Abstract:
A hydraulic motor is driven by a fixed displacement, three stage gear-type pump. The three equal displacement sections provide 3 equally-stepped flows so that the hydraulic motor can have three speeds. Valving and controls are provided for remote on-the-fly shifting of the speeds, automatic pump unloading in neutral, and adjustable maximum pressure. A closed loop system permits use of a relatively small reservoir. The contamination tolerance of the system is greater than that of variable displacement piston-type pumps typically used. Direct recirculation of hydraulic fluid is provided for unused speeds to permit hydraulic fluid to recirculate in the pump without doing work. A unique control circuit is provided to control the first speed valve in conjunction with a logic cartridge which controls hydraulic motor direction to permit fluid flow to the hydraulic motor to be stopped when coming to neutral without slamming the hydraulic motor and rotating drill pipe to a stop. The first speed valve also acts as a relief valve to provide a mechanism for adjusting maximum system pressure.

Description:
FIELD OF THE INVENTION 
       [0001]    In one aspect, this invention relates to a control system for a hydraulic pump. In another aspect, this invention relates to a method for operating a hydraulic pump. 
       BACKGROUND OF THE INVENTION 
       [0002]    Hydraulic pumps are used in many applications. In the oil and gas industry, one application is use of a hydraulic pump to power a hydraulic motor to turn a drill pipe. A specific example of this application is a power swivel, which is used to turn the drill pipe while suspended in the drilling. 
         [0003]    In power swivel applications, the pump is typically powered by a diesel engine or electric motor. The pumps in commercial use are usually infinitely variable displacement models which provide infinitely variable speed for the power swivel. However, these pumps are not particularly robust and are subject to failure, often by fluid contamination, if not adequately maintained by changing out the filters. 
         [0004]    Gear pumps provide a much more robust and contamination friendly design, but their use has not been favored because of difficulties in controlling their output. A control system which permits good control would enable gear pumps to be used for power swivel applications. It is an object of this invention to provide such a control system. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with one embodiment of the invention, an apparatus is provided comprising a pump, a hydraulic motor, structure forming a flow path between the pump and the hydraulic motor including a flow rate controller and a directional control valve, and actuators for the flow rate controller and the directional control valve. 
         [0006]    The pump provides a supply of pressurized hydraulic fluid, and is preferably a gear pump. The hydraulic motor is operable by supply of pressurized hydraulic fluid from the pump. The flow path structure carries the fluid between the pump and the hydraulic motor. 
         [0007]    The hydraulic motor is a bidirectional hydraulic motor having a first bifunctional fluid port to supply hydraulic fluid to the hydraulic motor in forward drive and to exhaust fluid from the hydraulic motor in reverse drive and a second bifunctional fluid port to supply hydraulic fluid to the hydraulic motor in reverse drive and to exhaust fluid from the hydraulic motor in forward drive. 
         [0008]    The directional control valves includes supply valves and exhaust valves of the type known in the hydraulic industry as the logic cartridge type. 
         [0009]    The directional control valves are selectively settable in configurations for forward drive, reverse drive, and lock-up. In the forward drive configuration, hydraulic fluid is supplied from the hydraulic pump to the first bifunctional fluid port of the bidirectional hydraulic motor. In the reverse drive configuration, hydraulic fluid is supplied from the hydraulic pump to the second bifunctional fluid port of the bidirectional hydraulic motor. In the neutral lock-up configuration, hydraulic fluid is blocked to and from the bidirectional hydraulic motor. 
         [0010]    The directional control valve is preferably mounted as an assembly to the casing of the pump. 
         [0011]    The flow rate controller includes a first speed valve selectively settable in a flow output configuration or a recirculation configuration. In the flow output configuration, a single gear section output of hydraulic fluid is supplied through the flow path from the hydraulic pump to the hydraulic motor and provides a first speed for the hydraulic motor. In the recirculation configuration, hydraulic fluid bypasses the hydraulic motor and is returned to the hydraulic pump. The flow rate controller is preferably mounted as an assembly to the casing of the pump. 
         [0012]    The actuator for the directional control valve is for simultaneously selectively setting the hydraulic motor supply valves and exhaust valves in cooperating configurations for forward drive, reverse drive, or lockup. The actuator is preferably mounted as an assembly to the flow rate controller. 
         [0013]    The actuator for the flow rate controller preferably includes functionality for simultaneously setting the first speed valve in a recirculation configuration when the hydraulic motor supply valves and the hydraulic motor exhaust valves are set to neutral lockup configuration. The actuator is preferably mounted as an assembly to the pump casing. 
         [0014]    This pump and control system is especially useful for drilling operations because it permits fluid flow to the hydraulic motor to be stopped when coming to neutral without slamming the motor and the rotating drill pipe to a stop, which could cause the drill pipe to become unthreaded or cause other damage. It also permits the driller to drill forward in a stop-start manner as is commonly required. The control system further permits use of the more-robustly designed gear pump for this particular application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic illustrating a control system according to certain aspects of the invention. 
           [0016]      FIG. 2  illustrates a unified pump and valve assembly from a top view 
           [0017]      FIG. 3  is a cross sectional view of the first manifold/valve module  310  along cut line  3  in  FIG. 2 . 
           [0018]      FIG. 4  is a cross sectional view of the second manifold/valve module  311  along cut line  4  in  FIG. 2 . 
           [0019]      FIG. 5  is a cross sectional view of the third manifold/valve module  312  along cut line  5  in  FIG. 2 . 
           [0020]      FIG. 6  is a cross-sectional view of a portion of the apparatus shown in  FIG. 2 , viewed from the side. 
           [0021]      FIG. 7  is a side view of the apparatus shown in  FIG. 2  showing the main inlets and outlets for the integrated unit. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    With reference to  FIG. 1 , an apparatus  10  comprises a pump  20  for providing a supply of pressurized hydraulic fluid, a hydraulic motor  30  operable by supply of pressurized hydraulic fluid from the pump  20 , and structure  40  for forming a hydraulic fluid flow path between the pump  20  and the hydraulic motor  30 . 
         [0023]    The hydraulic motor  30  preferably comprises a power swivel  31  as used in the oil and gas drilling industry, although the invention would be generally applicable to most any bidirectional hydraulic motor driven application. The invention will be described hereinafter with reference to power swivel  31 . 
         [0024]    The structure  40  forming a hydraulic flow path between the pump  20  and the power swivel  31  includes a directional control valve  41  for reversing the direction of hydraulic fluid flow through the power swivel  31 . In the illustrated embodiment, the directional control valve  41  includes a supply valve pair  43  including valves V 1  and V 3  and an exhaust valve pair  44  including valves V 2  and V 4 . Preferably, both the supply valves  43  and the exhaust valves  44  are provided in the form of a 4-way valve assembly  42 . The invention will be described hereinafter with reference to 4-way valve assembly  42 . 
         [0025]    The supply valves  43  in the 4-way valve assembly  42  are selectively settable in configurations to provide forward drive, reverse drive, and neutral lock-up for the power swivel  31 . In forward drive, hydraulic fluid is supplied from the pump  20  to the first port  32  of the power swivel  31  via a line  33  extending between the 4-way valve assembly and the power swivel. In reverse drive, hydraulic fluid is supplied from the pump  20  to the second port  34  of the power swivel  31  via a line  35  extending between the 4-way valve assembly and the power swivel. In neutral lock-up, no hydraulic fluid is supplied to the power swivel  31 . 
         [0026]    The exhaust valves  44  of the 4-way valve assembly  42  are selectively settable in configurations to provide forward drive, reverse drive and neutral lock-up for power swivel  31 . In forward drive, hydraulic fluid is exhausted from the second port  34  of the power swivel  31 . In reverse drive, hydraulic fluid is exhausted from the first port  32  of the power swivel  31 . In neutral lock-up, no hydraulic fluid is exhausted from the power swivel  31 . 
         [0027]    In the illustrated embodiment, the 4-way valve assembly  42  includes a first valve V 1 , a second valve V 2 , a third valve V 3  and a fourth valve V 4 . The second valve V 2  and the fourth valve V 4  form the exhaust valves  44  and the first valve V 1  and the third valve V 3  form the supply valves  43 . In forward drive, the second valve V 2  and the third valve V 3  are closed and the first valve V 1  and the fourth valve V 4  are open. In reverse drive, the first valve V 1  and the fourth valve V 4  are closed and the second valve V 2  and the third valve V 3  are open. In lock-up, the first valve V 1 , the second valve V 2 , the third valve V 3 , and the fourth valve V 4  are all closed. 
         [0028]    The valves V 1 , V 2 , V 3 , and V 4  are preferably hydraulic logic cartridge valves which are spring biased to the closed position and have a 1.6:1 area ratio to provide a multiplier for the actuating fluid. The valves have a damping nose. An actuator  60  for these valves is a 4-way directional control valve, 3-position, spring centered, air operated, with pressure to both A and B out lines when in the center position. 
         [0029]    The structure  40  forming a hydraulic flow path between the pump  20  and the power swivel  31  includes a flow rate controller  50  for controlling the flow rate of hydraulic fluid to the power swivel  31 , and thus the speed of the power swivel  31 . The flow rate controller  50  comprises a first speed valve assembly  52  selectively settable in configurations for flow output and flow recirculation. In flow output configuration, a first flow of hydraulic fluid is supplied through the hydraulic fluid flow path from the pump  20  to the power swivel  31 . In recirculation, hydraulic fluid bypasses the power swivel  31  and is returned to the pump  20 . 
         [0030]    The 4-way valve actuator  60  for the 4-way valve assembly  42  is for simultaneously selectively setting the swivel supply valves  43  and the swivel exhaust valves  44  to matching configurations forward drive, reverse drive, and lock-up and signaling an actuator  72  for the first speed valve  52  to set the first speed valve in configuration for recirculation when the swivel supply valves  43  and the swivel exhaust valves  44  are set to lock-up. 
         [0031]    In a preferred embodiment, the apparatus is controlled with a manually actuated shifter  80  with Forward, Neutral and Reverse positions. Preferably, the shifter is located on a remote control panel  81 . A means  90 , for example, pneumatic umbilical line  91 , establishes a signal path from the shifter  80  to the 4-way valve actuator  60 . Positioning the shifter in the Forward position signals the 4-way valve actuator  60  to simultaneously set the swivel supply valves  43  and the swivel exhaust valves  44  for forward drive. Positioning the shifter in the Neutral position signals the actuator  60  to simultaneously set the swivel supply valves  43  and the swivel exhaust valves  44  for lock-up. Positioning the shifter in the Reverse position signals the actuator  60  to simultaneously set the swivel supply valves  43  and the swivel exhaust valves  44  for reverse drive. The Neutral position on the shifter is preferably located between the Forward position and the Reverse position so that the Neutral position must be engaged to shift between Forward and Reverse. 
         [0032]    The apparatus preferably further includes a means  100 , for example, pneumatic line  101 , for establishing a signal path from the shifter  80  to the actuator  72  for the first speed valve  52  so that the signal from the neutral position on the shifter further signals the actuator  72  for the first speed valve to set the first speed valve to recirculation configuration. 
         [0033]    When the shifter is in the neutral position, the power swivel  31  is in neutral lock-up. To permit the power swivel to unwind, a torque release system is provided. The torque release system preferably comprises a manual actuator  82  positioned on the control panel  81 , a cartridge valve  83  positioned to open and close a crossover flow line interconnecting lines  33  and  35  between the 4-way valve and the power swivel, and a signal line  84 , such a pneumatic line, for conveying a signal from the actuator  82  to the cartridge valve  83 . To provide an indication of torque, as well as an indication of when the torque has been released, the control panel  81  preferably further carries a torque gauge  85 . A shuttle valve  86  is positioned in a second crossover flow line interconnecting the lines  33  and  35  between the 4-way valve and the power signal, and a hydraulic line  87  connects the shuttle valve and the gauge. In the illustrated embodiment, the crossover for the torque indicator system is positioned across the crossover for the torque release system. 
         [0034]    In the illustrated embodiment, the hydraulic pump flow rate controller  50  further includes a second speed valve  54  selectively settable in configurations for flow output and flow recirculation. In second speed drive, a second flow of hydraulic fluid is supplied from the hydraulic pump  20 , in combination with the first flow, to the power swivel  30 . In recirculation, hydraulic fluid bypasses the power swivel  30  and is returned to the hydraulic pump  20 . The apparatus is further provided with an actuator  74  for the second speed valve  54  and a manually actuated throttle  110  with at least first and second speed positions. A means  120 , for example, pneumatic line  121 , establishes a signal path from the throttle  110  to the actuator  74  for the second speed valve. The second speed position on the throttle  110  signals the actuator  74  to set the second speed valve  54  to the flow output configuration. 
         [0035]    In a further preferred embodiment, the pump flow rate controller  50  further includes a third speed valve  55  selectively settable in configurations for flow output and flow recirculation. In the configuration for third speed drive, a third flow of hydraulic fluid, in combination with the first and second flows, is supplied from the hydraulic pump  20  to the power swivel  30 . In recirculation, hydraulic fluid bypasses the power swivel  31  and is returned to the pump  20 . The manually actuated throttle  100  further has a third speed position, and the apparatus further comprises a means  130 , for example, pneumatic line  131 , establishing a signal path from the throttle  110  to an actuator  76  for the third speed valve  55 . The signal from the third speed position on the throttle  110  signals the actuator  76  for the third speed valve to set the third speed valve  55  in flow output configuration. 
         [0036]    In the illustrated embodiment, the first speed valve  52  comprises a valve element  56  defining an orifice  58 . The valve element is biased toward the flow output configuration by spring  57 , for example. The actuator  72  for the first speed valve  52  comprises a shuttle  78  defining a relief passage  77  therethrough The shuttle  78  is biased, such as by spring  79 , toward a first position wherein the relief passage is in flow communication with the orifice  58  and is movable to a second position in response to a signal to break the communication. The apparatus further comprises a conduit structure  150  defining a hydraulic fluid flow path from the orifice  58  to the shuttle  78  so that the valve element  56  of the first speed valve  52  moves to the flow recirculation configuration when the shuttle is in the first position. 
         [0037]    In a particularly preferred embodiment, the shifter  80  and the throttle  110  provide pneumatic signals and the signal from the neutral position on the shifter  110  received by the actuator  72  for the first speed valve is a null signal so that the shuttle  78  is spring biased in response thereto to the flow output configuration. 
         [0038]    In a further preferred embodiment, the apparatus further comprises a pressure gauge  160  and a conduit structure  170 , for example, hydraulic line  171 , connecting the pressure gauge to the hydraulic fluid flow path  150  between the orifice  58  and the shuttle. To avoid overpressure conditions, a relief valve  190  is preferably operably positioned downstream of the gauge  160  to relieve pressure above a predetermined upper limit from the hydraulic line  171 . 
         [0039]    In the illustrated embodiment, the signal produced when the shifter is in the Neutral position is a null signal. The 4-way valve actuator  60  includes a shuttle  200  having a passage  210  therethrough which is spring biased responsive to the null signal to a neutral configuration (illustrated) which permits passage therethrough of hydraulic fluid to set the swivel supply valves  43  and the swivel exhaust valves  44  to the lock-up configuration, for example, by springs  202  and  204 . A conduit  220  connects the 4-way valve actuator  60  with a conduit structure forming a hydraulic flow path between the supply valves  43  and the power swivel  31  to provide hydraulic fluid to the actuator  60  for setting the valves. 
         [0040]    Further in the illustrated embodiment, the signal produced when the throttle  110  is in the second speed position (illustrated) is a null signal and the actuator  74  for the second speed valve is spring biased responsive to the null signal to set the second speed valve  54  in the configuration for flow output. The signal produced when the throttle  110  is in the third speed position is a positive signal and moves the actuator  55  against a spring bias to set third speed valve  55  in configuration for flow output. 
         [0041]    The following features are not necessarily required in all embodiments of the invention but are described herein for the sake of completeness. 
         [0042]    A hydraulic fluid reservoir  230  is provided which in the invention may be sized smaller than is usually the case with fixed displacement pumps because of the unusual closed loop configuration of the invention. 
         [0043]    A charge pump  240  draws fluid filtered by strainer  260  from the reservoir  20  and charges the main pump  20 . An auxiliary pump  270  is provided to power optional features such as the hose reel motor  271  and winch motor  272 . Charge fluid from the pump  240  is cooled in cooler  280 , filtered in filter  290 , combined with fluid returning to the pump from the swivel  31 , and the combined flows are charged to the pump  20 . All pumps can be powered from a single shaft by engine  281 , such as a diesel engine. The cooler can be positioned adjacent to the engine radiator. An air compressor can be driven by the motor to charge an air reservoir for powering the controls. 
         [0044]    Relief valves  36  and  38  are provided on the power swivel pressure lines to avoid overpressure conditions. 
         [0045]    Although the actuating signals in the illustrated embodiment are pneumatic, it is to be understood that electrical, hydraulic, or mechanical linkages could be used if desired. It is preferred however, that the signals not rely on the same power source as the pump, as a power failure to the main motor could result in unwinding of the torque in the drill pipe without the ability to intervene. 
         [0046]    The pump  20  is preferably a fixed displacement, 3-stage gear pump having three equal displacement sections so that the hydraulic motor can have three speeds. The pump flow rate controller  50  and recirculation lines are preferably positioned within the pump casing for compactness and to reduce energy loss and heat buildup. The 4-way valve assembly  42  is also preferably integral with the pump as is the conduit which supplies fluid from the pump to the 4-way valve assembly. 
         [0047]    With reference to  FIG. 2 , a unified pump and valve assembly is shown from a top view. An engine  281 , for example, a diesel engine, drives a serially arranged gear pump assembly having a first gear section  301 , a second gear section  302 , and a third gear section  303 . As illustrated, the unit also includes auxiliary gear pump module  270  and charge gear pump module  240 . The engine  281  also drives an air compressor, not shown, which discharges into a reservoir tank to power the control system. A first manifold/valve module  310  is positioned adjacent the first gear section  301 , between the first gear section  301  and the second gear section  302 , a second manifold/valve module  311  is positioned adjacent the second gear section  302 , between the second gear section  302  and the third gear section  303 , and a third manifold/valve module  312  is positioned adjacent the third gear section  303 , between the third gear section  303  and the auxiliary gear pump module  270 . The pump flow controller  50  as well as the four-way valve assembly  42  is operably associated with the manifold/valve modules. 
         [0048]      FIG. 3  is a cross sectional view of the first manifold/valve module  310  along cut line  3  in  FIG. 2 .  FIG. 4  is a cross sectional view of the second manifold/valve module  311  along cut line  4  in  FIG. 2 .  FIG. 5  is a cross sectional view of the third manifold/valve module  312  along cut line  5  in  FIG. 2 .  FIG. 4  will be described first. 
         [0049]    The second manifold/valve module has an inlet  320  receiving flow from the 4-way valve assembly  42  and an outlet  321  for discharging flow to the 4-way valve assembly  42 . A suction chamber  322  draws fluid from the inlet  320  by action of the gears in adjacent gear section  302 . The gear section  302  has a suction chamber passage corresponding the chamber  322  passing through it adjacent to the draw-in convergence point of the gears and supplying the suction chamber in the manifold/valve module  310  with fluid. The gear section  302  discharges into a high pressure port  323  of the manifold/valve module  311 . When the second speed valve  54  is in the recirculate position, fluid flow is as indicated by the arrows, back to the suction chamber  322 . When the second speed valve is in the second speed position, fluid flow is out port  321 , to the 4-way valve. The manifold/valve module has a transverse borehole  324  for passage of the gear section drive shaft, and a transverse borehole  325  for passage of the gear section idler shaft. Boreholes  326  are provided for through bolts to hold the assembly of modules together. 
         [0050]    An opposed pair of transverse passages  327  open into the manifold/valve module  311  near the discharge  321  for receiving fluid flow from the manifold/valve modules  310  and  312 . As shown in  FIG. 2 , a conduit  329  carries high pressure fluid, when present, from the manifold/valve module  310  to the manifold valve module  311  and a conduit  328  carries high pressure fluid, when present, from the manifold/valve module  312  to the manifold/valve module  312 . 
         [0051]    The manifold/valve module  310  shown in  FIG. 3 , and the manifold/valve module  312  shown in  FIG. 5  are constructed similarly to the manifold/valve module  311  shown in  FIG. 4 . Flow to recirculation or discharge in the manifold/valve module  310  is controlled by the first speed valve  52 . Flow to recirculation or discharge in the manifold valve module  312  is controlled by the third speed valve  55 . Separator plates (not shown) direct fluid flow from the gear sections into the appropriate manifold valve modules. 
         [0052]      FIG. 6  is a cross-sectional view of a portion of the apparatus shown in  FIG. 2 , viewed from the side. Each gear section  301 ,  302 ,  303  contains a drive gear  330 /idler gear  331  pair for driving the fluid. The drive gears are carried on splined drive shaft sections  332  to facilitate assembly. 
         [0053]      FIG. 7  is a side view of the apparatus shown in  FIG. 2  showing the main inlets and outlets for the integrated unit. 
         [0054]    The apparatus of the invention can be used by setting the swivel supply valves  43  and the swivel exhaust valves  44  in configuration for forward drive, setting the first speed valve  52  in flow output configuration, and pumping pressurized hydraulic fluid to the power swivel  31  to drive the power swivel in a forward direction. 
         [0055]    The apparatus of the invention can also be used by setting the swivel supply valves  43  and the swivel exhaust valves  44  in matching configurations for lock-up, setting the first speed valve  52  in configuration for recirculation, and pumping pressurized hydraulic fluid into a return line to the pump  20  which bypasses the power swivel  31 . 
         [0056]    The apparatus of the invention can be further used by setting the swivel supply valves  43  and the swivel exhaust valves  44  in matching configurations for forward drive, setting the first speed valve  52  in configuration for flow output, setting the second speed valve  54  in configuration for flow output, and pumping pressurized hydraulic fluid to the power swivel  31  to drive the power swivel  31  in a forward direction. 
         [0057]    In the preferred embodiment, the pump and its associated valves and remote controls work together as one invention. The control panel arrangement uses identical three-position levers (F-N-R and 1-2-3) so that even an untrained operator has no difficulty understanding it. This is made possible by the comprehensive control circuitry, which permits smooth, seamless, on the fly shifting similar to a car transmission. When selecting neutral, the pump flow and the rotating string of drill pipe must come to a stop rapidly, but not harshly enough to cause damage or a safety concern. Also, when the neutral position is engaged with the pump operating at high pressure, that pressure must be maintained to prevent the drill pipe from freewheeling out of control in the reverse direction. The circuitry provides for these functions with conventional, time-tested, readily available components. 
         [0058]    The first speed valve with its control circuitry provides three important functions, enabling motor speed control, maximum pressure adjustment, and pump unloading when in neutral without slamming the motor to a stop, permitting out of control backspinning, or generating heat buildup in the hydraulic fluid. Motor speed control is provided by closing the first speed valve to provide full flow from the first section of the pump for motor first speed. At this time, the second and third speed valves are open to allow hydraulic fluid to recirculate in the pump without doing work or adding to motor speed. Maximum pressure control is provided by a remote relief valve controlling the first speed valve to provide that additional function. Pump unloading in neutral is a necessary function and is a design challenge because the gear pump is a fixed displacement pump so mechanically has no neutral or zero displacement position. Nonetheless, the motor must be positively stopped by moving a lever to a neutral position without slamming the motor and rotating drill pipe to a stop. Additionally, when stopped in neutral, the pump cannot generate heat or consume power as would be the result if a typical closed center directional control valve with a relief valve were used. Using a conventional open center directional control valve would permit the drill motor and pipe to spin rapidly backwards when moved to neutral, and also would not permit the driller to operate in a stop and go manner when required. Alternately, using a conventional closed center directional control valve would slam the drill motor and pipe to a stop when moving to neutral. The disclosed first speed valve with control circuitry provides the needed functions without the stated disadvantages. 
         [0059]    While certain preferred embodiments of the invention have been described herein, the invention is not to be construed as being so limited, except to the extent that such limitations are found in the claims.