JPS6238262Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a curl cord, and more particularly to a curl cord having a shielding layer suitable for connecting between a computer body and a keyboard.

In recent years, personal computers have been increasingly used at home.
In this case, the cord connecting the computer body and the keyboard may be tightly wrapped with thin metal wire suitable for curling to give it elasticity and resilience.
A curled cord is used, which is formed by curling a shielding layer made of a coarse braid of metal wire.
However, such a shielding structure has a problem in that high frequency components of logic signals or clock signals used in computers leak to the outside and cause radio wave interference to radio receivers, television receivers, etc.

In other words, shielding by tightly wound metal wires is usually used for electrostatic shielding in the audio frequency domain, whereas tightly wound metal wires are used to shield clock signals used in computers, logic signals, and their harmonics in frequency bands of the MHz order. A spiral current flows through the thin metal wire, making shielding useless. In addition, shielding using coarse braid is also used for electrostatic shielding, similar to densely wound metal wire, and at high frequencies, electromagnetic fields leak from the stitches of the braid, causing radio interference. In the case of coarse braiding, it is possible to increase the density of the braid in order to prevent electromagnetic field leakage, but this has the disadvantage of poor flexibility, stretchability, and restorability.

The present invention was created in view of the above points, and proposes a curl cord that has high shielding performance and has excellent flexibility, stretchability, and restorability. In order to make up for the lack of shielding properties by taking advantage of the mechanical properties of the cord, which is provided with a shielding layer obtained by closely winding thin metal wires with excellent resilience, we have created a laminated tape made of a composite of metal foil and plastic film with thin metal wires. It is added in the opposite winding direction to the tightly wound winding direction.

The curl cord according to the present invention has a wound layer of metal/plastic laminate tape and a tightly wound layer of thin metal wire on a core, and a winding direction of the wound layer of metal/plastic laminate tape and a tightly wound layer of thin metal wire. The winding direction of the laminate tape is opposite to the winding direction of the laminate tape, and the metal surface of the laminate tape and the tightly wound layer are provided in contact with each other to form a spiral shape.

The present invention will be explained below with reference to the drawings.

FIG. 1A is a side explanatory view showing the cord of the present invention, and FIG. 1B is an explanatory cross-sectional view taken along line BB in FIG. 1A. In FIGS. 1A and 1B, 10 is a cord of the present invention, and 1 is a core having multi-core wires.
2 is a metal or plastic laminate tape provided on the core 1 (for example, aluminum foil is used for the metal 21, and the thickness of the foil is usually 10 to 25 μm, and the thickness of the laminate tape 2 is 20 to 100 μm. 2
2 is a plastic film. ) is a lap-wound layer. 3 is a close-wound layer of thin metal wire provided on the winding layer 2, and the close-wound density is usually 90% or more. The metal surface 21 of the laminated tape 2 is in contact with the tightly wound layer 3, and the direction in which the laminated tape 2 is wound and the direction in which the tightly wound layer 3 of thin metal wire is wound are opposite to each other. provided. 4 is a rubber or plastic sheath. The cord 10 constructed in this manner is curled into a spiral shape to provide stretchability and restorability, thereby forming a curled cord. In the above, the tightly wound layer 3 of the thin metal wire is provided on the wound layer 2 of the laminated tape, but by doing so, the surface of the sheath 4 is finished in a relatively smooth state. However, the vertical positional relationship between the tightly wound layer 3 of the thin metal wire and the wound layer 2 of the laminated tape may be reversed, and in this case as well, the same shielding effect and flexibility can be obtained. In this case as well, it is necessary to bring the tightly wound layer into contact with the metal surface of the laminate tape.

By the way, in order to improve the shielding properties of the conventional tightly wound layer of thin metal wire, the present invention uses a double shielding structure with wound layers of metal and plastic laminate tape, and each winding is arranged in the same direction. Since the winding directions are opposite to each other, the contact between the metals is better than when the winding directions are the same, and the shielding effect is much higher. Furthermore, since the currents induced in the tightly wound layers 2 and 3 are in opposite directions, the magnetic fields generated based on the currents flowing in each layer cancel each other out, resulting in an even better shielding effect. It will be done. In addition, since a laminated tape of metal foil and plastic film is used as the laminated tape, the plastic film acts as a reinforcing layer and the metal foil can be made thinner, and the cord can be curled into a spiral shape. However, sufficient flexibility can be maintained.

As the metal, a conductive metal such as aluminum or copper is used, and as the plastic, a plastic that can be laminated with a conductive metal such as vinyl acetate or polyester is used.

FIG. 2 shows the shielding characteristic A of the cable according to the present invention in comparison with the characteristic B of the comparative example. C is the shielding property of the reference sample.

The cable sample according to the present invention consists of a cable core in which fine copper wire with a wire diameter of 0.12 mm is tightly wound at a density of 90%, and an aluminum polyester laminate tape with a thickness of 38 μm and an aluminum foil thickness of 10 μm is placed on top of the wire. The foil surface was in contact with the densely wound copper wire layer, and the same laminated tape was wound in the opposite direction to the winding direction of the densely wound copper wire layer to approximately 1/3 wrap. The example sample is the same as the cable sample of the present invention except that the winding direction of the laminated tape is the same as the winding direction of the densely wound copper wire layer. The reference sample is only a densely wound layer of fine copper wire. The measurement circuit used is as shown in FIG. In FIG. 3, _L1 is a guide line, which is made up of a 20AWG annealed copper wire with a diameter of 0.813 mm placed at a height of about 15 mm from a ground copper plate (not shown). X is the cable, a is the cable conductor, b
is a shielding layer. The arrangement height of the cable X is the same as that of the guide line, and the distance between the cable X and the guide line _L1 is 20 mm. SG is a resistor R ₁ at one end of the guiding wire L ₁
is the signal generator provided through the wire, and _R2 is the induction wire
A 50 ohm resistor connected to the other end of _L1 . LM is a voltmeter connected to one end of cable conductor a via a resistor R ₃ (50 ohms), and R ₄ is a 50 ohm resistor connected to the other end of cable conductor a. Note that both ends of cable X are completely shielded with shielded connectors.

The shielding effect α is determined by applying a signal of 0 to 1000 MHz at a voltage V ₁ to the induction line L ₁ using a signal generator SG, and measuring the induced voltage V of the conductor a of the cable X with a voltmeter LM, α = 20 log V ₂ /V Calculated at ₁ [dB].

As is clear from Fig. 2, according to the cable of the present invention (characteristic A), 0 to
Shielding characteristics can be improved by more than 30 dB in the 1000 MHz frequency band. On the other hand, in the comparative sample (characteristic B), the improvement was only 10 to 20 dB above 100 MHz, and there was almost no improvement below 100 MHz.

As mentioned above, according to the present invention, a flexible cable with excellent shielding characteristics can be provided, and the present invention can be used as a curl cord for connecting to a computer as described above, which requires excellent shielding characteristics especially in the high frequency band. Useful.

In addition, in the above-mentioned example, the tape was wound in an overlapping manner as the winding layer of the laminated tape, but even if the tape is wound with a gap in the longitudinal direction, the close-wound layer of the thin metal wire and the winding of the laminated tape will not overlap. the layers in such a way that they are in metal-to-metal contact, and
Since it is wound in the opposite direction, it exhibits almost the same shielding characteristics as when wrapped and wound, and has good elasticity and the like.

[Brief explanation of the drawing]

FIG. 1A is a side explanatory view showing the cord according to the present invention, FIG. 1B is an explanatory cross-sectional view taken along line B-B in FIG. 1A, FIG. 2 is a drawing showing the shielding characteristics of the cord according to the present invention, and FIG. 1 is a drawing showing a circuit for measuring the above-mentioned shielding characteristics. In the figure, 1 is a core, 2 is a laminated tape wound layer, and 3 is a densely wound metal wire layer.

Claims (1)

[Scope of utility model registration request] A wound layer of metal/plastic laminate tape and a tightly wound layer of thin metal wire are placed on the core, with the winding direction of the wound layer of metal/plastic laminate tape and the winding direction of the tightly wound layer of thin metal wire being opposite to each other. Moreover, the curl cord is characterized in that the metal surface of the laminate tape and the above-mentioned tightly wound layer are provided in contact with each other and configured in a spiral shape.