US3561466A

US3561466A - Anesthetist{3 s ventilator

Info

Publication number: US3561466A
Application number: US700668*A
Authority: US
Inventors: Edward Carden
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-01-08
Filing date: 1968-01-08
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09

Abstract

An anaesthetist''s ventilator in the form of a valve comprising a body having a gas inlet connection for connecting to anesthetic equipment, a breathing connection for enabling a patient to breathe through the valve and an outlet to atmosphere, a valve member, and biassing means biassing the valve member to a fixed rest position in the body wherein it closes the gas inlet connection and opens the breathing connection to the outlet, the valve member being adapted, upon buildup of pressure at the gas inlet connection momentarily to be displaced against the action of the biassing means to open the breathing connection to the gas inlet connection and at least partially close the outlet, and then, as a result of consequential lowering of the pressure at the gas inlet connection, and increase in pressure in the breathing connection to return to its rest position.

Description

United States Patent [72] Inventor Edwar Ca l 3,473,529 /1969 Wallace l/65X Stockport, Cheshire, England (Cavendish 2,667,895 2/1954 251/65 House, Pries'tnall Road, l-leaton Mersey) 2,807,421 9/1957 251/360 [2 1] Appl- N 700,668 3,063,461 11/1962 137/102 1 Filed J -8,1968 3,068,856 12/1962 128/1455 P n e F b. 1971 3,449,970 6/1969 Klatt 74/89 Primary Examiner-William F. ODea 5 AN Assistant Examiner-David J. 0 Claims 2 i g Figs. Attorney-Kenwood R058 [52] U.S.Cl 137/102,

128/ l 88; 251/65,}51/213 ABSTRACT: An anaesthetists ventilator in the form of a 6 m 17/00 valve comprising a body having a gas inlet connection for con- 128/188, necting to anaesthetic equipment, a breathing connection for 142, 185, 186; 137/102, 256, 588, 1 12, 458, enabling a patient to breathe through the valve and an outlet 505.11; 251/65, 630; 74/69, 89.15, 107, 89, 99, to atmosphere, a valve member, and biassing means biassing 3, 1 the valve member to a fixed rest position in the body wherein it closes the as inlet connection and 0 us the breathin con- [56] Refe'enm c'ted nection to th e outlet, the valve memb f being adapted, upon ITE STATES PATENTS buildup of pressure at the gas inlet connection momentarily to 2,811,979 11/1957 Presnell 25 l/X be disp a d against the action of the biassing means to p 3,203,439 3/1965 B k 251 /65X the breathing connection to the gas inlet connection and at 3,265,062 8/ 1966 Hesse 251/65X least partially close the outlet, and then, as a result of con- 3,27(),763 9/1966 Kief r 251/65X sequential lowering of the pressure at the: gas inlet connection, 3,279,487 10/1966 Elam 251/65X and increase in pressure in the breathing connection, to 3,351,092 1 1/1967 lngerfield et a1 251/65X return to its rest position.

ANAESTIIETISTS VENTILATOR This invention concerns an anaesthetists ventilator, that is to say a device enablingthe respiratory system of a patient (e.g. a paralyzed anaesthetised patient) to be ventilated, i.e. connected alternately to source of gases under pressure for inspiration and to atmospheric air for expiration.

An object of the invention is to provide a construction of ventilator as aforesaid which can conveniently be employed in conjunction with conventional anesthetic apparatus, which can be manufactured comparatively inexpensively so as to be readily portable, and which is simple and efficient in operation.

With these objects in view, the present invention provides an anaesthetists ventilator in the form of a valve comprising a body having a gas inlet connection for connecting to anesthetic equipment, a breathing connection for enabling a patient to breathe through the valve and an outlet to atmosphere, a valve member, and biassing means biassing the valve member to a fixed rest position in the body wherein it closes the gas inlet connection and opens the breathing conmotion to the outlet, the valve member being adapted, upon buildup of pressure at the gas inlet connection, momentarily to be displaced against the action of the biassing means to open the breathing connection to the gas inlet connection and at least partially toclose the outlet, and then, as a result of consequential lowering of the pressure at the gas inlet connection and increasing of the pressure in the breathing connection, to return to its rest position.

The biassing means may conveniently comprise one or more permanent magnets.

The valve body may conveniently be in the form of a T- member, the crossbar of the T providing respectively the gas inlet connection and the outlet at its two ends, the leg of the T providing the breathing connection. I

The valve may conveniently comprise a spool-type valve member axially movable in the crossbar of the T and adapted to cooperate, by its ends, with seats provided by annular shoulders provided in said crossbar.

In some circumstances, it is desirable for the period and/or extend of opening of the breathing connection to the gas inlet to be adjustable or variable, and this may be achieved by providing for variation of the possible extend of movement of the valve member, e. g. by making the position of the valve seat of the outlet variable. a

In a first preferred embodiment of the invention, there are two magnets, one of which serves as an attracting magnet which acts to attract the valve member'into and tends to retain it in the rest position, and the other of which serves as a repulsion magnet acting to repel the valve member from its position closing the outlet and tending to return it to its rest position.

In a second embodiment, only ,a single magnet, preferably an attracting magnet, is provided. a

It may be desirable to provide, in the outlet, a supplementary nonretum valve serving to prevent atmospheric air entering the valve body through such outlet;

In order that the invention may be fully understood, it will be described further, by way of example, with reference to the accompanying drawings which illustrate two practical embodiment of the ventilator of the invention, it being understood that the following details are illustrative and not limitative of the scope of the invention. In the drawings:

FIG. 1 is a cross-sectional side elevation of a first embodi-' ment of the ventilator of the invention; and

FIG. 2 is a view similar to FIG. 1, but showing a second embodiment.

As can be appreciated from FIG. 1, which illustrates a simple embodiment of the ventilator, such ventilator effectively being in the form of an automatically-actuated double-acting valve.

This valve comprises a body made of a suitable nonmagnetic metal (such as aluminum alloy) or of a tough plastics material and composed of three parts namely a main T-piece 11 and two extension pieces 12 and 13 respectively. The T- piece 11 is generally of conventional appearance, and comprises a hollow crossbar l4 and a hollow leg part 15, the latter connecting with the crossbar 14 substantially midway. along the length of the crossbar 14. The leg part 15 is of slightly tapered form, having its smallest diameter at its free end so that a flexible tube (not shown) leading to an endotracheal tube or an anaesthetist's face mask (not shown) may be fitted thereto. The leg part 15 of the T-piece ll accordingly constitutes a breathing connection of the valve body, enabling a patient to breathe through the valve.

Each end of the crossbar 14 of the T-piece ll is internally threaded and has screwed therein a respective one of the extension pieces 12 and 13 referred to above. Each such extension piece 12 and 13 comprises a sleeve l6, 17 respectively merging at one end with a respective slightly enlarged externally-threaded spigot part l8, 19 which screws into the respective end of the crossbar 14 of the T-piece 1]. Each of such sleeves l6, l7 merges with the respective spigot part l8, 19 to provide, within the body, a respective abrupt

annular shoulder

20, 21, these two

shoulders

20, 21 facing each other along the crossbar 14 of the T-piece 11 and each constituting a respective seat of the valve.

Internal circumferentially spaced ribs 20a and 21a respectively are provided within the spigot parts 18 and 19.

The extension piece 12 constitutes an outlet of the valve, and is formed with an internal diametrically disposed fixed web 22. This has an internally threaded hole approximately through its midpoint, this hole accommodating a rodlike outlet magnet 23 which is externally threaded to engage in the hole and extend axially of the respective extension piece 12. Within the valve body, the outlet magnet 23 terminatesin a slightly-tapered end 24 at a position short of the shoulder or seat 20 in the outlet 12; at the other end the outlet magnet 23 projects out of the outlet 12 and terminates in a knurled knob 25, whereby adjustment of the disposition of the inner end 24 of the outlet magnet 23 relative tothe plane of the seat 20 can be efiected.

The other extension piece 13 constitutes a gas inlet connection of the valve and accommodates a diametrically-disposed adjustable web 26 having a respective rodlike gas inlet magnet 27 extending therethrough, substantially along the axis of the crossbarl4 of the T1 T-piece 11. The adjustable web 26 has curved

feet

28, 29 at its radially-outward ends for lying snugly against the inner curved surface of the gas inlet connection 13, and the foot 28 has a slot therealong 30 extending part of the way parallel to the axis of the gas inlet connection. 13. A grub screw 31 set into the gas inlet connection 13 engages in the slot 30 to prevent the web 26 rotating relative to the gas inlet connection 13 whilst at'the same time permitting movement of the web 26 along the gas inlet connection 13. Since the slot 30 does not extend along the whole length of the foot 28, the web 26 is held captive by the screw 31 and is limited in its possible movement towards the open end of the gas inlet connection 13 by abutment of the screw against the end of the slot 30. An adjusting screw 32 extending radially through the gas inlet connection 13 about halfway along the sleeve 17, and having a knurled knob 33 on its outer end, engages an inclined surface on the adjustable web 26, so that screwing-in of the adjusting screw 32 serves to displace the adjustable web 26 and its magnet 27 away from the main T-piece 11, and unscrewing of the screw 32 permits displacement of the web 26 and magnet 27 towards the Tpiece 11, for adjustment of inner end 35 of the gas inlet magnet 27 relative to the seat 21. The magnet 27 is adjustably retained in the web 26 by the respective grub screws 36.

A spool valve member 37, in the fonn of a tubular hub 38 having disclike flanges 39 and 40 at each end, is accommodated in the crossbar 14 of 'the T-piece 11. The length of the valve member 37 is such that the flanges 39, 40 thereof are disposed one in each of the spigot parts 18, 19 of the extension pieces 12, 13 and are centralized by the respective ribs 20a and 21a0 whilst being readily slidable thereon, but the spacing between such flanges 39, 40 is shorter than the axial distance between the two

seats

20, 21 of the valve so that the valve member 37 can engage one only of the

seats

20, 21 by one of its flanges 39, 40 at any time. The flanges 39, 40 are a clearance fit in the respective spigots 18, 19, and the flange 39 in the outlet 12 of the valve is slightly smaller than the flange 40 which is in the gas inlet connection 13 of the valve.

Set into each end of the hub 38 of the valve member 37 is a respective rod-

like magnet

41, 42 respectively, these being axially disposed and projecting respectively towards the outlet magnet 23 and the gas inlet magnet 27, and being retained by respective

grub screws

43, 44 whereby the extend by which they project from the respective ends of the hub 38 is adjustable. The magnet 42 which faces the gas inlet magnet 27 constitutes a spool retaining magnet and the magnet 41 which faces the outlet magnet 23 constitutes a spool return magnet. The arrangement is such that like poles of the outlet magnet 23 and the spool return magnet 41 confront one another and tend to displace the spool valve member 37 towards a rest position wherein the disc of flange 40, which is chamfered as indicated at 45, engages with the seat 21 in the gas inlet connection 13. Further, the gas inlet magnet 27 and the spool retaining magnet 42 has have opposite poles confronting one another, so that these

magnets

27 and 42 attract one another and act to tend to retain the spool valve member 37 in its rest position aforesaid.

in operation of this embodiment of the ventilator, the breathing connection 15 will have an appropriate tube (not shown) connected thereto, this leading either to a face mask (not shown) applied over a patient's nose and/or mouth, or more usually to an endotracheal tube (not shown) appropriately fitted to the patient, and the gas inlet connection 13 will have connected thereto a respective flexible tube (not shown) leading to conventional anesthetic apparatus (not shown) for supplying gases under pressure, such apparatus including an inflatable bladder.

With the valve member 37 in the rest position, above described, wherein the flange 40 abuts the seat 21, gases issuing from the anesthetic apparatus initially build up the pressure in the inflatable bladder and in the flexible tube to the gas inlet connection 13, passage of the gases to the breathing connection 15 being prevented by the large diameter flange 40 of the spool valve member 37 abutting the seat 21 in the gas inlet connection 13, and the combined efforts of the gas inlet magnet 27 and the retaining magnet 42 serving to resist separation of such large diameter flange 40 from such seat 21.

As soon as the pressure in the gas inlet connection 13 is sufficient to overcome the force of the gas inlet magnet 27 and the retaining magnet 42, the spool valve member 37 is forced away from the seat 21 in the gas inlet connection 13 and the gases from the anesthetic apparatus can pass through the valve by way of the gas inlet connection 13 and the breathing connection 15 to the patient, so as to inflate the patients lungs. The movement of the spool valve member 37 is an impulse movement and is such that the smaller diameter flange 39 thereof moves towards the seat in the outlet 12, tending momentarily to-close the latter, although actual closure may not occur in practice since the return magnet 41 and the outlet magnet 23 tend to repel one another and have the effect of impulsing the spool valve member 37 back to its initial rest position whilst the patient is expiring spent air from his lungs through the breathing connection 15 and the outlet 12. Return of the spool valve member 37 to its rest position is possible, because of the opening of the gas inlet connection 13 to the breathing connection 15 causes a drop in the pressure in the inflatable bladder and the flexible tube to the gas inlet connection 13, permitting the large diameter flange 40 of the spool valve member 37 to move back into engagement with its seat 21.

Accordingly, so long as gases under pressure are supplied to the gas inlet connection 13, the valve member 37 will be periodically impulsed to open the gas inlet connection 13 to the breathing connection 15 for inflating the patients lungs and the valve member 37 will automatically return to its rest position permitting the patient to expire through the breathing connection 15 and the outlet 12.

Adjustment of the screw 32 by way of its knob 33 serves to' shift the gas inlet magnet away from or closer to the retaining magnet 42 and thereby vary the force with which the valve member 37 is biassed towards its rest position. This adjustment accordingly serves to determine the buildup of pressure necessary in the inlet connection 13 before the valve member 37 will be impulsed. correspondingly, adjustment of the outlet magnet 23 relative to the spool return magnet 41 serves to determine the actual stroke of movement of the spool valve member 37 and the force with which such member 37 will be returned toward its rest position.

ln practice the ventilator above described is found to operate particularly reliably and, of course, it is of simple construction having only one effective moving part.

Referring now to F IG. 2, the embodiment here illustrated is of more advanced design than that just described, but is again in the form of an automatically-actuated double-acting valve.

This valve again comprises a body made of a suitable nonmagnetic metal (such as aluminum alloy) or of a tough plastics material and composed of three parts namely a main T-piece 50 and two extension pieces 51 and 52. The T-piece 50 is generally of conventional appearance, and comprises a hollow crossbar 53 and a hollow leg part 54, the latter connecting with the crossbar53 substantially mid way along the length of the crossbar 53. The leg part 54 is of slightly tapered form, having its smallest diameter at its free end so that a flexible tube (not shown) leading to an endotracheal tube or an anaesthetist's face mask may be fitted thereto. The leg part 54 of the T-piece 50 accordingly constitutes a breathing connection of the valve body, enabling a patient to breath through the valve.

Each end of the crossbar 53 of the T-piece 50 is internally threaded and has screwed therein a respective one of the extension pieces 51,52 referred to above. Each such extension piece comprises a

sleeve

55,56 merging at one end with a respective slightly enlarged extemally-threaded spigot part 57,58 which screws into the respective end of the crossbar 53 of the T-piece 50. Each

sleeve

55,56 merges with the respective spigot part 57,58 to provide, within the body, a respective abrupt annular shoulder 59,60, the two shoulders 59,60 facing each other along the crossbar 55 of the T-piece 50. In this case, in contrast to the embodiment of FIG. 1, the shoulders 59,50 do not provide seats of the valve.

The extension piece 51 constitutes an outlet of the valve. Telescopically arranged in, and a close sliding fit in such an outlet 51 is a tubular outlet seat member 61 the innermost end of which is chamfored to constitute a seat 62 of the valve which projects past the adjacent shoulder 59 and a short distance into the crossbar 53 of the T-piece 50. Adjustment of the extent by which the seat 62 projects past the shoulder 59 is provided for by a radial adjusting screw 63 engaged into a threaded hole in the seat member 61 and extending through a slightly angled slot 64 in the outlet 51, the screw 63 carrying a collar 65 locating in the slot 64 and having an enlarged head 66 whereby it may be loosened or tightened manually. Accordingly, when the screw 63 is released, movement of the screw 63 and collar 65 along the slot 64 will cause the seat 62 to project into the crossbar 53 to a greater or lesser extent, the seat member 61 being subject, of course, to slight rotational movement within the outlet 51 during the adjustment.

The extension piece 52 is somewhat longer than the outlet 51 and constitutes a gas inlet connection of the valve, accommodating an adjustable guide plug 67, of a tough plastics material, having a rod-like gas inlet magnet 68 extending therethrough, substantially along the axis of the crossbar 53 of the T-piece 50, a grub screw (not shown) serving adjustably to locate the magnet 68 in a fixed position relative to the plug 67.

The guide plug 67 is externally generally of cylindrical configuration to fit snugly within the interior of the gas inlet connection 52. At one end a recess 69 is formed in the plug 67 for locating one end of a coil spring 70 the other end of which locates in an internal circumferential groove 71 in the gas inlet connection 52 near to the open end thereof. The spring 70 surrounds the gas inlet magnet 68. The other end 72 of the plug 67 is generally of frustoconical configuration, and gas passages 73 are provided through-the plug 67.

"l" he outer curved surface of the ,plug '67 has a slot 74 therealong parallel to the axis of the gas inlet connection 52, and a grub screw 75 set into the gas inlet connection 52 engages in the slot 74 to prevent the plug rotating within the gas inlet connection 52 whilst at the same time permitting it to move along the gas inlet connection 52. An adjusting peg 76 extends radially through the gas inlet connection 52 near to its spigot 58, and has a knurled screw cap 77 on its outer endin threaded engagement with a radial spigot 78. The peg 76 engages an inclined surface 79 on the plug 67, so that screwingin of the adjusting peg 76 serves to displace the adjustable plug 67 and itsmagnet 68 away from the main T-piece 50 and unscrewing of the peg 76 permits reverse movement of the plug 67 and magnet 68 towards the T-piece 50, under the action of the spring 70, for adjustment of the inner end 80 of the gas inlet magnet 68 relative to the T-piece 50. The inclined surface 79 has a steep portion 81 the purpose of which will be described later. a

The gas inlet connection 52 has a tubular valve housing 82 formed as an extension thereof. This housing 82 has one of its ends inwardly flanged as at83 to constitute a seat of the valve, such flanged end fittinginto and being secured into the spigot 58 of the gas inlet connection, so that the housing extends into the crossbar 53 of the T-piece 50 concentrically therewith. Slotted gas ports 84 are provided at intervals around the housing 82 adjacent the flange 83.

A spool valve member 85, in the form of a tubular hub 86 having disclike flanges 87 and 88 at each end, is accommodated in the housing 82. The length of the valve member 85 is such that it can engage only one of the seats 62 and 83 by one of its discs or flanges 87 or 88 at any time, even when the outlet seat member 61 is adjusted to project to the greatest possible extent towards the seat 83. The flanges 87,88 are, of course, a free sliding fit in the housing 82.

Set into one end of the hub 86 of the valve member 85 is a rodlike spool magnet 89, this being axially disposed and projecting towards the gas inlet magnet 68. The latter magnet 68 constitutes effectively a spool attracting magnet. The arrangement is such that the gas inlet magnet 68 and the spool magnet 89 have opposite poles confronting one another, so that these magnets 68 and 89 attract one another and act to tend to retain the spool valve member 85 in arest position wherein its corresponding disc or flange 88 engages with the seat 83 of the housing 82 so as to close off the gas inlet connection.

A pressure relief 'valve 90 connects with the crossbar 53 of the T-piece 50 at a position wherein it is always in communication with the breathing connection 54 regardless of the position of the spool valve member 85.

As shown, this relief valve 90 is a conventional Coxeter Heidbrink type valve and comprises an internally-threaded boss 91 formed integrally with or secured to the crossbar 53 so as to surround an aperture 92 in such crossbar, perforations 93 being provided at intervals. around such boss 91. A manually-rotatable valve screw 94 screws into'the boss 91, the extent by which it can be screwed in and out being restricted by a grub screw 95 extending through the boss 91 and engaging into a circumferential recess 96 around the screw 94. The screw has an axial bore 97 therethrough and a pin 98, having a valve disc 99 thereon, locates by one end in the bore 97. A spring 100 surrounding the pin 98 is accommodated in a recess 101 in the lower end of the screw 94 and this spring abuts by one end againstthe screw 94 and by the other end against the valve disc 99 to tend to hold the latter in a position closing off the aperture 92.

In operation of the ventilator, the breathing connection 54 will have a flexible tube (not shown) connected thereto, this leading either to a face mask applied over a patient's nose and/or mouth, or more usually to an endotracheal tube appropriately fitted to the patient, and the gas inlet connection 52 will have connected thereto a respective flexible tube (not shown) leading to conventional anesthetic apparatus for supplying gases under pressure such apparatus including an inflatable bladder.

The adjusting peg 76 is adjusted, by means of the screw cap 77, to a position wherein the spool attracting magnet 68 holds the spool valve member in its rest position, as above referred to, with the disc or flange 88 abutting the seat 83. In this position of adjustment of the peg 76, the latter contacts the inclined surface 79 of the plug 67 on the steep portion 81 of such surface 79, so that fine adjustment of the position of the spool attracting magnet 68 relative to the spool magnet 89 is possible to provide corresponding fine adjustment of the attractive force between the magnets 68 and 89.

With the ventilator so adjusted gases issuing from the anesthetic apparatus initially build up the pressure in the inflatable bladder and in the flexible tube to the gas inlet connection 52, passage of the gases to the breathing connection 54, being prevented by the flange 88 of the spool valve member 86 abutting the seat 83 to close off the gas inlet connection 52, and the combined efiorts of the gas inlet magnet 68 and the spool magnet 89 serving to resist separation of such flange 88 from such seat 83.

As soon as the pressure in the gas inlet connection 52 is sufficient to overcome the force of the gas inlet magnet 68 and the. spool magnet 89, the spool valve member 85 is forced away from the seat 83 and the gases from the anesthetic ap paratus can pass through the valve by way of the gas inlet connection 52, the ports 84 and the breathing connection 54 to the patient, so as to inflate the patient's lungs. The movement of the spool valve member 85 is an impulse movement and is such that the flange 87 thereof move'stowardsthe seat 62 of the outlet 51, tending momentarily to close the latter, although actual closure may not occur in practice, since the spool magnet 89 and the inlet magnet 68 tend to continue to attract one another and have the effect of impulsing the spool valve member 85 back to its initial rest position whilst the patient is expiring spent air from his lungs through the breathing connection 54 and the outlet 51. Return of the spool valve member 85 is possible because the opening of the gas inlet connection 52 to the breathing connection 54 causes a drop in the pressure in the inflatable bladder and the flexible tube to the gas inlet connection 52, permitting the flange 88 of the spool valve member 85 to move back into engagement with its seat 83, and it will be appreciated that telescopic adjustment of theoutlet seat member 61 will serve effectively, to vary the possible movement of the spool valve member 85 and thereby vary the period and/or extent of opening of the breathing connection 54 to the gas inlet connection 5 2.

So long as gases under pressure are supplied to the gas inlet connection 52, the valve member 85 will be periodically impulsed to open the gas inlet connection 52 to the breathing connection 54 for inflating the patient's lungs and the valve member will automatically return to its rest position permitting the patient to expire through the breathing connection 54 and the outlet 55.

The pressure-relief valve serves, of course, to ensure that gas inlet pressure cannot be reached in the breathing connection 54, (e.g. in the unlikely event of jamming of the spool valve member 85) and that any excessive buildup of pressure in the valve body can escape to atmosphere independently of the outlet 55, the pressure at which relief will occur being adjustable, of course, by means of the screw 94.

With this construction of the ventilator, the spool valve member 85, can, by adjustment of the peg 76, be retained in its position, as illustrated in FIG. 2, closing the outlet 51 and keeping the breathing connection 54 open to the gas inlet connection 52 so that, at the end of an operation on a patient, the patient has to breathe out against the pressure of the gases in the gas inlet connection 52 through the relief valve 90. Thus, at the end of an operation, when it is desired to stimulate the patient into full reliance upon his own. respiratory system, the relief valve 90 is adjusted to open under a predetermined pressure and then the adjusting peg 76 is adjusted to permit the s rin 70 to move the as inlet magnet 68 into engagement" with the spool magnet 89, to move the spool valve I member 85 into its position closing the seat 62 of the outlet 51 of the valve.

The breathing connection 54 is thereby opened permanently to the gas inlet connection 52, making it necessary for the patient, during his breathing, to expire against the gas pressure prevailing in the gas inlet connection 52, the relief valve 90 opening to permit escape of gas and/or expired air to the atmosphere when a predetermined pressure is exceeded in the gas inlet connection 52.

The invention is not confined to the precise details of the illustrated and above-described embodiments, and variations may be made thereto. For instance, in both instances, the ventilator may beformed with its outlet 12 or embodying a nonretum valve arrangement preventing entry of atmospheric air into the ventilator through the outlet 12 or 51. This could be achieved by the provision of an apertured partition across the outlet (the outlet 12 of the FIG. 1 embodiment being appropriately modified to allow for this) with a very lightlyloaded nonretum valve being provided to close the aperture in such partition.

It will be evident, of course, that instead of using magnet pairs, that is to say the magnets 23 and 41, the

magnets

27 and 42 and the magnet 68 and 89, use could be made in each case of a single magnet and an associated element of magnetic ma terial such as a soft iron rod.

Other modifications of the ventilator are, of course, possible. For instance, the valve member can be of a form other than a spool type member, and the means biassing the same towards its rest position may be resilient means, e.g. a spring. If desired, rubber pads may be provided upon the confronting ends of the magnets to minimize metallic contact thereof during operation of the ventilator. Also rubber seatings can be provided for the valve member to impinge upon to minimize noise.

Where a spool type member is employed in the ventilator, the dead space" in the valve body (i.e. the space therein occupied by gas or expired air) can be minimized by making the hub of the spool as large a diameter as is practicable.

An inflatable bladder could be provided, connected directly onto the gas inlet connection, and the gas supply fed into the gas inlet connection through a small side tube, to render the ventilator easily portable.

I claim:

1. An anaesthetist's lung ventilator communicating with anesthetic equipment for connecting the respiratory system of a patient alternately to a source of gas under pressure for inspiration and to atmosphere for expiration and comprising:

a valve body having a central bore communicating at one end with a gas inlet connecting to the anesthetic equipment for supplying the gas and at the opposite end with an outlet connecting to atmosphere and intennediate the gas inlet and outlet with a breathing inlet-outlet connecting to the patient;

an outlet seat telescopically and slidably mounted within the outlet and having an inner end facing the central bore and defining an outlet valve seat;

outlet seat adjustment means for selectively varying the extent of projection of the outlet seat into the central bore;

an adjustable apertured guide plug having an inclined surface and being slidably mounted within the gas inlet;

a guide plug adjustment means extending through the gas inlet and engageable with the guide plug for displacing the guide plug toward and away from the central bore;

a tubular valve housing fixed within the central bore and defining a gas inlet valve seat adjacent the gas inlet;

a spool valve reciprocable within the valve housing;

valve biasing means for biasing the spool valve to rest position and including a first magnet adjustably disposed in the gas inlet and a second magnet carried by the spool valve and disposed for being attracted by the first magnet;

and

all adapted and arranged upon the continuous supply of gas to the gas inlet for the successive and alternate shifting of the spool valve between non rest position adjacent the outlet valve seat for outlet closure assumed upon the buildup of pressure at the gas inlet and against the action of the valve biasing means for the patients inspiration through the gas inlet and breathing inlet-outlet and rest position adjacent the gas inlet valve seat for gas inlet closure assumed upon the consequential lowering of pressure at the gas inlet and increase of pressure at the breathing inlet-outlet for the patients unrestrained expiration through the breathing inlet-outlet through the outlet to atmosphere.

2. A ventilator as claimed in claim 1 wherein the first magnet cooperates with the second magnet carried by the spool valve to bias the latter to the rest position.

3. A ventilator as claimed in claim I wherein the first magnet extends through the guide plug adjustably arranged in the gas inlet.

4. A ventilator as claimed in claim 1 including a spring means wherein the guide plug is spring loaded toward the spool valve.

5. A ventilator as claimed in claim 1 wherein adjustment of the guide plug is provided for by the guide plug adjustment means radially movable through the-gas inlet and abutting the inclined surface on the guide plug.

6. A ventilator as claimed in claim 5 wherein the inclined surface includes a steep section providing for fine adjustment of the guide plug and first magnet relative to the spool valve in the rest position of the spool valve.

7. A ventilator as claimed in claim 1 wherein the guide plug can be adjusted to retain the spool valve in a position away from its rest position and closing the gas outlet.

8. A ventilator as claimed in claim 1 wherein an inwardlyflanged end of the valve housing fits into a spigot part of the gas inlet, the flange providing the gas inlet valve seat.

9. A ventilator as claimed in claim 1 wherein the outlet seat adjustment means comprises a screw projecting radially from the outlet seat and through an inclined slot in the outlet.

10. A ventilator as claimed in claim 1 wherein a pressure-relief valve is provided on the valve body for communication with the breathing connection.

Claims

1. An anaesthetist''s lung ventilator communicating with anesthetic equipment for connecting the respiratory system of a patient alternately to a source of gas under pressure for inspiration and to atmosphere for expiration and comprising: a valve body having a central bore communicating at one end with a gas inlet connecting to the anesthetic equipment for supplying the gas and at the opposite end with an outlet connecting to atmosphere and intermediate the gas inlet and outlet with a breathing inlet-outlet connecting to the patient; an outlet seat telescopically and slidably mounted within the outlet and having an inner end facing the central bore and defining an outlet valve seat; outlet seat adjustment means for selectively varying the extent of projection of the outlet seat into the central bore; an adjustable apertured guide plug having an inclined surface and being slidably mounted within the gas inlet; a guide plug adjustment means extending through the gas inlet and engageable with the guide plug for displacing the guide plug toward and away from the central bore; a tubular valve housing fixed within the central bore and defining a gas inlet valve seat adjacent the gas inlet; a spool valve reciprocable within the valve housing; valve biasing means for biasing the spool valve to rest position and including a first magnet adjustably disposed in the gas inlet and a second magnet carried by the spool valve and disposed for being attracted by the first magnet; and all adapted and arranged upon the continuous supply of gas to the gas inlet for the successive and alternate shifting of the spool valve between non rest position adjacent the outlet valve seat for outlet closure assumed upon the buildup of pressure at the gas inlet and against the action of the valve biasing means for the patient''s inspiration through the gas inlet and breathing inlet-outlet and rest position adjacent the gas inlet valve seat for gas inlet closure assumed upon the consequential lowering of pressure at the gas inlet anD increase of pressure at the breathing inlet-outlet for the patient''s unrestrained expiration through the breathing inlet-outlet through the outlet to atmosphere.

3. A ventilator as claimed in claim 1 wherein the first magnet extends through the guide plug adjustably arranged in the gas inlet.

5. A ventilator as claimed in claim 1 wherein adjustment of the guide plug is provided for by the guide plug adjustment means radially movable through the gas inlet and abutting the inclined surface on the guide plug.

8. A ventilator as claimed in claim 1 wherein an inwardly-flanged end of the valve housing fits into a spigot part of the gas inlet, the flange providing the gas inlet valve seat.