CA1189441A - Device for the dosed diffusion of gases in liquids - Google Patents

Abstract

A device is described, which is intended for the dosed diffusion of gases in liquids and which is used especially for small-scale application in the field of aquaria. The device consists essentially of a diffusor which can be filled with gas via an inlet device and round which liquid circulates and which is open in its lower region and is filled via an automatic-ally regulating pressure-regulating valve.

Description

f~

The invention relates to a device for the dosed di~usion of gases in liquid.s, consis-ting of a diffusor which can be fillecl with gas via an inlet device and round which liquid circulates Diffusion de~ices of the type mentioned are used, for example, in chemical process engineering and for water treatment They conventionally consist of a cylindrical di~fusor round which liquid circulates and which is filled with the desired gas via an inlet device.
In this way, an interface via which the gas di~uses into the liquid is formed in the diffusor.
A preferred embodiment of such devices is aimed at a small scale application in the field of aquaria, where the problem arises, above all, of a dosed enrich-ment of the aquarium water with carbon dioxide (CO2).
In addition to a function as a plant nutrient, carbon dioxide acts in the aquarium water as a chemical equili-brium component in the bicarbonate/carbonic acid system, the optimum establishment of which is of great importance for the biotope o~ the aquarium The demand for free carbon dioxide depends on the water volume of the aquarium and on the amoun-t of plant mass occupying it, on the type and intensity o~ the lighting influencing the assimilation process and on the natural proportion of chemical eq~ilibrium carbonic acid ~carbonate hardness).
The establishment of a supply of CO~ can be checked by measuring the pH value of the water.

- 2 A kno~ device for the diffusion of CO2 in aquaria consists OI a diffusion cyl inder which is mounted in a vertical posi-tion against the inner wall of the aquarium by means of a suction-cup sys-tem, for example two suc-tion cups at-tached laterally. The upper end face of the diffusion cylinder is desig~ed as a diffusion diaphragm, via which -the gas dissol~es directly into the water. For this purpose, -the dia-phragm must be completely covered with water and be loca-ted preferably at a height of approximately 4 cm below the water level. The dif~usion cylinder is filled via a hose connectionpiece mouldedonto thecylinder casing near the diaphragm. During the filling c~era-tion, water standing in the diffusion cylinder is dis-placed by CO2 o~er-pressure. Provided for this pur-pose in the end face lying opposite -the diaphragm is a bottom orifice, through which water flows, even ~uring the gradual dif~usion loss of CO2, in a pressure equili brium. To c~eck the filling level, the dif~usion cylinder is made of glass or a traIIsparent plastic.
Filling is carried out by hand, in portions, by means of a regulating valve in which a C02 cartridge is accommoda=
ted, Such a diffusion cylinder has to be filled up manually with C02 at least once a day.
A diffusion device of this type has a series of disadvantages. On the one hand, the size of the di~fusion diaphragm is predetermined owing to the con-struction, so that the diffusion rate can be adapted to the actual C02 requirement only by means of a complicated _ 3 _ parallel connecticn o~ several diffusion cylinders.
Adaptation to a varying C02 requirement re~uires expen-~
sive and disturbing modi~ications in the aquarium.
Furthermore, according to the findings of the present invention, the diffusion operation is at its most e~fec~
tive a-t a high pressure acting on the boundary layer between the gas and liquid In the known embodiment9 however, the diffusion diaphragm is located near the water surface, that is to say, precisely in the region lo of the lowest water pressure. Measurements on the known di~fusion cylinder gave the surprising result that at least a part of ~he C02 diffusion takes place not via the diaphragm, but via the pressure-stabilised gas/
water boundary layer at the bottom of the gas column.
Finally, the manual filling of the di~usion device according to the state of the art regularly requires the attention of an attendant. However, an outlay of this type is hardly acceptable for commercial breeding aquaria and for decorative aquaria in business premises a~d restaurants. Filling of the diffusion cylinder by hand will always be accompanied by extreme variations in the le~el and occasional irregularitie~ which have an adverse effect on the constancy o~ the C02 diffusion rate.
The object of the invention is -~ provide a device of the type mentioned in the introductiont which can be handled convenlently and easily and is easily adjustable and in which the ~i~fusion rate can be varied over a wide range withollt modi~ication~ and can conse-?

quently be adapted dynamic~lly to changLng re~uirements.
Thi~ object is achieved by means of a diffusor whioh is open in it~ lower region and which can be filled with gas via an automatically re~ulating pressure-regulating valve.
Advantageous embodiments of the device according to the inven-tion are characterised by -the features set out in the claims.
The device according to the invention does away with a costly diffusion diaphragm which, in addition9 in the biologically active environment of an aquarium is constantly in danger of being clogged by suspended particles and plant growth and has to be cleaned regu-larly. The shaping according to the invention of the diffusor makes it possible to fix -the size o~ the effec-tive diffusion interface between the gas and li~uid by presetting a mean regulating gas pressure. It can therefore be adjusted by preselecting a mean gas pres-sure, and the gas pressure can be stabilised automatic--~ ally round the preselected average value by means of apressure-regulating or pressure-reducing valve. For this purpose, the shape of the diffusor can be varied ~ithin ~ide limits according to the desired range of ad~ustment. Qfter the adjustment has been made, the desired pressure is kept constant o~er a long period of time by means o~ small regulating deflections. The automatic mechanism according to the in~ention for the self-~illing o~ the dif~usor permits, for the first time, a pressure regllation ~ith a control str~ke of ~ lO mb.

The diffusor designed in this way can be placed on the bottom of an aquarium, in such a way that the gas out-flow orifice is located near the bottom.
This has -the adv~ tage that the C02 is suppliecl in the root region of any plants present, which has a favourable e:Efect on their growth.
The inven-tion is explained in more detai 1 with reference -to an exemplary embodi men-t illustra-ted in -the drawi ngs in whi ch:
Figure 1 shows a cross-sec,ional;side view of a dif~usor according to the invention; and Figure 2 shows an enlarged cross-sectional view in an axial direction of an especially advantageous pressure-regulating valve connected in front of the diffusor.
The dif fusor 1 is a hollow body open in its lower region. Its shaping depends, in particular, on the desired variation in the effective diffusion interface with the set regulating gas pressure. Figure 1 shows an embodiment with a contour which ~idens conically downwards and in which an increase in the regulating pressure therefore takes place when the diffusion inter-face is enlarged. The diffusor 1 is preferably placed on the bottom of a vessel of liquid, for example an aquarium ~not shown).
In the exemplary embodiment illus-trated, a cylindrical ,end piece 3 perforated with large-area recesses 4 is moulded onto the conlcal part 2 of the diffusor 1 for this purpose . The irlt erior of the diffusor 1 communi-cates with the sur~ounding liquid via these recesses 4.
The top ed~e 5 of -the recesses 4 limits the maxi~um gas level in the diffusor 1. The outer surface of the end piece 3 be-tween -the recesses 4 con-stitutes a series of feet 6 which guarantees a sufficientdistance between the bottom of -the vessel of liquid (not shown) and the line of the maximum level in the diffusor 1 and, consequently, an unobstructed exchange of liquid. Instead of the recesses 4 in -the cylin-drical end piece 3, notches, supporting cams, etc (notshown) can also be p~ovided at the lower margin of the diffusor 1 The fixing or anchoring of the di~fusor 1 on the bottom o~ the vessel is made easier, for applications in the field of aquaria, by means of the conical shaping illustrated. Thus, the diffusor 1 can be tilted in a simple way between stones laid laterally against it and can, as a result, also be hiddenO To support weighting material, the end piece ~ of the diffusor 1 near the bottom can be provided with a continuous or interrupted projection 7 resembling ~
flange. Alternatively or additionally, further pro-jections 7~ can be ~ormed on the outer casing of the diXfusor l; and the top side of the dif~usor 1 can be designed as a supporting face9 for example in the form o~ a supporting plate ~. In an especially advantage-ous embodiment, the diffusor 1 i5 closed on its under-~ide with a releasably inserted or glued-in cover 87, so that weighting material can also be in~roduced into the in~erior of the dif f U50r 1 ~
Formed on -the top side of the diffusor 1 is a projecting connec-tion piece 9 which permits the inflow of gas into the interior of -the diffusor 1. A hose (not shown) leading to -the discharge side of the pres-sure-regulating valve is pushed onto the projecting connection piece 9. The diffusor 1 is preferably made in one piece of glass or a transparent or trans-lucent plastic.
The functioning parts of the pressure-regulating valve 10 (Figure 2) are mounted in a housing 11. This is an axially symmetrical shaped part open on t,he end face, with a continuous axial bore 12 having a stepped diameter. The housing 11 consists of a wide base cylinder 13 and of a conically tapering section 14 which ismouldedontothelatter and which merges, in turn, into a cylindrical housing projection 15 having a comparatively small diameter~ The axial bore 12 in the housing projection 15 is narrowed at approximately half its ~ height by a radial contraction 16 dividing the interior of the housing projection 15 into two chambers 1? and 18 of approximately equal size. The outer chamber 17 assi Bed to the free end of the housing projection 15 receives a spring-loaded small valve 19 and is subjected to the gas pressure on the supply side. On the other hand, the inner chamber 18 belongs to the reg~llating-pressure region o~ the pressure-re~ulating valve 10.
The control movement of all the components of this pressure-regulating ~alve 10 takes place in the axial direction of the housing 11.
The small valve 19 consists of an axially per-forated sleeve 20 open at both ends, which can be inserted coaxia]ly to fit in-to -the ou-ter chamber 17 of the housing projection 15. The sleeve 20 res-ts with a radially outwardly projecting flange 21 in a leak-tight manner on the end face of the housing projection 15. An 0-ring 22 which is pushed onto the sleeve 20 against the flange 21 and which is pressed into a coni-cal portion a-t the end of the axial bore 12 of the housing 11 serves as a seal. The pressing force is provided by a union nut 23 which rests in a sliding manner on the rear side of the flange 21 and which is screwed on-to an external thread on the housing projec-tion 15.
Moulded, in an axial prolongation, in one piece on-to the sleeve 20 is a projecting connection piece 24 which, when -the sleeve 20 is assembled, projects beyond the union nut 23 and permits the pushing-on of a hose (not shown) leading to the pressure source, for example a C02 cartridge. The clear wqdth of the projecting connection piece 24 is narrowed in relation to the sleeve 20. The narrowing point 25 constitutes the abutment for a compression spring 26 located in the interior of the sleeve 20. This compression spring 26 works against a valve head 27 which is guided in the interior of~the sleeve 20 and is mounted axially movably.
The axial play of movement is limited by a step 28 in the wall o~ the sleeve 20. The compression spring 26 1~ pushed onto a peg 29 moulded onto the valve head 27.
As a resul-t o~ the prestress of the com~ression spring 26, the v31ve head 27 lies against a sealing ring 30 in a leak-tight manner. The supply-pressure region of the pressure-regula-tlng ~alve is thereby shu-t off ~rom the regulating-pressure part, The sealin~ ring 30 is mounted in a leak-tight seat on the contraction 16 separating the chambers 179 18 o~ the housing projection 15. The internal dimension of the sealing ring 3O
corresponds approximately to the clear wldth of the con-traction 16.
The valve head 27 is lifted out of its sealing position from the regulating-pressure side of the pressure-regulating valve. This purpose is served by a mushroom-shaped th~ust member 31, the cylindrical shank of which slides axially in the inner chamber 18 of the housing projection 15. Located on the end face of the shank is a tappet 32 which passes through the con-traction 16 of the housing projection 15 and -the central orifice of the sealing ring 30 resting thereon. The tappet 32 acts operatively against the valve head 27, against which it rests loosely. The mushroom-shaped thrust member 31 rests loosely on the elastic diaphragm 35 which shuts off the regulating-pressure par-t of the pressure-regulating valve 10 in a leak-tight manner.
The diaphragm 35 consists of a round diaphragm disc which is retained,at its peripheral margin from the one side by a shoulder 36 on the inner wall of the housing 11 and from the other side by a retaining ring 37. The dia-phragm 35 forms the base o~ the conical housing section14 and lies approxima-tely flat in the closing posi-tion of the small valve 19, The thrust plate 33 of the ~ushroom-shaped thrust member 31 covers the central region of the diaphragm 35 and is movable in~he axial direction in the interior of the conical housing section limi-ted by the diaphragm. The play of movement of the mushroom-shaped thrust member 31 corresponds at least to the control stroke of the small valve 19.
The diaphragm 35 is moun-ted in aipressure-tigh~
manner between the retaining ring 37 and the housing 11.
The retaining ring 37 is a fitting part correspondir~ to the inte~nal dimension of the base cylinder 13. It is inserted coaxially into the base cylinder 13 from the side OL the housing lying opposite the housing projec-tion 15, is pressed against the elastic diaphragm 35 and is locked in the sealing position by one or more self-tapping screws 38.
The external~air side of the diaphragm 35 is loaded by a piston 39 which covers approximately the entire face of the diaphragm ~5 with the exception of a free region in the vicinity of the margin. T~e piston 39 is spring-loaded and mounted movably in an axial direction. For this purpose, an intermediate plate 40 o~fset in~ards from below in relation to the support ing face o~ -the pressure-regulating valve lO is drawn into the re~aining ring 37. This intermediate plate 40 is pro~ided with a central axial threaded bore 41 into which an adjusting bush 42 is screwed. The pis-ton rod 43 Gf the pis~on 3g loading the diaphragm 35 isretained an~ guided in the adjusting bush 42 with an ax~.al sliding play. Provided in the piston rod 43 is an axial blind bore 44 into which is inserted a com-pression spring 45 acting against the bottom o~ theadjusting bush 42. The screw-in depth of the adjus-t-ing bush 4Z thus de-termines the force with which the piston 39 presses against the diaphragm 35.
The chamber 46 formed by the casing and the intermediate plate 40 of the retaining ring 37 and the diaphragm 35 is connected to the external air by the thread turns o~ the ad~usting bush 42J Pressure compensation is thereby guaranteed sufficiently Finally, a gas outlet is located laterally on the housing 11 of the pressure-re~llating valve 10.
For thi purpose, in the embodiment illustrated, a bore ~7 meeting the regulating-pressure region of the valve is guided through the wall of the housing 11. Inserted from outside into the bore 47 is a hose connection piece 487 the wall of which has in the lower region a continu-ous circular groove for receiving a sealing ring 49 and in the upper region a retaining collar 50. The hose connection piece 48 is pushed into the bore 47 in a leak-tight manner and is locked against the housing 11 on the retaining collar 50 by means of a sel.f-tappîng screw 51. The end o~ the hose connection plece ~
which is wid~ned in the form o~ an olive ~or holding the hose is provided with a thread into which a reducing screw 52 is screwed from outside. The gas stream ~low~ ou-t essentially through the thread turns 3f the reducing screw 52 and is thereby strongly throttled.
The reducing screw 52 can be provided, according to requirements, wi-th one or more knurled inden-tations at right angles -to the thread turns and can accordingly present less ~low resistance.
The function of the pressure-regula-ting valve 10 according to the invention is characterised by an equilibrium of forces at the valve head 27 which has to be lifted out of its leak-tight seat agaiins-t the pres-sure prevailing on the gas inlet side and agains-t-the pres-tress of the compression spring 26. In the in-terests of a low actuating force, the face of the valve head 27 subjected to pressure on the inlet side must be minimum, for this purpose, and actuation of the valve head 27 must t~ke place with as little friction as possible, The actuating force re~uired is trans-mitted by the spring-loaded piston 39 via the elastic diapnragm 35 to the mushroom-shaped -thrust member 31 which acts with the tappet 32 on ,he valve head 27.
Until the regulating pressure falls below a nominal value determined by the spring prestress of the piston 39, this actuating force is compensated by the regulating pressure acting on the large-area diaphragm 35, and the valve head 27 remains in the sealing position. The nomlnal value is preselected on the adjusting bush 42.
After the va~ve head 27 has been lifted off, a suffici-ent pressure increase must result in the regulating-pressure region to close the gas inlet again. For this purpose, the outflow of gas ~rom the regulating-pressure region is prevented by strong throttling Because o~ the possîbility of pressure regulation in the low-pressure range with tolerances o~ approxi mately ~ lO mb, a preclse regulation of the level ln the dif~usor according to the invention is provided.
Constructional features of -the pressure-regulating valve which are material to the invention are the use of a low-friction sm~ll valve on the gas inlet side, the use o~ a large-area elastic diaphragm in the regulating-pressure region and a strong reduction of the gas stream in the ou-tlet.
The pressure-regulating valve according to the in~ention is designed for a supply pressure o~ between lOO mb and 2 b. In the exemplary embodiment illus-trated, the gas is supplied to the pressure-regulating valve via a hose connec-tion piece. Pressure reducers, reducing valves and/or expansion chambers (none of these sh~wnj, which may be necessary and are connected separately upstream of the pressure-regulating valve can, o~ course~ also be connected in one piece to the pressure-regulating valve.
Securing of the pressure regulating valve and gas supply container may be accomplished by the use o~ any suitable means. The valve and gas supply means may be either in or outside the liquid vessel; however, due to the ease of adjustment and/or gas supply replenishment when the valve and gas supply are situated outside the liquid vessel or at least above the water level, such arrangement is most preferred.
-, .

Claims (7)

1. Device for dosed diffusion of gases in liquids, particularly for application in the Field of aquaria, said device comprising an automatically regulating pressure-regulating valve and a diffusor adapted to be placed into a liquid-containing vessel with a lower open portion situated below the liquid level near or at the bottom of said vessel, said diffusor being formed as a hollow body having an upper portion with a gas inlet which is connectable to the pressure-regulating valve, said device being characterized in that said pressure-regulating valve (10) is blocked on the supply-pressure side by a small valve (19) operable by means of an actuating member subjected to a regulating pressure and to an adjusable prestress, said valve (19) consisting of a valve head (27) loaded by a compression spring and axially movable against a sealing ring (30), said valve head being lifted out of its leak-tight seat be means of a tappet (32) one end of which being directed to said valve head whereas a mushroom-shaped thrust member (31) is mounted on the opposite end of and movable with said tappet, said mushroom-shaped thrust member resting on an elastic disc-shaped diaphragm (35) which shuts off in a leak-tight manner a regulating-pressure region of the pressure-regulating valve (10).

2. Device according to claim 1, characterized in that the outer side of the diaphragm (35) facing away from the mushroom-shaped member (31) can be subjected to a definite force by an axially movable piston (39).

3. Device according to claim 1, characterized in that the valve head (27), the mushroom-shaped thrust member (31) and the piston (39) are guided movably in the axial direction of a housing (11) encasing the pressure-regulating valve (1), and the diaphragm (35) is retained in its peripheral margin in a shoulder (36) on the inner wall of the housing (11).

4. Device according to claim 2, characterized in that the diaphragm (35) is pressed in a leak-tight manner against the shoulder (36) by a retaining ring (37) insertable into the housing(11), and drawn in the retaining ring (37) is an intermediate plate intermediate plate (40) having a central threaded bore (41) for receiving an adjusting bush (42) forming the abutment for a piston rod (43) of the piston (39) loading the diaphragm (35).

5. Device according to claim 4, characterized in that the piston rod (48) is retained in the adjusting bush (42) with an axial play of movement and has a blind bore (44), into which is inserted a compression spring (45) acting against the adjusting bush (42).

6. Device according to claim 3, characterized in that provided in a wall of the housing (11) is a gas outlet communicating with the regulating-pressure region of the pressure-regulating valve (10) and having a hose connection piece (48), onto which a hose leading to the projecting connection piece (9) of the diffusor (1) can be pushed.

7. Device according to claim 6, characterized in that provided in the hose connection piece (48) is a thread for receiving a reducing screw (52) strongly throttling the gas stream.