Patent Publication Number: US-6702372-B2

Title: Synergistic body positioning and dynamic support system

Description:
RELATED APPLICATIONS 
     The present application is a divisional application of U.S. patent application Ser. No. 09/750,541, filed Dec. 28, 2000, which is a continuation-in-part application of U.S. patent application Ser. No. 09/513,374, filed Feb. 25, 2000 (now issued as U.S. Pat. No. 6,439,657) and is a continuation-in-part Ser. No. 09/257,900 filed Feb. 25, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a body positioner structured to provide healthy postures by promoting active sitting and proactive positioning. The positioner enables accurate and repeatable correlation between a user&#39;s body and a work station by enabling quick postural adjustments based on the preferred postural excursions of the user. Particularly, the body positioner is preferably integrated with at least one work station such as, for example, a computer or manufacturing station. More particularly, the invention provides integration of the positioner with a seating task station, enabling quick dynamic adjustments for optimal alignment and orientation of the positioner and the user relative to the seating task station within a plurality of healthy postures and ergonomic ranges to promote worker health, comfort and productivity. 
     2. Description of Related Art 
     In the early 1970&#39;s Jerome Congleton, a leading ergonomist, was the first to introduce the concept of the neutral position to the task seating industry. Further, A. C. Mandal, in a book relating to unhealthy postures of school children, emphasized the need to tilt the pelvis forward in order to maintain a proper balance of the weight of the upper body on the spine. These and other ergonomic research over the last three decades have shown that certain postural orientations, particularly during sitting, affect the body weight distribution on the spine and generally result in injury or long term pain. For the most part therefore, ergonomic research over the past three decades appears to support the concept of proper body weight distribution by maintaining certain postures. However, heretofore, no system exists which would enable a person, particularly engaged in work involving task seating systems and related operations, to shift into comfortable positions, quickly without disrupting work. 
     Several medical studies have shown that prolonged static postures in any of the natural configurations such as, for example, sitting and standing cause discomfort, pain and ultimately injury. Modem work stations such as computer related work at the office require that the operator be oriented in a sedentary position. When a subject is in a limited movement sitting position muscle stress and discomfort occur. Specifically, during sitting, the vertebral column transmits the weight of the body through the pelvis to the lower limbs. When the vertebral column experiences prolonged stress due to sedentary postures, a deformity of the spine may result leading to serious medical problems such as kyphosis which is characterized by a posterior curvature of the vertebral column. Further, prolonged sedentary sitting may contribute and/or aggravate scoliosis, characterized by a lateral curvature of the vertebral column and lordosis, characterized by an anterior curvature of the vertebral column. Movements of the vertebral column are freer in the cervical and lumbar regions and these regions are the most frequent sites of discomfort and pain. The main movements of the vertebral column are flexion or forward bending, extension or backward bending, lateral bending or lateral flexion, and rotation or twisting of the vertebra relative to each other. Some circumduction which consists of flexion-extension and lateral bending also occurs. It is imperative, therefore, that a body positioning system provide movement, at the very least, to the cervical and lumbar regions of the vertebral column. 
     In addition to the vertebral column, a body support system implemented to position a person proximal to a work station must be ergonomically balanced with the work station. In this regard the upper limb, which is the organ of manual activity, should be allowed to move freely. Further, the upper limb which includes the shoulder, arm, forearm and hand must be positioned to provide stability and to gain mobility. Because any slight injury to the upper limb is further aggravated by repeated motion of the hand and arm muscles, it is important to provide comfortable positioning and support to the upper limb at all postures related to a task seating work station. 
     Similarly, a well-designed body support system should consider neck and head position. The neck contains vessels, nerves, and other structures connect in the head and the trunk. There are several causes of neck pain. As it relates to neck pain resulting from bad postures, muscle strain and protrusion of a cervical intervertebral disc may be the cause. Many vital structures are located in the neck and proper positioning and support of the neck must be made to avoid muscle strain. Further, posterior positioning to the head is important to avoid strain, headache and head pain. 
     Lumbar and thoracic support are also vital to promote good breathing and elimination of stress on the lumbar and thoracic vertebrae. As it is well known clinically, the lungs are the essential organs of respiration. The inspired air is brought in close relationship to the blood in the pulmonary capillaries. Thus, proper positioning and thoracic support enhances the efficiency of the lungs to supply optimal oxygen levels to the blood. This is key to worker overall health and productivity. 
     The lower limb, including the upper and lower leg, ankle, and foot, is the organ of locomotion and is also a load bearing element. The parts of the lower limb are comparable to those of the upper limb. The lower limb is heavier and stronger than the upper limb. Since a vast number of vital networks of arterial vessels are located in the lower limb, it is medically important to promote the flow of blood through these arterial vessels. Thus, in sedentary postures, frequent removal of weight off the lower limb is recommended to eliminate muscle tension, fatigue and related degenerative joint disease. 
     In general, the present state of the art is incapable of providing a full authropometric range to users with the option to switch to different comfortable/healthy postures while keeping them within an ergonomic range of a work station in a manner that is non-disruptive to the task being performed. Particularly, the present state of the art does not provide an “active sitting and proactive positioning” system which incorporates the support of the various body parts and promotes healthy postures and comfort at work stations. 
     Accordingly, there is a need for a body positioning system capable of providing fluidic and timely transposition of a user into various preferred and healthy postural configurations, maintaining comfortable ergonomic ranges to a task seating work station at all postures and enhancing health and productivity relative to a defined space-volume envelope of the positioning system and, preferably to a work station integrated therewith. 
     SUMMARY OF THE INVENTION 
     The present invention is based on the heretofore unrealized objective to successfully integrate human performance with comfort and health. Specifically, in the preferred embodiment, the invention implements principles of “active sitting and proactive positioning” in which the subject is temporally encouraged to change to various comfort and health postures while maintaining ergonomically compatible access and reach to a work station at all times. 
     The invention provides a user with a selection of discrete and dynamic medically preferred health postures. Specifically, the invention utilizes, inter alia, the principle that to prevent cumulative trauma disorder (CTD) the pelvis must always be positioned in an orientation similar to an erect/tilted position during standing. The basic discrete postures of the present invention include a recline seated posture, a recline neutral posture/breath-easy posture and a recline standing posture. The invention incorporates these discrete postures to generate a full range of dynamic hybrid postures continuously shiftable and adjustable to prevent injury, discomfort and fatigue while enhancing health and comfort. Further, the invention proactively positions the user to be placed within an ergonomic range of the work station, at all postural configurations to enhance productivity. 
     The invention enables the user to move in and out of the discrete and dynamic postures without disrupting the task at hand. One of the significant benefits derived from this active sitting aspect of the invention is that the user is provided with a full range of joint movement in the legs and torso during the excursion through the various postures. Further, the postures enhance the respiratory fluid flow and joint lubrication systems and relieve muscle stress. The user may also perform occasional stretch exercises, by shifting through these various postures to increase vital fluid flow and circulation in the torso and lower parts of the body. 
     The invention includes a body positioning system having components designed to be compatible with human physiology and enhancement of healthy postures at work stations. Specifically, the major components include a seat/back support, a body support component for below the lower leg, and a foot rest body support all being independently and correlatively operable at the option(s) of the user to navigate through various postures while maintaining ergonomic reach to the work station. More specifically, the seat/back support and the support for below the lower leg comprise pressure surfaces having ergonomically optimized/compatible geometric shapes to enable a smooth transition from one posture to the next in addition to the provision of proper body support and healthy positions at all postural configurations. Further, the surfaces are made of materials specifically structured to eliminate excessive resistance, during the user&#39;s dynamic excursions through the various postures or during any static posture, irrespective of the type and fabric of clothing worn by the user. Since the pressure surfaces/bearing surfaces are implemented to shiftably serve as back and seat support at various postures, the interaction between the surfaces and the user&#39;s clothing is critical to promote smooth transition of the user from one posture to the other. 
     The controls and actuators implemented in the present invention, which control the body positioning system seat/back angle adjustment, seat height adjustment and lower body part support angle adjustment, are ergonomically designed to have a high level of accessibility and availability to the user. Further, the actuators are set to meet the anthropometric fit requirements of a world population. Particularly, the controls are designed and located to enable a user to quickly and easily shift from one posture to another without disruption of the task being performed. 
     The present invention further provides robust features integrated to enhance productivity and worker effectiveness. The user is generically integrated with the positioning system and work station such that all the components are positioned to be readily accessible and available to the user while enabling work to progress concurrent with multiple posture position shifting. Further, the work station is designed to attenuate the transfer of vibration to the positioner by strategically installing vibration dampeners and shock absorbing connections at points of contact between the user, the work station, work tools, and the positioner. 
     The office environment is one of the many work areas in which the present invention could be advantageously implemented. The body positioning system is dimensionally optimized to fit into most office space and is highly mobile to be compatible with movable wall offices. Further, the system of the present invention is modularized to stand alone or to be incorporated into multiple work station areas. 
     In the preferred embodiment, the controls and mechanical systems are versatile to adapt to various power supply systems. Further, ease of assembly and disassembly make the system advantageously flexible to accommodate the user&#39;s choices and be compatible with various production and work area environments. 
     With these and other features, advantages and objects of the present invention which may become apparent, the various aspects of the invention may be more clearly understood by reference to the following detailed description of the preferred embodiment, the appended claims and to the several drawings herein contained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view assembly drawing of the preferred embodiment; 
     FIG. 2 is an isometric view describing in greater detail correlatively adjustable joints and links; 
     FIG. 3 is an isometric view showing in greater detail adjustable support systems and mechanism; 
     FIG. 4 is an isometric view of the structural details of actuating members of the positioner; 
     FIG. 5 is a further detailed isometric view of actuating members and cooperative structural links; 
     FIG. 6 is an isometric view of position actuation and engagement details and structures for rotating pressure surfaces through a 90° angle; 
     FIG. 7 is an isometric view of the structure and actuation control lines from the triggers which operate the push-pull pistons; 
     FIG. 8 is a cross-section of the side support loop structure; 
     FIG. 9 is an isometric view of the control lock mechanism for the work surfaces such as the monitor and keyboard support including lower body support mechanism in greater detail; 
     FIG. 10 is an isometric view of the actuating mechanism for the lower body support; 
     FIG. 11 is an isometric view showing underlying structural connections and organization of a piston and the lower body support; 
     FIG. 12 is an isometric view of the rotational position control/lock mechanism for adjusting the work tool support surfaces and connections thereof; 
     FIG. 13 is an isometric view of the main structural base and support assembly; 
     FIG. 14 is a simulation view of the multi-posture range of the present invention; 
     FIG. 15 is an isometric view of the present invention integrated with a computer console/station; 
     FIG. 16 is an isometric view of the positioner being used in non-integrated set up in an assembly type environment; 
     FIG. 17 is an isometric view of an alternate embodiment of the positioner with the lower leg support structure and pad removed; 
     FIG. 18 is an isometric view showing detailed structural parts of the file holder; 
     FIG. 19 is a detailed isometric view of the mouse cage; 
     FIG. 20 is a detailed isometric view of the monitor platform with vibration dampener; 
     FIG. 21 is a front perspective view of an alternative embodiment of a work station of the present invention; 
     FIG. 22 is a rear perspective view of the alternative embodiment of the work station of FIG. 21; 
     FIG. 23 is a perspective view depicting the underside of the alternative embodiment of the work station of FIG. 21; 
     FIG. 24 shows the work station of FIGS. 21-23 wherein the work surface of the work station includes an additional articulating keyboard/work surface; 
     FIG. 25 is a front perspective view of an alternative embodiment of a body positioning system of the present invention; 
     FIG. 26 is a side perspective view of the alternative embodiment of the body positioning system of the present invention; 
     FIG. 27 is a rear plan view of the alternative embodiment of the body positioning system of the present invention; 
     FIG. 28 is a cross-sectional view taken along line A—A of FIG. 27; 
     FIG. 29 is an ensemble depiction of the work station of FIGS. 21-24 and the body positioning system of FIGS. 25-28 wherein both are in a seated operating position; 
     FIG. 30 is an ensemble depiction of the work station of FIGS. 21-24 and the body positioning system of FIGS. 25-28 wherein both are in a seated operating position; 
     FIG. 31 is a rear quarter perspective view of the work station assembly of a further preferred embodiment of the present invention; 
     FIG. 32 is a front quarter perspective view of the work station assembly of FIG. 31; 
     FIG. 33 is an underside view of the workstation planar work surface depicting the actuators affixed thereto; 
     FIG. 33 a  is a side perspective view of the key board suspension with portions thereof depicted in phantom; 
     FIG. 34 is a perspective view of the compressed gas spring assembly supporting the work surface; 
     FIG. 34 a  is a side elevational view of the actuator controlling the primary gas spring of FIG. 34, a portion of the depiction being cut away; 
     FIG. 34 b  is a side elevational view of an alternative embodiment of the compressed gas spring assembly supporting the work surface, a portion of the depiction being cut away; 
     FIG. 35 is a perspective view of the suspension system of the work surface; 
     FIG. 36 rear quarter perspective view of the body positioning system assembly of a further preferred embodiment of the present invention; 
     FIG. 37 is a sectional side elevational view of the chair back of the chair depicted in FIG. 36 disposed in the seated work position; 
     FIG. 38 is a side elevational view of the embodiment of FIG. 36 disposed in the lifted work position; 
     FIG. 39 is a side elevational view of the body positioning system in the lean stand position; 
     FIG. 40 is a side elevational view of the sectioned pedestal and the primary gas cylinder supporting the chair assembly; 
     FIG. 41 is a rear elevational view of the primary gas cylinder actuator assembly; 
     FIG. 42 is a side elevational view of the lower leg-support assembly with the forwardmost disposition thereof depicted in phantom; 
     FIG. 43 is a front perspective view of the lower leg-support assembly; and 
     FIG. 44 is a schematic representation of controllers and actuators for a powered embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is able to accommodate the various shifts in weight and pressure normally encountered by the body when an individual changes from one posture to another. More particularly, the invention mimics ergonomically desirable postural silhouettes to proactively support and position the user in the most healthy posture, such that body weight and pressure are distributed to eliminate undue discomfort, pain, fatigue, and muscular and skeletal strain. Thus, one of the significant features of the present invention is the elimination of discomfort and potential injury caused by most sitting postures when the individual is forced to sit in an upright posture or other unhealthy postures for an extended time period. 
     With reference to FIG. 1, a perspective assembly view is shown of the present invention. In particular, the body positioning system  10  is shown integrated with work station  12 . As depicted herein, work station  12  is a computer work station where any type of computer, small enough to fit on an office desk, is implemented. A desktop computer may be connected to the local area network and configured with sufficient memory and storage to perform standard or specialist business computing tasks. Current technology offers full-function desktop computers which can be turned into portable notebook computers. When in the office, the small computer sits in a docking station and can connect to a local area network. Although body positioning system  10  can be used independently, FIG. 1 shows one of the preferred embodiments in which a computer work station  12  is integrated with it. Specifically, the computer work station  12  includes support surfaces and structures for a monitor, keyboard and a central processing unit (CPU). As discussed hereinbelow, the integrated system is designed not only to promote medically advantageous ergonomic postures but incorporates bio-mechanical design features to eliminate any physical discomfort such as eye strain, muscle stress, and improper spinal configuration which occurs during long term task activity. Further, the present invention provides a user with a selection of discrete and dynamic medically preferred health postures based on a coordinated, accurate and repeatable orientation of body positioning system  10  and work station  12 . More specifically, a plurality of basic discrete postures including a recline seated posture, a recline neutral posture/breath-easy posture, and a recline standing posture are implemented to set a user at positioning system  10  at various orientations. The discrete postures are a distinct part of a full range of dynamic hybrid postures continuously shiftable and adjustable to prevent injury, discomfort and fatigue while enhancing health and comfort. The invention utilizes ease of adjustment and proactively motivates the operator/user to be positioned within an ergonomic range of work station  12  during all postures, thus enhancing health and productivity. As will be discussed hereinbelow, one of the advantages of the proactive aspect of the invention is the structural cooperation of the elements of positioning system  10  and work station  12  to advance, favor, promote motion and nimble transformation of the user from one posture to the next. Particularly, positioning system  10  is a synergistic bio-mechanical system designed to accommodate and become synergistic with the next best postural orientation of the human body ranging from a convention seated, with full body stretch option, to a lean-stand with the full body in a substantially vertical posture. 
     Still referring to FIG. 1 in more detail, an integrated body positioning and work station system is shown. Specifically, body positioning system  10  and work station  12  are shown integrated to correlatively operate as an integrated unit. Positioning system  10  includes pressure bearing surfaces  14  and  15  and a pair of articulating side supports  16 . An actuator  48   a  enables adjusting the height of the surface  15 . A corresponding actuator  48   b  on the second side support  16  enables adjusting the tilt of the surface  15 . Pressure bearing surfaces  14  and  15  are adjustably and resiliently attached at joint  18 . Pressure bearing surface  14  includes a contact surface (back support) and outer formed surface to encase reinforcing frames therein. The inner surface includes geometric shapes to cradle the user as lumbar, lower back and shoulder blade regions during sitting, neutral and lean-stand positions, and the several postures in between. The outer surface is preferably removable and is centrally cumbered to encase an upper end section of joint  18  which is secured to outer surface of pressure bearing surface  14 . Further, articulating side supports  16  are attached to pressure bearing surface  15 . Pressure bearing surface  15  is rotatably and tiltably connected to a top end of pedestal  20 . Pressure bearing surface  15  includes an upper and lower formed surfaces. The upper part of pressure bearing surface  15 , which functions as a seat and back support depending upon the user&#39;s temporal posture, generally includes a declivity with anticlined arcuate edges at opposite sides. This geometric shape of surface  15  provides a bio-medical system which articulates with the user&#39;s body to effectively support the gluteal and lumbosacral regions. At its bottom end, pedestal  20  is pivotally and adjustably secured to stabilizers  22  and connector arm  23 . Connector arm  23  interconnects stabilizers  22  with base structure  24 . Lower body support pad  26  including link member  27  are mounted on base structure  24 . 
     Work station  12  includes tool platforms  28  and  32  separated by connection members  34 . Further, work station  12  includes platforms  36 ,  38 , and  40  hingeably and adjustably connected to column  42 . Swivel mounted leg  44  provides support to tool platforms  28  and  32  at the fore end. Platform  45 , formed to support coffee cups, cans and similar containers in addition to writing tools, is adjustably and swingably mounted on swivel mounted work surface  32 . Mouse cage  39  is set on platform  38  where a keyboard is preferably located. As will be discussed hereinbelow, the platforms are adjustably interconnected by utilizing maneuverable compound linkage framework  46 . Specifically, as will be disclosed hereinbelow, when body positioning system  10  is translated through various postural positions, work station  12  is accurately and continuously maintained within the ergonomic range of the user by timely manipulating compound linkage framework  46 . Work station  12  preferably includes file holder  47  which is designed to be compatible with the many ergonomic features of the present invention. 
     Referring next to FIG. 2, a portion of work station  12  is removed to clearly show some of the major interactive elements of the invention. Particularly, body positioning system  10  is shown with triggers  48  embedded in articulating side supports  16 . Triggers  48  are located immediately forward under the declivity of articulating arm  16 . This arrangement proactively encourages the user to keep the elbows backwards thus pushing the thorax forward. As the user actuates triggers  48 , the thorax is extended anteriorily and this in turn tilts the pelvis forward throughout the various postural excursions of the user. This is one of the many distinguishing features of the present invention. Prior art devices, such as ergonomic chairs and supports, are generally designed to locate and provide lumbar support. In sharp contrast, the present invention enables the pelvis to be tilted forward irrespective of the position of the lumbar curve. Each basic posture of the present invention leans the upper body back about 15° beyond the vertical. This allows all of the upper body weight to be distributed throughout pressure bearing surfaces  14  and  15  while platforms  36  and  38  are moved to easily accessible positions. In the preferred embodiment, platform  36  is used to support a screen/monitor or similar device, and as indicated above, a keyboard is placed on platform  38 . Mouse cage  39  includes a pad and a structure to retain the mouse in place when platform  38  is shifted laterally and tilted toward or away from positioning system  10 . The tiltability/rotatability of platform  38  is one of the many innovative and bio-mechanical features of the invention. Platform  38  is independently tiltable to conform to the many various orientations of the user. Specifically, when the user is in stand/near stand or lean/stand, posture platform  38  is inclined away from positioning system  10  to provide an ergonomically healthy and non-stressful positioning of the hands. Platform  38  is rotatable toward and away from positioning system  10  to eliminate positions of the hand which may cause compression of the median nerve at specific postures. Generally, a prolonged compression of the median nerve will likely result in Carpal Tunnel Syndrome which results in a progressive loss of coordination and strength in the thumb if the cause of the median nerve compression is not alleviated. This further results in difficulty in performing fine movements. In cases of severe compression of the median nerve, there is a likely risk of atrophy of some of the muscles in the hand. Yet another innovative aspect of the present invention is mouse cage  39  which is designed to secure the mouse to be accessible and available at any of the positions of platform  38 . 
     Still referring to FIG. 2, support plate  50  is shown cantilevered from link arm  49 . Further, link arm  49  is secured to a telescoping section of support column  42 . Support plate  50  is adjustably pivotably and provides support for tool platforms  28  and  32  at the rear end. Compound linkage framework  46  includes flex joints  54  and connected to intermediate members  58 . Platform  36  is cantilevered at joint  57  via flex joint  56 . Further, compound linkage framework  46  includes flex joints  60  and  62  connected to intermediate members  64 . Platform  38  is cantilevered at joint  68  via flex joint  62 . 
     Directing attention to FIG. 3 now, a detailed section of a manual positioning and locking mechanism for pressure surface  14  is shown. Height adjustment mechanism  72  is a commercially available component such as one manufactured by Milsco or equivalent. Mechanism  72  enables pressure bearing surface  14  to be raised or lowered by the user to various positions along the upper end section of joint  18 . The mechanism enables height adjustment of pressure surface  14  to fit the user&#39;s specific physiological and lumbar configurations. Particularly, as pressure surfaces  14  and  15  articulate to assume a substantially vertical position, the relative adjustment and positioning of these surfaces become critical in providing proper support as selected parts of the body such as the dorsal, gluteal and lumbosacral regions. In this regard, mechanism  72  is integrated to enable an independent and coordinated adjustment of pressure surface  14 . 
     Referring now to FIG. 4, reinforcing structural frame  74  is shown. Structural frame  74  includes a plurality of parallel bars  75  with aft member  76  and fore member  78 . Structural frame  74  is secured to aft member  78 . Specifically, cap link  80  is rotatably secured to the top end of pedestal  20 . Cap link  80  is preferably an extruded substantially hollow cylindrical stub having a first open end and a second closed end. The top end of pedestal  20  is rotatably secured to the open end of cap link  80 . At the closed end of cap link  80 , a plurality of attachment brackets  81  are distally disposed thereon and provide a hinge connection and support to parallel bars  75 . 
     FIGS. 5 and 6 show in more detail the connection between cap link  80  and structural frame  74 . Specifically, FIG. 6 depicts one of the many significant and inventive features of the present invention. Pressure surface  15  and joint  18  are rotated through about a 90° displacement to create a near vertical orientation thereof. More specifically, whereas prior to rotation, structural frame  74  and joint  18  are substantially perpendicular to each other, after the 90° translation, they are transposed into a substantially co-planar relation. As described hereinbelow, this coordinated and dynamic orientation of structural frame  74  and joint  18  provides various ergonomically desirable positions of pressure surfaces  14  and  15  such that a user is enabled to progressively change postures from sitting to lean/stand positions. The mechanism for the rotation is preferably a position with pneumatic, hydraulic, electric or equivalent drive. For example, air cylinder  82  is shown bearing against fixed block  84 . Block  84  is pivotably connected to structural frame  74 . Cylinder  82  is linked to block  84  and when the piston is extended, structural frame  74  is rotated to the full extension of the piston. Preferably, structural frame  74  is rotated through 90° to assume a substantially vertical orientation. 
     Directing attention to FIG. 7, one of the many significant features of the present invention is shown. Specifically, parallel bars  75  and bar linkage  86  provide an articulating structural linkage which enables to maintain joint  18  perpendicular to the horizontal plane at all times. FIG. 7 shows the near side of 2-bar connection to joint  18 . A second set of symmetric 2-bar connection on the far side of joint  18  forms a 4-bar linkage. Each 2-bar linkage is connected to brackets  81 . Accordingly, when structural frame  74  translates from a horizontal to a substantially vertical position, joint  18  is elevated through the radius of rotation while maintaining its original vertical orientation relative to stabilizers  22  and connector arm  23 . This arrangement enables pressure surface  14  to maintain a vertical orientation at all times. Further, FIG. 7 shows cylinder  88  encased in pedestal  20 . Cylinder  88  is implemented to move or adjust structural frame  74  up or down. Both cylinders  82  and  88  are actuated by triggers  48  each embedded under articulating arm  16 . For example, right trigger  48  may be used to actuate cylinder  82  and left trigger  48  may be used to activate cylinder  88 . Exemplary control line  90  is shown connecting trigger  48  to cylinder  82 . Similarly control line  92  is partially shown extending from cylinder  88  to the other trigger  48  (not shown). Each side support  16  is secured to each parallel bar  75 . As discussed hereinbelow, side support  16  includes a geometric loop with various features adapted for articulation and enhancement of ergonomic positioning of the user. 
     FIG. 8 depicts a detailed structure of the two side supports  16  and control line  90  embedded therein. The shape of side support  16  is an ellipsoidal loop with one end narrower than the other and further having one side bulging outward and the opposite side depressed inward. Trigger  48   a ,  48   b  is secured on the inner surface of the narrower side proximate to the depressed region. Trigger  48   a ,  48   b  is set to be tactile and is accessible to a person resting the palm of the hand on the top surface of the depressed region. Further, the depressed region promotes sure-grip and control by users especially during the articulation of side support  16  which rotates in conjunction with structural frame  74 . Member  94  provides rigidity to the outer elastic member  96 . Member  94  may be made of structural grade steel, aluminum or equivalent, whereas member  96  is preferably semi-rigid urethane, rubber, polyvinyl or equivalent. Control line  90  is connected to trigger  48   a ,  48   b  through an internal cavity  98 . Retention bracket  100  is used to pivotally secure trigger  48   a ,  48   b  such that when trigger  48   a ,  48   b  is squeezed, control line  90  is activated to thereby actuate cylinder  82  or cylinder  88 , depending upon which one of the two triggers  48   a ,  48   b  is being used. Each of triggers  48   a ,  48   b  can be activated separately or can be used simultaneously together. 
     Referring now to FIG. 9, an isometric view of the control mechanism for the work surfaces such as monitor support platform  51  and keyboard support platform  61  including lower body support mechanism are shown. Specifically, compound linkage framework  46  includes flex joints  54  and  60  secured on support column  42 . The flex joints enable several degrees of freedom/adjustment in the thri-axis primary planes. One of the many unique aspects of the arrangement includes the use of single support column  42  to fixably secure articulating flex joints  46 . This arrangement and structure enables space-volume efficiencies and provides an interference free, independent and simultaneous adjustments of support platforms  51  and  61  on which monitor support  36  and keyboard support  38  are mounted, respectively. 
     Still referring to FIG. 9, lower body support pad  26  including link member  27  are shown mounted on base structure  24 . Base structure  24  includes a generally increasing gradient from the near end to the far end. This gradient is preferably about 15°. The gradient enables the user to assume a firm foot grip on the non-skid surface of base structure  24 . In an alternative embodiment, the gradient is preferably greater than 15° to provide support for the feet and provide balance in lieu of lower body support pad  26 . Lower body support pad  26  is articulated by cylinder  102 . Button  104  activates cylinder  102  to rotate and hold in place lower body support pad  26 . As will be seen hereinbelow, connector arm  23  is a tension member and serves as a bridge between lower body support structure and articulating pressure surfaces  14  and  15 . Further, base structure  24  operates as a counter-weight and center of gravity stabilizer against articulating pressure surfaces  14  and  15 , the associated structures therewith, and the weight of the user which generates variable dynamic rotational moments about pedestal  20 . 
     FIG. 10 shows further details of link member  27  and cylinder  102 . Button  104  is connected to control line  108  and actuates cylinder  102 . Cylinder  102  rotates link member  27  and fixes it at a desired angle. Support pad  26  is secured to support pad moving bracket  106 . Support pad  26  includes resilient outer surfaces having substantially parabolic shapes. Support pad  26  serves various functions. Some of the important bio-mechanical and structural advantages of support pad  26  include its implementation to provide an adjustable fulcrum to the user&#39;s body in cooperation with articulating pressure surfaces  14  and  15 . Further, pad  26  operates as a body balancer and posture adjustment mechanism. When the user shifts from a sitting posture to a lean/stand posture, support pad  26  is implemented to bear some of the shifting weight. In this regard, support pad  26  acts as a body balancer and a point at which the user may shift the center of gravity of both the user and positioning system  10  under both dynamic and static conditions without falling or sliding out of articulating pressure surfaces  14  and  15 . Yet another cooperative structural aspect of support pad  26  includes its implementation as a transitional dynamic weight support and stabilizer. The parabolic oblong shape of support pad  26  promotes rotation at the lower leg and shin regions such that the user is enabled to rotatably transpose from one posture to another by adjusting the pressure and angular orientation of support pad  26  using operating button  104 . Support pad  26  may also be implemented as an adjustable leg rest. The user may be positioned in a normal sitting position with the leg stretched out and the posterior aspect of the legs resting on support pad  26 . 
     Referring now to FIG. 11, a detailed view of support frame  26  is shown. Particularly link  107  provides a secure link between cylinder  102 , link member  27  and structural angle  106 . Link member  27  is rotatable through approximately 75° with about 45° toward the user from the vertical and about 30° away from the user from the vertical. The user presses button  104  to actuate cylinder  102  and applies bodily pressure on support pad  26  to adjust it away from the lower legs/legs. In the alternate, button  104  is pressed to allow support pad  26  to rotate towards the user. In either case, releasing button  104  locks support pad  26  into position. 
     FIG. 12 shows the rotation, articulation, and positioning in single or combination of three-dimensional planes of platforms  36  and  38 , including the compound linkage comprising intermediate member  58  and  64  preferably formed of bar linkages. Specifically, column  42  supports a plurality of work stations preferably cantilevered therefrom. More specifically, the use of single column  42  enables the stacking of various work stations without the complication of interference and crowding which may result due to multiple supports and columns. Flex joints  54 ,  56 ,  60 , and  62  enable articulation and rotation in three dimensions. Specifically, joints  54  and  60  coupled with threaded screw  103  enable universal adaptability for adjustment in three-dimensions. Screw  103  is adjusted by link member  109  indexing up or down. This movement results in changes of the leverage of gas spring  111  and thereby enables adjustment for varying weights. For example, when the load to be supported at platform  36  or  38  is heavy, link member  109  is indexed downward to shorten the extension of intermediate members  58  and  64 , thereby reducing the length of the cantilever and increasing the capacity to carry a heavy load. Alternately, when link member  109  is indexed upwards, joints  58  and  64  extend outward, thus reducing the capacity to carry a cantilevered load at platforms  36  and  38 , as well as extending the reach of the assembly orthogonally from column  42 . The flexibility and adjustability of each of the structural components, individually and in combination, enables the assembly of FIG. 12 to be most versatile for support of work tools and work surfaces and is highly synergistic with positioning system  10 . Flex joints  54  and  56  enable full 360° rotation at column  42 . Further, flex joints  56  and  62  provide a coupling for a full 360° rotation of joints  57  and  68 , respectively. Additionally, pivots  113  cooperate with bar linkage of intermediate members  58  and  64  to be responsive to the changes in leverage of gas spring  111 . Yet another feature of the invention includes the rotatability of platform  36  and the rotatability and tiltability of platform  38 . Platform  36  is structured to support a computer screen or similar work tools. Platform  38  is well suited to carry a keyboard or similar work tools which may need to be adjusted in several orientations. One of the many unique aspects of the structure includes its lockability in any position after adjustment. Specifically, the user is enabled to configure the position of the work tools to be compliant and ergonomically congruent with positioning system  10 . More specifically, the user applied minimum manual pressure to adjust the position of support platform  36  or  38  as needed. Platforms  36  and  38  remain locked in position after adjustments have been made. Thus, the tool support platform structure of the present invention provides several degrees of freedom to orient the work tools, and is designed to be synergistic with positioning system  10  by allowing quick dynamic adjustments relative to a desired postural configuration. 
     Referring now to FIG. 13, the underlying structural assembly of positioning system  10  is shown. Preferably, the material of construction is structural grade steel, aluminum or equivalent. The frame work includes fore and aft assemblies connected by member  123 . Aft assembly comprises members  122  which are preferably welded to member  123  and extend in symmetrical angular relations therefrom. The fore assembly includes rectangular structures  124  and  126  secured to member  123 . 
     FIG. 14 is a representation of the ergonomic multi-posture range of the present invention. In the seated position, the user preferably engages pressure surfaces  14  and  15  and support pad  26 . The user then activates trigger  48  and button  104  to shift to a breathe-easy position. As pressure surfaces  14  and  15  rotate, the angle between the torso and the lower part of the body increases and support pad  26  is actuated forward and rotated to prevent the user from sliding off pressure surface  15 . As the user continues to rotate with pressure surfaces  14  and  15 , it is preferable to adjust the position of support pad  26  and lock it in place so that the user can negotiably maintain contact with pressure bearing surfaces  14  and  15  and keep the body in balance. The user is also supported by foot platform  24  which is padded, and is surfaced with friction material to prevent slipping. The angle of foot platform  24  can be adjusted to facilitate comfort of the user. 
     FIG. 15 is a representative depiction of positioning system  10  integrated with computer work station  12 . Monitor or screen  130  is placed within the visual and ergonomic ranges of the operator. Keyboard  132  is set for easy access to the hands and CPU  134  is placed within the ergonomic range of the operator while clearing any possible interference with positioning system  10 , especially during articulation, thus allowing timely postural adjustments by the user. 
     FIG. 16 is another embodiment of the present invention. Positioning system  10  is shown with work station  136  not attached or integrated with positioning system  10 . In order to ensure stability and safety, base structure  24  is filled with stabilizing weights such as water, sand or equivalent. The embodiment shows a typical work station  136 , such as an assembly line, in which a task is performed in a substantially sitting position. The implementation of positioning system  10  advantageously enables the worker to shift through various ergonomic postures without interrupting the task at hand. As discussed hereinabove, the present invention enables the worker to benefit from active sitting through timely movements of the muscles and the body, and from proactive positioning which forms the body into medically advantageous postures. Specifically, three basic adjustment actuators which include (two) triggers  48  and button  104  are used to easily transform the user from a sitting to lean/stand posture. 
     FIG. 17 is yet another embodiment of the present invention. Positioning system  10  is shown without support pad  26 . In this embodiment, base structure  24  includes a gradient of about 25° or higher to enable balance and support of the user&#39;s weight. This embodiment is alternately advantageous in operations where support pad  26  may interfere with the work station or may be undesirable for other reasons. The omission of support pad  26  is compensated for by the increased inclination/gradient of base structure  24 . 
     FIG. 18 shows a reference holder/working file display  47 . Holder  47  includes support base  142  with telescoping column  144  supported at one end thereon. The other end of telescoping column  144  supports a substantially L-shaped structure  146  which includes a mortised section at the leg having edge structure  148  about the perimeter of the cutout. Files and folders are suspended through the cutout and supported on edge structure  148 . 
     Directing attention to FIG. 19, a detail of the mouse cage structure  39  is shown. Specifically, mouse  150  is supported on pad  152 . Retaining structure  154  forms a partial fence to secure mouse  150  in place. This is particularly important when platform  38  rotates/tilts away from the user to provide an ergonomically beneficial positioning of the user in the lean/stand posture. The aperture  153  defined in the structure  154  compressively engages the wire  149  of the mouse  150  to prevent the mouse  150  from sliding. Other means of preventing such sliding may include a clip on the wire  149  proximate the aperture  153  or an upright peg  151  around which the wire  149  can be wound. Mouse cage  39  allows mouse  150  to be accessible and available regardless of the tilt angle of platform  38 . 
     FIG. 20 is a detailed drawing showing vibration dampener  155  secured on top of platform  36 . Vibration dampener  155  may be constructed from 4# EVA black foam or equivalent. Dampener  155  advantageously reduces/eliminates the transfer of vibration and undulatory movement from the joints and links. 
     Accordingly, the present invention utilizes structures which cooperate with a user&#39;s body to form a dynamic bio-mechanical system to promote active sitting and proactive positioning within a range of medically preferred healthy human postures. Positioning system  10  is typically integrated with work station  12  although, as is shown in exemplary embodiment of FIG. 16, it can be independently used at various seated task operations. Similarly, some components of the present invention may be omitted to adapt to specialized applications. Further, various components may be modified to adapt to specific work environments. 
     An alternative embodiment  200  of work station  12  of the present invention is depicted in FIGS. 21-24. As shown, embodiment  200  of work station  12  generally comprises a support assembly  204 , a lift assembly  206 , and a work surface assembly  208 . 
     Support assembly  204  preferably comprises a pair of support legs  220 , which are preferably of a tubular configuration. Each support leg  220  is unitarily and/or fixedly secured to a stabilizing support  222 . Each stabilizing support  222  includes an elongated top portion  224  that is preferably semi-circular in configuration and a pair of side walls  226  that extend substantially perpendicularly down from each side of top portion  224 . Side walls  226  are preferably triangular in shape, the triangular shape adding structural rigidity to top portion  224 , having the base of the triangle secured to leg support  220  and the tip of the triangle reaching approximately half the length of top portion  224 . Each stabilizing support  222  further includes a rounded nose section  228  that preferably houses a height adjustment device  230 . Height adjustment device  230  preferably comprises a foot whose height may be mechanically adjusted, e.g., a threaded connection to adjust height, spring-adjusted height, hole and locking pin adjusted height, etc. Alternatively, nose section  228  may house a caster, preferably lockable in nature, allowing for easy positioning of work station  12 . 
     Lift assembly  206  generally comprises a support assembly  240  and a pivoting assembly  242 . Support assembly  240  preferably includes a back portion  244 , a wrap-around portion  246 , an exterior side portion  248 , and an interior side portion  250 . Back portion  244  extends laterally from first leg support  220  to second leg support  220  and is preferably secured thereto. Further, back portion  244  is preferably unitary with wrap around portion  246 ; the connection point of back portion  244  to wrap-around portion  246  indicated by arc  252 . Wrap-around portion  246  preferably wraps the circumference of each leg support  220  and, as such, is slidably positioned over each leg portion during assembly of work station  12 . Once positioned, wrap-around portion  246  is preferably secured in place. Exterior side portion  248  is substantially equivalent in height to the combined height of back portion  244  and wrap-around portion  246 , and is preferably secured tangentially thereto at the exterior. Exterior side portion  248  is defined by an upper side portion  254  and a lower side portion  256 . Lower side portion  256  is substantially equivalent in shape and in placement along leg support  220 , as interior side portion  250 . Interior side portion  250  is substantially equivalent in height to wrap-around portion  246  and is preferably secured tangentially thereto at the interior. 
     Pivoting assembly  242  of lift assembly  206  includes a pair of lift cylinders  260 , a pair of main lift arms  262 , a pair of follower arms  264 , and a slide adjustment assembly  266 . Each lift cylinder  260  is defined by a first end  268  and a second end  270  (see FIG.  23 ). First end  268  is maintained in a fixed position via a bracket  272  that is positioned between lower side portion  256  of exterior side portion  248  and interior side portion  250 , and that is secured to interior side portion  250 . Second end  270  is maintained in a fixed position by virtue of a bracket  274  secured to the underside of a support bar  276 , which forms a part of slide adjustment assembly  266 . Main lift arms  262  are pivotally secured between upper side portion  254  of exterior side portion  248  and legs  275  of a table support bracket  277 . Each follower arm  264  is positioned below a respective main lift arm  262  and is substantially parallel thereto. Like each main lift arm  262 , each follower arm  264  is preferably pivotally secured between upper side portion  254  of exterior side portion  248  and legs  275  of table support bracket  277 . 
     Slide adjustment assembly  266  includes support bar  276 , which is fixedly secured to second end  270  of the two lift cylinders  260 , and a slide wrap  278 . As indicated above, support bar  276  is preferably fixedly secured to second end  270  of lift cylinder  260  and is additionally preferably secured at its sides to each main lift arm  262 . Slide wrap  278 , to which may be attached an additional table surface  284  (shown in FIG.  21 ), is preferably unitary in configuration including a top portion  280 , a pair of side portions  282 , and a pair of bottom portions  286  (FIG.  23 ). Bottom portions  286  wrap to the underside of support bar  276  and include recesses  288  to accommodate the position of lift cylinders  260  allowing slide wrap  278  to be slid back and forth atop support bar  276 . Table surface  284  may be fixedly secured or alternatively, pivotally secured to slide wrap  278  to provide for angular adjustment, i.e., tilting of table surface  284 . 
     Work surface assembly  208  generally includes a rigid work surface  290  and table support bracket  277 . Work surface  290  may be of any desirable shape but preferably includes a recessed portion  292  allowing work surface  290  to surround a user and angled corner portions  294 . Work surface  290  is preferably provided with an aperture  296 , which may be used as a handle to aid in lifting and lowering work surface  290  in conjunction with lift cylinders  260  or alternatively, may be used as an opening through which computer cables, power cords, etc., may be inserted. 
     Alternatively, rigid work surface  290  may be replaced with a work surface that additionally incorporates an articulating keyboard surface/work surface  297 , see FIG. 24 like those available from Ergonomic Concepts of Raleigh, N.C. With the addition of an articulating keyboard surface/work surface  297 , slide adjustment assembly  266  may be replaced with a simple rigid member fixedly secured between main lift arms  262  or any semblance thereof. However, as with table surface  284 , keyboard surface  297  is preferably provided with the ability of angular adjustment, i.e., tilting by means of shiftable connector  298  affixed to the underside of work surfaces  290 ,  297 . 
     FIGS. 25-28 depict an alternative embodiment  299  of body positioning system  10 , the location of which may be established independently of the location of the work station  200 ,  12 . As shown, body positioning system  299 ,  10  generally includes a base structure  300 , a lower leg-support assembly  302 , and an adjustable chair structure  304 . 
     Base structure  300  includes a central member  310  that is supported between a T-end portion  312  and a Y-end portion  314 . Central member  310  is preferably a telescoping member having inner portion  316  that is slidably adjustable within an outer portion  318  of member  310 . The telescoping nature of central member  310  allows each user to determine their preferred distance of chair structure  304  to lower leg-support assembly  302 . Once at a preferred distance, outer portion  318  is preferably secured to inner portion  316  to prevent undesirable movement of central member  310 . Outer portion  318  of member  310  preferably includes an aperture  320  to allow for positioning of a depressible foot pedal  322  and an elongate aperture  324  configured to allow for movement of lower leg-support assembly  302 . 
     T-end portion  312  of base structure  300  includes an angled face plate  330  for supporting and positioning a user&#39;s feet. Angled face plate  330  includes a central recess  332  allowing face plate  330  to be positioned about central member  310  and lower leg-support assembly  302 . Face plate  330  is supported by a box structure  334  having a pair of side panels  336 , a rear panel  338 , and a lower panel  340 . A pair of wheels  342  are secured to and operate to support T-end portion  312 . 
     Y-end portion  314  of base structure  300  includes a pair of elongated arms  344  that extend angularly from inner portion  316  of base structure  300 . Each elongated arm  344  includes a downward extending nose portion  346  to which is secured a swiveling caster  348 . Y-end portion  314  further provides a central shaft  350  to which is secured to adjustable chair structure  304 . 
     Lower leg-support assembly  302  includes a central support member  360  and lateral lower leg support  362 . Central support member  360  includes a front plate  364  and a pair of side plates  366 . The rear of central support member  360  remains open allowing central support member  360  to house, at least in part, air cylinder  368 . Air cylinder  368  (see FIG. 28) is pivotally connected at one end to central support member  360  and at its other end to box structure  334  of T-end portion  312 . The pivotal connection of air cylinder  368  allows lower leg-support assembly  302  to be moved forward and back as desired using foot pedal  322 , which is operably connected to air cylinder  368 . Specifically, depressing foot pedal  322  operates air cylinder  368  such that lower leg-support assembly  302  is moved towards chair structure  304 . Releasing foot pedal  322  operates to stop movement of lower leg-support assembly  302  and locking lower leg support  302 . Lower leg-support assembly  302  is moved forward by manually pushing assembly  302  forward towards T-end portion  312  while operating foot pedal  322 . 
     Lateral lower leg support  362  is generally semi-circular in shape having a pair of side plates  370 , a planar front plate  372 , a rounded rear portion  374 , and an open lower portion  376  that allows for insertion of the upper portion of central support member  360 . Lateral lower leg support  362  is preferably pivotally secured to central support member  360  allowing the user to angularly adjust lateral lower leg support  362 . A rounded cushion  378  preferably covers front plate  372  and a portion of rounded rear portion  374 , as shown. 
     Adjustable chair structure  304  is substantially identical to the chair structure of earlier-described body positioning systems  10 , incorporating their components and manner of operation, however, adjustable chair structure  304  is supported by central shaft  350  of base structure  300  rather than by pedestal  20  of the earlier embodiments. As such, adjustable chair structure  304  in combination with base structure  300  and lower leg-support assembly  302  cooperate as body positioning system  10  to alternate between the “seated”, “breathe-easy”, and “lean/stand” positions of FIG.  14 . 
     FIG. 29 depicts embodiment  200  of work station  12  and embodiment  299  of body positioning system  10  in a seated working position where body positioning system  10  is positionable relative the position of work station  12 . FIG. 30 depicts embodiment  200  of work station  12  and embodiment  299  of body positioning system  10  in a lifted working position, e.g., the “breathe-easy” or “lean/stand” position. 
     A further alternate embodiment of the body positioning system  10  and computer work station  12  is depicted in FIGS. 31-43, with the computer work station  12  being depicted in FIGS. 31-35, and the body positioning system  10  being depicted FIGS. 36-43. Like numbers in these figures denote like components with respect to the figures discussed above. 
     Referring to FIGS. 31-35, the work station  12  includes a keyboard surface  297  supported by a work surface  290 , which is in turn supported by a frame  370 . The frame  370  has a pair of spaced apart tubular legs  371 . The tubular legs  371  are angled inward with respect to one another such that the distance between the front ends  371   a  is significantly less than the distance between the rear ends  371   b . Such angularity assists in defining a relatively wide space to permit the body positioning system  10  to be disposed relatively close to the work station  12 . Feet  372  for engaging the surface supporting the work station  12  are disposed proximate each of the front ends  371   a  and rear ends  371   b.    
     A pair of upright stanchions  373  are fixedly coupled to the tubular legs  371  approximately ⅓ of the distance from the respective front  371   a  to the respective rear  371   b . Each of the stanchions  373  is preferably formed of tubular metal construction and is fixedly coupled to the respective tubular leg  371 . A pair of cross-members  374   a ,  374   b  extend between the stanchions  373  and are fixedly coupled thereto. Further, a generally rectangular support panel  375  is fixedly coupled to each of the stanchions  373  and assists in providing structural rigidity to the frame  370 . The support panel  375  is preferably fixedly coupled to the cross-members  374   a ,  374   b . In addition to the support panel  375 , a decorative panel  376  may be affixed to the front surface of the stanchions  373 . 
     A pair of generally rearwardly directed work surface support brackets  377  are disposed proximate to the top margin of each of the stanchions  373 . Each of the work surface support brackets  377  is fixedly coupled to the respective stanchion  373  as by welding, suitable fasteners, or the like. The work surface support brackets  377  have a pair of pivot points  378   a ,  378   b  that are spaced apart and disposed in a generally vertical relationship. 
     The work surface member  290  and keyboard surface member  297  taken together comprise a working surface assembly  379 . The work surface member  290  has a generally upwardly directed planar margin comprising a work surface  380 . A suspension assembly  381  supports the planar work surface  380 . 
     The suspension assembly  381  includes a pair of generally mirror image, depending brackets  382  that depend from the work surface member  290  proximate the side margins thereof. Referring to FIG. 35, the two depending brackets  382  are coupled by a cross-member  384 . The cross-member  384  is fixedly coupled to the underside surface  383  of the work surface member  290 . Such coupling may be in the form of screws or other suitable fasteners. A pair of parallelogram support links  387   a ,  387   b  are coupled to each of the depending brackets  382  at pivot points  388   a ,  388   b , respectively. An underlying tray  387  extends between the two parallelogram support links  387   b . An actuator depression  386  is formed proximate to the center portion of the tray  385 . The actuator depression  386  accommodates the compressed gas spring assembly  456 , as will be described in detail below. 
     As depicted in FIGS. 33-35, a suspension  400  operably couples the keyboard surface  297  to the work surface  290 . The suspension  400  has three major subcomponents: work surface coupling assembly  402 , keyboard surface coupling assembly  404 , and hinge assembly  406 . 
     The work surface coupling assembly  402  includes a support flange  408 . As depicted in FIG. 33, the support flange  408  has both a left and a right side that are substantially mirror images of one another. Accordingly, the description below applies to both sides of the support flange  408 . The support flange  408  further includes two orthogonally disposed flanges, the first of which is a generally horizontal flange  410  and the second is a depending, generally vertical flange  414 . The two horizontal flanges  410  are fixedly coupled to the underside of the work surface  290  by fasteners  412  which may be screws or other suitable fasteners. It should be noted that the horizontal flange  410  and the vertical flange  414  may be formed of an integral unitary piece, preferably formed of metal. Alternatively, the horizontal flange  410  may be a plate that fits flush with the underside of the work surface  290 . The depending vertical flange  414  may be formed of a single U-shaped piece of metal that has the two depending vertical flanges  414  coupled by a generally planar cross-piece and is fixedly coupled to the plate forming the horizontal flange  410 . 
     Each of depending vertical flanges  414  has a pair of spaced apart hinge points  416 ,  418 . The hinge points  416 ,  418  have inwardly directed hinges. The hinge of the hinge point  416  is rotatably coupled to an outer upper link  422  and a hinge of the hinge point  418  is rotatably coupled to an inner lower link  420 . 
     The inner lower link  420  and the outer upper link  422  are generally disposed such that they define a shiftable parallelogram and remain generally parallel throughout their range of motion. Accordingly, the planar orientation of the keyboard surface  297  with respect to the work surface  290  remains constant throughout the range of motion of the lower link  420  and the upper link  422 . 
     The inner lower link  420  has a semi-circular groove  424  defined therein. The inner lower link  420  is rotatably coupled to the keyboard surface coupling assembly  404  at a hinge point  426 . Semi-circular groove  424  is in registry with a bore (not shown) defined in the distal end of the inner lower link  420 . The inner lower link  420  is rotatably coupled to the keyboard surface coupling assembly  404  by a hinge pin  428 . 
     The keyboard surface coupling assembly  404  includes a support flange  430 . Like the support flange  408  of the work surface coupling assembly  402 , the support flange  430  has a pair mirror-image horizontal flanges  432  and a pair of mirror-image depending vertical flanges  436 . The horizontal flanges  432  are fixedly coupled to the underside of the keyboard surface  297  by fasteners  434  which may be screws or other suitable fasteners. The depending vertical flange  436  has a semi-circular groove  438  defined therein. The semi-circular groove  438  has a generally smaller length dimension than the semi-circular groove  424  and has a generally similar radius acting about a common point of rotation. The semi-circular groove  438  is preferably disposed in registry with at least a portion of the semi-circular groove  424 . 
     The third sub-component of suspension  400  is the hinge assembly  406 . The hinge assembly  406  includes a hinge pin member  440 . The hinge pin member  440  includes the aforementioned hinge pin  428 . The hinge pin  428  acts to rotatably couple three separate components; the inner lower link  420  and the outer upper link  422  of the work surface coupling assembly  402  and the support flange  430  of the keyboard surface coupling assembly  404 . Accordingly, the hinge pin  428  passes through the semi-circular groove  424 , the bore (not show) defined in the distal end of the inner lower link  420 , and the semi-circular groove  438  defined in the vertical flanges  436  of the keyboard surface coupling assembly  404 . A coil spring  442  is disposed concentric with a portion of the hinge pin  428 . Under compression, the spring  442  acts to immobilize and lock in place all the aforementioned components that are rotatably coupled to the hinge pine  428 . 
     The spring  442  may be selectively put into compression for locking the aforementioned components supported by the hinge pin  428  and relaxed for permitting relative motion between such components. The spring  442  is actuated by an actuator member  444 . The actuator member  444  includes an actuator handle  446  that is operably coupled to a cam actuator  448 . Such coupling may be effected by an adjustable L-shaped rod  449  having a first end coupled to the actuator handle and a second end coupled to the cam actuator  448 . In the depiction of FIG. 33, the actuator handle  446  is in the engaged disposition wherein the cam actuator  448  is compressibly engaged with the spring  442 . Rotating the actuator handle  446  leftward to the disengaged disposition causes the L-shaped rod  449  to translate rearward, thereby rotating the cam actuator  448  about a pivot point. The cam actuator  448  rotatably translates relative to the spring  442  such that the compressive force exerted by the cam actuator  448  on the spring  442  is relaxed. The disengaged disposition is an over-center situation and the spring  442  stays relaxed until the operator returns the actuator handle  446  to the engaged disposition. 
     In operation, the unique hinged relationship of the suspension  400  permits the keyboard surface  297  to move relative to the work surface  290  while maintaining the angular relationship of the keyboard surface  297  to the work surface  290 . By this is meant that if the keyboard surface  297  is in a leveled relationship with the work surface  290 , the keyboard surface  297  may be raised or lowered relative to the work surface  290 , but the level relationship is maintained even though the keyboard surface  297  is in a different, parallel plane relative to the work surface  290 . This motion is indicated by arrow A of FIG. 33 a . Additionally, the keyboard surface  297  is tiltable with respect to the work surface  290 . This is indicated by the arrow B of FIG. 33 a.    
     To achieve a level displacement of the keyboard surface  297  relative to the work surface  290 , as indicated by the arrow A, the actuator handle  446  is moved leftward from the disposition depicted in FIG. 33 to a disengaged disposition. In such disposition, the cam actuator  448  has been rotated out of compressive engagement with the spring  442  and the spring  442  is not exerting any appreciable locking force on the above-noted components that are supported by the hinge pin  428 . The keyboard surface  297  may be pushed downward or raised upward by exerting pressure thereon. Such pressure results in motion of the inner lower link  420  and the outer upper link  422  that maintains a parallel relationship between the links  420 ,  422 . 
     In order to maintain such parallel relationship, the hinge pin  428  translates within the semi-circular groove  424 . In order to achieve a tilting relationship of the keyboard surface  297  to the work surface  290 , a rotational force may be imposed on the keyboard surface  297 . Such rotational force causes the tilting of the keyboard surface  297  and motion of the semi-circular groove  438  relative to the hinge pin  428 . Once the desired positional relationship of the keyboard surface  297  relative to the work surface  290  is achieved, the actuator handle  446  is again moved rightward to the engaged disposition, as depicted in FIG.  33 . 
     A further actuator is disposed on the underside of the keyboard surface  297 . This actuator is the work surface actuator assembly  450 . The work surface actuator assembly  450  is fixedly coupled to the underside surface of the keyboard surface  297 . The work surface actuator assembly  450  includes an actuator handle  452  that is operably coupled to the proximal end of the concentric coaxial cable  454 . 
     The concentric coaxial cable  454  is operably coupled to a compressed gas spring assembly  456  for selective control thereof. The compressed gas spring assembly  456  is best depicted in FIGS. 34 and 34 a . The compressed gas spring assembly  456  is operably coupled by a first support bracket  458  to the support panel  375  and the cross-member  374   b . The compressed gas spring assembly  456  is further operably coupled by a second support bracket  460  that is fixedly coupled to the cross-member  384  of the work surface  379 . As such, the compressed gas spring assembly  456  controls the spatial relationship of the work surface assembly  379  to the frame  370 . As will be seen, this spatial relationship is controlled by an operator primarily through actuation of the work surface actuator assembly  450  followed by application of a force to the work surface assembly  379 . 
     The compressed gas spring assembly  456  includes a primary gas spring  462 . The primary gas spring  462  is connected at a first end to an actuator body  476  as is described in greater detail below. The primary gas spring  462  is connected a second end to the second support bracket  460  by means of a connector  466  having a bore (not shown) defined therein through which a connector pin is disposed. 
     In order to assist in the support of relatively heavy objects borne on the work surface  290 , a plurality of secondary gas springs  464  may be included that extend from the support bracket  458  to the second support bracket  460 . Such secondary gas springs  464  exert a generally upward bias on the work surface  290  in order to minimize the force required of an operator to reposition the work surface  290 . A single such secondary gas spring  464  is depicted in FIG.  34 . The secondary gas spring  464  includes a cylinder  470  and a concentric slidable piston rod  472 . The secondary gas spring  464  is coupled at the first support bracket  458  and the second support bracket  460  by ball joints  474 . Ball joints  474  are included for the installation of additional secondary gas springs  464 , as needed. Instead of adding secondary gas springs  464 , the point of attachment of the primary gas spring  462  can be varied such as depicted in FIG. 12 where a threaded screw  103  adjusts the link member  109 . 
     A threaded screw may be used to similarly to adjust a pivoting link member as well, thereby adjusting the leverage point. Such a device is depicted in FIG. 34 b . The secondary gas spring  464  is coupled at a first end  802  to the bracket  460  and at a second end  804  to a sleeve  806 . The sleeve  806  has a threaded bore  808  defined therethrough. A threaded bolt  810  is rotatably engaged in the bore  808 . The threaded bolt  810  is rotatably borne in bushings  812 . There is no threaded engagement with the bushings  812 , such that rotation of the bolt  810  does not result in translation of the bolt  810  relative to the bracket  458 . A manually actuatable handle  814  is available at the exposed end of the bolt  810 . Rotation of the bolt  810  acts to move the sleeve  806  along the longitudinal axis of the bolt  810 . Such movement adjusts the leverage of the secondary gas spring  464  acting on the work surface  290 . Such variance in the force exerted by the secondary gas spring  464  permits readily supporting both relatively light and relatively heavy objects on the work surface  290 . 
     A fixed link  818  may also be used with this embodiment. The link  818  is pivotally coupled at a proximal end by pivot point  820  to the frame  370 . The distal end of the link  818  is pivotally coupled to the work surface  290  at a pivot point. The bracket  460  may be fixedly coupled to the link  818  proximate the distal end thereof. 
     As indicated above, the primary gas spring  462  is coupled at a first end to an actuator body  476 , as best depicted in FIG. 34 a . The actuator body  476  is coupled to the first support bracket  458  by a pin  477  that passes through bores (not shown) defined in both the actuator body  476  and the first support bracket  458 , which bores are brought into registry. 
     A coupler  478  fixedly couples the sheath  479  of the concentric cable  454  to the actuator body  476 . A cable  480  that is concentric with the sheath  479  is free to translate relative to the sheath  479  responsive to actuation of the actuator handle  452 . The cable  480  is coupled to a lever  484  by a suitable connector  482 . The connector  482  may be a sphere of metal formed on the end of the cable  480  and disposed in a bore defined in the lever  484 . 
     The lever  484  is preferably an elongate metal bar. The lever  484  is pivoted about a fulcrum  486  supported on a pin  487  that passes through a bore (not shown) defined on the lever  484  and bores defined in the walls of the actuator body  476 . A connector  488  is included at the distal end of the lever  484  for connecting the lever  484  to the primary gas spring  462 . 
     The primary gas spring  462  has three concentric components. The first such component is the cylinder  490 . The second component is a translatable piston  492  disposed within the cylinder  490 . The third component is a locking rod  494  disposed within the piston  492 . A first end of the locking rod  494  is coupled to the connector  488 . The primary gas spring  462  (and any secondary gas springs  464 ) generally bias the work surface assembly  379  upward relative to the frame  370  to the elevated spatial relationship generally as depicted in FIG. 32 as distinct from the depressed spatial relationship as depicted in FIG.  31 . 
     In operation, the primary gas spring  462  is locked at a specific length, the piston  492  being locked relative to the cylinder  490  when the locking rod  494  is disposed to the left as depicted in FIG. 34 a . To shift the work surface assembly  379  relative to the frame  370 , such as to move the work surface  379  from the disposition depicted in FIG. 31 to the disposition depicted in FIG. 32, the operator actuates the actuator handle  452 . Referring to FIG. 34 a , such actuation causes the cable  480  to retreat within the sheath  479 , resulting in counter clockwise rotation of the lever  484  as indicated by the arrow C. Such rotation results in an unlocking withdrawal of the locking rod  494  from the piston  492 . Such withdrawal is indicated by rightward motion as depicted by arrow D. When the primary gas spring  462  is unlocked, a relatively low level of upward or downward pressure exerted by an operator on the keyboard surface  297  will result in translation of the work surface assembly  379  either upward or downward relative to the frame  370 , as desired. When the work surface assembly  379  is in the desired spatial position relative to the frame  370 , the actuator handle  452  was released by the operator. The locking rod  494  is biased in the inward locked disposition and accordingly the locking rod  494  retreats leftward within the piston  492  into a locked engagement. Once locked, the work surface assembly  379  is held in a fixed spatial relationship relative to the frame  370 . 
     We turn now from the description of the work station  12  to the description of the positioning system  10 . The positioning system  10  is depicted in FIGS. 36-44. It is important to note that cooperative body support is provided at all surfaces indicated by arrows T-X, as depicted in FIG.  39 . As with the previous embodiments of the positioning system  10 , the positioning system  10  of the present embodiment includes a chair assembly  13  having a chair  13   a , the chair  13   a  having a back or pressure bearing surface  14  connected by joint  18  to a seat or pressure bearing surface  15 . A pair of side supports  16  are fixedly coupled to the seat  15 . One support  12  is disposed at either side of the seat  15 . 
     The back  14  and the seat  15  are supported on an upward directed pedestal  20 . The pedestal  20  is joined to two generally orthogonally disposed and outwardly directed stabilizers  22 . A connector arm  23  lies in substantially the same plane as the stabilizers  22  and provides for the connection to a base member  24 . Each of the two stabilizers  22  has a floor engaging caster thereon for providing ready mobility to the positioning system  10 . 
     As depicted in FIG. 37, a height adjustment mechanism  72  is included to adjust the height relationship of the back  14  relative to the joint  18 . In an embodiment, a plurality of ascending notches  500  are defined in the rear margin of the upper extension  511  of the joint  18 . Each of the notches  500  defines a step  501 . It should be noted that the lowest of the notches  500  includes a more pronounced lower step  502 . 
     The back  14  includes a biased pawl  504 . The pawl  504  is rotatable about a pivot point  506 . A spring  508  biases the engaging face  510  of the pawl  504  into engagement with the steps  501 ,  502 . It should be noted that the pawl  504  could as well be attached to the joint  18  and the notches  500  defined in the back  14 . 
     To adjust the height of the back  14  relative to the joint  18 , an operator simply grasps the lower portion of the back  14  and raises it slowly. The pawl  504  is heard sequentially engaging each of the ascending notches  500 . When the desired height is reached, the operator simply stops raising the back  14  and the back  14  stays at the desired height as maintained by the pawl  504  engaged in the selected notch  500 . 
     To lower the back  14  relative to the joint  18 , the back  14  is raised all the way up. When the uppermost notch  500  is bypassed by the pawl  504 , the pawl  504  is rotated by the bias of the spring  508  such that it no longer engages the steps  501 ,  502 . The back  14  is then free to descend relative to the joint  18 . When the pawl  504  engages the extended lower step  502  of the bottom notch  500  the pawl  504  is again rotated into engagement with the first notch  500 . This is the lowest disposition of the back  14  relative to the joint  18 . The back  14  may then be raised again to permit the pawl  504  to engage a selected notch  500  at a desired height. The range of motion of the back  14  relative to the joint  18  is approximately 6 inches from the disposition where the pawl  504  is engaged with the lowest notch  500  to the disposition in which the pawl  504  is engaged with the highest notch  500 . 
     The joint  18  includes the aforementioned upper extension  511  and a coupling end  512 . The coupling end  512  of the joint  18  is depicted in FIGS. 36,  38 , and  39 . The coupling end  512  has two generally spaced apart side margins  513  joined by a back margin  515  to define a channel within the coupling end  512 . A pair of pivot points  514 ,  516  are defined in each of the side margins  513 . When viewed from the side, pivot points  514 ,  516  defined in each of the side margins  513  are in registry. 
     A structural frame  74  is disposed beneath the seat  15  and is operably connected to the joint  18  to support the back  14  and the seat  15  of the positioning system  10 . The structural frame  74  includes a channel section  518  having spaced apart generally parallel side margins  518   a , connected by a transverse bottom margin  518   b . The two side margins  518   a  and the bottom margin  518   b  define the channel within the channel section  518 . 
     A flange support  520  extends outward from the upper margin of each of the side margins  518   a  and is disposed substantially orthogonal with respect to the side margins  518   a . The flange support  520  substantially underlies the seat  15  and provides the support for both the seat  15  and the side supports  16 . Suitable connectors  522 , which may be cap screws or screws connect the seat  15  to the flange support  520 . Likewise, similar type connectors  524  connect the lower margin of the side supports  16  to the flange support  520 . 
     A pair of parallel arms  526 , best depicted in phantom in FIG. 38, reside within the channel defined within the channel section  518 . The coupling end  512  of the joint  18  is pivotally coupled at pivot point  514  to the channel section  518  and is further pivotally coupled at pivot point  516  to a first end of each of the parallel arms  526 . The channel section  518  is connected at a pivot point  519  to each of the spaced apart arms  577  of the pedestal assembly  576 . Further, each of the parallel arms  526  is connected at pivot point  528  to a respective arm  577  of the pedestal assembly  576 . The aforementioned connecting arrangement functions to keep the joint  18  oriented spatially in the same position without regard to whether the seat  15  is disposed at a great incline such as depicted in FIGS. 36 and 39, or at a lesser incline as depicted in FIG.  38 . The effect of this is that the back  14  has a substantially fixed orientation in space and simply moves up and down with the same incline in space as the incline of the seat  15  is changed. 
     Referring to FIG. 39, an auxiliary gas spring  530 , depicted in phantom, is disposed between the two parallel arms  526 . The auxiliary gas spring  530  is connected at a first end at pivot point  532  to connector  534 . Connector  534 , in turn, is fixedly coupled to the channel section  518  (see FIG.  40 ). The auxiliary gas spring  530  is connected at a second end via a pin connector  538  to both of the parallel arms  526 . In such disposition, the auxiliary gas spring  530  exerts a bias that tends to tilt the seat  15  into the more tilted disposition as depicted in FIG. 39 as compared to the more level disposition as depicted in FIG.  38 . 
     The incline of the seat  15  is primarily effected by the primary gas cylinder  540 . The primary gas cylinder  540  is depicted in FIGS. 36,  38 , and  39  and in detail in the sectional representations of FIGS. 40 and 41. The primary gas cylinder  540  is connected at a first end to a cross-bracket  542 . The cross-bracket  542  is fixedly coupled to each of the margins  518   a  of the channel section  518 . The primary gas cylinder  540  has a piston  546  and a cylinder  548 . The cylinder  548  is disposed upward connected proximate the cross-bracket  542 . The piston  546  extends generally downward from the cylinder  548  and is coupled to a bracket  550 . 
     The bracket  550  has a generally inverted J-cross-sectional shape as depicted in FIG. 40. A connecting pin  552  passes through a bore (not shown) defined in the bracket  550  and through a bore (not shown) defined in a cross-pin  554  to couple the cross-pin  554  to the bracket  550 . The cross-pin  554  is pivotally coupled to and extends between the two parallel arms  577  of the pedestal assembly  576 . A lock nut  558  secures the piston  546  to the bracket  550 . 
     A shiftable concentric lock  560  is disposed coaxially with the piston  546  of the primary gas cylinder  540 . The concentric lock  560  extends through a bore (not shown) defined in the bracket  550 . The concentric lock  560  is biased in the outward, locked disposition relative to the piston  546 . As such, the concentric lock  560  normally resides in the fully extended and locked disposition as depicted in FIG. 41. A pivotable lever  562  is disposed within the bracket  550  and pivots about a pivot point  563 . In a preferred embodiment, a raised portion  561  of the lever  562  is in contact with the end of the concentric lock  560 . 
     A cable assembly  564  is coupled to the distal end of the lever  562 . The cable assembly  564  has a sheath  566  that is fixedly coupled to the bracket  550  by a coupler  570 . A shiftable cable  568  is disposed concentric (coaxial) with the sheath  566  and is selectably translatable relative to the sheath  566 . A first end of the shiftable cable  568  is coupled to the lever  562  by a suitable connector  572 . This connector may be a ball of metal affixed to the end of the shiftable cable  568 . The other end of the cable assembly  564  is connected to the trigger  48   a  substantially as indicated in FIG.  8 . 
     In operation, the tilt of the seat  15  is fixed relative to the pedestal assembly  566  by the locking engagement of the concentric lock  560  within the piston  546 . The outwardly directed bias on the concentric lock  560  acts to force lever  562  to rotate in a counter-clockwise direction relative to the pivot point  563 . Such action acts to extend the shiftable cable  568  in the downward direction, indicated by arrow G, as depicted in FIG.  41 . Actuation of the trigger  48   a  acts to retract the shiftable cable  568  upward as indicated by arrow G relative to the sheath  566 . The raised portion  561  of the lever  562  bears on the end of the concentric lock  560  forcing the lock  560  upward within the cylinder  548  and unlocking the concentric lock  560 . While the trigger  48   a  is held in the actuated position, the primary gas cylinder  540  is unlocked and the primary gas cylinder  540 , in cooperation with the auxiliary gas spring  530 , acts to tilt the seat  15  from the level disposition of FIG.  40  through an intermediate disposition of FIG. 38 to the fully tilted disposition as depicted in FIGS. 36 and 39. At any point in the travel of the seat  15  the inclination thereof can be fixed by simply releasing the trigger  48   a . Such release results in the bias acting on the concentric lock  560  to return the concentric lock  560  to the locked condition. 
     To return the seat  15  from an inclined disposition as depicted in FIG. 39 to a more level disposition as depicted in FIG. 40, the trigger  48   a  is again actuated to unlock the concentric lock  560 . An operator&#39;s pressure on the back of the seat  15  causes the primary gas cylinder  540  to compress downward as indicated by arrow E of FIG. 40 resulting in rotation downward as indicated by the arrow F in FIG.  38 . Again, the declination of the seat  15  can be arrested at any point in its travel as indicated by arrow F by simply releasing the trigger  48   a  and returning the concentric lock  560  to the locked position. 
     The pedestal  20  is a component of the pedestal assembly  576 . The pedestal assembly  576  is depicted in greatest detail in FIG.  40  and is also shown in FIGS. 36,  38 , and  39 . 
     The pedestal assembly  576  includes a unitary support component  575  that comprises a wrap around envelope  579  that substantially envelopes the pedestal  20  and extends outward to include the substantially parallel arms  577  which have been discussed without detail above. Preferably, the support component  575  that comprises the envelope  579  and arms  577  is a major structural element and is formed of ¼ inch thick steel plate. The support component  575  is free to rotate relative to the pedestal  20  so that an operator may swivel the unit comprising the back  14  and seat  15  relative to the pedestal  20 . 
     A gas cylinder assembly  578  is disposed substantially concentric with a bore defined within the pedestal  20 . A portion of the gas cylinder assembly  578  projects above the top margin of the pedestal  20 . As will be described, the gas cylinder assembly  587  facilitates substantially vertical translation of the support component  575  relative to the pedestal  20 . 
     The gas cylinder assembly  578  includes a cylinder  580  having a shiftable, translatable piston  582  disposed therein. The gas cylinder assembly  578  is mounted such that the cylinder  580  is disposed substantially within the pedestal  20  and the cylinder  580  projects upward therefrom. The distal end of the piston  582  is fixedly coupled to a mounting bracket  584  that is disposed proximate the top margin of the envelope  579 . The concentric lock  586  is disposed within the piston  582  and projects above the upper margin of the piston  582 . 
     A raised portion  587  of a lever  588  bears on the distal end of the concentric lock  586 . The lever  588  is pivotable about a lever pivot  590  that is operably coupled to the support component  575 . The pivoting motion of the lever  588  is indicated by arrow H. 
     A cable assembly  592  is operably coupled to the distal end of the lever  588 . The cable assembly  592  is a coaxial cable having a sheath  594  surrounding a shiftable, translatable coaxial cable  596  disposed within the sheath  594 . A first end of the cable  596  is coupled by a connector  600  to the distal end of the lever  588 . The sheath  594  of the cable assembly  592  is fixedly coupled by a coupler  598  to a small bracket  601  that is formed integral with the support component  575 . The second end of the cable  596  of the cable assembly  592  is coupled to the trigger  48   b , similar to the coupling of cable  90  and trigger  48   a ,  48   b  in FIG.  8 . 
     Vertical shifting of the support component  575  relative to the pedestal  20  of the pedestal assembly  576  is effected by actuation of the trigger  48   b . Such shifting carries with it both the back  14  and seat  15  of the positioning system  10  and accordingly affects the height of the back  14  and seat  15  above the floor surface on which the positioning system  10  is resting. In the depiction of FIG. 40, the support component  575  is in its full upper position. Accordingly, the seating surface of the seat  15  is at its highest disposition above the surface on which the positioning system  10  is resting. The concentric lock  586  is biased in its upward locked disposition, locking the back  14  and seat  15  at the depicted height. 
     To lower the support component  575  to the disposition indicated in phantom in FIG. 40, an operator actuates trigger  48   b . Such actuation causes the lever  588  to rotate generally counter-clockwise. The pressure of the raised portion  587  bearing on the distal end of the concentric lock  586  forces the concentric lock  586  inward into the piston  582 , thereby unlocking the concentric lock  586 . Downward pressure applied on the seat  15  will cause the seat  15  and the support component  575  to move downward as indicated by arrow I to the phantom position. Such pressure compresses the gas in the cylinder  580 . When the seat  15  has achieved its desired height, the operator simply releases the trigger  48   b  and the bias that biases the concentric lock  586  into the locked disposition forces the lever  588  in a clockwise rotation as indicated arrow H to the locked disposition of the concentric lock  586 , thereby locking the back  14  and seat  15  at the desired height. 
     To raise the height of the seat  15 , an operator merely again actuates the trigger  48   b  to unlock the concentric lock  586 . The energy stored within the gas cylinder assembly  578  causes the seat  15  mounted on the component comprising the arms  577  and envelope  579  to rise to a desired height as indicated by arrow I, at which point the operator simply releases the trigger  48   b  and the concentric lock  586  then again locks the gas cylinder assembly  578  in the desired position. 
     Reference has been made to the triggers  48   a ,  48   b  mounted on the two side supports  16 . The features of the side supports  16  will now be described. The side supports  16  are depicted in FIGS. 36-39. 
     Each of the side supports  16  has a generally kidney-shaped support loop  604 . The support loop  602  has an aperture  604  defined therein. A support web  605  is fixedly disposed within the aperture  604 . It is generally not intended that the support loop  602  provide arm support for a user of the positioning system  10 . That function is left to the arm supports  606 . 
     Each of the side supports  16  has an arm support  606  that is selectively, fixedly coupled to the respective support web  605 . This support arm  606  is coupled to the support web  605  by means of a mounting disk  607  that is interposed between the support web  605  and arm support  606 . The mounting disk  607  has a threaded bore (not shown) defined therein. 
     Each of the arm supports  606  has a curvilinear support surface  608 . The curvilinear support surface  608  is preferably cushioned and designed to support the arms of an operator. A support bracket  610  depends from the curvilinear support surface  608 . The support bracket  610  has an elongate slot  612  defined therein. A lock nut  614  is passed through the slot  612  and threadably engaged with the threaded bore defined in the mounting disk  607 . The lock nut  614  has a large knurled handle  615  that may be readily grasped by an operator to engage and disengage the lock nut  614  as desired. 
     The arm supports  606  are movable relative to the support loop  602  both rotatably and linearly translatably as indicated by arrows J and K, respectively. 
     To position the arm support  606  as desired, the operator simply loosens the lock nut  614 . The support bracket  610  may then be rotated as indicated by arrow J or moved linearly as indicated by arrow K and then relocked in the desired position by grasping an rotating handle  615  to retighten the lock nut  614 . 
     The final major element of the positioning system  10  is the base structure  24 . The base structure  24  is depicted in FIGS. 36,  38 ,  39 , and  42 . Generally, the base structure  24  is a major structural component of the support system  10 , cooperating with the stabilizers  22  and connector arm  23  to support the support system  10  on a surface. A lower leg support  25  is included at the forward portion of the base structure  24 . The lower leg support  25  includes a support pad  26  that is designed to support the knee and upper shin portion of the lower legs of an operator. The support pad  26  is supported on a link member  27  coupled to the base structure  24 , described in greater detail below. 
     The base structure  24  includes a forward directed support tube  618 . The support tube  618  acts as a receiver for the connector arm  23  as indicated in FIG. 38, the connector arm  23  is fixedly coupled to the support tube  618  by a fastener  620 . In an embodiment, the fastener  620  has a hex-type head, requiring a tool to engage and disengage the fastener  620 . The fastener  620  has a threaded shank that is threaded into a threaded bore  622  defined in the connector arm  623 . Preferably, there are plurality of threaded bores  622  disposed linearly along the upper margin of the connector arm  23 . In this manner, the total length of the combined connector arm  23  and support tube  618  can be adjusted as desired. This is an adjustment that is designed to not be made on a routine basis in an embodiment and accordingly, as indicated above, the fastener  620  requires a tool for engagement and disengagement. 
     A foot rest  624  may be fixedly coupled to the support tube  618  proximate the distal end thereof. See FIG.  37 . Alternatively, the foot rest  624  may be adjustable as desired to adjust the angle presented to the user&#39;s feet. A friction lock disposed between the foot rest  624  and the base structure  24 , augmented by a manually actuatable knob  627 , as depicted in FIG. 39, may be used to vary the tilt of the foot rest  624 , as indicated by the arrow M, about the pivot point  625 . The knob  726  is preferably coupled to a threaded rod (not shown) that passes through a friction material comprising the friction lock and is threaded into a threaded receiving bore (not shown) defined in the base structure  24 . Tightening the knob acts to compress the friction material, thereby fixing the angle of the foot rest  624 . 
     A pair of spaced apart wheels  626  are positioned beneath and supported by the foot rest  624 . As distinct from the casters  25 , the wheels  626  are mounted on a fixed axle such that they do not caster in the depicted embodiment. It is understood that the wheels  626  could be replaced with casters, as desired. 
     Details of the lower leg support  25  are as follows with reference to FIGS. 38,  42 , and  43 . The lower leg support pad  26  has a cushion  628  affixed to a support plate  629 . The support plate  629  is brought into flush engagement with a slotted plate  630  that is fixedly coupled to the link member  27 . Plates  629 ,  630  are shiftable relative to one another. A plurality of elongated slots  632  are defined generally vertically in the slotted plate  630 . A lock nut  633  is passed through the respective slots  632 . Each of the lock nuts  633  has a knurled handle  635  to facilitate manual engaging and disengaging of the lock nut  633 . The lock nuts  633  in combination with the slots  632  facilitate a generally vertical adjustment of the support pad  26  relative to the link member  27 , as indicated by the arrow L in FIG.  38 . By disengaging the lock nuts  633 , the support pad  26  may be moved as indicated by arrow L through a range of motion limited by the length of the slots  632 . When the desired height of the support pad  26  is achieved, the lock nuts  633  may be simply reengaged by an operator by rotating the handle  635  of the lock nut  633 , as depicted in FIG.  43 . 
     As indicated above, the support pad  26  is operably coupled to the base structure  24  by the link member  27 . As depicted in FIGS. 42 and 43, the link member  27  includes a structural upright  634 . The upright  634  has a channel defined therein. The channel is defined by a curved margin  639   a  connecting to generally parallel side margins  639   b  of the upright  634 . The curved margin  639   a  preferably faces an operator seated in the seat  15 . An opening  641  is defined by the edge margins of the side margins  639   b  and is generally opposite the curved margin  639   a . The upright  634  is pivotally coupled to the base  24  at a hinge point  637 . The upright  624  is capped with a dome  636 . 
     A gas spring  638  resides within the channel defined within the upright  634 . The gas spring  638  has a cylinder  640  and a concentric, translatable piston  642 . A connector  644  is fixedly coupled to the upper margin of the cylinder  640  and is rotatably coupled to the upright  634  proximate to the dome  636  by a pin  646 . The distal end of the piston  642  is fixedly coupled to a bracket  650  by a lock nut  648 . The bracket  650  is pivotally coupled to the base  24  at a pivot point  652 . It should be noted that the pivot point  652  is spaced apart from the hinge point  637  creating a moment arm therebetween. The bias exerted by the gas spring  638  and the upright  634  tends to bias the upright  634  into the rearward disposition indicated by solid lines in FIG.  42 . 
     A cam actuator  654  is disposed within the bracket  650 . The cam actuator  654  has a cam surface  655  that bears on a concentric lock  656  that is translatably disposed within the piston  642  of the gas spring  638 . The operation of such concentric lock  654  has been previously described. To reiterate, the concentric lock is biased in the locked disposition as indicated in FIG. 42, locking the cylinder  640  and piston  642  at a certain length. Generally upward pressure on the concentric lock  656  causes the concentric lock  656  to translate to an unlocked disposition, thereby permitting pivoting action of the link member  27  as will be described. 
     The cam actuator  654  is pivotally coupled at a pivot  659  to the bracket  650 . Rotating the cam actuator  654  about the pivot  659  results in the cam surface  655  bearing on the concentric lock  656  to unlock the concentric lock  656 . 
     An actuator assembly  658  is operably coupled to the cam actuator  654 . The actuator assembly  658  includes a foot pedal  660  that is translatable generally in a vertical direction. The foot pedal  660  is operably coupled to a lever  662 . A coaxial cable assembly  664  is operably coupled at a proximal end to the lever  662 . The cable assembly  664  is operably coupled at a distal end to the cam actuator  654 . The cable assembly  664  has a sheath  666  surrounding a shiftable coaxial cable  668  disposed therein. At a first end, the sheath  666  is fixedly coupled by a connector  670  to a pedal bracket  671 . At a second end, the sheath  666  is fixedly coupled by a connector  672  to the bracket  650 . The distal end of the cable  668  is coupled to the cam actuator  654  by a connector  674 . 
     To position the support pad  26  as desired between a leftmost (forward) disposition indicated in phantom in FIG. 42 and a rightmost (rearward) disposition depicted in solid in FIG. 42, an operator depresses the foot pedal  660 . Such action causes the cable  668  to translate in the direction indicated by the arrow L of FIG.  42 . Such translation rotates the cam actuator  654  about the pivot  659  causing the cam surface  655  to depress and unlock the concentric lock  656 . 
     When unlocked, the bias exerted by the gas spring  638  positions the support pad  26  and link member  27  as indicated in solid in FIG.  42 . The support pad  26  may be stopped at any disposition between the phantom depiction and the solid depiction thereof by simply releasing pressure on the foot pedal  660 . The downward bias of the concentric lock  656  will then cause the concentric lock  656  to retreat to its lowermost and locked disposition. 
     To move the support pad  26  from its rightmost disposition as depicted in FIG. 42 to its leftmost disposition, the foot pedal  660  is again depressed and leftward pressure must be applied to the support pad  26  to overcome the bias exerted by the gas spring  638 . Again, when the desired position is achieved, the downward pressure on the foot pedal  660  is simply released and the concentric lock  656  again locks the gas spring  638  at that position. 
     Up to this point, the body positioning system  10  of the present invention has been described as a purely mechanical device. Alternatively, the system  10  may be adapted to be powered. Referring to FIG. 44, any or all of the actuators comprising primary gas cylinder  540 , gas cylinder assembly  578 , and/or gas spring  638  (the aforementioned purely mechanical devices) may be replaced by powered actuators. Such powered actuators may include, for example, hydraulic actuator or pneumatic actuator  700  and rack and pinion actuator  702 . Other suitable powered linear actuators may also be used including, for example, a ball and screw device. 
     The hydraulic (or pneumatic) actuator  700  has a cylinder  704  with a translatable piston  706  disposed therein. The distal end of the cylinder  704  is fixed and the distal end of the piston  706  is affixed to the component of the system  10  to which motion is desired to be imparted. The motorized pump  708  selectively provides the flow of fluid (hydraulic fluid or air) via lines  710 ,  712  to the dual acting hydraulic (or pneumatic) actuator  700 . By reversing the flow in the lines  710 ,  712 , the piston  706  is either retracted or extended with respect to the cylinder  704 . 
     Similarly, the rack and pinion actuator  702  includes a rack receiver  714  and a translatable tooth rack  716 . The distal end of the rack receiver  714  is fixed, while the distal end of the rack  716  is attached to the component to which lineal motion is desired to be imparted. The pinion gear  718  is disposed proximate the rack  716  such that the teeth of the pinion gear  718  and the teeth of the rack  716  intermesh. A motor  720  imparts rotational motion to the pinion gear  718 . Reversing direction of rotation of the pinion gear  718  causes the gear to translate into or out of the rack receiver  714  as desired. 
     A control  724  is in communication with a source of power  726  and is in communication with the hydraulic pump  708  of the motor  720 . In an exemplary system, the controller  724  has three position switches thereon. Each of such switches has a neutral position and a first actuated position and a second actuated position. The first such switch is the seat up/down switch  728 . Switch  728  in the neutral disposition locks the chair  13   a  in the current position. Actuating the up direction of the switch  728  causes the chair  13   a  to rise as long as the switch  728  is held in such disposition. The switch  728  is spring loaded to the neutral position and releasing pressure on the up actuation causes the switch  728  to turn to the neutral disposition by locking the chair  13   a  at the present disposition. Similarly, the seat  15  may be lowered by selecting the down disposition. 
     The seat  15  is tilted by actuation of the seat tilt switch  730 . Selecting the first tilt actuation position tilts the seat  15  toward the generally level disposition and selecting the second tilt actuation tilts the seat  15  toward a more vertical disposition. Seat tilt switch  730  is also spring loaded to the neutral position in which the current tilt of the seat  15  is maintained. 
     The final switch on the controller  724  is for controlling the lower leg support  25 . In the neutral disposition, the switch  732  maintains the lower leg support  25  in its current disposition. Actuating the first portion of the switch  722  moves the lower leg support  25  forward and actuating the second portion of the switch  732  moves the leg support  25  rearward. Like the switches  728 ,  730 , the switch  732  is spring loaded to the neutral position. 
     An alternative controller  740  is also depicted in FIG.  44 . The alternative controller  740  would be used in place of the controller  724 . The controller  740  is operably coupled to a suitable source of power  726 . Significantly, the controller  740  is coupled to a processor  742 , the processor  742  permitting many more functions. For example, the controller  740  has three switches  744 ,  746 , and  748  that duplicate the functions of the previously described switches  728 ,  730 , and  732 . Additionally the controller  740  has three memory switches associated with the functions seat up/down, seat tilt, and lower leg support position. Accordingly, a user can position the height of the chair  13   a  as desired using the switch  744  and then actuate the initialize switch  756  simultaneously with one of the three switches  750  to enter the existing position into memory. Subsequently, simply selecting the respective switch  750  will automatically return the height of the chair  13   a  to the memorized position. Similar functions are available by using the switches  752  for seat tilt  15  and  754  for lower leg support  25  position. 
     In order to minimize the repetitive stress on a user when performing a repetitive task, the controller  740  can be programmed to automatically simultaneously change the position of at least the seat  15  tilt and the lower leg support  25  on a set schedule. For example, by selecting the program actuator  758 , a program is initiating in which a seat  15  tilt and the lower leg support  25  position is simultaneously changed automatically every 15 minutes of use to minimize user fatigue. 
     While the preferred embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changers, variations and modifications may be made therein without departing from the present invention in its broader aspects. 
     Thus, although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention in its broader aspects and, therefore, the aim in the appended claims is to cover such changes and modifications as fall within the scope and spirit of the invention.