US2505287A - Electrical condenser - Google Patents

Description

April 25, 1950 R. P. GUTTERMAN Erm.,

ELECTRICAL CONDENSER 2 Sheets-Sheet l Filed Nov. 1, 1948 miti,...

7 2 n M n t a 5, m m .z m 0 m 3 r k :w e k 2 m n e ,r M y .Tf M s B 2 G. P J .L 1/ x A e R E n R m M E u m m w m R m R. www, m QM. MN. .I he v\.\\\\\\\\.\`\\\\\\\\\\\\\\,\\\\\\`\`\\\,\\\N v 9 1 2 m m6 N o ...|n. d K p e A m Patented Apr. 25, 1950 ELECTRICAL CoNDENsER Robert P. Gutterman, Arlington, Va., and Alex J. Blelski, Minneapolis, Minn.,- assignors to Engineerlng Research Associates, Inc., St. Paul, Minn., a corporation oi' Minnesota.

Application November 1, 1948, Serial No. 57,778 15 Claims. (Cl. 175-41.5)

This invention relates to electricalcondensers. More particularly, it is concernedk with new forms of variable electrical condensers for use in radio, television or similar velectrical circuits.

A principal object of this invention is the provision of a new variety of variable electrical condensers.

Further objects are as follows:

(l) To provide a spring-loaded structure in an electrical condenser making possible highly accurate and reproduceable miniature condensers whose mechanical components need not be held to exceedingly close tolerances.

(2) To provide a miniature variable condenser which is electrically equivalent or superior to good quality variable condensers of standard types, but whose entire capacitive, actuating and indicating mechanism occupies a very much smaller space.

(3) To provide a miniature variable condenser of the nature described above, comprising several coacting variable capacitive elements adapted to track closely, electrically and mechanically, over the entire adjustment range.

(4) To provide an essentially totally shielded miniature variable condenser.

(5) To provide a miniature variable condenser of one or more coacting capacitive elements which may be conveniently adjusted and readjusted over its operating range with a relatively very high degree of accuracy.

(6) To provide a, variable condenser having control means and setting indicator means incorporated within a unitary casing.

(7) To provide a singleor multi-section miniature variable condenser whose settings are essentially unaffected by shock and vibration.

(8) T0. provide a singleor multiple-element Avariable condenser whose elements may be mechanically locked and unlocked at any point in their adjustment range without affecting their setting.

(9) To provide a singleor multiple-section variable condenser in which the capacitive elements consist of mating sleeves of metal coated with a solid dielectric.

(10) To provide new forms of single-or multiple-section variable condensers employing nickel oxide as the dielectric material.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description, while indicating preferred embodiments of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

These objects are accomplished in accordance with the present invention by forming variable condensers from pairs of telscoping metal tubes, having dielectric coatings interposed between engaging surfaces of the metal tubes, with the inner tubes of the pairs being carried axially within a surrounding casing with a spring-loaded a1'- rangement and providing the outer movable tubes with means for telescoping the tubes over the fixed inner tubes.

A more complete understanding of the structures involved with this invention may be had by reference to the accompanying drawing in which,

Figure 1 is a longitudinal sectional view of a variable condenser incorporating the features of this invention;

Figures 2 to 6 are transverse sectional views of the condenser of Figure 1, taken along the lines 2-2 to 6 6, respectively, of Figure l.

Figure 7 is a partial longitudinal sectional view of the condenser taken along the line 1 7 of Figure 4.

Figure 8 is a perspective view of the condenser.

Referring in detail to the drawings, the variable condenser 2 comprises a plurality of stationary metal sleeves 4 and 5 and movable sleeves 6 and 1, carried within a tubular casing or housing 8.

At least the outer surfaces I0 of the stationary sleeves or tubes 4 and 5 and at least the inner surfaces I2 of the movable sleeves 6 and 1 are provided with dielectric coatings. Preferably, the sleeves 4 and 6 are made from nickel and are so treated as to have formed over the entire surface thereof an adherent nickel oxide of sufficient thickness so as to serve as the dielectric coating, e. g., as prepared in accordance with the disclosure of my copending applicationSerial Number 49,022,

filed September 13, 1948. Such oxide coats, when properly formed, electrically insulate the one tube from the other and are of high abrasion resistance so that the coatings on the tubes may slidably engage during operation of the condenser without damage to the electrical properties of the unit. This permits the inner tube to serve as a bearing element for the outer, movable tube. The outside diameters of sleeves 4 and 5 and the inside diameters of sleeves 6 and 1 should be held to close tolerances so that clearance between the stationary and moving sleeves is made just great enough to allow free motion of the moving sleeves.

Sleeves l and 5 are electrically insulated from each other and correspond to the separate stator sections of a standard two-section variable condenser. Sleeves 8.and 1 are connected together electrically through metal sleeve or oscillatory member I3 and correspond to the double rotor elements of a standard two-section variable. condenser.

The tubular casing and sleeves are preferably of cylindrical shape, although they may be formed in other suitable configurations and the casing is preferably made of metal, so as to serve as a shield for the condenser, although it may be made of non-conducting material, such as syn..

thetic plastics or the like.

The stationary tubes 4 and 5 are carried axially within the casing 8 upon a rod or shaft I4 which is fixed axially within the casing by being fas-` tened at the end I8 to a bushing I8 which is pressed intothe end 20 of the casing. A rivet 22 extends through the casing, bushing and rod holding the three elements in fixed relative position. The inner end 24 of the rod I4 is of enlarged diameter having a circumference corresponding to about the outside diameter of the metal tubes 4 and 5 with the radial shoulder 28 between thel enlarged portion 24 of the rod and the reduced portion 28 of the rod serving as a stop for the tube 5. The tubes 4 and l5 are held in fixed position relative to one another upon the rod I4 by the non-conducting spacing member 38.

The rod I4 `is provided with a longitudinal groove 32 into which the leaf springs 34 are forced beneath the inside of the tubes 4, and 33 withthe sleeves 4 and 5 mounted comparatively loosely on insulator rod I4 and spaced by insulating member 30, these three tubular members are held slightly eccentric to shaft I4 by the action of springs 34. Despite the fact that the clearance between moving and stationary capacitive elements is very small, the requirement of high precision necessitates the use of some means toensure stable positioning of the active sleeves. This means must act independently of forces which might be applied to the over-all condenser structure, as well as those which might be occasioned by very small shifts of alignment in the internal structure of the condenser, particularly during adjustment. With the assembly of rod I4, bushing I8 and outer sleeve 8 being secured by pin 22, the opposite end of rod I4 is free to float radially as a cantilever beam. This floating action, taken together with the actions of springs 34, provides a spring-loaded locating force which is constant in direction and magnitude, tending to cause sleeves 4 and 5 to contact the cylindrical inner surfaces of sleeves 8 and 'I along an element line and with a pressure which does not vary with setting and resetting of the condenser or with the application of external forces. Thus, undesirable variation of positioning is restricted to a very much smaller range than could be achieved by allowing the sliding elements to move within their clearance in a random fashion. The clearance between rod I4 and sleeves 4, 5 and 30 is made greater than the clearance between sleeves 4 and 8 or 5 and 1. This is done in order to en sure free action of springs 34 in locating sleeves 4, 5 and 30 relative to the internal surfaces of sleeves 8 and 1.

A control knob 38 is rotatably carried upon the end of the casing 8. This knob consists of two separate portions 38 and 40 which surround a washer 42 that is fixed within the casing 8 with the outer edge of the washer 42 flush with the end of the casing 8. The two sections 38 and 48 of the knob 38 are urged toward one another and are pressed upon the sides of washer 42 by means oi' the screw 44, threaded into a unit 40. A coil spring 48 serves to press out screw 44 and keep knob 38 from binding when the screw is not fully tightened. The unit 40 is provided with a reduced neck portion having slots 48 therein into which protrusions 58 from the knob 38 extend and serve to form keys for keying the knob 38 to the unit 43. By tightening screw 44 to the limit, knob 38 is locked tight against thrust collar 42 and prevents further adjustment of the unit. 'I'his locking action can be relieved by loosening screw 44. When the screw is backed out of the unit 43, the pressure of the inside surfaces of the knob 38 and unit 40 against the washer 42 is reduced so that the force required to rotate the knob 38 is decreased and the condenser is easily readjusted to any desired position between its maximum and minimum capacities.

A tubular sleeve 52 is press-fltted at the end 54 over the recessed portion 58 of the knob section 40. Thus, rotation of the knob produces a corresponding rotation in the sleeve 52. The opposite end and enlarged end 58 of the sleeve 52 is provided with inside threads 80.

The oscillatory member II is slidably carried upon the inner surface of the casing 8. Springs 8l and 82 are fitted into and retained in grooves 83 and 8,4 and operate to take up play between member I3 and casing 8, causing member i') to move constantly against the same side of casing 8 during adjustment of the condenser. This ensures a constantly reproducible positioning action between casing 8 and member I3 despite the existence of clearance between these sleeves which may vary with machining tolerances. Springs II and 82 are so located that their action in taking up play between casing 8 and member I3 does not create any force in opposition to the above-describedactionsof springs 34, i. e., so that the resultant force of springs 8i and 82 is perpendicular to the force of springs 34.

The member I3 has an outside threaded end section 85 which intermeshes with the inside threads of the sleeve 52. The movable sleeves 8 and 1 are fitted within this oscillatory tube I3 kand are fastened to the tube by solder connections 88 and 88, thus electrically connecting the metal sleeves 8 and I to the member I3. This soldering is accomplished by scraping off the oxide coating from the sleeves 8 and 1 at the required place and dropping solder upon the scraped portion through matched holes in the member I3.

The casing 3 is provided with a longitudinal slot 18 and a small screw 12, which is threaded into the member I3, extends into this slot 10. This screw 12 is of such size that it may slide within the slot. Consequently, the screw 12 permits the member I3 to reciprocate within the casing 8, but does not allow the member I3 to rotate within the casing. Thus, it will be seen that rotation of the knob 38 by suitable torque causes the sleeve 52 to correspondingly rotate. and because of the intermeshing threaded areas 88 and 84. rotation of the sleeve 52 forces the member I3, which cannot rotate, toward or away from the knob 88. Since the metal sleeves 8 and 'I are fixed within the member I3, the sleeves 8 and 1 are caused to move in or out upon the stationary metal sleeves 4 and 5. Hence, rotation of the knob 38 causes a variable displacement between the stationary capacitive elements 4 and and the variable capacitive elements 6 and 'l of the condenser.

The portion of the casing 8 adjacent to the slot 'l0 is preferably provided with indicator markings and in cooperation with a recess 14, or some similar marking, in the screw 12, the setting of the condenser can be indicated.

The bottom side of the casing 8 is provided with a longitudinal slot 16 through which the electrical connections to the stationary and variable plates of the condenser extend. Thus, an electrical conductor 18 extends through the slot 'I6 and through a hole 80 in the tube 30 into the groove 32 and is soldered to the inner surface of the sleeve 5 at a point where the oxide coating of sleeve has been scraped away. Similarly, a second electrical conductor 82 extends through slot 16 through a hole 84I in the bushing I8 into the groove 32 and is soldered to the inside of the tube 4. The ground connection 86 to the condenser extends through the slot 'I6 and is fastened to the'oscillatory member I3.

The drawings show a casing containing two separate condensers provided with a common Iground connection. However it will Ibe realized that units comprising only one or more than two Separate condensers in the casing may be prepared in accordance with this invention, and that where two or more separate condensers are made in a separate unit, they may be provided with totally independent leads.

Because the condenserwstructures described above make use of the free-iioating, springloaded support means in ensuring stable and accurate radial positioning of the dielectric coated sleeves, they provide new degrees of mechanical and electrical stability in variable condensers. This makes possible the fabrication of an exceedingly accurate and stable miniature variable condenser without introducing the practical restriction of excessively ilne tolerances in the supporting elements. The spring-loading technique employed in this device makes possible for the rst time a highly accurate and reproducible miniature variable condenser whose mechanical components need not be held to exceedingly close tolerances in production. As has been pointed out, wide clearances are purposely introduced to allow free action of the spring-loading means.

We claim:

l. A variable condenser comprising a tube, a rod cantilevered axially Within said tube, a stationary metal sleeve embracing said xed rod, a dielectric coating upon the outside of said metal sleeve, a movable metal sleeve having a dielectric coating upon its inner surface, the movable metal sleeve telescoping upon the stationary metal sleeve with a portion of said dielectric coatings slidably engaging one another, separate electrical conductors connected to each of said metal sleeves, and means carried by said tube for moving said movable sleeve lengthwise to the stationary sleeve.

2. A variable condenser as claimed in claim l, wherein Said rod is provided with a longitudinal groove which has a spring member inserted therein beneath the inside of said stationary metal sleeve.

3. A variable condenser as claimed in claim 1, wherein said sleeve moving means comprises a tubular oscillatory member surrounding the movable sleeve, the said tubular member being slidably carried upon the inner surface of the casing.

4. A variable condenser as claimed in claim wherein said tubular oscillatory member com '15 tween the inside of the casing and the outside prises an outside threaded end portion which intermeshes with an inside threaded sleeve rotatably carried within the casing, said tubular member being provided with means which prevents said member irom rotating within said casing. and said sleeve being provided with means which prevents it from moving longitudinally in the casing.

5. A variable condenser comprising an elongated hollow casing, a stationary metal sleeve fixed axially within the casing, a dielectric coating upon the outside of said stationary sleeve, a movable metal sleeve having a dielectric coating upon its inner surface, the movable metal sleeve telescoping upon the stationary sleeve with a portion oi said dielectric coatings slidably engaging one another, a tubular oscillatory member carried upon the inner'surface of said casing surrounding said movable metal sleeve having an outside threaded end portion, an inside threaded sleeve rotatably carried within the casing which inter-meshes with said outside threaded end portion, said inside threaded sleeve being fastened at the end opposite to its inside threaded portion `to a knob which is carried upon the casing for axial rotation with the casing while being held against longitudinal movement relative to the casing.

6. A variable condenser as claimed in claim 5 wherein said knob is formed of two separate sections which have their opposite faces engaging the sides of a washer which is fastened flush with the end of the casing, said knob sections being urged toward one another against the washer facings by means of a screw.

7. A variable condenser comprising an elongated hollow casing, a stationary metal sleeve iixed axially within the casing, a dielectric coating upon the outside of said stationary sleeve, a movable metal sleeve having a dielectric coating upon its inner surface, the movable metal sleeve telescoping upon the stationary sleeve with a portion of said dielectric coatings slidably engaging one another, a tubular, oscillatory member carried upon the inner surface of said casing surrounding said movable metal sleeve having an outside threaded portion thereon, a threaded member carried by said casing that inter-meshes with said outsidethreaded portion, movement of said threaded member causing longitudinal movement in said oscillatory member, whereby an adjustment of said movable sleeve relative to said stationary sleeve is obtained, and electrical conductors electrically connected to said metal sleeves.

8. A variable condenser as claimed in claim 7, wherein the electrical conductor connected to the stationary metal sleeve extends through an opening in said casing-and is soldered to the inside of said stationary metal sleeve.

9. A variable condenser as claimed in claim 'l having spring loading means which operate in all three dimensions along lines essentially mutually perpendicular whereby all undesirable mechanical looseness between separate elements of the condenser is eliminated.

l0. A variable condenser as claimed in claim 7, wherein said stationary metal sleeve surrounds a non-conducting rod which is positioned axially within said casing.

1l. A variable condenser as claimed in claim 10, wherein said rod is fastened to the casing at one end, said rod being centered within the casing by means of a bushing which iills the space be- 7 of the rod while the opposite end of said rod is free.

12. Avariable condenser as claimed in claim 11, wherein there is a plurality of said stationary sleeves, each stationary sleeve being carried by said axially positioned rod, said stationary sleeves being spaced one from the other by means of nonconducting tubular members having the same radii as said stationary sleeves. y

13. A variable condenser comprising a tubular casing, a rod cantilevered axially within the casing, a stationary metal sleeve embracing said fixed rod, a dielectric coating upon the outside of said metal sleeve, a movable metal sleeve having a dielectric coating upon its inner surface, the movable metal sleeve telescoping upon the stationary metal sleeve with a portion of said dielectric coatings slidably engaging one another, separate electrical conductors connected to each of said metal sleeves, an operating knob rotatably carried axially in one end of said casing, said knob being retained against movement longitudinally with said casing, a threaded sleeve fastened to said knob, and an oscillatory member comprising a threaded tubular section intermeshing with said sleeve threads and means for preventing said member from rotating within said casing, said movable metal sleeve being connected to said oscillatory member for movement with the member.

14. A variable condenser comprising a cylindrical casing, a rod of dielectric material positioned axially within the casing by a bushing fixed in one end of the casing around one end of the rod, a longitudinal groove in said rod, a stationary nickel tube having an oxidized surface embracing said rod, a spring member forced into said groove beneath said metal tube, a movable nickel tube having an oxidized surface telescoping upon said stationary nickel tube with a portion of the outside oxide surface of the stationary tube slidably engaging a portion of the inside oxide surface of the movable tube, a washer fastened in the end of said casing opposite said bushing, an operating knob comprising two separable sections urged toward one another by a screw, said washer being positioned between said sections whereby said knob is rotatably carried in said casing and held against movement longitudinal with the casing, a tubular sleeve fixed by one end to the inner section of said knob having an inside threaded portion on the opposite end, an oscillatory member comprising a tube sliding on the inside of said casing having an outside threaded portion on one end which intermeshes with said inside threaded portion of said sleeve, and a retaining element extending outwardly from the oscillatory member slidably carried in a longitudinal slot in said casing preventing rotation of said oscillatory member within the casing, said oscillatory member being connected to said movable nickel tube whereby longitudinal movement of the oscillatory member within the casing causes a corresponding movement in said movable tube, and separate electrical conductors electrically connected to each of said nickel tubes.

15. A variable electrical condenser comprising a tubular casina, a shaft of dielectric material positioned axially within the casing and cantilevered in a bushing fixed in one end of the casing, a stationary tubular capacitive element having a dielectric surface coating `supported upon said shaft, a spring member positioned between said shaft and element holding an inside portion of the element always in engagement with an outside portion of said shaft, a movable tubular capacitive element having a dielectric surface coating telescoping upon said stationary element with a portion of the outside surface of the stationary element slidably engaging a portion of the inside surface of the movable element, an oscillatory tubular member slidably carried within said casing, spring members between said casing and said oscillatory member so positioned that the resultant force of said last-mentioned spring members is perpendicular to the force of said first-mentioned spring member, said movable element being carried by said oscillatory member for movement with said member, means for preventing said oscillatory member from rotating within said casing and means for oscillating said oscillatory. member longitudinally within said casing.

ROBERT P. GUT'IERMAN. ALEX J. BIELSKI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Clark Oct. l2, 1948

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