Digital protractor

A digital protractor for measuring an angular displacement from a reference surface, said protractor comprising:

• a substantially congruent pair of pivotally interconnected upper and lower arms, which arms are superposable upon one another, each arm having a pair of substantially parallel engagement edges extending longitudinally of said arm, one of said arms being engagable along an engagement edge thereof with the reference surface;
• an electronic sensor secured to said lower arm;
• a digital readout device secured to said upper arm for operatively cooperating with said electronic sensor to measure and display the angular displacement from the arm engaging the reference surface to the other arm and;
• a locking apparatus for holding said arms together to maintain a selected angular displacement between said arms, said arms being pivotally connected by a pivot pin and said locking apparatus including a lock plate secured by said upper arm and having a locking engagement surface and central opening through which said pivot pin extends, and a locking lever connected pivotally to said pin and extending outwardly of said upper arm and carrying a bearing for interengaging said locking engagement surface of said lock plate when said lock lever is rotated about said pivot pin in a selected direction to tighten interengagement between said arms and hold said arms with a selected angular displacement therebetween, said locking engagement surface including a tapered groove formed in said locking plate and said bearing including a ball bearing carried by said locking lever and received in said tapered groove whereby rotating said lever directs said ball bearing into a shallow portion of said groove to tighten interengagement between said upper and lower arms and hold said arms at the selected angular displacement.

A digital protractor for measuring an angular displacement from a reference surface to a second surface, each of which surfaces includes a magnetically attracted material, said protractor comprising:

• a substantially congruent pair of pivotally interconnected upper and lower arms, which arms are superposable upon one another, each arm having a pair of substantially parallel engagement edges extending longitudinally of said arm, one of said arms being engagable with the reference surface along a selected engagement edge of said arm, the other said arm being engagable with the second surface along a selected engagement edge of said other arm, each engagement edge in each arm including a longitudinal channel for receiving a respective magnetic element, which magnetic element is confined within said longitudinal channel such that said magnetic element does not extend laterally beyond said engagement edge;
• an electronic sensor secured to said lower arm;
• and
• a digital readout device secured to said upper arm for operatively cooperating with said electronic sensor to measure and display the angular displacement from said arm engaging the reference surface to the other said arm engaging the second surface, a respective pair of said magnetic elements for holding the angular displacement set between the arms and the resulting measurement thereof.