Layout for mixing polyurethane reagents - has circulation block with nozzle and valve plus overall control system so operating cycle does not suffer pressure drop

摘要

Circulation block for mixing heads, and partic. those with parallel nozzles for the prodn. of polyurethane foam, has a circulation nozzle with needle and seating in a flow bore, this needle having an annular surface exposed to the pressurised medium to stay open. The layout has an hydraulic controller with valve in two pipelines, one of which is the closing and the other on the opening side of the mixer head; the valve pressurises side(s); line to the opening side is also connected to an annular chamber so it can close its nozzle. This same line also has a shuttle valve to regulate an adjustable externally fed control device so set elevated pressure can be applied to and maintained in the annular chamber; the system also provides that when the nozzle needle is opened under the pressure of the liq. flowing and if the pressure in the annular chamber exceeds the set level the pressure is allowed to fall. ADVANTAGE - Design of block solves the problems of serious pressure dop in each cycle etc. and hence the loss of output rate.