WO1988006515A1

WO1988006515A1 - Construction of an extruder body which adsorbs thermal expansion

Info

Publication number: WO1988006515A1
Application number: PCT/NL1988/000008
Authority: WO
Inventors: Jan Anne Van Houten; Antonius Rudolf Louwes; Jan Hendrick Prenger
Original assignee: Wavin B.V.
Priority date: 1987-03-06
Filing date: 1988-03-03
Publication date: 1988-09-07
Also published as: AU1579188A; NL8701362A

Abstract

Device for forming a plastic product; extruder for such a device; extrusion line with one or more of such extruders; frame for an extrusion head and frame for an extruder, and plastic produkt obtained by extrusion. The invention relates to a device for forming a plastic product comprising at least an extruder and an extrusion head. According to the invention the extrusion head (20) is in a fixed position whereas the extruder (21, 22, 22') is capable of moving relative to said extrusion head (20). The invention also relates to various equipment for use with or incorporating such a movable extruder and also to a product obtained making use of such an extruder.

Description

Construction of ah extruder body which adsorbs thermal expansion.

The invention relates in the first place to a device for forming a plasti-c product, comprising at least an extruder and an extrusion head connected there¬ to.

Such devices are generally known and are described in detail in the trade literature.

In such known devices the extruder is generally connec¬ ted to an extrusion head which is of a shape cor¬ responding to the shape of the product to be produ- ced from thermoplastic material by extrusion.

Such known devices are generally installed in such a way that the extruder is anchored to the installa¬ tion floor or connected to a rigid frame. The extrusion head is generally connected to the extruder, for example by a screw or clamp connection; the extrusion head is generally free-standing, apart from its connection to the extruder, so that movement due to, for example, thermal expansion can take place freely. Such known devices have the disadvantage that in cer¬ tain cases, due to thermal expansion and/or mecha¬ nical stress, the extrusion head can shift in such a way that the line connection of, say, the extrusion ¹5 line containing the extruder and the extrusion head t- is upset, which can lead to unevenness in the product formed, for example as regards wall thickness, shape and/or appearance.

The object of the present invention is to find a -^■10 solution to the above-mentioned disadvantage in such a way that the extrusion head cannot shift in any circumstances and a product which is uniform in all respects is obtained.

For this purpose, the device according to the inven- *15 tion is characterized in that the extrusion head is * mounted in a fixed position and the extruder is oun-

**^* ted so that it can move as a whole relative thereto.

The fact that according to the invention the extruder -' is mounted so that it can move and is connected to

¹20 a fixed extrusion head means that thermal expansion and/or mechanical stress which could cause shifting ^■ of the extrusion head are absorbed through the extruder being movable.

In particular, at an essentially fixed height adjust- 25 ment the extruder can move in a horizontal plane, namely in the direction of its extruder axis.

It is advantageous to have extrusion head setting means to permit mounting of an extrusion head in a predetermined fixed position in which the extrusion 30 head setting means are such that a vertical and horizon¬ tal setting of the extrusion head is possible. The extrusion head mounted so that it can move is particularly important if the extrusion head is a so-called transverse extrusion head. A transverse extrusion head is known per se and is used in those cases where a product formed in an extrusion line must, for example, be coated with an additional layer of plastic, in general if additional material has to be supplied to the external surface of a plastic product. The infeed of the additional material will in such cases generally take place advantageously transverse to the direction of movement of the material being conveyed in the line; for that purpose extru¬ sion heads are known with a connection which is trans¬ verse to the direction of advance of the outcoming product. In such cases, such mechanical stress on the extrusion head can occur that the extrusion head shifts, which leads to unevenness of the finished product. If now at least the extruder which connects to the transverse infeed of the extrusion head is designed in the manner according to the invention, what is achieved is that excessive mechanical stress and/or thermal expansion result in relative displacement of the extruder, while the extrusion head remains in a fixed position. This ensures uniformity in the shaped product.

In the extruder according to the invention it is ad¬ vantageous for the extruder to be movably connected to movable attachment elements; while it is very advanta¬ geous for the attachment elements to be hinged suspen- sion elements which are fixed to an extruder carrying frame, the suspension elements being adjustable in length if desired.

It is extremely advantageous if the suspension elements are fixed to roller elements which are supported on a fixed frame, thereby ensuring freedom of movement of the extruder in the direction of its axis. The invention also related to an extruder which is suitable for accommodation in a device for forming a plastic product, which is characterized in that the extruder is fixed to movable attachment elements which permit a movement of the extruder round a mean position when the extruder is mounted in a device.

The invention also relates to an extrusion line compri¬ sing at least an extruder and an extrusion head for forming a plastic product, calibration means, and means for regulating the speed of movement of the formed product, which is characterized in that one or more of the extruders connecting to the line are mounted in such a way that the extruder is fixed to movable attachment elements which permit movement of the extruder round a mean position, essentially in a horizontal plane, while each of the extruders mounted in that way is connected to a fixed extrusion head.

Providing a movable extruder and making the head fixed means that the extrusion head is prevented from shifting and the line connection in the extrusion line is always maintained, which leads to a very uniform product.

The advantage described above of using (a) movable extruder(s) applies in particular also if the extruder axis is at an angle or staggered relative to the extru- sion line.

The invention also relates to an extrusion head for an extruder, which is characterized in that the extru¬ sion head is fastened in a fixed, essentially unmovable- extrusion head attachment frame. In the said frame a correct setting of the head can be produced by means of head setting means.

The invention is also embodied in a frame which is suitable for mounting an extrusion head for an extruder in a fixed position, and in a frame which is suitable for mounting an extruder which is movable relative to an extrusion head which can be mounted in a fixed position and can be combined with an extruder.

Finally, the invention relates to a plastic product obtained using extrusion with an extruder provided with an extrusion head, the plastic product being characterized in that it is obtained with a device or an extrusion line according to the invention. Such plastic objects produced with a device according to the invention, thus where the extruder is mounted so that it is movable relative to a fixed extrusion head, result in uniformity of the product as regards, for example, wall thickness, appearance etc.

The invention will now be explained with reference to the drawing, in which:

Fig. 1 gives a schematic illustration in perspective of an extruder forming part of a device according to the invention;

Fig. 2 shows in partial cross section a suspension element and its fastening for suspension of an extruder supporting frame;

Fig. 3 shows a schematic view of a fixed extrusion head according to the invention, parts being cut away for the sake of clarity; Fig. 4 gives a side view of a fixed extrusion head according to the invention;

Figs. 5 A-C show schematic views of extrusion lines according to the invention which are equipped with various types of extrusion heads;

Fig. 6 is a schematic view of another embodiment of an " extruder mounted so that it can move.

Fig. 1 shows schematically by reference number 1 an extruder with means 17, 15 fixed on bars 2, 3 which are suspended from rods 4. The rods 4 are hingedly attached to a suspension face 7, while the connection to the bars 2 and 3 is also hinged. The extruder outlet is indicated by 5, while the extruder filling aperture is indicated by 6.

The extruder worm is driven by a drive accommodated in compartment 15 and connected to the mains by cable 16.

When the extruder outlet 5 is connected to an extru¬ sion head, any thermal expansion or any mechanical stress occurring will result in a shifting of the extruder in a horizontal plane, provided that according to the invention the extrusion head is in a fixed position and cannot move.

Fig. 2 shows in greater detail how a suspension element 4 is fastened to the suspension face 7, on the one hand, and to the supporting bar 3, on the other. Fixing nuts are indicated by 8 and 9, the length of the respec¬ tive thread ends mating therewith providing that a certain degree of height adjustment can be achieved. If the height adjustment is greater than the indicated thread end, it is possible either to select a suspension element 4 with greater thread length or to use a suspen¬ sion element of a different length. Since the suspen¬ sion element 4 fits with play into the bush 11 on the top of the suspension element and by the space

12 in the bar 3 at the bottom side of the suspension element, a relatively great degree of deflection is ensured, which is sufficient to absorb the thermal expansion or deformation tendecy o-ccurring. A supporting frame 10 is provided between nesting plate 7 and bottom plate 13. Reference number 14 indicates a cross section of a U-bar which^' serves as a connection between the respective supporting frames for each of the suspension elements 4.

Fig. 3 shows an extrusion head 31 mounted on a frame, the extrusion head being disposed on a support plate 32 by means of support 30 and fixing screws 36 and 37.

The support plate 32 can be moved into a desired hori- zontal position with the aid of adjusting screws 34, while the vertical position can be set by means of adjusting screws 35. The setting of the support plate 32 with the extrusion head on it takes place relative to a frame 39, on which there is a top plate 38.

Fig. 4 shows the same arrangement as Fig. 3, but in side view. It can be seen in Figs. 3 and 4 that the adjusting screws 35 are passed with play through holes in the plate 32.

Figs. 5A-C show schematically three different extrusion lines according to the invention. In Fig. 5A movable extruders 21, 22 and 22' are connected to a fixed extrusion head 20. After leaving the head, the product goes through a calibration device 23, a cooling device 25, and a drawing device 24. After the drawing device there can be, for example, a cut¬ ting device 29 to cut off the shaped product to the desired length.

In Fig. 5B the extruder 22 is positioned in such a way that the extruder axis is staggered relative to the thrpughgoing line.

In Fig. 5C the extruder 22 is placed transversely to the head 20 and there is an additional extrusion head 27 and a transversely positioned movable extruder 28.

Also shown are a calibration device 23', a cooling device 25 ^r , and a drawing bench 24'. Through use of an extrusion line to which one or more extruders according to the invention are connected, it is possible to form a product which excels by its uniformity, due to the fact that shifting of the extrusion head relative to the line no longer takes place.

The arrangement outlined here is used, for example, for forming tubular products in which a centrally formed tube must be provided with, for example, one or more coverings of a different type of material.

Finally, Fig. 6 shows another embodimeπc of a mova- bly mounted extruder 40, which is provided with sup¬ porting sections 44. The supporting sections 44 have connected to them supporting bars 41, on the end of which there is an axle plate 45 through which an axle is passed with wheels or bearings 43 supported on support bars 42, which are in turn supported by uprights 46. Fig. 6a shows a side view of a movably mounted extruder, and Fig. 6b shows a front view. _ _

The extruders according to the invention, which are mounted so that they can move relative to a fixed extrusion head are usable for many purpose in this field, for example use in the production of plastic sections, shaping sheeting, sheathing cable, forming electric welding sleeves, forming corrugated plastic tubing etc; the thermoplastic materials used therefore are materials such as polyvinylchloride; polyethylene, polypropylene etc.

In the above description.it is specified in particular that the attachment elements by means of which the extruder is movably mounted can comprise movable suspen¬ sion elements. Of cource, the invention is not limited to such suspension elements; for example, supporting means in the form of ball bearings, air bearings, rollers, rubber- support blocks etc. could also be used. Instead of the suspension rods shown in Figs. 1, 2 and 6, it would also be possible to suspend the. extruder from cables.

Claims

1. Device for forming a plastic product, comprising at least an extruder and an extrusion head connected thereto, characterized in that the extrusion head (31) is mounted in a fixed position and the extruder

(1) is mounted so that is can move as a whole relative thereto.

2. Device according to Claim 1, characterized in that at an essentially fixed height adjustment the extruder (1) can move in a horizontal plane in the direction of its extruder axis.

3. Device according to Claim 1-2, characterized in that extrusion head setting means (33, 34, 35,

36, 37) are present to permit mounting of the extrusion head (31) in a predetermined fixed position and serve for vertical and horizontal setting of the extrusion head (31) said extrusion head (31) optionally being a tranverse extrusion head.

4. Device according to Claims 1-3, characterized in that the extruder (1) is fixed to movable attachment elements.

5. Device according to Claim 4, characterized in that the extruder (1) is suspended from hingedly movable suspension element (4; 41) which are attached to an extruder supporting frame (7, 10), the suspension elements (4) being adjustable in length if desired or which suspension elements (41) are attached to roller elements (43) resting on a fixed frame (42, 46).

6. Extruder suitable for mounting in a device for forming a plastic product, characterized in that the extruder (1) is fixed to movable attachment elements which permit a movement of the extruder round a mean position when the extruder is mounted in a device.

7. Extrusion line comprising at least an extruder and an extrusion head for forming a plastic product, calibration means, and means for regulating the speed of movement of the formed product, characterized in that one or more of the extruders connecting to the line are mounted in such a way that the extruder (1) is fixed to movable attachment elements which permit movement of the extruder (1) round a mean position, essentially in a horizontal plane, while each of the extruders mounted in that way is connected to a fixed extrusion head.

8. Extrusion line according to Claim 7, characteri¬ zed in that the extruder axis of one or more of the extruders connecting to the line is at an angle or staggered relative to the extrusion line.

9. Extrusion head suitable- for an extruder, charac¬ terized in that the extrusion head (31) is fastened in a fixed, essentially unmovable extrusion head attach¬ ment frame (32, 40).

10. Frame, characterized in that said frame is suitable for mounting an extrusion head (31) for an extruder (1) in a fixed position.

11. Frame, characterized in that said frame is suitable for mounting an extruder (1) which is movable relative to an extrusion head (31) which can be mounted in a fixed position and combined with an extruder.

12. Plastic product obtained using extrusion, cha¬ racterized in that the plastic product is obtained with a device according to one or more of Claims 1-5 or an extrusion line according to Claims 7-8.