US2319317A - Temperature sensitive device - Google Patents

Description

May 18, 1943 w. H. GlLLE TEMPERATURE SENSITIVE DEVICE Filed July 5, 1941 INVENTOR. Willis H. Gill-1,

Patented May 18, 1943 2,319,317 TEMPERATURE SENSITIVE DEVICE Willis H. Gille, St. Paul, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 5, 1941, Serial No. 401,205

Claims.

This invention relates generally to temperature responsive devices and is more particularly concerned with relatively sensitive devices which are adapted to respond to radiant heat. Speciflcally the present application is directed to a device employing a thin heat responsive metal ribbon which is mounted under tension.

In devices of this type it is obvious that the metal ribbon must be mounted on some sort of support. Great difliculty has been experienced in the past because of the effect which the support has on the ribbon as the support expands and contracts as a result of changes in temperature due to the radiant heat. For example, the sensitive metal ribbon will always heat and cool rapidly and, due to its expansion and contraction, actuate the control, but the support for the ribbon will heat up up and cool off more slowly, and unless the resultant expansion and contraction of this support is accurately compensated for, there will be a decided tendency for the controlled device to back up. This is due to the fact that expansion and contraction of the support will affect the tension of the ribbon. If the device is used as a combustion responsive device for example, the metal ribbon will heat up upon the appearance of a flame and operate to close a switch. The radiant heat will eventually be absorbed by the support for the ribbon and raise its temperature. The resultant expansion. of the support, if uncompensated, is apt to increase the tension in the ribbon and open the switch again, an operation which should not occur until the flame disappears. The compensation for the ex pension and contraction of the support often leads to complications which affect the reliability and sensitivity of the control.

It is therefore a prime object of this invention to provide a metal ribbon heat sensitive device in which the expansion and contraction of the support of the ribbon has substantially no effect upon the tension or operation of the ribbon.

A further object is to provide a control of the type set forth in the preceding paragraph in which the metallic ribbon is tensioned by a resilient member which absorbs expansions and contractions of the ribbon support without noticeably afiecting the tension of the ribbon.

A still further object of the invention is to provide a radiant heat responsive device in the form of a double ribbon with one leg of the ribbon in the path of radiant heat and the other shielded therefrom, and using the difierential expansion between the two legs for actuating a control device, both legs being maintained under tension.

Another object is to utilize the differential expansion between the two legs of the double ribbon by connecting the two legs at a mid point and forcing them out of the straight line position which the tensioning device tends to make them assume. In the present application hot and cold switches are operated by the movable mid point of the two legs. Obviously one leg compensates the other for variations in ambient temperature.

These and other objects will readily become apparent as the following specification is read in the light of the accompanyin drawing in which Fig. 1 shows more or less diagrammatically an oil burner as mounted adjacent a furnace for producing combustion therein and one manner in which the device of the present invention may be mounted in the furnace wall so as to respond to the radiant heat of combustion,

Figure 2 is a rear elevation of the device of the present invention Figure 3 is a side elevation of the same ]ooking toward the left, as seen in Figure 2, and

Figure 4 is a section taken along the line l4 of Fig. 2 and looking in the direction of the arrow's.

Referring now to Fig. 2 of the drawing, the reference numeral l0 indicates a U-shaped supporting member, the connecting part of the U of which has been punched to form a pair of projections H. A second U-shaped member 52 has also been punched to form projections I3, and the projections H seat in the depressions formed in making the projections 13 so that the member i2 may rotate about the projections l l. The member I2 is mounted on the support ID by means of the screws M which extend through slots 15 in the member [2 and screw into tapped holes in the support In.

Generally indicated at i6 is a relatively thin and flexible heat expansible metal ribbon which is bent double in the form of a U to form two legs 30 and 3|, the bend of th U being supported by means of the U-shaped member [2 as shown at H. The ends of the metal ribbon are seated in a U-shaped carrying member 18 and are clamped tightly therein by means of the screw 29 and clamping plate 20. The clamping plate 29 is provided with extensions 2| which are slidably received in slots 22 in the supporting member i 0 in order to guide the vertical movement of the carrying member l8.

The carrying member I8 is supported by means of a flexible plate 23, the two ends 24 of which seat on shoulders formed by the projections 25 on the two ends of the supporting member ID.

' functioning of the device.

a supporting sore hole 23 'tl in id ed hole 2: in a horizontally ex p of the carrying member it. .i c seen theu by rotating the supporting sc w 28 in a clockwise direction, the carrying member i8 will be drawn upwardly to produce t sion in the two :gs 38 and 3| of the double ribbon iii.

The effect of the tensioning plate 23 on the two legs 35 and 3t is to tend to cause them to assume straight line positions. These legs, however, are connected at a mid portion by a connecting memr 33. One end of the connecting member 33 fixed thereto the shouldered contact 2 and the shouldered contact 35 is fixed to the other end. The distance between these two contacts is such. that the two legs 30 and 3| are pulled inwardly away from their normal straight line position.

The U shaped support l6 has a pair of inwardly extending supporting members :ill and ll. [in insulating member 42 is mounted across these and this insulating member carries a contact bracket 13 which in turn adjustably carries the contact 3. Mounted over this contact bracket 33 is a second insulating member 555 over which is mounted a SE"Ol1d contact bracket 46 which extends downwardly through the legs of the U-shaped supporting member ill and adjust.- ably carries a second contact 41 on the opposite side of the double ribbon Hi. These various elements are fixed to the member ill by means of a pair of screws 48. The reference numerals 50 and represent a pair of terminals which are electrically connected selectively with the contact oraoke. at and hence contact; ll and contact bracket 33 and hence contact 46. A third terminal is indicated at 52 which is-electrically connected to the supportin member ID and hence the contacting device formed by 33, 34 and 35. This is of course the common terminal.

One of the objects of this invention is to design a device which is compensated for changes in ambient temperature, which is unaffected by expansion and contraction of the support, which is adapted to respond to radiant heat in such a manner that when radiant heat is absent, the device will close a first switch and when radiant heat is present the device will open the first switch and close a second switch. The following description of operation will show how all of these features are present in the above described device.

In the first place, there is only one end of the double ribbon |6 which is fixedly mounted on the support l9, this being the end H. The opposite end is floatingly mounted by means of the tensioning plate 23 which tends to maintain a. substantially constant tension in the legs 38 and Si. When the two legs 38 and 3| of the double ribbon iii are at the same temperature, the tension in is substantially the same although this is not absolutely necessary for the proper The contacts fi l and or are so adjusted that when the two legs 30 and 3% are at the same temperature, contacts 3 3 and ll will be engaged and the contacts 35 and 35 will be separated. As long as the two legs so and Si expand or contract similarly, the tension in them will remain substantially the same due to the tension plate 23 which absorbs the differential expansion between the two legs and the supporting member 33. Under these circumstances therefore, there will be no lateral moveloosely through a cent of the two contacts 3 and 35. This is also obviously true if the supporting member Ill should expand or contract. It will therefore be seen that this device is perfectly compensated for variations in ambient temperature which aifect all parts equally.

The device is adapted to be mounted in some such manner as indicated in Fig. 1 which shows diagrammatically an oil burner 55 which is adapted to be mounted adjacent a furnace, one wall of which is indicated in section at 56, the burner producing flame as shown at 51. Applicants radiant heat responsive device may be mounted in any manner in which the radiant heat may travel directly to the leg 30 but it must be so arranged that the leg 3| is shielded from the radiant heat. As shown in Fig. 1, this device, which may be indicated generally as 58, is mounted in an opening 59 in the furnace wall in such manner that the leg 30 faces the flame 51 and at the same time prevents direct heat radiations from the fiame 51 to the leg 3|. Therefore when combustion is produced within the furnace the heat radiated from the flame will strike the leg 30 and raise its temperature above that of the leg 3|. Eventhough heat may be readily conducted from the leg 30 to the leg 3|, there will be sufiicient heat dissipation from the device to prevent the temperature of leg 3| from ever attaining that of the leg 30 as long as there is combustion within' the furnace.

Therefore when combustion is established, the leg 30 will be raised to a higher temperature than leg 3| and as a result will expand more than the leg 3|. This differential expansion between the two legs will relieve the tension in the leg 30 with the result that the leg 3| must absorb more of the upward force exerted by the tensioning plate 23. Therefore, the leg 3| will tend to straighten out with the result that the mid portion of the two legs 30 and 3| will move toward the left and contact 34 will be moved out of engagement with the contact 41 and contact 35 will move into engagement with contact 44. As explained above, the subsequent absorption of heat by the supporting member l0 cannot affect the position of the two contacts 34 and 35 as this expansion of the support is absorbed by the tensioning plate 23. When the fiame in the furnace disappears, the two legs 30 and 3| will rapidly attain the same temperature and will return to the position shown in Fig. 4. It will be appreciated that the position assumed by the two contacts 34 and 35 depends only upon the differential expansion of the two legs 30 and 3| and is absolutely independent of the attainment of any predetermined temperature because as long as the two legs are at the same temperature, regardless of what that temperature is, the device will assume the position shown in Fig. 4.

This device has been described as a radiant heat responsive device but it will be appreciated that it could be used as any form switch which is compensated for changes in ambient temperature. For example, it would functioncqually well as a thermo relay if an electric heater or any other heatsource were applied to the leg 3|! and not; to the leg 3|. It is therefore not applicant's intention to be limited only to a radiant heat responsive device.

Various other changes and modifications will doubtlessly occur to those skilled in the art and the limits of this invention should therefore be determined by the scope of the appended claims,

asiasir rather than by the specific embodiment disclosed.

I claim as my invention:

A heat sensitive device comprising in cembination, an elongated metallic ribbon bent at a mid portion to form a pair of substantially arallel legs, means placing the two legs or said ribhon under tension, and means connecting said legs at a point intermemate their length and de forming them whereby said legs tend to move in opposite directions.

2. An ambient temperature compensated heat responsive device comprising in combination, two relatively flexible heat expansible elements, a single tensioning member for placing both oi said elements under tension and tending to cause them to assume straight line positions, and means connecting said elements at a mid point and maintaining them out of their normal straight line positions so that when both elements expand and contract similarly there is substantially no change in the relative tension of said elements and no movement at their mid points, but when one element expands relatively to the other there is a lateral movement of said mid points and connecting means.

3. An ambient temperature compensated heat responsive device comprising in combination, two

relatively flexible heat expansible elements, a

single tensioning member for placing both of said elements under tension and tending to cause them to assume straight line positions,-

means connecting said elements at a mid point and maintaining them out of their normal straight line positions so that when both elements expand, and contract similarly there is substantially no change in the relative tension of said elements and no movement at their mid points, but when one element expands relatively to the other there is a lateral movement of said mid points and connecting means, and switch means actuated by a movable portion of one of said elements,

4. An ambient temperature compensated heat responsive device comprising in combination, two relatively flexible heat expansible elements, a single tensioning member for placing both of said elements under tension and tending to cause them to assume straight line positions, and means connecting said elements at a mid point and maintaining them out of their normal straight line positions so that when both elements expand and contract similarly there is substantially no change in the relative tension of said elements and no movement at their mid points, but when one element expands relatively to the other there is a lateral movement of said mid points and connecting means, a movable contact carried by a movable portion of one of said elements, and a stationary contact cooperable with said movable contact.

5. A temperature sensitive device comprising in combination, a relatively fixed support, a second support, a flexible metallic ribbon supported in the middle by one of said supports and having its ends connected to the other support to form two legs, means cooperable with said second support for placing said legs under substantially equal tension tending to cause them to assume straight line positions, and means connecting mid portions of said two legs and maintaining them out of their straight line positions.

6, An ambient temperature compensated heat responsive device comprising in combination, two relatively flexible heat expansible elements. a

first movable contact when said single tensioning member for placing both of said elements under ension and tending to cause them to assume straight positions, a first contact carried by a movable portion of one element, a second contact carried by a movable portion of the other element, means connecting a mid portion of said elements together and pulling them inwardly away from their straight line positions, a first stationary contact engaging said elements are at the same temperature, and a second stationary contact spaced from said second movable contact, expansion of said one element due to temperature increase causing a reduction in the tension therein whereby the tension in said other element causes separation of said first contacts and engagement of said second contacts.

7. A temperature sensitive device comprising in combination, a relatively fixed support, a second support, a flexible metallic ribbon supported in the middle by one of said supports and having its ends connected to the other support to form two legs, means cooperable with said second support for placing said legs under substantially equal tension tending to cause them to nine straight line positions, an electrical contact ole ment carried jointly by a mid portion of said legs and pulling them inwardly out of their straight line position, a first stationary contact in engagement with said contact element when said legs are at the same temperature, and a second stationary contact, said contact element separating from said first stationary contact and moving into engagement with said second stationary contact when one of said legs is heated to a higher temperature than the other.

8. A temperature sensitive device comprising in combination, a relatively fixed support, a sec ond support, a flexible metallic ribbon supported in the middle by one of said suports and having its ends connected to the other support to form two legs, means cooperable with said second support for placing said legs under substantially equal tension tending to cause them to assume straight line positions, an electrical contact element carried jointly by a mid portion oi said legs and pulling them inwardly out of their straight line position, a first stationary contact in engagement with said contact element when said legs are at the same temperature, a second stationary contact, said contact element separating from said first stationary contact and moving into engagement with said second stationary contact when one of said legs is heated to a higher temperature than the other, and means for adjusting said relatively fixed support for adjusting the position of said electrical contact element with respect to said stationary contacts.

9. A radiant heat responsive device comprising a support, a double metallic ribbon including a pair of expansible legs mounted at one end to said support, a mounting member, the other end of said double ribbon being connected to said mounting member, a resilient strip mounted adjacent its ends on said support, means connecting said mounting member to a mid portion of said strip, said strip acting on said mounting member to produce a tension in the legs of said double ribbon and absorb expansion and contraction of said support without substantially affecting the relative tension of said legs, heating means for one leg only of said ribbon, and means movable in response to the differential expansion or? said two legs, said other leg compensating said one leg for variations in ambient temperature,

10. A radiant heat responsive device comprising a support, a double metallic ribbon including a pair of expansible legs mounted at one end to said support, a mounting member, the other end of said double ribbon being connected to said mounting member, means including a resilient element for mounting said mounting member on said support, said resilient element acting on said mounting member to produce a tension in the legs of said double ribbon and absorb expansion and contraction of said suport without substantially affecting the relative tension of said legs, heating means for one leg only of said ribbon,

and means connecting said two legs at a mid portion and forcing said legs from the straight line position which said resilient element tends to make them assume.

11. A radiant heat responsive device compris- I a mid portion thereof to tially affecting the relative tension of said legs, 7

means for mounting said device in such a manner that one of said legs is in the path of radiant heat and shields the other leg from the radiant heat, and means movable in response to the differential expansion in said two legs, the other of said legs compensating said one leg for variations in ambient temperature.

12. A heat sensitive device comprising in combination, two relatively flexible heat expansible elements, first and second supports, means connecting one end of said elements to said first support, means connecting the other end of said elements to said-second support, means associated with one of said supports for placing said elements under tension thereby tending to make them assume straight line positions, and a movable member associated with at least one of said elements for biasing it out of its straight line position whereby upon unequal expansion of said elements the change in tension of said one element causes a movement of said movable member.

13. A heat sensitive bination, a first fixed supporting means, a second movable supporting means, an elongated member bent double at form a pair of legs, said mid portion being supported by one of said supporting means, the two ends of said member being brought together and supported by said other supporting means, resilient means biasing said second supporting means in a direction to place both of said legs under tension and hence tend to make them assume straight line positions, and a movable member associated with at least one of said legs for biasing it out of its straight line position whereby upon unequal expansion of said legs the resultant change in tension of said one leg causes movement of said movable member.

14. A heat sensitive device comprising in comflexible heat responsive bination, two relatively flexible heat expansible elements, first and second supports, means connecting one end of said elements to said first support, means connecting the other end of said elements to said second support, means associated with'one of said supports for placing said elements under tension thereby tending to make them assume straight line positions, a movable member associated with at least one of said elements for biasing it out of its straight line position whereby upon unequal expansion of said elements the change in tension or said one element causes a movement of said movable member, and switch means operated to one position when said elements are at substantially the same temperature and to another position when said elements are at different temperatures.

15. A heat sensitive device comprising in combination, a first fixed supporting means, a second movable supporting means, an elongated flexible 7 heat responsive member bent double at a mid portion thereof to form a pair of legs, said mid portion being supported by one of said supporting means, the two ends of said member being brought together and supportedby said other supporting means, resilient means biasing said second supporting means in a direction to place both of said legs under tension and hence tend to make them assume straight line positions, a movable member associated with at least one of said legs for biasing it out of its straight line position whereby upon unequal expansion of said device comprising in comlegs the resultant change in tension of said one leg causes movement of said movable member, stationary contact means, and movable contact means movable into and out'of engagement with said stationary contact means by said movable member.

WILLIS I-I. GILLE.

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