NO754288L - - Google Patents

Description

Apparatus for the continuous production of oriented hollow bodies of thermoplastic material

This invention relates to an apparatus for the continuous production of oriented hollow bodies from a thermoplastic material, which apparatus allows the achievement of very high productivity.

It is previously known to produce hollow bodies from a thermoplastic material which has good mechanical properties in that the expansion and final shaping of the intermediate product takes place at a temperature which causes molecular orientation. Usually, the intermediate products are used at a temperature below the crystalline melting point of the thermoplastic of which they are composed.

Several different techniques have been developed for the production on an industrial scale of oriented hollow bodies of thermoplastics. One of the most attractive techniques is that intermediate products are produced by blowing a portion of a tubular post (a tubular blank), and where the intermediate product is brought up to a suitable temperature for orientation and then placed in molds for final shaping by blowing .

An apparatus for using this technique is described

in the U.S. patent 3,767,747 belonging to Owens Illinois Glass Co.

This apparatus consists of two mold units, each of which comprises a preform and a final blow mold placed on opposite sides of an extrusion device which delivers a tubular blank. Each unit performs a reciprocating movement, so that it can place its preform under the extrusion head and then under blow nozzles which are also arranged on either side of the extrusion device.

However, taking into account the sequential movement of the mold units, the necessarily limited number of molds and the need to keep each intermediate product in its preform for a sufficient time to complete thermal treatment, this apparatus only allows the achievement of fairly low production rates.

The purpose of the invention is to provide an apparatus for the continuous production of oriented hollow bodies from thermoplastic material, starting from blow-shaped intermediate products which allow the achievement of very high production rates.

The apparatus according to the invention comprises a device for producing a continuous tubular blank of thermoplastic material, a machine for blowing preformers which is fed with the continuous tubular blank and whose forms are arranged in line end to end one after the other on a first rotating carrier make it possible to produce separate intermediate pieces (intermediate products) the neck of which is formed into the final shape, a device for deburring the neck of the intermediate pieces, a device for thermal conditioning that brings the intermediate pieces up to their optimal orientation temperature, a blow machine for final shaping comprising a number of molds arranged on another rotating carrier and a transfer device which brings the intermediate pieces from the preform blowing machine to the blow machine for final blowing, while forcing the intermediate pieces to pass the deburring device and the thermal treatment device, and the transfer device consists of an endless chain equipped with carriers arranged s such that they support the middle pieces below their necks which are already fully formed.

The preforms transported by the endless chains are mostly cylindrical in shape. Their bottom part can have any design. It can e.g. end in an edge as is the case with a toothpaste tube or it may be hemispherical, such as for test tubes or test tubes used in chemical laboratories. Their neck already has the final shape of the neck of the finished hollow body. The central part is essentially cylindrical.

The carriers comprise vertically arranged seats which are open at least in their upper part and which also have a largely cylindrical shape and preferably a somewhat larger diameter than the middle part of the preforms, so that they can grip loosely on the latter so as not to damage them. Preferably, these seats are bottomless, so that they cannot damage the bottom parts of the intermediate pieces. In this case, the intermediate pieces must be provided with a ring-shaped bead in the neck area. Such a bead is not in any way unfavorable for the intermediate pieces because it must in any case be produced on the finished hollow bodies so that these can be segregated and closed.

A particularly advantageous embodiment of the carriers is that they are formed by two jaws which can be moved apart and which are designed so that they form a bottomless cylindrical seat between them when they are in the closed position. The jaws are moved apart for easier placement of the intermediate pieces in the carriers and easier gripping of these, which is necessary for transferring the intermediate pieces to the machine for final blowing. The jaws grip the spacers. middle part. Their height has no decisive significance.

The carriers are fixed at regular intervals on an endless chain. The chain, which preferably has vertical link pins, can be easily supported, driven and controlled using gears. Furthermore, the chain allows the carriers to be placed in the correct position in relation to the various devices and machines. However, it is also possible to use other transmission devices which can perform the same functions as the endless chain, e.g. a leash

which is provided with withdrawals, entries etc.

It is clear that it is desirable that the spaces between the carriers and the speed of movement of the endless chain are chosen so that all intermediate pieces can be transferred from the preform blowing machine to the final blowing machine, while each carrier of the chain contains one of the intermediate pieces (intermediate products) between the two machines. It is therefore necessary that the two blowers and the endless chain can work at the same speed.

The intermediate pieces are sent out from the preform blowing machine at regular intervals. Whenever an intermediate piece arrives, a carrier must be ready to receive it. It is therefore necessary that the dispensing from the preforms and the movement of the carriers are completely synchronized. In order to achieve complete synchronization, it is of course necessary to correctly and accurately determine the geometry of the individual elements of the plant.

On the other hand, however, it must be possible for the carriers to pick up the intermediate pieces at different rotational speeds of the rotating carrier of the preform blowing machine. This result can advantageously be achieved by driving the endless chain from the same motor which turns the rotatable carrier of the preform blowing machine.

It is then certain that the linear movement speed of the endless chain always varies proportionally to the rotational speed of the preform blowing machine, and the endless chain can therefore perform its function correctly in relation to this machine regardless of the machine's rotational speed.

Of course, it is also required that the final blowing machine is designed so that it receives and blows the successive intermediate pieces that are transported by means of the endless chain.

The correct feeding of the end-blowing machine in relation to the endless chain requires that there must be synchronization between the endless chain's carrier movement in the zone where this feeding takes place and the movement of the devices for taking up the intermediate pieces for their introduction into the end-blowing machine.

This goal could be achieved by driving the end blower from an endless chain. However, the great inertia of the blower would require the use of an oversized endless chain. It is therefore preferred, according to the invention, to achieve this goal by driving the final blowing machine from the same motor that drives the preform blowing machine and then through suitable transmissions.

In accordance with a preferred embodiment, they are thus

two rotatable carriers of the blowing machine driven from a single motor and this motor also drives the endless chain for transferring the intermediate pieces (intermediate products). By using this procedure, it is possible to ensure correct functioning of the device and the device's capacity can be varied by means of simple adjustments, i.e. by adjusting the only drive motor.

In accordance with a preferred embodiment of the invention, the endless chain is equipped with tensioning devices and is driven indirectly and twice through each of the two blowing machines.

It has been found that if the endless transmission chain is driven directly from the engine or through only one blowing machine, it is not always possible to ensure the correct synchronization of the endless chain in relation to the machines that do not participate in driving this chain. It has therefore been found that there are periodic variations in the movement of the chain carrier in relation to that of the blowing machines. This is due in particular to the clearance that may be present <between the various moving elements of the apparatus and also to the heating cycle which acts on the endless chain when it, together with the intermediate pieces, passes the device for thermal treatment.

When proceeding in the proposed manner, the position of the carriers is controlled in relation to each of the two blowing machines. The small transient variations in the speed of the endless chain in the vicinity of the two blowers are recorded and compensated for by means of an automatic shift in the tensioning device. This avoids the risk of the chain breaking. Furthermore, it is possible to arrange contacts such as

automatically stops the engine if one of the tensioning devices exceeds a permissible displacement.

There are preferably two tensioning devices arranged on either side of the endless chain's sections between the two drive positions for the chain.

In the preferred blowing machine, it is important that the successive forms, which are placed end to end, should be arranged as coherently as possible because this machine is fed with a continuous blank and every space that separates two successive forms therefore involves a loss of material.

On the other hand, however, the molds in the end blowing machine can be separated from each other because each of them is arranged to receive an independent intermediate piece.

The apparatus according to the invention will be explained in more detail below by means of examples and with reference to the drawings, where: Fig. 1 is a schematic ground plan of the apparatus according to the invention, fig. 2 a schematic perspective view of the drive system in the device, while fig. 3 partly shows in section a fixed mold half for an intermediate piece and which also shows the control device for the hollow blowing needle. Fig. 4 and 5 are a front view respectively. plan view of a portion of the endless chain for transferring intermediate pieces and showing one of the carriers with which this chain is equipped, and fig. 6 shows in cross-section part of a fixed mold half for an intermediate piece controlled with a differently designed ejection device.

As shown in fig. 1, the apparatus according to the invention comprises a device 1 for the production of a continuous tubular blank, a first rotating carrier 2 with a horizontal axis of rotation which carries continuous intermediate forms or preforms arranged end to end for receiving the continuous tubular blank, and a mold release device 3 which pulls successive intermediate pieces or intermediates from their molds and feeds them into interconnected jaws of successive carriers arranged on an endless transfer chain 4. The latter chain 4 passes a number of successive intermediate pieces through a neck deburring device 5 and through a heat treatment chamber 6. Then the endless chain secures 4 a correct placement of the deburred and thermally treated intermediate pieces for insertion into the final blow molds which are arranged on another rotating carrier 7 with a vertical axis of rotation.

As will be described below, the apparatus can be equipped with a cooling device 8 for the intermediate pieces and which is arranged between the deburring device 5 and the heat treatment chamber, as well as. with a reheating furnace 9 which is arranged after the final blowing device 7 and arranged to receive the oriented hollow bodies which are taken out of the device 7.

The endless chain 4 is driven twice in the zone for the mold release device 3 or for the deburring device 5 and in the zone for the device 10 for transferring the intermediate pieces to the final blow molds. The endless chain 4 is also equipped with two tensioning devices 11 and 12 arranged on each of the endless chain's sections between the chain's two drive positions.

As shown more clearly in fig. 2, the mechanical operation of the various moving parts of the apparatus takes place by means of a rotating shaft 13 which is turned from a motor unit 14 with variable speed, which constitutes the only source of energy that drives the entire apparatus.

Thus, the first rotating carrier 2, which is only indicated schematically, is driven by means of its drive ring gear 15 directly from a gear wheel 16 which is fixed on the pivot shaft 13 and is in engagement with the ring gear 15.

A gear wheel 17, which is also attached to the shaft 13, drives through a chain 18 and a bevel wheel 19 the device 3 which transfers the molded spacers to the transmission chain 4.

Another gear 20 which is attached to the shaft 13, through a chain 21 and a bevel gear 22, drives the device 5 which de-grades the neck parts of the intermediate pieces.

A further gear wheel 23 is fixed on the shaft 13 and drives through a chain 24 and a gear wheel 25 an intermediate cardan shaft 26. This shaft 26 drives through a bevel gear output gear 27, gears 29,30 and 31 and chain 32 a ring gear 28, which is carried out in one with the second rotating carrier 7, and further the shaft drives the transmission chain 4, where the operation takes place through a shaft 33, gears 34 and 35, a chain 36 and a gear 37 which is in engagement with the chain 4. This is therefore the first operating station for the chain 4.

The transfer chain 4 is also operated in the area of the preform blowing unit. This driving takes place either from the deburring device 5 or from the transfer device 3 for the intermediate pieces or from both of these devices.

The path that the transmission chain 4 follows is determined by the idler gear 38, and two tensioning devices 11 and 12 are arranged on the endless chain's run between the two drive positions for the chain 4.

The location of the tensioning devices is not important as long as each of them is located on one of the runs of the chain 4 between the two drive positions (where the chain is driven). Thus, the tensioning devices 11 and 12 in fig'. 1 different positions.

The directions of rotation or movement of the drive components are shown with arrows in fig. 1.

It thus appears that the device's moving components are all driven from the single motor 14 through the shaft 13, which allows complete synchronization during operation.

Furthermore, the transfer chain 4 is operated in two places arranged in zones where the chain receives the blow-molded intermediate pieces or intermediate products and where it delivers these intermediate pieces to the final blowing machine, so that this chain is completely synchronized at all points of contact with other components in the apparatus, regardless of any tightening of the chain.

In fig. 1 and 2, various details of the apparatus are intentionally removed for clarity. These details will be discussed below.

The device 1 for extruding the continuous tubular blank, which is only shown schematically in fig. 1, does not constitute any special feature compared to previously known devices. An extruder should, however, be chosen so that its withdrawal capacity is compatible with the large production capacity of the apparatus according to the invention. Furthermore, the extrusion device can be equipped with a device for programming the wall thickness in the continuous tubular blank that is produced.

As mentioned, the first rotating carrier 2 is equipped with continuous molds arranged end to end, where the inner cavity of the molds reproduces the shape of the intermediate piece or intermediate product to be produced.

In accordance with the preferred variant shown, this carrier, which is driven from the ring gear 15, rotates at constant speed about a horizontal axis and successively guides the various forms, which are arranged along its circumference, at right angles to the tubular blank which is continuously extruded tangentially to this rotating carrier.

The preform blowing machine can be of the same type as the rotary machine for blowing hollow objects described in Gelgic patent 723 419 except that each mold only produces an intermediate piece or an intermediate product and not two intermediate pieces which are welded together at the neck portions.

The rotating carrier 2 thus consists of a series of evenly spaced arms which run radially in a plane perpendicular to a rotation axis, and where the end of each of these arms is equipped with a mold casting unit, preferably consisting of a fixed mold half which is integral with the arm and a movable mold half which is hinged to the fixed mold half. Cam guides are provided for closing the successive dies at the time when their rotary motion brings them at right angles to the continuous tubular blank delivered from the extruder, for locking the dies in the closed position, for controlling blow molding of the intermediate products which are enclosed in these forms, for releasing the forms before they are opened and for opening the freed forms, so that the produced intermediate pieces can be pulled out.

Preferably, the cavity in each form represents the shape of an intermediate piece having a closed false neck and a hemispherical bottom, as described in French patent (application 74/09 380 of 15.3.1974 belonging to the applicants) and shown in fig. 1 in the said patent application.

Devices for chamfering the bottom of the intermediate pieces can be as described in the same French patent application and can advantageously be arranged between the continuous forms with which the rotating carrier is equipped and can be controlled from cam discs, so that direct production of separate intermediate pieces with a completely chamfered halygular bottom is permitted .

The cavity in each form can thus correspond to the design as described in French patent application 74/05 461 of 14.2.1974 and more particularly as shown in fig. 1 to 5 in the application. The chamfering of the bottom of these intermediate pieces does not pose any particular problem because the bottom is in the form of a straight edge.

The diameter of the cavity of the molds and thus the diameter of the intermediate pieces produced is only slightly larger than the diameter of the original tubular blank, so that the radial stretching of this tubular blank during forming into the intermediate piece is kept at a value that is less than 20%. The stretching of the blank must not actually be prevented or limited at this point, as account must be taken of the relatively high temperature in the thermoplastic material of which the blank is made, so that stretching at this point does not produce any molecular orientation.

The intermediate piece is preferably formed by blowing using a hollow needle which is connected to a fluid source under pressure. The needle penetrates the tubular blank at a location below the desired neck, i.e. in a portion of the blank used to form a closed false neck which is then to be removed.

The hollow blowing needle is preferably arranged on a movable control block arranged on the side of the fixed mold half and the movements of this block are controlled by turning the movable carrier which carries the molds and by means of cam discs.

A preferred embodiment of this device is shown on

fig. 3.

As shown in fig. 3 is the fixed mold half 39, whose cavity 40 reproduces the shape of an intermediate piece having a hemispherical bottom, equipped with a blowing device consisting mainly of a movable hollow needle 41 with a conical base 42. This needle 41 is inserted into a seat in the control block 43, the bottom of which has a conical part corresponding to the conical needle base 42. The needle 41 is held in the bottom of the seat by means of a clamping screw 44. The end of the screw is equipped with a central channel arranged in the extension of the central channel of the needle and connected to the screw's walls through radial channels 45. Furthermore, the end portion of the clamping screw 44 has a diameter such that an annular space or chamber 46 remains between the circumference of the seat in the control block 4 3 and the circumference of the end portion of the clamping screw 4 4 . A channel 47, which is arranged in the control block 43, opens into the annular space 46. This channel 47 is connected through a control valve, not shown, to a pressure fluid source.

The control block 4 3 is placed on a carrier 4 8 which is made integral with the side wall of the fixed mold half 39, so that the control block can slide in this carrier. The movement of the control block 43 on the carrier and along a direction at right angles to the axis of the fixed mold half 39 is provided in both directions by means of a control lever which can be swung and which is placed on a carrier 49 made in one with the fixed mold half 39. One of the lever's arms 50 is equipped with a loose disc 51 and can be moved, e.g. by means of a fixed cam disc, which is not shown, when the rotating carrier, which carries the preforms, rotates, while the second arm 52 influences the position of the guide block 43 on its carrier 48. As can also be seen from the figure, the needle arranged so that it can penetrate the cavity 40 in the zone 53 which delimits the forming part for a closed false neck on the molded intermediate piece or intermediate product. The assembly method for the needle makes it possible for the needle to be changed quickly when necessary because all that is needed is to loosen the clamping screw 44 to remove the needle from the seat in the control block 43. The new needle is placed in place by simply inserting the needle into the seat, after which the clamping screw 44 is put back in place. The arrangement of the chamber 46 and the radial channels 45 brings with it the advantage that it is not necessary to have a special setting of the needle 41 in the seat.

Apart from this feature, the execution and operation of the device for blow molding the intermediate pieces is practically identical to that described in the above-mentioned Belgian patent 723 419 and it will therefore not be repeated in detail.

The release and extraction of the shaped intermediate pieces when the mold is first open preferably takes place by means of devices similar to and described in the Belgian patent 772 264. The intermediate pieces which are extracted by a joint action of the ejectors in the preforms and the gripping devices placed on however, the arms with which the form release device is equipped are not placed on a conveyor as described in the Belgian patent 772 264, but are simply transferred to the carriers by the articulated jaws placed on the endless transfer chain 4. This transfer does not represent any particular synchronization problem more, because the endless chain 4 is driven in the vicinity of the mold release device 3 which is itself driven from the turntable of the preform blowing machine. This ensures complete synchronization of the movement of the gripper elements in mold release devices in relation to the carriers equipped with the hinged jaws and arranged on the endless chain 4.

The size of the form release device, the distance between the carriers on the endless chain and the ratio of the transmission between the form release device and the endless chain are chosen so that the intermediate pieces have the same linear velocity at exactly the time when they leave the form release device and at the time when they are carried away by the endless chain. This means that the device works absolutely without shocks and jerks.

Fig. 4 and 5 show a link or segment of the endless chain which is equipped with a carrier with hinged or articulated

The carrier with the jaws 54 is placed on a plate 55 which is attached to the 4 links of the chain. The carrier has two movable jaws 5,6,57 which are pivotable about pins 58,59 attached to the plate 55. A spring 60 tries to keep the jaws in a closed position. One of the jaws 56 is equipped with a weight arm 61 equipped with a loose disc 62 for steering purposes. Furthermore, two gears 63, 64 which engage each other are arranged firmly on each jaw in the place of the pivot pins.

The opening of the hinged jaws is controlled from the control disk 62 which cooperates with a fixed profile cam, which is not shown and lies in the disk's path of movement. This cam forces the jaw 56 to swing under the action of the weight arm 61 and while it swings it causes the other jaw 57 to swing in the opposite direction through the gears 63,64. The comb is arranged so that the jaws e.g. is in the open position at the time when an intermediate piece is withdrawn from the preform blowing machine and gripped by the mold release device and so as to cause a sudden closing of the jaws as a result of the action of the spring 60 at the time when the preform is released by the mold release device.

The intermediate pieces are gripped by the arms of the mold release device immediately below the neck. When these are released from the arms, as a result of their weight, they fall into the seat formed by the wearer's jaws, which have been closed in advance. They are held in place by means of the ring-shaped bead with which their neck is equipped.

When the preforms are opened, the shaped intermediate piece must remain in the fixed mold half at all times, so that it can be taken over by the mold release device. It has been found that this requirement can easily be satisfied in a reliable manner by keeping the blowing needle 41 inserted into the cavity 40 of the fixed mold half until the moment when the mold is partially opened. In this way, the needle actually holds the intermediate piece in place in the fixed mold half.

This can be achieved e.g. in that the cam which controls the retraction of the needle 41 only acts on the weight arm 50 after the corresponding mold has been partially opened. Obviously, the blowing must be stopped in this case before the mold is opened.

This can also be done with the help of mold ejectors or mold ejectors, as described in the previously mentioned Belgian patent 723 419. In this case, the ejector is retracted in the rest position into its seat below the bottom level of the mold cavity.

Another technique that also uses ejectors is illus-

shown in fig. 6.

As shown in the figure, the ejector 65, which is in its resting position, is flush with the level of the bottom of the cavity 40 in the fixed mold half 39 and has in its upper part a cutout in the form of half of a dovetail. Thus, during blowing of the intermediate piece or intermediate product 66, part of the thermoplastic material will penetrate into the cavity 67 formed by this cut-out and during the subsequent opening of the mold will squat down in the fixed mold half 39. The extraction of the intermediate piece 66 does not represent some problem because at the time when the ejector has guided the neck of the intermediate piece into a gripper with which the mold release device is equipped, the arm supporting this gripper will release the intermediate piece from the ejector's recess.

The intermediates or intermediates released from the mold and transferred to or into the carriers with the hinged jaws 54 placed on the endless conveyor chain 4 are then passed through a deburring device which trims off their false necks.

This operation can advantageously be carried out using a deburring device based on the principle described in Belgian patent 673 9o3 of 17.12.19 65 ..

In such a device, the step or the false neck is cut off with the help of a fixed knife, while the intermediate piece is subjected to a translational movement along the knife and at the same time a turning movement about its longitudinal axis.

The translational movement can be provided by means of a rotary table equipped with loose discs with appropriate profiles and corresponding to the profile of the false neck. These intermediate pieces are thus retained by means of their necks and are forced to move through the deburring device and to rotate around themselves between two loose discs and a fixed guide with an appropriate geometric design. The rotary table can be made to rotate by means of the endless chain 4 itself at such a speed that the translational movement of the intermediate pieces is exactly equal to the linear movement of this chain. According to another variant, this turntable can be driven directly from the motor that drives the two blowing machines. In this case, the turntable can drive the endless transfer chain at a speed consistent with the rotational speed of the blowing machines. This mode of operation can be supplemented or replaced with operation provided by the form release device and in this case the latter can be disconnected from the endless chain.

The result is that the operation of the endless chain in the area of the first blowing machine can either take place through the form release device or through the deburring device or by means of other intermediate devices connected to the motor which drives the two blowing machines.

The rotary table is preferably equipped with loose discs that are profiled so that they fit the profile of the intermediate pieces' false neck, and where the fixed guide is also profiled in the same way, in order to achieve a correct position of the intermediate pieces when the degree is removed.

The spacers must be held in their carriers as they pass the deburring device. They can also be lifted slightly as they pass and no longer need to rest on their ring bead on the neck.

In this case and in order not to prevent the turning movement which the intermediate pieces have been imparted during deburring, it is clearly necessary that the intermediate pieces are not held firmly in the carriers by the hinged or articulated jaws of the endless transmission chain 4 and at least while they pass the deburring device. With this in mind, the articulated jaws are preferably designed so that in the closed position they only loosely surround the main part of the intermediate pieces, so that the latter is suspended in the jaws and held by the neck. To facilitate the turning movement of the intermediate pieces, a fixed profile cam can be arranged. so that it causes the articulated jaws to open at the time when the intermediate pieces enter the deburring device and which forces the jaws to close around the intermediate pieces at the time when these leave the deburring device. In the latter case, the retaining discs, which are arranged on the rotary table, and the fixed circular guide or guide must be profiled so that the intermediate pieces stop not only at the false neck, but also at their real neck while the deburring is in progress, so that the mold pieces remain fixed between these components also after the false neck has been completely cut off and that they can thus be picked up again by the carrier with the articulated jaws when they leave the deburring device. However, this modification is not necessary if the comb is profiled so that it recloses the jaws exactly at the time when the cutting of the false neck is complete.

During the blow molding in the forms with which the first blowing machine is equipped, the formed intermediate pieces are obviously cooled down, e.g. by circulating a cooling fluid through the front walls to enable the intermediate pieces to be released from the molds without risk of deformation. As these intermediate pieces must then be subjected to orientation treatment, the cooling during forming in the preforms must be controlled so that the intermediate pieces that are released from the preforms have an average wall temperature that is in the appropriate temperature range for the subsequent orientation treatment. The outer wall of the intermediate pieces, which is in contact with the cavity of the mold during forming, will undoubtedly be cooled more than the inner wall.

If the coolant is water at ambient temperature, the outer wall of the spacer will have a temperature of approximately 30°C when it is released from the mold, while on the inner side the wall will have a temperature close to the extrusion temperature. The result is that the intermediate piece at the time it is released from the mold has a temperature gradient along the thickness which can extend from the ambient temperature (at the outer wall) to the extrusion temperature (at the inner wall).

During the subsequent transfer of the intermediate pieces, this temperature gradient will gradually disappear and the wall of the intermediate pieces will eventually have a constant or practically constant temperature over the entire thickness.

It is clear that the cooling of the preforms must be controlled in accordance with each thermoplastic material used so that the final average temperature is compatible with the subsequent orientation treatment.

However, taking into account the high work cycle for the production of the intermediate pieces, it may happen, especially when working with relatively thick tubular blanks, that the mold cooling turns out to be insufficient for the intermediate pieces, so that these are not cooled down to a sufficiently low average temperature for subsequent effective orientation.

In order to increase the cooling efficiency during the forming of such intermediate pieces or intermediate products, it is possible to arrange where necessary means for internal flushing of the intermediate pieces at the end of the blowing with a very cold fluid, such as run-down liquid nitrogen which is injected through the hollow needle.

However, this technique has proven to be rather inefficient when you take into account the small volume of the intermediate piece. Furthermore, in the case of the use of this method, the internal cooling will be limited to the area of the false neck and there is therefore a danger that the subsequent removal of the neck may become more inaccurate.

To complete the cooling of the intermediate pieces where necessary, according to the invention it has therefore been proposed to use internal flushing of the intermediate pieces "with cold fluid after the false neck has been removed.

This can be achieved by inserting into the intermediate pieces, from which the neck has been removed, needles which are in connection with a source of very cold fluid, such as liquid nitrogen (let-down liquid nitrogen). By varying the insertion speed and/or removal of the needles as well as the extent to which the needles are inserted, it is also possible to create a temperature gradient along the axis of the intermediate pieces which can prove to be advantageous in certain cases.

This subsequent cooling operation can advantageously be carried out in or on a round carousel device 8, which is schematically indicated in fig. 1, and which is driven from the transmission chain for the intermediate pieces or from the same engine as. the blowing machines. In this case, the movement of the cooling nozzles, which are arranged on the carousel, can be controlled by means of fixed cam discs.

If desired, it is also possible to provide cooling for the outer walls by blowing cold fluid against the walls.

After the intermediate pieces have passed the deburring device and, where necessary, the internal flush cooling device, the intermediate pieces, carried by the chain 4, move through a heat treatment chamber 6 which is maintained at a specific temperature for carrying out the final blowing or at a temperature slightly below or slightly above said temperature. In practice, the temperature in the chamber is regulated by trial and error, so that the intermediate pieces leaving this chamber have the optimum temperature for orientation and that their temperature is practically the same at any point of the wall thickness.

After leaving this chamber, the intermediate pieces are fed into the final blow molds placed on the second rotating carrier, which may be arranged in any suitable manner.

The latter carrier preferably rotates about a vertical axis and supports mold units consisting of two mold halves that can be separated axially. These form units do not have to be contiguous.

The transfer of the intermediate pieces or molded products to the blow molds is preferably by means of blow nozzles which are integral with the turning carrier, which grip the intermediate pieces at the formed neck at the time when the articulated jaws of their carrier are opened and the opening is controlled by a fixed profile cam, after which the intermediate pieces are fed vertically into the successive final blow forms which move below the endless transfer chain, and where it is possible to control these movements, e.g. using fixed chambers.

As mentioned, the complete synchronization of this transmission is ensured, firstly, by the rotary carrier of the final blowing machine being driven from the same motor as the rotary carrier of the preform blowing machine and, secondly, by the endless transmission chain being driven in the area of the final blowing machine from a drive device which is interconnected with this machine.

It is also important for the final blowing machine that it must work without shocks and jerks, and the geometry and speed of the rotation must therefore be chosen so that the linear speed of the nozzles is equal to the speed of the endless chain.

After each final blow mold has been closed, final blowing takes place by the corresponding blowing nozzle blowing up the heat-treating intermediate product.

The length of the intermediate pieces is preferably smaller than that of the desired oriented hollow bodies, and the ratio between the length of the finished hollow body and the length of the intermediate piece can vary between 1 and 5. In this way, the intermediate pieces are stretched both axially and radially during blowing, which leads to a biaxial orientation of the product which in turn brings with it excellent mechanical properties.

The blowing nozzles can advantageously be equipped with a movable central piston which ensures correct centering of the bottom of the intermediate pieces during the final blowing.

After blowing and cooling, the oriented hollow bodies are removed when the blow mold is opened and fall out due to its weight.

In a preferred embodiment, this operation is facilitated by removing the blow nozzle by initiating the opening of the corresponding mold, so that the cast hollow body, which is in contact with the blow nozzle, is held by means of the upper shoulders of the mold and thereby released from the nozzle. The release from the nozzle can also be made more reliable by introducing a further amount of blowing medium during the removal of the nozzles and/or by bringing the centering piston to a further movement.

The oriented hollow bodies, which have been released from the mold, can, if desired, be collected in an oven for reheating after release from the mold, and this oven is then kept at a temperature below the heat deformation point. It has been found that this reheating treatment can significantly improve the oriented hollow bodies' resistance to stress gaps or stress cracks.

Claims (7)

1. ' Apparatus for the continuous production of oriented hollow bodies from a thermoplastic material, comprising a device for producing a continuous tubular blank from a thermoplastic material, a machine for blowing intermediate products which are fed with the continuous tubular blank and whose molds are arranged in line end-to-end contiguous on the first rotating carrier and making it possible to produce separate intermediate products whose necks are formed into final shape or final shape, a device for deburring the necks of the intermediate products, a device for thermal conditioning which brings the intermediate products to their optimum orientation temperature, a final blowing machine comprising a number of molds arranged on another rotatable support and a transfer device which brings the intermediate products from the preform blowing machine to the final blowing machine and causes them to pass successively through the deburring device and the heat conditioning device, characterized in that the preform transfer device the arrangement comprises an endless chain (4) driven from the motor (14) which drives the rotatable carrier (2) of the preform blowing machine, and which is equipped with carriers (54) arranged to support the intermediate products under their necks which have already been formed, and that the preform blowing machine and the final blowing machine (7) are driven from the same motor (14). 2. Apparatus according to claim 1, characterized in that the endless chain. (4) is driven indirectly through the preform blowing machine (2) and the final blowing machine (7). 3. Apparatus according to claim 2, characterized in that the chain (4) is equipped with tensioning devices (11,12). 4. Apparatus according to claim 3, characterized in that the tensioning devices (11,12) are two in number and are distributed over each segment of the endless chain (4) between the two drive stations for the chain. 5. Apparatus according to one of claims 1-4, characterized in that it comprises a device (8) for internal cooling of the successive intermediate products by flushing with a cold fluid, which device is operated from the transmission chain (4) or from the same motor (14) such as the blowing machines and which are placed between the device (5) for deburring the neck of the intermediate products and the heat conditioning device (6). 6. Apparatus according to claims 1-5, characterized in that it comprises a reheating furnace (9) in which the oriented hollow bodies can remain after they have been pulled from the final blow moulds'. 7. Apparatus according to one of claims 1-6, characterized in that the preform blowing machine (2), the endless chain (4) and the final blowing machine (7) are all driven from a single rotating control shaft (13) which is driven from said motor (14).