# US 5,346,378 A · Apparatus for forming a curing envelope > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,346,378 A - Document ID: US5346378A - Status: Granted - Kind: A - Application number: 08/045,028 - Filed: 1993-04-09 - Granted: 1994-09-13 - Earliest claimed: 1992-01-21 - Assignees: Bridgestone/Firestone, Inc. - Inventors: Calvin M. Kassaw, Jr.; Jolanta K. Klimek - Web page: https://patentgrep.com/patent/US5346378A ## CPC - B29D 30/542: {using envelopes or membranes provided with sealings for curing} - B29C 43/104: {the mould cavity lying totally outside the axis of symmetry, e.g. toroidal moulds} - B29C 43/40: with means for cutting the article - B29C 43/3642: {Bags, bleeder sheets or cauls for isostatic pressing} - B29K 2105/24: crosslinked or vulcanised - B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00) - B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00) - B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS ## Abstract An apparatus for forming curing envelopes which apparatus enables the use of a conventional inner tube mold for making a curing envelope preform in the form of an envelope tube which may have a portion thereof easily removed to provide a curing envelope suitable for use in a tire retreading process. A curing envelope is made by placing an annular tube of uncured envelope material in a curing mold having a center core and a mold insert installed therein. The insert includes a pair of coaxial annular rings projecting radially outwardly from the center core and connecting straps for maintaining the axial spacing between the rings. The mold is closed and heat and internal pressure are applied to the envelope tube for curing the envelope tube and urging the tube against the interior cavity surface with the annular rings penetrating into the inner wall of the tube for forming therein corresponding annular grooves. The mold is then opened and the envelope tube is removed from the mold after which the envelope tube is severed along the annular grooves to remove the portion of the inner wall of the envelope tube between the grooves thereby to form a curing envelope of generally U-shape cross-section. ## Claims ### Claim 1 A mold insert for use in a curing mold for molding an inner tube, the mold having a center core against which an inside wall of the tube is urged by internal pressure in the tube during curing, said insert comprising a pair of coaxial rings adapted to closely circumscribe the center core of the curing mold for forming a pair of coaxial grooves in the inside wall of the tube being cured in the mold, and means interconnecting said rings for maintaining the axial spacing therebetween when assembled into the mold about the center core. ### Claim 2 (depends on 1) A mold insert as set forth in claim 1, wherein said interconnecting means includes a plurality of circumferentially spaced apart cross ties attached top and bottom to said coaxial rings. ### Claim 3 (depends on 2) A mold insert as set forth in claim 2, wherein said cross ties are curved to conform to the contour of the center core. ### Claim 4 (depends on 2) A mold insert as set forth in claim 2, wherein said rings have splits therein, and said plurality of cross ties include end cross ties attached to said rings at respective opposite sides of said splits in said rings, and further comprising means for interconnecting said end cross ties, whereby the mold insert can be locked around the center core of the curing mold. ### Claim 5 (depends on 1) A mold insert as set forth in claim 1, wherein said coaxial rings each have axially inner and outer side surfaces which converge to form a narrow outer edge. ### Claim 6 (depends on 5) A mold insert as set forth in claim 5, wherein said axially inner side surface is more radially disposed than said axially outer side surface of each ring. ### Claim 7 (depends on 2) A mold insert as set forth in claim 2, wherein said cross ties are formed by thin straps. ### Claim 8 In combination, a curing mold for molding an inner tube and a mold insert, said curing mold having a center core against which an inside wall of the tube is urged by internal pressure in the tube during curing, and said insert comprising a pair of coaxial rings and means interconnecting said rings for maintaining the axial spacing therebetween, said coaxial rings closely circumscribing and projecting from the center core of said curing mold for forming a pair of coaxial grooves in the inside wall of the tube being cured in said mold. ### Claim 9 (depends on 8) A combination as set forth in claim 8, wherein said interconnecting means includes a plurality of circumferentially spaced apart cross ties attached top and bottom to said coaxial rings. ### Claim 10 (depends on 9) A combination as set forth in claim 9, wherein said cross ties are curved to conform to the contour of the center core of said curing mold. ### Claim 11 (depends on 9) A combination as set forth in claim 9, wherein said rings have splits therein, and said plurality of cross ties include end cross ties attached to said rings at respective opposite sides of said splits in said rings and further comprising means for interconnecting said end cross ties, whereby the mold insert can be locked around the center core of said curing mold. ### Claim 12 (depends on 8) A combination as set forth in claim 8, wherein said coaxial rings each have axially inner and outer side surfaces which converge to form a narrow outer edge. ### Claim 13 (depends on 12) A combination as set forth in claim 12, wherein said axially inner side surface is more radially disposed than said axially outer side surface of each ring. ### Claim 14 (depends on 9) A combination as set forth in claim 9, wherein said cross ties are formed by thin straps.