Abstract:
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.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   None 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   N/A 
   BACKGROUND OF THE INVENTION 
   This invention relates to solenoid constructions, and in particular, to a low cost solenoid having improved operating characteristics. While the invention is described in particular detail with respect to certain preferred applications of the solenoid, those skilled in the art will recognize the wider applicability of the inventive principles disclosed hereinafter. 
   A conventional solenoid is designed so that magnetic force is exerted across an air gap generally perpendicular to the pole pieces in such a manner as to close the gap. Latching solenoids also are well known in this device, wherein a plunger moves from its first to second position. The plunger is maintained in the second position until a physical force is exerted on the plunger to return it to its initial starting position. 
   We have determined that a relatively efficient, and low cost solenoid construction can be obtained by utilizing in its simplest form, a freely moveable permanent magnet which operates between first and second pole pieces to operate the solenoid in a unique fashion. In this construction, a divider separates the first and second pole pieces. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a solenoid construction. In an embodiment, the present invention relates to a bobbin having an axial length, an external surface and an axial opening extending through the axial length. The bobbin comprises a divider mounted in the axial opening of the bobbin, which divides the axial opening into a first segment and a second segment. A first pole piece is moveable within the first segment between a retracted position and an extended position while a second pole piece is moveable within the second segment between an external position external of the axial opening and an internal position within the axial opening. 
   A permanent magnet is 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. In the second position, the permanent magnet 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. 
   In an embodiment, the present invention relates to method of operating the solenoid. The method of operation comprises segmenting the bobbin by a divider to form a first segment and a second segment. Next, a force is applied 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. The permanent magnet magnetically draws 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 in its second position. The divider separates the first pole piece and the permanent magnet. The force is then reapplied to the permanent magnet in order to reciprocate the permanent magnet through the second segment from the second position to the first position and to retract the first pole piece. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects of the invention are achieved as set forth in the illustrative embodiments shown in the drawings, which form a part of this specification. 
       FIG. 1  is a cross sectional view of an operating condition of one illustrative embodiment of a bobbin of the solenoid of the present invention; 
       FIG. 2  is a cross sectional view of a second operating condition of the bobbin of the present invention; 
       FIG. 3  is cross sectional view of a third operating condition of the bobbin of the present invention; 
       FIG. 4  is a cross sectional view of a fourth operating condition of the bobbin of the present invention; 
       FIG. 5  is a cross sectional view of another operating condition of another illustrative embodiment of the bobbin of the present invention; 
       FIG. 6  is cross sectional view of a second operating condition of the bobbin of  FIG. 5 ; 
       FIG. 7  is cross sectional view of a third operating condition of the bobbin of  FIG. 5 ; 
       FIG. 8  is cross sectional view of a fourth operating condition of the bobbin of  FIG. 5 ; 
       FIG. 9  is a breakaway perspective view of components of one illustrative embodiment of the solenoid of the present invention; and 
       FIG. 10  is a perspective view of one illustrative embodiment of the solenoid of the present invention. 
   

   Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention including what we presently believe is the best mode of carrying out the invention. As various changes could be made in the constructions discussed herein without departing from the scope of the invention, it is intended that all matter contained in the description are shown in the accompanying drawings shall be interpreted as illustrative and not in a limited sense. 
   Referring now to  FIG. 1 , reference numeral  10  indicates one illustrative embodiment of solenoid of the present invention wherein the solenoid  10  includes a bobbin  12  having an axial length  14 , an external surface  16  and an axial opening  18  extending through the axial length  14 . As known in the art, electrical coil  20  winds about the bobbin  12  along the external surface  16 . 
   A divider  22  mounted in the axial opening  18  divides the axial opening  18  into a first segment  24  and a second segment  26 . In an embodiment, the first segment  24  and the second segment  26  may have the same length. The segments  24 ,  26 , though, may be of any length depending on the construction, strength and package size of the solenoid  10 . The bobbin  12  further includes a first pole piece  28  and a second pole piece  30  positioned on opposite sides of the divider  22 . As shown, the first pole piece  28  is movable within the first segment  24  between a retracted position  32  and an extended position  34  ( FIG. 3 ). In the retracted position  32 , the first pole piece  28  does not contact the divider  22 . As such, a mechanical device  36  attaches to the first pole piece  28  to retract the first pole piece  28  axially outward from the divider  22  in the retracted position  32 . In an embodiment, the mechanical device  36  may comprise a spring such as, but not limited to, a coil compression spring. The mechanical device  36  connects with a portion (not shown) of the solenoid  10 . 
   Turning to  FIG. 2  and referring to  FIG. 1 , the second pole piece  30  is moveable within the second segment  26  between an external position  38  ( FIG. 1 ) and an internal position  40 . In the external position  38 , the second pole piece  30  may be fixed with respect to the bobbin  14 . In the internal position  40 , portions of the second pole piece  30  project into the axial opening  18 . In an embodiment, a manual connection  42  such as an actuator may reciprocate the second pole piece  30  between the external position  38  and the internal position  40 . 
   Referring to  FIG. 3 , the bobbin  12  further comprises a permanent magnet  44 , which is moveable within the second segment  26  between at least a first position  46  ( FIG. 1 ) and a second position  48 . In the first position  46 , the permanent magnet  44  magnetically couples with the second pole piece  30  when the second pole piece  30  is positioned in the external position  38  as shown in  FIG. 1 . In the second position  48 , the permanent magnet  44  is positioned adjacent to the divider  22 . In this position, the permanent magnet  44  magnetically draws the first pole piece  28  from the retracted position  32  ( FIG. 1 ) to the extended position  34  to magnetically couple the first pole piece  28  to the permanent magnet  44  as will be discussed. 
   As shown in  FIG. 4 , when the permanent magnet  44  reciprocates back to the first position  46  and adjacent the second pole piece  30 , the mechanical device  36  retracts the first pole piece  28  to its retracted position  32 . As such, the bobbin  12  of the solenoid  10  incorporates a freely moveable permanent magnet  44 , which operates between first and second pole pieces  28 ,  30  while the divider  22  separates the first and second pole pieces  28 ,  30 . 
   Referring to  FIGS. 1–4 , a manual method of operation of the present invention is shown. During operation, the divider  22  segments the bobbin  12  to form the first segment  24  and the second segment  26 . As shown in  FIG. 1 , the mechanical device  36  retracts the first pole piece  28  to its retracted position  32 . Additionally, the manual connection  42  positions the second pole piece  30  in the external position  38 . In this position, the permanent magnet  44  magnetically couples to the second pole piece  30  in the first position  46  of the permanent magnet  44 . 
   Turning to  FIG. 2 , the manual connection  42  actuates the second pole piece  30  to apply a force to the permanent magnet  44  while the permanent magnet  44  is disposed within the second segment  26  to reciprocate the permanent magnet  44  between the first position  46  and the second position  48 . As such, actuating the second pole piece  30  moves the coupled permanent magnet  44  and second pole piece  30  to the second position  48 . In the second position  48 , the permanent magnet  44  moves adjacent to the divider  22 . 
   Referring to  FIG. 3 , the permanent magnet  44  in the second position  48  magnetically draws the first pole piece  28  through the first segment  24  toward the permanent magnet  44  and adjacent the divider  22 . Accordingly, the first pole piece  28  moves to its extended position  34  within the first segment  24 . The first pole piece  28  magnetically couples to the permanent magnet  44  through the divider  22  when the permanent magnet  44  is in the second position  48 . The first pole piece  28 , the second pole piece  30  and the permanent magnet  44  will remain in this configuration until acted upon by another force. 
   As shown in  FIG. 4 , a force may be reapplied to the permanent magnet  44  which reciprocates the permanent magnet  44  and breaks the magnetic couple between the first pole piece  28  and the permanent magnet  44 . As such, the first pole piece  28  retracts through the first segment  24  via the mechanical device  36  while the permanent magnet  44  reciprocates through the second segment  26  from the second position  48  to the first position  46 . In an embodiment, reapplying the force to the permanent magnet  44  comprises actuating the second pole piece  30  via the manual connection  42  to move the coupled permanent magnet  44  and second pole piece  30  to the second position  48  which is separate from the divider  22 . Moving the coupled permanent magnet  44  decouples the first pole piece  28  from the permanent magnet  44  such that the first pole piece  28  moves to the retracted position  32 . As such, solenoid  10  of the present invention may use a manual operation by actuating the manual connection  42 . 
   Referring to  FIGS. 5–8 , an automatic method of operation of the present invention is shown. During this operation, the divider  22  segments the bobbin  12  to form the first segment  24  and the second segment  26 . As shown in  FIG. 5 , the mechanical device  36  retracts the first pole piece  28  to its retracted position  32 . Additionally, the manual connection  42  positions the second pole piece  30  in the external position  38 . In this embodiment, the second pole piece  30  remains fixed in the external position  38 . Furthermore, in this position, the permanent magnet  44  magnetically couples to the second pole piece  30  in the first position  46  of the permanent magnet  44 . 
   Turning to  FIG. 6 , the solenoid  10  applies a force to the permanent magnet  44  while the permanent magnet  44  is disposed within the second segment  26  to reciprocate the permanent magnet  44  between the first position  46  and the second position  48 . In an embodiment, applying the force to the permanent magnet  44  comprises creating a magnetic filed having the same polarity as the permanent magnet  44 . The solenoid  10  may create the magnetic field by energizing the electrical coils  20  with a small amount of current. In an embodiment, a power control device  50  attached to the electrical coil  20  may supply the current to the electrical coil  20 . Since the second pole piece  30  remains fixed in its external position  38 , the permanent magnet  44  decouples from the second pole piece  30  as the permanent magnet  44  moves to the second position  48 . As such, applying the force moves the permanent magnet  44  to the second position  48  that is adjacent the divider  22 . 
   Referring to  FIG. 7 , the permanent magnet  44  in the second position  48  magnetically draws the first pole piece  28  through the first segment  24  toward the permanent magnet  44  and adjacent the divider  22 . Accordingly, the first pole piece  28  moves to its extended position  34  within the first segment  24 . The first pole piece  28  magnetically couples with the permanent magnet  44  through the divider  22  when the permanent magnet  44  is in the second position  48 . The first pole piece  28 , the second pole piece  30  and the permanent magnet  44  will remain in this configuration until acted upon by another force. 
   As shown in  FIG. 8 , a force may be reapplied to the permanent magnet  44  that breaks the magnetic couple of the first pole piece  28  and the permanent magnet  44  across the divider  22 . As such, the first pole piece  28  retracts through the first segment  24  while the permanent magnet  44  reciprocates through the second segment  26  from the second position  48  to the first position  46 . Accordingly, moving the coupled permanent magnet  44  decouples the first pole piece  28  from the permanent magnet  44  such that the first pole piece  28  moves to the retracted position  32 . 
   In an embodiment, reapplying the force applied to the permanent magnet  44  comprises creating another magnetic field having the opposite polarity of the permanent magnet  44  wherein the other magnetic field reciprocates the permanent magnet  44  back to the first position  46 . At the first position  46 , the permanent magnet  44  magnetically couples with the second pole piece  30 . In another embodiment, reapplying the force applied to the permanent magnet  44  comprises de-energizing the electrical coil  20  such that the permanent magnet  44  magnetically couples again to the second pole piece  30 . As such, the solenoid  10  of the present invention may use an automatic operation by energizing the electrical coil  22 . In another embodiment, reapplying the force may comprise activating the manual connection  42  to move the second pole piece  30  in magnetic contact with the permanent magnet  44  and then retracting the permanent magnet  44  and second pole piece  30 . 
   Turning to  FIGS. 9 and 10 , an embodiment of the present invention is shown.  FIG. 9  illustrates in a perspective breakaway view components of the present invention. As shown, the solenoid  10  includes a protective cover mold  52  of non-electrically conductive material that surrounds at least the electrical coil  20 . Additionally,  FIG. 9  illustrates the bobbin  12 , permanent magnet  44  and mechanical device  36  along with other components.  FIG. 10  illustrates an embodiment of the solenoid  10  in assembled form. 
   In view of the above, it will be seen that the several objects of the disclosure are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.