Control device

Aug. 7, 1945.

2,381,784

C. K. STROBEL

CONTROL DEVICE

Filed June 22, 1942 __-t^ZcjC^- yL.

I 46 EC 3

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/ATTORNEY.

Patented Aug. 7, 194S

2,381,784

UNITED STATES PATENT OFFICE

2,381,784

CONTROL DEVICE

Charles K. Strobel, Pittsburgh, Pa., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania

Application June 22, 1942, Serial No. 447,933

Claims. (Cl. 200—122)

This invention relates to control devices and, more particularly, to electro-thermally operated relays.

An object of the invention is to incorporate a time-delay period of substantial uniformity fol- 5 lowing initial operation and prior to actual operation of the control.

.Another object of the invention is to render the time-delay period substantially constant irrespective of variables in the electro-thermal 10 conditions.

Another object of the invention is to permit rapid on-off-on operation or recycling following prolonged operation of the control while retaining the time delay interval unimpaired. ¹⁵

Another object of the invention is to maintain substantial uniformity of delay period throughout many recycling operations in rapid succession.

Other objects and advantages will become ap- 20 parent from the following description taken in connection with the accompanying drawing, wherein

Kg. 1 is an elevation in schematic form of a control device constructed in accordance with 25 the invention;

Fig. 1A is a plan view of the same;

Fig. 2 is an elevation in schematic form showing a modified arrangement of certain parts of the control device; and ³®

Fig. 2A is a plan view of the same.

Referring more particularly to the drawing and specifically to Figs. 1 and 1A, the control device of this arrangement may comprise a base member 10 having a support 12 at one end there- ³⁵of provided with a rectangular or other noneircular projection 14 to receive the suitably slotted end of a movable armature device, such ss an armature bar 16. The armature bar 16 is preferably made of iron and carries two spaced insulated contacts 18 and 20 at the end remote from the support 12 and which cooperate respectively with similar contacts 22 and 24 each can-led on one end of a separate leaf spring 26 which is biased upwardly. The contacts 18 and SS form with contacts 20 and 24 two contact pairs of which contacts 20 and 24 is the second pair. The opposite end of each leaf spring 26 is clamped in a post 28 mounted on the adjacent ₅₀end of the base member 10 and surmounted by a pair of arms 30 each carrying an adjustment screw 33 or other device by means of which movement of the leaf springs 26 in response to •the· bias thereof may be limited. 55

Positioned adjacent the support 12 and projecting from the base member 10 is a post 34 upon which the electro-thermal means is mounted. In this embodiment, this means comprises a bimetal strip 36 secured at one end to the post 34 and having depending from its opposite end an electromagnet 30 the core 40 of which has sufficient vertical dimension to overlap the adjacent side of the armature bar 16 in both directions. The bimetal strip is an element adapted to deflect upwardly or away from base 10 when heated. In addition to the support provided for the armature bar 16 by the support 12, the opposite end thereof rests upon a shoulder 44 formed on a pin 42 carried by the base 10 and which projects through an aperture formed in the armature bar 16 for the purpose. The armature bar may be urged into engagement with the shoulder 44 by means of a spring 46 extending between the base 10 and the armature 16 intermediate the pin 42 and the support 12.

The electrical connections for the structure so far described may include means for heating the element comprising a heating coil 48 so positioned relative to the strip 36 that a major portion thereof receives heat when the coil 48 is energized. One end of the coil 48 is connected by a wire 50 to a wire 52 leading from one terminal of the secondary of a transformer 54, while the opposite end of the coil 48 is connected by a wire 56 to one terminal of the electromagnet 38. The circuit in which the coil 48 is connected may further be traced by way of wire 58 from the other terminal of electromagnet 38 to one end of a resilient conductor 60, by wire 62 to the contact 18, from contact 22 by wire 64 to resilient conductor 66 and by wire 68 to wire 70 connected to one terminal of a main switch 71 the other terminal of which is connected to the other terminal of the transformer secondary.

The device to be controlled by the electrothermal means and indicated in Figs. 1 and 1A by the resistance 72, is connected at one end by a wire 74 to the wire 52 and at the other end by a wire 76 to any other element or series of elements included in the circuit. Such element or elements designated by the numeral 78 are shown connected in series with the element 72 to be controlled, such circuit being completed by the wire 80 connected to the wire 70. A shunt is established around the element 72 to be controlled by means of a wire 82 indicated in Fig. 1A as extending from one end of the element 72 to the contact 20 and by a wire 84 likewise indicated as extending from the opposite end of the ele2

2,381,784 ment 12 to the contact 24. Thus, elements 74 and 72 are in series circuit; coil 48, electromagnet 48, and contacts 18—22 are in another series circuit and are also in parallel circuit with elements 78 and 72.

In the operation of the device so far described, the main switch 71 is closed, causing energization of the heating coll 48, electromagnet 38 and the elements of the main circuit designated by the numeral 78. As the contacts 18, 22, 20 and 24 are at this time closed, the shunt established for element 72 to be controlled Is effective and this element receives insufficient current to become operative. The electromagnet 38 being energized, the core 40 thereof engages the armature bar 18 in its lowest position and simultaneously the heating coil 48 begins to heat and cause the bimetal strip 38 to deflect upwardly. Due to the attraction of the armature bar 18 by the electromagnet core 40, a joint upward movement occurs but the contacts remain closed until the leaf spring 28 associated with each contact 22 and 24 engages the end of the adjusting screw 32 therefor and is thus prevented from moving any further under its bias. Opening of the contacts thus occurs after a predetermined time-delay period which is set by the time required for tne heating coil 48 to heat and cause the bimetal strip SB to deflect sufficiently to open the contacts. In the arrangement shown, opening or the contacts removes the shunt from the element 72 which thereupon becomes operative alter tne specified time-delay period. However, in the arrangement thus far described (which description is as yet incomplete as to the features of this invention) the opening of the contacts would cause deenergization of the heater coil 48 and electromagnet 38 with consequent return of the armature bar IB to its initial position. Such operation would cause reclosing of the contacts 18—22, and the second pair of contacts 20—24 unless means were provided to prevent this occurrence.

To this end. a holding circuit for the armature bar 18 is provided and may comprise a second electromagnet 86 having one terminal thereof connected by a wire 88 to the wire 82 and the other terminal thereof connected by a wire 90 to the wire 70. Consequently, electromagnet 00 is energized when switch 71 is closed. This holding circuit is thus separate from the two previously described and places electromagnet 00 in parallel circuit with the heater coil 40 and other elements of the circuit in which the coil is connected. The electromagnet 06 is supported from the base 10 in spaced relation to the armature bar &lt;6 in its initial position but arranged so that the core 92 thereof is positioned to engage the armature bar 10 in its tilted position immediately prior to opening of the contacts IS—22. The electromagnet 86 is of sufficient strength to engage and hold the armature bar 16 only after the armature has been lifted partially by the electromagnet 38. Thus, when the contacts are opened by the leaf springs 26 engaging screws 32, the armature bar 16 is held in tilted position by the holding magnet 86 which remains energized due to its connection in a separate circuit. The holding circuit preferably becomes effective im-. mediately prior to the time when the contacts open but it will be apparent that a simultaneous action may be provided.

The heater coil 48 then begins to cool. If cooling proceeds to ambient temperature, the bimetal strip 36 and attached magnet 38 will return to their original positions. However, even if the bimetal strip does not &lt;ool completely before switch 7( is opened and then immediately reclosed, a time-delay substantially equal to the original period will be obtained.

Hence, should such recycling operation be conducted several times in succession, the overlapping arrangement of the core 40 with respect to the side of armature bar (6 will ensure the bar being within the field of the electromagnet 38, although the bimetal strip 38 does not have time to cool completely. It will furthermore be apparent that if the device 72 to be controlled is maintained in operation for a lengthy period, the temperature of the bimetal 36 Is not continuously increased during such period to its saturation point where the strip can deflect no further but, on the contrary, the period is utilized to provide time for the strip to cool sufficiently to regain its original position.

The relay thus described is intended to operate on alternating current from the secondary of the transformer 54. It will be understood that in this event the iron parts of the electromagnets and armature will be appropriately made. If it is desired to operate from such a current source while utilizing direct current magnets then suitable rectifiers could be incorporated in the device.

As an example of the use to which the control device of this invention may be put, the circuit element 78 may comprise an ignition coil adapted to ignite a fuel burner when energized. The element 72 to be controlled may comprise a normally closed electromagnetic valve interposed in the fuel line and adapted to be opened only after the ignition coil has reached igniting temperature. Thus, upon closing of the main switch 7 ( the electromagnetic fuel valve would remain closed due to the shunt effective as long as the second pair of contacts 20 and 24 remain closed and this valve would not be opened to admit fuel to the burner until after the time-delay interval set by the bimetal 36 had caused opening of the contacts. During this interval the igniter coil would have reached Igniting temperature and, as soon as the contacts open to remove the shunt and open the fuel valve, the fuel would be ignited by the ignition coil. This and other examples of systems having means to be operated at a predetermined interval following energization of the circuit wherein it is those skilled in the art.

In Figs. 2 and 2A a arrangement between contacts has been provided. Where parts similar to those disclosed in Figs. 1 and 1A are used similar reference numerals have been applied. Thus, the base member (0 supports a post &lt;00 provided with an horizontal pivot 102 for a contact carrying bar 104 which is not necessarily iron or other magnetically attractive material. The opposite end of the bar (04 carries the spaced contacts !8 and 20 arranged as in the preceding embodiment. A pin 106 positioned adjacent the contacts and abutting the underside of the bar 104 serves to support the bar 104 and is carried by the base member 10. As in the preceding embodiment, a spring 46 biases the armature 104 downwardly against the pin (06.

In this embodiment, the bimetal strip 108 carries the electromagnet 110 depending therefrom and having a core I (2 overlapping in vertical dimension the bar (04. In this instance, however, the bar is provided with a slot (14 extending Ionconnected will occur to modified form of coupling the bimetal strip and the

2,381,784 gitudinally immediate the ends of the bar for the reception of an operating pin 116. A head 118 on the pin 116 is exposed on one side of the bar and an armature ί 20 carried by the pin is exposed on the opposite side thereof. The armature 120 is located in opposed relation to the core 112 projecting from electromagnet 110 and carries a pair of guide pins 122 which straddle the core 112 and serve to maintain the armature adapted to attract said armature device after said movement has continued for. a predetermined period and to retain it in said one position with said contacts disengaged, said element thereby becoming unheated and returning toward urideflected position, and a second pair of contacts adapted for joint operation with the first said contact pair when said armature device _____.____________________________________ reaches said position to control a circuit extend120 in alignment with the core 112. An auxiliary 10 ing through said second contact pair, armature 124 is mounted on the bar 104 in operative relation with the electromagnet 86 and , / adapted to be attracted thereby after the bar/ has moved it into an appropriate part of the/ magnetic field of the electromagnet. The heater 15 coil 48 for the bimetal 108, together with the re- . maining parts of the device, may be precisely the same as those described in connection with the previous embodiment and further-description is deemed unnecessary. The modified arrangement permits free upward motion of the bar' 104 when the electromagnet 110 is energized so that the core 112 thereof engages the armature 120 and the bimetal strip 108 deflects upwardly due to heating by the heating coil 48. As soon as the 25 auxiliary armature 124 has moved a predetermined distance into juxtaposition to core 92 the bar 104 is held after the bimetal deflects downwardly due to opening of the contacts 18 and 22.

While the invention has been described and shown in its preferred embodiments, it will be understood that many changes may be made in the arrangement of parts and details of construction without departing from the spirit of the invention as expressed in the appended claims.