US2071464A - Ionic discharge tube - Google Patents

Description

Feb. 23, 1937. J. E HENDERSON ET AL 2,0711464 IONIC DISCHARGE TUBE Filed May 29. 1933 2 Sheets-Sheet 1 INVENTORS .lEHendersum ATTORNEYS.

Feb. 23, 19.37. .1. E. HENDERSON ET AL 2,071,464

IONIC DISCHARGE TUBE Fil'ed May 29, 1931 2 Sheets-Sheet 2 l6 INVENTORS 2a I.E.HET1 dEISElTL ATTRNEYs.

Patented Feb. 23, 1937 UNITED STATES PATENT OFFICE Seattle, Wash.,

assignors to Barkon Tube Lighting Corporation, Seattle, Wash., 'a corporation Application May 29, 1931, Serial No. 541,040

3 Claims.

The present invention relates to luminous tubes of the type generally referred to as spectral discharg or ionic discharge tubes. By our invention, we provide a luminous ionic discharge tube and a system of operation therefor in which electrical energy is supplied to the luminous gases by means of a large area conductor separated from the gas by a wall of dielectric material. By the use of such anelectrode, any gas which is stable under the action of an electrical discharge may be used as the illuminant, including the socalled active gases, because there is no contact between the gases and the conductor. Preferably the gas which we use may be entirely or in part carbon dioxide, since such a gas, when ionized, gives a light approximating daylight, but it is to be understood that any other stable gas may be used.

We. have found that, in order to pass through the gas in the tube sufficient 'current to give a steady and brilliant light, the electrode area must be very large as compared with the cross-sectional area of the luminous tube if a source of supply with the ordinary commercial frequencies is to be used. I

Electrostatic capacity electrodes for ionic discharge tubes as they have been suggested in the prior art, have been termed conducting caps with the caps covering as much as 40% of the tube length in extreme cases. Using the same ter-- minology to refer to the tube lighting system herein disclosed, the conducting caps would have to cover approximately of the length of the tube in order to obtain a steady and brilliant light, such as is desirable, and obviously such a length of tube devoted to the electrode would be undesirable.

It is one of the features of our invention to provide such an electrode as will have sufficient area to give the desired illumination and,,at the. same time, have it compact enough so as not to occupy an undue amount of space.

We have also found that in such a tube with such large electrodes, the use of the ordinarytransformer by which the voltage of a current supply of commercial frequencies is stepped up to the necessary potential is highly undesirable,if

not impossible, because of. the resulting unsteadithat this may be overcome by associating inductance with the external circuit, preferably in an amount sufficient to cause the current through the tube and the electromotive force to be substantially in phase. In this way, the effect of the 5 large electrostatic capacity, due to the large area electrodes, is substantially neutralized.

While the necessary inductance may be provided independently of the transformer, we have found it convenient to utilize the transformer 10 itself for this purpose. In order to accomplish this, we have found that a transformer having the proper amount of magnetic leakage can be used.

We have also found that good results may be 15 obtained when the current in the tube and the electromotive force are not exactly in phase, but, in such case, it is desirable to protect the windings of the transformer against puncturing which we have found to occur, under such circumstances, in the outside windings of the secondary of the transformer. To prevent such puncturing, we preferably provide a transformer in which these outside windings are more heavily insulated than the remainder of the windings. 25

Preferably we obtain the large surface area electrode by means of a plurality of small diameter tubes, each connected to the luminous tube, so that the interior of each small tube will be in communication with the interior of the luminous 30 tube. By using small diameter tubes for the electrode portion, we are able to make the walls thereof thinner than the walls of the luminous tube, with a corresponding increase in the electrostatic capacity. Furthermore, by associating thesev small tubes in parallel groups, as we prefer to do, we are able to support each tube by the adjacent tubes by providing a material to bridge over the spaces therebetween. The net result of our preferred arrangement is a compact group of small tubes, each of which, while thin and fragile and connected at one end only to the luminous tube, may nevertheless be supported in such a manner that a considerable strength to resist breakage is provided. 45

Our invention will be best understood from the following description of illustrative embodi- 'ments of our invention.

In the drawings:--

Figure 1 is a diagrammatic view showing the preferred form of luminous or ionic discharge tube and associated electrical circuit arrangement.

Figure 2 is an enlarged view, partly in side elevation and partly ,in longitudinal section, of one of the electrodes.

Figure 3 is an enlarged fragmentary transverse section on the line 3-3 of Figure 2.

Figure 4 is an enlarged fragmentary section on the line 44 of Figure 2.

Figure 5 is a view part in section and part in elevation of the electrode and showing a further method of operating the electrodes.

Figure 6 is a viewpf a type of the transformer that may be employed.

Figure 7 is a section on the line 1-1 of Figure 6.

Figure 8 is a purely diagrammatic view illustrating the method of Winding for the secondary coils of the transformer.

Figure 9 shows a modified form of electrode.

Figures 10 and 11 are enlarged fragmentary views on the respective lines in Figure 9 showing detailed features of construction.

Referring to the drawings in detail, and wherein similar reference characters designate corresponding parts thruout the several views, and referring particularly to the form of invention disclosed in Figures 1 to 8 inclusive, the letter A designates the luminous tube provided at its ends with the electrodes B. The tube A is preferably formed of glass and may be of any desired form and size desired in accordance with the type of illumination desired for the luminous portion of the tube. The electrodes B are shown connected in circuit with a transformer C of special construction which is for connection with a supply of low frequency low voltage alternating current, say of sixty cycle such as ordinarily supplied for commercial use.

Referring now to the specific construction of the large area capacity electrode B, which we have chosen for purposes of illustration, the same is made of a dielectric material such as glass and in one'practical size has an approximate dimension of eighteen inches in length and three inches in diameter. The electrode comprises a bell cap 5 for connection to an end of the tube A. The lower side of the hollow bell cap 5 is closed by a flat disc 6 to the under side of which is sealed a large number of small tubes I havin walls much thinner than the walls of the tube A. These small tubes 1 are closed at their lower ends and have their upper ends in communication with the interior of the hollow bell cap 5 thru apertures 8 formed thru the disc 6. These thin walled tubes 1 are of equal length and formed of a suitable di-electric material such as glass. By way of example, there may be about one hundred and fifty of these thin walled tubes 1 of about 3 mm. diameter connected in slightly spaced-apart relation to each other. This compact "bundling of the small tubes 1 provides a very large area electrode as to external surface area compared with the volume of the electrode as a whole.

While various forms of the so-called active gases may be employed, we prefer to use carbon dioxide, but it is to be distinctly understood that any gases which are stable under the action of electrical discharge may be employed. As will be observed, the interior of the electrode tubes 1 are in communication with the interior of the tube A and that the'electrode tubes form terminals of the container for the'gas to be ionized.

In the specific form illustrated, the plurality of small electrode tubes 1 are sealed within a capsule-like container or casing [0, preferably formed of a non-conducting material, such as glass, and, in the example shown, it is of tubular formation and is closed at its lower end. This casing I0 is sealed at its upper end to the hollow bell cap 5 and has an internal diameter slightly greater than the diameter of the group of electrode tubes 1 whereby the outermost annular series of the tubes are spaced slightly from the inner wall of the casing ID. The upper extremity of the casing is provided with an outwardlypressed annular bead ll providing an annular internal pocket about the upper extremity of the tubes 1. The lower end of the casing extends "slightly below the closed ends of the tubes 1 to provide a small chamber for a purpose to be subsequently explained.

The container or casing ill may be completely filled with a plastic mass of conducting material [2 forming a conductor for transfer of electrical energy to the gas to be ionized. By way of example, the mass may be agar mixed with salt water, this material being sufficiently stiff under the temperatures developed in the electrode to provide desired support for the tubes 1. In the form shown in Fig. 3 this plastic conductor l2 completely fills the casing l0 and entirely encircles each of the small electrode tubes 1. In the form shown in Figure 5, the casing I0 is only partially filled with the pastic conducting material l2 so as to form a support for the lower ends of the small electrode tubes 1, the remaining major portion of the casing being filled with either a luminous or non-luminous gaseous conductor such as neon or a liquid conductor such as water, if so desired. The pressure of the gaseous conductor used in the casing is not material. While it is preferred that the casing shall contain a sufficient quantity of the plastic conducting material to form a support for the electrode tubes 1, such material may be omitted and the casin may be filled completely with a gaseous or a liquid conductor.

For the purpose of filling the casing in with either a solid, liquid or gaseous conductor, it is provided at its upper end upon the bead II with a tip 13 and at its lower end with a tip M. In the manufacture of the electrode, the tips I3 and I4 are open, permitting the conducting material to be inserted through the tip l3 and the air in the casing to be expelled through the tip I4. After the casing is completely filled with the conducting material, the tip i4 is sealed off and the tip l3 may be also sealed off, as by heating. The tip l4 serves as an entrance opening for a lead-in wire having its end terminating in a coil or a plate of suitable area in the chamber formed below the tubes 1. This terminal conductor or plate I5 is in electrical contact with the conducting material l2. The tip 14 may be sealed about the lead-in wire.

The large number of small electrode tubes 1 form in effect a partition of large area between the conducting material l2 and the gas contained in the tube. This constitutes a condenser of considerable capacity, the conducting material l2 and the gas inside the tubes 1 being the plates and the walls of the tubes 1 being the dielectric.

As illustrated in Fig. 1, current is preferably supplied to our luminous tube by means of a transformer, one form of which is illustrated at C.

The primary 2| of the transformer is supplied preferably from a commercial source of alternating current 23, which may be a sixty cycle alternating current, such as is generally supplied for commercial use. The secondary coils I9 are wound on the core leg I! of the core l8, one on each side of the primary winding, the wires 20 bil extending from the respective secondaries to the respective electrodes B.

As we have already said, we have found that, if the transformer C is of the usual type, the light resulting from such an arrangement is unsteady, and that we have found that this difliculty can be overcome by associating inductance with the circuit.

In the arrangement illustrated, this inductance is provided by variable magnetic shunts produced by a series of soft iron plates 24 between the primary and the secondary windings, these plates being designed to give to the transformer the desired inductance to neutralize, or partially neutralize, the electrical effect of the large capacity electrodes.

In order to minimize the possibility of a potential breakdown in the circuit, we preferably insulate the outer turns of each secondary winding to a, greater extent than the remainder of the windings of the secondary, as diagrammatically illustrated in Fig. 8. This greater insulation may be provided by spacing the outer windings a greater distance apart than the inner windings of the coil,- by providing a heavier coating of insulation on the wire of these outer windings and by sheets of insulating material, as at l9, or by any one or more of these methods.

Referring now to the form of capacity or condenser electrode shown in Figures 9, 10 and 11 the casing shown in Figures 2 and is dispensed with and the grouped series of small electrode tubes 1' are connected to and are in communication with a hollow bell cap 5 for connection with the ends of the light tube A as in Figure l. The tubes 1' are coated with a metallic material 30, such as aluminum paint, carbon or graphite compositions, to provide a conducting coating upon the entire external surface of the tubes. After the metallic coating is applied, the tubes may be coated with one or more layers of lacquer or other suitable material to provide an insulating coating about and between the tubes to insulate the tubes against brush discharge and resultant production of ozone and consequent waste of energy. This coating of insulation also forms a binder for the tubes as shown in Figure 11 and reduces to a minimum the possibility of a tube being broken. Prior to application of the insulating coating 3-2, a terminal conductor 35 is electrically connected with the metallic coatings 30 at a point preferably midway the ends of the tubes 3'. This terminal 35 may consist cf strands of wire suitably interwoven between the tubes i so as to contact with the metallic coating of each tube as shown in Figure 10. This interweaving of the Wire 35 serves as a further reinforcement for the relatively small electrode tubes 71'.

it will be noted that the electrode shown in Figures 9, l0 and 11 does not difi'er to any great extent from the form shown in Figure 2 aside from the omission of the casing i0 permitting use of liquids, plastic and gaseous forms of conductors in connection with the bundled arrangement of small electrode tubes. In each form of electrode, the basic idea is retained; i. e., the provision of an electrode having a very large external surface area when compared with the overall dimensions of the electrode.

By our invention, the capacity of the condenser electrodes is notonly increased much beyond the prior art practices, but the electrodes are'also changed as to form and adaptability to various commercial uses.

When the electrode capacity is equivalent to that given by to feet of 25 mm. thin-walled glass tubing, electrical surges and flickering in the tube begin to be of importance and, as electrode capacities increase, it becomes essential to change the inductance of the circuit to an extent not heretofore known in the prior art of luminous tubes. When, however, sufilcient inductance is provided, a luminous tube of satisfactory brilliance and steadiness is attained. For example, in tests with one of our lamps, with forty feet of light tube, 10 mm. in diameter, with an impressed voltage of 15,000 volts, and with the adjustment of inductance properly made, and each electrode having one hundred feet of 25 mm. tubing, approximately 350 milliamperes of cur-- rent flows. 'Under these conditions, the intensity of illumination emitted by one foot of the light tube, at a distance of one foot, is sixteen foot being 5 mm. in diameter and about 27 inches long, each electrode having an area of approximately 18,000 sq. cm. From this example,v the large ratio between the area of our large capacity electrodes as compared with its volume will be evident.

It will be understood that, since nothing is in contact with the gas to be ionized except the glass walls, our tubes have an indefinitely long life.

Changes in the shape, size and arrangement of parts may be made to the form of invention herein shown and described, without departing from the spirit of the invention or the scope of the following claims.

We claim:

1. A luminous ionic discharge tube having a compact dielectric electrode for illuminating the gas in the tube, said electrode comprising a plurality of closely spaced small electrode tubes of dielectric material, each electrode tube being closed at one end and having its other end connected to the luminous tube, and a conducting material surrounding and contacting with the whole exterior of each of said electrode tubes, the material around any one tube being of a solid nature and being in contact with the material around adjacent tubes, whereby each tube is supported by adjacent tubes.

2. A. luminous ionic discharge tube having a dielectric electrode for illuminating the gas in the tube, said electrode comprising a plurality of electrode tubes of dielectric material, each electrode tube being closed at one end and having its other end connected to the luminous tube, the electrode tubes being arranged in a group side by side, a container surrounding the group, a plastic conducting material in the container and covering at least the sealed ends of the tubes in the group to support the same, substantially the remainder of the container also being filled with conducting material.

3. A luminous ionic discha ge tube having a dielectric electrode for illuminating the gas in the tube, said electrode comprising a plurality of electrode tubes of dielectric material with the interior of each of the electrode tubes in communication with the interior of the luminous tube, conducting material contacting with the exterior of each electrode tube and a casing in which said electrode tubes and conducting material are located, said conducting material being in contact with the inside surface of said casing and being supported thereby.

JOSEPH E. HENDERSON. BROUSSAIS C. BECK.

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