Optical: systems and elements – Mirror – With support
Reexamination Certificate
2000-01-21
2001-06-19
Shafer, Ricky D. (Department: 2872)
Optical: systems and elements
Mirror
With support
C359S883000, C359S514000, C359S515000
Reexamination Certificate
active
06247822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application relates to a reflector apparatus, in particular a parabolic mirror, with a plastic layer on which a plastic sheet with a metal structure is provided and with a casing consisting of two hollow cylinders which can be arranged inside one another and between which the reflector is held.
2. Description of the Prior Art
Reflectors or transreflectors are used for many applications, in particular for the orientation of radar waves. It is already known to produce reflectors for radar applications where a plastic sheet is coated with a metal, in particular aluminum, the plastic sheet is fixed in an injection moulding die and is then overfed with a plastic layer having the necessary shape, for example a parabolic shape. A parabolic mirror is thus formed which is arranged relative to a radar source by a casing. In many cases, this casing consists of a metal, for example of aluminum. A casing of this type can be produced as a cast casing.
It is also known to fix the parabolic mirror in the cast casing between an outer cylinder and an inner cylinder with a seal inserted in-between. In an outer hollow aluminum cylinder having a peripheral, inwardly orientated flange, a seal is placed against this flange, the reflector is subsequently introduced that is followed by an inner cylinder which presses the reflector and the seal against the flange of the outer cylinder.
It has been found that pronounced deformation of the components may occur owing to the different coefficients of thermal expansion of the casing and the reflector. Owing to this deformation, a precise orientation in the radial direction of the reflector relative to the radar transmitter is no longer ensured. As the centrality of the reflector relative to the transmitter is very important for applications where safety is paramount, it is necessary not only to accommodate production tolerances with a reflector apparatus consisting of reflector and casing but also to accommodate for the differing thermal expansion of the various components.
SUMMARY OF THE INVENTION
Starting from this state of the art, it is an object of the present invention to provide a reflector arrangement which ensures a defined position of the parabolic mirror over a predetermined temperature range. A further object of the invention is to provide a process for producing a reflector arrangement of this type.
The reflector arrangement according to the invention comprises a reflector with a first plastic layer on which a plastic sheet with a metal structure is provided and a further plastic layer which forms a substantially hollow cylindrical collar at the edge of the reflector as well as a casing which consists of two hollow cylinders adapted to be arranged inside one another, the collar of the second plastic layer being held between the hollow cylinders of the casing. As the collar of the reflector is fixed at the end remote from the reflector and the edge of the reflector is not fixed directly between the hollow cylinders, stresses between collar and hollow cylinders owing to differing thermal expansion have only a slight effect on the reflector itself.
The hollow cylinders and the plastic layers of the reflector are produced from different materials. These different materials also have different coefficients of thermal expansion, which results in differing expansion of casing and reflector. As the hollow cylindrical collar is accommodated between the hollow cylinders of the casing, the differing expansion of these components has to be absorbed. It is particularly advantageous to provide the collar with substantially axially extending slots which are distributed along the periphery, for example by milling material from the collar in these slots. If the collar and the hollow cylinders expand to different extents, this variation can be absorbed by the slots so that excessive stresses are avoided.
A further particular advantage is that catch fingers are arranged on the collar between the hollow cylinders for defined fastening of the collar. These catch fingers each comprise a catch projection and are also distributed along the periphery of the collar. They are separated from the collar by axially extending slots.
A further particular advantage is that one of the hollow cylinders includes a shoulder behind which the catch projection engages and that the second hollow cylinder comprises a stop for the edge of the collar. The position of the collar relative to the hollow cylinders is therefore defined in the axial direction.
It is also particularly advantageous to provide a resilient element which is part of the collar and is fixed between the shoulder and the stop of the hollow cylinders. This resilient element serves to compensate for production tolerances between the two hollow cylinders and the reflector.
It is also particularly advantageous to provide ribs on the collar which are deformed as the collar is inserted between the hollow cylinders of the casing. These ribs also serve to compensate for production tolerances.
It is also further advantageous to provide these ribs on the catch fingers, as this ensures that the catch fingers are fixed securely between the two hollow cylinders whereas the region between the catch fingers, which are separated from the catch fingers by slots, can shift between the two hollow cylinders of the casing if necessary due to different thermal expansion.
A further particular advantage is that a radially extending peripheral flange is provided outside the collar at the edge of the reflector. This flange serves as a seal seat for a seal that is arranged between the outer hollow cylinder and the collar and flange of the reflector. This is advantageously a low-pressure seal which does not exert a great force on the collar of the reflector and is able to absorb differing thermal expansions. A part of the seal is also located between the flange and the outer hollow cylinder. A rib, which serves to fasten the reflector on the outer hollow cylinder so it is sealed against contaminants such as spray water, is provided on the outer hollow cylinder in this region.
With the arrangement according to the invention, the production tolerances of the different components can be allowed for and it is also ensured that differing thermal expansion is compensated so that the variations in the centrality of the reflector arrangement lie within the permitted tolerances despite this differing thermal expansion.
REFERENCES:
patent: 1959055 (1934-05-01), Jeffery et al.
patent: 2255748 (1941-09-01), Haggart, Jr.
patent: 2627784 (1953-02-01), Pellar
patent: 3063343 (1962-11-01), Kaestner
patent: 3441336 (1969-04-01), Gunderson
patent: 3563638 (1971-02-01), Panozzo
patent: 5014174 (1991-05-01), Won et al.
patent: 5143338 (1992-09-01), Eberlin
patent: 5247395 (1993-09-01), Martinez
Jaklin Ralf
Mumper Guenther
Shafer Ricky D.
The Whitaker Corporation
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