JPS6130359Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a double shield case.

In small television receivers, because space within the cabinet is limited, circuit boards are placed close to each other and to other components. Therefore, leakage magnetic flux from the deflection yoke, transformer, etc. affects the local oscillation circuit of the tuner formed on the circuit board, causing a shift in the oscillation frequency of this oscillation circuit. This is because the inductance of the coil in the local oscillation circuit changes due to the leakage magnetic flux, and the oscillation frequency changes accordingly. In an intercarrier television receiver, even if the above frequencies shift, both VIF (video intermediate frequency) and SIF (sound intermediate frequency) shift by the same amount, so the difference between the two frequencies is kept at 4.5MHz. Since it is constant, there is no particular problem. However, in split carrier type television receivers, the SIF is taken out independently for detection, so if the frequency of the local oscillator circuit shifts and the SIF shifts accordingly, the center of the audio detection circuit A difference occurs between the frequencies and appears as noise.

Therefore, especially in split carrier type television receivers, the tuner is housed in a double shield case to prevent the frequency of the local oscillation circuit from shifting. Shield cases conventionally used for this purpose include a box-shaped outer case.
This outer case was made from stamped metal plates, then bent and joined together by caulking or welding. Therefore, the mold for molding is complicated and the number of manufacturing steps is increased. Furthermore, the outer shield case must have high dimensional accuracy in order to accommodate the inner shield case, which increases the cost.

The object of the present invention is to overcome these drawbacks and provide a double-shielded case that is easy to manufacture and does not require high precision.

The present invention will be explained in detail below with reference to illustrated embodiments. In this embodiment, the present invention is applied to a shield case for a tuner in a split carrier type television receiver. It is housed in a shield case 1. The inner shield case 1 includes a frame 2 consisting of four side plates, and a top plate 3 and a bottom plate 4 that close the upper and lower openings of the frame 2. The circuit board is fixedly held within the frame 2. A large number of elastic pieces 5 formed by folding back the peripheral edges of the top plate 3 and the bottom plate 4 elastically engage with protrusions formed on the outer surface of the frame 2. A box-shaped inner shield case 1 is constructed by closing the upper and lower openings. A pair of attachment pieces 6 are provided in series on the frame 2, and the case 1 is attached to a predetermined position by means of the attachment pieces 6.

An outer shield case 7 attached to surround the inner shield case 1 is composed of a pair of plate-like bodies 8 and 9. These plate-like bodies 8,
Reference numeral 9 is made of a magnetic material, for example, an iron plate, and is formed by punching with a press. The upper and lower plate-like bodies 8 and 9 have the same shape, and an engaging piece 10 is formed at the tip of one side thereof by bending the side part into a U-shaped cross section. Further, on the other side part, this side part is bent into an L-shaped cross section, and an engaged piece 11 is formed at the tip thereof. By engaging these engaging pieces 10 and engaged pieces 11 with each other, the pair of upper and lower plate bodies 8 and 9 are assembled together.

The operation of this combination will be explained with reference to FIGS. 2 and 3. In particular, as shown in FIG. The engaging piece 10 on one side of the lower plate-like body 9 is engaged with the engaged piece 11 on the side, and the engaging piece 10 on one side of the lower plate-like body 9 is engaged with the engaged piece 11 on the side of the plate-like body 8 on the upper side.
It is engaged with the engaged piece 11 on the other side. As a result, the pair of plate-shaped bodies 8 and 9 are engaged with each other, and the outer shield case 7 is assembled into a rectangular cylindrical shape. At this time, the distance between the pair of plate-like bodies 8 and 9 is slightly smaller than the thickness of the inner shield case 1 in the same direction. Therefore, as shown by the chain lines in FIG. 3, a force is applied from the lateral direction of the pair of plate-like bodies 8, 9 in a direction in which they are mutually compressed, and the upper and lower plate-like bodies 8, 9 are deformed into an arched shape. let When the distance between these plate-like bodies 8 and 9 is wide, the inner shield case 1 is inserted between them. When the applied force is subsequently released, the pair of plate-shaped bodies 8 and 9 elastically return to their original state and are elastically pressed against the top plate 3 and bottom plate 4 of the inner shield case 1. Therefore, a frictional force is generated between the inner shield case 1 and the outer shield case 7, and the outer shield case 7
will be attached to the outside of the outer shield case 1.

As described above, the outer shield case 7 of this embodiment consists of a pair of plate-shaped bodies 8 and 9, and these plate-shaped bodies 8 and 9 are punched into a predetermined shape and have a structure in which both sides are bent. Because of this, it is manufactured only by plastic working of steel plates. In other words, there is no need for a step to connect the two, which makes manufacturing easier and reduces the number of steps. Also, this outer shield case 7 has an engaging piece 10 of a pair of plate-shaped bodies 8 and 9.
The inner shield case 1 is inserted into the assembled state in which the and engaged piece 11 are engaged with each other, and at that time, the pair of plate-like bodies 8 and 9 are inserted.
They are elastically deformed to widen the gap between them. Therefore, even if there is variation in the dimensional accuracy of the pair of plate-shaped bodies 8, 9, this variation will be absorbed by the elastic deformation of the pair of plate-shaped bodies 8, 9, so it is necessary to increase the dimensional accuracy. There is no.

Further, according to the shield case 7 of this embodiment, since the pair of plate-like bodies 8 and 9 are elastically crimped to the inner shield case 1, the inner and outer shield cases 1 and 7 are electrically connected to each other for grounding. There is no need to connect to. In addition, since the pair of plate-shaped bodies 8 and 9 are elastically crimped with the inner shield case 1,
The inner and outer shield cases 1 and 7 do not move relative to each other and are not rattled. Further, according to the shield case 7 of this embodiment, the pair of upper and lower plate-like bodies 8,
Since the shields 9 have the same shape, the shield case 7 is formed by making one type of plate-like body and combining two of them. Therefore, it is also advantageous in terms of cost.

Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention. For example, the above embodiment relates to a shield case for a tuner of a television receiver, but the present invention can be used for shield cases for various other circuits and components. Further, in the above embodiment, the engaging piece 10 and the engaged piece 11 are each formed with unevenness, so that the pair of plate-like bodies 8 and 9 are mutually connected to each other.
In the figure, mutual displacement in the vertical direction may be prevented.

As described above, according to the present invention, the outer shield case consists of a pair of shield plates, which are combined by an engaging part and an engaged part and attached to the outside of the inner shield case. Therefore, there is no need to bond the pair of shield plates in advance, which reduces the number of manufacturing steps and facilitates manufacturing. Further, since dimensional errors can be absorbed by utilizing the elastic deformation of the pair of combined shield plates, there is no need to increase dimensional accuracy.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a shield case according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view taken along the line -- in FIG. 2. In addition, in the symbols used in the drawings, 1...Inner shield case, 7...Outer shield case,
8... Plate-shaped body (top), 9... Plate-shaped body (bottom), 10...
...an engaging piece, 11...an engaged piece.

Claims (1)

[Scope of utility model registration request] In the double shield case, the outer shield case is composed of a pair of shield plates, and an engaging part and an engaged part are formed on both sides of these shield plates, respectively. A double shield case characterized in that the pair of shield plates are combined with each other and attached to the outside of the inner shield case.