Adjustable Thermostat

This invention relates generally to adjustable thermostats and more particularly to adjustable thermostats incorporating an improved adjustment indicator or pointer having means to resist changes in the temperature setting of the thermostat.

Adjustable thermostats are normally provided with an indicator or pointer which provides a visual indication of the temperature setting of the thermostat. Examples of such thermostats are illustrated in the U.S. Pat. Nos. to Odson 3,442,129 issued May 6, 1969; and to Place 3,602,863 issued Aug. 31, 1971. Both of these patents are assigned to the assignee of the present invention.

Generally the manufacturer of an appliance or system, such as a water heater on which a thermostat is installed, specifies the temperature setting of the thermostat and the thermostat is set at such specified temperature during its manufacture.

In some instances, however, during the handling, shipping and use of the thermostat the adjusted temperature changes and the thermostat does not remain at the specified temperature setting. The Place patent mentioned above includes a wire clip which applies a frictional force to the adjusting stem to resist change of the temperature setting during shipping, handling and use of the device. In addition the Odson patent mentioned above discloses an adjustable thermostat having means to limit the range of adjustment to a range less than the full adjustment range of the thermostat by limiting the rotational travel of the indicator or pointer.

In the illustrated embodiment of the present invention a novel and improved adjustable thermostat structure is provided in which the adjustment indicator provides a deformable peripheral surface which engages a stationary surface on the body or case of the thermostat to provide friction resisting rotation of the adjusting stem. In addition, in the illustrated embodiment, a detent structure is provided which functions to provide a snap like action when the indicator is rotated to a predetermined temperature setting. Usually such detent structure is arranged to function at a temperature specified by the manufacturer of the system embodying the thermostat and is the recommended setting for the thermostat within the system. The illustrated structure completely eliminates the danger of accidental loss of the specified temperature adjustment setting during shipping, handling or use of the device.

FIG. 1 is a plan view illustrating a typical thermostat incorporating the present invention with the temperature indicator in the detent position;

FIG. 2 is an enlarged fragmentary perspective view illustrating the temperature indicator in a position displaced from the detent position;

FIG. 3 is an enlarged plan view of the indicator element per se; and

FIG. 4 is a side elevation of the indicator element per se.

The illustrated embodiment of this invention is applied to a thermostat of the type illustrated in the Place U.S. Pat. No. 3,602,863 referred to above. Such patent discloses the entire structural arrangement of the thermostat and is incorporated herein by reference.

Referring to the drawings, the thermostat includes a molded plastic body 10 preferably formed of a phenolic resin or the like and a metal cover 11 which includes means for mounting the thermostat. Switch means within the body 10 are connected to terminals 12 so that the thermostat can be wired to the system it controls.

An adjusting stem 13 is journaled in the body 10 for rotation about its axis 14. The upper end of the adjusting stem 13 is provided with a cross slot 16 best illustrated in FIG. 2 so that the adjusting stem can be easily rotated by a screwdriver or the like.

Mounted on the adjusting stem is an indicator or pointer 17 which is preferably molded from a deformable plastic material such as Nylon or the like. The indicator 17 is molded with a central aperture sized to receive the metal adjusting stem 13 with an interference fit. Preferably the surface of the adjusting stem 13 is knurled as illustrated at 19 to provide the surface of the stem 13 with a tooth like structure which bites into the surface of the indicator 17 and positively locks the indicator against rotation relative to the stem 13.

The indicator 17 in the illustrated embodiment is provided with a radially extending flange 21 adjacent to its lower surface which provides a peripheral surface 22 having a diameter greater than the diameter of the main cylindrical portion 23 of the indicator 17. The indicator 17 is also formed with a radially extending pointer portion 24 which is aligned during calibration of the thermostat with the appropriate indicia 26 printed on a plate 27 secured to the body 10 to provide a visual indication of the temperature setting of the thermostat. In FIG. 1 the thermostat is illustrated as set to operate at 140.degree. F. In FIG. 2 the temperature setting of the thermostat is 150.degree.. In the illustrated embodiment the thermostat can be adjusted from about 110.degree. F. to 170.degree. F. by rotation of the adjusting stem 13 and indicator 17.

The body 10 of the thermostat is provided with two wedge shaped projections 28 which are of uniform section in a direction parallel to the axis 14 of the adjusting stem 13. The two projections 28 provide similar but opposite planar surfaces 31 and 32 which are symmetrically positioned with respect to the axis 14 and are angulated with respect to each other with an included angle of about 60.degree..

The two planar surfaces 31 and 32 extend past a point of closest proximity to the axis 14 (a point at which a line perpendicular to the respective planar surfaces passes through the axis 14) to rounded extremities at 33. Therefore each surface 31 and 32 provide opposed surface portions which are inclined radially with respect to the axis 14.

The flange 21 is formed with two flatted portions 36 and 37 which are proportioned to closely fit and mate with the associated stationary planar surfaces 31 and 32 respectively on the body 10 when the indicator and, in turn, the adjusting stem 13 is rotated to a predetermined temperature setting. In the illustrated embodiment such temperature setting is 140.degree. F. The remaining portions of the peripheral surface 22 of the flange 21 have a radius greater than the minimum spacing between the stationary planar surfaces 31 and 32 and the axis 14. The flats also each provide opposed portions which are inclined radially with respect to the axis 14 and mate with the two surfaces 31 and 32 to resist rotation from the detent position. When the indicator 17 is rotated in either direction from the 140.degree. temperature setting, an interference is developed between the arcuate portions of the peripheral surface 22 and the two stationary surfaces 31 and 32 which creates deformation of the flange and creates substantial friction resisting such rotation. The indicator 17 is formed of a material such as Nylon which can be elastically deformed to allow such rotation.

The cooperation of the flats and the stationary planar surfaces, however, provides a detent-like function tending to cause the indicator to assume the 140.degree. temperature setting and to retain such setting. Since the indicator can be rotated only 90.degree. in either direction from the detent position the flats cannot move to a second detent position and the system provides only a single detent position.

As discussed above, in many instances the thermostat is installed in a system in which a specified temperature setting is established and the thermostat is set to such specified temperature during its manufacture. Preferably the specified temperature setting is the setting of the thermostat which exists when the detent functions. Consequently, there is substantially no possibility of accidental loss of the specified temperature setting during shipping, handling, or use of the thermostat. Further, the detent function provides means for the ultimate user of the system in which the thermostat is installed, to be aware of the preferred operating temperature, even though the user can adjust the thermostat to other operating temperatures within its range of temperature settings.

With the illustrated structure the frictional forces produced by the indicator's engagement with the thermostat body and the magnitude of the detent action can be varied within the design parameters of the device. For example, if greater frictional forces are required, the height of the flange can be increased, the radius of the flange can be increased or the indicator can be formed of harder material. Conversely, if lower frictional forces are required the height of the flange can be decreased, the radius of the flange can be decreased or the indicator can be formed of softer material.

The flats 36 and 37 in addition to providing the above discussed detent operation also facilitate the assembly of the indicator into its installed position since the flange 22 does not interfere with the ends of the projections 28 when properly aligned in the desired or specified temperature position.

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