Abstract:
A quick release detachable wheel hub assembly is shown for a lightweight manual wheelchair. The wheelchair wheels mount on exterior hubs and rotate therewith. The inner face out of each of the exterior hubs mates with an opposing outer face of interior hubs. One of the opposing faces on the hubs has a projection or a plurality of projections which fit snugly into corresponding openings on the opposing face of the other hub when the opposing faces of the hubs are mated. The interior hubs are mounted and rotate on detachable axles which screw into the wheelchair frame. A quick release, removable locking pin is inserted through the center of the hubs and into detachable axle and locked in place and thereby causing the hubs to be locked and rotate together. The wheels are quickly detached by simply removing the locking pins and pulling apart the hubs.

Description:
This is a divisional patent application based on U.S. Continuation patent application Ser. No. 10/154,356 filed on May 23, 2002, now a U.S. Pat. No. 6,634,665 B2 issued Oct. 21, 2003. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to the field of wheelchairs and, more specifically, to an electrical braking system and quick release, detachable wheels for manual wheelchairs. 
   2. Description of the Related Prior Arts 
   Numerous types of braking mechanisms for manual wheelchairs are known in the art. The most typical manual wheelchair brake is a manual “over center” locking device which is activated by a lever arm and, when forced into its locking position, presses a braking member against the surface of the wheelchair tire creating a frictional braking action. Several factors mitigate against the usefulness and reliability of these types of brakes. Loss of tire pressure reduces the frictional force exerted by the crossbar on the tire and hence reduces the braking effect. A significant air pressure loss leaves these brakes useless. During transfer in and out of the chair, this type of brake allows the tire to slide underneath the crossbar and the wheelchair to move. Similarly, the brakes are ineffective and will not adequately hold the wheelchair on an incline. Other types of manual brakes include caliper type brakes manually activated with a lever arm mounted to a cable and brake assembly causing brake pads to press against the rim of the wheelchair wheel. 
   In these types of brakes, the frictional braking force exerted is directly related to the manual force which must be exerted on the lever arm by the brake operator to activate the brake. Wheelchair users who have arm or hand limitations may not be physically able to operate these brakes. These braking mechanisms only apply a braking force to one wheel. If an equal braking force is desired on both wheels, the user is required to use both arms and attempt to apply an equal force to both lever arms at the same time. This is difficult, if not impossible. Wheelchair frame and wheel design most often require the placement of the lever arms on the frame of the wheelchair near the user&#39;s knees. The placement of these lever arms interferes with the user&#39;s transfer in and out of the wheelchair. These lever arms require lifting the user&#39;s body in order to clear the lever during transfer. 
   A patent to Ross and Gunther, U.S. Pat. No. 5,358,266 describes a plate attached to a braking member, which applies a braking frictional force to the wheelchair tire when electronically activated by a solenoid rod. The solenoid rod is activated by means of a switch attached to the seat of the wheelchair. When the wheelchair user is raised out of the seat, the switch is activated and operates the braking mechanism. Also disclosed in this patent is a manually activated lever arm to operate the same braking member when the wheelchair user is seated. The same deficiencies discussed above apply to this wheelchair while the wheelchair user is seated. A wheelchair user with arm or hand limitations may not be able to operate the hand lever and the lever arm braking mechanism to apply a braking force to one wheel. In addition, the position of the lever arm may interfere with transfer in and out of the wheelchair. 
   Electric wheelchairs with various forms of braking means are common in the prior art. These braking means include gear reduction mechanisms, electromagnetic braking by means of a resistance applied to the electric motors, electronically activated frictional braking mechanisms where a solenoid is electrically energized to move brake shoes into frictional contact with a brake drum, and conventional manual brakes operated by a lever mechanism. These electric wheelchairs are heavy, cumbersome, difficult to transport, and do not promote physical activity by the user. 
   Wheelchair users have reason to frequently remove the wheels from their wheelchairs. It is often done for storage purposes, for brake adjustment, for wheel repair, and for wheel exchange. For example, in order to store a wheelchair in a vehicle, it is often desirable to remove the wheels. 
   Heretofore, the wheels on manual wheelchairs and other types of wheelchairs have been attached to the wheelchair frame by some type of hub with the wheels secured to the hub with nuts and bolts. In order to remove the wheels from the wheelchair, it has been necessary to unscrew and remove each of the nuts and bolts securing the wheel to the hub. This is a time consuming and cumbersome process. Once again, wheelchair users who have arm or hand limitations may not be physically able to remove the nuts and bolts. 
   More recently, it has become common in the art to attach wheels to manual wheelchairs using quick release locking pins which hold the wheel to the axle. In this type of design, it is difficult to also have a braking means on the wheelchair wheel other than the manual “over center” locking device which presses a braking member against the surface of the tire as described herein. Heretofore, other brakes have been ineffective on wheelchairs with quick release locking pins because the braking means had to be released and moved or disassembled in order to remove the wheel and thereby defeating the purpose of the quick release locking pin. 
   It is desirable to have a lightweight, manual wheelchair with an effective easily operatable electronic braking mechanism and, at the same time, quick release detachable wheels. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to provide an electronically activated braking system for a lightweight, manual wheelchair, which allows the wheelchair to maintain its lightweight and maneuverability characteristics. 
   It is a further object of this invention to have an electronically activated braking system for manual wheelchairs which eliminates the need for users of the wheelchair to manually operate brakes by means of a lever mechanism. 
   It is a further object of this invention to provide a braking system for manual wheelchairs, which provides equal braking force to both wheels of a wheelchair simultaneously. 
   It is a further object of this invention to provide a braking means for a manual wheelchair, which can be activated without the use of a manually operated lever that interferes with transfer in and out of the wheelchair by the user. 
   It is a further object of this invention to provide a braking means for manual wheelchairs, which eliminates movement of the wheelchairs on inclines and during transfer in and out of the wheelchair by the user. 
   It is a further object of this invention to provide a braking means for manual wheelchairs, which allows for detaching the wheelchair wheels without disturbing the braking means. 
   It is a further object of this invention to provide for quick release, easily detachable wheels. 
   It is a further object of this invention to provide for detachable wheels, which eliminates the need for users of the wheelchair to unscrew numerous nut and bolt combinations in order to remove the wheel. 
   It is a further object of this invention to provide for quick release, easily detachable wheels which allow the wheels to be removed without removing the disk and brake assembly. 
   In order to achieve these objectives, this invention provides for an electronic braking system, which is comprised of a braking means, a cable pulley system for activating the braking means, a DC liner actuator with actuator rod connected to the cable pulley system, a motion limit switch, a rechargeable twelve-volt battery electronically connected to the DC actuator, and a double throw control switch electronically connected to the battery for activating the battery power. 
   It is anticipated that the preferred braking means is a caliper-type brake positioned to clamp onto a metal disk mounted axially to a hub which rotates on the axle of each wheelchair wheel. The hub on which the disk is mounted interlocks with the hub on which the wheelchair wheel is mounted. The interlocking hubs are locked together with a locking pin, which extends axially through the center of the mated hubs such that the hubs are locked and rotate together when the wheelchair wheel is turned. 
   The locking pin is equipped with retractable nipples which, when extended, hold the locking pin securely in place. The retractable nipples are spring biased in the extended position and are activated by a push button at one end of the locking pin which releases the spring and allows the nipples to retract. When the nipples are in the retracted position, the locking pin can be removed simply by sliding it out of the axle. This allows the wheelchair wheel to be removed since there is no longer anything holding the mated hubs together. 
   The braking means for each wheel are connected to opposite ends of a cable wire. The cable wire passes around a pulley such that displacement of the pulley provides equal force and displacement to said opposite ends of the cable wire. The ends of the cable wire are directed through small openings in a mounting bracket. The openings are spaced a distance equal to the diameter of the pulley so the cable wire remains parallel as it extends from the pulley through said openings. A circular pulley cap is placed concentrically over the pulley. The vertical side of the pulley cap has two openings to allow for the passage of the wire cable into the pulley cap through the first opening, around the pulley and out the second opening. The pulley cap, pulley, and cable wire assembly is then connected to the outer end of the actuator rod by a coupling bracket. 
   The DC linear actuator is mounted on the wheelchair in a manner to allow the actuator rod to extend and displace the pulley and cable wire in line with the actuator rod&#39;s axis. The DC linear actuator is electronically powered by a twelve-volt rechargeable battery mounted to the wheelchair. The battery power is activated by a double throw control switch mounted to the wheelchair in a position where it is easily accessed by both the wheelchair user and a person assisting the wheelchair user. 
   The double throw toggle switch can be thrown in two different directions. When the double throw toggle switch is thrown in the first direction, it will cause the actuator rod to retract, pulling the pulley and cable wires and activating the braking force. When the toggle switch is thrown in the second direction, it will cause the actuator rod to extend, pushing the pulley and cable wire and deactivating the braking force. 
   In order to limit the tension in the cable wire, a motion limit switch can be added to the electrical brake system. The motion limit switch is wired into the circuit between the double throw toggle switch and said DC linear actuator. The motion limit switch is activated by displacement of the actuator rod in the direction which pulls the cable wire and activates the braking means. Once a selected braking force is attained, the motion limit switch opens the circuit and stops the displacement of the actuator rod. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a elevational side view of a manual wheelchair depicting a caliper braking mechanism mounted to the wheelchair frame and positioned to clamp onto a metal disk mounted axially to the hub of the wheelchair wheel. 
       FIG. 2A  is an enlarged exploded perspective view depicting the locking pin, wheelchair wheel, hub, disk, and axle assembly which has a spring biased push button type locking pin and first interlocking hub design. 
       FIG. 2B  is an enlarged exploded perspective view depicting the locking pin, wheelchair wheel, hub, disk, and axle assembly wherein the locking pin is equipped with a lever which activates an expandable tip. 
       FIG. 2C  is an enlarged exploded perspective view depicting  FIG. 2A  from the opposite angle. 
       FIG. 2D  is an enlarged exploded perspective view depicting the locking pin, wheelchair wheel, hub, disk, and axle assembly. This figure depicts a second interlocking hub design. 
       FIG. 2E  is an enlarged exploded perspective view depicting  FIG. 2D  from the opposite angle. 
       FIG. 3  is a bottom view of the wheelchair seat depicting the toggle switch, the battery recharging outlet, the electrical wiring, the twelve-volt rechargeable battery, the DC linear actuator, the cable wire and pulley assembly, and the motion limit switch. 
       FIG. 4  is an enlarged perspective view depicting the caliper braking mechanism. 
       FIG. 5  is an exploded perspective view depicting the cable wire and pulley assembly and actuator rod mount. 
       FIG. 6  is a bottom view of the cable wire, pulley, and actuator rod assembly brackets and the motion limit switch. 
       FIG. 7  is a elevational side view of the coupling bracket. 
       FIG. 8  is an electrical circuit diagram illustrating the electrical control circuit of this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a lightweight manual wheelchair  10  is equipped with a solid seat base  11 , seat cushion  12 , and seat back  13  mounted between first and second wheelchair wheels  24  generally to a frame  14 . The frame  14  has a vertical component  15 , a side horizontal component  16 , a frontal curved component  17  and a lower curved component  20 . A footrest  19  is mounted at the frontal extremity of the lower curved component  20  of the frame  14 . First and second caster wheels  21  are pivotally mounted toward the frontal extremity of the lower curved component  20  of the frame  14 . The manual wheelchair  10  is symmetrical about a centre line and the opposed side is identical to the side visible in  FIG. 1 . Thus, when the first and second of numbered items are referred to without the second item being shown, it can be appreciated that the second numbered item is identical to the first but on the opposite side of the wheelchair. 
   First and second caliper brakes  18  are mounted to extension plates (not shown) which are in turn mounted to the frame  14 . The caliper brakes  18  are positioned to clamp onto first and second disks  22  (see  FIGS. 1 and 4 ). In the preferred embodiment of this invention, the first and second caliper brakes  18  are manufactured by Hayes/HMX, model number BR3920. However, numerous other cable actuated caliper brakes are available on the market and can be used in this invention. The first and second wheelchair wheels  24  can be detached without removal of the first and second disks  22  or the first and second caliper brakes  18 . 
   Referring to  FIGS. 2A through 2E , the first and second disks  22  are concentrically mounted to the inner face  83  first and second disk hubs  23  by means of a plurality of screws  29  passing through radially spaced interiorly threaded, aligned holes  51  in the first and second disk hubs  23  and the first and second disks  22 . In the preferred embodiment, as shown in  FIGS. 2A ,  2 B, and  2 C, the screws  29  are Allen screws where the heads  33  of the screws  29  extend from the outer vertical faces  27  of the first and second disk hubs  23  and are secured on the opposite end by nuts  38 . In a second preferred embodiment, as shown in  FIGS. 2D and 2E , the screws  29  are of a length insufficient to extend beyond the outer vertical faces  27  of the first and second disk hubs  23 . 
   The first and second disk hub  23  and disk  22  assemblies are concentrically mounted to outer ends of first and second detachable axle pieces  80  and rotate thereon. The first and second detachable axle pieces  80  are tubular with a smooth surface portion  82  at their outer end and a exteriorly threaded portion  84  at their inner end. The smooth surface portion  82  and the exteriorly threaded portion  84  are divided by a flange  86 . 
   The first and second detachable axle pieces  80  are mounted to the frame  14  of the wheelchair  10  (see  FIG. 1 ) by screwing the exteriorly threaded portion  84  into a tubular axle  25 . As shown in  FIG. 3 , the tubular axle  25  is clamped to the first and second lower curved components  20  of the frame  14  (See  FIG. 1 ) at its rear extremity by first and second frame clamps  72 . 
   Referring again to  FIGS. 2A through 2E , the outer ends of the tubular axle  25  have mounting heads  88 . Each mounting head  88  has a threaded bore  90  with a diameter sufficient to accept and secure the exteriorly threaded portion  84  of the first and second detachable axle pieces  80  therein. The first and second detachable axle pieces  80  are mounted to the tubular axle  25  by screwing the exteriorly threaded portion  84  into the threaded bore  90 . 
   The first and second disk hub  23  and disk  22  assemblies are secured to the first and second detachable axle pieces  80  by means of a clip ring  39 . The clip ring  39  is spring biased to close around and fit in to a circumferential groove  78  cut into the smooth surface portion  82  of the first and second detachable axle pieces  80  at their extreme outer end. In order to allow the first and second disk hub  23  and disk  22  assemblies to rotate on the first and second detachable axle pieces  80 , the smooth surface portion  82  of the first and second detachable axle pieces  80  extend axially through a tubular opening  92  at the center of the first and second disk hubs  23  and the outer face of flange  86  abuts a concentric circular shoulder  87  (see  FIGS. 2C and 2D ) on the inner face  83  of the first and second disk hubs  23  with a spacer ring  94  between. The spacer ring  94  prevents frictional contact between the outer face of flange  86  and the circular shoulder  87  on the inner face of the first and second disk hubs  23 . In the preferred embodiment, the spacer ring  94  is a Delrin washer. However it is anticipated that other smooth, durable material can be substituted. 
   Referring to  FIGS. 2A ,  2 B, and  2 E, the outer vertical face  27  of the first and second disk hub have a concentric circular recessed portion  93  surrounding the tubular opening  92 . The horizontal length of the smooth surface portion  82  of the detachable axle piece  80  is sufficient to allow the smooth surface portion  82  to extend through the tubular opening  92  of the first and second disk hubs  23  and expose the circumferential groove  78  on the opposite side of the first and second disk hubs  23  with minimal clearance at the concentric circular recessed portion  93 . This allows the clip ring  39  to close around circumferential groove  78  within the concentric circular recessed portion  93 . 
   As shown in  FIGS. 2A through 2C , the first and second wheelchair wheels  24  are concentrically mounted on the first and second wheel hubs  37 . The inner surface  57  of the first and second wheelchair wheels  24  (See  FIG. 2C ) is mounted flush against the outer vertical surface  70  (See  FIG. 2E ) of the flanged inner portion  31  of the first and second wheel hubs  37  and are secured to the first and second wheel hubs  37  by first and second nuts  45 , which screw onto exteriorly threaded outer ends  75  of the first and second wheel hubs  37 . The first and second wheel hubs  37  have a tubular opening  43  through their center. As shown in  FIGS. 2A and 2B , an outer circular bearing assembly  61  is pressed fit into the tubular opening  43  towards the outer end of the first and second wheel hubs  37 . 
   As shown in  FIGS. 2B ,  2 C, and  2 D, an inner circular bearing assembly  79  is pressed fit into the tubular opening  43  at the inner end of the first and second wheel hubs  37 . The outer bearing assembly  61  and inner bearing assembly  79  have inner rings  63  which turn within the bearing assemblies. The inner diameter of the inner rings  63  is equal to the inner diameter of first and second detachable axle pieces  80 . In the preferred embodiment, the outer circular bearing assembly  61  and inner circular bearing assembly  79  are manufactured by NICE, Model No. 1616 DC TN or KYK, Model No. R-8-DDHA1(IB). However, it is anticipated that other similar bearings could be used. 
   Referring again to  FIGS. 2A through 2E , when the first and second wheelchair wheels  24  are mounted to the wheel hub  37  and in turn mounted to the wheelchair  10  (See  FIG. 1 ), the outer vertical faces  27  of the first and second disk hubs  23  interlock with inner faces  77  of the flanged inner portion  31  of the first and second wheel hubs  37 . In the preferred embodiment, as shown in  FIGS. 2A ,  2 B, and  2 C, the inner faces  77  of the flanged inner portion  31  of the first and second wheel hubs  37  are flat with a plurality of radially spaced holes  96  shown in  FIG. 2C . The heads  33  of the plurality of screws  29  fit snugly into the corresponding radially spaced circular holes  96  in the flanged inner portion  31  of the first and second wheel hubs  37 . In an alternate embodiment, as shown in  FIGS. 2D and 2E , the inner face  77  of the flanged inner portion  31  of the first and second wheel hubs  37  have a raised surface  98  extending from the inner face  77 . The raised surface  98  is centered on the inner face  77  with parallel sides  100  extending to the circumference of the inner face  77 . The parallel sides  100  extend perpendicularly from the inner face. In this alternate embodiment, the outer vertical faces  27  of the first and second disk hubs  23  have a channel  102 . The placement and dimensions of the channel  102  are to allow the raised surface  98  to fit snugly into the channel  102  with minimal clearance at all contiguous surfaces when the first and second wheel hubs  37  are interlocked with the first and second disk hubs  23 . 
   In the preferred embodiment, as shown in  FIGS. 2A ,  2 B, and  2 C, the interlocking of heads  33  within the radially spaced circular holes  96  cause the first and second wheelchair wheels  24  and the first and second disks  22  to rotate together. In another alternate embodiment, as shown in  FIGS. 2D and 2E , the interlocking of the raised surface  98  on the inner face  77  of the first and second wheel hubs  37  with the channel  102  in the outer vertical faces  27  of the first and second disk hubs  23  cause the first and second wheelchair wheels  24  (See  FIG. 1 ) and the fist and second disks  22  to rotate together. 
   Still referring to  FIGS. 2A through 2E , in order to hold the first and second disk hubs and the first and second wheel hubs together when interlocked, first or second locking pins  35   a  and  35   b  (see  FIGS. 2A and 2B ) extend axially through the center of the first and second wheel hubs  37 , the first and second disk hubs  23 , and into the first and second detachable axle pieces  80 . The first or second locking pins  35   a  and  35   b  have a diameter which allows the first or second locking pins  35   a  and  35   b  to slide through the inner rings  63  of the outer circular bearing assembly  61  (See  FIGS. 2A and 2B ) and the inner circular bearing assembly  79  (See  FIGS. 2C and 2D ) and into the first and second detachable axle pieces  80  with minimal clearance. 
   The first and second wheelchair wheels  24  can be detached from the wheelchair  10  (See  FIG. 1 ) without removing the first and second disks  22  or disturbing the first and second caliper brakes  18  by removing the first and second locking pins  35   a  or  35   b  and separating the first and second wheel hubs  37  from the first and second disk hubs  23 . 
   In the preferred embodiment of the invention (see  FIGS. 2A ,  2 C,  2 D, and  2 E), the first and second locking pins  35   a  have a push button  47 , a rod  49 , an adjusting nut  53 , and a set of retractable nipples  55 . The push button  47  is spring biased in the released position, causing the retractable nipples  55  to extend from the rod  49 . When the push button  47  is depressed, the retractable nipples  55  retract into the rod  49 . The first and second locking pins  35   a  can be inserted through the inner ring  63  of the outer circular bearing assembly  61  and into the tubular openings  43  of the first and second wheel hubs  37  by depressing the push button  47  and thereby causing the retractable nipples  55  to retract. When the first and second locking pins  35   a  are further inserted through the first and second disk hubs  23  and into the first and second detachable axle pieces  80  and the push button  47  is released, the retractable nipples  55  extend into grooves (not shown) circumferentially cut into the tubular interior surface (not shown) of the first and second detachable axle piece  80 . The grooves (not shown) are of sufficient depth and width to allow the retractable nipples  55  to extend into the grooves (not shown) with minimal clearance. The grooves (not shown) are positioned in the first and second detachable axle pieces  80  to allow the retractable nipples  55  to extend into the first and second grooves (not shown) when the first and second locking pins  35   a  are fully inserted into the first and second wheel hubs  37  such that the adjustable nut  53  contacts the outer surface of the outer circular bearing assembly  61 . In the preferred embodiment, the first and second locking pins  35   a  are QRP Quick Release Push Button (large/small) Axle, Model No. 21QRP11CDASN. 
   In an alternate embodiment of the invention, the length of the exteriorly threaded portion  84  of the first and second detachable axle pieces  80  is sufficient to allow the position of the retractable nipples  55  on the first and second locking pins  35   a  to extend beyond the inner lip  85  of the first and second detachable axle pieces  80  when the first and second locking pins  35   a  are fully inserted into the first and second wheel hubs  37  such that the adjustable nut  53  contacts the outer surface of the outer circular bearing assembly  61 . Thus, when the first and second locking pins  35   a  are fully inserted and the push button  47  is released, the retractable nipples  55  extend adjacent to the inner lip  85  of the first and second detachable axle pieces  80  with minimal clearance and thereby holding the first and second locking pins  35   a  in place. In this embodiment, the first and second locking pins  35   a  are, once again, QRP, Quick Release Push Button (large/small), Axle Model No. 21QRP11CDASN. 
   In yet another embodiment of the invention (see  FIG. 2B ), the first and second locking pins  35   b  have a release lever  65  at one end of a rod  67 , a spacer joint  69  between the release lever  65  and the rod  67 , an expandable tip  71  attached to the other end of the rod  67 , and a wedging cap  73  attached to the expandable tip  71  opposite the rod  67 . When the release lever  65  is rotated to the released position so that it extends parallel with the rod  67 , the diameter of the expandable tip  71  is not expanded and is equal to the diameter of the rod  67 . When the release lever  65  is rotated perpendicular to the rod  67 , the wedging cap  73  is pulled toward the release lever  65  causing the expandable tip  71  to expand to a diameter greater than the diameter of the rod  67 . When the release lever  65  is in the released position, the first and second locking pins  35   b  can be inserted through the inner ring  63  of the outer circular bearing assembly  61  and into the tubular opening  43  of the first and second wheel hubs  37 . When the first and second locking pins  35   b  are inserted through the first and second wheel hubs  37 , and into the first and second detachable axle pieces  80  and the release lever  65  is then rotated perpendicular to the rod  67 , the expandable tip  71  expands into and makes frictional contact with the interior surface (not shown) of the first and second detachable axle pieces  80 . The frictional force created is great enough to hold the first and second locking pins  35   b  in place. The diameter of the spacer joint  69  is greater than the inner diameter of the inner ring  63  of the outer circular bearing assembly  61 , such that when the first and second locking pins  35   b  are fully inserted, the spacer joint  69  contacts the outer face of the outer circular bearing assembly  61 . In this preferred embodiment, the locking pin  35   b  is the Ultra Axle, 0.50″ O.D. manufactured by Rousson Chamoux. 
   The first and second caliper brakes  18  are activated by pulling a cable wire  26  (See  FIGS. 4 and 5 ) attached to the caliper brakes  18  at first and second ends of the cable wire  26 . The first and second ends of the cable wire  26  are directed to the first and second caliper brakes  18  through a cable wire housing  28  which is attached to a nozzle  30  on the first and second caliper brakes  18 . The first and second ends of the cable wire  26  are attached to the first and second caliper brakes  18 , respectively, in typical fashion. The cable wire  26  passes through the nozzle  30  of the first and second caliper brakes  18  and into the cable wire housing  28 . The cable wire housing  28  directs the cable wire  26  to a mounting bracket  32  (See  FIG. 5 ). The mounting bracket  32  has a vertical portion, and an upper horizontal portion. The mounting bracket  32  is mounted to the bottom of the solid seat base  11  by two screws (not shown) passing through interiorly threaded aligned holes in the solid seat base  11  and upper horizontal portion of the mounting bracket  32 . 
   The cable wire housing  28  is connected to the mounting bracket  32  by means of first and second hollow connectors  34 . The first ends of the first and second hollow connectors  34  fit snugly within first and second circular openings (not shown) in the mounting bracket  32  and the second ends of the first and second hollow connectors  34  fit snugly around the cable wire housing  28 . The centers of said first and second circular openings (not shown) are equidistant from the upper horizontal portion of the mounting bracket  32  and are horizontally spaced a distance equal to the diameter of the pulley  36 . The diameter of the first and second circular openings (not shown) is sufficient to allow the first and second hollow connectors  34  to fit snugly and the cable wire  26  to pass through first and second circular openings (not shown) within the first and second hollow connectors  34 . The cable wire  26  passes through the circular openings in the mounting bracket  32  within the first and second hollow connectors  34  and then passes around the pulley  36 . 
   The pulley  36  and cable wire  26  assembly is covered with a circular pulley cap  40 . The inner diameter of the circular pulley cap  40  is of sufficient dimension to cover the pulley  36  and wire cable  26  assembly with minimal clearance. The vertical side of the pulley cap  40  has first and second openings  41  spaced to allow the cable wire  26  to pass into the pulley cap  40  and around the pulley  36 . In the preferred embodiment of this invention, the segments of the cable wire  26  on opposite sides of the pulley  36  between the pulley  36  and mounting bracket  32  are parallel. Both segments of the cable wire  26  are perpendicular to the vertical side of the mounting bracket  32 . 
   The pulley cap  40 , pulley  36 , and wire cable  26  are connected to an actuator rod  42  of a DC linear actuator  50  (See  FIG. 3 ) by means of a coupling bracket  44 . The pulley cap  40 , pulley  36 , and wire cable  26  are connected to the coupling bracket  44  by a bolt and nut combination  46  passing through holes vertically aligned with the axis of the pulley cap  40  and pulley  36 . The actuator rod  42  is connected to the coupling bracket  44  by a bolt and nut combination  48  passing through holes horizontally aligned through the coupling bracket  44  and through the center of the outer end of the actuator rod  42 . 
   The DC linear actuator  50 , as shown in  FIG. 3 , is mounted to the solid seat base  11  by means of a mounting flange  56  and an actuator mounting piece  52 . The actuator mounting piece  52  is mounted to the solid seat base  11  by two nut and bolt combinations. The mounting flange  56  is mounted to the actuator mounting piece  52  by a nut and bolt combination passing through horizontally aligned holes in the mounting flange  56  and first and second vertical portions  54  of the actuator mounting piece  52 . The DC linear actuator is positioned so that displacement of the actuator rod  42  is in a direction perpendicular to the vertical portion of the mounting bracket  32  and centered between the first and second circular openings (not shown) in the vertical portion of the mounting bracket  32 . In the preferred embodiment, the DC linear actuator  50  is manufactured by Warner Electric, model number DE12Q17W41-02FHM3HN. 
   The DC linear actuator  50  is powered by a twelve-volt rechargeable battery  58  mounted to the bottom of the solid seat base  11 . In the preferred embodiment of this invention, the twelve volt rechargeable battery  58  is mounted to the solid seat base  11  by first and second Velcro straps  59 . Each of the first and second Velcro straps  59  pass through two slits (not shown) in the solid seat base  11  such that each of the first and second Velcro straps  59  pass through the first slit (not shown) to the top of the solid seat base  11  and back through the second slit (not shown) and around the twelve volt rechargeable battery  58 . In the preferred embodiment of this invention, the twelve volt rechargeable battery  58  is a sealed, non-spillable, lead battery manufactured by CSB Battery Company, Ltd. 
   A recharger outlet  68  is mounted to the frame  14  and is wired across the positive and negative leads of the twelve volt rechargeable battery  58 . In the preferred embodiment of this invention, the recharger outlet  68  is mounted to the rear of the solid seat base  11 . However, the recharger outlet  68  can be mounted generally to any part of the frame  14  where it is convenient and accessible. 
   As shown in  FIGS. 3 and 8 , the battery power is controlled by a double throw toggle switch  60  which is mounted to the frame  14 . In the preferred embodiment of this invention, the double throw toggle switch  60  is mounted to vertical component  15  of the frame  14 . (See  FIG. 1 .) However, the double throw toggle switch  60  can be mounted generally to any part of the frame  14  where it is convenient and accessible to the wheelchair user. The double throw toggle switch  60  is wired into the electrical circuit, as shown in  FIG. 7 , across the positive and negative leads of the twelve volt rechargeable battery  58 . The double throw toggle switch  60  can be thrown in a first direction  74  or a second direction  76 . If the double throw toggle switch  60  is thrown in the first direction  74 , it closes the circuit and powers the motion of DC linear actuator  50  and causes the actuator rod  42  to retract. The retraction of the actuator rod  42  pulls the pulley  36  and cable wire  26  assembly causing the displacement of the cable wire  26  within the cable wire housing  28  in a direction away from the first and second caliper brakes  18  (See  FIGS. 4 ,  5 , and  6  in combination). The displacement of the cable wire  26  away from the first and second caliper brakes  18  causes equal tension in the cable wire  26  on opposite sides of the pulley  36  and activates the first and second caliper brakes  18  with equal braking force. 
   If the double throw toggle switch  60  is thrown in the second direction  76 , it closes the circuit and the polarity and direction of current flow through the DC linear actuator  50  is reversed. This powers the motor of the DC linear actuator  50  in the reverse direction and causes the actuator rod  42  to extend. The extension of the actuator rod  42  displaces the pulley  36  and causes the cable wire  26  to move within the cable wire housing  28  toward the first and second caliper brakes  18 . This in turn releases the tension in the cable wire  26  created by retracting the activator rod and deactivates the first and second caliper brakes  18 . The first and second caliper brakes  18  are spring biased (not shown) toward the deactivated position which retains tension in the cable wire  26  while the actuator rod  42  is extending and prevents bunching of the cable wire  26 . 
   In order to control the tension in the cable wire  26  when the actuator rod  42  is retracting, a motion limit switch  62  is placed in the electrical circuit, as shown in  FIG. 7 , between the positive lead of double throw toggle switch  60 . When the double throw toggle switch  60  is thrown in the first direction  74 , the motion limit switch  62  limits movement of the DC linear actuator  50 . The motion limit switch  62  is equipped with a motion arm  64  as shown in  FIGS. 3 ,  6 ,  7 , and  8 . The motion arm  64  is spring biased to contact and press against an actuating pin  66  as shown in  FIGS. 3 ,  6 ,  7 , and  8 . The actuating pin  66  extends from, and is a part of, the coupling bracket  44  as more clearly illustrated in  FIG. 6 . The motion limit switch  62  is normally closed. Retraction of the actuator rod  42  causes displacement of the coupling bracket  44  and actuating pin  66 , which in turn displaces the motion arm  64 . Sufficient displacement of the motion arm  64  throws the motion limit switch  62  opening the circuit and preventing further retraction of the actuator rod  42 . The displacement of the motion arm  64  required to throw the motion limit switch  62  is adjustable to allow for control and selection of the tension in the cable wire  26  and the resulting braking force. 
   In the normal operation of the wheelchair  10 , it is desirable to have brakes activated during the transfer in and out of the wheelchair  10 . If the wheelchair user intends to transfer out of the wheelchair, he will throw the toggle switch  60  in the first direction  74  which causes the actuator rod  42  to retract and activates the first and second caliper brakes  18 . The wheelchair user should hold the toggle switch  60  in the first direction  74 , thereby increasing the braking force applied by the first and second caliper brakes  18  until the motion limit switch  62  is thrown and opens the circuit which stops the retraction of the actuator rod  42 . The user should then release the toggle switch  60  which is spring biased to the center, OFF position. The motor of the DC linear actuator  50  locks the actuator rod  42  in position when there is no power to the DC linear actuator  50 . Thus, the first and second caliper brakes  18  will remain activated and hold the wheelchair  10  in position while the wheelchair user transfers out of the chair. The first and second caliper brakes  18  will remain activated until the toggle switch  60  is thrown and held in the second direction  76  and thereby allowing the actuator rod  42  to extend a sufficient amount to deactivate the first and second caliper brakes  18  and allow the first and second wheelchair wheels  24  to rotate freely. The toggle switch  60  is then released allowing it to spring back to the center OFF position which opens the circuit and stops the flow of power to the DC linear actuator  50 . 
   Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.