Air-curtaining Apparatus For Forming An Internal-isolated Zone

Abstract

An apparatus for forming an air curtain encircling an internal zone completely isolated from surroundings. In preferred embodiment, a stratospheric air flow is simultaneously supplied into the isolated internal zone for removing harmful gaseous contaminant produced therein. Dimension of the air curtain forming air exhaust opening is selected in relation to the shuttering distance and that of the supply opening by application of critical mass flow ratio method theory.

Description

The present invention relates to an improved air-curtaining apparatus for forming an internal-isolated zone, and more particularly, relates to an improved air-curtaining apparatus for forming an internal zone pneumatically isolated from its surroundings and, when particularly required, for exhausting harmful gaseous contaminant contained within the zone encircled by the air curtain.

When a substance productive of harmful gaseous contaminant is to be processed through various operations, it is necessary to protect the operators concerned in the work from contact with the harmful gaseous contaminant. For example, in a metal-plating process, various harmful gaseous substances are produced by the metal-plating bath and they tend to contaminate and pollute the air in the vicinity of the bath. In order to avoid such contamination and pollution of the air, it is necessary to completely isolate the source of the harmful gaseous contaminant from its surroundings and effectively exhaust the produced harmful gaseous contaminant out from the isolated space. Conventionally, a canopy-type hood is often used for this purpose. However, in case of the conventional hood of this nature, it is necessary to make the opening of the hood considerably large so as to acquire a complete and sufficient exhausting of the harmful gaseous contaminant with a strong and reliable isolating effect by the air curtain. This resulted in expensive hood installation cost and considerably large power consumption. With the reason set forth above, the air curtain isolating system could not show a great penetration into the field of practical utilization and protection of the operators from contact with the harmful gaseous contaminant was mostly dependent upon the use of a protecting mask or the like.

A principal object of the present invention is to provide an improved air-curtaining apparatus capable of producing an internal zone completely isolated from its surroundings with minimum power consumption and small installation cost.

Another object of the present invention is to provide an improved air-curtaining apparatus capable of producing a cleaned internal zone isolated from the surroundings by the air curtain.

Still another object of the present invention is to provide an improved air-curtaining apparatus capable of protecting operators from contact with harmful gaseous contaminants.

In conformity to the referred objects, the air-curtaining apparatus of the present invention is characterized by forming an air curtain defining an internal zone in a condition completely isolated from its surroundings. In a particular embodiment, the air curtain is formed encircling a harmful gaseous contaminant producing source and the apparatus is further characterized by generating a stratospheric gaseous flow for positively exhausting the harmful gaseous contaminant from the isolated internal zone.

In the conventional-type air-curtaining system, the air flow ejected from a supply opening advances towards an exhaust opening while gathering air in the surroundings together with it. On arrival at the exhaust opening, the increased amount of airflow further tends to gather air in the vicinity of the exhaust opening. Further, in case any change takes place in the condition of the surroundings, the advancing direction of the air tends to deviate from its correct position. Faced with the above-described increase in the amount of the airflow to be exhausted and/or the probable change in the flow direction, it is necessary to design the dimensions of the exhaust opening larger than that of theoretical calculation.

As is well known by persons in the art, the airflow ejected from the supply opening advances towards the exhaust opening in a gradually diverging condition and the exhaust opening has to be completely receptacle of the air flow of thus diverged size. The longer the distance between the supply and exhaust opening, the larger the degree of the flow's divergence and the larger should be the dimensions of the exhaust opening. That is, the enlargement of the exhaust opening dimensions is further promoted by the flow divergence resulting in necessity for larger floor space.

Further, when the airflow is purposed for an air curtain, there are instances when the thickness of the curtain is required to be thin. For example, the airflow is often used as an air curtain for isolating an operator from a harmful gaseous material of a produceable nature. The operator extends his hands from outside of the air curtain to the material deposited inside the air curtain through the air curtain. To accomplish this, the thickness of the air curtain must be thin enough to isolate the operator completely from the material in the internal zone of the air curtain. The above-described diverging tendency of the ejected airflow prevents making the air curtain as thin as required.

A further object of the present invention is to provide an improved air-curtaining apparatus capable of producing a relatively thin air curtain without damaging its isolating effect.

A still further object of the present invention is to provide an improved air-curtaining apparatus which requires only a small floor space occupation with the reduced exhaust opening's dimensions.

A still further object of the present invention is to provide an improved air-curtaining apparatus capable of presenting a strong isolating effect with considerable reduction in power consumption.

In order to fulfill the above-described objects, the air-curtaining apparatus of the present invention, utilizing hood characteristics basing on "Critical flow ratio method," comprising an exhaust opening whose size in the direction of the air curtain's thickness is so designed as smaller than the thickness of the ordinary air curtain at the position of the exhaust opening. Based upon this principle, the referred size of the exhaust opening is adequately selected according to the conditional relationship between the surroundings and the isolated internal zone.

Further features and advantages of the present invention will be apparent from the ensuing description, reference being made to the accompanying drawings, in which;

FIG. 1 is an explanatory side view of an embodiment of the air-curtaining apparatus of the present invention,

FIG. 2 is an explanatory side view for showing a modified embodiment of the air-curtaining apparatus shown in FIG. 1,

FIGS. 3 and 4 are front and side explanatory views for showing an embodiment of a practical utilization of the air-curtaining apparatus of the present invention,

FIG. 5 is an explanatory side view of a conventional air-curtaining system,

FIG. 6 is an explanatory side view of an air-curtaining system according to the present invention.

Referring to FIG. 1, an embodiment of the air-curtaining apparatus is shown. In this case, the air curtain forming airflow is advanced from a floor side to a ceiling side. The air supplied from a given supply source (not shown) is processed through a supply duct 1 passing through an air filter 2 disposed therein and conducted towards a supply opening 3 by a fan 4 also disposed in the supply duct 1. Being ejected from the supply opening 3, the air is advanced towards an overhead canopy-type exhaust hood 6 forming an air curtain 7 encircling an inside zone 8. Being received by the exhaust hood 6, the air is conducted to an air cleaner 9 passing through an exhaust duct 11 and discharged outside the system by an exhaust fan 12 disposed in the exhaust duct 9. Thus, the internal zone 8 is completely isolated from the surroundings by the air curtain 7 formed encircling the same. The locational relationship between the supply opening 3 and the exhaust hood 6 and the dimensions of the two are adequately selected in conformity to the dimension of the required internal zone 8. When desired, a source of harmful gaseous contaminant is placed within the internal zone and in this case, the produced harmful gaseous contaminant is also absorbed into the exhaust hood 6 together with the airflow forming the air curtain 7.

During the flowing procedure, the air curtain forming airflow tends to attract additional amounts of air from its surroundings facing the air curtain 7. Thus, generally, the total amount of the gaseous flow to be discharged through the exhaust duct 11 is the sum of the supplied air curtain forming air, the harmful gaseous contaminant and the attracted air. However, in the case of a certain kind of harmful gaseous contaminant, the above-described total amount may be required to be only larger than the sum of the supplied air curtain forming air and the harmful gaseous contaminant.

The above-described air-curtaining apparatus can be used in a reverse manner too, i.e., the air curtain forming airflow may be advanced from a ceiling side to a floor side. This type of example is illustrated in FIG. 2 with some modification for positively discharging the harmful gaseous contaminant from the internal zone.

In the shown embodiment, the air supplied from a given supply source (not shown) is processed through a supply duct 13 and conducted to a canopy-type supply hood 14 by a fan 16 disposed in the supply duct 13. The supply hood 14 is divided into two parts by a deflector 17 disposed therein, i.e. an air curtain flow supply opening 18 of a slit type and a flow supply opening 19 of a filter type. So, a part of the airflow conducted by the fan 16 is advanced towards the air curtain flow supply opening 18 and ejected outside therefrom. Being ejected therefrom, the airflow advances towards the downwardly located exhaust opening 21 forming an air curtain 7 encircling an internal zone 8 and discharged outside the system by a fan 22 through an exhaust duct 23 connected to the exhaust opening 21. The thus-formed internal zone 8 is adapted for placing the source of the harmful gaseous contaminant (not shown in the drawing) and is completely isolated from the surroundings by the encircling air curtain 7. Aside from this air curtain formation, the remaining part of the airflow conducted by the fan 16 is advanced towards the airflow supply opening 19 and ejected into the internal zone 8 and this airflow then advances toward a downward exhaust hood 24 while urging the contaminated gas in the internal zone 8 towards the exhaust hood 24. Thus absorbed mixture of the ejected airflow with the contaminated gas is then discharged outside the system by a fan 26 through a discharge duct 27 connected to the exhaust hood 24 and an air cleaner 28 disposed to the discharge duct 27. The discharged air may then be partly or almost completely circulated back to the supply duct 13 and the contaminated gas can be completely removed from the above-described mixture by the function of the air cleaner 28. Thus, the internal zone 8 can be always maintained clean and free from contamination by the harmful gas.

The air-curtaining apparatus of this type may also be advantageously utilized for making a clean isolated zone within contaminated surroundings. In this case, invasion of the contaminated airflow into the zone is obstructed by the presence of the air curtain 7 encircling the internal zone 8 and the internal zone 8 can always be maintained in a cleaned condition because of a continuous supply of the airflow from the supply opening 19. By a suitable selection of the nature of the airflow to be supplied into the internal zone 8, any desired conditioning of the internal zone 8 can be attained. This is a great advantage when operators have to work within contaminated or polluted surroundings. It goes without saying that the direction of the airflows can be reversed from that shown in FIG. 2.

Referring to FIGS. 3 and 4, an embodiment of a practical utilization of the air-curtaining apparatus of the present invention is shown. In this case the air-curtaining apparatus is applied to a process for providing a roller with one or more rubber layers. It is well known that some harmful gas is produced during this process and operators must be completely protected from a physical attack by the harmful gas. For attaining this protection, it is necessary that the harmful gas be removed just after its formation without being scattered into the surroundings.

In the shown embodiment, a supply duct 29 connected to a given supply source is branched off in the vicinity of its flow issuing termination, i.e., a part of the supplied airflow is advanced to an operating station 31 and the remaining part of it is advanced to a drying chamber 32. On the operating area side, a branched supply duct 29a is provided with an air filter 33 disposed therein downstream of the branching point. At a position downstream of the air filter 33, a deflector 34 is disposed so as to divide the supplied airflow into two terminations. A part of the supplied air flows towards supply openings 36 being of a slit type and ejected therefrom towards respective downward exhaust openings 37 formed in the floor forming an air curtain 7 encircling an internal-isolated zone 8. In connection with the deflector 34, an internal duct 38 is disposed within the branched supply duct 29a with its downward termination directed to a porous plate 39 disposed within a space 41. The space 41 and a flow supply opening 42 formed downward of the space are divided into sections by a plurality of partitions 43 disposed therein for the purpose of flow rectification. So, the remaining part of the supplied air flows towards the supply opening 42 passing through the porous plate 39, ejected therefrom into the internal zone 8 and reaches the downward exhaust opening 37 together with the airflow forming the air curtain 7. Being received by the exhaust opening, the mixture of the air curtain forming air, air enticed from the surroundings, air supplied from the supply opening 42, and the produced harmful gaseous contaminant is conducted outside of the system through an underground exhaust duct 44 and a flow rate regulating damper 46 disposed in the exhaust opening 37. Aside from the above-described airflowing system, another branched supply duct 29b runs from the supply duct 29 to the drying chamber 32 neighboring the operating station 31 by way of suitable drying equipment 47 (See FIG. 4). A part of the air supplied through the supply duct 29 is conducted through the branched supply duct 29, brought into an upper space 48 of the drying chamber 32, ejected into the drying chamber 32 passing through a porous plate 49 and discharged outside the drying chamber 32 through an underground discharging conduit (not shown). The upper space 48 may be divided into sections by partitions 51 suitably disposed therein.

In combination with the above-described arrangement of the apparatus, a roller 52 to be treated is first brought to the operating station 31 into the internal-isolated zone 8 being carried on a suitable carrier 53. The carrier 53 may be moved either by a manual operation or by any known transportation means. The operator (not shown) standing outside the air curtain 7 prosecutes necessary operation on the roller by extending his hands into the internal zone 8 passing through the air curtain 7. The harmful gaseous contaminant produced during the operation does not scatter into the surroundings being barricaded by the air curtain 7 and the operator can be completely protected from direct contact with the produced harmful gaseous contaminant. After the operation, the roller 52 together with the carrier 53 is brought into the drying chamber 32 for drying and the harmful gaseous contaminant produced during the drying operation is also discharged outside the drying chamber 32 as already explained.

In the actual utilization of the air-curtaining apparatus of the present invention, there is a fundamental requirement for decreasing the floor space necessary for the installation of the airflow exhaust opening. This reduction in floor spacing should be preferably attained without lowering the shuttering effect of the air curtain and a wide adaptability of the apparatus for use under various conditions of the surroundings. In this connection, the inventor of the present invention has discovered that the above-described requirement can be fulfilled by defining the dimension of the airflow exhaust opening in relation to the mechanical condition of the whole system. In the following description, the term "opening's width" refers to the size of the quoted opening in the direction of the formed air curtain's thickness or, in a direction transverse to that of the airflow.

The term "shuttering distance" as hereinafter used refers to a distance to be shuttered by the air curtain.

For a better understanding of the air-curtaining system according to the present invention, a conventional type of air-curtaining system will first be discussed with reference to FIG. 5, wherein an air curtain forming flow 54 ejected from a supply opening 56 of a slit type advances in a gradually diverging condition and is received by an exhaust opening 57 located downward while attracting additional air from the surroundings.

Provided that the quantity of the air curtain forming airflow is Q.sub.0, the quantity of the air attracted from the surroundings is Q.sub.1, the quantity of the total airflow arriving at the exhaust opening 57 is Q.sub.2 and the quantity of the air attracted into the exhaust opening 57 from the surroundings in the vicinity thereof is Q.sub.3, the total quantity of airflow to be discharged outside the system through the exhaust opening 57 must be (Q.sub.2 +Q.sub.3). Consequently, the exhaust opening's width D is required to be at least larger than the thickness of the airflow whose quantity is Q.sub.2. Further, taking the diverging tendency of the air curtain forming airflow into consideration, it is quite obvious that an increase in the shuttering distance H entails a corresponding enlargement in the exhaust opening's width D. As already mentioned, such an enlargement in the exhaust opening dimension results in the requirement for an enlarged floor spacing together with considerably increased power consumption.

The flowing mode of the air curtain according to the art of the present invention is shown in FIG. 6, wherein the air curtain forming flow 54 developed by the fluid supply means and ejected from the supply opening 56 of a slit type advances in a gradually diverging condition to a certain distance. After passing a virtual plate A-B, the airflow tends to be gradually converged and received by the fluid-receiving means including the exhaust opening 57 while enticing or inducing additional air from the surroundings. In accordance with the requirement in actual utilization, this virtual plane A-B is so selected that the distance H' between the virtual plane A-B and the exhaust opening 57 corresponds to the required shuttering distance, i.e., the converging airflow part 58 forms an air curtain whose shuttering effect is expected. After selecting the location of this virtual plane A-B, the exhaust opening's width D' is calculated by application of the "Critical flow ratio method" theory and in relation to the supply opening's width E, the air curtain's thickness E' and the shuttering distance H' as follows.

E'/5 D' (1)

H' 3 E' /2 (2)

E/5 D' E (3)

Thus, it is possible to narrow the exhaust openings width D' smaller than that of the conventional air-curtain without any decrease in the shuttering distance.

A further preferable result can be obtained in the actual utilization of the apparatus of the present invention by giving a particularly defined dimensional relationship to the supply opening, exhaust opening and their related parts of the flowing system. In that preferred embodiment, the air curtain forming airflow is ejected from the supply opening in a condition having a uniform flow velocity distribution. The air curtain is mainly made up of a core portion of thus-ejected airflow. The width of the supply opening is required to be larger than one-fifth of a required shuttering distance and the width of the exhaust opening is required to be smaller than that of the supply opening. The mass of an exhausted flow must be so selected as is always larger than the mass of the supplied flow.

In case there is a temperature difference between the surroundings and the air curtain forming airflow or an internal-isolated zone encircled by the air curtain, a suitable compensation should be applied to the flowing system by mechanically adjusting the value of the critical flow ratio.

Claims

What is claimed is:

1. An improved air-curtaining apparatus comprising, in combination: means defining a supply opening configured to eject an airflow in the form of an air curtain to pneumatically encircle a space and isolate same from its surroundings, a supply conduit connecting said supply opening to a pneumatic supply source, means defining an exhaust opening dimensioned to receive both said air curtain forming airflow and additional air attracted from the surroundings by said air curtain forming airflow and positioned in spaced-apart relationship to and facing said supply opening, said exhaust opening having a width dimension defined by the relationships

E'/5 D'

H' 3E' /2

E/5 D' E

wherein D' represents said width of said exhaust opening in a direction transverse to the flowing air; E represents the width of said supply opening in a direction transverse to the flowing air; H' represents the desired shuttering distance; and E' represents the thickness of said air curtain at a distance H' from said exhaust opening, and an exhaust duct connected to said exhaust opening.

2. An improved air-curtaining apparatus as claimed in claim 1, further comprising means defining an additional supply opening configured and positioned to eject a stratospheric airflow into said internal space encircled by said air curtain, means connecting said additional supply opening to said pneumatic supply source, means defining an additional exhaust opening dimensioned to receive therein said stratospheric airflow and located in spaced apart relationship to and facing said additional supply opening independently from said first-mentioned exhaust opening, and an additional exhaust duct connected to said additional exhaust opening.

3. An improved air-cutaining apparatus as claimed in claim 2, including a common housing containing therein both said first-mentioned supply opening and said additional supply opening, and air deflectors mounted in said common housing separating said first-mentioned supply opening from said additional supply opening.

4. An improved air-curtaining apparatus comprising, in combination: means defining a supply opening configured to eject an airflow in the form of an air curtain to pneumatically encircle a space and isolate same from its surroundings, a supply conduit connecting said supply opening to a pneumatic supply source, means defining an exhaust opening dimensioned to receive both said air curtain forming airflow and additional air attracted from the surroundings by said air curtain forming airflow and positioned in spaced-apart relationship to and facing said supply opening, an exhaust duct connected to said exhaust opening, and means for delivering the airflow through said supply opening in a condition having a uniform flow velocity distribution, wherein the width of said supply opening is larger than one-fifth of the desired shuttering distance, and wherein the width of said exhaust opening is smaller than that of said supply opening.

5. An apparatus for fluidally isolating a space from its surrounding space comprising: fluid means for supplying a flow of fluid defining a fluid curtain around a space to be isolated and including means defining a supply opening having a width E extending in a direction transversely to the direction of fluid flow; fluid-receiving means spaced apart from said fluid supply means in the direction of fluid flow for receiving therein said fluid flow and cooperative with said fluid supply means to completely isolate said space from its surrounding space, said fluid-receiving means including means defining an exhaust opening having a width D' extending in a direction transversely to the direction of fluid flow; means locating and dimensioning said fluid supply means relative to said fluid-receiving means to effect first divergence and then convergence of said fluid flow between said fluid supply and receiving means; and wherein said supply opening and said exhaust opening are dimensioned in accordance with the expression

E/5 D' E.