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Double Ball Pressure Indicator

IP.com Disclosure Number: IPCOM000074953D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Eason, ED: AUTHOR [+3]

Abstract

The double-ball pressure indicator shown in Fig. 1 is a highly accurate device for sensing when pressure or vacuum exceeds a given level. It consists of a vertical clear plastic tube 18 which contains small ball 14 and large ball 16. When vacuum is applied at outlet 12 or pressure is applied at inlet 10, the large ball rises when the pressure differential is equal to the sum of the weights of the balls, divided by the cross sectional area of the small ball. When the device is used with a vacuum, as shown above, the tube must be sealed at the top by end cap 24, and bypass channels 22 are included to equalize the pressure in the tube. The large ball must not seal off the small tube; hence a stop such as low-pressure port 12 must be provided.

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Double Ball Pressure Indicator

The double-ball pressure indicator shown in Fig. 1 is a highly accurate device for sensing when pressure or vacuum exceeds a given level. It consists of a vertical clear plastic tube 18 which contains small ball 14 and large ball 16. When vacuum is applied at outlet 12 or pressure is applied at inlet 10, the large ball rises when the pressure differential is equal to the sum of the weights of the balls, divided by the cross sectional area of the small ball. When the device is used with a vacuum, as shown above, the tube must be sealed at the top by end cap 24, and bypass channels 22 are included to equalize the pressure in the tube. The large ball must not seal off the small tube; hence a stop such as low- pressure port 12 must be provided. Though a single ball in a tube will rise at a very low pressure differential, this device can be designed for a wide range of rise points. The phototransistor light-sensing system shown in Fig. 2 provides logic signals to indicate the ball position when visual inspection is undesirable.

To the precision of measurement, there is perfect correlation between the calculated and average measured rise points. The rise pressure is repeatable to within 1/10% and there is less than 1% hysteresis. As to reliability, all contact is rolling, and there are no critical wear points. In addition, the device has no electrical contacts or springs, and hence no material fatigue problems. A miniature light-sensing i...