Fallstudie in demnächst auf Deutsch

Capstar Checks Child-Proof Bottle Caps

May 1998
Child-proof caps on bottles of pharmaceutical products have undoubtedly been a major improvement in safety, preventing many tragic accidents. The push-and-twist variety of cap contains a simple but effective mechanism whereby the cap cannot be undone until it has been pushed down below a certain threshold - it then unscrews as for a normal threaded closure.

This design of child-proof cap is used by a number of leading manufacturers of pharmaceuticals, one of which is Pfizer which has a plant in Sandwich, Kent. As part of the quality assurance programme a sample is taken regularly from the production line and an in-process check carried out on the torque required to remove the cap. However, many torque testers are unable to give accurate readings for the push-and-twist caps as the downward force is translated into a false torque reading. It is important that the unscrewing torque is checked because a loose cap could cause the contents to leak or, in the case of the child-proof caps, a cap which is not tightened sufficiently may not be child-proof.

The Pharmaceutical Production Area Engineer is Barrie Davies, explains: "It is only a simple test to check that the caps are being placed on the bottles sufficiently tightly, but it is a crucial part of the QA process." The torque tester the company had before was unable to give true torque readings for the child-proof caps and now the company uses the Crane Electronics CapStar to test these caps. No matter how hard the cap is pushed down, the CapStar will only ever read the torque which is applied.

Tooling changes between different bottles and caps are not necessary - only minor adjustments are needed thanks to the simple but effective clamp pillars used on the platen.

Although the CapStar has the facility for downloading the data to a computer for recording or for more in-depth analysis Pfizer is only using the instrument as a stand-alone item for a simple in-process inspection.

Barrie Davies concludes that "The CapStar is a well-made, reasonably priced instrument that we have full confidence in. The pharmaceutical industry is very demanding in terms of quality assurance and the CapStar is perfect for what we need, giving a true torque reading regardless of how the operator handles the bottle and cap".