US2252375A - Electric clock - Google Patents

Description

Aug. 12, 1941.

J. W. HOBBS ELECTRIC CLOCK Filed March 3, 1939 2 Sheets-Sheet l Jo/m Aug. 12, 1941. J. w. HOBBS ELECTRIC cnocx Filed March 3, 1959 2 Sheets-Sheet 2 Patented Aug. 12, 1941 OFFICE 2,252,375 ELECTRIC CLOCK John W. Hobbs, Springfield, Ill., assignor to John W. Hobbs Corporation, Springfield, 111., a corporation of Delaware Applieation. March 3, 1939, Serial No. 259,535}

12 Claims. .(Cl. 185-40) The present invention relates in general to electric clocks of the type adapted for use, in connection with vehicles, such as automobiles, and is more particularly concerned with springactuated clocks Which are arranged to be automatically wound by an electrically actuated rewinding mechanism.

In general, clocks of this type embody a ratchet wheel which is connected with the main driving shaft of the timing mechanism and arranged to be actuated through suitable pawls carried on a movable armature by a tension spring connected to the armature. The pawls engage the ratchet wheel for driving it in a forward timing direction. Associated with the armature is a suitable electro-magnet for actuating the armature to a new position for tensioning the driving spring, whenever the driving spring has reached a predetermined unstressed condition.

The rewinding of the clock is automatically accomplished by means of a switch arranged to be actuated in response to the movement of the armature, so that as the armature reaches a position in which the driving spring is in an unstressed or run-down condition, the switch is snapped to closed position to energize the electro-magn'et and return the armature to a position wherein the driving spring is again stressed, and in which the spring may again operate to drive the timing mechanism. At this position, the movement of the armature operates to open the switch and demagnetize the electro-magnet.

While such an arrangement works satisfactorily under maintained voltage conditions, conditions may prevail when operating the clock from a storage battery of an automobile which will result in unsatisfactory operation of the rewinding mechanism. For example, when the voltage of the battery of an automobile is below normal, or during starting of the car, particularly in the winter time, there may be times when there is insufiicient voltage to energize the electro-magnet sufiiciently to move the armature to a position wherein it will open the de-energizing switch in'circuit with the electro-magnet wind-. I

ing. Under such conditions, the electro-magnet winding will be energized for an abnormal period of time, with the result thatthe coil of the electro-magnet becomes overheated and there is the possibility of its being burned out or otherwise damaged.

Various devices for opening the circuit under such conditions have been suggested, such as thermostatically operated switches, fuses and the like.

In the present invention, it is a primary object to provide a main control switch which will be positively opened independently of the armature position, especially a control switch mechanism which will open the energizing circuit of the electro-magnetic rewind mechanism, when there is insufficient voltage to actuate the armature to a position corresponding to the fully stressed condition of the main driving spring.

A further object of the invention is to provide improved means for actuating the switch contacts to closed position in response to the armature reaching a position corresponding with a run-down condition of a main winding spring, the actuating means for the contacts being so arranged as to assure operation of the switch contacts by the reduced energy stored in the spring.

It is another object of the invention to provide control contacts for controlling the rewinding mechanism which are so arranged that the contacts will be opened and closed in such a manner as to cause the contact surfaces to mutually wipe each other, thus keeping the contacts clean and in good operating condition.

It is a further object of the invention to provide a control switch for the rewinding mechanism which is arranged to be closed by the movement of the armature during driving of the timing mechanism by the main spring, wherein the contacts will be closed with a snap action, and in which pressure will be applied by the main driving spring against the contacts to subsequently force them together, in the event that the circuit of the electro-magnetic rewinding mechanism fails to be closed due to dirt, corrosion or other material having accumulated on the contacts to prevent completing the circuit under normal pressure of the contacts.

Still another object of the invention is to provide in connection with the control switch for the rewinding mechanism, novel resetting means for actuating the switch contacts to open position, wherein the resetting operation is motivated by the electro-magnet for attracting the armature during the rewinding operation.

It is also an object of the invention to improve the operation of the electro-magnet and associated armature by providing projecting polar portions which normally extend into the air gap between the armature and electro-magnet, when the clock is in substantially run-down condition, thereby securing a magnetic path of relatively lower reluctance to the flow of magnetic flux between the poles of the armature and the electromagnet. Such an arrangement gives the rewinding mechanism more positive actuating characteristics.

Other objects and features of the invention will more fully appear from the following de tailed description, taken in connection with the accompanying drawings, which illustrate several embodiments thereof, and in which:

Figure 1 is a side elevational view of an electric clock embodying the features of the present invention, taken on the side of the electro-magnet to show the cooperative relationship between the electro-magnet poles and the armature poles, when the rewinding mechanism is in substantially run-down condition;

Figure 2 is a transverse sectional view showing the positions of the control switch mechanism and the armature, when the rewinding mecha nism has been energized and the driving spring is in fully stressed condition, taken substantially on the line 11-41 of Figure 1;

Figure 3 is a similar View showing the armature approaching a position in which the driving spring is reaching unwound condition, the switching contacts having been moved to a position where they will pass through dead center and be snapped closed;

Figure 4 is a similar view showing the armature at the limit of its movement by the main driving spring, the contacts of the switch mechanism having been snapped to closed position for completing the circuit through the rewinding electromagnet;

Figure 5 is a side elevational view of the clock looking toward the switching mechanism;

Figure 6 is an enlarged detailed view showing the manner in which the driving mechanism is connected with the shaft of the timing mechanism through a friction drive;

Figure '7 is an enlarged fragmentary plan view showing a modified form of actuating mechanism for opening the switch contacts; and

Figure 8 is a similar view showing another construction of mechanism for opening the switch contacts.

As shown on the drawings:

Referring to Figures 1 and 5, the mechanism of the present invention is mounted on a frame structure comprising a back plate H), a front plate H, and an intermediate plate it, these plates being supported in spaced-apart relation by suitably distanced pieces !3 arranged to maintain the plates in rigid assembled relation. The frame structure also forms a support for a conventional timing mechanism (not shown) include;

ing a gear train for actuating the hour and minute hands in proper speed ratio, and a conventional escapement mechanism (not shown) for controlling the operation of the driving mechanism.

The timing train is associated with a shaft M which is rotatably supported in the plate I I and provided with a spring friction connection for engaging the surface of a gear !8, as shown in Figure 6. This arrangement is conventional and permits setting movements of the timing gears and hands with reference to the driving mechanism. The gear 56, which is drivingly connected with a conventional escapement mechanism, is threadedly secured to one end of a driving shaft ll rotatably supported in the back plate I!) and a bearing sleeve 98 which is supported at one end on the middle plate l2.

The outermost end of the shaft l'l carrie a ratchet driving wheel !9 arranged to be driven in one direction by a pair of push-pawls and 2| on an armature 22. This armature embodies a pair of radially extending arm 23 and 24 in angularly disposed relation. The armature is provided with a tubular hub portion 25 which is rotatably mounted on the sleeve bearing I8, this hub portion serving as a spring drum for a main driving spring 26 coiled therearound, the spring being anchored at one end to the intermediate plate I2 and at its other end to the armature. The spring is so arranged that when the armature is rotated in a clockwise direction as viewed in Figures 2, 3 and 4, the main driving spring 26 will be tensioned and the pawls 20 and 2| will ride over the ratchet teeth of the ratchet wheel 59. Rotation of the ratchet wheel in the opposite direction is prevented by means of a detent pawl 27 pivotally mounted on the back plate l0 and provided with a suitable spring for actuating it into engagement with the ratchet wheel teeth.

When the armature is released, the pawls, by virtue of their engagement with the teeth on the ratchet wheel, will carry the ratchet wheel with them as the driving mechanism is moved under the force of the main driving spring 26. This driving operation is, of course, controlled by the escapement mechanism in the usual manner.

Provision is made for electrically actuating the armature in a direction to tension the main driving spring, that is, to move the armature in clockwise direction. For this purpose, there is disposed for operative association with the armature an electro-magnet having an energizing coil 28 wound on a suitable magnetic core. This core is fitted at each end with a pole assembly composed of a pair of nested U-shaped members 29 and 39 having their leg portions in spaced-apart relation and their leg edges arcuate, as shown at 3!.

The electro-magnet thus formed is secured to the front plate as by rivets 32 which extend through the plate and engage the pole assembly at each end of the electro-magnet. It will be noted that the intermediate plate is discontinuedto provide space for the electro-magnet, and that the electro-magnet projects past the intermediate plate and has its opposite side from the side which is secured disposed adjacent the backplate It. The armature arms 23 and 24 are deflected to respectively form an armature pole 33 for cooperation with the associated pole of the electro-ma-gnet. Transversely, the armature poles are arcuate to conform to the arcuate edges of the electro-magnet poles, and each armature pole is provided with a laterally extending tapered projecting portion 34 which is arranged to extend into the gap between the associated poles and de-- fine a magnetic path of decreased reluctancecompared to that which would ordinarily be formed if the pole did not include the extention. In other Words, the polar projection establishes a flux path through the gap which augments the operation of the armature and enables it to be more readily attracted during the beginning of the rewinding operation, particularly when the energizin voltage of the coil is low.

Movement of the armature away from the electro-magnet poles, that is, during the driving operation of the timing mechanism, is limited by a struck up portion 35 in the intermediate plate, this portion defining a stop in the path of movement of the outermost end of the arm 23 of the armature. It will be seen that the assembly is simplified and the depth of the timing mechanism may be decreased by virtue of having the armature arms 23 and 24 disposed in angular relation. This enables the electro-magnet to be placed at one side of the driving shaft I1 and eliminates the necessity of having to discontinue this shaft directly over the electro-magnet or provide for its passage through the coil and core thereof, as in the usual arrangement.

For controlling the actuation of the rewinding mechanism, a switch is provided in the space between the front and intermediate frame plates H and I2. As shown in Figures 2, 3, and 4,. this switch includes a pair of contacts 35 and 31 which are arranged for relative movement into closed and opened relation. The contact 31 is mounted adjacent one end of a flexible strip 38, the contact being at the free end of the strip. At its other end, the strip 38 is anchored between a pair of insulating members 39 and 40 which are supportingly mounted on a suitable bracket 4| secured to the intermediate plate. The contact 35 is actuated by a multi-armed lever having a pivotal mounting as shown at 42 on the intermediate plate and comprising the angularly disposed arms 43, 44 and 45, the contact 35 being carried at the free end of the arm 45. Movement of the contact arm 45 in a direction to move the contact 35 away from the contact 31 to open position is limited by a bracket 43 secured to the intermediate plate and having an upstanding leg extending into the path of movement of the arm. 45, the upstanding leg being provided with a pad 41 of cushioning material, such as felt for cushioning the impact of the arm against the stop and rendering the impact substantially noiseless.

The arm 43, at its outermost end, is bifur cated to provide a V-notch 43. For imparting a snap-action movement of the contact 36 from a dead-center position either toward the stop 46 or toward the contact 37, there is associated with the arm 43 a second arm 49 which is pivoted adjacent one end for swinging movement in a post or bracket 53 on the intermediate plate. At its other end, the arm 49 is provided with a head portion 5i defining a knife edge arranged to seat" in the V-notch 48 of the arm 43. The head 5| is retained in the notch 48 by means of a U- shaped retaining member 52 having its legs respectively disposed over the opposite end surfaces of the arm 43. A spring 53 surrounds the arm 49 with one end bearing against the post 50 and its other end bearing against the bridging portion of the retaining member 52, this spring acting to move the multi-armed lever with a snap action in the opposite directions from the dead-center position in which the arms 43 and 49 are in axial alignment.

Means are provided for swinging the multiarmed lever in response to movements of the armature during the driving and rewinding operations. For this purpose, closing of the contacts and 31 is accomplished by providing a pair of radially aligned spaced apart pins 54 and 55 which with the associated part of the armature form in effect a crank of variable throw, since the pins arearranged to successively engage the arm 44 during rotational movement of the armature in a counter-clockwise direction while driving the clock, as shown in Figures 2, 3 and 4.

With the contacts 351 and 31 in fully opened position, as shown in Figure 2, it will be apparent that as the armature moves in counter-clockwise direction, the pin 54 will be the first pin to engage. the lever arm 44. Since the pin 54 is disposed.

relatively closely to the center of rotation of the armature, this pin will strike the arm 44 at its extreme end portion, with the result that the angular, movement of the arm 44 will be relatively slower than the angular movement of the armature. Moreover, due to the relatively short effective lever arm of the pin 54 and the relatively long effective lever arm of the arm 44, the forces applied by the pin 54 under this condition will be increased, thus assuring movement of the contact 36 during a weakened condition of the main driving spring 26 which is approaching an unwound condition.

The pin 54 is arranged to carry the arms 43 and 49 to a position approaching dead-center.

At this point in the movement, the pin 55 engages the lever arm 44 at a point spaced from its outer end, and as the movement of the armature continues the pin 54 disengages the lever 44. Since the pin 55 is radially spaced a greater distance from the center of rotation of the armature than the pin 54, it will be seen that the angular speed of rotation of the multi-armed lever will be increased in relation to the angular movement of the armature. Thus, it will take only a very small angular movement of the armature to actuate the arms 43 and 49 through a dead-center position. As soon as the arms pass through dead-center position, the spring 53 is effective to actuate the contact 33 into engagement with the contact 31 with a snap action.

Since the contact 31 is not rigidly supported, the strip 38 will be flexed slightly and thus cause a wiping movement between the engaged surfaces of the contacts 36 and 31 to provide a good electrical contact. There may be times, however, when the circuit is not completed due to improper contact between the contacts 35 and 31. Under such conditions, the armature will continue to move in counter-clockwise direction until the pin 55 again reaches the lever arm 44, whereupon the main spring acts to apply increased pressure between the contacts and force them into good surface engagement.

The rewinding operation is now ready to take place, and as soon as the contacts 36 and 3'! are in closed position, the circuit is completed to the actuating coil 28 of the electro-magnet. This circuit may be from a source of power, such as a storage battery 55 which may have one of its terminals connected, as by a connection 51, which may be a conductor or may be a ground circuit from this terminal of the battery. The other terminal of the battery is connected through a conductor 58 to one end of the actuating coil 28, the other end of this coil being connected through a suitable conductor 59 to the contact supporting strip 38. The circuit then continues through the contacts 36 and 31 to the multi-armed lever which is connected from a point adjacent its pivot by a bridging conductor 53!] to the post 50 which is in grounded connection with the frame plate [2, from whence the circuit is completed through the frame structure back to the grounded side of the battery.

The circuit thus being completed through the actuating coil, the electro-magnet is energized and functions to attract the armature, moving it in a clockwise direction. This movement of the armature acts to again tension the main driving spring 25. Provision is made for opening the contacts 35 and 31 by resetting themovable contact 36 to the position engaging the stop 46. The resetting operation is accomplished by means of a third pin 8! which is arranged to engage the lever 44 on the opposite side from the side which is engaged by the pins 54 and 55. With this resetting arrangement, in which case the pin 6| will move the multi-armed lever in a counter-clockwise direction through deadcenter position, it is necessary that the armature during the rewinding operation be moved to a position corresponding to the fully stressed condition of the main driving spring. With sufficient voltage on the battery, the armature will always be moved to such position, but in the event that the battery voltage is low, which may occur during cold weather or during the starting operations of an automobile engine, the electromagnet may not be sufiiciently energized to move the armature sufiiciently to cause resetting of the contact 36 to opened position.

In order to assure that the switch contacts 36 and 31 are actuated to opened position and prevent continuous energization of the electromagnet coil, which might result in the burning out of this coil, direct resetting means are provided for resetting the contact 36 to open position independently of the position of the armature during the rewinding operation.

The mechanism for independently resetting the contact 36 may assume various constructional forms or arrangements. Figures 2, 3 and 4 illustrate one construction in which a small pivotally mounted armature S2 is associated with one of the poles of the electro-magnet. This armature is pivotally mounted on the intermediate plate, as shown at 63, and is normally biased for movement in a counter-clockwise direction by a suitable spring 64, movement in this direction being limited by a stop which may comprise an extension 55 on the bracket M. In this position, the armature is spaced away from the associated pole of the electro-magnet. However, as soon as the contacts 36 and 3'! are closed to energize the actuating coil of the rewinding mechanism, the armature 62 will be moved in a clockwise direction toward the associated pole of the electro-magnet.

As a result of the clockwise movement of the armature, an angularly disposed arm 65 of insulating material, which is carried by the armature, is moved into engagement with the outermost end of the flexible strip 38 carrying the contact 31. If desired, the outermost end of the flexible strip 38 may be rounded, as shown at El, to provide a curved surface for decreasing the frictional engagement of the insulating member therewith. As a result, the contacts 3? and 3% are moved as a unit, and the throw of the member 65 is sufficient to carry these contacts to a position wherein the multi-armed lever will pass through dead-center position and the contact 35 actuated with snap-action to fully opened position against the stop 45. Of course, this opens the energizing circuit of the coil 28. The poles of the electro-magnet, now being de-energized, permit the armature 62 to be moved by the spring 54 back against the stop 65, thus permitting the contact 31 again to assume its normal position.

It will be noted that during the resetting operation in this manner, when the contacts 35 and 3'! are being moved as a unit, these contacts, due to their support on arms which will move about different centers, will cause wiping action between the contacts. It will thus be apparent that wiping action is obtained between the contacts 36 and 37 during both opening and closing movements, thus tending to keep these contacts clean at all times, so that good electrical contact may be established when the contacts are closed.

Referring to Figure '7, a modified form of resetting mechanism is shown. In this form, the armature 52a is supported for rectilinear movements toward and away from the adjacent pole of the electro-magnet. The armature is provided with a supporting stem 68 mounted for longitudinal movement in upright deflected ends 69 and 10 of a supporting bracket H secured to the intermediate plate. The armature is biased into abutting engagement with the leg 10 of the bracket by a spring 12 surrounding the stem 63, one end of this spring engaging the leg 79 and the other end engaging a collar 13 carried by the stem. Movement of the stem, when the armature 62a is attracted toward the adjacent pole of the electro-magnet is transmitted to the end of the flexible strip 33 by means of a bell crank i i having a pivotal mounting, as shown at 75, on the intermediate plate. One arm of this bell crank, which is preferably made of an insulating material, is normally engaged by a pin 16 carried by the stem 63. The other arm of the bell crank engages the outer end of the flexible strip 38.

It will therefore be apparent that when the contacts 36 and 3? are engaged and the armature 62a is attracted, the bell crank will be pivotally moved in a counter-clockwise direction and deflect the flexible support 38, so as to move the contacts 35 and 37 in unison and cause resetting of the multi-armed lever to opened position of the contact 35.

Another modification of the resetting mechanism is shown in Figure 8. In this arrangement, the armature, as indicated at 621), is supported at the free end of a support H which is pivotally mounted at its other end, as shown at 78, on the intermediate plate, the pivot of this support being disposed adjacent the pivotal mounting of the multi-armed lever. It will be noted that the outermost end of the support ll underlies the free end of the flexible strip 38 and that this end of the support is provided with a block 19 of insulating material. This block has a curved cam surface 80 which engages the free end of the flexible strip 38. It will be noted that this cam surface is so arranged that as the armature begins its movement toward the associated pole of the electromagnet, this being the time when the electrical attraction is least, there will be very little movement or flexing of the strip 38. However, as the armature approaches the associated magnet pole, the throw of the cam is gradually increased as the attractive forces are increased. In this arrangement, the spring effect of the strip 38 is utilized to return the armature to normal position away from the electro-"nagnetic pole, where it may be arranged to engage a suitable stop 8i which may, if desired, be one of the distance pieces $3 for interconnecting the frame plates.

From the foregoing description, it will be apparent that the herein described invention provides in a spring-driven clock or timing device an improved rewinding mechanism which embodies an improved arrangement of a rewinding electromagnet and armature, wherein projections are provided for extending into the gap between the electro-magnet poles and the armature poles, when the clock is in substantially run-down condition, thus providing and determining a magnetic path of decreased reluctance; which has improved contact actuating means for controlling the rewinding operation, particularly when the battery or supply voltage is low; which utilizes novel pin arrangements for actuating the switch contacts into open and closed positions in responseto armature movements; provides an improved switch having contactsarranged to beengaged and-disengaged with wiping movement, so as to :maintain the contacts in clean condition at all times; and which embodies an improved mechanism for positively opening the control contacts for resetting the contacts to open position, independently of the position of the armature, this resetting mechanism being actuated magnetically from one of .the poles of the rewinding electro-magnet.

It is, of course, to be understood that although I have described in detail several embodiments of my invention, the invention is not to be thus limited but only insofar as defined by the scope and spirit of the appended claims.

I claimas my invention:

1. ,A timing device including a driving mechanism having an actuating spring, electrically operable. means for intermittently stressing'said spring, a circuit connection to said means, a switch in said circuit arranged to be opened by the operation of said means'when substantially fully stressed condition of the spring is reached, and auxiliary means magnetically actuated by said first means for opening said switch in the event that the first means is energized insuiiiciently to fully stress the spring.

2. In a timing device, a movably mounted armature, a spring normally acting to move the armature in a direction for driving the device, an electro-magnet"energizable to move the armature in a non-driving direction for stressing said spring, an energizing circuit for said electromagnet, a switch having contacts in said circuit arranged to be closed in response to armature movement to a position in which-the spring is substantially unstressed, and auxiliary means magnetically operable by said electro-magnet, when it is energized, for opening the contacts of said switch.

3. In a spring driven timing device, a rewinding mechanism for intermittently stressing said spring and including an actuating electro-magnet, an energizing circuit for said magnet, a switch having contacts for normally opening and closing said circuit in response to operation of the rewinding mechanism, and auxiliary means actuated by said electro-magnet for opening said contacts to terminate each rewinding operation of said mechanism in the event of failure of the rewinding mechanism to open said contacts.

4. In a spring driven timing device, a rewinding mechanism comprising an electro-magnet including a pair of field poles, a rotatably mounted armature operatively associated with said poles and normally biased by said spring for movement away from said poles, said armature being moved in the opposite direction when the electro-magnet is energized, an energizing circuit for said electro-magnet, a switch having contacts in said circuit arranged to be closed in response to a predetermined movement of the armature away from said field poles, and auxiliary means for actuating the contacts to open position independ ently of said'first armature in response to the energization of said electro-magnet and including a second armature operatively associated with only one of said field poles.

5. In a timing device, a driving mechanism havingan actuating spring, electrically operable means including an operating coil for intermittently stressing said spring, a supply circuit for said coil, and a control switch in said circuit comprising av pair of contacts, a pivotally mounted support for one of said contacts swingable in reversed directions through a dead-center position between fully opened and fully closed relation, with respect to the other of said contacts, spring means for biasing the support away from its dead center position, and means operative for transmitting driving movements of the mechan'ism to the support for moving the support in a contact-closing direction, said operating means being so arranged that the ratio between the movements of the mechanism and the support will initially be of one value until the support approaches its dead-center position, and another value as the support is moved through its deadcenter position, said means comprising a pair of support contacting members moved by said mechanism and having diiferent effective lever arms;

6. In a timing device, .a spring actuated driving mechanism including a rotatable member, electrical rewind mechanism for rewinding the driving mechanism. and having an operating coil, asupply circuit for said coil, a control switch in said circuit including a pair of contacts, a pivotally mounted support forone of said contacts including an actuating arm, a pair of radially spaced pins carried by said member arranged to successively engage the actuating arm during driving movement of the driving mechanism and acting to move said support in contact-closing direction, the innermost of the pins engaging the arm prior to its engagement by the outermost of the pins.

7. In a spring actuated timing device, an electric rewind mechanism for intermittently stressing said spring, said rewind mechanism including an actuating coil, a switch for controlling said coil arranged to be normally opened in response to the operation of the rewind mechanism, said switch comprising a pivotally supported first contact arranged for snap movements to either side of a dead-center position, a resiliently supported second contact engageable by the first contact when the first contact is moved to one side of its dead center, and auxiliary means operable independently of the rewind mechanism and including an armature actuated by said coil for moving the second contact towards the first contact to cause simultaneous movement of the engaged contacts until the first contact has passed through its dead center, whereupon the first contact is snapped to open position on the other side of its dead center.

8. In a clock, a movable member, a driving spring biasing said member for movement in one direction, electro-magnetic means intermittently energizable to move the member in an opposite direction and stress the driving spring, contacts normally actuable in response to the movements of said member for controlling the connection and disconnection of said electro-magnetic means relative to an energizing circuit, and auxiliary mechanism for actuating the contacts from closed to open position independently of their actuation by said member, each time said electro-magnetic means is energized, said mechanism including a member magnetically influenced by said electromagnetic means.

9. In a timing device, a pivoted armature, a

spring for driving said device, said spring normally biasing the armature for movement in one direction, an electro-magnet energizable to move the armature in an opposite direction for stressing said spring, an energizing circuit for said electro-magnet, switch means having contacts for controlling said circuit, switch operating means including a pivoted arm biased for movement to opposite sides of a dead-center position for respectively opening and closing the switch contacts, means carried by the armature for actuating said arm through its dead-center position, said means including a pair of radially spaced projections for successively engaging the arm during movement of the armature in one direction, the innermost projection initially engaging the arm and the outermost projection being arranged to engage the arm when it is adjacent its dead-center position.

10. A timing device comprising a driving member actuated in one direction by a spring, electromagnetic means including a coil energizable to intermittently actuate the member in a direction to stress said spring, a supply circuit for said coil, a control switch in said circuit including a pair of contacts, a pivotal support for one of said contacts arranged for snap movements to either side of a dead-center position, a flexible support for the other of said contacts, means for moving said one of the contacts through dead-center position in a direction toward the'other contact in response to movement of the driving member by said spring, and means independently actuated by the energization of said coil for flexing the support of said other contact to move both contacts in a reversed direction with respect to the closing direction of said one contact, and carry said one of the contacts through its dead-center position to enable snap movement thereof to open position.

11. In a, spring actuated timing device, an electric rewind mechanism for intermittently stressing said spring, said rewind mechanism including an actuating coil, a switch for controlling said coil arranged to be opened in response to the operation of the rewind mechanism, said switch comprising a pivotally supported first contact arranged for snap movements to either side of a dead-center position, a resiliently supported second contact engageable by the first contact when the first contact is moved to one side of its dead center, an armature moved in response to the energization of said coil, and a cam surface movable in response to the movement of said armature, said surface being arranged to simultaneously move the engaged contacts in a direction to carry the first contact past its dead-center position and enable it to snap to open position on the other side of its dead center.

12. In a spring actuated timing device, an electric rewind mechanism for intermittently stressing said spring, said rewind mechanism including an actuating coil, a switch for controlling said coil arranged to be opened in response to the operation of the rewind mechanism, said switch comprising a pivotally supported first contact arranged for snap movements to either side of a dead-center position, a resiliently supported second contact engageable by the first contact when the first contact is moved to one side of its dead center, an armature supported for movement in response to the energization of said coil, and a cam member moved by said armature, said cam having a surface arranged to move both the engaged contacts in a direction to carry the first contact in an opening direction past its deadcenter position, said cam surface being arranged to move the contacts at an accelerating rate of movement.

JOHN W. HOBBS.

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