Importance

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Abstract

A high reliability drive arrangement produces a rate-controlled output displacement and is particularly suited for driving a medical infusion apparatus. Energy for producing the output displacement is derived from a wound spring which, in a preferred embodiment, is coupled to an output shaft by a redundant gearing system. First and second drive gears, and their associated pinions on the output shaft, are rotationally displaced with respect to one another to prevent alignment of potentially defective gear teeth and to align the teeth on one gear with the inter-tooth spacings on the other. The output shaft additionally engages a rate-control arrangement which governs the rate of rotation, and consequently, the rate of the displacement. The possibility of uncontrolled rotation is reduced by providing a safety arrangement having a safety gear plate which has fewer teeth than its associated drive gear. Additionally, an associated driven gear, which may be a pinion, is provided with at least one indentation which accommodates the teeth of the safety gear plate. A final gear in the rate-control system, which may be an escapement ratchet wheel, is provided with an associated centrifugal braking arrangement which operates to terminate rotation if a predetermined rate of rotation is exceeded.

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First Claim