Sliding brush system with shape memory alloy element for two-speed direct current motor

An apparatus for providing an electric connection between a voltage source and a rotating commutator wheel of an electric machine, comprising:

• a fixed brush in electrical connection with the commutator wheel;
• a first switched brush system;
• a second switched brsh system;
• a voltage switch for selectively providing electrical connection between the voltage source and the first switched brush system or the second switched brush system;
• wherein the first switched brush system and the second switched brush system each include;
• a switchable brush, switchable between a disengaged position and an engaged position in electrical connection with the commutator wheel, and
• a brush switch having a shape memory alloy element adapted to switch the switched brush between the engaged position when the shape memory alloy element is in a retracted shape and the disengaged position when the shape memory alloy element is in an extended shape;
• and
• a temperature condition in electrical connection with the brush switch so that the shape memory alloy element can be elevated to a transition temperature at which the shape memory alloy element takes the retracted shape when an electrical current is supplied to the brush switch.

A two-speed electric machine energized by a voltage source, comprising:

• a rotating commutator wheel;
• a fixed brush in electrical connection with the commutator wheel;
• a first switched brush system;
• a second switched brush system;
• a voltage switch for providing selective electrical connection between the voltage source and either the first switched brush system or the second switched brush system;
• wherein the first switched brush system and the
• second switched brush system each include
• a switched brush, switchable between a disengaged position and an engaged position in electrical connection with the commutator wheel;
• a brush switch having a shape memory alloy element adapted to switch the switched brush between the disengaged position and the engaged position;
• a housing, mounted adjacent to the commutator wheel, having a first compartment containing the switched brush and a second compartment containing the brush switch;
• a brush spring, disposed within the first compartment of the housing, providing an engagement force intended to maintain the switched brush in the engaged position;
• a bispring, disposed within the second compartment of the housing, coacting with the shape memory alloy element so that the bispring provides a disengagement force to the switched brush when the shape memory alloy element is in an extended position and the brush spring provides the engagement force to the switched brush when the shape memory alloy element is in a retracted position;
• so that the electrical machine operates at a first speed when the switched brush of the first switched brush system is in electrical connection with the voltage source and at a second speed when the switched brush of the second switched brush system is in electrical connection with the voltage source.