US2598808A - Heating apparatus and radiation relay therefor - Google Patents

Description

June 3, 1952 s. H. LEDIN HEATING APPARATUS AND RADIATION RELAY THEREFOR Filed April 20, 1949 v m Wm WM A mm 3% MUM/1!! H I 6 H A? 7 Patented June 3, 1952 HEATING AFPARATUS ND RAnlArioN RELAY THEREFOR Sven Harald Ledin, Malarhojden, Sweden Application April 20, 1949, Serial No. 88,596 In Sweden April 24, 1948 12 Claims. 1

The present invention relates to radiation relays and their application as temperature indicators praticularly for heating apparatus, such as "furnaces, stoves, oil or gas heated boilers etc., but, may be, also for fire alarm.

It is an object of the invention to provide a cheap and relatively robust relay or indicator which is comparatively simple in construction, and a particular object is to provide such a relay or indicator which is at least practically unresponsive or controllably responsive to variations in the temperature of the surroundings. One specific object is to provide a cheap and reliable safety relay for oil and gas heaters for cutting oft the supply of oil or gas and, if desired, of pressure air in case, for some reason, the flame should become extinguished and the fireplace be loaded with oil or gas which might cause explosion or other damage.

To obtain these and other valuable objects which will be apparent as the description proceeds or otherwise well understood by those skilled in the art, the relay comprises a contact lever carried by at least two expansion members arranged so that by their thermal expansion they will both displace the lever in the same direction, one of said members being adapted to receive radiation and thereby expand relative to the other member and thus tilt said lever to cause a contact member on said lever to engage a stationary contact member and close an electric current circuit. Most materials having a positive coefficient of thermal expansion the following description will refer to such materials but it is to be understood that the invention as claimed comprises also the use of expansion members having a negative coefficient.

Theinvention will now be described more in detail with reference to the accompanying drawing illustrating some embodiments to which it is, however, not restricted.

In the drawing:

Fig. 1 shows an assembled relay containing an aera in implement and Figs. 2 and 3 are semi-diagrammatic illustratiqns of two difierent embodiments of the radiation relay alternative to that shown in assembled relay of Fig. 1.

Fig. 4 shows a preferred mode of attaching the relay to an oil heated furnace.

Fig. 5 shows a modified construction of a detail of the structure illustrated in Fig. 1.

' In Figfl the thermal expansion members consist of metallic bands I and 2 which may be, for instance, 5 to 10 centimeters in length, 3 to 6 millimeters wide and 0.05 to 0.2 millimeter thick.

They are secured in a spaced relationship, for instance by soldering, to a support 3 which is in turn attached to the holder 4 by means of electrically insulating plates 8 bolted to support 3 and holder 4 by screws 5 and 6, respectively, and under the intermediation of an insulating pack ing 1. Packing 1 may be removed and replaced by an insulating air-gap. At their remote end the bands I and 2 are fixed to the contact lever is, for instance, by being double folded at the ends, preferably over a small pin and having such ends inserted into transversal outwardly tapering grooves H in the lever. The lever [0 has an arm l2 extending parallelly to, preferably along the bands 6 and 2. 'At its end the arm carries a contact point I3 opposite to a contact disc M mounted at the end of the screw I5 axially adjustable in a bore in holder 4. The point 13 should be at a distance from the attachment point of band 2 in lever ID at least as big as the distance between the attachment points of bands l and 2 in the lever. The lever I0 is, in the embodiment illustrated, suspended in holder 4 and will be kept stretched by a spring l6 secured to holder 4 and by the stud H to the lever ill. The electric circuit to be controlled by the relay is admitted through the wires H3 and E9 connected to screws 5 and 6.

When in use the relay will be so located as to expose band i to the radiation from the heat source to be observed, for instance the flame of a burner or an electric resistance. To promote the thermal expansion effect of the radiation the band I may be more or less black. Band 2, on the other hand, may be protected more or less from such radiation, for instance, by being screened off by band I. To reduce its radiation absorbing capacity it should be made bright or shiny, preferably by chromium, platinum and/or rhodium plating it which will render it a permanent right coating. Upon radiation the thermal expansion of band I will thus be in excess of that of band 2. As the radiation impinging upon the band i or bands and 2, respectively, increases, the difference in thermal expansion of the bands will become greater and contact point 53 will thereby approach contact disc I4, and at a given amount of radiation the contact members will contact one another and close the electric circuit, which is supposed to permit the normal supply of heat source (oil, gas, electric current etc.) or give a signal or the like, as the case may be. As long as the. heater is running normally the radiation from its heat source will be sufficient to maintain the contact, but should the flame become extinguished or any other heat source used become void, the band I will recontract and the contact I3-I4 be broken, which, in turn, will obstruct the supply of heat source or give a signal, as the case may be.

In order to become sensitive and quick-answering to the radiation the band I should have a small cross-section so as to reduce the mass that has to be heated by the radiation, and, if desired, be heat insulated from the other parts so as to avoid loss of heat by conduction. For the same object it should be made of a material having a high coefficient of thermal expansion, such as zink, aluminium, copper or brass.

Bands I and 2 should also be small in crosssection and preferably be practically equal in that respect for the reason that either band shall respond equally to variations in the surrounding temperature. For the same reason the heat capacities and coefficients of thermal expansion of them should not differ very much but rather be equal.

If the bands I and 2 are equal in length and made of the same or equivalent material their thermal expansion on account of variations in the temperature of the surroundings will be equal and merely result in parallel displacement of the lever I0, and if the contact surface of the contact disc I4 is parallel to such displacement no alteration in the spacing of the contact members will occur. Variations of the surrounding temperature will thus have no influence on the Working of the relay. Much the more so if the arm I2 is placed alongside of the bands and made of the same or equivalent material since in that case the upward elongation of the bands will be compensated by a downward elongation of arm I2.

On the other hand, by suitably varying the dimensions of and/or the materials chosen for the bands, the present instrument may be made to be influenced in a controllable way by the surrounding temperature or, as a corollary, may the variation of some of the factors be compensated by the variation of others. Thus, increase in length and coefficient of thermal expansion will promote the expansion as will, at least momentarily, increase in surface of a given volume, whereas increase in cross-sectional area of a given volume and heat capacity will, at least momentarily, retard expansion. The present relay usually being adapted for rapid response, even said factors having only a momentary influence will obviously be useful. If, for example, band 2 is made shorter than band I or is substituted to a greater or smaller extent by a material having a lower coefficient of thermal expansion relative to band I, an increase in the temperature of the surroundings will turn lever I0 so that contact point I3 will approach contact disc I4, and vice versa. If therefore, for instance, band I is made of plain steel and band 2 of aluminium, the lever will obtain no rotary movement provided band 2 is made about half as long as band I and is supported in a practically inexpansible piece of wood.

If desired, such temperature response may instead be compensated more or less by setting contact disc I4 at an adequate angle to the length direction of the bands, as shown in Fig. 5.

According to one embodiment of the invention the band I and/or band 2 may be thick enough or provided with reinforcing ribs or grooves. The suspension of lever ID in holder 4 may then be dispensed with, but for the reasons just described such instrument will usually be less sensitive due to the relatively great masses.

The embodiment shown in Fig. 2 is near related to that shown in Fig. 1 but in order to make the structure more compact and less bulky the bands I and 2 are in a helical or in a combined helical and screw arrangement. They are secured to a central support 3 and carry at their ends the lever I0 which is also fixed to a spring I6. The lever has an arm I2 which is in this case curved in accordance with the helix. At the end of the arm is a contact point I3 cooperating with a stationary contact segment I4 which is curved similarly to the arm and adjustable by means of a setting screw I5 secured to a holder 4. In principle, this device operates as that of Fig. 1.

Fig. 3 illustrates an embodiment having two diaphragms 2| and 22 fixed in annular supports 23 and 24, respectively, in such a manner as to bulge to the one sidei The diaphragms are secured to a contact lever 25 inserted between the diaphragms through the intermediation of connecting pieces 26 and 21, respectively, fixed at about the middle of the diaphragms and at places on the lever spaced from one another to form a moment arm. Due to their bulging state the diaphragms will move axially of the annular supports when expanding thermally. In agreement therewith the lever 25 has an arm 28 extending substantially in parallel with such axial movement and carrying at its extreme end a contact point I3 cooperating, as in the embodiment already described in connection with Fig. 1, with a stationary contact disc I4 fitted to the end of an adjustment screw I5 threaded in an insulated bushing 29 in a holder 4.

Although subject to such variations as explained above in connection with Fig. 1, the diaphragms 2I and 22 are now supposed to be equal enough to react identically upon variations in the temperature of the surroundings. Therefore such temperature variations will merely result in a translatory movement of lever 25 and the distance of contact point l3 from contact disc I4 will remain constant. If on the other hand radiation, indicated by the arrows, falls upon diaphragm 2I the thermal expansion of that diaphragm will be excessive of that of diaphragm 22 resulting in a turning of lever 25 and an approach of contact point I3 to contact disc I4, until upon sufiicient radiation these contact members will finally contact.

As illustrated in Fig. 1 the relay is preferably protected by a housing 3| having an opening 32 for admitting the radiation to the radiation absorbing member I of the relay. For excluding as far as possible foreign radiation a slit 35 is provided sufiiciently far in front of the opening 32, preferably in the form of the opening of a tube 34 attached to the housing 3I over the opening 32, which is preferably also shaped as a slit cooperating with slit 35. If desired or found practical slit 35 may be placed further away from opening 32, possibly in the formof a separate slit screen. The slits are preferably rectangular having a height about equal to the length of band I and a width not much greater than that of band I. By adequately spacing the slits relative to their lengths and breadths the angular portion of the space in front of the slit 35 from which radiation can pass the slit arrangement and reach the band I may be suitably restricted.

In order that the relay shall obtain as much as possible of the radiation permitted by the slits the opening .3 2 may be quite'open and not provided with a glass" window or the lik.' -iiiil'iis involves, however, a'certain disadvantage, inasmuch as dust andsoot and the like'may enter the housing and pollute the bands of the relay. Therefore, according to a further embodimentef the invention ages inlet 31 is provided for the admission of pressure air, preferably from the pressure air system of'the burne of aheat'er for which therelay maybe arranged. A Special outlet'for the air may be provided but usually the opening @Iwilfdd with gr at sax/asses. since'therby the admittance of pollutions will beprohibited ,7.

The device just described may readily be Slip-1 plemented so simultaneously to be useful as an automaticair pressure indicator. Fofthis object inlet'31 rec nnected to'the'compressed air systemb'y tube iiand' its interior projecting end is provided with afcove'r38 pivoted about'a stub :33 mounted in a bracket 44. Secured to said cover is a'contact' arrhtill carrying a contact point 3| arranged to cooperate with a stationary contact disc'z'conricted to the outer wire 43. The cover is normally'urged against the opening of inlet 37 bya spring 46 which is weak'enough to permit the pressure air stream passing through the inlet to lift the cover and bring about contact between contact point .4! and disc 42. electric conduit will be closed from wire 43 through the detailsfl, 4!, 4G, 39 and I9 to the holder 4 of the radiation relay and, if therein the contact H3 44 is closedas explained above; fur ther to wire i8 and the outer Wire 48.

By this'arrangement the radiation relay and the air pressure indicator are connected in series and if the wires 43 and 48 are connected to an electric relay, not shown, for a signal device, such as a bell or lamp, or for means for cutting off the supply of fuel or the like, a signal will be given, or the fuel supply be cut off, respectively, as soon as the flame becomes extinguished or the air compressor or'pressure air system gets out of function.

Fig. 4 shows an oil heated furnace 5| equipped with a relay 31' of the present kind. From the oil burner 52 projects the flame 53. The radia tion absorbing member of the relay 3! will be exposed to the radiationfrom the flame 53' through the relatively narrow channel 54 in the wall of the furnace. The'chann'el 54 is preferably'di rectedagainst a' remote point 55 of the inside wall of the combustion room 55 so as to minimize the radiationfromdhe wall to the relay. At point 55 the wall may be cooled or excavated so as to reduce the radiation from there; In order to increase the influence of the'radiation from the flame the relay is placed near the channel 55. Generally, the relay should be near the flame but far away from the wall 55.

Having now particularly described and ascertained the nature of my said invention and in What manner the same is to be performed, 1 declare that what I claim is:

l. A radiation relay comprising an elongated radiation absorbing expansion member, an clon gated temperature compensating expansion memher, a support on which each of said members is mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substan tially the same amount that said members expand Thereby due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotatesaid'lever about the point at which said temperaturecompensating member is fixed to said lever, a movable contact element mounted on one si'deof said lever which extends in a di rection substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said mem er 2, A radiation relay comprising an elongated radiation absorbing expansion member, an elonsated tempera u e c m n at xpa m ber, a support on which each of said members are mounted at one of the ends thereof, a contact lever. said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said mem bers expand, a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said members, and a projection portion on said lever, said portion extending in a direction parallel to the direction of expansion of said members and having said movable contact element mounted thereon.

3. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion member, a support on which each of said members are mounted at one of the ends thereof, a contact said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heatwill rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said members, anda'prqjection'portion on said lever, said portion extending in a direction parallel to and being located alongside of said members and said portidn having said movable contact element mounted thereon.

A radiation relay comprising an elongated radiation absorbing expansion member, an elona ed tem era compensa i exp s n em= per, a support on' which each of said members are mounted atone of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantiall parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given diiferential thermal expansion of said members, the distance between said movable contact element and the extended line connecting said points at which the expansion members are fixed to said lever being greater than the distance between the points at which said members are fixed to said lever.

5. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion memher, a support on which each of said members are mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at a the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact element engage each other as a result of a given differential thermal expansion of said members, one of said contact elements having a contact surface which is arranged at a slight angle with respect to the direction of thermal expansion of said members.

6. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion member, a support on which each of said members are mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said members, said radiation absorbing member being of a different length than said temperature compensating member.

'7. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion member, a support on which each of said members are mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given difierential thermal expansion of said members, said radiation absorbing member having a coeflicient of thermal expansion different from that of said temperature compensating member.

8. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion member, a support on which each of said members are mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said members, said radiation absorbing member having different surface areas than said temperature absorbing member so that said temperature compensating member reacts more quickly to changes in ambient temperature than said radiation absorbing member.

9. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion member, a support on which each of said members are mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said members, the heat capacity of said radiation absorbing member being difierent from that of said temperature compensating member so that one of said members reacts more quickly to changes in temperature than the other.

10. A radiation relay comprising an elongated radiation absorbing expansion member, an elongated temperature compensating expansion member, a support on which each of said members are mounted at one of the ends thereof, a contact lever, said members being fixed to said lever at the other ends thereof at spaced points on said lever, whereby said members move said lever in the same direction as and by substantially the same amount that said members expand due to variations in the ambient temperature of said relay, and whereby said radiation absorbing member upon absorbing radiation heat will rotate said lever about the point at which said temperature compensating member is fixed to said lever, a movable contact element mounted on one side of said lever which extends in a direction substantially parallel to the direction in which said members expand, and a stationary contact element mounted at a position opposite to said movable contact element, whereby said contact elements engage each other as a result of a given differential thermal expansion of said members, said radiation absorbing member having different cross sectional areas than said temperature absorbing member so that said temperature compensating member reacts more quickly to changes in ambient temperature than said radiation absorbing member.

11. A radiation relay, comprising in combination, a radiation absorbing expansion member having a fixedly mounted portion and having a portion thereof freely movable in a predetermined direction upon expansion or contraction of said radiation absorbing expansion member; a temperature compensating expansion member located adjacent to and spaced from said radiation absorbing expansion member and also having a fixedly mounted portion and a portion freely movable in said predetermined direction; a two-armed lever having the arms thereof located substantially at right angles to each other, having one of the arms thereof extending along a direction substantially parallel to said predetermined direction and having the other arm thereof fixedly connected to said expansion members at two spaced points of said other arm, respectively, so that when one of said expansion members moves, due to expansion or contraction, with respect to the other of said expansion members, said lever will be pivoted about the point thereof connected to said other expansion member; a, first contact element mounted on said one arm of said lever adjacent the end thereof distant from said other arm of said lever; and a second contact element located opposite said first contact element, so that said contact elements may engage each other as a result of a given different thermal expansion of said members.

12. A radiation relay, comprising in combination, a dish-shaped radiation absorbing expansion member having a fixedly mounted peripheral portion so that the central portion thereof moves upon expansion or contraction of said radiation absorbing expansion member; a dish-shaped temperature compensating expansion member mounted coaxially with respect to said radiation absorbing expansion member and being spaced therefrom and substantially parallel thereto, said temperature compensating expansion member also having a fixedly mounted peripheral portion so that the central portion thereof moves upon expansion or contraction of said radiation absorbing expansion member, the movement of said central portions of said expansion members being in the same direction; a two-armed lever having the arms thereof located substantially at right angles to each other and having one arm thereof extending along a line parallel to said direction and the other arm thereof located between said expansion members and being fixedly connected to the same at two spaced points on said other arm of said lever, respectively, so that when one of said expansion members moves with respect to the other of said expansion members, said lever is pivoted about the point thereof connected to said other of said expansion members; a first contact element mounted adjacent an end of said one arm located distant from said other arm of said lever; and a second contact element located opposite said first contact element, so that said contact elements may engage each other as a result of a different given thermal expansion of said members.

SVEN I-IARALD LEDIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,205,434 Connell Nov. 21, 1916 1,433,073 Davis Oct. 24, 1922 1,461,523 Fransson July 10', 1923 1,681,421 McCabe Aug. 21, 1928 1,829,944 Raney Nov. 3, 1931 1,832,761 Brady Nov. 17, 1931 1,853,444 McCabe Apr. 12, 1932 1,884,256 Rogers Oct. 25, 1932 2,154,644 Sweatt Apr. 18, 1939 2,171,957 Wallis Sept. 5, 1939 2,185,436 Gordon, Jr. Jan. 2, 1940 2,191,640 Beveridge Feb. 27, 1940 2,197,746 Matthes Apr. 16, 1940 2,299,533 Cyr Oct. 20, 1942 2,392,065 Rodgers Jan. 1, 1946 FOREIGN PATENTS Number Country Date 491,714 Great Britain Sept. 1, 1938

Images