CA2714344C

CA2714344C - Compression injection moulding method and device for preforms

Info

Publication number: CA2714344C
Application number: CA2714344A
Authority: CA
Inventors: Stefan Bock
Original assignee: Netstal Maschinen AG
Current assignee: Netstal Maschinen AG
Priority date: 2008-02-21
Filing date: 2009-02-20
Publication date: 2016-06-07
Anticipated expiration: 2029-02-20
Also published as: CA2714344A1; WO2009103800A9; WO2009103800A3; CN101945747A; EP2252446A2; CN101945747B; WO2009103800A2; EP2252446B1; ES2436798T3

Abstract

The invention relates to a method and a device for the compression injection moulding of preforms (10) by means of an injection moulding machine comprising one movable and one fixed tool carrier plate (2, 5) and a mould with a plurality of mould nests or cavities (60), the movable mould half (8) being designed with cores (24) and the melt being introduced into the cavities (60) on the fixed mould-half (9) side via controlled valves. The cores (24) penetrate the mould nests or cavities (60) before completion of the melt dosage to such a depth that said mould nests are at least substantially closed to the exterior. The melt is introduced into the mould nests or cavities (60) when the moulds are not completely sealed, the valves are closed and the compression pressure is produced by means of the cores (24) by the complete closure of the moulds.

Description

¨ 1 ¨
Compression Injection Moulding Method and Device for Preforms Field of the Invention The invention relates to a compression injection moulding method for preforms by means of an injection moulding machine, one movable and one fixed tool carrier plate, and a mould with a multitude of mould nests or cavities, the movable mould half being designed with cores and the melt being introduced into the cavities on the fixed tool carrier plate side in doses via controlled valves.
The invention further relates to a device for compression injection moulding for preforms by means of an injection moulding machine comprising one movable and one fixed tool carrier plate and a mould with a multitude of mould nests or cavities, the movable mould half being designed with cores and the melt being introduced into the cavities on the fixed tool carrier plate side in doses via controlled valves.
Background of the Invention When manufacturing flat discs, particularly CDs, compression injection moulding is a prerequisite. This process involved the melt being introduced into the cavity via one mould half under relatively low pressure at a time when the mould is already partially closed. The cavity is only partially filled with melt. As soon as the melt dosage has been ¨ 2 ¨
introduced, the movable mould half is moved towards the fixed mould half, which is then filled by reducing the cavity, and then the so-called embossed printing is applied.
The production of preforms is more problematic, as these are hollow forms with a substantial linear dimension. In industrial practice, preforms are generally produced by means of a classic injection moulding method using an injection moulding machine with a horizontal axis. As an example, please refer to WO 2004 /
073953 by the applicant. That method involves the raw material being introduced into a plasticizing unit in granular form via a hopper and then processed. During the injection cycle, a valve is opened between the plasticizing screw and an injection plunger and dosages are introduced into a melt repository upstream of the injection plunger. After the mould halves are closed and the valve opened, the melt is then injected in squirts into the individual cavities of the injection mould via hot runner nozzles. The injection plunger generates sufficient hydraulic after-pressure for the required period. The preform is rapidly cooled. For example, after 14 seconds the mould halves are opened by retracting the core side of the tool and the corresponding movable mould half, and the preforms are extracted from the open mould halves.
The corresponding technology has reached a rather high state of the art today, making it possible to produce up to 200 preforms of extremely high quality in short cycle periods.
The so-called compression injection moulding process has been known for more than twenty years, at least as far as the production of thin-walled moulds is concerned.
Patent JP-620 90 210 proposes a vertically positioned moulding press for this process.
A portion of processed melt is inserted into the still-open mould halves, and then the mould halves are closed in relation to the mould's outer contours. During the next stage, a press ram designed with the complementary bottom shape of the container is inserted with a corresponding compression pressure and moulds the injection parts into their definitive form.
EP 567 870 shows a hydraulic press for the production of plastic parts via compression processes. Here, too, the machine axis and/or direction of movement of the movable ¨ 3 ¨
mould half is vertical. One metered portion of melt is inserted into the open bottom mould half at a time and the exact part shape is then produced by closing the moulds.
The closing movement and/or the speed progression of the upper mould half can be controlled via appropriate controlling methods.
JP 202 21 0808 proposes that preforms be produced with an analogous concept.
Contrary to the above-mentioned solutions, this method involves liquid melt being introduced into the open cavity in doses. Then the core forming the interior of the preform is vertically inserted with the open mould half and the mould closing simultaneously. The selected melt quantity is such that the cavities are completely filled once the mould halves have been closed. The applicant does not know whether this solution was ever successfully put into practice.
JP 2001 000 219518 offers another solution for the automated production of preforms.
Here, the core is inserted into vertical cavities before the liquid melt is introduced.
The melt is then introduced into the cavity in doses from below via a valve-controlled injection nozzle; then the core with the movable mould half is completely inserted, the mould is closed simultaneously, and compression pressure is applied. The exact dosage can be adjusted by balancing the flows between the cavity and the valve needle antechamber.
Patent applications GB 2 430 642 and GB 2 430 643 show two further solutions for the compression injection moulding of preforms involving an injection mandrel moving horizontally in the direction of the cavity. The hot melt is introduced into the cavity based on the injection cycle on the fixed mould-half side via a controllable injection valve. The solution assumes several plates which can be moved in relation to the open side of the cavity. One movable plate with the cores and one plate with neck rings that can be adjusted in relation to the plate with cores are suggested. The plate with the cavities is designed ¨ 4 ¨
with a sealing contact to a cylindrical outer section of the cores. The suggested solution is to provide means by which the relative speed between the cores and cavities during the phase in which the core nears the cavity can be set as a function of the distance between the cores and cavities. It is assumed that it is not enough if only the pressure is regulated. During the injection phase, the cores can be pushed back by the injection pressure. The disadvantage of this solution is the complex design with several movable plates, while the concept is only suitable for a small number of cavities. The GB patent application 2 430 642 suggests a closing plate that can be moved independently of the cores. The closing plate allows the cores to be moved in relation to the cavities.
Description of the Invention The underlying task of this invention is to search for solutions that allow the production of large quantities of preforms in one cycle using the compression injection moulding method, with reduced cycle times and improved dosage accuracy, as well as reduced energy consumption.
The compression injection moulding method according to the invention is characterized in that a pre-dosed melt quantity is prepared for every injection in an individual dosage antechamber preceding each individual mould nest or cavity, with the pre-dosed melt quantity being simultaneously dosed into all mould nests.
The device according to the invention is characterized in that a dosage antechamber is provided before each mould nest or cavity for cyclical preparation and simultaneous insertion of a pre-dosed melt quantity into each individual mould nest or cavity.
The inventor has recognized that the melt dosing phase cannot be transferred to pressure moulding by the solutions of the current state of the art with respect to preform ¨ 5 ¨
production. In classic injection moulding, the plasticizing screw feeds in more melt during the after-pressure phase. With pressure moulding, the connection between the plasticizing cylinder or extruder and the mould nests is closed and the dosage is stopped during the pressure phase, i.e., the actual pressure moulding, thus making a dosage correction possible only in a very small scope.
The inventor has also recognized that high productivity was not possible with the compression injection moulding method of the current state of the art. For example, it was impossible to produce 200 preforms with cycle times of 8 to 15 seconds.
The new invention assumes that:
= melt is first prepared in a pre-dosed quantity for each individual mould nest;
= the mould nests are at least essentially closed to the exterior prior to dosing, and that the cores are arranged in a filling or dosing position;
= that a pre-dosed melt quantity is introduced into the cavity in this position as an annular flow, preferably until the cavity is completely filled;
= and that the compression pressure is produced by means of the cores, preferably by the closure of the moulds.
With the new invention, the actual injection process takes place in three main phases:
= Phase 1: After the open end side of the preform is closed, the cores are inserted in a controlled dosage position, preferably to a first stop;
= Phase 2: Close mould and dose;

¨ 6 ¨
= Phase 3: Release of the feed of the cores to produce the compression pressure, preferably to a second stop.
It is not necessarily required for the cores to occupy an exact position in the dosage position. Using a control device, the cores can be moved within a filling area in such a way that the annular inflow of the melt into the cavity is optimized. For example, with the flow pressure of the melt, the core can be slightly retracted until dosage is complete. What is important is that once the dosage has been completed, the cavity is filled completely with the pre-dosed melt quantity and the cores assume a definable dosage position before the compression pressure starts. The compression pressure is established and maintained for several seconds.
It is a well-known fact that with a pressure of about 1000 bar, a hot plastic mass turns into such elastic material that, like a spring, it can be compressed by more than 10%.
Since the dosage pressure can be set at much less than that, for example 50 to 200 bar, the dosage is accordingly less influenced by the compression behaviour of the melt mass. This means that the dosage can be controlled better and thus can be brought to a higher accuracy. Another advantage is that the sealing behaviour of the cores and the cavities increases as the compression pressure rises, since on the one hand, a higher sealing pressure is applied to the exterior sealing surfaces, and on the other hand, the sealing length increases as the cores penetrate deeper. However, it is of particular crucial importance that a dosage quantity has already been prepared for each = individual mould nest before the injection cycle is started. By preparing a dosage quantity in an antechamber for every mould nest, the corresponding filling time can be reduced to a fraction according to the state of the art, which directly results in a reduced cycle time. Thanks to the much smaller pressure, energy can be saved.
The decisive advantage of the new invention is that, on the one hand, with pre-dosed quantities:

¨ 7 ¨
a) the dosage for all preforms can be brought to a higher level regarding the dosage accuracy in terms of an exact and identical dosage for each of the mould nests;
b) the dosing time can be massively reduced. This is due to the dosing quantity being prepared directly before each mould nest or cavity and the pre-dosing being prepared during the period [between] the preform extraction and the next dosing phase.
A particularly important point is that a pre-dosed identical melt quantity is introduced into each of the mould nests. This has the great advantage in that an exact final dosage can be done by means of a correction from a shrinkage compensation space.
The new invention permits a wide range of particularly advantageous embodiments.
In one aspect of the present invention, there is provided a compression injection moulding method for preforms by means of an injection moulding machine, one movable and one fixed tool carrier plate and a tool with a multitude of mould nests or cavities. The movable mould half may be designed with cores and the melt may be introduced into the cavities in doses on the side of the fixed tool carrier plate via controlled valves. For every injection shot, a pre-dosed melt quantity may be prepared inside one dosing antechamber before every individual mould nest or cavity;
and the pre-dosed melt quantity may be dosed into all mould nests simultaneously.
The closing force may generate the necessary pressure for injecting the melt into the cavities and the injection time overlaps with the closing motion.
The introduction of melt into the cavities may be controlled in an overlapping fashion with the insertive motion of the cores into the cavities.
The individual antechambers may be designed as dosing cylinders with one ejector plunger moving inside of each relative to the dose, with the ejector plungers being arranged on a shared plunger plate and being powered jointly so that the prepared melt is introduced into all mould nests or cavities simultaneously.
The dosage quantity may be partially determined by a double valve assigned to each dosing antechamber which, by means of a controlled motion, alternately opens and ¨ 7a ¨
closes an injection valve to the mould nest or cavity, on the one hand, and a valve to the entry to the dosing antechamber, on the other hand, in a cyclical fashion.
A shrinkage compensation space may be designed upstream of each dosing antechamber, with the injection valve to the mould nest remaining open at least during the first shrinkage phase, so that melt from the shrinkage compensation space can subsequently flow into each mould nest to balance out the shrinkage of the preform.
The exact dosage may be determined by a controlled linear motion of the ejector plungers in the dosing antechamber and the injection valve may be closed after the dosage has been injected.
The exact dosage of the melt may take place inside the mould nest or cavity itself, with the cores being inserted into the cavities by appropriate control means and the injection valve may be closed after the dosage process.
Prior to the melt dosage process, the neck rings may be moved towards the mould nests or cavities and the cavities may be sealed off to the outside in a ring-shaped fashion between the cavity and the neck ring.
The compression injection moulding method may include a) after the open end side of the preforms has been closed, the cores [sic] are inserted in a controlled position; and b) the tool is placed into an initial dosing or injection position and the melt is dosed in; and c) the feed motion of the cores for producing the compression pressure is released and the compression pressure is generated.
The compression injection moulding method may include a) prior to the start of the melt injection into the cavities, the cores have penetrated far enough into the cavities that the mould nests are at least essentially sealed off to the exterior and the cavity is set to a dosage position; b) the melt is dosed into the cavities while the moulds are not fully closed yet; c) the compression pressure is produced by means of the cores by the complete closure of the moulds.
The injection of melt into the cavities may be controlled in such a way that it overlaps with the insertion motion of the cores into the cavities while the cavity is in a dosage position.

¨ 7b¨

The dosage quantity can be set as a function of a selectable dosage pressure and/or the dosage volume, with the dosage pressure preferably being within a range of 50 to 200 bar, ideally within the range between 100 and 150 bar.
The melt may be compacted using a compression pressure of 200 to 600 bar and more.
The mould half with the mould nests may be positioned in a movable arrangement relative to the fixed tool carrier plate or with a distribution plate of a hot runner system for the controlled activation of the ejector plungers for the dosage.
The cores may feature a cylindrical section in the rear, so that the cylindrical section forms a sealing closure for the compression phase in a corresponding drill hole of the neck rings.
In a further aspect of the present invention, there is provided a device for the compression injection moulding of performs by means of an injection moulding machine including one movable and one fixed tool carrier plate and a mould with a multitude of mould nests or cavities, the movable mould half being designed with cores and the melt being introduced into the cavities on the fixed tool carrier plate side via controlled valves, with a dosing antechamber being designed upstream of every mould nest or cavity for the cyclical preparation and simultaneous introduction of a pre-dosed melt quantity into each individual mould nest or cavity. The cores may be powered via a form closing device in such a way that the closing force generates the necessary pressure for injecting the melt into the cavities and the closing unit is designed in such a way that the injection time overlaps with the closing motion.
A double valve may be assigned to each dosing antechamber for alternately controlling the melt supply to the dosing antechamber, on the one hand, and as an injection valve opening into the mould nest, on the other hand.
All dosing antechambers may be designed as dosing cylinders. A shared plunger plate with a corresponding number of ejector plungers can be controlled in a coordinated fashion and moved in a relative fashion.
The movable plunger plate may be an integrated component of the movable mould half.

¨ 7c¨

The mould half may include the mould nests or cavities positioned in such a way that it can be moved relative to the fixed tool carrier plate or with a distributor plate of a hot runner system.
A cushioning device - preferably adjustable - such as an oil throttle, can be provided between the mould half with the cores and the plunger plate, in such a way that both can be moved together and independently for part of the path.
The plunger plate with one ejector plunger for each dosing antechamber can be moved relative to the cavities in such a way that the melt can be introduced into all mould nests or cavities in an identical and simultaneous fashion.
Control means may determine at least an approximate mould nest dosage volume and a dosage pressure inside the mould nests or cavities.
A shrinkage compensation space may be provided upstream of each dosing antechamber.
The double valve may open and close the entry from the melt supply line to the shrinkage compensation space.
A preferred embodiment involves the injection moulding machine being designed as a horizontal machine with a horizontally movable mould half. With a horizontally positioned machine or mould nests, after the valve needle has been opened symmetrically, the first shot of melt hits the tip of the cores and is then deflected.
Depending on the contours of the core tip, a part of this melt can stick to the tip, with the advantage that this particularly sensitive part is cooled first.
The dosage quantity is prepared in an upstream dosing antechamber for each dosing process, for each shot and each mould nest. The dosage quantity is partly determined in the dosing antechamber by a double valve assigned to each mould nest, which is designed as an injection valve on one end and a feed valve on the other end of a valve needle. Via controlled movement, the injection valve is opened alternately to the mould nest or the opening to the dosing antechamber in a shrinkage compensation space while the opposite exit is closed. Furthermore, the ¨ 8 ¨
individual dosing antechambers can be designed as dosing cylinders, with a plunger plate comprising ejectors for each dosing antechamber moving relative to the dosing cylinders, so that the pre-dosed melt quantity is identical and is introduced to all mould nests simultaneously. In this case, it is possible to control the introduction of the melt into the cavities in such a way that it overlaps with the insertion movement of the cores into the cavities. Especially in the case of a servo motor or linear motor drive, the core movement can be controlled to be infinitely repeatable with maximum accuracy, regulated during the cavity filling phase, and deliberately positioned or programmed as a sequence of motions without a mechanical stop.
= The first movement of the cores proceeds to the filling or dosing position very quickly almost without resistance, preferably with an adjustable first stop between the dosing phase and the compression phase.
= The second movement for the compression pressure can be delayed, but with the maximum possible sealing force near the extended position of the knee lever to a second adjustable stop.
According to another embodiment, the movable mould half can be powered by means of a hydraulic or electric drive, particularly a linear drive or servo motor.
Furthermore, it is possible to control the introduction of the melt into the cavities in such a way that it overlaps with the insertion movement of the cores into the cavities.
The pre-dosing quantity is determined by the path of the ejectors. By using dosing cylinders and ejectors of varying diameters and lengths, great leaps can be made with respect to the dosing quantities for preforms of varying thicknesses.
According to a particularly advantageous embodiment, an additional shrinkage compensation space is provided upstream of each mould nest before the dosing antechamber, so that melt can still ¨ 9 ¨
be replenished in the mould nest during the first shrinkage phase of the preforms.
During shrinkage compensation, the entry to the shrinkage compensation space is closed by the valve.
According to another advantageous embodiment, the melt dosage can be easily corrected inside the mould nest itself. The cores are moved far enough into the cavities in a controlled manner until a pre-determinable dosage volume is set.
This requires the movable tool carrier plate being position-controlled and path-controlled for the dosing position to achieve the desired dosing space in the cavity. At a melt pressure of more than 20 bar, the mould nest can already be essentially refilled an indefinite number of times and high dosing accuracy can be achieved for the melt quantity. A high dosing pressure, such as 50 to 250 bar, preferably 100 to 200 bar, is needed to introduce the melt into the most remote hollow areas of each cavity at high speed, especially the thread part of the preforms. A quick filling process prevents premature local cooling of the melt, for example in the edge regions of the cavities.
= Contrary to the relatively low dosing pressure ¨ as a rule, less than 200 bar ¨ the compression pressure should be brought to 200 to 600 bar. For this process, the new solution especially exploits the benefits of the compression pressure. Since the primary task of a plasticizing screw is melt processing, it is a low efficiency pressure pump. By contrast, mechanical pressure generation with the core is optimal in relation to the required energy, especially if the core is powered by mould closure by means of a knee lever and if the compression phase is used near the extended position of the knee levers.
Since the melt quantity for each cavity is prepared directly before the cavity for each shot, the injection phase can be abbreviated, higher dosing accuracy achieved and energy saved.

¨ 10 ¨
Brief Description of the Drawings The invention will now be explained using several embodiment examples. Shown are:
Figure 1 a schematic overview of a state of the art injection moulding machine;
Figure 2a shows a schematic representation of the melt feed into the cavities with a dosing space and a shrinkage compensation space for the melt according to the new invention;
Figure 2b shows a second adjustable stop;
Figure 2c shows a first adjustable stop;
Figure 3a shows the tool and injection sides of a device according to the invention;
Figures 3b to 3e show four different positions of the tool and/or the mould closure of an injection moulding machine according to the invention. Figure 3b shows a starting position with open moulds. Figure 3c shows the neck rings already inserted. Figure 3d shows the end of pre-dosing, and = Figure 3e shows a situation during the compression phase;
Figures 4a to 4c show three positions during insertion of a neck ring and a core into a cavity; Figure 4a shows the neck rink and the core in retracted position;
in Figure 4b, the neck ring is already in a sealing position; in Figure 4c, the core is shown inserted in a dosing position;
Figures 5a to 5g show seven positions during an injection cycle;
Figures 6a to 6e show five positions for the dosing process with a dosing antechamber and a shrinkage compensation space upstream of each cavity;
Figures 7a to 7c show three positions for the dosing and compression phases.

¨ 11 ¨
Detailed Description of the Invention Figure 1 shows a complete state of the art injection moulding machine for producing preforms (10) with a machine bed (1) on which a fixed tool carrier plate (2), an injection unit (3), and a carrier plate (4) are arranged. A movable tool carrier plate (5) is supported on the machine bed (1) in an axially adjustable manner. The fixed tool carrier plate (2) and the carrier plate (4) are connected by four bars (6) penetrating and guiding the movable tool carrier plate (5). Between the carrier plate (4) and the movable tool carrier plate (5) is a drive unit (7) to produce the closing motion and pressure. The fixed tool carrier plate (2) and the movable tool carrier plate (5) each carry one mould half (8, 9) in which a multitude of cores (24) and cavities (60) is arranged; together, these form the mould nests for producing a corresponding number of sleeve-shaped injection mould parts. After the mould halves (8 and 9) have been opened, the sleeve-shaped injection mould parts (10) adhere to the cores (24).
The preforms (10) are still in a semi-hardened state at this time and are indicated by dashed lines. The same injection-moulded parts (10) in fully cooled condition are shown in Figure 1, top left, where they are being ejected from an after-cooling device (19). In order to achieve a better representation of the details between the opened mould halves, the upper bars (6) are shown as interrupted.
Figure 1 shows the four most important handling phases for the preforms (10) after the injection process has been completed:
"A" shows the extraction of the injection-moulded parts or preforms (10) from both mould halves (8, 9). The still semi-hardened, sleeve-shaped parts are picked up by an extraction device (11) suspended into position "A" in the space between the opened mould halves (8, 9) and lifted into position "B" (mounting device 11' in Figure 1).
"B" is the transfer position of the extraction device (11) with the preforms (10) to a transfer ¨ 12 ¨
gripper (12) ("B" in Figure 1).
"C" is the transfer of the preforms (10) from the transfer gripper (12) to an after-cooling device (19).
"D" is the ejection of the cooled and dimensionally stable preforms (10) from the after-cooling device (19).
Figure 1 shows snapshots, so to speak, of the four main steps for the handling after extraction from the mould halves (8, 9). In position "B", the sleeve-shaped preforms (10) arranged vertically on top of each other are taken over by the transfer gripper (12 or 12') and brought into a position where they are arranged horizontally next to each other according to phase "C" by swivelling the transfer device towards the arrow P.
The transfer gripper (12) comprises a mounting armature (14) pivoting around an axis (13) and supporting a mounting plate (15) arranged at a parallel distance to a carrier plate (16) for cores (24). The carrier plate (16) is adjustable to be parallel to the mounting plate (15) by means of two hydraulic devices (17 and 18) so that the sleeve-shaped injection moulded parts (10) are taken from the extraction device (11) in position "B" and can be pushed from the adjusted position "C" into the after-cooling device (19) located above. The respective transfers are done by enlarging the distance = between the mounting plate (15) and the carrier plate (16). The still semi-hardened preforms (10) finish their cooling process in the after-cooling device (19) during three to four cycles, and after the after-cooling device (19) has been moved, they are then ejected in position "D" and thrown onto a conveyor belt (20).
Figure 2a shows a particularly advantageous embodiment of the melt dosage according to Figures 6a to 6e. For this purpose, the device features a dosing antechamber (70) which is connected to a melt transfer duct (100) with an extruder according to arrow 101. Inside the dosing antechamber (70) and a melt duct (102), a valve needle (105) is provided, which opens the injection aperture (103) with the valve needle tip (104), on the one hand, and closes it on the other hand. On its right end side, the valve needle (105) features a valve body (106) ¨ 13 ¨
which seals off the melt feed in the opposite position with the valve seat (107). The valve needle (105) is activated via a plunger (108) which is controlled within a cylinder (109) by means of a pneumatic fluid (112) and valves (110 and 111) at the required intervals of the injection cycle. The pneumatic fluid (112) is shown as larger dots and the melt as smaller dots. The melt is heated by means of heating elements (113) in the melt transfer duct (100), at least inside the dosing antechamber (70).
Figure 2a shows an interplay between refilling the dosing antechamber (70) and transferring the dosing antechamber volume into the cavities (60). For this purpose, the entire assembly (114) moves right. Since the melt transfer in the cavities (60) occurs independently of the flow in the melt transfer duct (100), the time previously required for filling the cavity (60) can be saved. The amount of time saved this way can be between 1 and 4 seconds, which means an enormous increase in productivity given a total cycle time of 10 to 14 seconds, for example.
Figure 2b shows an arrangement of two adjustable wedges (88, 89) between the hot runner plate (83) and the plate (90) as a second stop. By adjusting both wedges (88, 89), the second stop can be adjusted by means of a controlled drive (91). With the second adjustable stop, the exact dosage quantity or the path of the dosing plunger (71) can be pre-set.
A first stop is designed as a hydraulic cylinder (92) and as a stop bolt (93) according to Figure 2c. Figure 2c furthermore shows a compression spring (84). The spring (84) has the function of storing the mould closure force in its respective position. With the first stop, the way for the compression phase is freed via the hydraulic cylinder (92) at the end of the dosing position.
Figure 3a shows the injection moulding tool in the start-up phase for an injection cycle. The cores (24) have been extended. The tool is in an open position. The movable tool carrier plate (5) is on the far left. Correspondingly, the neck rings (62) with the neck ring carrier plate ¨ 14 ¨
(80) are shown in a disengaged position, directly after the extraction of the preforms (10). The neck ring carrier plate (80) is supported on the movable tool carrier plate (5) and can be moved by it or perform its own driving motion via the drive unit (23). A
core carrier plate (81) is connected to the movable tool carrier plate (5) so that the cores (24) are moved directly upon closure of the moulds. The neck ring carrier plate (80) is guided on the bars (6). Accordingly, a mould nest plate (82) is also guided along the bars (6). Directly on the fixed tool carrier plate (2), a hot runner plate (83) is located, which is part of a two-part tool comprising the hot runner plate and the mould nest plate (82). These two plates can be moved relative to each other. With the appropriate relative motion, melt can be dosed into the mould nests or cavities (60), as will be explained below. For this purpose, the mould nest plate (82) can be moved by means of a drive unit supported on the movable tool carrier plate (5). The drive unit (23) pushes the mould nest plate (82) towards the hot runner plate (83) while a spring (84) is being tensed. With the tensing of the spring (84), the mould nest plate (82) is moved towards the left while the mould closure performs and opening motion, and a dosing antechamber is filled with new melt. Instead of the spring, any drive, such as a throttled hydraulic cylinder, may also be used.
The injection unit (3) comprises a plasticizing unit (31) comprising a plasticizing screw (32) and a feeding hopper (26) for the granulate supply, with the appropriate drives (35). After an injection quantity is prepared, the valve (30) is redirected, freeing the way to the cavities (60). With an ejection motion of the cylinder (28), a pre-dosed melt quantity is injected into the cavities (60) or into the dosing antechambers (70).
Figures 3b to 3e show four subsequent situations for compression injection moulding according to the new invention. Figure 3b shows the injection moulding tool at the start phase for an injection cycle.

¨ 15 ¨
Figure 3c shows a second phase of preparation for an injection cycle. The neck rings (62) have already penetrated into the entry area of the cavities (60) and seal off the corresponding exterior rim. The valve is still in a closed position.
Figure 3d shows the subsequent step of inserting the cores (24) along the path of arrow 85 into a filling or dosing position of the cores (24) inside the cavities (60). At the same time, this marks the start of the melt dosing into the cavities (60) according to arrow 86.
Figure 3e shows the compression phase. The cores (24) are pressed into the cavity (60) with filled melt along the path of arrow 84 via a compression path. The valves are already closed for this. After the compression phase has begun, a new dose is already prepared for the next injection cycle.
Figures 4a to 4c show schematic representations of three situations during the insertion of a core (24) and the neck ring (62, 62', 62") into a cavity (60).
The cavity (60) is defined by a cooling sleeve (61) in the cylindrical part. In the area of the open end side of the preform, the exterior contour, particularly the entire screw part of the preform (10) is defined by a neck ring (62). The entire interior mould of the preform (10) is formed by the core (24) (Figure 4c). The core (24) moves in a horizontal direction with the movable mould half (8). The same applies to the neck ring (62, 62', 62"), as far as the insertion motion into the cavity (60) is concerned. To release the screw part of the preform (10), the neck ring (62) has to be designed in separate parts so that both halves can be retracted at right angles to the horizontal movement, as is =
shown in Figure 4a. At the start of an injection cycle, the neck ring (62) is first closed and then brought to a sealing closure towards the cavity (60) (Figure 4b).
Finally, the core (24) moves into the cavity (60) (Figure 4c).
Figures 5a to 5g show seven situations according to the new solution with the compression injection method. Figures 5a and Sc correspond to Figures ¨ 16 ¨
4a and 4b. Figure 5c shows (in deviation from Figure 4c) the cores (24) while they are not yet completely inserted into the cavity (60). Figure 5d shows the same core position as Figure 5c; however, a dosed melt quantity (dotted area) has already been injected into the cavity (60). The compression phase is demonstrated in Figure 5e (preform shown in black). For this purpose, the core (24) is pressed completely into the position in which the preform (10) is given its final injection shape.
Figure 5f shows the core (24) already extracted, while Figure 5g shows the release of the = preform (10).
Figures 6a to 6e show a preferred embodiment in which the melt is pre-dosed just before it is injected into the cavity (60). The dosing antechamber (70) has a cylindrical shape, so that a corresponding plunger (71) can perform a displacement motion that can be pre-set, analogous to a plunger pump. By varying diameter D and length L, the volume of the dosing antechamber (70) can be enlarged and reduced.
In Figure 6a, the dosing antechamber has been filled. In Figures 6b and 6c, the melt is injected into the cavity (60). For this purpose, the valve needle (73) is lifted from the injection nozzle (103). As the valve needle (73) is lifted, the entry to the dosing antechamber (70) is closed via a rear valve lip. According to Figure 6d, the dosing antechamber (70) is sealed off entirely and the valve needle (73) is moved left and brought into a closed position. Figure 6e shows the compression phase. In this preferred embodiment, the tool's hot runner serves as a "pre-distributor" in order to fill a melt chamber which can retain the melt up to the maximum injection weight of a preform (10) directly before the corresponding needle closure nozzles provided just before each cavity (60). These chambers are integrated into the hot runner and are sealed by plungers which are connected in a floating arrangement on a movable plate together with the nozzles. The sealing needles of the hot runner are guided up to the nozzle tip by these plungers. They can seal the nozzles in the front position. In the retracted position of the valve needle (73), the dosing antechamber (70) is separated from the melt supply. This advantageous design allows a utilization of the good melt distribution of a hot runner in AMENDED PAGE (RULE 91) ¨ 17 ¨
order to fill the subsequent melt chambers with a relatively low melt pressure. The melt chambers themselves guarantee a very precise injection shot weight per cavity (60). If the melt chambers were filled during the extraction period of the preforms (10) from the previous injection, limited by adjustable stops in the plunger plate, then the sealing unit can be engaged again after being released. During the melt chambers' filling phase, they are sealed off from the cavities (60) by sealing needles despite the relative movement of the plungers.
Figure 6a shows the filling phase of the dosing antechamber (70). The injection opening (103) is closed with the valve needle tip (104). At the same time as the dosing antechamber (70) is filled, a shrinkage compensation space (75) also remains completely filled. The core (24) is already moving into a dosing position. A
shrinkage compensation space (75) is provided upstream of the dosing antechamber (70).
Figure 6b shows the start of the dosing process. The dosing antechamber (70) and the shrinkage compensation space (75) are both still full.
Figure 6c shows the actual filling phase or dosing phase of the cavity (60).
The valve needle (73) is retracted towards the right. The injection nozzle (103) is open. The filling aperture (115) is sealed with the rear valve lip (106). The plunger (71) has already been moved towards the right along the path of corresponding arrow 116 and is about to displace the melt in the dosing antechamber (70) and start dosing the cavity (60).
Figure 6d shows the shrinkage compensation phase after the compression phase.
The valve (106) is in a retracted position and seals off the filling aperture (107). The compression pressure is present both in the shrinkage compensation space (75) and in the cavity (60). Via the free connection duct (117), a compensation flow is applied, at least during the first cooling or shrinking phase of the preform (10). The shrinkage is thus compensated for by the compression-pressurized melt in the shrinkage compensation space (75).
AMENDED PAGE (RULE 91) ISA/EP

¨ 18 ¨
Figure 6e shows the situation at the end of the cooling or shrinking phase.
The valve needle tip (104) has already sealed off the injection aperture (103). The dosing antechamber (70) and the shrinkage compensation space (75) can be refilled for the next injection cycle.
The great advantage of a solution according to Figures 6a to 6e is that a pre-dosed melt quantity can already be provided again while the mould opens and closes.
This results in a time savings of 1 to 3 seconds per injection cycle. For a preform with a wall thickness of 4 mm and a weight of 25 g, one can expect a cycle time of 14 seconds given the current state of the art, with an after-pressure period of about 6 seconds and a residual cooling time of about 3 seconds. In extreme cases, shrinkage can be up to 8%. The dosing phase as such can be newly reduced to 1/2 ¨ 1 second.
Once the optimal, freely pre-selectable closing position has been achieved (Figure 6c), the injection of melt from the chambers into the cavities (60) is induced.
Exactly at that "switch-point," the closing unit has to approach a cushioning device of some kind (Figure 2b), such as a spring (84) generating a higher counter-pressure against the closing forces than it requires for injecting the melt from the melt chambers to fill the cavities (60). One option envisioned here would be hydraulic cylinders which accompany the assembly the entire distance travelled and close the valve in the desired position via displacement transducers. These cylinders could also absorb the closing motion in a short-build embodiment in order to induce the injection motion.
However, after the injection process, a release would be required in order to close the closing unit completely. When the closing unit approaches the above-mentioned cushioning device, the melt is squeezed into the cavities by means of the force gathered on the plunger plate (Figure 6a).
Once the individual plungers have reached their final positions, the cushioning device is released in order to fully close the mould with the existing closing force, as previously mentioned, and to apply pressure for the "compression moulding" to the locked-in ¨ 19 ¨
melt inside each individual cavity. The dimensions of the individual plungers or chambers should be designed in such a way that the closing force can generate the necessary pressure for injecting the melt into the cavities. Due to the now largely identical melt quantities inside the individual cavities and the remaining melt chambers, an identical melt pressure is established in all cavities during the after-pressure phase, which balances out the melt volume shrinkage caused by cooling.
With the new solution, the melt path between the dosing antechamber and the individual cavities is identical for each cavity. This is different from the hot runner plate of the state of the art. Preforms of the highest quality are shaped under optimal conditions.
Once the after-pressure period has been completed, the needles close with the transition to the cooling period. Once the cooling period has been completed, the tool is opened in the usual manner. With the opening motion of the closing unit, the refilling of the melt chambers can be simultaneously induced and the cushioning device can be retracted into its initial position, depending on its design.
The plunger plate is again pushed into a pre-adjustable position by the inflowing melt.
The closing needles are controlled in such a way that they keep the nozzles closed during the filling process in order to prevent the filling pressure from causing the melt to flow into the cavities (Figure 6e).
Once the preforms have been extracted by an extraction robot according to the state of the art, the closing unit can once again be closed to the depth of the cushioning device, which in turn induces the injection of the melt. The advantage of this injection unit (3) is that it works in every slightly modified horizontal or vertical injection moulding machine with sufficient closing forces.
The injection time overlaps with the closing motions, which reduces the cycle time. The melt can be injected into the cavities against a smaller resistance, since the cores are not in ¨20¨

their final position yet. An even melt pressure is only generated inside the cavity once the cores are pushed into their final position by the residual closing motion as an "after-pressure function."
It can be assumed that the closing forces are significantly smaller compared to the state of the art, for example, according to WO 2004 / 073953. Tests have shown a force requirement of only 5 to 10 KN/cavity. Based on this knowledge, it can be assumed that the system will work with a third of the closing force.
The closing force reduction also will not result in any disadvantages for the injection phase initiated by the closing forces; the melt chambers are so close to the cavities that the pressure requirement for the filling phase can be assumed as the lowest level of approximately 50 to 200 bar.
With the new solution, a shot-pot is generally not necessary since the melt storage is now taken over by the hot runner. Advantageously, a significantly cheaper extruder can be used in combination with a Fi-Fo melt accumulator. Basically, energy is saved with both solutions, since the injection process is no longer performed by means of a separate drive, but by using the already existing closing motion.
The plunger plate has to be designed in such a way that it can be heated by means of integrated heating cartridges. For example, these can be arranged as a sandwich design inside the plungers or heating plates. It should also be ensured that the leakage material, which is expected to occur as chips, can freely fall from the individual plungers. The cleaning process could be significantly improved with fine air ducts inside the plungers from which the leakage material could be blown out via air blasts in yet to be defined intervals. The quantity of leakage material is going to be very small anyway, due to the expected small pressures, as described above.
Moreover, ¨ 21 ¨
this quantity can also be determined by designing the gap accordingly.
However, one cannot work without any leakage material at all, since the material also serves as a lubricant.
In the case of cavity damage, a method based on the state of the art can be applied.
The nozzle needle is frozen in the "nozzle closed" position. This causes the material intended for the damaged cavity (60) in the melt chamber in the hot runner to be pushed back into the hot runner instead of the cavity (60).
Figures 7a to 7c show the dosing and compression phases. In Figure 7a, the cavity (60) is used as a dosing antechamber (70) by means of a pre-set insertion of the core (24). On the open end side of the preform (10), the cavity (60) is essentially sealed off by the neck ring (62) and the core (24). According to Figure 7b, the melt is injected into the cavity (60) using a pre-selectable melt pressure, and the valve (30) is closed at the end of the dosing process (Figure 7c). Only now does the actual compression phase begin, during which the core (24) is pressed into the cavity (60) with full closing force and the melt is compacted.
AMENDED PAGE (RULE 91)

Claims

1. A compression injection moulding method for preforms (10) by means of an injection moulding machine, one movable and one fixed tool carrier plate (2, 5) and a tool with a multitude of mould nests or cavities (60), wherein - the movable mould half (8) is designed with cores (24) and the melt is introduced into the cavities (60) in doses on the side of the fixed tool carrier plate via controlled valves;
- for every injection shot, a pre-dosed melt quantity is prepared inside one dosing antechamber (70) before every individual mould nest or cavity (60); and - the pre-dosed melt quantity being dosed into all mould nests simultaneously;

characterized in that the closing force generates the necessary pressure for injecting the melt into the cavities and the injection time overlaps with the closing motion.

2. A compression injection moulding method according to Claim 1, characterized in that the introduction of melt into the cavities is controlled in an overlapping fashion with the insertive motion of the cores into the cavities.

3. A compression injection moulding method according to Claim 1 or 2, characterized in that the individual antechambers (70) are designed as dosing cylinders with one ejector plunger moving inside of each relative to the dose, with the ejector plungers being arranged on a shared plunger plate and being powered jointly so that the prepared melt is introduced into all mould nests or cavities (60) simultaneously.

4. A compression injection moulding method according to Claim 1 to 3, characterized in that the dosage quantity is partially determined by a double valve assigned to each dosing antechamber (70), which, by means of a controlled motion, alternately opens and closes an injection valve to the mould nest or cavity (60), on the one hand, and a valve to the entry to the dosing antechamber (70), on the other hand, in a cyclical fashion.

5. A compression injection moulding method according to one of Claims 1 to 4, characterized in that a shrinkage compensation space (75) is designed upstream of each dosing antechamber (70), with the injection valve to the mould nest remaining open at least during the first shrinkage phase, so that melt from the shrinkage compensation space (75) can subsequently flow into each mould nest (60) to balance out the shrinkage of the preform (10).

6. A compression injection moulding method according to one of Claims 1 to 4, characterized in that the exact dosage is determined by a controlled linear motion of the ejector plungers in the dosing antechamber (70) and the injection valve is closed after the dosage has been injected.

7. A compression injection moulding method according to one of Claims 1 to 4, characterized in that the exact dosage of the melt takes place inside the mould nest or cavity (60) itself, with the cores (24) being inserted into the cavities (60) by appropriate control means and the injection valve being closed after the dosage process.

8. A compression injection moulding method according to one of Claims 1 to 7, characterized in that prior to the melt dosage process, the neck rings (62) are moved towards the mould nests or cavities (60) and the cavities (60) are sealed off to the outside in a ring-shaped fashion between the cavity (60) and the neck ring (62).

9. A compression injection moulding method according to one of Claims 1 to 8, characterized in that a) after the open end side of the preforms (10) has been closed, the cores (60) [sic]
are inserted in a controlled position; and b) the tool is placed into an initial dosing or injection position and the melt is dosed in; and c) the feed motion of the cores (24) for producing the compression pressure is released and the compression pressure is generated.

10. A compression injection moulding method according to Claim 1, characterized in that a) prior to the start of the melt injection into the cavities (60), the cores (24) have penetrated far enough into the cavities (60) that the mould nests are at least essentially sealed off to the exterior and the cavity (60) is set to a dosage position;
b) the melt is dosed into the cavities (60) while the moulds are not fully closed yet;
c) the compression pressure is produced by means of the cores (24) by the complete closure of the moulds.

11. A compression injection moulding method according to one of Claims 1 to 10, characterized in that the injection of melt into the cavities (60) is controlled in such a way that it overlaps with the insertion motion of the cores (24) into the cavities (60) while the cavity (60) is in a dosage position.

12. A compression injection moulding method according to one of Claims 1 to 11, characterized in that the dosage quantity can be set as a function of a selectable dosage pressure and/or the dosage volume, with the dosage pressure preferably being within a range of 50 to 200 bar, ideally within the range between 100 and 150 bar.

13. A compression injection moulding method according to one of Claims 1 to 12, characterized in that the melt is compacted using a compression pressure of 200 to 600 bar and more.

14. A compression injection moulding method according to one of Claims 1 to 13, characterized in that the mould half with the mould nests is positioned in a movable arrangement relative to the fixed tool carrier plate (2) or with a distribution plate of a hot runner system for the controlled activation of the ejector plungers for the dosage.

15. A compression injection moulding method according to one of Claims 1 to 14, characterized in that the cores (24) feature a cylindrical section in the rear, so that the cylindrical section forms a sealing closure for the compression phase in a corresponding drill hole of the neck rings (62).

16. A device for the compression injection moulding of performs (10) by means of an injection moulding machine comprising one movable and one fixed tool carrier plate (2, 5) and a mould with a multitude of mould nests or cavities (60), the movable mould half (8) being designed with cores (24) and the melt being introduced into the cavities (60) on the fixed tool carrier plate (2) side via controlled valves, with a dosing antechamber (70) being designed upstream of every mould nest or cavity (60) for the cyclical preparation and simultaneous introduction of a pre-dosed melt quantity into each individual mould nest or cavity (60), characterized in that the cores (24) are powered via a form closing device in such a way that the closing force generates the necessary pressure for injecting the melt into the cavities and the closing unit is designed in such a way that the injection time overlaps with the closing motion.

17. A device according to Claim 16, characterized in that a double valve has been assigned to each dosing antechamber (70), for alternately controlling the melt supply to the dosing antechamber (70), on the one hand, and as an injection valve opening into the mould nest (60), on the other hand.

18. A device according to Claim 16 or 17, characterized in that all dosing antechambers (70) are designed as dosing cylinders wherein a shared plunger plate with a corresponding number of ejector plungers can be controlled in a coordinated fashion and moved in a relative fashion.

19. A device according to Claim 18, characterized in that the movable plunger plate is an integrated component of the movable mould half (8).

20. A device according to Claims 16 to 19, characterized in that the mould half comprising the mould nests or cavities (60) is positioned in such a way that it can be moved relative to the fixed tool carrier plate (2) or with a distributor plate of a hot runner system.

21. A device according to one of Claims 16 to 20, characterized in that a cushioning device ¨ preferably adjustable ¨ such as an oil throttle, is provided between the mould half with the cores (24) and the plunger plate, in such a way that both can be moved together and independently for part of the path.

22. A device according to one of Claims 16 to 21, characterized in that the plunger plate with one ejector plunger for each dosing antechamber (70) can be moved relative to the cavities (60), in such a way that the melt can be introduced into all mould nests or cavities (60) in an identical and simultaneous fashion.

23. A device according to one of Claims 16 to 22, characterized in that it features control means to determine at least an approximate mould nest dosage volume and a dosage pressure inside the mould nests or cavities (60).

24. A device according to one of Claims 16 to 23, characterized in that a shrinkage compensation space (75) is provided upstream of each dosing antechamber (70).

25. A device according to Claim 24, characterized in that the double valve opens and closes the entry from the melt supply line to the shrinkage compensation space (75).