Patent Description:
The document <CIT> discloses a method for positioning and bonding components of a high precision optical system or the like. Two components can be positioned relative to each other and adhesively bonded together without any displacement resulting from contraction of the adhesive by forming on the first component an annular protrusion having its center at a point to be aligned. On the second component is formed an annular groove having its center at a corresponding point to be aligned. The width of the groove is significantly larger than the width of the protrusion. The protrusion is aligned within the groove and then adhesive is poured into the gaps between the protrusion and the sides of the groove.

The document <CIT> discloses an image forming apparatus with a lens mounting device for an optical housing comprising a base, a lens bonding member provided on the base, an adhesive layer of a defined thickness applied to the lens bonding member, and a scanning lens mounted on the lens bonding member through the adhesive layer. The lens mounting device prevents the lens from being affected by fluctuations in an ambient temperature around the optical housing.

Precise adjustment of light sources and optical components, e.g. lenses, reflectors or optical waveguides, relative to each other is a key challenge in assembling lighting devices of motor vehicles. During mounting of the light source group and/or related optical components on a carrier of the lighting device, e.g. a platform or a holding frame, their relative positions are varied by a manipulator while the light source is operated and the resulting lighting effect is monitored. The target position of the components is then finally defined by the constitution of a desired target lighting effect. The fixation of the components in this target position is usually established by adhesive joints, especially between pin members of the first component and associated cavities of the carrier.

A major issue concerning such adhesive joints is the effect of volumetric shrinkage of the adhesive during curing, caused e.g. by the evaporation of a solvent or by a crosslinking reaction. This shrinkage effect yields a subsequent alteration of the adjusted position of the light source or optical component and therefore a potentially critical deterioration of the lighting effect generated by the lighting device.

In an exemplary process, a cavity of the carrier is filled with a flowable adhesive and the optical component is held and positioned by a manipulator so that a pin member of the optical component at least partially extends into the cavity and the adhesive. During the following fine adjustment of the optical component relative to an operating light source, the displacements of the pin remain confined to the cavity, e.g. the cavity exhibits a depth of <NUM>, the pin exhibits a length of > <NUM> and the displacement range of the pin in a vertical direction, i.e. along its longitudinal axis, during the fine adjustment amounts to about <NUM>. The shrinkage of a conventional ultraviolet(UV)-light curable adhesive then typically yields an undesired subsidence of the pin during curing on the order of <NUM> in the vertical direction.

In the context of a lighting device for a motor vehicle, such shifts along the vertical axis are most disadvantageous, because they strongly affect the position of the light cut-off line projected onto the road, which represents a key performance criterion of the lighting device subject to strict regulations and customer specifications.

The document <CIT> teaches a method for glueing two workpieces with an adhesive, wherein after adjustment of the workpieces connecting parts wetted with a fixing glue are placed against appropriate surfaces, so that the connecting parts are in contact with both workpieces and support the workpieces during curing of the adhesive.

It is an object of the present invention to provide a method of joining a pin member of a first component to a second component with a cavity by means of an adhesive in order to fasten the pin in a target position extending at least partially into the cavity with a distance between the bottom surface of the cavity and the facing end of the pin, wherein the method especially comprises measures to prevent the pin from repositioning towards the bottom surface of the cavity during curing of the adhesive.

This object is achieved by a method as taught by claim <NUM> of the present invention. Advantageous embodiments of the invention are defined in the subclaims.

The invention discloses the technical teaching that the method of joining comprises at least the following steps:.

The core of the invention lies in the use of a spacer filling the space between the bottom surface of the cavity and the facing end of the pin, thus eliminating basically any adhesive from the volume below the pin. The joint between the pin and the second component is constituted by the adhesive surrounding the circumferential surface of the pin. The shrinkage of the adhesive during curing therefore can only affect the horizontal position of the pin, which is much less critical regarding the aforementioned use in a lighting device, but the spacer prevents the pin from any repositioning towards the bottom surface of the cavity.

Due to its rigidity, the spacer cannot be deformed by the load applied by the first component via the pin. The rigid spacer is formed for instance by an appropriate plastic, e.g. a thermosetting polymer. In a typical application of the inventive method, the target position of the pin and therefore the required thickness of the spacer is unknown a priori. The required thickness of the spacer can only be determined after positioning of the pin in the target position and determination of the distance between the bottom surface of the cavity and the facing end of the pin in the target position. The inventive method thus may comprise an additional step of machining a dummy slice to a spacer of dedicated thickness equal to the distance between end of the tip and bottom surface of the cavity in the target position of the pin.

As a preferred embodiment of the invention the first component is chosen from a light source group or from an optical component associated with a light source and the second component is chosen from a carrier, wherein during positioning the pin inside the cavity the light source is operated and a resulting lighting effect is monitored in order to locate the target position by the constitution of a target lighting effect. The invention was motivated by this application and yields a major benefit over prior art joining methods in this context.

Advantageously, the rigid spacer is formed by a slice of cured adhesive, wherein applying the rigid spacer comprises the following steps:.

For ease of practical operation, the adhesive used to form the spacer preferably equals the adhesive used for the joint between the pin and the second component, but differing types of adhesives are in principle equally appropriate. The amount of shrinkage during curing of the adhesive used to build the spacer must be calculated and the amount of adhesive filled into the cavity must be dosed accordingly, so that after curing the thickness of the cured adhesive, i.e. the thickness of the rigid spacer, equals the distance between the bottom surface of the cavity and the facing end of the pin in the target position.

In a preferred embodiment of the inventive method, the distance between the bottom surface of the cavity and the facing end of the pin in the target position is determined by means of laser scanning. Laser scanning is a convenient technique to generated quantitative 3D-models of component assemblies and allows for a proper determination of the positioning of the first and the second component and thus of the detailed distance between the bottom surface of the cavity and the facing end of the pin in the target position.

Advantageously, the adhesive used for the joint between the pin and the cavity and/or the adhesive used to form the rigid spacer are chosen from an UV-light curing type. These adhesives allow for a fast and technically simple curing process compared to the use of heat-curable adhesives.

According to another preferred embodiment of the invention the first component is chosen from a light source group or from an optical component of a lighting device of a motor vehicle and the second component is chosen from a carrier of the lighting device. The optical component is for instance represented by a reflector, which is mounted on a mounting platform and adjusted to a target position relative to a fixed light source of a vehicle head light.

Furthermore, the invention concerns a joint assembly at least comprising a first component with a pin member and a second component with a cavity, wherein the pin extends at least partially into the cavity and a joint between the pin and the second component is formed by an adhesive inside the cavity, characterised in that a rigid spacer is positioned between the bottom surface of the cavity and the facing end of the pin.

Such joint assembly is advantageously established by the inventive joining method and in a preferred embodiment the thickness of the rigid spacer equals the distance between the bottom surface of the cavity and the facing end of the pin.

Additional details, characteristics and advantages of the object of the invention are disclosed in the following description of the respective figures - which in an exemplary fashion - shows preferred embodiments of the joining method and the joint assembly according to the invention.

The Figures show schematic illustrations of the seven steps <NUM> to <NUM> of the inventive method to yield an embodiment of the inventive joint assembly <NUM>, depicted in cross-sectional representation. The pin <NUM> is a member of a first component 1a, for instance an optical component to be positioned most accurately relative to a light source of a lighting device of a motor vehicle, and the second component 2a exhibits a cavity <NUM> to receive the pin <NUM>. In the depicted example, the pin <NUM> is formed by a cone with a flat end <NUM> and the cavity <NUM> exhibits a cylindrical volume, whereat matching pincavity combinations of differing shapes can be equally appropriate for the invention on hand.

<FIG> shows the pin <NUM> in the target position extending partially into the cavity <NUM> with the distance D between the bottom surface <NUM> of the cavity <NUM> and the facing end <NUM> of the pin <NUM>. Positioning <NUM> the pin <NUM> to this target position represents the first step of the inventive method. In the central application of the inventive method for mounting an optical component 1a relative to the light source of a vehicle lighting device, the target position is unknown a priori, because of manufacturing tolerances in the dimensions of the components 1a, 2a and other involved components. Therefore, during positioning <NUM> the optical component 1a the light source is operated and the resulting lighting effect is monitored, and the positioning <NUM> is only terminated if a desired target lighting effect is reached. It is the central task of the present invention to fasten the pin <NUM> in this target position inside the cavity <NUM> by means of a bonding process based on an adhesive, wherein during the curing of the adhesive the distance between the bottom surface <NUM> and the end <NUM> remains right at its target value D.

<FIG> illustrates the second step of the inventive method, namely determining <NUM> the distance D between the bottom surface <NUM> of the cavity <NUM> and the facing end <NUM> of the pin <NUM> in the target position. This task is performed with the laser scanner <NUM>, which is developed to generate a quantitative 3D-model of the assembly of the components 1a and 2a.

The <FIG> illustrate a preferred embodiment of the fourth step of the inventive method after removing <NUM> the pin out of the cavity, namely applying <NUM> a rigid spacer <NUM> on the bottom surface of the cavity <NUM>, wherein the thickness <NUM> of the rigid spacer <NUM> equals the target distance D. Beforehand, In the present embodiment, the spacer <NUM> consists of the UV-light curable adhesive <NUM> and it is applied by the steps of filling <NUM> the adhesive <NUM> into the cavity <NUM> and subsequent curing <NUM> of the adhesive <NUM> by irradiation with UV light <NUM>. Therein, the thickness <NUM> of the layer of adhesive <NUM> in its pourable, uncured state is dosed to such an amount that the shrinkage of the adhesive <NUM> during curing <NUM> is anticipated, so that the layer of cured adhesive <NUM> representing the spacer <NUM> exhibits the required thickness <NUM> equal to the target distance D.

<FIG> illustrates the fifth step of the inventive method, namely filling <NUM> the adhesive <NUM> into the cavity <NUM> onto the rigid spacer <NUM>. The pourable adhesive <NUM> preferably consists of an UV-light curable resin, alternatively, if the cavity <NUM> is not sufficiently accessible for illumination, a heat-curable type of adhesive can be deployed.

<FIG> illustrates the sixth step of the inventive method, namely repositioning <NUM> the pin <NUM> to the target position. At this stage of the process, the target position is well-known and for instance defined by a set of coordinates assigned to the manipulator, which is deployed for handling of the first component 1a. The bottom section of the pin <NUM> is dipped into the flowable adhesive <NUM> and placed on the rigid spacer <NUM>. Except for an insignificant amount of residual adhesive <NUM> on the mating surfaces of the pin <NUM> and the spacer <NUM>, the volume of the cavity <NUM> below the pin <NUM> in this assembly is free of adhesive <NUM>.

<FIG> illustrates the inventive joint assembly <NUM> and the last step of the inventive method, namely curing <NUM> the adhesive <NUM> and obtaining a joint between the pin <NUM> and the second component 2a. To this end, the adhesive <NUM> is irradiated by UV-light <NUM>, which typically yields a crosslinking reaction within the adhesive <NUM> and a related hardening effect. The adhesive joint is established between the circumferential sections of the pin <NUM> and the cavity <NUM> inside the component 2a. The volume of the cavity <NUM> below the pin <NUM> is filled by the rigid spacer <NUM> and thus basically free of any adhesive <NUM>. This represents the key innovation of the present invention, because in such an assembly, the shrinkage of the adhesive <NUM> during curing <NUM> does not affect the vertical position of the pin <NUM>, so that the end of the pin <NUM> remains unaltered at the target distance D above the bottom surface of the cavity <NUM>. Furthermore, the friction between the mating surfaces of the pin <NUM> and the rigid spacer <NUM> contributes to a certain fixation of the pin1 during curing <NUM> also in the horizontal plane.

Therefore, the inventive method of joining enables to build a highly precise joint assembly <NUM> of an optical component 1a in a carrier 2a relative to a light source as parts of a vehicle lighting device.

Claim 1:
Method of joining a pin (<NUM>) member of a first component (1a) to a second component (2a) with a cavity (<NUM>) by means of an adhesive (<NUM>) in order to fasten the pin (<NUM>) in a target position extending at least partially into the cavity (<NUM>) with a distance (D) between the bottom surface (<NUM>) of the cavity (<NUM>) and the facing end (<NUM>) of the pin (<NUM>), characterised in that the method comprises at least the following steps:
- positioning (<NUM>) the pin (<NUM>) to the target position,
- determining (<NUM>) the distance (D) between the bottom surface (<NUM>) of the cavity (<NUM>) and the facing end (<NUM>) of the pin (<NUM>) in the target position,
- removing (<NUM>) the pin (<NUM>) out of the cavity (<NUM>),
- applying (<NUM>) a rigid spacer (<NUM>) on the bottom surface (<NUM>) of the cavity (<NUM>), wherein the thickness (<NUM>) of the rigid spacer (<NUM>) equals the distance (D) between the bottom surface (<NUM>) of the cavity (<NUM>) and the facing end (<NUM>) of the pin (<NUM>) in the target position,
- filling (<NUM>) the adhesive (<NUM>) into the cavity (<NUM>) onto the rigid spacer (<NUM>),
- repositioning (<NUM>) the pin (<NUM>) to the target position,
- curing (<NUM>) the adhesive (<NUM>) and obtaining a joint between the pin (<NUM>) and the second component (2a).