Mechanical Lock definition
Mechanical Lock. The use of a mechanical lock to retain the admin set within the pump, unless purposefully unlock under program control.
a. Traditionally, unauthorized users can remove an administration set during an ongoing infusion. Even with “free flow” protection, this acts leads to an unwanted interruption of therapy and possible damage to the administration set. Traditionally, the incorporation of a set-locking mechanism has added cost and complexity to the design.
b. This design provides a locking mechanism that offers minimal control complexity and cost.
i. A simple pin is spring loaded to grab a detent of an admin set while it is being loaded. It is normally engaged. There are an endless variety of mechanisms to achieve this locking function.
ii. In order to retract the locking pin, the system retracts the pneumatic piston to its limit position, beyond the normal operation of the piston during pumping, and engages a pin lifting lever.
iii. The motor requires no power to retain its position, so the unlocking position does not consume any incremental energy to keep the system in a load/ unload position indefinitely.
iv. The design has a controllable vent feature, so the movement of the pneumatic piston, when the vent feature is activated, does not have any impact on the pressure of the fluid, which remains at atmospheric pressure without any opportunity for fluid flow, since both the inlet and outlet valves are closed in this instance.
v. The movement of the pin lever to load or unload the admin set provides another useful function. This movement provides a discrete switch function to identify the absolute position of the pneumatic piston. In this way, the position of the piston is re-calibrated with every new admin set.
c. The locking pin offers a powerful mechanical advantage so the user is not tempted to remove the set without first turning OFF the infusion via the pump’s user interface.
d. A purposely, but simple, procedure, using a commonly available tool to be determined, such as a tongue depressor, a pen tip, or a Luer fittling, can be used to remove the set in an emergency.