NO312486B1 - Device for preparing packaging for heat-sensitive materials - Google Patents

Description

Technical area

The present invention generally relates to devices and processes for hydrating and freezing a selected medium to keep various objects cold. More specifically, the present invention relates to a device for preparing a packaging material for use in shipping heat-sensitive materials by hydrating and freezing a superabsorbent polymer enclosed in a form cloth of a flexible, permeable material.

Background

The present invention is a device and a method for the hydration and freezing of superabsorbent, polymer-based cooling media similar to that described in the international patent with application number PCT/US92/06486 (compare US application 07/738835), or similar media used to keep easily perishable materials at a controlled cold or freezing temperature during shipment. In accordance with this, the discussion of the structures and properties of the described media in the referenced patents shall only be discussed to the extent that it is necessary to explain the media's connection with the components of the device and the method described herein, and likewise a detailed understanding of the chemical properties of the medium not necessary to understand the invention.

Prior to the use of superabsorbent polymers laminated into individual cells, only a few substances were used in shipping containers to maintain a cold temperature inside the shipping container. These include: ice sealed in pads, dry ice and gel blocks. However, due to high costs, pollution and handling problems, as well as difficulties in maintaining critical temperatures in a container during shipment, these shipping materials are eventually replaced with frozen, superabsorbent, polymer-based cooling media (hereafter media). One such medium is ThermaFreeze® manufactured by Thermafreeze, Inc. of Mobile, Alabama. ThermaFreeze® is produced in long rolls, typically 38 or 72 cm wide, containing a matrix of laminated, individual cells between elongated continuous sheets of thermoformable media, as described in the referenced patent. Each cell contains a measured amount of superabsorbent polymer that can absorb up to many times its own weight and size in water, thereby filling each cell upon exposure to water. Before the cells are exposed to an aqueous environment, the cells in the rollers are rinsed with superabsorbent polymer powder that occupies negligible space inside the cells. Before hydration, the cells are therefore unexpanded and the medium consists of a flat sheet or a form cloth of cells which are typically 38 or 72 cm wide and which have a pre-selected length (typically 100 metres).

According to a conventional method, medium is laid out, exposed to an aqueous environment which contributes to a rapid hydration of the medium, after which the medium is frozen and divided into sizes and shapes suitable for arrangement in shipping containers. This operation must take place ("on-site") in a production facility of a user who uses media for shipments. However, this method of preparing media is manual, and therefore time-consuming, which thus increases the total cost of using such media for shipments. The consumer also necessarily does not know how the preparation operation should be optimized so that media are properly prepared for arrangement in shipping containers of various sizes and designs. In addition, the product may have other areas of application that are difficult to exploit in the absence of sufficient knowledge and a usable automation system.

In connection with shipping packaging and in other industries, there is therefore a need for a device and method for automatically preparing superabsorbent polymer coolants which are then to be arranged in the shipping container. As many plants place a high value on floor space, it is therefore important to have a unit that has a relatively small footprint.

Description of the invention

The purpose of the present invention is to provide a device for automating the hydration and freezing of superabsorbent, polymer-based cooling media. A further purpose of the present invention is to provide a method for optimizing hydration and the freezing of superabsorbent, polymer-based cooling media.

Yet another purpose of the present invention is to provide a modular plant with a minimal footprint which includes a method for hydrating and freezing superabsorbent, polymer-based cooling media so that the medium can be prepared in a suitable manner at the consumer's place before it is placed in shipping carriers.

According to the present invention, the above-mentioned purpose is achieved by means of a device which is characterized by the features specified in the characterizing part of claim 1.

Preferred embodiments of the present invention are stated in the independent claims 2 to 11 and claim 13.

Claims 12 and 14 are independent claims which specify a modular packaging production device and an assembly plant, respectively.

Further features, purposes and advantages of the present invention will be understood by reading the following description with reference to the attached figures.

Brief description of the figures

The device comprising the features according to the invention is shown in the attached figures, which are part of the description and in which: fig. 1 is a cross-section of the hydration module along the longitudinal axis;

fig. 2 is a cross section of the cooling module along the longitudinal axis;

fig. 3 is a cross section of the shaker module along the longitudinal axis;

fig. 4 is a block diagram of the components in operational relation;

fig. 5 is a diagram of the second embodiment of the hydration freezer showing the most important internal elements;

fig. 6 is an expanded view of the hydration tank and the freezing chamber in the facility; and

fig. 7 is a detailed view of a conveyor belt roll showing "tractor feed type" surface features on the outside of the roll and cooperating, positioned perforations on the form cloth.

Best Mode for Carrying Out the Invention

With reference to the figures for a clearer understanding of the invention, fig. 1 shows that the first module 11 is a hydration unit which can be used as an individual unit, but which is specifically designed for use as a module in the medium preparation device. Module 11 includes an external frame 12 which has an inlet opening 13 through which pads or an undivided form cloth can be fed along a track 14. At the bottom of the track 14 is a conveyor belt 16 which runs along the bottom of the tank 37. The conveyor belt 16 has an inclined part extending up and over a wall in tank 37 and which serves as an emptying conveyor belt. A secondary conveyor belt 18 can optionally be mounted above the conveyor belt 16 at a height in the tank 37. A motor 19, which can be hydraulic or electric with suitable speed control, is mounted on a support frame within the framing 12 and has an output sheaf or a gear 21 which is connected to a drive roller 22 on conveyor belt 16 and a drive roller 23 on conveyor belt 18 through a suitable belt or chain.

Tank 37 serves as a sump for the accumulation of a hydrating fluid. The medium is a multi-cell layer that has a superabsorbent polymer in each cell in sufficient quantity to absorb a fluid that will later be frozen. The preferred fluid is water which has been pre-filtered to remove impurities, however other fluids may be suitable for given applications with specific polymers. The hydrating fluid can be filled to a given level as shown in fig. 1 so that the conveyor belt 18 is immersed in the medium below the surface of the fluid and forces the medium towards the outlet end of the conveyor belt 16. In this case, the fluid level is measured by a sensor 24 and additional hydrating fluid is introduced to the tank to replenish what hydrates the superabsorbent polymer. A small unit of this construction can, for example, consume approx. 40 liters of hydrating fluid per hour. Alternatively, a series of spray nozzles 26 can be mounted above tank 37 and the medium driven by conveyor belt 16 can be sprayed with fluid, and the excess fluid can be accumulated and sprayed on again through suitable pipe devices and pump mechanisms. In both cases, the conveyor belt is a stainless steel grid or a conveyor belt of a plastic type which allows a fluid to pass through, as it can still force the medium through tank 37. It may be necessary to heat the hydrating fluid to approx. 37°C, and thus an external reservoir 31 with preheated fluid can be used as a source for the refilled fluid. The speed of the conveyor belts can be adjusted through conventional control of motor 19 to ensure that the medium is fully hydrated before it is removed from tank 37 on conveyor belt 16.

After the medium leaves tank 37, it enters a drip conveyor belt 32 which is also an open stainless steel belt mounted above a drip tray 33 and which has a vibration assembly attached thereto so that external surface moisture is removed from the medium as it crosses the conveyor belt . The conveyor belt can be driven by a gear wheel on motor 19 so that the speed follows the conveyor belts 16 and 18. A plurality of eccentric rollers 35 as shown in fig. 3 can, for example, be used to transfer movement to the conveyor belt across the direction of movement to help remove external moisture. Excess fluid can also be removed from the medium using a high-pressure air knife.

Drip belt 32 terminates in an inlet 39 to a cooling module 40. Module 40 includes an insulating frame 41 in which a plurality of successive conveyor belts 42 are supported for adaptive movement, each conveyor belt corresponding to the conveyor belts used in the first module 11. The hydrated medium is moved successively. from one conveyor belt to another to discharge from outlet 44. The inside of framing 41 is kept at a temperature well below the freezing point of the hydrated polymer medium. Inlet 39 has a secondary inlet 39' for the introduction of dry ice in cases where dry ice is the preferred method of maintaining the sub-freezing temperature. A cover can be placed over the inlet if an alternative cooling method is used, which is described below.

In some cases, conventional mechanical cooling technology can be used to maintain the internal temperature. In these situations, the extracted heat can be used in a heat exchanger 50 to preheat the hydration fluid used in the first module. In other situations, an inert, condensed gas, such as carbon dioxide, nitrogen or a fluorocarbon, can be used as a cooling medium. A suitable arrangement of nozzles as shown in fig. 1 can inject the gas at 0 psig, which lowers the temperature significantly. As the gas heats up and rises, it can be taken out into recovery mixing cans 52 by an inlet fan on a compressor for recompression and recycling. The heat extracted from the recirculated gas can again be used to heat the hydrating fluid. In any case, it would be advantageous to include a baffle system or air curtain system at inlet 39 and outlet 44 to minimize ingress or outflow of gas in these areas. To the extent that dry ice can be retained on or other external solids accumulate on the frozen medium, the outlet 44 directs the frozen hydrated medium to a second vibrating grid conveyor belt 45 so that the particulate material is removed. This material can be quickly recycled to the inlet 39'.

A system described here can take up as little space as an area of 1 meter by 2.5 meters if the modules are placed as shown in fig. 4. The standing height will be less than approx. 2.5 meters. A machine of this size can process up to 550 kg of hydration fluid per hour, which would be sufficient to fully hydrate two rolls of polymer-coated formwork 100 meters long and 38 cm wide. This amount of medium will be sufficient to place a layer inside 80 cartons, each of which has an approx. 50 liter capacity per hour; which thus makes it ideal for small shipping operations where perishable or heat-sensitive products are packaged for cold shipping.

Figures 5 to 7 describe the second embodiment. Fig. 5 shows the hydration freezer system 110 with the main elements of the invention. The critical components of the facility 110 are housed in a conventionally insulated refrigerated trailer 111. The trailer includes a standard air conditioning unit 112 under the trailer that supplies cold, dry air to the interior of the facility. The trailer shell 113 includes insulation to protect the components of the trailer from exposure to high ambient temperatures outside the trailer. A power generator 114 on board supplies power to all the systems in the facility and includes a connection 116 for external power connections so that external AC voltage at a consumer point is used in the facility. An external water connection 131 allows water to be used in the consumer area.

The facility 110 includes three main divisions A, B and C separated by fore and aft partitions 115 and 120, respectively. Each partition includes a door for access (not shown)

•so that an operator can go through the entire plant for a one-time inspection of all the parts. The front part A is used as a storage area 125 for rolls of the medium 117. The ThermaFreeze® medium, which is suitable for use in this type of facility, is supplied in rolls with a width of 38 cm or 72 cm and a length of 100 metres. The rolls consist of continuous form cloth of a medium of a non-cloth material, such as a 55 gram polypropylene. The form cloth comprises several "cells" which typically have one

dimension of approx. 5 cm by 5 cm with a sealing zone of approx. 6 mm between each cell. A film of plastic polypropylene is laminated onto the non-woven material to create the cells

of 5 by 5 cm. With a sealing zone of 6 mm between the cells, a standard form cloth with a width of 38 cm has 6 cells across, giving 9000 cells in a 100 meter long roll, and double that for a 72 cm wide roll. Each cell contains a superabsorbent polymer, such as sodium polyacrylate, cross-linked, which conforms to FDA guidelines. The process of laminating film on the non-woven material, and of depositing the polymer inside each cell, is automated with a device that can be found in US patent 5628845 by Murray et al., thereby making the use of such medium more economical . Although these materials work well in the present invention, other materials with similar physical properties may also work well with this invention. It is assumed that different types of media will be developed over time to adapt to the needs of shipments, and the invention described here is designed to be able to use different types of media dimensions as they are developed.

In preparation for plant operation, a roll of the medium 117 is loaded onto a motorized shaft 118 to be unwound in the transport rollers 119 positioned in the plant. A motor on the shaft can provide for unwinding the medium roll on the conveyor belt rollers 119, and the motor can be electrically integrated in the transport system so that movement of the rollers 119 causes a synchronized movement of the shaft motor; however, it is considered that the conveyor belt rollers 119 in themselves provide enough power to unwind the medium roll as the form cloth is caught on the conveyor belt system and the drive rollers 121 are activated. A main part of the conveyor belt rollers 119 are passive and rotate due to the entrained form fabric which is pulled through the plant by the drive rollers 121. As can be seen in the figure, the drive rollers are positioned at various critical locations in the plant, which depends on the installed length of the conveyor belt system which can be varied with various consumer applications. In some applications, a single drive roller may be sufficient to pull the form fabric through the plant if the conveyor belt system is shortened sufficiently. It is also expected, even though several rollers are shown in the figures, that the density of rollers and the positioning varies with different media types.

In fig. 7, it can be seen that each conveyor roller 119 and operating roller 121 is typically surrounded by a slip belt ("Hi-Slip"), patterned rubber or Teflon® alloy 122 to support and propel the form cloth through the plant. Each roller is rotatably supported in each part by conventional devices well known in the industry, and since the method of rotation is not critical to the operation of the plant nor does it comprise new features of the invention, further discussion with regard to the mechanical features of the rollers and conveyor belt system will not be undertaken. Each roll includes a series of projecting tabs 123 positioned above the surface of the roll and the form cloth has correspondingly positioned perforations 124 along the second and fourth sealing zones of the form cloth to engage the corresponding projecting tabs on the roll as shown. This type of tractor feeding arrangement promotes the grip and support properties of the rollers as the form fabric is pulled through the plant.

Compartment B in fig. 6 shows a hydration tank 126 and a freezing chamber 127. Hydration tank 126 includes a pump/heating device 128 and a flow sensor 129 for regulating the water temperature and level in the tank 126. External water connection 131 allows connection to a water supply source at the consumer location to fill tank 126 via pump 128, and drain valve 132 allows rapid draining of the tank after preparation of the medium is complete. A heating element and temperature sensors in pump 128 maintain the temperature in the tank water between 32°C to 65°C (ie lukewarm). An operating roller 121 A adjacent to the partition wall 115 pulls the form cloth 117 through an opening in the partition wall 115 and into the aqueous environment of the contained tank 126 through opening 134. The rollers 119 within the tank 126 pull the form cloth 117 below the surface of the water as shown and transport the form cloth through the lukewarm water at a controlled rate to optimize the water absorption of the polymer within the cells. Although a full immersion tank is shown, alternative methods of hydration may be suitable for hydrating the media. For example, an overhead water nozzle configuration may provide a constant supply of water that is sprayed onto the form cloth as it is moved through the tank and will thus provide suitable hydration results Replacing the water reservoir with an overhead nozzle arrangement will simply require changing the distribution piping to the heating/pumping device

128 to recirculate water to the nozzles from a submerged position in the tank (shown shaded in Fig. 3).

After hydration, form cloth 117 rises to above water level 136 and is drawn through an insulating opening 138 into the freezing chamber 127 by drive roller 121 B. Opening 138 consists of a series of vertical non-sticky, rubbery flaps carried by a suitably sized hood for to allow the form cloth 117 to pass through the insulating panel 139, which panels 139 also surround the freezing chamber 127 as shown. Transport rollers 119 are positioned within the chamber 127 to increase the vertical distance to the form cloth and thereby increase the exposure time of the form cloth 117 to the freezing conditions in the freezing chamber. The freezer compartment 127 includes a dedicated cooling system. Twin containers for C02 142 supply gas to the expansion nozzles 141 in chamber 127. A mechanically based cooling unit 143 contributes to cooling through the C02 system. The mechanical unit 143 is conventional, but may have a higher cooling capacity to achieve lower temperatures in the chamber. Conventional air conditioning components, condenser 144, evaporator 145, compressor 146, expansion valve 147, refrigerant line 148, air ducts 149 and blower 150 are shown positioned above chamber 127, but various types of systems well known in the art can be positioned elsewhere to achieve optimum impact and economy. Temperature sensors and control circuits (not shown) control the cooperation between and the operation of the two cooling units so that the temperature in the chamber is below -23°C. This temperature is not critical for the freezing process as long as temperatures below -6.5°C are maintained inside the chamber 127. However, tests have shown that rapid freezing of the cells is optimally achieved at temperatures below -23°C. In addition, although two cooling systems are shown, it is expected that a single system of one type or another will be suitable for maintaining freezing temperatures inside the chamber.

After freezing, operating roller 121 adjacent to partition wall 120 pulls mold cloth 117 through chamber 127 and transports mold cloth through rear opening 151, corresponding to the construction of opening 138, through opening in partition wall 120 and into cutting area 150 in compartment C. Although the entire medium absorbs some moisture, the water is concentrated in the cells of the medium and the form cloth 117 remains relatively flexible. This allows the form cloth 117 to continue forming around the transport rollers without movement through the plant being significantly inhibited.

In fig. 5, the cut area in compartment C can be seen more easily. Table 153 holds a cutting lance 154 and servo-controlled mirrors 156 which control the cutting beam. Touch screen 157 enables an operator to select a pre-programmed cutting pattern adapted to particular consumer packaging needs. The table 153 also includes a vacuum holding system 158 to keep the frozen form cloth on the cutting table 153 for a predetermined duration. As the front end of the frozen mold cloth 117 moves over the cutting table 153 during operation, a sensing rod 159 on the far end of the table activates the vacuum system 158 to lock the mold cloth on the table in a stationary position upon contact with the mold cloth front end. The laser 154 then cuts the frozen formwork into cell groupings of appropriate size and shape for packaging according to the control program routines found in the control logic (not shown) which also coordinates the action of the laser, vacuum system and mirror servos. The program enables the operator to quickly select different cutting patterns from the touch screen 157. The cutting patterns found in the program are programmed to cut the media along the sealing areas so as not to break the individual cells and include the ability to cut shapes suitable for several different types of shipping containers . Upon completion of the cutting sequence, the vacuum system will automatically deactivate, after which an operator clears the table of cut cells into containers for removal through the rear doors of the trailer to the consumer shipping area. The next length of frozen form cloth then enters table 153 for cutting. Any laser with suitable cutting properties can be used, but tests indicate that high power, sealed CO2 lasers in the 75-500 watt range are most effective. A Plexiglas® shield (not shown) surrounds the laser cutting table so that an operator is protected from laser beams. Although a laser-based cutting system is shown, other suitable cutting methods, such as rotating knives or high-pressure water jets, can be used with similarly effective results.

Under optimal hydration and freezing conditions as described above, a selected form cloth can be hydrated, frozen and cut into sizes at a continuous rate of approx. 1.5 meters per minute. This allows the formation of large quantities of frozen medium which can be arranged in the shipping container around perishable materials in an economical manner.

The various forms of the inventions shown are intended as illustrations of the invention and are not intended to limit the scope of the invention described in the appended claims.

Claims (14)

1. Device for the preparation of a packaging material for use in shipping heat-sensitive materials by hydrating and freezing a superabsorbent polymer enclosed in a form cloth of a flexible, permeable material, characterized in that the device comprises: a. a first module device (11; 126) for hydrating the polymer including device (19; 121b, 121c) for driving the form cloth through the first module (11; 126); and b. cooling module device (40; 127) for freezing hydrated polymer as the form cloth is driven through the cooling module device (40; 127). 2. Device according to claim 1, characterized in that the first module device (11; 126) includes a conveyor belt (16; 119, 121b) for moving the form cloth through a sufficient amount of hydration fluid at a rate sufficient to achieve substantially complete hydration of the superabsorbent polymer. 3. Device according to claim 2, characterized in that the conveyor belt (16; 119, 121b) is arranged to immerse the form cloth in a base bed (37, 126, 136) of the hydration fluid. 4. Device according to claim 3, characterized in that the device further comprises devices (40; 129) for maintaining a quantity of the hydration fluid in the first module (11; 126) for essentially continuous hydration of the superabsorbent polymer in a form cloth which is passed through the first module (11; 126). 5. Device according to claim 2, characterized in that it further comprises means (19; 121b, 121c) for adjusting the speed of the conveyor belt (16; 119, 121b) to increase or decrease the time period during which the superabsorbent polymer is exposed to the hydration fluid. 6. Device according to claim 2, characterized in that the device further comprises devices (26) for spraying the hydration fluid on the mold cloth and the conveyor belt (16) as the mold cloth is moved through the first module (11). 7. Device according to claim 1, characterized in that the cooling module (40, 127) comprises a conveyor belt (16; 119, 121b) mounted therein to move a hydrated mold cloth through the module (40, 127) at a speed suitable to facilitate freezing of the hydration fluid in the mold cloth. 8. Device according to claim 7, characterized in that the cooling module (40, 127) has an input (39; 138) for receiving the hydrated form cloth and an output (44; 151) for withdrawal of the hydrated form cloth after freezing, and which includes devices to limit penetration and discharge of gases through the inlet and outlet. 9. Device according to claim 7, characterized in that the cooling module (40, 127) includes mechanical devices to keep the inside of the chamber at a temperature that is below the freezing point of the hydrated form cloth. 10. Device according to claim 1, characterized in that the device further comprises shaking devices (45) which are operationally positioned to receive a frozen, hydrated mold cloth from the cooling module (40) in order to remove external moisture and solids from the frozen, hydrated mold cloth. 11. Device according to claim 10, characterized in that the grating device (45) comprises an open conveyor belt (17) for supporting and transporting the form cloth as well as devices (35) for applying vibrations to the form cloth. 12. Modular packaging preparation device for hydrating and freezing a superabsorbent polymer enclosed in a form cloth of flexible, permeable material, characterized in that it comprises: a. a first modular device (11; 126) for hydrating the polymer including a device (19; 121b, 121c) to drive the form cloth through the first module (11; 126) including transport means (16; 119, 121b) for moving the form cloth through a hydration fluid at a rate sufficient to achieve complete hydration of the superabsorbent polymer, a means (24, 129) for maintaining a quantity of hydration fluid in the first module for continuously hydrating the superabsorbent polymer in the form cloth which is passed through the first module, a device (19; 121b, 121c) for adjusting the speed of the transport device to increase or decrease the period of time that the superabsorbent polymer is exposed to the hydration fluid; and b. a cooling module device (40; 127) for freezing hydrated polymer as the mold cloth is driven through the cooling module device (40; 127) includes a chamber having an inlet (39; 138) for receiving the hydrated mold cloth and an outlet (44; 151) for releasing the hydrated mold cloth after freezing, a device for limiting the ingress and emission of gases through the inlet (39; 139) and the outlet (44; 151), a secondary transport device (18, 129) mounted in the chamber to move the hydrated mold cloth through the chamber at a speed suitable to facilitate freezing of the hydration fluid in the mold cloth, as well as a device (50; 143) for maintaining the temperature inside the chamber so that it is below the freezing point of the hydrated form cloth. 13. Device as stated in claim 1, characterized in that it further includes a device (154, 156) for cutting the mold cloth into individual parts of a pre-selected size and shape after the mold cloth has been frozen in the freezing device. 14. Assembly plant for hydration and freezing of flexible refrigerants, characterized in that it comprises: a. a transport vehicle device (111) for transporting the plant so that the plant is mobile and independent; b. a device (40; 127) for hydrating the medium; c. a device (16; 119, 121b) for directing the medium into the hydration device; d. a device (50; 143) for freezing the medium; e. a device (39; 138) for transporting the medium from the hydration device to the freezing device.