METHOD FOR THE COLD STERILISATION OF A TUNNEL-TYPE OVEN FOR PHARMACEUTICAL USE, AND OVEN FOR CARRYING OUT SAID METHOD

Abstract: A method for the cold sterilisation of a tunnel-type oven (1), this latter being suitable for the hot sterilisation of bottles, comprising an input chamber (3), a hot sterilisation chamber (4), a cooling chamber (5) and a conveyor (6), consists of a sequence of operating phases which have to be carried out periodically. Said phases comprise: airtightly closing the input (31) and output (51) openings of the oven (1), the air input ducts (33, 43) and output duct (34); supplying a pre-defined amount of sterilisation fluid mixed with air, until all the inner surfaces of the oven (1) are reached by said fluid; opening a recycling duct (37); stopping the supply of sterilisation fluid, and supplying the oven (1) with humidity and temperature controlled air. The oven (1) design keeps it completely hermetic, once said input opening (31) and output opening (51) have been closed.

Description: METHOD FOR THE COLD STERILISATION OF A TUNNEL-TYPE OVEN FOR PHARMACEUTICAL USE, AND OVEN FOR CARRYING OUT SAID METHOD. TECHNICAL FIELD The present invention relates to the technical field concerning the sterilisation of apparatuses or bottles for pharmaceutical use. More particularly, the present invention relates to a method for sterilising the inside of a bottles sterilisation oven, and to an oven which carries out said method. BACKGROUND ART It is known that all the different kinds of bottles for pharmaceutical use, which are made of glass or the like, must be submitted to a sterilisa- tion process before filling them with a drug, in order to destroy or inactivate all the microorganisms that potentially could adulterate the bottles content, or that could be harmful for a patient to which said drug has to be given. The bottles sterilisation is usually carried out at high temperatures, inside a special sterilisation oven, which is configured as a "tunnel", and which is stepless operated, for productivity purposes. The known sterilisation tunnel -type ovens norm- ally comprise three cascade-connected and intercommunicating sections: an input chamber, a sterilisation chamber, also called hot chamber, and a cooling chamber for the sterilised bottles. The three above sections are crossed by a tape conveyor, that forwards the aforesaid bottles in sequence through all the sections. The input chamber has an input door, through which the bottles, coming from a washing station, are fed to the oven. At the opposite end, the cooling chamber is provided with an output door for communicating with a sterile room, wherein bottles are filled with a drug and then sealed. The hot chamber is provided with suitable heaters, operable to heat the said chamber to a given temperature, which is high enough to sterilise all the bottles continuously passing therein. Bottles stay in the cooling chamber until their temperature attains a value approaching that of the subsequent sterile room. Said chamber is suitably provided with working fluid type heat exchangers, which help in lowering the air temperature inside the chamber, and consequently in lowering the bottles temperature . All the sterilisation oven sections are normally submitted to a laminar flow of air filtered by H.E.P.A. filters of suitable retention characteristic features. They are kept in a slight plenum condition, in order to avoid any non-filtered air, which is therefore contaminated by particles and microorganisms, to flow into the oven. But, in the conventional sterilisation ovens, neither the input chamber nor the cooling chamber are intrinsically sterile. In fact, although they are subject to a continuous laminar flow of filtered air, their inner surfaces could contain some contaminating agent, that could pollute the bottles. This is a serious drawback, particularly for the cooling chamber, which contains already sterilised bottles. Of course, the hot chamber is intrinsically sterile. The aforesaid possibility of bottles contamination, although it is normally very poor, is taken in particular account by all the pharmaceutical companies and surveillance organisations, and a great number of requests for ovens provided with a sterile cooling chamber is arising. Some ovens provided with periodical sterilisation procedures for the cooling chamber are known, particularly by heating it to a temperature similar to those reached in the hot chamber, in order to kill all the pathogenic agents. This solution is extremely expensive and difficult to carry out and to sell. In fact, because of the cooling chamber size, high power heating assemblies must be provided; all the power lines and apparatuses that carry the power to the oven must be sized accordingly, and then practically doubled with respect to a conventional sterilisation oven. DISCLOSURE OF THE INVENTION It is an object of the present invention to propose a method for the periodical sterilisation of the cooling chamber, and of the whole sterilisation oven, which can be carried out without heating the same oven. A further object of the present invention is to propose a such method which doesn't significantly improve the oven production costs nor its power consumption. A further object is to propose a sterilisation oven which is totally cold sterilisable, accordingly to the aforesaid method. The aforesaid objects are achieved by a method comprising the steps of: airtightly closing oven input and output open- ings and input and output ducts; opening forced input means, for introducing a mixture of air and of sterilisation fluid into the oven; supplying a pre-defined amount of a mixture of sterilisation fluid and air, until a pre-defined static pressure is attained; opening at least one output duct for the sterilisation fluid; stopping the supply of the sterilisation fluid, and supplying the oven with humidity controlled air, until the percentage of said sterilisation fluid inside the oven falls down to a pre-defined value; closing said forced input means and said output duct, and re-opening the input and output opening. BRIEF DESCRIPTION OF THE DRAWINGS The characteristic features of the invention are set out in the following, with particular reference to the accompanying drawings, in which: Figure 1 shows a schematic sectional view of a sterilisation tunnel-type oven, made according to the present invention; - Figure 2 shows an enlarged view of the detail B of Figure 1 ; - Figure 3 shows a schematic front sectional view of the oven of Figure 1, at the input chamber; - Figure 4 shows an enlarged sectional view of the detail A of Figure 3 ; - Figure 5 shows a schematic front sectional view of the oven of Figure 1, at the hot chamber; - Figure 6 shows a schematic front sectional view of the oven of Figure 1, at the cooling chamber. BEST MODE OF CARRYING OUT THE INVENTION Referring now to Figure 1, numeral 1 indicates a sterilisation, tunnel-type oven, for the continuous hot sterilisation of bottles for pharmaceutical products. Said oven 1 substantially comprises a supporting frame 100, of approximately parallelepipedal shape. Inside the frame 100 an input chamber 3, a hot sterilisation chamber 4 and a cooling chamber 5 are successively arranged. These three chambers communicate one each other, by means of a first passage 134, between the input chamber 3 and the sterilisation chamber 4, and a second passage 145, between this latter and the cooling chamber 5. The input chamber 3 and cooling chamber 5 are also respectively provided with an input opening 31 and with an output opening 51, aligned with the passages 134,145. The input opening 31 receives the bottles coming from a previous washing apparatus, while the output opening 51 is connected in a know way to a sterile room, or to an insulating environment, wherein the sterilised bottles are filled with the corresponding pharmaceutical product, and then sealed. Chambers 3,4,5 are moreover crossed by a contin- uous tape conveyor 6, which is driven to a direction W at a given speed, generally variable according to known sequences. The tape conveyor 6 carries the above cited bottles on its upper branch 6a, during the normal oven operating procedures, from the input opening 31 to the output opening 51. The operating modes of the oven 1, fit to obtain a complete hot sterilisation of bottles, are known, and they will not be detailed in the following. They are totally automated and handled by an electronic control unit, not shown in the drawings. The input chamber 3 has a first ventilation assembly 36, provided with a flow conveyor 36a and with a corresponding H.E.P.A. filter, and fit to generate a laminar flow of sterile air in the said chamber 3, according to known techniques (see also figure 3) . The first ventilation assembly 36 is connected to the external environment by means of a first input duct 33, provided with a flow regulating valve 33a. An air output duct 34 is also provided at the upper end of the input chamber 3, and has an output flow regulating valve 34a and a discharge fan 34b. Said valve 34a and fan 34b are operated in a phase relationship with the first ventilation assembly 36. A first forced input duct 35 of a cold sterilisation fluid joins the first input duct 33 just downstream of the flow regulating valve 33a with respect to the air input flow, which is indicated with the V arrow in figure 1. Said duct 35 is provided with a first flow regulating valve 35a, driven according to pre-defined periodic sequences, in order to allow the input chamber to be cold sterilised. The first forced input duct 35 is connected to a source of that sterilisation fluid, not shown. This latter preferably consists of a suitably measured mixture of hydrogen peroxide and air, whose tempera- ture and humidity is suitably controlled. The mixture is provided by means of a known supply device, a rotating vane centrifugal pump. At the upper end of the input chamber 3, recycling or evacuating means 37 for the hydrogen peroxide is provided, fit to allow the same to be drained away from the oven 1, or its recycling and re-routing toward the supply device. The recycling or evacuating means consists of a duct, extending from the air output duct 34, just upstream of the flow regulating valve 34a and provided with its own flow regulating valve 37a, operated in a phase relationship with the same valve 34a. The duct 37 is connected to known recycling means for recycling the hydrogen peroxide or, optionally, to known exhausting means, both not shown. The hot sterilisation chamber 4 is provided in turn with a second ventilation assembly 46, provided with its own flow conveyor 46a and with a corresponding H.E.P.A. filter, and fit to generate a laminar flow of sterile air (see also figure 5) . The second ventilation assembly 46 is connected to the external environment by means of a second input duct 43, which is also provided with its flow regulating valve 43a. A second forced input duct 45 of hydrogen peroxide joins the second input duct 43, downstream of the flow regulating valve 43a. Said duct is provided with a second flow regulating valve 45a, operable according to pre-defined periodic sequences, in a phase relationship with the operation of the first flow regulating valve 35a. A suitably thick layer of insulating material 140 is externally wrapped all around the hot sterilisation chamber 4, for thermically insulating the same, as well as possible, from the input chamber 3, the cooling chamber 5 and the external environment. At the aforesaid passages 134,145, corresponding first and second control joints 141,142 are sealingly provided (see detail in figure 2) , fit to define the perimeter of said passages, to keep them airtight and to allow at the same time the sterilisation chamber 4 to expand and to contract according to its thermal variations. More particularly, each of said control joints, for instance the second control joint 142, consists of a corrugated plate 143 of elastic metal, which is fixed at its ends to the sterilisation chamber 4 and cooling chamber 5 walls by means of a continuous welding . A third ventilation assembly 56 is arranged in the upper side of the cooling chamber 5, provided with its own flow conveyor 56a with a corresponding H.E.P.A. filter, and fit to generate a laminar flow of sterile air inside the same chamber 5 (see also figure 6) . The third ventilation assembly 56 provides a closed loop air circulation, since it draws air from the inside of the same cooling chamber 5, in order to improve the air flow. A third forced input duct 55 of hydrogen perox- ide is arranged at the upper end of the cooling chamber 5. This is provided with a third flow regulating valve 55a, which is operated, according to predefined periodic sequences, in a phase relationship with the operation of the first regulating valve 35a and of the second regulating valve 45a, in order to allow the cooling chamber 5 to be cold sterilised. The third forced input duct 55 is also connected to the aforesaid source of hydrogen peroxide . The cooling chamber 5 has a pair of heat exchan- gers 57, respectively a first one 57a and a second one 57b, fit to drain the heat released by the cooling down bottles. They are arranged in the middle portion of the cooling chamber 5, where the laminar flow direction is reversed. In fact, the whole oven 1 is hermetically sealed. More particularly, all the frame 100 junctions are made with continuous weldings, and the same frame 100 is provided with side panels 7 for covering the input chamber 3, the hot sterilisation chamber 4 and the cooling chamber 5. (figures 3,5,6) . Each one of the above panels 7 has, all around the rim 7b of its inner wall 7a (see figure 4) , a gasket 71 which, when the panel is its operating position, interposes between the inner wall 7a of the same panel 7 and an outer face 101 of the frame 100. The gasket 71 is made of a shaped plate 73, which is fixed to the rim 7b and which extends all around its boundary, and of a pair of airtight curbs 74a, 74b, fixed in turn to the shaped plate 73 and respectively parallel. The plate 73 and the curbs 74a, 74b define, together with the outer face 101 of the frame 100, an airtight compartment 75. A suction duct 76 is fixed on the inner face 103 of the frame 100, exactly following the path of the airtight compartment 75. The suction duct 76 is connected to known suction means, which periodically bring said duct to a pressure lower than the atmospheric pressure. A plurality of through holes 77 is made in the frame 100, in order to establish a communication between the suction duct 76 and the airtight compartment 75. The input opening 31 and the output opening 51 are provided with airtight doors 38,58, connected to respective operating means 39,59, which are preferably automatically operated. According to the method for the cold sterilisa- tion of the present invention, a sterilisation sequence is periodically performed for the oven 1, and particularly for the input chamber 3 and the cooling chamber 5. These sequences are interlaced with the oven 1 normal operation periods. Of course, as pre- viously explained, due to its high operating temperature, the sterilisation chamber 4 is intrinsically sterile . Each cold sterilisation sequence happens after the oven 1 normal operation has stopped, and the sterilisation chamber 4 has reached a temperature as low as about 40° Centigrade. The following operating phases are then carried out : the input opening 31 and the output opening 51 are airtightly sealed, by closing their respective doors 38,59, and the flow regulating valves 33a, 43a, 53a of the input ducts 33,43 and output duct 34 are also closed; the flow regulating valves 35a, 45a, 55a of the forced input ducts 35,45,55 are opened, and a flow of humidity and temperature-controlled air is introduced into the oven 1 ; the first, second and third ventilation assemblies 35,45,55 are then activated, for a given period of time; a pre-defined amount of hydrogen peroxide is supplied to the oven 1, through the aforesaid forced input ducts 35,45,55, until the hydrogen peroxide propagates completely into the cooling chamber 5, the input chamber 4 and the hot sterilisation chamber 4, and until the air pressure inside the oven reaches a given static pressure; the recycling or evacuating duct 37 is opened, by opening the flow regulating valve 37a; the supply of hydrogen peroxide is stopped, and humidity and temperature-controlled air is continuously supplied to the oven 1, until the percentage of the hydrogen peroxide falls under a pre-defined value; the forced input ducts 35,45,55 and the recycling or evacuating duct 37 are closed, and the input opening 31 and output opening 51 are opened, by removing their closing doors 38,58. Before the said forced input ducts 35,45,55 opening phase is carried out, a further over-pressur- ized ventilation phase can be provided for the oven 1, which is carried out by opening the flow regulating valves 33a, 43a, 34a of the input ducts 33,43 and output duct 34, and simultaneously activating the ventilation assemblies 36,46,56 and the discharge fan 34b. Sterilisation sequences like that described above can be performed either with a given frequence, or after the oven 1 has been opened for maintenance purposes . The method and oven of the present invention give a first advantage in that they allow, not only the cooling chamber 5 to be perfectly sterilised, thus avoiding the sterilised, cooling down bottles, from being contaminated by micro-organisms or any other contaminating agent, which would be otherwise present on the inner surfaces of the same cooling chamber 5 , but also in that even the input chamber 3 and the hot sterilisation chamber 4, thus the whole oven 1, are perfectly sterilised. A further given advantage is that, for obtaining said sterilisation, there is no significant improvement in power consumption, and then of maximum required power supply. Moreover, the oven 1 can be operated, during its normal operating life, at an over-pressure regime, not only with respect to the external environment, but also with respect to the sterile room and to the insulating environment. This allows the oven 1 operating settings and maintenance can be made independently from those of the same sterile room. Moreover, the oven 1 can be advantageously placed even in a non-clean environment, since it is completely insulated from the external environment . The subject invention has been obviously described, with reference to the attached drawings, for exemplifying and not limitative purposes, and it is therefore evident that it is possible to apply to it all of those modifications or variations suggested by the practice and by its realisation and use, however included in the field defined by the following claims.

Claims: CLAIMS 1. A method for the cold sterilisation of a tunnel-type oven for pharmaceutical purposes, provided with at least one input chamber (3) , fit to receive a plurality of bottles to be sterilised from an input opening (31) , with at least one hot sterilisation chamber (4) of said bottles, subsequently arranged with respect to said input chamber (3) and communicating with the same, with at least one coo- ling chamber (5) , subsequently placed with respect to said hot sterilisation chamber (4) and communicating with the same, fit to receive said sterilised, cooling down bottles, and provided as well with at least one output opening (51) , and with conveying means (6) , for conveying said bottles from said input chamber (3), subsequently to said sterilisation chamber (4) and cooling chamber (5), said oven (1) being also provided with a plurality of input ducts (33,43) for introducing external air into said oven (1) , and with at least one output duct (34) for draining said air to the external environment, said method being characterised in that the following operating phases are periodically carried out: airtightly closing said input opening (31) and output opening (51) and of said input ducts (33,43) and output duct (34) ; opening forced input means (35,45,55), for introducing a mixture of air and of sterilisation fluid at least into said cooling chamber (5) ; supplying a pre-defined amount of said mixture of sterilisation fluid and air, until a pre-defined static pressure is attained; opening at least one output duct (37) for said sterilisation fluid; stopping the supply of said sterilisation fluid, and supplying said oven (1) with humidity controlled air, until the percentage of said sterilisation fluid inside said oven (1) falls down to a pre-defined value; closing said forced input means (35,45,55,) and said output duct (37) , and re-opening said input opening (31) and output opening (51) . 2. A method according to Claim 1, characterised in that said sterilisation fluid is supplied from three forced sterilisation fluid forced input ducts, respectively a first one (35) , a second one (45) and a third one (55) , respectively placed in said input chamber (3), hot sterilisation chamber (4) and cooling chamber (5) . 3. A method according to Claims 1 or 2 , characterised in that before said forced input ducts (35,45,55) opening phase, said oven (1) is subject to an over-pressurized ventilation, through said input ducts (33,43) and output duct (34). 4. A method according to Claim 1, characterised in that , simultaneously to said sterilisation fluid input phase, first ventilation means (36), second ventilation means (46) and third ventilation means (56) are operated, respectively in the said input chamber (3), sterilisation chamber (4) and cooling chamber (5) , for a pre-defined period of time. 5. A method according to any one of the previous Claims, characterised in that sterilisation fluid is hydrogen peroxide . 6. A method according to Claim 5, characterised in that said hydrogen peroxide is supplied in its vapour phase . 7. Tunnel-type oven for pharmaceutical purposes, provided with at least one input chamber (3) , fit to receive a plurality of bottles to be sterilised from an input opening (31) , with at least one hot sterilisation chamber (4) for said bottles, subsequently arranged with respect to said input chamber (3) and communicating with this latter, with at least one cooling chamber (5) , subsequently arranged with respect to said hot sterilisation chamber (4) and communicating with this latter, fit to receive said cooling down, sterilised bottles, and also provided with at least one output opening (51) , said oven (1) being furthermore provided with conveying means (6), for conveying said bottles from said input chamber (3), subsequently, to said sterilisation chamber 4 and cooling chamber (5) , with first ventilation means (36) , with second ventilation means (46) and with third ventilation means (56), for respectively ventilating said input chamber (3), hot sterilisation chamber (4) and cooling chamber (5), and being also provided with a plurality of external air input ducts (33,43) , and with at least one output duct (34) for draining said air to the external environment, said oven (1) being characterised in that it moreover comprises : - doors (38,58) for airtight closing said input opening (31) and output opening (51); - airtight closing means (70) of panels (7) for covering said input chamber (3), hot sterilisation chamber (4) and cooling chamber (5) ; - forced input means (35,45,55) of a cold sterilisation fluid, fit to supply said sterilisation fluid into said oven (1) ; - recycling or evacuating means (37) of said sterilisation fluid, for draining said sterilisation fluid out from said oven (1) , until the percentage of said sterilisation fluid inside the oven (1) falls down to a pre-defined value. 8. Oven according to Claim 7, characterised in that said forced input means consists of a first duct (35) , a second duct (45) and a third duct (55) , respectively provided with flow regulating valves (35a, 45a, 55a) , and connected to a sterilisation fluid supplying source. 9. Oven according to Claim 8, characterised in that said first duct (35) , second duct (45) and third duct (55) are respectively arranged in said input chamber (3), hot sterilisation chamber (4) and cooling chamber (5) . ιo. Oven according to Claim 7, characterised in that said recycling or evacuating means (37) consists of at least one recycling or evacuating duct, provi- ded with an output flow regulating valve (37a) . 11. Oven according to Claim 10, characterised in that said recycling or evacuating duct (37) is ar- ranged in said input chamber (3) . 12. Oven according to Claim 7, characterised in that said airtight closing means (70) comprises, for each one of said closing panel (7) : at least one gasket 71, interposed between an outer face (101) of a frame (100) of said oven (1) and the inner face (7a) of said panel (7) , near the rim (7b) of this latter and all around its boundary, said gasket (71) defining, with the cooperation of said outer face (101) , at least one airtight compartment (75) , fit to insulate said oven (1) from the external environment; at least one suction duct (76) , fixed to the inner face (103) of said frame (100) , exactly following the path of said airtight compartment (75) , a plurality of through holes (77) being provided in said frame (100) , for establishing a communication between said suction duct (76) and said airtight compartment (75) . 13. Oven according to Claim 12, characterised in that said gasket (71) consists of at least one shaped plate (73) , fixed to said rim (7b) and extending all around its boundary, and of at least one pair of parallel airtight curbs (74a, 74b), fixed to said shaped plate (73) . 14. Oven according to Claim 7, characterised in that said airtight closing doors (3 (,58) are provided with automatically operated operating means (39,59) . 15. Oven according to Claim 7, characterised in that a first control joint (141) and a second control joint (142), respectively arranged at said first passage (134) and second passage (145), for airtight- ly defining the perimeter of said passages (134,145) , and for allowing at the same time the aforesaid sterilisation chamber (4) to expand and to contract according to its thermal variations. 16. Oven according to Claim 15, characterised in that said control joints (141,142) consist of a corrugated plate (143) made of elastic metal, fixed at its ends to said sterilisation chamber (4) and cooling chamber 5) walls by means of a continuous welding.

Inventors: BECHINI CLAUDIO, BECHINI, CLAUDIO
Applicants: BECHINI CLAUDIO, LIBRA PHARMACEUTICAL TECHNOLOG, BECHINI, CLAUDIO, LIBRA PHARMACEUTICAL TECHNOLOGIES S.R.L.
Application year: 1998
Main classification: A61L2
IPC codes: A61L2