Abstract:
Manual braking system with a variable braking force for a wheelchair. Caliper type brakes positioned to mount on and exert braking force on disks mounted to interior “disk” hubs rotatably mounted to the wheelchair frame wheel hubs are mated with the “disk” hubs with a push button release pin allowing the wheel to be quickly removed without disturbing disk braking system. Caliper brakes are actuated by a manual lever arm, cable and pulley combination mounted to the frame of the wheelchair. The lever is provided with and without a plunger mechanism. A plunger mechanism allows the user to maintain the manual braking force exerted on lever without hands. The plunger mechanism is fixably mounted and positioned to insert a plunger head into notches on the lever. The force exerted by the plunger head is sufficient to hold the plunger head within the notch and prevent movement of the lever without manual force.

Description:
This application is a continuation in part of my now pending U.S. patent application Ser. No. 10/622,339 filed on Jul. 18, 2003 which is a divisional application based on patent application Ser. No. 10/154,356 filed on May 23, 2002 (now U.S. Pat. No. 6,634,665 B1) which is a continuation Ser. No. 09/921,498, now of U.S. Pat. No. 6,471,231 B1 issued Oct. 29, 2002 and filed Aug. 3, 2001. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to the field of wheelchairs and, more specifically, to a manual braking system with a variable braking force 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. Typically, braking mechanisms for wheelchairs only apply a braking force to one wheel. If an equal braking force is desired on both wheels, the user is required to perform the difficult task of using both arms at the same time. Finally, these types of manual brakes, whether caliper type brake or not, do not allow for a variable braking force to be exerted on the tire or rim. A variable braking force allows the user to both slow the wheelchair and ultimately stop it and hold it in place when desired. 
   Patents to Ross and Gunther, U.S. Pat. No. 5,358,266 and Lautzenhiber, U.S. Pat. No. 4,805,711 describe a braking member, which applies a braking frictional force directly to the wheelchair tire which is manually activated by a lever arm. There are also disclosed in the art several manual braking mechanisms which utilize a cable actuated caliper braking mechanism on the rim of one wheel or on the rims of both wheels with two distinct braking systems operating separately. Examples of these types of braking mechanisms are disclosed in patents to Herron, U.S. Pat. No. 4,560,181; Kawecki, U.S. Pat. No. 4,204,588; and Lemarie, U.S. Pat. No. 4,538,826. Finally, a patent to Berry, U.S. Pat. No. 5,492,355 discloses a caliper type braking mechanisms that discloses caliper type brakes which operate on the tire rim of each wheelchair wheel and can be activated by the use on one lever. Many of the same deficiencies discussed above apply to each of these braking mechanisms. 
   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 braking systems such as those which utilize caliper type brakes operating on the rim of the wheelchair wheel, 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 wheelchair with an effective easily operatable manual braking mechanism and, at the same time having quick release detachable wheels. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to provide a manually activated braking system for a wheelchair which provides a braking force to a disk, as opposed to the tire surface or rim of the wheelchair wheel and thereby provide more efficient braking action. 
   It is a further object of this invention to provide a manual braking system for a wheelchair which allows for a variable braking force to slow the wheelchair during operation. 
   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 manual 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 a manual braking system for a wheelchair which is comprised of a braking means, a cable pully system attached to the braking means, and a manual lever assembly pivotally mounted to the wheelchair frame for activating the braking means. 
   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 manual lever assembly comprises a mounting bracket having a mounting shoulder, a lever arm pivotally attached to the mounting bracket, and a linking member pivotally attached to both the lever arm and the pulley. The linking member is attached in such a manner that when the lever arm is rotated, the linking member is displaced horizontally and thereby causing horizontal displacement of the pulley. 
   The braking means for each wheel are connected to opposite ends of a cable wire. The ends of the cable wire are directed through small openings in perpendicular element of the mounting bracket and around the pulley such that displacement of the pulley provides equal force and displacement to said opposite ends of the cable wire. The small 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. The pulley is axially and pivotally connected to the linking member and positioned between the mounting bracket and the linking member. A pin connecting the pulley and the linking member also extends through and slides in a horizontal slot in the mounting bracket and thereby causing the displacement of the pulley to be in a horizontal plane. 
   The lever arm can be rotated in two different directions. When the actuating lever is rotated in a first direction, it will cause the linking member to displace horizontally pulling the pulley and cable wires and activating the braking force. The further the lever arm is rotated, the greater the braking force exerted on the disk and the operator can vary the braking for in this manner. When the lever arm is rotated in the opposite direction, it will cause the linking member to displace in the opposite horizontal direction pushing the pulley and cable wire and deactivating the braking force. 
   I an alternate embodiment of this invention, a plunger assembly with a spring biased rounded head is mounted through an opening in the mounting bracket. The plunger assembly is positioned to allow the rounded head to extend into a series of semi-hemispherical notches on the inner surface of the actuating lever. The notches are radially spaced around the pin connecting the lever arm to the mounting bracket. The notches are positioned such that each notch will separately receive the plunger pin as the lever arm is rotated. The force exerted by the spring and the plunger pin is sufficient to prevent the lever arm from rotating until it receives sufficient manual force. In this manner, each notch represents a different level of braking force to be applied to the disk. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a elevational side view of a manual wheelchair depicting manual brake actuator assembly and 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 manual brake actuator assembly mounted to the wheelchair frame. 
       FIG. 4  is a rear elevational view depicting the clamp and mounting bracket of the manual brake actuator assembly. 
       FIG. 5  is a perspective view depicting the caliper brake mechanism and disc. 
       FIG. 6  is an exploded perspective view depicting the manual brake actuator assembly. 
       FIG. 7  is a perspective view depicting the manual brake actuator assembly. 
       FIG. 8A  is a perspective view of the manual brake actuator assembly depicting the lever arm is a vertical non-braking position. 
       FIG. 8B  depicts the manual brake actuator assembly with the lever arm in a partially braking position. 
       FIG. 8C  depicts the manual brake actuator assembly with the lever arm in a horizontal full braking position. 
       FIG. 9A  is a side view of an alternative embodiment of the present invention depicting the manual brake actuator assembly with a plunger mechanism with the lever arm in a vertical non-braking position. 
       FIG. 9B  is the alternative embodiment of the present invention as shown in  FIG. 9A  with the actuating lever in a partial braking position. 
       FIG. 9C  is the alternative embodiment of the present invention as shown in  FIG. 9A and 9B  with the actuating lever in a horizontal full braking position. 
       FIG. 10  is an enlarged perspective view of the plunger mechanism provided in the alternative embodiment of the present invention depicted in  FIGS. 9A–9C . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a lightweight manual wheelchair  10  is equipped with a seat  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. 
   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.  2 A,  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. 
   Referring to  FIGS. 1 ,  3 ,  4 , and  6 , a manual brake actuator assembly  120  has a mounting bracket  122  which is fixed to the horizontal portion  16  of the frame  14  of the wheelchair  10  by a semi-circular mounting shoulder  124  and a clamp  126 . The clamp  126  has an upper element  128  and a lower element  130  which when clamped together with a screw  127 , form a first channel  129   a  and a second channel  129   b  at opposing ends of the clamp  126 . The first channel  129   a  and second channel  129   b  have curved interior surfaces (not shown). The radial dimensions of the curved interior surfaces (not shown) of the first channel  129   a  and second channel  129   b  are sufficient to allow the first channel  129   a  and second channel  129   b  to engage and clamp onto the horizontal portion  16  of the frame  124  and the mounting shoulder  124  respectively when the upper element  128  and the lower element  130  of the clamp  126  are clamped together. As shown in  FIG. 6 , the mounting shoulder  124  is mounted to a generally rectangular base portion  132  of the mounting bracket  122  with flathead screws  134 . 
   Referring to  FIGS. 6 ,  7 , and  8   a  through  8   c , the mounting bracket  122  has a straight, horizontal lower edge  136  and gradually narrows along its horizontal length from the base portion  132  at rearward end to a rounded tip  138  at forward end. A perpendicular element  140  which is generally rectangular in shape, extends perpendicularly and outward from the base portion  132  of the at its rearward end. 
   Still referring to  FIGS. 6 ,  7 , and  8   a  through  8   c , an elongated actuating lever  142  is pivotally mounted to the mounting bracket  122  with first allenhead screw  144  having a cylindrical head  146 , an intermediate smooth portion  148  and a threaded portion  150 . The first allenhead screw  144  is inserted through a non-threaded hole  152  in the actuating lever  142  and into a threaded hole  154  in the mounting bracket  122  such that the actuating arm  142  can pivot on the smooth portion  148  of the first allenhead screw  144 . 
   As shown in  FIG. 6 , a first protecting sleeve  156  is inserted in the non-threaded hole  152  of the actuating lever  142  around fist the allenhead screw  144 . A first washer  158  is axially mounted on the first allenhead screw  144  between the head  146  and the outer surface of the actuating lever  142 . A second washer  160  is axially mounted on the first allenhead screw  144  between the inner surface of the actuating lever  142  and the outer surface of the mounting bracket  124 . 
   Referring again to  FIGS. 6 ,  7 , and  8   a  through  8   c , a linking element  162 , having a circular rearward portion  188 , a circular forward portion  176  and a bridging member  177  extending between the rearward and forward portions, is pivotally connected to the actuating lever  142  with a second allenhead screw  164  having a head  166 , an intermediate smooth portion  168 , and a threaded portion  170 . The second allenhead screw  164  extends through a second non-threaded hole  172  in the actuating lever  142  and then through a threaded hole  173  in the center of the forward end  176  of the linking element  162 . The second allenhead screw is positioned such that the head extends from the inner surface of the actuating lever  142  and the rounded surface of the head engages and rides on the rounded surface  177  of the rounded tip  138  of the mounting bracket  122  as the actuating lever  142  is rotated. A third washer  178  is axially mounted on the second allenhead screw  164  between the head  166  and the inner surface of the actuating lever  142 . A fourth washer  180  is axially mounted to the second allenhead screw  164  between the outer surface of the actuating lever  142  and the inner surface of the linking element  162 . A second protective sleeve  182  is inserted into the second non-threaded hole  172  of the actuating lever  142  around the second allenhead screw  162  and pulley  184 . 
   Still referring to  FIGS. 6 ,  7 , and  8   a  through  8   c , a pulley  184  is axially and pivotally mounted between the mounting bracket  122  and the rearward end  188  of the linking element with a third allenhead screw  186 . The third allenhead screw  186  is inserted through a horizontal guiding slot  190  cut in the mounting bracket  122 . The third allenhead screw  186  has a head  192 , intermediate smooth portion  192 , and a threaded portion  196 . The third allenhead screw  186  is positioned such that the head  192  extends from the inner surface of the mounting bracket  122 ; the intermediate smooth portion  194  extends through the guiding slot  190  and an axial hole  198  in the pulley  184 ; and the threaded portion  196  extending into a threaded hole  200  in the center of the rearward end  188  of the linking element  162 . 
   Referring to  FIG. 6 , a fifth washer  202  is axially mounted on the third allenhead screw  186  between the head  192  and the inner surface of the mounting bracket  122 . A sixth washer  204  is axially mounted from the third allenhead screw  186  between the outer surface of the mounting bracket  122  and the inner surface of the pulley  184 . A seventh washer  206  is axially mounted on the third allenhead screw  186  between the outer surface of the pulley  184  and the inner surface of the linking element  162 . The protective sleeve  208  is inserted in the axial hole  198  of the pulley  184  around the third allenhead screw  186 . 
   As shown in  FIG. 7 , the guiding slot  190  is generally rectangular in shape and elongated horizontally. The horizontal centerline of the guiding slot is horizontally aligned with the centerline of the threaded hole  154  in the mounting bracket  122 . The inner face of the mounting bracket  122  has a recessed ledge  210  which surrounds the guiding slot  190 . The vertical width of the recessed ledge  210  around the guiding slot  190  sufficient to allow fifth Washer and head  192  of the third allen head screw  186  to fit between an upper lip and a lower lip  214  of the recessed ledge  210 . 
   Referring to  FIGS. 1 and 5 , first and second caliper brakes  18  are mounted to extension plates (not shown) which are in turn mounted to the frame  14  of the wheelchair  10 . The caliper brakes  18  are positioned to clamp onto first and second disks  22 . 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 . 
   Still referring to  FIGS. 1 and 5 , the first and second caliper brakes  18  are activated by pulling a cable wire  110  (See  FIGS. 4 and 5 ) attached to the caliper brakes  18  at first and second ends of the cable wire  110 . The first and second ends of the cable wire  110  are directed to the first and second caliper brakes  18  through a cable wire housing  112  which is attached to a nozzle  114  on the first and second caliper brakes  18 . The first and second ends of the cable wire  110  are attached to the first and second caliper brakes  18 , respectively, in typical fashion. The cable wire  110  passes through the nozzle  114  of the first and second caliper brakes  18  and into the cable wire housing  112 . 
   Referring now to  FIGS. 1 ,  7 , and  8   a  through  8   c , the cable wire  110  is directed from the first and second caliper brakes  18  through the cable wire housing  112  to the manual actuating brake assembly. The cable wire  110  extends to through small openings  116  and around the pulley  184  in the perpendicular element  140  of the mounting bracket  122 . The centers of the Small openings  116  are equal distance from the base portion  132  of the mounting bracket  122  and are vertically spaced a distance equal to the diameter of the pulley  184 . 
   Referring to  FIGS. 1 and 8   a  through  8   c , in operation of preferred embodiment of this invention, the first and second caliper brakes  18  are activated by rotating the actuating lever  142 . When the actuating lever  142  is in its upright, vertical positioned as shown in  FIG. 8   a , the first and second caliper brakes  18  are deactivated. As the actuating lever  142  is rotated in a forward direction as shown in  FIG. 8   b , it causes the linking element  162  to rotate and at the same time displace in a forward horizontal direction. The linking element  162 , in turn, causes the pulley  184  to displace in a forward, horizontal direction. As the pulley  184  displaces forward, the intermediate smooth portion  194  of the third allenhead screw  186  slides forward within the guiding slot  190  and thereby maintaining the movement of the pulley  184  in constant horizontal plane. Additionally, as the pulley  184  moves in a forward direction, it pulls the cable wire  110  and thereby activating the first and second caliper brakes  18  with equal force. The first and second caliper brakes  18  are released by rotating the actuating lever  142  backward towards its vertical, upright position as shown in  FIG. 8   a.    
   As shown in  FIGS. 8   a  and  8   c , as the actuating lever  162  is rotated forward, the curved surface  218  of the forward end  176  of the linking element  162  engages and rides on the curved surface of the head  146  of the first allenhead screw  144 . When the actuating lever  142  is rotated forward to a horizontal position, as shown in  FIG. 8   c , the linking element  162  moves to an “overcenter” locking position such that the curved surface  218  of the forward end  176  of the linking element  162  engages the curved surface of the head  146  of the first allenhead screw  144  at its forward most point. In this position, the maximum braking force of the caliper brake  18  is achieved and prevents further movement of the wheelchair. 
   An alternate embodiment of the invention is shown in  FIGS. 9   a  through  9   c  and  FIG. 10 . In this embodiment, a exteriorly threaded plunger assembly  220  extends through the mounting bracket  122  through an interiorly threaded hole (not shown) and is secured to the mounting bracket  122  with a nut  224 . The plunger assembly  220  has a spring biased rounded plunger head  226 . The plunger assembly  220  is positioned to allow the plunger head  226  to extend into a plurality of semi-hemispherical notches  228  on the inner surface of the actuating lever  142 . 
   The notches  228  are radially spaced around the first non-threaded hole  152  in the actuating lever  142 . The notches are positioned to receive the plunger head  226  when the actuating lever  142  is rotated to a series of positions equal to the number of notches  228 . The first in the series of notches  228  is positioned to the plunger head  226  when the actuating lever  142  when it is in an upright vertical position, as shown in  FIG. 9   a , and the braking force is deactivated. The last in the series of notches  228  is positioned to receive the plunger head  226  when the actuating lever  142  in the horizontal position, as shown in  FIG. 9   c , and the braking force is fully activated. Each of the intermediate notches  228  are positioned to receive the plunger head  226  when the actuating lever  142  is rotated to positions between the upright, vertical position and the horizontal position creating various levers of braking force. The spring biased plunger head  226  presses into the notches  228  with sufficient force to maintain the rotated position of the actuating lever  142  until sufficient manual force is exerted on the actuating lever  142 . 
   Although this alternative embodiment of the invention incorporates the use of notches  228  on the inner surface of the actuating lever  142  positioned to receive a plunger head  226 , it is anticipate that other means of maintaining the actuating lever  142  in a rotated position could be used. For instance, it is anticipated that a ratcheting or gear mechanism could be used for that purpose. 
   The operation of this alternative embodiment of the invention is identical to the operation of the preferred embodiment with the exception of the use of notches  228  and plunger assembly  220 . These additional elements allow the user to rotate the actuating lever  142  into varying positions to exert a varying braking force on the disks  22 . The combination of the plunger assembly  220  and the notches  228  allow the user to release the actuating lever  142  and maintain the desired braking force and thereby allowing the user to keep both hands on the wheels for steering or for other purposes while braking. 
   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.