Liquid management system

Abstract

A liquid management system for supplying or receiving liquid at a controlled pressure, comprising: a closed reservoir having an inlet for receiving liquid from a first remote location and an outlet for supplying liquid to a second remote location; and a pumped outlet disposed in the reservoir and arranged to remove liquid and gas contained within the reservoir, the pumped outlet being disposed such that the level of liquid in the reservoir can be maintained at a constant height.

Claims

1. A liquid management system for supplying or receiving liquid comprising solid particles in suspension at a controlled pressure, the liquid management system comprising: a reservoir having an inlet for receiving liquid from a first remote location and an outlet for removing liquid from the reservoir, the reservoir having a sloped bottom surface defining, at the lower end thereof, an apex, the inlet or the outlet being located adjacent the apex, wherein the liquid management system is arranged to provide a flow of liquid between the inlet and the outlet such that solid particles that fall out of the liquid flow are directed by the sloped bottom surface back into the liquid flow in the region of the apex to be recaptured into the flow of liquid, thereby causing solid particles suspended in the liquid to remain in or return to suspension in the liquid.

2. A system according to claim 1, wherein the inlet is located adjacent the apex.

3. A system according to claim 2, wherein the inlet is pumped to supply liquid into the reservoir.

4. A system according to claim 1, wherein the reservoir is a closed reservoir.

5. A system according to claim 1, wherein the outlet is a pumped outlet to a second remote location.

6. A system according to claim 5, wherein the pumped outlet is at a fixed height within the reservoir.

7. A system according to claim 1, wherein the outlet is located adjacent the apex.

8. A system according to claim 1, further comprising a re-circulating fluid system connected to the outlet for re-circulating fluid back into the reservoir.

9. A system according to claim 7, further comprising a liquid extraction outlet for supplying liquid to a second remote location.

10. A system according to claim 1, wherein the reservoir includes at least two chambers.

11. A system according to claim 10, wherein one or more of the chambers has a sloped bottom surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various examples will now be described with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic cross-section of one example of a system;

(3) FIG. 2 shows a cross-section view of a further example of a system;

(4) FIG. 3 shows a variation on the arrangement shown in FIG. 1;

(5) FIG. 4 shows a further example of a system having a sloped bottom to the reservoir;

(6) FIG. 4a shows another example of a system having a sloped bottom surface;

(7) FIG. 5 shows a variation on the arrangement of FIG. 4;

(8) FIG. 6 shows an example of a system utilising both a weir and sloped reservoir bottom; and

(9) FIG. 7 shows a further example of a system using a baffle.

DETAILED DESCRIPTION

(10) FIG. 1 shows a liquid reservoir 10 which is supplied with liquid 1 from a remote location (not shown) through an inlet pipe 11. Liquid exits the reservoir via an outlet pipe 12 to a liquid delivery device (not shown). In this example, the liquid delivery device could be a printhead, in which case the liquid is typically an ink, a sprayhead, in which case the liquid could be any suitable sprayable liquid, or any other aerosolising liquid delivery device. The liquid is typically a suspension in which sedimenting or poorly dispersed particles are included, although this is not a requirement.

(11) The reservoir is provided with a further outlet 13. The outlet 13 is a pumped outlet which is disposed at a fixed height within the reservoir. The outlet 13 is connected to a pump (not shown) such that, when the pump is operational, excess liquid and/or air from the reservoir 10 is drawn through the outlet 13 and removed from the reservoir 10. In this way, the outlet 13 ensures that the height of the liquid 1 in the reservoir 10 remains constant, as the height can never be above the outlet 13. Whilst in the preferred example the outlet 13 is at a fixed height, it is conceivable that the height of this outlet could be variable, such that the user can define the height of fluid within the reservoir 10. Such a variation would typically be only carried out prior to use, so as to set the parameters of the system.

(12) The air pressure in the reservoir 10 above the surface of the liquid is also controlled and can be measured by a pressure sensor 14. Alternatively and/or additionally, a liquid pressure sensor could be employed. Air can either be bleed into or out of the reservoir 10 through bleed valve 15, which can be supplied with air at any given pressure or it can be pumped in or out of the reservoir by a pump (not shown). The air pressure above the surface of the liquid can be controlled and set at a desired set point by controlled electronics (not shown) or programmed via a computer (not shown). Although air is described in this example, any other suitable gas could be used.

(13) The reservoir can be configured such that the air pump (not shown) is not required to control the air pressure above the surface of the liquid. In this example, the rate of pumping from the outlet 13 is greater than the rate at which liquid is supplied into the reservoir 10 and therefore both liquid and air will always be pumped out of the reservoir 10. This will reduce the pressure of air in the reservoir 10 and this can then be controlled by bleeding air through the air bleed valve 15 into the reservoir 10 in order to maintain the pressure at the desired set point. The pump connected to the pumped outlet 13 returns the excess liquid back to a main liquid reservoir (not shown) which can then be used to supply liquid to inlet 11.

(14) An alternative example is shown in FIG. 2 in which the vertically aligned outlet 13 from FIG. 1 is replaced by a fixed height outlet located in a side wall of the reservoir 10. The outlet, which may take the form of a tube, may extend into the first reservoir 10 or may simply be an opening in the side wall. In this arrangement, the height of the outlet is fixed and cannot be varied. A further example, of the system of FIG. 1 is shown in FIG. 3, which is identical save for the lower end of the outlet 13. In this example, the lower end of the outlet 13 has been cut away on a diagonal 16, thereby creating a tapered opening. Such a tapered opening reduces pressure fluctuations caused by fluid pinning to the tube opening. In this arrangement, the height of the fluid is defined by the highest portion of the cut away at the end of the outlet tube.

(15) In all three systems shown in FIGS. 1 to 3, the inlet 11 is shown below the surface of the liquid 1. This can be advantageous if it is desired to prevent turbulence that causes pressure fluctuations and bubble formation in a fluid. Alternatively, given the particular use of the invention, with liquids that have heavily sedimenting or poorly dispersed particles therein, it may be advantageous for the inlet to be located above the height of the liquid, such that the flow of liquid into the reservoir promotes mixing of the liquid that keeps the particles suspended. The optimum location for the inlet will be dependent upon the flow rate and subsequent level of turbulence and surface disruption and therefore the amount of pressure control that is required by the system.

(16) A further example is shown in FIG. 4 having a reservoir 30, an inlet 31 and a pumped outlet 32. An outlet to the remote location, such as a printhead or sprayhead, is not shown, but is contemplated. Further inlets may also be provided. The pumped outlet 32 is shown in a similar manner to that of FIG. 1, but it can, alternatively, take the configuration shown in either FIG. 2 or FIG. 3. Again, an air pressure sensor 33 and proportional bleed valve 34 are provided for the same purposes as described in relation to FIG. 1.

(17) In this example, the lower surface 36 of the reservoir is sloped to define an apex 35 at which the inlet 31 is located. The sloped surface of the reservoir may take the form of a cone or pyramid, but may also take the form shown in FIG. 4a in which the lower surface 36 is either a simple slope, i.e. planar surface which is angled relative to the horizontal, or alternatively a v-section channel which directs any sedimenting or poorly dispersed particles to an apex. The reservoir is typically circular or square in cross section, although other cross sections are possible.

(18) By virtue of the arrangement shown any sediment that does fall out of suspension drops towards the inlet 31 under gravity, at which point the sediment can be captured and re-suspended by the inlet flow, ensuring that the liquid composition remains constant in the bulk of the reservoir.

(19) An alternative configuration is shown in FIG. 5 in which the reservoir 40 is open and, whilst a sloped bottom 36 is provided in accordance with any of the variations discussed above, the apex 35 is provided with an inlet 41 which connects to a pump 42 and a re-circulating fluid system 43. A liquid supply line 44 is provided to supply liquid into the reservoir from a remote location. This may be above the level of the liquid as shown, or may be below as in other examples disclosed herein. The reservoir is provided with a liquid outlet 45 through which liquid is supplied to a remote location.

(20) The arrangement shown in FIG. 5 helps to keep the particles in suspension by capturing and re-circulating any particles that sediment at the bottom and by creating further agitation in the main tank at the point of return of the flow into the reservoir. Also, the liquid supplied through supply line 44 causes the bulk fluid in the reservoir to become agitated.

(21) The provision of one or more sloped bottoms to a reservoir can be applied, as shown in FIG. 6, to an arrangement similar to that disclosed in EP 2076395. In this case, one or each chamber of the reservoir 60, separated by weir 63 can be provided with a sloped bottom 67 having any of the forms described above. The system has a first chamber 61 and a second chamber 62 and the first chamber 61 is provided with an inlet 64 located at the apex of the bottom of the first chamber and an outlet 65. The second chamber 62 is provided with a pumped outlet 66 at the apex of the sloped bottom of the second chamber 62. Bleed valve 68 and pressure sensor 69 are provided as in the other examples

(22) A further example is shown in FIG. 7 which is, for the purposes of the description, the same system as that shown in FIG. 1. The only difference is the provision of a baffle 70 in the reservoir 10. However, the use of one or more baffles could be employed in any of the configurations described above. One or more baffles may be provided and they may be provided in any suitable configuration. The purpose of the baffles is to prevent any liquid that may form splashes from impacting on the pressure sensors and proportional valves placed in the reservoir as part of the pressure control apparatus, to break up the flow and to divert it such that any turbulence has minimal effect on the surface of the liquid and therefore the depth of the liquid from the reservoir, and also to smoothly separate the relatively high velocity liquid emerging from the liquid supply to the reservoir. One or more of these advantages may be achieved depending upon the particular configuration of the system and the location or locations of the or each baffle.

(23) As can be seen in FIG. 7, the baffle is provided with sloped surfaces 71 which assist disrupting the flow through inlet 72 such that turbulence is created. Further, it discourages any sediment from accumulating on the top surfaces. The location of the or each baffle is important so as to ensure that static regions of the flow are not created, for example, eddys or other regions of low flow, which might mean that heavier particles could start to fall out of suspension, thereby affecting the composition of the liquid supplied from the reservoir.

(24) Further features may be applicable to any or all of the examples described. These include: A filter placed in line with the re-circulating fluid of either the main reservoir in the supply or return line so as to continuously remove any unwanted particles from the liquid. The pump selection is very important. The pumped overflow design only works with pumps that can pump gas and liquid simultaneously, such as positive displacement pumps, but many of these are very pulsatile, such as diaphragm pumps or peristaltic pumps. Many pumps exhibit relatively low pulsatility cannot handle sedimenting fluids very easily, such as gear pumps. Therefore, in order to pump sedimenting fluids, it may be necessary to select a pulsatile pump and create fluidic damping in a system to aid the active feedback pressure compensation that is present. This can include the use of dampers designed specifically for the pump by the manufacturer, or other well known passive dampening techniques such as increasing the volume of air above the fluid in the reservoirs. It is typically advantageous to use a pinch valve with sedimenting liquids, as this minimises the chance of the particulates interfering with or damaging the operation of a valve. Reversing the pump supplying fluid into the main reservoir may allow the system to be drain efficiently allowing the majority of liquid to be recovered to the main reservoir.