US2849576A - Thermal relays - Google Patents

Description

Aug- 25, 1958 s. NAPoLlN ET AL 2,849,576

THERMAL RELAYS Filed May 21. 1957 INVENTORJ SEYMWI( NAPL/N BY WMM .HARwaoo AT-roRNEY `Patented Aug.. 26, 1958 THERNIAL RELAYS Seymour Napolin, Wiiiiston Para, and Mark H. Harwood, Syosset, N. Y.; said Harwood assigner to Grauen ProdI ucts Inc., a corporation of New York Application May 21, 1957, Serial No. 663,567

20 Claims. (Cl. 20d-138) This invention relates to thermal relays and especially relay elements which under control of heat provide one or more `substantially :simultaneous or successive `switching operations.

One of the objects of this invention is to provide a thermal relay which under control of heat produced by 'a predetermined amount of current causes one switching operation and which under control of other predetermined amounts of current exceeding that first current, .and/or any succeeding currents, produces a number of successive switching actions.

Another object of the invention is to provide a bimetallic element of helicoidal shape operative under control `of a certain current and amount of heat to cause switching; and, after a predetermined degree of switching action or movement, operative to increase the current and the amount of heat to actuate a lswitch arm controlled by the helix to short circuit a portion of the heat thereby reducing the amount of current and heat operative upon the helix and slowing down switching action or movement under control of a current exceeding the initial predetermined amount of current.

Still another object of the invention is under control of further predetermined amounts of currents following an initial predetermined amount of current operating upon a helicoidal bimetallic element to short circuit tirst one portion of the helix and thereafter to Ishort circuit one or several other portions of the same helix, and iinally to provide a complete short circuit of the entire helix, all these different short circuiting operations being under control of different predetermined currents and causing different switching operations producing among other operations, a number `of co-rresponding short circuitings.

A further object of the invention is to provide a helicoidal bimetallic strip formed of two oppositely wound helices arranged in series connection along :substantially the same axis and interconnected over a V-shaped movable switching arm cooperating with another relatively stationary switching arm of the thermo relay.

` A more specific object of the invention is to produce a helicoidal bimetallic spring consisting of two oppositely wound coils following each .other and interconnected by a V-shaped switching arm, `as a one piece unit, from a V-shaped bimetallic sheet of blank, by means of winding the two legs of the V-shaped blank in the same direction over a mandrel of predetermined diameter until at a predetermined distance from the tip of the V-rshaped blank, the tip forms a movable switching `arm and the starting ends :of the two helices form terminals for the application of current passing through the helices to the `switching arm, thereby causing the heat to actuate the switching arm into an angular movement around the common axis of the two helices.

These and further objects ofthe invention will be more fully described in the drawings annexed herewith in which:

Figures l and 2 represent in top Iand front views respectively a thermal relay assembly embodying certain features of the invention.

Fig. 3 represents a blank for the bimetallic coils and switching arm forming part of the relay assembly of Figs. l and 2.

In Figs. l and 2 a helicoidal spring consisting of a band shaped bimetallic strip material is schematically indicated at i and comprises two helicoidal portions 2, 3 interconnected by a V-shaped portion 4 forming a switching arm and having attached thereto in otherwise well-known manner a silver plated or solid silver contact or pair of contacts The outer ends 6 and 7 of spring coils 2, 3 are mechanically attached to and electrically connected with terminal strips 8 and 9 and through eyelets 10 and 11 attached to mounting plate 12, consisting of Bakelite or other insulating material.

There are additional contact arms 13, 14 mechanically `attached and electrically connected to eyelets 10 and 11 and preferably forming one piece with terminal strips 7 and 8 and also if desired additionally attached to mounting plate 12 by means of additional eyelets 15 and 16. Contact arms 13 and 14 extend at a slight langle with respect to the common axis of coil springs 2, 3 from opposite directions, overlapping each lother at their free ends 17, 18 respectively.

In normal position, contact arms 13, 14 are so arranged as to overlap each other at their free ends, 17, 18 without however makin7 any contact with each other.

ln addition, contact arms 13, 14 or at least upper con- I tact arm i3 shown in l and 2 consists of springy material so as to be able, after having been pressed `down into contact with the other contact arm 14, upon release of such contact pressure, to return immediately into an -out-of-contact position spaced from underlying contact arm 14.

, Furthermore, in accordance with this invention, there is provided another switch arm 19 consisting preferably also of bimetallic material of a springy nature or shape, and arranged spaced from and adjacent to at least Vone of the coil spring sections 2, 3. Switch arm 19 is also provided -or formed with a terminal strip 20 and tixedly attache-d by 21 at one end thereof. The `other free end of switch arm 19 has attached thereto a silver plated or :solid silver contact 22 adapted to cooperate with contact S `of switch arm 4 when the latter is actuated by currents applied to terminals 9, 10. Contact 22 of switch arm 19 is capable of cooperating with the free end 17 of upper contact arm 13.

Switch arm i9 also serves to compensate for changes in ambient temperature in otherwise well-known manner.

As apparent from Figs. 1 and 2, contact arms 13, 14 are arranged at a slight angle with respect to the axis of bimetallic spring coils 2, 3 so as t-o facilitate access to all the elements of the thermal relay, and to permit in a minimum of space, to control a number of well determined sequential switching operations.

In the example of the invention shown in Figs. l and 2, such operations may occur in the following manner:

After the application of a predetermined current on spring coils 2, 3 over terminals 9, 1i), these spring coils will heat up and cause a rotary movement of the V- shaped switch arm 4 thereby causing contact 5 to engage contact 22 of switch arm 19.

When the current applied to terminals 9, l0 will exceed ya predetermined amount, going up from say 850 milliamps to 2000 milliamps, V-shaped switch arm 4 and contact 5, under control of the increased heat (produced by and acting upon bimetallic spring coils 2, 3) will be rotated around a considerably larger angle than previously, thereby forcing switch arm 19 into engagement with the underlying free en d 17 of contact arm 13 thereby short circuiting the left coil section 2 of bimetallic coily sections 2, 3.

As a result of this short circuit, the currentflow and heat produced in the remaining c oil section 3, will be reduced and V-shaped switch arm 4 will either remain in the. position attained orl will move upward, thereby opening the short circuit of coil 2, increasing the heatproduced by and operating on spring coils 2, 3 and again enforcing a short circuit of coil 2. In other words, a sequence of slow closing and opening movements of switch arm 4, with upper contact arm 13 will result.

Such slow contact movements, however, will not cause any damage to the contacts because the volt-age existing between these contacts is usually very small, of the order of IAO of a volt or even less.

This arrangement, therefore, has the result that the thermal. relay switch assembly is notv only capable of eiiciently operating atone predetermined current or current range, such as the above mentioned 850 milliamps, but will also be capable of operating at a predetermined current lor current range which is substantially higher than the initial current or current range for example a multiple thereof, say 2000 milliamps.

Necessity for such wide range switching operations, f orexample, may occur when -a thermo relay switch assembly is to be used for several types of equipment of different current consumptions such as the operation of a U. H. F. converter or booster connectable to diierent types of television receivers and to receivers of similarA type butof different current consumption. Color receivers for example may require currents goingup to 3000 milliam-ps and more.

In the latter case, a further increase in the amount of current passing the thermo relay will have the following results, also in accordance. with the invention.

A s statedl previously, the passage of a current of the order of around 2000 milliamps, will cause continuous or slowly intermittent contacts of the switch arms 4, 19 with contact arm 13.

Now in accordance with a further embodiment of the invention, a further increase of current passing bimetallicspring coils 2, 3 or at least one of the spring coils 3 (the other spring coil 2, possibly, having been short circuited by a preceding switching operation), will cause under-control of a further rotational movement of switch arm 4 to bring switch arm 19, and upper contact arm 13y in contact with lower contact arm 14 at its free end 18.

This contact operation will cause a complete shortcircuiting of` both spring coils 2, 3 at least momentarily. Therefore, as a result of the cooling down of bimetallic coils 2, 3 the contact between upper and lower contac't arms 13, 14 may temporarily be interrupted, causing a reheating of coils 2, 3.

In other words here again we have a slowly intermittent contact operation under control of V-shaped switch arm 4, between upper contact arm 13 and lower contact arm 14 in a manner similar to that occurring previously, at an intermediate current passage, between switch arm 19 and upper Contact arm 13. Here too there will be no damage to the contacting parts or points because the voltages existing between these parts or points are relatively very small.

In any case, as a result of these arrangements and.

operations, the thermal relay assembly will be capable of eectively receiving and passing very large amounts of current, thereby being made adaptable to a number of diterent uses, or permitting the switch controlled apparatus (such as a U. H. F. converter or booster equipped with such a thermo relay) to be used with or connected toa great number of apparatus of different types and of diierent consumptions, such as television receivers ofdiierent typesand/or. sizes.

Obviously it is possible, as has been found from experiments underlying this invention, that upon exceeding a very large amount of current, the springiness of the bimetallic spring coils 2, 3 and the flexibility of the operation of V-shaped switch arm 4 may be impaired more or less seriously, if the elasticity limit of the bimetallic springs 2, 3 were exceeded.

In other words it is thinkable that upon the application of a very large amount of current, switch arm 4 might not be able to return exactly to its original position. llhilc in this way the relay perhaps becomes less usable for relatively small currents such as 850 milliamps it will still be usable for relatively large and intermediate currents.

This drawback however in practice has been found to be of relatively little importance because it was found highly improbable that for example a U. H. F. converter which has been once used for the high current consumption of a color televisiony receiver, would be used thereafter again` forthe relatively low consumption of a small= black and white receiver. On the contrary it may well` be assumed that in practice, once a relay equipped converter or booster has been used with one type of receiver, it will continuously be used with this particular receiver.

The advantage of the invention lies in the fact thatr on the dealers shelves, only one type of U. H. F. converter nee'd to be stocked which could be sold and usedfor all types of different current requirements without change in construction or adjustment.

As a fur-ther specific embodiment of the invention the bimetallic coils shown in Figs. l and 2 canbe manufactured in an extremely simple manner from a V-shape'd bimetallic blank such as shown in Fig. 3 consisting of: two legs, 23, 24 forming an angle of around 60 degrees.

By winding the two legs 23, 24 simultaneously inthe direction of arrow 25 over a mandril 26, two spring coilsofi predetermined diameter will be produced, leaving at the center a V-shaped section 27 capable of carrying-thev contact element or elements such as shown in Figs. l and 2 at 5 and 22. The starting end 27, 28 of coil 1egs23, 24 are dat and serve as an electrical connection as well as for supportV on mounting plate such as indicated in Figs. 1 and 2 at 12.

The' invention is not limited to the shape of the bimetallic strip, contact elements or any other parts' illustrated and described nor to the speciiic arrangements of these elements as illustrated in Figs. l and 2 but may be applied in any size, shape,A form or manner withouty departing from the scope of this disclosure.

We claim:

1. A thermal relay, comprising a spirally wound bimetallic element, at least one switching element attachedr to said bimetallic element, means for applying current to said bimetallic element to move said switching element, and means under control of said switching element for short-circuitingl at least a portion of said bimetallic element upon said current exceeding a predetermined value.

2. Relay according to claim l, comprising means under control of said switching element for short-circuitingsaid` entirebimetallic element upon exceeding a further predetermined current value passing therethrough.

3. Relay according to claim 1, wherein said bimetallic element consists of series connected coaxial spirals one' following the other; said switching' element interconnecting two of said spirals and arranged to rotate about the axis of said spirals under control of current applied to saidv spirals;

4. Relay according to claim 3, whereinsaid bimetallicV element consists of at leasttwo serially connected coaxial spirals one following the other; said switch element interconnecting said spirals; there being` provided at the end of said-switching element a contact member; and afnrther bimetallic element arranged relatively stationary with respect to the rotating element and engaged by said rotating switching element under control of current passing through said spirals.

5. Relay according to claim 4, comprising at least one contact element connected to and extending from the outer end of at least one said spirals to a position near the inner end forming a contact making portion at said end cooperating with said switching arm to cause shortcircuiting of at least said one spiral under control of a switching arm movement.

6. Relay according to claim 5, comprising at least another contact element connected to and extending from the outer end at least of the other spiral to a position near the inner end of said other spiral, forming a contact making portion at said end cooperating with said switching arm to cause short-circuiting at least of said other spiral.

7. Relay according to claim 1, comprising a further bimetallic switching element arranged to extend from a position near the end of at least one of said spirals towards a position near its other end, and having its inner end cooperating with said first switching element, and terminals connected to the outer ends of said spirals and said further switching element permitting current to pass through said further switching arm under control of said first switching element.

8. Relay according to claim 1, comprising a further bimetallic switching element arranged to extend from a position near the end of at least one of said spirals towards a position near its other end, and having its inner end cooperating with said first switching element, and terminals connected to the outer ends `of said spirals and said further switching element permitting current to pass through said further switching element under control of rst switching element in one position of said first switching element and further comprising at least one contact element connected to and extending from the outer end of at least one said spirals to a position near the inner end forming a contact-making portion of said end cooperating with further switching element to cause short-circuiting of at least said one spiral under control of a switching movement in a second position of said first switching element.

9. Relay according to claim 1, comprising of further bimetallic switching element arranged to extend from a position near the end of at least one of said spirals towards a position near its other end, and having its inner end cooperating with said first switching element, and terminals connected to the outer ends of said spirals and said further switching element permitting current to pass through said further switching element under control of said first switching element in one position of said first switching element; and further comprising at least one contact element connected to and extending from the outer end of at least one said spirals to a position near the inner end forming a contact-making portion at said end cooperating with said further switching to cause shortcircuiting of at least said one spiral under control of a switching movement in a second position of said first switching arm; and further comprising at least another contact element connected to and extending from the outer end at least of the other spiral to a position near the inner end of said other spiral, forming a contact making portion at said end cooperating with said further switching element to cause short-circuiting at least of said other spiral in a third position of said first switching arm.

10. A thermal relay, comprising a pair of Ibimetallic coils of helicoidal shape arranged coaxially with respect to each other, and a V-shaped switching element interconnecting said coils and being formed of one piece of bimetallic strip with said coils and arranged to be moved upon a predetermined current being applied to the outer ends of said coils; and a further bimetallic switching element having one end fixedly attached in a position near the outer ends of said coils; the free end of said further bimetallic switching element -being arranged to be engaged by the free end of said V-shaped switching element.

ll.. Relay according to claim 10, wherein said free end of said further switching element is arranged to extend below the free end of said V-shaped switching element.

12. Relay according to claim 10, comprising a further bimetallic switching element arranged to extend from a position near the end of at least one of said coils towards a position near its other end, and having its inner end cooperating with said first switching element, and terminals connected to the outer ends of said coils and said further switching element permitting current to pass through said further switching element under control of first switching element.

13. Relay according to claim 10, comprising a further bimetallic switching element arranged to extend from a position near the end of at least one of said coils toward a position near its other end, and having its inner end cooperating with said first switching element, and terminals connected to the outer ends of said coils and said further switching element permitting current to pass through said further switching element under control' of first switching element in one position of said first switching element; and further comprising at least one contact element connected to and extending from the outer end of at least one said coils to a position near the inner end forming a contact-making portion at said end cooperating with said further switching element to cause short-circuiting of at least said one coil under control of a switching movement in another position of said first switching element.

14. Relay according to claim 10, comprising a further bimetallic switching element arranged to extend from a position near the end of at least one of said coils towards a position near its other end, and having its inner end cooperating with said first switching element, and terminals connected to the outer ends of said coils and said further switching element permitting current to pass through said further switching element under control of first switching element in one position of said first Kswitching element; and further comprising at least one contact element connected to and extending from the outer end of at least one said coils to a position near the inner end forming a contact-making portion of said end cooperating with said further switching element to cause sho-rt-circuiting of at least said one coil under control of a switching movement in a second position of said first switching element and further comprising at least another contact element connected to and extending from the outer end at least of the other coil to a position near the inner end of said other coil, forming a contact making portion at said end cooperating with said further switching element to cause short-circuiting at least of said other coil in a third position of said first switching element. l

15. Relay according to claim 8, wherein said two contact elements are arranged to form a small angle with respect to the axis of said spirals.

16. Relay according to claim 15, wherein said further switching element is arranged to form a small angle opposing said rst angle, with respect to the axis of said spirals.

17. Relay according to claim 14, wherein said two contact elements are arranged to form a small angle with respect to the axis of said coils.

18. Relay according to claim 17, wherein said further switching element is arranged to form a small angle opposing said first angle, with respect to the axis of said spirals.

19. In a process for the manufacture of a bimetallic thermo-relay element, the steps of stamping a V-shaped strip from a metal sheet, winding said V-shaped strip, beginning at its basis around a mandril of a diameter which is small compared to the basis of said V-shaped strip, and continuing said winding operation in a direction substantially perpendicular to said' basis' until almost the entire V-shaped strip is wound around said mandril, forming thereon a pair of helicoidal coils' in'- terconnected by a V-shaped' center portion extending from said coils at the inner ends thereof.

20'. Process according to claim 19, wherein said V- shaped strip is provided at its base ends with large fiat portions forming conducting terminals as lWellv asmechanical supports for said coils and said tl-shaped center portion.

i l References Cited in the tile of this patent UNITED ATES` PATENTS

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