US3818410A - High voltage thermostat - Google Patents

Abstract

This thermostat comprises a cup-shaped metal cover, and a dielectric base which is secured in the open end of the cover. The base has a central chamber containing a flexible switch arm, which is secured at one end to one of a pair of terminals that are secured in the base. A flexible, dielectric cap is mounted over the chamber in the base; and a bimetallic disc is positioned between the cap and the cover to operate the switch arm through the cap. A tongue or flap is struck out of the cap to transmit movement between the disc and switch arm.

Description

United States Patent 1 1 3,818,410 Hire June 18, 1974 HIGH VOLTAGE THERMOSTAT Primary Examiner.l. D. Miller [75] Inventor. Charles John Hire, Pittsford, NY. Assistant Examiner Fred E. Bell Assignee: F8890 Industries, te Attorney, Agent, or Firm-Shlesinger, Fitzsimmons &

Shlesinger [22] Filed: Mar. 2, 1973 211 Appl. No: 337,693 [57] ABSTRACT This thermostat comprises a cup-shaped metal cover, and a dielectric base which is secured in the open end [52] US. Cl 337/354, 337/62. 333377013 253 of the Coven The base has a central chamber contaim 51] I t Cl 01h 37/52 ing a flexible switch arm, which is secured at one end [58] d 354 365 to one of a pair of terminals that are secured in the o are d base. A flexible, dielectric cap is mounted over the chamber in the base; and a bimetallic disc is posi- 56 R f Ct d tioned between the cap and the cover to operate the 1 e erences l e switch arm through the cap. A tongue or flap is struck UNITED STATES PATENTS out of the cap to transmit movement between the disc 3,139,500 6/1964 Fallow et al. 337/354 and switch arm. 3,297,845 1/1967 Mertler 3,649,943 3/1972 Mano 337/380 3 Claims, 2 Drawing Flgures "with/112,631? 4 HIGH VOLTAGE THERMOSTAT This invention relates to thermostats and more particularly to a thermostat of the type containing a snapaction switch.

Thermostats having snap-acting switch contacts are employed to control or protect electrically operated applicances such as heaters, refrigerators, computers, air conditioners, etc. Typically the snap-action switch contact is operated by a temperature-responsive, bimetallic member, such as a disc, which bows suddenly in opposite directions on predetermined changes in ambient temperature to open or close the circuit.

For a variety of reasons it is desirable, generally, to make such thermostats as small as possible. However, although it is customary to enclose or seal the switch contacts of the thermostat in a casing or housing to prevent corrosion, damage, or malfunction of the contacts during use, the very compactness of such thermostats renders them liable to grounding or shorting of the contacts especially when the thermostats are used in refrigeration systems or other damp locations. The path to the metal cover (ground) of the thermostat is very short. For this reason many conventional thermostats do not meet with the approval of the Underwriters Laboratories.

It is an object of this invention to provide an improved thermostat of the snap-action variety, which is particularly suited for use in high voltage circuits, circuits where low leakage is required and/or in moist or damp environments. To this end it is an object also to construct such a thermostat so as substantially to eliminate the possibility of grounding or shorting between its housing and the switch contacts enclosed therein.

Still another object of this invention is to provide a simple, inexpensive compact thermostat in which the switch contacts are so enclosed that there is high dielectric strength between the current carrying parts and ground, so that the possibility of the currentcarrying parts being shorted on the housing is minimized.

Other objects of this invention will be apparent hereinafter from the specification and the recital of the appended claims, particularly when read in conjunction with the accompanying drawing.

In the drawing:

FIG. 1 is a cross-sectional view of a thermostat made in accordance with one embodiment of this invention, the view being taken along the line l'-1 in FIG. 2 looking in the direction of the arrows; and

FIG. 2 is a sectional view of this thermostat taken along the line 2-2 in FIG. 1 looking in the direction of the arrows, and with portions of the thermostat broken away.

Referring now to the drawing by numerals of reference, denotes a thermostat comprising an inverted, can or cup-shaped metal cover 12, that is provided with an internal, circumferential shoulder 13 adjacent its closed end (upper end in FIG. 1). Press-fit in the cover l0is a cup-shaped base 15, which is made of dielectric material, and which has an integral annular wall 16 that projects upwardly in cover 12 toward shoulder 13. Two, right-angular terminals 18 are secured each at one end to the underside of base by electricallyconductive rivets 19, so that the opposite ends of the terminals project from housing 12 as at 20.

Secured at one end by one of the rivets 19 to the inside surface of base 15, and extending transversely across the center of the recess 21 therein is a flexible, electrically conductive switch arm 22. This arm extends upwardly from fastening rivet 19, and then is bent downwardly again intermediate its ends at 24, and at its free end has secured thereon a metal contact 23. Normally contact 23 is held resiliently by arm 22 in an open position in which it is disposed in spaced relation to the other conductive rivet 19.

The space in cover 12 beneath base 15 is filled or potted with a layer of epoxy resin, or the like.

Mounted over the upper end of wall 16 is an inverted, generally cup-shaped insulating cap 30. Around its outer edge cap 30 has an integral, annular skirt 31, which surrounds the upper end of wall 16 in the annular space formed between wall 16 and the surrounding cover 12. A tongue or flap 32 is struck out of the transverse, closed end of cap 30 along a U-shaped cut 33 to overlie the flexible switch arm 22 at bend 24.

Cap 30 is made from a flexible, dielectric material so that its tang 32 is free to flex or pivot toward and away from the switch arm 22 through the opening or cut 33 in the cap. Moreover, tang 32 extends parallel to arm 22, but in a direction opposite to that of the switch arm, so that the free end of the tang faces in the direction opposite the free end of the switch arm.

Mounted in housing 12 between cap 30 and the closed end of the housing is a temperature-responsive, bimetallic disc 35. The marginal edge of disc 35 is held between the housing shoulder 13 and the portion of the cap 30 which overlies wall 16 so that the center of the disc will flex in opposite directions in response to predetermined changes in ambient temperature.

In use, the terminal ends 20 are connected in known manner in an electrical circuit so that when arm 22 is in its open position, this circuit will be open; and, conversely, when disc 35 snaps downwardly upon a predetermined temperature change, arm 22 will be moved to closed position to complete this circuit. The deep wall 16 of the insulating base 15 will ordinarily prevent shorting of the switch; but insulating cap 30 is added protection against shorting. The tongue or flap 32 on dielectric cap 30, is provided, particularly in those cases where the movement of the actuating disc 35 is restricted by the cap 30. Without the tongue the disc might waste most of its energy bulging the cap 30. The tongue 32 acts somewhat as a multiplying lever to transmit a slight bulge of the disc to the switch arm 22. Of course the tongue 32 prevents the bimetallic disc 35 from shorting out the metal cover 12 on the switch arm 22.

Where there is sufficient room in the thermostat for the central portion of the disc 35 to move without being restricted by cap 30 and the cap is sufficiently flexible, the tongue 32 may be omitted and the cap may be made with a fully closed end.

I-Ieretofore it has been customary ordinarily in thermostats to employ a more or less flat base 15 without a wall such as 16. When these thermostats are used in a moist or damp environment, however, trouble may be encountered. Moisture may get in and cause currentcarrying parts to short out. The cap 30, however, when used in conjunction with a high-walled base I5,-operatively seals the upper end of the recess 21 relative to the cover 12, and thus precludes shorting.

While this invention has been described in connection with a specific embodiment thereof, it will be apparent to one skilled in the art that it is capable of further modification, and this application is intended to cover any modifications or variations that fall within the scope of the invention of the coverage of the appended claims.

Having thus described my invention, what I claim is:

l. A thermostat comprising a generally cup-shaped metal cover, a dielectric base secured transversely across the open end of said cover and having an annular wall prosaid terminals, and

a bimetallic disc mounted beneath said cover to overlie said cap and operative to flex at its center toward and away from said cap in response to predetermined changes in ambient temperature, thereby to cause the center of said cap to flex correspondingly toward and away from said switch arm to effect operation thereof,

said cap having around its periphery an integral, an-

nular skirt which extends coaxially downwardly into an annular space which surrounds the inner end of said annular wall on said base.

2. A thermostat as defined in claim 1, wherein a portion of said cap is cut to form on said cap a flexible tongue which overlies and is engageable with said switch arm.

3. A thermostat as defined in claim 2, wherein said tongue has straight sides and a curved free end and is pivotal relative to the remaining portion of said cap.

Claims (3)

1. A thermostat comprising a generally cup-shaped metal cover, a dielectric base secured transversely across the open end of said cover and having an annular wall projecting into said cover toward the closed end thereof to define in said base a central chamber, a pair of spaced terminals secured to said base at the bottom of said chamber, and projecting exteriorly for connection in an electric circuit, a flexible, dielectric cap positioned over the inner end of said annular wall to cover said chamber, a flexible switch arm in said chamber secured to one of said terminals and operable by said cap between closed and open positions in which said arm engages and disengages, respectively, the other of said terminals, and a bimetallic disc mounted beneath said cover to overlie said cap and operative to flex at its center toward and away from said cap in response to predetermined changes in ambient temperature, thereby to cause the center of said cap to flex correspondingly toward and away from said switch arm to effect operation thereof, said cap having around its periphery an integral, annular skirt which extends coaxially downwardly into an annular space which surrounds the inner end of said annular wall on said base.

2. A thermostat as defined in claim 1, wherein a portion of said cap is cut to form on said cap a flexible tongue which overlies and is engageable with said switch arm.

3. A thermostat as defined in claim 2, wherein said tongue has straight sides and a curved free end and is pivotal relative to the remaining portion of said cap.

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