Arrangement for the venting of a liquid.

TECHNICAL FIELD

The present invention relates to an arrangement for the venting of a liquid which flows through a duct comprising a throttling means, a suction pump arranged downstream of it and a venting chamber arranged downstream of the pump.

The invention is intended in particular for application in connection with an arrangement for the preparation of dialysis solution and the feed of this to a dialyser. For those versed in the art it will be clear, however, that the invention can also be applied more generally.

BACKGROUND ART

In the American patent specifications 4 158 034 and 4 293 409, for example, an arrangement of the abovementioned type is described which is intended for the preparation and feed of dialysis fluid to a dialyser. The present invention relates to a further development and improvement of the system in accordance with these patents.

DISCLOSURE OF INVENTION

The abovementioned improvement is brought about with the help of an expansion chamber arranged between the throttling means and the pump. Owing to this expansion chamber time is gained for the formation of bubbles of an appropriate size, which can be passed through the pump to the venting chamber without excessively being broken down in the pump.

The inlet to the expansion chamber is arranged preferably at its base and the outlet at its top. As a result bubbles formed in the chamber are conducted automatically direct towards the outlet. A non-return valve and a shunt line arranged parallel with the expansion chamber are arranged appropriately directly after the expansion chamber. This makes possible a complete emptying of the expansion chamber with the help of a pump arranged further on in the system.

In the shunt line a valve is suitably provided which is adapted so that it is kept shut at normal working pressure, but is opened when the normally negative pressure rises to nominally lower values, e.g. in connection with air entering into the expansion chamber when the system is emptied with the help of the abovementioned pump arranged further on in the system. The valve provided in the shunt line may simply be constituted of a compressible tube which is automatically sucked together at a nominally higher partial vacuum, that is to say the pressure corresponding to the normal working pressure.

To ensure a safe shutting off of the tube a pinch device may be arranged on the same which is adapted so as to press together the points which are to form the end points of the compressed tube already in the open position of the tube. Without this pinch device there is a danger of a certain leakage occurring just at these end points.

The inlet to the venting chamber is appropriately arranged tangentially at a higher level than the outlet of the same. In this manner the bubble separation is facilitated, by the difference in level as well as by the centrifugal forces which arise.

In a manner known in itself an outlet is arranged in the venting chamber at is highest point for air accumulated therein together with a float valve which is adapted so as to prevent any liquid being sucked out through the air outlet.

The throttling means provided upstream of the expansion chamber is appropriately adjustable. In this way, among other things, the degree of venting can be regulated and at the same time the dialysis flow can be modified.

To allow the effective emptying of the system as a whole it is provided appropriately with a suction pump arranged downstream of the venting chamber. This pump may be constituted, for example, of the pump which normally sucks dialysis fluid through the dialyser.

The invention is thus intended in the first place, as mentioned above, to form part of a system for the preparation of dialysis fluid through mixing of one or more concentrates with water. It will be described, therefore, in the following with reference to just such a system.

The bubble separation is facilitated further if the outlet is arranged tangentially but in countercurrent to the vortex formation produced by the inlet.

BRIEF DESCRIPTION OF DRAWINGS

<ul id="ul0001" list-style="none"><li>Fig.l shows schematically a flow diagram of a substantially complete system for the preparation of dialysis fluid.</li><li>Fig.2 shows in greater detail and as an example a possible design of an air separation chamber forming part of the said system.</li><li>Fig.3 shows schematically a section III-III through the same air separation chamber and is intended to illustrate the placing of the inlet and outlet respectively of the chamber.</li><li>Fig.4 shows how a tube forming part of the system may possibly be sucked together incompletely if it is not provided with a pinch device in accordance with fig.5 which has the effect that the sucking together will instead be as shown in fig.6.</li></ul>

BEST MODE OF CARRYING OUT THE INVENTION

In the system for the preparation of dialysis solution shown as an exmple the water is introduced at an inlet 1 into a duct 2 with a temperature measuring instrument 3 and an inlet valve 4. From the inlet valve 4 the water flows through a duct 5 to a heating vessel 6 with a level control float 7, a heating coil 8 and a stirrer 9. Alternatively the water can flow to the heating vessel through a duct 10 with a valve 11 which allows a greater flow so that an effective rinsing of the vessel can be achieved, e.g. in connection with sterilization.

From the vessel 6 the water flows via a duct 12, a flow valve 13 with an appropriately adjustable second flow valve or throttling means 14 to an inlet 15 arranged at the base of an expansion chamber 16. At the top of this chamber is arranged an outlet 17 to a duct 18 with a nonreturn valve 19. Parallel with the chamber, moreover, a shunt line 20 with a valve 21 is arranged. In a preferred embodiment this shunt line 20 and the valve 21 are constituted quite simply of the tube 20a with a pinch device 21a as shown in fig. 4-6. Thanks to this pinch device 21a the tube at a sufficient partial pressure is given the shape obtained in fig.6 instead of the shape as shown in fig.4 otherwise possible.

Before the liquid has reached the expansion chamber 16 concentrate is fed to it with the help of a pump through a duct 23 and prior to this, moreover, the temperature is measured once more with the help of a temperature measuring instrument 24.

The line 18 continues via a pressure gauge 25 and a pump 26 to a venting chamber 27. An example of such a chamber is shown in more detail in fig.2 and schematically in fig.3. The chamber 27 is thus provided with an inlet 28 and an outlet 29 arranged at a lower level for the liquid as well as an outlet 30 for the air accumulated in the chamber. A float 31 is arranged, moreover, in the chamber which closes the outlet 30 when the liquid level has risen so high that there is a risk of the liquid being sucked out through the outlet 30.

From the venting chamber 27, via a further outlet 32, extends a duct 33 via a valve 34 back to the heating vessel 6. This duct is intended to be used in connection with sterilization in a manner which is described in more detail in the abovementioned American patent 4 158 034.

From the venting chamber 27 the liquid proceeds via a duct 35 to a conductivity meter 36 and, in case of a second concentrate having to be added, a further conductivity meter 37. The second concentrate is fed in such a case with the help of a pump 38 through a duct 39. Owing to these two conductivity meters 36 and 37 the conductivity can be measured before and after the addition of the second concentrate. The liquid is then passed through a duct 40 via a flow meter 41, the temperature measuring instrument 42 and a valve 43 to the dialyser 44 indicated schematically. If for example the temperature or the conductivity do not have the desired values, the liquid is conducted instead with the help of a valve 45 into a duct 46 past the dialyser to a second conduit 41' in the aforementioned flow meter.

If on the other hand the desired conditions are met, the liquid is passed from the dialyser 44 through a duct 47 via a pressure gauge 48 and a valve 49 to the conduit 41' in the flow meter. From there the liquid is conducted via a duct 50 with a blood leakage detector 51 and a valve 52 to a suction pump 53. Thus the dialysis fluid is sucked through the dialyser 44 with the help of this suction pump. The same pump is also used for the emptying of the system as a whole. From the pump 53 the liquid is conducted normally via an outlet valve 54, a throttling means 55 and a safety control meter 56 for pH measurement to the outlet 57. Alternatively, for example in sequence dialysis, the ultrafiltrate sucked out may be passed from the valve 54 via a duct 58 to a special collecting point 59 for such filtrate.

A safety bypass designated 60 finally is used only in connection with sterilization of the arrangement. This may be of the type, for example, which is described in more detail in American patent 4 122 010.

Naturally the invention is not limited solely to the embodiment described above, but may be modified within the scope of the following claims. Thus the parts included in the system can be modified, of course, in respect of form as well as function. Furthermore the invention can be applied, for example, also to the venting of replacement liquid for haemofiltration or plasma- fers or for the venting of liquids in general. Reference is made, moreover, to the design according to the Swedish patent application 8306574-8 submitted at the same time which describes an alternative venting arrangement including parts which can be combined with the design according to the present invention.