IE42940B1 - Apparatus for the continuous production of oriented hollow bodies from a thermoplastic material - Google Patents

Abstract

1480322 Blow moulding SOLVAY & CIE 5 Jan 1976 [7 Jan 1975 27 June 1975] 166/76 Heading B5A A blow-moulding lay-out (see Fig. 1) comprises an extruder 1 which feeds a tubular parison to a series of axially aligned split moulds carried by a rotary carrier 2. The moulds blow the parison into preforms each having a final neck configuration above which is located a false neck (see Fig. 3). The preforms are removed from the moulds by a release device 3 and presented to the hinged jaws (see Figs. 4 and 5, not shown) of carriers carried by an endless chain 4 whence the false neck is removed by a deflashing device 5. The deflashed preforms are passed around a cooling device 8, at which a cooling fluid, such as liquid nitrogen is introduced into the preforms, and fed to a series of blow moulds carried by a rotating carrier device 7 via an oven 6 in which they are brought to molecular orientation temperatures. Finally, the blown articles are presented to a heating device 9 to thermally stabilize them against stress cracking. All the elements of the lay-out are driven through suitable gearing and chains (see Fig. 2, not shown) from a single motor to ensure synchronization and the chain is tensioned by a pair of adjustable devices 11 and 12. The chain is actually driven either by drive gears each located in a different stretch of chain between the tensioning devices or by the carriers 2 and 7 themselves. One of the drive gears may be attached either to the release device 3 or the deflashing device 5. The preform is blown from the parison by a needle 41 which pierces the false neck of the preform and which is carried by a block 43 reciprocable by a bent lever 52, 50 actuated from a fixed cam by a follower 51. The needle engages the end of a holding screw 44 having a central channel in communication with that of the needle at one end and at the other end with a source of fluid via radial passages 45 in the screw and passage 47 in the block 43. The needle is not withdrawn after the mould is open to retain the preform in the mould half 39 prior to ejection. Retention and ejection may alternatively be effected by an undercut recess 67 (see Fig. 6) in the mould wall and a reciprocable plunger 65 located in the base of the recess.

Description

The preseht invention relates to an apparatus for the continuous production of oriented hollow bodies from a thermoplastic material, v/hich apparatus makes it possible to achieve very high rates of production.

It is known to produce, from a thermoplastic material, hollow bodies v/hich have improved mechanical properties, by effecting the expansion and final shaping of preforms v/hich are at a temperature which favours molecular orientation. In general, the preforms are employed at a temperature below the crystalline melting point of the thermoplastic material of which they are composed.

Numerous techniques have been developed for the industrial-scale production of oriented hollow bodies from thermoplastic materials. One of the most attractive techniques comprises producing preforms by blowing a portion of a tubular parison in a preform mould, bringing these preforms to a suitable temperature for their orientation, and then introducing them into moulds in v/hich a final moulding by blowing Is carried out.

An apparatus which can be employed for this technique is described in U.S. Patent Specification No. 3,767,747 (Owens Illinois).

This apparatus comprises two moulding units, each comprising a preform mould and a final blowing mould, one moulding unit being mounted on’ each side of an extrusion installation which delivers a tubular parison.

Each moulding unit executes a reciprocating movement so as to present its - 2 43940 preform mould under· ihe extrusion head and then under blowing nozzles provided on the respective sides of the extrusion installation.

However, owing to the sequential movement of the moulding units, the necessarily limited number of moulds, and the need to keep each preform in its preform mould for a sufficient period to permit ics thermal conditioning, this apparatus can only achieve undesirably low production cycle speeds.

We nave now developed, however, an apparatus for the continuous production of oriented hollow bodies from a thermoplastic material, starting from blow-moulded preforms, which makes it possible to achieve extremely high production cycle speeds.

According to the present invention we provide an apparatus for the continuous production of oriented hollow bodies from a thermoplastic material, which comprises: a device for the production of a continuous tubular parison from a thermoplastic material; a preform blowing unit which is fed with the continuous tubular parison and which comprises a plurality of moulds, the moulds being aligned end to end contiguously on a first rotary carrier and being adapted to produce separate preforms which have a neck moulded to a predetermined final shape; a device for deflashing the neck of successive preforms; a thermal conditioning device whereby the preforms are brought to a predetermined optimum orientation temperature; a final blowing unit which comprises a plurality of moulds mounted on a second rotary carrier; and a transfer device adapted to convey the preforms from the preform blowing unit to the final blowing unit, by way of the deflashing device and the thermal conditioning device; in which apparatus the said transfer device comprises an endless chain (as herein defined) provided with carriers adapted to support the preforms, after the moulding of the preform neck, below the preform neck.

The preforms which are conveyed by the endless chain, being derived from a tubular parison, are of generally cylindrical shape. Their bottom portion can have any desired shape. It can, for example, terminate in an edge as in the case of a toothpaste tube, or can be hemispherical, as in test tubes used in chemical laboratories. Their neck already has its predetermined - 3 final shape, viz. the shape of the neck of the final hollow body. Their middle portion is substantially cylindrical.

Each of the carriers of the transfer device preferably has a vertically arranged generally cylindrical preform receiving chamber which is open at the top, this generally cylindrical chamber preferably having a slightly greater diameter than that of the middle portion of the respective preforms, so that these preforms are gripped only loosely, in order not to damage them. Preferably, each preform receiving chamber is bottomless, so as not to damage the bottom portions of the preforms; in this case, however, the preforms should have an annular bulge in their neck portion, although this bulge is not objectionable on the preforms, inasmuch as it has to be provided in any case on the final hollow bodies so as to allow closures to be fastened on to them.

In a particularly advantageous construction the carriers each comprise two pivoted jaws which can move apart and v/hich define a bottomless generally cylindrical preform receiving chamber between them, in their closed position. The jaws are moved apart to facilitate the placing of the preforms in the carriers and to facilitate the gripping of the preforms, which is needed to transfer them to the final blowing unit. The jaws grip the middle portion of the preform. Their height is not critical.

Preferably the carriers are fixed, at regular intervals, on an endless chain having vertical link-pins, this chain being easily supported, driven and guided by means of gearwheels. Furthermore, this chain allows the carriers to be positioned correctly relative to the various devices and units. However, it is also possible to use any other transfer device which is mechanically equivalent to the endless chain having vertical link-pins, for example, a notched belt, and the term endless chain used herein is to be construed accordingly.

It will be understood that it is desirable that the spacings of the carriers, and the speed of travel of the endless chain, should be so chosen that all the preforms can be conveyed from the preform blowing unit to the final blowing unit with each carrier of the chain carrying one of the preforms between the two blowing units. It is therefore desirable that the two blowing units and the endless chain should be capable of operating at the same speed. - 4 In norms! operation, the preforms are discharged from the preform blowing unit at regular intervals of time. Since it is desirable that, each time a preform presents itself, a carrier shoulc be ready to receive it, it is desirable also that the discharge of the preforms and the advance of the carriers should be synchronised, by appropriately selecting the geometry of the various components concerned.

On the other hand, it is desirable that the take-up of the preforms by the carriers shall be possible for different speeds of rotation of the rotary carrier of the preform blowing unit. This can advantageously be achieved by driving the endless chain by the same motor as that which drives the rotary carrier of the preform blowing unit.

This ensures that the linear speed of the endless chain always varies proportionately to the speed of rotation of the rotary carrier of the preform blowing unit, and consequently the endless chain can correctly perform its function in relation to this preform blowing unit regardless of the speed of rotation of this unit.

It will be appreciated that it is also necessary that the final blowing unit should be so designed that it dependably takes up and blows the successive preforms conveyed by the endless chain.

The correct feed of the final blowing unit by the endless chain requires that there should be synchronisation between (1) the travel of the carriers of the endless chain in the region in which this feed is to take place and (2) the travel of the feeding means whereby the preforms are engaged in order to introduce them into the final blowing unit.

This result would be achievable by driving the final blowing unit via the endless chain. However, the very high inertia of the final blowing unit would make it necessary to employ an endless chain of unduly heavy construction. He therefore prefer to meet the above-mentioned requirement by driving the final blowing unit by the same motor as that which drives the preform blowing unit, appropriate transmission being interposed for this purpose.

In a preferred arrangement, therefore, the two rotary carriers of the two blowing units are driven by a single motor, and this motor also drives the - 5 S2940 endless chain of the transfer device. By this means it is possible to ensure a correct overall functioning of the apparatus, and its speed can be modified by making a single adjustment, that is to say adjusting the single drive motor.

In a particularly preferred arrangement, the endless chain is provided with at least one tensioning unit and is driven indirectly and twice over, drive being transmitted to it both by the preform blowing unit drive and by the final blowing unit drive.

We have in fact found that if the endless chain is driven directly by the motor or via only one blowing unit, the synchronisation of the endless chain in relation to the units or devices which do not participate in driving the chain is not always properly ensured. As a result of this, we have found that there periodically occur slight fluctuations or drifts in the travel of the carriers of the chain in relation to the blowing units. These drifts are attributable more particularly to the play which can occur between the various movable components of the apparatus, and to the heat cycle v/hich is undergone by the endless chain, which passes through the thermal conditioning device together with the preforms.

In the preferred procedure, the positioning of the carriers is controlled in relation to each of the two blowing units, the slight temporary variations in speed of the endless chain near the two blowing units being taken up and compensated by an automatic shift in the tensioning unit(s).

This avoids any danger of breakage of the chain. It is furthermore possible to provide contacts v/hich automatically stop the motor if the (or a) tensioning unit exceeds a predetermined permitted shift.

Preferably, two tensioning units are provided, each being arranged to tension a respective stretch of the endless chain lying between two drive receiving points of the chain.

In the preform blowing unit, it is desirable that the successive moulds which are aligned end to end should be as nearly continuous as possible, because this unit is fed with a continuous parison and consequently any interval between two successive moulds entails a loss of material.

On the other hand, in the final blowing unit, the moulds can be spaced apart as desired, because each of them is intended to receive an - 6 4SS«<3 individual preform.

The apparatus of ths invention will be explained in greater detaiί ' with reference to a preferred embodiment thereof which, without implying an; limitation, will now be described with reference to the accompanying dia5 grammatic drawings, in which: Figure 1 is a schematic plan view of an apparatus according to-the invention, Figure 2 is a schematic perspective view which shows the drive system of the apparatus, i; Figure 3 is a view, partially in section, of a fixed mould-half for a preform, which shows the control device for the hollow blowing needle.

Figures 4 and 5 are a from; view and a plan view of a portion of the endless chain for the transfer cf pre1E forms, showing one of the carriers with which this chain is equipped, and Figure 6 is a view, partially in section, of a fixed mould-half for a preform, showing a different embodiment of the ejection. χ. ' As can be seen in Figure 1, the apparatus according to the invention comprises a device 1 for the production of a continuous tubular parison, a first rotary carrier 2, with a horizontal axis of rotation, which supports contiguous preform moulds arranged end to end so as to receive the continuous tubular parison, and a mould release device 3 which extracts successive preforms from their mould and introduces them into the hinged jaws of the successive carriers mounted on an endless transfer chain 4, The endless chain 4 causes successive preforms to travel through a □θ neck deflashing device 5 and through a thermal conditioning chamber 6. The endless chain 4 thereafter ensures the correct presentation of the deflashed and thermally conditioned preforms for the purpose of introducing them into - 7 3 40 the final blowing moulds located on a second rotary car'rier 7 having a vertical axis of rotation.

As will he described later, the apparatus can he supplemented with a cooling device 8 for the preforms, provided between the deflashing device 5 and the thermal conditioning chamber, and with a reheating oven 9 which follows the final blowing device 7 and is intended to receive the oriented hollow bodies taken out of the latter.

The endless chain 4 is driven in the zone of the mould release device 3 or of the deflashing device 5 and in the zone of the device lo for transferring the preforms into the final blowing moulds. The endless chain 4 is finally equipped with two tensioning devices 11 and 12 located on edch of the sections of endless chain between the two drive positions of the chain.

As can be seen more clearly from Figure 2, the mechanical drive of the various movable parts of the apparatus is effected by means of a rotating shaft 13 which is rotated by a variable-speed motor unit 14 which constitutes the sole source of energy which drives the whole apparatus.

Thus, the first rotary carrier 2, represented schematically hy its toothed drive rim 15, is driven directly by a gearwheel 16, fixed on the rotating shaft 13 and engaging in the toothed rim 15.

A gearwheel 17, also fixed on the shaft 13, drives, via the chain 18 and the bevel gear 19, the device 3 which transfers the moulded preforms onto the transfer chain 4.

Another gearwheel 20, fixed on the shaft 13, drives, - 8 4 g a ·, - ri o' 5 fc via ice chain 21 and the sevci gear 22, the device 5 which deftashes the necks of the preforms.

Finally, a last gearwheel 23, fixed or, the shaft 13, drives, via the chain 24 and the gearwheel 25, an intermediate Cardan shaft 26. This shaft 26 provides, via the bevel gear 27, firstly the drive of the toothed rim 28 which is integral with the second rotary carrier 7, via the gearwheels 29, 30 and 31 ana the cnain 32, and secondly, the first drive of the transfer chain 4, via the shaft 33, the gearwheels 34 and 35, the chain 36 and the gearwheel 37 which engages with the chain 4.

The transfer chain 4 is also driven in the zone of the preform blowing unit. This drive can be provided either by the deflashing device 5 or by the preform transfer device 3 or by both of these devices. Thus although one has various choices as to the two specific points at which, preferably, drive is imparted to the endless cnain, it is particularly to be preferred that the drive should be transmitted to those points through the drive mechanisms of both the blowing units.

The path followed by the transfer chain 4 is imposed by the idler gearwheels 38 and two tensioning devices 11 and 12 are provided on each segment of the endless chain between the two drive positions of the transfer chain 4.

The position of the tensioning devices is not critical as long as each is on one of the segments of the endless chain 4 between the drive positions. Thus, in Figure 1, the tensioning devices 11 and 12 occupy different positions.

In the figure, arrows indicate the direction of rotation or travel of all the drive components.

It can thus be seen clearly that all the moving components Of the apparatus are driven by the single motor 14 via the shaft 13, which makes ic possible to ensure perfect-·—-— --- 9 0.40 synchronisation during operation.

Furthermore, the transfer chain 4 is driven at two points located in the zones where the chain receives the moulded preforms and where it gives up these preforms to the final blowing machine, and. hence this chain is perfectly synchronised at its points of contact with the other components of the apparatus, notwithstanding possible stretching of the chain.

In Figures 1 and 2, the practical details of realisation of each constituent element of the apparatus have deliberately been omitted for the sake of clarity. These. details are explained below.

The device 1 for the extrusion of the continuous tubular parison, shown schematically in Figure 1, does not exhibit any inherent special feature compared to known conventional devices. However, an extruder should be chosen vzhich has an output compatible vzith the high production capacity of the apparatus for the production of oriented hollow bodies which the extruder must feed. Furthermore, the extrusion device can be equipped with a system for programming the wall thickness of the continuous tubular parison which is produced.

As has been stated, the first rotary carrier 2 is equipped with contiguous moulds arranged end to end, the internal cavity of the moulds reproducing the shape of the desired preform.

According to the preferred variant which is illustrated, this carrier, driven by the rim 15» revolves at - 10 42D4C constant speed about a horizontal axis and successively presents the various moulds mounted on its periphery at right angles to the tubular parison extruded continuously and tangentially to this rotary carrier.

The preform blowing machine can be of the same general design as the rotary machine for blowing hollow bodies described in Belgian Patent 723,419 filed cn δ.11.1968 by the applicant company, except that each mould only produces one preform ahd not two preforms welded together by the neck.

The rotary carrier 2 thus consists of a series of equidistant arms located radially in a plane perpendicular to a rotary shaft, the end of each of these arms being provided with a moulding unit consisting preferably of a fixed mould-half integral with the arm and a movable mouldhalf articulated by a hinge on the fixed mould-half. Cam controls are provided for closing the successive moulds at the instant that their rotation brings them at right angles to the continuous tubular parison delivered by the extrusion device, for locking the moulds in the closed position, for controlling the blow-moulding of the parison portions enclosed in these moulds, for unlocking the moulds before they are opened and for opening the unlocked moulds so as to to make it possible to extract the moulded preforms.

Preferably, the cavity of each mould reproduces the shape of a preform which has a closed false neck and a hemispherical bottom, as described in our French Patent Specification No. 2,263,374 ' ( patent Specification No. 40830) smo and illustrated by Figure 1 of the said patent specification.

Devices for deflashing the bottom of the preforms, such as described in this same French Patent Specification can advantageously he provided hetween the continguous moulds with which the rotary carrier is equipped and can be controlled by cams so as to permit the direct production of separate preforms of which the hemispherical bottom is perfectly deflashed.

The cavity of each mould can thus advantageously correspond to the shape of the preforms described in Patent Specification No. 2,261,117 (c.f. U.K. Patent Specification No'. 1,436,536), and more especially to Figures 1 to 5 of this patent specification. The deflashing of i the bottom of these preforms does not present any problem because the bottom is in the shape of a straight edge.

The diameter of the cavity of the moulds and hence the diameter of the preforms produced is only slightly greater than the diameter of the initial tubular parison so as to keep the radial stretching of this tubular parison, during the moulding of the preform, to a value of less than 20%. In fact, in this stage,the stretching of the parison should be restricted because, bearing in mind the relatively high temperature of the thermoplastic material of which the parison consists, this stretching does not produce any molecular orientation.

The preform is preferably moulded by blowing by means of a hollow needle connected to a source of a fluid - 12 td 42040 ι under pressure; this needle pierces the tubular parison at a point beyond the desired moulded neck, that is to say in a portion of the parison which isaiployed to form a closed false neck which is subsequently removed.

The hollow blowing needle is preferably mounted on a movable control block arranged at the side of the fixed mould-half, the movements of this block being controlled by the rotation of the movable carrier which supports the moulds, and by cams. Ιθ A preferred embodiment of this device is shown in Figure 3.

As can be seen in this figure, the fixed mouldhalf 39, of which the cavity 40 reproduces the shape of a preform having a hemispherical bottom, is provided with a blowing device consisting particularly of a movable hollow needle 41 having a conical base 42. This needle 41 is inserted into a seat provided into control block 43, the bottom of which has a conical part corresponding to the conical base 42 of the needle. The needle 41 is held in 2o the bottom of the seat by a clamping screw 44. The end of this screw is provided with a central channel located to form the extension of the central channel of the needle and connected to the walls of the screw by radial channels 45. Furthermore, the end of the clamping screw 44 has a dia25 meter which is such that an annular space or chamber 46 remains between the periphery of the seat in the control block 43 and the periphery of the end of the clamping screw 44. A channel 47 provided in the control block 43 opens t - 13 into the annular· space 46. This channel 47 is connected, to a source of fluid under pressure via a control valve which is not shown. The control block 43 is mounted on a carrier 48 which is integral with the side wall of the fixed mouldhalf 39, in such a way that -the block, can slide in this carrier. The travel of the control block 43 on this carrier and along a direction at right angles to the axis of the fixed mould-half 39 is brought about, in both directions, by the pivoting of a control lever mounted on a carrier 49 integral With the fixed mould-half 39. One of ths arms 50 of the lever, equipped with an idler pulley 51, can be shifted, for example by the action of fixed cams, which are not shown, during the rotation of the rotary carrier which supports the preform moulds, whilst the other arm alter acts to/ the position of the control block 43 on its carrier 48. Thus, as can also be seen from the figure, the needle is arranged so as to penetrate into the cavity 40 in the zone 53 which defines the formation of a closed false neck on the moulded preform. The system of mounting the needle makes it possible, where necessary, rapidly to replace the blowing needle because all that is required is to unscrew the clamping screw 44 in order to take out the needle from its seat in the control block- 43. The new needle is placed in position simply by introducing the needle, hy its point, into the seat, and replacing the clamping screw 44. The presence of the chamber 46 and of the radical channels 45 avoids any need for special positioning of the needle 41 in its seat. -..

Apart from this feature, the design and functioning of the device for the blow-moulding of the preforms are practically identical with those described in the abovementioned Belgian Patent No. 723,419 and it is g therefore not necessary to describe them in greater detail.

The mould release and extraction of the moulded preforms, when the preform moulds are open, are preferably effected by means of a mould release device like that described in Belgian Patent No. 772,264 filed on 7.9.1971 by the applicant company. However, the preforms extracted by the joint action of the ejectors of the preform moulds and the gripping devices located on the arms with which the mould release device is equipped are not deposited on a conveyor as described in Belgian Patent 772,264 but ars simply transferred into the carriers with articulated jaws located on the endless transfer chain 4. This transfer does not present any particular synchronisation problem because the endless chain 4 is driven in the vicinity of the mould release device 3 which is itself driven by the rotary platen of the preform blowing machine. This guarantees perfect synchronisation of the movements of the gripping members of the mould release device with those of the carriers with articulated jaws mounted on.the endless chain 4.

Preferably, the size of the mould release device, the spacing of the carriers on the endless chain and the gearing-down of the transmission between the mould release device and the endless chain are so chosen-'that the preforms - 15 JS940 are subjected to the same linear speed at the precise moment at which they leave the mould release device and at the moment at which they are carried away by the endless chain. This causes the apparatus to operate entirely without jerkiness.

Figures 4 and 5 of the attached drawings illustrate a segment of the endless chain equipped with a carrier with articulated jaws.

As can be seen in these figures, the carrier with articulated jaws 54 is mounted on a plate 55 fixed to the links of the endless chain 4. This carrier comprises two movable jaws 56 and 57 articulated about pivots 58 and 59 fixed to the plate 55. A spring 60 seeks to keep the jaws in the closed position. One of the jaws 56 is provided with a lever arm 61 equipped with an idler pulley 62 for control purposes. Furthermore, two gearwheels 63 and 64 engaging with one another are respectively fixed on each jaw, in the position of the pivots.

The opening of the articulated jaws is controlled by the control pulley 62 encountering a fixed profiled cam, which is not shown, in the path of the pulley. This cam causes the jaw 56 to pivot under the action of the lever arm 61 and this pivoting at the same time causes the pivoting, in the opposite direction, of the other jaw 57,via the gearwheels 63 and 64. The cam is so arranged that, for example, the jaws are in the open position at the instant that a preform extracted from' the; preform blowing machine is seized by the mould release, device and that it - 16 d£Dd causes abrupt closing of the jaws under the action of the spring 60 at the instant at which the preform is released by the mould release device.

The preforms are seized by the arms of the mould release device just below the neck. Wen they are released from these arms, they drop under gravity into the seat formed by the jaws of their carrier, which have beforehand been closed. They are held by the annular bulge which their neck portion possesses.

During opening of the preform moulds, the moulded preforms should throughout remain held in the fixed mouldhalf to enable them to be taken over by the mould releasedevice, The applicant company has found that this condition could easily be fulfilled reliably by keeping the blow15 ing needle 41 stuck into the cavity 40 of the fixed mouldhalf until the time at which the mould is partially open.

In this way the needle in effect retains the preform in the fixed mould-half.

This result is achieved, for example, by so arrang20 ing the cam which controls the retraction of the needle 41 that the cam only acts on the lever 50 after the corresponding mould has been partially opened. Obviously, in thi; case, the blowing should be discontinued before the mould is opened.

This condition can also be fulfilled by means of mould ejectors, as has been described in the previously cited Belgian Patent No. 723,419. . In this case, the ejector in the rest position is retracted into its seat - 17 S840 below the level of the bottom of the mould cavity.

Another technique which also employs ejectors is illustrated by Figure 6 of the attached drawings.

As can he seen in this figure, the eject.or 65, represented in its rest position, is flush with the level of the bottom of the cavity 40 of the fixed mould-half 39 and has, in its upper part, a cut-out in the shape of a half-dovetail. Thus, during blowing of the preform 66 a part of the thermoplastic penetrates into the cavity 67 determined hy this cut-out and during subsequent opening of the mould, the preform remains hooked in the fixed mould-half 39. The extraction of the preform 66 does not present any problem because when the ejector has introduced the neck of the preform into a gripper with which the mould release device is equipped, the arm which supports this gripper disengages the preform from the notch of the ejector.

The preforms which have been released from the mould and transferred into the .carriers with articulated jaws 54, located on the endless transfer chain 4, are then carried through a deflashing device which cuts off their false neck.

This operation can advantageously he carried out hy means of a deflashing device based on the principle described in Belgian Patent 673,913 filed on 17.12.1965 hy the applicant company.

In such a device, the flash or false neck is cut off by a fixed knife whilst the preforms are_ caused to undergo - 18 - , a -translational movement along the knife and a simultaneous rotational movement about their longitudinal axis.

The translational movement can be brought about by a rotary platen equipped with idler pulleys of appropriate profiles and corresponding to the profile of the false neck.

These preforms are thus held at their neck, caused to travel through the deflashing device and caused to rotate about themselves between two idler pulleys and a fixed guide of appropriate geometry. The-platen can be caused to rotate by 'iO the endless chain 4 itself, at a speed such that the translational speed of the preforms is exactly equal to the lines speed of travel of this chain. .According to another variant, this platen can be driven directly by the motor which actuates the two blowing machines. In that case, the platen can drive the endless transfer chain at a speed compatible with the speed of rotation of the blowing machines. This drive can supplement, or be substituted for, the drive provided at the mould release device, and in that case the latter can be uncoupled from the endless chain.

As a result,, the drive of the endless chain in the zone of the first blowing machine can be effected either via the mould release device or via the deflashing device or via any other intermediate device coupled to the motoi’ which drives the two blowing machines.

The rotary platen is preferably equipped with idler pulleys which are so profiled as to fit the profile of the false necks of the preforms, and the fixed guide is also profiled in the same way, so as to achieve correct - 19 positioning of the preforms when the flash is cut off.

The preforms must be held in their carriers whilst they pass through the deflashing device. They can also bo lifted slightly whilst passing through, and need no longer rest on the annular bulge of their neck portion.

In that case, in order not to impede the rotary movement imposed on the preforms during deflashing, it is obviously necessary that the preforms should not be held firmly in the carriers, with articulated jaws, of the endless transfer chain 4, at least whilst they are passing through the deflashing device. For this purpose, the articulated jaws are preferably so constructed that in the closed position they only loosely surround the body of the preforms, the latter thus being suspended in the jaws and held by their moulded neck. To facilitate the rotation of the preforms, a profiled fixed cam can be provided so as to cause the articulated jaws to open at the instant at which the preforms enter the deflashing device and to cause the jaws to close onto the preforms at the instant at which they leave the deflashing device. In this.latter case, the holding pulleys provided on the rotary platen and the circular fixed guide must be profiled so as to hold the preforms not only by the false neck but also, at their true neck during deflashing, so that the preforms remain held between these components even after the false neck has been completely cut off, and can thus be taken up again by the carriers with articulated jaws on issuing from the deflashing device. However, this modification is not necessary if - 20 4 23 £ 3 the- com ic so profiled as to rooj.ose the jaws of the carriers at the precise instant at which the cutting-off of the neck flash is completed.

In the course of blew moulding in the moulds with which the first blow-moulding machine is equipped, the moulded preforms are obviously cooled, for- example by circulation of a coolant fluid through the walls of the moulds, so as to permit mould release of the preforms without the danger of deforming them. Furthermore, because these preforms must subsequently undergo an orientation treatment, the cooling during the moulding of the preforms must be regulated so that the preforms released from the mould have an average wall temperature which is within the appropriate temperature range for their subsequent orientation. Inevitably, the outer wall of the preform, which is in contact with the wall of the mould cavity during moulding, is cooled more than the inner wall.

Thus, for example, if the coolant fluid is water at ambient temperature, the outer wall of the preform is at a temperature of about 3O°C when released from the mould whilst its inner wall remains at a temperature close to the extrusion temperature. As a result, the preform, at the instant at which it is released from the mould, has a temperature gradient, through its thickness, which can range from ambient temperature (at the outer wall) to the extrusion temperature (at the inner wail).

During the subsequent transfer of the preforms, this gradient tends gradually to disappear and the wall of the - 2] 40 preforms ultimately has a constant or practically constant mean temperature throughout its thickness.

Obviously, the cooling of the preform moulds should be regulated, for each thermoplastic employed, so that this final mean temperature is compatible with the subsequent orientation treatment.

However, taking into account the high cycle speeds of the production of the preforms, it can happen, particularly when working with relatively thick tubular parisons, that the mould cooling proves insufficient for the preforms to be able finally to be at a sufficiently low mean temperature to allow efficient subsequent orientation.

In order to increase the efficiency of cooling during the moulding of such preforms it is possible to provide, where necessary, that at the end of blowing the preforms are flushed internally with a very cold fluid such as let-down liquid nitrogen injected through the hollow needle.

However, this technique has proved rather inefficient, bearing in mind the low volume of the preform. Furthermore, if this method is used, the internal cooling is confined to the false neck zone and there is a danger that the subsequent removal of the neck can become more erratic.

To finish off the cooling of the preforms where necessary, the applicant company has found, and this is one of the aspects of her invention, that.it is preferable - 22 £2S 48 to resort to Internal flushing of the preforms with a cold fluid after removing the false necks.

This result can be achieved by inserting into the preforms, from which the necks have been removed, nozzles connected to a source of a very cold fluid such as let-down liquid nitrogen. 3y varying the. speed of introduction and/or of withdrawal of the nozzles and the distance to which the nozzles are inserted, it is furthermore possible to establish a temperature gradient along the axis of the preforms, which can prove beneficial in certain cases.

This subsequent cooling operation can advantageously be carried out on a circular carousel such as is shown schematically at 8 in Figure 1, the carousel being driven by the preform transfer chain or by the same motor as the ]5 blowing machines. In that case, the movement of the •cooling nozzles mounted on the carousel can be controlled by fixed cams.

Where desired, it is also possible to provide cooling of the external wall by blowing a cold fluid over it.

After having passed through the deflashing device and, where relevant, through the device for cooling by internal flushing, the preforms supported by the endless transfer chain 4 travel through a thermal, conditioning chamber 6 kept at the chosen temperature for carrying out the final blowing or at a temperature slightly below or slightly above this value. In practice, the temperature of the chamber is regulated by trial and error so that the preforms which leave this chamber are at the optimum tempera- 23 9 40 ture for orientation and. that their temperature is practically identical at every point of their thickness.

On issuing from this oven, the preforms are introduced into ihe final blowing moulds mounted on the second rotary carrier, which may be arranged in any desired way.

This latter carrier preferably revolves about a vertical axis hnd supports moulding units consisting of two mould-halves which can be separated axially; these moulding units need not necessarily be contiguous.

The transfer of the preforms into the blowing moulds is preferably effected by means of blowing nozzles integral with the rotary carrier, which seize the preforms by their moulded neck at the instant at which their carrier with articulated jaws opens, the opening being controlled by a profiled fixed cam, and introduce them vertically into the successive final blowing moulds travelling underneath the endless transfer chain, it being possible to control these movements, for example, by fixed cams.

As has been stated, the perfect synchronisation of this transfer is ensured by the fact that,firstly, the rotary carrier of the final blowing machine is driven by the same motor as the rotary carrier of the preform blowing machine and, secondly, the endless transfer chain is driven, in the zone of the final blowing machine, by a drive device which is coupled to this machine.

In the case of the final blowing machine it is again desirable, in order that the apparatus shall function without jerkiness, that the geometry and speed of rotation should be so chosen that the linear· speed of the nozzles is equal to - 24 42b · that of the endless chain.

After each final blowing mould has been closed, the corre.qnni ing blowing nozzle effects the final moulding by blowing of the conditioned preform. κ Preferably the length of the preforms is less than that of the desired oric-r/fced hollow bodies, and the ratio of the length of 'the final hollow body to 'the length of the preform can vary between 1 and 5. In this way, the preforms are stretched both axially and radially during blowing which ]q gives them a biaxial orientation and as a result gives them excellent mechanical properties.

The blowing nozzles can advantageously be equipped with a movable central piston which ensures correct centering of the bottoms of the preforms during the final blowing. ]g After blowing and cooling, the oriented hollow bodies are removed when the blowing mould opens, and fall out under gravity.

According to a preferred variant, this operation is facilitated by withdrawing the blowing nozzle at the start of 2c the opening of the corresponding mould, so that the moulded hollow body engaged on the blowing nozzle is held by the uppershoulders of its mould and is thus disengaged from the nozzle. The disengagement from the nozzle can also be made more reliable by injecting a supplementary amount of blowing fluid during withdrawal of the nozzles and/or by imposing a supplementary travel on the centering piston and with which the nozzles are equipped.

The oriented hollow bodies released from the mould can, - 25 >2 9 40 if desired, be collected in an oven for reheating after mould release, this oven being kept at a temperature below the heat distortion point. In fact, the applicant company has found that this reheating treatment can significantly improve the stress crack resistance of the oriented hollow bodies.

Claims (18)

1. Apparatus for the continuous production of oriented hollow bodies from a thermoplastic material, which comprises: a device for the production of a continuous tubular parison from a thermoplastic material; a preform blowing unit which is fed with the continuous tubular parison and which comprises a plurality of moulds, the moulds being aligned end to end contiguously on a first rotary carrier and being adapted to produce separate preforms v/hich have a neck moulded to a predetermined final shape; a device for deflashing the neck of successive preforms; a thermal conditioning device whereby the preforms are brought to a predetermined optimum orientation temperature; a final blowing unit v/hich comprises a plurality of moulds mounted on a second rotary carrier; and a transfer device adapted to convey the preforms'from the preform blowing unit to the final blowing unit, by v/ay of the deflashing device and the thermal conditioning device; in which apparatus the said transfer device comprises an endless chain (as herein defined) provided with carriers adapted to support the preforms, after the moulding of the preform neck, below the preform neck.

2. Apparatus according to Claim ί, in which said endless chain is driven by a motor which also drives the rotary carrier of the preform blowing unit.

3. Apparatus according to Claim 1 or 2, in v/hich the final blowing unit is driven by a motor v/hich also drives the preform blowing unit.

4. Apparatus according to Claim 1, in which the preform blowing unit, the endless chain and the final blowing unit are all driven by one and the same motor.

5. Apparatus according to Claim 4, in which the endless chain is driven indirectly, drive being transmitted to it both by the preform blowing unit drive and by the final blowing unit drive.

6. Apparatus according to Claim 5, in which the chain is provided with at least one tensioning unit. - 26 £2940

7. Apparatus according to Claim 6, in which the chain is provided vzith two tensioning units, each tensioning unit being arranged to tension a respective stretch of the endless chain lying between the two drive receiving points of the chain. c

8. Apparatus according to any of Claims 1 to 7, in which the preform moulds mounted on the first rotary carrier are each equipped with a blowing device comprising a movable hollow needle which penetrates into the cavity of the respective mould, and retracting means whereby the needle is retracted after partial opening of the moulds. -jq

9. Apparatus according to Claim 8, in which each preform mould blowing device has its hollow needle attached to a control block which is movable relative to the respective mould.

10. Apparatus according to any of the preceding claims, vzhich additionally comprises a cooling device which is adapted to effect internal cooling of in -,5 successive preforms by flushing with a cooling fluid and/which the endless chain is driven by a motor which also drives the blowing units, the cooling device being disposed between the deflashing device and the thermal conditioning devi ce.

11. Apparatus according to any of the preceding claims, which additionally 20 comprises a reheating oven in which successive mouldings extracted from the moulds of the final blowing unit are reheated.

12. Apparatus according to any of the preceding claims, in which each of the carriers of the transfer device has a vertically arranged generally cylindrical preform receiving chamber which is open at the top. 25

13. Apparatus according to Claim 12, in which the preform receiving chamber of each of the carriers of the transfer device is bottomless and is defined by two pivoted jaws which can move apart.

14. Apparatus according to Claim 13, in which the moving apart of the jaws of each of the said carriers is controlled by a cam. 30

15. Apparatus according to Claim 14, in which the said cam acts on a lever which is attached to or integral with one of the jaws of the respective carriers.

16. Apparatus according to Claim 4, or any of Claims 5 to 15 when read 429 40 with Claim 4, in which the preform blowing unit, the endless chain and the final blowing unit are all driven by the said motor by way of a single rotating master shaft which is driven by the said motor.

17. Apparatus according to Claim 1, substantially as described with reference to the accompanying drawings.

18. Oriented hollow thermoplastic material bodies produced by the operation of an apparatus according to any of Claims 1