This invention relates generally to rotary drums of tape recorders for recording and/or reproducing signals according to helical scan system and, more particularly, to an assembly of the rotary drum.
As is well known from video recorders, the rotary drum comprises a rotary part (upper drum) and a stationary part (lower drum), and forms a drum unit with a so-called drum base by means of which the drum is being arranged with a tilt angle with respect to the plane of recorder's tape deck chassis. For joining drum and drum base together, screw joints (as, for example, illustrated in
According to another solution, the tilt angle can be also realized by stamping the tape deck chassis accordingly. This solution is cheaper as it facilitates mounting the drum directly on the tape deck chassis, i.e. without the drum base mentioned before. This solution, however, has the drawback to be less accurate.
The present invention provides a solution which is economical and which facilitates accurate drum mounting.
It is object of the present invention to provide a solution which is economical and which facilitates to mount the drum accurately.
This object is solved by a drum unit as specified in claim 1. Advantageous embodiments are specified in the subclaims.
The present invention is based on the idea to join lower drum and drum base together by welding, particularly by means of laser welding. This solution simplifies assembly of lower drum and drum base, called lower drum assembly in the following.
As, according to the present invention, screw joints between drum base and the lower drum are not needed, screws can be saved and thus, drilling of tapped holes as well as screw holes can be avoided. Another benefit of this invention is that a machining regarding surface finish of the drum base and the lower drum for fitting them together (before assembling) is no more necessary and thus can be dispensed with.
Furthermore, measures may be provided to facilitate assembly procedure of the lower drum assembly which, particularly, can be realized by simple mouldings within lower drum and/or drum base.
Hence, costs of manufacturing drum units are greatly reduced.
The present invention will now be described in more detail with reference to the accompanying drawing which shows in:
It should be pointed out initially that throughout the
The drum base 2 has positioning pins 6b–6c for engaging corresponding holes of the tape deck chassis and a pin 6a for engaging a corresponding hole of an electronic board (not shown), and, furthermore, the lower drum base 2 has holes 7a–7c for screw joints (not shown) of the drum base 2 with the tape deck chassis when the drum unit is arranged on the tape deck chassis.
For lower drum assemblies—according to the present invention by welding lower drum 1 on drum base 2 and vice versa, respectively—it is advantageous when the same aluminium alloy is used for each part, notably, to have a similar melting temperature. For example, aluminium alloys according to type ADC12 (Japanese norm) or according to type AS9U3 have been proved (European norm) to be well suited. But also a combination of both, i.e. one part is of ADC12 and the other part is of AS9U3, has been proved to be suitable, too.
The first (
1. “Through-Welding”
The laser beam 8 is applied, for example, to the lower side of the drum base 2, called looking-down surface in the following. The alloy melts up to the upper surface of the drum base 2 and even on the lower surface of the lower drum 1. Welding is thus realized.
For facilitating the welding process the looking-down surface of the drum base 2 is provided with regions 9 of reduced thickness where the laser beam 8 is to be applied.
2. “Side-Welding”
The laser beam 8 is applied in a predetermined radial manner so that the alloys melt together accordingly at certain areas F at the circumference of the lower drum assembly where the drum base 2 and the lower drum 1 abut.
To avoid deforming the drum, it has to be considered that drum base 2 and lower drum 1 are fitted together closely during the laser welding process, particularly with regard to mass production line. This is achieved by uniform flatness of the upper surface of drum base 2 and the lower surface of lower drum 1 where drum base 2 and lower drum 1 abut so that both the drum base 2 and the lower drum 1 are very close to one another.
For generation of the laser beam 8, there can be used a laser type according to HAAS HPL 62P (from HAAS LASER), for example. A laser beam 8 having a beam diameter 1 mm and a beam angle 76°, for example, has been proved to be suitable.
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01400546 | Mar 2001 | EP | regional |
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Number | Date | Country | |
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20020122277 A1 | Sep 2002 | US |