Apparatus For Delivering A Predetermined Volume Of Fluid At Regular Intervals

Abstract

Fluid delivery apparatus for intermittently delivering a selected volume of fluid in which a resilient device is compressible by pressure of the fluid in a pressure chamber, a valve mounted on the resilient device being opened to deliver the fluid when a predetermined degree of compression has been achieved and being subsequently closed when the falling pressure in the pressure chamber permits a predetermined expansion.

Description

This invention relates to apparatus for providing an intermittent flow of fluid, and is particularly useful in devices used for administering artificial ventilation in which air, oxygen or other suitable gas mixture intermittently inflates a patients lungs.

It is an object of the present invention to provide apparatus which is simple and which intermittently delivers a fixed volume of fluid.

SUMMARY OF THE INVENTION

The present invention is fluid delivery apparatus including a pressure chamber, means for introducing fluid under pressure into the chamber, resilient means in the chamber compressible by the fluid, a valve operable upon compression of the resilient means and means for actuating the valve after a pre-determined movement thereof to permit fluid to exhaust from the chamber.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing, the single FIGURE of which diagrammatically illustrates an artificial ventilator for use with a human patient.

Referring now to the drawing, a ventilator for use with a human patient who cannot, or who finds it difficult to, breathe for himself comprises a pressure chamber 10 in which is mounted a resilient bellows device 11 and a valve 12.

The chamber 10 is provided with a gas inlet 14 and is gas tight at the pressures normally encountered in use.

The resilient bellows device 11 is sealed and at one end 17 is fixed to a bracket 16 on the walls of the chamber 10. The other end 18 of the bellows device 11 is free to move in the chamber and carries the valve 12.

The valve 12 includes two valve members, a valve cup 19 and a valve disc 20. The valve cup 19 is mounted on the end 18 of the bellows device 11 and moves with it. The interior of the valve cup 19 connects with an outlet line 21. The valve disc 20 is mounted by radial springs 24 on brackets 25 extending from the end 18 of the bellows device 11, the radial springs 24 providing a small bias of the valve disc 20 away from the valve cup 19. A pin 26 extends from the valve disc 20 on its side remote from the valve cup , passes through holes 27 in a bracket 28 and a lever 29, and is provided with collars 30 which are large enough to engage the edges of the holes 27 and thus act as stops to limit movement of the pin 27 and valve disc 20 towards the right and left respectively as seen in the drawing. The lever 29 has a fixed pivot 32 at one end and at its other end engages a cam 33 rotatable by a knurled control knob 34.

The outlet line 21 branches into two lines 35 and 36, one of which 35, is provided with a flow control valve 38 and the other of which, 36, terminates in a bellows valve 39.

In use the gas inlet 14 is connected to a suitable supply of pressurised gas, for example a pressure bottle, the line 35 is connected to the patient as the inspiratory line and the expiratory line 40 from the patient terminates at the bellows valve 39. Assuming that initially the chamber 10 is not pressurised, the bellows device 11 is expanded so that the valve cup 19 is in engagement with the valve disc 20 whose movement to the right has been restricted by engagement of a collar 30 with the bracket 28. As the pressure in the chamber 10 builds up, the bellows device 11 is compressed and its end 18 moves to the left as seen in the drawing. The valve disc 20 remains in engagement with the valve cup 19 as the pressure differential between the sides of the valve disc 20 maintaining such engagement is greater than the force exerted by the radial springs 24 tending to part the valve disc and cup. Compression of the bellows device 11 continues until engagement of the lever 29 with a collar 30. No further movement then occurs until the pressure in the chamber 10 has increased slightly and the force due to the pressure differential between the faces of the end 18 of the bellows device over the annular area around the valve cup 19 has increased to compensate for the force on the valve disc that has been taken up by the lever 29 and is no longer effective on the bellows device. When the pressure has built up sufficiently the valve springs open under the influence of the springs 24 and the increased pressure on the inside of the valve cup 19. The gas in the chamber passes to the outlet line 21 and thence through the line 36 to the bellows valve 39, to close the expiratory line from the patient, and, via the valve 38 to the patient to inflate the patient's lungs.

Gas flowing from the outlet line 21 causes the pressure in the chamber 10 to decrease causing a corresponding expansion of the bellows device. As the end 18 of the bellows device moves to the right it takes with it the brackets 25 and the valve disc 20 until the collar 30 engages the bracket 28. The bellows device continues to expand and closes the valve cup 19 against the stationary valve disc 20.

The pressure on either side of the bellows valve 39 now equalises, the valve 39 opens and the patient's lungs deflate. Meanwhile pressure in the chamber 10 is increasing and, when the valve 12 reopens deflation is terminated and inflation of the patient's lungs recommences.

It should be noted that the ventilator is essentially a constant volume device opprating as it does on pressure differentials with a constant volume, i.e., the pressure chamber. The volume passed in each cycle can however be varied by adjustment of the knob 34 and thereby of the cam 33 and the lever 29 thus effectively adjusting the travel of the pin 26. It should also be noted that the ventilator is extremely simple and is stable in both the open and closed positions.

Modifications may be made to the embodiment described. It may be desirable to ensure positive operation of the valve 12 by including in the line 21 a pressure opening non-return valve 41. Also it may be convenient to have access to the interior of the bellows to permit pressurisation thereof during manufacture for calibration purposes. Moreover the pressure chamber may be fitted with a heating element to vapourise water in the chamber. This arrangement permits humidification of gases leaving the chamber as well as sterilisation of the apparatus by boiling.

The ventilator may be adapted so that its operation is initiated by an external signal such as a change in pressure at the outlet caused by attempts by the patient to breathe. This can be achieved by rendering the stop involving the lever 29 inoperative, limiting the gas pressure in the chamber, and providing a conventional lever arrangement to change the pressure change, caused by a patient attempting to breathe into a force sufficient to open the valve 12.

The invention has been described in relation to a ventilator but is equally applicable in any system where intermittent supply of specified volumes of fluid is desired.

Claims

We claim:

1. Fluid delivery apparatus including:

a pressure chamber;

means for introducing fluid under pressure into the chamber;

resilient means in the chamber compressible by the fluid as the fluid pressure in the chamber increases;

a valve mounted on the resilient means and movable upon compression of the resilient means within the chamber; and

means for actuating the valve after a predetermined movement thereof to permit fluid to exhaust from the chamber.

2. Apparatus as claimed in claim 1, in which said valve comprises two members mounted on the resilient means, said two members being movable relative to each other and biased apart.

3. Apparatus as claimed in claim 2, in which said actuating means includes at least one stop to limit movement of one of the valve members in the chamber.

4. Apparatus as claimed in claim 3, in which said stop is variable.

5. Apparatus as claimed in claim 4, in which said resilient means comprises a bellows device, one end of which is fixed in the chamber and the other end of which carries the valve members.

6. Apparatus as claimed in claim 5 in which said one of the valve members is a valve disc and the other of said valve members is a valve cup secured to said other end of the bellows device.

7. Apparatus as claimed in claim 6, comprising a fluid outlet line from the chamber which communicates with the interior of the valve cup and includes a further pressure opening non-return valve.

8. Apparatus as claimed in claim 7, in which the outlet line branches, one branch including a flow control and serving as a line to exhaust fluid under pressure from the chamber and the other branch terminating in a valve which closes said other branch during exhaust of fluid under pressure from the chamber via said one branch, and which opens said other branch after exhaust of fluid under pres-sure from the chamber is terminated.

9. Apparatus as claimed in claim 1 in which said chamber includes means for evaporating water.

10. Apparatus as claimed in claim 8, wherein said other branch is adapted to receive input fluid to the chamber when the valve terminating said other branch is open.

11. Apparatus as claimed in claim 1, in which said resilient means comprises a bellows device, one end of which is fixed in the chamber and the other end of which carries the valve.

12. Apparatus as claimed in claim 11, in which said valve comprises two members mounted on the resilient means, said two members being movable relative to each other and biased apart, one of the valve members being a valve disc and the other of said valve members being a valve cup secured to said other end of the bellows device.

13. Apparatus as claimed in claim 1, comprising a fluid outlet line from the chamber which is operatively controlled by the valve, the outlet line branching into two branches, one branch including a flow control and serving as a line to exhaust fluid under pressure from the chamber and the other branch terminating in a valve which closes said other branch during exhaust of fluid under pressure from the chamber via said one branch, and which opens said other branch after exhaust of fluid under pressure from the chamber is terminated.