DE102011075001A1 - Transmitted light vacuum chuck has light transmissive platen that is made of porous material having multiple communicating pores which form gas passage channels - Google Patents

Abstract

The vacuum chuck (100) includes a housing (110) in which partially light transmissive platen (120) is supported. The gas passage channels are extended from rear face (124) of platen to front face (122) of platen. A lighting device (130) for illuminating the rear of clamping plate is provided with light of light source. The platen is made of porous material having multiple communicating pores which form the gas passage channels. The porous material is sintered ceramic.

Description

BACKGROUND OF THE INVENTION

Technical area

The invention relates to a transmitted light vacuum chuck according to the preamble of claim 1. Such a device may also be referred to as a translucent device for adhering bodies.

Description of the Prior Art

Vacuum clamping devices are devices that allow to fix an object by means of negative pressure on a clamping surface of the vacuum clamping device. Since no mechanical intervention on the object to be clamped is required for fixing, the object is protected against mechanical damage in this clamping technique. In transmitted-light vacuum clamping device of the generic type, it is also possible to illuminate the tensioned object from the side of the platen by means of transmitted light. As a result, it is possible, for example, to transparently tension transparent optical elements, such as, for example, lenses which have markings for better handling, and to identify them on the basis of the markings with the aid of an optical detection system. Other translucent objects, such as films, can be gently tensioned by means of a transmitted-light vacuum clamping device for optical inspection.

The EP 1 841 565 B1 describes a generic transmitted-light vacuum clamping device for fixing a flat object on a work surface by means of negative pressure. The device has an at least partially transparent support plate, one side of which forms the working surface and which has a rear side arranged at a distance from the working surface. The support plate has from the working surface to the back running vacuum channels that can be connected to a vacuum line and open into the work surface. A lighting device for the clamping plate has a radiation-reflecting structure, which is arranged in the region of the rear side of the support plate. The illumination device furthermore has a light source, the radiation of which can be fed laterally into the support plate such that the working surface can be illuminated homogeneously under the action of the radiation-reflecting structure. The light-reflecting structure is formed in various embodiments by depressions on the back of the transparent platen, which is to achieve sufficient transparency of a glass ceramic, quartz glass or other glassy material. The reflective structure serves to deflect the laterally irradiated light in the direction of the clamping surface or of the tensioned object.

TASK AND SOLUTION

The invention has for its object to provide a transmitted light vacuum clamping device of the type mentioned above, which has a robust, structurally simple structure and is easy to handle. The transmitted-light vacuum clamping device should in particular make it possible to illuminate the useful range of the clamping surface with a precisely controllable spatial intensity distribution of the illumination light.

To achieve this object, the invention provides a transmitted light vacuum chuck having the features of claim 1. Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

A transmitted-light vacuum clamping device of the generic type according to the invention is characterized in that the clamping plate consists, at least in one working region, of an open-pored material having a multiplicity of communicating pores which form the gas passage channels. The term "pore" here refers to an internal cavity in the otherwise more or less mechanically stable basic structure of the open-pored material. In the case of open-pore materials, the result is generally a largely statistical distribution of the gas passage channels over the entire useful range, so that a very uniform clamping effect can be achieved over the entire useful range. In addition, randomly distributed pores in the translucent material of the chuck plate can lead to scattering effects that can contribute to a homogenization or homogenization of the illumination of the clamping surface.

In preferred embodiments, the material is a microporous material, ie a porous material in which average pore sizes are well below one millimeter, resulting in a good homogenization of the suction and a particularly good light distribution. In particular, the pores may have a mean pore size in the range of 10 microns to 100 microns. When using a microporous material, it may be possible that even with only partial coverage of the working area, a more or less constant pressure drop results, so that unused areas in the clamping usually need not be covered to the suction effect on the object achieve. This results in a particularly simple and convenient handling for the user.

In some embodiments, the material is a sintered material, which preferably consists predominantly of a sinterable metal, a sinterable ceramic material or of a sinterable composite material with metal and ceramic components. In addition to the metallic and / or ceramic sintered material, a suitable binder may also be present. With the aid of sinterable solid-state materials, it is possible, with suitable material thickness, to manufacture clamping plates which have such high inherent rigidity that self-supporting clamping plates can be provided in many dimensions suitable for practical use.

In preferred embodiments, the material is a sintered ceramic. Suitable ceramic materials can have a high strength or inherent rigidity and, on the other hand, allow the material to have a translucency which is not too great.

In some embodiments, the platen has a thickness of less than 10 mm, at least in the effective region, wherein the thickness in the effective region is preferably less than 5 mm and may for example be between 1 mm and 5 mm. Such material thicknesses usually give sufficient translucency when using ceramic materials and possibly also in porous materials, which are mainly produced on the basis of metal and / or plastic.

As an alternative to a sintered material, it is provided in some embodiments that the material is a foam material, for example a metal foam or a ceramic foam.

In some cases, a plastic material can serve as the basis for the open-pore sintered material or foam material of the clamping plate.

In some embodiments, a translucent support plate is provided, which has a front side facing the back of the platen, wherein the platen rests in the region of one or more support zones on the support plate. When using such a support plate, it is not necessary that the platen with respect to material selection and / or dimensioning is designed so that it has sufficient inherent rigidity to be received cantilevered in the housing. Thus, also platens with relatively low rigidity and / or very thin platens are possible.

It is conceivable, for example, to use a clamping plate made of a porous hard rubber material, the clamping surface is accordingly elastically yielding to a minor extent and thus allows a particularly gentle clamping for the object to be clamped. Also, platens made of felt-like materials can be used in this case.

The support plate should have sufficient inherent rigidity to take over the support function for the clamping plate. The support plate may for example consist of a glass ceramic material, a glass material or a plastic material of suitable material thickness or of a sufficiently translucent composite material with one or more of these materials. Possibly. can also be provided a largely open lattice-like structure as a support plate, wherein the mesh openings of the grid are free of material and thus translucent and the relatively thin grid elements support the back of the platen.

In order to ensure that even when a support plate on the back of the platen, the suction power is distributed as evenly as possible on the clamping surface, projections and recesses extending between the projections are provided in preferred embodiments on the front and the platen is only in the region of the projections on the Support plate on. The spaces remaining between the projections communicate with a connection device of the housing, to which a vacuum generator can be connected, so that an extraction can take place through the free spaces.

In some embodiments, a channel system with crossing and / or non-crossing channels is formed on the front of the support plate, between which the projections are formed. The cross-sectional shape of the channels can be selected to optimize the functions. For example, rectangular channels, V-shaped channels, rounded channels or semicircular channels are possible in cross section. The channels can be crossed or star-shaped at any angle. Free-form channels are also possible. If required, chip islands can also be created, with channels having no direct connection to one another.

The area fraction of the areas covered in the region of the support zones to the free areas lying between the support zones, via which an extraction can take place directly, can be varied within wide limits. In some embodiments, the area fraction of the support zones is less than 10% of the total area or even less than 5% of the total area. As a result, it is possible to suck off nearly all of the back of the clamping plate, wherein the support between the clamping plate and the support plate only by individual Support points is made with relatively narrow support zones.

Alternatively or additionally, a channel system with crossing and / or non-crossing channels can be formed on the rear side of the clamping plate. In such an embodiment, the front side of the support plate facing the clamping plate may possibly be flat, so that the production of the support plate is simplified.

Instead of a support plate and a non-plate-shaped support means may be provided which provides a plurality of support zones for supporting the platen and further allows a back lighting of the platen. The support means may e.g. as a framework may be formed with a plurality of relatively thin, rigid struts, which may be interconnected at intersections to form a stable framework.

In transmitted-light vacuum chucks, different types of lighting devices can be used. In principle, all types of areal lighting and also all types of punctiform and / or linear lighting come into question. Preferably, the illumination device has a surface light source which is arranged between the clamping plate and a bottom of the housing. As a result, a planar illumination of the platen, possibly through a support plate, possible. It can be illuminated, the entire area of the back of the platen or only a portion of it. For example, if certain uneven spatial intensity distributions are desired on the chuck surface, very bright spot light may be combined with bright area light. In some embodiments, a uniform illumination of the entire back of the platen over a correspondingly large area light source is provided. For example, as an area light source, an LED panel, i. a field with LEDs, be provided.

Alternatively or additionally, organic light-emitting diodes (OLEDs) can also be used as surface light source. These energy-saving light sources have as "cold light sources", inter alia, the advantage of generating only a small heat input, so that such lighting devices can be used without complex cooling in vacuum jigs for precision machinery.

The radiation characteristic of the illumination device may vary with respect to the wavelength range depending on the application. It must be ensured that the platen is at least partially translucent for the light of the illumination device. Accordingly, the wavelength or the wavelength range of the light emitted by the illumination device can be adapted to the corresponding application. It can be generated in alternatively monochromatic light or polychromatic light.

These and other features, in addition to the claims, will be apparent from the description and drawings, in which the individual features may be implemented alone or in combination in the form of sub-combinations in one embodiment of the invention and in other fields, and advantageous embodiments that are capable of protection can represent. Embodiments are illustrated in the drawings and are explained in more detail below.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

1 shows a schematic vertical section through an embodiment of a transmitted light vacuum clamping device according to the invention; and

2 shows a schematic section through the open-pored structure of the platen of in 1 shown transmitted light vacuum clamping device in the area II 1 ,

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In 1 is a schematic vertical section through a vacuum chuck 100 shown with integrated transmitted light illumination. In the following, the device will also be referred to for short as "transmitted light vacuum clamping device" or "vacuum clamping device". The vacuum clamping device has a rectangular cross-section, upwardly open housing 110 , which essentially consists of a rectangular base plate 112 and a frame surrounding the base plate on all sides 114 consists. Base plate and frame are made of an aluminum material, they may in other embodiments also of another metallic or non-metallic material (eg steel or polymer material or composite material) exist. The base plate and the frame are connected airtight to each other in the area of the joining surfaces, for which elastic or inelastic seals may be provided in the region of the joining surfaces.

The housing carries on its upper side an at least partially translucent platen 120 , which serves as a clamping surface flat front side 122 and an opposite, also flat back 124 having. The rectangular, plane-parallel platen is at its side edges of the frame of the housing 110 held on all sides, wherein the joining zones can be hermetically sealed with sealant or sealing elements.

Optionally, the tightness in the joining areas of the frame components and / or between frame and clamping plate can be achieved without additional sealing measures solely due to precise production and connection of the parts.

The clamping plate 120 and the frame 110 form a torsion-resistant, stable unit and enclose a substantially hermetically sealed interior 115 of which only a single lateral passageway to a lateral connection device 116 leads, over which the vacuum chuck to a vacuum generator, such as a vacuum pump, can be connected. In other embodiments, two or more connection devices may be provided, wherein, for example, in the case of built-in appliances, a connection device may also be provided in the base plate.

The clamping plate 120 consists entirely of an open-pore material with a plurality of communicating pores, which form a fine system of gas passageways, from the back 124 the platen to the front 122 go through. The statistically distributed, multi-branched gas passage channels allow a balanced internal pressure distribution in the platen and allow the generation of a negative pressure on the clamping surface, even if uncovered exposed areas of the clamping surface are not covered by the object to be fixed.

2 shows a schematic section through the open-pored structure of the clamping plate 120 in area II 1 , In the example, the platen consists of an open-pored ceramic material, which was produced from a granular ceramic starting material in combination with binder material by sintering. The non-transparent ceramic material has sufficient light transmission (translucency) to form a luminous clamping surface when illuminated from the back, with the help of which spanned objects can be observed in a transmitted light process. The mean pore size of the pores 121 is in the range of about 10 microns to about 100 microns, so that at the clamping surface 122 a large number of statistically distributed small intake ports exist. The flow resistance of the open-pored structure is dimensioned such that an intake effect on an overlying object can also be established if adjacent areas remain free.

In other, non-illustrated embodiments, a sealing of the porous material is provided to the outside outside of the intended for clamping Nutzbereichs. The sealing of the non-absorbent surfaces can be achieved, for example, by sealing these regions with synthetic resin ink, adhesive, epoxy resin or comparable materials.

In some embodiments, the platens are used which consist of a microporous solid material which under the brand METAPOR ^® (trademark of Portec AG, Wintherthur / Switzerland) is available. The fine-pored ceramic material with a white, non-reflective surface is available in different material thicknesses from 10 mm thickness. In order to ensure adequate translucency for use in a transmitted-light vacuum fixture, lower material thicknesses are advantageous. In the exemplary embodiment, the material thickness in the clamping region is less than 5 mm. This material thickness can be achieved by machining the thicker starting material and ensures sufficient light transmission with good stability or inherent rigidity of the clamping plate.

To illuminate the platen from the back is a lighting device 130 provided by electrical connections 134 can be connected to a voltage source. The illumination device is designed as a surface light source and has a field of inorganic light-emitting diodes on its upper side facing the clamping plate 132 , so that the illumination device has a uniform luminous intensity substantially over the entire cross section. The integrated LED panel thus ensures uniform illumination of the clamping plate from its rear side.

As an alternative or in addition to an LED panel, it is also possible to provide other flat, punctiform or linear light sources. In particular, a surface light source with at least one organic light-emitting diode (OLED) can be provided, that is to say a film-like thin luminous component made of an organic, semiconducting material.

In embodiments where the platen 120 has sufficient inherent rigidity to meet the specifications for the surface shape (flatness tolerance) on the clamping surface, the compact design without further elements.

In the illustrated embodiments is between the illumination device 130 and the platen 120 a translucent support plate 140 arranged in the area of their Circumference fixed to the frame 110 of the housing is connected. The support plate 140 has one of the back 124 the platen facing front 142 and is arranged so directly below the platen that the platen through the support plate in the range of several support zones 145 with contact contact rests flat on the support plate.

The support plate of the embodiment has a plurality of uniformly distributed projections 146 whose front sides form the support zones. Between the projections are channel-like recesses 148 provided directly or indirectly via further connection channels with the connection device 116 communicate. The recesses form a channel system with partially intersecting and partially non-intersecting channels, between which the projections 146 protrude. Via the channel system an immediate connection of the thus communicating gas passage channels is ensured to the connection device.

The vacuum chuck is for use via the connection device 116 connected to a device for generating a pressure gradient between the front and the back. In the suction operation, a negative pressure relative to the environment is generated in the interior of the housing (except for the porous platen) in a hermetically sealed manner, so that air is sucked into the interior through the porous structure of the platen. As a result, even sensitive objects such as films or thin lenses can be fixed largely free of deformation on the clamping surface. These objects can be edited after clamping in the fixed state with tools. For example, a fixed film can be laser-welded to another fixed film.

The transmitted-light vacuum clamping device allows a full-surface clamping of workpieces of all kinds, whereby the entire clamping surface can be uniformly illuminated from below. Thus, for example, camera detection processes that work with transmitted light illumination, can be reliably realized.

Also, a pressure reversal is possible, so that in the interior of the housing, an overpressure is set to the environment. This pressure reversal can e.g. be used for active release or for repelling the fixed object. By overpressure, if necessary, an air cushion can be generated under a held object, so that it can float above the clamping surface without touching it. As a result, for example, films in a roll-to-roll machine or other thin objects can be transported gently. The functionality of "pushing away" by overpressure may e.g. lead to shorter processing times and better results in manufacturing processes.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1841565 B1 [0003]

Claims (9)

Transmitted-light vacuum clamping device ( 100 ) with: a housing ( 110 ); a supported by the housing, at least partially translucent backing plate ( 120 ), which is designed as a clamping surface front side ( 122 ), an opposite back ( 124 ) and from the front to the rear having through gas passage channels; and a lighting device ( 130 ) for illuminating the back of the platen with the light of at least one light source, characterized in that the platen ( 120 ) at least in a useful region of an open-pore material having a plurality of communicating pores ( 121 ), which form the gas passageways. A transmitted light vacuum chuck according to claim 1, wherein said material is a microporous material, said pores ( 121 ) preferably have a mean pore size in the range of 10 .mu.m to 100 .mu.m. A transmitted-light vacuum chuck according to claim 1 or 2, wherein the material is a sintered material, which preferably consists essentially of a sinterable metal and / or of a sinterable ceramic material, wherein the material is preferably a sintered ceramic. A transmitted light vacuum chuck according to any one of the preceding claims, wherein the chuck plate ( 120 ) has a thickness of less than 10 mm at least in the useful region, wherein the thickness in the effective region is preferably less than 5 mm. Transmitted-light vacuum clamping device according to one of the preceding claims, characterized by a light-permeable support plate ( 140 ), one of the back ( 124 ) of the clamping plate ( 120 ) facing front ( 142 ), wherein the clamping plate in the region of one or more support zones ( 145 ) rests on the support plate. A transmitted light vacuum chuck according to claim 5, wherein the front side is protrusions ( 146 ) and between the projections extending recesses ( 148 ) and the clamping plate ( 120 ) rests in the region of the projections on the support plate, wherein preferably at the front of the support plate ( 140 ) a channel system is formed with crossing and / or non-crossing channels and between the channels the projections ( 146 ) are formed. A transmitted light vacuum chuck according to claim 5 or 6, wherein the support plate ( 140 ) consists of a glass ceramic material, a glass material or a plastic material of suitable material thickness. A transmitted light vacuum chuck according to any one of the preceding claims, wherein the illumination device ( 130 ) has a surface light source between the platen ( 120 ) and a bottom of the housing ( 110 ) is arranged A transmitted light vacuum chuck according to any one of the preceding claims, wherein the illumination device ( 130 ) a field with light emitting diodes ( 132 ) and / or at least one organic light-emitting diode (OLED).

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