US2201725A - Electrical device - Google Patents

Description

May 21, 1940. F. w. GODSEY, JR

ELECTRICAL DEVICE Filed Jan. 18. 1938 3 Sheets-Sheet 1 INVENI' OR. FRANK WGODSEYJR.

M7 G-fl ATTORNEYS.

May 21, 1940- F. w. GDsEY. JR

ELECTRICAL DEVICE Filed Jan. 18, 1938 3 Sheets-Sheet 2 EEQEE? l lnl W E S a w@ M 0 0 0 1 W M 9 M M z 5 z 0 4 7 7 i5? i j WM W i a m 7 Mid w y 7 E H 5 m 00 l ATTORNEYS y 1940- F. w. GODSEY. JR

ELECTRICAL DEVICE Filed Jan. 18, 1938 3 Sheets-Sheet 3 57 53 INVENTOR.

FRANK W G'UDbTY-JR. W, Q6 y ATTORNEYS Patented May 21, 1940 UNITED STATES ELECTRICAL DEVICE Frank W. Godsey, Jr., signor to Sprague North Adams, Mass, as-

Specialties 00., North Adams, Mass, a corporation of Massachusetts Application January 18, 1938, Serial No. 185,596

4 Claims.

The present invention relates to electrical condensers and more particularly to a condenser assembly of the multi-unit type, each of the units of which may be independently adjusted.

Such condensers have many applications and will be illustrated in their use in radio receivers.

For example, in tuning the circuits of radio receivers into resonance at selected frequencies, a plurality of semi-adjustable condensers are used. In such receivers, one of the electrodes of several condensers can be electrically interconnected with each other without impairing the proper operation of the circuits. In accordance with the invention, I provide for this purpose a condenser assembly consisting of a plurality of semi-adjustaable condensers, mounted on a common metal base or bracket, said base serving both as a common support and a common electrode of the condensers.

Such a construction has various advantages. It is compact, eliminates much of the electrical wiring and provides for important electrical advantages later to be more fully explained.

The condenser assembly of my invention is particularly adapted for use in the automatic tuning of radio receivers by the so-called condenser substitution method, and will be-described in greater detail in this connection.

As is known, in this method of automatic tunsubstituted by semi-adjustable, so-called trimmer type condensers, which are pre-adjusted to the resonant frequency of the station selected.

As a rule, condenser assemblies comprising two or more sets of such semi-adjustable condensers are used, each set corresponding to one of the variable tuning condensers which they are to replace.

The condenser substitution method of automatic tuning has inherently various theoretical advantages over other automatic tuning methods, particularly with regard to a precise and permanent adjustment at the Dre-selected frequency. However, in practice such inherent advantages could not be fully realized mainly because of the high minimum and stray capacity effect produced by the interaction of the individual condenser units used in prior constructions. The high minimum capacity of such prior condenser assemblies was further increased by the switching arrangement employed with same, requiring individual wires leading from each of the condensers to a corresponding member of the switch.

In fact, frequently the total minimum capacity of the device was too high to permit tuning of the ing, the ganged variable tuning condensers" are receiver at the higher frequencies of the tunin band; whereas the high stray capacities referred to, deleteriously affect the stability and operating characteristics of the device.

A further important disadvantage of prior art" constructions was a high capacity drift resulting in detuning of the receiver produced by variations of the capacity of the connecting wires, due to. the temperature changes occurring within the radio receiver.

An object of the invention is therefore to provide a multi-unit condenser which gives a small minimum capacity and a negligible stray capacity and in which the inter-capacity effects are reduced to a minimum. 1

Another object of the invention is to provide a condenser assembly in which a. plurality of adjustable condensers are mounted on a common rigid metal base which base serves both as a support and common plate of the individual condensers.

A further object of the invention is to provide a multi-unit condenser assembly which lends itself to simple and economical manufacture.

A still further object of the invention is to, provide a multi-unit condenser assembly for automatic tuning of radio receivers, and in which the individual condensers have a very small minimum and stray capacity and retain indefinitely their adjusted capacity.

A still'further object of the invention is to provide a novel switching arrangement for the automatic tuning device above referred to.

Further objects of my invention, including various novel mechanical features which are also useful in other applications, will be more specifically pointed out in the specification and in the appended claims.

My invention will be further'described with reference to the appended drawings in which:

Figure 1-is a top view of the multiple condenser assembly made in accordance with the invention;

Fig. 2 is a front elevation of the condenser assembly shown in Fig. 1;

Fig. 3 'is a side elevation of Fig. 2;

Fig. 4 is a section along line 4-4 of Fig. 1;

Fig. 5 is a plan view of an automatic tuning device in accordance with my invention;

' Fig. 6 is a'side elevation partly in section of the device of Fig. 5;

Fig. 7 is a front elevation of 5 and 6; I

Fig. 8 is a partial bottom view of the base with the condenser assembly of the device of Figs. 5 to 7;

the device of Figs.

Fig. 9 is a sectional side view in part of Fig. 8 taken along line 9-8;

Fig. 10 is an enlarged sectional side elevation taken of part of Fig. 5 along the line Ill-40;

Fig. 11 is a fragmentary section in side elevation showing one switching element in the closed position.

Referring to the drawings, in Figs. 1 to 4 there is shown a condenser assembly comprising three condenser units provided on a U- shaped metal bracket 9, serving as a common mounting means thereof. The bracket 5 consists of a central or base portion l0 serving both as a common base and as the common fixed electrode of the condenser units, of two legs H-l I, and corresponding mounting feet l2--I2 provided with mounting holes 8-8.

One edge of the base I0 is bent to form a ledge l3, whereas its opposite edge is provided with three pairs of tongues H for a purpose later to be stated.

Each of the three condenser units comprises a block-shaped member l5, which abuts against metal, for example of phosphor bronze. Integral with the plate 20 is a bifurcated portion comprising two integrally interconnected bent spring arms 22-22, separated by a cut-out 2|. The spring arms 22 serve to support and tension the plate 20. The interconnection 98 of the spring arms 22-22 is provided on one side with an extension lug 23 serving as one terminal of the condenser and on its other side with a clip 24 extending into the cut-out portion 2|. The clip 24 is secured to the member l5 by means of a rivet IS.

The plate 20 is also provided with a cut-out 26 to prevent its contact with the rivet i6.

To assist in properly maintaining the shape and tension ofthe spring arms 22-22 there'is provided a reenforcing clamping member 25 of cold rolled steel or similar hard metal, clamping the interconnection 38 against the end of member IS. The clamp 25 is secured by means of an extension to the block member l5, together with the clip 24 by the rivet l3.

Interposed between the base l0 and each of the plates 20 is a corresponding layer of dielectric material, for example a mica plate l8, fixed in position by the rivets l3 and IS.

The block I! is provided with a tapped hole I02, which also passes through a central boss lfll provided integrally with the block IS. The hole I02 is adapted to receive a screw 21 which passes through holes of the base l0 and of the means of integral lugs 33 and a rivet 33.

assembly of a plurality of adjustable trimmertype condensers and correspor-iing switching means to place these condensers in circuit.

The condenser assembly shown in the drawings comprises three rows of six condensers each. The number of condensers per row corresponds to the number of frequencies, i. e. broadcasting stations, for which automatic tuning can be obtained with a given setting of the condensers, whereas the number of rows corresponds to the number of tuned circuits in which these condensers are to be inserted, i. e. to the number of gangs of an equivalent variable tuning condenser.

As will be later more fully explained, for any selected frequency three condensers arranged in a horizontal line of Fig. 8, are placed in circuit by a corresponding setting of the switch. The three condensers of each group have such capacity ranges that the circuits in which they are inserted can be tuned to their respective required frequency ranges, whereas the capacity ranges of the diflerent groups are preferably in overlapping progression of such values that the entire tuning band is covered. However, except for differences in capacity ranges, the construction of all of the. condensers is substantially the same.

For the sake of simplicity neither description nor illustration is given of the circuits of the radio receiver for which the device is used, such being well known to one skilled in the art.

All of the condensers of the assembly are disposed on a common metal base 30, which is preferably stamped from a sheet of cold rolled steel. The base 30 is provided with three longitudinal recesses 3| and various perforations later to be specified.

Disposed in each of the recesses 3|, is 9. rectangular strip of insulating material 32, for example of laminated Bake1ite," hard rubber or the like, fixedly secured to the base by rivet 32.

The base 30 forms a common armature plate or electrode for each of the condensers of the assembly. As a second armature plate or electrode I provide for each condenser individual rectangular plates 33 having an integral extension lug 34 secured to the insulating strip 32 by a rivet 35. The plate 33 and its extension lug 3| is preferably of a highly resilient metal, for example of phosphor bronze.

Interposed between the base 30 and the plate 33 is a layer of dielectric material 33. for example, a plate of mica.

For condensers of very small, minimum capacity, each of the electrodes consists of a single armature plate, as is the case for the condensers just described, which refers to those shown in the lowest horizontal row of Fig. 8. However, for condensers of higher capacity ranges additional interposed elements are used in known manner, and the condensers in the second horizontal row of Fig. 8 are of such construction.

The latter condensers, in addition to the elements just described, have one or more interme diate armature plates 31 having the same polarity as the base 30 to which they are electrically connected and mechanically secured by Furthermore, instead of a single plate 33. the condenser may have also a plurality of such plates which are interconnected and secured to the strip 32 by means of their respective lugs 3| and the rivet 35. Instead of a single mica plate 33, therewill be a plurality of same, as many as required 7 to dielectrically separate adjacent plates-of different polarities.

As will be noted, in the construction of the invention all of the condenser plates are fixedly secured to the base either directly--as are the plates having the same polarity as the base-or indirectly by being secured to the strip 32-as are the plates 33 of opposite polarity. The result is that the condensers of the invention will maintain their adjusted capacities irrespective of vi- I bration or other external influences, which is not the case with trimmer condensers of the prior art, which because of the loosening of their terminal connections, are subject to capacity changes due to vibration or other influences.

Each condenser is adjustable by means of an adjusting screw 40, centrally located with respect to its plates and passing through corresponding holes of same. The holes of the armature plates are sufficiently large to insure non-contacting passage of the screw 40, whereas the holes in the dielectric layers 36 are smaller to provide a margin of insulation between the armature plates around their holes. The end of the screw 40 engages a corresponding tapped hole I03 of the base 30.

Interposed between the top plate and the head I of the screw 40 there are provided one or two washers. If the top plate is a plate of the same polarity as the base 30, I may use a single metal washer. On the other hand, if the top plate is a plate 33, which is to be insulated from the base, I provide between the metal washer and the top plate a washer of insulating material, such being shown in the drawings, where interposed between the adjustable plate 33 and the screw 40 there is provided an upper metal washer 42 and a lower insulating washer 4|; the washer 4| may be of low-loss ceramic material or molded Bakelite, mica or the like.

The metal washer 42 reenforces the washer 4| by properly distributing the pressure of the adjusting screw on same. Nevertheless, particularly when the washer 4| is made of easily breakable material, as is usually the case when it is of ceramic material or molded Bakelite, I prefer to make the metal washer 42 cup-shaped whereby its downwardly-extending rim 3 helps to keep the insulating washer 4| in location, even if this washer should break into several pieces.

The base 30 is also provided with cut-outs 43, slots 44, and holes 45. Of these, the cut-outs 43 are rectangular openings around the lugs 34 so as to prevent their contact with the base 30 and also to permit non-contacting passage of the rivets 35.

The slots 44 are located to sidewise border the mica plates 36, and the holes 45 are disposed at the two sides of the lugs 38. The slots 44 and holes 45 jointly serve as locating guides for a templet which is used to properly position the electrode and mica plates during the assembly of the condenser. The templet is removed after these plates have been properly secured in position by their permanent locating means, namely, the rivets 35 and 39. a

To enclose the condenser asse ly, there is provided a removable cover 41, wh ch is secured to the base 30 by screws 48 passing through tapped holes 49 of the base.

As a common outside terminal for one of the electrodes of all of the condensers of the assembly, there is provided a lug 50 soldered or otherwise secured to the base 30, and which in radio receiver applications is as a rule grounded to the chassis of the receiver.

The second or individual outside terminal of the condensers is provided for as follows: Connected to each lug 34 by means of the rivet 35, but disposed on the upper side of the strip 32, and insulated from the base 30 by the cut-out 43, there is provided a resilient arm 5| (see Fig. 10) of phosphor bronze or similar material. The arm 5| extends into a portion 52 which serves as one of the two contact fingers of a switch later to be described.

Located over the insulating strip 32 and substantially co-extensive therewith, is a U-shaped metal contact bar 53 serving as a common connector for each row of condensers. The bar 53 is secured to the base 30 and insulated therefrom by means of two cylindrical insulators 5454 provided with reduced extending portions |04 fitting into corresponding holes of the base 30. Rivets 55-55 passing through the insulator 5454 engage the bar 53 and the insulating strip 32 on the opposite sides of the base 30, whereby the rivet also holds a lug 56 which makes electrical contact with bar 53 and serves as the other terminal for the electrodes of one row of condensers.

The contact bar 53 is provided with openings 51 to permit therethrough non-contacting passage of the contact arms 5|. The material corresponding to the openings 51, however, instead of being severed from bar 53, remains attached thereto and is bent to form a series of switch fingers 58, which are complementary to the switch fingers 52.

Disposed between each pair of switch fingers 52 and 58 and separating same, is a blade 6| of insulating material, for example of laminated Bakelite or the like. The switch blade 6| carries a contact, which may be a rivet but preferably consists of a thin bent metal strip 60, for example of silver, platinum, iridium alloy, tungsten or the like, snugly held in a slot I05 of the blade and is bent upwardly.

In the open position of the switch, fingers 52 and 58 are electrically separated by the interposition of the insulating blade 6|. However in the closed position of the switch, the blade 6|, as shall hereafter be more fully explained, is depressed, and the contact 60 is made to fall between the clips 52 and 58, and completes the electrical circuit between a selected condenser electrode 33 and the terminal 56.

As appears from Figs. 6 and 7, for the three condensers of a group, there is a single switch blade 6| and a single switch actuating mechanism; however, each blade 6| is provided with three contacts 60, so that the electrical connection for one group of condensers is simultaneously established by the activation of their common.

appears from Figs. 6 and 11, in which the switch is shown in its open and closed position respectively, comprises a latch 10, a flanged guide bar 1|, a lock bar 12, and a supporting bracket 13, all of which are preferably stampings of cold rolled steel or of a similar hard metal.

The latch 10 comprises a stem 14 and extends into a straight arm 15 and bent arm 16 respectively, the arms 15 and 16 having aflixed to them, by means of rivets 11-11, the blade 6|.

Proper guiding of the latch 10 in its vertical movement is insured by the stem 14 and the arm 15 passing through proper guiding slots I06 and I81 of the bracket 13 and the guide bar II respectively.

The arm 15 carries a coil spring 18 which abuts against the bar ll.

The latch 18 is provided on its side opposite to arm 15 with a projection tip 19 and a notch 88. On its portion falling beneath the bracket 173, the stem l4 carries two washers 82 and 83 of metal and felt respectively, and on its upper end which projects beyond the bracket 13 it is provided with a button 84 of hard rubber, Bake-- lite or like material.

The supporting bracket 13 is a U-shaped metal strap comprising two legs 8585, each provided with extensions 86-88 which pass throughcorrespending rectangular perforations 46 of the base 38 and secure the bracket 13 thereto. Between the extensions 8688 there is formed an opening 87 which prevents contact of the bracket 13 with the terminal 56 of the center row of condenser-s. Two singularly-disposed straps 88-88 welded or similarly secured to the bracket 13 serve to increase its rigidity.

For its support in the bracket 13, the guide bar ll is provided on each end with extensions 9i engaging corresponding slots 89 of bracket 13. The lock bar "I2 is supported in the bracket 13 by means of its extensions 92-92 engaging open slots 9898 of the bracket 13, this support being such as to permit the lock bar 12 to swing through a limited arc- The lock bar 12 is bent in its lower portion H8 with regard to its upper portion I89.

A helical tension spring 93 engaging with one end a hole I88 of lock bar 12 and with its other end a hole 94 provided in the oppositely disposed edge of the bracket 13, serves to bias the lock bar to stay in contact with the latch 18.

For the mounting of the device, the bracket 13 is provided with tapped holes 95-85 through which are inserted suitable mounting screws (not shown).

The operation of the device is as follows: The device is connected in the circuit of a radio receiving set by means of'its common terminal 58 and its three terminals 56--56-56. The adjust- -ment of the condensers to their required'capacity usually takes place after the device connected in the circuit. To permit their adjustment without removing the cover 41, I provide the latter with openings H2, corresponding in number and disposition to the adjusting screws 48, whereby capacity adjustment can be made through these holes. It should be noted that the holes H2 are smaller than the 'screw heads III, and the cover 41 is sufficiently shallow as to limit the unscrewing of the screws 48.

The three condensers of each group are adjusted to the capacity value corresponding to the frequency of one of the six selected broadcasting stations.

To tune the receiving set to one of the six selected stations, one depresses the button 84 actuating the switch blade iii of the three condensers tuned to the resonant frequency of the station. Depression of button 84 depresses latch II and blade 6|, whereby the contacts 88 are inserted between the switch fingers 52 and 58 of trodes of these condensers are permanently connectcd to terminal 58, the condensers are now inserted in their respective circuits.

As the latch I8 is depressed, its tip 19 presses against the inclined portion H8 of the lock bar 72 and pushes it out of its path against the tension of spring 93. However, as soon as the tip l9 has cleared the lock bar 12, the spring 93 returns the lock bar into its normal position and causes it to engage the notch 88. This looks the switch in its closed position.

The release 'of a locked switch is achieved by partly depressing any one of the other buttons. This causes the tip 19 of the partly depressed latch 78 to outwardly swing the lock bar 12 and disengages it from the notch 88 of the locked latch l8, thereby releasing the same.

To tune in from one station to another station, the procedure just described is followed, the release being effected by the button corresponding to the second station; however this button instead of being partly depressed is now fully depressed so that the lock bar 12 may look its latch .78.

If by any chance all of the switches should be simultaneously locked in their closed position, they can be released by depressing any one of the buttons 84 to the full extent of its travel. This causes the upper inclined edge 8| of the latch lease.

It should be noted that the felt washer as with its metal backing washer 82 properly cushions the impact of the latch 18 against thetbracket 13 when the switch is released.

From the above description it will be seen that the trimmer condensers of the invention in their combination with the novel switching device, produce a very compact and simple automatic tuning device of the condenser substitution type.

As will be noted, all electrical wiring is eliminated from the device and its electrical connections are kept at a minimum and so arranged that their capacity, and particularly their capacity drift, has 'no marked influence on the capacity adjustment of the device. Because of this and the fact that all the electrodes are rigidly secured :in position, the device retains its adjusted capacity values indefinitely and inter-capacity effects are practically eliminated.

I may also provide on the switch additional switching members which, instead of serving for the selective connection into circuit of condensers, serve to establish other electrical connections in the receiver, for example, to change over from manual to automatic tuning, switch on or off the receiver, etc.

It should be well understood that the number of condensers per row as well as per group can be easily varied in accordance with the requirements.

It should also be noted that many novel features of the invention are usable outside, of the illustrated combination, and that various modifications of the devices described are possible without departing from the spirit of the invention.

Thus while I have described my invention in specific embodiments and by means of specific examples, I do not 'wish to be limited thereto, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

' What I claim is:

. 1. A condenser assembly comprising a base, a

plurality of adjustable condensers provided on said base, each condenser comprising two electrodes, dielectric interposed between said electrodes and an adjusting screw, said adjusting screw having a head, a cover detachably secured to said base and having apertures disposed opposite the head of the adjusting screws, the dimensions of said holes being smaller than those of the heads, said screws being adjustable through said holes and being limited in their displacement by said cover.

2. An adjustable electrical condenser comprising a plurality of electrodes and a dielectrical material interposed between said electrodes and adjusting means toadjust the capacity of the condenser, said means comprising an adjustment screw having a head, a metal washer and an insulating washer disposed between said head and the adjacent electrode, said metal washer being cup-shaped and partly surrounding said insulating washer.

3. An automatic capacity selecting device comprising a metal base, a plurality of adjustable stacked condensers symmetrically disposed in two or more rows on one side of said base, each of said condensers having at least two electrodes and a dielectric between said electrodes, insulating strips secured to said base, one electrode of each condenser of one row being secured to one insulating strip, an apertured metal bar disposed alongside said insulating strip insulatingly secured to the other side of said base and forming a common terminal for the condensers of each row, a plurality of switch fingers integral with said bar and formed from the material removed from its apertured positions, a plurality of switch fingers complementary to said first fingers passing through the apertures 01 said bar and individual for each electrode secured to said strip, insulating means normally disposed between said complementary fingers said means provided with electrical conducting portions, and means to selectively actuate said insulating means and interpose said conducting portions between the complementary switch fingers.

4. An automatic capacity selecting device comprising. an apertured metal base, a plurality of adjustable stacked condensers symmetrically disposed on the one side of said base, an insulating strip mounted on said base, the electrodes of one polarity of said condensers being secured to said insulating strip, a plurality of switch fingers individual for each electrode secured to saidinsulating strip and protruding through the apertures of said base, an apertured metal bar forming a common terminal for said condensers and disposed alongside said insulating strip, said metal bar insulatingiy secured to said base on the opposite side thereof, a plurality of switch fingers integral with said bar and complementary to said first switch fingers, insulating means normally disposed between said complementary fingers said means comprising electrical conducting portions, and means to selectively actuate said insulating means and interpose said conducting portions between the complementary switch fingers said means comprising individual mechanical latches secured to said insulating means.

FRANK W. GDDBEY. J3.

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