Preload and Retraction Device of a Wheel Assembly and Self-Propelled Cart Comprising Said Device

A preload and retraction device of a wheel assembly, comprising:

• a linear guide;
• an internal slider freely movable along the linear guide;
• an external slider movable in controlled mode along the linear guide;
• an elastic member, arranged to connect the internal slider and external slider to each other so as to hinder relative movements of moving away or approaching the internal slider and the external slider with respect to a defined natural length distance;
• a first wheel support arm integral with the internal slider, extending substantially in the direction of the linear guide and suitable for supporting at least a first wheel in rotatable mode around a relative first axis with a rolling direction of the at least a first wheel substantially orthogonal to the direction of the linear guide;
• and
• a second wheel support arm integral with the external slider extending substantially in the direction of the linear guide and suitable for supporting at least a second wheel in rotatable mode around a related second axis with a rolling direction of the at least a second wheel parallel to the rolling direction of the at least a first wheel.

A self-propelled cart of the type suitable for moving in confined spaces between two substantially facing guide surfaces, comprising:

• a platform;
• and
• support and movement means on wheels;
• wherein the support and movement means on wheels comprises at least two preload and retraction devices of a wheel assembly thereof, the preload and retraction devices being mounted on the specular way with respect to a longitudinal axis of the platform defining a direction of advancement of the platform (30) itself, each of the preload and retraction devices comprising:
• a linear guide anchored to the platform so as to extend in the plane of the platform in a direction substantially orthogonal to the aforementioned direction of advancement of the self-propelled cart;
• an internal slider freely movable along the linear guide;
• an external slider movable in a controlled mode along the linear guide:
• an elastic member, arranged to connect the internal slider and external slider to each other so as to hinder relative movements of moving away or approaching the internal slider and the external slider with respect to a defined natural length distance;
• a first wheel support arm integral with the internal slider, extending substantially in the direction of the linear guide and suitable for supporting at least a first wheel in rotatable mode around a relative first axis with a rolling direction of the at least a first wheel substantially orthogonal to the direction of the linear guide and parallel to the longitudinal axis;
• a second wheel support arm integral with the external slider, extending substantially in the direction of the linear guide and suitable for supporting at least a second wheel in rotatable mode around a related second axis with a rolling direction of the at least a second wheel parallel to that of the at least a first wheel;
• drive members integral with at least one of the first wheel support arm and second wheel support arm to rotate at least one of the supported wheels thereof.