WO2001005570A1 - Method for producing complete units using internal pressure systems based on injection moulding with several components, and assemblies of said units - Google Patents

Abstract

The invention concerns a method for producing plastic objects having in particular a back draft, by injection moulding with several components. It consists in producing a first partial body (21) in a first step, then at least a second partial body (23, 24) in a second step. When the second partial body (23, 24) is being injected, a specific part of the surface of the first partial body (21), defining a cavity (29), is exposed to an incompressible fluid.

Description

Process for the production and connection of complete units using internal pressure systems in multi-component injection molding technology

The invention relates to a method for the production of at least one undercut plastic objects by multi-component injection molding according to the preamble of claim I. This is an extension of the art injection molding technology in the multi-component version by means of pneumatic and / or hydraulic back pressure systems in the mostly undercut interior of a flexible plastic molding.

As is known, the connection of several different plastic molded parts to a universal product takes place in a work tool or module via the melting or non-melting or formerly reacting or non-reacting connection or. Contact surfaces of various plastic molded parts, which are produced or assembled in several, but at least two, stations of the tool semi-automatically or fully automatically, the so-called multi-component injection molding technology.

A method of the type mentioned above or an injection molding machine for carrying out such a method is known from DE-OS 20 63 850. This known injection molding machine has two made of metal Drive piston on form devices movable relative to each other. A first colored molding compound can be injected into a first molding device for molding a preform and, after the preform has been transferred to a second molding device, a second colored molding compound can be injected into the second molding device. The known injection molding machine also has a plate-like, axially displaceable between upper and lower molds of the molding devices and over one

Gear drive rotatable molded part, which is rigidly connected to an axial adjustment axis and in which the molded parts are held after separating the molding devices. The plate-like molded part has, as a flat scraper plate on both sides, for immediate mounting of the molded parts, holding seats which, when the molding devices are closed, are part of the upper and lower molds

Form mold cavities. The adjustment axis is guided in the central drive piston and its connecting part for the one molding device. Stops are arranged for the axial stop of the stripper plate on the guide rods of the movable molding device.

EP 0 524 333 A1 discloses a method for producing a cast hollow body, in particular made of thermoplastic, by means of a hollow core made of a non-metallic material. There is a thin-walled, during the casting of the hollow body only stabilized by an inner gas support pressure against the outer casting pressure, contoured according to the shape of the hollow body

Hollow core used. After the casting compound has solidified, the thin-walled hollow mold core can remain as a lost core in the hollow body or can be removed from the hollow body by remelting or redissolving after the casting compound has solidified.

WO 84/03065 A1 describes a method for producing a hollow object from plastic material by injection molding, a core being introduced into an injection mold. The core is formed by a container which is filled with a non-compressible material. This non-compressible material is, for example, a liquid or an ice. The object is formed around the core. After injection molding, the incompressible material is removed through an opening formed in the article. The container remains in the object and forms an integral part of it.

The invention has for its object to provide a method of the type mentioned, with which it is easy and inexpensive to precisely produce at least one undercut plastic objects.

This object is achieved in a method of the type mentioned at the outset according to the features of patent claim 1. Preferred developments of the method according to the invention are specified in the subclaims.

Due to the invention described below with your claims, heavily undercut, difficult to connect, with metal parts or the like. Reinforced or general plastic parts can be connected using cost-effective multi-component or multi-color technology, since the interior of the flexible plastic part is caused by an alternating pressure from external pneumatic pressure to a hydraulic pressure that is to be held or locked after the supply (the latter can also be generated internally in the tool). or is kept pressure stable. This internal pressure using a liquid medium with precise volume metering and / or system pressure keeps the contour of the interior, so that the expected spray or. Reprinting of the molded plastic part to be connected to the flexible plastic part is compensated.

Further details and advantages result from the following description of the embodiments of the method according to the invention and their applications and implementations shown in the drawings. Show it: 1 shows a typical application, namely a metal shift lever with a sprayed-on ball sleeve, connected via C + D with an elastomer lower part rotatable in a housing with a protective sleeve connected via A + B,

FIG. 1A + connecting or retaining rings with back-molded keying or FIG. 1B anchoring,

FIG. 1 C + connecting or retaining rings with back-molded wedging or FIG. 1 D anchoring,

1C + connecting or mounting rings with pure front and 1 D side anchoring, the use or implementation of which is only possible through the invention,

FIG. 2 shows an elastomeric base body created in the first work process, which is filled with liquid in the inner cavity, which has been reduced in size by inserts, and thereby became sprayable with a different type of plastic in the second work process, i.e. in the upper area, a piston head with a rear-engaging connecting ring and in the lower area, a piston ring, which is injected or molded onto the surface in a rotationally shrinking manner and with the associated sprue channels. The mold jaws that release the external undercut move away from the viewer. The bores for pneumatics (left) and hydraulics (right) are shown in the lower area,

Figure 3 shows a half-cut area of Figure 1 in production-related

Representation with, from the side during mold closing cannula penetrating through the elastomer body, through which compressed air or liquid pressure medium enters the dense interior for the build-up of pressure and for suctioning off after the production process,

FIG. 3A shows an excerpt enlargement of FIG. 3 showing a molded connection and retaining ring with side, front and rear grip anchoring,

Figure 4 shows a half-section of Figure 1 with production-related

Representation of the pneumatic feed channel through the overmolded metal part; the necessary and not visible hydraulic feed channel must also be led through the metal part,

FIG. 5 shows a section of a production tool with a stationary core,

Scraper plate, duct system for molding on the same materials, sprue puller and hot runner nozzle tip,

Figure 6 shows a detail of a production tool with removable

Mold core, which is removed outside the tool in order to be able to run off or remove any residues of the pressure medium, two sprue systems, which allow the simultaneous injection of different plastics onto the carrier component, here e.g. three different injection molding materials,

Figure 7 is a shaping shown in the left area of the section

Inner contour sleeve (in the first work process in the same tool manufactured), which overmolded with an outer shell and which with

Support pins penetrated and is covered by molded jaws. The right-hand display area is basically to be described like the left-hand area, but without support elements. The filling medium that was pressed in via the central holes can also be seen here. The lower area specifically shows one with unsupported

Overmolding recommended internal ribbing.

The functional sequences of the printing systems are as follows: The upstream, highest possible pneumatic pressure presses the flexible plastic part against the stabilizing and sealing contour of the tool and / or, depending on the production situation, against the second article (Figures 3 to 6) or into the other one Completion processing necessary end position. Now, with the appropriate injection molding material, the injection and holding pressure etc. can begin with the best flowability.

If the above-mentioned pneumatic pressure is not sufficient, a second internal pressure must now be built up, preferably with water or emulsion or oil or easily evaporable liquids or liquid fat, which after hardening e.g. can be used as permanent lubrication (Figures 4 to 6).

After the filling and pressure-maintaining process, the liquid is squeezed out or sucked off and the completed injection-molded article can be ejected or removed from the mold as part of the normal multi-component production process not described here. It should also be mentioned that the pressure fluid as a cooling or tempering medium for the respective

Injection molding process can act. Any residues or hydraulic fluid inside the article dry in watery versions outside the tool or fly away with a special alcohol filling or have to be washed with disruptive oil become.

The entire novel manufacturing process opens up further possibilities, such as the injection molding of desired cavities (FIGS. 1 to 7), the back-pressure assisted injection molding of one or more connecting or locking rings, frames or partial strips or elements in back injection or wedging technology ( Figures 1A to 1C, 3A).

7 represents a special feature embedded in the invention, namely an inner shell made of elastomer injection-molded or externally supplied in the same tool, which can be removed after the sheathing through the plastic outer part, for reuse or for grinding in for another injection molding process.

The latter process detail (Figure 7) can also be used for other molded part productions such as curved or curved pipes, profiles etc. are used, which cannot be produced using known demolding technology.

Figure 1 shows a shift lever complex as a representative typical structural unit, i.e. Central metal part 1 with a spherical region 2 and sprayed-on plastic sleeve 3, this complete component is embedded in a housing 4, to which a flexible protective sleeve 5 with a movement cavity 9 is injection molded by means of an engaging connecting ring 6. The detail areas A to D show fastening variants which are possible by the invention and are described under FIGS. 1A to 1D. A flexible sealing component 8, which is embedded in a sliding link 10, is attached to the plastic sleeve 3 via a connecting ring 7 (see FIGS. 1C and 1 D).

The component 8 contains a cavity 11 which is used as a fat reservoir is usable, but is used as an important internal pressure space in parts production.

1A shows a sprayed-on connecting ring 6 or frame. or (not shown here) only partially, which forms a mechanically firm and extremely stable engaging counter anchor between the components 5 and 4 by means of flow bores 12 and 13. The connecting ring 6 is deeper in the area 15 than the housing area 16, so that here only a pneumatic counter-pressure can be used or can even be dispensed with entirely.

Fig. 1 B is basically like Fig. 1A, but the connecting ring has an optically better and contour-matching area 17, which makes it necessary to build up a back pressure relating to the invention in the cavity 18 in order to seal the component 5 during the filling process of the ring 6 to keep its shape.

1C shows a further variant of a sprayed-on connecting ring or frame 7, which hooks into the component 3 in a radially shrinking manner in the region 15a, but only forms a thermally melting or chemically reactive connection on the connecting surface 19 to the component 8. This means a high and effective injection and holding pressure for component 7, so that a counter pressure has to be built up via the cavity 11.

1 D is like FIG. 1 C, but with additional anchoring between component 7 and component 8 by means of a tongue and groove connection 20.

2 comprises, in part, the representation of the second station of a fully automatic 2-component production with the essential production and technology innovations relating to the invention.

The illustration shows an elastomeric base body 21, which is shown in FIG. Production station was manufactured and implemented in the second production station, which is now sprayed and connected with the completion articles 23 and 24 via the sprue system 22.

This is done as follows:

The base body 21 is encompassed by mold jaws 25, the mold cores 26 and 27 close on the plane 28, so that the base body 21 is fixed in its end position with a medium accuracy. Now, in the cavity 29, a high pneumatic pressure builds up via the bore 30, which firmly defines the base body 21 in the end position via the active surfaces P. Since the pneumatic pre-pressure in the cavity 29 is in no way sufficient to neutralize the surface forces due to extreme injection and holding pressures during the filling process of the articles 23 and 24, liquid medium is pre-metered into the cavity 29 and the bore 30 (up to the lock) and / or pressed with a slight excess pressure, the pneumatic system having an air evacuation effect through the bore 30. The hydraulic pressure now present is locked with

Refill or replenishment option, and the injection or filling process into the cavities 23 and 24 can begin.

After the holding pressure or cooling time of the molded articles 23 and 24, the pressure medium having a cooling or thermally influencing effect, the pressure medium located in the cavity 29 is sucked off via the bore 31, assisted by an auxiliary pneumatic pressure via bore 30. The tool now opens after the cooling time in all necessary levels and the completed product, consisting of 21, 23 and 24, can be ejected, a new production cycle begins.

Fig. 3 shows a half section through an elastomeric base body 8 via a connecting ring 6 connected to a plastic sleeve 3 which is partially injection molded over a metal part 1. This cut also shows a production position closed mold jaws 32. Here it can be seen that during the closing process of the slide jaw 32, a cannula 33 has penetrated through the elastomeric base body 8 in order to fill the cavity 11 with a pressure medium relating to the invention, as the basis or internal counterpressure for spraying of ring 6.

Fig. 3A shows the sprayed ring 6, which mechanically connects the articles 3 and 8, in a stable version, i.e. with hooking 15 in component 3, a filled flow bore 12 and an engaging counter anchor 14. This solid connection requires a relatively high filling and holding pressure of the plastic mass of 6, so that this is only possible through a higher back pressure from the cavity 11.

4 is basically the same as FIG. 3, but here the necessary pressure medium is brought or pressed into the inner cavity 11 via the hole 34 (the second hole is not visible) of the metal part 1.

FIG. 5 also shows a variant of FIG. 3 with corresponding deviations as follows:

On the metal part 1 is a shaft 37 which is in during the manufacturing process

Multi-component process in a fixed mandrel 35, it follows that the feed holes e.g. 34 of the internal pressure media over or through the core 35, it should be mentioned that in a possibly controlled by the tool dual operation of the pneumatics for hydraulics only one hole z. B. 34 is necessary.

In addition, it can be seen that two article areas 6 and 36 can be filled via the sprue system 22 and 39 serve as a sprue and 38 as a scraper plate. FIG. 6 represented a variant of FIG. 5, with the following additions or deviations:

The shaped core 35 is designed as an exchange or removal core, i.e. After removal from the tool, the core 35 is drawn from the completed plastic parts in a further external station with the advantage that any print media residues in the interior 11 cannot contaminate the tool when the product combination 1, 3, 6, 8 and 41 is removed ,

The mold core 35 is / is embedded for encapsulation in a socket insert 42 and is fitted with ball elements e.g. 43 locked, massive and movable locks 44 are necessary for the highest demands or loads.

The compressed air bore 30 and hydraulic bore 31 located in the core 35 are sealed between the core 35 and the plate 46 by a corresponding element 45.

Via the independent sprue systems 22 and 40, two different plastic materials for the molded parts 6 and 41 can be sprayed onto the base body 8 using the counterpressure built up in the interior 11.

Fig. 7 shows another innovation for multi-component injection molding technology and is in addition to the prescribed internal counter-pressure system. Reference is made to a flexible inner contour sleeve or molded part 47 made of plastic, which is / is overmolded or overmolded by an outer part 48 of different material. To enable the outer skin 48 to be encapsulated or overmolded, an internal counterpressure relating to the invention with the active surfaces P in the mold cavity 11 must be kept constant and constant during the production process. The cores 35 touching on the level T with the pressure feed bores 30 and 31, and the core 49 reduce the interior 11 for faster filling or suction. The mold jaws 25 lying between the nozzle side 55 and the ejector side 54 have, in the left-hand region, rigid support cores 50, or only auxiliary cores 50, which are withdrawn after the respective filling state of the plastic outer skin 48 in order to obtain a closed molded part 48.

The right area of the representation or the mold jaw 25 contains only the pure outer contour, but with a pressure-reducing ring or contour sprue 52, which is limited inwards by the insert 53. In this variant of the article it is useful, see lower section, in the inner (disposable) sleeve 47 radial stiffeners z. B. ribs 51 to be provided so as not to be extremely displaced by the injection molding mass flow.

In addition, with sufficient and independent feed bores 30 and 31, it is also possible to achieve different and -like inner chambers 11, see lower section, with differentiated pressures and pressure build-up times.

Claims

Expectations 1. A method for producing in particular at least one undercut plastic objects by multi-component injection molding, wherein in a first process step, a first partial body and in a subsequent second process step, a second or further partial body is produced, characterized in that during the injection molding of the second or further partial body, an incompressible fluid is applied to the first partial body at a defined surface section delimiting a cavity. 2. The method according to claim 1, characterized in that a liquid is used as the incompressible fluid. 3. The method according to claim 1, characterized in that a lubricant is used as the incompressible fluid. A method according to claim 1, characterized in that a cream-like substance is used as the incompressible fluid. 5. The method according to claim 1, characterized in that a powdery and / or granular as incompressible fluid Substance is used. 6. The method according to any one of claims 1 to 5, characterized in that, if necessary, a gaseous fluid under increased pressure is introduced into the cavity before the introduction of the incompressible fluid. 7. The method according to any one of claims 1 to 6, characterized in that the incompressible fluid and / or the gaseous fluid is introduced into the cavity through channels in the injection mold. 8. The method according to any one of claims 1 to 6, characterized in that the incompressible fluid and / or the gaseous fluid is introduced into the cavity through at least one rigid or replaceable inner body or through at least one inner molded part. 9. The method according to any one of claims 1 to 6, characterized in that the incompressible fluid and / or the gaseous fluid is introduced into the cavity through at least one cannula temporarily piercing the first partial body. 10.The method according to any one of claims 1 to 9, characterized in that the second part body is firmly connected to the first part body or the shaping inner body in multi-component injection molding. 11. The method according to any one of claims 1 to 9, characterized in that the first part body or a molding inner auxiliary body before the injection molding of the second part body with a release agent and that after the injection molding of the second part body, the first part body of the second Partial body is removed.