Abstract:
A temperature sensor assembly is provided. The temperature sensor includes an aluminum capillary soldered to an actuation unit. The actuation unit operably fluidly couples to the capillary to define an internal cavity storing a working fluid. The working fluid configured to manipulate the actuation unit when the working fluid changes temperature. Solder sealingly couples the capillary to the actuation unit.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention generally relates to temperature sensors for refrigerators such as thermostats and dampers for refrigerators. 
       BACKGROUND OF THE INVENTION 
       [0002]    Temperature sensors of refrigeration thermostats and damper controls are currently manufactured using a copper capillary. Copper is a high-priced commodity with a price that is constantly increasing in the market. Further, the copper capillary receives a tin bath in order to avoid oxidation and contamination of food inside refrigerators. Further, this avoids galvanic corrosion when in contact with aluminum, such as of the evaporator, due to the difference in electrical potential between these two materials, when in the presence of moisture. 
         [0003]    The present invention relates to improvements over the current state of the art as it relates to temperature sensors for refrigerators 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    Embodiments of the present invention relate to a new and improved temperature sensor assembly for use in temperature controlled environments and particularly in appliances such as refrigerators and freezers. The new and improved temperature sensor assembly reduces cost by using an aluminum capillary that is lower cost. Additionally, the new and improved temperature sensor assembly avoids oxidation contamination. Methods of forming the temperature sensor assembly as well as thermostats incorporating the temperature sensor assembly are provided. 
         [0005]    In one embodiment, the temperature sensor assembly includes an aluminum capillary soldered to an actuation unit to fluidly couple the capillary to the actuation unit and to form an internal cavity storing a working fluid. The working fluid manipulates the actuation unit when the working fluid changes temperature. 
         [0006]    In one embodiment the actuation unit is a bellows and the solder sealingly couples an open end of the capillary to an open end of the bellows such that the working fluid can actuate the bellows. 
         [0007]    In one embodiment, the temperature sensor assembly includes a sensor body in which the bellows is positioned. The solder seals an open end of the capillary to an internal surface of the sensor body and also seals an open end of the bellows to the internal surface of the sensor body to sealingly couple the bellows to the capillary. 
         [0008]    In one embodiment, the bellows is made from a phosphorous bronze; and the sensor body is made from a tin plated steel or aluminum. 
         [0009]    In one embodiment, the solder is a Zn/Al solder. More preferably, the Zn/Al solder has about 85 to 99% of Zn, and about 1 to 15% of Al. Even more preferably, the Zn/Al solder includes about 98+/−0.5% of Zn and about 2.0+/−0.5% of Al. 
         [0010]    In one embodiment, the solder is a Sn/Zn solder. More preferably, the Sn/Zn solder has about 85 to 99% of Sn, and about 1 to 15% of Zn. Even more preferably, the Sn/Zn solder has about 98+/−0.5% of Sn and about 2.0+/−0.5% of Zn. 
         [0011]    In one embodiment, the solder is a Sn/Cu/Ag solder. More preferably, the Sn/Cu/Ag solder has about 99%±0.1% of Sn, about 0.8±0.1% of Cu and 0.2±0.1% of Ag. 
         [0012]    In one embodiment, a thermostat comprising a switch assembly and a temperature sensor assembly is provided. The temperature sensor assembly includes an aluminum capillary and an actuation unit operably fluidly coupled to the capillary. The aluminum capillary and actuation unit define an internal cavity storing a working fluid. The working fluid manipulates the actuation unit when the working fluid changes temperature. Solder sealingly couples the capillary to the actuation unit. The actuation unit operably controls the switching unit in response to changes in temperature of the aluminum capillary and corresponding changes in pressure of the working fluid. 
         [0013]    In another embodiment, a method of forming a temperature sensor assembly is provided. The method includes soldering an aluminum capillary to an actuation unit to operably fluidly couple the capillary to the actuation unit such that the capillary and actuation unit define an internal cavity for storing a working fluid. The working fluid is configured to manipulate the actuation unit when the working fluid changes temperature. 
         [0014]    In a more particular method, the step of soldering is performed by either brazing or induction heating. 
         [0015]    In one embodiment, the actuation unit is a bellows formed from a phosphorous bronze and the solder is a Zn/Al solder having about 85 to 99% of Zn, and about 1 to 15% of Al; a Sn/Zn solder having about 85 to 99% of Sn, and about 1 to 15% of Zn; or a Sn/Cu/Ag solder having about 99%±0.1% of Sn, about 0.8±0.1% of Cu and 0.2±0.1% of Ag. 
         [0016]    In a further embodiment, the bellows is made from a phosphorous bronze. The step of soldering includes soldering an open end of the capillary to a sensor body defining an internal cavity in which the bellows is positioned. The sensor body is made a tin plated steel or aluminum. The step of soldering also includes soldering an open end of the bellows to the sensor body and soldering the capillary to the sensor body to sealingly couple the capillary to the bellows and form the internal cavity in which the working fluid is stored. 
         [0017]    Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0019]      FIG. 1  is a perspective illustration of a thermostat according to an embodiment of the present invention; 
           [0020]      FIG. 2  is a side illustration of a temperature sensor sub-assembly of the thermostat of  FIG. 1 ; and 
           [0021]      FIG. 3  is a cross-sectional illustration of the temperature sensor sub-assembly of  FIG. 3 . 
       
    
    
       [0022]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  illustrates a thermostat  100  for use in a refrigerator according to an embodiment of the present invention. While it is intended for the thermostat  100  to be used in a refrigerator, the thermostat  100  can be used in other similar environments and is not limited solely to a refrigerator unless expressly limited. 
         [0024]    The thermostat  100  generally includes a switch assembly  102  and a temperature sensor assembly  104 . The switch assembly  102  includes the control structure of the thermostat  100  which can be used to turn on or off a compressor of the refrigerator. 
         [0025]    The temperature sensor assembly  104  is exposed, at least in part, to the sensed environment where the temperature is being controlled. Changes in the sensed environment are sensed by the temperature sensor assembly  104  and relayed back to the switch assembly  102 . 
         [0026]    With reference to  FIGS. 2 and 3 , and with primary reference to the cross-sectional illustration of  FIG. 3 , the temperature sensor assembly  104  includes a sensor body  106  that defines an internal cavity  108 . The sensor body  106  is preferably formed from tin plated steel or aluminum. 
         [0027]    A bellows  110  is positioned within the sensor body  106 . The bellows  110  is formed from a phosphorous bronze. A bellows keeper  112  is fitted into an open end  114  of the sensor body  106 . The bellows  110  includes an actuation portion  118 , in the illustrated embodiment, that extends through an aperture  116  formed through bellows keeper  112 . The actuation portion  118  of the bellows  110  operably cooperates with and actuates switching structure within the switch assembly  102 . The bellows keeper  112  limits the axial expansion of the bellows  110  along axis  120  and may be formed from steel. 
         [0028]    An optional dust protector  122  is attached to the sensor body  106  and is preferably formed from a plastic material. The dust protector  122  prevents dust from passing into the temperature controlled environment. 
         [0029]    A capillary  130  fluidly communicates with an interior of the bellows  110 . The bellows and capillary  130  generally define an internal cavity that is filled with a gas or other fluid that expands and contracts depending on changes in temperature. The capillary will be positioned within the temperature controlled environment so that changes in temperature of the environment cause changes in the pressure of the fluid within the capillary  130 . As the fluid rises in temperature the fluid expands raising the pressure within the bellows  110  causing the bellows  110  to expand, and particularly, causing the actuation portion  118  to move along axis  120  in a first direction, illustrated by arrow  134 . When the temperature of the fluid drops, the pressure within the bellows  110  drops causing the bellows  110  to contract such that the actuation portion  118  of the bellows move along axis  120  in an opposite second direction, illustrated by arrow  136 . This movement of the actuation portion  118  actuates the switching structure within the switch assembly  102  to either turn on or off a unit for controlling the temperature of the temperature controlled environment. 
         [0030]    In the illustrated embodiment, the capillary  130  is hollow tubing formed from aluminum. One end of the tubing is closed with a first portion of solder  138 . The opposite end of the tubing extends through an aperture  140  in the sensor body  106  and is in fluid communication with the interior of the bellows  110 . The end of the tubing may include retaining flanges  142  that secure the tubing in the aperture  140 . 
         [0031]    A second portion of solder  144  seals the open end  146  of the bellows  110  to the open second end  148  of the capillary  130 . In the instant embodiment, the second portion of solder  144  also seals the open end  146  of the bellows  110  to a stepped bottom wall  150  of the sensor body  106 . The second portion of solder  144  also seals the open end  148  of the capillary  130  to the stepped bottom wall  150 . Preferably, the outer diameter of the open end  146  of the bellows  110  is smaller than the inner diameter of an axially extending portion of a stepped region  154  of the stepped bottom  150  such that a radial gap is formed therebetween. This allows the second portion of solder  144  to fully surround the open end of the bellows  146  and to extend into the gap formed between the stepped region  154  and the open end  146  of the bellows. The stepped bottom  150  may include an annular recess  155  in which the second portion of solder  144  sits to further improve engagement and sealing between the solder  144  and the sensor body  106 . 
         [0032]    In a preferred embodiment, a third portion of solder  156  is provided between one of the folds  158  of the bellows  110  and the stepped bottom  150  of the sensor body  106 . This improves the seal between the bellows and assists in preventing the forces acting on the bellows  110  due to the expansion and contraction of the bellows  110  due to changes in temperature of the fluid from applying stresses to the open end  146  of the bellows  110 . 
         [0033]    By providing an aluminum capillary  130 , the cost of the capillary  130  is significantly reduced. Further, the capillary  130  will not oxidize such that secondary processing of the capillary  130  is not necessary, e.g. tin plating, further reducing cost. 
         [0034]    In one embodiment, in order to allow the soldering process between aluminum capillary  100  and sensor body  106 , a Zn/Al solder is used. The solder composition may be from 85 to 99% of Zn and from 1% to 15% of Al. The preferred composition is 98.0+/−0.5% of Zn and 2.0+/−0.5% of Al. To solder the bellows  100  and sensor body  106  a Zn/Al solder may be used. The solder composition may be from 85 to 99% of Zn, and 1 to 15% of Al. The preferred composition is 98.0+/−0.5% of Zn and 2.0+/−0.5% of Al. To close the tip of the capillary  130 , a Zn/Al solder may be used. The solder composition may be from 85 to 99% of Zn, and 1 to 15% of Al. The preferred composition is 98.0+/−0.5% of Zn and 2.0+/−0.5% of Al. 
         [0035]    In another embodiment, a Sn/Zn solder is used. To solder the aluminum capillary  130  to the sensor body  106  the Sn/Zn solder may have from 85 to 99% of Sn and from 1% to 15% of Zn. The preferred composition is 98.0+/−0.5% of Sn and 2.0+/−0.5% of Zn. To solder the bellows  110  to the sensor body  106  the Sn/Zn solder may have the following composition: 85 to 99% of Zn, and from 1 to 15% of Zn. The preferred composition is 98.0+/−0.5% of Sn and 2.0+/−0.5% of Zn. To close the tip of the capillary  130 , the Sn/Zn solder may have the following composition: from 85 to 99% of Sn, and 1 to 15% of Zn. The preferred composition is 98.0+/−0.5% of Sn and 2.0+/−0.5% of Zn. 
         [0036]    In another embodiment, a Sn/Cu/Ag solder is used. To solder the aluminum capillary  130  to the sensor body  106  the Sn/Cu/Ag solder may have the following composition 99.0+/−0.1% of Sn, 0.8±0.1% of Cu and 0.2±0.1% of Ag. To solder the bellows  110  to the sensor body  106  the Sn/Cu/Ag solder may have the following composition: 99.0±0.1% of Sn, 0.8±0.1% of Cu and 0.2±0.1% of Ag. To close the tip of the capillary  130 , the Sn/Cu/Ag solder may have the following composition: 99.0%±0.1% of Sn, 0.8±0.1% of Cu and 0.2±0.1% of Ag. 
         [0037]    For all three soldering options above mentioned it is possible to use brazing or induction systems. 
         [0038]    All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0039]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0040]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.