US1621659A - Condenser - Google Patents

Description

March 1927 J. B. DEMPSTER CONDENSER Filed Dec. 14, 1922 w a j Patented Mar. 22 1927.

PATENT OFFICE.

JAMES B. DEMPSTER, OF IOWA CITY, IOWA.

coiaDENsER.

Application filed December 14, 1922.

My invention has to do with certain electrical condensers of the air insulated type. It is the object of my invention to provide a variable condenser of the type under consideration of simple, durable and inexpensive construction.

Another object of my invention is to provide/such a condenser, having a series of fixed plates and a. series of movable plates, so constructed and mounted that when the movable plates are moved to position for overlapping the fixed plates, the capacity of the condenser will be varied according to the square of the angular displacement of the plates.

Aparticular object is to provide a condenser, having plates of such shape and so mounted as to permit the movement of the plates to position where the capacity is substantially zero.

A further object is to provide such a condenser having a series of fixed and a series of movable plates, in which the movableplates may be operated with a rotary movement.

Another object is to provide such a condenser having plates of such shape as to permit the building of the condenser to occupy a minimum space, so that. it may be compact and thus convenient for storage, transportation and installation.

An additional object is to provide such a conden er having the parts so constructed and arranged as to give the condenser sufficient sturdiness or strength to insure the proper spacing of the movable plates with relation to the fixed plates during the operation of the condenser. Y

A further object is to provide a condenser of the type under consideration, which is peculiarly adapted foruse in radio telegraphy and telephony equipment.

With these and other objects in view, my invention consists in the construction, ar-

' rangement and combination of the various parts of my device. wherebv the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and

illustrated in the accompanying drawings, in which:

Figure 1 shows a front elevation of a com- Serial No. 606,898.

plete condenser installed on an instrument board.

Figure 2 shows a rear elevation of the same with the movable Vernier plate in raised position.

Figure 3 shows a. side elevation of the installed condenser with all the movable plates in their positions of minimum capacity.

Figure 4 shows a vertical, longitudinal, sectional view taken on the line 44 of Figure 1.

Figure 5' shows a transverse, detail, sectional view taken on the line 5-5 of Figure 3.

Figure 6 shows an enlarged, fragmentary top or plan view of a portion of the condenser; and

Figure 7 is a diagrammatic view illustrating a fixed and a movable plate, illustrating the various elements which are involved in a determination of the size and shape of the plates.

For convenience, I have shown the condenser installed upon an instrument board or panel or the like, which in the accompanying drawings, I have indicated by the reference character 10.

My condenser is of the type employing a number or series of fixed plates and a numher or series of movable plates adapted to be moved to various positions overlapping portions of the fixed plates.

In the accompanying drawings, I have disclosed a supporting frame, comprising the spaced end frame members 11 and 12 and an intermediate similar frame member 13. The frame members 11, 12 and 18 have projecting ears or the like 14, 15, 16 and 17.

The ears 14 of the various frame members mentioned are arranged in alignment with each other, and similarly the ears 15 are aligned, the ears 16 are aligned, and the ears 17 are aligned.

A rod 18 is extended through the ears 14 and has nuts 19 on the opposite sides of the ears 14.

A rod 20 is extended through and supports the ears 15 and also has nuts 19, similar to those already described, for holding the frame members 11, 12 and 13 properly spaced and rigidly supported.

A rod 21 is similarly extended through the ears 16.

It will be understood that the parts jus described form a rigid frame-work.

Extended through the ears 17 is a rod 22. The rod 22 is insulated from the frame memher 13 by means of a sleeve or the like 23 formed on the washer 24. On the rear end of the rod 22, I preferably mount a nut 22.

On what may be called the forward; end of the rod 22, a head 25 of hard rubber or other suitable insulating material is detachably mounted by means of a set screw or the like 26. Mounted on the rod 22 is a sleeve 27, which terminates short of the forward end of the rod 22, as shown in Figure 4, and has mounted on its forward end a suitable dial or the like 28.

The sleeve 27 terminates at its'rear end just rearwardly of the frame member 12, as shown in Figure 4. The sleeve 27 is insulated from the members 11 and 12 by means of sleeves 29 and 30 formed on washers 31 and 32.

The rod 22 and sleeve 27 are mounted to rotate freely with relation to the supports in which they are arranged and with relation to each other.

Supported on the frame formed by the parts hereinbefore described and preferably on the rods 20 and 21 is the series of fixed condenser plates. These plates are indicated on the drawing by the reference character 33. The peculiar shape of the plates will be hereinafter more particularly referred to, since therein lies one of the most important features of my invention.

The plates 33 are spaced from each other equidistantly on the rods 20 and 21 by means of spacer sleeves 34. For two of the spacer sleeves 34 on the rod 21, I substitute insulating sleeves or washers 35 of greater diameter than the sleeves 34 for the purpose of engaging the movable condenser plates, as hereinafter more fully explained.

A series of movable condenser plates 35 is arranged to coaotwith the plates 33. The bodies of the plates 35 and 33 are preferably of the same shape.

The plates 33 have ears 36 and 37 which project from the bodies of said plates and are mounted on the rods 20 and 21. The plates 35 have ears 38, which are mounted on the sleeve 27.

The ears 38 of the plates 35 are held equidistantly spaced apart from each other on the sleeve 27 by means of the spacer sleeves or washers 39, which are similar in construction to the washers or sleeves 34.

The parts are so arranged that when the sleeve 22 is rotated a certain distance in each direction two of the plates 35 engage the insulation washers 35 for limiting the rotation in one direction or in the other direction, as the case may be. (See Figure 6.)

The rotation of the sleeve 27 and the consequent movement of the plates 35 is accomplished by means of the dial 28.

The principal features of my invention are illustrated in the construction already described with the addition of some minor conducting parts, but for a commercial condenser,I use also what is sometimes called the Vernier attachment.

On the rod 20 between the frame members 12 and 13 and spaced therefrom and from each other, I place a pair of plates 33, similar in form and arrangement generally to the plates 33, and on the rod 22 between the frame members 12 and 13 and spaced therefrom and arranged in a plane between the planes in which the plates 33 lie, is a plate 35*, similar in general construction to the plates 35. A flexible wire 39 is connected with the rod 18. On the frame member 13 is' a binding post 40, with which is connected 2. wire 41. A connecting strip 42' extends from the post 40 to the post 43 and thence to the rod 22. The posts 40 and 43 are insulated from the frame by sleeves 40".

In order to insure absolute certainty 01 contact and electrical connection between the post 40 and the rod 22, there may be employed for connecting these two elements a. flexible wire 44.

It will be noted that the plates 35 may ferred to is used for securing even more accurate results with the condenser.

The plate 42 is of spring metal. The post 43 has a nut 45 on its rear end for permitting some adjustment, and the spring plate 42 thus serves to keep the rod 22 pressed to the limit of its forward movement.

On the frame member 12, another plate 42, similar in construction to the plate 42 is mounted in a manner similar to that of the plate 42. The plate 42 at its upper end engages the rear end of the sleeve 2'7 for pressing it towards its forward end.

In this connection, it will be noted that the condenser plates are adjustable by means of the nuts on the rods on which they are mounted, and that the spring plates 42 and 42 are slightly adjustable.

This makes possible the arrangementof the fixed and movable condenser plates, so that they will never contact during their overlapping movement.

111 any resonant electrical circuit, it: is desirable to have a variable condenser.

In the usual practice, there is employed an inductance'coil and a condenser.

1n the so-called inductance coils commonly employed, the inductance is varied by steps. This is accomplished by connecting or disconnecting a certain number of turns of the wire of the coil for each step.

Experiment and demonstration have shown that it is desirable in a condenser used with such an inductance device to be able to vary the capacity according to the square of the angle of displacement of the plates of the a variation of the wave-lengths to which the equipment will respond. The wave-lengths to which the equipment will respond varies directly according to the number of steps throughout the range of the inductance.

It therefore follows that the condenser should be so constructed that when the movable plates are moved to overlapping position with relation to the fixed plates, the capacity should increase according to the square of the angular displacement.

From the standpoint of practical commercial construction, it is desirable to have a condenser made with two series of plates, in which the plates of the respective series have pivotal movement with relation to each other. Such a construction makes for convenience in operation and convenience in installation of the condenser on 'a panel or instrument board, and for compactness and strength of structure.

I have found that I have had considerable difiiculty in ascertaining the proper shape for the plates of the condenser, which would permit the preferred construction and mounting above explained and which would be such that when the plates of the respective series were entirely disengaged, the capacity of the condenser would be approximately zero.

In Figure 7 is shown a plate 01, which may be one of a fixed series, and a plate 0, which may be one of a movable series. The plate a is pivoted'to rotate about the point e causing it to overlap the plate d. The shape of the plates shown in Figure 7 is such that the capacity of the condenser built with such plates varies according to the square of the angular displacement of the plates, when the movable series is actuated to overlap the fixed series.

It will be understood that my invention involves a structure in which either or both of the \series of plates are movable to rotate on a pivot, but for purposes of illustration, I have preferred to show a. fixed series and a movable series of plates.

I will now outline a method for determining the shapes of the condenser plates of the kind shown herein, which plates are illustrative of a form in which my invention may be embodied and a method of arriving at the theoretical outlines of such plates.

In the form shown, the plates 0 and d are made exactly alike with the exception of allowances made for the tongues or arms for mounting the movable plates on their pivots and the stationary plates on their supports.

It is understood that for purposes of practical construction, the actual plates must vary somewhat in outline from the outline of theoretically perfect plates.

The right and left halves of the plate (5 as divided on the line f g passing through the pivot point e are exactly similar except that the one-half is the reverse of the other. For our purpose then, we need consider only that portion of the plate 0 bounded by f k e f, so that j is any point on the outer curve f k and Z any point on the inner curve it 6. Then 6 j equals R and e Z equals 1*, and the angle a e 7' equals P. If the angle P is given in radian measure then R equals plus m i Where m is a constant, then; the

Either of these relations being satisfied, then calling S the area bounded by ll Z j it, then it follows that S equals P where k is a constant.

If we assume that the capacity varies as the overlapping area of the plates, then (3" (capacity) varies as S and equals 7:: P or the capacity varies directly as the square of the angle of displacement, and since the wave-length varies, as the square root of the capacity, then the wave-length will be directly as the angle of displacement, which is the result desired.

In the foregoing, I have considered only one plate, to-wit, the plate a of Figure 7, but it is obvious that if the plates 0 and d are of similar outline and are .nade to overlap, by moving the plate 0 on its pivot, then the overlapping area of the plates 0 and (5 will be twice that considered in the foregoing explanation of one plate, and the capacity will still vary directly as the .square of the angle and the wave-len th as before. varies directly as the angle.

In laying out the curves, f j h and e Z it (Figure 7) in the manner just de- /1- plus m P;

P being any angle through which any radius is drawn, m a constant, 1" the length of the radius from e to Z and R the length of the radius from c to j.

With equal facility, I may assume an outer curve f j h and lay ofi .theinner of both d (stationary plate) -(movableplate), and that c retains the curve 6 Z k and obtain the values of r from the equation 1' equals or any portions of either curve may be arbitrarily selected andlaid oif and the corresponding portions of the other curve constructed by the use of the proper one of the above formulae.

It is desirable to give to the plates a shape, such that when the movable plate does not at any point overlap the fixed plate, the capacity of the plates or condenser will be approximately zero. To accomplish this purpose, it is desirable in selecting a curve to start with, to select such a curve as will bring an apex h somewhere in the radius e a; that, isto say, the selection of a curve terminating at h in the line 6 a will give to the half plate an apex at-h' and thus give to the plate such a shape that when the movable plate and the fixed plate are in the osition, illustrated for instance in Figure the plates will have substantially zero capacity In order to facilitate the" construction of a condenser having approximately zero capacity in certain relative positions of the different series of plates, and also for securing practical commercial advantages in the structure of the condenesr, it is desirable to make the stationary and movable plates of substantially the same outlines, as for instance illustrated in'Figure 7, although from the foregoing equations, it'follows that one plate may have any shape, providing that a e coincides with e j which is a radius outline given from the foregoing equations,

andproviding that the outlines of 0 are such that the remaining parts of this plate completely cover 0 when 0 is in the position of highest capacity.

It thus follows that the plates of a condenser of the kind under consideration may be made with theoretically perfect shapes, as illustrated in Figure 7 It will be understood that in Figure 7, I have shown a theoretically perfect plate. .The plates shown in Figure 5 for instance illustrate the plate actually used in my condensels, which are correct according to the above formulae except that the have the projecting ears for mounting t em in the complete device.

It is obvious that the shapes of the plates may, vary from the perfect and still come within the spirit and purpose of-my invention, whereby plates are made of the proper outlines and are convenient for mounting in a device, which is compact, simple and cheap, andwhich'has its parts suitable for operation by a dial. This device is convenient for the ordinary panel or instrument board.

I claim as my invention:

1. In a condenser, fixed plates, coacting pivoted similar plates each having each half thereof outlined by two dissimilar curves,

the radius of one of said curves at any point therein equaling the square root of the sum of the square of the radius of the other curve to a point in the same radius plus the product of a constant times the angle through which the radius is drawn, thus:

substantially as shown and described.

2. In a condenser, a plurality of fixed plates and a plurality of coacting pivoted plates adapted to be moved to position overlapping with relation to the fixed plates, the overlapping portions of the plates'.being outlined by dissimilar curves produced according to the formula in which the radius of one curve equals the square root of the sum of the square of the radius of the other curve to a point in the same radius and the product of a constant times the angle through which the radius is drawn, thus:

Des Moines, Iowa, December. 4, 1922.

JAMES B. DEMPSTER.

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