Filling Principle And Classification of Liquid Filling Machines

Liquid filling machine is a device used to fill various liquid products (such as water, beverages, etc.) into containers. It has the characteristics of high efficiency and automation, and is widely used in food and other industries.

1. Classification of liquid filling machines

Liquid filling machines can be divided into normal pressure filling machines, pressure filling machines and vacuum filling machines according to the filling principle.

The normal pressure filling machine fills liquid by its own weight under atmospheric pressure. This type of filling machine is divided into two types: timed filling and constant volume filling. It is only suitable for filling low-viscosity gas-free liquids such as water, milk, wine, etc.

Pressure filling machines perform filling at a pressure higher than atmospheric pressure, and can also be divided into two types: one is that the pressure in the liquid storage cylinder is equal to the pressure in the bottle, and the liquid flows into the bottle by its own weight for filling, which is called isobaric filling；The other is that the pressure in the liquid storage cylinder is higher than the pressure in the bottle, and the liquid flows into the bottle due to the pressure difference. This method is often used in high-speed production lines.The pressure filling machine is suitable for filling liquids containing gas, such as beer, soda, champagne, etc.

Vacuum filling machine fills when the pressure in the bottle is lower than atmospheric pressure. This filling machine has a simple structure, high efficiency, and a wide adaptability to the viscosity of materials, such as oils, syrups, fruit wine, etc.

2. Filling method

Since the physical and chemical properties of liquid materials are different, there are also different requirements for filling. Liquid materials are poured into packaging containers from the liquid storage device, and the following methods are often used.

(1) Normal pressure filling. It refers to the filling method that directly relies on the weight of the liquid material to be filled into the packaging container under atmospheric pressure.The process of normal pressure filling is: 1. Liquid feeding and exhausting, that is, the liquid material enters the container and the air in the container is discharged at the same time; 2. Stop the liquid feeding, that is, when the liquid material in the container reaches the quantitative requirement, the liquid feeding stops automatically; 3. Remove the remaining liquid, that is, remove the residual liquid in the exhaust pipe.

The normal pressure method is mainly used for filling low-viscosity, non-gas liquid materials such as water, milk, liquor, etc.

(2) Isobaric filling method. It is a filling method that uses the compressed air in the upper air chamber of the liquid storage tank to inflate the packaging container so that the pressures of the two are close to equal, and then the liquid material flows into the packaging container by its own weight.The process of isobaric filling is: 1. Inflate and equalize pressure; 2. Inject liquid and return air; 3. Stop injecting liquid; 4. Release the pressure, that is, release the compressed gas remaining in the bottleneck to the atmosphere to avoid a sudden drop in pressure in the bottle that will cause a large amount of bubbling, affecting packaging quality and quantitative accuracy.

The isobaric method is suitable for filling carbonated beverages, such as beer, soda, etc., which can reduce the loss of carbon dioxide contained.

(3) Vacuum filling method. It is a method of filling under conditions below atmospheric pressure.It has two basic methods: one is the pressure vacuum type, which means that the inside of the liquid storage tank is at normal pressure, and only the packaging container is evacuated to form a certain degree of vacuum. The liquid relies on the pressure difference between the two containers to flow into the packaging container and complete filling;The other is the gravity vacuum type, which means that both the liquid storage tank and the packaging container are in a nearly equal vacuum state, and the liquid flows into the container by its own weight.At present, pressure vacuum type is usually used. Its equipment is simple and its work is reliable.

The process of vacuum filling is: 1. Evacuate the bottle; 2. Intake and exhaust the liquid; 3. Stop the liquid inflow; 4. Residual liquid reflux, that is, the residual liquid in the exhaust pipe flows back to the liquid storage tank through the vacuum chamber.

The vacuum method is suitable for filling liquid materials with lower viscosity (such as oils, syrups, etc.) and liquid materials containing vitamins (such as vegetable juice, fruit juice, etc.).This method can not only increase the filling speed, but also reduce the contact and interaction between the liquid material and the residual air in the container, so it is beneficial to extend the shelf life of certain products. In addition, the escape of gases and liquids is limited, thereby improving operating conditions.  

(4) Pressure filling. Pressure method filling uses mechanical or pneumatic hydraulic devices to control the reciprocating motion of the piston. The liquid material with reduced viscosity is sucked into the piston cylinder from the storage tank, and then forced into the container to be filled. This method is sometimes also used for filling gas-containing beverages. Since it does not contain colloidal substances, the foam formed disappears easily, so it can rely on its own gas pressure to be directly poured into bottles that have not been pre-inflated, thus greatly increasing the filling speed.

The selection of liquid filling machine should be determined based on the nature of the product and applicable scenarios. Different filling principles and classifications have their own advantages and scope of application. Production companies should choose according to actual needs, combined with correct operation and maintenance, to ensure an efficient and stable filling process.