DE29904902U1 - Tread spray head - Google Patents

Description

The invention relates to a tread spray head according to the preamble of claim 1.

Such a tread extrusion head has been known for a long time, for example from US Pat. No. 2,720,679. In this document, the extruded strip is adjusted in its exit geometry on the extrusion head extruder. For this purpose, a large number of vertically adjustable slides are provided, which enable the thickness of the tread to be adjusted. In addition, templates are provided on the sides, which determine the geometry of the converging flanks of the tread and are also adjustable to a certain extent.

However, such an injection head is not suitable for quickly changing between different extruded tread tires, as is necessary for retreading, for example. Instead, with this design, a large number of vertical sliders must be adjusted so that a new tread shape can be created. The design is relatively complex to build and prone to failure, and yet not very precise, because the flank templates used there tend to bend slightly elastically depending on the extrusion speed. In addition, scrap rubber is always produced, which can then only be processed separately later if necessary.

Numerous other tread injection heads have become known. For example, US-PS 38 70 453 concerns a tread injection head, which is characterized by a thickness adjustment slide that can be adjusted in one piece. Due to the essentially

Due to the trapezoidal shape of the tread profile and the fact that the thickness adjustment slide is brought in from below, i.e. from the longer trapezoid side, the width of the tread can be adjusted at the same time. However, this solution does not allow for fine adjustment, as the width and thickness of the tread profile are always changed in one step and at the same time. Due to the enormous pressures in the chamber downstream of the extruder, a stable crossbar is provided, and the thickness adjustment slide is supported by a special sliding plate that can be swiveled away using a lever mechanism, for example if the spray head needs to be cleaned. This design has a comparatively easy tendency to jam when the thickness adjustment slide is moved. In addition, there is no possibility of co-extruding binding rubber.

With tread spray heads that are used for different treads, there is a risk that the rubber mixture will start to stick in certain areas between the extruder screw and the nozzle mouthpiece. To prevent this, the swiveling spray head is often meticulously cleaned from the inside when the spray head is changed and the extruder is shut down. However, dead corners are created, which are particularly at risk, especially when the slides are moved to a position that corresponds to small tread dimensions.

Another tread injection head is known from DE-GM 88 10 470, which works with a fairly long channel between the end of the extruder screw and the injection head. Although the tendency to dead corners and material degradation is low with this solution, it is understood that in some cases it may be desirable to provide a wider main channel that is suitable for both thick and wide treads and small and thin treads.

In contrast, the invention is based on the object of creating a tread extrusion head according to the generic term of paragraph 1, which is basically suitable for large and wide treads as well as for small and thin treads, whereby changing between the tread sizes and switching off the extruder should also be unproblematic.

This object is achieved according to the invention by claim 1. Advantageous further developments emerge from the subclaims.

The invention offers the particular advantage that, in contrast to the prior art, the risk of starting is drastically reduced even with treads of small dimensions and correspondingly closely spaced sliders.

According to the invention, replaceable flow channel inserts are provided for this purpose, which enable a gentle transfer of the extruder cross-section to the target cross-section and, in particular, also cause the material flow to widen and flatten. It is particularly advantageous here that dead corners are practically avoided, so that no special additional mechanical cleaning is required when shutting down the extruder; it is sufficient to empty the extruder with non-critical cleaning material, whereby the rubber mixture is completely expelled.

It is particularly advantageous if, according to the invention, a set of flow channel inserts of different sizes and dimensions is kept ready, whereby it is sufficient if the exit profile and thus the shape of the flow channel insert is roughly adapted to the target cross-section. To change the tread, the spray head is then swiveled away and the flow channel insert that corresponds roughly to the target cross-section is inserted with two manual movements. According to the invention, it is particularly advantageous that the flow channel insert can be removed from the opposite side.

i.e. stable and safely supported by the spray head. This eliminates the need for special fastening measures, which would make replacement more difficult. Instead, by closing the spray head, each flow channel insert is automatically fixed in its position and at the same time the necessary sealing to the outside is carried out.

The fine adjustment can then be carried out in a conventional manner using the thickness adjustment slide and the flank template, preferably by motor.

According to another, particularly advantageous aspect of the invention, no flow peaks or areas of extremely low flow velocity occur along the course of the flow channel in the flow channel inserts. Rather, the uniform convergence towards the nozzle mouthpiece allows a continuous increase in the flow velocity, so that the shearing effect within the flow channel inserts does not become too great.

According to the invention, it is particularly advantageous that the extruder screw extends with its end cone into the area of the flow channel inserts. It is also particularly advantageous if the helix of the extruder screw tapers off towards the flow channel inserts so that the transition between the material being applied by the helix of the extruder screw and the pure flow area in the flow channel is made as uniform as possible.

Furthermore, it is particularly advantageous if, in an advantageous embodiment of the invention, the slides for the flank templates can be quickly adjusted when the spray head is open. For this purpose, for example, semi-circular threaded shoes can be provided, which allow the relevant spindle for the slides to be removed and reinserted quickly, without the spindle adjustment having to take a long time.

period of time. With the sliders being mounted open at the back, it is also possible to replace the sliders if necessary. For example, shorter sliders can be used for wider treads and for narrower treads
Longer sliders can be used so that only one
Fine adjustment is still required.

A motor drive of the slides is preferably designed in such a way that, in a manner known per se, a symmetrical
Movement is ensured. This can be achieved, for example, by having a threaded spindle in the left part of the spray head rotate anti-clockwise and in the right part of the spray head
is clockwise, whereby the thread shoes for the flank templates
are each appropriately designed.

According to the invention, it is also particularly advantageous that fairly large treads can be produced. For example, the total width of the spray head - without the
flanged units - 85 cm and the maximum opening width
of the die head, which corresponds to the widest extruded
tread, 50 cm.

It is understood that according to the invention and in itself
It is known that it is easily possible to use binding rubber
It is also particularly advantageous that the injection head according to the invention also due to the relatively low
Flow velocities over a large part of the flow channel are also suitable for extruding material with particularly thixotropic properties. Satisfactory throughputs can also be achieved with this type of material.

According to the invention, it is advantageous that the manner of ensuring the mobility of the injection head relative to the extruder body
can be selected depending on the application. It is particularly preferred if the spray head is mounted laterally via a solid joint with a vertical axis,

It is preferred if the spray head and the extruder body with its flange provided there have surfaces facing each other, matching each other and automatically adjusting to each other, which are then additionally screwed together symmetrically.

By decoupling the swivel movement and the adjustment between the extruder flange and the spray head, it can be ensured that there is easy mobility on the one hand, but on the other hand an exact fit is ensured, so that sealing problems are avoided from the outset. With a vertically arranged joint, manual swiveling is also still possible, provided that correspondingly smooth-running bearings are used.

Further advantages, details and features emerge from the following description of an embodiment based on the drawing.

Show it:

Fig. 1 is a view of an embodiment of a tread injection head according to the invention in a side sectional view;

Fig. 2 is a partially broken front view of the embodiment according to Fig. 1; and

Fig. 3 is a partially broken away top view of the embodiment according to Fig. 1.

The tread injection head 10 has, in the illustration according to Fig. 1, a thickness adjustment slide 12 and two facing and opposing flank templates, of which one flank template 14 can be seen in Fig. 1. The thickness adjustment slide 12 is driven by an electric motor,

preferably a stepper motor 16. It makes it possible to adjust the height of the tread 18 shown in Fig. 2, whereby it overlaps the flank templates 14.

Tread material 20 is fed via an extruder 22, wherein the extruder has an extruder screw 24 in a manner known per se. The extruder 22 has a flange 26 surrounding the front end of the extruder screw 24 on the outside, which flange provides passage recesses for screw bolts 28 and 30, which are intended for fastening the injection head 20 to the extruder 22.

For this purpose, the tread injection head 10 has threaded holes 32 and 34. The adjustment between the injection head 10 and the extruder 22 is carried out via shoulders, preferably with inclined surfaces, on the surfaces of the injection head 10 and the extruder 22 facing each other.

According to the invention, flow channel inserts 38 are exchangeably mounted in a recess 37 in the injection head 10. The flow channel inserts 38 preferably have a shape such that they are securely received in the tread injection head 10, even if the tread injection head 10 is pivoted away from the extruder 22, but on the other hand can be easily removed to the rear, i.e. pulled out.

By exchanging the flow channel inserts 3 according to the invention, the flow channel 40 between the extruder screw 24 and the area of the flank templates 14 can be adapted to the requirements in a wide range. It is preferred that the extruder screw ends in an end cone 42 and the flow channel inserts 38 have flow surfaces that extend essentially parallel to the surface of the end cone 42 until they end in a nozzle mouthpiece 45. The flow channel inserts 38 thus lead to a converging flow channel, the convergence being quite uniform, so that

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In particular, no dead corners are formed in which tread material 20 could remain.

According to the invention, it is particularly advantageous if the extruder screw 24 has a helix 44 that tapers off gently adjacent to the end cone. In this respect, an inclined surface 46 is indicated in Fig. 1, which is intended to show that the propulsion effect of the extruder screw 24 on the material 20 should not be abrupt, but rather slowly.

Fig. 2 shows a front view of the extruder 22 in connection with the tread injection head 10. It is clear that the injection head itself is extremely rigid and made with great strength. In contrast, the flank templates 14 and the thickness adjustment slides 12 can be made rather light. According to the invention, this is based on the fact that the extruder pressure can be absorbed almost completely by the flow channel inserts 38 according to the invention with their nozzle mouthpiece 45, while the thickness adjustment slides 12 and flank templates 14 only work in a forming manner and only a very small part of the existing pressure is absorbed there.

From Fig. 2 it can be seen that the injection head 10 is equipped with several joints. As can also be seen in Fig. 3, a primary joint 50, the design of which is described in detail below, allows the tread injection head 10 to be pivoted away from the extruder 22. A secondary joint 52 allows the front part 54 of the injection head 10 to be pivoted away from the rear part 56 of the injection head 10 and thereby exposes the flank templates 14. The flank templates 14 are arranged upstream of the thickness adjustment slide 12 in the flow direction and the parting plane between the parts 54 and 56 is selected so that the flank templates 14 are exposed at the rear on the front part and can be removed or moved.

Ii ·* ·

The primary joint and secondary joint 50 and 52 are each provided with a vertical axis and are both arranged on the same side of the spray head 10. This allows the front part and the rear part of the spray head 10 to be swiveled one after the other, without the required movement space being increased by the division of the spray head 10.

From Fig. 3 it can be seen that the flow channel inserts 38 shown there in dashed lines are expanded in the vertical direction, so that the width of the running strip is significantly larger than the exit width of the extruder 22. In the embodiment shown, the expansion is approximately three times as much, whereby the effective height for the material 20 as it exits the extruder is also reduced to approximately one third. Essentially the same flow cross sections are therefore available on the inlet side and outlet side of the flow channel inserts 38, whereby it is preferable to select a somewhat smaller exit cross section.

From Fig. 3 it is also apparent that the drive 57 for the thickness adjustment slide is provided centrally and that a drive 56 is provided for the thickness adjustment slide 12 and a further drive 58 for the flank templates 14.

As can be seen from Fig. 3, the primary joint has a main joint 60 and two secondary joints 62, 64, which are arranged in a substantially triangular manner relative to one another. This solution also makes it possible to pivot the spray head by 270 degrees if required.

Claims (13)

Utility model application Tread spray head Protection claims 1. Tread injection head for tire treads, with a thickness adjustment slide with which the height of the tread can be adjusted, whereby in particular laterally adjustable flank templates are also provided, characterized in that the injection head (10) is pivotally mounted on the extruder (22) and has a recess (37) facing the extruder screw (24) into which at least one flow channel insert (38) can be inserted. 2. Tread spray head according to claim 1, characterized in that the flow channel inserts (38) form a nozzle mouthpiece (45) which is arranged in the flow direction in front of the thickness adjustment slides (12) and/or the flank templates (14). 3. Tread injection head according to claim 1 or 2, characterized in that the flow channel inserts (38) surround the extruder screw (24) on the inlet side and the extruder screw (24) has a conveyor spiral (44) which is in particular approximately Transition between the extruder (22) and the flow channel inserts (38) ends. 4. Tread injection head according to one of the preceding claims, characterized in that the extruder screw (24) has an end cone (42) which is surrounded by the flow channel inserts (38), wherein the flow channels (40) delimited by the flow channel inserts (38) converge substantially at the same angle as the end cone (42). 5. Tread spray head according to one of the preceding claims, characterized in that with different flow channel inserts (38) the cross section of the nozzle mouthpieces (45) is adapted to the type of tread (18) to be produced. 6. Tread spray head according to one of the preceding claims, characterized in that the flow channel inserts (38) delimit the flow channel (40) in a vertical direction towards the nozzle mouthpiece (45) converging and in a horizontal direction diverging and in particular are designed free of dead corners. 7. Tread spray head according to one of the preceding claims, characterized in that the flow channel insert (38) is formed in one piece or from flow channel insert parts connected to one another. 8. Tread spray head according to one of the preceding claims, characterized in that the spray head (10) is designed in two parts and a front part (54) is mounted on a rear part (56) via a secondary joint (52) with a vertical axis and the pivoting of the front part (54) exposes at least the flank templates (14). 9. Tread spray head according to one of the preceding claims, characterized in that a primary joint (50) is formed between the extruder (22) and the injection head (10), which in particular has a main joint (60) and two secondary joints (62, 64) spaced apart from the main joint (60). 10. Tread spray head according to one of the preceding claims, characterized in that the spray head (10), in particular the rear part (56) of the spray head (10), is connected to the extruder (22) via screw bolts (28, 30) laterally next to the flow channel inserts (38). 11. Tread spray head according to one of the preceding claims, characterized in that the thickness adjustment slide (12) has a drive which allows its vertical movement and is in particular partially encompassed by the flow channel inserts (38). 12. Tread spray head according to one of the preceding claims, characterized in that the flow channel inserts (38) are divided in a vertical plane and can be replaced separately. 13. Extruder with a tread die head according to one of the preceding claims.