Abstract:
An infant support structure having a frame, a support, and a height adjustment mechanism. The frame includes telescoping legs that support the frame in selected positions above the support surface.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to a height adjustment mechanism for an infant support structure, and more particularly, to a height adjustment mechanism for a high chair. 
     Some conventional support structures have a seat that can be adjusted relative to a support surface. Such support structures are typically complex and difficult to use. Many support structures, such as high chairs, typically do not include a seat that can be adjusted, and thereby cannot be used in different scenarios. 
     A need exists for a support structure with a seat that can be adjusted relative to a support surface to better position a child for feeding and other activities. A need also exists for a support structure that has a height adjustment mechanism that is easy to use. 
     SUMMARY OF THE INVENTION 
     An infant support structure includes a height adjustment mechanism. In one embodiment, the infant support structure is a high chair. In other embodiments, the infant support structure is any support structure that can support an infant. 
     In one embodiment, the infant support structure includes a frame and a seat or support that is mounted to the frame. The frame includes several legs that can be adjusted to vary the height of the seat relative to a support surface. In one embodiment, the infant support structure includes front and rear height adjustment mechanisms. In one embodiment, each height adjustment mechanism includes a movable member that selectively engages the frame of the infant support structure to retain the seat at a particular height. The height adjustment mechanism includes an actuator that can manipulated to engage and move the movable member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an embodiment of an infant support structure according to the invention. 
         FIG. 2  is a bottom perspective view of the infant support structure of FIG.  1 . 
         FIG. 3  is an exploded perspective view of the bases and height adjustment mechanisms of the infant support structure of FIG.  1 . 
         FIG. 4  is a top view of an embodiment of a lock according to the invention. 
         FIG. 5  is a cross-sectional side view of the lock of  FIG. 4  taken along the line  5 — 5 . 
         FIG. 6  is a rear view of an embodiment of an actuator according to the invention. 
         FIG. 7  is a side view of the actuator of FIG.  6 . 
         FIG. 8  is a cross-sectional front view of the actuator of  FIG. 7  taken along the line  8 — 8 . 
         FIG. 9  is a top perspective view of an embodiment of a base according to the invention. 
         FIG. 10  is a bottom perspective view of the base of FIG.  9 . 
         FIG. 11  is a bottom view of the base of FIG.  9 . 
         FIG. 12  is a cross-sectional side view of the base of  FIG. 11  taken along the line  12 — 12 . 
         FIG. 13  is a cross-sectional side view of the base of  FIG. 11  taken along the line  13 — 13 . 
         FIG. 14  is a side view of an embodiment of a cap according to the invention. 
         FIG. 15  is a top view of the cap of FIG.  14 . 
         FIG. 16  is a cross-sectional side view of the cap of  FIG. 5  taken along the line  16 — 16 . 
         FIG. 17  is a front partial cross-sectional view of the height adjustment mechanism and legs of the infant support structure of FIG.  1 . 
         FIG. 18  is a side view of an infant support structure in multiple configurations. 
         FIG. 19  is a schematic view of an alternative embodiment of a locking mechanism according to the invention. 
         FIG. 20  is a schematic view of an alternative embodiment of a locking mechanism according to the invention. 
         FIG. 21  is a cross-sectional front view of an alternative embodiment of some components of a support structure according to the invention. 
         FIG. 22  is a front perspective schematic view of an alternative embodiment of a support structure according to the invention. 
         FIG. 23  is a front schematic view of the support structure of FIG.  22 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An infant support structure includes a height adjustment mechanism. In one embodiment, the infant support structure is a high chair. In other embodiments, the infant support structure is any support structure that can support an infant. 
     In one embodiment, the infant support structure includes a frame and a seat or support that is mounted to the frame. The frame includes several legs that can be adjusted to vary the height of the seat relative to a support surface. In one embodiment, the infant support structure includes front and rear height adjustment mechanisms. In one embodiment, each height adjustment mechanism includes a movable member that selectively engages the frame of the infant support structure to retain the seat at a particular height. The height adjustment mechanism includes an actuator that can be manipulated to engage and move the movable member. 
     A perspective view of an embodiment of a support structure according to the present invention is illustrated in  FIGS. 1 and 2 . In the illustrated embodiment, the support structure  10  is a high chair for an infant or a child. In alternative embodiments, the support structure may be any other structure that can support a child or infant, such as a swing, a stroller, etc. The support structure can be referred to alternatively as a child support structure or an infant support structure. 
     Support structure  10  includes a seat or support  12  that is coupled to a frame  300 . In one embodiment, the seat  12  includes a seat portion and a back portion that are integrally formed. The seat  12  is pivotally coupled to a mounting bar  17  that is coupled to the frame  300  (see FIG.  2 ). 
     In the illustrated embodiment, the frame  300  includes a front frame portion  310  and a rear frame portion  350 . The front frame portion  310  includes an upper end  312  and a lower end  314 . The rear frame portion  350  includes an upper end  352  and a lower end  354 . The upper ends  312  and  352  of the front frame portion  310  and the rear frame portion  350  are coupled to housings  380  and  382  that located on opposite sides of the frame  300  (see FIG.  2 ). In one embodiment, the seat  12  is coupled proximate to the upper ends  312  and  352  of the frame portions  310  and  350 . 
     The front frame portion  310  includes legs  320  and  330 . The front frame portion  310  also includes abase  20  at the lower end  314  of the front frame portion  310 . The lower ends of the legs  320  and  330  are coupled to the base  20 . The rear frame portion  350  includes legs  360  and  370 . The rear frame portion  350  also includes a base  60  at the lower end  354  of the rear frame portion  350 . The lower ends of the legs  360  and  370  are coupled to the base  60 . 
     In the illustrated embodiment, the support structure  10  includes a first or front height adjustment mechanism  100  and a second or rear height adjustment mechanism  200 . In alternative embodiments, the support structure can include a single height adjustment mechanism. 
     Height adjustment mechanism  100  is configured to adjust the length of legs  320  and  330  relative to the base  20 . Similarly, height adjustment mechanism  200  is configured to adjust the length of legs  360  and  370  relative to the base  60 . By adjusting the lengths of legs  320 ,  330 ,  360 , and  370 , the lengths of the front frame portion  310  and rear frame portion  350  change, thereby varying the height of the seat  12  relative to the bases  20  and  60  and to the support surface on which the support structure  10  is placed. 
     The support structure  10  also includes a tray  14  and a seat recline mechanism  16  that is operable via handle  18  (see FIG.  2 ). The handle  18  is slidably mounted along the back surface of the seat  12  and is biased by a spring (not shown) in a generally downward direction. A bar  19  is coupled to a lower end of the handle  18 . The bar  19  engages a series of notches formed on the inner surface of each of the housings  380  and  382 . 
     The angle of inclination of the seat  12  can be adjusted relative to the frame  300  by pulling upwardly on the handle  18  to disengage the bar  19  from notches, pivoting the seat  12  about bar  17  to the desired inclination position, and releasing the handle  18  so that the bar  19  engages the desired notches on the housings  380  and  382 . 
     Referring to  FIG. 2 , base  20  includes a cavity  30  and base  60  includes a cavity  70 . In the illustrated embodiment, height adjustment mechanism  100  is disposed in the cavity  30  of base  20 . Similarly, height adjustment mechanism  200  is disposed in the cavity  70  of base  60 . 
     Several components of an embodiment of the support structure are illustrated in FIG.  3 . Base  20  has receiving portions  32  and  34  located proximate to opposite ends of the base  20 . Receiving portion  32  includes an opening  36  that is configured to receive a lower end of leg  320 . Receiving portion  34  includes an opening  38  that is configured to receive a lower end of leg  330 . 
     Base  60  has receiving portions  72  and  74  located proximate to opposite ends of the base  60 . Receiving portion  72  includes an opening  76  that is configured to receive a lower end of leg  360 . Receiving portion  74  includes an opening  78  that is configured to receive a lower end of leg  370 . 
     In the illustrated embodiment, the lower end of leg  320  is inserted into opening  36  and leg  320  is coupled to the base  20 . Leg  330  is inserted into opening  38  and coupled to base  20 . Similarly, legs  360  and  370  are inserted into openings  76  and  78 , respectively, and coupled to base  60 . 
     As illustrated in  FIG. 3 , height adjustment mechanism  100  includes a first movable member or lock  120 , a second movable member or lock  140 , and a third movable member or actuator  160 . Actuator  160  is operatively engaged with the locks  120  and  140 . As described in greater detail below, movement of the actuator  160  causes movement of the locks  120  and  140  relative to legs  320  and  330  of the frame  300 . The locks can be referred to collectively as a coupling mechanism or individually as elongate members, coupling members, and engaging members. 
     In one embodiment, movement of the actuator  160  along the direction of arrow “A” causes lock  120  to move inwardly along the direction of arrow “C” and lock  140  to move inwardly along the direction of arrow “E.” As lock  120  moves along the direction of arrow “C,” the lock  120  disengages from leg  330 . Similarly, as lock  140  moves along the direction of arrow “E,” the lock  140  disengages from leg  320 . 
     As described in more detail below, the locks  120  and  140  are biased outwardly into engagement with legs  330  and  320 , respectively. In particular, lock  120  is biased along the direction of arrow “D” and lock  140  is biased along the direction of arrow “F.” Movement of actuator  160  along the direction of arrow “B” enables lock  120  to move outwardly along the direction of arrow “D” and lock  140  to move outwardly along the direction of arrow “F.” 
     Height adjustment mechanism  200  includes a first movable member or lock  220 , a second movable member or lock  240 , and a third movable member or actuator  260 . Actuator  260  and locks  220  and  240  function in the same manner and move generally along the same directions as actuator  160  and locks  120  and  140 , respectively. 
     As previously described, in the illustrated embodiment, each height adjustment mechanism includes a pair of movable members or locks that are moved substantially simultaneously. In an alternative embodiment, each height adjustment mechanism can include a pair of movable members or locks that are independently actuated. In such an embodiment, each movable member of the support structure can be independently actuated. 
     An embodiment of a movable member or lock according to the present invention is illustrated in  FIGS. 4 and 5 . In this embodiment, the lock  120  includes a first end  122 , a second end  126 , and a longitudinal axis  121  extending between the ends  122  and  126 . The lock  120  includes an opening  123  into which a protrusion or extension  124  can be inserted. The protrusion  124  is the portion of the lock  120  that engages leg  330 . While protrusion  124  is illustrated as being separate from the lock  120 , the protrusion can be integrally formed with the lock in alternative embodiments. 
     The lock  120  includes a lower surface that has a tapered portion or cam surface  128 . The lock  120  also includes a cavity  129  and a through opening  127 . In the illustrated embodiment, the other movable members or locks have substantially similar structures. 
     An embodiment of an actuator according to the present invention is illustrated in  FIGS. 6-8 . In this embodiment, the actuator  160  includes a side wall  162  and an engaging surface or wall  164 . During operation, a user can press on the engaging surface  164  to move the actuator  160 . 
     The actuator  160  includes tabs  166  and  168  that extend outwardly from opposite ends of the actuator  160 . Tabs  166  and  168  are used to couple the actuator  160  to base  20  as discussed in detail later. 
     As illustrated in  FIG. 8 , the side wall  162  and engaging wall  164  form an inner surface  172  that defines a cavity  170 . Actuator  160  includes cam members or plates  173  and  174  that are coupled to the inner surface  172  of the actuator  160 . Cam member  173  includes a cam surface  176 . Similarly, cam member  174  includes a cam surface  178 . During operation, the cam surface  176  of cam member  173  engages the tapered surface  148  of lock  140 . Similarly, the cam surface  178  of cam member  174  engages the tapered surface  128  of lock  120 . 
     In one embodiment, the angles of inclination of cam surfaces  176  and  178  are substantially the same as the angles of inclination of the tapered surfaces  128  and  148  of the locks  120  and  140 . In alternative embodiments, the cam surfaces  176  and  178  and the tapered surfaces  128  and  148  can have any shape or configuration that enables the corresponding surfaces to move relative to each other when the actuator  160  is pressed. 
     An embodiment of a base according to the present invention is illustrated in  FIGS. 9-13 . Base  20  includes a lower surface  22 , a front surface  24 , a rear surface  26 , and a upper surface  28 . Base  20  includes end portions  46  and  48  located proximate to the ends of the base  20 . As illustrated, receiving portion  32  is located proximate to end portion  46  and receiving portion  34  is located proximate to end portion  48 . 
     As illustrated in  FIG. 10 , the front surface  24  of the base  20  includes a recess  42  and the rear surface  26  of the base  20  includes a recess  44  that is aligned with recess  42 . Recesses  42  and  44  are configured to enable a user to engage the actuator  160  of the height adjustment mechanism  100  located in the base  20  from either side of the base  20 . In alternative embodiments, it is not necessary that recesses  42  and  44  have the same size or configuration. 
     The base  20  includes plates  51  and  52  located in cavity  30 . The plates  51  and  52 , front wall  24  and rear wall  26  collectively define a central cavity portion  50  therebetween. In the illustrated embodiment, the central cavity portion  50  is configured to receive the actuator  160  of height adjustment mechanism  100 . 
     The actuator  160  is pressed into the central cavity portion  50  so that the tabs  166  and  168  engage openings  53  and  54  in the plates  51  and  52  to couple the actuator  160  to the base  20 . The openings  53  and  54  are configured so that the actuator  160  can move or slide in the central cavity portion  50 . Opening  53  is also configured to slidably receive a portion of lock  140  therethrough. Similarly, opening  54  is configured to slidably receive a portion of lock  120  therethrough. 
     End portion  46  includes an internal mounting recess  56 . Mounting recess  56  is configured to receive a cap that is coupled to the lower end of the leg  320  that is inserted into receiving portion  32 . Similarly, end portion  48  includes an internal mounting recess  58 . Mounting recess  58  is configured to receive a cap that coupled to the lower end of the leg  330  that is inserted into receiving portion  34 . 
     An embodiment of a cap according to the present invention is illustrated in  FIGS. 14-16 . In this embodiment, cap  400  includes a body  402  with a lower surface  404  and an upper surface  406 . Cap  400  also includes a sleeve  408  that defines an opening into which the lower end of a leg is inserted. The sleeve  408  includes a lower surface  410  that functions as a stop surface that limits the insertion of the leg. Each leg is snapped into a corresponding cap. In one embodiment, each cap is coupled to the lower end of a leg via a conventional connector, such as a screw or rivet. The caps are discussed in detail with respect to FIG.  17 . 
     The body  402  of the cap  400  also includes mounting openings  412  and  414 . The cap  400  is coupled to the lower end of the base  20  via conventional fasteners that are inserted through openings  412  and  414 . 
     Lower surface  404  is disposed at an angle with respect to the body  402 . As illustrated in  FIG. 1 , legs  320 ,  330 ,  360 , and  370  are oriented so that the lower surface of each leg is disposed at an angle with respect to a support surface. When the support structure is assembled, angled lower surface  404  extends below the lower surface  22  of the base  20  and engages the support surface. 
     In the illustrated embodiment, the lower surface  404  is configured to have an angle that is complimentary to the angle between a longitudinal axis of a support structure leg and the lower surface of a base and the support surface. The lower surface of the cap is configured to provide an engagement surface that engages the support surface on which the support structure is placed. For example, in one implementation, if the legs are configured so that a longitudinal axis of each leg extends upwardly at an angle of approximately 80° with respect to the support surface, the angled lower surface of the cap is configured to be approximately 10° with respect to the body of the cap. 
     In an alternative embodiment, each cap can be integrally formed with a corresponding base. In another embodiment, some of the caps can be integrally formed with a base and other caps can be formed separately from and coupled to a base. 
     Now the operation of a height adjustment mechanism is described with reference to  FIGS. 17 and 18 . While in one embodiment the support structure includes height adjustment mechanisms  100  and  200 , only height adjustment mechanism  100  is discussed in detail to simplify the discussion. Also, the base  20  is not illustrated in  FIG. 17  to simplify the illustration. 
     In this embodiment, leg  320  includes an upper portion  328  and a lower portion  329 . Leg  330  includes an upper portion  338  and a lower portion  339 . In one embodiment, the portions of legs  320  and  330  are hollow tubular elements. 
     The lower end of lower portion  329  of leg  320  is fixedly coupled to the base  20 . The upper portion  328  of leg  320  is slidably mounted on lower portion  329 . The lower end of lower portion  339  of leg  330  is also fixedly coupled to the base  20 . The upper portion  338  of leg  330  is slidably mounted on lower portion  339 . 
     The upper portion  328  of leg  320  includes several openings or apertures  322 ,  324 , and  326 . The upper portion  338  of leg  330  includes several openings  332 ,  334 , and  336 . While the upper portions  328  and  338  are illustrated with three openings, any number of openings may be provided on the legs  320  and  330 . 
     The lower portions  329  and  339  of legs  320  and  330  include an opening that is aligned to receive the protrusions  144  and  124 , respectively. When a particular opening on an upper portion is aligned with the opening on a lower portion, a protrusion can be inserted into the aligned openings to coupled the upper and lower portions together. 
     In  FIG. 17 , locks  120  and  140  are illustrated in their engaging positions. In these positions, the locks  120  and  140  engage legs  330  and  320 , respectively. In one configuration, the protrusion  144  of lock  140  engages opening  326  of leg  320  and the protrusion  124  of lock  120  engages opening  336  of leg  330 . 
     Lock  140  is slidably mounted in the base  20 . In the illustrated embodiment, lock  140  extends through opening  53  in plate  51  on the base  20 . End  146  of the lock  140  is retained in the central cavity portion  150  of the base  20  where it is engaged by the actuator  160 . A fastener (not shown) is mounted through the opening  147  in the lock  140  to slidably couple the lock  140  to the base  20 . The range of motion of the lock  140  is determined by the length of the opening  147 . 
     Similarly, lock  120  is slidably mounted in the base  20 . Lock  120  extends through opening  54  in plate  52  on the base  20 . End  126  of the lock  120  is retained in the central cavity portion  150  of the base  20  where it is engaged by the actuator  160 . A fastener (not shown) is mounted through the opening  127  in the lock  120  to slidably couple the lock  120  to the base  20 . The range of motion of the lock  120  is determined by the length of the opening  127 . 
     As illustrated in  FIG. 17 , a biasing element  182 , such as a spring, is disposed in the cavity  129  of lock  120 . One end of the biasing element  182  engages an inner surface of the cavity  129 . The other end of the biasing element  182  engages a surface in the cavity  30  in the base  20 . In one embodiment, the biasing element  182  engages a rib in the cavity  30 . The biasing element  182  biases the lock  120  along the direction of arrow “D” into engagement with the leg  330 . 
     When the lock  120  is biased into engagement with the leg  330 , the protrusion  124  engages the particular opening  332 ,  334 , or  336  with which it is aligned. When the protrusion  124  engages an opening, the protrusion  124  engages the lower portion  339  and the upper portion  338  of the leg  330  and prevents the portions  338  and  339  from moving relative to each other. 
     A biasing element  184 , such as a spring, is disposed in the cavity  149  of lock  140 . One end of the biasing element  184  engages an inner surface of the cavity  149 . The other end of the biasing element  184  engages a surface in the cavity  70  in the base  60 . In one embodiment, the biasing element  184  engages a rib in the cavity  70 . The biasing element  184  biases the lock  140  along the direction of arrow “F” into engagement with the leg  320 . 
     When the lock  140  is biased into engagement with the leg  320 , the protrusion  144  engages the particular opening  322 ,  324 , or  326  with which it is aligned. When the protrusion  144  engages an opening, the protrusion  144  engages the lower portion  329  and the upper portion  328  of the leg  320  and prevents the portions  328  and  329  from moving relative to each other. 
     When the actuator  160  is moved upwardly along the direction of arrow “A,” the cam surfaces  178  and  176  engage the tapered surfaces  128  and  148  of locks  120  and  140 , respectively, and locks  120  and  140  are moved into their retracted positions (illustrated in dashed lines in FIG.  17 ). 
     As the cam surface  176  engages the tapered surface  148 , the lock  140  moves inwardly along the direction of arrow “E.” If the lock  140  moves a sufficient distance, the protrusion  144  disengages from the leg  320  and the upper portion  328  can slide relative to the lower portion  329 . As the cam surface  178  engages the tapered surface  128 , the lock  120  moves inwardly along the direction of arrow “C.” If the lock  120  moves a sufficient distance, the protrusion  124  disengages from leg  330  and the upper portion  338  can slide relative to the lower portion  339 . 
     When the actuator  160  is released, the biasing elements  182  and  184  bias the locks  120  and  140  along the directions of arrows “D” and “F,” respectively, into their extended positions as illustrated in FIG.  17 . As the locks  120  and  140  move in those directions, the tapered surfaces  128  and  148  engage the cam surfaces  178  and  176  and force the actuator  160  along the direction of arrow “B.” The locks  120  and  140  are then located in their extended positions. 
     In the illustrated embodiment, lock  140  moves along a direction that is substantially perpendicular to the longitudinal axis  321  of leg  320 . Similarly, lock  120  moves along a direction that is substantially perpendicular to the longitudinal axis  331  of leg  330 . Actuator  160  is mounted for movement along a direction that is substantially parallel to the longitudinal axes  321  and  331  of the legs  320  and  330 . 
     In alternative embodiments, the particular directions of movement of the locks and the actuator may vary respect to the legs  320  and  330  of the support structure  10 . The locks and the actuator can be mounted in any configuration or arrangement that enables them to move relative to and selectively engage the legs of the support structure. 
     In the illustrated embodiment, the lower leg portion  329  is snapped into cap  390  which retains the lower leg portion  329  to the base. Similarly, lower leg portion  339  is snapped into cap  392  which retains the lower leg portion  339  to the base. Each of the legs  360  and  370  includes a lower leg portion (not shown) that is coupled to the rear base via respective caps. 
     In one embodiment, a single biasing element can be located between the locks to bias the locks into their engagement positions. 
     In another embodiment, an actuator is configured to be pushed downwardly to move one or more locks inwardly and to be pulled upwardly to allow the lock to move outwardly to engage part of a support structure. 
     An embodiment of a support structure that can be disposed in several configurations is illustrated in FIG.  18 . In this embodiment, the support structure  500  includes a seat portion  502 , a front frame portion  504 , and a rear frame portion  506 . The support structure  500  also includes bases  507  and  508  to which the front frame portion  504  and the rear frame portion  506  are coupled, respectively. 
     The support structure  500  includes height adjustment mechanisms (not shown) that facilitate the adjustment of the lengths of the legs  504  and  506 . In particular, a user can adjust the length of the legs  504  and  506  via one or more of the height adjustment mechanisms. The lengths of the legs  504  and  506  can be adjusted to dispose the support structure  500  in multiple configurations and to adjust the height of the seat portion  502  relative to a support surface  530  and to the bases  507  and  508 . 
     The support structure  500  can be disposed in several configurations relative to the bases  507  and  508 . In one embodiment, the support structure  500  can be disposed in a first or lowered configuration  510  and a second or raised configuration  520 . In the first configuration  510 , illustrated in dashed lines, the lower ends of the legs  504  and  506  are spaced apart a distance “G.” In this configuration, the height of the seat portion  502  is represented by “I.” 
     The support structure  500  can be disposed in its second configuration  520  by lengthening the legs  504  and  506  as compared to the first configuration  510 . In configuration  520 , the lower ends of the legs  504  and  506  are spaced apart a distance “H” and the height of the seat portion  502  is represented by “J.” As illustrated in  FIG. 18 , distances “H” and “J” are greater than the distances “G” and “I,” respectively. 
     An alternative embodiment of a locking mechanism according to the invention is illustrated in FIG.  19 . The locking mechanism  600  is formed as a unitary member that can be activated and that can lock one or more legs of a support structure in place. The locking mechanism  600  includes an actuator portion  610 , an engaging portion  620 , and an engaging portion  630 . In this embodiment, the actuator portion  610  and the engaging portions  620  and  630  are integrally molded. In an alternative embodiment, the actuator portion  610  and the engaging portions  620  and  630  can be formed separately and coupled together. 
     The actuator portion  610  includes couplers  612  and  614  that couple the engaging portions  620  and  630  and the actuator portion  610 . Couplers  612  and  614  can be made of a springy, flexible material that has a sufficient strength to impart movement to the engaging portions  620  and  630 . 
     Engaging portion  620  includes a projection  622  that is configured to engage a hole or holes in a leg of a support structure. Similarly, engaging portion  630  includes a projection  632  that is configured to engage a hole or holes in another leg of a support structure. In one embodiment, the projections  622  and  632  are made of metal, such as steel. In other embodiments, any material that has a sufficient stiffness can be used for the projections. 
     In one embodiment, biasing elements  640  and  642 , such as springs, are used to bias the engaging portions  620  and  630  outwardly along the directions of arrows “K” and “L,” respectively, to their extended or locked positions. In another embodiment, a single biasing element can be used instead of biasing elements  640  and  642 . 
     As a user moves the actuator portion  610  along the direction of the arrow “M,” the engaging portions  620  and  630  move inwardly along the directions of arrows “N” and “O,” respectively, to their retracted or unlocked positions. When the user releases the actuator portion  610 , the biasing elements  640  and  642  force the engaging portions  620  and  630  outwardly along the directions of arrows “K” and “L.” 
     An alternative embodiment of a locking mechanism according to the invention is illustrated in FIG.  20 . In this embodiment, the locking mechanism  700  includes locks  710  and  720  that are mounted for movement relative to a support structure. Lock  710  includes a projection  712  that is configured to engage one or more holes on a leg of a support structure. Similarly, lock  720  includes a projection  722  that is configured to engage one or more holes of a leg of a support structure. 
     In this embodiment, the locking mechanism  700  does not include a separate actuator portion or member. Lock  710  includes a cam surface  714  that extends at an angle with respect to the remainder of the lock  710 . Similarly, lock  720  includes a cam surface  724  that extends at an angle with respect to the remainder of the lock  720 . The cam surfaces  714  and  724  can extend in any direction, such as upwardly, downwardly, or sideways, from the locks  710  and  720 , respectively. In alternative embodiments, the locks  710  and  720  can have any shape or configuration. 
     The locking mechanism  700  includes a biasing element  730 , such as a spring, that is disposed between the locks  710  and  720  to bias the locks  710  and  720  to their extended or locked positions along the directions of arrows “P” and “Q,” respectively. In an alternative embodiment, separate biasing elements can be used to bias the locks. 
     When a user wants to release lock  710 , the user engages cam surface  714  and moves it along the direction of arrow “R.” Similarly, when a user wants to release lock  720 , the user engages cam surface  724  and moves it along the direction of arrow “S.” Cam surfaces  714  and  724  can be engaged simultaneously to move the locks  710  and  720  at the same time. 
     An alternative embodiment of several components of a support structure according to the invention is illustrated in FIG.  21 . In this embodiment, the support structure  800  includes a base  810  that has a mounting portion  812 . The mounting portion  812  includes a substantially cylindrical sleeve  814  that is configured to receive a portion of a leg  820  of the support structure. The sleeve  814  is integrally molded with the base  810 . The sleeve  814  extends to the lower surface of the base  810  and contacts a support surface on which the base  810  is located. The sleeve  814  also includes a first portion  816  and a second portion  818  that collectively define the sleeve  814 . Portions  816  and  818  include aligned openings  817  and  819 , respectively. 
     A leg  820  can be inserted into the opening defined by the sleeve  814 . The leg  820  includes openings  822  and  824  that are aligned in opposite sides of the leg  820 . As illustrated, the leg  820  includes several pairs of aligned openings, such as openings  826  and  828  and openings  830  and  832 . The various pairs of openings enable the leg  820  to be coupled to the base  810  at different heights. 
     The support structure  800  includes a lock  840  that is selectively engageable with the leg  820 . In this embodiment, the lock  840  includes a projection  842  that is configured to be inserted into the openings on the leg  820  and the sleeve  814 . The lock  840  can be moved along the directions of arrow “T” either with or without the assistance of an actuator (not shown). 
     In an alternative embodiment, the projection  842  can be configured to engage only one side of the sleeve  814 . For example, projection  842  can be configured to engage opening  822  in sleeve  814  only and not extend to the other side of the sleeve  814 . In such an embodiment, the leg  820  can have openings only along one side, such as, openings  822 ,  826 , and  830 . 
     An alternative embodiment of a support structure according to the invention is illustrated in  FIGS. 22 and 23 . In this embodiment, the support structure  900  includes a support or seat  902  and a frame  904  that includes a front leg  906  and a rear leg  908 . The front leg  906  includes front leg portions  907   a  and  907   b . The rear leg  908  includes front leg portions  909   a  and  909   b.    
     The support structure  900  includes a front coupler  910  to which the ends of front leg  906  are slidably coupled and a rear coupler  912  to which the ends of rear leg  908  are slidably coupled. The front coupler  910  and the rear coupler  912  can be coupled to any surface of the support  902 , such as the lower surface. In one embodiment, each of the front coupler  910  and the rear coupler  912  can include a recess (not shown), the function of which is described later. 
     As illustrated in  FIG. 23 , front leg  906  is slidable relative to the front coupler  910  along the directions of arrow “U.” While not illustrated, rear leg  908  is independently slidable relative to the rear coupler  912  along the same directions. 
     The support structure  900  includes a front height adjustment mechanism  920  and a rear height adjustment mechanism (not shown). The front and rear height adjustment mechanism have substantially similar structures and operations. 
     In this embodiment, height adjustment mechanism  920  is disposed in the front coupler  910 . Height adjustment mechanism  920  includes an actuator  930  and locks  940  and  950 . The actuator  930  can be located proximate to a recess in the front coupler  910  that facilitates access to the actuator  930 . Locks  940  and  950  are biased outwardly along the directions of arrows “V” and “W,” respectively, into engagement with the upper end portions of the front leg  906 . In this embodiment, a biasing element  960 , such as a spring, is disposed between the locks  940  and  950 . In an alternative embodiment, separate biasing elements can be used to bias the locks individually. 
     When a user wants to change the height of the support  902  or the length of the front leg  906 , the user moves actuator  930  along the direction of arrow “X.” Movement of the actuator  930  in that direction causes the locks  940  and  950  to move inwardly along the directions of arrows “Y” and “Z,” respectively. The front leg  906  can then be moved downwardly to align another set of openings in the upper ends of the front leg  906  with the projections on the locks  940  and  950 . When the desired height of the support  902  is achieved, the actuator  930  is released and the locks  940  and  950  are biased into their extended or locked positions. 
     In alternative embodiments, a support structure may be disposed in any number of configurations. In such embodiments, the quantity of configurations is related to the quantity of positions in which the legs of the support structure can be disposed. 
     While the height adjustment mechanisms are illustrated as being operable in the same direction, in an alternative embodiment, the height adjustment mechanisms can be operable in different directions. For example, in the illustrated embodiment, the actuator is pressed upwardly to move the locks relative to the legs of the support structure. In an alternative embodiment, the actuator of one height adjustment mechanism can be oriented for actuation in an upward direction and the actuator of another height adjustment mechanism can be oriented for actuation in a downward direction. 
     In an alternative embodiment, the actuator of a height adjustment mechanism can be configured for movement in a substantially horizontal plane. Alternatively, the actuator can be oriented for movement in a plane disposed at an angle with respect to a horizontal plane. 
     In an alternative embodiment, the biasing elements of a height adjustment mechanism can be disposed at different locations. For example, the biasing elements can engage different surfaces of the locks to bias the locks in a particular direction. Alternatively, a biasing element can be disposed between the proximate ends of the locks to bias the locks outwardly and into engagement with the legs of the support structure. 
     In another embodiment, a biasing element, such as a spring, can be provided between an actuator and a base to bias the actuator away from the base. 
     In an alternative embodiment, a base of the support structure can include a single recess that enables access to an actuator in any one of the walls of the base. The recess can be any size and configuration that enables a user to actuate the height adjustment mechanism. 
     In an alternative embodiment, the actuator of a height adjustment mechanism can be accessible from a surface of the base other than lower surface. In one implementation, the actuator can be accessible via the front surface, the rear surface, or the top surface of a base. 
     In another embodiment, the support structure can include a single base in which one or more height adjustment mechanism are disposed. 
     While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope thereof. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.