ACTUATION FORCE testing
allows measurement of the force required to, for example, release
hair fixatives or air freshening sprays from aerosols; or liquid
soap, shampoo or cream from dispensers. Manually-actuated spray pump
dispensers or finger pumps rely on the consumer to generate a
hydraulic pressure in the pumping engine in order to dispense the
fluid. Dispenser designs may change or vary, or the ever-increasing
market for child friendly products may require adaptations.
When operating a pump-type liquid
soap dispenser, for example, a child may have difficulty applying
sufficient force in the appropriate direction to operate the pump,
which may cause the dispenser to move, tip, or otherwise fail to
discharge the product toward the intended target. An actuation force
test typically uses a hemispherical probe to apply the force and
provides an imitative test to assess such issues.
Drug delivery can also be as a
result of actuation. A metered dose inhaler (MDI) delivers a precise,
reproducible dose of drug accurately to the deep lung. It is also
well accepted by patients who depend on MDI's in their treatment and
therefore it is essential to constantly improve this technology.
Patients need to rely on their inhaler to provide them with the
required medication which is often at a crucial time when physical
strength may be very low.
The metering valve, whose
performance is assessed with this test, is a critical component of a
finished metered-dose inhaler. The interaction between the
elastomeric components and the formulation can significantly affect
product performance. A change in formulation, for example
implementing a new propellant system, may necessitate a complete
redesign of the valve system in order to successfully deliver the
drug with the minimum of difficulty.
Measuring actuation force does not
always apply to the delivery of a product as a result of the
actuation but is also applicable to the testing of, for example,
buttons for mobile phones, cameras etc. or defining the life of a
membrane switch. It is important that the switch or button under test
be pressed with a force hard enough to achieve switch contact closure
or the actuation of a motion.