Material and process of manufacture of steel components for screw gun clutches

Abstract

A process for manufacturing highly wear and fatigue resistant steel components for power tools includes melting and mixing together a readily available base steel and alloying elements. The molten steel is cast into near-net-shape in an investment casting process. This method is cost competitive with forming the same component from steel with fewer alloying elements. In particular, clutch plates for a drill / driver or screw gun can be formed in this manner from a steel containing relatively large amounts of nickel and chromium, such as SAE 9310 steel, or from a steel containing a relatively large total amount of molybdenum and tungsten, such as AISI M2 steel.

Description

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09 / 923,034 filed Aug. 8, 2001 (now U.S. Pat. No. ______), and also claims priority from provisional U.S. patent application Ser. No. 60 / 354,943 filed Feb. 11, 2002.BACKGROUND OF THE INVENTION [0002] The field of this invention is wear and fatigue resistant clutches for screw guns which automatically disengage when a screw is driven to a selected depth and which disengage positively to prevent clashing, and also materials and processes for manufacturing wear and fatigue resistant alloy steel components for screw gun clutches, and for power tools generally, especially hand-held power tools. [0003] The prior art includes several examples of positive disengagement clutches, or “quiet” clutches, for screw guns. Generally, these clutches include a mechanism for moving the clutch surfaces away from one another when they disengage to prevent the clutch surfaces from clashing. This positive disengagement le...

AI Technical Summary

Problems solved by technology

The increased stress could lead to a decrease in the fatigue life of each part.

While this steel has been selected because of its desirable wear and fatigue properties, clutches in screw guns nevertheless remain one of the shortest-lived wear components in these tools.

Breakdown of screw guns due to clutch failure causes the user to spend considerable time and money repairing the clutch or replacing the tool in its entirety.

Use of higher alloy steels can improve the wear and fatigue resistance of these components but does so typically at the expense of the cost competitiveness of the tool.

Higher alloy steels can lead to greater initial manufacturing and inventory costs and increased difficulty in final machining.

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