Method and device for producing injection-molded parts by a two-component injection-molding technique and injection-molded part

Abstract

A method for producing injection-molded parts by a two-component injection-molding technique in which a first material component is injected into a mold cavity and is displaced into peripheral regions of the mold cavity by injecting a second material component. The first material component is injected into a partial region of the mold cavity at a first gating point and the second material component is injected into the mold cavity at a second gating point and, as a result, the first material component is acted upon by the second material component and displaced in the direction of the regions of the mold to be filled with the first material component. The first material component is thereby displaced into regions of the mold at the wall, and the second material component is introduced in those regions of the mold as a core material and completely into other regions of the mold.

Claims

1. A method for producing injection-molded parts, which have at least one use area with a bristle region, by a two-component injection-molding technique comprising: injecting a first material component into a mold cavity of a mold comprising a wall at a first gating point; injecting a second material component into the mold cavity at a second gating point and displacing the first material into peripheral regions of the mold cavity with the second material component; wherein, the first material component is softer than the second material component and is acted upon by the second material component and is displaced in a direction of regions of the mold to be filled with the first material component, the first material component being displaced into regions of the mold at the wall; and wherein the second material component is introduced at least in certain regions as a core material into the regions of the mold to be filled with the first material and completely into other regions of the mold, and the second material component partially penetrates into the bristle region, wherein the regions of the mold to be filled with the first material component have a helical or spiral contour.

2. The method as claimed in claim 1, further comprising injecting more material of the first material component than is required for filling the regions of the mold that are to be filled with the first material component.

3. The method as claimed in claim 1, wherein the injecting of the second material component continues until the second material component flows into the gating point of the first material component.

4. The method as claimed in claim 1, wherein, during the injection of the second material component, a counter-pressure at the first gating point is increased.

5. The method as claimed in claim 1, wherein the injecting of the first material component and of the second material component takes place simultaneously.

6. The method as claimed in claim 1, wherein the injecting of the first material component and of the second material component begins simultaneously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The method according to the invention, the device and the injection-molded part are explained in more detail below on the basis of the drawings, in which, in a partly schematized form:

(2) FIG. 1 shows an injection mold during the injection of a first material component,

(3) FIG. 2 shows the injection mold during the injection of a second material component,

(4) FIG. 3 shows the injection mold after the ending of the injecting operation,

(5) FIG. 4 shows finished injection-molded parts molded in the injection mold according to FIGS. 1 to 3,

(6) FIG. 5 shows a further injection mold during the injection of a first material component,

(7) FIG. 6 shows the injection mold according to FIG. 5 during the injection of a second material component,

(8) FIG. 7 shows the injection mold according to FIGS. 5 and 6 after the ending of the injecting operation,

(9) FIG. 8 shows a detailed representation of a gating point of the injection mold from FIG. 7, and

(10) FIG. 9 shows a finished injection-molded part molded in the injection mold according to FIGS. 5 to 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) According to FIGS. 1 to 3, a device, denoted as a whole by 1, for producing injection-molded parts 2 by the two-component injection-molding technique has a mold 3 and two injection-molding units 4a, 4b. The mold 3 is formed as a multi-cavity mold for four injection-molded parts 2 (FIG. 4) and has four mold cavities 5 with corresponding feed lines 6 from the injection-molding units 4a, 4b to the mold cavities 5. The mold cavities 5 are respectively assigned two gating points 7a, 7b.

(12) The mold 3 according to FIGS. 1 to 3 is formed for the injection-molding of interdental cleaning brushes. For their production, first a first material component 8 is injected from the first injection-molding unit 4a via first gating points 7a into the individual mold cavities 5 (FIG. 1). The first material component 8 is in this case a soft-elastic plastic, which forms the cleaning area on the finished injection-molded part 2. The gating points 7a for the first material component 8 are respectively arranged in the area of the region of the mold 3 that forms the end on the side to be used. The first material component 8a thereby first flows past the lamella-like recesses 10, which form the cleaning areas of the finished interdental brush, since the first material component 8 can escape into the free region of the mold that is remote from the first gating point 7a. The keeping clear of the lamella-like recesses 10 can be seen in particular in the encircled representation of a detail that is additionally shown in FIG. 1.

(13) Subsequently, a second material component 9 is injected from the second injection-molding unit 4b via second gating points 7b into the mold cavities 5 of the mold 3 (FIG. 2). The second material component 9 thereby respectively fills the region of the mold cavity 5 that is facing the second gating point 7b and then acts upon the first material component 8. Due to the high pressure that is applied in the two injection-molding units 4a, 4b, the first material component 8 is displaced into the lamella-like recesses 10, which can be seen in particular in the encircled representation of a detail of FIG. 2. Moreover, the second material component 9 penetrates as core material into the first material component 8 in the region of the mold cavity 5 that forms the cleaning area.

(14) The injection of the first material component 8 and of the second material component 9 may take place one after the other or simultaneously.

(15) As illustrated in FIG. 3, the injection of the second material component 9 continues until the second material component 9 flows into the gating point 7a of the first material component 8. This over injection ensures that the entire cleaning area of the finished injection-molded part 2 that is provided with the first material component 8 in the outer region is provided with a core of the harder, second material component 9, which stabilizes the cleaning area and makes the handling of the interdental brush easier.

(16) FIG. 4 shows the finished-molded injection-molded parts 2 removed from the mold 3, together with the still molded-on sprues 11. The injection-molded parts 2 have in each case a handle area 12 of the second material component 9 and also an area of use 13. The area of use 13 in this case consists of an inner, stabilizing core of the second material component 9 and also an outer region of the first material component 8, which forms the cleaning area of soft-elastic plastic for tooth cleaning. The outer region is in this case helically or spirally formed. This continuous helix or spiral form makes particularly good cleaning results possible. Moreover, the demolding of the first material component (8) from the mold (3) is made easier.

(17) Consequently, injection-molded parts 2 in which, as a difference from previously known two-component injection-molding methods, both material components 8, 9 can be seen on the outside and perform a respective function can be produced in the device 1 by the two-component injection-molding technique. A transfer, difficult in particular in the case of small moldings, of a partial molding for the molding-on of a second material component, as in the case of conventional moldings in which a second material component is to be attached to a carrier part only in partial regions, is not required.

(18) FIGS. 5 to 9 show the production of a brush as an injection-molded part 2 from two material components 8, 9.

(19) Of the mold 3, only the inner contours of the mold cavity 5 and the feed lines 6 of the injection-molding units are in this case represented.

(20) Also in the case of this embodiment, the first material component 8 is injected into the mold cavity 5 at a first gating point 7a (FIG. 5). The first gating point 7a is in this case located in the region of recesses 14 to be filled with the first material component 8, which form bristles 15 of a brush on the finished injection-molded part 2 (FIG. 9). Since, when injecting the first material component 8, there is not yet any counter-pressure, the first material component 8 initially does not yet flow into the recesses 14.

(21) According to FIG. 6, the second material component 9 is injected into the mold cavity 5 at the second gating point 7b. Due to the high injection pressure at the two injection units, the first material component 8 is acted upon by the second material component 9 and displaced into the recesses 14. The first material component 8 thereby comes to lie against the walls of the mold cavity 5. The second material component 9 thereby also flows into the recesses 14 in certain regions and thus forms a core region, which stabilizes the bristles 15 in the area of use 13 of the injection-molded part 2. Since the second material component 9 requires a certain time before it reaches the region of the first material component, the injection of the two material components 8, 9 may also take place simultaneously.

(22) It can be seen in FIG. 7, and in particular the detailed representation according to FIG. 8, that the injection of the second material component 9 continues until the second material component 9 flows into the gating point 7a for the first material component 8.

(23) FIG. 9 shows the finished injection-molded part 2 with the handle area 12 of the second material component 9 and the area of use 13 with bristles 15 of the first material component 8, the bristles 15 having in certain regions a core of the second material component 9 (FIGS. 6 and 7).

(24) In order to ensure that material is also sufficiently available for all regions that are to be filled with the first material component 8, at first more material than would be computationally required is injected during the injection of the first material component 8. During the injection of the second material component 9, and as a result of the first material component 8 being acted upon by the second material component 9, any excess material of the first material component 8 can flow back again into the gating point 7a of the first material component 8.

(25) In order that the first material component 8 reliably flows into all the desired regions when it is acted upon by the second material component 9, and the second material component 9 also in certain regions flows into the corresponding regions of the mold as core material, the counter-pressure in the injection-molding unit 4a for the first material component 8 may be increased during the injection of the second material component 9.