LEAKLAB · TECHNICAL INSIGHTS
A manually controlled ball valve and an independent check valve form two barriers in series.
US12546300B2 · Milwaukee Electric Tool Corporation · published 10 February 2026 · granted patent.
Shutdown is a separate operating state
When the motor stops, the pumping action disappears but the pressure difference between the pump and the evacuated refrigeration circuit remains. Air, oil or contaminants may flow back through an open inlet. The patented assembly combines manual isolation with automatic reverse-flow protection.
How the inlet assembly works
Gas passes through an inlet, a controlled ball valve and then a check valve before reaching the pump. The first ball rotates to open or close a through-passage. A second ball moves independently relative to its own seat. During pumping it is supported away from the seat so gas can pass around it; reverse flow returns it to the seat.
The check valve can close with the manual valve still open. Closing the manual valve afterwards provides two successive barriers.
Practical verification
Seat contamination, seal damage, installation orientation and additional flow resistance affect real performance. The patent does not establish a universal leakage rate or vacuum-holding time.
Assess inlet conductance, material compatibility and service access. Repeated shutdown tests from the same initial pressure can compare the pressure rise with manual isolation open and closed. Pressure rise can include both leakage and outgassing, so it must be interpreted alongside circuit leak testing. The patent concerns a particular inlet assembly, not every possible combination of two valves.