WO2002031358A1

WO2002031358A1 - Dispenser for fluid medium

Info

Publication number: WO2002031358A1
Application number: PCT/FI2001/000894
Authority: WO
Inventors: Anssi Tammi
Original assignee: Cps Color Group Oy
Priority date: 2000-10-13
Filing date: 2001-10-15
Publication date: 2002-04-18
Also published as: FI20002270A0; AU2002210595A1; FI109104B

Abstract

A dispenser for a fluid medium, the dispenser comprising a first medium container (8) and a first servomotor-operated (2) piston pump (3) communicating therewith. According to the invention, it also comprises a second medium container (9), a second servomotor-operated (22) piston pump (23) communicating therewith, a feeding line (19) for connecting the output (13) of the first piston pump (3) to the second medium container (9) and a pump (20) for dispensing diluting agent of the medium to the second medium container (9), the output (39) of the dispenser being connected to the output (13, 33) of either the first or the second piston pump (3, 23).

Description

DISPENSER FOR FLUID MEDIUM

FIELD OF THE INVENTION

[0001] The invention relates to a dispenser for a fluid medium, the dispenser comprising a first medium container and a first servomotor-operated piston pump communicating therewith. Even though the dispensers for a fluid medium can be widely used in various industrial applications, the present invention primarily relates to an apparatus, which allows medium to be dispensed to an industrial process with good accuracy, but still within a wide range, i.e. such that the amount of the medium to be dispensed may vary within a relatively wide range without it having any effect on the dispensing accuracy.

[0002] The invention also relates to a dispenser for a fluid medium for dispensing a substantially steady medium flow, the dispenser comprising a first medium container and a first servomotor-operated piston pump unit com- municating therewith. An object of this steady dispensing is also to provide an apparatus, in which the amount to be dispensed may vary within a very wide range without it having any effect on the dispensing accuracy. One example of an industrial process, which requires a steady substance flow and possibly also a flow whose amount may vary within a wide range, is the manufacturing of plastic products, such as coloured plastic film. In connection with coloured plastic film manufacturing, it is necessary to feed colouring agent into a film extruder so as to give a desired tone to the plastic film. The desired colouring agent or colour paste, or several colour pastes according to the formula of the desired tone, must then be supplied such that their flow rates with respect to time remain as steady as possible, so that no colour variations occur in the film produced.

[0003] Typically, in cases as described above dispensing is performed by means of various pumps, and when a relatively solid paste is concerned, particularly by means of a gear pump. However, the gear pump is by no means optimal for this kind of dispensing. Firstly, the output of the gear pumps changes non-linearly depending on their rotation rate. Thus, output curves must be determined for each gear pump type on the basis of test runs, by means of which output curves it is possible to determine the rotation rate, at which the paste amount desired at any particular time can be fed. Secondly, the gear pumps may leak, which affects the output of the gear pump. In addi- tion, the leakage depends on the service life of the gear pump, i.e. the leakage tends to increase as the gear pump wears. Consequently, if it is desired that the output is exactly right, the gear pump must be calibrated relatively frequently, i.e. it must be found out how its output may have changed at each par- ticular rotation rate. In plastics industry, where production goes on as continuous three-shift work, possibly for several months without a break, there is no possibility, in practice, to arrange calibration sufficiently often.

SUMMARY OF THE INVENTION

[0004] The object of the present invention is to provide a novel type of dispenser for a fluid medium and also a dispenser for dispensing a substantially steady medium flow, whose output can be retained steady and whose controllability is excellent. In particular, the object is to provide a dispenser, whose dispensing amount can be changed within a very wide range without it having any effect on the dispensing accuracy. This is achieved by the dis- penser of the invention, which is characterized by also comprising a second medium container, a second servomotor-operated piston pump communicating therewith, for connecting the output of the first piston pump of a feeding line to the second medium container and a pump for dispensing diluting agent of the medium to the second medium container, the output of the dispenser being connected to the output of either the first or the second piston pump.

[0005] According to the invention, to extend the operating range provided by one piston pump, the apparatus of the invention also employs a second piston pump, which dispenses diluted medium. In order to keep the dilution ratio accurate and the process continuous, the apparatus is arranged such that the diluted medium container is filled by means of a piston pump dispensing undiluted medium. Hence, the amount of medium fed into the diluted medium container is accurately known and a desired amount of diluting agent can be added thereto in order to obtain diluted medium of desired concentration. Because the amount of the diluting agent can be e.g. hundred times greater than the amount of undiluted medium to be mixed therewith, the dispensing accuracy of the diluting agent need not be in the same order as the dispensing accuracy of the medium.

[0006] Advantageously, the first and the second piston pumps are arranged to have a clutch-operated coupling with an axle driven by one and the same servomotor. In this manner the apparatus will be compact and cost- effective.

[0007] As appears from the above, the invention also relates to a dispenser for dispensing a substantially steady medium flow. This dispenser, in turn, is characterized by also comprising a second medium container, a second sen/omotor-operated piston pump unit communicating therewith, for connecting the output of the first piston pump unit of a feeding line to the second medium container and a pump for dispensing diluting agent of the medium to the second medium container, the output of the dispenser being connected to the output of either the first or the second piston pump unit, and each piston pump unit comprising at least one pumping unit consisting of two piston pumps arranged to operate together but mutually in opposite directions, in which pumping unit the piston pumps are connected to an axle driven by the servomotor such that when the servomotor axle turns to a first direction, the first pump sucks and the second one exhausts, and when the axle driven by the servomotor turns to a second direction, the second pump sucks and the first one exhausts, and a control unit for controlling the axle driven by the servomotor to turn at a controlled rate a degree of a controlled torsion angle back and forth. [0008] The present dispenser dispensing a continuous, steady substance flow differs from the above-described dispenser only in the respect that the piston pumps pumping undiluted medium and diluted medium are now replaced by piston pump units, both comprising two piston pumps that are arranged to operate such that one of them always pumps, which results in steady medium flow.

[0009] As appears from the above, the dispenser of the invention comprises containers for both undiluted and diluted medium. Because the dilution ratio of the diluted medium can be adjusted as desired, the amount of the dispensed medium can now be set within considerably wider range than what would be possible by means of only one piston pump pumping undiluted medium. In practice, there may occur situations, where various colouring agents, for instance in connection with plastic film manufacturing, must be dispensed in widely varying amounts, such as tens of grams or tens of kilograms in an hour. When the dilution ratio used is, for instance, one to hundred, the dispensed amount of some tens of grams per hour changes to the dispensed amount of some tens of grams per minute. In this manner it is possible to achieve the same order as in dispensing tens of kilograms per hour.

[0010] In order that the dispenser of the invention can also be used in a practical process, the diluting agent used should be such that it is not harmful to the process itself, i.e. to the process into which the medium is dispensed. For instance, in connection with plastic film manufacturing the diluting agent used can be the plastic film softener that has to be fed into the process in any case. In connection with paint toning, it is naturally possible to use the base paint, into which the colour paste is dispensed, as the diluting agent. When the amount of the diluting agent fed together with the medium is taken into account in the proportioning of other process components, the dilution has no adverse effects on the process as a whole.

LIST OF THE DRAWINGS

[0011] In the following, the dispenser of the invention will be de- scribed in greater detail, with reference to the attached drawing, wherein

Figure 1 is a schematic view of an exemplary embodiment of the dispenser of the invention capable of steady dispensing;

Figure 2 shows one part of the dispenser in Figure 1 in greater detail.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Figure 1 is a schematic view of an exemplary embodiment of a dispenser of the invention, particularly of a dispenser being substantially capable of dispensing a steady medium flow.

[0013] Basically, the dispenser of Figure 1 comprises a medium container 8 for medium to be dispensed. There are two dispensing pipes from the medium container to piston pumps 3 and 4. Valves 15 and 17, respectively, are arranged in these dispensing pipes. The piston pumps 3 and 4 are driven by a common servomotor 2 according to the schematic view of Figure 1 , as will be described in greater detail in connection with Figure 2. Naturally, it would also be possible that both piston pumps have a specific servomotor. If the aim is to provide only separate medium doses, one piston pump, such as pump 3, will suffice. To provide a steady medium flow, it is necessary to have two piston pumps, as presented in Figure 1 and also in Figure 2.

[0014] A valve 16 is arranged in an output line 13 of the piston pump 3, and correspondingly, a valve 18 is placed in an output line 14 of the piston pump 4. The output lines 13 and 14 are connected with a line 19. From the line 19 the medium passes into a line 37, where a valve 38 is placed. If the arrangement of Figure 1 is desired to dispense undiluted medium of the container 8, the valve 38 is open and the valves 15 and 16, and 17 and 18, re- spectively, are controlled such that one of the piston pumps 3 and 4 is all the time in a dispensing phase and feeds medium to be dispensed into the line 37 and thereby through the valve 38. However, if the aim is to dispense diluted medium, the valve 38 is kept close and the pumping unit 1 , consisting of the piston pumps 3 and 4, with the proviso that it is in operation, is controlled to dispense medium via the line 19 into a container 9.

[0015] All the valves as well as the servomotors of the dispenser are controlled by a control unit 6, which, in practice, most preferably comprises a digital processor, and it can be a general-purpose personal computer provided with suitable software. [0016] If the objective is to provide a possibility for continuous dispensing, it is likely advantageous that the container 9 is made to comprise two compartments such that undiluted medium is fed into a compartment 9A thereof from the line 19 and diluting agent is fed by means of a pump 20, such as a gear pump, from a line 41. Because the amount of the diluting agent can be e.g. hundred times greater than the amount of undiluted medium to be mixed therewith, the dispensing accuracy of the diluting agent need not be in the same order as the dispensing accuracy of the medium.

[0017] It should be noted that the line 19 naturally comprises a valve 42, by means of which the line 19 can be closed, when it is desired that undiluted medium is dispensed through the line 37. A valve 43, in turn, is arranged in the line 41 to close the feed of the diluting agent into the container 9. As mentioned above, the undiluted medium and the diluting agent are fed into the compartment 9A of the container 9, where they are mixed. Thereafter, the mixed and diluted medium is let into a compartment 9B of the container, wherefrom it can be dispensed when desired. Dispensing is carried out by a pumping unit 21 which corresponds to the pumping unit 1 and comprises piston pumps 23 and 24 and a servomotor 22 arranged to drive them. In order to enable these two piston pumps 23 and 24 to provide a steady flow in the dispensing line 35, valves 35 and correspondingly 37 are arranged in the input lines of the piston pumps, and valves 36 and 38 are arranged in the output lines 33 and 34 of the piston pumps. The output 35 of the pumping unit 21 , in turn, is connected via the line 35 and the valve 36 to the output of the valve 38, from which output the entire dispenser output, i.e. the line 39 departs. A valve 40 is arranged in this line, too.

[0018] The above-described dispenser thus operates such that undiluted medium can be dispensed by the pumping unit 1 or the product of this pumping unit can be supplied to the container 9, where it is diluted, and in that case the diluted medium pumped by the pumping unit 21 constitutes the output of the dispenser. Depending on the dilution ratio used, it is possible to achieve dispensed amounts that vary within a very wide range. [0019] In the plastic film manufacture, which is given as an example in the above, it may be necessary to feed a colouring agent in amounts of e.g. 30 grams per hour, 10 kilograms per hour or 60 kilograms per hour. It is fully understandable that the same pumping unit does not allow accurate implementation of such extremely large variations, because in the case of the smallest dose it would be necessary to run the servomotor 2 at such a low rate that its operation would by no means be accurate. This is based on the assumption that the piston pumps are rated for a larger dispensed amount. When the dispenser of the invention, which has a specific container for diluted medium, is employed, a considerably more advantageous situation than that above will be achieved.

[0020] If the dilution ratio of the diluted medium in the container 9 is e.g. 1 to 100, in the case of diluted medium 30 grams of actual medium per hour makes 3 kilograms of diluted medium per hour, i.e. 50 grams per minute. If the pumping unit is designed such, for instance, that it most preferably dis- penses the middle amount of the above-mentioned substance amounts, i.e. 10 kilograms per hour, it means dispensing of 166 grams per minute, which does not deviate much from the value calculated above, 50 grams per minute. Thus, it is understandable that the unit, which reliably dispenses an average dose of 166 gram per minute, can also dispense 50 grams per minute very accurately and reliably. Hence, the dispenser of the invention is capable of operating within a very wide range without troubles in dispensing accuracy.

[0021] Figure 2 shows in greater detail the pumping unit 1 of Figure 1. For the sake of simplicity, in the schematic view of Figure 2, the medium container 8 is replaced by two separate medium containers 11 and 12, from which separate dispensing lines are led to the piston pumps 3 and 4, respectively, via the valves 15 and 17. Piston rods of the piston pumps 3 and 4 are formed into a gear rack 7, which is driven in a reciprocating manner by one servomotor 2 through a gearwheel 10. The servomotor 2 is controlled by a control unit 6. The output lines 13 and 14 of the piston pumps comprise valves 16 and 18, respectively. By suitably controlling the valves 15 and 16, and 17 and 18, respectively, a situation is achieved, where one piston pump sucks medium from the medium container and the other piston pump dispenses it to its output. When the dispensing phase of said latter piston pump ends, the servomotor 2 changes its direction, whereby the other piston pump starts dispensing medium into its output line. In this manner a steady medium flow is pro- vided at the outputs 13 and 14 by a combined effect. By suitably designing the piston pumps 3 and 4, it is possible to keep the servomotor 10 rate relatively low, whereby an interruption in dispensing, resulting from the change in direction, is minuscule, and does not appear at all in the combined output flow of the output lines 13 and 14. As stated above, the servomotor rate can be ad- justed by the control unit 6, and the rotation rate of the axle 5 can also be reduced by arranging a reduction gear between the servomotor axle and the axle 5, the reduction ratio being e.g. 1 :70. The reduction gear is not shown in Figure 2.

[0022] It should be noted that the structure of the pumping unit 21 shown in Figure 1 corresponds to that of the pumping unit 1. The only difference is that the medium container may comprise two compartments, if the undiluted medium and the diluting agent need to be mixed separately prior to allowing the diluted medium to pass to be dispensed, i.e. in practice, into the compartment 9b of the container 9, from which the substance is dispensed. [0023] Even though the servomotors 2 and 22 are described above as separate servomotors in connection with Figure 1 , it is possible to think that there is only one servomotor, and when necessary, the pumping units 1 and 21 are connected by means of a separate, controllable clutch to an axle driven by said servomotor. In practice, a procedure of this kind is possible and also eco- nomical, because the power required by the servomotors is relatively low when used as described.

[0024] The control unit 6 set forth in connection with Figure 2 is arranged to control the axle 5 driven by the servomotor 2 such that it turns at a controlled rate a degree of a controlled torsion angle back and forth. Adjusting the torsion angle is primarily based on the design of the piston pumps 3 and 4. Rate adjustment, in turn, is based on the amount of medium that the pumping unit is desired to dispense at any given time.

[0025] As appears from Figure 2, it is advantageous that the piston pumps of the pumping units are positioned opposite each other and their pis- ton rods are combined to form one rod, which the axle driven by the servomotor is arranged to move back and forth. It is also possible that the piston rods of the piston pumps of the pumping units are gear racks or said combined piston rod is a gear rack and the servomotor axle is provided with a gearwheel or gearwheels, which is/are arranged to be operationally connected with said gearwheel(s) so as to make the piston rods of the piston pumps of the pumping unit move simultaneously but in opposite directions.

[0026] One more option is an embodiment, where the piston rods of the piston pumps of the pumping unit are connected by means of a spring band, or a similar, elastic, yet longitudinally incompressible member, to the servomotor-driven axle, around which the member is arranged to wind or from which the member is arranged to unwind depending on the rotating direction of the axle. Corresponding solutions could also be implemented by means of a cogged belt or a cogged chain.

[0027] In the above, the dispenser for fluid medium and also the dispenser for providing a substantially steady medium flow according to the invention have been described by way of example by means of some embodiments and it should be understood that these embodiments can be modified considerably without deviating from the scope and basic idea of the invention defined in the attached claims. The basic idea of the invention is the use of two medium containers, into one of which is produced diluted medium so as to provide a wider range of dosage. Naturally, it should be understood that the dispenser may comprise a plurality of pumping units like those described, if larger dispensing amounts are desired or if several different substances are to be dispensed at the same time.

Claims

1. A dispenser for a fluid medium, the dispenser comprising a first medium container (8) and a first servomotor-operated (2) piston pump (3) communicating therewith, characterized by also comprising a second medium container (9), a second servomotor-operated (22) piston pump (23) communicating therewith, a feeding line (19) for connecting the output (13) of the first piston pump (3) to the second medium container (9) and a pump (20) for dispensing diluting agent of the medium to the second medium container (9), the output (39) of the dispenser being connected to the output (13, 33) of either the first or the second piston pump (3, 23).

2. A dispenser as claimed in claim 1, characterized in that the first and the second piston pumps (3, 23) are arranged to have a clutch- operated coupling with an axle driven by one and the same servomotor.

3. A dispenser as claimed in claim ^ characterized in that both of the first and the second piston pumps (3, 23) have a specific servomotor (2, 22) as a drive motor.

4. A dispenser for a fluid medium for dispensing a substantially steady medium flow, the dispenser comprising a first medium container (8; 11, 12) and a first servomotor-operated (2) piston pump unit (1) communicating therewith, characterized by also comprising a second medium container (9), a second servomotor-operated (22) piston pump unit (21) communicating therewith, a feeding line (19) for connecting the output (13, 14) of the first piston pump unit (1) to the second medium container. (9) and a pump (20) for dispensing diluting agent of the medium to the second medium container (9), the output (39) of the dispenser being connected to the output (37, 35) of either the first or the second piston pump unit (1 , 21) , and each piston pump unit (1, 21) comprising at least one pumping unit consisting of two piston pumps (3, 4, 23, 24) arranged to operate together but mutually in opposite directions, in which pumping unit the piston pumps are connected to an axle (5) driven by the servomotor (2, 22) such that when the axle turns to a first direction, the first pump (3, 23) sucks and the second one (4, 24) exhausts, and when the axle (5) turns to a second direction, the second pump (4, 24) sucks and the first one (3, 23) exhausts, and a control unit (6) for controlling the axle (5) driven by the servomotor to turn at a controlled rate a degree of a controlled torsion angle back and forth.

5. A dispenser as claimed in claim 4, characterized in that the piston pumps (3, 4) of the pumping unit are positioned opposite to one another and their piston rods are combined to form one rod (7), which the servomotor-driven axle is arranged to move back and forth.

6. A dispenser as claimed in claim 4 or 5, characterized in that the piston rods of the piston pumps (3, 4) of the pumping unit are gear racks or said combined piston rod (7) is a gear rack and the servomotor axle (5) is provided with a gearwheel (10) or gearwheels, which is/are arranged to be operationally connected with said gear rack(s) (7) so as to make the piston rods of the piston pumps of the pumping unit move simultaneously but in opposite directions.

7. A dispenser as claimed in claim 4, characterized in that the piston rods of the piston pumps of the pumping unit are connected by means of a spring band, or a similar, elastic, yet longitudinally incompressible member, to the servomotor-d riven axle, around which the member is arranged to wind or from which the member is arranged to unwind depending on the rotating direction of the axle.

8. A dispenser as claimed in any one of claims 4 to 7, character i z e d in that the first and the second piston pump units (1, 21) are ar- ranged to have a clutch-operated coupling with the axle (5) driven by one and the same servomotor (2).

9. A dispenser as claimed in any one of claims 4 to 7, character i z e d in that the first and the second piston pump units (1, 21) have a specific servomotor (2, 22) each as a drive motor.

10. A dispenser as claimed in any one of claims 1 to 9, character i z e d in that the second medium container (9) comprises a first compartment (9a), into which the medium and its diluting agent are fed and where they are mixed, and a second compartment (9b), into which the diluted medium is transferred after mixing and from which second medium container the dispensing is carried out.