Filter unit for whole blood and blood derivatives

Abstract

A filter unit for blood and blood derivatives comprises a body defined by two injection-moulded half-shells of thermoplastic polymer material, there being present between said half-shells a cavity containing a filtering element having two opposing flat faces, an inlet opening and an outlet opening made on the opposing outer surfaces of said body communicating with said cavity. Each of said half-shells comprises a projecting perimetral flange, the flanges of the overlapping half-shells being welded together to form a flange of the body of the filter unit and connect the two half-shells together, the filtering element being wholly contained within the cavity of such body and pressed by shelves projecting into such cavity from each half-shell in the vicinity of its perimetral border and on the two opposing faces, said shelves retaining said filtering element in a stable position within cavity, said thermoplastic polymer material being yielding and semi-rigid.

Claims

1. Filter unit for blood and blood derivatives comprising a body defined by two injection-moulded half-shells of thermoplastic polymer material, there being present between said half-shells a cavity containing a filtering element having two opposing flat faces, an inlet opening and an outlet opening made on the opposing outside surfaces of said body communicating with said cavity, wherein each of said half-shells comprises a projecting perimetral flange, the perimetral flanges of the overlapping half-shells in direct contact and welded together along a single weld line to define a flange of the body of the filter unit and join the two half-shells together, each perimetral flange projecting outwardly away from the cavity to define an inner surface, a first inner surface of a first half shell being mated to and directly engaged with a second inner surface of a second half shell, the filtering element being wholly contained within cavity of the body and pressed by shelves projecting into the cavity from each half-shell, at least in the vicinity of one of the perimetral edges and on the two opposing faces, said shelves holding said filtering element in a stable position within cavity, said thermoplastic polymer material being yielding and semi-rigid, the thermoplastic polymer material having a Shore A hardness of between 85 and 95.

2. Filter unit according to claim 1, wherein the filter has a packing factor of more than 100%.

3. Filter unit according to claim 1, wherein the perimetral flange of the two half-shells and therefore the flange of body of the filter unit projects by between 2 and 5 mm along the edges of the body.

4. Filter unit according to claim 3, wherein said perimetral flange of the body of the filter unit has a thickness which decreases outwards moving away from said body.

5. Filter unit according to claim 1, wherein said shelves are one of continuous or discontinuous and define a continuous or discontinuous ring close to the edges of the half-shells.

6. Filter unit according to claim 1, wherein the edge of the filtering element has a smaller thickness relative to the remaining part of said filtering element.

7. Filter unit according to claim 1, wherein said half-shells have a face facing the cavity of said body of the filter unit, and wherein ribs project from the face and are configured for pressing against the opposing faces of the filtering element, said ribs defining channels between them configured to encourage the movement of blood and blood derivative from inlet opening to outlet opening of said body of the filter unit.

8. Filter unit according to claim 1, wherein said inlet opening and said outlet opening are provided within appendages projecting from faces of said half-shells forming outer faces of body of the filter unit, said appendages being of one piece with the said half-shells.

9. Filter unit according to claim 8, further comprising a third appendage projecting from a face of one of said half-shells, said third appendages defining a vent hole being of one piece with the said half-shells.

10. Filter unit according to claim 1, wherein the perimetral flanges do not press against the filtering element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a better understanding of the present disclosure the following drawings are attached purely for indicative but non-limiting purposes, and in these:

(2) FIG. 1 and FIG. 2 show perspective views from different angles of a filter unit obtained according to the disclosure;

(3) FIG. 3 shows a cross-section view along the line 3-3 in FIG. 2;

(4) FIG. 4 shows a side view of the filter unit in FIG. 1;

(5) FIG. 5 shows a plan view of the filter unit from the side opposite that shown in FIGS. 1 and 2;

(6) FIG. 6 shows a side view of a component of the filter unit in FIGS. 1 and 2; and

(7) FIG. 7 shows a view from above of the component shown in FIG. 6, the side of this component shown in FIG. 7 being within the filter unit in FIGS. 1 and 2.

DETAILED DESCRIPTION

(8) With reference to the figures mentioned, a filter unit according to the disclosure comprises a body 1 defined by two half-shells 2 and 3 joined together and bounding a cavity or internal space 4 in which is placed a filter element 5 subdividing such cavity into two parts, a first cavity part 4A and a second cavity part 4B. Filter element 5 is defined, in a way in which it is in itself known, by a modular pack of filter layers which can be assembled according to the fluid to be filtered and/or the desired filtering effect.

(9) First half-shell 2 (positioned on top in FIGS. 2 and 3, for example) has a pierced external appendage 8 and an opening at 9. Between such appendage 8 (of one piece with half-shell 2) there is a conduit 10 which opens into first cavity part 4A.

(10) Similarly, second half-shell 3 (below in FIG. 3) comprises a first pierced external appendage 12, of one piece with half-shell 3, opening at 13 and having a conduit 14 opening into second cavity part 4B. A conduit 16 made between a second pierced external appendage 19 opening at 17 also opens into this cavity part 4B.

(11) Shells 2 and 3 are obtained by injection moulding and have the corresponding appendages of one piece with them. First appendage 8 can be attached to a flexible PVC, polyurethane or the like tube (not shown), second appendage 12 can also be attached to a flexible tube. Third appendage 19 only acts as a vent hole for the air present in filter 1 when second cavity part 4B receives blood or the blood-derivative fluid from first cavity part 4A through the filter element.

(12) Each half-shell 2, 3 has a first side 2K, 3K which defines a corresponding outer face of body 1, and a second face 2W, 3W, opposite the first, bounding cavity 4 (and therefore within body 1). On this second face 2W and 3W each half-shell 2, 3 has a plurality of ribs 20 of different lengths bounding a set of channels 21.

(13) These channels 21 in first half-shell 2 cause the fluid entering first cavity part 4A to become distributed over all a corresponding face 5A of filter element 5 (the face facing such cavity part 4A). In this way the fluid (for example blood) is correctly filtered through such element 5.

(14) Similarly, channels 20 in second half-shell 3 direct such filtered fluid present in second cavity part 4B towards appendage 12, from which it is drawn off.

(15) Filter element 5 and its opposing faces 5A, 5B is also supported on these ribs 20; the ribs ensure overall planarity and rigidity for such filter element 5, which is essential to obtain a correct distribution of blood fluid, in addition to having a correct containment factor for the filter element which is necessary to ensure that it has optimum filtering efficiency, as will be further indicated below.

(16) Half-shells 2, 3 are made of semi-rigid thermoplastic polymer material having a Shore A hardness of between 85 and 95. A material having these characteristics will also be indicated in this document as imparting a semi-rigid yielding property to body 1. In other words, body 1 will also be indicated as being “semi-rigid and yielding”, with the characteristics which will be indicated below.

(17) Suitable materials are known and are for example PVC, SBS, PU or the like.

(18) These half-shells 2, 3 are injection moulded. Thanks to the hardness of the material from which they are obtained, half-shells 2, 3 have a soft damping action in relation to impacts against external components. This is particularly advantageous during washing in a centrifuge because it prevents the components of the blood sampling and processing system (bags, tubes, filter units) present in such centrifuge from being broken in the event of contact with body 1.

(19) In addition to this, the (intrinsic) rigidity of the material used to make the half-shells makes it possible to adjust the density of filter element 5 (which, as mentioned, is usually defined by a plurality of filtering layers). It is in fact known that the efficiency of such element 5 is linked to its compression factor or “packing factor”. This is provided by the ratio between the density of the (layer-shaped) compressed filtering element and the density of the same filtering element when not compressed.

(20) Using a filter unit 1 having a filtering element 5 with different packing factors changes in the filtering efficiency of unit 1 have in fact been found, as may be seen from the table below.

(21) TABLE-US-00001 PACKING LEUCOCYTE/ WBC LOG FACTOR % UNIT POST REDUCTION =100% 4.97E+04 4 =110% 4.37E+04 5 =140% 3.88E+04 6.3 where Packing Factor=compression factor as indicated above Leucocyte/Unit Post=[residual leucocytes] WBC Log Reduction=[logarithmic reduction]

(22) It will be seen from the above how filtration efficiency is linked to the compression factor of the filtering element: the higher that factor, the greater the filtering capacity. This means that, for the same filtering elements, the filter unit in which such elements are not very compressed will filter less well than a filter unit in which such elements are more compressed.

(23) Through the particular choice of the hardness of the materials making up shells 2 and 3 of body 1, the disclosure makes it possible to obtain a sufficiently rigid filter unit to be able to contain a filter element which has undergone light compression and is at the same time sufficiently rigid to be able to suitably protect such element and make it easy to handle. At the same time, this hardness makes it possible to obtain a filter unit which is sufficiently soft not to damage other filter units, tubes, bags or other components of a blood sampling and processing system when this, together with similar systems, is placed in a centrifuge to perform the normal operations to which such systems are subjected.

(24) Three filter units according to “configurations”, 1, 2 and 3 in the table shown above were made in order to test the filtration efficiency of a filter unit according to the disclosure.

(25) In particular, in a first configuration (configuration 1) the filter unit comprised a filtering element 5 formed by a pack of forty filtering layers of PET/PBT having a theoretical thickness for each layer of 0.31 mm and a weight per surface area of 52 g/m2. In a second configuration (“configuration 2”) only the number of layers in the filtering element (now thirty six) was varied, and in a third configuration (“configuration 3”) the number of layers in the filtering element was again changed, to fifty.

(26) A set of three filter units for each configuration of the filtering means was prepared. A filter unit with PVC half-shells, but with different rigidities, that is a first unit having semi-rigid half-shells according to the disclosure (Shore A rigidity 93±2), with soft half-shells (Shore A rigidity 85±2) and with rigid half-shells (H358/30 rigidity 95 MPa) was produced for each configuration.

(27) Given that filter units having rigid half-shells make it possible to have a high packing factor (in that it is possible to create a high pressure on the inner filtering element), when reading the table shown above it is important to compare it with the example for a filtering unit obtained using rigid material.

(28) The various configurations of filter units (with a filtering element obtained in different ways) were used in a filtration test according to a test protocol comprising the following characteristics:

(29) TABLE-US-00002 Number of leucocytes/unit* 2.5-3.0 *109 Number of platelets/unit* depends on the method of centrifuging Temperature of the blood to between 4° C. and ambient be filtered temperature Age of the blood unit to be max 10 days after donation filtered Haematocrit (Hct)/unit* 0.65-0.75 added solution 0.50-0.70 Minimum haemoglobin 45 g content/unit* Unit volume* 280+ ml Distance between the unit of 180 cm blood to be filtered and the collection bag Leucocyte counting method Nageotte chamber, DNA marking or cytofluorometry Priming of the filter YES

(30) The results shown in the table below were obtained using the various units according to the different configurations.

(31) TABLE-US-00003 Semirigido Morbido Rigido Desnitá Densitá Densitá H nel filtro Packing Efficienza H morbido Packing Efficienza H rigido Packing Efficienza Semirigido [gr/dm3] factor Semirigido Morbido [gr/dm3] factor morbido Rigido [gr/dm3] factor morbido Con- 10 208 124% 5 LOG 12 173 103% 3.5 lOG 10 208 124% 5 LOG figurazione 1 Con- 10 187 112% 4 LOG 10 187 112% 4 LOG 10 187 112% 4 LOG figurazione 2 Con- 11.5 226 135% 6 LOG 14 186 111% 4 LOG 10 260 115% 6.5 LOG figurazione 3

(32) When what is shown in the above table is examined it will be noted that the filter units with semi-rigid body 1 have a density in the filter which is comparable to filter units with a rigid body with a consequent equivalent or identical packing factor. Vice versa, in the case of filter units with a soft body, the density in the filter is lower and the packing factor is also lower.

(33) The tests performed therefore demonstrate how the disclosure has the advantages associated with the fact that body 1 of the filter unit is of the yielding and semi-rigid half-shells indicated above, but at the same time has a packing factor of more than 110% and is in any event comparable with the packing factor of known rigid filter units.

(34) Each half-shell 2, 3 has a perimetral flange 30 projecting laterally from the shell. Flanges 30 of the two half-shells 2, 3 overlap when body 1 is formed and form an assembly (a perimetral flange 40 projecting from body 1) which is flexible (thanks to the material of which the half-shells are made) so that it can be comfortably handled.

(35) In addition to this, body 1 obtained in this way remains intact during the centrifuging process thanks to the flexibility and anti-impact properties of the semi-rigid or soft material, at the same time making it possible not to damage components of the adjacent blood sampling and processing systems (as indicated above) while centrifuging is in progress.

(36) Flanges 30 are welded together over their entire surface area along a single weld line and without any foreign component placed between them, and in particular without any filter element being present between them. The weld is normally made by heat welding or through the use of ultrasound and, thanks to the fact that it is made directly between uniform parts of the same material, the weld is durable and remains strong over time. The weld line is preferably continuous.

(37) Flanges 30 are made in such a way that when welded the thickness resulting from fusion is between 1 and 2.5 mm, and this, in combination with the material having a hardness in the preselected range indicated above helps to obtain a soft flange 40 which is comfortable to use.

(38) Such flange 40 may also be of variable thickness, diminishing outwards.

(39) Filtering element 5 is held by half-shells 2 and 3, in addition to ribs 20, and also through projecting ledges 55 located close to the edges of those half-shells on faces 2W and 3W of said half-shells, close to their perimetral edge. These shelves 55, which may be continuous on each face 2W or 3W or discontinuous, form a kind of (continuous or discontinuous) ring which presses on faces 5A and 5B of filtering element 5 securing that element between the half-shells. In particular, these shelves 55 press said filtering element 5 close to its perimetral edge 70 of small thickness. Thanks to this the modular combination of the number and type of filtering layers can be varied without interfering with the welding of flanges 30 and the consequent closing off of the perimeter of body 1 in that the filtering module does not interfere with the welding of the half-shells, but is wholly contained within them and compressed at its perimetral edge thus obtaining a product (the filtration unit) having performance characteristics suitable for specific applications or different types of blood derivatives.

(40) As mentioned, shelves 55 close off the periphery of cavity parts 4A and 4B. This feature, together with the configuration of ribs 20 bounding and defining channels 21, allows the fluid entering the filtering unit via appendage 8 to be conveyed in an optimum way towards filtering element 5 and, after passing through the latter, towards appendage 12. This avoids bypassing filtering element 5 at its perimetral edge 70.

(41) Through the disclosure a filter unit having the characteristics described above is obtained. Other embodiments are however possible while remaining within the scope of the disclosure defined by the following claims.