Abstract:
A motorized wheelchair kill switch for improving the safety of motorized wheelchairs is described. The motorized wheelchair kill switch includes a photoelectric sending unit and a photoelectric receiving unit that are used to kill the operation of a wheelchair joystick. The photoelectric sending unit emits a light beam toward the photoelectric receiving unit along a path that will be broken if a user is safely seated in the wheelchair. If the light beam is detected a determination is made that the user is not properly seated. In that case the joystick operation is disabled, locking the wheelchair motor and preventing accidental movement.

Description:
RELATED APPLICATIONS 
     There are no current co-pending applications. 
     FIELD OF THE INVENTION 
     The presently disclosed subject matter relates to protective devices for motorized wheelchairs. More particularly, that subject matter relates to kill switches that automatically disable motorized wheelchair motors to prevent accidents. 
     BACKGROUND OF THE INVENTION 
     Handicapped and elderly people confined to wheelchairs face numerous obstacles in their daily lives. Some of those obstacles involve simple matters that those without handicaps or disabilities would not even notice. The simple act of traveling from one place to another can easily become a major undertaking that requires great effort and that may involve excessive risk. 
     Devices that reduce the difficulties of the handicapped and elderly traveling from one (1) place to another include the motorized wheelchair and its close relative the motorized scooter. Such devices and their equivalents are referred to hereinafter generically, including in the claims, as motorized wheelchairs. Recent developments in battery technology and motion controls have enabled the development of moderately priced motorized wheelchairs that can turn on a dime, move fractions of an inch, and provide nearly complete mobility, at least on level surfaces. Such motorized wheelchairs have been very successful and have aided numerous handicapped and elderly to lead more productive and enjoyable lives. 
     While very successful, motorized wheelchairs are not without problems. For example, a motorized wheelchair is typically controlled by a joystick that is mounted near the user&#39;s hand at the far end of an armrest. The term joystick as used herein, including in the claims, refers to any manually-operated control mechanism used by a wheelchair occupant to control motion. For example, touch pads may be used instead of joysticks to the same effect. Unfortunately, such joysticks are often located in about the same position where a handicapped or elderly person leans while reaching for something, to eat, or to perform any of a variety of daily tasks. When their torso or other body area contacts the joystick the motorized wheelchair can shoot forward and cause damage to nearly objects and possibly injury to the wheelchair occupant or bystanders. 
     Accordingly, there exists a need for a device which protects the occupant of a motorized wheelchair, bystanders and property. Beneficially such a device would be useful on a wide range of motorized wheelchair and scooters and would disable the motorized wheelchair to reduce or eliminate problems caused by a user coming into accidental contact with the joystick. Such a device that acts as a kill switch that disables a motorized wheelchair when its occupant is not fully seated would be particularly useful. As used herein a kill switch generically refers to the operation of effectively disabling the operation of a joystick. For example, by removing power or electronically locking out control by the joystick. The components that comprise a kill switch would ideally not cause discomfort and would not have exposed wiring. Such kill switches would ideally be retrofit or come as part of a new wheelchair. 
     SUMMARY OF THE INVENTION 
     The principles of the present invention provide for kill switches that protect occupants of motorized wheelchairs, bystanders and property from inadvertent damage and injury. Such kill switches are useful on a wide range of motorized wheelchairs and operate by disabling the wheelchairs when their occupants are not fully seated. The components that comprise the kill switches are beneficially padded so as not to cause discomfort to a user and such that there are no exposed wires. Such kill switches that can be retrofit onto existing wheelchairs or come as part of new wheelchairs. 
     A device that is in accord with the present invention is a kill switch that is wired into the main power circuit of a motorized wheelchair such that the wheelchair can only operate when the user is fully seated and leaning back. Should the occupant lean forward, the kill switch de-energizes the wheelchair to prevent movement even if the joystick is pushed. The kill switch can be provided as standard or optional equipment on new wheelchairs and may be provided as an add-on aftermarket retro-kit for installation on existing motorized wheelchairs. 
     A motorized wheelchair with kill switch that is in accord with the present invention includes a motorized wheelchair having a propulsion system, a first armrest, a second armrest, a back seat, a power source, a motion controller, and a joystick for directing the motion controller to control the motion of the motorized wheelchair. There is a first adjustable mounting bracket attached to the first armrest and a second adjustable mounting bracket attached to the second armrest. A photoelectric sending unit is attached to the first adjustable mounting bracket. The photoelectric sending unit is for emitting a light beam. There is a photoelectric receiving unit attached to the second adjustable mounting bracket for receiving the emitted light beam. Electrical power is applied from the power source to the photoelectric sending unit by a photoelectric sending unit cable, while a photoelectric receiving unit cable applies electrical power to the photoelectric receiving unit. The motorized wheelchair with kill switch further includes a relay for selectively applying electrical power to the motion controller if the photoelectric receiving unit does not receive the light beam. 
     Beneficially the first adjustable mounting bracket enables the photoelectric sending unit to be raised or lowered, and the photoelectric sending unit includes a light emitting lens assembly that projects light across the back seat. Preferably electrical power for the photoelectric receiving unit passes through a coil of the relay, which beneficially includes normally closed contacts. 
     A motorized wheelchair that is in accord with the present invention includes a propulsion system, a first armrest, a second armrest, a back seat, a power source, a motion controller, and a joystick for directing the motion controller to control the motion of the motorized wheelchair using electrical power from the power source. The motorized wheelchair further includes a first adjustable mounting bracket attached to the first armrest, a second adjustable mounting bracket attached to the second armrest, a photoelectric sending unit for emitting a light beam across the back seat which is attached to the first adjustable mounting bracket, a photoelectric receiving unit for receiving the emitted light beam which is attached to the second adjustable mounting bracket, and a power control means for selectively preventing motorized wheelchair motion based on an output of the photoelectric sending unit. 
     The motorized wheelchair can be configured such that the power control means prevents motorized wheelchair motion if the photoelectric sending unit receives the emitted light beam. Alternatively, the motorized wheelchair can be configured such that the power control means prevents motorized wheelchair motion if the photoelectric sending unit does not receive the emitted light beam. Preferably the motorized wheelchair includes a photoelectric sending unit cable for applying electrical power from the power source to the photoelectric sending unit and a photoelectric receiving unit cable for applying electrical power from the power source to the photoelectric receiving unit. In practice the power control means may include a relay for selectively applying electrical power to the motion controller if the photoelectric receiving unit does not receive the light beam. For convenience the relay has normally closed contacts, the first adjustable mounting bracket enables the photoelectric sending unit to be raised or lowered, and the photoelectric sending unit includes a light-emitting lens assembly. 
     A motorized wheelchair kill switch that is in accord with the present invention includes a first adjustable mounting bracket for attaching to a first armrest, a second adjustable mounting bracket for attaching to the second armrest, a photoelectric sending unit for emitting a light beam and for attaching to the first adjustable mounting bracket, a photoelectric receiving unit for receiving the emitted light beam and for attaching to the second adjustable mounting bracket, and a power control means for selectively preventing motorized wheelchair motion based on reception of the emitted light beam by the photoelectric sending unit. 
     The motorized wheelchair kill switch may include a flexible photoelectric sending unit cable for applying power to the photoelectric sending unit and a flexible photoelectric receiving unit cable for applying electrical power to the photoelectric receiving unit. In practice the power control means can include a power control relay configured such that electrical power to the photoelectric receiving unit passes through the power control relay. Preferably the power control relay has normally closed contacts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features of the present invention will become better understood with reference to the following more detailed description and claims taken in conjunction with the accompanying drawings, in which like elements are identified with like symbols, and in which: 
         FIG. 1  is an isometric view of a motorized wheelchair kill switch  10  that is in accord with the preferred embodiment of the present invention when installed on a motorized wheelchair  15 ; 
         FIG. 2  is a detailed view of the photoelectric sending unit  55  of the motorized wheelchair kill switch  10  shown in  FIG. 1 ; 
         FIG. 3  is a detailed view of the photoelectric receiving unit  60  of the motorized wheelchair kill switch  10  shown in  FIG. 1 ; 
         FIG. 4  is a sectional view of the motorized wheelchair kill switch  10  taken along line I-I, of  FIG. 1 ; and, 
         FIG. 5  is a simplified electrical schematic diagram of the motorized wheelchair kill switch  10  shown in  FIG. 1 . 
     
    
    
     DESCRIPTIVE KEY 
     
         
         
           
               10  motorized wheelchair kill switch 
               15  motorized wheelchair 
               20  joystick 
               25  bottom seat 
               30  back seat 
               35  armrest 
               40  foot rest 
               45  wheel 
               50  propulsion system 
               55  photoelectric sending unit 
               60  photoelectric receiving unit 
               65  first adjustable mounting bracket 
               70  emitting lens assembly 
               75  light beam 
               80  flexible photoelectric sending unit cable 
               85  second adjustable mounting bracket 
               90  receiving lens assembly 
               95  flexible photoelectric receiving unit cable 
               100  on-board battery system 
               105  main control switch 
               110  relay coil 
               115  power control relay 
               120  relay contact 
               125  propulsion control module 
               130  first propulsion motor 
               135  second propulsion motor 
           
         
       
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The best mode for carrying out the invention is presented in terms of its preferred embodiment, herein depicted within  FIGS. 1 through 5 . However, the invention is not limited to the described embodiment, and a person skilled in the art will appreciate that many other embodiments of the invention are possible without deviating from the basic concept of the invention and that any such work around will also fall under scope of this invention. It is envisioned that other styles and configurations of the present invention can be easily incorporated into the teachings of the present invention, and only one particular configuration shall be shown and described for purposes of clarity and disclosure and not by way of limitation of scope. 
     The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. 
       FIG. 1  is an isometric view of a preferred embodiment motorized wheelchair kill switch  10  when installed on a motorized wheelchair  15 . The motorized wheelchair  15  is intended to represent a generic motorized wheelchair that is operated by a joystick  20 . Such motorized wheelchairs  15  can vary greatly in many details, thus the generic representation. It should be understood that the specifically illustrated motorized wheelchair  15  is not intended to be a limiting factor of the invention. 
     The motorized wheelchair  15  includes rather standard components such as a bottom seat  25 , a back seat  30 , armrests  35 , a foot rest  40 , wheels  45 , and a propulsion system  50 . However, the motorized wheelchair  15  also includes a photoelectric sending unit  55  and a photoelectric receiving unit  60  that are located on armrests near the back seat  30  as shown. 
     The photoelectric sending unit  55  and the photoelectric receiving unit  60  can be mounted on either the left or right side and thus the indicated positional placement is not intended to be a limiting factor of the present invention. Further disclosures of the photoelectric sending unit  55  and the photoelectric receiving unit  60  are provided below. It is envisioned that the motorized wheelchair kill switch  10  would be provided as standard or optional equipment on new motorized wheelchair  15 . It might also be provided as an add-on aftermarket kit for installation onto existing electric motorized wheelchairs  15 . 
       FIG. 2  presents a detailed view of the photoelectric sending unit  55  attached to the motorized wheelchair  15 . The photoelectric sending unit  55  is mounted upon a first adjustable mounting bracket  65  that is attached to one (1) armrest  35 . The first adjustable mounting bracket  65  allows the photoelectric sending unit  55  to be raised or lowered to compensate for different sized occupants of the motorized wheelchair  15 . The photoelectric sending unit  55  includes a light emitting lens assembly  70  which projects a light beam  75  across, but slightly elevated with respect to, the back seat  30 . The photoelectric sending unit  55  includes a flexible photoelectric sending unit cable  80  for receiving electrical power as is subsequently described. It is envisioned that the photoelectric sending unit  55  uses either visible or infrared light and that it includes a photoelectric emitter that can be emit light that can be detected at least two feet (2 ft.) away. 
     The position of the photoelectric sending unit  55  is preferably adjusted such that it does not interfere with a user&#39;s elbow or such that the photoelectric sending unit  55  is detrimental, annoying or aggravating. 
       FIG. 3  presents a detailed view of the photoelectric receiving unit  60  attached to the motorized wheelchair  15 . The photoelectric receiving unit  60  is mounted on a second adjustable mounting bracket  85  that is attached to another armrest  35 . The second adjustable mounting bracket  85  allows the photoelectric receiving unit  60  to be raised or lowered to compensate for different sized motorized wheelchair  15  occupants. The photoelectric receiving unit  60  includes a receiving lens assembly  90  that is capable of receiving the light beam  75  emitted by the photoelectric sending unit  55  (see  FIG. 2 ). The photoelectric receiving unit  60  is provided with a flexible photoelectric receiving unit cable  95  for receiving electrical power. Further disclosure of the flexible photoelectric receiving unit cable  95  is provided below. 
     The position of the photoelectric receiving unit  60  is such that is it should not interfere with the user&#39;s elbow or in fact be detrimental, annoying or aggravating. The operation of the motorized wheelchair kill switch  10  ideally would be automatic whenever the propulsion system  50  (see  FIG. 1 ) is operational. 
       FIG. 4  presents a sectional view of the motorized wheelchair kill switch  10  as seen along section line I-I of  FIG. 1 . Specifically,  FIG. 4  shows the view looking down on the top of the motorized wheelchair  15  when standing slightly behind it. As noted the photoelectric sending unit  55  is attached to one of the armrests  35  via the first adjustable mounting bracket  65 , while the photoelectric receiving unit  60  photoelectric sending to the other armrest  35  via the second adjustable mounting bracket  85 . The light beam  75  extends between the photoelectric sending unit  55  and the photoelectric receiving unit  60 , in front of the back seat  30  and well above the bottom seat  25 . 
     Should an occupant of the motorized wheelchair  15  sit against the back seat  30  the light beam  75  will be broken. When the light beam  75  is broken the motorized wheelchair  15  (see  FIG. 1 ) can be controlled by the joystick  20  (described below) in the normal fashion. Should the occupant lean forward or otherwise become displaced from the back seat  30 , the light beam  75  will be intact and will be received by the photoelectric receiving unit  60 . Reception of the light beam  75  will prevent operation by the joystick, thus causing the movement of the motorized wheelchair  15  to cease as described below. 
       FIG. 5  depicts the major electrical components of the motorized wheelchair kill switch  10  in a functional electrical schematic diagram format. Electrical power for the motorized wheelchair  15  is derived from an on-board battery system  100 , as is normal for a motorized wheelchair  15  (see  FIG. 1 ). That electrical power is routed through a main control switch  105  such as would normally be present on a motorized wheelchair  15  (see  FIG. 1 ). The main control switch  105  may be a key-operated switch to prevent un-authorized use of the motorized wheelchair  15  (see  FIG. 1 ). 
     The electrical power from the load side of the main control switch  105  is applied to the photoelectric sending unit  55  via the flexible photoelectric sending unit cable  80 . In response, the photoelectric sending unit  55  emits the light beam  75 . The photoelectric receiving unit  60  is powered by electrical power that passes through a relay coil  110  and the photoelectric receiving unit cable  95 . If the light beam  75  is received by the photoelectric receiving unit  60  the resistance of the photoelectric receiving unit  60  drops. This causes increased electrical current to flow through the relay coil  110  and the photoelectric receiving unit cable  95 . This causes the relay  115  to switch states, opening up its normally closed electrical contact, and thus removing electrical power from a propulsion control module  125 . With no electrical power applied to the propulsion control module  125  the motion controlling operation of the joystick  20  is killed since there is no electrical power available for a first propulsion motor  130  and/or a second propulsion motor  135 . 
     In contrast, if the light beam  75  is broken by an occupant properly seated in the motorized wheelchair  15  the photoelectric receiving unit  60  does not receive the light beam  75 . Thus causes the photoelectric receiving unit  60  to have a high resistance, which only allows a small amount of current to pass through the relay coil  110  and along the flexible photoelectric receiving unit cable  95 . This causes the relay coil  110  to be de-energized, which places the power control relay  115  in its normally-closed state such that the contacts  120  are closed. The propulsion control module  125  then receives electrical power. Movement commands from the joystick  20  then can be followed by the propulsion control module  125  by the application of appropriate power to the first propulsion motor  130  and/or the second propulsion motor  135  to fulfill the joystick commands. 
     The foregoing functional description is simply one (1) of an almost infinite number of electronic ways to kill the operation of the joystick  20 . For example, the photoelectric receiving unit  60  might apply one (1) logic level to a microcontroller port or to another logic network if the light beam  75  is detected or the other logic level if the light beam  75  is not detected. Then software controlling the microcontroller or the other logic network could cause the desired killing of the joystick  20  commands in a multitude of ways. Whatever the actual implementation, the desired result is that reception of the light beam  75  by the photoelectric receiving unit  60  kills the operation of the joystick. 
     While the preferred embodiment motorized wheelchair kill switch  10  only allows joystick  20  controlled operation of the motorized wheelchair  15  if the light beam  75  is not received, in some embodiments the opposite may be true. For example, if the photoelectric receiving unit  60  and the photoelectric sending unit  55  are located in front of a seated wheelchair occupant the joystick  20  may control, but if the wheelchair occupant leans forward to break the light beam  75  joystick  20  operation might be killed. However, the preferred embodiment as illustrated and described is far safer in most applications as an occupant getting into the motorized wheelchair  15  will not accidently cause joystick operations. 
     The preferred embodiment of the present invention can be utilized by the common user in a simple and effortless manner with little or no training. It is envisioned that the motorized wheelchair kill switch  10  would be constructed in general accordance with  FIG. 1  through  FIG. 5 . As described, the motorized wheelchair kill switch  10  could be provided as standard or as optional equipment on new motorized wheelchair  15 , or it could be provided as an add-on aftermarket kit for existing motorized wheelchairs  15 . The aftermarket kit would consist of the photoelectric sending unit  55 , the flexible photoelectric sending unit cable  80 , the first adjustable mounting bracket  65 , the photoelectric receiving unit  60 , the flexible photoelectric receiving unit cable  95 , the second adjustable mounting bracket  85 , the power control relay  115 , and associated mechanical components such as fasteners, and associated electrical components such as wiring and terminals. 
     In use the motorized wheelchair kill switch  10  is transparent to the user of the motorized wheelchair  15 . He or she would be instructed that the motorized wheelchair  15  is only operational when fully seated and upright against the back seat  30 . Minor variations to accommodate users of different sized can be made by sliding both the photoelectric sending unit  55  and the photoelectric receiving unit  60  up or down on the first adjustable mounting bracket  65  and the second adjustable mounting bracket  85  respectively. Once properly adjusted the motorized wheelchair kill switch  10  is ready for operation. 
     With the motorized wheelchair kill switch  10  installed the operation of the motorized wheelchair  15  is only possible when the user of the motorized wheelchair  15  is seated upright. Should the user reach forward to grasp something and accidentally contact the joystick  20  in any way, operation of the motorized wheelchair  15  is disabled. The user simply sits backward and upright to re-enable operation and allow for continued and repeated use. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.