Browse Prior Art Database

Override Slip Clutch

IP.com Disclosure Number: IPCOM000086499D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Fineran, WJ: AUTHOR [+4]

Abstract

The override slip clutch protects the wafers under test, the tester contactor and the "Z" mechanism, that is the up-and-down-motion mechanism of the wafer-carrying device.

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Override Slip Clutch

The override slip clutch protects the wafers under test, the tester contactor and the "Z" mechanism, that is the up-and-down-motion mechanism of the wafer- carrying device.

In operation, the motor 1 drives a gear set 2 which is directly coupled to a lead screw nut 3. The lead screw 4 is fastened to the ram 5 at the top of the mechanism via a coupling 7 and shaft 8, which form part of the slip clutch in such a manner that they do not rotate. For lead screw to ride up and down without rotating. This results in a "Z" motion of the ram 5 via the three guide slides 6.

The motor counts steps (1,000/revolution) by an encoder on its shaft and a series of light-emitting diodes which provide position sensing.

A limit switch is provided at the extreme travel position in case of a runaway situation. If the limit switch fails to drop power to the motor, the "Z" motion would continue until the end of the lead screw is reached or the slides travel to their extreme position. Both of these conditions would damage the "Z" mechanism or any wafer carried by the ram 5 of the mechanism and possibly the contactor (not shown) of the tester. The slip clutch prevents a damaging force being applied between the ram and the contactor tester.

At a preset torque of the elastic stop nut 9, a force is applied through the wave-washer spring 10 to the thrust washers 13 and thrust bearing 11. This force is selected to be greater than the sum of the friction force of the nut, th...