US3660793A

US3660793A - Thermostat with manual reset

Info

Publication number: US3660793A
Application number: US24605A
Authority: US
Inventors: Edward G Them; Walter C Kowalski
Original assignee: Therm O Disc Inc
Current assignee: Therm O Disc Inc
Priority date: 1970-04-01
Filing date: 1970-04-01
Publication date: 1972-05-02
Anticipated expiration: 1989-05-02

Abstract

A structurally simple low cost manual reset thermostat is disclosed. The thermostat includes a one piece body and two terminal assemblies. The rivet of one terminal assembly connects the switch arm and a reset retainer. The switch arm retains a snap disc in its assembled position. Four guide projections with two on each side of the spring arm laterally locate the snap disc. A reset member is positioned by the guide projections and is arranged to engage the snap disc on opposite sides of the spring arm. Stops are provided to prevent overstressing of the disc by the reset member.

Description

United States Patent 1151 3,660,793 Them et al. 1451 May 2, 1972 54] THERMOSTAT WITH MANUAL RESET 3,322,920 5/1967 Morris ..337/365 [72] Inventors: Edward G. Them; Walter C. Kowalski, FQREIGN PATENTS 0R APPUCATIONS both of Mansfield, Ohio v 691,167 5/1953 Great Brltain ..337/91 [73] Assignee: Therm-O-Disc, Incorporated, Mansfield,

Ohio Primary Examiner-Bemard A. Gilheany Assistant ExaminerDewitt M. Morgan [22] Flled' 1970 Attorney-McNenny, Farrington, Pearne & Gordon [21] Appl. No.: 24,605

[57] ABSTRACT [52] U.S. Cl ..337/348, 337/380 A r c urally simple low cost manual reset thermostat is dis- I 51 1111.0 ..H0lj 37/54, 110111 37/70, H01h 37/74 closed- The thermostat includes a one Piece y and two [58] Fie|d f Search; 337 9 3 3 354 3 7 3 2 minal assemblies. The rivet of one terminal assembly connects 337/380 the switch arm and a'reset retainer. The switch arm retains a snap disc in its assembled position. Four guide projections [56] References Cited with two on each side of the spring arm laterally locate the snap disc. A reset member is positioned by the guide projec- UNITED STATES PATENTS tions and is arranged to engage the snap disc on opposite sides of the spring arm. Stops are provided to prevent overstressing 2,839 637 6/1958 Epsteln ..337/9l ofthe disc by the reset'member 2,426,906 9/1947 Vaughan... ....337/9l X A 3,428,932 2/1969 Menecke ..337/348 4 Claims, 6 Drawing Figures j- 47 Z 2. jg 33 4a 14 .42 43 v nr: :2:

v 28 A 5 Z /0 l 1 22 1' fi -:2 g 7 I 4/ -1 2/ THERMOSTAT WITH MANUAL RESET BACKGROUND OF THE INVENTION This invention relates generally to bimetallic snap disc thermostats and more particularly to a novel and improved manual reset thermostat of such type.

PRIOR ART The U.S. Letters Patent to Morris, No. 3,322,920, assigned to the assignee of the present invention, discloses a simple, low cost thermostat. In this thermostat the structure is arranged to require a minimum number of parts and to minimize the labor required for assembly. The thermostat provides a single body member, two terminal assemblies, a spring switch arm secured to one terminal assembly, and engagable with the other, and a bimetallic snap disc for operating the switch arm. The structure is arranged'so that the disc is retained in position within the "body by the switch spring arm and so that only two rivets are required to, assemble all of the elements of the thermostats. Since a relatively small number of parts are required, and since assembly costs are low, the thermostat is low in cost even though it provides reliable and accurate operation.

SUMMARY OF THE INVENTION The present invention permits the manufacture of a thermostat of the type disclosed by Morris wherein the thermostat is a manual reset device. The manual reset feature is added to a thermostat of the type illustrated by Morris without substantially increasing the cost of theentire device.

The illustrated thermostat incorporating this invention includes a single body member with two terminal assemblies riveted thereon. A spring arm is secured at one end to one terminal assembly and provides a free arm portion engagable with the other terminal assembly. The disc is retained in the position within the body assembly by the spring arm. The body is formed with locating projections which laterally locate the disc in its assembled position. The same projections laterally position a reset member and limit the movement of the reset member to prevent damage to the disc. A single retaining element secured to one of the terminal assemblies retains'the reset member in position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a thermostat incorporating this invention;

FIG. 2 is a side elevation in longitudinal section taken generally along 2-2 of FIG. 1 illustrating thestructural arrangement of the thermostat when the thermostat switch is I trating the body structure for retaining the disc and the associated structure of the reset member.

DETAILED DESCRIPTION OF THE DRAWINGS The illustrated embodiment of this invention includes a molded body member preferably formed of a plastic material such as a phenolic resin. The body is generally rectangular in shape and is provided with openings 11 at its ends for mounting the thermostat on the associated devices. A switch recess 12 is formed in the central portion of the body 10 to receive the operating mechanism of the thermostat. A first terminal assembly 13 is mounted on the body 10 and includes a rivet 14 and a terminal element 16. A second terminal assembly l7'is mounted on the body 10 at a location spaced from the first terminal assembly 13 and includes a rivet 18 and a terminal element 19.

A cantilever spring contact arm 21 is mounted at one end by the rivet 18 and is provided with a free arm portion which extends to a position over the rivet 14. A contact 22 secured to the spring arm 21 is engagable with the rivet 14 when the switch is closed and is moved to a position spaced from the rivet 14 when the switch is open.

A bimetallic snap disc 23 is positioned between the spring arm 21 and a central projection 24 formed on a web portion 26 integrally fonned on the body 10. Lateral positioning of the disc is provided by four substantially symmetrically positioned

guide projections

27, 28, 29, and 30, integrally formed in the body 10. These guide projections are arranged with two spaced projections on each side of the spring arm 21.

The various elements are proportioned so that when the snap disc 23 is in one position of stability as illustrated in FIGS. 2 and 3, the contact 22 engages the rivet I4 and the switch is closed. However, when the disc snaps through to its other position of stability as illustrated in FIGS. 4 and 5, the.

spring arm 21 is deflected upwardly, as illustrated in the drawings, causing openingof the switch. In the open position the spring arm 21 engages diametrically opposite edges of the disc and the center portion of the disc rests against the central projection 24. Reference maybe made to the Morris patent, supra, for a more detailed description of the structure and operation of the basic thermostat and the Morris patent is hereby incorporated by reference for such details.

Manual reset is provided by a structure including a reset member 32 and a retainer member 33. The shape of the reset member 32 is best illustrated in FIG. 6. The reset member 32 is preferably molded from a plastic material and includes a cross portion 34 which extends between two substantially

parallel wall sections

36 and 37. Extending from the lower ends of the

wall sections

36 and 37, respectively, are disc en? gaging projecting

portions

38 and 39. The length of the

portions

38 and 39 is less than the spacing between the associated guide projections 27 through 30 so that theseportions can extend down between the guide projections and engage the edges of the disc 23 with one projection on each side of the spring arm 21. I

The reset retainer 33 is preferably formed of flat metal stock shaped to provide a mounting portion 41 secured under the head of .the rivet 18, two

upstanding portions

42 and 43, and a central portion 44 which extends substantially parallel to the spring arm. The central portion 44 extends between the

'walls

36 and 37 and on the side of the cross portion 34 opposite the spring arm 21. A clearance opening 46 is formed in the central portion 44 substantially in alignment with the center portion of the disc 23. A projection 47 on the reset member 32 extends through the opening 46 to assist in locating the reset member.

The various elements are proportioned so that the

projections

38 and 39 are spaced from the disc 23 when the disc is in the position of FIGS. 2 and 3 and the switch is closed. At this time the stop surfaces 48 engage the tops of the adjacent projections 27 through 30 to limit the movement ofthe reset member in a direction toward the disc. However when the disc snaps through to its opposite position of stability as illustrated in FIGS. 4 and 5, the lateral edges of the disc on opposite sides of the spring arm 21 engage the

portions

38 and 39 and raise the reset member to the illustrated position.

When reset is desired, the reset member 32 is pressed downward causing the

portions

38 and 39 to press down against the edges of the disc on opposite sides of the spring arm 21 and deflect the disc toward its first position of stability. However, because of the engagement of the stop surfaces 48 with the top of the associated guide projections, the movement of the reset member is limited and overstressing of the disc cannot occur. Therefore the disc calibration cannot be changed by the operation of the reset. When trip-free operation is required, the various elements are proportioned so that the disc will hold the switch open if it remains above a reset temperature even when the reset member is fully depressed. With such an arrangement the disc will only snap back through its initial position and allow the switch to close if the disc is below a reset temperature.

The end .of the portion 43 of the retainer engages the body at a location spaced from the first terminal assembly 13 on the side opposite the second terminal assembly 17 to provide support for the free end of the retainer. With this structure any downward force applied to the central portion 44 of the retainer is supported at both ends thereof. Upward forces of the free end of the retainer 33 normally are not encountered so it is not necessary to provide a positive connection at the free end. The manual reset function, in accordance with the present invention, is obtained in the present instance by the mere addition of two parts, namely, the reset member and the retainer. The retainer 33 is secured to the assembled condition by the same rivet 18 which is used to mount the terminal element 19 and the spring arm 21. Therefore the cost of manufacturing the parts and the cost of assembly is not increased materially even though the manual reset feature is provided.

Although a preferred embodiment of this invention is illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention disclosed.

What is claimed is:

l. A manual reset thermostat comprising a base, first and second terminal assemblies mounted on said base, a cantilever spring arm mounted on said first terminal assembly and having a free arm portion movable into and out of engagement with said second terminal assembly, said body providing guide projections on each side of said spring arm and a central projection, a bimetallic snap disc having two positions of stability laterally located by said guide projections and located between said central projection and said spring arm, said disc when in one position of stability permitting said free arm portion to engage said second terminal assembly and when in the other position of stability maintaining said free arm portion spaced from said second terminal assembly, and a reset member having a portion extending between said guide projections engagable with said disc on each side of said spring arm when said disc is in said other position of stability, movement of said reset member to an operative position causing said portions to cooperate with said central projections and cause movement of said disc toward said one position of stability, and a retainer member mounted in one of said terminal assemblies operating to retain said reset member in its assembled position.

2. A manual reset thermostat as set forth in claim 1 wherein said retainer member is secured to said first terminal and overlies said spring arm, said retainer member engaging said body on the side of said second terminal remote from said first terminal.

' 3. A manual reset thermostat as set forth in claim 2 wherein said reset member provides a cross portion position between said spring arm and said retainer member.

4. A manual reset thermostat as set forth in claim 3 wherein said retainer member is formed with an opening substantially coaxial with said disc, and said reset member provides a locating projection extending through said opening.

Claims

1. A manual reset thermostat comprising a base, first and second terminal assemblies mounted on said base, a cantilever spring arm mounted on said first terminal assembly and having a free arm portion movable into and out of engagement with said second terminal assembly, said body providing guide projections on each side of said spring arm and a central projection, a bimetallic snap disc having two positions of stability laterally located by said guide projections and located between said central projection and said spring arm, said disc when in one position of stability permitting said free arm portion to engage said second terminal assembly and when in the other position of stability maintaining said free arm portion spaced from said second terminal assembly, and a reset member having a portion extending between said guide projections engagable with said disc on each side of said spring arm when said disc is in said other position of stability, movement of said reset member to an operative position causing said portions to cooperate with said central projections and cause movement of said disc toward said one position of stability, and a retainer member mounted in one of said terminal assemblies operating to retain said reset member in its assembled position.

3. A manual reset thermostat as set forth in claim 2 wherein said reset member provides a cross portion position between said spring arm and said retainer member.