Title: Plunger damping means for an electromagnetic solenoid

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Abstract: An electromagnetic solenoid with a yoke defining a hollow cylinder, an electromagnetic coil wound around this cylinder for connection to a power source, a plunger inserted in the cylinder for sliding movement therein when the coil is energized and having a needle-like rod extending through the yoke bottom, the plunger and cylinder each having a confronting surface which is faced with a confronting surface of the other during the sliding movement. A plurality of spaces are formed on the confronting surface of at least either the cylinder or the plunger, and a braking substance consisting of a highly viscous liquid is applied to the confronting surfaces of the plunger and cylinder. Spring means may be operatively provided about the plunger to return the slidingly moved plunger to its original position. Upon energization of the solenoid, the downward movement speed of the plunger is limited by the braking substance. The spaces serve to keep the liquid braking substance therein and insure the braking effect of the substance. Thus, the smooth slow stroke of the plunger is free of impact and any noise resulting from the rod hitting the yoke end is eliminated. This solenoid can be prepared in a compact size and is suitable for slowly driving a light-weight object.


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