Method and Apparatus for Drying Photographic Strip Material

The present invention relates to dryers for photographic materials. In particular, the present invention is an improved multichamber drying system and method.

In the past, dryers for photographic materials have controlled the temperature and humidity in each drying chamber individually. The chambers are not interconnected, but rather utilize separate venting to supply and exhaust air used in drying. This arrangement wastes energy, since each chamber must heat the air it uses. In many cases, air being exhausted from one chamber because its temperature is too low or its humidity is too high for use in that chamber may still have the proper temperature and humidity to be usable in another chamber.

The present invention is specifically designed to provide a plurality of interactive zone drying chambers which recirculate substantial portions of the drying air within each chamber but exhaust heated air to another chamber in accordance with the individual humidity control mechanism in each chamber. This interactive zone drying arrangement provides increased efficiency of energy use and permits optimum drying conditions to be easily maintained in each drying chamber.

FIG. 1 is a vertical sectional view of a dryer embodying this invention and taken on the line 1--1 of FIG. 3.

FIG. 2 is a horizontal sectional view thereof taken substantially along the line 2--2 of FIG. 1.

FIG. 3 is a vertical sectional view taken substantially along the line 3--3 of FIG. 1.

FIGS. 4-7 schematically illustrate four different possible interconnections of three drying chambers in accordance with the interactive zone drying of the present invention.

A multiple chamber drying apparatus embodying this invention includes, in the form shown, a pair of dryer housings 10 and 11, each defining a drying chamber therewithin respectively designated by the reference characters 10a and 11a. Plenums 12 and 13 are respectively provided within said housings and divides the chambers 10a and 11a into high pressure zones respectively designated 10b and 11b and low pressure zones 10c and 11c.

Blowers 14 and 15 are provided for the respective drying chambers 10 and 11. The blower 14 has its air intake communicating with the low pressure zone 10c and its discharge outlet communicating directly with the upper portion of the plenum 12 and high pressure zone 10b defined therewithin. The blower 15 is similarly connected within drying chamber 11a. The plenums 12 and 13 have discharge openings such as slits 12a and 13a respectively formed in the sides thereof for discharging drying air from the high pressure zones 10b and 11b unto the low pressure zones 10c and 11c.

High pressure delivery ducts 14a and 15a respectively connect the blowers 14 and 15 to the upper ends of plenums 12 and 13, as illustrated, and are provided with heaters such as the electrical heating elements 16 for controlling the temperature of the high pressure air being delivered into the high pressure zones 10b and 11b. A conveyor system which includes a plurality of rollers 18 and belts 20, successively transports strips of photographic material such as photographic print paper P through the two drying chambers 10a and 11a. The belts and paper strips to be dried are conveyed into housing 10 through entrance opening 10d and out through exit opening 10e and into housing 11 through entrance opening 11d aligned with the exit opening 10e and out through its exit opening 11e of the second drying chamber to carry the paper being dried successively from one chamber to the next.

An intercommunicating humidity control duct 24 is provided for connecting drying chamber 10a to drying chamber 11a. The intake end of duct 24 is positioned at the top of high pressure zone 10b in drying chamber 10a and the discharge end of duct 24 is positioned in the upper portion of the low pressure zone 11c in close association to the intake of blower 15. A humidity control duct 26 is provided in housing 11 and has its intake end located in the upper portion of the high pressure zone 11b and exhausts to the ambient air surrounding housing 11, as best shown in FIG. 1.

The ducts 24 and 26 have flow control dampers 24a and 26a respectively mounted therein. The dampers are automatically controlled by a conventional humidity responsive system which includes a humidistat 28 with a conventional humidistat unit as described in U.S. Pat. No. 3,166,085 supplied by the Johnson Service Co., 507 East Michigan St., Milwaukee, Wis. 53201, part No. H-4100-203. The humidistat control embodies a pneumatic system which communicates with a suitable actuator such as a piston damper operator 30, part No. D 251-201 also manufactured by the Johnson Service Co. A suitable linkage, not shown, connects the operator piston to a crank arm which in turn opens and closes the damper elements 24a or 26a. The hot air from chamber 10a is ducted into the next successive chamber 11a thus reducing the heat energy required to maintain optimum temperature in the second chamber 11a.

A pair of thermostats 32 respectively mounted in the drying chambers 10a and 11a control the actuation of the two heater elements 16 to maintain the optimum temperature in each drying chamber. The two dryer housings 10 and 11 with their plenum and blower assemblies are of a modular construction to permit the drying capacity of the processor to be varied in accordance with each user's requirements and, of course, as the number of drying chambers is increased, the humidity control duct work is connected into other chambers in the manner herein disclosed and the final chamber is ducted to the ambient air as in the present disclosure.

It will be seen that this invention provides a system which is specifically designed to conserve and save energy thus resulting in cost savings for the user. Each housing provides a sealed chamber except for the first entrance opening and the last exit opening (in the form illustrated, entrance opening 10d and exit opening 11e). The relatively dry and cool ambient air will provide makeup air to replace the air exhausted through the high pressure duct 15a from the last chamber in the system; however, the system is otherwise a closed recirculating system which maintains maximum drying efficiency within the respective chambers 10a and 11a. By providing the interconnection between successive drying chambers, it is possible to maintain the humidity in the first chamber somewhat lower (in the range of 15 to 23% rh) than would be possible with other systems, thus obtaining more efficient first stage drying at a somewhat lower temperature (in the range of 150.degree. to 159.degree. F.). An even lower temperature is possible in the second stage (between 110.degree. and 120.degree. F.) with approximately 50% relative humidity which is similar to the humidity in the ambient air. This prevents the paper from becoming excessively dry and which would produce excessive distortion and curling thereof.

The interactive zone dryer of the present invention, in which substantial portions of the drying are are recirculated from one chamber to another, not only assists in the humidity control of the different chambers but also provides preheated air for such chambers. This is particularly important where more than two chambers are assembled for successively drying photographic strip material.

FIGS. 4 through 7 illustrate four possible configurations of a three chamber interactive zone dryer assembly in which the first chamber is designated by the letter A, the second chamber by the letter B and the third chamber in the succession by the letter C. For purposes of convenience, the numbers relating to chambers A and B shown FIGS. 1 through 3 will be carried forth into chambers A and B for FIGS. 4 through 7. The third drying chamber is designated by the letter C and includes a housing 35 having an entrance opening 35a and an exit opening 35b; a plenum 36 is provided therein and divides the chambers C into a high pressure zone 36b defined within the plenum 36 and a low pressure zone 36c.

A blower 37 draws air from the low pressure portion of the chamber and discharges the same into the plenum 36. An electrical heating element 16 is provided between the plenum and blower 36 and a plurality of rollers 18 define the necessary path for the belts 20 through the third chamber C. A humidity control duct 38 has its inner end connected to the high pressure zone 36b within the plenum 36 and in the arrangement illustrated in FIG. 4 exhausts air to the atmosphere. A damper 38a is provided in the duct to control the flow of exhaust air therethrough and a humidistat 28 and operator 30 are provided to automatically control the position of the damper. A thermostat 32 is provided to control the operation of the heating element 15 for chamber C.

Makeup air for chambers A and C is drawn in through the respective openings 10d and 35b respectively providing entrance and exit openings for the strip material for chambers A and C. The only source of makeup air for the central isolated chamber B is through the openings 11d and 11e respectively communicating with chambers A and C. For convenience, entrance and exit openings 10d, 10e, 11d, 11e, 35a and 35b, rollers 18, and belt 20 are shown only in FIG. 4. It should be understood, however, that the dryer assemblies shown in FIGS. 5 through 7 have similar openings, rollers, belt for conveying the prints through the assemblies.

FIG. 4 illustrates the ducts conducting the air successively from chambers A and B to C respectively from the high pressure zone 10b to the low pressure zone 11c and from the high pressure zone 11b to the low pressure zone 36c of chamber C. The intercommunication duct between chambers B and C is designated by the numeral 39, having a control damper 39a therein, the position of which is controlled by the humidistat 28 and operator 30 located in chamber B.

The arrangement of ducts in FIG. 5 shows the exhaust duct from chamber A extending into the low pressure zone of chamber C. This duct is designated by the numeral 40 and has a damper 40a therein which is responsive to the humidistat 28 and operator 30 located in chamber A. The humidity in chambers B and C is controlled by ducts 41 and 42 which are exhausted to the ambient air surrounding the dryer and suitable dampers 41a and 42a and provide for controlling the exhaust air respectively from chambers B and C in response to the humidity controls 28 and 30 located therein.

FIG. 6 shows the exhaust duct 43 from chamber C returning back to chamber A to supply makeup air thereto. The intercommunication duct 24 connects chambers A and B as previously described and chamber B is exhausted to the atmosphere through duct 41 similar to that shown in FIG. 5.

FIG. 7 shows an arrangement similar to FIG. 6 with the return duct 43 extending from chamber C back to chamber A. In FIG. 7, however, exhaust duct from chamber A exhausted to the atmosphere.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of this invention, which generally stated is set forth in the appended claims. For example, although the interactive zone dryer of the present invention has been described with reference to two and three chamber assemblies, workers skilled in the art will recognize that the invention may also be used to great advantage with dryers having more than three chambers.