Abstract:
A wheelchair is provided with a helical drive mechanism. A rectilinear input to the helical drive causes an output gear to rotate, thus providing power to rotate the driving wheels of a wheelchair. The helical drive may include, for example, a compound helix, a drive with a twisted flat bar, or a concentric helix drive. Add-on components may be provided to convert a conventional wheelchair to a wheelchair powered by a helical drive mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 08/771,982, filed on Dec. 23, 1996. This application also claims priority from the following provisional applications: Helical Drive Wheelchair, Lawnmower, and Golf Cart, filed Jun. 9, 1997; In-Line Multi-Gear System for Bicycles and Other Applications, Multiple Multi-Gear Systems, and Shifting Devices, filed, Jun. 20, 1997; Multi-Gear Hub, In-Line Multi-Gear System, and Vehicles, filed Jun. 9, 1997; Helical Drive and Motors, filed Apr. 7, 1997; Helical Drive Vehicles, filed Apr. 8, 1997; Improved Helical Drives, filed Apr. 16, 1997; Helical Fishing Reels, filed Apr. 7, 1997; Multiple Ratio Slotted Helix, filed May 1, 1997; Polycycle filed Apr. 7, 1997; Polycycle II, filed Apr. 17, 1997; Improved Slider and Helical Drives, filed Jun. 9, 1997; and Helical Drive Fitness Equipment, Wench, Contained Mono-Helix Drive, filed Jun. 9, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to wheelchairs. 
     2. Description of the Related Art 
     In a conventional non-motorized wheelchair, when powered by the user, the user must grab a large wheel or a hand rail disposed around the large wheel and push in a forward direction for forward movement. To move straight ahead, the user must simultaneously push the two large wheels, one on either side of the user. To cause the wheelchair to turn right, the user must push only on the large wheel or associated hand rail on a left side of the chair. To make a left turn, the user must push only on the wheel or associated hand rail on the right side of the wheelchair. 
     The motion of pushing the chair requires a certain level of manual dexterity and upper body strength not found in all wheelchair users. Those wheelchair users who lack the required manual dexterity and upper body strength must either have someone push their wheelchair or they must use a more expensive motorized wheelchair. Any speeds, except for very slow speeds, are awkward to obtain. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above problems in the related art and has as its object to provide a wheel chair which can be operated by wheelchair users having less upper body strength and manual dexterity than is required to operate a conventional non-motorized wheelchair. 
     It is further an object of the invention to provide add-on component parts for converting a conventional non-motorized wheelchair to one which requires less upper body strength and manual dexterity to operate than a conventional non-motorized wheelchair. 
     A first embodiment of the invention is a wheel chair having two large wheels. One large wheel is disposed on the left side of the wheelchair and another large wheel is disposed on the right side of the wheel chair. Both large wheels are disposed toward a front portion of the wheelchair. A single smaller pivoting wheel is disposed in a central position of a rear portion of the wheelchair. A helical drive is associated with each of the two large wheels. Each helical drive is powered by a rectilinear motion. Such a motion requires less manual dexterity and upper body strength than that which is required to power a non-motorized conventional wheelchair. 
     A second embodiment is identical to the first embodiment, but instead has two smaller wheels disposed at a rear portion of the wheelchair, one on the left and another on the right. This embodiment has the same advantages as the first embodiment. 
     A third embodiment has four wheels of equal size. The two front wheels are powered by two parallel mounted helical drives. 
     A fourth embodiment provides two helical drives for powering the two large rear wheels of a wheelchair. The two front wheels are small and are not powered. 
     A helical drive is provided which includes a helical member which is a twisted flat bar and a slider. The slider has an opening having the twisted flat bar disposed therethrough. A sliding motion of the slider causes the twisted flat bar to rotate. 
     Two helical drives for powering the wheelchair are on each wheelchair. Each helical drive includes a pinion gear which engages a crown gear. The crown gears are fixed to the drive wheels of the wheelchair, such that rotation of each of the crown gears causes rotation of the respective wheel. 
     Add-on components for converting a conventional wheelchair to one which is powered by a helical drive are provided, thereby gaining the advantages described in the embodiments described above. 
     Other objects and features of the invention will appear in the course of the description which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a first embodiment of a helical drive wheelchair having a single small pivoting wheel disposed in a rear portion of the wheelchair. 
     FIG. 2 is a side plan view of the wheel chair shown in FIG.  1 . 
     FIG. 3 is a top plan view of a second embodiment of the helical drive wheelchair having two small pivoting wheels disposed in a rear portion of the wheelchair. 
     FIG. 4 is a side plan view of the wheelchair shown in FIG.  3 . 
     FIG. 5 is a top plan view of a third embodiment of a wheelchair having four wheels of equal size. 
     FIG. 6 is a side plan view of the wheelchair shown in FIG.  5 . 
     FIG. 7 is a top plan view of a fourth embodiment of a wheelchair having two large wheels driven by helical drives and two small front wheels. 
     FIG. 8 is a side plan view of the wheelchair shown in FIG.  7 . 
     FIG. 9 is a side plan view of the components of an embodiment of a helical drive, as used in FIGS. 1,  2 ,  3 ,  4 ,  7 , and  8 . 
     FIG. 10 is a top plan view of an embodiment of two helical drives including a synchronizing gear and a single crown gear having an axle disposed therethrough, as used in FIG.  5  and FIG.  6 . 
     FIG. 11 is a top plan view of two helical drives including a separate crown gear being engaged by a pinion gear of each helical drive, as used in FIGS. 1,  2 ,  3 ,  4 ,  7 , and  8 . 
     FIG. 12 shows another embodiment. 
     FIGS. 13-16 show other helical drive configurations. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 show a first embodiment of the present invention, a helical drive wheelchair. As shown in the figures, two large wheels  10  are each attached to ends of their respective axles such that the two large wheels  10  protrude from a right and left side of a wheelchair frame  20  close to the front of the wheelchair. A single small pivoting wheel  25  is mounted in a central position of the rear of the wheel chair. 
     A helical drive is disposed on the right and left sides of the wheel chair. Each helical drive  30  is attached to the frame  20  via a rod  40  extending outward from the frame  20  on the left and right sides of the wheelchair, such that each helical drive  30  is disposed on an outer side of a corresponding large wheel  10 . An annular crown gear  50  protrudes outwardly from a hub of each large wheel  10 . The hub is fixedly attached to elongated sections or spokes  52  which extend from the hub to the annular rim of the wheel  10 . Each helical drive  30  has a pinion gear  55  protruding from an end of the helical drive. The pinion gear  55  is disposed in contact with the crown gear  50 , such that rotation of the pinion gear  55  causes the crown gear to rotate, thereby rotating the large wheel. The helical drive  30  has an input device including a handle  60 . Sliding the handle  60  along a slot formed in an outer casing  70  of the helical drive  30  in one direction causes a helical member within the outer casing  70  to rotate, thereby causing the pinion gear  55  to rotate. Moving the handle  60  in the other direction causes the helical drive to free wheel and resets the handle  60 . 
     FIGS. 3 and 4 show a second embodiment of the present invention. As shown in the figures, two large wheels  10  are each attached to ends of their respective axles such that the two large wheels  10  protrude from a right and left side of a wheelchair frame  120  close to the front of the wheelchair. Two small pivoting wheels  125  are mounted on left rear and right rear portions of the frame  120 . Two helical drives  30  are disposed on the right and left sides of the wheel chair. Each helical drive  30  is attached to the frame  120  via a rod  140  extending outward from the frame  120  on the left and right sides of the wheelchair, such that each helical drive  30  is disposed on an inner side of a corresponding large wheel  10 . An annular crown gear  150  protrudes inwardly from a hub portion of each large wheel  10 . Each helical drive has a pinion gear  55  protruding from an end of the helical drive. The pinion gear  55  is disposed in contact with the crown gear  150 , such that rotation of the pinion gear  55  causes the wheel driving gear to rotate, thereby rotating the large wheel  10 . The helical drive  30  has an input device including a handle  60 . Sliding the handle  60  in one direction along a slot formed in an outer casing  70  of the helical drive  30  causes a helical member within the outer casing  70  to rotate, thereby causing the pinion gear  55  to rotate. Moving the handle  60  in the other direction causes the helical drive to free wheel and resets the handle  60 . 
     The first two embodiments show a wheelchair having large wheels disposed toward the front of the wheelchair. However, the large wheels could be disposed toward the rear of the wheelchair and pivoting small wheels disposed toward the front of the wheelchair, as in FIGS. 7 and 8. 
     The embodiments in FIGS. 1,  2 ,  3 ,  4 ,  7 , and  8 , show helical drives directly connected to the drive wheels, and oriented radial to the wheels. However, other orientations are possible, with a linkage connecting the pinion gear of the helical drive with the crown gear on the wheel. The linkage could be, for example, a belt drive, a chain drive, or a drive shaft. For example, the helical drive may be horizontal, parallel to the ground, with a drive shaft connecting the pinion gear on the helical drive to the crown gear on the drive wheel. See for example, in FIG. 12, drive wheel  1201 , and front wheel  1202  are attached to the frame  1203 . Helical drive  1204 , with handle  1205  and pinion gear  1206 , drives wheel  1201 , through drive shaft  1207 . Shaft  1207  connects pinion gear  1206  to annular crown gear  1208  fixed to wheel  1201 . This drive shaft arrangement can also be used in the front wheel drive wheelchair in FIGS. 1 and 2. The helical drive can be installed at any angle. 
     FIGS. 5 and 6 show the next embodiment of the helical drive wheelchair. This embodiment comprises four wheels  200  of approximately the same size. Each wheel has a hub  202  fixedly attached to an end of an axle  204  or  202 . Each hub  202  is disposed in the center of an area defined by an annular rim of the wheel  200 . The hub is fixedly attached to elongated sections or spokes  206  which extend from the hub to the annular rim of the wheel  200 . The front axle  204  is received in an opening formed in two axle receiving sections  208  which are aligned such that the axle  204  passes through the opening formed in both axle receiving sections  208 . An annular crown gear  210  is disposed on a portion of the axle  204  such that the axle  204  is fixedly attached to and disposed through the center of the crown gear. Two parallel helical drives  212 , each having a slidable disposed handle  214 , are disposed such that a pinion gear  216  extending from an end of each helical drive  212  engages the crown gear  210 . The two helical drives  212  include a connecting section  217  which extends between the two helical drives  212  and integrally connects the helical drives  212 . A frame  218  extends from the axle receiving sections  208  toward the rear of the wheelchair. The rear of the frame  218  includes an opening forming a rear axle receiving section (not shown) through which the rear axle  202  passes. Like the front wheels  200 , a hub of each of the rear wheels  200  is attached to an end of the rear axle  202 . A seat  220  is disposed over a rear section of the frame  218  extending to the rear wheels  200 . A seat back  222  extends upward from an end of the seat  220  closest to the rear of the wheelchair such that the seat back  222  forms an angle with the seat  220  which is more than 90 degrees. 
     A seated user of the wheelchair operates the wheelchair by sliding the handles  214  of the helical drives  212 . The sliding motion causes a helical member in each helical drive to rotate. When viewed from a perspective of a person seated in the wheelchair, the right helical drive  212  causes the corresponding pinion gear  216  to rotate in a clockwise direction and the left helical drive  212  causes the corresponding pinion gear  216  to rotate in a counterclockwise direction. The pinion gears  216  engage the crown gear  210  thereby forcing the crown gear  210  to rotate in a forward direction. 
     FIGS. 7 and 8 show the next embodiment of the wheelchair. This embodiment includes two large wheels  224  disposed toward the rear of the wheel chair and two small wheels  226  disposed toward the front of the wheel chair. Each of the wheels has a hub  202  and spokes  206 . Each hub is attached to an axle. The front axle is disposed through openings formed in the frame. Extending outward from the hub of each of the rear wheels  202  is a crown gear  228 . A pinion gear  216  extending from an end of the helical drive  212  is engages the crown gear  228  such that when the pinion gear  216  rotates, the crown gear  228  rotates. 
     FIGS. 7 and 8 show the helical drives  212  and crown gears  228  being disposed on an outside portion of each large wheel  202 . However, the helical drives and crown gears  228  may be disposed on an inner portion of each large wheel  202 , as is the case for the embodiments in FIGS. 1,  2 ,  3 , and  4 . 
     A seated user of the wheelchair slides the handle  214  of each helical drive  212  in an up and down direction causing the helical member in each helical drive  212  to rotate. The rotation of the helical drive shaft thereby causes the corresponding pinion gear  216  to rotate. Each pinion gear  216  rotates in a manner such that the crown gear is engaged to rotate in a forward direction. As a result, the two large wheels  202  are thereby forced to rotate in a forward direction causing the wheel chair to move forward. 
     FIG. 9 illustrates a helical member  230  disposed within the helical drive. The helical member  230  comprises a twisted flat bar. A slider  232  forming a thin rectangular opening has the helical member  230  disposed therethrough. One end of the helical member  230  is disposed within a mounting bracket  234 . The other end of the helical member  230  is disposed within a roller clutch  236 . An rod extends from another end of the roller clutch  236  and is disposed within a center of a pinion gear  216 . An outer rim of the pinion gear engages the crown gear  238  such that rotation of the pinion gear  216  causes rotation of the crown gear  238 . Thus, sliding of the slider  232  along a length of the helical member  230  causes the helical member  230  to rotate, thereby rotating the pinion gear  216  and the crown gear  238 . 
     FIG. 10 shows an embodiment of a helical drive arrangement suitable for use with a helical drive wheelchair embodiment in FIGS. 5 and 6. Two helical drives are shown. Each helical drive  212  includes the helical member  230 , a roller clutch  236 , a mounting bracket  234 , and a slider  232  disposed in the manner shown in FIG.  9  and previously discussed. A handle  240  is attached to the slider  232 . An end of each of the helical drives  212  have a pinion gear. Disposed between the two pinion gears  216  is a single crown gear  238  such that each pinion gear  216  is engages the crown gear  238 . An axle is disposed through an opening in the crown gear  238  and is fixedly attached to the crown gear  238 . Extending from each mounting bracket  234  is a rod  242 . The rod  242  extends through a center of an output gear  244 . A synchronizing gear  246  is disposed between the two output gears  244 . A rod  248  is disposed through the center of the synchronizing gear  246 . A flange  250  is formed near each of the two ends of the rod  248 . A pull cable is attached to one end of the rod facing away from the crown gear  238 . A spring  254  is disposed around a section of the rod between the synchronizing gear  246  and the flange  250  closer to the pull cable  252 . 
     The helical drive  212  operates in the same manner as discussed previously. The synchronizing gear serves to preserve a relationship between the movement of a handle  240  of one helical drive with the movement of another handle  240  of the other helical drive  212 . By pulling on the pull cable  252 , readjusting the position of the handles  240 , and releasing the pull cable  252 , the relationship between the handles  240  can be altered. 
     FIG. 11 shows two helical drives  212  which are similar to the helical drives shown in FIG.  10 . The pinion gear  216  of each helical drive  212  is engages a separate crown gear  256 . An axle  258  is disposed between the two crown gears  256 . This is the same helical drive used in the helical drive wheelchair shown in FIGS. 7 and 8. 
     Sliding the handles  258  cause corresponding helical members  230  to rotate. The rotation of the helical members  230  cause the corresponding pinion gears  256  to rotate engaging the corresponding crown gears  256 , thereby causing the crown gears  256  to rotate. 
     The helical drive provides a constant torque to the wheels of the wheelchair. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention is not limited to the specific details and representative devices shown and described herein. Accordingly, various modifications to the embodiments of the invention may be made without departing from the spirit or scope of the invention as defined by the appended claims and their equivalents. 
     Also any embodiment may use other configurations of helical drives, such as, for example, a compound helix, or a concentric helix, or a contained helix. Also, motorized helical drives may be used. 
     Transmissions may be provided in the wheel chairs. Multi-gear hubs on the drive wheels may be used, or currently found on some bicycles. Or helical drive mechanisms can be used with in-line transmissions. 
     The wheel chairs of the present invention can be operated in reverse in the conventional manner, by the user manually grabbing the drive wheels and rotating them backwards manually, allowing the helical drive mechanisms to free-wheel. Alternatively, reverse gears can be installed in the helical drive mechanisms to allow helical driven reverse movement. 
     The helical drives shown herein deliver power only when the handle is used in one direction, and free-wheel when the handle is moved to reset in the other direction. However, other helical drives can be used, that give power in the same direction, when the handle is moved in both directions, such as the concentric helical drive and compound helical drive. 
     FIG. 13 shows a compound helix drive for powering a helical wheelchair. A first cylindrical screw  200  is disposed closer to an output gear  220  and a second cylindrical screw  210  is disposed further from the output gear  220 . In this embodiment, each cylindrical screw  200 ,  210  is a cylindrical tube with a groove  230  extending in a spiral around the cylindrical tube and along a length of the cylindrical tube. The groove  230  on the first cylindrical screw  200  extends in a direction opposite to the direction of the groove  230  on the second cylindrical screw  210 . Extending through the first and the second cylindrical screws  200 ,  210  is an axle  240 . Two roller clutches  245  are mounted on the axle  240  such that the axle  240  passes through the center of each of the two roller clutches and an outer rim of a respective roller clutch is in contact with an inside surface of a corresponding one of the cylindrical screws  200 ,  210 . A sleeve  255  of an input device is slidable disposed along the outer surface of the cylindrical screws  200 ,  210 . Two input shafts  248  extend from an inside surface of the sleeve  255  facing toward a respective one of the cylindrical screws  200 ,  210 . An end of each input shaft  248  is slidable disposed within a respective groove  230  of a corresponding cylindrical screw  200 ,  210 . An input device handle  260  extends outward from an outside surface of the sleeve  255  and passes through a slot (not shown) formed on the outer casing (not shown). The slot extends along a side of the outer casing in a direction parallel to the lengthwise direction of the two cylindrical screws  200 ,  210 . A bearing  275  is disposed around a first end of the axle  240  close to the output gear  220 . The outer surface of the bearing is in contact with an inner surface of the first cylindrical screw  200 . The first end of the axle  240  is disposed within a hole formed in the center of output gear  220 . A second bearing  275  is disposed around the axle  240 , such that the outer surface of the second bearing is in contact with an inner surface of the second cylindrical screw  210  close to an end of the second cylindrical screw  210  opposite to an end closer to the output gear  220 . The second bearing  275  is attached to an end cap (not shown), which, in turn, is attached to an inside end of the outer casing (not shown). A third bearing  275  is disposed around the axle  240 , such that the outer surface of the third bearing is in contact with an inner surface of the first cylindrical screw  200  close to an end of the first cylindrical screw  200  opposite to an end closer to the output gear  220 . A fourth bearing  275  is disposed around the axle  240 , such that the outer surface of the fourth bearing is in contact with the inner surface of the second cylindrical screw  210  near an end of the second cylindrical screw  210  closer to the output gear  220 . 
     Moving the handle  260  of the input device from a position within the slot in the outer casing further from the output gear  220  to a position within the slot of the outer casing near the output gear causes the input shafts  248  attached to the inner surface of the sleeve  55  to move along the grooves  230  of the first and second cylindrical screws, thereby forcing the second cylindrical screw  210  to move in a clockwise (when viewed from a direction of the output gear  220 ) and the first cylindrical screw  200  to move in a counterclockwise direction. Moving the input device across the slot of the outer casing in an opposite direction forces the first and second cylindrical screws  200 ,  210  to rotate in an opposite direction. When each of the two cylindrical screw rotates in the clockwise direction, the roller clutch  245 , which is in contact with a corresponding cylindrical screw  200 ,  210  will cause the axle  240  to remain stationary. Thus, the corresponding cylindrical screw  200 ,  210  is said to be free-wheeling and not producing any torque. When each of the two cylindrical screws  200 ,  210  rotates in a counterclockwise direction, the roller clutch  245 , which is in contact with a corresponding cylindrical screw  200 ,  210 , will cause the axle  240  to rotate in the counterclockwise direction. The rotation of the axle  240  in the counterclockwise direction causes the output gear  220  to rotate in a counterclockwise direction. 
     FIGS. 14,  15 , and  16  illustrate a concentric helix drive for a wheelchair. Only the differences from the previous embodiment of a helical drive, shown in FIG. 13, shall be discussed. 
     Instead of two cylindrical screws as shown in FIG. 13, this embodiment includes a left-handed (or “LH”) slotted helix cylinder  330  and a right-handed (or “RH”) slotted helix cylinder  335 , both disposed within an outer casing  325 . The RH slotted helix cylinder  335  is disposed within the LH slotted helix cylinder  330 . A stationary shaft  340  is disposed through a longitudinal hole formed through the RH slotted helix cylinder  335  and protrudes from two ends of the RH slotted helix cylinder  335 . An annular carrier  77  is disposed around a portion of the stationary shaft  340  extending beyond an end of the RH slotted cylinder  335 . A bearing  375  is disposed around another portion of the stationary shaft  340  protruding beyond another end of the RH slotted cylinder  335 . The bearing  375  has an annular portion disposed in contact with an inner surface of the LH slotted cylinder  330 . A roller clutch  345  has an outer surface disposed in contact with the inner surface of the LH slotted helix cylinder  330 . The roller clutch  345  is disposed around the carrier  377 . A bearing  375  is disposed around the stationary shaft  340  near an end of the RH slotted helix cylinder  335  further from the output gear  320  and contacts an inner surface of the RH slotted helix cylinder  335 . A roller clutch  345  is disposed around the stationary shaft  340  near another end of the RH slotted helix cylinder  335  closer to the output gear  320  and contacts an inner surface of the RH slotted helix cylinder  335 . An input device comprises a cylindrically-shaped sleeve  350  having a hole formed in a longitudinal direction. The stationary shaft  340  is disposed through the hole formed in the sleeve  350 , such that the sleeve  350  is slidable disposed along the stationary shaft  340 . An input shaft  355  of the input device extends from an outside surface of the sleeve  350  such that the input shaft  355  is disposed at an angle substantially perpendicular to the stationary shaft  340  and passes through a slot  365  formed in the outer casing  325  and extends in a lengthwise direction along a length of the outer casing  325 . A shaft roller  357  is disposed on the input shaft  355  such that the shaft roller  357  is slidable disposed in contact with the RH slotted helix cylinder  335 , Another shaft roller  357  is disposed on the input shaft  355  such that the shaft roller is slidable disposed in contact with the LH slotted helix cylinder  330 . An output sleeve  379 , with two ends, has one end disposed through an opening in a central portion of a bearing  375  which is attached to a central portion of an output gear  320 . The output sleeve  379  extends from the end near the output gear  320  through a central portion of the roller clutch  345  disposed within a central portion of the carrier  377 . 
     Moving the input shaft  355  in a direction toward output gear  320  causes the LH slotted helix cylinder  330  to rotate in a clockwise direction, when viewed from an end of the helical drive having the output gear  320 , and causes the RH slotted helix cylinder  335  to rotate in a counterclockwise direction. Moving the input shaft  355  in a direction away from the output gear  320  causes the LH slotted helix cylinder  330  to rotate in a counterclockwise direction and the RH slotted helix cylinder  335  to rotate in a clockwise direction. When either the LH slotted helix cylinder  330  or the RH slotted helix cylinder  335  is rotated in the clockwise direction, the respective roller clutch  345  causes the output sleeve  379  to rotate in the clockwise direction. When the output sleeve  379  rotates in the clockwise direction, the outer rim of the output gear  320  rotates in the clockwise direction.