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Research & Prototyping: Tools




The anti-slip pipe thread wrench was developed from a standard pipe thread wrench manufactured by Rigid Tool. This type of wrench has been on the market for many decades unchanged. To use the wrench, the die is inserted into the wrench head. The die, with attached wrench, is slipped over the end of an unthreaded pipe. The wrench handle is used to rotate the die and cut tapered threads into the pipe end.

The wrench head rotates the die in one direction and ratchets in the opposite direction, allowing the user to reassert leverage on the handle from the same position. The ratchetting action is accomplished via the pawl in the wrench head, which is tapered and spring loaded, and the ratchetting teeth in the die.  

The problem with this system is, that the pawl performs a second function. It holds the die in the wrench head by extending radially inward between the two die retaining rings. If the user moves the handle up or down out of the plane perpendicular to the pipe being threaded and passing through the pawl, the pawl will occasionally ride against one of the retaining rings and slip past the die ratchet teeth without engaging. If the user is pulling in a rhythm and standing precariously, the user may fall and be injured. The pulling necessary to thread a 2.5 inch or larger pipe is significant.  Accidents have happened in this manner resulting in the warning label on the wrench handle: WARNING Fully engage ratchet to prevent slipping and serious injury.

Restated, the problem is the pawl performing two functions: (1) ratchetting and (2) retaining the die in the wrench head. The retaining function causes a malfunction in the ratchetting function when the pawl rides one of the ring past the ratchetting teeth, resulting in slipping.

The BEAR engineering team developed a ratchetting pipe threader device separating the functions of ratchetting the die and retaining the die with a tube adjacent to the ratchetting pawl.

Patent Pending.

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