Abstract: A portable mechanical burglar alarm for monitoring doors and windows includes a base plate having a back surface provided with a plurality of suction cups for releasable securement adjacent a door or window. A pair of bells are secured in spaced relation on a front surface of the base plate and a pivotal oscillating clapper arm is disposed therebetween. A spring powered bell ringing mechanism is enclosed by a housing on a front surface of the base plate. A trigger mechanism within the housing is operative to actuate the bell ringing mechanism upon disengagement of an adjustable abutment stop member from contact with a door or window frame upon opening of the door or window. A retaining mechanism within the housing prevents unauthorized resetting of the trigger mechanism subsequent to activation, to prevent the ringing bells from being silenced.

Abstract: A motor bell alarm comprises an electric motor and a linkage by which the rotational motion generated by an electric motor is translated to a longitudinal oscillating motion so as to cause a plunger coupled to the linkage to cyclically strike a shell, thereby creating a ringing sound. The volume and clarity of the ringing sound are enhanced by minimizing the time in which the plunger is in contact with the shell and by minimizing the rest mass that is in contact with the shell as it is struck by interposing a lost-motion connection between the plunger and the linkage to the electric motor, whereby upon and after striking the shell the plunger is mechanically uncoupled from the lever.

Abstract: A device for striking a bell comprises a hammer head having a head portion composed of hard material and another head portion composed of soft material to obtain both hard and soft sounding bell rings. The hammer head is connected to a rockable striking hammer lever which is driven with a rocking motion by a rotating eccentric cam to cause the hammer head to strike the bell. The center of rocking motion of the striking hammer lever can be shifted both manually and automatically to selectively vary the hardness and softness of the bell ring.