US1599225A - Variable grid leak - Google Patents

Description

Sept. 7 1926; 1,599,225

y A. FRANKLIN VARIABLE GRID LEAK Filed oct. 5. 1/922 MEM v lum i- -39 INVENTOR A TTORNE Y Patented Sept. 7, 1926.

l UNITED STATES PATENT OFFICE;

ALBERT FRANKLIN, 0F NW YORK, N. Y., ASSIGNOR T0 CHAS. FRESHMN CO. INC.,

OF NEVI YORK, N. Y., A CORPORATION 0F NEW YORK.

VARIABLE Garn Laax.

Application filed October 5, 1922. Serial No. 592,574.

This invention relates to improve-ments in electrical apparatus with special re ference to devices known as variable resistances or grid leak in which the obstruction to flow of the current may be increased or diminished. f One of the objects of the invention is to provide a resistancel of the type described in which the conductivity of the apparatus may be varied minutely, the adjustment being graduated from substantially zero to full capacity.

Another purpose is in the provision yof an enclosed conductor the ,resistance of, which can be varied from its exterior in a known degree, the same being indicated as operated and capable of being accurately reset to.obtain like results. f

A further aim is to produce a neat and Vcompact apparatus, comprised of few and simple parts arranged for convenient and easy operation and relatively inexpensive 0 them` sald conductor making intimate electrical contact with the exposed and coated to construct.

These and analogous aims, objects and purposes are accomplished by. the novel structure hereinafter described rand illustrated in the accompanying drawing, forming an essential part of this disclosure, and in whiclizA Figure 1 is a plan view of one embodiment of the invention.

Figure 2 is a central longitudinal sectional view of vthe same.

Figure 3 is a perspective view of a grid leak plate and means for varying its resistance, the same being a simple form of the invention.

Y Figure 4 is a sectional view showing a further modification Vin construction.

As shown in the drawing the apparatus comprises an elongated rectangular housing Y or body 10 made of insulating material, as rubber, fiber, porcelain or other dielectric substance,ithe same having an open rectangular recess 11 in its bottom.

A pair of binding osts, respectively 12 and 13, are fixed in sai body to extend above thesurface near its ends, the same being provided with the usual means for connecting with conducting-wires, the lower ends of the posts entering the recess 11.

Encircling the inreaching ends of the posts and in electrical engagement therewith are metallic spacing collars 14 and 15 clamped by screws16 and 17.

Seatedagainst the upper surface of the recess 11 and extending to cover its full area` is a grid leak plate 18 made of dielectric material but so treated, asby a coating of carbon or other conducting substance, as fito act as a weak conductor for electric currents passing from one post to the other, the stems of which engage the plate in addition to the collars.

l 'l'hc stem 19 of a knurled knob 20 passes centrally through the body 10 and plate 18, and carried by the stem 19, below the knob, 1s a pointer 21 co-operating with a Acurved row of graduations 22 imprinted on the surface of the body l0 as shown in Figure'l.

Carried by the lower extremity of the knob stem 19 is a metallic conducting strip having., two equal tapering ends 23 and 24 rounded at their extremities and so proportioned as to nearly touch the collars 14 and 15 when the stripconductor is turned by the knob 20 to extend in register between tors` its upper Surface being treated to ren Y der it weakly conductive, and the strip conductor 23 and 24 operated over its treated or coated face by the knob 20', the broken lines showing the conductor as disposed transversely and hence substantially inoperative with reference to conducting current from one terminal to the other.

It will be apparent that when the conductor- elements 23 and 24 or 23 and 24 are directed to the terminals that they act as bridges conveying the maximum of current from one to the kother and thatby turning the knob the conductivity ofthe grid leak plate will be reduced proportionately to ractically nothing, the position of the con- Y uctor elements bemg indicated by the grad nations 22.

Returning to the embodiment shown in Figures 1 and 2, it will be seen that the screws 16 and 17 pass through the ends 27 and 28 of a'condenser 29 disposed in the recess 11, said recess being rendered air-tight 4, the casing is omitted and the arrangement of parts slightly varied.

A similar knob 32 is engaged on the screw-threaded stem of a stud 33 which carries a double ended conductor strip having opposed elements 3ft and 35 in electrical. engagement with the coated dielectric grid leak plate 36, the same being in contact with a condenser member.

Said member is secured at one end by a grommet terminal 38 and is separated from a similar member 39 by the interposition of a sheet'of mica 40 or like material.

The condenser member 39 is secured by a grommet terminal 4l, and held by an insulated backing plate 4Q, all of the several plates being firmly united by the grommets as shown, and obviously the operation is like the other devices described and by which similar results are. attained.

Although the invention has been described With considerable detail and With respect to certain particular forms, it is not desired to be limited to such details since many changes and other modifications may well be made Without departing from the spirit and scope of the invention in its broadest aspect.

Having thus described my invention, what I claim is new and desire to secure by Letters Patent, is

l. An electrical apparatus comprising a dielectric plate, a conducting coating on one -side thereof, terminals for connecting an plate haring a surface of weak conductivity, A

terminals for connecting an electric current to the opposite ends of said plate surface, an elongated strip conductor pivoted centrally on said plate with its entire contiguous surface in constant electrical contact with the conductive surface thereof, means for rotating said conductor into varying angular positions relative to said terminals, and means for registering the position of said conductor.

Signed at New York in the county of New York and State of New York this 30th day of September A. D. 1922.

ALBERT FRANKLIN.

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