Abstract:
A control system and method of use for controlling work output delivered to a floor surface by a work tool associated with a floor maintenance machine. The control system includes a hydraulic power source, a motor assembly coupled to the power source and the work tool, a pressure sensor in communication with the motor assembly, an actuator coupled to the work tool, and a controller in communication with the pressure sensor. A valve is configured to regulate the pressure provided by the power source and applied the actuator assembly. Based on a sensed pressure applied to the motor assembly, the controller causes the actuator assembly to adjust contact of the work tool with the floor surface. Work output delivered to the floor surface by the machine can be uniformly maintained during a cleaning period as the controller adjusts floor contact of the work tool via the hydraulic actuator.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Application No. 60/969,479, filed Aug. 31, 2007, and incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to floor maintenance or conditioning machines, and particularly those machines employing one or more floor maintenance or conditioning tools that perform tasks including scrubbing, sweeping, polishing or burnishing. 
       BACKGROUND OF THE INVENTION 
       [0003]    Surface maintenance machines that perform a single surface maintenance or surface conditioning task are well known. Surface maintenance machines are generally directed to applications such as floor surfaces, or simply floors. The term floor, as used herein, refers to any support surface, such as, among others, floors, pavements, road surfaces, ship decks, and the like. 
         [0004]    Many floor or surface maintenance machines are constructed so as to only sweep, others to scrub, while still others to polish or burnish. Other floor maintenance machines may be configured to perform multiple types of surface maintenance tasks. 
         [0005]    Surface maintenance machines which perform a burnishing task generally include a scheme for controlling the degree of burnishing applied to a floor surface depending upon the type of floor surface. Such machines commonly include a tool driver assembly which includes a working appliance or tool, such as a pad or brush, affixed to the driver that is rotatably driven by a driver motor. The driver assembly is selectively raised and lowered, for example by an actuator, to achieve a desired down-force or pressure against a floor surface. 
         [0006]    Surface maintenance machines which perform a scrubbing task also commonly include a driver assembly having a rotatable scrubber, such as a brush, pad, or the like, affixed to a scrubber head rotatably driven by a driver motor. The scrubber head typically is selectively raised and lowered by an actuator coupled to the driver to achieve a desired scrubbing down-force or pressure of the brush against a floor surface. Like burnishing machines, some scrubbing machines include a scheme for controlling the scrubbing force or pressure applied to the floor surface. 
         [0007]    Sweeper systems also are analogous to burnishing and scrubbing systems in that they too may include a rotatable sweeper tool (e.g., a brush) driven by a driver motor. Like burnishing and scrubbing systems, the sweeper system brush may be lowered and raised relative to a floor to achieve a desired sweeping result. 
         [0008]    Schemes for controlling the burnishing/scrubbing/sweeping force typically employ an electric current sensor to monitor the current drawn by the driver motor. In such schemes, a sensed motor current may be used to control torque load on the driver motor such that a desired burnishing/scrubbing/sweeping force may be achieved. However, such schemes may not provide accurate control of the work output applied to the floor, because the voltage and amperage applied to the driver motor may vary, thus causing corresponding variations in speed and work output of the rotatable work tool. 
         [0009]    In accordance with other control schemes, a “floor pressure” sensor is employed that provides a signal that is representative of the force of the work tool against the floor. This signal also may be used to control torque load on the motor to achieve a desired work force or output, although, again, variations in driver motor voltage are typically not taken into account. 
         [0010]    The shortcomings of such known control schemes are particularly noticeable in floor conditioning machines that are powered by a rechargeable battery supply. Although a rechargeable battery supply offers some conveniences, the battery voltage applied to the various floor conditioning systems or appliances, and particularly to the driver motor, decays in relation to the energy discharged by the battery and the total time of discharge. Thus, the available mechanical conditioning/working power that may be delivered to the floor varies dependent upon the voltage and current that the battery supply can deliver to the driver motor. That is, mechanical working power (i.e., work output delivered to the floor) is proportional to the power delivered to the driver motor. 
         [0011]    Thus, for example, if the driver motor current is held constant, the conditioning work delivered to the floor surface will vary as a function of voltage applied to the driver motor (e.g., the battery voltage). As a result, when the driver motor load current is held constant (as is the case with known control schemes), more working power is delivered to the working appliance (i.e., brush or pad) at the beginning of the battery life cycle, and less working power is available at the end of the battery life cycle as the battery voltage decays. Such variation in mechanical working power delivered to the floor, however, may not be desirable because it can affect the consistency of the work results, particularly when the floor conditioning task is burnishing, and, even more particularly, when the burnishing task is part of a multi-task floor conditioning machine. 
       SUMMARY OF THE INVENTION 
       [0012]    In accordance with a first aspect of the invention, a control system for controlling work output delivered to a floor surface by a work tool associated with a floor maintenance machine includes a hydraulic power source, a hydraulic motor assembly coupled to the power source and the work tool, a pressure sensor coupled between the power source and the motor assembly, an actuator assembly coupled to the work tool and coupled to the power source, and a controller in communication with the pressure sensor, the actuator assembly, and the motor assembly. A valve is configured to regulate the pressure provided by the power source and applied the actuator assembly. Based on the sensed pressure to the motor assembly, the controller generates a control signal which causes the actuator assembly to adjust contact of the work tool with the floor surface, thereby controlling work output delivered to the floor. 
         [0013]    In accordance with another aspect of the invention, a control system for controlling work output delivered to a floor surface by a work tool associated with a floor maintenance appliance includes a hydraulic power source, a hydraulic motor coupled to the power source and the work tool, a hydraulic actuator assembly coupled to the work tool, a pressure monitor circuit configured to monitor the pressure provided by the power source to the hydraulic motor, and a controller circuit. The controller circuit is configured to generate a control signal based on the monitored motor pressure. In response to the control signal, the hydraulic actuator adjusts contact of the work tool with the floor surface as appropriate to control the work output delivered to the floor. 
         [0014]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic diagram of an exemplary embodiment of a control system for a floor maintenance appliance for controlling the work output delivered to a floor surface; and 
           [0016]      FIG. 2  is a partial schematic diagram the control system of  FIG. 1  illustrating a worn pad condition and stop structure engagement. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring first to  FIG. 1 , a schematic diagram is illustrated representing one exemplary embodiment of a control system for a floor maintenance machine  8  capable of controlling the work output delivered to a floor by a rotatable work tool, such as a polishing pad, a scrubber, a brush, etc. In  FIG. 1 , a movable tool assembly  10  is configured as a scrubbing system suspended from a frame  22  associated with floor maintenance machine  8  by way of hydraulic actuator  20 . Floor maintenance machine  8  may assume a variety of configurations including, but not limited to, ride-on and walk-behind sweepers, scrubbers and burnishers. 
         [0018]    Hydraulic actuator  20  is configured to raise and lower the maintenance device  10  relative to the floor  24 . Although a floor scrubbing tool is illustrated in  FIG. 1 , it should be understood that the movable tool assembly  10  may be configured to perform other types of maintenance tasks, such as sweeping and burnishing, or a combination of maintenance tasks. 
         [0019]    As shown in  FIG. 1 , movable tool assembly  10  includes a rotatable driver  12  having a rotatable shaft  14  coupled to a hydraulic drive motor  16 . A rotatable work tool for performing the work task includes, in this example, a scrubbing pad  18  that is coupled to rotatable driver  12 . The movable tool assembly  10  and the actuator  20  may be implemented by way of a wide array of components and techniques. 
         [0020]    During operation of maintenance machine  8 , hydraulic motor  16  causes the pad  18  to rotate and the hydraulic actuator  20  causes the movable tool assembly  10  to move downward so that pad  18  contacts floor  24  with a certain down-force. Further downward movement of the movable tool assembly  10  toward the floor  24  causes an increase in the amount of force transferred through pad  18  against the floor  24 . 
         [0021]    A hydraulic power source  30  provides the hydraulic power to the movable tool assembly  10  and may include an electric hydraulic pump or a PTO driven pump, for example. The power source  30  may be any type of suitable hydraulic power source for the particular maintenance machine  8 . In the embodiment illustrated in  FIG. 1 , the power source  30  is an electric hydraulic pump. Pressurized hydraulic fluid is provided from power source  30  to motor  16  via a valve  32 . 
         [0022]    In the embodiment illustrated in  FIG. 1 , the work output to the floor surface  24  is controlled by adjusting the distance between movable tool assembly  10  and floor surface  24  in response to a signal (e.g., voltage) applied to the hydraulic actuator solenoid valve  50 . Pressure sensor  52  is configured to monitor the hydraulic pressure applied to drive motor  16  and provides a signal representative of the sensed pressure to controller  60 . Pressure sensor  52  may be configured in a wide variety of arrangements suitable to provide a signal that is representative of the pressure applied motor  16 . 
         [0023]    Controller  60  is configured to control the position of the movable tool assembly  10  relative to the floor  24  to achieve a desired work output, i.e., the amount of work (e.g., scrubbing, burnishing, sweeping) accomplished by the appliance. A work selector  61 , which may be coupled to a user interface and include push buttons, multi-position switches, menu displays, etc., allows a user to manually select a desired work output setting (e.g., high, medium and low). Based on the user&#39;s selection, the work selector  61  provides the controller  60  with an input signal representative of the selected work output. By comparing the actuator pressure and the desired work output as represented by another signal (via a lookup table, etc.), controller  60  generates a pulse-width-modulated (PWM) voltage signal applied to valve  50  which causes the actuator  20  to raise or lower the assembly  10  relative to the floor surface  24 , thereby controlling the level of work output. 
         [0024]    Controller  60  may be in communication with motor valve  32 . In some embodiments of the invention, valve  32  may be an electrically controllable valve such as valve  50 . In other embodiments of the invention, valve  32  may be fixed in position or replace or eliminated. 
         [0025]    Controller  60  in the control scheme illustrated in  FIG. 1  can minimize variations in work output that may be caused by variations of parameters that contribute to changes in the torque through the motor  16 , such as the characteristics of the floor surface (e.g., bumps, dips, tacky, slippery, etc.). Thus, the illustrated control scheme can beneficially maintain the work output at a desired level. 
         [0026]    In some floor maintenance applications, it may be desirable to vary the work output based on certain parameters as opposed to maintaining the work output at a constant level. For example, it may be desirable to control the rotational speed of the work tool over time (and thus the work output over time) based on the status of the actuator. In another example, it may be desirable to control the down pressure of the work tool over time (and thus the work output) based on the status of the actuator or pump  30 . In yet another example, a table or chart or equation may be referenced which relates tool work (either calculated directly with tool speed and torque measurements or motor current and voltage measurements) to a state of pump  30 . Such a table or chart or equation (implemented in software and/or hardware) could be used to provide different operational characteristics during a machine operational session. For example, a table may be used to relate work output to pump  30  state such that as the pump charge decreases, the work output would remain constant or follow some predetermined curve (increasing or decreasing over time). Such control schemes advantageously could provide more consistent work results. 
         [0027]    A mechanical stop structure  62  is provided on the machine frame  22  to limit the downward movement of assembly  10 . A stop engagement structure  64  contacts stop  62  when movable assembly  10  has reached a lower limit of movement. Further downward movement of movable assembly  10  is thus prevented by stop structure  64 . 
         [0028]      FIG. 2  illustrates movable assembly  10  in a most downward position wherein further downward movement is prevented by stop structure  64 .  FIG. 2  illustrates a worn condition of pad  18  as compared to pad  18  of  FIG. 1 .  FIG. 2  represents a portion of the machine  8  of  FIG. 1 . 
         [0029]    Controller  60  can indirectly evaluate a degree of brush  18  wear by monitoring motor  16  pressure sensed at pressure sensor  52 . When the brush  18  is new or relatively new, an increase in the pressure applied to hydraulic actuator  20  will cause an increase in motor  16  torque (sensed by increased pressure at sensor  52 ). When the brush  18  is worn to an unacceptable level, stop structure  64  is engaged as the movable assembly  10  has extended to its most downward position. As stop structure  64  engages stop  62 , the pressure applied to hydraulic actuator  20  will no longer influence motor  16  torque. By observing that the torque of motor  16  (as sensed by fluid pressure sensor  52 ) does not increase in relation to increased pressure applied by valve  50 , a judgment can be made that pad  18  has worn beyond a condition of desired performance. A similar judgment can be made by installing a torque sensor on drive motor  16 . 
         [0030]    The controller  60 , may be implemented in a variety of different manners, such as by discrete analog and/or digital circuitry, integrated circuits, programmable arrays, microprocessor or micro-controller based circuitry, software, firmware, etc., or any combination of the foregoing. Specific inputs that may be selected will vary, dependent upon the chosen circuit configurations and specific floor maintenance machine assembly characteristics. 
         [0031]    In practice, it has been found that stability and reliability of the control schemes illustrated in  FIGS. 1 and 2  outweigh the benefits of a control scheme that can more quickly respond to variations that cause changes in work output. For example, as the floor maintenance machine is moved over the floor  24 , floor surface variations can cause temporary variations in the motor  16  torque. Because the movable assembly  10  is configured to have a certain amount of resiliency to compensate for such floor surface variations and because such variations typically are short-lived, the controller  60  need not be configured to compensate for such variations, thus simplifying the design. Accordingly, in exemplary embodiments the controller  60  is configured to respond to a variation in the monitored pressure only if the variation has persisted longer than a given amount of time. 
         [0032]    Another advantage of a controller configuration that does not have a particularly quick response time is that movement of the assembly  10  relative to the floor  24  typically will occur infrequently. 
         [0033]    Further, it should be understood that although the foregoing exemplary embodiments contemplate the ability to select a desired work output, in alternative embodiments, the control system, including controller  60 , can be configured such that the work output is not a user-selectable parameter but rather is determined by the controller  60  based on other parameters, such as type of work tool and the task to be performed, sensed characteristics of the floor surface, etc. For example, an optical sensor may be utilized to provide floor type or condition as an input to controller  60 . 
         [0034]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.