Injection molding manifold system having balanced bridging manifold

A heated balanced bridging manifold system for a multi-cavity injection molding system in which a hot runner passage conveys pressurized melt from a molding machine, through manifolds and to a plurality of gates in a cooled cavity plate, each of the gates leading to a cavity and being at an equal fluid flow distance from the molding machine, the manifold system comprising:

• (a) spaced apart, separate support manifolds disposed substantially in a common plane, each support manifold having first and second support manifold opposed faces with at least one heater element embedded in at least one face and the portion of the hot runner passage which extends therethrough branches from a common support manifold inlet on the first face to a plurality of support manifold outlets on the second face and all bends in the said branches are smooth curves to streamline the flow of the presurized melt, the fluid flow distance from the common support manifold inlet to each support manifold outlet being the same, and the portion of the hot runner passage extending through each of the support manifolds has at least one junction whereat a pair of equal diameter downstream portions of the hot runner passage join an upstream portion of the hot runner passage, whereby an even number of support manifold outlets are provided and the pressure drop of the melt to each of the support manifold outlets on the second face is substantially equal;
• and
• (b) a separate, single heated bridging manifold having first and second bridging manifold opposed faces with at least one heater element embedded in at least one face and the portion of the hot runner passage which extends therethrough branches from a bridging manifold common inlet on the first face to a plurality of bridging manifold outlets on the second face and all bends in the said branches are smooth curves to streamline the flow of the pressurized melt, the number of bridging manifold outlets on the second face corresponding to the number of support manifolds, and the fluid flow distance from the bridging manifold common inlet to each bridging manifold outlets being the same, said bridging manifold being releasably secured across the top of the support manifolds with the second face of the bridging manifold abutting the first faces of each of the support manifolds and the common support manifold inlet of each of the support manifolds is in alignment with one of the outlets of the bridging manifold, the portion of the hot runner passage extending through the bridging manifold having at least one junction whereat a pair of equal diameter downstream portions of the hot runner passage join an upstream portion of the hot runner passage, whereby an even number of bridging manifold outlets are provided and the pressure drop of the melt to each of the bridging manifold outlets on the second face is substantially equal, whereby pressurized melt received at the hot runner passage bridging manifold inlet on the first face of the bridging manifold is conveyed an equal distance through the hot runner passage to each of the hot runner support manifold outlets on the second face of each of the support manifolds.