Small size plastic filter and its production process.

description

The invention relates to a small plastic filter with a made of injection-molded housing, in which between an inlet and an outlet of a leak-tight manner in its edge region to the housing is arranged associated filter membrane, and at the same time concerns a method of manufacturing such a small filter of plastic. Such Small filter of the prior art are used above all as a Syringe for sterile filtration of very small amounts, the total length of the filter housing between the inlet and outlet ends at about 20 mm and the filter diameter be about 3-5 mm. The filter membrane is connected on an inner shoulder of the filter housing by ultrasonic welding, adhesive bonding or Aufsiegelung. The preparation of these filters is far improved, as more steps are necessary to the finishing of the filter by using the very small items. The subsequent positioning of the punched filter membranes in the finished filter housings and their leak-tight connection is very difficult and the rejection rates are correspondingly high. The final filter should be subjected generally to sterilization.

Although it is known (US Patent No. 4,113,627), to join in a multi-part filter housing, the filter membrane in several steps by liquid plastic with the finished injection molded part made of plastic by injection molding and also known to position the filter membrane between two finished housing plastic parts and all three parts (housing parts and filter membrane) to the edge side overmolded together in a mold with liquid plastic, but this production is very expensive due to the many parts and manufacturing steps.

The invention is therefore based on the object to simplify the manufacture of such small filter, in particular the compound of the filter membrane to the housing and thereby to improve the leak-tight connection between the filter membrane and the housing.

This object is achieved in that the housing constructed in one piece and the filter membrane is at least one side overlaps the sealed edge area from solidified in the injection mold injection molding a one-piece filter housing and anchored in this.

The process for preparation is carried erfindungsmgemäß characterized in that the filter membrane is supported in such a way on both sides between two contra-movable mold members of a mold in a mold cavity, that the sealed edge region of the filter membrane is exposed at least on one side and covered by the introduced during the injection molding liquid plastic anchored in this and which solidified piece housing with integrated filter membrane is removed from the mold. Preferably, the introduction of small-sized filter membrane occurs in that it is punched out directly by a trained as punch molding of a filter band and this stamping positioned directly in the mold and molded thereafter. Characterized the empfindlicht filter membrane is punched out of a filter belt in a machine manufacturing step, positioned in the mold cavity and peripherally leak-tight encapsulated with a housing.

The inventive concept is explained in more detail in a preferred embodiment with reference to the enclosed drawing. In which:<ul><li>FIG. 1 shows a typical small filter in longitudinal section,</li><li>FIG. 2 a detail point enshrined in plastic one-piece filter housing Filter membrane</li><li>Fig. 3 shows a variant of this anchoring,</li><li>Fig. 4 schematically shows a vertical section through the mold in the open position,</li><li>Fig. 5 shows a vertical section through the mold in the closed position and</li><li>Fig. 6 is a horizontal section through the mold in the position of FIG. 5.</li></ul>

The small filter consists of a one-piece plastic housing 1 with an inlet 2, an outlet 3 and the anchored on an inner shoulder 4 in the edge region 6˝ the plastic of the housing 1 membrane filter 6. The anchoring is effected by the fuel injected into the mold liquid plastic package, which it the exposed edge region of the membrane filter 6˝ 6 dissolves depending on the filter material and combines with this or in the pore structure at least superficially penetrates and anchored in or on this.

In the detailed embodiment shown in FIG. 3, the inner shoulder 4 is expanded into a circumferential annular groove 5, so that the edge region of the filter membrane comprises 6˝ 6 U-shaped. In the embodiment shown in FIG. 1 of the inlet 2 and outlet 3 are adjusted as of the effective filtration area in size.

By a single or double surface arranged or integrated drainage layer 7 in form of a fleece or fabric thin and delicate membrane filter may be mechanically supported in larger filter surfaces, wherein the edge region of the drainage layer 7 is also anchored to the plastic of the one-piece filter housing first

Instead of the case 1 shown in FIG. 1, this can also be kept very flat and the shape of a ring 1 'formed in the opening of the filter membrane 6 is anchored in the plastic material and are, in turn, positioned in a surrounding housing.

The mold for the production consists of the fixed mold half 10 and the movable mold half 17. The fixed mold half 10 has a fixed core 11, which also serves as a punch. This stationary core 11, a movable mold insert 12 cooperates which has a slit-shaped membrane guide 13, an insert 14 and the punch 11 cooperating cutting sleeve and one half of the mold cavity 16th The movable mold insert 12 is guided in a recess 8 of the tool half 10 and is based on a return spring 15 in the recess from.

The movable mold half 17 has the other half of the mold cavity 16, and a on a return spring 18 which is supported movable core 19 to the diaphragm fixation.

According to Fig. 6 10 the runner 21 is arranged for supplying the liquid plastic 12˝ in the mold parting plane 20 and the fixed mold half. Optionally, the runner can also be arranged as a hot runner entirely in one half of the molding tool.

Referring to FIG. 4, the membrane filter belt 6 'guided step by step through the slit-shaped diaphragm guide 13. In the coaxial movement of the movable mold insert 12 and the movable mold half 17 in the closed position according to FIG. 5 is determined by the punch 11 and the cutting sleeve 14, a membrane filter 6 punched out of the filter belt 6 ', by the punch 11 and the counter-core 19 in the mold cavity 16 positioned and then anchored by the runner 21 injected liquid plastic mass 1˝ shown in FIG. 6 at the edge. After curing of the plastic mass 1˝ unmolding of the finished small filter of FIG. 1 and the continuation of the membrane strip 6 'within the membrane guide 13 takes place.

Similarly, a filter belt consisting processed from one or both sides with a drainage layer 7 reinforced membrane filter 6th

The production is very efficient and the anchoring of the membrane filter 6 in the plastic material of the one-piece plastic housing 1 leakproof and safe. With production under clean room conditions, the small dust leaving the mold cavity 16 virtually particle free. Because the liquid spray casting compound 1˝ as polypropylene in the cavity 16 as a temperature of about 230 ° C and in particular for small mold cavities 16 and particularly small male dies 11,19 and positioned thereon filter membrane 6, the temperature of the molding compound 1˝ briefly pre-sterilized to the filter membrane 6 radiates accordingly, this type of production for the one-piece plastic housing 1 under sterile conditions and with respect to the filter membrane 6 is performed at least germ-reducing and under certain conditions even sterilizing, which is advantageous for all areas of the filter. Optionally, which results in reduced a further treatment of the small filter.