https://www.datamp.org/ Recently added patents en-us https://www.datamp.org/patents/displayPatent.php?id=32922&pn=1,407,578 Wrench Patentee: Frederic P. Robert - Lynnbrook, L.I. NY Granted:1922-02-21

The wrench consists of a fixed jaw with a curved face, a movable jaw at an oblique angle, linkage between the two which keeps the gripping surface of the movable jaw approximately parallel to the curved fixed jaw, and a contractile spring in the linkage which tends to close the jaws. Initially produced by the inventor; most of those found were produced by the Hoe Corporation and incorporate refinements from patent nos. 1,515,618 and 1,681,184.
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