US3675178A

US3675178A - Manual reset thermostat

Info

Publication number: US3675178A
Application number: US117239A
Authority: US
Inventors: Donald E Place
Original assignee: Therm O Disc Inc
Current assignee: Therm O Disc Inc
Priority date: 1971-02-22
Filing date: 1971-02-22
Publication date: 1972-07-04
Anticipated expiration: 1989-07-04
Also published as: CA930708A

Abstract

A trip-free manual reset bimetal disc operated thermostat is disclosed. A unitary bumper operatively connects the disc to a pair of switches and a manual reset member. The travel of the manual reset member is limited, and the elements are proportioned so that full movement of the reset member does not cause switch operation unless the disc is at reset temperatures. The elements are arranged to cooperate to define a pair of switch chambers which are isolated from each other and are also isolated from a disc cavity.

Description

United States Patent Place I [1 1 3,675,178 July4, 1972 MANUAL RESET THERMOSTAT 3,219,783 11/1965 Odson ..337/348 sea 3,428,932 2/1969 Manecke ..337/348 Primary ExaminerBemard A. Gilheany Assistant ExaminerDewitt M. Morgan Attorney -McNenny, Farrington, Pearne & Gordon [57] ABSTRACT A trip-free manual reset bimetal disc operated thermostat is disclosed. A unitary .bumper oper'atively connects the disc to a pair of switches and a'manual reset member. The travel of the manual reset member is limited, and the elements are proportioned so that full movement of the reset member does not cause switch operation unless the disc is at reset temperatures. The elements are arranged to cooperate to define a pair of switch chambers which are isolated from each other and are also isolated from a disc cavity.

17 Claims, 5 Drawing Figures Patented July 4, 1972 3,675,178

, 2 Sheets-Sheet l INVENTOR DOA/440 E. PZACZ BY /6 n A/a/A/x/mee/A/ara Pam/5 {604 M MANUAL RESET THERMOSTAT BACKGROUND or THE INVENTION This invention relates generally to bimetal operated thermostats and more particularly to a novel and improved manual reset bimetallic disc operated thermostat.

PRIOR ART Manual reset bimetal disc operated thermostats are known. Examples of such thermostats are illustrated in the U.S. Pat. Nos. 2,714,644; 3,164,702; and 3,428,932. The latter of these patents describes a thermostat of this general type which may include either double pole or single pole switches and which may be trip-free" in that the reset mechanism is described as being arranged so that its operation cannot close the switch unless the disc has returned to a reset temperature.

SUMMARY OF THE INVENTION 7 A manual reset thermostat in accordance with this invention provides improved reliability with a simplified structure.

In the illustrated embodiment a double pole, double break switch mechanism is mounted in the body assembly in a symmetrical manner with respect to the central axis of the bimetallic snap disc. A single unitary bumper element engages the center of the disc and is provided with lateral arms which engage and operate the switches. A reset member is centrally mounted for movement along the central axis. When operated, the reset member engages the bumper and thereby moves the disc toward its reset position. Body stops limit the movement of the reset member to a position which does not cause the switches to close unless the disc has returned to reset temperatures. Therefore, operation of the reset does not result in switch closure if the disc remains above its reset temperature and the thermostat is trip-free. Further, the limited travel of the reset prevents damaging stresses from being applied to the disc.

Relatively stiff bridging contacts are provided in each switch. Consequently, they do not flex or elastically deform during operation and a reliable opening is provided even when contact welds occur. The structure is arranged so that the bridging contacts are retained in position by cooperating surfaces provided on the body and reset member and separate mounting or positioning means are not required. A spring extends between each bridging contact and the reset member and performs the dual function of urging the switches toward their closing position and the reset member toward its normal retracted position.

The structure is arranged so that the cavity in which the disc is located is completely isolated from the switch chambers, and the switch chambers are isolated from each other. Consequently, arc splatter or the like is confined and cannot reach the separated cavities or chambers of the mechanism.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a preferred embodiment of a thermostat incorporating the present invention;

FIG. 2 is a section taken along 2-2 of FIG. 1;

FIG. 3 is a enlarged fragmentary section taken along 3-3 of FIG. 1;

FIG. 4 is an exploded perspective view of the bumper, the bridging contacts of the switches, and the reset member; and

FIG. 5 is an enlarged fragmentary broken section illustrating the mechanism in a condition in which the reset member is fully depressed before the disc returns to a reset temperature with the reset position of the disc illustrated in phantom.

DETAILED DESCRIPTION OF THE DRAWINGS The illustrated embodiment of this invention includes a symmetrically positioned projections I7, two of which appear in the section of FIG. 2. The periphery of the disc is positioned against a step at 18 formed in the retainer I2 around a central recess 19 which provides clearance for the center portion of the disc.

The snap disc 16 is dished so that it has two positions of stability between which its central portion moves with snap action when it reaches predetermined temperatures. The line of action of such snap movement is along a central axis 30 of the thermostat. In FIG. 2 the disc is illustrated in its reset position and when it snaps through to its opposite position of stability, it is considered to be in its operated position. The disc is manufactured so that it snaps from the reset position to the ing temperature to normal environmental temperature. Consequently, it is necessary to manually move the disc from its operated position toward its reset position in order to reset the thermostat. The manner in which this is done while providing tion of the bumper is fonned with a cylindrical projection 23 body assembly consisting of a main body member 10, a cap member 11, both formed of insulating material such as a phenolic resin, and a disc retainer 12 preferably formed of having a reduced diameter extension 24 engageable with the center of the disc 16. Above the cylindrical portion 23, the bumper is provided with two oppositely extending

projections

26 and 27 which extend laterally from the central axis 30. The upper sides of the

projections

26 and 27 are rounded as best illustrated in FIG. 4, and the central portion therebetween is provided with an upper extension 28. Longitudinal guide projections 29 are provided on opposite sides of the bumper which fit into mating recesses formed in the body to assist in guiding the bumper for movement along the axis 30. The upper end of the bumper is provided with a projection 31 having a generally spherical configuration.

The main body 10 on the side of the wall 13 opposite the disc cavity 14 is formed with a pair of switch chambers 32 and 33on opposite sides of a central wall 34 which is interrupted in its center part to receive the bumper 22. The adjacent end faces of the wall 34 are provided with mating recesses 36 to receive the projections 29 for positively guiding the bumper for movement along the axis 30. The mating projections 29 and 36 extend a substantial distance along the bumper to provide positive guidance and to prevent the bumper from tipping laterally. This insures that the bumper reliably operates both switches. These mating grooves and projections also function to increase the length of the surfaces extending between the two switch chambers to prevent arcing between the switches and to prevent arc splatter from passing from one chamber to the other.

Similar switch mechanisms are provided in each of the switch chambers 32 and 33. The switch mechanism in the chamber 32 is best illustrated in FIG. 2, and it should be understood that the following description applies equally to the switch located in the chamber 33. The switch mechanism includes two

terminal elements

37 and 38 secured against the switch side of the wall 31 by rivets 39 and 41, respectively. The adjacent ends of the

terminal elements

37 and 38 are provided with stationary or

fixed contacts

42 and 43 respectively. A bridging contact 44 is proportioned to connect the

contacts

42 and 43 when it is in engagement therewith as illustrated in FIG. 2 and provide an electrical connection between the

terminals

37 and 38. The

terminals

37 and 38 are shaped to extend out of the switch cavities and are provided with terminal metal. The main body member 10 is provided with a lateral screws 46 for connection to external wiring circuits. The

bridging contacts are formed of relatively heavy gauge material to prevent them from bending or flexing when they are engaged' by the bumper. Therefore, substantially the entire kinetic energy of the mass in motion of the disc and bumper is available to break any welds which may occur between the contacts. This structure, therefore, insures that the contacts will open with reliability.

A reset member 47 having a shape best illustrated in FIG. 4

is preferably molded of an insulating material such as aphenolic resin and is provided with opposed depending legs 48 proportioned to straddle the central wall 34 and forming parallel surfaces 51 extending down along the sides of the wall 34 in all positions'of the reset member 47. In fact, the legs 48 extend past the upper end of the bumper and cooperate with the bumper and central wall to insure effective isolation of the two switch chambers. The bottom wall 52 of the recess defined by the legs 48 is engageable with the top surface 53 of the wall 34 on both sides of the bumper to limit movement of the reset member in a direction toward the disc beyond an actuated position illustrated in FIG. 5.

The upper end of the reset member 47 is formed with a cylindrical projection 54 which projects into an opening 56 formed in the cap 1 l. The upper surface 57 around the projection 54 engages a wall 58 to limit movement of the reset member in a direction away from the disc beyond the retracted position of FIGS. 2 and 3. The interengagement between the wall 52 of the reset member and the top surface 53 of the central wall 34 extends a substantial distance on both sides of the bumper, preferably beyond the edge of the projection 54. This insures exact positioning of the reset member in its actuated position even when the operating force is eccentrically applied to the projection 54.

A pair of depending projections 59 extend from the legs 48 along the associated switch cavity beyond the ends of the as sociated bridging elements 44 to longitudinally position the bridging'elements and cooperate with the lateral walls of the associated switch chambers 32 or 33 to entrap the bridging elements in their ,proper position. A spring 61 extends between each bridging element and the reset member and performs a combined function of urging the reset member 47 toward its retracted position and the associated bridging elements 44 toward their associated

contacts

42 and 43. Guide openings 62 formed in the reset member properly position the spring 61. I

When the disc 16 is in the reset position illustrated in FIGS. 2 and 3, each bridging element 44 engages its associated contacts and the two switches are closed. The bumper 22 is proportioned so that clearance is provided either between the extension 24 and the disc 16, or between the

projections

26 and 27 and their associated bridging contacts 44 at this time. Also, the projection 31 on the upper end of the bumper is spaced from the bottom wall 52 of the reset member. When the disc snaps through from its reset position to its operated position, the bumper 22 is moved upwardly causing the

projections

26 and 27 to engage the associated bridging elements after the disc is in snap movement and to thereafter lift the bridging elements against the action of the springs 61 to open the switches. The various elements are proportioned so that a spacing still exists between the projections 31 and the wall 52, so long as the reset member remains in the retracted position.

Resetting of the thermostat is accomplished by pressing in on the projection 54 to cause the reset member to move inwardly to the position illustrated in FIG. 5. At this time, the upper surface 53 of the wall 34 is engaged by the reset member wall 52 to prevent inward movement of the reset member beyond the illustrated actuated position. The various elements are proportioned so that movement of the reset to the actuated position of FIG. causes the reset member to engage the bumper and move the bumper in a direction causing movement of the disc from the operated position toward the reset position. v

The elements are sized, however, so that movement of the reset button is incapable of moving the disc all the way to its reset position or of moving the bumper a distance necessary to cause the bridging contacts toengage both of the associated fixed

contacts

42 and 43. Consequently, the switches remain open unless the temperature of the disc has reached a reset temperature at which such reset mo vement causes the disc to snap on through to its reset position (illustrated in phantom in FIG. 5). With this structure, the thermostat is trip-free in that the thermostat switches cannot be closed before the disc reaches reset temperature.

If, for some reason, the reset member is blocked in its actuated position, the thermostat automatically cycles in that the disc opens the switches when disc operating temperature is reached and snaps back to its reset position allowing the switches to close when the disc returns to reset temperatures. The projection 54 is proportioned so that it is recessed slightly below the surface of the cap 11 even when the reset is in its retracted position. This reduces the likelihood of accidental engagement of the reset member and reduces the likelihood of excessive forces being applied to the reset mechanism.

With the illustrated simplified structure, a single unitary bumper functions to operatively connect the disc to both switches and the reset member. Further, the structure is arranged so that the body assembly cooperates with the bumper and reset member to effectively isolate the two switch chambers from each other and from the disc cavity. Consequently, arc splatter is confined and reliable operation is provided through larger numbers of cycles.

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 and claimed herein.

I claim:

1. A thermostat comprising a body assembly, switch means in said body assembly including a fixed contact and a mobile contact movable into and out of engagement with said fixed contact, a bimetallic snap disc in said body assembly having a central portion movable along a line of action with snap movement between an operated position and a reset position, a unitary bumper in said body assembly having a first surface engageable with said disc and a second surface engageable with said mobile contact, said bumper operating said switch means when said disc moves between said reset position and said operated position, a reset member movable in said body toward and away from said disc between a retracted position and an actuated position, stop means including a surface of said body assembly engageable by a cooperating surface of the reset member preventing movement of said reset member toward said disc beyond said actuated position, said reset member including a face engageable with a portion of said bumper upon movement of said reset member to said actuated position when said disc is in said operated position, said reset member thereby causing movement of said bumper towards said disc, such movement of said bumper producing movement of said disc towards said reset position without causing said switch means to close when said disc is not at a reset temperature.

2. A thermostat as set forth in claim 1 wherein said body assembly includes a central wall which cooperates with said bumper to separate two switch chambers, similar switch means are provided with one located in each switch chamber, and said wall and bumper are formed with mating guide surfaces which guide said bumper for movement along said line of action. I

3. A thermostat as set forth in claim 2 wherein said guide surfaces include a pair of projections on said bumper extending a substantial distance in the direction of said line of action and a pair of mating recesses forrnedin said central wall.

4. A thermostat as set forth in claim 2 wherein said bumper is formed with opposed lateral projections extending into said switch chambers, each projection providing a surface engageable with an associated mobile contact.

5. A thermostat comprising a body assembly, switch means in said body assembly including a fixed contact and a mobile contact movable into and out of engagement with said fixed contact, a bimetallic snap disc in said body assembly having a central portion movable along a line of action with snap movement between an operated position and a reset position, a unitary bumper in said body assembly having a first surface engageable with said disc and a second surface engageable with said mobile contact, said bumper operating said switch means when said disc moves between said reset position and said operated position, a reset member movable in said body toward and away from said disc between a retracted position and an actuated position, stop means preventing movement of said reset member toward said disc beyond said actuated position, means engaged by said reset member upon movement of said reset member to said actuated position when said disc is in said operated position, said engaged means causing movement of said bumper towards said disc, such movement of said bumper producing movement of said disc towards said reset position without causing said switch means to close when said disc is not at a reset temperature, said body assembly including a central wall which cooperates with said bumper to separate two switch chambers, similar switch means located in each switch chamber, said wall and bumper having mating side surfaces which guide said bumper for movement along said line of action, said bumper having opposed lateral projections extending into said switch chambers, each projection providing a surface engageable with an associated mobile contact, said stop means being provided by a lateral surface on said central wall which extends a substantial distance on opposite sides of said bumper.

6. A thermostat as set forth in claim 5 wherein each switch means includes a pair of spaced fixed contacts, and said mobile contact is a bridging contact engageable with said fixed contact to provide an electrical connection therebetween.

7. A thermostat as set forth in claim 6 wherein said projections extend between the associated fixed contacts.

8. A thermostat as set forth in claim 7 wherein each switch means includes a spring extending between said bridging contact and said reset member, said spring urging the associated bridging contact toward its associated fixed contacts and said reset member toward its retracted position.

9. A thermostat as set forth in claim 8 wherein said reset member is provided with depending projections extending along both sides of said central wall, said depending projections cooperating with said body assembly to entrap said bridging contacts in proper position.

10. A thermostat as set forth in claim 9 wherein said depending projections extend along opposite sides of said central wall in all positions of said reset member and cooperate to insure complete isolation of said switch chambers.

11. A thermostat as set forth in claim 10 wherein said body assembly is provided with a lateral wall with an opening therein, said bumper extending through said opening with a close fit, said lateral wall and said bumper cooperating to isolate said disc from said switch means.

12. A thennostat comprising a body assembly, switch means in said body assembly including a fixed contact and a mobile contact movable into and out of engagement with said fixed contact, a bimetallic snap disc in said body assembly having a central portion movable along a line of action with snap movement between an operated position and a reset position, a unitary bumper in said body assembly having a first surface engageable with said disc and a second surface engageable with said mobile contact, said bumper operating said switch means when said disc moves between said reset position and said.

operated position, a reset member movable in said body toward and away from said disc between a retracted position and an actuated position, stop means preventing movement of said reset member toward said disc beyond said actuated position, means engaged by said reset member upon movement of said reset member to said actuated position when said disc is in said operated position, said engaged means causing movement of said bumper towards said disc, such movement of said bumper producing movement of said disc towards said reset position without causing said switch means to close when said disc is not at a reset temperature, said body assembly including a central wall which cooperates with said bumper to separate two switch chambers, similar switch means located in 7 assembly is provided with a lateral wall with an opening therethrough, said bumper extending through said opening with a close fit, said lateral wall and said bumper cooperating to isolate said disc from said switch means.

14. A thermostat comprising a body assembly having a central axis, a bimetallic snap disc in said body assembly having a central portion movable along said axis with snap action between a reset position and an operated position, a pair of similar switches symmetrically mounted with respect to said central axis on said body assembly, each switch including a contact movable to cause opening and closing of the associated switch, an elongated unitary bumper mounted in said body for movement along said central axis, a reset member mounted in said body for limited movement along said central axis between a retracted position and an actuated position, one end of said bumper engaging said central portion of said disc, the opposite end of said bumper being engageable with said reset member when said reset member is in said actuated position, said bumper being formed with a pair of lateral surfaces each engageable with one of said contacts, movement of said disc between said reset and operated positions causing said bumper to operate said switches after said disc is in snap movement, movement of said reset member to said actuated position when said disc is in said operated position causing movement of said bumper toward said disc and thereby causing said bumper to move said disc toward said reset position without causing operation of said switches so long as said disc is not at a reset temperature.

15. A thermostat as set forth in claim 14 wherein such movement of said reset member to said actuated position when said disc is at a reset temperature causes said disc to move to said reset position and causes operation of said switches.

16. A thermostat as set forth in claim 15 wherein said lateral surfaces of saidburnper are intermediate the ends thereof.

17. A thermostat as set forth in claim 15 wherein said body assembly, bumper and reset member cooperate to define isolated switch chambers each of which encloses a switch and an isolated disc cavity which encloses said disc.

I t l

Claims

2. A thermostat as set forth in claim 1 wherein said body assembly includes a central wall which cooperates with said bumper to separate two switch chambers, similar switch means are provided with one located in each switch chamber, and said wall and bumper are formed with mating guide surfaces which guide said bumper for movement along said line of action.

3. A thermostat as set forth in claim 2 wherein said guide surfaces include a pair of projections on said bumper extending a substantial distance in the direction of said line of action and a pair of mating recesses formed in said central wall.

12. A thermostat comprising a body assembly, switch means in said body assembly including a fixed contact and a mobile contact movable into and out of engagement with said fixed contact, a bimetallic snap disc in said body assembly having a central portion movable along a line of action with snap movement between an operated position and a reset position, a unitary bumper in said body assembly having a first surface engageable with said disc and a second surface engageable with said mobile contact, said bumper operating said switch means when said disc moves between said reset position and said operated position, a reset member movable in said body toward and away from said disc between a retracted position and an actuated position, stop means preventing movement of said reset member toward said disc beyond said actuated position, means engaged by said reset member upon movement of said reset member to said actuated position when said disc is in said operated position, said engaged means causing movement of said bumper towards said disc, such movement of said bumper producing movement of said disc towards said reset position without causing said switch means to close when said disc is not at a reset temperature, said body assembly including a central wall which cooperates with said bumper to separate two switch chambers, similar switch means located in each switch chamber, said wall and bumper having mating side surfaces which guide said bumper for movement along said line of action, said reset member including depending projections extending along both sides of said central wall in all positions of said reset member, said depending projections cooperating with said body assembly and bumper to isolate said switch chambers.

13. A thermostat as set forth in claim 12 wherein said body assembly is provided with a lateral wall with an opening therethrough, said bumper extending through said opening with a close fit, said lateral wall and said bumper cooperating to isolate said disc from said switch means.

16. A thermostat as set forth in claim 15 wherein said lateral surfaces of said bumper are intermediate the ends thereof.