Well or well strip and method for producing same

Abstract

A method for producing a well or a well strip made of plastic, as used in the pharmaceutical industry in microtiter systems is presented. The wells typically have undercuts and the well strips are connected to each other by connecting ribs. In order to produce a well with a larger undercut height or a well strip with higher connecting ribs, as the case may be, the method provides that the plastic, which is initially still liquid, is pressed through a portion of a runner which is arranged in a slider and out of the slider into a cavity of an injection mold.

Claims

1. A method for producing a well strip (230) having a plurality of wells (200) which are connected to one another by connecting ribs (232), the wells having an undercut (210) on their outer side, with an injection mold (100) having a runner (110), injection-side components (120), and closing-side components (130) including at least one slider (132) with slider elements (132), a closing-side core (134) and a scraper (136), comprising the following steps: closing the injection mold (100) by moving the closing-side components (130) and the injection-side components (120) towards each other relative to each other, by which a cavity (140) representing a negative mold for the wells (200) is formed in the injection mold (100) between the slider elements (132); pressing liquid plastic with the assistance of an injection molding machine (300) through a portion (118) of the runner (110) in the slider (132) and from the slider (132) into the cavity (140), wherein an injection point (119) is arranged on a side of the wells respectively on a side of the cavity (140) below a bottom of the wells; allowing the plastic in the cavity (140) to cure and form the wells (200) together with a sprue (115); opening the injection mold (100) by moving apart the closing-side components (130) together with the wells (200) and the injection-side components (120) relative to each other, wherein the sprue (115) is torn off the wells (200), and wherein the slider elements (132) are moved apart to release the undercut (210) on the well (210) only after the sprue (115) has been torn off the wells (200) and pulled out of the portion (118) of the runner (110) in the slider (132); and stripping the well strip (230) from the closing-side core (134) with the help of the scraper (136); wherein the undercut (210) or the connecting ribs (232) have a height (d) in a longitudinal direction (L) of the wells for which the following applies: 3.5 mm<d<10 mm.

2. The method as in claim 1, wherein 7.0 mm<d<10 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows the starting point of the method in the form of a closed injection mold.

(2) FIG. 1b shows a detailed view of FIG. 1a.

(3) FIG. 2a shows a first step of the method.

(4) FIG. 2b shows a detailed view of FIG. 2a.

(5) FIG. 3a shows a second step of the method.

(6) FIG. 3b shows a detailed view of FIG. 3a.

(7) FIG. 4 shows a third step of the method.

(8) FIG. 5 shows a fourth step of the method.

(9) FIG. 6 shows a well strip produced by the method.

(10) FIG. 7 shows a longitudinal section through the well strip according to FIG. 6.

DETAILED DESCRIPTION

(11) The invention is described in detail in the following with reference to the figures mentioned in the form of exemplary embodiments. In all figures, the same technical elements are marked with the same reference signs.

(12) FIGS. 1a and 1b show the injection mold 100 used in the method in a closed state. That is, its injection-side and closing-side components 120, 130 must move towards each other. In the exemplary embodiment shown in FIGS. 1a and 1b, the injection-side components 120 above the dividing line TR include a slider plate 122 with an injection-side core 123 embedded therein for a well 200 to be produced. Furthermore, a first portion 116 of the runner 110 is formed in the slider plate 122. In addition, the injection-side components 120 also include, for example, a slanted bolt 125, which is fixed in a slanted blind hole 126 in the slider plate 122.

(13) In addition to such injection-side components 120, the injection mold 100 also includes the following closing-side components: A scraper 136, by way of example designed in the form of a scraper plate, and a closing-side core 134 for the well 200, which is displaceably mounted in the scraper. The scraper 136 has an opening for receiving the slanted bolt 125 with a predetermined clearance or free stroke h. Two slider elements 132 or slider halves are mounted on the scraper 136 so that they can be displaced transversely to the longitudinal direction L. The closing-side core 134 for the well 200 is held at its well end by a core retaining plate 137.

(14) With the closed state of the injection mold 100 shown in FIGS. 1a and 1b, the closing-side and injection-side components 120, 130 are to be moved towards each other so far that they touch. In particular, the slider elements 132 touch the slider plate 122. Between the slider elements 132—and further limited by the clamp-side core 123 and the injection-side core 134—a cavity 140 is formed in the closed injection mold, which represents a negative mold for the well 200 to be produced.

(15) In addition to the first portion 116 of the runner 110, shown here only as an example as formed in the slider plate 122, a second portion 118 of the runner is visible in the slider 132, which opens into the cavity 140. The slanted bolt 125 does not prevent the injection mold 100 from closing, because its free end protrudes into openings in the slider elements 132, in the scraper 136 and possibly also in the core retaining plate 137.

(16) The method for producing at least one well or well strip made of plastic with an undercut on its outer side comprises the following steps:

(17) After closing the injection mold 100, the cavity 140 formed in it is filled with liquid plastic. Specifically, the liquid plastic is initially formed on the injection side with the assistance of an injection molding machine 300, first through the first portion 116 of the runner 110, in FIGS. 1a and 1b as an example, then through a second portion 118 of the runner in the slider 132 and from there pressed into the cavity 140. In FIG. 1b, the two portions of the runner are clearly visible. It is also clearly visible that the injection point 119 is located on the side of the well 200 or cavity 140, as the case may be, below the bottom 212 of the well.

(18) The plastic then cures in the cavity 140 and the runner 110; in the well, this leads to the formation of the well 200 and in the two portions 116 and 118 of the runner, the curing of the plastic leads to the formation of the sprue 115. The well 200 and the sprue 115 are initially formed in one piece with each other.

(19) In a subsequent method step, as shown in FIGS. 2a and 2b, the closing-side components 130 and the injection-side components 120 are moved apart along the longitudinal axis L, as an example. The well 200 breaks away from the sprue 115 at the injection point 119. Thereby, the sprue 115 is pulled out of the second portion 118 of the runner 110 and initially remains in the first portion 116 of the runner 110 on the injection molding side. There, the sprue 115 is held by a sprue retaining pin 127 with the assistance of the undercuts shown in FIG. 2b.

(20) FIGS. 3a and 3b illustrate the following method step, according to which only after the sprue 115 has been torn off from the slider 132 are the slider elements 132 on both sides of the well 200 moved apart on the scraper 136 or the scraper plate, as the case may be, transversely to the longitudinal direction L. The moving apart takes place in order to release the well 200 with its undercuts 210 or the well strip 200′, as the case may be, with its connecting ribs 232 for a subsequent ejection.

(21) FIG. 3b shows that the well-side contour of the slider elements 132 is complementary to the outer contour of the well 200.

(22) An overview of FIGS. 1a, 2a and 3a shows how the relative position of the slanted bolt 125, which is clamped in a fixed manner in the slider plate 122, changes within the openings of the slider elements 132, the scraper 136 and possibly also in the core retainer plate 137 as the injection-side and the closing-side components 120, 130 are increasingly moved apart. In FIGS. 1a and 2a, the relative position changes in each case; however, there is no displacement of the slider elements 132 in particular, because the slanted bolt 125 still moves within the free stroke h allowed to it in the opening of the slider elements. Only when the closing-side and injection-side components 120, 130 have been moved apart in the longitudinal direction L as far as shown in FIG. 2a, the free stroke h is used up and, as the components 120, 130 continue to move apart in the longitudinal direction L, due to the slanted position of the slanted bolt 125, the transverse dis-placement of the slider elements 132 occurs and thus the opening of the cavity 140 occurs, as shown in FIG. 3a.

(23) It is important that the mentioned moving apart of the slider elements 132 is not carried out at the beginning of the moving apart of the components 120, 130, because this would lead to an undesired shearing of the part of the sprue located in the second portion 118 of the runner from the part of the sprue located in the first portion 116. Such a shearing is undesirable, because, at that point, the part of the sprue 115 remaining in the slider could no longer be removed from the second portion 118 of the runner.

(24) To avoid this, the mentioned (time) delay between the moving apart of the components 120, 130 and the moving apart of the slider elements 132 is particularly important. Of course, the mentioned delay can also take place differently than by the slanted bolt 125 shown here by way of example. In principle, any other mechanical, hydraulic or electronic solutions are conceivable.

(25) Furthermore, it can be seen in FIG. 3a that the sprue 115 was pushed out of the first portion 116 of the runner with the help of a sprue ejector pin 128. However, it is still held by the sprue retaining pin 127.

(26) FIG. 4 shows the next method step, in which the sprue retaining pin 127 is separated from the sprue 115 by pulling it upwards from the sprue 115, while the sprue 115 is simultaneously held in its ejection position by the sprue ejector pin 128.

(27) FIG. 5 shows a final method step, according to which the well 200 is stripped off the core 134 on the closing-side. As shown in FIG. 5, this is done by moving the scraper 136 or the scraper plate, as the case may be, upwards in the longitudinal direction L relative to the core retaining plate 137. The edge of the opening for the closing-side core 134 in the scraper 136 is designed in such a manner that it engages the opening edge of the well 200 from below and thus strips the well 200 off the closing-side core 134 as it moves in the longitudinal direction L up-wards. Both the sprue 115 and the well 200 are subsequently ejected from the injection mold.

(28) FIG. 6 shows an example of a well strip 200′ produced according to the method in accordance with the invention. It consists of a plurality of individual wells 200 arranged in a line adjacent to each other. Recesses 214 can be seen on the outer side of the wells; these are used to snap the wells 200 or the well strip 200′ into the openings of a microtiter plate. The recesses here are, by way of example, de-signed in the form of a circumferential groove. Each of the upper and lower boundary walls 216 of the recess 214 can be formed to be straight or, as shown in FIG. 6, beveled or rounded.

(29) FIG. 7 shows a longitudinal section through the well strip 200′. The connecting ribs 232, with which the individual wells 200 are connected to each other, are particularly easily visible here. Each of such connecting ribs has a height d. Only the method in accordance with the invention makes it possible to form this piece height in a height range of 3.5 mm<d<10 mm, preferably 7.0 mm<d<10 mm, each measured from the edge of the openings of the wells 200.

LIST OF REFERENCE SIGNS

(30) 100 Injection mold

(31) 110 Runner

(32) 115 Sprue

(33) 116 First portion of the runner

(34) 118 Second portion of the runner

(35) 119 Injection point

(36) 120 Injection-side component

(37) 122 Slider plate

(38) 123 Injection-side core

(39) 125 Slanted bolt

(40) 126 Blind hole

(41) 127 Sprue retaining pin

(42) 128 Sprue ejector pin

(43) 130 Closing-side components

(44) 132 Slider/slider element

(45) 134 Closing-side core

(46) 136 Scraper

(47) 137 Core retaining plate

(48) 140 Cavity

(49) 200 Well

(50) 200′ Well strip

(51) 210 Undercut

(52) 212 Bottom of the well

(53) 214 Recess

(54) 216 Boundary walls

(55) 230 Well strip

(56) 232 Connecting ribs

(57) 300 Injection molding machine

(58) L Longitudinal direction

(59) TR Dividing line

(60) h Free stroke

(61) d Height of the connecting ribs