Apparatus for stretching sheet materials

Claim 1

AN APPARATUS FOR EFFECTING THE SIMULTANEOUS BIAXIAL STRETCHING OF SHEET MATERIAL COMPRISING TWO SPACED SETS OF MOVEABLY SUPPORTED GRIPPERS, EACH OF SAID SETS ADAPTED TO GRIP ONE OF TWO OPPOSING MARGINAL PORTIONS OF THE SHEET MATERIAL TO BE STRETCHED, EACH GRIPPER HAVING A PROJECTING PORTION FOR ENGAGEMENT WITH DRIVING MEANS; GUIDE MEANS, FOR EACH SET OF GRIPPERS, ARRANGED TO DEFINE SPACED PATHS WHICH DIVERGE OVER AT LEAST A PART OF THEIR LENGTH TO PROVIDE A STRETCHING ZONE BETWEEN SAID MEANS AND TO CONSTRAIN THE GRIPPERS TO THE STRETCHING ZONE AT THE END WHERE SAID PATHS DIVERGE; MEANS FOR CAUSING THE GRIPPERS TO GRIP SAID MARGINAL PORTIONS BEFORE THE GRIPPERS ENTER THE STRETCHING ZONE; MEANS FOR CAUSING THE GRIPPERS TO RELEASE THE MARGINAL PORTIONS AFTER THE MATERIAL HAS PASSED THROUGH THE STRETCHING ZONE; DRIVING MEANS ASSOCIATED WITH EACH SET OF GRIPPERS FOR MOVING THE GRIPPERS ALONG SAID PATHS THROUGH THE STRETCHING ZONE; EACH DRIVING MEANS INCLUDING A ROTATABLE MEMBER FORMED WITH AN ARRAY OF GENERALLY COPLANAR RIDGES FOR ENGAGING THE PROJECTING PORTIONS OF THE GRIPPERS, THE PLANE OF THE RIDGES BEING SUBSTANTIALLY NORMAL TO THE AXIS OF ROTATION OF THE ROTATABLE MEMBER, THE RIDGES EXTENDING OUTWARDLY FROM THE VICINITY OF SAID AXIS TO TERMINATE AT THEIR OUTER ENDS ON A CIRCLE CENTERED ON SAID AXIS AND BEING EQUALLY SPACED THEREAROUND; EACH ARRAY OF RIDGES BEING DISPOSED IN SPACED OVERLAPPING RELATIONSHIP WITH THE ASSOCIATED GUIDE MEANS SO THAT AT LEAST A SEGMENT OF THE DEFINED PATH THEREOF, INCLUDING AT LEAST PART OF THE DIVERGING PATH, CROSSES SUCCEEDING RIDGES AT EVER INCREASING DISTANCES FROM THE AXIS THEREOF; MEANS FOR ENGAGING THE PROJECTING PORTIONS OF EACH SET OF GRIPPERS SINGLY WITH THE ASSOCIATED DRIVING MEANS WHILE THE GRIPPERS ARE SITUTATED ALONG THE PATH SEGMENT DEFINED BY EACH GUIDE MEANS; MEANS FOR ROTATING EACH DRIVING MEANS TO URGE THE RIDGES OF EACH MEMBER AGAINST THE ENGAGING PROJECTING PORTIONS TO MOVE THE GRIPPERS ALONG THE PATH SEGMENTS AND THUS OUTWARDLY ALONG THE DIVERGING PATHS, AT INCREASING SPEED ALONG AT LEAST A PORTION THEREOF, THROUGH THE STRETCHING ZONE TO BIAXIALLY STRETCH THE SHEET AND MEANS FOR RECOVERING THE STRETCHED SHEET.

Claim 2

AN APPARATUS FOR EFFECTING THE SIMULTANEOUS BIAXIAL STRETCHING OF SHEET MATERIAL COMPRISING TWO SPACED SETS OF MOVEABLY SUPPORTED GRIPPERS, EACH OF SAID SETS ADAPTED TO GRIP ONE OF TWO OPPOSING MARGINAL PORTIONS OF THE SHEET MATERIAL TO BE STRETCHED, EACH GRIPPER HAVING A PROJECTING PORTION FOR ENGAGEMENT WITH DRIVING MEANS; GUIDE MEANS, FOR EACH SET OF GRIPPERS, ARRANGED TO DEFINE SPACED PATHS WHICH DIVERGE OVER AT LEAST A PART OF THEIR LENGTH TO PROVIDE A STRETCHING ZONE BETWEEN SAID MEANS AND TO CONSTRAIN THE GRIPPERS TO THE STRETCHING ZONE AT THE END WHERE SAID PATHS DIVERGE; MEANS FOR CAUSING THE GRIPPERS TO GRIP SAID MARGINAL PORTIONS BEFORE THE GRIPPERS ENTER THE STRETCHING ZONE; MEANS FOR CAUSING THE GRIPPERS TO RELEASE THE MARGINAL PORTIONS AFTER THE MATERIAL HAS PASSED THROUGH THE STRETCHING ZONE; DRIVING MEANS ASSOCIATED WITH EACH SET OF GRIPPERS FOR MOVING THE GRIPPERS ALONG SAID PATHS THROUGH THE STRETCHING ZONE; EACH DRIVING MEANS INCLUDING A ROTATABLE MEMBER FORMED WITH AN ARRAY OF GENERALLY COPLANAR RIDGES FOR ENGAGING THE PROJECTING PORTIONS OF THE GRIPPERS, THE PLANE OF THE RIDGES BEING SUBSTANTIALLY NORMAL TO THE AXIS OF ROTATION OF THE ROTATABLE MEMBER, THE RIDGES EXTENDING OUTWARDLY FROM THE VICINITY OF SAID AXIS TO TERMINATE AT THEIR OUTER ENDS ON A CIRCLE CENTERED ON SAID AXIS AND BEING EQUALLY SPACED THEREAROUND; EACH ARRAY OF RIDGES BEING DISPOSED IN SPACED OVERLAPPING RELATIONSHIP WITH THE ASSOCIATED GUIDE MEANS SO THAT AT LEAST A SEGMENT OF THE DEFINED PATH THEREOF, INCLUDING AT LEAST PART OF THE DIVERGING PATH, CROSSES SUCCEEDING RIDGES AT EVER INCREASING DISTANCES FROM THE AXIS THEREOF; MEANS FOR ENGAGING THE PROJECTING PORTIONS OF EACH SET OF GRIPPERS SINGLY WITH THE ASSOCIATED DRIVING MEANS WHILE THE GRIPPERS ARE SITUTATED ALONG THE PATH SEGMENT DEFINED BY EACH GUIDE MEANS; MEANS FOR ROTATING EACH DRIVING MEANS TO URGE THE RIDGES OF EACH MEMBER AGAINST THE ENGAGING PROJECTING PORTIONS TO MOVE THE GRIPPERS ALONG THE PATH SEGMENTS AND THUS OUTWARDLY ALONG THE DIVERGING PATHS, AT INCREASING SPEED ALONG AT LEAST A PORTION THEREOF, THROUGH THE STRETCHING ZONE TO BIAXIALLY STRETCH THE SHEET AND MEANS FOR RECOVERING THE STRETCHED SHEET.