US 2145196 A
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Description (OCR text may contain errors)
Jan, 24, 1939. H le 2,145,196
APPARATUS FOR TREATING IFOODSTUFFS Original Filed Nov. 16; 1935 TirTl. TAT-5.3
DURATION INTENSITY inventor attorney Patented Jan. 24, 1939 UNITED "STAT-E Hygrade Sylvania Corporation, Salem, Masa, a corporation of Massachusetts Original application November 1c, 1933, Serial No. 698,265. Divided and this application June 26, 1934, Serial No. 132,431
This-invention relates to methods and apparatus for treating materials by radiation and with particularity to an improved form of sterilizing chamber.
An object of the invention is to provide a sterilizing chamber particularly suited to the housing of foods, food products, etc.
Another object is to provide an improved re,- frigerator having automatically controlled sterilization. v v a A further object is to provide an improved method of subjecting foods, food products, etc., to measured radiation by employing sterilizing radiations of predetermined and repeated duration.
A feature of the invention relates to a housing for foods, food products, etc., having on its interior a source of sterilizing radiations together with means for enhancing the sterilizing action of said radiations.
Another feature relates to a refrigerator having an interior source of radiations which is rendered automaticaly eifective for a predetermined duration each time a door or similar member is opened or closed.
A further feature relates to a refrigerator or similar-device having its interior surface, or at least a suitable portion thereof,. provided with a specially designed coating for eificiently difiusing and/or reflecting sterilizing radiations such as ultra-violet rays or the like.
A further feature relates to the organization, arrangement and relative location of parts which go to make up a relatively simple and economical sterilizing refrigerator or similar device.
Other features and advantages not specifically enumerated will be apparent after a consideration of the following descriptions and the appended claims.
While the invention will be disclosed herein as embodied in particular. form of apparatus, it will be understood this is done merely for the purpose of explaining the invention. While, therefore, the drawing shows schematically a refrigerator embodying the invention, it will be apparent that the broad inventive concept can be embodied in other types of devices without departing fromthe spirit and scope of the invention.
Accordingly, in the drawing'Fig. l is a perspective view of a refrigerator embodying features ofthe invention;
(Cl. 6H9) relation between intensity and duration of the sterilizing rays;
Fig. 4 is a schematic diagram of one form of timing arrangement;and
Fig. 5 is a. schematic circuit diagram of an alternative timing arrangement for controlling the radiation lamps according to the invention.
' Referring more particularly to Figs. 1 and 2, the numeral 1 indicates. any suitable enclosure or housing adapted to contain foods, food-stuffs, or similarmaterials which tend to change their taste orchemical' characteristics by reasons of bacteria or'similar organisms. For convenience of description it will be assumed that the device i is a refrigerator of any well known construction. While the drawing shows a refrigerator of theartificial cooling type wherein, the cooling unit 2 is refrigerated by gas, electricity, etc., it will be understood that any other manner of cooling the interior of device I may be employed, for example, by ice, evaporation, or the like. Furthermore, while the drawing shows the refrigerator provided witha single main door or access memher 3, it will be understood that any other form of access member, such as a window or the like, may be provided in addition to the main door 3. Suitably mounted within the food compartment or compartments of the refrigerator are a pair of lamps a, 5, although it will be understood that in this respect the invention is not limited to any particular number or disposition of lamps.- For example, instead of employing two lamps disposed on opposite side walls of the refrigerator, one large lamp may be employed and suitably -mounted-within the compartment so as to radiate uniformly the entire interior of said compartment. It will also be understood that if the refrigerator is provided with separate food compartments, then one or more lamps may be pro--, vided in each compartment. While, therefore, 40 the drawing shows a refrigerator of the single compartment type provided with shelves 6 and I, this is merely for securing simplicity in the drawing. Where a single lamp or pair of lamps is employed as shown in Figs. 1 and 2, it is preferable that the shelves be of open-work construction so as to allow the sterilizing radiations from, the lamps to pass therethrough and thus enabling the lower and upper portions of the compartment to be radiated. If desired, these shelves. a
cient radiation for the entire contents of the compartment.
While the invention is not limited to any particular character of sterilizing radiations, it is preferred to employ radiations in the form of ultra-violet rays between 2500 and 28005. (Angstrom units) wave length, as set forth in copend- 'ing application Serial No. 699,696, filed Nov. 25,
1933. More particularly, the lamps 4, may be designed to generate rays having maximum intensity between 2530 and 2540 A. and with substantially ,negligible radiation above 2800 A. For a detailed description of such narrow-band" source of ultra-violet rays, reference may be had to said application Serial No. 699,696, of which a-- divisional application Ser. No. 732,430, was filed June 26, 1934.
If desired, the lamps l and 5 may be of the indirect illumination type, that is, with their bowl portions provided with a coating which is capable of efliciently reflecting the ultra-violet rays.
; Thusthe inner surface of the bowl portion of each lamp may be provided with a reflecting coating of aluminum in the manner disclosed in application'serial No. 623,504. I
I have found that the paints or enamels ordinarily employed on the interior of refrigerators are not suitable for conserving or efficiently reflecting ultra-violet rays, and this is probably caused by the fact that ordinary paints or enamels as used in refrigerators absorb a very considerable per cent. of the ultra-violet rays which are useful for bactericidal .purposes. ,I have found that if the interior of the refrigerator compartment or compartments is provided with a coating which is capable of reflecting to a considerable extent these bactericidal ultra-violet rays, the sterilizing action is improved and it is possible to employ lamps of smaller wattage. Entirely apart from the improved sterilizing action, therefore, the use of lower wattage lamps for the desired sterilizing action, enables less power to be used in maintaining the temperature of the compartment at a desired value. Thus, as indicated in the drawing, the major portion of the interior of the refrigerator compartment as well as the inner face of the door 3, is provided with a coating of aluminum or other similar material capable of efliciently reflecting the bactericidal rays.
This coating may be applied in any well known manner as by spraying, by the Schoop process, or even by painting andbaking. Preferably also, the coating is of diffusely reflecting character so as to reflect the rays as uniformly as possible 1 throughout the entire interior of the compartment.
Aspointed out above, one of the most serious drawbacks to the utilization of devices such as" ultra-violet lamps on the interior ofrasrefrigerm tor is that such lamps generate a co siderable amount of heat, thus reducing the ru ng efliciency of the refrigerator. It is highy'desirable, therefore, to employ ultra-violet lamps with as low a wattage as possible consistent with the desired bactericidal action. However, the problem is further complicated by the fact that there is a certain minimum intensity and a certain minimum time below which there is very little effective sterilization. I. have found that sterilization by ultra-violet rays of the'character set forth herein is normally governed by photochemical lainps; that is, the: total amount of sterilization is directly proportional to intensity andalso to duration, so that for a given degree of sterilization, one-half as much sterilizing. intensity is required if the duration is double, and vice-versa. However, while this relation is true for a relatively wide range of intensities, at the vlow intensities there is a threshold value below which the relation does not hold, as indicated by Fig. 3, wherein the point P represents this threshold intensity. If, therefore, the lamps 4 and 5 are designed to generate only a low intensity in the neighborhood of this threshold value, there will be considerable chance of the sterilization being ineffective or at least non-uniform. Instead, therefore, of employing low wattage lamps operating for a proportionately long time, I have found that reliable and uniform, sterilization can be achieved without undue heat generation by employing relatively high intensity lamps which are allowed to operate intermittently for predetermined fixed intervals, preferably every time the door or other access member is opened and closed. Since low intensity lamps require a relatively long time to achieve satisfactory sterilization, it is entirely possible that foods may be.
inserted and withdrawn from the compartment before the necessary sterilizing'action has taken place.
This and other disadvantages are overcome by employing sources which produce intensities of bactericidal rays well above the threshold intensity, and which are allowed to operate for a proportionately shorter duration each time the door-or other access chamber is closed after the insertion of food material or the like into the compartment.
By employing a narrow-band ultra-violet lamp of the type disclosed in said application Serial No. 699,696, the greater part of the electrical energy impressed upon the lamp is transformed into useful bactericidal flux, whereas with ordinary ultraviolet lamps of the broad-band type, a great deal of energy is expended in producing ultraviolet and other rays which are useless for bactericidal purposes and are even detrimental to the taste of the food, as disclosed in said application Serial No. 699,696. By employing relatively.
high intensity ultra-violet lamps which are designed to produce a relatively narrow band of light wavelengths, e. g., 2500 to 2800 A. and by operating these lamps for predetermined fixed and limited durations each time the door or other it will be seen that there is mounted within the refrigerator a timing control device indicated generally by the numeral 8. Slidably mounted in a wall of thedevice 8 is an arm 9 which carries at its inner end a one-way rack which is normally held in its forward position by spring II. The device is so positioned within the refrigerator that just as the defer 3 closes it engages the arm 9- and moves "It against the action of spring ll.
Rack ID in sliding, engages the associated ratchet wheel which winds up spring I2. Spring I2 in turn rotates the commutator l3 which is 'controlled by a timing escapement (not shown). When the refrigerator door is open the disc I3 brush I4 is out of contact with the metal segment I 15. When, however, the spring I2 is wound up due to rod 9 being engaged by the door as above described, the disc I3 is rotated completing the circuit from mains l6 and l t the lamps 4 and 5. Under control of the escapemerrt (not shown), the disc 13 rotates in the reverse ection and after apredetermined time interv the brush disengages segment l and thus breaks the lamp circuit. If desired, the escapement, may be adjustably variable so as to vary the period of illum-. ination of the lamps as desired. Thereis thus provided anarrangement whereby when the refrigerator door is open and then closed," the timing mechanism is set into operation to maintain the ultra-violet lamps lighted for a prede termined fixed interval. It will'be understood of course that instead of providing a single semi-. circular segment Hi, this segment may be replaced by a series of separate segments so as to repeat the illumination of thelamps at predetermined spaced intervals while the disc I3 is rotat- Instead of employing an escapement which is wound up by a rack and pinion, an ordinary e1ec'-' -mounted on the framework of the refrigerator.
When the door is open the circuits to the relays 2d and 25 are broken. When relay 25 is normal, the lamps t and 5 are disconnected from the mains 26 and 2?. As soon as the door 3 closes,
a circuit is completed from main 26, through the lowercontacts of relay 24, winding of relay 25, contacts 2!, i8, 20, to the main .21. Relay 25 immediately operates and causes lamps 4 and 5 to light. Relay 25 is preferably of the fast-tooperate slow-to-release type and may take the form of a dashpot relay, a thermostat relay, or the like. As soon as relay 25 operates, it completes through its lower contacts an operating circuit for relay 26, which upon operating, be-
comes looked under control of contacts 23, i9 and 22. When relay 2 operates it breaks'the-circuit for relay 25 which begins t release. After a definite time interval relay 25 completely restores 'to normal and breaks the circuit to the lamps which stay dark thereafter until the door is again opened and closed to repeat the. foregoing cycle of operations.
While specifloapparatus and circuits are disclosed herein, it will be understood that the invention is not limited thereto and that various changes and modifications may be made therein without departing from the spirit and scope of the invention. For example, while the drawing shows lamps 4 and 5 of the spherical bulb type,
any other shape of.lamp may be employed, for example, as disclosed in copending application Serial No. 699,696, and as illustratedschernatically in Fig. 6, which represents in half scale size a lamp that has'been found to produce the desired results. Thislamp comprises in general a tubular body 28 whichis evacuated and provided with a I filling of an inert gas such as neon at approximately 8 millimeters pressure, or with helium at approximately 12 millimeters pressure, or a suitable mixture of these gases; The tube 28 is-preferably made of material capable of transmittingrays in the band between2500 Land 2650 A. For example, this tube may be made of Corex tubingand preferably the center section 29 has a very thin wall section, preferably less than one- ,half, mm. in thickness. The electrodes 30 and 3| are preferably in the form of molybdenum coils which-are sealed into and supported at the ends of the tubes in any well-known manner. The partciular lamp shown is designed to operate at an impressed voltage of 220 v. A. C. and with a current of 12.5 'milliamperes flowing therethrough.
This is' a division of application Serial No.
698,265, filed November 16, 1933.
An application Serial No.' 243,574," has been filed December 2, 1938, as in part a continuation of the present application.
What I claim is:
1. In combination, a compartment for foods which tend to change their taste when subjected to general ultraviolet irradiation, means for refrigerating saidcompartment, a source of ultraviolet light for irradiating the contents of said compartment with radiation whose maximum intensity is at wavelengths between 2530 and 2540 Angstrom units, said radiation being substantially free'from wavelengths above 2800 Angstrom with a reflecting shield to providedndirect illumination within the compartment, and a coating,- on eaohinterior wall of the compartment, in'-- *cluding the top and bottom, of a material which 'light, and a reflecting coating over the interior surface of the compartment to insure their-,
radiation of both sides of said shelf by reflected ultraviolet light from said source.
3. In combination, a refrigerating compart ment having a diffusely reflecting coating of aluminum on each of its interior walls including the top and bottom, a source of ultraviolet light confined to the band 2500 to 2650 Angstrom units within said compartment, and a shield to prevent the irradiation of the interior of the compartment by the direct light from the lamp, said shield being symmetrically disposed with respect to said lamp, said shield being spaced from, and separate fr m, the boating on the walls of the cornpartment.
units, said source of radiation being arranged.
' 4. The combination of claim 2 in which the T shelf is of solid material transparent to ultraviolet light. r
5. In combination, a compartment for foods, a
door for said compartment, a source" of ultra-f violet light confined to the wavelength band 2500 to 2650 Angstrom units, arranged to irradiate said compartment, means actuated by the closing of said door to energize said ultraviolet source, means actuatedby said first-mentioned means to extinguish said'ultraviolet source after a predetermined interval, means to refrigerate said compartment, a shelf transparent to said radiation and within said compartment, a shield to prevent the 6. The combination of claim 5 in which the predirect irradiation of said shell by the source of determined interval is suflicient for complete ultraviolet light, and a reflecting coating over the surface sterilization of the food in the compartinterior surface of the compartment to insure the ment.
5 irradiation of both sides of said shelf by reflected ORRICK HOWARD BIGGS. 5 ultraviolet light from said source.