GB2097275A

GB2097275A - Improvements in fluid mixing devices

Info

Publication number: GB2097275A
Application number: GB8212123A
Authority: GB
Original assignee: BAILEY THOMAS GEORGE
Current assignee: BAILEY THOMAS GEORGE
Priority date: 1981-04-28
Filing date: 1982-04-27
Publication date: 1982-11-03
Also published as: GB2097275B

Abstract

A body part 100 comprises a main flow passage 110 formed with an emulsion chamber 120 and a discharge outlet 130, a bore 150 for supplying a first fluid to the chamber 120 by way of an inlet 160, and an internally threaded bore 180 for receiving a coupling piece for supplying a second fluid to the chamber 120. The inlet 160 is surrounded by a very thin annular wall 170 which forms a vena contracta at the inlet 160. In use a narrow jet of first fluid enters the chamber 120 by way of the inlet 160 and second fluid is drawn into the chamber 120 due to the creation of a low pressure zone in the chamber 120 and is thoroughly mixed with the first fluid. The resultant mixture is discharged from the device by way of the outlet 130 and a back flow of air along the main flow passage 110 is prevented by the decreasing cross-sectional area of the passage 110 in the opposite direction to the direction of flow of the mixture therethrough. <IMAGE>

Description

SPECIFICATION Improvements in fluid mixing devices The invention relates to fluid mixing devices and more particularly, but not exclusively, to devices suitable for mixing cleaning chemicals, engineering coolants, anti-freeze and the like with a stream of water.

In particular the invention relates to a fluid mixing device of the kind comprising a body part having a main inlet for connection to a source of a first fluid, such as water, under pressure, a main flow passage leading from said inlet to an outlet from the body part, means within the main flow passage for creating a low pressure zone in that passage during flow of the first fluid therethrough, and an auxiliary passage leading to said low pressure zone and for connection to a source of a second fluid, such as liquid detergent. In such a device, the creation of the low pressure zone due to the flow of the first fluid causes the second fluid to be drawn into the main flow passage and to be mixed with the first fluid so that a mixture of the two fluids emerges from the outlet of the device.

Known devices of this kind suffer from the disadvantage that, under certain circumstances, the creation of the low pressure zone is prevented by a back flow of air from the outlet along the main flow passage. This back flow of air, which generally takes place along a peripheral zone of the main flow passage surrounding the main flow of fluid therethrough, will tend to equalise the pressure in the low pressure zone, and this will prevent second fluid being drawn into the main flow passage so that only the first fluid will emerge from the outlet of the device, or will only enable second fluid to be drawn into the main flow passage under high operating pressures.

It has previously been suggested that a grid be disposed at the outlet for the purpose of preventing air from passing along the main flow passage, but this has proved unsatisfactory in practice. It is an object of the invention to provide a fluid mixing device which does not possess this disadvantage and is capable of functioning at low operating pressures.

According to the invention a fluid mixing device of the kind referred to includes means for obstructing the back flow of air along the main flow passage during flow of the first fluid therethrough, said means for obstructing the back flow of air comprising a portion of the main flow passage downstream of said low pressure zone, which portion increases in cross-sectional area in the direction of flow of the first fluid therethrough.

In the device according to the invention, the effect of the portion of increasing cross-section downstream of the low pressure zone is to provide a high pressure region in the main flow passage which prevents air from passing along the main flow passage from the outlet and reaching the low pressure zone. The portion of increasing cross-section may comprise an annular step between two coaxial circular bores of different diameter, the downstream bore being of greater diameter than the upstream bore.

The means for creating the low pressure zone within the main flow passage may comprise an annular shoulder in the main flow passage. The annular shoulder may be formed by a larger cross-section portion and a smaller cross-section portion disposed downstream of the larger cross-section portion and connected to the larger cross-section portion by said annular shoulder, said auxiliary passage being in communication with a part of the smaller cross-section portion adjacent said shoulder.

For high pressure use, the annular shoulder may alternatively be formed by a smaller cross-section portion and a larger cross-section portion disposed downstream of the smaller cross-section portion and connected to the smaller cross-section portion by said annular shoulder, said auxiliary passage being in communication with a part of the larger crosssection portion adjacent said shoulder.

The invention also provides a fluid mixing device of the kind first referred to which includes selection means for selectively connecting the auxiliary passage to a plurality of sources of second fluid. This enables two or more fluids, for example a detergent and an antiseptic or two different detergents or a detergent at two different concentrations, to be made available for mixing with the first fluid within the fluid mixing device for different applications. The selection means may be capable of connecting the auxiliary passage to a selected one of the sources of second fluid and of simultaneously preventing the supply of fluid from the other source(s) of second fluid to the auxiliary passage, and is preferably also capable of preventing the supply of fluid from the source of first fluid to the main flow passage.

In one embodiment of the invention the selection means is adapted to rotate the body part about an axis offset from an aperture where the auxiliary passage emerges from the body part so as to connect the aperture to a selected one of a plurality of auxiliary inlets.

In order that the invention may be more fully understood, two forms of fluid mixing device in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partially exploded view of a first form of device in axial section taken along the line l-l in Figs. 2 to 4; Figure 2 is a view from one end of a sleeve part of the device of Fig. 1; Figure 3 is a view from one end of a body part of the device of Fig. 1; Figure 4 is a view of a cam assembly of the device of Fig. 1; and Figure 5 is a view of part of a second form of device in axial section.

Referring to Fig. 1 the generally cylindrical body part 10 of the device is formed with a main flow passage 11 extending along its axis and comprising a narrow bore 12 which leads into a larger diameter bore 13 which leads into a still larger diameter bore 14. The bore 12 opens out into a recessed sector 15 (see Fig. 3) of one end 16 of the body part 10, and the bore 14 opens out into a substantially semi-circular slot 1 7 in the side 18 of the body part 10. An aperture 19 surrounded by an O-ring in the end 16 communicates by means of an auxiliary passage 21 with a zone 22 within the bore 12.

The body part 10 fits into a sleeve part 23 including an end cap 24 closing off one end.

The end cap 24 is provided with a main inlet 25 which is connected to a source (not shown) of water by a pipe 26 and which communicates with the recessed sector 15 in the end 16 of the body part 10 by means of a main aperture 27 (see Fig. 2) in an internal surface 28 of the end cap 24. Furthermore the end cap 24 is provided with three threaded subsidiary inlets such as 29 each provided with a respective inlet nozzle such as 30 which may be connected to a source of liquid by a flexible pipe pushed over the end of the nozzle 30. The three nozzles, which are indicated schematically by broken lines at 30, 31 and 32 in Fig. 2, may, for example, be connected to a source of first detergent solution, a source of second detergent solution and a source of antiseptic respectively.Each nozzle is provided with a threaded end 33 which is screwed into the inlet 29, the connection being maintained fluid-tight by an Oring 35 and a locking nut 34. The three auxiliary inlets communicate with apertures 36, 37 and 38 in the internal surface 28 of the end cap 24. Each of the three nozzles 30, 31 and 32 may be adjusted by rotating it in relation to its associated inlet so as to vary the amount of solution supplied to the associated aperture 36, 37 or 38.

The body part 10 is rotatable about its axis within the sleeve part 23 by means of a knob 39 which is attached to a shaft 40 fixed to the body part 10, in order to selectively connect the aperture 1 9 in the body part 10 to one of the apertures 36, 37 and 38 in the end cap 24. In Figs. 1 to 4 the aperture 36 is shown in communication with the aperture 19, the other apertures 37 and 38 being blocked off by portions 41 and 42 of the end 16 of the body part 10 surrounded by O-rings 43 and 44. A further portion 45 surrounded by an O-ring 46 is provided for blocking off the aperture 38 when the aperture 37 is in communication with the aperture 19. Furthermore a portion 47 surrounded by a larger 0ring is provided for blocking off the main aperture 27 in order to prevent flow of water, and hence the flow of detergent or antiseptic solution, through the device.The knob 39 therefore has an off-position and first, second and third on-positions corresponding to mixing of the first detergent solution, the second detergent solution and the antiseptic solution respectively with water.

A threaded outlet 49 is provided in the side wall 50 of the sleeve part 23 for communicating with the semi-circular slot 17 in the side 18 of the body part 10, whatever the angular position of the body part 10. A threaded end 51 of a pipe 52 is screwed into the outlet 49.

A fluid-tight seal is provided by two O-rings 53 and 54 surrounding the body part 10 and engaging the internal surface of the side wall 50 of the sleeve part 23.

The shaft 40 passes through a cover plate 55, a cam 56 and a collar part 57 adapted to be screwed to the sleeve part 23 and to the cover plate 55, and is fixed within an axial bore 58 in the body part 18 by a roll pin 59 which passes through a through bore 60 in the shaft 40 into a bore 61 in the body part 10 crossing the bore 58. The cam 56 is fixed to the shaft 40 by a roll pin (not shown) disposed in a bore 62 in the cam 56. Furthermore, as shown in Fig. 4, rollers 63 and 64 are disposed in slots 65 and 66 in the collar part 57 and are biased into engagement with the cam 56 by a spring 67 extending through a slot 69 in the collar part 57. The spring 67 and rollers 63 and 64 are not shown in Fig. 1 in order to render that figure easier to read. A needle roller thrust race 68 is disposed between the collar part 57 and the body part 10.

In operation of the device, with the aperture 36 in communication with the aperture 19 as shown in the drawings, water flows from the main inlet 25 into the main flow passage 11 and creates a low pressure in the zone 22 due to the effect of the water passing over the annular shoulder provided at the upper end of the bore 12. A "vena contracts is thus provided at the upper end of the bore 12, and detergent solution is drawn along the auxiliary passage 21 from the auxiliary inlet 29 in communication with this passage. The detergent solution is mixed with the water in the low pressure zone 22, and the resulting mixture of detergent solution and water passes out of the outlet 49. If the knob 39 is rotated clockwise by one notch of the cam 56, the aperture 19 is connected to the aperture 38, and antiseptic solution is drawn along the auxiliary passage 21 to be mixed with the water in the low pressure zone 22. Alternatively, if the knob 39 is rotated anticlockwise by one notch of the cam 56 from the position shown in the drawings, the aperture 19 is connected to the aperture 37, and a different detergent solution is drawn along the auxiliary passage 21 to be mixed with the water in the low pressure zone 22. If the knob 39 is rotated anticlockwise by one further notch of the cam 56, the flow of water to the main flow passage 11 is stopped and no liquid is therefore drawn along the auxiliary passage 21.

During the supply of liquid by the device, air is prevented from entering the main flow passage 11 by way of the outlet 49 in view of the increasing diameters of the bores 12, 13 and 14 in the direction of flow of the liquid through the main flow passage 11. This is thought to be due to the fact that a high pressure region is created within the main flow passage 11 downstream of the low pressure zone 22. A similar effect may be obtained by replacing the bores 12, 13 and 14 having annular shoulders therebetween by a single smooth bore which continuously tapers in the opposite direction to the direction of flow of the liquid. This tapering bore may be considered as constituting half a venturi.

Due to the invention, it is also possible to use the mixing device for the mixing of gels with water or other liquids in predetermined proportions. Detergents and the like are frequently supplied in the form of gels, but hitherto it has not generally been possible to employ such gels in automatic mixing devices.

Fig. 5 illustrates part of a further form of device in accordance with the invention capable of mixing a high proportion of an additive in the form of a liquid or gel with water supplied at low pressure. The device comprises a body part 100 incorporating a main flow passage 110 formed with an emulsion chamber 120 at one end and a discharge outlet 130 at the other end. The passage 110, which is of circular cross-section, tapers continuously from the discharge outlet 130 to just short of the emulsion chamber 120 and then widens at 140 before opening into the chamber 120. There also opens into the emulsion chamber 120, immediately opposite the passage 110, an inlet 160 in communication with a bore 150 for supplying water to the chamber 120.The inlet 160 is defined by a very thin annular wall 170 which typically has a thickness of five thousandths of an inch (about an eighth of a millimetre) and which forms a vena contracta at the inlet 160. The shape of the inlet 160 is such as to prevent additive from being drawn into the bore 150 if, for any reason, the direction of flow of water through the inlet 160 is reversed. In addition a further, internally threaded bore 180, intended for the liquid or gel to be mixed with water in the emulsion chamber 120, opens into the chamber 120.The bore 150 is coupled to a source of water by way of a coupling piece (not shown) which incorporates a shut-off valve and a non-return valve, and the bore 180 is coupled to a source of liquid or gel by way of a further coupling piece (not shown) which incorporates an adjustment valve capable of adjusting the supply of liquid or gel between zero and a maximum value and a cap which may be padlocked in position to prevent the adjustment valve being tampered with.

In operation of the device, with the shut-off valve open and the adjustment valve set to the appropriate position, a narrow jet of water enters the emulsion chamber 120 and liquid or gel is drawn into the chamber 120 by way of the bore 180 and thoroughly mixed with the water prior to the resultant mixture being discharged by way of the outlet 130. A back flow of air entering the main flow passage 110 by way of the outlet 130 is prevented in view of the continuously tapering cross-section of the passage 110 in the opposite direction to the direction of flow of the liquid.

In the particular example illustrated the angle of taper is 1 30', the maximum internal diameter of the passage 110 being 0.27 inch (about 7 millimetres) and the minimum internal diameter of the passage 110 being 0.21 inch (about 5 millimetres). The outlet end 200 of the body part 100 is shaped to receive a short length of flexible hose (not shown), and includes a pressure relief line 210 which ensures that liquid does not leak out of the end of the hose when the supply has been shut off.

The device of Fig. 5 may be used for mixing cleaning liquids or gels with a range of possible concentrations of additive to water from zero to 1:1 by volume. Alternatively the device may be used for mixing anti-freeze or engineering coolants with water. The use of the device for mixing such substances is particularly advantageous since it enables the mixing proportions to be accurately controlled and prevents the additive being drawn off in undiluted form which discourages pilfering.

Also the additive adjustment valve may be locked to prevent the proportion of additive being increased. It is even possible, with a modification of the device of Fig. 5, for the device itself and the drum containing the additive to be housed in a secure location and for the mixture to be supplied to the delivery point by a length of piping connected to the discharge outlet of the device and provided with an on/off control at the delivery point.

Claims

1. A fluid mixing device comprising a body part having a main inlet for connection to a source of a first fluid under pressure, a main flow passage leading from said inlet to an outlet from the body part, means within the main flow passage for creating a low pressure zone in that passage during flow of the first fluid therethrough, an auxiliary passage leading to said low pressure zone and for connection to a source of a second fluid, and means for obstructing the back flow of air along the main flow passage during flow of the first fluid therethrough, said means for obstructing the back flow of air comprising a portion of the main flow passage downstream of said low pressure zone, which portion increases in cross-sectional area in the direction of flow of the first fluid therethrough.

2. A device according to claim 1, wherein the portion of increasing cross-section comprises an annular step between two coaxial circular bores of different diameters, the downstream bore being of greater diameter than the upstream bore.

3. A device according to claim 1, wherein the portion of increasing cross-section comprises a continuously tapering bore whch tapers in the opposite direction to the direction of flow of the first fluid.

4. A device according to claim 1, 2 or 3, wherein the means for creating the low pressure zone within the main flow passage comprises an annular shoulder in the main flow passage.

5. A device according to claim 4, wherein the annular shoulder is formed by a larger cross-section portion and a smaller cross-section portion disposed downstream of the larger cross-section portion and connected to the larger cross-section portion by said annular shoulder, said auxiliary passage being in communication with a part of the smaller crosssection portion adjacent said shoulder.

6. A device according to claim 4, wherein the annular shoulder is formed by a smaller cross-section portion and a larger cross-section portion disposed downstream of the smaller cross-section portion and connected to the smaller cross-section portion by said annular shoulder, said auxiliary passage being in communication with a part of the larger crosssection portion adjacent said shoulder.

7. A device according to any preceding claim, which includes selection means for selectively connecting the auxiliary passage to a plurality of sources of second fluid.

8. A device according to claim 7, wherein the selection means is capable of connecting the auxiliary passage to a selected one of the sources of second fluid and of simultaneously preventing the supply of fluid from the other source(s) of second fluid to the auxiliary passage.

9. A device according to claim 7 or 8, wherein the selection means is capable of preventing the supply of fluid from the source of first fluid to the main flow passage.

10. A device according to claim 8, wherein the selection means is adapted to rotate the body part about an axis offset from an aperture where the auxiliary passage emerges from the body part so as to connect the aperture to a selected one of a plurality of auxiliary inlets.

11. A device according to any preceding claim, wherein the main flow passage incorporates an emulsion chamber into which the auxiliary passage and an inlet for first fluid open, the inlet for first fluid being defined by a thin annular wall for creating the low pressure zone within the main flow passage.

12. A fluid mixing device substantially as hereinbefore defined with reference to Figs. 1 to 4 or Fig. 5 of the accompanying drawings.