JPH0135521B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a helical filter used in the VHF/UHF band, which adjusts the frequency by varying the capacitance between a metal screw and a helical coil using the metal screw. .

Conventional configuration and its problems In general, in high frequency bands such as VHF and UHF bands, frequency adjustment (waveform adjustment) of helical filters is required.
A metal screw is used to perform this, but when the metal screw is at a high potential, the resonant frequency changes due to the influence of the driver used for adjustment, making it difficult to adjust the waveform, so the metal screw is used by grounding it. There are many things. By grounding the metal screw, the potential will be lowered and the effect of the screwdriver can be eliminated.

Here, a conventional example in which a metal screw is grounded will be explained. This type of helical filter is constructed as shown in FIG. That is, a metal ring 2 with a through hole provided with a screw as shown in FIG. While engaging the metal screw 3 with the threaded part of the ring 2,
It is constructed by inserting a cylindrical bobbin 5 made of plastic around which a helical coil 4 is wound, below a metal ring 2 in a shield case 1. Moreover, the metal screw 3 is made of a metal ring 2.
It is held only by the shielding case 1 and is in electrical contact with the shielding case 1. Furthermore, an input coil 6 and an output coil 7 for injecting and extracting signals are wound around the lower part of the helical coil 4.

A capacitance exists between the metal screw 3 and the helical coil 4, and by rotating and moving the metal screw 3, the capacitance changes, thereby changing the tuning frequency and making it possible to adjust the waveform.

However, in the helical filter of this structure, the metal screw 3 is held only by the metal ring 2, and the metal screw 3 rattles or moves due to vibration or excitation, resulting in tuning. The drawback was that the frequency would shift. Further, even if a rib is provided on the cylindrical bobbin 5 so that a part of the metal screw 3 can be engaged with it, the metal screw 3 cannot be completely locked. To prevent this, the metal screw 3 and the metal ring 2 are usually fixed by painting, soldering, or the like. However, when fixing with paint, there is a risk that the metal screw 3 and the metal ring 2 will be insulated if an insulating material is used, and if a conductive material is used, it will be expensive and the cost will increase significantly. There was also the uneconomic aspect of this.

Furthermore, during soldering, there was a risk that the helical coil 4 would be exposed to high heat due to the soldering, resulting in a significant change in its characteristics. Moreover, the paint application and soldering significantly impair workability.

Purpose of the Invention The present invention aims to eliminate such conventional drawbacks by bringing the metal screw into electrical contact with the shield case, securely locking the metal screw after adjusting the waveform, and making it resistant to vibration. The purpose is to provide a helical filter that is durable, has good workability, and has stable characteristics.

Structure of the Invention In order to achieve this object, the present invention increases the wall thickness of the ceiling surface of a shield case, provides a through hole in the ceiling surface consisting of at least two or more arc-shaped convex portions and concave portions, and A female thread is provided on the inner circumferential surface of the convex portion to which the metal screw for adjusting the waveform is rotatably engaged, and a part of the upper end of a cylindrical bobbin provided with a rib on which the metal screw for adjustment is engaged is inserted into the recess. It is composed of

With this configuration, the metal screw is engaged by the female thread of the convex part on the ceiling surface of the shield case, and by rotating it with a screwdriver, the upper end of the cylindrical bobbin is inserted into the recess of the shield case. The threaded part of the metal screw also bites into the rib provided in the
By stopping the rotation of the driver, the metal screw is locked to the cylindrical bobbin. Therefore, the metal screw is grounded by electrically contacting the shielding case through the female thread of the shielding case, and the ribs of the cylindrical bobbin prevent it from rattling or rotating due to vibrations. .

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings of FIGS. 3 to 6.

A through hole 1 consisting of four arc-shaped convex portions 12 and four concave portions 13 as shown in FIG.
4, and a metal screw 15 for corrugation adjustment is screwed into the inner circumferential surface of the convex portion 12, and the screw is provided so as to rotate up and down when turned with a screwdriver or the like. A perspective view of the ceiling surface of the shield case 11 is shown in FIG.

In addition, a rib 1 as shown in FIG.
An arc-shaped protrusion 19 having a diameter of 8 is provided, which is inserted into the arc-shaped recess 13 of the shield case 11, and is further inductively coupled to the helical coil 16 at the lower part of the helical coil 16 for signal injection and extraction. An input coil 20 and an output coil 21 are wound around each other. And the shield case 1
A metal screw 15 for corrugation adjustment is screwed into the through hole 14 in the ceiling surface of 1.

When this metal screw 15 is rotated with a screwdriver, it engages with the female thread of the protrusion 12 of the shield case 11, rotates and moves up and down, and at the same time the cylindrical bobbin 1 inserted into the recess 13 of the shield case 11
The threaded portion of the metal screw 15 also bites into the rib 18 of No. 7, and the thread is automatically cut. At this point, if the rotation of the driver is stopped, the threaded portion of the metal screw 15 bites into the rib 18 of the cylindrical bobbin 17 and is locked. Here, the metal screw 15 electrically contacts the shield case 11 through the female thread of the protrusion 12 of the shield case 11 and is grounded, and the rib 18 of the cylindrical bobbin 17
This prevents rotation and wobbling and secures it. Further, a capacitance exists between the helical coil 16 and the metal screw 15, and by rotating and moving the metal screw 15, the capacitance can be changed, and the waveform can be adjusted by changing the tuning frequency.

In this way, the metal screw 15 is connected to the shield case 11.
Since it is in electrical contact with the metal screw 15 and is fixed by the rib 18 provided on the cylindrical bobbin 17, it will not rotate naturally due to vibration etc. unless the metal screw 15 is rotated with a screwdriver or the like. . Therefore, there is no need to apply paint or solder to prevent the metal screw 15 from rattling, and since the metal screw 15 is grounded through the shield case 11, the waveform can be easily adjusted without being affected by an adjustment screwdriver. This means that a helical filter with stable characteristics can be provided because there is no rattling.

In addition, in order to reduce the wall thickness of the ceiling surface of the shield case as in the past, a through hole 24 consisting of a convex part 22 and a concave part 23 is provided as shown in FIG.
It can also be constructed by attaching a metal ring 25 with a female thread on the inner peripheral surface of the convex portion 22 to the ceiling surface of the shield case 26 by soldering, crimping, or the like. Furthermore, the through holes in the ceiling surface of the shield case 26 or the protrusions and recesses of the metal ring are shown in FIGS. 8 and 9.
As shown in the figure, the same effect can be obtained by using two or three each.

Effects of the Invention As described above, according to the helical filter of the present invention, unless the metal screw for frequency adjustment is brought into reliable electrical contact with the shield case and the metal screw is not rotated with a screwdriver, etc., it will rotate naturally due to vibration etc. It has a structure that does not cause any wobbling or wobbling, which improves reliability, and it also has the advantage of being easy to work with, such as painting and soldering, and is cost-effective and improves reliability. It will be done.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional helical filter, FIG. 2 is a perspective view of a conventional threaded ring that holds a metal screw, and FIG. 3 is a sectional view showing an embodiment of the helical filter of the present invention. , FIG. 4 is a top view of the shield case excluding the adjusting metal screw in the present invention, FIG. 5 is a perspective view of the top surface of the shield case in the present invention, and FIG. 6 is a top perspective view of the cylindrical bobbin in the present invention. , FIG. 7 is a perspective view of a threaded ring showing another embodiment of the present invention, and FIGS. 8 and 9 are top views of the shield case excluding the adjustment metal screw in another embodiment of the present invention. It is a diagram. 11, 26... Shield case, 12, 22...
... Convex portion, 13, 23 ... Concave portion, 14, 24 ... Through hole, 15 ... Metal screw, 16 ... Helical coil, 17 ... Cylindrical bobbin, 18 ... Rib, 19
... protrusion, 25 ... circular ring.

Claims (1)

[Scope of Claims] 1. It is constructed by storing a cylindrical bobbin wound with a helical coil in a shield case equipped with a metal screw for frequency adjustment, and the thickness of the ceiling surface of the shield case is increased to A through hole consisting of at least two or more arc-shaped convex portions and concave portions is provided on the surface, a female screw is provided on the inner circumferential surface of the convex portion into which a metal screw for corrugation is rotatably engaged, and the metal screw for adjustment is A helical filter formed by inserting a part of the upper end of a cylindrical bobbin provided with a rib for locking a screw into the recess. 2. A metal ring having at least two through holes consisting of an arc-shaped convex part and a concave part, and a threaded part into which an adjustment metal screw is screwed on the inner peripheral surface of the convex part is attached to the shield case. The helical filter according to claim 1, wherein the helical filter is mounted on a ceiling surface and the metal ring is in electrical contact with a shield case.