POWER TRANSFORMER FOR HI-FI EQUIPMENT

Abstract: An insulator device having a spacer to be inserted between a power transformer and a conductive chassis, which spacer mono­ lithically carries at least one insulation washer with a cylin­ drical portion for insulating a mounting screw.

Description: The invention relates to a power transformer for hi-fi equipment according to the introductory part of claim 1. In a conventional apparatus using a conductive chassis, a core of a power transformer is provided electrically conductive with the chassis, since, in general, a power transformer is fixedly mounted on a chassis by means of a metal band holding the transformer and of metal screws. This structure allows to form an imaginary circuit between the core and the ground with respect to high frequency noise currents which may flow through a primary coil of the transformer. In such circuit, the noise currents run through series of the stray capacity between the coil and the core as well as the chassis and the ground. To this end, appearance of such imaginary circuit is likely to lead fluctuation of the ground potential of electronic circuits formed on printed substrates, thereby causing undesirable operation of the apparatus, or deterioration of tone quality in case of hi-fi equipments. The invention, as claimed, is intended to remedy these drawbacks. The insulating spacer electrically disconnects the iron core of the transformer from the chassis of the hi-fi equipment. Therefore, any high frequency noise in the transformer's current will no longer have any influence on the hi-fi circuits. The improvement is simple and reliable in that special care is taken to ensure that the necessary fastening screws do not short circuit the chassis and the iron core of the transformer. Special improvements are referred to in the subclaims. US-A-4,054,856 describes a current transformer connected to a dynamo-electric machine housing. The current transformer includes three coils sensing the currents of the three neutral leads of the three-phase AC-generator. The generator and the transformer use one common housing and the three coils of the transformer are secured within the housing by respective fastening screws. In order to prevent an electrical short circuit and a magnetic coupling between the coils and the parts of the generator, an insulating and magnetically shielding material is used between the coils and the housing. Furthermore, the fastening screws rest on isolation material between the screws and the housing. Figure 1 is a perspective view of the first embodiment according to the present invention; Figure 2 is a fragmentary sectional view of the first embodiment according to the present invention. Figure 3 is a perspective view of an insulator device according to the second emobodiment of the present invention. Figures 1 and 2 show the first embodiment of the present invention. A power transformer 10 holded by a metal band 11 is mounted on a chassis 12 of an electronic apparatus by means of four screws 13, each screw passing through a corresponding hole 14 in the horizontal portion of the metal band 11 and engaging with a corresponding screw hole 15 provided in the chassis 12. In the above construction, electrically conductive materials are used for the transformer 10, the band 11, the chassis 12, and the screws 13. Between the bottom of the transformer 10 and the chassis 12, there is provided on insulation spacer 16 covering the bottom of the transformer 10 as well as one side of each horizontal portion of the band 11 which faces the chassis 12. This spacer 16 is made of electrically non-conductive and mechanically elastic material, for example, rubber, or synthetic resins. The spacer 16 carries two insulation washer portions 16a in each shorter side thereof, each washer portion 16a having a hole 16b and a cylindrical portion 16c extended to the opposite side the hole 16b. These portions 16a, 16b, 16c and the spacer 16 are monolithically formed, and the portion 16c is adapted to be inserted into the hole 14 of the band 11 when the washer portion 16a is folded to lay onto the horizontal portion of the metal band 11. On the spacer 16, four through holes 17 are provided to align with the holes 14 and the screw holes 15 so that the transformer 1 may be fixedly mounted on the chassis 12 by the screws 13. In this embodiment, the transformer 10 may by mounted on the chassis 12 in accordance with the following procedure: The spacer 16 is interposed between the transformer 10 with the band 11 and the chassis 12, and then, each washer portion 16a is folded back to lay on the corresponding hole 14 of the metal band 11, with each cylindrical portion 16c being inserted into the corresponding hole 14. In this state, screws 13 are put into the cylindrical portions 16c through the holes 16b and, reaches the screw holes 15 after passing through the holes 14 and the through holes 17. Finally, the transformer 10 is fixedly mounted on the chassis 12 by turning the screws 13. According to the above embodiment, the power transformer 10 is completely and effectively insulated from the chassis 12. In other words, insulation can be obtained between not only the transformer 10 and chassis 12 through the spacer 16 but also the screws 13 and the metal band 11 through the washer portion 16a and the cylindrical portion 16c. Furthermore this provision realizes complete insulation between the transformer 10 and the chassis 12 without using separate components for insulating screws, since the spacer 16 monolithically carries portions for insulation of screws 13. Figure 3 illustrates the second embodiment of the present invention, which can be accomodated to a plurality of sizes of transformers. In Figure 3, three pairs of the washer portion 16a and holes 17 are protruded from each shorter side of the spacer 16, one of the washer portion 16a having shorter length than others and its corresponding hole 17 being provided nearer to the washer portion. Another washer portion 16c has two corresponding holes 17, so that the washer portion 16c can be foled to lay onto one of these holes 17 depend on the position of the hole on the metal band.

Claims: Power transformer for hi-fi equipment, with a metal band (11) of U-shape form and flanges at the respective end portions of the U-form to mount the transformer (10) on a chassis (12) of the hi-fi equipment by screws (13) being inserted into respective screw holes (14) in the flanges, characterized in that, an insulation spacer (16) is provided, covering the bottom of the transformer (10) and the set flanges of the metal band (11), the spacer having screw holes (17) in alignment with the screw holes (14) in the flanges, the spacer (16) further having monolitically formed end portions (16a,16b,16c) to be folded 180 o around the flanges, these end portions (16a,16b,16c) being provided with screw holes (16b) and insulation washers (16a,16c) around these screw holes (16b) which have a form and size to be inserted into the screw holes (14) of the flanges in the metal band (11). Power transformer according to claim 1, characterized in that, the end portions (16a,16b,16c) of the spacer (16) have separate foldable areas for each screw hole (40) of the flanges (11). Power transformer according to claim 1 or 2, characterized in that, more than one screw hole (17) is provided in the spacer (16) for one washer (16a,16c) to adapt to different sizes of transformers.

Inventors: KAWAHARA, KATSUSHI,, MOCHIZUKI, KAZUTO,
Applicants: AKAI ELECTRIC CO., LTD.
Application year: 1988
Main classification: H01F27
IPC codes: H01F27