Patent Publication Number: US-2010127544-A1

Title: Lockable reclining adjustment device to control the tilting of the seat frame of a manual wheelchair

Description:
FIELD OF THE INVENTION 
     The present invention relates to manual wheelchairs with tiltable seat frames. More specifically, the present invention relates to a lockable reclining adjustment device to control the tilting of the seat frame of a manual wheelchair. 
     BACKGROUND OF THE INVENTION 
     It is common knowledge that wheelchairs are used by patients of varying degrees of paralysis. However, when patients are confined to a wheelchair for prolonged periods of time, pressure sores can appear on the buttock area of the patient. As a result, different types of reclining wheelchairs have been known in the art, that is, wheelchairs which have a reclining back. Such wheelchairs improve the comfort level of patients. 
     The safety of these wheelchairs with reclining or tilting back rests is an issue. Many of such wheelchairs have an all too high failure rate. 
     In U.S. Pat. No. 5,195,803 entitled “Reclining Seat Back Assembly for a Wheelchair”, the actuation of levers  104  compresses springs  90  which separates surface  84  from inner strut  66 . Then frame member  36  can be pivoted to desired angle as inner strut  66  slides within outer strut  64 . The release of  104  locks the position. There appears to be only one side of contact of the engaging member  84  and threaded shaft item  66 . 
     In U.S. Pat. No. 4,544,200 entitled “Wheelchair with Rocking Seat and Reclining Back Features” the position is locked via teeth  152 / 154  in tracks  82 / 84 . Actuation of lever  158  releases the lock so that the tracks can slide along track guides  86 / 88  to reposition the seat assembly and back. Release of the lever locks the teeth in a new position. There is a bar in the front of the chair which is controlled by the patient. This device is locked in place via teeth  152 / 154  in tracks  82 / 84 . 
     In U.S. Pat. No. 4,487,453 entitled “Seat Recliner Adjustment Mechanism”, there is a locking mechanism  38  engaged with rack member  32 . Upward movement of release arm  54  causes spring  64  to disengage the locking mechanism from the rack member so the seat can be re-positioned. This device uses a rod as an actuating means. 
     The device of U.S. Pat. No. 3,881,773 entitled “Reclining Back Wheelchair” uses a telescoping adjustable tube  21  having a number of slots. Actuation of handles release pawl  32  from the respective slot via a spring loaded bell crank assembly. When the pawl is released the tube is repositioned and the handle released to move the pawl into another slot. This mechanism relies on handle grip  35 , bell crank type bracket member  28  and release pawl  32  to allow the adjustable tube to be repositioned. 
     The device of U.S. Pat. No. 6,921,134 entitled “Apparatus for adjusting inclination of chair backs” uses many latch grooves item  22  on a positioning member  21 . This device is complex and has many parts that work with one another. 
     The device of U.S. Pat. No. 6,267,443 entitled “Reclining seat for vehicle” uses a cam groove where rolling element  23  are positioned and retained by item  24 . Release the rolling elements from the grooves allow the use to recline back. In the locked position the rolling elements fit in the groove. This patent uses radial movement to release the rolling elements from their position. The reference patent uses a cam groove, a fixed ring and rotary ring and is enclosed in a casing with many parts and sub components. 
     One device used to control the reclining action of a wheelchair already having a reclining back rest known in the art is a mechanical linear locking device which is retrofitted on such a wheelchair. Examples can be found at http://www.portergroupllc.com/solutions/mechlokhl.asp and http://www.craneae.com/Solutions/Cabin/mechlok.htm. The device has infinite positions where device can be locked along a shaft. 
     SUMMARY OF THE INVENTION 
     Disclosed is a reclining adjustment device to control the tilting of the seat frame of a manual wheelchair. In accordance with the teachings of this invention, the device is an ‘all in one’ assembly that includes an engaging means, guide means and locking means. The device in accordance with this invention has less moving parts compared to prior devices and a majority of its parts are confined between two locknuts on a shaft. The device in accordance with the teachings of this invention uses a simple mechanism that allows the recline angle of a wheelchair to be adjusted. The device in accordance with the teachings of this invention is smooth and small and does not interfere with the occupant or attendant. 
     Broadly speaking, there is provided a reclining adjustment device to control the reclining angle of a tiltable seat frame of a manual wheelchair, the device comprising a guiding mechanism for adjusting the reclining angle of the seat to a desired angle selectable from a fixed number of angles between a fully reclined position and a fully upright position; an engaging mechanism releasably engaging the guiding mechanism when the reclining angle of the seat frame is at the desired angle to fix the guiding mechanism in place; a locking mechanism for locking the engaging mechanism to the guiding mechanism at the desired angle; and an actuating mechanism, wherein upon actuation of the actuating mechanism, the engaging mechanism is released from the guiding mechanism to permit the guiding mechanism to be adjusted to the desired angle. 
     In one embodiment, the engaging mechanism comprises a slider with three ball bearings. Preferably, the three ball bearings are equally spaced around the stepped shaft. 
     In one embodiment, the guiding mechanism comprises a stepped shaft, the steps on the shaft each defining one of the fixed number of angles. Preferably, the fixed number of angles is 25. 
     In one embodiment, the locking mechanism comprises a lock cylinder. Preferably, the lock cylinder has holes for mounting the device to an existing wheelchair. In one embodiment, when the device is mounted to an existing wheelchair, the device is mounted between the frames of the wheelchair. 
     In one embodiment, the actuating mechanism comprises a handle controlling a cable assembly. Preferably, the cable assembly is controlled via a spring, which is preferably a compression spring. In one specific embodiment, the device in accordance with the teachings of this invention uses a cable assembly and lever to control the position of the slider assembly on the stepped shaft and engagement of the ball bearings. This is done by the attendant from the back side usually. In this way, in the event that case something drastic happens, at least the attendant can help the patient. 
     In one embodiment, a ball end of the cable is placed between a cable holder of the cable assembly and the lock cylinder. Preferably, the handle is located at the back of the wheelchair. 
     In one embodiment, the engaging mechanism and locking mechanism are located between two lock nuts on the guiding mechanism. This makes the device compact. 
     Preferably the parts that comprise the device in accordance with the teachings of this invention are either stainless steel or chrome plated which allows better durability and longevity over the long run. 
     Other aspects and advantages of embodiments of the invention will be readily apparent to those ordinarily skilled in the art upon a review of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described in conjunction with the accompanying drawings, wherein: 
         FIG. 1   a  is a perspective view of a typical manual wheelchair frame with a tiltable seat frame; 
         FIG. 1   b  is a side view of the wheelchair frame of  FIG. 1   a;    
         FIG. 2   a  is a perspective view of the wheelchair frame of  FIG. 1   a,  incorporating a device in acordance with the teachings of the present invention; 
         FIG. 2   b  is a side view of the wheelchair frame of  FIG. 2   a;    
         FIG. 3  illustrates a portion of a device in accordance with the teachings of the present invention, excluding the actuating mechanism; 
         FIG. 4  illustrates an exploded view of the device of  FIG. 3 ; 
         FIG. 5  illustrates a complete device in accordance with the teachings of this invention; and 
         FIG. 6  illustrates parts of a cable assembly that can be used in conjunction with a device in accordance with the teachings of this invention. This figure is Detail A of  FIG. 5 . 
     
    
    
     This invention will now be described in detail with respect to certain specific representative embodiments thereof, the materials, apparatus and process steps being understood as examples that are intended to be illustrative only. In particular, the invention is not intended to be limited to the methods, materials, conditions, process parameters, apparatus and the like specifically recited herein. 
     DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
     Referring to  FIGS. 1   a  and  1   b,  there is shown a typical manual wheelchair frame  100  with a tiltable seat frame  101 . Manual wheelchairs are hand-operated. This is in contrast to power or electric wheelchairs that are motorized. Since power or electric wheelchairs use linear actuators with built-in brakes to drive the tilt and recline features, there is no need for an additional locking device, such as a device in accordance with the teachings of this invention. It is assumed that such a wheelchair frame  100  is readily understood by those skilled in the art, so will be discussed only briefly. 
     Such a typical wheelchair frame  100  comprises an upper chair frame  102  and a lower chair frame  103 . The upper chair frame  102  typically includes a seat frame  101  supporting a seat  105 , and a back rest, leg rest, arm rests, head rest, and/or a foot rest. The lower chair frame supports wheel assemblies  111 . As can be seen, the wheelchair frame  100  described above is a standard, conventional wheelchair frame known by those skilled in the art. The present invention is directed to an additional device which is added to the above-described wheelchair or during the manufacture of new wheelchairs to achieve a new and advantageous result. Such a wheelchair is illustrated in  FIGS. 2   a  and  2   b.    
     A reclining mechanism  200  is used to selectively position the seat frame  101  of the wheelchair frame  100  with respect to the lower chair frame  103 . Generally, the seat frame  101  can be positioned between a plurality of positions varying from a fully upright position, where the seat frame  101  is vertical to a fully reclining position where seat frame  101  is fully horizontal. 
     Referring to  FIGS. 3 ,  4  and  5 , broadly, the device  200  in accordance with the teachings of this invention is a reclining adjustment device to control the reclining angle of a tiltable seat frame  101  of a manual wheelchair. In broad terms, the device  200  comprises a guiding mechanism for adjusting the reclining angle of the seat frame to a desired angle selectable from a fixed number of angles between a fully reclined position and a fully upright position; an engaging mechanism releasably engaging the guiding mechanism when the reclining angle of the seat frame is at the desired angle to fix the guiding mechanism in place; a locking mechanism for locking the engaging mechanism to the guiding mechanism at the desired angle; and an actuating mechanism, wherein upon actuation of the actuating mechanism, the engaging mechanism is released from the guiding mechanism to permit the guiding mechanism to be adjusted to the desired angle. 
     As illustrated, the engaging mechanism comprises a slider  10  with three ball bearings  2  (only one ball bearing is seen in  FIGS. 3 and 5 , and two ball bearing are seen in  FIG. 4 ). By using three ball bearings  2  for engagement, in the event that one ball bearing fails, the other ball bearings can function to still help to operate the device properly. By using three ball bearings, the reclining adjustment device uses radial movement rather than linear movement for control. The ball bearing is preferably ¼″ chrome. By using ball bearings over, for example, a teethed rack the index positions can be closer together giving more precision. 
     As mentioned above, the three ball bearings  2  are equally spaced relative to one another along the stepped shaft. Thus, the device  200  has three sides of contact, allowing the device  200  to have a better ‘hold’ than previously has been available. The device is designed to keep the center to center distance of the ball bearings at a minimum, which provides smaller increments of adjustment. The greater the number of indexes over a distance, the better the precision. 
     The guiding mechanism comprises a stepped shaft  7 , wherein recessed steps are provided in the shaft for the ball bearings to rest in. The steps  7   a  on the shaft  7  each defining one of the fixed number of angles. Preferably, the fixed number of angles is 25 over a travel distance of 5.68″. The deeper the steps in the shaft, the better the holding power of the ball bearings, but the center distance then increases. Preferably, the center distance is 0.22″. 
     The locking mechanism comprises a lock cylinder  1 . The device  200  uses a lock collar or cylinder  1  to lock the ball bearings  2  in place along the stepped shaft  7 . As illustrated, the lock cylinder  1  has holes  1   a  for mounting the device  200  to an existing wheelchair, as is described in detail below. 
     The actuating mechanism comprises a handle  20  controlling a cable assembly comprising cable bracket  3  and cable holder  4 . A cable  21  goes through splitter box  24  and is split into a lower long cable  21   a  and lower short cable  21   b  are flexible and can be placed in a convenient location for the attendant. The lower long cable  21   a  is connected to the device via lower adapter lock nuts  30  and a 7/32 retaining ring  31 . The lower short cable  21   b  is connected to a gas cylinder (not shown) for operation. The device uses a cable assembly and lever  20  to control the position of the slider assembly  10  on the stepped shaft  7  and engagement of the ball bearings. This is done by the attendant from the back side usually, as described in detail below. In this way, in the event that something drastic happens during operation, at least the attendant can help the patent. 
     As illustrated, the cable assembly is controlled via a spring  12 , which is preferably, a compression spring. The cable holder  4  and lock collar  1  are shaped to allow the ball end  25  of the steel cable  21  (used for actuating) to be permanently in place between these parts so that the device  200  functions properly. The lock collar uses an angle bracket to guide the cable to the side since it is blocked from coming through the center because of the shaft. The inventor has discovered that the optimal angle is 45°; if the angle is higher, the pull force is decreased and if the angle is less than 45°, the bracket will interfere with the seat frame positioning. 
     Preferably, the size of steel wire should be 16 ga (0.06) diameter. Preferably, the size of ball end should be 3/16″ diameter. 
     Preferably, the handle  20  is located at the back of the wheelchair. As will be discussed in detail below, in operation the device uses axial movement to release the ball bearings  2  from their position. The spring  12  is compressed and causes the lock collar  1  to move away from the ball bearings  2  because of spacer  11 . The bearings  2  then come out of the contact with the stepped shaft  7  and the position of the mechanism can be changed. 
     The engaging mechanism and locking mechanism are located between two lock nuts  6  on the guiding mechanism. Optionally, there may be a dust and duct protector  5 . 
     As can been seen and understood by the foregoing, the device  200  in accordance with the teachings of this invention is engineered in a manner that all of the components needed to engage, guide and lock the mechanism are located near one another. Thus the device can easily be replaced and through the use of wrenches taken apait and easily troubleshoot. 
     The device  200  in accordance with the teachings of this invention can be made from any suitable material such as metal, plastics, or synthetic resins which have the necessary characteristics, such strength to function suitably. Aluminum or other light-weight metals are used to help in controlling the overall weight of the wheelchair. Preferably, the device is stainless steel or chrome plated. 
     The maximum load on the tilting object is typically less than about 250 lbs. It will be understood by those skilled in the art that other design criteria must be considered in using a device in accordance with the teachings of this invention on a wheelchair. For example, the stroke length and holding force required must be suitable for use on wheelchairs. 
     Operation 
     To tilt the seat frame  101 , when the user pulls the handle  20 , the cable holder  4  moves down and compresses the spring  12 . The space caused by the compression of the spring  12  allows the lock cylinder  1  to move away from the ball bearings  2 . The ball bearings  2  are then released from the stepped shaft  7  and the shaft  7  is ‘free’ to move up or down. The patient can change the tilt angle of the object by moving the stepped shaft  7  up or down. Grease is used to allow the slider assembly  10  to move along the stepped shaft  7  in a smooth manner and also reduces the friction between the ball bearings  2  and stepped shaft  7  when the device is ‘locked’. Once the appropriate tilt angle is set the patient releases the handle  20  and the spring  12  expands  10  cause the lock cylinder  7  to move towards the ball bearings  2 . The ball bearings  2  are then placed in contact with the stepped shaft  7  and the shaft  7  is fixed in place. The lock cylinder  1  covers the ball bearings  2  and ‘locks’ the complete mechanism in place along the stepped shaft  7 . The complete process allows the tilting object to move to a new position-either away from the fixed object or towards the fixed object. 
     Mounting 
     To mount the device  200  in accordance with the teachings of this invention, one has to secure the device  200  to the tilting object by fastening a ¼-20 bolt (not shown) through hole  9   a  located at the end of the stepped shaft. The device also has to be secured to the fixed object by fastening a 5/16-18 bolt (not shown) through hole  9   b  located on the pivot block  8 . In order to connect the device  200  to handles  20  for proper operation a steel cable  21  needs to be used that preferable has a ball end that can be fastened to the cable holder  4  as shown in  FIG. 6  (detail A of  FIG. 5 ). When the device  200  is mounted to an existing wheelchair, the device  200  is mounted between the upper and lower frames of the wheelchair. Numerous modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.