Pneumatically disengageable self-threading yarn brake mechanism in a hollow spindle assembly of a textile yarn processing machine and related method

In a textile yarn processing machine, such as a two-for-one twister or the like, having a plurality of spindle assemblies, each having an elongate yarn passageway extending therethrough and including a threading mechanism having a compressed air operated injector nozzle operable for sucking a yarn into said yarn passageway at the inlet end thereof and for automatically threading the yarn through the yarn passageway during a thread-up operation, the combination therewith of an improved yarn brake mechanism for applying a desired tension to the yarn passing through said passageway during operation of the yarn processing machine, said yarn brake mechanism being constructed to cooperate with said threading mechanism to facilitate automatic threading of a yarn through said yarn passageway and comprising

• a tubular brake housing located in said spindle assembly with said yarn passageway extending axially therethrough,
• an upper hollow insert mounted within said brake housing with said yarn passageway extending therethrough, and including means defining the upper end of an enlarged cavity forming a part of and enlarging a portion of said yarn passageway, and an upper annular braking ring surrounding the yarn passageway at the entrance to said cavity,
• a lower hollow insert mounted within said brake housing with said yarn passageway extending therethrough, and including means defining the lower end of said enlarged cavity, and a lower annular braking ring surrounding the yarn passageway at the exit from said cavity,
• an elongate capsule-shaped braking cartridge positioned within said cavity with opposite ends thereof adapted to be positioned in engagement with said upper and lower braking rings,
• means for biasing said upper and lower inserts toward one another so that said upper and lower braking rings engage opposite ends of said braking cartridge for applying tension to a yarn passing therebetween,
• means cooperating with one of said upper or said lower inserts and actuable by the compressed air supplied to said threading mechanism for overcoming said biasing means and moving said one insert away from the other insert to release said braking cartridge from engagement by said upper and lower braking rings, and
• means for moving said braking cartridge upon the release thereof by said upper and lower braking rings laterally out of the path of the yarn being threaded through said cavity to thus provide a clear path for threading the yarn through said yarn passageway.