Cord lock with both sharp and dull teeth

Claim 1

A cord locking device comprising: a body containing a tapering passage through which two flexible cords are to extend and which is defined at opposite sides by two cam surfaces facing one another and converging toward one another as they advance in a predetermined direction; and a slide element having a portion received within said passage and between said converging cam surfaces, and having two sets of teeth at opposite sides of said element facing in opposite directions toward said two cam surfaces respectively to define therewith two spaces along which said two cords extend and within which they are clamped between said teeth and said cam surfaces in a relation locking said cords against movement in said predetermined direction; said element being movable along an axis in said predetermined direction relative to said body to grip the cords, and being movable in an opposite retracting direction along said axis to release the cords; each of said sets of teeth including a first relatively sharp tooth having leading and trailing faces converging to a substantially sharp outer edge near a corresponding one of said cam surfaces, and including a relatively blunt tooth with leading and trailing faces and an outer crest surface which faces toward said corresponding cam surface but is less sharp than said edge of the first tooth; said sharp edge and said blunt outer surface of the teeth of one of said sets of teeth having outermost portions lying essentially in a first plane which converges toward said axis and is approximately parallel to the corresponding one of said cam surfaces; and said sharp edge and said blunt outer surface of the teeth of the other set of teeth having outermost portions lying essentially in a second plane which converges toward said axis and toward said first plane and is approximately parallel to the other of said cam surfaces.