EP0007275A1 - Adjustable inductance and transmitter comprising same - Google Patents

Abstract

Variable inductor whose cursor pressure on the winding conductor decreases when the cursor is moving rapidly. The inductance comprises: a conductor (1) wound on a circular helix, a mechanical axis of rotation (2) arranged along the geometric axis (XX) of the helix and a cursor (3) mounted so as to remain in contact sliding with the conductor and sliding only longitudinally along the mechanical axis, so that its contact on the conductor moves along the propeller during a rotational movement of the mechanical axis. To reduce friction, and therefore wear, during a rapid rotational movement of the mechanical axis, a spacer device (8) is associated with the cursor (3) and tends, under the effect of force. centrifugal, to reduce the pressure of the cursor (3) on the conductor (1). Application, in particular, to variable inductances for medium power transmitters.

Description

The present invention relates to a variable inductor comprising: a fixed winding made of a conductor wound according to a circular helix and a cursor pressing on the conductor, the displacement of the fulcrum of the cursor on the conductor being by a screwing movement of the cursor around the axis of the propeller.

Such variable inductances are known in which the cursor is placed inside the propeller and presses and slides on the conductor; this cursor ensures the electrical connection with a rotary conductive axis disposed along the main axis of the propeller and. can move longitudinally on this conductive axis. The rotational movement of the conductor axis causes the cursor to move on the conductor, the latter serving as a guide rail for the cursor.

These inductors are generally used in medium power transmitters and in the matching circuits of the antennas associated therewith.

The conductive axis of the inductor is most often driven in rotation using a motor which, on the one hand, thanks to its speed of rotation, ensures rapid positioning of the cursor and which, on the other hand , allows remote control or servo control in automatically tuned devices.

This rapid positioning corresponds to a very high speed of sliding of the contact on the conductor. To limit wear on the contact and / or the conductor, the pressure exerted by the cursor on the conductor must remain low while the cursor is moving at high speed; however it should be noted that the movement of the cursor at high speed is very generally linked to a reduced current in the inductance, therefore to a current which does not require a strong pressure in the contact between the cursor and the conductor.

On the other hand, at standstill or at low speeds corresponding to the end of a servo period, the current in the inductor is maximum and the contact pressure must be high to limit resistance and overheating at the point of contact.

With known variable inductors, the contact pressure is fixed and is most often chosen to be fairly high, which, as seen above, is well suited when the cursor is stationary or slides at low speed on the conductor. but leads to significant wear of the contact and / or of the conductor during rapid positioning.

The present invention aims to reduce and, if possible, eliminate these drawbacks.

This is obtained thanks to a cursor exerting on the conductor a contact the pressure of which is linked to the sliding speed of the cursor and, therefore, to the speed of rotation of the conductive axis of the inductor.

According to the invention a variable inductor of the type indicated at the beginning of this text is characterized in that it comprises a spacer device associated with the cursor and which, under the effect of the centrifugal force produced during a movement of screwing, tends to move the cursor away from the driver.

• - la figure 1 une vue d'une partie d'une première inductance variable selon l'invention ;
• - la figure 2 des éléments d'une seconde inductance variable selon l'invention.

The present invention will be better understood and other characteristics will appear from the following description and the figures relating thereto which represent

• - Figure 1 a view of part of a first variable inductor according to the invention;
• - Figure 2 of the elements of a second variable inductor according to the invention.

Figure 1 is a view of a varia inductor ble, reduced, for convenience of drawing and reading the drawing, to the elements necessary for understanding the invention. It should also be noted that, for the same reasons, the dimensions of certain elements of the inductance have not been observed in FIG. 1.

• - environ quatre spires du bobinage, 1, d'une inductance variable,
• - une portion de chacune de trois barres isolantes 10, 11, 12 placées autour du bobinage 1 et servant à sa fixation
• - un axe mécanique de rotation, 2, de section carrée, dont l'axe géométrique de rotation est repéré XX ,
• - un curseur, 3.

In Figure 1 are shown:

• - about four windings of the winding, 1, with a variable inductance,
• a portion of each of three insulating bars 10, 11, 12 placed around the winding 1 and used for its fixing
• a mechanical axis of rotation, 2, of square section, the geometric axis of rotation of which is marked XX,
• - a cursor, 3.

The winding 1 is made of conductive wire of rectangular section with a thickness of 1.5 mm and a width of 8 mm; it comprises, in total, fifty coils wound in the form of a circular helix of axis XX. The dimensions of the winding are: overall length 300 mm, diameter 120 mm.

The insulating bars 10, 11, 12 are made of rigid plastic and have notches of 2mm in. depth in which the conducting wire of the winding rests they are arranged at 120 ° from one another around the axis XX and serve as spacers for the flanges, not shown, of the variable inductance.

The axis of rotation, 2, is a hollow square tube, 18 mm square, made of silver copper; it is connected to the flanges, in the vicinity of its ends, not shown, by means of plastic bearings. One of the ends of axis 2 crosses one of the flanges of the inductor and is designed to be coupled to the motor axis.

• - deux lames élastiques, 4, 5, de 10 mm de large et de cinq dizièmes de millimètre d'épaisseur, réalisées en bronze à ressort. Ces lames sont pliées, sensiblement à 90°, au voisinage de leur première extrémité, 40, 50, et sont en contact, toujours au voisinage de cette même extrémité avec l'une des faces de l'axe carré, 2, par l'intermédiaire de contacts en argent soudés sur les lames ces contacts en argent sont identiques aux contacts en argent qui apparaîtront sur la figure 2. Les lames 4 et 5 sont accolées sur leur partie médiane et s'écartent l'une de l'autre vers leur seconde extrémité pour former une sorte de pince dont les deux branches aboutissent de part et d'autre d'un même point du bobinage 1 ; là encore le contact se fait par l'intermédiaire de contacts en argent,soudés sur les lames,
• - deux guides isolants, 6 , 7, comportant une partie circulaire percée d'un trou à travers lequel passe l'axe 2 et l'une des extrémités repliées des lames (extrémité 40 pour le guide 6 et extrémité 50 pour le guide 7) ; les deux guides 6 et 7 comportent respectivement deux languettes 30, 31, formant.une étoile à trois branches avec les lames 4, 5, et deux parties en forme de gouttière, disposées selon la branche de l'étoile occupée par les lames, chacune des lames étant ainsi maintenue, dans sa partie médiane, à l'intérieur de la gouttière de l'un des guides. Les lames 4, 5 et les guides 6, 7 sont rendus solidaires par trois rivets 32, 33, 34 reliant entre elles les parties circulaires des guides. Ainsi les lames élastiques pincent une spire du bobinage 1 tandis que les guides 6 et 7, disposés à 120° de part et d'autre des lames élastiques, appuient respectivement au-dessous et au-dessus de cette même spire ; il s'en suit que, lorsque l'axe 2 tourne (flèches ^g ₁ ou g₂) , le curseur en forme d'étoile est maintenu en permanence dans un plan sensiblement perpendiculaire à l'axe 2 et le point de pincement entre les lames élastiques 4, 5 et le conducteur 1 glisse le long du conducteur.

Cursor 3 includes:

• - two elastic blades, 4, 5, 10 mm wide and five tenths of a millimeter thick, made of spring bronze. These blades are folded, substantially at 90 °, in the vicinity of their first end, 40, 50, and are in contact, always in the vicinity of this same end with one of the faces of the square axis, 2, by the intermediate silver contacts welded to the blades these silver contacts are identical to the silver contacts which will appear in FIG. 2. The blades 4 and 5 are placed side by side and move away from each other towards their second end to form a sort of clamp whose two branches end on either side of the same point of the winding 1; here again the contact is made by means of silver contacts, welded to the blades,
• - two insulating guides, 6, 7, comprising a circular part pierced with a hole through which the axis 2 passes and one of the folded ends of the blades (end 40 for guide 6 and end 50 for guide 7) ; the two guides 6 and 7 respectively have two tongues 30, 31, forming a three-pointed star with the blades 4, 5, and two gutter-shaped parts, arranged according to the branch of the star occupied by the blades, each blades thus being held, in its middle part, inside the gutter of one of the guides. The blades 4, 5 and the guides 6, 7 are made integral by three rivets 32, 33, 34 connecting together the circular parts of the guides. So the elastic blades pinch a turn of the winding 1 while the guides 6 and 7, arranged at 120 ° on either side of the elastic blades, press respectively below and above this same turn; it follows that, when the axis 2 rotates (arrows ^g ₁ or g ₂ ), the star-shaped cursor is permanently maintained in a plane substantially perpendicular to the axis 2 and the pinch point between the elastic blades 4, 5 and the conductor 1 slides along the conductor.

The slider 3 also includes a device for separating the two elastic blades 4, 5; this spacing device, 8, comprises a weight 81 of 0.5 gram and a lever 82 located on either side of a small pivot axis 80 with which they form a single piece. Part of the elastic blade 5 has been torn off to allow a better view of the spacer. The elastic blade 4 has, in its part forming one of the branches of the cursor clip, a hole 40 and, on either side of this hole, two tongues bent at 90 ° and each pierced with a circular hole and which serve as a bearing for the minor axis 80; the minor axis 80 and the lever 82 are located inside the branches of. the cursor clip; the counterweight 81 is connected to the minor axis 80 through the hole 40.

When the cursor is at rest the lever 82 hardly touches the elastic blade 5. On the other hand, when the cursor is in rapid displacement (in the case of the example described: 10 revolutions per second, which corresponds to a displacement of end to end of the winding in 5 seconds for a winding length of 17 meters) the counterweight 81, under the effect of centrifugal force, moves (arrow f), which causes the lever 82 to tilt and it presses d '' stronger on blade 5 to move it away from blade 4 than the centric force fuge is greater. Thus the pressure exerted by the elastic blades on the winding is reduced during rapid movements of the cursor which, consequently, reduces the wear of the cursor and the winding compared to a variable inductance of conventional type of the genre for example that of Figure 1 but without the elastic blade spacing device.

The variable inductance which has just been described is intended to operate with an average HF current of 12A when the cursor is stopped or traverses the last turn preceding its breakpoint and an average HF current of 0.5A when the cursor is moving fast.

Figure 2 shows, seen in section, an assembly consisting of two elastic blades 21, 22 and a device for spacing these blades, 23. This assembly replaced the assembly consisting of parts 4, 5 and 8 of FIG. 1 makes it possible to constitute another variable inductor according to the invention. In this variant, the spacing device 23 consists of a steel ball, placed between the two elastic blades and held in a pocket formed by two kinds of bumps, one per blade, the concave parts of which are opposite.

In FIG. 2 also appear four silver contacts, 24 to 27, welded to the blades. These contacts which have the shape of half-spheres of about 5mm in diameter, are intended to ensure the sliding contact of the cursor with the axis of the inductor (contacts 24, 25) and with the winding (contacts 26, 27) .

Under the action of the centrifugal force (arrow f) created by the rapid rotation of the variable inductance axis, the ball moves and tends to move aside the clamp formed by the two ends of the elastic blades terminated by the contacts 26, 27 this results in a dimi nution of the pressure force exerted by the cursor on the winding.

• - une petite barra montée en rotation autour d'un axe solidaire du bras,
• -une roulette solidaire de l'une des extrémités de la barre et qui vient en contact avec le conducteur du bobinage
• - une masselotte solidaire de l'autre extrémité
• de la barre et qui, lors d'une rotation rapide de l'axe de l'inductance, tend à réduire la pression de la roulette sur le conducteur,
• - et un ressort fixé entre le bras et la barre et tendant à augmenter la pression de la roulette sur le conducteur.

Various other variable inductors can be envisaged without departing from the scope of the invention, these inductors comprising a cursor with a first device applying pressure to the winding and a second device which, under the effect of the centrifugal force produced by the rapid rotation of the axis of rotation of the inductor, automatically reduces the pressure exerted by the first device on the winding. This is for example the case of an inductor where the cursor has a sliding arm and, at the end of this arm:

• - a small barra mounted in rotation around an axis secured to the arm,
• -a caster secured to one end of the bar and which comes into contact with the winding conductor
• - a counterweight secured to the other end
• of the bar and which, during a rapid rotation of the axis of the inductor, tends to reduce the pressure of the caster on the conductor,
• - And a spring fixed between the arm and the bar and tending to increase the pressure of the caster on the conductor.

The invention is applicable, in particular to transmitters and, more particularly to medium power transmitters.

Claims (5)

1. Variable inductance comprising: a fixed winding made of a conductor wound according to a circular helix and a cursor pressing on the conductor, the displacement of the fulcrum of the cursor on the conductor being by a screwing movement of the cursor around the axis of the propeller, characterized in that it comprises a spacer device associated with the cursor and which, under the effect of the centrifugal force produced by a screwing movement of the cursor, tends to reduce the pressure of the cursor on the driver. 2. Inductor according to claim 1, in which the cursor comprises a clamp, this clamp comprising two facing pieces and pinching the conductor, characterized in that the spacer device is associated with the two facing pieces for, under the effect of the centrifugal force produced by a screwing movement of the cursor, tend to separate the two facing pieces from each other. 3. Inductor according to claim 2, characterized in that the two facing pieces are two elastic blades and in that the spacing device comprises: a tilting axis the bearing of which is integral with one of the two blades, a lever secured at one of its ends to the tilting axis and a weight secured to the tilting axis so that, under the effect of the centrifugal force produced by a screwing movement of the slider, it tends to rotate the pivot axis and press the lever on the other of the two blades. 4. Inductor according to claim 2, characterized in that the two opposite parts are two blades elastic bands each having a hollow part, the hollow parts of the two blades facing each other to form a pocket and in that the spacing device comprises a ball placed inside the pocket and which, under the effect of the centrifugal force produced by a screwing movement of the cursor, tends to come out of the pocket. 5. Transmitter characterized in that it comprises at least one inductor according to one of the preceding claims.

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