US3348106A

US3348106A - Tubular condenser of variable capacity

Info

Publication number: US3348106A
Application number: US557792A
Authority: US
Inventors: Vinz Ottmar
Original assignee: Jenaer Glaswerk Schott and Gen
Current assignee: Schott AG
Priority date: 1965-06-16
Filing date: 1966-06-15
Publication date: 1967-10-17
Anticipated expiration: 1984-10-17
Also published as: DE1229189B; NL6607631A

Description

Get. 17, E967 0. VINZ- 3,348,106 Y TUBULAR CONDENSER OF VARIABLE CAPACITY Filed June 15, 1.966

INVENTOR 2 5772071572;

United States Patent 3,348,106 TUBULAR CONDENSER OF VARIABLE CAPACITY Ottmar Vinz, Landshut, Germany, assignor to JENAer Glaswerlr Schott dz Gem, Mainz, Germany, a corporation of Germany Filed June 15, 1966, Ser. No. 557,792 Claims priority, application Germany, June 16, 1965,

3 Claims. Ci. 317 249 ABSTRACT OF THE DISCLOSURE The invention relates to a tubular condenser of variable capacity in which a tubular member is provided on its outer circumference with a stationary electrode which is arranged opposite a slidable electrode arranged in the interior of the tubular member. The slidable electrode has the form of an axially adjustable piston which is mounted on an axially adjustable rod which may consist of a threaded spindle. Such type of condensers are used among other fields also in the UHF range.

Condensers of this type are known which are constructed as ceramic or glass tube trimmer. Furthermore, such condensers have been used in which the dielectric comprises an organic material.

These trimmer-type condensers are employed below 100 mHz. principally for a fine adjustment of circuits and in this type of use are suitably arranged in parallel to a condenser having a substantially greater capacity. In the case of higher frequencies, particularly above 100 mHz., these trimmer condensers are used directly for the construction of electric circuits, and in that case, they constitute exclusively the oscillatory circuit capacity. Furthermore, these condensers are used for resonance compensation of geometrically constructed oscillating systems, such as oscillating chambers, coaxial resonance lines, etc. Particularly their use in the last-mentioned field, the requirements on the condenser are particularly high, especially concerning its loss tangent, since on one hand the loss capacity increases proportional with the operating frequency, while on the other hand at these high frequencies the requirements concerning the resonance sharpness and therewith the circuit quality are frequently particularly high.

In order to fulfill these requirements, particularly With respect to a small loss tangent, it was heretofore believed that the deciding factor for this requirement resided in the loss producing property of the dielectric used in the condenser.

It was, however, discovered that also other factors influence the losses considerably, and it is an object of the invention to reduce these losses still more independently of the material which is used as dielectric.

In accordance with the invention, the tubular condenser of variable capacity comprises a tubular member provided with an exterior layer and piston axially slidably mounted in the interior of said tubular member and serving as an inner layer. The piston is axially adjusted by an axially extending threaded spindle which latter forms a path for the electric current to the piston, and this path is made shorter by changing the profile of the thread on the spindle.

It was discovered that when applying this means of the invention that the total loss tangent tg 5 of the condenser, when it otherwise has the same construction, is reduced from 15-10 to 1l-10 In the following, a few embodiments of condensers of the invention will now be described in greater detail by way of example with reference to the accompanying drawing, in which:

FIG. 1 illustrates in a longitudinally axial section a tubular condenser of variable capacity;

FIGS. 2 and 3 illustrate each, partially in section, a different threaded spindle which may be used in the condenser of the present invention; and

FIG. 4 illustrates in cross-section still another example of a threaded spindle which may be used in the condenser of the present invention.

Referring to FIG. 1, the condenser comprises a tubular member 5 made of a dielectric, such as glass, on one end of which is attached a mounting flange 1 provided With an exteriorly threaded mounting projection 1a and an interiorly threaded cylindrical projection 1b extending axially into the tubular member 5. A threaded spindle 2 extends through the threaded projection 1b and carries on its inner end a piston 3 which slidably engages the inner wall of the tubular member 5 and forms the inner layer or electrode of the condenser. The other electrode of the condenser is formed by an exterior layer 4 fixedly attached to the outer circumference of the tubular member 5. Upon rotation of the threaded spindle 2, the piston 3 is axially adjusted within the tubular member 5 relatively to the stationary outer layer 4.

According to FIG. 2, the thread of the spindle 2 has its crests removed to form a flattened helical perimeter 2a so as to make the thread profile trapezoidal, while according to FIG. 3 the root of the thread 2b on the spindle 201 is formed by flattened valleys 2e. In both these embodiments, the selected shape of the profile of the thread reduces considerably the path for the electric current between the fiange 1 and the piston 3.

In the embodiment of the invention illustrated in FIG. 4, the threaded spindle 2c is provided with three circumferentially lengthwise or axially extending grooves 2h which have a radial depth extending down to the root diameter of the thread.

What I claim is:

1. A tubular condenser of variable capacity comprising a dielectric in the form of a tubular member, an exterior electrode fixedly mounted on the outer circumference of said tubular member, a slidably mounted inner electrode within said tubular member, said slidable electrode comprising a piston axially slidably arranged in said tubular member and attached to an axially extending threaded spindle threadedly supported in a mounting flange at one end of said tubular member, the thread on said threaded spindle having flattened crests to have a trapezoidal profile which reduces at high frequencies the supply conductor resistance for the electric current passing from the spindle to the piston by reducing the length of the current path.

2. A condenser according to claim 1, in which the root portion of the thread on the threaded spindle is flattened.

3. A condenser according to claim 1, in which the thread on the threaded spindle is provided with a plurality of lengthwise extending grooves.

References Cited UNITED STATES PATENTS 2,922,093 1/1960 Kellerman 317-249 LEWIS H. MYERS, Primary Examiner.

E. GOLDBERG, Assistant Examiner.

Claims

1.A TUBULAR CONDENSER OF VARIABLE CAPACITY COMPRISING A DIELECTRIC IN THE FORM OF A TUBULAR MEMBER, AN EXTERIOR ELECTRODE FIXEDLY MOUNTED ON THE OUTER CIRCUMFERENCE OF SAID TUBULAR MEMBER, A SLIDABLY MOUNTED INNER ELECTRODE WITHIN SAID TUBULAR MEMBER, SAID SLIDABLE ELECTRODE COMPRISING A PISTON AXIALLY SLIDABLY ARRANGED IN SAID TUBULAR MEMBER AND ATTACHED TO AN AXIALLY EXTENDING THREADED SPINDLE THREADEDLY SUPPORTED IN A MOUNTING FLANGE AT ONE END OF SAID TUBULAR MEMBER, THE THREAD ON SAID THREADED SPINDLE HAVING FLATTENED CRESTS TO HAVE A TRAPEZOIDAL PROFILE WHICH REDUCES AT HIGH FREQUENCIES THE SUPPLY CONDUC-