Abstract:
A height adjustable work seat is disclosed. The work seat is collapsible and extendable, and has a base, a seat pan and four folding and lockable legs. Four wheels are mounted to the bottom of the base. The folding legs connect the seat pan to the base. Each folding leg pivots at the base, the seat pan and a center pivot. The seat pan is at a maximum height relative to the base with the four folding legs fully extended. The seat pan is at a minimum height relative to the base with the four folding legs fully folded. A releasable locking mechanism secures each of the folding legs in a fully extended condition. One or more crossbars may connect opposing sleeve locks, aiding in locking, unlocking, folding or extending the pair of legs between which each crossbar extends. The seat pan may have a seatback.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. provisional application Ser. No. 61/373,742, filed Aug. 13, 2010. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to mobile chairs and seats and more specifically to height adjustable or collapsible mobile chairs with plural operative configurations. 
     BACKGROUND 
     U.S. Pat. No. 7,237,781 (hereby incorporated by reference for all purposes herein) discloses a mechanics chair with at least one side tray. A frame onto which a seat is mounted has four wheels at corner locations of the frame. The bottom of the seat is not more than 12 inches from a surface on which the four wheels rest. 
     A variety of mechanics creepers are known and commercially available. Generally, a creeper has four wheels mounted at corner locations of a frame. In use, a mechanic lies down on the creeper and maneuvers the creeper around or underneath an automobile while working on the automobile. The creeper has a low profile in order to fit underneath the automobile, and may fit underneath the automobile with the mechanic atop the creeper when the automobile is on jack stands or otherwise lifted. A mechanic may also sit on the creeper. 
     Height adjustable office chairs using a gas lift for height adjustment are known and commercially available. Office chairs, with or without gas lift, are available with wheels such as casters or other types, for moving the office chair with or without a person seated on the chair. Gas lift mechanisms generally employ an inner and outer telescoping tube with a sealed gas chamber within the tubes, and are limited in a minimum height of the chair by the height of the greater of the outer tube and the inner tube. Generally, in a gas lift mechanism with two telescoping tubes, the height adjustment range is less than or equal to one half of the maximum extension of the two tubes. 
     It is a goal of the present invention to provide a movable or mobile chair for automotive or other use that improves upon the height adjustment range of a gas lift office chair. 
     SUMMARY 
     The above goals are met in a height adjustable work seat as described herein. The height adjustable work seat is mobile and collapsible, and has two operative configurations, namely a minimum height configuration and a maximum height configuration. The seat is dimensionally and operably suitable for automotive work. 
     In a first embodiment, a height adjustable work seat has a base and a seat pan. Four wheels are mounted to the bottom of the base. Four folding legs connect the seat pan to the base. 
     Each folding leg pivots at the base. Each folding leg pivots at the seat pan. Each folding leg pivots at a respective center pivot. 
     A releasable locking mechanism secures each of the folding legs in a fully extended condition. The seat pan is at a maximum height relative to the base with the four folding legs fully extended. The seat pan is at a minimum height relative to the base with the four folding legs fully folded. 
     In a second embodiment, an extendable seat has a seat pan, four wheels, a base and four legs. The base has the four wheels pivotably mounted to the bottom of the base. The four wheels are positioned outboard relative to the seat pan. 
     The legs are collapsed, extendable and lockable. Each leg is connected at a first end to a respective base pivot. Each leg is connected at a second end to a respective seat pan pivot. Each leg is folded at a respective center pivot. The extendable seat has a minimum height configuration with the legs collapsed. The extendable seat has a maximum height configuration with the legs extended and locked. 
     In a third embodiment, a collapsible mobile chair has a seat, a base, four wheels and four collapsible legs. The seat has a seat pan and a seatback. The base has first and second side sections that extend past respective sides of the seat pan. 
     Four caster wheels are mounted to the base. The first and second caster wheels are mounted to the first side section of the base. The third and fourth caster wheels are mounted to the second side section of the base. 
     The legs are extended and foldable. Each leg is connected foldably at a first end to the base. Each leg is connected foldably at a second end to the seat pan. Each leg is foldable at a respective center knee joint. When folded, the respective first and second ends of the leg meet. The center knee joints of the front legs fold towards each other. The center knee joints of the rear legs fold towards each other. Folding the front legs and the rear legs collapses the legs and the chair. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a height adjustable work seat in accordance with the present invention, shown at full height. 
         FIG. 2  is a perspective view of the height adjustable work seat of  FIG. 1 , shown collapsed at a minimum height. 
         FIG. 3  is a front view of the height adjustable work seat of  FIG. 1 , shown partially collapsed or partially extended. 
         FIG. 4  is a perspective view of the underside of the height adjustable work seat of  FIG. 1 . 
         FIG. 5  is an elevated front view of two legs of the height adjustable work seat of  FIG. 1 , with one leg being partially collapsed or folded. The rear legs are obscured in the view. 
         FIG. 6  is a close-up elevated view of a knee joint of a folding leg of the height adjustable work seat of  FIG. 1 , with a sleeve lock. 
         FIG. 7  is a close-up elevated view of a variation of the knee joint of  FIGS. 6 and 7 . 
         FIG. 8  is a close-up elevated view of the knee joint and sleeve lock of  FIG. 6 , with the sleeve lock having an attached crossbar. 
         FIG. 9  is an elevated view of a base of the height adjustable work seat of  FIG. 1 , with a side tray or tool tray. 
         FIG. 10  is a perspective view of a seat pan or a seat suitable for the height adjustable work seat of  FIG. 1 . 
         FIG. 11  is an elevated view of a seatback suitable for the height adjustable work seat of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a height adjustable work seat  100  suitable for use by an automotive mechanic or other professional is shown. The height adjustable work seat has two major positions of operation, namely a full or maximum height and a very low or minimum height. At intermediate positions of operation, the height adjustable work seat is partially collapsed or partially extended. 
     When working on an automobile, a mechanic may be standing, seated at a nominally conventional seating height, kneeling or sitting upon a floor, sitting or lying upon an automotive creeper or otherwise positioned so as to use tools and to access various regions at various heights of the automobile. Traditionally, the mechanic uses the creeper only for accessing very low points of the automobile, and the creeper is either in the way or is moved out of the way while the mechanic works on intermediate or higher points of the automobile, bending or kneeling accordingly. The height adjustable work seat  100  allows the mechanic to select a very low or full height position of the seat, as needed for working on various regions of the automobile. 
     As shown in  FIG. 1 , the base  102  of the height adjustable work seat  100  has four wheels  104 , which may have casters  106 , mounted at or near corners of the base  102 . In one example, the wheels  104  swivel with respect to the base  102 . 
     Various sizes of bases can, be devised. In the example shown in  FIG. 1 , the base  102  has first and second side sections  120 ,  122  that extend past respective sides of the seat pan. The first and second side sections  120 ,  122  extend further forward than the front edge  124  of the seat pan  112 , and extend further backward than the rear edge  126  of the seat pan  112 . The four wheels  104  are mounted accordingly, with the wheels being positioned outboard of the seat pan  112  for stability. In other words, the wheels  104  are positioned further fore and aft than the front to back extent of the seat pan  112 , and the wheels  104  are positioned further to the sides than the lateral extent of the seat pan  112 . 
     With the wheels mounted further apart than the dimensions of the seat pan  112 , as when the base  102  including the side sections  120 ,  122  is wider and deeper than the seat pan  112  and the wheels  104  are mounted near the outermost corners of the base  102 , the height adjustable work seat  100  exhibits stability both laterally and fore and aft. In one example, an upper surface  108  of the base may fit underneath the frame of the automobile, as when low-profile wheels such as found on a creeper are fitted to the frame. 
     At the fully extended or maximum height position of the height adjustable work seat, the mechanic is comfortably seated at a nominal seating height and may roll the seat about the workspace until a very low height of the work seat is desired. In one embodiment, the upper surface  110  of the seat pan  112 , not including the seatback  114 , is approximately seventeen inches above a floor or other surface upon which the wheels  104  roll, when the height adjustable work seat  100  is at the maximum height position. Further embodiments may have a seat pan  112  height of fourteen inches or other selected dimension above the floor. A mechanic, seated upon the height adjustable work seat in the maximum height position, can work upon the middle and upper regions of the front, sides and back of an automobile. At such time as a very low height of the work seat is desired, the mechanic collapses the work seat to the minimum height. 
     With reference to  FIG. 2 , when the legs of the height adjustable work seat are folded and the work seat is collapsed to the minimum height, the seat pan is very low to the ground. In one example, the seat pan is approximately as low to the ground in the minimum height position as a bottom portion of a seat of the mechanics chair with side tray disclosed in U.S. Pat. No. 7,237,781. 
     At the fully collapsed or minimum height position, the work seat is approximately as low to the ground as if a seat pan and seatback had been mounted to a mechanics creeper. The mechanic maneuvers the work seat in the minimum height position about the workspace to access lower regions of the automobile. In one embodiment, the upper surface of the seat pan, not including the seatback, is no more than twelve inches above a floor or other surface upon which the wheels roll, when the height adjustable work seat is at the minimum height position. In a further embodiment, a lowermost portion  202  of the top surface  110  of the seat pan  112 , not including the seat back  114 , is 6 inches above the floor when the height adjustable work seat is at the minimum height position. A mechanic, seated upon the height adjustable work seat in the minimum height position, can work upon the lowermost regions of the front, sides and back of an automobile. 
     With reference to  FIG. 3 , the height adjustable work seat is shown with all four legs  302 ,  304 ,  306  and  308  partially collapsed or partially extended. Seen from the front of the seat, the two front legs  302  and  304  collapse or fold towards each other, as do the two back legs  306  and  308 . The two front legs  302  and  304  fold along a front folding plane perpendicular to the floor, and the two back legs fold along a back folding plane perpendicular to the floor. Seen from either side of the seat the legs of that side collapse or fold away from the viewer, towards the opposed side legs. In a variation, the legs of one side collapse or fold towards each other in a side folding plane, the legs of the opposing side likewise collapsing or folding towards each other in a further side folding plane. Other leg-folding configurations may be devised by a person skilled in the art. 
     Further variations of the height adjustable work seat include various mechanisms for raising and lowering the seat. A scissors lift may be manually operated and have stops or ratchets at multiple positions. Further, a scissors lift may be operated by a screw, using a handle or a motor drive. Removable legs may be inserted into sockets in the base and the seat pan assembled onto the removable legs to raise the seat, with the legs removed for the lowered seat position. A seat may hang on upright rods or columns extending upward from a base, the seat being secured to the rods or columns at a variable height. A seat may spin on a large diameter screw that is threaded into the base, for height adjustment. Sliding ramps may move inward or outward to adjust a height of the seat relative to the base. One, too, three or four legs may be included. 
     With reference to  FIG. 4 , a placement of pivoting wheels  104  near the four outboard corners of the base  102  of the height adjustable work seat  100  is shown. Each wheel rolls about a horizontal axis and each wheel assembly pivots about a vertical axis, in a manner known in the art. Other arrangements of wheels, wheel types and mountings or placements of mountings may be devised. Placing the wheels farther away from a vertical centerline or a center of gravity of the height adjustable work seat provides additional stability. 
     With reference to  FIG. 5 , each leg  302 ,  304  has a center pivot  316  or knee joint allowing the leg  302  to fold or pivot. Each leg has a further pivot  318  at the top of the leg where the leg is pivotably connected to the seat pan or to a frame supporting the seat pan. Each leg has a still further pivot  310  at the bottom of the leg where the leg is pivotably connected to the base. 
     Thus, each leg has three pivots, one each at top, center and bottom of the leg. Equivalently, for each leg, the leg  302  has a lower leg  312  and an upper leg  314 . The bottom pivot  310  foldably connects the lower leg  312  to the base  102 . The center pivot  316  foldably connects the lower leg  312  to the upper leg  314  such that the lower leg  312  and the upper leg  314  can meet when folded together. The top pivot  318  foldably connects the upper leg  314  to the seat pan  112  or seat pan frame. 
     In  FIG. 5 , the height adjustable work seat is shown with the two legs of one side partially collapsed or partially extended, and the two legs of the opposed side fully extended, although a view of the rear legs is obscured by the front legs in the elevated front view. In the example shown, the respective center pivots  316  of the front legs  302 ,  304  fold towards each other, and the respective center pivots of the rear legs fold towards each other. 
     With reference to  FIGS. 5 ,  6  and  8 , a sleeve lock  502 ,  504  telescopically slides up or down an upper portion of each leg  302 ,  304 , and locks the leg in a fully extended position or unlocks the leg. The sleeve lock may be a section of tubing of slightly larger inside dimensions than the outside dimensions of the upper leg section or the center pivot section, allowing for a sliding fit. The sleeve lock  502 ,  504  slides over the center pivot  316  of the leg to lock the leg  302 ,  304 , and slides off of the center pivot  316  of the leg to unlock the leg  302 ,  304 . Each sleeve lock  502 ,  504  is a slidable locking sleeve on a respective leg, engaging and preventing the respective knee joint or other center pivot  316  from folding. Each sleeve lock  502 ,  504  is disengageable to enable folding the respective center pivot  316 . Other mechanisms may be devised to lock a folding leg in a fully extended position and unlock the leg for folding. 
     Sleeve locks of the two legs belonging to one side of the seat may be connected by a crossbar  116 , as shown in  FIGS. 1 ,  3 ,  4  and  8 . In one example, there are two crossbars  116  and  118 , a first crossbar  116  rigidly connecting sleeve locks of a first side of the chair and a second crossbar  118  rigidly connecting sleeve locks of a second side of the chair. In a further example, where the legs of the first side of the chair fold towards each other, a crossbar connects the sleeve locks of the front legs and a second crossbar connects the sleeve locks of the back legs. Each crossbar is oriented perpendicular to the respective folding planes of the legs between which the crossbar spans. Thus, a crossbar does not interfere with the folding of the legs that the sliding locks of the crossbar engage. 
     In order to raise the height adjustable work seat from the minimum height as shown in  FIG. 2  to the full height as shown in  FIG. 1 , the mechanic releases any holding device that retains the work seat or chair in the minimum height position, then grasps and lifts the upper portion of the work seat e.g. by the seatback or seat pan. The upper portion of the work seat may be lifted and kept parallel with the floor with all four legs extending or unfolding simultaneously as shown in  FIG. 3 , or lifted by one side followed by the other side as shown in  FIG. 5 . As the upper portion of the work seat is lifted, the folding legs of one or both sides straighten out, and the center pivots or knee joints move outward from the folded, collapsed or stowed position to the extended or upright position. The mechanic may pull on the crossbars to assist the legs in opening. Once the legs are fully extended, the mechanic pushes downward on the locking sleeves until each locking sleeve slides over the corresponding center pivot or knee joint, locking the center pivot or knee joint rigidly in place. As shown in  FIG. 8 , suitable protrusions or other stops  802  extending from a portion of each lower leg  804  serve to constrain each locking sleeve  808 , preventing the locking sleeve from sliding further downward on the leg  804  and unlocking the center pivot  806  or knee joint. The mechanic may push on each crossbar to assist the corresponding locking sleeves in sliding over the knee joints of the respective legs. Other mechanisms may be devised for retaining the locking sleeve in a locked position at the center pivot, such as a spring-loaded ball on the locking sleeve engaging a detent on a portion of a leg or vice versa. 
     In order to lower the height adjustable work seat from the full or maximum height as shown in  FIG. 1  to the minimum height as shown in  FIG. 2 , the raising procedure is reversed. The mechanic slides each locking sleeve upward, disengaging the locking sleeve from the corresponding center pivot or knee joint and allowing the respective leg to pivot at the center. The mechanic may pull on the crossbars to assist the corresponding locking sleeves in sliding off of the knee joints of the respective legs. Next, the legs are collapsed. Each leg may be folded in half, one at a time, or pairs of legs on a side or pairs of legs at a front or a back may be collapsed together, or all four legs may be folded at the same time. The mechanic may press on one or both crossbars to assist the corresponding legs in folding. Once the legs are fully collapsed, the mechanic may use the work seat in the minimum height position. In a variation, once the legs are fully collapsed, a holding device such as a latch, a pin or a hook is engaged that retains the work seat or chair in the minimum height position. 
     With reference to  FIG. 6 , an example of a knee joint  604  is shown, with the locking sleeve  602  in-place and rigidly securing the knee joint  604  in an open or fully extended position. In the example, the knee joint  604  has a center link  606  or plate with two pivots  608  and  610 , a first pivot  608  pivotally connecting the center link  606  to the upper leg  612 , and a second pivot  610  pivotally connecting the center link  606  to the lower leg  614 . The locking sleeve  602  may completely surround the knee joint  604  when the knee joint is in the fully extended position. 
     With reference to  FIG. 7 , variations of the knee joint may be devised. The knee joint may have a center link or one or more side plates or links. In one variation, the knee joint  702  has two side plates or links  704  and  706  flanking respective linking projections  708  and  710  from the lower leg  712  and the upper leg  714 . In order for the side plate or plates to be recessed and allow sliding clearance for a close-fitting locking sleeve, corresponding ends of the folding legs that join at a knee joint may be thinned or have recesses  716  fitting the plates. 
     With reference to  FIG. 8 , the extended knee joint is shown rotated by one quarter of a turn about a vertical axis from the view as shown in  FIG. 6 . The locking sleeve  808  slides upward  810  or downward  814  along the upper leg  816  to unlock or lock the center pivot  806  or knee joint. One or more of the locking sleeves may be secured in a locked or an unlocked position. A securing device, such as a pin through a hole in the locking sleeve and engaging a hole in an upper leg or in a knee joint plate, fixes the locking sleeve in a selected location. In a variation, the securing device may be a bolt  818  through a threaded hole  820  in the locking sleeve  808 , the bolt being tightened to a friction fit on the upper leg, on the knee joint plate or elsewhere. The pin or bolt may have a knob or other easily grasped head  822 . In a still further variation the securing device may be a bolt through a threaded hole in the locking sleeve and engaging a hole in an upper leg or in a knee joint plate or elsewhere. In one example all four locking sleeves have bolts. Other mechanisms for holding each locking sleeve in place with the corresponding leg in a locked or an unlocked position may be devised. 
     With reference to  FIG. 9 , the base  902  of the height adjustable work seat may have one or more side trays  904 , tool trays  906  or beverage holders  908  to one or both sides of the mountings for the legs of the seat. A tray or trays may be fixed or removable. A tray may be mounted to or integral with the base or extensions thereof. Tools or other working materials, or a beverage for the mechanic, may be placed or stored in the side tray without interfering with the folding mechanism for the legs of the seat. Further, with tools so positioned, a mechanic may reach down to grasp a tool rather than having to fumble underneath the seat as when tools are stored in an under-seat tray. 
     With reference to  FIGS. 10 and 11 , various seating devices may be attached to or otherwise incorporated into the height adjustable work seat. A seat pan  1000  and seatback  1100  provide a comfortable sitting arrangement for a mechanic. The seatback  1100  may be a half-height seatback. In a further example, a seat pan  1000  without a seatback may be fitted to the height adjustable work seat, which then functions as a height adjustable stool. A seat may be formed of a seat pan  1000  as shown in  FIG. 10  or a seat pan  112  and integrated seatback  114 , which may be a half-height seatback, as shown in  FIGS. 1-4 . In a still further example, a tray or a platform is fitted in place of the seat pan and seatback, and the height adjustable work seat functions as a height adjustable work tray, a height adjustable platform or a height adjustable seat and tray combination.