the accidental jamming together of two type-bars

http://www.google.com/patents?id=ibJnAAAAEBAJ

One object of my present invention is to
provide, preferably in connection with the
keyboard of a writing-machine of the class
specified, a simple and effective safety-stop
25 device of suitable construction supported in
cooperative relation with two or more key-
levers of the machine, and adapted, upon the
working stroke of a key-lever, to be actuated
by said key-lever and thrown into positive en-
30 gagement with one or more adjacent key-
levers to thereby positively lock said adjacent
key-levers against effective movement
until the aforesaid actuated key-lever is returned
to its normal inoperative position.
35 Another object of my invention is to provide,
in connection with the key-levers of a
writing-machine of the class specified, a multiplex
safety-stop device comprehending a
multiplicity of pivotally-supported coopera-
40 tive key-lever lockers or tumblers arranged
in cooperative relation with the key-levers
and adapted, upon the working stroke of one
key-lever, f or engaging and positively locking
those key-levers adjacent to opposite sides of
45 the key-lever operated and for preventing
an effecting movement of said adjacent key-
levers until the operated key-lever has returned
to its normal ineffective position and
thereby preventing the accidental jamming
50 together of two type-bars, which would occur
if two or more key-levers actuating said type-
bars were simultaneously operated.