A solenoid is provided which, in the preferred embodiment, has a bobbin having an axial opening in it. A divider is mounted within the opening. Respective ones of a first pole piece and a second pole piece are located on opposite sides of the divider. A permanent magnet is moveably mounted from the axial opening and is moveable independently of the second pole piece between at least a first position adjacent to the divider, and a second position adjacent the second pole piece. The construction provides a fast acting, low cost latching solenoid construction.
1. A bobbin having an axial length, an external surface and an axial opening extending through the axial length, comprising:
a divider mounted in the axial opening of the bobbin to divide the axial opening into a first segment and a second segment;
a first pole piece moveable within the first segment between a retracted position and an extended position;
a second pole piece moveable within the second segment between an external position external of the axial opening and an internal position within the axial opening; and
a permanent magnet movable within the second segment between a first position adjacent the second pole piece when the second pole piece is positioned in the external position and a second position adjacent the divider, wherein the permanent magnet in the second position magnetically draws the first pole piece from the retracted position to the extended position to magnetically couple the first pole piece to the permanent magnet.
2. The bobbin of claim 1 further comprising an electrical coil wound about the bobbin along the external surface thereof.
3. The bobbin of claim 2 further comprising a power control device attached to an end of the electrical coil.
4. The bobbin of claim 1 further comprising a mechanical device attached to the first pole piece, the mechanical device retracting the first pole piece axially outward from the divider in the retracted potion.
5. The bobbin of claim 4 wherein the mechanical device attached to the first pole piece is a spring.
6. The bobbin of claim 5 wherein the spring is a coil compression spring.
7. The bobbin of claim 1 further comprising a manual connection which reciprocates the second pole piece between the external position and the internal position of the second pole piece.
8. The bobbin of claim 1 wherein the first segment and the second segment are equal in length to one another.
9. A solenoid, comprising:
a bobbin having an axial length, an external surface and an axial opening extending through the axial length;
an electrical coil wound about the bobbin along the external surface thereof;
a divider mounted in the axial opening of the bobbin to divide the axial opening into a first segment and a second segment;
a first pole piece moveable within the first segment between a retracted position and an extended position;
a mechanical device attached to the first pole piece, the mechanical device retracting the first pole piece axially outward from the divider in the retracted potion;
a second pole piece moveable within the second segment between an external position external of the axial opening and an internal position within the axial opening; and
a permanent magnet movable within the second segment between a first position adjacent the second pole piece when the second pole piece is positioned in the external position and a second position adjacent the divider, wherein the permanent magnet in the second position magnetically draws the first pole piece from the retracted position to the extended position to magnetically couple the first pole piece to the permanent magnet.
10. The solenoid of claim 9 further comprising a power control device attached to an end of the electrical coil.
11. The solenoid of claim 9 further comprising a manual connection which reciprocates the second pole piece between the external position and the internal position of the second pole piece.
12. A method of operating a solenoid having a first pole piece, a second pole piece and a permanent magnet within a bobbin, comprising:
segmenting the bobbin by a divider to form a first segment and a second segment;
applying a force to the permanent magnet while the permanent magnet is disposed within the second segment to reciprocate the permanent magnet between a first position and a second position;
magnetically drawing the first pole piece through the first segment toward the permanent magnet in order to magnetically couple the first pole piece to the permanent magnet as the the permanent magnet moves toward the second position; and
reapplying the force applied to the permanent magnet in order to reciprocate the permanent magnet through the second segment from the second position to the first position.
13. The method of operating the solenoid of claim 12 further comprising magnetically coupling the permanent magnet to the second pole piece.
14. The method of operating the solenoid of claim 13 wherein applying the force to the permanent magnet comprises actuating the second pole piece to move the coupled permanent magnet and second pole piece to the second position.
15. The method of operating the solenoid of claim 14 wherein reapplying the force applied to the permanent magnet comprises actuating the second pole piece to move the coupled permanent magnet and second pole piece to the first position, wherein moving the coupled permanent magnet decouples the first pole piece from the permanent magnet such that the first pole piece moves to the retracted position.
16. The method of operating the solenoid of claim 13 wherein applying the force to the permanent magnet comprises creating a magnetic field having the same polarity as the permanent magnet wherein the magnetic field decouples the permanent magnet from the second pole piece and moves the permanent magnet to the second position which is adjacent to the divider.
17. The method of operating the solenoid of claim 16 wherein reapplying the force applied to the permanent magnet comprises creating another magnetic field having the opposite polarity as the permanent magnet wherein the other magnetic field moves the permanent magnet to the first position.
18. The method of operating the solenoid of claim 16 wherein creating the magnetic field comprises energizing an electrical coil which is wound about the bobbin.