| 摘要 |
An electromagnetic sound generator, such as an automobile horn, has a thin-walled ferromagnetic housing closed at one end by a membrane which carries an armature extending into an electromagnetic coil mounted in the housing. The rim of the membrane is embraced by a deformable peripheral housing wall bent back upon itself to form an outwardly projecting peripheral flange with a bight portion radially spaced from the membrane, the housing wall extending axially beyond this flange to engage a resonator adjoining the membrane. The armature has an eccentric lug which coacts with a contact spring of an interrupter in series with the coil and which can be limitedly adjusted, by rotation of the armature about its axis, to shift its point of engagement with the contact spring for varying the moment arm of the spring and thus the natural frequency of the sound generator. In assembling the housing and the membrane, a stepped portion of the peripheral housing wall is first deformed radially inwardly to form a beveled neck which is then flattened axially against the membrane resting on an internal shoulder of that wall. |
