Electric sound-producing device

Claim 2

An electrical sound-producing device comprising a resilient diaphragm of ferromagnetic material having a substantially flat portion, an electromagnet including a tubular core having one end adjacent said flat portion of the diaphragm and spaced therefrom by an air gap, the other end thereof being mounted on a spigot, whereby said diaphragm is deformed when current is supplied to said electromagnet, and an oscillator for repeatedly supplying current in short duration pulses to said electromagnet.

Claim 3

A device as claimed in claim 1 in which the oscillator produces pulses of duration approximately equal to half the period of the natural vibration of the diaphragm.

Claim 4

An electrical sound producing device comprising a resilient diaphragm of ferromagnetic material, an electromagnet whereby said diaphragm is deformed when current is supplied to said electromagnet, said electromagnet including a core having one end adjacent said diaphragm, a coil comprising a pair of windings on said core and an oscillator of which said core and windings form an essential part for repeatedly supplying current to the windings in short duration pulses.

Claim 5

An electrical sound producing device comprising a resilient diaphragm of ferromagnetic material, an electromagnet whereby said diaphragm is deformed when current is supplied to said electromagnet, said electromagnet including a core having one end adjacent said diaphragm, a coil comprising a pair of windings on said core and an oscillator of which said core and windings form an essential part for repeatedly supplying current to the windings in short duration pulses.

Claim 6

A device as claimed in claim 3 in which said oscillator comprises first and second terminals, an n-p-n transistor with its collector connected via one winding of said coil to the first terminal and its emitter connected to the second terminal, a first resistor and a diode in series circuit bridging said first winding, a capacitor connected in a circuit with the second winding of the coil connecting the second terminal to the base of the transistor and a charging circuit for said capacitor including a second resistor.

Claim 7

A device as claimed in claim 4 in which said charging circuit consists of said second resistor connected between the end of the second winding which is connected to the capacitor and the first terminal.

Claim 8

A device as claimed in claim 4 in which said charging circuit comprises a further resistor connecting the second resistor to the first terminal, a further transistor with its collector/emitter path connecting the interconnection of the second and further resistors to said second terminal and means for applying a signal to the base of said further transistor.

Claim 9

A device as claimed in claim 6 in which said further resistor and said further transistor form part of a multivibrator whereby the charging circuit is energized intermittently so that the device produces sound intermittently.

Claim 10

A device as claimed in claim 6 in which said further resistor and said further transistor form part of a sawtooth pulse generator circuit whereby the pulse repetition frequency of the oscillator is varied cyclically.

Claim 11

A device as claimed in claim 4 further comprising a further diode with its anode connected to the first terminal to prevent reverse voltages being applied to the first mentioned transistor.

Claim 12

A device as claimed in claim 4 in which the anode of the diode is connected to the collector of the transistor and its cathode is connected to the first resistor, and further comprising a further capacitor connecting the cathode of said diode to the emitter of the transistor.

Claim 13

A device as claimed in claim 4 further comprising a further capacitor interconnecting the first and second terminals.

Claim 14

A device as claimed in claim 4 further comprising a third resistor connecting said capacitor to the second winding.

Claim 15

An electrical sound producing device comprising a body formed in two parts, a flexible resilient diaphragm of ferromagnetic material supported by one body part, an electromagnet supported by the other body part whereby the diaphragm is deformed when current is supplied to the electromagnet, means for adjusting the position of said two parts relative to one another during assembly of the device to vary the air gap between the electromagnet and the diaphragm, sealing means joining the body parts together in an adjusted relationship and an oscillator contained within said body for repeatedly supplying current to the electromagnet in short duration pulses.

Claim 16

An electrical sound producing device comprising a body formed in two parts, a flexible resilient diaphragm of ferromagnetic material supported by one body part, an electromagnet supported by the other body part whereby the diaphragm is deformed when current is supplied to the electromagnet, means for adjusting the position of said two parts relative to one another during assembly of the device to vary the air gap between the electromagnet and the diaphragm, sealing means joining the body parts together in an adjusted relationship and an oscillator contained within said body for repeatedly supplying current to the electromagnet in short duration pulses.

Claim 17

A device as claimed in claim 13 in which said parts have mating cylindrical surfaces and are rotatable relative to one another about the common axis of said surfaces during assembly, said parts having interengaging means for displacing the two parts axially relative to one another on turning of one part relative to the other.

Claim 18

A device as claimed in claim 14, in which said interengaging means comprises a plurality of abutments on one part and a plurality of inclined ramps on the other part.

Claim 19

A device as claimed in claim 13, in which the part of the body which supports the diaphragm has an internal groove into which an external rib on a member of which the diaphragm is an integral part is a snap fit.

Claim 20

A device as claimed in claim 13, in which the part of the body which carries the electromagnet has an integral spigot on which there is fitted a tubular core forming part of said electromagnet.

Claim 21

A device as claimed in claim 17, in which a coil of the electromagnet is mounted on the core.

Claim 22

A device as claimed in claim 18, in which there is provided an annular insulation member surrounding the coils and supporting the component parts of the oscillator.

Claim 23

A device as claimed in claim 17, in which the electromagnet further comprises a cup-shaped member, having a hole fitted on said spigot and engaged by the core, forming a magnetic connection between the core and the periphery of the diaphragm, an air gap being defined between the core and the center of the diaphragm.

Claim 24

An electrical sound-producing device comprising a body, a flexible resilient diaphragm mounted in said body, a tubular acoustic resonator on the body tuned to the natural frequency of the diaphragm and whose axis is perpendicular to the plane of the diaphragm, an electromagnet in the body for deforming the diaphragm when current is supplied thereto and an oscillator contained in the body for repeatedly supplying current to the electromagnet in short duration pulses of lengths approximately equal to half the period of the natural vibration of the diaphragm, and wherein the internal diameter of the resonator is less than the diameter of the diaphragm.

Claim 25

An electrical sound-producing device comprising a body, a flexible resilient diaphragm mounted in said body, a tubular acoustic resonator on the body tuned to the natural frequency of the diaphragm and whose axis is perpendicular to the plane of the diaphragm, an electromagnet in the body for deforming the diaphragm when current is supplied thereto and an oscillator contained in the body for repeatedly supplying current to the electromagnet in short duration pulses of lengths approximately equal to half the period of the natural vibration of the diaphragm, and wherein the internal diameter of the resonator is less than the diameter of the diaphragm.

Claim 26

An electrical sound-producing device comprising a body, a diaphragm within the body dividing the interior of the body into two chambers, a horn on the body opening into one chamber and of increasing cross-sectional area in a direction away from said one chamber, an electromagnet having a pair of windings in the other chamber for deforming the diaphragm when the current is supplied to the electromagnet, and an oscillator circuit including said pair of windings within said other chamber for repeatedly supplying current to the electromagnet in short duration pulses.

Claim 27

An electrical sound-producing device comprising a body, a diaphragm within the body dividing the interior of the body into two chambers, a horn on the body opening into one chamber and of increasing cross-sectional area in a direction away from said one chamber, an electromagnet having a pair of windings in the other chamber for deforming the diaphragm when the current is supplied to the electromagnet, and an oscillator circuit including said pair of windings within said other chamber for repeatedly supplying current to the electromagnet in short duration pulses.

Claim 28

A device as defined in claim 22, further comprising a pulse rate control circuit in said other chamber connected to said oscillator and cyclically varying the pulse repetition rate of the oscillator.

Claim 29

A device as defined in claim 23, in which said pulse rate control circuit is a saw-tooth pulse generator circuit whereby the pulse repetition frequency of the oscillator is caused to commence each cycle at a low frequency and rise continuously to a high frequency, thereafter recommencing at said low frequency.