Patent Description:
Accurate delivery of fluid volumes is important in many areas. Syringe pumps and the like are popular laboratory equipment for accurate delivery of predetermined fluid volumes. Syringe pumps may be operated to gradually deliver small amounts of fluid. The pump operates to regulate the delivery of fluid and can be controlled to delivery specific rates and volumes. A typical syringe pump may hold around <NUM> of fluid and deliver at a pumping rate of around <NUM>/hr.

Some known drawbacks associated with syringe pumps are: the response time, which can vary from seconds to hours depending on the fluidic resistance and compliance; the flow rate, which, without flow meters, cannot be known during the transient period; and, associated fine-tuning difficulties.

An object of at least certain embodiments is to address one or more of these problems.

<CIT> discloses a fluid metering system for accurately measuring and dosing liquid chemical into a mixing unit. <CIT> discloses a continuous fluid metering system for continuously dispensing a fluid for injection and for accurately measuring the fluid dispensed. <CIT> discloses a continuous flow chemical metering apparatus.

According to a first aspect of this invention, there is provided a device for controlling flow of a fluid, comprising: a first valve, the first valve comprising: a selectively openable inlet; an opening; and, a selectively openable outlet, arranged such that fluid may enter the first valve through the inlet, exit the first valve through the opening, enter the first valve through the opening and exit the first valve through the outlet; a first sensor for detecting a fluid; a second sensor for detecting a fluid, the first sensor and second sensor in fluid communication with the first valve via the opening; a controller for receiving signals from the first sensor and second sensor and for controlling opening and closing of the inlet and outlet in response to receiving said signals, arranged to allow, in use, a fluid to flow through the device by flowing: into the first valve through the inlet of the first valve; out of the first valve through the opening of the first valve; past a first sensor for detecting a fluid; to a second sensor for detecting a fluid; into the first valve through the opening of the first valve; out of the first valve through the outlet of the first valve.

The valve of the device enables control a flow rate of a fluid at a desired value. The arrangement of the device can result in a highly precise delivery of fluid from the device. Such precision can be attributed to the arrangement of features and specifically the interaction between the inlet, outlet, sensors and the controller. Effects of such a device include maintenance of the flow rate from the device even with changing fluidic conditions. Furthermore, the device is able to ensure the same flow rate for multiple outlets.

In an embodiment the controller is arranged to: close the inlet in response to receiving a signal from the second sensor, the signal being sent in response to the second sensor detecting a fluid; and, close the outlet in response to receiving a signal from the first sensor, the signal being sent in response to the first sensor detecting a fluid after the signal from the second sensor is sent.

The device may reliably perform delivery of specific fluid amounts over many iterations.

In an embodiment, the signal being sent in response to the second sensor detecting a fluid is a close inlet signal; and, the signal being sent in response to the first sensor detecting a fluid is a close outlet signal.

In an embodiment, detecting a fluid comprises at least one of: detecting a fluid being adjacent a sensor; detecting a fluid passing a sensor; detecting a change in fluid from a first fluid to a second fluid being adjacent a sensor; and, detecting a change in fluid from a first fluid to a second fluid passing a sensor.

The sensors of the device may reliably detect fluids. The reliability of detection assists the device deliver repeatable doses of fluids from the device.

In an embodiment, the device further comprises a second valve, the second valve arranged downstream of the outlet of the first valve.

The second valve of the device may assist in controllably delivering predetermined amounts of fluid. The second valve enables an amount to be held for a period of time prior to delivery. This can be advantageous in situations where immediate delivery is not desirable. The second valve also provides failure resilience for the device.

In an embodiment, the device comprises a fluid channel arranged to carry a fluid between the first valve, the first sensor and the second sensor, wherein the fluid channel is arranged to hold a volume of fluid between the first valve and second sensor of around <NUM>µl to around <NUM>µl of fluid.

The device may provide fluid at specific flow rates, which are repeatable and durable for slight changes in fluidic conditions. The flow rates are typically of a durability that cannot be delivered accurately using current techniques. By durability it is meant that the flow rate is closely maintained even under changing fluid conditions and resistances. Such maintenance of flow rate is unavailable with current techniques.

In an embodiment, the device further comprises a fluid reservoir in fluid connection with the valve via the inlet, wherein the controller is arranged to control entry of fluid held, in use, in the fluid reservoir, to the valve via the inlet.

The device may enable fluid to be controllably delivered in predetermined doses from a store of fluid. The store may hold large volumes of fluid so that the device may operate over a relatively long period of time without requiring the device arrangement to be altered by a user. This in turn increases the ease of use of the device for a user.

In an embodiment, a device wherein the opening is a selectively openable opening.

The selectively openable opening of the device may enable greater user control over the operation of the device. Selective opening of the opening of the device enables an additional level of control over specific steps in the operation of the device for the user. The increase in complexity of device is offset by a greater level of control provided to the user.

In an embodiment, the fluid is a liquid.

According to a second aspect of this invention, there is provided a method of controlling flow of a fluid comprising: filling a fluid channel with a fluid to a first predetermined level; detecting the filling of the fluid channel to the first predetermined level; in response to the detecting, draining the fluid channel to a second predetermined level, wherein the second predetermined level is less than the first predetermined level; and, detecting the draining of the fluid channel to the second predetermined level.

The method may be enacted to control flow rate at a desired volume. The steps of the method result in a highly precise delivery of fluid from a fluid channel. Such precision can be attributed to the arrangement of steps and specifically the interaction between the filling, draining, and detecting. Effects of such a method include maintenance of the flow rate from the fluid channel even with changing fluidic conditions.

According to a third aspect of this invention, there is provided a method of controlling flow of a fluid, comprising: opening an inlet of a valve to allow a fluid to enter the valve; passing the fluid through an opening of the valve; detecting the fluid by a second sensor; in response to detecting the fluid by the second sensor, closing the inlet of the valve to prevent fluid entering the valve; after closing the inlet of the valve, opening an outlet of the valve to allow fluid to exit the valve; detecting a fluid by a first sensor; and, in response to detecting a fluid by the first sensor, closing the outlet of the valve to prevent fluid exiting the valve, wherein a greater volume of fluid is required to enter the valve for detection by the second sensor than for detection by the first sensor.

The method may be enacted to control flow rate at a desired volume. The steps of the method result in a highly precise delivery of fluid from a valve. Such precision can be attributed to the arrangement of steps and specifically the interaction between the inlet, outlet, opening and sensors. Effects of such a method include maintenance of the flow rate from the fluid channel even with changing fluidic conditions.

In an embodiment, the method further comprises in response to detecting the fluid by a second sensor, sending a message from the second sensor to a controller that fluid has been detected, and in response to receiving the message from the second sensor by the controller, sending a message to a valve to close the inlet of the valve to prevent fluid entering the valve.

Detection of the fluid by a second sensor and sending a message to a controller, which acts accordingly to the received message, increases the reliability of the delivery of predetermined amounts of fluid. The controller also increases the ease with which the device may operate, as it removes the need for a user to assist in specific phases of operation of the valve.

In an embodiment, the method further comprises in response to detecting the fluid by the first sensor, sending a message from the first sensor to a controller that fluid has been detected, and in response to receiving the message from the first sensor by the controller, sending a message to a valve to close the outlet of the valve to prevent fluid exiting the valve.

The method may be enacted to increase the reliability of the delivery of predetermined amounts of fluid. The controller also increases the ease with which the device may operate, as it removes the need for a user to assist in specific phases of operation of the valve.

In an embodiment, the method further comprises sending a message to a fluid delivery system of a fluid reservoir to initiate fluid delivery from the reservoir to the valve.

The method may be enacted to enable fluid to be controllably delivered in predetermined doses from a store of fluid. The store may hold large volumes of fluid so that the method may be used over a relatively long period of time without requiring the method to be altered by a user, for example by introducing fluid or a fluid source repeatedly. This in turn increases the ease of use of the method for a user.

In an embodiment, the method further comprises delivering a predetermined volume of fluid from the valve, wherein the predetermined volume is about <NUM>µl to around <NUM>µl of fluid.

The device may provide fluid at specific flow rates, which are repeatable and durable for slight changes in fluid resistances. The flow rates are typically of a durability that cannot be delivered accurately using current techniques. The flow rate is maintained even under changing fluid conditions and resistances unlike with current techniques.

In an embodiment, the method further comprises holding a fluid between the valve and the second sensor for a predetermined period of time prior to opening an outlet of the valve to allow fluid to exit the valve.

The method may be enacted to controllably deliver predetermined amounts of fluid. The method enables an amount of fluid to be held for a period of time prior to delivery. This can be advantageous in situations where immediate delivery is not desirable. The method also provides failure resilience as operational checks can be performed during the predetermined period of time to ensure standard, i.e. non erroneous, operation of the method occurs.

Specific embodiments will be described below by way of example only and with reference to the accompanying drawings, in which:.

<FIG> shows a schematic sectional view of a device <NUM> for controlling flow of a fluid. The device <NUM> has a valve <NUM>, a first sensor <NUM> and a second sensor <NUM>. The valve <NUM> has a selectively openable inlet <NUM>. The valve <NUM> has an opening <NUM>. The valve <NUM> has a selectively openable outlet <NUM>. The valve <NUM> is arranged such that fluid may enter the valve <NUM> through the inlet <NUM>, exit the valve <NUM> through the opening <NUM>, enter the valve <NUM> through the opening <NUM> and exit the valve <NUM> through the outlet <NUM>.

The device <NUM> also has a controller (not shown) for receiving signals from the first sensor <NUM> and the second sensor <NUM> and for controlling opening and closing of the inlet <NUM> and the outlet <NUM> in response to receiving the signals.

The device <NUM> operates to control flow of a fluid by allowing a fluid to flow into the valve <NUM> through the inlet <NUM> of the valve <NUM>. Fluid may flow out of the valve <NUM> through the opening <NUM>. Fluid exiting the valve <NUM> via the opening <NUM> may pass the first sensor <NUM>. If further fluid exits the valve <NUM> via the opening <NUM>, the fluid may then flow to the second sensor <NUM>. The fluid re-enters the valve <NUM> via the opening <NUM> and may exit the valve <NUM> through the outlet <NUM>.

Prior to use the device <NUM> is closed, in that the inlet <NUM> is closed and no fluid can enter the valve <NUM>. The outlet <NUM> may also be closed prior to the device <NUM> being used. When operated, the controller of the device <NUM> sends an open signal to the inlet <NUM>. The inlet <NUM> opens and fluid may enter the valve <NUM>. If the outlet <NUM> is open prior to fluid entering the valve <NUM>, the outlet <NUM> is closed prior to the inlet <NUM> being opened. Fluid enters the valve <NUM> and, as more fluid enters the valve <NUM>, passes through the open opening <NUM>. Fluid passes through the opening <NUM> and along a fluid channel <NUM>. The fluid passes the first sensor <NUM> after a specific volume of fluid has passed through the inlet <NUM> and out of the opening <NUM>. After a second specific volume of fluid has passed through the inlet <NUM> and out of the opening <NUM>, the fluid reaches the second sensor <NUM>. The first sensor <NUM> and second sensor <NUM> are arranged so that a greater volume of fluid is required to be present in the fluid channel <NUM> to activate the second sensor <NUM> than to activate the first sensor <NUM>.

The second sensor <NUM> sends a signal to the controller when a fluid is detected. The controller may then close the inlet <NUM> so as to prevent any further fluid entering the valve <NUM>. The volume of fluid held in the device <NUM> at this point is now a predetermined amount. This fluid may be held in the device <NUM> for a relatively long period of time if desired. When emission of the fluid is desired, the controller sends a signal to the outlet <NUM> to open. Fluid then flows from the fluid channel <NUM>, through the opening <NUM> and out of the valve <NUM> through the outlet <NUM>. As the fluid level (the boundary of the fluid) passes the first sensor <NUM>, the first sensor <NUM> sends a message to the controller. The controller may then close the outlet <NUM> so that no further fluid may exit the device <NUM>.

The sensors <NUM>, <NUM> detect fluids. The sensors <NUM>, <NUM> detect the presence or absence of fluids. Signals may be sent in response to an initial detection of fluid, such as for second sensor <NUM> to close the inlet <NUM>. Signals may be sent in response to a lack of detection of a fluid, such as for first sensor <NUM> to close the outlet <NUM>. In this manner, movement of the fluid level in the fluid channel <NUM> may be tracked by the sensors <NUM>, <NUM>. The sensors <NUM>, <NUM> may detect fluids via any suitable method including difference of light absorption, light diffraction, the use of a variable capacitor, or the like. The fluids used in the fluid channel <NUM> preferably show a well-defined interface with one another to enable accurate readings to be made by the sensors <NUM>, <NUM>.

The device <NUM> may then be refilled with fluid entering through the inlet <NUM>. The device <NUM> may be fed from a fluid source such as a fluid reservoir or the like. The fluid source is in fluid communication with the valve <NUM>. The fluid source may be pressurised to provide fluid to the device <NUM>. The device <NUM> may be advantageously arranged such that on a second operation, fluid present in the device <NUM> does not exit the device <NUM> through the re-opened inlet <NUM> towards the fluid source.

In this way, a predetermined and carefully controlled volume of fluid may be provided in doses by the present device <NUM>. Moreover, this predetermined volume of fluid may be provided in a repeatable manner. The volume provided will be the volume held by the device <NUM> in the fluid channel <NUM> between the first sensor <NUM> and the second sensor <NUM>. This amount can be carefully controlled by virtue of the size of the fluid channel between the sensors <NUM>, <NUM> and the sensitivity of the sensors.

Pressure may be applied to the volume of fluid contained within the device <NUM> prior to fluidic emission so as to push the fluid through the outlet <NUM>. This may be particularly advantageous under certain atmospheric conditions or the like wherein the fluid contained in the device <NUM> benefits from additional thrust to exit the device <NUM>. This pressure may be applied by a further fluid (which may or may not be immiscible with the fluid that entered the valve <NUM> through the inlet <NUM>) or a plunger or the like.

The periodicity of the opening and closing of the inlet <NUM> and the outlet <NUM> may control the <NUM>-step process (as described above) and therefore the overall flow rate. The present device <NUM> may therefore maintain a controlled flow rate even with changing fluidic conditions such as fluidic resistance or the like.

<FIG> shows a schematic sectional view of an apparatus <NUM> comprising a device <NUM> for controlling flow of a fluid. Features of <FIG> that have been described previously in relation to <FIG> have the same numerals and, for improved readability, may not be described in detail here. In particular, the previously-described features of the device <NUM> will not be repeated here.

The apparatus <NUM> has a fluid source <NUM>, a pressure source <NUM>, and a delivery manifold <NUM>. The fluid source <NUM> provides fluid for entering the device <NUM> via the inlet <NUM>. The pressure source <NUM> provides a pressure P1 to the fluid source <NUM> for forcing the fluid into a conduit <NUM>, through the inlet <NUM> and into the device <NUM>. The pressure source <NUM> may also provide a pressure P2 to the fluid channel <NUM> of the device <NUM>. The pressure source <NUM> therefore controls the respective pressure ΔP (ΔP = P1 - P2) between the fluid source <NUM> and the fluid channel <NUM>. The pressure source <NUM> is therefore able to control the direction of flow of the fluid when the inlet <NUM> is open. The pressure source <NUM> may be controlled by the controller of the device <NUM>, or by any other means such as an integrated controller (not shown) of the pressure source <NUM>.

The device <NUM> in the example shown in <FIG> has a second valve <NUM> in fluid communication with the outlet <NUM>. The second valve <NUM> enables a volume of fluid to be held between the first valve <NUM> and the second valve <NUM> for a desired period. The second valve <NUM> may introduce an additional level of control over the flowing out of the first valve <NUM> of the fluid. The second valve <NUM> may have an inlet and an outlet, or may simply be a movable blocking element to prevent the passage of fluid. The second valve <NUM> may be activated (opened and closed) by a controller or may be pressure activated, such that a fluid pressure above a predetermined fluid pressure level forces the second valve <NUM> to be open.

The apparatus <NUM> has a delivery manifold <NUM>. The delivery manifold <NUM> may have a single fluid inlet and multiple fluid outlets. The manifold <NUM> may have multiple outlet channels linking the multiple outlets to the inlet. The multiple outlet channels may branch off from a central inlet channel in fluid communication with the inlet. The manifold <NUM> may have openable valves arranged to allow a controllable distribution of the fluid from the device <NUM> along a specific outlet channel and out of a specific outlet of the multiple fluid outlets. The multiple channels within the manifold may not have the same resistance to fluid flow. As such, the device <NUM> advantageously enables controllable fluid delivery rate from a manifold <NUM> with differing resistances to fluid flow.

In reality, the volume delivered by the device <NUM> to the manifold <NUM> may be just greater than the volume contained between the first sensor <NUM> and the second sensor <NUM> due to the reaction times associated with the detection of the fluid (or fluid level) by the sensors <NUM>, <NUM>, sending a message to the controller and then subsequently the complete closing of the inlet <NUM> or the outlet <NUM> (as appropriate according to the stage in the process). In any event, these reaction times may be calculated, and accounted for accordingly, such that a predetermined and desired amount of fluid may be delivered to the manifold <NUM>. The location of the sensors <NUM>, <NUM> may be movable along the fluid channel <NUM> to enable a change in the volume of fluid delivered.

The user may be able to calibrate the flow rate controllably delivered by the device <NUM> by adjusting: the pressure P1 delivered by the pressure source <NUM> along conduit <NUM> to the fluid source <NUM>; the pressure P2 delivered by the pressure source <NUM> along conduit <NUM> to the device <NUM>; and, the periodicity of the opening and closing of the valves <NUM>, <NUM>.

The periodicity is calculated taking into account the volume of fluid delivered by the device <NUM> over one use iteration. To ensure repeatability over many runs, the pressures P1, P2 delivered along the conduits <NUM>, <NUM> may be provided at set values. Where there is pressure loss along the conduits <NUM>, <NUM>, this should be taken into account accordingly to ensure the loss along one conduit does not prevent the balance of pressures being that required to maintain flow of fluid through the device <NUM> in the manner desired.

<FIG> shows a schematic sectional view of a portion of an apparatus <NUM> comprising a device <NUM> for controlling flow of a fluid in accordance with a third embodiment. Features of <FIG> that have been described previously in relation to <FIG> or <FIG> have the same numerals and, for improved readability, may not be described in detail here. In particular, the previously-described features of the device <NUM> will not be repeated here.

<FIG> shows a portion of the apparatus <NUM> shown in <FIG> with the manifold <NUM> connected to a series of fluid outlets <NUM>. In an example, the fluid outlets <NUM> may be a series of nozzles, or exits, or the like for a controlled delivery of fluid from the manifold <NUM>. The manifold <NUM> has an inlet channel <NUM> connected to a plurality of outlet channels <NUM>. In the example shown, there are an equivalent number of outlet channels <NUM> to fluid outlets <NUM>.

The device <NUM> operates as previously described to iteratively deliver set volumes of fluid to the manifold <NUM>. The manifold <NUM> may route a specific volume of fluid to a particular fluid outlet 240A, 240B etc. In this manner, the apparatus <NUM> may controllably deliver specific set volumes of fluid from a fluid source (not shown in <FIG>). As shown in the time line <NUM>, fluid delivery points <NUM>, <NUM>, <NUM>, <NUM> occur in regular intervals. Each fluid delivery point <NUM>, <NUM>, <NUM>, <NUM> occurs via delivery of fluid through an outlet 240A, 240B, 240C, etc..

<FIG> shows a schematic sectional view of a portion of a device <NUM> for controlling flow of a fluid in accordance with a first embodiment. <FIG> shows the first sensor <NUM>, the second sensor <NUM> and the fluid channel <NUM> of the device <NUM>.

<FIG> shows the two stages of operation of the device <NUM>. The filling stage is shown in <FIG> and the emptying stage is show in <FIG>. The pressures P1, P2 provided by the pressure source <NUM> to the fluid source <NUM> and to the device <NUM> respectively, are shown as activating in their relevant stages. In the emptying stage, shown in <FIG>, pressure P2 applied along the conduit <NUM> linking the pressure source <NUM> to the device <NUM> operates. In the filling stage, shown in <FIG>, pressure P1 applied along the conduit <NUM> linking the pressure source <NUM> to the fluid source <NUM> operates.

<FIG> highlights three portions 140A, 140B, 140C of the fluid channel <NUM>. The uppermost portion 140A represents the volume Ve<NUM>, Vf<NUM> of fluid contained in the fluid channel <NUM> above the second sensor <NUM> as a result of the reaction time associated with fluid passing the second sensor <NUM> and the closing of the inlet <NUM> of the valve <NUM> to prevent any further fluid entering the device <NUM>. As this reaction time is non-zero, there is some volume of fluid held in the fluid channel <NUM> above the second sensor <NUM>.

The middle portion 140B represents the volume Ve<NUM>, Vf<NUM> of fluid contained in the fluid channel <NUM> between the first sensor <NUM> and the second sensor <NUM>. In a preferred embodiment this volume Ve<NUM>, Vf<NUM> is greater than the volume Ve<NUM>, Vf<NUM> held in the portion 140A above the second sensor <NUM> and the volume Ve<NUM>, Vf<NUM> held in the portion 140C below the first sensor <NUM>. This ensures that the error to be corrected by the volume Ve<NUM>, Vf<NUM>, Ve<NUM>, Vf<NUM> held in these portions 140A, 140C is not significant in comparison to the volume Ve<NUM>, Vf<NUM> held in the middle portion 140B.

The lowermost portion 140C represents the volume Ve<NUM>, Vf<NUM> of fluid drained from the fluid channel <NUM> below the first sensor <NUM> as a result of the reaction time associated with fluid (fluid level) passing the first sensor <NUM> and the closing of the outlet <NUM> of the valve <NUM> to prevent any further fluid emptying from the device <NUM>.

The volumes for the three portions 140A, 140B, 140C in <FIG> are the same, despite their labelling in <FIG>, due to the size of the fluid channel <NUM> not changing during draining (<FIG>) or filling (<FIG>) stages. By this it is meant that, volume Ve<NUM> of portion 140A in <FIG> is the same as volume Vf<NUM> of portion 140A in <FIG>, and so on for middle portion 140B and lowermost portion 140C.

Turning specifically to <FIG>, an emptying (or draining) stage is shown. The pressure P2 applies to the fluid contained within the fluid channel <NUM>. The time taken for the fluid to empty from the fluid channel <NUM> so as to have a fluid level at the second sensor <NUM> is Te<NUM>. The time then taken for the fluid to empty from the fluid channel <NUM> so as to have a fluid level at the first sensor <NUM> is Te<NUM>. The reaction time then taken for the first sensor <NUM> to send a signal and the resultant closing of the outlet <NUM> of the valve <NUM> to prevent further fluid emptying from the fluid channel <NUM> is Te<NUM>. The final fluid level FFL is shown below the first sensor <NUM>. The flow of the fluid out of the fluid channel <NUM>, for the emptying phase, is indicated by the arrow fe.

Turning specifically to <FIG>, a filling stage is shown. The filling stage shown is that occurring following an emptying stage, such that some fluid is already present in the fluid channel <NUM> prior to filling. The initial fluid level IFL is the fluid level of that fluid remaining in the fluid channel <NUM> following an emptying stage (as shown in <FIG>). The initial fluid level IFL is shown in <FIG>. The initial fluid level IFL of the filling stage is at the same level as the final fluid level FFL of the emptying stage shown in <FIG>. Pressure P1 may be applied to the fluid contained within the fluid source <NUM> to push fluid into the device <NUM> as described earlier. The time taken for the fluid to enter the fluid channel <NUM> so as to move the fluid level from the initial fluid level IFL to the first sensor <NUM> is Tf<NUM>. The time then taken for the fluid to enter the fluid channel <NUM> so as to move the fluid level to the second sensor <NUM> is Tf<NUM>. The reaction time then taken for the second sensor <NUM> to send a signal and the resultant closing of the inlet <NUM> of the valve <NUM> to prevent further fluid entering from the fluid source <NUM> is Tf<NUM>. Tf<NUM> is dependent on the same parameters as Tf<NUM>, but it can not be directly measured. So by controlling Tf<NUM>, we indirectly control Tf<NUM>, which in turn ensures the volume over the second sensor <NUM> remains constant. The flow of the fluid into the fluid channel <NUM>, for the filling phase, is indicated by the arrow ff.

When the volumes Vf<NUM> and Vf<NUM> at either ends are maintained so as to be constant and the volume Vf<NUM> in between the sensors <NUM>, <NUM> is kept constant, the total volume delivered by the device <NUM> is kept constant.

The device <NUM> disclosed herein is able to account for changing fluidic conditions, e.g. resistances in the fluid or the pipes into which the fluid is delivered, by for example adapting the refilling pressure P1 applied to the fluid source <NUM>.

On re-filling, the volume Vf<NUM> needs to be re-filled and this volume Vf<NUM> depends on the pressure and fluidic resistance during the emptying phase. As mentioned above, this volume Vf<NUM> (equivalently Ve<NUM>) is allowed to exit the device <NUM> during the "reaction time" of the first sensor <NUM> during emptying. To keep the time Tf<NUM> constant across multiple iterations of filling and emptying, the time Te<NUM> can be adapted. This may be coordinated by the controller of the device <NUM>. This in turn may be used to ensure the volume below the first sensor <NUM> is constant.

In the case of a pressure loss, pressure P1 delivered to the fluid source <NUM> may be adapted. This adaptation affects the time taken Tf<NUM> for the fluid to fill the volume Vf<NUM> between both sensors <NUM>, <NUM>. This time should be kept constant. As fluidic resistance increases, pressure P1 should increase so as to maintain the same time Tf<NUM> for filling the volume Vf<NUM>. time Tf<NUM> is controlled by the pressure P1. Tf<NUM> is also dependent on the volume Vf<NUM> however for constant dimensions of the fluid channel <NUM>, this volume Vf<NUM> is constant.

The relationship between the pressure P1 applied to the fluid source <NUM> and the pressure P2 through the conduit <NUM> is managed to ensure the time Tf<NUM> is constant across multiple iterations of fluid delivery. This is due to the pressure difference felt at both ends of the fluid channel <NUM> being a controlling factor to the delivery of fluid to and from the fluid channel <NUM>.

Fluid herein may refer to a gas or a liquid. Detection of fluid relates to the detection of the fluid which enters the device <NUM> from a reservoir or the like. The device <NUM> does not ideally contain a vacuum and, as such, a secondary fluid will be present in the device <NUM> and replaced by the primary fluid entering the device <NUM> from the fluid source <NUM> or the like. It is this fluid which is transiently in the device <NUM> which is detected by the first and second sensors <NUM>, <NUM>. Such sensors may operate using IR spectroscopy, magnetism (alongside a magnetic float), a conductive sensor or pneumatic sensors to detect fluid.

The phrase "detecting a fluid" may be used herein to refer to at least one of the following: detecting a fluid being adjacent a sensor; detecting a fluid passing a sensor; detecting a change in fluid from a first fluid to a second fluid being adjacent a sensor; and, detecting a change in fluid from a first fluid to a second fluid passing a sensor. "Adjacent" may be used herein as meaning in the vicinity of, or nearby, and is not limited necessarily to being directly adjacent a sensor.

Fluid that is replaced in the fluid channel <NUM> during use may exit the device <NUM> via a one way valve such as a pressure release valve, or the fluid may be pressurised elsewhere in the device <NUM>. This may assist in overfilling the device <NUM> with fluid as the entering fluid has to work against the pressure of the replaced fluid.

Claim 1:
A device (<NUM>) for controlling flow of a fluid, comprising:
a first valve (<NUM>), the first valve comprising:
a selectively openable inlet (<NUM>);
an opening (<NUM>); and,
a selectively openable outlet (<NUM>),
arranged such that fluid may enter the first valve through the inlet, exit the first valve through the opening, enter the first valve through the opening and exit the first valve through the outlet;
a fluid channel (<NUM>) arranged such that fluid may enter and exit the fluid channel through the opening (<NUM>) of the first valve;
a first sensor (<NUM>) for detecting when a fluid level of the fluid passes the first sensor during emission of the fluid from the fluid channel;
a second sensor (<NUM>) for detecting when the fluid level reaches the second sensor during filling of the fluid channel;
a controller for receiving signals from the first sensor and second sensor and for controlling opening and closing of the inlet (<NUM>) and outlet (<NUM>) in response to receiving said signals,
arranged to allow, in use, the fluid to flow through the device by flowing:
into the first valve through the inlet (<NUM>) of the first valve;
out of the first valve through the opening (<NUM>) of the first valve;
past the first sensor (<NUM>);
to the second sensor (<NUM>);
into the first valve through the opening (<NUM>) of the first valve;
out of the first valve through the outlet (<NUM>) of the first valve.