US 2286053 A
Description (OCR text may contain errors)
June 9, 1942. BLETZ 2,286,053
THERMOS TAT Filed Sept. 10, 1940 Fig.5. Q IHHHE! 45a WITNESSES: INVENTOR Edward Blzz.
Patented June 9, 1942 THERMOSTAT Edward Bletz, Lexington, Ohio, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,- a corporation of Pennsylvania Application September 10, 1940, Serial No. 356,134 7 Claims. (Cl. 297-15) My invention relates to thermostats and more particularly to bimetallic elements and structures therefor.
An object of my invention is to provide a simple, inexpensive, efiicient bimetallic thermal responsive element adapted to be attached to a supporting structure so as to move from one operative position to another with a snap action.
A further object of my invention is to provide a bimetallic element for a thermostat having a relatively transverse slot therein for receiving a mounting device for attaching such element to the thermostat supporting structure.
Another object of my invention is to provide an elongated bimetallic element which is normally flat and in a stable condition and which upon being attached to a supporting structure is maintained in an unstable condition due to such attachment.
Other objects of my invention will either be pointed out specifically in the course of the i'ollowing description of a device embodying my invention, or will be apparent from such description.
In the accompanying drawing:
Figures 1 and 2 are side elevational and bot-- tom views, respectively, of a thermostatic structure embodying my invention;
Fig. 3 is a sectional view taken along the line IIIIII of Fig. 1; and
Figs. 4 and 5, respectively, show plan views of bimetallic elements which may be used in the thermostat embodying my invention.
Referring to the accompanying drawing, in which like reference characters indicate like parts in the several figures, I show a thermostat I0 comprising a supporting structure l2, cooperating contacts I4, an adjusting member l6 and a bimetallic thermal responsive element l8 which is rigidly attached at one end thereof to the supporting structure.
The supporting structure I2 is in this instance a flat rectangularly shaped metallic bar-like member having a depending inwardly extending ledge portion or flange 20. A plurality of apertures 22, 24, 26 and 28 are located within the hat supporting structure l2 to receive various parts of the thermostatic structure, as hereinafter described. The apertures 22 and 24 are located along the longitudinal axis of 'the structure I 2 with the aperture 24 being positioned substantially at the midpoint thereof, and the aperture 22 is located within the supporting structure 12 at a point opposite to that at which the ledge 20 is located. The apertures 26 and 28 are located along a transverse line which is above the ledge'20. These apertures 26 and 28 are adapted to receive the stationary contacts and terminal structures for the thermostat, as hereinafiter described.
The cooperating contacts l4 comprise, in this instance, a plurality of stationary contacts 30 and a movable bar-like jumper contact 32. The stationary contacts 30 constitute the lower ends of suitable metallic terminal structures 34 which are adapted to be passed through the apertures 26 and 28 and to be insulated from the supporting structure l2 by means of suitable insulating members 36 (see Fig. 3). The lower end of the terminal structures 34 are then spun or peened over tightly against suitable washer-like members 38 so as to rigidly attach the terminal structures 34 to the supporting structure. The spun or peened over portions of the terminal structures 34 thus function as the stationary contacts 38.
The movable contact 32 is in this instance an elongated bar-like member rigidly attached to and insulated from the free end of the bimetallic element l8 and is adapted to engage, when in its closed or operated position, both of the stationary contacts 30. However, it is to be understood that the cooperating contacts 30 and 32 may be formed in any other suitable manner and that such contacts may be attached to the corresponding structure in any other desired manner.
The adjusting member It comprises, in this instance, an elongated threaded member which is adapted to be threaded through the aperture 24 located at substantially the midpoint of the supporting structure l2.- The threaded member l6 engages and is rotatably attached to the midpoint of the central leg of bimetallic element [8 as hereinafter described. However, such adjusting member may be formed or attached to the bimetallic element in any other suitable manner.
The bimetallic element l8 comprises, in this instance, an elongated bimetallic strip-like member having a relatively narrow portion 48 at one end and a relatively wide portion 46 at the other end thereof so as to form substantially a irustum of an'isosceles triangle. A plurality of elongated, longitudinally extending, substantially triangular apertures 40 are located within the bimetallic element l8 to form a centrally located parallelsided strip portion 42 and an exterior strip portion having two parallel-sided lateral strips or portions 44 and a wide end strip or portion 48.
In addition, a relatively transversely extending substantially V-shaped aperture or slot 45 is disposed between the short bases of the triangularly shaped apertures 40 across the wide end portion 46 so as to completely separate the end portion 46 and the tapering end of the centrally located strip portion 42 (see Figs. 2 and 3). The exterior strips 44 may or may not have, however in this instance they do haye,- a plurality of crimps therein to, in effect, reduce the length thereof. The transverse apertures 45 in cooperation with the supporting structure l2 tends to produce the required stress arrangement within the bimetallic elementto produce a snap action thereof, as hereinafter described.
The transverse apertures or slots 45, in this instance, are adapted to extend obliquely into the central portion of the wide end strip 46 to form substantially a V-shaped notch therein and 'a complementary outwardly extending V-shaped end of the central strip 42. An arcuately shaped notch is formed at the apices of such a V-shaped portion toreceive a suitable mounting member or screw 50. However, such space formed by the notches is smaller than the mounting member or screw 50 to cause a buckling action of the element i8 as such element is attached to the supporting structure, as hereinafter described.
The bimetallic element 18 is rigidly attached to the supporting structure I2 by means of a suitable wedging means or shoulder screw 50 and a sleeve-like member 56 surrounding the screw 50. The shoulder screw 50 is adapted to fit within the arcuately shaped space located between the end of the central strip 42 and wide end portion 46 adjacent the apex of the transverse aperture 45. The gap between the end of the central strip 42 and end portion 46 is somewhat smaller than the distance across the shoulder portion of shoulder screw 50, as noted above. In other words, as the shoulder screw 50'is forced within the space between the central strip 42 and end portion 46, such central strip 42 will be bowed or wedged outwardly or will be put under a longitudinal compressive force, while the exterior strips 44 will have a tensile or stretching force applied thereon through the end portion 46. This uneven force distribution through the element l8 causes such element to assume a flexed condition when in a normal operative or closed-contact position and insures the snap movement of such element as it moves from one position to another as indicated by the solid and dotted lines in Fi 1.
When attaching the element l8 to the supporting structure i2 by means of shoulder screw 50, such screw is threadedly engaged within the aperture 22 and is drawn tightly against the supporting structure i2 through the sleeve 56. The movable free end of the bimetallic element It is then located between the ledge 20 and stationary contacts 30 so, that the movable contact 32, in-
sulatedly attached to the free end oi element 18, may engage such stationary contacts when the element is in its upper or operated position, see Fig. 1. The lower position of the element l8 as it flexes to an open or inoperative position is selectively determined by means of a suitable set screw 58 threadedly positioned upon the ledge 20.
It will be observed that the wide end portion 46, being retained at its midpoint by means oi shoulder screw 50, is free to flex along the transverse line passing through such. screw. This transversely flexing action, in turn, is adapted to change the overcenter snapping position of such form a uniform rectangularly shaped end portion or strip 45a, and, in turn, upon being attached to a supporting structure, as hereinabove described, produce uneven stresses on forces within the element, buckling the middle leg and causing such member to snap from one position to another in a well known manner.
It is, therefore, obvious that I have provided a bimetallic element or snap-acting thermostat which need not have any crimping of its outer legs or strip, for example, but may have an uneven stress formation positioned therein. by means of a wedging or longitudinally compressing action as the element is rigidly attached to I a suitable supporting structure.
While I have shown my invention in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of further changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth'in the appended claims.
I claim as my invention:
1. A thermostat element comprising an elongated bimetallic plate forming a central strip, two exterior lateral strips and end portions joining said lateral strips, one of said end portions being substantially wider than the other end portion, said central strip joined to the narrow end portion and extending relatively close to the wide end portion and mounting means disposed within the adjacent edges of the central strip and wide end portion for compressing the central strip 'and elongating the exterior strips.
2. A thermostat element comprising an elongated bimetallic plate forming a central strip, two exterior lateral strips and end portions joining said lateral strips, one of said end portions being substantially wider than the other end portion and having a notched portion within the i inner edge thereof, said central strip joined to the narrow end portion and extending with a complementary free end portion relatively ,to
' metallic element forming a centralstrip, two
exterior lateral strips and end portions joining said lateral strips, said central strip joined to one end portion and extending relatively close to the second end portion with a small gap therebetween, and 'means passing through said gap for attaching the element to the supporting structure and for longitudinally compressing the central strip and tensioning thev exterior strips to produce an unstable condition within the element, whereby said element will move from one position to another with a snap action in response to the changes in temperature thereof.
4. In a snap-acting thermostat comprising a supporting structure, the combination or a bimetallic element forming a central strip, two exterior lateral strips and end portions Joining said lateral strips. said central strip Joined to one end portion and extending relatively close to the second end portion with a small gap therebetween, and means passing through said gap for attaching the element to the supporting structure and for longitudinally compressing the central strip and 'tensioning the exterior strips to produce an unstable condition within the ele-, ment, whereby said element will move from one position to another with a snap action in response to the changes in temperature thereof, and adjusting means rotatively supported by the supporting structure engaging the central strip for selectively adjusting the operating characteristics of thebimetallic element.
5. A thermostatic element comprising an elongated bimetallic plate iorming a central strip, two exterior lateral strips and end portions Joining said lateral strips, said central strip being Joinedto one end portion and having one end extending relatively close to the second end portion to leave a gap therebetween, and means having a greater dimension than said gap in the direction oi said gap disposed between said one end and said second end portion to widen said gap and thereby distort said central strip, said means also attaching said plate to a supporting structure.