DE20310882U1 - Knob for vehicle gear lever includes core and skin in different plastics - Google Patents

Abstract

At least two casings are included in the knob molding. They cover a core providing volume. There is an outer skin. The core comprises a plastic (9), its skin being a second, different plastic (10).

Description

Description;

Dura Automotive Systems GmbH, Schießstr. 60, D-40549 Düsseldorf

Gear knob

The invention relates to a gear knob, in particular for gear levers on motor vehicles, with a core element for fastening to the gear lever and a plastic fitting designed as a molded part.

The gear knobs of gear shift levers are usually manufactured as separate parts and connected to the gear shift lever, for example, via a thread or a clamp. In many cases, such gear knobs are constructed with two shells. They have a core element, usually in the form of a sleeve, made of metal or hard plastic and a plastic sheath surrounding the core element. The core element is designed in such a way that it can be placed on the free end of a gear lever and connected to it. The plastic sheath has a certain elasticity compared to the core element. It has a good feel and can be colored in any color. The plastic sheath largely or exclusively determines the external shape of the gear knob. In many cases, it is also provided with applications on the outside, for example

with plaques showing the circuit diagram and/or the make of the vehicle, or the plastic casing is covered with leather.

To manufacture such gear knobs, a process is commonly used in the state of the art in which the core element is covered with a plastic, usually polyurethane (PUR), in a mold. The plastic casing formed in this way therefore consists of a single material. The material must meet high requirements, namely be abrasion-resistant, have a high lightfastness and be resistant to hand sweat and liquids, e.g. ethanol, benzine, windshield washer fluid or surfactants. In addition, it must not cause any fumes even when exposed to heat. Only high-quality plastic materials can meet these requirements, which are correspondingly expensive. In addition, the plastic casing must form a good adhesive bond or mechanical connection with the material of the core element.

The price of the gear knob is also determined by the cost of production. The known method requires high investment costs for machinery and also has the disadvantage that so-called "webs" form in the area of the gaps in the tool mold during the foaming process. These are thin, film-like attachments that have to be laboriously removed by hand using knives after the gear knob has been removed from the tool mold. This must be done very carefully so that the optimal

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The appearance of the gear knob is not affected.

The invention is based on the object of designing a gear knob of the type mentioned above in such a way that its manufacturing costs are considerably lower.

This object is achieved according to the invention in that the plastic casing is constructed in at least two shells with a volume-forming casing core and an outer skin that at least partially envelops the casing core on the outside, the casing core consisting of a first plastic component and the outer skin consisting of a second plastic component that differs from the first. The basic idea of the invention is therefore to construct the plastic casing in at least two shells and to use a different plastic component for the outer skin than for the casing core. This is based on the knowledge already part of the invention that the above-mentioned requirements placed on the gear knob, namely in particular abrasion resistance, light fastness, resistance to hand sweat and certain liquids, must be met by the surface of the gear knob alone, i.e. it is sufficient if these properties are provided by a plastic component that is only used to form an outer skin. The sheath core does not need to meet these requirements, so that a standard plastic component can be used for it, which is considerably cheaper than the one for

the outer skin. Since the casing core essentially forms the volume of the plastic casing, this results in considerable cost savings on the material side without having to accept a loss in quality. A further cost advantage is achieved by the fact that the coloring, which is associated with considerable costs, can be limited to the outer skin, so the first plastic component does not need to be colored.

By using a standard plastic for the first plastic component, the hardness or elasticity of the plastic coating can be adjusted over a wide range, for example in a range of 20 to 85 Shore A hardness, but also softer or harder. The hardness of the second plastic component can be adjusted according to the respective wishes and requirements and can be, for example, between 50 and 90 Shore A hardness, but also higher or lower.

It is understood that a plastic is used for the second plastic component which is more abrasion-resistant, lightfast and also more chemical-resistant than the first plastic component. A thermoplastic elastomer is suitable for the first plastic component, whereby, according to the teaching of the invention, no high demands are placed on this material. An aliphatic thermoplastic polyurethane is particularly suitable for the second plastic component, whereby

a modification should be selected that meets the above requirements.

The outer skin does not have to cover the entire surface of the plastic casing. It can be omitted where applications are to be applied later. In order to achieve good adhesion between the core element and the plastic casing, it is advisable for the outer skin to also cover the inside of the casing core, forming an inner skin, and in this way to act as an adhesion promoter between the core element and the casing core. It is particularly advantageous if the inner skin and outer skin are connected to one another via preferably radially extending webs, which also consist of the second plastic component, i.e. are formed when this component is injected. The number and thickness of these webs can be adapted to the respective requirements. By connecting the outer and inner skin and thus the core element, it is not necessary to use an adhesion-modified material for the first and second plastic components. This means there is a greater choice of materials and therefore a correspondingly greater possibility of variation in terms of degrees of hardness and feel.

If the sheathing core is in direct contact with the core element, the first plastic component should be adhesion-modified in such a way that it forms a direct adhesive bond with the core element and thus ensures that the plastic sheathing sits firmly on it.

In principle, the thickness of the outer skin can be any, but should be low in accordance with the connection's design in order to achieve the greatest possible cost-saving effect. In order to meet the requirements mentioned, a maximum thickness of 1 mm has proven to be appropriate. However, the thickness can also be greater.

The gear knob according to the invention can be manufactured by injection molding the plastic casing using at least two different plastic components in such a way that a volume-forming casing core is formed from a first plastic component and an outer skin is formed from a second plastic component that at least partially envelops the casing core on the outside in a melted bond. This process saves costs because it requires lower investment costs and no complex rework is required because no so-called "webbed skin" is created, but at most a sprue has to be removed. Even this can be avoided by using coaxial needle valve nozzles.

Injection molding can be done in several ways. For example, the sheathing core can be molded onto the core element first and then the outer skin onto the sheathing core. This can be done in two different injection molding machines, but this requires removal after the first injection molding stage and transfer to the second injection molding machine. It is more cost-effective to

if the injection molding of the plastic casing is carried out one after the other in a single mold. Two-component molds with a rotating plate are suitable for this. In order to achieve good adhesion between the core element and the plastic casing, a first plastic component with appropriate adhesion modifications can be used.

As an alternative to the above-mentioned method, the plastic casing can also be produced by means of sandwich injection molding. This can be done by first injecting the second plastic component into the mold, only partially filling the mold, and then injecting the first plastic component into the still plastic second plastic component in such a way that the second plastic component is pressed onto the outer contour of the mold and the core element to form the outer skin. This creates an outer skin of uniform thickness, with the outer skin serving as an adhesion promoter at the connection between the core element and the casing core, so that it is not necessary to use an adhesion-modified plastic component for the casing core. It is expedient if the first and second plastic components are injected via a single injection channel, which can be alternately connected to the melting devices of the two plastic components. This makes it possible to inject the second plastic component again after the first plastic component has been injected.

material component to achieve further compaction and seal the sprue.

The core element can be made of metal or of an injection-molded plastic, for example glass-fiber-reinforced polyamide 6. This can be done separately from the aforementioned processes, so that the core element is inserted into the mold as a finished part before these processes are used. However, with core elements made of plastic, it is also possible to injection-mold the core element in the same mold, e.g. a three-component injection molding machine, by immediately afterward injecting the plastic casing. In this way, the transport and insertion of the core element into the mold can be omitted, even if this requires a more complicated injection molding machine. With high quantities, this nevertheless has a cost-reducing effect.

In the drawing, the invention is illustrated using an embodiment by showing the sandwich injection molding process. Shown are:

Figure 1 shows a longitudinal section through the interval unit and the mold of an injection molding machine during injection of the second plastic component;

Figure 2 shows the representation according to Figure 1 during injection of the first plastic component into the mold;

Figure 3 shows the representation according to Figures 1 and 2 during the injection molding of the second plastic component at the end of the injection molding process;

Figure 4 shows a longitudinal section through a gear knob according to the invention and

Figure 5 shows a cross section through the gear knob according to Figure 4.

The part of an injection molding machine 1 shown in the figures consists of a mold 2 and an interval unit 3. The mold 2 has a cavity 4, which forms the mold in which the plastic coating is injected onto the core element. The interval unit 3 is attached to the mold 2. Both are connected to one another via an injection channel 5, which opens into the cavity 4. Not shown are the melting devices of the injection molding machine 1, which melt the plastic components and feed them into the interval unit 3.

The interval unit 3 is penetrated by a first feed channel 6 and a second feed channel 7. The first feed channel 6 is connected, which is not shown here, to the melting device for the first plastic component 9.

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while the second feed channel 7 - also not shown - is coupled to the melting device for the second plastic component 10. Both feed channels 6, 7 open into a changeover valve 8, the outlet of which is connected to the injection channel 5. It is pressure-controlled in such a way that it only opens towards the feed channel 6, 7 in which the higher feed pressure prevails. In this way, mixing of the two plastic components 9, 10 is impossible. The feed channels 6, 7 can be heated continuously.

Before the injection molding process begins, a previously manufactured core element, which usually has a kind of sleeve shape, is placed in the cavity 4. This is not shown here for the sake of simplicity. Then, delivery pressure is applied to the second plastic component 10, with the result that the reversing valve 8 connects the second feed channel 7 to the injection channel 5. The second plastic component 10 flows into the cavity 4 and fills it with a fixed, defined degree of filling. This situation can be seen in Figure 1.

After completion of the conveying of the second plastic component 10, conveying pressure is applied to the first plastic component 9, so that the switching valve 8 switches to the connection of the first feed channel 6 with the injection channel 5 while blocking the second feed channel 7. In this way, the first plastic component 9 is fed into the middle of the cavity 4 and thus also into the core area of the second plastic component 10 located therein.

injected and thereby displaces the still plastic second plastic component 10. This situation can be seen in Figure 2.

The first plastic component 9 forms a core which - not shown in detail here - also envelops the core element and is covered like an outer skin by the second plastic component 10. This measure fills the cavity 4 to approximately 98%.

The conveying of the first plastic component 9 is then interrupted again and the conveying of the second plastic component 10 is resumed, with the result that the pressure generated in the second feed channel 7 switches the reversing valve 8 again, so that the first feed channel 6 is blocked and the second feed channel 7 is connected to the injection channel 5. This situation is shown in Figure 3. A small amount of the second plastic component 10 is then injected into the cavity 4, which causes further compaction, with the result that the second plastic component 10 comes to rest completely on the inner contour of the cavity 4.

After cooling, the mold 2 is opened so that the finished gear knob can be removed from the cavity 4. Then only the sprue, which consists of the second plastic component remaining in the injection channel 5, needs to be removed.

Figures 4 and 5 show a typical gear knob 11 that has been manufactured using the method described above. It has a core element 12 made of hard plastic that has a blind hole 13 through which the gear knob 11 can be placed on a gear lever.

The core element 12 is surrounded by an inner skin 14 made of the second plastic component. The inner skin 14 adheres to the core element 12. The outside of the gear knob 11 is formed by an outer skin 15, which also consists of the second plastic component. The outer skin 15 and the inner skin 14 are - as can be seen from Figure 5 - connected to one another via webs 16, 17, which consist of the same plastic component, so that the inner skin 14, outer skin 15 and the webs 16 and 17 form a single plastic element.

The cavity between the inner skin 14 and the outer skin 15 is filled by a sheathing core 18 made of the first plastic component. It is divided into two segments by the webs 16, 17.

Claims (13)

1. Gear knob ( 11 ), in particular for gear levers on motor vehicles, with a core element ( 12 ) for attachment to the gear lever and a plastic casing designed as a molded part, characterized in that the plastic casing is constructed in at least two shells with a volume-forming casing core ( 18 ) and an outer skin ( 15 ) at least partially enveloping the casing core ( 18 ) on the outside, wherein the casing core ( 18 ) consists of a first plastic component ( 9 ) and the outer skin ( 15 ) consists of a second plastic component ( 10 ) which differs from the first. 2. Gear knob according to claim 1, characterized in that the first plastic component ( 9 ) has a Shore A hardness of 20 to 85. 3. Gear knob according to claim 1 or 2, characterized in that the second plastic component ( 10 ) has a Shore A hardness of 50 to 90. 4. Gear knob according to one of claims 1 to 3, characterized in that the second plastic component ( 10 ) is more abrasion-resistant and lightfast than the first plastic component ( 9 ). 5. Gear knob according to one of claims 1 to 4, characterized in that the first plastic component ( 9 ) is a thermoplastic elastomer. 6. Gear knob according to one of claims 1 to 5, characterized in that the second plastic component ( 10 ) is a thermoplastic polyurethane, in particular an aliphatic polyurethane. 7. Gear knob according to one of claims 1 to 6, characterized in that the second plastic component ( 10 ) also envelops the sheathing core ( 18 ) on the inside, forming an inner skin ( 14 ) as an adhesion promoter between the core element ( 12 ) and the sheathing core ( 18 ). 8. Gear knob according to claim 7, characterized in that the inner skin ( 14 ) and outer skin ( 15 ) are connected to one another via webs ( 16 , 17 ) which also consist of the second plastic component ( 10 ). 9. Gear knob according to claim 8, characterized in that the webs ( 16 , 17 ) extend radially. 10. Gear knob according to claim 8 or 9 , characterized in that the webs ( 16 , 17 ) divide the casing core ( 18 ). 11. Gear knob according to one of claims 1 to 10, characterized in that the second plastic component ( 10 ) has a melt connection with the sheathing core ( 18 ). 12. Gear knob according to one of claims 1 to 6 or 11, characterized in that the first plastic component ( 9 ) is adhesion-modified such that it has an adhesive connection to the core element ( 12 ). 13. Gear knob according to one of claims 1 to 12, characterized in that the outer skin ( 15 ) has a maximum thickness of 5 mm.