Medicinal blood-sampling syringe - includes locking device holding plunger against internal vacuum

摘要

The medicinal syringe is particularly for taking blood samples. It has a freely-sliding plunger forming a seal in a cylinder, there being a grip plate at the outer end of the plunger rod. A locking device (9) is provided, holding the plunger (4) in position in opposition to the vacuum generated in the cylinder (2) after pulling it rapidly outwards. Typically this can comprise portions on plunger and cylinder engaging together on turning the former. The plunger rod can be of cruciform section, with a notch in one of the webs engaged by a lug on the cylinder.