Method and device for an actuator motor including an air-actuated brake device
A plurality of fan blades are secured to a rotor assembly of a single directional motor. When the motor is powered on, a force generated by the fan blades pushes the rotor assembly in a direction of a low friction thrust interface. When the motor is backdriven in a direction opposite the powered direction, the force generated by the fan blades pushes the rotor assembly in a direction of a higher-friction thrust interface, causing a tapered surface of the pinion and a tapered surface of a bearing retainer to be pressed against each other to produce a frictional braking force. The backdriven speed of the motor and drive device is therefore reduced, improving the reliability of the motor assembly. The invention can be applied to motor actuators used to control air dampers and other valves in gas or fluid delivery systems. The invention can also be used to reduce water hammer in water delivery systems.
1. A motor apparatus, comprising:
a rotor assembly including a rotor shaft, the rotor assembly being configured to be rotatable about an axial direction, the rotor assembly being also adapted to be movable between a first position and a second position along the axial direction, the first and second positions being characterized by a first frictional braking force and a second frictional braking force, respectively;
a motor pinion coupled to the rotor assembly via the rotor shaft;
a thrust pin, the thrust pin being configured to be in contact with the rotor shaft when the rotor assembly is in the first position;
a bearing retainer, configured to support the rotor shaft during rotation, the bearing retainer being configured to be in contact with the motor pinion when the rotor assembly is in the second position; and
a plurality of fan blades coupled to the rotor assembly, the fan blades being configured to generate a first force that pushes the rotor assembly to the first position when the rotor assembly rotates in a first direction, the fan blades being further configured to generate a second force that pushes the rotor assembly to the second position during a portion of time when the rotor assembly rotates in a second direction opposite of the first direction.
2. The motor apparatus as recited in claim 1 , wherein the first frictional braking force is generated when the rotor shaft is rotating and the rotor shaft in contact with the thrust pin, and wherein the second frictional braking force is generated when the motor pinion is rotating and the rotor pinion is in contact with the bearing retainer.
3. The motor apparatus as recited in claim 1 , wherein the first braking force is smaller than the second braking force.
4. The motor apparatus as recited in claim 1 , wherein the motor pinion includes a first tapered surface and the bearing retainer includes a second tapered surface, the second surface being characterized by a substantially same tapered angle the first tapered surface.
5. The motor apparatus as recited in claim 1 , wherein the thrust pin is positioned such that when the rotor shaft is in contact with the thrust pin, the first tapered surface of the motor pinion is separated from the second tapered surface of the bearing retainer by a predetermined distance.
6. The motor apparatus as recited in claim 1 , wherein the motor pinion is made of powered metal and the bearing retainer is made of hardened steel.
7. The motor apparatus as recited in claim 1 , wherein the motor pinion includes a surface layer that is made of powered metal, and the bearing retainer includes a surface layer that is made of hardened steel.
8. The motor apparatus as recited in claim 1 , wherein the thrust pin is made of hardened steel and the rotor shaft is made of hardened steel.
9. The motor apparatus as recited in claim 1 , further comprising a spring device, the spring device being configured to backdrive the rotor device in the second direction opposite the first direction.
10. The motor apparatus as recited in claim 1 , wherein the fan blades are configured to reduce the rotational speed of the rotor assembly when the spring device backdrive the rotor assembly in the second direction opposite the first direction.