US3897532A
Expired / Lapsed
US
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Method of manufacturing thin-walled hollow articles of polytetrafluorethylene, apparatus for performing the method and articles manufactured by the method
Abstract A method of manufacturing thin-walled hollow articles of polytetrafluorethylene (PTFE) is described, comprising feeding PTFE powder into the interstice formed between the elastic matrices of a mold and a rigid core floatingly supported within said matrices, applying pressure onto the matrices and compressing the powder within the interstice, while preventing the lateral expansion of the matrices, releasing the pressure and withdrawing the article from the mold. The method is economical even when small lots are to be manufactured. The apparatus for performing the method comprises feeding means, for feeding powder into an elastic mold, mold means comprising one or more matrices of rubber or of a rubber-like material, a mold cavity provided in or between the matrices, and a rigid core, simple or composite, elastically suspended within the cavity, bracing means for confining the matrices and for preventing their lateral expansion, and means for applying pressure onto the matrix or the matrices. The articles manufactured by the method comprise thin-walled hollow articles, straight or curved and having relatively complex shapes, as for example elbow-shaped fittings, T-shaped fittings, reducing fittings, or multi-branch fittings, of polytetrafluorethylene or of other suitable material.
A METHOD OF MANUFACTURING THIN-WALLED HOLLOW ARTICLES OF POLYTETRAFLUOROETHYLENE, WHICH METHOD COMPRISES THE STEPS OF: LOCATING A RIGID CORE WITH A MOLD COMPRISING AT LEAST ONE FEMALE MATRIX MADE OF A COMPRESSIBLE ELASTIC MATERIAL WHILE SPACING THE CORE FROM THE INNER WALLS OF THE MOLD BY FORAMINOUS MEANS BY A PREDETERMINED DISTANCE, INTRODUCING POLYTETRAFLUORETHYLENE POWDER INTO SAID MOLD THROUGH SAID FORAMINOUS MEANS TO FORM A MASS BEARING AGAINST BOTH THE CORE AND THE INNER WALL OF SAID MATRIX WHICH SUBSTANTIALLY FILLS THE SPACE BETWEEN SAID CORE AND MATRIX, COMPRESSING SAID COMPRESSIBLE MATRIX INWARDLY BY APPLYING PRESSURE THERETO IN A SINGLE DIRECTION WHILE PREVENTING PERIPHERAL EXPANSION THEREOF, UNTIL SAID POWDER IS FORMED INTO A PREDETERMINED ARTICLE, RELEASING SAID PRESSURE, AND REMOVING SAID ARTICLE FROM SAID MOLD.
Claim 2
Independent Claim
125 words
A METHOD OF MANUFACTURING THIN-WALLED HOLLOW ARTICLES OF POLYTETRAFLUOROETHYLENE, WHICH METHOD COMPRISES THE STEPS OF: LOCATING A RIGID CORE WITH A MOLD COMPRISING AT LEAST ONE FEMALE MATRIX MADE OF A COMPRESSIBLE ELASTIC MATERIAL WHILE SPACING THE CORE FROM THE INNER WALLS OF THE MOLD BY FORAMINOUS MEANS BY A PREDETERMINED DISTANCE, INTRODUCING POLYTETRAFLUORETHYLENE POWDER INTO SAID MOLD THROUGH SAID FORAMINOUS MEANS TO FORM A MASS BEARING AGAINST BOTH THE CORE AND THE INNER WALL OF SAID MATRIX WHICH SUBSTANTIALLY FILLS THE SPACE BETWEEN SAID CORE AND MATRIX, COMPRESSING SAID COMPRESSIBLE MATRIX INWARDLY BY APPLYING PRESSURE THERETO IN A SINGLE DIRECTION WHILE PREVENTING PERIPHERAL EXPANSION THEREOF, UNTIL SAID POWDER IS FORMED INTO A PREDETERMINED ARTICLE, RELEASING SAID PRESSURE, AND REMOVING SAID ARTICLE FROM SAID MOLD.
Claim 3
Dependent Claim
35 words
The method claimed in claim 1 in which said compression is continued until the thickness of the space between said mold and said core is reduced to between one-half and two-fifths of its original thickness.
Claim 4
Dependent Claim
21 words
The method claimed in claim 1 wherein the the increase and decrease in pressure are carried out at a slow rate.
Claim 5
Dependent Claim
22 words
The method claimed in one of the claim 1 wherein a pressure of a magnitude between 150 and 350 kg/cm2 is developed.
Claim 6
Dependent Claim
19 words
The method claimed in claim 1, wherein polytetrafluoroethylene powder is introduced into the mold by way of a funnel.