Reverse Pyramid Winder Mandrels

Reverse pyramid winder mandrels have been designed and built for up to 132,000 lbs. maximum tension. T. Sendzimir, Inc. has designed over 120 pairs of controlled collapse winder mandrels. The Sendzimir mandrel design has evolved through 3 successive stages:

Reverse Pyramid Winder Mandrels

The Reverse Pyramid winder mandrel design was originally developed in 1968 at the request of DEW (Deutsche Edelstahlwerke) and Sudwestfallen (both German companies) in order to meet the demands of higher tension mills. The Reverse Pyramid design has been extremely successful in the years since it was introduced.

Standard Features

All the above features increase the initial cost of our mandrels, but all result in safer operation, greater ruggedness, easier maintenance, and lower overall service costs.

Typical Mandrel Specification

Two (2) - 24" (610 mm) diameter reverse pyramid design collapsible block winder sized for maximum strip width, both arranged for under-winding and each consisting of a mandrel, low speed gear shaft, rotating cylinder, and outboard gearing gate.

Expand-Collapse - of the mandrel is by a rotating hydraulic cylinder which is mounted on the back end of the output shaft and can be removed without disturbing the shaft or segments. The connection of the pyramid shaft to the rotating cylinder is provided by a threaded nut with integral shear ring.

Collapsible Mandrel Assembly - consists of four segments mounted on a four step reverse pyramid shaft. Segments are designed to minimize coil breaks at the segment joints.

Pyramid and Segments - are fabricated of forged, heat treated alloy steel with AMPCO bronze overlay weld deposited on the pyramid shaft surfaces.

Pyramid Shaft - is an integral forged steel heat-treated unit. The pyramid shaft is mounted on sleeve bearings in the gearbox output shaft. The gearbox output shaft rotates in anti-friction bearing in the gearcase. The pyramid shaft extends through the output shaft with the back end connected to the piston of the rotating cylinder and therefore becomes the draw rod for expanding and collapsing the mandrel. The pyramid shaft is spline driven for the gearbox output shaft. Screwed connection of the pyramid shaft to the rotating cylinder piston is provided in the design. This design ensures that there is no lateral movement of the segments during expand and collapse. This mandrel is designed for controlled collapse when subjected to hoop stress loading as the coil is wound onto the mandrel.

Gripper - is hydraulically operated. The gripper profile is designed to minimize coil breaks.

Outboard Bearing Gate - is designed to be easily aligned to the mandrel centerline by wedge adjustment in two planes.

Outboard Bearing - is supported by a cylindrical sleeve within the outboard bearing gate which allows the mandrel shaft to move axially while still ensuring that the outboard bearing gate remains fixed. The sleeve will not engage with the outboard bearing on the mandrel unless the gate is properly aligned.