WO2007020469A1

WO2007020469A1 - Processing method, apparatus and product

Info

Publication number: WO2007020469A1
Application number: PCT/GB2006/003117
Authority: WO
Inventors: Richard Walden
Original assignee: Zinetec Limited
Priority date: 2005-08-19
Filing date: 2006-08-18
Publication date: 2007-02-22
Also published as: GB2442432A; GB0517054D0; GB2442432B

Abstract

A processing method for thermally treating a container (containing a product) characterised by three processing zones (12, 13A, 13B 14) in which are carried out a sequence of steps comprising: causing the container (C, Cl) in the first zone (12) to pass along a first direction (D) of travel; preheating the container (C, Cl( during the first zone (12) to a first pre-determined temperature and agitating the container (C, Cl) during the first stage wherein the minimum acceleration amount to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the first pre-determined temperature is: firstly reduced by at least 90% compared to the heating time required to reach the first pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; passing the preheated container (C, Cl) from the first zone (12) to the second zone (13A) by way of a pressure lock (Pl) providing for the maintenance of an ambient pressure difference between the first zone (12) and second zone (13A); heating the, or each, container (C, Cl) to a second pre-determined temperature in order to sterilise the container (Cl) and its contents; and agitating the, or each, container (Cl) in the second zone (13A) wherein the minimum acceleration to which the, or each, container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the second pre-determined temperature is: firstly reduced by at least 90% compared to the heating time required to reach the second pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; passing the treated container (Cl) from the second zone 13A to the third zone 13B by way of a pressure lock (P2) providing for the maintenance of an ambient pressure difference between the second zone 13A and third zone 13(B) ; and causing the sterilised container (Cl) in the third zone (13B) to pass through the third zone (13b) while being subjected to the simultaneous steps ot: cooling of the container (Cl) and its contents, in at least two stages, to a third pre-determined temperature while agitating the container (Cl) -wherein the minimum acceleration amount to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the cooling time required for the contents to reach the third pre-determined temperature is: firstly reduced by at least 90% compared to the cooling time required to reach the third pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation. According to another aspect there is provided apparatus for undertaking the method.

Description

PROCESSING METHOD, APPARATUS AND PRODUCT

TECHNICAL FIELD

This invention relates to a processing method, apparatus and product involving the thermal processing of metal containers containing a food product for human or animal consumption...

BACKGROUND TO THE INVENTION

In a conventional canning process a food product is filled into empty cans to an appropriate level, leaving a headspace above the product. The open end of each can is hermetically sealed with end closures, and then the cans and their contents are then sterilised by means of heat. The heating medium used is normally either steam or hot water at a temperature usually of between 115° C. and 130° C. To achieve this, temperature the steam or hot water has to be held at a super-atmospheric pressure, and accordingly it is contained in a pressure vessel known as a retort or cooker. The cans, after filling and closing, are placed in the retort, the retort is dosed, and steam or water is introduced. Temperature controllers are usually present on the retort to maintain the heating medium at the desired temperature. While the cans are located in the retort, heat from the heating medium is conducted through the container walls whence into the product.

As regards their behaviour during thermal sterilisation, food products are usually classified into three categories, namely:

(1) those that transfer heat internally largely by convection,

(2) those where internal heat transfer is largely by conduction, and

(3) those in which internal heat transfer involves substantial amounts of both conduction and convection. Category 1 food products have a very thin consistency and the application of heat generates convection currents in the product and these currents act to disperse heat throughout the pack.

Category 2 products are thick, relatively viscous or physically inhomogeneous, where internal heat transfer is largely by conduction since no significant movement occurs within the container when heat is applied to it.

Category 3 products, transfer heat internally by means of both conduction and convection and include those products which either thicken or become substantially more fluid as heating progresses.

Because of the need for complete sterilisation all parts of the food product in a can must reach a sufficient temperature for a long enough time to achieve so-called commercial sterility. With non-acid (pH>4.5) products which heat largely by convection (Le. category 1 products) this occurs fairly quickly; for example, a cylindrical can of 73 mm diameter and 110 mm length typically takes 15-20 minutes in a retort at 121° C. ('heat-up time') to heat to sterilisation temperature. The product needs to remain at that temperature for as long as is necessary to achieve commercial sterility ("dwell time"). The 15-20 minute period, thus made up of the heat-up time and any dwell time of the can in the retort at sterilisation temperature, is commonly referred to as the 'process' time, which nomenclature will be used hereafter. The process time is subsequent to any time which may be allowed for the retort itself to heat to sterilisation temperature, hereinafter referred to as the 'come-up' time. Conventionally the come-up time may be considerable, e.g. up to half hour, and some heating of the cans will occur during this time. The time period formed of the heat-up time of the cans and any come-up time of the retort is significant because it represents the time during which the product in the cans is being heated to the sterilisation temperature by heat passing through the can wall. This time period, hereinafter referred to as the 'heating time/ (of the cans), may be supplemented by any dwell time to form the total time during which the cans are subjected to the heating medium and which accordingly is hereinafter referred to as the 'sterilisation', or more generally, 'thermal treatment; time.

It will be seen that, using the definitions given above, the sterilisation time is equal to the process time plus any come-up time. It is also equal to the heating time plus any dwell time.

Category 2 products require much longer heating times than category 1 products because of their lesser mobility; a can as described above but charged with a category 2 product may typically have a process time of 80-90 minutes at 121° C, and to this must be added any retort come-up time allowed and, in addition, the time required for the hot and sterile can to cool to a predetermined temperature at which it may safely be removed from the retort. This latter time duration is hereinafter referred to as the 'cooling' time of the can. Thus the total time required by the complete sterilisation cycle, i.e. from admission of the heating medium to the end of cooling, may be 2 hours or more; this overall time is hereinafter called the 'total cycle time'.

The long heating times required by Category 2 packs (in particular) often lead to overcooking of the product, especially where it lies adjacent to the container wall. In commercial practice it is already well known to reduce the heating time and possible overcooking of a category 2 food product in a static retort by agitating the can by rotating it whilst in the retort. The rotation of the can has been either about its cylindrical axis, or "end-over-end" about a transverse (diametral) axis through its centre. The first form of agitation can be generated by rolling cans of circular section about their longitudinal axis, and is used in "Reel" and Spiral" cookers; however, it is well recognised that it does not induce efficient mixing, and the required process times are reduced by a factor of only about 2. Εnd-over-end' rotation induces better mixing, and reduction factors in process time of 3 or 4 can be expected.

In addition to the commercially used methods described above there are proposals in the patent literature for achieving process time reduction by agitation. These proposals have variously employed vertical or horizontal reciprocation (i.e. back-and-forth movement along a substantially straight path), or angular movement, possibly with reversals, along a circular path, or compound movement having both reciprocating and angular components.

By way of example, vertical reciprocation is featured in U.S. Patent 1,709,175 and German Patent Publication 031822, whilst horizontal reciprocation is featured in U.S.Patents 2,052,096 and 2,134,817, and Japanese Patent Publication JP 56-21584. Angular movement is featured in GB Patent Specification 1,593,962 in Figures 12, 13 and in figures 14, 15, whilst compound movement is featured in Figures 16, 17 of GB 1,593,962 and in French Patent Publication 2096516.

These and other proposals in the patent literature might be expected to achieve useful reductions in process time with the attendant advantages However they contain no indication that the severity of the agitation is important and, moreover, the maximum acceleration given to the container must exceed a certain minimum value if the process is to be reliably reproducible whilst achieving high levels of process time reduction.

For example, in the process particularly described in US Patent 2,134,817 above, the amplitude of the horizontal reciprocating movement between limiting positions (Le. the peak-to-peak or double amplitude) is said to be usually less than one inch, and the reciprocation frequency is said to be in the neighbourhood of 140 times (i.e. cycles) per minute.

Assuming a sinusoidal waveform for the reciprocation, these parameter values given for the process of US Patent 2,134,817 correspond to a maximum value of acceleration of approximately 0.3 times that due to gravity (i.e.0.3 g). It has been found by the present applicants that horizontal reciprocation using accelerations of this magnitude tend only to achieve a reduction of heating times (in relation to the same process without reciprocation) which is little or no better than the reduction which is commonly achieved by the commercially practiced methods described above in which the cans are rotated either about their longitudinal axes or end-over-end. Moreover our tests have indicated that the process described in U.S. Patent 2,134,817 will be subject wide random variations, and as a result the sterilisation process which would be required in practice to ensure commercial sterility using that process would have to be made considerably greater than the sterilisation times which can be achieved.

As mentioned above, in US Patent 2,134,817, the cans are reciprocated horizontally. Comparative tests performed by the present Applicants have shown that horizontal reciprocation offers more efficient and more uniform product mixing of Category 2 food products than does vertical reciprocation, and for this and other reasons horizontal reciprocation is preferred. For some containers, for example, cylindrical cans which are longer than they are wide, it is advantageous for them to be generally aligned with the reciprocation path. For other containers however (for example, squat cylindrical cans_ it may be preferred for them to be orientated differently in relation to the reciprocation path. In our International Application PCT/GB95/02407 from which corresponding patents have been obtained in a range of countries there is described a process for thermally treating a product in a container having a headspace above the product, in which the container is subjected to a heated or cooled environment and is simultaneously agitated. The acceleration to which the container is subjected by the agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating or cooling time required for the product to reach a predetermined temperature is very substantially reduced and moreover is substantially insensitive to changes in the acceleration.

DISCLOSURE OF INVENTION

In what follows reference is made to 'a container' which should be taken to include

'one or more containers' where appropriate.

According to a first aspect of the present invention there is provided a processing method for thermally treating a container (containing a product) characterised by three processing zones (12, 13A, 13B, 14) in which are carried out a sequence of steps comprising: causing the container (Cl) in the first zone (12) to pass along a first direction (D) of travel; preheating the container (Cl) during the first zone (12) to a first predetermined temperature and agitating the container (Cl) during the first stage wherein the minimum, acceleration amount to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the first pre-determined temperature is: firstly reduced by at least 90% compared to the heating time required to reach the first pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; passing the preheated container (C, Cl) from the first zone (12) to the second zone (13A) by way of a pressure lock (Pl) providing for the maintenance of an ambient pressure difference between the first zone (12) and second zone (13A); heating the, or each, container (Cl) to a second pre-determined temperature in order to sterilise the container (Cl) and its contents; and agitating the, or each, container (Cl) in the second zone (13A, 13B) wherein the minimum acceleration to which the, or each, container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the second pre-determined temperature is: firstly reduced by at least 90% compared to the heating time required to reach the second pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; passing the treated container (Cl) from the second zone (13B) to the third zone (14) by way of a pressure lock (P2) providing for the maintenance of an ambient pressure difference between the second zone (13B) and third zone (14); and causing the sterilised container (Cl) in the third zone (14) to pass through the third zone (14) while being subjected to the simultaneous steps of: cooling of the container (Cl) and its contents, in at least two stages, to a third pre-determined temperature while agitating the container (Cl) wherein the minimum acceleration amount to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the cooling time required for the contents to reach the third pre-determined temperature is: firstly reduced by at least 90% compared to the cooling time required to reach the third predetermined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation. According to a first preferred version of the first aspect of the present invention with the container (Cl) passing along a given direction of travel (D) in a given zone (12, 13A, 13B, 14) then the step of agitation is applied to the container (Cl) in a direction (A) transverse the direction of travel (D) in that zone.

According to a second preferred version of the first aspect of the present invention or of the first preferred version thereof agitation of the container (Cl) involves reciprocation of the container (Cl). Typically with the container (Cl) in the form of a metal can with at least one plane end closure, the reciprocation of the container (Cl) is in a direction (A) perpendicular to the, or at least one, plane end closure.

According to a third preferred version of the first aspect of the present invention or of any preceding preferred version thereof agitation of the container (Cl) is sinusoidal in terms of position relative to a datum as against time.

According to a second aspect of the present invention there is provided a processing installation for subjecting a container (containing a product) to thermal treatment characterised by three processing zones (12, 13A, 13B 14) each providing for an environment for the container during thermal treatment within the given zone, each processing zone including: heating means whereby the zone (12, 13A, 13B, 14) can have its ambient temperature maintained at a pre-determined level; a conveyor system (15, 16, 17) for conveying the container in a given direction (D) of travel through the processing zone (12, 13A, 13B, 14); the conveyor (15, 16, 17) being equipped with support means (C) for the container (Cl); drive means (R) for the container (Cl) when supported by way of the support means (C) to enable the container (Cl) to be subject to agitation wherein the minimum acceleration to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the pre-determined temperature in that processing zone (12, 13A, 13B, 14) is: firstly reduced by at least 90% compared to the heating time required to reach the same pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; a first pressure lock (Pl) between the first zone (12) and second zone (13A); and a second pressure lock (P2) between the second zone (13B) and third zone (14); the first and second pressure locks (pi, P2) between them serving to maintain the second processing zone (13A, 13B) at predetermined ambient pressure greater than that in the first zone (12) and third zone (14) while allowing transfer of the container (Cl) from the first zone (12) into the second zone (13A, 13B) and thereafter from the second zone (13B) into the third zone (14) without substantial change in the predetermined ambient pressure in the second zone (13A, 13B).

According to a first preferred version of the second aspect of the present invention the container (Cl), in passing along the direction of travel (D) through a given processing zone (12, 13A, 13B, 14) can be subject to agitation applied to the container in a direction (A) transverse the direction of travel (D).

According to a second preferred version of the second aspect of the present invention or of the first preferred version thereof agitation of the container (Cl) amounts to reciprocation of the container (Cl).

According to a third preferred version of the second aspect of the present invention or of any preceding preferred version thereof the container (Cl) is a metal can and the agitation of the can (Cl) is perpendicular to one or more plane end closures thereof. According to a fourth preferred version of the second aspect of the present invention or of any preceding preferred version thereof agitation of the container (Cl) is sinusoidal in terms of position relative to a datum position as against time.

According to a fifth preferred version of the second aspect of the present invention or of any preceding preferred version thereof the first processing zone (12) serves as a pre-heating stage for a container (Cl) providing for the ambient temperature to be raised to a first pre- determined value; the second zone (13A, 13B) serves as a sterilising stage for a container (Cl) when transferred from the first processing zone providing for the ambient temperature in the second zone (13A) to be raised to a second pre-determined value; and the third processing zone (14) serves as a cooling stage for a container (Cl) when transferred from the second zone (13B) and providing for the ambient temperature in the third zone (14) to be reduce to a third predetermined temperature.

According to a sixth preferred version of the second aspect of the present invention or of any preceding preferred version thereof pressurising means are included whereby the ambient pressure in the second zone (13A, 13B) can be raised above that in the first zone (12) and the third zone (14).

According to a seventh preferred version of the second aspect of the present invention or of any preceding preferred version thereof at least one of the pressure locks (Pl, P2) is a rotary valve.

According to an eighth preferred version of the second aspect of the present invention or of any preceding preferred version thereof at least one of the pressure locks (Pl, P2) comprises a pressurisible housing (27) having a path there through with entry (31) into the housing (27) to the path and exit from the housing (27) from the path being by way of pressure tight closure means (26).

According to a third aspect of the present invention there is provided a container which has been subjected to a processing method according to the first aspect or any preceding preferred version thereof.

According to a fourth aspect of the present invention there is provided a container which has been subjected to processing in an installation according to the second aspect of any preceding preferred version thereof.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings of a can processing installation of which:

Figure 1 is a general diagram of an installation making up a first embodiment;

Figure 2 shows components making up a first zone of Figure 1;

Figure 3 shows components making up a second zone of Figure 1;

Figure 4 shows components making up a third zone Figure 1; and

Figure 5 is a sectional elevation of a device used to separate zones described with reference to the foregoing figures;

Figure 6 is a general diagram of an installation making up a second embodiment; and

Figure 7 is a diagram of a part of Figure 6.

MODE FOR CARRYING OUT THE INVENTION

Figure 1

Enclosure 11 is divided into separate zones namely first processing zone 12, second processing zone 13A, B and third processing zone 14. Conveyor belts 15, 16, 17 enable cans loaded into entry end E to pass through the enclosure 11 from entry M of conveyor belt 15 to exit X of conveyor belt 17 during which passage the cans are subject to a sterilising process which is very rapidly and economically completed by comparison with presently known processes.

The conveyor belts 15, 16, 17 are each driven by electric motors and serve to move cans in overall direction of travel D from zone 12 to zone 14. There is a need to maintain different thermal environments in each zone. To try and provide this by means of a single belt passing through all three zones 12 - 14 could in practice give rise to pressure integrity problems. Consequently three separate belts 15, 16, 17 are provided with synchronising means for transfer of cans from the end of one belt to the next in the sequence. The belts 15 - 17 are further provided with means for lateral horizontal reciprocatory agitation in direction A to provide for continuous agitation of the cans carried on the conveyor in passing through each of the three zones 12, 13, 14 to ensure rapid heat transfer between ambient conditions and the content of each can.

Zones 12 - 14

The function and parameters of each zone are as follows.

Zone Function Wkng Temp Wkng Press Heating/ Cooling Medium

12 Pre heating 100⁰C atmospheric Steam heating

13A Sterilising 130⁰C 30psi Steam heating

13B Pre-cooling 90-100⁰C 30psi Air cooling

14 Spray cooling 40⁰C atmospheric Water spray cooling

The heating and cooling mediums used and their method of application in the zones is not discussed hereafter since there provision and use is already well established in the field of can sterilisation.

Because of the pressure differential that needs to be maintained between Zone 12 and Zone 13A and between Zone 13B and 14 rotary transfer valves Pl and P2 (respectively) are provided to ensure that continuous flow of product can be maintained throughout the installation.

Figure 2 (Zone 12)

This serves to provide a pre-heating environment for cans to be sterilised and is steam heated to provide an ambient temperature of about 100° C. For this temperature the zone 12 can be operated at atmospheric pressure.

Arrays of cans arrive at the entry to zone 12 as sealed items having contents which leave a working volume at the top of the can. The arrays are located on carriers.

The conveyor belt 15 has an input end M on which are the incoming sealed cans are loaded. The conveyor 15 is driven in the direction D towards zone 13A. The conveyor 15 has attached to it support carriers, typically carrier C, for a set of cans, typically can Cl. The can Cl is positioned on the carrier C to lie with its longitudinal axis transverse the direction of travel D of the conveyor 15. The conveyor 15 is adapted to provide for lateral reciprocation of the carrier C, and so of each can and its contents, in direction of arrow A relative to the direction of travel D. The extent of lateral displacement available from the conveyor 15 is shown with one limit indicated by a continuous line Kl and the other limit by broken line K2. The other two conveyors 16, 17 are similarly adapted.

In each case lateral displacement of the conveyor is carried out by way of a crank and connecting rod assembly powered by an electric motor. For conveyor 15 this is shown diagrammatically as assembly R. The assembly R has a crank R' with two throws rl, r2. Throw rl provides the reciprocatory motion require for cans carried by conveyor 16. Throw r2 provides a similar function for a second conveyor system installation (not shown) installed alongside installation 11. Rotary Valve Assembly Pl

Cans on the conveyor 15 are passed from first processing zone 12 to conveyor 16 in second zone 13 by way of a rotary valve assembly Pl shown in Figure 5 . End 15A of conveyor 15 serves to present a sequence of cans to rotary valve 25 within housing 27. The valve 25 contains a series of compartments 25' each separated from the next by flaps such as flap 26. As a can (typically can 28) arrives at the end of belt 15 it is caused by a spoke 29 on wheel 30 to pass into compartment 31 of valve 25. The can 28 is one end of a line of such cans extending transversely across the conveyor 15. The conveyor 15 is not subject to lateral reciprocation in the vicinity 15A of the assembly Pl to provide for simple aligning of cans immediately prior to entry to the assembly.

The valve 25 is caused to rotate in an anti-clockwise direction. The can 28, and so the row of cans of which can 28 is one end, are carried around by the valve 25 before being released onto belt 16. The row of transferred cans is then carried off to the right into second zone 13 A for sterilisation. In this case the valve assembly 22 provides for cans from first processing zone 12, at about atmospheric pressure, to be transferred to second processing zone 13 at a higher ambient pressure.

Processing Zone 13A

This provides a sterilising stage for cans conveyor 16 and utilises steam or water heating to about 130 ° C. from the pre-heated temperature from zone 12 of about 100⁰C This elevated temperature of 130⁰C leads to a need for the processing zone 13A to be maintained at a raised ambient over-pressure of about 30 p.s.i. relative, to that in the pre-heating zone 12. Conveyor 16 is operated to pass pre-heated cans through the second zone 13A at a speed at which the cans and their contents will be raised to, and be maintained at, the required sterilising temperature while being subject to further lateral agitation to ensure that the can and its contents are rapidly brought up to the sterilising temperature of 130⁰C and maintained there to complete the required period of sterilisation.

Processing Zone 13B

Following the sterilising process of Zone 13A conveyor 16 carries the sterilised cans into Zone 13B where they are subject to pre-cooling by means of an air flow while still being maintained at the overpressure of the sterilising zone 13A. Whilst in this zone 13B the cans are subject to further agitation to ensure that the can and its contents are cooled promptly and uniformly.

Rotary Valve Assembly P2

This provides for similar type of valve assembly to that of Pl to be located between the end of the pre-cooling zone 13B and the start of the spray cooling zone 14. The assembly P2 provides for cans to pass continuously from the relatively high ambient pressure of second zone 13A, 13B to the atmospheric pressure of spray cooling zone 14. Since the form and function of the assembly P2 mirrors that of assembly Pl the function will not be explained further.

Third Processing Zone 14

This provides a cooling environment for heated cans conveyed into the zone 14 from zone 13B. leaving the zone 13B the cans are at a temperature of between 9O⁰C and 100⁰C. In this zone the cans are moved on conveyor 17 which is again subject to lateral agitations as described in connection with stages 12, 13A and 13B. This serves to ensure that the cooling of the can and its contents rapidly reaches the required final temperature of about 4O⁰C.

Once the cooled cans reach output end X of the conveyor belt 17 the sterilising processing is complete and the cans can be removed from the enclosure 11. The embodiment serves to exemplify how a sterilisation process for cans and their contents can be carried out on a continuous processing basis rather than, as heretofore, as a batch process. Further by using controlled agitation the time required by presently known methods of heat treatment can be very considerably reduced. This serves to provide both a substantially increased through put of cans in a given period and a substantial saving in the thermal energy required for such processing.

Figures 6 and 7

Figure 6 shows a second embodiment of an installation according to the present invention. The installation shown in Figure 6 is similar in most respects to that shown in Figure 1 and consequently components in Figure 6 virtually identical in form and function to those shown in Figure 1 are given the same reference numerals as that shown in Figure 1 with the addition of an inverted comma and are not described further.

The difference between the two installations lies in the means for providing for pressure differentials between the zones, in the first embodiment the pressure differentials are maintained by means of the rotary valve assemblies Pl (Figure 5) and P2. In this second embodiment these are replaced by pressure locks are replaced by pressure locks Ql and Q2. Through the preheating zone 12' baskets holding containers to be sterilised are passed by way of conveyor 15', on which they are agitated, towards pressure lock Ql. This comprises a pressurisable housing 60 with pressure tight closable pairs of doors 61, 62 and 63, 64. With doors 63, 64 of lock Ql closed pressure in housing 61 is reduced to atmospheric similar to that in zone 12'. The doors 61, 62 are then opened to enable entry of one or more baskets into the compartment. Doors 61, 62 are then closed and pressure in the housing 60 raised to that corresponding to that in zone 13 A⁷. Doors 63, 64 are then opened and the baskets within the housing are caused to pass into zone 13A' and are passed through the zone 13A' and 13B' by means of conveyor 16.

Having reached pressure lock Q2 the method provided for by pressure lock Ql is in effect reversed with the baskets being conveyed into, and then being held within housing 70. Pressure within the housing 70 is then reduced from that obtaining in zone 13B' to that established in zone 14. The appropriate doors of pressure lock Q2 are then opened to provide for the baskets to move through the cooling zone 14.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention provide for the very rapid sterilisation processing (in comparison with conventional existing methods) of canned foodstuffs and other canned materials. This leads to considerable increases in efficiency and economics of such processing with benefits of significantly increased throughput and substantial savings in heating costs.

Claims

1 A processing method for thermally treating a container (containing a product) characterised by three processing zones (12, 13A₇ 13B and 14) in which are carried out a sequence of steps comprising: causing the container (Cl) in the first zone (12) to pass along a first direction (D) of travel; preheating the container (Cl) during the first zone (12) to a first predetermined temperature and agitating the container (Cl) during the first stage wherein the minimum acceleration amount to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the first pre-determined temperature is: firstly reduced by at least 90% compared to the heating time required to reach the first pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; passing the preheated container (Cl) from the first zone (12) to the second zone (13A) by way of a pressure lock (Pl) providing for the maintenance of an ambient pressure difference between the first zone (12) and second zone (13A); heating the, or each, container (Cl) to a second pre-determined temperature in order to sterilise the container (Cl) and its contents; and agitating the, or each, container (Cl) in the second zone (13A) wherein the minimum acceleration to which the, or each, container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the second pre-determined temperature is: firstly reduced by at least 90% compared to the heating time required to reach the second pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; passing the treated container (Cl) from the second zone (13B) to the third zone 14 by way of a pressure lock (P2) providing for the maintenance of an ambient pressure difference between the second zone (13B) and third zone (14); and causing the sterilised container (Cl) in the third zone (14) to pass through the third zone (14) while being subjected to the simultaneous steps of: cooling of the container (Cl) and its contents, in at least two stages, to a third pre-determined temperature while agitating the container (Cl) wherein the minimum acceleration amount to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the cooling time required for the contents to reach the third predetermined temperature is: firstly reduced by at least 90% compared to the cooling time required to reach the third pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation.

A processing method as claimed in Claim 1 characterised in that when the container (Cl) is passing along a given direction of travel (D) in a given zone (12, 13A, 13B, 14) then the step of agitation is applied to the container (Cl) in a direction (A) transverse the direction of travel (D) in that zone.

A processing method as claimed in any preceding claim characterised in that the agitation of the container (Cl) involves reciprocation of the container (Cl). A processing method as claimed in Claim 3 characterised in that the container (Cl) is a metal can with at least one plane end closure and the reciprocation of the container (Cl) is in a direction (A) perpendicular to the, or at least one, plane end closure.

A processing method as claimed in any preceding claim characterised in that the agitation of the container (Cl) is sinusoidal in terms of position relative to a datum as against time.

A processing installation for subjecting a container (containing a product) to thermal treatment characterised by three processing zones (12, 13A, 13B 14) each providing for an environment for the container during thermal treatment within the given zone, each processing zone including: heating means whereby the zone (12, 13A, 13B, 14) can have its ambient temperature maintained at a pre-determined level; a conveyor system (15, 16, 17) for conveying the container in a given direction (D) of travel through the processing zone (12, 13A, 13B, 14); the conveyor (15, 16, 17) being equipped with support means (C) for the container

(Ci); drive means (R) for the container (Cl) when supported by way of the support means (C) to enable the container (Cl) to be subject to agitation wherein the minimum acceleration to which the container (Cl) is subjected during agitation is of sufficient magnitude to cause the process to operate in a regime in which the heating time required for the product to reach the predetermined temperature in that processing zone (12, 13A, 13B, 14) is: firstly reduced by at least 90% compared to the heating time required to reach the same pre-determined temperature but without agitation; and secondly substantially insensitive to increase in the magnitude of the agitation; a first pressure lock (Pl) between the first zone (12) and second zone (13A); and a second pressure lock (P2) between the second zone (13A) and third zone (14); the first and second pressure locks (pi, P2) between them serving to maintain the second processing zone (13 A, 13B) at predetermined ambient pressure greater than that in the first zone (12) and third zone (14) while allowing transfer of the container (Cl) from the first zone (12) into the second zone (13 A, 13B) and thereafter from the second zone (13B) into the third zone (14) without substantial change in the predetermined ambient pressure in the second zone (13B).

A processing installation as claimed in Claim 7 characterised in that the container (Cl), in passing along the direction of travel (D) through a given processing zone (12, 13A, 13B, 14) can be subject to agitation applied to the container in a direction (A) transverse the direction of travel (D).

A processing installation as claimed in Claims 7 or Claim 8 characterised in that agitation of the container (Cl) amounts to reciprocation of the container (Cl).

A processing installation as claimed in any of preceding claims 7 to 9 characterised in that the container (Cl) is a metal can and the agitation of the can (Cl) is perpendicular to one or more plane end closures thereof.

A processing installation as claimed in any of preceding claims 7 to 10 characterised in that agitation of the container (Cl) is sinusoidal in terms of position relative to a datum position as against time. A processing installation as claimed in any of preceding claims 7 to 11 characterised in that: the first processing zone (12) serves as a pre-heating stage for a container (Cl) providing for the ambient temperature to be raised to a first predetermined value; the second zone (13A, 13B) serves as a sterilising stage for a container (Cl) when transferred from the first processing zone providing for the ambient temperature in the second zone (13A) to be raised to a second pre-determined value; and the third processing zone (14) serves as a cooling stage for a container (Cl) when transferred from the second zone (13B) and providing for the ambient temperature in the third zone (14) to be reduced to a third predetermined temperature.

A processing installation as claimed in any of preceding claims 7 to 12 characterised by pressurising means whereby the ambient pressure in the second zone (13A, 13B) can be raised above that in the first zone (12) and the third zone (14).

A processing installation as claimed in any of preceding claims 7 to 13 characterised in that at least one of the pressure locks (Pl, P2) is a rotary valve.

A processing installation as claimed in any of preceding claims 7 to 13 characterised in that at least one of the pressure locks (Pl, P2) comprises a pressurisible housing (27) having a path there through with entry (31) into the housing (27) to the path and exit from the housing (27) from the path being by way of pressure tight closure means (26). A container subjected to a processing method as claimed in Claims 1 to 6.

A container subjected to processing in an installation as claimed in Claims 7 to 16.