Importance

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Abstract

A syringe is provided with a helical spring, which furnishes an upper limit to a pressure employed via a plunger to move a fluid or paste through an opening in a syringe. The plunger is maintained in a low compressing state versus the fluid with the helical spring. A toothed rack is attached to the plunger. The toothed rack is engaged by a ratchet forming part of a lever. The lever is hinged on an axially movable assembly. Actuation of the lever drives the ratchet and therewith toothed rack and plunger forward against the force of the spring. As more force is applied to the plunger the resilient force of the compression spring allows the axially movable assembly to move backward and thus to limit the pressure exerted by the plunger on the fluid. A second ratchet can be provided for preventing a backward motion of the toothed rack while the lever seeks a new point of engagement for the ratchet with the toothed rack. A spring can be employed for assuring simultaneous engagement of first and second ratchet with the toothed rack. The helical spring can be round or rectangular.

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First Claim