Developing machine

Depending on the application, the developing machines may vary in size, performance and other functional characteristics. In addition to cinema, automatic developing machines are used in film photography ^[4] , printing ^{[5] [6]} and medicine (for example, radiography ). Film developing machines have the highest productivity of all existing, because they are used for mass processing of film print runs. Developing workshops at film studios and film copying factories are large-scale production and are equipped with machines, sometimes occupying a whole two-story building tens of meters long ^[7] . In addition to double-decker development machines, single-decker ones are produced for processing a relatively small number of negative films at film studios ^[3] . Developing machines for film can be one-sided and two-sided, that is, designed for single or pairwise installation. Bilateral machines are produced in the “left” and “right” versions, that is, their device is mirror-image relative to each other. This allows you to install the “left” and “right” machines in the workshop in pairs, serving both with one operator from a common passage. Also, developing machines are classified by the type of room in which they are installed: in ordinary or darkened, illuminated with inactive light. In closed-cycle film-copying factories, developing machines can dock directly with film-copying machines , the exposed positive film of which immediately goes to the loading store ^[8] . Small-sized small-capacity developing machines for film amateur associations were also produced, for example, the domestic MPM-16-3M designed for a narrow film ^[9] .

Developing machines designed for processing film and photo paper are also called film processors and have a compact design that does not require a special room for installation ^[10] . Just like developing machines for cinema, compact photoprocessors require connection to the water supply and sewerage . Most processors for photo paper combine with a photo printer to form a single unit called a minilab . In some cases, compact machines can even have a desktop design if the format of the processed material is small and requires only two operations. Such machines include, for example, processors for processing dental x-ray films ^[11] .

The work of most developing machines is based on alternately immersing the photographic material in vertical tanks with processing solutions ^[7] . For the first time, machines of this type were used at the Gaumont Film Factory in 1906 ^[12] . There are continuous development machines, or with lifting frames, which are successively immersed in special solution tanks in a special mechanism ^[13] . The most widespread are continuous machines based on a tape drive mechanism in which the film makes vertical loops between the pairs of rows of rollers 1 and 2 arranged in pairs, the lower of which (2) is immersed in a solution tank ^{[* 1]} . During movement along the loop, the film is in solution, undergoing chemical-photographic processing ^[14] . The processing time is controlled by the loop length and speed. To carry out several processing operations, the film sequentially passes through several tanks with different solutions. After the chemical-photographic treatment is completed, the film enters the drying department, where it is dried with heated air and wound into a roll. The figure shows a diagram of a simple developing machine designed to process black and white negative or positive film. The exposed film located in the lightproof cassette in roll 3 goes to the loading magazine 5. After the loading compartment, the film goes to the developing one, where the tanks with the developer 6 are located, water for intermediate washing 7 and a fixer 8. The part of the casing, which should be opaque or in a darkened room. After fixing, the film enters the tank 9, where it is finally washed, after which the finished film enters the drying compartment 10. The dried film is rolled into a roll 4 through the unloading magazine 11. The existing developing machines used in film production are much more complicated. They can contain several tens of tanks and sections of rollers, ensuring the performance of any number of operations. A separate category of developing machines uses viscous processing pastes applied to the photosensitive layer of photographic material instead of liquid solutions. This technology is most typical for compact types of processors, since it eliminates most of the devices of traditional machines.

The developing machine, designed for working with liquid solutions, consists of tape and drive mechanisms, tanks for solutions and water, pumps , a drying cabinet and numerous auxiliary devices: cartridges , temperature control systems for solutions and air, dispensers , dehumidifiers, blocking devices and a control panel . In some developing machines, all nodes are assembled in a rigid order, designed for a specific technological process of processing film films, for example, only for color negative or for counter-type . In other machines, the nodes are made of standardized blocks, allowing them to be assembled in various combinations, ensuring the implementation of any technological process of processing film films: negative, positive or reversible . In modern film production, developing machines are designed mainly for two technological processes: ECN-2 ^[15] for negative and counter-type films, and ECP-2 for positive ^[16] .

Tape Drive

The tape drive mechanism of the developing machine can be single-loop or multi-loop ^{[3] [17]} . In single-loop machines, film makes one loop between the upper and lower rollers, plunging into the tank only once. Multi-loop tape drives include several coaxial rollers at the bottom and top, between which the film makes several loops, moving in a spiral. This design allows you to extend the path of the film in each tank and thus increase its speed, raising the productivity of the machine. Low-performance machines are carried out according to a simpler one-loop scheme, which is more compact. The bottom row of rollers can be freely suspended on film loops, or moved with a special carriage, adjusting the length of the loops and the processing time in each tank.

According to the film path, the developing machines are also divided into machines with full and partial immersion of the mechanism in the processing solutions ^[3] . The mechanism with partial immersion provides for the presence of upper rollers located above the surface of the solution, while mechanisms with full immersion are designed to move the film without leaving the solution. The second type is preferable from the point of view of processing quality, since it allows avoiding contact of the emulsion with air that oxidizes the solution and leads to the formation of a veil . However, the complete immersion of the mechanism requires its careful sealing and manufacture of parts from chemically inert materials.

The tape drive mechanism of any developing machine is designed for non-stop operation. Therefore, at the beginning and end of the tract, each machine is equipped with stores with a supply of film strip ^[18] . Located at the beginning of the tract loading store 5 is designed to recharge cassettes. At the end of the film in one cassette, the lower branch of the rollers begins to rise, choosing the stock of film that has formed, and does not require the machine to stop while recharging. After charging the next cassette and gluing its film to the end of the previous one remaining at the mouth, the movement resumes and the store again regains film supply. A similar role is played by the unloading magazine 11 from the side of the finished roll ^{[* 2]} . The alarm system automatically reports the end of the roll of undeveloped film or the filling of the receiving roll.

The film was transported until the mid -1950s by gear drums, but modern machines are equipped with mechanisms with a friction method for moving the film with smooth rollers made of materials operating on the principle of a suction cup ^[19] . Friction rollers do not damage the perforation and make machines multi-format, that is, suitable for processing films of different widths ^[8] . The use of elastic rollers instead of rollers in the tape drive mechanism allows you to process sheet photo materials. In combination with the use of viscous processing solutions, the friction tape drive is used in universal compact processors for sheet films of various formats in radiography, printing and aerial photography . The mechanism of the developing machines is driven by one or more electric motors . Solution tanks, which can be very aggressive, are most often made of stainless steel or chemically resistant polymers. Each operation is performed in a separate tank or in several tanks filled with the same solution. Tanks of cars designed for work in a darkened room are open. In machines installed in a lit room, the tanks are closed with a lightproof lid ^[3] .

Circulation and maintenance of solutions

Individual devices are responsible for maintaining a constant temperature of the processing solutions, continuously circulating in the tanks using special pumps. Such devices are called thermostats and operate on the principle of heat exchange with water heated or cooled by a machine. Heat transfer occurs in special heat exchangers ^[20] . To increase the uniformity of processing, the countercurrent principle is often applied, that is, the circulation of solutions in the tanks in the opposite direction to the motion of the film. In addition, special devices provide continuous mixing of solutions or even their supply under pressure on a film.

Changes in the properties of solutions as a result of their chemical consumption are compensated by dispensers - special devices that supply additives of fresh solutions. Dispensers can be float-filled, adding fresh solution as the flow of the worker, piston or other design. Compensation for a decrease in the activity of solutions is often made by solutions containing, in a concentrated form, the components that are most actively consumed during processing. For example, in the developer, the developing substances are consumed to the greatest extent; therefore, they are contained in a concentrated form in the compensating additive, while potassium bromide and other antivalents are not contained at all ^[16] . Despite the constant refreshment of solutions, their periodic replacement is necessary due to contamination with development products, other solutions and gelatinous emulsions . In large developing machines, a complete replacement of the developing solutions is performed monthly ^[16] . The most unpretentious of solutions is the fixer, which can "walk in a circle", constantly updated, up to three years ^[16] . Somewhat less fixative is bleach.

To prevent the introduction of one solution into another when the film is transferred from one tank to another, special moisture collectors are installed between the tanks, which can be based on blowing the solution from the surface using an air stream or can be made in the form of elastic wringes. The same devices remove residual water before drying the emulsion in the drying compartment.

In addition to the above devices, for the full-fledged operation of the developing machine, technological peripherals should be organized ^[16] :

• high-quality water preparation for washing film and preparing processing solutions;
• a system for recycling excess processing solutions formed during the replenishment of fresh additives and the use of this excess in the preparation of new additives ^{[* 3]} ;
• a system for the neutralization and treatment of wastewater , as well as the disposal of waste solutions - including silver recovery ;

The composition and characteristics of the processing solutions, as well as the quality of the water are constantly monitored in a special laboratory of the film processing workshop. Machines installed in one workshop and operating in the same process are most often combined according to the system of circulation and regeneration of solutions, which simplifies their preparation and increases the uniformity of characteristics ^[21] .

Dryer

Drying the photographic material is an equally important stage of its processing, since the characteristics of the image may change in case of violation of its modes. There are two ways to remove moisture from film and other types of photographic materials: convective and radiation ^[3] . In the convective method, drying is carried out by a stream of heated air supplied to the drying compartment by nozzles or perforated pipes. The final image quality depends on the purity of the air, since dust and solid particles that have fallen on the film form difficult to remove defects on the emulsion. An open or closed system can be used to prepare the air. An open preparation system takes air directly from the room in which the machine is installed. After cleaning with filters and heating, air enters the drying compartment and is discharged outside the premises. The closed-loop system provides the best drying conditions since it provides almost complete cleaning. The basis of such a system is an air conditioner with a desiccant. At the same time, one installation can supply several developing machines installed in one workshop with air for drying at once.

The radiation drying method involves heating the film with infrared or microwave radiation ^[18] . This method allows you to significantly speed up the drying, but requires an individual selection of the irradiation mode for each type of film. In addition, the radiation method, to a much greater extent than the convective method, poses a danger of twisting the film and damage to the emulsion layers.

The performance of the developing machines differs depending on their purpose and size. At film copying factories involved in duplicating film copies, productivity can reach 3000-6000 linear meters per hour ^[3] . A modern large film copying factory is capable of producing 150-200 film copies per day, which should be processed by the film processing department during the same time ^[22] . In the studios' workshops, they use machines with an average productivity of 800-2000 m / h. Special machines for expeditionary work and film processors for film have a low productivity of 25-100 m / h. The performance of the machine depends on the speed of motion of the film and the volume of its tanks. Large tanks with multi-loop carriages make it possible to provide high speeds of motion of the film due to the long path and long stay in each tank. An increase in machine productivity is possible with an increase in the temperature of the processing solutions, which reduces the time of each operation ^[23] . However, an increase in temperature negatively affects the preservation of the emulsion layer, which can peel off or become damaged when solutions are too hot. Most of today's standardized processes for laboratory processing of photographic materials are designed for high temperatures of 38 ° C and above.

High-performance machines of film copying plants need constant work loading, due to the technological complexity of the launch. The total length of the trajectory of the film in such a machine can reach several kilometers and at the same time in the machine there can be several parts of film copies going through different stages of processing. Starting the machine requires charging the record filling the entire tape drive and pouring several tons of solutions. Therefore, the shutdown of such machines can occur once every several years during repair or cleaning. The rest of the time, the machine runs around the clock ^[8] .

• Miniphotolaboratory
• Film copier

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