How Butter Churns Work: Batch and Continuous Butter Making Equipment

Butter churns of batch and continuous type differ from one another in the mechanism by which butter is produced, the way they act on the cream, and the design of their working parts.

Butter production in batch churns happens in two stages: first the fat globules form butter grains, then those grains are worked into a layer of butter. In continuous churns, the formation of the butter grain and the butter layer takes place within a flow. In batch churns (without rollers), the cream is beaten as it moves under the force of gravity. As the working vessel — filled to 30–50% of its capacity — rotates, the cream first rises to a certain height and then drops under gravity, undergoing strong mechanical action.

The height to which the cream rises, the pressure, and the character of the liquid's movement are all determined by the dimensions of the working vessel and the frequency of its rotation. In this case the cream moves at a speed of 5–7 m/s.

In continuous churns the cream moves considerably faster (18–22 m/s). The intense action of the beater blades produces a turbulent flow of cream inside the apparatus, which intensifies the aggregation (sticking together) of fat globules and the formation of butter grain.

What are the main types of batch butter churns?

Batch butter churns can be divided into three broad types, distinguished by how the vessel and the working parts move:

• Type one — a vessel acting as the working part. Its shape may be cylindrical, conical, pear-shaped, cubic and so on. There are no internal mixing devices inside the vessel.
• Type two — a rotating vessel with fixed internal parts such as spirals, blades, strings and the like, rigidly secured inside it. Churns of this type are used most often.
• Type three — a stationary vessel with rotating working parts turning inside it. This type is most often built as small-capacity churns.

The design and operating principle of the roller-free batch churns produced by industry are practically identical and differ only in certain details.

How is the RZ-OBE butter churn built?

The RZ-OBE butter churn consists of the following main assemblies (Fig. 1): the vessel; the frame with the gearbox and controls; the support post; the guard; the spray device; the trolley; and the control cabinet.

The vessel is made of two cones of sheet stainless steel welded together at their bases. A hatch for unloading the butter is mounted at the apex of one of the cones. The vessel is fitted with an inspection window and two taps for releasing air and buttermilk.

On one side the vessel is joined to the support post, and on the other to the drive output shaft. Inside the vessel are obliquely welded blades for beating the cream and working the butter grain. The inner surface of the churn is specially treated to prevent the butter from sticking.

The vessel is rotated by a two-speed electric motor through a V-belt drive and a gearbox. The drive provides for rotation of the vessel and its stopping by means of a braking device and a friction clutch. Figure 1 — RZ-OVE batch butter churn: 1 — support post; 2 — vessel; 3 — spray device (shower); 4 — guard; 5 — frame with gearbox; 6 — trolley.

Speeds are switched using a lever brought out to the front of the gearbox, together with the start buttons that control the two-speed electric motor.

The braking device consists of a drum with a tensioned steel band and a lever brought out to the front of the gearbox. Turning this lever to its lower position disengages the brake and at the same time engages the friction clutch, through which torque is transmitted from the electric motor to the gearbox and the vessel.

The upper position of the lever disengages the clutch while simultaneously applying the brake. The electric motor is mounted on the frame on a swivel plate, which makes it possible to adjust the belt tension. The churn has a guard made of bent tube fitted with levers for counterweights.

This guard is fastened to a bracket installed on the gearbox housing and to the cover of the support post. Thanks to hinges, the guard can swing around a horizontal axis. The guard is interlocked with a limit switch, so in the raised position it prevents the electric motor from being started.

The spray device is a perforated pipe positioned above the vessel between the support post and the gearbox cover. At the inlet of the device there is a valve used to regulate the supply of cold and hot water. When required, the steel vessel is sprayed with cold and hot water to maintain the set temperature of the cream being churned.

How does the RZ-OBE churn operate?

To run the RZ-OBE churn, the cream intended for churning is poured into the vessel to 40–50% of its capacity, the hatch is closed, and the arc of the guard is lowered to its bottom position. A time relay is used to set the duration of churning, and the packet switch is turned on at the control panel.

After this the drive's electric motor is switched on to the required speed, the brake is released, and the friction clutch is engaged at the same time — that is, the churn is put into operation. Periodically the vessel is stopped and, with the tap in its upper position, the air is released.

Once the set churning time has elapsed and the butter grain has formed, the time relay switches off the electric motor and sounds an audible signal. The buttermilk is drained off, the butter grain is worked, and the finished butter is unloaded into the trolley.

The main technical figures of the RZ-OBE churn are a vessel capacity of 2 m³, a vessel rotation frequency of 0.4 and 0.6 s^-1, and an electric motor power of 6 kW.