Apparatus for binding stacks of flat parts

Abstract

An apparatus for binding stacks of flat parts comprising a fixing unit for fixing a stack consisting of a plurality of flat parts, a binder application device for applying liquid binder along a narrow face of the stack, and an irradiating unit for curing the binder by irradiating the binder on the narrow face of the stack, a light-emitting diode unit being used for irradiation.

Claims

1. An apparatus for binding stacks of flat parts comprising a plurality of flat parts, each flat part having opposing faces and a plurality of edges, a fixing unit for fixing a stack, the fixed stack comprising the plurality of flat parts arranged in face to face orientation with edges aligned to provide the stack with opposing faces and a plurality of stack edges extending between the faces, one of the stack edges being an unbound spine edge, a binder application device for heating a hot melt adhesive to a liquid state and applying the liquid hot melt adhesive along the unbound spine edge, the adhesive comprising photoinitiators which are activatable by exposure to radiation in a wavelength range of 320 nm to 410 nm to cure the adhesive along the unbound spine edge, an irradiating unit for curing the adhesive by irradiating the adhesive on the unbound spine edge, the irradiating unit comprising a plurality of semiconductor light-emitting diode units, wherein the light-emitting diode units exclusively emit radiation with a wavelength in a wavelength range of 320 nm to 410 nm.

2. The apparatus according to claim 1, wherein the light-emitting diode unit comprises at least one LED lighting panel.

3. The apparatus according to claim 1, wherein the light-emitting diode unit is arranged such that the binder is irradiated on an edge of the stack at a distance in a range from 1 to 10 cm.

4. The apparatus according to claim 1 wherein the stack of flat parts is bound only by cured binder.

5. A method for binding stacks of flat parts comprising the following steps providing a plurality of flat parts, each flat part having opposing faces and a plurality of edges fixing the plurality of flat parts into a stack, the stack comprising the plurality of flat parts arranged in face to face orientation with edges aligned, the flat part edges defining respective stack edges, one of the stack edges being an unbound spine edge, heating a radiation curing hot melt adhesive to a liquid form, applying the liquid, radiation crosslinking hot melt adhesive along the unbound spine, cooling the liquid hot melt adhesive to solid form on the spine edge, curing the hot melt adhesive by means of two-dimensional irradiation of the binder on the spine edge of the fixed stack, a light-emitting diode unit being used for irradiation; wherein the light-emitting diode unit exclusively emits radiation with a wavelength in a wavelength range of 320 nm to 410 nm.

6. An apparatus for binding stacks of flat parts comprising a plurality of flat parts, each flat part having opposing faces and a plurality of edges, a fixing unit for fixing a stack, the fixed stack comprising the plurality of flat parts arranged in face to face orientation with edges aligned to provide the stack with opposing faces and a plurality of stack edges extending between the faces, one of the stack edges being an unbound spine edge, a binder application device for heating a hot melt adhesive to a liquid state and applying the liquid hot melt adhesive along the unbound spine edge, the hot melt adhesive comprising photoinitiators with are activatable by exposure to radiation in a wavelength range of 320 nm to 410 nm to cure the adhesive along the unbound spine edge, wherein the binder application device comprises a heatable tank for melting the hot melt adhesive, an irradiating unit for curing the applied adhesive by irradiating the adhesive on the unbound spine edge, a light-emitting diode unit being used for irradiation, wherein the light-emitting diode unit exclusively emits radiation with a wavelength in a wavelength range of 320 nm to 410 nm.

Description

(1) A preferred exemplary embodiment of the present invention is described below, the sole FIG. 1 showing an apparatus for binding stacks of flat parts.

(2) In the schematic view shown in FIG. 1, the apparatus according to the invention is used as a bookbinding machine 10. Such bookbinding machines 10, such as for example perfect binders, are used to produce adhesively bound brochures or book blocks for hardcover books, the flat parts, for example folded sheets and/or individual sheets, assembled into a stack 14 being bound by application of an adhesive or binder onto a narrow face 15 or block spine. This narrow face 15 is frequently additionally machined, in particular by fanning, notching, sawing, milling, grinding, brushing and/or cleaning, prior to application of the binder.

(3) The bookbinding machine 10 shown comprises a fixing unit 20 for fixing the stack 14 of a plurality of flat parts. In the exemplary embodiment shown, the flat parts are stacked in known manner in a part of the bookbinding machine 10 which is not known. The prior art describes many solutions to this end. The stacks here comprise at least one narrow face 15 which is used for binding. In the present exemplary embodiment, a binder which is applied onto the narrow faces 15 of the stack 14 is used for this purpose. Curing of the binder is then provided in order to obtain brochures or book blocks from the stacks.

(4) The stacks 14 are conveyed by a conveyor belt-like feed means 11 for further machining and processing. The feed means 11 is arranged such that the stack 14 is guided from below to clamps 21 open at the bottom, the stacks 14 in turn being arranged on the feed means 11 such that said narrow face 15 is located opposite the feed means 11 and is thus uncovered.

(5) These clamps 21 are part of the fixing unit 20 and serve to fix the stack 14 for further machining and processing. The clamps 21 grip around the stack 14 in places and are constructed such that at least said narrow face 15 is uncovered. The clamps 21 are constructed such that a region of the side faces, adjacent to the narrow face 15, of a stack 14 is also uncovered, in order for example to apply binder in places thereto. The clamps 21 are fixedly connected to a conveyor system 12. Such conveyor systems 12 are known in the prior art. The part to which the clamps 21 are fastened may here in particular be of chain-like construction. By moving the chain-like part in a conveying direction 13, the stacks 14 fixed in the clamps 21 may be moved for further machining and processing in the bookbinding machine 10.

(6) A machining unit (not shown) may be provided for further machining, in particular of the narrow face 15. The narrow face 15 may here in particular be machined by fanning, notching, sawing, milling, grinding, brushing and/or cleaning prior to application of binder.

(7) The stacks 14 fixed in the clamps 21 are conveyed by moving the clamps 21 in the conveying direction 13 by means of the conveyor system 12 to a binder application device 30 located downstream of the fixing unit 20 or of the machining unit (not shown) for applying a liquid binder onto the narrow face 15. The binder application device 30 comprises an application unit 31 for applying the binder via a plurality of nozzles 32 and a tank 33 for the binder. It goes without saying that an individual nozzle may also be used for applying the binder. As an alternative to the nozzles 32, the binder may also be applied via one or more rollers or another suitable application element. In addition, the tank 33 may comprise a heating unit in particular in order to heat the binder, for example a hot-melt adhesive. The application unit 31 and the nozzles 32 and any hose connections in particular between the tank 33 and application unit 31 may furthermore be heatable, in order to heat the binder, for example a hot-melt adhesive. An in particular externally arranged storage tank (not shown) may also be provided, in which the binder, in particular a hot-melt adhesive, may be heated up to a premelting range.

(8) A hot-melt adhesive is preferably used as the binder in the bookbinding machine 10 shown. A hot-melt adhesive is taken to mean those adhesives which are solid at room temperature (25 C.), but melt at elevated temperature and are may be applied in the liquid state. Particularly suitable hot-melt adhesives are radiation-crosslinking adhesives. In particular, a suitable hot-melt adhesive is one which comprises photoinitiators which are activatable for curing under UVA radiation. A hot-melt adhesive is preferably used which comprises photoinitiators which are activatable under radiation with a wavelength in a range of 320 nm-410 nm. A hot-melt adhesive is particularly preferably used which comprises photoinitiators which are activatable under radiation with a wavelength in a wavelength range of 375 nm-405 nm.

(9) A suitable hot-melt adhesive manner preferably exhibits a viscosity in a range of 2500 mPa.Math.s to 15000 mPa.Math.s, particularly preferably in a range of 3000 mPa.Math.s to 8000 mPa.Math.s (measured to EN ISO 2555, Brookfield viscometer, at 130 C.) and a premelting range of 60 to 120. The application temperature of the adhesive is selected such that the adhesive may be applied in liquid or flowable form by the apparatus according to the invention, for example between 110 C. and 140 C. It is furthermore suitable for a such hot-melt adhesive to use a heatable glue reservoir or tank 33 which is capable of heating the hot-melt adhesive to at least 110 to 140, and said nozzles 32 in a range of 110 to 140. If, when gluing or applying binder to very thick stacks 14, the delivery capacity is no longer sufficient, an option may be provided for increasing the temperature by up to 50. Where cooling occurs after application of the adhesive layer, an initial adhesive bond is provided by solidification of the hot-melt adhesive. After irradiation, the final adhesive bond strength is achieved.

(10) In addition, the binder application device 30 may comprise an additional application option for a binder as side glue. A binder is here applied in places to the side faces, adjacent to the narrow face 15, of the stack 14 in order in a further step for example to bond a title page or an end sheet adhesively to the stack 14. This title page in particular serves to cover the adhesive strip, i.e. it conceals lateral visibility of the binder arranged on the narrow face 15. Binder is preferably applied via the application unit 31 both onto the narrow face 15 and onto said side faces via further nozzles (not shown). Different binders are preferably used for the side faces and the narrow face 15, in order to enable different curing and effective adhesive bonding for example of a front page after prior curing of the binder on the narrow face 15. It is, however, also conceivable to use the same binder for all the above-stated regions.

(11) The binder application device 30 furthermore comprises a stripper unit 34 with a stripper element 35. In the exemplary embodiment shown, this takes the form of a doctor blade. The stripper unit 34 ensures a uniform film thickness of binder on the narrow face 15. The stripper unit 34 may here be adjusted such that the thickness of the binder on the narrow face 15 may be adjusted to a film thickness in a range of 0.1 mm to 1.0 mm, preferably in a range of 0.3 mm to 0.6 mm.

(12) The stacks 14 provided with binder are then conveyed onwards by means of the clamps 21 in the conveying direction 13 to a curing unit or irradiating unit 40 for curing the binder by means of two-dimensional irradiation of the binder on the narrow face 15 of the stack 14. In the exemplary embodiment shown, the irradiating unit 40 comprises a light-emitting diode unit 41 for irradiation of the binder. The light-emitting diode unit 41 used emits radiation in a specific UV spectrum. The above-stated binder here comprises photoinitiators which are activatable under the radiation emitted by the light-emitting diode unit, in order to enable curing of the binder by means of the light-emitting diode unit 41. The radiation emitted by the light-emitting diode unit 41 is here within the UVA spectrum. Thanks to the use of such a light-emitting diode unit 41, it is in particular possible to dispense with elaborate shielding of said unit.

(13) The light-emitting diode unit 41 used comprises a plurality of light-emitting diodes 43 which exclusively emit radiation with a wavelength in a wavelength range of 320 nm-410 nm. A wavelength in a range from 375 nm-405 nm is here particularly preferred. It is here conceivable for the wavelength of the light-emitting diodes 43 to be adjustable, such that a wavelength from the above-stated wavelength ranges may be selected in order to adapt the radiation to the binder used. More precisely, the light-emitting diode unit 41 comprises at least one LED lighting panel 42 which in turn comprises a plurality of light-emitting diodes 43. The light-emitting diode unit 41 additionally comprises a control unit 45 for controlling the lighting panel 42 and electrical lines 44 via which the lighting panel 42 is connected to the control unit 45. The lighting panel furthermore comprises a reflecting arrangement (not shown) in order to deflect radiation which does not extend in the main emission direction, thus preferably in the direction of the narrow face 15. The light-emitting diodes 43 are here positioned in front of a reflecting surface of the reflecting arrangement, a direction of emission of a ray from the light-emitting diodes 43 extending contrary to the main emission direction of the lighting panel 42 and the ray from the light-emitting diodes 43 being deflected by reflection via the reflecting arrangement into the main emission direction of the lighting panel 42.

(14) The lighting panel 42 is here arranged such that the main radiation direction or main emission direction of the light-emitting diodes 43 is oriented in the direction of the narrow face 15 provided with binder. In addition, the lighting panel 42 and/or the entire light-emitting diode unit 41 may be displaced in height with regard to the stack 14 such that the distance of the light-emitting diodes 43 from the surface of the narrow face 15 provided with binder may be varied in order to set an ideal irradiation distance for curing the binder. Stacks 14 with different dimensions may accordingly also be processed using the bookbinding machine 10 shown. In the exemplary embodiment shown, the narrow face 15 is irradiated at a distance in a range of 1 cm to 10 cm, preferably in a range of 4 cm to 6 cm. The light-emitting diode unit 41 is preferably positioned such that the light-emitting diodes 43 are arranged at a distance of roughly 5 cm from a central binder surface on the narrow face 15.

(15) The binder is here cured using a lighting panel 42 with light-emitting diodes 43 which are capable of providing an intensity in a range of 100 mW/cm.sup.2 to 300 mW/cm.sup.2, preferably in a range of 180 mW/cm.sup.2 to 200 mW/cm.sup.2, particularly preferably an intensity of roughly 190 mW/cm.sup.2.

(16) The irradiating unit 40 furthermore comprises a first light barrier 46 and a second light barrier 47. Both light barriers 46, 47 are connected via electrical lines 44 to the control unit 45. The light barriers 46, 47 may, it goes without saying, also be replaced by other sensors known to a person skilled in the art which are suitable for detecting the presence a stack 14. When a stack 14 is moved by means of the clamp 21 and the conveyor system 12 towards the irradiating unit 40, it passes through a detection zone of the first light barrier 46. Said light barrier is arranged such that the stack 14 reaches the detection zone before reaching the irradiation field of the lighting panel 42. When a stack 14 reaches the detection zone of the first light barrier 46, the latter transmits a signal to the control unit 45, which thereupon switches on the lighting panel 42 for irradiation of the binder on the narrow face 15. The second light barrier 47 is arranged such that departure of the stack 14 from the irradiation field of the lighting panel 42 may be detected. The signal detected in this manner by the second light barrier 47 is in turn transmitted to the control unit 45, which switches off the lighting panel 42. It this manner, it is possible to ensure that the lighting panel 42 only emits radiation when there actually is a stack 14 in the irradiation field. In addition, the irradiating unit 40 may additionally or alternatively for example be connected directly via the control unit 45 to the conveyor system 12 in such a manner that for example details regarding the speed or position of the clamps 21 in the bookbinding machine 10 may be picked up, whereby switching of the lighting panel 42 for irradiation of the narrow face 15 may be enabled in addition or as an alternative to the light barriers 46, 47.

(17) It is also conceivable to use a delay circuit (not shown), for example as part of the control unit 45, which switches on the lighting panel 42 as soon as a stack 14 reaches or passes through the first light barrier 46. If, however, in a predetermined period, for example in a period selectable from a range of 1 s to 10 s, no further stack 14 is detected by the first light barrier 46 and/or the second light barrier 47, the control unit 45 switches the lighting panel 42 off. By means of such a delay circuit, it is in particular possible to provide an irradiating unit 40 which is usable and operable independently of the other modules of the bookbinding machine 10. Such a solution is advantageous in particular for retrofitting existing bookbinding machines 10 with a described irradiating unit 40, since the irradiating unit need not be connected to the control system of the bookbinding machine 10 as switching of the lighting panel 42 is exclusively effected by the detection of data and measured values carried out by the irradiating unit 40 itself.

(18) The bookbinding machine 10 furthermore comprises a measuring apparatus (not shown) for detecting the radiation dose input by the irradiating unit 40 via the lighting panel 42 onto the substrate, thus in particular the narrow face 15, or onto the binder on the narrow face 15. Said measuring apparatus may for example be part of the irradiating unit 40. Preferably, however, this measuring apparatus is connected to the conveyor system 12 and moves for example with the clamps 21. In this manner, the measuring apparatus passes through the irradiating unit 40 at the same speed as the stack 14, such that the dose may be accurately detected. The measuring apparatus may here be connected to the control unit 45 of irradiating unit 40 via a wireless data transmission means in order optionally to adapt the radiation dose or the speed of the conveyor system 12.

(19) The light-emitting diode unit 41 may additionally comprise further lighting panels 42 or the described lighting panel 42 may be constructed such that binder possibly applied in the binder application device as side glue onto regions of the side face of the stack 14 may be irradiated. To this end, it may also be appropriate to design the lighting panel 42 such that the light-emitting diodes 43 are arranged in the manner of a tunnel in the lengthwise direction with regard to the narrow face 15 of a stack 14 and in this manner are capable of irradiating both the narrow face 15 itself and the side faces.

(20) Using the bookbinding machine 10 shown, it is accordingly possible to provide a method for binding stacks 14 of flat parts, which method comprises the following steps: fixing a stack 14 consisting of a plurality of flat parts by means of a fixing unit 20, applying liquid binder along a narrow face 15 of the stack 14 by means of a binder application device 30, curing the binder by means of two-dimensional irradiation of the binder on the narrow face 15 of the stack 14 by means of an irradiating unit 40, a light-emitting diode unit 41 being used for irradiation.

(21) The irradiating unit 40 shown may also be used for retrofitting to an existing bookbinding machine 10. Known bookbinding machines 10 may often comprise means for curing which inter alia emit hazardous UVB and UVC radiation. In this case, an irradiating unit 40 shown in FIG. 1 may be used which replaces the existing means for curing. In this case too, the irradiating unit 40 for retrofitting to the bookbinding machine 10 comprises said light-emitting diode unit, preferably comprising a lighting panel 42. A lighting panel 42 used here may also comprise a described reflecting arrangement. In addition, the installed light-emitting diodes 43 preferably exhibit the above-described properties.

LIST OF REFERENCE NUMERALS

(22) 10 Bookbinding machine 11 Feed means 12 Conveyor system 13 Conveying direction 14 Stack 15 Narrow face 20 Fixing unit 21 Clamp 30 Binder application device 31 Application unit 32 Nozzles 33 Tank 34 Stripper unit 35 Stripper element 40 Irradiating unit 41 Light-emitting diode unit 42 LED lighting panel 43 LED 44 Electrical line 45 Control unit 46 First light barrier 47 Second light barrier