A valve of this kind is shown and described in US-PS 5 265 594. It is highly important, particularly in the supply of gas to a patient on a ventilator, to ensure that the amount of gas supplied through such a valve is regulated with great accuracy and repeatability. In order to achieve this, the membrane must lift off the valve seat, parallel to same, every time the valve opens. When the membrane is closed with by the end of the plunger, which is flat with a surface area somewhat larger than the surface area of the valve seat, the end of the plunger must press against the valve seat with an evenly applied force. This can sometimes be difficult to achieve, since the valve seat and plunger are not always perfectly aligned. If their positions are disturbed so e.g.

the plunger tilts in relation to the valve seat, this tilted, often uncontrolled, plunger position can result in leakage between the membrane and valve seat and to impaired regulation of gas flow through the valve. Even small angular deviations can greatly impair regulation of the flow of gas.

The purpose of the invention is to achieve a valve of the initially described kind with which a flow of gas can be regulated, using simple and, accordingly, inexpensive means,

with great accuracy and repeatability and which forms a hermetic seal when in the closed position.

This purpose is achieved with a rigid, flat plate, arranged opposite the valve seat, said plate having a surface area which is at least equal to the surface area of the valve seat, the plate being arranged in such a way that it follows the membrane's axial movements and can be tilted in relation to the plunger's longitudinal axis. The part of the plunger end acting on the membrane has a surface area which is smaller than the surface area of the valve seat. As a result of the surface area of the part of the plunger end acting on the membrane and on the plate respectively, the rigid plate is able to tilt towards the plunger when the valve opening is opened or closed respectively, thereby compensating for any misalignment of the plunger or valve seat, and controlled, repeatable membrane movement is accordingly achieved. The end of the plunger, according to the invention, can advan- tageously be convex.

According to one advantageous embodiment of the valve according to the invention, the plate is part of the membrane. The plate can be advantageously integrated into the membrane or also glued onto it.

According to an additional embodiment of the valve according to the invention, the plate is part of a spiral-shaped washer which presses firmly against the membrane, said washer being mounted inside the valve body. As a result, the washer and, accordingly, the plate are a separate part which can be replaced when needed without any need to replace the membrane as well.

According to the invention, the plate can also be part of leaf spring which presses firmly against the membrane, said

leaf spring being mounted inside the valve body. Here, the plate can also be replaced when needed.

The spiral-shaped washer and leaf spring can be advan- tageously arranged on the side of the membrane facing away from the valve seat.

According to the invention, the plate can be made of metal, preferably spring steel, about 0.15 mm thick.

The invention will be explained in greater detail below, referring to the attached drawings in the figures which show FIG. 1 A diagrammatic sketch of a valve with a closure part, according to the invention, in an open position; FIG. 2 A valve, according to FIG. 1, with the closure part in a closed position; FIG. 3 A sub-section of a valve according to FIGS. 1 and 2 in an additional embodiment of the closure section according to the invention; FIG. 4 A view of a component in the closure part according to FIG. 3; FIG. 5 Another embodiment of the component according to FIG. 4.

FIG. 1 shows, partially in cross-section, one possible embodiment of a valve, according to the invention, shown here in an open position. The valve has a valve hood 1, in which a valve body 2 is removably arranged, and a solenoid 3 permanently attached to the valve hood 1. The valve body 2 is provided with a through channel to pass the flow of a gas to be regulated, said channel being subdivided into an inlet 4, an outlet 5 and a valve opening 6 between same. A tensioned membrane 7, which is mounted inside the valve body 2 and which serves to regulate the flow of fluid, e.g. a gas, to a

patient when the patient is on a respirator (not shown) is arranged opposite the valve opening 6. A rigid, flat plate 9 is attached to the side of the membrane 7 facing away from the valve seat 8 of the valve opening 6. The surface area of the plate 9 is somewhat larger than the surface area of the valve seat 8. In the FIG., the end 13 of the solenoid's 3 plunger 10 presses against the plate 9, said plunger end 13 being advantageously convex.

In order to achieve an open valve position, as shown in FIG.

1, larger or smaller amounts of current are applied to the solenoid 3 across the cable 11, causing the plunger 10 to retract into the solenoid body, i.e. downward in this FIG. 1, whereupon the membrane 7, due to the membrane material's elasticity and the force of the application pressure, can be made to lift off the valve seat 8 in the desired manner, enabling gas to flow through the valve opening 6 via the outlet 5 and on to the patient. When current to the solenoid 3 is turned off, power to the solenoid plunger 10 is also turned off, whereupon the plunger 10, through the action of pressure springs 12, presses the rigid plate 9 and, accor- dingly, the membrane 7 against the valve seat 8 with suf- ficient force to shut the valve opening 6, as shown in FIG.

2. This therefore achieves a desirable safety feature, viz.

valve shutdown in the event of a power failure, thereby preventing an uncontrolled flow of gas to the patient.

Accurate and repeatable membrane movement, i.e. flow regulation and closure of the valve opening, is achieved without difficulty, as a rule, when the plunger's 10 longi- tudinal axis is aligned with the fictitious longitudinal axis of the part of the inlet channel 4 which opens onto the valve opening 6, as illustrated with the dash-dotted line 17 in the FIG.

If the solenoid 3 and, accordingly, the plunger 10 have been displaced out of position and shifted position, in relation

to the valve seat 8 and the membrane 7, and the membrane 7 is to lift off the valve seat 8, the membrane 7 always tips, with the aid of the plate 9 and the membrane's own elastic force, towards the convex end of the plunger 13 to a position in which the membrane during opening is parallel to the valve seat 8. When, during closure of the valve opening 6, the membrane 7 is pressed in the described manner by the plunger 10 towards the valve seat 8, this is accomplished when the plate 9 and the membrane 7 tip towards the plunger end 13 in such a way that the membrane 7 always remains parallel to the valve seat 8. When the valve is in the closed position, the membrane 7 therefore presses with an evenly applied force against the valve seat 8. In the same way as described above, accurate and repeatable membrane movement and optimal closure of the valve opening 6 are always achieved, even when the valve seat 8 and the plunger 10 are misaligned.

The same advantageous effects cited in conjunction with the descriptions of FIGS. 1 and 2 are achieved when the plate 9 is integrated into the membrane, as shown with dash-dotted outlines in FIGS. 1 and 2. The plate 9 is advantageously made of spring steel with an approximate thickness of 0.15 mm. The plate can naturally be made of some other suitable material.

FIG. 3 shows that the plate 9 can be a part of a spiral- shaped washer 14 which presses firmly against the side of the membrane 7 facing away from the valve seat 8. The washer 14, like the membrane 7, is mounted inside the valve body 2.

FIG. 4 shows the washer. FIG. 5 shows that the plate 9 can also be part of a leaf spring 15. The plate 9 and leaf spring 15 can be advantageously punched out of a washer so the washer can be mounted more firmly inside the valve body 2.

In one embodiment within the scope of the invention, the plate 9 can be attached by a hinge to the end 13 of the plunger. In another conceivable embodiment, the washer 14 and the leaf spring 15 can be arranged between the membrane 7 and the valve seat 8. In yet another embodiment, the plate 9 can be glued to the side of the membrane 7 facing the valve seat 8. In the latter two instances, either the plate 9 or the valve seat 8 is provided with a soft coating which forms a seal when the valve is in the closed position. In this embodiment, the membrane only serves to prevent the egress of gas which would otherwise flow out into ambient air.