DEVICE AND METHOD FOR PRODUCING A READY-TO-USE SOLUTION FROM A CONCENTRATE

Abstract

A device and related method for producing a ready-to-use solution from a concentrate and a diluent includes an inlet for the diluent; an inlet for the concentrate; an outlet for the solution; a line extending from the inlet for the diluent via a confluence where diluent and concentrate meet, to the outlet; a mixing container arranged in the line between the confluence and the outlet and having a larger cross-section than parts of the line, which are arranged upstream and downstream of the mixing container; and a metering pump for the concentrate, which is connected on the suction side to the inlet for the concentrate and on the pressure side to the confluence and which operates in a pulsed manner. The metering pump works with a clock frequency, in which a plurality of pump surges are attributable to the dwell time of the liquid in the mixing container.

Claims

1. A device for producing a ready-to-use solution from a concentrate and a diluent, comprising an inlet for the diluent, an inlet for the concentrate, an outlet for the solution, a line which extends from the inlet for the diluent to the outlet via a confluence, at which the diluent and the concentrate converge, a mixing container which is disposed in the line between the confluence and the outlet and which has a larger cross section than parts of the line which are located upstream and downstream of the mixing container, and a metering pump for the concentrate, which is connected on the suction side to the inlet for the concentrate and on the pressure side to the confluence, which operates in pulsed mode and which is designed to operate at a clock frequency, in which a plurality of pump surges are attributable to the dwell time of the liquid in the mixing container, wherein the interior space of the mixing container has a longitudinal dimension in the direction of flow and a transverse dimension in a direction at right angles relative to the direction of flow and the ratio of the maximum longitudinal dimension of the mixing container to the maximum transverse dimension of the mixing container is in a range of 1 to 4.

2. The device of claim 1, wherein the line is designed so as to be pressure-proof.

3. The device of claim 1, wherein at a recommended nominal pressure at the inlet for the diluent, the throughput through the line per minute is a multiple of the volume of the mixing container.

4. The device of claim 3, wherein the throughput through the line per minute is in a range between 10 and 20 times the volume of the mixing container.

5. The device of claim 1, wherein the clock frequency of the metering pump is in a range of 1 Hz to 10 Hz.

6. The device of claim 1, wherein the inlet for the diluent is designed in such a manner that in a section between the inlet for the diluent and the confluence, a defined throughput D through the line is ensured, that clock frequency f is assigned to the metering pump, and wherein the volume V of the mixing container is $V=\frac{k.Math.D}{f}$ where the parameter k is in a range of 1 to 15.

7. The device of claim 6, wherein the parameter k is in a range of 4 to 8.

8. The device of claim 1, wherein mixing container has a cylindrical shape and wherein in the upstream direction, the mixing container has an inlet opening in one end surface, and in the downstream direction, the mixing container has an outlet opening in the other end surface, with the inlet opening and the outlet opening, relative to an axis of the cylindrical mixing container being offset with respect to one another.

9. The device of claim 8, wherein the ratio of the surface area of the inlet opening to the mean cross-sectional area of the mixing container is in a range of 1/30 to 1/200.

10. The device of claim 1, wherein a shut-off valve is disposed between the inlet for the diluent and the confluence.

11. The device of claim 1, wherein the inlet for the diluent is connected to a water supply system.

12. The device of claim 1, wherein a storage tank for the concentrate is replaceably connected to the inlet for the concentrate.

13. The device of claim 1, wherein a foam generator is disposed downstream of the mixing container.

14. A vehicle wash facility, comprising the device of claim 1.

15. A method for producing a ready-to-use solution from a concentrate and a diluent, in which the diluent is fed into a line, at a confluence of the line, the concentrate is metered in by a metering pump in pulsed mode at a defined clock frequency, and the liquid mixture of the diluent and the concentrate is fed to a mixing container which is disposed in the line between the confluence and an outlet for the solution and which has a larger cross section than parts of the line located upstream and downstream of the mixing container, wherein the volume V of the mixing container is $V=\frac{k.Math.D}{f}$ where D stands for the throughput through the line in a section from the inlet for the diluent and the confluence, f stands for the clock frequency of the metering pump, and the parameter k is in a range of 1 to 15 and the interior space of the mixing container has a longitudinal dimension in the direction of flow and a transverse dimension in a direction at right angles relative to the direction of flow and ratio of the maximum dimension of the mixing container to the maximum transverse dimension of the mixing container is in a range of 1 to 4.

16. The method of claim 15, wherein the parameter k is in a range of 4 to 8.

Description

[0041] Additional characteristics and advantages of the invention follow from the description of embodiment examples below with reference to the appended drawings. The drawings show:

[0042] FIG. 1 a diagrammatic representation of a diluting device according to the present invention;

[0043] FIG. 2 a section through an entrance portion of the mixing container;

[0044] FIG. 3 a section through a confluence of water and concentrate; and

[0045] FIG. 4 a line section between the confluence and a mixing container.

[0046] FIG. 1 shows a diagrammatic representation of a diluting device 1 in a vehicle wash facility. The diluting device 1 serves to dilute a detergent concentrate from a storage tank 2 with water so as to be able to foam the resulting diluted detergent solution in a foam generator 4 downstream of the diluting device 1 and to apply it to a vehicle that is to be washed.

[0047] A water inlet 5 of the diluting device 1 is connected via a shut-off valve 6 to a water tank 7. The water tank 7 can be an overhead tank of a public water supply system which maintains a constant water pressure of typically approximately 4 bar at the shut-off valve 6. However, the tank can also be a pressurized tank of a water treatment system of the vehicle wash facility. If the water tank 7 itself is unpressurized, a pump 8 can be disposed between said tank and the water inlet 5 so as to provide the positive pressure required to operate the diluting device 1 and the foam generator 4.

[0048] A line 9 of the diluting device 1 branching off the water inlet 5 sequentially comprises a first pipe section 10, a confluence 11, a second pipe section 12, a mixing container 13 and a third pipe section 14, which latter at the same time forms an outlet 15 to the foam generator 4. All of the pipe sections 10, 12, 14 can have the same cross section; the cross section of the mixing container 13 is multiple times larger than that of the pipe sections 10, 12. 14. A metering pump 16 is disposed between an inlet 3 for the concentrate, here, e.g., a hose immersed in the storage tank 2, and a branch line 17 which leads to the confluence 11. The metering pump 16 can be a piston pump which, although not pumping continuously, delivers a precisely defined amount of concentrate with each stroke of its piston. In this embodiment example, the clock frequency of the metering pump 16 is 1 Hz. However, in other embodiment examples, the clock frequency of the metering pump 16 can be in a range of 1 Hz to 10 Hz or a multiple of 10 Hz.

[0049] When the shut-off valve 6 is open and the metering pump 16 is operating, the water and the concentrate are mixed as they pass from the confluence 11 to the outlet 15, as will be explained in greater detail below. In a chamber 18 filled with granules or a porous, e.g., fibrous, material of the foam generator 4, the solution obtained is initially combined with a stream of compressed air 19. The foam being generated during passage through the granules is transported from the chamber 18 into a distributor pipe, 20 which extends at right angles across the vehicle (not shown in the figure) and flows out of nozzles 21 of the distributor pipe 20 over the vehicle.

[0050] As the solution enters the foam generator 4, its pressure must be at least as high as the pressure of the stream of compressed air 19. To maintain this pressure level, the line 9 is pressure-proof over its entire length. Along the line 9, the pressure decreases continuously from the water inlet 5 to the outlet 15, with the result that the metering pump 16 must work against the water pressure prevailing at the confluence 11.

[0051] This leads to transient phenomena, in particular when the diluting device is first placed in operation. While the water pressure on the upstream side of the shut-off valve 6 almost instantaneously spreads into the line 9 and water begins to flow through the line 9 as soon as this valve opens, the metering pump 16 must first accelerate against this pressure in order to reach a delivery rate sufficiently high to deliver the concentrate. This means that as long as the metering pump 16 has not yet reached its desired delivery rate, not enough concentrate is delivered to ensure that the solution has the desired concentration. However, as this extremely thin solution flows at a high velocity into the mixing container 13, it is mixed with solution which is left over from a previous application and which has the correct concentration, so that the deviation from the desired value of the concentration of the solution leaving the mixing container 13 is considerably smaller than that of the solution flowing into the container.

[0052] The volume of the mixing container 13 is correlated with the flow rate of the water, which ensues when a nominal operating pressure is applied to the water inlet 5. If the diluting device is supplied with tap water, this nominal pressure should be the usual line pressure of approximately 4 bar, at which water is supplied by the public water supply system. The volume of the mixing container 13 measures 5-12%, in particular 5-10%, of the amount of water that flows under nominal pressure per minute through the line 2. In other words, if mixing were not to take place, the water in the mixing container 13 would be completely replaced within a period of 3-6 s. The time that the metering pump 16 needs to reach the stationary delivery rate should be no longer than the time it takes to completely replace the water.

[0053] In the current embodiment example, the mixing container has a circular cylindrical shape. It is 30 cm long, its diameter measures 11.4 cm, and on the upstream end surface, the mixing container has an inlet opening with a diameter of 15 mm. Thus, the ratio of the length of the mixing container 13 to its maximum dimension in the transverse direction, i.e., in a direction at right angles relative to the axis of the cylindrical mixing container 13, is 2.6. In other embodiment examples, this ratio is in a range of 0.5 to 5.

[0054] On the downstream side, the end surface of the mixing container 13 has an outlet opening with the same diameter. However, the inlet opening and the outlet opening are not disposed centro-symmetrically with respect to the axis of the cylindrical mixing container 13, but at a distance from the axis and offset with respect to one another. In the current embodiment example, the inlet opening relative to the axis of the mixing container 13 is disposed opposite to the outlet opening. During operation of the device and during implementation of the method, the throughput, i.e., the volume of the water flow, in the line 9 measures 30 L/min at the confluence 11. Thus, the volume of the mixing container 13 is

[00003]$V=\frac{k.Math.D}{f},$

[0055] wherein V stands for the volume of the mixing container 13, D stands for the throughput through the line 9 between the inlet 5 for the diluent and the confluence 11, in particular directly upstream of the confluence 11, and f stands for the clock frequency of the metering pump 16. The parameter k specifies how many pump surges are mixed into the mixing container 13. The parameter k is in a range from 1 to 15, in particular in a range from 4 to 8. In the current embodiment example, the value of the parameter k at a clock frequency of 1 Hz upstream of the metering pump equals 6, so that the mixing container 13 holds the equivalent of six pump surges as the concentrate is being metered in.

[0056] To ensure turbulent mixing of the inflowing and the already present solution in the mixing container 13, it may suffice if the cross section of line 9 abruptly changes in the transition from the pipe section 12 to the mixing container 13. Measures to increase the mixing efficiency include, inter alia:

[0057] a pipe connector 22, which, at the entrance to the mixing container 13 in extension of the pipe section 12, projects beyond a face wall 24 of the mixing container 13 into the inside of said container,

[0058] a nozzle 25, which, at the end of the pipe section 12, narrows the cross section of said pipe section and thereby forces the solution to accelerate as it enters the mixing container,

[0059] a jet pump 26, through which the entering solution flows and which at the same time takes in solution already present in the mixing container 13,

[0060] a baffle plate 27 disposed at the entrance 23 to the mixing container so as to disperse the flow of the entering solution and/or

[0061] an agitator vane 28 in the mixing container 13, here in the form a rotary-driven vane wheel 29.

[0062] Even after the metering pump 16 has reached its stationary delivery rate, homogeneous mixing of the concentrate with water may be prevented if the viscosity of the concentrate is high. As shown in a section in FIG. 3, to compensate for this problem, at the confluence 11, the branch line can empty via a nozzle 30 into the line 9, the flow direction of which is oriented opposite to the flow direction of the water. Here again, the large difference between the velocity of the water and the velocity of the concentrate jet 31 exiting the nozzle 30 causes turbulence, thereby ensuring that the concentrate is dispersed across a large portion of the cross section of the pipe section 12 and is highly diluted even before it reaches the mixing container.

[0063] Another method of promoting mixing of concentrate and water already in the pipe section 12 can be implemented in a portion of the pipe section 12 by means of a swirl generator 33, as shown in FIG. 4, here in the form of blades 35 that cause the liquid jet to rotate about the longitudinal axis 32 of the pipe section 12 and that are oriented at an oblique angle relative to the longitudinal axis 32 and project from an outside wall 34 of the pipe section 12 toward the longitudinal axis 32. In addition, a turbine wheel (not shown), with blades oriented in a direction opposite to that of the blades 35, can be disposed downstream of the swirl generator 33, and set into rotary motion by the liquid jet in the pipe section 12, which in turn drives the vane wheel 29.

LIST OF REFERENCE NUMBERS

[0064] 1 Diluting device [0065] 2 Storage tank [0066] 3 Inlet for the concentrate [0067] 4 Foam generator [0068] 5 Inlet for water [0069] 6 Shut-off valve [0070] 7 Water tank [0071] 8 Pump [0072] 9 Line [0073] 10 Pipe section [0074] 11 Confluence [0075] 12 Pipe section [0076] 13 Mixing container [0077] 14 Pipe section [0078] 15 Outlet [0079] 16 Metering pump [0080] 17 Branch line [0081] 18 Chamber [0082] 19 Stream of compressed air [0083] 20 Distributor pipe [0084] 21 Nozzle [0085] 22 Pipe connector [0086] 23 Entrance [0087] 24 Face wall [0088] 25 Nozzle [0089] 26 Jet pump [0090] 27 Baffle plate [0091] 28 Agitator vane [0092] 29 Vane wheel [0093] 30 Nozzle [0094] 31 Jet of concentrate [0095] 32 Longitudinal axis [0096] 33 Swirl generator [0097] 34 Outside wall [0098] 35 Blade