Method and apparatus for improved stiffness in the linkage assembly of a flexible arm

Abstract

The invention includes linkage assemblies comprising coupled links with metallic contact surfaces with improved stiffness. The inventors found significant mechanical problems with all previous descriptions of metallic contact links sufficient to preclude their commercial use. These metallic contact links are a significant improvement over existing plastic ball and metal joint, or all plastic beads as found in the prior art. The invention includes methods providing these links and high friction couplings between them, as well as the linkage assemblies and flexible arms resulting from these processes.

Description

CROSS-REFERENCE TO PRIORITY APPLICATION DOCUMENTS [0001] This application is a continuation of application Ser. No. 10 / 268,397, filed Oct. 9, 2002, which claims the benefit of provisional patent application Ser. No. 60 / 327,990 filed Oct. 9, 2001, the specifications and drawings of which are hereby incorporated by reference in their entirety.TECHNICAL FIELD [0002] The present invention relates to articulating load bearing flexible arms, particularly suited for use as surgical tissue stabilizers, and more particularly to increasing the stiffness of such an articulating column when in the locked configuration. BACKGROUND ART [0003] Flexible arms or, as they are often called, articulable columns, have many uses. For example, they are often used for positioning tools, article supports, or for locking measuring apparatus. In surgery, it is common practice to mount them as adjustable supporting brackets on a side rail of an operating table to support retractors, endoscopes and other surgic...

AI Technical Summary

Benefits of technology

[0024] The invention addresses the needs discussed in the background. The invention increases the stiffness of flexible arm linkage assemblies, by increasing the friction between link contacts when in a locked configuration.

[0027] A flexible arm including the invention provides an increased range of motion and better stabilization of surgical instruments.

[0029] Metallic links have a significant advantage when used in a surgery, they can be sterilized and reused many times. Using metal linkage assemblies reduces the waste products and lowers the costs associated with the use of flexible arms.

[0031] Another embodiment of the invention includes optimization of metallic bead to metallic bead contact friction comprising the following steps. Maximizing the coefficient of friction between the first contact material of the first contact surface and second contact material of the second contact surface by selecting the first and second contact materials. Determining a ball diameter and conical angle to maximize frictional forces in static equilibrium based upon the coefficient of friction.

[0034] The inventors further experimentally proved that they could make an even better joint using contact materials of stainless steel and titanium for the respective contact surfaces based upon the optimized interface geometry. The joint formed from the stainless steel contacting titanium beads had greatly improved stiffness over anything the inventors know of.

Problems solved by technology

Plastic links have a significant problem when used in a surgical theatre, they often cannot be reused due to difficulties in cleaning them.

By having the low coefficient of friction, such links slipped easily, far below the point of usefulness.

First, maximizing the stainless steel contact area actually reduces the frictional force needed for stiffness.

The disclosure from the Summary was appropriate for a plastic link component, but failed to account for the physical characteristics of stainless steel as well as alloys of iron and titanium, which do not deflect anywhere near as much as plastics.

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