Abstract:
A lift mechanism a power wheelchair includes linear actuators on opposing sides of the chair that provide a space into which a tilt mechanism can nest when the lift mechanism is in its retracted position. The linear actuators perform both the function of operating the lift mechanism and structurally supporting at least a part of the lift mechanism. The lift mechanism and tilt mechanism are each self-contained modules that can be optionally installed into the power wheelchair.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This claims the benefit of U.S. Patent Application Ser. No. 61/792,437 filed Mar. 15, 2013, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. 
    
    
     BACKGROUND 
     This invention relates to personal mobility products and more particularly to aids for lifting and/or seats for people with low mobility. 
     Conventional power wheelchairs for the rehabilitation market often have a power base unit and a seating system that is capable of both tilting the chair and lifting the chair. A tilting capability is useful to manage pressure on the occupant&#39;s skin. A lifting capability is useful to enable the occupant to access heights. 
       FIGS. 15A and 15B  illustrate a lift and tilt system for a power wheelchair from Balle Lift Systems. The system  200  includes a lift frame  202 , a pair of opposing scissors lift mechanisms  204 , a lift actuator  206 , a tilt frame  210 , a tilt mechanism  212 , and a tilt actuator  214 . Each one of the left and right scissor mechanisms has a first leg  220  and a front leg  230  (that is, the lower portion is toward the front). A lower end  232  of front leg  230  is attached to frame  202  at a pivot  234 . A lower end  222  of first or rear leg  220  has a sliding support  224  on frame  202 . 
     When lift actuator  206  operates to lower the lift system from its extended position of  FIG. 15A  to its retracted position of  FIG. 15B , actuator  206  retracts, lower end  222  of scissor rear leg  220  moves rearward (that is, toward the left as oriented in  FIG. 15A ) from the force applied by the actuator and/or by the weight of the occupant. Frame  202  provides the support for lower end  222 —that is, a surface of lower end  222  contacts a surface of frame  202  and bears on it. 
       FIG. 15A  shows the tilt mechanism  212  in an extended position in which tilt actuator  214  is extended relative to tilt frame  210 .  FIG. 15B  showss lift mechanism  204  and tilt mechanism  212  in a fully retracted position. Tilt frame  210  is stacked on top of lift frame  202 . In some embodiments, tilt actuator  214  is offset relative to lift actuator  206  such that the actuators are side by side when in their retracted positions. 
     SUMMARY 
     The inventive aspects of a chair assembly for a power wheelchair include a pair of linear actuators on opposing sides of the chair that provide a space into which a tilt mechanism can nest when the lift mechanism is in its retracted position; a pair of linear actuators that perform both the function of operating the lift mechanism and structurally supporting at least a part of the lift mechanism; and forming the lift mechanism and tilt mechanism into self-contained modules that can be optionally installed into the power wheelchair. The lift mechanism can raise the seating height of the wheelchair for the purpose of putting the occupant near normal eye level or to access elevated objects. The tilt mechanism can move the occupant to a position that relieves pressure on a selected area of the occupant. 
     According to a first inventive aspect, a lift cartridge and tilt cartridge are configured in the wheelchair such that the tilt cartridge and lift cartridge nest when in the retracted position. A chair assembly for a power wheelchair includes: a seat assembly including a seat base and a seat back; a tilt cartridge unit including an actuator, a linkage, and a frame, such that the actuator is configured to tilt the seat assembly in response to a signal from a controller; a lift cartridge unit including left and right actuators and left and right scissor mechanisms, the left actuator operatively coupled to the left scissor mechanism and the right actuator operatively coupled to the right mechanism, each scissor mechanism including first and second scissor legs, the left actuator and left scissor mechanism being located on an opposing side of the chair assembly from the right actuator and right scissor mechanism to define a central space therebetween in which the tilt mechanism nests at least when the tilt cartridge unit is in a retracted position. The lift actuators are configured to vertically lift the seat base, without tilting the seat base, in response to a signal from a controller, and the tilt actuator being configured to tilt the seat base, without lifting the seat base, in response to a signal from the controller. 
     Preferably, each one of the left and right scissor mechanisms includes at least one moveable connection to a portion of the corresponding actuator, and is a linear actuator, such as a power screw that translates a nut, that translates a portion of the first scissor leg. Preferably, the first scissor leg has a translatable end that is affixed to the nut, and the translatable ends of the first legs are supported entirely from the nut and are not supported by the frame, and each one of the second scissor legs has a lower end that is longitudinally fixed by the frame. The linear actuators preferably are oriented parallel to a forward-rearward axis of the chair assembly, especially where the legs are bars that are oriented parallel to the forward rearward axis. 
     As explained more fully below, the tilt cartridge unit can consists of a single module that can be removed from the seat assembly and from the lift cartridge unit as a module. And the lift cartridge unit consists of a single module that can be removed from the seat assembly and from the tilt cartridge unit as a module. 
     A corresponding method of operating a power wheelchair that includes a seat lift feature and a seat tilt feature described above includes the steps of: in response to a signal from a controller, operating a tilt actuator that is part of a tilt unit such that operation of the tilt actuator is capable of tilting a seat base frame; in response to a signal from a controller, operating left and right linear lift actuators such that operation of the actuators operates the left and right scissor mechanisms for vertical movement of the seat base frame, such that upon retraction of the scissor lift mechanisms the tilt unit nests in the space between the lift actuators. The translating step is translating the moveable connection of each one of the left and right scissor mechanisms. 
     According to another aspect, the actuator combines the functional movement of the lift mechanism and structural support for the lift mechanism, including that one of the scissor legs is supported by a translatable element of the actuator without direct support by the frame—in this regard, the translatable element is supported by the screw. A chair assembly for a power wheelchair includes: a tilt cartridge unit including an actuator, a linkage, and a frame such that the actuator is configured to tilt the seat assembly in response to a signal from a controller; a lift cartridge unit including left and right linear actuators and left and right scissor mechanisms on opposing sides of the chair assembly. Each one of the scissor mechanisms includes a left leg and a second leg. An end of the left scissor leg is structurally supported by a translatable element of the actuator without direct support by the frame during operation of the actuator. And the end of the second scissor leg is structurally supported by the frame. The chair includes at least one drive for operating the actuator. 
     In a preferred configuration, the actuator translation is approximately horizontal. In this regard, the frame is usually horizontal or almost horizontal and the actuator translation is most cases is parallel to the frame. Where the actuator is a power screw and the translatable element is a nut, and the end of the first scissor leg is pivotally connected to the nut, each one of the second scissor legs has a fixed leg that is pivotably supported by a frame such that operation of the actuator translates an end of the first leg to extend or retract the scissor mechanisms. Preferably, the opposing the power screws and scissor mechanisms being define a central space therebetween in which the tilt mechanism nests at least when the tilt cartridge unit is in a retracted position. And the linear actuators are oriented parallel to a forward-rearward axis of the chair assembly; the legs may be bars that are oriented parallel to the forward rearward axis. The tilt cartridge unit and consist of a single module that can be removed from the seat assembly and from the lift cartridge unit as a module; and the lift cartridge unit can consist of a single module that can be removed from the seat assembly and from the tile cartridge unit as a module. The lift actuators are configured to vertically lift the seat base, without tilting the seat base, in response to a signal from a controller, and the tilt actuator being configured to tilt the seat base, without lifting the seat base, in response to a signal from the controller. 
     According to another aspect, the tilt mechanism and the lift mechanism each are optional, which enable the wheelchair to be fitted with the appropriate mechanism at the appropriate time according to the occupant&#39;s needs. A power wheelchair having lift and tilt capabilities includes: a power base that includes a frame, wheels, a suspension, at least one motor for driving at least some of the wheels, and a controller; a seat assembly including a seat base and a seat back; an optional tilt module including an actuator, a linkage, and a frame; the tilt module being capable of being connected to the seat assembly as a standalone unit; an optional lift module including at least one motor, left and right actuators and left and right scissor mechanisms, the left actuator operatively coupled to the left scissor mechanism and the right actuator operatively coupled to the right mechanism, each scissor mechanism including first and second scissor legs, the left actuator and left scissor mechanism being located on an opposing side of the chair assembly from the second actuator and second scissor mechanism to define a central space therebetween in which the tilt module is capable of nesting at least when the tilt cartridge unit is in a retracted position. The lift actuator is configured to vertically lift the seat base, without tilting the seat base, in response to a signal from a controller, and the tilt actuator being configured to tilt the seat base, without lifting the seat base, in response to a signal from the controller. 
     The structure of functional components of the tilt module and the lift module are as described as above for the tilt mechanism and the lift mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of a wheelchair assembly of the type that can include a lift mechanism and a tilt mechanism. 
         FIG. 2A  is a view of the lift mechanism and the tilt mechanism combined with the rest of the wheelchair removed for clarity of illustration. The lift mechanism and the tilt mechanism are shown in their retracted positions. 
         FIG. 2B  is a perspective view of the lift mechanism and tilt mechanism in the positions of  FIG. 2A . 
         FIG. 3  is an image of the lift mechanism and the tilt mechanism in their extended positions. 
         FIG. 4  is a side image of the lift mechanism nearly fully retracted and the tilt mechanism extended. 
         FIG. 5  is an image of a portion of the lift mechanism in its extended position. 
         FIG. 6  is a side view of the lift mechanism and the tilt mechanism, each in its retracted position, and showing each in its extended position in relief 
         FIG. 7  is a perspective view of the lift mechanism with the tilt mechanism removed for clarity. The lift mechanism is shown in its retracted position with a portion of the frame removed to show the screw.  FIG. 7  accurately depicts the lift mechanism, except for showing the screw without threads for convenience of illustration. 
         FIG. 8  is a side view of the lift mechanism with the tilt mechanism and some structure of the lift mechanism removed for clarity. The lift mechanism is shown in its retracted position and shown in its extended position in relief. 
         FIG. 9  is a cross sectional view of the lift mechanism with the tilt mechanism and some structure of the lift mechanism removed for clarity. 
         FIG. 10A  is a perspective view of the tilt mechanism shown in its retracted position. 
         FIG. 10B  is another perspective view of the tilt mechanism shown in its retracted position. 
         FIG. 11  is a side view of the tilt mechanism with some structure of the tilt mechanism removed for clarity. 
         FIGS. 12A ,  12 B,  12 C, and  12 D are perspective views of a portion of the tilt mechanism in its retracted position. 
         FIGS. 13A and 13B  are perspective views of a portion of the seat base assembly that is coupled to the tilt mechanism. 
         FIG. 14  is a schematic of the screw mechanism of the lift mechanism. 
         FIG. 15A  is an image of a prior art lift and tilt mechanism in which the tilt mechanism stacks on top of the lift mechanism; 
         FIG. 15B  is an image of the prior art lift and tilt mechanism of  FIG. 15A  shown in its retracted position; 
     
    
    
     DETAILED DESCRIPTION 
     A power wheelchair  10  ( FIG. 1 ) includes a power base  12  and a chair assembly  18 . Power base  12  includes a frame  13 , wheels including a pair of drive wheels  14 , a suspension (not identified by a reference numeral), a pair of motors and drives (not shown in the figures) for powering the drive wheels  14 , a battery pack, and a controller for accepting user input and controlling motors and other wheelchair functions. The battery pack and controller are not shown in the figures. Preferably, power base  12  is conventional, and the present invention encompasses other powerbases, such as bases having four drive wheels and other variations. 
     Chair assembly  18  includes a lift unit  22 , a tilt unit  70 , and a seat assembly  90 , as shown in  FIGS. 2A ,  2 B,  13 A, and  13 B. Seat assembly  90  includes a seat base  92  and a seat back  94 , each of which is pivotable relative to power base frame  13 . Chair assembly  18  defines a main axis A that is horizontal and parallel to a forward-rearward direction of the chair. 
       FIGS. 7 through 9  and  14  illustrate lift mechanism or lift unit  22  separated from other structure for clarity. Lift unit  22  includes a frame  24 , a pair of actuators  26 , a power system  28 , and a lift mechanism  30 . Frame  24  includes lateral structural members, preferably steel, that are parallel to main axis A and transverse members that connect between the lateral members. Frame  24  includes slots or holes  25  for connecting to power base frame  13  by fasteners, such as bolts. 
     The actuators include a first actuator  26   a  and a second actuator  26   b  that are located on opposing sides of chair assembly  18  parallel to main axis A. Actuators  26   a  and  26   b  preferably are oriented horizontally or parallel to the top surface of power base frame  13  for efficient use of space, but the present invention encompasses actuators (not shown in the figures) that are not horizontal and/or not parallel to the top of frame  13 . As shown in the figures, and illustrated in  FIG. 7  by the removal of some structure of the lift mechanism, each of actuators  26   a  and  26   b  preferably is a power screw that includes a screw  32 , a proximal end support  34 , a distal end support  36 , and a nut  38 . 
     As shown in  FIGS. 5 ,  7 , and  14 , proximal end support  34  is located near the rear of seat assembly  90  and distal end support  36  is located forward of the proximal end support  34  such that screw  32  extends forward, but the opposite orientation is contemplated. Each one of supports  34  and  36  are supported on lift system frame  24 . Nut  38  is prevented from rotation such that rotation of screw  32  causes translation of nut  38 . Preferably actuators  26   a  and  26   a  are commercially available acme screws. Throughout the specification, a reference numeral appended with an “a” and a “b” designation generally refers to left and right structures or components. When the specification intends to refer generally to the structure or component without regard to whether it is the left or right one, the reference numeral lacks the appended letter. 
     Power system  28  includes a pair of electric motors  42   a  and  42   b  that are supported on lift frame  24 . The output shafts  44   a  and  44   b  are operatively coupled to the inputs of power screws  32   a  and  32   b . A timing chain  46  runs between opposing sprockets  48   a  and  48   b  that are mechanically connected to the inlet sides of power screws  32   a  and  32   b  to synchronize the operation of screws  32   a  and  32   b . Other drive means and synchronization methods are contemplated.  FIG. 2  shows an option in which both the front and rear of frame  24  each include a pair of electric motors  42   a  and  42   b  and a timing chain  46 . In the embodiment of  FIG. 2 , the power screws extend between the motor assemblies such that each end of each screw is driven. 
     Lifting mechanism  30  includes a pair of opposing scissor mechanisms  50   a  and  50   b , each of which includes a first scissor leg  52  and a second scissor leg  54  that are joined together at pivot  56 . Preferably, legs  52  and  54  are bars that are approximately flat and oriented parallel to the main axis A. First leg  52  includes a lower end  58  that is located rearward from a lower end  60  of second leg  54 . First leg  52  also includes an upper end  62  that is located forward from an upper end  64  of second leg  54 . First lower end  58  is pivotably connected to nut  38  and second lower end  60  is pivotally connected to fixed power screw support  36 , lift frame  24 , or power base frame  13 . Upper ends  62  and  64  are operatively coupled to tilt unit  70  by pivotable or slideable connections to raise and alternately lower tilt unit  70 . 
     Upon supply of electricity from the wheelchair battery pack in response to a signal from the controller, lift motors  42  operate to turn screws  32   a  and  32   b , which are synchronized via timing chain  46 . As screws  32   a  and  32   b  turn, nuts  38   a  and  38   b  translate to move first leg lower ends  58   a  and  58   b  either toward or away from second leg lower ends  60   a  and  60   b  depending on the direction of screw rotation. In this way, scissor mechanisms  50   a  and  50   b  are operated to lower or raise seat base  92  and/or tilt unit  70 . 
       FIGS. 10 through 13  illustrate the tilt mechanism or tilt unit  70 . Tilt unit  70  includes a frame  72 , an actuator  74 , and a tilt mechanism  76 . Frame  72  preferably is formed of structural steel and includes pivotable connections for first scissor leg upper end  62  and a pivotable and slideable connection for second scissor leg upper end  64 . Actuator  74  may be a linear actuator of any type, preferably is electrically powered, and preferably includes proximal end that is attached to frame  72  and a distal end that is attached to lift mechanism frame  72 . 
     Upon supply of power to actuator  74 , tilt mechanism  76  may tilt the seat of wheelchair. As for example shown in  FIG. 12D , elements of the seat base structure  90  are connected to the tilt mechanism structure  76  such that upon movement of actuator  74 , the upper structure of tilt mechanism tilts the seat base structure  90 . In most circumstances, the tilt mechanism is oriented to pivot the occupant rearward or backward from an upright sitting position to a laid back position. 
     Tilt unit frame  72  is coupled to lift mechanism frame  24  to enable tilt unit frame  72  to be removeable from lift mechanism frame  24 . Accordingly, either one of lift unit  30  to tilt unit  70 , or neither, may be fitted into a power wheelchair. The unit  30  and/or  70  may be added by a retrofit. Only conventional fasteners would be required to add either unit to the wheelchair. 
     A preferred embodiment of a lift mechanism and a tilt mechanism has been used to illustrate aspects and advantages of the present invention. The invention is not limited to the specific structure shown or described herein, nor is it required that the invention embody every aspect or advantage described in the specification or claimed. Rather, each claim is intended to be entitled to its full scope.