordingly, the pistons 201b of the solution distributors 201 are moved backward in accordance with the left-hand movement of the supporting block 305, so that the ingredient solutions in the solution tanks 204 are sucked into the cylinders 201a. In this way, the controller 30 will repeat the operations mentioned above until the solution distributors 101 attain their target discharge amounts. Also, in this operation, the solution distributors 201 will repeat the operations mentioned above corresponding to the solution distributors 101 so as to perform the automatic solution dispensing operation. Thus, in this embodiment of the automatic solution dispensing apparatus, by providing a plurality of solution distributors 101 and 201 located on either side of the common base plate 302 on the supporting block 305 which is movable right-to-left with the pistons 101b and 201b of the solution distributors 101 and 201 connected to the common base plate 302, dual solution dispensing operations can be performed in the solution distributors 101 and 201 arranged bilaterally. Therefore, even in the case where a number of solution distributors are required, it is not necessary to install many assemblies in which the driving gear of pistons and the solution distributors are combined, and therefore, the automatic solution dispensing apparatus is not made large in size. Moreover, since the movement accuracy of the pistons in the solution distributors are common for a number of solution distributors, the solution dispensing accuracy also becomes common for the respective ingredient solutions. Accordingly, the accuracy of proportional distribution ratio between the respective ingredient solutions can be improved. Moreover, since a stepping motor is utilized as the driving motor, the control of the operation thereof can be performed by controlling the number of pulses of the pulse signal supplied to the driving motor 310, resulting in elimination of a rotary encoder utilized in a conventional apparatus. Therefore, cost reduction may be realized together with a simplification of the apparatus because of the elimination of the signal processing system for a rotary encoder, and faults relating to the rotary encoder can be removed. The automatic solution dispensing apparatus according to the present invention without utilizing a rotary encoder can attain the same solution dispensing accuracy as that in the conventional apparatus. As described above, according to the present invention, by provision of pistons of pairs of solution distributors placed face to face each other which move in opposite directions each other with respect to their respective cylinders by the same movement amount, while the solution distributors on one side perform the solution distribution, the solution distributors on the other hand can perform solution suction. As a result, a number of solution distribution operations can be performed with a single solution dispensing operation without making the automatic solution dispensing apparatus large in size. In addition, since the piston movement amounts of the solution distributors on both sides are the same, an identical accuracy for solution distribution may be effected for every distributor.

Claims: An automatic solution dispensing apparatus comprising: at least one pair of solution distributors (101,201), each of said distributors including a cylinder (101a,201a) and a piston (101b,201b) slidably received in said cylinder so as to be reciprocatable relative to said cylinder, and the distributors of each said pair being disposed opposite one another with the pistons thereof extending from their cylinders in opposite directions, at least one pair of solution tanks (104,204) provided to supply solutions to said solution distributors, at least one pair of solution receivers (105,205) provided to receive solution from said solution distributors, three-way solenoid valves (103,203) operatively interposed between each of said solution distributors and respective ones of the solution tanks and the solution receivers associated therewith, said solenoid valves (103,203) selectively placing the solution distributors (101,201) in communication with any one of the solution tanks (104,204) and the solution receivers (105,205), depending on control signals, for selectively moving said valves between positions at which valve passages of the valves are in open communication with the solution tank (104,204) and with the solution receiver (105,205) associated with the distributor (101,201), respectively, characterized by a common base plate (302) interposed between the distributors of each said pair thereof, a piston coupling mechanism (106,107,206,207) coupling each of said pistons to said common base plate, wherein said coupling mechanism comprises a forked member (50) and a joint member (51) engaging with this forked member a supporting block (305) supporting said common base plate in the apparatus, a shifting screw (304) operatively connected to said supporting block so as to move said supporting block in the apparatus in respective directions causing the piston of each said solution distributor on one side of said common base plate to extend and the piston of each said solution distributor disposed opposite thereto on the other side of said common base plate to concurrently retract, wherein said shifting screw has first pulley means (308) connected thereto for transmitting drive to said shifting screw to rotate said screw, a stepping motor (310) having an output shaft to which second pulley means (309) is connected for transmitting output of the stepping motor, solenoid valve control means (38) for feeding the control signals to said three-way solenoid valves, calculation means (32,37,39,41) for calculating data corresponding to a predetermined target quantity of solution to be discharged into said receivers from each of said distributors, driving motor control means (40) operatively connected to said stepping motor for controlling said stepping motor, and control unit means (36) operatively connected to said solenoid valve control means, to said calculation means and to said driving motor control means, said solenoid valve control means (38) and said driving motor control means (40) being controlled by said control unit means (36) based on the data calculated by said calculation means (32,37,39,41). The apparatus as claimed in claim 1, wherein said calculation means (32,37,39,41) calculates data of a number of pulses by which said stepping motor (310) operates to cause the predetermined target quantity of solutions to be discharged from each of said solution distributors (101,201) by executing the following equation: PQiL = POiL x QiL, and PQiR = POiR x QiR wherein PQiL is the number of pulses by which said stepping motor (310) operates to cause a predetermined quantity of solution to be discharged from a respective one of the solution distributors on one side of said common base plate (302), PQiR is the number of pulses by which said stepping motor (301) operates to cause a predetermined quantity of solution to be discharged from a respective one of the solution distributors (101,201) on the other side of said common base plate (302), POiL is the number of pulses by which said stepping motor (301) operates to cause a unit amount of solution to be discharged from the respective one of the solution distributors on said one side of said common base plate (302), POiR is the number of pulses by which said stepping motor (301) operates to cause a unit amount of solution to be discharged from the respective one of the solution distributors on said other side of said common base plate (302), QiL is the predetermined target quantity of solution to be discharged from the respective one of said solution distributors (101,201) on said one side of said common base plate (302), and QiR is the predetermined target quantity of solution to be discharged from the respective one of said solution distributors (101,201) on said other side of said common base plate (302). The apparatus as claimed in claim 1 or 2, wherein said forked member (50) has a pair of arms (50a,50b) each having a recessed portion (50c) defining a recess therein, and said joint member (51) is received in the recesses defined in the arms of said forked member and detachably connected to said forked member at the recessed portions of the arms thereof. The apparatus as claimed in one of claims 1-3, wherein said first and second pulley means (308,309) are operatively connected by a transmission belt which extends around said first and second pulley means for transmitting the output of said stepping motor (310) from said second pulley means to said first pulley means to rotate said shifting screw (304) and move said supporting block (302).

Inventors: ATSUKI WADA, NOBUAKI AOKI, SATO KOICHI, ATSUKI, WADA, NOBUAKI, AOKI, SATO, KOICHI
Applicants: KURASHIKI BOSEKI KK, KURASHIKI BOSEKI KABUSHIKI KAISHA
Application year: 1990
Main classification: B01F15
IPC codes: G05D11, G03D3, B01F15, D06B23, B05C5