The invention relates to a mixing apparatus for the mixing of two gaseous or liquid media with a controlled ratio, comprising respective input connections for receiving the media, which are connected through respective pressure controllers to input ports of a mixing unit. The mixing unit comprises at least one inner space communicating with the associated one of the input ports, and respective second inner spaces communicating through respective sections with the associated first inner space, wherein the second inner spaces communicate with a uniting space, preferably a bore with the output port of the mixing unit. In said communicating sections respective control means are arranged for adjusting the flow cross sections through the associated one of the sections wherein the opening and closing of the control means occurs in opposite directions by means of a handling unit.

For the mixing of flowing gaseous or liquid media several solutions are known, among them those having the aforementioned properties. Such apparatus are used mainly in life support systems, i.e. respirators for adjusting the ration of air and oxygen.

In US 3,809,109 following a pressure redactor a conical valve is moved by a common adjusting means which ensures that the resulting flow volume remains unchanged. The device provides both for the mixing ration and the flow rate and these tasks cannot be solved independently from each other or only after long delays. The pressure reduction is resolved by a separate electrically controlled system.

A further mixing apparatus is disclosed in US 5,671,767 in which the mixing ratio is adjusted by a cam disc turned by an adjusting means so that two specially designed pistons move in opposite directions and in this solution the mixing ration can depend on the flow volume, and it comprises a further control. This solution works under small pressure, and with regard to the fact that in case of assisted respiration the flow rate of the mixture should be adjusted quickly and to a substantial extent, and the adjusted ratio of the components cannot be made independently from the flow rate, thus there is no possibility here for the independent adjustment of the ratio of the components from the flow rate. In addition to this problem, with regard to the low pressure, the mixing requires the use of high volumes that increases both the size and weight of the apparatus, and the time required for carrying of the adjustments is also longer. The task of the invention is to provide a mixing apparatus that improves these known solutions and can adjust the required mixing ratio in small volume and in a reliable manner and independent from the flow rate required by the user, wherein the speed of adjustment is fast.

A further task is to solve is ensuring said properties solely mechanically, i.e. without any electrical or electronic control.

For solving these tasks, it has been realized that in case of gases, the mixing should be carried out at a high pressure being between 2 and 10 bar, preferably between 3 and 6 bars, because with such pressure smaller volumes can be used and the mixing ratio can be made largely independent from the required flow rate, while the response time of the control is short.

According to the invention, a mixing apparatus has been provided for the mixing of two gaseous or liquid media with a controlled ratio that comprises respective input connections for receiving the media, which are connected through respective pressure controllers to input ports of a mixing unit. The mixing unit comprises respective inner spaces communicating with the associated one of the input ports, and respective second inner spaces communicating through respective sections with the associated first inner space, wherein the second inner spaces communicate with a uniting space, preferably a bore with the output port of the mixing unit. In said communicating sections respective control means are arranged for adjusting the flow cross sections through the associated one of the sections, wherein the opening and closing of the control means occurs in opposite directions by means of a handling unit, wherein according to the invention in the mixing unit the first and second inner spaces are constituted by respective separate stepped bores that have sections with a smaller and a greater diameter and they are made in a block so that the first inner spaces are in the smaller diameter sections and the second inner spaces are in the greater diameter sections, and the respective control means are turned and axially displaced under the effect of moving the handling unit in the same extent but in opposite sense in their associated stepped bores and change the flow cross section through said communicating sections in the same or substantially the same extent but in opposing senses, whereas the combined flow cross section of the two controlled communicating sections remains the same or nearly the same. In a preferred embodiment the greater diameter portions of the two stepped bores are open to a side, generally the upper side of the block, and respective support cylinders each having an inner threaded bore are fixed in the greater diameter portions and the support cylinders have upper parts extending out of the body of the block, and the control means are constituted by respective elongated control spikes provided by respective threaded upper parts fitted in the inner threaded bores of the associated support cylinder, and the control spikes extend centrally in the bores till the smaller diameter part of the associated stepped bore.

In an embodiment the bottom portion of the greater diameter part of the stepped bore a sleeve is arranged holding a seal, in which a sealing ring is arranged cooperating with a lower cylindrical portion of the control spike, and the lower end portion of the control section of the control spike is formed as a downwardly tapering truncated cone, and in the control section of the control spike a plurality of inward cuts are provided, each having a V-profile through which respective passages are formed that interconnect said inner and outer spaces, and the cross-section of the passages depends on the axial position of the associated control spike.

It is preferred for the perfect sealing in the end positions if the upper and inner portion of the sealing ring respective nests are provided, and respective further sealing rings are arranged on the control spikes at positions that correspond to the end of their control sections, and in such end positions the sealing rings abutting the associated one of the nests.

In an alternative embodiment in the lower ends of the support cylinders respective control sleeves are fixed that have respective lower cylindrical sections and in the wall of these cylindrical sections openings are provided, and the control spikes have lower cylindrical sections that are moved in and along the control section of the associated control sleeve and fully closes or opens these openings between the end positions of the control.

On the bottom of the greater diameter sections of the stepped bores respective sealing rings are provided to which in the closing end positions of the adjustment the end of the lower cylindrical portion of the associated control spike gets pressed and seals the spaces from each other. It is preferred if the shape of the openings is rectangular, circular or triangular, and they are arranged evenly around the perimeter of the cylinder.

The adjustment is easier if the control spikes have upper outer portions that extend out from the support cylinder on which extending portions respective cooperating gears are arranged having identical size and number of teeth.

In the adjustment range the control spikes take at least six full revolutions.

The realization gets easier if in the block respective separate bores are provided having axes normal to the axis of the stepped bores and they constitute the input ports or are connected thereto, and the block comprises a further pair of stepped bores with axes parallel to the axes of the previous stepped bores but arranged inversely thereto and having the greater diameter portions opening to the base of the block and the bores communicate with the section with smaller diameter of the associated one of the further stepped bores, and a unidirectional valve is arranged in the section with greater diameter of the further stepped bores which allows a flow passage between these two bore sections with differing diameter when the pressure of the associated medium is present, furthermore the section with greater diameter of the further stepped bores communicates with the lower and smaller diameter section of the associated stepped bore.

In this case it is preferred if the unidirectional valve comprises a closing member arranged in the bore with greater diameter of the further stepped bore and opening to the base of the block and closing it from the bottom, in which a spring is arranged with an axis being the axis of the stepped bore, and a valve ring is arranged at the upper end of the spring that can close the communication between the two sections of the further stepped bore but it is kept pressed by the operational pressure against the bias of the spring.

From the greater diameter section of the stepped bore that performs the control function a blind bore leads to the bore constituting the mixing space, and the passages associated with the respective media meet only at the mouth of the associated blind bores at the beginning of the mixing space.

The opposite movement of the control means associated with the respective media is realized in such a way that the respective control means comprise a straight treated spur gear and identical size and the two gears are in mutual engagement, one of them is turned by the handling unit, and as a result of their mutual engagement within the control range, the gears get displaced in opposite axial directions.

The block receiving the mixing unit has preferably the shape of a brick.

In case of mixing gaseous media the pressure controllers keep the pressure at the input ports of the mixing unit to respective predetermined constant values between 2 to 10 bars.

The mixing apparatus according to the invention will now be described in connection with preferred embodiments thereof in which reference will be made to the accompanying drawings. In the drawing:

Fig. 1 is the schematic arrangement of the mixing apparatus according to the invention;

Fig. 2 is the elevation sectional view of an exemplary embodiment, wherein the sec tional plane is the line ll-ll shown in Fig. 4;

Fig. 3 is a side sectional view taken along line Ill-Ill of Fig.2;

Fig. 4 is a top sectional view taken along line IV-IV of Fig.2;

Fig. 5 is a top sectional view taken along line V-V of Fig.2;

Fig. 6 is a sectional view similar to Fig. 3 showing an end position of the adjustment; Fig. 7 is a sectional view similar to Fig. 6 showing the central position of the adjustment;

Fig. 8 is a sectional view similar to Fig. 6 showing the other end position of the adjustment;

Fig. 9 shows the flow rate versus adjustment revolution curve of the control in case of mixing air and oxygen under a pressure of 3 bars;

Fig. 10 is a sectional view similar to Fig. 3 in case of a second embodiment;

Fig. 11 is the enlarged sectional view of the detail encircled in Fig, 10 by the line XI;

Fig. 12 is a sectional view similar to Fig. 3 in case of a third embodiment;

Fig. 13 is the enlarged sectional view of the detail encircled in Fig, 12 by the line XIII; Fig. 14 is the sectional view of a control sleeve provided with rectangular openings; Fig. 15 is a section taken along line XV-XV on Fig. 14;

Fig. 16 is the sectional view of a control sleeve provided with circular openings;

Fig. 17 is the sectional view of a control sleeve provided with triangular openings; and Fig. 18 shows the flow rate curve through three different control sleeves as a function of the revolutions of the control member.

In Fig. 1 the functional schematic layout of a preferred embodiment of the mixing apparatus 10 according to the invention is shown. The liquid or gaseous media to be mixed can be coupled to an input connection block 11. In the exemplary embodiment the input block 11 has two connections 11a and lib, both provided with appropriate filters, and to the connection 11a air and to the connection lib oxygen is coupled which have a pressure varying between about 2 to 6 bars, preferably higher than 3 bars. The changing pressure of the media to be mixed respective pressure controllers 12a and 12b adjust to constant levels predetermined for each of the branches. The pressure controllers 12a and 12b have per se known designs. Their respective two outputs are coupled to input ports 21a and 21b of mixing unit 20 designed according to the invention. The task of the mixing unit 20 is to mix the two media according to a proportion defined and adjusted previously by a user. To this end, a handling unit 13 is connected to the mixing unit 20 or constitutes a part thereof that comprises and adjustment means 15 by which the mixing rate can be adjusted and a display 14 the shows this adjusted rate. The adjustment means 15 is preferably a turning knob but it can be designed as a slider or in any other version. The mixing unit 20 has a common output port 22 for leading out the mixed medium connected to a further unit 16 not forming part of the present invention and shown in schematic way only. A characteristic property of the mixing unit 20 is that both the pressure present in the output port 22 and the ratio of the respective components are independent within wide ranges from the flow rate required by further unit 16.

Reference is made now to Figs. 2 to 5 in which the different sectional views of the mixing unit 20 have been shown. Te body of the mixing unit 20 is constituted by an oblong shaped block 23 which will be explained starting from the elevation sectional view of Fig. 2. At the left side of Fig. 2 a bore 24b is shown which has an inner thread and its axis is horizontal and lies slightly higher than the central plane of the block 23, which corresponds to the input port 21b shown in Fig. 1 and the gas component of the mixture e.g. oxygen can be connected here. In the top view of Fig. 4 it can be seen that with a predetermined distance above the bore 24b another similar bore 24a is provided that corresponds to the other input port 21a and the other component of the mixture, e.g. air can be connected there. The axes of both bores 24a and 24b are horizontal i.e. parallel with base plate 25 and side plates 26 of the block 23. The respective ends of the bores 24a and 24b are in communication with smaller diameter portions of respective stepped bores 27a, 27b that have axes normal to the axis of the bores 24a, 24b and these portions appear in Fig. 2 as upper portions. The stepped bores 27a, 27b have larger diameter lower portions in which closing member 28b is fitted in a sealed manner that has a short cylindrical central portion with a diameter smaller that the diameter of the smaller upper portion of the stepped bore 27b and extends further than this smaller upper portion. This shorter central part is surrounded by a spring 29b and above it a valve ring 30b. For receiving the lower part of the spring 29b an appropriate nest is provided in the closing member 28b. In initial or base state the spring 29b presses the valve ring 30b to the narrowing wall of the stepped bore 27b, therefore in this state there is no passage between the larger and smaller portions of the stepped bore 27b. This design is the same at both of the input ports 21a and 21b but of them in Fig. 2 only the parts belonging to the port 21b can be seen. When during operation gas is arriving with their respective adjusted pressures to the input ports 21a and 21b, this pressure acts on the valve ring 21a and/or 21b and acts against the biasing force of the springs 29a and/or 29b, the valve pens and the passages between the smaller and larger diameter portions of the stepped bores 27a, 27b opens and the inflowing gas will flow in the lower portion of the stepped bores 27a, 27b with greater diameter. If the pressure of the inflowing gas disappears because of any reason or drops below a minimum value required for the operation, the passage will become closed. Such a design acts as a unidirectional valve called also as check valve and ensures that in the concerned branch gas can flow only in the required direction where the required input pressure is present.

A further pair of stepped bores 31a, 31b are provided in the right side of the block 23 which have axes normal to the base plate 25 and parallel to the side plates 26 which are oppositely directed so that their portions with greater diameter are open towards top plate 32 of the block 23, and their lower smaller diameter portions are blind bores. Fig. 3 is a sectional side view taken along lines Ill-Ill interconnecting the axes of the stepped bores 31a, 31b in which it can be well observed that in the continuation of both input ports 21a and 21b and fitted into both stepped bores 31a, 31b respective flow control assemblies are placed. The two gases can pass from the larger diameter lower portions of the stepped bores 27a and 27b to the smaller diameter sections of the second stepped bores 31a and 31b that (as can be observed in the top view of Fig. 5) the larger diameter portion of the first stepped bores 27a, 27b communicate with the respective smaller diameter portions of the second stepped bores 31a, 31b at lower level under the plane defined by the lines V- V.

To understand the design, it should be mentioned that at the opposite side of the block 23 relative to the blind bores centrally as shown in Fig. 2 (being covered in that figure but can be seen in Fig. 4) a bore 33 is provided that has a larger diameter with horizontal axis. From the inner end of the bore 33 two separate blind bores 34a, 34b are extending into the interior of the block 23 which have parallel axes and extend behind each other, which communicate with a respective one of the larger diameter upper portion of the second stepped bores 31a, 31b.

The bore 33 constitutes the output port 22 of the mixing unit 20, in which the two separate gas flow paths meet.

The control of the cross section of the flow path takes place by changing the passage way between the narrow lower portions and wider upper portions of the second stepped bores 31a and 31b.

For this purpose, respective support cylinders 35a and 35b are fixed (by pressing or by threaded connection) into the open larger diameter portion of the second stepped bores 31a, 31b, wherein the support cylinders 35a, 35b have respective throughgoing bores, and the support cylinders 31a, 31b extend out from the top plate 32 of the block 23 and have respective inner threads at the upper portion and their bottom extend till slightly above the axes of the bores 24a, 24b. To the steps of the second stepped bores 31a, 31b (where the portions with smaller and greater diameter meet) respective sleeves 36a, 36b are fixed that have dome shaped upper portions, that hold respective sealing. The bores in the sleeves 36a, 36b fit to the lower cylindrical portion of control spikes 37a, 37b, and in both sleeves 36a, 36b a respective sealing ring 38a, 38b are arranged which allows the axial displacement of the control spikes 37a, 37b in the vertical inner bores of the support cylinders 35a, 35b. At the lower ends of the smaller diameter portions of the second stepped bores 31a, 31b one can observe in Fig. 3 the bottom of the springs 29a, 29b. The upper portions of the control spikes 37a, 37b are threaded that engage the inner threaded parts of the support cylinders 35a, 35b. When the control spikes 37a and 37b are turned, they will move either in downward or upward direction depending on the direction of the twist because the support cylinders 35a, 35b cannot be displaced relative to the block 23. During such linear displacement appropriate sealing makes it possible that the gas present in the second stepped bore 31a, 31b can flow only in the direction towards the second bore 33, and no oozing or discharge can occur through the bore of the support cylinders 35a or 35b.

The upper portions of the control spikes 37a, 37b extend out vertically from the support cylinders 35a, 35b at respective predetermined length and on these upper portions a pair of mutually engaging respective gears 40a, 40b are fixed, which are designed as straight treated spur gears and have identical size. If any of the two gears 40a, 40b is turned in a certain direction, the other one will be turned in the opposite direction. Under this effect the control spike 37a will move vertically in a direction and the other control spike 37b will vertically move in the opposite direction. The vertical size of the gears 40a and 40b is sufficient to retain engagement even in the extreme positions of their turning range, whereas their axial positions are continuously changing. The gears 40a and 40b form part of the handling unit 13 shown in Fig. 1, and the adjustment means 15 can be preferably not else than further gears coupled to one of the gears 40a or 40b that ensure a required step up ratio or a turning knob placed on the shaft of one of these gears.

The step up ratio should preferably be provided bearing in mind that to cover the full displacement range of the control spikes 37a, 37b there can be a need of providing 6 to 8 full revolutions. The composition of the gas mixture depends on the actual positions of the control spikes 37a, 37b in their linear displacement paths. In the simplest case the display 14 shown in Fig. 1 is the front face of a gear that is provided with a scale containing and showing the associated percentual mixture ratios and it is coupled to one of the afore mentioned gears that the full adjustment range can be arranged in a full revolution or in a major part thereof.

The adjustment characteristic of the control is defined by the design of the lower sections of the control spikes 37a, 37b. In Fig. 3 the mixing unit 20 is shown in one of the extreme positions of the adjustment range in which the control spike 37b is in the most open position i.e. in its uppermost position. In this case air introduced through the input port 21b and through the bore 24b can reach the bore 33 and in this way to the output port 22. At the same time the other control spike 37a is in its lowermost position and fully closes the passage between the two portions of the second stepped bore 31a, thus oxygen lead to the input port 21a and to the bore 24a cannot flow to the output port 22, and the mixing unit 20 supplies only air.

The control section of the control spikes 37a, 37b starts where (in Fig. 3) the 38b sealing ring is located. This control section has a specific design. In downward direction from the upper end of the control section downwardly and inwardly widening V-profiled cuts 41 are provided in the initially cylindrical control section, wherein respective pairs of opposite cuts 41 are arranged, then the cylindrical surface is continued in a conical frustum 42 and the depth of the cuts is decreased accordingly. In the control spikes 37a, 37b the cross section of the V-shaped cuts 41 (their width and depth) is designed so that in case of identical axial displacements are associated with proportional changes of the flow cross sections. Such a design is rather similar to the shape of the tip of a cross recess screwdriver, although the depth and width of the cuts are determined by different calculations.

For the sake of completeness, it is mentioned that the block 23 can be fixed by three bores 43, 44, 45 shown in Fig. 5 which have no role in the control.

The way how the flow of the media is adjusted is explained in connection with Figs. 6 to 8 in which the reference numerals were shown only to the extent required not to disturb understanding. Fig. 6 shows substantially the same position as sown in Fig. 3. The rotation of one of the gears 4a or 40b rotates the other gear in the opposite direction, therefore the control spikes 37a, 37b are not only rotated but they are also displaced oppositely (up and down) in axial direction. As described earlier, the inflowing medium reaches the portion with the smaller diameter of the stepped bores 31a, 31b, which have the inner space A. The path of the medium can be continued from the inner space A only to the portion with larger diameter of the stepped bore 31a, 31b i.e. in upward direction which is indicated in Fig. 6 as inner space B.

In Fig. 6, as has been mentioned, at the side a the path of the medium leading upward is closed because the four cuts 41 are shut by the sealing 38a. Conversely, at the side b the opposite situation is experienced because the controls spike 37b is in its highest position, and between the inner spaces A and B a free passage is established through the four cuts 41 and the conical section.

In Fig. 7 both control spikes are in the middle of the adjustment range and through the passages identical volume of media can flow towards the space where mixing takes place defined by the interior of the bore 33. In Fig. 8 the roles of the two sides are interchanged and the side a is open and the side b is closed.

Concerning the flow pattern it has also significance that after the respective media leaves the control passage section that constitutes the choking will not meet immediately with the other medium only after a short passage route provided by the presence of the blind bores 34a, 34b both having horizontal axes. As a result of this design, the other medium cannot flow in reverse direction back to the control passage of the concerned medium which could otherwise influence the accuracy or characteristics of the adjustment.

The characteristic adjustment diagram of the described mixing apparatus 10 is shown in Fig. 9 that was taken a 3 bar input pressure and in the vertical axis the flow rate q can be seen in liters/min units as a function of the number of turns n taken by the control spikes 37a, 37b. The initial maximum flow rate of 97 l/min relates to air and the initial zero flow rate relates to oxygen. On the curve it can be observed that by the number of revolution (by the opposite displacement of the control spikes) the flow rate of air decreases in a nearly linear manner and the flow rate of oxygen increases in a nearly linear way and the sum of the two flow rates remains constant. In the mixture the ratio of the components changes continuously: the air decreases and the oxygen increases.

Reference is made now to Figs. 10 and 11 in which a further embodiment of the mixing apparatus according to the invention has been shown. This embodiment differs from the previous one only in the design of the lower parts of control spikes 47a, 47b and the connecting elements to these parts. The differences can be best observed in the enlarged detail encircled by the curve XI. of Fig. 10 that is shown in Fig. 11. In the drawing the left control spike 47b is in a fully open state while the right control spike 47a is in a fully closed position.

On the cylindrical wall of the control spikes 47a, 47b, just above the conical control section a respective second sealing ring 48a, 48b is provided, which in the highest position of the control spike 47a, 47b (Fig. 11 left side position) is just at the lowest end part of the cylindrical inner bore of the support cylinder 35b. At the end of the control path i.e. in the lower end position of the control spikes 47a, 47b shown in Fig. 11 on the right side, the respective sealing ring 48a or 48b abuts a conical nest 59a or 59b provided in the central upper portion of the associated sleeve 46a or 46b, whereby separates the spaces A and B from each other. This embodiment merely has the task of the secure separation of these two spaces because in the previous embodiment the sealing rings arranged in the inner bore of the sleeves 36a, 36b could realize only a less secure separation that could cause problem at the end of the control path.

The sealing rings 48a, 48b have no role in the control process but in the end position they provide a definite separation between the spaces A and B.

Reference is made now to a third embodiment shown in Figs. 12 to 17. The control is not defined here by the conical or cut design of the lower end part of the control spikes 49a, 49b. The differing design can best be seen in Fig. 13 which is the enlarged sectional view taken along the curve XIII shown in Fig. 12. Similar to the illustration of the previous embodiment the left and right parts of the figure show the two end positions of the control path when the control spike 49b shown in the left side of the figure is in fully open position and the control spike 49a at the right side of the figure is in fully closed position.

The lower ends of cylinders 51a and 51b that hold and guide the control spikes 49a, 49b comprise bore which have larger diameter than in the previous embodiments. Into these bores respective control sleeves 50a and 50b are inserted from below. The connection is stable, and during the control process the positions of the control sleeves 50a, 50b remain unchanged as shown in Fig. 13, and they are sealed from the interior of the cylinders 51a, 51b by respective sealing rings 52a, 52b arranged at their upper portions. At the lower end portions of the control sleeves 50a, 50b i.e. at the bottom of the larger diameter section of the stepped bore further sealing rings 53a, 53b are arranged that have smaller inner diameter than the inner diameter of the lower cylindrical end portion of the control cylinders 50a, 50b.

In the cylindrical wall of the lower portion of the control cylinders 50a, 50b identical openings are provided so that between them there will be an identical angular spacing. The shape of such openings defines the control curve of the adjustment. In Fig. 14 there are openings 54 which are narrow elongated rectangles, in Fig. 16 there are circular openings 55 and in Fig. 17 openings 56 are shown that have triangular shapes that narrow in downward direction. In the sectional view of Fig. 15 it can be seen that the control sleeves 50a, 50b comprise four of the rectangular openings 54. In case of the openings 55 and 56 the use of respective four pieces is preferred, but they can have any number above 2.

The bottom end portion of the control spikes 49a, 49b have preferably a hollow design so that in case of a full closure of the adjustment a sufficient inner gas space remains. In the embodiment shown in Fig. 13 this hollow space has a conical shape but the profile of the hollow space is not critical. The lower end portions of the control spikes 49a, 49b constitute respective narrow rings. These rings are abutting the inner upper faces of the sealing rings 53a, 53b at the end position of the control (shown in the right illustration in Fig. 13) providing thereby a definite sealing between the spaces A and B.

During adjustment the control spikes 49a, 49b move in axial direction (and also turn around their respective axes) and depending on the momentary height of their lower ends they allow passage through the openings 54, 55 or 56 between the spaces A and B. The cross section of flow depends on the position of the control spikes 49a, 49b and the maximum cross section is determined by the sum of the open cross sections of the individual openings, and in case of closure no flow pass is provided.

Fig. 18 shows the characteristic curve of the flow rate as a function of the turns of the control member in case of the three exemplary shapes of the openings. The curve drawn in full line is associated with the opening 54 with rectangular shape, the curve drawn by dash line is associated with the circular openings 55 and the dash dot lined curve is associated with the triangular openings 56. Naturally, by designing openings with appropriate shapes, any required curves can be realized.

The examples and embodiments shown have outstanding simplicity and reliability of operation. Compared to the sizes of the drawing, the actual size of the apparatus is by about 40% smaller, thus the mixing apparatus 10 can be realized in small volume and weight. It will be apparent for the person skilled in the art that certain details can be replaced by equivalent solutions. For example the control spikes 37a, 37b can be replaced by respective circular apertures opened and closed by turning which should be arranged in the sections separating the inner spaces A and B. Further possibilities can be the omission of the blind bores 34a and 34b and the leading of the bore 33 to the portions of the stepped bore 31a, 31b where they have greater diameters, but this can be associated with the drawback referred to earlier.

Further advantages of the mixing apparatus 10 according to the invention that in the selected operational pressure range the percentual ration of the components is highly independent from the flow rate of the media, which is a substantial advantage because in case of certain user's demand the required flow volume can rapidly change like a pulse between zero and a maximum value whereas in the mix the adjusted ratio of the components should be kept unchanged.

Although the invention has been shown primarily for the mixing of gases, it can be appreciated that it is equally usable for mixing of liquids, although in case of liquids (owing to their constant volume) the problems associated with the task are less serious. In such cases the simple and linear adjustment of the mixing ratio and the flow rate represent the greatest advantages.