Dynamic response time for electromagnetic valving

Abstract

An electromagnetic valving assembly for viscous fluid material having a solenoid body with an axial flow passageway and an outlet port. A ferromagnetic pole piece is attached at an upstream end of the solenoid body and is in fluid communication with a source of viscous material, such as hot-melt adhesive. An armature is reciprocatingly mounted within the flow passageway and a spring biases the armature in a closed position which blocks the outlet port. A solenoid coil is disposed to cause magnetization of the pole piece during conduction of current through the solenoid coil. The magnetization provides an attractive force between the pole piece and the armature to draw the armature into contact with the downstream surface of the pole piece. The upstream end geometry of the armature includes a center bore for passage of the viscous material and includes a recessed inner region and raised C-shaped edges. Contact between the pole piece and the armature is limited to the C-shaped raised edges. De-energization of the solenoid coil releases the armature. Movement of the armature as a result of the spring bias, however, requires a migration of the viscous material between the abutting pole piece and armature. Because the abutment is limited to the outside edge of the upstream end of the armature, migration is restricted to a short distance and the dynamic closing response time is significantly improved.