GB2164571A - Pressure limiting valve assembly - Google Patents

Abstract

A unitary valve assembly 1 particularly for use with lung ventilators includes an adjustable pressure limiting device 80 and also a pressure relief valve 90. Should the normal flow of exhaled gas from a patient passing through the pressure limiting device be impeded, then the pressure of said gases will operate the pressure relief valve, thereby permitting the escape of the exhaled gases from the assembly 1. <IMAGE>

Description

SPECIFICATION Improvements in valve assemblies The present invention relates to unitary valve assemblies and more particularly to unitary valve assemblies for use with lung ventilators.

The use in lung ventilators of adjustable pressure limiting devices is known. The purpose of the adjustable pressure limiting device (APL device) is to offer an adjustable resistance to the flow of expired gases emanating from a patient during the expiratory phase of a respiratory cycle. The APL device includes a spring loaded valve which controls the flow of expired gases from an inlet of the device in communication with the patient to an outlet usually connected to a scavenging system.

The scavenging system removes the expired gases which frequently contain anaesthetic agents.

Frequently, the outlet of the device is connected to the scavenging system by a flexible rubber hose. It has been known for such a hose to become badly positioned and obstructed such that the flow of expired gases is impeded, thereby causing a buildup of pressure in the hose and in the device. This pressure build-up can prevent correct operation of the spring loaded valve with possible dire results to the patient.

It is known to obviate this problem by incorporating a pressure relief valve in the flexible hose which operates to release expired gases when the pressure build-up in the hose exceeds a predetermined value.

However, since the fitting to a hose of such pressure relief valves is not universal, then it is always possible for a technician to connect a hose to the outlet of the device which does not incorporate a pressure relief valve.

It is known from U.K. Patent No. 1202606 to provide a combined pressure regulating and relief valve for fluid systems requiring accurate controlor which involve structurally fragile elements.

However, the relief valve is complicated and comprises two telescopic members which enable a desired proportional relationship to be established between regulated pressure and pressure relief.

It is an aim of the present invention to provide a valve assembly which incorporates a pressure relief valve and an adjustable pressure limiting device in one unit which valve assembly is simple in operation and economic to manufacture.

According to the present invention, a unitary valve assembly comprises a first valve for controlling the flow of gas from an inlet to a first outlet of the assembly and a second relief valve for permitting the exit of gas from the assembly from a second outlet when said first outlet is obstructed and the pressure of the gas within the assembly exceeds a predetermined value, in which both the first valve and the second relief valve each include a valve head, resilient means for biasing the valve head towards a a cooperating valve seat and means for varying the pressure exerted by the resilient means on its respective valve head.

An embodiment of the invention will now be described by way of example, reference being made to the Figures of the accompanying diagrammatic drawings, in which:~ Figure 1 is a vertical cross section through a unitary valve assembly; Figure 2 is a vertical cross-section through a main hollow tubular body forming part of the valve assembly of Figure 1; Figure 3 is an elevation of the main hollow tubular body of Figure 2; and Figure 4 is a vertical cross-section through a tubular regulator body forming part of the valve assembly of Figure 1.

Referring first to Figures 1 to 3, and in particular to Figure 1, a unitary valve assembly 1 includes an adjustable pressure limiting device 80 for controlling the flow of expired gases from a patient through the assembly and a pressure relief valve 90.

The unitary valve assembly 1 comprises a main hollow tubular body 2 which on its external surface is formed adjacent each end with grooves dimension to receive 0 ring seals 3, 4. At its upper (as shown) end 7 the body 2 has a flange 6 defining on its lower face an abutment 8. At its lower (as shown) end 9, the body 2 has a threaded portion 10.

Between its upper and lower ends 7, 9, the body 2 is formed with a groove 5 dimensioned to receive a retaining clip 12 and also a portion formed by spaced ribs 16.

Internally, the body 2 has at its upper end 7 a threaded portion 18which leads into a right cylindrical portion 20. Adjacent its lower end 9, the body 2 is formed with a recess 22.

Referring also to Figure 4, screw threaded into the upper end 7 of body 2 is a tubular regulator body 24.

Regulator body 24 has on its external surface screw threads 26 for cooperating with the screw threads 18 of the body 2; an abutment surface 28; and a groove dimensioned to receive an 0 ring seal 30.

Internally, the body 24 is formed with a counterbore 32 at its upper (as shown) end, a main chamber 34 including a threaded portion 35, a cylindrical bore portion 36 and a lower section 38 for supporting an adjustor 66 forming part of the adjustable pressure limiting device 80. Formed in the wall of the main chamber 34 below the screw thread portion 35 are through passages 40 which define outlets for gas when the pressure relief valve 90 is activated. The lower section 38 includes three segmental passages 41 (only one shown) which permit the flow of gas from the lower section 38 towards the cylindrical bore portion 36 as will be explained.

Referring in particulartothe pressure relief valve, this comprises an adjustor cap 42 screw threaded tightly into the threaded portion of the main chamber 34 of body 24. The adjustor cap 42 has a central through bore into which slides the tail 44 of a valve head 46. The adjustor cap 42 is formed with an annular groove adapted to receive the upper (as shown) end of a compression spring 48 the other, lower end of which bears down on the valve head 46, thereby biasing the valve head 46 towards a cooperating valve seat 50 positioned in the cylindrical bore portion 36.

To vary the pressure at which the pressure relief valve operates the adjustor cap 42 can be screwed towards or away from the valve head 46 thereby varying the force exerted on the valve head 46 by compression spring 46.

A cover43 is a press-fit in the counterbore 32 to prevent unauthorised tampering with the adjustor cap 42.

It will be apparent that under normal operating conditions the pressure relief valve 90 will remain closed with the valve head 46 in contact with the valve seat 50. However, as will be explained, the pressure relief valve 90 becomes operational should a blockage occur to prevent normal exit of expired gases from the valve assembly 1.

Referring now to the adjustable pressure limiting device, this comprises a valve seat 60 positioned in recess 22 which cooperates with a valve head 62 having a tail 64 slidable within the bore of the adjustor 66. The adjustor 66 is screw threaded in lower section 38 of body 24. Depending from the adjustor 66 is a compression spring 68. As shown in Figure 1, with the body 24 in its closed condition the free end of spring 68 will engage the valve head 62.

However, under normal conditions of use the free end of the spring 68 will be spaced from the valve head 62. A further compression spring 70 also extends between the valve head 62 and a lower facing abutment formed in the lower section 38 of the body 24.

Again, it will be apparent that the springs 68,70 bias the valve head 62 towards its closed position against the valve seat 60.

To alterthe pressure being exerted by spring 68 against the valve head 62 when the body 24 is screwed fully into the body 2, the adjustor 66 is screwed downwardly (as shown) to increase pressure or upwardly (as shown) to decrease pressure. This adjustment is effected during manufacture and prior to the assembly together of the body 2, and the body 24. The threads of adjustor 66 bind so as to avoid loosening of the adjustment.

To reiterate, in normal use the spring 68 does not engage the valve head 62. However, should the body 24 be inadvertently screwed fully into the body 2, the pressure of the patients expired breath can still lift the valve head 62 against the combined pressure of springs 68,70.

The main hollow tubular body 2 is assembled within a swivel outlet body 71 and the seals 3,4 engage the inside surface of the swivel outlet body 71 in a gas tight manner.

When the valve assembly 1 is assembled ready for use, the body 24 can be screwed into the tubular body 2 until the abutment surface 28 engages the upper end 7 of the body 2. The O-ring seal 30 engages the surface of the right cylindrical portion 20 in a gas tight manner. Finally, the threaded portion 10 is screwed into a pipe (not shown) through which exhaled gases pass from a patient.

The lower end 9 of the tubular body 2 thus becomes an inlet for gases exhaled by the patient and the open right hand (as shown) end 72 of the swivel outlet body acts as an outletforsaid exhaled gases.

In use, exhaled gases from a patient enter the valve assembly 1 via the inlet at the lower end 9 of the body 2 such that when the patient exerts sufficient force, the valve head 62 will be lifted from it cooperating valve seat 60 against the bias of spring 70, to permit the flow of the exhaled gases from the assembly 1 via outlet 72. Under normal working conditions, only spring 70 is acting on the valve head 62 and the expired pressure is determined by the setting of the regulator body 24, as set by the user. Spring 68 will become effective if the patient's expired pressure reaches the maximum (factory) set safety pressure, and in this way spring 68 acts as a pressure relief in the circumstance that the body 24 has been set in the fully shut down position.

Under normal working conditions the regulator body 24 cannot be unscrewed completely from the body 2 by virtue of the retaining clip 12. The length of the co-operating threads is such that between 2 and 2) turns of the regulator body 24 gives the range of adjustment normally required to spring 70.

It will be appreciated that flexible hosing is attached to the swivel outlet body such that said gases when leaving the outlet 72 pass along the hose towards a scavenging system. Should the hose be blocked for any reason to impede the flow of exhaled gases through the hose, then the pressure in the hose and the valve assembly 1 will increase until the force exerted by said exhaled gases lifts the valve head 46 from its seat 50 against the bias of spring 48, thereby allowing the gases to pass from the valve assembly via segmented passages 41 and through the passages 40 formed in the wall of the main chamber 34.

The advantage of the particular embodiment described above is that it provides a valve assembly which incorporates an adjustable pressure limiting device and a pressure relief valve in the same unitary body and thereby removes any danger that the exhaled gases, should their flow be blocked, will affect the adjustable pressure limiting valve 80 to such an extent that it will cause harm to a patient.

Claims (4)

1. A unitary valve assembly comprising a first valve for controlling the flow of a gas from an inlet to a first outlet of the assembly and a second relief valve for permitting the exit of gas from the assemblyfrom a second outlet when said first outlet is obstructed and the pressure of the gas within the assembly exceeds a predetermined value, in which both the first valve and the second relief valve each include a valve head, resilient means for biasing the valve head#towards a cooperating valve seat and means for varying the pressure exerted by the resilient means on its respective valve head.

2. A unitary valve assembly as claimed in claim 1, in which the second relief valve is mounted in a regulator body attached to a main tubular body housing the first valve and in which the main tubular body is assembled within a swivel outlet body in a gas tight manner.

3. A lung ventilator including a unitary valve assembly as claimed in claim 1 or claim 2.

4. A unitary valve assembly constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the Figures of the accompanying drawings.