Abstract:
A dynamic chair providing automatic motion in a seat. The chair has bottom, a support means disposed between the base and the seat bottom, a drive motor. A first drive wheel driven by the drive motor has a first mounting point offset from a first distance from the center of the first drive wheel; a second drive wheel driven by the first drive wheel, the second drive wheel having a different diameter from the diameter of the first drive wheel; and a crankshaft having a first crankshaft end and a second crankshaft end, the first crankshaft end connected to the second drive wheel and rotatably driven by the second drive wheel, the second crankshaft end having an eccentric providing a second offset mounting point offset from a second distance from the center of the second crankshaft end.

Description:
RELATED APPLICATION 
     This application is a Continuation-in-Part of co-pending patent application Ser. No. 11/333,948, filed Jan. 17, 2006, which is a Continuation of patent application Ser. No. 11/088,011, filed Mar. 22, 2005, now issued as U.S. Pat. No. 7,008,017, which claims priority to U.S. Provisional Patent Application Ser. No. 60/581,099, filed Jun. 16, 2004, the entirety of are hereby incorporated by reference herein. 
    
    
     FIELD 
     The present invention relates broadly to chairs having powered motion. Specifically, the present invention relates to a chair seat that travels through a preferred range of motion to distribute pressure over a large area beneath a seated person and to induce dynamic motion in the lower back of a seated person. 
     BACKGROUND 
     In a seated position, a very small area under the buttocks supports the majority of a person&#39;s weight. In this small area, capillaries and soft tissue are compressed. Blood circulation is restricted and soft tissue is put under stress. Prolonged sitting over time can damage the tissue being compressed. The simple solution is to avoid sitting for prolonged periods, but such a solution is not realistic for many people who must sit for prolonged periods to perform many necessary functions such as driving or working. 
     Two major factors that contribute to the physical detriments described above are time and compressive pressure. Reducing one or both of these factors reduces the stress on the soft tissue. If the compressive pressure under the buttocks is shifted back and forth between two locations, then the duration of compressive pressure experienced at one position is reduced by half. This would allow some measure of periodical relief of the pressure points. If the compressive pressure point could be rotated between several positions over time, then the time of tissue stress at each position can be further reduced. As the number of pressure points is increased, the period of stress is reduced at each pressure point. In order to obtain the maximum number useful pressure points, the pressure points need to be evenly distributed over the entire buttocks area. 
     One solution to this problem is a seat that tilts in two dimensions with a pivot that is located under the center of the seat. Such a seat can continuously rotate in a circular manner, thus distributing pressure over a large number of pressure points, as shown in the motion path illustrated in  FIG. 1 . The problem with this method is that all pressure points are limited to only one circular path under the buttocks area. This simple motion path misses the majority of possible pressure point locations. 
     U.S. Pat. No. 5,976,097 to Jensen and U.S. Pat. No. 5,113,851 to Gamba both disclose a chair having a seat that is permanently tilted at a fixed angle with respect to the center of the seat. The chair seat is motor-driven to rotate this tilted fixed angle in a circular manner with respect to the center of the seat. It is important to point out that the seat does not rotate. It is the seat&#39;s tilting fixed angle that rotates around the center of the seat. The direction of this circular tilting motion remains constant and the circular tilt pattern repeats identically on each rotation. Since the seat is always tilted, the seat needs to be always in motion or a seated person will be sitting in a twisted fashion, trying to compensate for the static, tilted nature of the chair. While the purpose of the chairs described in Jensen and Gamba is to prevent sitting in a static position and thus holding the same posture for prolonged period of time, sitting in these chairs requires continuous posture adjustments.  FIG. 1  illustrates a graphical plot of the circular tilted motion generated by the chairs described in Jensen and Gamba. At location  1 , seat  10  is tilted backwards only, as shown in  FIGS. 2A and 2B . At location  2  of  FIG. 1 , seat  10  is tilted to the right side only, as shown in  FIGS. 3A and 3B . At location  3  of  FIG. 1 , seat  10  is tilted to the right and tilted forward, as illustrated in  FIGS. 4A and 4B . At location  4  of  FIG. 1 , seat  10  is tilted forward only, as shown in  FIGS. 5A and 5B . For seat  10  to be level, as shown in  FIGS. 6A and 6B , seat  10  travels through a path taking it through location  5  of  FIG. 1 . But because the seats of Jensen and Gamba rotate at a fixed angle, they never pass through this horizontal position. 
     While Jensen and Gamba both address part of the problem described above, and it is desirable for a seated person to change posture and not sit in a static position for extended periods of time, it is not desirable to be forced to make continuous postural changes while seated over prolonged periods of time. Due to the fixed angle of the chairs described in Jensen and Gamba and their inability to ever become level, these seats always need to be moving, thus requiring constant posture changes for a seated person, and the seat cannot be used as a regular level chair. Also, neither Jensen nor Gamba disclose or suggest any manner in which the seat can be easily stopped, or how the seat can be stopped periodically. 
     U.S. Pat. No. 6,033,021 to Udo discloses a self-tilting seat that utilizes two independent, unsynchronized tilting mechanisms to generate a path from two separate motors. There is no disclosure in Udo for detecting a level position. If a level position of the seat is ever reached it is achieved randomly, and not in a repeatable manner, as the two independent tilting mechanisms are not synchronized. There is a heartfelt need for a dynamic chair having a repeatable and deterministic motion path to generate a known range of postural changes to alleviate compressive pressure at as many pressure points as possible. 
     SUMMARY OF THE INVENTION 
     The present invention provides a dynamic chair having a deterministic motion path that allows a variety to different paths to be selected depending of needs of user. By changing the ratio between drive wheels that control the pitch, roll and yaw of the seat, motion paths can be selected to help a person assume and/or avoid certain postures while seated. Embodiments of the present invention move the seat of the dynamic chair through a deterministic path to dictate how often and when the seat is in a level position with respect to pitch and roll. 
     The present invention provides a dynamic chair providing automatic motion in a seat. The chair includes a Chair seat, a Motor Drive, a motorized dynamic Tilting and rotating Assembly, a backrest, two stationary arm rests, a manual tilting mechanism, a chair adjustable center post, chair base and a Microcomputer Controller. The seat is attached to the top of the Dynamic Tilting and rotating Assembly. Under the Dynamic tilting and rotating assembly is the manual tilting and height adjustment mechanism. The stationary member of the manual chair tilting and height adjustment mechanism is connected to the chair&#39;s adjustable center post, and backrest. The tilting member of the manual chair tilting and height adjustment mechanism is connected to the chair&#39;s two arm rests. The center post bottom is attached to the chair&#39;s wheeled base. The motorized chair tilting and rotating assembly consist of a back tilting assembly and a front tilting and rotating assembly. The front tilting assembly is driven by the motor drive through a first roller chain. A second roller chain connects the front seat tilting and rotating assembly to the back tilting assembly. The second roller chain connects the front ratiometric drive wheel to the back ratiometric drive wheel. A ratiometric drive wheel is a fixed drive ratio between two such wheels. These two ratiometric drive wheels are configured in a none equal ratio of diameters within a range of 20.0:1.0 and 1.0:20.0, such that a changing, substantially ellipsoidal tilting pattern of movement is produced in the seat. 
     The back tilting assembly has a first distance, which is the difference between the high, and low points on a cam. The front tilting and rotational assemble has a second distance which is the sum to the first and second offset points to the center of the two eccentrics respectfully. The first distance determines a range of pitch of the seat&#39;s first rotational degree of freedom. The seat&#39;s first rotational degree of freedom, pitch, is a front to back tilt. The second distance determines a range of roll and yaw of the seat&#39;s second and third degree rotational degree of freedom respectfully. The seat&#39;s second and third rotational degree of freedom is tilt left to right and clockwise to counterclockwise rotation with respect to the center of the front tilting and rotating assembly. The first, second and third ranges of rotational freedom are within −5 degrees to +5 degrees. 
     In an embodiment, the chair has a tilting plane, which is a fixed vertical distance below the seat on center of the axes of rotation of the front tilting and rotational assembly, i.e. pivot point. The seat bottom is attached in two locations to the chair front tilting and rotational assembly and at one location on the back tilting assembly. When the seat moves in the first and second degree of rotational freedom, i.e. roll and pitch, this fixed vertical distance produces a first degree of linear freedom of horizontal movement for the seat and a second degree of linear freedom of horizontal motion for the seat. The first degree of freedom of linear motion orthogonal to the second degree of freedom of linear movement. The length of the fixed distance determines a radial distance from the pivot point in the chair tilting assembly to the seat, so that as the chair tilting assembly rotates, the radial distance and a rotational angle of the pivot point determine a first linear travel distance for the first degree of freedom of linear motion and a second linear travel distance for the second degree of freedom of linear motion. The horizontal distances of the linear travel of the seat is within range of +/−1.0 inch. 
     In an embodiment, the front ratiometric wheel is connected to a drive shaft with an eccentric attached at each end of the drive shaft. The two eccentrics offset points are by opposed 180 degrees. Each eccentric is connected to a rod end. The two rod ends are connected the bottom of seat at a front right and front left location. The back ratio metric drive sprocket is attached to a cam that rides on a cam follower. The cam is connected to the bottom of seat at back center, thorough a tilt arm, tilt bearing and tilt bearing guide. The motion produced is essentially a series of changing ellipsoidal tilting patterns of movement, such as a Lissajou pattern, with an oscillation clockwise and counterclockwise yaw motion of the seat. 
     In various embodiments, the dynamic chair of the present invention can include a motor speed controller that controls the rotational speed of the motor drive wheel, a motor timer that provides periodic motor stop time, and a plurality of level sensors that indicate that the seat is level with respect to pitch and roll so that the chair motion can be temporarily halted when the seat is level. A seat occupied sensor is used to enable the drive motor when the chair is occupied and stop the drive motor when the seat is empty. The useful speed range of the seat is between 0.1 rpm and 20 rpm. 
     In an embodiment a microcomputer may be employed to run a user-selected series variable motion speed and motion direction programs. 
     In an embodiment as the seat tilts and rotates the backrest and two armrests are stationary. 
     Many other features and advantages of the present invention will be realized upon reading the following detailed description, when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a graphical plot of a range of motion in an existing chair. 
         FIGS. 2A and 2B  illustrate a profile view and elevation view, respectively, of a position of an existing chair that corresponds with a point on the plot of  FIG. 1  and  FIG. 11 . 
         FIGS. 3A and 3B  illustrate a position of an existing chair that corresponds with a point on the plot of  FIG. 1   
         FIGS. 4A and 4B  illustrate a profile view and elevation view, respectively, of a position of an existing chair that corresponds with a point on the plot of  FIG. 1  and  FIG. 11   
         FIGS. 5A and 5B  illustrate a profile view and elevation view, respectively, of a position of an existing chair that corresponds with a point on the plot of  FIG. 1  and  FIG. 11 . 
         FIGS. 6A and 6B  illustrate a profile view and elevation view, respectively, of a position of a chair that corresponds with a level point on the plot of  FIG. 1  and  FIG. 1 . 
         FIG. 7  illustrates the dynamic chair of the present invention. 
         FIG. 8A  illustrates a front bottom view of the motor driven tilting assembly without seat. 
         FIG. 8B  illustrates a top side view of the dynamic chair without seat. 
         FIG. 8C  Illustrates a side top view of the dynamic chair with seat attached. 
         FIG. 9A  illustrates the front tilting and rotating assembly at 0 degrees. 
         FIG. 9B  illustrates the tilting and rotating assembly at 90 degrees. 
         FIG. 9C  illustrates the front tilting and rotating assembly at 180 degrees. 
         FIG. 9D  illustrates the right left tilting and rotating assembly at 270 degrees. 
         FIG. 10  illustrates the motor drive assembly and sensors connected to the chair electronic controller. 
         FIG. 11  illustrates a motion path of six cycles of the dynamic chair of the present invention when configured with drive wheels having a 7:6 ratio. 
         FIG. 12  illustrates a motion path of the first of six cycles of the dynamic chair configured in accordance with  FIG. 11 . 
         FIG. 13  illustrates a motion path of the second of six cycles of the dynamic chair configured in accordance with  FIG. 1 . 
         FIG. 14  illustrates a motion path of the third of six cycles of the dynamic chair configured in accordance with  FIG. 1 . 
         FIG. 15  illustrates a motion path of the fourth of six cycles of the dynamic chair configured in accordance with  FIG. 1 . 
         FIG. 16  illustrates a motion path of the fifth of six cycles of the dynamic chair configured in accordance with  FIG. 1 . 
         FIG. 17  illustrates a motion path of the sixth of six cycles of the dynamic chair configured in accordance with  FIG. 1 . 
         FIG. 18  illustrates a motion path of 20 cycles of the dynamic chair of the present invention when configured with drive wheels having a 1:20 ratio. 
         FIG. 19  illustrates a motion path of 20 cycles of the dynamic chair of the present invention when configured with drive wheels having a 20:1 ratio. 
     
    
    
     DETAILED DESCRIPTION 
     Directing attention to  FIG. 7 , the present invention provides chair  100  having seat  200  that is manipulated through a large number of different tilting and rotating motion paths. The seat moves in a synchronized motion path employing two or more degrees of freedom, depending on the embodiment. Directing attention to  FIG. 8A , the chair seat motion is driven by gear motor  401  and attached motor sprocket  402  through roller chain  403  to speed modification sprocket  501 . Speed modification sprocket  501  drives front drive shaft  503 , which drives the first ratiometric sprocket  502 . Directing attention to  FIG. 8B , first ratio metric sprocket  502  drives a second roller chair  516 , which is connected, to second ratio metric sprocket  601 . 
     Drive shaft  503  ( FIG. 8A ), is attached to eccentrics  507  and  508 . Rod ends  509  and  510  are attached to eccentrics  507  and  508  respectively at offset points on the eccentrics. The offset points on eccentrics  507 ,  508  are positioned so they are disposed at 180 degrees in relation to each other through connecting drive shaft  503 . Attached to the second end of the rods ends  509 ,  510  are rod end mounts  511 ,  512  respectively which are mounted to the seat bottom  200 . Rod ends  509 ,  510  screw into end rod mounts  511 ,  512  and are adjustable in length. 
     Directing attention to  FIG. 8B , the first ratiometric sprocket  502  drives the second roller chain  516  which drives the second ratiometric sprocket  601 . The second ratiometric sprocket  601  is attached to cam  606  and both are mounted to tilt arm  602  that pivots on drive shaft  503 . Cam  606  rides on cam follower  603 . Cam follower  603  is mounted in a fixed position to manual tilt and height mechanism  703 . When cam  606  rotates, tilt arm  602  moves up and down in an arc of five degrees of motion. 
     Tilt bearing  604  is attached to tilt arm  602  and moves up and down in an arc as cam  606  rotates. Directing attention to  FIG. 8C , tilt bearing  604  rides in seat bearing guide  607 . Seat bearing guide is attached to bottom of seat  200 . Tilt bearing  604  transfers up and down motion to the back of the seat  200  thru seat bearing guide  607 . As the back of seat  200  moves up and down, seat  200  pivots on end rods  509 ,  510  producing a front to back tilting motion of seat  200 . Seat  200  and attached bearing guide  607  are free to move left or right without hindrance from tilt bearing  604 . This is preferred for seat rotation. 
     Directing attention to  FIG. 8B , as shaft  503  rotates 1 cycle or 0 to 360 degrees, seat  200  tilts and rotates, ie. yaw, roll and pitch in the following manor. Directing attention to  FIG. 9A , shaft  503  is rotated to 0 degrees, seat  200  is tilting left with no rotation. In  FIG. 9B , shaft  503  is rotated to 90 degrees; seat  200  is not tilting, but has counter clockwise rotation. In  FIG. 9C , shaft  503  is rotated to 180 degrees; seat  200  is tilting right with no rotation. In  FIG. 9D , shaft  503  is rotated to 270 degrees, seat  200  is not tilting, but has counter clockwise rotation. In  FIG. 9A , shaft  503  is rotated to 360 degrees in which the cycle ends and starts over again. As the repeating tilting cycle continues 0 to 360 degrees, seat  200  rotates clockwise and counterclockwise around a pivot point, which is below seat  200 . Please note, as the seat  200  rotates clockwise/counterclockwise and tilts left/right the seat also is tilting front/back. 
     Directing attention to  FIG. 8B  the ratio between the diameters of the ratiometric sprockets  502 ,  601  determines the motion paths for seat  200  in  FIG. 7 . If the diameters of sprockets  502 ,  601  are equal, a circular tilting pattern occurs and the seat is never in a horizontal position. Thus, in a preferred embodiment, drive wheels  502 ,  601  are of different diameters to generate a periodic path of varying ellipsoidal tilting motions. The number of tilting motion iterations per repeating pattern is determined by the ratio between sprockets  502 ,  601 . If the ratio is not equal the seat of the chair will be horizontal or nearly horizontal a minimum of two times during each period. In a preferred embodiment, the present invention utilizes a ratio of 6:7 between sprockets  502 ,  601 . A useful range of ratios is about 1:20 to about 20:1, excluding the ratio of 1:1. A ratio close to 1:1 will make the number of roll to pitch tilts per repeating motion path more equal. 
     Directing attention to  FIG. 7 , in an embodiment, seat  200  supported by the front tilting and rotational assembly  500  and the back tilting assembly  600 . While in motion, front tilting and rotational assembly  500  allows seat  200  to pivot about a central point located in the center of and at midpoint on drive shaft  503  between rod ends  509  and  510 . A fixed vertical position is the distance between the central point of drive shaft  503  and the top of seat  200  in  FIG. 7 . When the seat moves in the first and second degree of rotational freedom, this fixed vertical distance produces a first degree of linear freedom of horizontal movement for the seat and a second degree of linear freedom of horizontal motion for the seat. The first degree of freedom of linear motion orthogonal to the second degree of freedom of linear movement. The length of the fixed vertical distance determines a radial distance from the pivot point in the chair tilting assembly to the top of seat  200 , so that as the chair tilting assembly tilts, the radial distance and a rotational angle of the pivot point determine a first linear travel distance for the first degree of freedom of linear motion and a second linear travel distance for the second degree of freedom of linear motion. The horizontal distances of the linear travel of the seat is within a range of +/−1.0 inch. 
     In  FIG. 8C , eccentrics  507 ,  508  may have a plurality of off-center mounting points located at different, but equal radii from the center of rotation, to provide adjustments to the magnitude of seat  200  left and right tilt changes, horizontal motion changes, and rotational changes to seat  200 . 
     Directing attention to  FIG. 8B , the offset of cam  606  may have a plurality of offset distances depending of the difference between low and high points on the cam. This variation in offset distances is to provide adjustments to the magnitude of seat  200  back and front tilt changes and horizontal motion changes to seat  200  by linkages i.e. cam  606 , tilt arm  602 , tilt bearing  604  and seat bearing guide way  607  respectively. 
     While in a preferred embodiment, drive wheels  402 ,  501 ,  502 , and  601  are sprockets that are connected by roller chains  403 ,  516  in alternative embodiment drive wheels  402 ,  501 ,  502 , and  601  are pulleys and belts  403 ,  516  In another embodiment, drive wheels  402 ,  501 ,  502 , and  601  can be gears that interface directly with each other, or through intermediate gearing. In yet another embodiment, drive wheels  502 ,  601  be independently powered by separate drive motors that turn drive wheels  502 ,  601  at respective rotational speeds to achieve the same motion paths generated by drive wheels  601 ,  502  having the range of diameter ratios between about 1:20 through 20:1. 
     The motion paths generated in the present invention cause seat  200  to tilt between a level, horizontal position and various tilted positions. The periodic deterministic and repeatable complex motion path generated by the present invention allows seat  200  to tilt in a much larger range of positions than the circular path methods of the prior art. This complex tilting path is illustrated in a graphical plot in  FIG. 11 . As shown in  FIG. 11 , seat  200  is moved in accordance with a Lissajou pattern. To generate the path in  FIG. 11 , a drive wheel ratio of 6:7 was used. This path consists of six cycles. A more detailed graphical representation of each cycle of this path is shown in  FIG. 12  through  FIG. 17 . Directing attention to  FIG. 11  the X indicates the location where seat  200  is level. With a ratio of 7:6 the seat becomes level twice during the six angular path cycles this ratio generates. This ratio metric angular motion path has the ability to reverse direction without reversing the direction of the motor. In  FIG. 13 , the direction of the angular motion changes from clockwise to counter clockwise and reverses again to clockwise in  FIG. 16 . Comparing  FIG. 11  to the angular path of the prior art in  FIG. 1 , it should be obvious the angular path of this invention provides a much larger range of angular motions than the prior art circular motion method. While ratio of 7:6 was used in this invention, a much larger set of other ratios will generate many desirable angular motion paths. Different ratio metric ratios will produce different repeating angular paths and a different number of cycles before the pattern repeats. 
     Directing attention to  FIG. 10 , in an embodiment, motor  401  and the motion of seat  200  are controlled by controller  800 . Controller  800 , which has a variable speed adjustment control  801  connected to motor driver  804 . In an embodiment, motor timer  803 , which provides periods where motion of seat  200  is temporarily suspended. This allows the motion to be stopped for periodic rest times and thus constant postural changes are not required. 
     In an embodiment, the present invention detects when seat  200  is level with respect to pitch and roll. To detect when seat  200  is level, two horizontal seat sensors  806 ,  807  are disposed approximate to first and second level seat detection points  812 ,  811 . Sensor  807  determines when seat  200  is horizontal with respect to left/right tilt. Sensor  806  determines when seat  200  is horizontal with respect to front/back tilt. In an embodiment, sensor  806 ,  807  utilizes a stationary, mechanically activated electrical switch such as a limit switch. Sensors  806 ,  807  are triggered when detection points  812 ,  811 , makes contact with sensors. Microcomputer  805  detects when sensors  806 ,  807  make contact and when sensors lose contact with detection points  811 ,  812 . When level seat sensors both  806 ,  807  make or loses contact within 0.2 seconds of each other, seat  200  is declared level with respect to pitch and roll. spectfully within 0.2 seconds. 
     In an embodiment, when motor timer  803  is in the SEAT ON mode, motor  401  is powered on. When motor timer  703  is in the SEAT OFF mode and horizontal seat sensors  806 ,  807  and microcomputer  805  detects level seat, motor  401  us turned off. The timer allows for periodic no motion time off periods. 
     In an embodiment, microcomputer  805  contains logic that allows an adjustable time interval, starting when a level seat is detected and motor  401  is powered off. This is especially useful for accommodating individual needs such as an injury where the seated person finds comfort in a slightly off-level position. 
     In an embodiment, when seat is empty, spring  809  raises tilt arm  602 , thus lifts cam  606  off of cam follower  603 . When cam  606  is lifted off of cam follower it de-activates seated person sensor  808  and turns off motor. When seat is occupied seated person sensor  808  is activated and enables motor. 
     In an embodiment, the motor  401  may be turned off with switch  810 . This allows the chair to be used as a regular non-moving chair. 
     While in a preferred embodiment, the motor speed is adjustable. With a useful range of seat cycling from 0.1 to 20 rpm. In another embodiment the motor can have a fixed speed, within the above useful range, thus eliminating the motor driver  804  and speed adjustment control  801 . 
     While in a preferred embodiment, the dynamic chair is controlled by a microcomputer controller. In another embodiment the dynamic chair can be controlled by a single on/off switch, thus eliminating all electronic components except the motor  401  and the on/off switch  810 . 
     In a preferred embodiment, Chair motion parameters may be computer controlled using the following programmable parameters: Selection of continuous motion or segmented distance moves with stop periods. Length of distance between stop periods. Length of time during stop period. Programmable speeds over time. Reversing the direction of motion path. Periodic stopping in a level position. Selector switch  802  allows for selection of various motion programs. 
     While the preferred embodiment of the present invention uses a drive wheel ratio of 6:7, reversing this ratio to 7:6 will yield similar results. While chair  100  is illustrated herein as a conventional chair, chair  100  is also particularly useful when incorporated into the design of a wheelchair, and is also useful in vehicles such as automobiles, trucks, airplanes, or other applications where a person remains seated for prolonged periods of time. 
     While the preferred embodiment of the present invention uses two eccentrics  FIG. 8C   507 , 508  with attached rod ends  509 ,  510  and cam  606  to generate motion in the seat  200 , other combination of offset generating means such a different combinations of eccentrics with rod ends, cams and crankshafts cam be employed to generate motion of a chair seat. 
     While various embodiments of the dynamic chair of the present invention have been described and illustrated in detail, it is to be understood that many changes to the embodiments can be realized without departing from the spirit of the invention.