Arkwin’s experience with lock actuators dates from 1964. Since this time, we have built lock actuators using roller, toggle and slider locks. Mechanical detents have used for very low locking loads too. Arkwin offers single and dual position mechanical locks. In addition to this production hardware experience, we have conducted design studies and tests of other types of locks. Finally, Arkwin also manufactures actuators which maintain position using hydraulic locking. This allows load resistance in any stroke position. With this wide background to draw upon, Arkwin has the ability to select that type of locking mechanism best suited to each application.
In general, lock actuators operate by interposing a radially displaced locking member between the moving piston and the stationary housing. In all locking actuators, the locking surface cone angle is steep enough to assure unlock under friction coefficients greater than those anticipated in service. The radial component of the axial locked load is a function of this angle and the coefficient of friction. With friction variations, there is a large variation in the radial force component in service. Radial motion of the locking surface is controlled by an axial plunger. The pressure at which this plunger will operate is thus dependent upon the sliding friction in the lock. Arkwin has developed a number of techniques to mitigate friction and the effect on unlocking pressures. Critical to the design of the lock actuators is the need for lock integrity, the smoothness and the repeatability of unlocking. To assure long and trouble-free life of lock actuators, a great deal of attention has been paid to the reduction of friction and the effects of sliding contacts in lock actuators. Features normally incorporated in lock actuators include lock indication switches, visual indicators, manual releases, emergency system operation, and lock out devices. Locking actuators can be provided with internal rate controls including flow regulators, relief valves, and restrictors. Integral control valves are offered too.
The long life and repeatability of the Arkwin lock mechanism has been demonstrated through field history and laboratory testing. F-16 lock actuators mechanisms have been subjected to Highly Accelerated Life Testing for determining suitability in other applications. This included unlocking with loads in excess of rated design valves. No appreciable change in performance or wear was noted at the end of 130,000 cycles. Production designs have unlock loads up to 20,000 pounds and ultimate loads over 50,000 pounds. These designs maintain very low unlock differential pressure values without the use of sequencing even under high load conditions. Usage spans from the C-5 to the CH-53K and many aircraft in between including 777, F-16, B-2, F-35 and more.