The Micro Extrusion Line is designed by BCH Ltd to economically handle small production runs of extruded liquorice. As food machinery, cleaning is an essential requirement and the connection between the drive gearbox and rotary heat exchanger needs to be regularly stripped down. BCH found an economical solution in the ETP-Express locking bush from Lenze Ltd. This bush with single screw operation creates a cost effective connection that is very quick and easy to disassemble for cleaning.
The heating of the raw materials is done in a scraped surface heat exchanger called a Viscotator which is effectively a heated tube with an internal shaft and blades. The raw materials pass through the tube under pumped pressure and their temperature increases by about 100ºc. The Viscotator is driven by a Lenze helical bevel geared motor, chosen to accept the high axial loads from the pumped ingredients. In operation it is necessary to disconnect the Viscotator shaft from the gearbox for cleaning, at least every two weeks. Keyway and spline solutions were rejected. Keyways are liable to wear over time and jam. Splines are expensive to machine, and require a non-standard gearbox incurring extra cost and a long lead time.
BCH found the ideal solution in ETP-Express locking bush from Lenze Ltd. ETP-Express consists of a double-walled hardened steel sleeve filled with a pressure medium, and a flange. The flange contains a radially mounted pressure screw and piston. The bush sits between the Viscotator shaft and the gearbox hollow shaft. When the single screw is tightened, the walls of the bush expand and create a friction connection that transmits both the torque and the axial force. As well as making a simple and compact assembly without the cost of thrust bearings, the ETP bush gives real benefit when disassembly is needed for cleaning. Loosening the single screw gives full and fast release of the Viscotator shaft with no tendency to stick or jam. The ETP bush suits repeated fixing and release, and will last the lifetime of the machine.
The Micro Extrusion Line for small production runs allowed BCH to rethink their design. Combining the Lenze gearbox with an ETP-Express bush gives technical advantages – quick to fix and transmits both torque and axial forces – as well as cost reductions compared to splines. The final advantage for the machine users is the time saved when the machine needs to be cleaned.