A vacuum filler is a machine used for filling pasty products. The pasty products are moved with the aid of a vane cell feed system under a vacuum.
Levelling the weight of pre-packaged goods in the food sector, especially those involving viscous or pasty products, places extremely high demands on the reproducible accuracy of filling and portioning systems. In order to achieve this, technical and technological issues as well as product-specific characteristics have to be taken into account. In addition to the aforementioned factors, the requirements on the quality of an end product is a key issue when selecting or implementing a technical process solution. The development of vacuum filling machines has made it possible to fulfill both the technical and the quality-related requirements.
In the food sector, moving or transporting fluids is achieved with the aid of pump technology. Colloquially, this is known as filling or portioning. Various different types of pumps are used, depending on the type of filling products to be moved. Vacuum fillers with vane cell feed systems and vacuum feeding are commonly used for viscous products. The products are transported with the aid of a hopper with a feeding device, a vane cell feed system under a vacuum and appropriate volume expulsion in the pump housing. This is basically a volumetric feed principle, which means that a certain weight is defined via a volume. In addition to the vane cell feed systems, also known as rotary vane pumps, there are also screw feed systems with feed augers, toothed wheel feed systems and evacuated lifting cylinders. With all these systems, transportation is achieved via volume expulsion under a vacuum. Vacuum fillers are traditionally used in the meat processing industry as well as in other food sectors. They can also be found in some non-food sectors. Generally speaking, vacuum fillers can be used for filling pasty and compressible products.
The first vacuum filler was developed in the early 1960s. The technology has been refined since then.
The pumpability of viscous or pasty products has a key effect on the reliable function of a vacuum filler. Filling products in the food sector can be characterised with the aid of various different properties related to their pumpability (“fillability”). They are either physical characteristics that can be measured directly or they are sensory attributes.
The key element of a vacuum filler is the vacuum filling principle. The filling product is fed into the feed system mechanically via a hopper with actively driven feeding auger, as well as via vertical “vacuum suction”. Pre-evacuated cells of a vane cell feed system move underneath the hopper. The pressure difference relative to the ambient pressure (underpressure) caused by the evacuation ensures that the cells are filled with product. The feed system moves continuously, thus generating a continuous filling flow. The product is portioned by means of cyclic movements of the feed system. Each cell of the feed system has a particular volume. The portion is defined by the rotation distance of the rotor. The portioning volume is therefore set in the control system by multiplying the rotor’s rotation distance by the number of the feed system cells within it. The portion weight must be determined in the control system via the portion volume parameter with the aid of scales.
Vacuum fillers are primarily used in the food trade and in the food industry. Special criteria apply to the design of machines in the food sector due to specific hygiene standards and hygiene regulations. This includes, for example, ensuring that they are easy to dismantle, have level surfaces and seals that can be rinsed from the rear, no dead spaces, ergonomic shapes, a small range of parts and detectable materials/materials suitable for food use. Relatively aggressive ambient conditions, such as reactive detergents, reactive or abrasive filling media, intensive high-pressure cleaning and extreme ambient temperatures, are also faced.
Vacuum fillers are therefore made of a high proportion of stainless steel with a very robust design. Moving parts can be easily dismantled and can be cleaned individually. In addition to the mechanical or design-related issues, complex electronic components in a vacuum filler also have to be taken into account.
The vane cell feed system mainly consists of a rigid pump housing with attached side plate that is fixed to the pivoting hopper, and a removable rotor with pump vanes and cam. Depending on the machine size there are various different sizes of vane cell feed systems with parts with appropriate dimensions. The hopper can be swivelled to clean and dismantle surfaces and parts that come into contact with filling product. The driven rotor with an appropriate number of slots is located in the pump housing, in which pump vanes form cells with defined volumes when the machine is closed, supported by the cam. Induced by the rotor movement when the machine is started, the cells move in the direction of the vane cell feed system outlet and therefore ensure that a defined product flow is achieved. The weight accuracy of a feed system is partially dependent upon the production precision of the parts and their degree of wear.
The cells are filled by evacuating the vane cell feed system. By applying a vacuum via a vacuum pump, the filling products are gently drawn out of the hopper into the feed system as soon as an evacuated cell moves underneath the hopper. The vacuum pump is protected by an integrated water separator. The level of vacuum can be set according to the filling product. In addition to the feed effect, the filling product is simultaneously evacuated to a certain extent (approx. 2–4 %). This means that the air content of the filling product decreases and the filling product becomes denser.
The term feeding in the context of vacuum fillers refers to actively moving the filling media in the direction of the lower part of the hopper to support the vacuum approach within the hopper. Feeding is achieved by using moveable feeding augers with scrapers/rigid counter arms. The feeding auger is driven in synchronisation with the rotation of the rotors. Due to the special geometry of both augers and the parallel rotation movement, the filling product is moved vertically in the direction of the vane cell feed system. The required feed intensity depends on the viscosity of the media to be filled. Less active feed is needed with low-viscosity media than with high-viscosity product. There are therefore a variety of combinations or versions of the parts involved in the feeding process.
The machine base acts as the stand for a vacuum filler. For hygiene reasons, bases are made completely of stainless steel. The compact machine base is designed to ensure that it can be moved easily using lifting equipment.
Lifting devices allow the hopper to be loaded using standard trolleys. They can either be fixed onto the vacuum filler or a mast type lifting device can be positioned separately next to the vacuum filler. Lifting devices can be driven hydraulically or electrically.
A computer-aided control system is required for operating the various functions associated with a vacuum filler. Usually, several drives are integrated into the vacuum fillers for the various different applications. With the most modern generations of vacuum fillers, the drives are implemented by means of servo motors and appropriate bus systems.
To produce individual portions from homogenous product via a feed system, a “sealing device” is always required at the feed system outlet. This device separates portions and is controlled in synchronisation with the portion output. These devices could be linking devices for sausages, clippers for portionable sausages, dosing valves for tubs and cans, cutting devices for dough as well as forming equipment for dumplings.
Generally speaking, vacuum fillers can be equipped with various different feed systems. However, in principle, the basic machine structure, with a hopper, vacuum system, feeding device, machine base, lifting device, control system and sealing device, is very similar. Depending on the application, each type of feed system has advantages and disadvantages.
Many problems may occur when filling viscous media. The problems are often product-specific and are revealed when the product to be filled takes on an a-typical appearance. Examples of this are an inhomogeneous product appearance with sausage goods or when inserts are ground too finely during the pumping process. However commercial or legal problems can also arise, in the form of weight deviations or non-compliance with the specified quality regulations (e.g. the guidelines for meat products).
These problems are caused by a variety of influences, such as air content or viscosity being too high, insufficient feed volume in the feed system, temperature-related influences and mechanical influences such as friction and fragmentation. The aforementioned problems can be eradicated by modifying upstream process steps, adapting recipes and making technical modifications.
Hanging lines in the field of sausage production are auxiliary devices for linking and hanging portions of sausage. In principle, the application is similar to that of a holding device, however significantly higher filling capacities can be achieved. Hanging lines are available with various different degrees of automation.
Multi-machine electronic control and documentation systems are used to document a filling process involving vacuum fillers or to monitor filling weights.
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