RIASORB® consists of a moment arm coupled to a lobed shaft, which applies torque to an elastomeric material contained in and bonded to a housing. Central to the success of RIASORB® technology is the zero to limited torque angles around which a material shears (the basis of the primary patent).
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Under applied load the elastomer is subjected to shear around the central bushing. The designed development of 'convergence of force' illustrates the controlled failure that can be built into the system to protect against overload, preventing catastrophic failure.
Why Elastomers?
The use of an elastomeric material to absorb energy and react to force is not new, but in most cases is delivered through linear compression – limiting effectiveness. RIASORB® utilises the properties of an elastomer in shear resulting from torsional resistance, rather than compression. This exploits the natural properties of the elastomer and significantly broadens the potential applications.
The bearing forces uniform shear to prevent compression set (creep) and enhances the characteristics of the elastomer by forcing it to stay concentric to the shaft.
Key Elements of RIASORB®
1. Patented ‘Limited Torque Angle’ Configuration
Of primary importance in the design of RIASORB® is the lobed shaft, which when under torque exhibits a zero to limited shear force in the valleys of the shaft. Being a rheopectic material, the polyurethane viscosity (and similarly the rebound) increases in the valley due to the shear gradients experienced. This characteristic of RIASORB® provides a suspension system with the unique ability to increase reaction force in response to a greater impact.
The lobed shaft has the effect of pushing and pulling the elastomer, in a similar fashion to a square shaft, without having the stress rises associated with pressure angles that cause catastrophic failure. A round shaft will also result in catastrophic failure as de-lamination can occur simultaneously around the shaft surface.
2. Bond Integrity
Bond Integrity is the strict process through which the bond between the elastomer and the shaft and housing is achieved and is of critical importance to the performance of RIASORB®.
3. Depth of Elastomer Understanding
Designing elastomers to meet the needs of critical suspension and impact absorption solutions requires a depth of understanding as to the interrelationship of a number of key variables including hardness, temperature influence, abrasion resistance, tensile properties, bashore rebound (damping), chemical resistance, elongation and hydrolytic stability.
RIASORB® Elastomer Characteristics and Formulations
RIASORB® utilises polyurethanes (PU) instead of rubber or silicone. PU properties are designed on an individual project basis to meet the specific characteristics required:
Hardness (between an average 3Nm to 300Nm of torque per degree of rotation on a 54mm diameter housing)
Damping (2% to 98% rebound)
Temperature (-50°C to 150°C)
Chemical resistance (polyethers - hydrolytic stability; polyesters - solvent or oil environments)
The specialised expertise developed by RIAS Technologies in the formulation, casting and bonding processes can be applied to a wide variety of industries and uses.
