A device for switching off and switching on the operation of a spindle of a textile twisting or spinning machine having a running thread, said device comprising:
- pneumatic switching means adapted to be operatively connected to a spindle stop mechanism of the textile machine for actuation and de-actuation thereof;
- movable running thread sensor means for being held in a first normal operating position by the running thread in the textile machine and for moving to a second switching position upon breakage of the running thread;
- movable braking sensor means adapted to be operatively connected to a spindle braking mechanism of the textile machine for moving between a first position during normal operation of the spindle to a second position upon actuation of the spindle braking mechanism after thread breakage;
- and
- pneumatic control means operatively connected to said pneumatic switching means, said running thread sensor means and said movable braking sensor means for operating said switching means to actuate the spindle stop mechanism upon breaking of the running thread to stop the spindle operation and for de-actuating the spindle stop mechanism upon actuation of the spindle braking mechanism and before said running thread sensor means has returned to its normal operating position by the running thread during subsequent start up of the spindle operation, said pneumatic control means comprising
- compressed air source means,
- first compressed air line means connecting said compressed air source means to said pneumatic switching means,
- first control valve means positioned in said first compressed air line means for blocking the flow of compressed air to said switching means from said source in a first position thereof to deactuate the spindle stop mechanism during normal operating conditions of the spindle and for opening the flow of compressed air to said switching means from said source in a second position thereof to operate said switching means to actuate said spindle stop mechanism upon breakage of the running thread,
- second compressed air line means extending between said thread sensor means, said compressed air source means and said first control valve means for maintaining said first control valve means in its first air blocking position under normal air pressure therein,
- second control valve means positioned in said second compressed air line means for opening the flow of compressed air in said second compressed air line means in a first position thereof during normal operation of the spindle and for throttling the flow of compressed air in said second compressed air line means in a second position thereof,
- first venting means in said second compressed air line means for being closed when said running thread sensor means is held in the first normal operating position thereof and for being opened upon thread breakage and said thread sensor means moving to its second switching position for venting air pressure in said second compressed air line means to effect movement of said first control valve means to open the flow of compressed air to said pneumatic switching means to operate the spindle stop mechanism,
- third compressed air line means extending between said second compressed air line means, said movable braking sensor means and said second control valve means, and
- second venting means in said third compressed air line means for being closed when said braking sensor means is in the first position thereof and for being opened upon actuation of the spindle braking mechanism and movement of said braking sensor means to the second position thereof for venting air pressure in said third compressed air line means to effect movement of said second control valve means to the second air throttling position thereof for effecting movement of said first control valve means to the first air blocking position to allow start up of normal operation of the spindle and until said first venting means closes by said running thread sensor means returning to its normal operating position to close said first venting means to move said second cotnrol valve means to its first position for normal operation of the spindle.