Large Angle Flexible Pivots (LAFP)

Ref-Nr:

C-flex pivot from C-Flex Bearing Co. (US).

Technology abstract

Almatech is a privately-held Swiss SME specialized in structures and mechanisms for space applications.
Flexible pivots are frictionless rotational bearings that replaced lubricated ball bearings in applications requiring oscillatory motion.
Almatech LAFP achieves infinite life up to an amplitude of ±90° with easily customizable characteristics and is ideally suited for harsh conditions where reliability matters.
 

Technology Description

Frictionless rotational bearings or “flexible pivots” are used as key engineering components for multiple applications. Their working principle relies on the material elasticity of the internal blades to offer a limited rotational oscillatory motion without any sliding contact.
Current flexible pivots commercially-available present many technical limitations, such as very small angular motion <10°, significant center shift which is problematic for optical applications, non-linear behaviour which make it impossible to predict their characteristics via numerical tools, sensitivity to Stress-Cracking Corrosion and Cold Welding, etc
Almatech has developed a monolithic and symmetric design consisting of a static ring attached to a fixed-support structure. The moving ring is fixed to a rotation shaft. The two rings are connected by a series of blades that deform elastically to allow the relative rotation of the two rings.
The design of Almatech Large Angle Flexible Pivots (LAFP) allows to reach much greater rotational amplitudes on top of numerous additional benefits.
Almatech LAFP can be customized in two ways:

  1. To maximize the rotational amplitude and minimize the rotational stiffness,  relevant for applications seeking to transmit motion without wasting energy
  2. To maximize the energy stored elastically, relevant for applications where systems are loaded mechanically (e.g. anti-backlash systems)

Almatech design of the LAFP is subject to patent pending intellectual property rights. Almatech conducted the feasibility study during which the concept was validated and the performances estimated by numerical tools (structural Finite Element Analysis). Demonstrators are currently being manufactured for physical testing and performance characterization.
Developed originally for space applications, Almatech is convinced that its characteristics will bring significant benefits to terrestrial applications as well. Examples of applications or fields are:
-Any application where oscillatory motion is required along with an extensive service life will be relevant. Applications such as radars, lidars, scanners are foreseen where a greater rotational amplitude may become a benefit.
-Applications in which rotational amplitude combined with precision is required, e.g. pointing mechanism.
-Applications in robotics where flexible pivots can provide the mechanical connection between parts moving repeatedly in the same motion, e.g. switches, calibration mechanisms.
-Applications in in harsh environment in which maintenance is limited or expensive (e.g. sub-marine, nuclear, etc). Due to its monolithic design, the LAFP is more robust than conventional pivots that are composed of multiple parts assembled and then subject to failure.
Almatech is looking for applications, future customers and co-development partners.

Innovations & Advantages

The main advantages of the Almatech LAFP are:
- Angular Range of Motion of up to ±90ᴼ for a single pivot and up to ±120ᴼ in series. This is much more than existing products limited to ±20ᴼ max and only ±10ᴼ for extended service life.
-Life expectancy: 500 million cycles for ±90° combined with the possibility to estimate it accurately using mathematical models.
-Centre shift geometrically inexistant thanks to the fully symmetric design, it garantees pointing accuracy as well as precision
-Radial and axial stiffness highly customizable by playing with design parameters according to customer specifications. Allows to design the pivots either for energy storage (high rotational stifness) or for high rotational amplitude (low rotational stiffness). 
-Linear behavior along the full range of motion coupled with an average rotational stiffness over stroke < 0.2 Nm/rad : Much lower than current solutions thus minimizing power consumption (or increasing motorization margins)
-Better corrosion resistance thanks to monolithic design : improves durability
-Simple and precise mounting interface : easier and faster to handle during MAIT
-Almatech LAFP concept can either be custom-made or industrialized in series.

Further Information

As opposed to conventional ball bearings Almatech LAFP is relying on the elasticity of its blades to provide a friction-less and lubrication-free oscillatory motion.
The LAFP design was thought first as monolithic for space applications but can be tailored to meet higher series and lower costs requirements. A monolithic design brings several advantages such as robustness, linear behaviour on the full rotational amplitude, low sensitivity to temperature changes, higher precision.
The LAFP presents no geometrical center shift thanks to its symmetric design (as opposed to existing flexible pivots).
The LAFP includes provision of simple means of mounting and securing the pivots on both the static interface and the moving interface. Interfaces on the external diameter can be either bolted or bonded or custom-made for higher precision.
The main characteristics of the LAFP are provided in table 1.
Custom designs for heavy duty, special materials and high volume / low cost are possible.

Current and Potential Domains of Application

Almatech LAFP has been originally developed for space applications but considering it as basic engineering component it can be used in a large variety of fields as conventional ball bearings are today.
Examples of fields and applications where the LAFP would bring a competitive advantage vs existing products:

  • Robotics
  • Automation
  • Marine
  • Bio-tech
  • Military – Defense
  • Aeronautics
  • Food processing
  • Watch-making
  • Power plants

 

The LAFP will outperform conventional ball bearings and existing flexible pivots for any oscillatory applications.