Patent Description:
The background information herein below relates to the present disclosure but is not necessarily prior art.

In domestic refrigerators, frost is formed around the coils as well as in and around the freezer cabinet that is surrounded with evaporator coils, due to humidity on the outside and due to water vapour released by the foodstuff stored therein. Frost formed on the evaporator coils acts as an insulator and thus lowers the efficiency of cooling of the evaporator coils of the refrigerator. This frost needs to be removed periodically to optimize cooling effect and to save energy.

Defrosting in refrigerators can be implemented automatically and periodically, or can be done manually too. Automatic defrosting is done by heating the evaporator coils, typically using a defrost heating element.

In a market where the atmospheric humidity level is high, a defrost mechanism is typically employed in the thermostat of the refrigeration system, and the final user is obliged to run a periodical manual activation of the defrost mechanism. To realize the manual defrost function, the hitherto known defrost mechanism requires a relatively larger number of components, typically <NUM> to <NUM>. This affects the repeatability in the switching ON operation of the refrigerator after defrosting. Further, the increased number of components results in increase in the cost of the thermostat, as well as makes the manufacturing of the thermostat complex. The document <CIT> D1 teaches a defrosting control mechanism.

There is, therefore, felt a need of a defrost mechanism in a thermostat of a refrigeration system to tackle the aforementioned problems.

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

An object of the present disclosure is to provide a defrost mechanism in a thermostat of a refrigeration system that has relatively less number of components.

Another object of the present disclosure is to provide a defrost mechanism in a thermostat of a refrigeration system that is easy to manufacture.

Yet another object of the present disclosure is to provide a defrost mechanism in a thermostat of a refrigeration system that is relatively less expensive.

Yet another object of the present disclosure is to provide a thermostat for a refrigerator provided with an improved defrost mechanism.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

The present disclosure discloses a defrost mechanism of a refrigerator thermostat. The defrost mechanism is configured to be actuated by an actuating pin. The defrost mechanism comprises a first link, a second link and a switch. The first link cooperates with the actuating pin that is defined by a first end having a pivot and a second end. A bellow lever is fastened to the second end. The second link is defined by a third end pivotably supported in the pivot and a fourth end. An adjusting lever is engaged with the fourth end. The switch forms a part of the electrical circuit supplying power to the refrigerator. The switch is configured to be operated by the manual actuation of the actuating pin via the first link or the second link and the bellow lever, to cut-off power supply of the refrigerator.

According to the invention, the defrost mechanism includes a spring attached between the bellow lever and the adjusting lever to facilitate snap action of the first link and the second link. Further, a temperature adjustment screw is provided on the adjusting lever. The temperature adjustment screw is configured to limit linear displacement of the fourth end of the second link by adjusting tension exerted in the spring.

In an embodiment, the spring is a coil spring.

In an embodiment, the adjusting lever is slidably engaged with the fourth end.

The defrost mechanism in a thermostat of a refrigeration system of the present disclosure will now be described with the help of the accompanying drawing, in which:.

Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.

Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises", "comprising", "including" and "having" are open-ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof.

When an element is referred to as being "mounted on", "engaged to", "connected to" or "coupled to" another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.

Terms such as "inner", "outer", "beneath", "below", "lower", "above", "upper" and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.

Referring to the <FIG>, a typical defrost mechanism <NUM>' of a thermostat of a domestic refrigerator is shown comprising an actuating pin <NUM>', a circlip <NUM>', a roller <NUM>', an adjusting lever <NUM>', a link <NUM>', a roller pin <NUM>', a defrost screw <NUM>' and a spring (not shown in any figures). The actuating pin <NUM>' extends in an operative vertical direction of the thermostat with its lower end secured to the link <NUM>'. The link <NUM>' is in the form of a plate supported in a switch box of the thermostat. The roller <NUM>' is supported on a roller pin <NUM>' mounted on the adjusting lever <NUM>'. The adjusting lever <NUM>' acts as a spring which is in the form of a plate when subjected to bending loads. The defrost screw <NUM>' adjusts the tension in the adjusting lever <NUM>' on account of bending of the adjusting lever <NUM>'. The working of the mechanism <NUM>' will now be explained. To manually realize the defrosting function of the mechanism <NUM>', the actuating pin <NUM>' is pressed, which causes the actuating pin <NUM>' to push on the link <NUM>'. This lowers the link <NUM>' to a point when the edge of the link <NUM>' is obstructed by the roller <NUM>' causing a projecting part of the link <NUM>' to exert a compressive force on a bellow located below the projecting part of the link <NUM>'. A switch mounted on the switch base gets pressed leading to power supply cut off to the compressor. Thus, cooling of the space in the refrigerator is stopped. However, the mechanism <NUM>' of the prior art involves usage of a large number of components to effect the manual defrost function. This poses difficulties in assembly of components as well as increases the manufacturing costs involved therein. Moreover, a roller arrangement is incorporated which necessitates the need of an additional pin for mounting the roller, which ultimately results in increased friction and wear among the assembled parts. In addition, the adjusting lever <NUM>' is in the form of a plate which has to undergo bending, further complicating the mechanism <NUM>'. A mechanism of the present disclosure has been disclosed which presents a solution for addressing the aforementioned problems of the prior art.

Referring to <FIG>, a defrost mechanism <NUM> (hereinafter referred to as mechanism <NUM>) of a domestic refrigerator is shown. The mechanism <NUM> comprises a first link <NUM> and a second link <NUM> that are connected together pivotably. A first end of the first link <NUM> is configured with a pivot while the second end of the first link <NUM> is configured to be supported by a bellow lever <NUM>. A first end of the second link <NUM> is configured to be pivotably supported by the pivot, while a second end of the second link <NUM> is configured to be slidably supported in a slot contained on the adjusting lever <NUM>. An actuating pin <NUM> is configured to be displaced vertically, and is positioned within the mechanism <NUM> such that one of its ends is configured to be manually operated by a user, while its other end is configured to be in contact with a surface of the first link <NUM>. A temperature adjustment screw <NUM> is disposed on the outside surface of the adjusting lever <NUM>, and is configured to alter displacement limit of the second end of the second link <NUM>.

A bellow cup <NUM>, a capillary <NUM> and a bellow <NUM> provide feedback of temperature of the evaporator and thus form a closed loop system for handling refrigerant inside the evaporator. As the temperature of the refrigerant increases, the gas inside the bellow <NUM> expands and as a result the pressure inside the bellow <NUM> increases. This causes the bellow <NUM> to exert a force on the bellow lever <NUM>. The bellow lever <NUM> is pivoted on a frame <NUM> which forms a casing of the thermostat. The bellow lever <NUM> touches the operative top surface of the bellow <NUM> and is firmly biased against the operative top surface of the bellow <NUM> by a spring <NUM>. The spring <NUM> is disposed between the adjusting lever <NUM> and the bellow lever <NUM> to facilitate resilient deformation between the adjusting lever <NUM> and the bellow lever <NUM>. The bellow lever <NUM> is connected to a switch <NUM>. Change in pressure inside the bellow <NUM> due to a change in temperature of the evaporator coil causes displacement of the switch <NUM> through the bellow lever <NUM>. The switch <NUM> switches ON or switches OFF the electric current supply to the compressor through a first terminal <NUM> and a second terminal <NUM>. A mounting plate <NUM> lies on a top end of the thermostat. The frame <NUM> is supported by the plate <NUM>. A screw <NUM> is mounted on a switch base <NUM> that is supported by the mounting plate <NUM>. A switch base cover <NUM> is provided on the switch base <NUM> to facilitate providing of a cover to the switch base <NUM>. A cam <NUM> is provided concentric to the actuating pin <NUM> and extends vertically to maintain contact with a rod <NUM>. One end of the rod <NUM> is connected to the bottom of the cam <NUM> while its other end rests on the bellow <NUM>. The rod <NUM> passes through a hole inside the bellow lever <NUM>, and has a variable cross section along its span. The rod <NUM> is configured to transfer the vertical displacement of the bellow lever <NUM> to the bottom of the cam <NUM>. A second screw <NUM> is provided on the adjusting lever <NUM> to alter the tension in the spring <NUM>. The thermostat of the present disclosure further includes a q-blade assembly <NUM> and a contact <NUM> of the switch <NUM>.

The working of the mechanism <NUM> will now be described referring to the <FIG>. To actuate the defrost mechanism <NUM>, the user pushes on to the actuating pin <NUM> from the top which causes the first link <NUM> and the second link <NUM> to be tilted downwards. Downward rotation of first link <NUM> moves the second end of the second link <NUM> operatively backward in the slot provided on the adjusting lever <NUM>. This causes the adjusting lever <NUM> to be displaced away from the second end of the second link <NUM>. Thus, the spring <NUM> in connection with the adjusting lever <NUM> is deformed, and thus energy of deformation is stored in the spring <NUM>. Displacement of the second link <NUM> increases the force exerted by the spring <NUM> on the bellow lever <NUM>. This continues as long as the angle between the first link <NUM> and the second link <NUM> is less than <NUM> degrees the spring <NUM>. However, when the first link <NUM> and the second link <NUM> are pushed further by the actuating pin <NUM>, the angle between the first link <NUM> and the second link <NUM> increases beyond <NUM> degrees, and the spring force no longer resists the downward tilting of the first link <NUM> and the second link <NUM>. Rotation of the first link <NUM> and the second link <NUM> in the downward direction is permitted as long as the bottom surface of the first link <NUM> comes in contacts with the bellow lever <NUM>. Due to continued application of force on the actuating pin <NUM> by the user, the bellow lever <NUM> exerts a pressing force on the switch <NUM> mounted on the switch base cover <NUM>. This causes switching OFF of the compressor. Also, the thermostat is switched OFF. The cooling action inside the refrigerator is stopped and therefore defrosting takes place. To switch ON the thermostat for resumption of cooling action inside the refrigerator after completion of the defrosting action, the first link <NUM> and the second link <NUM> are required to be moved vertically upward again. This will happen when the bellow lever <NUM> moves up due to high pressure in the bellow <NUM> exerted by the expanding gas due to increase in the temperature of the evaporator coil. The bottom surface of the first link <NUM>, that is resting on the bellow lever <NUM>, is then pushed vertically upwards. As the first link <NUM> and the second link <NUM> are pushed to be tilted upwards beyond <NUM> degrees, the actuating pin <NUM> is reset to its original position. Also, the thermostat is then caused to be switched ON once again and cooling action of the refrigerator resumes. This completes the defrosting cycle.

Advantageously, the snap action of the manual defrost mechanism <NUM> of the thermostat of the present disclosure is realized using minimum number of components, i.e., the first link <NUM> and the second link <NUM>, as compared to the roller <NUM>', adjusting lever <NUM>' and the roller <NUM>' of the prior art. Also, the construction is simplified. The operation becomes reliable and repeatability in the switching ON operation of the refrigerator after defrosting is enhanced. The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure.

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a defrost mechanism for a refrigerator that:.

The foregoing disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

Claim 1:
A manual defrost mechanism (<NUM>) of a thermostat for a refrigerator, said defrost mechanism (<NUM>) configured to be actuated by an actuating pin (<NUM>), said defrost mechanism (<NUM>) comprising:
• a first link (<NUM>) cooperating with the actuating pin (<NUM>) defined by a first end having a pivot and a second end, a bellow lever (<NUM>) fastened to said second end;
• a second link (<NUM>) defined by a third end pivotably supported in said pivot and a fourth end, an adjusting lever (<NUM>) engaged with said fourth end;
• a switch (<NUM>) forming a part of the electrical circuit supplying power to the refrigerator, characterized in that said switch (<NUM>) is configured to be operated by the manual actuation of the actuating pin (<NUM>) via said first link (<NUM>) or said second link (<NUM>) and said bellow lever (<NUM>), to cut-off power supply of the refrigerator; and wherein the defrost mechanism (<NUM>) further comprises
• a spring (<NUM>) attached between said bellow lever (<NUM>) and said adjusting lever (<NUM>) to facilitate snap action of said first link (<NUM>) and said second link (<NUM>).