Abstract:
An anti-rollback assembly adapted or adaptable for use in combination with a wheelchair. The anti-rollback assembly includes a one-way brake assembly automatically immobilizing the wheelchair against rearward movement when the occupant attempts to rise from or sit in a seat member of the wheelchair, yet at the same time does not prevent the wheelchair from moving in a forward direction. Conversely, when the occupant is fully seated in the seal member, the one-way brake assembly is disengaged so that the wheelchair can move freely in forward or rearward directions. The assembly can be retrofitted onto existing wheelchairs, and is adjustable to fit various size wheelchairs.

Description:
This is a continuation of application Ser. No. 09/026,902, filed Feb. 20, 1998, now U.S. Pat. No. 6,092,824. This application claims the benefit of Provisional Application Ser. No. 60/039,485, filed Feb. 28, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to wheelchairs and more particularly to an anti-rollback assembly that operatively associates with a wheelchair to prevent the wheelchair from rolling backwards and away from its occupant as the occupant attempts to mount or dismount the wheelchair, yet permits the wheelchair in an unoccupied state to be moved in a forward direction. 
     The anti-rollback assembly of the present invention is especially suitable for wheelchairs of invalids, the cognitively impaired, the elderly, and sufferers of physically and mentally disabling diseases such as Alzheimer&#39;s. 
     2. Description of the Related Art 
     Almost all wheelchairs possess a parking brake in one form or another which, when actuated, maintains the wheelchair in a stationary position by preventing one or both of the large drive wheels of the wheelchair from rotating about a common central axis. Perhaps the most crucial periods for the wheelchair to remain stationary are when a person attempts to sit down in and occupy the wheelchair and when the occupant attempts to stand up from and vacate the wheelchair. The natural motion of a person performing these acts imparts a force in the rearward direction on the wheelchair, which, without the benefit of an actuated parking brake, causes the wheelchair to move backwards and away from the person. 
     As a consequence of the mental and physical infirmities suffered by many wheelchair occupants, especially patients suffering from Alzheimer&#39;s disease and other mental frailties, occupants often forget to actuate manually-operated parking brakes prior to attempting to rise from the wheelchair, or neglect to inspect the parking brake to ensure it is engaged in a locked position prior to attempting to sit down into the wheelchair. Failure to engage the manually-operated parking brake in its locked position presents a serious hazard of injury to both the occupant and his or her caretaker, since the wheelchair is unimpeded from rolling back and away from the occupant as the occupant attempts to rise from or sit down in the wheelchair. 
     To address the shortcomings of manually-operated parking brakes, several different automatically-operated locking brake assemblies have been proposed. U.S. Pat. No. 5,203,433 sets forth a discussion of some conventional automatic locking brake assemblies. Each of the conventional assemblies mentioned in U.S. Pat. No. 5,203,433 is characterized by the provision of a locking member that, unless manually disengaged, prevents or at least substantially obstructs both the forward or rearward movement of the wheelchair with which the assembly is associated when the wheelchair is unoccupied. 
     However, one of the most important functions served by an automatic wheelchair brake is that it not only prevent the wheelchair from rolling backwards and away from its occupant as the occupant mounts or dismounts the wheelchair, but that the brake also not substantially obstruct the forward motion of the wheelchair when unoccupied so that the unoccupied wheelchair can be easily maneuvered to a desirable location for use or temporary storage. 
     A long-felt need therefore exists to provide an automatically-operated anti-rollback assembly for a wheelchair that biases a braking mechanism into an activated position when the wheelchair is unoccupied to prevent the wheelchair from rolling back when it is mounted or dismounted in normal operation, yet, while in the activated position, permits the forward motion of the unoccupied wheelchair. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide an anti-rollback assembly that solves the aforementioned problems associated with the related art as well as other problems and addresses the long-felt need outlined above. 
     It is another object of the present invention to provide an automatic anti-rollback assembly which is reliable in operation, easy to use, and economical to manufacture. 
     A further object of the present invention is to provide an automatic anti-rollback assembly that can be easily and inexpensively retrofitted to existing wheelchairs. 
     It is another object of the present invention to provide an automatic anti-rollback assembly that, when operatively associated with a wheelchair, permits the unoccupied wheelchair to freely roll in a forward direction, yet impedes only the rearward motion of the wheelchair, so that the unoccupied wheelchair can be used, for example, as a walker. 
     Still another object of the present invention is the provision of a wheelchair having an automatic anti-rollback assembly with an ambulation monitor which activates an alarm when the wheelchair occupant attempts to vacate the wheelchair. 
     In accordance with the principles of the present invention, these and other objects are attained by the provision of an automatic anti-rollback assembly that is adapted or adaptable for use in combination with a wheelchair. The automatic anti-rollback assembly generally comprises a one-way brake assembly supportable on a frame structure of a wheelchair, biasing member, and a brake releasing assembly. The one-way brake assembly includes a one-way brake member (or brake arm). When used in combination with a wheelchair, the one-way brake assembly is movable between a non-activated position in which the one-way brake member is positioned to permit the rear drive wheel assembly to rotate in forward and rearward directions to enable the wheelchair to move freely in both the forward and rearward directions, and an non-activated position in which the one-way brake member is positioned to prevent rotation of the rear drive wheel assembly in the rearward direction so as to prevent movement of the wheelchair in the rearward direction, yet continues to permit rotation of the rear drive wheel assembly in the forward direction for forward movement of the wheelchair. The biasing member serves to impart a biasing force to urge the one-way brake assembly towards the activated position. The brake releasing assembly is operatively associated with the one-way brake assembly and the biasing member, and is movable in response to the wheelchair being occupied to overcome the biasing force of the biasing member so as to move the one-way brake assembly from the activated position to the non-activated position, thereby enabling the wheelchair to freely move in both the forward and rearward directions unencumbered by the one-way brake member. 
     In accordance with the present invention, the occupant of the wheelchair is not required to set a conventional parking brake. Instead, the wheelchair is automatically immobilized against backward movement by the anti-rollback device when the occupant is attempting to rise from or sit himself in the seat member. In addition, when the occupant is fully seated in the seat member, the anti-rollback device is disengaged, i.e., the one-way brake assembly is moved into a non-activated position, so that the wheelchair can be freely moved forward or backwards unencumbered by the one-way brake member. 
     These and other objects, features, and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate an embodiment of the present invention. In such drawings: 
     FIG. 1 is a perspective rear view of a wheelchair including an anti-rollback assembly in accordance with a preferred embodiment of the present invention, in which the range of movement of the anti-rollback assembly between non-activated and activated positions is depicted by arrows; 
     FIGS. 2A and 2B are side elevational views of the wheelchair of FIG. 1 in occupied and unoccupied states, respectively; 
     FIG. 3 is an exploded view of mounting and brake releasing assemblies of the anti-rollback assembly of FIG. 1; 
     FIG. 4 is a perspective view of a bracket and brake arm supporting member of the mounting assembly of FIGS. 1 and 3; 
     FIG. 5 is a rear view of the bracket of the mounting assembly depicting a biasing member; 
     FIG. 6 is a side view of an ambulation monitor according to one embodiment of the present invention; and 
     FIG. 7 is an exploded view of the ambulation monitor of FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of a conventional wheelchair structure will be discussed hereinbelow for the purposes of assisting in the detailed description of the anti-rollback assembly of the present invention and explaining the manner in which the anti-rollback assembly is operatively supported on a wheelchair. It is understood, however, the present invention is not restricted to the illustrated wheelchair or the construction and arrangement of the individual components of the illustrated wheelchair. 
     Referring now to the drawings, there is shown in FIGS. 1,  2 A, and  2 B a wheelchair generally designated by reference numeral  10 . The wheelchair  10  includes a frame structure  12  comprising a pair of opposing side frames  14   a  and  14   b  laterally spaced from and substantially parallel with one another. The opposing side frames  14   a  and  14   b  have respective front upright members  16   a  and  16   b  and respective rear upright members  18   a  and  18   b.  In the illustrated embodiment, the front upright member  16   a  and the rear upright member  18   a  of the side frame  14   a  include longitudinal axes oriented substantially vertical, and are interconnected with crossbars  19   a  and  20   a.  The front upright member  16   b  and the rear upright member  18   b  of the other side frame  14   b  are arranged and interconnected in a similar manner with crossbars  19   b  and  20   b.  Handles  22   a  and  22   b  are fitted onto upper ends (unnumbered) of the rear upright members  18   a  and  18   b,  respectively. Arm rests  24   a  and  24   b  are secured to upper surfaces of the crossbars  19   a  and  19   b,  respectively. 
     The wheelchair  10  further includes a flexible seat member  26  extending between the opposing side frames  14   a  and  14   b  and arranged in a substantially horizontal orientation so as to permit an occupant to sit thereon. A flexible back support member  28  extends between the rear upright members  18   a  and  18   b  and, together with the seat member  26 , define a seating area (unnumbered) for supporting the wheelchair occupant. 
     As shown in FIG. 1, the wheelchair  10  further includes rear drive wheel assemblies comprising two large rear drive wheels  30   a  and  30   b  which are manually rotatable by the occupant to rotate about hubs  32   a  and  32   b,  respectively. The hubs  32   a  and  32   b  are respectively attached to the rear upright members  18   a  and  18   b  with axle bolts (unnumbered) and each include a plurality of spokes (not shown) extending therefrom to interconnect the hubs  32   a  and  32   b  to their respective drive wheels  30   a  and  30   b.  Front wheel assemblies comprise small wheels  34   a  and  34   b  swivably connected to the front upright members  16   a  and  16   b,  respectively, to facilitate turning of the wheelchair  10 . 
     Although not shown, it is understood that in accordance with the present invention, the wheelchair  10  can include additional components, such as footrests. It is further understood that in accordance with the present invention the wheelchair can omit one or more of the components discussed above and illustrated in the drawings, so long as the wheelchair is characterized as being capable of operatively supporting the anti-rollback feature of the present invention. 
     One embodiment of the automatic anti-rollback assembly of the present invention, which is generally designated by reference numeral  40 , will now be described with greater specificity hereinbelow. 
     Referring to FIGS. 3 and 4, the illustrated automatic anti-rollback assembly  40  includes two mounting assemblies. For explanatory purposes, only one of the two mounting assemblies, which is generally designated by reference numeral  42 , will be described below. 
     The mounting assembly  42  includes a mounting bracket  44  with a discontinuous circular clamping end  46 , which accommodates the rear upright member  18   a.  Nut-bolt combinations  48  and  50  serve to secure the mounting bracket  44  to the rear upright member  18   a.  Reinforcement spacers  52  may be used in combination with the nut-bolt combinations  48  and  50  to prevent bowing of the bolts. The reinforcement spacers  52  can be made of, for example, nylon or other plastics. As shown in FIGS. 1,  2 A, and  2 B, the clamping end  46  of the mounting bracket  44  is positioned immediately above the axle bolt associated with hub  32   a.    
     The mounting assembly  42  further includes a movable brake-arm supporting member  54  (also referred to as a brake-member supporting member or pivotable collar), which is substantially configured as a clevis yoke. In the illustrated embodiment, the brake-arm supporting member  54  is rotatable about its longitudinal axis between first and second positions. Opposing sides of the mounting bracket  44  define aligned apertures, one of which is designated by reference numeral  56  in FIG.  4 . The apertures  56  are sized to receive a shaft  58  co-axially extending from and integral with the pivotable collar  54 . The shaft  58  is secured to the mounting bracket  44  with, for example, a lock cap  60 . As shown in FIG. 5, a torsion spring  62  is accommodated in the mounting bracket  44  and connected to the shaft  58  of the pivotable collar  54  via pin  63  to urge the pivotable collar  54  into its first position. 
     The opposite end (unnumbered) of the pivotable collar  54  defines a slot  66  diametrically positioned and axially extending a certain depth into pivotable collar  54 . A first bore  68  is diametrically defined within the pivotable collar  54 , and arranged orthogonally relative to the slot  66  to intersect the slot  66 . Second and third bores  70  and  72  are each diametrically disposed, arranged orthogonally relative to each other to intersect each other, and are interposed between the slot  66  and the shaft  58 . The functions of the slot  66  and the first, second, and third bores  68 ,  70 , and  72  will be described below. 
     Still referring to FIG. 3, the automatic anti-rollback assembly  40  further includes a brake releasing assembly, which is generally designated by reference numeral  74 . 
     The brake releasing assembly  74  includes a substantially L-shaped actuator lever  76 , adjustor plate  78 , and connector plates  80 . For explanatory purposes, the connector plate  80  and the side of the adjustor plate  78  operatively associated with mounting assembly  42  will be described below. 
     The actuator lever  76  is cantilevered at a central portion (unnumbered) of the adjustor plate  78 . The end (unnumbered) of the adjustor plate  78  defines an exposed lateral port  82 , which receives a portion of the connector plate  80 . The upper region of the adjustor plate  78  has an elongated slot  84  defined therethrough in communication with the lateral port  82 . (As shown in FIG. 3, the slots  84  are located on each side of the central portion of the adjustor plate  78 .) A nut-washer combination  86  engages a first aperture  88  of the connector plate  80  and the elongated slot  84  to thereby secure the adjustor plate  78  to the connector plate  80 . The end of the connector plate  80  opposite to the first aperture  88  defines a second aperture  90 . 
     As shown in FIGS. 2A and 2B, when the brake releasing assembly  74  is connected to the mounting assembly  42 , the brake releasing assembly  74  is positioned immediately underneath the seat member  26 . The connection of the brake releasing assembly  74  to the mounting assembly  42  will now be described with reference to FIG.  3 . 
     The slot  66  of the pivotable collar  54  receives the end of the adjustor plate  78  containing the second aperture  90  so that the first bore  68  and the second aperture  90  are aligned. A quick-release pin  92  is inserted through the aligned first bore  68  and second aperture  90  to secure the brake releasing assembly  74  to the mounting assembly  42 . The provision of the quick-release pin  92  or similar connecting device facilitates the quick and easy separation and removal of the brake releasing assembly  74 . When the wheelchair  10  is of the collapsible variety, the frames  14   a  and  14   b  and associated wheels on either side of the seat member  26  can thereby be folded together for convenient stowage. The provision of a quick-releasing mechanism to facilitate the ability of the wheelchair  10  to be collapsed and stored represents one of the many advantages of the present invention. 
     Another of the advantages of the illustrated embodiment rests in the configuration of the elongated slots  84  of the adjustor plate  78 , which provides for an adjustable positional relationship with the first aperture  88  of connector plate  80 . This feature makes the illustrated anti-rollback assembly  40  adaptable and retrofittable to wheelchairs of various widths. Although not shown, it is noted that the elongated slots  84  can be replaced with, for example, a series of spaced apertures. 
     The anti-rollback assembly  40  also includes a brake member (or brake arm)  94 , a proximal end portion  96  of which is received in the second bore  70  of the pivotable collar  54  and secured thereto with a set screw  98  (FIG.  3 ). (The brake member  94  and mounting assembly  42  collectively form a one-way brake assembly in this embodiment.) As respectively shown in FIGS. 2A and 2B, a distal end portion  99  of the brake arm  94  either is spaced from a rear region of the drive wheel  30   a  (when the wheelchair  10  is occupied) or rests on the drive wheel  30   a  (when the wheelchair  10  is unoccupied or the occupant attempts to rise from or sit down into the wheelchair  10 ). As is believed evident from this description, the positional relationship of the brake arm  94  to the pivotable collar  54  can be adjusted (by loosening set screw  98 ) to make the brake arm  94  adaptable and retrofittable to wheelchairs of various drive wheel sizes. 
     The operational movement of the anti-rollback assembly  40  will be described below with reference to FIGS. 1,  2 A,  2 B, and  3 . 
     In its unoccupied state, the torsion spring  62  imparts a biasing force to urge the brake-arm supporting member  54  towards the first position, which in turn urges the seat member  26  towards its upper position and the distal end portion  99  of the brake arm  94  into the activated position. As is seen from the arrows in FIGS. 1,  2 A, and  2 B, in the illustrated embodiment the axis of the pivotal collar  54  is located higher and to the rear of the axis of the drive wheels  30   a  and  30   b.  As a consequence, the torsion spring  62  applies a biasing force along a non-radial direction relative to the drive wheels  30   a  and  30   b.  As shown by the arrows in FIGS. 1,  2 A, and  2 B, this biasing force urges the end portion  99  along a direction substantially parallel to a tangent at the point at which the brake arm end portion  99  engages the peripheral surface of the associated drive wheel. In this manner, the end portion  99  pivots upward and downward on a smaller and intersecting arc to that of the associated drive wheel. In the activated position, the distal end portion  99  of the brake arm  94  prevents the first drive wheel  30   a  from rotating about a central axis thereof in a rearward direction, yet does not prevent the first drive wheel  30   a  from rotating about the central axis thereof in a forward direction. 
     When a patient attempts to rest into the seating area of the wheelchair  10 , the weight of the patient imparts a downward force on the seat member  26 , which causes the seat member  26  to flex, bend, slide, or otherwise move in a downward direction to its lower position. The downward movement of the seat member  26  translates the downward force to the actuator lever  76 , thereby pivoting the actuator lever  76  downward as indicated by the arrow in FIG.  2 A. As the actuator lever  76  pivots, the adjustor plate  78  is rotated about its longitudinal axis to translate a corresponding rotational movement to pivotable collar  54 . As the collar  54  rotates about its axis, the brake arm  94  operatively associated therewith is pivoted about the region of its proximal end portion  96  accommodated in the second bore  70  so that the distal end portion  99  is moved substantially along the forward rotational direction from the activated position to a non-activated position. In the non-activated position, the distal end portion  99  is radially spaced from the drive wheel  30   a  and, hence, does not interfere with manual operation (including both forward and rearward motion) of the wheelchair  10 . 
     Conversely, when an occupant of the wheelchair  10  attempts to rise from the seating area, the torsion spring  62  imparts a biasing force to urge the brake-arm supporting member  54  towards the first position, which in turn urges the seat member  26  towards its upper position and the distal end portion  99  of the brake arm  94  to move in a downward manner along an arcuate path (as shown by the arrow in FIG.  2 B), that is, substantially along a rearward rotational direction into the activated position. 
     In the illustrated embodiment, the arcuate path that the distal end portion  99  of the brake arm  94  follows between the activated and non-activated positions intersects the circumference of the drive wheel  30   a.  Consequently, the amount of frictional force applied to the brake arm  94  by the drive wheel  30   a  is proportional to the rearward force applied to the wheelchair  10 . Stated differently, when the wheelchair  10  is moved rearwardly, frictional force between the drive wheel  30   a  and the brake arm  94  causes the distal end portion  99  of the brake arm  94  to move in a generally radially inward direction towards the hub  32   a,  which further presses the distal end portion  99  into the drive wheel  30   a.  Consequently, continued rearward motion of the wheelchair  10  has a corresponding immobilizing effect on the drive wheel  30   a  of the wheelchair  10 . 
     Accordingly, even though the occupant of the wheelchair  10  may neglect to set a conventional parking brake (not shown), the chair  10  is automatically immobilized against backward movement by the anti-rollback device when the occupant is attempting to rise from or seat himself in the seat member  26 . 
     Referring now to FIGS. 6 and 7, according to another embodiment of the present invention the wheelchair is equipped with an ambulation monitor, generally designated by reference numeral  100 , for activating an alarm when the occupant of the wheelchair  10  attempts to rise from the seat member  26 . 
     As shown in FIG. 7, the ambulation monitor includes a housing structure  102 , which houses a horn  104 , an on/off switch  106  and a switch jack  108  electrically connected to the horn  104 , and an energy source  110 , e.g., a battery, electrically connected to the on/off switch  106 . The housing structure  102  is supported on the mounting bracket  44  with a mounting bracket  112 , a mounting bracket clamp knob  114 , and screws  116   a  and  116   b.    
     Referring now to FIG. 6, a connector wire  120  electrically connects the switch jack  108  to a cam actuator switch  122 . A cam  124  is cooperatively associated with the pivotable collar  54  by providing the cam  124  with an eccentrically disposed aperture  126  through which a portion of the pivotable collar  54  is disposed. Accordingly, when the occupant begins to rise from the seat member  26 , the pivotable collar  54  is rotated about its longitudinal axis as described above. The cam  124 , by virtue of its cooperative association with the pivotable collar  54 , rotates to actuate the switch  122 , thereby activating the horn  104  to alert staff of the occurrence. 
     In its broadest aspects, several variations and modifications to the above-discussed anti-rollback assembly can be implemented without departing from the scope of the present invention. For example, the anti-rollback assembly  40  may include a separate biasing member or members, such as springs, to urge the seat member into its upper position independent of or in conjunction with the torsion spring  62 . Also, although in the illustrated embodiment each of the drive wheels  30   a  and  30   b  and a one-way brake assembly (that is, a mounting assembly and brake arm) associated therewith, it is understood that the anti-rollback assembly  40  may include only one mounting assembly  42  and brake arm  94 , in which case, for example, a pivotable bar (not shown) may interconnect the brake releasing assembly  74  with the side frame  14   b  not associated with the mounting assembly  42  and brake arm  94 . Where the anti-rollback assembly includes one-way brake assemblies respectively associated with each of the drive wheels  30   a  and  30   b  (as shown in FIGS. 1,  2 A, and  2 B), a second torsion spring (not shown) may be accommodated in the mounting bracket associated with the second drive wheel  30   b;  alternatively, the anti-rollback assembly  40  may include only a single torsion spring, since the pivotable collar  54  associated with the first drive wheel  30   a  rotates in unison with the pivotable collar associated with the second drive wheel  30   b  due to the interconnection provided by the brake releasing assembly  74 . 
     The one-way brake assemblies may respectively engage portions of the rear drive wheel assemblies at positions other than the rear drive wheel. For example, although not shown, the assemblies could include ratchet and pawl wheel assemblies to accomplish the anti-rollback function of the present invention. 
     These and other modifications to the assembly, when viewed with reference to this disclosure, are within the purview of those skilled in the art. 
     If desired, the automatic anti-rollback assembly  40  of the present invention may be used in conjunction with conventional supplemental braking devices well known in the art, including, for example, a manually-operated parking brake to immobilize the wheelchair from forward or rearward movement when occupied. 
     The foregoing detailed description of the preferred embodiments of the invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.