US1557316A

US1557316A - Variable condenser

Info

Publication number: US1557316A
Application number: US756222A
Authority: US
Inventors: George H Nobbs
Original assignee: Individual
Current assignee: Individual
Priority date: 1924-12-16
Filing date: 1924-12-16
Publication date: 1925-10-13
Anticipated expiration: 1942-10-13

Description

Oct. 13, 1925. 1,557,316

G. H. Nolnas` VARIABLE CONDENSER Filed Dec. 16, 1924 Patented Oct. 13, 1925.

UNITED STATES GEORGE H. NOBBS, OF WATERTOWN, MASSACHUSETTS.

VARIABLE CONDENSER.

Application nled December 16, 1924. Serial No. 756,222.

To all whom zt may concern Be it known that I, GEORGE H. Nons, a citizen of the United States, and resident of Watertown, in the county of Middlesex and State of Massachusetts, have invented an Improvement in Variable Condensers, of which the following is a s ecification.

This invention relates to t at class of electrical variable capacity condensers of the plate type, which are widely used in radio receiving sets and which generally comprise two sets 0r groups of parallel, semicircular plates, one group, called the stator, being stationary, and the other, called the rotor, being mounted for rotation to permit interposition of its plates with the stationary plates to a varying extent, thereby to vary the capacity of the apparatus.

It is Well known that, to secure satisfactory results in a radio receiving set, a balance, which is as nearly perfect as possible, must be secured between the inductance and capacity of the receiving circuits. Variation of the inductance is usually secured by means of the taps which are placed in contact with one or more turns of wire on the inductance coil, but the variation secured by cutting in or out of even a single turn of the coil is so great that accurate adjustment of the inductance to the capacity of the circuit in this manner is ordinarily impossible. The adjustment of the capacity to the inductance is usually secured by means of a condenser of the type above referred to, but even where the inductance has been adjusted to established conditions as closely as possible by means of the taps, yet inductance is likely to vary to such an extent under different conditions, that it is usually ditlicult to determine, without making numerous tests, what range of capacity will be necessary to secure the desired balance.

Condensers of the type referred to are now made to secure widely varying ranges of capacity between a minimum, which is usually nearly the same, and the maximum which is required, this variation being usually secured by varying the number, size and proximity of the plates. At present dealers carry condensers in five or more different sizes, designed to give a corresponding number of stages of maximum capacity. In many instances it is necessary to make tests with several condensers havin r different maximum capacities, before it 1s ascertained what particular condenser will give the most satisfactory result under the conditions at hand.

The principal reason for the necessity or desirability of using condensers having'different degrees of maximum capacity for different conditions is as follows :-The whole range of capacity of any given condenser of the above type is secured by turning the rotor through 180. If a condenser of sufficient maximum capacity for all conditions is employed, the result will be that the correct tuning positions of the rotor for certain stations which are broadcasting within certain relatively low limits of wave length, requiring capacities much less than the maximum, will be crowded into a relatively small portion of its total range of adjustment, so that the extent of adjustment of the rotor necessary to tune to these stations of relatively low wave length will be so slight that the different adjustments will practically coincide, thereby making it impossible to tune out one station in favor of another. On the other hand, if the range of capacity of the condenser is so reduced that the rotor must be adjusted throughout its entire range of movement to adjust the capacity to all of these stations of relatively low wave length, the extent of adjustment from one' position to another to secure the correct tuning therefor will be greatly increased, thereby correspondingly increasing the selectivity of the receiving set for these stations, and making it possible to tune in stations which could not be tuned in if the maximum capacity Vof the condenser was substantially greater.

It has been attempted to obviate the necessity of making tests with condensers of different maximum capacity to secure desired results by providing a condenser having several groups of plates, one or more of which may or may not be employed according to conditions, and, while such an apparatus, to some extent, obviates the difficulty, yet the step up from one maximum capacity to the next is so great with such an arrangement that it is still impossible to adjust the rotor so as to secure the desired degree of selectivity as to certain stations requiring intermediate degrees of capacity.

The objects of my invention are to provide a condenser of the type above referred to, having means whereby its maximum capacity may be readily increased by small steps or stages from a fixed minimum capacity to any maximum capacity which is ikely to bek required, the numbersfof stages of increase in maximum capacity of the condenser to be in direct proportion to its greatest possible .range of capacity, so.that

a correspondingly large number of `ranges a,con enservof the type above identiiiedv with means whereby any one Kor more of the stator vplates :may be.readily placed in or ren'li'oved fromi thei condenser circuit, inde .@Jldently, as circumstances may require.

or a more complete understandlng of my inventionure-,ference is `made to the accompanyingudrawingLfornng a .parti of this specifcafiom in w ich:

Fig. 1 is :a nyiewof an electrical condenser. einv ying a Ipreferred form I,of my invention.

yis a sectional ,View atline 2-2 pf 1. ig.i 3 isY an end zvieW vthereof.

Fig.4 is sectional view at,1ine 4 5-4 of Fig. l'on an enlarged scale.

Fig-.35 is a sectional view, atline 5-5 of Fig,r 1 Vonen, enlarged scale. f

ig6 is a detailE view of portion .of .one of the stator plates .and itsvconnecting device.

As'shown in themdrawing-I providela main ,framewhich' consists of a pair of end platesylOand `12, of electrical insulating material, which arefconnected by a series of bolts. 14v having clamp'

g nuts

15 ,and 16 at 'each end, the nuts 1 Y,being ada tedcto be connected to the instrument pane in the usual r:mannen The -usual l semifcircular,

ectvrically connected toa shaft 20, which is,rotatablyA mounted iin the! end plates 10 and 12and, in' practice, willbe provided witha handle .infrontpf the panel for convenient manipulation.` VA s ring contact 22 is provided fortherearfen of the shaft 20to Whichone lterminal, of the circuit, is,,connected.` Thel stator platesf24, which are similar in thickness and spacing to the rotor plates, are,mounted in parallelism thereto on the bolts. 14, said plates 24 bein ,electrically ,insulated froml .said bolts byf g ass ybushingst and from 'each other by interposed, 1nsulating, s acing Washers 26,I washers or bushings 2 ofr lsor'nevvhat greater thicknessfor len li than the washers i latina-Srs cess 36Ysiee spaced rotor plates 18- are mounted on, and. e

` will be my i a,

26, bein provided between ,the re r, stator plateau 'tle rearend au 10, a thi end plates, stator plates an washers being all clamped firmly together by means of the nuts on boltshlh 'Ill'esrran ment of the 'i0 stator Vplates is such that w en the rotor plates are rot-ated they will be interposed y bet\veen,thestatorpltes without actually A coming in contact therewith, as is usual ing this class of devices. Itis to beiunderstood'g'l in this connection that thenumber of y and rotor plates shown ;is 1:nerelyV illustrasf,` tive and that.-, in factice, the .number einen ployed .will,.,be,sucent to'givetbef :narici` mum capacity -1ikelyf,to.be requiredfundarrgso all co-nditOD6;of use." A

A metal rod 28 is muntednthe .

back plates

10 and 12 adiacenti one1of-,the tiem rods 14,.,and is held; inpgsitioabynut 1 threaded thereon and clamped ain'st- @5 plates. The rear end portlono said rod, is preferably used .asabindingrpost andq has .a .thumb nut 30 thereon .for connecti t the other.circuit terminal 31 thereto. series of switch levels, 32 are pivotally. mounted uon said rod 28.. in electricalioon. tact therewith and vvitlijeach,.othelysairl.n levers4 being spaced apart by, non-insulati washers 34 and held inrclose Contact wit eachqother, by ,a coileiprigthe alifj` nm ement 'being .auch .thatach Alever #mom hel that is,sw1ngs. .inthe, ane of a spend" stator plate 24.. oh lever 32",i8i1i provid with a contaet-faeeBB atione ,andli which is madesnghny manica um axisjoo aboutwhic hf it swings, and is so arranged; that it may be swuugil linto. .wedging engagfljj meut with the lcorresponding statonlatefinf, 1 the'planeof which `Vit swings. Fort e pulii l i pose of incneasingthe arc'cr area of ,nou-.10 tact between lthalevers. and lates,.-eacli{` ,plateale it;` refembh/.prowid with is f f h ig.,6, irtggwihich theocmii aoeO L e, correspon everswmgs' ,t 1;; shapelof the. reeess .being,fsueh that,.whgn f}1 thelevervis pushed, ntoasrm en gagnent; as bpossi with the late, the. evergamLE-j; plate wf iba; enga throughout practiqfrl, cally` the entire .bottom surface off the k A` stop 10d, 38 may, be proyidedio limit. l0 opcningfmswinging,movement.,of the `lejfe i. In adj the ,device to 'any ,particular set of conditions, itfwilLfrst be decided agg proximateiy how many stator plateswi11 ,Y i required to secure themaximum capacity" i necessaryfor such conditiensfand then a oor-,ff responding number of the switch levers .32?, swung into operative relation. withf the corresponding plates, so that electrinxiid V connect-ion will be established between Suehf plates and the terminal attached f4) le'lodjf 28. .The rotor will then from the;` minimum ca acit position of 'g'.'2 to s e-fj i cure, if possile, e correct balance with th l. i inductanoe in the usual manner. If the' maxi-"f mum capacity is found to be too high then one or more of the levers will be restored to its vertical position, or, if it is found to be too low, then one or more additional plates will be placed in the circuit by moving the corresponding switch levers 32 to their engaging positions, as will be obvious. As all the stator plates are insulated from each other, and are only electrically connected to each other and to the terminal 3l through their corresponding switch levers 32, it follows that the plates not connected will, for the time being at least, be merely dead metal, but as it has been conclusively proven that the presence of tlie dead plates does not appreciably eii'ect the eiciency of the receiving set, this fact is not objectionable. The variation in maximum capacity secured by cutting in or cutting out a single plate is so small that a very accurate adJustment of the maximum capacity desired may be secured, so that any one of a large series of ranges of capacity from the minimum may be brought in by a semi-revolution ol the iotor in al single condenser constructed as above described.

It will be apparent that, under all ordinary conditions of use, a substantial number of stator plates will always be employed, so that, under such conditions the connect-ion between such plates and their terminal might be of a more permanent form than through the switch levers. However, so far as my invention is concerned it will be apparent that it is immaterial whether the disconnectable plates are used in connection with permanently connected plates or not.

l/Vhile I have shown the most satisfactory means of which I am at present aware for cutting the stator lates in and out of action, yet it will be un erstood that other satisfactory means for lthe purpose may be employed which are Within the scope of my invention.

I claim:

1. An electrical condenser comprising a group of stator plates and a group of rot-or plates arranged to be moved between said stator plates to vary the capacity, a terminal for each group of plates, the terminal for the rot-or plates being electrically conneet-ed thereto, means for supporting said stator plates out of electrical contact with each other and the terminal thereof and a series of switches corresponding in number to the stator plates and movable independently of each other to establish electrical connection between the respective stator plates and their terminal.

2. An electrical condenser comprising a group of stator plates and a group of rotor plates arranged to be moved between said plates out of electrical contact with each f other and the terminal thereof and al series of switch levers electrically connected to the stator terminal and arranged to be swung separately from an inactive position into engagement with a corresponding stator plate to establish an electrical connection with its terminal.

3. An electrical condenser comprising a series ot stator plates and a series of rotor plates arranged in parallelism therewith for variable interposition with the stator plates to vary the capacity, means for supporting said stator plates out ot electrica-l contact with cach other, a series ot switch levers, each mounted to swing in the plane of one of said stator plates and having a contact face arranged to be engaged with the edge thereof to make electrical connection therewith when the lever is swung from a disengaged to an engaging position and a pair of electrical terminals one being connected to the rotor plates and the other to said switch levers.

4. Au electrical condenser comprising a series ot stator plates and a series of rotor plates arranged in parallelism therewith for variable iuterposition with the stator plates to vary the capacity, means for supporting said stator plates out of electrical cont-act with each other, a. pivot rod having a series of switch levers each mounted on said rod in electrical Contact therewith to swing in the plane ot one of said stator plates and having a contact face arranged to be engaged with the edge of its corresponding stator plate to make electrical contact therewith and a pair of terminals one electrically connected to said rotor plates and the other to said pivot rod.

5. An electrical condenser comprising a series of stator plates and a. series of rotor plates arranged in parallelism therewith tor variable interposition with the stator plates to vary the capacity, means for supporting said stator plates out of electrical contact with each other, a series ot switch levers, each mounted to swing in the plane of one of said stator plates and having a cam. face arranged to be swung into wedging engagement with the edge of its corresponding stator plate to make electrical contact therewith, and a pair of terminals electrically connected respectively, one tol said rotor plates and one to said switch levers.

In testimony whereof, I have signed my name to this specification.

GEORGE H. NOBBS,

llO