Electricity: conductors and insulators – Covers or face plates
Reexamination Certificate
1999-12-22
2002-11-05
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Covers or face plates
C174S0170CT, C174S050000, C174S017070
Reexamination Certificate
active
06476320
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to an indicating instrument, in particular for a motor vehicle, having a housing with a front frame holding a cover pane, and an elastic spacing element arranged between the cover pane and front frame. The invention also relates to a method for connecting a cover plate to a front frame of such an indicating instrument.
Such an indicating instrument is known, a cover pane engaging in a radial cutout, forming an axial recess, in an instrument housing, and in this case bracing a sealing ring likewise arranged in the radial cutout. The cover pane must be cambered for mounting, and a special mounting tool is required for inserting the pane into the housing. This assembly is expensive and complicated, as a result of which it is virtually impossible to automate the production. Moreover, the choice of material for the cover pane is fixed to the greatest possible extent, since the latter must have at least slight intrinsic elasticity, and there is the risk of damaging the pane during installation.
Moreover, indicating instruments are known in which the cover glasses are each welded to the front frame. This is an expensive production method which, in addition, can be applied only to a few pairs of materials. It is also known for the cover pane and front frame to be clipped. These clip connections are affected by play as a result of which noise is continuously developed in the event of flexing of the indicating instrument such as occurs regularly, in particular in motor vehicles, through persistent vibrational excitation. Moreover, in the case of these connections dust penetrates into the indicating instrument, as a result of which both the legibility of the instrument can be worsened and its operating reliability is reduced.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to create an indicating instrument of the type mentioned at the beginning which on the one hand at least largely excludes penetration of pollutants into the instrument, and on the other hand ensures a permanent connection, without play, between the cover pane and front frame. Moreover, it is to be possible to produce the indicating instrument in a particularly simple and cost-effective fashion in large batch numbers. Moreover, the aim is to develop a method for simplified connection of a cover pane to a front frame of such an indicating instrument.
The first-named object is achieved according to the invention wherein the spacing element is placed in an axial cutout which is arranged in the region of the circumference of the front frame and faces the cover pane, and in which the cover pane can engage. Such a design ensures that the cover pane bears securely against the front frame without a relative movement of the components with respect to one another, for example excited by external vibrations, causing the elements to slide on one another, thus excluding undesired noise development. Moreover, it is possible in a simple way with the aid of the indicating instrument according to the invention to even out between the cover pane and front frame manufacturing tolerances which can reach a substantial dimension, particularly in the case of large-area indicating instruments. In addition, together with the axial cutout the spacing element permits optical concealment of the connecting region between the cover pane and front frame; it is possible to eliminate an additional cover for this, and the complete circumference of the indicating instrument can be directly visible to a viewer in a fashion which reduces the installation space of the indicating instrument. Because the cover pane can engage in the axial cutout, the indicating instrument according to the invention is particularly simple to mount, since the cover pane can be directly connected to the front frame from the front without being tilted or cambered.
It is conceivable that the axial cutout is arranged only in sections in the region of the circumference of the front frame. However, a particularly tight and homogenous connection between the cover pane and front frame is permitted when, in accordance with an advantageous development of the invention, the axial cutout in the region of the circumference of the front frame runs continuously around the latter. As a result, the operation of joining the cover pane and front frame is also simplified at the same time.
In accordance with another advantageous development of the invention, the axial cutout has a groove-shaped cross section such that on the one hand an exact position of the cover pane with respect to the front frame is ensured, and on the other hand the groove base can form an axial stop in a simple way when the cover pane and front frame are joined. Both the joining operation and the insertion of the spacing element into the axial cutout are advantageously substantially simplified when the groove has flanks diverging toward the cover pane.
A particularly reliable fixing of the spacing element on the front frame can be achieved when, in accordance with another advantageous development of the invention, the groove base of the axial cutout has an indentation pointing away from the cover pane, in which the spacing element can be held.
It would be possible, for example, to imagine that the spacing element is a rubber element and can be laid in the axial cutout in the front frame. By contrast, the spacing element can be arranged in a particularly simple way on the front frame when it advantageously consists of a hard-setting material. In addition, adaptation to the part of the cover pane engaging in the axial cutout can be performed in this case during hardening.
In accordance with another advantageous development of the invention, a particularly simple and reliable connection between the cover pane and front frame is achieved when the spacing element has an adhesive. The spacing element thus simultaneously fulfills the functions of sealing the instrument, connecting the cover pane to the front frame and mechanically decoupling and damping these components.
It is basically the case that the most varied materials, which advantageously simplify the processing and installation of the spacing element, for example thermoplastic elastomers, are suitable for the spacing element. However, it is particularly advantageous when the spacing element preferably consists of a polymer foam. This material flows easily even under a slight pressure in the case of conventional processing temperatures, and sets hard without volatile byproducts. Moreover, virtually no shrinkage occurs during the hard-setting, with the result that the spacing element is dimensionally correct and not prone to stress cracking.
In accordance with another advantageous development of the invention, the spacing element can be clamped between the front frame and cover pane so that, as a result of the clamping force, it ensures a sealing connection and reliable decoupling of the front frame and cover pane over the entire service life of the indicating instrument.
It is conceivable for the front frame and the cover pane to be screwed together or merely interconnected by means of an adhesive. The indicating instrument is, by contrast, particularly durable even under vibrating stress such as occurs in motor vehicles, and it can also be mounted very simply when the front frame and the cover pane can advantageously be interconnected by means of a clip device. In this case, a particularly reliable connection is ensured when arranged at a mutual spacing in the region of the circumference of the cover pane are at least two clips which can engage in corresponding clip lugs arranged on the front frame. A particularly high pressure can advantageously be exerted on the spacing element when the clip device is arranged in the region of the spacing element. In order in this case to maintain the full functionality of the spacing element, it is particularly advantageous when, in accordance with another development of the invention, the spacing element has indentations or cutouts through which the clips
Ehmes Harald
Ritter Thomas
Zeiss Manfred
Estrada Angel R.
Farber Martin A.
Mannesmann VDO AG
Reichard Dean A.
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