Patent Publication Number: US-2023133183-A1

Title: Height-adjustable folding table

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Chinese Utility Model Applications CN 202122651506.7 filed Nov. 1, 2021, and CN 202122651186.5 filed Nov. 1, 2021. The disclosure of each application is incorporated herein for all purposes by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention generally relates to tables, and in particular, relates to height-adjustable folding tables. 
     BACKGROUND 
     Most existing folding tables are not adjustable in height. Some are adjustable but the structure for adjusting the height is complex and often involves multiple parts. For instance, CN209185890U discloses a folding table with a control switch to adjust its height, the disclosure of which is incorporated herein for all purposes by reference in its entirety. However, the control switch is often not protected or locked. End users may press the switch by accident or children may play with the switch out of curiosity, causing unexpected folding or collapsing of the table. In some cases, this may lead to hands caught by the table or other safety issues. 
     Given the current state of the art, there remains a need for tables that address the abovementioned issues. 
     The information disclosed in this Background section is provided for an understanding of the general background of the invention and is not an acknowledgement or suggestion that this information forms part of the prior art already known to a person skilled in the art. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides table leg assemblies and folding tables that are simple, easy-to-use, and height-adjustable. 
     In various exemplary embodiments, the present disclosure provides a table including a tabletop and a leg assembly to support the tabletop. The leg assembly includes a first support movably connected to the tabletop at a first portion of the tabletop and a second support movably connected to the tabletop at a second portion of the tabletop. The first support includes a first bar, and the second support includes a second bar. The first bar of the first support and the second bar of the second support are pivotally connected to each other at their middle portions. The leg assembly also includes a mechanism for adjusting height of the leg assembly. The mechanism includes a first coupling piece disposed at the first bar of the first support and a second coupling piece pivotally connected to the second bar of the second support. One of the first and second coupling pieces includes a plurality of positioning slots, and the other of the first and second coupling pieces is selectively engageable with any one of the plurality of positioning slots, thereby allowing changing a first angle between the first bar of the first support and the second bar of the second support to change the height of the leg assembly. 
     In some exemplary embodiments, the first coupling piece is fixedly connected to or integrally formed with the first bar of the first support. 
     In some exemplary embodiments, the first bar of the first support and the second bar of the second support are connected to each other at a first pivotal point. The first coupling piece of the mechanism is disposed at the first bar of the first support adjacent to or above the first pivotal point, and the second coupling piece of the mechanism is pivotally connected to the second bar of the second support above the first pivotal point. 
     In some exemplary embodiments, the first support includes a pair of first bars, a first upper crossbar and a first lower crossbar. The first bars are spaced apart from each other in a first direction of the table. Each first bar has an upper end portion connected to the first upper crossbar and a lower end portion connected to the first lower crossbar. Similarly, the second support includes a pair of second bars, a second upper crossbar and a second lower crossbar. The second bars are spaced apart from each other in the first direction of the table. Each second bar has an upper end portion connected to the second upper crossbar and a lower end portion connected to the second lower crossbar. 
     In an exemplary embodiment, the tabletop includes first, second, third and fourth engagement slots. The first and second engagement slots are disposed in the first portion of the tabletop, and spaced apart in the first direction of the table with openings of the first and second engagement slots facing each other. The third and fourth engagement slots are disposed in the second portion of the tabletop, and spaced apart in the first direction of the table with openings of the third and fourth engagement slots facing each other. The first upper crossbar of the first support has a first end received in the first engagement slot and a second end received in the second engagement slot such that the first upper crossbar is slidable along the first and second engagement slots in a second direction of the table. The second upper crossbar of the second support has a first end received in the third engagement slot and a second end received in the fourth engagement slot such that the second upper crossbar is slidable along the third and fourth engagement slots in the second direction of the table. 
     In some exemplary embodiments, the second coupling piece is connected to the second bar of the second support at a second pivotal point. The mechanism further includes a torsion spring disposed at the second pivotal point between the second coupling piece and the second bar of the second support. The torsion spring is connected to the second coupling piece and the second bar of the second support, and configured to prevent accidental disengagement of the first and second coupling pieces. 
     In an exemplary embodiment, the leg assembly further includes a third bar to help support the tabletop. The third bar is pivotally connected to the tabletop and pivotally connected to the first bar of the first support or the second bar of the second support. 
     In some exemplary embodiments, the second coupling piece includes a channel generally elongated in a length direction of the second coupling piece and a plurality of positioning slots formed at a side of the channel. The first coupling piece is received, cross-sectional-wise, in the channel of the second coupling piece. The first coupling piece is movable along the channel and selectively engageable with any one of the plurality of positioning slots, thereby allowing the leg assembly to be selectively positioned at any one of a plurality of heights. 
     In an exemplary embodiment, the first coupling piece is a pin or a post. 
     In some exemplary embodiments, the channel of the second coupling piece includes a first portion and a second portion at a second angle with respect to the first portion. 
     In some exemplary embodiments, two or more positioning slots in the plurality of positioning slots are formed along the first portion of the channel. 
     In an exemplary embodiment, a positioning slot in the plurality of positioning slots is formed at an end of the second portion of the channel. When the first coupling piece engages with the positioning slot formed at the end of the second portion of the channel, the first angle is substantially 180 degrees. 
     In some exemplary embodiments, the plurality of positioning slots is formed on an edge of the first coupling piece. The second coupling piece includes an end portion releasably engageable with any one of the plurality of positioning slots. 
     In an exemplary embodiment, the end portion of the second coupling piece is a hook, a clamp, or a hook toggle clamp. 
     In some exemplary embodiments, when engaging with a respective positioning slot in the plurality of positioning slots, the end portion of the second coupling piece abuts a corresponding tooth formed on the edge of the first coupling piece adjacent to the respective positioning slot. 
     In an exemplary embodiment, the second coupling piece includes an opening adjacent to the end portion of the second coupling piece. The opening allows a portion of the first coupling piece to pass through when the end portion of the second coupling piece is engaged with a positioning slot in the plurality of positioning slots. 
     In various exemplary embodiments, the present disclosure provides a table including a tabletop and a leg assembly to support the tabletop. The tabletop includes first, second, third and fourth engagement slots. The first and second engagement slots are disposed in a first portion of the tabletop and spaced apart in a first direction of the table with openings of the first and second engagement slots facing each other. The third and fourth engagement slots are disposed in a second portion of the tabletop and spaced apart in the first direction of the table with openings of the third and fourth engagement slots facing each other. The leg assembly includes a first support, a second support and a mechanism for adjusting a height of the leg assembly. The first support includes a first upper crossbar. The first upper crossbar has a first end received in the first engagement slot and a second end received in the second engagement slot such that the first upper crossbar is slidable along the first and second engagement slots in a second direction of the table. The second support includes a second upper crossbar. The second upper crossbar has a first end received in the third engagement slot and a second end received in the fourth engagement slot such that the second upper crossbar is slidable along the third and fourth engagement slots in the second direction of the table. The mechanism includes a first coupling piece fixedly connected to or integrally formed with the first support and a second coupling piece pivotally connected to the second support. The second coupling piece includes a channel generally elongated in a length direction of the second coupling piece and a plurality of positioning slots formed at a side of the channel. The first coupling piece is received, cross-sectional-wise, in the channel of the second coupling piece. The first coupling piece is movable along the channel and selectively engageable with any one of the plurality of positioning slots, thereby allowing the leg assembly to be selectively positioned at any one of a plurality of heights. 
     In some exemplary embodiments, the channel of the second coupling piece includes a first portion and a second portion at an obtuse angle with respect to the first portion. Two or more positioning slots in the plurality of positioning slots are formed along the first portion of the channel, and at least one positioning slot in the plurality of positioning slots is formed at an end of the second portion of the channel. 
     In various exemplary embodiments, the present disclosure provides a table including a tabletop and a leg assembly to support the tabletop. The tabletop includes first, second, third and fourth engagement slots. The first and second engagement slots are disposed in a first portion of the tabletop and spaced apart in a first direction of the table with openings of the first and second engagement slots facing each other. The third and fourth engagement slots are disposed in a second portion of the tabletop and spaced apart in the first direction of the table with openings of the third and fourth engagement slots facing each other. The leg assembly includes a first support, a second support and a mechanism for adjusting a height of the leg assembly. The first support includes a first upper crossbar. The first upper crossbar has a first end received in the first engagement slot and a second end received in the second engagement slot such that the first upper crossbar is slidable along the first and second engagement slots in a second direction of the table. The second support includes a second upper crossbar. The second upper crossbar has a first end received in the third engagement slot and a second end received in the fourth engagement slot such that the second upper crossbar is slidable along the third and fourth engagement slots in the second direction of the table. The mechanism includes a first coupling piece fixedly connected to or integrally formed with the first support and a second coupling piece pivotally connected to the second support. The first coupling piece includes a plurality of positioning slots formed on an edge of the first coupling piece. The second coupling piece includes an end portion releasably and selectively engageable with any one of the plurality of positioning slots, thereby allowing the leg assembly to be selectively positioned at any one of a plurality of heights. 
     In some exemplary embodiments, the end portion of the second coupling piece is a hook, a clamp, or a hook toggle clamp. The second coupling piece includes an opening adjacent to the end portion of the second coupling piece. The opening allows a portion of the first coupling piece to pass through when the end portion of the second coupling piece is engaged with a positioning slot in the plurality of positioning slots. 
     The tables of the present disclosure have other features and advantages that will be apparent from, or are set forth in more detail in, the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of exemplary embodiments of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more exemplary embodiments of the present disclosure and, together with the Detailed Description, serve to explain the principles and implementations of exemplary embodiments of the invention. 
         FIG.  1 A  is a top perspective view illustrating an exemplary table in accordance with exemplary embodiments of the present disclosure. 
         FIG.  1 B  is an enlarged view taken along circle A of  FIG.  1 A . 
         FIG.  2    is a bottom perspective view illustrating the exemplary table of  FIG.  1 A  at a first height in accordance with exemplary embodiments of the present disclosure. 
         FIG.  3    is a bottom perspective view illustrating the exemplary table of  FIG.  1 A  at a second height in accordance with exemplary embodiments of the present disclosure. 
         FIG.  4    is a bottom perspective view illustrating the exemplary table of  FIG.  1 A  at a third height in accordance with exemplary embodiments of the present disclosure. 
         FIG.  5    is a bottom perspective view illustrating the exemplary table of  FIG.  1 A  in a folded state in accordance with exemplary embodiments of the present disclosure. 
         FIG.  6 A  is a perspective view illustrating an exemplary leg assembly in accordance with exemplary embodiments of the present disclosure. 
         FIG.  6 B  is an enlarged view taken along circle B of  FIG.  6 A . 
         FIG.  7    is a perspective view illustrating the exemplary leg assembly of  FIG.  6 A  in a folded state in accordance with exemplary embodiments of the present disclosure. 
         FIG.  8 A  is a top perspective view illustrating an exemplary table in a locked state in accordance with exemplary embodiments of the present disclosure. 
         FIG.  8 B  is an enlarged view taken along circle C of  FIG.  8 A . 
         FIG.  9 A  is a top perspective view illustrating the exemplary table of  FIG.  8 A  in an unlocked state in accordance with exemplary embodiments of the present disclosure. 
         FIG.  9 B  is an enlarged view taken along circle D of  FIG.  9 A . 
         FIG.  10    is a perspective view illustrating an exemplary leg assembly at a first height in accordance with exemplary embodiments of the present disclosure. 
         FIG.  11    is a perspective view illustrating the exemplary leg assembly of  FIG.  10    at a second height in accordance with exemplary embodiments of the present disclosure. 
         FIG.  12    is a perspective view illustrating the exemplary leg assembly of  FIG.  10    at a third height in accordance with exemplary embodiments of the present disclosure. 
         FIG.  13 A  is a perspective view illustrating the exemplary leg assembly of  FIG.  10    in a folded state in accordance with exemplary embodiments of the present disclosure. 
         FIG.  13 B  is a partially enlarged view of the exemplary leg assembly of  FIG.  10     
         FIG.  14 A  is a partially cutout side view illustrating the exemplary leg assembly of  FIG.  10    in accordance with exemplary embodiments of the present disclosure. 
         FIG.  14 B  is an enlarged view taken along circle E of  FIG.  14 A . 
     
    
    
     As will be apparent to those of skill in the art, the components illustrated in the figures described above are combinable in any useful number and combination. The figures are intended to be illustrative in nature and are not limiting. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to implementation of exemplary embodiments of the present disclosure as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts. Those of ordinary skill in the art will understand that the following detailed description is illustrative only and is not intended to be in any way limiting. Other embodiments of the present disclosure will readily suggest themselves to such skilled persons having benefit of this disclosure. 
     In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will be appreciated that, in the development of any such actual implementation, numerous implementation-specific decisions are made in order to achieve the developer&#39;s specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure. 
     Many modifications and variations of the exemplary embodiments set forth in this disclosure can be made without departing from the spirit and scope of the exemplary embodiments, as will be apparent to those skilled in the art. The specific exemplary embodiments described herein are offered by way of example only, and the disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     Embodiments of the present disclosure are described in the context of leg assemblies and tables having such leg assemblies. A leg assembly of the present disclosure generally includes a first support and a second support that collectively form one or more scissor lifts each having one or more pairs of crisscrossed bars. A leg assembly of the present disclosure also includes a mechanism connected to the first and second supports and configured to control the expansion and contraction of the one or more scissor lifts, and thus changes the height of the leg assembly. For instance, in various exemplary embodiments, a mechanism includes a first coupling piece and a second coupling piece. The first coupling piece is disposed at one of the first and second supports, and the second coupling piece is disposed at the other of the first and second supports. In some exemplary embodiments, the first coupling piece is fixedly connected to or integrally formed with one of the first and second supports, and the second coupling is pivotally connected to the other of the first and second supports. In some exemplary embodiments, one of the first and second coupling pieces includes a plurality of positioning slots, and the other of the first and second coupling pieces is selectively engageable with any one of the plurality of positioning slots, thereby allowing changing an angle between the first support and the second support and consequently changing the height of the leg assembly and the height of the table. The leg assembly of the present disclosure can be made of various materials including but not limited to metals (e.g., iron, steel, and aluminum), plastics and woods. 
     A table of the present disclosure generally includes a tabletop and a leg assembly to support the tabletop. It can be of various sizes. For instance, a table of the present disclosure can be a coffee table, a dining table, a picnic table or the like. The tabletop can be of various shapes including but not limited to a square shape, a round shape or a rectangular shape, and can be made of various materials including, but not limited to, plastics and woods. In some exemplary embodiments, the tabletop includes a table panel made of plastics by injection molding, blow molding or any other suitable processes. 
     Referring now to  FIGS.  1 A- 7   , there is depicted an exemplary table  100  in accordance with some embodiments of the present disclosure. As shown, table  100  includes a tabletop, such as tabletop  200 . While tabletop  200  is of a rectangular shape in the figures, it should be noted that tabletop  200  can be of any suitable shapes including but not limited to rectangular, square, round, oval, oblong or the like. 
     In various exemplary embodiments, tabletop  200  includes an upper surface such as upper surface  202 , a lower surface such as lower surface  204 , and an edge such as edge  206 . In some exemplary embodiments, the edge is extended downward beyond the lower surface of the tabletop. 
     In some exemplary embodiments, tabletop  200  also includes a plurality of engagement slots for coupling with the leg assembly. For instance, by way of example,  FIGS.  2  and  5    illustrate first engagement slot  210 , second engagement slot  220 , third engagement slot  230  and fourth engagement slot  240 . The first and second engagement slots are spaced apart in a first direction (e.g., x-direction in  FIG.  2   ) of the table with openings of the first and second engagement slots facing each other. The third and fourth engagement slots are spaced apart in the first direction of the table with openings of the third and fourth engagement slots facing each other. It should be noted that the first and third engagement slots can be but are not necessarily aligned in a second direction (e.g., y-direction in  FIG.  2   ), and similarly the second and fourth engagement slots can be but are not necessarily aligned in the second direction. By way of example,  FIG.  2    illustrates the first and third engagement slots aligned in the second direction, and the second and fourth engagement slots aligned in the second direction. 
     In some exemplary embodiments, an engagement slot (e.g., the first, second, third or fourth engagement slot) is formed at least partially in a protrusion. For instance, first engagement slot  210  is formed at least partially in a protrusion, such as protrusion  212 . In some exemplary embodiments, the protrusion is integrally formed or coupled with the lower surface of the tabletop. For instance, in an exemplary embodiment, the upper surface, the lower surface, the edge, and the protrusion are elements of a table panel formed by injection or blow molding of plastics, with the protrusion protruding downward from the lower surface of the tabletop. While  FIGS.  2  and  5    illustrate the protrusion at, or adjacent to, the edge of the tabletop, it should be noted that the protrusion does not necessarily need to be disposed at, or adjacent to, the edge of the tabletop. The protrusion for the second, third or fourth engagement slot can be configured similarly to the first engagement slot or differently from the first engagement slot. 
     Table  100  also includes a leg assembly, such as leg assembly  300 . The leg assembly is coupled with the tabletop and supports the tabletop when in use. In various exemplary embodiments, leg assembly  300  includes a first support, such as first support  310 , and a second support, such as second support  320 . The first support is movably connected to the tabletop at a first portion of the tabletop, and the second support is movably connected to the tabletop at a second portion of the tabletop. Leg assembly  300  also includes a mechanism, such as mechanism  330 , connected to the first and second supports for adjusting a height of the leg assembly, and consequently adjusting a height of the table. 
     In some exemplary embodiments, the first and second supports of the leg assembly collectively form one or more scissor lifts each including one or more pairs of crisscrossed bars. For instance, in an exemplary embodiment, the first and second supports of the leg assembly collectively form a scissor lift including a pair of crisscrossed bars, two pairs of crisscrossed bars, or more than two pairs of crisscrossed bars. In another exemplary embodiment, the first and second supports of the leg assembly collectively form a pair of scissor lifts, each scissor lift including a pair of crisscrossed bars, two pairs of crisscrossed bars, or more than two pairs of crisscrossed bars. In still another exemplary embodiment, the first and second supports of the leg assembly collectively form more than two scissor lifts. 
     By way of example, it is illustrated that first support  310  and second support  320  collectively form a scissor lift including two pairs of crisscrossed bars. Specifically, first support  310  includes a pair of first bars, such as first bar  312 , spaced apart from each other in the first direction (e.g., x-direction in  FIG.  2   ) of the table. Similarly, second support  320  includes a pair of second bars, such as second bar  322 , spaced apart from each other in the first direction of the table. The two first bars can be disposed between the second bars in the first direction of the table (e.g., the distance between the two first bars is smaller than the distance between the two second bars), or outside of the second bars in the first direction of the table (e.g., the distance between the two first bars is greater than the distance between the two second bars), or alternating with the second bars in the first direction of the table (e.g., the distance between the two first bars is substantially the same as the distance between the two second bars). A first bar of the first support and a second bar of the second support are pivotally connected to each other at their middle portions. It should be noted that the pivotal connection point at the middle portions can be but is not necessarily a central point of the bars. 
     In some exemplary embodiments, first support  310  also includes an upper crossbar, such as upper crossbar  316 , to which upper end portions of the first bars of the first support are connected. The upper crossbar of the first support is movably connected to the tabletop. For instance, in an exemplary embodiment, the upper crossbar of the first support has a first end received in the first engagement slot (e.g., inserted into the first engagement slot) and a second end received in the second engagement slot. The first and second engagement slots allow the upper crossbar of the first support to slide along the first and second engagement slots in the second direction (e.g., the y-direction in  FIG.  2   ) of the table. In some exemplary embodiments, the first and second engagement slots also allows the upper crossbar of the first support to rotate with respect to the first and second engagement slots. 
     Similarly, in some exemplary embodiments, second support  320  includes an upper crossbar such as upper crossbar  326 , to which upper end portions of the second bars of the second support are connected. The upper crossbar of the second support is movably connected to the tabletop. For instance, in an exemplary embodiment, the upper crossbar of the second support has a first end received in the third engagement slot and a second end received in the fourth engagement slot. The third and fourth engagement slots allow the upper crossbar of the second support to slide along the third and fourth engagement slots in the second direction of the table. In some exemplary embodiments, third and fourth engagement slots allow the upper crossbar of the second support to rotate with respect to the first and second engagement slots. 
     In some exemplary embodiments, first support  310  further includes a lower crossbar, such as lower crossbar  318 , to which lower end portions of the first bars of the first support are connected. Similarly, in some exemplary embodiments, second support  320  further includes a lower crossbar, such as lower crossbar  328 , to which lower end portions of the second bars of the second support are connected. 
     Referring in particular to  FIGS.  1 B and  6 B , in some exemplary embodiments, mechanism  330  includes a first coupling piece, such as first coupling piece  340 , and a second coupling piece, such as second coupling piece  350 . The first coupling piece is disposed at one of the first and second supports, and the second coupling piece is pivotally connected to the other one of the first and second supports. In some exemplary embodiments, the first coupling piece is fixedly connected to or integrally formed with one of the first and second supports. 
     As a non-limiting example, it is illustrated that first coupling piece  340  is disposed at (e.g., fixedly connected to or integrally formed with) first bar  312  of the first support and second coupling piece  350  is pivotally connected to second bar  322  of the second support. The first and second coupling pieces of the mechanism can be disposed at the first bar of the first support and the second bar of the second support at any suitable positions, e.g., either adjacent to, above, or below a pivotal point at which the first bar of the first support and the second bar of the second support are connected to each other. In the illustrated embodiment, the first coupling piece and the second coupling piece of the mechanism are disposed respectively at the first bar of the first support and the second bar of the second support above the pivotal point at which the first bar of the first support and the second bar of the second support are connected to each other. 
     In some exemplary embodiments, one of the first and second coupling pieces includes a plurality of positioning slots, and the other of the first and second coupling pieces is selectively engageable with any one of the plurality of positioning slots, thereby allowing changing an angle between the first bar of the first support and the second bar of the second support and consequently changing the height of the leg assembly and the height of the table. 
     For instance, in the illustrated embodiment, second coupling piece  350  includes a channel, such as channel  352 . The channel is generally elongated in a length direction of the second coupling piece and the plurality of positioning slots is formed at a side of the channel. The channel can be straight, curved or angled. As a non-limiting example, it is illustrated that channel  352  includes two portions, e.g., first portion  352   a  and second portion  352   b . The first and second portions of the channel are at an angle with respect to each other, generally designated as “β”. Usually, the angle β is greater than 90 degrees, or is an obtuse angle. 
     The second coupling piece also includes a plurality of positioning slots, such as positioning slots  354 , formed at a side of the channel. The second coupling piece can have any suitable number of positioning slots, e.g., two, three, four, five, six or more than six positioning slots. Moreover, the positioning slots can be arranged along the length direction of the second coupling piece uniformly or nonuniformly. Further, different positioning slots can have the same configuration (e.g., size, shape) or different configurations. In some exemplary embodiments, two or more positioning slots, such as positioning slot  354   a , are formed on a side of the first portion of the channel, and/or at least one positioning slot, such as positioning slot  354   b , is formed on a side of the second portion of the channel. 
     Cross-sectional-wise, first coupling piece  340  is received in the channel of the second coupling piece. The first coupling piece can move along the channel and selectively engage with any one of the plurality of positioning slots. The engagement of the first coupling piece with a respective positioning slot in the plurality of positioning slots sets the first bar of the first support and the second bar of the second support at a corresponding angle, generally designated as “a”. The engagement of the first coupling piece with different positioning slots changes the angle “a” between the first bar of the first support and the second bar of the second support, resulting in the leg assembly (and thus the table) at different heights. 
     For instance, in the illustrated embodiment, three positioning slots  354   a  are formed on a side of the first portion of the channel, and one positioning slot  354   b  is formed at an end of the second portion of the channel (e.g., the distal end of the second coupling piece that is away from the pivotal connection of the second coupling piece with second bar  322  of the second support). The engagement of the first coupling piece with three positioning slots  354   a  results in the leg assembly (and thus the table) at three different heights as illustrated in  FIGS.  2 ,  3 , and  4   , respectively. In an exemplary embodiment, the three different heights are about 700 mm, about 650 mm, and about 600 mm, respectively. 
     In some exemplary embodiments, when the first coupling piece engages with one positioning slot  354   b  formed at the end of the second portion of the channel, the first angle is substantially 180 degrees. In other words, the first bar of the first support and the second bar of the second support are disposed substantially in a common plane, and in some cases, are folded onto the table panel as illustrated in  FIG.  5   . Folded tables can be stacked together, require less storage space and are convenient for transportation. 
     Referring in particular to  FIG.  6 B , in some exemplary embodiments, mechanism  330  includes a torsion spring, such as torsion spring  360 , to prevent accidental disengagement of the first and second coupling pieces. The torsion spring is disposed between the second coupling piece and the second bar of the second support at a pivotal point to which the second coupling piece is connected to the second bar of the second support. The torsion spring is connected to the second coupling piece and the second bar of the second support, and exerts a torque on the second coupling piece to prevent accidental separation or disengagement of the first coupling piece from the selected positioning slot formed in the second coupling piece. The torsion spring helps to stabilize the table when in use. 
     In some exemplary embodiments, to help support the tabletop, the leg assembly further includes one or more additional supports. For instance, in some exemplary embodiments, the leg assembly includes one or more third bars, such as third bar  370 , connected to the tabletop, the first support, and/or the second support. In an exemplary embodiment, third bar  370  is pivotally connected to the tabletop and pivotally connected to the first bar of the first support or the second bar of the second support. 
     Referring now to  FIGS.  8 A- 14 B , there is depicted an exemplary table  400  in accordance with some embodiments of the present disclosure. Table  400  is substantially the same as table  100  except the mechanism for adjusting the height of the leg assembly and the height of the table. For instance, as shown, table  400  includes a tabletop, such as tabletop  200  disclosed herein, and a leg assembly, such as leg assembly  500 , coupled with the tabletop and supports the tabletop when in use. Leg assembly  500  includes a first support, such as first support  310  disclosed herein, and a second support, such as second support  320  disclosed herein. The first support movably connected to the tabletop at a first portion of the tabletop, and the second support movably connected to the tabletop at a second portion of the tabletop. Leg assembly  500  also includes a mechanism, such as mechanism  530 , connected to the first and second supports for adjusting a height of the leg assembly, and consequently adjusting a height of the table. 
     Referring in particular to  FIGS.  8 B,  9 B,  13 B and  14 B , in some exemplary embodiments, mechanism  530  includes a first coupling piece, such as first coupling piece  540 , and a second coupling piece, such as second coupling piece  550 . The first coupling piece is disposed at (e.g., fixedly connected to or integrally formed with) one of the first and second supports, and the second coupling piece is pivotally connected to the other one of the first and second supports. As a non-limiting example, it is illustrated that first coupling piece  540  is disposed at first bar  312  of the first support and second coupling piece  550  is pivotally connected to second bar  322  of the second support. The first and second coupling pieces of the mechanism can be disposed at the first bar of the first support and the second bar of the second support at any suitable positions, e.g., adjacent to, above, or below the pivotal point at which the first bar of the first support and the second bar of the second support are connected to each other. As a non-limiting example, it is illustrated that the first coupling piece of the mechanism is disposed at or adjacent to the pivotal point and the second coupling piece is disposed above the pivotal point. 
     In some exemplary embodiments, first coupling piece  540  includes a plurality of positioning slots (e.g., two, three, four, five, six or more than six positioning slots), such as slot  544 , that is formed on an edge of the first coupling piece. In some exemplary embodiments, the plurality of positioning slots is formed along with a plurality of teeth, such as tooth  542 , on the edge of the first coupling piece. 
     Second coupling piece  550  is configured to releasably engage with any one of the plurality of positioning slots. The second coupling piece is generally perforated or indented. For instance, in some exemplary embodiments, second coupling piece  550  is perforated or indented to form an end portion, such as end portion  552 , so that it can be placed (at least partially) in any one of the plurality of positioning slots and abuts the tooth formed on the edge of the first coupling piece adjacent to the positioning slot. The end portion of the second coupling piece can have any suitable configurations, including but not limited to a hook, a clamp, a hook toggle clamp, or the like. 
     Engagement of the second coupling piece with a positioning slot in the first coupling piece sets the first bar of the first support and the second bar of the second support at a specific angle “a”. Engagement of the first coupling piece with different positioning slots changes the angle “a” between the first bar of the first support and the second bar of the second support, resulting in the leg assembly (and thus the table) at different heights, as illustrated in  FIGS.  10 ,  11  and  12   . In an exemplary embodiment, the three different heights are about 700 mm, about 650 mm, and about 600 mm, respectively. Releasing of the second coupling piece from the first coupling piece allows the first bar of the first support and the second bar of the second support to rotate with respect to each other, and to be disposed substantially in a common plane as illustrated in  FIG.  13 A . 
     In some exemplary embodiments, the second coupling piece is perforated, e.g., including an opening, such as opening  554 . The opening is formed adjacent to the end portion of the second coupling piece. As such, when the end portion of the second coupling piece is engaged with a positioning slot in the plurality of positioning slots (e.g., the lowest slot in  FIG.  14 B ), the opening allows a portion of the first coupling piece to pass through to ensure that the end portion of the second piece can be properly engaged with the selected positioning slot. 
     In some exemplary embodiments, the second coupling piece includes a lug, such as lug  556 , formed at a side of the second coupling piece. The lug allows easy operation of the mechanism. For instance, to adjust the height of the table, one can pull the lug (e.g., lift the lug upward) to disengage the end portion of the second coupling piece from the current slot, place the end portion of the second piece into a desired slot, and then release the lug to allow the end portion of the second coupling piece to engage with the desired slot. 
     Similar to mechanism  330 , in some exemplary embodiments, mechanism  530  also includes a torsion spring, such as torsion spring  360 , to prevent accidental disengagement of the first and second coupling pieces. The torsion spring is disposed between the second coupling piece and the second bar of the second support at a pivotal point to which the second coupling piece is connected to the second bar of the second support. The torsion spring is connected to the second coupling piece and the second bar of the second support, and exerts a torque on the second coupling piece to prevent accidental separation or disengagement of the end portion of the second coupling piece from the selected positioning slot formed in the first coupling piece. The torsion spring helps to stabilize the table when in use. 
     With the mechanisms disclosed herein, the leg assemblies and tables of the present invention are simple, easy-to-use, foldable and height-adjustable. 
     The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting of the claims. As used in the description of the implementations and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be understood that the terms “top” or “bottom”, “lower” or “upper”, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. It will be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first bar could be termed a second bar, and, similarly, a second bar could be termed a first bar, without changing the meaning of the description, so long as all occurrences of the “first bar” are renamed consistently and all occurrences of the “second bar” are renamed consistently.