Title:
ELECTRONIC CHIME ALARM
United States Patent 3653040


Abstract:
An electronic chime alarm includes a Hartley oscillator having a center-tapped coil which is electromagnetically coupled to a magnetic reed. The reed is supported at one end thereof by a yoke arrangement. By design, the oscillator may pulse the reed at a frequency lower than the reed's resonant frequency. The resultant reed vibrations, which include harmonics dependent upon reed structure, of which a number of examples are shown, may be coupled to an amplifier and a speaker by either a nonmagnetic transducer or by a filter circuit connected across the coil. In addition, various examples of an oscillator unit structure including the reed, yoke, coil and transducer are illustrated. Finally, various switching arrangements which enable the chime alarm to be used with standard synchronous motor clocks or with clock-radios are described.



Inventors:
HOAG YATES M
Application Number:
05/006993
Publication Date:
03/28/1972
Filing Date:
01/30/1970
Assignee:
GENERAL ELECTRIC CO.
Primary Class:
Other Classes:
368/259, 968/596
International Classes:
G04C21/28; G08B3/10; (IPC1-7): G04C21/28; G10K10/00
Field of Search:
340/384E,392,224,261 58
View Patent Images:
US Patent References:
3284791Near alarm receiver having-time delay of discharge type1966-11-08Voigt et al.
2971187Tone generator1961-02-07Marr et al.
0026817N/A1860-01-10



Primary Examiner:
Caldwell, John W.
Assistant Examiner:
Swann III, Glen R.
Claims:
What is claimed and desired to be secured by Letters Patent of the United States is

1. An electronic chime alarm for use with a clock employing a motor supplied from an alternating current source, the clock including an alarm setting means for providing a mechanical movement thereof at a variable, desired alarm time, comprising:

2. The electronic chime alarm of claim 1 wherein said vibration sensing means includes a transducer acoustically coupled to said reed.

3. The electronic chime alarm of claim 2 wherein said coil, said metallic reed and said transducer are disposed in a common oscillator unit comprising:

4. The electronic chime alarm of claim 3 wherein said metallic reed consists of a flat, hardened steel strip having a diagonal cut on a free end thereof.

5. The electronic chime alarm of claim 3 wherein said metallic reed consists of a flat, hardened steel strip having portions cut from the sides thereof.

6. The electronic chime alarm of claim 3 wherein said metallic reed consists of a flat, hardened steel strip having a free end rolled in a spiral.

7. The electronic chime alarm of claim 3 wherein said securing means includes an auxiliary, sheet metal strip extending approximately parallel to said reed from said yoke, means fastening said auxiliary sheet weld strip to said yoke, and means fastening said transducer to said auxiliary strip.

8. The electronic chime alarm of claim 1 wherein said vibration sensing means includes a filter network connected across said coil, said filter network comprising:

9. The electronic chime alarm of claim 8 wherein said coil and said metallic reed are disposed in a common oscillator unit comprising:

10. The electronic chime alarm of claim 9 wherein said metallic reed consists of a flat, hardened steel strip having a diagonal cut in a free end thereof.

11. The electronic chime alarm of claim 9 wherein said metallic reed consists of a flat, hardened steel strip having portions cut from the sides thereof.

12. The electronic chime alarm of claim 9 wherein said metallic reed consists of a flat, hardened strip having a free end rolled in a spiral.

13. The electronic chime alarm of claim 3 adapted for use with a clock-radio including detector and discriminator stages furnishing a radio signal and an audio stage normally amplifying and coupling the radio signal to a speaker, the clock further including a selector switch having first and second position, said electronic chime alarm further comprising:

Description:
BACKGROUND OF THE INVENTION

This invention relates generally to alarms for clocks employing an alternating current synchronous motor and, more particularly, to a means for electronically producing an alarm signal having tone qualities similar to a chine or bell.

Alarm devices for use with electric clocks employing synchronous motors have generally comprised in the past a buzzer alarm which comprises a thin metal strip mounted in close proximity to the core of the synchronous motor. At a selected alarm time as determined by the position of a first cam coupled to an alarm setting mechanism, a second cam coupled to the clock driving gear train engages the first cam to move a restraining lever out of engagement with the sheet metal strip. Thereafter, the strip vibrates against the core because of reversing magnetic flux produced by the 60 Hz. alternating current waveform impressed on the synchronous motor field coil. The alarm sound produced thereby is a mechanical, raucous buzz which is generally considered unpleasant by an awakening sleeper.

Although a number of techniques have been proposed for producing a more pleasing alarm sound, none of them have found commercial acceptance, as can be evidenced by the large number of buzzer type alarm clocks on the market at present. In situations where the alarm clock is combined with a radio, it has been proposed to use portions of the radio audio amplifier output stage as an oscillator to produce a ringing sound for alarm purposes. Although such an approach eliminates the raucous buzz associated with the vibration of a sheet metal strip, the oscillation obtained is generally devoid of harmonics and other qualities required to produce a pleasing sound. For these reasons and others, such circuits have not found widespread usage.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide an alarm for a clock employing a synchronous motor which has a generally pleasing sound to the ear of an awakening listener.

It is yet a further object of this invention to provide such an alarm in combination with a clock radio.

Briefly, these objects and others are achieved, according to one embodiment of the invention, by providing oscillator means employing a reed whose oscillations are made audible by a transducer, amplifier and sound reproducing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject of the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. For a complete understanding of the invention together with further objects and advantages thereof, reference should be made to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a preferred embodiment of the invention;

FIG. 2 illustrates an oscillator unit constructed according to the teachings of this invention;

FIGS. 3a-3d show various reed configurations suitable for use with the oscillator unit of FIG. 2;

FIGS. 4a and 4b show variations on the oscillator unit structure;

FIG. 5 is a schematic diagram of an alternate embodiment of the invention; and,

FIG. 6 is a schematic diagram of the electronic chime alarm which is adapted for use with a clock radio.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, an electric clock 1 employs an alarm setting mechanism and an alternating current synchronous motor of a type commonly known to the art. The motor field coil is supplied with 120-volt, 60 Hz. power through terminals 2 and 3. In addition, the alarm setting mechanism may comprise any known to the art whereby the alarm can be st at a predetermined time. For instance, a first cam could be coupled to the alarm setting mechanism and a second cam could be coupled to the clock driving gear train. By engagement of the two cams at the desired alarm time, a restraining arm could be moved out of engagement with a spring-loaded lever. The lever movement could then be utilized to perform a desired switching operation.

The electronic chime alarm of this invention is generally known in FIG. 1 at 4 and includes a DC voltage supply V which is connected to one terminal of a switch device 6. The movable arm of switch 6 is in turn connected to the alarm setting mechanism of the clock 1; the connection is illustrated in FIG. 1 by means of dotted line therebetween. At the desired alarm time, the alarm setting mechanism of clock 1 closes the movable arm of switch 6 to present the voltage V to the remainder of chime alarm 4.

In general, chime alarm 4 includes an oscillator 8 which is electromagnetically coupled to a reed 10 supported by a yoke 12. Resultant vibrations of the reed 10 are sensed by a transducer 14 and coupled through an amplifier 16 to a speaker or sound reproducing means 18. More specifically, by closure of the switch 6 at the desired alarm time, the voltage supply V is coupled to the oscillator 8. Thereafter, the oscillator electromagnetically pulses the reed 10 at a low frequency, such as 10 or 20 Hz. These pulses produced in reed 10 are equivalent to a mechanical tapping of the reed so that the reed thereafter oscillates at a frequency close to its resonant or natural frequency Of course, this frequency is much higher than 10 or 20 Hz. for a reed of practical length. The resultant vibrations in reed 10 are picked up by transducer 14, amplified, and reproduced.

The combination of the oscillator 8 and the particular design of reed 10 produces a sound in sound reproduction means 18 which has a pleasing pitch and timbre. As a large number of harmonics are present therein, the sound which the awakening listener experiences from speaker 18 is very similar to that of a chime of bell with "strikes" of the chime occuring at a rate of 10 to 20 cycles per second.

The oscillator 8 will now be described in more detail, although it is to be clearly understood that the invention is not to be limited to this specific embodiment thereof. The embodiment illustrated in FIG. 1 is that commonly known as a Hartley oscillator; included therein is a transistor 20 emitter is coupled directly to ground. The voltage supply +V is coupled by means of switch 6 and a resistor 22 to the base of transistor 20. The collector of transistor 20 is tied to one side of a centertapped coil 24 whose center tap is connected directly to the common point of switch 6 and resistor 22. The other side of coil 24 is coupled to one side of a capacitor 26 whose other side is coupled to the base of transistor 20 through a variable resistor 28. Finally, a capacitor 30 is connected across the extremities of coil 24. From an examination of this circuitry, it can be seen that the basic oscillator elements comprise the two sections of coil 24 and two feedback paths, these being formed from the center tap through resistor 22 and from the other side of coil 24 through capacitor 26 and variable resistor 28. The values of the various components therein must be chosen to yield oscillation through coil 24 of a waveform having a frequency between 10 and 20 cycles per second. Moreover, the value of variable resistor 28 may be changed to increase or decrease the magnitude of the oscillations in the coil 24.

Reed 10 is electromagnetically pulsed by the oscillations in coil fundamental The reed is fixedly maintained at one end thereof by the yoke 12 but is otherwise free to vibrate in any mode. The reed comprises an alloy of steel which is responsive to electromagnetic variations, changes in the electromagnetic flux adjoining the coil 24 accordingly producing physical displacements of the reed 10. Each pulse vibrates reed 10 at a fundamental frequency equal to or near its natural frequency which is primarily determined by the physical configuration and length of the reed. The vibrations of reed 10 also contain harmonics of that fundamental frequency which are dependent on the particular alloy and temper of steel used and many other factors known to those in the acoustical art. Therefore, by proper choice of the reed 10, a great variation in pitch, tone or timbre of vibrations can be made.

These vibrations are coupled to the transducer 14 through the yoke 12. Transducer 14 is preferably a piezo-electric crystal; for instance, any common phonograph pickup would suffice. In general, transducer 14 may be any other nonmagnetic device which is sensitive to physical vibrations and which produces an electrical output signal in proportion to such vibrations. Of course, the transducer should have the frequency range to reproduce both the fundamental frequency of reed vibration and any harmonics thereof.

The output of transducer 14 is coupled through a capacitor 32 to the input of amplifier 16 which may be referenced to a source of ground potential. As previously described the small electrical signal obtained from the output of transducer 14 is amplified in amplifier 16 and reproduced in speaker 18. By control of the gain of amplifier 16, the amplitude of the vibrations can be varied to suit the particular individual. Moreover, as the setting of variable resistor 28 determines the amplitude of the pulses coupled to reed 10 and thus the energy supplied thereto, variable resistor 28 may be used by the listener as a rough volume control apart from amplifier 16. At this point, it should be clearly noted that the particular configuration of amplifier 16 or speaker 18 forms no part of this invention and that it is envisaged that the signal obtained from transducer 14 can be amplified and reproduced in any suitable manner.

Referring now to FIG. 2, one embodiment of an oscillator unit is illustrated comprising choke 24, reed 10, yoke 12 and transducer 14 for use with this invention as shown generally in FIG. 1. Reed 10 is supported and surrounded by the yoke 12 which comprises two similar pole pieces 40 and 42 held together by a bolt and nut 43 and 44 passing through apertures therein and through a matching aperture in reed 10. Pole pieces 40 and 42 also clamp the coil 24 which comprises a winding 45 about a spool 46 through which reed 10 passes. For convenience, the terminals corresponding to the two extremities and the center tap of coil 24 have not been shown. In addition, two biasing magnets 47 and 48 are disposed adjacent the reed 10 and supported by pole pieces 40 and 42. Finally, the transducer 14 is mounted on top of pole piece 40 by means of a screw 50.

The transducer 14 is so positioned on the yoke 12 as to provide optimum coupling between the reed 10 and the transducer 14. For example, in some applications optimum coupling will be that which results in vibrations of the reed being coupled to the transducer with an amplitude large enough to provide the desired electrical output signal while at the same time precluding mechanical feedback between the transducer and a nearby speaker which could result in spurious operation. For example, it has been found that by mounting the body of a common phonograph pickup directly to the yoke 12 as shown in FIG. 2 optimum coupling can be readily achieved even where the speaker is in close proximity to the transducer. Where feedback is not a problem more efficient coupling between the transducer 14 and yoke 12 can be employed. For example, in some applications it might be desirable to have the stylus arm of a phonograph pickup rather than the body of the pickup directly contact the yoke.

From this description, it can be seen that the oscillator unit structure illustrated in FIG. 2 forms a simple, compact, and easily reproduced means for coupling the electromagnetic pulses in coil 24 to the reed 10, for supporting the reed 10 in convenient fashion, and for coupling the reed vibrations to a suitable transducer 10.

In FIG. 3, four examples of particular configurations of reed 10 which would be suitable for use with the oscillator unit structure illustrated in FIG. 2 are shown. FIG. 3a depicts a simple reed configuration comprising a flat strip of hardened steel. In FIG. 3b, the acoustical length of reed 10 is increased with consequent savings of material by way of a diagonal cut at one end thereof. FIG. 3c illustrates a preferred reed structure for both an increased acoustical length and pleasing timbre of the resultant vibrations wherein portions are cut from the reed sides. In FIG. 3d, means for lengthening the reed 10 is illustrated wherein one end thereof is rolled in a spiral-like fashion.

Although the embodiments of the reed 10 illustrated in FIG. 3 are preferable for this invention, let it be clearly understood that the invention is not limited thereto and, in fact, may comprise any particular reed configuration whereby a pleasing sound may be produced in the ear of an awakening listener.

In FIG. 4, two alternate means for optimally coupling the transducer 14 to the reed 10 are shown. In FIG. 4a, the yoke 12 is provided with an auxiliary, sheet metal strip 52, generally extending parallel to reed 10; transducer 14 is mounted thereon by screw 50. Any physical displacement of reed 10 may then be coupled to transducer 14 through yoke 12 and, by means of sound waves, through sheet metal strip 52. In FIG. 4b, the transducer 14 is mounted by suitable means directly on the portion of sheet metal strip 52 adjacent reed 10 to effect more direct coupling of the sound waves and to effect a saving in space taken by the oscillator unit.

If space limitations are a critical factor in the combination of the electronic chime alarm with a clock and housing, the alternate embodiment illustrated in FIG. 5 can be utilized. In FIG. 5, like reference numerals designate those elements common to FIG. 1. Oscillator 8 is now supplied by the voltage supply V having one side connected directly to the emitter of transistor 20. Switch 6 may connect a source of reference or ground potential to the other side of voltage source V. In addition, the center tap of coil 24 is connected directly to ground. The modification comprises essentially the replacement of capacitor 30 and transducer 14 by a filter network comprising series-connected resistor 54 and 56 disposed between the extremities of coil 24 and a capacitor 58 connected from the common point of resistors 54 and 56 to the common point of capacitor 26 and coil 24. An output may be taken from the common point of resistors 54 and 56 and capacitor 58.

In this embodiment, the closing of switch 62 initiates oscillation through oscillator 8 in much the same manner as before. However, the vibrations in reed 10 create in turn variations in the flux adjacent coil 24 thus inducing a voltage in the sections of coil 24. This voltage is coupled by by means of the network including resistors 54 and 56 and capacitor 58 to the output thereof, the network also serving to filter out the low frequency pulses produced by oscillator 8. In this manner the transducer 14 of the embodiment of FIG. 1 is eliminated.

In another embodiment, the chime alarm unit 4 may be adapted for usage with a clock-radio. Such an embodiment is illustrated in FIG. 6 wherein the voltage supply V is coupled directly to oscillator 8. As before, an output is taken from transducer 14 by means of capacitor 32. Oscillator 8 is caused to oscillate by means of a switch 60, having a movable arm 61 disposed between the emitter of transistor 20 and ground. Associated with switch 60 is a single-pole double-throw switch 62; one stationary terminal 63 of switch 62 is connected to capacitor 32. A movable contact arm 64 is connected directly to the radio audio stage. The other stationary terminal 65 has coupled thereto an input from the detector and discriminator stages of the radio. Finally, the movable contact arms 61 and 64 of switches 60 and 62 respectively are connected by a mechanical linkage to the alarm setting mechanism of the clock 1: a dotted line denotes this connection in FIG. 6.

A mechanical switching arrangement may be provided within clock 1 whereby a number of functions for the clock-radio may be chosen. Such switching arrangements are well-known to the art. For example, by means of a selector switch, the radio may be manually turned on or off or placed in an automatic radio or in an automatic alarm function. By manual switching between the on or off positions or by actuation of the alarm setting mechanism at a desired alarm time in the automatic radio or automatic alarm functions, a power supply or the voltage source V can be connected to the radio stages to activate the radio in known fashion. In addition, by selecting the automatic radio function, the alarm setting mechanism can be disabled so that no mechanical movement is provided between switches 60 and 62 at the desired alarm time and a chime alarm does not occur.

More specifically, included with switches 60 and 62 are means for maintaining the movable contact arm of switch 60 in an open position and the movable contact arm 64 of switch 62 in engagement with the first stationary terminal 65 connected to the audio stage. Such means may include a spring or a latching mechanism. Thus, when the selector switch is in the automatic radio function, the alarm setting mechanism of clock 1 couples the DC voltage source V or a power supply to the radio stages but leaves switches 60 and 62 in the positions illustrated in FIG. 6 at the desired alarm time. The oscillator 8 is not energized and the radio signal from the detector and discriminator stages is coupled directly to the audio stage thereof, the sleeper awakening to the selected program material. If the automatic alarm function has been chosen, the alarm setting mechanism is not disabled and upon reaching the desired alarm time, the alarm setting mechanism closes switch 60 and simultaneously moves the movable contact arm 64 into engagement with the second stationary terminal connected to capacitor 32. Therefore, the output signal from transducer 14 is directly coupled to the audio stage of the radio and reproduced in the speaker thereof.

Thus, a particular advantage of this invention lies in such a use with a clock-radio, since the amplifying means 16 and sound reproduction means 18 are included therein without additional modification. However, it is to be understood that the invention is not limited thereto, as previously described.

Of course, when a clock-radio is used, adjustment of the vibration amplitude may be made by adjusting the volume control of the radio set or by adjustment of variable resistor 28. In addition, the invention is not limited to the particular switching arrangement shown in FIG. 6 but can be used with any arrangement which would permit energization of the oscillator 8 and coupling of its signal to the audio stages of the radio at a desired alarm time. Moreover, the particular embodiments of the oscillator including the oscillator unit structural modifications illustrated in FIGS. 4a and 4b and the transducer modification in FIG. 5 can be used with equal facility in the clock-radio unit of FIG. 6.

While this invention has been described with respect to a preferred embodiment and several illustrative examples thereof, it is to be clearly understood by those skilled in the art that the invention is not limited thereto and is intended to be bounded only by the limits of the appended claims.