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Bearing Collapse Top Reference

IP.com Disclosure Number: IPCOM000038056D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Clothier, RW: AUTHOR [+2]

Abstract

In the drilling of printed circuit panels the detection of the top surface of the panel relative to the drill tip is sometimes required, but detection is difficult to achieve with reasonable repeatability. The detection of the collapse of an air thrust bearing in the spindle mechanism accomplishes this by giving an accurate sense of drill tip position because of the direct coupling between the drill tip and bearing. The bearing collapse can be detected in the following manner. (Image Omitted)

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Bearing Collapse Top Reference

In the drilling of printed circuit panels the detection of the top surface of the panel relative to the drill tip is sometimes required, but detection is difficult to achieve with reasonable repeatability. The detection of the collapse of an air thrust bearing in the spindle mechanism accomplishes this by giving an accurate sense of drill tip position because of the direct coupling between the drill tip and bearing. The bearing collapse can be detected in the following manner.

(Image Omitted)

A drill spindle 1 is driven by an air, or electric, turbine 2, which is connected to a vertical drive mechanism 3 which provides the vertical motion to drill the holes (not seen) of the circuit panels (not seen).

A Hall effect eddy current probe 6 is mounted on the drive mechanism 3 so that a tick mark 5 on the rim of the turbine 2 produces an electrical pulse at each revolution of the spindle 1 as the mark passes the probe 6.

An air thrust bearing 7 separates the piston 3 from the turbine 2. As the drill 4 contacts the panel the air bearing 7 will compress a small distance until it reaches a stiffness value that is greater than the upward force exerted by the drill 4 at which point the drill 4 enters into the panel.

An RPM sensor 6 produces a greater peak-to-peak signal when the bearing 7 is under compression because the sensor 6 is closer to the tick mark 5, thus producing a signal amplitude increase.

This top reference concept is implemented...