US2306333A - Concentric line inductance - Google Patents

Description

Dec. 22, 1942. w. H. CONRON' ETAL CONCENTRIC LINE INDUCTANCE Filed March 1, 1941 Patented Dec. 22, 1942- CONCENTRIC LINE INDUCTANCE William H. Conron, Haddonfleld, N. J., and Benjamin W. Suckle, Philadelphia, Pa., assignors to Radio Corporation of America, a corporation of Delaware Application March 1, 1941, Serial No. 381,214

7 Claims. (01. 178-44) This invention relates to concentric line in ductances of the type comprising a center conductor and an outer sleeve conductor joined atone end to form a concentric line inductance and provided at the opposite end with a tuning capacitor connected between the inner conductor-and the outer conductor. Such a device is disclosed by the U. S. Patent 1,955,093.

When it is desired to cover a frequency range involving a change in frequency of the order of 3 to 1 or greater with a concentric line inductance in a tunable circuit, it is found that the Q of the circuit is reduced rapidly as the tuning approaches the low frequency end of the tuning range. It is, therefore, an object of this invention to provide an improved concentric line tuning inductance for a tunable high frequency circuit for efiectively covering a relatively wide'frequency band without impairing the efliciency thereof.

Another object is to .provide a concentric line tuning system comprising a concentric line element and a variable tuning capacitor for effectively covering a relatively wide frequency band involving a frequency change of the order of 3 to 1 or greater without loss in the value of the Q of the circuit as the tuning approaches the low frequency end of the range.

It has been found that a relatively wide frequency band or tuning range may be divided into two or more overlapping frequency ranges and the tuning may be accomplished with a concentric line inductance by short-circuiting a portion of the center conductor to the outer 'conductor, thereby reducing the inductance of the line. However, since such inductances are utilized in relatively high frequency circuits, slight variations in the length and other constants of the line ordinarily caused by switching means have an amplifying eilect upon the frequency of the tunable circuit in which the line is utilized.

It is a further object of this invention to proing radial and in parallel. This fact has not heretofore been appreciated in providing various expedients for changing the length or inductance of a concentric line tuning system.

It is a further object of this invention to provide a concentric line tuning inductance having a switching means for short-circuiting the inner conductor to the outer conductor at one or more points along the line, thereby to change the length and inductance of the line and an improved switching means for this purpose which may be reset over long periods of time with extreme accuracy to provide the same inductance at each resetting.

It is also an object of this invention to provide an improved switching means for a concentric line inductance to short-circuit the inner conductor tp the outer conductorfthereby to adjust the effective length of the line at a point between its ends, said switching means providing a multiple path. circuit between said conductors, whereby said circuits through the inner and outer conductors may be maintained in parallel, and to preserve the operatingefficiency of the, line over an extended operating period.

The invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope is pointed out in the appended claims.

In the drawing, Figure 1 is a longitudinal view,

. substantially full size and partly in cross section,

vide an improved concentric line tuning inductance provided with means for adjusting the ffective length of the inner conductor to cover a,

relatively wide frequency band in tuning, the adjustment of which is accurate and constant,

and provided with a tuning capacitor at the opposite end provides a multiple path circuit through thejouter conductor from the inner conductcr, thecir cuit elements or current paths beof a concentric line tuning inductance circuit and inductance adjusting means embodying the invention; and

Figure 2 is a transverse cross sectional view of the inductance changing means of Fig. 1, and on the same scale;

Referring to the drawing, the concentric line conductor comprises a center conductor having a low frequency portion 6 anda high frequency portion 5 serially connected between a low potential end terminal 1 and a high potential end I sired.

' the input grid 42 of a tube 43.

In the present example, the switch housing contains two spaced outer contact rings I4 and I5 electrically connected directly by clamping means I2 to the casing II and, therefore, to the outer conductor and having radially inwardly extending spring contact fingers I6 which grip the periphery of a rotatable contact ring or annular member II, which is located in a plane normal to the axis of the line between the outer and inner conductors, and provided with radially inwardly projecting spaced blades or contact elements I8.

degrees by an operating handle or lever I9 which projects through a slot in the switching housing I I. In the present example, the contact ring may be rot ted to the left as viewed in Fig. 2, to carry the b ades I8 into engagement between opposed contact fingers 22 and 23 arranged in pairs about the periphery of a flanged head 25 for the high frequency portion of the inner conductor 5. The fingers are clamped to the flange head 25 by a clamping ring 26, and extend radially from the head to positions between the blades I8 as shown. When the lever I9 is moved to the left, contact between the head 25 and the casing II forming part of the outer conductor is made through a plurality of radially extending paths, thereby maintaining the multiple path circuit of the line complete when the inductance is changed. A

The lever I9 represents any suitable operating device for rotating the annular contact member I! through a small angle, and is preferably of metal or conducting material whereby it is grounded through the ring to the outer casing or conductor.

When the switch is open in the position shown, the entire length of the inner conductor is effective with the sections 5 and 6 in series. In this position, the capacity between the edges of the blades I8 and the contacts 2223 is negligible in its effect on the line. Section 6 is connected to the head 25 by a terminal 28. The low potential terminal I is connected through a conducting end cover or plate 29 to the outer conductor section III. The head 25 and the terminal 28 are rigidly supported by insulators 21 which join them respectively to the terminal I and end plate 29.

At the opposite high potential end of the line,

a similar conducting end plate 30 is provided to which is connected one element 3| of a variable capacitor 32, and the remaining element or electrode of the capacitor 33 is connected directly to the flanged end 8 of the inner conductor as by a rigid conductor 34. The variable capacitor shown may be of any suitable type. In the present example, the element 3| is the rotor, while the element 32 is the stator of the usual rotary variable capacitor having a tuning shaft 35 which ex; tends through the end plate 30 on which the frame 36 is mounted.-

Coupling to the line may be made in any suit- The ring I! is concentric with theline and is rotatable to a small angle such as 30 able manner and is here shown as comprising in effect a high potential end connection 38 on the inner conductor 5 for the anode lead 39 of an am, plifler or oscillator tube 40, and a grid tap 4| at a suitable point also on the inner conductor 5, for The tap is made by passing an insulated grid lead 44 through an opening 45 in the inner conductor which is pref-.

erably hollow, as is also the conductor 6, so that the lead may be continued through the center of the latter conductor to one of a plurality of insulated potential supply terminals 41 secured to the bottom or low potential end or the line, as shown. The plate tap likewise is provided in effeet by the lead 39 at the point 38 where it enters the head 8 of the center conductor. This lead then extendsthrough the interior of the center conductor to one of the supply terminals 41 along with the grid conductor.

Repeated operation of the switch, over a long period of time, does not change the accuracy of the inductance change, and this is of importance in covering a wide band of frequencies rapidly in tuning, since the inductance change is the same for each resetting of the switch.

We claim as our invention:

1. The combination with a concentric line inductance, of switching means for shortening the effective length of the line comprising conductive elements connecting the inner and outer conductors of said inductance through a plurality of substantially equal and uniformly spaced radially conducting paths in a plane substantially normal to the axis of the inductance at a point intermediate between the ends thereof, one of said conducting elements bein movable to interrupt said conducting paths, and means controllable externally of said inductance for moving said last-named element.

2. The combination with a concentric line comprising an inner central conductor and an outer conducting sleeve, of a rotary annular contact member concentric with the line between the inner conductor and outer sleeve, means providing a plurality of radial conducting paths between the central conductor and the outer sleeve through said annular contact member, and means for rotating said contact member selectively to establish and interrupt said paths.

3. The combination with a concentric line comprising'an inner central conductor and an outer conducting sleeve, of means for establishing a short-circuit connection between said sleeve and conductor at a point intermediate the ends of said line, comprising a rotary ring member having radially inwardly projecting blades lying in a plane normal to the axis of the line, means providing a flexible connection with the outer sleeve radially about the periphery of said member, and means carried by and connected with the inner conductor providing radially extending spaced flexible contacts for engaging said blades when said ring member is rotated, thereby to lestablish a plurality of radially extending cur-- rent conducting paths between the central conductor and the outer sleeve.

4. A concentric line inductance comprising in combination, inner and outer conductors, and a switch structure for establishing a short-circuit connection between said conductors at a point intermediate between the ends of said line, comprising an annular rotary conducting element interposed between said conductors in a plane normal to the axis of the line, said conducting element having inwardly projecting radial spaced blades, contact elements providing a plurality of radial conducting paths between said conducting element and the outer conductor, and a plurality of fixed radial contact elements carried by the inner conductor and interposed between said blades in spaced relation thereto for engaging said blades upon rotation of said conducting element to provide a plurality of radially extending current conducting paths through said annular member between the inner and outer conductors.

5. A concentric line inductance comprising in combination a central tubular conductor and an outer concentric conducting sleeve, an annular conducting element interposed between the central conductor and the outer conducting sleeve in a plane normal to the axis of the line, said conducting element having inwardly projecting radial spaced blades, a plurality of fixed radial contact elements carried by the inner conductor and interposed between said blades in spaced relation thereto for engaging said blades upon rotation of said conducting element to provide a plurality of radially extending current conducting paths through said annular element between the inner conductor and the outer sleeve, means for applying signals to said inductance comprising an insulated conductor extending through said tubular central conductor, and means for deriving an output potential from said inductance comprising a second insulated conductor extending through at least a portion of the central con-. ductor;

6. A concentric line inductance, comprising an inner and an outer conductor, a switch housing interposed in and forming part of the outer conductor sleeve, a pair of spaced contact rings carried by the housing having radially inwardly extending spring contact fingers, a rotary annular contact member engaged adjacent its periphery by said spring contact fingers and having radially inwardly projecting spaced blades, means carried by and connected with the inner conductor providing radially extending spaced flexible contacts between saidblades in spaced relation thereto for engaging the latter when the contact member is rotated, and means extending externally of the housing for rotating said contact member to carry the blades into engagement with said flexible contacts, thereby to establish a plurality of radially extending current conducting paths between said conductors.

7. An adjustable concentric line inductance having an inner central conductor and an outer sleeve conductor, and means for establishing a short circuit connection between said sleeve and conductor in a plane normal to the axis of the line at a point intermediate the ends of said line comprising a rotary flat annular member concentric with the line between the inner and outer conductors having radially inwardly projecting blades, flexible contacts extending radially inwardl'y about the periphery of said annular member providing a plurality of radial conducting paths therefrom to the outer conductor, and a plurality of radially outwardly extending spaced flexible contacts connected with and carried by the inner conductor for engaging said blades upon rotation of said annular member from one predetermined position to another, thereby to establish a plurality of radially extending current conducting paths between the inner and outer conductors, and means for rotating said annular member from one to the other of said positions to adjust the inductance of the line.

WILLIAM H. CONRON. BENJAMIN W. SUCKLE.

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