US2381784A - Control device - Google Patents

Description

' Aug. 7, 1945. c. K. STROBEL CONTROL DEVICE Filed June 22, 1942 INVENTOR. (harks jgdtrobeb.

[WW/m ATTORNEK Patented Aug; 7, 1945 ,784

omfrso STATES PATENT OFFICE 2,381,784 GONTR-OL DEVICE Charles K. Strobe], Pittsburgh, Pa., assign'or to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania Application June 22, 1942, Serial No. 447,933 4 Claims. "('01. 200-122) l'liisinvention relates to control devices and, Positioned adjacent the support l2 and proparticularly, to electrc-thermally operated jecting from the base member In is a post 34 upon relays. which the electro-thermal means is mounted. In

An object of the invention is to incorporate a this embodiment, this means comprises a bitii'ne-delay period of substantial uniformity fol 5 metal strip 36 secured at one end to the post 34 lowing initial operation and prior to actual opand having depending from its opposite end an eration of the control. electromagnet 3B the core 40 of which has sufll- Another object of the invention is to render cient vertical dimension to overlap the adjacent the time-delay period substantially constant irside of the armature bar IS in both directions. respective of variables in the electro-thermal 10, The bimetal strip is an element adapted to deconrlitions. liect upwardly or away from base l when [Another object of the invention is to permit heated. In addition to the support provided for rapid on cii on operation or recycling following the armature bar l6 by the support I2, the opprolcneed operation of the control while retain- P0 6 end t e efi rest-S p a Shoulder 44 the time delay interval unimpaired. formed on a pin 42 carried by-the base Ill and Another object of the invention is to maintain which projects through an aperture formed in sulcstantiaiuniformity of delay period throughthe armature bar I6 for the purpose. The annaout many recycling operations in rapid succesture bar may be urged into en ag ment wi h he a: shoulder 44 by means of a spring 46 extending Other objects and advantages will become apbetween. the base I 0 and the armature l6 interparent from the following description taken in mediate the pin 42 and the support l2. connection with the accompanying i The electrical connections for the structure so "wherein far described may include means for heating the Fig. l is an elevation in schematic form of a element comprising a heating Coil 43 50 P08 eontroi device constructed in accordance with ned re t e to e St p 36 that a majo D the invention; tion thereof receives heat when the coil 48 is Fig 1 1 aplan view of t same; energized. One end of the coil 48 is connected Fig. 2 is an elevation in schematic form showby a i e i to a wi 51 leading r one ering a modified arrangement of t in parts of minal of the secondary Of a transformer 54, while the control devi e; n the opposite end of the coil 48 is connected by a Fig. 2A is a plan vi f th same wire 56 to one terminal of the electromagnet 38.

Referring more particularly to the drawing The circuit in which the C011 43 s connected y and specificall to Fi s, 1 and 1 t control further be traced by way of wire 58 from the device of this arrangement may comprise a base other terminal f electromagnet 38 to one end member Hi having a support I: t one thereof a resilient conductor 60, by wire 62 to'the conhg' ppm idea t a rectangular or other mm tact I8, from contact 22 by wire 64 to resilient al.3111211, projectmn H to receive the suitably conductor 68 and by wire 88 to wire 10 connected slotted end of a movable armature device, such to one terminal of a main switch H the other an armature bar 6' The armature bar Is is terminal of which is connected to the other terpreierably made 01' iron and carries two spaced mmal of the transformer secondaryinsulated contacts l8 and 20 at the end remote fi f ffll i gnz i i c il n i the1 glgfitrlcz from the support l2 and which cooperate re 9 a s I spectiveiy with similar contacts 22 and 24 each fi ig g g z 2; 3 2 25 23232;

arre f g g g g iz ss g i ig z fg i fi g g by a wire 16 to any other element or Series of 3 an elements included in the circuit. Such element iorm with contacts 20 and 24 two contact mug p or elements designated by the numeral 18 are P11 which cqmacts and u the shown connected in series with the element 12 to t ,opposlte. end of each leaf f 25 be controlled, such circuit being completed by the is damped In a post 28 mounted on the adlacent wire 80 connected to the wire 10. A shunt is esf Q f base member and surmounted by a tablished around the element 12 to be controlled pair or arms 36 each carrying an adjustment by means of a w 82 indicated in Fig, 1A as exscrew or other device by means of which tending from one end of the element '12 to the movement Of the leaf spri gs 26 in response to contact 20 and by a wire 84 likewise indicated nias thereof may be limited. as extending om e Opposite end of the ment 1! to the contact 24. Thus, elements 18 and 12 are in series circuit; coil 48, electromagnet 08, and contacts, I8-22 are in another series circuit and are also in parallel circuit with elements I8 and II.

In the operation of the device so far described, the main switch II is closed, causing energization of the heating coil 48, electromagnet 38 and the elements of the main circuit designated by the numeral 10. As the contacts I8, 22, 20 and 04 are at this time closed, the shunt established for element I2 to be controlled is effective and this element receives insufficient current to become operative. The electromagnet 30 being energized, the core 40 thereof engages the armature bar I8 in its lowest position and simultaneously the heating coil 48 begins to heat and cause the bimetal strip 08 to deflect upwardly. Due to the attraction of the armature bar ll 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 the heating coil 48 to heat and cause the bimetal strip 88 to deflect sufficiently to open the contacta. In the arrangement shown, opening or the contacts removes the shunt from the element. I! which thereupon becomes operative alter me specified time-delay period. However, in the arrangement thus far described (which description is as yetincomplete as to the features of this invention) the opening of the contacts would cause deenergizationof the heater coil 48 and electromagnet 38 with consequent return of the armature bar I8 to its initial position. Such operation would cause reclosing of the contacts "-42. and the second pair of contacts 20-44 unless means were provided to prevent this occurrence.

To this end, a holding circuit for the armature bar I is provided and may comprise a second electromagnet 86 having one terminal thereof connected by a wire 08 to the wire 82 and the other terminal thereof connected by a wire 00 to the wire I0. Consequently, electromagnet 88 is energized when switch II is closed. This holdin circuit is thus separate from the two previously described and places electromagnet 08 in parallel circuit with the heater coil 40 and other elements of the circuit in which the coil is connected; The electromagnet 86 is supported from the base ID in spaced relation to the armature bar I8 in its initial position but arranged so that the core 02 thereof is positioned to engage the armature bar l8 in its tilted position immediately prior to opening of the contacts I8--22. The electromagnet 88 is of suflicient strength to engage and hold the armature bar I8 only after the armature has been lifted partially by the elec tromagnet 38. Thus, when the contacts are opened by the leaf springs 28 engaging screws 32, the armature bar I8 is held in tilted position by the holding magnet 88 which remains energized due to its connection in a separate circuit. The

holding circuit preferably becomes efiective 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 cool completely before switch II 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 I8 will ensure the bar being within the field of the electromagnet 30, although the bimetal strip 38 does not have time to cool completely. It will furthermore be apparent that if the device I2 to be controlled is maintained in operation for a lengthy period, the temperature of the bimetal 86 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 rectiflers 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 I8 may comprise an ignition coil adapted to ignite a fuel burner when energized. The element 12 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 I I the electrornagnetic 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 38 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 connected will occur to those skilled in the art.

In Figs. 2 and 2A a modified form of coupling arrangement between the bimetal strip and the 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 I0 supports a post I00 provided with an horizontal pivot I02 for a contact carrying bar I04 which is not necessarily iron or other magnetically attractive material. The opposite end of the bar I04 carries the spaced contacts i8 and 20 arranged as in the preceding embodiment. A pin I08 positioned adjacent the contacts and abutting the underside of the bar I04 serves to support the bar I04 and is carried by the base member I0. As in the preceding embodiment, a spring 46 biases the armature I04 downwardly against the pin I08.

In this embodiment, the bimetal strip I08 carries the electromagnet IIO depending therefrom and having a core H2 overlapping in vertical dithis instance, however, slot I14 extending ionmension the bar I04. In the bar is provided with a heating by the heating coil 48.

the core] I2 and serve to maintain the armature I20 in alignment with the core I I2. armature I24 is mounted on the bar An auxiliary I04 in operative relation with the electromagnet 06 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 adapted to attract said armature device after said movement has continued for. a predeterminedperiod and to retain it in said one position with said contacts disengaged, said element thereby becoming unheated and returning toward 'undeflected position, and a second pair of contacts adapted for joint operation with the first said contact pair when gs'aid armature device reaches said position to/control a circuit extending through said second contact pair.

" 3. An electro-thermal relay comprising a movcoil 48 for the bimetal I08, together with theremaining parts of the device, may be precisely the same as those described in connection with the previous embodiment and further I 'descriptionis deemed unnecessary. The modified arrangement permits free upward motion or the bar I04 when the electromagnet H0 is energized'so that the core H2 thereof engages the armature I20 and the bimetal strip I08 deflects upwardly due to As soon as the auxiliary armature I24 has moved a predetermined distance into juxtaposition to core 92 the bar I04 is held after the bimetal deflects downwardly due'to opening of the contacts I8 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.

I claim:

1. An electro-thermal relay comprising a movable armature device, a pair of initially closed contacts adapted to be opened upon movement of said armature device to one position, said contacts remaining closed until said armature device reaches said position, an element adapted to defiect when heated and cause movement of said armature device toward said position, means effective when said contacts are closed for heating said element and being ineffective for said purpose when said contacts are opened, an electromagnet 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 opened, said element thereby becoming unheated and returning toward undefiected 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 extending therethrough.

2. An electro-thermal relay comprising a movable armature device carrying a contact, a springmountedcontact initially engaging said armature contact, means for disengaging said pair of contacts to interrupt a circuit extending therethrough upon movement of said armature device to one position, said contacts remaining engaged until said armature device reaches said position, an element adapted to deflect when heated and cause movement of said armature device toward said position, a heater coil connected in said circuit for heating said element in response to current flow through said coil when said contacts are engaged, an electromagnet able armature device carrying a contact,- a springmounted contact initially engaging said armature cbntact, means for disengaging said pair of contacts to interrupt a circuit extending therethrougl lupon movement of said armature device to one ,position, said contacts remaining engaged until said armature device reaches said position,

an electromagnet connected in said circuit and ad pted to attract said armature device during the period that said contacts are engaged and to release said armature device upon said contact disengagement, an element secured to said electromagnet and adapted to deflect when heated for causing movement of said armature device toward said position, a heater coil connected in said circuit for heating said element in response to current flow through said coil when said contacts are engaged, a second electromagnet adapt. ed 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 undefiected 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 extending through said second contact pair.

4. An electro-thermal relay comprising an armature device pivoted at one end for relative movement at the other, two contacts carried on said other end of the armature device, two springmounted contacts each adapted to engage with a related one of said armature contacts to form two contact pairs, means for restraining said spring-mounted contacts from following movement of said armature contacts and causing disengagement therebetween after a limited joint movement of said pairs, a circuit controlled by one of said contact pairs, an electromagnet connected in said circuit and adapted to attract said armature device at'the inception of said joint contact movement, a bimetal strip carrying said electromagnet and operable when heated for causing said armature device movement, a heater coil connected inseries circuit with said electromagnet for heating said strip in response to current flow through said coil when said one contact pair is engaged, a second electromagnet connected in another circuit and adapted to attract said armature device substantially simultaneously with operation of said restraining means to disengage said contact pairs, said strip thereby becoming unheated while said armature device remains in attracted relation with said second electromagnet for maintaining both contact pairs disengaged, and a third circuit controlled by the other of said contact pairs.

CHARLES K. S'I'ROBEL.

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