Plastic article or earthenware shaping or treating: apparatus – Product or preform repair or restoring means
Patent
1988-06-21
1989-08-29
Hoag, Willard
Plastic article or earthenware shaping or treating: apparatus
Product or preform repair or restoring means
1563941, 156909, 425 17, 425 281, 425 58, B29C 3300, B29C 3500
Patent
active
048612472
DESCRIPTION:
BRIEF SUMMARY
The invention concerns an expandable ring for sealing an envelope against the bead of a tire to be retreaded during the pressure and heat application in an autoclave.
A corresponding ring is for instance known from the German Offenlegungsschrift 29 40 314. The spreading is carried out by inflating a tube like rubber ring which is supported on the inside by a metal ring. These known rings have failed to achieve a practical relevance. Firstly, the longevity of the inflatable rubber chambers is too small, secondly, the form stability leaves something to be desired since, when inflated, not only the side facing the bead is increased but also the remaining rubber walls of the ring, fabricated from rubber, are blown so that the ring very easily jumps off the beads. Further, in spite of the adaption by inflating, the big tolerances as to the diameter of the tires of a certain size can hardly be coped with.
It is the object of the invention to improve a ring of the mentioned kind so that in spite of the spreadability a safe and stable sealing of an envelope against the bead of a tire to be retreaded is possible and also big diameter tolerances can be managed.
For fulfilling this object the invention proposes that the ring has overlapping end portions and consists of a ridgid elastic material such as metal, hard plastics or fiber reinforced plastics and that the opened section has at least one joint running in the circumferential direction within an overlapping section.
In the most humble case the overlapping end portions having interfitted rebbeted ends or lap joints adjacent each other on both sides of the end portions. There is a more or less strong overlapping section which depends on the spreading. The overlapping is to be chosen so that a joint of approximately 15 mm remains even when used with the biggest tire bead diameters.
Especially for small tire sizes the ring may have an expansion tension which is sufficient to automatically achieve the sealing just by releasing the ring after a manual compression onto a shrinked diameter, provided that the ring was positioned correctly into the bead and that the ring presses the envelope everywhere against the bead.
The handling is strongly faciliated when a spread clamp is used which guarantees in one end position the sealing spread and in the other end position the maximum shrinkage of the ring.
With a ring completed in this kind the following steps are carried out for achieving a sealing. After the application of the envelope onto the green tire to be retreaded a ring in accordance with the invention is placed from outside into the circular bead opening whereby the projecting rim sections of the envelope are automatically laid onto the beads. The inserting of the ring is continued so far until it is nearly completely plunged into the bead opening. During this step a circumferential lip facilitates the positioning which is provided on the ring. Afterwards, the tensioning lever of the spread clamp is swivelled so that the ring grows. Possible bead tolerances are compensated in that the spreading link of the spread clamp is resiliently mounted. If correspondingly designed, the tensioning lever of the spread clamp falls into an overcenter position in the maximum spreading position so that no separate locking is necessary.
The explained handling is still facilitated if a handle is fixed on the inside of the ring which is arranged on the opposite side of the tensioning lever of the spreading clamp in its maximum shrinkage position. In this way the ring may be diagonally grabbed and placed into the bead whereby the spreading can be accomplished immediately after the inserting by pivoting the tensioning lever. During this step, more or less in a natural way, the grip from the inserting of the ring into the bead opening until the end of the pivotal movement for the spreading is not released.
Especially with very big rings, for instance for so-called EM-tires, the own stability of the ring is so big that a manual spreading cannot be asked from a person using the ring. Then
REFERENCES:
patent: 2697853 (1954-12-01), Smyser
patent: 2700795 (1955-02-01), Kraft
patent: 2817877 (1957-12-01), Fannen
patent: 2988750 (1961-06-01), Dennis et al.
patent: 3227251 (1966-01-01), Ross
patent: 4634357 (1987-01-01), Brewer et al.
Bandag's, "Advanced Radial Curing System", (The ARC.TM. System), 2 pages, no date given.
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