The pneumatically or hydraulically actuated machine bolt shut-off nozzles type BHP are used in processing of thermoplastics. In this nozzle’s favour are:
Cycle time reduction, shut-off in the nozzle of the melt-stream while withdrawing or dosing. With the BHP nozzle Herzog has designed a system which allows a single throughgoing melt flow channel. Therefore a much bigger flow channel is possible and that is responsible for a reduced pressure drop. With this single channel principle the so called “Memory effect” can be avoided. With the single channel system a cleaning of the unit is done within very short time (similar to an open nozzle). Finds application in:
Packaging, automobile and leisure industries, medicinal and electronic equipment. Operation:
The assembly integrated actuator (pneumatically or hydraulically activated) controls a radial positioned bolt via a lever mechanism. The melt flow is therefore process dependently separated. The bolt mechanism is constructed in such a way, that with overpressure an automatic opening of the nozzle is ensured. In contrast to a needle shut-off system, the separation takes place further back. Because of this a longer bore exists between the nozzle orifice and the shut-off unit. For some applications this may not be suitable. Modules for filters, mixers and GAIM-applications broaden the range of shut-off nozzle
products. Prevents:
• Air pockets during screw retraction
• Material leakage when dosing with a withdrawn injection unit
• Material leakage while vertically injecting Applicable for special applications such as:
• Physical foaming Supported process control:
• Actuator piston position sensors (indicates if nozzle is “open” or “closed”) Productivity factors:
• Shorter cycle times - increase in productivity
• Increased process reliability and repeatability
• Usability with increased back pressure - improved homogenization
• Add-on capability (on tool side) Options:
• Filter module
• Mixer
• GIT
• Process monitoring with piston position sensors on the actuator | 
