Folding wheelchair mechanism
View Patent ↗Disclosed is a method and device for varying the width of a wheelchair. The disclosed embodiments utilize a plurality of vertical pivots and linkages to facilitate the manipulation of a pair of horizontally oriented “scissor” linkages in order to reduce the track of the wheels for use in close quarter environments, such as commercial airlines, or to collapse the chair for transport or storage.
1. An apparatus that supports and adjusts the width of a wheelchair comprising:
a first side frame assembly that rigidly affixes the position and orientation of a right rear wheel and a right front wheel of said wheelchair;
a second side frame assembly that rigidly affixes the position and orientation of a left rear wheel and a left front wheel of said wheelchair;
a right scissor linkage pivot secured to a rearward portion of said first side frame assembly and left scissor linkage pivot secured to a rearward portion of said second side frame assembly;
a first scissor linkage pivotally secured between said right scissor linkage pivot on one end, and pivotally secured with a forward pivot to a left pivot linkage on an opposing end of said first scissor linkage, wherein said axis of said right scissor linkage pivot and said axis of said left forward pivot are approximately parallel, thereby facilitating coplanar rotation of said first scissor linkage and said left pivot linkage, said right scissor linkage pivot that is affixed to a rearward portion of said first side frame assembly and said left forward pivot that is pivotally secured to a forward portion of said first side frame assembly;
a second scissor linkage pivotally secured between said left scissor linkage pivot on one end, and pivotally secured with a forward pivot to a right pivot linkage on an opposing end of said second scissor linkage, wherein said axis of said left scissor linkage pivot and said axis of said right forward pivot are approximately parallel, thereby facilitating coplanar rotation of said second scissor linkage and said right pivot linkage, said left scissor linkage pivot that is affixed to a rearward portion of said second side frame assembly and said right forward pivot that is pivotally secured to a forward portion of said second side frame assembly;
a central pivot that pivotally secures said first scissor linkage to said second scissor linkage approximately midway between, and parallel to, said pivot axis of said scissor linkage pivots and said forward pivots of each said scissor linkage;
a left release cross member pivotally secured at a lateral end to said first scissor linkage between, and parallel to, said pivot axis of said central pivot and said left forward pivot;
a right release cross member pivotally secured at a lateral end to said second scissor linkage between, and parallel to, said pivot axis of said central pivot and said right forward pivot; and,
a release shaft pivotally secured to a medial end of said right release cross member and said left release cross member, and positioned such that when said release shaft is displaced in a forward direction, said release cross members apply force to said scissor linkages in a medial direction, causing said scissor linkages to close, thereby causing the distance between said first side frame assembly and said second side frame assembly to decrease, and when said release shaft is displaced in a rearward direction, said release cross members apply force to said scissor linkages in a lateral direction, causing said scissor linkages to open, thereby causing the distance between said first side frame assembly and said second side frame assembly to increase.
2. The apparatus of claim 1 wherein said first side frame assembly and said second side frame assembly each further comprise:
an upper lateral frame;
a lower lateral frame;
a forward vertical frame support;
a rear vertical frame support;
a rear wheel mount; and,
a front wheel mount.
3. The apparatus of claim 1 wherein said release shaft further comprises:
a release handle disposed on a forward end of said release shaft; and,
a release slide comprising a channel that a extends over a length of a rearward end of said release shaft, said release slide that facilitates slidable retention of said central pivot, and along with said central release pivot, sets the orientation and limits of movement of said release shaft.
4. The apparatus of claim 3 wherein said release slide is disposed from the approximate center of said release shaft to nearly a rearward end of said release shaft.
5. The apparatus of claim 3 wherein said central pivot may be secured to said release shaft at one or more positions within said release slide, thereby locking the width of said wheelchair in one or more positions.
6. The apparatus of claim 1 wherein the orientation of said first side frame assembly remains substantially parallel to said second side frame assembly when said release shaft is displaced and said width of said wheelchair is varied.
7. The apparatus of claim 1 wherein the position of said left front wheel remains constant to said left rear wheel, and the position of said right front wheel remains constant to said right rear wheel when said release shaft is displaced and said width of said wheelchair is varied.
8. The apparatus of claim 1 wherein a wheel base distance of said wheelchair remains constant when said release shaft is displaced and said width of said wheelchair is varied.
9. An adjustable width wheelchair comprising:
a base structure comprising:
a first side frame assembly that rigidly affixes the position and orientation of a right rear wheel and a right front wheel of said wheelchair;
a second side frame assembly that rigidly affixes the position and orientation of a left rear wheel and a left front wheel of said wheelchair;
a right scissor linkage pivot secured to a rearward portion of said first side frame assembly and left scissor linkage pivot secured to a rearward portion of said second side frame assembly;
a first scissor linkage pivotally secured between said right scissor linkage pivot on one end, and pivotally secured with a forward pivot to a left pivot linkage on an opposing end of said first scissor linkage, wherein said axis of said right scissor linkage pivot and said axis of said left forward pivot are approximately parallel, thereby facilitating coplanar rotation of said first scissor linkage and said left pivot linkage, said right scissor linkage pivot that is affixed to a rearward portion of said first side frame assembly and said left forward pivot that is pivotally secured to a forward portion of said first side frame assembly;
a second scissor linkage pivotally secured between said left scissor linkage pivot on one end, and pivotally secured with a forward pivot to a right pivot linkage on an opposing end of said second scissor linkage, wherein said axis of said left scissor linkage pivot and said axis of said right forward pivot are approximately parallel, thereby facilitating coplanar rotation of said second scissor linkage and said right pivot linkage, said left scissor linkage pivot that is affixed to a rearward portion of said second side frame assembly and said right forward pivot that is pivotally secured to a forward portion of said second side frame assembly;
a central pivot that pivotally secures said first scissor linkage to said second scissor linkage approximately midway between, and parallel to, said pivot axis of said scissor linkage pivots and said forward pivots of each said scissor linkage;
a left release cross member pivotally secured at a lateral end to said first scissor linkage between, and parallel to, said pivot axis of said central pivot and said left forward pivot;
a right release cross member pivotally secured at a lateral end to said second scissor linkage between, and parallel to, said pivot axis of said central pivot and said right forward pivot; and,
a release shaft pivotally secured to a medial end of said right release cross member and said left release cross member, and positioned such that when said release shaft is displaced in a forward direction, said release cross members apply force to said scissor linkages in a medial direction, causing said scissor linkages to close, thereby causing the distance between said first side frame assembly and said second side frame assembly to decrease, and when said release shaft is displaced in a rearward direction, said release cross members apply force to said scissor linkages in a lateral direction, causing said scissor linkages to open, thereby causing the distance between said first side frame assembly and said second side frame assembly to increase;
a seat frame laterally supported by said base structure;
a seat laterally supported by said seat frame;
a rear frame supported by said seat frame; and,
a backrest laterally supported by said rear frame.
10. A method of manufacture of an apparatus that adjusts the width of a wheelchair comprising the steps:
rigidly fixing the position and orientation of a right rear wheel and a right front wheel of said wheelchair with a first side frame assembly;
rigidly fixing the position and orientation of a left rear wheel and a left front wheel of said wheelchair with a second side frame assembly;
securing a right scissor linkage pivot to a rearward portion of said first side frame assembly and left scissor linkage pivot to a rearward portion of said second side frame assembly;
pivotally securing a right pivot linkage to a forward portion of said first side frame assembly with a first lateral pivot and pivotally securing a left pivot linkage to a forward portion of said second side frame assembly with a second lateral pivot;
pivotally securing a first scissor linkage between said right scissor linkage pivot on one end, and said left pivot linkage with a first forward pivot on an opposing end of said first scissor linkage, maintaining all pivot axis in an approximately parallel manner, thereby facilitating coplanar rotation of said first scissor linkage and said left pivot linkage;
pivotally securing a second scissor linkage between said left scissor linkage pivot on one end, and said right pivot linkage with a second forward pivot on an opposing end of said second scissor linkage, maintaining all pivot axis in an approximately parallel manner, thereby facilitating coplanar rotation of said second scissor linkage and said right pivot linkage;
pivotally securing said first scissor linkage to second scissor linkage with a central pivot located approximately midway and between and parallel to said pivot axis of said scissor linkage pivots and said forward pivots;
pivotally securing a lateral end of a left release cross member to said first scissor linkage between, and parallel to, said pivot axis of said central pivot and said left forward pivot;
pivotally securing a lateral end of a right release cross member to said second scissor linkage between, and parallel to, said pivot axis of said central pivot and said right forward pivot; and,
pivotally securing a release shaft to a medial end of said right release cross member and said left release cross member, such that a displacement to said release shaft in a forward direction causes said release cross members apply force to said scissor linkages in a medial direction, effecting said scissor linkages to close, thereby causing the distance between said first side frame assembly and said second side frame assembly to decrease, and that a displacement to said release shaft in a rearward direction causes said release cross members to apply force to said scissor linkages in a lateral direction, effecting said scissor linkages to open, thereby causing the distance between said first side frame assembly and said second side frame assembly to increase.
11. A method of manufacture of the apparatus of claim 10 further comprising the steps:
rigidly fixing the position and orientation of a top portion of a forward vertical frame support to an upper lateral frame near a forward end and to a top portion of rearward vertical frame near a rearward end of said upper lateral frame;
rigidly fixing the position and orientation of a bottom portion of said forward vertical frame support to a lower lateral frame near a forward end and to a bottom portion of said rearward vertical frame near a rearward end of said lower lateral frame;
rigidly fixing the position and orientation of a rear wheel mount to said rearward vertical frame and a front wheel mount to said forward vertical frame to create said side frame assembly.
12. A method of manufacture of the apparatus of claim 10 further comprising the steps:
rigidly fixing the position and orientation of a release handle on a forward end of said release shaft; and,
creating a release slide comprising a channel that extends over a length of a rearward end of said release shaft to facilitate slidable retention of said central pivot, thereby orienting and limiting the movement of said release shaft.
13. A method of manufacture of the apparatus of claim 10 further comprising the steps:
creating a release slide comprising a channel that extends from the approximate center of said release shaft to nearly a rearward end of said release shaft.
14. A method of manufacture of the apparatus of claim 10 further comprising the steps:
securing said central pivot to said release shaft at one or more positions within said release slide, thereby locking the width of said wheelchair in one or more positions.
15. An article of manufacture for an apparatus that adjusts the width of a wheelchair comprising the steps:
a means for rigidly fixing the position and orientation of a right rear wheel and a right front wheel of said wheelchair with a first side frame assembly;
a means for rigidly fixing the position and orientation of a left rear wheel and a left front wheel of said wheelchair with a second side frame assembly;
a means for securing a right scissor linkage pivot to a rearward portion of said first side frame assembly and left scissor linkage pivot to a rearward portion of said second side frame assembly;
a means for pivotally securing a right pivot linkage to a forward portion of said first side frame assembly with a first lateral pivot and pivotally securing a left pivot linkage to a forward portion of said second side frame assembly with a second lateral pivot;
a means for pivotally securing a first scissor linkage between said right scissor linkage pivot on one end, and said left pivot linkage with a first forward pivot on an opposing end of said first scissor linkage, maintaining all pivot axis in an approximately parallel manner, thereby facilitating coplanar rotation of said first scissor linkage and said left pivot linkage;
a means for pivotally securing a second scissor linkage between said left scissor linkage pivot on one end, and said right pivot linkage with a second forward pivot on an opposing end of said second scissor linkage, maintaining all pivot axis in an approximately parallel manner, thereby facilitating coplanar rotation of said second scissor linkage and said right pivot linkage;
a means for pivotally securing said first scissor linkage to a second scissor linkage with a central pivot located approximately midway between, and parallel to, said pivot axis of said scissor linkage pivots and said forward pivots;
a means for pivotally securing a lateral end of a left release cross member to said first scissor linkage between, and parallel to, said pivot axis of said central pivot and said left forward pivot;
a means for pivotally securing a lateral end of a right release cross member to said second scissor linkage between, and parallel to, said pivot axis of said central pivot and said right forward pivot; and,
a means for pivotally securing a release shaft to a medial end of said right release cross member and said left release cross member, such that a displacement to said release shaft in a forward direction causes said release cross members apply force to said scissor linkages in a medial direction, effecting said scissor linkages to close, thereby causing the distance between said first side frame assembly and said second side frame assembly to decrease, and that a displacement to said release shaft in a rearward direction causes said release cross members apply force to said scissor linkages in a lateral direction, effecting said scissor linkages to open, thereby causing the distance between said first side frame assembly and said second side frame assembly to increase.