DE102011010185A1 - Device for producing and regulating discontinuous production process of annular moldings, has strand-type melt strand that is separated by pre-distribution system into one or multiple spiraly extending channels - Google Patents

Abstract

The device has a strand-type melt strand that is separated by a pre-distribution system into one or multiple spirally extending channels. The channel height decreases over a channel length and the channel length is guided with an increasing gap in opposite directions to annular outlet geometry. An independent claim is also included for a method for producing and regulating discontinuous production process of annular moldings, particularly for cross-linked molding materials such as rubber or rubber compounds.

Description

Process for the material and energy-efficient production of annular injection molded parts from crosslinking molding compositions by the use of a temperature-controlled inverted radial spiral distributor with adjustable circular outlet gap.

field of use

In rubber processing, among other things, the injection molding process for the production of molded parts is used. Injection molding is a discontinuous process. In this case, the starting material, the rubber mixture, is conveyed with a screw and formed in a tool to the desired geometry. Subsequently, the mass is vulcanized in the tool until it reaches the dimensional stability. The rubber mixture must be converted from a highly viscous state at room temperature in a low-viscosity state in the temperature range of 120 ° C to 300 ° C to carry out the vulcanization process. The temperature increase of the rubber mixture is usually carried out by heat conduction from the wall of the injection cylinder in the rubber composition and by dissipation (internal friction). In order to avoid premature crosslinking (scorch), the temperature in the areas of feeder, material preparation and injection cylinder or injection chamber is generally limited to max. 120 ° C (or less) limited. This also applies to the cold runner distributor, if one is used. In contrast to this, a drastic increase in temperature and an incubation reduction are aimed at with the entry into the mold cavity (to a mold wall temperature in the range of 180 ° C. and incubation degrees of about 30%). A significant increase in the melt temperature shortly before entry into the mold cavity allows a more economical process, since the high cycle time and energy required for vulcanization in the mold cavity can be reduced as measured by the total cycle. After vulcanization, the rubber molding has its desired elastic properties. Ring-shaped moldings such as radial shaft seals or O-rings are currently usually sprayed on a centrally arranged Schirmanguss. The sprue volume can comprise 20-80% of the material used, regardless of the tooling and machine technology used. As the sprue is usually vulcanized, this production waste is. In many cases, the materials used are very expensive, high-quality types of rubber.

State of the art

Conventionally, annular moldings, such as O-rings or radial shaft seals, are supplied with injection molding via a central screen sprue or one or more point sprues. In Punktangüssen to keep the sprue to be demoulded later as small as possible, used in the thermoplastic processing formnestnah, to avoid premature solidification of the molding compound, hot runners with corresponding nozzles. In elastomer processing, cold runner systems are used analogously to avoid premature crosslinking, before the actual cavity.

The heating of a hot runner system is carried out in the channel or in the actual nozzle tip. So will in DE19848508B4 presented an electrically heated hot runner nozzle. In US 4911636 and US 4758945 Injectors are described in the electrical resistance heaters encircle a melt channel in front of the nozzle orifice in grooves provided for this purpose. A similar structure is in US 7407379 to find. DE 8717790U1 presents an electrically heated nozzle tip. In DE 102005044586A1 a heatable nozzle made of a ceramic or glass-like material is shown, which is to heat the material before tool entry through a fully embedded infrared heating element. In DE 3590090T1 The injection nozzles of a hot runner injection molding are heated inductively. In addition to active heaters, channel and nozzle systems also use dissipative effects. In DE 202007002817U1 a nozzle is presented, the nozzle mouthpiece is provided with shear elements. These internals are intended to mix and homogenize the mass flow. In DD 232456B1 / DE 3533349A1 Shear elements are used for heating plastic molding compounds in injection molding in a channel, wherein the shear slots are adjustable. A used for the processing of crosslinking molding compounds cold runner systems is in DE 9110897U1 presented. DE 4014244 C2 presents the modification of a cold runner block for processing one-component silicone.

Process engineering implementations for producing annular hollow geometries, such as, for example, pipes, hoses or casings, are known from the extrusion, in particular of thermoplastics. In the simplest case, the molding compound, comparable to the umbrella gate during injection molding, is shaped by a displacement body from the strand to the tubular shape. In contrast to injection molding, however, this displacement body (mandrel) must be held and fixed during extrusion in the molding compound. This is done by simple mounts or, as in DE 19846158 A1 described, achieved by screen baskets. Mandrel holder tools usually produce flow marks and thus mechanical weaknesses in the extrudate. Screen basket tools, on the other hand, weaken them significantly. Due to the large deformations and orientations of the molding compound, however, the individual strands can be imaged in the extrudate. In DE 202004004920 U1 a Pinolenverteiler is described. In this distribution system, the molding compound is deflected in the extrusion direction. In the quill a mass distribution channel is incorporated with downstream throttle gap. The mass is divided into two streams, which flow together counter to the direction of flow and here can form a weld line. A good thermal and dispersive homogenization, no weld lines or flow marks and low mechanical stress of the melt can be achieved by the use of spiral distributors. The melt is first divided into several spiral channels. Due to an opposite size profile of helical channel depth and overflow, the leakage flow increases and the helical flow decreases over the channel length. It is between the eg. In DE 102007029310 A1 or DE 000002320687 A described Axialwendelverteilern and the ua in DE 000004115229 A1 distinguished radial spiral distributors differ. Radial coil distributors consist of a circular distributor disc and a flat disc as a counterpart, which together form a coaxial concentric annular gap. The radial annular gap increases in the direction of the exit, the channel depth of the helix decreases inwardly along the channel, ie in the direction of the exit.

Disadvantages of the prior art

Due to the separate construction of the top and bottom of the distributor, the screen gates currently used in the discontinuous processing of crosslinking plastic molding compounds can not be designed as cold runner manifolds and heated to a homogeneous temperature. Therefore, the entire mass must be demoulded and forms the production waste. Umbrella guards also have a low mixing effect and can only be interpreted rheologically. When using point distributors flow fronts meet each other, weld lines and thus optical and mechanical defects form at these points. The distribution systems known today do not allow control of the starting melt temperature at an annular outlet cross-section by means of a dynamic adjustment of a shear gap.

Object of the invention

The invention describes a method which does not have the disadvantages of the solutions which represent the prior art and fulfills the tasks of supplying the molding compound of the mold cavity at a controlled temperature via an annular injection slot. An early crosslinking of the molding compound in the distribution and Angusssystem is avoided by the temperature. The molding compound is thermally, mechanically and dispersively homogenized and the start-mass temperature at tool entry can be selectively influenced.

Solution of the task

The object is achieved by a device having the features of claims 1 to 12. The solution of the problem will become apparent from the following description of the method. The discharged from the injection molding compact, strand-like mass flow is first divided symmetrically by means of a primary distribution system in the center of the temperature-controlled radial spiral distributor and fed to the spiral melt channels. The melt channel depth tapers to the outer edge of the manifold, while the depth of an overflow gap increases. As a result, the leakage flow increases at the outlet of the spiral distributor and a tear-free structure of the outlet molding compound is achieved. The distributor plate with the spirally running melt channels is mechanically connected to the counter plate. In the components of the device cooling channels are integrated. The annular outlet gap is designed to be variable in height and may, depending on the requirements, have specially designed surfaces or other designs. It rests against the likewise ring-shaped entrance gap of the tool cavity. They are suitably thermally separated from each other.

Advantages of the invention

The method outlined above solves the disadvantages of the prior art and fulfills the objects of the invention, which represents the advantages of the invention. The implementation of the distribution system as an inversely constructed spiral distributor, ie with decreasing radially from inside to outside channel height of the spirally extending melt channels in countercurrent gap, allows the mechanical connection of distributor and counter element at the same homogeneous properties of the exit molding compound. Due to the mechanical coupling of distributor plate and counter plate, the temperature control channels can be connected to one another and a closed temperature control system with an absolutely necessary homogeneous temperature distribution can be realized for the first time for annular injection molded parts. The distributor thus minimizes the use of material by replacing a sprue to be demoulded. The spiral distributor also ensures good homogenization of the molding compound. It thus increases the quality of the molded parts and lowers the rejects. For the first time, the invention combines the principle of a spiral distributor with an effective cold runner system in the injection molding of annular moldings of crosslinking molding compounds. Due to the possibility of variable height adjustment of the sprue gap, a shear gap can also be generated shortly before the tool enters and the starting mass Temperature of the molding material can be influenced. By increasing the start-mass temperature, the material must be supplied with less energy for vulcanization after the injection process. In addition to an increase in energy efficiency, this leads to a shortening of the cycle time-determining heating phase.

Description of exemplary embodiments

In order to use the described advantages of the invention, the in 1 developed module developed. Two mold plates ( 1 ; 13 ) form the mold cavity ( 6 ) and a central cavity in which the distribution system sits. The distribution system consists of an upper tempering body ( 2 ) with integrated temperature control channels ( 3 ), the distributor disc ( 4 ) with pre-distribution of the melt into the distribution channels ( 5 ) and the counter plate ( 9 . 11 ) also with integrated temperature control channels ( 8th ), which are each thermally separated from the mold plates. The counter plate is designed divided in this version. The outer ring ( 11 ) is variably mounted in its axial position and is thus capable of the injection gap ( 12 ) and thus to open or close access to the molding cavity. The injection gap is closed during the heating time and briefly open during the injection phase. For this purpose, three variants for the movement system are possible. In the illustrated passive system, the injection gap opens by the injection pressure. The gap is then replaced by integrated counterpressure springs ( 7 ) closed. The opening stroke is a function of pressure and spring constant and is fixed. In an active system, the opening stroke can be controlled and controlled by actuators. This allows Nachdruck Lind wave movements can be realized. In another system, the active and passive solution is combined in a parallel or sequential process. The system also allows the possibility of creating a defined shear gap before the cavity enters, which can also be changed by the motion system during the injection cycle. Thus, the molding compound can be dissipatively heated by shearing and the resulting temperature development can be controlled specifically. The centerpiece ( 9 ) of the counter plate is via screw ( 10 ) firmly connected to the distributor plate. Through the connection of the temperature control medium circuits, a homogeneous, closed temperature control is achieved and premature crosslinking of the material in the distributor is prevented. The temperature control can also be used in material changes for heating the distributor geometry for the purpose of Ausvulkanisierens and subsequent ejection of the molding material in the manifold.

LIST OF REFERENCE NUMBERS

1

Obere Formplatte

2

Oberes Temperierelement

3

Temperierkanal

4

Verteilerplatte

5

Vorverteiler in Materialkanäle,

6

Formteilkavität

7

Federpaket

8

Temperierkanal

9

Mittelstück der Gegenplatte

10

Verschraubung

11

Randring der Gegenplatte

12

Anspritzspalt/Kavitäteintritt

13

Untere Formplatte

Fig. 1

1

Upper mold plate

2

Upper tempering element

3

tempering

4

distribution plate

5

Pre-distributor in material channels,

6

Formteilkavität

7

spring assembly

8th

tempering

9

Centerpiece of the counter plate

10

screw

11

Edge ring of the counter plate

12

Anspritzspalt / Kavitäteintritt

13

Lower mold plate

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19848508 B4 [0004]
• US 4911636 [0004]
• US 4758945 [0004]
• US 7407379 [0004]
• DE 8717790 U1 [0004]
• DE 102005044586 A1 [0004]
• DE 3590090 T1 [0004]
• DE 202007002817 U1 [0004]
• DD 232456 B1 [0004]
• DE 3533349 A1 [0004]
• DE 9110897 U1 [0004]
• DE 4014244 C2 [0004]
• DE 19846158 A1 [0005]
• DE 202004004920 U1 [0005]
• DE 102007029310 A1 [0005]
• DE 000002320687 A [0005]
• DE 000004115229 A1 [0005]

Claims (14)

Device for producing and controlling the discontinuous production process of annular moldings, in particular for crosslinkable molding compounds such as rubbers or rubber mixtures, characterized in that a strand-like melt strand is divided by a pre-manifold into one or more spirally extending channels whose channel height decreases over the channel length and with lead a counter-rising gap to an annular exit geometry. A method according to claim 1, characterized in that the melt distribution takes place by means of an inverse radial spiral distributor. Method according to one of claims 1 or 2, characterized in that the device has channels for guiding tempering. A method according to claim 1 to 3, characterized in that the melt distribution between 30 ° C and 250 ° C can be controlled. A method according to claim 1 to 4, characterized in that the melt distribution on the circumference of the annular outlet gap be homogeneous, inhomogeneous or can be specifically controlled. Method according to one of claims 1 to 5, characterized in that the opening movement of the injection gap is preferably orthogonal to the distribution direction. Method according to one of claims 1 to 6, characterized in that the opening movement of the injection gap is passively via the injection pressure during the injection process. Method according to one of claims 1 to 6, characterized in that the opening movement of the injection gap can be made active via an actuator on electric, pneumatic, hydraulic or combined form of movement generation. Method according to one of claims 1 to 6, characterized in that the opening movement of the injection gap can be carried out actively via a piezoelectric actuator. Method according to one of claims 1 to 9, characterized in that the opening movement of the injection gap actively terminated via an actuator that performs a 180 ° of the opening movement opposing closing movement on electric, pneumatic, hydraulic or piezoelectric ways and targeted, controlled or regulated ends , closed or extended. Method according to one of claims 1 to 10, characterized in that the closing movement by a passive suspension system, which counteracts the opening movement, can be supported and terminated. Method according to one of claims 1 to 9, characterized in that over the height of the injection gap, the energy supply to the material and / or the starting melt temperature can be influenced at tool entry. Method according to one of claims 1 to 5, characterized in that the heating system for cavity heating is installed konturnah. Method according to one of claims 1 to 5, characterized in that the heating of the cavity surface by an external, contour-matched infrared or induction heating system, takes place independently or in combination with the tool-own system.

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