Device for removing gases from fluids

Details Device for removing gases from fluids Device for removing gases from fluids

1997-05-22

2001-01-23

Woo, Jay H. (Department: 1724)

Gas separation: apparatus

Degasifying means for liquid

Liquid flow slinger, spreader, deflector, disperser, or...

C096S209000, C096S210000, C096S212000, C096S213000, C210S436000, C210S472000

Reexamination Certificate

active

06176903

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a device for removing gases from fluids, in particular from a dialyzing fluid.
BACKGROUND INFORMATION
When setting up an extracorporeal blood circuit, as well as when preparing dialyzing fluids for dialysis, a plurality of devices for separating out air are known, such as bubble traps or air-venting devices, whose task is to effectively separate out the gases, which are present and partly dissolved in the fluid from the fluid.
The dialyzing fluids used in dialysis release gases in response to low pressure air separators which usually include a laterally disposed upper inlet, whose intended use is to impress a helical path upon the inflowing fluid. In this context, the air bubbles are to be separated out through a hydrophobic filter situated at the top. An arrangement of this kind is disclosed, for example, by the German Patent No. 32 15 003. However, in practical use, it was determined that the suction created partly entrains the separated air into the outflow so that further precautions had to be taken to improve the separation. Thus, for example, separation aids in the form of small plates were introduced into the venting space. Furthermore, the air separators were often built with very long dimensions to form the largest possible separation surface.
A device is disclosed in U.S. Pat. No. 4,061,031 that can be used both as a flow meter as well as an air separator. The known device has a container, which is divided by a partition wall that includes two chambers, one chamber being provided with an inlet orifice, and the other chamber with an outlet orifice. The partition wall includes an opening, and extends from the bottom of the container up to near the container cover, forming a gap-shaped interstitial space between the inlet chamber and the outlet chamber as well as the container cover.
The cut-through partition wall is comprised of two plate-shaped elements in a staggered arrangement, the orifices of the inlet and outlet chambers being situated at the bottom of the container. Since the opening in the partition wall has a smaller cross-section than the inlet orifice, fluid columns of different heights form in the chambers, making it possible to measure the flow rate. In this context, the difference between the two fluid columns is a measure of the level of the flow rate.
In the known device, the two chambers function as bubble traps. The air bubbles entrapped in the fluid rise to the top of the chambers and remain as gas above the fluid level. An active separation is no longer possible when working with the known device. To keep the fluid from flowing over the top edge of the partition wall into the outlet chamber, the inlet chamber has an elongated shape, which leads to a relatively substantial overall height.
SUMMARY OF THE INVENTION
It is the underlying object of the invention to create a device for removing gases from fluids, which, with a compact and simple type of construction, will enable a high separation rate to be attained.
In the device according to the invention, the partition wall is formed as a continuous traversing body, so that the first orifice and the second orifice are in fluid communication only via a gap-shaped interstitial space. Furthermore, provision is made on the container cover for a venting orifice that is sealed by a vent unit, which permits gas to pass through, but not fluid. During operation, the container, i.e., the two chambers and the gap-shaped interstitial space, are completely filled with fluid. The is fluid to be degassed flows out of the one chamber, across the gap-shaped interstitial space beneath the container cover, into the other chamber. At the partition wall, a reversal of the flow direction takes place, the gases entrapped in the fluid are able to escape through the venting orifice provided on the container cover.
An especially high separation rate is achieved with a device of a compact design, particularly when the partition wall is conceived in the form of a hollow body, which, while forming the first and second chamber, is so arranged inside the container that the inner first chamber has a smaller cross-section than the outer second chamber. In this arrangement, the first chamber forms the inlet chamber and the second chamber the outlet chamber. Since the inlet chamber has a smaller cross-section than the outlet chamber, the flow rate in the first chamber and, thus, the static pressure acting on the venting orifice is increased. On the other hand, the dynamic pressure at the venting orifice is kept low, so that in spite of the increased flow rate in the first chamber, virtually no air is entrained.
In the device according to the invention, the vent unit can be designed, for example, as a hydrophobic membrane. This membrane is advantageously integrated in the container cover, so that the fluid to be degassed is pressed against the membrane. The hydrophobic membrane should form the largest possible working surface for the fluid and preferably extend nearly over the entire cross-sectional surface of the gap-shaped interstitial space.
In one preferred specific embodiment, provision is made for the influx of fluid to be able to take place horizontally into the first orifice to the first chamber, this horizontal influx of fluid advantageously provides a tangential flow component. As a result, the inflowing fluid is essentially carried upwards in a spiral shape, thereby improving the air separation. Thus, the inflowing fluid mixture is set into a rotational motion within the air separator according to the invention, through which means gas is automatically conveyed in the direction of the shared axis.
In another preferred specific embodiment, the bottom of the tubular inside part of the first chamber is elongated toward the lower end with respect to the bottom of the outside part of the second chamber and, accordingly, extends out downwardly. In this specific embodiment, the first orifice is arranged on the tubular side wall adjacent to the bottom and the intake connector is in fluid communication with the first orifice. Preferably, the connector is advantageously positioned tangentially to the partition wall.
Similarly, the outflow connector in fluid communication with the second orifice can likewise be arranged horizontally adjacent to the bottom of the container and open through into the second orifice. The outflow connector is preferably positioned tangentially to the container wall.
Especially preferred is the specific embodiment where the horizontal walls of the first chamber and of the second chamber are formed in an annular shape and, thus, constitute a tube-in-tube arrangement, so that a circular annular space is formed between the first chamber and the second chamber.


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