US2287787A - Thermostatic switch - Google Patents

Description

June 30, 1942. R. N. DICKEY 2,287,787

THERMOSTATIC SWITCH Filed Sept. 4, 1940 2 Sheets-Sheet 1 l0 45 20 l 20 30 zfigci June 30, 1942. R. N. DICKEY 2,287,787

THERMOSTATIC SWITCH Filed Sept. 4, 1940 2 Sheets- Sheet 2 INVENTOR R0; N. D/CKE Y 2 BY ATTORN EYS Patented f June 30, 1942 THERMOSTATIC SWITCH Roy N. Dickey, Seattle, Wash, assignor to Meets- A-Need Manufacturing Company,

Seattle,

Wash, a corporation oi Washington Application September 4, 1940, Serial No. 355,355

Claims.

This invention relates to switches, and has reference more particularly to improvements in circuit control switches of those types especiallydesigned for use with the electric heating circuits of cooking appliances such as waille irons, toasters, and the like, and which operate to automatically open the circuit after the appliance has been heated to a predetermined degree.

It is the principal object of the present invention to provide an improved type of thermostatic switch, having a single control whereby the switch may be opened and closed, and whereby, upon closing the circuit, a thermostaticv element may be set to effect the opening of the circuit at any selected degree of heat within the range provided.

'It is a further object of this invention to provide a switch of the above stated character wherein a quick breakof the circuit is effected upon reaching the predetermined degree of heat.

Other objects of the. invention reside in the adaptation of a magnet in a novel combination of elements for accomplishing the quick breaking of the circuit at a predetermined degree of heat.

Still further objects of the invention reside in the details of construction of parts, in their relationship and mode of operation, as will hereinafter be fully described.

In accomplishing these and other objects of the invention, I have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawings, wherein Fig. 1 is a side view of a switch embodying the present invention, showing the switch open.

Fig. 2 is a top or plan view of the same.

Fig. 3 is a bottom, or underside view of the switch.

Fig. Us a cross section on line 4-4 in Fig. 1.

Fig. 5 isa sectional detail of the switch settingmeans.

Fig. 6 is a perspective view of .the rocker frame whereby the thermostatic arm is mounted. Fig. '7 is a perspective view of the main frame of the switch.

Fig. 8 is a perspective view of the movable switch plate.

Fig. 9 is a view, diagrammatically illustrating the switch controlled circuit.

Fig. 10,is 'a plan view showing the markings on a housing adjacent the switch knob.

Referring more in detail to the drawings- In its present preferred formof construction, the switch is designed for use in connection with cooking appliance such as that disclosed in my copending application for patent, filed on May 16, 1940, under Serial No. 335,539. For that particular use, the switch comprises a rigid frame plate I, shown in'perspective view in Fig. 7, and which is formed at one end with laterally and oppositely extending arms 2 and 2' whereby the switch is to be fixedly mounted in the housing or frame of the appliance with which it is used. To facilitate the mounting of the switch, the arms 2 and 2 are formed with holes '3 to receive attaching screws or rivets. -It is to be understood, however, that the character and design ofmeans for mounting the switch plate would bedete'rmined to a great extent by the design or type of device in which" the switch is to be used.

At the end of plate I, opposite that from which the arms 2 and 2' extend, the plate I is bent in such manner as to provide a transverse channel portion 4. Seated in this channel is the base or cross bar 5' of a permanent horse shoe magnet 5. v

The magnet is secured in place by means of cars '6 that extend from the end of the plate I and which are turned back over the top of the base bar of the magnet, as shown in Figs. 1 and 2. The two legs of the magnet, designated by numerals 5a and 5b, extend downwardly to an equal zontally through the flanges 8 and 8' and the overlying ears II and II, and thus pivotally the electrical heating circuit of a wallle and cake attaches the switch plate- I0 to the plate I in a manner permitting the plate III to be oscillated vertically at its outer end. The pin I2, in this instance, extends pivotally through holes l3 and I3 provided in the flanges 8' and 8', see Fig. 8, and has its ends extended through holes I4 and I4 'in the ears II and II' ,and riveted in the latter.

At is outer or. oscillating end, the plate I0 is formed with a crosshead I5 that directly underlies the magnet and operates as an armature which is attracted by the magnet to draw, or

lift, the outer end of the plate l0 upwardly, thus I 53 and. a source of electricity at 54.

in Fig. 9 at l8 and Ma, are connected. The posts I8 and H are mounted in alinement in their respective plates and have contact heads l8 and H at their adjacent ends adapted to be moved into circuit closing contact. The posts also are suitably insulated from their respective plates and are equipped at their outer ends with nuts IQ for the securement of the circuit wires thereto.

The opening and closing of the switch, as well as the setting of the thermostatic arm presently to be described, is under control of a switch knob 20 that is fixed to the upper, or outer end of a shaft 2| that is threaded through a bearing portion 22 located centrally in the mounting end portion of plate I. The shaft has a pin 23 fixed therein and extending radially therefrom, and

side of the-element,'and a circuit wire 55 leads from the other side of the element to'the source of current.

The arrangement of the circuit in combination with the switch control parts and the thermostatic arm, as above described, are such that upon turning the knob 20-to off" position;

that is, upon turning it to its limit in .a counterthus is adapted to engage with a downwardly directed stop 25 to limit the extent of rotation of the shaft to substantially one turn.

Inthe present instance, the stop 25 depends from a plate 26 that is fixed to plate I. Plate 26 serves to mount a small plate 21 of red glass, beneath which an incandescent lamp 28, connected in the circuit, is supported to indicate that the circuit is closed.

Supported pivotally from the plate I is a rocker frame 30. This frame, as seen in Fig. 6, has opposite side members 3|3l overlying the opposite side wings 88 of plate I, and pivotally attached thereto by a cross shaft 32 that extends through these parts. The parts 3| and 3| are joined across their lower endsby a cross bar 35, and this bar has a central, rearwardly extending member 36 that is slotted as at 31. Fitted pivotally in the slot 31 is a collar 38 through which the shaft 2| extends and the collar is held yieldingly against a shoulder 39 on the shaft by means of a coiled spring 40 that surrounds the lower end' portion of the shaft and bears against a nut 4| on the shaft. Thus, incident to rotation of the shaft 2| by means of the knob 20, the shaft will be shifted lengthwise and this, through the connections described, will cause a rocking action of the frame 30. Across their upper ends, the side members 3| 45, and secured to this at one end, and extending forwardly over and along the plate, is an arm or lever 46 of thermostatic metal adapted to warp downwardly at its outer end with the increase of 50 that is adjustably fixed in plate In, thus to provide a means through which the plate Ill may be actuated downwardly against the pull of the magnet, to disengage the contacts l6 and I1,

. and thus to manually open the circuit. The

downward action of the plate I0 is limited by means of a screw 5| that is adiustably mounted in plate I and extends downwardly therefrom through-a hole 52 in plate l0 and has a head.

5| to be engaged by the plate. In Fig. 9, wherein the circuit is diagrammatically shown, a heating element is designated at leads from the source of current to binding post "and wire l8 leads from binding post I8 t0 the Wire I81: 5

- for an adjustment in the circuit closing and I I and 3| of frame 30, are joined by a cross plateclockwise direction, as noted in Fig. 10, the shaft 2| will, by reason of its threaded connection with' plate 'I, be shifted upwardly, thereby rocking the frame 30 to'such position that the lever arm 48 will engage the upper end of screw 50 and thus actuate the plate I0 downwardly to disengage the twp contacts I6 and 11', thus to open the heating circuit.

, Upon turning the knob 20 in a clockwise direction, to position for opening the circuit at any designated heat, the initialaction disengages the I lever arm 48 froms crew 5lland permits the up ward rocking of the frame 30, and the incident closing of the circuit by reason of the magnet drawing the plate l0 upwardly and thus engaging the contact H with the contact IS. The farther the knob 20 is turned in the clockwise direction, the more will the frame 30 be rocked and the higher will the outer end of the thermostatic arm 46 be lifted above the upper end of the leg 41 of plate 10. Thus, the higher will be the heat required in order that the arm will be warped downwardly into contact with leg 41 to push the plate l0 downwardly for breaking the circuit.

A quick break of the circuit will be effected by reason of the fact that the magnet 5 has a holding effect on the armature portion l5 of plate l0 and power to overcome this magnetic pull must be built up in the thermostatic arm. In building this up, the resilient arm springs and finally when sufiicient tension has been produced therein, it breaks the hold of the magnet and the plate [0 is-actuated instantly to its downward limit to quickly open the circuit.

The provision of screw 50 as shown, provides opening position of the knob 20, and permits it to be used not only for setting the thermostatic arm, but also as a switch control.

In the wiring diagram of Fig. 9, I have shown that the pilot lamp .28 is connected in'the circuit 2 through suitable resistance R in such manner that the light is on whenever the circuit is closed. It is to be understood also that this lamp might be so connected as to come on when the predetermined temperature for which the device is set is reached.

Switches of this character are especially useful in waffle irons, and the like, ,where it is desired to keep the elements at a predetermined degree of heat. The device is extremely sensitive and the life of the contacts is considerably lengthened by reason of the provision for the quick break of the circuit.

Having thus describedmy invention, what I claim as new therein and desire to secure by Letters Patent is:

1. A switch of the character described comprising a main frame, a switch plate pivotally mounted thereon for oscillating action, switch contacts mounted by the frame and plate respectively for connection in the electric circuit that is to be controlled by the switch and adapted to be engaged and-disengaged by movement of the said plate to close and open'the circuit, a magnet disposed in position to magnetically resist movement of the plate for open ing of the closed circuit, a rocker frame pivoted on the mainframe, a rigid arm thereon for engaging the switch plate to open the circuit, a thermostatic arm fixed on the rocker frame for engaging the switch plate and adapted to be raised and lowered relative thereto by adjustment of the rocker frame, and a control member for adjusting the rocker frame in one direction for positive opening of the switch and in the other direction to first close the switch and then determine the position of the thermostatic arm for its actuation of the switch frame to open position at a predetermined temperature.

2. A switch of the character described comprising a main frame, a switch plate pivotally mounted thereon for oscillating action, coacting contacts mounted on the frame and plate for connection in an electric circuit and adapted to be engaged and disengaged by oscillating movement of the plate to close and open the circuit, a magnet mounted by the frame, an armature for the magnet formed as a part of the switch plate and adapted to be magnetically attracted for closing the circuit and to resist movement of the plate for opening the circuit, a rocker frame, pivotally mounted on the main frame, a control member for rocking the rocker frame, means on the rocker frame for actuating the switch plate to open the circuit when the frame is rocked in one direction, and adapted to release the switch plate when moved in the opposite direction, for closing under the action of the magnet, and a thermostatic lever mounted on the rocker frame and adjustable to different positions thereby and operable to engage the switch plate to move it to disengage the contacts at a predetermined temperature.

3. A switch as recited in claim 2 wherein means is provided for limiting the opening action of the switch plate to retain the armature within the magnetic field. a

4. A switch of the character described comprising a main frame member, a switch plate pivotally attached thereto, coacting contacts on the frame and plate adapted to be connected in the circuit that is to be controlled by the switch and to be engaged and disengaged by movement of the plate to close and open the circuit, a magnet mounted by the frame, an armature for the magnet formed as a partof the switch plate, meansfor limiting the opening movement of the switch plate to retain the armature within the influence of the magnet, a rocker frame pivoted on the main frame, a switch arm on the rocker frame, a thermostatic lever fixed on the rocker frame for actuation of the switch plate, a switch control means comprising a shaft threaded in the main frame and having operative connection with the rocker frame whereby rotation of the shaft in one direction will tilt the rocker frame to cause said arm thereon to actuate the switch plate to open the circuit, and rotation of the shaft in the other direction will tilt the frame in an opposite direction to allow the closing of the switch, and effect an adjustment of the thermostatic lever for actuation of the switch plate to open the circuit at a predetermined temperature, I

5. In a switch of the character described, a stationary member, a movable switch plate, contacts mounted by the said member and plate for connection in an electric circuit and adapted to be engaged and disengaged by movement of the plate, a magnet operable to magnetically urge the plate to circuit closing engagement of the contacts, a thermostatic lever disposed for actuating the switch plate to open the circuit, a movable support for the lever and for positive actuation of the switch plate, and a setting means operable to adjust the support to effect the closing of the switch and for the subsequent positioning of the thermostatic arm whereby it will effect the opening of the switch at a preo determined temperature for which the adjustment is made.

ROY N. DICKEY.

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