Bolt fixing device of jet pump beam

Abstract

A jet pump is provided with a riser as a coolant supply tube, an inlet mixer forming a turn-around path for the coolant, a diffuser and a jet pump beam provided with a bolt fixing device. The bolt fixing device includes: a head bolt of a jet pump beam for pushing and supporting the inlet mixer from an upper side of the riser, the head bolt being provided with a polygonal head portion; a lock cap provided on the polygonal head portion of the head bolt to be slidable in an axial direction thereof and integrally rotatable; a body housing disposed on an upper surface of the jet pump beam and adapted to accommodate the lock pin; a plurality of tapered external teeth formed on an outer peripheral side surface of the lock cap; and a plurality of internal tooth-shaped grooves formed to the body housing so as to be selectively engaged with the external teeth of the lock cap so as to fix the head bolt of the jet pump beam.

1 . A bolt fixing device of a jet pump beam of a jet pump provided with a riser as a coolant supply tube, an inlet mixer forming a turn-around path for the coolant and a diffuser, the bolt fixing device comprising:
 a head bolt of a jet pump beam for pushing and supporting the inlet mixer from an upper side of the riser, the head bolt being provided with a polygonal head portion;   a lock cap provided on the polygonal head portion of the head bolt to be slidable in an axial direction thereof and integrally rotatable;   a body housing disposed on an upper surface of the jet pump beam and adapted to accommodate the lock pin;   a plurality of tapered external teeth formed on an outer peripheral side surface of the lock cap; and   a plurality of internal tooth-shaped grooves formed to the body housing so as to be selectively engaged with the external teeth of the lock cap so as to fix the head bolt of the jet pump beam.   
   
   
       2 . The bolt fixing device of the jet pump beam according to  claim 1 , further comprising an elastic member interposed between the upper surface of the jet pump beam and the lock cap and adapted to urge the external teeth of the lock cap always upwardly so as to be engaged with the internal tooth-shaped grooves of the body housing. 
   
   
       3 . The bolt fixing device of the jet pump beam according to  claim 2 , wherein the elastic member is a compression spring or a leaf spring. 
   
   
       4 . The bolt fixing device of the jet pump beam according to  claim 1 , wherein the body housing is provided with an outer peripheral flange at a lower portion thereof, the outer peripheral flange being fixed to an upper surface of the jet pump beam by a base plate having an inner peripheral flange, and the body housing includes a rotation restraint mechanism mounted to the base plate. 
   
   
       5 . The bolt fixing device of the jet pump beam according to  claim 4 , wherein the rotation restraint mechanism of the body housing includes a restraint spring disposed in a recessed portion of the base plate and a housing opening opened in an outer side surface of the body housing so as to be engageable with the restraint spring, and rotation of the body housing is restrained at an arbitrary position within a pitch angle range of the housing opening. 
   
   
       6 . The bolt fixing device of the jet pump beam according to  claim 5 , wherein the restraint spring of the rotation restraint mechanism disposed in the recessed portion of the base plate has a tip end portion tapered so as to converge toward the body housing to restrain the rotation of the body housing at an arbitrary position. 
   
   
       7 . The bolt fixing device of the jet pump beam according to  claim 4 , wherein the base plate is provided with a movable pin to be inserted into an opening formed in a side surface of the body housing so as to restrain the rotation of the body housing. 
   
   
       8 . The bolt fixing device of the jet pump beam according to  claim 1 , wherein the external teeth of the lock cap and the internal tooth-shaped grooves of the body housing are formed of a hard material. 
   
   
       9 . The bolt fixing device of the jet pump beam according to  claim 1 , wherein the external teeth of the locking cap and the internal tooth-shaped grooves of the body housing are composed of a rigid weld overlay material that does not contain cobalt.