US3337714A

US3337714A - Heating device

Info

Publication number: US3337714A
Application number: US342197A
Authority: US
Inventors: Werner W Buechner
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-02-03
Filing date: 1964-02-03
Publication date: 1967-08-22
Anticipated expiration: 1984-08-22

Description

" 22,1967 w. w; BUECHNER I 3,337,714

HEATING DEVICE Fil ed Feb. 5-, 1964 N82 ans United States Patent 3,337,714 HEATING DEVICE Werner W. Buechner, 4407 Cladding Court, Midland, Mich. 48640 Filed Feb. 3, 1964, Ser. No. 342,197 9 Claims. (Cl. 219331) This application is a continuation-in-part of my copending applications Ser. No. 23,313, filed Apr. 19, 1960, now Patent No. 3,124,051, and Ser. No. 52,524, filed Aug. 29, 1960, now Patent No. 3,236,649.

This invention relates to a method and apparatus for producing a stream of temperature conditioned water, and more particularly, to a process and apparatus for the provision of a flowing temperature conditioned medium, to be used in photographic treating processes and in photographic treating apparatus.

Most photographic treating processes, and particularly the photographic developing methods used in the production of actual images from latent images, contained on photographic materials, require some kind of temperature control of the treating media, if it is desired to obtain predictable or reproducible results. Temperature control is of paramount importance in the development and other treatment of the multilayer photographic color materials. Most of the complex multistep color processes, such as those used for the development of color negative films, color reversal films, and the processes used for the production of color positive paper prints or positive transparencies from negative or positive originals require extremely close temperature control, particularly in the first developing step. Usually, absolute temperature constancy within /2" F. is desirable for best results. Depending on the nature and origin of the material, temperature control within 1 to 2 F. is desirable in most of the succeeding steps. Various methods and devices are commercially available which permit the control of the temperature in the said photographic treating process within the stated limits.

However, most of the available apparatus and devices are, because of their high price or because of the nonavailability of suitable water supplies and other reasons not accessible to the amateur who intends to produce occasionally a few color prints or who intends to develop occasionally one or a few color films. The relatively high initial cost of the commercially available automatic mixing devices, their dependency on a source of running cold and hot water and the time consuming initial adjustment of the desired temperature by trial and error show the existence of a need for a method and apparatus which provides a stream of running water of a predetermined, essentially constant temperature which method is simple to practice also by the inexperienced photographic amateur with apparatus and devices which are inexpensive and readily available.

It is therefore the primary object of the present invention to provide a process which produces a stream of water of a predetermined constant temperature, requiring merely a source of running cold water and a source of electricity.

Another object of the invention is the provision of inexpensive apparatus and device capable of providing a stream of water having a predetermined constant temperature.

Additional objects of the invention will become apparent from the accompanying drawings and from the following description of the invention. The objects of the invention are accomplished by a method which comprises the steps of contacting a stream of essentially constant flow rate of a liquid medium, having an essentially constant temperature lower than said desired constant temperature with at least one heating means and controlling the heat output of said heating means such that the heat supplied to said stream of liquid medium essentially equals the heat energy required for continuously heating said streaming liquid medium to the said desired higher temperature.

The liquid medium preferred in the process of the invention is water from a supply which delivers a stream of Water of an essentially constant temperature which temperature is lower than the desired temperature. The heating means employed in the process of the invention are preferably electric heaters and most advantageously electric iI nmersion heaters which are completely or at least with their heated parts immersed in the flowing stream of heating medium. Though the process may be practiced with a single heater having the required heating capacity, it was found to be of great advantage if a multiplicity of heaters is employed, which may be individually energized or deenergized as is needed. For more accurate control, at least one of the heaters should be provided with means which permit the variation of the power input in a wide range and preferably in a range from zero input to the full rated input. If desired, a thermostatic control means may be used as the means for the variation of the power input or more than one heater may be provided with means permitting control of the power input and/or with thermostatic control means.

A stream of liquid medium of essentially constant flow rate may be conveniently produced in accordance with the present invention by flowing the liquid medium through an orifice at an essentially constant hydrostatic pressure. The preferred process of providing a stream of liquid medium of an essentially constant flow rate comprises the steps of maintaining a column of liquid medium of a predetermined, essentially constant height over an orifice through which the metered liquid medium flows. Conveniently, the column of essentially constant height is provided by flowing liquid medium to said column at a rate which exceeds the rate at which the liquid medium emanates from said orifice and disregarding the excess of liquid medium overflowing at the top of the column. If desired, other means may be used for the maintenance of an essentially constant hydrostatic pressure at said orifice.

The invention comprises also a device which comprises essentially a heating chamber, means for the provision of a stream of a liquid medium, means adapted to pass said stream of liquid medium through said heating chamber and heating means provided in said heating chamber and adapted to supply the heat energy required for heating said stream of liquid medium to a predetermined higher, essentially constant temperature. The heating chamber is preferably a receptacle, having an inlet and outlet, located such that the liquid medium passes preferably in a vertical or in an essentially vertical direction through said receptacle. If desired, the heating chamber may be comprised of a multiplicity of cells for the containment of the multiplicity of heating elements. Additional means for mixing the heated liquid medium or for equalizing the flow of the heated liquid medium are with advantage provided in the heating chamber or in the conduit for the heated liquid medium.

The present invention concerns also a device adapted to supply a continuously flowing stream of liquid medium of essentially constant flow rate which device comprises a receptacle or conduit having an inlet, an outlet comprised of an orifice of predetermined aperture size in a low position in said receptacle and overflow means at a position essentially higher than said outlet. The said receptacle is preferably oblong and advantageously vertically oriented and the said inlet is desirably located at a position away from said outlet, so that turbulence or eddying motion of the streaming liquid medium above the said outlet is re- C9 duced to a minimum. If desired, bafiles or other means capable of reducing turbulence or eddying motion in the liquid medium flowing in said receptacle are provided in said receptacle.

The process and the apparatus and device of the invention are particularly useful for the maintenance of an essentially constant temperature in photographic treating apparatus and particularly in a photographic bath containing at least one treating and/ or wash vessel, in which the temperature conditioned liquid medium may advantageously serve also as the washing medium. Any part of the apparatus and device may be integrated with such photographic treating apparatus. For most effective operation of the process, the streaming temperature conditioned liquid medium is flown in the said photographic treating apparatus in an essentially vertical flow pattern and preferably in such manner that it flows by the walls of said treating vessels and, if applicable, through said wash vessel in an essentially vertical direction.

Further embodiments and modifications of the process, device and apparatus of the present invention are described in my Patent No. 3,124,051 and in the following detailed description and in the accompanying drawings, wherein:

FIG. 1 is an isometric water metering device.

FIG. 2 is a vertical section of an embodiment of a heating chamber taken along line 1212 of FIG. 3,

FIG. 3 is a horizontal section of the heating chamber taken along line 13-13 of FIG. 2, and

FIG. 4 is a schematic representation of a variable transformer modified in accordance with the present invention.

The novel process and apparatus of the present invention may be widely used in combination with photographic liquid treatments, and especially with the development of photographic positive and negative film and sheet materials such as films, reversal films and paper base materials. The process and apparatus of the present invention are especially useful and beneficial if they are used in combination with the more recently introduced multistep photographic developing and treating processes available for the processing of color positive and negative multilayer color film and sheet material. My invention includes many modes of operation and many modifications of the process and apparatus which make it particularly suited for application in combination with the said multistep color developing processes.

Prefatory to a detailed description of the process and apparatus of the invention some of the more important terms used herein will be explained in order to provide a better understanding of the nature of the invention and of its scope.

The term essentially constant temperature as used herein is meant to designate a narrow temperature range falling around a desired or predetermined constant temperature. Depending on the particular use to which the temperature conditioned liquid medium provided by the process and apparatus of the invention is put, the permitted deviation from the desired temperature may vary to a difi'ferent degree. For some uses variations of F. are acceptable. For other uses the variation should not exceed :2 F. For most exacting uses, such as in color developing processes, the variation of the temperature should not exceed :1 F. and preferably be not more than /2 F. Variations of the temperature from the desired or predetermined value by the just described values fall under the term essentially constant temperature.

Temporary variations, exceeding these limits are not critical and are permissible, provided they are for short periods of time only in relation to the total time of operation, because a streaming medium is used a the temperature conditioning medium in accordance with the invention. The medium travels rapidly through the receptacle view of an embodiment of the or other containers where it is used as the temperature conditioning medium so that constantly new portions of medium contact the photographic vessel or other containers in which the temperature is to be kept essentially constant.

The phrase essentially constant flow rate refers to a flow rate which does beneficially not vary more than :10 percent from a predetermined value over longer periods of time. Preferably, the flow rate does not vary by more than :5 percent and for most exacting uses, it should not vary by more than :3 percent from a predetermined value.

The novel water and temperature control device of the invention operate substantially on the following principles. Water taken from the ground or from the faucet of the conventional water supply lines generally hasafter it has run for a certain length of time and after the water lines and other parts of the supply system, through which the running water passes have taken on the temperature of the running water--a substantially constant temperature, which is usually lower than the processing temperature required for most photographic processes. Many color developing processes are adjusted to be carried out most accurately at a standard 75 F. temperature. Only in extreme cases such as in heat waves in summer will the tap water in some localities have a temperature, which exceeds the recommended processing temperature just mentioned. Thus, generally the addition of heat energy will be necessary to raise the temperature of the water supply to the level of the desired processing temperature. Equal amounts of water of constant temperature require identical amounts of heat energy in order to raise the temperature of the running stream of water to a constant higher temperature. In the practical operation, it is only necessary to measure the temperature of the water supply and determine, by simple calculation, the heat energy required for the desired increase of the temperature of the water passing at a'constant, predetermined rate over the source of heat energy. As long as the three factors, namely temperature of the water supply, amount of water supplied to the heating means per time unit and amount of electrical energy supplied and converted into heat energy are kept constant, the temperature of the water emerging from the heating device will be constant and exactly at the predetermined and desired level.

The principles of this novel process of the invention can be put into practice by help of simple steps and apparatus. The first step in the process comprises opening the water supply line and taking a few readings of the temperature from time to time. As soon as the temperature of the emerging water has reached a constant level, which will normally be the case after about 5 to 15 minutes running time, depending on the local circumstances and on the time of the year, a final reading of the temperature is taken and recorded as Temperature A. Conveniently, the thermometer indicating the temperature of the tap water, is built into the water supply line. By well-known physical principles, the amount of Water flowing by gravity through an orifice of given size is dependent on the hydrostatic pressure of the water at the location or level of the orifice. Conversely, at constant hydrostatic pressure, constant amounts of water per time unit flow out of an orifice of controlled size thus providing a flow of water at constant rate. By the application of this principle, viz. keeping the hydrostatic pressure of a free flowing water supply constant, while the water is flowing through an orifice of a predetermined size, the process of the present invention provides the desired constant flow rate of the water supply. There are several means available which permit the maintenance of a constant hydrostatic pressure directly at the orifice. Generally, applicable for this purpose are the commercially available pressure valves, which by diaphragm and springs or other means provide an even, predetermined water pressure at the orifice regardless of reasonable pressure variations which might occur upstream in the water supply line. However, reliable, accurately operating instruments of this type are rather expensive and may require constant maintenance and service to keep them in top operating condition.

In accordance with my invention a simple device may be used for the control of the rate of flow of the water. In spite of its apparent simplicity the novel device operates trouble-free for long periods of time, requiring only a minimum of care and maintenance.

Various embodiments of this device are shown in FIGS. 19 to 21 of my Patent No. 3,124,051 and are described in said patent. Special reference thereto is made herewith.

Another preferred embodiment of the water metering device is illustrated in FIG. 1 of the accompanying drawings.

The metering device 3100 comprises principally three vertical tubes 3101, 3102 and 3103, running side by side and being mounted on a backrest 3104. Tube 3102 in the center is advantageously made wider than tube 3101 and/ or 3103. Giving it a cross section 4 to 5 times that of tube 3101 was found desirable, :as it reduces turbulence in the flow pattern of the water in tube 3102. The top end of tube 3101 is communicatingly connected to the bottom section of closed funnel-like receptacle 3106, opening 3107 in the top. Receptacle 3106 contains overflow funnel 3109, the narrow bottom section of which is communicatively connected to the top end of tube 3102, which penetrates through the bottom section of receptacle 3106. Tube 3103, which also penetrates the bottom of receptacle 3106 in sealing relationship is extended upwardly and communicatively joined to a side Wall section of overflow funnel 3109. The horizontal edges 3110 at the top end of overflow funnel 3109 serve as overflow passages for the incoming water. The free bottom end 3118 of tube 3103 is bent to a vertical direction and provided with means for communicating connection of tube 3101 to a source of running water such as tap water (not shown).

To the bottom end of the centrally positioned tube 3102 is removably joined orifice 3112, which together with the bottom end of tube 3102 is surrounded and contained by aerated but otherwise closed funnel-like receptacle 3114, with outlet 3115 at the bottom. The lower end 3117 of tube 3101 is bent to the left and provided with means for communicatively connecting tube 3101 to conduit, leading to a sink or other water disposal means. The device is advantageously hung by eye 3116 to a wall or other support, preferably in a generally vertical orienta tion. This mode of support assures at all times essentially vertical orientation of the device, increasing the accuracy and reproducibility at all times. The metering device may however also be attached by the bottom end of the backrest directly to a photographic bath or to any other desired supporting means.

The operation of the device corresponds in many ways to that of the metering devices described hereinbefore. Tube 3103 is connected to a source of running water, which flows upwardly in said tube 3103, entering overflow funnel 3109 and flowing downwardly in tube 3102, leaving it through orifice 3112 and outlet 3115, from where it may be led to a heating chamber or to a photographic 'bath by suitable conduit, as described hereinbefore. By providing the water, entering through tube 3103 at a flow rate exceeding the rate of flow of water through orifice 3112, tube 3102 will soon be filled with water, the excess of which, when it has reached horizontal edges 3110 of overflow funnel 3109, overflows continuously into receptacle 3106, from where the excess water leaves through tube 3101 to flow into a sink or other place of disposal.

The stream of water, emanating from outlet 3115 is accurately metered as described hereinbefore. The accuracy of the device may be readily adjusted to the needs and re- 6 quirements in the particular use for which the device is designed. Increasing the total length of tube 3102 and/ or increasing the size of the horizontal top opening of receptacle 3106 will tend to increase the accuracy of the metering device. It was, however, found that a degree of accuracy, required for the purposes of most photographic processes could be readily achieved with devices, having relatively short tubes 3102. Lengths of tube 3102 of one or two feet have excellent results in most instances, sometimes shorter lengths were found satisfactory. Only rarely will it be necessary to give tube 3102 a length greater than two feet. As is readily ap parent, the just described embodiment of the metering device may be readily made from plastic materials e.g. by extrusion methods and/or injection molding methods or by the use of pre-extr-uded plastic tubing and parts, requiring simple assemblage and low labor cost, thus permitting economical eflicient mass production of the device.

If desired, the water metering device of the invention may be further modified by running the water in two or more stages, i.e. by using metered water as the feed water, including again an excess in a second metering device. This expedient permits sometimes to achieve even greater accuracy. It is important to note, that for highest accuracy of the metering device of the present invention the stream of water, emanating from the orifice, should be permitted to fall freely for at least one inch or so. Placing an obstruction close to or at the orifice will usually affect the accuracy and often reduce the amount of water flowing from the device per unit of time.

As has been shown, the device and process of the invention are operated by the provision of a column of water of substantially constant height over a fixed orifice, through which water flows at a substantially constant rate, which rate is determined by the size of the orifice and by the hydrostatic pressure exerted by the water column of controlled height. It is of advantage to use an orifice which has a relatively large opening e.g. of one or several millimeters up to one centimeter or more and preferably of 2 to 6 mm., depending on the dimension and size of the apparatus. The expedient of using relatively wide orifices will avoid plugging or partial obstruction of the orifice by particles contained in the water supply and carried to the orifice with the streaming water. If a narrow orifice is desired to be used, a filter or sieve of a pore or mesh size, which will hold back particles of appreciable size, may be placed upstream of the orifice e.g. into the inlet tube of the metering device. Thus, the effective size of the orifice may be readily kept constant by avoiding its partial obstruction by foreign matter. Occasional cleaning of the orifice will assist in maintaining the desired effective size accurately. If desired, the socalled self-cleaning type of orifice may be used.

The proper ratio of orifice size to the height of the column or to the hydrostatic pressure, respectively, depends on the amount of water which is desired to be delivered per time unit and on the particular design of apparatus used. Experiments have shown that one liter of water per minute passes through an orifice of approximately 3 to 4 mm. diameter, if it is under the hydrostatic pressure exerted by a Water column of approximately 20 cm. height. Proper orifice size and height of the water column can be readily established by simple tests or by calculation for any desired rate of water flow. The above values will serve as an indication of the relationship of the factors. Doubling the cross sectional areas ofthe orifice, while maintaining the height of the water column constant will approximately double the rate of water flow through the orifice. Depending on the size of the photographic treating apparatus, several hundred cubic centimeters to several liters of water per minute will be suflicient to accomplish the aims of the present invention.

As was shown hereinbefore, the height of the water column is readily maintained at a constant value or level by feeding the water, upstream of the orifice, at a rate exceeding the desired downstream flow and removing the excess water by way of an overflow. Highest accuracy is achieved if the linear extension of the overflow is kept as large as possible under the circumstances. In the practical operation the operator need only observe the overflow and adjust it in such way that it does not cease at the lowest line pressure expected during any operating session. Adjustment and readjustment of the rate of overflow is possible without any adverse effect on the accuracy of the method.

If desired the hydrostatic pressure exerted by the water column may be supplied by a diaphragm-spring arrangement which is adjusted to provide the desired water pressure at the orifice. It may be of a type which permits escape of excessive amounts of water through an overflow venting tube. Other pressure controlling devices may be used with similarly good effect.

By the steps and device described in the foregoing a stream of water of constant rate of flow and of known constant temperature (temperature reading A) emerges from the downstream side of the orifice. In order to raise the temperature of this stream of water to the desired value, e.g. 75 F. it is only necessary to supply the differential in heat energy to the water. The approximate heat energy required per minute may be calculated by multiplying the specific heat of water with the amount of water emerging from the downstream side of the orifice and the number degrees of the temperature differential between the desired working temperature and the measured temperature of the incoming water supply. The heat energy can readily be calculated as its electrical energy equivalent which may be supplied to electrical heating elements and converted to heat energy which in turn is transferred upon the water stream. Usually the electrical energy supplied to the heating element or elements may need to be slightly higher than the values calculated by the equivalency of electrical and heat energy. A constant factor representing the efliciency of the particular heating element and the heat losses inherent in the particular device can readily be determined. The data and corrective factor thus established may form the basis for the determination and calculation of the electrical energy required to bring about the desired temperature change in a given apparatus under reproducible conditions, and can be incorporated in an emperical factor or equation which can be used for all successive operations.

For practical operation of the process it is only necessary to multiply the electrical energy, required for the raising of the temperature of the incoming water by one degree, with the number of degrees represented by the difference of the desired temperature B minus actual measured temperature (temperature A) of the incoming water. Multiplying the electrical energy thus calculated by said empirical factor will directly give the electrical energy requirement for a given apparatus to produce a stream of water of constant temperature regardless of the initial temperature of the incoming water, the only requirement being that the temperature of the incoming water and its flow rate be constant over the duration of the operation. 7

A convenient means of adjusting the electrical energy, fed to the heating elements, to the temperature of the incoming water-this being the only variable in a system in accordance with this embodiment of the present inventionis a continuously variable resistor which may be included in the electrical heating circuit. The resistor may be provided with markings which indicate the correct setting required for each temperature of the incoming water (temperature A). Thus a single setting of the resistor or rheostat to the temperature marking indicating the actual reading of the temperature of the incoming water will automatically provide for the correct temperature of the water leaving the device at the outlet side.

The preferred modification of the apparatus of the in.- vention does not require a high powered resistor or rheostat. The temperature control device in this preferred embodiment of the apparatus comprises primarily a multiplicity of heating elements which are suitably varied with regard to their full heating capacity and consumption of electrical energy. By proper combination and correlation of two or more of the multiple heating elements any desired increase of the temperature of the known amount of water of known constant temperature, passing by the heating elements per time unit, can readily be achieved by switching in or out one or more of the heating elements as needed without the undesirable generation of excessive heat and loss of electrical energy in the rheostat or resistor. Closest control of the temperature of the water stream by simple and inexpensive device and construction is thus possible.

The temperature of the incoming tap water may vary from the approximately 32 to 75 F. or higher depending on the season of the year and the special local conditions. A minimum of six heating elements of various definite capacities are needed to cover the range from 32 to 75 F. in steps of 1 F. Covering this range in steps of 2 P. will require five heating elements of correspondingly spaced capacities. With steps of 5 F. the number of heating elements may be reduced to only three. Economy of construction and simplicity of design make it desirable to employ the smallest possible number of heating elements, if this can be accomplished without sacrificing the desired close control of the temperature of the outgoing stream of water say within i /z F. This accuracy is possible to a very high degree by the provision of three major heating elements with the said 5 F. steps of capacity and of an additional smaller heating element whose capacity covers the gap of 5 F. left by the major heating elements. This additional or adjuvant heating element may be rheostatically or thermostatically controlled as will be shown hereinafter, providing the fine control of the temperature within a 5 F. range.

A temperature control arrangement which may be used with advantage in the practice of the present invention, employing four heating elements has been illustrated in FIGS. 2226 of my Patent No. 3,124,051 to which special reference is made herewith.

Instead of controlling the major heating elements by the actuation of individual switches, as shown in FIG. 3 of the attached drawings as optional feature, one may with advantage employ a switching arrangement as is shown in FIGURES 23 and 24 of my Patent No. 3,124,- 05 1.

It is generally preferred that the range of temperature increase or capacity provided by the adjuvant heating element and its coordinated rheostat to be somewhat larger than the temperature gap actually to be covered. The device is thus made more flexible by the fact that it is capable of providing temperature increases larger than that required by the gap left by the major heating element combination. Depending on the circumstances and conditions the adjuvant heating element and the coordinated rheostat, if such is used, may be designed to cover up to double or three times the gap i.e. 4 to 6 degrees or more in the case of a 2 degree gap and up to 10 degrees 01' more in the case of the 5 degree gap. With this provision the device is capable of meeting even the most unusual conditions such as line voltage deviations of 20% or more as well as other unusual conditions in the rate of water supply, extreme heat losses by low room temperature and so forth.

If desired, a thermometer may be provided in the water stream, downstream of the main heating elements but upstream of the adjuvant heating element. The additional thermometer permits the taking of intermediary readings of the preheated water which can be directly utilized for the setting of the rheostat. This mehod provides for even higher accuracy and convenience in the operation of the process, because it compensates for any inaccuracies and deviations introduced by an inaccurate rate of flow of the Water stream and by uncontrollable fluctuations of the voltage of the power supply. As can be readily visualized, deviations of the flow rate of the water stream or of the electric power of for instance percent will in the case of the two degree step result in a deviation of the final temperature of the outgoing water stream of only 0.2 F. and with the five degree step of only 0.5 R, if the expedient of taking intermediary readings on the additional thermometer is used. These deviations are the maximum and will often be smaller depending on how much of the capacity of the adjuvant heating element is utilized. Deviations of O.2 to 0.5 F. from the desired mean value are acceptable even in those photographic processes which require the most exacting temperature control. Using the direct method of heating the water stream by a single correspondingly high powered rheostatically controlled heating element a deviation of the line voltage of 10 percent from its mean value would result in a deviation of the temperature of the outgoing water by at least 3 F. in the case of a temperature reading A of 45 of the incoming water. The method of the invention can be made to be even more accurate, if this is desired, by providing a second independently rheostatically controlled adjuvant heating element. The capacity of this element need be only small to serve for the compensations found necessary by the reading of the downstream thermometer, which in this case would be placed downstream of the first adjuvant heating element.

Of course, variations of the line voltage may also be compensated by adjustment of the electrical power input into the heating elements as a group e.g. by the provision of a master rheostat in the power supply line which is adjusted in accordance with readings taken from a volt meter at the power line. If desired, any of the commercially available voltage stabilizers may be used with equal benefit. However, any of the high powered equipment of this type is rather expensive and will not be in reach of the average amateur photographer. The rheostats employed in the device of the present invention, as described hereinbefore, are designed for a small power input and thus relatively inexpensive.

In a further modification of this device the rheostats and thermometers are dispensible if the adjuvant heating element in thermostatically controlled. This modification is the preferred one because of its completely automatic operation and independence of any reasonable fluctuations of flow rate and line voltage. The small power input of the adjuvant heating element permits the use of a relative small thermostat which should be accurate within /2 or better A" F. and optionally F. The thermostat will be employed with the above described switch device of which only the rheostat and its controls have been omitted. The periodical opening and closing of the power supply by the thermostat will only aifect and act on the adjuvant heating element thus producing only small fluctuations of the water temperature between on and off cycles. This is much to be preferred to the relatively large fluctuations of the water temperature between on and off cycles which cannot be avoided if a high powered heating element is controlled by a correspondingly larger thermostat.

The thermostat and its heat sensitive element are generally located downstream of all heating elements including the adjuvant heating element controlled by it. As has been mentioned, the thermostat opens and closes the power supply to the adjuvant heating element only and does not affect the supply of electricity to the major heating elements. An even higher accuracy and completely automatic temperature control, independent of fluctuations in the water supply and of the line voltage, can be achieved by combining the above described switch device, with three major and one adjuvant heating elements, with an additional very small powered auxiliary heating element which is independently controlled by a small, sensitive thermostat.

As in the rheostatic control method described above, the adjuvant heating element is here with advantage also designed for a somewhat higher capacity than is needed to bridge the gap left by the major heating elements. It is also of advantage to locate the thermostat in a position in the water stream where it has a wide cross section and accordingly a low flow velocity.

The heating element or elements, in any of the water temperature control devices described hereinbefore are provided in a confined area through which the stream of water passes. Though the orientation and arrangement of the heating elements relative to the path of the water stream is not critical, it is generally preferred that the Water passes first over the higher powered elements with the lowest powered or the adjustable and variable element last. The heating elements are preferably designed in such manner that they olfer a large surface to the flowing water for ready heat exchange. Guide walls or bafiles, diverting the flow of the water, for instance in a zig-zag manner permit a more compact design of the heating device. Obstructions or other means such as sudden turns in the direction of the path of the water stream will assist in the mixing of the water so that it assumes the desired average temperature over its entire cross section. In order to avoid accumulation of gas bubbles or gas pockets in the heating chamber or channel with the resultant loss in efiiciency of heat exchange between the heating elements and the water it is generally of advantage to have the water stream flow at an angle to the horizontal and preferably slightly upwards. This expedient permits any gas or air bubbles which enter the heating device or which form therein by the effect of the heat at the heating elements (dissolved air and gases), to travel upwards by their own buoyancy in the direction of the traveling water stream. Thus any undesirable accumulation of air or gas bubbles in the heating zone is virtually impossible.

An embodiment of the heating chamber, utilizing these expedients, is shown in FIGURES 25 and 26 of my Patent No. 3,124,051.

In another modification of the invention the water stream may flow in a vertical direction, for instance in an alternating downward and upwards path which may be oriented horizontally or vertically. The heating zone may be designed as an integral part of the water metering device or of the photographic treating apparatus or water bath respectively or, if desired, as an independent selfsufficient unit. The latter may find wide use in applications other than for photographic treating apparatus. In its application to the photographic processes and apparatus employing a bath for temperature control the heating chamber is located between the water metering device and the water bath surrounding the vessels or troughs. In order to assure an even, uniform flow rate of the water stream through the system certain critical limitations must be observed with respect to the relative vertical positioning of the various units. The orifice of the metering unit should be located higher than the highest point reached by the Water in the heating chamber or unit. The latter may be located higher or lower than the level or surface of the water in the bath surrounding the vessels or troughs. However, the orifice of the metering device must in any event be located higher than the surface of the water in the bath. At least an inch and preferably several inches up to 10 inches or more height differential will ensure steady, trouble-free flow of the water stream from the metering device through the heating device into and through the water bath and from there into the sink or other place of disposal. The individual devices or units, if not constructed as a unitary device or apparatus, may be connected by tubing or pipes or other suitable conduit.

In a preferred embodiment of the invention the heating chamber is located in a low position such as underneath the bottom of the water bath, where it may form an integral part of the latter as is shown, for instance, in FIGS. 30 and 31 of my Patent No. 3,124,051 to which special reference is made herewith.

Another embodiment of the composite bath and heating chamber of the present invention, described and illustrated in my Patent No. 3,236,649 and in my copending application Ser. No. 342,029, filed Feb. 3, 1964, is equally useful, offering all the advantages of the invention as described hereinbefore.

As stated hereinbefore, the rheostats described herein as the means for controlling the heat output of the adjuvant heating element may be conveniently substituted by voltage regulators such as variable voltage transformers which are provided with suitable scales and markings indicating the temperature values or differentials in the settings of the regulator.

The heating chamber or the heating devices of the present invention may be provided with a multiplicity of heating elements of essentially equal heating capacity instead of the elements having different stepped down heating capacities. In either embodiment of the heating device of the invention, when it is operated with a stream of water of a predetermined constant rate of flow, each heating element can be assigned a temperature value or a temperature rating, which equals and simply expresses the number degrees, by which the temperature of the stream of flowing water is raised by the particular heating element, when it is operated with full capacity. If the heating elements in a given apparatus are selected such that they have, for practical purposes, the same or at least essentially the same heating capacity, the operator can achieve a desired rise of the temperature by switching or plugging in a number of heating elements corresponding to the quotient of the temperature diflerential (desired temperature minus actual temperature of the incoming water) rounded to the next lower integer. The adjuvant variable or thermostatically controlled adjuvant heating element is always used. The heating capacity of the adjuvant heating element should with this arrangement be at least equal to and preferably essentially higher than the capacity of the main heating elements, so as to be capable of supplying the heat energy required to bring the water temperature to the exact level between the said temperature values or ratings of the uncontrolled heating elements.

By way of example, if the temperature value or rating of the main heating elements is 6 F. and the temperature of the water is to be raised from 42 F. to 68 F., four main or full capacity heating elements must be switched in and additional heat energy, corresponding to a temperature value or rating of 2 F., is to be supplied by the adjuvant heating element. The output of the adjuvant heating element may be reduced to this value either by reducing the input of electric energy correspondingly or by reducing the on-time accordingly, e.g. by the use of a thermostat which shuts for the adjuvant heating element or elements intermittently off such that it supplies in a given time period just the required heat energy. The just described embodiment of the heating device may be conveniently constructed for the use of commercially available immersion heaters which are provided in the flowing stream of water. Each heater may be supplied with its own on-off switch or with provisions for plugging it in or out of operation. To avoid accidents, it is naturally desirable, to ground all electrically conducting parts in the heating devices of the present invention in accordance with accepted standards. It is also beneficial to incorporate into the heating device at least one device which protects the apparatus for overheating e.g. in the case that the operator accidentally energizes the heaters prior to the opening of the water supply. The said safety device, such as a thermostatically controlled on-ofl switch controlling the main power input is conveniently placed close to or between the heating elements, so that any rise of temperature beyond that encountered in the normal operation of the device will immediately shut off all power to all heating elements. The shut-off control may be set at a relatively low temperature such as F. The temperature of e.g. 120 or P. will never be reached in the heating device in normal operation unless the water flow is completely or at least partially blocked or unless the heating chamber is run dry.

An embodiment of the heating device of the present invention, incorporating the just described principles, is illustrated in FIGS. 2 and 3 of the accompanying drawings. Cylindrical heating device 3150 comprises cylindrical receptacle 3151, made up of cylindrical wall 3152 and bottom 3153 and lid section 3154. Water inlet tube 3158 enters the cylindrical wall 3152 at a position close to the upper edge, to continue downwardly as an integral conduit 3159 alongside the inside of the vertical cylindrical wall 3152 to a location close to the bottom 3153 of receptacle 3151, communicatively connecting into the circular flat cell 3161 located underneath perforated distributor plate 3162. Horizontal plate 3162 is joined to the lower portion of cylindrical wall 3152 and provides even distribution of the flowing incoming water over the whole horizontal cross section of the receptacle 3151 by perforations 3164 through which the water passes. A troughlike circular overflow 3166 is provided horizontally around the inside of the upper portion of cylindrical wall 3152. Trough 3166 is communicatively connected to vertical conduit 3169, which extend vertically downwards along the inside of the cylindrical wall 3152, penetrating the said cylindrical wall at a position close to the bottom and continuing as outlet tubing 3170. The upper edge of circular trough 3166 is located at a level as is required for keeping the water at the desired level in the receptacle 3151 which is needed to insure the complete immersion in the flowing water of the hot parts of the heaters 3172 at all times.

The receptacle 3151 is covered by lid 3174 with drainage hole 3175 into which the immersion heaters 3172 and thermostatically controlled safety shut-off switch 3176 are removably fastened so as to extend vertically downwardly, with their electrical connections above the lid 3174 and with their heating elements and hot parts extending into the water passing through the receptacle 3151. To the lid is joined dome-shaped cover 3179 with opening 3180 at its apex, through which the electrical conductors 3177 serving the heater and safety shut-off switch are led to be connected to a multiple switch arrangement and to the source of electricity (not shown).

If desired, individual switches 3173 may be provided for the individual heaters for the energization and deenergization of the heaters independently of each other.

The cover 3179 is perforated around its base and at its top so as to permit circulating of air, preventing overheating of the space above the lid. The lower peripheral perforations 3182 serve also the purpose of draining any liquid or water which should accidentally find its way inside the cover, thus reducing the danger of shock and the accident hazard appreciably.

The heating device may be operated as described hereinbefore. A stream of water of a measured temperature and of a predetermined constant flow rate enters through inlet tube 3158, flowing downwardly therein into cell 3161 and is evenly distributed by perforated distributor plate 3162 to flow upwardly in the receptacle 3151, passing by the energized heating elements 3172. Thereafter the water, with its temperature raised to the desired higher level leaves the heating chamber by overflowing into circular trough 3166 and from there to vertical conduit 3169 leaving the receptacle 3151 through outlet tube 3170. From there it may be conducted into a composite apparatus comprising a photographic bath and inserted therein treating vessels, where it is to serve as the temperature conditioning and/ or washing medium.

The heating chamber may conveniently be produced from plastics by the injection blowing or vacuum forming methods or by other suitable methods, preferably with the inlet and outlet conduits and, if possible, the distributor plate all integrated in the design of the receptacle making the production a one step operation. Alternatively, the distributor plate may be inserted and joined to the chamber subsequently by attaching it in essentially liquid tight relationship to a suitable rim 3186 provided in the bottom portion of the chamber.

The lid 3174 is advantageously made from metal e.g. by stamping and the heating elements are inserted therein removably in the usual manner e.g. by the use of threaded nuts etc. The construction of the lid from metal permits the grounding of all metal parts by one grounding wire, thus simplifying the construction of the device and at the same time increasing the safety. The dome-shaped cover 3179' is advantageously made from plastic and is removably joined to the lid, so as to permit access to the electrical connections and wiring and the exchange of the heating elements, if this should be necessary. With the just described construction, the operator does not run the risk of electric shock, because all electrically conducting parts are enclosed by electrical insulators. The overheating protection device 3176 prevents fire hazard and removes the danger that the parts of the device soften or melt due to overheating of the device.

The heating device may be provided with a smallpowered thermostat, which is provided close to the water outlet 3170. A thermostat 3190 has been indicated in dotted lines in FIGS. 2 and 3. The thermostat may be wired to control one of the heating elements 3172 or preferably an additional adjuvant heating element (not shown) of small heating capacity, having a temperature value of e.g. 2 or 3 F. and being provided within the heating chamber next to the elements 3172. Though the heating device of the present invention is operative and produces excellent results without the use of a thermostat,

the provision of the thermostat renders the operation stillmore accurate and provides fully automatic operation, as has been explained hereinbefore.

As is well known, the use of voltage stabilizers or regulators is recommended to be used in the exposure of color negatives in the enlarger so as to insure consistent results and consistent predictable color rendering. By the provision of suitable electrical connections and switches one and the same variable transformer or other voltage regulator may be used for the voltage control of both the adjuvant heating element in the temperature control device of the present invention as exemplified, for instance, in FIGS. 2 and 3 of the attached drawings, and of the light in the enlarger. The brief periods of time required for the actual exposure are too short to bring about any appreciable falsification of the temperature in the treating baths, when the adjuvant heating element is briefly disconnected because it does usually contribute relatively little heat energy to the water. More advantageously, one may employ in accordance with the invention a modified variable transformer in which the movable brush and the control means on the output side are duplicated so as to be operable and adjustable independently of each other. Accordingly, each of the output brushes and its controls can be used independently of the other, such that one brush may serve and control the adjuvant heating element and the other brush controls the enlarger lamp. As can be readily seen, the circuit of the adjuvant heating element need not be broken with this embodiment of the -modified variable transformer when an exposure is to be made. The enlarger circuit is not materially affected by the power drawn from the heater circuit as long as the transformer is designed with a capacity enabling it to carry the combined load. The enlarger circuit is provided with a voltmeter, permitting the adjustment of the voltage in the enlarger circuit to a predetermined, constant level every time an exposure is made, independently of the power output required for the adjuvant heating element.

Conveniently, the circuit of the adjuvant heater e.g. one of the heaters 3172 in FIG. 2 of the attached drawings is supplied by the brush normally provided on the transformer. The slidable brush or other contact means serving the second or the enlarger circuit may be arranged in various ways as is convenient and desired for the particular needs of operation. In those embodiments of the variable transformer, in which the brush or other slidable contact means are arranged opposite the circular face of the transformer windings, the adjuvant brush may conveniently be placed at and in sliding contact with the windings of wire located at the opposite unoccupied circular face of the transformer. Suitable changes and variations in the design of the transformer make this arrangement practical and useful for the purposes of the present invention.

With the commercially available transformers it was found, however, to be preferable to locate the adjuvant brush or slideable contact means opposite the peripheral portion of the transformer windings. Since the voltage in the enlarger lamp is to be controlled in a relatively narrow range to be maintained at a predetermined value close to the input value, it is generally not necessary that the adjuvant brush serving the enlarger circuit is capable of rotating fully around the periphery of the transformer. Complete control of the enlarger lamp is possible if said adjuvant brush is adapted to cover only a small segment of the periphery of the cylindrical transformer windings.

An embodiment of a variable transformer modified in accordance with these principles is illustrated in FIG. 4 of the accompanying drawings. Cylindrical core 3400 carries all around windings 3401 of insulated wire wound on a winding form surrounding core 3400. The exposed sides of the wires at the circular face 3402 of the body are stripped from insulation so as to permit the passage of electricity between said wires and brush 3403, which is slideably and rotatably contained on rotatable lever 3404 mounted on rotatable shaft 3407. The core 3400 and shaft 3407 are mounted on and contained in base 3409.

Outside the cylindrical periphery of core 3400 is fixedly mounted to perpendicular extension 3411 of base 3409 cross sectionally triangular member 3414 comprising partial cylindrical face 3415 and circular slot 3416 both being located concentrically with the axis of core 3400. Adjuvant brush 3417 is set, with the use of suitable taps 3420 and mechanical means in insulating fashion with member 3414, so that it is slideable in a partial circular path and in contact with the windings of the transformer. The portions of the windings contacted by adjuvant brush 3417, as it travels in its partial circular path are stripped at their surface from insulation so as to establish electrical contact between the individual windings and the adjuvant brush 3417 in its various settings.

The adjustment of adjuvant brush 3417 to the various positions providing the desired voltage may be achieved by the provision of insulated knob 3421 at an extension of t-a'b 3420 and its mechanical holding means. The variation of the position of adjuvant brush 3417 may also be achieved by the use of gears and other suitable mechanical means which cooperate to forward brush 3417 to the desired setting by rotating a shaft provided at the front of the transformer.

The enlarger circuit connected to and supplied by adjuvant brush 3417 includes advantageously a voltmeter indicating the voltage in said circuit. Provision of marks, preferably of luminescent marks at the pointer and at the position on the scale corresponding to the desired voltage facilitate the adjustment of the line voltage to the desired value prior to the making of an exposure in the enlarger and make it possible to make suitable adjustment by moving adjuvant brush 3417 to the appropriate position on the windings of the transformer, even in the dark. As can be readily seen, the operation of the enlarger circuit does not affect the operation of the heater circuit, and both circuits can be independently adjusted to the voltage required in the respective circuits, even though both are fed by a common variable transformer, as modified in accordance with the present invention, which may find many uses for purposes other than in the temperature control device of the present invention. The rheostats and/ or voltage regulators or variable voltage transformers, respectively, are conveniently combined with the switches and other electrical means required for the operation of the heating device and/ or of the enlarger, so as to form one central control panel for the electrical controls needed in the operation of the apparatus and process.

In the embodiments of the invention specifically described hereinbefore, the exact temperature in the stream of flowing temperature conditioning medium is achieved by assuring a constant flow rate of the stream of water and adjusting the heat input so that exactly the quantity of heat is supplied which is required to achieve the desired temperature. The present invention comprises also .an embodiment of the process and apparatus, in which the quantity of heat supplied, is kept constant, while the rate of flow of the stream of water or the throughput per time unit is adjusted and controlled, so as to produce exactly the desired temperature in the stream of water.

This concept is employed with greatest advantage in :an embodiment of the process and apparatus which combines this concept with the principle of using a multiplicity of heaters as described hereinbefore. The apparatus comprises as before means for metering a stream of water, heating means, and means for the control of the heating means. With the heat energy input kept constant, one varies the flow rate of the stream of water, so as to .adjust the quantity of water to be heated to the heat energy available per unit of time, to achieve an essentially constant temperature of the stream of water. This expedient can be readily achieved by employing in the apparatus variable metering means, which are preferably an orifice having a variable aperture and means, which .are capable of automatically controlling the aperture size or available opening of the orifice in relation to changes in the voltage of the power supply.

This may be achieved, for instance, by the placing of a movable constricting means into the aperture of the orifice, which constricting means is capable of either completely or partially closing the aperture or moving completely out of the way, so as to permit unrestricted flow of the water through the aperture. The constricting means are furthermore adapted to assume any intermediary position, so as to permit the passage of the water at any desired rate. The motion and relative positioning of the constricting means is directly controlled by the wattage in the supply line to the electrical heater, e.g. by the use of movable electromagnets or magnets in a spool of wire, through which the electric power flows before it enters the heating elements. Advantageously, the means are connected by suitable mechanical means to the said restricting means, such that the rate of flow of water is directly proportional to the electrical or heat energy available at the various line voltages. In this manner, continuous control of the rate of flow of the stream of water can readily be achieved as a function of the line voltage, providing automatically a constant ratio of the quantity of water to be heated per time unit and the heat energy provided by the heating elements, thus assuring a constant temperature of the stream of water at all times, without requiring any attention of the operator to the fluctuations in the line voltage and without requiring the use of a costly, high powered voltage stabilizer. As is readily apparent, the adjustable voltage controlled orifice is only needed in locations where uncontrolled heavy fluctuations in the line voltage can not be avoided.

If a source of incoming water is available, which has l ab o ly Constant temperature, that is a temperature, which does not fluctuate by more than /2 F. the stream of water, emanating from the apparatus employing the just described principle or in an apparatus of the invention which is operated at reasonably constant line voltage, will be constant at all times within :L-% F. and thus satisfy the most exacting requirements in any of the photographic processes available today.

If in a particular location the source of incoming water does not have an absolutely constant temperature, it may be of advantage to provide in the metered stream of water, upstream of the heating elements, a thermostatically controlled auxiliary heating element of relatively small heating capacity, e.g. one having a rating of 2 F. i.e. one, which has a capacity high enough to heat the stream of water by 2 P. if it is continuously on, which assures that the incoming stream of water is heated to a slightly higher, but constant temperature, which then serves as the basis for the setting of the heater controls as described herein. This expedient may be conveniently combined with the voltage controlled adjustable orifice, if the instability of the line voltage makes this desirable.

The foregoing discussion shows that the process and apparatus of the present invention may be readily adapted to meet even the most unfavorable conditions in the water and power supply without detracting from the accuracy and reliability of the process and apparatus of the invention. Thus, even under diflicult circumstances a continuous stream of temperature conditioned water is readily provided for the carrying out of the photographic processes. As shown, the process and apparatus of the invention provide also the possibility of making the control of the temperature automatic, requiring only a few initial temperature readings and settings and yet providing an extremely high accuracy in the temperature control over long operating sessions, which cannot be readily achieved with similarly inexpensive equipment by the methods and means known in the prior art. The operator who wishes to economize in the initial investment and who is willing to make occasionally during the operation of the process and apparatus of the invention a few temperature readings and if necessary, a few adjustments in the setting of the rheostate, or variable transformer or other control means can achieve perfect temperature control at every little expense and with the minimum of attention and effort. This flexibility of the equipment renders the process and apparatus of the invention useful for most any situations, as they may occur in the practice of photographic processes by the inexperienced amateur, by the skilled and demanding amateur or by the professional.

The water metering device and the heating chamber and, if desired, the various auxiliary components described hereinbefore may conveniently be combined to a unitary apparatus with suitable conduit provided in the device, to make the required communicating connections for the establishment of the flow pattern in accordance with the foregoing teachings. The apparatus may be completely enclosed and need be provided only with a water inlet connection, an outlet connection for the excess of running overflow water, an outlet for the stream of metered temperature conditioned water and electrical connections, powering and controlling the heating elements in the heating chamber and, if necessary, the electrical adjuvant devices.

The features, components and elements described hereinbefore with respect to specific embodiments of the various devices and components may be modified in many ways and/or recombined to form new embodiments of the apparatus and devices of the invention.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is understood, that the invention is not limited to the specific embodiments thereof, except as defined in the appended claims.

I claim:

1. A device which is adapted for controlling and maintaining the temperature in photographic developing equipment at a desired temperature B, which device comprises means capable of providing a continuously flowing stream of water, having an essentially constant flow rate and an essentially constant temperature A, which temperature A is lower than the said temperature B, said device comprising in addition at least one heating chamber and means which are adapted to pass through the heating chamber said continuously flowing stream of Water, and disposed in said heating chamber a multiplicity of electric immersion heaters, each of said heaters having a known heating capacity corresponding to a temperature value, the sum total of the temperature values of said heaters being at least as high as the maximum temperature differential between temperature A and B for which the device is built, each of said heaters being provided with on-off switching means, whereby only those heaters and as many of the heaters are activated, whose temperature values add up approximately to the temperature differential by which the flowing stream of water is to be heated to achieve the said temperature B.

2. The heating device of claim 1, in which the heaters have different heating capacities and temperature values.

3. The heating device of claim 1, which comprises in addition at least one ajuvant heater in combination with means which are adapted to continuously vary the heating capacity and the temperature value of said adjuvant heater or heaters.

4. The heating device of claim 1, which comprises in addition an adjuvant heater in combination with a thermostat, which thermostat is provided in the stream of water, downstream of the heaters, and which thermostat is adapted to control the operation of said adjuvant heater by suitable switching means.

5. The device of claim 1, in which at least one of the heaters is conductively connected to control means adapted to control the electric power fed to said heating element from zero to the full rated input.

6. The device of claim 5, in which said control means is a continuously variable transformer controlling the electric power input of at least one heating element.

7. The device of claim 1, in which a thermostat is positioned downstream of 011 heating elements, in contact with the flowing water stream and controlling the electric power input of at least one adjuvant heating element. 1

8. The device of claim 6, in which said variable transformer is adapted to control independently of the heater circuit the voltage of a second electrical circuit containing the lamp of a photographic enlarger.

9. The device of claim 1, in which said means for the provision of a continuously flowing stream of water of essentially constant flow rate is a device which comprises a vertically oriented, oblong receptacle having a water inlet, a water outlet comprised of an orifice of predetermined aperture size in a low position in said receptacle and overflow means at a position essentially higher than said water outlet.

References Cited UNITED STATES PATENTS 1,183,925 5/1916 Waters 219-486 1,746,522 2/ 1930 Carleton 219-307 1,772,834 8/ 1930 Hopkins -96 1,792,757 2/1931 Parker et a1. 137-577 X 1,967,889 7/1934 Kitroser 95-94 1,985,280 12/1934 Carleton 219-296 X 2,690,764 10/1954 Hotfmann 137-563 2,743,909 5/1956 Lawlor 137-563 X 2,790,890 4/1957 Kasuga 219-287 2,852,232 9/1958 Marwell -30 2,969,451 1/1961 Logan 219-306 X RICHARD M. WOOD, Primary Examiner. C. L. ALBRITTON, Assistant Examiner.