The plunger of the pump has a radially extending lug near its upper end which can be inserted down into a notch in the stationary pump collar when the plunger is fully depressed, so that when the plunger is then rotated in a clockwise direction relative to the collar, the lug is brought under an overhanging...http://www.google.es/patents/US4538748?utm_source=gb-gplus-sharePatente US4538748 - Tamper deterring unlocking restricter for down locking pump dispensers
Tamper deterring unlocking restricter for down locking pump dispensers
