Patent Publication Number: US-7583037-B2

Title: Mobile storage unit with holding brake and single status line for load and drive detection

Description:
FIELD OF THE INVENTION 
     The present invention relates to a mobile storage unit powered by an electric motor, and more specifically to a motor-powered storage unit that includes a holding brake to prevent the storage unit from drifting when the electric motor is not powered, and a monitoring arrangement for the motor of the storage unit. 
     BACKGROUND OF THE INVENTION 
     In a large number of mobile storage systems, the mobile storage units are selectively movable along rails to which the units are mounted. The units can be moved on the rails in a manually operated manner, or through the use of a motor, such as an electric motor operably connected to wheels that move the storage unit along the rails. In such motor-powered units, the user selectively actuates a switch to operate the motor, and a drive system between the motor output shaft and the wheels is operable to rotate the wheels in order to move the unit along the rails in the desired direction. 
     When a storage system including a number of mobile units is employed, once the units are loaded, the floor or other surface underlying the rails tends to deflect under the weight of the storage units and the items loaded in each unit. This deflection of the floor or other underlying surface causes deflection of the rails, which creates a curved rail profile defining a lowermost point between the opposite ends of the rails. As a consequence, the wheels of each storage unit have a tendency to move along the rails under the influence of gravity toward the lowermost point of the rails. Thus, when the motor of each storage unit is not being operated to move the storage unit along the rails, the rotational tendency of the wheels causes the unit to drift from the stationary position away from the desired position toward the lowermost point of the rails caused by deflection of the floor or other underlying surface. To prevent this, a number of different locking mechanisms have been developed which engage adjacent storage units with one another and/or with stops or end panels positioned at each end of the storage system to prevent the inadvertent or unintended movement of the units in response to deflection of the rails. However, such locking mechanisms normally require a number of additional components to be integrated into each unit of the storage system, which increases the overall complexity and cost of the each unit, and for the overall mobile storage system. Furthermore, such locking mechanisms are often manually operated, and therefore require an individual to actively engage the locking mechanism in order to prevent the movement of the movement of the units with respect to one another. 
     Therefore, it is desirable to develop a storage system that prevents inadvertent or unintended movement of the storage units when the storage units are placed in a desired position. It is further desirable to provide a storage system that includes a number of motor-driven storage units, and which includes an automatically operated locking or braking mechanism that holds each storage unit in a desired location when the motor is not being operated to move the storage unit. The locking or braking mechanism should be automatically engageable when operation of the motor is stopped, and should have a minimum number of components to reduce cost and the facilitate incorporation into both new and existing storage units. 
     SUMMARY OF THE INVENTION 
     According to a primary aspect of the present invention, a mobile storage system includes a number of storage units that are movable along a number of rails, and each storage unit includes wheels that ride on the rails and a drive arrangement responsive to operation of an electric motor for moving the storage unit along the rails. The electric motor includes an output shaft that provides rotary power to the drive arrangement. The electric motor is operated to move the storage unit in a desired direction until the unit is located in a position as desired by an operator, to create an aisle between a pair of storage units, in a manner as is known. The storage unit includes an automatic locking or braking mechanism, to positively maintain the storage unit in the desired position when driving movement of the storage unit is stopped by stopping operation of the electric motor. The automatic locking or braking mechanism is in the form of a motor brake that is selectively engageable with the motor output shaft to selectively prevent the motor output shaft from rotating when operation of the motor is stopped, to thereby prevent rotation of the wheels and to thus maintain the storage unit in the desired position at which the storage unit is located when operation of the motor is stopped. When the storage unit is to be moved from its location, the motor brake is automatically disengaged from the motor output shaft prior to operation of the motor, to allow the motor output shaft to freely rotate and to thereby move the storage unit on the rails. The motor brake and motor are each operably connected to the main control of the storage unit, such that the operation of the motor brake is efficiently synchronized with operation of the motor in order to ensure that operation of the motor brake and the motor do not interfere with one another during use of the mobile storage system. 
     According to another aspect of the present invention, the motor brake is connected to a status monitor with a pair of connections that provide source and return signals indicative of operation of the motor brake. The system includes a main control board. The connection between the main control board and the motor brake runs through a motor brake and status board. The connection between the status board and the main control board is made by a single status line. The single status line provides signals to the main control board indicative of both the connection of the motor brake and the status board to a load as sensed by the motor brake and to a high side drive. By providing status signals for both the high side drive and the motor brake, through a single status line to the main control board, the construction and operation of the control system for the motor brake and electric motor of each mobile storage unit in a storage system is significantly simplified. 
     Numerous other features, aspects and advantages of the present invention will be made apparent from the following detailed description taken together with the drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawing figures illustrate the best mode currently contemplated for practicing the present invention. 
       In the drawings: 
         FIG. 1  is an isometric view of a mobile storage unit system incorporating the motor brake and single status line of the present invention; 
         FIG. 2  is a schematic view of the mobile storage system of  FIG. 1  and a control arrangement incorporated in the mobile storage system; 
         FIG. 3  is an enlarged partial section view taken along line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is a partial section view taken along line  4 - 4  of  FIG. 3 ; and 
         FIG. 5  is a schematic circuit diagram of the main control board and the motor brake and status board shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, a mobile storage system is indicated generally at  10  in  FIG. 1 . The storage system  10  is mounted over a floor or other supporting surface  11 , and includes a pair of end panels or members  12  between which extend a pair of rails  14 , in a manner as is known. The rails  14  support a number of storage units  16 , each of which is movable on the rails  14  via one or more wheels  18  rotatably mounted to the storage unit  16 . Representatively, each wheel  18  may include a pair of flanges  19  between which rail  14  is received, to guide movement of the storage unit on the rail  14 . The particular manner in which the wheels  18  are engaged with the rails  14  is known in the art. 
     Each set of wheels  18  on each storage unit  16  is interconnected by a transverse shaft  20 , so that the wheels  18  rotate together. One of the shafts  20  is operably connected to an electric motor  22 , which may be secured to a cross member  23  forming a part of the carriage of the storage unit  16 . The cross member  23  may be in the form of an inverted channel member, and preferably serves to mount the wheels  18  to the carriage of storage unit  16 . 
     As shown in  FIGS. 3 and 4 , mounting bracket  27  is secured to one of the vertical walls of cross member  23 . Mounting bracket  27  has an inverted L-shape, and a pair of spaced apart openings are formed in the upper horizontal wall of mounting bracket  27 . A motor bracket  28  is operable to mount motor  22  to mounting bracket  27 . Motor bracket  28  also has an inverted L-shape, and includes an upper horizontal wall that overlaps the upper horizontal wall of mounting bracket  27 . Motor  22  is secured to the vertical wall of motor bracket  28 , and is oriented horizontally such that the output shaft of motor  22  extends through an opening in the vertical wall of motor bracket  28 . The upper horizontal wall of motor bracket  28  includes a pair of slots, which are configured to overlie the openings in the upper horizontal wall of mounting bracket  27 . A pair of fasteners F extend through the aligned openings and slots, and are employed to selectively fix motor bracket  28  to mounting bracket  27 , and to thereby fix the position of motor  22 . 
     The output shaft of motor  22  drives rotation of a drive gear  35 , which in turn is engaged with a driven gear  37  mounted to an axle  39 , to which shaft  20  is secured. Wheel  18  is secured to axle  39 , such that operation of motor  22  results in driving rotation of wheel  18  through drive gear  35 , driven gear  37  and axle  39 . In this manner, the motor  22  drives one of the wheels  18  into rotation, which is transferred by shaft  20  to the other wheel  18  in the set of wheels. The other set of wheels  18  rotate synchronously with rotation of the driven wheels  18 , to move the storage unit  16  in a desired direction on the rails  14 . 
     It is also understood that the output shaft of motor  22  may be drivingly engaged with a drive shaft interconnected with wheels  18  in any other satisfactory manner, e.g. through a belt or chain drive arrangement, in a manner as is known. The motor output shaft is representatively illustrated at  25 , and is rotatable in response to operation of motor  22  to provide rotary output power. The motor  22  is operated in response to actuation through an operator control panel  24  disposed on the storage unit  16 , in order to move the particular storage unit  16  along the rails  14  to a desired position. When the motor  22  is not in use to rotate the output shaft  25 , the output shaft  25  is free to rotate within the motor  22  and the drive shaft  20  is thus free to rotate along with wheels  18 . 
     It is understood that the drive system as shown and described represents one embodiment of a satisfactory drive system that may be used to impart movement to storage units  16 . Many other types of drive systems are known in the art, and may be used to move storage units  16  on rails  14 . The present invention is not limited to the specific type of drive system used to move storage units  16  in response to operation of motor  22 . 
       FIG. 2  illustrates deflection of the surface  11  to which the rails  14  are mounted, under the weight of the loaded storage units  16 . The deflection of the surface  11  is shown with reference to the dotted line in  FIG. 2 , which illustrates a normal flat, planar orientation and attitude of surface  11 . Surface  11  deflects under the weight of the storage units  16  to a deflected position, shown at  30 . Due to the deflection of the surface  26  and correspondingly of the rails  14  mounted to the surface  26 , each storage unit  16  tends to drift or move toward the lowermost point  31  of the deflected surface  30 , each storage unit  16  tends to move or drift toward the lowermost deflected point  31  under the force of gravity, when motor  22  is not being operated to move the storage unit  16  on the rails  14 . Such movement or drifting of the storage unit  16  is caused by rotation of the wheels  18  on the rails  14  and the ability of the drive shaft  20  to rotate relative to the motor  22  when motor  22  is not being operated. 
     In accordance with the present invention, to prevent the inadvertent movement or drifting of each storage unit  16  along the rails  14  to the lowermost point  31  of the deflected rails  14 , the electric motor  22  is also operably connected to a motor brake  32 . The brake  32  is mounted to the motor  22  generally at the end of motor  22  opposite the motor bracket  28 , and is engaged with the motor output shaft  25 . In the illustrated embodiment, the motor brake  32  includes a recess  33  into which the end of motor output shaft  25  extends. Alternatively, the motor brake  32  may be positioned so as to act on the drive shaft  20  or the axle  39 . The motor brake  32  may be any satisfactory shaft brake, and representatively may be a Power Off type brake such as is available from Inertia Dynamics of Torrington, Connecticut under its model number 1702-2521. It is understood, however, that any other type of satisfactory shaft brake may be employed. 
     Referring to  FIG. 2 , in order to enable the motor  20  and motor brake  32  to be operated in concert with one another, the motor brake  32  is connected via suitable connectors or wires  34  and  38  to a motor brake and status board  36 , which can send control signals to operate the brake  32  and also receive an electronic indication of the status of the brake  32 . The status board  36  is also operably connected to a main control board  40 , from which control signals for the operation of the motor  22  can be sent to the motor  22  in response to user operation of the control panel  24  on the storage unit  16 . 
     In operation, when an individual utilizes the control panel  24  to move a specific storage unit  16 , the control board  40  of the specified storage unit  16  sends a signal to the electric motor  22 , and to the status board  36  connected to the motor brake  32 . This signal, which can be a power signal, causes the electric motor  22  to operate and cause the rotation of the axle  39  and shaft  20  to move the unit  16  in a specified direction. Simultaneously, a signal, such as power signal, is sent to the motor brake  32  from the status board  36  in order to disengage the brake  32  from the shaft  20  through the various drive components, or maintain the brake  32  in a disengaged position, such that the shaft  20  is free to rotate in conjunction with the electric motor  22 . Once the unit  16  is positioned where desired, the operator depresses or releases a stop switch (not shown) on the control panel  24 . This generates a stop signal that is sent from the control panel  24  to the control board  40 , which in turn sends terminates the power signal to the motor  22  to cease operation of the motor  22 . Simultaneously, the power signal sent from the control board  40  through the motor brake and status board  36  to the motor brake  32  is terminated, causing the brake  32  to engage the motor shaft  25 , and the shaft  20  through the various drive components, and prevent any further rotation of the shaft  20 , for maintaining the unit  16  at the specified location. 
     Looking now at  FIG. 5 , a circuit diagram of the main control board  40 , the motor brake and status board  36 , the motor brake  32 , and the connections between them is illustrated. There is a multi-wire connection (not shown) between the main control board  40  and the motor brake and status board  36 , but only a single wire forms the single status line  42  functions to enable signals from the status board  36  concerning the connection of the status board  36  to the main board  40 , and of the connection of the board  36  to a load, via the brake  32 . The connection between the motor and brake status board  36  and the motor brake  32  is formed with a pair of wires  34  and  38 . These wires  34  and  38  provide the source and the return signals from the status board  36  to control the operation of the brake  32  that enables the holding brake  32  and status board  36  to prevent the storage unit  16  from drifting along the rails  14 . 
     The main control board  40  includes a digital or analog input  44  that is pulled-up to 5V through a resistor  46 . Both the input  44  and the resistor  46  are located on the main control board  40  that is connected to the motor brake and status board  36  through the single status line  42 . On the motor brake and status board  36 , an output  50  of a high side drive  52  is connected to a resistor-ladder  54  including resistors  56 ,  58  and  60 , as well as to the motor brake sourcing output  62 . The resistor ladder  54  scales the voltage coming from the high side drive  52  to the positive input  64  of an op-amp  66 . A second resistor ladder  68  includes resistors  70  and  72  and provides the switching threshold for the op-amp  66 . A resistor divider  74 , including resistors  76  and  78 , scales the voltage out of the op-amp  66  to be a “high” (3.5V-5.5V) or lower. The resistor  78  of the divider  74  also pulls down the voltage from resistor  46  to a “low” when the divider  74 , and thus the status board  36 , is connected to the main control board  40 . A second op-amp  80  uses a third resistor ladder  82  including resistors  84  and  86  for the switching threshold of the op-amp  80 . The positive input  88  of the op-amp  80  is connected between a resistor  90  and the motor brake return output  92 . Also, a capacitor  94  is connected to the op-amp  80  at the power input  96  to help provide some noise filtering. The supply voltage Ua for the motor brake and status board  36  is variable, and preferably between 18V-25V. 
     In operation, the electronic circuit of the motor brake and status board  36  provides a status signal along the single status line  42  to the main control board  40  of whether or not the circuit is connected to the main control board  40 , and also whether or not a load is connected to the high side drive  52  via the brake  32 . More specifically, if the motor brake and status board  36  are not connected to the main control board  40 , and the load is or is not connected to the motor brake and status board  36 , a “high” (high=3.5 Volts-5.5 Volts) will always be seen on the status line  42  when the high side drive  52  is in either the on or off state. Further, if the motor brake and status board  36  is connected to the main control board  40  and the load is not connected to the high side drive  52 , a “low” (low=less than 0.5 Volts) will always be seen on the status line  42  when the high side drive  52  is in either the on or off state. If the motor brake and status board  36  is connected to the main control board  40  and the load is connected to the high side drive  52 , a “low” will be seen on the status line  42  if the high side drive  52  is in the off state. In this case a “high” will only be seen on the status line  42  if the high side drive  52  is on and the load is being driven at a defined minimum current or greater (about 90 mA-125 mA or greater), barring any fault conditions. 
     Fault conditions can also be determined using the status line  42  and the commanded state of the high side driver  52 . For example, a short to Ua (STUa) with the proper load connected to the high side drive  52  looks to the main control board  40  like the control board  40  is not connected to the motor brake and status board  36 . Further, a STUa with the load not connected to the high side drive  52  looks to the main control board  40  like an open load. Also, a short to ground (STG) with or without the load connected to the high side drive  52  looks like an open load. Table 1 shows an exhaustive listing of the states aforementioned. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Brake Status States 
               
            
           
           
               
               
               
            
               
                   
                 Motor Brake Control Board not connected to 
                   
               
               
                   
                 Main Control Board and/or STUa 
               
               
                   
                 w/ load connected 
               
               
                   
                 Motor Brake and Status Board has Open Load 
               
               
                   
                 and/or STG w/ or w/o load connected and/or 
               
               
                   
                 STUa w/o load connected 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Main 
                   
                   
                   
                   
                   
               
               
                   
                 Control 
               
               
                 Con- 
                 Board 
                 Load 
                   
                   
                 High-Side 
               
               
                 dition 
                 Con- 
                 Con- 
                 FIG. 3, 
                 FIG. 3, Item 
                 Drive 
                 Status 
               
               
                 # 
                 nected? 
                 nected? 
                 Item 92 
                 62 
                 State 
                 Line 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 NO 
                 X 
                 X 
                 X 
                 OFF 
                 HIGH 
               
               
                 2 
                 NO 
                 X 
                 X 
                 X 
                 ON 
                 HIGH 
               
               
                 3 
                 YES 
                 YES 
                 NORMAL 
                 NORMAL 
                 ON 
                 HIGH 
               
               
                 4 
                 YES 
                 YES 
                 NORMAL 
                 NORMAL 
                 OFF 
                 LOW 
               
               
                 5 
                 YES 
                 NO 
                 NORMAL 
                 NORMAL 
                 ON 
                 LOW 
               
               
                 6 
                 YES 
                 NO 
                 NORMAL 
                 NORMAL 
                 OFF 
                 LOW 
               
               
                 7 
                 YES 
                 YES 
                 NORMAL 
                 STUa 
                 ON 
                 HIGH 
               
               
                 8 
                 YES 
                 YES 
                 NORMAL 
                 STUa 
                 OFF 
                 HIGH 
               
               
                 9 
                 YES 
                 NO 
                 NORMAL 
                 STUa 
                 ON 
                 LOW 
               
               
                 10 
                 YES 
                 NO 
                 NORMAL 
                 STUa 
                 OFF 
                 LOW 
               
               
                 11 
                 YES 
                 YES 
                 STUa 
                 NORMAL 
                 ON 
                 HIGH 
               
               
                 12 
                 YES 
                 YES 
                 STUa 
                 NORMAL 
                 OFF 
                 HIGH 
               
               
                 13 
                 YES 
                 NO 
                 STUa 
                 NORMAL 
                 ON 
                 LOW 
               
               
                 14 
                 YES 
                 NO 
                 STUa 
                 NORMAL 
                 OFF 
                 LOW 
               
               
                 15 
                 YES 
                 YES 
                 NORMAL 
                 STG 
                 ON 
                 LOW 
               
               
                 16 
                 YES 
                 YES 
                 NORMAL 
                 STG 
                 OFF 
                 LOW 
               
               
                 17 
                 YES 
                 NO 
                 NORMAL 
                 STG 
                 ON 
                 LOW 
               
               
                 18 
                 YES 
                 NO 
                 NORMAL 
                 STG 
                 OFF 
                 LOW 
               
               
                 19 
                 YES 
                 YES 
                 STG 
                 NORMAL 
                 ON 
                 LOW 
               
               
                 20 
                 YES 
                 YES 
                 STG 
                 NORMAL 
                 OFF 
                 LOW 
               
               
                 21 
                 YES 
                 NO 
                 STG 
                 NORMAL 
                 ON 
                 LOW 
               
               
                 22 
                 YES 
                 NO 
                 STG 
                 NORMAL 
                 OFF 
                 LOW 
               
               
                   
               
            
           
         
       
     
     Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.