Abstract:
A manual wheelchair having a tilt mechanism that allows a user positioned on the wheelchair to control the tilt angle of the wheelchair seat. The manual wheelchair has a base frame with arm rests that are fixed in position with respect to the base frame. The tilt mechanism includes a controller that is affixed to the manual wheelchair at a location proximate to one of the arm rests within the ready reach of the user and which can be manipulated by the user without assistance from a caregiver to allow the seat of the manual wheelchair to freely pivot about a pivot point such that the user can locate the seat at a desired tilt angle by pushing or pulling on the arm rest. A further manipulation of the controller allows the user to lock the seat in the desired tilt angle and remain in that angle.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to a manual tilt wheelchair having a seat that can be tilted and, more particularly, to a manual wheelchair having a seat that can be adjusted in its angular orientation by the user without assistance by a caregiver. 
       BACKGROUND OF THE INVENTION 
       [0002]    A tilt-in-space wheelchair provides the necessary change in position for the user who cannot effectively shift their body weight or change their position. These individuals are at a higher risk for skin breakdown and their sifting tolerance is compromised. A typical tilt-in-space wheelchair frame tilts up to 45 degrees from horizontal while maintaining the same back to seat angle. This feature provides a change in position for those people who have a difficult time maintaining their pelvic, trunk, and head position against gravity for extended periods of time. This feature can also assist in preventing postural collapse which puts them at risk for respiratory or digestive complications. Individuals who suffer from postural hypotension also benefit from tilt-in-space chairs. 
         [0003]    Despite the fact that the wheelchair industry offers several models with a tilting seating system, no manual wheelchairs currently on the market are designed so that the user can tilt independently, that is, none can be tilted without the assistance of an attending caregiver. Tilt wheelchairs were designed so that the user&#39;s body can be angled at various degrees so that pressure points are redistributed and their upper body can be positioned for optimal posture and comfort. The existing manual tilt wheelchairs have to be activated by a caregiver with the control located in the back of the chair, or to the side, out of the users reach. They are also designed with the armrest and seat attached to each other, therefore, the design does not give the user a place to push and pull from to activate the tilt feature. 
         [0004]    The average wheelchair user spends 8-14 hours in their wheelchairs daily. These individuals who spend these extended hours in a static upright position often end up needing additional medical treatments. They are at risk for pressure ulcers, skin tears, skeletal deformities (specifically kyphosis or “C” curve posture), impaired respiration and digestion from forward flexed postures, joint contractures, pain and discomfort, agitation, decreased mobility, and falls, which can result in injuries. 
         [0005]    For the average, able-bodied person, relief from discomfort during prolonged sitting is made by frequent, small, unconscious body adjustments that maintain comfort levels. For persons with physical disabilities and generalized muscle weakness, the discomfort and pain from daily wheelchair sitting can be chronic and debilitating. In addition to the potential for developing decubitus ulcers, many people in this population experience intolerable periods of discomfort and pain, which can lead to reduced participation in daily activities including, work, education, and recreation, and retrieval. (D. Hobson &amp; Barbara Crane: State of the Science White Paper on Wheelchair Seating Comfort Feb. 9, 2001) 
         [0006]    According to the National Pressure Ulcer Advisory Panel (NPUAP) the treatment costs for patients who developed ulcers were estimated to be as much as $6 billion per year. In elderly populations and in those who are institutionalized, pressure ulcers are one of the most costly diseases to treat. These ulcers add an estimated burden of over $1 billion in expenditures and an additional 2.2 million Medicare hospital days to the United States healthcare system. The bottom line alone, without considering the cost of human suffering, demonstrates the importance of preventing pressure ulcers. 
         [0007]    Accordingly, it would be advantageous to have a manual wheelchair with a user controlled seat tilt mechanism that can be readily operated by the user while sitting in the wheelchair without the need for assistance of a caregiver so as to allow the user to make desired adjustments to the angular orientation of the seat of the wheelchair. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is therefore directed to a manual wheelchair where the user has full control of the tilt angle of the wheelchair seat. As used herein the term “user” will mean the patient or person actually seated in and supported by the wheelchair. As also used herein, the wheelchair is described as a “manual wheelchair” and that means that the wheelchair is propelled solely by the user and no external motive system is employed. 
         [0009]    With the present invention, the user can independently perform the tilt operation on the wheelchair so that the user can execute pressure relief and postural changes throughout the day in order to maintain optimal comfort and skin integrity during the many hours spent in the wheelchair without assistance from a caregiver. 
         [0010]    The wheelchair is designed to have a base frame with a seat that pivots backward and forward with respect to the base frame and is also provided with a user controlled actuator that can be released to allow the seat to freely tilt about the base frame as well as to again lock the seat in the desired tilt angle selected by the user. 
         [0011]    Unlike other tilt wheelchairs, the armrests of the present manual wheelchair are fixed to the base frame instead of the seat in order to provide the user with a fixed structure to push and pull against while tilting the seat. This allows the user to operate a controller that is located proximate to at least one of the arm rests to allow the user to use the stability of one or both of the armrests to tilt the seat by pushing and/or pulling on an armrest for leverage to independently tilt the seat of the wheelchair. Releasing the controller automatically relocks the system into position. No assistance is required from a caregiver to adjust the angle of the seat of the wheelchair. 
         [0012]    Other features of the tilt mechanism of the present invention will become more apparent in light of the following detailed description of a preferred embodiment thereof and as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a side view of a wheelchair having the tilt mechanism of the present invention with the seat in its upright position; 
           [0014]      FIG. 2  is a side view of the wheelchair of  FIG. 1  with the seat in its tilted position; 
           [0015]      FIG. 3  is an enlarged perspective view illustrating the pivot point for the seat; 
           [0016]      FIG. 4  is a schematic view illustrating the control system for a hydraulic cylinder used with the tilt mechanism of the present invention; and. 
           [0017]      FIG. 5  is a side view of the wheelchair of  FIG. 1  illustrating the system for compensating for the weight of a user. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring to  FIGS. 1 and 2 , there is shown side views of a wheelchair  10  having a tilt mechanism constructed in accordance with the present invention. As can be seen, the wheelchair  10  is made up of a base frame  12  that may include lower horizontal members  14  as well as upper horizontal members  16  joined by vertical members  18 . As will be described, only one side of the wheelchair  10  that appears in  FIGS. 1 and 2  will be described, however it is well known that an opposite side of the wheelchair  10  is present and which is similar to or a mirror image of the side shown in  FIGS. 1 and 2 . 
         [0019]    There may also be conventional wheels  20  located at the bottom of the base frame  12  to enable the wheelchair  10  to be freely movable along a planar surface. 
         [0020]    A pair of drive wheels  22  are also provided (again, only one of which is shown in the Figures) and which enable the user to move the wheelchair  10  in a desired direction and the drive wheels  22  may be grasped by the user of the wheelchair  10  or by a caregiver, or by some other propulsion system so as to cause rotation of the drive wheels  22  to move the wheelchair  10 . 
         [0021]    A seat  24  is pivotally affixed to the base frame  12  so as to be rotatable about a pivot point in order to allow the seat  24  to be tilted to a desired orientation. In an exemplary embodiment, the seat  24  is comprised of a seat frame including a bottom seat frame member  26  and a back seat frame member  28  that are generally L-shaped so that the seat  24  can comfortably accommodate and support a user. 
         [0022]    The bottom seat frame member  26  and back seat frame member  28  can be individual members affixed together or can be a unitary member that is bent into the proper shape. Again, as is conventional, there is a similar bottom seat frame member and back seat frame member located on the opposite side to the wheelchair  10  as well as horizontal members that are secured together in making up the seat  24 . 
         [0023]    There is also included a head rest  30  and a bottom cushion  32  for the comfort of the user and which are affixed to frame members of the seat  24 . The seat  24  may also include a leg rest  34  that includes a leg cushion  36 , again, for the comfort of the user. 
         [0024]    As can now be seen, the seat  24  is affixed to the base frame  12  such that the seat  24  pivots about a pivot point  38  while retaining its L-shaped configuration to support the user. 
         [0025]    Turning briefly to  FIG. 3 , taken along with  FIGS. 1 and 2 , there can be seen an enlarged perspective view of the pivot point  38  where the seat  24  is pivotally affixed to the base frame  12 . In  FIG. 3  there can be seen a cross member  40  that spans the width of the wheelchair  10  and connects to the bottom seat frame members  26  on each side of the wheelchair  10 . 
         [0026]    A coupling  42  connects the cross member  40  to each bottom seat frame member  26  so that the bottom seat frame member  26  can rotate with respect to the cross member  40  in order to allow the seat  24  to tilt with respect to the base frame  12 . 
         [0027]    As can now be seen, the seat  24  can pivot about the pivot point  38  to enable the seat  24  to move to various tilt positions and, in  FIG. 1 , the seat  24  is in the upright position and in  FIG. 2 , the seat  24  has been moved to a tilted position. In an exemplary embodiment, the tilt angle A ( FIG. 2 ) of the seat  24  between its upright position and its maximum tilt position is about 45 degrees. 
         [0028]    The present invention includes a tilt mechanism that allows the user to control the amount of tilt of the seat  24 . As previously explained, the tilting of the seat  24  is controllable by the user by simply grasping onto the arm rest  44  and using that grip on the arm rest  44  as a steady site to move the seat  24  to the desired tilt angle. The arm rest  44  is not movable with respect to the seat  24  but is fixed with respect to the base frame  12 . In this manner, the user can grip the immovable arm rest  44  and use it for leverage to tilt the seat  24  about the pivot point  38  to the desired tilt angle. 
         [0029]    Once the desired tilt angle A has been attained, the tilt mechanism allows the user to lock the seat  24  firmly at that tilt angle. As such, the tilt mechanism includes a linear actuator  46  that is connected between the seat  24  and the base frame  12 . In the exemplary embodiment, the linear actuator can be a locking gas spring and one conventional locking gas spring that can be used is commercially available from Suspa Holding GmbH of Altdorf, Germany. Such locking gas spring is a combination spring and locking mechanism. The linear actuator  46  of the exemplary embodiment comprises an outer cylinder  48  and a piston  50  movably located therein. The linear actuator  46  has one end  52  affixed to the seat  24  at a location  54  along the bottom seat frame member  26  that is displaced a linear distance away from the pivot point  38  and the other end  56  is attached at a fixed location  58  with respect to the base frame  12 . 
         [0030]    The fixed location  58  is on a support bracket  60  that is solidly affixed to the base frame  12  and the support bracket  60  is an arcuate or curved bracket having a plurality of openings  62  formed therealong. Accordingly, the other end  56  of the hydraulic cylinder  46  can be attached to the support bracket  60  at any of the openings  62  so that the hydraulic cylinder  46  can be set in order to compensate or adjust for the weight of the user. With the use of the support bracket  60 , the other end  56  of the linear actuator  46  can be affixed to a selected opening  62  in the support bracket  60  depending upon the weight of the user. 
         [0031]    Accordingly, as the seat  24  is tilted by the user, the piston  50  moves inwardly or outwardly with respect to the outer cylinder  48  to contract or extend the liner actuator  46 . The movement of the piston  50  is controlled so that it can be allowed to freely move or be prevented from movement such that the angle A of the seat  24  can also be controlled, that is, when the piston  50  is free to move within the outer cylinder  48 , the seat  24  can be moved by the user to a desired tilt angle and when the piston  50  is prevented from moving within the outer cylinder  48 , the seat  24  will be retained and held in whatever angle has been set by the user. 
         [0032]    Turning then to  FIG. 4 , there is shown a schematic view of an exemplary system that can be used to control the movement or non-movement of the piston  50  within the outer cylinder  48 . As can be seen, the hydraulic cylinder  46  includes the outer cylinder  48  and the piston  50  having a piston head  64 . A hydraulic line  66  is shown in dotted lines and which forms a closed loop between a port  68  on one side of the piston head  64  and another port  70  that is located on the other side of the piston head  64 . As such, as the piston  50  moves in either direction within the outer cylinder  48 , the hydraulic fluid readily flows through the closed loop of the hydraulic line  66  such that the piston  50  is free to move within the outer cylinder  48 . 
         [0033]    There is, however, a controller  72  that can be activated by the user to close the hydraulic line  66  by pinching the hydraulic line  66  to stop the flow of hydraulic fluid therein, and which renders the piston  50  immovable within the outer cylinder  48 . 
         [0034]    As such, the controller  72  may include a pinch member  74  that is spring biased by means of a spring  76  to its closed position pinching the hydraulic line  66  to prevent movement of the piston  50  within the outer cylinder  48 . The controller  72  may comprise a lever  78 , operable, by the user of the wheelchair  10  to move the pinch member  74  against the bias of spring  76  to open the hydraulic line  66  to allow the piston  50  to move within the outer cylinder  48 . 
         [0035]    The controller  72  can be located on the wheelchair  10  within ready reach of the user of the wheelchair  10  proximate to the arm rest  44 , such as attached to the arm rest  44  so that the user can simply move the actuator  72  to its open position to open the hydraulic line  66  so that the piston  50  can move and the user can adjust the tilt angle of the seat  24  to any desired position using the leverage of the arm rest  44 . By locating the controller  72  proximate to the arm rest  44 , the user can release the controller  72  and then, since the arm rest  44  is fixed with respect to the base frame  12  and therefore does not move when the seat  44  is tilted, the user can use the leverage provided by the fixed arm rest  44  to push or pull on the arm rest  44  to move the seat  24  to the desired tilt angle. 
         [0036]    As can be seen, while the present controller  72  controls the flow of hydraulic fluid to allow the piston  50  to move and to be prevented from moving, other types of controllers can be used, including air activated controllers that are activated by the breath of a user. 
         [0037]    When the user has the seat  24  in the desired tilt angle, the user simply releases the actuator  72  so that the actuator  72  moves the actuator  72  to its closed position and stops the flow of the hydraulic fluid in the hydraulic line  66  and thereby holds the piston  50  in that exact position thereby retaining the angular orientation of the seat  24  as desire by the user. 
         [0038]    According as can now be seen, the patient or user has full control of the angular tilt of the seat  24  and the user can simply activate the actuator  72  to open the flow of hydraulic fluid in the hydraulic line  66  to allow the user to move the seat  24  to any desired tilt angle, and, when that tilt angle has been realized, the user can release the actuator  72 , thereby stabilizing the piston  50  and the seat  24  to maintain the particular tilt angle. 
         [0039]    Turning to  FIG. 5 , there is shown a side view of the wheelchair  10  with the seat  24  in its upright position. In  FIG. 5 , there can be seen a controller  80  that is positioned at a location that is convenient to the user and is pivotally affixed to a stmt  82  that is fixed to the arm rest  44  at a pivot point  84  on that strut  82 . In the location as shown, the controller  80  is located so that the user can operate the controller  80  to control the tilt angle of the seat  24 . Due to the location of the controller  80  proximate to and just underneath the arm rest  44 , the user can activate the controller  80  while gripping the arm rest  44  to use the arm rest  44  to move the seat  24  to the desired tilt angle, and then release the controller  80  to retain the seat  24  at that angle. 
         [0040]    The present invention also includes a compensation system to compensate or adjust for the weight of the user seated in the seat and that compensation system can be carried out in different ways. One way is to change location of the pivot point  38  with respect to the base frame  12 . In the exemplary embodiment, the location of the pivot point  38  can be moved (see  FIG. 3 ) by loosening the coupling  42  and simply moving the coupling  42  along the bottom seat frame member  26  and re-tightening the coupling when the pivot point  38  has been moved to a desired position. By moving the pivot point  38  forward and rearward, compensation can be made for the weight of the user. If the user seated in the wheelchair  10  is light, the pivot point  38  can be moved forward; if heavy, the pivot point  38  can be moved rearwardly. 
         [0041]    In addition, as explained, the other end  56  of the hydraulic cylinder  46  can be moved with respect to the base frame  12  to a selected opening  62  in the support bracket  60 . For a light user, an opening can be selected in the upper part of the support bracket and, for a heavier user, the selected opening  62  can be moved to a lower located opening  62 . 
         [0042]    While the present invention has been set forth in terms of a specific embodiment, or embodiments, it will be understood that the present tilt mechanism for a wheelchair herein disclosed may be modified or altered by those skilled in the art to other configurations. Accordingly, the invention is to be broadly construed and limited only by the scope and spirit of the claims appended hereto.