Browse Prior Art Database

Air Track Control

IP.com Disclosure Number: IPCOM000088433D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 119K

Publishing Venue

IBM

Related People

Hassan, JK: AUTHOR [+2]

Abstract

Shown are control units for automatic motion control of wafers and similar units on air tracks. Basically, the units provide for wafer position sense, acceleration or deceleration of the wafer, and stopping the wafer for a given period with its subsequent dispatch in a given direction.

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Air Track Control

Shown are control units for automatic motion control of wafers and similar units on air tracks. Basically, the units provide for wafer position sense, acceleration or deceleration of the wafer, and stopping the wafer for a given period with its subsequent dispatch in a given direction.

The structure of the position sensor is illustrated in Figs. 1A and 1B. As shown, the air inlet is provided with a dual diameter stepped bore for increased sensitivity at lower flow rates. At wafer position 1 (Fig. 1A), a suction pressure exists in the larger cavity due to flow separation. With the wafer in position 2 (Fig. 1B), the axis radial attraction causes an abrupt increase in supply pressure from p(s1) to p(s2), and a flow rate decrease from m(1) to m(2) (Fig. 1C). In contrast to smooth or single bore units, the double diameter bore gives a stronger pressure characteristic for a given flow rate. In any event, the sensor flow issues through the air track film field without adverse effects on its characteristics.

The elements of the control valve connecting the sensor and motion control are illustrated in Figs. 2A-2C. In wafer position 1 (Fig. 1A), the valve elements are relatively positioned as shown in Fig. 2A with air supply pressure F adjusted to a predetermined value.

As the wafer comes into position 2 (Fig. 1B), the p(s1) increases to p(s2), causing opening of the lower valve element, motion of the slider and flow to the stop device (or to a speed chan...