Dairy Process Engineering

Module 5. Packaging Machines for Milk & Milk Products

Lesson 24
PACKAGING MACHINES FOR MILK

Introduction

The Form Fill Seal(FFS) machines are a genre of filling equipment that can fill in a flexible packing material. The product should be free flowing type, either liquid or even granular. The equipment may be controlled electro-pneumatically or mechanically.

The process involves certain steps, which will take place cyclically in auto operation.

There is option for variation in size and quantity of the product packed. To a large extent, the market milk is now being sold by packing in these machines.

The following are the operations that go cyclically.

1. Forming of tube of packing material from film in rolled state

2. Simultaneous operation of filling and sealing

3. Movement of film to form next package

4. Simultaneous separation of filled and sealed packet while filling of next packet.

Sequence of Operation

With reference to the fig. the film roll is loaded at the backside of the filling machine on a sliding platform. The film edge is passed over end of role contact lever, dancer roller, UV tube and brought to the front side over to forming plates. The forming plates rolled the flat film in to tube a certain band of overlap. Within the tube is the fluid filling pipe enveloped. The tube then passes over to vertical seal jaws that are engaged and disengaged with the help of an air operated piston, or in machines by mechanical means. In between the jaws, the overlapped part of the film tube passes. The set of jaws have one stationary and one moving jaw. The moving jaw has a nichrome rod, supplied with variable voltage such that the heat is generated when the current passes intermittently. During the period when the current does not pass, when the jaws are disengaged, the cooling water being circulated in the moving jaw, cools it and prevents continuous over heating of the sealing rod. The film is supported by Teflon cloth and rubber cushion, as well as protected by Teflon cloth from sealing rod. This arrangement prevents electricity passing on to the film and other parts, while allowing only the heat to pass on to the film and partly melting and fusing the vertical joint.

Lower down the film tube, there are a pair of nip rollers giving a holding and pulling down action, when the jaws are disengaged, making the film to move to seal the next portion of vertical overlap.

Further lower down the film tube is engaged by horizontal jaws, at a sufficiently below the lower edge of fluid filling pipe. This arrangement allows the formation of lower seal of the packet, while the fluid is being filled to a known quantity. The quantity of flow is controlled by a valve operated by a rod which is lifted by a solenoid coil position at the top of machine, just at the feeding line from the over head tank carrying the fluid to be filled. While filling is taking place, a pair of flat blades operated by spring keeps the film perfectly flat at horizontal edge so that there is no folds and horizontal seal is perfect.

When the filling of fluid and the horizontal sealing is complete, the horizontal jaws (as well as vertical jaws) get disengaged, and the nip rollers start rolling to bring the next length of film tube to be filled for next packet. While the second packet is being filled, the first packet already filled will be getting the horizontal seal of top portion of the filled packet. When the next time the jaws open, the first packet drops down by its own weight and weakened connection to the rest of the tube.

The above cycle of operation is repeated when the controls are in automatic operation, while single action takes place when in manual operation during initial adjustment of time and temperature combination for obtaining proper seal.

Controls

The Form Fill Seal Machine has various controls for the following operations.

1. Adjusting the temperature of sealing rod by controlling the electric supply, to match to the thickness of the film to be sealed.

2. Adjusting the timing for the jaws to be engaged and simultaneously filling operations to take place, with a known quantity of fluid.

3. Adjusting the quantity of fluid to be filled when jaws are engaged

4. Adjusting the timing for the jaws to be engaged and allow time for movement of film to the required length of package.

The other useful instrumentation are the end of film indicator (gives audio signal), so that the new film roll can be changed easily, fine adjustments for the quantity of fluid filled in few grams range, fine adjustment of timings, etc.

The equipment will require water for cooling the jaws at a fixed flow rate and of low temperature. Also, compressed air is required which is at required pressure and free of condensed moisture.

Fig. 24.1 Film feed circuit

UHT milk packing machine

Introduction

The UHT milk packing machine is different than the usual FFS machine in that the packaging material is multi layered, and the filling is done in an absolutely asceptic condition. The filling room is kept in a positive pressure, and the air inlet is through HEPA filters. Starting out from a reel of packaging material, the Tetra Brick Asceptic (TBA ) filling machine produces filled packages. The packaging material is first sterilized and then formed into a tube. The tube is filled with product and then shaped and cut into individual packages.

The package

There is a range of Asceptic packages , all deriving their origin from the same forming technique. In India, the commonly available Asceptic packaging machine is from Tetrapak company.

Package terminology

Creases are the folding instructions on the packaging material, to ensure the Creases package’s final shape. The creases are pressed into the material by the creasing tools in the converting process.

The longitudinal seal (LS) is accomplished when forming the packaging material seals into a tube. It seals the package along the side. A strip of laminated plastic, the LS-strip, covers the seal on the inside. The area of the overlap joint is called the longitudinal overlap.

The transversal seal (TS) is made when the tube is filled with product. It seals the package at top and bottom. The sealing takes place below the product level in the tube.

The fins are the areas, at top and bottom of the package, where it is sealed and Fins cut.

The flaps would be the corners of the package, if you flattened it out. When Flaps shaping the package, the flaps are folded down and in, and then sealed to the package body.

Machine introduction

Tetra Brik filling machines are built from so called modules or main groups with similar functions in the various machines. The machines may also have different additional equipment and accessories.

Fig. 24.8 Tetra brik aseptic (TBA)filling machine

1. ASU Automatic splicing unit(ASU): The automatic splicing unit splices reels of packaging material. This means that production can continue uninterrupted when one reel of packaging material comes to an end.

2. During splicing though, the packaging material has to remain still in the splicing head. The magazine provides the necessary supply of material so that the machine does not have to stop.

PullTab unit

2.The PullTab unit is additional equipment, providing the packaging material with a PullTab opening before it enters the peroxide bath. The PullTab opening is created by punching a hole in the packaging material. The hole is sealed with plastic on the inside and aluminium on the outside.

3. Strip applicator: The strip applicator applies a plastic strip, the LS-strip, along one edge of the packaging material. The strip is applied on the inside of the packaging material and is intended to prevent product from being soaked into the raw paper edge of the longitudinal seal. The strip will also support the seal. Only half of the LS-strip is sealed to this edge of the packaging material. The other half will be sealed to the other edge later, when the packaging material is formed into a tube.

4. Peroxide bath: The packaging material will be sterilized in the peroxide bath. In machines with deep baths, as shown in the example, the packaging material will be immersed into warm peroxide and both sides will be sterilized. In machines with shallow baths the inside of the packaging material will merely be covered with cold peroxide and the sterilization will be finished in the tube heater.

5. Aseptic chamber: The packaging material will be dried with heated air. In machines with deep baths, as shown in the example, an aseptic environment around the sterilized packaging material is maintained with an overpressure of heat-sterilized air. This takes place in the aseptic chamber. Machines with shallow baths, which have no aseptic chamber, heat-sterilized air will be blown into the tight tube. This way a sterile area is maintained where the tube is to be filled with product. The packaging material will be formed into a tube and sealed longitudinally. Finally, the tube will be filled with product.

6. Jaw system: In the jaw system the tube is sealed transversally and cut into separate packages. The sealing is made by induction heating, using the aluminum in the packaging material to melt the plastic. It is important that the package design, with the creases, appear in accordance with the jaws. This is controlled and corrected by the jaw system.

7. Final folder: In the final folder the separate package gets its final shape. The fins are folded and the flaps are folded and sealed. Hot air is used to seal the flaps. The plastic outer coating on the package material is heated and the flaps are pressed against the sides and the bottom of the package. When the plastic gets cool the flap is sealed.

8. Operator panel: The operator panel allows the operator to communicate with the machine. It is used to start and stop or make the machine take any other action.

9. Electrical cabinet: In the electrical cabinet a great part of the electrical components are included, such as:

● Temperature regulators
● Control system
● Contactors
● Induction Heating unit, etc.

 

10. Service unit: The service unit includes parts and supply systems needed for the machine function, for example:

● Water and air system
● Lubrication and hydraulic oil system
● Pneumatic and peroxide systems

11. Drive system: The drive system includes motor, gear and cam. These parts run the jaw system and also the final folder on certain machines.