DESCRIPTION

TECHNICAL FIELD

The present invention relates to apparatus for use in mixing fluids, in particular but not exclusively a gas blender for use in mixing medical gases.

DISCLOSURE OF INVENTION

According to the present invention, there is provided apparatus for use in mixing fluids (e.g. gas mixing apparatus) comprising:

a first fluid valve (e.g. first gas valve) actuable by a controller;

a second fluid valve (e.g. second gas valve) actuable by said controller;

a fluid mixing region (e.g. gas mixing region) connected to respective outlets of said first and second fluid valves;

the controller being configured to open said first and second fluid valves alternately.

The first fluid valve may be connectable to ^■ a first fluid source (e.g. first gas source) and the second fluid valve may be connectable to a second fluid source {e.g. second gas source) .

Opening the fluid valves alternately, i.e. keeping one fluid valve closed while the other is open, avoids the pressure at the outlet from the first fluid valve feeding back to the second fluid source via the fluid mixing region. It similarly avoids the pressure at the outlet from the second fluid valve feeding back to the first fluid source via the fluid mixing region.

In one embodiment, the apparatus further comprises a fluid supply outlet {e.g. gas supply outlet) for receiving fluid from the fluid mixing region.

The controller may be configured to repeatedly open said first and second fluid valves alternately (e.g. in a repeated cycle) . In one embodiment, the controller is configured to open each of the first and second fluid valves for a duration of no more than 1 second at a time. In this way, a fluid stream (e.g. gas stream) is generated at the fluid supply outlet in which packets of first and second fluids are mixed sequentially (e.g. in a manner analogous to the way in which packets of digitised data are transmitted over a communications network) . By keeping fluid valve opening times below 1 second, the sequentially mixed first and second fluids can be supplied to a mixing chamber for subsequent uniform mixing of the component fluids in the fluid stream without the sequential delivery of the fluids to the mixing ' chamber interfering with the subsequent uniform mixing process.

In one embodiment, the controller is configured to 5 open one or both of the first and second fluid valves for a duration of no more than 750 milliseconds. For example, the controller may be configured to open one or both of the first and second fluid valves for a duration of no more than 500 milliseconds or no more than about 250

10 milliseconds.

The controller may be configured to open said first and second fluid valves alternately with substantially no time delay between the closing of one fluid valve and the opening of the other. For example, the time delay between

15 the closing of one fluid valve and the opening of the other may be less than (e.g. substantially less than) the duration either the first or second fluid valves are open (e.g. substantially instantaneous) . In one embodiment, the time delay is less than 50 milliseconds (e.g. around

20 25 milliseconds) .

In one embodiment, the mixing region comprises a passageway connecting the respective outlets of said first and second fluid valves to the fluid supply outlet. The passageway may comprise a flexible or non-flexible tube.

25 In one embodiment, the apparatus further comprises breathing apparatus and the fluid supply outlet is configured to supply fluid to the breathing apparatus. In this way, the apparatus may be used to supply medical gas mixtures to a patient for inhalation using the breathing apparatus with the body of the patient forming the mixing chamber for uniformly mixing the sequentially mixed gases present in the gas stream formed in the mixing region. The breathing apparatus may be configured to supply gas to a patient orally (e.g. in the form of a mouthpiece), nasally or by a combination of the two (e.g. in the form of a face mask) .

The apparatus may comprise a first fluid pressure regulator (e.g. first gas pressure regulator) connected to an inlet of the first fluid valve.

The apparatus may comprise a second fluid pressure regulator (e.g. second gas pressure regulator) connected to an inlet of the second fluid valve.

The fluid mixing apparatus may comprise a sensor for measuring the fluid pressure in said mixing region and sending a corresponding signal to said controller. In this way, the pressure of the mixture of first and second fluids in the mixing region can be controlled: when a predetermined pressure is reached, the controller can shut both fluid valves. This advantageously allows operation of the valves to be stopped as soon as the sensor indicates that the fluid supply is not required (e.g. in the case of apparatus comprising breathing apparatus, when a patient stops inhaling gas through the breathing apparatus and pressure builds in the mixing region as a result of gas being prevented from leaving the breathing apparatus) .

The controller may be configured to alternately open the first fluid valve for a first period of time and the second fluid valve for a second period of time. The fluid regulators and fluid valves may be configured such that the amount of fluid that flows through the first fluid valve in said first period of time is equal to the amount of fluid that flows through the second fluid valve in said second period of time. Where the controller is further configured to actuate said first and second fluid valves for equal numbers of periods, equal amounts of said first and second fluids will be supplied to said mixing region.

In another embodiment, the apparatus may be configured such that the amount of fluid that flows through the first fluid valve in said first period of time is different to the amount of fluid that flows through the second fluid valve in said second period of time. In this way, different ratios of fluid mixtures may be achieved. In one embodiment, the difference in fluid amounts supplied at the mixing region/fluid supply outlet may be achieved by configuring the controller to alternately open the first fluid valve for a first (fixed) period of time and the second fluid valve for a second (fixed) period of time which is different to the first period of time. The opening times of the first and second valves may be configured so that the valve with the shorter opening time opens briefly but frequently.

The fluid valves may be solenoid valves. They may be non-proportional valves, i.e. they open completely when actuated and shut completely when not . The apparatus may comprise non-return valves between each fluid source and its respective fluid valve (e.g. between each regulator and its respective fluid valve) or after each fluid valve to prevent flow from the inlet of a fluid valve into the fluid source/regulator. In this way, the risk of mixed fluids contained in the mixing region contaminating the fluid sources may be minimised whilst additionally providing protection against malfunction of either of the first or second fluid valves or the controller.

The invention also provides a corresponding method for mixing fluids (e.g. gases), the method comprising the steps of:

providing a first fluid valve (e.g. first gas valve); providing a second fluid valve (e.g. second gas valve) ;

providing a fluid mixing region (e.g. gas mixing region) connected to the respective outlets of said first and second fluid valves; and

opening said first and second fluid valves alternately.

The first fluid valve may be connected to a first fluid source (e.g. gas source) and the second fluid valve may be connected to a second fluid source (e.g. gas source) .

The method may further comprise providing a fluid supply outlet (e.g. gas supply outlet) for receiving fluid from the fluid mixing region. In one embodiment, the step of opening said first and second fluid valves alternately comprises repeatedly opening said first and second fluid valves alternately. In one embodiment, each of the first and second fluid valves is opened for a duration of no more than 1 second at a time. For example, one or both of the first and second fluid valves may be opened for a duration of no more than 750 milliseconds (e.g. a duration of no more than 500 milliseconds or no more than about 250 milliseconds) .

In one embodiment, the opening of the first and second fluid valves alternately occurs with substantially no time delay between the closing of one fluid valve and the opening of the other. For example, the time delay between the closing of one fluid valve and the opening of the other may be less than (e.g. substantially less than) the duration either the first of second fluid valves are open {e.g. substantially instantaneous) . In one embodiment, the time delay is less than 50 milliseconds (e.g. around 25 milliseconds) .

In one embodiment, the method further comprises providing a passageway connecting the respective outlets of said first and second fluid valves to the fluid supply outlet .

In one embodiment, the fluid supply outlet is configured to supply fluid to breathing apparatus. The breathing apparatus may be configured to supply gas to a patient orally, nasally or by a combination of the two.

The method may further comprise providing a first fluid pressure regulator (e.g. first gas pressure regulator) connected to an inlet of the first fluid valve.

The method may further comprise providing a second fluid pressure regulator (e.g. second gas pressure regulator) connected to an inlet of the second fluid valve.

The method may comprise the step of sensing the fluid pressure in said mixing region and shutting both valves when a predetermined pressure is reached.

The first fluid valve may be opened for a first maximum period of time and the second fluid valve for a second maximum period of time. The fluid regulators and fluid valves may be configured such that the amount of fluid that flows through the first fluid valve in said first period of time is equal to the amount of fluid that flows through the second fluid valve in said second period of time. The method may comprise opening the first and second fluid valves for equal numbers of first and second periods. In another embodiment, the amount of fluid that flows through the first valve in said first period of time is different to the amount of fluid that flows through the second fluid valve in said second period of time . For example, the first period of time may be different to the second period of time .

The method may further comprise providing non-return valves between each fluid source and its respective fluid valve (e.g. between each regulator and its respective fluid valve) or after each fluid valve to prevent flow from the inlet of a fluid valve into the fluid source/regulator. BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described by way of example with reference to the accompanying figures, in which:

Figure 1 is a schematic view of one embodiment of apparatus according to the present invention;

Figure 2 illustrates the operation of the apparatus of Figure 1.

Figure 3 is a schematic view of a second embodiment of apparatus according to the present invention; and

Figure 4 illustrates three modes of operation of the apparatus of Figure 3.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Figure 1 is a schematic view of apparatus 10 for mixing first and second gases according to the present invention.

A first gas enters the apparatus at inlet A, where it is regulated to a fixed pressure by pressure regulator A. As is well-known, a gas pressure regulator serves to maintain a constant gas outlet pressure that is independent of variations in the inlet (supply) pressure or changes in the demand for gas (load flow) at the outlet. Where the supply pressure is high, as is typically the case with bottled gas, the regulator reduces the outlet pressure to a level at which the gas can be breathed without injury, e.g. atmospheric pressure level.

The first gas leaving the outlet of the regulator A then passes through a non return valve (N VA) and thence to solenoid valve A. Flow of gas through solenoid' alve A is electronically controlled by means of an electrical signal from a controller (not shown) that is fed to the coil {coil A) of the actuating solenoid for valve A, thereby opening the valve .

A second gas enters the apparatus at inlet B and is similarly regulated to a fixed pressure by a pressure regulator B. The supply pressure of the second gas may of course be different to the supply pressure of the first gas. The second gas leaving the outlet of the regulator B then passes through a non return valve (NRVB) and thence to solenoid valve B. Flow of gas through solenoid valve B is similarly enabled when an electrical signal from a controller is fed to the coil (coil B) of the actuating solenoid for valve B.

In the embodiment shown, both solenoid valves are of the non-proportional type, i.e. they open completely when actuated by an electrical signal and shut completely when not.

The two gas streams SA, SB flowing out of solenoid valves A and B are mixed as indicated at M, the pressure of the mixed gas prior being measured by a pressure sensor which sends a signal to the controller. The mixed gas then passes out of the apparatus via the gas outlet.

As illustrated in the table of figure 2 , the controller actuates solenoid valves A and B alternately for fixed periods of time until the required pressure level, as signalled by the pressure sensor, is reached. Keeping one solenoid valve closed while the other -is open avoids the pressure at the outlet from solenoid valve A feeding back to regulator B and the pressure at the outlet from solenoid valve B feeding back to regulator A.

In the example shown, the respective supply pressures to the solenoid valves, the solenoid valve flow characteristics and the opening periods for each valve are chosen such that equal quantities of gas pass through each valve in each respective opening period. Accordingly, when each solenoid valve is actuated for the same number of periods, as is the case in table 1 where the valves are alternately actuated for five periods, a 50:50 mixture of gases is obtained.

Figure 1 is a schematic view of apparatus 10 for mixing first and second gases according to the present invention.

A first gas enters the apparatus at inlet A, where it is regulated to a fixed pressure by pressure regulator A. As is well-known, a gas pressure regulator serves to maintain a constant gas outlet pressure that is independent of variations in the inlet (supply) pressure or changes in the demand for gas (load flow) at the outlet. Where the supply pressure is high, as is typically the case with bottled gas, the regulator reduces the outlet pressure to a level at which the gas can be breathed without injury, e.g. atmospheric pressure level. The first gas leaving the outlet of the regulator A then passes through a non return valve (N VA) and thence to solenoid valve A. Flow of gas through solenoid valve A is electronically controlled by means of an electrical signal from a controller {20) that is fed to the coil (coil A) of the actuating solenoid for valve A, thereby opening the valve .

A second gas enters the apparatus at inlet B and is similarly regulated to a fixed pressure by a pressure regulator B. The supply pressure of the second gas may of course be different to the supply pressure of the first gas. The second gas leaving the outlet of the regulator B then passes through a non return valve (NRVB) and thence to solenoid valve B. Flow of gas through solenoid valve B is similarly enabled when an electrical signal from a controller is fed to the coil (coil B) of the actuating solenoid for valve B .

In the embodiment shown, both solenoid valves are of the non-proportional type, i.e. they open completely when actuated by an electrical signal and shut completely when not .

The two gas streams SA, SB flowing out of solenoid valves A and B are mixed as indicated at M, the pressure of the mixed gas prior being measured by a pressure sensor which sends a signal to the controller. The mixed gas then passes out of the apparatus via the gas outlet.

As illustrated in the table of figure 2, the controller actuates solenoid valves A and B alternately for fixed periods of time until the required pressure level, as signalled by the pressure sensor, is reached. Keeping one solenoid valve closed while the other is open avoids the pressure at the outlet from solenoid valve A feeding back to regulator B and the pressure at the outlet from solenoid valve B feeding back to regulator A.

In the example shown, the respective supply pressures to the solenoid valves, the solenoid valve flow characteristics and the opening periods for each valve are chosen such that equal quantities of gas pass through each valve in each respective opening period. Accordingly, when each solenoid valve is actuated for the same number of periods , as is the case in table 1 where the valves are alternately actuated for five periods, a 50:50 mixture of gases is obtained.

Figure 3 is a schematic view of apparatus 10' for mixing first and second medical gases according to the present invention. Apparatus 10' operates in the same manner as apparatus 10 shown in Figure 1 and includes breathing apparatus 100 (e.g. a mouthpiece, mask or nasal inhalation device) . In apparatus 10' , controller 20' is configured to open each valve for around 250 milliseconds when operating to produce a 50:50 mix of two gases (e.g. a 50:50 mix of 0 ₂ and N ₂ 0) for administering to a patient. Packets of gas are mixed at M to form a stream of gas in which the two gas components are sequentially mixed. The stream of gas passes through the gas outlet into breathing apparatus 100 for a patient to inhale. A valve (not shown) in the breathing apparatus 100 prevents the steam of gas from exiting the breathing apparatus when the patient is not inhaling. The pressure sensor detects when pressure in the mixing region reaches a predetermined level and triggers the controller to immediately close any open valve to prevent further gas supply.

The valve sequencing tables of figure 4 illustrate how the controller in apparatus 10' may vary the proportion of the two gases to be mixed by actuating solenoid valves A and B alternately for different fixed periods of time. In the case of a 70:30 mix of gases 0 ₂ and N ₂ 0 (i.e. as shown in the first table), valve A connected to the 0 ₂ gas source is opened for around 500 milliseconds at a time and valve B connected to the N ₂ 0 gas source is opened for around 250 milliseconds at a time. In the case of a 40:60 mix of gases 0 ₂ and N ₂ Q (i.e. as shown in the third table) , valve A connected to the 0 ₂ gas source is opened for around 250 milliseconds at a time and valve B connected to the N ₂ 0 gas source is opened for around 500 milliseconds at a time.

It should be understood that this invention has been described by way of examples only and that a wide variety of modifications can be made without departing from the scope of the invention. For example, although the invention is described for mixing two gases the invention equally applies to an apparatus or method for mixing three or more gases.