WO1990011880A1

WO1990011880A1 - An extrusion tool to shape viscous compounds

Info

Publication number: WO1990011880A1
Application number: PCT/EP1990/000490
Authority: WO
Inventors: Erich Beck
Original assignee: Erich Beck
Priority date: 1989-04-01
Filing date: 1990-03-27
Publication date: 1990-10-18
Also published as: JPH03501712A; DE3910493A1; EP0417236A1

Abstract

In order to match the compound temperature to the wall temperature of the distribution channel (12) as accurately as possible in an extrusion tool for producing tubular foil, tubes or the like, it is proposed that the distribution channel (12) extend only in a radial tool plane within a wall region formed by the tool casing (10) and/or a spindle head (21) radially covering the tool casing (10).

Description

Nozzle tool for forming viscous masses

Description

The invention relates to a nozzle tool according to the preamble of claim 1. Such a nozzle tool is known from DE-GebrMS 1 927 405.

For the production of blown films, tubes and the like from viscous masses, in particular from plasticized plastic extrudate, nozzle tools (also "blow heads" or "quill heads") are used which have an annular gap at their axial end, through which the mass passes and thereby to a bubble is formed. After exiting, the bubble is cooled down by a cooling ring until the viscous material solidifies. The difficulty lies in distributing the material with the same possible viscosity, the same temperature and the same shear stress in the annular gap in order to keep the wall thickness tolerances of the end product within narrow limits.

In a known design of such nozzle tools (DE-GebrMS 1 927 405), a mandrel is arranged within a hollow cylindrical housing and is screwed to the upper axial end of the tool housing with an axial end flange (“mandrel head”). At the lower axial tool end, the annular gap extends between the mandrel end and the tool housing. The viscous mass is supplied through a radial inlet channel in the region of the upper axial housing end, which opens into a distributor channel formed on the mandrel jacket. The distribution channel initially has two branches fed by the inlet channel, each of which extends over the fourth circumference of the mandrel and then extends several times in the axial direction. branch cessively. The ends of this tree structure open into the annular gap at the lower end of the tool. The advantage of this axial distribution channel is first of all that each partial stream flowing into the annular gap has the same length. However, f-ö + rs = t the pressure loss along the distribution channel of, for example, 300 bar, which has to be applied by a corresponding pumping power of the extrudate pump, to a temperature increase of the mass progressing in the axial direction corresponding to the pumping power conversion of, for example, 15 ° C. Since the duct wall temperatures remain the same over the entire length of the distributor duct because of the axial extension of the distributor duct, there is an axially increasing temperature gradient between the molten mass and the distributor duct walls. The result of such locally different temperature differences are correspondingly different sliding conditions of the molten mass on the distributor channel walls, which in turn leads to different flow velocities of the mass within the branches of the distributor channel and ultimately to thickness fluctuations in the end product. Furthermore, the overlap of the individual partial flows within the annular gap is insufficient, which leads to visible seams (strips) between the wall segments of the end product resulting from the individual partial flows. The use of a helical distributor known per se following the distributor channel would improve the overlap, but at the same time the axial overall length of the dome would be considerably increased, which would impair its rigidity as a prerequisite for a uniform gap width of the annular gap. In contrast, the object of the invention is to achieve the most exact possible adaptation of the melt temperature to the wall temperature of the distributor channel in a nozzle tool of the type mentioned at the outset.

According to the invention, this object is achieved by the characterizing features of patent claim 1.

Advantageous developments and refinements of the nozzle tool according to the invention result from the subclaims.

The invention is based on the consideration of arranging the distributor channel in a radial and not in an axial tool plane, which has two advantages. On the one hand, a radial distributor channel can easily be combined with an axial spiral distributor, since the mandrel length is only determined by the length of the spiral distributor and can therefore be dimensioned sufficiently short and stiff. By connecting a swirl duct, a satisfactory overlap of the partial mass flows of the distributor duct is obtained, with the result that stripes in the end product are avoided. On the other hand, a distribution channel running in a radial plane is subject with its channel wall to the temperature gradient of the tool material from the inside to the outside. Since the molten mass is increasingly mentioned as it moves from radially outside to radially inside as a result of the aforementioned conversion of the pump power into heat, the mass has the same temperature as the channel wall at all points on its way through the distributor channel designed according to the invention . This independent temperature adjustment ensures constant sliding and friction conditions and thus - -V -

a constant and uniform flow velocity of the mass in the distribution channel, as a result of which thickness fluctuations in the end product are substantially reduced.

The invention is explained in more detail using exemplary embodiments in the drawings. It shows:

1 shows a longitudinal section through a first embodiment of a nozzle tool according to the invention;

2 shows a cross section through the distributor channel of the nozzle tool according to FIG. 1 along the section line II-II;

Fig. 3 shows a detail section similar to that in Fig. 1 for

^• a slightly modified form of erfindungsgemäßeπ nozzle tool

3a shows a plan view of the transition region between the distribution channel and a collecting channel of the nozzle tool according to FIG. 3, and

4 shows a longitudinal section through a further embodiment of a nozzle tool according to the invention with a multilayer structure.

The nozzle tool illustrated in FIG. 1 for producing film bubbles, tubes and the like from a viscous material such as, for. B. plasticized plastic (PVC, polyethylene and the like) has a hollow cylindrical tool housing 10 which has a flange-shaped projection 10a at its upper axial end. In the cylindrical bore 10b of the tool housing 10, a cylindrical mandrel 20 is inserted, which on its upper 1 axial end is provided with a mandrel head 21. The mandrel head lies flush on the flange-shaped extension 10a of the tool housing 10 and is connected to the. By means of several bolts 13, which are evenly distributed over the circumference of the head

Screwed approach 10a. The diameter of the dome 20 is chosen to be somewhat smaller than the diameter of the bore 10b in order to form annular and helical overflow gaps (in the region of webs of a rotation) between the outer surface of the mandrel 20 to be explained in more detail and the smooth, cylindrical inner surface 0 of the bore 10b ¬ symmetrical collecting duct 22 or swirl ducts 23 of a spiral distributor) and an annular gap 30 extending to the lower axial end. About _j e existing at the lower end of the annular gap 30, narrow nozzle gap 31 exits the molded into a tube or a pipe, viscous mass, and is then - as is not shown - is solidified by a cooling air ring or any other cooling device.

“ _Q In the production of plastic films, the width of the annular gap 30 is approximately 3 mm, while the nozzle gap 31 is only approximately 0.8 mm wide. The inlet for the viscous mass is in the region of the upper axial end of the tool and is formed by a radial inlet channel 25 11, which extends in the flange-shaped extension 10 a of the tool housing 10. The inlet duct 11 has a radially extending section 11a, which continues via a 90 ° bend 11b into an axially extending end section 11c up to a distributor duct gθ 12.

According to the invention, the distributor channel 12 runs exclusively in a radial tool plane and, in the example shown according to FIGS. 1 and 3, is in the contact surface gc between the mandrel head 21 and the flange-shaped extension 10a of the tool housing 10, in such a way that the channel sections of the distributor channel 12 provided with a circular cross section, each with half the cross section, are machined into the surface of the nozzle head 21 or the attachment 10a, as the sectional view according to FIG. 2 shows. The course of the distribution channel 12, which is yet to be described, is intended to divide the mass flow into a multiplicity of equally long partial flows, which end in a uniform distribution on the circumference of the mandrel 10. This is necessary in order to distribute the mass evenly over the annular gap 30 despite the introduction of the mass only at a single "punctiform" point on the circumference of the tool, which in turn is a prerequisite for a uniform thickness of the plastic hose or tube produced.

The division into individual partial streams takes place successively within the distribution channel 12, the cross sections of the individual channel sections decreasing in accordance with the increase in the partial streams. In detail, the distributor channel 12 initially has two subchannels 12a, 12b, each of which extends over a circumferential section of 45 ° and is fed at its common origin by the axially extending end section 11c of the inlet channel 11. Because of the 90 ° transition from the axial end section 11c into the radial subchannels 12a, 12b, the flow conditions for an exact halving of the mass flow onto the two subchannels 12a, 12b are more favorable than with a mass supply without angling 12b and end section 11c. The ends of the subchannels 12a, 12b are thus diametrically opposite and branch into two subchannels 12al, 12a2 and 12bl, 12b2, respectively, which are located radially further inwards than the subchannels 12a, 12b and run in opposite directions. This The branching is repeated, the subchannels 12ala and 12alb arising from the subchannel 12al, the subchannels 12a2a and 12a2b from the subchannel 12a2, the subchannels 12bla and 12blb from the subchannel 12bl and the subchannels 12b2a and 12b2b from the subchannel 12b2 .

As can be seen from the _Q cross sections of the subchannels 12a, 12a2 and 12a2a shown in FIG. 3, which are drawn to scale, the cross sections decrease with a progressively increasing division of the partial streams. while the flow velocity remains the same, the pressure in the subchannels decreases. A decreasing pressure in the partial streams means at the same time a correspondingly increasing temperature of the partial streams, which can be explained by the fact that the power of the pump (not shown) arranged in front of the inlet duct 11 is converted into thermal energy. The mentioned temperature rise of the partial flows from radial

The outside to the inside radially corresponds to a rectified temperature profile of the distributor channel wall, which results from the fact that the material of the tool exhibits a temperature gradient from the inside to the outside due to the cooling. This temperature gradient can be

25 adjust the outside wall of the tool by regulated heating. With the correct dimensioning of the tool dimensions, subchannel diameter and pump power, the melt temperature profile can be largely adapted to the temperature profile of the channel wall.

30

The primary deflection of the radial mass flow into an axial mass flow, which is provided for the region where the inlet channel 11 opens into the two first subchannels 12a, 12b, can — as is not shown — also on all or

35 can be provided at least at some further branching points of the distribution channel 12 in order to achieve the greatest possible to achieve an even distribution of the mass over the mandrel circumference.

As from fig. 3 and 3a, the ends of the subchannels 12ala to 12b2b pass over fishtail-like deflection regions 12c into a rotationally symmetrical, annular collecting channel 22 on the mandrel circumference or mandrel jacket. Adjoining the collecting duct 22 is an axial spiral distributor, which consists of a plurality of swirl ducts 23, corresponding to the number of sub-ducts 12ala to 12b2b or partial flows, which are designed to be helical on the mandrel jacket. The annular collecting duct 22 becomes closed the swirl channels 23 bounded by a web section 22a of the mandrel jacket. The web section 22a has, for example, a radial distance of 1.5 mm from the inner surface of the housing bore 10b, the gap in question ensuring an evening of the partial flows when they enter the swirl channels 23.

The webs 23a between the individual swirl channels 23 have, for example, a radial distance of 0.5 mm to 1.0 mm from the inner surface of the housing 10b, the gaps between webs 23a and the bore surface serving to ensure that material from the swirl channels overflows and thus the overlap of the partial streams is improved.

The spiral distributor (swirl channels 23) extends in the case of FIGS. 1 and 3 over a third or over half the axial length of the mandrel 20 and merges into the annular gap 30, which in the case of FIG. 3 is bent towards the mandrel axis, in order to adapt a standard tool size to different nozzle gaps -To achieve diameter. For this purpose, the tool housing 10 and the mandrel 20 have screwable insert pieces 101 in the lower region respectively . 201 on.

The embodiment according to FIG. 4 differs from FIG. 1 by a multilayer structure of the mandrel in an actual (inner) mandrel 20 and two mandrel sleeves 40, 50 arranged concentrically to the mandrel 20. Such a multilayer construction serves to to produce so-called composite films from a corresponding number of film layers. The individual film layers can consist of different materials. The mandrel sleeves 40, 50 each have a radial flange 41 or 51 corresponding to the mandrel head 21, in which a further inlet channel 42 or 52 assigned to the respective mandrel sleeve 40, 50 runs in the same way as the inlet channel 11 in the Embodiment according to FIG. 1. The further inlet ducts 41, 51 each open into an associated distributor duct 43 or 53, which extends in a radial tool plane, the design of which corresponds to the distributor duct 12 according to FIG. 1. The same applies to the collecting and swirl channels 44, 45 and 54, 55 formed on the outer jacket of each mandrel sleeve 40, 50. The annular gaps adjoining the swirl channels 45 and 55 open obliquely into the nozzle gap 31 at the axial lower end of the tool according to FIG 4, so that all the annular mass flows formed by the "layers" (mandrel 20. mandrel sleeves 40, 50) of the tool are combined in front of the nozzle gap 31.

Claims

CAN TOOL FOR MOLDING POWDERED MASS PATENT claims

1. Nozzle tool for molding. viscous masses, in particular plasticized plastic extrudate, to tubular films, pipes or the like

- a hollow cylindrical tool housing (10) in which a cylindrical mandrel (20) is arranged, and

- A radial inlet channel (11) for the viscous-liquid mass, which is connected via a manifold and successively branching distribution channel (12) with an annular gap (30) between the tool housing (10) and mandrel (20), characterized in that the distributor channel (12) extends exclusively in a radial tool plane within a wall area which is formed by the tool housing (10) and / or a mandrel head (21) radially covering the tool housing (10).

2. Nozzle tool according to claim 1, characterized gekennzeich¬ net that the radial distributor channel (12) is followed by a collecting channel (22) at Dornu faπg, which leads via swirl channels (23) to the annular gap (30). - // _-

3. Nozzle tool according to claim 1 or 2, characterized in that one or more concentric mandrel sleeves (40 or 50) are arranged between the tool housing (10) and the mandrel (20), that each mandrel sleeve (40; 50) one of the mandrel head (21) has a corresponding radial flange (41 or 51), in which an assigned, further inlet channel (42 or 52) runs radially, that each further inlet channel (42 or 52) via a further distributor channel assigned to it ( 43 or 53) is connected to the annular gap (30), and that each further distribution channel (43 or 53) extends exclusively in a radial tool plane within a wall area which is from the flanges or flanges (41, 51), the mandrel head (21) and / or the tool housing (10) is formed.

4. Nozzle tool according to claim 3, characterized gekennzeich¬ net that each mandrel sleeve (40; 50) on its periphery from the associated radial distribution channel 5 (43 or 53) fed further collecting channel (44 or 54), which has associated other . Swirl channels (45 or 55) leads to the annular gap (30).

θ 5. Nozzle tool according to one of claims 1 to 4, characterized in that each inlet channel (11; 41; 51) has an axial angle at its transition to the associated distributor channel (12 or 42 or 52).

5 - / 2. -

6. nozzle tool according to one of claims 1 to 5, characterized in that an axial angle is provided at each branching point of a distributor channel (12; 42; 52).

7. Nozzle tool according to one of claims 1 to 6, characterized in that the mandrel head (21) and optionally the flanges (41; 51) are regulated heats bar.

8. Nozzle tool according to one of claims 1 to 7, characterized in that the annular gap (30) has a funnel-shaped axial cross-sectional profile, the gap width tapering towards the exit end of the annular gap (30),