LU102983B1 - Method for gluing a coil spring to a spring base - Google Patents

Abstract

Disclosed is a method for bonding a coated coil spring for a vehicle to a spring base, wherein the coil spring has an end coil portion and wherein the spring base includes a receptacle for the end coil portion of the coil spring. The method comprises the following steps: a1) applying a heat-curing adhesive to an adhesive surface of the receptacle for the first end turn region of the spring base; and/or a2) applying the thermosetting adhesive to an adhesive surface of the end turn region of the coil spring; b) joining the first end turn region of the coil spring (12) with the receptacle for the first end turn region of the spring base, so that the thermosetting adhesive (16) is located between the adhesive surface and the end turn region; c) heating the first end turn area of the coil spring (12) to a target temperature in order to also heat the adhesive (16) indirectly through the heated end turn area and thus harden it, with steps b) and c) being carried out in the specified order.

Description

200165P00LU

LU102983

Method for gluing a coil spring to a spring base

Description

The invention relates to a method for gluing a coated

Coil spring for a vehicle on a spring base.

The rolling behavior of coil springs in their working area, i.e. between the upper stop (LOA) and lower stop (LUA), creates the

Spring end coils cause a relative movement between the spring coil and

Spring pad. The relative movement creates a gap that allows dirt (stones/dust/liquids) to penetrate between the coil and the base.

Due to the movement of the spring, these dirt particles act like an abrasive paste and can destroy the paint layer and thus the corrosion protection of the spring. This results in the spring becoming damaged due to strong corrosion at the ends

Has a weak point and therefore the service life is reduced.

These disadvantages are eliminated by gluing the spring to the spring base. In the currently known solutions, the spring is glued to the

Spring underlay usually uses cold-curing adhesive systems. These are usually 2-component systems that only harden after both components have been mixed together. At room temperature, such systems usually require a few minutes to several hours to harden. With some

systems, increased curing temperatures lead to shortened curing times.

The problem is that the components are in place during the entire curing time

Position must be maintained. When curing at room temperature, racks (also known as positioning tools) must be provided in which the springs remain clamped for a few minutes or possibly up to several hours until they have completely hardened. For efficient

Large-scale production can produce several hundred such clamping devices or

Positioning tools are needed to achieve the necessary throughput.

Accordingly, there are costs for the racks and storage space. For 1

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For curing at elevated temperatures, in addition to the frames, LU102983 also requires a heating device, e.g. an oven. The curing time is shorter, but additional energy and system costs are incurred. One like this

Hardening is disclosed, for example, in WO 2019 172 327 A1.

DE 10 2011 002 06 541, EP 2 697 084 B1, EP 3 109 500 B1, EP 3 724 821 B1 describe either classic cold-curing adhesives or the type of

Hardening is not mentioned.

WO 2019 167 780 A1 discloses heating the spring for

Coating process. The residual heat is used to make the adhesive cure faster. However, this method reveals some shortcomings. First of all, it cannot be easily integrated into existing manufacturing processes. Coated springs are often pre-produced or supplied by other manufacturers, so that coating and gluing are combined with the spring base

Utilizing the residual heat of the coating process is not very practical due to the temporal and sometimes spatial separation between the coating and the gluing. In addition, the feather varnish needs some time after curing until it reaches its final strength and usage properties. Gluing directly after painting can damage the feather paint or lead to incorrect formation of the adhesive bond. Furthermore, the spring is already warmed up when it comes into contact with the adhesive. This means that the adhesive begins to harden immediately and quickly and small corrections in the position of the spring in relation to the spring base are difficult to make. Another negative effect is that the heat radiation leads to premature hardening of the adhesive surface or adhesive edge layer if the spring is already heated before it comes into contact with the adhesive. A (partially) cured skin would form on the adhesive bead, so that there would be no adhesive

Connection between feather varnish and adhesive can be made.

The object of the present invention is therefore to provide an improved

Creating a concept for gluing a coil spring onto a spring base. 2

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The task is solved by the subject matter of the independent patent claims. LU102983

Further advantageous embodiments are the subject of the dependent

Patent claims.

Embodiments show a method for gluing a coated

Coil spring (hereinafter also referred to as spring) for a vehicle on a

Spring pad. The spring is provided with a coating that protects the spring

Should protect against stone chips and corrosion. The coating can be, for example, a

Be powder coating or dip coating. The preferred coating material is a suitable plastic, in particular epoxy resin.

It can be a single coating, where the spring is first zinc phosphated and then powder coated, or a

Act double coating. Also other coatings made from other suitable ones

Coating materials are possible.

The spring base can be made of an elastic material, in particular a

Plastic, preferably made of natural or synthetic rubber (rubber), consist or have this. The spring base can be designed like a ring and extend over an angle of at least 180°, preferably at least 270° and in particular up to 360°. If the angle is less than 360°, the spring base is designed in the manner of an open ring and, for example, has the shape of a crescent at an angle of 180°. Is that

Angle at which the spring base extends around a central axis, for example 360°, can be designed as a slotted ring. A first end region of the spring base rests on the spring plate, and a second

The end region of the spring base moves with the spring coil of the spring. The

Spring pad should not be confused with that located on the vehicle

Spring plate on which the spring base rests.

The coil spring has an end turn area considered here. The

However, statements regarding the end turn area can also be transferred to the opposite (second) end turn area of the coil spring. This means that both end winding areas can be designed the same. As

End turn area is called an area of the coil spring, the 3rd

200165P00LU, for example, includes the last two turns of the coil spring or part LU102983 thereof. The spring base has a receptacle for the

End turn area of the coil spring.

The method has the following steps: al) applying a heat-curing adhesive to an adhesive surface

Recording for the first end turn area of the spring base. The

Spring pad has an adhesive surface on which the spring pad is connected to the

End turn area of the coil spring is glued. The adhesive area can

Have the shape of a circumferential recess into which the end turn area can be glued. The depression can have an approximately semicircular cross section. Additionally or alternatively, in step a2), the hot-curing adhesive can be applied to the adhesive surface of the end turn area of the

Coil spring can be applied. In step a1) and/or a2), the hot-curing adhesive is applied to the surface(s) that are to be glued later.

The adhesive is designed as an adhesive that hardens above room temperature. The adhesive can be a one-component or multi-component adhesive, for example a two-component adhesive. Suitable adhesives are, for example, 1- or 2-component reaction adhesives, such as epoxy resin or

Polyurethane adhesives. Preferably the adhesive cures above a certain point

temperature (>50°C, >75°C or >85°C) completely within a few seconds.

In a step b), the first end turn region of the coil spring is connected to the

Recording for the first end turn area of the spring base is joined together so that the hot-curing adhesive is between the adhesive surface and the

End winding area is located.

This is followed in step c) by heating the first end turn region

Coil spring to a target temperature in order to also heat the adhesive, especially indirectly, through the heated end turn area and thus 4

200165P00LU to cure. Indirect heating refers to indirect heating of the LU102983 adhesive, which does not occur directly through the energy used for heating, but through contact with another heated material, here the coil spring. The spring can be heated, for example, by induction or by means of

Radiation, for example infrared radiation, occurs, so that it is the

Heating is inductive heating or heating by radiation (hereinafter referred to as thermal irradiation).

Through inductive heating or heat irradiation the

End coil area heated very effectively and quickly so that the adhesive comes through

Heat transfer from the coil spring to the entire contact surface between

Coil spring and adhesive is heated. The heat therefore penetrates exactly to that point

Place in the adhesive where the adhesive effect is needed. Furthermore, this is done

Heating the adhesive over a large area and evenly so that the adhesive quickly hardens completely.

Inductive heating has several advantages over thermal radiation.

First, by induction, both the covered and the uncovered

Parts of the end turn area heated. This means that the end winding area is heated quickly and evenly.

Furthermore, inductive heating has many advantages over heating in an oven

Advantages. So the induction coils are much smaller than an oven that

Coil spring including spring pad and optional frame that spring pad and

The coil spring holds it in position. They also need

Induction coils for heating the spring and thus hardening it

Adhesive uses less energy than the oven and the spring heats up much faster. It should also be noted that the spring can only be heated in the oven as a whole and not just locally at the end coil areas as with inductive heating. This means that temperature limits for heating the

Spring cannot be maintained so well because the heat of the end winding areas cannot be transferred to other parts of the spring due to the uniform heating. Furthermore, an oven is more expensive to purchase and maintain than that

Induction coils. 5

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LU102983

It is self-evident to the person skilled in the art that the coil spring must have a ferromagnetic material, for example steel, in order to be able to operate by means of

Induction to be heated. The same advantages apply to heating using

Radiation, whereby the induction coils are replaced by a radiation source.

Finally, in step d), the target temperature is optionally maintained

End turn area until the hot-curing adhesive has hardened and the

Coil spring sticks to the spring base. In a further optional step e), the coil spring can be cooled, the adhesive being completely hardened after the coil spring has cooled down, in particular completely. The coil spring cools down, for example, when the energy supply to the

Heating the coil spring (see step c)) is switched off and the

Coil spring is exposed to ambient temperature.

It may be sufficient if the adhesive is not cured completely but only partially while maintaining (step d)) the target temperature. It may also be sufficient to completely forego maintaining the target temperature. It may be possible to forego holding if the value is rather high

Target temperature is used. Additionally or alternatively, it may be possible to forgo holding if the environmental conditions are slow

Cooling of the coil spring is encouraged, for example at a high temperature

Ambient temperature of the coil spring. Even without further energy supply, the residual heat in the coil spring can then be large enough to completely harden the adhesive until the coil spring has completely cooled down. Allow the adhesive to harden completely until it has completely cooled down

Coil spring is preferably the criterion for deciding whether it is necessary

Step d) to be carried out or not.

At least steps b), c) and optionally d) must be in the specified

order to be executed. Steps a1) and a2) are typically carried out

Step b). If steps a1) and a2) are carried out together, the

The order of execution of these two steps is obsolete. 6

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The idea is therefore, preferably by inductive heating of the coil spring, the 10102983

To optimize curing of the adhesive. Optimizing affects both the time and energy required for curing. This enables faster and more efficient series production with lower energy consumption.

Production is also cheaper because no oven is required for heating and fewer clamping frames are required. Finally, the system can be made more compact.

In exemplary embodiments, the heating in step c) takes place to a target temperature greater than 50 ° C, in particular greater than 75 ° C or greater than 85 ° C. At a

The temperature of the adhesive above 50°C results in a significant acceleration of the adhesive

Curing of hot-curing adhesive. From a temperature of 85°C, curing occurs more homogeneously, so that curing occurs even faster. The higher the target temperature of the coil spring, the faster the full thickness of the adhesive will be heated, starting from the area in contact with the coil spring.

In exemplary embodiments, the heating takes place in step c) to a target temperature of less than 200°C, in particular less than 150°C or less than 130°C. Although the adhesive cures faster at higher temperatures, the properties of the coil spring can change if the temperatures are too high. That's how it is

Coil spring already started, i.e. set to a specified strength. This happens at tempering temperatures of, for example, >320°C. However, this also depends on the material used for the coil spring. Will the

If the coil spring is heated again to such an extent that it reaches similar temperatures, the set strength changes and the coil spring can no longer be used for its intended purpose.

Furthermore, the coil spring is typically shot peened. By the

Shot peening creates residual compressive stresses in the coil spring. These can be broken down if the temperature is too high. This can be the case

Temperatures from around 200°C happen. 7

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A spring varnish with which the coil spring is painted can also be used on an LU102983

Temperatures from approx. 160°C to 180°C can cause damage.

It is therefore advantageous, for example, to set the target temperature in a range between 50°C and 200°C, in particular between 75°C and 150°C, between 75°C and 130°C, between 85°C and 150°C or between 85 °C and 130°C to choose.

In further exemplary embodiments, the coil spring and the

Spring pad in step b) is additionally positioned in a predetermined relative orientation to one another and this position is maintained until the adhesive has hardened

Step ¢) and optionally in step d) if this is carried out. For this purpose, the coil spring and the spring base can be inserted, in particular clamped, into a positioning tool.

In exemplary embodiments, the coil spring can be used in step c) and optionally in

Step d), if this is carried out, act on the spring base with a force that corresponds to the weight of the coil spring or the sum of the weight of the coil spring and optionally a positioning tool for adjusting the relative orientation. The weight of the positioning tool, for example, then also acts on the spring base and thus the intermediate

Spring pad and coil spring arranged adhesive if that

Positioning tool is firmly connected to the coil spring, but the spring pad in the positioning tool is arranged movably in the direction of the coil spring, for example in a guide. In other words, this is enough

Fall out of gravity so that the adhesive adheres to the coil spring and the

Spring base connects reliably.

Alternatively, in step ¢) and optionally in step d), if this is carried out, the coil spring can be tensioned onto the spring base with a force that is greater than the weight of the coil spring and optionally the

Positioning tool for adjusting relative orientation. In this case, the positioning tool can be designed to tension the coil spring and spring base and to exert a defined force. 8th

200165P00LU

This means that during the heating and curing process, the spring in the LU102983

Essentially unpressurized or subjected to a preload force. With im

Substantially pressure-free should in particular include that the spring due to its own weight and possibly the own weight of a

Positioning tool, with which the spring is aligned relative to the spring holder for the time the adhesive is hardening, is pressed against the spring holder.

In further exemplary embodiments, the spring base will be activated before step b) or if step a1) is carried out before step a1). Additionally or alternatively, the coil spring can be activated before step b) or if step a2) is carried out before step a2). By activating the

Spring underlay improves the adhesion/adhesion between adhesive and spring underlay or spring coating. In particular, the one with the adhesive in

The surface of the spring base to be brought into contact can be activated. That's how it can

Surface can be activated in the circumferential recess of the spring base, into which the spring coil of the spring is glued. Alternatively or additionally, the

Surface of the spring coil can be activated to ensure better adhesion of the

To achieve adhesive on the surface of the spring coil. The activation of the

Spring padding can be done before applying the adhesive to the spring pad or coil spring. The activation can, for example, be a chemical activation, an activation by plasma treatment or an

Activation through laser treatment or any combination thereof.

According to further exemplary embodiments, the adhesive has a layer thickness between the coil spring and the spring bases of at least 0.1 mm, in particular at least 0.5 mm. Furthermore, the adhesive can have a

Have a layer thickness between the coil spring and the spring pads of a maximum of 3.0 mm, in particular of a maximum of 1.5 mm or a maximum of 1 mm. This is preferred

Adhesive layer made with a minimum thickness that allows the fully cured adhesive (and therefore also the uncured one).

Adhesive) accommodates any displacements up to a predetermined degree and

can bridge gaps. This means that the adhesive is elastic to a certain extent 9

should be 200165P00LU. However, layers that are too thick are not advantageous because the adhesive then LU102983 does not harden or does not harden with the desired material properties.

For example, the spring base, in particular its adhesive surface,

Spacers included to ensure minimum adhesive thickness. The

Spacers can be manufactured as part of the spring base integrally with it.

For example, the spacers can be designed as knobs that are located on the adhesive surface. For example, the spring pad is in one

Manufactured using an injection molding process so that the knobs are part of the injection mold and are also injected. It is also possible for the spacers to be integrated into the adhesive. For example, the adhesive can be small solid spheres

Spacers included.

In exemplary embodiments, the adhesive (i.e. type of adhesive, layer thickness of the

Adhesive, etc.) and the target temperature are selected and coordinated with one another in such a way that maintaining the target temperature in step d) is necessary for a holding time of a maximum of 30 seconds, preferably a maximum of 20 seconds or a maximum of 10 seconds, in order to cure the adhesive, at least sufficiently . Different adhesives require different target temperatures in order to cure optimally.

The target temperature must therefore be selected depending on the adhesive used, in particular the type of adhesive and the layer thickness of the adhesive, so that the curing time mentioned is adhered to.

The holding or holding time is understood to be the phase or the time in which energy is supplied in order to keep the coil spring approximately constant at the target temperature. However, the goal is not for the spring to warm up further. After the hold time has elapsed, the energy supply is switched off. This causes the coil spring to slowly cool down.

The adhesive has cured sufficiently when the adhesive has completely hardened by the time the coil spring has completely cooled down. It should be noted that the adhesive continues to harden even below the target temperature until it falls below a minimum temperature threshold. It is therefore not absolutely necessary for the adhesive to last 10 minutes within the holding time

200165P00LU is completely cured. In this respect, sufficient curing in this LU102983 is sufficient

phase off. However, since the cooling time also depends on the

Ambient temperature dependent and the curing behavior of the adhesive cannot be completely predicted, the cooling time should be taken into account when considering

A generous buffer should preferably be provided during the curing process of the adhesive. In other words, the holding time should be chosen so that the adhesive has already completely hardened well above the minimum temperature threshold.

Further exemplary embodiments show that the adhesive is selected such that it has a greater elongation at break than the spring coating and the

Spring pad. The adhesive therefore has a certain flexibility and does not pose any problems

Predetermined breaking point between the spring base and the coil spring.

In further exemplary embodiments, the adhesive has fully cured

Condition is less hard than the spring coating. This is advantageous because the adhesive absorbs part of the energy acting on the arrangement of coil spring and spring base when under load. The load on the coil spring and spring base is therefore reduced. In particular, the load in the

Boundary layer between spring base and coil spring through the flexible

Adhesive reduced. This also reduces shear forces, which reduce wear. Under very high loads, the soft adhesive also prevents the coating of the coil spring from being damaged.

Preferred embodiments of the present invention are set forth below

explained with reference to the accompanying drawings. Show it:

Fig. 1: a schematic perspective side view of a coil spring on a spring base;

Fig. 2: a schematic detailed view of an end turn area of the

Coil spring from Fig. 1, which is glued to the spring base.

Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it should be noted that 11

200165P00LU identical, functionally identical or equivalent elements, objects and/or LU102983

Structures in the different figures are provided with the same reference numerals, so that those shown in different exemplary embodiments

Description of these elements is interchangeable or can be applied to one another.

Fig. 1 shows a schematic perspective side view of a coil spring 12 on a spring base 14. The spring base 14 is designed to be slotted. The

The end turn area of the coil spring 12 lies in a circumferential recess in the spring base 14.

Fig. 2 shows a detailed view of the end turn area or a cross section through the end turn area of the coil spring 12 from Fig. 1. Here is the

Adhesive 16 can be seen, which is arranged between the adhesive areas of the coil spring 12 and the spring base 14

Although some aspects have been described in connection with a device, it is to be understood that these aspects also represent a description of the corresponding method, so that a block or a component one

Device is also to be understood as a corresponding process step or as a feature of a process step. Analogous to this, aspects that

In connection with a or as a method step, also represents a description of a corresponding block or detail or feature of a corresponding device.

The exemplary embodiments described above represent only one

Illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and described herein

Details will be clear to other experts. Therefore, the invention is intended to be limited only by the scope of the following

Patent claims and not by the specific details that are based on the

Description and explanation of the exemplary embodiments presented herein are limited. 12

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List of reference numbers: LU102983 12 coil spring 14 spring pad 16 adhesive 13

Claims (17)

200165P00LU LU102983 patent claims 1. A method for gluing a coated coil spring (12) for a vehicle to a spring base (14), wherein the coil spring (12) has an end turn area and wherein the spring base (14) has a receptacle for the end turn area of the coil spring (12). the following steps: a1) applying a heat-curing adhesive to an adhesive surface of the receptacle for the first end turn region of the spring base; and/or a2) applying the thermosetting adhesive to an adhesive surface of the end turn region of the coil spring; b) joining the first end turn region of the coil spring (12) with the receptacle for the first end turn region of the spring base, so that the thermosetting adhesive (16) is located between the adhesive surface and the end turn region; c) heating the first end turn region of the coil spring (12) to a target temperature in order to also heat and thus harden the adhesive (16) indirectly through the heated end turn region; where steps b) and c) are carried out in the order given. 2. The method according to claim 1, wherein the heating in step c) takes place by means of induction. 3. Method according to one of the preceding claims, 14 200165P00LU wherein the coil spring (12) has a ferromagnetic material or 10102983 consists of it. 4. Method according to one of the preceding claims, wherein the heating in step c) takes place to a target temperature greater than 50°C, in particular greater than 75°C or greater than 85°C. 5. The method according to any one of the preceding claims, wherein the heating in step c) takes place to a target temperature of less than 200°C, in particular less than 150°C or less than 130°C. 6. The method according to any one of the preceding claims, wherein the coil spring (12) and spring base (14) are additionally positioned in a predetermined relative orientation to one another in step b) and this position is maintained until the adhesive has hardened in step c). 7. The method according to any one of the preceding claims, wherein in step c) the coil spring (12) acts on the spring base (14) with a force which is the weight of the coil spring (12) or the sum of the weight of the coil spring (12) and optionally one Positioning tool for adjusting the relative orientation according to claim 6. 8. Method according to one of the preceding claims, 15 200165P00LU wherein in step c) the coil spring (12) is tensioned on the spring base 10102983 (14) with a force that is greater than the weight of the coil spring (12) and optionally a positioning tool for adjusting the relative orientation according to claim 6. 9. Method according to one of the preceding claims, wherein before step b), or if step a1) is carried out before step a1), the spring base (14) is activated. 10. The method according to any one of the preceding claims, wherein before step b) or if step a2) is carried out before step a2), the coil spring (12) is activated. 11. The method according to any one of the preceding claims, wherein the adhesive (16) has a layer thickness between the coil spring (12) and the spring pads of at least 0.1 mm, in particular at least 0.5 mm. 12. The method according to any one of the preceding claims, wherein the adhesive (16) has a layer thickness between the coil spring (12) and the spring pads of a maximum of 3.0 mm, in particular of a maximum of 1.5 mm or a maximum of 1 mm. 13. Method according to one of the preceding claims, 16 200165P00LU wherein after step c) step LU102983 d) maintaining the target temperature of the end winding area until the heat-curing adhesive (16) has hardened, in particular sufficiently, and the coil spring (12) sticks to the spring base (14). 14. The method according to claim 13, wherein the adhesive (16) and the target temperature are selected and coordinated with one another in such a way that maintaining the target temperature in step d) is necessary for a maximum of 30 seconds, preferably a maximum of 20 seconds or a maximum of 10 seconds Adhesive (16) to harden. 15. The method according to any one of the preceding claims, wherein the adhesive (16) is selected such that it has a greater elongation at break than the spring coating and the spring base. 16. The method according to any one of the preceding claims, wherein the adhesive in the fully cured state has a lower hardness than the spring coating. 17. The method according to any one of the preceding claims, wherein after step c) or if carried out after step d), step 17 200165P00LU e) Cooling of the coil spring, with the adhesive being completely hardened after the LU102983 cooling of the coil spring is carried out. 18