liquid filter

Abstract

A liquid filter, for example for a condensate reservoir 1, is formed from a printed circuit board 8 with a plurality of holes 9 forming a filter screen with the plurality of holes 9 passing through the printed circuit board. A first set of capacitive elements 16, 17 are formed on the printed circuit board 8 to form a first capacitive sensor 12 capable of measuring the depth of liquid adjacent to the filter. The capacitive elements 16, 17 may be shielded on one side to measure the depth on one side of the filter. A second set of capacitive elements 16', 17' may be provided to measure the depth of liquid on the opposite side of the filter.

Description

Technical Field

[0001] The present invention relates to a filter. This filter is specifically designed to be used together with a condensate tray assembly for use below a condensate generator. However, this filter can be used in any situation where a liquid is filtered and measurement of the liquid level near the filter is required.

Background Art

[0002] Such a condensate generator can be, for example, a type of refrigeration unit found in a supermarket or the like, or a boiler or an air conditioning unit.

[0003] In a refrigeration unit, usually, the tray is placed below the generator to receive any condensate generated by the generator. It is necessary to empty the tray regularly to prevent overflow. Usually, this is done by having a high-level sensor that senses when the depth reaches a predetermined level. At this time, the pump is driven to empty the tray until the level drops to a second level determined by a low-level sensor. This has the problem that due to the influence of surface tension and contamination of the sensor, the low-level sensor cannot reliably detect the level of the liquid very close to the bottom of the tray. Furthermore, the tray being in a wide and shallow configuration means that a moderate amount of liquid remains in the tray when it reaches the low level. This can be addressed by continuing to operate the pump for a short time after the low-level sensor is reached. However, for example, when the pipe starts to clog, it is difficult to reliably estimate how much time is required because the pumping flow rate of the pump is not constant over time. Furthermore, continuing to operate the pump after the tray is empty causes unpleasant noise.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, in practice, a considerable amount of liquid remains in the tray and pump when the pump operation ends. This is a sanitary hazard because microorganisms will eventually grow in the tray and pump. The present invention aims to provide a filter that can help address this problem and can also be used in other applications. [Means for solving the problem]

[0005] According to the present invention, the filter described in claim 1 is provided.

[0006] Such a device provides an integrated component capable of filtering a liquid and determining its depth. A PCB is an inexpensive and simple way to achieve these dual purposes. A capacitive sensor can be easily incorporated into the PCB, as this simply involves forming several conductive tracks on the PCB. The capacitive sensor can provide accurate measurements and information about the rate of depth change because its capacitance changes continuously as the liquid level decreases.

[0007] A capacitive sensor may be configured to measure the average depth of the liquid on both sides of the filter. If the filter becomes clogged, the level may be higher on one side of the filter and lower on the other, and the sensor may only be able to display a measurement that shows the midpoint of the depth. Therefore, it is preferable that the capacitive element be shielded on one side so that it measures the depth on only one side of the filter. For example, the sensor may be configured to measure the liquid depth on the downstream side of the filter so that it can prevent the pump from running if the filter becomes clogged and the downstream side of the filter is completely drained.

[0008] The filter preferably comprises a second set of capacitive elements formed on a printed circuit board, the second set of capacitive elements preferably forming a second capacitive sensor capable of measuring the depth of liquid adjacent to the filter on the side opposite to that measured by the first set of capacitive elements. This is preferably achieved by shielding the second set of capacitive elements with a shield on the opposite side of the capacitive elements compared to the shield of the first set of capacitive elements.

[0009] Therefore, a filter that changes the liquid depth on both sides of the filter can be provided in a very simple way, requiring only a few additional tracks to be printed on the printed circuit board.

[0010] Such a device can sense the rate of change in liquid level on both sides of the filter element. This not only makes it possible to determine the percentage of the tray that is empty, but also to determine information about the condition of a potentially clogged filter by comparing the rate of change in depth on both sides of the filter, thereby providing the controller with additional diagnostic information.

[0011] The printed circuit board preferably has rows of holes that decrease in size towards the bottom of the printed circuit board. This removes particles that gradually become smaller towards the bottom of the tray. The circuit board may be copper-plated near the holes. This gives the filter antibacterial properties and can be easily formed during the construction of the printed circuit board.

[0012] The sensor can be used in the aforementioned condensate tray. Because the sensor can determine the rate of change in liquid depth, it is possible to determine much more accurately how much longer the pump needs to run to empty the tray. Therefore, as the pump's efficiency decreases, the rate of change decreases accordingly, and this can be taken into account in the calculation. Furthermore, when paired with a self-priming pump, there is no need to leave water in the pump at the end of its operation.

[0013] Such a device can sense the rate of change in liquid level on both sides of the filter element. This not only makes it possible to determine the percentage of the tray that is empty, but also to determine information about the condition of a potentially clogged filter by comparing the rate of change in depth on both sides of the filter, thereby providing the controller with additional diagnostic information.

[0014] An example of a filter according to the present invention will be described below with reference to the attached drawings. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic plan view of a tray assembly with a filter incorporated into it. [Figure 2] This is a perspective view of the tray assembly. [Figure 2A] This figure shows the details of the filter in circle A of Figure 2. [Figure 3] This is a cross-sectional view of the tray during use. [Figure 3A] This figure shows the details of circle A in Figure 3. [Figure 4] This is a cross-sectional view of the filter in the horizontal plane along the line IV-IV in Figure 2. [Figure 5] This is a perspective view of the refrigeration unit. [Figure 6] This is a plan view of the refrigeration unit. [Figure 6A] This is a cross-sectional view through line AA in Figure 6, showing the second tray assembly. [Figure 6B] This figure shows the details of circle B in Figure 6A. [Figure 7] This is a perspective view of the tray of the second tray assembly, which is equipped with various accessories. [Figure 8] This is a front view of the air conditioning unit. [Figure 8A] This is a cross-sectional view through line AA in Figure 8, showing the third tray assembly. [Figure 8B]A diagram showing details of the circle B in FIG. 8A. [Figure 9] A plan view showing a part of the tray and a connection part of the third tray assembly. [Figure 10] A partial perspective view showing the tray of the third tray assembly and a part of the air conditioning unit. [Figure 11] A perspective view of the second filter in different types of reservoirs. [Figure 12] A plan view of FIG. 11. [Figure 13] A front view of the second filter. [Figure 14] A perspective view of the second air conditioning unit equipped with a reservoir. [Figure 14A] A diagram showing details of the circle A in FIG. 1P.

Mode for Carrying Out the Invention

[0016] The assembly shown in FIG. 1 includes a tray 1 having a wide and shallow configuration, and the floor surface of the tray 1 is inclined into one corner. Actually, the tray is covered with a lid, which is not shown, so the internal arrangement of the tray can be seen. A discharge pipe 3 is provided at this corner. There is an inlet 3A at the diagonally opposite corner, through which condensed water enters the tray. The lowermost end 4 of the discharge pipe 3 is arranged as close as possible to the deepest part of the floor surface 2, but still sufficiently separated from the floor surface 2 to allow liquid to enter through the lowermost end 4. The discharge pipe 3 is connected to the pump 5 shown in FIG. 1.

[0017] This pump 5 is a self-priming pump, for example, a reciprocating or rotary diaphragm pump or a peristaltic pump.

[0018] As shown in the figure, the filter assembly 6 is mounted across one corner of the tray 1. It is held in place by a pair of lugs 7 molded together with the tray 1. The body of the filter assembly 6 is provided by a printed circuit board 8 (PCB) that fits within the tray such that the edges of the seal form a substantially liquid-tight seal with the tray. Although there may be some leakage around the edges of the printed circuit board, the majority of the fluid passes through a row of holes 9 in the PCB 8, which form the main flow path from the main part 10 of the tray to the discharge part 11 on the opposite side of the tray.

[0019] As shown in Figure 2A, the size of the openings in PCB8 increases with increasing depth in the tray, allowing the flow rate through the filter to increase at a disproportionately high rate as the depth increases. During periods of relatively low flow rates, PCB8 can filter relatively small particles, but as the flow rate increases, larger particles can pass through. The size of the maximum hole 9 is determined so that particles that can pass through do not pass through the pump.

[0020] The first capacitive sensor 12 and the second capacitive sensor 13 are incorporated into the printed circuit board. Referring to Figure 2, these capacitive sensors are located directly beneath the control electronic circuit enclosure 14, which houses the sensor control circuits. Power lines 15 run from this enclosure 14.

[0021] The first capacitive sensor 12 extends downward from the enclosure 14. As shown in Figure 4, the first capacitive sensor 12 has a ground electrode 16 and a sensing electrode 17, which are formed in the PCB in the form of a layer of conductive material such as copper, extending vertically downward from the enclosure 14. A first shield 18 in the form of a further conductive layer is positioned between the two electrodes. As shown in Figure 4, a second shield 19 is formed as a layer of conductive material positioned behind the electrodes 16, 17 and the first shield 18. By shielding, the capacitance between electrodes 16, 17 changes based on the capacitance of the medium on the right side of the PCB 8 in Figure 4. The shields 18, 19 hinder or reduce the sensitivity of the electrodes to capacitance through the PCB material or the medium on the opposite side of the PCB. In this way, the first capacitive sensor measures the depth of the medium on the right side of the PCB 8, as shown in Figure 4.

[0022] The second capacitive electrode 13 shown in Figure 4 is effectively a mirror image of the first capacitive sensor 12 described above, and the same parts are each given the same reference numerals 16' to 19'.

[0023] Therefore, the second capacitive sensor 13 senses the depth of the material on the left side of the PCB 8 shown in Figure 4.

[0024] Referring to Figure 3, this shows the high liquid depth in the main section 10 and the low liquid depth in the discharge section 11 as shown in Figure 3. This can occur near the end of the pump cycle when the filter becomes clogged to some extent, such that the liquid passing through the PCB 8 flows at a lower flow rate than the liquid being discharged from the discharge section 11. In this situation, the sensor described in relation to Figure 4 has the main section 10 on the left side of the PCB 8 and the discharge section 11 on the opposite side. In the case of the first sensor 122, for most of the depth, electrodes 16 and 17 measure the capacitance between the electrodes through water. The second capacitive sensor 13, on the other hand, measures the capacitance between electrodes 16' and 17' mainly through air. Between these, at intermediate levels, the capacitance changes in a continuous ratio between these two values ​​depending on how far each electrode is submerged in water.

[0025] These electrodes allow the control electronics to determine the rate of change in depth, so that they can recognize how quickly the liquid level is changing on both sides of the PCB. In this way, the pump 5 can continue operating until almost all of the liquid has been discharged from the discharge section 11. As seen in Figure 3, the lower end of the pipe 4 is below the lower edge of the PCB 8. However, by estimating the discharge rate, the pumping of liquid can continue even if the liquid level drops below the level of the printed circuit board 8.

[0026] This allows the liquid level in the tray to be kept very low. Since the pump is self-priming, there is little to no residual liquid left in the tray.

[0027] Furthermore, by recognizing the rate of change in the liquid on both sides of PCB 8, the control electronic circuit can determine not only how quickly the discharge section 11 is being emptied, but also how efficiently the filter is functioning when there is a difference in the rate of change in the level on both sides.

[0028] Figures 5 to 7 show a refrigeration unit incorporating a filter assembly similar to the one described above.

[0029] The refrigerated unit 20 shown in Figures 5, 6, and 6A is a type of unit found in supermarkets. It comprises a base 21 with several shelves 22 and an upper part 23.

[0030] A collection plate 24, best shown in Figure 6B, is incorporated within the upper portion of the base 21. This plate has a substantially flat configuration extending across the base 21 and has a gradually sloping lower wall 25, which slopes toward the central opening of the outlet duct 26. This duct 26 leads to the inlet duct 3A of the condensate tray 1. The tray 1 is, with respect to most materials, the same as the tray described in relation to Figures 1 to 4, and therefore the same reference figures are used. Only the differences are described below.

[0031] Tray 1 has a channel 27 in its lower wall to facilitate the flow of condensed water toward the outlet. As shown in Figure 7, tray 1 protrudes from a plate 28 that forms part of the base 21 of the refrigeration unit 20. Tray 1 can be pushed back from the extended position shown in Figure 7, further below the plate 28, until the inlet 3A abuts against the surrounding housing.

[0032] As shown in Figure 7, the control electronic circuit enclosure 14 is divided into two parts 14A and 14B. Part 14A includes the necessary connections for the two capacitive sensors 12 and 13 mentioned above. Part 14B includes the necessary external connections, such as the power lead wire 29. Figure 7 also shows a second power lead wire 30 for the pump.

[0033] During use, condensed water from the refrigeration unit 20 flows into the collection plate 24 under gravity, enters the tray 1 along the outlet duct 26, and is discharged from the inlet as described above in relation to the first example. Level sensing is as described above.

[0034] Figures 8 to 10 show an example of a condensate tray assembly incorporating a filter. Here, the tray assembly is located beneath an air conditioning unit 40, rather than a refrigeration unit. The air conditioning unit 40 is a conventional wall-mounted unit with an outlet duct 41 through which condensate is discharged. As shown in Figures 8A and 8B, beneath a fan coil 42, the outlet duct 41 is connected to a condensate tray 43 via an outlet orifice 44. Inside the tray 43 is a filter assembly 45, which is essentially formed in the same way as the filter assembly 6 described above. In particular, the filter assembly 45 consists of a PCB with several holes 46, the same capacitive sensor 47, and a control electronic circuit enclosure 48.

[0035] As mentioned above, the capacitive sensor can determine the rate of change in depth within tray 43, and the pump can be operated accordingly. This brings about the advantages mentioned in relation to the first two examples.

[0036] A second example of the filter is shown in Figures 11-13. In this case, instead of a tray, there is a reservoir 50, which may be in some fluid line where depth measurement is required.

[0037] In this case, the reservoir 50 has an inlet 51 on one side and an outlet 52 on the opposite side. The PCB 8' is positioned diagonally across the reservoir to maximize the surface area of ​​the filter. However, the PCB 8' may be oriented in other ways. The PCB 8' has multiple holes 9' that provide the filter screen. In this case, all the openings are the same size (however, as mentioned above, they may be different sizes).

[0038] Figure 13 shows the PCB with layers removed so as to show the plane passing through one side of each of the sensors 12' and 13'. The first sensor 12' is designed to sense the liquid level on the side that PCB 8' in Figure 13 is facing. Thus, a shield (not visible in Figure 13) is present behind the three electrodes, as shown in Figure 4. The second capacitive sensor 13' senses the liquid level on the opposite side and has three electrodes (not visible in Figure 13) behind the shield. In this example, the control electronics enclosure 14' is in the center of PCB 8, and accordingly the power lines 15' are connected as shown in Figures 11 and 12. Otherwise, the filters and sensors function as described above in relation to the first example.

[0039] Figures 14 and 14A show an air conditioning unit 60 similar to the air conditioning unit 40 shown in Figure 10. The air conditioning unit 60 in Figure 14 has a reservoir 50 similar to the reservoirs in Figures 11-13, attached to the condensate outlet 61 from the air conditioning unit 60, rather than having a condensate tray 43 below the unit. The reservoir 50 is effectively the same as those described in Figures 11-13, except that the power lines 15" and outlet 52' are oriented from the top of the reservoir. A pump (not shown) is provided above the outlet 52 to pump the condensate out of the reservoir 50 when the level is sufficiently high. This example does not require modification of the air conditioning unit itself and can therefore be provided as an add-on component to conventional air conditioning units of the type shown in Figures 8-10.

Claims

1. A liquid filter formed from a printed circuit board having a plurality of holes, wherein the plurality of holes form a filter screen through the printed circuit board, A liquid filter comprising a first set of capacitive elements formed on the printed circuit board, which form a first capacitive sensor capable of measuring the depth of liquid adjacent to the filter when the filter is immersed in the liquid in a direction substantially perpendicular to the direction in which the liquid passes through the filter screen.

2. The filter according to claim 1, wherein the capacitive element is shielded on one side such that it measures depth on the side opposite to the one side of the filter.

3. The filter according to claim 1 or 2, further comprising a second set of capacitive elements formed on the printed circuit board, wherein the second set of capacitive elements forms a second capacitive sensor capable of measuring the depth of liquid adjacent to the filter on the side opposite to the side measured by the first set of capacitive elements.

4. The filter according to any one of claims 1 to 3, wherein the printed circuit board has rows of holes that become smaller in size toward the bottom of the printed circuit board.

5. The filter according to any one of claims 1 to 4, wherein the printed circuit board is copper-plated near the holes.

6. A condensate tray having the filter described in any one of claims 1 to 5 upstream of the outlet duct.

7. A reservoir having the filter according to any one of claims 1 to 5 upstream of the outlet duct.

Images