This invention relates to drying apparatus and method for drying out books or documents or restoring them to a condition in which they can be handled.

Problems which can be encountered when attempting to dry out important documents are well known. Such documents may be the product of, for example, flood damage and the pages of the documents may be stuck together and deteriorating, and could have a substantial mould growth. Often the documents may be legal in nature and circumstances may be such that only the original documents will suffice. Where large numbers of documents are involved the restoration of same to a form in which they can be handled can pose a marathon task. Pages of the documents have to be separated by hand by various methods whilst still wet and laid out to dry. Large numbers of sheets of, for example A4 size, would occupy a considerable floor space area whilst drying and then there is the added problem of collating all the sheets together in the correct order once they are dry. It is estimated that only 1500 sheets of A4 paper would occupy an area of some 94 sg. metres when placed side-by-side and so it should be seen immediately that there tend to be considerable problems in drying out large numbers of pages simply because of the size of the task, the space involved and the final collating work required.

Additionally, there are the problems posed by mould and bacteria and the documents could even be harbouring spirochete micro organisms responsible for causing Weil's disease or the like.

Additional problems are posed in drying out of books or bound documents. If the books are dried in a heated room then, apart from severe wrinkling, the centre of each book remains comparatively wet when the outside cover of the book has dried out. Thus, in order to alleviate this problem, in the past the books would have been freeze-dried and allowed to dry out relatively slowly in a vacuum chamber. Such a process would normally take 2 or 3 weeks and require a considerable expenditure of energy since vacuum conditions have to be continuously maintained by a compressor in order to draw off the moisture which is continuously being evaporated off the wet books. Thus, such processes can be very slow and very expensive and often require a large vacuum chamber. The more books that are placed in the chamber the longer the drying time. Additionally, the vacuum equipment itself tends to be very expensive.

It is an object of the present invention to at least alleviate one or more of the aforementioned, or other, problems associated with the drying out of documents or restoration to a form in which they can be safely handled.

According to one aspect of the present invention there is provided a method of drying out or restoring books or documents, comprising:

(a) placing sheets of release paper or the like in between individual pages of the books or documents,

(b) arranging the books or documents in a stack, each book or document being sandwiched in between layers of a moisture absorbing medium such that moisture is drawn from the books into the moisture absorbing layers,

(c) inducing air to flow over the moisture absorbing layers in order to dry out said layers until the books/documents have dried out.

Preferably, the stack of books or documents is placed in a chamber and subjected to a circulating or recirculating airflow with moisture from the air being removed by dehumidification means. Usually, the air flowing over the moisture absorbing medium will be heated air and normally the temperature of the air will be a maximum of 50°C.

Usually the layers of heat absorbing medium will be separated from one another by spacers in order to allow a good airflow through the stack. The moisture absorbing medium may be any suitable material which is capable of withstanding the temperatures involved and capable of

withstanding being continuously wet and dried. Thus far, the Applicant has found unglazed ceramic tiles to be the most suitable medium for this application. In order to seemingly optimise the drying-out process the books may be sandwiched in between the layers of moisture absorbing medium under pressure and so a weight will usually in practice be placed on top of the stack of books or documents and the weight may be in the order of five to fifteen kilograms.

In practice, a plurality of stacks, (for example 4) of books or documents with the layers of moisture absorbing medium therebetween may be placed side-by-side in a special drying chamber and in any event, advantageously, the conditions for drying-out the books or documents may be balanced (more particularly where the books or documents are placed in recirculating air) such that the moisture extraction from the air takes place at a known rate, in order to prevent the books from drying out too quickly or too slowly. In one embodiment of the present invention, five air changes take place per hour in the space surrounding the books, and the books or documents are dried so that a 9% moisture content or less is retained in the paper, this being the usual moisture content. In particular mould dies below this moisture content level. Advantageously, the drying time involved for drying books and documents can be dramatically reduced by the above method from two or three weeks down

to as low as approximately 24 hours or less for books of half-an-inch thickness or less.

It is possible that the method could be modified so that the books or documents are not necessarily stacked one on top of the other, the important feature being that moisture from inside the book is drawn through to a layer of moisture absorbing medium which is dried and, therefore, more generally according to this aspect of the present invention there is provided a method of drying out or restoring a book or document, comprising:

(a) placing a moisture absorbing medium in contact with the book or document in order to draw moisture from the inner regions of same to the outside thereof and into the medium, and

(b) inducing air to flow over or around said medium in order to evaporate the moisture from the medium until the book or document is dry.

Further according to this aspect of the present invention there is provided apparatus adapted for drying out or restoring books or documents, comprising a drying- out chamber arranged to receive said books or documents, means, for example a fan, to induce an air flow through the chamber and around the books and dehumidification means to remove moisture from the air.

Preferably the apparatus will comprise a unit

housing the dehumidification means and the means inducing the airflow with air being recirculated around the unit and through the chamber. Preferably the dehumidification means is set to remove moisture from the air at a controlled balanced rate and could be adjusted to remove moisture from the air at a different selected rate.

The apparatus may also comprise layers of moisture absorbing medium in between which individual books or documents may be placed in close contact therewith. Said apparatus may also comprise spacer means for separating the layers of moisture absorbing material from one another and the moisture absorbing medium itself may be unglazed ceramic tile.

In order to utilise the drying chamber within the apparatus effectively, the spacing in between said layers should be as small as possible and the thickness of the layers should also be as small as possible. In practice, a thickness of layer of moisture absorbing medium of 6mm with a gap in between layers of 6mm has proved effective. The Applicant has successfully dried stacks of papers within the drying chamber in which approximately 3000 sheets of paper are contained within one stack.

From a second aspect of the present invention there is provided apparatus adapted to dry-out or restore individual sheets of paper, said apparatus comprising

conveyor means for conveying individual sheets of paper to a treatment location and then to a collection point after treatment, said apparatus being arranged to selectively control the removal of moisture from said sheets.

Further according to this second aspect of the present invention there is provided a method of drying out or restoring individual sheets of paper, comprising: conveying individual sheets of paper in succession to a treatment location on conveyor means,

selectively drying out said sheets of paper at the treatment location, and

Conveying the sheets to a collection point after treatment.

In one embodiment of the present invention the treatment location comprises an initial treatment station in which the paper is bombarded with germicidal ultraviolet light i.e. ultraviolet light emitted at a frequency sufficient to kill bacteria, mould, yeast and virus (for example ultraviolet radiation between 220 and 300 nanometers) and, preferably, the sheets of paper are then subjected to infrared radiation and, preferably, with an airflow being induced over the paper.

The conveyor means may comprise a lower conveyor belt, on which the individual sheets are placed, operating in co-operation with an upper conveyor belt, said upper conveyor belt preferably resting loosely on the paper as it is drawn into the apparatus.

Most preferably, the apparatus is arranged to treat the paper on each side thereof as it is conveyed through the apparatus and accordingly each side of the paper may be treated with ultravoilet radiation, infrared radiation and an airflow as it is conveyed through the apparatus.

Preferably, the material of the conveyor belt is a stainless steel mesh although any suitable material may be used. Most preferably, the apparatus has a speed control setting so that sheets of paper may be drawn through the apparatus on the conveyor means at a selectively controlled rate and, preferably, temperature control means is provided to closely control the temperature within the apparatus. In order to effect the temperature control, temperature control probes may be placed at suitable locations along the apparatus to give temperature read-outs and, in particular the apparatus may be provided with means to display the temperature at both the input and output ends of the apparatus.

One embodiment of the apparatus has upper and lower ultravoilet lamps comprising 24 tubes in each with two

pairs of fans located one behind the other in direction of movement of the paper through the apparatus, above the paper, and two pairs of fans located one behind the other in direction of movement of the paper, underneath the paper. Preferably, said pairs of fans are arranged to be operated selectively to induce a lateral airflow across the top and across the bottom of the paper and four infra-red units may be positioned above the paper with another four units being positioned therebelow as the paper is drawn through the apparatus.

Many advantages of the present invention will be apparent from the following description and drawings.

Embodiments of apparatus and method for drying-out or restoring books, documents or sheets of paper or the like will now be described with reference to the accompanying simplified diagrammatic drawings, by way of example only, in which:

FIGURE 1 shows apparatus for drying out stacks of books;

FIGURE 2 shows an embodiment of apparatus adapted for drying-out single sheets of paper;

FIGURE 3 shows the interior of the apparatus shown in

FIGURE 3, in more detail;

FIGURE 4 shows a diagrammatic sectional view through the apparatus of FIGURE 3 taken on line III-III; and

FIGURE 5 shows a detail of a control panel of the

apparatus shown in FIGURES 2 to 4.

FIGURE 1 of the drawings shows schematically apparatus 1, including an upper drying-out compartment or chamber 2 in which can be located approximately four book stacks 3 (only one shown in the FIGURE; a second book stack being represented by chain-dotted lines only). The apparatus includes a dehumidifier unit 4 housed in a lower compartment or chamber 5 and a high pressure fan heater 6 which acts to draw the air through the upper compartment 2 in the direction of the arrows and through the dehumidifier 4 in a recirculating fashion. The sides of the apparatus 1 are shaped (tapered) as shown in the drawings in order to encourage the circulation of air into the drying-out chamber 2 (via entrance aperture 2a) through the book stacks 3 and out through exit aperture 2b into the right-hand side chamber 7, through entrance aperture 5a into the lower chamber 5 housing the de¬ humidifier and through the dehumidifier 4 and out through exit aperture 5b into the opposite side chamber 8 housing the fan heater 6.

The capacity of the drying out chamber 2 is such that it will hold up to about 10,000 pages and, in practice, a weight of 10 to 15 kilograms may be placed on the top of each stack. Each stack 3 comprises books 9 sandwiched inbetween layers of moisture-absorbing medium 10 (in this instance unglazed ceramic tiles) which are in

close contact with the outside of each book 9 and pressed firmly against the associated book by the weight on top of the stack. As should be evident from FIGURE 1, the ceramic tiles 10 are spaced from one another by spacers 11 in order to allow the air circulating in the apparatus 1 to flow over and around the ceramic tiles in the stack.

The ceramic tiles 10 act to draw moisture from the interior of the book and the tiles themselves are dried by the heated air circulated by the fan heater 6. As the tiles are dried out, further moisture is extracted from the books 9 by the tiles 10 which are then dried out again by the heated air-flow passing over and around them. This process can be continued until the books 9 are dry and this can take as little as 24 hours for books of half an inch thickness. The drying time will depend to some extent on the thickness of books being dried out. The books 9 are dried out to about 9% moisture content in the paper and are uniformly dry throughout rather than being dried merely on the outside whilst remaining wet on the inside. Additionally, in practice, before arranging the books in the stack the individual pages are separated from one another by sheets of release paper (not shown) or the like (the release paper may be any known type and could be for example certain types of porous greaseproof paper). Said release paper acts to restrain the individual pages of the book from adhering to one another as they are dried out, and is removed once the book is

dry.

Where the wet books have been stored in a frozen state in practice they will be warmed first in a micro- wave before treatment can begin.

It is possible that the apparatus 1 could be used without the air being heated, the fan heater being replaced by a fan although of course the drying time would be longer. In practice the air is heated to a temperature which does not exceed 50°C and the removal of moisture from the recirculating air by the dehumidifier 4 takes place at a balanced rate so that the books 9 are dried uniformly throughout. In the apparatus 1 as shown there will be in the order of five air changes per hour in the drying out chamber 2. The Applicant has found that if there are less than five air changes per hour then, disadvantageously, a high density vapour layer can form around the unglazed tiles 10.

Using the aforedescribed apparatus 1 a large number of books can be dried simultaneously in a drying time which is extremely short in relation to that achieved with previous methods (i.e. with freeze-drying and vacuum drying processes can, as aforementioned, take 2 to 3 weeks). It is also feasible that the books could be arranged in some other configuration in the drying chamber and they could be arranged vertically with the

ceramic tiles arranged vertically if desired, although the ceramic tiles should be held under pressure in contact with the books in order to achieve best results. In order to stack as many books in the chamber as possible the ceramic tiles need to be made as thin as reasonably possible and spaced apart from one another by as small a gap as reasonably possible yet still provide efficient drying. The Applicant believes that a thickness of tile of approximately 6 mm and gap of 6 mm between the tiles represents somewhere near the optimum conditions for space saving and drying.

FIGURES 2 to 5 show apparatus 101 for drying out or restoring individual sheets of paper or the like. FIGURE 2 shows an exterior perspective view of the apparatus 101 whilst FIGURE 3 shows a view of the apparatus 101 with the outer casing c removed. The apparatus 101 includes conveyor means comprising upper and lower conveyor belts 102, 103. Individual sheets (not shown) of wet paper are laid out on the stainless steel wire mesh of the lower conveyor belt 103 and conveyed into the interior of the apparatus 101 to a treatment location and out of the apparatus in a dried-out restored state ready for collating. Such apparatus, therefore, greatly aids in the collating of restored documents since individual sheets of a file can be laid out onto the conveyor belt 103 whilst it is moving, and correctly collated as they are taken off the conveyor belt at the far end. Thus the

process is virtually automatic and pages of documents are treated continuously as they pass through the apparatus 101. The apparatus 101 has a control box 104, the function of which will be explained later on with reference to FIGURE 5 of the drawings, which shows details of a control panel 104a.

As the sheets of paper are conveyed through the apparatus 101 on the lower belt 103 the upper conveyor belt 102 rests loosely on the top of the paper so that the sheets of paper are held sandwiched in between the stainless steel wire mesh of the belts for treatment on either side thereof. FIGURE 3 shows front rollers 105 and 106 of the conveyor belts which are arranged to operate in unison.

As the sheets of paper pass through the apparatus 101 they are conveyed to an initial treatment station 107 where they are bombarded with germicidal ultraviolet radiation of a wavelength between 220 and 300 nanometers. The treatment is carried out by upper and lower ultraviolet radiation units each including 24 ultraviolet tubes of a known type. The ultra-violet tubes are located at about 10mm away from the paper. This treatment thus ensures that mould spores and the like are killed and it is preferred that the sheets of paper be subjected to this treatment first so that any mould, bacteria or virus present on the paper is not carried

further into the apparatus 101.

After the sheets of paper have been bombarded with ultra-violet radiation from both sides, they are then heated by infra-red radiation up to about 60 ^β C by infra¬ red units 108 arranged on each side of the paper as should be evident from FIGURE 3 of the drawings. The treatment equipment 107,108,109 located above the paper is identical to the equipment 107,108,109 located below it, with the equipment located below being a mirror image of that located above. The air heated by the infra-red units 108 is blown laterally across the paper and across the direction of the conveyor belt by fans 109 arranged in pairs in a direction along the belt above and below it as should be evident from FIGURE 3. Each pair of fans 109 is arranged on the central axis of the belt 103 and inbetween infra-red units 108 and circulates air more particularly as shown in FIGURE 4 of the drawings. The length of the conveyor belt run may be in the order of eight to twelve feet and the wire mesh of the conveyor belt is arranged to offer an 89% free surface area of the paper sheets for drying. The control box 104 provides for the apparatus to be controlled in various ways, for example, to control the speed of the belt which may be varied from approximately two feet a minute up to twenty feet a minute as well as temperature controls. In practice, it has been found that the presence of the infra-red lamps is extremely important in order to raise

the surface temperature of the paper to a sufficient level as it is passed through the apparatus 101.

A safety device is provided at the front of the apparatus 101 in the form of safety bar 110 so that if the bar is touched by a hand or the like, for example while placing paper with the belt 103, a micro-switch (not shown) is activated in order to switch off the motor - controlled conveyor belt drive.

Normally, a sheet of paper will take approximately thirty or forty seconds to pass through the apparatus 101, and once it has gone therethrough it is in a restored state. The apparatus can be provided with a range of temperature monitoring and sensing devices in order to ensure that the paper is not scorched as it is passed through the apparatus and to yield a desired moisture content in the restored document.

The apparatus 101 is arranged to operate on a three phase power supply. Temperature read-outs of the temperature at the front of the apparatus and at the back of the apparatus will normally be taken.

Although the apparatus 101 has been described in relation to a lateral air flow in a further version of the apparatus (not shown), hot air may be ducted into one end (e.g. the front end) of the apparatus and along the

length of the conveyor.

FIGURE 5 shows details of the particular controls used in this embodiment. The control panel 104a has upper read-out displays A and B giving digital read-outs of the temperature of the front and rear of the apparatus respectively. Proceeding down the display panel 104a the next control section is a usage monitor C noting the number of sheets passed through the apparatus. The next control section has an on/off switch D which shows whether the ultra-voilet germicidal lamps are on or off by way of the light emitting diode L. The next control section E is the fan and infra-red heater control block which provides for individual control of each of the pair of fans 109 by the switches El to E4 as well individual control of each of the eight infra-red heaters 108 by control buttons E5 to E12. Control section F has switch FI which switches on the conveyor belts (this is indicated by indicator lights L' ) and an analogue control knob F2 allows the speed of the conveyor belts 102,103 to be varied. Control G is an on/off power input switch to the apparatus 101.

It is to be understood that the scope of the present invention is not to be unduly limited by the particular choice of terminology and that a specific term may be replaced by any equivalent or generic term where sensible. Further it is to be understood that individual

features, method or functions related to the drying apparatus might be individually patentably inventive. In particular, any disclosure in this specification of a range for a variable or parameter shall be taken to include a disclosure of any selectable or derivable sub¬ range within that range and shall be taken to include a disclosure of any value for the variable or parameter lying within or at an end of the range. Thus, still further according to the present invention there is provided any automatic or semi-automatic apparatus for (usually sequentially) drying-out single sheets of paper. It is possible that the drying-out apparatus could be moved relative to the paper rather than the paper being conveyed through the apparatus. Additionally, it is possible that the apparatus may be computer-controlled.