US1979087A - Alarm clock - Google Patents

Description

Oct. 30, 1934. H, WARREN 1,979,087

ALARM CLOCK Fild Oct. 29, 1952' Z InvenLoP Henm BWaPPen, 'b Wm His AGEOPne Patented Oct. 30, 1934 ALARM CLOCK Henry E. Warren, Ashland, Mass., assignor to Warren Telechron Company, Ashland, Mass., a

corporation of Maine Application October 29,

4 Claims.

My invention relates to alarm clocks and in particular to the alarm mechanism thereof as applied to electric motor driven clocks arranged to have the alarm spring wound by the clock 8 motor.

In an electrically driven clock the driving motor is usually a small, low power, synchronous motor geared directly to the clock hands. If this same motor is employed to wind an alarm spring the 10 power available for the latter purpose is necessarily limited. Nevertheless it is desirable to store sufficient energy between alarm periods to operate an alarm mechanism for several minutes and produce a loud, clear alarm when the mecha- 16 nism is called upon to function. It is the primary object of my invention to provide a simple alarm mechanism which utilizes the energy stored in a spring or its equivalent in a highly efficient manner and requires no additional '20 power-absorbing attachment for its regulation when in operation. In carrying my invention into effect in its preferred form I provide a bell with a rotary hammer driven directly by a spring.

The hammer utilizes centrifugal force and grav- 26 ity for its own regulation, acting in the manner of an escapement for the driving spring in a simple and efficient manner more fully explained hereinafter. i

The accompanying drawing shows in Fig.1 a perspective view of the essential parts of an electrically driven alarm clock with which my invention is combined, and Fig. 2 is a detail view of the hammer of my alarm mechanism showing its position just after striking the bell and before completing its gravity escapement operation. The features of the invention which are believed to be novel and patentable will be pointed out in the appended claims.

In Fig. 1, I show a somewhat exploded perspective view of an alarm clock, omitting the clock dial and casing. The clock is of the type having the hands driven through gearing from a small synchronous motor 10 which motor also stores energy in a spring 11 for operating the rotary alarm mechanism which acts upon a bell or gong 12. It will be understood that some of the supporting structure has been omitted for the sake of clearness.

Integral with the motor 10 is a casing 14 which contains reduction gears reducing the speed from the motor rotor, not shown, to a terminal shaft 15. A pinion 16 on this shaft drives a train of gears 1'7, 18 and 19 leading to the clock hands through a friction clutch 20 having one part secured to the minute hand shaft 21. 22 repre- 1932, Serial No. 640,269

sents the minute hand of the clock secured to shaft 21. The hour hand 23 is mounted on 1101- low shaft 24 and this shaft is driven through back gears 24, 25, 26 and 2?, gear 24 being secured 1 to shaft 21 and gear 27 to hollow shaft 24. The 6 clutch 20 permits the clock hands to be set by hand.

Adjacent gear 27 is an alarm-setting gear 31 secured with a pointer 32 to a hollow shaft 33. The alarm-setting pointer and gear may be set from the rear of the clock by turning a shaft 28 having a knurled head 29 on its rear end and a pinion 30 on its forward end meshing with the alarm-setting gear 31. The alarm-setting gear. 31 is normally stationary in the position to which 7 it has been set and is lightly pressed towards gear 27 by a spring member 34.- The lower portion of this spring member is attached to clock plate 35, the central portion surrounds hollow shaft 33 and has portions bulged to press against gear 31 and the upper end is bent to the rear and is formed with an offset finger 36 which normally prevents the alarm mechanism from functioning by blocking rotation of the hammer support 3'7. The gear 27 which in this case makes one revolution in twelve hours is provided with cam-like finger 38 extending from its forward face and against which spring member 34 normally presses gear 31.. In the path of rotation of finger 38, gear 31 has an opening 39 such that when the opening registers with the finger 38, gear 31 moves axially towards gear 27, finger 38 entering opening 39. This allows sufficient movement of spring 34 towards the rear that its finger 36 is moved to disengage the rotary hammer support 37 whereupon if the hammer is otherwise in condition to operate it does so and rings the bell 12. It is seen that this alarm release may be set to operate at any time during a twelve hour period depending upon the rotary setting of gear 31. If a twentyfour hour alarm is desired the alarm setting and release device just described will be associated with a gear or other rotary member which makes one revolution in a twenty-four hour period. A short time after finger 38 enters opening 39, gear 31 will be moved axially away from gear 27 by the forward sloping surface of finger 38 moving against the adjacent surface of opening 39 as gear 2'7 rotates. This will return the finger 36 to alarm-blocking position which is the position represented in Fig. 1. It will be understood that the alarm-setting pointer 32 will indicate on a suitable dial the time for which the alarm is set to be released.

The motor 10 also supplies energy to wind the alarm spring 11 through gears 40, 41, 42 and a friction clutch 43 having one part secured to the winding arbor 44 of the spring. The gear reduction between motor 10 and the spring-winding arbor will be sufficiently large that the spring is very slowly wound up and energy stored therein very gradually over a considerable period of. time so as not to overtax the synchronous motor: and cause it to drop out or run below exact synchronism. If motor 10 is overloaded so as to cause it to operate below synchronism the device becomes. useless as a clock. The clutch 43 is provided to prevent blocking the synchronous motor in case the spring becomes wound uptoo. tight. This clutch should be adjusted. to. slip at: a torque practice, such for example as a drop in voltage to;

15 percent below normal. By choosing a proper gear reduction and a sufficiently long winding period, ample energy may be stored in the alarm spring to satisfactorily operate my improved alarm mechanism without interfering with the time-keeping qualities of the ordinary synchronous clockmotor. What has been said about winding the alarm spring by the same synchronous motor which drives the clock should not be construed to mean that I intend to limit my invention in this respect sincemy improved alarm mechanism might be operated with a handwound spring-or'by aweight although it does not require'so much energy as has heretofore: been requiredto operate mechanical bell alarms-in a the hammer 50.- Aligned' openings are provided ismoved automatically to and. from a blocking near the ends of the two limbs of "the u-shaped holder 37 andthe hammer 5'0 is'loosely' inserted. in these openings with the shaft 46 passing.v freely through a slot 5 1 at the center of the hammer. The hammer 50 is thus free to slideendwise' in member 37"to the extent-permitted by theslength of slot 51. Thishammer is positioned-beneath one edge of the gong 12- substantially'as represented in Fig. 2'. The spring 11 tends tO I'0tate=.the1.ham;- mer assembly in a-clockwise direction.

The operation may be describedlas follows: If the hammer'is rotated slowly it is evident that every half revolution the double-ended hammer part will dropby' gravity sothat shaft 46 rests against the upper end of the slot. Thisdropping action will take-place as the hammer; part: approaches avertical position. Under these con.- ditions it will clear the bell and be unimpeded. If, however, the device isrotated rapidly,.centrifugal force will cause-theunbalancedhammer slide 50 to remain in an unbalanced position against the force of gravity-asit approaches a positionwhere it would" otherwise. drop' to: the oppositeend of the slot 5'12 Under these conditions the end of the-hammer which is then uppermost willnot clear the bell (see. Fig. 2) and thehammer will strike the bell: a sharp square blow. This brings the rotary movement to a sudden stopand' causes a slight. reboundof the hammer. C'entrifugalforce is. entirely removed by the stopping of rotation andthe hammer member drops to theposition shown inFiig; 1 during the period of rebound so that when rotatedfurther in the clockwise' direction it clearsthebell without again contacting therewith for that half revolution. The sharp blow between the striking surfaces at substantially right angles to the direction of impact, the immediate rebound of the hammer and the clearing of the bell produce a loud, clear ring of the bell without mufiiing. The energy of momentum of the revolvingparts which isexpended when the bell is struck is mostly in the hammer itself. Under the influence of the energy stored in spring 11 the action of this device is such that it accelerates for one half revolution, gaining sufficient speed to hold the hammer out in the unbalanced position to strike a sharp. clear hammer blow on the bell, the hammer is stoppedand rebounds and drops by gravity and starts to accelerate again without again touching the bell until the next half revolution when the opposite end is held out by centrifugal force and strikes the bell. The harder the blow struck the greater the rebound so that the devicetends. to operate. at a fairly constant. average speed" and cannot: run away. If and when the spring. becomes sufiiciently run. downso that. the device will no longer: accelerate sufliciently to hold the hammer in the unbalanced condition against the force of gravityas. it approaches the bell during. a; half revolution, it. clears the. bell every halfrevolution and continues to accelerrate for a complete revolution. so. as to strike. a blowv every complete revolution. Finally it may make. one and one-half or two revolutions between striking operations. It is' thus evident. that the device in its action in striking the bell becomes its own speed. regulator'and escapement. The energy from the spring is very efficiently utilized since practically: all isexpended in striking sharp, square hammer blows against the. bell and none is wasted in a separate speed governor or in a fric-- tional wiping action of the hammeracross the edge of: the. bell.v

In addition to the. alarm release finger 36 which positionwith respect. to the hammer in accordance with. the time of day and the setting of the; alarm pointer 32, I alsoprovidea manually operated slide 52 which may be shoved forward from the rear of the clock to bring the downwardly-bent forward end into the path of rotation of; the-hammer support 37. This slide 52 may beusedto stop the ringing of the alarm-after being released automatically or it may be used to prevent the ringing of the alarm entirely.

What. I claim as new and desire to secure by Letters Patent in theUnited States is:

1. An alarm mechanism comprising a horizontally disposedrotary shaft, motor means for urging said shaft to rotate in a given direction, a hammer member rotated by said shaft, said ham.- mer member being supported on said shaft so as to be freely movable to a limited extentalong a.

given radial line with respect to said shaft, whereby when said shaft is rotated slowly the hammer member seeks positions and has a path of movement determined by the force of gravity, and when rotated rapidly the position of said hammer and path of movement is determined by centrifugal force and a bell having a portion, a surface of which extends into and at right angles to the path of movement of said hammer above said. shaft only when the position of the hammer is determined by centrifugal force, the arrangement being such that the bell acts as a stop for the rotary movement of said hammer when. the latter strikes said surface. of the bell andcauses a rebound of the hammer in, thereverse direction of rotation during which the hammer drops by gravity to a non-striking position.

carried by said shaft, said support having members on opposite sides of the shaft provided with radially aligned openings, a hammer slidably mounted through said openings, said hammer having a slot through which the shaft extends for limiting the radial sliding movement of the hammer, and a bell above said shaft in the path of movement of the outer end of said hammer only when the latter is slid towards the bell, the striking surfaces of said bell and hammer being substantially at right angles to the direction of impact.

3. A bell-ringing mechanism comprising a horizontal shaft, a bar-like hammer mounted transversely to said shaft and rotatable therewith, guiding means for said hammer permitting limited endwise movement thereof in opposite directions from a central position with respect to said shaft, a bell having a surface portion above said shaft positioned to be squarely in the path of rotation of only that end of the hammer which is furthest from the shaft when the hammer is slid to either of its extreme positions and is substantially vertical, and means for rotating said shaft and accelerating said hammer from standstill to a speed where the hammer remains in either of its extreme positions by centrifugal force against the force of gravity, whereby the hammer strikes said surface of the bell, stops rotating and rebounds, drops from one extreme position to the other by gravity and then repeats the cycle of operation.

4. A bell-ringing mechanism comprising a horizontal shaft, 3, support having guides transverse to the shaft, a bar-like hammer supported for limited endwise movement in said guides, said parts being rotatable with said shaft, a bell having a surface above said shaft extending squarely into the path of rotation of an end of said hammer only when said end is in its furthest position from the shaft, and means for rotating said shaft and accelerating said hammer from standstill to a speed where the hammer bar will be retained in striking position by centrifugal force against the force of gravity, whereby when said hammer is in substantially a vertical position an end of said hammer strikes said surface of said bell, stops, rebounds and drops by gravity to a position where it clears the bell and then starts accelerating again to repeat the operation.

HENRY E. WARREN.

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