Liner wall movement and vacuum changes in the teat cup chamber are depicted in Figure 3, indicating the four phases of the pulsators’ waveform and method of analysis.

Waveform and description of liner wall movement.

It can be seen that the liner movement follows the vacuum increase in the ‘a’ phase of the vacuum change with a slight delay. Conversely, liner movement precedes the decay in vacuum to atmospheric conditions in the ‘c’ phase of the vacuum waveform.
To characterize the waveform of the liner, we used a method similar to describing the waveform of the liner as is used by ISO 3918 for analyzing the pulsator waveform. The two waveforms are differentiated by the use of lowercase letters to characterize the waveform of the vacuum changes and uppercase letters to characterize the waveform of the liner wall position. The suggested intersect is 1 mm from the liner fully open and less than 1 mm to closure at the initial touch point of the liner walls. This contrasts to the characterization of the chamber vacuum utilizing pressure thresholds of __4 kPa. The details of characterizing the waveform of the liner are shown in Figure 4.Table 1 shows the duration of chamber vacuum and liner position in the four phases of pulsation with an artificial teat cup plug. The WC01 liner wall opened in a period of 87 ms, while closure time was 23 ms. In contrast, the chamber vacuum was 146-ms opening (increasing vacuum) and 97-ms closure (decreasing vacuum). Liner ratio was 57:43 with a chamber vacuum ratio of 64.4:35.6.

The ‘b’ phase of the chamber vacuum and the ‘B’ phase of the liner are similar at 498 and 483 ms, respectively. The ‘D’ phase of the liner is considerably longer than the ‘d’ phase in the vacuum chamber (407 vs. 259 ms). The ‘A’ and ‘C’ phases of the liner are shorter than the ‘a’ and ‘c’ chamber vacuum phases. The liner position is related to the vacuum conditions of the pulse chamber; however, the waveform of the pulsator chamber vacuum does not precisely correspond to the liner position.
Table 2 indicates the chamber vacuum at the initiation of each phase of the pulsation cycle. Claw vacuum was 46 kPa. Because the liner wall moves with the differential pressures across the walls of the barrel, each liner has movement characteristics dependent on its physical design. The WC01 liner began to open when chamber vacuum reached 36.7 kPa. The liner was fully open at 45.9 kPa. Thus, the pressure difference across the walls is virtually equal (45.9 vs. 46 kPa). In the ‘c’ phase of the pulsators cycle, the liner begins to close at 34.1 kPa. This point is known as the CCPD. The liner walls touched when chamber vacuum reached 20.5 kPa. This point is known as the TPPD (10).
Table 3 presents the data obtained by milking three cows at different stages of the milking period. Liner wall movement was slightly slower in the opening and closing phases during milking when contrasted to the artificial teat. Opening time increased by 11 ms and closure increased by 19 ms. The ‘B’ phases remained nearly constant, while the ‘C’ phase of liner closure was 19 ms shorter during milking. The ‘D’ phase of the liner was 31 ms shorter during milking compared with the artificial teat.

Chamber ratio was 64.5:35.5 and liner ratio was 58.2:41.8 during milking. Mean claw vacuum was 45 kPa. Thus, there was similarity between the use of a teat cup plug and actual milking conditions.
Some differences between the artificial teat are expected because milk flow changes the interior vacuum of the liner and the artificial teat does not compress under load compared with a normal teat.
Table 4 shows the vacuum at the initiation of each liner phase of the pulsation cycle during milking. The vacuum at the initiation of the ‘B’ and ‘C’ phases of liner position was similar. However, chamber vacuum was lower by 4.8 kPa at the start of opening and 7.8 kPa different when measured at liner closure. These data indicate slightly different liner movement characteristics during milking compared with liner movement with an artificial teat.