US2407764A - Thermostatic switch plug - Google Patents

Description

Sept 17, 1946- B. F. oEBBEcKE 2,407,764

THERMOSTATIC SWITCH PLUG Filed April 23, 1943 .8 BY A ATI'D RN EYS UVVENYUR.

Patented Sept. 17,Y 1946 UNITED STATES PATENT OFFICE THERMOSTATIC SWITCH PLUG Bernard F. Oebbecke, Pittsburgh, Pa.

ApplicationApril 23, 1943, Serial No. 484,307

(Cl. 20G-136.5)

4 Claims. 1

My invention relates to circuit controls for electrical appliances, and has among its objects and advantages the provision of an improved thermostatic switch. Y

An object of my invention is to provide a thermostatic switch wherein the operator is en` abled to vary the point at which the thermostat automatically opens and closes the circuit so that the electrical appliance can be maintained substantially at a predetermined and constant temperature.

A further object is to provide a thermostatic switch wherein a contact carrying thermostatic member of novel construction associates with the pilot terminal only when the current flows to the heating element from which it derives the proportional temperature to open the circuit at a predetermined set standard; while in closing the circuit, the thermostat reacts to the accelerated cooling iniluence of the surrounding air of room temperature on the interior of the switch through openings of novel design on the sides of the casing in conjunction with a spring.

A further object is to provide a thermostatic switch so designed as to function in a highly efficient manner for use on electric irons, but in which the design is such as to be applicable to the other types of electrical appliances.

In the accompanying drawing:

Figure 1 is a face View of a thermostatic switch in accordance with my invention.

Figure 2 is a sectional view along the line 2 2 of Figure 1.

Figure 3 is a View taken from the position indicated by line 3 3 of Figure 2.

Figure 4 is an enlarged sectional View of an adjusting knob.

Figure 5 is a view taken from the position indicated by line 5 5 of Figure 4.

Figure 6 is a sectional View of the switch housing illustrating the air circulating openings therein.

Figure 7 is a sectional view along the line '1 1 of Figure 1, and

Figure 8 is an enlarged side View of a bimetallic element.

In the embodiment of the invention selected for illustration, the switch housing I5 comprises sections I2 and I4 of insulative material and appropriately recessed to provide accommodation for the structure forming the switch mechanism. These sections are connected into a unitary structure by a U-shape spring clamp I6 lying in a groove I8 in the outer side faces and one end face of each ofthe sections I2 and I4.

The opposite ends of the sections I2 and I4 are shaped to provide an annular neck 2B having a circumferential groove 22 for the reception of a tie element 24. The structure so far described is more or less conventional with respect to size and general contour.

In the section I4 is mounted the usual conductor strip 25 and socket 23 for connection with one prong of the appliance. This strip is made secure by a screw 35 and includes the usual terminal screw 32 for connection with the wire 34 of the cord 35.

A second conductor strip 38 is mounted in the section I4 and is made secure by a screw 40. This strip is also provided with a terminal screw 42 connecting with the second wire 44 of the cord 36.

One end of the strip 38 underlies the short leg 46 of a U-shaped thermostatic element 48 of bimetallic construction. Two screws 50 are threaded through the strip 33 and the leg 46 for Xedly securing the thermostatic element in addition to electrically connecting the two. A recess 52 is formed in the outer face of the section i4 or accommodating the heads of the screws 55, which recess is lled with an insulative material 54.

The second socket 55 is electrically connected with a lateral extension 58 provided with a contact point E55 best illustrated in Figure '7. Screws 52 secure the sockets 28 and 5t to the section I4. The contact point 60 is arranged in axial alignment with a second contact 64 carried by the longer leg GS of the thermostatic element 48, so as to close the circuit through the appliance through electrical engagement between the two contact points.

In Figure 8 the thermostatic element 48 is so designed as to cause its longer leg 66 to bend upwardly throughout its length 68 and its remaining length 'I5 to bend downwardly, as when viewing Figure 8, when heated. The propo-rtional lengths 58 and lil are calculated so that their compound deflection maintains the contact point 64 substantially parallel to the stationary contact point E5 at any desired temperature within the desired limit. This arrangement reduces arcing to a minimum, thereby prolonging the life of the contact points.

A further advantage in the compound arrangement of the thermostatic element resides in the shortening ci the travel distance of the movable contact point, which permits both cooperating forces, active in opening and closing the circuit, to be kept relatively small, which results in a liner interplay of those two cooperating forces and in turn permits a iiner regulation to and maintenance of the desired predetermined temperature.

The thermostatic element responds to the direct heat of the heating element only in opening the circuit at the desired set temperature. This is the exact proportional temperature in the interior of the switch structure about which the thermostat functions to maintain the desired predetermined temperature: in the heating appliance. Non-association of terminal and thermostat during the orf periods prevents a further increase of temperature in the latter by direct contact, leaving only the possibility of a slight increase through radiation from the other parts of the switch. This low marginal increase of heatin the interior of the switch above the proportional is easier absorbed by the surrounding air thereby promoting an accelerated cooling of the thermostat below the proportional to close the circuit. F'or an exceptional appliance such as an electric iron, the cooling process within the switch structure is carried further. During the unavoidable rest periods in which the cloth is prepared for ironing, a greater amount of heat is absorbed by the switch through radiationwith a tendency toward equalization, causing a slightly larger temperatural margin above the proportional heat within the switch structure. This constitutes on the one hand a saving of electricity, and on the other hand it may cause delay in recontacting depending on the duration of the rest periods. To limit this increase of marginal temperature abc-ve the proportional and to assure a speedy decrease and recontacting after resumption of ironing, the

surrounding air of room temperature is brought intov direct contact with the interior of the switch structure through slanted and rectangularly contoured openings 'E2 in the sections I 2 and Ill. The cooling is further accelerated at the resumption of ironing by the air currents created within the switch structure by each stroke of the iron through the reversed angularity and arrangement of the openings 12. The air flows in on one side and out the other at each stroke, the change in direction of movement of the iron reversing the direction of, travel of the air currents.

In the section I i2 is rotatably journaled a shaft 'I4 having a knob i6 of insulative material attached thereto. This shaft extends through an opening '53 in the section I3 and carries a spring washer 80. of saucer like contour and slit radially to provide spring ngers 82f engaging the section I2; This washer is. held. in place on the shaft 'I4 byY a split latch ring made of spring steel, which is slipped over the end of the shaft 'I4 and closes in acircumferentlal groove 85 in this shaft. Metallic bearing plates 88 are respectively attached to the knob 'is and the section I2 to limit wear between the relative movable parts.

To the inner end of the shaft 'I is connected a body lii having a screw thread formation 92. This body is provided with a central opening tting `the neck 94 at the end of the shaft 74., and the body is clampedV in position against the resultant shoulder on the shaft lby means of a lock washer d3 and a screw Sli) passing through the lock washer and threaded into the shaft 14.

A spring wire Idd is provided with a loop H32 atone end of such diameter as to have threaded engagement with the body 9?).l This wire includes a bend Iiii engaging a body 96 on the section lf2, which body is provided with a slot 108 which loosely receives the wire it!) but restrains the wire from rotation when the knob 'I6 is turned. The

body 9U is secured to the shaft T4 for rotation therewith as a unit after radial adjustment by means of the tool receiving slot |09 across the lower face of the body 90. The free end of the wire IUD is inclined in the direction of the thermostatic element 48 and has its free end resting on the upper leg 66 slightly rearwardly of the contact point B4.

Rotation of the knob 'I6 in a clockwise direction imparts axial movement to the loop I 02 in the direction of the knob. Such movement causes the free end of the spring wire to pivot against the leg B6 about the bend |04 as a iulcrum, thus the spring pressure on the leg B6 may be adjusted through rotation of the knob 16, which in turn conditions the thermostatic element so that it may effect the desired temperatures in the appliance.

A projection III) is formed on the section I2 to constitute a pointer arranged for indicating coaction with respect to a scale. I I2 on the flared face II4on the. knob 16- The knob 1.6i in. Figure l is illustrated in its oi position, with the lateral projection II'u` on the knob engaging a-stop II81 on the section I2, while the other side of the lateral projection II 6 limits the rotation of the knob 'I6 by engaging thev adjacent side cfthe pointer III). are marked Oif'j Rayon Silkl, WooL Cotton and Linen Rotation of the-'knob 16 to bring any marking o-n the scale other than the Oii marking into registration with the pointer II Il` increases-the tension of the spring I0@ to bring the contact point Bft into engagement with the contact point to effect an initialV closing oi the circuit. The spring tension increases through continued clockwise rotation of the knob andthe scale is marked in accordance with the respective temperatures required'for the materials indicated thereon.r The intermediate markings on thev scale II-2 arenumbered from Zero to ten, and for convenience read oppositely in cases where the switch is to be employed in connection with appliances other than electric irons.

When the knob 'I6-is rotated clockwise,4 the pressure brought to bea-r on the resilientY steel wire I (I0-is transmitted to the free end oi the compound thermostat, which closes the circuit to pass current to the heating appliance. When the heat in the appliance reaches the desiredV predetermined temperature, a considerably' lower temperature, but in direct proportion to that prevailing in the heatingappliance, reaches the switch through the-conducting terminals, thereby increasing the temperature of the compound'thermostat and in proportion the value of theV torque of the latter to the point where the pressure of the resilient steel wire and the value of the torque balance. This temperature is the proportional temperature-of each desired setting around which the two forces interplay to maintain the predetermined temperature in the heating' appliance, which dilers by each different setting.

A further increase in temperature above the proportional will increase the value of the torque of the compound thermostat abovethe pressure of the wire, thus breaking the circuit4 automatically andseparating the compound thermostat from direct Contact with the terminal. It is obvious that through this non-association of the rminal and thermostat the temperature of the latter must necessarily decrease and consequently the valuev of the torque to the point' where the latter sinks below the pressure of the The graduations of the scale I-I-2 wire to again close the circuit. Thus it will be seen that the variable pressures applied to the wire i) through rotation of the knob 'IS results in corresponding proportional temperatures in the switch around which the pressure of the wire and the torque of the thermostat interplay to maintain automatically the predetermined temperature in the heating appliance.

My invention is in the nature of an ordinary plug wherein there is incorporated thermostatic automatic electric irons, the thermostatic switch may be manufactured at a low cost and may be used in connection with other electrical appliances. The sturdy construction of the switch makes it possible to service the device by any one acquainted with such work without injuring the switch mechanism. The two sections I2 and l are easily separated without danger of injuring the thermostatic structure.

Without further elaboration, the foregoing will so fully explain my invention, that others may, by applying current knowledge, readily adapt the same for use under various conditions of service.

I claim:

l. A thermostatic switch plug comprising first and second terminal means for connection with an electrical appliance, said iirst terminal means being adapted for connection with a circuit wire, a stationary contact electrically connected with said second terminal means, a temperature responsive thermostat adapted for connection with a second circuit wire and having a second contact engageable with said stationary Contact. adjustable resilient means bearing against said tl'iermostat to yieldingly hold the second contact in engagement with the stationary contact to close the circuit through the appliance but yielding upon a predetermined temperature condition of the appliance to cause the second contact to move away from said stationary contact and break the circuit through the appliance f' means for adjusting said resilient means to vary its resisting pressure on said thermostat, means for holding the adjusting means in adjusted position, a visible indicating means on the adjusting means for displaying the extent of adjustment,

and second terminal means for connection with an electrical appliance, said iirst terminal means being adapted for connection with a circuit Wire, a stationary contact electrically connected with said second terminal means, a temperature responsive thermostat adapted for connection with a second circuit wire and having a second contact engageable with said stationary contact, an adjustable elongated wire bent intermediate its extremities and having one end bearing against said thermostat to yieldingly hold the second contact in engagement with the stationary contact to close the circuit through the appliance but yielding upon a predetermined temperature condition of the appliance to cause the second contact to move away from said stationary contact and break the circuit through the appliance, a visible indicator for showing the extent of adjustment of the wire, and an insulative housing for said terminal means, said thermostat and the resilient means, said housing having oppositely angled openings to circulate air through the housing through movement thereof.

3. In a switch plug of the type described, a casing, the combination of a stationary contact, a heat responsive thermostat, a second contact carried by said thermostat for engagement with said stationary contact, said stationary and second contacts having meeting faces, said thermostat comprising a bimetallic member having a iirst length flexing in one direction, a second length carrying said second contact flexing in a reverse direction to maintain said meeting faces in parallelism, an elongated adjustable Wire bearing on said second length to yieldingly hold the second Contact in engagement with said stationary contact and a rotary screw means connected with the wire for adjusting said wire, means for indicating the extent of adjustment, said means accessible from without the casing, and means for holding the screw means in adjusted position against accidental displacement.

ll. In a switch of the type described, comprising a casing, a stationary contact, a heat responsive thermostat, a seco-nd contact carried by said thermostat for engagement with said stationary contact, said stationary and second contacts having meeting faces, said thermostat comp-rising a bimetallic member having a, first length flexing in one direction, a second length carrying said second contact flexing in the reverse direction to maintain said meeting faces in parallelism, an elongated adjustable spring wire fulcrumed intermediate its ends having one end bearing on said second length to yieldingly hold it in engagement with said stationary contact, a rotary screw means threadedly connected with the opposite end of the spring wire for rocking the same on its fulcrum, means on the outside oi the casing for operating said screw, and means cri-operating with the screw operating means and casing for indicating the extent of the adjustment of said screw.

BERNARD F. OEBBECKE.

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