A method for lighttightly wrapping a stack of rectangular photographic light-sensitive sheets and for loading them by daylight in a lighttight cabinet

Abstract: A method for lighttightly wrapping a stack of rectangular photographic light-sensitive sheets and for loading them by daylight in a lighttight cabinet arranged for opening said wrapped stack to set the light-sensitive sheets free for further treatment, which comprises the steps of : wrapping said photographic light-sensitive sheets (50) in a wrapper formed by two congruent lighttight wrapping foils (51,52) and providing said wrapper with a first peripheral lighttight closure (53) spaced from the four edges of said stack of sheets, providing said wrapper with a clamping, second peripheral lighttight closure (54) located between said first one and the perimeter of said sheet stack, opening said first closure in daylight and loading said wrapped stack of sheets while still closed by said second closure in said opened cabinet, and lighttightly closing said cabinet, unclamping said second closure and removing the wrapping foil lying on top of said stack of sheets to set them free for further processing.

Description: BACKGROUND OF THE INVENTION Field of the invention. The present invention relates to a method for lighttightly wrapping a stack of photographic light-sensitive sheets and loading them by daylight in a lighttight cabinet, and to a photographic sheet stack lighttightly wrapped in back-folded wrapping foils. Description of the prior art. It is known to avoid the use of a darkroom for loading light-sensitive sheets into a sheet processor such as a cassette-loading apparatus, which automatically reloads radiographic film cassettes with a fresh film after an X-ray exposed film has been removed. These processors usually comprise a film supply magazine in the form of a drawer or the like that can be opened and into which a lighttightly wrapped stack of film is put in daylight conditions. Next, the drawer is closed and an appropriate mechanism cuts the wrapper so that it can be withdrawn from the film stack manually or automatically. One example of suchlike system is disclosed in US-A-4 909 389 relating to a film-sheet package for use in the magazine of a reloader for radiographic film cassettes. The film wrapper is in the form of a sleeve having a sealed flap for engagement by a winding mechanism. The end opposite to the sealed flap has an open flap folded inwardly to lighttightly close the package. Opening of the package occurs by winding the sealed flap by means of a winding mechanism, the film stack as such being withheld, so that the sleeve is stripped from the stack of film sheets. Another example of suchlike system is disclosed in Research Disclosure 22936 of May 1983, Havant, Hampshire, GB. While these systems work satisfactorily for sheetlike materials such as radiographic film, they are unsuited for larger and heavier sheets such as aluminium offset printing plates, that are image-wise exposed in a plate setter. The size of these plates can amount to 81 x 111 cm, and the weight of a stack of 30 of such plates can amount to 32 kgs. Attempts have been made to provide a package form that readily lends itself to daylight loading of such plates in a plate setter. However, because of the combined use of wood, cardboard and plastic, these package concepts are expensive and ecologically unacceptable. SUMMARY OF THE INVENTION. It is one object of the present invention to provide a method for lighttightly wrapping photographic light-sensitive sheets and loading them by daylight in a lighttight cabinet, in particular in a plate setter for the image-wise exposure of aluminium offset printing plates. It is a further object of the invention to provide a novel photographic sheet package which readily lends itself to daylight loading. Statements of the invention. In accordance with the present invention, a method comprising the steps set out in claim 1. The word "cabinet" stands in the present specification for any device which gives the photographic material some treatment. This can be the loading of a fresh film sheet in a radiographic film cassette, the imagewise exposure of film sheets or plates, as in an image setter, or simply the dispensing of film sheets removed from their package to another apparatus for exposing, developing, rinsing, etc. the sheets. The term "light-sensitive sheets" stands for photographic material on a paper, cellulose triacetate, polyester, or glass base in general but for aluminium lithographic printing plates in particular. The lighttight clamping of a sheet package can be done by means of two co-operating clamping surfaces that can be urged onto each other, but said clamping can also occur by means of the lateral walls of the base and the telescoping cover of a set-up box into which the package is packed. Suitable embodiments of the method according to the invention are as follows. The first lighttight closure of the wrapper is formed by a peelable seal, and the opening of the package occurs by peeling said seal. The first lighttight closure of the wrapper is formed by a non-peelable seal, and the opening of the package occurs by cutting at least one of two adjacent plies of the wrapping foil along a peripheral line located between said seal and the peripheral clamping zone. The first lighttight closure of the wrapper is formed by back-folded margins of the two wrapping foils. These margins can be backfolded to and temporarily withheld at a position where they remain beyond the reach of said clamping means. These back-folded margins can be withheld from spontaneous unfolding by strips of self-adhesive tape, which can function also as warranty seals. The present invention includes also a novel photographic sheet package. In accordance with the invention, suchlike photographic sheet package comprises a stack of light-sensitive sheets lighttightly wrapped between two lighttight wrapping foils of a size larger than that of the sheets, the flaps of said wrapping foils extending beyond the sheet package being backfolded on the package and being peripherally lighttightly closed near their edges, the size of the flaps being such as to allow in their unfolded condition lighttight clamping of the wrapping foils onto each other along a peripheral zone located within said peripheral closure and the perimeter of said sheet stack. According to a suitable embodiment of the invention, the distance between the peripheral closure and the perimeter of the stack of sheets amounts to at least four times the thickness of the stack. The peripheral closure of the wrapping foils can be formed by a heatseal of their corresponding edges, but also by margins of the flaps back-folded or back-rolled onto each other. Brief description of the drawings. The invention will be described hereinafter by way of example with reference to the accompanying drawings, wherein : Fig. 1 illustrates the principle of the present invention, Figs. 2a to 2g illustrate a first embodiment of the method according to the invention, Fig. 3 shows one embodiment of an etui for a sheet package, Figs. 4a to 4g illustrate a second embodiment of the inventive method, and Fig. 5 illustrates a third embodiment of a package according to the invention. Detailed description of the invention. The drawing of Fig. 1 diagrammatically illustrates the principle of the present invention. A stack of rectangular photographic light-sensitive film sheets 50 is lighttightly wrapped between two lighttight wrapping foils 51 and 52 that notably extend over the four lateral sides of the stack. The foils have a first, peripheral lighttight closure near their edges as indicated by arrows 53. This closure can be formed by heatseals, folded margins of the wrapping foils, etc. Next a second, clamping lighttight closure is produced that is located between the perimeter of the stack and the first closure, as indicated by arrows 54. This second closure is obtained by clamping the two wrapping foils between suitable clamping means. Then the wrapping foils are peripherally cut at a location between the first and second closure as diagrammatically shown by knives 56. The second closure takes over the function of the first one so that sheets 50 remain lighttightly protected although the first lighttight closure is in fact opened. The thus clamped package is now ready for movement into a lighttight device in which the clamping means will be opened and at least one (the upper) wrapping foil will be removed so that the sheets can be gripped one by one by a suitable dispensing mechanism for their feeding to a further destination. Referring to Figs. 2a to 2g, seven consecutive steps are shown illustrating the execution of a first embodiment of the method according to the invention. Fig. 2a shows a stack 10 of aluminium lithographic printing plates, which may be conventional printing plates that are blue-sensitive if their image-wise exposure will occur scanningwise in an imagesetter by means of a modulated laser, or red-sensitive if they are intended for being integrally exposed to an original image in an optical camera. Two congruent foils 11 and 12 of wrapping material are used to wrap the stack as shown in Fig. 2b. Foils 11 and 12 are air- and lighttight foils known in the art, such as blackpigmented polyethylene foils either of a single or a multiply composition. The foils have a heatsealable layer facing stack 10 and are heatsealed to each other near their edges to form a peripheral seal 13 whereby the wrapped sheets are air- and lighttightly enclosed, see Fig. 2b. The distance a separating seal 13 from the peripheral edge of stack 10 depends on the type of dispenser, the thickness of the stack, etc. A suitable value of a is between 4 and 10 times the thickness of the pack. Preferably, the air is removed up to a given degree from the package so that atmospheric pressure firmly keeps the plates together. Interleaving foils can optionally be provided to protect the light-sensitive surface of the plates. Next, package 9 is put in a box or etui forming a protection for the wrapped plates during common transport conditions. The four wrapping flaps are folded on top of the plate stack, as illustrated for the transverse flaps 14 and 15, and the pack is placed in an etui comprising a bottom 16, a peripheral frame 17 and a cover 18, see Fig. 2c. The etui being shown diagrammatically only, a more detailed embodiment is shown in Fig. 3 wherein 20 is a corrugated board cut and creased to form the package. After a package 9 of aluminium plates has been placed on bottom panel 23, transverse wall sections 24 and 25 are inwardly folded to constitute buffers shown in broken lines 26 and 27. The particular triangular design of the buffers near their corners prevents the corners of the plates from cutting the wrapping material since there is no anvil to cut on. Next, longitudinal wall sections 28 and 29 are folded over the plate stack and the buffers to close the package and keep it that way by means of a suitable adhesive, a self-adhesive tape or the like. An etui as described hereinbefore is disclosed in Research Disclosure 34303 of November 1992. The etui thus described is opened, the plate pack is taken out and the flaps are unfolded as shown in Fig. 2d. Then the pack is placed in a clamping arrangement allowing the wrapper to be cut open (see Fig. 2e). This arrangement can comprise a tray-like base 30 and a cover 31. Tray and cover can be separate elements, one embodiment being illustrated in Figs. 5c to f in the form of a telescope-type box, but they can also be parts of a mechanism arranged in a drawer or the like making part of a lighttight device which in the open position allows the package to be placed in tray 30, mounted e.g. on the bottom of the drawer, cover 31 to be placed in lighttight contact on the tray while withheld by suitable clamping means as shown diagrammatically by clamps 32 in dashed lines in Fig. 2f, and then the outwardly extending portion of the wrapper to be cut, as represented diagrammatically by knife 34, and next removed. Lighttight engagement of cover 31 with tray 30 can be improved by a labyrinth-like lock 33 in the form of a groove into which fits the top of the upstanding side wall of the tray. Tray 30 need not necessarily be a base with upstanding metal walls as shown, but may in its simplest form even be a rectangular framework, open on top and bottom, the four upstanding walls of which co-operate with cover 31. In a similar way, the function of cover 31 can likewise be performed by a frame-like structure co-operating with the bottom frame to provide uninterrupted clamping surfaces. The drawer is then lighttightly closed and appropriate means in lighttight device 35 shown in broken lines (see Fig. 2g), open the clamps, lift cover 31, remove the upper wrapper foil 11, and take out the printing plates one by one. Removal of wrapping foil 11 can occur by suction cups or the like but said foil can also have been previously attached with its extending margins to cover 31 by means of strips of self-adhesive tape, by clamps, etc., and thus become removed simultaneously with the cover. The position of the package for its opening is horizontal in Figs. 2e to g, but it is clear that it may be slanting as well, e.g. tilted 10 angular degrees with respect to the vertical. This has the advantage that the foot print of the device can be considerably reduced and that removal of the upper wrapping foil 11 can occur occasionally by gravity. The use of gravity may likewise be interesting in case the printing plates are separated from each other by interleaving foils. Removal of a plate then causes the thin interleaving foil covering the next plate to slightly buckle by the air withdrawal whereby it can fall over the bottom edge of the tray into a foil collector. Removal of the plates from the stack can occur by suction cups, friction fingers or rollers, fingers engaging perforations in one of the margins of the sheets, as known in the art. Figs. 4a to 4g show a second embodiment of the method according to the invention which differs from the first one by the way in which the wrapper is lighttightly closed. A plate stack 10 is enclosed between two lighttight wrapping foils 40, 41 that may be similar to foils 11, 12 except for a thermoplastic sealing layer which is not needed in the present embodiment. Margins of the extending flaps of the wrapper are backfolded or -rolled in small folds 43 which can be temporarily fixed to the wrapper by means of some strips of self-adhesive tape 45 so as not to unroll spontaneously. Closed flaps 14 and 15 (only two of the four flaps being shown) are folded over the stack, and then the package is packed in a holder (see Fig. 4c), which can be an etui as described hereinbefore. The user of the plates removes plate package 9 from the etui, unfolds flaps 14 and 15, see Fig. 4d, and puts the package in a clamping arrangement 30, 31 that may be similar to the one shown in Fig. 2e. Removal of sealing strips 45 allows unrolling of folds 43 and this opens the wrapper the contents of which, however, remains lighttight because of the closure produced by cover 31 and base 30. The package thus prepared is then moved into a lighttight device 35 as described with reference to Fig. 2g. Fig. 5 illustrates another embodiment of the present invention. A stack of printing plates 10 is lighttightly wrapped between two foils 40, 41 with folded marginal portions 43 as described hereinbefore and put in a full telescope set-up box having a base 44, and a cover 46. This box is a package made of non-bending boxboard, having a thickness assuring sufficient rigidity to the loaded box. The box forms a shipping carton for the sheet pack and can be sealed by a warranty label. The user opens the box, unfolds the four flaps of the plate package (see Fig. 5d for flaps 14 and 15), and next replaces cover 46 on base 44 (see Fig. 5e). The flaps of the wrapping foils deflected by the co-operating adjacent lateral walls of the box provide an efficient light lock for the contents of the box. Then backfolded margins 43 of the wrapping foils are unrolled after locking tapes 45 have been removed (see Fig. 5f), and the plate pack thus prepared is put in device 35 of a type as described hereinbefore but which has appropriate means for lifting cover 46 from base 44. Opening the package has been illustrated in the present drawings as occurring by means of a simple knife 34, 56 for the sake of simplicity. In practice, safety tools or systems will be used for opening a wrapper, such as a knife-like envelope opener, scissors, a tearstrip, etc.

Claims: A method for lighttightly wrapping a stack of rectangular photographic light-sensitive sheets, thus forming a package, and for loading the wrapped stack by daylight in a lighttight cabinet arranged for opening said wrapped stack to set the light-sensitive sheets free for further treatment, characterised by the steps of: wrapping said light-sensitive sheets (10,50) in a wrapper formed by two congruent lighttight wrapping foils (11,40,51, 12,41,52) and providing said wrapper with a first peripheral lighttight closure (53) spaced from the four edges of said stack of sheets, providing said wrapper with a clamping, second peripheral lighttight closure (54) located between said first one and the perimeter of said sheet stack, opening said first closure in daylight and loading said wrapped stack of sheets while still closed by said second closure in said opened cabinet, and lighttightly closing said cabinet, unclamping said second closure and removing the first wrapping foil (11,40,51) lying on top of said stack of sheets while leaving the stack of sheets lying on the second wrapping foil (12,41,52), thus setting said stack of sheets free for further processing. A method according to claim 1, wherein said first lighttight closure of the wrapper is formed by a peelable seal, and said opening of the package occurs by peeling said seal. A method according to claim 1, wherein said first lighttight closure of the wrapper is formed by a non-peelable seal (13), and said opening of the package occurs by cutting (34) at least one (11) of said two wrapping foils (11,12) along a peripheral line located between said seal and said clamping second peripheral closure. A method according to claim 3, comprising cutting said two wrapping foils (11,12) simultaneously. A method according to claim 1, wherein said first lighttight closure of the wrapper is formed by back-folded margins (43) of said two wrapping foils (40,41). A method according to claim 5, wherein said margins (43) are backfolded and temporarily withheld at a position where they remain beyond the reach of said clamping second peripheral closure. A method according to claim 6, wherein said back-folded margins (43) are withheld from spontaneous unfolding by tabs (45). A method according to claim 7, wherein said tabs are strips of self-adhesive tape. A method according to any of claims 1 to 8, wherein said clamping second peripheral closure is produced by two co-operating peripheral clamping surfaces that can be urged onto each other. A method according to claim 9, wherein one of said clamping surfaces belongs to an open holder (30) into which said package can fit, and the other one belongs to a cover (31) for closing such holder. A method according to claim 9, wherein said clamping surfaces provide a labyrinth-like closure (33). A method according to any of claims 1 to 8, wherein said clamping second peripheral closure is formed by the co-operating lateral walls of the base (44) and the lid (46) of a telescope type set-up box. A method according to claim 12, wherein said set-up box forms a shipping carton for the photographic sheets. A method according to any of claims 1 to 13, further comprising the step of locating said stack of sheets in a tilted position in said cabinet to remove by gravity said first wrapping foil (11,40,51) lying on top of said stack of sheets. A method according to any of claims 1 to 14, wherein said first peripheral closure is airtight. A method according to claim 15, wherein said sheet package has a low-air content. A method according to any of claims 1 to 16, wherein said photographic sheets are aluminium lithographic printing plates. A photographic sheet package comprising a stack of light-sensitive sheets (10), lighttightly wrapped between two lighttight wrapping foils (40,41) of a size larger than that of the sheets, the flaps (47) of said wrapping foils extending beyond the sheet package, being backfolded on the package and being peripherally lighttightly closed near their edges, the size of the flaps being such as to allow in their unfolded condition lighttight clamping of the wrapping foils onto each other along a peripheral zone located within said peripheral closure and the perimeter of said sheet stack. A photographic sheet package according to claim 18, wherein the distance (a) between the peripheral closure and the perimeter of the stack of sheets is at least four times the thickness of the stack of sheets. A photographic sheet package according to claim 18, wherein the peripheral lighttight closure of the wrapping foils is formed by a heatseal (13) of their corresponding edges. A photographic sheet package according to claim 20, wherein the lighttight closure of said wrapping foils is formed by margins (43) of the flaps (47) back-folded onto each other. A photographic sheet package according to claim 19, which is packed in a telescope type set-up box, the distance between said lighttight closure and the perimeter of the stack of sheets being sufficiently large to allow said closure to remain outside of the box if the flaps are unfolded, and wherein the cover (46) is fitted over the base (44) of the box, thus deflecting the flaps between the lateral walls of the base and the cover of the box.

Inventors: LIEVEN DIRX, LIEVEN, DIRX, Lieven, Dirx, c/o Agfa-Gevaert N.V.
Applicants: AGFA GEVAERT NV, AGFA-GEVAERT N.V.
Application year: 1995
Main classification: G03C3
IPC codes: G03C3