Solenoid

• US 3,947,788 A
• Filed: 09/03/1974
• Issued: 03/30/1976
• Est. Priority Date: 09/03/1974
• Status: Expired due to Term

• Current Assignee: Spencer C. Schantz
• Original Assignee: Spencer C. Schantz
• Inventors: Berry, William R.
• Primary Examiner(s): Harris, G.
• Application Number:
  US05/502,579
• Time in Patent Office: 574 Days
• Field of Search: 335/68, 335/76, 335/274, 335/279, 335/278, 335/251, 335/260, 335/261, 335/262, 335/255, 222/70, 68/17 R, 318/225 R, 251/141
• US Class Current: 335/68
• CPC Class Codes: H01F 2007/083 External yoke surrounding the coil bobbin, e.g. made of bent magnetic sheet
• CPC Class Codes: H01F 3/02 made from sheets
• CPC Class Codes: H01F 7/10 specially adapted for alternating current
• CPC Class Codes: H01F 7/1607 Armatures entering the winding

Abstract

A solenoid coil is connected in series with an electric motor. The spring which urges the solenoid plunger away from the coil is of such strength that it will yield to the magnetic attraction of the coil when the motor-starting inrush current is flowing through the coil, but will not yield when the motor-running current is flowing through the coil. Thus the solenoid plunger reciprocates each time the motor is started. The solenoid plunger is formed of a flat sheet of magnetic material curled into the shape of a hollow cylindrical shell. The solenoid frame has a forked portion through which the plunger extends, the forked portion having sufficient depth to minimize side loading of the plunger. An end of the frame is also shaped to act as a spring in holding the solenoid parts in assembled relationship.

Claims

1. In an electric circuit having an electric motor and having a starting switch for said motor, a solenoid having a coil and having a plunger mounted for movement in one direction as a result of magnetic attraction when the coil is energized, and there being spring means associated with the plunger to normally urge the latter in a return direction, the improvement comprising having the solenoid coil in series in the electric circuit with said motor and starting switch, and having said spring means of less strength than the strength of the magnetic attraction between the coil and plunger when motor-starting inrush current is flowing through said coil but being of greater strength than the strength of said magnetic attraction when motor-running current is flowing through the coil to automatically cause quick return movement of the plunger while the coil is still energized, whereby quick movement of the plunger in both directions is initiated whenever the motor is started.

2. In a solenoid having a coil, a magnetic plunger mounted for movement in one direction as a result of magnetic attraction when the solenoid is energized, and spring means associated with said coil to normally urge said plunger in a return direction, said spring means being of less strength than the magnetic attraction between the coil and plunger when the current flowing through said coil on initial energization is above a predetermined level, but being of greater strength than the magnetic attraction when current thereafter drops below said predetermined level to cause return movement of the plunger while the coil is still energized, whereby there is automatic movement of the plunger in both directions following initial energization of the coil.

3. The solenoid of claim 2 and further comprising a magnetic frame for said solenoid having a forked end embracing one end of said plunger, said forked end encluding a U-shaped opening with an open end and a closed end, said closed end being spaced sufficiently from the sides of said plunger as to minimize side loading due to unequal magnetic forces acting laterally on the plunger.

4. Apparatus as claimed in claim 3 wherein the legs of one of said spaced ends of the frame are transversely kinked along a transverse line, with said transverse line yieldingly bearing against the end of the coil housing and constituting the only contact between said frame end and said coil housing.

5. Apparatus as claimed in claim 4 in which said coil housing is circular in cross section, and in which said transverse line of kink bears against the end of the coil housing along a diameter thereof.

6. Apparatus as claimed in claim 4 wherein the legs which are transversely kinked are bent from the base of the U-shaped frame, with the portions of said legs which are near the line of bend at an acute angle with respect to the base of the U-shaped frame.

7. In a solenoid having a coil, a magnetic plunger mounted for movement within said coil so that a portion is movable into and out of an end thereof, a magnetic frame for said solenoid having forked ends with each forked end including spaced legs, one end of said plunger projecting through one of said forked ends, said last-mentioned forked end including a U-shaped opening with an open end and a closed end, said closed end being spaced sufficiently from the sides of said plunger as to minimize side loading due to unequal magnetic forces acting laterally on the plunger, the coil being wound on a bobbin, and said bobbin having a cylindrical extension at one end, in which the spaced legs at one end of the frame embrace said cylindrical extension, and in which there is an electrical insulating washer surrounding the cylindrical extension of the bobbin and located between the spaced legs and the end of the coil housing, said washer having a cylindrical extension surrounding the cylindrical extension of the bobbin and also embraced by the spaced legs of the frame.

9. Apparatus as claimed in claim 7 in which there is an electrically insulating end piece having a cylindrical extension positioned adjacent the end of the bobbin which is opposite the end of the bobbin having said washer, and in which spaced legs at the adjacent end of the frame maintain said end piece in assembled relationship with the cylindrical extension aligned with and of a size to accommodate the plunger, said cylindrical extension having a closed outer end forming a stop to limit the return stroke of the plunger.

8. In a solenoid having a coil, a magnetic plunger mounted for movement within said coil so that a portion is movable into and out of an end thereof, a magnetic frame for said solenoid having forked ends with each forked end including spaced legs, one end of said plunger projecting through one of said forked ends, said last-mentioned forked end including a U-shaped opening with an open end and a closed end, said closed end being spaced sufficiently from the sides of said plunger as to minimize side loading due to unequal magnetic forces acting laterally on the plunger, the coil being wound on a bobbin having end portions and there being an end piece having a cylindrical extension aligned with and of a size to accommodate said plunger, and in which the spaced legs at one end of the frame embrace said cylindrical extension to maintain said end piece in assembled relationship against one end of the bobbin, said cylindrical extension having a closed outer end forming a stop to limit the return stroke of the plunger.