Patent Application
20080128227
The present invention relates to braking systems. More particularly, the present invention relates to a gravity reacting anti-rollback braking system for wheel chairs on inclined surfaces.
The invention of the wheel greatly revolutionized the transportation of persons and materials. As will be appreciated, wheels must have brakes or a means to cease the rotation of the wheel to stop the movement of the vehicle to which they are attached. With vehicles powered manually, such as strollers, carts, stretchers, and the like, the provision of braking mechanisms poses unique challenges. As will be appreciated, without a braking mechanism, these vehicles cannot be left unattended on slopes or non-flat surfaces in view of the fact that the force of gravity will induce the wheels (and thus the vehicle) to roll in the descending direction. This problem is a particular concern with manually or arm-powered devices, such as wheelchairs, for example, where the safety of an occupant is of utmost importance.
As will be appreciated, caregivers attending to a wheelchair occupant sometimes need to leave the occupant unattended to, for example, open a door or prepare a car lift. In these periods, the occupant may need to prevent the wheelchair from descending an incline, or from undergoing what is know in the art as a “rollback.” Some occupants do not have the stamina, strength, or mental faculties to prevent a rollback on inclines.
In an effort to prevent rollbacks, some prior artisans crafted wheelchairs with wheel locks for locking the large, rear wheels against rotation. With these prior art devices, a wheel lock assembly is typically mounted to the frame of the wheelchair adjacent each rear wheel. Each wheel lock assembly includes a hand-operated lever which is connected by mechanical means to a braking member for engaging the tire tread at the periphery of the wheel. Accordingly, when the lever is disposed in a free wheeling position, the braking member is spaced away from the wheel and the tire so as to allow the wheel to rotate freely. Likewise, when the handle is moved to the locked position, the brake member is moved into contact with the tire with sufficient force so as to press into, and temporarily deform, the outer surface of the tire to frictionally hinder rotation of the tire.
One of the drawbacks with these prior art rear wheel locks is that they require either a large manual effort or a long throw to lock the wheels from further rotation. Another drawback of these prior art devices is that the braking mechanism prevents any rotation of the tires in either direction. As will be appreciated, it is desirable at times to allow the wheels to move in the ascending direction while inhibiting movement in the descending direction, such as with a patient being transported or ascending an incline. For example, if the operator were to stop propelling the wheelchair up a hill and relax, gravity would urge the chair to roll backwards. Similarly, if the occupant removed his hands from the wheels to push open a door, the pushing tends to force the wheelchair in the opposite direction. This is true even with automatic doors, wherein the occupant is forced to press against a button to actuate the door. Oftentimes, an occupant must engage the brake to prevent a rollback when pressing the open button for a door; and unfortunately, by the time the occupant disengages the brake to egress through the door, the door would close again.
Accordingly, it is desirable to provide a one-way braking mechanism to provide for rotation of the wheels in only the forward direction. In an effort to meet this need, some prior artisans crafted “hill holder” mechanisms, or one-way clutches, to attach to the hub of the rear wheels. These prior art clutches are relatively expensive and mechanically complex. Other hill holders have been devised which also incorporate a wheel lock assembly. However, these combination devices suffer from numerous drawbacks as well. For example, U.S. Pat. No. 4,887,830 to Frough et al discloses a wheelchair with a combined wheel lock and hill holder. The device uses a cam to engage the brake. However, the device is spring loaded and must thus be manually engaged and disengaged. Once engaged, the wheelchair is hindered from movement in the rearward direction completely. Furthermore, once engaged, the drag of the device on a user's forward motion remains a noted drawback.
More significantly, with these prior art wheelchairs, the braking device needs to be disengaged anytime the wheels are to be rolled in the rearward direction. The constant burden of manually engaging and disengaging a device depending on whether the occupant is on level ground or desires to move rearwardly is a significant drawback to such devices. As will be appreciated, for wheelchair occupants of limited cognitive ability, upper body strength, dexterity, range of motion, coordination, or the like, manually engaging and disengaging a safety device is not a viable option.
One particularly advantageous braking system for overcoming the problems and drawbacks associated with prior art rollback prevention systems was described by the present inventor in U.S. Ser. No. 10/425,034, filed Apr. 29, 2003, entitled “Gravity Reacting Anti-Rollback Brake,” the contents of which are hereby incorporated by reference in their entirety. As set forth in the application, a preferred embodiment of the Gravity Reacting Anti-Rollback Brake system, or “GRAB” system, comprises a pair of graded brake cam structures disposed on opposite ends of a connecting rod. The connecting rod and cams are operatively disposed adjacent the back wheels of a wheelchair via a lever assembly mount. The natural pull of gravity and the configuration of the cams operate to allow passage of wheels in both directions when on flat surfaces and in only a single direction when on an incline. Specifically, when on an incline, gravity operates to dispose cams relative to the wheels such that rotation of the wheels in one direction is hindered by a thickening of the cam body caused by rotation of the cam about its axis. The system also includes an adjustment mechanism for setting the incline angle at which the cams will operate to stop wheel rotation in the undesired direction.
The GRAB system poses a novel and advantageous apparatus for dealing with the problem of rollback with wheelchair devices and the like and is the focus of the present application.
It will also be appreciated that there are times when it would be advantageous for controlling the speed and movement of a wheelchair or other wheeled craft or device when descending an incline in the forward direction. To exemplify the long-felt need in the art, consider electric wheelchairs for instance. Electric wheelchairs not only provide users with powered movement, but also provide automatic braking. Thus, electric wheelchairs inherently prevent unwanted rollback and govern forward speed on inclines or slopes regardless of the weight, strength or endurance of the user. By contrast, manually powered wheelchairs do not. Manually powered wheelchairs require a constant force grip that is affected by the weight, strength and endurance of the operator. Not all wheelchair users need the assistance of an electric wheelchair because these individuals have sufficient strength and dexterity to propel and navigate themselves. However, all wheelchair users can benefit from automatic assisted braking when descending a steep hill. Accordingly, without a braking system, manual wheelchair users attempting to navigate a hilly or steep terrain are at a disadvantage to an electric wheelchair user. Thus, paradoxically, users not requiring the assistance of an electric wheelchair find their community mobility more compromised than those in need of an electric wheelchair.
Applicant's co-pending U.S. application Ser. No. 11/167,931, filed Jun. 28, 2005, now allowed, the contents of which are hereby incorporated by reference in their entirety, disclosed and claimed a braking system making use of a forward movement braking system and also a hybrid braking system using both a forward movement braking system and an anti-rollback brake. The present application is particularly focused on the anti-rollback aspect of the invention.
The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.
The present invention is based, in part, on the concept that a gravity reacting braking system can prevent undesired movement of objects disposed on an incline. While the present invention will be described in connection with a wheelchair, it will be readily apparent to one of ordinary skill in the art that the present invention can be applied to a multiplicity of fields and uses. In particular, the present invention may find use for preventing the movement of other manually powered vehicles such as carts, stretchers, strollers and the like.
According to the presently preferred embodiment, brake system 10 preferably utilizes a pair of graded brake cams 20A, 20B, one for each rear wheel 101 of chair 100. Although this embodiment features brake cams operatively positioned to engage the outer surface of the tire of the wheels, any alternative positioning which allows the cams to hinder rotation of a body, axle, or the like is understood to be within the scope of the invention. Graded brake cams 20A, 20B are graded such that their gripping power is increased as the face 21 of the cam is engaged. Any suitable configuration of brake cams is understood to be within the scope of the invention. For example, it is well within the skill of the ordinary artisan to adapt a configuration which allows for free movement of the wheels in both directions when on flat terrain and prevents movement in one direction when a predetermined incline is reached.
Graded brake cams 20A, 20B are preferably disposed on opposite ends of connecting rod 30. Preferably, connecting rod 30 extends through and serves as the fulcrum for each brake cam. Further, according to this embodiment of the invention, connecting rod 30 and brake cams 20A, 20B are configured to allow the weight of rod 30 to be such that gravity keeps the cams operatively positioned. One of ordinary skill in the art will appreciate this as the principal behind so-called “broom holders” that use the weight (force) of the broom to keep the holder engaged.
Preferably, connecting rod 30 also serves to insure simultaneous engagement of both rear wheels 101, 102. Simultaneous and uniform engagement is preferable to prevent lateral movement, misalignment, or spinning of the wheelchair.
Presently preferred brake cams comprise a durable material, such as lightweight and strong metal alloy(s). According to the invention, brake pads can be used with brake cams to accommodate a range of wheels and environments. Alternatively, to prevent wear, it is possible to construct brake cams from a strong unitary material, such as metal, and provide the outer cam surface with serrations or teeth for grip. Likewise, brake pads may comprise any suitable material. If used, brake pads are preferably interchangeable and thus may be easily replaced when worn.
To attach brake system to the wheelchair, a lever assembly mount 25 is provided. The assembly mount 25 preferably couples to the wheelchair to provide rigid support for the brake system. The assembly mount preferably is used to secure the brake device to the lower frame 103 of the chair in an area just forward of the larger wheel 101. The lever assembly 25 in this embodiment is of a clamp design to allow fore and aft adjustment. Adjustment is desirable when two brake cams are used to help ensure simultaneous engagement of the cams with the wheels. The lever assembly 25 may be mechanically mounted to chair via a nut and bolt, or any other suitable means. Any assembly which allows for secure connection to a vehicle while allowing gravitational disposition of the cam(s) is understood to be within the scope of the invention. Preferably, the assembly will also provide for simultaneous engagement if a plurality of cams are used.
Disposed between brake cams 20A, 20B on connecting rod 30 is adjustment mechanism or adjuster 40. The adjuster 40 preferably comprises an adjustable weight 41 which may be positioned to influence the slope at which the cams will contact the tires. The adjuster 40 according to this embodiment of the invention has a weight which can be adjusted to cause cams to engage at a specified slope angle or desired sensitivity.
As will be appreciated, gravity keeps the weight at a constant 180 degrees from the brake cam fulcrum 22 regardless of the angle of the wheelchair. The cams are configured such that on level surfaces, the cam is not in contact with the wheel thereby allowing freewheeling in a forward and rearward direction. However, the changing of the angle of the wheelchair frame (i.e., via an incline) in relation to the constant, gravity-induced brake-cam position results in a diminishing clearance between the braking surface of cam surface and the rear wheel. Since the grade of the cam lessens 23 in favor of the intended direction of movement, the cam does not impede movement of the rear wheel. However, the grade of the cam increases 24 in the opposite direction. The cam's movement towards the wheel periphery directly correlates to the wheelchair's rotation around the hub of the main wheels. Once in contact with the wheel, any rearward rotation leads to an increasing grip by the cam as it thickens when rotated about its axle 22. Accordingly, the cam serves to prevent further rotation of the wheels in that direction.
Extending from the brake cam is short rod 50 that moves through slotted arc 60 in lever assembly mount 30. The arc provides the travel limits of the brake cam's rotation and ultimately the stopping force from the immobile wheelchair frame.
In the present embodiment, brake 10 is configured and disposed to prevent rearward movement of wheelchair 100 when wheelchair 100 is on an incline. According to this embodiment, depending on the user's needs and abilities, the brake 10 can be configured to engage at a specific incline. By contrast, according to another preferred embodiment, and as will be appreciated by one of ordinary skill in the art, the brake system can be configured and disposed on a wheelchair to allow the user to move rearwardly and not forwardly when on an incline (for users who prefer or need to move up inclines backwards). It is well within the ability of one of ordinary skill in the art armed with the present specification to modify the shape, configuration or disposition of the system to achieve the intended purpose.
According to the present invention, the brake system 10 may include a release mechanism 70 for releasing the rollback protection when needed, for example, when having to move back from an outwardly opening automatic door. A presently preferred embodiment is depicted in
The GRAB assembly of
As depicted in
Presently preferred brake cams comprise a durable material, such as lightweight and strong metal alloy(s). According to the invention, brake pads can be used with brake cams to accommodate a range of wheels and environments. Alternatively, to prevent wear, it is possible to construct brake cams 170 from a strong unitary material, such as metal, and provide the outer cam surface 171 with serrations or teeth 172 for grip (or for interlocking with cooperating teeth or serrations disposed on the axle in a preferred embodiment). Likewise, brake pads may comprise any suitable material. If used, brake pads are preferably interchangeable and thus may be easily replaced when worn.
As shown in
As alluded to above, according to a presently preferred embodiment, the axle or inner ring 151 connected to the axle is provided with teeth 176 or the like for mating with reciprocal interlocking teeth on the cam head. Accordingly, the teeth interlock as the axle rotates to cause stoppage of the rotation in a rearward direction when on incline terrain. Furthermore, stop 175 acts as the final reinforcement to cam to stop any further movement in the rearward direction.
Operatively disposed in connection with brake cams 170 is adjustment mechanism or adjuster 180 (see
Also according to the invention, the brake system may include a release mechanism for releasing the rollback protection when needed, for example, when having to move back from an outwardly opening automatic door. It is well within the ability of one of ordinary skill in the art to provide a mechanism which moves the cam brakes out of operational position with their respective wheels.
Likewise, it is well within the ability of one of ordinary skill in the art armed with the present specification and Applicant's previously identified co-pending application to modify the shape, configuration or disposition of the GRAB system and/or its components to achieve the intended purpose.
However, as depicted in
By contrast, as depicted in
In the embodiment of
The control panel can also include a display 250 to provide the user with information relating to the brake settings. In addition to the settings, the display 250 can include other information that may be of interest to a user of the device. The system can also include an “on” switch 260 and an “off” switch 270 (or a toggle switch that provides both functions). The on/off switching ability could allow a user to turn of the system when automatic braking is not desired or necessary. Numerous permutations of functions can be included in connection with the control or artificial intelligence built into the controller. For example, the control panel can be provided with memory that allows predetermined settings to be saved and stored for use at a later. The explication of every feature that could be included in the operation of an electrical or intelligent switching system are beyond the scope of the present invention. Suffice it to say that one of ordinary skill in the art armed with the present specification can use other types of reliable switches to eliminate the pendulum type activation previously described and/or allow a user to adjust the sensitivity of the braking systems selectively.
Those skilled in the art will appreciate that various adaptations and modifications of the above-described preferred embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
This application is a continuation-in-part of co-pending U.S. application Ser. No. 11/167,931, filed Jun. 28, 2005, which is a continuation-in-part of now abandoned U.S. application Ser. No. 10/425,034, filed Apr. 29, 2003, which is a nonprovisional of U.S. Provisional Application 60/375,815, filed Apr. 29, 2002. Each of these patent applications is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60375815 | Apr 2002 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11167931 | Jun 2005 | US |
| Child | 11929184 | US | |
| Parent | 10425034 | Apr 2003 | US |
| Child | 11167931 | US |
