Ratchet-type systems

Loss of torque against time has been well documented with plastic caps on plastic bottles. This does not necessarily mean that the closure becomes ineffective, but there are occasions when a low torque only needs the vibration effects of transportation to become an unsatisfactory (loose/leaking) closure. Certain tamper-evident/resistant features such as sealed diaphragms and ratchet-type closure systems are likely to overcome such problems. Having the right combination of plastics may also eliminate or reduce this loss of torque. However, there is the converse where the use of the incorrect combination of plastics, or plastics with undesirable constituents such as lubricants, mould release agents, internal release agents, may actually exacerbate the loss of closure torque. This loss may be associated with thread forms, area of thread contacts, cold flow or creep of plastics involved, lubricants, etc. 

In 2005 and 2007 (Phase 2), a more recent study for the U. S. Marine Corps, by Hill et al., evaluated 13 self-applied tourniquets for their applicability in combat applications. This study attempted to measure the functionality of the candidate tourniquets in battlefield conditions by immersing them in a simulated blood/sand mixture prior to testing. In contrast to the earlier Army study by Walters et al., the conclusion drawn from this study was the recommendation that one of the ratcheting or stretch-retention type tourniquet systems be adopted for combat deployment. These types had the best user subjective ratings as well as the lowest application times especially on the upper extremities where one-handed application was required. The recommended group had application times 30-50% lower on the upper extremities than the windlass types recommended by the Army study. Velcro was observed to lose its effectiveness as a clamp when it became fouled with wet sand or mud and, therefore, should be avoided. It should be noted that none of the tourniquet types used in the Marine Corps study were pneumatic. 

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