US 2532463 A
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R. w. SAMER 2,532,463
TEMPERATURE CALIBRATED METAL VAPOR DISCHARGE LAMP Dec. 5, 1950 3 Sheets-S'neet 1 Filed March 23, 1949 IN VEN TOR.
RUDOL W. SAMER OQNEY TEMPERATURE CALIBRATED METAL VAPOR DISCHARGE LAMP Filed March 23, 1949 R. W. SAMER Dec. 5, 1950 5 Sheets-Sheet 2 RUDOLF w. SAMER 8% A TTO/?NEY R. w. SAMER 2,532,463
TEMPERATURE CALIBRATED METAL VAPOR DISCHARG LAMP Dec. 5, 1950 3 Sheets-Sheet 3 Filed March 23, 1949 f lr lll INVENTOR. RUDOLF W. SAMER TTOQNEY Patented Dec. 5, 1950 UNITED STATES PATENT OFFICE TEMPERATURE CALIBRATED METAL VAPOR DISCHARGE LAMP Rudolf W. Samer, Elizabeth, N. J., assignor to Hanovia Chemical and Manufacturing Company, Newark, N. J., a corporaticn of New Jersey Application March 23, 1949, Serial No. 83,004
1 4 Claims.
The present invention deals with a metal vapor discharge lamp and more particularly with a temperature calibrated metal vapor discharge larnp.
The intensity of radiation obtained from a metal vapor discherge lamp is dependent, among other factors, upon the temperature at which the larnp is operated. Ordinarily, for operation in some medium, such as air or a liquid, metal vapor discharge lamps are designed to give a peak output at a specific ambient temperature. Where it is desirecl to keep the lamp output substantially constant, for example in regard to photochemical reactions or bactericidal effects, even while operation in ambient temperatures which differ appreeiahly from the temperature for which the lamp was designed, the lamp is usually provided with a heat insulating means which may he in the form of a light transrnissive jacket having appropriate light transmission characteristics. such a jacket, however, absorbs some of the available light output of the lamp, for instance as much as approximately sixty percent (50%) of the ultraviolet radiations and twenty percent (20%) of the visible radiatiohs may be ahsorhed. Maintaining a peak intensity of radiation by such known means is disadvantageous nct only because oi the loss of output efliciency but also in view of the limited heat insulation possible under changing temperatures. For example, although a heat insulating means is advantageous to the extent that it enables a lamp to operate under a greater ambient temperature range, the mere addition of the jacket introduces a less of about twenty percent (20%) and more of the radiation due to absorption by the jacket, hence, with a constant power input the available radiation can not exceed about eighty peroent (89%) of the cptiznum value for the unjacketed lamp.
It is an object of this invention to provide a metal vapor discharge lamp adapted to give suhstantially uniforin peak intensity under Various ambient temperature& It is another object of this invention to provide a metal vapor discharge larnp adjustable to temperature changes. It is a further object of this invention to provide metal vapor discharge lanp which can he adjusted at will or automatically to give the same pearl: intensity at constant power input for any selected ambient temperature within a specified range of temperatures. Other objects and ad vantages oi the present invention Will be apparent from the following description and the accompanying drawings in which:
Figure 1 schematically illustrates one View of a metal vapor discharge lamp in bi-laterally symmetrical aspect,
Figure 2 schematically illustrates another view of a metal vapor discharge lamp taken at right angles to Figure 1,
Figure 3 graphically illustrates a section of a temperature calibrated metal vapor discharge lamp,
Figure 4 schematically illustrates another ernhodiment of the present invention,
Figure 5 illustrates a front view of the apparatus of the invention, and
Figure 6 illustrates a cross-sectional view of the apparatus of the invention.
The present invention provides an efcient metal vapor diseharge lamp for use, for example, as a germicidal lamp in refrigerators, particularly of the type known as show case or reach-in." In such refrigerators, the frequently handled contents are subject to bacterial infection and bactericidal lamps have been resorted to in order to prevent contamination. I have provided a hactericidal metal vapor discharge lamp which is superior to bactericidal lamps heretofore known in that the intensity of radiation remains at its peak or optimum value regardless of temperature changes. Thus, in cases where a lowering of the temperature in a refrigerator would ordinarly so affect the operation of a conventional lamp that its bactericidal efiiciency is substantially reduced, the larnp of the present invention maintains the desiresi optimun ultraviolet radiation and, consequently, a coinparatively high bactericidal efcieney.
According to Figure 1, the lamp oi the present invention comprises essentially a glass envelope i of suitable transmission characteristics provided With an evacuation and filling tube 2 through which appropriate gases, e. g. argon or neon, and a low melting point vaporizable metal 3, e. g. mercury, may be admitted. The four lead-in wires serve as supports for two electrodes 5, for example, coil coiled tungsten activated with alkaline earth metals or oxides or other suitable activation material, in such a mauner that each pair of lead-in wires on either side of the filling tube form a continuous and independent electrical circuit through the electrodes in their respective sides of the envelope, as more particularly illustrated in Figure 2.
The lamp is operated With the dome-shaped end in a lower position than the end containing the lead-in wires. Thus, if the lamp axis LL is maintained vertical, the mercury 3 will roll to in space located in the plane of the electrodes and half way between the centers of the electrodes. The true position of A in an actual lamp is dependent upon the individual design, geom etry and physical and Chemical properties off 'the Component parts. For example, a lamp may be constructed to have one or more electrodes ;of suitable form depending upon whether 'thelamp is a high or low pressure lamp and point A may be established in accordance therewith.
For illustrative purposes with :respect to the position of A as shown in Figure 2, the distance AB corresponds to the proper spacing that is necessary for optimum output of the desired radiation when the lamp is operated in a medium, such as air, at an ambient temp rature corresponding to the upper limit of the calibration range for the lamp. Similarly, the distance AC corresponds to the proper spacing that is necessary for optimum output of the same radiation when the lamp is ,operated in the same medium at an ambient temperature corresponding to the lower limit of the calibration range for the lamp.
Figure 3 illustrates a graphic representation of a section of a calibrated metal vapor `discharge lamp as drawn to scale from ,an actual lamp. In ,this particular calibration, the temperature range is from 36 F. to 70 F. and point A is located in space halfway 'between the Centers of two coil diseharge areas of which one such discharge area is shown. Both discharge ,areas and point A are in the same plane and the discharge areas are so located that ,they are in the same relative position With regard to their individual coils. The lower 'limit of the calibration range, e. g. 30 F., 'is so located with respect to th arc portion of the glass envelope that ,it is nearest to 'point A ,while the upper limit of the calibration range,
e. g 70 F., is farthest from point A. The spacing ;between point A and a point on the glass envelope is determined by the proper spacing that is necessary for optimum output of the same radiation over .the calibrated temperature range. The temperature points on the glassenvelope, although the distanees from point A to ,the temperature points ,are critical, may be separated from each other by a distance depending upon the shap and size of the bottom or arced .por tion of the glass envelope.
With the axis LL vertical, as shown in Figures 1 and2, .and the lamp Operating in a medium at an ambient ,temperatur corresponding to the up r temperature calibration limit, the rate of evaporation of the vaporizab-le metal, for example mercury, is just snoient to maintain the ,lamp wall at optimum Operating temperature'due to the heat transfer to the envelope wall by the mercury vapor as it condenses on the wall and rolls ,back down to the lowest point in the lamp. However, ii th ambient temperature outside the lamp i lowered, then the temperature difierential ,between the envelope and the outside surrounding medium is increased and, as a result, the rate of heat transfer away from the envelope to the outside surrounding medium is increased and the envelope temperature will be lowered unt-il a new condition of equilibrium exists where the rate of heat transfer away from the envelope equals the rate of heat transfer to the envelope.
This corresponding lower envelope temperature is now lower than the optimum temperature for the production of the desired radiation, and in conventional lamps the efiiciency drops In the lamp of the present invention, the shape of the envelope is such that as 'the lamp aXis LL is tilted away from the vertical, the liquid metal, e. g.
mercury, rolls along the envelope wall from point `B towards point C, hence, the distance between the 'mercury 'drop and point A becomes progressively shorter. In this manner, the rate of evap- Qration of mercury isregulated and, consequently, 'the .rate of heat transfer to the envelope wall increases. If theilamp is tilted to the proper angle, the mercury drop .will come to rest at such point where its increased or regulated rate of evaporation and the -consequent increased rate of heat transfer to the envelope Will just compensate for the increased rate of heat transfer away from the envelope occasioned ,by the aforementioned drop in ambient temperature, and the net result is that 'the lamp will, with a constant .power input, continue Operating with'the optimum envelope temperatureand optimum output of the desired radiation .at any ambient temperature within a specified range of 'temperatures The lamp 'may be fitted with a standard four prong base. Thus, it `can be plugged into a standardzfourprong tube socket.
Temperature caiibration may be achieved, among other methods, by mounting th lamp in a holding device which will permit angular displacenent of the lamp axis LL relative to some arbitrarily chosen fixed reference place in the holding device or to the earths surface. The amount of .dispiacement is measnred by the relative motion between an index or pointer and a numbered scale, .one of which is fixed in .position while the other moves with the lamp axis 'the displacement of which may correspond to the positions of Li, L2, LB, ,LG or L5 of Figure '3. The scale may be marked directly in terms of temperature.
Figure 4 illustrates another embodiment of the present invention with respect to a preferred type of envelope Construction.
With reference to Figures 1 and .2, although the glass envelope may be adequate it has the disadvantage that over a prolonged period of time the condensed mercury vapor may become partially permanently deposited along the envelope wall farthest removed from the lamp filaments. The Construction of the envelope of Figure 4 is such that a substantially large portion of the glass envelope is domashaped and lies below the electrodes and is suitable for calibration according to the invention, while the portion of the envelope wall above the filaments is substantially near the filaments and shaped to ,allow free flow of the condensed mercnry vapor to the lower portion of the glass envelope. In this case, even though impcrfections in the smcothness of the glass envelope may act to retard the flow of the condensed mercury vapor to the lower portion of the envelope, the heat 'from the filaments acts to 'limit undesired condensation of mercury above the electrodes and thereby insures a proper amount of vaporizable metal for the efcient operation of the lamp. To further insure the availability of a proper amount of vaporizable metal when the rate of vaporization is substantially high, an excess of vaporizable metal is always present in an amount sunicient for eicient operation of the lamp so that at all times there is at least some metal in un- Vaporized form.
Figures 5 and 6 illustrate the complete apparatus of the invention With emphasis on the automatic tilting mechanism for the temperature calibrated metal vapor discharge lamp.
In Figure 6, the protective housing 6 has mounted therein a thermal spring l wound in the shape of a spiral as shown in Figure 5. The outside end of the spiral is anchored around an anchor pin 8 and the inside of the spiral is rigidly held in the slot 9 of the pivot shaft la. Spring clips l l prevent lateral displacement of the pivot shaft along its aXis. The lamp bracket !2 is firmly attached to the pivot shaft so that the lamp bracket and pivot shaft revolve as one unit.
The principle of operation of this mechanism is based on the fact that the thermal spring will Wind itself tghter as it is heated, and Will unwind as it is cooled. This is the case when the thermal spring consists of a bimetallic strip having the metal of greater coefficient of expansion on the outside. If the spring were coiled with the metal of greater coefficient of expansion on the inside, the spring would wind tighter upon cooling. Either type of spring may be used provided due consideration is given to the position of the lamp and to the calibration of the unit.
Since the outer end of the spring is held in place by the anchor pin 8, the expansion and contraction of the spring due to temperature change is translated into rotary motion and is imparted as such to the pivot shaft se.
The unit is properly calibrated when the spring imparts the proper angular displacement to the pivot shaft as is required by the lamp for optimum output of the desired radiation at any ambient temperature within the calibration range of the lamp. Calibration may be accomplished by control of the thermal properties of the spring in regard to its metallic composition and by the dimensions and position of the bimetallic strip, e. g. diameter, spacing, number of turns, and initial orientation relative to the lamp axis.
Figures 5 and 6 are not intended as detailed designs, but merely represent schematic illustrations showing one mode of operation of the apparatus by automatic control. The apparatus may have manually controlled tilting means so that when the ambient temperature of the medium in which the lamp operates is below a designated temperature range, the lamp may be manually tilted to correspond to the readings of a thermometer.
The invention is not limited to the specific illustrations and description herein set forth, but may be construed to include various Operating means and functions within the true scope of the invention.
What I claim is:
l. A metal vapor discharge lamp for maintaining substantially uniform intensity under changing ambient temperatures, comprising a light transmissive glass envelope containing at least a normally liquid vaporizable metal and a pair of spaced electrodes, said envelope having an inverted dome-shaped portion, the inner surface of said dome-shaped portion being concave, said electrodes being spaced from said inner surface so that the distance from a point between said electrodes to a location at the vertex of said concave inner surface is greater than any other distance from said point to any other location on said concave inner surface, a rotatable mounting means for said lamp, said rotatable mounting means having a rotational axis perpendicular to a vertical line from said point to a location on the said inner surface of said dome-shaped portion, said metal being clisplaceable along the said inner surface upon rotation of said mounting and the distance between said point and said metal being thereby changeable for regulating the rate of vaporization of said metal to maintain substantially uniiorm intensity.
2. A metal vapor discharge lamp for maintaining substantially uniform intensity under changing ambient temperatures, comprising a light transmissive glass envelope containing at least a normally liquid vaporizable metal and a pair of spaced electrodes, said envelope having an inverted dome-shaped portion, the inner surface of said dome-shaped portion being concave, said electrocles being spaced from said inner surface so that the distance from a point between said electrodes to a location at the vertex of said concave inner surface is greater than any other distance from said point to any other loca tion on said concave inner surface, said locations on said inner surface being temperature calibrated locations, a rotatable mounting means for said lamp, said rotatable mounting means having a rotational axis perpendicular to a vertical line from said point to a location on the said inner surface of said done-shaped portion, said metal being displaceable along said calibrated inner surface upon rotation of said mounting and the distance between said point and said metal being thereby changeable for regulating the rate of vaporization of said metal to maintain substantially uniform intensity under changing ambient temperatures.
3. A metal vapor discharge lamp according to claim 1 wherein said vaporizable metal is mercury.
4. A metal vapor discharge lamp according to claim 1, comprising means for automatically rotating said rotatable mounting in accordance with changing ambient temperatures, said auto matic means comprising a temperature sensitive bimetallic thermal spring connected to a pivot shaft having an axis corresponding to said rotational axis.
RUDOLF W. SAMER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS' Number Name Date 950,'709 Thomas Mar. 1, 1910 10063166 Ludwig July 2, 1935 2,110,603 Knowles Mar. 8, 1938 2,326346 Foote Aug. 10, 1943