Vacuum packaging apparatus and process

0001The present invention relates to an apparatus and method for vacuum packaging a product in a flexible receptacle, such as a bag.

BACKGROUND OF THE INVENTION

0002A number of methods and apparatuses are available in the prior art for vacuum packaging food products in flexible containers such as bags or pouches. For instance, US 3,832,824 discloses a method and an apparatus wherein a filled bag is placed in a vacuum chamber which has two portions, the first portion enclosing the mouth of the bag and the second portion enclosing the product-containing part of the bag. Initially vacuum is applied only in the portion of the chamber in which the product is contained causing the wall of the bag to "balloon" away from the enclosed product thereby allowing a more efficient removal of air from within the bag; vacuum is then applied also in the portion of the chamber in which the mouth of the bag is located, consequently evacuating the interior of the "ballooned" bag; when the evacuation of the bag is complete the bag can be closed and atmospheric pressure re-established inside the chamber. Such a process can be succesfully applied only to products that can tolerate a long evacuation step or a high vacuum, wherein the term high vacuum indicates a very low pressure level. In fact, when packaging products having a porous structure, such as certain types of cheeses, the high vacuum applied can remove air out of the product so that the structure of the product will be damaged. Methods for the vacuum packaging of sensitive products are disclosed in US 4,583,347 and in US 4,922,686, both describing a single-chamber apparatus having an air admission valve located on the cover of the vacuum chamber for allowing air inside the chamber during the vacuumization step. The admission of air in the vacuum chamber once or more times during the vacuumization stage of the process generates a pulsating effect which facilitates the extraction of air from within the bag without the need of generating a high level of vacuum. To carry out such process the apparatus described in US 4,583,347 and in US 4,922,686 relied on one air extraction duct located close to the mouth of the bag, so that the amount of air extracted form the side of the chamber holding the product and the speed of air extraction depend on how much the passage between one side of the chamber and the other is obstructed by the bag and the product, often leading to non uniform levels of vacuum from one package to the other during high speed packaging operations. Therefore the need still exsist for an apparatus and a method for reliably packaging articles under vacuum in a flexible receptacle, such as a bag.

SUMMARY OF THE INVENTION

0003Accordingly, a first object of the present invention is an apparatus for vacuum packaging a product in a flexible receptacle, such as a bag, comprising a first vacuum chamber and a second vacuum chamber adjacent to it and an aperture connecting the two chambers for passing the neck of the receptacle, means to evacuate the first and second chambers and means to close the package when its evacuation is completed characterised in that means are present in the aperture to prevent the passage of air from one chamber to the other and air admission means are present in the first chamber.

0004A second object of the present invention is a method of vacuum packaging a product in a flexible receptacle, comprising the steps of loading the article in the receptacle, extracting gas from around the exterior of the receptacle to lower the surrounding pressure, extracting gas from within the receptacle, partially restoring the pressure surrounding the exterior of the receptacle, further extracting gas from around the exterior of the receptacle, and again partially restoring the pressure surrounding the exterior of the receptacle, then further extracting gas from around the exterior of the receptacle before closing the receptacle characterised in that the extraction of air from within the receptacle is independent of the extraction of air from around the receptacle and constant in time.

0005These and other objects, advantages, and features of the invention will be more readily understood and appreciated by reference to the detailed description of the invention and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0006<ul id="ul0001" list-style="none" compact="compact"><li>Fig. 1 is a section of an apparatus according to the present invention in which the vacuum chambers of the apparatus are closed;</li><li>Fig. 2 is a view similar to Fig. 1 showing the apparatus during operation when vacuum is applied in the chamber containing the product.</li></ul>

DETAILED DESCRIPTION OF THE INVENTION

0007Figure 1 shows a section of the vacuum packaging apparatus 1 of the invention. As used herein, the phrase "vacuum packaging" refers to a method wherein at least one product is placed in a receptacle having one opening, such as a bag, then the receptacle is evacuated and closed.

0008Vacuum packaging apparatus 1 includes a cover 2 hinged to base member 3 which is divided by lower chamber divider wall 12 which cooperates with the upper divider wall 11 to separate apparatus 1 into the two chambers 4 and 5. Upper divider wall 11 is optionally removable from cover 2. The first and larger chamber 4 is the product chamber in which the portion of a receptacle or bag 9 containing a product 8 is placed. The receptacle opening (9a) or bag neck is extended into the second and smaller chamber 5 through aperture 15. Aperture 15 is formed in the wall which divides chambers 4 and 5 when the cover 2 is rotated into position. Gaskets 16 and 16a on the lower divider wall (12) and on the upper divider wall (11), respectively, hold the bag neck in place without choking it and isolate first chamber 4 from second chamber 5. The first chamber 4 is evacuated through vacuum port 6 and the second chamber is evacuated through vacuum port 7. Air admission port 10 admits air into the first chamber. A receptacle-closing unit 21 is located in one of the chambers. Although figures 1 and 2 show the receptacle-closing unit 21 located in chamber 5, the mechanism could also be located in chamber 4. Suitable receptacle-closing units are for instance heat sealing bars, impulse sealing bars or clipping mechanisms. In a preferred embodiment of the apparatus of the invention the receptacle-closing unit 21 is a pair of opposed heat sealing bars. The apparatus further includes a pressure sensing mean 22 in chamber 4 and optionally a second pressure sensing mean 23 in chamber 5 and a programmable logic control system (not shown) which monitors and sequences each phase of the apparatus during operation and in particular controls the operation of vacuum ports 6 and 7, of air admission port 10 and of heat sealing bars 21.

0009To perform the process according to the present invention the operator of apparatus 1 places the bag 9 filled with product 8 in the first chamber 4 and brings the neck of the bag down over gasket 16 and across sealing bars 21, so that the open end of the bag 9a is located in the second chamber 5. When cover 2 is rotated in the closed position, the neck of the bag will be held in place, without being choked, by gaskets 16 and 16a on the lower and upper dividing walls, respectively. Suitable materials for gaskets 16 and 16a are for instance flexible plastic materials such as rubber and foams. Gaskets 16, 16a and the bag neck fill the aperture between chambers 4 and 5 so that very little air is leaked from one chamber to the other. Once the chamber is closed evacuation of chamber 4 begins through vacuum port 6. Any conventional vacuum pump which is well known in the art may be used to evacuate chamber 4. In this first phase, shown in Fig. 2, bag 9 will balloon outwardly due to the pressure difference between the interior of the bag 9 and the chamber 4. When the pressure in chamber 4 reaches a value P1, set by the operator, evacuation of the second chamber 5 begins through vacuum port 7. Due to its smaller size the evacuation of chamber 5 will proceed more rapidly than the evacuation of chamber 4, so that the vacuum level in chamber 5, and consequently within bag 9, will drop below that in chamber 4 causing the bag to collapse back onto product 8. When the pressure in chamber 4 reaches a value P2 a signal is sent to a control unit to stop evacuation of chamber 4. Due to the time needed for the effective closing of vacuum port 6 and to the minimal passage of air from one chamber to the other, the pressure in chamber 4 will drop further from value P2 to value P3. When the pressure inside chamber 4 reaches value P3 air is allowed into the chamber through air admission port 10 to return to pressure value P2. Air admission port 10 is then closed and vacuum is applied again through port 6 until the pressure is reduced to value P3. The air admission-evacuation cycle between pressure values P2 and P3 respectively is repeated at least once and usually more times until the desired packaging result is obtained, at which time bag 9 is closed by operation of heat sealing bars 21. Vacuum port 7, connected to chamber 5, is held in the open position throughout the air admission-evacuation cycles carried out in chamber 4. Pressure values P1, P2, P3 and the time during which the air admission-evacuation cycles are repeated are set by the operator in the programmable logic control at the beginning of the operations and are chosen according to the nature of the product being packaged. In general pressure value P1 ranges from 500 to 950 mbar, preferably from 600 to 900 mbar; pressure value P2 ranges from 200 to 800 mbar, preferably from 250 to 650 mbar; pressure value P3 is set to be from 20 to 130 mbar lower than P2, preferably from 30 to 100 mbar lower than P2. The time period during which the air admission-evacuation cycles are repeated is usually from 3 to 20 seconds, preferably from 5 to 15 seconds.

0010Suitable settings for the packaging of sensitive products such as Raclette cheese and pate according to the process of the invention are reported in the following table: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="5" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="31.50mm" /><colspec colnum="2" colname="col2" colwidth="31.50mm" /><colspec colnum="3" colname="col3" colwidth="31.50mm" /><colspec colnum="4" colname="col4" colwidth="31.50mm" /><colspec colnum="5" colname="col5" colwidth="31.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">PRODUCT</entry><entry namest="col2" nameend="col2" align="center">P1 (mbar)</entry><entry namest="col3" nameend="col3" align="center">P2 (mbar)</entry><entry namest="col4" nameend="col4" align="center">P3 (mbar)</entry><entry namest="col5" nameend="col5" align="center">Time (s)</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">Raclette cheese</entry><entry namest="col2" nameend="col2" align="center">800</entry><entry namest="col3" nameend="col3" align="center">450</entry><entry namest="col4" nameend="col4" align="center">400</entry><entry namest="col5" nameend="col5" align="center">5</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">Pate</entry><entry namest="col2" nameend="col2" align="center">800</entry><entry namest="col3" nameend="col3" align="center">500</entry><entry namest="col4" nameend="col4" align="center">400</entry><entry namest="col5" nameend="col5" align="center">12</entry></row></tbody></tgroup></table></tables>

0011In one embodiment of the apparatus of the present invention, upper chamber divider wall 11 is connected to vacuum chamber cover 2 through a lateral guide and held in place by means of a clamp. When needed it can be disengaged from cover 2 and removed from the apparatus by manually releasing the clamp. This can be conveniently done when the products to be packaged are hard, non-porous products and therefore are not damaged by a high vacuum packaging process.

0012The apparatus described above offers several advantages with respect to prior art ones. First of all it allows to pack both sensitive and non-sensitive products by simply removing upper chamber divider wall 11. Furthermore, when packaging sensitive products, the possibility of independently controlling the level of vacuum in the two chambers offers a great reliability in the end result in particular in packaging processes with high turnovers.