Animal husbandry – Milkers – With fluid compression
Patent
1992-01-07
1993-05-04
Weiss, John G.
Animal husbandry
Milkers
With fluid compression
119 1441, 137112, A01J 514
Patent
active
052071774
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a pulsator, comprising first and second valve devices, each of which has a pulsation outlet, a pressure inlet to be connected to a first source of pressure generating a first pressure, and a pressure outlet to be connected to a second source of pressure generating a second pressure, which is lower than said first pressure. Means is provided for adjusting each valve device for alternately connecting the pulsation outlet of the valve device to said first source of pressure via the pressure inlet of the valve device and to said second source of pressure via the pressure outlet of the valve device.
DESCRIPTION OF THE PRIOR ART
There is a known pulsator of this kind which among other things is utilized in milking machines for providing cyclic pressure alternation in the pulsation spaces of the teat cups, i.e. the spaces formed in the teat cups between the walls of the teat cups and the liners mounted in the teat cups. In this case, four teat cups are usually connected in pairs to each one of the two pulsation outlets of the first and second valve devices in the known pulsator, and said first source of pressure is constituted by atmosphere, while said second source of pressure is constituted by a source of subatmospheric pressure.
The known pulsator is operated with the two valve devices offset in phase relative to each other, which means that when vacuum (subatmospheric pressure) prevails in the pulsation spaces of one of the pairs of teat cups, atmospheric pressure can prevail in the pulsation spaces of the other pair of teat cups. However, during each pulsation cycle comprising a period of atmospheric pressure and a period of vacuum, the period of atmospheric pressure normally has a shorter duration than the period of vacuum. During a certain time of each pulsation cycle, vacuum therefore prevails simultaneously in the pulsation spaces of all of the four teat cups. This has the consequence that when the pulsation outlet of one of the valve devices communicates with the source of subatmospheric pressure and the other valve device is operated by the adjustment means to adjust the pulsation outlet from communication with atmosphere to communication with the source of subatmospheric pressure, for a short moment atmosphere can also communicate with the pulsation outlet of said one valve device via the necessary conduit connections between the two valve devices and the source of subatmospheric pressure. During said short moment atmospheric pressure thus occurs in the pulsation spaces of the pair of teat cups connected to said one valve device, which is felt by a cow being milked as unpleasant pressure impacts against her teats.
Of course, it would be possible to avoid occurrence of such unpleasant pressure impacts if each valve device were constructed such that during each alternation operation, the pulsation outlet of the valve device is kept closed, when the adjustment means adjusts the pulsation outlet from connection with the pressure inlet (atmospheric pressure) to connection with the pressure outlet (subatmospheric pressure). However, valve devices constructed in this way would substantially increase the price of the pulsator.
The intensity of said pressure impacts could also be reduced so that the cows would feel the impacts less unpleasant, if the alternation operation of the valve devices could take place in a faster rate. However, this would require complicated valve devices, probably including servo systems, which would lead to too expensive pulsators.
In milking pulsators it is known to arrange two non-return valves in the connections between the two pressure outlets of the valve devices and the source of subatmospheric pressure to eliminate said pressure impacts or at least reduce their intensity. During the adjustment of one of the two valve devices for alternating the pulsation outlet from connection with the pressure inlet, which communicates with atmosphere, to connection with the pressure outlet, the non-return valve between the sour
REFERENCES:
patent: 1159103 (1915-11-01), Sabroe
patent: 1322589 (1919-11-01), Leitch
patent: 1641316 (1927-09-01), Bruun
patent: 2160651 (1939-05-01), Erling
patent: 4354518 (1982-10-01), Kuroda et al.
AB Manus
Weiss John G.
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