US3796982A - Thermostat construction - Google Patents

Abstract

An elongated bimetallic strip has a first end portion and a spaced second end portion which is adapted to be connected to a support. A conductive copper strip is fastened at one end to the first end portion and extends with the remainder thereof spaced from the bimetallic strip towards the second end portion thereof. The conductive strip has opposite the fastened end a free end portion. A first abutment is provided on the conductive strip in the region of the free end portion thereof, and a second abutment on the bimetallic strip in the region of the first end portion thereof. An elongated spring member extends longitudinally of the strips and its spaced opposite ends respectively pivotally and under stress engage the first and second abutment means in line contact therewith.

Description

United States Patent [1 1 Auracher Mar. 12, 1974 I THERMOSTAT CONSTRUCTION Robert Auracher, Stuttgart-Stamm-l-Ieim, Germany 22 Filed: Mar. 8, 1971 21 Appl. No.: 121,926

[75] Inventor:

[30] Foreign Application Priority Data Feb. 16, 1971 Germany 2010715 [52] US. Cl 337/343, 337/345, 337/375 [51] Int. Cl. HOlh 37/74 [58] Field of Search 200/67 B, 67 D, 89; 337/343, 345, 365, 373, 375

[5 6] References Cited UNITED STATES PATENTS 2,825,779 3/1958 Kelleigh 200/67 D 2,236,699 4/1941 Riche..... 337/343 3,349,202 10/1967 Beer 200/67 B 3,358,110 12/1967 Perkins... 200/67 D X 2,228,522 1/1941 Johnson I 337/343 X 3,459,912 8/1969 Bauer et al. 200/67 D 2,644,052 6/1953 Martin 200/67 D 3,358,095 12/1967 Arlin 337/88 X 2,237,705 4/1941 Kohl 337/370 X 3,533,039 10/1970 Mundt 337/100 X FOREIGN PATENTS OR APPLICATIONS 816,642 7/1959 Great Britain 200/67 D Primary ExaminerHarold Broome Assistant Examiner-E. E. Bell Attorney, Agent, or FirmMichael S. Striker [5 7] ABSTRACT An elongated bimetallic strip has a first end portion and a spaced second end portion which is adapted to be connected to a support. A conductive copper strip is fastened at one end to the first end portion and extends with the remainder thereof spaced from the bimetallic strip towards the second end portion thereof. The conductive strip has opposite the fastened end a free end portion. A first abutment is provided on the conductive strip in the region of the free end portion thereof, and a second abutment on the bimetallic strip in the region of the first end portion thereof. An elongated spring member extends longitudinally of the strips and its spaced opposite ends respectively pivotally and under stress engage the first and second abutment means in line contact therewith.

14 Claims, 7 Drawing Figures PATENTEUHAR 12 I974 SHEET 1 [1F 2 INVENTOR: Queen? AUHHHE'A lied liar? PATENTEDHAR 12 1914 3796582 SHEET 2 [JF v2 Fig. 6

THERMOSTAT CONSTRUCTION BACKGROUND OF THE INVENTION The present invention relates generally to a thermostat construction, and more particularly to a thermostat construction using a bimetallic element.

Bimetallic-element thermostats are already known. It is also known that they utilize a spring member one end of which is stationarily mounted and the other end of which usually bears upon the angled bimetallic strip. The purpose of this arrangement is to provide a rapid separation of the movable contact of the thermostatwhich contact is carried by the bimetallic strip-from the other contact which is usually stationary.

The problem with these known constructions is that quite frequently there are undesired and uncontrollable delays in the displacement of the movable contact out of engagement with the stationary contact, due to uncontrolled stress distribution in the spring member. This is obviously undesirable and equally obviously an avoidance of this problem is desirable.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the disadvantages of the prior art.

More particularly it is an object of the present invention to provide a thermostat construction utilizing a bimetallic element, wherein these disadvantages are avoided.

Still more particularly it is an object of the present invention to provide such a construction in which the arrangement of the spring member is such that it is evenly flexed at all points thereof and that the force distribution in the spring member is even and uniform throughout, with a concomitant controlled and reliable snap-action displacement of the bimetallic strip under requisite conditions, to a position in which the movable contact of the thermostat becomes displaced out of engagement with the stationary contact.

Furthermore, it is an object of the present invention to provide for a construction in which the contact which opens and closes the circuit is so mounted that sparking is avoided.

In pursuance of the above objects, and of others which will become apparent hereafter, one feature of the invention resides in a thermostat construction which, briefly stated, comprises an elongated bimetallic strip having a first end portion and a spaced second end portion adpated to be connected to a support. A conductive strip is fast at one end with the first end portion and the remainder of the conductive strip extends extends spaced from the bimetallic strip towards the second end portion thereof. The conductive strip has opposite its fastened end a free end portion. First and second abutment means are provided on the conductive strip and the bimetallic strip in the region of the free end portion and of the first end portion, respectively. An elongated spring member extends longitudinally of the strips and has spaced opposite ends which respectively pivotally and under stress engage the first and second abutment means in line contact therewith.

Sparking in operation of the thermostat construction is avoided by having the movable contact springily mounted in a manner still to be discussed.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a somewhat diagrammatic side view illustrating a thermostat constructed according to one embodiment of the invention;

FIG. 2 is a fragmentary detail view, on an enlarged scale of one abutment in the construction of FIG. 1;

FIG. 3 is a further fragmentary detail view, on an enlarged scale, of FIG. 1;

FIG. 4 is a top-plan view of the spring member in the embodiment of FIGS. 1-3;

FIG. 5 is a fragmentary detail view, on an enlarged scale, of the embodiment of FIG. 1;

FIG. 6 is a view similar to FIG. 1 but illustrating a further embodiment of the invention; and

FIG. 7 is a view similar to FIG. 3 but of the embodiment illustrated in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before entering into a detailed discussion of the illustrated embodiments it is pointed out that it is believed possible to dispense with a detailed discussion of the operation of a bimetallic-element thermostat in view of the fact that such operation is generally known.

Keeping this in mind, and now discussing the embodiment illustrated in FIGS. 1-5, it will be seen that reference numeral 18 identifies one portion of an elongated bimetallic strip, the other portion 7 of which is upwardly angled as illustrated in FIG. 1. At 21 the portion 18 is connected as by riveting with a conductive strip 19, usually consisting of copper. The strip 19 is frame-shaped in its outline, that is it has a substantially annular configuration and in the inner free space of the strip 19 there extends the angled portion 7 of the bimetallic strip.

The illustrated thermostat, the other components of which are not discussed in more detail because they do not have a bearing upon the present invention, has two contacts 20 and 20a. The contact 20a is a stationary contact and the contact 20 is carried by the copper strip 19. In the illustrated embodiment the contact 20 is carried not directly by the strip 19, but rather by a discrete section 9 which is secured as by rivets l0 to the frame-shaped copper strip 19 as shown for instance in FIG. 3. In the embodiment of FIGS. 1-5 the section 9 has two tongues 3 which are bent in one direction here in downward directtion at any desired angle, preferably at an angle of approximately 45- whereas an additional tongue 2 is located between the tongues 3 and is bent in the opposite direction here in upward direction. FIG. 2 shows that the base line about which the tongue 2 is bent in upward direction is rearwardly offset as indicated by 22 with reference to the baseline about which the tongues 3 are downwardly bent. The configuration of the elongated spring member 1 is shown inFIG. 4 and it will be seen that one end portion thereof has a projecting tongue 4 and two shoulders 5. The tongue 4 extends under the tongue 2 of the section 9 arid abuts with the lower edge 11 of shoulders 5 against the upper surface of the tongues 3,'

that is it has line contact with the tongues 3 where the latter are downwardly bent along their base line. Thus, along this line contact the spring member 1 is pivotable and at this abutment line the same abutment forces are obtained as at the opposite abutment line where the end edge 13 of the spring member 1 abuts as will be discussed subseqently. The abutment line along the edges 11 is identified with reference numeral 16 and the extent by which the base line of the tongue 2 is rearwardly offset from the base line of the tongues 3 corresponds approximately to the thickness of the spring member 1, although this has not been drawn to scale in the draw- The upwardly angled portion 7 of the bimetallic strip is provided with a notched recess 12 bounded by surface portions 14 and 15 which define with one another an obtuse angle. The end portion 13 of the spring member 1 is lodged in the thus produced recess and the end face 17 defines with the surface portion 14 of the recess 12 a clearance angle which preferably but not necessarily may be between substantially 3 and 8. The clearance angle is identified with reference numeral 6 and the pivotal line contact with reference numeral 8.

The flexing of the spring member 1, which latter engages at both abutments 8 and 16 with identical abutment forces, corresponds to a parabola whereby an even stress distribution along the spring member 1 is assured.

The angle 6 could be greater than 8 but it must always be assured that the end face 17 and the surface portion 14 will not abut in surface-to-surface contact in any position of the spring member 1.

It is clear that it falls with the concept of the invention that the abutment 16 could be associated with the strip 19 and that the arrangement of the components 2, 3 and 4 could be reversed, so that in place of the single tongue 4 several tongues could be provided, whereas only one or two tongues would be provided on the section line.

In the embodiment of FIGS. 6 and 7 the contact 20 has been mounted in a manner to avoid sparking. Like reference numerals identify like components as in the preceding embodiment. Here, however, there is provided a delaying spring 23 which is of substantially U- shaped configuration and which embraces the free end portion of the strip 19. Below the strip 19 the spring 23 is secured to the strip 19, for instance by the rivets 10, and where in FIGS. 1-5 the contact 20 is mounted on the section 9, that is in the same location, the contact 20 is in the embodiment of FIGS. 6 and 7 mounted on that leg or portion of the spring 23 which overlies the upper side of the section 9.

With the embodiment of FIGS. 6 and 7 a very small lifting of the spring member 1 with reference to the stationary contact 20a will not cause the contact 20 to move out of engagement with the contact 20a or to become displaced in a sense tending to move out of such engagement. Such small displacements are compensated for by delaying spring 23. Thus, the contact 20 can move out of engagement with the contact 20a only when the spring 1 has been stressed to such an extent that it provides for a positive displacement of the contact 20, that is when it has been stressed beyond its neutral point. In this case the spring 23 also acts and now the contact 20 is displaced very rapidly out of engagement with the contact 20a, a displacement which is considerably faster than previously because the spring member 1 has already reached a certain displacement speed by passing beyond its neutral point. This arrangement is necessary because the spring forces in bimetallic-element thermostats are low. Of course, the spring 23 must not cause in itself a displacement of the contact 20 out of engagement with the contact 20a because this would lead to improper operation of the device.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a thermostat construction, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a thermostat, in combination, an elongated bimetallic strip having a first end portion and a spaced second end portion adapted to be connected to a support; a conductive strip fast at one end with said first end portion and extending with a portion thereof spaced from said one end along and spaced from said bimetallic strip towards said second end portion thereof, said conductive strip having opposite said one end thereof a free end portion; first and second abutment means on said conductive strip and said bimetallic strip in the region of said free end portion and of said first end portion, respectively; and an elongated strip-shaped leaf spring member extending Iongitudinally of said strips and having spaced opposite free ends which respectively pivotally and under stress engage said first and second abutment means in line contact therewith.

2. In a thermostat as defined in claim 1, one of said opposite ends having two shoulders which engage said first abutment means, and said second abutment means comprising a notched recess in which the other of said opposite ends is received in pivotal line contact.

3. ha thermostat as defined in claim 2, said one opposite end further having at least one tongue portion projecting beyond said shoulders.

4. In a thermostat as defined in claim 1, said conductive strip comprising a discrete section fast with said free end portion and having a pair of first lugs bent about a common transverse base line in one direction, and at least one second lug bent about an other base line in an opposite direction, both of said base lines extending transversely to the elongation of said strips and said other base line being farther spaced from said first end portion of said bimetallic strip than said common base line, said lugs constituting said first abutment means and one of said spaced opposite ends being pivotally and in line-contact engagement received between said first and second lugs.

5. In a thermostat as defined in claim 4, said spring member having a predetermined thickness; and wherein said other base line is spaced from said common base line by a distance corresponding at least substantially to said predetermined thickness.

6. In a thermostat as defined in claim 1, said second abutment means comprising a notched recess provided in said bimetallic strip in the region of said first end portion thereof facing towards said second end portion and bounded by a pair of inner surfaces which are mutually inclined at an obtuse angle; and wherein one of said spaced opposite ends of said spring member is freely pivotably and in line-contact engagement received in said notched recess and has an end face defining with one of said inner surfaces a clearance angle.

7. In a thermostat as defined in claim 6, wherein said clearance angle is on the order of 5.

8. In a thermostat as defined in claim 1; further comprising a stationary contact and a movable contact, the latter being mounted on said conductive strip.

9. In a thermostat as defined in claim 8, said conductive strip comprising a discrete section fast with said free end portion, and said movable contact being mounted on said discrete section.

10. In a thermostat as defined in claim 8, and further comprising a delay spring fixed to said conductive strip and carrying said movable contact.

ll. In a thermostat as defined in claim 10, wherein said delay spring engages said conductive strip at a location remote from said movable contact.

12. In a thermostat as defined in claim 11, wherein said delay spring is of elongated but other-than-straight configuration.

13. In a thermostat as defined in claim 10, wherein said delay spring engages said conductive strip and is of elongated but other-that-straight configuration.

14. In a thermostat as defined in claim 10, wherein said delay spring is of substantially U-shaped configuration and has one leg connected with said conductive strip and an other leg facing said stationary contact; and wherein said movable contact is mounted on said other leg.

Claims (14)

1. In a thermostat, in combination, an elongated bimetallic strip having a first end portion and a spaced second end portion adapted to be connected to a support; a conductive strip fast at one end with said first end portion and extending with a portion thereof spaced from said one end along and spaced from said bimetallic strip towards said second end portion thereof, said conductive strip having opposite said one end thereof a free end portion; first and second abutment means on said conductive strip and said bimetallic strip in the region of said free end portion and of said first end portion, respectively; and an elongated strip-shaped leaf spring member extending longitudinally of said strips and having spaced opposite free ends which respectively pivotally and under stress engage said first and second abutment means in line contact therewith.

2. In a thermostat as defined in claim 1, one of said opposite ends having two shoulders which engage said first abutment means, and said second abutment means comprising a notched recess in which the other of said opposite ends is received in pivotal line contact.

3. In a thermostat as defined in claim 2, said one opposite end further having at least one tongue portion projecting beyond said shoulders.

4. In a thermostat as defined in claim 1, said conductive strip comprising a discrete section fast with said free end portion and having a pair of first lugs bent about a common transverse base line in one direction, and at least one second lug bent about an other base line in an opposite direction, both of said base lines extending transversely to the elongation of said strips and said other base line being farther spaced from said first end portion of said bimetallic strip than said common base line, said lugs constituting said first abutment means and one of said spaced opposite ends being pivotally and in line-contact engagement received between said first and second lugs.

5. In a thermostat as defined in claim 4, said spring member having a predetermined thickness; and wherein said other base line is spaced from said common base line by a distance corresponding at least substantially to said predetermined thickness.

6. In a thermostat as defined in claim 1, said second abutment means comprising a notched recess provided in said bimetallic strip in the region of said first end portion thereof facing towards said second end portion and bounded by a pair of inner surfaces which are mutually inclined at an obtuse angle; and wherein one of said spaced opposite ends of said spring member is freely pivotably and in line-contact engagement received in said notched recess and has an end face defining with one of said inner surfaces a clearance angle.

7. In a thermostat as defined in claim 6, wherein said clearance angle is on the order of 5*.

8. In a thermostat as defined in claim 1; further comprising a stationary contact and a movable contact, the latter being mounted on said conductive strip.

9. In a thermostat as defined in claim 8, said conductive strip comprising a discrete section fast with said free end portion, and said movable contact being mounted on said discrete section.

10. In a thermostat as defined in claim 8, and further comprising a delay spring fixed to said conductive strip and carrying said movable contact.

11. In a thermostat as defined in claim 10, wherein said delay spring engages said conductive strip at a location remote from said movable contact.

12. In a thermostat as defined in claim 11, wherein said delay spring is of elongated but other-than-straight configuration.

13. In a thermostat as defined in claim 10, wherein said delay spring engages said conductive strip and is of elongated but other-that-straight configuration.

14. In a thermostat as defined in claim 10, wherein said delay spring is of substantially U-shaped configuration and has one leg connected with said conductive strip and an other leg facing said stationary contact; and wherein said movable contact is mounted on said other leg.

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