US1994537A - Automatic control plug for electrical appliances - Google Patents

Description

D. B. SCOVILLE March 19, 1935.

AUTOMATIC CONTROL PLUG FOR ELECTRICAL APPLIANCES Filed Aug. 18, 1953 Patented Max'.l 19, 1935 PATENT OFFICE AUTOMATIC CNTRL PLUG FOR ELECTRICAL APPLIANCES David B. Scoville, Crystal Lake, lil.

Application august i8,

i933, Serial Nm 685,674.-

e: emma tcl. coo-es) This invention relates to improvements in auto1 matic control plugs for electrical appliances, and more particularly for electric toasters, grills and like utensils for the cooking or preparation of food products wherein the application of heat requires` more or less accurate control.

The object of the invention is to provide a plug of substantially the same size and design as the standard plug used for connecting the cord or conductor cable directly with the appliance and incorporating therein a compact time switch mechanism which can be set to operate automatically to shut oil the current after the lapse of a given period of time.

A further object of the invention is to provide for the varying of the period of time during which the current is supplied to the heating element of the appliance in order to regulate the application of heat to the degree of toasting or cooking required.

A further object of the invention is to provide a device which may be substituted for the stand ard plug oi a non-automatic electrical appliance and thus convert it into an automatic device at very little cost. Perhaps the best example of its utility is in the ileld of electric toasters which are 'now being made to operate automatically, but at a cost considerably more than the ordinary or nonautomatic styles and so much so that they are, at present atleast, beyond the means of the average pmchaser. Moreover, the vast majority of the toasters in use are of the non-automatic type, so that the ability to equip relatively inexpensive toasters either old or new, to operate automatically by merely substituting one plug for another at buts. triiiing additional cost is a real boon to the users as well as to the manufacturers of I the older style devices.

Thus, while the idea of an automatic toaster is already a reality, the merit of the present invention resides in the simplicity and compactness of the control mechanism which permits it to be incorporated in a plug which can be interchanged with the ordinary type of plug, without otherwise altering the toaster or its electrical connections.

A preferred embodiment of the invention is disclosed in the accompanying drawing, in which Figure l is a view of the plug in elevation;

Figure 2 is a view in longitudinal section taken on line 2-2 of Figure l;

Figure 3 is a view in elevation of the inside of the top section of the plug when the same is parted along the line 3-3 of Figure 2;

Figure 4 is aview in elevation of the inside of the bottom section of the plug when parted along the same line as in Figure 3 but in the di rection oi the arrows llm-5i;

Ngure 5 is an enlarged detail view in cross section through the plug as taken on line 55 of Figure 2; and i3 Figure 6 is a detail view oi' the escapemerrt mechanism of the clock movement as taken on line 6 6 of Figure 2.

lt will be observed at the outset that, so far as the electrical connections are concerned, the l@ automatic plug follows closely the construction and design of the ordinary plug, in fact, theonly departure is a slight increase in the length to accommodate the added switch control mechanism. is well known in the art, a more or less 35 standard type of plug and plug connection has been developed for electrical household appliences, namely, a casing of 'insulating material having a pair of connectors exposed at one end to 'lt a pair of post-like terminals on the appli- 20 ance, the plug itself being attachedto one end of a cord having the usual connector at the other end for inserting into a light socket or outlet.

Following the standard design,`the plug con sists of a flat elongated casing l of a suitable 25 insulating material such as bakelite which is moulded in two sections 1a and 1b parted on a plane bisecting the casing in the direction of its Width. Bosses 2, 2 are moulded on the in-v terior of each half or section near opposite ends, 30

and screws 3, 3 are inserted through registering holes drilled and tapped in these bosses. When assembled the two halves of the casing 1 provide a chamber in which are mounted the electrical conductors and the time switch mechcmsm.

The electrical conductorsnin the plug have the form o! flat metal strips 4 and 5 vand are anchored in the upper sect-ion 1a (Figure 3) by ,means of rivets 6, 6 passing through enlarged 40 portions at their ends. AOne of the'strips 4 is continuous and lies along the side of the casing, whereas the other strip 5 is divided into two parts to forma simple formof switch for making and breaking the circuit, as will presently be described in greater detail. v

At the inlet end o f the plug the ends of the conductor strips4 and 5 are provided with the usualbinding posts`7, '7 to which the ends of the wires forming the cord s are attached, said 5 cord-entering through an opening 9 in the end of the plug. At the outlet end of the plug are the endwise opening sockets 10, 10 before mentioned, and separated by the longitudinally. elongated boss 3. within these sockets are the connector clips 11, 11 electrically connected at their inner ends to the conductor strips by the same rivets 6, 6 which anchor both to the casing section 1.

Located centrally of the interior of the plug and between the two conductor strips 4 and 5 is the time controlled switch mechanism, the parts thereof being rotative about two parallel axes spaced apart along the longitudinal center line of. the plug and extending transversely of the depth of the casing. This mechanism is essentially a variation of the so-called clock movement including a winding spring operatively connected with a train of gears controlled by a simple form of escapement, and a driven cam member which acts directly upon the switch to make and break the circuit through the plug.

For convenience in assembly a part of the control mechanism, consisting of the gear train and escapement `of the clock movement, is mounted in one section (the lower section 1b) of the plug casing, while the remainder, including a winding spring and knob together with the cam are mounted on the other (upper) half of the casing carrying also the conductor strips 4 and 5. The parts of the control mechanism are thus separated into groups which are assembled independently of eachother on their respective casing sections, the connections between them being made. by means of .spring fingers on the cam which register with projections on the face of the adjacent Wheel of the clock movement when the two halves of the plug are assembled. y

Referring first to the4 parts carried by the upperhalf of the plug casing, the winding spring 131s a simple form of clock spring coiled about a cylindric boss 14 on the inner face of the casing section and having an axial bore in which is a shaft 15 (Figure 5). On the inner end of the shaft is fixed the cam 16 consisting of a disc having a deep marginal fiange surrounding and enclosing the winding spring, the outer end of v the latter being fixed to a cam by means of a rivet 1'7 which projects from the outer face of the flange to provide a stop member for a pur- DOse to be later setforth. The inner end of the' spring is anchored to the boss 14 as by bending the end of the spring at rightangles, as at 13a, and inserting it into a slot 14 in the surface of the boss (Figure 5). Fixed to the outer end of the shaft 15 and exterior of the plug casing is the spring winding knob 18, preferably of frustro-conical shape having its tapered face knurled and direction and position arrow marked on its circular end face as shown in Figure 1.

Formed in the face of the cam flange is a notch 16 having a radial stop shoulder on one side and a gradually inclined surface leading from the periphery of the cam to the base of the notch. Now lying adjacent the'cam and in a general tangential relation thereto is the longer portion 5Il of the conductor strip 5, bent to curve inwardly toward theL cam and thence beyond where it terminates in overlapping and normally spaced relation to the shorter portion 5h of the same conductor strip. These overlapping portions thus form the make and break contact of the circuit, and if desired may be provided with suitable contact points. On the longer flexible contact strip 5n is a finger .19 projecting toward the cam and adapted in normal position to engage the cani notch .18% in which position cam are fixed a pair of spring ratchet fingers 20, 20 curvedv to conform to the arcof a circle and riveted at their corresponding ends at points diametrically opposite each other and midway between the center and periphery .of the cam face. These ratchet fingers extend in the same direction, that is, clockwise from their fixed ends and through an arc of and are bent outwardly from the face of the cam so that their free ends are spaced a short distance therefrom. Asheretofore explained, these ratchet fingers provide the connection between the parts of the control mechanism carried by the upper half section of the casing just described, and those parts of the mechanism carried by the lower section now to be described and identified. Briefly, the parts on the lower section constitute a simple clock movement made up of two series of alternatingly intermeshing gears and pinions, one series being journalled on a stub shaft 21 anchored at one end in the wall of the casing section and in axial alignment with the winding spring 13, and the other series on a similar stub shaft 22 spaced a short distance from it.

Since clock movements are well known, it will not be necessary to identify each individual gear and pinion, except to point out that it is made up of several units, 4each consisting of an inte,-l gral gear wheel and pinion, which progressively mesh with each other throughout the complete train, the gear of first unit of one series meshing with the pinion of the next unit, and so on. In this manner the desired gear reduction is obtained between the first and last units in the train. And finally, the rotation of the units is stamped therein and registering with the spring,

fingers 20, 20 on the cam. This gear wheel 23 meshes with the pinion of a unit 24 on the shaft.

22, which in turn drives a similar unit-25 on the shaft 21, this last unit driving still another 4unit 26 on the shaft 22. Now, the gear wheel of this last unit acts as the escapement wheel, having pointed teeth as shown in Figure 6. On the shaft 2l opposite the escapement wheel is a disc 27, somewhat thicker andheavier than the gear wheels and having a boss 27a to which is fixed the escapement lever 28 consisting of a metal strip vbent in U-shape with inwardly curved fingers engaging the teeth of the escapement wheel. The disc or balance wheel 27 rocks or oscillates on the shaft 2l with the escapement movement and by reason of its weight and-inertia controls the timing of the movement. 2

As hereinbefore pointed out, the gear train or clock movement just described is a self-contained unit wound by the lower section of the plug casing, and in assembling the two sections the projections or ratchet teeth 23'l on the gear wheel 23 register with the spring fingers 20 on the cam 16 and establish a pawl and ratchet connection between the two groups or parts of the switch control mechanism.

The manipulation of the switch control mechanism isquite simple, consisting merely in turning the knob in a clockwise direction through something less than one complete turn for the maximum heating period; about one-half turn for the minimum period and to an intermediate position for one corresponding intermediate period of heating. These stages of heat duration are gauged to the degree of toasting that may be desired, as for example, well done or dark, slightly done or light and medium done. Suitable position indicators are marked on the casing around the edge of the knob together with spaced markers corresponding in numberto the projections or ratchet teeth 23a over which the spring pawl fingers 20 click when turning the knob in the clockwise direction to wind the spring.

Thus assuming that the toaster is connectedl with the knob in the o ff position and the bread to be toasted is in place, the operator merely turns the knob in a clockwise direction to the position for the desired degree of toasting and then releases it. Now in turning the knob, the cam 16 rotates with it but its rotation is not transmitted to the gear train because the ratchet fingers 20 on the cam merely click over the teeth 23a on the rst wheel 23 of the clock movement. However, with the initial turning of the cam, the circuit is closed by the cam action of the finger 19 on the switch member 5a sliding out of the cam notch 16a and into the flange of the cam. Moreover, the spring 13 is wound by the rotation of the cam, so that on releasing the knob the cam is turned in the oppov site direction under `the action of the spring unwinding, but its return movement is regulated by the clock movement .which now functions through the pawl and ratchet connection.' 'I'his return movement of the knob and cam is relatively slow, taking, say, one or more minutes, depending upon the length of time required for toasting, and when the return movement is complete the cam comes to a stop at its starting point simultaneously opening the circuit as the' finger 19 on the switch member 5 again'enters the cam slot.

This procedure is repeated for each toasting operation, in each case the duration of the toast- I n ing being controlled by the position to which the winding knob is turned from the oil position before releasing it. And in this connection it will be noted that the mechanism is so designed that one revolution of the knob is the maximum of the winding movement. Therefore, to prevent an inexperienced person from turning the knob in excess of this limit, the stop member 17 is provided on the cam. Thus when the knob has been turned through one revolution, the stop 17 will strike the finger 19 and prevent its iurther turning. i

vSince different makes of toasters vary somewhat in the intensity of heat andtherefore the period required for toasting, the time adjustments of the plug can also be utilized in adapting it to the particular toaster to which it is applied, so that once the required period of time for proper toasting is determined by experiment, uniform toasting can be obtained thereafter by turning the knob to the same point. In fact, it would be an obvious expedient to provide means for limiting the turning of the knob to any desired amount, and when once set there would be no need thereafter for visually. determining the point at which the knob is to be released. In other words, it is equally if not more important that the lplug be adjustable to different makes oi' appliances, as it is that it can be regulated for diierent degrees of toasting, since uniform performance is the essential requirement.

In conclusion, therefore, the merit of the inventionresides in its construction as well as its application in the art. Thus, aside from the fact that makes possible the automatic operation of electric toasters and like appliances at but little additional cost and without altering its construction or design, the mounting of a simple yet practical time controlled switch mechanism within a plug of substantially standard dimensions is a novel accomplishment, particularly in the grouping of the parts into separate units mounted in the sections of a two-part casing, a construction that aifords ease of manufacture and assembly, not to mention the simplicity of repairs and replacement of parts.

Having set forth 'a preferred embodiment of my invention, I claim:

1. In a connector plug for electrical appliances comprising a casing divided longitudinally into sections, the combination of a contact switch, a switch operating cam and a winding spring mounted in one section and a clock movement mounted in the other section and including a' disc adapted in the assembly of said casing to be positioned face to face with said cam, and pawl and ratchetmembers carried by said cam and disc and providing a detachable connection between said cam and clock movement.

.2. In a connector plug for electrical appliances comprising a casing divided into sections and nav- 'ing a switch mounted therein, the combination of a rotative cam mounted on one of said sections i and having operative connection with said switch whereby the latter is shifted into circuit closing position in the rotation of said cam from a normally oif" position, a coil spring mounted in said section adjacent said cam and connected therewith for winding in the rotation of said cam, and a clock movement mounted in the other section and including a disc rotative on an axis coincident with the axis of said cam, the latter having resilient fingers adapted to. engage teeth on the face of said disc to interconnect the same when the sections of said casing are assembled.

3. In a connector plug for electrical appliances comprising a casing divided longitudinally into two half sections, the combination of a switch, a manually rotative switch operating cam, and a winding spring mounted in one of said sections, and a clock movement mounted in the other section and including a gear wheel rotative on an axis coincident with the axis of said cam, the latter having resilient fingers adapted to engage teeth on the face of said gear wheel to interconnect the same when the sections of said casing are assembled. f

4. In a plug connector for electrical appliances comprising an insulatedcasing parted longitudinally into two sections and enclosing a switch including a flexible metal strip adapted to be flexed into and out of circuit closing position, the combination of a rotative cam having a notch in its periphery to receive a projection on said contact strip in the oiI position of said switch, a

manually rotative finger piece exterior said castion between 'theunits mounted in their respective sections in the assembly of the casing.

5. In a plug connector for electrical appliances comprising an insulated casing parted 1ongitudinally into two sections, the `combination of a. switch including a metal contact strip adapted to be flexed into and out of circuit closing position, a cam adapted for bearing contact at its periphery with said strip and having a notch therein normally positioned to receive a projection on said strip in the olf position of said switch, a manually operative finger piece exterior said casing for rotating said cam disc, and a coil spring adapted to be wound in the rotation of said ilnger piece, all oi' said parts forming a unit mounted in one of said casing sections, and a clock movement journalled on stub shafts supported by the other section of the casing and including a gear wheel spaced from and in axial alignment with said cam and having annularly arranged projections in the face thereof, and spring fingers mounted on the face oi' said cam and adapted to engage the projections on said gear wheel to connect the clock movement in one section with 1 the parts in the other section when the same are assembled.

DAVID B. SCOVILLE.

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