Abstract:
A dampener includes an external reservoir which stores hydraulic fluid due to fluid expansion caused by heat generated by fluid flow through valves that cause a drop in fluid pressure. The primary manifold controls hydraulic fluid flow within the dampener. A diverter valve communicates with the passageways between the dampener and the external reservoir. Hydraulic flow is bi-directional between the primary manifold and the accumulator. Hydraulic fluid flow is restricted when flowing from the primary manifold to the accumulator but is unrestricted when flowing from the accumulator back to the primary manifold and dampener.

Description:
BACKGROUND 
       [0001]    The bucket-ends of shovels used in open pit mine operations are typically composed of a large central body to hold and move material with a rear door for dumping. The doors are typically a hinge-style design and, if not controlled, will swing wildly when opened or closed. The door can contact the main boom when opened and can impact the bucket structure when closed. Repeated door impacts will cause the bucket structure to fatigue and crack. Impact noise is an issue. 
         [0002]    To reduce door-induced damage and noise, the industry installs various types of door-rotation inhibiting devices in an effort to reduce the momentum of the door. Of these, the majority are variations of either a friction-disk or a hydraulic design. 
         [0003]    Friction-disk designs offer excellent resistance torques in relatively small packaging envelopes when adjusted properly; however, torque quickly reduces as friction plates wear. Maintenance and adjustment is frequent to maintain good performance. The required maintenance cycle is impractical and seldom followed leading to poor overall performance. 
         [0004]    For various reasons, hydraulic designs do not match the high-torque versus small-size combination offered by friction disks; however, maintenance on hydraulic units is typically not required once they are operational so the overall performance is better than the previous option. However, hydraulic units have design challenges of their own. Among these are torque adjustability, ease of installation, fluid volumetric changes due to temperature, and internal pressure spikes. 
       SUMMARY OF THE INVENTION 
       [0005]    This invention uses fully self-contained hydraulic rotary actuator assemblies also known as dampeners to impose a counter-torque to dampen the rotation of the door to reduce door impact damage to the bucket structure and reduce noise. Once the dampeners are attached to the bucket structure and the dampener arm is attached to the door linkage, they are ready for service. No additional plumbing or electrical connections are required. 
         [0006]    The invention utilizes an external hydraulic manifold and valve design. This provides an opportunity to adjust output torque in the field without exposing sensitive hydraulic pressure seals to contamination and damage. The primary external manifold also houses a flow restriction valve (needle valve) that can be quickly accessed and adjusted in the field. Adjusting this flow restriction valve (needle valve) greatly decreases torque required to rotate the dampener arm which is helpful during installation to align and attach the arm to the door linkage. 
         [0007]    The invention uses a unique fluid management design to maintain fluid level within the dampener regardless of fluid temperature. The invention allows the dampeners to be completely filled with oil thereby eliminating air from the system and its potential for cavitation damage. The system uses an external accumulator reservoir to collect excess fluid as it expands due to added heat but can return it to the dampener via accumulator-induced pressure as it is needed. 
         [0008]    As an added safety measure, the invention incorporates relief valves inside the dampener that are triggered by abnormal pressure spikes. The additional valves increase the internal flow rate thereby decreasing spike pressure and its damage potential. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective schematic view of the right and left hand dampeners on the bucket wherein the dampeners are pinned (connected) to mounting structures on top of the bucket, the dampener arms are connected to the bucket door linkage and the linkage attaches to the door mounting/pivot arm. 
           [0010]      FIG. 1A  is a schematic view of the right hand dampener mounted on top of the bucket with vertical and horizontal orientations shown from the perspective of line  1 A- 1 A and with the bucket at rest or in the loading position with the door closed. 
           [0011]      FIG. 1B  is a schematic view of the right hand dampener mounted on top of the bucket with vertical and horizontal orientations shown from the perspective of line  1 B- 1 B and with the bucket rotated in the dumping position with the door closed. 
           [0012]      FIG. 1C  is a schematic view of the right hand dampener mounted on top of the bucket with vertical and horizontal orientation shown from the perspective of line  1 C- 1 C and with the bucket rotated in the dumping position and the door open. 
           [0013]      FIG. 2  is a side view of the right hand dampener assembly from the perspective of line  2 - 2  in  FIG. 1 . 
           [0014]      FIG. 3  is a top view of a right hand dampener assembly from the perspective of line  3 - 3  in  FIG. 1 . 
           [0015]      FIG. 4  is a rear view of the right hand dampener assembly similar to  FIG. 3  without the protective armor and the dampener arm shown. 
           [0016]      FIG. 5  is top view of the right hand dampener assembly similar to  FIG. 3  without the protective armor and arm from the perspective of line  5 - 5  in  FIG. 4 . 
           [0017]      FIG. 6  is a perspective view of the right hand dampener from the perspective of line  6 - 6  in  FIG. 5  without one head, the protective armor, and the dampener arm shown. 
           [0018]      FIG. 7  is a cross-sectional view of the right hand dampener assembly taken along the line  7 - 7  in  FIG. 3 . 
           [0019]      FIG. 8A  is a cross-sectional view of the primary manifold in the door opening condition taken along the line  8 - 8  in  FIG. 4 . 
           [0020]      FIG. 8B  is a cross-sectional view of the primary manifold in the door closing condition taken along the line  8 - 8  in  FIG. 4 . 
           [0021]      FIG. 9  is a cross-sectional view of the accumulator manifold taken along the line  9 - 9  in  FIG. 7 . 
           [0022]      FIG. 10A  is a cross-sectional view of the accumulator in the start-up condition with oil at ambient temperature taken along the line  10 - 10  in  FIG. 5 . 
           [0023]      FIG. 10B  is a cross-sectional view of the accumulator with oil at expected maximum operating temperature taken along line  10 - 10  in  FIG. 5 . 
           [0024]      FIG. 11  is a perspective view illustrating the position of the primary manifold, accumulator manifold, accumulator reservoir, as well as, the interconnecting hosing. 
           [0025]      FIG. 12  is a view of the dampener shaft illustrating the shaft vane and valving. 
           [0026]      FIG. 12A  is a sectional view of the shaft vane taken along the lines  12 A- 12 A in  FIG. 12 . 
           [0027]      FIG. 12B  is a sectional view of the shaft vane taken along the lines  12 B- 12 B in  FIG. 12 . 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0028]      FIG. 7  is a cross-sectional view of the right hand dampener assembly  2  taken along the line  7 - 7  in  FIG. 3 . Referring to  FIG. 7 , a rotatable actuator arm  6 R operates in the closed direction when the arm rotates clockwise and the actuator arm operates in the open direction when the arm rotates in the counter-clockwise direction. The arm is connected by way of linkage to a door which is used on a bucket which excavates earth. As the bucket is filled with earth or minerals, it becomes full and must be dumped quickly so it can continue with the excavation process. When dumping the bucket, the door must open quickly to evacuate the bucket and the contents of the bucket (plus door weight) force the door open when the door is unlatched from the bucket. After the contents are dumped, the door of the bucket closes under its own weight. 
         [0029]      FIG. 1  is a perspective schematic view of the right hand dampener  2  and the left hand dampener  1  wherein the dampeners are pinned (connected) to mounting structures on top of the bucket (not shown). The dampener arms  6 L,  6 R are connected to the bucket door linkage  4 L,  4 R and the linkage attaches to a door pivot arm  5 L,  5 R.  FIG. 1  illustrates a typical mounting configuration for the hydraulic dampeners. Pins  3 P,  3 P secure the dampener to the bucket structure  3 L,  3 R as illustrated in  FIGS. 1, 1A, 1B, and 1C . Typically two dampeners, a right hand and a left hand dampener, are employed with a bucket. Right hand and left hand is determined when viewing the dampeners from the operator&#39;s seat and when viewing  FIG. 1  from the left most part of the drawing sheet. Dampener assemblies  1 ,  2  are attached to the top of the bucket utilizing existing mounting structures  3 L,  3 R on the bucket. 
         [0030]    Dampener arm  6 L is connected to door linkage  4 L. Movement of the door creates rotational movement about the door pivot  5 A. The same movement also imposes a compression/tensile load through the door linkage  4 L. Door linkage  4 L loading is transmitted to the dampener arm  6 L and causes a rotational movement of the arm  6 L at the dampener  1 . 
         [0031]    In reference to dampener  2 , dampener arm  6 R is connected to door linkage  4 R. Movement of the door creates rotational movement about the door pivot  5 A. The same movement also imposes a compression/tensile load through the door linkage  4 R. Door linkage  4 R loading is transmitted to the dampener arm  6 R and causes a rotational movement of the arm  6 R at the dampener  2 . 
         [0032]      FIG. 1A  is a schematic view of the right hand dampener  2  mounted on top of the bucket  3 R with vertical and horizontal orientations shown from the perspective of lines  1 A- 1 A of  FIG. 1  and with the bucket at rest or in the loading position with the door closed. Bucket door linkage  5 R is illustrated. 
         [0033]      FIG. 1B  is a schematic view of the right hand dampener  2  mounted on top of the bucket with vertical and horizontal orientations shown from the perspective of lines  1 B- 1 B of  FIG. 1  and with the bucket rotated in the dumping position and the door closed. 
         [0034]      FIG. 1C  is a schematic view of the right hand dampener  2  mounted on top of the bucket, with vertical and horizontal orientations shown from the perspective of lines  1 C- 1 C of  FIG. 1 , with the bucket rotated in the dumping position, and with the door open. Dampener arm  6 R is illustrated rotated counter clockwise to the door open position when viewing  FIG. 1C . Also see  FIG. 7  wherein dampener arm  6 R rotates counter clockwise to open the bucket door. 
         [0035]      FIG. 2  is a side view of a right hand dampener assembly from the perspective of line  2 - 2  in  FIG. 1 . Referring to  FIG. 2 , each dampener has a large bottom base plate  7 . Pins are slid through the large holes in the base plate to secure the dampener to the bucket structure  3 R,  3 L. 
         [0036]      FIG. 3  is a top view of a right hand dampener assembly from the perspective of line  3 - 3  in  FIG. 1 .  FIG. 5  is a top view of a right hand dampener similar to  FIG. 3  without the protective armor and dampener arm from the perspective of line  5 - 5  in  FIG. 4 . Referring to  FIGS. 3 and 5 , the dampener arm  6 R has a mechanical spline connection on shaft  12  to transmit torque from one component to the other. Referring to  FIG. 3 , a shaft end plate  6 A prevents the dampener arm  6  from sliding off the end of the shaft  12 . 
         [0037]    Referring to  FIGS. 2 and 3 , the dampener has a couple pieces of armor  8 ,  9  to protect various hydraulic fluid management components to be described later from damage during use. The primary manifold armor  8  has relief cut-outs to access fluid fill ports  11  as well as a removable cover plate  10  to access flow control valve  14  necessary for arm  6  positioning during installation of the dampener and which will be described later. 
         [0038]      FIG. 4  is a rear view of the right hand dampener assembly similar to  FIG. 3  without the protective armor and arm shown. Referring to  FIGS. 4 and 5 , under the armor  8 ,  9 , the dampener has a primary hydraulic manifold  13  housing two pressure relief valves  15 ,  16 , a flow control valve  14 , and a fluid diverter valve  17 . A hose  21  connects the top/primary manifold to a secondary accumulator manifold  18 . The accumulator manifold houses a manual flow control valve  19  and a pressure relief valve  20 . A second hose  22  connects the accumulator manifold  18  to the accumulator reservoir  23 . Both the accumulator manifold  18  and accumulator reservoir  23  are held in place via the protective armor  9 . 
         [0039]      FIG. 6  is a perspective view of the right hand dampener  2  from the perspective of line  6 - 6  in  FIG. 5  without one head  24 B, the protective armor  8 ,  9 , and the dampener arm  6 R shown. Referring to  FIGS. 5 and 6 , the main dampener housing is composed of two heads  24 A,  24 B, a central body  25 , the shaft  12 , and an internal shoe  28 . Only one head is shown in  FIG. 6 .  FIGS. 4 and 5  illustrate heads  24 A,  24 B and the central body  25 . Shaft  12  is axially and radially held in place by the heads  24 A,  24 B but is free to rotate. As shaft  12  rotates, shaft vane  12 A rotates within the central body  25 . Shaft  12  and shaft vane  12 A are embodied within a single component. Shoe  28 , shoe seals  28 A, vane  12 A, and vane seals  12 B divide the central body  25  into two pressure-tight cavities  29 ,  30 . Reference numeral  29  denotes the first central cavity and reference numeral  30  denotes the second central cavity. 
         [0040]    The opening of the bucket door causes the shaft  12  to rotate in a clockwise (CW) direction as seen in  FIG. 6  and in a counter-clockwise (CCW) direction as viewed in  FIG. 7 . Referring to  FIG. 7 , a CCW rotation will cause a pressure increase in the first central cavity  29  and a decrease in pressure in the second central cavity  30 . High pressure in the first central cavity  29  will be transmitted to the first body port  31  leading to the primary manifold  13 . 
         [0041]      FIG. 8A  is a cross-sectional view of the primary manifold  13  taken along the line  8 - 8  in  FIG. 4  and illustrates the door-opening condition. Referring to  FIG. 8A , high pressure at the first body port  31  will pressurize second manifold passageway  34 . At this point, pressure and the majority of flow are blocked by pressure relief valves  15 ,  16 . A small regulated amount of fluid is able to flow through the flow control needle valve  14  and into the first manifold passageway  33  where it can reenter the dampener second central cavity  30  via second body port  32 . However, the flow rate is negligible and pressure continues to increase in the second manifold passage  34 . 
         [0042]    Referring to  FIG. 8A , primary flow path  50  is indicated by a solid line in the door opening cycle. Primary flow path  50  extends during the door open cycle from the first body port  31 , through the door open pressure relief valve  15 , first manifold passage  33 , and into the second body port  32 . Dashed line  51  indicates a secondary minimal flow path from first body port  31 , second manifold passage  34 , across the exterior of pressure relief valve  16 , through needle valve  14  and into second body port  32 . Dashed line  52  indicates a tertiary minimal flow path through diverter valve  17 , manifold  13 , fitting  35 , and into the accumulator manifold  18  and accumulator reservoir  23 . 
         [0043]    Fluid pressure acts against all internal surfaces on the high pressure side of the dampener including the shaft vane  12 A. Pressure multiplied by vane surface area multiplied by the average radial distance between the shaft vane  12 A and the shaft rotation axis equates to a “dampening” or counter-torque that works against the rotation of arm  6  and shaft  12 . Internal pressure will continue to rise until the opening pressure of relief valve  15  is reached. At that point, fluid can flow from the second manifold passageway  34  to the first manifold passageway  33  by traveling through the door open relief valve  15 . Fluid flows from the first manifold passageway  33 , through the second body port  32 , and into the dampener housing second internal cavity  30 . Shaft rotation, internal fluid flow, and dampening counter-torque will continue until the bucket door fully opens or comes in contact with an external stop. 
         [0044]    The developed torque from the dampener can be adjusted. Referring to  FIG. 8A , the opening pressure of the door open pressure relief valve  15  and the opening pressure of the door close pressure relief valve  16  directly affects the resistance torque of the dampener. Resistance torque increases as opening pressure increases and resistance torque decreases as opening pressure decreases. The opening pressures of each pressure relief valve  15 ,  16  are increased by turning the valve  15 ,  16  adjustment screw CW and reduced by turning the adjustment screw CCW. The valves  15 ,  16  and their adjustment screws are easily accessed by removing the primary manifold armor  8 . This feature increases the flexibility of the dampeners. The same dampener can be used on multiple bucket platforms with the resistance torque adjusted accordingly. 
         [0045]      FIG. 8B  is a cross-sectional view of the primary manifold  13  taken along the line  8 - 8  in  FIG. 4  which illustrates the door closing condition. The closing of the bucket door creates a CCW rotation of the shaft as seen in  FIG. 6  and CW as seen in  FIG. 7 . Referring to  FIGS. 7 and 8B , this creates high pressure in the second central cavity  30  and low pressure in the first central cavity  29 . High pressure in second central cavity  30  pressurizes second body port  32  and first manifold passageway  33 . Referring to  FIG. 8B , at this point fluid pressure and the bulk of fluid flow are stopped by the door close pressure relief valve  16  and the door open pressure relief valve  15 . A small quantity of hydraulic fluid is able to flow  61  through the flow control needle valve  14  where it can reenter the dampener via first body port  31  and then into first central cavity  29  which is at relatively low pressure. In addition, a small quantity of fluid can also pass through the diverter valve  17 , manifold  13 , and fitting  35  where it can then travel to the accumulator manifold  18  and accumulator reservoir  23 . However, fluid loss through the flow control valve  14  and diverter valve  17  is negligible and fluid pressure continues to rise in the first manifold passageway  33 . Fluid pressure acts on all internal surfaces on the high pressure side of the dampener including the shaft vane  12 A. Fluid pressure multiplied by the shaft vane  12 A surface area multiplied by the average radial distance from the shaft vane  12 A to the shaft axis of rotation equates to a dampening or counter-torque to resist shaft rotation. Pressure continues to rise in the high pressure cavities  30 ,  32 , and  33  until the opening pressure of the door close pressure relief valve  16  is reached. At that point fluid is able to flow from second body port  32 , into first manifold passageway  33 , through relief valve  16 , through second manifold passageway  34  which is at low pressure, through the first body port  31 , and into the first central cavity  29  which is at low pressure. Arm  6 , shaft  12 , and shaft vane  12 A rotation as well as the dampening torque continue until the door comes to a stop. 
         [0046]    Referring to  FIG. 8B , primary flow path  60  is indicated by a solid line in the door close cycle. Primary flow path  60  extends through second body port  32 , first manifold passageway  33 , door close relief valve  16 , second manifold passageway  34 , and first body port  31 . Dashed line  61  indicates a secondary minimal flow path through needle valve  14 , across the exterior of door close relief valve  16  and into the first body port  31 . Dashed line  62  indicates a tertiary minimal flow path through diverter valve  17 , manifold  13 , and fitting  35  to the accumulator manifold  18  and accumulator reservoir  23 . 
         [0047]    The invention has an additional feature to protect itself from pressure spikes. Occasionally, entire sections of wall will collapse during material removal. Operators are instructed to open the bucket door during collapse events to reduce damage to the bucket. Due to the weight of the door, the weight of material within the bucket, and kinetic energy added from falling debris, door rotational/accelerations speeds can be very fast. This has the potential to create large pressure spikes within the dampener and subsequent damage. To reduce damage from this or other pressure spike instances, additional pressure relief valves  26  have been installed in either face of the shaft vane  12 A. See  FIGS. 6, 7, 12, 12A, and 12B .  FIG. 12  is an illustration of the dampener shaft  12  such its overall design can be seen.  FIG. 12A  is a section view of the shaft vane  12 A along the line  12 A- 12 A in  FIG. 12 .  FIG. 12B  is a section view of the shaft vane  12 A along the line  12 B- 12 B in  FIG. 12 . The pressure valves  26  sense pressure on the opposite sides of vane  12 A from which they are installed. Once pressure reaches the opening pressure of the valves  26 , fluid is able to flow into the valves  26 , through the vane passageways  27 , and out the opposite side of the vane to the low pressure cavity. In this way, fluid is able to bypass the external primary manifold  13  and flow directly from one internal cavity to the other. This flow is in addition to the flow that travels via the normal route through the manifold  13  described previously. The added flow capacity reduces internal pressure and related over-pressurization damage. The shaft vane  12 A pressure relief valves  26  are installed in opposite faces of the vane such that the dampener has protection from pressure spikes in either shaft rotation direction. 
         [0048]    The pressure relief valves  26  opening pressure is factory-set near the maximum recommended pressure and is not accessible or adjustable in the field. Because of this, the shaft vane valves  26  also help to protect the dampener from excessive pressure adjustment of the primary manifold  13  pressure relief valves  15 ,  16 . The primary manifold  13  pressure relief valves  15 ,  16  can be field-adjusted to reduce dampener output torque or can be field-adjusted up to the maximum recommended dampener pressure. Any further adjustment of the external valves  15 ,  16  will cause an increasing amount of fluid to be diverted through the shaft vane valves  26  thereby reducing potential damage from maladjustment of the external valves  15 ,  16 . 
         [0049]    Referring to  FIG. 7 , channels  28 B,  28 C are illustrated in shoe  28  and these facilitate flow through the first body port  31  and second body port  32 . Shoe stop  28 D engages vane  12 A preventing over travel of vane  12 A and pressure relief valves  26 . In this way relief valves  26  do not engage the shoe  28 . 
         [0050]    The invention incorporates structure to prevent over-pressurization from heat. As the dampeners are cycled, heat is generated as fluid flows across the relief valves  15 ,  16 , and  26 , see  FIGS. 6, 7 . An operator controls the bucket operation. The dampeners are cycled through the operation of the bucket and the door which holds the contents of the bucket in place. The door is alternately closed and opened. When the bucket door is closed by the operator, the bucket is used to scoop up (pick up) earthen material or minerals or the bucket is used to dig into (pick up) earthen material or minerals. When the bucket door is opened, the contents of the bucket fall out and are dumped. 
         [0051]    The dampeners transform the kinetic energy removed from the swinging door into heat at the dampener pressure relief valves  15 ,  16 , and  26 . Heat migrates throughout the dampener structure and component temperatures increase until a temperature equilibrium is reached where the dampener dissipates heat to the surrounding atmosphere and bucket structure at an equal rate as it is created. If a fully enclosed dampener is filled completely with oil and the oil experiences an increase in temperature, its volumetric expansion will greatly exceed the fixed volume of the dampener housing and manifold due to the differences in the coefficient of thermal expansion of the hydraulic fluid and the metallic parts of the dampener. A substantial portion of the dampener and manifold is made of metal. Since hydraulic fluid is essentially non-compressible, a pressure spike is seen throughout the dampener on both sides of the shaft vane  12 A. Internal pressure will continue to increase proportional to temperature until a weak area in the structure of the dampener gives way and fluid is allowed to escape or expand its volume. The weak area is typically at a seal and the dampener may lose oil and become operationally ineffective. 
         [0052]    The invention moves small quantities of oil to an external accumulator reservoir  23 , see  FIGS. 4, 6, 7, 10A, and 10B . Referring to  FIGS. 8A and 8B , whenever first manifold passageway  33  is suitably pressurized (pressure higher than that found in accumulator reservoir  23 ), diverter valve  17  allows fluid to move to and through the fitting  35  where it travels by way of conduit  21  (hose) to a secondary accumulator manifold  18 , through a second conduit  22  (hose), and then to the external accumulator reservoir  23 . The diverter valve  17  is adjusted such that when the manifold first passageway  33  is suitably pressurized, a small metered stream of fluid is allowed to pass into the manifold fitting  35 . The accumulator downstream from manifold fitting  35 , will not experience large pressure variations in the dampener. In addition, the diverter valve  17  prevents large quantities of fluid from passing into the accumulator whenever the dampener goes through an open or close cycle. The diverter valve highly restricts fluid going into the accumulator; however, fluid coming into the dampener from the accumulator is unrestricted. If the dampener is experiencing internal pressure from fluid expansion, the first manifold passageway  33  will be pressurized for a longer period of time and more fluid will be diverted to the accumulator reservoir  23 . Proper dampener fluid level is maintained by the constant metering-out of fluid to the accumulator reservoir  23 , and return of fluid from the accumulator to the dampener. 
         [0053]    It is specifically envisioned that conduits other than hoses may be used to interconnect the fittings  35 ,  36 ,  37 , and  23 E. For instance, and without limitation, the conduit could be metal tubing, a metal reinforced hose, or braided metal conduit. 
         [0054]      FIG. 10A  is a cross-sectional view of the accumulator reservoir  23  taken along the line  10 - 10  in  FIG. 5  as it appears upon initial start-up when the dampener is at ambient temperature. The accumulator  23  is composed of a central cylindrical body with heads  23 H,  23 H on both sides thereof The interior of the accumulator is separated into two pressure tight cavities by a moveable/sliding piston  23 D. One side of the piston  23 D the accumulator is full of compressed gas  23 B. On the other side of the piston, the accumulator is full of hydraulic oil  23 A. The gas  23 B is pressurized nitrogen gas which is introduced through the gas charge fitting  23 C into the accumulator prior to installation. The pressure of the initial nitrogen gas charge is high enough: to overcome any friction from movement of the piston  23 D, and, to pressurize the hydraulic oil  23 A to overcome pressure losses through fittings, valves, and tubing up to the dampener. This induced positive pressure attempts to return fluid back to the dampener. The pressure induced by the accumulator permeates throughout the dampener and becomes the starting (low) pressure of the dampener. The dampener pressure relief valves  15 ,  16 ,  26  opening pressures are based on set pressure differences between low and high pressure sides of the dampener. As a result, the absolute pressure on both the low and high pressures sides of the dampener will vary based on the gas pressure induced into the system from the accumulator. Upon initial start-up, due to gas pressure, the accumulator piston  23 D will be up against the head on the hydraulic side of the accumulator and the accumulator will contain relatively little oil. However, there will be hydraulic fluid (oil) in the conduits  21 ,  22  and the accumulator manifold  18 . 
         [0055]      FIG. 10B  is a cross-sectional view of the accumulator reservoir  23  taken along the line  10 - 10  in  FIG. 5  as it appears after the dampener has been working at an elevated temperature and the oil volume has expanded and filled a significant portion of the oil-side  23 A of the accumulator. Due to reduction of volume and higher temperature, the gas  23 B pressure rises and imposes a larger force on the piston than on initial start-up. The piston  23 D in turn transmits this force to the hydraulic fluid  23 A. The pressure imposed on the fluid  23 A will attempt to force it to a lower pressure area. As such, some of the fluid in the accumulator  23  flows back into the dampener where needed and becomes the low/starting pressure in the dampener. As the dampener temperature increases, the hydraulic oil will expand and fill a larger portion of the accumulator, which will induce a higher pressure on the oil in the accumulator, which then induces a higher starting (low) pressure value in the dampener, which then causes a higher absolute top-end working pressure since the relief valves  15 ,  16 ,  23  pressure settings are based on a set “delta” pressure over the starting/low pressure level. Therefore, proper sizing (volume capacity) of the accumulator reservoir is important otherwise an excessive high pressure can be induced back into the dampener. 
         [0056]      FIG. 9  is a cross-sectional view of the accumulator manifold  18  taken along the line  9 - 9  in  FIG. 7 . Referring to  FIGS. 9 and 11 , hydraulic fluid leaves the dampener via fitting  35  on the primary manifold  13 . From there it travels down conduit  21  where it enters the accumulator manifold  18  via fitting  36 . Inside the manifold  18 , the fluid travels through passageway  34 A and then out again via fitting  37  where it then travels down conduit  22  and into the accumulator reservoir  23 . As discussed previously, as the dampener works, heat is generated and the hydraulic fluid expands into the accumulator reservoir  23 , and the accumulator in-turn imposes a counter-pressure back onto the fluid attempting to return it to the dampener. This counter pressure then becomes the low/starting pressure of the dampener. During normal operation, fluid simply travels unaffected back and forth through the accumulator manifold  18 . Depending on specific operating conditions and design specifications, the accumulator-induced counter-pressure can be relatively high and should be relieved prior to servicing the dampener. A manual pressure relief valve  19  is installed in the accumulator manifold  18 . The valve  19  can be opened using hand pressure on a knurled knob at the top of the valve. Turning the knob CCW opens the valves and sends pressurized fluid out of the dampener via fitting  38  thereby reducing internal pressure and making the dampener safer to service. In addition, the invention incorporates another pressure relief valve  20  into the accumulator manifold  18 . The valve  20  senses the difference in fluid pressure between the accumulator side of the system, specifically in passage  34 A in the accumulator manifold, and compares it to atmospheric pressure. If the pressure differential exceeds that of the open pressure of the relief valve  20 , fluid will automatically be sent out of the dampener via fitting  38  until the pressure reduces to a proper level where the relief valve will close and block further release of oil. This feature prevents the dampener from over-pressurizing due to abnormal events such as excessive operating temperature. 
         [0057]    Referring to  FIG. 1 , the invention incorporates a feature to aid attachment of the arm  6  to the door linkage  4 . The manifold armor  8  has a removable cover  10  as seen in  FIG. 3 . Removing the cover plate  10  allows the installer access to the flow control valve  14  as seen in  FIG. 5, 8A, and 8B  which is adjustable. Backing-off the adjustment screw allows fluid to travel freely between manifold passages  33 ,  34  without building pressure, and counter-torque, reference  FIGS. 8A and 8B . As a result the shaft  12  and arm  6  are able to freely rotate and allows the installer to line-up the arm  6  with the door linkage  4 . After installation, the adjustment screw is fully tightened and then backed-off a specified fraction of a turn. 
         [0058]    The invention allows door travel even when dampener internal pressures are not sufficient to open relief valves  15 ,  16 , and  26 . Depending on the relative alignment at any particular time between the center of gravity of the door, the door pivot point, and bucket frame in combination with the kinetic energy of the door, there is potential that the counter-torque produced by the dampeners equal that induced by the movement of the bucket door and the door stops prior to closing. Referring to  FIGS. 8A and 8B , in this scenario, the pressure inside the manifold  13  lowers to a point below the opening pressure of the relief valves  15 ,  16 , and  26  and flow through them is stopped. However, the flow control valve  14  when properly adjusted as described previously will still allow fluid to pass in either direction but at a relatively slow rate. The effect of this is that the shaft  12 , dampener arm  6 , and bucket door assembly will continue to rotate at a much reduced rate until the door closes or until the door center of gravity relative to its pivot point prevents further rotation. 
       REFERENCE NUMERIALS 
       [0000]    
       
           1  left hand dampener 
           2  right hand dampener 
           3 L bucket structure to mount dampener 
           3 R bucket structure to mount dampener 
           3 P pins securing the dampener to the bucket structure  3 L,  3 R 
           4 L bucket linkage arm to connect dampener arm  6 L to bucket door mounting arm  5 L 
           4 R bucket linkage arm to connect dampener arm  6 R to bucket door mounting arm  5 R 
           4 P pin to connect dampener arm to bucket linkage arm 
           5 A door pivot 
           5 L bucket door mounting arm 
           5 R bucket door mounting arm 
           5 P pin to connect door mounting arm to bucket linkage arm 
           6 A dampener arm end plate 
           6 L dampener arm 
           6 R dampener arm 
           7  dampener mounting base 
           8  primary manifold and valve armor 
           9  accumulator reservoir and accumulator manifold mounting and protective armor 
           10  arm position valve access plate 
           11  dampener oil fill ports 
           12  vane shaft one piece assembly 
           12 A shaft vane 
           12 B shaft vane seal 
           13  primary manifold 
           14  arm position valve 
           15  door open pressure relief valve 
           16  door close pressure relief valve 
           17  fluid diverter valve 
           18  accumulator manifold 
           19  manual pressure relief valve 
           20  accumulator system pressure relief valve 
           21  primary manifold to accumulator manifold supply/return hose 
           22  accumulator manifold to accumulator reservoir supply/return hose 
           23  hydraulic oil accumulator reservoir 
           23 A hydraulic oil side of accumulator 
           23 B pressurized gas side of accumulator 
           23 C gas charge valve 
           23 D movable piston 
           23 E accumulator oil inlet fitting 
           23 H accumulator head 
           24 A dampener head 
           24 B dampener head 
           25  dampener central body 
           26  vane pressure valves 
           27  vane pressure valve relief passages 
           28  shoe 
           28 A shoe seal 
           28 B,  28 C channels in shoe 
           28 D stop 
           29  first central cavity 
           30  second central cavity 
           31  first body port 
           32  second body port 
           33  first manifold passageway 
           34  second manifold passageway 
           34 A passageway in the accumulator manifold  18   
           35  diverter valve fitting 
           36  accumulator manifold inlet fitting 
           37  accumulator manifold outlet fitting 
           38  accumulator manifold overflow fitting 
           50  primary flow path during door open cycle through first body port  31 , door open pressure relief valve  15 , first manifold passageway  33 , and into second body port  32   
           51  dashed line indicating secondary minimal flow path 
           52  dashed line indicating a tertiary minimal flow path through diverter valve  17 , manifold  13 , and fitting  35  to the accumulator manifold  18  and accumulator  23   
           60  primary flow path during door close cycle through second body port  32 , first manifold passageway  33 , door close relief valve  16 , second manifold passageway  34 , and into body first port  31   
           61  dashed line indicating secondary minimal flow path 
           62  dashed line indicating a tertiary minimal flow path through diverter valve  17 , manifold  13 , fitting  35 , and onto accumulator manifold  18  and accumulator  23   
           70  primary flow path in accumulator manifold  18 , fluid enters via fitting  36 , through passageway  34 A, and exits to accumulator via fitting  37   
           71  dashed line indicating a secondary flow path used when high pressure is found in the accumulator-side of the system, fluid travels through passageway  34 A, into pressure valve  20 , and exits the manifold and dampener via fitting  38 . 
           72  dashed line indicating a tertiary flow path used when pressure in accumulator-side of the system is manually reduced, fluid travels through passageway  34 A, into flow valve  19 , and exits the manifold and dampener via fitting  38