Pressure Drop Alarm Device

Abstract

An alarm device for indicating a drop in pressure, particularly but not exclusively in automatic artificial respiration apparatus. The device functions pneumatically. A source of pressure fluid is connected to a timing device connected in its turn by an outlet to a pressure fluid feed conduit, via a manometric capsule which is normally closed. The latter opens when the pressure in the conduit reaches a certain maximum pressure, in order to evacuate the timing circuit. The aforementioned outlet is likewise connected to a pneumatic cell with the logical function "YES," normally closed, in order to prevent communication between at least one alarm device and the source of pressure fluid. This cell opens if the pressure in the timing circuit exceeds a certain predetermined threshold, as a result of the fact that, since the pressure in the feed conduit has not reached the maximum value, the manometric capsule has not opened.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an alarm device for indicating a drop in pressure, and is particularly but not exclusively suitable for use with automatic artificial respiration apparatus. Such a device is associated with a feed or supply conduit for fluid under pressure, to be supplied from a source of fluid. The device to which the present invention relates is intended to indicate any pressure drops occurring in the said feed or supply conduit, if after a certain pre-selected period the pressure has not reached a certain nominal level.

Pressure drop alarm devices of this type are already known, actuated either mechanically or electrically. It has been found in practice that these devices are not entirely reliable, to the extent necessary in the case of automatic artifical respiration.

The monitoring of long-term ventilation processes calls for costly electrical and electronic apparatus. The most important ventilation parameter to be monitored is the stoppage of the respirator or the disconnection of one of the channels connecting it to the patient. In this case the pressure of the source of fluid continues but the fluid feed conduit under pressure suffers a pressure drop to which attention has to be drawn by an alarm device.

The purpose of the present invention is to propose an extremely reliable alarm device. It is intended to give warning, by optical and/or sound signals, of any maximum insufflation pressure below a certain predetermined threshold, after a period of which the minimum duration exceeds the longest period of the cycle of the respirator.

SUMMARY OF THE INVENTION

According to the present invention there is provided a pressure drop alarm device; particularly but not exclusively for use with automatic respiration apparatus, and associated with and between a feed or supply conduit for fluid under pressure and a source of pressure fluid, the device indicating that, after a certain preselected period, the pressure in the feed conduit has failed to reach a predetermined maximum P, wherein the device functions pneumatically and wherein the source of pressure fluid is connected to a timing device having an outlet connected to the feed conduit, via a manometric capsule which is normally closed and which opens when the pressure in the said feed conduit reaches the maximum pressure P in order to evacuate pressure fluid from the timing device, the said outlet of the timing device also being connected to a pneumatic cell with a logical function "YES" normally closed to prevent the feed of fluid from the said source to at least one alarm, and opened to actuate the or each alarm if the pressure in the timing device exceeds a certain preselected threshold P.sub.c1 caused by manometric capsule remaining closed due to the pressure in the feed conduit failing to reach the said maximum pressure P.

The main advantage of the present invention by comparison with devices of the same kind hitherto known resides not only in its low cost but in its high operating reliability. This can only be obtained by the use of the fluid (gas) under pressure, supplying the fluid under pressure to the feed conduit, as an information transport agent which monitors the pressure in order to indicate the respective pressure drop. The gas under pressure, in the case of artificial respiration apparatus, consists of compressed oxygen. It is available without interruption in establishments where artificial respiration is carried out.

BRIEF DESCRIPTION OF THE DRAWING

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a synoptic schematic diagram of a device according to the present invention;

FIG. 2 is a pneumatic diagram of the same device; and

FIG. 3 is a graph showing the course taken by the pressure in the feed conduit for the fluid under pressure, as a function of time, and also the course taken by the pressure in the container of the timing system of the pressure drop alarm device to which the present invention relates.

DESCRIPTION OF PREFERRED EMBODIMENT

A device according to the present invention and as shown in FIGS. 1 and 2 is associated with a feed or supply conduit 4 for fluid under pressure, mainly consisting of a respiratory circuit of an automatic artifical respiration apparatus. It is intended to indicate any abnormal pressure drop in this conduit, e.g. resulting from the stoppage of the respirator, if the pressure in this conduit has not reached a certain level after a certain preselected period.

It has been found that only one alarm device of which the energy source consists of gas suffices to give all the necessary guarantees as to reliable operation. The device of this kind according to the present invention and as shown in FIG. 1 is thus connected to a source of fluid 1 consisting of the compressed gas. This source of fluid 1 feeds the supply conduit 4 with fluid under pressure and also a pneumatic timing device 2, to the entry E.sub.2 of which it is connected.

The timing device 2 is connected by its outlet S.sub.2 to the entry E.sub.3 of a manometric capsule 3. The latter is normally closed at its outlet S.sub.3 which is connected to the feed conduit 4 for fluid under pressure, placed under the control of the alarm device.

The outlet S.sub.2 of the timing circuit 2 is likewise connected to a control inlet C.sub.5 of a pneumatic cell 5 for a logical function "YES." The latter is connected by its entry E.sub.5 to the source of fluid 1 and by its outlet S.sub.5, normally closed, with at least one sound alarm device 6 and/or optical alarm device of a sufficient number, usually a whistle 7 and a pneumatic visual signal 8, placed in any suitably chosen spot.

The alarm device to which the present invention relates and as constructed is furthermore provided, as shown in the pneumatic diagram in FIG. 2, at a point of connection 20 to the source of fluid 1 under pressure, with a distribution tap or cock 10, of the "ON" and "OFF" type.

The timing circuit 2 comprises a constriction 11, constituting a resistance connected in series to the passage of the gas arriving from the source of fluid 1 and a container 12 fed through the constriction 11.

The manometric capsule 3 is in fact a valve normally closed and included in the passage of the gas between a conduit 21, connecting the entry E.sub.3 to the outlet S.sub.2 of the timing device 2, and a conduit 22 connecting the outlet S.sub.3 to the feed conduit 4 for fluid under pressure (respiratory circuit), placed under the control of the alarm device.

The manometric capsule or valve 3 comprises a housing 31 made in two parts, inside which is accommodated an elastic diaphragm 32 delimiting two chambers 33 and 34. A spring 35, of which the tension can be regulated according to the value P of the opening pressure of the valve by means of a knob, not shown in the drawing, is accommodated in the upper chamber 33. The spring 35 bears on the diaphragm 32 via a disc 36.

A clack valve 38 is provided in the lower chamber 34. It may or may not cut off the communication between the entry E.sub.3 and the interior of the said chamber, into which the outlet S.sub.3 leads. A thrust member 40 provided with a flat head 41 integral with the membrane 32 is likewise provided with a rod 42 integral with the clack valve 38. Normally the spring 35 presses on the diaphragm 32, and the flat 41 of the thrust member, by means of its rod 42, presses the clack valve 38 on the entry E.sub.3 in order to seal it.

The pneumatic cell 5, with a logical function "YES," is a control valve, normally closed, positioned on a conduit 23, connecting its control inlet C.sub.5 to the outlet S.sub.2 of the timing device 2. The pneumatic cell 5 is likewise positioned on the passage of the gas coming from the source of fluid 1, connected to its entry E.sub.5. Being normally closed, it prevents this gas from reaching the alarm devices 7 and 8 connected to the outlet S.sub.5 of the said cell.

The pneumatic cell 5 comprises a body 51 bored with three orifices, i.e., the entry orifice E.sub.5 for compressed gas, the outlet orifice S.sub.5 and the control inlet orifice C.sub.5. The entry E.sub.5 communicates with an upper chamber 52; the outlet orifice S.sub.5 communicates with an upper middle chamber 53, and the control inlet orifice C.sub.5 is in communication with a lower chamber 55. The two chambers 52 and 55 are delimited by fixed walls having apertures 56 and 57 respectively. The aperture 56, towards the upper chamber 52, accommodates a ball 58 constituting a movable clack valve which can be applied to a seat surrounding the aperture 56, thus providing a hermetic closure. A rod 59 of a thrust member 60 accommodated in a lower middle chamber 54 passes through the aperture 57 towards the ball 58. The thrust member 60 bears against a diaphragm 61 forming an elastic wall between the lower chamber 55 and the lower middle chamber 54.

The gas from the source of fluid 1 normally presses the ball 58 onto its seat and obstructs the passage of fluid to the upper middle chamber 53 and the outlet orifice S.sub.5. The pneumatic alarm devices 7 and 8 are not then fed with gas under pressure.

The operation of the principle of the alarm device according to the present invention is shown by the graph in FIG. 3, in which the curve in the lower part indicates the course taken by the pressure in the feed conduit 4 for fluid under pressure, as a function of time. Under normal operating conditions this pressure increased from a marked initial value O at a moment O, to a value P. Once this latter has been reached the pressure rapidly decreases to the marked initial value O. This takes place for a certain time t.sub.1, after which the cycle recommences and repeats.

The curve of the upper part of the graph in FIG. 3 at the same time shows the course taken by the pressure in the container 12, in the conduit 23 and in the lower chamber 55 of the pneumatic cell 5; under normal operating conditions this pressure increases from an initial value P.sub.c, depending on the source of fluid 1 and the constriction 11. When the pressure in the feed conduit 4 has increased sufficiently to open the manometric capsule 3, the container 12 commences to empty. The pressure in the container 12 decreases fairly rapidly, so that it does not reach the level P.sub.c1 necessary to actuate the pneumatic cell 5; the signalling devices then remain inoperative.

If the pressure in the feed conduit 4 for fluid under pressure, after a time t.sub.2 > T.sub. 1, only reaches a pressure P.sub.1 > P, the manometric capsule 3 cannot open the conduit 21 and the cell or container 12 increasingly fills, reaching, after a time t.sub.2 > t.sub.1, a value P.sub.c1 > P.sub.c. The pneumatic cell 5 is then actuated. The gas under pressure arriving from the source of fluid passes to the alarm devices 7,8 and the alarm is given. A timing device is thus necessary in order to ensure that the alarm will only be set up if the pressure p.sub.c1 > P.sub.c has been reached in the container 12.

The gas under pressure supplied by the source of fluid 1, when the circuit is placed under pressure, will encounter during its passage to the alarm devices, the pneumatic cell 5, which is closed. The visual indiator 8 is thus "extinguished" and the whistle 7 does not sound. The container 12 fills via the constriction 11, and the pressure in the lower chamber 55 of the pneumatic cell 5 increases, but it does not exceed the value P.sub.c, which is reached after a time t.sub.1, which is not sufficient to actuate this cell.

On the other hand, the maximum respiratory pressure P corresponding to each breathing cycle will open the manometric capsule 3, because the pressure reaching this cell from the outlet S.sub.3 acts on the diaphragm 32, in opposition to the spring 35. This diaphragm raises the thrust member 40, of which the rod 42 opens the clack valve 38. The container 12 then empties via the conduit 21. A correct cycle takes place and the alarm is not given. If the signal coming from the respiratory circuit disappears or after a time t.sub.2, which is insufficient to actuate the manometric capsule 3, the timing system commences to function. The pressure in the container 12 increases, as it can no longer empty through the conduits 21 and 22. When the timing operation is terminated, owing to the fact that the pressure at the outlet S.sub.2 of the timing device 2 has reached the pressure P.sub.c1 > P.sub.c, the pneumatic cell 5, with the logical function "YES," is actuated. The pressure of the gas arriving through the conduit 23 at the pressure P.sub.c1 raises the diaphragm 61 and the thrust member 60. The ball 58 is raised and opens the communication between the chambers 52 and 53. The gas supplied by the source of fluid 1 passes to the outlet S.sub.5 and thence to the signalling devices 7 and 8, which give the alarm.

It is obvious that the device according to the present invention may be applied to the signalling of a pressure drop in any circuit involving fluid under pressure, whether operating by the pulsating system or not. The application of the alarm device to a fault in an installation with an artificial breathing apparatus has merely been described by way of an example, without any limitative effect, and the apparatus could be constructed in numerous ways having no effect on the principle on which it is based, within the scope of the appended claims.

Claims

I claim:

1. A pressure drop alarm device; particularly but not exclusively for use with automatic respiration apparatus, and associated with and between a feed or supply conduit for fluid under pressure and a source of pressure fluid, the device indicating that, after a certain preselected period, the pressure in the feed conduit has failed to reach a predetermined maximum P, wherein the device functions pneumatically and wherein the source of pressure fluid is connected to a timing device having an outlet connected to the feed conduit via a manometric capsule which is normally closed and which opens when the pressure in the said feed conduit reaches the maximum pressure P in order to evacuate pressure fluid from the timing device, the said outlet of the timing device also being connected to a pneumatic cell with a logical function "YES" normally closed to prevent the feed of fluid from the said source to at least one alarm, and opened to actuate the or each alarm if the pressure in the timing device exceeds a certain preselected threshold P.sub.c1 caused by manometric capsule remaining closed due to the pressure in the feed conduit failing to reach the said maximum pressure P.

2. A device in accordance with claim 1, wherein the timing device includes a restriction and a container connected in series with the source of pressure fluid, the said timing device also comprising an inlet upstream of the said restriction connected to the source of pressure fluid, the outlet being downstream of the said container.

3. A device in accordance with claim 2, wherein the manometric capsule has an inlet connected by a conduit to the outlet of the timing device and an outlet connected by a conduit to the feed conduit.

4. A device in accordance with claim 3, wherein the manometric capsule functions as a valve having its inlet normally closed, the said inlet being opened and placed in fluid communication with the outlet of the timing device when the pressure in the feed conduit reaches the predetermined maximum pressure P.

5. A device in accordance with claim 4, wherein the pneumatic cell functions as a control valve normally closing fluid communication between an inlet of the cell connected to the source of pressure fluid and an outlet of the cell connected to the or each alarm.

6. A device in accordance with claim 5, wherein a conduit connects the outlet of the timing device to a control inlet of the pneumatic cell and wherein the pneumatic cell opens when the pressure fluid reaching it from the container through the said conduit reaches the said preselected threshold P.sub.c1, thereby connecting the or each alarm with the source of pressure fluid to actuate the or each alarm.

7. A device in accordance with claim 1, wherein the alarms comprise at least one whistle and/or at least one pneumatic visual indicator.

8. A device according to claim 1, wherein the supply of pressure fluid from the source of pressure fluid is controlled by a distribution tap or cock of the "ON" and "OFF" type.