Pressure-determined blowdown period for each of multiple, commonly manifolded curing presses

• US 4,721,590 A
• Filed: 07/24/1986
• Issued: 01/26/1988
• Est. Priority Date: 07/24/1986
• Status: Expired due to Term

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Uniroyal Goodrich Tire Co. (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Trapp, Dennis L.
• Primary Examiner(s): Silbaugh, Jan H.
• Assistant Examiner(s): McCarthy, Neil M.
• Application Number:
  US06/888,896
• Time in Patent Office: 551 Days
• Field of Search: 264/40.1, 264/40.5, 264/40.6, 264/315, 264/326, 425/29, 425/33, 425/36, 425/52, 425/139, 425/149, 425/150, 425/151, 425/153
• US Class Current: 264/40.5
• CPC Class Codes: B29C 2037/90 Measuring, controlling or regulating
• CPC Class Codes: B29C 2037/903 by means of a computer
• CPC Class Codes: B29C 43/10 Isostatic pressing, i.e. using non-rigid pressure-exerting members against rigid parts or dies
• CPC Class Codes: B29C 43/58 Measuring, controlling or regulating for bank adjustment in calendering B29C43/245
• CPC Class Codes: B29D 30/0601 Vulcanising tyres; Vulcanising presses for tyres
• 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

Abstract

A curing press for tires, commonly manifolded to other curing presses in a curing room, are operated with a minimum blowdown time which is variable from one cycle of each press to another cycle. A first signal is generated by a pressure transducer ("PT") in pressure communication with the bladder(s) of each curing press; this first signal is compared to a second signal corresponding to a target pressure, which second signal is stored in a programmable controller ("PC"). The PC controls operation of the press, and is used to provide a variable blowdown period; how quickly this target in the PC is reached, is a function of the pressure in a common blowdown manifold for plural presses. Instead of setting a mean blowdown period arrived at by trial and error over years of operation in a particular curing room, and relying on a mechanical safety pressure switch to override the opening of the press if the pressure is too high at the end of the mean period set, the press is opened reliably and reproducibly when the target pressure is matched by the pressure in the bladder. The mechanical pressure switch is nevertheless necessary. But the reliance on the mechanical pressure safety switch is reduced only to those instances when there is (i) a power failure which wipes out the instructions of the PC, so that whether the press will open at any preset pressure is not predictable; and (ii) a failure of any valve which results in leakage of steam or water into the bladder.

Claims

1. In a curing room containing plural curing presses for tires, each of which presses is provided with an elastomeric curing bladder deployed within separable upper and lower mold halves, and a blowdown conduit through which a blowdown fluid is to be blown down from within said curing bladder, near the end of a curing cycle, into a common manifold which places two or more bladders in pressure-sensing, relationship with each other during a portion of the blowdown period, the improvement comprising,

pressure transducer means distally located relative to said halves but in pressure sensing communication with the interior of said bladder so as to generate a first signal correlatable with an instantaneous pressure within said bladder during the blowdown period;

programmable controller means including

(i) means for storing and executing a sequence of instructions determinative of fixed intervals of time for shaping said tire and thereafter curing it with a curing fluid at adequate temperature and sufficient pressure for the purpose;

(ii) means for comparing said first signal generated during the blowdown period with a second signal corresponding to a preselected low pressure within the range from about 1 to about 10 psig; and

,

(iii) means to actuate the separation of said halves when said first and second signals are matched; and

,

mechanical pressure safety switch means in pressure sensing relationship with the interior of said bladder preset for a preselected pressure at which the press may be safely opened;

whereby the blowdown time for each said press is variable from one curing cycle to another, depending upon the difference in pressure between said interior of the bladder and the common manifold, but said mold halves are separable at the end of a blowdown cycle soon after said first and second signals are matched.

2. The apparatus of claim 1 wherein said first signal generated during the blowdown period corresponds to an instantaneous pressure within the bladder in the range from about 1 psig to about 5 psig.

3. The apparatus of claim 2 wherein said pressure transducer includes a pressure sensor chosen from a capacitive type and a piezoelectric type.

4. In a process for shaping and curing a tire including storing and executing with programmable controller means a sequence of instructions determinative of fixed intervals of time for shaping said tire and thereafter curing said tire with a curing fluid at adequate temperature and pressure, said process including blowing down a curing fluid near the end of said curing cycle from within a bladder used to cure said tire disposed between mold halves in a curing press equipped with a mechanical pressure safety switch to prevent the press from opening when the pressure of curing fluid in said bladder is greater than 10 psig, the improvement comprising,

electronically sensing the instantaneous pressure within the bladder during said blowdown at a location distally located relative to said mold halves so as to generate a first signal correlatable with said instantaneous pressure;

setting a preselectable press-opening pressure within the range from about 1 to about 10 psig and generating a second signal corresponding thereto in said programmable controller means;

comparing said first signal with said second signal; and

, actuating separation of said halves with said programmable controller means when said first and second signals are matched.

5. The process of claim 4 wherein said first signal corresponds to an instantaneous pressure within the bladder in the range from about 1 psig to about 5 psig.

6. The process of claim 5 wherein said pressure transducer includes a pressure sensor chosen from a capacitive type and a piezoelectric type.