Abstract:
A system for measuring the distance of a hydraulic movement including an engine supplying power, a hydraulic cylinder for supplying hydraulic movement, and a pump coupled to the hydraulic cylinder for providing hydraulic fluid to the hydraulic cylinder. A power take off is coupled to the engine and supplies power from the engine to the pump. A measuring device measures the amount of fluid provide to the hydraulic cylinder by counting engine revolutions enabling a determination of the distance of the movement.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/233,555, filed Sep. 19 2000. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to hydraulic systems. 
     More particularly, the present invention relates to controlling hydraulic systems. 
     In a further and more specific aspect, the instant invention concerns control of a hydraulically operated loader mechanism. 
     BACKGROUND OF THE INVENTION 
     Hydraulic cylinders have been used to provide the motive force for mechanical articulated assemblies for many years. They are particularly useful when great force is required. When employing hydraulic cylinders there has conventionally been two ways to control hydraulic movement such as extension and retraction of the cylinder. The least complex mechanically is to simply let an operator control the cylinder and extend and retract it as necessary. While effective in very simple applications, this approach can be less than satisfactory in more complex systems having multiple articulations. Additionally, close supervision of the articulated device is not always possible. The other approach is to employ limit switches to indicate position of the articulated segments or a combination of the two approaches. Limit switches have limitations which often necessitate the combined approach. Specifically, this is the case when it is necessary to vary a motion such as to adapt to a situation. Additionally, limit switches are relatively expensive and can be a main trouble spot with frequent maintenance required. 
     A specific example of a complex articulated system is a loading arm for refuse collection. The systems employ hydraulic cylinders to extend and retract, pivot, dump and grip. Some of these functions do not vary, and limit switches are effective. Others, such as extending to grip a container can vary and require an observer. Loading arms typically employ an operator who must be located near the container for proper manipulation and limit switches which require high maintenance. 
     It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art. 
     Accordingly, it is an object of the present invention to provide a new and improved system for measuring hydraulic movements. 
     Another object of the invention is to provide a new and improved system for controlling hydraulic systems. 
     And another object of the invention is to provide a new and improved loading mechanism for loading refuse in a refuse vehicle. 
     SUMMARY OF THE INVENTION 
     Briefly, to achieve the desired objects of the instant invention in accordance with a preferred embodiment thereof, provided is a system for measuring the distance of a hydraulic movement. The system includes an engine supplying power, a hydraulic cylinder for supplying hydraulic movement, and a pump coupled to the hydraulic cylinder for providing hydraulic fluid to the hydraulic cylinder. A power take off is coupled to the engine and supplies power from the engine to the pump. A measuring device measures the amount of fluid provided to the hydraulic cylinder by counting engine revolutions. 
     Also provided is a method of operating a mechanized refuse collection vehicle including providing a refuse collection vehicle having an engine supplying power, an extendable arm moveable between an extended position and a retracted position by a hydraulic cylinder, the hydraulic cylinder providing an extension movement of the extendable arm toward the extended position and a retraction movement of the extendable arm toward the retracted position, a gripping mechanism coupled to the extendable arm and movable between an open configuration and a gripping configuration, and a pump coupled to the hydraulic cylinder for providing hydraulic fluid to the hydraulic cylinder and driven by the engine. A control system is provided including a computational device and a first control and a second control. The computational device measures the amount of fluid provide to the hydraulic cylinder by counting revolutions of the engine. The first control is actuated to accomplish a discharge cycle including extending the extendable arm in an extension movement, ending the extension movement of the extendable arm and ending counting by the computational device. The computational device factors the total count to determine the distance of the movement. The cycle continues by gripping a container, retracting the extendable arm to the retracted position and moving the gripping mechanism into a dumping orientation over the vehicle. The second control is actuated to accomplish a return cycle including lowering the extendable arm, recreating the extension movement by actuating the hydraulic cylinder and counting the engine revolutions, comparing the count to the stored count, and ending the movement when the counts match. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings, in which: 
     FIG. 1 is a partial perspective view illustrating a refuse collection vehicle according to the present invention with portions of the cab cut-away; 
     FIG. 2 is a top plan view of the refuse collection vehicle of FIG. 1; 
     FIG. 3 is a partial perspective view of the loader mechanism of the collection vehicle of FIGS. 1 and 2; 
     FIG. 4 is a perspective view of a gripping mechanism of the loader mechanism as it appears in an open configuration approaching a refuse container; 
     FIG. 5 is a perspective view of the gripping mechanism of as it would appear gripping the refuse container; and 
     FIGS. 6 a - 6   h  illustrate a refuse collection sequence. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is first directed to FIG. 1 which illustrates a refuse collection vehicle  10 . A conventional loader mechanism  12  is mounted on a frame  13  of refuse collection vehicle  10 . Loader mechanism  12  is illustrated engaging a refuse container  14  which will be hoisted and dumped into a hopper  15  as will be described presently. The refuse will then be compressed into a storage body  17  located rearward of hopper  15 . A cab  18  is positioned forward of loader mechanism  12 , and contains controls for the operation of vehicle  10  and loader mechanism  12 . Vehicle  10  is powered by a conventional engine  19  such as an internal combustion engine. 
     The following description describes a system for operating mechanized refuse collection equipment in which the operator actuates two controls to complete a loading cycle. A control system having logic circuitry, various sensors and a hydraulic movement measuring system enable a two control loading cycle. The system applies to most loading equipment for side loaders with which the operator uses hydraulically operated and electrically controlled equipment to collect household refuse. The operator uses electrical switches within cab  18  to actuate loading mechanism  12  remotely to pick up containers beside collection vehicle  10 . The system enables an operator to observe container  14  from within cab  18  of vehicle  10  and operate the collection sequence as can be seen with reference to FIG.  2 . 
     Still referring to FIG. 1, with additional reference to FIG. 3, loading mechanism  12  includes an arm  22  and a gripping mechanism  23 . Arm  22  is movable between a retracted position and an extended position by a hydraulic cylinder  24 . Gripping mechanism  23  is pivotally coupled to an end of arm  22  and pivoted by a dump hydraulic cylinder  25 . Gripping mechanism  23  can be substantially any conventional gripping mechanism. With reference to FIG. 4, in this embodiment gripping mechanism  23  includes a base  27  from which a pair of opposing gripping arms  28  and  29  pivotally extends. Arms  28  and  29  are moved between an open position (FIG. 4) and a gripping position (FIG. 5) by a hydraulic cylinder  30 . 
     Turning to FIGS. 4 and 5, a measuring system is employed to actuate cylinder  30  and begin moving gripping mechanism  23  from the open position to the gripping position. The measuring system includes a pair of proximity sensors  32  and  33  mounted on base  27  of gripping mechanism  23  whose purpose is to sense the proximity of container  14 . These measuring devices can include both infrared and ultrasonic devices. At a pre-set distance, such as eighteen inches in this embodiment, sensor  32  detects a container and initiates the gripping action of gripping mechanism  23 . The pre-set distance is a function of the speed with which gripping mechanism  23  moves from the open position to the closed position. When sensor  33  detects the container, it is at the correct position to stop extension of arm  22 , in this embodiment, approximately three inches. Upon detection, sensor  33  sends a signal which terminates the extension of arm  22 . 
     With the loader no longer extending, gripping arms  28  and  29  engage the container. As gripping arms  28  and  29  engage the container, hydraulic pressure builds up in gripping actuation cylinder  30 . This pressure is sensed by a pressure switch which switches the logic circuit from gripping movement to hoisting movement, in the conventional way. Further, also according to the previous convention, the hoisting circuit actuates the circuits that operate and control to retract the loader and to dump the container. The control system initiates these functions through operation of a valve assembly  40  as shown in FIGS. 1 and 3. Valves  40  control operation of individual hydraulic cylinders by permitting or preventing fluid flow thereto. Thus, fluid flows to cylinder  24  to extend arm  22  until the valve is closed upon the control system receiving a signal from sensor  33 . Cylinder  30  continues to close gripping arms  28  and  29  about container  14  until the pressure sensor, located at or proximate the appropriate valve, signals that a pre-set pressure has been achieved. 
     As briefly mentioned previously, the control system additionally includes a hydraulic movement measuring system. Hydraulic movement, in this specific embodiment includes the extension or retraction of a hydraulic cylinder. A counter is actuated to count the revolutions of engine  19  as arm  22  moves out toward the container. This is accomplished by counting pulses from an alternator  44 . When arm  22  stops, the counter stops. A computational device  42 , containing the counter in this embodiment, factors the resultant count and stores the answer. It should be understood that various other methods of counting engine revolutions may be employed, such as using a tachometer, etc. The stored data can then be employed to match the hydraulic movement. When retracted during the dumping process, arm  22  can be re-extended the same distance by again counting engine revolutions and comparing the count against the stored data. When the counts match the extension is terminated at the same spot. 
     Hydraulic fluid is provided to valve assembly  40  by a pump  50 . Pump  50  is driven by engine  19  through a power take off  52 . It should be noted that the system works because the hydraulic control valves are in series and the pump is a fixed displacement pump. That is to say that the pump forces a fixed quantity (about 2 cubic inches) of oil into the system during each revolution. Thus, since pump  50 , alternator  44  and engine  19  revolution rate are all directly proportional (within reasonable tolerance for belt, clutch slippage, minor hydraulic leakage), measuring engine turns allows the system to make a reasonable estimate of the location of the piston in the hydraulic cylinder and, therefore, the location of the device it is actuating. 
     In combination with other equipment on the vehicle, the effect is to enable the operator to empty a container using only two controls  43 . The first control is actuated after aligning the vehicle with the container. Upon actuation of the first control, arm  22  is extended as previously described. The operator simply holds the control down and the loading sequence is continued to completion. When the container has been discharged, the operator actuates the second control to lower the container and return it to its original location. When loader mechanism  12  is operated to lower the container, the computational device actuates the out control to move the loader back to the position it was in when the container was engaged, returning the container to its original position beside the vehicle. The second control is released when the gripping arms are retracted and ready for the vehicle to move to the next container. 
     Turning now to FIGS. 6 a - 6   g,  a loading cycle is illustrated. Referring to FIG. 6 a,  the operator drives vehicle  10  to a position to align gripping arms  28  and  29  with the refuse container to be collected. A control  43  (FIG. 6 b ), which in this embodiment is a rocker switch, is operated to extend loader  12  toward the container. While loader  12  extends, computational device  42  records the number of engine revolutions. This can be accomplished in numerous ways. In the preferred embodiment, computational device  42  receives a pulsing signal from alternator  44  of vehicle  10 . The pulses from alternator  44  correspond to revolutions of engine  19  (FIG. 6 c ). 
     When loader  12  has extended to a position a set distance away from the container, about 18″ in practice (FIG. 6 d ), computational device  42  receives a signal from proximity sensor  32  mounted on base  27  of gripping mechanism  23 . The signal from sensor  32  actuates the control which begins closing gripping arms  28  and  29  by opening the valve supplying fluid to cylinder  30 . As gripping arms  28  and  29  close, arm  22  continues to extend toward the container. When loader  12  has extended to a position a pre-set distance away from the container, about 3″ in practice (FIG. 6 e ), computational device  42  receives a signal from second proximity sensor  33  mounted with sensor  32  and actuated by the container. These distance measuring devices or proximity sensors can include both infrared and ultrasonic devices. Either work satisfactorily. At the second signal, computational device  42  stops counting engine turns, factors the total and stores the result for later use. 
     The operator continues to hold the out control. If he releases it, the operation stops. If he re-engages it, the operation continues. With the loader no longer extending, gripping arms  28  and  29  engages the container. The hydraulic pressure built up in gripping actuation cylinder  30  is sensed and the circuit is changed from a gripping movement to a hoisting movement, in the conventional way. Further, also according to previous convention, the hoisting circuit actuates the circuits which retract the loader and dump the container (FIG. 6 g ). 
     The operator observes the container discharge. He may shake the container by using the two controls. When he is satisfied that the container is empty, he operates the second control. The container begins to retract from dumping. According to the previous convention, a timer actuates the control to lower the hoist after a short (¼ second) delay. The container continues to retract from dumping while it lowers. When it is completely retracted, a limit switch  60  (see FIG. 6 f ) opens the circuit. The lowering motion continues. The second control also signals computational device  42  to actuate the circuit to extend the loader. The device again counts engine revolutions until it reaches the factored, sorted number at which point it disengages the circuit (FIG. 6 h ). 
     When the container has been lowered by the loader arm to a position near the ground and near the end of the actuating cylinder stroke, a limit switch is tripped which switches the circuit from lowering the container to releasing it. The operator continues to hold the second control, with the circuitry now engaged to open the gripping arms. Next, according to the previous convention, after a short delay (¼ second) to allow the arms to clear the container, the signal to retract the loader is added and the grip arms release while the loader retracts until both reach their stowed positions. With the container dumping cycle complete, the operator moves the truck to next container. The system permits the regular and efficient operation of the loader using two controls and two actuations, whereas the conventional system required five. 
     It is apparent that the application described is only one of many where a simple, relatively inexpensive method of measuring the location of a hydraulically driven device will be useful. 
     Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims. 
     Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same,