AU704707B2

AU704707B2 - Installation for the production of plastic pipes by the centrifugal casting method

Info

Publication number: AU704707B2
Application number: AU75422/96A
Authority: AU
Inventors: Bengt Carlstrom
Original assignee: Hobas Engineering AG
Current assignee: Hobas Engineering AG
Priority date: 1995-12-22
Filing date: 1996-12-18
Publication date: 1999-04-29
Anticipated expiration: 2016-12-18
Also published as: ATE193671T1; CN1069078C; ES2146857T3; GR3034313T3; HK1005087A1; PT790114E; TR199601043A2; JPH09187827A; JP3234518B2; EP0790114A1; EP0790114B1; CN1165075A; DE59605399D1; SI0790114T1; AU7542296A

Abstract

Installation for centrifugally casting pipes from plastic containing filler, glass fibres, and, optionally, other additives has a rotary stand (1) with a horizontal axis on which 6 - 8 motor-driven centrifugal moulds (31-38) are rotatable mounted, uniformly distributed at the same axial distance from the axis (11k) of the stand, each independently driven by its own drive motor (40). A drive (25-28) and fixing device (11a-11h,19,20) enable the stand to be rotated in steps so that each mould, in turn, reaches the position previously occupied by the preceding mould. Heating elements enable each mould to be heated in at least one of its position and an extraction device extracts gases liberated from the individual moulds during curing. A feed device (2), movable only parallel to the axis during operation, introduces the pipe composition into one mould, or two moulds simultaneously, and a demoulding device draws a finished pipe out of each mould at a fixed point (G). A control device (29) controls the stepped rotation of the rotary stand, the rotation of each mould at a speed dependent on the position in which it is located, the movement of the feed device relative to the rotary stand, the feed rate and total amount of composition introduced, and the operation of the demoulding device.

Description

ut Ret. o2314o.1 PJ(0W.( I I RegUlation 3:2 A USTRA LI A Patents Act 1990 ORI GIN AL COMPLETE SPECIFICATION STANDARD PATENT 9* *99* Applicant(s): Ad ess for Service: Invention Title: [lobas Engineering AG Birsigstrasse 2 4054 Basel

SWITZERLAND)

DAVIES COLLISC)N CAVE Patent Trade Mark Attorneys Level 10. 10 Barrack Street SYDNEY NSW 2000 Installation for the production of'plastic pipes by the centrifugal casting method

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9* 9*99SS performing it known to me:- 020 Installation for the production of plastic pipes by the centrifugal casting method The present invention relates to an installation for the production of plastic pipes by the centrifugal casting method from the following starting materials: filler-containing synthetic resin, glass fibres and, if desired, further additives, such as, for example, sand.

Such installations are disclosed, inter alia, in Swiss Patent 684,326 and PCT WO 93/08009. These known installations are used for producing pipes having a large length, i.e. for example of 6 metres or more, and a diameter of at least 30 cm. It has now been found that the production of pipes having a smaller diameter, i.e.

a diameter of, for example, 10 20 cm, by means of such installations is possible but that there is a desire to have, for the production of such pipes, installations which possess a greater capacity but without the required space increasing in proportion to the output.

German Patent 2,911,369 discloses an installation for the production of polyamide pipes. In this installation, caprolactam or laurolactam is introduced :into a rotating mould at a certain initial temperature.

For the formation of a pipe, the material introduced is 25 then spun onto the wall of the mould by rapid rotation *of the rotating mould. After the centrifugal process, the rotating mould is allowed to cool for a time which is a multiple of the centrifuging time so that the diameter of the resulting pipe is slightly reduced and the pipe can be readily removed from the rotating mould.

One of the installations described has a drum S magazine with five cylindrical chambers arranged therein and displaceable and heatable on both sides, a rotating mould removable axially from said chambers being housed in each of these chambers. A single drive motor serves for generating the centrifugal motion of the rotating mould. By stepwise rotation of the drum magazine, one chamber after the other can be brought to the position in which the rotating mould housed therein can be caused to rotate by the drive motor. After several rotary steps of the drum magazine, during which the temperature of the product decreases, the rotating mould with the finished product is removed axially from the chamber and the resulting pipe is then drawn out of the rotating mould.

The disadvantage of this installation is that it can be used for producing only those pipes which consist of homogeneous material, i.e. neither pipes whose wall has incorporated components nor those whose wall is formed from different layers firmly connected to one another.

According to one aspect of the present invention there is provided installation for the production of pipes by centrifugal casting, the popes including filler-containing plastic, glass fibres and, optionally, further additives, the installation including a rotary stand having a 15 generally horizontal stand axis and on which a plurality of motor-drivable centrifugal moulds are mounted, each being rotatable about a generally horizontal respective mould axis and uniformly disposed at generally the same axial distance from the stand axis of the rotary stand, the rotary stand being rotatable stepwise in such a way that, with etch rotational step, 9 a mould reaches the position in which the adjacent mould was previously present, characterised in S" that the rotary stand includes six to eight centrifugal moulds, each of which is provided with a drive motor, that a drive and fixing device is provided for stepwise rotation of the rotary stand, that heating elements are provided for heating each mould in at least one of its 25 positions, that an extraction device is provided for extracting from the individual moulds gases liberated during curing, that a feed device displaceable only parallel to the mould axis during operation is provided for introducing materials of which the pipe is composed into one mould or simultaneously into two moulds,

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I 11 I T Vl -3that a demoulding device is provided for drawing a finished pipe out of each mould at a fixed point, and that a control device is provided for controlling the following the stepwise rotation of the rotary stand, the rotation of each mould at a speed dependent on the position in which it is located, the displacement movement of the feed device relative to the rotary stand, and the instantaneous and the total amount of materials to be introduced, and the mode of operation of the demoulding device.

A preferred embodiment of the invention is described below with reference to the attached, rather highly schematic drawing. In the drawing, in which the individual Figures are shown on different scales, Fig. 1 shows a general view of the entire installation, but without heating elements, 15 without extraction device, without demoulding device and without the control device, Fig. 2 shows details of the drive device for the rotary stand, Fig. 3 shows the drive and fixing device of the rotary stand, S' Fig. 4 shows an end view ot the rotary stand.

Fig. 5 shows a perspective view of an individual centrifugal mould.

25 Fig. 6 and 7 each show a perspective view of the annular end disc.

Fig. 8 shows a section through one end of a centrifugal mould and Fig. 9 and 10 show the essential part of the 7.1 demoulding device in two different operation states.

The general view of the entire installation shown very schematically in Fig. 1 reveals that it consists essentially of two parts, a rotary stand having a horizontal axis and denoted here as a whole by 1 and a feed device denoted as a whole by 2. The rotary stand 1 has, at the end facing the feed device 2, a circular disc 11 which is connected via several rods 12 and spokes 13 to a shaft stub 14 coaxial with the circular disc 11. The circular disc itself, which is provided with a tyre lli, is mounted on two freely rotatable rollers 15 and 16, as can be seen in Fig. 3, which rollers in turn are held in a freely rotatable manner on a crossarm 17.

Eight regularly distributed fixing tabs lla, llb, llc, lld, lle, llf, llg and llh are fastened to the circular disc 11, each of which tabs is provided with a hole. A fixing pin 21 which can be actuated by a solenoid 19 is accommodated in a housing 18 fastened to the crossarm 17, which fixing pin can be inserted into the hole of the fixing cab located at the bottom "relative to the disc axis llk, which is also the axis of 'the rotary stand, i.e. into the hole of fixing tab lla in the drawinq, in order to prevent the circular disc 11 from rotating. At the other end of the rotary stand 1, the shaft stub 14 coaxial with the circular disc 11 is freely rotatably mounted in a bearing 22, which in turn is held fixed in a stand 23. The driver sleeve 27 provided with a driver pin 26 actuatable by a solenoid 25 is mounted at the free end of this shaft stub. In the region of this driver pin 26, the shaft stub 14 has eight regularly distributed holes, channels or grooves to enable the driver pin 26 to engage the shaft. The driver sleeve 27 in turn is provided with two arms 27a and 27b, the free ends of which are connected by a hinge joint to the piston 28a of a pneumatic or hydraulic cylinder 28.

The dimensions of the arms 27a, 27b and the displacement distance of the piston 28a are such that the driver sleeve 27 is rotated through 450 during one piston movement.

This results in the rotary stand once again assuming its original position after eight rotational steps. The positions or points at which the individual centrifugal moulds are present when rotary stand 1 is stationary are therefore denoted by A, B, C, D, E, F, G and H, the position denoted by A being the lowermost position and the other positions following one another in the counterclockwise direction when viewed in a direction from the feed device 2 towards the rotary stand.

Sixteen bearings 30, each pair of which serves for supporting one of the eight centrifugal moulds 31, 32, 33, 34, 35, 36, 37 and 38, are fastened to the rods 12 of the rotary stand 1 in such a way that they hold these moulds so that their axis is parallel to the axis llk of the rotary stand. Each of these eight moulds is connected by means of a belt drive 39 to a drive motor 40 assigned to it.

Although in the drawing all eight centrifugal moulds have the same internal diameter, it is entirely possible to arrange on a rotary stand centrifugal moulds "having different internal diameters. In such a case, it will be expedient to provide each centrifugal mould with two bearings 30 and to design the bearing housings so that they can be fastened to the rotary stand i and detached from it again by simple means, the bearing housings 30a being dimensioned so that, regardless of the internal diameter of the individual moulds, the geometric axes 31a of all moulds mounted on the rotary stand 1 are the same distance from the axis llk of the rotary stand. In such a case, however, it is advantageous if the belt pulleys 31b of all moulds have the same external diameter.

I 6 As is evident from Fig. 4, five stationary heaters 41, 42, 43, 44 and 45, which partly surround the stand i, are arranged outside the rotary stand i. Each heater extends over the entire length of the centrifugal moulds so that it can readily heat the centrifugal mould presenf in its immediate vicinity to a predetermined temperature or can keep the heated mould at a certain temperature. In the position of the rotary stand 1 which is shown, the centrifugal moulds 38, 31, 32, 33 and 34 can thus be heated, i.e. the moulds which are present in the positions H, A, B, C and D. Each heater contains one or more heating elements which can be heated electrically or with hot air or with hot water or with steam, the temperature required for pipe production being controlled by means of the control device described below.

However, heating the moulds can also be carried out by another method: the mould 31 shown in Fig. 5 has an electrical heating element 31c which is wound onto it and whose lead is connected to a current source controllable by the control device, via a slip ring connection which is not shown.

As is evident from Fig. 5 and 8, each centrifugal mould 31 has a conical end piece 31k at its end facing 25 away from the feed orifice 31e, all end pieces, regardless of the internal diameter of the pipe, expediently having the same orifice diameter 31d. These orifices denoted by 31f are adjacent to the stationary annular end disc 50 which is shown in Fig. 6 and 7 and which is provided with eight extraction fans 50b, each of which is arranged behind an inlet orifice 50a and the outlet orifices 50c of which lead into a blow-out duct, which is not shown.

As is particularly readily evident from Fig. 8, S 35 each centrifugal mould has, before the beginning of the conical surface of the conical end piece 31k, an annular insert 31r which, on the one hand, serves for giving the resulting centrifugally cast pipe 100 an exactly defined end face and, on the other hand, serves as a guide for the four ejection rods 31s. These four rods are each passed through a slot 31e in the conical end piece 31k to the outside, where they are fixed to a ring 31i.

Mounted on the annular end disc 50 in the position G are two radial tabs 51, to each of which is fastened an ejection cylinder 46 whose piston rod serves for pushing the ring 31i away from the annular end disc 50 against the force of two restoring springs 48 and thus for displacing the finished centrifugally cast pipe 100 through the distance s, i.e. a few cm to the right, i.e. in the direction towards the feed orifice 31e, so that it no longer sticks to the inner wall of the centrifugal mould 31 and can be easily drawn out of it by means of a demoulding device. For this purpose, the demoulding device, whose essential components are shown in Fig. 9 and 10, is arranged on the other side of the centrifugal mould 31, in the same position G. Said demoulding device has a draw-out rod 52 displaceable in its longitudinal direction. A cylinder 53 having a connection 53b for the supply of compressed air and the extraction of air is mounted at the free forward end of said draw-out rod, which end faces the centrifugal mould 25 31. A closed rubber bellows 54 fits on said cylinder with several radial holes 53a and can be inflated by the compressed air flowing into it from the holes 53a so that said belilows can rest tightly and firm.l along its entire length, against the inner surface of a plastic pipe 100 produced in the centrifugal mould 31, when the cylinder 53 is present inside such a plastic pipe.

The feed device denoted as a whole by 2 has two pedestals 55 and 56 which are connected to one another, are displaceably guided on a guide rail 59 parallel to the axis Ilk of the rotary stand and are displaceable from the position indicated to the left and back again to the position indicated by means of a motor 8 accommodated in the housing 24, via cable lines which are not visible. Each of these two pedestals 55 and 56 contains, as disclosed in PCT WO 93/08009, storage containers provided with metering pumps and intended for the individual components of the liquid plastic, i.e. of the resin and of the curing agent, and for the sand and also the necessary storage space for the glass fibre bobbins. Each of the two pedestals 55 and 56 is provided with a loading arm 57 and 58, respectively, in which the transport devices and the delivery devices for these starting materials are housed, i.e. inter alia the tubes for the liquid plastic components, which tubes are provided with nozzles at their ends, a conveyor screw for sand transport and a pulling device and rotating cutter for the glass fibre strands. The geometric arrangement is such that the loading arm 57 is introduced into the feed orifice 31e of a centrifugal mould present at position A and the loading arm 58 is simultaneously introduced into the feed orifice of the adjacent mould 32 present at position B. The two loading arms 57 and 58 are so long that their free end on which the delivery orifices for the plastic resin, sand and the glass fibres are arranged is present at the end of the displacement, at a point inside a centrifugal mould 25 at which the cylindrical section 31g is connected to the conical section 31k.

The control devices, connected to computers, and the measuring and monitoring devices for the entire installation are housed in a box 29 which Is connected by lines 29a to the rotary stand 1 and by lines 29b to the feed device 2, i.e. including, for the rotary stand 1, the controllers for the rotary stand drive device consisting of the parts 22, 25, 26, 27 and 28, for the r"fixing device consisting of the parts 19 and 21, for the S 35 drive motors 40, for the extraction fans 50b, for the compressed air-operated cylinders 46 of the ejection device, for the actuation of the demoulding device, namely for displacement of the draw-out rod 52, and for inflating and evacuating the rubber bellows 54 and for the switches for switching the mould heaters on and off, which switches are controlled by programs and by temperature sensors mounted on the moulds.

A device not shown in the drawing may of course also be present, by means of which a mould release agent can be introduced into each centrifugal mould, after removal of a completely produced pipe but before the introduction of the materials used for the production of the next pipe, in order to prevent the material from sticking to the mould wall.

The drive and control devices for the feed device incluute, inter alia, the control members for moving this device to and fro and of course the measuring and metering devices for delivery of the construction materials for the production of the pipes, i.e. the metering pumps for the resin components, the conveyor screw for the sand and the transport and comminution device for the glass fibres.

The mode operation of the installation described above is explained below.

In the state shown, the rotary stand 1 is prevented from rotating by the fixing pin 21 inserted in the fixing tab Ila. The mould 31 is present in position A, the mould 32 in position B, the mould 33 in position C, the mould 34 in position D, the mould 35 in position E, the mould 36 in position F, the mould 37 in position G and the mould 38 in position H. All moulds, with the 30 exception of mould 37 in position are driven by their associated motor 40 by means of the belt drive 39, for example in such a way that the speed at positioL H is 200 min that at position A is 455 min', that at position B is 655 min' and that at positions C, H, D and E is about 300 min' and at position F the speed decreases until the mould is stationary.

The mould release agent which prevents the subsequently introduced construction materials used for constructing a pipe from sticking to the mould wall is sprayed into the mould 38 present in position H, by means of a nozzle not shown in the drawing. The mould rotates at a speed which ensures uniform distr ition of the mould release agent over the entire inner surface.

At positions A and B, loading arms 57 and 58 travel simultaneously at constant speed into the moulds 31 and 32, respectively, standing in front of them and rotating at high speed, and travel out of these again.

This may take place once or several times. They deliver the construction materials required for the construction of a glass fibre-reinforced plastic pipe 100, i.e. resin enriched with fillers, and curing agent and sand and glass fibres in accordance with a program stored in the controller, the loading arm 57 producing the cuter layers of the pipe and the loading arm 58 the inner layers. Since the mould heating is in operation, curing of the plastic resin begins simultaneously.

At positions C, D and E, the introduced material from which a pipe has been formed by the centrifugal process cures completely at slightly reduced speed, and compaction may also take place at the beginning, i.e.

position C, where the material is still fairly soft.

25 Depending on the requirement, which is determined by heat sensors mounted on the moulds and which is dependent on the pipe diameter, the pipe wall thickness and of course also the prevailing room temperature, heat can be supplied by the heating elements at positions H, A, B, C and D. The pipe produced in this manner now undergoes final curing in position F, the speed of the mould being decreased until the mould is stationary. At the same time, the ejection cylinder 46 is first S. actuated in the mould present in position G, in order to detach the plastic pipe 100 tightly fitting in the mould from said mould, as described further above. At the same time, the demoulding device travels from the other side into the plast2ic- Pipe 100 1:o: such an extent that its rubber bellows 54 is located completely inside the pipe.

As soon as this is pushed out slightly, the rubber bellows is inflated by intlowing compressed air to such an extent that it fits firmly in the pipe and is capable of drawing out the pipe towards the right during subsequent displacement of the draw-ou: rod 52..

The appropriate fan 50b which blows the gases into the waste gas duct is switched on by the control device in all positions where vapours or gases are liberated during curing of the plastic.

When all these movements described above and taking place simultaneously are complete, the solenoid 19 draws the fixing pin 21 out of the hole in the fixing tab hla, whereupon the piston 28a ot the hydraulic cylinder 28 is pushed out and the shaft stub 14 and hence the entire rotary stand 1, whose circular disc 11 rotates on the two rollers 15 and 16, rotates through 4~50 so that the fixing tab 11b is located in front of the fixing pin 2-1 which is pushed into the hole in this fixing tab by the solenoid 21, with the result that the stand is once again fixed in the new position.

In this new position, ti a mould 31 is thus in G% 6 position B, the mould 32 in position C, etc., i.e. a 25 subsequent working process, as described above, takes place in each mould. Thus, a finished plastic pipe is drawn out after each one eighth rotation. If, as is quite possible, 2.5 s are requilred Eor releasing and locking a fixing tab and 7 s are required for rotating 30 the stand i through 4 180 are available, in a 192 second cycle, for repeatedly inserting and o 0: withdrawing each of the two loading arms 57 and 58, i.e.

a total of 6 min for introducing the material required for the construction of a pipe, which experience -'-iows is in general complete~ly sufficient. in other words, a time of 2-5 min 36 s is required tor the production of a pipe, the installation thus delivers a pipe every 192 seconds or 75 pipes of, for example, 6 m in 4 hours, i.e. 450 linear metres of pipe.

With such a production rate, production costs of such high-quality, reinforced plastic pipes are no greater than the production costs of metal pipes.

However, since such plastic pipes are substantially lighter, the transport and laying costs are lower than in the case of metal pipes. Since moreover the life is several times that of metal pipes, pipes produced in this manner constitute a substantial advance compered with all conventional pipes of comparable dimensions.

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Claims

1111. 1 1. 1 T i THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Installation for the production of pipes by centrifugal casting, the popes including filler-containing plastic, glass fibres and, optionally, further additives, the installation including a rotary stand having a generally horizontal stand axis and on which a plurality of motor-drivable centrifugal moulds are mounted, each being rotatable about a gener.'ly horizontal respective mould axis and uniformly disposed at generally the same axial distance from the stand axis of the rotary stand, the rotary stand being rotatable stepwise in such a way that, with each rotational step, a mould reaches the position in which the adjacent mould was (1 previously present, characterised in S that the rotary stand includes six to eight centrifugal moulds, each of which is provided with a drive motor, that a drive and fixing device is provided for stepwise rotation of the rotary stand, that heating elements are provided for heating each mould in at least one of its ;5 positions, that an extraction device is provided for extracting from the individual moulds gases liberated during curing, that a feed device displaceable only parallel to the mould axis during operation is S provided for introducing materials of which the pipe is composed into one mould or 20 simultaneously into two moulds, that a demoulding device is provided for drawing a finished pipe out of each mould Sat a fixed point, and that a control device is provided for controlling the following the stepwise rotation of the rotary stand, 25 the rotation of each mould at a speed dependent on the po:,tion in which it is located, S" the displacement movement of the feed device relative to the rotary stand, and the instantaneous and the total amount of materials to be introduced, and the mode of operation of the demoulding device.

2. Installation according of Claim 1, characterised in that all centrifugal moulds have the 14- same internal diameter.

3. Installation according to Claim I, cnaracterised in that at least one centrifugal mould has an internal diameter differing from that of a centrifugal mould adjacent to it.

4. Installation according to any one of Claims I to 3. characterised in that se"eral heating elements are arranged in a stationary manner for heating the centrifugal moulds which are located in their immediate vicinity.

5. Installation according to any one of Claims 1 to 3, characterised in that each centrifugal mould is provided with a heater which "an be switched on and off.

6. Installation according to any one of Claims 1 to 5, characterised in that, for each mould, a stationary connecting orifice of the demoulding device is present at the end facing away from the feed device.

7. Installation according to any one of Claims 1 to 6, characterised in that the feed device has two loading arms which are arranged in such a way that, when the feed device is displaced parallel to the axis, they are inserted into two pipes adjacent to one another.

8. Installation according to any one of Claims 1 to 7, characierisd in that the control device for each centrifugal mould contains a temperature controller which serves for controlling the mould heating, in order to heat the mould to a preprogramrnable temperature. 8 *8 *8 *0 88 8 8 *8 0 8 8 9 8*8 *8 8 25

9. Installation substantially as herein drawings. Dated this 24th day of February, 1999 HOBAS ENGINEERING AG Ey Their Patent Attorneys DAVIES COLLISON CAVE before describe with reference to the accompanying ABSTRACT The production of reinforced plastic pipes having a diameter of 30 cm or more by the centrifugal casting method is known per sn. It is true that the installations used for this purpose, in which pipes having a length of 6 10 m are produced, can also be used for producing pipes having a smaller diameter. However, since the capacity of such an installation is independent of the diameter of the pipes to be produced, a novel installation was provided which has a larger capacity for thinner pipes, i.e. pipes having a diameter of the order of 10 20 cm. This installation contains, as an essential part, a rotary stand which has a horizontal axis and on which at least six, preferably eight, centrifugal moulds (31, 32, 33, 34, 35, 36, 37, 38) mounted rotatable about a horizontal axis are arranged in such a way that their axes are all the same distance from the axis of the rotary stand and from the axis of the adjacent moulds. Each mould is provided with a drive motor (40) in order to spin the introduced construction materials onto the mould wall. Heating elements serve for keeping the optimum curing temperature constant, extraction devices for removing liberated gases and a demoulding device for drawing out the finished pipes. A drive device serves for rotating the rotary stand in 450 steps in order to bring each mould to the point at which the adjacent mould is present beforehand. A different manufacturing step in pipe production takes place at each of the eight points or positions, the construction materials being introduced by loading arms (57, 58) of the feed device at two of these eight' positions, into the moulds present there. Such an installation permits efficient and economical production of thin plastic pipes. (Fig. 1)