Electron beam emitting device for sterilizing a web of packaging material

Abstract

There is described an electron beam emitting device (11) comprising: a generation member (12) configured to be supplied with electrical energy and to emit an electron beam; a hollow casing (14) housing at least the generation member (12), the casing (14) extending along a longitudinal axis (A) and including an aperture (14a) at one axial end portion (16) thereof; and a thermally and / or electrically insulating cover (17) coupled with the casing (14) at said axial end portion (16) for closing said aperture (14a); the emitting device (11) further includes a cooling device (18) configured for cooling the insulating cover (17), the cooling device (18) comprising a hollow flange (19) coupled with the casing (14) at said axial end portion (16), extending at least in part around the longitudinal axis (A) and delimiting, together with an outer surface (16a) of the axial end portion (16), an inner chamber (20) which defines a flow channel for a cooling medium; the flange (19) is welded to said casing (14) at said axial end portion (16).

Description

[0001] ELECTRON BEAM EMITTING DEVICE FOR STERILIZING A WEB OF PACKAGING MATERIAL

[0002] TECHNICAL FIELD

[0003] The present invention relates to an electron beam emitting device configured to sterilize a web of packaging material for the production of packages containing a pourable product, preferably a pourable food product .

[0004] BACKGROUND ART

[0005] As it is generally known, many pourable food products, such as fruit juice, UHT (ultra-high temperature-treated) milk, wine, tomato sauce, etc . , are sold in packages made of sterilized packaging material .

[0006] A typical example is the parallelepiped-shaped package for pourable food products known as Tetra Brik Aseptic (registered trademark) , which is made by folding and sealing a laminated web of packaging material .

[0007] The packaging material has a multilayer structure comprising a base layer, e . g. made of paper, covered on both sides with layers of heat-seal plastic material, e . g. polyethylene .

[0008] In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of oxygen-barrier material, e . g. an aluminum foil, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product .

[0009] Packages of this sort are normally produced on fully automatic packaging machines, which form and fill the packages starting from a multilayer web of packaging material .

[0010] In particular, according to a non-limiting example of a packaging machine, a continuous tube is formed from the web of packaging material which is initially wound in a reel and fed through a plurality of unwinding rollers .

[0011] The web of packaging material is typically maintained in a closed, sterile environment, and, while advanced by the aforementioned unwinding rollers, is folded to form the tube by means of a known web folding unit and then sealed longitudinally.

[0012] In order to perform the package forming operations, the tube is continuously fed along a straight vertical direction, is filled with the sterilized food product from above and is formed, sealed and subsequently cut along equally spaced transversal cross-sections extending along a direction orthogonal to the vertical direction, according to a manner known and not described in detail .

[0013] So-called pillow packs are obtained thereby, whichhave a longitudinal sealing band, a top transversal sealing band and a bottom transversal sealing band. The pillow packs are then cut at the cross-sections to be separated from one another and directed to a folding unit of the packaging machine for the final folding thereof .

[0014] The finished packages are thereby obtained.

[0015] It is known in the field the need for sterilizing the web of packaging material before the forming and filling operations, with the aim to extend the shelf-life of the products being packed.

[0016] According to a first configuration, the web is sterilized chemically. In particular, the web is sterilized by applying a chemical sterilizing agent, such as hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e . g. evaporated by heating.

[0017] According to a second configuration, the advancing web is irradiated with electron beams emitted by an electron beam emitting device, at a sterilization station .

[0018] A typical electron beam emitting device includes an electron generation member, usually defined by a filament, which is connected to a (high) voltage power supply. As a result of being powered, the generation member undergoes a so-called thermionic emission wherebystarts to emit electrons .

[0019] The emitting device also includes two electrode members, that is a cathode member and an anode member .

[0020] The electrode members are configured to focus the generated electrons towards a target, i . e . the web at the sterilization station.

[0021] In detail, the emitting device comprises a bent metal sheet extending along a longitudinal axis, normally having a U-shaped cross section, and therefore defining a sort of tubular body open upwards .

[0022] In greater detail, the bent sheet includes an upper aperture extending axially, thereby defining the U-shaped cross section.

[0023] The generation filament is arranged within the bent sheet and extends in the axial direction. In particular, the bent sheet partially surrounds the generation filament, so as to protect it, and so as to deviate the generated electrons towards the upper aperture .

[0024] Accordingly, the bent sheet defines the cathode member and therefore is electrically charged (negatively) . In this way, the electrons emitted by the filament interact with the electric field defined by the bent sheet / cathode member, and are deviated towards the upper aperture .

[0025] The emitting device further includes an outer casingdefined by a tubular body extending along the longitudinal axis and surrounding the bent sheet .

[0026] The outer casing includes an elongated opening extending axially and facing, on one side, the sterilization station, and, on the other side, the upper aperture of the bent sheet . The elongated opening defines an exit window for the electron beams .

[0027] The anode member is arranged at the exit window, in order to attract the electrons thereat, thereby focusing the electrons into an electron beam.

[0028] Accordingly, the anode member is electrically charged (positively) .

[0029] The emitting device further comprises a thermally and / or electrically insulating cover coupled to the casing at said one axial end thereof for closing said aperture .

[0030] The need is known for cooling such insulating cover . To this end, the emitting device includes a cooling device which comprises a concave flange coupled in a removable manner to the casing at said axial end thereof .

[0031] In detail, the concave flange has an annular shape and presents an inner annular cavity.

[0032] The concave flange is coupled with the casing by means of removable fastening elements, such as bolts orscrews .

[0033] When coupled to the casing, the concave flange internally delimits, together with an outer annular surface of the casing (at said axial end) , an annular chamber .

[0034] That is, the portion of the outer annular surface radially facing the concave flange closes the cavity of this latter, thereby delimiting the annular chamber .

[0035] The annular chamber defines a flow channel for a cooling medium, usually a cooling liquid, for flowing therethrough, thereby cooling the insulating cover through the casing.

[0036] The cooling device further includes a pair of sealing members, such as o-rings, arranged on both axial sides of the annular chamber, into specific annular seats obtained in the concave flange at opposite respective sides of the annular chamber .

[0037] The sealing members are pressed in abutment against the outer annular surface of the casing for preventing the cooling medium to exit the annular chamber .

[0038] Although the electron beam emitting devices of the aforementioned type work satisfyingly well, the Applicant has observed that they are still open for further improvement, in particular as per the reduction of the components involved, as per the increase in their lifespanand as per a decrease in the assembly and maintenance time and costs .

[0039] DISCLOSURE OF INVENTION

[0040] It is therefore an obj ect of the present invention to provide an electron beam emitting device which is designed to meet at least one of the above-mentioned needs in a straightforward and low-cost manner.

[0041] This obj ect is achieved by an electron beam emitting device as claimed in the appended independent claim 1 . Preferred embodiments of the present invention are laid down in the appended dependent claims .

[0042] BRIEF DESCRIPTION OF THE DRAWINGS

[0043] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

[0044] Figure 1 is a schematic perspective view, with parts removed for clarity, of a packaging machine comprising an electron beam emitting device according to the present invention;

[0045] Figure 2 is a larger-scale, partially sectioned view, with parts removed for clarity, of the emitting device ;

[0046] Figure 3 is a larger-scale detail of the sectioned view of Figure 2 ; and

[0047] Figure 4 is a larger-scale perspective view, withparts removed for clarity, of the emitting device .

[0048] BEST MODE FOR CARRYING OUT THE INVENTION

[0049] With reference to Figure 1, number 1 indicates as a whole a non-limiting example of a packaging machine configured to produce sealed packages 2 containing a pourable product, preferably a pourable food product such as pasteurized or UHT milk, water, fruit juice, wine, peas, beans, etc .

[0050] In detail, packaging machine 1 is configured to form, seal and fold packages 2 starting from a web 4 of packaging material, which is e . g. initially wound in a reel 4a, and then folded into a tube 3 of packaging material .

[0051] As shown in Figure 1, packaging machine 1 comprises : - conveying means configured to advance web 4 along an advancement path P;

[0052] - a tube folding device 5 configured to progressively fold web 4 into a tube 3;

[0053] - a sealing element 40 for longitudinally seal tube 3, in a manner known and not described in detail;

[0054] - a filling device 7 for filling tube 3 ( from above) with the pourable product;

[0055] - a forming and sealing unit 6 configured to form tube 3 and seal tube 3 along successive transversal crosssections thereof in order to obtain a sequence of pillowpacks 2a, in a manner known and not described in detail; an isolation chamber 8 internally defining an environment containing a controlled atmosphere, in particular sterile and / or aseptic gas, preferably sterile and / or aseptic air, and housing at least the forming and sealing unit 6, the tube folding device 5, the sealing element 40 and at least part of the filling device 7 ;

[0056] a folding device (not shown) configured to sequentially fold packs 2a in order to obtain a plurality of sealed packages 2.

[0057] Tube folding device 5 and sealing element 40 define together a tube forming unit .

[0058] Preferably, forming and sealing unit 6 has an axis X along which tube 3 is fed, in use .

[0059] Axis X is parallel to a straight direction, which preferably is a straight vertical direction.

[0060] Hence, in use, tube 3 is fed along axis X, downwards, and while being filled from above is formed and sealed by forming and sealing unit 6.

[0061] More specifically, tube 3 is drawn (downwards) along axis X by forming and sealing unit 6 in a known manner .

[0062] In this way, a plurality of pillow packs 2a are obtained .

[0063] In light of the above, packaging machine 1 is configured to form and seal a plurality of pillow packs 2acontaining the pourable product starting from web 4 and tube 3 and then to fold the pillow packs 2a for obtaining the aforementioned formed, sealed and folded packages 2 containing the pourable product .

[0064] As schematized in Figure 1, packaging machine 1 further comprises a sterilization unit 10 arranged at a sterilization station S along advancement path P, in a position upstream of tube folding device 5 and configured to perform a sterilizing treatment on web 4.

[0065] In particular, sterilization unit 10 is configured to sterilize web 4 by means of electron beam irradiation.

[0066] To this end, sterilization unit 10 comprises at least one electron beam emitting device 11.

[0067] In detail, sterilization unit 10 comprises a pair of emitting devices 11 (only one shown in Figure 1 ) , arranged at opposite sides of web 4 at sterilization station S, for irradiating web 4 from both sides in order to obtain the desired level of sterilization.

[0068] In light of the above, each emitting device 11 is configured to sterilize the packaging material for the production of packages 2.

[0069] Reference will be made in the following to a single emitting device 11. However, the structural and functional features described therefor are equally applicable to the other emitting device 11.Emitting device 11 comprises a generation member 12 configured to be supplied with electrical energy and to convert the electrical energy into an electron beam.

[0070] In particular, emitting device 11 includes an electron beam generation circuit, and generation member 12 is part of such generation circuit .

[0071] In detail, generation member 12 comprises a filament of electrically conductive material .

[0072] In greater detail, generation member 12 comprises a filament of tungsten.

[0073] In use, generation member 12 is supplied with electrical energy ( from a known power supply source) and heats up due to Joule effect . When generation member 12 reaches a predetermined temperature, a so-called thermionic emission establishes . Thermionic emission is the liberation of charged particles from a hot electrode whose thermal energy gives some particles enough kinetic energy to escape the electrode surface .

[0074] In this way, the electron beam is generated.

[0075] Accordingly, generation member 12 is electrically connected to the power source .

[0076] Emitting device 11 further comprises a cathode member 40 and an anode member 13 configured to be electrically charged with opposite electric charge,respectively, for focusing the (generated) electron beam towards a target to be sterilized, i . e . towards the web 4 passing through sterilization station S .

[0077] More precisely, emitting device 11 comprises an inner casing 40 which is made of electrically conductive material, such as aluminum, and is defined by a tubular body surrounding generation member 12.

[0078] More in detail, inner casing 40 internally defines (and delimits) a generation chamber 40a housing the generation member 13.

[0079] Preferably, generation chamber 40a is a vacuum chamber, i . e . is an environment maintained under vacuum conditions .

[0080] Inner casing 40 has an aperture (or slit) which allows chamber 40a to open upwards .

[0081] In light of the above, inner casing 40 extends around generation member 12, with the exception of its portion provided with such aperture .

[0082] Inner casing 40 defines the aforementioned cathode member . Hence, inner casing 40 is electrically charged, with a negative electric charge . In this way, in use, the electrons emitted by the generation member 12 are deflected towards the aperture .

[0083] Emitting device 11 further comprises an outer casing 14 which internally defines a vacuum chamber 15 and housesthe inner casing 40 and, therefore, the generation member 12 .

[0084] As it is known, the vacuum is needed to ensure the generation and a smooth travel of the electron beam from the cathode to the anode and outwards .

[0085] In detail, inner casing 40 is arranged within outer casing 14 .

[0086] Preferably, casing 14 has a tubular shape, extends along a longitudinal axis A and includes an aperture 14a at one axial end portion 16 thereof .

[0087] In particular, aperture 14a serves for allowing, during assembly of emitting device 11, the insertion of at least the generation member 12 and preferably of other parts of the emitting device 11, such as inner casing 40, within vacuum chamber 15.

[0088] Casing 14 further includes an elongated slit (not shown) extending axially and facing the sterilization station S . The elongated slit defines an exit window for allowing the electron beam to exit from emitting device 11. Opportunely, such elongated slit is aligned with the aperture of the inner casing 40.

[0089] In practice, the elongated slit is superimposed on the aperture of the inner casing 40, along the radial direction (with respect to axis A) .

[0090] Opportunely, anode member 13 (which is known per seand will not be described in detail) is arranged at the elongated slit for attracting the electron beam thereat and directioning the electron beam towards said target .

[0091] Accordingly, anode member 13 is arranged between the generation member 12 and the sterilization station S . In this way, the generated electron beam is directed and focused towards sterilization station S, and thus towards the web 4 to be sterilized.

[0092] Emitting device 11 further includes a thermally and / or electrically insulating cover 17 coupled with casing 14 at axial end portion 16 for closing aperture 14a .

[0093] In particular, cover 17 is internally coupled with an inner surface 16b of axial end portion 16.

[0094] Preferably cover 17 is made of a ceramic material . In use, high temperatures are reached within casing 14. Hence, a thermal insulation is needed to prevent heat to transmit outwards .

[0095] The need is known for cooling cover 17.

[0096] To this end, emitting device 11 further comprises a cooling device 18 configured to cool cover 17.

[0097] Cooling device 18 comprises a hollow flange 19 which is coupled with casing 14 at axial end portion 16, which extends (at least in part) around axis A, and which delimits, together with an outer surface 16a of axial endportion 16, an inner chamber 20 defining a flow channel for a cooling medium to flow therethrough.

[0098] In particular, flange 19 presents a concave inner cavity .

[0099] In practice, when coupled to casing 14, flange 19 internally delimits, together with outer surface 16a, inner chamber 20. That is, the portion of outer surface 16a radially facing flange 19 closes the inner cavity of this latter, thereby delimiting inner chamber 20.

[0100] Preferably, flange 19 is annular about axis A. Hence, inner chamber 20 extends annularly about axis A.

[0101] Opportunely, flange 19 includes an inlet opening (not shown) , through which the cooling medium (such as water) is fed to inner chamber 20, and an outlet opening (not shown) through which the cooling medium exits from inner chamber 20, after having exchanged heat with cover 17 through axial end portion 16.

[0102] According to an important aspect of the present disclosure, flange 19 is welded to casing 14 at axial end portion 16.

[0103] In particular, flange 19 is welded to casing 14 by means of at least one welding seam 21a, 21b extending in a circumferential direction about axis A.

[0104] More in particular, given the annular configuration of flange 19, the at least one welding seam 21a, 21bextends annularly about axis A.

[0105] As visible in detail in Figure 3, flange 19 includes a main body 22, a first protrusion 23 extending radially from main body 22 and a second protrusion 24 extending radially from main body 22.

[0106] In detail, first protrusion 23 and second protrusion 24 extend from main body 22 in a cantilevered manner towards axial end portion 16, up to abut against the latter .

[0107] Hence, main body 22 is arranged in a position radially more external than first protrusion 23 and second protrusion 24, with respect to axis A.

[0108] First protrusion 23 and second protrusion 24 are arranged at opposite lateral sides of inner chamber 20 and delimit inner chamber 20 in the axial direction.

[0109] An inner surface 22a of main body 22, which is axially interposed between first protrusion 23 and second protrusion 24, delimits inner chamber 20 in the radial direction .

[0110] According to an aspect of the present disclosure, flange 19 is welded to casing 14, and particularly to axial end portion 16, by means of a first welding seam 21a connecting first protrusion 23 to casing 14, and a second welding seam 21b connecting second protrusion 24 to casing 14 .Conveniently, both first welding seam 21a and second welding seam 21b extend annularly about axis A.

[0111] In light of the above, flange 19 of cooling device 18 is rigidly coupled with casing 14, at the axial end portion 16 thereof, in a non-removable manner .

[0112] Thanks to the welded coupling of flange 19 with casing 14, cooling device 18 (and hence emitting device 11 ) entails a reduced number of components, with respect to the known configurations .

[0113] In fact, due to the presence of the welding seams 21a, 21b, there is no need for any o-ring, and in fact no o-ring or other sealing element is provided in cooling device 18 according to the invention. This results in a reduction of wear and in a significant reduction of the risk of leakage due to a possible fault of the o-rings . Moreover, the risk of human error during assembly of emitting device 11 is highly reduced.

[0114] Furthermore, there is no need for any fastening element to couple flange 19 to casing 14, nor for any auxiliary coupling flange to support such fastening elements . This results in a significant reduction of components, and therefore in an increase of the overall reliability of emitting device 11 and in a further reduced human error during assembly thereof .

[0115] Advantageously, the at least one welding seam, andin particular both first welding seam 21a and second welding seam 21b, extend in the radial direction with respect to axis A.

[0116] This feature has the double effect of : allowing better access for executing the welding between flange 19 and axial end portion 16; and providing an improved resistance and stiffness against the axial loads which may derive from thermal expansion of casing 14 and flange 19.

[0117] As visible in Figure 2, casing 14 has a first longitudinal portion 25 and a second longitudinal portion, the second longitudinal portion defining the axial end portion 16.

[0118] In light of the above, in the following the expressions "axial end portion" and "second longitudinal portion" may be used interchangeably, since they indicate the same part of casing 14.

[0119] Second longitudinal portion 16 is welded to first longitudinal portion 25 to define, with this latter, a single tubular body extending along axis A.

[0120] Such tubular body defines casing 14 in its entirety. Since flange 19 is coupled to axial end portion 16, i . e . second longitudinal portion, such second longitudinal portion defines a support bushing for the flange 19, the flange 19 being welded to outer surface16a of the second longitudinal portion.

[0121] Advantageously, second longitudinal portion (i . e . axial end portion 16, i . e . the support bushing for flange 19) is made of an alloy comprising nickel, cobalt and iron .

[0122] Preferably, second longitudinal portion 16 is made of an alloy having a composition, in weight percentage :

[0123] - Ni (nickel) 29%;

[0124] - Co (cobalt) 17%;

[0125] - Mn (manganese) 0, 3%;

[0126] - Si (silicon) 0, 2%;

[0127] - C (carbon) 0, 01% or less;

[0128] the balance being Fe (iron) and impurities .

[0129] More preferably, second longitudinal portion 16 is made of Kovar ® alloy.

[0130] Preferably, flange 19 is made of stainless steel or of a stainless steel alloy.

[0131] Preferably, first longitudinal portion 25 is made of stainless steel or of a stainless steel alloy.

[0132] The Applicant has observed how the use of the aforementioned alloy for the axial end portion 16 (support bushing of flange 19) is particularly advantageous . In fact, this particular alloy is subj ected to a small thermal expansion, as the thermal expansion of cover 17 (which is made of ceramic material) . This results in asignificant reduction of mechanical stresses (derived from the thermal expansion) at the junction of the materials, which then results in less risk of damages and in a prolonged lifespan of emitting device 11.

[0133] Preferably, first longitudinal portion 25 has a first (preferably positive and linear) thermal expansion coefficient and second longitudinal portion (i . e . axial end portion 16) has a second (preferably positive and linear) thermal expansion coefficient, wherein the second thermal expansion coefficient is lower than the first thermal expansion coefficient . The flange 19 may have a third (preferably positive and linear) thermal expansion coefficient, wherein the second thermal expansion coefficient is lower than the third thermal expansion coefficient .

[0134] The aforementioned alloy is also particularly suitable for welding with stainless steel or a stainless steel alloy, which is the material of which flange 19 and first longitudinal portion 25 of casing 14 are composed.

[0135] Conveniently, insulating cover 17 is internally brazed to second longitudinal portion 16, and in particular to inner surface 16b of second longitudinal portion 16.

[0136] The Applicant has found that the aforementioned alloy provides the optimal material for brazing withceramic, thereby further improving the overall thermal behavior of emitting device 11.

[0137] As visible in Figure 3, second protrusion 24 advantageously includes :

[0138] - a curved stretch 24a extending in a cantilevered manner from main body 22 towards axial end portion 16;

[0139] a straight stretch 24b extending from curved stretch 24a up to the outer surface 16a of axial end portion 16.

[0140] In detail, straight stretch 24b extends in the axial direction, whereas curved stretch 24a is interposed between main body 22 and straight stretch 24b and defines a fillet connecting these latter to one another .

[0141] In greater detail, curved stretch 24a has both an axial component and a radial component .

[0142] Curved stretch 24a has a radius with a center of curvature lying outside inner chamber 20 (and preferably also outside of the vacuum chamber 15, even more preferably curved stretch 24a and its center are positioned on the same side with respect to axial end portion 16) .

[0143] That is, curved stretch 24a has a concavity facing the environment outside of inner chamber 20 (and preferably also outside of the vacuum chamber 15) .

[0144] Furthermore, curved stretch 24a is connected to mainbody 22 via an inner fillet 24c facing inner chamber 20. That is, inner fillet 24c has a concavity facing the environment inside of inner chamber 20.

[0145] In one embodiment, inner fillet 24c has a radius with a center of curvature lying inside inner chamber 20.

[0146] In one embodiment, the center of curvature of the radius of inner fillet 24c may lie within axial end portion 16 or within vacuum chamber 15 (i . e . the inner environment of casing 14 ) .

[0147] The peculiar configuration of second protrusion 24 as described above significantly improved the thermal behavior of flange 19. In particular, the Applicant has observed, through an extended campaign of simulation and experiments, that the particular curved shape described above allows for compensating the stresses which the material is subj ected to in use due to the operative thermal loads .

[0148] This is especially advantageous during the so-called bakeout process, during which emitting device is subj ected to very high temperatures (and possibly vacuum) for removing volatile compounds from materials and obj ects before placing them into situations where the slow release of the same volatile compounds would contaminate the contents of a container or vessel, spoil a vacuum, or cause discomfort (odor or irritation) orillness . Hence, bake-out is an artificial acceleration of the process of outgassing.

[0149] During the bakeout process, emitting device 11, and therefore also cooling device 18, is subj ected to temperatures which are higher than the normal operative temperatures . It is of outmost importance that emitting device 11 passes the bakeout process without incurring in any damage or breakage .

[0150] Since the second protrusion 24 is a portion of flange 19 particularly subj ected to mechanical stresses deriving from thermal loads, the curved shape as described above allows for compensating and alleviating such stresses, thereby reducing the risk of irreversible plastic damages .

[0151] Advantageously, curved stretch 24a has a variable thickness and tapers from main body 22 towards straight stretch 24b .

[0152] In detail, curved stretch 24a has a curved inner surface 24aa facing inner chamber 20 and a curved outer surface 24ab facing outside of inner chamber 20.

[0153] Expediently, curved inner surface 24aa has a radius bigger than the radius of curved outer surface 24ab .

[0154] Moreover, the centers of curvature of curved inner surface 24aa and curved outer surface 24ab do not coincide with one another .In particular, both curved inner surface 24aa and curved outer surface 24ab have radiuses with respective centers of curvature lying outside inner chamber 20 (and preferably also outside of the vacuum chamber 15, even more preferably curved inner surface 24aa and curved outer surface 24ab and the respective centers thereof are positioned on the same side with respect to axial end portion 16) .

[0155] That is, both curved inner surface 24aa and curved outer surface 24ab have a concavity facing the environment outside of inner chamber 20 (and preferably also outside of the vacuum chamber 15) .

[0156] The Applicant has observed that such features contribute to further reducing the thermal stresses and therefore the risk of damage of flange 19 during the bakeout process and during normal operation.

[0157] Preferably, first protrusion 23 extends linearly along the radial direction.

[0158] In this way, the presence of first protrusion 23 does not hinder the coupling of other devices, such as a plug member of a power supply source or generator, to casing 14 at axial end portion 16.

[0159] In fact, as shown in the Figures, first protrusion 23 is located at the free end edge of axial end portion 16.More in particular, first welding seam 21a joins the free end of first protrusion 23 with the free end edge of axial end portion 16.

[0160] The curved conformation of second protrusion 24 as described above compensates also for the thermal stresses generated at first protrusion 23.

[0161] As visible in Figure 4, flange 19 comprises, at a peripheral portion 19a thereof, a series of through seats 26 adapted to receive fastening elements (such as bolts, not shown) for the coupling of the emitting device 11 with a further device (such as the plug member of the aforementioned power supply source) .

[0162] Advantageously, flange 19 is provided with a plurality of inserts 27, each insert 27 being arranged within one respective seat 26.

[0163] Each insert 27 is configured to receive in engagement one respective fastening element, so that the fastening element cooperates in contact only with such insert 27 without touching the delimiting walls of the respective seat 26.

[0164] Each insert 27 is advantageously removable from the respective seat 26.

[0165] More in particular, each insert 27 is removably coupled with the respective seat 26.

[0166] For example, each insert 27 is fastened to a supportwall of the respective seat 26.

[0167] Each insert 27 defines a through hole 28 engageable by the fastening element to define the coupling between flange 19 and the aforementioned power supply member .

[0168] In this way, in case a fastening element remains stuck within the respective seat 26, it is sufficient to decouple the respective insert 27 from that seat 26 in order to remove the fastening element .

[0169] Conversely, without the inserts 27, if one or more fastening elements are stuck in respective seats 26 without the possibility to be removed, the whole emitting device 11 may be discarded or dismissed.

[0170] The advantages of emitting device 11 according to the present invention will be clear from the foregoing description .

[0171] In particular, thanks to the welded coupling of flange 19 with casing 14 (and in particular to the axial end portion 16 thereof ) , cooling device 18 (and hence emitting device 11 ) has reduced number of components, with respect to the known configurations . In fact, due to the presence of the welding seams 21a, 21b, there is no need for any o-ring or other sealing elements . This results in a reduction of wear and in a significant reduction of the risk of leakage due to a possible fault of the o-rings . Moreover, the risk of human error duringassembly of emitting device 11 is highly reduced.

[0172] Furthermore, there is no need for any fastening element to couple flange 19 to casing 14, nor for any auxiliary coupling flange to support such fastening elements . This results in a significant reduction of components, and therefore in an increase of the overall reliability of emitting device 11 and in a further reduced human error during assembly thereof .

[0173] In summary, the architecture and assembly of emitting device 11 are simplified, while at the same time reducing the need for maintenance .

[0174] The use of an axial end portion 16 (acting as a support bushing for flange 19) made of a nickel-cobalt-iron alloy as the one described, further enhances the thermal properties of cooling device 18.

[0175] Moreover, the peculiar curved shape of second protrusion 24 enhances the structural behavior of flange 19 under thermal stresses deriving especially from preoperative bakeout processes and / or from normal use .

[0176] Clearly, changes may be made to emitting device 11 as described herein without, however, departing from the scope of protection as defined in the accompanying claims .

Claims

CLAIMS1 . - Electron beam emitting device ( 11 ) , comprising :a generation member ( 12 ) configured to emit electrons as a result of electrical energy being supplied thereto ;- a hollow casing ( 14 ) internally defining a vacuum chamber ( 15 ) and housing at least the generation member ( 12 ) and extending along a longitudinal axis (A) ;the emitting device ( 11 ) further including a cooling device ( 18 ) comprising a hollow flange ( 19 ) coupled with the casing ( 14 ) at an axial end portion ( 16 ) thereof , extending at least in part around the longitudinal axis (A) and delimiting, together with an outer surface ( 16a ) of the axial end portion ( 16 ) , an inner chamber ( 20 ) which defines a flow channel for a cooling medium; wherein the flange ( 19 ) is welded to said casing ( 14 ) at said axial end portion ( 16 ) .2 . - Electron beam emitting device ( 11 ) as claimed in the preceding claim, wherein the flange ( 19 ) is welded to said casing ( 14 ) by means of at least one welding seam ( 21a, 21b ) extending in a circumferential direction about said longitudinal axis (A) .

3. - Electron beam emitting device ( 11 ) as claimed in any one of the preceding claims , wherein the flange ( 19 ) includes a main body ( 22 ) , a first protrusion ( 23 )28extending radially from the main body (22 ) and a second protrusion (24 ) extending radially from the main body (22 ) , the first protrusion (23) and the second protrusion (24 ) being arranged at opposite lateral sides of the inner chamber (20) and delimiting the inner chamber (20) in the axial direction, an inner surface (22a) of the main body (22 ) , which is axially interposed between the first protrusion (23) and the second protrusion (24 ) , delimiting the inner chamber (20) in the radial direction; wherein the second protrusion (24 ) includes a curved stretch (24a) extending in a cantilevered manner from the main body (22 ) towards said axial end portion ( 16) and / or the first protrusion (23) extends linearly along the radial direction.

4. - Electron beam emitting device ( 11 ) as claimed in the preceding claim, wherein the second protrusion (24 ) includes a straight stretch (24b) extending from the curved stretch (24a) up to the outer surface ( 16a) of the axial end portion ( 16) , the straight stretch (24b) extending in the axial direction, the curved stretch (24a) being interposed between the main body (22 ) and the straight stretch (24b) .

5. - Electron beam emitting device ( 11 ) as claimed in the preceding claim, wherein the curved stretch (24a) has a radius with a center of curvature lying outside theinner chamber (20) .

6. - Electron beam emitting device ( 11 ) as claimed in the previous claim or claim 4, wherein the curved stretch (24a) is connected to the main body (22 ) via an inner fillet (24c) facing the inner chamber (20) .

7. - Electron beam emitting device ( 11 ) as claimed in any one of claims 4 to 6, wherein the curved stretch (24a) has a variable thickness, tapering from the main body (22 ) towards the straight stretch (24b) .

8. - Electron beam emitting device ( 11 ) as claimed in any one of the claims 4 to 7, wherein the curved stretch (24a) has a curved inner surface (24aa) facing the inner chamber (20) and a curved outer surface (24ab) facing outside of the inner chamber (20) , the curved inner surface (24aa) having a radius bigger than the radius of the curved outer surface (24ab) .

9. - Electron beam emitting device ( 11 ) as claimed in any one of claims 2 to 8, wherein the at least one welding seam (21a, 21b) extends in the radial direction with respect to said longitudinal axis (A) .

10. - Electron beam emitting device ( 11 ) as claimed in any one of the foregoing claims, wherein the casing ( 14 ) has a first longitudinal portion (25) and a second longitudinal portion ( 16) , the second longitudinal portion defining said axial end portion ( 16) and beingwelded to the first longitudinal portion ( 25 ) to define , with this latter, a single tubular body extending along said longitudinal axis (A) ;wherein the second longitudinal portion ( 16 ) defines a support bushing for the flange ( 19 ) , the flange ( 19 ) being welded to an outer surface of the second longitudinal portion ( 16 ) ;and wherein the second longitudinal portion ( 16 ) is made of an alloy comprising nickel , cobalt and iron .11 . - Electron beam emitting ( 11 ) device as claimed in claim 10 , wherein the second longitudinal portion ( 16 ) is made of an alloy having a composition, in weight percentage :- Ni 29% ;- Co 17 % ;- Mn 0 , 3% ;- Si 0 , 2 % ;- C 0 , 01 % or less ;the balance being Fe and impurities .12 . - Electron beam emitting device ( 11 ) according to any of the previous claims , comprising an electrically insulating cover ( 17 ) coupled with the casing ( 14 ) at said axial end portion ( 16 ) , the cooling device ( 18 ) configured to cool the insulating cover ( 17 ) ; preferably wherein the insulating cover ( 17 ) is made of a ceramicmaterial and is internally brazed to the second longitudinal portion ( 16 ) .

13. - Electron beam emitting device ( 11 ) according to any of the previous claims , wherein the flange ( 19 ) is made of stainless steel or of a stainless steel alloy .14 . - Electron beam emitting device ( 11 ) as claimed in any one of the foregoing claims , wherein the flange ( 19 ) comprises , at a peripheral portion ( 19a ) thereof peripheral with respect to the longitudinal axis (A) , a series of through seats ( 26 ) adapted to receive fastening elements for the coupling of the emitting device ( 11 ) with a further device ;and wherein the flange ( 19 ) is provided with a plurality of inserts ( 27 ) , each insert ( 27 ) being arranged within one respective seat ( 26 ) , each insert ( 27 ) being configured to receive in engagement a respective fastening element , so that the fastening element cooperates in contact only with the insert ( 27 ) without touching the delimiting walls of the respective seat ( 26 ) , each insert ( 27 ) being removable from the respective seat ( 26 ) .

15. - Packaging machine ( 1 ) configured for producing packages ( 2 ) containing a pourable product starting from a web ( 4 ) of packaging material , the packaging machine ( 1 ) comprising a sterili zation unit ( 10 ) arranged alongthe advancement path (P) and configured to sterilize the packaging material; wherein the sterilization unit ( 10) comprises at least one electron beam emitting device ( 11 ) as claimed in any one of the foregoing claims .33

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