DE102007024744A1 - Injection molding tool for plastic bottle with screw neck has transposed water cooling ducts - Google Patents

Abstract

Claimed is an injection molding tool for the manufacture of a plastic bottle with a screw-neck. The tool has an adjustable screw die with a first cooling duct around the neck aperture. The tool has a second cooling duct separated axially from the first. The wall between the first and second water cooling ducts has a number of cooling passages distributed along the length of the cooling ducts. The injection-molding tool has two halves that separate along a centerline after completion of the cooling process. The two assembled halves form a cylindrical void. In proximity to the threaded neck the cooling ducts each define a semicircle along the inner mantle surface. At this position, they are axially transposed with respect to each other in different planes.

Description

The The invention relates to an injection mold for the production of Preforms for the production of plastic bottles with threaded neck, the injection mold sliding threaded jaws for forming a thread and a gain in particular in the form of a neck ring, wherein the threaded jaws in the pushed together working position a cylindrical cavity enclose and thread contours on their inner circumferential surfaces surrounding the cavity and ring contours, further comprising the threaded jaws the inner shell surfaces Have cooling channels, the above each a feed channel and an outlet channel can be connected to a coolant supply device, wherein the cooling channels in the circumferential direction part of a circle along the inner circumferential surface directed directed and axially offset in different planes one above the other are formed.

typically, with such an injection mold have produced preforms or bottles made from them a neck on and a thread formed on the neck for screwing a lock. Furthermore, these preforms and / or Bottles between the outlet of the thread and the bottle body a gain preferably in the form of a so-called neck ring.

at the production of plastic bottles and especially in the production of preforms for PET bottle making, the thread is made in the way that an injection mold is provided with two sliding threaded jaws. Before start During the injection process, the jaws move together into the working position and enclose a cylindrical cavity. The inner circumferential surfaces of the cavity surrounding Areas of the thread jaws have the corresponding thread contour and also a ring contour on the shape of the thread to be formed or the shape of the reinforcement to be formed or the neck ring corresponds. After the injection process, the jaws spread apart to the sprue and in particular to release the thread and the neck ring, so that the molded plastic part can be removed from the mold. Both the threads themselves as well as the reinforcement below the thread are formed by accumulations of material, so that the entire preform or the bottle is not over its entire dimension constant wall thickness but in the area of the thread and the reinforcement in particular Neckringes a greater material thickness having. When forming a preform, this has below the thread a several millimeters thick retaining ring, also neck ring called, which is relatively thick-walled. Before demoulding the molding This area of threading and retaining ring must be intense chilled become. Only after sufficient cooling the demolding can take place. Thus, the cooling on the one hand for the quality of the preform or the bottle and on the other hand for the speed the injection cycle essential.

Usually become preforms after removal from the injection mold in a aftercooling station transported. The threaded part and the so-called neck ring are in the aftercooling station only slightly cooled, there is no physical contact to the metal of the aftercooling station can be produced. The choice of the cooling channel and the thereby influenced Pressure losses in the coolant are essential as any additional pressure loss Energy for the transport of the coolant needed. When coolant becomes common Used water. Likewise, the temperature distribution must be uniform, to ensure a perfect round shape of the molding or the bottle to be able to.

at the previously known sliding threaded jaws either no special separate cooling, so that the cooling off This area is done by the normal heat flow in the injection molded part. In this case, the cooling effect very low, so a longer one Cycle time is necessary, or in cooled threaded jaws have this only two holes arranged at right angles to each other, so that only a point cooling of the preform takes place. Again, the cycle time is relative long, in addition, the round shape accuracy adversely affected becomes.

Farther a training is known in which an annular cooling channel in the respective displaceable Threaded jaw is introduced. The cooling water occurs at one end in the annular channel, is then from one end of the annular channel to whose other end led, deflected by 180 ° in the return channel, to then exit the slide.

at Such an arrangement, the pressure loss is quite high, since the coolant in each slider half is deflected at right angles. On top of that, the temperature distribution in the circumferential direction, so that the temperature difference between Entry and exit also on the entire circumference of the molding takes effect. Due to the fact that the cooling channels in different Layers lie, that is for the preform effective cooling surface also limited.

The object of the invention is to have the largest possible cooling surface, especially in the threaded area of the displaceable threaded jaws who effective to let the same while achieving the lowest possible pressure losses in the cooling water flow, and to obtain a very good temperature distribution. With the largest possible cooling surface, the outer dimensions of the displaceable threaded jaws should be minimized.

to solution this task strikes the invention provides that a first cooling channel of a threaded jaw the feed channel has, a second cooling channel, which is axially spaced from the first, has the exit channel, and that between the first cooling channel and the second cooling channel located wall of the threaded jaw a plurality of distributed over the length of the cooling channels arranged passage openings for the coolant having.

By the training of the invention will not just a cooling achieved in the circumferential direction, but it is a relatively uniform cooling in reaches the axial direction of the threaded neck or the threaded jaw, because the cooling water on the one hand in the circumferential direction through the cooling channels and on the other hand into a axial flow from the first cooling channel to the second cooling channel is forced back. The effective cooling channels can have different cross-sectional shapes have adjusted and the Werkzeugwandung in the same distance be formed.

Around the wished cooling effect still to improve, to further minimize the cycle time and also to favorably influence the basic shape accuracy of the molded part, is provided that the feed channel approximately in the middle of the longitudinal course of the first cooling channel in this opens and the outlet channel approximately in the middle of the longitudinal course of the second cooling channel emanates from this.

Thereby, that the coolant over the feed approximately in the middle of the first cooling channel supplied will be, a homogenization of the cooling effect achieved, which is just as favorably influenced, because of the Outlet channel for the coolant from the second cooling channel approximately in the middle of this goes off. The cooling channels extend in preferably two-part Threaded over each almost 180 ° of Scope of molding to be molded.

Around the corresponding passage openings form in a simple manner and in the threaded jaws of the tool to be able to bring in is provided that between the first cooling channel and the second cooling channel a baffle is arranged, which the passage openings has, through which the cooling channels with each other are connected.

For example each thread can be composed of two parts, which lie in the desired position on each other. In these individual elements can the cooling channels and also the feed channels or outlet channels be formed in a simple manner. It can then be the appropriate baffle be put on and the parts are placed on top of each other so that they are connected to a solid entity.

Around a particularly uniform flow behavior of the coolant To achieve, it is provided that the passage openings with increasing distance from the mouth of the feed channel in the first cooling channel and from the outlet the discharge channel from the second cooling channel increasing flow cross-sections exhibit.

Out For the same reason, it is preferably provided that in the area near the confluence of the feed channel in the first cooling channel and in the area of the outlet the outlet channel from the second cooling channel fewer passage openings are provided as in the areas near the ends of the cooling channels.

moreover it can be provided that the threaded jaws are made of steel, wherein at least the material between the cooling channels and the inner circumferential surface of a highly heat-conductive material consists.

hereby will be the desired heat transport from molding to coolant encouraged.

Preferably It is envisaged that a highly heat-conductive material Kupferberillium alloy is used.

Around To minimize the dimension of the thread jaws, can also be provided be that the feed channel across from the exit channel about the cross section of the channels in the circumferential direction offset from one another.

One embodiment The invention is illustrated in the drawing and in the following explained.

It shows:

1 seen two sliding threaded jaws in the working position in plan view;

2 likewise in section BB the 1 seen;

3 likewise in section AA the 1 seen;

4 likewise in section CC the 3 seen;

5 likewise on average DD the 3 seen.

In the drawing, an essential part of the invention for an injection molding tool for the production of preforms for the production of plastic bottles with threaded neck is shown. For this purpose, the injection mold has displaceable threaded jaws 6 . 6 ' on, which serve to form a thread and a reinforcement, in particular in the form of a neck ring. The thread jaws 6 . 6 ' enclose a cylindrical cavity in the collapsed working position shown in the drawing 7 where the thread jaws 6 . 6 ' on her the cavity 7 surrounding inner circumferential surface thread contours 8th and ring contours 9 in the form of grooves or the like to form the preform with a thread formation and a neck ring or the like. To demould the molded product, the threaded jaws 6 . 6 ' in the direction of the movement arrow 10 in 1 be pushed apart. The thread jaws 6 . 6 ' have near the inner circumferential surfaces cooling channels 2 . 4 on, each with a feed channel 1 and an exit channel 5 can be connected to a supply device for coolant. The cooling channels 2 . 4 run in the circumferential direction approximately in the form of a semicircle along the inner circumferential surface and at a small distance from it, wherein cooling channels 2 . 4 axially offset in two different planes are formed one above the other, as in particular in 3 is illustrated.

A first cooling channel 2 a threaded jaw 6 . 6 ' has the feed channel 1 on while a second cooling channel 4 that of the first cooling channel 2 axially spaced, the outlet channel 5 having. The spatially between the first cooling channel 2 and the second cooling channel 4 located wall of each thread 6 . 6 ' has several over the length of the cooling channels 2 . 4 distributed through openings 11 for the coolant on. In the exemplary embodiment, and this is preferred, the feed channel opens 1 approximately in the middle of the longitudinal course of the respective first cooling channel 2 in this one, while the exit channel 5 approximately in the middle of the longitudinal course of the second cooling channel 4 goes off and ends. For formation of through holes 11 is between the first cooling channel 2 and the second cooling channel 4 one baffle each 3 arranged, which the passage openings 11 through which the cooling channels 2 . 4 connected to each other. As in particular from the illustration according to 4 can be seen, have the through holes 11 with increasing distance from the mouth of the feed channel 1 in the first cooling channel 2 and from the mouth of the exit channel 5 from the second cooling channel 4 increasing flow cross sections. In the exemplary embodiment, therefore, are in the central region of the cooling channels 2 . 4 Through holes relatively small, while in the end portions of the cooling channels 2 . 4 are relatively large. In addition, in the area near the mouth of the feed channel 1 in the first cooling channel 2 and in the area of the outlet of the outlet channel 5 from the second cooling channel 4 fewer passage openings provided, as in the end portions of the cooling channels 2 . 4 ,

Preferably, there are the threaded jaws 6 . 6 ' made of steel, with at least the material between the cooling channels 2 . 4 and the cavity 7 enclosing inner lateral surface made of a highly heat conductive material, preferably a Kupferberillium alloy.

To the dimensions of the thread jaws 6 to minimize, is the feed channel 1 in each case opposite the outlet channel 5 offset in the circumferential direction, so that these channels 1 . 5 not on top of each other, but next to each other.

According to the embodiment of the invention occurs when using the injection mold in the cooling cycle, the cooling water via the feed channel 1 in the middle of the first cooling channel 2 and flows from there evenly to the ends of the cooling channel 2 , That between the lower cooling channel 2 and the upper cooling channel 4 lying baffle 3 has outlet openings 11 , Which are designed so that on the entire circumference the most uniform flow in the axial direction and a uniform pressure build-up takes place. As a result, a very uniform temperature is achieved on the circumference. The necessary for the heat absorption temperature difference is thus not only distributed radially, but also axially. After the cooling water the through holes 11 the bark 3 flows through in the axial direction, it collects in the upper second cooling channel 4 and enters through the exit channel 5 centrally located.

In previously conventional methods, either only a point cooling or cooling takes place in the circumferential direction. By the invention it is possible to achieve a large effective cooling surface and a uniform temperature distribution on the circumference, due to the combination of radial and axial flow of the cooling water. The described construction additionally allows a hybrid function in the threaded jaw 6 . 6 ' to realize in the way that between the cooling channels 2 . 4 and the cylindrical cavity 7 located preform a material for the formation of the threaded jaw 6 . 6 ' is used, which has higher heat flow properties than the base material from which the threaded jaws 6 . 6 ' are shaped. Preferably, a Kupferberillium alloy is used for this purpose.

The invention is not limited to the embodiment Example limited, but in the context of the disclosure often variable.

All new individual items disclosed in the description and / or drawing. and combination features are considered essential to the invention.

Claims (8)

Injection molding tool for the production of preforms for the production of plastic bottles with threaded neck, wherein the injection molding tool displaceable threaded jaws ( 6 . 6 ' ) for forming a thread and a reinforcement, in particular in the form of a neck ring, wherein the threaded jaws ( 6 . 6 ' ) in the pushed together working position a cylindrical cavity ( 7 ) and on their the cavity ( 7 ) surrounding inner circumferential surfaces thread contours ( 8th ) and ring contours ( 9 ), further wherein the threaded jaws ( 6 . 6 ' ) near the inner surface cooling channels ( 2 . 4 ), which in each case have a feed channel ( 1 ) and an exit channel ( 5 ) are connectable to a supply device for coolant, wherein the cooling channels ( 2 . 4 ) in the circumferential direction part-circularly along the inner lateral surface directed directed and axially offset in different planes are formed one above the other, characterized in that a first cooling channel ( 2 ) a threaded jaw ( 6 . 6 ' ) the feed channel ( 1 ), a second cooling channel ( 4 ), which is axially spaced from the first, the outlet channel ( 5 ), and that between the first cooling channel ( 2 ) and the second cooling channel ( 5 ) located wall of the threaded jaw ( 6 . 6 ' ) several over the length of the cooling channels ( 2 . 4 ) distributed through openings ( 11 ) for the coolant. Injection mold according to claim 1, characterized in that the feed channel ( 1 ) approximately in the middle of the longitudinal course of the first cooling channel ( 2 ) opens into this and the exit channel ( 5 ) approximately in the middle of the longitudinal course of the second cooling channel ( 4 ) emanates from this. Injection mold according to claim 1 or 2, characterized in that between the first cooling channel ( 2 ) and the second cooling channel ( 4 ) a baffle ( 3 ) is arranged, which the passage openings ( 11 ), through which the cooling channels ( 2 . 4 ) are interconnected. Injection mold according to one of claims 1 to 3, characterized in that the passage openings ( 11 ) with increasing distance from the mouth of the feed channel ( 1 ) in the first cooling channel ( 2 ) and from the mouth of the exit channel ( 5 ) from the second cooling channel ( 4 ) have increasing flow cross sections. Injection mold according to one of claims 1 to 4, characterized in that in the region near the mouth of the feed channel ( 1 ) in the first cooling channel ( 2 ) and in the region of the outlet of the outlet channel ( 5 ) from the second cooling channel ( 4 ) fewer passage openings ( 11 ) are provided as in the areas near the ends of the cooling channels ( 2 . 4 ). Injection mold according to one of claims 1 to 5, characterized in that the threaded jaws ( 6 . 6 ' ) consist of steel, wherein at least the material between the cooling channels ( 2 . 4 ) and the inner circumferential surface consists of a highly heat-conductive material. injection mold according to one of the claims 1 to 6, characterized in that as a high heat conducting material a Copper beryllium alloy is used. Injection mold according to one of claims 1 to 7, characterized in that the feed channel ( 1 ) opposite the outlet channel ( 5 ) about the cross section of the channels ( 1 . 5 ) is arranged offset in the circumferential direction to each other.