GB2228782A - A method of mixing and a mixing unit therefor - Google Patents

Abstract

A method of mixing first and second fluids, which are at different pressures, provides for the flow of said fluids along respective first and second flow paths which converge in a mixing zone. A mixing unit for carrying out the above method includes a housing 1 to which are attached valves (13, 14) which control the flow of said first and second fluids through first and second flow paths 24, 23 respectively. A nozzle 22 reduces the cross sectional area of the second flow path 23 through which the second flow passes to create in a mixing zone a jet or thrust of the second fluid which draws from the first flow path 24 a greater volume of fluid to improve throughput of the first flow and the mixing characteristics of the fluids. <IMAGE>

Description

A MIXING UNIT The invention relates to a mixing unit and particularly to a mixing unit suitable for mixing hot and cold liquids prior to discharge of the mixed liquids.

At present a number of systems are available for mixing hot and cold liquids, particularly water, and an example is the mixing unit designed by the applicants and described in their New Zealand patent specification No.

219777. Although the unit described in specification No.

219777 is a clear improvement over mixing units used in the past it suffers from the disadvantage that it was designed for a particular plumbing situation and does not lend itself to adaption to situations where there is only a confined space available for plumbing. For example, in an existing plumbing situation where a person wishes to install a mixing unit into an existing plumbing system. That is the unit described in specification No. 219717 is only suitable for situations where the mixing unit is mounted on a pedestal above or spaced from a back surface where space is available to accommodate the unit.

An object of the invention is therefore to provide a method of mixing first and second fluids, which can be at the same or different pressures, in a confined space, which method overcomes the problems inherent in existing hot and cold fluid mixing systems and is pas;ticularly suitable for mixing water for a shower, sink, basin or bath.

Further objects and advantages of the invention will become apparent from the following description which is given by way of example.

According to a first aspect of the invention there is provided a method of mixing first and second fluids, which can be at different pressures, the method including providing for the fluid at a first pressure a first flow path having a larger cross sectional area than a second flow path provided for the fluid at a second pressure, said flows of fluid through the first and second flow paths converging to a mixing zone in which the fluids are mixed.

The method is particularly useful for mixing fluids which are at different pressures, for example, the first pressure can be at a lower pressure than the second pressure which is higher than the first pressure.

The second flow path can be restricted in cross sectional area by an insert through which a higher pressure flow of fluid passes to the mixing zone.

The mixing zone can include a secondary nozzle through which the mixed flow of fluid passes to an outlet.

According to a second aspect of the invention there is provided a mixing unit for carrying out the above method of mixing fluids.

According to a third aspect of the present invention there is provided a mixing unit for mixing first and second fluids which can be at different pressures, said mixing unit including a housing to which are attached control means which control the flow of said first and second fluids through first and second flow paths respectively, the housing can have formed therein or inserted therein a nozzle which reduces the cross sectional area of the second flow path through which the second flow passes to thereby create in a mixing zone a jet or thrust of the second fluid which draws from the first flow path a greater volume of fluid to improve throughput of the first flow and the mixing characteristics of the fluids.

The mixing unit can be used for mixing fluids at different pressures wherein the first flow is at a lower pressure than the second flow.

Further aspects of the invention which should be considered in all its novel aspects will become apparent from the following descriptions which are given by way of example only.

Examples of the invention will now be described with reference ot the accompanying drawings in which: ZiSYL shows a section through a mixing body of a unit according to the invention which is designed to be used with a basin faucet; Figure 2: shows a plan view of the unit shown in Figure l with a set of control means fitted thereto, the control means being adapted to operate the unit; ZigMrR shows a section through a mixing body of a unit according to the invention which is designed to be used in the plumbing for a path; Figure 4: shows a plan view of the unit shown in Figure 3 in association with a set of taps which act as control means for operation of the unit; Figure5: shows a section through a mixing body of a unit according to the invention which is designed to be used as a shower mixer; and ;gLS-iL shows a plan view of the unit shown in Figure 5 installed with a set of controls, In the following examples the invention is described with reference to the control of high pressure cold water to be mixed with hot water at a lower pressure. The pressures respectively of the hot and cold water are standard domestic or industrial pressures as currently available and used in New Zealand and the United Kingdom which are to a limited degree also used in Australia.Typically in New Zealand the pressure of domestic cold water supplies are at about 70-100 psi and the thermostats of hot water systems are set to supply hot water at a temperature of about 55-65 C. Typical New Zealand domestic hot water supply pressures from header tanks and pressure reduction valves are about 2 to 10 psi.

It is to be appreciated that with minor modifications, the invention can be adapted to operate with other fluids and other than standard fluid pressures, for example, in equal pressure situations.

The first example shown in Figures 1 and 2 is a mixing unit adapted to mix ho1- and cold water for a basin faucet.

The unit is generally indicated by'arrow 1 and has a housing 2 to which are fixed or attachable connecting tubes 3 and 4 for hot and cold water supplies respectively. In normal domestic situations the tubes 3 and 4 are constructed from 15an tube. The housing 2 is closed at one end 5 and in the example the housing 2 is closed by a plug 7.

The opposite end 6 of the housing 2 has mounted therein a spigot 8 an inner end 9 of which is constructed to act as a support for a primary nozzle 10. The inner end 9 also includes an aperture 11 through which the end of the hot water tube 3 is fitted. The end 9 of the spigot 8 has mounted therein the primary nozzle 10 which has a flow path 12 therethrough.

In use the flow of hot and cold water is controlled by valves 13 and 14 (shown only in Figure 2) and either a direct unmixed cold or hot flow can be obtained via the flow paths indicated by arrows 15 and 16 respectively (shown only in Figure 1). The spigot 8 can have mounted thereon a pivotable faucet arm (not shown). In a situation where a mixed flow of water is required the applicants have discovered that the flow of water from the low pressure hot system is increased presumably because it is drawn through the tube 3 by the high pressure flow from nozzle 10.

In toto the applia3ntc havo vEcortainod that witk a primary nozzle 10 having a bore diameter of 2.5mm and with the water being supplied at typical pressures and temperatures referred to above an acceptable flow of mixed water is obtained through the spigot 8 at normally required temperatures typically 360 - 440C which is the comfort zone for domestic situations. The unit can be used with equal pressure water systems without the primary nozzle 10 to mix equal pressure water at a desired comfort zone.

In the second example shown in Figures 3 and 4 the mixing unit 17 has a housing 18 to which hot and cold water connecting tubes 19 and 20 respectively are attached. The housing 18 having a bore 21 shaped to have fitted therein a primary nozzle 22. The flow path 23 for cold water is reduced by the nozzle 22 to less than the flow path 24 for the low pressure hot water.

The housing 18 has a mixing zone 25 which in this example the applicants have found should have a secondary nozzle 26 inserted therein. The applicants trials with low pressure hot and high pressure cold water have revealed that with the primary nozzle 22 having a bore diameter of 4mm and with the secondary nozzle 26 having a bore diameter of 10rm there is produced an acceptably high level flow of mixed water at a temperature suitable for a normal bath ie between 36oC to 440C. In Figure 4 is shown a set of hot and cold taps 28 and 29 which are used to control the flow of water for the mixing unit 17 from which a spout 30 extends. The standard pipes and connecting tubes through which the hot and cold water is supplied being l9mm internal diameter pipe.In an equal pressure situation the first and second nozzles 22 and 26 respectively are removed to allow mixing at normal comfort zone temperatures.

In Figures 5 and. 6 is shown a mixing unit 31 for a shower. In this example the housing 32 is of the same shape as the housing 2 of the first example shown in Figure 1. In this case the plug 33 supports a filter 34. In this construction the spigot 8 is replaced by a nozzle holder 35 the outlet end 36 of which is a different shape. In this construction there is provision for a secondary nozzle 37.

In trials the applicants have established that with a bore 38 of 2.15mm in a primary nozzle 39 the bore 40 in the secondary nozzle 37 should be 6mm in diameter. In use the flow of water is controlled by hot and cold taps 41 and 42 (Figure 6) and mixing of the water is enhanced in the mixing zone 43 by the high pressure water jet drawing water from the hot connecting tube 44.

In an equal pressure situation the nozzle 39 is removed and the secondary nozzle 37 relocated into the hole vacated by the nozzle 39.

In all of the three examples it will be noted that the size of the mixing unit is about the size of a standard plumbing elbow or T-joint and therefore can easily be inserted behind or as a replacement for existing fittings to improve plumbing performance.

In the examples the mixing of high pressure cold water with low pressure hot water has been described. It is envisaged that alternatively the mixing may be of equal pressure hot and cold water or the high pressure liquid may be at a higher temperature for mixing with a low pressure liquid at a lower temperature.

Thus by this invention there is provided a method and apparatus for mixing first and second fluids which can be at different pressures, the method and apparatus being suitable for use in mixing water for showers, sinks, basins and baths.

Particular examples of the inventions have been described and it is envisaged that improvements and modifications can take place without departing from the scope of the appended claims.

Claims (13)

1. A method of mixing first and second fluids, which can be at different pressures, the method including providing for the fluid at a first pressure a first flow path having a larger cross sectional area than a second flow path provided for the fluid at a second pressure, said flows of fluid through the first and second flow paths converging to a mixing zone in which the fluids are mixed.

A method oo cloBlmedl in clews; 1 wlluselll t11e flow of fluid through the first flow path is at a lower pressure than that of the second pressure.

3. A method as claimed in claim 1 or claim 2 wherein the second flow path is restricted in cross sectional area by an insert through which a higher pressure flow of fluid passes to the mixing zone.

4. A method as claimed in any one of claims 1 to 3 wherein the mixing zone includes a secondary nozzle through which the mixed flow of fluid passes to an outlet.

5. A method of mixing first and second fluids, which can be at different pressures, substantially as herein described with reference to the drawings.

6. A mixing unit for carrying out the method of mixing fluids as claimed in any one of claims 1 to 5,

7. A mixing unit for mixing first and second fluids, which can be at different pressures, said mixing unit including a housing to which are attached control means which control the flow of said first and second fluids through first and second flow paths respectively, the housing can have formed therein or inserted therein a nozzle which reduces the cross sectional area of the second flow path through which the second flow passes to thereby create in a mixing zone a jet or thrust of the second fluid which draws from the first flow path a greater volume of fluid to improve throughput of the first flow and the mixing characteristics of the fluids.

8. A mixing unit as claimed in claim 7 wherein the second flow path is restricted in cross sectional area by an insert through which a higher pressure flow of fluid passes to the mixing zone.

9. A mixing unit as claimed in claim 7 or claim 8 wherein the mixing zone includes a secondary nozzle through which the mixed flow of fluid passes to an outlet.

10. A mixing unit as claimed in claim 8 suitable for a basin faucet wherein connecting tubes supplying the first and second fluids from their respective control means are lSmm external diameter pipe and the primary nozzle has a bore with a diameter of about 2*5mm so that mixed water is produced with a temperature of 360C to 440C.

11. A mixing unit as claimed in claim 8 or claim 9 suitable for a bath situation wherein the first and second fluids from their respective control means are l9mm internal diameter pipe and the primary nozzle has a bore diameter of about 4mm and the secondary nozzle if included has a bore diameter of lOmm so that mixed water with a temperature of between 360C to 440C is produced.

12. A mixing unit as claimed in claim 8 or claim 9 suitable for a shower situation wherein the first and second fluids from their respective control means are 15mm external diameter and the primary nozzle has a bore diameter of about 2.1Smm and the secondary nozzle has a bore diameter of about 6mm.

13. A mixing unit for mixing first and second fluids, which can be different pressures, as claimed in claim 7 and substantially as hereinbefore described with reference to the accompanying drawings.