Abstract: Composite paperboard container constructions, providing optimized axial crush strength, and related properties, are formed of one, two, or three structural paperboard plies that are arranged to form a layered body wall having a cross-section of the construction in the ordered structure, high compression strength paperboard layer\low compression strength paperboard layer\high compression strength paperboard layer. Preferably, the container body is formed of one or two structural plies and at least one structural ply is a multiple layer paperboard having both high compression strength and low compression strength paperboard layers.

Abstract: A multi-grade spirally wound paperboard winding core of enhanced resistance to inside diameter deformation includes a plurality of structural paperboard layers having at least two predetermined densities including a lower density and a higher density wherein the lower density is at least about 3% less than the higher density. The cylindrical bodywall is defined in radial cross section by at least one centrally located paperboard layer disposed between at least one radially inwardly located structural paperboard layer and at least one radially outwardly located structural paperboard layer. The centrally located paperboard layer is formed from the lower density paperboard and the inwardly and outwardly located structural paperboard layer are formed from higher density paperboard.

Abstract: The invention provides spirally wound paperboard cores for winding of textiles and other materials and which have enhanced high speed winding capability. The spirally wound paperboard plies forming the body wall of the paperboard core have a predetermined spiral winding angle with respect to the axis of the cylindrical body wall of greater than 71 degrees. In winding cores having a relatively large ID of between about 4.8 in. (120 mm) and 6 in. (150 mm), the paperboard plies forming the spirally wound cores have a winding angle of greater than 74 degrees. In winding cores having a lower ID of less than 4.8 inches (120 mm), all of the paperboard plies have a width of 3.5 in. (89 mm) or less and a spiral winding angle of greater than 71 degrees.

Abstract: The invention provides multi-grade spirally wound paperboard tubes of enhanced flat crush strength construction. The multi-grade spirally wound paperboard tubes of the invention include a plurality of structural paperboard plies having at least two predetermined densities including a lower density and a higher density wherein the higher density is at least about 3% greater than the lower density. The cylindrical bodywall is defined in radial cross section by at least one centrally located paperboard layer disposed between at least one radially inwardly located structural paperboard layer and at least one radially outwardly located structural paperboard layer. The centrally located paperboard layer is formed from the higher density paperboard and the inwardly and outwardly located structural paperboard layers are formed from lower density paperboard.

Abstract: Apparatus and method for experimentally determining the compressive material strength of tubular products includes a housing having a cylindrical cavity therein, top and bottom end caps closing opposite ends of the cavity, tubular bladder means mounted in the cavity and defining a pressure chamber larger than the tubular products to be tested and a fluid receiving space between the bladder means and the wall of the cavity, a plurality of small balls substantially filling the pressure chamber around the tubular product being tested, means for pumping hydraulic fluid into the fluid receiving space to cause the bladder means to apply pressure uniformly to said small balls and thence uniformly over the external curved surface of the tubular product. Means are included to continuously monitor and display the magnitude of the pressure applied to the tubular specimen, and to detect and signal tube failure. Tubular specimens can be instrumented to monitor additional testing characteristics.