GB2041233A - Blood filter - Google Patents

Abstract

A blood filter comprises a core (1) within a housing and on which is mounted a packing of a single plastics monofilament or strands of long monofilaments of a diameter approximately equal to the diameter of the blood corpuscles. The packing comprises a single uniform winding (2) in or a succession of uniform windings of the filamentary material. In the case of successive windings, the winding density increases in the direction of the blood flow. A partition wall (6) is provided within the housing below the core to define a drip chamber (8) leading the filter outlet (5), and the filter inlet (4) may be in the form of a hollow needle. Core (1) is a filter screen, but in Figs. 2, 3 (not shown) the core is impervious with external grooves for filtered blood flow. A by-pass bridged by a hydrophobic membrane conveys air past the filter element. <IMAGE>

Description

SPECIFICATION Blood filter The invention relates to a blood filter for removing from the blood dead blood corpuscles, blood constituents and/or constituents which are foreign to the blood, comprising an unwoven dense packing of fibres which in diameter approximately correspond to the diameter of the blood corpuscles, and wherein the packing is formed from a single plastics monofilament or strands of long monofilaments.

In a prior proposal, the present applicants envisaged a design in the form of a plate filter which is formed from disorderly felted layers of a single monofilament or long strands of monofilaments.

Such a filter is known for example from German Patent Specification No. 25 16 175.

Filters of this kind have the advantage that they have a high capacity and thus long service lives and have a good filter action down to very small particles.

The disadvantages of such filters are that discontinuities due to 'channel formation' are possible as a result of the non-uniform packing, when the filter is subjected to an overload or excessively high pressure.

There remains the problem of so designing such a blood filter in accordance with the prior proposal, that it receives a uniform packing so as to produce a filter action which is equal throughout.

In such a blood filter, the present invention provides that the packing comprises at least one uniform winding of the monofilament or monofilaments on a hollow, transmissive core.

In this arrangement, a plurality or windings of respectively different packing density can also be arranged one over the other. Preferably, the density of the packings is so selected as to increase in the direction of the flow of blood.

The windings may advantageously be in the form of a cross winding. In orderto increase reliability, the winding core may be in the form of a screen filter or a screen filter may be disposed at a downstream position in the flow path.

Manufacture in accordance with the invention of such a blood filter makes it possible to produce a constant density of packing over the entire filter area so that the 'mesh width' or'pore size' of the filter layer which is formed in this way is also virtually constant at all points. By suitably selecting the thread spacing with a given thread density, it is possible to provide a filter layer with the desired 'pore size'.

The invention is described in greater detail hereinafter with reference to the accompanying drawings, in which :- Fig. 1 is a purely diagrammatic view in crosssection of a blood filter according to one embodiment of the invention, Fig. 2 shows a section corresponding to Fig. 1 of another embodiment of the invention, and Fig. 3 shows a view on a larger scale of a detail of the Fig. 2 construction.

Referring to Figure 1, disposed on a hollow transmissive, preferably cylindrical core 1 is a winding 2 which serves as a filter. The core with the winding is disposed at a distance from the walls, within a housing 3. The tubular housing 3 has connection pipes 4 and 5 respectively at its two ends, for the feed and the discharge respectively of the blood.

Arranged at the discharge between the connection pipe 5 and the winding core is a partition wall 6 with a central bore 7. The connection pipe 5 is formed as a drip chamber 8.

The partition wall 6 serves at the same time as a delimiting means for the winding 2 at the discharge end. A plate 9 which seals the winding and the core at the end thereof is arranged at the feed end.

Arranged between the plate 9 and the feed pipe 4 is a displacement means 10 which provides for uniform distribution of the in-flowing blood to the periphery of the winding. For this purpose the displacement means 10 may be constructed in a particular manner and may carry for example guide ribs which impart a tangential direction of flow to the blood. The inflowing blood passes through the feed pipe 4 into the annular flow passage between the wall of the housing and the displacement means 10. From there the blood flows through the cylindrical chamber between the wall of the housing 3 and the outer peripheral surface of the winding 2, through the winding 2 and the wall of the core 1, and then passes through the central bore 7 in the partitioning wall 6 into the drip chamber from which it flows out through the discharge pipe 5.

In the embodiment shown in Figure 1, the wall of the core 1 is designed as a fine-pore screen filter.

However, such a screen filter could also be arranged parallel to the partitioning wall 6 above to the drip chamber 8, or could be disposed in a downstream position in the blood flow, in a separate housing.

The monofilament which is used forthe winding is of a plastics material and may be crimped and/or of a star-shaped cross-section.

In order to further improve the blood flow and in order to provide for uniform distribution thereof, the housing may be designed in suitably known manner.

In the drawing, the winding 2 is only indicated generally and diagrammatically. It may be unitary in itself or may comprise layers of different packing density, and the packing density may preferably increase from the outside inwardly, that is to say, in the direction in which the blood flows.

In the embodiment shown in Figure 2, the filter 12 is disposed on a tubular core 11 which is nontransmissive and closed on all sides. A transmissive wall is formed by the inner wall of the filter itself.

This filter is designed in the same manner as that of the above-described embodiment.

The arrangement is disposed in a housing 13 which has a sealingly inserted partition wall 14. The partition wall divides the interior of the housing into an upper filter portion and a lower chamber 15 which serves as a drip chamber. The housing has a feed pipe 16 and a discharge pipe 17, and the feed pipe 16 may be in the form of a piercing spike or hollow needle.

The core 11 is preferably hollow and at its upper end carries a conical displacement means for dis tributing the inflow of blood. In the region of the displacement means, channels of a helical configuration which are distributed over the periphery of the core body, are formed in the core body, and also serve to distribute the inflow of blood to the filter.

Below the displacement means 18, the actual filter 12 is held sealingly to the core 11. The lower end of the filter is fitted sealingly on the partition wall 14. In the region in which the filter lies against the core 11, grooves 20 are formed on the outer peripheral surface thereof, to provide for discharge of the filtered blood.

The grooves 20 open into an annular collecting chamber 21 at the lower end of the core, which is formed in a disc-like collecting chamber 22 between the core and the partition wall and opens into the discharge opening 23. A sealing ring 24 is provided for sealing the lower end of the filter to the partition wall 14.

In the region of the annular chamber which is formed between the filter and the wall of the housing, the partition wall 14 has at least one through opening 25 which is in communication with an arrangement of grooves 26. A hydrophobic membrane 26 is applied to the partition wall, being held firmly and sealingly pressed against the top side of the partition wall on the one hand by means of a shoulder 27 and on the other hand by means of the sealing ring 24. The air which is collected in the annular chamber between the filter and the wall of the housing can flow off into the chamber 15 through the membrane 26.

Afilter as shown in Figure 2 is made ready for operation in the following manner. With the filter in the inverted position relative to that shown in the drawing the piercing spike is firstly stuck into a bag containing a blood conserve. The bag is compressed. When this is done the blood rises within the housing of the filter over the surface of the displacement means through the helical grooves into the annular chamber between the filter and the housing. While now the blood is passing through the filter and is filling the chamber up to the partition wall, the displaced air can pass into the chamber 15 through the membrane 26 and the openings 25. The filling operation can be easily observed if the housing is made from a translucent or transparent material. As soon as the air has been displaced out of the filter chamber and the blood has approximately half filled the drip chamber, the bag with the filter is turned round and hung upto provide forthe transfusion.

Forthis purpose, a tube system with infusion canula is connected to the connection 17.

Claims (16)

1. A blood filter for removing from the blood dead blood corpuscles, blood constituents and/or constituents which are foreign to the blood, compris ing an unwoven dense packing of fibres which in diameter approximately correspond to the diameter of the blood corpuscles, wherein the packing is formed from a single plastics monofilament or strands of long monofilaments, and comprises at least one uniform winding of the moriofilament or monofilaments on a hollow, transmissive core.

2. A blood filter according to claim 1, wherein the winding is formed as a cross winding.

3. A blood filter according to claim 1 or 2, wherein the core is formed as a screen filter.

4. A blood filter according to claim 1 or 2, wherein the core is formed as a closed, nontransmissive tube.

5. A blood filter according to any of claims 1-4, wherein a screen filter is connected thereto at a downstream position.

6. A blood filter according to any of claims 1-5, wherein a plurality of windings of different packing density are arranged on the core.

7. A blood filter according to any of claims 1-6, including a housing which includes a drip chamber.

8. A blood filter according to claim 7, wherein the housing has guide means on the inflow side, for optimising the flow of blood.

9. A blood filter according to any of claims 1-8, wherein, on the inflow side, the core is formed as a cone or carries a substantially conical displacement means.

10. A blood filter according to claim 9, wherein, on the inflow side, the core has guide means, for optimising the flow of blood.

11. A blood filter according to claim 7 or 8, wherein, adjacent its lower end, the core forms a collecting chamber between the core and a partition wall which closes the drip chamber at its top end.

12. A blood filter according to claim 7 or 8, wherein a partition wall, which closes the drip chamber at its top end, has a central opening for the discharge of blood and air.

13. A blood filter according to claim 11, wherein the partition wall has, in an annular region between a housing and the filter, openings which are covered with an air-transmissive membrane.

14. A blood filter according to any of claims 1-13, wherein the core has guide means for guiding the filtered blood away.

15. A blood filter according to any of claims 1-14, wherein the inlet connection is formed as a piercing spike.

16. A blood filter constructed and arranged substantially as hereinbefore described and shown in Fig. 1 or Figs. 2 and 3 of the accompanying drawings.