GB2492741A - Film strip dryer - Google Patents

Abstract

A film strip dryer 10 is provided for use in processing photographic and movie film 20. The film strip dryer 10 comprises a plurality of resilient members 26 for wiping excess liquid from the film surfaces and a bank of air jets 24 for drying the film 20. In use, the film strip dryer 10 is mounted between adjacent chemical tanks 36 containing, for example, developer or fixer solution. The film 20 is dried in between process steps, preventing chemical residue from being transported through to subsequent tanks 36. Such chemical residue dilutes and reduces the efficiency of subsequent process chemicals, and ultimately leads to film 20 wastage and production downtime.

Description

Title: Film Strip Dryer The present invention rdates to a film strip dryer and particularly to a film strip dryer for use in processing photographic film.

Background to the Invention

Films or movies are typically shot and projected using film stock, otherwise known as photographic film. Often, a film soundtrack is recorded simultaneously with the shooting of the picture and is embedded into the film stock. Traditionally, film stock has a transparent celluloid, acetate or polyester base and is coated with an emulsion containing light-sensitive chemicals, such as the silver halides. During shooting, the film stock is exposed to produce a negative latent image. The photographic film is then processed to develop the latent image into a visible image and to make the image permanent and insensitive to light.

In commercial film processing. a wet chemica' process is typically used in which the film is passed through a series of tanks or reservoirs containing liquid chemicals. The film typically travels through the line at a speed of approximately 750 feet per minute (fpm). Between process steps, the film passes through a set of wipers or squeegees' located within the tanks, which remove the excess chemicah from the film surface before the film enters the next tank. Typically up to sixteen pairs of squeegees are used in the art. However, these squeegees have a limited effect; as such, chemical residue remains on the film surface and is carried through to the next and subsequent tanks. The chemicals from one tank mix with the chemicals of subsequent tanks, reducing the efficiency of chemicals in subsequent process steps. This leads to wasted film stock because the ifim has not been properly processed.

Furtheimore. the process must be hailed in order to drain and replenish the tanks with fresh chemicals and to replace the film. Such process downtime is an inconvenience and incurs a cost.

Additionally, the used or spent' chemicals must be treated before they can be drained into the sewage system as they are potentially harmful to the environment. If the constitution of the used chemicals falls outside acceptable Umits, financial penahies may be levied by government agencies. This treatment is costly, time consuming and potentially hazardous for operators.

Finally, a by-product of the development stage is metallic silver. This metallic silver is recoverable from the tanks and may be sold for profit. However, if some of the metallic silver is carried through to certain subsequent tanks. it is convened out of its pure form into, for example, a silver salt. As much as 3O% of the metallic silver is then no longer recoverable, leading to lost potential profits.

It is an object of the invention to provide a film strip dryer which reduces or substantially obviates the above mentioned problems.

Statement of Invention

According to a first aspect of the invention there is provided a film strip dryer comprising a housing having an inlet, an outlet and a guide path for a film strip, at least one resilient wiping member disposed adjacent to the guide path for wiping residue from a surface of the film strip, and a plurality of air jets directed at or towards the guide path for drying the film strip.

The film strip dryer is advantageous because, in use, it substantially reduces the amount of residue that is transported to successive tanks in the film processing process. This is partly due to the wiping action of the at least one resilient member which returns excess liquid and particulates back into the tank, but also partly due to the drying action of the air jets.

Furthermore, use of the dryer maximises the amount of metallic silver that is potentially recoverable from the process. If the metallic silver is carried through to certain subsequent tanks, notably an acid stop tank or a Neach accelerator tank, then it is converted into a less profitable form, such as one of the silver halides.

Preferably, the at least one resilient member is disposed intermediate the inlet of the housing and the plurality of air jets along the guide path. This arrangement is ci advantageous as work done by the air jets in removing moisture from the film surfaces requires electrical power, with an associated cost. By conveying film passed the at least one resilient member in advance of the film passing before the plurality of air jets, the air jets have to do less work to remove residue from the film because the majority of the residue has already been removed mechanically.

Preferably, the at least one resilient member is provided as a cooperating pair, arranged for wiping opposing sides of the film strip. This arrangement is useful as residue is removed from both sides of the film stnp, increasing the amount of residue that is removed from the film before the film continues on to the next tank.

Preferably, three cooperating pairs of resilient members are provided. For commercial processing, this is an optimum number of resilient members to provide a wiping action whilst running the film processing line at speed. In fact, line speeds of around l300fpm are achievaHe with six resilient members. It is envisaged that only two cooperating pairs of resilient members may be provided, with additional drying being provided by the air jets to compensate for the reduced number of resilient members.

The three cooperating pairs of resilient members may be arranged adjacent one-another in a line along the guide path. Such a configuration is desirable as it reduces the amount of space required within the housing for the resilient members. This ultimately reduces the overall size of the housing and reduces the weight of the film strip dryer.

Preferably, at least one base is provided for receiving the or each resilient member, said base being fixed relative to the guide path. This reduces. if not eliminates, the risk of operator errors when fitting or replacing the or each resilient member.

The base may be oriented at an an&e of approximately 6° from a plane that is parallel with the guide path. By fixing the angle of the base (and therefore the resilient member) with respect to the guide path at around 6°, the resilient member is optimally angled to wipe moisture from the film as it travels pass without scratching the film surfaces. Incorrectly set resilient members and bases cause the resilient member to impinge on the film surface, leading to scratched and defective film.

An outlet of each air jet may be angled for directing air towards film approaching along the guide path. The effect of this in use is that air pushes residue back towards the tank. The amount of metallic silver that may be recovered from the tanks is therefore maximised.

Preferably, the or each air jet is oriented at an angle of approximately 45° from a plane that is parallel with the guide path. This facilitates a tight configuration of air jets, reducing the amount of space required by the air jets within the housing.

The housing optionally accommodates a plurality of guide rollers. These rollers support the film as it travels within the housing.

Preferably, each guide roller is mounted on a shaft, there being a bearing element disposed intermediate the roller and the shaft.

The bearing element may be a bali-race, which reduces rotational friction and supports radial and axial loads.

The balls of the ball-race may be made from glass and the race of the ball-race may be made from PEEK (polyetheretherketone). Both glass and PEEK have excellent high temperature and chemical resistance, making the ball bearing suitable for use in the film processing environment.

The drive shaft may be made from titanium. Titanium and titanium alloys have a very good corrosion resistance; their use prolongs the service life of the film strip dryer.

Each resilient member may be made from a chemical resistant rubber. This minimises colTosion of the resilient members during a prolonged period of exposure to the film processing chemicals.

The rollers may be made from PVC (polyvinyl chloride). The housing may also be made from PVC. Use of PVC in the rollers and/or housing reduces the overall weight of the film strip dryer. making it more portable.

According to a second aspect of the invention there is provided an apparatus for processing a film strip comprising a plurality of reservoirs for storing film processing chemicals, each reservoir having a film strip inlet, a film strip ouflet, and a guide path therebetween along which a film strip travels in use, and a diyer unit bridging the guide path between the film strip outlet and film strip inlet of at least two of said reservoirs respectively.

The apparatus substantially removes an residue from the film in preparation for subsequent reservoirs. This avoids process chemicals in subsequent reservoirs or tanks from becoming dilute andlor less efficient for their purpose.

The dryer unit may be a film strip dryer according to the first aspect of the invention.

The film strip dryer is simple to set-up and maintain, and its components are easy to access.

Optionally. the dryer unit is removably attached to a surface of one of the reservoirs.

This improves the ease with which maintenance, especially of the resilient members, may be carried out.

Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic perspective view of a film strip dryer; Figure 2 shows a schematic perspective view of a film processing apparatus, including several film strip dryers; and Figure 3 show's a schematic flow diagram of the film processing process, which incorporates use of film sttip dryers.

Description of Preferred Embodiments

Referring firstly to Figure 1, a film strip dryer is indicated generally at 10. The film strip diyer 10 includes a substantially rectangular housing 12 having an inlet 14 and an outlet 16. and a plurality of rollers ISa, I Sb, I Sc for directionally winding a strip of film 20 around a guide path within the housing 12. A plurality of squeegees 22 is provided either side of the guide path for removing excess liquid and particulates from a surface of the film stnp 20. A plurality of air jets 24 is also disposed on opposing sides of the guide path for drying the film stnp.

The plurality of squeegees 22 is provided in the lower half of the housing 12, intenilediate the housing inlet 14 and the outlet 16 along the guide path. There are six squeegees 22, arranged in pairs, with the guide path passing through the middle of each pair. Each squeegee 22 comprises an elongate resilient member 26. which is inserted into a fixed position base 28. At the free end of the resilient member is a wiper blade. The bases, made from PVC, are arranged such that the elongate resilient members 26 lie in a nested configuration, which reduces the amount of space required within the housing 10 for the squeegees 22. The angle of each base 28 with respect to the vertical is approximately 6°. Therefore the angle of each squeegee 22 with respect to the guide path is fixed. This is advantageous because it is almost impossible for operators to incorrectly fit or incorrectly replace the elongate members 26. III fitting elongate members 26 can cause scratches on the film strip 20 in use; consequently operators waste valuable production time trying to identify offending elongate members 26 and correcting the positional settings. The elongate member 26 is available commercially and is made from a chemical resistant rubber.

The bank of air jets 24 is located intermediate the plurality of squeegees 22 and the housing outlet 16 along the guide path. There are ten air jets 24, arranged in pairs, with five air jets 24 disposed to one side of the guide path and five air jets 24 to the other side. Each air jet 24 is angled at approximately 45° to the vertical and the outlet of each air jet 24 is directed upstream of the guide path. Each air jet 24 has a rectangular nozzle fitted within the housing and an interface (not shown) for connecting to a compressed air supply. The compressed air may be heated.

The housing 12 is oriented longitudinally vertically and has all opaque base 30 and a transparent slidable cover 32. The cover 32 retains chemical splashes within the housing 12. The housing 12 is made from a plastics material, for example, polyvinylchioride (PVC). although other suitable materials may be used.

There are three rollers within the housing 12: one roller I 8a is proximate the housing inlet and one roller lSb is proximate the housing outlet, both disposed at one end of the housing 12. A larger third roller I Sc is provided at the opposite end of the housing 12. These rollers ISa, 18b, 18c help to tension the film strip 20 as its passes along the guide path in use. Each roller ISa. 18b, lSc is made from PVC and is rotatable by a drive shaft, facilitated by a ball bearing element.

The film strip dryer 10 is attached at one end of the housing 12 to a roller 34 within a tank 36 that is part of a film processing apparatus 38, which is best seen in Figure 2.

Each film processing apparatus 38 is approximately 12m long and 3m wide, and includes fifteen tanks 36. In each tank 36, one or more racks are provided that each support a roller 34, with each roller 34 being adapted to spiral film 20 across the breadth of the film processing apparatus 38.

The squeegees 22 are spaced apart from the process chemicals. This is beneficial because accessing the squeegees for maintenance and repair does not involve work in close proximity to the chemicals. Easy access to the squeegees 22 also means that production downtime, which is essentially lost production time, is reduced.

In use, each tank 36 contains liquid chemicals used for processing film. Film 20 passes from each tank 36 through the inlet 14 of the housing 12 to the plurality of squeegees 22, which wipe excess liquid and particulates from the two suitaces of the film 20. The film 20 is then dried by compressed air as it passes through the bank of air jets 24. before being wound around the third roller I 8c and directed towards the outlet 16 of the housing 12. Primarily, the compressed air blows any remaining residue from the surfaces of the film 20. Secondarily, the compressed air dries the film 20 due to a cooling effect. The line can be run faster than in the art, at speeds around l300fpm due to the reduced number of squeegees 22.

In Figure 3, an overview of the film processing process is indicated generally at 10.

Initially, the film 20 is immersed in a first 40 and then a second 42 developer tank containing industry standard developing solution. This solution transforms the latent image into a visible image. It develops the exposed silver halide in the film and reacts with cothur coupling agents in the film to create dye layers along with a silver image.

The film 20 then leaves the two developer tanks 40, 42 and passes through a film strip dryer l0a, as described earlier, to dry the film. Drying the film 20 substantially reduces the amount of residue, for example, process chemicals or by-products, from being carried over into subsequent tanks 36. After the first film strip dryer lOa, the film passes through a first acid stop tank 44 containing a dilute acid solution. This acid solution arrests the development of the film and removes the developer solution from the film surface. The film 20 then passes though a further film strip dryer I Gb before passing though a second acid stop tank 46. The film 20 is then dried by a further film strip dryer lOc.

The film 20 subsequently passes through a first acid stop wash 48 to substantially remove the dilute acid solution residue that remains from the stop tanks 44, 46. A further film strip dryer lOd is then used to dry the film 20 before it passes through a second acid stop wash 50 tank. The film 20 is then dried by a further film strip dryer I Oe.

The film 20 then passes through a bleach accelerator lank 52, which contains industry standard bleach accelerator solution, before being dried by a further strip film dryer lOf.

The film 20 subsequently passes through a bleach tank 54 containing an industry standard persulfate bleach solution, which converts the visible image formed by the developer solution into silver halide. The film 20 is then dried by a further film strip dryer lOg.

First 56, second 58 and third 60 bleach wash tanks follows the persulfate bleach tank 54. After each bleach wash tank is a further film strip dryer lOh, lOi, lOj respectively.

The film 20 subsequently passes through a first fixer tank 62 containing industry standard fixer solution. This solution makes the visible image permanent and insensitive to light. The film 20 is then dried by a further film strip dryer 10k before passing through a first fixer wash tank 64. The film 20 is then dried by a further film strip dryer 101. A second fixer tank 66 then foflows. The film 20 is then dried by a further film strip dryer 1 Urn.

Subsequently. the film passes through a combined wash and stabiliser tank 68. Finally the film is thorouglfly dried as it passes through a dry box 70 which is set at industry standard drying temperatures. Thereafter the dried film is wound on spools for subsequent projecdon or printing.

The film strip dryer 10 is beneficia' as it substantially reduces the amount of residue carried over into subsequent tanks and it maximises the amount of metallic silver that can be recovered from processing photographic or movie film. Squeegee elongate members 26 are easy to set and maintain, which reduces lost production time due to incorrectly set squeegees and inconvenient locations. The film strip dryer is suitable for use with black and white, and colour film.

Claims (1)

1. <claim-text>Claims 1. A film strip dryer comprising a housing having an inlet, an outlet and a guide path for a film strip, at least one resilient wiping member disposed adjacent to the guide path for wiping residue from a surface of the film strip, and a plurality of air jets directed at or towards the guide path for drying the film strip.</claim-text> <claim-text>2. A film strip dryer as claimed in claim 1, in which the at least one resilient member is disposed intermediate the inlet of the housing and the plurality of air jets along the guide path.</claim-text> <claim-text>3. A film strip dryer as claimed in claims 1 or 2, in which the at least one resilient member is provided as a cooperating pair. arranged for wiping opposing sides of the film strip.</claim-text> <claim-text>4. A film strip dryer as claimed in claim 3. in which three cooperating pairs of resilient members are provided.</claim-text> <claim-text>5. A film strip dryer as claimed in claim 4, in which the three cooperating pairs of resilient members are arranged adjacent one-another in a line along the guide path.</claim-text> <claim-text>6. A film strip dryer as claimed in any preceding claim, in which at least one base is provided for receiving the or each resilient member, said base being fixed relative to the guide path.</claim-text> <claim-text>7. A film strip dryer as claimed in claim 6, in which the or each base is oriented at an angle of approximately 6° from a plane that is parallel with the guide path.</claim-text> <claim-text>8. A film strip dryer as claimed in any preceding claim, in which an outlet of each air jet is angled for directing air towards film approaching along the guide path.</claim-text> <claim-text>9. A film strip dryer as claimed in any preceding claim, in which each of the plurality of air jets is oriented at an angle of approximately 45° from a plane that is parallel with the guide path.</claim-text> <claim-text>10. A film strip dryer as claimed in any preceding claim, in which the housing accommodates a plurality of guide rollers.</claim-text> <claim-text>11. A film strip dryer as claimed in claim 10, in which each guide roller is mounted on a shaft, there being a bearing element disposed intermediate the guide roller and the shaft.</claim-text> <claim-text>12. A film strip dryer as claimed in claim 11, in which the bearing element is a bail-race.</claim-text> <claim-text>13. A film strip dryer as claimed in claim 12, in which the balls of the ball-race are made from glass and the race of the ball-race is made from PEEK.</claim-text> <claim-text>14. A film strip dryer as claimed in any one of claims 11 to 13, in which the shaft is made from titanium.</claim-text> <claim-text>15. A film strip dryer as claimed in any preceding claim, in which the or each resilient member is made from a chemical resistant rubber.</claim-text> <claim-text>16. A film strip diyer as claimed in any one of claims 10 to 15, in which the guide rollers are made from PVC.</claim-text> <claim-text>17. A film strip dryer as claimed in any preceding claim, in which the housing is made from PVC.</claim-text> <claim-text>18. An apparatus for processing a film strip comprising a plurality of reservoirs for storing film processing chemicals, each reservoir having a film strip inlet, a film strip outlet, and a guide path therebetween along which a film strip travels in use, and a dryer unit bridging the guide path between the film strip outlet and film strip inlet of at least two of said reservoirs respectively.</claim-text> <claim-text>19. An apparatus as claimed in claim 17, in which the dryer unit is a film strip dryer as claimed in any one of claims I to 16.</claim-text> <claim-text>20. An apparatus according to claim 17 or 18. in which the dryer unit is removably attached to a surface of one of said reservoirs.</claim-text> <claim-text>21. A film strip dryer substantially as herein described with reference to and as illustrated in Figure I to 3 of the accompanying drawings.</claim-text>