Abstract:
An obstruction sensing system is provided for a lift vehicle ( 10 ) with a lift platform ( 20 ). The system includes a plurality of sensors ( 32 ) mounted to the lift platform ( 20 ) and a control system ( 18 ) coupled with a drive system of the lift vehicle. The sensors collectively detect a profile of an area on a sensor side of the platform, and the control system generates a signal according to the profile detected by the plurality of sensors. The profile detected by the sensors may be compared with a stored plurality of area profiles by the control system based on a position of the lift platform or profiles of substantially symmetrical areas may be compared. If an obstruction is sensed during platform descent, further descent is halted and an alarm is sounded. The system also includes structure for overriding the disabling function.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/188,616, filed Mar. 13, 2000, the entire content of which is herein incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention relates generally to obstruction sensing systems and, more particularly, to an obstruction sensing system that effects detection beneath the entire area of a platform and includes override functionality.  
           [0003]    There are many uses for vertical lift products, including in large retail establishments, where inventory may be stored on high shelves and the like, and the vertical lift products are thus in use near customers. As such, it may be desirable to ensure that the area beneath the lift platform is clear from obstructions before lowering the platform. It is also advantageous to ensure that the area is clear from boxes, products, etc., to prevent damage to both the obstruction and the lift platform.  
         SUMMARY OF THE INVENTION  
         [0004]    According to the present invention, an obstruction sensing system for a vertical lift product or stock picker incorporates sensors such as ultrasonic transducers or the like to detect an obstruction under any portion of the platform. The system is only active during platform descent, and the lift horn is sounded in a distinct pattern to signal the operator in the event of an obstruction. The system prevents the operator from further lowering the platform once an obstruction has been detected, and to acknowledge that an obstruction has been detected, the operator is required to sound the lift&#39;s horn momentarily using the platform button, raise the platform slightly, or recycle the main power system to re-enable lift functionality. Override capability is also provided, requiring the operator to hold the horn button and operate the lift down control implement at the same time.  
           [0005]    In an exemplary embodiment of the invention, an obstruction sensing system for a lift vehicle including a lift platform has a plurality of sensors mountable to the lift platform and a control system coupleable with a drive system of the lift vehicle. The sensors collectively detect a profile of an area on a sensor side of the platform, and the control system generates a signal according to the profile detected by the sensors. The sensing system may include physical shielding cooperating with the plurality of sensors that prevents errant detection of objects that are not in the detected area. The control system may include a memory storing a plurality of area profiles based on a position of the lift platform. The control system compares the profile detected by the sensors with at least one of the stored plurality of area profiles according to a position of the lift platform. Alternatively, the sensors may detect the profile of separate substantially symmetrical areas, and the control system compares the first and second area profiles. Preferably, the sensors are ultrasonic transducers. In one exemplary arrangement, the plurality of sensors are mountable to an underside of the lift platform, wherein the area profile is a profile of a base of the lift vehicle and the ground.  
           [0006]    In another exemplary embodiment of the invention, a lift vehicle includes a chassis supporting a lift platform, a driving system coupled with the lift platform for driving a lift platform, and the obstruction sensing system according to the invention. If the control system detects an obstruction according to the profile comparison during a lift down function by the driving mechanism, the control system generates a signal to halt further lowering of the lift platform. The vehicle may additionally include a horn operatively coupled with the control system, wherein the signal generated by the control system to halt further lowering of the lift platform additionally activates the horn. More generally, the control system includes structure for disabling the driving system when the control system detects an obstruction according to the profile detected by the sensors. The system is preferably also provided with structure for overriding the disabling structure, which may include the vehicle horn and a control implement that activates the driving system. In this context, the disabling function is effected when the horn and the control implement are activated simultaneously.  
           [0007]    In still another exemplary embodiment of the invention, a method of sensing obstructions in the traveling path of a lift vehicle lift platform includes (a) detecting a profile of an area on a traveling path side of the lift platform, and (b) generating a signal according to the profile detected in step (a). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    These and other aspects and advantages of the present invention will be described in detail with reference to the accompanying drawings, in which:  
         [0009]    [0009]FIG. 1 is a side view of a stock picker in a raised position with the obstruction sensing system according to the invention;  
         [0010]    [0010]FIG. 1A is a close-up view of the sensor shielding;  
         [0011]    [0011]FIG. 2 is a schematic circuit diagram for the obstruction sensing system; and  
         [0012]    [0012]FIG. 3 shows an exemplary alternative application of the obstruction sensing system. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0013]    As shown in FIG. 1, a stock picker  10  typically includes a chassis or base  12  mounted on wheels  14 , a boom or lift assembly  16 , power and control units  18  mounted to the boom or lift assembly, and a vertically movable platform  20 , which also likely has lift controls. The obstruction sensing system according to the invention comprises a microprocessor  30  (FIG. 2) communicating with a plurality of sensors such as ultrasonic transducers. The transducers  32  are mounted to the underside of the platform  20  to sense the entire area beneath the platform, while preventing sensing more than three inches (3″) beyond the area beneath the platform.  
         [0014]    The system preferably contains a series of transducer pairs mounted underneath the platform floor. One of the transducers in each pair sends out an ultrasonic signal, and the other of the pair listens for a reflection as shown schematically in FIG. 1. The transducers  32  may be attached to the platform in any suitable manner.  
         [0015]    The sensing area is limited by physical shielding  24  and software intelligence to prevent errant detection of objects that are not directly under the platform. As shown in FIG. 1A, the physical shielding  24  limits a sensing area of the sensors, showing a potential path  24 A of the sensing signal and a shielded path  24 B. The sensors  32  are thus configured to sense substantially all of the area on the sensor side of the platform. The system is programmed to check for obstructions within a preset distance from the platform  20 . When the platform  20  is within this distance from the base  12  of the machine, the microprocessor  30  is programmed to recognize the profile (signature) of the machine and floor beneath the platform  20  and determines whether an obstruction is present by comparing the profile that it expects to see with the detected profile. The profiles are preferably pre-programmed for the port and starboard sides, as well as fore and aft sides, which profiles further differ depending on the height of the platform. The system recognizes the base  12  of the machine in relation to the ground. Any differences from the expected profile will cause the lift down function to be stopped.  
         [0016]    In an alternative arrangement, the sensors  32  are connected to both a receiving multiplexer and a transmit multiplexer. During operation, the microprocessor  30  causes the transmitting transducers in the sensors to transmit ultrasonic pulses that travel through the air beneath the lift platform  20 . The ultrasonic waves reflect from objects in their path, and the resulting echoes return to receiving transducers in the sensors  32 , which convert the acoustic echoes into electrical signals that represent the machine profiles. The received echo signals are then amplified and detected by the system. The microprocessor  30  uses a processing algorithm based on a comparison of the symmetry of the echoes from one side of the lift platform to the other to determine if an obstacle is present under the platform. If the echoes are symmetric, no obstacle is present beneath the lift. If the echoes are not symmetric, an obstacle is present.  
         [0017]    In addition to doing profile comparisons to determine if an obstruction is present, the system is also monitoring the profiles via the return echoes to determine if the echoes are returning too quickly. If the echoes are returning too quickly and the system does not see a preprogrammed profile, the system will stop the platform  20  regardless of symmetry or profile comparison.  
         [0018]    For example, presume the system is programmed to trigger if an obstruction is detected 20″ (about 51 cm) or less from the platform. (This value is programmable.) If the system sees any obstructions within 20″ (about 51 cm) of the platform (regardless of symmetry or which transducer detects it) and it does not detect a profile that it has been programmed to ignore, it will stop the platform. If the platform is elevated to 10′ (about 3 m) and an attempt is made to lower the platform over a flat shelf, which is symmetrical in reference to the sensor system, once within 20″ (about 51 cm) of the shelf, the system will think there is a problem. It will then determine whether what it sees matches any of the preprogrammed profiles. If not, it will stop the platform. It would also perform this way if the obstruction were not symmetrical.  
         [0019]    Any suitable sensors  32  can be incorporated into the obstruction sensing system of the invention, and the invention is not meant to be limited to a particular transducer. An example of a suitable transducer is available from MASSA Products Corporation of Hingham, Mass. Of course, the invention may also be used with sensors other than ultrasonic transducers, provided they are suitable for the described purpose.  
         [0020]    [0020]FIG. 2 is a schematic circuit diagram for the obstruction sensing system according to the invention. A microprocessor  30  controls the operation of the system based on signals from the ultrasonic transducers  32  mounted to the platform  20 . In a preferred embodiment, the system is only active during platform descent, and the lift up signal via  34  from the control panel is received by the microprocessor  30 , which activates the components to effect platform lift. When an operator moves the controls to initiate a lift down signal via  36 , the microprocessor  30  polls the ultrasonic transducers  32  to determine if there is an obstruction beneath the platform.  
         [0021]    If there is no obstruction, the microprocessor  30  activates the lift down function via a lift down switch  38 , and an activate signal via  40  is sent to the vehicle components that effect lowering of the platform, such as a lift down solenoid or the like. If the ultrasonic transducers  32  detect an obstruction before or during the lift down function, the microprocessor  30  prevents further lowering of the platform by switch  38 , and the microprocessor  30  activates the horn via a horn switch  42  to send a signal via  44  to sound the vehicle horn. Preferably, the horn is sounded in a distinct pattern to alert the operator of the obstruction. Additionally, a warning light may be caused to illuminate or flash. In order to re-enable lift down functionality, the system is programmed to require the operator to sound the horn from the control panel, which sends an acknowledgment signal via  46  to the microprocessor  30 , activate the lift up function of the control system to slightly raise the platform  20 , or recycle the main power system. When the operator again moves the controls to lower the platform  20 , the process is repeated with the microprocessor  30  polling the ultrasonic transducers  32 .  
         [0022]    The obstruction sensing system according to the invention also enables the system to be overridden, if necessary. The system is programmed to allow the lift to be lowered when the operator holds the vehicle horn button and a vehicle control implement such as the lift down controls at the same time. That is, when a lift down signal is received by the microprocessor  30  via  36 , the microprocessor will enable the lift down switch  38  when there is no obstructions sensed by the ultrasonic transducers  32  or when the microprocessor  30  is receiving a signal from the vehicle horn via  46 .  
         [0023]    As discussed above, if the ultrasonic transducers  32  detect an obstruction before or during the lift down function, the microprocessor  30  prevents further lowering of the platform by switch  38 . Thus, during the lift down function, the microprocessor  30  is continuously polling the ultrasonic transducers  32 , and further lowering is quickly halted upon the detection of an obstruction.  
         [0024]    The obstruction sensing system according to the present invention effects safe operation of a lift vehicle lift platform by detecting obstructions in the traveling path of the lift platform during platform descent. Upon detection of an obstruction, further descent of the platform is prevented, thereby protecting the vehicle as well as the obstruction itself. Of course, as shown in FIG. 3, the obstruction sensing system according to the invention may apply to various types of industrial machinery and not just the exemplary vertical lift product shown in FIG. 1. For example, the system may apply to other aerial lifts working in a sensitive environment where the items sensed are at some predetermined horizontal distance from the encroaching surface of the machine (e.g., aircraft assembling machine or other such apparatus, etc.). The system may also be used on all surfaces of a fully enclosed moving structure where contact may occur with other sensitive surfaces (e.g., aircraft de-icing machines, underground rock mining machines, etc.).  
         [0025]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be 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.