WO2010012977A1

WO2010012977A1 - Gas flowmeter

Info

Publication number: WO2010012977A1
Application number: PCT/GB2009/001750
Authority: WO
Inventors: Richard Radford; David Edgar Peel; Andrew Richard Thomas Tatarek-Gintowt
Original assignee: BPR Medical Ltd
Current assignee: BPR Medical Ltd
Priority date: 2008-07-23
Filing date: 2009-07-16
Publication date: 2010-02-04
Anticipated expiration: 2011-01-23
Also published as: GB2462104A; GB0813544D0

Abstract

A therapeutic gas flowmeter comprises a body connectable to a therapeutic gas source, a gas flow tube connected to the body, a flow indicator element housed within the gas flow tube, and an electrostatic charge conductor, which extends along the gas flow tube. Said electrostatic charge conductor is in contact with the gas flow tube along said extent. The electrostatic charge conductor is connectable to electrical earth and arranged to disperse electrostatic charge accumulated on the gas flow tube and/or flow indicator element.

Description

Gas Flowmeter

Field of Invention

The present invention relates to a gas flowmeter. In particular, the present invention relates to a therapeutic gas flowmeter.

Background of invention

Therapeutic gas flowmeters are known. For example, a therapeutic gas flowmeter typically comprises a body connectable to a therapeutic gas source, a gas flow tube including a flow scale, and an outlet connectable to gas apparatus to be used by an end user. Within the gas flow tube there is a flow indicator, typically a ball. When connected to a source of therapeutic gas, and supplying a flow of gas to an end user, movement of the ball within the gas flow tube acts as an indication that therapeutic gas is flowing from the source to an end user. The position of the ball within the gas flow tube in relation to the flow scale offers a user an indication of the rate of flow of gas to the end user. The gas flow tube may, for example, include a calibrated flow scale along its length and the position of the ball within the gas flow tube may thus show the rate of flow of therapeutic gas being delivered to an end user.

The gas flow tube and ball housed therein are typically constructed from electrically insulating materials. The gas flow tube may, for example, be made from a plastics material or from glass, and the ball may be made from a suitable plastics material. A static electrical charge tends to build up within the therapeutic gas flowmeter and can cause malfunction of the gas flowmeter.

When an electrostatic charge builds up within the flowmeter the ball may be attracted to the wall of the flowmeter. The ball may creep up the side of the tube rather than freely float on the flow of air through the flowmeter within the gas flow tube. Static charge may build up to such a level that the flowmeter may give a false reading. It may also be the case that the static builds up to such a level that even when no therapeutic gas is flowing through the flowmeter the ball may be suspended by static charge on the side of the gas flow tube thereby giving a false flow reading.

Since the relevant components of a therapeutic gas flowmeter are electrically insulating, static charges within the flowmeter tend to gccumulate over time. It has been found that the build up of electrical charge within the flowmeter is not attributable to the flow of gas through the flowmeter. The static charge build up can be attributed to a number of events, all of which involve the ball contacting the gas flow tube. The first of those events is the physical impact of the ball against the wall of the gas flow tube. The second of those events is attributable to gas line spikes: when a therapeutic gas source is connected to the flowmeter, or when other apparatus is linked to the flowmeter, spikes in the supply of therapeutic gas from the source to the end user cause "bursts" of gas which cause the ball to impact upon the side or the top of the gas flow tube. Furthermore, initial application of the therapeutic gas flowmeter to a gas source tends to cause agitation of the ball within the gas flow tube.

It is an object of the present invention to provide a therapeutic gas flowmeter which mitigates some of the issues associated with known gas flowmeters.

Summary of the invention

Accordingly, one aspect of the current invention provides a therapeutic gas flowmeter comprising: a body connectable to a therapeutic gas source, a gas flow tube connected to the body, a flow indicator element housed within the gas flow tube, and an electrostatic charge conductor, which extends along the gas flow tube, is in contact with the gas flow tube along said extent, and wherein said electrostatic charge conductor is connectable to electrical earth and arranged to disperse electrostatic charge accumulated on the gas flow tube and/or flow indicator element.

Provision of an electrostatic charge conductor which is in contact with the gas flow tube along a significant portion of the length of the gas flow tube allows electrostatic charge that accumulates or is created on the gas flow tube as a result of an impact between the flow indicator element and gas flow tube to flow to ground rather than accumulate on the gas flow tube.

Arranging the electrostatic charge conductor to extend in a direction substantially parallel to the longitudinal axis of the gas flow tube allows any impact along the length of the gas flow tube between the flow indicator element and the gas flow tube to result in discharge of electrostatic charge rather than build up of electrostatic charge.

The electrostatic charge conductor may be provided on the inner or outer surface of the gas flow tube. The electrostatic charge conductor may take the form of an electrically conducting foil, wire, or other conductive medium, which extends from the flowmeter body towards the distal end of the gas flow tube. The electrostatic charge conductor may extend substantially all the way along the gas flow tube from the flowmeter body to the distal end of the gas flow tube. The therapeutic gas flowmeter may further comprise an electrostatically conducting cradle located in the body of the flowmeter, connectable to electrical earth and arranged to disperse electrostatic charge accumulated on the flow indicator element.

Provision of an electrostatically conducting cradle within the body of the flowmeter allows any electrostatic charge accumulated on the flow indicator element to be discharged when the flow indicator element is at rest within the body of the flowmeter. It will thus be understood that when no therapeutic gas is flowing through the flowmeter electrostatic charge that has built up on the flow indicator element may be discharged.

The electrostatically conducting cradle may take the form of a single loop of conducting wire or may take the form of a substantially tubular or annular electrically conductive seating on which the flow indicator element may rest when no therapeutic ' gas is flowing through the flowmeter.

The therapeutic gas flowmeter may further comprise an energy dissipation device located in the distal region of the end of a gas flow tube and arranged to prevent the flow indicator element impacting on the distal end of the gas flow tube.

Preventing or limiting the manner in which the flow indicator element impacts the end of the gas flow tube helps to minimise static creation within the therapeutic gas flowmeter. Arrangement of an energy dissipation device (a "buffer" or soft stop) allows some of the energy of an impact between the flow indicator element and the gas flow tube to be absorbed. That absorbed energy is not then transformed or stored as electrostatic energy (i.e. as a potential difference).

The energy dissipation device may, for example, take the form of a resilient deformable element, for example, a spring loop. The energy dissipation device may, for example, take the form of some kind of physical stop provided in the region of the distal end of the gas flow tube.

The energy dissipation device may be connected to the electrostatic charge conductor. The energy dissipation device may be electrically conducting. Ensuring that the energy dissipation device is electrically conducting and that it is connected to the electrostatic charge conductor allows any static charge that results from an impact between the flow indicator element and the energy dissipation device to disperse to earth via the electrostatic charge conductor. The body of the flowmeter may include an electrically conducting portion. The electrostatically conducting cradle and / or electrostatic charge conductor may be connectable to electrical earth via the body of the flowmeter. The body of the flowmeter may be formed to include an electrically conducting portion for example, a wire or metal element. Alternatively the body of the flowmeter may be made from an electrically conducting material for example metal or a conducting plastics material.

The flow indicator element may be shaped such that a flow of therapeutic gas through the gas flow tube causes rotation of the flow indicator element.

Appropriately shaping the flow indicator element, for example, by inclusion of a plurality of flow vanes, such that it rotates in a therapeutic gas flow may lessen the effect of any static charge that has accumulated on the gas flow tube or flow indicator element on the operation of the therapeutic gas flowmeter. Rotation of the element may help to prevent electrostatic "sticking" of the flow indicator element to the walls of the gas flow tube.

Furthermore, the shape of the flow indicator element may be chosen to optimise the speed of rotation of the element in the therapeutic gas flow. That optimisation may be achieved by altering the number of flow vanes provided on a flow element or by alteration of the pitch of the flow vanes.

Experiments have shown that at a flow rate of 0.5 litres per minute, rotation of the flow indicator element at around 60 rpm (rotations per minute) will allow the flow indicator element to be more robust and less susceptible to any static. At a gas flow rate of 1.0 litres per minute, a rate of rotation in the region of 120 rpm, and at a gas flow rate of 2.0 litres per minute a rate of rotation in the region of 270rpm has been found to produce similar robustness and less susceptibility to static.

Furthermore, a rotating gas flow indicator, if provided with appropriate visual markings, can offer a user some visual reassurance that therapeutic gas is flowing through the gas flowmeter. No rotation of the gas flow indicator can occur without a flow of therapeutic gas through the therapeutic gas flowmeter.

The flow indicator element may be of an elongate shape and include a plurality of flow veins arranged to substantially spiral around the longitudinal axis of the flow indicator element. Spiralled flow veins are a convenient way to induce rotation of the flow indicator element within the gas flow tube.

It will be understood that any suitable shaping of the flow indicator element that causes rotation in a flow of gas may be utilised. For example, appropriate fan blade or paddle shaping.

The flow indicator element may be arranged to rotate around an axis which is substantially parallel to the axis of the gas flow tube. .

The flow indicator element may include a visual marker located such that, in use, the rate of gas flow through the gas flowmeter is clearly indicated. Provision of a clear visual marker on the flow indicator element allows a user to easily read off the flow of gas through the therapeutic gas flowmeter when, for example, the gas flowmeter is provided with a calibrated scale.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependant claims. Features of the dependant claims may be combined with features of the independent claims as appropriate, and in combinations other than those specifically set out in the claims.

Brief description of the drawings

Embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:

Figure Ia is a perspective view of a therapeutic gas flowmeter in accordance with the first embodiment of the present invention;

Figure 1 b is a cross sectional view of the therapeutic gas flowmeter as shown in

Figure Ia; Figure 2 is an enlarged cross sectional view taken across the region of the body of the flowmeter of Figure 1 a;

Figure 3 is a partial perspective cut away view of the area shown in Figure 2;

Figure 4 is also a partial cutaway perspective view of the area shown in Figure 2;

Figure 5 is a cross sectional view of the distal end of the gas flow tube of the gas flowmeter as shown in Figure 1 a;

Figure 6 is a perspective view of the distal end of the gas flowmeter shown in

Figure 1 a; and Figure 7α and Figure 7b are perspective views of the flow indicator element shown in the therapeutic gas flow meter of Figure Ia.

Description of the embodiments Figure 1 a is a perspective view of a therapeutic gas flowmeter 1 in accordance with a first embodiment of the present invention. The gas flowmeter 1 includes a body 2. That body 2 has an input connector 3, connectable to a source of therapeutic gas, and an outlet connector 4 which, in this case, is connected to a firebreak device 8 from which therapeutic gas is directed towards an end user.

The gas flowmeter 1 further comprises a gas flow tube 5 within which a flow indicator element 6 is housed. The therapeutic gas flowmeter further comprises a flow adjustment control knob 7 provided on the body 2. Turning the flow adjustment control 7 determines the flow of therapeutic gas from the source (not shown) to the end user, as will be described in more detail below.

Figure 1 b is a cross-sectional view of the therapeutic gas flowmeter shown in Figure 1 a. The internal structure of the gas flowmeter 1 is shown in more detail. It can be seen that the body of the gas flowmeter is integrally formed with an input connector 3. The input connector is, in use, connected to a source of therapeutic gas, for example, a ward supply outlet port. The input connector 3 includes a high flow valve 10. A conduit 1 1 leads through the body 2 from the input connector 3 towards the gas flow tube 5. From the conduit 1 1 therapeutic gas may pass up through the centre of gas flow tube 5 until it reaches the distal end of the gas flow tube. When it reaches the distal end of the gas flow tube the therapeutic gas is forced to undergo an 180 turn and flow down the outside of the gas flow tube 5. The upper section of the gas flowmeter 1 , including the gas flow tube 5 is thus exposed to ("charged" with) the full pressure of the therapeutic gas source. The gas is then directed towards the outlet connector 4. To exit the flowmeter 1 gas must pass an open needle valve 12 associated with the flow adjustment control knob 7. When in a closed position the needle valve 12 prevents any therapeutic gas leaving the gas flow tube of the flowmeter and being directed to the user via the outlet connector 4.

The needle valve 12 seals the gas flow path against the flow of therapeutic gas. The seal is made via o-ring seals 13 connected to the needle valve 12. When in an open position, the o-ring seals are no longer compressed by the needle valve. Therapeutic gas is then free to flow between a conduit 14 in the body of the gas flowmeter and a conduit 15 provided in the outlet connector 4. In Figure 1 b it can be seen that the outlet connector 4 is connected to a firebreak device 8. Therapeutic gas leaves the outlet connector 4, enters the firebreak device 8 and exits the nozzle provided on the firebreak device 8 from where it is directed towards an end user. A non-return valve 16 is provided in the region of the outlet connector 4 to ensure that no gas may re-enter the therapeutic gas flowmeter once it has been directed towards an end user.

A flow indicator element 6 is provided within the gas flow tube 5. When needle valve 12 is open and gas is free to flow through the therapeutic gas flowmeter 1 , the flow of gas through the gas flowmeter and in particular through the gas flow tube 5 causes the flow indicator element to move along ("up" as shown in the drawings) the longitudinal axis of the gas flow tube 5.

The greater the rate of flow of gas through the therapeutic gas flowmeter 1 , the further the gas flow indicator element 6 is moved along the longitudinal axis of the gas flow tube 5. When no gas is flowing through the gas flowmeter and needle valve 12 is in a closed position, the flow indicator element 6 rests at the base of the gas flow tube, in the region of the body 2 of the therapeutic gas flowmeter. It is this position that is shown in Figure 1 b.

A calibrated scale may be provided along the length of the gas flow tube. That calibrated scale may indicate the rate of flow of gas through the gas flowmeter. The position of the flow indicator element 6 can be read against the calibrated scale.

Figure 1 b also shows a conductive wire 20 provided on the outside surface of the gas flow tube (5). That conductive wire extends from a coil 21 around the base of the gas flow tube, along the surface of the gas flow tube, towards a shaped soft stop 25.

A conductive cradle 30 is also shown at the base of the gas flow tube 5. The conductive wire 20 and conductive cradle 30 are electrically connected to the input connector 3. The input connector 3 is itself made of a conductive material. In the embodiment shown, that material is brass, but it will be appreciated that any suitable conductive material may be used. The connector 3 is both physically and electrically connected to the source of therapeutic gas and the source itself will typically be electrically grounded. The operation of the conductive wire 20 and the conductive cradle 30 can be understood in relation to the more detailed views of the device shown in Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6. It can be seen from Figure 2 and Figure 3 (both of which show the base of the gas flow tube and body of the gas flowmeter in more detail) that the conductive wire 20 is provided on the external surface of the gas flow tube 5. The wire is in contact with the external surface of the gas flow tube along the length of the gas flow tube. At the base of the tube, the wire 20 performs a number of loops around the gas flow tube 5 to ensure that the wire is in contact with the surface of the gas flow tube along its length. After performing loops around the external surface of the gas flow tube 5, the wire performs a loop 22 around the input connector 3. That loop 22 around the input connector 3 serves to electrically connect the conductive wire 20 to the electrically conductive input connector 3.

In relation to Figure 2 and Figure 4 it can be seen that, at the base of the. gas flow tube 5, there is provided a conductive cradle 30. When no gas is flowing through the gas flowmeter 1 , the flow indicator element rests upon the conductive cradle 30. It is this position that is illustrated in Figure 2 and Figure 4.

The conductive cradle 30 is urged into electrically conductive contact with the input connector 3 by the base of the gas flow tube 5. In particular, the ends of the conductive cradle 30 are compressed into contact with the conductive inlet connector 3.

The conductive wire 20 and conductive cradle 30 act to allow any static charge that builds up within the gas flow tube 5 to disperse from the gas flow tube 5 and gas flow indicator 6, both of which are typically constructed from an electrically insulating material - in this embodiment, suitable plastics materials.

Figure 5 and Figure 6 show the distal end of the gas flow tube in more detail. It can be seen that the conductive wire 20 extends along the external surface of the gas flow tube 5 until it reaches the distal end of the gas flow tube. At that end, the wire is shaped to form a deformable springy soft stop 25. In use, if the flow indicator element 6 reaches or is abruptly forced towards the top of the gas flow tube 5 it will impact against the soft stop 25. The soft stop 25 deforms, thus dispersing a certain amount of the energy of the impact. Any static created by the impact of the flow indicator element 6 with the distal end of the gas flow tube will be dispersed through the conductive soft stop 25 which is integrally formed with the conductive wire 20. It can be seen that the soft stop 25 and the top of the gas flow tube 5 is shaped to substantially conform to the shape of the gas flow indicator element 6. Such shaping helps to ensure a good electrical connection is made.

Figures 7a and 7b show the flow indicator element 6 in more detail. The flow indicator element is generally shaped to be stable in the flow of therapeutic gas through the gas flow tube (5) of the flowmeter 1. The flow indicator element takes the form of a substantially hollow elongate spindle portion 40, which acts as a main body of the flow indicator element. Attached to the elongate spindle portion 40 is a head portion 41. The head portion is substantially frustroconical in shape and, on its underside, includes three substantially spiralled veins shaped to cause rotation of the flow indicator element when subjected to a gas flow through the gas flow tube 5. On the inner surface of the ^■ head 41 there are provided a number of coloured level indicators 43. The flow indicator element 6 is typically constructed from a transparent material and the coloured level indicators 43 can be read through the main body of the flow indicator element 6. The coloured level indicators 43 result in a clear indicator and can be read by a user against any calibrated flow markers on the side of the gas flow tube 5.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A therapeutic gas flowmeter comprising: a body connectable to a therapeutic gas source, a gas flow tube connected to the body, a flow indicator element housed within the gas flow tube, and an electrostatic charge conductor, which extends along the gas flow tube, is in contact with the gas flow tube along said extent, and wherein said electrostatic charge conductor is connectable to electrical earth and arranged to disperse electrostatic charge accumulated on the. gas flow tube and/or flow indicator element.

2. A therapeutic gas flowmeter according to claim 1 , wherein the electrostatic charge conductor takes the form of an electrically conducting wire which extends from the flowmeter body towards the distal end of the gas flow tube.

3. A therapeutic gas flowmeter according to claim 1 or claim 2, further comprising an electrostatically conducting cradle located in the body of the flowmeter, connectable to electrical earth and arranged to disperse electrostatic charge accumulated on the flow indicator element.

4. A therapeutic gas flowmeter according to any preceding claim, further comprising an energy dissipation device located in the region of the distal end of the gas flow tube, and arranged to prevent the flow indicator element impacting the distal end of the gas flow tube.

5. A therapeutic gas flowmeter according to claim 4, wherein the energy dissipation device is connected to the electrostatic charge conductor.

6. A therapeutic gas flowmeter according to any preceding claim, wherein the body of the flowmeter includes an electrically conducting portion.

7. A therapeutic gas flowmeter according to any preceding claim, wherein said flow indicator element is shaped such that a flow of therapeutic gas through the gas flow tube causes rotation of the flow indicator element.

8. A therapeutic gas flowmeter according to claim 7, wherein the flow indicator element is of an elongate shape, includes a plurality of spiralled flow vanes arranged around the longitudinal axis of the flow indicator element.

9. A therapeutic gas flowmeter according to claim 7 or claim 8, wherein the flow indicator element includes a visual marker located such that, in use, the level of gas flow through the gas flowmeter is clearly indicated.