Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Utility Patent
1998-12-08
2001-01-02
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S216100, C359S871000, C359S877000, C359S855000
Utility Patent
active
06169620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application is based on the European Patent Application No. 97830655.3, the content of which is incorporated hereinto by reference.
The present invention relates to a mirror mount having faces provided with projections defining a supporting plane, a method of manufacture comprising the mounting of mirrors on said faces and connection of said mirror mount to a suitable electric motor to form a mirror rotor and a mirror rotor obtained by said method.
2. Discussion of Prior Art
Many devices exist which in order to function need to generate, divert and deflect light beams, particularly laser light beams and which perform scanning of surfaces with such light beams, for example, scanners, optical code readers, fax machines, laser printers, medical apparatus, laser type measuring instruments for the construction industry, uneven surface detection instruments, etc.
These devices use mirror rotors for diversion, deflection and/or generation of light beam scanning.
The known mirror rotors comprise a polyhedral mirror mount and an electric motor capable of causing said mirror mount to rotate at preselected speeds. More particularly, the polyhedral mount is provided with a preselected number of absolutely flat external faces on which mirrors capable of guiding the optical beams are mounted and with an internal cylindrical cavity for connecting the mount to the rotor of the electric motor.
Said known polyhedral mounts are made of aluminium and are manufactured by machining the aluminium blank by means of machine tools. The faces defined to receive the mirrors are rendered perfectly smooth and free from burrs and the internal cylindrical cavity for connection to the rotor of the electric motor must have a very accurate diameter in order to prevent movements.
The mirrors are in turn obtained by depositing various numbers of layers (usually from 10 to 20) of a suitable dielectric material, e.g. silicon oxide, titanium oxide, magnesium fluoride, etc., on ordinary glass plates.
Production of the mirror rotor using such a conventional polyhedral mount comprises the following steps:
application of a layer of a two-component adhesive, e.g. UHU PLUS on the rotor of the electric motor,
insertion of the motor in the polyhedral mount taking care to slide said rotor of the motor inside the internal cylindrical cavity of the polyhedral mount up to a stop flange,
waiting the necessary time (usually from 20 to 30 minutes) for the adhesive to rigidly connect the rotor of the motor to the polyhedral mount,
application of the above-mentioned two-component adhesive to the external faces of said polyhedral mount,
waiting approximately 15 minutes for the viscosity of said adhesive to increase,
placing the mirrors on the external faces of said polyhedral mount,
waiting the necessary time (usually from 90 to 150 minutes) for the adhesive to rigidly fix the mirrors to the external faces of said polyhedral mount,
startup and running of the mirror rotor thus produced, in order to test alignment of the mirrors with a reference point placed a distance of approximately 500 mm away.
This conventional production method has various disadvantages:
production of the aluminium blank mount made from bar aluminium and subsequent finishing of the same on a machine tool are somewhat laborious and lead to a certain percentage of wastes;
whilst drying, the adhesive is subject to shrinkage and therefore, during the step of fitting the mirrors on the faces of the polyhedral mount, a continuous supervision by an operator is necessary in order to gradually correct the position of the mirrors with a rubber pad and return the same to the correctly aligned position. The operator consequently has to carefully and continuously supervise each rotor throughout the complete drying step of the adhesive, which since it has to take place at ambient temperature, takes several hours (approximately 4). Execution of this step must therefore be entrusted to very expert operators and for a long period of time.
SUMMARY OF THE INVENTION
The object of the present invention is therefore that of obviating the above-mentioned disadvantages and thus substantially reducing the cost of production of mirror rotors. This object is achieved by means of an substantially basket-shaped mount having external faces provided with projections defining a plane of support and which enables simplification of the method of manufacture of a mirror rotor.
Therefore, a first aspect of the invention is constituted by a mirror mount for a rotor provided with a preselected number of external faces suitable for covering with mirrors and an internal structure for connection to an electric motor, characterized in that at least one of the external faces thereof has projections for supporting a mirror and recesses capable of holding an adhesive compound for fixing said mirror to said face.
In accordance with a preferred embodiment, said mirror mount is substantially basket-shaped and its internal structure consists of a cavity the surface of which also comprises projections capable of maintaining said motor axially centred inside said mirror mount and recesses suitable for holding an adhesive fixing compound. Typically, said projections consist of ribs and said recesses consist of grooves extending parallel to the axis of rotation of said mirror mount.
Advantageously, the projections and the recesses of said external face follow a linear course. In such a case, said face presents a succession of alternating ribs and grooves. Typically, said ribs and said grooves are extended parallel to the axis of rotation of said mirror mount. Preferably there are at least two grooves.
In a further preferred embodiment, the external faces of said mirror mount all have the same configuration.
The ratio between the surface area of the recesses and the total surface area of the face may vary within very wide limits given that the existing projections on a face may also comprise only four stems. Preferably said ratio will nevertheless be between 30% and 70% inclusive and, even more preferably, between 40% and 60%.
The number of external faces of the mirror mount, and hence of the mirrors, is not a crucial characteristic of the present invention, since this datum will be determined in the individual case by the skilled in the art according to the performance required of the mirror rotor. This number, however, generally ranges between 6 and 12 inclusive.
Advantageously, the lower base of said mirror mount is provided with an annular flange extending towards the outside and supporting the lower edge of the mirrors. Preferably said annular flange also has a positioning slot. Even more preferably, said mirror mount is provided at the opposite end with a second annular flange extending towards the inside and abutting on the motor.
Advantageously, said recesses of the external face end up in an area which is inclined in relation to the external face and the internal cavity. In addition, said annular flange has holes communicating with the recesses in the internal cavity.
Nor is the material used to make the substantially basket-shaped mirror mount in accordance with the present invention a crucial condition provided said material is stable against changes of temperature and humidity. The skilled in the art will be able to select a suitable metal or polymeric material from a wide range of materials available on the market.
Typically, a composite pressure moulding material consisting of fibreglass or carbon buried in a polymeric matrix may be used. For example, good results have been obtained with a material manufactured by the Lati Company which is marketed as Larton™ G40 and which consists of approximately 40% fibreglass buried in a polymeric matrix of PPS (polyphenylene sulphide) type.
Nor, depending on the preselected material, is the production technique crucial. For example, in the particular case of Larton™ G40, the use of injection moulding by the particular method known as “fan moulding” is preferred.
A second aspect of the invention consists o
Angelini Claudio
Zucchini Maurizio
Assaf Fayez
Datalogic S.p.A.
Nixon & Vanderhye P.C.
Schuberg Darren
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