Abstract:
A method and apparatus for reducing or eliminating the energy required by an operator of a delivery cart to start the cart moving in a predetermined direction at a predetermined speed as well as to recover some or all of the energy used to start the cart moving. The apparatus includes a cart, a drive wheel, a motor for driving the drive wheel, and a rechargeable energy source to power said motor where the rechargeable energy source is recharged during normal, unpowered movement of the cart. The method includes charging a power source while moving the cart, actuating a directional button to initiate movement in a desired direction, energizing a clutch to couple the motor to the driven wheel, energizing the motor to drive the driven wheel in the desired direction. After a predetermined time period, set by a run timer, the clutch is decoupled while the motor remains activated, and thereafter the motor is deactivated.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to carts and, more particularly, toward delivery carts having means for facilitating movement thereof. 
   2. Description of the Related Art 
   During an assembly process, it is frequently necessary to deliver parts to the assembly line. The parts are generally delivered to the assembly line by material handling personnel. The material handling personnel load a part transportation cart with the appropriate parts, and the loaded carts are then delivered to the appropriate workstation along the assembly line. The delivery process often involves towing the carts to the workstation. However, the line-side area of most assembly lines is very crowded and does not allow for the exact placement of a parts cart by a towing rig. Therefore, once the carts reach the assembly line, the carts must be manually moved by the material handling personnel to the correct line-side position for ease of access by the assembly line personnel. 
   A problem arises in that the carts can be very heavy and difficult to move. This is especially so when the carts are loaded with parts. Therefore, there exists a need or a method and apparatus to make it easier to start moving loaded carts. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus and method for reducing or eliminating the effort required by an operator of a delivery cart to start the cart moving as well as to recover some or all of the energy used to start the cart moving. 
   More specifically, an apparatus according to the present invention is adapted for use in conjunction with a part holding cart and includes a drive wheel, a motor for rotatably driving the drive wheel, and a rechargeable energy source to power the motor. The apparatus further includes an assembly for recharging the rechargeable energy source through rotation of the drive wheel, and a clutch disposed between the motor and the drive wheel to permit the drive wheel to spin freely when not being powered. 
   In further accordance with the present invention, a method for operating a cart includes energizing the motor and engaging the clutch to drive the drive wheel and initiate movement of the cart, operating a run timer and, when the run timer times-out, sequentially disengaging the clutch and de-energizing the motor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and further features of the invention will be apparent with reference to the following description and drawings, wherein: 
       FIG. 1  is a perspective view of a cart used for transporting materials with a motor drive and energy recovery unit according to the present invention; 
       FIG. 2A  schematically illustrates a rear view of the wheel unit of the delivery cart with the motor drive and energy recovery unit affixed thereto; 
       FIG. 2B  schematically illustrates a side view of the wheel unit of the delivery cart with the motor drive and energy recovery unit affixed thereto; and, 
       FIG. 3  is a diagram illustrating the operation of the cart&#39;s circuitry. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The invention will now be described in accordance with its preferred embodiments. The description with reference to the figures is intended to simplify the explanation of the invention and is not meant to limit the scope of the invention. The invention will be described in conjunction with a part transportation cart. This is not meant to limit use of the invention to such a car, as the invention can be used with any assembly having wheels which is at least in part human-powered. 
   With reference to  FIGS. 1-3 , an apparatus  100  for cart movement and energy recovery according to the present invention is incorporated into a cart assembly  102 , and includes a motor drive and energy recovery unit  106  and a power control unit  108 . 
   The delivery cart assembly  102 , which includes a part carrying basket  110  and a plurality of wheels  112 , is illustrated as having four vertical walls, a horizontal floor and an open top surface. A handle  104  is affixed to an exterior side of one of the vertical walls of the basket  110  to facilitate manual movement and steering of the cart  102 . The wheels  112  are attached to a bottom side of the horizontal floor of the carrying basket  110 . Preferably, two of the wheels  112  are swivel-mounted to permit turning of the cart, while one or more of the remaining wheels  112  is a powered or drive wheel  114 . 
   The power control unit  108  is located along a vertical wall of delivery cart assembly  102  near the handle  104 . A forward button  150  and a reverse button  152  ( FIG. 3 ) are provided by the power control unit  108  at a location that is convenient for the operator, such as adjacent to or on the handle  104 . The power control unit  108  is electrically connected to the motor drive and energy recovery unit  106  and adapted to control energization thereof, as will be apparent from the following description. 
   The motor drive and energy recovery unit  106  includes the drive wheel  114 , a motor  116 , a right angle gear reduction unit  118 , a run timer  120 , a generator assembly  121 , a disengaged power supply circuit  124 , a battery  126 , a mounting assembly  127 , a clutch  128 , a clutch control circuit  136 , and a motor energizing circuit  137 . 
   The mounting assembly  127  includes a mounting plate secured to the underside of the basket  110  from which extend first and second drive wheel supporting brackets  129   a ,  129   b , and a pair of generator assembly support arms  131 . A generator bracket  135  is adjustably mounted to the support arms  131  so as to properly position the friction drive wheel  140 , described hereinafter, relative to the drive wheel  114 . Each of the drive wheel supporting brackets  129   a ,  129   b  have bearings  133  mounted thereon to rotatably support the drive wheel shaft  132 , as described hereinafter. 
   An output shaft (not shown) of the motor  116  serves as an input to the gear reduction unit  118 . An output shaft  134  of the gear reduction unit  118  serves as an input to the clutch  128 , while an output shaft of the clutch  128  serves as a drive wheel shaft  132  that is affixed to the drive wheel  114 . As such, the drive wheel  114  is selectively coupled to the motor  116  through the gear reduction unit  118  and the clutch  128 . 
   The clutch  128  is preferably an electrically actuated magnetic clutch having a coil  130   a  and a drive plate  130   b . The coil  130   a  is attached to the output shaft  134  of the gear reduction unit  118  and, when energized, engages or couples the drive plate  130   b , which is secured to the drive wheel shaft  132 , to the output shaft  134  and thereby forces the drive wheel shaft  132  to rotate with the output shaft  134  of the gear reduction unit  118 . The clutch  128  selectively couples the drive wheel  114  to the motor  116  in response to control signals provided by the power control unit  108  via the clutch control circuit  136 , described hereinafter. 
   With reference to  FIG. 2A , the interconnection of the drive wheel  114  with the motor  116  through the gear reduction unit  118  and clutch  128  is shown in more detail. The drive wheel  114  is located on the bottom side of the horizontal floor of the basket  110  between the first and second drive wheel support brackets  129   a ,  129   b . The drive wheel shaft  132 , which is affixed to and extends from the clutch drive plate  130   b , is rotatably supported by the bearings  133  disposed in the first and second drive wheel support brackets  129   a ,  129   b . As such, the drive wheel  114 , drive wheel shaft  132 , and clutch drive plate  130   b  are secured to one another for common rotation about an axis defined by the drive wheel shaft  132 . 
   The gear reduction unit  118  and clutch  128  allow the drive wheel  114  to be selectively coupled to the motor  116  so as to be either driven by the motor or to be free-wheeling. Therefore, the drive wheel  114  is coupled to the motor  116  when the clutch  128  is engaged to permit the motor  116  to drive the drive wheel  114 , but is de-coupled from the motor  116  when the clutch  128  is disengaged to permit the drive wheel  114  to freely rotate. 
   The engagement or coupling of the clutch drive plate  130  to the gear reduction unit output shaft  134  by the clutch  128  is electrically actuated by the clutch control circuit  136 . The clutch control circuit  136  is energized by the battery  126  through the run timer  120  when one of the directional buttons  150 ,  152  is actuated, as will be clear from the following discussion. 
   The generator assembly  121  includes the generator  122 , the generator mounting bracket  135 , the friction drive wheel  140 , and a rectifier  142  ( FIG. 3 ). The friction drive wheel  140  is mounted upon a generator shaft  141  such that the friction drive wheel  140  and generator  122  rotate as a unit on the generator shaft  141 . Rotation of the generator shaft  141  drives the generator  122 , causing the generator  122  to generate a current that flows to the rectifier  142  where it is selectively passed through to the battery  126 , charging the battery  126 . The battery  126  is also connected to a line voltage battery charger  123  ( FIG. 3 ) to permit the battery to be charged via line voltage when the cart is not in use. 
   The friction drive wheel  140  is in frictional engagement with the outer circumference of the drive wheel  114  such that the friction drive wheel  140  is rotated by the drive wheel  114 . The friction drive wheel  140  is preferably made from a high friction material that enhances rotational engagement between the friction drive wheel  140  and the drive wheel  114 . Additionally, engagement between the friction drive wheel  140  and the drive wheel  114  can be adjusted via the mounting of the generator assembly bracket  135  and the generator support arms  131  so that the friction drive wheel  140  engages the drive wheel  114  with sufficient pressure to prevent or minimize rotary slippage therebetween. 
   The power control unit  108  allows the operator to activate the assisted cart motion apparatus  100 . The operator activates the apparatus  100  using either the forward button  150  or the reverse button  152 , depending on the desired direction of cart  102  motion. The directional buttons  150 ,  152  are electrically connected to the motor energizing circuit  137  through the run timer  120 , and through a directional diode  158  (for the reverse button  152 ). 
   With reference to  FIG. 3 , the electrical circuit of the motor drive and power recovery apparatus  100  according to the present invention is illustrated. 
   The disengaged power supply circuit  124  includes a disengaged power relay RLY 3 , a disengaged power capacitor  144 , and a variable resistor  146 . The disengaged power relay RLY 3  is energized via the run timer and electrically connects the motor  116  to the battery  126  upon actuation of the forward button  150 . The disengaged capacitor  144  stores energy and supplies current to continue energizing the disengaged power relay RLY 3  for a period of time after the run timer  120  has timed-out. As such, the disengaged power supply circuit  124  allows the motor  116  to run briefly after the clutch  128  is de-energized to disengage the motor  116  from the drive wheel  114 . 
   The clutch control circuit  136  includes a clutch relay RLY 1  that is energized by an output of the run timer  120  and supplies current to the clutch coil  130   a  to engage the clutch  128  whenever one of the forward or reverse buttons  150 ,  152  is actuated. 
   The motor energizing circuit  137  includes a motor relay RLY 2 , which has normally closed contacts electrically connected to the motor to energize the motor  116  to operate in the forward direction and normally open contacts that, when closed, energize to operate the motor  116  to operate in the reverse direction. The motor relay RLY 2  is energized by actuation of the reverse button  152 , described hereinafter, to switch the direction of motor operation. The motor energization circuit further includes a motor capacitor  138  and variable resistor  139  that cooperate to supply power to the energized motor relay RLY 2  to maintain reverse-operation of the motor  116  for a predetermined period of time after the run timer  120  times out. 
   The battery  126  is electrically connected to the run timer  120  through the closed contacts of the forward button  150  or the reverse button  152 . When neither button  150 ,  152  is actuated, the battery  126  is not connected with the run timer  120 . 
   When the forward button  150  is pushed to initiate forward motion, power from the battery  126  is supplied to the run timer  120 , and the run timer  120  energizes the relay RLY 1  of the clutch control circuit  136  via clutch diode  148 , thereby energizing the clutch coil  130   a  and mechanically coupling the motor  116  to the drive wheel  114 , as discussed previously. Battery power is also supplied from the run timer  120  to the disengaged power supply circuit  124 , energizing the disengaged power supply relay RLY 3  to close its contacts and supply battery power, via the normally closed contacts of the motor relay RLY 2 , to the motor  116 , which operates in the forward direction. Current supplied to the disengaged power supply capacitor  144  charges the capacitor  144 , and provides a store of energy that is later used to continue energizing the disengaged power supply relay RLY 3  so as to supply battery power to the motor  116  when the run timer  120  times out. 
   The run timer  120  energizes the clutch  128 , and connects the motor  116  to the battery  126  (via the disengaged power supply circuit  124 ) for a predetermined amount of time after actuation of the forward button  150 . After the predetermined amount of time, the switch provided by the run timer  120  opens, cutting off power to the clutch relay RLY 1  and to the disengage power supply circuit  124 . Cutting off power to the clutch relay RLY 1  causes the relay contacts to open, de-energizing the clutch coil  130   a  and de-coupling the drive wheel  114  from the motor  116 . 
   When the run timer  120  times-out, cutting power off to the disengage power supply circuit  124 , the disengage power supply capacitor  144  continues to provide current to the disengage power supply relay RLY 3 , thereby maintaining power supply to the motor  116  via the normally closed contacts of the motor relay RLY 2 . Once the capacitor  144  discharges (which is a variable time based upon the setting of the variable resistor  146 ), the contacts of the disengage power supply relay RLY 3  open, and power to the motor  116  is cut off. 
   Therefore, according to the present invention, the motor  116  continues to operate for a period of time during and after the clutch  128  decouples the drive wheel  114  from the motor  116 , and thereby prevents the motor  116  from being a drag on movement of the cart  102  during the interval in which the clutch  128  is decoupling. 
   On the other hand, when the reverse button  152  is actuated to initiate rearward motion, battery power is supplied to the run timer  120  via the diode  154 , and the run timer  120  energizes the relay RLY 1  of the clutch control circuit  136  via clutch diode  148 , thereby energizing the clutch coil  130   a  and mechanically coupling the motor  116  to the drive wheel  114 , as discussed previously. Current flows through the reverse button  150 , via the diode  156 , to the coils of the motor relay RLY 2  and to the motor capacitor  138 . The motor relay RLY 2  is energized to close its normally open contacts. Simultaneously, current supplied to the motor capacitor  138  charges the motor capacitor  138 , and provides a store of energy that is later used to continue energizing the motor relay RLY 2  when the run timer  120  times out. 
   Power is also supplied from the run timer  120  to the disengaged power supply circuit  124 , energizing the disengaged power supply relay RLY 3  to close its contacts and supply battery power to the motor  116  via the normally open contacts of the motor relay RLY 2 , and thereby energizes the motor  116  to operating in the reverse direction. Current supplied to the disengaged power supply capacitor  144  charges the disengage power capacitor  144 , and provides a store of energy that is later used to energize the disengage power supply relay RLY 3  when the run timer  120  times out and cuts off power to the disengaged power supply circuit  124 . It will be noted that the supply of power to the clutch control circuit  136  and the disengaged power supply circuit  124  when operated in the reverse direction is generally identical to operation in the forward direction, described hereinbefore. 
   The run timer  120  provides current to the clutch  128  and the motor  116  (via the disengaged power supply circuit  124 ) for a predetermined amount of time after the reverse button  152  is actuated. After the predetermined amount of time, the switch provided by the run timer  120  opens, cutting off power to the clutch relay RLY 1  and to the disengage power supply circuit  124 . Cutting off power to the clutch relay RLY 1 , causes the contacts of the relay RLY 1  to open, and de-energizing the clutch coil  130   a  and de-coupling the drive wheel  114  from the motor  116 . 
   When run timer  120  times-out, cutting power off to the disengage power supply circuit  124 , the disengage capacitor  144  continues to energize the disengage power supply relay RLY 3 , thereby maintaining power supply to the motor  116  via the normally open contacts of the motor relay RLY 2 . Once the capacitor  144  discharges (which is a variable time based upon the setting of the variable resistor), the contacts of the disengage power supply relay RLY 3  open, and power to the motor  116  is cut off. 
   Similarly, when run timer  120  times-out, power to the motor relay RLY 2  is supplied by the motor capacitor  138 , which maintains the normally open contacts of the motor relay RLY 2  closed for a predetermined amount of time (which is variable based upon the setting of the variable resistor  139 ). When the motor relay capacitor  138  is completely discharged, the motor relay RLY 2  is de-energized and returns to its normal condition. 
   As will be apparent from the foregoing, the present invention is directed toward power-driving the drive wheel  114  for a predetermined time period to overcome the inertia of the resting cart  102 . Once the inertia is overcome and the cart  102  is in motion, the operator effort required to move and direct the cart  102  is sufficiently reduced. Accordingly, the run timer  120  cuts off power to the drive wheel  114  once a sufficient amount of time has passed for the cart  102  to be moving at a predetermined speed in the desired direction. The sufficient amount of time is the predetermined time the run timer  120  allows the motor  116  to remain energized and coupled to drive wheel  114 . 
   With continued reference to  FIG. 3 , when the cart  102  is being moved in a forward direction such as when being towed or manually pushed, the friction drive wheel  140  and generator shaft  141  cooperate to turn the generator  142 , which generates a current that passes through the rectifier  142  and into the battery  126 , thereby charging the battery  126 . When the cart is moved in a rearward direction, the current generated by the generator is of a reverse polarity, and does not pass the rectifier  142 . 
   It should be noted that the delivery cart apparatus  100  is illustrated as having only one drive wheel  114 , however the apparatus  100  can have a plurality of drive wheels  114 . Further the drive wheels  114  can be driven by a single motor  116  or they can each have a dedicated motor  116 . 
   While the present invention has been described with particularity herein, it is considered apparent that the present invention is capable of numerous modifications, substitutions, and rearrangements of parts without departing from the scope and spirit of the present invention. Therefore, the invention is not to be limited to the particular preferred embodiments described hereinbefore, but rather only defined by the claims appended hereto.