Precast panel construction

Claim 1

A PREFABRICATED PANEL FOR USE IN CONSTRUCTION OF A CURTAIN WALL COMPRISING: AN OPEN CENTER FRAME OF A RELATIVELY LIGHT WEIGHT, RELATIVELY HIGH EXPANSION CO-EFFICIENT MATERIAL, SAID FRAME INCLUDING TWO END MEMBERS SECURED TO TWO SIDE MEMBERS AND HAVING A FRONT AND A REAR, EACH OF SAID MEMBERS HAVING AN INTERIOR SURFACE WHICH FACES SAID OPEN CENTER OF SAID FRAME, EACH OF SAID SIDE MEMBER HAVING ADJACENT ITS FRONT EDGE PROTION OF REARWARDLY DISPOSED GROOOVE, A RETAINER DISPOSED ADJACENT SAID INTERIOR SURFACE OF EACH SIDE MEMBER, EACH RETAINER HAVING A FRONT EDGE PORTION WITH A GROOVE INTERENGAGED WITH THE GROOVE IN THE SIDE MEMBER ADJACENT THERETO, SAID INTERENGAGED GROOVES FORMING JOINTS BETWEEN THE FRONT EDGE PORTIONS OF SAID RETAINERS AND SIDE MEMBERS BY WHICH SAID RETAINERS ARE FRONTALLY HELD WITHIN SAID FRAME, SAID MEMBER HAVING ADJACENT THEIR REARWARD PORTIONS FLANGES WHICH PROJECT INWARDLY TOWARD SAID OPEN CENTER OF SAID FRAME, A CLOSURE FOR THE REAR OF SAID FRAME WHICH INCLUDES A BACK PLATE RETAINED WITHIN SAID FRAME BY SAID FLANGES, SAID RETAINERS HAVING REARWARD EDGE PORTIONS ENGAGED AGAINST SAID CLOSURE AND THEREBY HOLDING SAID CLOSURE AGAINST SAID FLANGES, SAID RETAINERS HAVING ADJACENT THEIR SAID FRONT EDGE PORTIONS FLANGES WHICH PROJECT INWARDLY TOWARD SAID OPEN CENTER OF SAID FRAME, A BLOCK OF RELATIVELY LOW EXPANSION CO-EFFICIENT MATERIAL HAVING EDGE PORTIONS IN INTIMATE CONTACT WITH SAID RETAINERS AND THE REGION OF CONTACT INCLUDING THE REARWARD FACES OF SAID FLANGES ON SAID RETAINERS, SAID BLOCK HAVING A REARWARDLY DISPOSED PORTION ENGAGED AGAINST SAID CLOSURE, INTERGAGED PORTION OF SAID GROOVES BEING DISPOSED AT AN OBLIQUE ANGLE TO THE SIDE-MEMBER-TO-SIDE-MEMBER DIRECTION OF SAID FRAME SO THAT SAID JOINTS ARE EXPANSIBLE IN SAID DIRECTION RESPONSIVE TO DIFFERENTIAL EXPANSION OF SAID FRAME AND BLOCK.