NZ227746A - Mixing unit for hot and cold water; supplies may be at different pressures - Google Patents

Description

N ^ \ - A a juiv*s<) ij ♦. it . fo/ ^ " r ^ v' Patents Form 5 —- ' PATENTS. ACT. 19.5 3 COMPLETE. SPECIFICATION After. Provisional No... 227746 26 Japuary. .lff.89 "A. FIXING, UNIT" WE, G METHVEN & COMPANY LIMITED of 374 Andersons Bay Road, Dunedin, New Zealand being a New Zealand company, hereby declare this invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: - 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 system 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 disadvantages 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 system. That is the unit described in specification No. 219777 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 mixing unit for first and second fluids, which can be at different pressures, in a confined space, which unit overcomes the problems inherent in existing hot and cold fluid mixing systems and is particularly suitable for mixing water for a shower, 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 mixing unit for mixing first and second liquids, which can be at different pressures, said mixing unit including a housing to which are attached control means which control the flows of said first and second liquids through first and second flow paths respectively, the housing having formed therein or inserted therein a primary 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 of the housing a jet or thrust of the second liquid which draws from the first flow path a greater volume of liquid to improve throughput of the first flow and the mixing characteristics of the liquids. 227746 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: Figure..J-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. 2shows a plan view of the unit shown in • Figure 1 with a set of control means fitted thereto, the control means being adapted to operate the unit; E.i.gPEg- 3_: 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 bath; Figure. 4jl 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; \o P* Figure.5.:. 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 EigUEg. £i. shows a plan view of the unit shown in 5 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 10 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 15 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 20 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 hot and cold water for a basin faucet.

The unit is generally indicated by arrow 1 and has a housing 25 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 ?27746 f * 15mm external diameter tube. The housing 2 is closed at one end 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 tests the applicants have ascertained that with the 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 36"C to 44°C which is the comfort zone for domestic situations. The unit can be used with equal pressure water at a desired comfort zone. ? 2 7 7 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 has 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 10mm there is produced an acceptably high level flow of mixed water at a temperature suitable for a normal bath i.e. between 26 °C to 44 °C. 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 are 19mm internal diameter pipes. 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 support a filter 34. In this • •VHCE 7 "9 DEC 1991 heceived 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 5 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 10 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 15 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 20 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 * J * t * -* * (it I

Claims (7)

l^-77c/£ <:P .. r What we claim is : " %

1. A mixing unit for mixing first and second liquids, which can be at different pressures, said mixing unit including a housing to which are attached control means which control the flows of said first and second liquids through first and second flow paths respectively, the housing having formed therein or inserted therein a primary 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 of the housing a jet or thrust of the second liquid which draws from the first flow path a greater volume of liquid to improve throughput of the first flow and the mixing characteristics of the liquids.

2. A mixing unit as claimed in claim 1 wherein the second flow path is restricted in cross sectional area by the primary nozzle through which a higher pressure flow of liquid passes to the mixing zone.

3. A mixing unit as claimed in claim 1 or claim 2 wherein the mixing zone includes a secondary nozzle through which the mixed flow of liquid passes to an outlet.

4. A mixing unit as claimed in claim 2 suitable for a basin faucet wherein connecting tubes supplying the first and second liquids from their respective control means are 15mm external diameter pipe and the primary nozzle has a bore with a diameter of about 2.5mm so that mixed water depending on the settings of the control means normally has a temperature of between 36°C and 44 °C.

5. A mixing unit as claimed in claim 2 or claim 3 suitable for a bath installation wherein the first and second liquids from their respective control means are 19mm internal diameter pipe and the primary nozzle has a bore dicimeter of about 4mm and the secondary nozzle if included has a bore diameter of 10mm so that mixed water depending on the settings of the control means normally has a temperature of between 36 °C and 44°C.

6. A mixing unit as claimed in claim 2 or claim 3 suitable for a shower installation wherein the first and second liquid paths from their respective control means are 15mm external diameter pipe and the primary nozzle has a bore diameter of about 2.15nun and the secondary nozzle has a bore diameter of about 6mm.

7. A mixing unit for mixing first and second liquids, which can be at different pressures, as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings. G. METHVEN & COMPANY LIMITED By Their Attorneys BALDWIN, SON & CAREY