US20170224190A1

US20170224190A1 - Dishwasher Rack Lift Mechanism

Info

Publication number: US20170224190A1
Application number: US15/016,333
Authority: US
Inventors: Dhinesh Babu Sakthivel; Ashutosh Kulkarni
Original assignee: Haier US Appliance Solutions Inc
Current assignee: Haier US Appliance Solutions Inc
Priority date: 2016-02-05
Filing date: 2016-02-05
Publication date: 2017-08-10

Abstract

A rack lifting assembly for a dishwasher appliance is provided. The rack lifting assembly includes a lower rack suspended within the wash chamber by one or more linkage arms. A biasing assembly is configured for rotating the linkage arms to swing the lower rack up and out of the wash chamber. The rack lifting assembly may further include a slide assembly that couples the lower rack to the linkage arms such that the lower rack may extend in the transverse direction.

Description

FIELD OF THE INVENTION

The subject matter of the present disclosure relates generally to a dishwasher, and more particularly, to a system for lifting a lower rack of a dishwasher appliance.

BACKGROUND OF THE INVENTION

Dishwasher appliances generally include a tub that defines a wash chamber. Rack assemblies can be mounted within the wash chamber of the tub for receipt of articles for washing. Spray assemblies within the wash compartment can apply or direct wash fluid towards articles disposed within the rack assemblies in order to clean such articles. Multiple spray assemblies can be provided including e.g., a lower spray arm assembly mounted to the tub at a bottom of the wash compartment, a mid-level spray arm assembly mounted to one of the rack assemblies, and/or an upper spray assembly mounted to the tub at a top of the wash compartment. Other configurations may be used as well.
Typically, the lower rack of a dishwasher is pulled out for loading and unloading of dishes. A dishwasher door pivots into an open, horizontal position and may define a surface having one or more tracks for receiving wheels rotatably mounted on the lower rack. The lower rack is rolled out of the tub onto the open dishwasher door to simplify the loading or unloading process, e.g., by not requiring a user to reach into the wash chamber to add or remove dishes. However, even when the rack is extended outside the wash chamber, consumers must often bend over to reach the dishes located in the lower rack, resulting in discomfort and ergonomic issues. While some dishwashers have incorporated means for lifting the lower rack, these mechanisms often lift the lower rack in a jerky and non-uniform manner. Alternatively, these systems are complex, expensive, and difficult to maintain.
Accordingly, a dishwashing appliance having a system for lifting the lower rack when loading or unloading dishes would be useful. More particularly, a cost effective rack lifting system that may lift the lower rack in a smooth and uniform manner to provide a simple, ergonomic method of loading and unloading dishes would be especially beneficial.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a rack lifting assembly for a dishwasher appliance. The rack lifting assembly includes a lower rack suspended within the wash chamber by one or more linkage arms. A biasing assembly is configured for rotating the linkage arms to swing the lower rack up and out of the wash chamber. The rack lifting assembly may further include a slide assembly that couples the lower rack to the linkage arms such that the lower rack may extend in the transverse direction. In this manner, the lower rack of a dishwasher appliance may be raised in a smooth and uniform manner to simplify loading or unloading dishes. Additional aspects and advantages of the invention will be set forth in part in the following description, may be apparent from the description, or may be learned through practice of the invention.
In one exemplary embodiment, a dishwasher appliance is provided. The dishwasher appliance defines a vertical, a lateral, and a transverse direction. The dishwasher appliance includes a wash tub that defines a wash chamber, a fluid circulation assembly for providing a fluid flow for cleaning articles placed within the wash chamber; and a lower rack lifting assembly. The lower rack lifting assembly includes a lower rack configured for receipt of the articles for washing; a linkage arm having a first end and a second end, the first end being rotatably mounted to the lower rack; and a biasing assembly operably coupled to the second end of the linkage arm. The biasing assembly is configured for rotating the linkage arm about the second end to swing the lower rack up and out of the wash chamber.
In another exemplary embodiment, a rack lifting assembly for a dishwasher appliance defining a vertical, a lateral, and a transverse direction is provided. The rack lifting assembly includes a lower rack configured for receipt of articles for washing and a slide assembly slidably coupled to the lower rack to allow the lower rack to extend in the transverse direction. The rack lifting assembly further includes a linkage arm having a first end and a second end, the first end being rotatably mounted to the slide assembly. A biasing assembly is operably coupled to the second end of the linkage arm, the biasing assembly being configured for rotating the linkage arm about the second end to swing the lower rack up and out of the wash chamber.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a front view of a dishwashing appliance according to an exemplary embodiment of the present subject matter.

FIG. 2 provides a side cross sectional view of the exemplary dishwashing appliance of FIG. 1.

FIG. 3 provides a perspective view of a rack lifting assembly according to an exemplary embodiment of the present subject matter.

FIG. 4 provides a perspective view of the exemplary rack lifting assembly of FIG. 3, with the lower rack and slide assembly removed for clarity.

FIG. 5 provides a side view of the exemplary rack lifting assembly of FIG. 3 in a lowered position.

FIG. 6 provides a perspective view of the exemplary rack lifting assembly of FIG. 3 in a raised and extended position.

FIG. 7 provides a side view of the exemplary rack lifting assembly of FIG. 3 in a raised and extended position.

FIG. 8 provides a close up perspective view of a biasing assembly of the exemplary rack lifting assembly of FIG. 3.

FIG. 9 provides a perspective, cross sectional view of the biasing assembly of the exemplary rack lifting assembly of FIG. 3, taken along Line 9-9 of FIG. 8.

FIG. 10 provides a close up perspective view of the slide assembly of the exemplary rack lifting assembly of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
As used herein, the term “article” may refer to, but need not be limited to, dishes, pots, pans, silverware, and other cooking utensils and items that can be cleaned in a dishwashing appliance. The term “wash cycle” is intended to refer to one or more periods of time during the cleaning process where a dishwashing appliance operates while containing articles to be washed and uses a detergent and water, preferably with agitation, to e.g., remove soil particles including food and other undesirable elements from the articles. The term “rinse cycle” is intended to refer to one or more periods of time during the cleaning process in which the dishwashing appliance operates to remove residual soil, detergents, and other undesirable elements that were retained by the articles after completion of the wash cycle. The term “drying cycle” is intended to refer to one or more periods of time in which the dishwashing appliance is operated to dry the articles by removing fluids from the wash chamber. The term “fluid” refers to a liquid used for washing and/or rinsing the articles and is typically made up of water that may include additives such as e.g., detergent or other treatments. The use of the terms “top” and “bottom,” or “upper” and “lower” herein are used for reference only as exemplary embodiments disclosed herein are not limited to the vertical orientation shown nor to any particular configuration shown; other constructions and orientations may also be used.
FIGS. 1 and 2 depict an exemplary domestic dishwasher 100 that may be configured in accordance with aspects of the present disclosure. Dishwasher 100 generally defines a vertical direction V, a lateral direction L, and a transverse direction T, each of which is mutually perpendicular, such that an orthogonal coordinate system is generally defined. For the particular embodiment of FIGS. 1 and 2, the dishwasher 100 includes a cabinet 102 having a tub or inner liner 104 therein that defines a wash chamber 106. The tub 104 includes a front opening (not shown) and a door 110 hinged at its bottom 112 for movement between a normally closed vertical position (shown in FIGS. 1 and 2), wherein the wash chamber 106 is sealed shut for washing operation, and a horizontal open position for loading and unloading of articles from the dishwasher 100. Latch 116 is used to lock and unlock door 110 for access to wash chamber 106.
Upper guide rails 120 are mounted on tub side walls 124 and accommodate roller-equipped rack assemblies. More specifically, according to the illustrated exemplary embodiment, upper rack assembly 126 is slidably received on upper guide rails 120. As will be discussed in detail below, lower rack 128 is received within a rack lifting assembly 130. Each of upper rack 126 and lower rack 128 is fabricated into lattice structures including a plurality of elongated members 132 (for clarity of illustration, not all elongated members making up upper rack 126 and lower rack 128 are shown in FIG. 2). Each rack 126, 128 is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outside the wash chamber 106, and a retracted position (shown in FIGS. 1 and 2) in which the rack is located inside the wash chamber 106. For upper rack 126, this movement is facilitated by rollers 134. As will be described in more detail below, lower rack 128 may move between the raised and lowered position using rack lifting assembly 130. A silverware basket (not shown) may be removably attached to lower rack 128 for placement of silverware, utensils, and the like, that are otherwise too small to be accommodated by the racks 126, 128.
The dishwasher 100 further includes a lower spray-arm assembly 140 that is rotatably mounted within a lower region 142 of the wash chamber 106 and above a tub sump portion 144 so as to rotate in relatively close proximity to lower rack 128. A mid-level spray-arm assembly 146 is located in an upper region of the wash chamber 106 and may be located in close proximity to upper rack 126. Additionally, an upper spray assembly 148 may be located above the upper rack 126.
The lower, mid-level, and upper spray- arm assemblies 140, 146, and 148 are part of a fluid circulation assembly 150 for circulating water and dishwasher fluid in the tub 104. The fluid circulation assembly 150 also includes a pump 152 positioned in a machinery compartment 158 located below the tub sump portion 144 (i.e., bottom wall) of the tub 104, as generally recognized in the art. Pump 152 receives fluid from sump 144 and provides a flow to the inlet 154 of a diverter 156. Diverter 156 can be used to selectively place pump 152 in fluid communication with spray assemblies 140, 146, or 148 by way of various outlet ports (not shown). Other spray assemblies and connection configurations may be used as well.
Each spray- arm assembly 140, 146 includes an arrangement of discharge ports or orifices for directing washing liquid received from diverter 156 onto dishes or other articles located in rack assemblies 126 and 128. The arrangement of the discharge ports in spray- arm assemblies 140, 146 provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of the spray- arm assemblies 140, 146 and the operation of spray assembly 148 using fluid from diverter 156 provides coverage of dishes and other dishwasher contents with a washing spray. Other configurations of spray assemblies may be used as well. For example, dishwasher 100 may have additional spray assemblies for cleaning silverware, for scouring casserole dishes, for spraying pots and pans, for cleaning bottles, etc. One skilled in the art will appreciate that the embodiments discussed herein are used for the purpose of explanation only, and are not limitations of the present subject matter.
Each spray assembly may receive an independent stream of fluid, may be stationary, and/or may be configured to rotate in one or both directions. For example, a single spray arm may have multiple sets of discharge ports, each set receiving wash fluid from a different fluid conduit, and each set being configured to spray in opposite directions and impart opposite rotational forces on the spray arm. In order to avoid stalling the rotation of such a spray arm, wash fluid is typically only supplied to one of the sets of discharge ports at a time.
The dishwasher 100 is further equipped with a controller 160 to regulate operation of the dishwasher 100. The controller 160 may include one or more memory devices and one or more microprocessors, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor.
The controller 160 may be positioned in a variety of locations throughout dishwasher 100. In the illustrated embodiment, the controller 160 may be located within a control panel area 162 of door 110 as shown in FIGS. 1 and 2. In such an embodiment, input/output (“I/O”) signals may be routed between the control system and various operational components of dishwasher 100 along wiring harnesses that may be routed through the bottom 112 of door 110. Typically, the controller 160 includes a user interface panel/controls 164 through which a user may select various operational features and modes and monitor progress of the dishwasher 100. In one embodiment, the user interface 164 may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface 164 may include input components, such as one or more of a variety of electrical, mechanical or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface 164 may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. The user interface 164 may be in communication with the controller 160 via one or more signal lines or shared communication busses.
It should be appreciated that the invention is not limited to any particular style, model, or configuration of dishwasher 100. The exemplary embodiment depicted in FIGS. 1 and 2 is for illustrative purposes only. For example, different locations may be provided for user interface 164, different configurations may be provided for racks 126, 128, different spray arm assemblies 140, 146, 148 may be used, and other differences may be applied as well.
Referring now generally to FIGS. 3-10, lower rack lifting assembly 130 will be described in more detail. According to the exemplary illustrated embodiment, lower rack 128 has a first side 170 and a second side 172 spaced apart along the lateral direction L. Rack lifting assembly 130 may include a first linkage system 174 operably coupled with first side 170 and a second linkage system 176 operably coupled with second side 172 which may suspend lower rack 128 within wash chamber 106. Using rack lifting assembly 130, lower rack 128 may be moved between a first position where it is lowered and retracted within wash chamber 106 (see FIG. 2), and a second position where it is raised and/or extended out of wash chamber 106 (see FIGS. 6 and 7), as described below.
The structure and operation of each linkage system 174, 176 will now be described referring specifically to first linkage system 174. Although the description below refers to first linkage system 174, one skilled in the art will appreciate that second linkage system 176 may have a similar construction and operate in a similar manner.
First linkage system 174 includes a first linkage arm 180 having a first end 182 and a second end 184 and a second linkage arm 186 having a first end 188 and a second end 190. According to the illustrated embodiment, linkage arms 180, 186 are wider at first ends 182, 188 than at second ends 184, 190. As described in more detail below, second ends 184, 190 are rotatably mounted to biasing assembly 220 and wash tub 104, respectively. Wider first ends 182, 188 may be pivotally connected at two points along the width of linkage arms 180, 186. For example, first ends 182, 188 may be pivotally connected to slide assembly 200 and connecting arm 240, as described in detail below. According to the illustrated embodiment, the various rotatable connections to linkage arms 180, 188 are made using rigid steel pins. However, according to alternative embodiments, other suitable mounting mechanisms may be used, e.g., bush bearings.
According to the illustrated embodiment, first ends 182, 188 are rotatably attached to a slide assembly. In this regard, rack lifting assembly 130 may include a first slide assembly 200 and a second slide assembly 202 which are mounted on opposing sides of lower rack 128 to allow lower rack 128 to slide in the transverse direction T relative to linkage arm 180. More particularly, first slide assembly 200 is mounted to first side 170 of lower rack 128 and second slide assembly 202 is mounted to second side 172 of lower rack 128 to allow lower rack 128 to extend away from linkage arms 180, 186.
Each slide assembly 200, 202 may include a guide 204 and one or more slide members 206 that move linearly relative to guide 204 via a suitable bearing arrangement. In an alternative embodiment, multiple slide members may telescope relative to each other. Slide member 206 may be mounted to lower rack 128 using a suitable support. More specifically, a first support 210 and a second support 212 may be mounted on opposing sides of lower rack 128 and be configured for receiving drawer slide assemblies 200, 202. In this regard, first support 210 may be mounted to first side 170 and second support 212 may be mounted to second side 172 of lower rack 128.
Slide assemblies 200, 202 and supports 210, 212 may be constructed from any suitably rigid material. For example, first support 220 and second support 222 may be constructed from steel. Lower rack 128 may be attached to slide 206 and linkage arms 180, 186 may be attached to guide 204 using any suitable mechanical fastener, such as screws, bolts, rivets, etc. Similarly, glue, snap-fit mechanisms, interference-fit mechanisms, or any suitable combination thereof may secure lower rack 128 and linkage arms 180, 186 to slide assemblies 200, 202. In addition, linkage arms 180, 186 may be rotatably connected to guide 204 of slide assemblies 200, 202, such that linkage arms 180, 186 rotate, but do not slide, relative to slide assemblies 200, 202. Other attachment means are also possible.
According to the illustrated embodiment, second end 184 of first linkage arm 180 is operably coupled to a biasing assembly 220. In general, biasing assembly 220 is any mechanism configured for urging first linkage arm 180 to rotate about its second end 184. More particularly, biasing assembly 220 urges first linkage arm 180 to rotate in the clockwise direction (as viewed in FIG. 5). In this manner, first linkage arm 180 may swing lower rack 128 up and out of wash chamber 106. For example, biasing assembly 220 may be an electric or hydraulic motor that is mounted to wash tub 104 and is configured to rotate first linkage arm 180. Motor may be powered, for example, directly from a power supply that is internal or external to dishwasher 100.
Alternatively, according to the illustrated exemplary embodiment, biasing assembly 220 includes a support bracket 222 having a geared rack 224 slidably mounted thereto. In this regard, support bracket 222 is a rigid plate with flanges turned in on either side to form a U-shape and thereby defining a space to receive geared rack 224. Support bracket 222 may be attached to wash tub 104 using any suitable means, e.g., by welding or using mechanical fasteners such as bolts or rivets. One skilled in the art will appreciate that other configurations of support bracket 222 and geared rack 224 are possible. Moreover, according to some exemplary embodiments, no support bracket 222 may be used and geared rack 224 and other components of biasing assembly 220 may be mounted directly to wash tub 104.
Geared rack 224 may be configured to slide along a longitudinal axis A of support bracket 222 (FIG. 5). According to some exemplary embodiments, geared rack 224 may slide along the base or flange of support bracket 222. Alternatively, geared rack 224 may define a slot that slides along a pin (not shown) protruding from support bracket 222. According to the illustrated embodiment, a support pin 226 is instead positioned underneath geared rack 224 to ensure it slides along a direction corresponding to the longitudinal axis A. Other means for supporting geared rack 224 are also possible and within the scope of the present subject matter.
A pinion gear 230 may be coupled to first linkage arm 180 and rotatably mounted to support bracket 222 such that pinion gear 230 engages geared rack 224. As best shown in FIG. 9, pinion gear 230 may be fixed to first linkage arm 180 and support bracket 222 by a fastener, e.g., bolt 232. Bolt 232 may engage pinion gear 230 and first linkage arm 180 in a manner that ensures that they rotate together. For example, bolt 232 may have a shaft with two keyed portions that engage keyed apertures in linkage arm 180 and pinion gear 230, respectively. In this manner pinion gear 230 and first linkage arm 180 may be configured to rotate together. Notably, support pin 226 may be positioned such that geared rack 224 remains engaged with pinion gear 230 as it slides along longitudinal axis A. In this manner, as geared rack 224 moves along the longitudinal axis A, pinion gear 230 is rotated along with first linkage arm 180.
A biasing member may be configured to urge geared rack 224 to move along the longitudinal axis A. According to the illustrated embodiment, biasing member is one or more springs 234. A spring base 236 is fixed to support bracket 222 and oriented perpendicular to the longitudinal axis A. A spring bar 238 may be slidably mounted within the support bracket 222 and may be attached to geared rack 224. Springs 234 may extend along the longitudinal axis A between spring base 236 and spring bar 238. According to the illustrated embodiment, there are four springs 234, however springs of varying size and stiffness may be used depending on the spring force required.
Springs 234 may be in a compressed state when lower rack 128 is positioned within wash chamber 106 (as shown in FIG. 2). In this manner, as lower rack 128 is pulled out of wash chamber 106 to its extended position, springs 234 urge spring bar 238 along the longitudinal axis A, thereby also urging geared rack 224 to rotate pinion gear 230. In this manner, first linkage arm 180 rotates in a clockwise direction (as shown in FIG. 5) and assists the user in raising lower rack 128 to the raised position. Notably, springs 234 may both urge lower rack 128 into the raised position as well as decelerate lower rack 128 as it moves into the lowered position. In this manner, springs 234 prevent lower rack 128 from slamming into the back wall of wash tub 104 when being pushed by the user.
Although the exemplary embodiment described the use of springs 234 to urge geared rack 224 in a manner that raises lower rack 128 out of wash chamber 106, one skilled in the art will appreciate that other means for moving geared rack 224 may be used. For example, one or more gas springs, hydraulic cylinders, or mechanical actuators may be used instead of mechanical springs 234. Other configurations are possible and within the scope of the present subject matter.
According to the illustrated exemplary embodiment, biasing assembly 220 is angled with respect to the transverse direction T of dishwasher 100. More specifically, the longitudinal axis A of biasing assembly 220 is oriented at an angle, e.g., 15 degrees, relative to the transverse direction T. This may help reduce the force required by springs 234 to rotate pinion gear 230 and prevent rack lifting assembly 130 from binding in wash chamber 106. However, according to alternative exemplary embodiments, biasing assembly 220 may instead have any other suitable orientation, e.g., its longitudinal axis may be parallel to the transverse direction T.
According to an exemplary embodiment, first linkage arm 180 is the drive arm that urges lower rack 128 into a raised position. First end 188 of second linkage arm 186 may also be rotatably mounted to slide assembly 200 and second end 190 of second linkage arm may be rotatably mounted to wash tub 104 or support bracket 222. In addition, a connecting arm 240 may be rotatably attached to first end 182 of first linkage arm 180 and first end 188 of second linkage arm 186. More particularly, linkage arms 180, 186 may be pivotally connected to connecting arm 240 using pins that are positioned on wide first ends 182, 188 and below slide assemblies 200, 202. In this manner, the pins that connect linkage arms 180, 186 to connecting arm 240 may rotate around the pins that connect linkage arms 180, 186 to slide assemblies 200, 202. In this manner, linkage arms 180, 186 and connecting arm 240 may form a four bar linkage and provide additional structural support to first linkage system 174.
Although the illustrated embodiment shows first linkage system 174 and second linkage system 176 each having a separate biasing assembly 220 driving a four bar linkage system, one skilled in the art will appreciate that this is only one exemplary configuration of rack lifting assembly 130. Modifications and variations are possible. For example, a single linkage arm might be used on each side of lower rack 128 instead of a four bar linkage system. In addition, a single biasing assembly 220 may be used instead of two or biasing assembly 220 may drive second linkage arm 186 instead of first linkage arm 180. Such variations and modifications are considered to be within the scope of the present disclosure.
According to the illustrated exemplary embodiment, rack lifting assembly 130 may further include a stopper bracket 250 that extends along the lateral direction L and is connected between first linkage system 174 and second linkage system 176. More particularly, stopper bracket 250 may extend between second linkage arms 186 of first and second linkage systems 174, 176. Stopper bracket 250 may ensure that linkage systems 174, 176 move in unison. In addition, stopper bracket may contact a back wall of wash chamber 106 when lower rack 128 reaches the lowered position. In this manner, stopper bracket may be configured to prevent lower rack 128 from knocking into back wall. According to another exemplary embodiment, stopper bracket 250 may have a pad or bumper on its rear surface to absorb any impact of rack lifting assembly 130 and reduce the noise of any such impact.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

What is claimed is:

1. A dishwasher appliance defining a vertical, a lateral, and a transverse direction, the dishwasher appliance comprising:

a wash tub that defines a wash chamber;

a fluid circulation assembly for providing a fluid flow for cleaning articles placed within the wash chamber; and

a lower rack lifting assembly comprising:

a lower rack configured for receipt of the articles for washing;

a linkage arm having a first end and a second end, the first end being rotatably mounted to the lower rack; and

a biasing assembly operably coupled to the second end of the linkage arm, the biasing assembly being configured for rotating the linkage arm about the second end to swing the lower rack up and out of the wash chamber.

2. The dishwasher appliance of claim 1, wherein the linkage arm is a first linkage arm, the lower rack lifting assembly further comprising:

a second linkage arm having a first end and a second end, the first end being rotatably mounted to the lower rack and the second end being rotatably mounted to the wash tub; and

a connecting arm attached to the first end of the first linkage arm and the first end of the second linkage arm, thereby forming a four bar linkage system.

3. The dishwasher appliance of claim 1, wherein the lower rack lifting assembly further comprises a slide assembly, the slide assembly slidably coupling the lower rack to the linkage arm to allow the lower rack to extend in the transverse direction relative to the linkage arm.

4. The dishwasher appliance of claim 3, wherein the slide assembly comprises a slide fixed to the lower rack and a guide fixed to the first end of the linkage arm such that the slide may be received in the guide.

5. The dishwasher appliance of claim 1, wherein the biasing assembly comprises:

a support bracket;

a geared rack slidably mounted to the support bracket;

a pinion gear coupled to the linkage arm and rotatably mounted to the support bracket such that the pinion gear engages the geared rack; and

a biasing member configured to urge the geared rack to slide within the support bracket, thereby rotating the pinion gear and the linkage arm.

6. The dishwasher appliance of claim 5, wherein the biasing member is one or more springs, wherein the one or more springs are in compression when the lower rack is in a lowered position within the wash chamber.

7. The dishwasher appliance of claim 5, wherein the biasing assembly defines a longitudinal axis that corresponds to a direction of motion of the geared rack, the longitudinal axis being inclined relative to the transverse direction.

8. The dishwasher appliance of claim 5, wherein the biasing member is a gas spring or a hydraulic cylinder.

9. The dishwasher appliance of claim 1, wherein the biasing assembly comprises a motor configured for rotating the linkage arm about the second end of the linkage arm.

10. The dishwasher appliance of claim 1, wherein the lower rack lifting assembly is a first rack lifting assembly disposed at a first lateral side of the lower rack, the dishwasher appliance further comprising a second rack lifting assembly disposed at a second lateral side of the lower rack.

11. The dishwasher appliance of claim 10, wherein a stopper bracket extends along the lateral direction and is connected between the first rack lifting assembly and the second rack lifting assembly, the stopper bracket configured for contacting a back wall of the wash chamber when the lower rack is in a lowered position.

12. A rack lifting assembly for a dishwasher appliance defining a vertical, a lateral, and a transverse direction, the rack lifting assembly comprising:

a lower rack configured for receipt of articles for washing;

a slide assembly slidably coupled to the lower rack to allow the lower rack to extend in the transverse direction;

a linkage arm having a first end and a second end, the first end being rotatably mounted to the slide assembly; and

13. The rack lifting assembly of claim 12, wherein the linkage arm is a first linkage arm, the lower rack lifting assembly further comprising:

a second linkage arm having a first end and a second end, the first end being rotatably mounted to the slide assembly and the second end being rotatably mounted to the wash tub; and

14. The rack lifting assembly of claim 12, wherein the slide assembly comprises a slide fixed to the lower rack and a guide fixed to the first end of the linkage arm such that the slide may be received in the guide.

15. The rack lifting assembly of claim 12, wherein the biasing assembly comprises:

a support bracket;

a geared rack slidably mounted to the support bracket;

16. The rack lifting assembly of claim 15, wherein the biasing member is one or more springs, wherein the one or more springs are in compression when the lower rack is in a lowered position within the wash chamber.

17. The rack lifting assembly of claim 15, wherein the biasing assembly defines a longitudinal axis that corresponds to a direction of motion of the geared rack, the longitudinal axis being inclined relative to the transverse direction.

18. The rack lifting assembly of claim 12, wherein the biasing assembly comprises a motor configured for rotating the linkage arm about the second end of the linkage arm.

19. The rack lifting assembly of claim 12, wherein the lower rack lifting assembly is a first rack lifting assembly disposed at a first lateral side of the lower rack, the dishwasher appliance further comprising a second rack lifting assembly disposed at a second lateral side of the lower rack.

20. The rack lifting assembly of claim 19, wherein a stopper bracket extends along the lateral direction and is connected between the first rack lifting assembly and the second rack lifting assembly, the stopper bracket configured for contacting a back wall of the wash chamber when the lower rack is in a lowered position.