PRESSURE INDICATOR FOR BREATHING EQUIPMENT, BREATHING EQUIPMENT AND METHOD FOR PRESSURE INDICATION AT A BREATHING EQUIPMENT

FIELD OF THE INVENTION

The present invention relates in general terms to breathing apparatuses. The present invention especially relates to pressure indication in such breathing apparatuses .

BACKGROUND

It is absolutely necessary to ensure that a breathing apparatus which is used by a diver or a fireman, for example, is fully functional and free from faults before a non-breathable atmosphere is entered. Examples of such an atmosphere are water, a smoke-filled environment, and a toxic environment.

It is necessary, inter alia, to check that the gas containers of the system are full and are thus holding the quantity of respiratory gas which may be expected to be consumed, that hoses leading to a breathing mask are seal-tight, i.e. do not leak into the environment and thereby reduce the quantity of gas available for breathing, that respiratory gas has the facility to flow from the gas container freely and without hindrance and arrive at a breathing mask in sufficient volumes, i.e. that the gas resistance between the container and the breathing mask is kept sufficiently low.

A normal respiratory gas supply has the form of a gas cylinder which contains respiratory gas, for example at a pressure of 200 or 300 bar when the cylinder is full.

The respiratory gas is normally air, even though, under special circumstances, it may be other gas mixtures. Since the gas supply is relatively small, it is important that the supply pressure is sufficiently high to provide the user with an anticipated necessary gas volume.

EP 0 956 065 Bl describes a pressure indicator for a breathing apparatus which provides the facility to monitor the pressure in a gas cylinder. This pressure indicator is relatively advanced with a number of functions, which means that a number of fault modes exist and that there is an increased risk of misuse.

BRIEF SUMMARY OF THE INVENTION

One object of the present invention is to provide a pressure indicator which minimizes the risk of misuse. Another object of the present invention is to provide a breathing apparatus which minimizes the risk of misuse. A further object of the present invention is to provide a way of minimizing the risk of misuse.

These objects, inter alia, are achieved with a pressure indicator and a breathing apparatus and a method as claimed in the accompanying claims.

One advantage of a pressure indicator and a breathing apparatus and a method according to the present invention is that a fully automatic pressure indication is obtainable with a very user-friendly indicator which minimizes misuse of the pressure indicator.

A further advantage of a pressure indicator and a breathing apparatus and a method according to the present invention is that, automatically, no current is consumed in the passive state, which helps to minimize misuse and offers the potential for much improved user-

friendliness.

Further characteristics and advantages of the present invention will emerge from the following description.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be fully understood through the following detailed description of a preferred embodiment and the accompanying figures, which are given merely by way of illustration and are not therefore limiting for the present invention and in which:

fig. 1 shows in diagrammatic representation a breathing apparatus according to the present invention.

fig. 2 illustrates parts of a pressure cylinder according to a preferred embodiment of the present invention.

fig. 3-7 illustrate how the pressure indicator illustrated in fig. 2 functions with varying pressure.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In the following description, specific details, such as special techniques and applications, are given for illustrative and non-limiting purposes in order to produce a thorough understanding of the present invention. However, it will be evident to a person skilled in the art that the present invention can be realized in different embodiments which differ from these specific details. In other examples, a detailed description of well-known methods and devices is omitted so as not to obfuscate the description of the present invention with unnecessary details.

A preferred embodiment of a pressure indicator for a breathing apparatus according to the present invention will now be described with reference to fig. 1-7.

A normal breathing apparatus comprises a gas cylinder 1, having a valve 2, which is connected by a hose to a breathing mask 3. The pressure in the gas cylinder 1, the so-called primary pressure, is about 300 bar, for example, when the gas cylinder is full. This pressure falls as the gas is consumed. In order to be able to maintain a substantially constant pressure in the breathing mask 3, the so-called respiratory pressure, there is a regulator 4 installed between the valve 2 and the breathing mask 3. A desired pressure in the breathing mask is substantially the same as the ambient pressure. Since it may be difficult to design a regulator which works well with such a pressure maintenance, a further regulator 5 is normally employed between the regulator 4 and the breathing mask 3.

A pressure indicator 6 is designed to detect and indicate the primary pressure in the breathing apparatus. The pressure indicator can either be connected up to the primary pressure close to the valve 2 or, preferably, close to the regulator 4, upstream of the regulator 4. The pressure indicator comprises an indicator unit, preferably a visual indicator such as a light emitting diode (LED) , which can be fitted onto the breathing mask within the field of vision of the user. In this way, the user can easily perceive when the indicator unit gives warning of too low a pressure. Another advantage of a visual indicator is that if it is placed next to/on the mask glass of the breathing mask, it can also be read by another person close to the user, so called "buddy reading". When the indicator unit is constituted by a LED, it is preferably powered by a battery.

The pressure indicator β further comprises a pressure sensor, which is designed to detect pressure in a range above a predetermined base level. If the regulator 4 is designed to maintain a predetermined pressure, for example about 7 bar above the ambient pressure, then the regulator 4 will only function satisfactorily as long as the primary pressure is higher than the predetermined pressure, in this case about 7 bar. Advantageously, an extra warning is therefore given from the indicator unit whenever the primary pressure is dangerously close to, in this case, about 7 bar. With a small safety margin to this, the extra warning can be given at a primary pressure of about 10 bar. In normal use, a warning at a primary pressure of about 55 bar is preferred. A suitable pressure range for the pressure sensor is preferably, therefore, about 10-55 bar. By starting the indication at about 55 bar and ending the indication at about 10 bar, the extra warning is thereby obtained by the indicator unit ceasing to be lit below about 10 bar.

The pressure sensor comprises a body 7, a pin 8 and a spring 9. The body 7 comprises a rotationally symmetric part 10 of generally T-shaped axial section. The part 10 is disposed in a part 11, fitting tight around the part 10, of a coupling unit to the primary pressure. At the transition between the primary pressure and the ambient pressure, a seal 15 is fitted. The part 10 is exposed to the primary pressure, which forces the body 7 to the right in fig. 2, and which primary pressure is countered by the spring 9. This causes the body 7 to move left-right in fig. 2 with changing primary pressure. Without any primary pressure, the body 7 will be positioned as shown in fig. 3, and at full primary pressure, for example 300 bar, the body will be positioned as shown in fig. 5. The pin 8 is preferably also spring-loaded, so that it can cooperate with the body 7 and be moved up-down in fig. 2.

The body 7 has a rσtationally symmetric part having a waist portion. The waist portion represents an activation zone 12 between a first deactivation zone 13 and a second deactivation zone 14. At pressure below about 10 bar, such as when the pressure indicator 6 is not connected to the primary pressure, the pin 8 is positioned at the first deactivation zone 13, as illustrated in fig. 3. In this position, the LED does not receive any current. When the pressure indicator 6 is connected to a primary pressure, preferably by opening of the valve 2 after the coupling unit to the primary pressure has been fixed to the regulator 4, the body 7 will move rapidly to the right, see fig. 3-5. For a short moment, the pin 8 will be in the activation zone 12, see fig. 4, and the LED will then be briefly lit. After this, the pin 8 will be in the second deactivation zone 14, as illustrated in fig. 5. The LED is once again devoid of current and will therefore go out. The moment in which the pin 8 is in the activation zone 12 is so short that the LED only appears to have blinked once. This can be used to check that the pressure indicator is functioning when primary pressure is connected to the breathing mask prior to the apparatus being used.

As the respiratory gas in the gas cylinder 1 is consumed, the primary pressure falls and the body 7 will move to the left, see fig. 6-7. When the primary pressure goes below, in this example, about 55 bar, the pin 8 will again be in the activation zone 12, which is illustrated in fig. 6. This means that the LED is relit. In order to spare the battery, the LED is advantageously designed to blink instead of being constantly lit. Moreover, it is easier to detect a blinking lamp than a constantly lit lamp.

The LED continues to blink until the primary pressure

goes below, in this example, about 10 bar, when the pin returns to the first deactivation zone 13, which is illustrated in fig. 7. When the LED now goes out, it is an extra warning which clearly denotes to the user that the respiratory gas is about to run out.

A major handling advantage of a pressure indicator according to the present invention is that, since current is only consumed, in the above example, within the range 10-55 bar, no external circuit breakers are required for the system. With a long-life battery and normal use, very long service intervals will able to be obtained. This means, moreover, that the pressure indicator can be more easily encapsulated, since no external circuit breaker is required and since the battery can be molded into the pressure indicator as the battery does not need to be able to be replaced for a very long time.

If a large-scale test of the pressure indicator against a manometer is wished to be conducted, this shall proceed as follows. The pressure indicator is connected to the primary pressure, in this example about 300 bar. The valve on the gas cylinder is shut when the manometer shows about 300 bar. A bypass valve is used to release the gas mixture, so that the pressure falls in the gas line. When the manometer shows about 55 bar, the indicator unit should start to blink. When the manometer shows about 10 bar, the indicator unit should stop blinking. In this way, a complete check of the pressure indicator has been able to be conducted.

It is clear that the present invention can be varied in a number of different ways. Such variations should not be regarded as a divergence from the scope of the present invention as claimed in the accompanying claims. All such variations which would be evident to a person skilled in the art are intended to be included

within the accompanying claims .