Hydraulic tapper unit with means to permit yielding of the feed nut

Claim 1

A TAPPER UNIT COMPRISING A BASE, A CARRIER ELEMENT LINEARLY RECIPROCABLE ON SAID BASE, A TAP SPINDLE ELEMENT SUPPORTED BY SAID CARRIER ELEMENT ROTATABLE RELATIVE TO SAID CARRIER ELEMENT AND MOVABLE RELATIVE THERETO ALONG THE AXIS OF ROTATION THEREOF, LEAD SCREW AND NUT MEMBERS, ONE OF SAID MEMBERS BEING MOUNTED ON SAID CARRIER ELEMENT FIXED AGAINST SUBSTANTIAL AXIAL MOVEMENT RELATIVE THERETO AND ROTATABLE IN RESPONSE TO AXIAL THRUST ON SAID SPINDLE GREATER THAN A PREDETERMINED VALUE AND THE OTHER OF SAID MEMBERS BEING MOUNTED ON SAID SPINDLE ELEMENT, SAID MEMBERS INTERENGAGING TO AXIALLY MOVE SAID SPINDLE RELATIVE TO SAID CARRIER IN RESPONSE TO RELATIVE ROTATION THEREBETWEEN, ROTARY MEANS CONNECTED TO ROTATE SAID SPINDLE, ACTUATOR MEANS VONNECTED TO MOVE SAID CARRIER, A FIRST CONTROL CONNECTED TO SAID ROTARY MEANS AND ACTUATOR MEANS OPERATING SAID ACTUATOR MEANS TO MOVE SAID SPINDLE ELEMENT TO A FIRST PREDETERMINED POSITION RELATIVE TO SAID BASE AND ENERGIZE SAID ROTARY MEANS, A SECOND CONTROL OPERABLE TO REVERSE SAID ROTARY MEANS WHEN SAID SPINDLE REACHES A SECOND PREDETERMINED POSITION RELATIVE TO SAID BASE, AND A THIRD CONTROL OPERABLE TO STOP SAID ROTARY MEANS WHEN SAID SPINDLE REACHES A THIRD PREDETERMINED POSITION RELATIVE TO SAID CARRIER AND OPERATE SAID ACTUATOR MEANS TO MOVE SAID CARRIER RELATIVE TO SAID BASE.