Electromagnetic bell unit, its fitting structure and a method of welding the bell and the yoke of the unit

An electromagnetic bell unit and external fixing means therefor comprising:

• a drive block assembly comprised of a curved yoke having an extended arm, a coil fixedly arranged within the yoke and a bell hammer having a magnet attached thereto and having one end thereof fixed to a projected portion of the yoke and having a hammer head at the other end thereof;
• a bell housing therein the drive block assembly, the bell having an inner bottom surface connected to the yoke for fixing the yoke to the bell such that the extended arm of the yoke extends outwardly of the yoke;
• means defining a hole in the bottom of the bell to enable insertion therethrough of a jig to bend the projected portion of the yoke for adjusting the distance between the hammer head and the bell;
• and
• external fixing means having one portion fixed to the extended arm of the yoke and another portion fixed to an end of the yoke by a snap-fit thereby firmly fixing the yoke.

An electromagnetic bell unit comprising:

• a drive block assembly comprised of a stationary yoke having two end portions for attachment to a support structure during use of the bell unit and a bendable projection, a bell hammer having one end thereof connected to the yoke projection and having a hammer head connected to the other end thereof, an energizeable coil attached to the yoke opposite the bell hammer, and a movable yoke connected to the bell hammer and coacting with the coil to effect vibration of the hammer head;
• a bell having a dome-shaped portion at least partially enclosing the drive block assembly;
• means fixedly connecting the yoke to the bell to position the hammer head in spaced relation from the bell whereby vibration of the hammer head causes the hammer head to strike the bell;
• and means including a hole in the bell to enable bending of the yoke projection to adjust the distance between the hammer head and the bell.