Milking Machine, Top Cover with Four Suction Devices

Milking Machine Top cover for collecting bowl, or "claw" with handle with four suction devices, or teat-cups. Stainless steel and aluminum. Mid-20th century, c.e.

Gift of Jon Gilbert Fox, Hanover, New Hampshire.

rl.563.2358.su

Mechanical Milking Overview

It is made up of a claw, four teatcups, (Shells and rubber liners) long milk tube, long pulsation tube, and a pulsator. The claw is an assembly that connects the short pulse tubes and short milk tubes from the teatcups to the long pulse tube and long milk tube. (Cluster assembly) Claws are commonly made of stainless steel or plastic or both. Teatcups are composed of a rigid outer shell (stainless steel or plastic) that holds a soft inner liner or inflation. Transparent sections in the shell may allow viewing of liner collapse and milk flow. The annular space between the shell and liner is called the pulse chamber.

The machine includes teat cups that contact the cow’s teats and remove the milk, a claw where milk pools as it is removed from the four teats, vacuum tubes that provide vacuum to the teat cups and a milk tube that removes milk away from the claw, a source of vacuum for the machine, and a pulsator that regulates the on-off cycle of the vacuum.

Most cows have four functional teats. Therefore, milking machines are designed with four teat cups. These are composed of an inner rubber liner and an outer shell, usually made of metal. The rubber liner is relatively thin in the section that sits inside of the shell, while the liner’s tube below the shell is thicker rubber.

If you consider this arrangement for a moment, you will realize that the teat cup assembly results in two chambers A) one inside of the liner and B) one between the metal shell and the outside of the liner. A vacuum is pulled in both chambers; the vacuum in chamber A is continuous, while the vacuum in chamber B alternates between atmospheric pressure and the vacuum.

When the teat cup is applied to the teat, the end of the inside chamber is filled by the teat. During the milk phase the vacuum applied inside the liner is constant and keeps a constant negative pressure at the end of the teat, drawing milk (in yellow) from the gland. The vacuum applied to chamber B, between the shell and the thinner walled part of the liner, keeps the liner from collapsing under the vacuum. During the rest phase, the vacuum inside chamber B is monetarily off. Air enters chamber B instantly reaches atmospheric pressure, colapsing the rubber liner around the teat end, massaging the teat and maintaining blood flow. This alternating vacuum-atmospheric pressure in chamber B is controlled by a pulsator.

To prevent teat-end trauma, This alternating vacuum-atmospheric pressure, referred to as pulsation, is important for maintaining teat end health.

A proper pulsation rate, that is the number of cycles of vacuum on - vacuum off, or milk phase–rest phase cycles, usually is about 45-60 per minute. The ratio of time that the machine is in milk phase vs rest phase should be between 50/50 to 60/40 (pulsation ratio). In some systems, pulsation ratios are slightly different for teat cups milking the fore quarters vs the rear quarters. This is done because typically the rear quarters are larger and contain more milk than fore quarters. Therefore, rear quarters usually take slightly longer to milk out compared with fore quarters. The adjusted pulsation to rear vs. fore can account for this difference so that the rear quarters milk out faster and all quarters are properly milked out when the automatic take-offs detach the machine.

References

http://www.americanartifacts.com/smma/milker/milker.htm http://classes.ansci.illinois.edu/ansc438/Mastitis/milkmachine.html