Method for ventless tire molding and tire resulting therefrom

• US 4,597,929 A
• Filed: 11/23/1984
• Issued: 07/01/1986
• Est. Priority Date: 11/23/1984
• Status: Expired due to Fees

• Current Assignee: Goodrich Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Goodrich Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Blayne, Jerome J.
• Primary Examiner(s): Silbaugh, Jan
• Application Number:
  US06/674,396
• Time in Patent Office: 585 Days
• Field of Search: 264/501, 264/502, 264/102, 425/405 R, 425/DIG. 812, 425/DIG. 60, 425/36
• US Class Current: 264/102
• CPC Class Codes: B29C 2791/006 Using vacuum
• CPC Class Codes: B29C 37/006 Degassing moulding material or draining off gas during moulding venting means in moulds B29C33/10
• CPC Class Codes: B29C 43/3607 with sealing means or the like
• CPC Class Codes: B29C 43/56 Compression moulding under special conditions, e.g. vacuum
• CPC Class Codes: B29D 30/0606 Vulcanising moulds not integral with vulcanising presses for solid tyres B29D30/02
• CPC Class Codes: B29L 2030/00 Pneumatic or solid tyres or parts thereof conveyor belts B29L2031/7092; drive belts B29L2031/7094; fourdrinier belts B29L2031/733
• CPC Class Codes: Y10S 425/06 Vacuum
• CPC Class Codes: Y10S 425/812 Venting

Abstract

A method and apparatus whereby tire mold is closed to within approximately one inch of full closure with a green tire in place therein for molding, and the mold is then evacuated employing a vacuum conduit prior to full mold closure whereby air within the mold cavity is evacuated and the necessity for vent holes in the mold is eliminated. A mold for practice in the invention is free of vent holes in the thread, sidewall, and bead portions of the mold and includes, along the parting line, at least one vacuum conduit whereby the mold cavity may be evacuated to not more than 16932 Pa within not more than about 60 seconds employing a source of vacuum. Seals are provided radially outward of the vacuum conduit along the parting line, and, where necessary, adjacent any moveable bead ring associated with the tire mold. Seals are preferably of a type wherein a differential between pressures experienced by one seal surface and obverse seal surface cause a more effective sealing arrangement. Tires emerging from the mold in accordance with the processes of this invention are free of rubber projections associated with cured rubber entering into vent holes associated with ordinary tire molds.

Claims

1. In a process wherein a green tire having tread, sidewall and bead portions is formed and then molded under internal pressure within a tire mold having tread, sidewall and bead components defining a mold cavity, with at least one bead component being moveable relative to a sidewall component of one of the mold sections, each of said components having essentially no venting aperatures for venting from the mold cavity to a point external to the mold, and including a circumferential parting line dividing the mold into at least two sections, one such section being moveable away from the other, the improvement comprising forming a cured tire essentially free of protruding sidewall, bead, and tread vents while avoiding formation of a light tire by the steps of:

providing at least one point of communication with a conduit means along the parting line radially outwardly of the tread components interruptably joined to a source of vacuum;

placing the green tire within the mold cavity;

thereafter closing the mold until the mold sections are spaced apart by not more than about 5.08 centimeters and not less than about 0.10 centimeters along the parting line;

circumferentially sealing the parting line of the spaced apart mold sections radially outwardly of the conduit means point of communication whereby movement of air into the mold cavity along the parting line is substantially precluded, and sealingly closing any other pathways by which air may enter the mold cavity to substantially preclude the movement of air into the mold cavity including providing a seal configured to substantially preclude the movement of air into the mold between the moveable bead and sidewall components at least while evacuation of the mold cavity is accomplished;

applying the source of vacuum to the conduit means after said sealing whereby the mold is evacuated to an obsolute pressure not exceeding 16932 Pa in not more than about 60 seconds;

closing the evacuated mold; and

curing the tire.

2. The method of claim 1, the absolute Pressure being not greater than about 8466 Pa and the evaculation time being not more than about 45 seconds.

3. The method of any one of claim 1-2, the parting line being open between about 1.27 and 3.81 centimeters during evacuation.

4. The method of claim 3, including the step of evacuating the mold prior to full closure but while sealed by providing a plurality of vacuum accumulators and consecutively interconnecting the accumulators to the conduit means to achieve an internal mold pressure of not more than 8466 Pa in not more than 45 second.

5. In a process wherein a green tire having tread sidewall and bead portions is formed and then molded under internal pressure within a tire mold having tread, sidewall and bead components defining a mold cavity, with at least one bead component being moveable relative to a sidewall component of one of the mold sections, such components having essentially no venting aperatures leading from a point internal to the mold to a point external to the mold, and a parting circumferential line dividing the mold into at least two sections, at least one section being moveable away from the other relative to the parting line, the mold closing to the parting line to effectuate tire molding, the improvement comprising forming a cured tire essentially free of protruding sidewall, bead, and tread vents while avoiding formation of alight tire by the steps of:

providing at least one point of communication with a conduit means along the parting line radially outwardly of the tread components interruptedly joined to a source of vacuum;

placing the green tire within the mold;

thereafter partially closing the mold to be open along the parting line not more than about 5.08 and not less than about 0.10 centimeters;

circumferentially sealing the parting line of the spaced apart mold sections radially outwardly of the conduit means point of communication whereby movement of air into the mold cavity along the parting line is substantially precluded, and sealingly closing other pathways by which air may enter the mold cavity to substantially preclude the movement of air into the mold cavity including providing a seal configured to substantially preclude the movement of air into the mold between the moveable bead and sidewall components while the evacuation of the mold cavity is accomplished;

applying the source of vacuum to the conduit means after said sealing whereby the mold is evacuated to an obsolute pressure not exceeding 16932 Pa in not more than about 60 seconds;

closing the evacuated mold; and

curing the tire.

6. The method of claim 5, the absolute pressure being not greater than about 8466 Pa and the evacuation time being not more than about 45 seconds.

7. The method of claim 5, including the step of evacuating the mold prior to full closure but while sealed by providing a plurality of vacuum accumulators and consecutively interconnecting the accumulators to the conduit means to achieve an internal mold pressure of not more than 8466 Pa in not more than 45 seconds.

8. The method of any one of claims 5 and 6, the parting line being open between about 1.27 and 3.81 centimeters during evacuation.

9. In a process wherein a green tire having tread, sidewall and bead portions is formed and then molded under internal pressure within a tire mold having tread, sidewall and bead components defining a mold cavity, with at least one bead component being moveable relative to a sidewall component of one of the mold sections, such components being essentially free of venting aperatures leading from within the mold cavity to a point external to the mold, and a parting circumferential line dividing the mold into sections, the mold closing to the parting line to effectuate tire molding, the improvement comprising forming a cured tire essentially free of protruding sidewall, bead, and tread vents while avoiding formation of a light tire by the steps of:

placing the green tire within the mold;

thereafter partially closing the mold to be open along the parting line not more than about 5.08 and not less than about 0.10 centimeters;

circumferentially sealing the parting line of the spaced apart mold sections radially outwardly of the tread components whereby movement of air into the mold cavity along the parting line is substantially precluded, and sealingly closing other pathways by which air may enter the mold cavity to substantially preclude the movement of air into the mold including providing a seal configured to substantially preclude the movement of air into the mold between the moveable bead and sidewall components at least while evacuation of the mold cavity is accomplished;

applying a source of vacuum to at least one point on the parting line radially intermediate the tread component and the seal after said sealing whereby the mold cavity is evacuated to an absolute pressure not exceeding 16932 Pa in not more than about 60 seconds;

fully closing the evacuated mold; and

curing the tire.

10. The method of claim 9, the absolute pressure being not greater than about 8466 Pa and the evacuation time being not more than about 45 seconds.

11. The method of any one of claims 9, 10, the parting line being open between about 1.27 and 3.81 centimeters during evacuation.

12. The method of claim 9, including the step of evacuating the mold prior to full closure but while sealed by providing a plurality of vacuum accumulators and consecutively interconnecting the accumulators to the conduit means to achieve an internal mold pressure of not more than 8466 Pa in not more than 45 seconds.