DE2261226A1 - Making thermoplastics bottle from injection moulded blank - with preadjust-ment of blank temperature throughout its length before blow moulding - Google Patents

Abstract

A method of making a hollow blown object from an injection moulded thermoplastics blank is as follows: after the blank or parison has been made, its cooling is regulated and the temperature of the blank mould, mandrel and nozzle are also regulated, in particular to compensate for the heat generated by friction in the nozzle, so that a temperature profile over the entire length of the blank is achieved which can be maintained fairly constant, esp. with fluctuations not exceeding 10 (1-2) degrees C in regular mass production.

Description

Method and device for the production of hollow bodies by inflation of preforms The invention relates on the one hand to a method for production of hollow bodies by inflating thermoplastic material by injection molding Preforms produced by an injection nozzle into a preform with a mandrel. On the other hand, the invention also relates to a device for producing Hollow bodies by inflating preforms, in particular to carry out of the method according to the invention is determined and suitable.

For various further processing purposes into end products, for example to bottles, preforms, in particular made of thermoplastic material, for example made of PVC, required and used, whereby the further processing is almost immediately, i.e. only with the interposition of preparatory steps, at the production of the preforms follows. Usually the production takes place and further processing by means of a single, appropriately designed device. Such a device then consists of a conventional injection molding device connectable preform with an injection nozzle, wherein a mandrel can be introduced into the preform is to give the preform a certain hollow shape from the start. To When it is manufactured, the preform remains on the mandrel and becomes together with it removed from the preform and fed to a further work station of the device. At this station and, if necessary, at other intermediate stations, it is first a preparatory treatment is carried out so that the final further processing to the hollow body, for example by inflation, only at a further station he follows. At this last station, one of the final forms of the desired hollow body corresponding blow mold guided around the mandrel and the preform, the inflation carried out, the blow mold carried away again and the finished hollow body thrown by Dorib.

In this production of the hollow body it is both in terms of their later usefulness as well as with regard to a reject-free production especially in the context of a series production of very considerable importance that the preforms initially produced until they are inflated to form the hollow bodies have a special temperature profile in the direction of their longitudinal axis. Outgoing from the fact that by the temperature of the heated to processing temperature Starting material, the temperature change of the plasticized material in its Injection into the preform for the preform, the environmental conditions in the vicinity of a corresponding manufacturing facility and the like by default a certain temperature profile of the preform is built up, however, is at the same time it can be seen that this temperature profile is proportionate in the context of series production can be subject to strong fluctuations. Because the influencing factors just mentioned are subject to on their part not insignificant fluctuations or changes. As each preform a certain, optimally possible temperature profile in view of its inflation must have, care must therefore be taken that this temperature profile of Preform to preform is adhered to.

For this it is necessary to start the production of the preform to be included in the structure of the temperature profile, otherwise the between Manufacturing and inflation lying treatment already very different Preforms were supplied whose piece-wise adaptation to one another is not possible were.

The invention is therefore based on the object mentioned at the beginning Process to develop and improve so that the inflation to the desired end product hollow bodies as completely identical preforms as possible are supplied with an optimal temperature profile, so that the process is trouble-free and scrap can be carried out, in particular in the form of a series or Large-scale production with a correspondingly high output rate or a correspondingly short cycle time.

According to the invention, this task is achieved in that by a Raw coordinated measures, too which cooling the preform after its manufacture in several places of its scope and soil as well as regulation the temperature of the preform, mandrel and injection nozzle and the heat input by friction in the injection nozzle include a temperature profile over the length of the preform is generated that is constant from preform to preform during series production is held.

In this way, preforms are fed to the inflator despite the aforementioned tendency of the various influencing factors, fluctuations in bring about the temperature profiling, with regard to their temperature profiling are practically identical. That means, corresponding parts of a series of preforms have almost identical temperatures. This quasi temperature constancy should be designed so well, namely due to the proposed according to the invention mutual coordination of the individual measures that the temperature differences each other corresponding locations of various preforms are less than 100C, preferably not more than 1 0C to 2 0C. This small temperature difference is insofar of particular importance, since the preforms are exposed in temperature ranges must be worked in which the elongation at break and the F-modulus strongly tmpcrturbni are.

For advantageous further development it can be provided that the intensity if necessary, each individual measure that is coordinated with one another according to the invention Measures of the length of the cycle time within which the measure is to be carried out is controlled. The advantage of this training is that in a sequence-controlled mode of operation with the method according to the invention even with above average long or short cycle times in one case only and in the other case even the desired target can be achieved in the same way as in the case of the average cycle time.

On the other hand, for further training at the same time, if necessary it is also provided that the intensity of an individual measure depends on the degree of effectiveness the previous individual measure is controlled. This makes it possible to have a To compensate for too much or too little of the previous measure.

In particular, in the context of the method according to the invention, a selective blowing of the preforms after their production with hot or cold air be carried out. On the one hand through selective inflation and on the other hand By choosing between hot and cold air, this can be done by the production. originating Temperature profile can be influenced easily, quickly and in practically any desired manner and be changed.

For the blowing, such an orientation is particularly recommended, that a possibly occurring convection compensates or its formation is prevented at all. This is particularly recommended for everyone Cases in which the parison longitudinal axis is not vertically aligned with it A constant temperature is always observed along all circumferential lines, i.e. no temperature gradient different from zero in the circumferential direction - detectable is.

Particularly recommended to prevent convection from occurring it is to blow around the preform in a helical manner, creating such an environment is created, which in any case does not allow any significant free convection.

Furthermore, within the scope of the process according to the invention, to it Further training can be provided that the thorn in Geen or direct current a coolant flows through it towards the injection direction of the plasticized material will. By the optional flow through the mandrel in one or the other weighting is a coordination of the management of the mandrel temperature with the other Yaßnahnen to achieve a certain temperature profile of the preform in its longitudinal direction and a temperature profile that is constant from preform to preform is possible. the The effectiveness of all these measures naturally depends on the minor.

On the other hand, it is recommended to further develop the Process according to the invention that the rule of the Tomperature of preform, mandrel and injection nozzle as a function of the frictional heat generated in the injection nozzle is carried out. This further training can then be used for appropriate further training still be provided that for the regulation of the temperature control of the preform, The mandrel and injection nozzle are used to inject a certain amount of the plasticized Material time is used as a measurable variable.

The last-mentioned improvement in particular is very special Advantage as it enables it; both thermometrically and mathematically koum and only with great difficulty and at the same time only approximately detectable Frictional heat in actual size in the shielding of the individual mas hahmen Achieving the desired constant temperature profile should also be included. The co-registration the heat of friction is of considerable importance because the coefficient of friction is for example PVC in the relevant range of working temperature with increasing The temperature in turn increases, so that if the frictional heat is not completely dissipated an increase in temperature would occur, leading to an increased development of Frictional heat would result.

Finally, it is recommended to improve coordination and dC it Improvement of the constancy of the desired temperature profiles so that the heat supply or

discharges at the preform, mandrel and injection nozzle continuously and can be carried out continuously regulated.

With regard to the forming a further object of the invention Device for the production of hollow bodies by inflating preforms thermoplastic material, in particular made of PVC, the invention is based on a Device with an injection molding device, an injection nozzle, a preform and a mandrel which can be introduced into this for the production of the preforms and with a around the mandrel attachable blow mold for opening the preform line.

According to the invention, this device is provided with means for monitoring or discharge to the preform, preform, Finspritzdüse and mandrel provided with regard to the effectiveness and regulation in such a way coupled with one another or coordinated with one another are that the successively to be produced in the device or to be treated further Preforms have a specific temperature profile that is constant from preform to preform can be distributed over the length of the preforms.

The advantages of this inventive design of the device and the developments of the device specified in the context of the invention are above already explained in connection with the embodiment of the method according to the invention been. With regard to the further developments of the device, to avoid repetitions refer to the corresponding subclaims, without this being referred to their more inventive Character and its meaning limited will.

In the following the invention is illustrated with reference to one in the drawing preferred embodiment of the device according to the invention explained what at the same time a more detailed explanation of the method according to the invention results.

The drawings show: FIG. 1 a schematic representation of FIG Device and FIGS. 2-4 each a schematic representation of a detail of the device.

Between one at a work station A for producing the preforms arranged preform 1, which via an injection nozzle 2 a usual ,, only in Fig. 2 illustrated injection molding device S is connected downstream, and one on one Work station B for inflating the preforms arranged blow mold from two Half-shells 3, 4, a mandrel turret 5 with several mandrels 6, 7, 8 and 9 is provided. The mandrel turret 5, the preform 1 and the blow mold 3, 4 are movable such that each individual mandrel 6,7,8 and 9 in succession to all * work stations of the device is feedable.

The following is to be stated in general for the operation of the device. In station A, plasticized material is passed through from the injection molding device the injection nozzle 2 is injected into the interior of the preform 1, in eler to the in Figure 1 shown Zcitpunkt the mandrel G is eir brought coaxially. The one on this Way produced preform remains on the mandrel 6 and will with this, together after separation of mandrel 6 and preform 1 of the next work station, e.g. C, supplied. In the course of this continuation of the mandrel 6 and get on his preform finally to the work station B, where the two-part Blow mold 3, 4 is delivered to the mandrel 6, as shown in FIG. 1 for the mandrel 8 it is shown that the preform still sitting on the mandrel 6 is approaching the desired hollow body is inflatable. On the outer circumference of the injection nozzle 2, the actual nozzle part of which is denoted by 2a, is a heating band according to FIG. 2 10 for temperature control of the injection nozzle and the injection material contained therein arranged. In the same way, there is a cooling device on the bottom 11 of the preform 1 12 arranged. The temperature or the temperature profile is determined by means of the heating band 10 the preform can be influenced by preheating the injection material; the cooling device 12 also serves the same purpose. On the other hand, the temperature respectively.

the temperature profile of the preform also through the passage of the injection material is influenced by the frictional heat generated by the nozzle part 2a. The frictional heat is understandably dependent on the time in which the Screw-piston unit 13 of the injection molding device for injecting the plasticized Material is moved from its Enteren end position to its front end position. Because in The speed of passage changes depending on the duration of this movement in the nozzle part 2a and thus the friction occurring there, the cause of the resulting Frictional heat is.

Adjustment means are also included in the device shown 14 for the heating tape 10 and the cooling device 12 and a timekeeper 15 is provided, which is in Vertindunq with the screw 'piston unit 13, and in such a way that it measures the time of the movement of this unit from its rear to to its front extreme position.

The connection of the timer 15 to the SchnecYen piston unit, 13 is shown in the drawing only as line 16 and can in practice look in such a way that a first impulse is sent to the timer via this line 15 is forwarded, namely at the moment in which the unit 13 its rear Leaves end position to initiate the injection process. Via the Leitunn 16 the Timer 15 finally supplied a second pulse at the moment in which the unit 13 reaches its front end position. The triggering of the pulses can, for example through a tear-off contact in one case and a stop contact in the other be effected.

The timer 15 is on the other hand via a line 17 with the Setting means 14 in connection, which in the usual way via lines 18 and 19 with the IIcizbnd 10 or with the cooling device 12 are in connection.

In practice it should be noted that the line 17 is, for example, the Syinbol can be for a control pulse sent by the timer 15 to the setting means 14 is forwarded. On the other hand, the line 17 can also have the symbol for a manual adjustment of the adjustment means 14 can be, which then as a function of a time indicated on the timer 15 of the movement of the screw-piston unit 13 is carried out.

This detailed description just given explains the mutual Coordination of the individual measures to achieve the desired constancy of the temperature profiles already so obvious that nothing more needs to be added.

Referring to Fig. 3, at station C of Fig. 1 and optionally on Intensive pretreatment of the other identical or similar intermediate stations Preforms produced in station A can be carried out before they are inflated to be subjected to the end product hollow bodies.

For the purpose of this pretreatment, one possible example is given in the Embodiment shown formation of the station C a two-part hollow shape 20, 21 is provided, which is arranged around the mandrel when it reaches station C. Blowing means are only shown schematically at the open end 23 of the hollow mold 20, 21 24 is provided, the tearing or cold air between the mandrel and the inner wall, as required Blow in the hollow mold 20, 21.

Preferably, as shown in the figure, for example by suitable design of the gap width, ensured that the Preform helically circulating air flow on this in the longitudinal direction acts to different degrees.

To achieve the helical blowing of the seated on the mandrel Preforms, for example, guide plates 25 can be used. on the other hand however, the blowing means 24 can instead also be appropriately inclined to the longitudinal axis of the mandrel be arranged. Of course, both are also possible at the same time. Further it is possible to blow the air through channels 26 in the Rohlformwandung in the hollow mold interior to introduce. As a result, if several channels are provided in corresponding areas inside the hollow mold, a larger stream of blown air flows around the preform than in other areas. On the other hand, the channels 26 can also be used for tapping a Partial flow of the Bln slllft can be used. By varying the slope of the guide plates 25 or the angle of attack of the blowing means 24 or the Xanc; le 26 can be the same Changeability of the brain-effect inks sity of the air flow the length of the preform can be achieved as shown by that shown in the figure Change in the gap width.

Regarding the coordination of the blown air blowing on the preforms the other individual measures are not particularly reciprocal in the drawing of the individual assemblies or elements. In this regard, only notes that for this purpose all possible comparison, follow-up, series and the like Find circuits of electrical, mechanical or combined design use can without thereby affecting the essence of the invention.

Another measure to achieve the desired Vonstand des Temperature profile that is used in the inventive coordination of the diverson individual measures is included, can be seen from Fig. 4, the structure of the florne on the example of the mandrel 6 located at station A Bomäß FiC 1 shows.

The mandrel 6 shown in Fig. 4 as a blow pin is only used in the following with regard to the measures for the temperature profile constancy in more detail described walking.

The interior of the mandrel 6 is through a manner not shown Partition 27 mounted in the mandrel turret 5 is divided into zriei coaxial channels 28 and 29. A coolant is passed through these channels 28, 29, e.g. of the arrow P, i.e. in countercurrent to the injection direction of the plasticized material, guided. The guidance of the Kühimitteis can also counter to the direction of the arrow P take place. The coolant is the channels of a symbol only shown Coolant source 30 from supplied.

via a line 31 with regard to the direction of flow the anal and throughput is controlled.

Zor control of the coolant source 30 is a control device 32, which via a line 33, a comparing circuit or the like 34 and a Line 35 with the cooling device 12, not shown in FIG. 4, in connection stands. This is how the cooling of the mandrel 6 is coordinated with the cooling the preform 1 causes.

By a different connection of the circuit 34, for example to the heating band 10 of FIG. 2 or to the Tjeizband 10 and the cooling device 12 at the same time, is a coordination of the "1) orn cooling with the heat supply to the injection nozzle 2 or with the heat supply or removal via the heating band 10 or the cooling device 12 possible.

Thus, in the illustrated preferred embodiment of the invention Device all heat movements to achieve a constant specific temperature profile coordinated or dependent on each other in terms of intensity their effect.

Claims (25)

P a t o n t a n s n r u c h e 1. Process for the production of Nohlkkörper by inflation of by Injection molding of thermoplastic material through an injection nozzle into a preform Preforms produced with a mandrel, characterized in that by a Series of coordinated frames to which cooling of the preform after its Adjustment of several Stellons of its circumference and floor as well as regulation of the temperature of the preform, mandrel and injection nozzle and the supply of heat through friction in the injection nozzle belong, a temperature profile is generated over the length of the preform, which essentially constant from preform to preform during series production is held. 2. The method according to claim 1, characterized in that the temperature from corresponding points of different preforms not more than 10 ° C, preferably not more than 1 to 20C, different from each other. 3. The method according to claim 1 or 2, characterized in that the intensity of each individual measure depending on the length of the cycle time, within which the measure is to be carried out is controlled. 4. The method according to at least one of the preceding claims, characterized characterized in that the intensity of an individual measure depends on the degree of effectiveness the previous individual measure is controlled. 5. Verfahron according to at least one of the preceding claims, thereby indicates that the preform selective after its manufacture with hot. or cold air is blown. 6. The method according to claim 5, characterized in that the air blowing is aligned so that any convection that may occur compensates bzv. is prevented. 7. The method according to claim 5 or 6, characterized in that each preform is blown around in an approximately helical shape. 8. The method according to claims 5 to 7, characterized in, that the intensity of the action of the blown air varies over the length of the preform will. 9. The method according to claim 8, characterized in that the variation the intensity of the action of the blown air on the preform by design the gap width, pitch of the guide plates, the blowing angle and / or the angle the blowing ducts is effected. 10. The method according to at least one of the preceding claims, characterized in that the mandrel is in countercurrent or cocurrent to the injection direction the plasticized material is traversed by a coolant. 11. The method according to at least one of the preceding claims, characterized in that the regulation of the temperature of the preform, mandrel and injection nozzle carried out as a function of the frictional heat generated in the injection nozzle will. 12. The method according to claim 11, characterized in that for the Regulation of the temperature control of the preform, mandrel and fuel injector needed to inject a certain amount of the plasticized material Time is used as a measured variable. 13. The method according to at least one of the preceding claims, characterized in that heat is supplied or removed at the preform, mandrel and injection nozzle can be carried out continuously and steplessly regulated. 14. Device for the production of hollow bodies by inflating thermoplastic preforms previously produced within the device Material containing an injection molding device, an injection nozzle, a preform and a mandrel which can be introduced into this for producing the preforms and a Blow mold which can be attached around the mandrel for inflating the preforms, characterized in that that the means to discharge (10, 12, 28 and 29) on the preform, on the preform (1) on the Injection nozzle (2) and on the mandrel (6, 7, 8 and 9) with regard to their effectiveness and if necessary, control manure is coupled with one another or coordinated with one another in this way are that the successively to be produced in the device and treated further Preforms have a constant temperature profile from preform to preform the length of the preforms can be given. 15. The device according to claim 14, characterized gekennzeiclmet that optionally every single means of heat supply or discharge (10, 12, 28 and 29) in terms of intensity in terms of control technology is connected to the length of the cycle time within which the individual means is active or is working. 16, device according to 2nsprucl-l 14 or 15, characterized by 1; that the individual means for heat supply or discharge (10, 12, 28 and 29) with regard to their intensity in terms of control technology the degree of intensity of another previously used remedy for wart resp. removal are included. 17. The device according to at least one of claims 14 to 16, thereby characterized in that means for selective inflation (20, 21, 24, 25 and 26) of the Preforms with hot or cold air are provided, 18. Device according to claim 17, characterized in that the blowing means (20, 21, 24, 25 and 26) such are aligned so that any convection that may occur is compensated or whose emergence is prevented at all. 19. Apparatus according to claim 17 or 18, characterized in that Means for helical blowing (20, 21, 24, 25 and 26) of the preforms are provided. 20. Apparatus according to claim 19, characterized in that means for helical blowing (20, 21, 24, 25 and 26) from an actual blowing agent (24) and a means for spiral-shaped guidance (e.g. 25) of the blown air. 21. The device according to claim 20, characterized in that the Means for helically guiding the blown air from a space around the preform TIohlform (20, 21) to be arranged bristles, although the space is already the inner wall the hollow mold (20, 21) and the preform are connected to the actual blowing means 24 is. 22. The device according to at least one of claims 14 to 21, characterized geke = azeicl-met that the thorn (6, 7, 8, 9) is two interrelated having coaxial coolant channels (28, 29), through which a I'üElmittel selectively can be passed through in cocurrent or countercurrent to the injection direction of the plasticized material is. 23. The device according to at least one of claims 14 to 22, characterized characterized in that the Itittel for heat addition or. discharge (10, 12, 28, 29) on preform (1), mandrel (6, 7, 8, 9) and injection nozzle (2) to those in the injection nozzle (2) resulting frictional heat are connected. 24. The device according to claim 23, characterized in that the Means for supplying and removing heat (10, 12, 28, 29) on the preform (1), mandrel (6, 7, 8, 9) and injection nozzle (2) in terms of control technology to a timer (15) for the Injection of a certain amount of the plasticized material takes time are connected. 25. The device according to at least one of claims 14 to 24, characterized characterized in that the smocks for heat or. discharge (10, 12, 28, 29) on preform Ci), mandrel (6, 7, 8, 9) and injection nozzle (2) working continuously and steplessly Control switch (32) are connected upstream.