US3440814A

US3440814A - Electric clock alarm system

Info

Publication number: US3440814A
Application number: US691301A
Authority: US
Inventors: Robert L Reimann
Original assignee: General Time Corp
Current assignee: General Time Corp
Priority date: 1967-12-18
Filing date: 1967-12-18
Publication date: 1969-04-29
Anticipated expiration: 1986-04-29

Description

April 1969 R. L. REIMANN 3,440,814

ELECTRIC CLOCK ALARM SYSTEM Filed Dec. 18, 1967 FIG. 2

INVENTOR ROBERT L. Rsmmu United States Patent 3,440,814 ELECTRIC CLOCK ALARM SYSTEM Robert L. Reimann, La Salle, Ill., assignor to General Time Corporation, Stamford, Conn., a corporation of Delaware Filed Dec. 18, 1967, Ser. No. 691,301 Int. Cl. G04c 21/16 US. Cl. 58-38 7 Claims ABSTRACT OF THE DISCLOSURE An alarm system for electric alarm clocks, including an electromagnetic vibrator driven by a synchronous motor, with the vibratory element being driven by A.C. flux from buzzer poles formed as integral parts of the synchronous motor. The electromagnetic vibrator acts as a frequency divider so that the striking frequency at the free end of the vibratory element is lower than the frequency at which most other buzzer alarms are driven. The first frequency division is achieved by means of a permanent magnet mounted on the vibratory element adjacent the buzzer poles so as to reduce the frequency of the driving impulses to the same frequency as that of the A.C. flux generated by the buzzer poles. The vibratory element is illustrated as a reed, made of magnetically impermeable material to avoid the shunting of magnetic flux away from the permanent magnet. Further frequency division may be achieved by designing the vibratory system to have a natural frequency of oscillation even lower than that of the frequency of the driving impulses, so that a striker element mounted on the opposite end of the reed from the permanent magnet strikes a cooperating bell at a submultiple of the frequency of the driving impulses. The reed is pivotally mounted between the permanent magnet on one end, and the striker on the other end, to permit greater latitude in manufacturing tolerances, and at the same time improve the performance and reliability of the alarm system. More particularly, the vibratory system can be mounted in any desired position, and thus with any desired orientation relative to the clock housing, without adversely affecting the performance thereof.

The present invention relates generally to electromagnetic vibrators of the type used in alarm systems in synchronous motor-driven electric alarm clocks and, more particularly, to an alarm system including a frequency dividing electromagnetic vibrator driven by A.C. flux from the same synchronous motor which drives the clock.

In copending application Ser. No. 634,687, filed Apr. 28, 1967, by Walter F. Kolodziej, entitled, Electromagnetic Vibrator, and assigned to the assignee of the present invention, there is described and claimed an improved alarm system for electric alarm clocks driven by synchronous motors. The present invention relates to 'an improvement in the alarm system described in the aforesaid copending application.

Thus, it is a primary object of the present invention to provide an alarm system having an improved frequency dividing electromagnetic vibrator which permits consid erable latitude in manufacturing tolerances while at the same time providing improved operating characteristics. More particularly, itis an object of this invention to pro vide such an alarm system in which the electromagnetic vibrator can be operated in any desired position, without being adversely affected by gravitational forces, for example. A related object is to provide such a system which permits the electromagnetic vibrator to be mounted with any desired orientation relative to the clock housing.

Another object of the present invention is to provide an improved alarm system of the foregoing type which 3,440,814 Patented Apr. 29, 1969 greatly facilitates manufacturing and assembling operation, thereby reducing the cost of the system.

It is a further object of the invention to provide an improved alarm system of the type described above which operates more eiiiciently than systems proposed heretofore.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIGURE 1 is a rear plan view of an electric alarm clock driven by a synchronous motor and including an electromagnetic vibrator embodying the present invention;

FIG. 2 is a top view of the electric alarm clock shown in FIGURE 1;

FIG. 3 is a perspective view of the alarm system included in the electric alarm clock of FIGS. 1 and 2, and embodying the present invention; and

FIG. 4 is a series of representative waveforms illustrating the operation of the alarm system shown in FIGS. 1-3.

While the invention will be described in connection with certain preferred embodiments, it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Turning now to the drawings, the illustrative electric alarm clock includes a conventional synchronous motor 10 mounted on the back of a mounting plate 11, which in turn is mounted on the back of a dial plate 12 and and spaced therefrom by means of a plurality of spacer posts 13. Since electric alarm clock mechanisms are well known in the :art, elements common to such clocks have been purposely omitted or shown simply diagrammatically. Thus, the synchronous motor 10 drives a conventional gear train (not shown) mounted between the mounting plate 11 and the dial plate 12 and including a pair of alarm control gear wheels 14 and :15. In order to pre-set the alarm for actuation at a preselected time while normally disabling the alarm, the forward gear wheel 14 is rotated by turning a manual control shaft 16 via alarm set knob so as to position a cam 17 on the back side of the forward gear wheel 14 relative to a cooperating slot 18 in the rear gear wheel 15. The rear wheel 15, which may be the hour wheel, is driven at a constant speed by the timing train, so that the slot 18 will always come into register with the cam 17 at a predetermined time, depending on the position at which the cam 17 is set. When the cam 17 and slot 18 are not in register, the cam serves to press the rear wheel 15 away from the forward wheel 14.

For the purpose of triggering the alarm mechanism for actuation at the pre-set time, a control lever 19 having a forward arm 19a and a rear arm 1% is pivoted on the mounting plate 11 so as to bias the rear gear wheel 15 forwardly toward the forward wheel 14 when the lever 19 is in its advanced position. The lever 19 which is biased clockwise by a spring 22, is normally held in a retracted position by means of an alarm-plunger 20 which serves to cam the rear arm 19b of the lever away from the motor 10, in a counterclockwise direction, thereby pivoting the lever about its pivot point on the mounting frame 11 to tilt the forward arm 19a of the lever rearwardly away from the gear wheel 15. When the alarm plunger 20 is retracted to trigger the alarm mechanism for actuation at a pre-set time, a slot 21 in the plunger comes into register with a projection 21a on the rear arm 1% of the lever so as to permit the lever to pivot in a clockwise direction to an intermediate or trigger position where the forward arm 19a bears against the back side of the gear wheel 15 under the urging Of the lever bias spring 22.

At the pre-set time, the slot 18 in the wheel rotates into register with the cam 17 so that drop-off occurs, permitting the control lever 19 to rock clockwise under the urging of the biasing spring 22, thereby freeing the resilient vibratory element 24 of the alarm system for actuation by A.-C. flux from a pair of

auxiliary poles

25, 26 formed as integral parts of the pole structure of the drive motor 10. This is the position shown in FIGS. 2 and 3.

In accordance with the present invention, the resilient vibratory element is a reed made of a magnetically impermeable material and pivotally mounted between the ends thereof with a striker mounted on one end of the reed for striking a sounding element, and a permanent magnet mounted on the other end of the reed for alternatively attracting and repelling the reed relative to the auxiliary poles in response to the A.-C. flux. A sounding element is mounted adjacent the striker, and the reed, striker, and permanent magnet form a spring-mass sys tern having a natural frequency which is a sub-multpile of the frequency of the A.-C. flux so that the striking frequency is a sub-multiple of the A.-C. flux. Thus, in the illustrative embodiment, the vibratory element 24 is in the form of a reed made of brass or other suitable magnetically impermeable material. The central portion of the reed is pivotally mounted on a fixed shaft 30 projecting rearwardly from the mounting plate 11 to permit the opposite ends of the reed to swing or pivot around the shaft 30.

For the purpose of providing an alarm sound, a striker element 31 mounted on one end of the reed 24 strikes a bell 32 in response to vibratory movement of the reed. The bell 32 is preferably mounted on the mounting plate 12 on the opposite side of the reed 24 from the

auxiliary poles

25, 26. With the arrangement provided by the present invention, the exact spacing between the striker 31 and the bell 32 is not critical, thereby permitting greater latitude in manufacturing tolerances with the attendant cost reductions. In fact, it has been found that the spacing between the striker 31 and the bell 32 can be varied by as much as 0.1 inch in a typical alarm clock movement without adversely affecting the performance thereof.

In order to apply periodic dirving impulses to the reed 24 at the same frequency as that of the A.-C. flux from the

auxiliary poles

25, 26, a permanent magnet 33 is mounted on the other end of the reed 24 directly opposite the

poles

25, 26. The alternating magnetic flux in the air gap between the

poles

25, 26 and the reed 24 attracts the permanent magnet 33 toward the

poles

25, 26 during one half of each cycle of the A.-C. flux, and repels the magnet during the other half cycle. Consequently, it can be seen that the alternate attraction and repulsion of the permanent magnet 33 toward and away from the

poles

25, 26 due to the alternating magnetic flux tends to vibrate the reed 24 at the same frequency as that of the A.-C. current which energizes the synchronous motor 10. Thus, with a conventional 60 cycle supply, the reed 24 is driven at a rate of 60 pulses per second, which is only half as fast as the more conventional driving rate of 120 pulses per second.

In keeping with the present invention, the permanent magnet 33 is mounted on the opposite side of the reed 24 from the

auxiliary poles

25, 26, and the reed 24 is made of a magnetically impermeable material so as to avoid the shunting of magnetic flux away from the permanent magnet 33. This feature, combined with the central pivotal mounting of the reed 24, permits considerable variations in the spacing between the

poles

25, 26 and the magnet 33 without any noticeable changes in the performance of the alarm system. For example, in a typical alarm clock embodying this invention, it has been found that the air gap between the auxiliary poles and the permanent magnet can be varied from 0.09 to 0.10 inch without any noticeable change in the operation of the system. It has also been found that the improved vibratory system provided by this invention can be operated in any desired position, without being adversely affected by gravitational forces, and thus the vibrator can be mounted with any desired orientation relative to the clock housing. These significant advantages not only improve the performance and reliability of the alarm system, especially when manufactured in mass production, but also permit considerable reductions in the cost of the system.

To further reduce the frequency of the oscillating striker 31 at the opposite end of the reed 24 from the magnet 33, the vibratory system is preferably designed to have a natural frequency of oscillation even lower than that of the driving impulses, e.g., a sub-multiple of the frequency of the driving impulses. The vibratory system should also have an amplitude considerably larger than that of the driving impulses, so that the impulses are in effect superimposed on the natural oscillatory motion of the vibratory spring-mass system to act as a synchronizing signal, as well as serving as a power input to sustain the vibratory movement of the reed. The natural frequency of the vibratory system is determined primarily by the dimensions and resiliency of the vibratory reed 24, and the weight and location of the permanent magnet 33 and the striker element 31 which are mounted on the reed. As will be apparent to those familiar with this art, the reed 24, the permanent magnet 33, and the striker element 31, which are the three main elements of the spring-mass system in the illustrative embodiment, may be varied in their relative dimensions, physical configurations, and materials of construction to provide a natural oscillatory motion of practically any desired frequency and amplitude. For example, the driving frequency of 60 cycles per second effected by the cooperation of the permanent magnet 33 with the AC. flux may be reduced to a striking frequency of 30 cycles per second, which produces a pleasant bell sound, by designing the springmass system to have a natural frequency of 30 cycles per second. Since the frequency of the driving impulses is already reduced to sixty cycles per second by the permanent magnet 33, the driving impulses are extremely effective in synchronizing the natural motion of the spring mass system at the desired frequency.

The frequency division effected by the electromagnetic vibrator when used as an alarm striker will be more clearly understood by reference to the wave forms in FIG- URE 4. Thus, waveform A represents the A.-C. flux generated by the

auxiliary poles

25, 26, and is the same waveform as the motor signal except that it is out of phase therewith. This A.-C. flux continually attracts and repels the permanent magnet 33 so as to apply driving impulses to the reed 24 as represented by waveform B in FIGURE 4. It can be seen that the driving impulses have exactly the same 60 cycle frequency as, and are in phase with, the A.-C. flux from the

auxiliary poles

25, 26. The vibratory motion of the reed 24 is represented by waveform C in FIGURE 4; thus, the striker element 31 strikes the alarm bell 32 at each of the three peaks C C C which occur at a frequency of 30 cycles per second, i.e., the same as the natural frequency of the mechanical resonant system comprising the reed 24, the striker element 31, and the permanent magnet 33. By comparing waveforms B and C, it can be seen that the strikes occur in synchronism with, but at half the frequency of, the driving impulses applied to the reed due to the cooperation of the permanent magnet 33 with the A.-C. flux generated by the synchronous motor. Since the frequency of the driving impulses is twice as great as the natural frequency of the vibratory system, intervening pulses represented by peaks C and C in Waveform C are also superimposed on the vibratory motion of the reed; however, these impulses are applied exactly half-way between successive striking peaks C C C i.e., when the striker element 31 is farthest away from the bell 32, so that they do not give rise to secondary strikes of the bell between the primary strikes represented by peaks 0,, C and C In accordance with one particular aspect of the present invention, the resilient reed 24 is pivotally mounted on the fixed shaft 30 by means of integralmounting members struck out of the body portion of the reed on opposite sides thereof. Thus, in the illustrative embodiment, a pair of generally V-shaped members, 40 are struck out on one side of the reed 24, and a similar Y-shaped member 41 is struck out on the other side-It can be seen that these oppositely facing V-shaped members 40, 41 cooperate to form a channel for receiving the fixed shaft 30. By appropriate dimensioning of the V-shaped members 40, 41, the shaft 30 may be held frictionally therein while still permitting free pivotal movement of the reed 24. More importantly, however, the mounting members 40, 41 are integral with the reed 24 so that vibration initiated by the driving impulses at one end of the reed, are readily transmitted through the reed to the striker element 31 at the opposite end. This particular mounting arrangement is also very economical to manufacture, since the mounting members 40, 41 can be formed by simply forming two slits in the reed and then stamping out the desired V-shaped configuration. During assembly, an appropriate high film strength lubricant should be placed between the shaft 30 and the mounting members 40, 41 to facilitate the pivotal movement of the reed 24 during operation.

As can be seen from the foregoing detailed description, this invention provides an alarm system having an improved frequency dividing electromagnetic vibrator which permits considerable latitude in manufacturing tolerances while at the same time providing improved operating characteristics. The electromagnetic vibrator can be operated in any desired position, withoutbeing adversely affected by gravitational forces, and thus can be mounted with any desired orientation relative to the clock housing. The particular embodiment illustrated greatly facilitates manufacturing and assembling operations, thereby reducing the resultant cost of the system. It has been found that an alarm system of the type illustrated operates considerably more efiiciently than systems proposed heretofore.

I claim as my invention:

1. In an alarm system for an electric clock driven by a synchronous motor which includes an auxiliary pole for generating alternating flux, an improved electromagnetic vibrator comprising the combination of a sounding element, a resilient vibratory element 'pivotally mounted between the ends thereof, a striker mounted on said resilient element on one side of said pivotal mounting for striking said sounding element when said resilient element is vibrated, and a permanent magnet mounted on said resilient element on the other side of said pivotal mounting adjacent said auxiliary pole so that said permanent magnet is alternately attracted and repelled relative to said auxiliary pole by said alternating flux to apply driving impulses to said resilient element at the same frequency as that of the alternating flux.

2. An alarm system as defined in claim 1 in which said resilient vibratory element, said striker, and said permanent magnet form a spring-mass system having a natural frequency which is sub-multiple of the frequency of said driving impulses so as to reduce the striking frequency to a sub-multiple of the frequency of the driving impulses.

3. An alarm system as defined in claim 1 in which said resilient vibratory element is made of a material which is magnetically impermeable.

4. An alarm system as defined in claim 1 in which said resilient vibratory element is a reed.

5. An alarm system as defined in claim 1 in which said sounding element is located on one side of said resilient element and said auxiliary pole is located on the other side of said resilient element.

6. An alarm system as defined in claim 1 in which integral mounting members are struck out of said resilient element on opposite sides thereof at an intermediate position relative to said striker and said permanent magnet, and a shaft is inserted through said mounting members to form said pivotal mounting for said resilient element.

7. In an alarm system for an electric clock driven by a synchronous motor which includes an auxiliary pole for generating alternating flux, an improved electromag netic vibrator comprising the combination of a resilient reed made of a magnetically impermeable material and pivotally mounted between the ends thereof, a sounding element mounted on one side of said reed near one end thereof, a striker mounted on said one end of said reed for striking said sounding element when said reed is vibrated, a permanent magnet mounted on the other end of said reed on the same side as said striker for alternately attracting and repelling said other end of said reed relative to said auxiliary pole in response to said alternating flux, said auxiliary pole being located on the opposite side of said reed from said permanent magnet, said reed, striker, and permanent magnet forming a springmass system having a natural frequency which is a submultiple of the frequency of said alternating flux so that the striking frequency is a sub-multiple of said alternating flux.

References Cited UNITED STATES PATENTS 2,092,715 9/1937 Grayson 58-21.l4 2,094,989 10/1937 Kohlhagen 5821.15 X 2,562,734 7/1951 Pheneuf 5838 2,782,592 6/1956 Gallagher et al. 5819 X 3,314,228 4/1967 Bowden 58-38 RICHARD B. WILKINSON, Primary Examiner.

LAWRENCE H. HAMBLEN, Assistant Examiner.

US. Cl. X.R. 5819