US1819692A

US1819692A - Variable condenser

Info

Publication number: US1819692A
Application number: US611667A
Authority: US
Inventors: Shapiro Lazarus
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1923-01-09
Filing date: 1923-01-09
Publication date: 1931-08-18
Anticipated expiration: 1948-08-18

Description

Aug. 18, 1931. SHAPIRO VARIABLE CONDENSER Filed Jan. 9, 1923 gvwemtoz L HAPIRO 35% k1 adieu W1 3i M Patented Aug. 18, 1931 UNITED STATES PATENT OFFICE LAZARUS SHAPIRO, OF BRONX, NEW YORK, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE VARIABLE CONDENSER This invention relates to variable condensers such as are employed in wireless telegraphy and telephony.

As is well known, wireless transmittersand receivers comprise circuits which may be tuned to the length of the waves which 1t is desired to transmit or receive. .As is also well known, the tuning of a circuit depends on the inductive and capacitive efi'ects of the 'circuit. In such circuits it is customary to maintain the inductive effect substantially constant and to vary the tuning or wave length of the circuit by regulating the capacity. The capacity effect is obtained by the use of condensers, and the length of the wave transmitted or the length of the wave to which a receiver is tuned is usually varied by adjusting certain elements of a condenser relatively to certain other elements.

,vide a variable condenser, articularly for use in receivers, with means or adjusting the condenser approximately to the wave length which it is desired to receive and auxiliary means for effecting minute adjustments of the condenser to tune the receiver exactly to the length of the incoming waves. Such condensers have also been provided with scales for indicating the capacity to which the condenser is set by actuation of the primary adjusting means. The arrangement of such condensers has, however, generally been such that the reading of the scale has not been affected by the auxiliary means for making the minute adjustments, and that the capacity of the condenser might be varied by operation of the auxiliary adjusting means through a range corresponding to a number of graduations on the scale, with the result that yvhen the condenser was first set to the approximate wave length by the primaryadjusting means and was then adjusted by the auxiliary adjusting means, as nearly as the construction of the condenser would permit, to the exact length of the incoming waves, the indicating means no longer showed theprecise capacity to which the condenser had been set,

It is an object of this invention to provide a variable condenser which can be It has heretofore been proposed to proquickly set by primary adjusting means approximately to the incoming wave length,

and which may then be adjusted by auxiliary adjusting means exactly to the incoming Wave length with appropriate movement of the indicating means so as to cause such means to invariably show the precise capacity to which the condenser is set, or in other words, assuming that the inductive effect of the receiver is constant, the wave length to which the circuit, of which the condenser is a part, is tuned.

It is frequently important in the design of radio receiving sets, particularly for the reception of broadcasted speech or music, to employ a condenser occupying a minimum amount of space in proportion to its capacity. Such a condenser is, for example, of great advantage in the construction of a sound reproducing machine, such as that shown in the co-pending ap lication of Alfred N. Goldsmith, Serial 0. 587,067, filed Sept. 9, 1922, which comprises a combined phonograph and radio receiver in which the radio receiving apparatus is mounted in the cover of the machine casing. The space available in the cover of such a machine is limited, particularly in its vertical dimensions, and it is accordingly necessary that the condensers employed in the radio receiving apparatus shall be small, particularly in thickness.

A further object of this invention is to provide a condenser which will aflord maximum capacity in proportion to the amount of space occupied by it.

An important feature of the invention resides in the provision of a condenser, includmore movable plates mounted on a shaft and having curved outer. edges, of indicating means connected with the movable plates and meansfor positively engaging the outer edges of the movable plates to effect minute adjustments of said plates relatively to the stationary plates. In the preferred form of the invention, the movable plates are mounted rigidly on a shaft having a dial constructed for manipulation by the hand, and the curved outer edges of the movable plates are toothed for engagement with a gear, so that the approximate setting of the condenser can be quickly effected by rotation of thedial and the capacity of the condenser can be regulated and the dial simultaneously rotated by actuation of the gear to adjust the condenser exactly to the wave length, which it is de-' sired to receive, the result being that the scale on the dial at the point of best reception invariably indicates both the exact capacity of the condenser and the precise length of the incoming wave.

A still further feature of the invention contemplates the provision of a condenser including a shaft having longitudinal ridges thereon and plates mounted on the shaft and having portions cooperating with the rid es to maintain the plates and the shaft rigidly together.

Other objects and features of the invention will appear as the description proceeds and will be pointed out in the appended claims.

In the drawings, in which like reference numerals indicate like parts throughout the various views,

Fig. 1 is a view in'elevation of a variable condenser embodying the invention;

Fig. 2 is a view in horizontal section taken along the line 2-2 of Fig. 1;

F i 3 is a view showing the manner in whic the plates of the condenser are assembled upon the shaft; and

Fig. 4 is a sectional detail taken along the line 44 of Fig. 3.

The frame of the illustrated device comprises a circular top 2 and bottom 4 composed of insulating material and connected by

upright rods

6, 8 and 10, Fig. 2. Stationarily mounted on the frame is a set of plates 12 of enerally semi-circular form provided with lots or notches 14 to receive the rods. The plates .12 are supported and spaced from each other by suitable washers 16 sleeved upon the rods, and arranged in interdigital relation with the stationary plates 12 is a set of movable plates 18. As shown, the plates 18 are of somewhat smaller size than the plates 12, but are also generally of semi-circular form. The plates 18 are carried by a shaft 20 journaled in the top 2 and bottom 4 of the frame of the device.

The movable lates 18 are connected rigidly to' the shaf t 20 for rotation therewith in both directions. The preferred means for thus connecting the plates 18 and the shaft is shown in Figs. 3 and 4 and comprises ridges 22 extending longitudinally of the shaft 20 and provided with sharp outer edges 24 which will hereinafter, for the sake of convenience, be referred .to as knife ed es. In the assembly of the plates 18 and s aft 20, the plates may be driven upon the shaft by a suitable tool indicated by dotted lines 25 in Fig. 3, thereby causin the knife edges of the ridges 22 to enter t e material of the plates 18 around the central openings 26 therein, so asto cause portions 27 of the plates 18 in the assembled construction to interlock with the ridges 22 of the shaft. The interlockin of the portions 27 of the plates 18 with tie ridges 22 of the shaft 20 causes the plates 18 to be rigidly joined to the shaft 20, so as to move therewith without lost motion, even after extended use of the condenser. Preferably, and as indicated in Fig. 4, the openings 26 in the plates 18 are made of slightly greater diameter than that of the shaft 20 exclusive of the ridges 22, thereby enabling the plates 18 to be readily driven upon the shaft without warping them. The plates 18 are spaced from each other by suitable washers 28, Fig. 2, on the shaft 20.

Mounted on the upper end of the shaft 20 is a dial 29 provided with a peripheral scale 30, and preferably constructed so that it may be'readily manipulated by the hand. To this end, the dial may, for example, be provided with a knob 32 having its periphery knurled as indicated at 33. With this construction, it is apparent that upon rotation of the knob 32 or plates 18 in either direction, such rotation will be communicated to the entire assembly consisting of the set of plates 18, dial 29 and knob 32. In other words, it will be clear not only that the set of movable plates 18 may be adjusted relatively to the stationary plates 12 by rotation of the dial 29 in either direction but also that rotary movement of the set of plates 18 however effected, will be communicated to the dial 29 and scale 30;

mg means for rotatin the movable p ates 18 relatively to the stationary plates 12. In the use of the condenser, such means may conveniently be employed for quickly setting the condenser so as to tune the receiver containing the condenser approximatel to the wave length of the signals which it is desired to receive. It is found, however,

The knob 32 constitutes primary adjust-.

to positively engage, and operate the plates 18, and as shown comprises gear teeth 34: formed on the outer curved edges of each of the plates 18 and meshing with a gear 36 composed of insulatin material and carried by a shaft or spin le 38 journaled in the top 2 of the condenser frame. In order to facilitate rotation of the gear 36, the spindle 38 is preferabl provided" adjacent to the dial 29 with a nob 40 or the like. The condenser may be provided in a known manner with means for making electrical connections to the set of stationary plates 12 and the set of movable plates 18.

It will be apparent from the foregoing that very minute adjustments of the set of movable plates 18 relative to the set'of stationary p ates 12 may be effected by operation of the gear 36, and that movement of the plates 18 by the gear 36 produce simultaneous movements of the dial 29 and scale 30 so as to cause the dial to indicate the true capacity of the condenser, both when the condenser is set solel by movement of the knob 32 and when t e settin of the condenser involves the use of t e peripheral gear 36. It will also be understood that, assuming that the inductive effect of a circuit in which the condenser is to be em- 'ployed, is maintained constant, the scale 30 of the dial 29 may be calibrated in wave lengths so that at the point of best reception, the scale 30 will indicate directly the length of the incoming wave.

It is recognized that the broad principles of the invention may be embodied in a condenser in which one or other number less than all of the movable plates 18 are engaged at their outer edges with the gear 36 or other operating means separate from the shaft 20. It is preferred, however, that the gear 36 be caused to operatively engage Elsie peripheries of all of the movable plates In the use of condensers, as heretofore constructed, it frequentl occurs that the joints between the mova le plates and the shaft on which they are mounted become loosened, so that lost motion is developed between some or all of the plates and the shaft. The plates, consequently, become displaced to a greater or less degree with re- Epect to each other and to the shaft. Such isplacement obviously affects the capacity of the condenser so that the indicating means which is commonly operated from the shaft of the condenser no longer shows its real capacity. -As :heretofore pointed out, the

occurrence of such lost motion between the 1 movable plates and the shaft is largely revented by the special connecting means i ustrated in the accompanying drawing. If however, 11 tween a o the plates 18 and the shaft 20, tliegar 36, in the event that it is operatively described for efi'ectin looseness should develop b eefl'ect rotation of the gear 36, and the gear 36 will in turn rotate any plate, which may be loose on the shaft 20, to exactly the same extent as that to which the first-mentioned plates are rotated. From these considerations, it will be seen that the gear 36 not only constitutes auxiliary adjusting means for effecting minute relative adjustments of the sets of-movable and stationary plates, but that such gear also constitutes means for positively maintaining the movable plates 18 in proper relation to each other and to the shaft 20, so that the capacity of the condenser cannot be changed by displacement of the plates relatively to each other or the shaft, thereby eliminating all possibility of errors arising from such displacement in the indicated capacity of the condenser.

The provision of the means here-inbefore minute relative adjustments of the sets 0 movable and stationary' plates enables a condenser to be made of small dimensions, particularly in regard to height or thickness, in proportion to its capacity because it avoids the necessit of the provision of driving gears or the li e separate from the movable plates for operating them and because it simplifies generally the construction of the condenser, diminishing the number of parts required and consequently reducing the space requirements of the parts. i

Although the condenser is herein described as being of the type comprising generally semi-circular plates, certain of which are carried. by a shaft, it is recognized that the stationary plates of the condenser is intended to embrace a single plate as well as a plural- 't of plates, in the event that the context of a claim is consistent with the interpretation of the term as including a single plate only.

Having fully described my invention what I claim is:

1. A variable condenser comprising a shaft having ridges extending longitudinally thereof and a plate inounted on the shaft, said ridges being embedded in a portion of the plate to cause the plate to be held rigidly upon the shaft for rotary movement therewith without lost motion.

2. A variable condenser comprisin a shaft provided with integral ridges exten ing longitudinally of the shaft and having sharp outer edges, and plates mounted upon the shaft, the ridges being embedded in a portion of each plate to hold the plates and shaft rigidly together.

3. A variableeondenser comprising stationary plates, a rotatable shaft having serrations formed thereon, and movable lates mounted on said shaft, said serrations ing embedded in a portion of each plate, whereby said movable plates may be moved relatively to said fixed plates, without backlash between the said movable plates and the rotatable shaft.

4. A variable condenser comprising a shaft having longitudinal ridges, a series of lates mounted upon said shaft, said ridges ing embedded in a portion of each plate in order to provide a firm union between said plates and shaft, means carried by said shaft to rotate the plates, and separate means spaced from said first mentioned means .to provide a Vernier adjustment of said plates.

5. In a condenser, a rotatable shaft rovided with a plurality of sharp-edged, we geshaped projections, one or more rotor plates mounted on said shaft, said projections being embedded in a portion of each plate 6. In a condenser, a shaft provided with a plurality of sharp-edged projections, one or more plates mounted on said shaft, said projections being embedded in a portion of each late. I) 7. In a condenser, a rotatable shaft provided with a plurality of gripping members, one or more rotor plates mounted on said shaft, said gripping members being embedded in a portion of each plate.

LAZARUS SHAPIRO.