A debris collection vehicle having an enclosed volume for collecting debris and a hydraulic fan drive system for creating vacuum condition in the enclosed volume is disclosed. In one embodiment, the hydraulic fan system includes a closed loop hydraulic circuit, a variable displacement hydraulic pump disposed within the closed loop circuit, and a hydraulic motor disposed within the closed loop circuit. The hydraulic fan drive system can also include an electronic or hydraulically actuated control valve constructed and arranged to adjust the output of the hydraulic motor via a displacement actuator based on pressure in the closed loop hydraulic circuit.

BACKGROUND 
       [0001]    Debris collection vehicles, such as sewer cleaners, hydro-excavators, and street sweeping vehicles are often provided with an enclosed volume, for example a hopper or collection tank, for retaining collected debris. Generally, a fan is also provided that is configured to draw a vacuum condition within the enclosed volume. In some implementations, the fan is directly driven by an auxiliary engine of the vehicle via a gear box. However, such an approach limits the fan performance by the amount of torque that can be produced by the auxiliary engine. In other implementations, the fan is driven by a fixed displacement hydraulic motor that is driven by a pump. However, this approach can require the motor and the pump to operate at or over their respective maximum rated speeds for successful operation, which can decrease equipment life. Improvements are desired. 
       SUMMARY 
       [0002]    A debris collection vehicle having a hydraulic fan drive system is disclosed. The debris collection vehicle can include a main power plant that powers vehicle driving functions and an optional auxiliary power plant that powers vehicle non-driving functions. The debris collection vehicle can also include a tank or hopper for collecting debris. 
         [0003]    In one aspect, the hydraulic fan system includes a closed loop hydraulic circuit, a hydraulic pump disposed within the closed loop circuit and having an inlet and an outlet, and a hydraulic motor disposed within the closed loop circuit. The hydraulic motor can be provided with an output shaft, an inlet in direct fluid communication with the variable displacement pump outlet, and an outlet in direct fluid communication with the variable displacement pump inlet. In one embodiment, the hydraulic pump is driven by the primary or auxiliary power plant. 
         [0004]    The hydraulic fan drive system can also include a fan coupled to the output shaft of the hydraulic motor. In one aspect the fan includes an inlet that is in fluid communication with the vehicle tank or hopper such that the fan can draw a vacuum condition within the tank or hopper. The hydraulic fan drive system can also include a control valve constructed and arranged to adjust the output of the hydraulic motor based on pressure in the closed loop hydraulic circuit. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0005]    Non-limiting and non-exhaustive embodiments are described with reference to the following figures, which are not necessarily drawn to scale, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
           [0006]      FIG. 1  is a side view of a debris collection vehicle and hydraulic vacuum fan drive system having features that are examples of aspects in accordance with the principles of the present disclosure. 
           [0007]      FIG. 2  is a perspective view of a hydraulic fan drive system suitable for use in a debris collection vehicle. 
           [0008]      FIG. 3  is a schematic view of the hydraulic fan drive system shown in  FIG. 2 . 
           [0009]      FIG. 4  is a schematic view of a first embodiment of a drive portion of the hydraulic fan drive system shown in  FIG. 3 . 
           [0010]      FIG. 5  is a schematic view of a second embodiment of a drive portion of the hydraulic fan drive system shown in  FIG. 3 . 
           [0011]      FIG. 6  is a side view of a second embodiment of a debris collection vehicle and hydraulic vacuum fan drive system having features that are examples of aspects in accordance with the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims. 
         [0013]    Referring to  FIGS. 1 and 6 , examples of debris collection vehicles  1  are shown. In the embodiment shown at  FIG. 1 , the vehicle  1  is a sewer cleaning vehicle. As shown, the sewer cleaning vehicle  1  includes a chassis  2 , a debris collection tank  3 , wheels  4 , a hose reel  11 , water tanks  13 , and a water pumping system  15 . The vehicle  1  can also include a power delivery system having a chassis or primary power system  7 , which may be an internal combustion engine. The vehicle  1  may also be provided with an optional auxiliary power system. The primary power system  7  provides power for both the driving and non-driving functions of the vehicle  1 . Examples of driving functions that require power are the vehicle drive train, the steering system, and the braking system. Examples of non-driving functions associated with the vehicle  1 , are pumps and motors relating to the debris collection process. Vehicle  1  is also shown as including a hydraulic vacuum fan drive system  10 , shown at  FIG. 2 , that is powered by the primary power system  7 , or optionally, an auxiliary power system. The fan drive system  10  is connected to the debris collection tank  3  such that debris can be collected by a suction hose  14  that is also connected to the debris collection tank  3 . 
         [0014]    In the embodiment shown at  FIG. 6 , the vehicle  1  is a street sweeping vehicle. As shown, the street sweeping vehicle  1  includes a chassis  2 , a hopper  3 , wheels  4 , brooms  5 , and a vacuum nozzle  6 . The vehicle  1  can also include a power delivery system having a chassis or primary power system  7  and an optional auxiliary power system  8 , both of which may be internal combustion engines. The primary power system  7  is primarily responsible for providing power for the driving functions of the vehicle  1 . Examples of driving functions that require power are the vehicle drive train, the steering system, and the braking system. The auxiliary power system  8  is primarily for providing power to auxiliary operations associated with the vehicle  1 , for example hydraulic functions can be driven by a hydraulic pump. Examples of auxiliary components that require power in a street sweeper application are fans/blowers, scarifying brooms, and the hopper. It is noted that the vehicle  1  can be provided with only a primary power system  7  and that the auxiliary functions can be driven from the primary power system  7 . As shown at  FIG. 6 , vehicle  1  includes a hydraulic vacuum fan drive system  10  that is powered by the auxiliary power system  8 . 
         [0015]    Referring to  FIG. 2 , the hydraulic fan drive system  10  is shown in greater detail. Hydraulic fan drive system  10  is for providing a vacuum in the hopper  3  such that debris can be collected into enclosed volume or hopper  3 . As shown, the hydraulic fan drive system  10  includes a fan assembly  40  having a fan  41  (see  FIGS. 4 ,  5 ) within a housing  42  provided with an air inlet  44  and an air outlet  46 . As the fan  41  is rotated, air is moved from the inlet  44  to the outlet  46 . In the configuration shown at  FIG. 1 , the fan inlet  44  is in fluid communication with the enclosed volume  3  such that operation of the fan assembly  40  causes the interior of the enclosed volume  3  to be drawn into a vacuum condition. 
         [0016]    The hydraulic fan drive system  10  can also be provided with a hydraulic motor  30 . Hydraulic motor  30  is for driving the fan  41  of the fan assembly  40 . As shown, the hydraulic motor  30  has an output shaft  32  ( FIG. 4 ) which drives the gear train within a gear box  48  ( FIG. 2 ) which in turn drives the fan of the fan assembly  40 . The gear box  48  can be configured as step up or a step down gear configuration in which the rotational speed of the fan  41  will be either greater than or less than, respectively, the rotational speed of the output shaft  32 . Alternatively, the output shaft  32  of the hydraulic motor  30  can be directly connected to the fan  41  of the fan housing  40 . 
         [0017]    The hydraulic motor  30  may be configured as variable displacement motor, such as an axial variable displacement motor with a swash plate or a bent axis variable displacement motor. A suitable hydraulic motor  30  is an H1 Series variable displacement bent axis hydraulic motor available from Danfoss Power Solutions US of Ames, Iowa. 
         [0018]    With reference to  FIG. 3 , a hydraulic schematic of the hydraulic fan drive system  10  is shown. As can be seen, the hydraulic fan system  10  further includes a hydraulic pump  20  that has an input shaft  22  that may be driven by, for example, the primary power plant or engine  7  (e.g.  FIG. 1 ) or the auxiliary power plant or engine  8  (e.g.  FIG. 6 ). Where the hydraulic pump  20  is driven by the primary power plant  7 , the hydraulic pump  20  may be mounted to a gear box or to the front crank of the power plant. Hydraulic pump  20  further includes an inlet port  24  and an outlet port  26 . In operation, and as the input shaft  22  is rotated, hydraulic fluid is moved from the inlet port  24  to the outlet port  26 . The hydraulic pump  20  is shown as being configured as a variable displacement pump. 
         [0019]    With reference to  FIG. 4 , which shows section  10 A of system  10  in greater detail, the hydraulic motor  30  may be provided with an inlet port  34  for receiving pumped hydraulic fluid from the pump outlet port  26  and an outlet port  36  for returning the hydraulic fluid back to the pump inlet port  24 . In operation, as the pump  20  delivers hydraulic fluid to the hydraulic motor inlet port  34 , through the hydraulic motor  30 , and to the outlet port  36 , the output shaft  32  is caused to rotate, thereby powering the fan assembly  40  ( FIG. 2 ). In such a configuration where the pump outlet  26  is in direct fluid communication with the motor inlet  34  and the pump inlet  24  is in direct fluid communication with the motor outlet  36  (i.e. the pump inlet  24  and motor outlet  36  are not in direct fluid communication with the reservoir  12 ), the fluid circuit may be termed herein as closed hydraulic circuit. However, it is noted that even in such a circuit, fluid is allowed to enter and leave the system through other components provided in the system, such as the flushing valve and control valve  60  (discussed later). 
         [0020]    As stated previously, hydraulic motor  30  may be provided as a variable displacement motor. In such a configuration, the hydraulic fan system  10  may be provided with an actuator  50  that is provided with a piston  52  to modify the displacement of the hydraulic motor  30 . As shown, actuator  50  also has an inlet port  54  and an outlet port  56 . In operation, when hydraulic fluid is allowed to flow into the inlet port  54  and force the piston  52  in a first direction, and thereby causing hydraulic fluid to purge from the outlet port  56  on the other side of the piston  52 , the displacement of the motor  30  is decreased. This results in the hydraulic motor  30  (and connected fan  41 ) having a decreased rotational speed and a high torque output. Oppositely, when hydraulic fluid is allowed to flow in to the outlet port  56  and force the piston in  52  in a second direction opposite the first direction such that hydraulic fluid is purged from the inlet port  54 , the displacement of the motor  30  is increased. This condition results in the hydraulic motor  30  (and connected fan  41 ) having an increased rotational speed, but at a lower torque output. 
         [0021]    In one aspect, a control valve  60  ( FIG. 4 ) is provided that is in fluid communication with the hydraulic pump  20  and with the actuator  50  ( FIG. 4 ). The control valve  60  is for controlling the flow of hydraulic fluid to the actuator  50  such that the displacement of the hydraulic motor  30  is ultimately controlled by the operation of the control valve  60 . As shown, the control valve  60  is configured as a two-position, three port valve having, as shown in  FIG. 4 , a first position A, a second position B, a first port  62 , a second port  64 , and a third port  66 . The control valve  60  may be provided as a spool and sleeve type valve although other configurations and types are possible without departing from the concepts presented herein. 
         [0022]    In the first position A of the control valve  60 , the first port  62  is placed in fluid communication with the third port  66  such that pumped fluid from the hydraulic pump  20  flows into the inlet port  54  of the actuator  50 . Accordingly, when the control valve  60  is moved towards the first position A, the displacement of the hydraulic motor is minimized thereby placing the motor  30  in a low speed, high torque condition. In the second position B of the control valve  60 , the first port  62  is blocked, the second port  64  is placed in fluid communication with the reservoir  12 , and the third port  66  remains in fluid communication with the actuator inlet port  54 . 
         [0023]    As shown at  FIG. 4 , the control valve  60  is biased towards the first position A by a spring  69 , which may be configured as a variable resistance spring. The control valve  60  is also provided with a pilot actuator  68  that moves the control valve towards the second position B when system pressure is sufficient to overcome the resistance of the spring  69 . With this configuration, the displacement of the hydraulic motor  30  is controlled by the system pressure such that the displacement is increased when system pressure is high and decreased when system pressure is low, which would respectively correspond to high and low torque load conditions on the fan  41  of the fan assembly  40 . 
         [0024]    In contrast to the entirely hydraulic system shown in  FIG. 4 , the hydraulic fan drive system may also include an electronic controller  500  to control the output of the hydraulic motor based on operational parameters of the system, for example a sensed system pressure and a sensed fan/shaft rotational speed. Such a configuration is shown at  FIG. 5 . The electronic controller  500  is schematically shown as including a processor  500 A and a non-transient storage medium or memory  500 B, such as RAM, flash drive or a hard drive. Memory  500 B is for storing executable code, the operating parameters, and the input from the operator user interface  500 D while processor  500 A is for executing the code. The electronic controller is also shown as including a transmitting/receiving port  500 C, such as a vehicle CAN bus. A user interface  500 D may also be provided to activate and deactivate the system, allow a user to manipulate certain settings or inputs to the controller  500 , and to view information about the system operation. 
         [0025]    The electronic controller  500  typically includes at least some form of memory  500 B. Examples of memory  500 B include computer readable media. Computer readable media includes any available media that can be accessed by the processor  500 A. By way of example, computer readable media include computer readable storage media and computer readable communication media. 
         [0026]    Computer readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any device configured to store information such as computer readable instructions, data structures, program modules or other data. Computer readable storage media includes, but is not limited to, random access memory, read only memory, electrically erasable programmable read only memory, flash memory or other memory technology, compact disc read only memory, digital versatile disks or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by the processor  500 A. 
         [0027]    Computer readable communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, computer readable communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable media. 
         [0028]    Electronic controller  500  is also shown as having a number of inputs/outputs that may be used for implementing desired operational modes of the hydraulic fan drive system  10 . For example, electronic controller  500  provides outputs for commanding the control valve  60  via an electric or electronic actuator  502  (e.g. modulating solenoid valve, voice coil, etc.) as needed to meet the output demands of the system  10  (e.g. a fan speed set point, a vacuum pressure set point, a hydraulic system pressure set point, etc.). Likewise, electronic controller  500  receives inputs for the control of the fan drive system, for example an input from pressure sensor  504  and an input from shaft speed sensor  506 . 
         [0029]    In such a configuration, the hydraulic pilot actuator  68  is no longer utilized and the actuator  502  controls motor displacement. In the example shown at  FIG. 5 , the control valve  50  controls the displacement of motor  30  such that the displacement is increased when the actuator  502  is de-energized and decreased when the actuator  502  is energized. In one configuration, the spring  69  can be placed connected to the piston rod  52  of the actuator  50  such that the movement of the piston  52  acts to move the valve  60  into the first position A. 
         [0030]    The fan operation and speed may be established as an electronic set point within controller  500  or may be set through the use of one or more physical knobs, switches, and/or buttons. For example, the fan speed operation can be enabled by an ON/OFF rotary switch while the desired fan speed setting can be established by a LOW/MEDIUM/HIGH rotary switch configured to limit the maximum flow of hydraulic fluid out of the hydraulic pump  20  such that the maximum fan speed is controlled. In one example, the controller  500  is configured to provide a proportional output signal to a control valve that controls the displacement of the pump  20  based on the setting of the rotary switch. 
         [0031]    In one aspect, the LOW setting can be configured such that vacuum airflow, and thus power consumption, is minimized. Such a configuration would supply just enough air to minimize fluid (sewage) dripping from a suction hose while the operator changes vacuum tubing. The MEDIUM setting can be configured to allow the vacuum fan  41  to consume a fixed portion of the engine's reserve power, for example a portion which is not already allocated to the other truck systems (e.g. auxiliary hydraulics, high pressure water pump, electrical, air conditioning, cooling fan, etc.). The engagement, or disengagement, of these other truck systems does not alter the level of power apportioned to the vacuum fan. At this fixed power limit, the use of a variable displacement hydraulic motor  30  allows for a wider range of fan speeds than that which would be available using a fixed displacement hydraulic motor  30 , resulting in a more versatile system. The HIGH setting can be configured to allow the vacuum fan to consume as much power as is needed to maintain maximum vacuum performance, up to the intended system maximum. At this power setting, the variable displacement motor  30  continues to provide the wide range of fan speeds desired but at a horsepower level that is lower than that of a comparable system using a fixed displacement motor. This speed versus torque tradeoff can be accomplished completely within the hydraulic motor  30  and is transparent to the user. 
         [0032]    The above described hydraulic fan drive system  10 , in both the purely hydraulic embodiment and the electronically controlled embodiment, decreases maintenance, lowers noise and emissions, and has less weight that conventional fan drive systems. Also, the use of the disclosed system with a variable output hydraulic motor allows for the system to more easily accommodate the typical varying fan loading conditions that are experienced when utilizing a fan to produce a vacuum in an enclosed volume into which debris is being collected. Additionally, the hydraulic pump and motor are expected to have significantly longer operational lives as neither component is required to be continuously run at maximum rated speed for successful operation. Furthermore, the disclosed hydraulic fan drive system  10  allows for a relatively smaller pump which reduces system first costs and operational costs. 
         [0033]    The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the disclosure.