US 3462920 A
Description (OCR text may contain errors)
Aug. 26, 1969 D. F- DENNY GASEOUSLY FORMED CURTAINS 5 Sheets-Sheet 1 Filed Dec. 15. 196'? D. F. DENNY 3,462,920
GASEOUSLY FORMED CURTAINS Aug. 26, 1969 5 Sheets-Sheet 5 Filed Dec. 15. 1967 United States Patent 3,462,920 GASEOUSLY FORMED CURTAINS Douglas Frank Denny, Stoke Poges, England, assiguor,
by mesne assignments, to Bells Medical Products Limited, Slough, England, a British company Filed Dec. 15, 1967, Ser. No. 690,877 Claims priority, application Great Britain, Dec. 16, 1966, 56,352/ 66 Int. 'Cl. B01d 46/42 US. Cl. 55-413 7 Claims ABSTRACT OF THE DISCLOSURE A germ-free environment for a patient provided by novel gaseous curtain. Apparatus includes first and second nozzle means mounted to communicate with means for simultaneously projecting an isolating gaseous medium through both of said nozzle means, the first nozzle means being adapted to project a first stream of isolating gaseous medium to provide a gaseous curtain between the volume or area to be isolated and the environmental gaseous medium and the second nozzle means being located adjacent to the first nozzle means and adapted to project a second stream of the isolating gaseOus medium in substantially the same direction as the first stream to provide a further gaseous curtain between the first stream and the environmental gaseous medium.
This invention relates to the provision of a gaseously formed curtain and is particularly applicable to the provision of an air curtain which curtain can be so located to isolate air in a given space from extraneous air, dust or the like in the atmosphere surrounding the given space.
Air in hospitals or like institutions is known to be heavily contaminated with various types of bacteria, many of which are pathogenic to humans and also resistant to the commonly used anti-biotics. It has been shown that if the air in the vicinity of a patient during pre and post-operative periods is maintained virtually free from pathogenic organisms, then the incidence of wound and like infection is only a fraction of that existing under uncontrolled air conditions.
A previously proposed method of preventing bacteria laden air from reaching a patient is by the physical isolation of a specific part, or even the whole of the patient within a plastic envelope or enclosure into which is pumped clean, bacteria-free air. Physical isolation of a patient in an envelope or enclosure suffers from two main disadvantages in that, total enclosure of the patient creates a severe claustrophobic environment which it will be appreciated is highly undesirable, and further, since direct physical entry into the enclosure is to be avoided, all treatment and nursing must be carried out through glove ports or air locks which demands considerable patience and effort from the attendant staff.
The provision of an air formed curtain in the broad sense, is an attractive proposition as it offers the opportunity of isolating a patient invisibly and without physical restraint and yet is capable of providing a germ free environment surrounding the patient.
Air formed curtains for isolation purposes have hitherto been proposed but have so far been unsuccessful in use. When a high pressure air stream discharges from a nozzle into a mass of air, air from the surrounding mass is mixed with it by a momentum transfer. The entrained air causes the air stream to lose its velocity and momentum. The momentum transfer further causes turbulent eddy currents to be formed within the air stream even when the nozzle is discharging into still air and by this [means 3,462,920 Patented Aug. 26, 1969 contaminated air can penetrate a space which is desired to be isolated by the air stream. This effect is greatly accentuated by the presence of side draughts which can only be nullified by the use of air streams having velocities several times higher than that of the draught. Unfortunately, low volume per second, high velocity, air streams which are stiff to side draughts or winds cannot be used successfully to blanket an area with clean air because they entrain substantial volumes of contaminated air from the surrounding atmosphere and also tend to pick up dust and the like from exposed external surfaces.
It is an object of the present invention to provide an apparatus and method by which an improved isolation system can be obtained which system utilizes a gaseously formed curtain adapted to protect a patient from bacteria or other impurities which may be present in environmental air and which avoids the aforementioned disadvantages of hitherto proposed isolation systems.
According to the present invention there is provided apparatus for producing a gaseous curtain for isolating a given volume or area from an environmental gaseous medium and impurities in said medium which includes first and second nozzle means mounted to communicate with means for simultaneously projecting an isolating gaseous medium through both of said nozzle means, the first nozzle means being adapted to project a first stream of the isolating gaseous medium to provide a gaseous curtain between the volume or area to be isolated and the environmental gaseous medium and the second nozzle means being located adjacent to the first nozzle means and adapted to project a second stream of the isolating gaseous medium in substantially the same direction as the first stream to provide a further gaseous curtain between the first stream and the environmental gaseous medium.
Further, according to the present invention there is provided a method of producing a gaseous curtain for isolating a given volume or area from an environmental gaseous medium and impurities in said medium which includes projecting a first stream of an isolating gaseous medium to provide a gaseous curtain between the volume or area to be isolated and the environmental gaseous medium and simultaneously projecting a second stream of the isolating gaseous medium in substantially the same direction as, and adjacent to, the first stream to form a curtain of the isolating gaseous medium between the first stream and the environmental gaseous medium.
It is to be appreciated that the apparatus and method of the present invention can be utilised for purposes other than that of isolating patients, for example in the isolation of sterilised instruments or clean working areas which are often required in modern laboratories and work shops. It will further be appreciated that although the isolating gaseous curtain is preferably formed by a stream of purified air, other gases can be utilised when required, for example, oxygen and in some instances inert gases.
By the present invention the gaseous curtain derived from the first nozzle means is surrounded (or substantially separated from the environmental gaseous medium) by at least one gaseous curtain derived from the second nozzle means and the outer gaseous curtain serves to protect the inner curtain from the influence of unclean air or other undesirable gaseous currents approaching the inner curtain from a transverse direction. Preferably the stream of isolating gaseous medium from the second nozzle means is relatively smaller than the stream from the first nozzle means. The velocity of the gaseous stream from the second nozzle means can be arranged to be relatively higher than the velocity of the gaseous stream from the first nozzle means. Consequently the first stream of the isolating gaseous medium is substantially isolated by allowing the relatively smaller second stream or streams of isolating gaseous medium to mix with external side currents of the environmental gaseous medium which may be present. The second stream or streams are thereby caused to be deflected from the first stream which thus remains uncontaminated.
Preferably the volume or area which is to be isolated from an environmental gaseous medium and impurities therein is located within the stagnation zone of the first nozzle means. The stagnation zone is a region in the vicinity of the first nozzle means in which turbulent exchange of the isolating gaseous medium with an extraneous gaseous medium does not occur. The meaning of stagnation zone is well known in the relevant art and will best be understood from the following example. Assuming gas under pressure is passed through an annular aperture defined by a nozzle, the gas stream at the outlet of the aperture would be of substantially tubular form pro vided that the gas stream is projected into a relatively still atmosphere. However, as the gas stream flows further from the aperture, the density of the gas stream decreases and its form varies from tubular by the inner surface of the stream converging in the direction from the nozzle and the other surface of the stream diverging in the direction from the nozzle. Eventually the inner surface of the stream merges (neglecting turbulence). The region in the vicinity of the nozzle and which is effectively surrounded by the tubular curtain of the air stream prior to the inner surface of the gas stream merging is the stagnation zone. By locating the space to be isolated (e.g., an operating table or hospital bed) within the stagnation zone of a large, slow moving stream of clean air, all the contaminated surrounding air can be effectively excluded.
The stagnation zone can be further substantiated by providing third nozzle means which is mounted to communicate with means for projecting the isolating gaseous medium through the third nozzle means simultaneously with the projection of the isolating gaseous medium through the first and second nozzle means. The third nozzle means is located to project a third stream of the isolating gaseous medium substantially in the same direction as the first stream to envelop the area or volume which is to be isolated. Since the volume to be isolated is frequently a hospital bed, in this application it is necessary to ensure that the gaseous stream is projected from the third nozzle means at a velocity which is so low as to be virtually imperceptible to a patient in the bed. Consequently the third nozzle means can be arranged to project a large volume of the isolating gaseous medium at a low velocity whereas the first nozzle means is preferably arranged to project a relatively smaller stream of the isolating gaseous medium, if necessary, at a relatively higher velocity and the second stream is preferably arranged to project a relatively still smaller stream of the isolating gaseous medium, if necessary, at a relatively still higher velocity.
By use of the present invention an air curtain has been formed the effectiveness of which has been experimentally determined by submitting the curtain to external currents of carbon-dioxide which acted as a contaminant.
The streams of carbon-dioxide were released in the form of side draughts of variable intensity. Sensitive infrared detection apparatus capable of detecting two parts of carbon-dioxide in ten thousand parts was located on the side of the first and second streams of air (the isolating gaseous medium) remote from the streams of carbon-dioxide to measure contamination. The streams of air were projected from their respective nozzle means at approximately 100 feet per minute. With side draughts of carbon-dioxide in streams which attained speeds of approximately 90 feet per minute no contamination could be detected in the isolated area which was located approximately 4 feet from the nozzle means. The flow pattern of the isolating gaseous medium is virtually unaiTected by cross-flow currents of up to 50 feet per minute (which constitutes a severe draft and is frequently encountered in hospital wards). Further, convection currents arising from the generation of body heat which may be present in the area or volume being isolated have little or no effect on the flow pattern of the streams of the isolating gaseous medium.
The apparatus of the present invention is convenient for use in a hospital ward to provide a simple, efiicient, and relatively inexpensive form of patient isolation which permits normal access of medical staff to the patient without inconvenience to themselves and without undue disturbance of the fiow pattern of the streams of isolating gaseous medium.
The present invention can conveniently be incorporated in a self-contained ward unit for use in hospitals or the like which unit has a built-in fan, means for supplying the isolating gaseous medium to the fan, and filters, purifiers or the like through which the isolating gaseous medium can be passed prior to flowing through the nozzle means.
One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings in which:
FIG. 1 is a perspective view of a ward unit which incorporates the apparatus of the present invention and is adapted to isolate a hospital bed from environmental air by a clean-air curtain;
FIG. 2 is a side view of the ward unit shown in FIG. 1;
FIG. 3 is a cross-section of the ward unit taken on the line IlIIlI of FIG. 2 and shows nozzle means adapted to form the clean-air curtain;
FIG. 4 is a part section of the ward unit taken on the line IV-IV of FIG. 3 and illustrates the nozzle means in further detail;
FIG. 5 is an end view of the ward unit shown in FIG. 1 and illustrates the flow pattern of the streams of cleanair projected through the nozzle means; and
FIG. 6 is a similar view to that shown in FIG. 5 and illustrates a modification of the nozzle means so that the flow pattern of the clean-air streams provide a potential core in the vicinity of the hospital bed.
Where possible throughout the following description like parts or members have been accorded like references.
The ward unit illustrated includes a hollow canopy 1 which is secured to extend horizontally from a substantially vertical hollow body 2 having a stand 2a. The body 2 houses a fan and motor assembly shown generally at 3 by which air is drawn through a grid and pre-filter 4 in the side of the body 2 and blown therefrom through a bacteria filter (or similar air purifier) 5. After passing through the filter 5 the blown air passes into the canopy 1 from which it emerges through an array of nozzles mounted in a wall 1a of the canopy to be projected downwardly towards a ward bed 6 which is to be isolated from its environmental air. Conveniently the grid and prefilter 4 is washable and a passage or passages within the body 2 from the absolute filter 5 to the canopy 1 are arranged so that clean-air flow from the body to the canopy is laminar.
The body 2 is provided with a console 7 from which the motor and fan 3 can be controlled. The console can conveniently incorporate auxiliary services such as piped gases, electrical supply for reading and inspection lamps and a nurse-call system as may be required in a hospital ward.
The canopy 1 is intended to project over the bed 6 and the wall In of the canopy opposed to the bed 6 is provided with a first nozzle 8 which defines an elongated aperture 8a of U shape in profile (see FIG. 3). The aperture 8a corresponds in length approximately to the total length of the perimetral foot end and sides of the bed 6. The wall 1a further carries a second nozzle 9 which defines an elongated aperture 9a of U shape in profile which aperture 9a is spaced from the aperture 8a and is located between the aperture 8a and the peripheral edge of the canopy *1. The wall 1a carries a third nozzle which defines a rectangular aperture 10a. The aperture 10a is spaced from the aperture 8a of the first nozzle and, as will be apparent from FIG. 3, is located between the legs formed by the U shape of the first nozzle 8. Each of the apertures 8a, 9a and 10a is provided with an air diffuser 12 which is well known in the relevant art and can conveniently comprise, for example non-woven felt, woven fabrics, polyurethane foam or foam material of a similar nature, grills, gride meshes or the like. The gaseous diffusers 12 ensure that the flow of gas through the apertures 8a, 9a and 10a is substantially uniform.
Preferably the elongated apertures 8a and 9a of the first and second nozzles are parallel and the elongated aperture 10a of the third nozzle is parallel with the legs of the U shaped elongated apertures 8a and 9a.
The nozzles 8 to 10 can be fixedly secured in the wall 1a and side vanes 8b, 9b and 10b respectively of nozzles 8 to 10 are preferably arranged so that air is projected, in the case of nozzle 8 so that the curtain formed thereby diverges outwardly from the canopy in the direction of arrow A, in the case of nozzle 9 so that the curtain formed thereby diverges outwardly from the canopy in the direction of arrow B, and in the case of nozzle 10 so that the stream of air itself (rather than the curtain formed thereby) diverges outwardly from the canopy.
As illustrated in FIG. 5, the hospital bed 6 is located substantially beneath the third nozzle 10. When air is blown into the canopy 1 and then through the nozzles 8 to 10, the air stream which is projected through the first nozzle 8 effectively forms an air curtain between relevant part of the bed 6 (that part in the vicinity of the patient) and the environmental air; the air stream which is projected from the second nozzle 9 effectively forms a further air curtain adjacent to the air curtain formed from the first nozzle 8. Consequently the relevant part of the bed 6 is effectively surrounded by the air curtains formed from nozzles 8 and 9 and the adjacent face 11 of the body 1 against which the head of the bed is situated. If required the apertures 8a and 9a can be extended across the free ends of the legs of their respective U shapes at a position adjacent the face 11 to provide air curtains which are endless to completely surround the bed.
The stream of air which is projected from the third nozzle 10, as above mentioned, diverges outwardly (see FIG. 4) and envelops the relevant part of the bed 6. Any cross currents of environmental air which occur and flow towards the bed 6 first encounter the air curtain projected from the nozzle 9 turbulent mixing occurs between the clean air stream from the nozzle 9 and the environmental air and the inner curtain which is projected from the nozzle 8 remains unaffected (as does the central stream of air which is projected from the nozzle 10).
Preferably the nozzles 8 and 9 are arranged so that the velocity of the stream of air which is projected through the nozzle 9 is greater than the velocity of the stream of air which is projected through the nozzle 8. Such an arrangement is conveniently achieved by ensuring that the width X of the aperture 8a (see FIG. 3) is considerably larger than the width Y of the aperture 9a.
In application of the above described unit for isolating a patient in a ward bed, it is essential that the air stream which is projected from the nozzle 10 has a velocity which is so low as to be undetectable by the patient. For this reason the nozzle 10 is so designed relative to the flow capacity of the fan that the stream of air through the aperture 10a comprises a large slow moving volume of air. If required the nozzles 8 and 9 can be similarly de signed so that the streams of air which are projected therefrom comprise large volumes of slow moving air. However, the velocities of the streams from the nozzles 8 and 9 need not be so low as the velocity of the stream which is projected from the nozzle 10 since the patient in the bed 6 is not enveloped in these streams.
In a practical construction of the ward unit illustrated in FIGS. 1 to 5 the canopy 1 is carried by the body 2 at the height of 6 /2 feet above the floor. The canopy projects approximately 7 feet from the face 11 of the body 2 and is approximately 4 /3 feet wide. The depth of the canopy is approximately 9 inches. The three nozzles 8 to 10 are symmetrically arranged in the wall 1a of the canopy and the width Z of the third nozzle 10 is 8 inches, the width X of the first nozzle 8 is 6 inches and the width Y of the second nozzle 9 is 1 inch. The apertures of the first and third nozzles 8 and 10 respectively are spaced by approximately 7 inches and the apertures of the first and second nozzles 8 and 9 respectively are spaced by approximately 6 inches. Conveniently the length of the aperture 10a of the third nozzle is 5 feet and the part of the apertures 8a and 9a remote from the face 11 of the body 2 are conveniently semi-circular. The fan and motor assembly 3 are designed to pass air into the canopy 1 at a low rate, approximately 1,200 cubic feet per minute, and to provide air pressure in the canopy of approximately 0.25 inch water gauge. It will be apparent that the total area of the apertures 80, 9a and 10a of the nozzles is approximately 12 square feet and consequently the velocity of the three streams of air as they issue from their nozzles is approximately 100 feet per minute nomi nal.
In the modification of the ward unit illustrated in FIG. 6 the third nozzle is omitted and the nozzles 8 and 9 are arranged to project streams of air in a similar manner as that above described with reference to FIGS. 1 to 5. In this case the relevant part of the bed 6 is arranged to be located within the stagnation zone defined by the effective curtain formed by the stream of air which is projected through the aperture 8a.
It will be apparent that several modifications are possible to the apparatus as above described and illustrated for example each of the first and second nozzle means 8 and 9 can be formed by a plurality of nozzles each nozzle having an elongated aperture and which nozzles are symmetrically arranged in the canopy, this is conveniently achieved by manufacturing the canopy without the semicircular end part of the nozzles 8 and 9 so that the nozzles in the canopy comprise the portions between the face 11 of the body 2 and the broken line G-H in FIG. 3. The second nozzle means 9 can conveniently comprise an array of separate nozzles located adjacent to each other. For example, a vane (see FIGS. 3 and 4) can be provided in the aperture 9a for the length thereof. If required the vanes 8b, 9b and 10b can be adjustably mounted in a manner well known in the art to vary the direction of flow of the air streams which issue from the nozzles.
Conveniently the apparatus above described and illustrated is manufactured in three sections, the fan and motor section, the filter section, and the canopy so that it can be easily assembled and disassembled for storage, transportation and other purposes.
By use of apparatus constructed in accordance with the present invention it is only necessary to provide large volumes of purified air (or other isolating gaseous medium) at a relatively low pressure in the canopy. Consequently power and noise level during the formation of the air curtains are insignificant and the effectiveness of the protection obtained is dependent only on the performance of the air filters since almost complete isolation from external environment, particularly germ laden air, is possible. The isolation afforded by use of the apparatus is particularly useful in hospitals for the post-operative treatment of kidney transplants and severe burns. It is also suitable for the protection of patients subsequent to irradiation therapy or inadvertent exposure to radioactivity. Further protection of patients after general surgery by the apparatus will eliminate post-operative sepsis thereby reducing hospitalisation time which is of considerable economic advantage.
The isolating gaseous medium can be treated in the apparatus, for example, by incorporating heaters, humidifiers, coolers or the like in the gaseous flow system.
What we claim is:
1. Apparatus for producing a gaseous curtain for isolating a given volume from an environmental gaseous medium, which comprises a base part;
a support structure upwardly extending from said base a chamber defined by a hollow canopy carried on said support structure above said base part and forwardly extending from said support structure;
an upstanding and forwardly directed side face on said support structure extending from said base part to said canopy and defining a side of the volume to be isolated;
passage means incorporating filter means carried by said support structure and communicating between a gas inlet and said chamber;
a gas impeller in said pasage means for impelling gas into said chamber and an electrically operated motor carried by said support structure and coupled to said gas impeller for operation of the gas impeller;
a downwardly directed canopy face on said canopy extending forwardly from said side face and defining the upper parameter of the volume to be isolated;
first nozzle means defining a first substantially parallelsided elongated aperture in said canopy face and communicating with the chamber, said first elongated aperture and said side face defining therebetween a first enclosed area of said canopy face;
one side of said first area being defined by said side face;
second nozzle means defining a second substantially parallel-sided elongated aperture in said canopy face and communicating with the chamber;
the second elongated aperture extending substantially parallel to, and laterally spaced from, the first elongated aperture and the second elongated aperture and said side face defining therebetween a second enclosed aperture and said side facedefining therebetween a second enclosed area of said canopy face;
one side of said second enclosed area being defined by said side face, and said first area being located within said second area;
said second nozzle means projecting downwardly to diverge from said canopy face and said first nozzle means projecting downwardly to diverge from said canopy face at a lesser extent relative to the divergence of said second nozzle means; and
wherein the second aperture has a lateral dimension substantially less than the lateral dimension of the first aperture.
2. Apparatus as defined in claim 1, which includes downwardly projecting third nozzle means defining a third elongated aperture in said canopy face, said third aperture being spaced from said first aperture and said third aperture being located within said first area.
3. Apparatus as defined in claim 1, in which the area of the aperture defined by said second nozzle means is less than the area of the aperture defined by said first nozzle means.
4. Apparatus as defined in claim 2, in which the area of the aperture defined by said second nozzle means is less than the area of the aperture defined by said first nozzle means and the area of the aperture defined by said first nozzle means is less than the area of the aperture defined by said third nozzle means.
5. Apparatus as defined in claim 1, wherein the apertures defined by said first and second nozzle means are of substantially U form, the free ends of which U forms are located adjacent said side face.
6. Apparatus as defined in claim 1, wherein said canopy is carried on said support structure with said first nozzle means situated at a height above said base part consistent with the volume to be isolated being located within the stagnation zone of gas projected through said first nozzle means.
7. Apparatus as defined in claim 2, wherein said canopy is carried on said support structure with said third nozzle means situated at a height above said base part consistent with the volume to be isolated being located within the stagnation zone of gas projected through said third nozzle means.
References Cited UNITED STATES PATENTS 3,021,776 2/1962 Kennedy 9836 X 3,207,056 9/1965 Flebu 98-36 3,282,193 11/1966 Jennings 98-36 3,380,369 4/1968 Allander 98-36 3,385,036 5/1968 Webb -418 3,394,755 7/1968 Morrison 62256 X WILLIAM E. WAYNER, Primary Examiner US. Cl. X.R.
z gz g- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,462,920 Dated August 26, 1969 Inventor(fl) D. F. Denny It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
In column 7, line 43, the word "aperture" should have been area In column 7, lines 44 and 45, the entire phrase "and said side race defining therebetween a second enclosed area" erroneously has been repeated.
It respectfully is noted that lines 43 and 44 should read as follows:
- closed area of said canopy face;
SIGNED Am) scum APR 7 1970 Edmum mm 1:. summon, m. A Gums-1 m or Paton.