FR2548908A1 - Gas mixer for anaesthesia and resuscitation apparatus - Google Patents

Abstract

The mixer 1 comprises a pneumatic circuit with sequential feed consisting of two coupled pressure-reducing members 4, 5 fed via separate conduits, these pressure-reducing members 4, 5 directing a gas through a respective conduit 6, 7 into a multi-directional valve 8 having two stable positions, where, in one or other position of the valve 8, one or other chamber 9, 10 of a jack 11 with free piston 25 connected via a conduit 12, 13 to the said valve 8 is filled alternately with one or other gas, while, at the same time, the opposite chamber 9, 10 is set to the escape mode, the escaping gas passing into an escape conduit 14, then into a second safety valve 15, into a constriction area 17, and finally into a buffer reservoir 18 in order to be subsequently discharged via a pressure-reducing member 21 into a fourth safety valve 22 before being fed to a patient at 23.

Description

 The present invention relates to a gas mixer for anesthesia and resuscitation apparatus provided with a plurality of intrinsic safety means.

According to the prior art, in almost all cases, the third gas mixture supplying the anesthesia and resuscitation respirators comes from equipment called a rotametric block and formed by two needle valves, one supplied by oxygen and the other by nitrous oxide N2O (or by another gas) and simultaneously discharging darus a common piping. The part of the circuit placed between the needle valves and the junction comprises two flowmeters generally with float and conical tube. These equipments have a major drawback which is that nothing signai ~ a failure on the oxygen supply circuit, In in such a case, the nitrous oxide sees its flow increase and the patient is supplied with gas
not breathable. We can easily understand the danger that can result.

 The object of the present invention is to remedy the drawbacks of the otametric blocks according to the prior art and the gas mixer or generator according to the invention is designed so that it contains a plurality of intrinsic safety means, thus iVne can operate only in the presence of both gases simultaneously e. at a pressure which ensures a minimum percentage of oxygen.

 The gas mixer according to the present invention allows both adjustment of the titer of the gas administered and of its pressure.

 The intrinsic safety circuit incorporated in the gas mixer of the present invention is arranged such that two volumes of the same value are alternately filled each of the two gases at a known pressure which may be different. The gas resulting from the mixture is therefore composed of two parts, the ratio of which is that of the two volumes of gas expanded at the operating pressure, that is to say that of their absolute pressures. To obtain the same total volume at each cycle, it is therefore sufficient for the sum of these absolute pressures to be constant. A particularly simple solution, according to the present invention, consists in using two spring and diaphragm regulators mounted in opposition so that the total length of the springs remains constant. The alternative filling of the two chambers is obtained by a set of valves and the two chambers are the two sides of a piston with sealing or membrane joints. The speed regulation is carried out by throttles and the minimum operating pressure of one of the two gases can be limited, which makes it possible to define a minimum percentage threshold for this gas. Conventionally, the selected threshold is 21S oxygen.

 According to the present invention, the gas mixer for anesthesia and resuscitation apparatus provided with at least two gas inlets comprises a pneumatic circuit with sequential supply consisting of two coupled regulators located downstream of the gas inlets and supplied by separate lines, said regulators conveying each gas by a respective line in a multi-way valve with two stable positions, where, in one or the other position of the valve, one or the other chamber of a jack with free piston, connected by a pipe to said valve, is alternately filled with one or the other gas while simultaneously the opposite chamber is exhausted, the escaping gas passing through the valve and terminating in the through an exhaust pipe in a second safety valve from which it is transported by a pipe in a constriction before accumulating in a buffer tank for receiving each gas and whose p reduction is limited by a stop device and a third safety valve, the gas mixture delivered from the buffer tank then passing through another regulator and being finally introduced into a fourth safety valve before being delivered to a patient.

The present invention may also have the following characteristics, taken individually or in all their technically possible combinations:
the mixer further comprises, on each pipe interposed between the multi-way valve and each chamber of the free piston cylinder, a speed regulation assembly both of the intake gas and of the exhaust gas of each respective chamber
- the speed regulation set includes two similar regulation devices, one for each direction of operation,
- Each regulating device has a body comprising a piston rod provided with a central seal, said rod being held in the middle position by one or more springs and carrying rolling throttles placed one on the circuit of intake and the other on the exhaust system;
- The two coupled regulators are controlled by a single rod assuJettie by any suitable device chosen from a cam, a lever, a screw and a nut and similar means;
- the second safety valve comprises an operating means which acts on its slide balanced by a spring when the pressure exceeds a predetermined value
- The third safety valve whose drawer is also subjected to a spring also comprises an actuating means and is connected to one of the gas inlets;
- the stop device is a means of gas exhaust,
- the safety valve is a multi-way valve comprising a body provided with grooves and 7 supply orifices where a rod called a drawer provided with gaskets and orifices slides ending in a piston or a membrane pushed in one direction by a spring and receiving in the other direction the necessary supply pressure;
- A synchronization link connects the multi-way valve to each end of displacement of the piston.

Various advantages and characteristics of the present invention will emerge from the detailed description below made with reference to the appended drawings in which
Fig.1 is a block diagram of the gas mixer according to the present invention;
Fig.2 is a longitudinal section of two coupled regulators;
Fig. 3 is a longitudinal section of the speed regulation assembly,
Fig.4 is a longitudinal section of a safety valve.

 In the block diagram of FIG. 1, the gas mixer according to the present invention is generally designated by 1. The mixer 1 comprises two gas supply lines or gas inlets 2 and 3 delivering each respective gas in two regulators 4 and 5. Two pipes 6,7 start from each regulator 4,5 to end up in a multi-way valve 8. The multi-way valve 8 is connected by two lines 12,13 with a piston 11 with piston 25 moves erating in two chambers 9 and 10. Each respective gas is supplied sequentially and not simultaneously. For each line 12,13 there is provided a speed control assembly 24 which will be described in more detail below. The piston 25 arriving at the end of its travel in one or the other chamber 9, 10 switches the multi-way valve 8 via the synchronization assemblies 41 and 42. Each gas which escapes sequentially through the line 14 is brought to a second safety valve 15, the structure of which will be described in detail below. The gas leaving the second safety valve 15 is conveyed through a pipe 16 in a constriction 17 before accumulating in a buffer tank 18 for receiving each gas. The pressure in the buffer tank 18 is limited by a device for stop 19 and by a third safety valve 20, the operation of which will also be described in more detail below.

The gas mixture located in the buffer tank 18 which is at the pressure and at the correct titer is finally sent to another regulator 21 and is introduced into a fourth safety valve 22 before being delivered to a patient at 23.

 The multi-way valve 8 is a valve with two stable positions, The gases each arriving at one of the orifices of the valve 8 are directed in turn to the side of the jack 11 which is assigned to it while the other side of said jack 11 is connected to the exhaust where a throttle laminates the flow and regulates it. The multi-way valve 8 prevents any possibility of direct passage between the arrivals of the two gases.

The piston 25 opposes a continuous barrier and its presence Sié that of the valve 8 makes aue each quantum of gas can not go to the exhaust only after having passed through one of the two chambers 9 or 10. The throttle 17 mine the exhaust therefore regulates the flow rate, in the case where the pressure of one of the chambers 9 or 10 of the cylinder is appreciably higher than the other, there is the risk of a sudden departure of the piston 25 when the high pressure is allowed since the # uth side is at a lower pressure. To prevent such a sudden departure of the piston 25 there is provided according to the present invention a speed regulating assembly 26. The regulating assembly speed 24 is felt more in detail in Figure 3. This assembly includes two regulating devices 40 having the same structure. Each regulating device 40 has a body 25 ′ comprising a piston rod 26 provided with a central seal 27, said rod 26 being held in the middle position by one or more springs 28 29, rolling throttles 30% 31 one placed 30 on the intake circuit 32, 33 and the other 31 on the exhaust circuit 34, 35. The operation of such a speed control assembly 24 is as follows: in direction I of operation of the jack, the engine gas coming from the valve 8 enters through the orifice 33 crosses the throttle 30 comes out at 32 from where it goes towards the driving chamber concerned; thus, the side 43 of the piston 26 is at the pressure of the chamber being filled. On the other hand, the exhaust gas coming from the chamber being emptied from the jack 11 enters through the orifice 35 passes through the rolling 31 and comes out through the orifice 34. Thus the side 44 of the piston 26 is under the pressure of the chamber being emptied. Operation is normal when the pressure on the intake side is slightly higher than that on the exhaust side so that the speed of the cylinder is regulated. This is achieved by constantly throttling the exhaust circuit.

 It is possible to have significant differences in pressure on both sides of the cylinder, in this case, there is either a very sudden movement or a delayed movement. With the device described above, the piston 26 moves as a function of the existing pressure state and increases the value of the two rolls 30 and 31. If the admitted pressure is higher than the exhaust pressure, this therefore delays the pressure drop on the exhaust side and delays the pressure build-up on the intake side. If the opposite appears, the inlet speed is increased and the pressure drop speed is increased on the exhaust side. In the direction of operation illustrated in FIG. 3, the device must be reversed to avoid accentuation of the deviations. This is the reason why a second regulating device similar to the first device is provided, the two regulating devices. 40 being connected, suitably by non-return valves 45 placed in such a way that for each direction of operation only the appropriate equipment is concerned.

 From the description above, it is easy to understand that in a position of the multi-way valve 8, one of the gases is conveyed by the line 12 to one of the chambers 10 of the jack 11 with free piston 25 while the passage of the other gas is closed off and the other chamber 9 of the cylinder ll is exhausted through the valve 8 along the line 13. In the other position the opposite occurs, the gas which was previously closed this time feeds the chamber 9 of the actuator la through the line 13 while the other gas which previously supplied the chamber 10 is this time closed and the chamber 10 is exhausted through the line 12. L exhaust in the pipe 14 of one and the other gas leads to a second safety valve 15 which blocks the flow of gas in the event of too low a pressure.

Each gas sent into the pipe 16 passes through a constriction 17, the adjustment of which gives the flow rate and accumulates in the buffer tank 18, the volume of which is sufficient to absorb variations in titre, the pressure of the buffer tank 18 being limited by the device 19 and the safety valve 20. The gas mixture leaving the buffer tank 18 passes through the pressure reducer 21 which reduces the pressure to that necessary for the use for the patient by means of the safety valve 22 which when the pressure drops below a safety threshold puts the patient in direct communication with the air as illustrated in 40?, the spring 62 then acting to allow such communication
The safety valve 15 placed on the exhaust 14 only opens when the pressure is above a predetermined value and remains closed otherwise.

 thus, the movement of the piston 25 can only take place if the pressure on the side during admission is at least equal to the setting pressure. Given that the two regulators 4 and 5 are coupled in such a way that the length of their compression springs therefore controls the force of said springs and therefore finally the sum of their calibration pressures is constant, it is easily understood that all of these regulators 4 and 5 and valve 15 limits the minimum percentage of one of the two gases to a chosen value.

 Such an embodiment ensures a minimum percentage of oxygen and even protects against a reversal of connection of the gas inlet pipes since even in this case, the minimum of oxygen making the gas breathable is supplied.

 The resulting gas is stored in the reservoir 18 and can finally supply the patient with 23 via the valve 22 controlled by a membrane which, in the absence of pressure in the reservoir 16 leaves an air inlet available. On the other hand, if the pressure rises above the preset value, the supply to the appliance is cut off using the safety valve 20 or, alternatively, one of the gases is cut off and in this case, the mixer according to the present invention stops until a demand for gas is felt.

 FIG. 2 represents an example of a device for controlling the regulators 4 and 5. These devices are conventionally formed of a membrane 47,48 receiving the relaxed pressure balanced by a spring 49,50 and according to whether the force resulting from said pressure is higher or not than that of the respective spring, a displacement occurs which closes or opens the inlet valve upstream. The resulting pressure being a function of the force of a spring and the latter varying linearly with the length of said spring, it is easy to understand that if two similar regulators are mounted face to face and if the length of the springs is adjusted by the same rod 51, their length is maintained constant and therefore also the sum of their pressure. This is relative pressure but it is the same for absolute pressure since it only varies by a constant. The single rod 51 controls the two regulators 4 and 5 which are of a conventional structure and which include two membranes 47, 46 and two springs 49, 50, the single rod 51 is itself fixed by a suitable device which can be a screw, a cam, a nut and in general any suitable means shown diagrammatically at 63.

 It is possible to plan to have the two regulators 4 and 5 next to each other.

 FIG. 4 represents a safety solution for a safety valve of the device according to the present invention. In the majority of cases, the mixer supplies a separate respirator or, as indicated above, the device is shutdown when one of the two gases runs out. So that in this case the respirator can nevertheless be supplied with breathable gas, the outlet of the mixer is effected with a multi-way valve controlled by its own outlet pressure. If this is sufficient, the valve opens and supplies the outlet circuit at 23 to the patient.

If, however, the mixer pressure is insufficient, the valve closes and the breathing circuit is put into communication with the ambient air. In Figure 4, a multi valve
safety ways includes a body 52 provided with grooves and supply orifices 55 and r, ~ a rod 53 sliding in the body # 2, iaqThe rod is provided with an * ancheite seal and ori ice and is terminated by a piston or a membrane 57 pushed by a spring 54 receiving the necessary supply pressure. In FIG. 1, 58 designates a means for operating the valve 15 which can be a piston or a membrane and which operates the valve balanced by a spring 59 when the pressure exceeds a predetermined value, if this is not the case, the valve 15 is closed while always being subjected to the spring 59
The device 19 is an exhaust which, when an overpressure develops at the level of the buffer tank 18a, allows the quantity of gas under overpressure to escape to the atmosphere. It is therefore an additional safety means. It should be noted that the safety valve 15, the safety valve 20 as well as the safety valve 22 has a similar structure but that their operation is not not identical.

 The valve 20 is connected by a set of pipes 60, 61, shown in dashed lines in FIG. 1, to the gas inlet 3 in order to admit additional gas when necessary.

 It is easily understood that the piston 25 at each end of travel switches the multi-way valve 8 by means of the synchronization assemblies 41 and 42.

 The sequential intrinsic safety gas mixer according to the present invention is of a simple embodiment and provides excellent results.

 In Figure 3, arrow A means direction I of the cylinder exhaust, arrow B direction I towards the cylinder inlet, arrow C direction II towards the cylinder inlet, arrow D direction II of the exhaust cylinder, arrow E in direction I of the valve, arrow F in direction Il towards the valve, arrow G in direction I towards the valve and arrow H in direction Il of the valve.

Claims (10)

 1 Gas mixer for anesthesia and resuscitation device with at least two gas inlets (293) characterized in that it comprises a pneumatic circuit with sequential flow consisting of two coupled regulators (4,5) located downstream gas inlets (2,3) and supplied by separate pipes, said regulators  (4,5) conveying each gas through a respective pipe (5, y7) in a multi-way valve (8) with two stable positions where in one or the other position of the valve (8), one or the other chamber (9,10) of a free piston cylinder (11) (25), connected by a line (12,13) to said valve (8), is alternately filled with one or the other gas while simultaneously the opposite chamber (9, 10) is exhausted, the escaping gas passing through the valve (8) and terminating via an exhaust pipe (14) in a second safety valve (lez) from which it is transported by a pipe (16) in a constriction (17) before accumulating in a buffer tank (18) of the reception of each gas and whose pressure is limited by a shut-off device (19) and a third safety valve (20), the gas mixture supplied from the buffer tank (18) then passing through another regulator (21) and finally being introduced into a fourth valve security (22) before being delivered in (23) to a patient.  2. Mixer according to claim l, characterized in that it further comprises, on each pipe (12,13) interposed between the multi-way valve (8) and each chamber (9,10) of the jack (11) with free piston (25) a speed regulation assembly (24) for both the intake gas and the exhaust gas of each respective chamber (9,10).  3.Mixer according to one of claims 1 or 2, characterized in that the speed regulation assembly (24) comprises two similar regulation devices (403un for each direction of operation.  4.Gas mixer according to any one of claims 1 to 3, characterized in that each regulating device (40) has a body (25 ') comprising a piston rod (26) provided with a seal central (27), said rod (26) being held in the middle position by one or more springs (28, 29) and carrying rolling throttles (30, 31), placed one (30) on the circuit d intake (32, 33) and the other (31) on the exhaust circuit (34, 35).  5. Mixer according to claim 1, characterized in that the two regulators (4. 5) coupled are controlled by a single rod (51) assuJettie by any suitable device chosen from a cam, a lever, a screw and a nut and similar means (63).  6. Mixer according to claim 1, characterized in that the second safety valve (15) comprises an operating means (58) which acts on its slide balanced by a spring (59) when the pressure exceeds a predetermined value.  7. Mixer according to claim 1, characterized in that the third safety valve (20) whose slide is also subjected to a spring (59) also comprises an actuating means (58) and is connected to one of the gas inlets (3).  8. Mixer according to claim 1, characterized in that the stop device (19) is a gas exhaust means.  9. Mixer according to claim 1, characterized in that the safety valve is a multi-way valve comprising a body (52) provided with grooves and supply orifices (55, 56) where a rod slides (53 ) called drawer provided with Seals and orifices terminated by a piston or a membrane pushed in one direction by a spring (54) and receiving in the other direction the necessary supply pressure.  10. Mixer according to claim 1, characterized in that a synchronization link (41,42) connects the multi-way valve (8) at each end of displacement of the piston (25).