Apparatus and method for thermal and vibrational stress screening

Environmental screening apparatus for screening a product under different screening conditions, comprising:

• a plurality of testing compartments positioned in an array in relation to each other, each of said compartments having an entrance doorway and an exit doorway with a thermally insulated wall separating adjacent compartments in the array, each of said walls having a doorway opening that is both the exit doorway in one of the compartments and the entrance doorway in an adjacent compartment, each of said compartments also having a gas pressure within the compartment and an atmospheric pressure of an ambient environment outside the compartment;
• openable and closeable door means positioned in each of said doorway openings for alternately opening and closing said doorway openings;
• temperature control means in each compartment for providing a unique temperature environment in each compartment, wherein the temperature control means in at least one of the compartments includes a gas expansion nozzle for introducing liquid under pressure into the compartment to flash evaporate and cool the compartment by absorbing heat of vaporization, and exhaust means for exhausting gas from the compartment to the ambient environment outside the compartment, said exhaust means including a conduit extending from the compartment to the ambient environment with one-way valve means in said conduit for allowing gas to flow only out of the compartment through the conduit, wherein said one-way valve means includes a seat, a pivotal flapper closure piece positioned to open and close on said seat, servo means connected to said flapper closure piece for pivoting said flapper closure piece to open or closed position, and control means connected to said servo means for causing said servo means to close said flapper closure means onto said seat so as to maintain said gas pressure within the compartment close to the atmospheric pressure of the ambient environment outside the compartment to prevent gas from flowing back into the compartment;
• pallet means for mounting and carrying the product sequentially through the compartments in the array;
• vibrating means in said compartments for imparting vibrating motion to said pallet means;
• and
• transfer means operatively engageable with the pallet means for transporting the pallet means and the product mounted on the pallet means between the compartments when the door means have opened said doorway openings between said compartments.