DE202015005162U1 - sprue bushing - Google Patents

Abstract

A sprue bushing (1) for an injection molding tool, the sprue bushing (1) having a channel (9) for guiding flowable plastic mass extending from a channel inlet end (11) to a channel outlet end (13) having an increasingly flared flow area through the sprue bushing (1), wherein a channel wall (15) of the channel (9) has a ribbing (17).

Description

The present invention relates to a sprue bushing according to claim 1.

For injection molding tools with standard gating systems for low wall thickness products, the design of the gating system, consisting of sprue and sprue headers, significantly determines the cycle time of the manufacturing process. The sprue itself is represented in the injection mold by means of a sprue bushing. In conventional sprue bushes, the channel for guiding the flowable plastic mass is designed with a conical inner geometry, resulting in a relatively larger flow cross section at the transition from the sprue bushing to the sprue splitter and a relatively smaller flow cross section at the mass inlet into the sprue bushing. The larger flow cross-section determines - in case of cold curing plastics such as thermoplastics - the solidification time of the melt and thus the time of the possibility of demoulding, thus ultimately the cycle time of the production process for products with small wall thicknesses. Also in the processing of thermoset materials, the thickness of the injection molding component and the runner and the distribution channels determines the curing time of the plastic mass, in which case it must be ensured that the amount of heat necessary for curing and crosslinking in the interior of the injection molding. Components and the respective sprue and distribution channels is registered.

Proceeding from this, it is an object of the present invention to provide a sprue bush, with which a faster heat transfer to the guided plastic mass and thus an advantageously lower cycle time, thus a cycle optimization can be achieved.

This object is achieved with a sprue bushing according to claim 1.

Further advantageous embodiments and modifications of the invention are specified in the further claims.

According to the invention, a sprue bushing is proposed for an injection molding tool, preferably for use with an injection molding process, which provides for the use of a thermosetting plastic, in particular a thermoplastic, or alternatively for use with an injection molding process which involves the use of a crosslinkable and / or curable material Plastic provides, in particular a thermosetting plastic.

The sprue bush is intended to be accommodated on the injection molding tool, in particular to be supplied via a nozzle of an injection molding machine with a flowable plastic compound, in particular a (thermoplastic) melt or a (not yet cross-linked) thermoset material, in particular pressurized. The sprue bushing has a channel for guiding such a flowable plastic mass, which extends from a channel inlet end - for placement on a nozzle - to a channel outlet end - for placement on a sprue hub - with an increasingly flared flow cross section through the Sprue bushing extends therethrough.

Here, the channel wall on a ribbing. By ribbing, compared to the prior art reduced flow cross-section at the channel outlet end, d. H. at the transition point of the sprue bush to a sprue splitter, while increasing the contact area between the guided plastic mass and the interior of the sprue bushing. This allows a faster heat transfer to the plastic mass, d. H. between sprue bush and plastic mass, thus advantageously a cycle optimization. In an injection molding with a thermoplastic material, the melt can be cooled more quickly, in an injection molding of thermosetting or -vernetzenden plastic can be a faster heat input into the not yet cross-linked plastic mass (because the distance for the energy transfer to heat or heat the inner core the plastic mass is lower).

It is preferably provided that the ribbing is formed by ribs of the channel wall, z. B. five to ten ribs which extend in the channel extension direction, d. H. in the direction from the channel inlet end to the channel outlet end (the number of ribs may, however, also be larger, depending on the geometry of the sprue channel, for example). In this case, the ribs are preferably arranged equidistantly from one another in the circumferential direction of the channel. Furthermore, the ribs preferably grow in height from the inlet end to the outlet end. By such an inner geometry of the channel wall, the surface for the heat transfer advantageously increases, while at the same time a simple, low-friction removal of the solidified plastic material (the sprue) is made possible from the sprue bushing in the context of demolding.

In general, the channel inlet end preferably has a circular inlet cross section, so that an unobtrusive arrangement is made possible on the nozzle together with a simple plastic mass feed of the sprue bushing, whereas the channel outlet end has a star-shaped outlet cross section formed by the ribbing.

In particular, the channel of the sprue bushing can be surrounded by a peripheral surface which surrounds the channel over its length with a circular cross section on the outer peripheral side, and is frustoconical from the channel inlet end to the channel outlet end.

Also proposed by the invention is an injection molding tool which has a sprue bushing as discussed above, in particular a thermoplastic injection molding tool or a thermoset injection molding tool.

To reinforce the thermal transfer effect can - if the geometric conditions of the injection mold permit this in the vicinity of the sprue bushing - an additional external temperature, depending on the type of plastic for targeted cooling or heating of the sprue bush in the region of the largest flow cross-section can be provided.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features may be implemented individually for themselves or for a plurality of different combinations in a variant of the invention.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

1 exemplary and schematically a sprue bushing in a transparent representation according to a possible embodiment of the invention.

2 exemplary and schematic sprue bushing in half section.

In the following description and the drawings, the same reference numerals correspond to elements of the same or comparable function.

The 1 and 2 each show a sprue bush 1 for an injection molding tool, which is intended to be arranged thereon, in particular in a bushing receptacle of the injection molding tool.

The sprue bush 1 comprises a substantially cylindrical bushing body 3 , which at one end 5 , which is provided for placement on a nozzle of an injection molding machine, is radially expanded. By means of this (ring) supernatant or this shoulder 7 is formed an enlarged end face for support on a clamping plate of the injection mold or a nozzle as mentioned above.

Through the sprue bush 1 through a channel continues to extend 9 , Preferably formed by means of a bore, for guiding a flowable plastic material, in particular z. As a molten thermoplastic or a non-crosslinked thermoset.

The channel 9 extends between a channel inlet end 11 For placement on the nozzle of an injection molding machine, and a duct outlet end 13 - For placement on a sprue distributor of an injection mold - with a in the direction of the inlet end 11 to the outlet end 13 increasing flow cross-section through the sprue bushing 1 through, cf. z. B. 2 ,

The channel points clearly 9 here a canal wall 15 on, which by means of a ribbing 17 or a number of ribs 19 , in this case preferably eight ribs 19 , is formed. Ribs 19 the ribbing 17 extend in the channel extension direction A, ie in the direction of the channel inlet end 11 to the duct outlet end 13 and grow in that direction in height, so that a respective rib 19 approximately triangular over its length.

With this embodiment of the sprue bushing 1 has the inlet end 11 the channel further has a circular inlet cross-section, while the channel outlet end 13 has an approximately star-shaped outlet cross-section, that is formed by means of the ribbing 17 , In this way, an optimized heat transfer, in particular at the transition to a sprue distributor, allows, in addition a simple sprue removal (hardened plastic material) from the channel along with advantageous good plastic mass transport and charging properties.

Ribs 19 are in the circumferential direction of the sprue bush 1 equidistant from each other, in particular also designed identically.

LIST OF REFERENCE NUMBERS

1

sprue bushing

3

bush body

5

The End

7

shoulder

9

channel

11

Channel inlet end

13

Channel outlet

15

channel wall

17

ribbing

19

rib

A

Channel extension direction

Claims (9)

Sprue bushing ( 1 ) for an injection mold, wherein the sprue bushing ( 1 ) a channel ( 9 ) for guiding flowable plastic mass extending from a channel inlet end ( 11 ) to a channel outlet end ( 13 ) with an increasingly widening flow cross-section through the sprue bushing ( 1 ), wherein a channel wall ( 15 ) of the channel ( 9 ) a ribbing ( 17 ) having. Sprue bushing ( 1 ) according to claim 1, wherein the ribbing ( 17 ) by means of ribs ( 19 ) is formed, which extend in the channel extension direction (A). Sprue bushing ( 1 ) according to one of the preceding claims, wherein the ribbing ( 17 ) Ribs ( 19 ) coming from the inlet end ( 11 ) to the outlet end ( 13 ) increase in height. Sprue bushing ( 1 ) according to one of the preceding claims, wherein the channel inlet end ( 11 ) has circular inlet cross section and / or the channel outlet end ( 13 ) by means of the ribbing ( 17 ) formed, star-shaped outlet cross-section. Sprue bushing ( 1 ) according to any one of the preceding claims, wherein an envelope enclosing the channel ( 9 ) about its length with a circular cross-section on the outer peripheral side to tangent is frusto-conical. Sprue beech ( 1 ) according to one of the preceding claims, wherein the ribbing ( 17 ) a number of ribs ( 19 ) between five to ten. Sprue bushing ( 1 ) according to one of the preceding claims, wherein the ribbing ( 17 ) Ribs ( 19 ), which are circumferentially spaced from each other. Injection mold, comprising a sprue bush ( 1 ) according to any one of the preceding claims. An injection molding tool according to claim 8, wherein the injection molding tool is a thermoplastic injection molding tool or a thermoset injection molding tool.

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