Design of Post Curing Inflator

Bi-stable locking mechanism

In tire manufacturing industries Curing is the chemical cross-linking of rubber and vulcanising agents, resulting in an elastomer. Curing of the tire is done by applying pressure on the green tire in a mold for giving the tire its final shape and heat is applied via high-temperature steam flow to simulate the chemical reaction between the rubber and the other constituents used in making of the tire. Temperatures of the tire after the curing process is around 200 °C. The tire contain Nylon fibres and hot nylon has the property to deform upon cooling. If the hot post cured tire is kept in open environment then this rapid cooling could cause deformation the tire and tire may lose its characteristic shape. Hence the tire is pressurised to a certain limit and is allowed to cool under inflated condition. For this purposes, post curing inflator is used by the tire manufacturer to provide constraint cooling and avoid the deformation of tire shape.

The post curing inflator (PCI) setup used in the industries is quite bulky. The present design uses external force loop which requires lots of space as well as materials to manufacture such setups. The external force loop can be shorted using an internal force loop. This would reduce a lot of space and materials as well as manufacturing cost. One of the solutions for this is to employ a multi-stable mechanism for the locking and sealing of the system with the tire.

The multi-stable system contains two or more than two stable equilibrium where the system maintains its state without any input power. At these position on the application of small disturbance would results in oscillation of the system about the equilibrium position. This system can be exploited to achieve various day to day as well as industrial purposes. These can be seen in switches, knobs, self-closing doors, product packaging etc.

Multi-stable mechanisms are mainly classified into two categories depending upon the number of stable equilibrium states or positions. These are Bi-stable mechanisms (example electricity switch and valves) and Mechanisms with more than two stable positions such as tri-stable mechanisms and quad stable mechanism (example knobs, ratchets).

The compliant mechanism has several benefits over customary joints and springs. Its benefit can be considered in two domains: First, It's low-cost manufacturing as compared to complex joints due to a lesser number of parts reduced assembly time and simplified the manufacturing process.Second, its improved performances due to reduced wear, reduced weight, increased performance and reliability and reduced maintenance. Compliant multi-stable mechanism stores its energy in the flexures instead of using springs and joints.